Evaluating the Improvement in Shear Wave Speed Image Quality Using Multidimensional Directional Filters in the Presence of Reflection Artifacts.

PubMed

Lipman, Samantha L; Rouze, Ned C; Palmeri, Mark L; Nightingale, Kathryn R

2016-08-01

Shear waves propagating through interfaces where there is a change in stiffness cause reflected waves that can lead to artifacts in shear wave speed (SWS) reconstructions. Two-dimensional (2-D) directional filters are commonly used to reduce in-plane reflected waves; however, SWS artifacts arise from both in- and out-of-imaging-plane reflected waves. Herein, we introduce 3-D shear wave reconstruction methods as an extension of the previous 2-D estimation methods and quantify the reduction in image artifacts through the use of volumetric SWS monitoring and 4-D-directional filters. A Gaussian acoustic radiation force impulse excitation was simulated in phantoms with Young's modulus ( E ) of 3 kPa and a 5-mm spherical lesion with E = 6, 12, or 18.75 kPa. The 2-D-, 3-D-, and 4-D-directional filters were applied to the displacement profiles to reduce in-and out-of-plane reflected wave artifacts. Contrast-to-noise ratio and SWS bias within the lesion were calculated for each reconstructed SWS image to evaluate the image quality. For 2-D SWS image reconstructions, the 3-D-directional filters showed greater improvements in image quality than the 2-D filters, and the 4-D-directional filters showed marginal improvement over the 3-D filters. Although 4-D-directional filters can further reduce the impact of large magnitude out-of-plane reflection artifacts in SWS images, computational overhead and transducer costs to acquire 3-D data may outweigh the modest improvements in image quality. The 4-D-directional filters have the largest impact in reducing reflection artifacts in 3-D SWS volumes.

The Detection of Gravitational Waves

NASA Astrophysics Data System (ADS)

Blair, David G.

2005-10-01

Part I. An Introduction to Gravitational Waves and Methods for their Detection: 1. Gravitational waves in general relativity D. G. Blair; 2. Sources of gravitational waves D. G. Blair; 3. Gravitational wave detectors D. G. Blair; Part II. Gravitational Wave Detectors: 4. Resonant-bar detectors D. G. Blair; 5. Gravity wave dewars W. O. Hamilton; 6. Internal friction in high Q materials J. Ferreirinko; 7. Motion amplifiers and passive transducers J. P. Richard; 8. Parametric transducers P. J. Veitch; 9. Detection of continuous waves K. Tsubono; 10. Data analysis and algorithms for gravitational wave-antennas G. V. Paalottino; Part III. Laser Interferometer Antennas: 11. A Michelson interferometer using delay lines W. Winkler; 12. Fabry-Perot cavity gravity-wave detectors R. W. P. Drever; 13. The stabilisation of lasers for interferometric gravitational wave detectors J. Hough; 14. Vibration isolation for the test masses in interferometric gravitational wave detectors N. A. Robertson; 15. Advanced techniques A. Brillet; 16. Data processing, analysis and storage for interferometric antennas B. F. Schutz; 17. Gravitational wave detection at low and very low frequencies R. W. Hellings.

Numerical Modeling of Infragravity Wave Runup on Steep and Mildly Sloping Natural Beaches

NASA Astrophysics Data System (ADS)

Fiedler, J. W.; Smit, P.; Brodie, K. L.; McNinch, J.; Guza, R. T.; Gallien, T.

2016-12-01

We present ongoing work which aims to validate the non-hydrostatic model SWASH for wave runup and infragravity waves generated by a range of different incident wave spectra at the offshore boundary, including the effect of finite directional spread. Flume studies of wave runup are limited to normally incident (1D) sea and infragravity waves, but natural waves are directionally spread (2D), with substantially different dynamics from 1D. For example, refractive trapping (edge waves) is only possible with 2D waves, and the bound infragravity wave response to short wave groups is highly amplified for the special case of normal incidence. Selected case studies are modeled at Agate Beach, Oregon, a low slope (1:80) beach with maximum offshore wave heights greater than 7m, and Cardiff, California, a steep (1:8) beach with maximum wave heights of 2m. Peak periods ranged between 5-20 s at both sites. On both beaches, waves were measured on a transect from approximately 10m depth to the runup, using pressure sensors, current meters, and a scanning lidar. Bulk short wave quantities, wave runup, infragravity frequency spectra and energy fluxes are compared with SWASH. On the low slope beach with energetic incident waves, the observed horizontal runup excursions reach 140m ( 100s periods). Swash front velocities reached up to several m/s, causing short waves to stack up during runup drawdown. On reversal of the infragravity phase, the stacked short waves are swept onshore with the long wave front, effectively enhancing runup by phase coupling long and short waves. Statistical variability and nonlinearity in swash generation lead to time-varying runup heights. Here, we test these observations with 2D SWASH, as well as the sensitivity of modeled runup to the parameterization of bottom friction.

The K-π+ S-wave from the D+→K-π+π+ decay

NASA Astrophysics Data System (ADS)

FOCUS Collaboration; Link, J. M.; Yager, P. M.; Anjos, J. C.; Bediaga, I.; Castromonte, C.; Machado, A. A.; Magnin, J.; Massafferri, A.; de Miranda, J. M.; Pepe, I. M.; Polycarpo, E.; Dos Reis, A. C.; Carrillo, S.; Cuautle, E.; Sánchez-Hernández, A.; Uribe, C.; Vázquez, F.; Agostino, L.; Cinquini, L.; Cumalat, J. P.; Frisullo, V.; O'Reilly, B.; Segoni, I.; Stenson, K.; Butler, J. N.; Cheung, H. W. K.; Chiodini, G.; Gaines, I.; Garbincius, P. H.; Garren, L. A.; Gottschalk, E.; Kasper, P. H.; Kreymer, A. E.; Kutschke, R.; Wang, M.; Benussi, L.; Bianco, S.; Fabbri, F. L.; Zallo, A.; Casimiro, E.; Reyes, M.; Cawlfield, C.; Kim, D. Y.; Rahimi, A.; Wiss, J.; Gardner, R.; Kryemadhi, A.; Chung, Y. S.; Kang, J. S.; Ko, B. R.; Kwak, J. W.; Lee, K. B.; Cho, K.; Park, H.; Alimonti, G.; Barberis, S.; Boschini, M.; Cerutti, A.; D'Angelo, P.; Dicorato, M.; Dini, P.; Edera, L.; Erba, S.; Inzani, P.; Leveraro, F.; Malvezzi, S.; Menasce, D.; Mezzadri, M.; Moroni, L.; Pedrini, D.; Pontoglio, C.; Prelz, F.; Rovere, M.; Sala, S.; Davenport, T. F.; Arena, V.; Boca, G.; Bonomi, G.; Gianini, G.; Liguori, G.; Pegna, D. Lopes; Merlo, M. M.; Pantea, D.; Ratti, S. P.; Riccardi, C.; Vitulo, P.; Göbel, C.; Otalora, J.; Hernandez, H.; Lopez, A. M.; Mendez, H.; Paris, A.; Quinones, J.; Ramirez, J. E.; Zhang, Y.; Wilson, J. R.; Handler, T.; Mitchell, R.; Engh, D.; Hosack, M.; Johns, W. E.; Luiggi, E.; Moore, J. E.; Nehring, M.; Sheldon, P. D.; Vaandering, E. W.; Webster, M.; Sheaff, M.

2009-10-01

Using data from FOCUS (E831) experiment at Fermilab, we present a model independent partial-wave analysis of the K-π+ S-wave amplitude from the decay D+→K-π+π+. The S-wave is a generic complex function to be determined directly from the data fit. The P- and D-waves are parameterized by a sum of Breit-Wigner amplitudes. The measurement of the S-wave amplitude covers the whole elastic range of the K-π+ system.

Removal of pinned scroll waves in cardiac tissues by electric fields in a generic model of three-dimensional excitable media

PubMed Central

Pan, De-Bei; Gao, Xiang; Feng, Xia; Pan, Jun-Ting; Zhang, Hong

2016-01-01

Spirals or scroll waves pinned to heterogeneities in cardiac tissues may cause lethal arrhythmias. To unpin these life-threatening spiral waves, methods of wave emission from heterogeneities (WEH) induced by low-voltage pulsed DC electric fields (PDCEFs) and circularly polarized electric fields (CPEFs) have been used in two-dimensional (2D) cardiac tissues. Nevertheless, the unpinning of scroll waves in three-dimensional (3D) cardiac systems is much more difficult than that of spiral waves in 2D cardiac systems, and there are few reports on the removal of pinned scroll waves in 3D cardiac tissues by electric fields. In this article, we investigate in detail the removal of pinned scroll waves in a generic model of 3D excitable media using PDCEF, AC electric field (ACEF) and CPEF, respectively. We find that spherical waves can be induced from the heterogeneities by these electric fields in initially quiescent excitable media. However, only CPEF can induce spherical waves with frequencies higher than that of the pinned scroll wave. Such higher-frequency spherical waves induced by CPEF can be used to drive the pinned scroll wave out of the cardiac systems. We hope this remarkable ability of CPEF can provide a better alternative to terminate arrhythmias caused by pinned scroll waves. PMID:26905367

Factorization breaking of A d T for polarized deuteron targets in a relativistic framework

DOE PAGES

Jeschonnek, Sabine; Van Orden, J. W.

2017-04-17

We discuss the possible factorization of the tensor asymmetrymore » $$A^T_d$$ measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if $p$-waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the $d$-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions.« less

Laser-based linear and nonlinear guided elastic waves at surfaces (2D) and wedges (1D).

PubMed

Hess, Peter; Lomonosov, Alexey M; Mayer, Andreas P

2014-01-01

The characteristic features and applications of linear and nonlinear guided elastic waves propagating along surfaces (2D) and wedges (1D) are discussed. Laser-based excitation, detection, or contact-free analysis of these guided waves with pump-probe methods are reviewed. Determination of material parameters by broadband surface acoustic waves (SAWs) and other applications in nondestructive evaluation (NDE) are considered. The realization of nonlinear SAWs in the form of solitary waves and as shock waves, used for the determination of the fracture strength, is described. The unique properties of dispersion-free wedge waves (WWs) propagating along homogeneous wedges and of dispersive wedge waves observed in the presence of wedge modifications such as tip truncation or coatings are outlined. Theoretical and experimental results on nonlinear wedge waves in isotropic and anisotropic solids are presented. Copyright © 2013 Elsevier B.V. All rights reserved.

Describing Site Amplification for Surface Waves in Realistic Basins

NASA Astrophysics Data System (ADS)

Bowden, D. C.; Tsai, V. C.

2017-12-01

Standard characterizations of site-specific site response assume a vertically-incident shear wave; given a 1D velocity profile, amplification and resonances can be calculated based on conservation of energy. A similar approach can be applied to surface waves, resulting in an estimate of amplification relative to a hard rock site that is different in terms of both amount of amplification and frequency. This prediction of surface-wave site amplification has been well validated through simple simulations, and in this presentation we explore the extent to which a 1D profile can explain observed amplifications in more realistic scenarios. Comparisons of various simple 2D and 3D simulations, for example, allow us to explore the effect of different basin shapes and the relative importance of effects such as focusing, conversion of wave-types and lateral surface wave resonances. Additionally, the 1D estimates for vertically-incident shear waves and for surface waves are compared to spectral ratios of historic events in deep sedimentary basins to demonstrate the appropriateness of the two different predictions. This difference in amplification responses between the wave types implies that a single measurement of site response, whether analytically calculated from 1D models or empirically observed, is insufficient for regions where surface waves play a strong role.

Brain stem auditory-evoked response of the nonanesthetized dog.

PubMed

Marshall, A E

1985-04-01

The brain stem auditory evoked-response was measured from a group of 24 healthy dogs under conditions suitable for clinical diagnostic use. The waveforms were identified, and analysis of amplitude ratios, latencies, and interpeak latencies were done. The group was subdivided into subgroups based on tranquilization, nontranquilization, sex, and weight. Differences were not observed among any of these subgroups. All dogs responded to the click stimulus from 30 dB to 90 dB, but only 62.5% of the dogs responded at 5 dB. The total number of peaks averaged 1.6 at 5 dB, increased linearly to 6.5 at 50 dB, and remained at 6.5 to 90 dB. Frequency of recognizability of each wave was tabulated for each stimulus intensity tested; recognizability increased with increased stimulus intensity. Amplitudes of waves increased with increasing stimulus intensity, but were highly variable. The 4th wave had the greatest amplitude at the lower stimulus intensities, and the 1st wave had the greatest amplitude at the higher stimulus intensities. Amplitude ratio of the 1st to 5th wave was greater than 1 at less than or equal to 50 dB stimulus intensity, and was 1 for stimulus intensities greater than 50 dB. Interpeak latencies did not change relative to stimulus intensities. Peak latencies of each wave averaged at 5-dB hearing level for the 1st to 6th waves were 2.03, 2.72, 3.23, 4.14, 4.41, and 6.05 ms, respectively; latencies of these 6 waves at 90 dB were 0.92, 1.79, 2.46, 3.03, 3.47, and 4.86 ms, respectively. Latency decreased between 0.009 to 0.014 ms/dB for the waves.

High interobserver variability in the assessment of epsilon waves: Implications for diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia.

PubMed

Platonov, Pyotr G; Calkins, Hugh; Hauer, Richard N; Corrado, Domenico; Svendsen, Jesper H; Wichter, Thomas; Biernacka, Elżbieta Katarzyna; Saguner, Ardan M; Te Riele, Anneline S J M; Zareba, Wojciech

2016-01-01

Revision of the Task Force diagnostic criteria for arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) has increased their sensitivity for the diagnosis of early and familial forms of the disease. The epsilon wave is a major diagnostic criterion in the context of ARVC/D, which, however, remains not quantifiable and therefore may leave room for substantial subjective interpretation. The purpose of this study was to assess interobserver agreement in epsilon wave definition and epsilon wave importance for ARVC/D diagnosis. Electrocardiographic (ECG) tracings depicting leads V1, V2, and V3 collected from individuals evaluated for ARVC/D (n = 30) were given to panel members who were asked to respond to the question whether ECG patterns meet epsilon wave definition outlined by the Task Force diagnostic criteria. The prevalence and importance of epsilon waves for ARVC/D diagnosis were assessed in a pooled data set of patients with definite ARVC/D from European and American registries (n = 815). The number of ECG patterns identified as epsilon waves varied from 5 to 18 per reviewer (median 13 per reviewer). A unanimous agreement was reached for only 10 cases (33%), 2 of which qualified as epsilon waves and 8 as non-epsilon waves by all panel members. From a pooled data set, 106 patients reportedly had epsilon waves (13%). In 105 of 106 patients with epsilon waves (99%), exclusion of epsilon waves from the diagnostic score would not affect the "definite" diagnostic category. Interobserver variability in the assessment of epsilon waves is high; however, the impact of epsilon waves on ARVC/D diagnosis is negligibly low. The results urge to exercise caution in the assessment of epsilon waves, especially in patients who would not otherwise meet diagnostic criteria. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Assessing TMS-induced D and I waves with spinal H-reflexes.

PubMed

Niemann, Niclas; Wiegel, Patrick; Kurz, Alexander; Rothwell, John C; Leukel, Christian

2018-03-01

Transcranial magnetic stimulation (TMS) of motor cortex produces a series of descending volleys known as D (direct) and I (indirect) waves. In the present study, we questioned whether spinal H-reflexes can be used to dissect D waves and early and late I waves from TMS. We therefore probed H-reflex facilitation at arrival times of D and I waves at the spinal level and thereby changed TMS parameters that have previously been shown to have selective effects on evoked D and different I waves. We changed TMS intensity and current direction and applied a double-pulse paradigm known as short-interval intracortical inhibition (SICI). Experiments were conducted in flexor carpi radialis (FCR) in the arm and soleus (SOL) in the leg. There were two major findings: 1) in FCR, H-reflex facilitation showed characteristic modulations with altered TMS parameters that correspond to the changes of evoked D and I waves; and 2) H-reflexes in SOL did not, possibly because of increased interference from other spinal circuits. Therefore, the most significant outcome of this study is that in FCR, H-reflexes combined with TMS seem to be a useful technique to dissect TMS-induced D and I waves. NEW & NOTEWORTHY Questions that relate to corticospinal function in pathophysiology and movement control demand sophisticated techniques to provide information about corticospinal mechanisms. We introduce a noninvasive electrophysiological technique that may be useful in describing such mechanisms in more detail by dissecting D and I waves from transcranial magnetic stimulation (TMS). Based on the combination of spinal H-reflexes and TMS in the flexor carpi radialis muscle, the technique was shown to measure selective effects on D and I waves from changing TMS parameters.

Two-dimensional Shear Wave Elastography on Conventional Ultrasound Scanners with Time Aligned Sequential Tracking (TAST) and Comb-push Ultrasound Shear Elastography (CUSE)

PubMed Central

Song, Pengfei; Macdonald, Michael C.; Behler, Russell H.; Lanning, Justin D.; Wang, Michael H.; Urban, Matthew W.; Manduca, Armando; Zhao, Heng; Callstrom, Matthew R.; Alizad, Azra; Greenleaf, James F.; Chen, Shigao

2014-01-01

Two-dimensional (2D) shear wave elastography presents 2D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2D shear wave elastography on conventional ultrasound scanners, however, is challenging due to the low tracking pulse-repetition-frequency (PRF) of these systems. While some clinical and research platforms support software beamforming and plane wave imaging with high PRF, the majority of current clinical ultrasound systems do not have the software beamforming capability, which presents a critical challenge for translating the 2D shear wave elastography technique from laboratory to clinical scanners. To address this challenge, this paper presents a Time Aligned Sequential Tracking (TAST) method for shear wave tracking on conventional ultrasound scanners. TAST takes advantage of the parallel beamforming capability of conventional systems and realizes high PRF shear wave tracking by sequentially firing tracking vectors and aligning shear wave data in the temporal direction. The Comb-push Ultrasound Shear Elastography (CUSE) technique was used to simultaneously produce multiple shear wave sources within the field-of-view (FOV) to enhance shear wave signal-to-noise-ratio (SNR) and facilitate robust reconstructions of 2D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner (the General Electric LOGIQ E9). A phantom study showed that the shear wave speed measurements from the LOGIQ E9 were in good agreement to the values measured from other 2D shear wave imaging technologies. An inclusion phantom study showed that the LOGIQ E9 had comparable performance to the Aixplorer (Supersonic Imagine) in terms of bias and precision in measuring different sized inclusions. Finally, in vivo case analysis of a breast with a malignant mass, and a liver from a healthy subject demonstrated the feasibility of using the LOGIQ E9 for in vivo 2D shear wave elastography. These promising results indicate that the proposed technique can enable the implementation of 2D shear wave elastography on conventional ultrasound scanners and potentially facilitate wider clinical applications with shear wave elastography. PMID:25643079

Investigation of surface wave amplitudes in 3-D velocity and 3-D Q models

NASA Astrophysics Data System (ADS)

Ruan, Y.; Zhou, Y.

2010-12-01

It has been long recognized that seismic amplitudes depend on both wave speed structures and anelasticity (Q) structures. However, the effects of lateral heterogeneities in wave speed and Q structures on seismic amplitudes has not been well understood. We investigate the effects of 3-D wave speed and 3-D anelasticity (Q) structures on surface-wave amplitudes based upon wave propagation simulations of twelve globally-distributed earthquakes and 801 stations in Earth models with and without lateral heterogeneities in wave speed and anelasticity using a Spectral Element Method (SEM). Our tomographic-like 3-D Q models are converted from a velocity model S20RTS using a set of reasonable mineralogical parameters, assuming lateral perturbations in both velocity and Q are due to temperature perturbations. Surface-wave amplitude variations of SEM seismograms are measured in the period range of 50--200 s using boxcar taper, cosine taper and Slepian multi-tapers. We calculate ray-theoretical predictions of surface-wave amplitude perturbations due to elastic focusing, attenuation, and anelastic focusing which respectively depend upon the second spatial derivative (''roughness'') of perturbations in phase velocity, 1/Q, and the roughness of perturbations in 1/Q. Both numerical experiments and theoretical calculations show that (1) for short-period (~ 50 s) surface waves, the effects of amplitude attenuation due to 3-D Q structures are comparable with elastic focusing effects due to 3-D wave speed structures; and (2) for long-period (> 100 s) surface waves, the effects of attenuation become much weaker than elastic focusing; and (3) elastic focusing effects are correlated with anelastic focusing at all periods due to the correlation between velocity and Q models; and (4) amplitude perturbations are depend on measurement techniques and therefore cannot be directly compared with ray-theoretical predictions because ray theory does not account for the effects of measurement techniques. We calculate 3-D finite-frequency sensitivity of surface-wave amplitude to perturbations in wave speed and anelasticity (Q) which fully account for the effects of elastic focusing, attenuation, anelastic focusing as well as measurement techniques. We show that amplitude perturbations calculated using wave speed and Q sensitivity kernels agree reasonably well with SEM measurements and therefore the sensitivity kernels can be used in a joint inversion of seismic phase delays and amplitudes to simultaneously image high resolution 3-D wave speed and 3-D Q structures in the upper mantle.

The Effect of Sedimentary Basins on Through-Passing Short-Period Surface Waves

NASA Astrophysics Data System (ADS)

Feng, L.; Ritzwoller, M. H.

2017-12-01

Surface waves propagating through sedimentary basins undergo elastic wave field complications that include multiple scattering, amplification, the formation of secondary wave fronts, and subsequent wave front healing. Unless these effects are accounted for accurately, they may introduce systematic bias to estimates of source characteristics, the inference of the anelastic structure of the Earth, and ground motion predictions for hazard assessment. Most studies of the effects of basins on surface waves have centered on waves inside the basins. In contrast, we investigate wave field effects downstream from sedimentary basins, with particular emphasis on continental basins and propagation paths, elastic structural heterogeneity, and Rayleigh waves at 10 s period. Based on wave field simulations through a recent 3D crustal and upper mantle model of East Asia, we demonstrate significant Rayleigh wave amplification downstream from sedimentary basins in eastern China such that Ms measurements obtained on the simulated wave field vary by more than a magnitude unit. We show that surface wave amplification caused by basins results predominantly from elastic focusing and that amplification effects produced through 3D basin models are reproduced using 2D membrane wave simulations through an appropriately defined phase velocity map. The principal characteristics of elastic focusing in both 2D and 3D simulations include (1) retardation of the wave front inside the basins; (2) deflection of the wave propagation direction; (3) formation of a high amplitude lineation directly downstream from the basin bracketed by two low amplitude zones; and (4) formation of a secondary wave front. Finally, by comparing the impact of elastic focusing with anelastic attenuation, we argue that on-continent sedimentary basins are expected to affect surface wave amplitudes more strongly through elastic focusing than through the anelastic attenuation.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Multi-mode Spiral Wave in a Coupled Oscillatory Medium

NASA Astrophysics Data System (ADS)

Wang, Qun; Gao, Qing-Yu; Lü, Hua-Ping; Zheng, Zhi-Gang

2010-05-01

Multi-mode spiral wave and its breakup in 1-d and 2-d coupled oscillatory media is studied here by theoretic analysis and numerical simulations. The analysis in 1-d system shows that the dispersion relation curve could be non-monotonic depending on the coupling strength. It may also lead to the coexistence of different wave numbers within one system. Direct numerical observations in 1-d and 2-d systems conform to the prediction of dispersion relation analysis. Our findings indicate that the wave grouping can also be observed in oscillatory media without tip meandering and waves with negative group velocity can occur without inhomogeneity.

Determination and Correction of Persistent Biases in Quantum Annealers

DTIC Science & Technology

2016-08-25

programmable parameters and their user-specified values. We applied the recalibration strategy to two D-Wave Two quantum annealers, one at NASA Ames...The quantum annealers used for this study are of the second generation of D-Wave devices, also called D-Wave Two2: one located at NASA Ames Research...Center in Moffett Field, California, (“ NASA device”), and another located at D-Wave Systems in Burnaby, Canada (“Burnaby device”). These consist of 64

Fundamental understanding of wave generation and reception using d(36) type piezoelectric transducers.

PubMed

Zhou, Wensong; Li, Hui; Yuan, Fuh-Gwo

2015-03-01

A new piezoelectric wafer made from a PMN-PT single crystal with dominant piezoelectric coefficient d36 is proposed to generate and detect guided waves on isotropic plates. The in-plane shear coupled with electric field arising from the piezoelectric coefficient is not usually present for conventional piezoelectric wafers, such as lead zirconate titanate (PZT). The direct piezoelectric effect of coefficient d36 indicates that under external in-plane shear stress the charge is induced on a face perpendicular to the poled z-direction. On thin plates, this type of piezoelectric wafer will generate shear horizontal (SH) waves in two orthogonal wave propagation directions as well as two Lamb wave modes in other wave propagation directions. Finite element analyses are employed to explore the wave disturbance in terms of time-varying displacements excited by the d36 wafer in different directions of wave propagation to understand all the guided wave modes accurately. Experiments are conducted to examine the voltage responses received by this type of wafer, and also investigate results of tuning frequency and effects of d31 piezoelectric coefficient, which is intentionally ignored in the finite element analysis. All results demonstrate the main features and utility of proposed d36 piezoelectric wafer for guided wave generation and detection in structural health monitoring. Copyright © 2014 Elsevier B.V. All rights reserved.

3D Ultrasonic Wave Simulations for Structural Health Monitoring

NASA Technical Reports Server (NTRS)

Campbell, Leckey Cara A/; Miler, Corey A.; Hinders, Mark K.

2011-01-01

Structural health monitoring (SHM) for the detection of damage in aerospace materials is an important area of research at NASA. Ultrasonic guided Lamb waves are a promising SHM damage detection technique since the waves can propagate long distances. For complicated flaw geometries experimental signals can be difficult to interpret. High performance computing can now handle full 3-dimensional (3D) simulations of elastic wave propagation in materials. We have developed and implemented parallel 3D elastodynamic finite integration technique (3D EFIT) code to investigate ultrasound scattering from flaws in materials. EFIT results have been compared to experimental data and the simulations provide unique insight into details of the wave behavior. This type of insight is useful for developing optimized experimental SHM techniques. 3D EFIT can also be expanded to model wave propagation and scattering in anisotropic composite materials.

Self-similar gravity wave spectra resulting from the modulation of bound waves

NASA Astrophysics Data System (ADS)

Michel, Guillaume; Semin, Benoît; Cazaubiel, Annette; Haudin, Florence; Humbert, Thomas; Lepot, Simon; Bonnefoy, Félicien; Berhanu, Michaël; Falcon, Éric

2018-05-01

We experimentally study the properties of nonlinear surface gravity waves in a large-scale basin. We consider two different configurations: a one-dimensional (1D) monochromatic wave forcing, and a two-dimensional (2D) forcing with bichromatic waves satisfying resonant-wave interaction conditions. For the 1D forcing, we find a discrete wave-energy spectrum dominated at high frequencies by bound waves whose amplitudes decrease as a power law of the frequency. Bound waves (e.g., to the carrier) are harmonics superimposed on the carrier wave propagating with the same phase velocity as the one of the carrier. When a narrow frequency random modulation is applied to this carrier, the high-frequency part of the wave-energy spectrum becomes continuous with the same frequency-power law. Similar results are found for the 2D forcing when a random modulation is also applied to both carrier waves. Our results thus show that all these nonlinear gravity wave spectra are dominated at high frequencies by the presence of bound waves, even in the configuration where resonant interactions occur. Moreover, in all these configurations, the power-law exponent of the spectrum is found to depend on the forcing amplitude with the same trend as the one found in previous gravity wave turbulence experiments. Such a set of bound waves may thus explain this dependence that was previously poorly understood.

Observations of plan-view sand ripple behavior and spectral wave climate on the inner shelf of San Pedro Bay, California

USGS Publications Warehouse

Xu, J. P.

2005-01-01

Concurrent video images of sand ripples and current meter measurements of directional wave spectra are analyzed to study the relations between waves and wave-generated sand ripples. The data were collected on the inner shelf off Huntington Beach, California, at 15 m water depth, where the sea floor is comprised of well-sorted very fine sands (D50=92 ??m), during the winter of 2002. The wave climate, which was controlled by southerly swells (12-18 s period) and westerly wind waves (5-10 s period), included three wave types: (A) uni-modal, swells only; (B) bi-modal, swells dominant; and (C) bi-modal, wind-wave dominant. Each wave type has distinct relations with the plan-view shapes of ripples that are classified into five types: (1) sharp-crested, two-dimensional (2-D) ripples; (2) sharp-crested, brick-pattern, 3-D ripples; (3) bifurcated, 3-D ripples; (4) round-crested, shallow, 3-D ripples; and (5) flat bed. The ripple spacing is very small and varies between 4.5 and 7.5 cm. These ripples are anorbital as ripples in many field studies. Ripple orientation is only correlated with wave directions during strong storms (wave type C). In a poly-modal, multi-directional spectral wave environment, the use of the peak parameters (frequency, direction), a common practice when spectral wave measurements are unavailable, may lead to significant errors in boundary layer and sediment transport calculations. ?? 2004 Elsevier Ltd. All rights reserved.

Rapid Response: D-Wave Effort Debrief Welcome, Logistics

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

Eidenbenz, Stephan Johannes

The main objects of this project is to develop a diverse and sizable workforce, community, interest within LANL for D-Wave and Quantum Computing; identify promising application areas/problems for future projects; and complement other D-Wave work at LANL (LDRD DR, ASC).

Rapid decay of nonlinear whistler waves in two dimensions: Full particle simulation

NASA Astrophysics Data System (ADS)

Umeda, Takayuki; Saito, Shinji; Nariyuki, Yasuhiro

2017-05-01

The decay of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave is investigated by utilizing a two-dimensional (2D) fully relativistic electromagnetic particle-in-cell code. The simulation is performed under a low-beta condition in which the plasma pressure is much lower than the magnetic pressure. It has been shown that the nonlinear (large-amplitude) parent whistler wave decays through the parametric instability in a one-dimensional (1D) system. The present study shows that there is another channel for the decay of the parent whistler wave in 2D, which is much faster than in the timescale of the parametric decay in 1D. The parent whistler wave decays into two sideband daughter whistlers propagating obliquely with respect to the ambient magnetic field with a frequency close to the parent wave and two quasi-perpendicular electromagnetic modes with a frequency close to zero via a 2D decay instability. The two sideband daughter oblique whistlers also enhance a nonlinear longitudinal electrostatic wave via a three-wave interaction as a secondary process.

Variance of transionospheric VLF wave power absorption

NASA Astrophysics Data System (ADS)

Tao, X.; Bortnik, J.; Friedrich, M.

2010-07-01

To investigate the effects of D-region electron-density variance on wave power absorption, we calculate the power reduction of very low frequency (VLF) waves propagating through the ionosphere with a full wave method using the standard ionospheric model IRI and in situ observational data. We first verify the classic absorption curves of Helliwell's using our full wave code. Then we show that the IRI model gives overall smaller wave absorption compared with Helliwell's. Using D-region electron densities measured by rockets during the past 60 years, we demonstrate that the power absorption of VLF waves is subject to large variance, even though Helliwell's absorption curves are within ±1 standard deviation of absorption values calculated from data. Finally, we use a subset of the rocket data that are more representative of the D region of middle- and low-latitude VLF wave transmitters and show that the average quiet time wave absorption is smaller than that of Helliwell's by up to 100 dB at 20 kHz and 60 dB at 2 kHz, which would make the model-observation discrepancy shown by previous work even larger. This result suggests that additional processes may be needed to explain the discrepancy.

Quantum interference effects on tunneling conductance and shot noise in ferromagnet/ferromagnet/d-wave superconductor double tunnel junctions

NASA Astrophysics Data System (ADS)

Dong, Z. C.; Xing, D. Y.; Dong, Jinming

2002-06-01

We study the oscillatory behavior of differential conductance (G) and shot noise (S) in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor (FM/I/FM/I/d-wave SC) structures by applying an extended Blonder-Tinkham-Klapwijk approach. There are two oscillation components with different periods in either G or S. It is found that the short-period component can be separated from the long-period one by increasing the exchange splitting in FM's and the barrier strength at the FM/SC interface, and vice versa, indicating that the long- and short-period components arise from quantum interference effects, respectively, due to the Andreev and normal reflections at the FM/SC interface. It is also shown that zero-bias G and S in the d-wave SC case is quite different from in the s-wave SC case, which may be used to distinguish between d-wave and s-wave SC's.

3D Modeling of Ultrasonic Wave Interaction with Disbonds and Weak Bonds

NASA Technical Reports Server (NTRS)

Leckey, C.; Hinders, M.

2011-01-01

Ultrasonic techniques, such as the use of guided waves, can be ideal for finding damage in the plate and pipe-like structures used in aerospace applications. However, the interaction of waves with real flaw types and geometries can lead to experimental signals that are difficult to interpret. 3-dimensional (3D) elastic wave simulations can be a powerful tool in understanding the complicated wave scattering involved in flaw detection and for optimizing experimental techniques. We have developed and implemented parallel 3D elastodynamic finite integration technique (3D EFIT) code to investigate Lamb wave scattering from realistic flaws. This paper discusses simulation results for an aluminum-aluminum diffusion disbond and an aluminum-epoxy disbond and compares results from the disbond case to the common artificial flaw type of a flat-bottom hole. The paper also discusses the potential for extending the 3D EFIT equations to incorporate physics-based weak bond models for simulating wave scattering from weak adhesive bonds.

Optical Kerr spatiotemporal dark extreme waves

NASA Astrophysics Data System (ADS)

Wabnitz, Stefan; Kodama, Yuji; Baronio, Fabio

2018-02-01

We study the existence and propagation of multidimensional dark non-diffractive and non-dispersive spatiotemporal optical wave-packets in nonlinear Kerr media. We report analytically and confirm numerically the properties of spatiotemporal dark lines, X solitary waves and lump solutions of the (2 + 1)D nonlinear Schr odinger equation (NLSE). Dark lines, X waves and lumps represent holes of light on a continuous wave background. These solitary waves are derived by exploiting the connection between the (2 + 1)D NLSE and a well-known equation of hydrodynamics, namely the (2+1)D Kadomtsev-Petviashvili (KP) equation. This finding opens a novel path for the excitation and control of spatiotemporal optical solitary and rogue waves, of hydrodynamic nature.

d -wave superconductivity in the presence of nearest-neighbor Coulomb repulsion

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

Jiang, M.; Hahner, U. R.; Schulthess, T. C.

Dynamic cluster quantum Monte Carlo calculations for a doped two-dimensional extended Hubbard model are used to study the stability and dynamics of d-wave pairing when a nearest-neighbor Coulomb repulsion V is present in addition to the on-site Coulomb repulsion U. We find that d-wave pairing and the superconducting transition temperature Tc are only weakly suppressed as long as V does not exceed U/2. This stability is traced to the strongly retarded nature of pairing that allows the d-wave pairs to minimize the repulsive effect of V. When V approaches U/2, large momentum charge fluctuations are found to become important andmore » to give rise to a more rapid suppression of d-wave pairing and T c than for smaller V.« less

Foreshock Langmuir Waves for Unusually Constant Solar Wind Conditions: Data and Implications for Foreshock Structure

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Robinson, P. A.; Anderson, Roger R.; Strangeway, R. J.

1997-01-01

Plasma wave data are compared with ISEE 1's position in the electron foreshock for an interval with unusually constant (but otherwise typical) solar wind magnetic field and plasma characteristics. For this period, temporal variations in the wave characteristics can be confidently separated from sweeping of the spatially varying foreshock back and forth across the spacecraft. The spacecraft's location, particularly the coordinate D(sub f) downstream from the foreshock boundary (often termed DIFF), is calculated by using three shock models and the observed solar wind magnetometer and plasma data. Scatterplots of the wave field versus D(sub f) are used to constrain viable shock models, to investigate the observed scatter in the wave fields at constant D(sub f), and to test the theoretical predictions of linear instability theory. The scatterplots confirm the abrupt onset of the foreshock waves near the upstream boundary, the narrow width in D(sub f) of the region with high fields, and the relatively slow falloff of the fields at large D(sub f), as seen in earlier studies, but with much smaller statistical scatter. The plots also show an offset of the high-field region from the foreshock boundary. It is shown that an adaptive, time-varying shock model with no free parameters, determined by the observed solar wind data and published shock crossings, is viable but that two alternative models are not. Foreshock wave studies can therefore remotely constrain the bow shock's location. The observed scatter in wave field at constant D(sub f) is shown to be real and to correspond to real temporal variations, not to unresolved changes in D(sub f). By comparing the wave data with a linear instability theory based on a published model for the electron beam it is found that the theory can account qualitatively and semiquantitatively for the abrupt onset of the waves near D(sub f) = 0, for the narrow width and offset of the high-field region, and for the decrease in wave intensity with increasing D(sub f). Quantitative differences between observations and theory remain, including large overprediction of the wave fields and the slower than predicted falloff at large D(sub f) of the wave fields. These differences, as well as the unresolved issue of the electron beam speed in the high-field region of the foreshock, are discussed. The intrinsic temporal variability of the wave fields, as well as their overprediction based on homogeneous plasma theory, are indicative of stochastic growth physics, which causes wave growth to be random and varying in sign, rather than secular.

Unconventional pairing symmetry of interacting Dirac fermions on a π -flux lattice

NASA Astrophysics Data System (ADS)

Guo, Huaiming; Khatami, Ehsan; Wang, Yao; Devereaux, Thomas P.; Singh, Rajiv R. P.; Scalettar, Richard T.

2018-04-01

The pairing symmetry of interacting Dirac fermions on the π -flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s*- (i.e., extended s -) and d -wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional d s* -wave phase consisting of alternating stripes of s*- and d -wave phases. A complementary mean-field analysis shows that while the s*- and d -wave symmetries individually have nodes in the energy spectrum, the d s* channel is fully gapped. The results represent a new realization of pairing in Dirac systems, connected to the problem of chiral d -wave pairing on the honeycomb lattice, which might be more readily accessed by cold-atom experiments.

3-D FDTD simulation of shear waves for evaluation of complex modulus imaging.

PubMed

Orescanin, Marko; Wang, Yue; Insana, Michael

2011-02-01

The Navier equation describing shear wave propagation in 3-D viscoelastic media is solved numerically with a finite differences time domain (FDTD) method. Solutions are formed in terms of transverse scatterer velocity waves and then verified via comparison to measured wave fields in heterogeneous hydrogel phantoms. The numerical algorithm is used as a tool to study the effects on complex shear modulus estimation from wave propagation in heterogeneous viscoelastic media. We used an algebraic Helmholtz inversion (AHI) technique to solve for the complex shear modulus from simulated and experimental velocity data acquired in 2-D and 3-D. Although 3-D velocity estimates are required in general, there are object geometries for which 2-D inversions provide accurate estimations of the material properties. Through simulations and experiments, we explored artifacts generated in elastic and dynamic-viscous shear modulus images related to the shear wavelength and average viscosity.

Rogue-wave bullets in a composite (2+1)D nonlinear medium.

PubMed

Chen, Shihua; Soto-Crespo, Jose M; Baronio, Fabio; Grelu, Philippe; Mihalache, Dumitru

2016-07-11

We show that nonlinear wave packets localized in two dimensions with characteristic rogue wave profiles can propagate in a third dimension with significant stability. This unique behavior makes these waves analogous to light bullets, with the additional feature that they propagate on a finite background. Bulletlike rogue-wave singlet and triplet are derived analytically from a composite (2+1)D nonlinear wave equation. The latter can be interpreted as the combination of two integrable (1+1)D models expressed in different dimensions, namely, the Hirota equation and the complex modified Korteweg-de Vries equation. Numerical simulations confirm that the generation of rogue-wave bullets can be observed in the presence of spontaneous modulation instability activated by quantum noise.

Value of the Electrocardiographic (P Wave, T Wave, QRS) Axis as a Predictor of Mortality in 14 Years in a Population With a High Prevalence of Chagas Disease from the Bambuí Cohort Study of Aging.

PubMed

Moraes, Diego N; Nascimento, Bruno R; Beaton, Andrea Z; Soliman, Elsayed Z; Lima-Costa, Maria Fernanda; Dos Reis, Rodrigo C P; Ribeiro, Antonio Luiz P

2018-02-01

We sought to investigate the prognostic value of the electrocardiogram (ECG) electrical axes (P wave, T wave and QRS) as predictors of mortality in the 14-year follow-up of the prospective cohort of all residents ≥60 years living in the southeastern Brazilian city of Bambuí, a population with high prevalence of Chagas disease (ChD). Baseline ECG axes were automatically measured with normal values defined as follows: P-wave axis 0° to 75°, QRS axis -30° to 90°, and T axis 15° to 75°. Participants underwent annual follow-up visits and death was verified using death certificates. Cox proportional hazards regression was used to assess the prognostic value of ECG axes for all-cause mortality, after adjustment for potential confounders. From 1,742 qualifying residents, 1,462 were enrolled, of whom 557 (38.1%) had ChD. Mortality rate was 51.9%. In multivariable adjusted models, abnormal P-wave axis was associated with a 48% (hazard ratio [HR] = 1.48 [95% confidence interval (CI) 1.16-1.88]) increased mortality risk in patients with ChD and 43% (HR = 1.43 [CI 1.13-1.81]) in patients without ChD. Abnormal QRS axis was associated with a 34% (HR = 1.34 [CI 1.04-1.73]) increased mortality risk in patients with ChD, but not in individuals without ChD. Similarly, in the ChD group, abnormal T-wave axis was associated with a 35% (HR = 1.35 [CI 1.07-1.71]) increased mortality, but not in patients without ChD. In conclusion, abnormal P-wave, QRS, and T-wave axes were associated with increased all-cause mortality in patients with ChD. Abnormal P-wave axis was associated with mortality also among those without ChD, being the strongest predictor among ECG variables. Copyright © 2017 Elsevier Inc. All rights reserved.

Determination of wave speed and wave separation in the arteries.

PubMed

Khir, A W; O'Brien, A; Gibbs, J S; Parker, K H

2001-09-01

Considering waves in the arteries as infinitesimal wave fronts rather than sinusoidal wavetrains, the change in pressure across the wave front, dP, is related to the change in velocity, dU, that it induces by the "water hammer" equation, dP=+/-rhocdU, where rho is the density of blood and c is the local wave speed. When only unidirectional waves are present, this relationship corresponds to a straight line when P is plotted against U with slope rhoc. When both forward and backward waves are present, the PU-loop is no longer linear. Measurements in latex tubes and systemic and pulmonary arteries exhibit a linear range during early systole and this provides a way of determining the local wave speed from the slope of the linear portion of the loop. Once the wave speed is known, it is also possible to separate the measured P and U into their forward and backward components. In cases where reflected waves are prominent, this separation of waves can help clarify the pattern of waves in the arteries throughout the cardiac cycle.

Numerical Simulation of Floating Bodies in Extreme Free Surface Waves

NASA Astrophysics Data System (ADS)

Hu, Zheng Zheng; Causon, Derek; Mingham, Clive; Qiang, Ling

2010-05-01

A task of the EPSRC funded research project 'Extreme Wave loading on Offshore Wave Energy Devices: a Hierarchical Team Approach' is to investigate the survivability of two wave energy converter (WEC) devices Pelamis and the Manchester Bobber using different CFD approaches. Both devices float on the water surface, generating the electricity from the motion of the waves. In this paper, we describe developments of the AMAZON-SC 3D numerical wave tank (NWT) to study extreme wave loading of a fixed or floating (in Heave motion) structure. The extreme wave formulation as an inlet condition is due to Dalzell (1999) and Ning et. al. (2009) in which a first or second-order Stokes focused wave can be prescribed. The AMAZON-SC 3D code (see e.g. Hu et al. (2009)) uses a cell centred finite volume method of the Godunov-type for the space discretization of the Euler and Navier Stokes equations. The computational domain includes both air and water regions with the air/water boundary captured as a discontinuity in the density field thereby admitting the break up and recombination of the free surface. Temporal discretisation uses the artificial compressibility method and a dual time stepping strategy to maintain a divergence free velocity field. Cartesian cut cells are used to provide a fully boundary-fitted gridding capability on an regular background Cartesian grid. Solid objects are cut out of the background mesh leaving a set of irregularly shaped cells fitted to the boundary. The advantages of the cut cell approach have been outlined previously by Causon et al. (2000, 2001) including its flexibility for dealing with complex geometries whether stationary or in relative motion. The field grid does not need to be recomputed globally or even locally for moving body cases; all that is necessary is to update the local cut cell data at the body contour for as long as the motion continues. The handing of numerical wave paddles and device motion in a NWT is therefore straightforward and efficient. Firstly, extreme design wave conditions are generated in an empty NWT and compared with physical experiments as a precursor to calculations to investigate the survivability of the Bobber device operating in a challenging wave climate. Secondly, we consider a bench-mark test case involving in a first order regular wave maker acting on a fixed cylinder and Pelamis. Finally, a floating Bobber has been simulated under extreme wave conditions. These results will be reported at the meeting. Causon D.M., Ingram D.M., Mingham C.G., Yang G. Pearson R.V. (2000). Calculation of shallow water flows using a Cartesian cut cell approach. Advances in Water resources, 23: 545-562. Causon D.M., Ingram D.M., Mingham C.G. (2000). A Cartesian cut cell method for shallow water flows with moving boundaries. Advances in Water resources, 24: 899-911. Dalzell J.F. 1999 A note on finite depth second-order wave-wave interactions. Appl. Ocean Res. 21, 105-111. Ning D.Z., Zang J., Liu S.X. Eatock Taylor R. Teng B. & Taylor P.H. 2009 Free surface and wave kinematics for nonlinear focused wave groups. J. Ocean Engineering. Accepted. Hu Z.Z., Causon D.M., Mingham C.M. and Qian L.(2009). Numerical wave tank study of a wave energy converter in heave. Proceedlings 19th ISOPE conference, Osaka, Japan Qian L., Causon D.M. & Mingham C.G., Ingram D.M. 2006 A free-surface capturing method for two fluid flows with moving bodies. Proc. Roy. Soc. London, Vol. A 462 21-42.

Visual and refractive outcomes of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-q excimer lasers: a prospective, contralateral study.

PubMed

Mearza, Ali A; Muhtaseb, Mohammed; Aslanides, Ioannis M

2008-11-01

To compare the safety, efficacy, and predictability of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer laser platforms. This prospective study comprised 44 eyes of 22 consecutive patients who were treated with LASIK using the Moria M2 microkeratome. One eye was treated with the SCHWIND ESIRIS laser and the fellow eye treated with the WaveLight ALLEGRETTO WAVE Eye-Q laser. All eyes operated with the SCHWIND ESIRIS were treated with standard aspheric ablation, whereas the eyes operated with the WaveLight ALLEGRETTO WAVE Eye-Q received treatment with three different ablation types according to the common practice at our clinic. Outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and proximity to target refraction at 6-month follow-up. At 6 months postoperative, mean decimal UCVA was 0.96+/-0.22 (range: 0.3 to 1.2) for ESIRIS eyes and 0.98+/-0.17 (range: 0.6 to 1.2) for ALLEGRETTO eyes (P=.57). Mean postoperative spherical equivalent refraction was -0.02+/-0.28 diopters (D) (range: -0.75 to +0.75 D) for ESIRIS eyes and 0.11+/-0.91 D (range: -1.00 to +3.88 D) for ALLEGRETTO eyes (P=.49). Of the ESIRIS eyes, 20/22 (91%) were within +/-1.00 D of target refraction and 20/22 (91%) were within +/-0.50 D of target refraction. Of the ALLEGRETTO eyes, 20/22 (91%) and 19/22 (86%) were within +/-1.00 D and +/-0.50 D, respectively, of target refraction. No patient lost > or =2 lines of BSCVA in either group. No differences were seen in safety and efficacy outcome parameters between the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer lasers when used according to a previously established treatment algorithm at our clinic in the treatment of refractive error.

Simulations of Seismic Wave Propagation on Mars

DOE PAGES

Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan; ...

2017-03-23

In this paper, we present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust. For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE against the 2D axisymmetric wave propagation solver AxiSEM at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on raymore » theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars’ northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. Finally, we conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.« less

Simulations of Seismic Wave Propagation on Mars

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

Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan

In this paper, we present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust. For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE against the 2D axisymmetric wave propagation solver AxiSEM at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on raymore » theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars’ northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. Finally, we conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.« less

Study of 2 S - and 1 D -excitations of observed charmed strange baryons

NASA Astrophysics Data System (ADS)

Ye, Dan-Dan; Zhao, Ze; Zhang, Ailin

2017-12-01

Strong decays of Ξc baryons with radial or orbital λ - and ρ -mode excitations with positive parity have been studied in a 3P0 model. As candidates of these kinds of excited charmed strange baryons, possible configurations and JP quantum numbers of Ξc(2930 ), Ξc(2980 ), Ξc(3055 ), Ξc(3080 ), and Ξc(3123 ) have been assigned based on experimental data. There are 40 kinds of configurations to describe the first radial or orbital excited Ξc in λ - and ρ -mode excitations with positive parity. In these assignments, Ξc(2930 ) may be a 2 S -wave excited Ξ˜c 1(1/2+) or Ξ˜c 1(3/2+), or a D -wave excited Ξ^c 1 '(1/2+) , Ξˇc 1 0(1/2+) , Ξˇc 1 2(1/2+) , Ξ^c 1 '(3/2+) , Ξˇc1 0(3/2+), or Ξˇc1 2(3/2+). Ξc(2980 )+ may be a 2 S -wave excited Ξ˜c 1(1/2+)or Ξ˜c0 '(1/2+) with JP=1/2+, or a D -wave excited Ξˇc0 '0(1/2+) or Ξˇc 1 0(1/2+) with JP=1/2+. Ξc(3055 )+may be a 2 S -wave excited Ξ´c 1 '(3/2+) or Ξ´c 0(1/2+). It may be a D -wave excited Ξc1 '(3/2+), Ξc2 '(5/2+), Ξc 2(3/2+) , or Ξc 2(5/2+) . Ξc(3080 )+is very possibly a 2 S -wave excited Ξ´c 0(1/2 +) and seems not to be a D -wave excitation of Ξc. Because of the poor experimental information for Ξc(3123 ), it is impossible to identify this state at present. It is found that the channel Λ D vanishes in the strong decay of P -wave, D -wave, and 2 S -wave excited Ξc without ρ -mode excitation between the two light quarks (nρ=Lρ=0 ). In different configurations, some branching fraction ratios related to the internal structure of the 2 S -wave and D -wave of Ξc are different. These ratios have been computed and can be employed to distinguish different configurations in forthcoming experiments.

Design on an Enhanced Interactive Satellite Communications System Analysis Program

DTIC Science & Technology

1991-09-01

openStack message is sent from the stack up the hierarchy to HyperCard. When the stack opens, the first card in the stack is displayed and an openCard... openStack global orbitPage,groundPage.commPage,beginmuRe,c.dBker2d.d2r,we global earth-e.NoiseTIV.Losses put false into orbitPage put false into groundPage...menultem 2 of menu "Options" to D end openStack function FreqToWave freq global c put c)(freq* 109) into wave return wave end FreqToWave function log

Nonlinear Decay of Alfvén Waves Driven by Interplaying Two- and Three-dimensional Nonlinear Interactions

NASA Astrophysics Data System (ADS)

Zhao, J. S.; Voitenko, Y.; De Keyser, J.; Wu, D. J.

2018-04-01

We study the decay of Alfvén waves in the solar wind, accounting for the joint operation of two-dimensional (2D) scalar and three-dimensional (3D) vector nonlinear interactions between Alfvén and slow waves. These interactions have previously been studied separately in long- and short-wavelength limits where they lead to 2D scalar and 3D vector decays, correspondingly. The joined action of the scalar and vector interactions shifts the transition between 2D and 3D decays to significantly smaller wavenumbers than was predicted by Zhao et al. who compared separate scalar and vector decays. In application to the broadband Alfvén waves in the solar wind, this means that the vector nonlinear coupling dominates in the extended wavenumber range 5 × 10‑4 ≲ ρ i k 0⊥ ≲ 1, where the decay is essentially 3D and nonlocal, generating product Alfvén and slow waves around the ion gyroscale. Here ρ i is the ion gyroradius, and k 0⊥ is the pump Alfvén wavenumber. It appears that, except for the smallest wavenumbers at and below {ρ }i{k}0\\perp ∼ {10}-4 in Channel I, the nonlinear decay of magnetohydrodynamic Alfvén waves propagating from the Sun is nonlocal and cannot generate counter-propagating Alfvén waves with similar scales needed for the turbulent cascade. Evaluation of the nonlinear frequency shift shows that product Alfvén waves can still be approximately described as normal Alfvénic eigenmodes. On the contrary, nonlinearly driven slow waves deviate considerably from normal modes and are therefore difficult to identify on the basis of their phase velocities and/or polarization.

5-D interpolation with wave-front attributes

NASA Astrophysics Data System (ADS)

Xie, Yujiang; Gajewski, Dirk

2017-11-01

Most 5-D interpolation and regularization techniques reconstruct the missing data in the frequency domain by using mathematical transforms. An alternative type of interpolation methods uses wave-front attributes, that is, quantities with a specific physical meaning like the angle of emergence and wave-front curvatures. In these attributes structural information of subsurface features like dip and strike of a reflector are included. These wave-front attributes work on 5-D data space (e.g. common-midpoint coordinates in x and y, offset, azimuth and time), leading to a 5-D interpolation technique. Since the process is based on stacking next to the interpolation a pre-stack data enhancement is achieved, improving the signal-to-noise ratio (S/N) of interpolated and recorded traces. The wave-front attributes are determined in a data-driven fashion, for example, with the Common Reflection Surface (CRS method). As one of the wave-front-attribute-based interpolation techniques, the 3-D partial CRS method was proposed to enhance the quality of 3-D pre-stack data with low S/N. In the past work on 3-D partial stacks, two potential problems were still unsolved. For high-quality wave-front attributes, we suggest a global optimization strategy instead of the so far used pragmatic search approach. In previous works, the interpolation of 3-D data was performed along a specific azimuth which is acceptable for narrow azimuth acquisition but does not exploit the potential of wide-, rich- or full-azimuth acquisitions. The conventional 3-D partial CRS method is improved in this work and we call it as a wave-front-attribute-based 5-D interpolation (5-D WABI) as the two problems mentioned above are addressed. Data examples demonstrate the improved performance by the 5-D WABI method when compared with the conventional 3-D partial CRS approach. A comparison of the rank-reduction-based 5-D seismic interpolation technique with the proposed 5-D WABI method is given. The comparison reveals that there are significant advantages for steep dipping events using the 5-D WABI method when compared to the rank-reduction-based 5-D interpolation technique. Diffraction tails substantially benefit from this improved performance of the partial CRS stacking approach while the CPU time is comparable to the CPU time consumed by the rank-reduction-based method.

3D Guided Wave Motion Analysis on Laminated Composites

NASA Technical Reports Server (NTRS)

Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

2013-01-01

Ultrasonic guided waves have proved useful for structural health monitoring (SHM) and nondestructive evaluation (NDE) due to their ability to propagate long distances with less energy loss compared to bulk waves and due to their sensitivity to small defects in the structure. Analysis of actively transmitted ultrasonic signals has long been used to detect and assess damage. However, there remain many challenging tasks for guided wave based SHM due to the complexity involved with propagating guided waves, especially in the case of composite materials. The multimodal nature of the ultrasonic guided waves complicates the related damage analysis. This paper presents results from parallel 3D elastodynamic finite integration technique (EFIT) simulations used to acquire 3D wave motion in the subject laminated carbon fiber reinforced polymer composites. The acquired 3D wave motion is then analyzed by frequency-wavenumber analysis to study the wave propagation and interaction in the composite laminate. The frequency-wavenumber analysis enables the study of individual modes and visualization of mode conversion. Delamination damage has been incorporated into the EFIT model to generate "damaged" data. The potential for damage detection in laminated composites is discussed in the end.

Guided waves in anisotropic and quasi-isotropic aerospace composites: three-dimensional simulation and experiment.

PubMed

Leckey, Cara A C; Rogge, Matthew D; Raymond Parker, F

2014-01-01

Three-dimensional (3D) elastic wave simulations can be used to investigate and optimize nondestructive evaluation (NDE) and structural health monitoring (SHM) ultrasonic damage detection techniques for aerospace materials. 3D anisotropic elastodynamic finite integration technique (EFIT) has been implemented for ultrasonic waves in carbon fiber reinforced polymer (CFRP) composite laminates. This paper describes 3D EFIT simulations of guided wave propagation in undamaged and damaged anisotropic and quasi-isotropic composite plates. Comparisons are made between simulations of guided waves in undamaged anisotropic composite plates and both experimental laser Doppler vibrometer (LDV) wavefield data and dispersion curves. Time domain and wavenumber domain comparisons are described. Wave interaction with complex geometry delamination damage is then simulated to investigate how simulation tools incorporating realistic damage geometries can aid in the understanding of wave interaction with CFRP damage. In order to move beyond simplistic assumptions of damage geometry, volumetric delamination data acquired via X-ray microfocus computed tomography is directly incorporated into the simulation. Simulated guided wave interaction with the complex geometry delamination is compared to experimental LDV time domain data and 3D wave interaction with the volumetric damage is discussed. Published by Elsevier B.V.

Revisiting linear plasma waves for finite value of the plasma parameter

NASA Astrophysics Data System (ADS)

Grismayer, Thomas; Fahlen, Jay; Decyk, Viktor; Mori, Warren

2010-11-01

We investigate through theory and PIC simulations the Landau-damping of plasma waves with finite plasma parameter. We concentrate on the linear regime, γφB, where the waves are typically small and below the thermal noise. We simulate these condition using 1,2,3D electrostatic PIC codes (BEPS), noting that modern computers now allow us to simulate cases where (nλD^3 = [1e2;1e6]). We study these waves by using a subtraction technique in which two simulations are carried out. In the first, a small wave is initialized or driven, in the second no wave is excited. The results are subtracted to provide a clean signal that can be studied. As nλD^3 is decreased, the number of resonant electrons can be small for linear waves. We show how the damping changes as a result of having few resonant particles. We also find that for small nλD^3 fluctuations can cause the electrons to undergo collisions that eventually destroy the initial wave. A quantity of interest is the the life time of a particular mode which depends on the plasma parameter and the wave number. The life time is estimated and then compared with the numerical results. A surprising result is that even for large values of nλD^3 some non-Vlasov discreteness effects appear to be important.

Emergence of fully gapped s++-wave and nodal d-wave states mediated by orbital and spin fluctuations in a ten-orbital model of KFe2Se2

NASA Astrophysics Data System (ADS)

Saito, Tetsuro; Onari, Seiichiro; Kontani, Hiroshi

2011-04-01

We study the superconducting state in recently discovered high-Tc superconductor KxFe2Se2 based on the ten-orbital Hubbard-Holstein model without hole pockets. When the Coulomb interaction is large, a spin-fluctuation-mediated d-wave state appears due to the nesting between electron pockets. Interestingly, the symmetry of the body-centered tetragonal structure in KxFe2Se2 requires the existence of nodes in the d-wave gap, although a fully gapped d-wave state is realized in the case of a simple tetragonal structure. In the presence of moderate electron-phonon interaction due to Fe-ion optical modes, however, orbital fluctuations give rise to the fully gapped s++-wave state without sign reversal. Therefore, both superconducting states are distinguishable by careful measurements of the gap structure or the impurity effect on Tc.

Fast shear compounding using robust 2-D shear wave speed calculation and multi-directional filtering.

PubMed

Song, Pengfei; Manduca, Armando; Zhao, Heng; Urban, Matthew W; Greenleaf, James F; Chen, Shigao

2014-06-01

A fast shear compounding method was developed in this study using only one shear wave push-detect cycle, such that the shear wave imaging frame rate is preserved and motion artifacts are minimized. The proposed method is composed of the following steps: 1. Applying a comb-push to produce multiple differently angled shear waves at different spatial locations simultaneously; 2. Decomposing the complex shear wave field into individual shear wave fields with differently oriented shear waves using a multi-directional filter; 3. Using a robust 2-D shear wave speed calculation to reconstruct 2-D shear elasticity maps from each filter direction; and 4. Compounding these 2-D maps from different directions into a final map. An inclusion phantom study showed that the fast shear compounding method could achieve comparable performance to conventional shear compounding without sacrificing the imaging frame rate. A multi-inclusion phantom experiment showed that the fast shear compounding method could provide a full field-of-view, 2-D and compounded shear elasticity map with three types of inclusions clearly resolved and stiffness measurements showing excellent agreement to the nominal values. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Global Hybrid Simulation of Alfvenic Waves Associated with Magnetotail Reconnection and Fast Flows

NASA Astrophysics Data System (ADS)

Cheng, L.; Lin, Y.; Wang, X.; Perez, J. D.

2017-12-01

Alfvenic fluctuations have been observed near the magnetotail plasma sheet boundary layer associated with fast flows. In this presentation, we use the Auburn 3-D Global Hybrid code (ANGIE3D) to investigate the generation and propagation of Alfvenic waves in the magnetotail. Shear Alfven waves and kinetic Alfven waves (KAWs) are found to be generated in magnetic reconnection in the plasma sheet as well as in the dipole-like field region of the magnetosphere, carrying Poynting flux along magnetic field lines toward the ionosphere, and the wave structure is strongly altered by the flow braking in the tail. The 3-D structure of the wave electromagnetic field and the associated parallel currents in reconnection and the dipole-like field region is presented. The Alfvenic waves exhibit a turbulence spectrum. The roles of these Alfvenic waves in ion heating is discussed.

Image Registration and Data Assimilation as a QUBO on the D-Wave Quantum Annealer

NASA Astrophysics Data System (ADS)

Pelissier, C.; LeMoigne, J.; Halem, M.; Simpson, D. G.; Clune, T.

2016-12-01

The advent of the commercially available D-Wave quantum annealer has for the first time allowed investigations of the potential of quantum effects to efficiently carry out certain numerical tasks. The D-Wave computer was initially promoted as a tool to solve Quadratic Unconstrained Binary Optimization problems (QUBOs), but currently, it is also being used to generate the Boltzmann statistics required to train Restricted Boltzmann machines (RBMs). We consider the potential of this new architecture in performing numerical computations required to estimate terrestrial carbon fluxes from OCO-2 observations using the LIS model. The use of RBMs is being investigated in this work, but here we focus on the D-Wave as a QUBO solver, and it's potential to carry out image registration and data assimilation. QUBOs are formulated for both problems and results generated using the D-Wave 2Xtm at the NAS supercomputing facility are presented.

Optimal insulin pump dosing and postprandial glycemia following a pizza meal using the continuous glucose monitoring system.

PubMed

Jones, Susan M; Quarry, Jill L; Caldwell-McMillan, Molly; Mauger, David T; Gabbay, Robert A

2005-04-01

We attempted to identify an optimal insulin pump meal bolus by comparing postprandial sensor glucose values following three methods of insulin pump meal bolusing for a consistent pizza meal. Twenty-four patients with type 1 diabetes participated in a study to compare postprandial glucose values following three meal bolus regimens for a consistent evening pizza meal. Each participant utilized the following insulin lispro regimens on consecutive evenings, and glucose values were tracked by the Continuous Glucose Monitoring System (CGMS, Medtronic MiniMed, Northridge, CA): (a) single-wave bolus (100% of insulin given immediately); (b) 4-h dual-wave bolus (50% of insulin given immediately and 50% given over a 4-h period); and (c) 8-h dual-wave bolus (50% of insulin given immediately and 50% given over a 8-h period). Total insulin bolus amount was kept constant for each pizza meal. Divergence in blood glucose among the regimens was greatest at 8-12 h. The 8-h dual-wave bolus provided the best glycemic control and lowest mean glucose values (singlewave bolus, 133 mg/dL; 4-h dual-wave bolus, 145 mg/dL; 8-h dual-wave bolus, 104 mg/dL), leading to a difference in mean glucose of 29 mg/dL for the single-wave bolus versus the 8-h dual-wave bolus and 42 mg/dL for the 4-h dual-wave bolus versus the 8-h dual-wave bolus. The lower mean glucose in the 8-h dual-wave bolus was not associated with any increased incidence of hypoglycemia. Use of a dual-wave bolus extended over an 8-h period following a pizza meal provided significantly less postprandial hyperglycemia in the late postprandial period (8-12 h) with no increased risk of hypoglycemia.

2-D Path Corrections for Local and Regional Coda Waves: A Test of Transportability

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

Mayeda, K M; Malagnini, L; Phillips, W S

2005-07-13

Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. [2003] has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regionsmore » of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. We will compare performance of 1-D versus 2-D path corrections in a variety of regions. First, the complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Next, we will compare results for the Italian Alps using high frequency data from the University of Genoa. For Northern California, we used the same station and event distribution and compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7 {le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2-D direct wave-based measures.« less

Three-dimensional waveform sensitivity kernels

NASA Astrophysics Data System (ADS)

Marquering, Henk; Nolet, Guust; Dahlen, F. A.

1998-03-01

The sensitivity of intermediate-period (~10-100s) seismic waveforms to the lateral heterogeneity of the Earth is computed using an efficient technique based upon surface-wave mode coupling. This formulation yields a general, fully fledged 3-D relationship between data and model without imposing smoothness constraints on the lateral heterogeneity. The calculations are based upon the Born approximation, which yields a linear relation between data and model. The linear relation ensures fast forward calculations and makes the formulation suitable for inversion schemes; however, higher-order effects such as wave-front healing are neglected. By including up to 20 surface-wave modes, we obtain Fréchet, or sensitivity, kernels for waveforms in the time frame that starts at the S arrival and which includes direct and surface-reflected body waves. These 3-D sensitivity kernels provide new insights into seismic-wave propagation, and suggest that there may be stringent limitations on the validity of ray-theoretical interpretations. Even recently developed 2-D formulations, which ignore structure out of the source-receiver plane, differ substantially from our 3-D treatment. We infer that smoothness constraints on heterogeneity, required to justify the use of ray techniques, are unlikely to hold in realistic earth models. This puts the use of ray-theoretical techniques into question for the interpretation of intermediate-period seismic data. The computed 3-D sensitivity kernels display a number of phenomena that are counter-intuitive from a ray-geometrical point of view: (1) body waves exhibit significant sensitivity to structure up to 500km away from the source-receiver minor arc; (2) significant near-surface sensitivity above the two turning points of the SS wave is observed; (3) the later part of the SS wave packet is most sensitive to structure away from the source-receiver path; (4) the sensitivity of the higher-frequency part of the fundamental surface-wave mode is wider than for its faster, lower-frequency part; (5) delayed body waves may considerably influence fundamental Rayleigh and Love waveforms. The strong sensitivity of waveforms to crustal structure due to fundamental-mode-to-body-wave scattering precludes the use of phase-velocity filters to model body-wave arrivals. Results from the 3-D formulation suggest that the use of 2-D and 1-D techniques for the interpretation of intermediate-period waveforms should seriously be reconsidered.

Secondary Generation of Mountain Waves in the Stratosphere

NASA Astrophysics Data System (ADS)

Woods, Bryan K.

Secondary generation of mountain waves was documented using in situ aircraft data from the Terrain-Induced Rotor Experiment (T-REX). Mountain waves propagating from the Sierra Nevada generated secondary waves due to stratospheric wave breaking. The seminal Eliassen and Palm (1961) relation of mountain wave energy and momentum fluxes is observationally verified for the first time. One case of reversed wave fluxes in the stratosphere is shown to be the result of multiscale secondary waves propagating down from the stratosphere. The Tropopause Inversion Layer (TIL) is shown to be capable of serving as a wave duct trapping such secondary waves. Simple idealized 2D simulations are shown to reproduce secondary wave patterns that bare striking resemblance to those observed in T-REX. However, 3D simulations are shown to fail to reproduce realistic secondary waves.

D-Wave Heavy Baryons from QCD Sum Rules

NASA Astrophysics Data System (ADS)

Mao, Qiang; Chen, Hua-Xing; Hosaka, Atsushi; Liu, Xiang; Zhu, Shi-Lin

We study the D-wave heavy baryons using the method of QCD sum rules in the framework of heavy quark effective theory. Our results suggest that the Λc(2860), Λc(2880), Ξc(3055) and Ξc(3080) complete two D-wave SU(3) flavor 3¯F charmed baryon doublets of JP = 3/2+ and 5/2+.

Shear wave velocity measurements for differential diagnosis of solid breast masses: a comparison between virtual touch quantification and virtual touch IQ.

PubMed

Tozaki, Mitsuhiro; Saito, Masahiro; Benson, John; Fan, Liexiang; Isobe, Sachiko

2013-12-01

This study compared the diagnostic performance of two shear wave speed measurement techniques in 81 patients with 83 solid breast lesions. Virtual Touch Quantification, which provides single-point shear wave speed measurement capability (SP-SWS), was compared with Virtual Touch IQ, a new 2-D shear wave imaging technique with multi-point shear wave speed measurement capability (2D-SWS). With SP-SWS, shear wave velocity was measured within the lesion ("internal" value) and the marginal areas ("marginal" value). With 2D-SWS, the highest velocity was measured. The marginal values obtained with the SP-SWS and 2D-SWS methods were significantly higher for malignant lesions and benign lesions, respectively (p < 0.0001). Sensitivity, specificity and accuracy were 86% (36/42), 90% (37/41) and 88% (73/83), respectively, for SP-SWS, and 88% (37/42), 93% (38/41) and 90% (75/83), respectively, for 2D-SWS. It is concluded that 2D-SWS is a useful diagnostic tool for differentiating malignant from benign solid breast masses. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Magnetic helicity conservation and inverse energy cascade in electron magnetohydrodynamic wave packets.

PubMed

Cho, Jungyeon

2011-05-13

Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.

Cases Study of Nonlinear Interaction Between Near-Inertial Waves Induced by Typhoon and Diurnal Tides Near the Xisha Islands

NASA Astrophysics Data System (ADS)

Liu, Junliang; He, Yinghui; Li, Juan; Cai, Shuqun; Wang, Dongxiao; Huang, Yandan

2018-04-01

Nonlinear interaction between near-inertial waves (NIWs) and diurnal tides (DTs) after nine typhoons near the Xisha Islands of the northwestern South China Sea (SCS) were investigated using three-year in situ mooring observation data. It was found that a harmonic wave (f + D1, hereafter referred to as fD1 wave), with a frequency equal to the sum of frequencies of NIWs and DTs (hereafter referred to as f and D1, respectively), was generated via nonlinear interaction between typhoon-induced NIWs and DTs after each typhoon. The fD1 wave mainly concentrates in the subsurface layer, and is mainly induced by the first component of the vertical nonlinear momentum term, the product of the vertical velocity of DT and vertical shear of near-inertial current (hereafter referred to as Component 1), in which the vertical shear of the near-inertial current greatly affects the strength of the fD1 current. The larger the Component 1, the stronger the fD1 currents. The background preexisting mesoscale anticyclonic eddy near the mooring site may also enhance the vertical velocity of DT and thus Component 1, which subsequently facilitates the nonlinear interaction-induced energy transfer to the fD1 wave and enhances the fD1 currents after the passage of a typhoon.

Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT.

PubMed

Patra, Subir; Ahmed, Hossain; Banerjee, Sourav

2018-01-18

Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D) Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS) and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT) transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D) in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM) of plate-like structures and nondestructive evaluation (NDE) of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

Two-dimensional topological superconducting phases emerged from d-wave superconductors in proximity to antiferromagnets

NASA Astrophysics Data System (ADS)

Zhu, Guo-Yi; Wang, Ziqiang; Zhang, Guang-Ming

2017-05-01

Motivated by the recent observations of nodeless superconductivity in the monolayer CuO2 grown on the Bi2Sr2CaCu2O8+δ substrates, we study the two-dimensional superconducting (SC) phases described by the two-dimensional t\\text-J model in proximity to an antiferromagnetic (AF) insulator. We found that i) the nodal d-wave SC state can be driven via a continuous transition into a nodeless d-wave pairing state by the proximity-induced AF field. ii) The energetically favorable pairing states in the strong field regime have extended s-wave symmetry and can be nodal or nodeless. iii) Between the pure d-wave and s-wave paired phases, there emerge two topologically distinct SC phases with (s+\\text{i}d) symmetry, i.e., the weak and strong pairing phases, and the weak pairing phase is found to be a Z 2 topological superconductor protected by valley symmetry, exhibiting robust gapless nonchiral edge modes. These findings strongly suggest that the high-T c superconductors in proximity to antiferromagnets can realize fully gapped symmetry-protected topological SC.

Non-filamentated ultra-intense and ultra-short pulse fronts in three-dimensional Raman seed amplification

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

Lehmann, G.; Spatschek, K. H.

Ultra-intense and ultra-short laser pulses may be generated up to the exawatt-zetawatt regime due to parametric processes in plasmas. The minimization of unwanted plasma processes leads to operational limits which are discussed here with respect to filamentation. Transverse filamentation, which originally was derived for plane waves, is being investigated for seed pulse propagation in the so called π-pulse limit. A three-dimensional (3D) three-wave-interaction model is the basis of the present investigation. To demonstrate the applicability of the three-wave-interaction model, the 1D pulse forms are compared with those obtained from 1D particle in cell and Vlasov simulations. Although wave-breaking may occur,more » the kinetic simulations show that the leading pumped pulse develops a form similar to that obtained from the three-wave-interaction model. In the main part, 2D and 3D filamentation processes of (localized) pulses are investigated with the three-wave-interaction model. It is shown that the leading pulse front can stay filamentation-free, whereas the rear parts show transverse modulations.« less

Ground States of Random Spanning Trees on a D-Wave 2X

NASA Astrophysics Data System (ADS)

Hall, J. S.; Hobl, L.; Novotny, M. A.; Michielsen, Kristel

The performances of two D-Wave 2 machines (476 and 496 qubits) and of a 1097-qubit D-Wave 2X were investigated. Each chip has a Chimera interaction graph calG . Problem input consists of values for the fields hj and for the two-qubit interactions Ji , j of an Ising spin-glass problem formulated on calG . Output is returned in terms of a spin configuration {sj } , with sj = +/- 1 . We generated random spanning trees (RSTs) uniformly distributed over all spanning trees of calG . On the 476-qubit D-Wave 2, RSTs were generated on the full chip with Ji , j = - 1 and hj = 0 and solved one thousand times. The distribution of solution energies and the average magnetization of each qubit were determined. On both the 476- and 1097-qubit machines, four identical spanning trees were generated on each quadrant of the chip. The statistical independence of these regions was investigated. In another study, on the D-Wave 2X, one hundred RSTs with random Ji , j ∈ { - 1 , 1 } and hj = 0 were generated on the full chip. Each RST problem was solved one hundred times and the number of times the ground state energy was found was recorded. This procedure was repeated for square subgraphs, with dimensions ranging from 7 ×7 to 11 ×11. Supported in part by NSF Grants DGE-0947419 and DMR-1206233. D-Wave time provided by D-Wave Systems and by the USRA Quantum Artificial Intelligence Laboratory Research Opportunity.

Banded Structures in Electron Pitch Angle Diffusion Coefficients from Resonant Wave-Particle Interactions

NASA Technical Reports Server (NTRS)

Tripathi, A. K.; Singhal, R. P.; Khazanov, G. V.; Avanov, L. A.

2016-01-01

Electron pitch angle (D(sub (alpha alpha))) and momentum (D(sub pp)) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic (ECH) and whistler mode chorus waves. Calculations have been performed at two spatial locations L=4.6 and 6.8 for electron energies less than or equal to 10 keV. Landau (n=0) resonance and cyclotron harmonic resonances n= +/- 1, +/-2, ... +/-5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (alpha) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusion coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECH waves in pitch angle diffusion coefficient is due to resonances n=+1 and n=+2. A major contribution to momentum diffusion coefficients appears from n=+2. However, the banded structures in D(sub alpha alpha) and D(sub pp) coefficients appear only in the profile of diffusion coefficients for n=+2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band chorus waves, the banded structures appear only in Landau resonance. The D(sub pp) diffusion coefficient for ECH waves is one to two orders smaller than D(sub alpha alpha) coefficients. For chorus waves, D(sub pp) coefficients are about an order of magnitude smaller than D(sub alpha alpha) coefficients for the case n does not equal 0. In case of Landau resonance, the values of D(sub pp) coefficient are generally larger than the values of D(sub alpha alpha) coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECH waves, resonant frequencies have been estimated for wave normal angle 89 deg and harmonic resonances n= +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10 deg and Landau resonance. Further, in ECH waves, the banded structures appear for electron energies 1 greater than or equal to keV, and for whistler mode chorus waves, structures appear for energies greater than 2 keV at L=4.6 and above 200 eV for L=6.8. The results obtained in the present work will be helpful in the study of diffusion curves and will have important consequences for diffuse aurora and pancake distributions.

Quantum oscillations in the mixed state of d -wave superconductors

NASA Astrophysics Data System (ADS)

Melikyan, Ashot; Vafek, Oskar

2008-07-01

We show that the low-energy density of quasiparticle states in the mixed state of ultraclean dx2-y2 -wave superconductors exhibits quantum oscillations even in the regime where the cyclotron frequency ℏωc≪Δ0 , the d -wave pairing gap. Such oscillations as a function of magnetic field B are argued to be due to the internodal scattering of the nodal quasiparticles near wave vectors (±kD,±kD) by the vortex lattice as well as their Zeeman coupling. While the nominal periodicity of the oscillations is set by the condition kD[hc/(eB)]1/2≡kD'[hc/(eB')]1/2(mod2π) , we find that there is additional structure within each period that grows in complexity as the Dirac node anisotropy increases.

Erosional Equivalences of Levees: Steady and Intermittent Wave Overtopping

DTIC Science & Technology

2010-01-01

represents the proportion of the individual wave period for which the runup exceeds the levee crest. We require that the average Still Water Level1 tan α zc R... Levee Fig. 5. Definition sketch for potential wave runup. Runu p , R Centroids of Equal Runup Probabilities R m in = z c Pr ob ab ili ty D en si...Erosional equivalences of levees : Steady and intermittent wave overtopping R.G. Dean a, J.D. Rosati b, T.L. Walton c, B.L. Edge d , a Department of

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Measurements of laser-induced shock waves in aluminium

NASA Astrophysics Data System (ADS)

Werdiger, M.; Arad, B.; Moshe, E.; Eliezer, S.

1995-02-01

A simple optical method for measurements of high-irradiance (3×1013 W cm-2) laser-induced shock waves is described. The shock wave velocity (~13 km s-1) was measured with an error not exceeding 5%. The laser-induced one-to-two-dimensional (1D-to-2D) shock wave transition was studied.

Fast Shear Compounding Using Robust Two-dimensional Shear Wave Speed Calculation and Multi-directional Filtering

PubMed Central

Song, Pengfei; Manduca, Armando; Zhao, Heng; Urban, Matthew W.; Greenleaf, James F.; Chen, Shigao

2014-01-01

A fast shear compounding method was developed in this study using only one shear wave push-detect cycle, such that the shear wave imaging frame rate is preserved and motion artifacts are minimized. The proposed method is composed of the following steps: 1. applying a comb-push to produce multiple differently angled shear waves at different spatial locations simultaneously; 2. decomposing the complex shear wave field into individual shear wave fields with differently oriented shear waves using a multi-directional filter; 3. using a robust two-dimensional (2D) shear wave speed calculation to reconstruct 2D shear elasticity maps from each filter direction; 4. compounding these 2D maps from different directions into a final map. An inclusion phantom study showed that the fast shear compounding method could achieve comparable performance to conventional shear compounding without sacrificing the imaging frame rate. A multi-inclusion phantom experiment showed that the fast shear compounding method could provide a full field-of-view (FOV), 2D, and compounded shear elasticity map with three types of inclusions clearly resolved and stiffness measurements showing excellent agreement to the nominal values. PMID:24613636

Advanced Gravitational Wave Detectors

NASA Astrophysics Data System (ADS)

Blair, D. G.; Howell, E. J.; Ju, L.; Zhao, C.

2012-02-01

Part I. An Introduction to Gravitational Wave Astronomy and Detectors: 1. Gravitational waves D. G. Blair, L. Ju, C. Zhao and E. J. Howell; 2. Sources of gravitational waves D. G. Blair and E. J. Howell; 3. Gravitational wave detectors D. G. Blair, L. Ju, C. Zhao, H. Miao, E. J. Howell, and P. Barriga; 4. Gravitational wave data analysis B. S. Sathyaprakash and B. F. Schutz; 5. Network analysis L. Wen and B. F. Schutz; Part II. Current Laser Interferometer Detectors: Three Case Studies: 6. The Laser Interferometer Gravitational-Wave Observatory P. Fritschel; 7. The VIRGO detector S. Braccini; 8. GEO 600 H. Lück and H. Grote; Part III. Technology for Advanced Gravitational Wave Detectors: 9. Lasers for high optical power interferometers B. Willke and M. Frede; 10. Thermal noise, suspensions and test masses L. Ju, G. Harry and B. Lee; 11. Vibration isolation: Part 1. Seismic isolation for advanced LIGO B. Lantz; Part 2. Passive isolation J-C. Dumas; 12. Interferometer sensing and control P. Barriga; 13. Stabilizing interferometers against high optical power effects C. Zhao, L. Ju, S. Gras and D. G. Blair; Part IV. Technology for Third Generation Gravitational Wave Detectors: 14. Cryogenic interferometers J. Degallaix; 15. Quantum theory of laser-interferometer GW detectors H. Miao and Y. Chen; 16. ET. A third generation observatory M. Punturo and H. Lück; Index.

Validation and Comparison of 2D and 3D Codes for Nearshore Motion of Long Waves Using Benchmark Problems

NASA Astrophysics Data System (ADS)

Velioǧlu, Deniz; Cevdet Yalçıner, Ahmet; Zaytsev, Andrey

2016-04-01

Tsunamis are huge waves with long wave periods and wave lengths that can cause great devastation and loss of life when they strike a coast. The interest in experimental and numerical modeling of tsunami propagation and inundation increased considerably after the 2011 Great East Japan earthquake. In this study, two numerical codes, FLOW 3D and NAMI DANCE, that analyze tsunami propagation and inundation patterns are considered. Flow 3D simulates linear and nonlinear propagating surface waves as well as long waves by solving three-dimensional Navier-Stokes (3D-NS) equations. NAMI DANCE uses finite difference computational method to solve 2D depth-averaged linear and nonlinear forms of shallow water equations (NSWE) in long wave problems, specifically tsunamis. In order to validate these two codes and analyze the differences between 3D-NS and 2D depth-averaged NSWE equations, two benchmark problems are applied. One benchmark problem investigates the runup of long waves over a complex 3D beach. The experimental setup is a 1:400 scale model of Monai Valley located on the west coast of Okushiri Island, Japan. Other benchmark problem is discussed in 2015 National Tsunami Hazard Mitigation Program (NTHMP) Annual meeting in Portland, USA. It is a field dataset, recording the Japan 2011 tsunami in Hilo Harbor, Hawaii. The computed water surface elevation and velocity data are compared with the measured data. The comparisons showed that both codes are in fairly good agreement with each other and benchmark data. The differences between 3D-NS and 2D depth-averaged NSWE equations are highlighted. All results are presented with discussions and comparisons. Acknowledgements: Partial support by Japan-Turkey Joint Research Project by JICA on earthquakes and tsunamis in Marmara Region (JICA SATREPS - MarDiM Project), 603839 ASTARTE Project of EU, UDAP-C-12-14 project of AFAD Turkey, 108Y227, 113M556 and 213M534 projects of TUBITAK Turkey, RAPSODI (CONCERT_Dis-021) of CONCERT-Japan Joint Call and Istanbul Metropolitan Municipality are all acknowledged.

Correlates of mothers' persistent depressive symptoms: a national study.

PubMed

Pascoe, John M; Stolfi, Adrienne; Ormond, Mary B

2006-01-01

The purpose of this study was to examine the prevalence, persistence, and correlates of mothers' depressive symptoms over a 5-year period in a nationally representative sample of the United States population. Data from 2235 mothers in the National Survey of Families and Households, Wave I, 1987-1988, and Wave II, 1992-1994, were analyzed. Outcome measures were scores on the Center for Epidemiological Studies Depression Scale (CES-D, 12-item version) and a validated three-item depression screen. One fifth of study mothers had positive CES-D scores and almost half (48%) had negative CES-D scores in both waves. Wave I risk factors for persistent "positive" CES-D scores were maternal age less than 30 years (24%), African-American (33%), never married (26%) or divorced (32%), education less than high school (35%), and indigent (32%). Adjusted odds ratios (AOR) and 95% confidence intervals for persistent "positive" versus persistent "negative" CES-D scores were: age less than 30 years (Wave I), AOR = 1.64, (1.22-2.21); unmarried (Wave II), AOR = 2.60, (1.89-3.56); education less than high school (Wave II), AOR = 2.18, (1.41-3.38); and indigent (Wave II), AOR = 2.09 (1.36-3.21). About one fifth of the study sample reported high depressive symptoms twice over a 5-year period. Depression in women, especially mothers, is an urgent public health problem.

The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

NASA Astrophysics Data System (ADS)

Tsiklauri, D.

2014-12-01

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refaction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph=ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011) [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013) [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012) [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014) [5] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 21, 012903 (2014)

Modelling of radio frequency sheath and fast wave coupling on the realistic ion cyclotron resonant antenna surroundings and the outer wall

NASA Astrophysics Data System (ADS)

Lu, L.; Colas, L.; Jacquot, J.; Després, B.; Heuraux, S.; Faudot, E.; Van Eester, D.; Crombé, K.; Křivská, A.; Noterdaeme, J.-M.; Helou, W.; Hillairet, J.

2018-03-01

In order to model the sheath rectification in a realistic geometry over the size of ion cyclotron resonant heating (ICRH) antennas, the self-consistent sheaths and waves for ICH (SSWICH) code couples self-consistently the RF wave propagation and the DC SOL biasing via nonlinear RF and DC sheath boundary conditions applied at plasma/wall interfaces. A first version of SSWICH had 2D (toroidal and radial) geometry, rectangular walls either normal or parallel to the confinement magnetic field B 0 and only included the evanescent slow wave (SW) excited parasitically by the ICRH antenna. The main wave for plasma heating, the fast wave (FW) plays no role on the sheath excitation in this version. A new version of the code, 2D SSWICH-full wave, was developed based on the COMSOL software, to accommodate full RF field polarization and shaped walls tilted with respect to B 0 . SSWICH-full wave simulations have shown the mode conversion of FW into SW occurring at the sharp corners where the boundary shape varies rapidly. It has also evidenced ‘far-field’ sheath oscillations appearing at the shaped walls with a relatively long magnetic connection length to the antenna, that are only accessible to the propagating FW. Joint simulation, conducted by SSWICH-full wave within a multi-2D approach excited using the 3D wave coupling code (RAPLICASOL), has recovered the double-hump poloidal structure measured in the experimental temperature and potential maps when only the SW is modelled. The FW contribution on the potential poloidal structure seems to be affected by the 3D effects, which was ignored in the current stage. Finally, SSWICH-full wave simulation revealed the left-right asymmetry that has been observed extensively in the unbalanced strap feeding experiments, suggesting that the spatial proximity effects in RF sheath excitation, studied for SW only previously, is still important in the vicinity of the wave launcher under full wave polarizations.

Transport Theory for Propagation and Reverberation

DTIC Science & Technology

2016-07-20

mentioned that our transport theory method is essentially 2-D (range and depth), so that out-of- plane forward scattering (a 3-D effect) is not treated...roughness spectrum, it is useful to consider scattering based on perturbation theory in some detail with a plane wave incident on the rough surface. The...the wave vector for the water wave. Let an incident acoustic plane wave have wave vector ki = kiH + kiz, where kiH denotes the horizontal component

First tomographic observations of gravity waves by the infrared limb imager GLORIA

NASA Astrophysics Data System (ADS)

Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Dörnbrack, Andreas; Eckermann, Stephen D.; Ern, Manfred; Friedl-Vallon, Felix; Kaufmann, Martin; Oelhaf, Hermann; Rapp, Markus; Strube, Cornelia; Riese, Martin

2017-12-01

Atmospheric gravity waves are a major cause of uncertainty in atmosphere general circulation models. This uncertainty affects regional climate projections and seasonal weather predictions. Improving the representation of gravity waves in general circulation models is therefore of primary interest. In this regard, measurements providing an accurate 3-D characterization of gravity waves are needed. Using the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA), the first airborne implementation of a novel infrared limb imaging technique, a gravity wave event over Iceland was observed. An air volume disturbed by this gravity wave was investigated from different angles by encircling the volume with a closed flight pattern. Using a tomographic retrieval approach, the measurements of this air mass at different angles allowed for a 3-D reconstruction of the temperature and trace gas structure. The temperature measurements were used to derive gravity wave amplitudes, 3-D wave vectors, and direction-resolved momentum fluxes. These parameters facilitated the backtracing of the waves to their sources on the southern coast of Iceland. Two wave packets are distinguished, one stemming from the main mountain ridge in the south of Iceland and the other from the smaller mountains in the north. The total area-integrated fluxes of these two wave packets are determined. Forward ray tracing reveals that the waves propagate laterally more than 2000 km away from their source region. A comparison of a 3-D ray-tracing version to solely column-based propagation showed that lateral propagation can help the waves to avoid critical layers and propagate to higher altitudes. Thus, the implementation of oblique gravity wave propagation into general circulation models may improve their predictive skills.

2-D or not 2-D, that is the question: A Northern California test

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

Mayeda, K; Malagnini, L; Phillips, W S

2005-06-06

Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions ofmore » approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2-D direct wave-based measures.« less

Magnetostatic wave tunable resonators

NASA Astrophysics Data System (ADS)

Castera, J.-P.; Hartemann, P.

1983-06-01

Theoretical principles and techniques for the implementation of magnetostatic surface wave and volume wave resonators in high frequency oscillators are discussed. Magnetostatic waves are magnetic waves that propagate in materials exposed to a polarized magnetic field. The propagation speed ranges from 3-300 km/sec for wavelengths between 1 micron and 10 mm, in the presence of lags from 10-1000 nsec/ cm. Tunable resonators in the 1-20 GHz frequency range have been manufactured with YIG using liquid phase epitaxy for deposition on gadolinium and gallium substrates. Distributed-mirror Fabry-Perot cavity resonators are described and performance tests results are reported, including losses of 8 dB, a quality coefficient under voltage of 450, and frequency rejection outside of resonance better than 10 dB. However, saturation occurs at low power levels at frequencies lower than 4.2 GHz, a feature overcome with forward volume magnetostatic wave generators, which have a quality factor of 500, an insertion loss of 22 dB, and rejection around 15 dB.

Analysis of Fluctuations of Electron Density in the D-region During the 2017 Solar Eclipse using a Very Low Frequency Receiver

NASA Astrophysics Data System (ADS)

Hernandez, E.; Mathur, S.; Fenton, A.; Behrend, C. C.; Bering, E., III

2017-12-01

As part of the Undergraduate Student Instrumentation Project (USIP) at the University of Houston, multiple Very Low Frequency (VLF) Radio Receivers will be set up during the 2017 solar eclipse. They will be taking data from Omaha, Nebraska and Casper, Wyoming. The receiver, using an air loop antenna, will record magnetic field fluctuations caused by VLF waves. The purpose of this experiment is to study the effects of the sudden change in electromagnetic radiation from the sun on the D-region of the ionosphere. VLF waves were chosen for measurement because naturally occurring VLF waves propagate through the Earth-ionosphere waveguide, which can be used to remotely observe the ionosphere. The D-region reduces the energy in propagating waves due to absorption. This means that any fluctuations in the D-region are inversely correlated to the strength of VLF waves being received. The experiment will focus on receiving waves transmitted from specific stations that are on the other side of totality. The amplitude and phase of the received waves will be measured and analyzed. It is hoped that this experiment will help us gain a better understanding of VLFs from the D-region during the solar eclipse, as well as increasing the overall data available for use by the community.

Study of Proximity Effect at D-Wave Superconductors in Quasiclassical Methods

NASA Astrophysics Data System (ADS)

Tanuma, Y.; Tanaka, Y.; Kashiwaya, S.

2005-08-01

Tunneling spectra via Andreev bound states between a normal metal (N) / dx2-y2-wave superconductor (S) (in the presence of a subdominant s-wave pair potential) junction are investigated. In the present work, in order to study the role of proximity effect, we employ quasiclassical Green's function methods. This merit is that we can determine the spatial variation of the pair potentials self-consistently, where the leaking of pair potentials into the N side is involved. In the N/S junction with orientational angle θ = π/4, we can regard as the isolated d-wave superconductor, where attractive interaction in the N side is negligible. On the other hand, in the case of a high transparent contact to the d-wave superconductor (θ = 0), the pair potential penetrates into the inside of the N due to the proximity effect, where the is-wave is not indued at all. Then, the tunneling spectra has a very sharp zero-energy peak (ZEP). This ZEP originates from the fact that quasiparticles feel different sign of the pair potentials between normal metals and d-wave superconductors through Andreev reflections. We show that the spatial dependence of pair potentials is significantly sensitive to the transparency of the junction.

Numerical modeling of porosity waves in the Nankai accretionary wedge décollement, Japan: implications for aseismic slip

NASA Astrophysics Data System (ADS)

Joshi, Ajit; Appold, Martin S.

2017-01-01

Seismic and hydrologic observations of the Nankai accretionary wedge décollement, Japan, show that overpressures at depths greater than ˜2 km beneath the seafloor could have increased to near lithostatic values due to sediment compaction and diagenesis, clay dehydration, and shearing. The resultant high overpressures are hypothesized then to have migrated in rapid surges or pulses called `porosity waves' up the dip of the décollement. Such high velocities—much higher than expected Darcy fluxes—are possible for porosity waves if the porous media through which the waves travel are deformable enough for porosity and permeability to increase strongly with increasing fluid pressure. The present study aimed to test the hypothesis that porosity waves can travel at rates (kilometers per day) fast enough to cause aseismic slip in the Nankai décollement. The hypothesis was tested using a one-dimensional numerical solution to the fluid mass conservation equation for elastic porous media. Results show that porosity waves generated at depths of ˜2 km from overpressures in excess of lithostatic pressure can propagate at rates sufficient to account for aseismic slip along the décollement over a wide range of hydrogeological conditions. Sensitivity analysis showed porosity wave velocity to be strongly dependent on specific storage, fluid viscosity, and the permeability-depth gradient. Overpressure slightly less than lithostatic pressure could also produce porosity waves capable of traveling at velocities sufficient to cause aseismic slip, provided that hydrogeologic properties of the décollement are near the limits of their geologically reasonable ranges.

Rayleigh-wave dispersive energy imaging and mode separating by high-resolution linear Radon transform

USGS Publications Warehouse

Luo, Y.; Xu, Y.; Liu, Q.; Xia, J.

2008-01-01

In recent years, multichannel analysis of surface waves (MASW) has been increasingly used for obtaining vertical shear-wave velocity profiles within near-surface materials. MASW uses a multichannel recording approach to capture the time-variant, full-seismic wavefield where dispersive surface waves can be used to estimate near-surface S-wave velocity. The technique consists of (1) acquisition of broadband, high-frequency ground roll using a multichannel recording system; (2) efficient and accurate algorithms that allow the extraction and analysis of 1D Rayleigh-wave dispersion curves; (3) stable and efficient inversion algorithms for estimating S-wave velocity profiles; and (4) construction of the 2D S-wave velocity field map.

Universal heat conduction in Ce 1-xYb xCoIn 5: Evidence for robust nodal d-wave superconducting gap

DOE PAGES

Xu, Y.; Petrovic, C.; Dong, J. K.; ...

2016-02-01

In the heavy-fermion superconductor Ce 1-xYb xCoIn 5, Yb doping was reported to cause a possible change from nodal d-wave superconductivity to a fully gapped d-wave molecular superfluid of composite pairs near x ≈ 0.07 (nominal value x nom = 0.2). Here we present systematic thermal conductivity measurements on Ce 1-xYb xCoIn 5 (x = 0.013, 0.084, and 0.163) single crystals. The observed finite residual linear term κ 0/T is insensitive to Yb doping, verifying the universal heat conduction of the nodal d-wave superconducting gap in Ce 1-xYb xCoIn 5. Similar universal heat conduction is also observed in the CeCo(Inmore » 1–yCd y) 5 system. Furthermore, these results reveal a robust nodal d-wave gap in CeCoIn 5 upon Yb or Cd doping.« less

Brain stem auditory-evoked response in the nonanesthetized horse and pony.

PubMed

Marshall, A E

1985-07-01

The brain stem auditory-evoked response (BAER) was measured in 10 horses and 7 ponies under conditions suitable for clinical diagnostic testing. Latencies of 5 vertex-positive peaks and interpeak latency and amplitude ratio on the 1st and 4th peaks were determined. Data from horses and ponies were analyzed separately and were compared. The stimulus was a click (n = 3,000) ranging from 10- to 90-dB hearing level (HL). Neither horses nor ponies responded with a BAER at 10 dB nor did they give reliable responses at less than 50 dB. The 2nd of the BAER waves appeared in the record at lower stimulus intensities than did the 1st wave for the horse and pony. Horses and ponies had a decreasing latency for all waves, as a result of increasing stimulus intensity. Latencies were shorter for the ponies than for the horses at all stimulus intensities for the 1st, 2nd, 3rd, and 4th waves, but not the 5th wave. At 60-dB HL, the mean latencies for the 1st through 5th wave, respectively, for the horse were 1.73, 3.08, 3.93, 4.98, and 6.00 ms and for the pony 1.48, 2.73, 3.50, 4.56, and 6.58 ms. Interpeak latencies, 1st to 4th wave, averaged 3.22 ms (horse) and 3.11 ms (pony) for all stimulus intensities from 50- to 90-dB HL and had a tendency to decrease slightly as stimulus intensity increased. Amplitude ratios (4th wave/1st wave) were less than 1 for all stimulus intensities in the horse. In the pony, the ratio was less than 1 at greater than or equal to 70-dB HL and greater than 1 at less than or equal to 60-dB HL.

Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

NASA Astrophysics Data System (ADS)

Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

2016-11-01

A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

Crack Detection with Lamb Wave Wavenumber Analysis

NASA Technical Reports Server (NTRS)

Tian, Zhenhua; Leckey, Cara; Rogge, Matt; Yu, Lingyu

2013-01-01

In this work, we present our study of Lamb wave crack detection using wavenumber analysis. The aim is to demonstrate the application of wavenumber analysis to 3D Lamb wave data to enable damage detection. The 3D wavefields (including vx, vy and vz components) in time-space domain contain a wealth of information regarding the propagating waves in a damaged plate. For crack detection, three wavenumber analysis techniques are used: (i) two dimensional Fourier transform (2D-FT) which can transform the time-space wavefield into frequency-wavenumber representation while losing the spatial information; (ii) short space 2D-FT which can obtain the frequency-wavenumber spectra at various spatial locations, resulting in a space-frequency-wavenumber representation; (iii) local wavenumber analysis which can provide the distribution of the effective wavenumbers at different locations. All of these concepts are demonstrated through a numerical simulation example of an aluminum plate with a crack. The 3D elastodynamic finite integration technique (EFIT) was used to obtain the 3D wavefields, of which the vz (out-of-plane) wave component is compared with the experimental measurement obtained from a scanning laser Doppler vibrometer (SLDV) for verification purposes. The experimental and simulated results are found to be in close agreement. The application of wavenumber analysis on 3D EFIT simulation data shows the effectiveness of the analysis for crack detection. Keywords: : Lamb wave, crack detection, wavenumber analysis, EFIT modeling

Beating HF waves to generate VLF waves in the ionosphere

NASA Astrophysics Data System (ADS)

Kuo, Spencer; Snyder, Arnold; Kossey, Paul; Chang, Chia-Lie; Labenski, John

2012-03-01

Beat-wave generation of very low frequency (VLF) waves by two HF heaters in the ionosphere is formulated theoretically and demonstrated experimentally. The heater-induced differential thermal pressure force and ponderomotive force, which dominate separately in the D and F regions of the ionosphere, drive an electron current for the VLF emission. A comparison, applying appropriate ionospheric parameters shows that the ponderomotive force dominates in beat-wave generation of VLF waves. Three experiments, one in the nighttime in the absence of D and E layers and two in the daytime in the presence of D and E layers, were performed. X mode HF heaters of slightly different frequencies were transmitted at CW full power. VLF waves at 10 frequencies ranging from 3.5 to 21.5 kHz were generated. The frequency dependencies of the daytime and nighttime radiation intensities are quite similar, but the nighttime radiation is much stronger than the daytime one at the same radiation frequency. The intensity ratio is as large as 9 dB at 11.5 kHz. An experiment directly comparing VLF waves generated by the beat-wave approach and by the amplitude modulation (AM) approach was also conducted. The results rule out the likely contribution of the AM mechanism acting on the electrojet and indicate that beat-wave in the VLF range prefers to be generated in the F region of the ionosphere through the ponderomotive nonlinearity, consistent with the theory. In the nighttime experiment, the ionosphere was underdense to the HF heaters, suggesting a likely setting for effective beat-wave generation of VLF waves by the HF heaters.

Poisson's ratio model derived from P- and S-wave reflection seismic data at the CO2CRC Otway Project pilot site, Australia

NASA Astrophysics Data System (ADS)

Beilecke, Thies; Krawczyk, Charlotte M.; Tanner, David C.; Ziesch, Jennifer; Research Group Protect

2014-05-01

Compressional wave (P-wave) reflection seismic field measurements are a standard tool for subsurface exploration. 2-D seismic measurements are often used for overview measurements, but also as near-surface supplement to fill gaps that often exist in 3-D seismic data sets. Such supplementing 2-D measurements are typically simple with respect to field layout. This is an opportunity for the use of shear waves (S-waves). Within the last years, S-waves have become more and more important. One reason is that P- and S-waves are differently sensitive to fluids and pore fill so that the additional S-wave information can be used to enhance lithological studies. Another reason is that S-waves have the advantage of higher spatial resolution. Within the same signal bandwidth they typically have about half the wavelength of P-waves. In near-surface unconsolidated sediments they can even enhance the structural resolution by one order of magnitude. We make use of these capabilities within the PROTECT project. In addition to already existing 2-D P-wave data, we carried out a near surface 2-D S-wave field survey at the CO2CRC Otway Project pilot site, close to Warrnambool, Australia in November 2013. The combined analysis of P-wave and S-wave data is used to construct a Poisson's Ratio 2-D model down to roughly 600 m depth. The Poisson's ratio values along a 1 km long profile at the site are surprisingly high, ranging from 0.47 in the carbonate-dominated near surface to 0.4 at depth. In the literature, average lab measurements of 0.22 for unfissured carbonates and 0.37 for fissured examples have been reported. The high values that we found may indicate areas of rather unconsolidated or fractured material, or enhanced fluid contents, and will be subject of further studies. This work is integrated in a larger workflow towards prediction of CO2 leakage and monitoring strategies for subsurface storage in general. Acknowledgement: This work was sponsored in part by the Australian Commonwealth Government through the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC). PROTECT is funded through the Geotechnologien research programme in Germany (grant 03G0797).

Effects of Isotropic and Anisotropic Structure in the Lowermost Mantle on High-Frequency Body Waveforms

NASA Astrophysics Data System (ADS)

Parisi, L.; Ferreira, A. M. G.; Ritsema, J.

2015-12-01

It has been observed that vertically (SV) and horizontally (SH) polarised S waves crossing the lowermost mantle sometimes are split by a few seconds The splitting of such waves is often interpreted in terms of seismic anisotropy in the D" region. Here we investigate systematically the effects of elastic, anelastic, isotropic and anisotropic structure on shear-wave splitting, including 3-D variations in some of these physical properties. Taking advantage of accurate waveform modeling techniques such as Gemini and the Spectral Element Method we generate three-component theoretical waveforms in a wide set of 1-D and 3-D, isotropic and radially anisotropic earth models, accurate down to a wave period of T~5.6s. Our numerical simulations in isotropic earth models show that the contamination of S waves by other phases can generate an apparent splitting between SH and SV waves. In particular, in the case of very shallow sources, the sS phase can interfere with the direct S phase, resulting in split SH and SV pulses when the SH and SV (or sSH and sSV) waves have different polarity or a substantial amplitude difference. In the case of deep earthquake sources, a positive shear velocity jump at the top of the D" can cause the triplication of S waves and the ScSH and ScSV phases can have different polarity. Thus, when the triplicated S wave is combined with the ScS phase, the resulting SH-ScSH and SV-ScSV phases may seem split. On the other hand, in the absence of a sharp vertical variation in the shear wave velocity, the difference in polarity between ScSH and ScSV can make the SH pulse larger than SV and thus also lead to apparent splitting between these phases. This effect depends on the thickness of the D" and the Vs gradient within it. S waveforms simulated in radially anisotropic models reveal that a radial anisotropy of ξ=1.07 in the D" seems to be necessary to explain the 2-3s of splitting observed in waveforms recorded in Tanzania from an event in the Banda Sea. However, our analysis also shows that other factors such as sharp vertical variations at the top of D" and gradients of Vs and η within the D'' may also affect the observed waveforms. This study suggests that caution should be taken when interpreting SH-SV splitting of deep mantle body waves exclusively in terms of anisotropy in the lowermost mantle.

The effects of plastic waves on the numerical convergence of the viscous-plastic and elastic-viscous-plastic sea-ice models

NASA Astrophysics Data System (ADS)

Williams, James; Tremblay, L. Bruno; Lemieux, Jean-François

2017-07-01

The plastic wave speed is derived from the linearized 1-D version of the widely used viscous-plastic (VP) and elastic-viscous-plastic (EVP) sea-ice models. Courant-Friedrichs-Lewy (CFL) conditions are derived using the propagation speed of the wave. 1-D numerical experiments of the VP, EVP and EVP* models successfully recreate a reference solution when the CFL conditions are satisfied, in agreement with the theory presented. The IMplicit-EXplicit (IMEX) method is shown to effectively alleviate the plastic wave CFL constraint on the timestep in the implicitly solved VP model in both 1-D and 2-D. In 2-D, the EVP and EVP* models show first order error in the simulated velocity field when the plastic wave is not resolved. EVP simulations are performed with various advective timestep, number of subcycles, and elastic-wave damping timescales. It is found that increasing the number of subcycles beyond that needed to resolve the elastic wave does not improve the quality of the solution. It is found that reducing the elastic wave damping timescale reduces the spatial extent of first order errors cause by the unresolved plastic wave. Reducing the advective timestep so that the plastic wave is resolved also reduces the velocity error in terms of magnitude and spatial extent. However, the parameter set required for convergence to within the error bars of satellite (RGPS) deformation fields is impractical for use in climate model simulations. The behavior of the EVP* method is analogous to that of the EVP method except that it is not possible to reduce the damping timescale with α = β.

Simulations of Seismic Wave Propagation on Mars

NASA Astrophysics Data System (ADS)

Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan; Khan, Amir; Leng, Kuangdai; van Driel, Martin; Wieczorek, Mark; Rivoldini, Attilio; Larmat, Carène S.; Giardini, Domenico; Tromp, Jeroen; Lognonné, Philippe; Banerdt, Bruce W.

2017-10-01

We present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust (Sohl and Spohn in J. Geophys. Res., Planets 102(E1):1613-1635, 1997). For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE (Komatitsch and Tromp in Geophys. J. Int. 149(2):390-412, 2002a; 150(1):303-318, 2002b) against the 2D axisymmetric wave propagation solver AxiSEM (Nissen-Meyer et al. in Solid Earth 5(1):425-445, 2014) at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on ray theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars' northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D (Fichtner et al. Geophys. J. Int. 179:1703-1725, 2009) based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. We conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.

One-dimensional optical wave turbulence: Experiment and theory

NASA Astrophysics Data System (ADS)

Laurie, Jason; Bortolozzo, Umberto; Nazarenko, Sergey; Residori, Stefania

2012-05-01

We present a review of the latest developments in one-dimensional (1D) optical wave turbulence (OWT). Based on an original experimental setup that allows for the implementation of 1D OWT, we are able to show that an inverse cascade occurs through the spontaneous evolution of the nonlinear field up to the point when modulational instability leads to soliton formation. After solitons are formed, further interaction of the solitons among themselves and with incoherent waves leads to a final condensate state dominated by a single strong soliton. Motivated by the observations, we develop a theoretical description, showing that the inverse cascade develops through six-wave interaction, and that this is the basic mechanism of nonlinear wave coupling for 1D OWT. We describe theory, numerics and experimental observations while trying to incorporate all the different aspects into a consistent context. The experimental system is described by two coupled nonlinear equations, which we explore within two wave limits allowing for the expression of the evolution of the complex amplitude in a single dynamical equation. The long-wave limit corresponds to waves with wave numbers smaller than the electrical coherence length of the liquid crystal, and the opposite limit, when wave numbers are larger. We show that both of these systems are of a dual cascade type, analogous to two-dimensional (2D) turbulence, which can be described by wave turbulence (WT) theory, and conclude that the cascades are induced by a six-wave resonant interaction process. WT theory predicts several stationary solutions (non-equilibrium and thermodynamic) to both the long- and short-wave systems, and we investigate the necessary conditions required for their realization. Interestingly, the long-wave system is close to the integrable 1D nonlinear Schrödinger equation (NLSE) (which contains exact nonlinear soliton solutions), and as a result during the inverse cascade, nonlinearity of the system at low wave numbers becomes strong. Subsequently, due to the focusing nature of the nonlinearity, this leads to modulational instability (MI) of the condensate and the formation of solitons. Finally, with the aid of the probability density function (PDF) description of WT theory, we explain the coexistence and mutual interactions between solitons and the weakly nonlinear random wave background in the form of a wave turbulence life cycle (WTLC).

Unconventional pairing symmetry of interacting Dirac fermions on a π -flux lattice

DOE PAGES

Guo, Huaiming; Khatami, Ehsan; Wang, Yao; ...

2018-04-20

The pairing symmetry of interacting Dirac fermions on the π-flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s*- (i.e., extended s-) and d-wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional ds*-wave phase consisting of alternating stripes of s*- and d-wave phases. A complementary mean-field analysis shows that while the s*- and d-wave symmetries individually have nodes in the energy spectrum, the ds* channel is fully gapped. The results represent amore » new realization of pairing in Dirac systems, connected to the problem of chiral d-wave pairing on the honeycomb lattice, which might be more readily accessed by cold-atom experiments.« less

Are snakes particles or waves? Scattering of a limbless locomotor through a single slit

NASA Astrophysics Data System (ADS)

Qian, Feifei; Dai, Jin; Gong, Chaohui; Choset, Howie; Goldman, Daniel

Droplets on vertically vibrated fluid surfaces can walk and diffract through a single slit by a pilot wave hydrodynamic interaction [Couder, 2006; Bush, 2015]. Inspired by the correspondence between emergent macroscale dynamics and phenomena in quantum systems, we tested if robotic snakes, which resemble wave packets, behave emergently like particles or waves when interacting with an obstacle. In lab experiments and numerical simulations we measured how a multi-module snake-like robot swam through a single slit. We controlled the snake undulation gait as a fixed serpenoid traveling wave pattern with varying amplitude and initial phase, and we examined the snake trajectory as it swam through a slit with width d. Robot trajectories were straight before interaction with the slit, then exited at different scattering angle θ after the interaction due to a complex interaction of the body wave with the slit. For fixed amplitude and large d, the snake passed through the slit with minimal interaction and theta was ~ 0 . For sufficiently small d, θ was finite and bimodally distributed, depending on the initial phase. For intermediate d, θ was sensitive to initial phase, and the width of the distribution of θ increased with decreasing d.

Banded structures in electron pitch angle diffusion coefficients from resonant wave-particle interactions

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

Tripathi, A. K., E-mail: aktrip2001@yahoo.co.in; Singhal, R. P., E-mail: rpsiitbhu@yahoo.com; Khazanov, G. V., E-mail: George.V.Khazanov@nasa.gov

2016-04-15

Electron pitch angle (D{sub αα}) and momentum (D{sub pp}) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic (ECH) and whistler mode chorus waves. Calculations have been performed at two spatial locations L = 4.6 and 6.8 for electron energies ≤10 keV. Landau (n = 0) resonance and cyclotron harmonic resonances n = ±1, ±2, … ±5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (α) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusionmore » coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECH waves in pitch angle diffusion coefficient is due to resonances n = +1 and n = +2. A major contribution to momentum diffusion coefficients appears from n = +2. However, the banded structures in D{sub αα} and D{sub pp} coefficients appear only in the profile of diffusion coefficients for n = +2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band chorus waves, the banded structures appear only in Landau resonance. The D{sub pp} diffusion coefficient for ECH waves is one to two orders smaller than D{sub αα} coefficients. For chorus waves, D{sub pp} coefficients are about an order of magnitude smaller than D{sub αα} coefficients for the case n ≠ 0. In case of Landau resonance, the values of D{sub pp} coefficient are generally larger than the values of D{sub αα} coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECH waves, resonant frequencies have been estimated for wave normal angle 89° and harmonic resonances n = +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10° and Landau resonance. Further, in ECH waves, the banded structures appear for electron energies ≥1 keV, and for whistler mode chorus waves, structures appear for energies >2 keV at L = 4.6 and above 200 eV for L = 6.8. The results obtained in the present work will be helpful in the study of diffusion curves and will have important consequences for diffuse aurora and pancake distributions.« less

Generalized thermoelastic wave band gaps in phononic crystals without energy dissipation

NASA Astrophysics Data System (ADS)

Wu, Ying; Yu, Kaiping; Li, Xiao; Zhou, Haotian

2016-01-01

We present a theoretical investigation of the thermoelastic wave propagation in the phononic crystals in the context of Green-Nagdhi theory by taking thermoelastic coupling into account. The thermal field is assumed to be steady. Thermoelastic wave band structures of 3D and 2D are derived by using the plane wave expansion method. For the 2D problem, the anti-plane shear mode is not affected by the temperature difference. Thermoelastic wave bands of the in-plane x-y mode are calculated for lead/silicone rubber, aluminium/silicone rubber, and aurum/silicone rubber phononic crystals. The new findings in the numerical results indicate that the thermoelastic wave bands are composed of the pure elastic wave bands and the thermal wave bands, and that the thermal wave bands can serve as the low boundary of the first band gap when the filling ratio is low. In addition, for the lead/silicone rubber phononic crystals the effects of lattice type (square, rectangle, regular triangle, and hexagon) and inclusion shape (circle, oval, and square) on the normalized thermoelastic bandwidth and the upper/lower gap boundaries are analysed and discussed. It is concluded that their effects on the thermoelastic wave band structure are remarkable.

Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

PubMed Central

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

2017-01-01

Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

Estimation of fast and slow wave properties in cancellous bone using Prony's method and curve fitting.

PubMed

Wear, Keith A

2013-04-01

The presence of two longitudinal waves in poroelastic media is predicted by Biot's theory and has been confirmed experimentally in through-transmission measurements in cancellous bone. Estimation of attenuation coefficients and velocities of the two waves is challenging when the two waves overlap in time. The modified least squares Prony's (MLSP) method in conjuction with curve-fitting (MLSP + CF) is tested using simulations based on published values for fast and slow wave attenuation coefficients and velocities in cancellous bone from several studies in bovine femur, human femur, and human calcaneus. The search algorithm is accelerated by exploiting correlations among search parameters. The performance of the algorithm is evaluated as a function of signal-to-noise ratio (SNR). For a typical experimental SNR (40 dB), the root-mean-square errors (RMSEs) for one example (human femur) with fast and slow waves separated by approximately half of a pulse duration were 1 m/s (slow wave velocity), 4 m/s (fast wave velocity), 0.4 dB/cm MHz (slow wave attenuation slope), and 1.7 dB/cm MHz (fast wave attenuation slope). The MLSP + CF method is fast (requiring less than 2 s at SNR = 40 dB on a consumer-grade notebook computer) and is flexible with respect to the functional form of the parametric model for the transmission coefficient. The MLSP + CF method provides sufficient accuracy and precision for many applications such that experimental error is a greater limiting factor than estimation error.

Full-wave Moment Tensor and Tomographic Inversions Based on 3D Strain Green Tensor

DTIC Science & Technology

2010-01-31

propagation in three-dimensional (3D) earth, linearizes the inverse problem by iteratively updating the earth model , and provides an accurate way to...self-consistent FD-SGT databases constructed from finite-difference simulations of wave propagation in full-wave tomographic models can be used to...determine the moment tensors within minutes after a seismic event, making it possible for real time monitoring using 3D models . 15. SUBJECT TERMS

2D and 3D graphical representation of the propagation of electromagnetic waves at the interface with a material with general effective complex permittivity and permeability

NASA Astrophysics Data System (ADS)

Diaz, A.; Ramos, J. G.; Friedman, J. S.

2017-09-01

We developed a web-based instructional and research tool that demonstrates the behavior of electromagnetic waves as they propagate through a homogenous medium and through an interface where the second medium can be characterized by an effective complex permittivity and permeability. Either p- or s-polarization wave components can be chosen and the graphical interface includes 2D wave and 3D component representations. The program enables the study of continuity of electromagnetic components, critical angle, Brewster angle, absorption and amplification, behavior of light in sub-unity and negative-index materials, Poynting vector and phase velocity behavior, and positive and negative Goos- Hänchen shifts.

Differential geometric treewidth estimation in adiabatic quantum computation

NASA Astrophysics Data System (ADS)

Wang, Chi; Jonckheere, Edmond; Brun, Todd

2016-10-01

The D-Wave adiabatic quantum computing platform is designed to solve a particular class of problems—the Quadratic Unconstrained Binary Optimization (QUBO) problems. Due to the particular "Chimera" physical architecture of the D-Wave chip, the logical problem graph at hand needs an extra process called minor embedding in order to be solvable on the D-Wave architecture. The latter problem is itself NP-hard. In this paper, we propose a novel polynomial-time approximation to the closely related treewidth based on the differential geometric concept of Ollivier-Ricci curvature. The latter runs in polynomial time and thus could significantly reduce the overall complexity of determining whether a QUBO problem is minor embeddable, and thus solvable on the D-Wave architecture.

Energy spectra and wave function of trigonometric Rosen-Morse potential as an effective quantum chromodynamics potential in D-dimensions

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

Deta, U. A., E-mail: utamaalan@yahoo.co.id; Suparmi,; Cari,

2014-09-30

The Energy Spectra and Wave Function of Schrodinger equation in D-Dimensions for trigonometric Rosen-Morse potential were investigated analytically using Nikiforov-Uvarov method. This potential captures the essential traits of the quark-gluon dynamics of Quantum Chromodynamics. The approximate energy spectra are given in the close form and the corresponding approximate wave function for arbitrary l-state (l ≠ 0) in D-dimensions are formulated in the form of differential polynomials. The wave function of this potential unnormalizable for general case. The wave function of this potential unnormalizable for general case. The existence of extra dimensions (centrifugal factor) and this potential increase the energy spectramore » of system.« less

Review and New Results of Local Helioseismology

NASA Astrophysics Data System (ADS)

Chou, Dean-Yi

2011-10-01

We briefly review various methods used in local helioseismology, and discuss our recent results on the acoustic waves scattered by sunspots. We use a deconvolution method to obtain the 2-D wavefunction of the scattered wave from the cross correlations between the incident wave and the signal at various points on the surface. The wavefunctions of scattered waves associated with various incident waves could be used to probe the sunspot. The interference fringes between the scattered wave and the incident wave are detected because the coherent time of the incident wave is of the order of wave period. These interference fringes play the same role as a hologram in optics. We demonstrate that these interference fringes (hologram) can be used to reconstruct the 2-D scattered wavefield of the sunspot.

Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.

Imaging two-dimensional mechanical waves of skeletal muscle contraction.

PubMed

Grönlund, Christer; Claesson, Kenji; Holtermann, Andreas

2013-02-01

Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Prototype of web-based database of surface wave investigation results for site classification

NASA Astrophysics Data System (ADS)

Hayashi, K.; Cakir, R.; Martin, A. J.; Craig, M. S.; Lorenzo, J. M.

2016-12-01

As active and passive surface wave methods are getting popular for evaluating site response of earthquake ground motion, demand on the development of database for investigation results is also increasing. Seismic ground motion not only depends on 1D velocity structure but also on 2D and 3D structures so that spatial information of S-wave velocity must be considered in ground motion prediction. The database can support to construct 2D and 3D underground models. Inversion of surface wave processing is essentially non-unique so that other information must be combined into the processing. The database of existed geophysical, geological and geotechnical investigation results can provide indispensable information to improve the accuracy and reliability of investigations. Most investigations, however, are carried out by individual organizations and investigation results are rarely stored in the unified and organized database. To study and discuss appropriate database and digital standard format for the surface wave investigations, we developed a prototype of web-based database to store observed data and processing results of surface wave investigations that we have performed at more than 400 sites in U.S. and Japan. The database was constructed on a web server using MySQL and PHP so that users can access to the database through the internet from anywhere with any device. All data is registered in the database with location and users can search geophysical data through Google Map. The database stores dispersion curves, horizontal to vertical spectral ratio and S-wave velocity profiles at each site that was saved in XML files as digital data so that user can review and reuse them. The database also stores a published 3D deep basin and crustal structure and user can refer it during the processing of surface wave data.

Effects of salt-related mode conversions on subsalt prospecting

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

Ogilvie, J.S.; Purnell, G.W.

1996-03-01

Mode conversion of waves during seismic reflection surveys has generally been considered a small phenomenon that could be neglected in data processing and interpretation. However, in subsalt prospecting, the contrast in material properties at the salt/sediment interface is often great enough that significant P-to-S and/or S-to-P conversion occurs. The resulting converted waves can be both a help and a hindrance for subsalt prospecting. A case history from the Mississippi Canyon area of the Gulf of Mexico demonstrates strong converted-wave reflections from the base-of-salt that complicate the evaluation of a subsalt prospect using 3-D seismic data. Before and after stack, themore » converted-wave reflections are evident in 2-D and 3-D surveys across the prospect. Ray-tracing synthetic common midpoint (CMP) gathers provides some useful insights about the occurrence of these waves, but elastic-wave-equation modeling is even more useful. While the latter is more time-consuming, even in 2-D, it also provides a more realistic simulated seismic survey across the prospect, which helps to reveal how some converted waves survive the processes of CMP stack and migration, and thereby present possible pitfalls to an unwary interpreter. The insights gained from the synthetic-data suggest some simple techniques that can assist an interpreter in the 3-D interpretation of subsalt events.« less

Full wave simulations of fast wave efficiency and power losses in the scrape-off layer of tokamak plasmas in mid/high harmonic and minority heating regimes

DOE PAGES

Bertelli, N.; Jaeger, E. F.; Hosea, J. C.; ...

2015-12-17

Here, several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves (HHFW), have found strong interaction between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 2D and 3D AORSAmore » results for the National Spherical Torus eXperiment (NSTX) have shown a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is removed from in front of the antenna by increasing the edge density. Here, full wave simulations have been extended for 'conventional' tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results in HHFW regime show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for C-Mod and EAST, which operate in the minority heating regime.« less

Molding acoustic, electromagnetic and water waves with a single cloak

PubMed Central

Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

2015-01-01

We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves. PMID:26057934

Molding acoustic, electromagnetic and water waves with a single cloak.

PubMed

Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

2015-06-09

We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves.

Nonlinear interaction of an intense radio wave with ionospheric D/E layer plasma

NASA Astrophysics Data System (ADS)

Sodha, Mahendra Singh; Agarwal, Sujeet Kumar

2018-05-01

This paper considers the nonlinear interaction of an intense electromagnetic wave with the D/E layer plasma in the ionosphere. A simultaneous solution of the electromagnetic wave equation and the equations describing the kinetics of D/E layer plasma is obtained; the phenomenon of ohmic heating of electrons by the electric field of the wave causes enhanced collision frequency and ionization of neutral species. Electron temperature dependent recombination of electrons with ions, electron attachment to O 2 molecules, and detachment of electrons from O2 - ions has also been taken into account. The dependence of the plasma parameters on the square of the electric vector of the wave E0 2 has been evaluated for three ionospheric heights (viz., 90, 100, and 110 km) corresponding to the mid-latitude mid-day ionosphere and discussed; these results are used to investigate the horizontal propagation of an intense radio wave at these heights.

The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

NASA Astrophysics Data System (ADS)

Tsiklauri, David

2015-04-01

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refraction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph = ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011); http://dx.doi.org/10.1063/1.3590928 [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013); http://dx.doi.org/10.1063/1.4812453 [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012); http://dx.doi.org/10.1063/1.4768429 [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014); http://dx.doi.org/10.1063/1.4871723 [5] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 21, 012903 (2014); http://dx.doi.org/10.1063/1.4863494 This research is funded by the Leverhulme Trust Research Project Grant RPG-311

A new algorithm for three-dimensional joint inversion of body wave and surface wave data and its application to the Southern California plate boundary region

NASA Astrophysics Data System (ADS)

Fang, Hongjian; Zhang, Haijiang; Yao, Huajian; Allam, Amir; Zigone, Dimitri; Ben-Zion, Yehuda; Thurber, Clifford; van der Hilst, Robert D.

2016-05-01

We introduce a new algorithm for joint inversion of body wave and surface wave data to get better 3-D P wave (Vp) and S wave (Vs) velocity models by taking advantage of the complementary strengths of each data set. Our joint inversion algorithm uses a one-step inversion of surface wave traveltime measurements at different periods for 3-D Vs and Vp models without constructing the intermediate phase or group velocity maps. This allows a more straightforward modeling of surface wave traveltime data with the body wave arrival times. We take into consideration the sensitivity of surface wave data with respect to Vp in addition to its large sensitivity to Vs, which means both models are constrained by two different data types. The method is applied to determine 3-D crustal Vp and Vs models using body wave and Rayleigh wave data in the Southern California plate boundary region, which has previously been studied with both double-difference tomography method using body wave arrival times and ambient noise tomography method with Rayleigh and Love wave group velocity dispersion measurements. Our approach creates self-consistent and unique models with no prominent gaps, with Rayleigh wave data resolving shallow and large-scale features and body wave data constraining relatively deeper structures where their ray coverage is good. The velocity model from the joint inversion is consistent with local geological structures and produces better fits to observed seismic waveforms than the current Southern California Earthquake Center (SCEC) model.

Dopamine D1 Receptors Regulate the Light Dependent Development of Retinal Synaptic Responses

PubMed Central

He, Quanhua; Xu, Hong-ping; Wang, Ping; Tian, Ning

2013-01-01

Retinal synaptic connections and function are developmentally regulated. Retinal synaptic activity plays critical roles in the development of retinal synaptic circuitry. Dopamine receptors have been thought to play important roles in the activity-dependent synaptic plasticity in central nervous system. The primary goal of this study is to determine whether dopamine D1 receptor regulates the activity-dependent development of retinal light responsiveness. Accordingly, we recorded electroretinogram from wild type mice and mice with genetic deletion of D1 dopamine receptor (D1−/− mice) raised under cyclic light conditions and constant darkness. Our results demonstrated that D1−/− mice have reduced amplitudes of all three major components of electroretinogram in adulthood. When the relative strength of the responses is considered, the D1−/− mice have selective reduction of the amplitudes of a-wave and oscillatory potentials evoked by low-intermediate intensities of lights. During postnatal development, D1−/− mice have increased amplitude of b-wave at the time of eye-opening but reduced developmental increase of the amplitude of b-wave after eye opening. Light deprivation from birth significantly reduced the amplitudes of b-wave and oscillatory potentials, increased the outer retinal light response gain and altered the light response kinetics of both a- and b-waves of wild type mice. In D1−/− mice, the effect of dark rearing on the amplitude of oscillatory potentials was diminished and dark rearing induced effects on the response gain of outer retina and the kinetics of a-wave were reversed. These results demonstrated roles of dopamine D1 receptor in the activity-dependent functional development of mouse retina. PMID:24260267

3D radiation belt diffusion model results using new empirical models of whistler chorus and hiss

NASA Astrophysics Data System (ADS)

Cunningham, G.; Chen, Y.; Henderson, M. G.; Reeves, G. D.; Tu, W.

2012-12-01

3D diffusion codes model the energization, radial transport, and pitch angle scattering due to wave-particle interactions. Diffusion codes are powerful but are limited by the lack of knowledge of the spatial & temporal distribution of waves that drive the interactions for a specific event. We present results from the 3D DREAM model using diffusion coefficients driven by new, activity-dependent, statistical models of chorus and hiss waves. Most 3D codes parameterize the diffusion coefficients or wave amplitudes as functions of magnetic activity indices like Kp, AE, or Dst. These functional representations produce the average value of the wave intensities for a given level of magnetic activity; however, the variability of the wave population at a given activity level is lost with such a representation. Our 3D code makes use of the full sample distributions contained in a set of empirical wave databases (one database for each wave type, including plasmaspheric hiss, lower and upper hand chorus) that were recently produced by our team using CRRES and THEMIS observations. The wave databases store the full probability distribution of observed wave intensity binned by AE, MLT, MLAT and L*. In this presentation, we show results that make use of the wave intensity sample probability distributions for lower-band and upper-band chorus by sampling the distributions stochastically during a representative CRRES-era storm. The sampling of the wave intensity probability distributions produces a collection of possible evolutions of the phase space density, which quantifies the uncertainty in the model predictions caused by the uncertainty of the chorus wave amplitudes for a specific event. A significant issue is the determination of an appropriate model for the spatio-temporal correlations of the wave intensities, since the diffusion coefficients are computed as spatio-temporal averages of the waves over MLT, MLAT and L*. The spatiotemporal correlations cannot be inferred from the wave databases. In this study we use a temporal correlation of ~1 hour for the sampled wave intensities that is informed by the observed autocorrelation in the AE index, a spatial correlation length of ~100 km in the two directions perpendicular to the magnetic field, and a spatial correlation length of 5000 km in the direction parallel to the magnetic field, according to the work of Santolik et al (2003), who used multi-spacecraft measurements from Cluster to quantify the correlation length scales for equatorial chorus . We find that, despite the small correlation length scale for chorus, there remains significant variability in the model outcomes driven by variability in the chorus wave intensities.

Oblique Propagation of Electrostatic Waves in a Magnetized Electron-Positron-Ion Plasma in the Presence of Heavy Particles

NASA Astrophysics Data System (ADS)

Sarker, M.; Hossen, M. R.; Shah, M. G.; Hosen, B.; Mamun, A. A.

2018-06-01

A theoretical investigation is carried out to understand the basic features of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an external magnetic field in an electron-positron-ion plasma that consists of cold magnetized positively charged heavy ion fluids and superthermal distributed electrons and positrons. In the nonlinear regime, the Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations describing the propagation of HIA waves are derived. The latter admits a solitary wave solution with both positive and negative potentials (for K-dV equation) and only positive potential (for mK-dV equation) in the weak amplitude limit. It is observed that the effects of external magnetic field (obliqueness), superthermal electrons and positrons, different plasma species concentration, heavy ion dynamics, and temperature ratio significantly modify the basic features of HIA solitary waves. The application of the results in a magnetized EPI plasma, which occurs in many astrophysical objects (e.g. pulsars, cluster explosions, and active galactic nuclei) is briefly discussed.

Three-dimensional Fréchet sensitivity kernels for electromagnetic wave propagation

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

Strickland, C. E.; Johnson, T. C.; Odom, R. I.

2015-08-28

Electromagnetic imaging methods are useful tools for monitoring subsurface changes in pore-fluid content and the associated changes in electrical permittivity and conductivity. The most common method for georadar tomography uses a high frequency ray-theoretic approximation that is valid when material variations are sufficiently small relative to the wavelength of the propagating wave. Georadar methods, however, often utilize electromagnetic waves that propagate within heterogeneous media at frequencies where ray theory may not be applicable. In this paper we describe the 3-D Fréchet sensitivity kernels for EM wave propagation. Various data functional types are formulated that consider all three components of themore » electric wavefield and incorporate near-, intermediate-, and far-field contributions. We show that EM waves exhibit substantial variations for different relative source-receiver component orientations. The 3-D sensitivities also illustrate out-of-plane effects that are not captured in 2-D sensitivity kernels and can influence results obtained using 2-D inversion methods to image structures that are in reality 3-D.« less

Wideband radar cross section reduction using two-dimensional phase gradient metasurfaces

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

Li, Yongfeng; Qu, Shaobo; Wang, Jiafu

2014-06-02

Phase gradient metasurface (PGMs) are artificial surfaces that can provide pre-defined in-plane wave-vectors to manipulate the directions of refracted/reflected waves. In this Letter, we propose to achieve wideband radar cross section (RCS) reduction using two-dimensional (2D) PGMs. A 2D PGM was designed using a square combination of 49 split-ring sub-unit cells. The PGM can provide additional wave-vectors along the two in-plane directions simultaneously, leading to either surface wave conversion, deflected reflection, or diffuse reflection. Both the simulation and experiment results verified the wide-band, polarization-independent, high-efficiency RCS reduction induced by the 2D PGM.

Does Explosive Nuclear Burning Occur in Tidal Disruption Events of White Dwarfs by Intermediate-mass Black Holes?

NASA Astrophysics Data System (ADS)

Tanikawa, Ataru; Sato, Yushi; Nomoto, Ken'ichi; Maeda, Keiichi; Nakasato, Naohito; Hachisu, Izumi

2017-04-01

We investigate nucleosynthesis in tidal disruption events (TDEs) of white dwarfs (WDs) by intermediate-mass black holes. We consider various types of WDs with different masses and compositions by means of three-dimensional (3D) smoothed particle hydrodynamics (SPH) simulations. We model these WDs with different numbers of SPH particles, N, from a few 104 to a few 107 in order to check mass resolution convergence, where SPH simulations with N > 107 (or a space resolution of several 106 cm) have unprecedentedly high resolution in this kind of simulation. We find that nuclear reactions become less active with increasing N and that these nuclear reactions are excited by spurious heating due to low resolution. Moreover, we find no shock wave generation. In order to investigate the reason for the absence of a shock wave, we additionally perform one-dimensional (1D) SPH and mesh-based simulations with a space resolution ranging from 104 to 107 cm, using a characteristic flow structure extracted from the 3D SPH simulations. We find shock waves in these 1D high-resolution simulations, one of which triggers a detonation wave. However, we must be careful of the fact that, if the shock wave emerged in an outer region, it could not trigger the detonation wave due to low density. Note that the 1D initial conditions lack accuracy to precisely determine where a shock wave emerges. We need to perform 3D simulations with ≲106 cm space resolution in order to conclude that WD TDEs become optical transients powered by radioactive nuclei.

3D structure and kinematics characteristics of EUV wave front

NASA Astrophysics Data System (ADS)

Podladchikova, T.; Veronig, A.; Dissauer, K.

2017-12-01

We present 3D reconstructions of EUV wave fronts using multi-point observations from the STEREO-A and STEREO-B spacecraft. EUV waves are large-scale disturbances in the solar corona that are initiated by coronal mass ejections, and are thought to be large-amplitude fast-mode MHD waves or shocks. The aim of our study is to investigate the dynamic evolution of the 3D structure and wave kinematics of EUV wave fronts. We study the events on December 7, 2007 and February 13, 2009 using data from the STEREO/EUVI-A and EUVI-B instruments in the 195 Å filter. The proposed approach is based on a complementary combination of epipolar geometry of stereo vision and perturbation profiles. We propose two different solutions to the matching problem of the wave crest on images from the two spacecraft. One solution is suitable for the early and maximum stage of event development when STEREO-A and STEREO-B see the different facets of the wave, and the wave crest is clearly outlined. The second one is applicable also at the later stage of event development when the wave front becomes diffuse and is faintly visible. This approach allows us to identify automatically the segments of the diffuse front on pairs of STEREO-A and STEREO-B images and to solve the problem of identification and matching of the objects. We find that the EUV wave observed on December 7, 2007 starts with a height of 30-50 Mm, sharply increases to a height of 100-120 Mm about 10 min later, and decreases to 10-20 Mm in the decay phase. Including the 3D evolution of the EUV wave front allowed us to correct the wave kinematics for projection and changing height effects. The velocity of the wave crest (V=215-266 km/s) is larger than the trailing part of the wave pulse (V=103-163 km/s). For the February 9, 2009 event, the upward movement of the wave crest shows an increase from 20 to 100 Mm over a period of 30 min. The velocity of wave crest reaches values of 208-211 km/s.

Very low frequency (VLF) waves as diagnostic tool in remote sensing of D-region Ionosphere

NASA Astrophysics Data System (ADS)

Singh, Ashok; Verma, Uday Prakash

Large currents along the magnetic field transmit stresses between ionosphere and magnetosphere. If the electrons carrying such currents have high enough drift velocity, waves are generated. A wave is a disturbance that propagates through space and time, usually with transference of energy. Waves play major part in the Earth’s ionospheric dynamics. Since both the Earth and the ionosphere are good reflectors at very low frequencies (3 kHz 30 kHz), the lightning radiated impulses commonly known as radio atmospheric or sferics or tweeks travel thousands of kilometers in the Earth Ionosphere Wave Guide (EIWG) with low attenuation of ~ 2-3 dB/1000km. Since vlf waves are reflected by ionosphere, they can be used as potential tool to study the D-region ionosphere which plays a key role in the radio wave propagation. Since the year 2010, vlf waves are continuously being recorded at low latitude ground based Indian station Lucknow (Geomag. Lat. 17.60 N; Geomag. Long. 154.50 E) using Automatic Whistler Detector (AWD). More than 100 tweeks of multimode harmonics (n ≥ 3) observed during the year 2010-2011 are analyzed. Using these multimode tweeks as remote sensing tool to explore D-region ionosphere we have estimated various medium parameters such as electron density, ionospheric reflection height and the propagation distance etc. Electron density in the D-region ionosphere varies from 40-160 cm-3 for various modes, ionospheric reflection height varies in the range 70 - 85 km, and the propagation distance was found to vary from 2 km - 6 km in the waveguide to the receiving site.

Quasiparticle conductance-voltage characteristics for break junctions involving d-wave superconductors: charge-density-wave effects.

PubMed

Ekino, T; Gabovich, A M; Suan Li, Mai; Szymczak, H; Voitenko, A I

2017-12-20

Quasiparticle tunnel conductance-voltage characteristics (CVCs), [Formula: see text], were calculated for break junctions (BJs) made up of layered d-wave superconductors partially gapped by charge-density waves (CDWs). The current is assumed to flow in the ab-plane of electrodes. The influence of CDWs is analyzed by comparing the resulting CVCs with CVCs calculated for BJs made up of pure d-wave superconductors with relevant parameters. The main CDW-effects were found to be the appearance of new CVC peculiarities and the loss of CVC symmetry with respect to the V-sign. Tunnel directionality was shown to be one of the key factors in the formation of [Formula: see text] dependences. In particular, the orientation of electrodes with respect to the current channel becomes very important. As a result, [Formula: see text] can acquire a large variety of forms similar to those for tunnel junctions between superconductors with s-wave, d-wave, and mixed symmetry of their order parameters. The diversity of peculiarities is especially striking at finite temperatures. In the case of BJs made up of pure d-wave superconductors, the resulting CVC can include a two-peak gap-driven structure. The results were compared with the experimental BJ data for a number of high-T c oxides. It was shown that the large variety of the observed current-voltage characteristics can be interpreted in the framework of our approach. Thus, quasiparticle tunnel currents in the ab-plane can be used as an additional mean to detect CDWs competing with superconductivity in cuprates or other layered superconductors.

Quasiparticle conductance-voltage characteristics for break junctions involving d-wave superconductors: charge-density-wave effects

NASA Astrophysics Data System (ADS)

Ekino, T.; Gabovich, A. M.; Li, Mai Suan; Szymczak, H.; Voitenko, A. I.

2017-12-01

Quasiparticle tunnel conductance-voltage characteristics (CVCs), G(V) , were calculated for break junctions (BJs) made up of layered d-wave superconductors partially gapped by charge-density waves (CDWs). The current is assumed to flow in the ab-plane of electrodes. The influence of CDWs is analyzed by comparing the resulting CVCs with CVCs calculated for BJs made up of pure d-wave superconductors with relevant parameters. The main CDW-effects were found to be the appearance of new CVC peculiarities and the loss of CVC symmetry with respect to the V-sign. Tunnel directionality was shown to be one of the key factors in the formation of G(V) dependences. In particular, the orientation of electrodes with respect to the current channel becomes very important. As a result, G(V) can acquire a large variety of forms similar to those for tunnel junctions between superconductors with s-wave, d-wave, and mixed symmetry of their order parameters. The diversity of peculiarities is especially striking at finite temperatures. In the case of BJs made up of pure d-wave superconductors, the resulting CVC can include a two-peak gap-driven structure. The results were compared with the experimental BJ data for a number of high-T c oxides. It was shown that the large variety of the observed current-voltage characteristics can be interpreted in the framework of our approach. Thus, quasiparticle tunnel currents in the ab-plane can be used as an additional mean to detect CDWs competing with superconductivity in cuprates or other layered superconductors.

2.5-D frequency-domain viscoelastic wave modelling using finite-element method

NASA Astrophysics Data System (ADS)

Zhao, Jian-guo; Huang, Xing-xing; Liu, Wei-fang; Zhao, Wei-jun; Song, Jian-yong; Xiong, Bin; Wang, Shang-xu

2017-10-01

2-D seismic modelling has notable dynamic information discrepancies with field data because of the implicit line-source assumption, whereas 3-D modelling suffers from a huge computational burden. The 2.5-D approach is able to overcome both of the aforementioned limitations. In general, the earth model is treated as an elastic material, but the real media is viscous. In this study, we develop an accurate and efficient frequency-domain finite-element method (FEM) for modelling 2.5-D viscoelastic wave propagation. To perform the 2.5-D approach, we assume that the 2-D viscoelastic media are based on the Kelvin-Voigt rheological model and a 3-D point source. The viscoelastic wave equation is temporally and spatially Fourier transformed into the frequency-wavenumber domain. Then, we systematically derive the weak form and its spatial discretization of 2.5-D viscoelastic wave equations in the frequency-wavenumber domain through the Galerkin weighted residual method for FEM. Fixing a frequency, the 2-D problem for each wavenumber is solved by FEM. Subsequently, a composite Simpson formula is adopted to estimate the inverse Fourier integration to obtain the 3-D wavefield. We implement the stiffness reduction method (SRM) to suppress artificial boundary reflections. The results show that this absorbing boundary condition is valid and efficient in the frequency-wavenumber domain. Finally, three numerical models, an unbounded homogeneous medium, a half-space layered medium and an undulating topography medium, are established. Numerical results validate the accuracy and stability of 2.5-D solutions and present the adaptability of finite-element method to complicated geographic conditions. The proposed 2.5-D modelling strategy has the potential to address modelling studies on wave propagation in real earth media in an accurate and efficient way.

Spin wave steering in three-dimensional magnonic networks

NASA Astrophysics Data System (ADS)

Beginin, E. N.; Sadovnikov, A. V.; Sharaevskaya, A. Yu.; Stognij, A. I.; Nikitov, S. A.

2018-03-01

We report the concept of three-dimensional (3D) magnonic structures which are especially promising for controlling and manipulating magnon currents. The approach for fabrication of 3D magnonic crystals (MCs) and 3D magnonic networks is presented. A meander type ferromagnetic film grown at the top of the initially structured substrate can be a candidate for such 3D crystals. Using the finite element method, transfer matrix method, and micromagnetic simulations, we study spin-wave propagation in both isolated and coupled 3D MCs and reconstruct spin-wave dispersion and transmission response to elucidate the mechanism of magnonic bandgap formation. Our results show the possibility of the utilization of proposed structures for fabrication of a 3D magnonic network.

Transdimensional Bayesian tomography of the lowermost mantle from shear waves

NASA Astrophysics Data System (ADS)

Richardson, C.; Mousavi, S. S.; Tkalcic, H.; Masters, G.

2017-12-01

The lowermost layer of the mantle, known as D'', is a complex region that contains significant heterogeneities on different spatial scales and a wide range of physical and chemical features such as partial melting, seismic anisotropy, and variations in thermal and chemical composition. The most powerful tools we have to probe this region are seismic waves and corresponding imaging techniques such as tomography. Recently, we developed compressional velocity tomograms of D'' using a transdimensional Bayesian inversion, where the model parameterization is not explicit and regularization is not required. This has produced a far more nuanced P-wave velocity model of D'' than that from traditional S-wave tomography. We also note that P-wave models of D'' vary much more significantly among various research groups than the corresponding S-wave models. This study therefore seeks to develop a new S-wave velocity model of D'' underneath Australia by using predominantly ScS-S differential travel times measured through waveform correlation and Bayesian transdimensional inversion to further understand and characterize heterogeneities in D''. We used events at epicentral distances between 45 and 75 degrees from stations in Australia at depths of over 200 km and with magnitudes between 6.0 and 6.7. Because of globally incomplete coverage of station and earthquake locations, a major limitation of deep earth tomography has been the explicit parameterization of the region of interest. Explicit parameterization has been foundational in most studies, but faces inherent problems of either over-smoothing the data, or allowing for too much noise. To avoid this, we use spherical Voronoi polygons, which allow for a high level of flexibility as the polygons can grow, shrink, or be altogether deleted throughout a sequence of iterations. Our technique also yields highly desired model parameter uncertainties. While there is little doubt that D'' is heterogeneous, there is still much that is unclear about the extent and spatial distribution of different heterogeneous domains, as there are open questions about their dynamics and chemical interactions in the context of the surrounding mantle and outer core. In this context, our goal is also to quantify and understand the differences between S-wave and P-wave velocity tomographic models.

Gravity-Capillary Lumps

NASA Astrophysics Data System (ADS)

Akylas, Triantaphyllos R.; Kim, Boguk

2004-11-01

In dispersive wave systems, it is known that 1-D plane solitary waves can bifurcate from linear sinusoidal wavetrains at particular wave numbers k = k0 where the phase speed c(k) happens to be an extremum (dc/dk| _0=0) and equals the group speed c_g(k_0). Two distinct possibilities thus arise: either the extremum occurs in the long-wave limit (k_0=0) and, as in shallow water, the bifurcating solitary waves are of the KdV type; or k0 ne 0 and the solitary waves are in the form of packets, described by the NLS equation to leading order, as for gravity-capillary waves in deep water. Here it is pointed out that an entirely analogous scenario is valid for the genesis of 2-D solitary waves or `lumps'. Lumps also may bifurcate at extrema of the phase speed and do so when 1-D solitary waves happen to be unstable to transverse perturbations; moreover, they have algebraically decaying tails and are either of the KPI type (e.g. in shallow water in the presence of strong surface tension) or of the wave packet type (e.g. in deep water) and are described by an elliptic-elliptic Davey-Stewartson equation system to leading order. Examples of steady lump profiles are presented and their dynamics is discussed.

Research on the middle-of-receiver-spread assumption of the MASW method

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2009-01-01

The multichannel analysis of surface wave (MASW) method has been effectively used to determine near-surface shear- (S-) wave velocity. Estimating the S-wave velocity profile from Rayleigh-wave measurements is straightforward. A three-step process is required to obtain S-wave velocity profiles: acquisition of a multiple number of multichannel records along a linear survey line by use of the roll-along mode, extraction of dispersion curves of Rayleigh waves, and inversion of dispersion curves for an S-wave velocity profile for each shot gather. A pseudo-2D S-wave velocity section can be generated by aligning 1D S-wave velocity models. In this process, it is very important to understand where the inverted 1D S-wave velocity profile should be located: the midpoint of each spread (a middle-of-receiver-spread assumption) or somewhere between the source and the last receiver. In other words, the extracted dispersion curve is determined by the geophysical structure within the geophone spread or strongly affected by the source geophysical structure. In this paper, dispersion curves of synthetic datasets and a real-world example are calculated by fixing the receiver spread and changing the source location. Results demonstrate that the dispersion curves are mainly determined by structures within a receiver spread. ?? 2008 Elsevier Ltd. All rights reserved.

Wavenumber distribution in Hopf-wave instability: the reversible Selkov model of glycolytic oscillation.

PubMed

Dutt, Arun K

2005-09-22

We have investigated the short-wave instability due to Hopf bifurcation in a reaction-diffusion model of glycolytic oscillations. Very low values of the ratio d of the diffusion coefficient of the inhibitor (ATP) and that of the activator (ADP) do help to create short waves, whereas high values of the ratio d and the complexing reaction of the activator ADP reduces drastically the wave-instability domain, generating much longer wavelengths.

Two-dimensional numerical simulation of acoustic wave phase conjugation in magnetostrictive elastic media.

PubMed

Voinovich, Peter; Merlen, Alain

2005-12-01

The effect of parametric wave phase conjugation (WPC) in application to ultrasound or acoustic waves in magnetostrictive solids has been addressed numerically by Ben Khelil et al. [J. Acoust. Soc. Am. 109, 75-83 (2001)] using 1-D unsteady formulation. Here the numerical method presented by Voinovich et al. [Shock waves 13(3), 221-230 (2003)] extends the analysis to the 2-D effects. The employed model describes universally elastic solids and liquids. A source term similar to Ben Khelil et al.'s accounts for the coupling between deformation and magnetostriction due to external periodic magnetic field. The compatibility between the isotropic constitutive law of the medium and the model of magnetostriction has been considered. Supplementary to the 1-D simulations, the present model involves longitudinal/transversal mode conversion at the sample boundaries and separate magnetic field coupling with dilatation and shear stress. The influence of those factors in a 2-D geometry on the potential output of a magneto-elastic wave phase conjugator is analyzed in this paper. The process under study includes propagation of a wave burst of a given frequency from a point source in a liquid into the active solid, amplification of the waves due to parametric resonance, and formation of time-reversed waves, their radiation into liquid, and focusing. The considered subject is particularly important for ultrasonic applications in acoustic imaging, nondestructive testing, or medical diagnostics and therapy.

Two-dimensional numerical simulation of acoustic wave phase conjugation in magnetostrictive elastic media

NASA Astrophysics Data System (ADS)

Voinovich, Peter; Merlen, Alain

2005-12-01

The effect of parametric wave phase conjugation (WPC) in application to ultrasound or acoustic waves in magnetostrictive solids has been addressed numerically by Ben Khelil et al. [J. Acoust. Soc. Am. 109, 75-83 (2001)] using 1-D unsteady formulation. Here the numerical method presented by Voinovich et al. [Shock waves 13(3), 221-230 (2003)] extends the analysis to the 2-D effects. The employed model describes universally elastic solids and liquids. A source term similar to Ben Khelil et al.'s accounts for the coupling between deformation and magnetostriction due to external periodic magnetic field. The compatibility between the isotropic constitutive law of the medium and the model of magnetostriction has been considered. Supplementary to the 1-D simulations, the present model involves longitudinal/transversal mode conversion at the sample boundaries and separate magnetic field coupling with dilatation and shear stress. The influence of those factors in a 2-D geometry on the potential output of a magneto-elastic wave phase conjugator is analyzed in this paper. The process under study includes propagation of a wave burst of a given frequency from a point source in a liquid into the active solid, amplification of the waves due to parametric resonance, and formation of time-reversed waves, their radiation into liquid, and focusing. The considered subject is particularly important for ultrasonic applications in acoustic imaging, nondestructive testing, or medical diagnostics and therapy.

Wave-front singularities for two-dimensional anisotropic elastic waves.

NASA Technical Reports Server (NTRS)

Payton, R. G.

1972-01-01

Wavefront singularities for the displacement functions, associated with the radiation of linear elastic waves from a point source embedded in a finitely strained two-dimensional elastic solid, are examined in detail. It is found that generally the singularities are of order d to the -1/2 power, where d measures distance away from the front. However, in certain exceptional cases singularities of order d to the -n power, where n = 1/4, 2/3, 3/4, may be encountered.

Geophysical Modeling in Eurasia: 2D Crustal P and LG Propagation; Upper- Mantle Shear Wave Propagation and Anisotropy; and 3D, Joint, Simultaneous Inversions

DTIC Science & Technology

2008-09-01

improved resolution for shallow geologic structures . Jointly inverting these datasets with seismic body wave (S) travel times provides additional...constraints on the shallow structure and an enhanced 3D shear wave model for our study area in western China. 2008 Monitoring Research Review...for much of Eurasia, although the Arabian Shield and Arctic are less well recovered. The upper velocity gradient was tested for 10-degree cells

The big bang as a higher-dimensional shock wave

NASA Astrophysics Data System (ADS)

Wesson, P. S.; Liu, H.; Seahra, S. S.

2000-06-01

We give an exact solution of the five-dimensional field equations which describes a shock wave moving in time and the extra (Kaluza-Klein) coordinate. The matter in four-dimensional spacetime is a cosmology with good physical properties. The solution suggests to us that the 4D big bang was a 5D shock wave.

Influence of surface gravity waves on near wake development behind a towed model horizontal axis marine current turbine

NASA Astrophysics Data System (ADS)

Luznik, Luksa; Flack, Karen; Lust, Ethan

2016-11-01

2D PIV measurements in the near wake flow field (x/D<2) are presented for a 1/25 scale, 0.8 m diameter (D) two bladed horizontal axis tidal turbine. All measurements were obtained in the USNA 380 ft tow tank with turbine towed at a constant carriage speed (Utow = 1.68 m/s), at the nominal tip speed ratio (TSR) of 7 and incoming regular waves with a period of 2.3 seconds and 0.18 m wave height. Near wake mapping is accomplished by "tiling" phase locked individual 2D PIV fields of view (nominally 30x30 cm2) with approximately 5 cm overlap. The discussion will focus on the downstream evolution of coherent tip vortices shed by the rotor blades and their vertical/horizontal displacements by the wave induced fluctuations. This observed phenomena ultimately results in significantly increased downstream wake expansion in comparison with the same conditions without waves. Office of Naval Research.

Acoustic Waves in a Three-Dimensional Stratified Atmosphere

NASA Astrophysics Data System (ADS)

Kalkofen, W.; Massaglia, S.; Bodo, G.; Rossi, P.

2000-05-01

We investigate the propagation of acoustic waves in a three-dimensional, nonmagnetic, isothermal atmosphere stratified in plane-parallel layers in a study of oscillations in chromospheric calcium bright points. We present analytic results for the linear and numerical results for the nonlinear evolution of a disturbance. An impulsively excited acoustic disturbance emanates from a point source and propagates outward as a spherical acoustic wave, amplifying exponentially in the upward direction. A significant wave amplitude is found only in a relatively narrow cone about the vertical. The amplitude of the wave and the opening angle of the cone decrease with time. Because of the lateral spread of the upward-propagating energy, the decay is faster in 2D and 3D simulations than in 1D. We discuss observational consequences of this scenario, some of which are not anticipated from 1D calculations. We acknowledge support from NASA, NSF and the Ministero per l'Università e la Ricerca Scientifica e Tecnologica.

Pre-coding assisted generation of a frequency quadrupled optical vector D-band millimeter wave with one Mach-Zehnder modulator.

PubMed

Zhou, Wen; Li, Xinying; Yu, Jianjun

2017-10-30

We propose QPSK millimeter-wave (mm-wave) vector signal generation for D-band based on balanced precoding-assisted photonic frequency quadrupling technology employing a single intensity modulator without an optical filter. The intensity MZM is driven by a balanced pre-coding 37-GHz QPSK RF signal. The modulated optical subcarriers are directly sent into the single ended photodiode to generate 148-GHz QPSK vector signal. We experimentally demonstrate 1-Gbaud 148-GHz QPSK mm-wave vector signal generation, and investigate the bit-error-rate (BER) performance of the vector signals at 148-GHz. The experimental results show that the BER value can be achieved as low as 1.448 × 10 -3 when the optical power into photodiode is 8.8dBm. To the best of our knowledge, it is the first time to realize the frequency-quadrupling vector mm-wave signal generation at D-band based on only one MZM without an optical filter.

Using AORSA to simulate helicon waves in DIII-D

NASA Astrophysics Data System (ADS)

Lau, C.; Jaeger, E. F.; Bertelli, N.; Berry, L. A.; Blazevski, D.; Green, D. L.; Murakami, M.; Park, J. M.; Pinsker, R. I.; Prater, R.

2015-12-01

Recent efforts have shown that helicon waves (fast waves at > 20ωci) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIII-D, ITER and DEMO. For DIII-D scenarios, the ray tracing code, GENRAY, has been extensively used to study helicon current drive efficiency and location as a function of many plasma parameters. The full wave code, AORSA, which is applicable to arbitrary Larmor radius and can resolve arbitrary ion cyclotron harmonic order, has been recently used to validate the ray tracing technique at these high cyclotron harmonics. If the SOL is ignored, it will be shown that the GENRAY and AORSA calculated current drive profiles are comparable for the envisioned high beta advanced scenarios for DIII-D, where there is high single pass absorption due to electron Landau damping and minimal ion damping. AORSA is also been used to estimate possible SOL effects on helicon current drive coupling and SOL absorption due to collisional and slow wave effects.

Stability of the Superconducting d-Wave Pairing Toward the Intersite Coulomb Repulsion in CuO_2 Plane

NASA Astrophysics Data System (ADS)

Val'kov, V. V.; Dzebisashvili, D. M.; Korovushkin, M. M.; Barabanov, A. F.

2018-06-01

Taking into account the real crystalline structure of the CuO_2 plane and the strong spin-fermion coupling, we study the influence of the intersite Coulomb repulsion between holes on the Cooper instability of the spin-polaron quasiparticles in cuprate superconductors. The analysis shows that only the superconducting d-wave pairing is implemented in the whole region of doping, whereas the solutions of the self-consistent equations for the s-wave pairing are absent. It is shown that intersite Coulomb interaction V_1 between the holes located at the nearest oxygen ions does not affect the d-wave pairing, because its Fourier transform V_q vanishes in the kernel of the corresponding integral equation. The intersite Coulomb interaction V_2 of quasiparticles located at the next-nearest oxygen ions does not vanish in the integral equations, however, but it is also shown that the d-wave pairing is robust toward this interaction for physically reasonable values of V_2.

Stability of the Superconducting d-Wave Pairing Toward the Intersite Coulomb Repulsion in CuO_2 Plane

NASA Astrophysics Data System (ADS)

Val'kov, V. V.; Dzebisashvili, D. M.; Korovushkin, M. M.; Barabanov, A. F.

2018-03-01

Taking into account the real crystalline structure of the CuO_2 plane and the strong spin-fermion coupling, we study the influence of the intersite Coulomb repulsion between holes on the Cooper instability of the spin-polaron quasiparticles in cuprate superconductors. The analysis shows that only the superconducting d-wave pairing is implemented in the whole region of doping, whereas the solutions of the self-consistent equations for the s-wave pairing are absent. It is shown that intersite Coulomb interaction V_1 between the holes located at the nearest oxygen ions does not affect the d-wave pairing, because its Fourier transform V_q vanishes in the kernel of the corresponding integral equation. The intersite Coulomb interaction V_2 of quasiparticles located at the next-nearest oxygen ions does not vanish in the integral equations, however, but it is also shown that the d-wave pairing is robust toward this interaction for physically reasonable values of V_2.

3D Imaging Millimeter Wave Circular Synthetic Aperture Radar

PubMed Central

Zhang, Renyuan; Cao, Siyang

2017-01-01

In this paper, a new millimeter wave 3D imaging radar is proposed. The user just needs to move the radar along a circular track, and high resolution 3D imaging can be generated. The proposed radar uses the movement of itself to synthesize a large aperture in both the azimuth and elevation directions. It can utilize inverse Radon transform to resolve 3D imaging. To improve the sensing result, the compressed sensing approach is further investigated. The simulation and experimental result further illustrated the design. Because a single transceiver circuit is needed, a light, affordable and high resolution 3D mmWave imaging radar is illustrated in the paper. PMID:28629140

General method for eliminating wave reflection in 2D photonic crystal waveguides by introducing extra scatterers based on interference cancellation of waves

NASA Astrophysics Data System (ADS)

Huang, Hao; Ouyang, Zhengbiao

2018-01-01

We propose a general method for eliminating the reflection of waves in 2 dimensional photonic crystal waveguides (2D-PCWs), a kind of 2D material, by introducing extra scatterers inside the 2D-PCWs. The intrinsic reflection in 2D-PCWs is compensated by the backward-scattered waves from these scatterers, so that the overall reflection is greatly reduced and the insertion loss is improved accordingly. We first present the basic theory for the compensation method. Then, as a demonstration, we give four examples of extremely-low-reflection and high-transmission 90°bent 2D-PCWs created according to the method proposed. In the four examples, it is demonstrated by plane-wave expansion method and finite-difference time-domain method that the 90°bent 2D-PCWs can have high transmission ratio greater than 90% in a wide range of operating frequency, and the highest transmission ratio can be greater than 99.95% with a return loss higher than 43 dB, better than that in other typical 90°bent 2D-PCWs. With our method, the bent 2D-PCWs can be optimized to obtain high transmission ratio at different operating wavelengths. As a further application of this method, a waveguide-based optical bridge for light crossing is presented, showing an optimum return loss of 46.85 dB, transmission ratio of 99.95%, and isolation rates greater than 41.77 dB. The method proposed provides also a useful way for improving conventional waveguides made of cables, fibers, or metal walls in the optical, infrared, terahertz, and microwave bands.

Effects of obliquely opposing and following currents on wave propagation in a new 3D wave-current basin

NASA Astrophysics Data System (ADS)

Lieske, Mike; Schlurmann, Torsten

2016-04-01

INTRODUCTION & MOTIVATION The design of structures in coastal and offshore areas and their maintenance are key components of coastal protection. Usually, assessments of processes and loads on coastal structures are derived from experiments with flow and wave parameters in separate physical models. However, Peregrin (1976) already points out that processes in natural shallow coastal waters flow and sea state processes do not occur separately, but influence each other nonlinearly. Kemp & Simons (1982) perform 2D laboratory tests and study the interactions between a turbulent flow and following waves. They highlight the significance of wave-induced changes in the current properties, especially in the mean flow profiles, and draw attention to turbulent fluctuations and bottom shear stresses. Kemp & Simons (1983) also study these processes and features with opposing waves. Studies on the wave-current interaction in three-dimensional space for a certain wave height, wave period and water depth were conducted by MacIver et al. (2006). The research focus is set on the investigation of long-crested waves on obliquely opposing and following currents in the new 3D wave-current basin. METHODOLOGY In a first step the flow analysis without waves is carried out and includes measurements of flow profiles in the sweet spot of the basin at predefined measurement positions. Five measuring points in the water column have been delineated in different water depths in order to obtain vertical flow profiles. For the characterization of the undisturbed flow properties in the basin, an uniformly distributed flow was generated in the wave basin. In the second step wave analysis without current, the unidirectional wave propagation and wave height were investigated for long-crested waves in intermediate wave conditions. In the sweet spot of the wave basin waves with three different wave directions, three wave periods and uniform wave steepness were examined. For evaluation, we applied a common 3D wave analysis method, the Bayesian Directional Spectrum method (BDM). BDM was presented by Hashimoto et al. (1988). Lastly, identification of the wave-current interaction, the results from experiment with simultaneous waves and currents are compared with results for only-currents and only-waves in order to identify and exemplify the significance of nonlinear interaction processes. RESULTS The first results of the wave-current interaction show, as expected, a reduction in the wave height in the direction of flow and an increase in wave heights against the flow with unidirectional monochromatic waves. The superposition of current and orbital velocities cannot be conducted linearly. Furthermore, the results show a current domination for low wave periods and wave domination for larger wave periods. The criterion of a current or wave domination will be presented in the presentation. ACKNOWLEDGEMENT The support of the KFKI research project "Seegangsbelastungen (Seele)" (Contract No. 03KIS107) by the German "Federal Ministry of Education and Research (BMBF)" is gratefully acknowledged.

Exploring Wave-Wave Interactions in a General Circulation Model

NASA Astrophysics Data System (ADS)

Nystrom, Virginia; Gasperini, Federico; Forbes, Jeffrey M.; Hagan, Maura E.

2018-01-01

Nonlinear interactions involving Kelvin waves with (periods, zonal wave numbers) = (3.7d, s =- 1) (UFKW1) and = (2.4d, s =- 1) (UFKW2) and s = 0 and s = 1 quasi 9 day waves (Q9DW) with diurnal tides DW1, DW2, DW3, DE2, and DE3 are explored within a National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulation driven at its ˜30 km lower boundary by interpolated 3-hourly output from Modern-Era Retrospective Analysis for Research and Applications (MERRA). The existence of nonlinear wave-wave interactions between the above primary waves is determined by the presence of secondary waves (SWs) with frequencies and zonal wave numbers that are the sums and differences of those of the primary (interacting) waves. Focus is on 10-21 April 2009, when the nontidal dynamics in the mesosphere-lower thermosphere (MLT) region is dominated by UFKW and when identification of SW is robust. Fifteen SWs are identified in all. An interesting triad is identified involving UFKW1, DE3, and a secondary UFKW4 = (1.5d, s =- 2): The UFKW1-DE3 interaction produces UFKW4, the UFKW4-DE3 interaction produces UFKW1, and the UFKW1 interaction with UFKW4 produces DE3. At 120 km the dynamic range of the reconstructed latitude-longitude zonal wind field due to all of the SW is roughly half that of the primary waves, which produced them. This suggests that nonlinear wave-wave interactions could significantly modify the way that the lower atmosphere couples with the ionosphere.

A wave-bending structure at Ka-band using 3D-printed metamaterial

NASA Astrophysics Data System (ADS)

Wu, Junqiang; Liang, Min; Xin, Hao

2018-03-01

Three-dimensional printing technologies enable metamaterials of complex structures with arbitrary inhomogeneity. In this work, a 90° wave-bending structure at the Ka-band (26.5-40 GHz) based on 3D-printed metamaterials is designed, fabricated, and measured. The wave-bending effect is realized through a spatial distribution of varied effective dielectric constants. Based on the effective medium theory, different effective dielectric constants are accomplished by special, 3D-printable unit cells, which allow different ratios of dielectric to air at the unit cell level. In contrast to traditional, metallic-structure-included metamaterial designs, the reported wave-bending structure here is all dielectric and implemented by the polymer-jetting technique, which features rapid, low-cost, and convenient prototyping. Both simulation and experiment results demonstrate the effectiveness of the wave-bending structure.

Prospects for Off-axis Current Drive via High Field Side Lower Hybrid Current Drive in DIII-D

NASA Astrophysics Data System (ADS)

Wukitch, S. J.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Holcomb, C.; Park, J. M.; Pinsker, R. I.

2017-10-01

An outstanding challenge for an economical, steady state tokamak is efficient off-axis current drive scalable to reactors. Previous studies have focused on high field side (HFS) launch of lower hybrid waves for current drive (LHCD) in double null configurations in reactor grade plasmas. The goal of this work is to find a HFS LHCD scenario for DIII-D that balances coupling, power penetration and damping. The higher magnetic field on the HFS improves wave accessibility, which allows for lower n||waves to be launched. These waves penetrate farther into the plasma core before damping at higher Te yielding a higher current drive efficiency. Utilizing advanced ray tracing and Fokker Planck simulation tools (GENRAY+CQL3D), wave penetration, absorption and drive current profiles in high performance DIII-D H-Mode plasmas were investigated. We found LH scenarios with single pass absorption, excellent wave penetration to r/a 0.6-0.8, FWHM r/a=0.2 and driven current up to 0.37 MA/MW coupled. These simulations indicate that HFS LHCD has potential to achieve efficient off-axis current drive in DIII-D and the latest results will be presented. Work supported by U.S. Dept. of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facility DIII-D, under Award No. DE-FC02-04ER54698 and Contract No. DE-FC02-01ER54648 under Scientific Discovery through Advanced Computing Initiative.

Self-Propagating Combustion Triggered Synthesis of 3D Lamellar Graphene/BaFe12O19 Composite and Its Electromagnetic Wave Absorption Properties

PubMed Central

Zhao, Tingkai; Ji, Xianglin; Jin, Wenbo; Yang, Wenbo; Peng, Xiarong; Duan, Shichang; Dang, Alei; Li, Hao; Li, Tiehu

2017-01-01

The synthesis of 3D lamellar graphene/BaFe12O19 composites was performed by oxidizing graphite and sequentially self-propagating combustion triggered process. The 3D lamellar graphene structures were formed due to the synergistic effect of the tremendous heat induced gasification as well as huge volume expansion. The 3D lamellar graphene/BaFe12O19 composites bearing 30 wt % graphene present the reflection loss peak at −27.23 dB as well as the frequency bandwidth at 2.28 GHz (< −10 dB). The 3D lamellar graphene structures could consume the incident waves through multiple reflection and scattering within the layered structures, prolonging the propagation path of electromagnetic waves in the absorbers. PMID:28336889

Pulsed-wave Doppler ultrasonographic evaluation of hepatic vein in dogs with tricuspid regurgitation

PubMed Central

Kim, Jaehwan; Kim, Soyoung

2017-01-01

This study was performed to identify the relationships between hepatic vein (HV) measurements, including flow velocity and waveform, using pulsed-wave (PW) Doppler ultrasonography, and the severity of tricuspid regurgitation (TR) in dogs. The study included 22 dogs with TR and 7 healthy dogs. The TR group was subdivided into 3 groups according to TR jet profile obtained by echocardiography. The hepatic venous waveform was obtained and classified into 3 types. A variety of HV measurements, including the maximal velocities of the atrial systolic, systolic (S), end ventricular systolic, and diastolic (D) waves and the ratio of the S- and D- wave velocities (S/D ratio), were acquired. TR severity was significantly correlated with the S- (r = −0.380, p = 0.042) and D- (r = 0.468, p = 0.011) wave velocities and the S/D ratio (r = −0.747, p < 0.001). Receiver operating characteristic curve analysis revealed the highest sensitivity and specificity for the S/D ratio (89% and 75%, respectively) at a threshold of 0.97 with excellent accuracy (AUC = 0.911, p < 0.001). In conclusion, PW Doppler ultrasonography of the HV can be used to identify the presence of significant TR and to classify TR severity in dogs. PMID:27515264

Noninvasive estimation of cardiac systolic function using continuous-wave Doppler echocardiography in dogs with experimental mitral regurgitation.

PubMed

Asano, K; Masui, Y; Masuda, K; Fujinaga, T

2002-01-01

To evaluate the feasibility of noninvasive estimation of cardiac systolic function using transthoracic continuous-wave Doppler echocardiography in dogs with mitral regurgitation. Seven mongrel dogs with experimental mitral regurgitation were used. Left ventriculography and measurement of pulmonary capillary wedge pressure were performed under inhalational anaesthesia. A micromanometer-tipped catheter was placed into the left ventricle and transthoracic echocardiography was carried out. The peak rate of left ventricular pressure rise (peak dP/dt) was derived simultaneously by continuous-wave Doppler and manometer measurements. The Doppler-derived dP/dt was compared with the catheter-measured peak dP/dt in the dogs. Classification of the severity of mitral regurgitation in the dogs was as follows: 1+, 2 dogs; 2+, 1 dog; 3+, 2 dogs; 4+, 1 dog; and not examined, 1 dog. We were able to derive dP/dt from the transthoracic continuous-wave Doppler echocardiography in all dogs. Doppler-derived dP/dt had a significant correlation with the catheter-measured peak dP/dt (r = 0.90, P < 0.0001). It was demonstrated that transthoracic continuous-wave Doppler echocardiography is a feasible method of noninvasive estimation of cardiac systolic function in dogs with experimental mitral regurgitation and may have clinical usefulness in canine patients with spontaneous mitral regurgitation.

Pulsed-wave Doppler ultrasonographic evaluation of hepatic vein in dogs with tricuspid regurgitation.

PubMed

Kim, Jaehwan; Kim, Soyoung; Eom, Kidong

2017-03-30

This study was performed to identify the relationships between hepatic vein (HV) measurements, including flow velocity and waveform, using pulsed-wave (PW) Doppler ultrasonography, and the severity of tricuspid regurgitation (TR) in dogs. The study included 22 dogs with TR and 7 healthy dogs. The TR group was subdivided into 3 groups according to TR jet profile obtained by echocardiography. The hepatic venous waveform was obtained and classified into 3 types. A variety of HV measurements, including the maximal velocities of the atrial systolic, systolic (S), end ventricular systolic, and diastolic (D) waves and the ratio of the S- and D- wave velocities (S/D ratio), were acquired. TR severity was significantly correlated with the S- ( r = -0.380, p = 0.042) and D- ( r = 0.468, p = 0.011) wave velocities and the S/D ratio ( r = -0.747, p ＜ 0.001). Receiver operating characteristic curve analysis revealed the highest sensitivity and specificity for the S/D ratio (89% and 75%, respectively) at a threshold of 0.97 with excellent accuracy (AUC = 0.911, p ＜ 0.001). In conclusion, PW Doppler ultrasonography of the HV can be used to identify the presence of significant TR and to classify TR severity in dogs.

Silicon millimetre-wave integrated-circuit (SIMMWIC) SPST switch

NASA Astrophysics Data System (ADS)

Stabile, P. J.; Rosen, A.

1984-10-01

The first silicon millimetre-wave integrated circuit (SIMMWIC) has been successfully fabricated. This circuit is a monolithic SPST switch with a 3 dB bandwidth of 20 percent and a minimum isolation of 21.6 dB across the band (centre frequency is 36.75 GHz). This monolithic circuit is a low-cost reproducible building block for all millimetre-wave control applications.

78 FR 49990 - Dean Foods Company and WhiteWave Foods Company; Filing of Food Additive Petition

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-16

.... FDA-2013-N-0888] Dean Foods Company and WhiteWave Foods Company; Filing of Food Additive Petition... the WhiteWave Foods Company proposing that the food additive regulations be amended to provide for the expanded safe uses of vitamin D 2 and vitamin D 3 as nutrient supplements in food. DATES: The food additive...

Generation of Rising-tone Chorus in a Two-dimensional Mirror Field by Using the General Curvilinear PIC Code

NASA Astrophysics Data System (ADS)

Ke, Y.; Gao, X.; Lu, Q.; Wang, X.; Wang, S.

2017-12-01

Recently, the generation of rising-tone chorus has been implemented with one-dimensional (1-D) particle-in-cell (PIC) simulations in an inhomogeneous background magnetic field, where both the propagation of waves and motion of electrons are simply forced to be parallel to the background magnetic field. We have developed a two-dimensional(2-D) general curvilinear PIC simulation code, and successfully reproduced rising-tone chorus waves excited from an anisotropic electron distribution in a 2-D mirror field. Our simulation results show that whistler waves are mainly generated around the magnetic equator, and continuously gain growth during their propagation toward higher-latitude regions. The rising-tone chorus waves are formed off the magnetic equator, which propagate quasi-parallel to the background magnetic field with the finite wave normal angle. Due to the propagating effect, the wave normal angle of chorus waves is increasing during their propagation toward higher-latitude regions along an enough curved field line. The chirping rate of chorus waves are found to be larger along a field line more close to the middle field line in the mirror field.

Generation of rising-tone chorus in a two-dimensional mirror field by using the general curvilinear PIC code

NASA Astrophysics Data System (ADS)

Ke, Yangguang; Gao, Xinliang; Lu, Quanming; Wang, Xueyi; Wang, Shui

2017-08-01

Recently, the generation of rising-tone chorus has been implemented with one-dimensional (1-D) particle-in-cell (PIC) simulations in an inhomogeneous background magnetic field, where both the propagation of waves and motion of electrons are simply forced to be parallel to the background magnetic field. In this paper, we have developed a two-dimensional (2-D) general curvilinear PIC simulation code and successfully reproduced rising-tone chorus waves excited from an anisotropic electron distribution in a 2-D mirror field. Our simulation results show that whistler waves are mainly generated around the magnetic equator and continuously gain growth during their propagation toward higher-latitude regions. The rising-tone chorus waves are observed off the magnetic equator, which propagate quasi-parallel to the background magnetic field with the wave normal angle smaller than 25°. Due to the propagating effect, the wave normal angle of chorus waves is increasing during their propagation toward higher-latitude regions along an enough curved field line. The chirping rate of chorus waves is found to be larger along a field line with a smaller curvature.

Damage detection in composite panels based on mode-converted Lamb waves sensed using 3D laser scanning vibrometer

NASA Astrophysics Data System (ADS)

Pieczonka, Łukasz; Ambroziński, Łukasz; Staszewski, Wiesław J.; Barnoncel, David; Pérès, Patrick

2017-12-01

This paper introduces damage identification approach based on guided ultrasonic waves and 3D laser Doppler vibrometry. The method is based on the fact that the symmetric and antisymmetric Lamb wave modes differ in amplitude of the in-plane and out-of-plane vibrations. Moreover, the modes differ also in group velocities and normally they are well separated in time. For a given time window both modes can occur simultaneously only close to the wave source or to a defect that leads to mode conversion. By making the comparison between the in-plane and out-of-plane wave vector components the detection of mode conversion is possible, allowing for superior and reliable damage detection. Experimental verification of the proposed damage identification procedure is performed on fuel tank elements of Reusable Launch Vehicles designed for space exploration. Lamb waves are excited using low-profile, surface-bonded piezoceramic transducers and 3D scanning laser Doppler vibrometer is used to characterize the Lamb wave propagation field. The paper presents theoretical background of the proposed damage identification technique as well as experimental arrangements and results.

Effect of sound on boundary layer stability

NASA Technical Reports Server (NTRS)

Saric, William S. (Principal Investigator); Spencer, Shelly Anne

1993-01-01

Experiments are conducted in the Arizona State University Unsteady Wind Tunnel with a zero-pressure-gradient flat-plate model that has a 67:1 elliptical leading edge. Boundary-layer measurements are made of the streamwise fluctuating-velocity component in order to identify the amplified T-S waves that are forced by downstream-travelling, sound waves. Measurements are taken with circular 3-D roughness elements placed at the Branch 1 neutral stability point for the frequency under consideration, and then with the roughness element downstream of Branch 1. These roughness elements have a principal chord dimension equal to 2(lambda)(sub TS)/pi, of the T-S waves under study and are 'stacked' in order to resemble a Gaussian height distribution. Measurements taken just downstream of the roughness (with leading-edge T-S waves, surface roughness T-S waves, instrumentation sting vibrations and the Stokes wave subtracted) show the generation of 3-D-T-S waves, but not in the characteristic heart-shaped disturbance field predicted by 3-D asymptotic theory. Maximum disturbance amplitudes are found on the roughness centerline. However, some near-field characteristics predicted by numerical modelling are observed.

Effect of sound on boundary layer stability

NASA Technical Reports Server (NTRS)

Saric, William S.; Spencer, Shelly Anne

1993-01-01

Experiments are conducted in the Arizona State University Unsteady Wind Tunnel with a zero-pressure-gradient flat-plate model that has a 67:1 elliptical leading edge. Boundary-layer measurements are made of the streamwise fluctuating-velocity component in order to identify the amplified T-S waves that are forced by downstream-traveling sound waves. Measurements are taken with circular 3-D roughness elements placed at the Branch 1 neutral stability point for the frequency under consideration, and then with the roughness element downstream of Branch 1. These roughness elements have a principal chord dimension equal to 2 lambda(sub TS)/pi of the T-S waves under study and are 'stacked' in order to resemble a Gaussian height distribution. Measurements taken just downstream of the roughness (with leading-edge T-S waves, surface roughness T-S waves, instrumentation sting vibrations, and the Stokes wave subtracted) show the generation of 3-D T-S waves, but not in the characteristic heart-shaped disturbance field predicted by 3-D asymptotic theory. Maximum disturbance amplitudes are found on the roughness centerline. However, some near-field characteristics predicted by numerical modeling are observed.

Enhanced traveling wave amplification of co-planar slow wave structure by extended phase-matching

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

Palm, Andrew; Sirigiri, Jagadishwar; Shin, Young-Min, E-mail: yshin@niu.edu

2015-09-15

The electron beam co-propagating with slow waves in a staggered double grating array (SDGA) efficiently amplifies millimeter and sub-millimeter waves over a wide spectrum. Our theoretical and numerical analyses show that the power amplification in the fundamental passband is enhanced by the extended beam-wave phase-matching. Particle-in-cell simulations on the SDGA slow wave structure, designed with 10.4 keV and 50–100 mA sheet beam, indicate that maintaining beam-wave synchronization along the entire length of the circuit improves the gain by 7.3% leading to a total gain of 28 dB, corresponding to 62 W saturated power at the middle of operating band, and a 3-dB bandwidthmore » of 7 GHz with 10.5% at V-band (73.5 GHz center frequency) with saturated peak power reaching 80 W and 28 dB at 71 GHz. These results also show a reasonably good agreement with analytic calculations based on Pierce small signal gain theory.« less

Topics in two-body hadronic decays of D mesons

NASA Astrophysics Data System (ADS)

El Aaoud, El Hassan

We have carried out an analysis of helicity and partial- wave amplitudes for the decay of D mesons to two vector mesons V 1V2, D --> V1V2. In particular we have studied the Cabibbo-favored decays D+s --> ρφ and D --> K*ρ in the factorization approximation using several models for the form factors. All the models, with the exception of one, generate partial-wave amplitudes with the hierarchy |S| > |P| > | D|. Even though in most models the D-wave amplitude is an order of magnitude smaller than the S-wave amplitude, its effect on the longitudinal polarization could be as large as 30%. Due to a misidentification of the partial-wave amplitudes in terms of the Lorentz structures in the relevant literature, we cast doubt on the veracity of the listed data for the decay D --> K*ρ, particularly the partial-wave branching ratios. We have also investigated the effect of the isospin ½, JP = 0+ resonant state K*0 (1950) on the decays D0 --> K¯0η and D0 --> K¯0η' as a function of the branching ratio sum r = Br( K*0 (1950) --> K¯0η) + Br( K*0 (1950) --> K¯0η ') and the coupling constants gK*0 K0h , and gK*0 K0h' . We have used a factorized input for the D 0 --> K*0 (1950) weak transition through a πK loop. We estimated both on- and off-shell contributions from the loop. Our calculation shows that the off-shell effects are significant. For r >= 30% a fit to the decay amplitude |A(D 0 --> K¯0η' )| was possible, but the amplitude A(D 0 --> K¯0η) remained at its factorized value and hence a branching ratio too low compared to data. For small values of r, r <= 18%, we were able to fit |A(D0 --> K¯0η)|, and despite the fact that | A(D0 --> K¯ 0η') | could be raised by almost 100% over its factorized value, it still falls short of its experimental value. A simultaneous fit to both amplitudes |(A(D0 --> K¯0η')| and | A(D0 --> K¯ 0η| was not possible. We have also determined the strong phase of the resonant amplitudes for both decays.

Does Explosive Nuclear Burning Occur in Tidal Disruption Events of White Dwarfs by Intermediate-mass Black Holes?

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

Tanikawa, Ataru; Sato, Yushi; Hachisu, Izumi

We investigate nucleosynthesis in tidal disruption events (TDEs) of white dwarfs (WDs) by intermediate-mass black holes. We consider various types of WDs with different masses and compositions by means of three-dimensional (3D) smoothed particle hydrodynamics (SPH) simulations. We model these WDs with different numbers of SPH particles, N , from a few 10{sup 4} to a few 10{sup 7} in order to check mass resolution convergence, where SPH simulations with N > 10{sup 7} (or a space resolution of several 10{sup 6} cm) have unprecedentedly high resolution in this kind of simulation. We find that nuclear reactions become less activemore » with increasing N and that these nuclear reactions are excited by spurious heating due to low resolution. Moreover, we find no shock wave generation. In order to investigate the reason for the absence of a shock wave, we additionally perform one-dimensional (1D) SPH and mesh-based simulations with a space resolution ranging from 10{sup 4} to 10{sup 7} cm, using a characteristic flow structure extracted from the 3D SPH simulations. We find shock waves in these 1D high-resolution simulations, one of which triggers a detonation wave. However, we must be careful of the fact that, if the shock wave emerged in an outer region, it could not trigger the detonation wave due to low density. Note that the 1D initial conditions lack accuracy to precisely determine where a shock wave emerges. We need to perform 3D simulations with ≲10{sup 6} cm space resolution in order to conclude that WD TDEs become optical transients powered by radioactive nuclei.« less

Every slow-wave impulse is associated with motor activity of the human stomach.

PubMed

Hocke, Michael; Schöne, Ulrike; Richert, Hendryk; Görnert, Peter; Keller, Jutta; Layer, Peter; Stallmach, Andreas

2009-04-01

Using a newly developed high-resolution three-dimensional magnetic detector system (3D-MAGMA), we observed periodical movements of a small magnetic marker in the human stomach at the typical gastric slow-wave frequency, that is 3 min(-1). Thus we hypothesized that each gastric slow wave induces a motor response that is not strong enough to be detected by conventional methods. Electrogastrographies (EGG, Medtronic, Minneapolis, MN) for measurement of gastric slow waves and 3D-MAGMA (Innovent, Jena, Germany) measurements were simultaneously performed in 21 healthy volunteers (10 men, 40.4+/-13.6 yr; 11 women, 35.8+/-11.6 yr). The 3D-MAGMA system contains 27 highly sensitive magnetic field sensors that are able to locate a magnetic pill inside a human body with an accuracy of +/-5 mm or less in position and +/-2 degrees in orientation at a frequency of 50 Hz. Gastric transit time of the magnetic marker ranged from 19 to 154 min. The mean dominant EGG frequency while the marker was in the stomach was 2.87+/-0.15 cpm. The mean dominant 3D-MAGMA frequency during this interval was nearly identical; that is, 2.85+/-0.15 movements per minute. We observed a strong linear correlation between individual dominant EGG and 3D-MAGMA frequency (R=0.66, P=0.0011). Our findings suggest that each gastric slow wave induces a minute contraction that is too small to be detected by conventional motility investigations but can be recorded by the 3D-MAGMA system. The present slow-wave theory that assumes that the slow wave is a pure electrical signal should be reconsidered.

Detonation shock dynamics with an acceleration relation for nitromethane and TATB

NASA Astrophysics Data System (ADS)

Swift, Damian; Kraus, Richard; Mulford, Roberta; White, Stephen

2015-06-01

The propagation of curved detonation waves has been treated phenomenologically through models of the speed D of a detonation wave as a function of its curvature K, in the Whitham-Bdzil-Lambourn model, also known as detonation shock dynamics. D(K) relations, and the edge angle with adjacent material, have been deduced from the steady shape of detonation waves in long rods and slabs of explosive. Nonlinear D(K) relations have proven necessary to interpret data from charges of different diameter, and even then the D(K) relation may not transfer between diameters. This is an indication that the D(K) relation oversimplifies the kinematics. It is also possible to interpret wave-shape data in terms of an acceleration relation, as used in Brun's Jouguet relaxe model. One form of acceleration behavior is to couple an asymptotic D(K) relation with a time-dependent relaxation toward it from the instantaneous, local speed. This approach is also capable of modeling overdriving of a detonation by a booster. Using archival data for the TATB-based explosive EDC35 and for nitromethane, we found that a simple linear asymptotic D(K) relation with a constant relaxation rate was able to reproduce the experimental wave-shapes better, with fewer parameters, than a nonlinear instantaneous D(K) relation. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Analysis of D’Alembert Unfolding Technique for Hopkinson Bar Gage Records

DTIC Science & Technology

1992-06-01

MIPH No. 90652 The lfnorcqs in ttn:s ýprrt 7-n Deoarirne~nt o ý te Ip~ A~ r chn ;r vF’ pl J<P D lne! I~rozgj~lj~ The ccnitpnts of trhi-, repoit w;’ rf...0 -I0u’ -4 S.2 ,i i I II III i 00 0 04 ( d )3dflSS8dd 4 pulse is applied. This pressure pulse propagates down...GAGE WAVE TRAVEL WHEN STRESS WAVE IS AT WAV TAVE POSITIONS A, B, C, AND D Figure 2. Description of wave propagation and strain gage output in a bar

Stability of Nonlinear Wave Patterns to the Bipolar Vlasov-Poisson-Boltzmann System

NASA Astrophysics Data System (ADS)

Li, Hailiang; Wang, Yi; Yang, Tong; Zhong, Mingying

2018-04-01

The main purpose of the present paper is to investigate the nonlinear stability of viscous shock waves and rarefaction waves for the bipolar Vlasov-Poisson-Boltzmann (VPB) system. To this end, motivated by the micro-macro decomposition to the Boltzmann equation in Liu and Yu (Commun Math Phys 246:133-179, 2004) and Liu et al. (Physica D 188:178-192, 2004), we first set up a new micro-macro decomposition around the local Maxwellian related to the bipolar VPB system and give a unified framework to study the nonlinear stability of the basic wave patterns to the system. Then, as applications of this new decomposition, the time-asymptotic stability of the two typical nonlinear wave patterns, viscous shock waves and rarefaction waves are proved for the 1D bipolar VPB system. More precisely, it is first proved that the linear superposition of two Boltzmann shock profiles in the first and third characteristic fields is nonlinearly stable to the 1D bipolar VPB system up to some suitable shifts without the zero macroscopic mass conditions on the initial perturbations. Then the time-asymptotic stability of the rarefaction wave fan to compressible Euler equations is proved for the 1D bipolar VPB system. These two results are concerned with the nonlinear stability of wave patterns for Boltzmann equation coupled with additional (electric) forces, which together with spectral analysis made in Li et al. (Indiana Univ Math J 65(2):665-725, 2016) sheds light on understanding the complicated dynamic behaviors around the wave patterns in the transportation of charged particles under the binary collisions, mutual interactions, and the effect of the electrostatic potential forces.

Localization of ultra-low frequency waves in multi-ion plasmas of the planetary magnetosphere

DOE PAGES

Kim, Eun -Hwa; Johnson, Jay R.; Lee, Dong -Hun

2015-01-01

By adopting a 2D time-dependent wave code, we investigate how mode-converted waves at the Ion-Ion Hybrid (IIH) resonance and compressional waves propagate in 2D density structures with a wide range of field-aligned wavenumbers to background magnetic fields. The simulation results show that the mode-converted waves have continuous bands across the field line consistent with previous numerical studies. These waves also have harmonic structures in frequency domain and are localized in the field-aligned heavy ion density well. Lastly, our results thus emphasize the importance of a field-aligned heavy ion density structure for ultra-low frequency wave propagation, and suggest that IIH wavesmore » can be localized in different locations along the field line.« less

Signatures of Nonlinear Waves in Coronal Plumes and Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

1999-01-01

In recent Ultraviolet Coronagraph Spectrometer/Solar and Heliospheric Observatory (UVCS/SOHO) White Light Channel (WLC) observations we found quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes at heliocentric distances of 1.9-2.45 solar radii. The motivation for the observation is the 2.5D Magnetohydrodynamics (MHD) model of solar wind acceleration by nonlinear waves, that predicts compressive fluctuations in coronal holes. To help identify the waves observed with the UVCS/WLC we model the propagation and dissipation of slow magnetosonic waves in polar plumes using 1D MHD code in spherical geometry, We find that the slow waves nonlinearly steepen in the gravitationally stratified plumes. The nonlinear steepening of the waves leads to enhanced dissipation due to compressive viscosity at the wave-fronts.

Dynamics in Layer Models of Solid Flame Propagation

NASA Technical Reports Server (NTRS)

Aldushin, A. P.; Bayliss, A.; Matkowsky, B. J.; Gokoglu, S. (Technical Monitor)

2000-01-01

Self-propagating high-temperature synthesis (SHS) is a process in which combustion waves, e.g., "solid flames", which are considered here, are employed to synthesize desired materials. Like many other systems, SHS is a pattern forming system. The problem of describing experimentally observed patterns and of predicting new, as yet unobserved, patterns continues to attract the attention of scientists and mathematicians due to the fundamental significance of the phenomena in combustion in particular, and in nonlinear science in general. Here, we analyze the dynamics of solid flame propagation in a 2D region by considering the region to be composed of parallel, identical layers aligned along the direction of propagation and having thermal contact. Each layer is then described by wave propagation in 1D, with the transverse Laplacian replaced by a term describing heat exchange between neighboring layers. This configuration is the simplest model of a 2D system because it accounts, in a simple way, for the principal feature of the problem, i.e., heat exchange between neighbors in the transverse direction. For simplicity, we describe the situation for two layers. Because the layers are identical, uniformly propagating waves in each layer must be identical, independent of the heat exchange rate alpha. When the Zeldovich number Z exceeds a critical value Z(sub c), which depends on alpha, uniformly propagating waves become unstable. The stability diagram for the two coupled layers reproduces that for the full 2D problem after appropriate identification of parameters in the two problems. Depending on parameter values, we determine three different steady-state dynamical behaviors (though additional behaviors are also expected to occur). The three behaviors are: (i) waves in each layer which pulsate in phase as they propagate, so that together they form a single pulsating propagating wave; (ii) the waves in each layer are no longer identical, and antiphase pulsations occur, with the two waves alternately advancing and receding as they propagate. This wave is the analog of the spinning wave on the surface of a circular cylinder; (iii) finally, there is a region of bistability between the in phase and antiphase waves. with each having its own domain of attraction, so that which of the two behaviors occur depends on the condition of initiation of the wave. The results of our computations indicate a qualitative similarity in the behavior of combustion waves in the layer model and in the full 2D model. Specifically, due to the similarity between the small alpha wave behavior in the layer model and the large diameter behavior in the model of waves on the surface of a cylinder, we are able to predict the behavior of the mean velocity for the waves on the cylinder, where computations of the full problem can be rather difficult. We also compute solutions for three or more layers. The results of our computations prompt us to predict that, while planar uniformly propagating waves are unstable, the wave will be quasiplanar, i.e., the resulting spinning waves have very low amplitude hot spots, and travel with the velocity close to that of the uniformly propagating wave. Such waves may be difficult to distinguish from uniformly propagating waves in experiments. We also find that for both the layer model and full 2D problem, steady-state time-dependent waves, e.g., pulsating and spinning wave, have a conserved quantity H which characterizes the excess energy in the wave, just as in the case of uniformly propagating waves. The quantity H, which is generated by dissipation, does not vary in time and is proportional to the diffusivity and caloricity of the system, and inversely proportional to the mean wave velocity.

Simulation of 2D Waves in Circular Membrane Using Excel Spreadsheet with Visual Basic for Teaching Activity

NASA Astrophysics Data System (ADS)

Eso, R.; Safiuddin, L. O.; Agusu, L.; Arfa, L. M. R. F.

2018-04-01

We propose a teaching instrument demonstrating the circular membrane waves using the excel interactive spreadsheets with the Visual Basic for Application (VBA) programming. It is based on the analytic solution of circular membrane waves involving Bessel function. The vibration modes and frequencies are determined by using Bessel approximation and initial conditions. The 3D perspective based on the spreadsheets functions and facilities has been explored to show the 3D moving objects in transitional or rotational processes. This instrument is very useful both in teaching activity and learning process of wave physics. Visualizing of the vibration of waves in the circular membrane which is showing a very clear manner of m and n vibration modes of the wave in a certain frequency has been compared and matched to the experimental result using resonance method. The peak of deflection varies in time if the initial condition was working and have the same pattern with matlab simulation in zero initial velocity

Accuracy Study of the Space-Time CE/SE Method for Computational Aeroacoustics Problems Involving Shock Waves

NASA Technical Reports Server (NTRS)

Wang, Xiao Yen; Chang, Sin-Chung; Jorgenson, Philip C. E.

1999-01-01

The space-time conservation element and solution element(CE/SE) method is used to study the sound-shock interaction problem. The order of accuracy of numerical schemes is investigated. The linear model problem.govemed by the 1-D scalar convection equation, sound-shock interaction problem governed by the 1-D Euler equations, and the 1-D shock-tube problem which involves moving shock waves and contact surfaces are solved to investigate the order of accuracy of numerical schemes. It is concluded that the accuracy of the CE/SE numerical scheme with designed 2nd-order accuracy becomes 1st order when a moving shock wave exists. However, the absolute error in the CE/SE solution downstream of the shock wave is on the same order as that obtained using a fourth-order accurate essentially nonoscillatory (ENO) scheme. No special techniques are used for either high-frequency low-amplitude waves or shock waves.

On the construction of a direct numerical simulation of a breaking inertia-gravity wave in the upper mesosphere

NASA Astrophysics Data System (ADS)

Fruman, Mark D.; Remmler, Sebastian; Achatz, Ulrich; Hickel, Stefan

2014-10-01

A systematic approach to the direct numerical simulation (DNS) of breaking upper mesospheric inertia-gravity waves of amplitude close to or above the threshold for static instability is presented. Normal mode or singular vector analysis applied in a frame of reference moving with the phase velocity of the wave (in which the wave is a steady solution) is used to determine the most likely scale and structure of the primary instability and to initialize nonlinear "2.5-D" simulations (with three-dimensional velocity and vorticity fields but depending only on two spatial coordinates). Singular vector analysis is then applied to the time-dependent 2.5-D solution to predict the transition of the breaking event to three-dimensional turbulence and to initialize three-dimensional DNS. The careful choice of the computational domain and the relatively low Reynolds numbers, on the order of 25,000, relevant to breaking waves in the upper mesosphere, makes the three-dimensional DNS tractable with present-day computing clusters. Three test cases are presented: a statically unstable low-frequency inertia-gravity wave, a statically and dynamically stable inertia-gravity wave, and a statically unstable high-frequency gravity wave. The three-dimensional DNS are compared to ensembles of 2.5-D simulations. In general, the decay of the wave and generation of turbulence is faster in three dimensions, but the results are otherwise qualitatively and quantitatively similar, suggesting that results of 2.5-D simulations are meaningful if the domain and initial condition are chosen properly.

WAVE2 regulates epithelial morphology and cadherin isoform switching through regulation of Twist and Abl.

PubMed

Bryce, Nicole S; Reynolds, Albert B; Koleske, Anthony J; Weaver, Alissa M

2013-01-01

Epithelial morphogenesis is a dynamic process that involves coordination of signaling and actin cytoskeletal rearrangements. We analyzed the contribution of the branched actin regulator WAVE2 in the development of 3-dimensional (3D) epithelial structures. WAVE2-knockdown (WAVE2-KD) cells formed large multi-lobular acini that continued to proliferate at an abnormally late stage compared to control acini. Immunostaining of the cell-cell junctions of WAVE2-KD acini revealed weak and heterogeneous E-cadherin staining despite little change in actin filament localization to the same junctions. Analysis of cadherin expression demonstrated a decrease in E-cadherin and an increase in N-cadherin protein and mRNA abundance in total cell lysates. In addition, WAVE2-KD cells exhibited an increase in the mRNA levels of the epithelial-mesenchymal transition (EMT)-associated transcription factor Twist1. KD of Twist1 expression in WAVE2-KD cells reversed the cadherin switching and completely rescued the aberrant 3D morphological phenotype. Activity of the WAVE2 complex binding partner Abl kinase was also increased in WAVE2-KD cells, as assessed by tyrosine phosphorylation of the Abl substrate CrkL. Inhibition of Abl with STI571 rescued the multi-lobular WAVE2-KD 3D phenotype whereas overexpression of Abl kinase phenocopied the WAVE2-KD phenotype. The WAVE2 complex regulates breast epithelial morphology by a complex mechanism involving repression of Twist1 expression and Abl kinase activity. These data reveal a critical role for WAVE2 complex in regulation of cellular signaling and epithelial morphogenesis.

Damping of quasi-two-dimensional internal wave attractors by rigid-wall friction

NASA Astrophysics Data System (ADS)

Beckebanze, F.; Brouzet, C.; Sibgatullin, I. N.; Maas, L. R. M.

2018-04-01

The reflection of internal gravity waves at sloping boundaries leads to focusing or defocusing. In closed domains, focusing typically dominates and projects the wave energy onto 'wave attractors'. For small-amplitude internal waves, the projection of energy onto higher wave numbers by geometric focusing can be balanced by viscous dissipation at high wave numbers. Contrary to what was previously suggested, viscous dissipation in interior shear layers may not be sufficient to explain the experiments on wave attractors in the classical quasi-2D trapezoidal laboratory set-ups. Applying standard boundary layer theory, we provide an elaborate description of the viscous dissipation in the interior shear layer, as well as at the rigid boundaries. Our analysis shows that even if the thin lateral Stokes boundary layers consist of no more than 1% of the wall-to-wall distance, dissipation by lateral walls dominates at intermediate wave numbers. Our extended model for the spectrum of 3D wave attractors in equilibrium closes the gap between observations and theory by Hazewinkel et al. (2008).

Direct ambient noise tomography for 3-D near surface shear velocity structure: methodology and applications

NASA Astrophysics Data System (ADS)

Yao, H.; Fang, H.; Li, C.; Liu, Y.; Zhang, H.; van der Hilst, R. D.; Huang, Y. C.

2014-12-01

Ambient noise tomography has provided essential constraints on crustal and uppermost mantle shear velocity structure in global seismology. Recent studies demonstrate that high frequency (e.g., ~ 1 Hz) surface waves between receivers at short distances can be successfully retrieved from ambient noise cross-correlation and then be used for imaging near surface or shallow crustal shear velocity structures. This approach provides important information for strong ground motion prediction in seismically active area and overburden structure characterization in oil and gas fields. Here we propose a new tomographic method to invert all surface wave dispersion data for 3-D variations of shear wavespeed without the intermediate step of phase or group velocity maps.The method uses frequency-dependent propagation paths and a wavelet-based sparsity-constrained tomographic inversion. A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. The wavelet coefficients of the velocity model are estimated with an iteratively reweighted least squares (IRLS) algorithm, and upon iterations the surface wave ray paths and the data sensitivity matrix are updated from the newly obtained velocity model. We apply this new method to determine the 3-D near surface wavespeed variations in the Taipei basin of Taiwan, Hefei urban area and a shale and gas production field in China using the high-frequency interstation Rayleigh wave dispersion data extracted from ambient noisecross-correlation. The results reveal strong effects of off-great-circle propagation of high-frequency surface waves in these regions with above 30% shear wavespeed variations. The proposed approach is more efficient and robust than the traditional two-step surface wave tomography for imaging complex structures. In the future, approximate 3-D sensitivity kernels for dispersion data will be incorporated to account for finite-frequency effect of surface wave propagation. In addition, our approach provides a consistent framework for joint inversion of surface wave dispersion and body wave traveltime data for 3-D Vp and Vs structures.

Spectral-Element Seismic Wave Propagation Codes for both Forward Modeling in Complex Media and Adjoint Tomography

NASA Astrophysics Data System (ADS)

Smith, J. A.; Peter, D. B.; Tromp, J.; Komatitsch, D.; Lefebvre, M. P.

2015-12-01

We present both SPECFEM3D_Cartesian and SPECFEM3D_GLOBE open-source codes, representing high-performance numerical wave solvers simulating seismic wave propagation for local-, regional-, and global-scale application. These codes are suitable for both forward propagation in complex media and tomographic imaging. Both solvers compute highly accurate seismic wave fields using the continuous Galerkin spectral-element method on unstructured meshes. Lateral variations in compressional- and shear-wave speeds, density, as well as 3D attenuation Q models, topography and fluid-solid coupling are all readily included in both codes. For global simulations, effects due to rotation, ellipticity, the oceans, 3D crustal models, and self-gravitation are additionally included. Both packages provide forward and adjoint functionality suitable for adjoint tomography on high-performance computing architectures. We highlight the most recent release of the global version which includes improved performance, simultaneous MPI runs, OpenCL and CUDA support via an automatic source-to-source transformation library (BOAST), parallel I/O readers and writers for databases using ADIOS and seismograms using the recently developed Adaptable Seismic Data Format (ASDF) with built-in provenance. This makes our spectral-element solvers current state-of-the-art, open-source community codes for high-performance seismic wave propagation on arbitrarily complex 3D models. Together with these solvers, we provide full-waveform inversion tools to image the Earth's interior at unprecedented resolution.

3-D Upper-Mantle Shear Velocity Model Beneath the Contiguous United States Based on Broadband Surface Wave from Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Xie, Jun; Chu, Risheng; Yang, Yingjie

2018-05-01

Ambient noise seismic tomography has been widely used to study crustal and upper-mantle shear velocity structures. Most studies, however, concentrate on short period (< 50 s) surface wave from ambient noise, while studies using long period surface wave from ambient noise are limited. In this paper, we demonstrate the feasibility of using long-period surface wave from ambient noise to study the lithospheric structure on a continental scale. We use broadband Rayleigh wave phase velocities to obtain a 3-D V S structures beneath the contiguous United States at period band of 10-150 s. During the inversion, 1-D shear wave velocity profile is parameterized using B-spline at each grid point and is inverted with nonlinear Markov Chain Monte Carlo method. Then, a 3-D shear velocity model is constructed by assembling all the 1-D shear velocity profiles. Our model is overall consistent with existing models which are based on multiple datasets or data from earthquakes. Our model along with the other post-USArray models reveal lithosphere structures in the upper mantle, which are consistent with the geological tectonic background (e.g., the craton root and regional upwelling provinces). The model has comparable resolution on lithosphere structures compared with many published results and can be used for future detailed regional or continental studies and analysis.

Spectral-element simulations of wave propagation in complex exploration-industry models: Mesh generation and forward simulations

NASA Astrophysics Data System (ADS)

Nissen-Meyer, T.; Luo, Y.; Morency, C.; Tromp, J.

2008-12-01

Seismic-wave propagation in exploration-industry settings has seen major research and development efforts for decades, yet large-scale applications have often been limited to 2D or 3D finite-difference, (visco- )acoustic wave propagation due to computational limitations. We explore the possibility of including all relevant physical signatures in the wavefield using the spectral- element method (SPECFEM3D, SPECFEM2D), thereby accounting for acoustic, (visco-)elastic, poroelastic, anisotropic wave propagation in meshes which honor all crucial discontinuities. Mesh design is the crux of the problem, and we use CUBIT (Sandia Laboratories) to generate unstructured quadrilateral 2D and hexahedral 3D meshes for these complex background models. While general hexahedral mesh generation is an unresolved problem, we are able to accommodate most of the relevant settings (e.g., layer-cake models, salt bodies, overthrusting faults, and strong topography) with respectively tailored workflows. 2D simulations show localized, characteristic wave effects due to these features that shall be helpful in designing survey acquisition geometries in a relatively economic fashion. We address some of the fundamental issues this comprehensive modeling approach faces regarding its feasibility: Assessing geological structures in terms of the necessity to honor the major structural units, appropriate velocity model interpolation, quality control of the resultant mesh, and computational cost for realistic settings up to frequencies of 40 Hz. The solution to this forward problem forms the basis for subsequent 2D and 3D adjoint tomography within this context, which is the subject of a companion paper.

Three-dimensional manipulation of single cells using surface acoustic waves.

PubMed

Guo, Feng; Mao, Zhangming; Chen, Yuchao; Xie, Zhiwei; Lata, James P; Li, Peng; Ren, Liqiang; Liu, Jiayang; Yang, Jian; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2016-02-09

The ability of surface acoustic waves to trap and manipulate micrometer-scale particles and biological cells has led to many applications involving "acoustic tweezers" in biology, chemistry, engineering, and medicine. Here, we present 3D acoustic tweezers, which use surface acoustic waves to create 3D trapping nodes for the capture and manipulation of microparticles and cells along three mutually orthogonal axes. In this method, we use standing-wave phase shifts to move particles or cells in-plane, whereas the amplitude of acoustic vibrations is used to control particle motion along an orthogonal plane. We demonstrate, through controlled experiments guided by simulations, how acoustic vibrations result in micromanipulations in a microfluidic chamber by invoking physical principles that underlie the formation and regulation of complex, volumetric trapping nodes of particles and biological cells. We further show how 3D acoustic tweezers can be used to pick up, translate, and print single cells and cell assemblies to create 2D and 3D structures in a precise, noninvasive, label-free, and contact-free manner.

Benchmark Modeling of the Near-Field and Far-Field Wave Effects of Wave Energy Arrays

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

Rhinefrank, Kenneth E; Haller, Merrick C; Ozkan-Haller, H Tuba

2013-01-26

This project is an industry-led partnership between Columbia Power Technologies and Oregon State University that will perform benchmark laboratory experiments and numerical modeling of the near-field and far-field impacts of wave scattering from an array of wave energy devices. These benchmark experimental observations will help to fill a gaping hole in our present knowledge of the near-field effects of multiple, floating wave energy converters and are a critical requirement for estimating the potential far-field environmental effects of wave energy arrays. The experiments will be performed at the Hinsdale Wave Research Laboratory (Oregon State University) and will utilize an array ofmore » newly developed Buoys' that are realistic, lab-scale floating power converters. The array of Buoys will be subjected to realistic, directional wave forcing (1:33 scale) that will approximate the expected conditions (waves and water depths) to be found off the Central Oregon Coast. Experimental observations will include comprehensive in-situ wave and current measurements as well as a suite of novel optical measurements. These new optical capabilities will include imaging of the 3D wave scattering using a binocular stereo camera system, as well as 3D device motion tracking using a newly acquired LED system. These observing systems will capture the 3D motion history of individual Buoys as well as resolve the 3D scattered wave field; thus resolving the constructive and destructive wave interference patterns produced by the array at high resolution. These data combined with the device motion tracking will provide necessary information for array design in order to balance array performance with the mitigation of far-field impacts. As a benchmark data set, these data will be an important resource for testing of models for wave/buoy interactions, buoy performance, and far-field effects on wave and current patterns due to the presence of arrays. Under the proposed project we will initiate high-resolution (fine scale, very near-field) fluid/structure interaction simulations of buoy motions, as well as array-scale, phase-resolving wave scattering simulations. These modeling efforts will utilize state-of-the-art research quality models, which have not yet been brought to bear on this complex problem of large array wave/structure interaction problem.« less

Max dD/Dt: A Novel Parameter to Assess Fetal Cardiac Contractility and a Substitute for Max dP/Dt.

PubMed

Fujita, Yasuyuki; Kiyokoba, Ryo; Yumoto, Yasuo; Kato, Kiyoko

2018-07-01

Aortic pulse waveforms are composed of a forward wave from the heart and a reflection wave from the periphery. We focused on this forward wave and suggested a new parameter, the maximum slope of aortic pulse waveforms (max dD/dt), for fetal cardiac contractility. Max dD/dt was calculated from fetal aortic pulse waveforms recorded with an echo-tracking system. A normal range of max dD/dt was constructed in 105 healthy fetuses using linear regression analysis. Twenty-two fetuses with suspected fetal cardiac dysfunction were divided into normal and decreased max dD/dt groups, and their clinical parameters were compared. Max dD/dt of aortic pulse waveforms increased linearly with advancing gestational age (r = 0.93). The decreased max dD/dt was associated with abnormal cardiotocography findings and short- and long-term prognosis. In conclusion, max dD/dt calculated from the aortic pulse waveforms in fetuses can substitute for max dP/dt, an index of cardiac contractility in adults. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Excitation of acoustic oscillations in superconducting films

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

Golub, A.A.

1973-11-01

A study is made of the excitation of sound in a superconducting film by electromagnetic waves incident on the surface of the film. It is assumed that the thickness of the film d is much greater than the penetration depth of the field. If the acoustic wave is damped over a distance of the order of d, traveling acoustic waves can be excited in the superconductor; otherwise, standing waves are excited. The low-temperature contribution of acoustic oseillations to the surface resistence of pure superconductors ia calculated. At very low temperatures, the absorption of electromagnetic waves is mainly governed by themore » loss due to acoustic oscillations. (auth)« less

Using wave intensity analysis to determine local reflection coefficient in flexible tubes.

PubMed

Li, Ye; Parker, Kim H; Khir, Ashraf W

2016-09-06

It has been shown that reflected waves affect the shape and magnitude of the arterial pressure waveform, and that reflected waves have physiological and clinical prognostic values. In general the reflection coefficient is defined as the ratio of the energy of the reflected to the incident wave. Since pressure has the units of energy per unit volume, arterial reflection coefficient are traditionally defined as the ratio of reflected to the incident pressure. We demonstrate that this approach maybe prone to inaccuracies when applied locally. One of the main objectives of this work is to examine the possibility of using wave intensity, which has units of energy flux per unit area, to determine the reflection coefficient. We used an in vitro experimental setting with a single inlet tube joined to a second tube with different properties to form a single reflection site. The second tube was long enough to ensure that reflections from its outlet did not obscure the interactions of the initial wave. We generated an approximately half sinusoidal wave at the inlet of the tube and took measurements of pressure and flow along the tube. We calculated the reflection coefficient using wave intensity (R dI and R dI 0.5 ) and wave energy (R I and R I 0.5 ) as well as the measured pressure (R dP ) and compared these results with the reflection coefficient calculated theoretically based on the mechanical properties of the tubes. The experimental results show that the reflection coefficients determined by all the techniques we studied increased or decreased with distance from the reflection site, depending on the type of reflection. In our experiments, R dP , R dI 0.5 and R I 0.5 are the most reliable parameters to measure the mean reflection coefficient, whilst R dI and R I provide the best measure of the local reflection coefficient, closest to the reflection site. Additional work with bifurcations, tapered tubes and in vivo experiments are needed to further understand, validate the method and assess its potential clinical use. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

D-Wave Electron-H, -He+, and -Li2+ Elastic Scattering and Photoabsorption in P States of Two-Electron Systems

NASA Technical Reports Server (NTRS)

Bhatia, A. K.

2014-01-01

In previous papers [A. K. Bhatia, Phys. Rev. A 85, 052708 (2012); 86, 032709 (2012); 87, 042705 (2013)] electron-H, -He+, and -Li2+ P-wave scattering phase shifts were calculated using the variational polarized orbital theory. This method is now extended to the singlet and triplet D-wave scattering in the elastic region. The long-range correlations are included in the Schrodinger equation by using the method of polarized orbitals variationally. Phase shifts are compared to those obtained by other methods. The present calculation provides results which are rigorous lower bonds to the exact phase shifts. Using the presently calculated D-wave and previously calculated S-wave continuum functions, photoionization of singlet and triplet P states of He and Li+ are also calculated, along with the radiative recombination rate coefficients at various electron temperatures.

Effects of dopamine D1 receptor blockade on the ERG b- and d-waves during blockade of ionotropic GABA receptors.

PubMed

Popova, Elka; Kostov, Momchil; Kupenova, Petia

2016-01-01

Some data indicate that the dopaminergic and GABAergic systems interact in the vertebrate retina, but the type of interactions is not well understood. In this study we investigated the effect of dopamine D 1 receptor blockade by 75 μM SCH 23390 on the electroretinographic ON (b-wave) and OFF (d-wave) responses in intact frog eyecup preparations and in eyecups where the ionotropic GABA receptors were blocked by 50 μM picrotoxin. Student's t -test, One-way repeated measures ANOVA with Bonferroni post-hoc test and Two-way ANOVA were used for statistical evaluation of the data. We found that SCH 23390 alone significantly enhanced the amplitude of the b- and d-waves without altering their latency. The effect developed rapidly and was fully expressed within 8-11 min after the blocker application. Picrotoxin alone also markedly enhanced the amplitude of the ERG ON and OFF responses and increased their latency significantly. The effect was fully expressed within 25-27 min after picrotoxin application and remained very stable in the next 20 min. The effects of SCH 23390 and picrotoxin are similar to that reported in our previous studies. When SCH 23390 was applied on the background of the fully developed picrotoxin effect, it diminished the amplitude of the b- and d-waves in comparison to the corresponding values obtained during application of picrotoxin alone. Our results demonstrate that the enhancing effect of D 1 receptor blockade on the amplitude of the ERG b- and d-waves is not evident during the ionotropic GABA receptor blockade, indicating an interaction between these neurotransmitter systems in the frog retina. We propose that the inhibitory effect of endogenous dopamine mediated by D 1 receptors on the ERG ON and OFF responses in the frog retina may be due to the dopamine-evoked GABA release.

Wave Function and Emergent SU(2) Symmetry in the νT=1 Quantum Hall Bilayer

NASA Astrophysics Data System (ADS)

Lian, Biao; Zhang, Shou-Cheng

2018-02-01

We propose a trial wave function for the quantum Hall bilayer system of total filling factor νT=1 at a layer distance d to magnetic length ℓ ratio d /ℓ=κc 1≈1.1 , where the lowest charged excitation is known to have a level crossing. The wave function has two-particle correlations, which fit well with those in previous numerical studies, and can be viewed as a Bose-Einstein condensate of free excitons formed by composite bosons and anticomposite bosons in different layers. We show the free nature of these excitons indicating an emergent SU(2) symmetry for the composite bosons at d /ℓ=κc 1, which leads to the level crossing in low-lying charged excitations. We further show the overlap between the trial wave function, and the ground state of a small size exact diagonalization is peaked near d /ℓ=κc 1, which supports our theory.

Performance of Quantum Annealers on Hard Scheduling Problems

NASA Astrophysics Data System (ADS)

Pokharel, Bibek; Venturelli, Davide; Rieffel, Eleanor

Quantum annealers have been employed to attack a variety of optimization problems. We compared the performance of the current D-Wave 2X quantum annealer to that of the previous generation D-Wave Two quantum annealer on scheduling-type planning problems. Further, we compared the effect of different anneal times, embeddings of the logical problem, and different settings of the ferromagnetic coupling JF across the logical vertex-model on the performance of the D-Wave 2X quantum annealer. Our results show that at the best settings, the scaling of expected anneal time to solution for D-WAVE 2X is better than that of the DWave Two, but still inferior to that of state of the art classical solvers on these problems. We discuss the implication of our results for the design and programming of future quantum annealers. Supported by NASA Ames Research Center.

Wave interactions in a three-dimensional attachment line boundary layer

NASA Technical Reports Server (NTRS)

Hall, Philip; Mackerrell, Sharon O.

1988-01-01

The 3-D boundary layer on a swept wing can support different types of hydrodynamic instability. Attention is focused on the so-called spanwise contamination problem, which occurs when the attachment line boundary layer on the leading edge becomes unstable to Tollmien-Schlichting waves. In order to gain insight into the interactions important in that problem, a simplified basic state is considered. This simplified flow corresponds to the swept attachment line boundary layer on an infinite flat plate. The basic flow here is an exact solution of the Navier-Stokes equations and its stability to 2-D waves propagating along the attachment can be considered exactly at finite Reynolds number. This has been done in the linear and weakly nonlinear regimes. The corresponding problem is studied for oblique waves and their interaction with 2-D waves is investigated. In fact, oblique modes cannot be described exactly at finite Reynolds number so it is necessary to make a high Reynolds number approximation and use triple deck theory. It is shown that there are two types of oblique wave which, if excited, cause the destabilization of the 2-D mode and the breakdown of the disturbed flow at a finite distance from the leading edge. First, a low frequency mode related to the viscous stationary crossflow mode is a possible cause of breakdown. Second, a class of oblique wave with frequency comparable with that of the 2-D mode is another cause of breakdown. It is shown that the relative importance of the modes depends on the distance from the attachment line.

An intuitive two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation

NASA Astrophysics Data System (ADS)

Yoon, Young Dae; Bellan, Paul M.

2018-05-01

An intuitive and physical two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation is presented in the framework of 3D electron-magnetohydrodynamics. In this regime, canonical circulation (Q =me∇×u +qeB ) flux tubes can be defined in analogy to magnetic flux tubes in ideal magnetohydrodynamics. Following the 3D behavior of these Q flux tubes provides a new perspective on collisionless reconnection—a perspective that has been hard to perceive via examinations of 2D projections. This shows that even in a 2D geometry with an ignorable coordinate, a 3D examination is essential for a full comprehension of the process. Intuitive answers are given to three main questions in collisionless reconnection: why is reconnection spontaneous, why do particles accelerate extremely fast, and why are whistler waves generated? Possible extensions to other regimes are discussed.

2.5D S-wave velocity model of the TESZ area in northern Poland from receiver function analysis

NASA Astrophysics Data System (ADS)

Wilde-Piorko, Monika; Polkowski, Marcin; Grad, Marek

2016-04-01

Receiver function (RF) locally provides the signature of sharp seismic discontinuities and information about the shear wave (S-wave) velocity distribution beneath the seismic station. The data recorded by "13 BB Star" broadband seismic stations (Grad et al., 2015) and by few PASSEQ broadband seismic stations (Wilde-Piórko et al., 2008) are analysed to investigate the crustal and upper mantle structure in the Trans-European Suture Zone (TESZ) in northern Poland. The TESZ is one of the most prominent suture zones in Europe separating the young Palaeozoic platform from the much older Precambrian East European craton. Compilation of over thirty deep seismic refraction and wide angle reflection profiles, vertical seismic profiling in over one hundred thousand boreholes and magnetic, gravity, magnetotelluric and thermal methods allowed for creation a high-resolution 3D P-wave velocity model down to 60 km depth in the area of Poland (Grad et al. 2016). On the other hand the receiver function methods give an opportunity for creation the S-wave velocity model. Modified ray-tracing method (Langston, 1977) are used to calculate the response of the structure with dipping interfaces to the incoming plane wave with fixed slowness and back-azimuth. 3D P-wave velocity model are interpolated to 2.5D P-wave velocity model beneath each seismic station and synthetic back-azimuthal sections of receiver function are calculated for different Vp/Vs ratio. Densities are calculated with combined formulas of Berteussen (1977) and Gardner et al. (1974). Next, the synthetic back-azimuthal sections of RF are compared with observed back-azimuthal sections of RF for "13 BB Star" and PASSEQ seismic stations to find the best 2.5D S-wave models down to 60 km depth. National Science Centre Poland provided financial support for this work by NCN grant DEC-2011/02/A/ST10/00284.

Predictive Sea State Estimation for Automated Ride Control and Handling - PSSEARCH

NASA Technical Reports Server (NTRS)

Huntsberger, Terrance L.; Howard, Andrew B.; Aghazarian, Hrand; Rankin, Arturo L.

2012-01-01

PSSEARCH provides predictive sea state estimation, coupled with closed-loop feedback control for automated ride control. It enables a manned or unmanned watercraft to determine the 3D map and sea state conditions in its vicinity in real time. Adaptive path-planning/ replanning software and a control surface management system will then use this information to choose the best settings and heading relative to the seas for the watercraft. PSSEARCH looks ahead and anticipates potential impact of waves on the boat and is used in a tight control loop to adjust trim tabs, course, and throttle settings. The software uses sensory inputs including IMU (Inertial Measurement Unit), stereo, radar, etc. to determine the sea state and wave conditions (wave height, frequency, wave direction) in the vicinity of a rapidly moving boat. This information can then be used to plot a safe path through the oncoming waves. The main issues in determining a safe path for sea surface navigation are: (1) deriving a 3D map of the surrounding environment, (2) extracting hazards and sea state surface state from the imaging sensors/map, and (3) planning a path and control surface settings that avoid the hazards, accomplish the mission navigation goals, and mitigate crew injuries from excessive heave, pitch, and roll accelerations while taking into account the dynamics of the sea surface state. The first part is solved using a wide baseline stereo system, where 3D structure is determined from two calibrated pairs of visual imagers. Once the 3D map is derived, anything above the sea surface is classified as a potential hazard and a surface analysis gives a static snapshot of the waves. Dynamics of the wave features are obtained from a frequency analysis of motion vectors derived from the orientation of the waves during a sequence of inputs. Fusion of the dynamic wave patterns with the 3D maps and the IMU outputs is used for efficient safe path planning.

Solitary wave for a nonintegrable discrete nonlinear Schrödinger equation in nonlinear optical waveguide arrays

NASA Astrophysics Data System (ADS)

Ma, Li-Yuan; Ji, Jia-Liang; Xu, Zong-Wei; Zhu, Zuo-Nong

2018-03-01

We study a nonintegrable discrete nonlinear Schrödinger (dNLS) equation with the term of nonlinear nearest-neighbor interaction occurred in nonlinear optical waveguide arrays. By using discrete Fourier transformation, we obtain numerical approximations of stationary and travelling solitary wave solutions of the nonintegrable dNLS equation. The analysis of stability of stationary solitary waves is performed. It is shown that the nonlinear nearest-neighbor interaction term has great influence on the form of solitary wave. The shape of solitary wave is important in the electric field propagating. If we neglect the nonlinear nearest-neighbor interaction term, much important information in the electric field propagating may be missed. Our numerical simulation also demonstrates the difference of chaos phenomenon between the nonintegrable dNLS equation with nonlinear nearest-neighbor interaction and another nonintegrable dNLS equation without the term. Project supported by the National Natural Science Foundation of China (Grant Nos. 11671255 and 11701510), the Ministry of Economy and Competitiveness of Spain (Grant No. MTM2016-80276-P (AEI/FEDER, EU)), and the China Postdoctoral Science Foundation (Grant No. 2017M621964).

Using AORSA to simulate helicon waves in DIII-D

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

Lau, C., E-mail: lauch@ornl.gov; Blazevski, D.; Green, D. L.

2015-12-10

Recent efforts have shown that helicon waves (fast waves at > 20ω{sub ci}) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIII-D, ITER and DEMO. For DIII-D scenarios, the ray tracing code, GENRAY, has been extensively used to study helicon current drive efficiency and location as a function of many plasma parameters. The full wave code, AORSA, which is applicable to arbitrary Larmor radius and can resolve arbitrary ion cyclotron harmonic order, has been recently used to validate the ray tracing technique at these high cyclotron harmonics. If the SOL is ignored,more » it will be shown that the GENRAY and AORSA calculated current drive profiles are comparable for the envisioned high beta advanced scenarios for DIII-D, where there is high single pass absorption due to electron Landau damping and minimal ion damping. AORSA is also been used to estimate possible SOL effects on helicon current drive coupling and SOL absorption due to collisional and slow wave effects.« less

Identifying the chiral d-wave superconductivity by Josephson φ0-states.

PubMed

Liu, Jun-Feng; Xu, Yong; Wang, Jun

2017-03-07

We propose the Josephson junctions linked by a normal metal between a d + id superconductor and another d + id superconductor, a d-wave superconductor, or a s-wave superconductor for identifying the chiral d + id superconductivity. The time-reversal breaking in the chiral d-wave superconducting state is shown to result in a Josephson φ 0 -junction state where the current-phase relation is shifted by a phase φ 0 from the sinusoidal relation, other than 0 and π. The ground-state phase difference φ 0 and the critical current can be used to definitely confirm and read the information about the d + id superconductivity. A smooth evolution from conventional 0-π transitions to tunable φ 0 -states can be observed by changing the relative magnitude of two types of d-wave components in the d + id pairing. On the other hand, the Josephson junction involving the d + id superconductor is also the simplest model to realize a φ 0 - junction, which is useful in superconducting electronics and superconducting quantum computation.

Identifying the chiral d-wave superconductivity by Josephson φ0-states

PubMed Central

Liu, Jun-Feng; Xu, Yong; Wang, Jun

2017-01-01

We propose the Josephson junctions linked by a normal metal between a d + id superconductor and another d + id superconductor, a d-wave superconductor, or a s-wave superconductor for identifying the chiral d + id superconductivity. The time-reversal breaking in the chiral d-wave superconducting state is shown to result in a Josephson φ0-junction state where the current-phase relation is shifted by a phase φ0 from the sinusoidal relation, other than 0 and π. The ground-state phase difference φ0 and the critical current can be used to definitely confirm and read the information about the d + id superconductivity. A smooth evolution from conventional 0-π transitions to tunable φ0-states can be observed by changing the relative magnitude of two types of d-wave components in the d + id pairing. On the other hand, the Josephson junction involving the d + id superconductor is also the simplest model to realize a φ0- junction, which is useful in superconducting electronics and superconducting quantum computation. PMID:28266582

Using AORSA to simulate helicon waves in DIII-D

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

Lau, Cornwall H; Jaeger, E. F.; Bertelli, Nicola

2015-01-01

Recent efforts have shown that helicon waves (fast waves at >20 omega(ci)) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIII-D, ITER and DEMO. For DIII-D scenarios, the ray tracing code, GENRAY, has been extensively used to study helicon current drive efficiency and location as a function of many plasma parameters. The full wave code, AORSA, which is applicable to arbitrary Larmor radius and can resolve arbitrary ion cyclotron harmonic order, has been recently used to validate the ray tracing technique at these high cyclotron harmonics. If the SOL is ignored, itmore » will be shown that the GENRAY and AORSA calculated current drive profiles are comparable for the envisioned high beta advanced scenarios for DIII-D, where there is high single pass absorption due to electron Landau damping and minimal ion damping. AORSA is also been used to estimate possible SOL effects on helicon current drive coupling and SOL absorption due to collisional and slow wave effects.« less

Waves at Navigation Structures

DTIC Science & Technology

2014-10-27

upgrades the Coastal Modeling System’s (CMS) wave model CMS-Wave, a phase-averaged spectral wave model, and BOUSS-2D, a Boussinesq -type nonlinear wave...nearshore wave processes in practical applications. These capabilities facilitate optimization of innovative infrastructure for navigation systems to...navigation systems . The advanced models develop probabilistic engineering design estimates for rehabilitation of coastal structures to evaluate the

Propagation of 3D internal gravity wave beams in a slowly varying stratification

NASA Astrophysics Data System (ADS)

Fan, Boyu; Akylas, T. R.

2017-11-01

The time-mean flows induced by internal gravity wave beams (IGWB) with 3D variations have been shown to have dramatic implications for long-term IGWB dynamics. While uniform stratifications are convenient both theoretically and in the laboratory, stratifications in the ocean can vary by more than an order of magnitude over the ocean depth. Here, in view of this fact, we study the propagation of a 3D IGWB in a slowly varying stratification. We assume that the stratification varies slowly relative to the local variations in the wave profile. In the 2D case, the IGWB bends in response to the changing stratification, but nonlinear effects are minor even in the finite amplitude regime. For a 3D IGWB, in addition to bending, we find that nonlinearity results in the transfer of energy from waves to a large-scale time-mean flow associated with the mean potential vorticity, similar to IGWB behavior in a uniform stratification. In a weakly nonlinear setting, we derive coupled evolution equations that govern this process. We also use these equations to determine the stability properties of 2D IGWB to 3D perturbations. These findings indicate that 3D effects may be relevant and possibly fundamental to IGWB dynamics in nature. Supported by NSF Grant DMS-1512925.

Flexible and wearable 3D graphene sensor with 141 KHz frequency signal response capability

NASA Astrophysics Data System (ADS)

Xu, R.; Zhang, H.; Cai, Y.; Ruan, J.; Qu, K.; Liu, E.; Ni, X.; Lu, M.; Dong, X.

2017-09-01

We developed a flexible force sensor consisting of 3D graphene foam (GF) encapsulated in flexible polydimethylsiloxane (PDMS). Because the 3D GF/PDMS sensor is based on the transformation of an electronic band structure aroused by static mechanical strain or KHz vibration, it can detect frequency signals by both tuning fork tests and piezoelectric ceramic transducer tests, which showed a clear linear response from audio frequencies, including frequencies up to 141 KHz in the ultrasound range. Because of their excellent response with a wide bandwidth, the 3D GF/PDMS sensors are attractive for interactive wearable devices or artificial prosthetics capable of perceiving seismic waves, ultrasonic waves, shock waves, and transient pressures.

Two-dimensional linear and nonlinear Talbot effect from rogue waves.

PubMed

Zhang, Yiqi; Belić, Milivoj R; Petrović, Milan S; Zheng, Huaibin; Chen, Haixia; Li, Changbiao; Lu, Keqing; Zhang, Yanpeng

2015-03-01

We introduce two-dimensional (2D) linear and nonlinear Talbot effects. They are produced by propagating periodic 2D diffraction patterns and can be visualized as 3D stacks of Talbot carpets. The nonlinear Talbot effect originates from 2D rogue waves and forms in a bulk 3D nonlinear medium. The recurrences of an input rogue wave are observed at the Talbot length and at the half-Talbot length, with a π phase shift; no other recurrences are observed. Differing from the nonlinear Talbot effect, the linear effect displays the usual fractional Talbot images as well. We also find that the smaller the period of incident rogue waves, the shorter the Talbot length. Increasing the beam intensity increases the Talbot length, but above a threshold this leads to a catastrophic self-focusing phenomenon which destroys the effect. We also find that the Talbot recurrence can be viewed as a self-Fourier transform of the initial periodic beam that is automatically performed during propagation. In particular, linear Talbot effect can be viewed as a fractional self-Fourier transform, whereas the nonlinear Talbot effect can be viewed as the regular self-Fourier transform. Numerical simulations demonstrate that the rogue-wave initial condition is sufficient but not necessary for the observation of the effect. It may also be observed from other periodic inputs, provided they are set on a finite background. The 2D effect may find utility in the production of 3D photonic crystals.

The effect of wave current interactions on the storm surge and inundation in Charleston Harbor during Hurricane Hugo 1989

NASA Astrophysics Data System (ADS)

Xie, Lian; Liu, Huiqing; Peng, Machuan

The effects of wave-current interactions on the storm surge and inundation induced by Hurricane Hugo in and around the Charleston Harbor and its adjacent coastal regions are examined by using a three-dimensional (3-D) wave-current coupled modeling system. The 3-D storm surge and inundation modeling component of the coupled system is based on the Princeton ocean model (POM), whereas the wave modeling component is based on the third-generation wave model, simulating waves nearshore (SWAN). The results indicate that the effects of wave-induced surface, bottom, and radiation stresses can separately or in combination produce significant changes in storm surge and inundation. The effects of waves vary spatially. In some areas, the contribution of waves to peak storm surge during Hurricane Hugo reached as high as 0.76 m which led to substantial changes in the inundation and drying areas simulated by the storm surge model.

New aspects of whistler waves driven by an electron beam studied by a 3-D electromagnetic code

NASA Technical Reports Server (NTRS)

Nishikawa, Ken-Ichi; Buneman, Oscar; Neubert, Torsten

1994-01-01

We have restudied electron beam driven whistler waves with a 3-D electromagnetic particle code. The simulation results show electromagnetic whistler wave emissions and electrostatic beam modes like those observed in the Spacelab 2 electron beam experiment. It has been suggested in the past that the spatial bunching of beam electrons associated with the beam mode may directly generate whistler waves. However, the simulation results indicate several inconsistencies with this picture: (1) whistler waves continue to be generated even after the beam mode space charge modulation looses its coherence, (2) the parallel (to the background magnetic field) wavelength of the whistler wave is longer than that of the beam instability, and (3) the parallel phase velocity of the whistler wave is smaller than that of the beam mode. The complex structure of the whistler waves in the vicinity of the beam suggest that the transverse motion (gyration) of the beam and background electrons is also involved in the generation of whistler waves.

Waves at Navigation Structures

DTIC Science & Technology

2015-10-30

upgrades the Coastal Modeling System (CMS) wave models CMS-Wave, a phase- averaged spectral wave model, and BOUSS-2D, a Boussinesq type nonlinear wave...developing WaveNet and TideNet, two Web-based tool systems for wind and wave data access and processing, which provide critical data for USACE project...practical applications, resulting in optimization of navigation system to improve safety, reliability and operations with innovative infrastructures

High-frequency homogenization for travelling waves in periodic media.

PubMed

Harutyunyan, Davit; Milton, Graeme W; Craster, Richard V

2016-07-01

We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 1 plus a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 2 . We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω 1 = ω 2 and [Formula: see text] where Λ =(λ 1 λ 2 …λ d ) is the periodicity cell of the medium and for any two vectors [Formula: see text] the product a ⊙ b is defined to be the vector ( a 1 b 1 , a 2 b 2 ,…, a d b d ). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

WAVE2 Regulates Epithelial Morphology and Cadherin Isoform Switching through Regulation of Twist and Abl

PubMed Central

Bryce, Nicole S.; Reynolds, Albert B.; Koleske, Anthony J.; Weaver, Alissa M.

2013-01-01

Background Epithelial morphogenesis is a dynamic process that involves coordination of signaling and actin cytoskeletal rearrangements. Principal Findings We analyzed the contribution of the branched actin regulator WAVE2 in the development of 3-dimensional (3D) epithelial structures. WAVE2-knockdown (WAVE2-KD) cells formed large multi-lobular acini that continued to proliferate at an abnormally late stage compared to control acini. Immunostaining of the cell-cell junctions of WAVE2-KD acini revealed weak and heterogeneous E-cadherin staining despite little change in actin filament localization to the same junctions. Analysis of cadherin expression demonstrated a decrease in E-cadherin and an increase in N-cadherin protein and mRNA abundance in total cell lysates. In addition, WAVE2-KD cells exhibited an increase in the mRNA levels of the epithelial-mesenchymal transition (EMT)-associated transcription factor Twist1. KD of Twist1 expression in WAVE2-KD cells reversed the cadherin switching and completely rescued the aberrant 3D morphological phenotype. Activity of the WAVE2 complex binding partner Abl kinase was also increased in WAVE2-KD cells, as assessed by tyrosine phosphorylation of the Abl substrate CrkL. Inhibition of Abl with STI571 rescued the multi-lobular WAVE2-KD 3D phenotype whereas overexpression of Abl kinase phenocopied the WAVE2-KD phenotype. Conclusions The WAVE2 complex regulates breast epithelial morphology by a complex mechanism involving repression of Twist1 expression and Abl kinase activity. These data reveal a critical role for WAVE2 complex in regulation of cellular signaling and epithelial morphogenesis. PMID:23691243

Field lens multiplexing in holographic 3D displays by using Bragg diffraction based volume gratings

NASA Astrophysics Data System (ADS)

Fütterer, G.

2016-11-01

Applications, which can profit from holographic 3D displays, are the visualization of 3D data, computer-integrated manufacturing, 3D teleconferencing and mobile infotainment. However, one problem of holographic 3D displays, which are e.g. based on space bandwidth limited reconstruction of wave segments, is to realize a small form factor. Another problem is to provide a reasonable large volume for the user placement, which means to provide an acceptable freedom of movement. Both problems should be solved without decreasing the image quality of virtual and real object points, which are generated within the 3D display volume. A diffractive optical design using thick hologram gratings, which can be referred to as Bragg diffraction based volume gratings, can provide a small form factor and high definition natural viewing experience of 3D objects. A large collimated wave can be provided by an anamorphic backlight unit. The complex valued spatial light modulator add local curvatures to the wave field he is illuminated with. The modulated wave field is focused onto to the user plane by using a volume grating based field lens. Active type liquid crystal gratings provide 1D fine tracking of approximately +/- 8° deg. Diffractive multiplex has to be implemented for each color and for a set of focus functions providing coarse tracking. Boundary conditions of the diffractive multiplexing are explained. This is done in regards to the display layout and by using the coupled wave theory (CWT). Aspects of diffractive cross talk and its suppression will be discussed including longitudinal apodized volume gratings.

S-wave velocity measurements along levees in New Orleans using passive surface wave methods

NASA Astrophysics Data System (ADS)

Hayashi, K.; Lorenzo, J. M.; Craig, M. S.; Gostic, A.

2017-12-01

In order to develop non-invasive methods for levee inspection, geophysical investigations were carried out at four sites along levees in the New Orleans area: 17th Street Canal, London Avenue Canal, Marrero Levee, and Industrial Canal. Three of the four sites sustained damage from Hurricane Katrina in 2005 and have since been rebuilt. The geophysical methods used include active and passive surface wave methods, and capacitively coupled resistivity. This paper summarizes the acquisition and analysis of the 1D and 2D passive surface wave data. Twelve wireless seismic data acquisition units with 2 Hz vertical component geophones were used to record data. Each unit includes a GPS receiver so that all units can be synchronized over any distance without cables. The 1D passive method used L shaped arrays of three different sizes with geophone spacing ranging from 5 to 340 m. Ten minutes to one hour of ambient noise was recorded with each array, and total data acquisition took approximately two hours at each site. The 2D method used a linear array with a geophone spacing of 5m. Four geophones were moved forward every 10 minutes along 400 1000 m length lines. Data acquisition took several hours for each line. Recorded ambient noise was processed using the spatial autocorrelation method and clear dispersion curves were obtained at all sites (Figure 1a). Minimum frequencies ranged from 0.4 to 0.7 Hz and maximum frequencies ranged from 10 to 30 Hz depending on the site. Non-linear inversion was performed and 1D and 2D S-wave velocity models were obtained. The 1D method penetrated to depths ranging from 200 to 500 m depending on the site (Figure 1b). The 2D method penetrated to a depth of 40 60 m and provided 400 1000 m cross sections along the levees (Figure 2). The interpretation focused on identifying zones beneath the levees or canal walls having low S-wave velocities corresponding to saturated, unconsolidated sands, or low-rigidity clays. Resultant S-wave velocity profiles are generally consistent with existing drilling logs and the results of laboratory tests.

See-through Detection and 3D Reconstruction Using Terahertz Leaky-Wave Radar Based on Sparse Signal Processing

NASA Astrophysics Data System (ADS)

Murata, Koji; Murano, Kosuke; Watanabe, Issei; Kasamatsu, Akifumi; Tanaka, Toshiyuki; Monnai, Yasuaki

2018-02-01

We experimentally demonstrate see-through detection and 3D reconstruction using terahertz leaky-wave radar based on sparse signal processing. The application of terahertz waves to radar has received increasing attention in recent years for its potential to high-resolution and see-through detection. Among others, the implementation using a leaky-wave antenna is promising for compact system integration with beam steering capability based on frequency sweep. However, the use of a leaky-wave antenna poses a challenge on signal processing. Since a leaky-wave antenna combines the entire signal captured by each part of the aperture into a single output, the conventional array signal processing assuming access to a respective antenna element is not applicable. In this paper, we apply an iterative recovery algorithm "CoSaMP" to signals acquired with terahertz leaky-wave radar for clutter mitigation and aperture synthesis. We firstly demonstrate see-through detection of target location even when the radar is covered with an opaque screen, and therefore, the radar signal is disturbed by clutter. Furthermore, leveraging the robustness of the algorithm against noise, we also demonstrate 3D reconstruction of distributed targets by synthesizing signals collected from different orientations. The proposed approach will contribute to the smart implementation of terahertz leaky-wave radar.

Gravitational waves and core-collapse supernovae

NASA Astrophysics Data System (ADS)

Bisnovatyi-Kogan, G. S.; Moiseenko, S. G.

2017-11-01

A mechanism of formation of gravitational waves in the Universe is considered for a nonspherical collapse of matter. Nonspherical collapse results are presented for a uniform spheroid of dust and a finite-entropy spheroid. Numerical simulation results on core-collapse supernova explosions are presented for the neutrino and magneto-rotational models. These results are used to estimate the dimensionless amplitude of the gravitational wave with a frequency ν ~ 1300 Hz, radiated during the collapse of the rotating core of a pre-supernova with a mass of 1.2 M⊙ (calculated by the authors in 2D). This estimate agrees well with many other calculations (presented in this paper) that have been done in 2D and 3D settings and which rely on more exact and sophisticated calculations of the gravitational wave amplitude. The formation of the large-scale structure of the Universe in the Zel’dovich pancake model involves the emission of very long-wavelength gravitational waves. The average amplitude of these waves is calculated from the simulation, in the uniform spheroid approximation, of the nonspherical collapse of noncollisional dust matter, which imitates dark matter. It is noted that a gravitational wave radiated during a core-collapse supernova explosion in our Galaxy has a sufficient amplitude to be detected by existing gravitational wave telescopes.

Relation Between the 3D-Geometry of the Coronal Wave and Associated CME During the 26 April 2008 Event

NASA Technical Reports Server (NTRS)

Temmer, M.; Veronig, A. M.; Gopalswamy, N.; Yashiro, S.

2011-01-01

We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of approx 240 km/s. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations. We find that the wave structure is asymmetric with an inclination toward East. The associated CME has a deprojected speed of approx 750 +/- 50 km/s, and it shows a non-radial outward motion toward the East with respect to the underlying source region location. Applying the forward fitting model developed by Thernisien, Howard, and Vourlidas we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding flanks of the CME most likely drive and shape the coronal wave.

The Influence of Surface Gravity Waves on Marine Current Turbine Performance

NASA Astrophysics Data System (ADS)

Lust, E.; Luznik, L.; Flack, K. A.; Walker, J.; Van Benthem, M.

2013-12-01

Surface gravity waves can significantly impact operating conditions for a marine current turbine, imparting unsteady velocities several orders of magnitude larger than the ambient turbulence. The influence of surface waves on the performance characteristics of a two-bladed horizontal axis marine current turbine was investigated experimentally in a large towing tank facility at the United States Naval Academy. The turbine model had a 0.8 m diameter (D) rotor with a NACA 63-618 cross section, which is Reynolds number independent with respect to lift coefficient in the operating range of Rec ≈ 4 x 105. The torque, thrust and rotational speed were measured at a range of tip speed ratios (TSR) from 5 < TSR < 11. Tests were performed at two rotor depths (1.3D and 2.25D) with and without waves. The average turbine performance characteristics were largely unchanged by depth or the presence of waves. However, tests with waves indicate large variations in thrust, rotational speed, and torque occurred with the passage of the wave. These results demonstrate the impact of surface gravity waves on power production and structural loading and suggest that turbines should be positioned vertically within the water column at a depth which maximizes power output while minimizing material fatigue. Keywords-- marine current turbine, tidal turbine, towing-tank experiments, surface gravity waves, fatigue loading, phase averaging

Splash singularity for water waves.

PubMed

Castro, Angel; Córdoba, Diego; Fefferman, Charles L; Gancedo, Francisco; Gómez-Serrano, Javier

2012-01-17

We exhibit smooth initial data for the two-dimensional (2D) water-wave equation for which we prove that smoothness of the interface breaks down in finite time. Moreover, we show a stability result together with numerical evidence that there exist solutions of the 2D water-wave equation that start from a graph, turn over, and collapse in a splash singularity (self-intersecting curve in one point) in finite time.

Splash singularity for water waves

PubMed Central

Castro, Angel; Córdoba, Diego; Fefferman, Charles L.; Gancedo, Francisco; Gómez-Serrano, Javier

2012-01-01

We exhibit smooth initial data for the two-dimensional (2D) water-wave equation for which we prove that smoothness of the interface breaks down in finite time. Moreover, we show a stability result together with numerical evidence that there exist solutions of the 2D water-wave equation that start from a graph, turn over, and collapse in a splash singularity (self-intersecting curve in one point) in finite time. PMID:22219372

Advanced Waveform Simulation for Seismic Monitoring

DTIC Science & Technology

2008-09-01

velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radial components), Rayleigh (vertical and...ranges out to 10°, including extensive observations of crustal thinning and thickening and various Pnl complexities. Broadband modeling in 1D, 2D...existing models perform in predicting the various regional phases, Rayleigh waves, Love waves, and Pnl waves. Previous events from this Basin-and-Range

Well log analysis to assist the interpretation of 3-D seismic data at Milne Point, north slope of Alaska

USGS Publications Warehouse

Lee, Myung W.

2005-01-01

In order to assess the resource potential of gas hydrate deposits in the North Slope of Alaska, 3-D seismic and well data at Milne Point were obtained from BP Exploration (Alaska), Inc. The well-log analysis has three primary purposes: (1) Estimate gas hydrate or gas saturations from the well logs; (2) predict P-wave velocity where there is no measured P-wave velocity in order to generate synthetic seismograms; and (3) edit P-wave velocities where degraded borehole conditions, such as washouts, affected the P-wave measurement significantly. Edited/predicted P-wave velocities were needed to map the gas-hydrate-bearing horizons in the complexly faulted upper part of 3-D seismic volume. The estimated gas-hydrate/gas saturations from the well logs were used to relate to seismic attributes in order to map regional distribution of gas hydrate inside the 3-D seismic grid. The P-wave velocities were predicted using the modified Biot-Gassmann theory, herein referred to as BGTL, with gas-hydrate saturations estimated from the resistivity logs, porosity, and clay volume content. The effect of gas on velocities was modeled using the classical Biot-Gassman theory (BGT) with parameters estimated from BGTL.

Quantification of site-city interaction effects on the response of structure under double resonance condition

NASA Astrophysics Data System (ADS)

Kumar, Neeraj; Narayan, Jay Prakash

2018-01-01

This paper presents the site-city interaction (SCI) effects on the response of closely spaced structures under double resonance condition (F_{02{{D}}}^{{S}} = F_{02{{D}}}^{{B}}), where F_{02{{D}}}^{{S}} and F_{02{{D}}}^{{B}} are fundamental frequencies of 2-D structure and 2-D basin, respectively. This paper also presents the development of empirical relations to predict the F_{02{{D}}}^{{B}} of elliptical and trapezoidal basins for both the polarizations of the S wave. Simulated results revealed that F_{02{{D}}}^{{B}} of a 2-D basin very much depends on its geometry, shape ratio and polarization of the incident S wave. The obtained spectral amplification factor (SAF) at F_{02{{D}}}^{{S}} of a standalone structure in a 2-D basin is greater than that in the 1-D case under double resonance condition. A considerable reduction of the fundamental resonance frequency of structures due to the SCI effects is observed for both the polarizations of the S wave. The SAFs at F_{02{{D}}}^{{S}} of closely spaced structures due to SCI effects is larger in the case of SV than SH waves. A splitting of the fundamental-mode frequency bandwidth along with the drastic decrease of SAF due to the SCI effects is obtained. The findings of this paper raise the question concerning the validity of the predicted response of standalone structure based on soil-structure interaction for the design of structures in a 2-D small basin, in an urban environment.

Wave-induced fluid flow in random porous media: Attenuation and dispersion of elastic waves

NASA Astrophysics Data System (ADS)

Müller, Tobias M.; Gurevich, Boris

2005-05-01

A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. .

Heat Wave and Mortality: A Multicountry, Multicommunity Study

PubMed Central

Gasparrini, Antonio; Armstrong, Ben G.; Tawatsupa, Benjawan; Tobias, Aurelio; Lavigne, Eric; Coelho, Micheline de Sousa Zanotti Stagliorio; Pan, Xiaochuan; Kim, Ho; Hashizume, Masahiro; Honda, Yasushi; Guo, Yue-Liang Leon; Wu, Chang-Fu; Zanobetti, Antonella; Schwartz, Joel D.; Bell, Michelle L.; Scortichini, Matteo; Michelozzi, Paola; Punnasiri, Kornwipa; Li, Shanshan; Tian, Linwei; Garcia, Samuel David Osorio; Seposo, Xerxes; Overcenco, Ala; Zeka, Ariana; Goodman, Patrick; Dang, Tran Ngoc; Dung, Do Van; Mayvaneh, Fatemeh; Saldiva, Paulo Hilario Nascimento; Williams, Gail; Tong, Shilu

2017-01-01

Background: Few studies have examined variation in the associations between heat waves and mortality in an international context. Objectives: We aimed to systematically examine the impacts of heat waves on mortality with lag effects internationally. Methods: We collected daily data of temperature and mortality from 400 communities in 18 countries/regions and defined 12 types of heat waves by combining community-specific daily mean temperature ≥90th, 92.5th, 95th, and 97.5th percentiles of temperature with duration ≥2, 3, and 4 d. We used time-series analyses to estimate the community-specific heat wave–mortality relation over lags of 0–10 d. Then, we applied meta-analysis to pool heat wave effects at the country level for cumulative and lag effects for each type of heat wave definition. Results: Heat waves of all definitions had significant cumulative associations with mortality in all countries, but varied by community. The higher the temperature threshold used to define heat waves, the higher heat wave associations on mortality. However, heat wave duration did not modify the impacts. The association between heat waves and mortality appeared acutely and lasted for 3 and 4 d. Heat waves had higher associations with mortality in moderate cold and moderate hot areas than cold and hot areas. There were no added effects of heat waves on mortality in all countries/regions, except for Brazil, Moldova, and Taiwan. Heat waves defined by daily mean and maximum temperatures produced similar heat wave–mortality associations, but not daily minimum temperature. Conclusions: Results indicate that high temperatures create a substantial health burden, and effects of high temperatures over consecutive days are similar to what would be experienced if high temperature days occurred independently. People living in moderate cold and moderate hot areas are more sensitive to heat waves than those living in cold and hot areas. Daily mean and maximum temperatures had similar ability to define heat waves rather than minimum temperature. https://doi.org/10.1289/EHP1026 PMID:28886602

Exploration of S-wave velocity profiles at strong motion stations in Eskisehir, Turkey, using microtremor phase velocity and S-wave amplification

NASA Astrophysics Data System (ADS)

Yamanaka, Hiroaki; Özmen, Ögur Tuna; Chimoto, Kosuke; Alkan, Mehmet Akif; Tün, Muammer; Pekkan, Emrah; Özel, Oguz; Polat, Derya; Nurlu, Murat

2018-05-01

We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area.

A full-wave Helmholtz model for continuous-wave ultrasound transmission.

PubMed

Huttunen, Tomi; Malinen, Matti; Kaipio, Jari P; White, Phillip Jason; Hynynen, Kullervo

2005-03-01

A full-wave Helmholtz model of continuous-wave (CW) ultrasound fields may offer several attractive features over widely used partial-wave approximations. For example, many full-wave techniques can be easily adjusted for complex geometries, and multiple reflections of sound are automatically taken into account in the model. To date, however, the full-wave modeling of CW fields in general 3D geometries has been avoided due to the large computational cost associated with the numerical approximation of the Helmholtz equation. Recent developments in computing capacity together with improvements in finite element type modeling techniques are making possible wave simulations in 3D geometries which reach over tens of wavelengths. The aim of this study is to investigate the feasibility of a full-wave solution of the 3D Helmholtz equation for modeling of continuous-wave ultrasound fields in an inhomogeneous medium. The numerical approximation of the Helmholtz equation is computed using the ultraweak variational formulation (UWVF) method. In addition, an inverse problem technique is utilized to reconstruct the velocity distribution on the transducer which is used to model the sound source in the UWVF scheme. The modeling method is verified by comparing simulated and measured fields in the case of transmission of 531 kHz CW fields through layered plastic plates. The comparison shows a reasonable agreement between simulations and measurements at low angles of incidence but, due to mode conversion, the Helmholtz model becomes insufficient for simulating ultrasound fields in plates at large angles of incidence.

A Parametric Study of the Acoustic Mechanism for Core-collapse Supernovae

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

Harada, A.; Nagakura, H.; Iwakami, W.

We investigate the criterion for the acoustic mechanism to work successfully in core-collapse supernovae. The acoustic mechanism is an alternative to the neutrino-heating mechanism. It was proposed by Burrows et al., who claimed that acoustic waves emitted by g -mode oscillations in proto-neutron stars (PNS) energize a stalled shock wave and eventually induce an explosion. Previous works mainly studied to which extent the g -modes are excited in the PNS. In this paper, on the other hand, we investigate how strong the acoustic wave needs to be if it were to revive a stalled shock wave. By adding the acousticmore » power as a new axis, we draw a critical surface, which is an extension of the critical curve commonly employed in the context of neutrino heating. We perform both 1D and 2D parametrized simulations, in which we inject acoustic waves from the inner boundary. In order to quantify the power of acoustic waves, we use the extended Myers theory to take neutrino reactions into proper account. We find for the 1D simulations that rather large acoustic powers are required to relaunch the shock wave, since the additional heating provided by the secondary shocks developed from acoustic waves is partially canceled by the neutrino cooling that is also enhanced. In 2D, the required acoustic powers are consistent with those of Burrows et al. Our results seem to imply, however, that it is the sum of neutrino heating and acoustic powers that matters for shock revival.« less

Comb-push Ultrasound Shear Elastography (CUSE): A Novel Method for Two-dimensional Shear Elasticity Imaging of Soft Tissues

PubMed Central

Song, Pengfei; Zhao, Heng; Manduca, Armando; Urban, Matthew W.; Greenleaf, James F.; Chen, Shigao

2012-01-01

Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ultrasound shear elastography (CUSE), is introduced in which only one rapid data acquisition (less than 35 ms) is needed to reconstruct a full field-of-view 2D shear wave speed map (40 mm × 38 mm). Multiple unfocused ultrasound beams arranged in a comb pattern (comb-push) are used to generate shear waves. A directional filter is then applied upon the shear wave field to extract the left-to-right (LR) and right-to-left (RL) propagating shear waves. Local shear wave speed is recovered using a time-of-flight method based on both LR and RL waves. Finally a 2D shear wave speed map is reconstructed by combining the LR and RL speed maps. Smooth and accurate shear wave speed maps are reconstructed using the proposed CUSE method in two calibrated homogeneous phantoms with different moduli. Inclusion phantom experiments demonstrate that CUSE is capable of providing good contrast (contrast-to-noise-ratio ≥ 25 dB) between the inclusion and background without artifacts and is insensitive to inclusion positions. Safety measurements demonstrate that all regulated parameters of the ultrasound output level used in CUSE sequence are well below the FDA limits for diagnostic ultrasound. PMID:22736690

A numerical investigation of wave-breaking-induced turbulent coherent structure under a solitary wave

NASA Astrophysics Data System (ADS)

Zhou, Zheyu; Sangermano, Jacob; Hsu, Tian-Jian; Ting, Francis C. K.

2014-10-01

To better understand the effect of wave-breaking-induced turbulence on the bed, we report a 3-D large-eddy simulation (LES) study of a breaking solitary wave in spilling condition. Using a turbulence-resolving approach, we study the generation and the fate of wave-breaking-induced turbulent coherent structures, commonly known as obliquely descending eddies (ODEs). Specifically, we focus on how these eddies may impinge onto bed. The numerical model is implemented using an open-source CFD library of solvers, called OpenFOAM, where the incompressible 3-D filtered Navier-Stokes equations for the water and the air phases are solved with a finite volume scheme. The evolution of the water-air interfaces is approximated with a volume of fluid method. Using the dynamic Smagorinsky closure, the numerical model has been validated with wave flume experiments of solitary wave breaking over a 1/50 sloping beach. Simulation results show that during the initial overturning of the breaking wave, 2-D horizontal rollers are generated, accelerated, and further evolve into a couple of 3-D hairpin vortices. Some of these vortices are sufficiently intense to impinge onto the bed. These hairpin vortices possess counter-rotating and downburst features, which are key characteristics of ODEs observed by earlier laboratory studies using Particle Image Velocimetry. Model results also suggest that those ODEs that impinge onto bed can induce strong near-bed turbulence and bottom stress. The intensity and locations of these near-bed turbulent events could not be parameterized by near-surface (or depth integrated) turbulence unless in very shallow depth.

Short-Term Perturbations Within the D-Region Detected Above the Mediterranean

NASA Astrophysics Data System (ADS)

Silber, I.; Price, C. G.

2015-12-01

The ionospheric D-region lies in the altitude range of ~65-95 km. This part of the atmosphere is highly sensitive to waves propagating upwards from the troposphere, either as pressure perturbations (gravity and acoustic waves) or electromagnetic perturbations from lightning discharges (resulting in EMPs, sprites, elves, etc.). These perturbations can affect the temperature, wind, species concentration, and even ionization in the upper atmosphere. Very low frequencies (VLF) radio signals, generated by man-made communication transmitters, have been recorded using ground-based VLF receivers in Israel. These radio waves propagate over long distances within the Earth-ionosphere waveguide, reflected off the Earth's surface and the D-region. The characteristics of the received signals depend on several parameters along the path, but are fairly constant over short periods of time. In this study we present analysis of VLF narrowband data transmitted from Sicily, Italy, spanning one year, and detected in Tel Aviv, Israel. We show observations of the interaction between both pressure and EM perturbations from thunderstorms with the narrowband VLF data aloft. We clearly observe short period (~2-4 minutes) acoustic waves, longer period gravity waves (~5-7 minutes periods), while also many transient events related to heating and ionization of the D-region. Comparisons with WWLLN lightning data show the link between tropospheric thunderstorms and D-region variability.

Complex Modeling of the Seismic Structure of the Trans-European Suture Zone's Margin from Receiver Function Analysis

NASA Astrophysics Data System (ADS)

Wilde-Piorko, M.; Chrapkiewicz, K.; Lepore, S.; Polkowski, M.; Grad, M.

2016-12-01

The Trans-European Suture Zone (TESZ) is one of the most prominent suture zones in Europe separating the young Paleozoic Platform from the much older Precambrian East European Craton. The data recorded by "13 BB Star" broadband seismic stations (Grad et al., 2015) are analyzed to investigate the crustal and upper mantle structure of the margin of the Trans-European Suture Zone (TESZ) in northern Poland. Receiver function (RF) locally provides the signature of sharp seismic discontinuities and information about the shear wave (S-wave) velocity distribution beneath the seismic station. Recorded seismograms are rotated from ZNE to LQT system with method using the properties of RF (Wilde-Piórko, 2015). Different techniques of receiver function interpretation are applied, including 1-D inversion of RF, 1-D forward modeling of RF, 2.5D forward modeling of RF, 1-D join inversion of RF and dispersion curves of surface wave, to find the best S-wave velocity model of the TESZ margin. A high-resolution 3D P-wave velocity model in the area of Poland (Grad et al. 2016) are used as a starting model. National Science Centre Poland provided financial support for this work by NCN grant DEC-2011/02/A/ST10/00284.

Fidelity study of the superconducting phase diagram in the two-dimensional single-band Hubbard model

NASA Astrophysics Data System (ADS)

Jia, C. J.; Moritz, B.; Chen, C.-C.; Shastry, B. Sriram; Devereaux, T. P.

2011-09-01

Extensive numerical studies have demonstrated that the two-dimensional single-band Hubbard model contains much of the key physics in cuprate high-temperature superconductors. However, there is no definitive proof that the Hubbard model truly possesses a superconducting ground state or, if it does, of how it depends on model parameters. To answer these longstanding questions, we study an extension of the Hubbard model including an infinite-range d-wave pair field term, which precipitates a superconducting state in the d-wave channel. Using exact diagonalization on 16-site square clusters, we study the evolution of the ground state as a function of the strength of the pairing term. This is achieved by monitoring the fidelity metric of the ground state, as well as determining the ratio between the two largest eigenvalues of the d-wave pair/spin/charge-density matrices. The calculations show a d-wave superconducting ground state in doped clusters bracketed by a strong antiferromagnetic state at half filling controlled by the Coulomb repulsion U and a weak short-range checkerboard charge ordered state at larger hole doping controlled by the next-nearest-neighbor hopping t'. We also demonstrate that negative t' plays an important role in facilitating d-wave superconductivity.

Banded Structures in Electron Pitch Angle Diffusion Coefficients from Resonant Wave Particle Interactions

NASA Technical Reports Server (NTRS)

Tripathi, A. K.; Singhal, R. P.; Khazanov, G. V.; Avanov, L. A.

2016-01-01

Electron pitch angle (D (alpha)) and momentum (D(pp)) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic (ECH) and whistler mode chorus waves. Calculations have been performed at two spatial locations L = 4.6 and 6.8 for electron energies 10 keV. Landau (n = 0) resonance and cyclotron harmonic resonances n = +/-1, +/-2,...+/-5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (alpha) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusion coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECH waves in pitch angle diffusion coefficient is due to resonances n = +1 and n = +2. A major contribution to momentum diffusion coefficients appears from n = +2. However, the banded structures in D alpha and Dpp coefficients appear only in the profile of diffusion coefficients for n = +2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band chorus waves, the banded structures appear only in Landau resonance. The Dpp diffusion coefficient for ECH waves is one to two orders smaller than D alpha coefficients. For chorus waves, Dpp coefficients are about an order of magnitude smaller than D alpha coefficients for the case n does not = 0. In case of Landau resonance, the values of Dpp coefficient are generally larger than the values of D alpha coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECH waves, resonant frequencies have been estimated for wave normal angle 89 deg and harmonic resonances n = +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10 deg and Landau resonance. Further, in ECH waves, the banded structures appear for electron energies (is) greater than1 keV, and for whistler mode chorus waves, structures appear for energies greater than 2 keV at L = 4.6 and above 200 eV for L = 6.8. The results obtained in the present work will be helpful in the study of diffusion curves and will have important consequences for diffuse aurora and pancake distributions.

Nearshore Current Model Workshop Summary.

DTIC Science & Technology

1983-09-01

dissipation , and wave-current interaction. b. Incorporation into models of wave-breaking. c. Parameterization of turbulence in models. d. Incorporation...into models of surf zone energy dissipation . e. Methods to specify waves and currents on the boundaries of the grid. f. Incorporation into models of...also recommended. Improvements should include nonlinear and irregular wave effects and improved models of wave-breaking and wave energy dissipation in

Description of an α-cluster tail in 8Be and 20Ne: Delocalization of the α cluster by quantum penetration

NASA Astrophysics Data System (ADS)

Kanada-En'yo, Yoshiko

2014-10-01

We analyze the α-cluster wave functions in cluster states of ^8Be and ^{20}Ne by comparing the exact relative wave function obtained by the generator coordinate method (GCM) with various types of trial functions. For the trial functions, we adopt the fixed range shifted Gaussian of the Brink-Bloch (BB) wave function, the spherical Gaussian with the adjustable range parameter of the spherical Tohsaki-Horiuchi-Schuck-Röpke (sTHSR), the deformed Gaussian of the deformed THSR (dTHSR), and a function with the Yukawa tail (YT). The quality of the description of the exact wave function with a trial function is judged by the squared overlap between the trial function and the GCM wave function. A better result is obtained with the sTHSR wave function than the BB wave function, and further improvement can be made with the dTHSR wave function because these wave functions can describe the outer tail better. The YT wave function gives almost an equal quality to or even better quality than the dTHSR wave function, indicating that the outer tail of α-cluster states is characterized by the Yukawa-like tail rather than the Gaussian tail. In weakly bound α-cluster states with small α separation energy and the low centrifugal and Coulomb barriers, the outer tail part is the slowly damping function described well by the quantum penetration through the effective barrier. This outer tail characterizes the almost zero-energy free α gas behavior, i.e., the delocalization of the cluster.

Lapse-time-dependent coda-wave depth sensitivity to local velocity perturbations in 3-D heterogeneous elastic media

NASA Astrophysics Data System (ADS)

Obermann, Anne; Planès, Thomas; Hadziioannou, Céline; Campillo, Michel

2016-10-01

In the context of seismic monitoring, recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane. Locating the depth of the changes, however, remains a challenge. In this paper, we use 3-D wavefield simulations to address two problems: first, we evaluate the contribution of surface- and body-wave sensitivity to a change at depth. We introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model. We show that the depth sensitivity can be modelled as a linear combination of body- and surface-wave sensitivity. The lapse-time-dependent sensitivity ratio of body waves and surface waves can be used to build 3-D sensitivity kernels for imaging purposes. Second, we compare the lapse-time behaviour in the presence of a perturbation in horizontal and vertical slabs to address, for instance, the origin of the velocity changes detected after large earthquakes.

3D MHD Simulations of Waves Excited in an Accretion Disk by a Rotating Magnetized Star

NASA Astrophysics Data System (ADS)

Lovelace, R. V. E.; Romanova, M. M.

2014-01-01

We present results of global 3D MHD simulations of warp and density waves in accretion disks excited by a rotating star with a misaligned dipole magnetic field. A wide range of cases are considered. We find for example that if the star's magnetosphere corotates approximately with the inner disk, then a strong one-arm bending wave or warp forms. The warp corotates with the star and has a maximum amplitude (|zω|/r ~ 0.3) between the corotation radius and the radius of the vertical resonance. If the magnetosphere rotates more slowly than the inner disk, then a bending wave is excited at the disk-magnetosphere boundary, but it does not form a large-scale warp. In this case the angular rotation of the disk [Ω(r,z = 0)] has a maximum as a function of r so that there is an inner region where dΩ/dr > 0. In this region we observe radially trapped density waves in approximate agreement with the theoretical prediction of a Rossby wave instability in this region.

Ionospheric modification by radio waves: An overview and novel applications

NASA Astrophysics Data System (ADS)

Kosch, M. J.

2008-12-01

High-power high-frequency radio waves, when beamed into the Earth's ionosphere, can heat the plasma by particle collisions in the D-layer or generate wave-plasma resonances in the F-layer. These basic phenomena have been used in many research applications. In the D-layer, ionospheric currents can be modulated through conductance modification to produce artificial ULF and VLF waves, which propagate allowing magnetospheric research. In the mesopause, PMSE can be modified allowing dusty plasma research. In the F-layer, wave-plasma interactions generate a variety of artificially stimulated phenomena, such as (1) magnetic field-aligned plasma irregularities linked to anomalous radio wave absorption, (2) stimulated electromagnetic emissions linked to upper-hybrid resonance, (3) optical emissions linked to electron acceleration and collisions with neutrals, and (4) Langmuir turbulence linked to enhanced radar backscatter. These phenomena are reviewed. In addition, some novel applications of ionospheric heaters will be presented, including HF radar sounding of the magnetosphere, the production of E-region optical emissions, and measurements of D-region electron temperature for controlled PMSE research.

Intertwined Orders in Heavy-Fermion Superconductor CeCoIn 5

DOE PAGES

Kim, Duk Young; Lin, Shi-Zeng; Weickert, Franziska; ...

2016-12-20

The appearance of spin-density-wave (SDW) magnetic order in the low-temperature and high-field corner of the superconducting phase diagram of CeCoIn 5 is unique among unconventional superconductors. The nature of this magnetic $Q$ phase is a matter of current debate. Here, we present the thermal conductivity of CeCoIn 5 in a rotating magnetic field, which reveals the presence of an additional order inside the $Q$ phase that is intimately intertwined with the superconducting d-wave and SDW orders. A discontinuous change of the thermal conductivity within the $Q$ phase, when the magnetic field is rotated about antinodes of the superconducting d-wave ordermore » parameter, demands that the additional order must change abruptly, together with the recently observed switching of the SDW. Lastly, a combination of interactions, where spin-orbit coupling orients the SDW, which then selects the secondary p -wave pair-density-wave component (with an average amplitude of 20% of the primary d-wave order parameter), accounts for the observed behavior.« less

Quasi-optical theory of relativistic surface-wave oscillators with one-dimensional and two-dimensional periodic planar structures

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

Ginzburg, N. S.; Zaslavsky, V. Yu.; Institute of Applied Physics of Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950

2013-11-15

Within the framework of a quasi-optical approach, we develop 2D and 3D self-consistent theory of relativistic surface-wave oscillators. Presenting the radiation field as a sum of two counter-propagating wavebeams coupled on a shallow corrugated surface, we describe formation of an evanescent slow wave. Dispersion characteristics of the evanescent wave following from this method are in good compliance with those found from the direct cst simulations. Considering excitation of the slow wave by a sheet electron beam, we simulate linear and nonlinear stages of interaction, which allows us to determine oscillation threshold conditions, electron efficiency, and output coupling. The transition frommore » the model of surface-wave oscillator operating in the π-mode regime to the canonical model of relativistic backward wave oscillator is considered. We also described a modified scheme of planar relativistic surface-wave oscillators exploiting two-dimensional periodic gratings. Additional transverse propagating waves emerging on these gratings synchronize the emission from a wide sheet rectilinear electron beam allowing realization of a Cherenkov millimeter-wave oscillators with subgigawatt output power level.« less

A first-order statistical smoothing approximation for the coherent wave field in random porous random media

NASA Astrophysics Data System (ADS)

Müller, Tobias M.; Gurevich, Boris

2005-04-01

An important dissipation mechanism for waves in randomly inhomogeneous poroelastic media is the effect of wave-induced fluid flow. In the framework of Biot's theory of poroelasticity, this mechanism can be understood as scattering from fast into slow compressional waves. To describe this conversion scattering effect in poroelastic random media, the dynamic characteristics of the coherent wavefield using the theory of statistical wave propagation are analyzed. In particular, the method of statistical smoothing is applied to Biot's equations of poroelasticity. Within the accuracy of the first-order statistical smoothing an effective wave number of the coherent field, which accounts for the effect of wave-induced flow, is derived. This wave number is complex and involves an integral over the correlation function of the medium's fluctuations. It is shown that the known one-dimensional (1-D) result can be obtained as a special case of the present 3-D theory. The expression for the effective wave number allows to derive a model for elastic attenuation and dispersion due to wave-induced fluid flow. These wavefield attributes are analyzed in a companion paper. .

Three-dimensional ground-motion simulations of earthquakes for the Hanford area, Washington

USGS Publications Warehouse

Frankel, Arthur; Thorne, Paul; Rohay, Alan

2014-01-01

This report describes the results of ground-motion simulations of earthquakes using three-dimensional (3D) and one-dimensional (1D) crustal models conducted for the probabilistic seismic hazard assessment (PSHA) of the Hanford facility, Washington, under the Senior Seismic Hazard Analysis Committee (SSHAC) guidelines. The first portion of this report demonstrates that the 3D seismic velocity model for the area produces synthetic seismograms with characteristics (spectral response values, duration) that better match those of the observed recordings of local earthquakes, compared to a 1D model with horizontal layers. The second part of the report compares the response spectra of synthetics from 3D and 1D models for moment magnitude (M) 6.6–6.8 earthquakes on three nearby faults and for a dipping plane wave source meant to approximate regional S-waves from a Cascadia great earthquake. The 1D models are specific to each site used for the PSHA. The use of the 3D model produces spectral response accelerations at periods of 0.5–2.0 seconds as much as a factor of 4.5 greater than those from the 1D models for the crustal fault sources. The spectral accelerations of the 3D synthetics for the Cascadia plane-wave source are as much as a factor of 9 greater than those from the 1D models. The differences between the spectral accelerations for the 3D and 1D models are most pronounced for sites with thicker supra-basalt sediments and for stations with earthquakes on the Rattlesnake Hills fault and for the Cascadia plane-wave source.

Interaction of Lamb Waves with Fatigue Cracks in Aluminum

DTIC Science & Technology

2011-09-01

Interaction of Lamb Waves with Fatigue Cracks in Aluminum E. D. SWENSON, C. T. OWENS and C. ALLEN ABSTRACT Elastic waves can travel across...the interaction of Lamb waves with both open and closed low-cycle fatigue cracks in aluminum plates using a three-dimensional laser Doppler vibrometer...and antisymmetric Lamb wave modes differ upon encountering fatigue cracks. INTRODUCTION The use of guided elastic waves (Lamb waves) has shown

A 3D staggered-grid finite difference scheme for poroelastic wave equation

NASA Astrophysics Data System (ADS)

Zhang, Yijie; Gao, Jinghuai

2014-10-01

Three dimensional numerical modeling has been a viable tool for understanding wave propagation in real media. The poroelastic media can better describe the phenomena of hydrocarbon reservoirs than acoustic and elastic media. However, the numerical modeling in 3D poroelastic media demands significantly more computational capacity, including both computational time and memory. In this paper, we present a 3D poroelastic staggered-grid finite difference (SFD) scheme. During the procedure, parallel computing is implemented to reduce the computational time. Parallelization is based on domain decomposition, and communication between processors is performed using message passing interface (MPI). Parallel analysis shows that the parallelized SFD scheme significantly improves the simulation efficiency and 3D decomposition in domain is the most efficient. We also analyze the numerical dispersion and stability condition of the 3D poroelastic SFD method. Numerical results show that the 3D numerical simulation can provide a real description of wave propagation.

Geothermal exploration in the German Molasse Basin - Supplementary exploration using integrated 3-component data and shear wave measurements

NASA Astrophysics Data System (ADS)

Wawerzinek, Britta; Buness, Hermann; Lüschen, Ewald; Thomas, Rüdiger

2017-04-01

To establish a dense area-wide network of geothermal facilities, the Stadtwerke München initiated the joint research project GRAME together with the Leibniz Institute for Applied Geophysics (GeoParaMoL*). As a database for the project, a 3D seismic survey was acquired from November 1015 to March 2016 and covers 170 km2 of the southern part of Munich. 3D seismic exploration is a well-established method to explore geothermal reservoirs, and its value for reservoir characterization of the Malm has been proven by several projects. A particular challenge often is the determination of geophysical parameters for facies interpretation without any borehole information, which is needed for calibration. A new approach to facilitate a reliable interpretation is to include shear waves in the interpretation workflow, which helps to tie down the range of lithological and petrophysical parameters. Shear wave measurements were conducted during the regular 3D seismic survey in Munich. In a passive experiment, the survey was additionally recorded on 467 single, 3-component (3C), digital receivers that were deployed along one main line (15 km length) and two crosslines (4 km length). In this way another 3D P-wave as well as a 3D shear wave dataset were acquired. In the active shear wave experiment the SHOVER technique (Edelmann, 1981) was applied to directly excite shear waves using standard vertical vibrators. The 3C recordings of both datasets show, in addition to the P-wave reflections on the vertical component, clear shear-wave signals on the horizontal components. The structural image of the P-waves recorded on the vertical component of the 3C receivers displays clear reflectors within the Molasse Basin down to the Malm and correlates well with the structural image of the regular survey. Taking into account a travel time ratio of 1.6 the reflection patterns of horizontal and vertical components approximately coincide. This indicates that Molasse sediments and the Malm can also be imaged by shear waves. Further processing steps will derive geophysical parameters (e.g. vp/vs) and clarify the amount of converted waves. GeoParaMoL (FKZ 0325787B) is funded by the Federal Ministry for Economic Affairs and Energy (BMWi). Edelmann, H.A.K. (1981): SHOVER shear-wave generation by vibration orthogonal to the polarization. Geophysical Prospecting 29, 541-549. * http://www.liag-hannover.de/en/fsp/ge/geoparamol.html

Seismic Waveform Tomography of the Iranian Region

NASA Astrophysics Data System (ADS)

Maggi, A.; Priestley, K.; Jackson, J.

2001-05-01

Surprisingly little is known about the detailed velocity structure of Iran, despite the region's importance in the tectonics of the Middle East. Previous studies have concentrated mainly on fundamental mode surface wave dispersion measurements along isolated paths (e.g.~Asudeh, 1982; Cong & Mitchell, 1998; Ritzwoller et.~al, 1998), and the propagation characteristics of crust and upper mantle body waves (e.g. Hearn & Ni 1994; Rodgers et.~al 1997). We use the partitioned waveform inversion method of Nolet (1990) on several hundred regional waveforms crossing the Iranian region to produce a 3-D seismic velocity map for the crust and upper mantle of the area. The method consists of using long period seismograms from earthquakes with well determined focal mechanisms and depths to constrain 1-D path-averaged shear wave models along regional paths. The constraints imposed on the 1-D models by the seismograms are then combined with independent constraints from other methods (e.g.~Moho depths from reciever function analysis etc.), to solve for the 3-D seismic velocity structure of the region. A dense coverage of fundamental mode rayleigh waves at a period of 100~s ensures good resolution of lithospheric scale structure. We also use 20~s period fundamental mode rayleigh waves and some Pnl wavetrains to make estimates of crustal thickness variations and average crustal velocities. A few deeper events give us some coverage of higher mode rayleigh waves and mantle S waves, which sample to the base of the upper mantle. Our crustal thickness estimates range from 45~km in the southern Zagros mountains, to 40~km in central Iran and 35~km towards the north of the region. We also find inconsistencies between the 1-D models required to fit the vertical and the tranverse seismograms, indicating the presence of anisotropy.

Propagation and damping of Alfvén waves in low solar atmosphere

NASA Astrophysics Data System (ADS)

Ryu, Chang-Mo; Huynh, Cong Tuan

2017-10-01

Propagation and damping of Alfvén waves in the inner solar corona are studied using a 2D magnetohydrodynamics (MHD) simulation code with realistic density and temperature profiles in a uniform background magnetic field. A linear wave is launched by ascribing a sinusoidal fluid motion at about 1000 km from the surface of the Sun, which is shown to generate Alfvénic wave motions along the height. The 2D MHD simulation shows that for B0 ≈ 3 G, Alfvén waves of about 10-2 Hz with an infinite horizontal length-scale can penetrate into the corona, transferring about 90 per cent their energies. This raises the possibility that the wave can be dissipated by various physical processes. The results show that the propagating wave can effectively damp via viscosity in the lower region of the corona, if a horizontal scale of granular size is incorporated.

p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor.

PubMed

Di Bernardo, A; Millo, O; Barbone, M; Alpern, H; Kalcheim, Y; Sassi, U; Ott, A K; De Fazio, D; Yoon, D; Amado, M; Ferrari, A C; Linder, J; Robinson, J W A

2017-01-19

Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

PubMed Central

Di Bernardo, A.; Millo, O.; Barbone, M.; Alpern, H.; Kalcheim, Y.; Sassi, U.; Ott, A. K.; De Fazio, D.; Yoon, D.; Amado, M.; Ferrari, A. C.; Linder, J.; Robinson, J. W. A.

2017-01-01

Electron pairing in the vast majority of superconductors follows the Bardeen–Cooper–Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K. PMID:28102222

Experimental observation of steady inertial wave turbulence in deep rotating flows

NASA Astrophysics Data System (ADS)

Yarom, Ehud; Sharon, Eran

2015-11-01

We present experimental evidence of inertial wave turbulence in deep rotating fluid. Experiments were performed in a rotating cylindrical water tank, where previous work showed statistics similar to 2D turbulence (specifically an inverse energy cascade). Using Fourier analysis of high resolution data in both space (3D) and time we show that most of the energy of a steady state flow is contained around the inertial wave dispersion relation. The nonlinear interaction between the waves is manifested by the widening of the time spectrum around the dispersion relation. We show that as the Rossby number increases so does the spectrum width, with a strong dependence on wave number. Our results suggest that in some parameters range, rotating turbulence velocity field can be represented as a field of interacting waves (wave turbulence). Such formalism may provide a better understanding of the flow statistics. This work was supported by the Israel Science Foundation, Grant No. 81/12.

VLF wave injections from the ground

NASA Technical Reports Server (NTRS)

Helliwell, R. A.

1983-01-01

Experiments on wave-particle interactions using VLF whistler-mode waves injected into the magnetosphere from Antartica are described. The injected signals are single-frequency coherent waves whose amplitudes and frequencies may be changed slowly with time, or else two or more coherent wave trains transmitted simultaneously to determine the nature of the response to multifrequency excitation. The waves may be amplified 30 dB or more and may trigger intense emissions having bandwidths that vary from a few to several hundred Hertz. In most cases significant growth and triggering occur only when the driving signal is essentially monochromatic (bandwidth 10 Hz). If two frequencies are transmitted simultaneously the signal at the lower frequency tends to be suppressed by 20 dB or more. These results are interpreted in terms of a feedback interaction between the waves and counter-streaming cyclotron resonant electrons in a region several hundred wavelengths long, centered on the magnetic equator.

Modeling the NF-κB mediated inflammatory response predicts cytokine waves in tissue

PubMed Central

2011-01-01

Background Waves propagating in "excitable media" is a reliable way to transmit signals in space. A fascinating example where living cells comprise such a medium is Dictyostelium D. which propagates waves of chemoattractant to attract distant cells. While neutrophils chemotax in a similar fashion as Dictyostelium D., it is unclear if chemoattractant waves exist in mammalian tissues and what mechanisms could propagate them. Results We propose that chemoattractant cytokine waves may naturally develop as a result of NF-κB response. Using a heuristic mathematical model of NF-κB-like circuits coupled in space we show that the known characteristics of NF-κB response favor cytokine waves. Conclusions While the propagating wave of cytokines is generally beneficial for inflammation resolution, our model predicts that there exist special conditions that can cause chronic inflammation and re-occurrence of acute inflammatory response. PMID:21771307

Hidden order and flux attachment in symmetry-protected topological phases: A Laughlin-like approach

NASA Astrophysics Data System (ADS)

Ringel, Zohar; Simon, Steven H.

2015-05-01

Topological phases of matter are distinct from conventional ones by their lack of a local order parameter. Still in the quantum Hall effect, hidden order parameters exist and constitute the basis for the celebrated composite-particle approach. Whether similar hidden orders exist in 2D and 3D symmetry protected topological phases (SPTs) is a largely open question. Here, we introduce a new approach for generating SPT ground states, based on a generalization of the Laughlin wave function. This approach gives a simple and unifying picture of some classes of SPTs in 1D and 2D, and reveals their hidden order and flux attachment structures. For the 1D case, we derive exact relations between the wave functions obtained in this manner and group cohomology wave functions, as well as matrix product state classification. For the 2D Ising SPT, strong analytical and numerical evidence is given to show that the wave function obtained indeed describes the desired SPT. The Ising SPT then appears as a state with quasi-long-range order in composite degrees of freedom consisting of Ising-symmetry charges attached to Ising-symmetry fluxes.

The exploration technology and application of sea surface wave

NASA Astrophysics Data System (ADS)

Wang, Y.

2016-12-01

In order to investigate the seismic velocity structure of the shallow sediments in the Bohai Sea of China, we conduct a shear-wave velocity inversion of the surface wave dispersion data from a survey of 12 ocean bottom seismometers (OBS) and 377 shots of a 9000 inch3 air gun. With OBS station spacing of 5 km and air gun shot spacing of 190 m, high-quality Rayleigh wave data were recorded by the OBSs within 0.4 5 km offset. Rayleigh wave phase velocity dispersion for the fundamental mode and first overtone in the frequency band of 0.9 3.0 Hz were retrieved with the phase-shift method and inverted for the shear-wave velocity structure of the shallow sediments with a damped iterative least-square algorithm. Pseudo 2-D shear-wave velocity profiles with depth to 400 m show coherent features of relatively weak lateral velocity variation. The uncertainty in shear-wave velocity structure was also estimated based on the pseudo 2-D profiles from 6 trial inversions with different initial models, which suggest a velocity uncertainty < 30 m/s for most parts of the 2-D profiles. The layered structure with little lateral variation may be attributable to the continuous sedimentary environment in the Cenozoic sedimentary basin of the Bohai Bay basin. The shear-wave velocity of 200 300 m/s in the top 100 m of the Bohai Sea floor may provide important information for offshore site response studies in earthquake engineering. Furthermore, the very low shear-wave velocity structure (200 700 m/s) down to 400 m depth could produce a significant travel time delay of 1 s in the S wave arrivals, which needs to be considered to avoid serious bias in S wave traveltime tomographic models.

Generalized analytical model for benthic water flux forced by surface gravity waves

USGS Publications Warehouse

King, J.N.; Mehta, A.J.; Dean, R.G.

2009-01-01

A generalized analytical model for benthic water flux forced by linear surface gravity waves over a series of layered hydrogeologic units is developed by adapting a previous solution for a hydrogeologic unit with an infinite thickness (Case I) to a unit with a finite thickness (Case II) and to a dual-unit system (Case III). The model compares favorably with laboratory observations. The amplitude of wave-forced benthic water flux is shown to be directly proportional to the amplitude of the wave, the permeability of the hydrogeologic unit, and the wave number and inversely proportional to the kinematic viscosity of water. A dimensionless amplitude parameter is introduced and shown to reach a maximum where the product of water depth and the wave number is 1.2. Submarine groundwater discharge (SGD) is a benthic water discharge flux to a marine water body. The Case I model estimates an 11.5-cm/d SGD forced by a wave with a 1 s period and 5-cm amplitude in water that is 0.5-m deep. As this wave propagates into a region with a 0.3-m-thick hydrogeologic unit, with a no-flow bottom boundary, the Case II model estimates a 9.7-cm/d wave-forced SGD. As this wave propagates into a region with a 0.2-m-thick hydrogeologic unit over an infinitely thick, more permeable unit, the Case III quasi-confined model estimates a 15.7-cm/d wave-forced SGD. The quasi-confined model has benthic constituent flux implications in coral reef, karst, and clastic regions. Waves may undermine tracer and seepage meter estimates of SGD at some locations. Copyright 2009 by the American Geophysical Union.

Three-dimensional simulations of ground motions in the San Bernardino Valley, California, for hypothetical earthquakes on the San Andreas Fault

USGS Publications Warehouse

Frankel, A.

1993-01-01

Three-dimensional finite difference simulations of elastic waves in the San Bernardino Valley were performed for two hypothetical earthquakes on the San Andreas fault: a point source with moment magnitude M5 and an extended rupture with M6.5. A method is presented for incorporating a source with arbitrary focal mechanism in the grid. Synthetics from the 3-D simulations are compared with those derived from 2-D (vertical cross section) and 1-D (flat-layered) models. The synthetic seismograms from the 3-D and 2-D simulations exhibit large surface waves produced by conversion of incident S waves at the edge of the basin. Seismograms from the flat-layered model do not contain these converted surface waves and underestimate the duration of shaking. Maps of maximum ground velocities occur in localized portions of the basin. The location of the largest velocities changes with the rupture propagation direction. Contours of maximum shaking are also dependent on asperity positions and radiation pattern. -from Author

Three-dimensional manipulation of single cells using surface acoustic waves

PubMed Central

Guo, Feng; Mao, Zhangming; Chen, Yuchao; Xie, Zhiwei; Lata, James P.; Li, Peng; Ren, Liqiang; Liu, Jiayang; Yang, Jian; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2016-01-01

The ability of surface acoustic waves to trap and manipulate micrometer-scale particles and biological cells has led to many applications involving “acoustic tweezers” in biology, chemistry, engineering, and medicine. Here, we present 3D acoustic tweezers, which use surface acoustic waves to create 3D trapping nodes for the capture and manipulation of microparticles and cells along three mutually orthogonal axes. In this method, we use standing-wave phase shifts to move particles or cells in-plane, whereas the amplitude of acoustic vibrations is used to control particle motion along an orthogonal plane. We demonstrate, through controlled experiments guided by simulations, how acoustic vibrations result in micromanipulations in a microfluidic chamber by invoking physical principles that underlie the formation and regulation of complex, volumetric trapping nodes of particles and biological cells. We further show how 3D acoustic tweezers can be used to pick up, translate, and print single cells and cell assemblies to create 2D and 3D structures in a precise, noninvasive, label-free, and contact-free manner. PMID:26811444

Diffraction of waves past two vertical thin plates on the free surface: A comparison of theory and experiment

NASA Astrophysics Data System (ADS)

Shin, Dong Min; Cho, Yeunwoo

2017-11-01

Diffraction of waves past two vertical thin plates on the free surface is studied theoretically and experimentally. A particular attention is paid to the wave motions depending on the relationship between the wavelength (λ) and the width (b) between the two plates for a given draft (d) and water depth (h). For d/h =0.19, at resonance modes when b/ λ = 0.245 (first), 0.695 (second), 1.11 (third), 1.55 (fourth), etc., the overall transmission features the maximum with no reflection. In the first mode, the water column between the plates moves up and down with no wave motions. In the second mode, it shows the fundamental standing wave motion. In the remaining modes, it shows another standing wave motions with relatively higher frequencies. As d/h increases (0.1-0.4), the resonance points move to values b/ λ = 0, 0.5, 1, 1.5, etc., and, at those resonance points, the peaks of reflection and transmission coefficients become more sharp and narrow. The loss of energy of incoming waves is also observed at every transmission in the two plate system, and, in particular, more energy loss near a resonant frequency. In addition, it is found that energy is lost mainly due to the transmission process not the reflection process. This work was supported by the National Research Foundation of Korea (NRF). (NRF-2017R1D1A1B03028299).

Effect of dopaminergic drugs on the reserpine-induced lowering of hippocampal theta wave frequency in rats.

PubMed

Nakagawa, T; Ukai, K; Ohyama, T; Gomita, Y; Okamura, H

2000-05-01

The effects of dopaminergic drugs on the lowering of hippocampal theta wave frequency induced by reserpine 1 mg/kg s.c. were examined. Sibutramine (monoamine reuptake inhibitor) 10 mg/kg p.o., methamphetamine (monoamine releaser) 1 mg/kg, quinpirole (dopamine D2 receptor agonist) 10 mg/kg i.p., and SKF 38393 (dopamine D1 receptor agonist) 10 mg/kg i.p. each antagonized the reserpine-induced lowering of hippocampal theta wave frequency in rats. Moreover, the combined administration of SKF 38393 1 mg/kg i.p. and quinpirole 1 mg/kg i.p. synergistically antagonized a reserpine-induced lowering of this frequency. Dosulepin, amitriptyline, and desipramine, which are weak inhibitors of dopamine reuptake, each had little effect on the reserpine-induced lowering of theta wave frequency at a dose of 40 mg/kg p.o. Furthermore, atropine (muscarinic anticholinergic drug) 20 mg/kg p.o. decreased theta wave power in the low-frequency range following a shift to the lower range by reserpine. A positive correlation was observed for each of the above drugs between a reversal of reserpine-induced lowering of theta wave frequency and a reversal of impairment of reserpine-induced conditioned avoidance responses (ACAR) in rats. These results suggest that the reserpine-induced lowering of hippocampal theta wave frequency plays a role in the impairment of reserpine-induced ACAR, and that dopamine D1 and D2 receptors play important roles in antagonizing this lowering of frequency.

Cauchy problem with general discontinuous initial data along a smooth curve for 2-d Euler system

NASA Astrophysics Data System (ADS)

Chen, Shuxing; Li, Dening

2014-09-01

We study the Cauchy problems for the isentropic 2-d Euler system with discontinuous initial data along a smooth curve. All three singularities are present in the solution: shock wave, rarefaction wave and contact discontinuity. We show that the usual restrictive high order compatibility conditions for the initial data are automatically satisfied. The local existence of piecewise smooth solution containing all three waves is established.

Topological guiding of elastic waves in phononic metamaterials based on 2D pentamode structures.

PubMed

Guo, Yuning; Dekorsy, Thomas; Hettich, Mike

2017-12-22

A topological state with protected propagation of elastic waves is achieved by appropriately engineering a phononic metamaterial based on 2D pentamode structures in silicon. Gapless edge states in the designed structure, which are characterized by pseudospin-dependent transport, provide backscattering-immune propagation of the elastic wave along bend paths. The role of the states responsible for forward and backward transfer can be interchanged by design.

Body and Surface Wave Modeling of Observed Seismic Events. Part 2.

DTIC Science & Technology

1987-05-12

is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical S coordinates in an asymptotic form which...using line source (2-D) theory. It is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical...generating synthetic point-source seismograms for shear dislocation sources using line source (2-D) theory. It is based on expanding the complete three

Design and analysis of tubular permanent magnet linear generator for small-scale wave energy converter

NASA Astrophysics Data System (ADS)

Kim, Jeong-Man; Koo, Min-Mo; Jeong, Jae-Hoon; Hong, Keyyong; Cho, Il-Hyoung; Choi, Jang-Young

2017-05-01

This paper reports the design and analysis of a tubular permanent magnet linear generator (TPMLG) for a small-scale wave-energy converter. The analytical field computation is performed by applying a magnetic vector potential and a 2-D analytical model to determine design parameters. Based on analytical solutions, parametric analysis is performed to meet the design specifications of a wave-energy converter (WEC). Then, 2-D FEA is employed to validate the analytical method. Finally, the experimental result confirms the predictions of the analytical and finite element analysis (FEA) methods under regular and irregular wave conditions.

Dispersion relations with crossing symmetry for {pi}{pi}D- and F1-wave amplitudes

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

Kaminski, R.

Results of implementation of dispersion relations with imposed crossing symmetry condition to description of {pi}{pi}D and F1 wave amplitudes are presented. We use relations with only one subtraction what leads to small uncertainties of results and to strong constraints for tested {pi}{pi} amplitudes. Presented equations are similar to those with one subtraction (so called GKPY equations) and to those with two subtractions (the Roy's equations) for the S and P waves. Numerical calculations are done with the S and P wave input amplitudes tested already with use of the Roy's and GKPY equations.

Working towards a numerical solver for seismic wave propagation in unsaturated porous media

NASA Astrophysics Data System (ADS)

Boxberg, Marc S.; Friederich, Wolfgang

2017-04-01

Modeling the propagation of seismic waves in porous media gets more and more popular in the seismological community. However, it is still a challenging task in the field of computational seismology. Nevertheless, it is important to account for the fluid content of, e.g., reservoir rocks or soils, and the interaction between the fluid and the rock or between different immiscible fluids to accurately describe seismic wave propagation through such porous media. Often, numerical models are based on the elastic wave equation and some might include artificially introduced attenuation. This simplifies the computation, because it only approximates the physics behind that problem. However, the results are also simplified and could miss phenomena and lack accuracy in some applications. We present a numerical solver for wave propagation in porous media saturated by two immiscible fluids. It is based on Biot's theory of poroelasticity and accounts for macroscopic flow that occurs on the same scale as the wavelength of the seismic waves. Fluid flow is described by a Darcy type flow law and interactions between the fluids by means of capillary pressure curve models. In addition, consistent boundary conditions on interfaces between poroelastic media and elastic or acoustic media are derived from this poroelastic theory itself. The poroelastic solver is integrated into the larger software package NEXD that uses the nodal discontinuous Galerkin method to solve wave equations in 1D, 2D, and 3D on a mesh of linear (1D), triangular (2D), or tetrahedral (3D) elements. Triangular and tetrahedral elements have great advantages as soon as the model has a complex structure, like it is often the case for geologic models. We illustrate the capabilities of the codes by numerical examples. This work can be applied to various scientific questions in, e.g., exploration and monitoring of hydrocarbon or geothermal reservoirs as well as CO2 storage sites.

Hydro and morphodynamic simulations for probabilistic estimates of munitions mobility

NASA Astrophysics Data System (ADS)

Palmsten, M.; Penko, A.

2017-12-01

Probabilistic estimates of waves, currents, and sediment transport at underwater munitions remediation sites are necessary to constrain probabilistic predictions of munitions exposure, burial, and migration. To address this need, we produced ensemble simulations of hydrodynamic flow and morphologic change with Delft3D, a coupled system of wave, circulation, and sediment transport models. We have set up the Delft3D model simulations at the Army Corps of Engineers Field Research Facility (FRF) in Duck, NC, USA. The FRF is the prototype site for the near-field munitions mobility model, which integrates far-field and near-field field munitions mobility simulations. An extensive array of in-situ and remotely sensed oceanographic, bathymetric, and meteorological data are available at the FRF, as well as existing observations of munitions mobility for model testing. Here, we present results of ensemble Delft3D hydro- and morphodynamic simulations at Duck. A nested Delft3D simulation runs an outer grid that extends 12-km in the along-shore and 3.7-km in the cross-shore with 50-m resolution and a maximum depth of approximately 17-m. The inner nested grid extends 3.2-km in the along-shore and 1.2-km in the cross-shore with 5-m resolution and a maximum depth of approximately 11-m. The inner nested grid initial model bathymetry is defined as the most recent survey or remotely sensed estimate of water depth. Delft3D-WAVE and FLOW is driven with spectral wave measurements from a Waverider buoy in 17-m depth located on the offshore boundary of the outer grid. The spectral wave output and the water levels from the outer grid are used to define the boundary conditions for the inner nested high-resolution grid, in which the coupled Delft3D WAVE-FLOW-MORPHOLOGY model is run. The ensemble results are compared to the wave, current, and bathymetry observations collected at the FRF.

Quantum Assisted Learning for Registration of MODIS Images

NASA Astrophysics Data System (ADS)

Pelissier, C.; Le Moigne, J.; Fekete, G.; Halem, M.

2017-12-01

The advent of the first large scale quantum annealer by D-Wave has led to an increased interest in quantum computing. However, the quantum annealing computer of the D-Wave is limited to either solving Quadratic Unconstrained Binary Optimization problems (QUBOs) or using the ground state sampling of an Ising system that can be produced by the D-Wave. These restrictions make it challenging to find algorithms to accelerate the computation of typical Earth Science applications. A major difficulty is that most applications have continuous real-valued parameters rather than binary. Here we present an exploratory study using the ground state sampling to train artificial neural networks (ANNs) to carry out image registration of MODIS images. The key idea to using the D-Wave to train networks is that the quantum chip behaves thermally like Boltzmann machines (BMs), and BMs are known to be successful at recognizing patterns in images. The ground state sampling of the D-Wave also depends on the dynamics of the adiabatic evolution and is subject to other non-thermal fluctuations, but the statistics are thought to be similar and ANNs tend to be robust under fluctuations. In light of this, the D-Wave ground state sampling is used to define a Boltzmann like generative model and is investigated to register MODIS images. Image intensities of MODIS images are transformed using a Discrete Cosine Transform and used to train a several layers network to learn how to align images to a reference image. The network layers consist of an initial sigmoid layer acting as a binary filter of the input followed by a strict binarization using Bernoulli sampling, and then fed into a Boltzmann machine. The output is then classified using a soft-max layer. Results are presented and discussed.

Scalar resonances in a unitary {pi}{pi} S-wave model for D{sup +} {r_arrow} {pi}{sup+}{pi}{sup-}{pi}{sup+}.

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

Boito, D. R.; Dedonder, J.-P.; El-Bennich, B.

We propose a model for D{sup +} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup +} decays following experimental results which indicate that the two-pion interaction in the S wave is dominated by the scalar resonances f{sub 0}(600)/{sigma} and f{sub 0}(980). The weak decay amplitude for D{sup +} {yields} R{pi}{sup +}, where R is a resonance that subsequently decays into {pi}{sup +}{pi}{sup -}, is constructed in a factorization approach. In the S wave, we implement the strong decay R {yields} {pi}{sup +}{pi}{sup -} by means of a scalar form factor. This provides a unitary description of the pion-pion interaction in the entire kinematically allowedmore » mass range m{sub {pi}{pi}}{sup 2} from threshold to about 3 GeV{sup 2}. In order to reproduce the experimental Dalitz plot for D{sup +} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup +}, we include contributions beyond the S wave. For the P wave, dominated by the {rho}(770){sup 0}, we use a Breit-Wigner description. Higher waves are accounted for by using the usual isobar prescription for the f{sub 2}(1270) and {rho}(1450){sup 0}. The major achievement is a good reproduction of the experimental m{sub {pi}{pi}}{sup 2} distribution, and of the partial as well as the total D{sup +} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup +} branching ratios. Our values are generally smaller than the experimental ones. We discuss this shortcoming and, as a by-product, we predict a value for the poorly known D {yields} {sigma} transition form factor at q{sup 2} = m{sub {pi}}{sup 2}.« less

Scalar resonances in a unitary {pi}{pi} S-wave model for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +}

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

Boito, D. R.; Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05315-970, Sao Paulo, SP; Dedonder, J.-P.

We propose a model for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +} decays following experimental results which indicate that the two-pion interaction in the S wave is dominated by the scalar resonances f{sub 0}(600)/{sigma} and f{sub 0}(980). The weak decay amplitude for D{sup +}{yields}R{pi}{sup +}, where R is a resonance that subsequently decays into {pi}{sup +}{pi}{sup -}, is constructed in a factorization approach. In the S wave, we implement the strong decay R{yields}{pi}{sup +}{pi}{sup -} by means of a scalar form factor. This provides a unitary description of the pion-pion interaction in the entire kinematically allowed mass range m{sub {pi}}{sub {pi}}{sup 2}more » from threshold to about 3 GeV{sup 2}. In order to reproduce the experimental Dalitz plot for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +}, we include contributions beyond the S wave. For the P wave, dominated by the {rho}(770){sup 0}, we use a Breit-Wigner description. Higher waves are accounted for by using the usual isobar prescription for the f{sub 2}(1270) and {rho}(1450){sup 0}. The major achievement is a good reproduction of the experimental m{sub {pi}}{sub {pi}}{sup 2} distribution, and of the partial as well as the total D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +} branching ratios. Our values are generally smaller than the experimental ones. We discuss this shortcoming and, as a by-product, we predict a value for the poorly known D{yields}{sigma} transition form factor at q{sup 2}=m{sub {pi}}{sup 2}.« less

Analysis of Site Effect in the Izmit Basin of Turkey by Wave Propagation Simulation Using the Spectral Element Method: Preliminary Results

NASA Astrophysics Data System (ADS)

Firtana Elcomert, K.; Kocaoglu, A. H.

2013-12-01

Sedimentary basins generally cause significant ground motion amplification during an earthquake. Along with the resonance controlled by the impedance contrast between the sedimentary cover and bedrock, surface waves generated within the basin make the waveforms more complex and longer in duration. When a dense network of weak and/or strong motion sensors is available, site effect or more specifically sedimentary basin amplification can be directly estimated experimentally provided that significant earthquakes occur during the period of study. Alternatively, site effect can be investigated through simulation of ground motion. The objective of this study is to investigate the 2-D and/or 3-D site effect in the Izmit Basin located in the eastern Marmara region of Turkey, using the currently available bedrock topography and shear-wave velocity data. The Izmit Basin was formed in Plio-Quaternary period and is known to be controlled by the northern branch of the North Anatolian Fault Zone. A thorough analysis of seismic hazard is important since the city of Izmit and its metropolitan area is located in this region. This work presents some of the preliminary results obtained from 2-D and 3-D seismic wave propagation simulations using the spectral element method, which is based on high order polynomial approximation of the weak formulation of the wave equation. In this study, the numerical simulations were carried out with SPECFEM2D/3D program. Comparison of seismograms recorded on the top of sedimentary layer with those recorded on the bedrock show more complex waveforms with higher amplitudes on seismograms recorded at the free surface. Furthermore, modeling clearly reveals that observed seismograms include surface waves whose excitation is clearly related with the basin geometry.

Spin-waves in thin films with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Diep, H. T.; El Hog, Sahbi; Puszkarski, Henryk

2018-05-01

Using the Green's function method, we calculate the spin-wave (SW) spectrum in a thin film with quantum Heisenberg spins interacting with each other via an exchange interaction J and a Dzyaloshinskii-Moriya interaction of magnitude D. Due to the competition between J and D, the ground state is non collinear. We show that for large D, the first mode in the SW spectrum is proportional to the in plane wave-vector k at the limit k tending to zero. For small D, it is proportional to k2. We show that the surface modes may occur depending on the surface exchange interaction. We calculate the layer magnetizations at temperature T and the transition temperature as a function of the film thickness.

Two different kinds of rogue waves in weakly crossing sea states

NASA Astrophysics Data System (ADS)

Ruban, V. P.

2009-06-01

Formation of giant waves in sea states with two spectral maxima centered at close wave vectors k0±Δk/2 in the Fourier plane is numerically simulated using the fully nonlinear model for long-crested water waves [V. P. Ruban, Phys. Rev. E 71, 055303(R) (2005)]. Depending on an angle θ between the vectors k0 and Δk , which determines a typical orientation of interference stripes in the physical plane, rogue waves arise having different spatial structure. If θ≲arctan(1/2) , then typical giant waves are relatively long fragments of essentially two-dimensional (2D) ridges, separated by wide valleys and consisting of alternating oblique crests and troughs. At nearly perpendicular k0 and Δk , the interference minima develop to coherent structures similar to the dark solitons of the nonlinear Schrodinger equation, and a 2D freak wave looks much as a piece of a one-dimensional freak wave bounded in the transversal direction by two such dark solitons.

Development of Wave Turbine Emulator in a Laboratory Environment

NASA Astrophysics Data System (ADS)

Vinatha, U.; Vittal K, P.

2013-07-01

Wave turbine emulator (WTE) is an important equipment for developing wave energy conversion system. The emulator reflects the actual behavior of the wave turbine by reproducing the characteristics of real wave turbine without reliance on natural wave resources and actual wave turbine. It offers a controllable test environment that allows the evaluation and improvement of control schemes for electric generators. The emulator can be used for research applications to drive an electrical generator in a similar way as a practical wave turbine. This article presents the development of a WTE in a laboratory environment and studies on the behavior of electrical generator coupled to the emulator. The structure of a WTE consists of a PC where the characteristics of the turbine are implemented, ac drive to emulate the turbine rotor, feedback mechanism from the drive and power electronic equipment to control the drive. The feedback signal is acquired by the PC through an A/D converter, and the signal for driving the power electronic device comes from the PC through a D/A converter.

Automated liver elasticity calculation for 3D MRE

NASA Astrophysics Data System (ADS)

Dzyubak, Bogdan; Glaser, Kevin J.; Manduca, Armando; Ehman, Richard L.

2017-03-01

Magnetic Resonance Elastography (MRE) is a phase-contrast MRI technique which calculates quantitative stiffness images, called elastograms, by imaging the propagation of acoustic waves in tissues. It is used clinically to diagnose liver fibrosis. Automated analysis of MRE is difficult as the corresponding MRI magnitude images (which contain anatomical information) are affected by intensity inhomogeneity, motion artifact, and poor tissue- and edge-contrast. Additionally, areas with low wave amplitude must be excluded. An automated algorithm has already been successfully developed and validated for clinical 2D MRE. 3D MRE acquires substantially more data and, due to accelerated acquisition, has exacerbated image artifacts. Also, the current 3D MRE processing does not yield a confidence map to indicate MRE wave quality and guide ROI selection, as is the case in 2D. In this study, extension of the 2D automated method, with a simple wave-amplitude metric, was developed and validated against an expert reader in a set of 57 patient exams with both 2D and 3D MRE. The stiffness discrepancy with the expert for 3D MRE was -0.8% +/- 9.45% and was better than discrepancy with the same reader for 2D MRE (-3.2% +/- 10.43%), and better than the inter-reader discrepancy observed in previous studies. There were no automated processing failures in this dataset. Thus, the automated liver elasticity calculation (ALEC) algorithm is able to calculate stiffness from 3D MRE data with minimal bias and good precision, while enabling stiffness measurements to be fully reproducible and to be easily performed on the large 3D MRE datasets.

Geospace ionosphere research with a MF/HF radio instrument on a cubesat

NASA Astrophysics Data System (ADS)

Kallio, E. J.; Aikio, A. T.; Alho, M.; Fontell, M.; van Gijlswijk, R.; Kauristie, K.; Kestilä, A.; Koskimaa, P.; Makela, J. S.; Mäkelä, M.; Turunen, E.; Vanhamäki, H.

2016-12-01

Modern technology provides new possibilities to study geospace and its ionosphere, using spacecraft and and computer simulations. A type of nanosatellites, CubeSats, provide a cost effective possibility to provide in-situ measurements in the ionosphere. Moreover, combined CubeSat observations with ground-based observations gives a new view on auroras and associated electromagnetic phenomena. Especially joint and active CubeSat - ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere. Furthermore using several CubeSats to form satellite constellations enables much higher temporal resolution. At the same time, increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionospheric model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatiotemporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests. We present computational simulation results and measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat whose novel AM radio instrument measures HF and MF waves. The cubesat, which contains also a white light aurora camera, is planned to be launched in 2017 (http://www.suomi100satelliitti.fi/eng). We have modelled the propagation of the radio waves, both ground generated man-made waves and space formed space weather related waves, through the 3D arctic ionosphere with (1) a new 3D ray tracing model and (2) a new 3D full kinetic electromagnetic simulation. These simulations are used to analyse the origin of the radio waves observed by the MH/HF radio instrument and, consequently, to derive information about the 3D ionosphere and its spatial and temporal variations.

Geometry and velocity structure of the northern Costa Rica seismogenic zone from 3D local earthquake tomography

NASA Astrophysics Data System (ADS)

Deshon, H. R.; Schwartz, S. Y.; Newman, A. V.; Dorman, L. M.; Protti, M.; Gonzalez, V.

2003-12-01

We present results of a 3D local earthquake tomography study of the Middle America Trench seismogenic zone in northern Costa Rica. Local earthquake tomography can provide constraints on the updip, downdip, and lateral variability of seismicity and P- and S-wave velocities; these constraints may in turn provide information on compositional and/or mechanical variability along the seismogenic zone. We use arrival time data recorded by the Nicoya Peninsula seismic array, part of the Costa Rica seismogenic zone experiment (CRSEIZE), a collaborative effort undertaken to better understand seismogenic behavior at the Costa Rica subduction zone using data from land and ocean bottom seismic arrays, oceanic fluid flux meters, and GPS receivers. We invert ˜10,000 P-wave and S-wave arrival times from 475 well-recorded local earthquakes (GAP < 180° , >8 P-wave arrivals) to solve for the best-fitting 1D P- and S-wave velocity models, station corrections, and hypocenters using the algorithm VELEST. These 1D velocity models are used as a starting models for 3D simultaneous inversion using the algorithm SIMULPS14. Preliminary P-wave inversions contain a positive velocity anomaly dipping beneath the Nicoya Peninsula, interpreted as the subducting Cocos Plate. Earthquakes occur in a narrow band along the slab-continent interface and are consistent with the results of Newman et al. (2002). The updip limit of seismicity occurs ˜5 km deeper and 5-10 km landward in the northern vs. the southern Nicoya Peninsula, and this shift spatially correlates to the change from Cocos-Nazca to East Pacific Rise derived oceanic plate. P-wave velocities in the upper 5-10 km of the model are consistent with the geology of the Nicoya Peninsula. We will correlate relocated microseismicity to previously noted variability in oceanic plate morphology, heat flow, fluid flow, and thermal structure and compare the resulting P- and S-wave velocity models to wide-angle refraction models and hypothesized mantle wedge compositions.

Fluid nonlinear frequency shift of nonlinear ion acoustic waves in multi-ion species plasmas in the small wave number region

NASA Astrophysics Data System (ADS)

Feng, Q. S.; Xiao, C. Z.; Wang, Q.; Zheng, C. Y.; Liu, Z. J.; Cao, L. H.; He, X. T.

2016-08-01

The properties of the nonlinear frequency shift (NFS), especially the fluid NFS from the harmonic generation of the ion-acoustic wave (IAW) in multi-ion species plasmas, have been researched by Vlasov simulation. Pictures of the nonlinear frequency shift from harmonic generation and particle trapping are shown to explain the mechanism of NFS qualitatively. The theoretical model of the fluid NFS from harmonic generation in multi-ion species plasmas is given, and the results of Vlasov simulation are consistent with the theoretical result of multi-ion species plasmas. When the wave number k λD e is small, such as k λD e=0.1 , the fluid NFS dominates in the total NFS and will reach as large as nearly 15 % when the wave amplitude |e ϕ / Te|˜0.1 , which indicates that in the condition of small k λD e , the fluid NFS dominates in the saturation of stimulated Brillouin scattering, especially when the nonlinear IAW amplitude is large.

Three-dimensional continuous particle focusing in a microfluidic channel via standing surface acoustic waves (SSAW).

PubMed

Shi, Jinjie; Yazdi, Shahrzad; Lin, Sz-Chin Steven; Ding, Xiaoyun; Chiang, I-Kao; Sharp, Kendra; Huang, Tony Jun

2011-07-21

Three-dimensional (3D) continuous microparticle focusing has been achieved in a single-layer polydimethylsiloxane (PDMS) microfluidic channel using a standing surface acoustic wave (SSAW). The SSAW was generated by the interference of two identical surface acoustic waves (SAWs) created by two parallel interdigital transducers (IDTs) on a piezoelectric substrate with a microchannel precisely bonded between them. To understand the working principle of the SSAW-based 3D focusing and investigate the position of the focal point, we computed longitudinal waves, generated by the SAWs and radiated into the fluid media from opposite sides of the microchannel, and the resultant pressure and velocity fields due to the interference and reflection of the longitudinal waves. Simulation results predict the existence of a focusing point which is in good agreement with our experimental observations. Compared with other 3D focusing techniques, this method is non-invasive, robust, energy-efficient, easy to implement, and applicable to nearly all types of microparticles.

AORSA full wave calculations of helicon waves in DIII-D and ITER

NASA Astrophysics Data System (ADS)

Lau, C.; Jaeger, E. F.; Bertelli, N.; Berry, L. A.; Green, D. L.; Murakami, M.; Park, J. M.; Pinsker, R. I.; Prater, R.

2018-06-01

Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D, FNSF, and DEMO tokamaks. Previous ray tracing modeling using GENRAY predicts strong single pass absorption and current drive in the mid-radius region on DIII-D in high beta tokamak discharges. The full wave code AORSA, which is valid to all order of Larmor radius and can resolve arbitrary ion cyclotron harmonics, has been used to validate the ray tracing technique. If the scrape-off-layer (SOL) is ignored in the modeling, AORSA agrees with GENRAY in both the amplitude and location of driven current for DIII-D and ITER cases. These models also show that helicon current drive can possibly be an efficient current drive actuator for ITER. Previous GENRAY analysis did not include the SOL. AORSA has also been used to extend the simulations to include the SOL and to estimate possible power losses of helicon waves in the SOL. AORSA calculations show that another mode can propagate in the SOL and lead to significant (~10%–20%) SOL losses at high SOL densities. Optimizing the SOL density profile can reduce these SOL losses to a few percent.

AORSA full wave calculations of helicon waves in DIII-D and ITER

DOE PAGES

Lau, Cornwall; Jaeger, E.F.; Bertelli, Nicola; ...

2018-04-11

Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D, FNSF, and DEMO tokamaks. Previous ray tracing modeling using GENRAY predicts strong single pass absorption and current drive in the mid-radius region on DIII-D in high beta tokamak discharges. The full wave code AORSA, which is valid to all order of Larmor radius and can resolve arbitrary ion cyclotron harmonics, has been used to validate the ray tracing technique. If the scrape-off-layer (SOL) is ignored in the modeling, AORSA agrees with GENRAY in both the amplitude and location of driven current for DIII-D and ITER cases.more » These models also show that helicon current drive can possibly be an efficient current drive actuator for ITER. Previous GENRAY analysis did not include the SOL. AORSA has also been used to extend the simulations to include the SOL and to estimate possible power losses of helicon waves in the SOL. AORSA calculations show that another mode can propagate in the SOL and lead to significant (~10-20%) SOL losses at high SOL densities. Optimizing the SOL density profile can reduce these SOL losses to a few percent.« less

Plane Wave SH₀ Piezoceramic Transduction Optimized Using Geometrical Parameters.

PubMed

Boivin, Guillaume; Viens, Martin; Belanger, Pierre

2018-02-10

Structural health monitoring is a prominent alternative to the scheduled maintenance of safety-critical components. The nondispersive nature as well as the through-thickness mode shape of the fundamental shear horizontal guided wave mode (SH 0 ) make it a particularly attractive candidate for ultrasonic guided wave structural health monitoring. However, plane wave excitation of SH 0 at a high level of purity remains challenging because of the existence of the fundamental Lamb modes (A 0 and S 0 ) below the cutoff frequency thickness product of high-order modes. This paper presents a piezoelectric transducer concept optimized for plane SH 0 wave transduction based on the transducer geometry. The transducer parameter exploration was initially performed using a simple analytical model. A 3D multiphysics finite element model was then used to refine the transducer design. Finally, an experimental validation was conducted with a 3D laser Doppler vibrometer system. The analytical model, the finite element model, and the experimental measurement showed excellent agreement. The modal selectivity of SH 0 within a 20 ∘ beam opening angle at the design frequency of 425 kHz in a 1.59 mm aluminum plate was 23 dB, and the angle of the 6 dB wavefront was 86 ∘ .

AORSA full wave calculations of helicon waves in DIII-D and ITER

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

Lau, Cornwall; Jaeger, E.F.; Bertelli, Nicola

Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D, FNSF, and DEMO tokamaks. Previous ray tracing modeling using GENRAY predicts strong single pass absorption and current drive in the mid-radius region on DIII-D in high beta tokamak discharges. The full wave code AORSA, which is valid to all order of Larmor radius and can resolve arbitrary ion cyclotron harmonics, has been used to validate the ray tracing technique. If the scrape-off-layer (SOL) is ignored in the modeling, AORSA agrees with GENRAY in both the amplitude and location of driven current for DIII-D and ITER cases.more » These models also show that helicon current drive can possibly be an efficient current drive actuator for ITER. Previous GENRAY analysis did not include the SOL. AORSA has also been used to extend the simulations to include the SOL and to estimate possible power losses of helicon waves in the SOL. AORSA calculations show that another mode can propagate in the SOL and lead to significant (~10-20%) SOL losses at high SOL densities. Optimizing the SOL density profile can reduce these SOL losses to a few percent.« less

Seismic Wave Propagation in Fully Anisotropic Axisymmetric Media: Applications and Practical Considerations

NASA Astrophysics Data System (ADS)

van Driel, Martin; Nissen-Meyer, Tarje; Stähler, Simon; Waszek, Lauren; Hempel, Stefanie; Auer, Ludwig; Deuss, Arwen

2014-05-01

We present a numerical method to compute high-frequency 3D elastic waves in fully anisotropic axisymmetric media. The method is based on a decomposition of the wavefield into a series of uncoupled 2D equations, for which the dependence of the wavefield on the azimuth can be solved analytically. The remaining 2D problems are then solved using a spectral element method (AxiSEM). AxiSEM was recently published open-source (Nissen-Meyer et al. 2014) as a production ready code capable to compute global seismic wave propagation up to frequencies of ~2Hz. It accurately models visco-elastic dissipation and anisotropy (van Driel et al., submitted to GJI) and runs efficiently on HPC resources using up to 10K cores. At very short period, the Fresnel Zone of body waves is narrow and sensitivity is focused around the geometrical ray. In cases where the azimuthal variations of structural heterogeneity exhibit long spatial wavelengths, so called 2.5D simulations (3D wavefields in 2D models) provide a good approximation. In AxiSEM, twodimensional variations in the source-receiver plane are effectively modelled as ringlike structures extending in the out-of-plane direction. In contrast to ray-theory, which is widely used in high-frequency applications, AxiSEM provides complete waveforms, thus giving access to frequency dependency, amplitude variations, and peculiar wave effects such as diffraction and caustics. Here we focus on the practical implications of the inherent axisymmetric geometry and show how the 2.5D-features of our method method can be used to model realistic anisotropic structures, by applying it to problems such as the D" region and the inner core.

A 1D-2D Shallow Water Equations solver for discontinuous porosity field based on a Generalized Riemann Problem

NASA Astrophysics Data System (ADS)

Ferrari, Alessia; Vacondio, Renato; Dazzi, Susanna; Mignosa, Paolo

2017-09-01

A novel augmented Riemann Solver capable of handling porosity discontinuities in 1D and 2D Shallow Water Equation (SWE) models is presented. With the aim of accurately approximating the porosity source term, a Generalized Riemann Problem is derived by adding an additional fictitious equation to the SWEs system and imposing mass and momentum conservation across the porosity discontinuity. The modified Shallow Water Equations are theoretically investigated, and the implementation of an augmented Roe Solver in a 1D Godunov-type finite volume scheme is presented. Robust treatment of transonic flows is ensured by introducing an entropy fix based on the wave pattern of the Generalized Riemann Problem. An Exact Riemann Solver is also derived in order to validate the numerical model. As an extension of the 1D scheme, an analogous 2D numerical model is also derived and validated through test cases with radial symmetry. The capability of the 1D and 2D numerical models to capture different wave patterns is assessed against several Riemann Problems with different wave patterns.

The Λc(2860), Λc(2880), Ξc(3055) and Ξc(3080) as D-wave baryon states in QCD

NASA Astrophysics Data System (ADS)

Wang, Zhi-Gang

2018-01-01

In this article, we tentatively assign the Λc (2860), Λc (2880), Ξc (3055) and Ξc (3080) to be the D-wave baryon states with the spin-parity JP = 3/2+, 5/2 +, 3/2+ and 5/2+, respectively, and study their masses and pole residues with the QCD sum rules in a systematic way by constructing three-types interpolating currents with the quantum numbers (Lρ ,Lλ) = (0 , 2), (2 , 0) and (1 , 1), respectively. The present predictions favor assigning the Λc (2860), Λc (2880), Ξc (3055) and Ξc (3080) to be the D-wave baryon states with the quantum numbers (Lρ ,Lλ) = (0 , 2) and JP = 3/2+, 5/2+, 3/2+ and 5/2+, respectively. While the predictions for the masses of the (Lρ ,Lλ) = (2 , 0) and (1 , 1) D-wave Λc and Ξc states can be confronted to the experimental data in the future.

TRILEX and G W +EDMFT approach to d -wave superconductivity in the Hubbard model

NASA Astrophysics Data System (ADS)

Vučičević, J.; Ayral, T.; Parcollet, O.

2017-09-01

We generalize the recently introduced TRILEX approach (TRiply irreducible local EXpansion) to superconducting phases. The method treats simultaneously Mott and spin-fluctuation physics using an Eliashberg theory supplemented by local vertex corrections determined by a self-consistent quantum impurity model. We show that, in the two-dimensional Hubbard model, at strong coupling, TRILEX yields a d -wave superconducting dome as a function of doping. Contrary to the standard cluster dynamical mean field theory (DMFT) approaches, TRILEX can capture d -wave pairing using only a single-site effective impurity model. We also systematically explore the dependence of the superconducting temperature on the bare dispersion at weak coupling, which shows a clear link between strong antiferromagnetic (AF) correlations and the onset of superconductivity. We identify a combination of hopping amplitudes particularly favorable to superconductivity at intermediate doping. Finally, we study within G W +EDMFT the low-temperature d -wave superconducting phase at strong coupling in a region of parameter space with reduced AF fluctuations.

Wave Function and Emergent SU(2) Symmetry in the ν_{T}=1 Quantum Hall Bilayer.

PubMed

Lian, Biao; Zhang, Shou-Cheng

2018-02-16

We propose a trial wave function for the quantum Hall bilayer system of total filling factor ν_{T}=1 at a layer distance d to magnetic length ℓ ratio d/ℓ=κ_{c1}≈1.1, where the lowest charged excitation is known to have a level crossing. The wave function has two-particle correlations, which fit well with those in previous numerical studies, and can be viewed as a Bose-Einstein condensate of free excitons formed by composite bosons and anticomposite bosons in different layers. We show the free nature of these excitons indicating an emergent SU(2) symmetry for the composite bosons at d/ℓ=κ_{c1}, which leads to the level crossing in low-lying charged excitations. We further show the overlap between the trial wave function, and the ground state of a small size exact diagonalization is peaked near d/ℓ=κ_{c1}, which supports our theory.

Importance of d-wave contributions in the charge symmetry breaking reaction dd →4Heπ0

NASA Astrophysics Data System (ADS)

Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F. S.; Berłowski, M.; Bondar, A.; Büscher, M.; Calén, H.; Ciepał, I.; Clement, H.; Czerwiński, E.; Demmich, K.; Engels, R.; Erven, A.; Erven, W.; Eyrich, W.; Fedorets, P.; Föhl, K.; Fransson, K.; Goldenbaum, F.; Goswami, A.; Grigoryev, K.; Gullström, C.-O.; Hanhart, C.; Heijkenskjöld, L.; Hejny, V.; Hüsken, N.; Jarczyk, L.; Johansson, T.; Kamys, B.; Kemmerling, G.; Khatri, G.; Khoukaz, A.; Khreptak, O.; Kirillov, D. A.; Kistryn, S.; Kleines, H.; Kłos, B.; Krzemień, W.; Kulessa, P.; Kupść, A.; Kuzmin, A.; Lalwani, K.; Lersch, D.; Lorentz, B.; Magiera, A.; Maier, R.; Marciniewski, P.; Mariański, B.; Morsch, H.-P.; Moskal, P.; Ohm, H.; Parol, W.; Perez del Rio, E.; Piskunov, N. M.; Prasuhn, D.; Pszczel, D.; Pysz, K.; Pyszniak, A.; Ritman, J.; Roy, A.; Rudy, Z.; Rundel, O.; Sawant, S.; Schadmand, S.; Schätti-Ozerianska, I.; Sefzick, T.; Serdyuk, V.; Shwartz, B.; Sitterberg, K.; Skorodko, T.; Skurzok, M.; Smyrski, J.; Sopov, V.; Stassen, R.; Stepaniak, J.; Stephan, E.; Sterzenbach, G.; Stockhorst, H.; Ströher, H.; Szczurek, A.; Trzciński, A.; Wolke, M.; Wrońska, A.; Wüstner, P.; Yamamoto, A.; Zabierowski, J.; Zieliński, M. J.; Złomańczuk, J.; Żuprański, P.; Żurek, M.; WASA-at-COSY Collaboration

2018-06-01

This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd →4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q = 60MeV. The determined differential cross section can be parametrized as d σ /d Ω = a + bcos2 ⁡θ*, where θ* is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a = (1.55 ± 0.46(stat) + 0.32 - 0.8 (syst)) pb /sr and b = (13.1 ± 2.1 (stat)-2.7+1.0 (syst)) pb /sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd →4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.

Investigation of hydroelastic ship responses of an ULOC in head seas

NASA Astrophysics Data System (ADS)

Wang, Xue-liang; Temarel, Pandeli; Hu, Jia-jun; Gu, Xue-kang

2016-10-01

Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed.

Landau damping in space plasmas

NASA Technical Reports Server (NTRS)

Thorne, Richard M.; Summers, Danny

1991-01-01

The Landau damping of electrostatic Langmuir waves and ion-acoustic waves in a hot, isotropic, nonmagnetized, generalized Lorentzian plasma is analyzed using the modified plasma dispersion function. Numerical solutions for the real and imaginary parts of the wave frequency omega sub 0 - (i)(gamma) have been obtained as a function of the normalized wave number (k)(lambda sub D), where lambda sub D is the electron Debye length. For both particle distributions the electrostatic modes are found to be strongly damped at short wavelengths. At long wavelengths, this damping becomes less severe, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. It is concluded that Landau damping of ion-acoustic waves is only slightly affected by the presence of a high energy tail, but is strongly dependent on the ion temperature.

Multiple scattering induced negative refraction of matter waves

PubMed Central

Pinsker, Florian

2016-01-01

Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to ‘untouchable’ quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging.

PubMed

Tiran, Elodie; Deffieux, Thomas; Correia, Mafalda; Maresca, David; Osmanski, Bruno-Felix; Sieu, Lim-Anna; Bergel, Antoine; Cohen, Ivan; Pernot, Mathieu; Tanter, Mickael

2015-11-07

Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable. Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients. The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8  ±  0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz(-1) cm(-1)). In shear wave elastography, the same multiplane wave configuration yields a 2.07  ±  0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in deep structures of the rodent brain.

Effective modeling and reverse-time migration for novel pure acoustic wave in arbitrary orthorhombic anisotropic media

NASA Astrophysics Data System (ADS)

Xu, Shigang; Liu, Yang

2018-03-01

The conventional pseudo-acoustic wave equations (PWEs) in arbitrary orthorhombic anisotropic (OA) media usually have coupled P- and SV-wave modes. These coupled equations may introduce strong SV-wave artifacts and numerical instabilities in P-wave simulation results and reverse-time migration (RTM) profiles. However, pure acoustic wave equations (PAWEs) completely decouple the P-wave component from the full elastic wavefield and naturally solve all the aforementioned problems. In this article, we present a novel PAWE in arbitrary OA media and compare it with the conventional coupled PWEs. Through decomposing the solution of the corresponding eigenvalue equation for the original PWE into an ellipsoidal differential operator (EDO) and an ellipsoidal scalar operator (ESO), the new PAWE in time-space domain is constructed by applying the combination of these two solvable operators and can effectively describe P-wave features in arbitrary OA media. Furthermore, we adopt the optimal finite-difference method (FDM) to solve the newly derived PAWE. In addition, the three-dimensional (3D) hybrid absorbing boundary condition (HABC) with some reasonable modifications is developed for reducing artificial edge reflections in anisotropic media. To improve computational efficiency in 3D case, we adopt graphic processing unit (GPU) with Compute Unified Device Architecture (CUDA) instead of traditional central processing unit (CPU) architecture. Several numerical experiments for arbitrary OA models confirm that the proposed schemes can produce pure, stable and accurate P-wave modeling results and RTM images with higher computational efficiency. Moreover, the 3D numerical simulations can provide us with a comprehensive and real description of wave propagation.

Sound Waves Induce Neural Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells via Ryanodine Receptor-Induced Calcium Release and Pyk2 Activation.

PubMed

Choi, Yura; Park, Jeong-Eun; Jeong, Jong Seob; Park, Jung-Keug; Kim, Jongpil; Jeon, Songhee

2016-10-01

Mesenchymal stem cells (MSCs) have shown considerable promise as an adaptable cell source for use in tissue engineering and other therapeutic applications. The aims of this study were to develop methods to test the hypothesis that human MSCs could be differentiated using sound wave stimulation alone and to find the underlying mechanism. Human bone marrow (hBM)-MSCs were stimulated with sound waves (1 kHz, 81 dB) for 7 days and the expression of neural markers were analyzed. Sound waves induced neural differentiation of hBM-MSC at 1 kHz and 81 dB but not at 1 kHz and 100 dB. To determine the signaling pathways involved in the neural differentiation of hBM-MSCs by sound wave stimulation, we examined the Pyk2 and CREB phosphorylation. Sound wave induced an increase in the phosphorylation of Pyk2 and CREB at 45 min and 90 min, respectively, in hBM-MSCs. To find out the upstream activator of Pyk2, we examined the intracellular calcium source that was released by sound wave stimulation. When we used ryanodine as a ryanodine receptor antagonist, sound wave-induced calcium release was suppressed. Moreover, pre-treatment with a Pyk2 inhibitor, PF431396, prevented the phosphorylation of Pyk2 and suppressed sound wave-induced neural differentiation in hBM-MSCs. These results suggest that specific sound wave stimulation could be used as a neural differentiation inducer of hBM-MSCs.

Stability of post-fertilization traveling waves

NASA Astrophysics Data System (ADS)

Flores, Gilberto; Plaza, Ramón G.

This paper studies the stability of a family of traveling wave solutions to the system proposed by Lane et al. [D.C. Lane, J.D. Murray, V.S. Manoranjan, Analysis of wave phenomena in a morphogenetic mechanochemical model and an application to post-fertilization waves on eggs, IMA J. Math. Appl. Med. Biol. 4 (4) (1987) 309-331], to model a pair of mechanochemical phenomena known as post-fertilization waves on eggs. The waves consist of an elastic deformation pulse on the egg's surface, and a free calcium concentration front. The family is indexed by a coupling parameter measuring contraction stress effects on the calcium concentration. This work establishes the spectral, linear and nonlinear orbital stability of these post-fertilization waves for small values of the coupling parameter. The usual methods for the spectral and evolution equations cannot be applied because of the presence of mixed partial derivatives in the elastic equation. Nonetheless, exponential decay of the directly constructed semigroup on the complement of the zero eigenspace is established. We show that small perturbations of the waves yield solutions to the nonlinear equations decaying exponentially to a phase-modulated traveling wave.

Sensitivity Tests Between Vs30 and Detailed Shear Wave Profiles Using 1D and 3D Site Response Analysis, Las Vegas Valley

NASA Astrophysics Data System (ADS)

West, Loyd Travis

Site characterization is an essential aspect of hazard analysis and the time-averaged shear-wave velocity to 30 m depth "Vs30" for site-class has become a critical parameter in site-specific and probabilistic hazard analysis. Yet, the general applicability of Vs30 can be ambiguous and much debate and research surround its application. In 2007, in part to mitigate the uncertainty associated with the use of Vs30 in Las Vegas Valley, the Clark County Building Department (CCBD) in collaboration with the Nevada System of Higher Education (NSHE) embarked on an endeavor to map Vs30 using a geophysical methods approach for a site-class microzonation map of over 500 square miles (1500 km2) in southern Nevada. The resulting dataset, described by Pancha et al. (2017), contains over 10,700 1D shear-wave-velocity-depth profiles (SWVP) that constitute a rich database of 3D shear-wave velocity structure that is both laterally and vertical heterogenous. This study capitalizes on the uniquely detailed and spatially dense CCBD database to carry out sensitivity tests on the detailed shear-wave-velocity-profiles and the Vs30 utilizing 1D and 3D site-response approaches. Sensitivity tests are derived from the 1D oscillator response of a single-degree-of-freedom-oscillator and from 3D finite-difference deterministic simulations up to 15 Hz frequency using similar model parameters. Results demonstrate that the detailed SWVP are amplifying ground motions by roughly 50% over the simple Vs30 models, above 4.6 Hz frequency. Numerical simulations also depict significant lateral resonance, focusing, and scattering from seismic energy attributed to the 3D small-scale heterogeneities of the shear-wave-velocity profiles that result in a 70% increase in peak ground velocity. Additionally, PGV ratio maps clearly establish that the increased amplification from the detailed SWVPs is consistent throughout the model space. As a corollary, this study demonstrates the use of finite-differencing numerical based methods to simulate ground motions at high frequencies, up to 15 Hz.

Phase control of spin waves based on a magnetic defect in a one-dimensional magnonic crystal

NASA Astrophysics Data System (ADS)

Baumgaertl, Korbinian; Watanabe, Sho; Grundler, Dirk

2018-04-01

Magnonic crystals are interesting for spin-wave based data processing. We investigate one-dimensional magnonic crystals (1D MCs) consisting of bistable Co 20 Fe 60 B 20 nanostripes separated by 75 nm wide air gaps. By adjusting the magnetic history, we program a single stripe of opposed magnetization in an otherwise saturated 1D MC. Its influence on propagating spin waves is studied via broadband microwave spectroscopy. Depending on an in-plane bias magnetic field, we observe spin wave phase shifts of up to almost π and field-controlled attenuation attributed to the reversed nanostripe. Our findings are of importance for magnetologics, where the control of spin wave phases is essential.

Variability in Benthic Exchange Rate, Depth, and Residence Time Beneath a Shallow Coastal Estuary

NASA Astrophysics Data System (ADS)

Russoniello, Christopher J.; Heiss, James W.; Michael, Holly A.

2018-03-01

Hydrodynamically driven benthic exchange of water between the water column and shallow seabed aquifer is a significant and dynamic component of coastal and estuarine fluid budgets. Associated exchange of solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times constrains coastal chemical cycling estimates. We present the first combined field, numerical, and analytical modeling investigation of wave-induced exchange. Temporal variability of exchange was calculated with data collected by instruments deployed in a shallow estuary for 11 days. Differential pressure sensors recorded pressure gradients across the seabed, and up- and down-looking ADCPs recorded currents and pressures to determine wave parameters, surface-water currents, and water depth. Wave-induced exchange was calculated (1) directly from differential pressure measurements, and indirectly with an analytical model based on wave parameters from (2) ADCP and (3) wind data. Wave-induced exchange from pressure measurements and ADCP-measured wave parameters matched well, but both exceeded wind-based values. Exchange induced by tidal pumping and current-bed form interaction—the other primary drivers in shallow coastal waters were calculated from tidal stage variation and ADCP-measured currents. Exchange from waves (mean = 20.0 cm/d; range = 1.75-92.3 cm/d) greatly exceeded exchange due to tides (mean = 3.7 cm/d) and current-bed form interaction (mean = 6.5 × 10-2 cm/d). Groundwater flow models showed aquifer properties affect wave-driven benthic exchange: residence time and depth increased and exchange rates decreased with increasing hydraulic diffusivity (ratio of aquifer permeability to compressibility). This new understanding of benthic exchange will help managers assess its control over chemical fluxes to marine systems.

Secretary of the Navy, Processor of Oceanography

DTIC Science & Technology

2009-07-20

earliest days of SOFAR transmissions. We proposed that scattering from internal waves could account for the penetration, and this has now been confirmed...related to change in obliquity (C2). D. Acoustic Noise generated by Ocean Waves . Farrell and I have found that the acoustic noise background in the...deep ocean down to 5 km is associated with short surface waves . There is some evidence for a noise minimum centered at 27 Hz (Dl, D2). This might be

Galerkin Spectral Method for the 2D Solitary Waves of Boussinesq Paradigm Equation

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

Christou, M. A.; Christov, C. I.

2009-10-29

We consider the 2D stationary propagating solitary waves of the so-called Boussinesq Paradigm equation. The fourth- order elliptic boundary value problem on infinite interval is solved by a Galerkin spectral method. An iterative procedure based on artificial time ('false transients') and operator splitting is used. Results are obtained for the shapes of the solitary waves for different values of the dispersion parameters for both subcritical and supercritical phase speeds.

Non-contact rapid optical coherence elastography by high-speed 4D imaging of elastic waves

NASA Astrophysics Data System (ADS)

Song, Shaozhen; Yoon, Soon Joon; Ambroziński, Łukasz; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T.; O'Donnell, Matthew; Wang, Ruikang K.

2017-02-01

Shear wave OCE (SW-OCE) uses an OCT system to track propagating mechanical waves, providing the information needed to map the elasticity of the target sample. In this study we demonstrate high speed, 4D imaging to capture transient mechanical wave propagation. Using a high-speed Fourier domain mode-locked (FDML) swept-source OCT (SS-OCT) system operating at 1.62 MHz A-line rate, the equivalent volume rate of mechanical wave imaging is 16 kvps (kilo-volumes per second), and total imaging time for a 6 x 6 x 3 mm volume is only 0.32 s. With a displacement sensitivity of 10 nanometers, the proposed 4D imaging technique provides sufficient temporal and spatial resolution for real-time optical coherence elastography (OCE). Combined with a new air-coupled, high-frequency focused ultrasound stimulator requiring no contact or coupling media, this near real-time system can provide quantitative information on localized viscoelastic properties. SW-OCE measurements are demonstrated on tissue-mimicking phantoms and porcine cornea under various intra-ocular pressures. In addition, elasticity anisotropy in the cornea is observed. Images of the mechanical wave group velocity, which correlates with tissue elasticity, show velocities ranging from 4-20 m/s depending on pressure and propagation direction. These initial results strong suggest that 4D imaging for real-time OCE may enable high-resolution quantitative mapping of tissue biomechanical properties in clinical applications.

Localization and oscillations of Majorana fermions in a two-dimensional electron gas coupled with d -wave superconductors

NASA Astrophysics Data System (ADS)

Ortiz, L.; Varona, S.; Viyuela, O.; Martin-Delgado, M. A.

2018-02-01

We study the localization and oscillation properties of the Majorana fermions that arise in a two-dimensional electron gas (2DEG) with spin-orbit coupling (SOC) and a Zeeman field coupled with a d -wave superconductor. Despite the angular dependence of the d -wave pairing, localization and oscillation properties are found to be similar to the ones seen in conventional s -wave superconductors. In addition, we study a microscopic lattice version of the previous system that can be characterized by a topological invariant. We derive its real space representation that involves nearest and next-to-nearest-neighbors pairing. Finally, we show that the emerging chiral Majorana fermions are indeed robust against static disorder. This analysis has potential applications to quantum simulations and experiments in high-Tc superconductors.

Tidal waves in 102Pd: a rotating condensate of multiple d bosons.

PubMed

Ayangeakaa, A D; Garg, U; Caprio, M A; Carpenter, M P; Ghugre, S S; Janssens, R V F; Kondev, F G; Matta, J T; Mukhopadhyay, S; Patel, D; Seweryniak, D; Sun, J; Zhu, S; Frauendorf, S

2013-03-08

Low-lying collective excitations in even-even vibrational and transitional nuclei may be described semiclassically as quadrupole running waves on the surface of the nucleus ("tidal waves"), and the observed vibrational-rotational behavior can be thought of as resulting from a rotating condensate of interacting d bosons. These concepts have been investigated by measuring lifetimes of the levels in the yrast band of the (102)Pd nucleus with the Doppler shift attenuation method. The extracted B(E2) reduced transition probabilities for the yrast band display a monotonic increase with spin, in agreement with the interpretation based on rotation-induced condensation of aligned d bosons.

Multiphoton excitation and high-harmonics generation in topological insulator.

PubMed

Avetissian, H K; Avetissian, A K; Avchyan, B R; Mkrtchian, G F

2018-05-10

Multiphoton interaction of coherent electromagnetic radiation with 2D metallic carriers confined on the surface of the 3D topological insulator is considered. A microscopic theory describing the nonlinear interaction of a strong wave and metallic carriers with many-body Coulomb interaction is developed. The set of integrodifferential equations for the interband polarization and carrier occupation distribution is solved numerically. Multiphoton excitation of Fermi-Dirac sea of 2D massless carriers is considered for a THz pump wave. It is shown that in the moderately strong pump wave field along with multiphoton interband/intraband transitions the intense radiation of high harmonics takes place.

Multiphoton excitation and high-harmonics generation in topological insulator

NASA Astrophysics Data System (ADS)

Avetissian, H. K.; Avetissian, A. K.; Avchyan, B. R.; Mkrtchian, G. F.

2018-05-01

Multiphoton interaction of coherent electromagnetic radiation with 2D metallic carriers confined on the surface of the 3D topological insulator is considered. A microscopic theory describing the nonlinear interaction of a strong wave and metallic carriers with many-body Coulomb interaction is developed. The set of integrodifferential equations for the interband polarization and carrier occupation distribution is solved numerically. Multiphoton excitation of Fermi–Dirac sea of 2D massless carriers is considered for a THz pump wave. It is shown that in the moderately strong pump wave field along with multiphoton interband/intraband transitions the intense radiation of high harmonics takes place.

Left ventricular ejection time, not heart rate, is an independent correlate of aortic pulse wave velocity.

PubMed

Salvi, Paolo; Palombo, Carlo; Salvi, Giovanni Matteo; Labat, Carlos; Parati, Gianfranco; Benetos, Athanase

2013-12-01

Several studies showed a positive association between heart rate and pulse wave velocity, a sensitive marker of arterial stiffness. However, no study involving a large population has specifically addressed the dependence of pulse wave velocity on different components of the cardiac cycle. The aim of this study was to explore in subjects of different age the link between pulse wave velocity with heart period (the reciprocal of heart rate) and the temporal components of the cardiac cycle such as left ventricular ejection time and diastolic time. Carotid-femoral pulse wave velocity was assessed in 3,020 untreated subjects (1,107 men). Heart period, left ventricular ejection time, diastolic time, and early-systolic dP/dt were determined by carotid pulse wave analysis with high-fidelity applanation tonometry. An inverse association was found between pulse wave velocity and left ventricular ejection time at all ages (<25 years, r(2) = 0.043; 25-44 years, r(2) = 0.103; 45-64 years, r(2) = 0.079; 65-84 years, r(2) = 0.044; ≥ 85 years, r(2) = 0.022; P < 0.0001 for all). A significant (P < 0.0001) negative but always weaker correlation between pulse wave velocity and heart period was also found, with the exception of the youngest subjects (P = 0.20). A significant positive correlation was also found between pulse wave velocity and dP/dt (P < 0.0001). With multiple stepwise regression analysis, left ventricular ejection time and dP/dt remained the only determinant of pulse wave velocity at all ages, whereas the contribution of heart period no longer became significant. Our data demonstrate that pulse wave velocity is more closely related to left ventricular systolic function than to heart period. This may have methodological and pathophysiological implications.

Climatology of the quasi-2-day waves observed in the MLS/Aura measurements (2005-2014)

NASA Astrophysics Data System (ADS)

Pancheva, Dora; Mukhtarov, Plamen; Siskind, David E.

2018-06-01

The paper presents the climatology and interannual variability of both eastward- and westward-propagating ∼2-day waves (QTDW) observed in the MLS/Aura geopotential height data for a period of 10 full years (2005-2014). The climatology of the QTDWs has been studied in two steps: (i) by using average 2D-wavelet spectra both the dominant modes of variability and how these modes vary in time and space have been determined, and (ii) by applying a 2D decomposition procedure, where all planetary waves are simultaneously extracted from the data, the average global spatio-temporal distributions of all defined by the 2D-wavelet analysis modes have been obtained. It is found that the westward-propagating waves at mid-high latitudes have zonal wave numbers 2, 3 and 4 and are observed mainly in summer hemisphere. Two different types of eastward-propagating waves have been identified: (i) waves at mid-high latitudes with zonal wave numbers 2 and 3 observed in the winter hemisphere, and (ii) waves observed predominantly over the equator with zonal wave number 2, which do not have a well-defined seasonal variability but show some enhancement in both solstices. While the climatological features of the MLS/Aura QTDWs for the considered period are robust the interannual variations have to be adopted cautiously. The primary reason is that the length of the considered period of 10 years is not enough for finding clear variability pattern. The only long-term variability which appears to have some robustness is that of the W3 wave in the Southern Hemisphere where the influence of the solar cycle has been distinguished.

Sedimentary basin effects in Seattle, Washington: Ground-motion observations and 3D simulations

USGS Publications Warehouse

Frankel, Arthur; Stephenson, William; Carver, David

2009-01-01

Seismograms of local earthquakes recorded in Seattle exhibit surface waves in the Seattle basin and basin-edge focusing of S waves. Spectral ratios of Swaves and later arrivals at 1 Hz for stiff-soil sites in the Seattle basin show a dependence on the direction to the earthquake, with earthquakes to the south and southwest producing higher average amplification. Earthquakes to the southwest typically produce larger basin surface waves relative to S waves than earthquakes to the north and northwest, probably because of the velocity contrast across the Seattle fault along the southern margin of the Seattle basin. S to P conversions are observed for some events and are likely converted at the bottom of the Seattle basin. We model five earthquakes, including the M 6.8 Nisqually earthquake, using 3D finite-difference simulations accurate up to 1 Hz. The simulations reproduce the observed dependence of amplification on the direction to the earthquake. The simulations generally match the timing and character of basin surface waves observed for many events. The 3D simulation for the Nisqually earth-quake produces focusing of S waves along the southern margin of the Seattle basin near the area in west Seattle that experienced increased chimney damage from the earthquake, similar to the results of the higher-frequency 2D simulation reported by Stephenson et al. (2006). Waveforms from the 3D simulations show reasonable agreement with the data at low frequencies (0.2-0.4 Hz) for the Nisqually earthquake and an M 4.8 deep earthquake west of Seattle.

First 3D measurements of temperature fluctuations induced by gravity wave with the infrared limb imager GLORIA

NASA Astrophysics Data System (ADS)

Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Friedl-Vallon, Felix; Riese, Martin

2017-04-01

Gravity waves (GWs) are one of the most important coupling mechanisms in the atmosphere. They couple different compartments of the atmosphere. The GW-LCYCLE (Gravity Wave Life Cycle) project aims on studying the excitation, propagation, and dissipation of gravity waves. An aircraft campaign has been performed in winter 2015/2016, during which the first 3D tomographic measurements of GWs were performed with the infrared limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere). GLORIA combines a classical Fourier Transform Spectrometer with a 2D detector array. The capability to image the atmosphere and thereby take several thousand spectra simultaneously improves the spatial sampling compared to conventional limb sounders by an order of magnitude. Furthermore GLORIA is able to pan the horizontal viewing direction and therefore measure the same volume of air under different angles. Due to these properties tomographic methods can be used to derive 3D temperature and tracer fields with spatial resolutions of better than 30km x 30km x 250m from measurements taken during circular flight patterns. Temperature distributions measured during a strong GW event on the 25.01.2016 during the GW-LCycle campaign over Iceland will be presented and analyzed for gravity waves. The three dimensional nature of the GLORIA measurements allows for the determination of the gravity wave momentum flux, including its horizontal direction. The calculated momentum fluxes rank this event under one of the strongest 1% observed in that latitude range in January 2016. The three dimensional wave vectors determined from the GLORIA measurements can be used for a ray tracing study with the Gravity wave Regional Or Global RAy Tracer (GROGRAT). Here 1D ray tracing, meaning solely vertical column propagation, as used by standard parameterizations in numerical weather prediction and climate models is compared to 4D ray tracing (spatially three dimensional with time varying background) for the presented event on the 25.01.2016. Here it is shown, that in the 1D case the GWs are filtered at lower altitudes, whereas in the 4D case the rays were able to propagate to altitudes of above 30km. Besides the forward propagation up to higher altitudes, also the backward propagation to the source region can be study with GROGRAT. Here the mountains of Iceland could be clearly identified as the source region of the measured GWs.

Short-Term Perturbations Within the D-Region Detected Above the Mediterranean

NASA Astrophysics Data System (ADS)

Silber, Israel; Price, Colin

2016-04-01

The ionospheric D-region lies in the altitude range of ~60-95 km. This part of the atmosphere is highly sensitive to waves propagating upwards from the troposphere, either as pressure perturbations (gravity and acoustic waves) or electromagnetic (EM) perturbations from lightning discharges (resulting in EMPs, sprites, elves, etc.). These perturbations can affect the temperature, wind, species concentration, conductivity, and ionization in the upper atmosphere. Very low frequencies (VLF) radio signals, generated by man-made communication transmitters, have been recorded using ground-based VLF receivers in Israel. These radio waves propagate over long distances within the Earth-ionosphere waveguide, reflected off the Earth's surface and the D-region. The characteristics of the received signals depend on several parameters along the path, but are fairly constant over short periods of time. In this study we present analysis of VLF narrowband data transmitted from Sicily, Italy, spanning one year, and detected in Tel Aviv, Israel. We show observations of the interaction between both pressure and EM perturbations from thunderstorms with the narrowband VLF signals aloft. We clearly observe short period (~2-4 minutes) acoustic waves, longer period gravity waves (~5-7 minutes periods), while also many transient events related to heating and ionization of the D-region. Comparisons with WWLLN lightning data show the potential link between tropospheric thunderstorms and D-region variability.

Short-Term Perturbations Within the D-Region Detected Above the Mediterranean

NASA Astrophysics Data System (ADS)

Price, Colin; Silber, Israel

2016-07-01

The ionospheric D-region lies in the altitude range of ~60-95 km. This part of the atmosphere is highly sensitive to waves propagating upwards from the troposphere, either as pressure perturbations (gravity and acoustic waves) or electromagnetic (EM) perturbations from lightning discharges (resulting in EMPs, sprites, elves, etc.). These perturbations can affect the temperature, wind, species concentration, conductivity, and ionization in the upper atmosphere. Very low frequencies (VLF) radio signals, generated by man-made communication transmitters, have been recorded using ground-based VLF receivers in Israel. These radio waves propagate over long distances within the Earth-ionosphere waveguide, reflected off the Earth's surface and the D-region. The characteristics of the received signals depend on several parameters along the path, but are fairly constant over short periods of time. In this study we present analysis of VLF narrowband data transmitted from Sicily, Italy, spanning one year, and detected in Tel Aviv, Israel. We show observations of the interaction between both pressure and EM perturbations from thunderstorms with the narrowband VLF signals aloft. We clearly observe short period (~2-4 minutes) acoustic waves, longer period gravity waves (~5-7 minutes periods), while also many transient events related to heating and ionization of the D-region. Comparisons with WWLLN lightning data show the potential link between tropospheric thunderstorms and D-region variability.

Nonlinear dynamics of 3D beams of fast magnetosonic waves propagating in the ionospheric and magnetospheric plasma

NASA Astrophysics Data System (ADS)

Belashov, V. Yu.; Belashova, E. S.

2016-11-01

On the basis of the model of the three-dimensional (3D) generalized Kadomtsev-Petviashvili equation for magnetic field h = B / B the formation, stability, and dynamics of 3D soliton-like structures, such as the beams of fast magnetosonic (FMS) waves generated in ionospheric and magnetospheric plasma at a low-frequency branch of oscillations when β = 4 πnT/ B 2 ≪ 1 and β > 1, are studied. The study takes into account the highest dispersion correction determined by values of the plasma parameters and the angle θ = ( B, k), which plays a key role in the FMS beam propagation at those angles to the magnetic field that are close to π/2. The stability of multidimensional solutions is studied by an investigation of the Hamiltonian boundness under its deformations on the basis of solving of the corresponding variational problem. The evolution and dynamics of the 3D FMS wave beam are studied by the numerical integration of equations with the use of specially developed methods. The results can be interpreted in terms of the self-focusing phenomenon, as the formation of a stationary beam and the scattering and self-focusing of the solitary beam of FMS waves. These cases were studied with a detailed investigation of all evolutionary stages of the 3D FMS wave beams in the ionospheric and magnetospheric plasma.

Flexural-gravity Wave Attenuation in a Thick Ice Shelf

NASA Astrophysics Data System (ADS)

Stephen, R. A.; Bromirski, P. D.; Gerstoft, P.; Chen, Z.; Wiens, D.; Aster, R. C.; Nyblade, A.

2016-12-01

A thirty-four station broadband seismic array was deployed on the Ross Ice Shelf, Antarctica from November 2014 to November 2017. Analyses indicate that phase speeds of infra-gravity wave and tsunami excitation in the 0.003 to 0.02 Hz band are 70 m/s, corresponding to the low frequency limit of flexural-gravity waves. Median spectral amplitudes in this band decay exponentially with distance from the shelf edge in a manner consistent with intrinsic attenuation. Seismic Q is typically 7-9, with an RMS amplitude decay of 0.04-0.05dB/km and an e-folding distance of 175-220 km. Amplitudes do not appear to drop crossing crevasse fields. Vertical and horizontal acceleration levels at stations on the floating ice shelf are 50 dB higher than those on grounded ice. Horizontal accelerations are about 15 dB higher than vertical accelerations. Median spectral levels at 0.003 Hz are within 6 dB for stations from 2 to 430 km from the shelf edge. In contrast, the levels drop by 90 dB at 0.02 Hz. Ocean gravity wave excitation has been proposed as a mechanism that can weaken ice shelves and potentially trigger disintegration events. These measurements indicate that the propensity for shelf weakening and disintegration decays exponentially with distance from the ice front for gravity waves in the 0.003 to 0.02Hz band.

A numerical study on the effects of wave-current-surge interactions on the height and propagation of sea surface waves in Charleston Harbor during Hurricane Hugo 1989

NASA Astrophysics Data System (ADS)

Liu, Huiqing; Xie, Lian

2009-06-01

The effects of wave-current interactions on ocean surface waves induced by Hurricane Hugo in and around the Charleston Harbor and its adjacent coastal waters are examined by using a three-dimensional (3D) wave-current coupled modeling system. The 3D storm surge modeling component of the coupled system is based on the Princeton Ocean Model (POM), the wave modeling component is based on the third generation wave model, Simulating WAves Nearshore (SWAN), and the inundation model is adopted from [Xie, L., Pietrafesa, L. J., Peng, M., 2004. Incorporation of a mass-conserving inundation scheme into a three-dimensional storm surge model. J. Coastal Res., 20, 1209-1223]. The results indicate that the change of water level associated with the storm surge is the primary cause for wave height changes due to wave-surge interaction. Meanwhile, waves propagating on top of surge cause a feedback effect on the surge height by modulating the surface wind stress and bottom stress. This effect is significant in shallow coastal waters, but relatively small in offshore deep waters. The influence of wave-current interaction on wave propagation is relatively insignificant, since waves generally propagate in the direction of the surface currents driven by winds. Wave-current interactions also affect the surface waves as a result of inundation and drying induced by the storm. Waves break as waters retreat in regions of drying, whereas waves are generated in flooded regions where no waves would have occurred without the flood water.

Nonlinear Evolution of Counter-Propagating Whistler Mode Waves Excited by Anisotropic Electrons Within the Equatorial Source Region: 1-D PIC Simulations

NASA Astrophysics Data System (ADS)

Chen, Huayue; Gao, Xinliang; Lu, Quanming; Sun, Jicheng; Wang, Shui

2018-02-01

Nonlinear physical processes related to whistler mode waves are attracting more and more attention for their significant role in reshaping whistler mode spectra in the Earth's magnetosphere. Using a 1-D particle-in-cell simulation model, we have investigated the nonlinear evolution of parallel counter-propagating whistler mode waves excited by anisotropic electrons within the equatorial source region. In our simulations, after the linear phase of whistler mode instability, the strong electrostatic standing structures along the background magnetic field will be formed, resulting from the coupling between excited counter-propagating whistler mode waves. The wave numbers of electrostatic standing structures are about twice those of whistler mode waves generated by anisotropic hot electrons. Moreover, these electrostatic standing structures can further be coupled with either parallel or antiparallel propagating whistler mode waves to excite high-k modes in this plasma system. Compared with excited whistler mode waves, these high-k modes typically have 3 times wave number, same frequency, and about 2 orders of magnitude smaller amplitude. Our study may provide a fresh view on the evolution of whistler mode waves within their equatorial source regions in the Earth's magnetosphere.

Quantifying seismic anisotropy induced by small-scale chemical heterogeneities

NASA Astrophysics Data System (ADS)

Alder, C.; Bodin, T.; Ricard, Y.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

2017-12-01

Observations of seismic anisotropy are usually used as a proxy for lattice-preferred orientation (LPO) of anisotropic minerals in the Earth's mantle. In this way, seismic anisotropy observed in tomographic models provides important constraints on the geometry of mantle deformation associated with thermal convection and plate tectonics. However, in addition to LPO, small-scale heterogeneities that cannot be resolved by long-period seismic waves may also produce anisotropy. The observed (i.e. apparent) anisotropy is then a combination of an intrinsic and an extrinsic component. Assuming the Earth's mantle exhibits petrological inhomogeneities at all scales, tomographic models built from long-period seismic waves may thus display extrinsic anisotropy. In this paper, we investigate the relation between the amplitude of seismic heterogeneities and the level of induced S-wave radial anisotropy as seen by long-period seismic waves. We generate some simple 1-D and 2-D isotropic models that exhibit a power spectrum of heterogeneities as what is expected for the Earth's mantle, that is, varying as 1/k, with k the wavenumber of these heterogeneities. The 1-D toy models correspond to simple layered media. In the 2-D case, our models depict marble-cake patterns in which an anomaly in shear wave velocity has been advected within convective cells. The long-wavelength equivalents of these models are computed using upscaling relations that link properties of a rapidly varying elastic medium to properties of the effective, that is, apparent, medium as seen by long-period waves. The resulting homogenized media exhibit extrinsic anisotropy and represent what would be observed in tomography. In the 1-D case, we analytically show that the level of anisotropy increases with the square of the amplitude of heterogeneities. This relation is numerically verified for both 1-D and 2-D media. In addition, we predict that 10 per cent of chemical heterogeneities in 2-D marble-cake models can induce more than 3.9 per cent of extrinsic radial S-wave anisotropy. We thus predict that a non-negligible part of the observed anisotropy in tomographic models may be the result of unmapped small-scale heterogeneities in the mantle, mainly in the form of fine layering, and that caution should be taken when interpreting observed anisotropy in terms of LPO and mantle deformation. This effect may be particularly strong in the lithosphere where chemical heterogeneities are assumed to be the strongest.

Evidence for a Significant Level of Extrinsic Anisotropy Due to Heterogeneities in the Mantle.

NASA Astrophysics Data System (ADS)

Alder, C.; Bodin, T.; Ricard, Y. R.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

2017-12-01

Observations of seismic anisotropy are used as a proxy for lattice-preferred orientation (LPO) of anisotropic minerals in the Earth's mantle. In this way, it provides important constraints on the geometry of mantle deformation. However, in addition to LPO, small-scale heterogeneities that cannot be resolved by long-period seismic waves may also produce anisotropy. The observed (i.e. apparent) anisotropy is then a combination of an intrinsic and an extrinsic component. Assuming the Earth's mantle exhibits petrological inhomogeneities at all scales, tomographic models built from long-period seismic waves may thus display extrinsic anisotropy. Here, we investigate the relation between the amplitude of seismic heterogeneities and the level of induced S-wave radial anisotropy as seen by long-period seismic waves. We generate some simple 1D and 2D isotropic models that exhibit a power spectrum of heterogeneities as what is expected for the Earth's mantle, i.e. varying as 1/k, with k the wavenumber of these heterogeneities. The 1D toy models correspond to simple layered media. In the 2D case, our models depict marble-cake patterns in which an anomaly in S-wave velocity has been advected within convective cells. The long-wavelength equivalents of these models are computed using upscaling relations that link properties of a rapidly varying elastic medium to properties of the effective, i.e. apparent, medium as seen by long-period waves. The resulting homogenized media exhibit extrinsic anisotropy and represent what would be observed in tomography. In the 1D case, we analytically show that the level of anisotropy increases with the square of the amplitude of heterogeneities. This relation is numerically verified for both 1D and 2D media. In addition, we predict that 10 % of chemical heterogeneities in 2D marble-cake models can induce more than 3.9 % of extrinsic radial S-wave anisotropy. We thus predict that a non-negligible part of the observed anisotropy in tomographic models may be the result of unmapped small-scale heterogeneities in the mantle, mainly in the form of fine layering, and that caution should be taken when interpreting observed anisotropy in terms of LPO and mantle deformation. This effect may be particularly strong in the lithosphere where chemical heterogeneities are assumed to be the strongest.

Global smooth solutions of 3-D null-form wave equations in exterior domains with Neumann boundary conditions

NASA Astrophysics Data System (ADS)

Jun, Li; Huicheng, Yin

2018-05-01

The paper is devoted to investigating long time behavior of smooth small data solutions to 3-D quasilinear wave equations outside of compact convex obstacles with Neumann boundary conditions. Concretely speaking, when the surface of a 3-D compact convex obstacle is smooth and the quasilinear wave equation fulfills the null condition, we prove that the smooth small data solution exists globally provided that the Neumann boundary condition on the exterior domain is given. One of the main ingredients in the current paper is the establishment of local energy decay estimates of the solution itself. As an application of the main result, the global stability to 3-D static compressible Chaplygin gases in exterior domain is shown under the initial irrotational perturbation with small amplitude.

The Space-Time Conservation Element and Solution Element Method-A New High-Resolution and Genuinely Multidimensional Paradigm for Solving Conservation Laws. 2; Numerical Simulation of Shock Waves and Contact Discontinuities

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen; Chow, Chuen-Yen; Chang, Sin-Chung

1998-01-01

Without resorting to special treatment for each individual test case, the 1D and 2D CE/SE shock-capturing schemes described previously (in Part I) are used to simulate flows involving phenomena such as shock waves, contact discontinuities, expansion waves and their interactions. Five 1D and six 2D problems are considered to examine the capability and robustness of these schemes. Despite their simple logical structures and low computational cost (for the 2D CE/SE shock-capturing scheme, the CPU time is about 2 micro-secs per mesh point per marching step on a Cray C90 machine), the numerical results, when compared with experimental data, exact solutions or numerical solutions by other methods, indicate that these schemes can accurately resolve shock and contact discontinuities consistently.

Frequency-controls of electromagnetic multi-beam scanning by metasurfaces.

PubMed

Li, Yun Bo; Wan, Xiang; Cai, Ben Geng; Cheng, Qiang; Cui, Tie Jun

2014-11-05

We propose a method to control electromagnetic (EM) radiations by holographic metasurfaces, including to producing multi-beam scanning in one dimension (1D) and two dimensions (2D) with the change of frequency. The metasurfaces are composed of subwavelength metallic patches on grounded dielectric substrate. We present a combined theory of holography and leaky wave to realize the multi-beam radiations by exciting the surface interference patterns, which are generated by interference between the excitation source and required radiation waves. As the frequency changes, we show that the main lobes of EM radiation beams could accomplish 1D or 2D scans regularly by using the proposed holographic metasurfaces shaped with different interference patterns. This is the first time to realize 2D scans of antennas by changing the frequency. Full-wave simulations and experimental results validate the proposed theory and confirm the corresponding physical phenomena.

Manipulation of Bloch surface waves: from subwavelength focusing to nondiffracting beam

NASA Astrophysics Data System (ADS)

Kim, Myun-Sik; Herzig, Hans Peter

2018-01-01

We present a different type of electromagnetic surface wave than a surface plasmon polariton (SPP), called Bloch surface wave (BSW). BSWs are sustained by dielectric multilayers, and therefore they do not suffer from dissipation. Their propagation length is unbeatably long, e.g., over several millimeters. Thanks to this feature, larger integrations of 2D photonic chips are realizable. To do this, 2D optical components and corresponding techniques are necessary to manipulate in-plane propagation of surface waves. We overview recent progresses of the BSW research on manipulation techniques and developed components. Our study will provide a good guideline of the BSW components for users.

The Development of Drift Wave Turbulence in Magnetic Reconnection

NASA Astrophysics Data System (ADS)

McMurtrie, L.; Drake, J. F.; Swisdak, M. M.

2013-12-01

An important feature in collisionless magnetic reconnection is the development of sharp discontinuities along the separatrices bounding the Alfvenic outflow. The typical scale length of these features is ρs (the Larmor radius based on the sound speed) for guide field reconnection. Temperature gradients in the inflowing plasma (as might be found in the magnetopause) can lead to instabilities at these separatrices, specifically drift wave turbulence. We present standalone 2D and 3D PIC simulations of drift wave turbulence to investigate scaling properties and growth rates. Further investigations of the relative importance of drift wave turbulence in the development of reconnection will also be considered.

Estimation of pseudo-2D shear-velocity section by inversion of high frequency surface waves

USGS Publications Warehouse

Luo, Y.; Liu, J.; Xia, J.; Xu, Y.; Liu, Q.

2006-01-01

A scheme to generate pseudo-2D shear-velocity sections with high horizontal resolution and low field cost by inversion of high frequency surface waves is presented. It contains six steps. The key step is the joint method of crossed correlation and phase shift scanning. This joint method chooses only two traces to generate image of dispersion curve. For Rayleigh-wave dispersion is most important for estimation of near-surface shear-wave velocity, it can effectively obtain reliable images of dispersion curves with a couple of traces. The result of a synthetic example shows the feasibility of this scheme. ?? 2005 Society of Exploration Geophysicists.

Effects of sea water on elongated duration of ground motion as well as variation in its amplitude for offshore earthquakes

NASA Astrophysics Data System (ADS)

Todoriki, Masaru; Furumura, Takashi; Maeda, Takuto

2017-01-01

We investigated the effects of sea water on the propagation of seismic waves using a 3-D finite-difference-method simulation of seismic wave propagation following offshore earthquakes. When using a 1-D layered structure, the simulation results showed strong S- to P-wave conversion at the sea bottom; accordingly, S-wave energy was dramatically decreased by the sea water layer. This sea water de-amplification effect had strong frequency dependence, therefore resembling a low-pass filter in which the cut-off frequency and damping coefficients were defined by the thickness of the sea water layer. The sea water also acted to elongate the duration of Rayleigh wave packet. The importance of the sea water layer in modelling offshore earthquakes was further demonstrated by a simulation using a realistic 3-D velocity structure model with and without sea water for a shallow (h = 14 km) outer-rise Nankai Trough event, the 2004 SE Off Kii Peninsula earthquake (Mw = 7.2). Synthetic seismograms generated by the model when sea water was included were in accordance with observed seismograms for long-term longer period motions, particularly those in the shape of Rayleigh waves.

Development of FullWave : Hot Plasma RF Simulation Tool

NASA Astrophysics Data System (ADS)

Svidzinski, Vladimir; Kim, Jin-Soo; Spencer, J. Andrew; Zhao, Liangji; Galkin, Sergei

2017-10-01

Full wave simulation tool, modeling RF fields in hot inhomogeneous magnetized plasma, is being developed. The wave equations with linearized hot plasma dielectric response are solved in configuration space on adaptive cloud of computational points. The nonlocal hot plasma dielectric response is formulated in configuration space without limiting approximations by calculating the plasma conductivity kernel based on the solution of the linearized Vlasov equation in inhomogeneous magnetic field. This approach allows for better resolution of plasma resonances, antenna structures and complex boundaries. The formulation of FullWave and preliminary results will be presented: construction of the finite differences for approximation of derivatives on adaptive cloud of computational points; model and results of nonlocal conductivity kernel calculation in tokamak geometry; results of 2-D full wave simulations in the cold plasma model in tokamak geometry using the formulated approach; results of self-consistent calculations of hot plasma dielectric response and RF fields in 1-D mirror magnetic field; preliminary results of self-consistent simulations of 2-D RF fields in tokamak using the calculated hot plasma conductivity kernel; development of iterative solver for wave equations. Work is supported by the U.S. DOE SBIR program.

Highly efficient multifunctional metasurface for high-gain lens antenna application

NASA Astrophysics Data System (ADS)

Hou, Haisheng; Wang, Guangming; Li, Haipeng; Guo, Wenlong; Li, Tangjing

2017-07-01

In this paper, a novel multifunctional metasurface combining linear-to-circular polarization conversion and electromagnetic waves focusing has been proposed and applied to design a high-gain lens antenna working at Ku band. The multifunctional metasurface consists of 15 × 15 unit cells. Each unit cell is composed of four identical metallic layers and three intermediate dielectric layers. Due to well optimization, the multifunctional metasurface can convert the linearly polarized waves generated by the source to circularly polarized waves and focus the waves. By placing a patch antenna operating at 15 GHz at the focal point of the metasurface and setting the focal distance to diameter ratio ( F/ D) to 0.34, we obtain a multifunctional lens antenna. Simulated and measured results coincide well, indicating that the metasurface can convert linearly polarized waves to right-handed circularly polarized waves at 15 GHz with excellent performances in terms of the 3 dB axial ratio bandwidth of 5.3%, realized gain of 16.9 dB and aperture efficiency of 41.2%. Because of the advantages of high gain, competitive efficiency and easy fabrication, the proposed lens antenna has a great potential application in wireless and satellite communication.

A Polarization Responsive System for Microwaves

DTIC Science & Technology

1980-12-01

radioastronomy employs much longer wave- lengths than optics, but the electromagnetic wave formulation of polari- zation is the same for optics as it is for... Radioastronomy . New York: McGraw-Hill, 1966. 8. Kuck, D. J., D. Lawrie and A. H. Samek. High Speed Computer and Algorithm Organization. New York: Academic

Deciphering the embedded wave in Saturn's Maxwell ringlet

NASA Astrophysics Data System (ADS)

French, Richard G.; Nicholson, Philip D.; Hedman, Mathew M.; Hahn, Joseph M.; McGhee-French, Colleen A.; Colwell, Joshua E.; Marouf, Essam A.; Rappaport, Nicole J.

2016-11-01

The eccentric Maxwell ringlet in Saturn's C ring is home to a prominent wavelike structure that varies strongly and systematically with true anomaly, as revealed by nearly a decade of high-SNR Cassini occultation observations. Using a simple linear "accordion" model to compensate for the compression and expansion of the ringlet and the wave, we derive a mean optical depth profile for the ringlet and a set of rescaled, background-subtracted radial wave profiles. We use wavelet analysis to identify the wave as a 2-armed trailing spiral, consistent with a density wave driven by an m = 2 outer Lindblad resonance (OLR), with a pattern speed Ωp = 1769.17° d-1 and a corresponding resonance radius ares = 87530.0 km. Estimates of the surface mass density of the Maxwell ringlet range from a mean value of 11g cm-2 derived from the self-gravity model to 5 - 12gcm-2 , as inferred from the wave's phase profile and a theoretical dispersion relation. The corresponding opacity is about 0.12 cm2 g-1, comparable to several plateaus in the outer C ring (Hedman, M.N., Nicholson, P.D. [2014]. Mont. Not. Roy. Astron. Soc. 444, 1369-1388). A linear density wave model using the derived wave phase profile nicely matches the wave's amplitude, wavelength, and phase in most of our observations, confirming the accuracy of the pattern speed and demonstrating the wave's coherence over a period of 8 years. However, the linear model fails to reproduce the narrow, spike-like structures that are prominent in the observed optical depth profiles. Using a symplectic N-body streamline-based dynamical code (Hahn, J.M., Spitale, J.N. [2013]. Astrophys. J. 772, 122), we simulate analogs of the Maxwell ringlet, modeled as an eccentric ringlet with an embedded wave driven by a fictitious satellite with an OLR located within the ring. The simulations reproduce many of the features of the actual observations, including strongly asymmetric peaks and troughs in the inward-propagating density wave. We argue that the Maxwell ringlet wave is generated by a sectoral normal-mode oscillation inside Saturn with ℓ = m = 2 , similar to other planetary internal modes that have been inferred from density waves observed in Saturn's C ring (Hedman, M.N., Nicholson, P.D. [2013]. Astron. J. 146, 12; Hedman, M.N., Nicholson, P.D. [2014]. Mont. Not. Roy. Astron. Soc. 444, 1369-1388). Our identification of a third m = 2 mode associated with saturnian internal oscillations supports the suggestions of mode splitting by Fuller et al. (Fuller, J., Lai, D., Storch, N.I. [2014]. Icarus 231, 34-50) and Fuller (Fuller, J. [2014]. Icarus 242, 283-296). The fitted amplitude of the wave, if it is interpreted as driven by the ℓ = m = 2 f-mode, implies a radial amplitude at the 1 bar level of ∼ 50 cm, according to the models of Marley and Porco (Marley, M.S., Porco, C.C. [1993]. Icarus 106, 508).

Wave-current interactions in three dimensions: why 3D radiation stresses are not practical

NASA Astrophysics Data System (ADS)

Ardhuin, Fabrice

2017-04-01

The coupling of ocean circulation and wave models is based on a wave-averaged mass and momentum conservation equations. Whereas several equivalent equations for the evolution of the current momentum have been proposed, implemented, and used, the possibility to formulate practical equations for the total momentum, which is the sum of the current and wave momenta, has been obscured by a series of publications. In a recent update on previous derivations, Mellor (J. Phys. Oceanogr. 2015) proposed a new set of wave-forced total momentum equations. Here we show that this derivation misses a term that integrates to zero over the vertical. This is because he went from his depth-integrated eq. (28) to the 3D equation (30) by simply removing the integral, but any extra zero-integrating term can be added. Corrected for this omission, the equations of motion are equivalent to the earlier equations by Mellor (2003) which are correct when expressed in terms of wave-induced pressure, horizontal velocity and vertical displacement. Namely the total momentum evolution is driven by the horizontal divergence of a horizontal momentum flux, ----- --- ∂^s- Sαβ = ^uα^uβ + δαβ ∂ς (^p- g^s) (1) and the vertical divergence of a vertical flux, Sαz = (p^-g^s)∂^s/∂xα, (2) where p is the wave-induced non-hydrostatic pressure, s is the wave-induced vertical displacement, and u^ α is the horizontal wave-induced velocity in direction α. So far, so good. Problems arise when p and s are evaluated. Indeend, Ardhuin et al. (J. Phys. Oceanogr. 2008) showed that, over a sloping bottom ∂Sαβ/∂xβ is of order of the slope, hence a consistent wave forcing requires an estimation of Sαz that must be estimated to first order in the bottom slope. For this, Airy wave theory, i.e. cosh(kz-+-kh) p ≃ ga cosh (kD ) cosψ, (3) is not enough. Ardhuin et al. (2008) has shown that using an exact solution of the Laplace equations the vertical flux can indeed be computed. The alternative of neglecting completely Sαz, as suggested by Mellor (2011) for small slopes, will always generate spurious currents because of the unbalanced forcing ∂Sαβ/∂xβ. Fortunately, there are many explicit versions of the wave-averaged equations without the wave momentum in them (Suzuki and Fox-Kemper 2016), with or without vortex force which are all consistent with the exact 3D equations of Andrews and McIntyre (1978). There is thus no need to stumble again and again on this fundamental problem of vertical momentum flux, which is a flux of wave momentum. The problem simply goes away by writing the equations for the current momentum only, without the problematic wave momentum. The current and wave momentum are coupled by forcing terms, and the wave momentum can be solved in 2D, the vertical distribution of momentum being maintained by the complex flux Sαz.

Generation of noninductive current by electron-Bernstein waves on the COMPASS-D Tokamak.

PubMed

Shevchenko, V; Baranov, Y; O'Brien, M; Saveliev, A

2002-12-23

Electron-Bernstein waves (EBW) were excited in the plasma by mode converted extraordinary (X) waves launched from the high field side of the COMPASS-D tokamak at different toroidal angles. It has been found experimentally that X-mode injection perpendicular to the magnetic field provides maximum heating efficiency. Noninductive currents of up to 100 kA were found to be driven by the EBW mode with countercurrent drive. These results are consistent with ray tracing and quasilinear Fokker-Planck simulations.

Automated Liver Elasticity Calculation for 3D MRE

PubMed Central

Dzyubak, Bogdan; Glaser, Kevin J.; Manduca, Armando; Ehman, Richard L.

2017-01-01

Magnetic Resonance Elastography (MRE) is a phase-contrast MRI technique which calculates quantitative stiffness images, called elastograms, by imaging the propagation of acoustic waves in tissues. It is used clinically to diagnose liver fibrosis. Automated analysis of MRE is difficult as the corresponding MRI magnitude images (which contain anatomical information) are affected by intensity inhomogeneity, motion artifact, and poor tissue- and edge-contrast. Additionally, areas with low wave amplitude must be excluded. An automated algorithm has already been successfully developed and validated for clinical 2D MRE. 3D MRE acquires substantially more data and, due to accelerated acquisition, has exacerbated image artifacts. Also, the current 3D MRE processing does not yield a confidence map to indicate MRE wave quality and guide ROI selection, as is the case in 2D. In this study, extension of the 2D automated method, with a simple wave-amplitude metric, was developed and validated against an expert reader in a set of 57 patient exams with both 2D and 3D MRE. The stiffness discrepancy with the expert for 3D MRE was −0.8% ± 9.45% and was better than discrepancy with the same reader for 2D MRE (−3.2% ± 10.43%), and better than the inter-reader discrepancy observed in previous studies. There were no automated processing failures in this dataset. Thus, the automated liver elasticity calculation (ALEC) algorithm is able to calculate stiffness from 3D MRE data with minimal bias and good precision, while enabling stiffness measurements to be fully reproducible and to be easily performed on the large 3D MRE datasets. PMID:29033488

3D ultrafast ultrasound imaging in vivo.

PubMed

Provost, Jean; Papadacci, Clement; Arango, Juan Esteban; Imbault, Marion; Fink, Mathias; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

2014-10-07

Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32  ×  32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra--and inter-observer variability.

Travel-time sensitivity kernels in long-range propagation.

PubMed

Skarsoulis, E K; Cornuelle, B D; Dzieciuch, M A

2009-11-01

Wave-theoretic travel-time sensitivity kernels (TSKs) are calculated in two-dimensional (2D) and three-dimensional (3D) environments and their behavior with increasing propagation range is studied and compared to that of ray-theoretic TSKs and corresponding Fresnel-volumes. The differences between the 2D and 3D TSKs average out when horizontal or cross-range marginals are considered, which indicates that they are not important in the case of range-independent sound-speed perturbations or perturbations of large scale compared to the lateral TSK extent. With increasing range, the wave-theoretic TSKs expand in the horizontal cross-range direction, their cross-range extent being comparable to that of the corresponding free-space Fresnel zone, whereas they remain bounded in the vertical. Vertical travel-time sensitivity kernels (VTSKs)-one-dimensional kernels describing the effect of horizontally uniform sound-speed changes on travel-times-are calculated analytically using a perturbation approach, and also numerically, as horizontal marginals of the corresponding TSKs. Good agreement between analytical and numerical VTSKs, as well as between 2D and 3D VTSKs, is found. As an alternative method to obtain wave-theoretic sensitivity kernels, the parabolic approximation is used; the resulting TSKs and VTSKs are in good agreement with normal-mode results. With increasing range, the wave-theoretic VTSKs approach the corresponding ray-theoretic sensitivity kernels.

Dopamine D2 receptors preferentially regulate the development of light responses of the inner retina

PubMed Central

Tian, Ning; Xu, Hong-ping; Wang, Ping

2014-01-01

Retinal light responsiveness measured via electroretinography undergoes developmental modulation and is thought to be critically regulated by both visual experience and dopamine. The primary goal of this study is to determine whether the dopamine D2 receptor regulates the visual experience-dependent functional development of the retina. Accordingly, we recorded electroretinograms from wild type mice and mice with a genetic deletion of the gene that encodes the dopamine D2 receptor raised under normal cyclic light conditions and constant darkness. Our results demonstrate that mutation of the dopamine D2 receptors preferentially increases the amplitude of the inner retinal light responses evoked by high intensity light measured as oscillatory potentials in adult mice. During postnatal development, all three major components of electroretinograms, the a-wave, b-wave and oscillatory potentials, increase with age. Comparatively, mutation of the dopamine D2 receptors preferentially reduces the age-dependent increase of b-waves evoked by low intensity light. Light deprivation from birth reduces the amplitude of b-waves and completely diminishes the increased amplitude of oscillatory potentials. Taken together, these results demonstrate that the dopamine D2 receptor plays an important role in the activity-dependent functional development of the mouse retina. PMID:25393815

Efficient non-hydrostatic modelling of 3D wave-induced currents using a subgrid approach

NASA Astrophysics Data System (ADS)

Rijnsdorp, Dirk P.; Smit, Pieter B.; Zijlema, Marcel; Reniers, Ad J. H. M.

2017-08-01

Wave-induced currents are an ubiquitous feature in coastal waters that can spread material over the surf zone and the inner shelf. These currents are typically under resolved in non-hydrostatic wave-flow models due to computational constraints. Specifically, the low vertical resolutions adequate to describe the wave dynamics - and required to feasibly compute at the scales of a field site - are too coarse to account for the relevant details of the three-dimensional (3D) flow field. To describe the relevant dynamics of both wave and currents, while retaining a model framework that can be applied at field scales, we propose a two grid approach to solve the governing equations. With this approach, the vertical accelerations and non-hydrostatic pressures are resolved on a relatively coarse vertical grid (which is sufficient to accurately resolve the wave dynamics), whereas the horizontal velocities and turbulent stresses are resolved on a much finer subgrid (of which the resolution is dictated by the vertical scale of the mean flows). This approach ensures that the discrete pressure Poisson equation - the solution of which dominates the computational effort - is evaluated on the coarse grid scale, thereby greatly improving efficiency, while providing a fine vertical resolution to resolve the vertical variation of the mean flow. This work presents the general methodology, and discusses the numerical implementation in the SWASH wave-flow model. Model predictions are compared with observations of three flume experiments to demonstrate that the subgrid approach captures both the nearshore evolution of the waves, and the wave-induced flows like the undertow profile and longshore current. The accuracy of the subgrid predictions is comparable to fully resolved 3D simulations - but at much reduced computational costs. The findings of this work thereby demonstrate that the subgrid approach has the potential to make 3D non-hydrostatic simulations feasible at the scale of a realistic coastal region.

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

Roberts, Jesse D.; Chang, Grace; Magalen, Jason

A modified version of an indust ry standard wave modeling tool was evaluated, optimized, and utilized to investigate model sensitivity to input parameters a nd wave energy converter ( WEC ) array deployment scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that wave direction and WEC device type we r e most sensitive to the variation in the model parameters examined in this study . Generally, the changes in wave height we re the primary alteration caused by the presencemore » of a WEC array. Specifically, W EC device type and subsequently their size directly re sult ed in wave height variations; however, it is important to utilize ongoing laboratory studies and future field tests to determine the most appropriate power matrix values for a particular WEC device and configuration in order to improve modeling results .« less

2D instabilities of surface gravity waves on a linear shear current

NASA Astrophysics Data System (ADS)

Francius, Marc; Kharif, Christian

2016-04-01

Periodic 2D surface water waves propagating steadily on a rotational current have been studied by many authors (see [1] and references therein). Although the recent important theoretical developments have confirmed that periodic waves can exist over flows with arbitrary vorticity, their stability and their nonlinear evolution have not been much studied extensively so far. In fact, even in the rather simple case of uniform vorticity (linear shear), few papers have been published on the effect of a vertical shear current on the side-band instability of a uniform wave train over finite depth. In most of these studies [2-5], asymptotic expansions and multiple scales method have been used to obtain envelope evolution equations, which allow eventually to formulate a condition of (linear) instability to long modulational perturbations. It is noted here that this instability is often referred in the literature as the Benjamin-Feir or modulational instability. In the present study, we consider the linear stability of finite amplitude two-dimensional, periodic water waves propagating steadily on the free surface of a fluid with constant vorticity and finite depth. First, the steadily propagating surface waves are computed with steepness up to very close to the highest, using a Fourier series expansions and a collocation method, which constitutes a simple extension of Fenton's method [6] to the cases with a linear shear current. Then, the linear stability of these permanent waves to infinitesimal 2D perturbations is developed from the fully nonlinear equations in the framework of normal modes analysis. This linear stability analysis is an extension of [7] to the case of waves in the presence of a linear shear current and permits the determination of the dominant instability as a function of depth and vorticity for a given steepness. The numerical results are used to assess the accuracy of the vor-NLS equation derived in [5] for the characteristics of modulational instabilities due to resonant four-wave interactions, as well as to study the influence of vorticity and nonlinearity on the characteristics of linear instabilities due to resonant five-wave and six-wave interactions. Depending on the dimensionless depth, superharmonic instabilities due to five-wave interactions can become dominant with increasing positive vorticiy. Acknowledgments: This work was supported by the Direction Générale de l'Armement and funded by the ANR project n°. ANR-13-ASTR-0007. References [1] A. Constantin, Two-dimensionality of gravity water flows of constant non-zero vorticity beneath a surface wave train, Eur. J. Mech. B/Fluids, 2011, 30, 12-16. [2] R. S. Johnson, On the modulation of water waves on shear flows, Proc. Royal Soc. Lond. A., 1976, 347, 537-546. [3] M. Oikawa, K. Chow, D. J. Benney, The propagation of nonlinear wave packets in a shear flow with a free surface, Stud. Appl. Math., 1987, 76, 69-92. [4] A. I Baumstein, Modulation of gravity waves with shear in water, Stud. Appl. Math., 1998, 100, 365-90. [5] R. Thomas, C. Kharif, M. Manna, A nonlinear Schrödinger equation for water waves on finite depth with constant vorticity, Phys. Fluids, 2012, 24, 127102. [6] M. M Rienecker, J. D Fenton, A Fourier approximation method for steady water waves , J. Fluid Mech., 1981, 104, 119-137 [7] M. Francius, C. Kharif, Three-dimensional instabilities of periodic gravity waves in shallow water, J. Fluid Mech., 2006, 561, 417-437

Solitary wave runup and force on a vertical barrier

NASA Astrophysics Data System (ADS)

Liu, Philip L.-F.; Al-Banaa, Khaled

2004-04-01

In this paper we investigate the interaction between a solitary wave and a thin vertical barrier. A set of laboratory experiments was performed with different values of incident wave height to water depth ratio, H/h, and the draught of the barrier to water depth ratio, D/h. While wave gauges were used to measure the reflected and transmitted waves, pressure transducers were installed on both sides of the barrier, enabling the calculation of wave force. The particle image velocimetry (PIV) technique is also employed to measure the velocity field in the vicinity of the barrier. A numerical model, based on the Reynolds-averaged Navier Stokes (RANS) equations and the k - epsilon turbulence closure model, was first checked with experimental data and then employed to obtain additional results for the range of parameters where the laboratory experiments were not performed. Using both experimental data and numerical results, formulae for the maximum runup height, and the maximum wave force are derived in terms of H/h and D/h.

Insight into large-scale topography on analysis of high-frequency Rayleigh waves

NASA Astrophysics Data System (ADS)

Ping, Ping; Chu, Risheng; Chong, Jiajun; Ni, Sidao; Zhang, Yu

2018-03-01

The dispersion of surface waves could be biased in regions where topography is comparable to the wavelength. We investigate the effects on high-frequency Rayleigh waves propagating in a typical massif model through numerical simulations. High-frequency Rayleigh waves have relatively higher signal-to-noise ratios (SNR) using the Q component in the LQT coordinate system, perpendicular to the local free surface in these topographic models. When sources and stations are located at different sides of the massif, the conventional dispersion image overestimates phase velocities of Rayleigh waves, as much as 25% with topographic height/width ratio (H/r) > 0.5. The dispersion perturbation is more distinctive for fundamental modes. Using a two-layer model, the thickness deviation (ΔD/D) may be significant in surface-wave inversion due to the variation of H/r and the thickness of the first layer. These phenomena cannot be ignored in surface-wave interpretations, nevertheless they are trivial for the source and stations located at the same side of the massif.

Time-Lapse Monitoring with 4D Seismic Coda Waves in Active, Passive and Ambient Noise Data

NASA Astrophysics Data System (ADS)

Lumley, D. E.; Kamei, R.; Saygin, E.; Shragge, J. C.

2017-12-01

The Earth's subsurface is continuously changing, due to temporal variations in fluid flow, stress, temperature, geomechanics and geochemistry, for example. These physical changes occur at broad tectonic and earthquake scales, and also at very detailed near-surface and reservoir scales. Changes in the physical states of the earth cause time-varying changes in the physical properties of rocks and fluids, which can be monitored with natural or manmade seismic waves. Time-lapse (4D) seismic monitoring is important for applications related to natural and induced seismicity, hydrocarbon and groundwater reservoir depletion, CO2 sequestration etc. An exciting new research area involves moving beyond traditional methods in order to use the full complex time-lapse scattered wavefield (4D coda waves) for both manmade active-source 3D/4D seismic data, and also to use continuous recordings of natural-source passive seismic data, especially (micro) earthquakes and ocean ambient noise. This research involves full wave-equation approaches including waveform inversion (FWI), interferometry, Large N sensor arrays, "big data" information theory, and high performance supercomputing (HPC). I will present high-level concepts and recent data results that are quite spectacular and highly encouraging.

Wave Propagation in 2-D Granular Matrix and Dust Mitigation of Fabrics for Space Exploration Mission

NASA Technical Reports Server (NTRS)

Thanh, Phi Hung X.

2004-01-01

Wave Propagation study is essential to exploring the soil on Mars or Moon and Dust Mitigation is a necessity in terms of crew's health in exploration missions. The study of Dust Mitigation has a significant impact on the crew s health when astronauts track dust back into their living space after exploration trips. We are trying to use piezoelectric fiber to create waves and vibrations at certain critical frequencies and amplitudes so that we can shake the particles off from the astronaut s fabrics. By shaking off the dust and removing it, the astronauts no longer have to worry about breathing in small and possibly hazardous materials, when they are back in their living quarters. The Wave Propagation in 2-D Granular Matrix studies how the individual particles interact with each other when a pressure wave travels through the matrix. This experiment allows us to understand how wave propagates through soils and other materials. By knowing the details about the interactions of particles when they act as a medium for waves, we can better understand how wave propagates through soils and other materials. With this experiment, we can study how less gravity effects the wave propagation and hence device a way to study soils in space and on Moon or Mars. Some scientists treat the medium that waves travel through as a "black box", they did not pay much attention to how individual particles act as wave travels through them. With this data, I believe that we can use it to model ways to measure the properties of different materials such as density and composition. In order to study how the particles interact with each other, I have continued Juan Agui's experiment of the effects of impacts on a 2-D matrix. By controlling the inputs and measuring the outputs of the system, I will be able to study now the particles in that system interact with each other. I will also try to model this with the software called PFC2D in order to obtain theoretical data to compare with the experiment. PFC2D is a program that allows the user to control the number of particle's characteristic, and the environment of the particle. With this I can run simulations that mimic the impulse test. This software uses a language called FISH, probably created by the creator of the software. This means that in order to model anything, one must use the command terminal instead of GUI's. I will also use this program to simulate the Moon/Mars simulate adhering to the fabric for the Dust Mitigation project. My goals for this summer are just to complete preliminary studies of the feasibility of the Shaking Fabric, learn the PFC-2D program, and to complete building and testing the wave propagation experiment.

Magnetic Helicity of Alfven Simple Waves

NASA Technical Reports Server (NTRS)

Webb, Gary M.; Hu, Q.; Dasgupta, B.; Zank, G. P.; Roberts, D.

2010-01-01

The magnetic helicity of fully nonlinear, multi-dimensional Alfven simple waves are investigated, by using relative helicity formulae and also by using an approach involving poloidal and toroidal decomposition of the magnetic field and magnetic vector potential. Different methods to calculate the magnetic vector potential are used, including the homotopy and Biot-Savart formulas. Two basic Alfven modes are identified: (a) the plane 1D Alfven simple wave given in standard texts, in which the Alfven wave propagates along the z-axis, with wave phase varphi=k_0(z-lambda t), where k_0 is the wave number and lambda is the group velocity of the wave, and (b)\\ the generalized Barnes (1976) simple Alfven wave in which the wave normal {bf n} moves in a circle in the xy-plane perpendicular to the mean field, which is directed along the z-axis. The plane Alfven wave (a) is analogous to the slab Alfven mode and the generalized Barnes solution (b) is analogous to the 2D mode in Alfvenic, incompressible turbulence. The helicity characteristics of these two basic Alfven modes are distinct. The helicity characteristics of more general multi-dimensional simple Alfven waves are also investigated. Applications to nonlinear Aifvenic fluctuations and structures observed in the solar wind are discussed.

Double Alfvén waves

NASA Astrophysics Data System (ADS)

Webb, G. M.; Hu, Q.; Dasgupta, B.; Zank, G. P.

2012-02-01

Double Alfvén wave solutions of the magnetohydrodynamic equations in which the physical variables (the gas density ρ, fluid velocity u, gas pressure p, and magnetic field induction B) depend only on two independent wave phases ϕ1(x,t) and ϕ2(x,t) are obtained. The integrals for the double Alfvén wave are the same as for simple waves, namely, the gas pressure, magnetic pressure, and group velocity of the wave are constant. Compatibility conditions on the evolution of the magnetic field B due to changes in ϕ1 and ϕ2, as well as constraints due to Gauss's law ∇ · B = 0 are discussed. The magnetic field lines and hodographs of B in which the tip of the magnetic field B moves on the sphere |B| = B = const. are used to delineate the physical characteristics of the wave. Hamilton's equations for the simple Alfvén wave with wave normal n(ϕ), and with magnetic induction B(ϕ) in which ϕ is the wave phase, are obtained by using the Frenet-Serret equations for curves x=X(ϕ) in differential geometry. The use of differential geometry of 2D surfaces in a 3D Euclidean space to describe double Alfvén waves is briefly discussed.

Photonic band structures solved by a plane-wave-based transfer-matrix method.

PubMed

Li, Zhi-Yuan; Lin, Lan-Lan

2003-04-01

Transfer-matrix methods adopting a plane-wave basis have been routinely used to calculate the scattering of electromagnetic waves by general multilayer gratings and photonic crystal slabs. In this paper we show that this technique, when combined with Bloch's theorem, can be extended to solve the photonic band structure for 2D and 3D photonic crystal structures. Three different eigensolution schemes to solve the traditional band diagrams along high-symmetry lines in the first Brillouin zone of the crystal are discussed. Optimal rules for the Fourier expansion over the dielectric function and electromagnetic fields with discontinuities occurring at the boundary of different material domains have been employed to accelerate the convergence of numerical computation. Application of this method to an important class of 3D layer-by-layer photonic crystals reveals the superior convergency of this different approach over the conventional plane-wave expansion method.

Development of 2-D horn-antenna millimeter-wave imaging device (HMID) for the plasma diagnostics

NASA Astrophysics Data System (ADS)

Nagayama, Y.; Ito, N.; Kuwahara, D.; Tsuchiya, H.; Yamaguchi, S.

2017-04-01

The two-dimensional (2-D) Horn-antenna Millimeter-wave Imaging Device (HMID) has been developed for the O-mode Microwave Imaging Reflectometry (O-MIR) in the Large Helical Device (LHD). The detectable frequency range of the HMID is 23-33 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 1019 m-3 in the O-MIR. The HMID is a 2-D imaging device that improves on the horn-antenna mixer array, which had been developed for the X-mode MIR in the LHD. In the HMID, the signal (RF) wave from the horn antenna is transmitted to the microstrip line by the finline transmitter, and this is mixed by the double-balanced-mixer with the local oscillation wave that is fed by a coaxial cable. By using the HMID, the MIR optical system can be significantly simplified.

Development of 2-D horn-antenna millimeter-wave imaging device (HMID) for the plasma diagnostics.

PubMed

Nagayama, Y; Ito, N; Kuwahara, D; Tsuchiya, H; Yamaguchi, S

2017-04-01

The two-dimensional (2-D) Horn-antenna Millimeter-wave Imaging Device (HMID) has been developed for the O-mode Microwave Imaging Reflectometry (O-MIR) in the Large Helical Device (LHD). The detectable frequency range of the HMID is 23-33 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 10 19 m -3 in the O-MIR. The HMID is a 2-D imaging device that improves on the horn-antenna mixer array, which had been developed for the X-mode MIR in the LHD. In the HMID, the signal (RF) wave from the horn antenna is transmitted to the microstrip line by the finline transmitter, and this is mixed by the double-balanced-mixer with the local oscillation wave that is fed by a coaxial cable. By using the HMID, the MIR optical system can be significantly simplified.

Development of CIP/graphite composite additives for electromagnetic wave absorption applications

NASA Astrophysics Data System (ADS)

Woo, Soobin; Yoo, Chan-Sei; Kim, Hwijun; Lee, Mijung; Quevedo-Lopez, Manuel; Choi, Hyunjoo

2017-09-01

In this study, the electromagnetic (EM) wave absorption ability of carbonyl iron powder (CIP)/graphite composites produced by ball milling were studied in a range of 28.5 GHz to examine the effects of the morphology and volume fraction of graphite on EM wave absorption ability. The results indicated that a ball milling technique was effective in exfoliating the graphite and covering it with CIP, thereby markedly increasing the specific surface area of the hybrid powder. The increase in the surface area and hybridization with dielectric loss materials (i.e., graphite) improved EM absorbing properties of CIP in the range of S and X bands. Specifically, the CIP/graphite composite containing 3 wt% graphite exhibited electromagnetic wave absorption of -13 dB at 7 GHz, -21 dB at 5.8 GHz, and -29 dB at 4.3 GHz after 1 h, 8 h, and 16 h of milling, respectively. [Figure not available: see fulltext.

Dispersion relations with crossing symmetry for {pi}{pi} D- and F-wave amplitudes

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

Kaminski, R.

A set of once subtracted dispersion relations with imposed crossing symmetry condition for the {pi}{pi} D- and F-wave amplitudes is derived and analyzed. An example of numerical calculations in the effective two-pion mass range from the threshold to 1.1 GeV is presented. It is shown that these new dispersion relations impose quite strong constraints on the analyzed {pi}{pi} interactions and are very useful tools to test the {pi}{pi} amplitudes. One of the goals of this work is to provide a complete set of equations required for easy use. Full analytical expressions are presented. Along with the well-known dispersion relations successfulmore » in testing the {pi}{pi} S- and P-wave amplitudes, those presented here for the D and F waves give a complete set of tools for analyses of the {pi}{pi} interactions.« less

Full wave simulations of helicon wave losses in the scrape-off-layer of the DIII-D tokamak

NASA Astrophysics Data System (ADS)

Lau, Cornwall; Jaeger, Fred; Berry, Lee; Bertelli, Nicola; Pinsker, Robert

2017-10-01

Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D. Previous modeling using the hot plasma, full wave code AORSA, has shown good agreement with the ray tracing code GENRAY for helicon wave propagation and absorption in the core plasma. AORSA, and a new, reduced finite-element-model show discrepancies between ray tracing and full wave occur in the scrape-off-layer (SOL), especially at high densities. The reduced model is much faster than AORSA, and reproduces most of the important features of the AORSA model. The reduced model also allows for larger parametric scans and for the easy use of arbitrary tokamak geometry. Results of the full wave codes, AORSA and COMSOL, will be shown for helicon wave losses in the SOL are shown for a large range of parameters, such as SOL density profiles, n||, radial and vertical locations of the antenna, and different tokamak vessel geometries. This work was supported by DE-AC05-00OR22725, DE-AC02-09CH11466, and DE-FC02-04ER54698.

Electrostatic Wave Generation and Transverse Ion Acceleration by Alfvenic Wave Components of BBELF Turbulence

NASA Technical Reports Server (NTRS)

Singh, Nagendra; Khazanov, George; Mukhter, Ali

2007-01-01

We present results here from 2.5-D particle-in-cell simulations showing that the electrostatic (ES) components of broadband extremely low frequency (BBELF) waves could possibly be generated by cross-field plasma instabilities driven by the relative drifts between the heavy and light ion species in the electromagnetic (EM) Alfvenic component of the BBELF waves in a multi-ion plasma. The ES components consist of ion cyclotron as well as lower hybrid modes. We also demonstrate that the ES wave generation is directly involved in the transverse acceleration of ions (TAI) as commonly measured with the BBELF wave events. The heating is affected by ion cyclotron resonance in the cyclotron modes and Landau resonance in the lower hybrid waves. In the simulation we drive the plasma by the transverse electric field, E(sub y), of the EM waves; the frequency of E(sub y), omega(sub d), is varied from a frequency below the heavy ion cyclotron frequency, OMEGA(sub h), to below the light ion cyclotron frequency, OMEGA(sub i). We have also performed simulations for E(sub y) having a continuous spectrum given by a power law, namely, |Ey| approx. omega(sub d) (exp -alpha), where the exponent alpha = _, 1, and 2 in three different simulations. The driving electric field generates polarization and ExB drifts of the ions and electrons. When the interspecies relative drifts are sufficiently large, they drive electrostatic waves, which cause perpendicular heating of both light and heavy ions. The transverse ion heating found here is discussed in relation to observations from Cluster, FAST and Freja.

Association Between Sex and Speech Auditory Brainstem Responses in Adults, and Relationship to Sex Hormone Levels.

PubMed

Liu, Jinfeng; Wang, Dan; Li, Xiaoting; Ningyu, Wang

2017-05-14

BACKGROUND The aim of this study was to investigate the association between sex and speech-ABR in adults, and its relationship to sex hormone levels. MATERIAL AND METHODS Speech-ABR were elicited with the consonant-vowel syllable (/da/) in a total of 35 adults. Reproductive hormone levels were also measured. RESULTS The transient response of the speech-ABR (waves V, A, and O) in females show a shorter latency (waves V, A and O) and a larger amplitude (waves V and A) than in males (P<0.05), except for the amplitude of peak O (P>0.05). The sustained response of females exhibited a larger amplitude (wave F, P<0.05) and a shorter latency (wave D, E, and F, P<0.05) than in males, except for the amplitude of peak D and E (P>0.05). The latencies of speech-ABR were positively correlated with testosterone level (P<0.05), and were negatively correlated with estradiol (E2) levels (P<0.05), except for wave E (P>0.05). The E2 showed a positive correlation with the absolute value of amplitude of the speech-ABR (P < 0.05). On the contrary, total testosterone showed a negative correlation with the absolute value of amplitude the speech-ABR (P<0.05), except for wave D and wave O (P>0.05). CONCLUSIONS Sex differences in speech-ABR are significant in adults. The latencies and amplitude of the speech-ABR waves were correlated with the E2 concentration and testosterone level. The sex hormones likely affect speech encoding in the brainstem.

Bi-directional vibration control of offshore wind turbines using a 3D pendulum tuned mass damper

NASA Astrophysics Data System (ADS)

Sun, C.; Jahangiri, V.

2018-05-01

Offshore wind turbines suffer from excessive bi-directional vibrations due to wind-wave misalignment and vortex induced vibrations. However, most of existing research focus on unidirectional vibration attenuation which is inadequate for real applications. The present paper proposes a three dimensional pendulum tuned mass damper (3d-PTMD) to mitigate the tower and nacelle dynamic response in the fore-aft and side-side directions. An analytical model of the wind turbine coupled with the 3d-PTMD is established wherein the interaction between the blades, the tower and the 3d-PTMD is modeled. Aerodynamic loading is computed using the Blade Element Momentum method where the Prandtls tip loss factor and the Glauert correction are considered. JONSWAP spectrum is adopted to generate wave data. Wave loading is computed using Morisons equation in collaboration with the strip theory. Via a numerical search approach, the design formula of the 3d-PTMD is obtained and examined on a National Renewable Energy Lab (NREL) monopile 5 MW baseline wind turbine model under misaligned wind, wave and seismic loading. Dual linear tuned mass dampers (TMDs) deployed in the fore-aft and side-side directions are utilized for comparison. It is found that the 3d-PTMD with a mass ratio of 2 % can improve the mitigation of the root mean square and peak response by around 10 % when compared with the dual linear TMDs in controlling the bi-directional vibration of the offshore wind turbines under misaligned wind, wave and seismic loading.

Comparing a quasi-3D to a full 3D nearshore circulation model: SHORECIRC and ROMS

USGS Publications Warehouse

Haas, Kevin A.; Warner, John C.

2009-01-01

Predictions of nearshore and surf zone processes are important for determining coastal circulation, impacts of storms, navigation, and recreational safety. Numerical modeling of these systems facilitates advancements in our understanding of coastal changes and can provide predictive capabilities for resource managers. There exists many nearshore coastal circulation models, however they are mostly limited or typically only applied as depth integrated models. SHORECIRC is an established surf zone circulation model that is quasi-3D to allow the effect of the variability in the vertical structure of the currents while maintaining the computational advantage of a 2DH model. Here we compare SHORECIRC to ROMS, a fully 3D ocean circulation model which now includes a three dimensional formulation for the wave-driven flows. We compare the models with three different test applications for: (i) spectral waves approaching a plane beach with an oblique angle of incidence; (ii) monochromatic waves driving longshore currents in a laboratory basin; and (iii) monochromatic waves on a barred beach with rip channels in a laboratory basin. Results identify that the models are very similar for the depth integrated flows and qualitatively consistent for the vertically varying components. The differences are primarily the result of the vertically varying radiation stress utilized by ROMS and the utilization of long wave theory for the radiation stress formulation in vertical varying momentum balance by SHORECIRC. The quasi-3D model is faster, however the applicability of the fully 3D model allows it to extend over a broader range of processes, temporal, and spatial scales.

Comparing a quasi-3D to a full 3D nearshore circulation model: SHORECIRC and ROMS

USGS Publications Warehouse

Haas, K.A.; Warner, J.C.

2009-01-01

Predictions of nearshore and surf zone processes are important for determining coastal circulation, impacts of storms, navigation, and recreational safety. Numerical modeling of these systems facilitates advancements in our understanding of coastal changes and can provide predictive capabilities for resource managers. There exists many nearshore coastal circulation models, however they are mostly limited or typically only applied as depth integrated models. SHORECIRC is an established surf zone circulation model that is quasi-3D to allow the effect of the variability in the vertical structure of the currents while maintaining the computational advantage of a 2DH model. Here we compare SHORECIRC to ROMS, a fully 3D ocean circulation model which now includes a three dimensional formulation for the wave-driven flows. We compare the models with three different test applications for: (i) spectral waves approaching a plane beach with an oblique angle of incidence; (ii) monochromatic waves driving longshore currents in a laboratory basin; and (iii) monochromatic waves on a barred beach with rip channels in a laboratory basin. Results identify that the models are very similar for the depth integrated flows and qualitatively consistent for the vertically varying components. The differences are primarily the result of the vertically varying radiation stress utilized by ROMS and the utilization of long wave theory for the radiation stress formulation in vertical varying momentum balance by SHORECIRC. The quasi-3D model is faster, however the applicability of the fully 3D model allows it to extend over a broader range of processes, temporal, and spatial scales. ?? 2008 Elsevier Ltd.

High Power Radio Wave Interactions within the D-Region Ionosphere

NASA Astrophysics Data System (ADS)

Moore, R. C.

2014-12-01

This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we have seen a tremendous improvement in ELF/VLF wave generation efficiency. We have identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.

The choice of speed and clearance for RAS on 3D method

NASA Astrophysics Data System (ADS)

Wang, Jian-Fang; Li, Ji-De; Cai, Xin-Gong

2003-12-01

In this paper, a 3D source distribution technique is used to calculate the coupled motions between two ships which advance in the wave with the same speed. The numerical results of coupled motions for a frigate and a supply ship have a good agreement with the experimental results. Based on the 3D coupled motions of two ships, a spectral analysis is employed to clearly observe the effect of speed, clearance and wave heading on the significant relative motion amplitude (SRMA) of two ships. The method presented in this paper will be helpful to select suitable clearance, speed and wave heading for underway replenishment at sea(RAS).

Vector matter waves in two-component Bose-Einstein condensates with spatially modulated nonlinearities

NASA Astrophysics Data System (ADS)

Xu, Si-Liu; He, Jun-Rong; Xue, Li; Belić, Milivoj R.

2018-02-01

We demonstrate three-dimensional (3D) vector solitary waves in the coupled (3 + 1)-D nonlinear Gross-Pitaevskii equations with variable nonlinearity coefficients. The analysis is carried out in spherical coordinates, providing novel localized solutions that depend on three modal numbers, l, m, and n. Using the similarity transformation (ST) method in 3D, vector solitary waves are built with the help of a combination of harmonic and trapping potentials, including multipole solutions and necklace rings. In general, the solutions found are stable for low values of the modal numbers; for values larger than 2, the solutions are found to be unstable. Variable nonlinearity allows the utilization of soliton management methods.

Correlation of field seismic refraction data with 3-D laboratory ultrasonic sounding data during exploration of a dimension stone deposit

NASA Astrophysics Data System (ADS)

Přikryl, Richard; Vilhelm, Jan; Lokajíček, Tomáš; Pros, Zdeněk; Klíma, Karel

2004-05-01

Multidirectional field seismic refraction data have been combined with 3-D laboratory ultrasonic sounding data in a preliminary exploration of a new dimension stone deposit in the Czech Republic. Rock fabric was interpreted from a detailed laboratory analysis of a 3-D P-wave velocity pattern and can be classified as pronounced orthorhombic due to a complex tectonometamorphic history of the rock. The P-wave velocity pattern recorded from laboratory measurements can be satisfactorily correlated with the anisotropy of P-wave velocity data acquired from field seismic refraction data. Rock fabric anisotropy also contributes to the observed anisotropy of strength and static deformational properties.

Performance of quantum annealing on random Ising problems implemented using the D-Wave Two

NASA Astrophysics Data System (ADS)

Wang, Zhihui; Job, Joshua; Rønnow, Troels F.; Troyer, Matthias; Lidar, Daniel A.; USC Collaboration; ETH Collaboration

2014-03-01

Detecting a possible speedup of quantum annealing compared to classical algorithms is a pressing task in experimental adiabatic quantum computing. In this talk, we discuss the performance of the D-Wave Two quantum annealing device on Ising spin glass problems. The expected time to solution for the device to solve random instances with up to 503 spins and with specified coupling ranges is evaluated while carefully addressing the issue of statistical errors. We perform a systematic comparison of the expected time to solution between the D-Wave Two and classical stochastic solvers, specifically simulated annealing, and simulated quantum annealing based on quantum Monte Carlo, and discuss the question of speedup.

Amplitude mode oscillations in pump-probe photoemission spectra from a d -wave superconductor

NASA Astrophysics Data System (ADS)

Nosarzewski, B.; Moritz, B.; Freericks, J. K.; Kemper, A. F.; Devereaux, T. P.

2017-11-01

Recent developments in the techniques of ultrafast pump-probe photoemission have made possible the search for collective modes in strongly correlated systems out of equilibrium. Including inelastic scattering processes and a retarded interaction, we simulate time- and angle-resolved photoemission spectroscopy (trARPES) to study the amplitude mode of a d -wave superconductor, a collective mode excited through the nonlinear light-matter coupling to the pump pulse. We find that the amplitude mode oscillations of the d -wave order parameter occur in phase at a single frequency that is twice the quasi-steady-state maximum gap size after pumping. We comment on the necessary conditions for detecting the amplitude mode in trARPES experiments.

Development of a GPU-Accelerated 3-D Full-Wave Code for Electromagnetic Wave Propagation in a Cold Plasma

NASA Astrophysics Data System (ADS)

Woodbury, D.; Kubota, S.; Johnson, I.

2014-10-01

Computer simulations of electromagnetic wave propagation in magnetized plasmas are an important tool for both plasma heating and diagnostics. For active millimeter-wave and microwave diagnostics, accurately modeling the evolution of the beam parameters for launched, reflected or scattered waves in a toroidal plasma requires that calculations be done using the full 3-D geometry. Previously, we reported on the application of GPGPU (General-Purpose computing on Graphics Processing Units) to a 3-D vacuum Maxwell code using the FDTD (Finite-Difference Time-Domain) method. Tests were done for Gaussian beam propagation with a hard source antenna, utilizing the parallel processing capabilities of the NVIDIA K20M. In the current study, we have modified the 3-D code to include a soft source antenna and an induced current density based on the cold plasma approximation. Results from Gaussian beam propagation in an inhomogeneous anisotropic plasma, along with comparisons to ray- and beam-tracing calculations will be presented. Additional enhancements, such as advanced coding techniques for improved speedup, will also be investigated. Supported by U.S. DoE Grant DE-FG02-99-ER54527 and in part by the U.S. DoE, Office of Science, WDTS under the Science Undergraduate Laboratory Internship program.

Predicting conditions for the reception of one-hop signals from the Siple transmitter experiment using the Kp index

NASA Astrophysics Data System (ADS)

Li, J. D.; Spasojevic, M.; Inan, U. S.

2015-10-01

Wave injection experiments provide an opportunity to explore and quantify aspects of nonlinear wave-particle phenomena in a controlled manner. Waves are injected into space from ground-based ELF/VLF transmitters, and the modified waves are measured by radio receivers on the ground in the conjugate hemisphere. These experiments are expensive and challenging projects to build and to operate, and the transmitted waves are not always detected in the conjugate region. Even the powerful transmitter located at Siple Station, Antarctica in 1986, estimated to radiate over 1 kW, only reported a reception rate of ˜40%, indicating that a significant number of transmissions served no observable scientific purpose and reflecting the difficulty in determining suitable conditions for transmission and reception. Leveraging modern machine-learning classification techniques, we apply two statistical techniques, a Bayes and a support vector machine classifier, to predict the occurrence of detectable one-hop transmissions from Siple data with accuracies on the order of 80%-90%. Applying these classifiers to our 1986 Siple data set, we detect 406 receptions of Siple transmissions which we analyze to generate more robust statistics on nonlinear growth rates, 3 dB/s-270 dB/s, and nonlinear total amplification, 3 dB-41 dB.

Spectrally formulated user-defined element in conventional finite element environment for wave motion analysis in 2-D composite structures

NASA Astrophysics Data System (ADS)

Khalili, Ashkan; Jha, Ratneshwar; Samaratunga, Dulip

2016-11-01

Wave propagation analysis in 2-D composite structures is performed efficiently and accurately through the formulation of a User-Defined Element (UEL) based on the wavelet spectral finite element (WSFE) method. The WSFE method is based on the first-order shear deformation theory which yields accurate results for wave motion at high frequencies. The 2-D WSFE model is highly efficient computationally and provides a direct relationship between system input and output in the frequency domain. The UEL is formulated and implemented in Abaqus (commercial finite element software) for wave propagation analysis in 2-D composite structures with complexities. Frequency domain formulation of WSFE leads to complex valued parameters, which are decoupled into real and imaginary parts and presented to Abaqus as real values. The final solution is obtained by forming a complex value using the real number solutions given by Abaqus. Five numerical examples are presented in this article, namely undamaged plate, impacted plate, plate with ply drop, folded plate and plate with stiffener. Wave motions predicted by the developed UEL correlate very well with Abaqus simulations. The results also show that the UEL largely retains computational efficiency of the WSFE method and extends its ability to model complex features.

Forced sound transmission through a finite-sized single leaf panel subject to a point source excitation.

PubMed

Wang, Chong

2018-03-01

In the case of a point source in front of a panel, the wavefront of the incident wave is spherical. This paper discusses spherical sound waves transmitting through a finite sized panel. The forced sound transmission performance that predominates in the frequency range below the coincidence frequency is the focus. Given the point source located along the centerline of the panel, forced sound transmission coefficient is derived through introducing the sound radiation impedance for spherical incident waves. It is found that in addition to the panel mass, forced sound transmission loss also depends on the distance from the source to the panel as determined by the radiation impedance. Unlike the case of plane incident waves, sound transmission performance of a finite sized panel does not necessarily converge to that of an infinite panel, especially when the source is away from the panel. For practical applications, the normal incidence sound transmission loss expression of plane incident waves can be used if the distance between the source and panel d and the panel surface area S satisfy d/S>0.5. When d/S ≈0.1, the diffuse field sound transmission loss expression may be a good approximation. An empirical expression for d/S=0  is also given.

Second harmonic generation at fatigue cracks by low-frequency Lamb waves: Experimental and numerical studies

NASA Astrophysics Data System (ADS)

Yang, Yi; Ng, Ching-Tai; Kotousov, Andrei; Sohn, Hoon; Lim, Hyung Jin

2018-01-01

This paper presents experimental and theoretical analyses of the second harmonic generation due to non-linear interaction of Lamb waves with a fatigue crack. Three-dimensional (3D) finite element (FE) simulations and experimental studies are carried out to provide physical insight into the mechanism of second harmonic generation. The results demonstrate that the 3D FE simulations can provide a reasonable prediction on the second harmonic generated due to the contact nonlinearity at the fatigue crack. The effect of the wave modes on the second harmonic generation is also investigated in detail. It is found that the magnitude of the second harmonic induced by the interaction of the fundamental symmetric mode (S0) of Lamb wave with the fatigue crack is much higher than that by the fundamental anti-symmetric mode (A0) of Lamb wave. In addition, a series of parametric studies using 3D FE simulations are conducted to investigate the effect of the fatigue crack length to incident wave wavelength ratio, and the influence of the excitation frequency on the second harmonic generation. The outcomes show that the magnitude and directivity pattern of the generated second harmonic depend on the fatigue crack length to incident wave wavelength ratio as well as the ratio of S0 to A0 incident Lamb wave amplitude. In summary, the findings of this study can further advance the use of second harmonic generation in damage detection.

High Reynolds Number Wave Force Investigation in a Wave Flume.

DTIC Science & Technology

1985-03-01

RESULTS 43 6.0 CONCLUSIONS 45 7.0 REFERENCES 49 8.0 ACKNOWLEDGEMENTS 51 9.0 TABLES 53 10.0 FIGURES 93 11.0 APPENDIX A" 11.1 Druck Pressure Transducer...adjoining test cylinder by 0.7 mm, which had a negligible influence on the resulting measurements. After the Druck pressure transducers were installed and...dC C 3d 4 ;88dC 38dC CI8 cninfl"nV0to .t" o ,t in cv d-. ,0 en w . nC M..r nin - -0 - I!- I!- V! - -i !V L4JN C; .0 d C0000000 40000008 o .6 C

Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling (Invited)

NASA Astrophysics Data System (ADS)

Maceira, M.; Zhang, H.; Rowe, C. A.

2009-12-01

We focus on the development and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets. Building on previous efforts of joint invesion using surface wave dispersion measurements, gravity data, and receiver functions, we have added a fourth dataset, seismic body wave P and S travel times, to the simultaneous joint inversion method. We present a 3D seismic velocity model of the crust and upper mantle of northwest China resulting from the simultaneous, joint inversion of these four data types. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations. Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of the fourth dataset, consisting of seismic travel-time data, helps to constrain the shear wave velocities both vertically and horizontally in the model cells crossed by the ray paths. Incorporation of both P and S body wave travel times allows us to invert for both P and S velocity structure, capitalizing on empirical relationships between both wave types’ seismic velocities with rock densities, thus eliminating the need for ad hoc assumptions regarding the Poisson ratios. Our new tomography algorithm is a modification of the Maceira and Ammon joint inversion code, in combination with the Zhang and Thurber TomoDD (double-difference tomography) program.

Seismic structure of the crust and uppermost mantle of north America and adjacent oceanic basins: A synthesis

USGS Publications Warehouse

Chulick, G.S.; Mooney, W.D.

2002-01-01

We present a new set of contour maps of the seismic structure of North America and the surrounding ocean basins. These maps include the crustal thickness, whole-crustal average P-wave and S-wave velocity, and seismic velocity of the uppermost mantle, that is, Pn and Sn. We found the following: (1) The average thickness of the crust under North America is 36.7 km (standard deviation [s.d.] ??8.4 km), which is 2.5 km thinner than the world average of 39.2 km (s.d. ?? 8.5) for continental crust; (2) Histograms of whole-crustal P- and S-wave velocities for the North American crust are bimodal, with the lower peak occurring for crust without a high-velocity (6.9-7.3 km/sec) lower crustal layer; (3) Regions with anomalously high average crustal P-wave velocities correlate with Precambrian and Paleozoic orogens; low average crustal velocities are correlated with modern extensional regimes; (4) The average Pn velocity beneath North America is 8.03 km/sec (s.d. ?? 0.19 km/sec); (5) the well-known thin crust beneath the western United States extends into northwest Canada; (6) the average P-wave velocity of layer 3 of oceanic crust is 6.61 km/ sec (s.d. ?? 0.47 km/sec). However, the average crustal P-wave velocity under the eastern Pacific seafloor is higher than the western Atlantic seafloor due to the thicker sediment layer on the older Atlantic seafloor.

Measurement of Rayleigh wave Z/H ratio and joint inversion for a high-resolution S wave velocity model beneath the Gulf of Mexico passive margin

NASA Astrophysics Data System (ADS)

Miao, W.; Li, G.; Niu, F.

2016-12-01

Knowledge on the 3D sediment structure beneath the Gulf of Mexico passive margin is not only important to explore the oil and gas resources in the area, but also essential to decipher the deep crust and mantle structure beneath the margin with teleseismic data. In this study, we conduct a joint inversion of Rayleigh wave ellipticity and phase velocity at 6-40 s to construct a 3-D S wave velocity model in a rectangular area of 100°-87° west and 28°-37° north. We use ambient noise data from a total of 215 stations of the Transportable Array deployed under the Earthscope project. Rayleigh wave ellipticity, or Rayleigh wave Z/H (vertical to horizontal) amplitude ratio is mostly sensitive to shallow sediment structure, while the dispersion data are expected to have reasonably good resolution to uppermost mantle depths. The Z/H ratios measured from stations inside the Gulf Coastal Plain are distinctly lower in comparison with those measured from the inland stations. We also measured the phase velocity dispersion from the same ambient noise dataset. Our preliminary 3-D model is featured by strong low-velocity anomalies at shallow depth, which are spatially well correlated with Gulf Cost, East Texas, and the Lower Mississippi basins. We will discuss other features of the 3-D models once the model is finalized.

Maturation of the auditory system in clinically normal puppies as reflected by the brain stem auditory-evoked potential wave V latency-intensity curve and rarefaction-condensation differential potentials.

PubMed

Poncelet, L C; Coppens, A G; Meuris, S I; Deltenre, P F

2000-11-01

To evaluate auditory maturation in puppies. Ten clinically normal Beagle puppies. Puppies were examined repeatedly from days 11 to 36 after birth (8 measurements). Click-evoked brain stem auditory-evoked potentials (BAEP) were obtained in response to rarefaction and condensation click stimuli from 90 dB normal hearing level to wave V threshold, using steps of 10 dB. Responses were added, providing an equivalent to alternate polarity clicks, and subtracted, providing the rarefaction-condensation differential potential (RCDP). Steps of 5 dB were used to determine thresholds of RCDP and wave V. Slope of the low-intensity segment of the wave V latency-intensity curve was calculated. The intensity range at which RCDP could not be recorded (ie, pre-RCDP range) was calculated by subtracting the threshold of wave V from threshold of RCDP RESULTS: Slope of the wave V latency-intensity curve low-intensity segment evolved with age, changing from (mean +/- SD) -90.8 +/- 41.6 to -27.8 +/- 4.1 micros/dB. Similar results were obtained from days 23 through 36. The pre-RCDP range diminished as puppies became older, decreasing from 40.0 +/- 7.5 to 20.5 +/- 6.4 dB. Changes in slope of the latency-intensity curve with age suggest enlargement of the audible range of frequencies toward high frequencies up to the third week after birth. Decrease in the pre-RCDP range may indicate an increase of the audible range of frequencies toward low frequencies. Age-related reference values will assist clinicians in detecting hearing loss in puppies.

Born scattering of long-period body waves

NASA Astrophysics Data System (ADS)

Dalkolmo, Jörg; Friederich, Wolfgang

2000-09-01

The Born approximation is applied to the modelling of the propagation of deeply turning long-period body waves through heterogeneities in the lowermost mantle. We use an exact Green's function for a spherically symmetric earth model that also satisfies the appropriate boundary conditions at internal boundaries and the surface of the earth. The scattered displacement field is obtained by a numerical quadrature of the product of the Green's function, the exciting wavefield and structural perturbations. We study three examples: scattering of long-period P waves from a plume rising from the core-mantle boundary (CMB), generation of long-period precursors to PKIKP by strong, localized scatterers at the CMB, and propagation of core-diffracted P waves through large-scale heterogeneities in D''. The main results are as follows: (1) the signals scattered from a realistic plume are small with relative amplitudes of less than 2 per cent at a period of 20s, rendering plume detection a fairly difficult task; (2) strong heterogeneities at the CMB of appropriate size may produce observable long-period precursors to PKIKP in spite of the presence of a diffraction from the PKP-B caustic; (3) core-diffracted P waves (Pdiff) are sensitive to structure in D'' far off the geometrical ray path and also far beyond the entry and exit points of the ray into and out of D'' sensitivity kernels exhibit ring-shaped patterns of alternating sign reminiscent of Fresnel zones; (4) Pdiff also shows a non-negligible sensitivity to shear wave velocity in D'' (5) down to periods of 40s, the Born approximation is sufficiently accurate to allow waveform modelling of Pdiff through large-scale heterogeneities in D'' of up to 5 per cent.

On the generation of internal wave modes by surface waves

NASA Astrophysics Data System (ADS)

Harlander, Uwe; Kirschner, Ian; Maas, Christian; Zaussinger, Florian

2016-04-01

Internal gravity waves play an important role in the ocean since they transport energy and momentum and the can lead to mixing when they break. Surface waves and internal gravity waves can interact. On the one hand, long internal waves imply a slow varying shear current that modifies the propagation of surface waves. Surface waves generated by the atmosphere can, on the other hand, excite internal waves by nonlinear interaction. Thereby a surface wave packet consisting of two close frequencies can resonate with a low frequency internal wave (Phillips, 1966). From a theoretical point of view, the latter has been studied intensively by using a 2-layer model, i.e. a surface layer with a strong density contrast and an internal layer with a comparable weak density contrast (Ball, 1964; Craig et al., 2010). In the present work we analyse the wave coupling for a continuously stratified fluid using a fully non-linear 2D numerical model (OpenFoam) and compare this with laboratory experiments (see Lewis et al. 1974). Surface wave modes are used as initial condition and the time development of the dominant surface and internal waves are studied by spectral and harmonic analysis. For the simple geometry of a box, the results are compared with analytical spectra of surface and gravity waves. Ball, F.K. 1964: Energy transfer between external and internal gravity waves. J. Fluid Mech. 19, 465. Craig, W., Guyenne, P., Sulem, C. 2010: Coupling between internal and surface waves. Natural Hazards 57, 617-642. Lewis, J.E., Lake, B.M., Ko, D.R.S 1974: On the interaction of internal waves and surfacr gravity waves, J. Fluid Mech. 63, 773-800. Phillips, O.M. 1966: The dynamics of the upper ocean, Cambridge University Press, 336pp.

Coupling Hydrodynamic and Wave Propagation Codes for Modeling of Seismic Waves recorded at the SPE Test.

NASA Astrophysics Data System (ADS)

Larmat, C. S.; Rougier, E.; Delorey, A.; Steedman, D. W.; Bradley, C. R.

2016-12-01

The goal of the Source Physics Experiment (SPE) is to bring empirical and theoretical advances to the problem of detection and identification of underground nuclear explosions. For this, the SPE program includes a strong modeling effort based on first principles calculations with the challenge to capture both the source and near-source processes and those taking place later in time as seismic waves propagate within complex 3D geologic environments. In this paper, we report on results of modeling that uses hydrodynamic simulation codes (Abaqus and CASH) coupled with a 3D full waveform propagation code, SPECFEM3D. For modeling the near source region, we employ a fully-coupled Euler-Lagrange (CEL) modeling capability with a new continuum-based visco-plastic fracture model for simulation of damage processes, called AZ_Frac. These capabilities produce high-fidelity models of various factors believed to be key in the generation of seismic waves: the explosion dynamics, a weak grout-filled borehole, the surrounding jointed rock, and damage creation and deformations happening around the source and the free surface. SPECFEM3D, based on the Spectral Element Method (SEM) is a direct numerical method for full wave modeling with mathematical accuracy. The coupling interface consists of a series of grid points of the SEM mesh situated inside of the hydrodynamic code's domain. Displacement time series at these points are computed using output data from CASH or Abaqus (by interpolation if needed) and fed into the time marching scheme of SPECFEM3D. We will present validation tests with the Sharpe's model and comparisons of waveforms modeled with Rg waves (2-8Hz) that were recorded up to 2 km for SPE. We especially show effects of the local topography, velocity structure and spallation. Our models predict smaller amplitudes of Rg waves for the first five SPE shots compared to pure elastic models such as Denny &Johnson (1991).

International Conference on Numerical Ship Hydrodynamics (2nd) Held in Berkeley, California on 19-21 September 1977

DTIC Science & Technology

1977-09-01

ORDERING INFORMATION Sec d Internat nal Contere ce on Nu erical Ship ydro nermics ay be order by mallin a req~uest the folio ng ad ess: Firt ilererin I...f(x)dx - 0 (f ’ J d Gd(x’,X 3) dx’ -D0 (jx) 0 d.’ d’U is a closed subspacs of aUoxV ’XT,. hence I O Gde Loach space. d o l , Aw D(4 (x U ’!’ ) Proofs...crest of unbro- domain as an initial-value problem advancing in Ken waves. The inception of wave breaking is time until a steady-state condition has

Analysis of vegetation effect on waves using a vertical 2-D RANS model

USDA-ARS?s Scientific Manuscript database

A vertical two-dimensional (2-D) model has been applied in the simulation of wave propagation through vegetated water bodies. The model is based on an existing model SOLA-VOF which solves the Reynolds-Averaged Navier-Stokes (RANS) equations with the finite difference method on a staggered rectangula...

Alfvén wave dynamics at the neighborhood of a 2.5D magnetic null-point

NASA Astrophysics Data System (ADS)

Sabri, S.; Vasheghani Farahani, S.; Ebadi, H.; Hosseinpour, M.; Fazel, Z.

2018-05-01

The aim of the present study is to highlight the energy transfer via the interaction of magnetohydrodynamic waves with a 2.5D magnetic null-point in a finite plasma-β regime of the solar corona. An initially symmetric Alfvén pulse at a specific distance from a magnetic null-point is kicked towards the isothermal null-point. A shock-capturing Godunov-type PLUTO code is used to solve the ideal magnetohydrodynamic set equations in the context of wave-plasma energy transfer. As the Alfvén wave propagates towards the magnetic null-point it experiences speed lowering which ends up in releasing energy along the separatrices. In this line owing to the Alfvén wave, a series of events take place that contribute towards coronal heating. Nonlinear induced waves are by products of the torsional Alfvén interaction with magnetic null-points. The energy of these induced waves which are fast magnetoacoustic (transverse) and slow magnetoacoustic (longitudinal) waves are supplied by the Alfvén wave. The nonlinearly induced density perturbations are proportional to the Alfvén wave energy loss. This supplies energy for the propagation of fast and slow magnetoacoustic waves, where in contrast to the fast wave the slow wave experiences a continuous energy increase. As such, the slow wave may transfer its energy to the medium at later times, maintaining a continuous heating mechanism at the neighborhood of a magnetic null-point.

The factorial invariance of the CES-D during adolescence: are symptom profiles for depression stable across gender and time?

PubMed

Verhoeven, Marjolein; Sawyer, Michael G; Spence, Susan H

2013-02-01

This study examined the factorial invariance of the Center for Epidemiologic Studies of Depression Scale (CES-D) across gender and time during adolescence. The factor structure of the CES-D was compared at four annual measurement waves in a community sample of 2650 Australian adolescents. Confirmatory factor analyses showed that the factor structure of the CES-D was generally invariant across gender and time. However, gender differences were found on three items: for all waves the item 'I had crying spells' was a stronger indicator for depressive affect in females than males. On the final three waves the item 'people were unfriendly' loaded significantly higher on the factor 'Interpersonal Relations' for males than females. On Wave 2 and 3 males interpreted the item 'everything I did was an effort' with a positive connotation, whereas females interpret it with a negative association. These gender-differences are discussed from both a theoretical and a methodological perspective. Copyright © 2012 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Investigation of structural heterogeneity at the SPE site using combined P–wave travel times and Rg phase velocities

DOE PAGES

Rowe, Charlotte A.; Patton, Howard J.

2015-10-01

Here, we present analyses of the 2D seismic structure beneath Source Physics Experiments (SPE) geophone lines that extended radially at 100 m spacing from 100 to 2000 m from the source borehole. With seismic sources at only one end of the geophone lines, standard refraction profiling methods cannot resolve seismic velocity structures unambiguously. In previous work, we demonstrated overall agreement between body-wave refraction modeling and Rg dispersion curves for the least complex of the five lines. A more detailed inspection supports a 2D reinterpretation of the structure. We obtained Rg phase velocity measurements in both the time and frequency domains,more » then used iterative adjustment of the initial 1D body-wave model to predict Rg dispersion curves to fit the observed values. Our method applied to the most topographically severe of the geophone lines is supplemented with a 2D ray-tracing approach, whose application to P-wave arrivals supports the Rg analysis. In addition, midline sources will allow us to refine our characterization in future work.« less

Non-reciprocal elastic wave propagation in 2D phononic membranes with spatiotemporally varying material properties

NASA Astrophysics Data System (ADS)

Attarzadeh, M. A.; Nouh, M.

2018-05-01

One-dimensional phononic materials with material fields traveling simultaneously in space and time have been shown to break elastodynamic reciprocity resulting in unique wave propagation features. In the present work, a comprehensive mathematical analysis is presented to characterize and fully predict the non-reciprocal wave dispersion in two-dimensional space. The analytical dispersion relations, in the presence of the spatiotemporal material variations, are validated numerically using finite 2D membranes with a prescribed number of cells. Using omnidirectional excitations at the membrane's center, wave propagations are shown to exhibit directional asymmetry that increases drastically in the direction of the material travel and vanishes in the direction perpendicular to it. The topological nature of the predicted dispersion in different propagation directions are evaluated using the computed Chern numbers. Finally, the degree of the 2D non-reciprocity is quantified using a non-reciprocity index (NRI) which confirms the theoretical dispersion predictions as well as the finite simulations. The presented framework can be extended to plate-type structures as well as 3D spatiotemporally modulated phononic crystals.

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

PubMed

Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

2014-12-02

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia-gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia-gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia-gravity waves dominate at scales smaller than 500 km.

Transition from geostrophic turbulence to inertia–gravity waves in the atmospheric energy spectrum

PubMed Central

Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

2014-01-01

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth’s rotation and the atmosphere’s stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia–gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia–gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia–gravity waves dominate at scales smaller than 500 km. PMID:25404349

Comparison of a Classical and Quantum Based Restricted Boltzmann Machine (RBM) for Application to Non-linear Multivariate Regression.

NASA Astrophysics Data System (ADS)

Dorband, J. E.; Tilak, N.; Radov, A.

2016-12-01

In this paper, a classical computer implementation of RBM is compared to a quantum annealing based RBM running on a D-Wave 2X (an adiabatic quantum computer). The codes for both are essentially identical. Only a flag is set to change the activation function from a classically computed logistic function to the D-Wave. To obtain greater understanding of the behavior of the D-Wave, a study of the stochastic properties of a virtual qubit (a 12 qubit chain) and a cell of qubits (an 8 qubit cell) was performed. We will present the results of comparing the D-Wave implementation with a theoretically errorless adiabatic quantum computer. The main purpose of this study is to develop a generic RBM regression tool in order to infer CO2 fluxes from the NASA satellite OCO-2 observed CO2 concentrations and predicted atmospheric states using regression models. The carbon fluxes will then be assimilated into a land surface model to predict the Net Ecosystem Exchange at globally distributed regional sites.

Landslide Spreading, Impulse Water Waves and Modelling of the Vajont Rockslide

NASA Astrophysics Data System (ADS)

Crosta, Giovanni B.; Imposimato, Silvia; Roddeman, Dennis

2016-06-01

Landslides can occur in different environments and can interact with or fall into water reservoirs or open sea with different characteristics. The subaerial evolution and the transition from subaerial to subaqueous conditions can strongly control the landslide evolution and the generated impulse waves, and consequently the final hazard zonation. We intend to model the landslide spreading, the impact with the water surface and the generation of the impulse wave under different 2D and 3D conditions and settings. We verify the capabilities of a fully 2D and 3D FEM ALE approach to model and analyse near-field evolution. To this aim we validate the code against 2D laboratory experiments for different Froude number conditions (Fr = 1.4, 3.2). Then the Vajont rockslide (Fr = 0.26-0.75) and the consequent impulse wave are simulated in 2D and 3D. The sliding mass is simulated as an elasto-plastic Mohr-Coulomb material and the lake water as a fully inviscid low compressibility fluid. The rockslide model is validated against field observations, including the total duration, the profile and internal geometry of the final deposit, the maximum water run-up on the opposite valley flank and on the rockslide mass. 2D models are presented for both the case of a dry valley and that of the impounded lake. The set of fully 3D simulations are the first ones available and considering the rockslide evolution, propagation and interaction with the water reservoir. Advantages and disadvantages of the modelling approach are discussed.

Reverse process of usual optical analysis of boson-exchange superconductors: impurity effects on s- and d-wave superconductors.

PubMed

Hwang, Jungseek

2015-03-04

We performed a reverse process of the usual optical data analysis of boson-exchange superconductors. We calculated the optical self-energy from two (MMP and MMP+peak) input model electron-boson spectral density functions using Allen's formula for one normal and two (s- and d-wave) superconducting cases. We obtained the optical constants including the optical conductivity and the dynamic dielectric function from the optical self-energy using an extended Drude model, and finally calculated the reflectance spectrum. Furthermore, to investigate impurity effects on optical quantities we added various levels of impurities (from the clean to the dirty limit) in the optical self-energy and performed the same reverse process to obtain the optical conductivity, the dielectric function, and reflectance. From these optical constants obtained from the reverse process we extracted the impurity-dependent superfluid densities for two superconducting cases using two independent methods (the Ferrel-Glover-Tinkham sum rule and the extrapolation to zero frequency of -ϵ1(ω)ω(2)); we found that a certain level of impurities is necessary to get a good agreement on results obtained by the two methods. We observed that impurities give similar effects on various optical constants of s- and d-wave superconductors; the greater the impurities the more distinct the gap feature and the lower the superfluid density. However, the s-wave superconductor gives the superconducting gap feature more clearly than the d-wave superconductor because in the d-wave superconductors the optical quantities are averaged over the anisotropic Fermi surface. Our results supply helpful information to see how characteristic features of the electron-boson spectral function and the s- and d-wave superconducting gaps appear in various optical constants including raw reflectance spectrum. Our study may help with a thorough understanding of the usual optical analysis process. Further systematic study of experimental data collected at various conditions using the optical analysis process will help to reveal the origin of the mediated boson in the boson-exchange superconductors.

Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes

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

Bertelli, N., E-mail: nbertell@pppl.gov; Gerhardt, S.; Hosea, J. C.

2015-12-10

Several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves, have found strong interactions between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 3D AORSA results for the Nationalmore » Spherical Torus eXperiment (NSTX), where a full antenna spectrum is reconstructed, are shown, confirming the same behavior found for a single toroidal mode results in Bertelli et al, Nucl. Fusion, 54 083004, 2014, namely, a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is moved away from in front of the antenna by increasing the edge density. Additionally, full wave simulations have been extended to “conventional” tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for Alcator C-Mod and EAST, which operate in the minority heating regime unlike NSTX/NSTX-U and DIII-D, which operate in the mid/high harmonic regime. A substantial discussion of some of the main aspects, such as (i) the pitch angle of the magnetic field; (ii) minority heating vs. mid/high harmonic regimes is presented showing the different behavior of the RF field in the SOL region for NSTX-U scenarios with different plasma current. Finally, the preliminary results of the impact of the SOL region on the evaluation of the helicon current drive efficiency in DIII-D is presented for the first time and briefly compared with the different regimes mentioned above.« less

Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes

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

Bertelli, Nicola; Jaeger, E. F.; Lau, Cornwall H

2015-01-01

Several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves, have found strong interactions between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 3D AORSA results for the Nationalmore » Spherical Torus eXperiment (NSTX), where a full antenna spectrum is reconstructed, are shown, confirming the same behavior found for a single toroidal mode results in Bertelli et al, Nucl. Fusion, 54 083004, 2014, namely, a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is moved away from in front of the antenna by increasing the edge density. Additionally, full wave simulations have been extended to "conventional" tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for Alcator C-Mod and EAST, which operate in the minority heating regime unlike NSTX/NSTX-U and DIII-D, which operate in the mid/high harmonic regime. A substantial discussion of some of the main aspects, such as (i) the pitch angle of the magnetic field; (ii) minority heating vs. mid/high harmonic regimes is presented showing the different behavior of the RF field in the SOL region for NSTX-U scenarios with different plasma current. Finally, the preliminary results of the impact of the SOL region on the evaluation of the helicon current drive efficiency in DIII-D is presented for the first time and briefly compared with the different regimes mentioned above.« less

3D crustal structure of the Alpine belt and foreland basins as imaged by ambient-noise surface wave

NASA Astrophysics Data System (ADS)

Molinari, Irene; Morelli, Andrea; Cardi, Riccardo; Boschi, Lapo; Poli, Piero; Kissling, Edi

2016-04-01

We derive a 3-D crustal structure (S wave velocity) underneath northern Italy and the wider Alpine region, from an extensive data set of measurements of Rayleigh-wave phase- and group-velocities from ambient noise correlation among all seismographic stations available to date in the region, via a constrained tomographic inversion made to honor detailed active source reflection/refraction profiles and other geological information. We first derive a regional-scale surface wave tomography from ambient-noise-based phase- and group- surface wave velocity observations (Verbeke et al., 2012). Our regional 3D model (Molinari et al., 2015) shows the low velocity area beneath the Po Plain and the Molasse basin; the contrast between the low-velocity crust of the Adriatic domain and the high-velocity crust of the Tyrrhenian domain is clearly seen, as well as an almost uniform crystalline crust beneath the Alpine belt. However, higher frequency data can be exploited to achieve higher resolution images of the Po Plain and Alpine foreland 3D crustal structure. We collected and analyze one year of noise records (2011) of ~100 North Italy seismic broadband stations, we derive the Green functions between each couple of stations and we measure the phase- and group-Rayleigh wave velocity. We conduct a suite of linear least squares inversion of both phase- and group-velocity data, resulting in 2-D maps of Rayleigh-wave phase and group velocity at periods between 3 and 40s with a resolution of 0.1x0.1 degrees. The maps are then inverted to get the 3D structure with unprecedented details. We present here our results, we compare them with other studies, and we discuss geological/geodynamical implications. We believe that such a model stands for the most up-to-date seismological information on the crustal structure of the Alpine belt and foreland basins, and it can represent a reliable reference for further, more detailed, studies to come, based on the high seismograph station density being accomplished by the AlpArray project.

Variability in benthic exchange rate, depth, and residence time beneath a shallow coastal estuary

NASA Astrophysics Data System (ADS)

Russoniello, C. J.; Michael, H. A.; Heiss, J.

2017-12-01

Hydrodynamically-driven exchange of water between the water column and shallow seabed aquifer, benthic exchange, is a significant and dynamic component of coastal and estuarine fluid budgets, but wave-induced benthic exchange has not been measured in the field. Mixing between surface water and groundwater solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times, constrains estimates of coastal chemical cycling. In this study, we present the first field-based direct measurements of wave-induced exchange and compare it to exchange induced by the other primary drivers of exchange - tides, and currents. We deployed instruments in a shallow estuary to measure benthic exchange and temporal variability over an 11-day period. Differential pressure sensors recorded pressure gradients across the seabed, and up-and down-looking ADCPs recorded currents and pressures from which wave parameters, surface-water currents, and water depth were determined. Wave-induced exchange was calculated directly from 1) differential pressure measurements, and indirectly with an analytical solution based on wave parameters from 2) ADCP and 3) weather station data. Groundwater flow models were used to assess the effects of aquifer properties on benthic exchange depth and residence time. Benthic exchange driven by tidal pumping or current-bedform interaction was calculated from tidal stage variation and from ADCP-measured currents at the bed, respectively. Waves were the primary benthic exchange driver (average = 20.0 cm/d, maximum = 92.3 cm/d) during the measurement period. Benthic exchange due to tides (average = 3.7 cm/d) and current-bedform interaction (average = 6.5x10-2 cm/d) was much lower. Wave-induced exchange calculated from pressure measurements and ADCP-measured wave parameters matched well, but wind-based rates underestimated wave energy and exchange. Groundwater models showed that residence time and depth increased in high-permeability, incompressible aquifers, and exchange rates increased in low-permeability, compressible aquifers. These findings support and extend the utility of existing wave-induced exchange solutions and will help managers assess the importance of benthic exchange on coastal chemical cycling.

Time-domain separation of interfering waves in cancellous bone using bandlimited deconvolution: simulation and phantom study.

PubMed

Wear, Keith A

2014-04-01

In through-transmission interrogation of cancellous bone, two longitudinal pulses ("fast" and "slow" waves) may be generated. Fast and slow wave properties convey information about material and micro-architectural characteristics of bone. However, these properties can be difficult to assess when fast and slow wave pulses overlap in time and frequency domains. In this paper, two methods are applied to decompose signals into fast and slow waves: bandlimited deconvolution and modified least-squares Prony's method with curve-fitting (MLSP + CF). The methods were tested in plastic and Zerdine(®) samples that provided fast and slow wave velocities commensurate with velocities for cancellous bone. Phase velocity estimates were accurate to within 6 m/s (0.4%) (slow wave with both methods and fast wave with MLSP + CF) and 26 m/s (1.2%) (fast wave with bandlimited deconvolution). Midband signal loss estimates were accurate to within 0.2 dB (1.7%) (fast wave with both methods), and 1.0 dB (3.7%) (slow wave with both methods). Similar accuracies were found for simulations based on fast and slow wave parameter values published for cancellous bone. These methods provide sufficient accuracy and precision for many applications in cancellous bone such that experimental error is likely to be a greater limiting factor than estimation error.

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2001-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear. time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that nonlinear waves are generated in coronal holes by torsional Alfv\\'{e}n waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the, fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature. and magnetic field geometry,) that will become available from the recently launched SOHO spacecraft.

Model of electron lifetimes inside the plasmasphere calculated using a CRRES derived hiss wave amplitude model

NASA Astrophysics Data System (ADS)

Orlova, Ksenia; Spasojevic, Maria; Shprits, Yuri

Particle populations in the inner magnetosphere can change by orders of magnitude on very short time scales. For the last decade observations and theoretical computations showed that resonant interaction of electrons with various plasma waves plays an important role in acceleration and loss mechanisms. Using data from the CRRES plasma wave experiment, we develop quadratic fits to the mean of the wave amplitude squared for plasmaspheric hiss as a function of geomagnetic activity (Kp) and magnetic latitude (lambda) for the dayside (6

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2000-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear, time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that solitary-like waves are generated in coronal holes nonlinearly by torsional Alfven waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature, and magnetic field geometry) that will become available from the recently launched SOHO spacecraft.

Intra-operative recording of motor tract potentials at the cervico-medullary junction following scalp electrical and magnetic stimulation of the motor cortex.

PubMed Central

Thompson, P D; Day, B L; Crockard, H A; Calder, I; Murray, N M; Rothwell, J C; Marsden, C D

1991-01-01

Activity in descending motor pathways after scalp electrical and magnetic brain stimulation of the motor cortex was recorded from the exposed cervico-medullary junction in six patients having trans-oral surgery of the upper cervical spine. Recordings during deep anaesthesia without muscle paralysis revealed an initial negative potential (D wave) at about 2 ms with electrical stimulation in five of the six patients. This was followed by a muscle potential which obscured any later waveforms. Magnetic stimulation produced clear potentials in only one patient. The earliest wave to magnetic stimulation during deep anaesthesia was 1-2 ms later than the earliest potential to electrical stimulation. Following lightening of the anaesthetic and the administration of muscle relaxants a series of later negative potentials (I waves) were more clearly seen to both electrical and magnetic stimulation. More I waves were recorded to magnetic stimulation during light anaesthesia than during deep anaesthesia. Increasing the intensity of electrical stimulation also produced an extra late I wave. At the highest intensity of magnetic stimulation the latency of the earliest potential was comparable to the D wave to electrical stimulation. The intervals between these various D and I waves corresponded to those previously described for the timing of single motor unit discharge after cortical stimulation. PMID:1654395

Melt-rock reaction in the asthenospheric mantle: Perspectives from high-order accurate numerical simulations in 2D and 3D

NASA Astrophysics Data System (ADS)

Tirupathi, S.; Schiemenz, A. R.; Liang, Y.; Parmentier, E.; Hesthaven, J.

2013-12-01

The style and mode of melt migration in the mantle are important to the interpretation of basalts erupted on the surface. Both grain-scale diffuse porous flow and channelized melt migration have been proposed. To better understand the mechanisms and consequences of melt migration in a heterogeneous mantle, we have undertaken a numerical study of reactive dissolution in an upwelling and viscously deformable mantle where solubility of pyroxene increases upwards. Our setup is similar to that described in [1], except we use a larger domain size in 2D and 3D and a new numerical method. To enable efficient simulations in 3D through parallel computing, we developed a high-order accurate numerical method for the magma dynamics problem using discontinuous Galerkin methods and constructed the problem using the numerical library deal.II [2]. Linear stability analyses of the reactive dissolution problem reveal three dynamically distinct regimes [3] and the simulations reported in this study were run in the stable regime and the unstable wave regime where small perturbations in porosity grows periodically. The wave regime is more relevant to melt migration beneath the mid-ocean ridges but computationally more challenging. Extending the 2D simulations in the stable regime in [1] to 3D using various combinations of sustained perturbations in porosity at the base of the upwelling column (which may result from a viened mantle), we show the geometry and distribution of dunite channel and high-porosity melt channels are highly correlated with inflow perturbation through superposition. Strong nonlinear interactions among compaction, dissolution, and upwelling give rise to porosity waves and high-porosity melt channels in the wave regime. These compaction-dissolution waves have well organized but time-dependent structures in the lower part of the simulation domain. High-porosity melt channels nucleate along nodal lines of the porosity waves, growing downwards. The wavelength scales with compaction length and varies slowly and systematically as a function of time. In the presence of a sustained porosity perturbation at the inflow (due to presence of low solidus materials), formation of self-organized wave fields is delayed. A single high-porosity dunite channel first develops, similar to those observed in the stable regime [1]. With increasing time, the amplitude of the wave increases, eventually overwhelms the high-porosity channel. A self-organized wavefield then emerges. The wave pattern depends weakly on the sustained porosity perturbation. The strong correlation in spatial distribution between dunite channel and mantle heterogeneity therefore is lost in the wave regime. In 3D, the idealized dunite channel is cylindrical, not tabular as often inferred from field observations. The latter may be formed in the presence of shear deformation, a subject that we are actively exploring [4]. [1] Schiemenz et al. (2011) Geohpys. J. Int. 186, 641-664. [2]. Bangerth et al. (2007) ACM Trans. Math. Software 33, doi: 10.1145/1268776.1268779. [3] Hesse et al. (2011) Geohpys. J. Int. 187, 1057-1075. [4]. Baltzell et al. (2013) AGU abstract.

Optical Kerr Spatiotemporal Dark-Lump Dynamics of Hydrodynamic Origin

NASA Astrophysics Data System (ADS)

Baronio, Fabio; Wabnitz, Stefan; Kodama, Yuji

2016-04-01

There is considerable fundamental and applicative interest in obtaining nondiffractive and nondispersive spatiotemporal localized wave packets propagating in optical cubic nonlinear or Kerr media. Here, we analytically predict the existence of a novel family of spatiotemporal dark lump solitary wave solutions of the (2 +1 )D nonlinear Schrödinger equation. Dark lumps represent multidimensional holes of light on a continuous wave background. We analytically derive the dark lumps from the hydrodynamic exact soliton solutions of the (2 +1 )D shallow water Kadomtsev-Petviashvili model, inheriting their complex interaction properties. This finding opens a novel path for the excitation and control of optical spatiotemporal waveforms of hydrodynamic footprint and multidimensional optical extreme wave phenomena.

Optical Kerr Spatiotemporal Dark-Lump Dynamics of Hydrodynamic Origin.

PubMed

Baronio, Fabio; Wabnitz, Stefan; Kodama, Yuji

2016-04-29

There is considerable fundamental and applicative interest in obtaining nondiffractive and nondispersive spatiotemporal localized wave packets propagating in optical cubic nonlinear or Kerr media. Here, we analytically predict the existence of a novel family of spatiotemporal dark lump solitary wave solutions of the (2+1)D nonlinear Schrödinger equation. Dark lumps represent multidimensional holes of light on a continuous wave background. We analytically derive the dark lumps from the hydrodynamic exact soliton solutions of the (2+1)D shallow water Kadomtsev-Petviashvili model, inheriting their complex interaction properties. This finding opens a novel path for the excitation and control of optical spatiotemporal waveforms of hydrodynamic footprint and multidimensional optical extreme wave phenomena.

Position-dependent radiative transfer as a tool for studying Anderson localization: Delay time, time-reversal and coherent backscattering

NASA Astrophysics Data System (ADS)

van Tiggelen, B. A.; Skipetrov, S. E.; Page, J. H.

2017-05-01

Previous work has established that the localized regime of wave transport in open media is characterized by a position-dependent diffusion coefficient. In this work we study how the concept of position-dependent diffusion affects the delay time, the transverse confinement, the coherent backscattering, and the time reversal of waves. Definitions of energy transport velocity of localized waves are proposed. We start with a phenomenological model of radiative transfer and then present a novel perturbational approach based on the self-consistent theory of localization. The latter allows us to obtain results relevant for realistic experiments in disordered quasi-1D wave guides and 3D slabs.

Modeling of Synergy Between 4th and 6th Harmonic Absorptions of Fast Waves on Injected Beams in DIII-D Tokamak

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

Choi, M.; Pinsker, R. I.; Chan, V. S.

2011-12-23

In recent moderate to high harmonic fast wave heating and current drive experiments in DIII-D, a synergy effect was observed when the 6{sup th} harmonic 90 MHz fast wave power is applied to the plasma preheated by neutral beams and the 4{sup th} harmonic 60 MHz fast wave. In this paper, we investigate how the synergy can occur using ORBIT-RF coupled with AORSA. Preliminary simulations suggest that damping of 4{sup th} harmonic FW on beam ions accelerates them above the injection energy, which may allow significant damping of 6{sup th} harmonic FW on beam ion tails to produce synergy.

Spread spectrum communication link using surface wave devices

NASA Technical Reports Server (NTRS)

Hunsinger, B. J.; Fugit, B. B.

1971-01-01

A fast lock-up, 8-MHz bandwidth 8,000 bit per second data rate spread spectrum communication link breadboard is described that is implemented using surface wave devices as the primary signal generators and signal processing elements. It uses surface wave tapped delay lines in the transmitter to generate the signals and in the receiver to detect them. The breadboard provides a measured processing gain for Gaussian noise of 31.5 dB which is within one dB of the theoretical optimum. This development demonstrates that spread spectrum receivers implemented with surface wave devices have sensitivities and complexities comparable to those of serial correlation receivers, but synchronization search times which are two to three orders of magnitude smaller.

TSA - A Two Scale Approximation for Wind-Generated Ocean Surface Waves

DTIC Science & Technology

2012-09-30

broad-scale version of TSA, or ‘ dTSA ’. In this manner dTSA is able to respond to changing wind situations. Results were shown to compare well with ‘exact...We also implemented the revised version of TSA, denoted ‘ dTSA ’, in WW3 for tests with a storm case, hurricane Juan, which made landfall as a...manner in which the broad-scale of TSA was defined, developing ‘ dTSA ’ as described above, so that in complicated rapidly changing wave spectra cases, a

Synchronization of follicular wave emergence in the seasonally anestrous ewe: the effects of estradiol with or without medroxyprogesterone acetate.

PubMed

Barrett, D M W; Bartlewski, P M; Duggavathi, R; Davies, K L; Huchkowsky, S L; Epp, T; Rawlings, N C

2008-04-15

Fertility is often lower in anestrous compared to cyclic ewes, after conventional estrus synchronization. We hypothesized that synchronization of ovarian follicular waves and ovulation could improve fertility at controlled breeding in anestrous ewes. Estradiol-17beta synchronizes follicular waves in cattle. The objectives of the present experiments were to study the effect of an estradiol injection, with or without a 12-d medroxyprogesterone acetate (MAP) sponge treatment, on synchronization of follicular waves and ovulation in anestrous ewes. Twenty ewes received sesame oil (n=8) or estradiol-17beta (350 microg; n=12). Eleven ewes received MAP sponges for 12d and were treated with oil (n=5) or estradiol-17beta (n=6) 6d before sponge removal. Saline (n=6) or eCG (n=6) was subsequently given to separate groups of ewes at sponge removal in the MAP/estradiol-17beta protocol. Estradiol treatment alone produced a peak in serum FSH concentrations (4.73+/-0.53 vs. 2.36+/-0.39 ng/mL for treatment vs. control; mean+/-S.E.M.) after a short-lived (6 h) suppression. Six of twelve ewes given estradiol missed a follicular wave around the time of estradiol injection. Medroxyprogesterone acetate-treated ewes given estradiol had more prolonged suppression of serum FSH concentrations (6-18 h) and a delay in the induced FSH peak (32.3+/-3.3 vs. 17.5+/-0.5 h). Wave emergence was delayed (5.7+/-0.3 vs. 1.4+/-0.7d from the time of estradiol injection), synchronized, and occurred at a predictable time (5-7 vs. 0-4d) compared to ewes given MAP alone. All ewes given eCG ovulated 3-4d after injection; this predictable time of ovulation may be efficacious for AI and embryo transfer.

Investigating Deep-Marine Sediment Waves in the Northern Gulf of Mexico Using 3D Seismic Data

NASA Astrophysics Data System (ADS)

Wang, Z.; Gani, M. R.

2016-12-01

Deep-water depositional elements have been studied for decades using outcrop, flume tank, sidescan sonar, and seismic data. Even though they have been well recognized by researchers, the improvements in the quality of 3D seismic data with increasingly larger dimension allow detailed analysis of deep-water depositional elements with new insights. This study focuses on the deep-marine sediment waves in the northern Gulf of Mexico. By interpreting a 3D seismic dataset covering 635 km2 at Mississippi Canyon and Viosca Knoll areas, large sediment waves, generated by sediment gravity flows, were mapped and analyzed with various seismic attributes. A succession of sediment waves, approximately 100 m in thickness, is observed on the marine slope that tapers out at the toe of the slope. The individual sediment wave exhibits up to 500 m in wavelength and up to 20 m in height. The wave crests oriented northeast-southwest are broadly aligned parallel to the regional slope-strike, indicating their sediment gravity flow origin. The crestlines are straight or slightly sinuous, with sinuosity increasing downslope. Their anti-dune patterns likely imply the presence of supercritical flows. The sediment waves have a retrogradational stacking pattern. Seismic amplitude maps of each sediment wave revealed that after depositing the majority of sheet-like sands on the upper slope, sediment gravity flows started to form large sediment waves on the lower slope. The steep and narrow upcurrent flanks of the sediment waves always display higher amplitudes than the gentle and wide downcurrent flanks, indicating that the sands were likely preferentially trapped along the upcurrent flanks, whereas the muds spread along the downcurrent flanks. The formation of sediment waves likely requires a moderate sand-mud ratio, as suggested by these observations: (1) absence of sediment waves on the upper slope where the sands were mainly deposited as unconfined sheets with a high sand-mud ratio; (2) absence of sediment waves on the basin floor, which is covered mainly by muds and hemipelagic sediments with a low sand-mud ratio; and (3) presence of sediment waves on the lower slope with a moderate sand-mud ratio.

Investigation of sinkhole areas in Germany using 2D shear wave reflection seismics and zero-offset VSP

NASA Astrophysics Data System (ADS)

Tschache, Saskia; Wadas, Sonja; Polom, Ulrich; Krawczyk, Charlotte M.

2017-04-01

Sinkholes pose a serious geohazard for humans and infrastructure in populated areas. The Junior Research Group Subrosion within the Leibniz Institute for Applied Geophysics and the joint project SIMULTAN work on the multi-scale investigation of subrosion processes in the subsurface, which cause natural sinkholes. In two case studies in sinkhole areas of Thuringia in Germany, we applied 2D shear wave reflection seismics using SH-waves with the aim to detect suitable parameters for the characterisation of critical zones. This method has the potential to image near-surface collapse and faulting structures in improved resolution compared to P-wave surveys resulting from the shorter wavelength of shear waves. Additionally, the shear wave velocity field derived by NMO velocity analysis is a basis to calculate further physical parameters, as e.g. the dynamic shear modulus. In both investigation areas, vertical seismic profiles (VSP) were acquired by generating P- and SH-waves (6 component VSP) directly next to a borehole equipped with a 3C downhole sensor. They provide shear and compressional wave velocity profiles, which are used to improve the 2D shear wave velocity field from surface seismics, to perform a depth calibration of the seismic image and to calculate the Vp/Vs ratio. The signals in the VSP data are analysed with respect to changes in polarisation and attenuation with depth and/or azimuth. The VSP data reveal low shear wave velocities of 200-300 m/s in rock layers known to be heavily affected by subrosion and confirm the low velocities calculated from the surface seismic data. A discrepancy of the shear wave velocities is observed in other intervals probably due to unsymmetrical travel paths in the surface seismics. In some VSP data dominant conversion of the direct SH-wave to P-wave is observed that is assumed to be caused by an increased presence of cavities. A potential fault distorting the vertical travel paths was detected by abnormal P-wave first arrivals in the VSP dataset of a borehole located near the city of Bad Frankenhausen. In addition, a strong attenuation of the source signals may indicate areas influenced by subrosion.

Microfabricated Millimeter-Wave High-Power Vacuum Electronic Amplifiers

DTIC Science & Technology

2015-01-01

Applications filed 2012). In spite of the challenges, high power sources of electromagnetic radiation are needed in the mmW bands for advanced DoD...Research Laboratory is demonstrating and developing millimeter-wave vacuum electronic traveling wave tube amplifiers at W- and G- band in the 10’ s to 100... s of watts power range at several percent instantaneous bandwidth. Keywords: Traveling wave tube; millimeter wave; vacuum electron device

Nonlinear and Dissipation Characteristics of Ocean Surface Waves in Estuarine Environments

DTIC Science & Technology

2014-09-30

transformation and evolution . In addition these modules would allow for feedback between the surface wave and the energy dissipating feature. OBJECTIVES...dissipation on wave processes. 3) Develop and test low-dimension, reduced representations of estuarine effects for inclusion into operational wave models...Sheremet (PI), Miao Tian and Cihan Sahin (Ph.D. students) who are working on modeling nonlinear wave evolution in dissipative environments (mud), and

Towards a new technique to construct a 3D shear-wave velocity model based on converted waves

NASA Astrophysics Data System (ADS)

Hetényi, G.; Colavitti, L.

2017-12-01

A 3D model is essential in all branches of solid Earth sciences because geological structures can be heterogeneous and change significantly in their lateral dimension. The main target of this research is to build a crustal S-wave velocity structure in 3D. The currently popular methodologies to construct 3D shear-wave velocity models are Ambient Noise Tomography (ANT) and Local Earthquake Tomography (LET). Here we propose a new technique to map Earth discontinuities and velocities at depth based on the analysis of receiver functions. The 3D model is obtained by simultaneously inverting P-to-S converted waveforms recorded at a dense array. The individual velocity models corresponding to each trace are extracted from the 3D initial model along ray paths that are calculated using the shooting method, and the velocity model is updated during the inversion. We consider a spherical approximation of ray propagation using a global velocity model (iasp91, Kennett and Engdahl, 1991) for the teleseismic part, while we adopt Cartesian coordinates and a local velocity model for the crust. During the inversion process we work with a multi-layer crustal model for shear-wave velocity, with a flexible mesh for the depth of the interfaces. The RFs inversion represents a complex problem because the amplitude and the arrival time of different phases depend in a non-linear way on the depth of interfaces and the characteristics of the velocity structure. The solution we envisage to manage the inversion problem is the stochastic Neighbourhood Algorithm (NA, Sambridge, 1999), whose goal is to find an ensemble of models that sample the good data-fitting regions of a multidimensional parameter space. Depending on the studied area, this method can accommodate possible independent and complementary geophysical data (gravity, active seismics, LET, ANT, etc.), helping to reduce the non-linearity of the inversion. Our first focus of application is the Central Alps, where a 20-year long dataset of high-quality teleseismic events recorded at 81 stations is available, and we have high-resolution P-wave velocity model available (Diehl et al., 2009). We plan to extend the 3D shear-wave velocity inversion method to the entire Alpine domain in frame of the AlpArray project, and apply it to other areas with a dense network of broadband seismometers.

CMS-Wave

DTIC Science & Technology

2014-10-27

a phase-averaged spectral wind-wave generation and transformation model and its interface in the Surface-water Modeling System (SMS). Ambrose...applications of the Boussinesq (BOUSS-2D) wave model that provides more rigorous calculations for design and performance optimization of integrated...navigation systems . Together these wave models provide reliable predictions on regional and local spatial domains and cost-effective engineering solutions

PROGRESS TOWARDS NEXT GENERATION, WAVEFORM BASED THREE-DIMENSIONAL MODELS AND METRICS TO IMPROVE NUCLEAR EXPLOSION MONITORING IN THE MIDDLE EAST

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

Savage, B; Peter, D; Covellone, B

2009-07-02

Efforts to update current wave speed models of the Middle East require a thoroughly tested database of sources and recordings. Recordings of seismic waves traversing the region from Tibet to the Red Sea will be the principal metric in guiding improvements to the current wave speed model. Precise characterizations of the earthquakes, specifically depths and faulting mechanisms, are essential to avoid mapping source errors into the refined wave speed model. Errors associated with the source are manifested in amplitude and phase changes. Source depths and paths near nodal planes are particularly error prone as small changes may severely affect themore » resulting wavefield. Once sources are quantified, regions requiring refinement will be highlighted using adjoint tomography methods based on spectral element simulations [Komatitsch and Tromp (1999)]. An initial database of 250 regional Middle Eastern events from 1990-2007, was inverted for depth and focal mechanism using teleseismic arrivals [Kikuchi and Kanamori (1982)] and regional surface and body waves [Zhao and Helmberger (1994)]. From this initial database, we reinterpreted a large, well recorded subset of 201 events through a direct comparison between data and synthetics based upon a centroid moment tensor inversion [Liu et al. (2004)]. Evaluation was done using both a 1D reference model [Dziewonski and Anderson (1981)] at periods greater than 80 seconds and a 3D model [Kustowski et al. (2008)] at periods of 25 seconds and longer. The final source reinterpretations will be within the 3D model, as this is the initial starting point for the adjoint tomography. Transitioning from a 1D to 3D wave speed model shows dramatic improvements when comparisons are done at shorter periods, (25 s). Synthetics from the 1D model were created through mode summations while those from the 3D simulations were created using the spectral element method. To further assess errors in source depth and focal mechanism, comparisons between the three methods were made. These comparisons help to identify problematic stations and sources which may bias the final solution. Estimates of standard errors were generated for each event's source depth and focal mechanism to identify poorly constrained events. A final, well characterized set of sources and stations will be then used to iteratively improve the wave speed model of the Middle East. After a few iterations during the adjoint inversion process, the sources will be reexamined and relocated to further reduce mapping of source errors into structural features. Finally, efforts continue in developing the infrastructure required to 'quickly' generate event kernels at the n-th iteration and invert for a new, (n+1)-th, wave speed model of the Middle East. While development of the infrastructure proceeds, initial tests using a limited number of events shows the 3D model, while showing vast improvement compared to the 1D model, still requires substantial modifications. Employing our new, full source set and iterating the adjoint inversions at successively shorter periods will lead to significant changes and refined wave speed structures of the Middle East.« less

Reversible electron heating vs. wave-particle interactions in quasi-perpendicular shocks

NASA Technical Reports Server (NTRS)

Veltri, P.; Mangeney, A.; Scudder, J. D.

1992-01-01

The energy necessary to explain the electron heating in quasi-perpendicular collisionless shocks can be derived either from the electron acceleration in the d.c. cross shock electric potential, or by the interactions between the electrons and the waves existing in the shock. A Monte Carlo simulation has been performed to study the electron distribution function evolution through the shock structure, with and without particle diffusion on waves. This simulation has allowed us to clarify the relative importance of the two possible energy sources; in particular it has been shown that the electron parallel temperature is determined by the d.c. electromagnetic field and not by any wave-particle-induced heating. Wave particle interactions are effective in smoothing out the large gradients in phase space produced by the 'reversible' motion of the electrons, thus producing a 'cooling' of the electrons.

Importance of a 3D forward modeling tool for surface wave analysis methods

NASA Astrophysics Data System (ADS)

Pageot, Damien; Le Feuvre, Mathieu; Donatienne, Leparoux; Philippe, Côte; Yann, Capdeville

2016-04-01

Since a few years, seismic surface waves analysis methods (SWM) have been widely developed and tested in the context of subsurface characterization and have demonstrated their effectiveness for sounding and monitoring purposes, e.g., high-resolution tomography of the principal geological units of California or real time monitoring of the Piton de la Fournaise volcano. Historically, these methods are mostly developed under the assumption of semi-infinite 1D layered medium without topography. The forward modeling is generally based on Thomson-Haskell matrix based modeling algorithm and the inversion is driven by Monte-Carlo sampling. Given their efficiency, SWM have been transfered to several scale of which civil engineering structures in order to, e.g., determine the so-called V s30 parameter or assess other critical constructional parameters in pavement engineering. However, at this scale, many structures may often exhibit 3D surface variations which drastically limit the efficiency of SWM application. Indeed, even in the case of an homogeneous structure, 3D geometry can bias the dispersion diagram of Rayleigh waves up to obtain discontinuous phase velocity curves which drastically impact the 1D mean velocity model obtained from dispersion inversion. Taking advantages of high-performance computing center accessibility and wave propagation modeling algorithm development, it is now possible to consider the use of a 3D elastic forward modeling algorithm instead of Thomson-Haskell method in the SWM inversion process. We use a parallelized 3D elastic modeling code based on the spectral element method which allows to obtain accurate synthetic data with very low numerical dispersion and a reasonable numerical cost. In this study, we choose dike embankments as an illustrative example. We first show that their longitudinal geometry may have a significant effect on dispersion diagrams of Rayleigh waves. Then, we demonstrate the necessity of 3D elastic modeling as a forward problem for the inversion of dispersion curves.

Demonstration of a Sub-Millimeter Wave Integrated Circuit (S-MMIC) using InP HEMT with a 35-nm Gate

NASA Technical Reports Server (NTRS)

Deal, W. R.; Din, S.; Padilla, J.; Radisic, V.; Mei, G.; Yoshida, W.; Liu, P. S.; Uyeda, J.; Barsky, M.; Gaier, T.;

Analytical studies on the Benney-Luke equation in mathematical physics

NASA Astrophysics Data System (ADS)

Islam, S. M. Rayhanul; Khan, Kamruzzaman; Woadud, K. M. Abdul Al

2018-04-01

The enhanced (G‧/G)-expansion method presents wide applicability to handling nonlinear wave equations. In this article, we find the new exact traveling wave solutions of the Benney-Luke equation by using the enhanced (G‧/G)-expansion method. This method is a useful, reliable, and concise method to easily solve the nonlinear evaluation equations (NLEEs). The traveling wave solutions have expressed in term of the hyperbolic and trigonometric functions. We also have plotted the 2D and 3D graphics of some analytical solutions obtained in this paper.

Numerical solution of equations governing longitudinal suspension line wave motion during the parachute unfurling process. Ph.D. Thesis - George Washington Univ., Washington, D. C.

NASA Technical Reports Server (NTRS)

Poole, L. R.

1973-01-01

Equations are presented which govern the dynamics of the lines-first parachute unfurling process, including wave motion in the parachute suspension lines. Techniques are developed for obtaining numerical solutions to the governing equations. Histories of tension at test data, and generally good agreement is observed. Errors in computed results are attributed to several areas of uncertainty, the most significant being a poorly defined boundary condition on the wave motion at the vehicle-suspension line boundary.

Features of Chaotic Transients in Excitable Media Governed by Spiral and Scroll Waves

NASA Astrophysics Data System (ADS)

Lilienkamp, Thomas; Christoph, Jan; Parlitz, Ulrich

2017-08-01

In excitable media, chaotic dynamics governed by spiral or scroll waves is often not persistent but transient. Using extensive simulations employing different mathematical models we identify a specific type-II supertransient by an exponential increase of transient lifetimes with the system size in 2D and an investigation of the dynamics (number and lifetime of spiral waves, Kaplan-Yorke dimension). In 3D, simulations exhibit an increase of transient lifetimes and filament lengths only above a critical thickness. Finally, potential implications for understanding cardiac arrhythmias are discussed.

Effect of water depth on wind-wave frequency spectrum I. Spectral form

NASA Astrophysics Data System (ADS)

Wen, Sheng-Chang; Guan, Chang-Long; Sun, Shi-Cai; Wu, Ke-Jian; Zhang, Da-Cuo

1996-06-01

Wen et al's method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m 0 and peak frequency {ie97-1}, contains in addition to the peakness factor {ie97-2} a depth parameter η=(2π m o)1/2/ d ( d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.

Optical theorem for two-dimensional (2D) scalar monochromatic acoustical beams in cylindrical coordinates.

PubMed

Mitri, F G

2015-09-01

The optical theorem for plane waves is recognized as one of the fundamental theorems in optical, acoustical and quantum wave scattering theory as it relates the extinction cross-section to the forward scattering complex amplitude function. Here, the optical theorem is extended and generalized in a cylindrical coordinates system for the case of 2D beams of arbitrary character as opposed to plane waves of infinite extent. The case of scalar monochromatic acoustical wavefronts is considered, and generalized analytical expressions for the extinction, absorption and scattering cross-sections are derived and extended in the framework of the scalar resonance scattering theory. The analysis reveals the presence of an interference scattering cross-section term describing the interaction between the diffracted Franz waves with the resonance elastic waves. The extended optical theorem in cylindrical coordinates is applicable to any object of arbitrary geometry in 2D located arbitrarily in the beam's path. Related investigations in optics, acoustics and quantum mechanics will benefit from this analysis in the context of wave scattering theory and other phenomena closely connected to it, such as the multiple scattering by a cloud of particles, as well as the resulting radiation force and torque. Copyright © 2015 Elsevier B.V. All rights reserved.

Intermittency and emergence of coherent structures in wave turbulence of a vibrating plate.

PubMed

Mordant, Nicolas; Miquel, Benjamin

2017-10-01

We report numerical investigations of wave turbulence in a vibrating plate. The possibility to implement advanced measurement techniques and long-time numerical simulations makes this system extremely valuable for wave turbulence studies. The purely 2D character of dynamics of the elastic plate makes it much simpler to handle compared to much more complex 3D physical systems that are typical of geo- and astrophysical issues (ocean surface or internal waves, magnetized plasmas or strongly rotating and/or stratified flows). When the forcing is small the observed wave turbulence is consistent with the predictions of the weak turbulent theory. Here we focus on the case of stronger forcing for which coherent structures can be observed. These structures look similar to the folds and D-cones that are commonly observed for strongly deformed static thin elastic sheets (crumpled paper) except that they evolve dynamically in our forced system. We describe their evolution and show that their emergence is associated with statistical intermittency (lack of self similarity) of strongly nonlinear wave turbulence. This behavior is reminiscent of intermittency in Navier-Stokes turbulence. Experimental data show hints of the weak to strong turbulence transition. However, due to technical limitations and dissipation, the strong nonlinear regime remains out of reach of experiments and therefore has been explored numerically.

Intermittency and emergence of coherent structures in wave turbulence of a vibrating plate

NASA Astrophysics Data System (ADS)

Mordant, Nicolas; Miquel, Benjamin

2017-10-01

We report numerical investigations of wave turbulence in a vibrating plate. The possibility to implement advanced measurement techniques and long-time numerical simulations makes this system extremely valuable for wave turbulence studies. The purely 2D character of dynamics of the elastic plate makes it much simpler to handle compared to much more complex 3D physical systems that are typical of geo- and astrophysical issues (ocean surface or internal waves, magnetized plasmas or strongly rotating and/or stratified flows). When the forcing is small the observed wave turbulence is consistent with the predictions of the weak turbulent theory. Here we focus on the case of stronger forcing for which coherent structures can be observed. These structures look similar to the folds and D-cones that are commonly observed for strongly deformed static thin elastic sheets (crumpled paper) except that they evolve dynamically in our forced system. We describe their evolution and show that their emergence is associated with statistical intermittency (lack of self similarity) of strongly nonlinear wave turbulence. This behavior is reminiscent of intermittency in Navier-Stokes turbulence. Experimental data show hints of the weak to strong turbulence transition. However, due to technical limitations and dissipation, the strong nonlinear regime remains out of reach of experiments and therefore has been explored numerically.

Very narrow excited Ωc baryons

NASA Astrophysics Data System (ADS)

Karliner, Marek; Rosner, Jonathan L.

2017-06-01

Recently, LHCb reported the discovery of five extremely narrow excited Ωc baryons decaying into Ξc+K-. We interpret these baryons as bound states of a c quark and a P -wave s s diquark. For such a system, there are exactly five possible combinations of spin and orbital angular momentum. The narrowness of the states could be a signal that it is hard to pull apart the two s quarks in a diquark. We predict two of spin 1 /2 , two of spin 3 /2 , and one of spin 5 /2 , all with negative parity. Of the five states, two can decay in S -wave, and three can decay in D -wave. Some of the D -wave states might be narrower than the S -wave states. We discuss the relations among the five masses expected in the quark model and the likely spin assignments, and we compare them with the data. A similar pattern is expected for negative-parity excited Ωb states. An alternative interpretation is noted in which the heaviest two states are 2 S excitations with JP=1 /2+ and 3 /2+, while the lightest three are those with JP=3 /2- , 3 /2- , 5 /2- , expected to decay via D -waves. In this case, we expect JP=1 /2- Ωc states around 2904 and 2978 MeV.

Monte-Carlo Orbit/Full Wave Simulation of Fast Alfvén Wave (FW) Damping on Resonant Ions in Tokamaks

NASA Astrophysics Data System (ADS)

Choi, M.; Chan, V. S.; Tang, V.; Bonoli, P.; Pinsker, R. I.; Wright, J.

2005-09-01

To simulate the resonant interaction of fast Alfvén wave (FW) heating and Coulomb collisions on energetic ions, including finite orbit effects, a Monte-Carlo code ORBIT-RF has been coupled with a 2D full wave code TORIC4. ORBIT-RF solves Hamiltonian guiding center drift equations to follow trajectories of test ions in 2D axisymmetric numerical magnetic equilibrium under Coulomb collisions and ion cyclotron radio frequency quasi-linear heating. Monte-Carlo operators for pitch-angle scattering and drag calculate the changes of test ions in velocity and pitch angle due to Coulomb collisions. A rf-induced random walk model describing fast ion stochastic interaction with FW reproduces quasi-linear diffusion in velocity space. FW fields and its wave numbers from TORIC are passed on to ORBIT-RF to calculate perpendicular rf kicks of resonant ions valid for arbitrary cyclotron harmonics. ORBIT-RF coupled with TORIC using a single dominant toroidal and poloidal wave number has demonstrated consistency of simulations with recent DIII-D FW experimental results for interaction between injected neutral-beam ions and FW, including measured neutron enhancement and enhanced high energy tail. Comparison with C-Mod fundamental heating discharges also yielded reasonable agreement.

A staggered-grid finite-difference scheme optimized in the time–space domain for modeling scalar-wave propagation in geophysical problems

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

Tan, Sirui, E-mail: siruitan@hotmail.com; Huang, Lianjie, E-mail: ljh@lanl.gov

For modeling scalar-wave propagation in geophysical problems using finite-difference schemes, optimizing the coefficients of the finite-difference operators can reduce numerical dispersion. Most optimized finite-difference schemes for modeling seismic-wave propagation suppress only spatial but not temporal dispersion errors. We develop a novel optimized finite-difference scheme for numerical scalar-wave modeling to control dispersion errors not only in space but also in time. Our optimized scheme is based on a new stencil that contains a few more grid points than the standard stencil. We design an objective function for minimizing relative errors of phase velocities of waves propagating in all directions within amore » given range of wavenumbers. Dispersion analysis and numerical examples demonstrate that our optimized finite-difference scheme is computationally up to 2.5 times faster than the optimized schemes using the standard stencil to achieve the similar modeling accuracy for a given 2D or 3D problem. Compared with the high-order finite-difference scheme using the same new stencil, our optimized scheme reduces 50 percent of the computational cost to achieve the similar modeling accuracy. This new optimized finite-difference scheme is particularly useful for large-scale 3D scalar-wave modeling and inversion.« less

Atmospheric waves and the nature of buoyancy turbulence in the context of the waves VS 2D-turbulence debate

NASA Technical Reports Server (NTRS)

Dewan, E. M.

1986-01-01

The problem of how to empirically distinguish between velocity fluctuations due to turbulence and those due to atmospheric waves is addressed. The physical differences between waves and turbulence are reviewed. New theoretical ideas on the subject of bouyancy range turbulence are presented. A unique scale K sub B is given that allows one to differentiate between waves and turbulence for the special case of theta = 0 (i.e., horizontal propagating waves).

Visualization of interaction of Mach waves with a bow shock

NASA Astrophysics Data System (ADS)

Pavlov, Al.; Golubev, M.; Kosinov, A.; Pavlov, A.

2017-10-01

The work presents results of investigation of couple weak waves with a bow shock at Mach number M = 2. The waves produced by a small 2D roughness installed on the nozzle inset or side wall of working section. Hot-wire measurements revealed profile of the waves to be similar to N-wave. The visualization was done by means of schlieren technique and interferential AVT SA method. The inclination angle change of the Mach waves at free-stream section and bow shock section was found.

Antiferromagnetism and DX2-Y2-WAVE Pairing in the Colored Hubbard Model

NASA Astrophysics Data System (ADS)

Baier, Tobias; Bick, Eike

2001-08-01

We introduce a new formulation of the 2d Hubbard model on a square lattice (the "colored" Hubbard model). In this formulation interesting physical nonlocal properties as antiferromagnetic or dx2-y2-wave superconducting behavior are included in an explicit way. Analyzing the phase diagram in a mean field approximation numerically, we show that our approach yields results which are in qualitative agreement with experiment.

Optical and thermal-transport properties of an inhomogeneous d-wave superconductor.

PubMed

Atkinson, W A; Hirschfeld, P J

2002-05-06

We calculate transport properties of disordered 2D d-wave superconductors from solutions of the Bogoliubov-de Gennes equations, and show that weak localization effects give rise to a finite-frequency peak in the optical conductivity similar to that observed in experiments on disordered cuprates. At low energies, order parameter inhomogeneities induce linear and quadratic temperature dependencies in microwave and thermal conductivities respectively, and appear to drive the system towards a quasiparticle insulating phase.

Three-dimensional transient rip currents: Bathymetric excitation of low-frequency intrinsic variability

NASA Astrophysics Data System (ADS)

Uchiyama, Yusuke; McWilliams, James C.; Akan, Cigdem

2017-07-01

The ROMS-WEC model [Uchiyama et al., 2010] based on an Eulerian wave-averaged vortex-force asymptotic theory of McWilliams et al. (2004) is applied to analyze 3-D transient wave-driven rip currents and associated intrinsic very low-frequency (VLF) variability in the surf zone on a surveyed bathymetry under spatiotemporally uniform offshore incident waves. The 3-D rip currents are substantially depth-dependent due to the vertical recirculation, composed of pairs of counter-rotating longitudinal overturning roll cells that promote surface convergence. The vortex force plays an important role in vorticity budget, preconditioning overall vorticity reduction. These rip currents are intrinsically unstable and contribute about 70% to kinetic energy (KE) as eddy kinetic energy (EKE), consistent with observations. The dominant fluctuation period fits the VLF band, at about 18 min. The current effect on waves (CEW) alters not only the mean rip structure, but also the associated turbulence as the modified cross-shore EKE profile with considerable accentuation in the inner surf zone. Increased alongshore bathymetric variability proportionally intensifies KE and intrinsic EKE, whereas it reduces the VLF period. With a guide of a pseudo 2D model, we reveal that vortex tilting effect due to the horizontal vorticity inherent in the 3-D rip currents promotes collapse of the 3-D eddies through an enhanced forward kinetic energy cascade, leading to short-lived, laterally-stretched 3-D eddies resulting in elongated filaments that decay more quickly than coherent, long-lived, circular 2-D eddies.

Non-Additive Voltametric Currents From a Mixture of Two, Three and Four Redox-Active Compounds and Electroanalytical Implications

NASA Technical Reports Server (NTRS)

Dass, Amala; Oh, Woon Su; Gao, Xue-Rong; Rawashdeh, Abdel M.; Leventis, Nicholas

2004-01-01

We have published recently the effect of dissimilar diffusion coefficients on the size of the voltammetric waves from a mixture of two redox-active compounds. Similarly, at the potential range where three redox-active species, decamethylferrocene (dMeFc), ferrocene (Fc) and N-methylphenothiazine (MePTZ), are oxidized simultaneously with rates controlled by linear diffusion, electrogenerated radicals diffusing outwards from the electrode react with the original species diffusing towards the electrode from the bulk; thus, Fc(+) reacts with dMeFc producing Fc and dMeFc(+), while MePTZ(+) reacts both with dMeFc producing MePTZ and dMeFc(+), and with Fc producing MePTZ and Fc(+). These reactions replace dMeFc with Fc at the second plateau, and both dMeFc and Fc with MePTZ at the third plateau. Since the diffusion coefficients of the three species are not equal, the mass-transfer limited currents of the second and the third oxidation wave plateaus change by approx. 10%. Numerical simulations of the experimental voltamograms support this mechanism. Similar results were also obtained for a mixture of four redoxactive compounds. The implications of this non-additive nature of currents on: (a) the use of internal voltammetric standards for quantitative analysis of a mixture of redox-active compounds; and, (b) the half wave potentials (E1/2) of the 2nd, 3rd and 4th waves for qualitative analysis, will be discussed.

Advanced Tsunami Numerical Simulations and Energy Considerations by use of 3D-2D Coupled Models: The October 11, 1918, Mona Passage Tsunami

NASA Astrophysics Data System (ADS)

López-Venegas, Alberto M.; Horrillo, Juan; Pampell-Manis, Alyssa; Huérfano, Victor; Mercado, Aurelio

2015-06-01

The most recent tsunami observed along the coast of the island of Puerto Rico occurred on October 11, 1918, after a magnitude 7.2 earthquake in the Mona Passage. The earthquake was responsible for initiating a tsunami that mostly affected the northwestern coast of the island. Runup values from a post-tsunami survey indicated the waves reached up to 6 m. A controversy regarding the source of the tsunami has resulted in several numerical simulations involving either fault rupture or a submarine landslide as the most probable cause of the tsunami. Here we follow up on previous simulations of the tsunami from a submarine landslide source off the western coast of Puerto Rico as initiated by the earthquake. Improvements on our previous study include: (1) higher-resolution bathymetry; (2) a 3D-2D coupled numerical model specifically developed for the tsunami; (3) use of the non-hydrostatic numerical model NEOWAVE (non-hydrostatic evolution of ocean WAVE) featuring two-way nesting capabilities; and (4) comprehensive energy analysis to determine the time of full tsunami wave development. The three-dimensional Navier-Stokes model tsunami solution using the Navier-Stokes algorithm with multiple interfaces for two fluids (water and landslide) was used to determine the initial wave characteristic generated by the submarine landslide. Use of NEOWAVE enabled us to solve for coastal inundation, wave propagation, and detailed runup. Our results were in agreement with previous work in which a submarine landslide is favored as the most probable source of the tsunami, and improvement in the resolution of the bathymetry yielded inundation of the coastal areas that compare well with values from a post-tsunami survey. Our unique energy analysis indicates that most of the wave energy is isolated in the wave generation region, particularly at depths near the landslide, and once the initial wave propagates from the generation region its energy begins to stabilize.

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography.

PubMed

Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

2016-09-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) "push beam" to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a "strain-like" compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥ 19 dB) between the target and background.

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography

PubMed Central

Mellema, Daniel C.; Song, Pengfei; Kinnick, Randall R.; Urban, Matthew W.; Greenleaf, James F.; Manduca, Armando; Chen, Shigao

2017-01-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) “push beam” to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a “strain-like” compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥19 dB) between the target and background. PMID:27076352

Ground Signatures of EMIC Waves obtained From a 3D Global Wave Model

NASA Astrophysics Data System (ADS)

Rankin, R.; Sydorenko, D.; Zong, Q.; Zhang, L.

2016-12-01

EMIC waves generated in the inner magnetosphere are important drivers of radiation belt particle loss. Van Allen Probes and ground observations of EMIC waves suggest that localized magnetospheric sources inject waves that are guided along geomagnetic field lines and then reflected and refracted in the low altitude magnetosphere [Kim, E.-H., and J. R. Johnson (2016), Geophys. Res. Lett., 43, 13-21, doi:10.1002/2015GL066978] before entering the ionosphere. The waves then spread horizontally within the F-region waveguide and propagate to the ground. To understand the observed properties of EMIC waves, a global 3D model of ULF waves in Earth's magnetosphere, ionosphere, and neutral atmosphere has been developed. The simulation domain extends from Earth's surface to a spherical boundary a few tens of thousands of km in radius. The model uses spherical coordinates and incorporates an overset Yin-Yang grid that eliminates the singularity at the polar axis and improves uniformity of the grid in the polar areas [Kageyama, A., and T. Sato (2004), Geochem. Geophys. Geosyst., 5, Q09005, doi:10.1029/2004GC000734]. The geomagnetic field in the model is general, but is dipole in this study. The plasma is described as a set of electron and multiple species ion conducting fluids. Realistic 3D density profiles of various ion species as well as thermospheric parameters are provided by the Canadian Ionosphere Atmosphere Model (C-IAM) [Martynenko O.V. et al. (2014), J. Atmos. Solar-Terr. Phys., 120, 51-61, doi:10.1016/j.jastp.2014.08.014]. The global ULF wave model is applied to study propagation of EMIC waves excited in the equatorial plane near L=7. Wave propagation along field lines, reflection and refraction in the zone of critical frequencies, and further propagation through the ionosphere to the ground are discussed.

Wave-CAIPI ViSTa: highly accelerated whole-brain direct myelin water imaging with zero-padding reconstruction.

PubMed

Wu, Zhe; Bilgic, Berkin; He, Hongjian; Tong, Qiqi; Sun, Yi; Du, Yiping; Setsompop, Kawin; Zhong, Jianhui

2018-09-01

This study introduces a highly accelerated whole-brain direct visualization of short transverse relaxation time component (ViSTa) imaging using a wave controlled aliasing in parallel imaging (CAIPI) technique, for acquisition within a clinically acceptable scan time, with the preservation of high image quality and sufficient spatial resolution, and reduced residual point spread function artifacts. Double inversion RF pulses were applied to preserve the signal from short T 1 components for directly extracting myelin water signal in ViSTa imaging. A 2D simultaneous multislice and a 3D acquisition of ViSTa images incorporating wave-encoding were used for data acquisition. Improvements brought by a zero-padding method in wave-CAIPI reconstruction were also investigated. The zero-padding method in wave-CAIPI reconstruction reduced the root-mean-square errors between the wave-encoded and Cartesian gradient echoes for all wave gradient configurations in simulation, and reduced the side-main lobe intensity ratio from 34.5 to 16% in the thin-slab in vivo ViSTa images. In a 4 × acceleration simultaneous-multislice scenario, wave-CAIPI ViSTa achieved negligible g-factors (g mean /g max  = 1.03/1.10), while retaining minimal interslice artifacts. An 8 × accelerated acquisition of 3D wave-CAIPI ViSTa imaging covering the whole brain with 1.1 × 1.1 × 3 mm 3 voxel size was achieved within 15 minutes, and only incurred a small g-factor penalty (g mean /g max  = 1.05/1.16). Whole-brain ViSTa images were obtained within 15 minutes with negligible g-factor penalty by using wave-CAIPI acquisition and zero-padding reconstruction. The proposed zero-padding method was shown to be effective in reducing residual point spread function for wave-encoded images, particularly for ViSTa. © 2018 International Society for Magnetic Resonance in Medicine.

Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

NASA Astrophysics Data System (ADS)

Wu, Jian-Wei; Qiu, Qi; Hyub Won, Yong

2017-04-01

In this paper, a semiconductor laser system consisting of a conventional multimode Fabry-Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to -22 dB and 15 dB, respectively.

External vibration multi-directional ultrasound shearwave elastography (EVMUSE): application in liver fibrosis staging.

PubMed

Zhao, Heng; Song, Pengfei; Meixner, Duane D; Kinnick, Randall R; Callstrom, Matthew R; Sanchez, William; Urban, Matthew W; Manduca, Armando; Greenleaf, James F; Chen, Shigao

2014-11-01

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called external vibration multi-directional ultrasound shearwave elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A 2-D shear wave speed map was reconstructed from each individual shear wave field, and a final 2-D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver magnetic resonance elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging.

External Vibration Multi-directional Ultrasound Shearwave Elastography (EVMUSE): Application in Liver Fibrosis Staging

PubMed Central

Zhao, Heng; Song, Pengfei; Meixner, Duane D.; Kinnick, Randall R.; Callstrom, Matthew R.; Sanchez, William; Urban, Matthew W.; Manduca, Armando; Greenleaf, James F.

2014-01-01

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called External Vibration Multi-directional Ultrasound Shearwave Elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A two-dimensional (2D) shear wave speed map was reconstructed from each individual shear wave field, and a final 2D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver Magnetic Resonance Elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging. PMID:25020066

Using Adjoint Methods to Improve 3-D Velocity Models of Southern California

NASA Astrophysics Data System (ADS)

Liu, Q.; Tape, C.; Maggi, A.; Tromp, J.

2006-12-01

We use adjoint methods popular in climate and ocean dynamics to calculate Fréchet derivatives for tomographic inversions in southern California. The Fréchet derivative of an objective function χ(m), where m denotes the Earth model, may be written in the generic form δχ=int Km(x) δln m(x) d3x, where δln m=δ m/m denotes the relative model perturbation. For illustrative purposes, we construct the 3-D finite-frequency banana-doughnut kernel Km, corresponding to the misfit of a single traveltime measurement, by simultaneously computing the 'adjoint' wave field s† forward in time and reconstructing the regular wave field s backward in time. The adjoint wave field is produced by using the time-reversed velocity at the receiver as a fictitious source, while the regular wave field is reconstructed on the fly by propagating the last frame of the wave field saved by a previous forward simulation backward in time. The approach is based upon the spectral-element method, and only two simulations are needed to produce density, shear-wave, and compressional-wave sensitivity kernels. This method is applied to the SCEC southern California velocity model. Various density, shear-wave, and compressional-wave sensitivity kernels are presented for different phases in the seismograms. We also generate 'event' kernels for Pnl, S and surface waves, which are the Fréchet kernels of misfit functions that measure the P, S or surface wave traveltime residuals at all the receivers simultaneously for one particular event. Effectively, an event kernel is a sum of weighted Fréchet kernels, with weights determined by the associated traveltime anomalies. By the nature of the 3-D simulation, every event kernel is also computed based upon just two simulations, i.e., its construction costs the same amount of computation time as an individual banana-doughnut kernel. One can think of the sum of the event kernels for all available earthquakes, called the 'misfit' kernel, as a graphical representation of the gradient of the misfit function. With the capability of computing both the value of the misfit function and its gradient, which assimilates the traveltime anomalies, we are ready to use a non-linear conjugate gradient algorithm to iteratively improve velocity models of southern California.

Finite-frequency sensitivity kernels for head waves

NASA Astrophysics Data System (ADS)

Zhang, Zhigang; Shen, Yang; Zhao, Li

2007-11-01

Head waves are extremely important in determining the structure of the predominantly layered Earth. While several recent studies have shown the diffractive nature and the 3-D Fréchet kernels of finite-frequency turning waves, analogues of head waves in a continuous velocity structure, the finite-frequency effects and sensitivity kernels of head waves are yet to be carefully examined. We present the results of a numerical study focusing on the finite-frequency effects of head waves. Our model has a low-velocity layer over a high-velocity half-space and a cylindrical-shaped velocity perturbation placed beneath the interface at different locations. A 3-D finite-difference method is used to calculate synthetic waveforms. Traveltime and amplitude anomalies are measured by the cross-correlation of synthetic seismograms from models with and without the velocity perturbation and are compared to the 3-D sensitivity kernels constructed from full waveform simulations. The results show that the head wave arrival-time and amplitude are influenced by the velocity structure surrounding the ray path in a pattern that is consistent with the Fresnel zones. Unlike the `banana-doughnut' traveltime sensitivity kernels of turning waves, the traveltime sensitivity of the head wave along the ray path below the interface is weak, but non-zero. Below the ray path, the traveltime sensitivity reaches the maximum (absolute value) at a depth that depends on the wavelength and propagation distance. The sensitivity kernels vary with the vertical velocity gradient in the lower layer, but the variation is relatively small at short propagation distances when the vertical velocity gradient is within the range of the commonly accepted values. Finally, the depression or shoaling of the interface results in increased or decreased sensitivities, respectively, beneath the interface topography.

ARRA-funded VS30 measurements using multi-technique approach at strong-motion stations in California and central-eastern United States

USGS Publications Warehouse

Yong, Alan; Martin, Antony; Stokoe, Kenneth; Diehl, John

2013-01-01

Funded by the 2009 American Recovery and Reinvestment Act (ARRA), we conducted geophysical site characterizations at 191 strong-motion stations: 187 in California and 4 in the Central-Eastern United States (CEUS). The geophysical methods used at each site included passive and active surface-wave and body-wave techniques. Multiple techniques were used at most sites, with the goal of robustly determining VS (shear-wave velocity) profiles and VS30 (the time-averaged shear-wave velocity in the upper 30 meters depth). These techniques included: horizontal-to-vertical spectral ratio (HVSR), two-dimensional (2-D) array microtremor (AM), refraction microtremor (ReMi™), spectral analysis of surface wave (SASW), multi-channel analysis of surface waves (Rayleigh wave: MASRW; and Love wave: MASLW), and compressional- and shear-wave refraction. Of the selected sites, 47 percent have crystalline, volcanic, or sedimentary rock at the surface or at relatively shallow depth, and 53 percent are of Quaternary sediments located in either rural or urban environments. Calculated values of VS30 span almost the full range of the National Earthquake Hazards Reduction Program (NEHRP) Site Classes, from D (stiff soils) to B (rock). The NEHRP Site Classes based on VS30 range from being consistent with the Class expected from analysis of surficial geology, to being one or two Site Classes below expected. In a few cases where differences between the observed and expected Site Class occurred, it was the consequence of inaccurate or coarse geologic mapping, as well as considerable degradation of the near-surface rock. Additionally, several sites mapped as rock have Site Class D (stiff soil) velocities, which is due to the extensive weathering of the surficial rock.

Dynamical relationship between wind speed magnitude and meridional temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM

NASA Astrophysics Data System (ADS)

Yamamoto, Masaru; Takahashi, Masaaki

2018-03-01

We derive simple dynamical relationships between wind speed magnitude and meridional temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed UMAX, meridional wind speed VMAX, and equator-pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general circulation forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin-Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

The Vajont disaster: a 3D numerical simulation for the slide and the waves

NASA Astrophysics Data System (ADS)

Rubino, Angelo; Androsov, Alexey; Vacondio, Renato; Zanchettin, Davide; Voltzinger, Naum

2016-04-01

A very high resolution O(5 m), 3D hydrostatic nonlinear numerical model was used to simulate the dynamics of both the slide and the surface waves produced during the Vajont disaster (north Italy, 1963), one of the major landslide-induced tsunamis ever documented. Different simulated wave phenomena like, e.g., maximum run-up on the opposite shore, maximum height, and water velocity were analyzed and compared with data available in literature, including the results of a fully 3D simulation obtained with a Smoothed Particle Hydrodynamic code. The difference between measured and simulated after-slide bathymetries was calculated and used in an attempt to quantify the relative magnitude and extension of rigid and fluid motion components during the event.

Simulation and Analysis of Converging Shock Wave Test Problems

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

Ramsey, Scott D.; Shashkov, Mikhail J.

2012-06-21

Results and analysis pertaining to the simulation of the Guderley converging shock wave test problem (and associated code verification hydrodynamics test problems involving converging shock waves) in the LANL ASC radiation-hydrodynamics code xRAGE are presented. One-dimensional (1D) spherical and two-dimensional (2D) axi-symmetric geometric setups are utilized and evaluated in this study, as is an instantiation of the xRAGE adaptive mesh refinement capability. For the 2D simulations, a 'Surrogate Guderley' test problem is developed and used to obviate subtleties inherent to the true Guderley solution's initialization on a square grid, while still maintaining a high degree of fidelity to the originalmore » problem, and minimally straining the general credibility of associated analysis and conclusions.« less

Amplitude mode oscillations in pump-probe photoemission spectra from a d -wave superconductor

DOE PAGES

Nosarzewski, B.; Moritz, B.; Freericks, J. K.; ...

2017-11-20

Recent developments in the techniques of ultrafast pump-probe photoemission have made possible the search for collective modes in strongly correlated systems out of equilibrium. Including inelastic scattering processes and a retarded interaction, we simulate time- and angle-resolved photoemission spectroscopy (trARPES) to study the amplitude mode of a d-wave superconductor, a collective mode excited through the nonlinear light-matter coupling to the pump pulse. We find that the amplitude mode oscillations of the d-wave order parameter occur in phase at a single frequency that is twice the quasi-steady-state maximum gap size after pumping. As a result, we comment on the necessary conditionsmore » for detecting the amplitude mode in trARPES experiments.« less

Amplitude mode oscillations in pump-probe photoemission spectra from a d -wave superconductor

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

Nosarzewski, B.; Moritz, B.; Freericks, J. K.

Recent developments in the techniques of ultrafast pump-probe photoemission have made possible the search for collective modes in strongly correlated systems out of equilibrium. Including inelastic scattering processes and a retarded interaction, we simulate time- and angle-resolved photoemission spectroscopy (trARPES) to study the amplitude mode of a d-wave superconductor, a collective mode excited through the nonlinear light-matter coupling to the pump pulse. We find that the amplitude mode oscillations of the d-wave order parameter occur in phase at a single frequency that is twice the quasi-steady-state maximum gap size after pumping. As a result, we comment on the necessary conditionsmore » for detecting the amplitude mode in trARPES experiments.« less

Large-scale experimental observations of sheet flow on a sandbar under skewed-asymmetric waves

NASA Astrophysics Data System (ADS)

Mieras, Ryan S.; Puleo, Jack A.; Anderson, Dylan; Cox, Daniel T.; Hsu, Tian-Jian

2017-06-01

A novel large wave flume experiment was conducted on a fixed, barred beach with a sediment pit on the sandbar, allowing for the isolation of small-scale bed response to large-scale forcing. Concurrent measurements of instantaneous sheet layer sediment concentration profiles and near-bed velocity profiles were obtained on a sandbar for the first time. Two sediment distributions were used with median grain diameters, d50, of 0.17 and 0.27 mm. Sheet flow occurred primarily under wave crests, where sheet thickness increased with increasing wave height. A proportionality constant, Λ, was used to relate maximum Shields parameter to maximum sheet thickness (normalized by d50), with bed shear stress computed using the quadratic drag law. An enhanced sheet layer thickness was apparent for the smaller sediment experiments (Λ = 18.7), when directly compared to closed-conduit oscillatory flow tunnel data (Λ = 10.6). However, Λ varied significantly (5 < Λ < 31) depending on the procedure used to estimate grain roughness, ks, and wave friction factor, fw. Three models for ks were compared (keeping the model for fw fixed): constant ks = 2.5d50, and two expressions dependent on flow intensity, derived from steady and oscillatory sheet flow experiments. Values of ks/d50 varied by two orders of magnitude and exhibited an inverse relationship with Λ, where Λ ˜ 30 for ks/d50 of O(1) while Λ ˜ 5 for ks/d50 of O(100). Two expressions for fw were also tested (with the steady flow-based model for ks), yielding a difference of 69% (Λ ˜ 13 versus Λ ˜ 22).

WASS: An open-source pipeline for 3D stereo reconstruction of ocean waves

NASA Astrophysics Data System (ADS)

Bergamasco, Filippo; Torsello, Andrea; Sclavo, Mauro; Barbariol, Francesco; Benetazzo, Alvise

2017-10-01

Stereo 3D reconstruction of ocean waves is gaining more and more popularity in the oceanographic community and industry. Indeed, recent advances of both computer vision algorithms and computer processing power now allow the study of the spatio-temporal wave field with unprecedented accuracy, especially at small scales. Even if simple in theory, multiple details are difficult to be mastered for a practitioner, so that the implementation of a sea-waves 3D reconstruction pipeline is in general considered a complex task. For instance, camera calibration, reliable stereo feature matching and mean sea-plane estimation are all factors for which a well designed implementation can make the difference to obtain valuable results. For this reason, we believe that the open availability of a well tested software package that automates the reconstruction process from stereo images to a 3D point cloud would be a valuable addition for future researches in this area. We present WASS (http://www.dais.unive.it/wass), an Open-Source stereo processing pipeline for sea waves 3D reconstruction. Our tool completely automates all the steps required to estimate dense point clouds from stereo images. Namely, it computes the extrinsic parameters of the stereo rig so that no delicate calibration has to be performed on the field. It implements a fast 3D dense stereo reconstruction procedure based on the consolidated OpenCV library and, lastly, it includes set of filtering techniques both on the disparity map and the produced point cloud to remove the vast majority of erroneous points that can naturally arise while analyzing the optically complex nature of the water surface. In this paper, we describe the architecture of WASS and the internal algorithms involved. The pipeline workflow is shown step-by-step and demonstrated on real datasets acquired at sea.

Effect of strong elastic contrasts on the propagation of seismic wave in hard-rock environments

NASA Astrophysics Data System (ADS)

Saleh, R.; Zheng, L.; Liu, Q.; Milkereit, B.

2013-12-01

Understanding the propagation of seismic waves in a presence of strong elastic contrasts, such as topography, tunnels and ore-bodies is still a challenge. Safety in mining is a major concern and seismic monitoring is the main tool here. For engineering purposes, amplitudes (peak particle velocity/acceleration) and travel times of seismic events (mostly blasts or microseismic events) are critical parameters that have to be determined at various locations in a mine. These parameters are useful in preparing risk maps or to better understand the process of spatial and temporal stress distributions in a mine. Simple constant velocity models used for monitoring studies in mining, cannot explain the observed complexities in scattered seismic waves. In hard-rock environments modeling of elastic seismic wavefield require detailed 3D petrophysical, infrastructure and topographical data to simulate the propagation of seismic wave with a frequencies up to few kilohertz. With the development of efficient numerical techniques, and parallel computation facilities, a solution for such a problem is achievable. In this study, the effects of strong elastic contrasts such as ore-bodies, rough topography and tunnels will be illustrated using 3D modeling method. The main tools here are finite difference code (SOFI3D)[1] that has been benchmarked for engineering studies, and spectral element code (SPECFEM) [2], which was, developed for global seismology problems. The modeling results show locally enhanced peak particle velocity due to presence of strong elastic contrast and topography in models. [1] Bohlen, T. Parallel 3-D viscoelastic finite difference seismic modeling. Computers & Geosciences 28 (2002) 887-899 [2] Komatitsch, D., and J. Tromp, Introduction to the spectral-element method for 3-D seismic wave propagation, Geophys. J. Int., 139, 806-822, 1999.

Mechanistic insights of the Min oscillator via cell-free reconstitution and imaging

NASA Astrophysics Data System (ADS)

Mizuuchi, Kiyoshi; Vecchiarelli, Anthony G.

2018-05-01

The MinD and MinE proteins of Escherichia coli self-organize into a standing-wave oscillator on the membrane to help align division at mid-cell. When unleashed from cellular confines, MinD and MinE form a spectrum of patterns on artificial bilayers—static amoebas, traveling waves, traveling mushrooms, and bursts with standing-wave dynamics. We recently focused our cell-free studies on bursts because their dynamics recapitulate many features of Min oscillation observed in vivo. The data unveiled a patterning mechanism largely governed by MinE regulation of MinD interaction with membrane. We proposed that the MinD to MinE ratio on the membrane acts as a toggle switch between MinE-stimulated recruitment and release of MinD from the membrane. In this review, we summarize cell-free data on the Min system and expand upon a molecular mechanism that provides a biochemical explanation as to how these two ‘simple’ proteins can form the remarkable spectrum of patterns.

Macroscopic character of composite high-temperature superconducting wires

NASA Astrophysics Data System (ADS)

Kivelson, S. A.; Spivak, B.

2015-11-01

The "d -wave" symmetry of the superconducting order in the cuprate high temperature superconductors is a well established fact [J. Tsuei and J. R. Kirtley, Rev. Mod. Phys. 72, 969 (2000), 10.1103/RevModPhys.72.969 and D. J. Vanharlingen, Rev. Mod. Phys. 67, 515 (1995), 10.1103/RevModPhys.67.515], and one which identifies them as "unconventional." However, in macroscopic contexts—including many potential applications (i.e., superconducting "wires")—the material is a composite of randomly oriented superconducting grains in a metallic matrix, in which Josephson coupling between grains mediates the onset of long-range phase coherence. [See, e.g., D. C. Larbalestier et al., Nat. Mater. 13, 375 (2014), 10.1038/nmat3887, A. P. Malozemoff, MRS Bull. 36, 601 (2011), 10.1557/mrs.2011.160, and K. Heine et al., Appl. Phys. Lett. 55, 2441 (1989), 10.1063/1.102295] Here we analyze the physics at length scales that are large compared to the size of such grains, and in particular the macroscopic character of the long-range order that emerges. While X Y -superconducting glass order and macroscopic d -wave superconductivity may be possible, we show that under many circumstances—especially when the d -wave superconducting grains are embedded in a metallic matrix—the most likely order has global s -wave symmetry.

Pseudopotential Method for Higher Partial Wave Scattering

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

Idziaszek, Zbigniew; Centrum Fizyki Teoretycznej, Polska Akademia Nauk, 02-668 Warsaw; Calarco, Tommaso

2006-01-13

We present a zero-range pseudopotential applicable for all partial wave interactions between neutral atoms. For p and d waves, we derive effective pseudopotentials, which are useful for problems involving anisotropic external potentials. Finally, we consider two nontrivial applications of the p-wave pseudopotential: we solve analytically the problem of two interacting spin-polarized fermions confined in a harmonic trap, and we analyze the scattering of p-wave interacting particles in a quasi-two-dimensional system.

Effect of fuel stratification on detonation wave propagation

NASA Astrophysics Data System (ADS)

Masselot, Damien; Fievet, Romain; Raman, Venkat

2016-11-01

Rotating detonation engines (RDEs) form a class of pressure-gain combustion systems of higher efficiency compared to conventional gas turbine engines. One of the key features of the design is the injection system, as reactants need to be continuously provided to the detonation wave to sustain its propagation speed. As inhomogeneities in the reactant mixture can perturb the detonation wave front, premixed fuel jet injectors might seem like the most stable solution. However, this introduces the risk of the detonation wave propagating through the injector, causing catastrophic failure. On the other hand, non-premixed fuel injection will tend to quench the detonation wave near the injectors, reducing the likelihood of such failure. Still, the effects of such non-premixing and flow inhomogeneities ahead of a detonation wave have yet to be fully understood and are the object of this study. A 3D channel filled with O2 diluted in an inert gas with circular H2 injectors is simulated as a detonation wave propagates through the system. The impact of key parameters such as injector spacing, injector size, mixture composition and time variations will be discussed. PhD Candidate.

Exploring dynamic events in the solar corona

NASA Astrophysics Data System (ADS)

Downs, Cooper James

With the advent of modern computational technology it is now becoming the norm to employ detailed 3D computer models as empirical tools that directly account for the inhomogeneous nature of the Sun-Heliosphere environment. The key advantage of this approach lies in the ability to compare model results directly to observational data and to use a successful comparison (or lack thereof) to glean information on the underlying physical processes. Using extreme ultraviolet waves (EUV waves) as the overarching scientific driver, we apply this observation modeling approach to study the complex dynamics of the magnetic and thermodynamic structures that are observed in the low solar corona. Representing a highly non-trivial effort, this work includes three main scientific thrusts: an initial modeling effort and two EUV wave case-studies. First we document the development of the new Low Corona (LC) model, a 3D time-dependent thermodynamic magnetohydrodynamic (MHD) model implemented within the Space Weather Modeling Framework (SWMF). Observation synthesis methods are integrated within the LC model, which provides the ability to compare model results directly to EUV imaging observations taken by spacecraft. The new model is then used to explore the dynamic interplay between magnetic structures and thermodynamic energy balance in the corona that is caused by coronal heating mechanisms. With the model development complete, we investigate the nature of EUV waves in detail through two case-studies. Starting with the 2008 March 25 event, we conduct a series of numerical simulations that independently vary fundamental parameters thought to govern the physical mechanisms behind EUV waves. Through the subsequent analysis of the 3D data and comparison to observations we find evidence for both wave and non-wave mechanisms contributing to the EUV wave signal. We conclude with a comprehensive observation and modeling analysis of the 2010 June 13 EUV wave event, which was observed by the recently launched Solar Dynamics Observatory. We use a high resolution simulation of the transient to unambiguously characterize the globally propagating front of EUV wave as a fast-mode magnetosonic wave, and use the rich set of observations to place the many other facets of the EUV transient within a unified scenario involving wave and non-wave components.

A Kosloff/Basal method, 3D migration program implemented on the CYBER 205 supercomputer

NASA Technical Reports Server (NTRS)

Pyle, L. D.; Wheat, S. R.

1984-01-01

Conventional finite difference migration has relied on approximations to the acoustic wave equation which allow energy to propagate only downwards. Although generally reliable, such approaches usually do not yield an accurate migration for geological structures with strong lateral velocity variations or with steeply dipping reflectors. An earlier study by D. Kosloff and E. Baysal (Migration with the Full Acoustic Wave Equation) examined an alternative approach based on the full acoustic wave equation. The 2D, Fourier type algorithm which was developed was tested by Kosloff and Baysal against synthetic data and against physical model data. The results indicated that such a scheme gives accurate migration for complicated structures. This paper describes the development and testing of a vectorized, 3D migration program for the CYBER 205 using the Kosloff/Baysal method. The program can accept as many as 65,536 zero offset (stacked) traces.

General Notions on Macroscopic Theory of Waves in Plasmas; NOTIONS GENERALES SUR LA THEORIE MACROSCOPIQUE DES ONDES DANS LES PLASMAS

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

Allis, W.P.; Delcroix, J.L.

1963-01-01

The propagation of monochromatic plane waves in an indefinite plasma is treated in the hydrodynamic theory of two fluids. Plasmas with isotropic pressure and waves obeying exact adiabaticity are considered. (D.C.W.)

Nucleon-nucleon interactions from dispersion relations: Elastic partial waves

NASA Astrophysics Data System (ADS)

Albaladejo, M.; Oller, J. A.

2011-11-01

We consider nucleon-nucleon (NN) interactions from chiral effective field theory. In this work we restrict ourselves to the elastic NN scattering. We apply the N/D method to calculate the NN partial waves taking as input the one-pion exchange discontinuity along the left-hand cut. This discontinuity is amenable to a chiral power counting as discussed by Lacour, Oller, and Meißner [Ann. Phys. (NY)APNYA60003-491610.1016/j.aop.2010.06.012 326, 241 (2011)], with one-pion exchange as its leading order contribution. The resulting linear integral equation for a partial wave with orbital angular momentum ℓ≥2 is solved in the presence of ℓ-1 constraints, so as to guarantee the right behavior of the D- and higher partial waves near threshold. The calculated NN partial waves are based on dispersion relations and are independent of regulator. This method can also be applied to higher orders in the calculation of the discontinuity along the left-hand cut and extended to triplet coupled partial waves.

SH wave structure of the crust and upper mantle in southeastern margin of the Tibetan Plateau from teleseismic Love wave tomography

NASA Astrophysics Data System (ADS)

Fu, Yuanyuan V.; Jia, Ruizhi; Han, Fengqin; Chen, Anguo

2018-06-01

The deep structure of southeastern Tibet is important for determining lateral plateau expansion mechanisms, such as movement of rigid crustal blocks along large strike-slip faults, continuous deformation or the eastward crustal channel flow. We invert for 3-D isotropic SH wave velocity model of the crust and upper mantle to the depth of 110 km from Love wave phase velocity data using a best fitting average model as the starting model. The 3-D SH velocity model presented here is the first SH wave velocity structure in the study area. In the model, the Tibetan Plateau is characterized by prominent slow SH wave velocity with channel-like geometry along strike-slip faults in the upper crust and as broad zones in the lower crust, indicating block-like and distributed deformation at different depth. Positive radial anisotropy (VSH > VSV) is suggested by a high SH wave and low SV wave anomaly at the depths of 70-110 km beneath the northern Indochina block. This positive radial anisotropy could result from the horizontal alignment of anisotropic minerals caused by lithospheric extensional deformation due to the slab rollback of the Australian plate beneath the Sumatra trench.

An Experimental Study of Droplets Produced by a Plunging Breakers

NASA Astrophysics Data System (ADS)

Erinin, Martin; Wang, Dan; Towle, David; Liu, Xinan; Duncan, James

2016-11-01

In this study, the production of droplets by a mechanically generated plunging breaking water wave is investigated in a wave tank. The breaker, with an amplitude of 0.070 m, is generated repeatedly with a programmable wave maker by using a dispersively focused wave packet (average frequency 1.15 Hz). The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a cinematic digital in-line holographic system positioned at 30 locations along a horizontal plane that is 1 cm above the maximum wave crest height. This measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d >100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the breaking wave is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. The support of the National Science Foundation under Grant OCE0751853 from the Division of Ocean Sciences is gratefully acknowledged.

Shock wave attenuation by grids and orifice plates

NASA Astrophysics Data System (ADS)

Britan, A.; Igra, O.; Ben-Dor, G.; Shapiro, H.

2006-11-01

The interaction of weak shock waves with porous barriers of different geometries and porosities is examined. Installing a barrier inside the shock tube test section will cause the development of the following wave pattern upon a head-on collision between the incident shock wave and the barrier: a reflected shock from the barrier and a transmitted shock propagating towards the shock tube end wall. Once the transmitted shock wave reaches the end wall it is reflected back towards the barrier. This is the beginning of multiple reflections between the barrier and the end wall. This full cycle of shock reflections/interactions resulting from the incident shock wave collision with the barrier can be studied in a single shock tube test. A one-dimensional (1D), inviscid flow model was proposed for simulating the flow resulting from the initial collision of the incident shock wave with the barrier. Fairly good agreement is found between experimental findings and simulations based on a 1D flow model. Based on obtained numerical and experimental findings an optimal design procedure for shock wave attenuator is suggested. The suggested attenuator may ensure the safety of the shelter’s ventilation systems.

Versatile rogue waves in scalar, vector, and multidimensional nonlinear systems

NASA Astrophysics Data System (ADS)

Chen, Shihua; Baronio, Fabio; Soto-Crespo, Jose M.; Grelu, Philippe; Mihalache, Dumitru

2017-11-01

This review is dedicated to recent progress in the active field of rogue waves, with an emphasis on the analytical prediction of versatile rogue wave structures in scalar, vector, and multidimensional integrable nonlinear systems. We first give a brief outline of the historical background of the rogue wave research, including referring to relevant up-to-date experimental results. Then we present an in-depth discussion of the scalar rogue waves within two different integrable frameworks—the infinite nonlinear Schrödinger (NLS) hierarchy and the general cubic-quintic NLS equation, considering both the self-focusing and self-defocusing Kerr nonlinearities. We highlight the concept of chirped Peregrine solitons, the baseband modulation instability as an origin of rogue waves, and the relation between integrable turbulence and rogue waves, each with illuminating examples confirmed by numerical simulations. Later, we recur to the vector rogue waves in diverse coupled multicomponent systems such as the long-wave short-wave equations, the three-wave resonant interaction equations, and the vector NLS equations (alias Manakov system). In addition to their intriguing bright-dark dynamics, a series of other peculiar structures, such as coexisting rogue waves, watch-hand-like rogue waves, complementary rogue waves, and vector dark three sisters, are reviewed. Finally, for practical considerations, we also remark on higher-dimensional rogue waves occurring in three closely-related (2  +  1)D nonlinear systems, namely, the Davey-Stewartson equation, the composite (2  +  1)D NLS equation, and the Kadomtsev-Petviashvili I equation. As an interesting contrast to the peculiar X-shaped light bullets, a concept of rogue wave bullets intended for high-dimensional systems is particularly put forward by combining contexts in nonlinear optics.

Ultrafast Ultrasound Imaging With Cascaded Dual-Polarity Waves.

PubMed

Zhang, Yang; Guo, Yuexin; Lee, Wei-Ning

2018-04-01

Ultrafast ultrasound imaging using plane or diverging waves, instead of focused beams, has advanced greatly the development of novel ultrasound imaging methods for evaluating tissue functions beyond anatomical information. However, the sonographic signal-to-noise ratio (SNR) of ultrafast imaging remains limited due to the lack of transmission focusing, and thus insufficient acoustic energy delivery. We hereby propose a new ultrafast ultrasound imaging methodology with cascaded dual-polarity waves (CDWs), which consists of a pulse train with positive and negative polarities. A new coding scheme and a corresponding linear decoding process were thereby designed to obtain the recovered signals with increased amplitude, thus increasing the SNR without sacrificing the frame rate. The newly designed CDW ultrafast ultrasound imaging technique achieved higher quality B-mode images than coherent plane-wave compounding (CPWC) and multiplane wave (MW) imaging in a calibration phantom, ex vivo pork belly, and in vivo human back muscle. CDW imaging shows a significant improvement in the SNR (10.71 dB versus CPWC and 7.62 dB versus MW), penetration depth (36.94% versus CPWC and 35.14% versus MW), and contrast ratio in deep regions (5.97 dB versus CPWC and 5.05 dB versus MW) without compromising other image quality metrics, such as spatial resolution and frame rate. The enhanced image qualities and ultrafast frame rates offered by CDW imaging beget great potential for various novel imaging applications.

Spectral modelling of ice-induced wave decay: implementation of a new viscoelastic theory in WAVEWATCH III

NASA Astrophysics Data System (ADS)

Liu, Q.; Rogers, W. E.; Babanin, A. V.; Squire, V. A.; Mosig, J. E. M.; Li, J.; Guan, C.

2017-12-01

A new viscoelastic ice layer model is implemented in the third generation spectral wave model WAVEWATCH III to estimate the ice-induced, frequency-dependent wave attenuation rate. Two case studies are then conducted with this viscoelastic model: one is the hindcast of waves in the autumn Beaufort Sea, 2015, and the other is the modelling of wave fields in the Antarctic marginal ice zone (MIZ), 2012. It is demonstrated that the viscoelastic model is capable of reproducing the measured significant wave heights (Ηs) in these two different geophysical regions. The sensitivity of the simulated wave height on different source terms -- ice-induced decay Sice and other physical processes Sother such as wind input Sin, nonlinear four-wave interaction Snl -- is also investigated in this study. For the Antarctic MIZ experiment, Sother is found to be much less than Sice and thus contributes little to the simulated Hs. The trend of the wave height decay (dHs/dx) discovered recently -- saturating at large wave heights -- is well reproduced by the standalone linear viscoelastic model. The flattening of dHs/dx is most likely due to the only presence of longer waves, with the shorter waves having been already low-pass filtered. Nonetheless, Sother should not be disregarded within a more general modelling perspective as Sin and Snl is shown to be comparable or even much higher than Sice in the Beaufort Sea case.

The Effects of Realistic Geological Heterogeneity on Seismic Modeling: Applications in Shear Wave Generation and Near-Surface Tunnel Detection

NASA Astrophysics Data System (ADS)

Sherman, Christopher Scott

Naturally occurring geologic heterogeneity is an important, but often overlooked, aspect of seismic wave propagation. This dissertation presents a strategy for modeling the effects of heterogeneity using a combination of geostatistics and Finite Difference simulation. In the first chapter, I discuss my motivations for studying geologic heterogeneity and seis- mic wave propagation. Models based upon fractal statistics are powerful tools in geophysics for modeling heterogeneity. The important features of these fractal models are illustrated using borehole log data from an oil well and geomorphological observations from a site in Death Valley, California. A large part of the computational work presented in this disserta- tion was completed using the Finite Difference Code E3D. I discuss the Python-based user interface for E3D and the computational strategies for working with heterogeneous models developed over the course of this research. The second chapter explores a phenomenon observed for wave propagation in heteroge- neous media - the generation of unexpected shear wave phases in the near-source region. In spite of their popularity amongst seismic researchers, approximate methods for modeling wave propagation in these media, such as the Born and Rytov methods or Radiative Trans- fer Theory, are incapable of explaining these shear waves. This is primarily due to these method's assumptions regarding the coupling of near-source terms with the heterogeneities and mode conversion. To determine the source of these shear waves, I generate a suite of 3D synthetic heterogeneous fractal geologic models and use E3D to simulate the wave propaga- tion for a vertical point force on the surface of the models. I also present a methodology for calculating the effective source radiation patterns from the models. The numerical results show that, due to a combination of mode conversion and coupling with near-source hetero- geneity, shear wave energy on the order of 10% of the compressional wave energy may be generated within the shear radiation node of the source. Interestingly, in some cases this shear wave may arise as a coherent pulse, which may be used to improve seismic imaging efforts. In the third and fourth chapters, I discuss the results of a numerical analysis and field study of seismic near-surface tunnel detection methods. Detecting unknown tunnels and voids, such as old mine workings or solution cavities in karst terrain, is a challenging prob- lem in geophysics and has implications for geotechnical design, public safety, and domestic security. Over the years, a number of different geophysical methods have been developed to locate these objects (microgravity, resistivity, seismic diffraction, etc.), each with varying results. One of the major challenges facing these methods is understanding the influence of geologic heterogeneity on their results, which makes this problem a natural extension of the modeling work discussed in previous chapters. In the third chapter, I present the results of a numerical study of surface-wave based tunnel detection methods. The results of this analysis show that these methods are capable of detecting a void buried within one wavelength of the surface, with size potentially much less than one wavelength. In addition, seismic surface- wave based detection methods are effective in media with moderate heterogeneity (epsilon < 5 %), and in fact, this heterogeneity may serve to increase the resolution of these methods. In the fourth chapter, I discuss the results of a field study of tunnel detection methods at a site within the Black Diamond Mines Regional Preserve, near Antioch California. I use a com- bination of surface wave backscattering, 1D surface wave attenuation, and 2D attenuation tomography to locate and determine the condition of two tunnels at this site. These results compliment the numerical study in chapter 3 and highlight their usefulness for detecting tunnels at other sites.

On the origin of heavy-tail statistics in equations of the Nonlinear Schrödinger type

NASA Astrophysics Data System (ADS)

Onorato, Miguel; Proment, Davide; El, Gennady; Randoux, Stephane; Suret, Pierre

2016-09-01

We study the formation of extreme events in incoherent systems described by the Nonlinear Schrödinger type of equations. We consider an exact identity that relates the evolution of the normalized fourth-order moment of the probability density function of the wave envelope to the rate of change of the width of the Fourier spectrum of the wave field. We show that, given an initial condition characterized by some distribution of the wave envelope, an increase of the spectral bandwidth in the focusing/defocusing regime leads to an increase/decrease of the probability of formation of rogue waves. Extensive numerical simulations in 1D+1 and 2D+1 are also performed to confirm the results.

Detonator Performance Characterization using Multi-Frame Laser Schlieren Imaging

NASA Astrophysics Data System (ADS)

Clarke, Steven; Landon, Colin; Murphy, Michael; Martinez, Michael; Mason, Thomas; Thomas, Keith

2009-06-01

Multi-frame Laser Schlieren Imaging of shock waves produced by detonators in transparent witness materials can be used to evaluate detonator performance. We use inverse calculations of the 2D propagation of shock waves in the EPIC finite element model computer code to calculate a temporal-spatial-pressure profile on the surface of the detonator that is consistent with the experimental shock waves from the schlieren imaging. Examples of calculated 2D temporal-spatial-pressure profiles from a range of detonator types (EFI --exploding foil initiators, DOI -- direct optical initiation, EBW -- exploding bridge wire, hotwire), detonator HE materials (PETN, HMX, etc), and HE densities. Also pressure interaction profiles from the interaction of multiple shock waves will be shown. LA-UR-09-00909.

1D GAS-DYNAMIC SIMULATION OF SHOCK-WAVE PROCESSES VIA INTERNET

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

Khishchenko, K. V.; Levashov, P. R.; Povarnitsyn, M. E.

2009-12-28

We present a Web-interface for 1D simulation of different shock-wave experiments. The choosing of initial parameters, the modeling itself and output data treatment can be made directly via the Internet. The interface is based upon the expert system on shock-wave data and equations of state and contains both the Eulerian and Lagrangian Godunov hydrocodes. The availability of equations of state for a broad set of substances makes this system a useful tool for planning and interpretation of shock-wave experiments. As an example of simulation with the system, results of modeling of multistep shock loading of potassium between polytetrafluoroethylene and stainlessmore » steel plates are presented in comparison with experimental data from Shakhray et al.(2005).« less

Modelling strong seismic ground motion: three-dimensional loading path versus wavefield polarization

NASA Astrophysics Data System (ADS)

Santisi d'Avila, Maria Paola; Lenti, Luca; Semblat, Jean-François

2012-09-01

Seismic waves due to strong earthquakes propagating in surficial soil layers may both reduce soil stiffness and increase the energy dissipation into the soil. To investigate seismic wave amplification in such cases, past studies have been devoted to one-directional shear wave propagation in a soil column (1D-propagation) considering one motion component only (1C-polarization). Three independent purely 1C computations may be performed ('1D-1C' approach) and directly superimposed in the case of weak motions (linear behaviour). This research aims at studying local site effects by considering seismic wave propagation in a 1-D soil profile accounting for the influence of the 3-D loading path and non-linear hysteretic behaviour of the soil. In the proposed '1D-3C' approach, the three components (3C-polarization) of the incident wave are simultaneously propagated into a horizontal multilayered soil. A 3-D non-linear constitutive relation for the soil is implemented in the framework of the Finite Element Method in the time domain. The complex rheology of soils is modelled by mean of a multisurface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan type. The great advantage of this choice is that the only data needed to describe the model is the modulus reduction curve. A parametric study is carried out to characterize the changes in the seismic motion of the surficial layers due to both incident wavefield properties and soil non-linearities. The numerical simulations show a seismic response depending on several parameters such as polarization of seismic waves, material elastic and dynamic properties, as well as on the impedance contrast between layers and frequency content and oscillatory character of the input motion. The 3-D loading path due to the 3C-polarization leads to multi-axial stress interaction that reduces soil strength and increases non-linear effects. The non-linear behaviour of the soil may have beneficial or detrimental effects on the seismic response at the free surface, depending on the energy dissipation rate. Free surface time histories, stress-strain hysteresis loops and in-depth profiles of octahedral stress and strain are estimated for each soil column. The combination of three separate 1D-1C non-linear analyses is compared to the proposed 1D-3C approach, evidencing the influence of the 3C-polarization and the 3-D loading path on strong seismic motions.

Pitch Angle Scattering of Energetic Electrons by Plasmaspheric Hiss Emissions

NASA Astrophysics Data System (ADS)

Tobita, M.; Omura, Y.; Summers, D.

2017-12-01

We study scattering of energetic electrons in pitch angles and kinetic energies through their resonance with plasmaspheric hiss emissions consisting of many coherent discrete whistler-mode wave packets with rising and falling frequencies [1,2,3]. Using test particle simulations, we evaluate the efficiency of scattering, which depends on the inhomogeneity ratio S of whistler mode wave-particle interaction [4]. The value of S is determined by the wave amplitude, frequency sweep rate, and the gradient of the background magnetic field. We first modulate those parameters and observe variations of pitch angles and kinetic energies of electrons with a single wave under various S values so as to obtain basic understanding. We then include many waves into the system to simulate plasmaspheric hiss emissions. As the wave packets propagate away from the magnetic equator, the nonlinear trapping potential at the resonance velocity is deformed, making a channel of gyrophase for untrapped electrons to cross the resonance velocity, and causing modulations in their pitch angles and kinetic energies. We find efficient scattering of pitch angles and kinetic energies because of coherent nonlinear wave-particle interaction, resulting in electron precipitations into the polar atmosphere. We compare the results with the bounce averaged pitch angle diffusion coefficient based on quasi-linear theory, and show that the nonlinear wave model with many coherent packets can cause scattering of resonant electrons much faster than the quasi-linear diffusion process. [1] Summers, D., Omura, Y., Nakamura, S., and C. A. Kletzing (2014), Fine structure of plasmaspheric hiss, J. Geophys. Res., 119, 9134-9149. [2] Omura, Y., Y. Miyashita, M. Yoshikawa, D. Summers, M. Hikishima, Y. Ebihara, and Y. Kubota (2015), Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere, J. Geophys. Res. Space Physics, 120, 9545-9562. [3] Nakamura, S., Y. Omura, D. Summers, and C. A. Kletzing (2016), Observational evidence of the nonlinear wave growth theory of plasmaspheric hiss, Geophys. Res. Lett., 43, 10,040-10,049. [4] Omura, Y., Katoh, Y., and Summers, D., Theory and simulation of the generation of whistler-mode chorus (2008), J. Geophys. Res., 113, A04223.

Developments in Marine Current Turbine Research at the United States Naval Academy (Invited)

NASA Astrophysics Data System (ADS)

Flack, K. A.; Luznik, L.

2013-12-01

A series of tests have been performed on a 1/25th scale model of a two bladed horizontal axis marine current turbine. The tests were conducted in a large tow tank facility at the United States Naval Academy. The turbine model has a 0.8 m diameter (D) rotor with a NACA 63-618 cross section, which is Reynolds number independent with respect to the lift coefficient in the operating range of Rec ≈ 4 x 105. Baseline test were conducted to obtain torque, thrust and rotational speed at a range of tip speed ratios (TSR) from 5 < TSR < 11. The power and thrust coefficients for the model turbine match expected results from blade-element-momentum theory. The lift and drag curves for the numerical model were obtained by testing a 2D NACA 63-618 airfoil in a wind tunnel. Additional tests were performed at two rotor depths (1.3D and 2.25D) in the presence of intermediate and deep water waves. The average values for power and thrust coefficient are weakly dependent on turbine depth. The waves yield a small increase in turbine performance which can be explained by Stokes drift velocity. Phase averaged results indicate that the oscillatory wave velocity results in significant variations in measured turbine torque and rotational speed as a function of wave phase. The turbine rotation speed, power, and thrust reach a maximum with the passing of the wave crest and a minimum with the passing of the wave trough. The torque appears dependent on vertical velocity, which lags the horizontal velocity by 90° of wave phase. Variations of the performance parameters are of the same order of magnitude as the average value, especially when the turbine is near the mean free surface and in the presence of high energy waves. These results demonstrate the impact of surface gravity waves on power production and structural loading. Future tests will focus on measuring and modeling the wake of the turbine for unsteady flow conditions. Model Turbine Power Coefficient vs, Tip Speed Ratio

Toward 2D Seismic Wavefield Monitoring: Seismic Gradiometry for Long-Period Seismogram and Short-Period Seismogram Envelope applied to the Hi-net Array

NASA Astrophysics Data System (ADS)

Maeda, T.; Nishida, K.; Takagi, R.; Obara, K.

2015-12-01

The high-sensitive seismograph network Japan (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED) has about 800 stations with average separation of 20 km. We can observe long-period seismic wave propagation as a 2D wavefield with station separations shorter than wavelength. In contrast, short-period waves are quite incoherent at stations, however, their envelope shapes resemble at neighbor stations. Therefore, we may be able to extract seismic wave energy propagation by seismogram envelope analysis. We attempted to characterize seismic waveform at long-period and its envelope at short-period as 2D wavefield by applying seismic gradiometry. We applied the seismic gradiometry to a synthetic long-period (20-50s) dataset prepared by numerical simulation in realistic 3D medium at the Hi-net station layout. Wave amplitude and its spatial derivatives are estimated by using data at nearby stations. The slowness vector, the radiation pattern and the geometrical spreading are extracted from estimated velocity, displacement and its spatial derivatives. For short-periods at shorter than 1 s, seismogram envelope shows temporal and spatial broadening through scattering by medium heterogeneity. It is expected that envelope shape may be coherent among nearby stations. Based on this idea, we applied the same method to the time-integration of seismogram envelope to estimate its spatial derivatives. Together with seismogram envelope, we succeeded in estimating the slowness vector from the seismogram envelope as well as long-period waveforms by synthetic test, without using phase information. Our preliminarily results show that the seismic gradiometry suits the Hi-net to extract wave propagation characteristics both at long and short periods. This method is appealing that it can estimate waves at homogeneous grid to monitor seismic wave as a wavefield. It is promising to obtain phase velocity variation from direct waves, and to grasp wave packets originating from scattering from coda, by applying the seismic gradiometry to the Hi-net.

Combined illumination cylindrical millimeter-wave imaging technique for concealed weapon detection

NASA Astrophysics Data System (ADS)

Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.

2000-07-01

A novel millimeter-wave imaging technique has been developed for personnel surveillance applications, including the detection of concealed weapons, explosives, drugs, and other contraband material. Millimeter-waves are high-frequency radio waves in the frequency band of 30 - 300 GHz, and pose no health threat to humans at moderate power levels. These waves readily penetrate common clothing materials, and are reflected by the human body and by concealed items. The combined illumination cylindrical imaging concept consists of a vertical, high-resolution, millimeter-wave array of antennas which is scanned in a cylindrical manner about the person under surveillance. Using a computer, the data from this scan is mathematically reconstructed into a series of focused 3D images of the person. After reconstruction, the images are combined into a single high-resolution 3D image of the person under surveillance. This combined image is then rendered using 3D computer graphics techniques. The combined cylindrical illumination is critical as it allows the display of information from all angles. This is necessary because millimeter-waves do not penetrate the body. Ultimately, the images displayed to the operate will be icon-based to protect the privacy of the person being screened. Novel aspects of this technique include the cylindrical scanning concept and the image reconstruction algorithm, which was developed specifically for this imaging system. An engineering prototype based on this cylindrical imaging technique has been fabricated and tested. This work has been sponsored by the Federal Aviation Administration.

Study of Perturbations on High Mach Number Blast Waves in Various Gasses

NASA Astrophysics Data System (ADS)

Edens, A.; Adams, R.; Rambo, P.; Shores, J.; Smith, I.; Atherton, B.; Ditmire, T.

2006-10-01

We have performed a series of experiments examining the properties of high Mach number blast waves. Experiments were conducted on the Z-Beamlet^1 laser at Sandia National Laboratories. We created blast waves in the laboratory by using 10 J- 1000 J laser pulses to illuminate millimeter scale solid targets immersed in gas. Our experiments studied the validity of theories forwarded by Vishniac and Ryu^2-4 to explain the dynamics of perturbations on astrophysical blast waves. These experiments consisted of an examination of the evolution of perturbations of known primary mode number induced on the surface of blast waves by means of regularly spaced wire arrays. The temporal evolution of the amplitude of the induced perturbations relative to the mean radius of the blast wave was fit to a power law in time. Measurements were taken for a number of different mode numbers and background gasses and the results show qualitative agreement with previously published theories for the hydrodynamics of thin shell blast wave. The results for perturbations on nitrogen gas have been recently published^5. .^1 P. K. Rambo, I. C. Smith, J. L. Porter, et al., Applied Optics 44, 2421 (2005). ^2 D. Ryu and E. T. Vishniac, Astrophysical Journal 313, 820 (1987). ^3 D. Ryu and E. T. Vishniac, Astrophysical Journal 368, 411 (1991). ^4 E. T. Vishniac, Astrophysical Journal 274, 152 (1983). ^5 A. D. Edens, T. Ditmire, J. F. Hansen, et al., Physical Review Letters 95 (2005).

The Complex-Step-Finite-Difference method

NASA Astrophysics Data System (ADS)

Abreu, Rafael; Stich, Daniel; Morales, Jose

2015-07-01

We introduce the Complex-Step-Finite-Difference method (CSFDM) as a generalization of the well-known Finite-Difference method (FDM) for solving the acoustic and elastic wave equations. We have found a direct relationship between modelling the second-order wave equation by the FDM and the first-order wave equation by the CSFDM in 1-D, 2-D and 3-D acoustic media. We present the numerical methodology in order to apply the introduced CSFDM and show an example for wave propagation in simple homogeneous and heterogeneous models. The CSFDM may be implemented as an extension into pre-existing numerical techniques in order to obtain fourth- or sixth-order accurate results with compact three time-level stencils. We compare advantages of imposing various types of initial motion conditions of the CSFDM and demonstrate its higher-order accuracy under the same computational cost and dispersion-dissipation properties. The introduced method can be naturally extended to solve different partial differential equations arising in other fields of science and engineering.

Nonlinear to Linear Elastic Code Coupling in 2-D Axisymmetric Media.

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

Preston, Leiph

Explosions within the earth nonlinearly deform the local media, but at typical seismological observation distances, the seismic waves can be considered linear. Although nonlinear algorithms can simulate explosions in the very near field well, these codes are computationally expensive and inaccurate at propagating these signals to great distances. A linearized wave propagation code, coupled to a nonlinear code, provides an efficient mechanism to both accurately simulate the explosion itself and to propagate these signals to distant receivers. To this end we have coupled Sandia's nonlinear simulation algorithm CTH to a linearized elastic wave propagation code for 2-D axisymmetric media (axiElasti)more » by passing information from the nonlinear to the linear code via time-varying boundary conditions. In this report, we first develop the 2-D axisymmetric elastic wave equations in cylindrical coordinates. Next we show how we design the time-varying boundary conditions passing information from CTH to axiElasti, and finally we demonstrate the coupling code via a simple study of the elastic radius.« less

Measurement of {pi}{sup -}p{yields}{eta}n from threshold to p{sub {pi}}{sub {sup -}}=747 MeV/c

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

Prakhov, S.; Nefkens, B.M.K.; Clajus, M.

2005-07-01

The differential cross section for {eta} production in reaction {pi}{sup -}p{yields}{eta}n has been measured over the full angular range at seven incident {pi}{sup -} beam momenta from threshold to p{sub {pi}}{sub {sup -}}=747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total {eta} production cross section {sigma}{sup tot} is obtained by integration of d{sigma}/d{omega}. Starting at threshold, {sigma}{sup tot} rises rapidly, as expected for S-wave-dominated production. The features of the {pi}{sup -}p{yields}{eta}n cross section are strikinglymore » similar to those of the SU(3) flavor-related process K{sup -}p{yields}{eta}{lambda}. Comparison of the {pi}{sup -}p{yields}{eta}n reaction is made with {eta} photoproduction.« less

P- and S-Wave Speeds of the Very Upper Crust Estimated by a New Technique Based Upon Body-Wave Polarization

NASA Astrophysics Data System (ADS)

Park, S.; Ishii, M.

2017-12-01

Various seismic imaging methods have been developed, such as traveltime, waveform, and noise tomography, improving our knowledge of the subsurface structure and evolution. Near-surface structure, in particular, is crucial in understanding earthquake and volcano hazards. Seismic speed is directly related to the level of ground shaking, and monitoring its temporal change is valuable in volcanic hazard assessment. Here, we introduce a novel technique to constrain seismic wave speed of the very upper crust based upon the polarization measurements of teleseismic body-wave arrivals. The technique relates the orientation of recorded body waves to the wave speed immediately beneath a seismic instrument. We develop a counter-intuitive relationship that the P-wave polarization direction is only sensitive to subsurface shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. This approach is applied to the High-Sensitivity Seismograph Network in Japan, where the results are benchmarked against the borehole well data available at most stations. There is a good agreement between polarization-based estimates and the well measurements at as shallow as 100 m, confirming the efficacy of the new method in resolving the shallow structure. The lateral variation of wave speeds shows that sedimentary basins and mountainous regions are characterized by low and high wave speeds, respectively. It also correlates with volcano locations and geological units of different ages. Moreover, the analysis is expanded into 3D by examining the frequency dependence, where some preliminary results using broadband data are presented. These 2D and 3D wave speed estimates can be used to identify zones of high seismic risk by comparison with population distribution. This technique requires minimal computation resources and can be applied to any single three-component seismograph. It opens a new path to a reliable, non-invasive, and inexpensive earthquake hazard assessment in any environment where a drilling or a field experiment using vibro-trucks or explosives is not a practical option for measuring the near-surface seismic wave speeds. It can also provide means of monitoring changes that occur within the very upper crust such as from volcanic or hydrological phenomena.

Electromagnetic wave absorbing properties of amorphous carbon nanotubes.

PubMed

Zhao, Tingkai; Hou, Cuilin; Zhang, Hongyan; Zhu, Ruoxing; She, Shengfei; Wang, Jungao; Li, Tiehu; Liu, Zhifu; Wei, Bingqing

2014-07-10

Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7-50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was -25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at -10 dB was up to 5.8 GHz within the frequency range of 2-18 GHz.

On the Benefits of Creeping Wave Antennas in Reducing Interference Between Neighboring Wireless Body Area Networks.

PubMed

Tsouri, Gill R; Zambito, Stephanie R; Venkataraman, Jayanti

2017-02-01

We consider the on-body, off-body, and body-to-body channels in wireless body area networks utilizing creeping wave antennas. Experimental setups are used to gather measurements in the 2.4 GHz band with body area networks operating in an office environment. Data packets providing received signal strength indicators are used to assess the performance of the creeping wave antenna in reducing interference at a neighboring on-body access point while supporting reliable on-body communications. Results demonstrate that creeping wave antennas provide reliable on-body communications while significantly reducing inter-network interference; the inter-network interference is shown to be 10 dB weaker than the on-body signal. In addition, the inter-network interference when both networks utilize creeping wave antennas is shown to be 3 dB weaker than the interference when monopole antennas are used.

The influence of surface waves on tidal turbine performance characteristics

NASA Astrophysics Data System (ADS)

Van Benthem, M.; Luznik, L.; Flack, K.; Lust, E.

2012-12-01

Performance characteristics are presented for a 1/25th scale horizontal axis marine current turbine operating in calm conditions and in the presence of intermediate and deep water waves. The two-bladed turbine has radius of 0.4 m and a maximum blade pitch of 17°. The hydrofoil is a NACA63-618 which was selected to be Reynolds number independent in the operational range (ReC = 2 - 4 x 105). The experiments were performed in the 116 m towing tank at the United States Naval Academy at two depths 0.8D and 1.6D measured from the blade tip to the mean free surface. The performance characteristics without waves match expected results from blade-element-momentum theory. Results show that the average power coefficient is unaffected by the presence of waves, however, the phase averaged results indicate significant variation with wave phase.

Model-independent partial wave analysis using a massively-parallel fitting framework

NASA Astrophysics Data System (ADS)

Sun, L.; Aoude, R.; dos Reis, A. C.; Sokoloff, M.

2017-10-01

The functionality of GooFit, a GPU-friendly framework for doing maximum-likelihood fits, has been extended to extract model-independent {\\mathscr{S}}-wave amplitudes in three-body decays such as D + → h + h + h -. A full amplitude analysis is done where the magnitudes and phases of the {\\mathscr{S}}-wave amplitudes are anchored at a finite number of m 2(h + h -) control points, and a cubic spline is used to interpolate between these points. The amplitudes for {\\mathscr{P}}-wave and {\\mathscr{D}}-wave intermediate states are modeled as spin-dependent Breit-Wigner resonances. GooFit uses the Thrust library, with a CUDA backend for NVIDIA GPUs and an OpenMP backend for threads with conventional CPUs. Performance on a variety of platforms is compared. Executing on systems with GPUs is typically a few hundred times faster than executing the same algorithm on a single CPU.

Turbulence generation by waves

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

Kaftori, D.; Nan, X.S.; Banerjee, S.

The interaction between two-dimensional mechanically generated waves, and a turbulent stream was investigated experimentally in a horizontal channel, using a 3-D LDA synchronized with a surface position measuring device and a micro-bubble tracers flow visualization with high speed video. Results show that although the wave induced orbital motion reached all the way to the wall, the characteristics of the turbulence wall structures and the turbulence intensity close to the wall were not altered. Nor was the streaky nature of the wall layer. On the other hand, the mean velocity profile became more uniform and the mean friction velocity was increased.more » Close to the free surface, the turbulence intensity was substantially increased as well. Even in predominantly laminar flows, the introduction of 2-D waves causes three dimensional turbulence. The turbulence enhancement is found to be proportional to the wave strength.« less

Molecular isomerization induced by ultrashort infrared pulses. II. Pump-dump isomerization using pairs of time-delayed half-cycle pulses.

PubMed

Uiberacker, Christoph; Jakubetz, Werner

2004-06-22

We investigate population transfer across the barrier in a double-well potential, induced by a pair of time-delayed single-lobe half-cycle pulses. We apply this setup both to a one-dimensional (1D) quartic model potential and to a three-dimensional potential representing HCN-->HNC isomerization. Overall the results for the two systems are similar, although in the 3D system some additional features appear not seen in the 1D case. The generic mechanism of population transfer is the preparation by the pump pulse of a wave packet involving delocalized states above the barrier, followed by the essentially 1D motion of the delocalized part of wave packet across the barrier, and the eventual de-excitation by the dump pulse to localized states in the other well. The correct timing is given by the well-to-well passage time of the wave packet and its recurrence properties, and by the signs of the field lobes which determine the direction and acceleration or deceleration of the wave packet motion. In the 3D system an additional pump-pump-dump mechanism linked to wave packet motion in the reagent well can mediate isomerization. Since the transfer time and the pulse durations are of the same order of magnitude, there is also a marked dependence of the dynamics and the transfer yield on the pulse duration. Our analysis also sheds light on the pronounced carrier envelope phase dependence previously observed for isomerization and molecular dissociation with one-cycle and sub-one-cycle pulses. (c) 2004 American Institute of Physics.

206Pb+n resonances for E=600-900 keV: Neutron strength functions

NASA Astrophysics Data System (ADS)

Horen, D. J.; Harvey, J. A.; Hill, N. W.

1981-11-01

Data from high resolution neutron transmission and differential scattering measurements performed on 206Pb have been analyzed for E=600-900 keV. Resonance parameters (i.e., E, l, J, and Γn) have been deduced for many of the 161 resonances observed. Strength functions and potential phase shifts for s-, p-, and d-wave neutrons for En-0-900 keV are compared with optical model calculations. It is found that the phase contributed by the external R function as well as the integrated neutron strength functions can be reproduced for the s and d waves with a well depth of V0=50.4 MeV for the real potential and WD=6.0 MeV for an imaginary surface potential. Somewhat smaller values (V0=48.7 MeV and WD=2.0 MeV) are required to reproduce the p-wave data. These values of the real potential are also found to give the experimentally observed binding energies for the 4s12, 3d32, and 3d52 single particle levels (V0=50.4 MeV), and the 3p12 single particle level (V0=48.7 MeV). Nuclear level densities for s and d waves are found to be well represented by a constant temperature model. However, the model under estimates the number of p-wave resonances. NUCLEAR REACTIONS 206Pb(n), (n,n), E=600-900 keV; measured σT(E), σ(E,θ). 207Pb deduced resonance parameters, Jπ, Γn, neutron strength functions, optical model parameters for l=0,1,2.

Shape optimization of solid-air porous phononic crystal slabs with widest full 3D bandgap for in-plane acoustic waves

NASA Astrophysics Data System (ADS)

D'Alessandro, Luca; Bahr, Bichoy; Daniel, Luca; Weinstein, Dana; Ardito, Raffaele

2017-09-01

The use of Phononic Crystals (PnCs) as smart materials in structures and microstructures is growing due to their tunable dynamical properties and to the wide range of possible applications. PnCs are periodic structures that exhibit elastic wave scattering for a certain band of frequencies (called bandgap), depending on the geometric and material properties of the fundamental unit cell of the crystal. PnCs slabs can be represented by plane-extruded structures composed of a single material with periodic perforations. Such a configuration is very interesting, especially in Micro Electro-Mechanical Systems industry, due to the easy fabrication procedure. A lot of topologies can be found in the literature for PnCs with square-symmetric unit cell that exhibit complete 2D bandgaps; however, due to the application demand, it is desirable to find the best topologies in order to guarantee full bandgaps referred to in-plane wave propagation in the complete 3D structure. In this work, by means of a novel and fast implementation of the Bidirectional Evolutionary Structural Optimization technique, shape optimization is conducted on the hole shape obtaining several topologies, also with non-square-symmetric unit cell, endowed with complete 3D full bandgaps for in-plane waves. Model order reduction technique is adopted to reduce the computational time in the wave dispersion analysis. The 3D features of the PnC unit cell endowed with the widest full bandgap are then completely analyzed, paying attention to engineering design issues.

Wavelength selection and symmetry breaking in orbital wave ripples

NASA Astrophysics Data System (ADS)

Nienhuis, Jaap H.; Perron, J. Taylor; Kao, Justin C. T.; Myrow, Paul M.

2014-10-01

Sand ripples formed by waves have a uniform wavelength while at equilibrium and develop defects while adjusting to changes in the flow. These patterns arise from the interaction of the flow with the bed topography, but the specific mechanisms have not been fully explained. We use numerical flow models and laboratory wave tank experiments to explore the origins of these patterns. The wavelength of "orbital" wave ripples (λ) is directly proportional to the oscillating flow's orbital diameter (d), with many experimental and field studies finding λ/d ≈ 0.65. We demonstrate a coupling that selects this ratio: the maximum length of the flow separation zone downstream of a ripple crest equals λ when λ/d ≈ 0.65. We show that this condition maximizes the growth rate of ripples. Ripples adjusting to changed flow conditions develop defects that break the bed's symmetry. When d is shortened sufficiently, two new incipient crests appear in every trough, but only one grows into a full-sized crest. Experiments have shown that the same side (right or left) wins in every trough. We find that this occurs because incipient secondary crests slow the flow and encourage the growth of crests on the next flank. Experiments have also shown that when d is lengthened, ripple crests become increasingly sinuous and eventually break up. We find that this occurs because crests migrate preferentially toward the nearest adjacent crest, amplifying any initial sinuosity. Our results reveal the mechanisms that form common wave ripple patterns and highlight interactions among unsteady flows, sediment transport, and bed topography.

Single-scatter vector-wave scattering from surfaces with infinite slopes using the Kirchhoff approximation.

PubMed

Bruce, Neil C

2008-08-01

This paper presents a new formulation of the 3D Kirchhoff approximation that allows calculation of the scattering of vector waves from 2D rough surfaces containing structures with infinite slopes. This type of surface has applications, for example, in remote sensing and in testing or imaging of printed circuits. Some preliminary calculations for rectangular-shaped grooves in a plane are presented for the 2D surface method and are compared with the equivalent 1D surface calculations for the Kirchhoff and integral equation methods. Good agreement is found between the methods.

Collision-Driven Negative-Energy Waves and the Weibel Instability of a Relativistic Electron Beam in a Quasineutral Plasma

NASA Astrophysics Data System (ADS)

Karmakar, Anupam; Kumar, Naveen; Shvets, Gennady; Polomarov, Oleg; Pukhov, Alexander

2008-12-01

A new model describing the Weibel instability of a relativistic electron beam propagating through a resistive plasma is developed. For finite-temperature beams, a new class of negative-energy magnetosound waves is identified, whose growth due to collisional dissipation destabilizes the beam-plasma system even for high beam temperatures. We perform 2D and 3D particle-in-cell simulations and show that in 3D geometry the Weibel instability persists even for collisionless background plasma. The anomalous plasma resistivity in 3D is caused by the two-stream instability.

Membrane-bound MinDE complex acts as a toggle switch that drives Min oscillation coupled to cytoplasmic depletion of MinD

PubMed Central

Vecchiarelli, Anthony G.; Li, Min; Mizuuchi, Michiyo; Hwang, Ling Chin; Seol, Yeonee; Neuman, Keir C.; Mizuuchi, Kiyoshi

2016-01-01

The Escherichia coli Min system self-organizes into a cell-pole to cell-pole oscillator on the membrane to prevent divisions at the cell poles. Reconstituting the Min system on a lipid bilayer has contributed to elucidating the oscillatory mechanism. However, previous in vitro patterns were attained with protein densities on the bilayer far in excess of those in vivo and failed to recapitulate the standing wave oscillations observed in vivo. Here we studied Min protein patterning at limiting MinD concentrations reflecting the in vivo conditions. We identified “burst” patterns—radially expanding and imploding binding zones of MinD, accompanied by a peripheral ring of MinE. Bursts share several features with the in vivo dynamics of the Min system including standing wave oscillations. Our data support a patterning mechanism whereby the MinD-to-MinE ratio on the membrane acts as a toggle switch: recruiting and stabilizing MinD on the membrane when the ratio is high and releasing MinD from the membrane when the ratio is low. Coupling this toggle switch behavior with MinD depletion from the cytoplasm drives a self-organized standing wave oscillator. PMID:26884160

Membrane-bound MinDE complex acts as a toggle switch that drives Min oscillation coupled to cytoplasmic depletion of MinD.

PubMed

Vecchiarelli, Anthony G; Li, Min; Mizuuchi, Michiyo; Hwang, Ling Chin; Seol, Yeonee; Neuman, Keir C; Mizuuchi, Kiyoshi

2016-03-15

The Escherichia coli Min system self-organizes into a cell-pole to cell-pole oscillator on the membrane to prevent divisions at the cell poles. Reconstituting the Min system on a lipid bilayer has contributed to elucidating the oscillatory mechanism. However, previous in vitro patterns were attained with protein densities on the bilayer far in excess of those in vivo and failed to recapitulate the standing wave oscillations observed in vivo. Here we studied Min protein patterning at limiting MinD concentrations reflecting the in vivo conditions. We identified "burst" patterns--radially expanding and imploding binding zones of MinD, accompanied by a peripheral ring of MinE. Bursts share several features with the in vivo dynamics of the Min system including standing wave oscillations. Our data support a patterning mechanism whereby the MinD-to-MinE ratio on the membrane acts as a toggle switch: recruiting and stabilizing MinD on the membrane when the ratio is high and releasing MinD from the membrane when the ratio is low. Coupling this toggle switch behavior with MinD depletion from the cytoplasm drives a self-organized standing wave oscillator.

A nodal discontinuous Galerkin approach to 3-D viscoelastic wave propagation in complex geological media

NASA Astrophysics Data System (ADS)

Lambrecht, L.; Lamert, A.; Friederich, W.; Möller, T.; Boxberg, M. S.

2018-03-01

A nodal discontinuous Galerkin (NDG) approach is developed and implemented for the computation of viscoelastic wavefields in complex geological media. The NDG approach combines unstructured tetrahedral meshes with an element-wise, high-order spatial interpolation of the wavefield based on Lagrange polynomials. Numerical fluxes are computed from an exact solution of the heterogeneous Riemann problem. Our implementation offers capabilities for modelling viscoelastic wave propagation in 1-D, 2-D and 3-D settings of very different spatial scale with little logistical overhead. It allows the import of external tetrahedral meshes provided by independent meshing software and can be run in a parallel computing environment. Computation of adjoint wavefields and an interface for the computation of waveform sensitivity kernels are offered. The method is validated in 2-D and 3-D by comparison to analytical solutions and results from a spectral element method. The capabilities of the NDG method are demonstrated through a 3-D example case taken from tunnel seismics which considers high-frequency elastic wave propagation around a curved underground tunnel cutting through inclined and faulted sedimentary strata. The NDG method was coded into the open-source software package NEXD and is available from GitHub.

Fourier optics of constant-thickness three-dimensional objects on the basis of diffraction models

NASA Astrophysics Data System (ADS)

Chugui, Yu. V.

2017-09-01

Results of investigations of diffraction phenomena on constant-thickness three-dimensional objects with flat inner surfaces (thick plates) are summarized on the basis of our constructive theory of their calculation as applied to dimensional inspection. It is based on diffraction models of 3D objects with the use of equivalent diaphragms (distributions), which allow the Kirchhoff-Fresnel approximation to be effectively used. In contrast to available rigorous and approximate methods, the present approach does not require cumbersome calculations; it is a clearly arranged method, which ensures sufficient accuracy for engineering applications. It is found that the fundamental diffraction parameter for 3D objects of constant thickness d is the critical diffraction angle {θ _{cr}} = √ {λ /d} at which the effect of three-dimensionality on the spectrum of the 3D object becomes appreciable. Calculated Fraunhofer diffraction patterns (spectra) and images of constant-thickness 3D objects with absolutely absorbing, absolutely reflecting, and gray internal faces are presented. It is demonstrated that selection of 3D object fragments can be performed by choosing an appropriate configuration of the wave illuminating the object (plane normal or inclined waves, spherical waves).

Waveform complexity caused by near trench structure and its impact on earthquake source study: application to the 2015 Illapel earthquake sequence

NASA Astrophysics Data System (ADS)

Qian, Y.; Wei, S.; Wu, W.; Ni, S.

2017-12-01

Among various types of 3D heterogeneity in the Earth, trench might be the most complex systems, which includes rapidly varying bathymetry and usually thick sediment below water layer. These structure complexities can cause substantial waveform complexities on seismograms, but their corresponding impact on the earthquake source studies has not yet been well understood. Here we explore those effects via studies of two moderate aftershocks (one near the coast while the other close to the Peru-Chile trench axis) in the 2015 Illapel earthquake sequence. The horizontal locations and depths of these two events are poorly constrained and the reported results of various agencies display substantial variations. Thus, we first relocated the epicenters using the P-wave first arrivals and determined other parameters by waveform fitting. In a jackknifing way, we found that the trench event has large differences between regional and teleseismic solutions, in particular for depth, while the coastal event shows consistent results. The teleseismic P/Pdiff waves between these two events also display distinctly different features. More specifically, the trench event has more complex P/Pdiff waves and stronger coda waves, in terms of amplitude and duration (longer than 100s). The coda waves are coherent across stations at different distances and azimuths, indicating a more likely origin of scattering waves due to 3D heterogeneity near trench. To quantitatively model those 3D effects, we adopted a hybrid waveform simulation approach that computes the 3D wavefield in the source region by the Spectral Element Method (SEM) and then propagates the wavefield to teleseismic and shadow zone distances through the Direct Solution Method (DSM). We incorporated the GEBCO bathymetry and water layer into the SEM simulations and assumed the IASP91 1D model for DSM computation. Comparing with the poor 1D synthetics fitting to the data, we do obtain dramatic improvement in 3D waveform fittings across a series of frequency bands. With sensitivity tests of 3D waveform modeling, the centroid longitude and depth for the near trench event are refined. Our study suggests that the complex trench structure must be taken into account for a reliable analysis of shallow earthquake near trench, in particular for the shallowest tsunamigenic earthquakes.

Theory of quantum metal to superconductor transitions in highly conducting systems

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

Spivak, B.

2010-04-06

We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure whichmore » is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.« less