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1

Seismic anisotropy estimated from P-wave arrival times in crosshole measurements  

NASA Astrophysics Data System (ADS)

Seismic anisotropy is evidenced in the inner core, upper mantle and the lower crust in large scale, and the evidence is generally provided by shear wave splitting analysis. Here this paper searches for the evidence of anisotropy in the uppermost crust, by using P-wave arrival times from crosshole seismic measurement to directly estimate velocity anisotropy associated with the fine-layering effect of multiple sedimentary beds. Conceptually fine layering causes the so-called VTI (vertical transverse isotropy) anisotropy with a vertical symmetry and the effect is parametrized by the horizontal and vertical velocity ratio. It is found however that the VTI anisotropic parameter does not have a simple vertical symmetry but is also azimuth dependent. This azimuthal anisotropy may reflect the fracture orientation due to large-scale tectonic movements, and is very important in the production of oil reservoirs, as the seismically fast directions can indicate preferred directions of fluid flow. This paper presents innovative methods for anisotropy analysis in both vertical and horizontal plane. Integrated seismic anisotropy interpretation clearly indicates distinguished strain orientations forming fractures in Oligocenic, Miocenic and Pliocenic sediment, in the edge of the extensional basin immediately next to Tan-Lu Fault, an active continental strike-slip fault zone.

Wang, Yanghua

2011-03-01

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

Evidence for a bimaterial interface along the Mudurnu segment of the North Anatolian Fault Zone from P wave arrival times and polarization analysis  

NASA Astrophysics Data System (ADS)

We present results on imaging the contrast of seismic velocities across the Mudurnu segment of the North Anatolian Fault Zone (NAFZ) in northwestern Turkey with two new basic techniques using signals in P waveforms generated by near-fault seismicity and recorded by near-fault stations. The first technique uses changes in motion polarity from fault-normal to source-receiver directions to identify early-arriving fault zone head wave on the slow side of the fault, and measure the arrival times of the head and direct P waves. The moveout between the head and direct waves with increasing source-receiver distance along the fault provides an estimate of the average contrast of seismic velocities across the fault. The second technique involves measuring travel times from near-fault earthquakes to a pair of stations located at similar distances across the fault, and using the results to estimate average velocities associated with the different ray paths. The results from both techniques indicate that the average contrast of P wave velocities across the Mudurnu segment of the NAFZ is at least 6%, with the south block being the faster side. The findings provide a basis for deriving improved event locations, focal mechanisms and estimated shaking hazard associated with earthquakes on the fault. The analysis techniques can be used in other fault zones monitored using sparse seismic instrumentation.

Bulut, F.; Ben-Zion, Y.; Bohnhoff, M.

2011-12-01

4

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

2014-09-01

5

Resolving P-wave travel-time anomalies using seismic array observations of oceanic storms  

E-print Network

Resolving P-wave travel-time anomalies using seismic array observations of oceanic storms Jian California reveals P-wave arrivals from distant storms in open oceans. In this case, the noise can results suggest using oceanic storms as additional seismic sources for resolving P-wave travel

Gerstoft, Peter

6

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

7

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

8

Weak measurement of arrival time  

SciTech Connect

The arrival time probability distribution is defined by analogy with classical mechanics. The difficulty of requiring knowledge of the values of noncommuting operators is circumvented using the concept of weak measurements. The proposed procedure is suitable for free particles as well as for those subjected to an external potential. It is shown that such an approach imposes an inherent limitation on the accuracy of the arrival time determination.

Ruseckas, J.; Kaulakys, B. [Institute of Theoretical Physics and Astronomy, A. Gostauto 12, 2600 Vilnius (Lithuania)

2002-11-01

9

Arrival time and backflow effect  

NASA Astrophysics Data System (ADS)

We contrast the average arrival time at x according to the Bohmian mechanics of one dimensional free Schrödinger evolution with the standard quantum mechanical one. For positive momentum wave functions the first cannot be larger than the second one. Equality holds if and only if the wave function does not lead to position probability backflow through x. This position probability backflow has the least upper bound of approximately 0.04. We describe a numerical method to determine this backflow constant, introduced by Bracken and Melloy, more precisely and we illustrate the approximate wave function of maximal backflow.

Grübl, Gebhard; Kreidl, Sabine; Penz, Markus; Ruggenthaler, Michael

2006-06-01

10

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

11

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume I P-Wave Measurements in Borehole C4993 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (I), all P-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 370 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4993, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06

12

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume III P-Wave Measurements in Borehole C4997 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (III), all P-wave measurements are presented that were performed in Borehole C4997 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 390 to 1220 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 40 ft (later relocated to 27.5 ft due to visibility in borehole after rain) in Borehole C4997, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4997, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-06-06

13

Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume II P-Wave Measurements in Borehole C4996 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.  

SciTech Connect

In this volume (II), all P-wave measurements are presented that were performed in Borehole C4996 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 360 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1180 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4996, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4996, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

2007-07-06

14

Quantum arrival time for open systems  

SciTech Connect

We extend previous work on the arrival time problem in quantum mechanics, in the framework of decoherent histories, to the case of a particle coupled to an environment. The usual arrival time probabilities are related to the probability current, so we explore the properties of the current for general open systems that can be written in terms of a master equation of the Lindblad form. We specialize to the case of quantum Brownian motion, and show that after a time of order the localization time of the current becomes positive. We show that the arrival time probabilities can then be written in terms of a positive operator-valued measure (POVM), which we compute. We perform a decoherent histories analysis including the effects of the environment and show that time-of-arrival probabilities are decoherent for a generic state after a time much greater than the localization time, but that there is a fundamental limitation on the accuracy {delta}t, with which they can be specified which obeys E{delta}t>>({h_bar}/2{pi}). We confirm that the arrival time probabilities computed in this way agree with those computed via the current, provided there is decoherence. We thus find that the decoherent histories formulation of quantum mechanics provides a consistent explanation for the emergence of the probability current as the classical arrival time distribution, and a systematic rule for deciding when probabilities may be assigned.

Yearsley, J. M. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2010-07-15

15

Quantum Arrival Time For Open Systems  

E-print Network

We extend previous work on the arrival time problem in quantum mechanics, in the framework of decoherent histories, to the case of a particle coupled to an environment. The usual arrival time probabilities are related to the probability current, so we explore the properties of the current for general open systems that can be written in terms of a master equation of Lindblad form. We specialise to the case of quantum Brownian motion, and show that after a time of order the localisation time the current becomes positive. We show that the arrival time probabilities can then be written in terms of a POVM, which we compute. We perform a decoherent histories analysis including the effects of the environment and show that time of arrival probabilities are decoherent for a generic state after a time much greater than the localisation time, but that there is a fundamental limitation on the accuracy, $\\delta t$, with which they can be specified which obeys $E\\delta t>>\\hbar$. We confirm that the arrival time probabilities computed in this way agree with those computed via the current, provided there is decoherence. We thus find that the decoherent histories formulation of quantum mechanics provides a consistent explanation for the emergence of the probability current as the classical arrival time distribution, and a systematic rule for deciding when probabilities may be assigned.

J. M. Yearsley

2010-03-31

16

Teleseismic P-wave Tomography Image for Northeastern Tibet  

Microsoft Academic Search

We present a new teleseismic P-wave tomographic image of the upper mantle beneath northeastern Tibet based on seismic data collected by the INDEPTH IV and ASCENT deployments in central and northeastern Tibet. Our aim is to shed light on the deep process and mechanism for crustal thickening at the northwestern Tibetan Margin. We determined teleseismic P wave relative arrival times

H. Chow; F. J. Tilmann; K. F. Priestley; W. Zhao; Z. Wu; D. Shi; E. A. Sandvol; J. F. Ni; J. Mechie; J. Chen

2009-01-01

17

Acceleration of stable TTI P-wave reverse-time migration with GPUs  

NASA Astrophysics Data System (ADS)

When a pseudo-acoustic TTI (tilted transversely isotropic) coupled wave equation is used to implement reverse-time migration (RTM), shear wave energy is significantly included in the migration image. Because anisotropy has intrinsic elastic characteristics, coupling P-wave and S-wave modes in the pseudo-acoustic wave equation is inevitable. In RTM with only primary energy or the P-wave mode in seismic data, the S-wave energy is regarded as noise for the migration image. To solve this problem, we derive a pure P-wave equation for TTI media that excludes the S-wave energy. Additionally, we apply the rapid expansion method (REM) based on a Chebyshev expansion and a pseudo-spectral method (PSM) to calculate spatial derivatives in the wave equation. When REM is incorporated with the PSM for the spatial derivatives, wavefields with high numerical accuracy can be obtained without grid dispersion when performing numerical wave modeling. Another problem in the implementation of TTI RTM is that wavefields in an area with high gradients of dip or azimuth angles can be blown up in the progression of the forward and backward algorithms of the RTM. We stabilize the wavefields by applying a spatial-frequency domain high-cut filter when calculating the spatial derivatives using the PSM. In addition, to increase performance speed, the graphic processing unit (GPU) architecture is used instead of traditional CPU architecture. To confirm the degree of acceleration compared to the CPU version on our RTM, we then analyze the performance measurements according to the number of GPUs employed.

Kim, Youngseo; Cho, Yongchae; Jang, Ugeun; Shin, Changsoo

2013-03-01

18

Cascadia tremor located near plate interface constrained by S minus P wave times.  

PubMed

Nonvolcanic tremor is difficult to locate because it does not produce impulsive phases identifiable across a seismic network. An alternative approach to identifying specific phases is to measure the lag between the S and P waves. We cross-correlate vertical and horizontal seismograms to reveal signals common to both, but with the horizontal delayed with respect to the vertical. This lagged correlation represents the time interval between vertical compressional waves and horizontal shear waves. Measurements of this interval, combined with location techniques, resolve the depth of tremor sources within +/-2 kilometers. For recent Cascadia tremor, the sources locate near or on the subducting slab interface. Strong correlations and steady S-P time differences imply that tremor consists of radiation from repeating sources. PMID:19179527

La Rocca, Mario; Creager, Kenneth C; Galluzzo, Danilo; Malone, Steve; Vidale, John E; Sweet, Justin R; Wech, Aaron G

2009-01-30

19

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.

20

Relativistic free-motion time-of-arrival  

E-print Network

Relativistic free-motion time-of-arrival theory for massive spin-1/2 particles is systematically developed. Contrary to the nonrelativistic time-of-arrival operator studied thoroughly in previous literatures, the relativistic time-of-arrival operator possesses self-adjoint extensions because of the particle-antiparticle symmetry. The nonrelativistic limit of our theory is in agreement with the nonrelativistic time-of-arrival theory. By comparing the time-of-arrival operator with the Hamiltonian operator of a free Dirac particle, one can show a duality between position space and momentum space.

Zhi-Yong Wang; Cai-Dong Xiong

2007-01-17

21

Pre-Stack Depth Migration and Attribute Analysis of 3-D Time-Lapse P-wave Data  

E-print Network

Pre-Stack Depth Migration and Attribute Analysis of 3-D Time-Lapse P-wave Data Vacuum Field, New the application of Pre-Stack Depth Migration (PSDM) and innovative window-based attribute analysis applied to 4-D-stack time migration (PostSTM). Better amplitude handling, higher frequency content, increase in vertical

22

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

23

A 1D P wave velocity model under the pacific region using multiply reflected P waves  

NASA Astrophysics Data System (ADS)

In order to constrain the shallow structure of the Earth in global tomography, Love and Rayleigh waves are often used. However these waves are mostly sensitive to the S wave velocity structure. P-wave energy is either evanescent, or leaking away at every surface reflection that generates an S wave which travels much deeper into the mantle. For that reason, to study the shallow P velocity structure of the Earth, we need to study P-waves at regional distances if a good seismic station coverage is available. Otherwise we can use multiply reflected P waves at teleseismic distance when regional data are not available (as in the oceans for instance). We used 203 events of magnitude Mw > 6.0 recorded from the dense network of US ARRAY, which allows us to make a very large number of group arrival and slowness measurements of multiply reflected P waves . Our study shows that two times reflected PPP and three times reflected PPPP waves are very well observed despite the ray- theoretical prediction that at certain distances almost all of their compressional energy is converted to shear waves. We also observed Four times reflected 5P and five times reflected 6P which show a strong interference for epicentral distances larger than 80 degree. These observations of multiply reflected P waves allow us to inferred a 1D P wave model for the shallow structure under the pacific region.

Foundotos, M.; Nolet, G.

2012-12-01

24

An Exploratory Study of Runway Arrival Procedures: Time Based Arrival and Self-Spacing  

NASA Technical Reports Server (NTRS)

The ability of a flight crew to deliver their aircraft to its arrival runway on time is important to the overall efficiency of the National Airspace System (NAS). Over the past several years, the NAS has been stressed almost to its limits resulting in problems such as airport congestion, flight delay, and flight cancellation to reach levels that have never been seen before in the NAS. It is predicted that this situation will worsen by the year 2025, due to an anticipated increase in air traffic operations to one-and-a-half to three times its current level. Improved arrival efficiency, in terms of both capacity and environmental impact, is an important part of improving NAS operations. One way to improve the arrival performance of an aircraft is to enable the flight crew to precisely deliver their aircraft to a specified point at either a specified time or specified interval relative to another aircraft. This gives the flight crew more control to make the necessary adjustments to their aircraft s performance with less tactical control from the controller; it may also decrease the controller s workload. Two approaches to precise time navigation have been proposed: Time-Based Arrivals (e.g., required times of arrival) and Self-Spacing. Time-Based Arrivals make use of an aircraft s Flight Management System (FMS) to deliver the aircraft to the runway threshold at a given time. Self-Spacing enables the flight crew to achieve an ATC assigned spacing goals at the runway threshold relative to another aircraft. The Joint Planning and Development Office (JPDO), a multi-agency initiative established to plan and coordinate the development of the Next Generation Air Transportation System (NextGen), has asked for data for both of these concepts to facilitate future research and development. This paper provides a first look at the delivery performance of these two concepts under various initial and environmental conditions in an air traffic simulation environment.

Houston, Vincent E.; Barmore, Bryan

2009-01-01

25

Path Integral Analysis of Arrival Times with a Complex Potential  

E-print Network

A number of approaches to the arrival time problem employ a complex potential of a simple step function type and the arrival time distribution may then be calculated using the stationary scattering wave functions. Here, it is shown that in the Zeno limit (in which the potential becomes very large), the arrival time distribution may be obtained in a clear and simple way using a path integral representation of the propagator together with the path decomposition expansion (in which the propagator is factored across a surface of constant time). This method also shows that the same result is obtained for a wide class of complex potentials.

J. J. Halliwell

2008-01-28

26

Wave separation: application for arrival time detection in ultrasonic signals.  

PubMed

A method to detect and accurately measure the arrival time of wave packets in ultrasonic signals using a nonlinear decomposition technique is presented. We specifically address the problem of extracting events that are not well separated in the time, space and frequency domains. Analysis of complex ultrasonic signals, even those composed of poorly separated echoes, provided exceptional estimates of the desired time of arrival, from the media under investigation. PMID:25194641

Avanesians, Patrick; Momayez, Moe

2015-01-01

27

Constraining dark matter late-time energy injection: decays and p-wave annihilations  

NASA Astrophysics Data System (ADS)

We use the latest cosmic microwave background (CMB) observations to provide updated constraints on the dark matter lifetime as well as on p-wave suppressed annihilation cross sections in the 1 MeV to 1 TeV mass range. In contrast to scenarios with an s-wave dominated annihilation cross section, which mainly affect the CMB close to the last scattering surface, signatures associated with these scenarios essentially appear at low redshifts (zlesssim50) when structure began to form, and thus manifest at lower multipoles in the CMB power spectrum. We use data from Planck, WMAP9, SPT and ACT, as well as Lyman-? measurements of the matter temperature at z ~ 4 to set a 95% confidence level lower bound on the dark matter lifetime of ~ 4 × 1025 s for m? = 100 MeV. This bound becomes lower by an order of magnitude at m? = 1 TeV due to inefficient energy deposition into the intergalactic medium. We also show that structure formation can enhance the effect of p-wave suppressed annihilation cross sections by many orders of magnitude with respect to the background cosmological rate, although even with this enhancement, CMB constraints are not yet strong enough to reach the thermal relic value of the cross section.

Diamanti, Roberta; Lopez-Honorez, Laura; Mena, Olga; Palomares-Ruiz, Sergio; Vincent, Aaron C.

2014-02-01

28

Time of Arrival Estimation for UWB Localizers in Realistic Environments  

E-print Network

This paper investigates time of arrival (ToA) estimation methods for ultra-wide bandwidth (UWB) propagation signals. Different algorithms are implemented in order to detect the direct path in a dense multipath environment. ...

Falsi, Chiara

29

Time-of-arrival formalism for the relativistic particle  

E-print Network

A suitable operator for the time-of-arrival at a detector is defined for the free relativistic particle in 3+1 dimensions. For each detector position, there exists a subspace of detected states in the Hilbert space of solutions to the Klein Gordon equation. Orthogonality and completeness of the eigenfunctions of the time-of-arrival operator apply inside this subspace, opening up a standard probabilistic interpretation.

J. Leon

1996-08-09

30

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

31

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

32

Photon arrival time quantum random number generation  

Microsoft Academic Search

We present an efficient random number generator based on the randomness present in photon emission and detection. The interval between successive photons from a light source with Poissonian statistics is separated into individual time bins, which are then used to create several random bits per detection event. Using a single-photon counter and FPGA-based data processing allows for a cost-efficient and

MICHAEL ALAN WAYNE; Evan R. Jeffrey; Gleb M. Akselrod; Paul G. Kwiat

2009-01-01

33

Inter-arrival times of message propagation on directed networks  

E-print Network

One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails (SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the inter-arrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM arriving to a single user. We study the behavior of the message inter-arrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networ...

Mihaljev, Tamara; Herrmann, Hans J

2010-01-01

34

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

E-print Network

depth-dependent velocity, the polarization of P waves and also of Rayleigh waves is parallelUpper mantle anisotropy beneath Australia and Tahiti from P wave polarization: Implications December 2008; published 20 March 2009. [1] We report measurements of long-period P wave polarization (Ppol

Barruol, Guilhem

35

Detection of multiple transient signals with unknown arrival times  

Microsoft Academic Search

The problem of optimal detection of signal transients with unknown arrival times contaminated by additive Gaussian noise is considered. The transients are assumed to be time continuous and belong to a parameterized family with the uncertainty about the parameters described by means of an a priori distribution. Under the assumption of a negligible probability that the independent transient observations overlap

Daniel E. Asraf; Mats G. Gustafsson

2005-01-01

36

HF (High Frequency) absolute time of arrival sensing  

NASA Astrophysics Data System (ADS)

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric height estimation and its temporal stability. Traditional ionospheric research resources did not address the issue in sufficient detail and time resolution to be of any assistance. In order to understand the exact nature of the ionospheric uncertainties and to quantify their extent, experimentation was proposed to sense the variation in the refraction height of the ionosphere as it relates to the time of arrival of the HF signal. The objective of this work was to determine the range of environmentally induced errors in a skywave Time Difference of Arrival (TDOA) measurement, thereby bounding the ultimate geolocation accuracy one could expect from this technique. The first experimental measurement system started operation in early 1981. This effort involved establishing a continuous absolute Time of Arrival (TOA) experiment over the one-hop midlatitude path between San Diego, California and Fort Collins, Colorado. The system is fully digital and stabilized with a cesium beam standard. This work was supplemented with vertical incidence sounder data at both ends of the path, a collateral Doppler sensing system, and coincident satellite solar data.

Rose, R. B.

1986-02-01

37

HF (High Frequency) absolute time of arrival sensing  

Microsoft Academic Search

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric height estimation and

R. B. Rose

1986-01-01

38

A Comparison of CTAS and Airline Time of Arrival Predictions  

NASA Technical Reports Server (NTRS)

A statistically-based comparison of aircraft times of arrival between Center/TRACON Automation System (CTAS) air traffic control scheduling and airline predictions is presented. CTAS is found to provide much improved values, forming the foundation for airline operational improvements, as observed during an airline field trial of a CTAS display.

Heere, Karen R.; Zelenka, Richard E.; Hsu, Rose Y.

1999-01-01

39

Ambiguities of arrival-time distributions in quantum theory  

E-print Network

We consider the definition that might be given to the time at which a particle arrives at a given place, both in standard quantum theory and also in Bohmian mechanics. We discuss an ambiguity that arises in the standard theory in three, but not in one, spatial dimension.

J. Finkelstein

1998-09-28

40

Probability distribution of arrival times in quantum mechanics  

Microsoft Academic Search

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

V. Delgado

1998-01-01

41

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

42

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

43

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 ...

44

Velocity Structure of the Tibetan Lithosphere: Constraints from P-Wave Travel Times of Regional Earthquakes  

E-print Network

tracing to model the travel times, and the results indicate that the Moho beneath the Lhasa terrane of southern Tibet is over 73 km deep, with a Pn speed of about 8:2 km=s. The Qiangtang terrane north into the Qiangtang terrane in cen- tral Tibet (Fig. 1). Between 2002 and 2005, the Hi-CLIMB array was deployed

Nowack, Robert L.

45

Space-time properties of free motion time-of-arrival eigenstates  

E-print Network

The properties of the time-of-arrival operator for free motion introduced by Aharonov and Bohm and of its self-adjoint variants are studied. The domains of applicability of the different approaches are clarified. It is shown that the arrival time of the eigenstates is not sharply defined. However, strongly peaked real-space (normalized) wave packets constructed with narrow Gaussian envelopes centred on one of the eigenstates provide an arbitrarily sharp arrival time.

J. G. Muga; C. R. Leavens; J. P. Palao

1998-07-23

46

Current status of CME/shock arrival time prediction  

NASA Astrophysics Data System (ADS)

of the major solar transients, coronal mass ejections (CMEs) and their related interplanetary shocks have severe space weather effects and become the focus of study for both solar and space scientists. Predicting their evolutions in the heliosphere and arrival times at Earth is an important component of the space weather predictions. Various kinds of models in this aspect have been developed during the past decades. In this paper, we will present a view of the present status (during Solar Cycle 24 in 2014) of the space weather's objective to predict the arrival of coronal mass ejections and their interplanetary shock waves at Earth. This status, by implication, is relevant to their arrival elsewhere in the solar system. Application of this prediction status is clearly appropriate for operational magnetospheric and ionospheric situations including A - > B - > C…solar system missions. We review current empirical models, expansion speed model, drag-based models, physics-based models (and their real-time prediction's statistical experience in Solar Cycle 23), and MHD models. New observations in Solar Cycle 24, including techniques/models, are introduced as they could be incorporated to form new prediction models. The limitations of the present models and the direction of further development are also suggested.

Zhao, Xinhua; Dryer, Murray

2014-07-01

47

UCSF Shuttle GPS coming May 1, 2013 View real-time shuttle arrival times on your  

E-print Network

real-time arrival predictions via phone, cell phone, or SMT (Text) messaging. · Obtain NextBus alerts UCSF Shuttle GPS coming May 1, 2013 View real-time shuttle arrival times on your phone students, faculty, staff, patients and affiliates will be able use the latest GPS technology to view, track

Yamamoto, Keith

48

Early magnitude estimation for the MW7.9 Wenchuan earthquake using progressively expanded P-wave time window  

NASA Astrophysics Data System (ADS)

More and more earthquake early warning systems (EEWS) are developed or currently being tested in many active seismic regions of the world. A well-known problem with real-time procedures is the parameter saturation, which may lead to magnitude underestimation for large earthquakes. In this paper, the method used to the MW9.0 Tohoku-Oki earthquake is explored with strong-motion records of the MW7.9, 2008 Wenchuan earthquake. We measure two early warning parameters by progressively expanding the P-wave time window (PTW) and distance range, to provide early magnitude estimates and a rapid prediction of the potential damage area. This information would have been available 40 s after the earthquake origin time and could have been refined in the successive 20 s using data from more distant stations. We show the suitability of the existing regression relationships between early warning parameters and magnitude, provided that an appropriate PTW is used for parameter estimation. The reason for the magnitude underestimation is in part a combined effect of high-pass filtering and frequency dependence of the main radiating source during the rupture process. Finally we suggest only using Pd alone for magnitude estimation because of its slight magnitude saturation compared to the ?c magnitude.

Peng, Chaoyong; Yang, Jiansi; Zheng, Yu; Xu, Zhiqiang; Jiang, Xudong

2014-10-01

49

Early magnitude estimation for the MW7.9 Wenchuan earthquake using progressively expanded P-wave time window.  

PubMed

More and more earthquake early warning systems (EEWS) are developed or currently being tested in many active seismic regions of the world. A well-known problem with real-time procedures is the parameter saturation, which may lead to magnitude underestimation for large earthquakes. In this paper, the method used to the MW9.0 Tohoku-Oki earthquake is explored with strong-motion records of the MW7.9, 2008 Wenchuan earthquake. We measure two early warning parameters by progressively expanding the P-wave time window (PTW) and distance range, to provide early magnitude estimates and a rapid prediction of the potential damage area. This information would have been available 40?s after the earthquake origin time and could have been refined in the successive 20?s using data from more distant stations. We show the suitability of the existing regression relationships between early warning parameters and magnitude, provided that an appropriate PTW is used for parameter estimation. The reason for the magnitude underestimation is in part a combined effect of high-pass filtering and frequency dependence of the main radiating source during the rupture process. Finally we suggest only using Pd alone for magnitude estimation because of its slight magnitude saturation compared to the ?c magnitude. PMID:25346344

Peng, Chaoyong; Yang, Jiansi; Zheng, Yu; Xu, Zhiqiang; Jiang, Xudong

2014-01-01

50

Early magnitude estimation for the MW7.9 Wenchuan earthquake using progressively expanded P-wave time window  

PubMed Central

More and more earthquake early warning systems (EEWS) are developed or currently being tested in many active seismic regions of the world. A well-known problem with real-time procedures is the parameter saturation, which may lead to magnitude underestimation for large earthquakes. In this paper, the method used to the MW9.0 Tohoku-Oki earthquake is explored with strong-motion records of the MW7.9, 2008 Wenchuan earthquake. We measure two early warning parameters by progressively expanding the P-wave time window (PTW) and distance range, to provide early magnitude estimates and a rapid prediction of the potential damage area. This information would have been available 40?s after the earthquake origin time and could have been refined in the successive 20?s using data from more distant stations. We show the suitability of the existing regression relationships between early warning parameters and magnitude, provided that an appropriate PTW is used for parameter estimation. The reason for the magnitude underestimation is in part a combined effect of high-pass filtering and frequency dependence of the main radiating source during the rupture process. Finally we suggest only using Pd alone for magnitude estimation because of its slight magnitude saturation compared to the ?c magnitude. PMID:25346344

Peng, Chaoyong; Yang, Jiansi; Zheng, Yu; Xu, Zhiqiang; Jiang, Xudong

2014-01-01

51

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

52

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

53

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

54

Global-scale P wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 1. Data set development  

NASA Astrophysics Data System (ADS)

We extend the Bayesloc seismic multiple-event location algorithm for application to global arrival time data sets. Bayesloc is a formulation of the joint probability distribution spanning multiple-event location parameters, including hypocenters, travel time corrections, pick precision, and phase labels. Stochastic priors may be used to constrain any of the Bayesloc parameters. Markov Chain Monte Carlo sampling is used to draw samples from the joint probability distribution, and the posteriori samples are summarized to infer conventional location parameters such as the hypocenter. The first application of the broad area Bayesloc algorithm is to a data set consisting of all well-recorded events in the Middle East and the most well-recorded events with 5° spatial sampling globally. This sampling strategy is designed to provide the ray coverage needed to determine lithospheric-scale P wave velocity structure in the Middle East using the complementary ray geometry provided by regional (subhorizontal) and teleseismic (subvertical) raypaths and to determine a consistent, albeit lower-resolution, image of global mantle structure. The data set consists of 5401 events and 878,535 P, Pn, pP, sP, and PcP arrivals recorded at 4606 stations. Relocated epicenters are an average of 16 km from bulletin locations. The data set included events that are known to an accuracy of 1 km (a.k.a. GT1) based on nonseismic information. The average distance between GT1 epicenters and our relocated epicenters is 5.6 km. For arrivals labeled P, Pn, and PcP, ˜92%, ˜90%, and 96% are properly labeled with probability >0.9, respectively. Incorrect phase labels are found to be erroneous at rates of 0.6%, 0.2%, 1.6%, and 2.5% for P, Pn, PcP, and depth phases (pP and sP), respectively. Labels found to be incorrect, but not erroneous, were reassigned to another phase label. P and Pn residual standard deviation with respect to ak135 travel times are dramatically reduced from 3.45 s to 1.01 s. The differences between travel time residuals for nearly reciprocal raypaths are significantly reduced from the input event locations, suggesting that Bayesloc relocation improves data set consistency. The reciprocity tests suggest that the dominant contribution to travel time residuals calculated from information provided in global bulletins is location and picks errors, not travel time prediction errors due to 3-D structure. Modeling the whole multiple-event system results in accurate locations and an internally consistent data set that is ideal for tomography and other travel time calibration studies. Simmons et al. (2011) (companion paper) use the Bayesloc-processed data set to develop a 3-D tomographic image, which further reduces residual standard deviation to 0.50 s.

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

2011-04-01

55

Theoretical P-Wave Travel Times, Magnitude 6.7 Island of Hawaii, Hawaii, Sunday, October 15, 2006 at 17:07:49 UTC  

NSDL National Science Digital Library

This page from the USGS displays the predicted travel times of the P-Waves originating from the 6.7 magnitude earthquake that struck near Puako, HI on October 15th, 2006. There is a table of data as well as the map visualization.

Program, Earthquake H.; Usgs

56

Time of Arrival Retrievals on an Oblate Spheroidal Earth  

NASA Technical Reports Server (NTRS)

The current National Lightning Detection Network (NLDN) retrieval algorithm is based on a chi sq minimization. This numerical approach finds the lightning ground strike location on an ellipsoidal Earth that optimally agrees with multiple station time of arrival (TOA) measurements and, if available, magnetic bearing data. In addition, an analytic solution for determining lightning ground strike locations on a spherical Earth using only TOA data has been recently introduced. In the current work, a quasi-analytic approach is suggested for determining lightning ground strike locations on an oblate spheroidal Earth by perturbing the spherical model results proposed by Koshak. Latitude, longitude, time, and the associated perturbed quantities are related through terms in a Taylor series. The correction terms may be considered collectively as a vector which may be calculated by an overconstrained inversion. Expressions for the derivatives contained in the Taylor series are given in terms of elliptic integrals.

Solakiewicz, Richard J.; Koshak, William J.

1999-01-01

57

Rounding of Arrival and Departure Times in Travel Surveys: An Interpretation in Terms of Scheduled Activities  

Microsoft Academic Search

In travel surveys most respondents apply rounding of departure and arrival times to multiples of 5, 15 and 30 minutes: in the annual Dutch travel survey about 85-95 percent of all reported times are 'round' ones. We estimate rounding models for departure and arrival times. The model allows one to compute the probability that a reported arrival time m (say

Piet Rietveld

2001-01-01

58

Arrival timing and hematological parameters in Gray Catbirds ( Dumetella carolinensis )  

Microsoft Academic Search

Early arrival at the breeding grounds for migratory birds is associated with greater reproductive success. According to the\\u000a condition-dependent arrival hypothesis, only those individuals in superior physiological condition are able to bear the costs\\u000a (e.g., poor environmental conditions, limited food availability) of early arrival. Condition has usually been measured in\\u000a terms of energy reserves or mass but other physiological measures

Margret I. HatchRobert; Robert J. Smith; Jennifer C. Owen

2010-01-01

59

Measuring pulse times of arrival from broadband pulsar observations  

E-print Network

In recent years, instrumentation enabling pulsar observations with unprecedentedly high fractional bandwidth has been under development which can be used to substantially improve the precision of pulsar timing experiments. The traditional template-matching method used to calculate pulse times-of-arrival (ToAs), may not function effectively on these broadband data due to a variety of effects such as diffractive scintillation in the interstellar medium, profile variation as a function of frequency, dispersion measure (DM) evolution and so forth. In this paper, we describe the channelised Discrete Fourier Transform method that can greatly mitigate the influence of the aforementioned effects when measuring ToAs from broadband timing data. The method is tested on simulated data, and its potential in improving timing precision is shown. We further apply the method to PSR J1909$-$3744 data collected at the Nan\\c{c}ay Radio Telescope with the Nan\\c{c}ay Ultimate Pulsar Processing Instrument. We demonstrate a removal ...

Liu, K; Cognard, I; Stappers, B W; Verbiest, J P W; Lee, K J; Champion, D J; Kramer, M; Freire, P C C; Karuppusamy, R

2014-01-01

60

P wave travel times: Stability and change within the source volume of a M = 7.2 earthquake  

NASA Astrophysics Data System (ADS)

The dense seismograph network on the south flank of Kilauea afforded a unique opportunity to study travel time changes as a function of space and time within the source volume of the Hawaii earthquake (Ms = 7.2) of 1975. Careful analysis of more than 600 teleseismic P arrivals from deep Fiji-Tonga earthquakes revealed the following: out of eight stations studied, six showed constant travel times to within ±0.03 s for up to 10 years with the exception of some small changes of about 0.03 s at the time of the main shock. One station, AHU, showed a highly significant and unique travel time decrease by 0.13 s during 1971/1972. At the beginning of this velocity anomaly a southwest rift intrusion caused closure of surface cracks associated with normal faults located near the station AHU. Also, geodetic measurements revealed that between August and October 1971 compressive strain of 4×10-5 was accumulated perpendicular to the southwest rift in the area of AHU. We conclude that these data show for the first time that in situ velocity increases occur due to the closure of cracks by tectonic forces. The AHU residuals returned to normal approximately at the time of a major earthquake swarm on the fault zone near AHU, during which surface cracks were observed to have opened again. This travel time decrease was corroborated by residuals from Novaya Zemlya explosions, but highfrequency local signals did not show it. Assuming that the stress sensitivity of the velocity was similar to that found by Reasenberg and Aki (1974), we have interpreted the teleseismic residual change at AHU as due to a P velocity increase of about 10% in the top 3.5±1.5-km of the crust. The only station, WHA, which showed a large (0.2 s) and extended (1972 to 1975) travel time increase was located only 4-km from the main shock epicenter. We interpret this velocity decrease as a precursor to the 1975 main shock, and we hypothesize that a process reverse from that at AHU caused this anomaly by first opening and then closing cracks in the crust below WHA. Both of these velocity anomalies were extremely localized in crustal volumes of dimensions of about 5±3-km.

Johnston, Arch C.; Wyss, M.; Koyanagi, R.; Habermann, R. E.

1982-08-01

61

Lithosphere-asthenosphere interaction beneath Ireland from joint inversion of teleseismic P-wave delay times and GRACE gravity  

NASA Astrophysics Data System (ADS)

The nature and extent of the regional lithosphere-asthenosphere interaction beneath Ireland and Britain remains unclear. Although it has been established that ancient Caledonian signatures pervade the lithosphere, tertiary structure related to the Iceland plume has been inferred to dominate the asthenosphere. To address this apparent contradiction in the literature, we image the 3-D lithospheric and deeper upper-mantle structure beneath Ireland via non-linear, iterative joint teleseismic-gravity inversion using data from the ISLE (Irish Seismic Lithospheric Experiment), ISUME (Irish Seismic Upper Mantle Experiment) and GRACE (Gravity Recovery and Climate Experiment) experiments. The inversion combines teleseismic relative arrival time residuals with the GRACE long wavelength satellite derived gravity anomaly by assuming a depth-dependent quasilinear velocity-density relationship. We argue that anomalies imaged at lithospheric depths probably reflect compositional contrasts, either due to terrane accretion associated with Iapetus Ocean closure, frozen decompressional melt that was generated by plate stretching during the opening of the north Atlantic Ocean, frozen Iceland plume related magmatic intrusions, or a combination thereof. The continuation of the anomalous structure across the lithosphere-asthenosphere boundary is interpreted as possibly reflecting sub-lithospheric small-scale convection initiated by the lithospheric compositional contrasts. Our hypothesis thus reconciles the disparity which exists between lithospheric and asthenospheric structure beneath this region of the north Atlantic rifted margin.

O'Donnell, J. P.; Daly, E.; Tiberi, C.; Bastow, I. D.; O'Reilly, B. M.; Readman, P. W.; Hauser, F.

2011-03-01

62

Optimal convolutive filters for real-time detection and arrival time estimation of transient signals  

Microsoft Academic Search

Linear convolutive filters are fast in calculation and in application, and thus, often used for real-time processing of continuous data streams. In the case of transient signals, a filter has not only to detect the presence of a specific waveform, but to estimate its arrival time as well. In this study, a measure is presented which indicates the performance of

Michal Natora; Felix Franke; Klaus Obermayer

2009-01-01

63

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

64

Community assembly in experimental grasslands: suitable environment or timely arrival?  

PubMed

It is hard to defend the view that biotic communities represent a simple and predictable response to the abiotic environment. Biota and the abiotic environment interact, and the environment of an individual certainly includes its neighbors and visitors in the community. The complexity of community assembly calls forth a quest for general principles, yet current results and theories on assembly rules differ widely. Using a grassland microcosm as a model system, we manipulated fertility, disturbance by defoliation, soil/microclimate, and arrival order of species belonging to two groups differing in functional attributes. We analyzed the outcome of community assembly dynamics in terms of species richness, invasibility, and species composition. The analyses revealed strong environmental control over species richness and invasibility. Species composition was mainly determined by the arrival order of species, indicating that historical contingency may change the outcome of community assembly. The probability for multiple equilibria appeared to increase with productivity and environmental stability. The importance of arrival order offers an explanation of the difficulties in predicting local occurrences of species in the field. In our experiment, variation in fertility and disturbance was controlling colonization with predictable effects on emergent community properties such as species richness. The key mechanism is suggested to be asymmetric competition, and our results show that this mechanism is relatively insensitive to the species through which it works. While our analyses indicate a positive and significant correlation between richness and invasibility, the significance disappears after accounting for the effect of the environment. The importance of arrival order (historical contingency) and environmental control supports the assumption of the unified neutral theory that different species within a trophic level can be considered functionally equivalent when it comes to community assembly. However, our results indicate that variation in asymmetric competition is the key factor determining the richness of the resulting communities, and this is far from neutral. PMID:16761601

Ejrnaes, Rasmus; Bruun, Hans Henrik; Graae, Bente J

2006-05-01

65

Moho depth variations in the Taiwan orogen from joint inversion of seismic arrival time and Bouguer gravity data  

NASA Astrophysics Data System (ADS)

The joint inversion of different geophysical datasets is an effective means to reduce the non-uniqueness and improve the reliability of geophysical inversion. In this study, seismic arrival time and Bouguer gravity datasets are jointly inverted to obtain an image of 3-D velocity structures in the Taiwan orogen. The model obtained from joint inversion fits the arrival time observations at least as well as when inverted individually, and the gravity observations are much better fit when included in the inversion, implying a reduction in ambiguity by simultaneously modeling the disparate datasets. Moho depth variations estimated by the 3-D P wave velocity model suggest a maximum Moho depth of 56 km located beneath the Backbone Central Range, and the trend of the Moho is largely consistent with the topography of the Central Range with eastward, asymmetric crustal thickening. The root beneath the Central Range appears to be smaller in lateral extent than previously imaged, and the velocity gradients into the uppermost mantle are significantly higher. The lack of evidence for a significant amount of Eurasian crust in the mantle supports geodynamical models of accreted, rather than consumed, continental crust in a collisional environment.

Li, Zhiwei; Roecker, Steven; Kim, Kwanghee; Xu, Ya; Hao, Tianyao

2014-09-01

66

Arrival timing in subadult and adult Black Redstart males: competition-dependent behaviour?  

Microsoft Academic Search

The different arrival times of 1-year-old and older males is a widely recognised phenomenon in most migrating passerines. The converse pattern, i.e. the yearlings arriving at the breeding grounds at the same time as adults, has been reported only exceptionally. Two hypotheses have been formulated to explain the delayed arrival of yearling males: investment reduction, and energetic constraint hypotheses, respectively.

L. Schwarzová; P. Štros; D. Frynta; R. Fuchs

2010-01-01

67

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

68

Emitter Position and Velocity Estimation Given Time and Frequency Differences of Arrival  

E-print Network

Emitter Position and Velocity Estimation Given Time and Frequency Differences of Arrival Alon Amar of an emitter given time and frequency differences of arrival acquired by a passive sensor array. By jointly Emitter localization using a passive sensor array continues to attract attention and interest due to its

Langendoen, Koen

69

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

70

Timing of arrival from spring migration is associated with flight performance in the migratory barn swallow.  

PubMed

Timing of arrival at the breeding grounds by migratory birds affects their mating success and access to superior resources, thus being a major factor associated with fitness. Much empirical work has been devoted to investigate the condition dependence of arrival sequence of migrants and characteristics of individuals that influence arrival time from migration. Surprisingly, there are no studies examining the relationship between flight performance of individual birds and their arrival time. I investigated the relative importance of direct effects of short-term flight performance, age, body condition and the degree of sexual ornamentation (tail length) on timing of spring arrival in the barn swallow (Hirundo rustica), a long-distance trans-equatorial passerine migrant. I evaluated short-term flight performance (a composite variable comprising flight manoeuvrability, velocity and acceleration) in a standardised manner using flight tunnels. Short-term flight performance was a significant and important predictor of spring arrival date. Furthermore, locomotion predicted arrival date of individual birds independently of morphological variables-the degree of sexual ornamentation (the length of the tail) and wing aspect ratio and body condition. I discuss the possible role short-term flight performance may have in determining migratory performance. This is the first time flight performance has been shown to be associated with timing of arrival from migration in a migratory bird. PMID:23293424

Matyjasiak, Piotr

2013-01-01

71

Incorporating fault zone head wave and direct wave secondary arrival times into seismic tomography: Application at Parkfield, California  

NASA Astrophysics Data System (ADS)

Large crustal faults such as the San Andreas fault (SAF) often juxtapose rocks of significantly different elastic properties, resulting in well-defined bimaterial interfaces. A sharp material contrast across the fault interface is expected to generate fault zone head waves (FZHW's) that spend a large portion of their propagation paths refracting along the bimaterial interface (Ben-Zion 1989, 1990; Ben-Zion & Aki 1990). Because of this FZHW's provide a high-resolution tool for imaging the velocity contrast across the fault. Recently, Zhao et al. (2010) systematically analyzed large data sets of near-fault waveforms recorded by several permanent and temporary seismic networks along the Parkfield section of the SAF. The local-scale tomography study of Zhang et al. (2009) for a roughly 10 km3 volume centered on SAFOD and the more regional-scale study of Thurber et al. (2006) for a 130 km x 120 km x 20 km volume centered on the 2004 Parkfield earthquake rupture provide what are probably the best 3D images of the seismic velocity structure of the area. The former shows a low velocity zone associated with the SAF extending to significant depth, and both image the well-known velocity contrast across the fault. Seismic tomography generally uses just first P and/or S arrivals because of the relative simplicity of phase picking and ray tracing. Adding secondary arrivals such as FZHW's, however, can enhance the resolution of structure and strengthen constraints on earthquake locations and focal mechanisms. We present a model of 3D velocity structure for the Parkfield region that utilizes a combination of arrival times for FZHW's and the associated direct-wave secondary arrivals as well as existing P-wave arrival time data. The resulting image provides a higher-resolution model of the SAF at depth than previously published models. In addition, we plan to measure polarizations of the direct P and S waves and FZHW's and incorporate the data into our updated velocity tomography/relocation inversion. Through these efforts, we hope to refine the 3D tomographic image of seismic velocity structure and the complex geometry of the active fault strands near SAFOD and along the Parkfield rupture zone.

Bennington, N. L.; Thurber, C. H.; Zhang, H.; Peng, Z.; Zhao, P.

2011-12-01

72

Automated determination of P-phase arrival times at regional and local distances using higher order statistics  

NASA Astrophysics Data System (ADS)

We present an algorithm for automatic P-phase arrival time determination for local and regional seismic events based on higher order statistics (HOS). Using skewness or kurtosis a characteristic function is determined to which a new iterative picking algorithm is applied. For P-phase identification we apply the Akaike Information Criterion to the characteristic function, while for a precise determination of the P-phase arrival time a pragmatic picking algorithm is applied to a recalculated characteristic function. In addition, an automatic quality estimate is obtained, based on the slope and the signal-to-noise ratio, both calculated from the characteristic function. To get rid of erroneous picks, a Jackknife procedure and an envelope function analysis is used. The algorithm is applied to a large data set with very heterogeneous qualities of P-onsets acquired by a temporary, regional seismic network of the EGELADOS-project in the southern Aegean. The reliability and robustness of the proposed algorithm is tested by comparing more than 3000 manually derived P readings, serving as reference picks, with the corresponding automatically estimated P-wave arrival times. We find an average deviation from the reference picks of 0.26 +/- 0.64s when using kurtosis and 0.38 +/- 0.75s when using skewness. If automatically as excellent classified picks are considered only, the average difference from the reference picks is 0.07 +/- 0.31s and 0.07 +/- 0.41s, respectively. However, substantially more P-arrival times are determined when using kurtosis, indicating that the characteristic function derived from kurtosis estimation is to be preferred. Since the characteristic function is calculated recursively, the algorithm is very fast and hence suited for earthquake early warning purposes. Furthermore, a comparative study with automatically derived P-readings using Allen's and Baer & Kradolfer's picking algorithms applied to the same data set demonstrates better quantitative and qualitative performance of the HOS approach. This study shows, that precise automatic P-onset determination is feasible, even when using data sets with very heterogeneous signal-to-noise ratio.

Küperkoch, L.; Meier, T.; Lee, J.; Friederich, W.; Working Group, EGELADOS

2010-05-01

73

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

74

Closed-form solution for determining emitter location using time difference of arrival measurements  

Microsoft Academic Search

A direct and short derivation of an algorithm based on the closed-form solution of the nonlinear equations for emitter location using time difference of arrival (TDOA) measurements from N + 1 receivers, N ? 3, is given.

M. Pachter; J. Raquet

2003-01-01

75

Arrival Time Dependent Shortest Path by On-Road Routing in Mobile Ad-Hoc Network  

Microsoft Academic Search

\\u000a Arrival time dependent shortest path finding is an important function in the field of traffic information systems or telematics.\\u000a However large number of mobile objects on the road network results in a scalability problem for frequently updating and handling\\u000a their real-time location. In this paper, we propose a query processing method in MANET(Mobile Ad-hoc Network) environment\\u000a to find an arrival

Kyoung-sook Kim; So-young Hwang; Ki-joune Li

2004-01-01

76

Weather-mediated natural selection on arrival time in cliff swallows ( Petrochelidon pyrrhonota )  

Microsoft Academic Search

An unusually long period of cold weather in May 1996 caused extensive mortality among insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern and central Great Plains. We analyzed how viability selection affected spring arrival time in a migratory\\u000a Nebraska population by comparing capture histories of survivors with those of birds known to have died and by documenting\\u000a how arrival time

Charles R. Brown; Mary Bomberger Brown

2000-01-01

77

Effects of time-varied arrival rates: an investigation in emergency ambulance service systems  

Microsoft Academic Search

This paper addresses the problem of modeling timevaried arrival rates in Emergeney Ambulance Service (EAS) systems. The approach is to break down a 24hour period into several equal-length time durations such that the arrival rate during each time duration can be reasonably viewed as stationary. A d~crete event simulation model was developed to describe the operations of the EAS center

Zhiwei Zhu; Mark A. McKnew; Jim Lee

1992-01-01

78

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

79

Characterizing the nonlinear interaction of S- and P-waves in a rock sample  

E-print Network

The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility the nonlinear characterization of rocks as an imaging tool in a field scenario. The nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a high-amplitude 50 kHz S-wave pump has been studied on a room-dry 15 x 15x 3 cm slab of Berea sandstone. Changes in the arrival time of the P-wave probe as it passes through the perturbation created by the traveling S-wave pump were recorded. Waveforms were time gated to simulate a semi-infinite medium. The shear wave phase relative to the P-wave probe signal was varied with resultant changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. In order to estimate the ...

Gallot, Thomas; Szabo, Thomas L; Brown, Stephen; Burns, Daniel; Fehler, Michael

2014-01-01

80

A Bayesian approach to stochastic capture zone delineation incorporating tracer arrival times, conductivity measurements, and hydraulic head observations  

Microsoft Academic Search

This paper presents a methodology to invert tracer arrival times and to incorporate travel time data in the delineation of well capture zones. Within a Bayesian framework the observed arrival times are used to obtain probability-based weights for each realization of the hydraulic conductivity field. Realizations that closely reproduce the observed arrival times are more likely to represent the “true”

L. Feyen; J. J. Gómez-Hernández; P. J. Ribeiro; K. J. Beven; F. De Smedt

2003-01-01

81

A Bayesian approach to stochastic capture zone delineation incorporating tracer arrival times, conductivity measurements, and hydraulic head observations  

Microsoft Academic Search

This paper presents a methodology to invert tracer arrival times and to incorporate travel time data in the delineation of well capture zones. Within a Bayesian framework the observed arrival times are used to obtain probability-based weights for each realization of the hydraulic conductivity field. Realizations that closely reproduce the observed arrival times are more likely to represent the ``true''

L. Feyen; J. J. Gómez-Hernández; P. J. Ribeiro; K. J. Beven; F. De Smedt

2003-01-01

82

NONNEGATIVE DECONVOLUTION FOR TIME OF ARRIVAL ESTIMATION Yuanqing Lin1  

E-print Network

of microphones, although generalization to a larger acous- tic sensing array with more sources is certainly the location of a sound source. Time-delay estimation has been used for video con- ferences to track the active speaker, and in surveillance ap- plications to locate people and vehicles [1]. With the emer- gence of low

Saul, Lawrence K.

83

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

Microsoft Academic Search

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. Villaseñor; H. M. Benz; L. Filippi; G. De Luca; R. Scarpa; G. Patanè; S. Vinciguerra

1998-01-01

84

Mobile TV’s Time to Shine Has Arrived  

Microsoft Academic Search

\\u000a MoFilm, the first mobile film festival, achieved some legitimacy when multiple Academy Award-winning actor Kevin Spacey hosted\\u000a the show in 2009. Spacey commented: “[I]n some countries, this might be the first time they [people] ever see a movie. … They\\u000a won’t see it on that big screen; they’ll see it on a small one.”1 According to a 2007 Gartner report,

Fred Kitson

2010-01-01

85

Different motion cues are used to estimate time-to-arrival for frontoparallel and looming trajectories.  

PubMed

Estimation of time-to-arrival for moving objects is critical to obstacle interception and avoidance, as well as to timing actions such as reaching and grasping moving objects. The source of motion information that conveys arrival time varies with the trajectory of the object raising the question of whether multiple context-dependent mechanisms are involved in this computation. To address this question we conducted a series of psychophysical studies to measure observers' performance on time-to-arrival estimation when object trajectory was specified by angular motion ("gap closure" trajectories in the frontoparallel plane), looming (colliding trajectories, TTC) or both (passage courses, TTP). We measured performance of time-to-arrival judgments in the presence of irrelevant motion, in which a perpendicular motion vector was added to the object trajectory. Data were compared to models of expected performance based on the use of different components of optical information. Our results demonstrate that for gap closure, performance depended only on the angular motion, whereas for TTC and TTP, both angular and looming motion affected performance. This dissociation of inputs suggests that gap closures are mediated by a separate mechanism than that used for the detection of time-to-collision and time-to-passage. We show that existing models of TTC and TTP estimation make systematic errors in predicting subject performance, and suggest that a model which weights motion cues by their relative time-to-arrival provides a better account of performance. PMID:22056519

Calabro, Finnegan J; Beardsley, Scott A; Vaina, Lucia M

2011-12-01

86

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

87

Delay Analysis in Temperature-Constrained Hard Real-Time Systems with General Task Arrivals  

E-print Network

Delay Analysis in Temperature-Constrained Hard Real-Time Systems with General Task Arrivals study temperature-constrained hard real- time systems, where real-time guarantees must be met with- out exceeding safe temperature levels within the proces- sor. Dynamic speed scaling is one of the major

Wang, Shengquan

88

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

89

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

90

Arrival Times of Air Shower Particles at Large Distances from the Axis  

Microsoft Academic Search

A study has been made of the relative times of arrival of shower particles at large distances (200 to 1500 m) from the shower axis. Data were obtained at the MIT Volcano Ranch Station, using an array of 20 scintillation detectors, one of which was shielded part of the time. The shower size, direction, and core location were determined for

John Linsley; Livio Scarsi

1962-01-01

91

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

92

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

93

HF (high-frequency) absolute time of arrival sensing. Interim report, September 1981May 1985  

Microsoft Academic Search

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high-frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric-height estimation and its temporal

Rose

1986-01-01

94

Lateral density and arrival time distributions of Cherenkov photons in extensive air showers: a simulation study  

E-print Network

We have investigated some features of the density and arrival time distributions of Cherenkov photons in extensive air showers using the CORSIKA simulation package. The main thrust of this study is to see the effect of hadronic interaction models on the production pattern of Cherenkov photons with respect to distance from the shower core. Such studies are very important in ground based $\\gamma$-ray astronomy for an effective rejection of huge cosmic ray background, where the atmospheric Cherenkov technique is being used extensively within the energy range of some hundred GeV to few TeV. We have found that for all primary particles, the density distribution patterns of Cherenkov photons follow the negative exponential function with different coefficients and slopes depending on the type of primary particle, its energy and the type of interaction model combinations. Whereas the arrival time distribution patterns of Cherenkov photons follow the function of the form $t (r) = t_{0}e^{\\Gamma/r^{\\lambda}}$, with different values of the function parameters. There is no significant effect of hadronic interaction model combinations onthe density and arrival time distributions for the $\\gamma$-ray primaries. However, for the hadronic showers, the effects of the model combinations are significant under different conditions. There are some contributions from shower to shower fluctuations to the density and arrival time deviations of Cherenkov photons apart from the contribution due to inherent differences in hadronic interaction models.

P. Hazarika; U. D. Goswami; V. R. Chitnis; B. S. Acharya; G. S. Das; B. B. Singh; R. Britto

2014-04-08

95

Ready…Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time  

Microsoft Academic Search

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations,

Xu Cui; Chess Stetson; P. Read Montague; David M. Eagleman

2009-01-01

96

Pay on time Your payment must arrive by the due date or  

E-print Network

payments. Student account Can't pay your entire balance due? If you have been officially acceptedPay on time Your payment must arrive by the due date or you will be assessed a $30 late payment fee payments are posted instantly to your student account. Produced by One Stop Student Services, Academic

Minnesota, University of

97

Nie and Fan THE ARRIVING ON TIME PROBLEM: A DISCRETE ALGORITHM THAT ENSURES  

E-print Network

Nie and Fan THE ARRIVING ON TIME PROBLEM: A DISCRETE ALGORITHM THAT ENSURES CONVERGENCE Yu Nie1 Ph Tel: 530 754 6429 Email: ynie@ucdavis.edu Yueyue Fan Assistant Professor Department of Civil Corresponding author. 1 #12;Nie and Fan Abstract Finding optimal paths in stochastic networks is an important

Fan, Yueyue

98

Node Localization in Unsynchronized Time of Arrival Sensor Networks Simon Burgess, Yubin Kuang and Kalle Astrom  

E-print Network

. The problem arises naturally in microphone arrays for audio sens- ing. Using multiple unsynchronized microphones or recorded sound files, and matching sounds emanating from unknown locations and unknown time of arrival data. The same problem is present in node localization of micro- phone and antenna arrays

Lunds Universitet

99

Multiband Time-of-Arrival Positioning Technique for Cognitive Radio Systems  

E-print Network

Multiband Time-of-Arrival Positioning Technique for Cognitive Radio Systems Robin R. Thomas, Bassem.knopp}@eurecom.fr Abstract--Accurate information regarding a cognitive radio user's location and environment can enhance the adaptive and spectral awareness capabilities of cognitive radio systems. In this paper, a single

Gesbert, David

100

Inversion of qP wave travel times from the URL experiment 1 Ivan Psenc'ik \\Lambda , JingSong Liu \\Lambda\\Lambda , R. Paul Young \\Lambda\\Lambda\\Lambda  

E-print Network

Inversion of qP wave travel times from the URL experiment 1 Ivan PŸsenŸc'ik \\Lambda , JingSong Liu an experiment in the vicinity of the Underground Research Laboratory (URL) in Manitoba, Canada are inverted heterogeneity and anisotropy of rocks surrounding the tunnel of the URL is made except the variation of elastic

Cerveny, Vlastislav

101

Techniques for measuring arrival times of pulsar signals 1: DSN observations from 1968 to 1980  

NASA Technical Reports Server (NTRS)

Techniques used in the ground based observations of pulsars are described, many of them applicable in a navigation scheme. The arrival times of the pulses intercepting Earth are measured at time intervals from a few days to a few months. Low noise, wide band receivers, amplify signals intercepted by 26 m, 34, and 64 m antennas. Digital recordings of total received signal power versus time are cross correlated with the appropriate pulse template.

Downs, G. S.; Reichley, P. E.

1980-01-01

102

Carbon isotope turnover in blood as a measure of arrival time in migratory birds using isotopically distinct environments  

Microsoft Academic Search

Arrival time on breeding or non-breeding areas is of interest in many ecological studies exploring fitness consequences of\\u000a migratory schedules. However, in most field studies, it is difficult to precisely assess arrival time of individuals. Here,\\u000a we use carbon isotope turnover in avian blood as a technique to estimate arrival time for birds switching from one habitat\\u000a or environment to

Steffen Oppel; Abby N. Powell

2010-01-01

103

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

Microsoft Academic Search

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

Yimin Zhang; Baha Adnan Obeidat; Moeness G. Amin

2006-01-01

104

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

Microsoft Academic Search

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

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

105

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

106

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

107

Observations of teleseismic P wave coda for underground explosions  

NASA Astrophysics Data System (ADS)

The early P 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 band for both Yucca Flat and Pahute Mesa explosions. Coda complexity in this low-frequency passband is negatively correlated with burial depth for Pahute Mesa events but is only weakly correlated with depth for Yucca Flat events. Enhanced excitation of relatively long-period scattered waves for smaller, less deeply buried events is required to explain this behavior. Coda complexity in the 0.8 1.1 Hz band is positively correlated with magnitude and depth for Pahute Mesa events, but has no such dependence for Yucca Flat events. This may result from systematic variations between the spectra of direct signals and coda arrivals caused by pP interference for the largest events, all of which were detonated at Pahute Mesa. Another possible explanation is a frequency-dependent propagation effect on the direct signals of the larger events, most of which were located in the center of the mesa overlying strong lateral velocity gradients in the crust and upper mantle. Event average complexity varies spatially for both test sites, particularly in the 0.8 1.1 Hz band, providing evidence for frequency-dependent focussing or scattering by near-source structure. Both the direct arrivals and the early coda have strong azimuthal amplitude patterns that are produced by defocussing by mantle heterogeneity. The direct arrivals have stronger coherent azimuthal patterns than the early coda for Pahute Mesa events, indicating more pronounced deep crustal and shallow mantle defocussing for the direct signals. However, for Yucca Flat events the direct arrivals have less coherent azimuthal patterns than the coda, suggesting that a highly variable component of near-source scattering preferentially affecting the downgoing energy is superimposed on a pattern produced by mantle heterogeneity that affects the entire signal. This complicated behavior of the direct arrivals may be the result of triplications and caustics produced by the complex basement structure known to underlie the Yucca Flat test site. The presence of strong azimuthal patterns in the early coda indicates that source strength estimates based on early coda are subject to biases similar to those affecting estimates based on direct arrivals.

Lynnes, Christopher S.; Lay, Thorne

1988-03-01

108

HF (high-frequency) absolute time of arrival sensing. Interim report, September 1981-May 1985  

SciTech Connect

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high-frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric-height estimation and its temporal stability. Traditional ionospheric research resources did not address the issue in sufficient detail and time resolution to be of any assistance. In order to understand the exact nature of the ionospheric uncertainties and to quantify their extent, experimentation was proposed to sense the variation in the refraction height of the ionosphere as it relates to the time of arrival of the HF signal. The objective of this work was to determine the range of environmentally induced errors in a skywave Time Difference of Arrival (TDOA) measurement, thereby bounding the ultimate geolocation accuracy one could expect from this technique. The first experimental measurement system started operation in early 1981. This effort involved establishing a continuous absolute Time of Arrival (TOA) experiment over the one-hop midlatitude path between San Diego, California and Fort Collins, Colorado. The system is fully digital and stabilized with a cesium-beam standard. This work was supplemented with vertical incidence sounder data at both ends of the path, a collateral Doppler sensing system, and coincident satellite solar data. A fully annotated database was prepared and is maintained by the Naval Ocean Systems Center Advanced Propagation Forecasting System (PROPHET).

Rose, R.B.

1986-02-01

109

VLF lightning location by time of group arrival (TOGA) at multiple sites  

Microsoft Academic Search

Lightning is located by using the time of group arrival (TOGA) of the VLF (3–30kHz) radiation from a lightning stroke. The dispersed waveform (“sferic”) of the lightning impulse is processed at each receiving site. The TOGA is determined relative to GPS at each site from the progression of phase versus frequency using the whole wave train. Unlike current VLF methods

Richard L. Dowden; James B. Brundell; Craig J. Rodger

2002-01-01

110

Speeds and Arrival Times of Solar Transients Approximated by Self-similar Expanding Circular Fronts  

NASA Astrophysics Data System (ADS)

The NASA Solar TErrestrial RElations Observatory (STEREO) mission offered the possibility to forecast the arrival times, speeds, and directions of solar transients from outside the Sun-Earth line. In particular, we are interested in predicting potentially geoeffective interplanetary coronal mass ejections (ICMEs) from observations of density structures at large observation angles from the Sun (with the STEREO Heliospheric Imager instrument). We contribute to this endeavor by deriving analytical formulas concerning a geometric correction for the ICME speed and arrival time for the technique introduced by Davies et al. ( Astrophys. J., 2012, in press), called self-similar expansion fitting (SSEF). This model assumes that a circle propagates outward, along a plane specified by a position angle ( e.g., the ecliptic), with constant angular half-width ( ?). This is an extension to earlier, more simple models: fixed-? fitting ( ?=0°) and harmonic mean fitting ( ?=90°). In contrast to previous models, this approach has the advantage of allowing one to assess clearly if a particular location in the heliosphere, such as a planet or spacecraft, might be expected to be hit by the ICME front. Our correction formulas are especially significant for glancing hits, where small differences in the direction greatly influence the expected speeds (up to 100 - 200 km s-1) and arrival times (up to two days later than the apex). For very wide ICMEs (2 ?>120°), the geometric correction becomes very similar to the one derived by Möstl et al. ( Astrophys. J. 741, 34, 2011) for the harmonic mean model. These analytic expressions can also be used for empirical or analytical models to predict the 1 AU arrival time of an ICME by correcting for effects of hits by the flank rather than the apex, if the width and direction of the ICME in a plane are known and a circular geometry of the ICME front is assumed.

Möstl, C.; Davies, J. A.

2013-07-01

111

AIMBAT: A Python/Matplotlib Tool for Measuring Teleseismic Arrival Times  

NASA Astrophysics Data System (ADS)

Python is an open-source, platform-independent, and object-oriented scripting language. It became more popular in the seismologist community since the appearance of ObsPy (Beyreuther et al. 2010, Megies et al. 2011), which provides a powerful framework for seismic data access and processing. This study introduces a new Python-based tool named AIMBAT (Automated and Interactive Measurement of Body-wave Arrival Times) for measuring teleseismic body-wave arrival times on large-scale seismic event data (Lou et al. 2013). Compared to ObsPy, AIMBAT is a lighter tool that is more focused on a particular aspect of seismic data processing. It originates from the widely used MCCC (Multi-Channel Cross-Correlation) method developed by VanDecar and Crosson (1990). On top of the original MCCC procedure, AIMBAT is automated in initial phase picking and is interactive in quality control. The core cross-correlation function is implemented in Fortran to boost up performance in addition to Python. The GUI (graphical user interface) of AIMBAT depends on Matplotlib's GUI-neutral widgets and event-handling API. A number of sorting and (de)selecting options are designed to facilitate the quality control of seismograms. By using AIMBAT, both relative and absolute teleseismic body-wave arrival times are measured. AIMBAT significantly improves efficiency and quality of the measurements. User interaction is needed only to pick the target phase arrival and to set a time window on the array stack. The package is easy to install and use, open-source, and is publicly available. Graphical user interface of AIMBAT.

Lou, X.; van der Lee, S.; Lloyd, S.

2013-12-01

112

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

113

Spatial factors in visual attention: some compensatory effects of location and time of arrival of nontargets.  

PubMed

It is well established that the identity of nontarget events may affect reaction to a target event, but that spatial separation between the two will reduce such an influence. Two experiments are reported in which an attempt was made to distinguish between two accounts of this effect. On one, some of the information about events spatially distant from the target is shut out from analysis altogether. On the other, such events are fully analysed, but either the analysis proceeds more slowly or else it starts only after a delay. In the experiments the time of arrival of, and the distance between, the target and nontarget events were systematically varied. The conventional effects of the distance of nontargets from target were greatly reduced when the target and nontarget events were asynchronous. If the nontargets arrived first, they had an effect on reaction to the target whether they were near to or far from it. If they arrived second, their identity had no effect at either separation. These results appear to rule out any simple view of attention according to which information outside the target region is denied analysis. Rather, distant nontarget events are analysed, but produce their effects at a later time than less peripheral events. PMID:3444724

Gathercole, S E; Broadbent, D E

1987-01-01

114

Accurate tremor locations from coherent S and P waves  

NASA Astrophysics Data System (ADS)

Nonvolcanic tremor is an important component of the slow slip processes which load faults from below, but accurately locating tremor has proven difficult because tremor rarely contains clear P or S wave arrivals. Here we report the observation of coherence in the shear and compressional waves of tremor at widely separated stations which allows us to detect and accurately locate tremor events. An event detector using data from two stations sees the onset of tremor activity in the Cascadia tremor episodes of February 2003, July 2004, and September 2005 and confirms the previously reported south to north migration of the tremor. Event detectors using data from three and four stations give Sand P arrival times of high accuracy. The hypocenters of the tremor events fall at depths of ˜30 to ˜40 km and define a narrow plane dipping at a shallow angle to the northeast, consistent with the subducting plate interface. The S wave polarizations and P wave first motions define a source mechanism in agreement with the northeast convergence seen in geodetic observations of slow slip. Tens of thousands of locations determined by constraining the events to the plate interface show tremor sources highly clustered in space with a strongly similar pattern of sources in the three episodes examined. The deeper sources generate tremor in minor episodes as well. The extent to which the narrow bands of tremor sources overlap between the three major episodes suggests relative epicentral location errors as small as 1-2 km.

Armbruster, John G.; Kim, Won-Young; Rubin, Allan M.

2014-06-01

115

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

116

Fast P wave propagation in subducted Pacific lithosphere: Refraction from the plate  

NASA Astrophysics Data System (ADS)

P waves traveling from events in the Tonga-Kermadec seismic zone to stations in New Zealand are very fast with highly emergent, dispersed waveforms. Ray tracing has shown the waves to travel close to the subducted Pacific plate throughout their length, and synthetic seismogram calculations have shown the dispersion requires a very thin (8-12 km) fast layer. Previous work has been based on data from analog records and one digital, single-component short-period instrument; no polarization analysis was possible, and measurements of dispersion were limited by the bandwidth. From January 1991 to August 1992 we deployed nine broad band, three-component seismometers in good sites for observing these arrivals; the data are augmented by three-component, short-period digital records from new stations of the New Zealand National Network. In this study we analyze 1191 broad-band and 2076 short period seismograms from 71 events for polarization of the initial P wave. The polarization directions are found to be up to 30 deg off the great circle path and consistently steep (20 deg from vertical). They are too steep to be explained by standard ray paths or refraction from a fast horizontal layer. We invert the polarization directions for a tilted interface beneath the array and use arrival times to control the depth to the interface, which is found to lie close to the top of the subducted plate inferred from the seismicity. We conclude that these precursive, emergent P waves have traveled through a fast layer close to the top of the subducted plate and refract upward to the station. A second arrival, with lower dominant frequency near 1 Hz and normal travel time, is occasionally seen on both broad band and short-time stations. Its polarization direction is similarly steep but difficult to measure; the evidence suggests that it also travels within the plate with similar ray path to the precursor.

Smith, Gideon; Gubbins, David; Mao, Weijian

1994-12-01

117

Crustal parameters estimated from P-waves of earthquakes recorded at a small array  

USGS Publications Warehouse

The P-arrival times of local and regional earthquakes that are outside of a small network of seismometers can be used to interpret crustal parameters beneath the network by employing the time-term technique. Even when the estimate of the refractor velocity is poorly determined, useful estimates of the station time-terms can be made. The method is applied to a 20 km diameter network of eight seismic stations which was operated near Castaic, California, during the winter of 1972-73. The stations were located in sedimentary basins. Beneath the network, the sedimentary rocks of the basins are known to range from 1 to more than 4 km in thickness. Relative time-terms are estimated from P-waves assumed to be propagated by a refractor in the mid-crust, and again from P-waves propagated by a refractor in the upper basement. For the range of velocities reported by others, the two sets of time-terms are very similar. They suggest that both refractors dip to the southwest, and the geology also indicates that the basement dips in this direction. In addition, the P-wave velocity estimated for the refractor of mid-crustal depths, roughly 6.7 km/sec, agrees with values reported by others. Thus, even in this region of complicated geologic structure, the method appears to give realistic results. ?? 1980 Birkha??user Verlag.

Murdock, J.N.; Steppe, J.A.

1980-01-01

118

Phase sensitive monitoring of electron bunch form and arrival time in superconducting linear accelerators  

SciTech Connect

In this Letter, we present a simple approach for monitoring electron bunch form and arrival time combining electro-optic sampling and phase and frequency sensitive signal detection. The sensitivity of the technique has the potential to allow online diagnostics to be performed down to bunch charges in the femto coulomb regime. The concept has high impact for the developments of the next generation of 4th generation x-ray light sources working with long pulse trains or continuous wave mode of operation.

Kaya, C.; Schneider, C.; Seidel, W.; Kuntzsch, M.; Bhattacharyya, J.; Mittendorff, M.; Winnerl, S.; Staats, G.; Helm, M.; Michel, P.; Gensch, M. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328, Dresden (Germany); Al-Shemmary, A.; Stojanovic, N. [DESY, Notkestr. 85, 22607 Hamburg (Germany); Evtushenko, P. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States)

2012-04-02

119

Processing advances for localization of beaked whales using time difference of arrival.  

PubMed

This paper is concerned with the localization of clicking Blainville's beaked whales (Mesoplodon densirostris) using an array of widely spaced bottom-mounted hydrophones. A set of signal and data processing advances are presented that together make reliable tracking a possibility. These advances include a species-specific detector, elimination of spurious time-difference-of-arrival (TDOA) estimates, improved tracking of TDOA estimates, positive association of TDOA estimates using different hydrophone pairs, and joint localization of multiple whales. A key innovation in three of these advances is the principle of click-matching. The methods are demonstrated using real data. PMID:23742359

Baggenstoss, Paul M

2013-06-01

120

Continuous estimation of systolic blood pressure using the pulse arrival time and intermittent calibration.  

PubMed

A continuous noninvasive method of systolic blood pressure estimation is described. Systolic blood pressure is estimated by combining two separately obtained components: a higher frequency component obtained by extracting a specific frequency band of pulse arrival time and a lower frequency component obtained from the intermittently acquired systolic blood pressure measurements with an auscultatory or oscillometric system. The pulse arrival time was determined by the time interval from QRS apex in electrocardiogram to the onset of photoplethysmogram in a fingertip beat-by-beat via an oximetric sensor. The method was examined in 20 patients during cardiovascular surgery. The estimated values of systolic blood pressure were compared with those measured invasively using a radial arterial catheter. The results showed that the correlation coefficients between estimated values and invasively obtained systolic blood pressure reached 0.97 +/- 0.02 (mean +/- SD), and the error remained within +/- 10% in 97.8% of the monitoring period. By using a system with automatic cuff inflation and deflation to acquire intermittent systolic blood pressure values, this method can be applicable for the continuous noninvasive monitoring of systolic blood pressure. PMID:11094816

Chen, W; Kobayashi, T; Ichikawa, S; Takeuchi, Y; Togawa, T

2000-09-01

121

On the relationship between pedestrian gap acceptance and time to arrival estimates.  

PubMed

The identification of safe gaps between passing cars when crossing a street is a task most of us accomplish successfully on a daily basis. Objectively, how safe a specific gap is, is mainly dependent on how long it would take the approaching vehicle to arrive (time to arrival; TTA). Common sense might suggest that TTA is the basis for pedestrians' gap selection. However, it has been shown repeatedly that vehicle approach speed has a substantial influence on the size of chosen gaps. At higher speeds, pedestrians tend to accept smaller time gaps, i.e. they initiate riskier crossings. Some researchers have gone so far as to suggest that pedestrians rely more on physical distance of a vehicle in their crossing decisions than TTA. Yet, at the same time, there is evidence that TTA estimates themselves are influenced by object approach speed. It is suspected that pedestrians are more apt to base their decisions on systematically distorted TTA estimates, rather than physical distance. The goal of the two experiments described in this article was to explore the relationship between gap acceptance and TTA estimation. Participants were presented with video clips of approaching vehicles, and were either required to indicate a crossing decision, or to estimate TTA. Results show the typical effects of speed (smaller gaps at higher speed, lower TTA estimate at lower speed) and age (larger gaps for older participants). However, when using subjective time gap size (the TTA estimate) instead of objective time gap size to predict gap acceptance, the effect of speed either disappeared (Experiment I) or decreased substantially (Experiment II). The results indicate that systematic differences in TTA estimates can be a reasonable explanation for the effect of speed on gap acceptance. PMID:25035969

Petzoldt, Tibor

2014-11-01

122

Airborne Evaluation and Demonstration of a Time-Based Airborne Inter-Arrival Spacing Tool  

NASA Technical Reports Server (NTRS)

An airborne tool has been developed that allows an aircraft to obtain a precise inter-arrival time-based spacing interval from the preceding aircraft. The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast (ADS-B) data to compute speed commands for the ATAAS-equipped aircraft to obtain this inter-arrival spacing behind another aircraft. The tool was evaluated in an operational environment at the Chicago O'Hare International Airport and in the surrounding terminal area with three participating aircraft flying fixed route area navigation (RNAV) paths and vector scenarios. Both manual and autothrottle speed management were included in the scenarios to demonstrate the ability to use ATAAS with either method of speed management. The results on the overall delivery precision of the tool, based on a target spacing of 90 seconds, were a mean of 90.8 seconds with a standard deviation of 7.7 seconds. The results for the RNAV and vector cases were, respectively, M=89.3, SD=4.9 and M=91.7, SD=9.0.

Lohr, Gary W.; Oseguera-Lohr, Rosa M.; Abbott, Terence S.; Capron, William R.; Howell, Charles T.

2005-01-01

123

Relaxing the closure assumption in occupancy models: staggered arrival and departure times.  

PubMed

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. PMID:23687887

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

2013-03-01

124

CELEBRATION 2000: P-wave velocity models of the Bohemian Massif  

NASA Astrophysics Data System (ADS)

Deep structure of the Bohemian Massif (BM), the largest stable outcrop of Variscan rocks in Central Europe, was studied along two refraction profiles, CEL09 that traverses the whole massif in the NW-SE direction, and CEL10 that extends along its eastern edge almost perpendicularly to CEL09. Good quality recordings with clear first arrivals of crustal and upper mantle phases show apparent velocity 5.9 km/s for the upper crust with slightly higher gradient in NW part of the BM and app. velocity 8.0 to 8.1 km/s for the upper mantle. Decrease of amplitudes of crustal phases visible in some sections may be connected with a specific upper crustal structure (zero to negative velocity gradient zone). Pronounced Moho reflections in central part of the BM suggest well-defined Moho in that part and not so clear Moho with smaller velocity contrast in other parts of the BM. For interpretation, the tomographic inversion routine of Hole (1992) was used as an efficient tool to determine seismic P-wave velocity distribution in the crust using first arrivals. Tomographic models were verified by forward ray tracing modelling based on well-established algorithm developed by Cerveny et al. (1983), where apart from first arrivals also further phases were included. 2-D velocity models of first arrivals and reflected phases show high P-wave velocity gradient zone reaching the depth of 5-7 km followed by small gradient and laterally homogeneous P-wave velocity distribution in the middle crust. Differences in velocity distribution in the lower crust delimit central part of the BM (sharp Moho discontinuity) from other tectonic units within the BM (lower crust high gradient transition zone). Position of Moho discontinuity ranging from 32 km to 40 km and reflectors within the crust complement the P-wave velocity distribution. Presented models also show the contact of the BM with its neighbouring units - Carpathians, Paleozoic Platform, Vienna Basin and the Alps. References: Cerveny, V., Psencik, I., 1983. Program SEIS83, Numerical Modelling of Seismic Wave Fields in 2-D Laterally Varying Layered Structures by the Ray Method, Charles University, Prague. Hole, J.A. 1992: Non-linear high-resolution three-dimensional seismic travel time tomography, J. Geophys. Res. 97, 6553-6562.

Hrubcova, P.

2003-04-01

125

Timing of initial arrival at the breeding site predicts age at first reproduction in a long-lived migratory bird.  

PubMed

In long-lived vertebrates, individuals generally visit potential breeding areas or populations during one or more seasons before reproducing for the first time. During these years of prospecting, they select a future breeding site, colony, or mate and improve various skills and their physical condition to meet the requirements of reproduction. One precondition of successful reproduction is arrival in time on the breeding grounds. Here, we study the intricate links among the date of initial spring arrival, body mass, sex, and the age of first breeding in the common tern Sterna hirundo, a long-lived migratory colonial seabird. The study is based on a unique, individual-based, long-term dataset of sexed birds, marked with transponders, which allow recording their individual arrival, overall attendance, and clutch initiation remotely and automatically year by year over the entire lifetime at the natal colony site. We show that the seasonal date of initial arrival at the breeding grounds predicts the individual age at first reproduction, which mostly occurs years later. Late first-time arrivals remain delayed birds throughout subsequent years. Our findings reveal that timing of arrival at the site of reproduction and timing of reproduction itself are coherent parameters of individual quality, which are linked with the prospects of the breeding career and may have consequences for fitness. PMID:18711134

Becker, Peter H; Dittmann, Tobias; Ludwigs, Jan-Dieter; Limmer, Bente; Ludwig, Sonja C; Bauch, Christina; Braasch, Alexander; Wendeln, Helmut

2008-08-26

126

Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses  

NASA Astrophysics Data System (ADS)

The advent of few femtosecond x-ray light sources brings promise of x-ray/optical pump-probe experiments that can measure chemical and structural changes in the 10-100 fs time regime. Widely distributed timing systems used at x-ray Free-Electron Laser facilities are typically limited to above 50 fs fwhm jitter in active x-ray/optical synchronization. The approach of single-shot timing measurements is used to sort results in the event processing stage. This has seen wide use to accommodate the insufficient precision of active stabilization schemes. In this article, we review the current technique for "measure-and-sort" at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The relative arrival time between an x-ray pulse and an optical pulse is measured near the experimental interaction region as a spectrally encoded cross-correlation signal. The cross-correlation provides a time-stamp for filter-and-sort algorithms used for real-time sorting. Sub-10 fs rms resolution is common in this technique, placing timing precision at the same scale as the duration of the shortest achievable x-ray pulses.

Bionta, M. R.; Hartmann, N.; Weaver, M.; French, D.; Nicholson, D. J.; Cryan, J. P.; Glownia, J. M.; Baker, K.; Bostedt, C.; Chollet, M.; Ding, Y.; Fritz, D. M.; Fry, A. R.; Kane, D. J.; Krzywinski, J.; Lemke, H. T.; Messerschmidt, M.; Schorb, S.; Zhu, D.; White, W. E.; Coffee, R. N.

2014-08-01

127

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

Code of Federal Regulations, 2011 CFR

...departure/arrival dates and times on my travel claim? 301-11.10...departure/arrival dates and times on my travel claim? You must record...record departure/arrival times, but you must annotate your travel claim when your travel...

2011-07-01

128

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

...departure/arrival dates and times on my travel claim? 301-11.10...departure/arrival dates and times on my travel claim? You must record...record departure/arrival times, but you must annotate your travel claim when your travel...

2010-07-01

129

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

130

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

132

Measuring pulse times of arrival from broad-band pulsar observations  

NASA Astrophysics Data System (ADS)

In recent years, instrumentation enabling pulsar observations with unprecedentedly high fractional bandwidth has been under development which can be used to substantially improve the precision of pulsar timing experiments. The traditional template-matching method used to calculate pulse times of arrival (ToAs) may not function effectively on these broad-band data due to a variety of effects such as diffractive scintillation in the interstellar medium, profile variation as a function of frequency, dispersion measure (DM) evolution, and so forth. In this paper, we describe the channelized discrete Fourier transform method that can greatly mitigate the influence of the aforementioned effects when measuring ToAs from broad-band timing data. The method is tested on simulated data, and its potential in improving timing precision is shown. We further apply the method to PSR J1909-3744 data collected at the Nançay Radio Telescope with the Nançay Ultimate Pulsar Processing Instrument. We demonstrate removal of systematics due to the scintillation effect as well as improvement on ToA measurement uncertainties. Our method also determines temporal variations in DM, which are consistent with multichannel timing approaches used earlier.

Liu, K.; Desvignes, G.; Cognard, I.; Stappers, B. W.; Verbiest, J. P. W.; Lee, K. J.; Champion, D. J.; Kramer, M.; Freire, P. C. C.; Karuppusamy, R.

2014-10-01

133

Probability distribution of the inter-arrival time to cellular telephony channels  

Microsoft Academic Search

This paper is focused on the statistical analysis of the call arrival process in channels of mobile telephony access networks. The approach is fully empirical, and is based on actual activity data, collected from real base stations in a working mobile network. The arrival process of the merged “fresh” (new calls) and handover traffic is proved to be smoother than

Francisco Barceló; José Ignacio Sánchez

1999-01-01

134

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

135

An effect of arrival time differences in space-time coded communication systems  

Microsoft Academic Search

One of main goals in developing next generation wireless communication systems is increasing the data rates and high reliability. A promising way to achieve this is combination of multiple-input and multiple-output signal processing with space-time coding scheme. Naguib et al. (1988), Tarokh et al. (1998), and Hammons et al. (2000) proposed several space-time code schemes, which offer higher coding and

Ji-Won Jung; Duk-Gun Choi; Ki-Man Kim; Xinping Huang; Mario Caron

2005-01-01

136

Measurement of arrival time of particles in extensive air showers using TDC32  

NASA Astrophysics Data System (ADS)

Arrival time of particles in an extensive air shower (EAS) is a key physical parameter to determine its direction. EAS direction is useful for studies of anisotropy and composition of cosmic rays, and search for multi-TeV ?-rays sources. Accurate timing may be used to search exotic phenomena such as production of new particles at extremely high energies available during early stages of development of EAS and also for detecting sub-relativistic hadrons in EAS. Time to digital converters (TDCs) are used to perform this task. Traditional TDCs operate in the START-STOP mode with limited dynamic range and single-hit capability. With the advent of high luminosity collider LHC, need for TDCs with large dynamic range, multi-hit capability and TRIGGERED mode of operation became necessary. A 32 channel TDC was designed for the GRAPES-3 experiment on a CAMAC platform around TDC32, an ASIC developed by micro-electronics group at CERN, Geneva. Four modules were operated in the GRAPES-3 experiment. Here, we present details of the circuit design and their performance over several years. The multi-hit feature of this device was used to study the time structure of particles in the EAS on time scale of ~1 ?s. The distribution of time intervals in the multi-hit data shows an exponential profile with a time constant of ~370 ns. These delayed particles are likely to be neutrons produced in the EAS core that were recorded in the scintillator detectors following the relativistic EAS front.

Gupta, S. K.; Christiansen, J.; Hayashi, Y.; Jain, A.; Mohanty, P. K.; Ravindran, K. C.; Satyanarayana, B.

2013-04-01

137

Priority Effects of Time of Arrival of Plant Functional Groups Override Sowing Interval or Density Effects: A Grassland Experiment  

PubMed Central

Priority effects occur when species that arrive first in a habitat significantly affect the establishment, growth, or reproduction of species arriving later and thus affect functioning of communities. However, we know little about how the timing of arrival of functionally different species may alter structure and function during assembly. Even less is known about how plant density might interact with initial assembly. In a greenhouse experiment legumes, grasses or forbs were sown a number of weeks before the other two plant functional types were sown (PFT) in combination with a sowing density treatment. Legumes, grasses or non-legume forbs were sown first at three different density levels followed by sowing of the remaining PFTs after three or six-weeks. We found that the order of arrival of different plant functional types had a much stronger influence on aboveground productivity than sowing density or interval between the sowing events. The sowing of legumes before the other PFTs produced the highest aboveground biomass. The larger sowing interval led to higher asymmetric competition, with highest dominance of the PFT sown first. It seems that legumes were better able to get a head-start and be productive before the later groups arrived, but that their traits allowed for better subsequent establishment of non-legume PFTs. Our study indicates that the manipulation of the order of arrival can create priority effects which favour functional groups of plants differently and thus induce different assembly routes and affect community composition and functioning. PMID:24497995

von Gillhaussen, Philipp; Rascher, Uwe; Jablonowski, Nicolai D.; Pluckers, Christine; Beierkuhnlein, Carl; Temperton, Vicky M.

2014-01-01

138

Time of Arrival at Hospital Impacts Time to Treatment and Survival of Heart Attack Patients  

MedlinePLUS

... hospital impacts time to treatment and survival of heart attack patients American Heart Association Rapid Access Journal Report July 29, 2014 ... University HealthSystem, Evanston, IL. Download (1.8 MB) Heart illustration Copyright American Heart Association Download (90.3 ...

139

Performance of real-time distributed arrival time control in heterarchical manufacturing systems  

Microsoft Academic Search

A highly distributed feedback control algorithm for autonomous part entities in heterarchical manufacturing systems is presented in this paper. A difference equation-based model is developed to analyze the discrete time dynamics of the resulting nonlinear control system. Control parameters are found analytically that guarantee that the system is bounded under disturbances. The dynamic response to: (i) changes in due dates;

Vittaldas V. Prabhu

2000-01-01

140

Detection of Lightning Events by Time Of Group Arrival (TOGA) Technique  

NASA Astrophysics Data System (ADS)

The stochastic behaviour of lightning events has compelled scientists to study the various aspects related to this form of atmospheric electricity Severe lightning and thunderstorm activities inflict extensive loss to mankind and property Hence one becomes greatly interested to investigate the occurrence of lightning events This paper discusses about the lightning strokes detected near low latitudinal region using the Time Of Group Arrival TOGA technique Bhopal 23 2 r N 77 4 r E is chosen as one of the multiple stations involved in recording the lightning activity because of its congenial geographic location We present some results for the month of July 2004 that indicates enhanced lightning activities recorded around the low latitude region The time period between June and August is most suitable for making such studies as chances for occurrence of lightning events is maximum It is believed that the paper reflects on the location of this atmospheric phenomena and can be used for suitable studies in future beneficial to the field of global atmospheric sciences

Bhattacharya, S.; Sarkar, S.; Saini, S.; Gwal, A. K.

141

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

142

Fault zone structure determined through the analysis of earthquake arrival times  

SciTech Connect

This thesis develops and applies a technique for the simultaneous determination of P and S wave velocity models and hypocenters from a set of arrival times. The velocity models are parameterized in terms of cubic B-splines basis functions which permit the retrieval of smooth models that can be used directly for generation of synthetic seismograms using the ray method. In addition, this type of smoothing limits the rise of instabilities related to the poor resolving power of the data. V{sub P}/V{sub S} ratios calculated from P and S models display generally instabilities related to the different ray-coverages of compressional and shear waves. However, V{sub P}/V{sub S} ratios are important for correct identification of rock types and this study introduces a new methodology based on adding some coupling (i.e., proportionality) between P and S models which stabilizes the V{sub P}/V{sub S} models around some average preset value determined from the data. Tests of the technique with synthetic data show that this additional coupling regularizes effectively the resulting models.

Michelini, A.

1991-10-01

143

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

144

A two-station lightning location method based on a combination of difference of time of arrival and amplitude attenuation  

Microsoft Academic Search

We propose a lightning location method that uses a combination of peak electric or magnetic field amplitude information at two spatially separated sensors and the difference of time of arrival information at the same two stations to obtain an estimate of the location of a lightning strike point. We derive analytical expressions for the coordinates of the fix and we

M. Rubinstein; Carlos Romero; Farhad Rachidi; Abraham Rubinstein; Felix Vega

2010-01-01

145

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

146

Relation Between First Arrival Time and Perme-ability in Self-Affine Fractures with Areas in Con-  

E-print Network

epl draft Relation Between First Arrival Time and Perme- ability in Self-Affine Fractures ­ Suspensions, dispersions, pastes, slurries, colloids PACS 46.50.+a ­ Fracture mechanics, fatigue and cracks in self-affine fractures are governed by the same length scale characterizing the fractures as that which

Paris-Sud XI, Université de

147

2The InSight Seismographic Station Wave Arrival Times NASA's new mission to Mars called InSight  

E-print Network

to `orbit' the surface of Mars and return once again as a second pair of weaker seismic signals called R3 are detected by the seismometer, that the waves will continue to `orbit' the surface of Mars and return once2The InSight Seismographic Station ­ Wave Arrival Times NASA's new mission to Mars called In

148

NOTE: An automatic approach for estimating bolus arrival time in dynamic contrast MRI using piecewise continuous regression models  

NASA Astrophysics Data System (ADS)

We present two regression models for the automatic estimation of bolus arrival times (BATs) in dynamic contrast MRI datasets. Results of Monte Carlo simulation experiments show that the means and standard deviations of the estimated BATs are within the sampling interval even in the presence of significant noise.

Cheong, L. H.; Koh, T. S.; Hou, Z.

2003-03-01

149

`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

150

Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease  

PubMed Central

Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD. Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2. A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD. PMID:25379411

Al-Bachari, Sarah; Parkes, Laura M.; Vidyasagar, Rishma; Hanby, Martha F.; Tharaken, Vivek; Leroi, Iracema; Emsley, Hedley C.A.

2014-01-01

151

Analysing and Predicting Patient Arrival Times in Hospitals using Hidden Markov Models  

E-print Network

schedule. The HMM is validated by comparing means, standard deviations and autocorrelation functions of raw has been tested using metrics such as SENSI- TIVITY and SPECIFICITY of the data examples used- tiple sequences with HMM pairs, etc. In this paper, however, we focus on mod- elling patient arrivals

Imperial College, London

152

P-Wave Wave in a Slinky  

NSDL National Science Digital Library

This animation shows how P-waves (primary, or compressional, waves) travel through a Slinky toy. It is accompanied by a brief written explanation that describes some of the properties of P-waves and how they are generated in a real Slinky.

Lahr, John

153

Three-dimensional seismic tomography from P wave and S wave microearthquake travel times and rock physics characterization of the Campi Flegrei Caldera  

Microsoft Academic Search

The Campi Flegrei (CF) Caldera experiences dramatic ground deformations unsurpassed anywhere in the world. The source responsible for this phenomenon is still debated. With the aim of exploring the structure of the caldera as well as the role of hydrothermal fluids on velocity changes, a multidisciplinary approach dealing with three-dimensional delay time tomography and rock physics characterization has been followed.

T. Vanorio; J. Virieux; P. Capuano; G. Russo

2005-01-01

154

Using lightning locating system based on time-of-arrival technique to study three-dimensional lightning discharge processes  

Microsoft Academic Search

A time-of-arrival (TOA) system based on GPS technology for locating VHF radiation sources from lightning has been developed\\u000a and used in observation sites in the northern Shandong Province, China. The 3D images of the lightning progression have been\\u000a obtained successfully for the first time in China. The 3D-channel evolutions of typical negative CG, positive CG and IC lightning\\u000a flashes have

GuangShu Zhang; YanHui Wang; XiuShu Qie; Tong Zhang; YuXiang Zhao; YaJun Li; DongJie Cao

2010-01-01

155

Sexual selection and spring arrival times of red-necked and Wilson's phalaropes  

Microsoft Academic Search

Seasonal changes in sex ratios during a 4-year study of red-necked phalaropes and a 3-year study of Wilson's phalaropes showed that females preceded males to breeding and\\/or courtship areas. The degree to which females preceded males may have been constrained by harsh weather, as the arrival of red-necked phalaropes was synchronous in 1983, when spring was unusually late. Neither sex

John D. Reynolds; Mark A. Colwell; Fred Cooke

1986-01-01

156

Age-Correlated Incremental Consideration of Velocity Information in Relative Time-to-Arrival Judgments  

Microsoft Academic Search

One hundred fifty-one children and 43 adults judged which of 2 cartoon birds would be the first to arrive at a common finish line. Objects moved unidirectionally along parallel trajectories, either at the same or different speeds, and disappeared at different distances from the goal. Overall, 9–10-year-old children performed as well as adults, but 4–5- and 6–8-year-olds erred significantly more

Behrang Keshavarza; Klaus Landwehra; Robin Baurèsa; Daniel Oberfelda; Heiko Hechta; Nicolas Benguiguib

2010-01-01

157

The gravity dual of a p-wave superconductor  

E-print Network

We construct black hole solutions to the Yang-Mills equations in an AdS_4-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.

Steven S. Gubser; Silviu S. Pufu

2008-05-19

158

Three dimensional P-wave velocity structure at Popocatépetl Volcano, Mexico  

NASA Astrophysics Data System (ADS)

Popocatépetl Volcano is an active andesitic stratovolcano (5460m) of the Trans Mexican Volcanic Belt that has been erupting since December 1994. We used three-dimensional seismic tomography to detect variations in the P-wave velocity structure during three different volcanic cycles, which are separated by the two largest eruptions that occurred at Popocatépetl on June 30th, 1997 and January 22nd, 2001. The start of the first dataset is defined by the eruption in June 1996; the last dataset ends with the eruption in September 2003. The P-wave velocity structure of the volcano has been determined to 10 km depth below the summit using nearly 4000 P-arrival times from about 900 volcano tectonic events recorded on a local 10-station network. The Root Mean Square (RMS) of the arrival time residuals was reduced by 22% - 30% from the initial RMS of about 0.30 s, after running seven iterations of our tomography code. In the three eruption cycles, we observe velocity structures which complement the results of former studies, as well as image previously unrecognized velocity anomalies. We observe velocity changes of ~1km/s in certain areas before and after large eruptions. We compare the tomographic results with geologic, geophysical and geochemical investigations and interpret low velocity zones as fractured rock (SE-zone) or as thermally disturbed zones including hot rock and melt (below the crater region and north flank), from which unexpected future eruptions or flank collapses may occur. High velocity zones are interpreted as roofs of magma reservoirs, old dike systems or relicts of the ancient volcano. The observed changes in velocity anomalies before and after large eruptions, determined by four-dimensional tomography, indicate a change in the internal volcanic fluid-filled structures during volcanic eruptions and show the need for time-resolved geophysical techniques when investigating volcanic structures.

Berger, P.; Valdes-Gonzales, C. M.

2009-12-01

159

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

160

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

161

Arrival time pattern and waiting time distribution of patients in the emergency outpatient department of a tertiary level health care institution of North India  

PubMed Central

Background: Emergency Department (ED) of tertiary health care institute in India is mostly overcrowded, over utilized and inappropriately staffed. The challenges of overcrowded EDs and ill-managed patient flow and admission processes result in excessively long waits for patients. Aim: The objective of the present study was to analyze the patient flow system by assessing the arrival and waiting time distribution of patients in an Emergency out Patient Department (EOPD). Materials and Methods: This short cross-sectional descriptive study was conducted in the EOPD of a Tertiary level health care Institution in North India in the month of May, 2011. The data was obtained from 591 patients, who were present in the EOPD during the month of May, 2011. The waiting time, inter arrival time between two consecutive patients were calculated in addition to the daily census data (discharge rate, admission rate and transfer out rates etc.) of the emergency. Results: Arrival time pattern of patients in the EOPD was highly stochastic with the peak arrival hours to be 9.00-12.00 h in which around 26.3% patients arrived in the EOPD. The primary waiting areas of patients included patients under observation (29.6%); waiting for routine diagnostic tests (16.4%) and waiting for discharge (14.6%). Around 71% patients were waiting due to reasons within emergency complex. Conclusion: The patient flow of the ED could only be addressed by multifaceted, multidisciplinary and hospital wide approach. PMID:25114424

Tiwari, Yogesh; Goel, Sonu; Singh, Amarjeet

2014-01-01

162

Regional P wave velocity structure of the Northern Cascadia Subduction Zone  

Microsoft Academic Search

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

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

2006-01-01

163

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

164

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

165

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

DOEpatents

An apparatus is disclosed 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. 3 figs.

Benjamin, R.F.

1987-03-10

166

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

167

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

168

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

169

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

170

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

NASA Astrophysics Data System (ADS)

Position surveillance using one active ranging/communication satellite and the time-of-arrival of signals from an independent satellite was shown to be feasible and practical. A towboat on the Mississippi River was equipped with a tone-code ranging transponder and a receiver tuned to the timing signals of the GOES satellite. A similar transponder was located at the office of the towing company. Tone-code ranging interrogations were transmitted from the General Electric Earth Station Laboratory through ATS-6 to the towboat and to the ground truth transponder office. Their automatic responses included digital transmissions of time-of-arrival measurements derived from the GOES signals. The Earth Station Laboratory determined ranges from the satellites to the towboat and computed position fixes. The ATS-6 lines-of-position were more precise than 0.1 NMi, 1 sigma, and the GOES lines-of-position were more precise than 1.6 NMi, 1 sigma. High quality voice communications were accomplished with the transponders using a nondirectional antenna on the towboat. The simple and effective surveillance technique merits further evaluation using operational maritime satellites.

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

1980-01-01

171

Magnetotelluric apparent conductivity and seismic p-wave tomography comparison, Rio Grande Rift, Southwestern USA  

NASA Astrophysics Data System (ADS)

During the summers of 2012 and 2013, magnetotelluric (MT) data was collected in three transects across the Rio Grande Rift in Colorado and New Mexico. Previous seismological studies, including both regional deployments and EarthScope USArray Transportable Array (TA), have shown that a wide area of upper mantle below the Rio Grande Rift is seismically slow, but the cause of this is unclear. MT has the potential to help reduce the ambiguity in determining the cause of the seismically slow anomaly. Electrical conductivity determined from MT and elastic parameters determined from seismic experiments have different sensitivities to temperature, partial melt, hydration and composition; together these methods can be used to constrain the physical, chemical, and thermal state of the lithosphere, and to investigate changes in it throughout the rift. These constraints can help distinguish between different rift opening models such as the rift unzipping south to north or being rotated open. We have used a cross correlation algorithm to pick teleseismic P-wave arrival times from twenty-two events recorded by TA stations in Colorado and New Mexico from 2008 - 2010. Our teleseismic picks were used to create maps and profiles of travel time residuals that can be compared with existing tomographic images and with our new MT data. We have forward modeled select MT data to produce 1-D models of conductivity versus depth, which can then be compared to the average travel time residuals at TA stations in proximity to the MT profile. The travel time residuals across the three MT lines are also qualitatively compared to cross-sections of the Schmandt & Humphreys (2010) P-wave tomography model.

Harding, J.; Sheehan, A. F.; Feucht, D. W.; Bedrosian, P.; O'Rourke, C. T.

2013-12-01

172

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

...record departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11...Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ALLOWABLE TRAVEL EXPENSES...

2013-07-01

173

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

Code of Federal Regulations, 2012 CFR

...record departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11...Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ALLOWABLE TRAVEL EXPENSES...

2012-07-01

174

Lightning First Pulses Used in the "Last" (Time-of-Arrival) and "Atlas" (Single Station) Total Lightning Mapping Systems  

NASA Technical Reports Server (NTRS)

The first RF pulse from "total lightning' discharges (cloud and ground flashes) has been used in different ways to locate the origin of flashes in two new types of lightning detection systems. The multisensor LASI time-of-arrival (TOA) system uses GPS timing of the first pulse. The ATLAS single sensor system uses the amplitude of the first pulse, which is invariant in magnitude and polarization for all lightning discharges, to determine distance from the sensor. It is significantly more accurate than past single sensor lightning mapping systems. The polarity of the first pulse generally identifies lightning type (IC or CG). Both systems utilize only the first pulse which makes signal processing much simpler than with previous lightning locating systems. Knowing the position where lightning begins (maximum electric fields, mixed phase hydrometeors and updrafts) is valuable for identifying convective cells producing the hazardous meteorological conditions caused by thunderstorms. It is also important for research studying thunderstorm electrification and associated microphysical problems.

Markson, Ralph; Ruhnke, Lothar

1999-01-01

175

Supplementary Movie: Breaking the fixed-arrival-time restriction in reaching movements of neural prosthetic devices  

E-print Network

This supplementary movie demonstrates three neural prosthetic algorithms in the simulated control of an overactuated 3-dimensional virtual robotic arm with a real-time inverse kinematics engine. Specifically, this movie ...

Srinivasan, Lakshminarayan

2010-12-15

176

Energy-Efficient, Utility Accrual Real-Time Scheduling Under the Unimodal Arbitrary Arrival Model  

E-print Network

components also consume energy. The characteristics of the power/performance trade- offs of CMOS circuits. These uncertainties include transient and sustained overloads on the CPU (due to context dependent execution times

Paris-Sud XI, Université de

177

EVALUATION OF OPERATIONAL PROCEDURES FOR USING A TIME-BASED AIRBORNE INTER ARRIVAL SPACING TOOL  

Microsoft Academic Search

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

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

178

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1987 Annual Report.  

SciTech Connect

This project monitored the daily passage of smolts during the 1988 spring outmigration at two migrant traps; one each on the Snake and Clearwater 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. 10 figs, 15 tabs.

Buettner, Edwin W.; Nelson, V. Lance

1990-01-01

179

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

180

Practical and fast quantum random number generation based on photon arrival time relative to external reference  

NASA Astrophysics Data System (ADS)

We present a practical high-speed quantum random number generator, where the timing of single-photon detection relative to an external time reference is measured as the raw data. The bias of the raw data can be substantially reduced compared with the previous realizations. The raw random bit rate of our generator can reach 109 Mbps. We develop a model for the generator and evaluate the min-entropy of the raw data. Toeplitz matrix hashing is applied for randomness extraction, after which the final random bits are able to pass the standard randomness tests.

Nie, You-Qi; Zhang, Hong-Fei; Zhang, Zhen; Wang, Jian; Ma, Xiongfeng; Zhang, Jun; Pan, Jian-Wei

2014-02-01

181

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

182

Signal Processing 85 (2005) 177204 Time difference of arrival estimation of speech source in a  

E-print Network

.e. the received signals at the microphone array). In the dual-step approaches, the location estimate is obtained with a dual-step approach. In the preliminary stage a microphone array is used to extract the time difference scenarios where automated camera steering and tracking are required. Microphone arrays, which are usually

Gannot, Sharon

183

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

184

Post-Arrival Screening for Malaria in Asymptomatic Refugees Using Real-Time PCR  

PubMed Central

Malaria is a significant health risk to refugee populations originating from endemic areas, but there is little consensus on screening and/or treatment approaches for malaria in this population. Furthermore, detection of malaria in semi-immune asymptomatic refugees is limited by the sensitivity of diagnostic tests used for screening. We determined the prevalence of malaria by microscopy and real-time polymerase chain reaction (PCR) in a consecutive population of 324 asymptomatic refugees examined in Edmonton, Canada, during 2009–2010. Although all thick and thin blood smear results were negative, 10 subjects (3.1%) tested PCR positive for Plasmodium DNA. Interestingly, 6 of 10 PCR positive subjects are at risk of malaria relapse by P. vivax or P. ovale infections. These results suggest that appropriate guidelines for malaria screening should consider the risk of relapsing infections, and they highlight the potential usefulness of real-time PCR in the diagnosis of asymptomatic malaria. PMID:21212221

Matisz, Chelsea E.; Naidu, Prenilla; Shokoples, Sandra E.; Grice, Diane; Krinke, Valerie; Brown, Stuart Z.; Kowalewska-Grochowska, Kinga; Houston, Stan; Yanow, Stephanie K.

2011-01-01

185

OneBusAway: results from providing real-time arrival information for public transit  

Microsoft Academic Search

Public transit systems play an important role in combating traffic congestion, reducing carbon emissions, and promot- ing compact, sustainable urban communities. The usability of public transit can be significantly enhanced by providing good traveler information systems. We describe OneBus- Away, a set of transit tools focused on providing real-time ar- rival information for Seattle-area bus riders. We then present results

Brian Ferris; Kari Watkins; Alan Borning

2010-01-01

186

STRONG FIELD EFFECTS ON PULSAR ARRIVAL TIMES: CIRCULAR ORBITS AND EQUATORIAL BEAMS  

SciTech Connect

If a pulsar orbits a supermassive black hole, the timing of pulses that pass close to the hole will show a variety of strong field effects. To compute the intensity and timing of pulses that have passed close to a nonrotating black hole, we introduce here a simple formalism based on two 'universal functions', one for the bending of photon trajectories and the other for the photon travel time on these trajectories. We apply this simple formalism to the case of a pulsar in circular orbit that beams its pulses into the orbital plane. In addition to the 'primary' pulses that reach the receiver by a more-or-less direct path, we find that there are secondary and higher-order pulses. These are usually much dimmer than the primary pulses, but they can be of comparable or even greater intensity if they are emitted when pulsar is on the side of the hole furthest from the receiver. We show that there is a phase relationship of the primary and secondary pulses that is a probe of the strongly curved spacetime geometry. Analogs of these phenomena are expected in more general configurations, in which a pulsar in orbit around a hole emits pulses that are not confined to the orbital plane.

Wang Yan [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Jenet, Frederick A.; Creighton, Teviet; Price, Richard H. [Center for Gravitational Wave Astronomy and Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States)], E-mail: Richard.Price@utb.edu

2009-05-20

187

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

188

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1986 Annual Report.  

SciTech Connect

This project monitored the daily passage of smolts during the 1986 spring outmigration at two migrant traps, one each on the Snake and Clearwater rivers. Average migration rates for freeze-branded chinook salmon smolts were 28.2 km per day and 22.1 km per day for steelhead trout smolts between release sites and the head of Lower Granite Reservoir. The yearling chinook salmon migration begins in earnest when Salmon River discharge makes a significant rise in early to mid-April. Most yearling chinook salmon pass into Lower Granite Reservoir in April followed by passage of steelhead trout in May. Chinook salmon smolt recapture data from the Snake River trap suggest a strong dependence of migration rate on quantity of Snake and Salmon River discharge, although no statistical correlation exists at this time. Daily and seasonal descaling rates were calculated for each species at each trap. Rates were highest for hatchery steelhead trout, intermediate for yearling chinook salmon, and lowest for wild steelhead trout. Descaling rates were generally higher in 1986 than those observed in 1984 and 1985. 4 refs., 9 figs., 15 tabs.

Buettner, Edwin W.; Nelson, V. Lance

1987-09-01

189

Constraining the Size and Depth of a Shallow Crustal Magma Body at Newberry Volcano Using P-Wave Tomography and Finite-Difference Waveform Modeling  

NASA Astrophysics Data System (ADS)

Imaging magmatic systems improves our understanding of magma ascent and storage in the crust and contributes to hazard assessment. Seismic tomography reveals crustal magma bodies as regions of low velocity; however the ability of delay-time tomography to detect small, low-velocity bodies is limited by wavefront healing. Alternatively, crustal magma chambers have been identified from secondary phases including P and S wave reflections and conversions. We use a combination of P-wave tomography and finite-difference waveform modeling to characterize a shallow crustal magma body at Newberry Volcano, central Oregon. Newberry's eruptions are silicic within the central caldera and mafic on its periphery suggesting a central silicic magma storage system. The system may still be active with a recent eruption ~1300 years ago and a drill hole temperature of 256° C at only 932 m depth. A low-velocity anomaly previously imaged at 3-5 km beneath the caldera indicates either a magma body or a fractured pluton. With the goal of detecting secondary arrivals from a magma chamber beneath Newberry Volcano, we deployed a line of densely-spaced (~300 m), three-component seismometers that recorded a shot of opportunity from the High Lava Plains Experiment in 2008. The data record a secondary P-wave arrival originating from beneath the caldera. In addition we combine travel-time data from our 2008 experiment with data collected in the 1980's by the USGS for a P-wave tomography inversion to image velocity structure to 6 km depth. The inversion includes 16 active sources, 322 receivers and 1007 P-wave first arrivals. The tomography results reveal a high-velocity, ring-like anomaly beneath the caldera ring faults to 2 km depth that surrounds a shallow low-velocity region. Beneath 2.5 km high-velocity anomalies are concentrated east and west of the caldera. A central low-velocity body lies below 3 km depth. Tomographic inversions of synthetic data suggest that the central low-velocity body beneath 3 km depth is not well resolved and that, for example, an unrealistically large low-velocity body with a volume up to 72 km3 at 40% velocity reduction (representing 30±7% partial melt) could be consistent with the observed travel-times. We use the tomographically derived velocity structure to construct 2D finite difference models and include synthetic low-velocity bodies in these models to test various magma chamber geometries and melt contents. Waveform modeling identifies the observed secondary phase as a transmitted P-wave formed by delaying and focusing P-wave energy through the low-velocity region. We will further constrain the size and shape of the low-velocity region by comparing arrival times and amplitudes of observed and synthetic primary and secondary phases. Secondary arrivals provide compelling evidence for an active crustal magmatic system beneath Newberry volcano and demonstrate the ability of waveform modeling to constrain the nature of magma bodies beyond the limits of seismic tomography.

Beachly, M. W.; Hooft, E. E.; Toomey, D. R.; Waite, G. P.

2011-12-01

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

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1983-1984 Technical Report.  

SciTech Connect

Hatcheries released 9.3 million chinook salmon and 6.3 million steelhead smolts and presmolts upriver from Lower Granite Reservoir for migration In spring, 1984. We operated smolt monitoring traps at Whitebird from March 14 to May 12, Snake River from March 22 to May 15 and Clearwater from March 29 to May 13. Peak passage of yearling chinook salmon occurred the third week In April at both Whitebird and Snake River traps. Passage of steelhead was still increasing when high water stopped trapping in mid-May. Median migration rates for branded chinook salmon between release sites and Whitebird were 3, 17 and 15 miles/day for Rapid River, South Fork Salmon and Decker Flat smolts, respectively, an average of 11.6 miles/day. Average migration rate for these three groups between Whitebird and Snake River trap was 28 miles/day. Average migration rate between release sites and Snake River (the head of Lower Granite Reservoir) was 13.2 miles/day and from that point on through the reservoir to the dam, 1.9 miles/day. Salmon River discharge, when considered along with other environmental factors, had the greatest effect on migration rate of smolts branded both at hatcheries and at the Whitebird trap and migrating to the head of Lower Granite Reservoir. Migration rate for steelhead released from Dworshak Hatchery and recaptured at the Clearwater trap was 34 miles/day. Survival rates to the Snake River trap of branded chinook salmon smolts released at Hells Canyon Dam, Rapid River, South Fork Salmon and Decker Flat were 52%, 65%, 68% and 35%, respectively. Classical descaling, where at least 40% of the scales are missing from at least two of five areas on the side of a smolt, ranged from 0 to 5.3% at hatcheries for chinook salmon and was less than 1% for steelhead. Descaling rate often Increased about 1% at release sites. Classical descaling at Whitebird, Clearwater and Snake River traps averaged 4.5, 2.5 and 1.5% for chinook salmon, 2.1, 0.4 and 1.4% for wild steelhead and 8.7, 4.1 and 5.5% for hatchery steelhead, respectively. Scattered descaling, where at least 10% of scales are missing from at least one side of a fish, was always more extensive than was classical descaling, ranging from 2.5 times greater for Clearwater hatchery steelhead to 6.8 times greater for Clearwater wild steelhead. Mean total length of chinook salmon yearlings was the same at all the traps, i.e., 128 mm (117 mm fork length) + 1 mm. The largest chinook salmon smolts came from Dworshak National Fish Hatchery on the Clearwater River. Hatchery steelhead were smallest (2 = 203 mm) at the Clearwater trap and largest (2 = 239 mm) at the Whitebird trap. Wild steelhead were also smallest at Clearwater trap ({bar x} = 178 mm) and largest at Whitebird trap ({bar x} = 193 mm). Purse seining to evaluate rates of descaling before and after smolts passed Lower Granite Dam was largely ineffective since we were unable to catch sufficient numbers of smolts in the tailrace, and winds in the forebay area altered descaling rates in sampled smolts.

Scully, Richard J.; Buettner, Edwin W.

1985-12-01

192

Magnitude estimation using high-frequency acceleration of initial P-wave  

NASA Astrophysics Data System (ADS)

Recently various methods to estimate earthquake parameters (epicentral location and magnitude) have been proposed, and some of those are applied to an earthquake early warning system. For example, the method to estimate epicentral location using single station data (the B-delta method (Odaka et al., 2003) and the Principal component analysis (Meteorological Research Institute, 1985)) is used by Japan Meteorological Agency(JMA) EEW system and the Shinkansen EEW system. Improvement of its accuracy and rapidness is discussed by Noda et al., 2011. As for estimating a magnitude from the initial phase data, the method using the maximum amplitude (Odaka et al., 2003) and the ?c method (Wu and Kanamori, 2005) are proposed. The present JMA EEW and the Shinkansen EEW system use the maximum displacement amplitude for estimating the magnitude. On the other hand, Hoshiba et al. (2010) indicated that the maximum value of acceleration amplitude tends to appear earlier than that of displacement amplitude, thus the maximum magnitude may be estimated earlier by acceleration amplitude than by displacement. In this study, we examined a method to estimate the magnitude from the amplitude of vertical acceleration in order to improve rapidness of its estimation. 10342 K-NET waveform data of 190 earthquakes (M<3.9, focal depth <150km) were used for the analysis. First, we grouped seismic waveform data according to hypocentral distances and magnitudes, then we averaged time histories of vertical acceleration of each group to examine their features. As the result, we found that the amplitude of the very initial phase (about 0.5 sec after the arrival of P-wave) mainly depends not on magnitude, but on hypocentral distances. So as to reduce the effect of hypocentral distance, we divided the high-frequency (10-20 Hz) vertical acceleration time history by the amplitude value at 0.5 sec after the arrival of P-wave, and examined statistical relationship between the normalized value and the magnitude. It was found out that correlation between the normalized value and the magnitude is significantly high. For example, the relational expression between the magnitude and the normalized value at 1.5 sec after the arrival of P-wave is A = 0.0212 * e ^ (0.9075 * M) where A and M denote the normalized value and the magnitude. To validate the accuracy of this method, we calculate differences (RMS) between the magnitude published by JMA and the magnitude estimated from the relationship obtained above. In this case, estimation error is found to be 0.6. It is obvious that high-frequency acceleration waveform is superposition of various waves radiated from fracture surface, and growth in the amplitude of observed acceleration corresponds to spreading of the fault area of rupture front. That is, it is thought that the magnitude estimated by this method using high-frequency acceleration is equivalent to the magnitude obtained by the conventional technique using low-frequency seismic data. Therefore, it would be possible to estimate the growth of the magnitude earlier by using acceleration data characterized by rapidness.

Korenaga, M.; Yamamoto, S.; Noda, S.; Iwata, N.

2011-12-01

193

The upper crustal P-wave velocity structure of Newberry volcano, Central Oregon.  

E-print Network

?? The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected… (more)

Beachly, Matthew William

2011-01-01

194

The Upper Crustal P-wave Velocity Structure of Newberry Volcano, Central Oregon .  

E-print Network

??The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected in… (more)

Beachly, Matthew William, 1986-

2011-01-01

195

Landing together: how flocks arrive at a coherent action in time and space in the presence of perturbations  

E-print Network

Collective motion is abundant in nature, producing a vast amount of phenomena which have been studied in recent years, including the landing of flocks of birds. We investigate the collective decision making scenario where a flock of birds decides the optimal time of landing in the absence of a global leader. We introduce a simple phenomenological model in the spirit of the statistical mechanics-based self-propelled particles (SPP-s) approach to interpret this process. We expect that our model is applicable to a larger class of spatiotemporal decision making situations than just the landing of flocks (which process is used as a paradigmatic case). In the model birds are only influenced by observable variables, like position and velocity. Heterogeneity is introduced in the flock in terms of a depletion time after which a bird feels increasing bias to move towards the ground. Our model demonstrates a possible mechanism by which animals in a large group can arrive at an egalitarian decision about the time of swit...

Ferdinandy, Bence; Abel, Daniel; Vicsek, Tamas; 10.1016/j.physa.2011.10.010

2012-01-01

196

One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion  

SciTech Connect

A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299 Degree-Sign were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

Supardiyono; Santosa, Bagus Jaya [Physics Department, Faculty of Mathematics and Natural Sciences, State University of Surabaya, Surabaya (Indonesia) and Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia); Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia)

2012-06-20

197

Tomographic P-wave velocity images of the Loma Prieta earthquake asperity  

SciTech Connect

Tomographic inversion is applied to delay times from local earthquakes to image 3-D velocity variations surrounding the main rupture of the 1989 Loma Prieta earthquake. The 55{times}45 square km region is represented by blocks of 1 km per side laterally and by 8 layers of varying thickness to 18 km depth. High quality P-wave arrival times recorded on the USGS CALNET array from 549 crustal earthquakes with depths of 0 to 25 km were used as sources. Preliminary results note several velocity variations (5-12%) that correlate with specific characteristics of the 1989 rupture. These include prominent high-velocity anomalies near the mainshock hypocenter and prominent low-velocity anomalies where the dip of the San Andreas fault appears to change significantly. The termination of prominent low velocity features existing primarily in the hanging wall to depths of 7-9 km, correlates with the top of the rupture zone. High-velocity variations along the fault dominate where aftershock activity is high. The high velocity anomaly located at depth along the fault is interpreted as imaging the asperity on which the Loma Prieta earthquake occurred.

Lees, J.M. (Yale Univ., New Haven, CT (USA))

1990-08-01

198

P-Wave Electron-Hydrogen Scattering  

NASA Technical Reports Server (NTRS)

A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off factors has been used to calculate P-wave phase shifts for electron-hydrogen scattering. This approach gives the direct r(exp -4) potential and a non-local optical potential which is definite. The resulting phase shifts have rigorous lower bounds and the convergence is much faster than those obtained without the modification of the target function. Final results will be presented at the conference.

Bhtia, Anand

2012-01-01

199

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

E-print Network

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 $34.9 \\pm 7.1$ degrees elongation from the Sun with J-maps constructed using the SATPLOT tool, resulting in prediction lead times of $-26.4 \\pm 15.3$ hours. The geometrical models we use assume different CME front shapes (Fixed-$\\Phi$, Harmonic Mean, S...

Möstl, C; 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

2014-01-01

200

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

201

Analysis of teleseismic P waves with a 5200-station array in Long Beach, California: Evidence for an abrupt boundary to Inner Borderland rifting  

NASA Astrophysics Data System (ADS)

analyze teleseismic P waves from four Mw ? 6.5 earthquakes recorded by a petroleum industry survey in Long Beach, California. The survey used a 2-D array with up to 5200 seismometers, 120 m mean spacing, and 7 - 10 km aperture. At frequencies near 1 Hz, P wave travel times and amplitudes exhibit coherent lateral variations over scales as short as ~400 m, including locally delayed travel times and increased amplitudes at the crest of the Long Beach anticline. Deeper heterogeneity is indicated by P wave phase velocities that deviate from reference model predictions for events from southwestern azimuths. We postulate that a sharp northeastward increase in Moho depth from the Inner Borderland (IB) to mainland southern California causes the anomalous phase velocities. Elastic forward modeling finds the travel times are fit well by a Moho that dips 65° to the northeast and flattens ~10 km southwest of the Newport-Inglewood fault zone. Constraining the felsic thickness of mainland crust to 28 km requires an 8 km thick layer with a P-velocity of 7 km/s beneath it, which could result from basal accretion of former Farallon ocean crust or magmatic underplating during Miocene volcanism. Forward models with a 65° Moho dip predict a P-to-s conversion with a phase velocity of ~5 km/s. Deconvolution of the array's mean P wave signal isolates a similar later arriving phase. The steep crust thickness transition supports a locally abrupt boundary to IB rifting. Our results highlight the utility of dense short-period arrays for passive imaging at near surface to uppermost mantle depths.

Schmandt, Brandon; Clayton, Robert W.

2013-10-01

202

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

203

Anomalous delays of teleseismic P waves in Yellowstone National Park  

USGS Publications Warehouse

TELESEISMIC P waves recorded by a short-period seismic network, comprising 12 stations, in Yellowstone National Park, show anomalous delays of 1-2 s in their travel times in the central region of the park relative to the surrounding area. To explain this phenomenon, I propose that a substantial body of low velocity material is present beneath the park, with horizontal dimensions of several tens of kilometres; it may be the magma chamber associated with the volcanism of Yellowstone (ref. 1, and G. P. Eaton et al., unpublished). ?? 1975 Nature Publishing Group.

Iyer, H. M.

1975-01-01

204

Quench-Induced Floquet Topological p-Wave Superfluids  

NASA Astrophysics Data System (ADS)

Ultracold atomic gases in two dimensions tuned close to a p-wave Feshbach resonance were expected to exhibit topological superfluidity, but these were found to be experimentally unstable. We show that one can induce a topological Floquet superfluid if weakly interacting atoms are brought suddenly close ("quenched") to such a resonance, in the time before the instability kicks in. The resulting superfluid possesses Majorana edge modes, yet differs from a conventional Floquet system as it is not driven externally. Instead, the periodic modulation is self-generated by the dynamics.

Foster, Matthew S.; Gurarie, Victor; Dzero, Maxim; Yuzbashyan, Emil A.

2014-08-01

205

Quench-induced Floquet topological p-wave superfluids.  

PubMed

Ultracold atomic gases in two dimensions tuned close to a p-wave Feshbach resonance were expected to exhibit topological superfluidity, but these were found to be experimentally unstable. We show that one can induce a topological Floquet superfluid if weakly interacting atoms are brought suddenly close ("quenched") to such a resonance, in the time before the instability kicks in. The resulting superfluid possesses Majorana edge modes, yet differs from a conventional Floquet system as it is not driven externally. Instead, the periodic modulation is self-generated by the dynamics. PMID:25170716

Foster, Matthew S; Gurarie, Victor; Dzero, Maxim; Yuzbashyan, Emil A

2014-08-15

206

Evidence for a bimaterial interface along the Mudurnu segment of the North Anatolian Fault Zone from polarization analysis of P waves  

NASA Astrophysics Data System (ADS)

We present results on imaging contrast of seismic velocities across the Mudurnu segment of the North Anatolian Fault Zone (NAFZ) in northwestern Turkey with polarization analysis of early P waveforms generated by near-fault seismicity and recorded by near-fault stations. The analysis uses changes in motion polarity from fault-normal to source-receiver directions to identify early-arriving fault zone head waves on the slow side of the fault, and measure the arrival times of the head and direct P waves. The moveout between the head and direct waves with increasing source-receiver distance along the fault provides an estimate of the average contrast of seismic velocities across the fault. The results indicate that the average contrast of P wave velocities across the Mudurnu segment of the NAFZ is at least 6%, with the south block being the faster side. The findings provide a basis for deriving improved event locations, focal mechanisms and estimated shaking hazard associated with earthquakes on the fault. The analysis technique can be used in other fault zones monitored with sparse seismic instrumentation.

Bulut, Fatih; Ben-Zion, Yehuda; Bohnhoff, Marco

2012-04-01

207

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. PMID:25006682

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

208

Holographic p-wave Superconductor with Disorder  

E-print Network

We implement the effects of disorder on a holographic p-wave superconductor by introducing a random chemical potential which defines the local energy of the charge carriers. Since there are various possibilities for the orientation of the vector order parameter, we explore the behavior of the condensate in the parallel and perpendicular directions to the introduced disorder. We clarify the nature of various branches representing competing solutions and construct the disordered phase diagram. We find that moderate disorder enhances superconductivity as determined by the value of the condensate. The disorder we introduce is characterized by its spectral properties, and we also study its influence on the spectral properties of the condensate and charge density. We find fairly universal responses of the resulting power spectra characterized by linear functions of the disorder power spectrum.

Arean, Daniel; Zayas, Leopoldo A Pando; Landea, Ignacio Salazar; Scardicchio, Antonello

2014-01-01

209

A holographic p-wave superfluid  

E-print Network

In the probe limit, we numerically construct a holographic p-wave superfluid model in the 4D and 5D AdS black holes coupled to a Maxwell-complex vector field. We find that, for the condensate with the fixed superfluid velocity, the results are similar to the s-wave cases in both 4D and 5D spacetimes. In particular, "The Cave of Winds" and the phase transition always being the second order take place in the 5D case. Moreover, we find the second-first order translating point $\\frac{S_y}{\\mu}$ increases with the mass squared. Furthermore, for the supercurrent with the fixed temperature, the results agree with the GL prediction near the critical temperature. In addition, this complex vector superfluid model is still a generalization of the SU(2) superfluid model, and also provides a holographic realization of the $He_3$ superfluid system.

Wu, Ya-Bo; Zhang, Wen-Xin; Zhang, Cheng-Yuan; Lu, Jian-Bo; Yu, Fang

2014-01-01

210

P wave radial anisotropy tomography of the upper mantle beneath the North China Craton  

NASA Astrophysics Data System (ADS)

present the first P wave radial anisotropy tomography of the crust and upper mantle beneath the North China Craton (NCC), determined using a large number of high-quality arrival-time data of local earthquakes and teleseismic events. Our results show a prominent high-velocity (high-V) anomaly down to ˜250 km depth beneath the Ordos block, a high-V anomaly in the mantle transition zone beneath the eastern NCC, and a low-velocity (low-V) anomaly down to ˜300 km depth beneath the Trans-North China Orogen (TNCO). The Ordos block exhibits significant negative radial anisotropy (i.e., vertical Vp > horizontal Vp), suggesting that its cratonic lithosphere has kept the frozen-in anisotropy formed by vertical growth via high-degree melting mantle plume in the early Earth. Prominent low-V anomalies with positive radial anisotropy (i.e., horizontal Vp > vertical Vp) exist beneath the Qilian and Qaidam blocks down to ˜400 km depth, suggesting that the horizontal material flow resulting from the Tibetan Plateau is blocked by the Ordos thick lithosphere. Beneath the eastern NCC, high-V anomalies with negative radial anisotropy exist in the upper mantle, possibly reflecting sinking remains of the Archean cratonic lithosphere. A high-V anomaly with positive radial anisotropy is revealed in the mantle transition zone under the eastern NCC, which reflects the stagnant Pacific slab.

Wang, Jian; Wu, Huohua; Zhao, Dapeng

2014-06-01

211

32ND INTERNATIONAL COSMIC RAY CONFERENCE, BEIJING 2011 Arrival of an Interplanetary Shocks at the Earth: a Real-Time Forecast Based on ACE Space-  

E-print Network

at the Earth: a Real-Time Forecast Based on ACE Space- craft Data S.A. STARODUBTSEV1 , V.G. GRIGORYEV1 , I by the ACE spacecraft. 291 #12;STARODUBTSEV et al. ARRIVAL OF AN INTERPLANETARY SHOCKS AT THE EARTH 2 Data

Usoskin, Ilya G.

212

Velocity ratio variations in the source region of earthquake swarms in NW Bohemia obtained from arrival time double-differences  

NASA Astrophysics Data System (ADS)

Crustal earthquake swarms are an expression of intensive cracking and rock damaging over periods of days, weeks or month in a small source region in the crust. They are caused by longer lasting stress changes in the source region. Often, the localized stressing of the crust is associated with fluid or gas migration, possibly in combination with pre-existing zones of weaknesses. However, verifying and quantifying localized fluid movement at depth remains difficult since the area affected is small and geophysical prospecting methods often cannot reach the required resolution. We apply a simple and robust method to estimate the velocity ratio between compressional (P) and shear (S) waves (vP/vS-ratio) in the source region of an earthquake swarm. The vP/vS-ratio may be unusual small if the swarm is related to gas in a porous or fractured rock. The method uses arrival time difference between P and S waves observed at surface seismic stations, and the associated double differences between pairs of earthquakes. An advantage is that earthquake locations are not required and the method seems lesser dependent on unknown velocity variations in the crust outside the source region. It is, thus, suited for monitoring purposes. Applications comprise three natural, mid-crustal (8-10 km) earthquake swarms between 1997 and 2008 from the NW-Bohemia swarm region. We resolve a strong temporal decrease of vP/vS before and during the main activity of the swarm, and a recovery of vP/vS to background levels at the end of the swarms. The anomalies are interpreted in terms of the Biot-Gassman equations, assuming the presence of oversaturated fluids degassing during the beginning phase of the swarm activity.

Dahm, Torsten; Fischer, Tomas

2014-02-01

213

Comparison of P-Wave and S-Wave Reflection Surveying Effectiveness for Detection of Mine-Related Subsidence Activity Beneath a Heavily Traveled Roadway  

NASA Astrophysics Data System (ADS)

We acquired high-resolution multicomponent seismic reflection data along an undermined 2200 ft (671 m) section of Interstate highway 70 (I-70) in eastern Ohio, in order to identify areas of active subsidence or soil piping into subsurface collapse features. This paper presents results from research conducted: 1) to investigate potential advantages and disadvantages associated with near-surface P- and S-wave reflection surveys, and 2) to determine the subsidence detection potential of common-mode P- and S-wave data components acquired in the study area. P-wave data have traditionally been acquired during shallow reflection surveys, however, the number of reports concerning shallow S-wave surveys is relatively small, and very few reports concerning the concurrent acquisition and analysis of P- and S-wave reflection data exist. Although S-wave reflections from the top-of-bedrock (located above the coal mine and targeted for subsidence detection purposes) were consistently observed in both XX component (inline-inline, SV-SV) and YY component (crossline-crossline, SH-SH) data, surface wave noise resulted in the optimum reflection window of XX data being relatively narrow. Stacks produced using YY data had a higher signal-to-noise ratio and better imaged the target horizon than those produced using XX data. Whereas S-waves were relatively insensitive to changes in overburden moisture content, P-wave reflections from the top-of-saturated-overburden (located above bedrock) were recorded in ZZ component (vertical-vertical, P-P) data. The arrival times of P-wave reflections and the characteristics of the recorded noise modes made it difficult to process and use P-wave reflections from this interface. P-wave events from deeper impedance contrasts were not observed in field data due to several factors: surface wave and air wave noise, a high P-wave reflection coefficient at the top-of-saturated-overburden, low P-wave reflection coefficients at deeper interfaces, and interference effects/resolution issues. Calculations suggest that the resolution of S-waves in the study area dry overburden is more than 1.7 times that of P-waves, and that the resolution of S-waves in the study area saturated overburden is more than 4.5 times that of P-waves. Given the study area subsurface conditions and acquired data characteristics, areas of the subsurface where subsidence processes have been active could be most accurately delineated through the processing and interpretation of YY (relative to XX and ZZ) data. Processed YY data indicate that the bedrock horizon is significantly disrupted due to mine-related subsidence processes at numerous locations along the roadway in the study area. Hence, these locations are regarded as having a relatively high risk for future mine-related surface failure.

Guy, E. D.; Daniels, J. J.

2002-12-01

214

Teleseismic P wave coda from oceanic trench and other bathymetric features  

NASA Astrophysics Data System (ADS)

Teleseismic P waves are essential for studying rupture processes of great earthquakes, either in the back projection method or in finite fault inversion method involving of quantitative waveform modeling. In these studies, P waves are assumed to be direct P waves generated by localized patches of the ruptured fault. However, for some oceanic earthquakes happening near the subductiontrenches or mid-ocean ridges, we observed strong signals between P and PP are often observed on theat telseseismic networkdistances. These P wave coda signals show strong coherence and their amplitudes are sometimes comparable with those of the direct P wave or even higher for some special frequenciesfrequency band. With array analysis, we find that the coda's slowness is very close to that of the direct P wave, suggesting that they are generated near the source region. As the earthquakes occur near the trenches or mid-ocean ridges which are both featured by rapid variation of bathymetry, the coda waves are very probably generated by the scattered surface wave or S wave at the irregular bathymetry. Then, we apply the realistic bathymetry data to calculate the 3D synthetics and the coda can be well predicted by the synthetics. So the topography/bathymetry is confirmed to be the main source of the coda. The coda waves are so strong that it may affect the imaging rupture processes of ocean earthquakes, so the topography/bathymetry effect should be taken into account. However, these strong coda waves can also be used utilized to locate the oceanic earthquakes. The 3D synthetics demonstrate that the coda waves are dependent on both the specific bathymetry and the location of the earthquake. Given the determined bathymetry, the earthquake location can be constrained by the coda, e.g. the distance between trench and the earthquake can be determine from the relative arrival between the P wave and its coda which is generated by the trench. In order to locate the earthquakes using the bathymetry, it is indispensible to get all the 3D synthetics with possible different horizontal locations and depths of the earthquakes. However, the computation will be very expensive if using the numerical simulation in the whole medium. Considering that the complicated structure is only near the source region, we apply ray theory to interface full wave field from spectral-element simulation to get the teleseismic P waves. With this approach, computation efficiency is greatly improved and the relocation of the earthquake can be completed more efficiently. As for the relocation accuracy, it can be as high as 10km for the earthquakes near the trench. So it provides us another, sometimes most favorable, method to locate the ocean earthquakes with ground-truth accuracy.

Wu, W.; Ni, S.

2012-12-01

215

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

216

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

217

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA  

Microsoft Academic Search

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the first arrival of the airborne fission products 131-I, 132-I, 132-Te, 134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristic gamma

J. Diaz Leon; D. A. Jaffe; J. Kaspar; A. Knecht; M. L. Miller; R. G. H. Robertson; A. G. Schubert

2011-01-01

218

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA  

Microsoft Academic Search

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17–18 March 2011, we registered the first arrival of the airborne fission products 131I, 132I, 132Te, 134Cs, and 137Cs in Seattle, WA, USA, by identifying their characteristic gamma

J. Diaz Leon; D. A. Jaffe; J. Kaspar; A. Knecht; M. L. Miller; R. G. H. Robertson; A. G. Schubert

2011-01-01

219

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

220

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA  

E-print Network

We report results of air monitoring started due to the recent natural catastrophe on March 11, 2011 in Japan and the severe ensuing damage to the Fukushima nuclear reactor complex. On March 17-18, 2011 we detected the first arrival of the airborne fission products 131-I, 132-I, 132-Te, 134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. The highest detected activity to date is <~32 mBq/m^3 of 131-I.

Leon, J Diaz; Knecht, A; Miller, M L; Robertson, R G H; Schubert, A G

2011-01-01

221

Arrival time calculation for interplanetary coronal mass ejections with circular fronts and application to STEREO observations of the 2009 February 13 eruption  

E-print Network

A goal of the NASA 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 assumptions of constant velocity and direction. We show that for the slow (350 km/s) 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 hours 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 ho...

Möstl, C; Lugaz, N; Farrugia, C J; Davies, J A; Temmer, M; Veronig, A M; Harrison, R; Crothers, S; Luhmann, J G; Galvin, A B; Zhang, T L; Baumjohann, W; Biernat, H K

2011-01-01

222

Arrival times of Flare/Halo CME associated shocks at the Earth: comparison of the predictions of three numerical models with these observations  

NASA Astrophysics Data System (ADS)

The arrival times at L1 of eleven travelling shocks associated both with X-ray flaring and with halo CMEs recorded aboard SOHO/LASCO have been considered. Close to the Sun the velocities of these events were estimated using either Type II radio records or CME speeds. Close to the Earth the shocks were detected in the data of various solar wind plasma, interplanetary magnetic field (IMF) and energetic particle experiments aboard SOHO, ACE, WIND, INTERBALL-1 and IMP-8. The real-time shock arrival predictions of three numerical models, namely the Shock Time of Arrival Model (STOA), the Interplanetary Shock Propagation Model (ISPM) and the Hakamada-Akasofu-Fry Solar Wind Model (HAFv.2) were tested against these observations. This is the first time that energetic protons (tens of keV to a few MeV) have been used to complement plasma and IMF data in validating shock propagation models. The models were all generally successful in predicting shock arrivals. STOA provided the smallest values of the "predicted minus measured" arrival times and displayed a typical predictive precision better than about 8 h. The ratio of the calculated standard deviation of the transit times to Earth to the standard deviation of the measurements was estimated for each model (treating interacting events as composite shocks) and these ratios turned out to be 0.60, 1.15 and 1.02 for STOA, ISPM and HAFv.2, respectively. If an event in the sample for which the shock velocity was not well known is omitted from consideration, these ratios become 0.36, 0.76 and 0.81, respectively. Larger statistical samples should now be tested. The ratio of the in situ shock velocity and the "Sun to L1" transit velocity (Vsh /Vtr) was in the range of 0.7 0.9 for individual, non-interacting, shock events. HAFv.2 uniquely provided information on those changes in the COBpoint (the moving Connection point on the shock along the IMF to the OBserver) which directly influenced energetic particle rise times. This model also illustrated the non-uniform upstream conditions through which the various shocks propagated; furthermore it simulated shock deformation on a scale of fractions of an AU. On the spatial scale (300 RE ), where near-Earth spacecraft are located, the passing shocks, in conformity with the models, were found to be locally planar. The shocks also showed tilting relative to the Sun-Earth line, probably reflecting the inherent directionality associated with their solar origin.

McKenna-Lawlor, S. M. P.; Dryer, M.; Smith, Z.; Kecskemety, K.; Fry, C. D.; Sun, W.; Deehr, C. S.; Berdichevsky, D.; Kudela, K.; Zastenker, G.

2002-07-01

223

Seismic Imaging of a Bimaterial Interface Along the Hayward Fault, CA, with Fault Zone Head Waves and Direct P Arrivals  

NASA Astrophysics Data System (ADS)

We observe fault zone head waves (FZHW) that are generated by and propagate along a roughly 80 km section of the Hayward fault in the San Francisco Bay area. Moveout values between the arrival times of FZHW and direct P waves are used to obtain average P-wave velocity contrasts across different sections of the fault. The results are based on waveforms generated by more than 5,800 earthquakes and recorded at up to 12 stations of the Berkeley digital seismic network (BDSN) and the Northern California seismic network (NCSN). Robust identification of FZHW requires the combination of multiple techniques due to the diverse instrumentation of the BDSN and NCSN. For single-component short-period instruments, FZHW are identified by examining sets of waveforms from both sides of the fault, and finding on one (the slow) side emergent reversed-polarity arrivals before the direct P waves. For three-component broadband and strong-motion instruments, the FZHW are identified with polarization analysis that detects early arrivals from the fault direction before the regular body waves which have polarizations along the source-receiver backazimuth. The results indicate average velocity contrasts of 3-8 % along the Hayward fault, with the southwest side having faster P wave velocities in agreement with tomographic images. A systematic moveout between the FZHW and direct P waves for about a 80 km long fault section suggests a single continuous interface in the seismogenic zone over that distance. We observe some complexities near the junction with the Calaveras fault in the SE-most portion and near the city of Oakland. Regions giving rise to variable FZHW arrival times can be correlated to first order with the presence of lithological complexity such as slivers of high-velocity metamorphic serpentinized rocks and relatively distributed seismicity. The seismic velocity contrast and geological complexity have important implications for earthquake and rupture dynamics of the Hayward fault, including a statistically preferred propagation direction of earthquake ruptures to the SE.

Allam, A. A.; Ben-Zion, Y.; Peng, Z.

2014-02-01

224

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA  

E-print Network

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the first arrival of the airborne fission products 131-I, 132-I, 132-Te, 134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. We measured the evolution of the activities over a period of 23 days at the end of which the activities had mostly fallen below our detection limit. The highest detected activity amounted to 4.4 +/- 1.3 mBq/m^3 of 131-I on 19-20 March.

J. Diaz Leon; D. A. Jaffe; J. Kaspar; A. Knecht; M. L. Miller; R. G. H. Robertson; A. G. Schubert

2011-03-24

225

A scheme for a shot-to-shot, femtosecond-resolved pulse length and arrival time measurement of free electron laser x-ray pulses that overcomes the time jitter problem between the FEL and the laser  

NASA Astrophysics Data System (ADS)

The recent entry of X-ray free electron lasers (FELs) to all fields of physics has created an enormous need, both from scientists and operators, for better characterization of the beam created by these facilities. Of particular interest is the measurement of the arrival time of the FEL pulse relative to a laser pump, for pump-probe experiments, and the measurement of the FEL pulse length. This article describes a scheme that corrects one of the major sources of uncertainty in these types of measurements, namely the jitter in the arrival time of the FEL relative to an experimental laser beam. The setup presented here uses a combination of THz streak cameras and a spectral encoding setup to reduce the effect of an FEL's jitter, leaving the pulse length as the only variable that can affect the accuracy of the pulse length and arrival time measurement. A discussion of underlying principles is also provided.

Jurani?, P. N.; Stepanov, A.; Peier, P.; Hauri, C. P.; Ischebeck, R.; Schlott, V.; Radovi?, M.; Erny, C.; Ardana-Lamas, F.; Monoszlai, B.; Gorgisyan, I.; Patthey, L.; Abela, R.

2014-03-01

226

Respiration affects on P wave alignment and averaging  

Microsoft Academic Search

Root-mean-square values of the residual signals between a P wave template and individual P waves were computed and a tachogram was made. Using Autoregressive (AR) modelling, a major spectral peak was observed at 0.2 Hz for both this tachogram and the respiratory volume signal. A similiar spectrum was obtained from the RMS tachogram of the isoelectric signal segments prior to

M. C. Saki; Y. Z. Ider; B. Ozin; A. Oto

1992-01-01

227

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

228

P-Wave Holographic Insulator/Superconductor Phase Transition  

E-print Network

Using a five dimensional 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 zero temperature limit of the p-wave holographic superconductor in four dimensions.

Amin Akhavan; Mohsen Alishahiha

2010-11-29

229

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

230

Repeatable timing of northward departure, arrival and breeding in Black-tailed Godwits Limosa l. limosa , but no domino effects  

Microsoft Academic Search

When early breeding is advantageous, migrants underway to the breeding areas may be time stressed. The timing of sequential\\u000a events such as migration and breeding is expected to be correlated because of a “domino effect”, and would be of particular\\u000a biological importance if timings are repeatable within individuals between years. We studied a colour-marked population of\\u000a Black-tailed Godwits Limosa l.

Pedro M. Lourenço; Rosemarie Kentie; Julia Schroeder; Niko M. Groen; Jos C. E. W. Hooijmeijer; Theunis Piersma

231

An Approach for Performance Analysis of Discrete-Time Finite Capacity Open Queuing Network with Correlated arrivals  

E-print Network

1 An Approach for Performance Analysis of Discrete-Time Finite Capacity Open Queuing Network in [5, 9]. We have extended the approach of [5] for the analysis of general open networks of discrete buffer queue. Approaches have been proposed for the performance analysis of discrete-time, finite buffer

Singh Yatindra Nath

232

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

233

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

234

Assessment of performance of the inter-arrival time algorithm to identify ice shattering artifacts in cloud particle probes measurements  

NASA Astrophysics Data System (ADS)

Shattering presents a serious obstacle to current airborne in-situ methods of characterizing the microphysical properties of ice clouds. Small shattered fragments result from the impact of natural ice crystals with the forward parts of aircraft-mounted measurement probes. The presence of these shattered fragments may result in a significant overestimation of the measured concentration of small ice crystals, contaminating the measurement of the ice particle size distribution (PSD). One method of identifying shattered particles is to use an interarrival time algorithm. This method is based on the assumption that shattered fragments form spatial clusters that have short interarrival times between particles, relative to natural particles, when they pass through the sample volume of the probe. The interarrival time algorithm is a successful technique for the classification of shattering artifacts and natural particles. This study assesses the limitations and efficiency of the interarrival time algorithm. The analysis has been performed using simultaneous measurements of 2-D optical array probes with the standard and antishattering "K-tips" collected during the Airborne Icing Instrumentation Experiment (AIIE). It is shown that the efficiency of the algorithm depends on ice particle size, concentration and habit. Additional numerical simulations indicate that the effectiveness of the interarrival time algorithm to eliminate shattering artifacts can be significantly restricted in some cases. Improvements to the interarrival time algorithm are discussed.

Korolev, A.; Field, P. R.

2014-10-01

235

Detection of the electrocardiogram P-wave using wavelet analysis  

SciTech Connect

Since wavelet analysis is an effective tool for analyzing transient signals, we studied its feature extraction and representation properties for events in electrocardiogram (EKG) data. Significant features of the EKG include the P-wave, the QRS complex, and the T-wave. For this paper the feature that we chose to focus on was the P-wave. Wavelet analysis was used as a pre-processor for a backpropagation neural network with conjugate gradient learning. The inputs to the neural network were the wavelet transforms of EKGs at a particular scale. The desired output was the location of the P-wave. The results were compared to results obtained without using the wavelet transform as a pre-processor.

Anant, K.S.; Rodrigue, G.H. [California Univ., Davis, CA (United States). Dept. of Applied Science]|[Lawrence Livermore National Lab., CA (United States); Dowla, F.U. [Lawrence Livermore National Lab., CA (United States)

1994-01-01

236

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

237

Detection of the electrocardiogram P-wave using wavelet analysis  

NASA Astrophysics Data System (ADS)

Since wavelet analysis is an effective tool for analyzing transient signals, we studied its feature extraction and representation properties for events in electrocardiogram (EKG) data. Significant features of the EKG include the P-wave, the QRS complex, and the T-wave. For this paper the feature that we chose to focus on was the P-wave. Wavelet analysis was used as a preprocessor for a backpropagation neural network with conjugate gradient learning. The inputs to the neural network were the wavelet transforms of EKGs at a particular scale. The desired output was the location of the P-wave. The results were compared to results obtained without using the wavelet transform as a preprocessor.

Anant, Kanwaldip S.; Dowla, Farid U.; Rodrigue, Garry H.

1994-03-01

238

Determination of three-dimensional velocity anomalies under a seismic array using first P arrival times from local earthquakes 1. A homogeneous initial model  

Microsoft Academic Search

Geiger's method of locating local earthquakes has been extended to include the effect of P velocity variation along the ray paths in three dimensions. The crustal structure was modeled by rectangular blocks, and a parameter was assigned to each block describing the perturbation of P wave slowness in the block. On the basis of an initial model, a set of

Keiiti Aki; W. H. K. Lee

1976-01-01

239

A point process can be characterized by a sequence of durations(inter-arrival times). This research  

E-print Network

stationary sequence. However, the trade durations exhibits intraday seasonality. � Preprocess data by fitting a deterministic trend by Smoothing Spline Preprocessing: Benchmark Models: (2) Negative log-likelihood on the test with regression to capture long memory. -0.3-0.2-0.10.00.10.20.30.4 Moving Average Intraday Mean Trend clock time

240

A 3-D P wave velocity model of the crust and uppermost mantle of the Mariana volcanic arc  

NASA Astrophysics Data System (ADS)

As part of the Izu-Bonin-Mariana subduction factory project, a 3-D seismic refraction survey was acquired in 2002 over the Mariana volcanic arc between 14.5 and 18.5 degrees N using a combination of ocean-bottom seismometers, Reftek receivers on land, and large airgun shots from the R/V Maurice Ewing. First arrival travel times have been combined with similar data from an approximately east-west 2-D airgun refraction profile across the arc acquired by the JAMSTEC R/V Kaiyo using ocean-bottom seismometers spaced at intervals of approximately 5 km. We inverted these 277,000 travel times for a 3-D subsurface P wave velocity model using isotropic iterative first arrival seismic tomography (FAST). Forward travel times were calculated through a 500 m model grid, and the inverted model velocities were recovered in 1000 m cubic cells. The starting velocity model did not vary laterally beneath a rugged seafloor interface, which was fixed in subsequent iterations, and a 0-1250 m-thick sediment layer that was introduced in areas where the water depth exceeded 1000 m. The sediment layer simulated well deposits both on the flanks of the volcanoes and in the deep ocean basin, was updated in subsequent iterations of the inversion, and served to remove unrealistic small-scale structure in the final model. After nine iterations of the non-linear inversion, the RMS traveltime residual was reduced from 0.672 s to 0.127 s, equivalent to a normalised chi-squared value of 1.0. First arrival tomography does not typically recover sharp velocity contrasts at deep interfaces such as the Moho. Therefore in our preliminary interpretations we have employed the 7.6 km/s isovelocity contour as a proxy for the location of the Moho. The thickness of the igneous forearc crust decreases from 14 km in the north of the survey area to 9 km in the south. The Eocene arc, which is no longer active, exhibits an igneous crustal thickness of 21-24 km with much of this variability associated with the topography of the volcanic edifices. An 18-22 km thick igneous crust characterizes the 3-4 Ma active Mariana arc, which is located approximately 40 km west of the inactive Eocene arc. P wave velocities within the upper crust of the active arc appear to be systematically lower than in the inactive arc, by approximately 450 m/s. At a depth of 15 km, in contrast, velocities are around 350 m/s higher in the active arc. These results suggest an evolution of arc structure with increasing age: closure of fractures and porosity in the upper crust through hydrothermal circulation and a reduction in the mafic character of the mid-lower crust, presumably as a result of some degree of crustal differentiation.

Calvert, A. J.; Klemperer, S. L.; Takahashi, N.; Kerr, B. C.

2005-12-01

241

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

242

Frequency dependent P-wave speed in a porous medium with aligned fractures  

NASA Astrophysics Data System (ADS)

In an elastic medium, fractures can be modeled as thin layers, the elastic stiffnesses of which approach zero as the volume fraction of the fractures hf-->0. This yields linear slip theory [M. Schoenberg, J. Acoust. Soc. Am. 68, 1516-1521 (1980)], shown to be a robust way to account for the acoustic effect of fracturing. From Norris' [J. Acoust. Soc. Am. 94, 359-370 (1993)] dispersion relation for alternating porous layers, fractures must be modeled similarly in porous media. However, another fracture parameter of great interest is permeability. If fracture permeability is taken to be O(hf-1) or taken to be independent of hf, one arrives at a dispersion relation for the fast P-wave dependent on porous background properties and a real excess compliance which takes the fractures into account. However, if fracture permeability is assumed to be small, and is taken to be O(hf), the P-wave dispersion dependence on background parameters remains the same, but the term accounting for the fractures is frequency dependent. Only in the zero frequency limit does this result agree with that of the other two cases.

Brajanovski, Miroslav; Gurevitch, Boris; Schoenberg, Michael

2001-05-01

243

Sub-femtosecond precision measurement of relative X-ray arrival time for free-electron lasers  

NASA Astrophysics Data System (ADS)

Today's brightest coherent X-ray sources, X-ray free-electron lasers, produce ultrafast X-ray pulses for which full-width at half-maximum durations as short as 3?fs have been measured. There has been a marked increase in the popularity of such short pulses now that optical timing techniques have begun to report an X-ray/optical delay below ?10?fs r.m.s. errors. As a result, sub-10?fs optical pulses have been implemented at the Linac Coherent Light Source (LCLS) X-ray beamlines, thus warranting a push to reduce the error in X-ray/optical delay measurements to the 1?fs level. Here, we report a unique two-dimensional spectrogram measurement of the relative X-ray/optical delay. This easily scalable relative delay measurement already surpasses previous techniques by an order of magnitude with its sub-1?fs temporal resolution and opens up the prospect of time-resolved X-ray measurements to the attosecond community.

Hartmann, N.; Helml, W.; Galler, A.; Bionta, M. R.; Grünert, J.; L. Molodtsov, S.; Ferguson, K. R.; Schorb, S.; Swiggers, M. L.; Carron, S.; Bostedt, C.; Castagna, J.-C.; Bozek, J.; Glownia, J. M.; Kane, D. J.; Fry, A. R.; White, W. E.; Hauri, C. P.; Feurer, T.; Coffee, R. N.

2014-09-01

244

Vortex with fractional quantum numbers in a chiral p-wave superconductor  

Microsoft Academic Search

We show that a vortex in a chiral p-wave superconductor, which has the px+ipy-wave pairing state and breaks U(1), parity and time reversal symmetry simultaneously, has fractional charge -ne\\/4 and fractional angular momentum -n2\\/16 (n; vorticity). This suggests that the vortex could be anyon and could obey fractional statistics. Electromagnetic property of the vortex is also discussed and we find

J. Goryo

2000-01-01

245

Detection of regular variations in the intensity and pulse time of arrival of the anomalous pulsar PSR B0943+10  

NASA Astrophysics Data System (ADS)

Timing of the anomalous pulsar PSR B0943+10 during 2007-2013 was carried out on the Large Phased Array radio telescope of the Pushchino Radio Astronomy Observatory at 112 MHz. The astrometric and rotational parameters for epoch MJD=56 500 have been determined. Considerable deviations of the pulse times of arrival from the precalculated values with a characteristic period of several years due to the presence of correlated low-frequency noise in the pulsar spin phase have been detected. These deviations can be explained in a planetary model by the presence of two companions of the pulsar, whose orbital parameters have been determined. A continuous increase in the longitude of the pulse maximum within the emission window, the pulse width, and the intensity have been detected after each switch to the burst mode. Together with the changes in pulse shape, degree of linear polarization of the pulse, and drift rate of individual pulses detected earlier, this indicates that all the main parameters of the radio emission in the B mode are unstable. This distinguishes PSR B0943+10 from all other modes-witching pulsars. The origin of the observed properties of this pulsar are probably associated with the interaction of its extended magnetosphere with the surrounding medium.

Suleymanova, S. A.; Rodin, A. E.

2014-11-01

246

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

247

Seismic Arrival Time Tomography as a Complementary Geophysical Exploration Tool in the Characterization of Structural Settings of Mineral Ore Deposits in Chile  

NASA Astrophysics Data System (ADS)

The abundant earthquake activity in the Chilean crust and upper mantle make Chile an outstanding environment for applications of seismological arrival time tomography. For the most part, applications of this type of imaging technique, which involves the joint determination of hypocenters and P- and S-wavespeed variations from the arrival times of primary phases, have focused on seismotectonics associated with subduction along the Andean margin. Recent images that we have obtained using these types of observation from networks in Chile, combined with a few explosions related to mining activity, show that passive source tomography can be effectively applied in refining the definition of structures within the upper 20-30 km, making it a useful geophysical tool in the regional characterization of ore deposits. Specifically, we are able to characterize more precisely the spatial distribution and depth of seismically active fault systems and anomalies associated with intrusive bodies. Our images reveal several heterogeneous regions within the Chilean crust with dimensions on the order of tens of km with wavespeed contrasts on the order of 10-15% for Vp, Vs and Vp/Vs. We find that all of the largest Cu-porphyry deposits in Central Chile are located at the edges of these structures, or in other words where the gradient in wavespeeds is greatest. Moreover, these areas are associated with high levels of ambient seismic activity, suggesting the presence of deep faulting in these regions. One possible interpretation of this pattern is that the late-stage intrusives that formed these deposits were transported along zones of weakness at the borders of existing structures, exploiting zones of relative weakness between them. These patterns show that passive source tomography can illuminated deep (i.e., mid-crustal) structures related to the genesis of mineral deposits and provide a useful tool for mining exploration in extensive areas covered by post-mineral deposits. Application of this type of tool is particularly advantageous in an area like Chile where ambient levels of seismicity can provide an adequate amount of observations within a few months.

Charrier, R.; Comte, D.; García, M.; Carrizo, D.; Roecker, S.

2010-12-01

248

INTEGRATING P-WAVE AND S-WAVE SEISMIC DATA TO IMPROVE CHARACTERIZATION OF OIL RESERVOIRS  

SciTech Connect

The data used in this study were acquired by nine-component (9C) vertical seismic profile (VSP), using three orthogonal vector sources. The 9C vertical seismic profile is capable of generating P-wave mode and the fundamental S-wave mode (SH-SH and SV-SV) directly at the source station and permits the basic components of elastic wavefield (P, SH-SH and SV-SV) to be separated from one another for the purposes of imaging. Analysis and interpretations of data from the study area show that incident full-elastic seismic wavefield is capable of reflecting four different wave modes, P, SH , SV and C which can be utilized to fully understand the architecture and heterogeneities of geologic sequences. The conventional seismic stratigraphy utilizes only reflected P-wave modes. The notation SH mode is the same as SH-SH; SV mode means SV-SV and C mode which is a converted shear wave is a special SV mode and is the same as P-SV. These four wave modes image unique geologic stratigraphy and facies and at the same time reflect independent stratal surfaces because of the unique orientation of their particle-displacement vectors. As a result of the distinct orientation of individual mode.s particle-displacement vector, one mode may react to a critical subsurface sequence more than the other. It was also observed that P-wave and S-wave do not always reflect from the same stratal boundaries. At inline coordinate 2100 and crossline coordinates of 10,380, 10430, 10480 and 10,520 the P-wave stratigraphy shows coherency at time slice 796 m/s and C-wave stratigraphy shows coherency at time slice 1964 m/s at the same inline coordinate and crossline coordinates of 10,400 to 10470. At inline coordinate 2800 and crossline coordinate 10,650, P-wave stratigraphy shows coherency at time slice 792 m/s and C-wave stratigraphy shows coherency at time slice 1968 m/s. The utilization of full-elastic seismic wavefield needs to be maximized in oil and gas explorations in order to optimize the search for hydrocarbons.

Innocent J. Aluka

2004-12-01

249

Electrocardiographic P-wave characteristics in patients with psoriasis vulgaris  

PubMed Central

Purpose Psoriasis vulgaris is one of the most common skin disorders. Patients with psoriasis carry an excessive risk of atrial fibrillation (AF). The differences between the maximum (Pmax) and the minimum (Pmin) P-wave duration on ECG are defined as P-wave dispersion (PWD). Prolongation of PWD is an independent risk factor for the development of AF. The aim of this the study was to investigate P-wave duration and PWD in patients with psoriasis. Methods Sixty-one adult patients with psoriasis vulgaris (group 1) and 58 age and sex-matched healthy individuals (group 2) were included in this study. ECG recordings were obtained, and the P-wave variables were calculated. Results were reported as mean ± standard deviation and percentages. Continuous variables were analysed using Student's t test. A value of P < 0.05 was considered statistically signi?cant. Results Pmax and PWD were significantly higher in group 1 than in group 2 (108.8 ± 21.3 ms versus 93.3 ± 13.0 ms, P < 0.001; 67.4 ± 22.9 ms versus 45.0 ± 19.6 ms, P < 0.001, respectively). Also, Pmin was significantly lower in group 1 (41.3 ± 12.3 ms versus 48.3 ± 14.3 ms, P = 0.04). The psoriasis disease activity score and hsCRP correlated with PWD (P < 0.01). Conclusions Atrial conduction of sinus impulses was impaired in patients with psoriasis vulgaris. It was more prominent in patients with severe disease. Physicians caring for patients with psoriasis vulgaris should screen them for AF development. PMID:23153368

Erdogan, Ercan; Tasal, Abdurrrahman; Vatankulu, Mehmet Akif; Kul, Seref; Sevgili, Emrah; Ertas, Gokhan; Dizman, Didem; Onsun, Nahide; Uysal, Omer

2013-01-01

250

Decays rates for S- and P-wave bottomium  

SciTech Connect

The authors use the Bodwin-Braaten-Lepage factorization scheme to separate the long- and short-distance factors that contribute to the decay rates of {Upsilon}, {eta}{sub b} (S-wave) and {chi}{sub b},h{sub b} (P-wave). The long distance matrix elements are calculated on the lattice in the quenched approximation using a non-relativistic formulation of the b quark dynamics.

Bodwin, G.T.; Kim, S.; Sinclair, D.K.

1994-11-01

251

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

252

Kondo resonance from p-wave hybridization in graphene.  

PubMed

The p-wave hybridization in graphene present a distinct class of Kondo problem in pseudogap Fermi systems with bath density of states (DOS) ?0(?) ? |?|. The peculiar geometry of substitutional and hollow-site ad-atoms, and effectively the vacancies allow for a p-wave form of momentum dependence in the hybridization of the associated local orbital with the Dirac fermions of the graphene host which results in a different picture than the s-wave momentum independent hybridization. For the p-wave hybridization function, away from the Dirac point we find closed-form formulae for the Kondo temperature TK which in contrast to the s-wave case is non-zero for any value of hybridization strength V of the single impurity Anderson model (SIAM). At the Dirac point where the DOS vanishes, we find a conceivably small value of Vmin above which the Kondo screening takes place even in the presence of particle-hole symmetry. We also show that the non-Lorentzian line shape of the local spectrum arising from anomalous hybridization function leads to much larger TK in vacant graphene compared to a metallic host with similar bandwidth and SIAM parameters. PMID:25237820

Jafari, S A; Tohyama, T

2014-10-15

253

Kondo resonance from p-wave hybridization in graphene  

NASA Astrophysics Data System (ADS)

The p-wave hybridization in graphene present a distinct class of Kondo problem in pseudogap Fermi systems with bath density of states (DOS) ρ0(ε) ∝ |ε|. The peculiar geometry of substitutional and hollow-site ad-atoms, and effectively the vacancies allow for a p-wave form of momentum dependence in the hybridization of the associated local orbital with the Dirac fermions of the graphene host which results in a different picture than the s-wave momentum independent hybridization. For the p-wave hybridization function, away from the Dirac point we find closed-form formulae for the Kondo temperature TK which in contrast to the s-wave case is non-zero for any value of hybridization strength V of the single impurity Anderson model (SIAM). At the Dirac point where the DOS vanishes, we find a conceivably small value of Vmin above which the Kondo screening takes place even in the presence of particle–hole symmetry. We also show that the non-Lorentzian line shape of the local spectrum arising from anomalous hybridization function leads to much larger TK in vacant graphene compared to a metallic host with similar bandwidth and SIAM parameters.

Jafari, S. A.; Tohyama, T.

2014-10-01

254

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

255

A near-optimal low complexity sensor fusion technique for accurate indoor localization based on ultrasound time of arrival measurements from low-quality sensors  

NASA Astrophysics Data System (ADS)

A fusion-based localization technique for location-based services in indoor environments is introduced herein, based on ultrasound time-of-arrival measurements from multiple off-the-shelf range estimating sensors which are used in a market-available localization system. In-situ field measurements results indicated that the respective off-the-shelf system was unable to estimate position in most of the cases, while the underlying sensors are of low-quality and yield highly inaccurate range and position estimates. An extensive analysis is performed and a model of the sensor-performance characteristics is established. A low-complexity but accurate sensor fusion and localization technique is then developed, which consists inof evaluating multiple sensor measurements and selecting the one that is considered most-accurate based on the underlying sensor model. Optimality, in the sense of a genie selecting the optimum sensor, is subsequently evaluated and compared to the proposed technique. The experimental results indicate that the proposed fusion method exhibits near-optimal performance and, albeit being theoretically suboptimal, it largely overcomes most flaws of the underlying single-sensor system resulting in a localization system of increased accuracy, robustness and availability.

Mitilineos, Stelios A.; Argyreas, Nick D.; Thomopoulos, Stelios C. A.

2009-05-01

256

Temporal velocity variations beneath the Coso geothermal field observed using seismic double difference tomography of compressional and shear wave arrival times  

NASA Astrophysics Data System (ADS)

Microseismic imaging can be an important tool for characterizing geothermal reservoirs. Since microseismic sources occur more or less continuously due to the operations of a geothermal plant and the naturally occurring background seismicity, passive seismic monitoring is well suited for quantifying the temporal variations in reservoir properties that occur within the geothermal reservoir during production. In this study we will use microseismic data recorded between 1996 and 2008 to investigate the temporal variations in seismic velocity below the Coso geothermal field in California. In this study we will apply the double difference tomography method to simultaneously locate a suite of microseismic events and determine the compressional and shear wave velocity as well as their ratio. The double-difference method uses both absolute and relative arrival times of earthquakes measured at the same station, which allows a more precise determination of the relative locations of earthquakes. In particular, we apply a cross-correlation technique to improve the measurement of relative traveltimes. The large number of microearthquakes observed between 1996 and 2008 allows us to characterize subsurface velocity and to investigate changes in velocity that accompany production from the geothermal reservoir.

Seher, T.; Zhang, H.; Fehler, M. C.; Newman, G. A.

2011-12-01

257

Scattered P'P' waves observed at short distances  

USGS Publications Warehouse

We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (?t, ?r) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P?•d•P?, which can scatter from any depth, d, in the mantle.

Earle, Paul S.; Rost, Sebastian; Shearer, Peter M.; Thomas, Christine

2011-01-01

258

Crustal structure beneath Long Valley caldera from modeling of teleseismic P wave polarizations and Ps converted waves  

SciTech Connect

In this study, the authors present new constraints on the nature of the low-velocity zone beneath Long Valley caldera, based on the measured propagation directions of teleseismic P waves and on modeling of P to S converted waves. The low-velocity body is a large asymmetrical volume which deepens to the east, extending from depths of 7 to 30 km. It contains lower velocities than originally proposed by earlier teleseismic studies. In particular, there is a tabular feature between 7 and 11 km depth that has a reduction in velocity of about 30%. These low velocities imply a much greater percentage of melt in the crust beneath Long Valley caldera than previously estimated. Array analysis of large delayed arrivals identifies them to be Ps converted waves from the shoulders and roof of this tabular zone. These conversions bound the depth to the magma chamber roof to be within about 10 km of the surface. These results are consistent with elements from several other studies, and the authors present an integrated and improved model of crustal structure at Long Valley. The concordance of the deeper low-velocity zones with regional structural trends implies that the shallow low-velocity feature is a cupola on top of an asymmetric diapiric ridge rising up from the migmatized lower crust of the Basin and Range. The authors present two contrasting interpretations of the geometry of low-velocity zones in the crust: one implies a time-invariant magma chamber and conduit system for Long Valley caldera, the other implies an evolution of that system from a simple vertical regime to its current asymmetrical geometry. 37 refs., 19 figs., 1 tab.

Steck, L.K. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States); Prothero, W.A. Jr. [Univ. of California, Santa Barbara, CA (United States)] [Univ. of California, Santa Barbara, CA (United States)

1994-04-10

259

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

260

Development of the county database: Estimates of exposure rates and times of arrival of fallout in the ORERP Phase-2 area. Comparison with cumulative deposition-density estimates based on analyses of retrospective and historical soil samples.  

National Technical Information Service (NTIS)

Estimates of exposure rates and fallout-arrival times have been made for each of 142 counties or county segments for 55 nuclear events producing significant deposition downwind from the Nevada Test Site. All sources of available data were examined to prov...

H. L. Beck, L. R. Anspaugh

1991-01-01

261

Hydrodynamic Modes of a holographic $p-$ wave superfluid  

E-print Network

In this work we analyze the hydrodynamics of a $p-$ wave superfluid on its strongly coupled regime by considering its holographic description. We obtain the poles of the retarded Green function through the computation of the quasi-normal modes of the dual AdS black hole background finding diffusive, pseudo-diffusive and sound modes. For the sound modes we compute the speed of sound and its attenuation as function of the temperature. For the diffusive and pseudo-diffusive modes we find that they acquire a non-zero real part at certain finite momentum.

Arias, Raul E

2014-01-01

262

Hydrodynamic Modes of a holographic $p-$ wave superfluid  

E-print Network

In this work we analyze the hydrodynamics of a $p-$ wave superfluid on its strongly coupled regime by considering its holographic description. We obtain the poles of the retarded Green function through the computation of the quasi-normal modes of the dual AdS black hole background finding diffusive, pseudo-diffusive and sound modes. For the sound modes we compute the speed of sound and its attenuation as function of the temperature. For the diffusive and pseudo-diffusive modes we find that they acquire a non-zero real part at certain finite momentum.

Raul E. Arias; Ignacio Salazar Landea

2014-09-22

263

p -Wave Superfluidity by Spin-Nematic Fermi Surface Deformation  

NASA Astrophysics Data System (ADS)

We study attractively interacting fermions on a square lattice with dispersion relations exhibiting strong spin-dependent anisotropy. The resulting Fermi surface mismatch suppresses the s -wave BCS-type instability, clearing the way for unconventional types of order. Unbiased sampling of the Feynman diagrammatic series using diagrammatic Monte Carlo methods reveals a rich phase diagram in the regime of intermediate coupling strength. Instead of a proposed Cooper-pair Bose metal phase [A. E. Feiguin and M. P. A. Fisher, Phys. Rev. Lett. 103, 025303 (2009)], we find an incommensurate density wave at strong anisotropy and two different p -wave superfluid states with unconventional symmetry at intermediate anisotropy.

Gukelberger, Jan; Kozik, Evgeny; Pollet, Lode; Prokof'ev, Nikolay; Sigrist, Manfred; Svistunov, Boris; Troyer, Matthias

2014-11-01

264

HAS EDUCATIONAL TELEVISION ARRIVED?  

Microsoft Academic Search

After nearly 20 years of educational television, it can still be argued that ETV has not yet ‘arrived’ in the sense of being an accepted, taken?for?granted teaching tool. Although production standards are high, both technically and educationally, and although applications of television to learning are well established, television has certain limitations and deficiencies as a presentation medium. This paper discusses

D. K. Roach

1980-01-01

265

1478 IEEETRANSACTIONS ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOL. ASSP-31, NO. 6 , DECEMBER 1983 Estimation of Time Differences of Arrival  

E-print Network

, such as astronomy, defense, and geophysics [11. The array sensors may comprise a group of antennas,microphones of arrival (TDOA's) of emitter wave fronts to a spatially distributed array of sensors can be used to determine the source location. In this paper, we suggest a new method of TDOA esti- mation for multiple

Nehorai, Arye

266

p-Wave superconductors in D-brane systems  

NASA Astrophysics Data System (ADS)

In this work we take the intersecting D-brane models to explore some properties of p-wave superconductor at strong coupling. Our studies are focused on four-dimensional spacetime, which is not completely researched as in planar case. Optimistically, the AdS/CFT approach to superconductor, or more precisely superconducting-like phase transition, can give us some intuitions about mysterious high Tc superconductors. Concretely, we use defect D4/D6 and D4/D4 (noncritical) models to carry out comparative investigations. To make the system in the finite temperature bath, we assume that the superconducting phase is in the deconfined and chiral symmetry restoring phase for black D4-brane geometry. For the background fields, we use both analytical and numerical methods to solve the coupled nonlinear equations of motion. Near the phase transition, both methods give the mean filed behavior for the superconducting condensate. We then study gauge field perturbations of the systems to probe the AC conductivity. Similar to previous results, there comes out a gap in low frequency regime and the conductivity gets exponentially small as the condensation is enhanced. In contrast to previous investigations, we also compute the AC conductivity along the x direction, which needs to study a coupled sets of fluctuation modes. This shows us the anisotropic feature of p-wave superconductors.

Bu, Yanyan

2012-11-01

267

Time-of-Arrival Measurements of X-ray Emission Associated with Dart-Stepped Leader Steps in Natural and Rocket-and-Wire Triggered Lightning  

NASA Astrophysics Data System (ADS)

Time-of-arrival (TOA) techniques were used to determine the three-dimensional locations and emission times of x-ray and dE/dt sources measured at ground level in association with dart-stepped leader steps in natural and rocket-and-wire triggered lightning discharges recorded during summer 2011 at Camp Blanding, FL. The measurement network consisted of ten flat plate dE/dt antennas approximately co-located with eight plastic and two Lanthanum Bromide scintillation detectors arrayed around the launching facility over an area of about 0.25 square kilometers. For two triggered lightning dart-stepped leaders, x-ray sources were emitted from locations separated by average distances of 22.7 m and 29 m, respectively, from the locations of the associated dE/dt pulse peaks. The x-ray sources occurred beneath the dE/dt sources in 88% of the cases. X-rays were emitted from 20 ns to 2.16 ?s following the dE/dt pulse peaks, with average temporal separations of 150 ns and 290 ns, respectively, for the two triggered lightning events. For one natural lightning dart-stepped leader, x-ray sources were emitted an average total distance of 39.2 m from the associated dE/dt pulse peak, and occurred beneath the location of the dE/dt source in 86% of the cases. The x-rays were emitted from 10 ns to 1.76 ?s following the dE/dt pulse peak with an average temporal separation of 280 ns. In each of the three events, the altitude displacement between the dE/dt and x-ray sources dominated the total separation, accounting for 90%, 63%, and 72%, respectively, of the total separation. X-ray sources were distributed randomly in the lateral directions about the lightning channel in each event. For the triggered lightning events, x-rays were located from 2.5-83.5 ?s prior to the return stroke at altitudes ranging from 24-336 m. For the natural lightning event, x-rays were located from 40.4-222.3 ?s prior to the return stroke at altitudes ranging from 99-394 m. Cumulatively, 67% of the located x-ray sources occurred between 60-280 m in altitude. Inferences on the properties of the propagating dart-stepped leaders are given based on the TOA analyses and observations of the x-ray emission at ground level as a function of the leader-tip altitude are discussed.

Jordan, D. M.; Hill, J. D.; Uman, M. A.; Dwyer, J. R.; Rassoul, H. K.

2012-12-01

268

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

269

Crustal P-wave velocity model for the central-western region of Mexico  

NASA Astrophysics Data System (ADS)

Several studies require a p-wave velocity model to obtain accurate results moreover such models could provide an insight of the tectonic structure of the study area. Accordingly, in this study we estimate the crustal 3D p-wave velocity model for the Jalisco Block located at the central-western region of Mexico. The Jalisco Block is limited on its eastern side by the Colima and Tepic-Zacoalcos Rifts, and the Trans-Mexican Volcanic Belt; while on its western side it is limited by the Mesoamerican Trench. Cocos and Rivera plates are subducting beneath the Jalisco Block conforming a tectonically complex region. We used earthquakes occurring within the limits of lithosphere volume from which we want to estimate the velocity model. Such events were registered by the Mapping the Rivera Subduction Zone experiment (MARS) and the Seismic and Acelerometric Network of Jalisco (RESAJ). During MARS experiment 51broadband stations active from January 2006 to June 2007 were deployed while RESAJ by July of 2012consists of nine active stations however more stations will be deployed until reach 30 stations. The velocity model is estimated using the Fast Marching Tomography (FMTOMO) software. FMTOMO uses the Fast Marching Method (FMM) in order to solve the forward problem; the FMM is a numerical algorithm that tracks the interfaces evolution along a nodes narrow band, and travel times are updated solving the eikonal equation. Finally , the inverse problem is about adjusting the model parameters (interface depth, velocity, hypocenter location) in order to try to satisfy the observed data (travel times). We perform a resolution test using several events that show good resolution results up to a 60 km depth. We present a 3D p-wave velocity model, we compare our results within the MARS data with previous results for greater depths, approximately the upper mantle, finally we also present studies towards the northern portion of the Jalisco Block using the RESAJ data.

Ochoa, J.; Escudero, C. R.; Perez, O. G.; Nunez-Cornu, F. J.

2012-12-01

270

Month Date Day Time Schedule Place 10 Tue. Arrival in Japan (Narita) Registration and Check-in International Garden Hotel Narita  

E-print Network

and Check-in International Garden Hotel Narita 9:30 Departure (Chartered Buses) 12:00 Arrival in Shonan for Japanese Studies) 12:00 - 13:00 Lunch SVC Cafeteria OAK (SVC) 13:00 - 13:15 Japanese Language Class Orientation 13:30 - 17:30 Japanese Classes 18:00 - 19:00 Dinner Cafeteria OAK (SVC) 19:00 - 20:00 Japanese

Kinosita Jr., Kazuhiko

271

Research on probability distribution of container liners’ arrival  

Microsoft Academic Search

The vesselspsila arriving law is generally considered to obey Poisson distribution, and inter-arrival time is used to be considered to accord with negative exponential distribution, which fit general cargo transport mode well. However, it will induce significant error if we apply this law into vesselspsila arrival in container transport mode. Itpsilas because that general cargo transport is constitutionally different from

Zhi-gang Chai; Xiao-dong Liu; Zhi-de Cai; Yue-qiong Zhao

2008-01-01

272

Estimation of Radiated Seismic Energy from Teleseismic P Waves  

NASA Astrophysics Data System (ADS)

Earthquake radiated energy is a fundamental parameter for understanding source physics. Using teleseismic waveforms, we can estimate the radiated energy for a wide range of focal mechanisms and tectonic setting. We are especially interested in studying the apparent stress (rigidity multiplied by the ratio of radiated energy to seismic moment) of strike-slip earthquakes in the oceanic lithosphere, for which there are often high reported values (Choy and McGarr, 2002). Estimates of radiated energy from teleseismic P waves can be unstable, because take-off angles from the source are often close to nodes in the focal mechanisms, which can cause large variations in the estimated values of the apparent stress. In this study, we use only P waves for the teleseismic waveform, because of the strong attenuation of teleseismic S waves and interference with other phases. We use data recorded by teleseismic stations (epicentral distances of 30 to 90deg) recorded on the GSN network and focal mechanisms published by USGS and Global CMT Project. For the teleseismic waveforms, we need to account for the radiation pattern of the direct P and depth phase, pP and sP (Boatwright and Choy, 1986). For strike-slip events with where many data are close to nodes in the focal mechanisms, this is a large and often unstable correction. We use an improved method which takes into account a range of values for the strike, dip and rake angles. Also, we use station corrections determined from a selected set of well determined events. We show the result of estimated radiated seismic energy for 188 recent earthquakes (>Mw 7.0, since 2000 ). We discuss the differences of the radiated energy as a function of focal mechanisms, and oceanic/continental sources. Fig. Radiated seismic energy and correction for radiation pattern calculated using a range of focal mechanisms.

Kiuchi, R.; Mori, J. J.

2013-12-01

273

A Study of Process Arrival Patterns for MPI Collective Operations  

Microsoft Academic Search

Process arrival pattern, which denotes the timing when different processes arrive at an MPI collective operation, can have a significant impact on\\u000a the performance of the operation. In this work, we characterize the process arrival patterns in a set of MPI programs on two\\u000a common cluster platforms, use a micro-benchmark to study the process arrival patterns in MPI programs with

Ahmad Faraj; Pitch Patarasuk; Xin Yuan

2008-01-01

274

Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography  

SciTech Connect

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-01-10

275

Rupture history of the 1997 Cariaco, Venezuela, earthquake from teleseismic P waves  

USGS Publications Warehouse

A two-step finite-fault waveform inversion scheme is applied to the broadband teleseismic P waves recorded for the strike-slip, Cariaco, Venezuela, earthquake of 9 July 1997 to recover the distribution of mainshock slip. The earthquake is first analyzed using a long narrow fault with a maximum rise time of 20 sec. This line-source analysis indicates that slip propagated to the west with a constant rupture velocity and a relatively short rise time. The results are then used to constrain a second inversion of the P waveforms using a 60-km by 20-km two-dimensional fault. The rupture shows a zone of large slip (1.3-m peak) near the hypocenter and a second, broader source extending updip and to the west at depths shallower than 5 km. The second source has a peak slip of 2.1 meters and accounts for most of the moment of 1.1 × 1026 dyne-cm (6.6 Mww) estimated from the P waves. The inferred rupture pattern is consistent with macroseismic effects observed in the epicentral area.

Mendoza, C.

2000-01-01

276

Effects of autonomic stimulation and blockade on signal-averaged P wave duration  

Microsoft Academic Search

Objectives. This study sought to evaluate the effects of autonomic stimulation and blockade on the signal-averaged P wave duration.Background. Signal-averaged P wave duration has been shown to have prognostic implications for patients prone to develop atrial fibrillation, but autonomic influences on the signal-averaged P wave duration have not been studied.Methods. In 14 healthy volunteers (8 men, 6 women; mean [±SD

Asim N. Cheema; Mirza W. Ahmed; Alan H. Kadish; Jeffrey J. Goldberger

1995-01-01

277

The P-wave boundary of the Large-Low Shear Velocity Province beneath the Pacific  

NASA Astrophysics Data System (ADS)

The Large Low Shear Velocity Provinces (LLSVPs) in the lower mantle represent volumetrically significant thermal or chemical or thermo-chemical heterogeneities. Their structure and boundaries have been widely studied, mainly using S-waves, but much less is known about their signature in the P-wavefield. We use an extensive dataset recorded at USArray to create, for the first time, a high-resolution map of the location, shape, sharpness, and extent of the boundary of the Pacific LLSVP using P(Pdiff)-waves. We find that the northern edge of the Pacific LLSVP is shallow dipping (26° relative to the horizontal) and diffuse (?120 km wide transition zone) whereas the eastern edge is steeper dipping (70°) and apparently sharp (?40 km wide). We trace the LLSVP boundary up to ?500 km above the CMB in most areas, and 700 km between 120° and 90°W at the eastern extent of the boundary. Apparent P-wave velocity drops are ?1-3% relative to PREM, indicating a strong influence of LLSVPs on P-wave velocity, at least in the high-frequency wavefield, in contrast to previous studies. A localised patch with a greater velocity drop of ?15-25% is detected, defined by large magnitude gradients of the travel-time residuals. We identify this as a likely location of an Ultra-Low Velocity Zone (ULVZ), matching the location of a previously detected ULVZ in this area. The boundary of a separate low velocity anomaly, of a similar height to the LLSVP, is detected in the north-west Pacific, matching tomographic images. This outlier appears to be connected to the main LLSVP through a narrow channel close to the CMB and may be in the process of joining or splitting from the main LLSVP. We also see strong velocity increases in the lower mantle to the east of the LLSVP, likely detecting subducted material beneath central America. The LLSVP P-wave boundary is similar to that determined in high-resolution S-wave studies and follows the -0.4% ?VS iso-velocity contour in the S40RTS tomography model. Additionally, the LLSVP boundary roughly matches the shape of the -0.4% ?VP iso-velocity contour of the P-wave model GyPSuM but defines an area more similar to that defined by the 0.0% VP iso-velocity contour. High resolution P-wave velocity determination allows for estimation of the ratio of P- and S-wave velocity anomalies (RS,P) which can be used to indicate dominantly thermal or chemical control of seismic velocities. Although the RS,P is found here to be approximately 2.4, which is indicative of a thermo-chemical anomaly. However, this result contains a large amount of uncertainty and the implications for the origin of LLSVPs likely remain inconclusive. Nonetheless, other observations of the Pacific LLSVP are consistent with a thermo-chemical anomaly whose shape and boundary sharpness are controlled by proximity to active and past subduction.

Frost, Daniel A.; Rost, Sebastian

2014-10-01

278

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

279

Nonlinear teleseismic tomography at Long Valley caldera, using three-dimensional minimum travel time ray tracing  

Microsoft Academic Search

The authors explore the impact of three-dimensional minimum travel time ray tracing on nonlinear teleseismic inversion. This problem has particular significance when trying to image strongly contrasting low-velocity bodies, such as magma chambers, because strongly refracted\\/and\\/or diffracted rays may precede the direct P wave arrival traditionally used in straight-ray seismic tomography. They use a simplex-based ray tracer to compute the

Charles M. Weiland; Lee K. Steck; Phillip B. Dawson; Valeri A. Korneev

1995-01-01

280

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

281

High-frequency P-wave seismic noise driven by ocean winds Jian Zhang,1  

E-print Network

High-frequency P-wave seismic noise driven by ocean winds Jian Zhang,1 Peter Gerstoft,1 and Peter M] Earth's background vibrations at frequencies below about 0.5 Hz have been attributed to ocean-wave with the offshore wind speed, demonstrating that these high-frequency P- waves are excited by distant ocean winds

Shearer, Peter

282

Magnetic-field effects on p-wave phase transition in Gauss-Bonnet gravity  

NASA Astrophysics Data System (ADS)

In the probe limit, we study the holographic p-wave phase transition in the Gauss-Bonnet gravity via numerical and analytical methods. Concretely, we study the influences of the external magnetic field on the Maxwell complex vector model in the five-dimensional Gauss-Bonnet-AdS black hole and soliton backgrounds, respectively. For the two backgrounds, the results show that the magnetic field enhances the superconductor phase transition in the case of the lowest Landau level, while the increasing Gauss-Bonnet parameter always hinders the vector condensate. Moreover, the Maxwell complex vector model is a generalization of the SU(2) Yang-Mills model all the time. In addition, the analytical results backup the numerical results. Furthermore, this model might provide a holographic realization for the QCD vacuum instability.

Wu, Ya-Bo; Lu, Jun-Wang; Jin, Yong-Yi; Lu, Jian-Bo; Zhang, Xue; Wu, Si-Yu; Wang, Cui

2014-07-01

283

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

284

Increased P-wave dispersion in patients with newly diagnosed lichen planus  

PubMed Central

OBJECTIVE: Lichen planus is a chronic inflammatory autoimmune mucocutaneous disease. Recent research has emphasized the strong association between inflammation and both P-wave dispersion and dyslipidemia. The difference between the maximum and minimum P-wave durations on an electrocardiogram is defined as P-wave dispersion. The prolongation of P-wave dispersion has been demonstrated to be an independent risk factor for developing atrial fibrillation. The aim of this study was to investigate P-wave dispersion in patients with lichen planus. METHODS: Fifty-eight patients with lichen planus and 37 age- and gender-matched healthy controls were included in this study. We obtained electrocardiographic recordings from all participants and used them to calculate the P-wave variables. We also assessed the levels of highly sensitive C-reactive protein, which is an inflammatory marker, and the lipid levels for each group. The results were reported as the means ± standard deviations and percentages. RESULTS: The P-wave dispersion was significantly higher in lichen planus patients than in the control group. Additionally, highly sensitive C-reactive protein, LDL cholesterol, and triglyceride levels were significantly higher in lichen planus patients compared to the controls. There was a significant positive correlation between highly sensitive C-reactive protein and P-wave dispersion (r?=?0.549, p<0.001) in lichen planus patients. CONCLUSIONS: P-wave dispersion increased on the surface electrocardiographic measurements of lichen planus patients. This result may be important in the early detection of subclinical cardiac involvement. Increased P-wave dispersion, in terms of the tendency for atrial fibrillation, should be considered in these patients. PMID:23778479

Sahin, Musa; Bilgili, Serap Gunes; Simsek, Hakki; Akdag, Serkan; Akyol, Aytac; Gumrukcuoglu, Hasan Ali; Yaman, Mehmet; Bayram, Yasemin; Karadag, Ayse Serap

2013-01-01

285

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

286

A model of seismic coda arrivals to suppress spurious events.  

NASA Astrophysics Data System (ADS)

We describe a model of coda arrivals which has been added to NET-VISA (Network processing Vertically Integrated Seismic Analysis) our probabilistic generative model of seismic events, their transmission, and detection on a global seismic network. The scattered energy that follows a seismic phase arrival tends to deceive typical STA/LTA based arrival picking software into believing that a real seismic phase has been detected. These coda arrivals which tend to follow all seismic phases cause most network processing software including NET-VISA to believe that multiple events have taken place. It is not a simple matter of ignoring closely spaced arrivals since arrivals from multiple events can indeed overlap. The current practice in NET-VISA of pruning events within a small space-time neighborhood of a larger event works reasonably well, but it may mask real events produced in an after-shock sequence. Our new model allows any seismic arrival, even coda arrivals, to trigger a subsequent coda arrival. The probability of such a triggered arrival depends on the amplitude of the triggering arrival. Although real seismic phases are more likely to generate such coda arrivals. Real seismic phases also tend to generate coda arrivals with more strongly correlated parameters, for example azimuth and slowness. However, the SNR (Signal to Noise Ratio) of a coda arrival immediately following a phase arrival tends to be lower because of the nature of the SNR calculation. We have calibrated our model on historical statistics of such triggered arrivals and our inference accounts for them while searching for the best explanation of seismic events their association to the arrivals and the coda arrivals. We have tested our new model on one week of global seismic data spanning March 22, 2009 to March 29, 2009. Our model was trained on two and half months of data from April 5, 2009 to June 20, 2009. We use the LEB bulletin produced by the IDC (International Data Center) as the ground truth and computed the precision (percentage of reported events which are true) and recall (percentage of true events which are reported). The existing model has a precision of 32.2 and recall of 88.6 which changes to a precision of 50.7 and recall of 88.5 after pruning. The new model has a precision of 56.8 and recall of 86.9 without any pruning and the corresponding precision recall curve is dramatically improved. In contrast, the performance of the current automated bulletin at the IDC, SEL3, has a precision of 46.2 and recall of 69.7.

Arora, N.; Russell, S.

2012-04-01

287

Joint Tomography of Body Wave and Surface Wave Phase Arrival Times for Lithospheric Structure beneath Central Tibet Using a Fully 3-D Multi-scale Finite-frequency Approach  

NASA Astrophysics Data System (ADS)

As body and surface wave phase arrivals provide complementary constraints on crust and mantle structures, we here introduce a self-consistent methodology to jointly invert body and surface wave data for shear velocity variations under regional arrays. The approach combines a fully 3-D finite-frequency theory and wavelet-based, multi-scale parameterization to deal with two major concerns in tomographic inverse problems that inevitably arise from the intrinsic wave diffraction and scattering and from uneven source-receiver distributions. To properly account for finite-frequency wave propagation, we use the computationally-efficient expressions of 3-D Born-Fréchet kernels, formulated in the framework of body-wave ray summation and surface-wave mode summation, respectively, to construct the partial derivatives of frequency-dependent arrival time data to 3-D elastic wavespeed perturbations. To achieve both spectral resolution for long-wavelength structure in regions of sparse data coverage and spatial resolution in densely-sampled regions, we employ a flexible, data-adaptive scheme of non-stationary parameterization and regularization by means of the hierarchical wavelet decomposition. We demonstrate this innovated method by applying it to tomographic imaging of shear wave velocity structure beneath central Tibet, where Project Hi-CLIMB deployed a dense seismic array of over 200 broadband stations across the Himalayan-Tibetan orogen during 2002-2005, used to illuminate the geodynamic nature responsible for the most prominent zone of active continental collision.

Hung, S.; Jheng, Y.; Zhou, Y.

2012-12-01

288

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

289

Evolution of upper mantle beneath East Asia and the Tibetan Plateau from P-wave tomography  

E-print Network

The main objective of the research presented in this thesis is to improve our understanding for the evolution of the upper mantle beneath East Asia and the Tibetan Plateau through high resolution P-wave tomography. The ...

Li, Chang, Ph.D.

2007-01-01

290

Breakdown of QCD Factorization for P-Wave Quarkonium Production at Low Transverse Momentum  

E-print Network

Quarkonium production at low transverse momentum in hadron collisions can be used to extract Transverse-Momentum-Dependent(TMD) gluon distribution functions, if TMD factorization holds there. We show that TMD factorization for the case of P-wave quarkonium with $J^{PC}=0^{++}, 2^{++}$ holds at one-loop level, but is violated beyond one-loop level. TMD factorization for other P-wave quarkonium is also violated already at one-loop.

J. P. Ma; J. X. Wang; S. Zhao

2014-05-14

291

Breakdown of QCD factorization for P-wave quarkonium production at low transverse momentum  

NASA Astrophysics Data System (ADS)

Quarkonium production at low transverse momentum in hadron collisions can be used to extract Transverse-Momentum-Dependent (TMD) gluon distribution functions, if TMD factorization holds there. We show that TMD factorization for the case of P-wave quarkonium with J=0,2 holds at one-loop level, but is violated beyond one-loop level. TMD factorization for other P-wave quarkonium is also violated already at one-loop level.

Ma, J. P.; Wang, J. X.; Zhao, S.

2014-10-01

292

Signal processing and tracking of arrivals in ocean acoustic tomography.  

PubMed

The signal processing for ocean acoustic tomography experiments has been improved to account for the scattering of the individual arrivals. The scattering reduces signal coherence over time, bandwidth, and space. In the typical experiment, scattering is caused by the random internal-wave field and results in pulse spreading (over arrival-time and arrival-angle) and wander. The estimator-correlator is an effective procedure that improves the signal-to-noise ratio of travel-time estimates and also provides an estimate of signal coherence. The estimator-correlator smoothes the arrival pulse at the expense of resolution. After an arrival pulse has been measured, it must be associated with a model arrival, typically a ray arrival. For experiments with thousands of transmissions, this is a tedious task that is error-prone when done manually. An error metric that accounts for peak amplitude as well as travel-time and arrival-angle can be defined. The Viterbi algorithm can then be adapted to the task of automated peak tracking. Repeatable, consistent results are produced that are superior to a manual tracking procedure. The tracking can be adjusted by tuning the error metric in logical, quantifiable manner. PMID:25373953

Dzieciuch, Matthew A

2014-11-01

293

Monte Carlo Study of the Arrival Time Distribution of Particles in Extensive Air Showers in the Energy Range 1--100 TeV  

E-print Network

A detailed simulation of vertical showers in atmosphere produced by primary gammas and protons, in the energy range 1-100 TeV, has been performed by means of the FLUKA Monte Carlo code, with the aim of studying the time structure of the shower front at different detector heights. It turns out that the time delay distribution can be fitted using few parameters coincident with the distribution central moments. Such parameters exhibit a smooth behaviour as a function of energy. These results can be used both for detector design and for the interpretation of the existing measurements. Differences in the time structure between gamma and proton induced showers are found and explained in terms of the non-relativistic component of extensive air showers.

G. Battistoni; M. Carboni; A. Ferrari; V. Patera

1998-06-19

294

Prediction of New Onset Atrial Fibrillation Through P Wave Analysis in 12 Lead ECG.  

PubMed

It is unknown whether 12-lead ECG can predict new-onset AF. In the present study, we identified patients with new onset AF from our digitally stored ECG database, and the P wave morphologies were analyzed in their preceding sinus rhythm recordings as the precursor state for AF. The P wave was analyzed in the most recent ECG recording of sinus rhythm preceding new onset AF within 12 months. The duration and amplitude of P waves were analyzed in 12 leads and compared between the 2 groups with the other clinical parameters. The study population consisted of 68 patients with new-onset AF and 68 age and sex-matched controls. Multivariate analysis revealed that the P wave amplitude in leads II and V1 (0.157 ± 0.056 versus 0.115 ± 0.057 mV, P = 0.032, and 0.146 ± 0.089 versus 0.095 ± 0.036 mV, P = 0.002) and P wave dispersion (56.9 ± 14.8 versus 33.5 ± 12.9 ms, P = 0.001) were significant independent factors for the prediction of new-onset AF. By using these factors, new-onset AF could be predicted with a sensitivity of 69.1% and specificity of 88.2%. P wave analysis is useful for predicting new onset AF. PMID:25098176

Yoshizawa, Tomoharu; Niwano, Shinichi; Niwano, Hiroe; Igarashi, Tazuru; Fujiishi, Tamami; Ishizue, Naruya; Oikawa, Jun; Satoh, Akira; Kurokawa, Sayaka; Hatakeyama, Yuko; Fukaya, Hidehira; Ako, Junya

2014-09-10

295

Fluid pressure arrival time tomography: Estimation and assessment in the presence of inequality constraints, with an application to a producing gas field at Krechba, Algeria  

SciTech Connect

Deformation in the overburden proves useful in deducing spatial and temporal changes in the volume of a producing reservoir. Based upon these changes we estimate diffusive travel times associated with the transient flow due to production, and then, as the solution of a linear inverse problem, the effective permeability of the reservoir. An advantage an approach based upon travel times, as opposed to one based upon the amplitude of surface deformation, is that it is much less sensitive to the exact geomechanical properties of the reservoir and overburden. Inequalities constrain the inversion, under the assumption that the fluid production only results in pore volume decreases within the reservoir. We apply the formulation to satellite-based estimates of deformation in the material overlying a thin gas production zone at the Krechba field in Algeria. The peak displacement after three years of gas production is approximately 0.5 cm, overlying the eastern margin of the anticlinal structure defining the gas field. Using data from 15 irregularly-spaced images of range change, we calculate the diffusive travel times associated with the startup of a gas production well. The inequality constraints are incorporated into the estimates of model parameter resolution and covariance, improving the resolution by roughly 30 to 40%.

Rucci, A.; Vasco, D.W.; Novali, F.

2010-04-01

296

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

297

Comparison of interplanetary CME arrival times and solar wind parameters based on the WSA-ENLIL model with three cone types and observations  

NASA Astrophysics Data System (ADS)

We have made a comparison between coronal mass ejection (CME)-associated shock propagations based on the Wang-Sheeley-Arge (WSA)-ENLIL model using three cone types and in situ observations. For this we use 28 full-halo CMEs, whose cone parameters are determined and their corresponding interplanetary shocks were observed at the Earth, from 2001 to 2002. We consider three different cone types (an asymmetric cone model, an ice cream cone model, and an elliptical cone model) to determine 3-D CME cone parameters (radial velocity, angular width, and source location), which are the input values of the WSA-ENLIL model. The mean absolute error of the CME-associated shock travel times for the WSA-ENLIL model using the ice-cream cone model is 9.9 h, which is about 1 h smaller than those of the other models. We compare the peak values and profiles of solar wind parameters (speed and density) with in situ observations. We find that the root-mean-square errors of solar wind peak speed and density for the ice cream and asymmetric cone model are about 190 km/s and 24/cm3, respectively. We estimate the cross correlations between the models and observations within the time lag of ± 2 days from the shock travel time. The correlation coefficients between the solar wind speeds from the WSA-ENLIL model using three cone types and in situ observations are approximately 0.7, which is larger than those of solar wind density (cc ˜0.6). Our preliminary investigations show that the ice cream cone model seems to be better than the other cone models in terms of the input parameters of the WSA-ENLIL model.

Jang, Soojeong; Moon, Y.-J.; Lee, Jae-Ok; Na, Hyeonock

2014-09-01

298

Reflection tomography: How to handle multiple arrivals?  

NASA Astrophysics Data System (ADS)

Applications of reflection tomography for the determination of copmplex geologic structures calls for the generalization of this method so that it can take triplications and other multiple arrivals into account. In this way, we propose a new formulation of travel time inversion. It relies on the choice of an adequate parametric representation of travel time information: the parameters we have chosen for this representation are the receiver location and the ray parameter at the receiver, some quantities directly measured from seismic data. The forward problem involved in the solution of this new inverse problem consists in shooting rays from a receiver according to the measured values of the ray parameter at the receiver. We can thus predict for a given model the emergence point of the reflected ray (i.e., the shot location) and the associated reflection arrival time. The least squares formulation of the inverse problem consists in minimizing an objective function that measures the mismatch between predicted and actual shot locations on one side and predicted and actual reflection arrival times on the other side, for the considered receiver locations and the associated measured ray parameters. However, inversion of noise corrupted kinematic data calls for a realistic definition of the uncertainties associated with the data. In particular, those uncertainties should take into account the sensitivity of reflection arrival times and shot locations to an error in the measurement of the ray parameter at the receiver. The objective function to minimize being chosen, the solution of the inverse problem is performed by a Gauss-Newton method, the Jacobian of the forward modeling operator being computed by the adjoint state technique. It is interesting to note that no two-point ray tracing is required in our method which is therefore cheaper than classical reflection tomography. The effectiveness of this approach is illustrated on a difficult synthetic example with large lateral velocity variations and strongly noise corrupted data.

Delprat-Jannaud, F.; Lailly, P.

1995-01-01

299

The Mantle Structure beneath SE Asia from P-wave Tomograpy  

NASA Astrophysics Data System (ADS)

Southeastern Asia is a tectonically diverse and active area. In the west, the continental collision and post- collision conversion between Indian and Eurasian plat have created the Tibetan Plateau. The retreating western Pacific slabs in the east have generated the extensional basins in China. These two systems have set up a large-scale dynamic clockwise rotation in the southeastern Asia, controlling the evolution of the tectonic settings inside. With high resolution models of the mantle beneath southeastern Asia we can understand this large-scale mantle system better. P-wave travel time data from more than 1000 stations of Chinese Seismological Network from 1964 to 2004 and from several temporal seismic arrays in and near the Tibetan plateau were combined with data from the International Seismological Centre. We nonlinearly relocated the earthquake hypocenters and generated new EHB dataset (Engdahl et al., 1998). The spectacular (dense and more uniform) data coverage ensures unprecedented resolution of P-wave velocity perturbations in the upper mantle beneath southeastern Asia. Following Li et al (PEPI, 2006) we corrected for crustal structure and used an adaptive grid to assure the high resolution when the dense data coverage is available. The model reveals high velocity anomaly roots of the Archaean Ordos and Sichuan basins down to at least 250 km depth. These tectonically stable structures influence the deformation of the eastward Tibetan plateau. Slow wave propagation marks the shallow mantle beneath eastern Tibet and beneath the Red River fault system (all the way to the South China Sea). These anomalies are separated by a zone of high wavespeeds between the Sichuan basin and the Burma ranges, which may mark a transition in tectonic regime from collision controlled in the NW to Pacific (subduction) controlled to the SE. A fast velocity anomaly structure is located along the Himalayan Frontal Thrust down to 400 km depth, indicating the subduction of Indian lithospheric mantle. In the eastern part of the collision, this high velocity anomaly structure remains South of the Yarlun-Zangbo suture (~30N), implying the most of mantle beneath central and eastern Tibet is of Eurasian origin. The retreating western Pacific slabs subducting from the Japan and Izu Bonin trenches are deflected in the transition zone beneath the Korea and Northeast and eastern coast of China. These stagnant slabs shape upper mantle circulation beneath SE Asia and might be related to volcanism in Korea and NE China (such as the Changbai volcanic area).

Li, C.; Sun, R.; van der Hilst, R.; Meltzer, A.; Engdahl, R.

2006-12-01

300

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

301

Floquet engineering of long-range p-wave superconductivity  

E-print Network

Floquet Majorana Fermions appear as steady states at the boundary of time-periodic topological phases of matter. In this work, we theoretically study the main features of these exotic topological phases in the periodically driven one-dimensional Kitaev model. By controlling the ac fields, we can predict new topological phase transitions that should give rise to signatures of Majorana states in experiments. Moreover, the knowledge of the time-dependence of these Majorana states allows one to manipulate them. Our work contains a complete analysis of the monochromatic driving in different frequency regimes.

Mónica Benito; Álvaro Gómez-León; Victor Bastidas; Tobias Brandes; Gloria Platero

2014-09-01

302

Arrivals and Arrivals: Royal Travel at Botany Bay  

Microsoft Academic Search

This article looks at how the sites of the beach and the airport have functioned as chronotopes of 'arrivalism' in Australian history. I suggest that narratives surrounding Queen Elizabeth's 1970 royal tour of Australia, initiated and terminated at Sydney Airport, drew on existing structures of primitivism and modernity at the site of the beach. A re-enactment of Cook's landing at

Justine Lloyd

2003-01-01

303

Relations between 8o, Lehmann and X discontinuities based on first arrival travel times from selected events in North America and Europe.  

NASA Astrophysics Data System (ADS)

Analysing a traveltime curve for the "standard" model of the upper mantle (up to 3000 km dinstance), we can generally distinguish several offset ranges and respective branches. Offsets up to ca. 800 km are characterized by seismic phases belonging to the crust and Moho. Observed traveltime delay at ca. 800 km marks the top of mantle low velocity zone (Thybo and Perchuc, 1997). The next phases, named "Lehman" phases are characterized by the scatter both in time and amplitudes. At ca. 2000 2200 km offsets signals from 410 km discontinuity are usually observed. We focus on the differences between `cold' and `hot' upper mantle in North America and Central Europe. There is a significant delay for phases sampling the upper mantle low velocity zone (LVZ) below a depth of about 100 km. The delay depends on the thickness and velocity drop of the LVZ and appears to correlate with the tectonic state of the region. For `hot' regions there is a large delay for phases that have crossed the LVZ, which corresponds to a thick LVZ; whereas the delay is smaller for phases that have propagated in `cold' regions. For three events from Texas we identified some delay from the LVZ for recordings in the eastern US and much larger delay for recordings in the western US in the offset range of 800-1600 km. The difference between these delays amounts to 3-5 s. A similar difference has been observed for two events in northern Algeria for recordings in Europe between ray paths that traverse the `hot' Alpine region and outside. For all five events the situation is reversed at offsets beyond ~1600 km where phases from around the mantle transition zone are observed. At these large offsets seismic phases with velocities that are characteristic of the depth interval below the `410-km' discontinuity in `cold' regions, are recorded 2-3 seconds later than those in `hot' regions. This implies a much shallower 410's below active areas, which is clearly contradictory to phase transformation interpretation of this discontinuity. Our modeling indicates another boundary located at ca. 250-350 km depth, characterized by abnormally high seismic velocities. We see a refracted phases in first impulses from ca. 1600 km to 2500 km offset with velocity about 8.9 km/s. A likely interpretation is that it represents the X-discontinuity of Revenaugh and Jordan (1991). We suggest that it forms a bottom of the mantle LVZ. The increase in velocity at those depths causes that the velocity contrast at the 410 km discontinuity is 2-4% higher than in standard mantle models like IASPEI91 or PREM.

Perchuc, E.; Malinowski, M.; Sroda, P.; Thybo, H.

2006-12-01

304

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

305

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

306

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 ( Zhu and 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.

2014-07-01

307

Chiral superfluidity with p-wave symmetry from an interacting s-wave atomic Fermi gas.  

PubMed

Chiral p-wave superfluids are fascinating topological quantum states of matter that have been found in the liquid (3)He-A phase and arguably in the electronic Sr2RuO4 superconductor. They are fundamentally related to the fractional 5/2 quantum Hall state, which supports fractional exotic excitations. Past studies show that they require spin-triplet pairing of fermions by p-wave interaction. Here we report that a p-wave chiral superfluid state can arise from spin-singlet pairing for an s-wave interacting atomic Fermi gas in an optical lattice. This p-wave state is conceptually distinct from all previous conventional p-wave states as it is for the centre-of-mass motion, instead of the relative motion. It leads to spontaneous generation of angular momentum, finite Chern numbers and topologically protected chiral fermionic zero modes bounded to domain walls, all occuring at a higher critical temperature in relative scales. Signature quantities are predicted for the cold atom experimental condition. PMID:25266996

Liu, Bo; Li, Xiaopeng; Wu, Biao; Liu, W Vincent

2014-01-01

308

What Do s- and p-Wave Neutron Average Radiative Widths Reveal  

SciTech Connect

A first observation of two resonance-like structures at mass numbers 92 and 112 in the average capture widths of the p-wave neutron resonances relative to the s-wave component is interpreted in terms of a spin-orbit splitting of the 3p single-particle state into P{sub 3/2} and P{sub 1/2} components at the neutron separation energy. A third structure at about A = 124, which is not correlated with the 3p-wave neutron strength function, is possibly due to the Pygmy Dipole Resonance. Five significant results emerge from this investigation: (i) The strength of the spin-orbit potential of the optical-model is determined as 5.7 {+-} 0.5 MeV, (ii) Non-statistical effects dominate the p-wave neutron-capture in the mass region A = 85 - 130, (iii) The background magnitude of the p-wave average capture-width relative to that of the s-wave is determined as 0.50 {+-} 0.05, which is accounted for quantitatively in tenns of the generalized Fermi liquid model of Mughabghab and Dunford, (iv) The p-wave resonances arc partially decoupled from the giant-dipole resonance (GDR), and (v) Gamma-ray transitions, enhanced over the predictions of the GDR, are observed in the {sup 90}Zr - {sup 98}Mo and Sn-Ba regions.

Mughabghab, S.F.

2010-04-30

309

Chiral superfluidity with p-wave symmetry from an interacting s-wave atomic Fermi gas  

NASA Astrophysics Data System (ADS)

Chiral p-wave superfluids are fascinating topological quantum states of matter that have been found in the liquid 3He-A phase and arguably in the electronic Sr2RuO4 superconductor. They are fundamentally related to the fractional 5/2 quantum Hall state, which supports fractional exotic excitations. Past studies show that they require spin-triplet pairing of fermions by p-wave interaction. Here we report that a p-wave chiral superfluid state can arise from spin-singlet pairing for an s-wave interacting atomic Fermi gas in an optical lattice. This p-wave state is conceptually distinct from all previous conventional p-wave states as it is for the centre-of-mass motion, instead of the relative motion. It leads to spontaneous generation of angular momentum, finite Chern numbers and topologically protected chiral fermionic zero modes bounded to domain walls, all occuring at a higher critical temperature in relative scales. Signature quantities are predicted for the cold atom experimental condition.

Liu, Bo; Li, Xiaopeng; Wu, Biao; Liu, W. Vincent

2014-09-01

310

Murray Edwards Arriving by Road  

E-print Network

to take a taxi from the Rail Station to Murray Edwards College. Alternatively, during the day, a regularMurray Edwards College Arriving by Road To reach the Storey's Way car park using sat-nav, enter-through road for wide vehicles/coaches. Murray Edwards College is situated on Huntingdon Road, 1 mile west

Goldschmidt, Christina

311

Recording of anomalous shear energy in the teleseismic P-wave coda at Long Valley Caldera, California, on a small aperture array  

SciTech Connect

Anomalous energy in the coda of teleseismic P-waves at Long Valley caldera has been suggested to be a P to S converted arrival, perhaps with the conversion occurring at the boundaries of magma bodies beneath the caldera. We have collected new data with a small-aperture, three-component array located in the northwestern quadrant of the caldera with the purpose of testing this hypothesis. An examination of three teleseismic events using array and particle motion techniques shows that converted P- to S-waves comprise a significant fraction of the early arriving anomalous energy. In volcanic areas such as Long Valley, the scattered energy could originate at a high velocity contrast feature such as magma body interface. In addition, later arriving energy was detected with slow phase velocity and is tentatively identified as body wave to surface wave scattering. Our interpretation is illustrated with waveforms of two earthquakes from the Kuril Islands and one in northern Peru. Our results show that a small-aperture, three-component array can be used to perform detailed analysis of the coda. 12 refs., 8 figs., 1 tab.

Zucca, J.J.; Zandt, G. (Lawrence Livermore National Lab., CA (USA)); Steck, L.K.; Prothero, W.A. (California Univ., Santa Barbara, CA (USA). Dept. of Geology)

1990-03-01

312

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

313

Possible realization of a chiral p-wave paired state in a two-component system  

NASA Astrophysics Data System (ADS)

There is much interest in the realization of systems with p-wave pairing in one dimension or chiral p-wave pairing in two dimensions, because these are believed to support Majorana modes at the ends or inside vortices. We consider a two-component system of composite fermions and provide theoretical evidence that, under appropriate conditions, the screened interaction between the minority composite fermions is such as to produce an almost exact realization of a p-wave paired state described by the so-called anti-Pfaffian wave function. This state is predicted to occur at filling ? =3/8 or 13/8 in GaAs when the Zeeman energy is sufficiently small, and at ? =±3/8 or ±13/8 in single layer graphene when either the Zeeman or the valley splitting is sufficiently small.

Mukherjee, Sutirtha; Jain, J. K.; Mandal, Sudhansu S.

2014-09-01

314

Near-surface seismic attenuation of P-waves in West Texas  

E-print Network

(Member) Robert R. Berg (Member) el S. Watkins (Head of Department) August 1992 ABSTRACT Near-surface Seismic Attenuation of P-Waves in West Texas. (August 1992) Said Awdhah AI-Zahrani, B. S, University of Petroleum and Minerals, Dhahran, Saudi... (Member) Robert R. Berg (Member) el S. Watkins (Head of Department) August 1992 ABSTRACT Near-surface Seismic Attenuation of P-Waves in West Texas. (August 1992) Said Awdhah AI-Zahrani, B. S, University of Petroleum and Minerals, Dhahran, Saudi...

Al-Zahrani, Said Awdhah

2012-06-07

315

Spatial and Temporal Variations in t s \\/t p and in P Wave Residuals at Blue Mountain Lake, New York: Application to Earthquake Prediction  

Microsoft Academic Search

Renewed earthquake activity at Blue Mountain Lake (BML), New York, in July 1973 provided an excellent opportunity to monitor the travel time ratio of $ to P waves (ts\\/t,) in real time and to test the ts\\/t, technique as a predictive tool. From a mean value of 1.73 on July 30, 1973, ts\\/t, decreased to about 1.5 over the next

Yash P. Aggarwal; Lynn R. Sykes; David W. Simpson; Paul G. Richards

1975-01-01

316

Spatial and temporal variations in ts\\/tp and in P wave residuals at Blue Mountain Lake, New York: Application to earthquake prediction  

Microsoft Academic Search

Renewed earthquake activity at Blue Mountain Lake (BML), New York, in July 1973 provided an excellent opportunity to monitor the travel time ratio of S to P waves (ts\\/tp) in real time and to test the ts\\/tp technique as a predictive tool. From a mean value of 1.73 on July 30, 1973, ts\\/tp decreased to about 1.5 over the next

Yash P. Aggarwal; Lynn R. Sykes; David W. Simpson; Paul G. Richards

1975-01-01

317

Upper mantle P wave velocity structure of the eastern Snake River Plain and its relationship to geodynamic models of the region  

Microsoft Academic Search

Tomographic inversions of ~5( teleseismic P wave travel time residuals image a narrow, deep, low-velocity region centered beneath the eastern Snake River Plain, Idaho. Aligned in the direction of North American plate motion, the eastern Snake River Plain is the locus of time-progressive volcanism leading to the Yellowstone hotspot. The low-velocity ano- maly extends to depths of at least 200

Rebecca L. Saltzer; Eugene D. Humphreys

1997-01-01

318

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

319

Drought in Africa caused delayed arrival of European songbirds.  

PubMed

Despite an overall advancement in breeding area arrival, one of the latest spring arrivals in northwest Europe since 1950 of several trans-Saharan songbird species occurred in 2011. Year-round tracking of red-backed shrikes and thrush nightingales revealed that the cause of the delay was a prolongation of stopover time during spring migration at the Horn of Africa, which was affected by extreme drought. Our results help to establish a direct link at the individual level between changes in local climate during migration and arrival and breeding condition in Europe thousands of kilometers further north. PMID:23224549

Tøttrup, A P; Klaassen, R H G; Kristensen, M W; Strandberg, R; Vardanis, Y; Lindström, Å; Rahbek, C; Alerstam, T; Thorup, K

2012-12-01

320

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

321

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

322

The India Asia Collision Zone In The Mantle Beneath Central Tibet Revealed By P Wave Tomography  

Microsoft Academic Search

A wide variety of tectonic models have been proposed for the mechanics of the col- lision between India and Asia and the subsequent raising of the Tibetan plateau. In order to help discriminate these models, the INDEPTH collaboration carried out a se- ries of geophysical experiments across the Tibetan plateau in 1999 and 2000. We have measured P wave residuals

F. Tilmann; J. Ni

2002-01-01

323

Crustal structure of China and surrounding regions from P wave traveltime tomography  

E-print Network

Crustal structure of China and surrounding regions from P wave traveltime tomography Youshun Sun1 the 3-D velocity model. Citation: Sun, Y., and M. N. Tokso¨z (2006), Crustal structure of China is probably Grenville age (about 1.0 Ga). The Cathaysia Block is situated along the coast (partly in the South

Sun, Youshun

324

P-wave seismic attenuation by slow-wave diffusion. Effects of ...  

E-print Network

saturated with small amounts of gas (around 10 % saturation) and water. Grain- .... tained the P-wave quality-factor as a function of frequency for 1D finely ..... erties of granular sedimentary materials, Ph.D. Thesis, Stanford University. Norris

2005-09-20

325

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

326

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

E-print Network

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.

Yusuke Nishida; Shina Tan

2010-10-29

327

Magnitude estimation using the first three seconds P-wave amplitude in earthquake early warning  

E-print Network

shows that for earthquakes in southern California the Pd magnitudes agree with the catalog magnitudes of the P wave. We investigated the attenuation of Pd with the hypocentral distance R in southern California) in Taiwan [Wu and Kanamori, 2005a] and in Southern California. This suggests that we can predict

Wu, Yih-Min

328

P-wave image of the upper mantle structure of central California and southern Nevada  

Microsoft Academic Search

We image the upper mantle velocity structure of central California and southern Nevada by inverting teleseismic P-wave residuals. Beneath the southern Great Valley and adjacent Sierran foothills 4% high velocities extend to a depth of 200–240 km. The magnitude and the depth extent of this anomaly suggest that it is sinking lithosphere. Possible sources of lithospheric material include fragments of

Glenn P. Biasi; Eugene D. Humphreys

1992-01-01

329

ccsd00003592, Resonant scattering properties close to a p-wave Feshbach resonance  

E-print Network

ccsd­00003592, version 2 ­ 29 Mar 2005 Resonant scattering properties close to a p-wave Feshbach resonance F. Chevy 1 , E. G.M. van Kempen 2 , T.Bourdel 1 , J. Zhang 3 , L. Khaykovich 4 , M.Teichmann 1 , L-wave Feshbach resonance. Our model is based on a simple three channel system that reproduces more elaborate

330

The Multiple Runway Planner (MRP): Modeling and Analysis for Arrival Planning  

Microsoft Academic Search

The multiple runway planner (MRP) is a tool that has been developed at Boeing for system effectiveness analysis of arrival sequencing, scheduling, and runway assignment. Given a set of arrivals, with pre-determined meter fix assignments and estimated times of arrival (ETA), the algorithm determines runway assignments and preferred sequences and schedules at the fixes and at the assigned runways. Separation

Matthew E. Berge; Aslaug Haraldsdottir; J. Scharl

2006-01-01

331

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

332

Anisotropic changes in P-wave velocity and attenuation during deformation and fluid infiltration of granite  

USGS Publications Warehouse

Fluid infiltration and pore fluid pressure changes are known to have a significant effect on the occurrence of earthquakes. Yet, for most damaging earthquakes, with nucleation zones below a few kilometers depth, direct measurements of fluid pressure variations are not available. Instead, pore fluid pressures are inferred primarily from seismic-wave propagation characteristics such as Vp/Vs ratio, attenuation, and reflectivity contacts. We present laboratory measurements of changes in P-wave velocity and attenuation during the injection of water into a granite sample as it was loaded to failure. A cylindrical sample of Westerly granite was deformed at constant confining and pore pressures of 50 and 1 MPa, respectively. Axial load was increased in discrete steps by controlling axial displacement. Anisotropic P-wave velocity and attenuation fields were determined during the experiment using an array of 13 piezoelectric transducers. At the final loading steps (86% and 95% of peak stress), both spatial and temporal changes in P-wave velocity and peak-to-peak amplitudes of P and S waves were observed. P-wave velocity anisotropy reached a maximum of 26%. Transient increases in attenuation of up to 483 dB/m were also observed and were associated with diffusion of water into the sample. We show that velocity and attenuation of P waves are sensitive to the process of opening of microcracks and the subsequent resaturation of these cracks as water diffuses in from the surrounding region. Symmetry of the orientation of newly formed microcracks results in anisotropic velocity and attenuation fields that systematically evolve in response to changes in stress and influx of water. With proper scaling, these measurements provide constraints on the magnitude and duration of velocity and attenuation transients that can be expected to accompany the nucleation of earthquakes in the Earth's crust.

Stanchits, S. A.; Lockner, D. A.; Ponomarev, A. V.

2003-01-01

333

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

334

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.

335

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

336

X-36 arrival at Dryden  

NASA Technical Reports Server (NTRS)

NASA and McDonnell Douglas Corporation (MDC) personnel steady the X-36 Tailless Fighter Agility Research Aircraft following arrival at NASA Dryden Flight Research Center, Edwards, California, on July 2, 1996. The aircraft is being hoisted out of it's shipping crate. The NASA/Boeing X-36 Tailless Fighter Agility Research Aircraft program successfully demonstrated the tailless fighter design using advanced technologies to improve the maneuverability and survivability of possible future fighter aircraft. The program met or exceeded all project goals. For 31 flights during 1997 at the Dryden Flight Research Center, Edwards, California, the project team examined the aircraft's agility at low speed / high angles of attack and at high speed / low angles of attack. The aircraft's speed envelope reached up to 206 knots (234 mph). This aircraft was very stable and maneuverable. It handled very well. The X-36 vehicle was designed to fly without the traditional tail surfaces common on most aircraft. Instead, a canard forward of the wing was used as well as split ailerons and an advanced thrust-vectoring nozzle for directional control. The X-36 was unstable in both pitch and yaw axes, so an advanced, single-channel digital fly-by-wire control system (developed with some commercially available components) was put in place to stabilize the aircraft. Using a video camera mounted in the nose of the aircraft and an onboard microphone, the X-36 was remotely controlled by a pilot in a ground station virtual cockpit. A standard fighter-type head-up display (HUD) and a moving-map representation of the vehicle's position within the range in which it flew provided excellent situational awareness for the pilot. This pilot-in-the-loop approach eliminated the need for expensive and complex autonomous flight control systems and the risks associated with their inability to deal with unknown or unforeseen phenomena in flight. Fully fueled the X-36 prototype weighed approximately 1,250 pounds. It was 19 feet long and three feet high with a wingspan of just over 10 feet. A Williams International F112 turbofan engine provided close to 700 pounds of thrust. A typical research flight lasted 35 to 45 minutes from takeoff to touchdown. A total of 31 successful research flights were flown from May 17, 1997, to November 12, 1997, amassing 15 hours and 38 minutes of flight time. The aircraft reached an altitude of 20,200 feet and a maximum angle of attack of 40 degrees. In a follow-on effort, the Air Force Research Laboratory (AFRL), Wright-Patterson Air Force Base, Ohio, contracted with Boeing to fly AFRL's Reconfigurable Control for Tailless Fighter Aircraft (RESTORE) software as a demonstration of the adaptability of the neural-net algorithm to compensate for in-flight damage or malfunction of effectors, such as flaps, ailerons and rudders. Two RESTORE research flights were flown in December 1998, proving the viability of the software approach. The X-36 aircraft flown at the Dryden Flight Research Center in 1997 was a 28-percent scale representation of a theoretical advanced fighter aircraft. The Boeing Phantom Works (formerly McDonnell Douglas) in St. Louis, Missouri, built two of the vehicles in a cooperative agreement with the Ames Research Center, Moffett Field, California.

1996-01-01

337

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

338

Evaluation of QT and P Wave Dispersion and Mean Platelet Volume among Inflammatory Bowel Disease Patients  

PubMed Central

Background: In inflammatory bowel disease (IBD) number of thromboembolic events are increased due to hypercoagulupathy and platelet activation. Increases in mean platelet volume (MPV) can lead to platelet activation, this leads to thromboembolic events and can cause acute coronary syndromes. In IBD patients, QT-dispersion and P-wave dispersion are predictors of ventricular arrhythmias and atrial fibrilation; MPV is accepted as a risk factor for acute coronary syndromes, we aimed at evaluating the correlations of these with the duration of disease, its localization and activity. Methods: The study group consisted of 69 IBD (Ulcerative colitis n: 54, Crohn's Disease n:15) patients and the control group included 38 healthy individuals. Disease activity was evaluated both endoscopically and clinically. Patients with existing cardiac conditions, those using QT prolonging medications and having systemic diseases, anemia and electrolyte imbalances were excluded from the study. QT-dispersion, P-wave dispersion and MPV values of both groups were compared with disease activity, its localization, duration of disease and the antibiotics used. Results: The P-wave dispersion values of the study group were significantly higher than those of the control group. Duration of the disease was not associated with QT-dispersion, and MPV levels. QT-dispersion, P-wave dispersion, MPV and platelet count levels were similar between the active and in mild ulcerative colitis patients. QT-dispersion levels were similar between IBD patients and the control group. No difference was observed between P-wave dispersion, QT-dispersion and MPV values; with regards to disease duration, disease activity, and localization in the study group (p>0.05). Conclusions: P-wave dispersion which is accepted as a risk factor for the development of atrial fibirilation was found to be high in our IBD patients. This demonstrates us that the risk of developing atrial fibrillation may be high in patients with IBD. No significant difference was found in the QT-dispersion, and in the MPV values when compared to the control group. PMID:21960745

DOGAN, Yuksel; SOYLU, Aliye; EREN, Gulay A.; POTUROGLU, Sule; DOLAPCIOGLU, Can; SONMEZ, Kenan; DUMAN, Habibe; SEVINDIR, Isa

2011-01-01

339

Rupture details of the 28 March 2005 Sumatra Mw 8.6 earthquake imaged with teleseismic P waves  

E-print Network

Rupture details of the 28 March 2005 Sumatra Mw 8.6 earthquake imaged with teleseismic P waves of the 28 March 2005 Sumatra Mw 8.6 earthquake by back-projecting teleseismic P waves recorded by the Global. Shearer (2005), Rupture details of the 28 March 2005 Sumatra Mw 8.6 earthquake imaged with teleseismic P

Shearer, Peter

340

Three-Dimensional P-Wave Velocity Structure and Precise Earthquake Relocation at Great Sitkin Volcano, Alaska  

E-print Network

Three-Dimensional P-Wave Velocity Structure and Precise Earthquake Relocation at Great Sitkin Volcano, Alaska by Jeremy D. Pesicek, Clifford H. Thurber, Heather R. DeShon,* Stephanie G. Prejean-difference tomography to increase the precision of earthquake locations and constrain regional 3D P-wave velocity

341

The rupture process and asperity distribution of three great earthquakes from long-period diffracted P-waves  

NASA Technical Reports Server (NTRS)

The variation of maximum earthquake size along the subduction zones has been interpreted as a variation in the seismic coupling ostensibly related to the mechanical conditions of the fault zone. Great differences are noted between the seismographs of the three great earthquakes whose rupture processes are presently considered: in the Kurile Islands (1963), The Rat Islands (1965) and Alaska (1964). On-scale long period P waves were recorded in all cases. Source time functions are deconvolved from the observed periods. It is concluded that maximum earthquake size is related to the asperity distribution on the fault. The subduction zones with the largest earthquakes have very large asperities, as in the Alaskan case, while the zones with the smaller great earthquakes, such as the Kurile Islands, have smaller scattered asperities.

Ruff, L.; Kanamori, H.

1983-01-01

342

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

343

Electron-He{sup +} P-wave elastic scattering and photoabsorption in two-electron systems  

SciTech Connect

In a previous paper [A. K. 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{sup +} 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{sup -} are calculated in the elastic region--i.e., leaving He{sup +} and H in their respective ground states--and compared with previous calculations. Radiative attachment rates are also calculated.

Bhatia, A. K. [NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2006-01-15

344

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

345

Variation of P-Wave Velocity before the Bear Valley, California, Earthquake of 24 February 1972.  

PubMed

Residuals for P-wave traveltimes at a seismnograph station near Bear Valley, California, for small, precisely located local earthquakes at distances of 20 to 70 kilometers show a sharp increase of nearly 0.3 second about 2 months before a magnitude 5.0 earthquake that occurred within a few kilometers of the station. This indicates that velocity changes observed elsewhere premonitory to earthquakes, possibly related to dilatancy, occur along the central section of the San Andreas fault system. PMID:17784227

Robinson, R; Wesson, R L; Ellsworth, W L

1974-06-21

346

Testable Signatures of Quantum Nonlocality in a Two-Dimensional Chiral p-Wave Superconductor  

SciTech Connect

A class of topological excitations--the odd-winding number vortices--in a spinless 2D chiral p-wave (p{sub x}+ip{sub y}) superconductor traps Majorana fermion states in the vortex cores. For a dilute gas of such vortices, the lowest energy fermionic eigenstates are intrinsically nonlocal. We predict two testable signatures of this unusual quantum nonlocality in quasiparticle tunneling experiments. We discuss why the associated teleportationlike phenomenon does not imply the violation of causality.

Tewari, Sumanta; Zhang Chuanwei; Das Sarma, S. [Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Nayak, Chetan [Microsoft Station Q, CNSI Building, University of California, Santa Barbara, California 93108 (United States); Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States); Lee, Dung-Hai [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2008-01-18

347

Testable signatures of quantum nonlocality in a two-dimensional chiral p-wave superconductor.  

PubMed

A class of topological excitations-the odd-winding number vortices-in a spinless 2D chiral p-wave (px+ipy) superconductor traps Majorana fermion states in the vortex cores. For a dilute gas of such vortices, the lowest energy fermionic eigenstates are intrinsically nonlocal. We predict two testable signatures of this unusual quantum nonlocality in quasiparticle tunneling experiments. We discuss why the associated teleportationlike phenomenon does not imply the violation of causality. PMID:18232909

Tewari, Sumanta; Zhang, Chuanwei; Das Sarma, S; Nayak, Chetan; Lee, Dung-Hai

2008-01-18

348

P-wave and S-wave velocity structure of northern Cascadia margin gas hydrates  

NASA Astrophysics Data System (ADS)

Single-channel seismic and wide-angle reflection data collected in September 2005 were analysed along a 2-D profile of 10 ocean bottom seismometers (OBSs) on the continental slope region off Vancouver Island, near ODP Site 889 and IODP Site U1327. The objectives were to determine the shallow P-wave and S-wave velocity structure associated with marine gas hydrates and to estimate the hydrate concentration and distribution in the sediment pore space. Combined traveltime inversion of single-channel and OBS data produced a P-wave velocity model down to the depth of the bottom-simulating reflector (BSR) at 230(±5) m below the seafloor (mbsf). Mean velocities, which increased from 1.50 km s-1 at the seafloor to 1.88 km s-1 at the BSR, are in good agreement with the sonic log data from Sites 889 and U1327. The increase in P-wave velocity of the hydrate-bearing sediments relative to a background no-hydrate velocity was utilized to estimate the hydrate concentration by using effective medium theory. An average concentration of 13 per cent in the interval from 120-230 mbsf was estimated from the P-wave velocity model. Lateral continuity of the model data confirms that these average hydrate concentrations are also found around the drillsites out to distances of a few kilometres. Forward modelling of S-waves was carried out using the data from the OBS horizontal components. Above the BSR, S-wave velocities are higher than a background velocity profile based on a rock physics model and on global averages for unconsolidated sediments. This increase in velocity suggests that the hydrate is distributed as part of the load-bearing matrix to increase the rigidity of the sediment.

Dash, Ranjan; Spence, George

2011-12-01

349

Effect of P-wave interaction in 6He and 6Li photoabsorption  

E-print Network

The total photoabsorption cross sections of six-body nuclei are calculated including complete final state interaction via the Lorentz Integral Transform method. The effect of nucleon-nucleon central P-wave forces is investigated. Comparing to results with central potentials containg S-wave forces only one finds considerably more strength in the low-energy cross sections and a rather strong improvement in comparison with experimental data, in particular for 6Li.

Sonia Bacca; Nir Barnea; Winfried Leidemann; Giuseppina Orlandini

2003-11-06

350

High-frequency P-wave seismic noise driven by ocean winds  

Microsoft Academic Search

Earth's background vibrations at frequencies below about 0.5 Hz have been attributed to ocean-wave energy coupling into the ground and propagating as surface waves and P-waves (compressional waves deep within the Earth). However, the origin and nature of seismic noise on land at frequencies around 1 Hz has not yet been well studied. Using array beamforming, we analyze the seismic

Jian Zhang; Peter Gerstoft; Peter M. Shearer

2009-01-01

351

Three-dimensional P wave velocity model for the San Francisco Bay region, California  

Microsoft Academic Search

A new three-dimensional P wave velocity model for the greater San Francisco Bay region has been derived using the double-difference seismic tomography method, using data from about 5,500 chemical explosions or air gun blasts and approximately 6,000 earthquakes. The model region covers 140 km NE-SW by 240 km NW-SE, extending from 20 km south of Monterey to Santa Rosa and

Clifford H. Thurber; Thomas M. Brocher; Haijiang Zhang; Victoria E. Langenheim

2007-01-01

352

Status of some P-wave baryon resonances and importance of inelastic channels  

E-print Network

We analyze the current status of three P-wave baryon states $N(1710){1/ 2}^+$, $N(1900){3/2}^+$, and $\\Delta(1600){3/2}^+$ as given in the Review of Particles Physics (RPP). Since the evidence for a particle's existence is linked to its RPP "star" rating, we discuss its subjective present definition. We also present the accumulating evidence supporting these states and give our new "star" rating recommendations.

Burkert, Volker D; Klempt, Eberhard; Ronchen, Deborah; Sarantsev, Andrey V; Sato, Toru; Svarc, Alfred; Tiator, Lothar; Workman, Ron L

2014-01-01

353

At the beginning of April 1911 Albert Einstein arrived in Prague to become full professor of theoretical physics at the German part of Charles University. It was there, for the first time, that  

E-print Network

At the beginning of April 1911 Albert Einstein arrived in Prague to become full professor anticipated what a future theory of gravity should look like. At the occasion of the Einstein and sightseeing (e.g., places associated with Einstein, Mach, Doppler, Kepler, and Brahe). We are considering

Cerveny, Vlastislav

354

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

355

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

356

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

357

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 p(x)+ip(y)-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

358

Low-frequency P-wave logging for improved compressional velocity in slow formation gas zones  

SciTech Connect

The ratio of compressional to shear velocity is commonly used as a gas indicator, for seismic correlation, and for rock mechanical properties evaluation in the oil industry. However, in soft rock gas zone, it is difficult to obtain a good measure of compressional velocity. Traditional monopole sonic logging tools operate with source frequencies above 10 kHz, giving rise to large amplitude borehole fluid modes which dominate compressional wave traveling with speed slower than the fluid speed. Numerical modeling of monopole sonic waveforms in a fluid-filled borehole in porous formations confirms these observations, but also shows that at significantly lower frequencies two important changes occur: (1) the non-Stoneley fluid modes becomes extremely small, and (2) the P-wave amplitude is greatly increased. Therefore, at low frequencies, logging of these very slow P-waves in gas zones should be feasible. A field example shows the value of this low frequency technique, resulting in measurements of P-wave velocities substantially lower than the fluid speed.

Wu, P.T.; Darling, H.L.; Scheibner, D.

1995-12-31

359

Three-dimensional P wave azimuthal anisotropy in the lithosphere beneath China  

NASA Astrophysics Data System (ADS)

anisotropy in the upper mantle beneath East Asia has been studied extensively using shear wave (SKS) splitting measurements, which have provided important information on mantle dynamics in this region. However, SKS measurements have poor vertical resolution, and so their interpretations are usually not unique. In this work we use a large number of traveltime data from 34,036 local earthquakes recorded by 1563 seismic stations to determine the first model of 3-D P wave azimuthal anisotropy in the lithosphere beneath China. Our results show that the fast velocity directions (FVDs) are generally correlated with the surface geologic features, such as the strikes of the orogens, active faults, and tectonic boundaries. The FVDs in the upper crust are normal to the maximal horizontal stress (?H) in regions with extensive compression such as the Tibetan Plateau, whereas they are subparallel to ?H in strike-slip shear zones such as the western and eastern Himalayan syntax. The comparison of the FVDs of P wave anisotropy with SKS splitting measurements indicates that beneath the Tibetan Plateau the seismic anisotropy in the lithosphere contributes significantly to the SKS splitting observations. In contrast, in east China the P wave FVDs in the lithosphere are different from the SKS splitting measurements, suggesting that the SKS splitting is mainly caused by the anisotropy in the deeper mantle such as the asthenosphere and the mantle transition zone under east China. These novel results provide important new information on the lithospheric deformation and mantle dynamics in East Asia.

Huang, Zhouchuan; Wang, Pan; Zhao, Dapeng; Wang, Liangshu; Xu, Mingjie

2014-07-01

360

Arrival time parametric imaging of the hemodynamic balance changes between the hepatic artery and the portal vein during deep inspiration, using Sonazoid-enhanced ultrasonography: A case of Budd-Chiari syndrome  

PubMed Central

This case report concerns a 40-year-old male who had previously been treated for an esophageal varix rupture, at the age of 30 years. The medical examination at that time revealed occlusion of the inferior vena cava in the proximity of the liver, leading to the diagnosis of the patient with Budd-Chiari syndrome. The progress of the patient was therefore monitored in an outpatient clinic. The patient had no history of drinking or smoking, but had suffered an epileptic seizure in 2004. The patient's family history revealed nothing of note. In February 2012, color Doppler ultrasonography (US) revealed a change in the blood flow in the right portal vein branch, from hepatopetal to hepatofugal, during deep inspiration. Arrival time parametric imaging (At-PI), using Sonazoid-enhanced US, was subsequently performed to examine the deep respiration-induced changes observed in the hepatic parenchymal perfusion. US images captured during deep inspiration demonstrated hepatic parenchymal perfusion predominantly in red, indicating that the major blood supply was the hepatic artery. During deep expiration, the portal venous blood flow remained hepatopetal, and hepatic parenchymal perfusion was displayed predominantly in yellow, indicating that the portal vein was the major source of the blood flow. The original diagnostic imaging results were reproduced one month subsequently by an identical procedure. At-PI enabled an investigation into the changes that were induced in the hepatic parenchymal perfusion by a compensatory mechanism involving the hepatic artery. These changes occurred in response to a reduction in the portal venous blood flow, as is observed in the arterialization of hepatic blood flow that is correlated with the progression of chronic hepatitis C. It has been established that the peribiliary capillary plexus is important in the regulation of hepatic arterial blood flow. However, this case demonstrated that the peribiliary capillary plexus also regulates acute changes in portal venous blood flow, in addition to the chronic reduction in blood flow that is observed in patients with chronic hepatitis C. PMID:23935711

WAKUI, NORITAKA; TAKAYAMA, RYUJI; MATSUKIYO, YASUSHI; KAMIYAMA, NAOHISA; KOBAYASHI, KOJIRO; MUKOZU, TAKANORI; NAKANO, SHIGERU; IKEHARA, TAKASHI; NAGAI, HIDENARI; IGARASHI, YOSHINORI; SUMINO, YASUKIYO

2013-01-01

361

The P-wave velocity of the uppermost mantle of the Rio Grande rift region of north central New Mexico.  

USGS Publications Warehouse

A network of seismograph stations has operated in north-central New Mexico since 1975. The network is approximately 200 by 300 km in size and encompasses the Rio Grande rift there. Several seismic refraction experiments have been reported in the literature for the region of the network and adjacent areas. Because all of the seismic refraction lines are unreversed, Pn velocities reported were mainly of the inverse travel time slope for the direction of the corresponding line. The values of the inverse slope for those studies range from 7.6 to 8.2 km/s. The purpose of our study is to estimate the P-wave velocity of the uppermost mantle by using the time term method. First, we timed the Pn waves of strong signals from five explosions and eight shallow earthquakes recorded by the network. The main data set, which contains 87 time-distance pairs, was processed by using the time term method. The Pn velocity estimated by this method is 8.0 + or - 0.1 km/s. To corroborate this estimate, we then processed 10 subsets of the main data set in the same way. Almost all of the solutions show velocities of 7.9-8.1 km/s, in agreement with the velocity determined for the main data set. -Authors

Murdock, J. N.; Jaksha, L. H.

1981-01-01

362

Induced p-wave superfluidity in strongly interacting imbalanced Fermi gases  

SciTech Connect

The induced interaction among the majority spin species, due to the presence of the minority species, is computed for the case of a population-imbalanced resonantly interacting Fermi gas. It is shown that this interaction leads to an instability, at low temperatures, of the recently observed polaron Fermi liquid phase of strongly imbalanced Fermi gases to a p-wave superfluid state. We find that the associated transition temperature, while quite small in the weakly interacting BCS regime, is experimentally accessible in the strongly interacting unitary regime.

Patton, Kelly R.; Sheehy, Daniel E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2011-05-15

363

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

364

Condensates of p-Wave Pairs Are Exact Solutions for Rotating Two-Component Bose Gases  

SciTech Connect

We derive exact analytical results for the wave functions and energies of harmonically trapped two-component Bose-Einstein condensates with weakly repulsive interactions under rotation. The isospin symmetric wave functions are universal and do not depend on the matrix elements of the two-body interaction. The comparison with the results from numerical diagonalization shows that the ground state and low-lying excitations consist of condensates of p-wave pairs for repulsive contact interactions, Coulomb interactions, and the repulsive interactions between aligned dipoles.

Papenbrock, T [UTK/ORNL/GSI-Darmstadt/Inst. für Kernphysik, Tech. Univ. Darmstadt-Germany; Reimann, S. M. [Lund University, Sweden; Kavoulakis, G. M. [Technological Educational Institute of Crete, Heraklion, Greece

2012-01-01

365

Effective Field Theory for a p-wave Superconductor in the Subgap Regime  

E-print Network

We construct an effective field theory for the 2d spineless p-wave paired superconductor that faithfully describes the topological properties of the bulk state, and also provides a model for the subgap states at vortex cores and edges. In particular it captures the topologically protected zero modes and has the correct ground state degeneracy on the torus. We also show that our effective field theory becomes a topological field theory in a well defined scaling limit and that the vortices have the expected non-abelian braiding statistics.

Hansson, Thors Hans; Nair, V Parameswaran; Sreejith, G J

2014-01-01

366

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

367

hal-00166351,version2-1Apr2008 Three fully polarized fermions close to a p-wave Feshbach resonance  

E-print Network

hal-00166351,version2-1Apr2008 Three fully polarized fermions close to a p-wave Feshbach resonance´erieure, UPMC, CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France. 2 LENS - European Laboratory for Non

Boyer, Edmond

368

Simulated annealing inversion of teleseismic P-wave slowness and azimuth for crustal velocity structure at Long Valley Caldera  

Microsoft Academic Search

Simulated annealing, a non-linear global search algorithm, is used to invert teleseismic P-wave slowness and azimuth data for crustal velocity structure. Synthetic tests show that simulated annealing is able to locate low P-wave velocity zones with reasonable accuracy in space, and recovers almost 70% of the target velocity perturbations. Testing suggests that significant results can be obtained with as few

Lee K. Steck

1995-01-01

369

THE EFFECT OF CORRELATED ARRIVALS ON QUEUES  

Microsoft Academic Search

Using Markov renewal arrival processes, a study of the effect of serial correlations in the arrival process on the mean queueing performance has been done. We show that positive serial correlations may have major impact on the mean queue lengths (and consequently on other performance measures).

B. EDDY PATUWO; RALPH L. DISNEY; DONALD C. McNICKLE

1993-01-01

370

Late Arriving Particles in Cosmic Ray Air Showers and AGASA's Determination of UHECR Energies  

E-print Network

We give the first detailed study of the arrival time distribution of nucleons in UHECR air showers. We analyze in detail the influence of late arriving particles on the energy determination of the AGASA experiment, as well as how the arrival time distribution changes with distance from shower core. Our calculations are consistent with experimental observations of the AGASA group. Crucial to obtaining agreement, is the correct implementation of the energy loss for low-energy protons. We confirm AGASA's estimation of the error in their energy determination associated with late-arriving particles, assuming primary protons.

Hans-Joachim Drescher; Glennys R. Farrar

2005-06-08

371

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

372

First-order reflection/transmission coefficients for unconverted plane P waves in weakly anisotropic media  

NASA Astrophysics Data System (ADS)

We present approximate formulae for the plane-wave displacement reflection/transmission (R/T) coefficients for interfaces of arbitrary contrast, separating two homogeneous, weakly anisotropic media. They result from boundary conditions requiring continuity of displacement vector and traction, in which coupled S waves are considered as a single S wave and exact quantities are replaced by first-order quantities used in first-order ray tracing. Specifically, the phase velocities, slowness and polarization vectors of P and coupled S waves appearing in the boundary conditions are of the first-order with respect to the deviations of anisotropy from isotropy. Application of the derived R/T coefficients transforms the amplitude of an incident P wave into amplitudes of reflected/transmitted P or coupled S waves. Coefficients can be computed for any incidence angle between 0° and 90°, and for any azimuth. In this paper, we test the accuracy of the derived R/T coefficients of unconverted plane P waves. We show that, except for critical regions, first-order coefficients approximate the exact coefficients with accuracy comparable or better than accuracy of linearized weak-contrast coefficients, which are, however, applicable only in subcritical regions.

Farra, Véronique; Pšen?ík, Ivan

2010-12-01

373

P-Wave to Rayleigh-wave conversion coefficients for wedge corners; model experiments  

USGS Publications Warehouse

An analytic solution is not available for the diffraction of elastic waves by wedges; however, numerical solutions of finite-difference type are available for selected wedge angles. The P- to Rayleigh-wave conversion coefficients at wedge tips have been measured on two-dimensional seismic models for stress-free wedges with wedge angles, ??0, of 10, 30, 60, 90 and 120??. The conversion coefficients show two broad peaks and a minimum as a function of the angle between the wedge face and the direction of the incident P-wave. The minimum occurs for the P wave incident parallel to the wedge face and one maximum is near an incidence angle of 90?? to the wedge face. The amplitude of this maximum, relative to the other, decreases as the wedge angle increases. The asymmetry of the conversion coefficients, CPR(??; ??0), relative to parallel incidence (?? = 0) increases as the wedge angle increases. The locations of the maxima and the minimum as well as the asymmetry can be explained qualitatively. The conversion coefficients are measured with an accuracy of ??5% in those regions where there are no interfering waves. A comparison of the data for the 10?? wedge with the theoretical results for a half plane (0?? wedge) shows good correlation. ?? 1978.

Gangi, A.F.; Wesson, R.L.

1978-01-01

374

1 Models for Bid Arrivals and Bidder Arrivals in Online Auctions  

Microsoft Academic Search

Abstract The arrival process of bidders and bids in online auctions is important for studying and modeling supply and demand,in the online marketplace. Whereas bid arrivals are observable in online auction data, bidder behavior is typically not. A popular assumption in the online auction literature is that a homogeneous,Poisson bidder arrival process is a reasonable approximation. This approximation underlies statistical

Ralph P. Russo; Galit Shmueli; Wolfgang Jank; Nariankadu D. Shyamalkumar

375

STS-114: Discovery Crew Arrival  

NASA Technical Reports Server (NTRS)

George Diller of NASA Public Affairs narrates the STS-114 Crew arrival at Kennedy Space Center aboard a Gulf Stream aircraft. They were greeted by Center Director Jim Kennedy. Commander Eileen Collins introduced each of her crew members and gave a brief description of their roles in the mission. Mission Specialist 3, Andrew Thomas will be the lead crew member on the inspection on flight day 2; he is the intravehicular (IV) crew member that will help and guide Mission Specialists Souichi Noguchi and Stephen Robinson during their spacewalks. Pilot James Kelly will be operating the shuttle systems in flying the Shuttle; he will be flying the space station robotic arm during the second extravehicular activity and he will be assisting Mission Specialist Wendy Lawrence during the other two extravehicular activities; he will be assisting on the rendezvous on flight day three, and landing of the shuttle. Commander Collins also mentioned Pilot Kelly's recent promotion to Colonel by the United States Air Force. Mission Specialist 1, Souichi Noguchi from JAXA (The Japanese Space Agency) will be flying on the flight deck for ascent; he will be doing three spacewalks on day 5, 7, and 9; He will be the photo/TV lead for the different types of cameras on board to document the flight and to send back the information to the ground for both technical and public affairs reasons. Mission Specialist 5, Charles Camada will be doing the inspection on flight day 2 with Mission Specialist Thomas and Pilot Kelly; he will be transferring the logistics off the shuttle and onto the space station and from the space station back to the shuttle; He will help set up eleven lap tops on board. Mission Specialist 4, Wendy Lawrence will lead the transfer of logistics to the space station; she is the space station arm operator during extravehicular activities 1 and 3; she will be carrying the 6,000 pounds of external storage platform from the shuttle payload bay over to the space station; she is also in charge of the shuttle storage. Mission Specialist 2, Stephen Robinson is the flight engineer of the shuttle; he will be doing spacewalks with Mission Specialist Noguchi; he will set up the 11 lap top computers on board. Each crew member gave a brief message to the press. Commander Eileen later gave her final message and the crew walked back to the Astronaut Corps.

2005-01-01

376

High-resolution 3-D P-wave tomographic imaging of the shallow magmatic system of Erebus volcano, Antarctica  

NASA Astrophysics Data System (ADS)

Erebus volcano (Ross Island), the most active volcano in Antarctica, is characterized by a persistent phonolitic lava lake at its summit and a wide range of seismic signals associated with its underlying long-lived magmatic system. The magmatic structure in a 3 by 3 km area around the summit has been imaged using high-quality data from a seismic tomographic experiment carried out during the 2008-2009 austral field season (Zandomeneghi et al., 2010). An array of 78 short period, 14 broadband, and 4 permanent Mount Erebus Volcano Observatory seismic stations and a program of 12 shots were used to model the velocity structure in the uppermost kilometer over the volcano conduit. P-wave travel times were inverted for the 3-D velocity structure using the shortest-time ray tracing (50-m grid spacing) and LSQR inversion (100-m node spacing) of a tomography code (Toomey et al., 1994) that allows for the inclusion of topography. Regularization is controlled by damping and smoothing weights and smoothing lengths, and addresses complications that are inherent in a strongly heterogeneous medium featuring rough topography and a dense parameterization and distribution of receivers/sources. The tomography reveals a composite distribution of very high and low P-wave velocity anomalies (i.e., exceeding 20% in some regions), indicating a complex sub-lava-lake magmatic geometry immediately beneath the summit region and in surrounding areas, as well as the presence of significant high velocity shallow regions. The strongest and broadest low velocity zone is located W-NW of the crater rim, indicating the presence of an off-axis shallow magma body. This feature spatially corresponds to the inferred centroid source of VLP signals associated with Strombolian eruptions and lava lake refill (Aster et al., 2008). Other resolved structures correlate with the Side Crater and with lineaments of ice cave thermal anomalies extending NE and SW of the rim. High velocities in the summit area possibly constitute the seismic image of an older caldera, solidified intrusions or massive lava flows. REFERENCES: Aster et al., (2008) Moment tensor inversion of very long period seismic signals from Strombolian eruptions of Erebus volcano. J. Volcanol. Geotherm. Res., 177, 635-647. Toomey et al., (1994), Tomographic imaging of the shallow crustal structure of the East Pacific Rise at 9°30'N. J. Geophys. Res., 99 (B12), 24,135-24,157. Zandomeneghi et al., (2010), Seismic Tomography of Erebus Volcano, Antarctica, Eos, 91, 6, 53-55.

Zandomeneghi, D.; Aster, R. C.; Barclay, A. H.; Chaput, J. A.; Kyle, P. R.

2011-12-01

377

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

378

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

379

Energy space entanglement spectrum of pairing models with s-wave and p-wave symmetry  

NASA Astrophysics Data System (ADS)

We study the entanglement between blocks of energy levels in 1D models for s-wave and p-wave superconductivity. The ground state entanglement entropy and entanglement spectrum (ES) of a block of ? levels around the Fermi point is obtained and related to its physical properties. In the superconducting phase at large coupling, the maximal entropy grows with the number of levels L as 1/2ln(L). The number of levels presenting maximal entanglement is shown to estimate the number of Cooper pairs involved in pairing correlations. Moreover, the properties of the ES signal the presence of the Read-Green quantum phase transition in the p +ip model, and of the Moore-Read line, which is difficult to characterize. This work establishes a link between physical properties of superconducting phases and quantum entanglement.

Rodríguez-Laguna, Javier; Berganza, Miguel Ibáñez; Sierra, Germán

2014-07-01

380

Towards complete phase diagrams of a holographic p-wave superconductor model  

NASA Astrophysics Data System (ADS)

We study in detail the phase structure of a holographic p-wave superconductor model in a five dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. To construct complete phase diagrams of the model, we consider both the soliton and black hole backgrounds. In both two cases, there exist second order, first order and zeroth order phase transitions, and the so-called "retrograde condensation" also happens. In particular, in the soliton case with the mass of the vector field being beyond a certain critical value, we find a series of phase transitions happen such as "insulator/superconductor/insulator/superconductor", as the chemical potential continuously increases. We construct complete phase diagrams in terms of temperature and chemical potential and find some new phase boundaries.

Cai, Rong-Gen; Li, Li; Li, Li-Fang; Yang, Run-Qiu

2014-04-01

381

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

NASA Astrophysics Data System (ADS)

We have studied semileptonic B meson decays with a p-wave charm meson in the final state using 3.29×106 BB¯ events collected with the CLEO II detector at the Cornell Electron-Positron Storage Ring. We find a value for the exclusive semileptonic product branching fraction B\\(B--->D01l-?¯l\\)B\\(D01-->D*+?-\\) = \\(0.373+/-0.085+/-0.052+/-0.024\\)% and an upper limit for B\\(B--->D*02l-?¯l\\)B\\(D*02-->D*+?-\\)<0.16% (90% C.L.). Furthermore, we present the first measurement of the q2 spectrum for B--->D01l-?¯l.

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.; Nemati, B.; Richichi, S. J.; Ross, W. R.; Skubic, P.; Bishai, M.; Fast, J.; Hinson, J. W.; Menon, N.; Miller, D. H.; Shibata, E. I.; Shipsey, I. P.; Yurko, M.; Glenn, S.; Johnson, S. D.; Kwon, Y.; Roberts, S.; Thorndike, E. H.; Jessop, C. P.; Lingel, K.; Marsiske, H.; Perl, M. L.; Savinov, V.; Ugolini, D.; Wang, R.; Zhou, X.; Coan, T. E.; Fadeyev, V.; Korolkov, I.; Maravin, Y.; Narsky, I.; Shelkov, V.; Staeck, J.; Stroynowski, R.; Volobouev, I.; Ye, J.; 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.; Bartelt, J.; Csorna, S. E.; Jain, V.; McLean, K. W.; Marka, S.; Godang, R.; Kinoshita, K.; Lai, I. C.; Pomianowski, P.; Schrenk, S.; Bonvicini, G.; Cinabro, D.; Greene, R.; Perera, L. P.; Zhou, G. J.; Barish, B.; Chadha, M.; Chan, S.; Eigen, G.; Miller, J. S.; O'Grady, C.; Schmidtler, M.; Urheim, J.; Weinstein, A. J.; Würthwein, F.; Bliss, D. W.; Masek, G.; Paar, H. P.; Prell, S.; Sharma, V.; Asner, D. M.; Gronberg, J.; Hill, T. S.; Lange, D. J.; Menary, S.; Morrison, R. J.; Nelson, H. N.; Nelson, T. K.; Qiao, C.; Richman, J. D.; Roberts, D.; Ryd, A.; Witherell, M. S.; Balest, R.; Behrens, B. H.; Ford, W. T.; Park, H.; Roy, J.; Smith, J. G.; Alexander, J. P.; Bebek, C.; Berger, B. E.; Berkelman, K.; Bloom, K.; Cassel, D. G.; Cho, H. A.; Crowcroft, D. S.; Dickson, M.; Drell, P. S.; Ecklund, K. M.; Ehrlich, R.; Foland, A. D.; Gaidarev, P.; Gibbons, L.; Gittelman, B.; Gray, S. W.; Hartill, D. L.; Heltsley, B. K.; Hopman, P. I.; Jones, S. L.; Kandaswamy, J.; Kim, P. C.; Kreinick, D. L.; Lee, T.; Liu, Y.; Mistry, N. B.; Ng, C. R.; Nordberg, E.; Ogg, M.; Patterson, J. R.; Peterson, D.; Riley, D.; Soffer, A.; Valant-Spaight, B.; Ward, C.; Athanas, M.; Avery, P.; Jones, D. C.; Lohner, M.; Prescott, C.; Yelton, J.; Zheng, J.; Brandenburg, G.; Briere, R. A.; Ershov, A.; Gao, Y. S.; Kim, D. Y.-J.; Wilson, R.; Yamamoto, H.; Browder, T. E.; Li, Y.; Rodriguez, J. L.; Bergfeld, T.; Eisenstein, B. I.; Ernst, J.; Gladding, G. E.; Gollin, G. D.; Hans, R. M.; Johnson, E.; Karliner, I.; Marsh, M. A.; Palmer, M.; Selen, M.; Thaler, J. J.; Edwards, K. W.; Bellerive, A.; Janicek, R.; Macfarlane, D. B.; Patel, P. M.; Sadoff, A. J.; Ammar, R.; Baringer, P.; Bean, A.; Besson, D.; Coppage, D.; Darling, C.; Davis, R.; Hancock, N.; Kotov, S.; Kravchenko, I.; Kwak, N.; Anderson, S.; Kubota, Y.; Lee, S. J.; O'Neill, J. J.; Patton, S.; Poling, R.; Riehle, T.; Smith, A.; Alam, M. S.; Athar, S. B.; Ling, Z.; Mahmood, A. H.; Severini, H.; Timm, S.; Wappler, F.

1998-05-01

382

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

383

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

384

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

385

Effects of p-wave annihilation on the angular power spectrum of extragalactic gamma-rays from dark matter annihilation  

SciTech Connect

We present a formalism for estimating the angular power spectrum of extragalactic gamma-rays produced by dark matter annihilating with any general velocity-dependent cross section. The relevant density and velocity distribution of dark matter is modeled as an ensemble of smooth, universal, rigid, disjoint, spherical halos with distribution and universal properties constrained by simulation data. We apply this formalism to theories of dark matter with p-wave annihilation, for which the relative-velocity-weighted annihilation cross section is {sigma}v=a+bv{sup 2}. We determine that this significantly increases the gamma-ray power if b/a > or approx. 10{sup 6}. The effect of p-wave annihilation on the angular power spectrum is very similar for the sample of particle physics models we explored, suggesting that the important effect for a given b/a is largely determined by the cosmic dark matter distribution. If the dark matter relic from strong p-wave theories is thermally produced, the intensities of annihilation gamma-rays are strongly p-wave suppressed, making them difficult to observe. If an angular power spectrum consistent with a strong p wave were to be observed, it would likely indicate nonthermal production of dark matter in the early Universe.

Campbell, Sheldon; Dutta, Bhaskar [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States)

2011-10-01

386

Time-resolved velocity tomography at Mount Etna (Italy) volcano during 2000-2008  

NASA Astrophysics Data System (ADS)

The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography (4D tomography) to detect variations in elastic parameters during different volcanic cycles in the period November 2000-May 2008, that includes several flank eruptions. The use of a large number of permanent seismic stations and the abundance of local earthquakes, occurring both before and during the eruptions, guarantee consistent and high-resolution velocity models. First, we performed a tomographic inversion of the whole data set to define the 3D P-wave velocity (VP) and the structure of the P- to S-wave velocity ratio (VP/VS). A total of ca. 3,000 well constrained earthquakes (root mean square time residuals ? 0.4 s; horizontal and vertical hypocentral location errors ? 1.5 km; azimuthal gap of the stations ? 180°), ca. 40,000 P-wave arrivals, and ca. 9,000 S-wave arrivals were inverted to model a grid, 2 km by 2 km by 1 km spaced, with the use of SIMULPS-14 software. Then, on the basis of geophysical and geochemical observations indicating some cyclic recharging and discharging (eruptions) phases, we inverted different sub-periods to investigate time variations in the elastic parameters. The observed time changes of velocity-oriented anomalies suggest that four-dimensional tomography could provide a basis for more efficient volcano monitoring and short- and midterm eruption forecasting.

Barberi, G.; Cocina, O.; Chiarabba, C.; De Gori, P.; Patane', D.

2012-04-01

387

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...

388

University of Birmingham International Student Arrival Guide 2013 / 14 1 INTERNATIONAL STUDENT  

E-print Network

during term time and will be showing the major sporting games on its big screens. The Duck and Scholar the site reception when you arrive. We do advise however that you purchase these in advance of your arrival of cleaning in the communal areas, i.e. the kitchen. Equipment will be provided for this purpose but you

Birmingham, University of

389

Arrival Guide. For international students  

E-print Network

and inspiring. By the end of your studies you will be well equipped to play your part in the advancement is well under way, earning it a New York Times ranking of second best city to visit in the world in 2014 and boasts its own symphony orchestra. For the sports-minded, Christchurch is hard to beat whether you

Hickman, Mark

390

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. PMID:22870246

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

2012-01-01

391

Revision of P-wave velocity and thickness of hydrate layer in Shenhu Area, South China Sea  

NASA Astrophysics Data System (ADS)

To revise P-wave velocity and thickness of the hydrate layer in the Shenhu area of the South China Sea, acoustic and resistivity logging curves are reanalyzed. The waterlogging phenomenon is found in the shallow sediments of five drilling wells, which causes P-wave velocity to approximate the propagation velocity of sea water (about 1500 m s-1). This also affects the identification of the hydrate layer and results in the underestimate of its thickness. In addition, because there could be about a 5 m thick velocity ramp above or below the hydrate layer as interpreted by acoustic and resistivity logging curves, the recalibrated thickness of this layer is less than the original estimated thickness. The recalibrated P-wave velocity of the hydrate layer is also higher than the original estimated velocity. For the drilling well with a relatively thin hydrate layer, the velocity ramp plays a more important role in identifying and determining the thickness of the layer.

Gong, Jianming; Zhang, Xunhua; Zou, Changchun; Chen, Qiang; Wang, Lichen; Yuan, Chunfang; Hu, Gaowei; Jiang, Yubo

2014-10-01

392

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

393

Predicted signatures of p-wave superfluid phases and Majorana zero modes of fermionic atoms in rf absorption  

SciTech Connect

We study the superfluid phases of quasi-two-dimensional atomic Fermi gases interacting via a p-wave Feshbach resonance. We calculate the absorption spectra of these phases under a hyperfine transition for both nonrotating and rotating superfluids. We show that one can identify the different phases of the p-wave superfluid from the absorption spectrum. The absorption spectrum shows clear signatures of the existence of Majorana zero modes at the cores of vortices of the weakly pairing p{sub x}+ip{sub y} phase.

Grosfeld, Eytan; Stern, Ady; Ilan, Roni [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Cooper, Nigel R. [T.C.M. Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2007-09-01

394

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

395

Token-passing Systems with Batch Arrivals and their Application to Multimedia File Transfer over Token-ring LANs  

Microsoft Academic Search

The performance of token-passing systems with limited service and Poisson arrivals is investigated. For pure Poisson arrivals, a Laplace-Stieltjes transform (LST) of an approximate customer\\/packet waiting time distribution is derived and expressed as a functional equation, from which the approximate mean and the variance of waiting time are obtained; for batch Poisson arrivals, an approximate mean of waiting time is

Robert H. Deng; Xian-yu Zhang; Kuan-Tase Huangl

1991-01-01

396

Analysis of the effects of tectonic release on short-period P waves observed from Shagan River explosions. Final report, September 1985-September 1986  

SciTech Connect

Large samples of teleseismic P-wave amplitude and waveform data recorded from Shagan River underground explosions were collected and systematically analyzed in an attempt to identify any effects which may correlate with the amount of tectonic release accompanying these explosions. Results of these analyses indicate that these teleseismic P-wave data do not provide any unambiguous evidence of effects of tectonic release in the short-period range of interest in m/sub b/ determination. However, the results of a preliminary theoretical analysis indicate that such negative evidence is not definitive in that there are plausible models of tectonic release for which no detectable variations in the observed teleseismic P waveforms are theoretically expected to result from the superposition of these two sources. At the same time, such models of tectonic release predict significant positive bias in the network-averaged m/sub b/ values for explosions accompanied by the mode of tectonic release traditionally associated with the Shagan River test site. Thus, the currently available seismic data do not exclude the possibility that tectonic release may be introducing a positive bias of as much as several tenths of a magnitude unit into the network-averaged m/sub b/ values computed for some Shagan River explositons.

Barker, B.W.; Murphy, J.R.

1987-02-01

397

Zero-Field Vortex-Induced Hall Effect and Polar Kerr Effect in Chiral p-Wave Superconductors near Kosterlitz-Thouless Transition  

NASA Astrophysics Data System (ADS)

In this work, we investigate polar Kerr effect and Ohmic conductivity induced by vortex dynamics in a chiral p-wave superconducting thin film near Kosterlitz-Thouless (KT) transition without explicitly applying magnetic field. Due to the broken time reversal symmetry in the superconducting state and the breaking of Galilean invariance by forces originated from impurities, a conductivity tensor with nonzero off-diagonal element is expected. We generalize the dynamical theory developed by Ambegaokar, Halperin, Nelson, and Siggia to obtain a matrix dielectric function describing vortex screening, which is further related to the conductivity tensor. Polar Kerr effect due to the nonzero Hall conductivity is studied. The corresponding Kerr angle is shown to be proportional to the imaginary part of off-diagonal component of the dielectric function in certain parameter regime. While the frequency and temperature dependence of dissipation in chiral p-wave context behave similarly to those of s-wave results, the Kerr angle exhibits some novel features near the KT transition. As a result, Kerr angle measurement in experiment can provide a probe of vortex dynamics described in this work.

Chung, C. K.; Kato, Y.

2014-04-01

398

Mass arrival of sorptive solute in heterogeneous porous media  

Microsoft Academic Search

The stochastic arrival time analysis of nonreactive solute movement in heterogeneous porous media is extended to consider solute that undergo sorption-desorption goverened by first-order linear kinetics. For an instantaneous solute injection, a general expression for the expected mass flux at any distance fro the injection point is derived in terms of the three-dimensional velocity field and the forwart-and reverse-sorption rate

Vladimir D. Cvetkovic; Allen M. Shapiro

1990-01-01

399

Effect of Biotite On P-wave Velocity of Metamorphic Rocks  

NASA Astrophysics Data System (ADS)

It is well known that P-wave velocities (Vp) of rocks are strongly affected by mineral assemblages. To elucidate effect of biotite on rock velocities, we measured Vp for highly metamorphosed basic rocks with various quantity of biotite from the early Pa- leozoic Lützow-Holm Complex, East Antarctica. The measurements were performed at pressures from 0.1 GPa to 1.0 GPa and at temperatures from 25C to 400C with a piston-cylinder apparatus. Vp has a negative relationship with volume percentage of biotite. In addition, the biotite-rich rocks (over 10 vol. % of biotite) show the strong negative thermal effect of Vp with increment of temperature from 25 C to 400 C (e.g. 0.45 km/s at 1.0 GPa). It is also noteworthy that the velocity anisotropy signif- icantly increases with temperature (max. 8 %) at 1.0 GPa. These characteristics of physical properties of biotite-rich rocks are attributed to the preferred orientation of biotite, as suggested by the previous study on velocity anisotropy of single crystal of biotite.

Kitamura, Keigo

400

Finite nuclear size and Lamb shift of p-wave atomic states  

SciTech Connect

We consider corrections to the Lamb shift of the p-wave atomic states due to the finite nuclear size (FNS). In other words, these are radiative corrections to the atomic isotope shift related to the FNS. It is shown that the structure of the corrections is qualitatively different to that for the s-wave states. The perturbation theory expansion for the relative correction for a p{sub 1/2} state starts with a {alpha} ln(1/Z{alpha}) term, while for the s{sub 1/2} states it starts with a Z{alpha}{sup 2} term. Here, {alpha} is the fine-structure constant and Z is the nuclear charge. In the present work, we calculate the {alpha} terms for that 2p states, the result for the 2p{sub 1/2} state reads (8{alpha}/9{pi}){l_brace}ln[1/(Z{alpha}){sup 2}]+0.710{r_brace}. Even more interesting are the p{sub 3/2} states. In this case the 'correction' is several orders of magnitude larger than the 'leading' FNS shift. However, absolute values of energy shifts related to these corrections are very small.

Milstein, A.I.; Sushkov, O.P.; Terekhov, I.S. [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); School of Physics, University of New South Wales, Sydney 2052 (Australia); Novosibirsk University, 630090 Novosibirsk (Russian Federation)

2003-06-01

401

Finite nuclear size and Lamb shift of p-wave atomic states  

E-print Network

We consider corrections to the Lamb shift of p-wave atomic states due to the finite nuclear size (FNS). In other words, these are radiative corrections to the atomic isotop shift related to FNS. It is shown that the structure of the corrections is qualitatively different from that for s-wave states. The perturbation theory expansion for the relative correction for a $p_{1/2}$-state starts from $\\alpha\\ln(1/Z\\alpha)$-term, while for $s_{1/2}$-states it starts from $Z\\alpha^2$ term. Here $\\alpha$ is the fine structure constant and $Z$ is the nuclear charge. In the present work we calculate the $\\alpha$-terms for $2p$-states, the result for $2p_{1/2}$-state reads $(8\\alpha/9\\pi)[\\ln(1/(Z\\alpha)^2)+0.710]$. Even more interesting are $p_{3/2}$-states. In this case the ``correction'' is by several orders of magnitude larger than the ``leading'' FNS shift.

Milstein, A I; Terekhov, I S

2003-01-01

402

Finite nuclear size and Lamb shift of p-wave atomic states  

E-print Network

We consider corrections to the Lamb shift of p-wave atomic states due to the finite nuclear size (FNS). In other words, these are radiative corrections to the atomic isotop shift related to FNS. It is shown that the structure of the corrections is qualitatively different from that for s-wave states. The perturbation theory expansion for the relative correction for a $p_{1/2}$-state starts from $\\alpha\\ln(1/Z\\alpha)$-term, while for $s_{1/2}$-states it starts from $Z\\alpha^2$ term. Here $\\alpha$ is the fine structure constant and $Z$ is the nuclear charge. In the present work we calculate the $\\alpha$-terms for $2p$-states, the result for $2p_{1/2}$-state reads $(8\\alpha/9\\pi)[\\ln(1/(Z\\alpha)^2)+0.710]$. Even more interesting are $p_{3/2}$-states. In this case the ``correction'' is by several orders of magnitude larger than the ``leading'' FNS shift.

A. I. Milstein; O. P. Sushkov; I. S. Terekhov

2002-12-03

403

Hybrid Theory of P-Wave Electron-Hydrogen Elastic Scattering  

NASA Technical Reports Server (NTRS)

We report on a study of electron-hydrogen scattering, using a combination of a modified method of polarized orbitals and the optical potential formalism. The calculation is restricted to P waves in the elastic region, where the 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. 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 35-term correlation function is needed in the wave function compared to the 220-term wave function required in the above-mentioned previous calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts.

Bhatia, Anand

2012-01-01

404

Singularity analysis of Ginzburg-Landau energy related to p-wave superconductivity  

NASA Astrophysics Data System (ADS)

The following Ginzburg-Landau energy in the absence of a magnetic field E_\\varepsilon(?) = intlimits_G[1/2|nabla?|^2 + 1/4\\varepsilon^2(1-|?|^2)^2]dx was well studied during recent twenty years. Here, {G subset {R}^2} is a bounded smooth domain, {?} is an order parameter, {\\varepsilon >0 } . In particular, several global properties including the weighted energy estimation, the concentration compactness properties and the quantization effect of the energy had been established. This paper is concerned with another Ginzburg-Landau type free energy associated with p-wave superconductivity E_\\varepsilon (?, u; G) = 1/2 intlimits_G(|nabla ?|^2 + |nabla u|^2 - |nabla|?||^2)dx + 1/4\\varepsilon^2 intlimits_G(1-|?|^2)^2dx. Here, u is also an order parameter. We will prove that those global properties still hold for this more complicated energy functional. Such global properties describe the locations of the regular and the singular domains, and also show the convergence relation between the Ginzburg-Landau minimizers and the harmonic maps.

Lei, Yutian

2013-08-01

405

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

406

High-temperature thermodynamics of strongly interacting s-wave and p-wave Fermi gases in a harmonic trap  

SciTech Connect

We theoretically investigate the high-temperature thermodynamics of a strongly interacting trapped Fermi gas near either s-wave or p-wave Feshbach resonances, using a second-order quantum virial expansion. The second virial coefficient is calculated based on the energy spectrum of two interacting fermions in a harmonic trap. We consider both isotropic and anisotropic harmonic potentials. For the two-fermion interaction, either s-wave or p-wave, we use a pseudopotential parametrized by a scattering length and an effective range. This turns out to be the simplest way of encoding the energy dependence of the low-energy scattering amplitude or phase shift. This treatment of the pseudopotential can be easily generalized to higher partial-wave interactions. We discuss how the second virial coefficient and thermodynamics are affected by the existence of these finite-range interaction effects. The virial expansion result for a strongly interacting s-wave Fermi gas has already been proved very useful. In the case of p-wave interactions, our results for the high-temperature equation of state are applicable to future high-precision thermodynamic measurements for a spin-polarized Fermi gas near a p-wave Feshbach resonance.

Peng Shiguo [Department of Physics, Tsinghua University, Beijing, 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Li Shiqun [Department of Physics, Tsinghua University, Beijing, 100084 (China); Drummond, Peter D.; Liu Xiaji [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)

2011-06-15

407

Teleseismic P wave imaging of the 26 December 2004 Sumatra-Andaman and 28 March 2005 Sumatra  

E-print Network

Teleseismic P wave imaging of the 26 December 2004 Sumatra-Andaman and 28 March 2005 Sumatra the characteristics of the 26 December 2004 Sumatra-Andaman and the 28 March 2005 Sumatran earthquakes. The onset, in general, consistent with those obtained from more involved source inversion methods. The 2004 Sumatra

Shearer, Peter

408

Crustal structure beneath Long Valley caldera from modeling of teleseismic P wave polarizations and Ps converted waves  

Microsoft Academic Search

In this study, the authors present new constraints on the nature of the low-velocity zone beneath Long Valley caldera, based on the measured propagation directions of teleseismic P waves and on modeling of P to S converted waves. The low-velocity body is a large asymmetrical volume which deepens to the east, extending from depths of 7 to 30 km. It

Lee Karl Steck; William A. Prothero

1994-01-01

409

Physics of the Earth and Planetary Interiors 154 (2006) 180195 Constraining P-wave velocity variations in the upper  

E-print Network

Physics of the Earth and Planetary Interiors 154 (2006) 180­195 Constraining P-wave velocity¨oz Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 sensitivity kernels to combine the datasets, and mantle structure was parameterized with an irregular grid

van der Hilst, Robert Dirk