Imaging Crustal Structure with Waveform and HV Ratio of Body-wave Receiver Function

NASA Astrophysics Data System (ADS)

Chong, J.; Chu, R.; Ni, S.; Meng, Q.; Guo, A.

2017-12-01

It is known that receiver function has less constraint on the absolute velocity, and joint inversion of receiver function and surface wave dispersion has been widely applied to reduce the non-uniqueness of velocity and interface depth. However, some studies indicate that the receiver function itself is capable for determining the absolute shear wave velocity. In this study, we propose to measure the receiver function HV ratio which takes advantage of the amplitude information of the radial and vertical receiver functions to constrain the shear-wave velocity. Numerical analysis indicates that the receiver function HV ratio is sensitive to the average shear wave velocity in the depth range it samples, and can help to reduce the non-uniqueness of receiver function waveform inversion. A joint inversion scheme has been developed, and both synthetic tests and real data application proved the feasibility of the joint inversion. The method has been applied to the dense seismic array of ChinArray program in SE Tibet during the time period from August 2011 to August 2012 in SE Tibet (ChinArray-Himalaya, 2011). The measurements of receiver function HV ratio reveals the lateral variation of the tectonics in of the study region. And main features of the velocity structure imagined by the new joint inversion method are consistent with previous studies. KEYWORDS: receiver function HV ratio, receiver function waveform inversion, crustal structure ReferenceChinArray-Himalaya. 2011. China Seismic Array waveform data of Himalaya Project. Institute of Geophysics, China Earthquake Administration. doi:10.12001/ChinArray.Data. Himalaya. Jiajun Chong, Risheng Chu*, Sidao Ni, Qingjun Meng, Aizhi Guo, 2017. Receiver Function HV Ratio, a New Measurement for Reducing Non-uniqueness of Receiver Function Waveform Inversion. (under revision)

Wave steering effects in anisotropic composite structures: Direct calculation of the energy skew angle through a finite element scheme.

PubMed

Chronopoulos, D

2017-01-01

A systematic expression quantifying the wave energy skewing phenomenon as a function of the mechanical characteristics of a non-isotropic structure is derived in this study. A structure of arbitrary anisotropy, layering and geometric complexity is modelled through Finite Elements (FEs) coupled to a periodic structure wave scheme. A generic approach for efficiently computing the angular sensitivity of the wave slowness for each wave type, direction and frequency is presented. The approach does not involve any finite differentiation scheme and is therefore computationally efficient and not prone to the associated numerical errors. Copyright © 2016 Elsevier B.V. All rights reserved.

Metal-induced gap states in ferroelectric capacitors and its relationship with complex band structures

NASA Astrophysics Data System (ADS)

Junquera, Javier; Aguado-Puente, Pablo

2013-03-01

At metal-isulator interfaces, the metallic wave functions with an energy eigenvalue within the band gap decay exponentially inside the dielectric (metal-induced gap states, MIGS). These MIGS can be actually regarded as Bloch functions with an associated complex wave vector. Usually only real values of the wave vectors are discussed in text books, since infinite periodicity is assumed and, in that situation, wave functions growing exponentially in any direction would not be physically valid. However, localized wave functions with an exponential decay are indeed perfectly valid solution of the Schrodinger equation in the presence of defects, surfaces or interfaces. For this reason, properties of MIGS have been typically discussed in terms of the complex band structure of bulk materials. The probable dependence on the interface particulars has been rarely taken into account explicitly due to the difficulties to include them into the model or simulations. We aim to characterize from first-principles simulations the MIGS in realistic ferroelectric capacitors and their connection with the complex band structure of the ferroelectric material. We emphasize the influence of the real interface beyond the complex band structure of bulk materials. Financial support provided by MICINN Grant FIS2009-12721-C04-02, and by the European Union Grant No. CP-FP 228989-2 ``OxIDes''. Computer resources provided by the RES.

Cigar-shaped quarkonia under strong magnetic field

NASA Astrophysics Data System (ADS)

Suzuki, Kei; Yoshida, Tetsuya

2016-03-01

Heavy quarkonia in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the anisotropic wave functions are expanded by a Gaussian basis in the cylindrical coordinates. Deformation of the wave functions and the mass shifts of the S-wave heavy quarkonia (ηc, J /ψ , ηc(2 S ), ψ (2 S ) and bottomonia) are examined for the wide range of external magnetic field. The spatial structure of the wave functions changes drastically as adjacent energy levels cross each other. Possible observables in heavy-ion collision experiments and future lattice QCD simulations are also discussed.

Extracting a shape function for a signal with intra-wave frequency modulation.

PubMed

Hou, Thomas Y; Shi, Zuoqiang

2016-04-13

In this paper, we develop an effective and robust adaptive time-frequency analysis method for signals with intra-wave frequency modulation. To handle this kind of signals effectively, we generalize our data-driven time-frequency analysis by using a shape function to describe the intra-wave frequency modulation. The idea of using a shape function in time-frequency analysis was first proposed by Wu (Wu 2013 Appl. Comput. Harmon. Anal. 35, 181-199. (doi:10.1016/j.acha.2012.08.008)). A shape function could be any smooth 2π-periodic function. Based on this model, we propose to solve an optimization problem to extract the shape function. By exploring the fact that the shape function is a periodic function with respect to its phase function, we can identify certain low-rank structure of the signal. This low-rank structure enables us to extract the shape function from the signal. Once the shape function is obtained, the instantaneous frequency with intra-wave modulation can be recovered from the shape function. We demonstrate the robustness and efficiency of our method by applying it to several synthetic and real signals. One important observation is that this approach is very stable to noise perturbation. By using the shape function approach, we can capture the intra-wave frequency modulation very well even for noise-polluted signals. In comparison, existing methods such as empirical mode decomposition/ensemble empirical mode decomposition seem to have difficulty in capturing the intra-wave modulation when the signal is polluted by noise. © 2016 The Author(s).

Statistical anisotropy in free turbulence for mixing layers at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1996-08-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after propagating through free turbulent mixing layers. Shearing interferometers provide a two-dimensional flow visualization that is nonintrusive. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Experiments were performed on an unbounded, plane shear mixing layer of helium and nitrogen gas at fixed velocities and high Reynolds numbers for six locations in the flow development. Statistical autocorrelation functions and structure functions were computed on the reconstructed phase maps. The autocorrelation function results indicated that the turbulence-induced phase fluctuations were not wide-sense stationary. The structure functions exhibited statistical homogeneity, indicating that the phase fluctuations were stationary in first increments. However, the turbulence-corrupted phase was not isotropic. A five-thirds power law is shown to fit orthogonal slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence. Strehl ratios were computed from the phase structure functions and compared with classical estimates that assume isotropy. The isotropic models are shown to overestimate the optical degradation by nearly 3 orders of magnitude compared with the structure function calculations.

Longitudinal direct and indirect pathways linking older sibling competence to the development of younger sibling competence.

PubMed

Brody, Gene H; Kim, Sooyeon; Murry, Velma McBride; Brown, Anita C

2003-05-01

A 4-wave longitudinal model tested direct and indirect links between older sibling (OS; M = 11.7 years) and younger sibling (YS; M = 9.2 years) competence in 152 rural African American families. Data were collected at 1-year intervals. At each wave, different teachers assessed OS competence, YS competence, and YS self-regulation. Mothers reported their own psychological functioning; mothers and YSs reported parenting practices toward the YS. OS competence was stable across time and was linked with positive changes in mothers' psychological functioning from Wave 1 to Wave 2. Mothers' Wave 2 psychological functioning was associated with involved-supportive parenting of the YS at Wave 3. OS Wave 2 competence and Wave 3 parenting were indirectly linked with Wave 4 YS competence, through Wave 3 YS self-regulation. Structural equation modeling controlled for Wave 1 YS competence; thus, the model accounted for change in YS competence across 3 years.

Transdimensional inversion of scattered body waves for 1D S-wave velocity structure - Application to the Tengchong volcanic area, Southwestern China

NASA Astrophysics Data System (ADS)

Li, Mengkui; Zhang, Shuangxi; Bodin, Thomas; Lin, Xu; Wu, Tengfei

2018-06-01

Inversion of receiver functions is commonly used to recover the S-wave velocity structure beneath seismic stations. Traditional approaches are based on deconvolved waveforms, where the horizontal component of P-wave seismograms is deconvolved by the vertical component. Deconvolution of noisy seismograms is a numerically unstable process that needs to be stabilized by regularization parameters. This biases noise statistics, making it difficult to estimate uncertainties in observed receiver functions for Bayesian inference. This study proposes a method to directly invert observed radial waveforms and to better account for data noise in a Bayesian formulation. We illustrate its feasibility with two synthetic tests having different types of noises added to seismograms. Then, a real site application is performed to obtain the 1-D S-wave velocity structure beneath a seismic station located in the Tengchong volcanic area, Southwestern China. Surface wave dispersion measurements spanning periods from 8 to 65 s are jointly inverted with P waveforms. The results show a complex S-wave velocity structure, as two low velocity zones are observed in the crust and uppermost mantle, suggesting the existence of magma chambers, or zones of partial melt. The upper magma chambers may be the heart source that cause the thermal activity on the surface.

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions.

PubMed

West, Aaron C; Schmidt, Michael W; Gordon, Mark S; Ruedenberg, Klaus

2017-02-09

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the juxtaposed nonbonded quasi-atoms and a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions, and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. The theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.

Influence of the Spatial Dimensions of Ultrasonic Transducers on the Frequency Spectrum of Guided Waves.

PubMed

Samaitis, Vykintas; Mažeika, Liudas

2017-08-08

Ultrasonic guided wave (UGW)-based condition monitoring has shown great promise in detecting, localizing, and characterizing damage in complex systems. However, the application of guided waves for damage detection is challenging due to the existence of multiple modes and dispersion. This results in distorted wave packets with limited resolution and the interference of multiple reflected modes. To develop reliable inspection systems, either the transducers have to be optimized to generate a desired single mode of guided waves with known dispersive properties, or the frequency responses of all modes present in the structure must be known to predict wave interaction. Currently, there is a lack of methods to predict the response spectrum of guided wave modes, especially in cases when multiple modes are being excited simultaneously. Such methods are of vital importance for further understanding wave propagation within the structures as well as wave-damage interaction. In this study, a novel method to predict the response spectrum of guided wave modes was proposed based on Fourier analysis of the particle velocity distribution on the excitation area. The method proposed in this study estimates an excitability function based on the spatial dimensions of the transducer, type of vibration, and dispersive properties of the medium. As a result, the response amplitude as a function of frequency for each guided wave mode present in the structure can be separately obtained. The method was validated with numerical simulations on the aluminum and glass fiber composite samples. The key findings showed that it can be applied to estimate the response spectrum of a guided wave mode on any type of material (either isotropic structures, or multi layered anisotropic composites) and under any type of excitation if the phase velocity dispersion curve and the particle velocity distribution of the wave source was known initially. Thus, the proposed method may be a beneficial tool to explain and predict the response spectrum of guided waves throughout the development of any structural health monitoring system.

Influence of the Spatial Dimensions of Ultrasonic Transducers on the Frequency Spectrum of Guided Waves

PubMed Central

Samaitis, Vykintas; Mažeika, Liudas

2017-01-01

Ultrasonic guided wave (UGW)-based condition monitoring has shown great promise in detecting, localizing, and characterizing damage in complex systems. However, the application of guided waves for damage detection is challenging due to the existence of multiple modes and dispersion. This results in distorted wave packets with limited resolution and the interference of multiple reflected modes. To develop reliable inspection systems, either the transducers have to be optimized to generate a desired single mode of guided waves with known dispersive properties, or the frequency responses of all modes present in the structure must be known to predict wave interaction. Currently, there is a lack of methods to predict the response spectrum of guided wave modes, especially in cases when multiple modes are being excited simultaneously. Such methods are of vital importance for further understanding wave propagation within the structures as well as wave-damage interaction. In this study, a novel method to predict the response spectrum of guided wave modes was proposed based on Fourier analysis of the particle velocity distribution on the excitation area. The method proposed in this study estimates an excitability function based on the spatial dimensions of the transducer, type of vibration, and dispersive properties of the medium. As a result, the response amplitude as a function of frequency for each guided wave mode present in the structure can be separately obtained. The method was validated with numerical simulations on the aluminum and glass fiber composite samples. The key findings showed that it can be applied to estimate the response spectrum of a guided wave mode on any type of material (either isotropic structures, or multi layered anisotropic composites) and under any type of excitation if the phase velocity dispersion curve and the particle velocity distribution of the wave source was known initially. Thus, the proposed method may be a beneficial tool to explain and predict the response spectrum of guided waves throughout the development of any structural health monitoring system. PMID:28786924

Comparison of measured and computed Strehl ratios for light propagated through a channel flow of a He N 2 mixing layer at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1997-04-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after they propagated through a He N 2 mixing layer in a rectangular channel. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Phase structure functions, computed from the reconstructed phase surfaces, were stationary in first increments. A five-thirds power law is shown to fit streamwise and cross-stream slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence, which describes the structure function with a single parameter. Strehl ratios were computed from the phase structure functions and compared with a measured experiment obtained from simultaneous point-spread function measurements. Two additional Strehl ratios were calculated by using classical estimates that assume statistical isotropy throughout the flow. The isotropic models are a reasonable estimate of the optical degradation only within a few centimeters of the initial mixing, where the Reynolds number is low. At higher Reynolds numbers, Strehl ratios calculated from the structure functions match the experiment much better than Strehl ratio calculations that assume isotropic flow.

Measuring the band structures of periodic beams using the wave superposition method

NASA Astrophysics Data System (ADS)

Junyi, L.; Ruffini, V.; Balint, D.

2016-11-01

Phononic crystals and elastic metamaterials are artificially engineered periodic structures that have several interesting properties, such as negative effective stiffness in certain frequency ranges. An interesting property of phononic crystals and elastic metamaterials is the presence of band gaps, which are bands of frequencies where elastic waves cannot propagate. The presence of band gaps gives this class of materials the potential to be used as vibration isolators. In many studies, the band structures were used to evaluate the band gaps. The presence of band gaps in a finite structure is commonly validated by measuring the frequency response as there are no direct methods of measuring the band structures. In this study, an experiment was conducted to determine the band structure of one dimension phononic crystals with two wave modes, such as a bi-material beam, using the frequency response at only 6 points to validate the wave superposition method (WSM) introduced in a previous study. A bi-material beam and an aluminium beam with varying geometry were studied. The experiment was performed by hanging the beams freely, exciting one end of the beams, and measuring the acceleration at consecutive unit cells. The measured transfer function of the beams agrees with the analytical solutions but minor discrepancies. The band structure was then determined using WSM and the band structure of one set of the waves was found to agree well with the analytical solutions. The measurements taken for the other set of waves, which are the evanescent waves in the bi-material beams, were inaccurate and noisy. The transfer functions at additional points of one of the beams were calculated from the measured band structure using WSM. The calculated transfer function agrees with the measured results except at the frequencies where the band structure was inaccurate. Lastly, a study of the potential sources of errors was also conducted using finite element modelling and the errors in the dispersion curve measured from the experiments were deduced to be a result of a combination of measurement noise, the different placement of the accelerometer with finite mass, and the torsional mode.

Drift-wave turbulence and zonal flow generation.

PubMed

Balescu, R

2003-10-01

Drift-wave turbulence in a plasma is analyzed on the basis of the wave Liouville equation, describing the evolution of the distribution function of wave packets (quasiparticles) characterized by position x and wave vector k. A closed kinetic equation is derived for the ensemble-averaged part of this function by the methods of nonequilibrium statistical mechanics. It has the form of a non-Markovian advection-diffusion equation describing coupled diffusion processes in x and k spaces. General forms of the diffusion coefficients are obtained in terms of Lagrangian velocity correlations. The latter are calculated in the decorrelation trajectory approximation, a method recently developed for an accurate measure of the important trapping phenomena of particles in the rugged electrostatic potential. The analysis of individual decorrelation trajectories provides an illustration of the fragmentation of drift-wave structures in the radial direction and the generation of long-wavelength structures in the poloidal direction that are identified as zonal flows.

Fine structure of transient waves in a random medium: The correlation and spectral density functions

NASA Technical Reports Server (NTRS)

Wenzel, Alan R.

1994-01-01

This is essentially a progress report on a theoretical investigation of the propagation of transient waves in a random medium. The emphasis in this study is on applications to sonic-boom propagation, particularly as regards the effect of atmospheric turbulence on the sonic-boom waveform. The analysis is general, however, and is applicable to other types of waves besides sonic-boom waves. The phenomenon of primary concern in this investigation is the fine structure of the wave. A figure is used to illustrate what is meant by finestructure.

General method of solving the Schroedinger equation of atoms and molecules

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

Nakatsuji, Hiroshi

2005-12-15

We propose a general method of solving the Schroedinger equation of atoms and molecules. We first construct the wave function having the exact structure, using the ICI (iterative configuration or complement interaction) method and then optimize the variables involved by the variational principle. Based on the scaled Schroedinger equation and related principles, we can avoid the singularity problem of atoms and molecules and formulate a general method of calculating the exact wave functions in an analytical expansion form. We choose initial function {psi}{sub 0} and scaling g function, and then the ICI method automatically generates the wave function that hasmore » the exact structure by using the Hamiltonian of the system. The Hamiltonian contains all the information of the system. The free ICI method provides a flexible and variationally favorable procedure of constructing the exact wave function. We explain the computational procedure of the analytical ICI method routinely performed in our laboratory. Simple examples are given using hydrogen atom for the nuclear singularity case, the Hooke's atom for the electron singularity case, and the helium atom for both cases.« less

Effect of Forcing Function on Nonlinear Acoustic Standing Waves

NASA Technical Reports Server (NTRS)

Finkheiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh; Daniels, Chris; Steinetz, Bruce

2003-01-01

Nonlinear acoustic standing waves of high amplitude have been demonstrated by utilizing the effects of resonator shape to prevent the pressure waves from entering saturation. Experimentally, nonlinear acoustic standing waves have been generated by shaking an entire resonating cavity. While this promotes more efficient energy transfer than a piston-driven resonator, it also introduces complicated structural dynamics into the system. Experiments have shown that these dynamics result in resonator forcing functions comprised of a sum of several Fourier modes. However, previous numerical studies of the acoustics generated within the resonator assumed simple sinusoidal waves as the driving force. Using a previously developed numerical code, this paper demonstrates the effects of using a forcing function constructed with a series of harmonic sinusoidal waves on resonating cavities. From these results, a method will be demonstrated which allows the direct numerical analysis of experimentally generated nonlinear acoustic waves in resonators driven by harmonic forcing functions.

Algebraic Theory of Crystal Vibrations: Localization Properties of Wave Functions in Two-Dimensional Lattices

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

Dietz, Barbara; Iachello, Francesco; Macek, Michal

The localization properties of the wave functions of vibrations in two-dimensional (2D) crystals are studied numerically for square and hexagonal lattices within the framework of an algebraic model. The wave functions of 2D lattices have remarkable localization properties, especially at the van Hove singularities (vHs). Finite-size sheets with a hexagonal lattice (graphene-like materials), in addition, exhibit at zero energy a localization of the wave functions at zigzag edges, so-called edge states. The striped structure of the wave functions at a vHs is particularly noteworthy. We have investigated its stability and that of the edge states with respect to perturbations inmore » the lattice structure, and the effect of the boundary shape on the localization properties. We find that the stripes disappear instantaneously at the vHs in a square lattice when turning on the perturbation, whereas they broaden but persist at the vHss in a hexagonal lattice. For one of them, they eventually merge into edge states with increasing coupling, which, in contrast to the zero-energy edge states, are localized at armchair edges. The results are corroborated based on participation ratios, obtained under various conditions.« less

Algebraic Theory of Crystal Vibrations: Localization Properties of Wave Functions in Two-Dimensional Lattices

DOE PAGES

Dietz, Barbara; Iachello, Francesco; Macek, Michal

2017-08-07

The localization properties of the wave functions of vibrations in two-dimensional (2D) crystals are studied numerically for square and hexagonal lattices within the framework of an algebraic model. The wave functions of 2D lattices have remarkable localization properties, especially at the van Hove singularities (vHs). Finite-size sheets with a hexagonal lattice (graphene-like materials), in addition, exhibit at zero energy a localization of the wave functions at zigzag edges, so-called edge states. The striped structure of the wave functions at a vHs is particularly noteworthy. We have investigated its stability and that of the edge states with respect to perturbations inmore » the lattice structure, and the effect of the boundary shape on the localization properties. We find that the stripes disappear instantaneously at the vHs in a square lattice when turning on the perturbation, whereas they broaden but persist at the vHss in a hexagonal lattice. For one of them, they eventually merge into edge states with increasing coupling, which, in contrast to the zero-energy edge states, are localized at armchair edges. The results are corroborated based on participation ratios, obtained under various conditions.« less

Crustal and uppermost mantle structures of the South China from joint analysis of receiver functions and Rayleigh wave dispersions

NASA Astrophysics Data System (ADS)

Guo, Zhi; Gao, Xing; Li, Tong; Wang, Wei

2018-05-01

We use P-wave receiver function H-k stacking and joint inversion of receiver functions and Rayleigh wave dispersions to investigate crustal and uppermost mantle structure beneath the South China. The obtained results reveal prominent crustal structure variations in the study area, Moho depth increases from ∼30 km in the Cathaysia Block to more than ∼60 km in the eastern Tibetan Plateau. A Moho undulation and Vp/Vs ratio variations can be observed from the Cathaysia Block to Yangtze Craton. These observations consistent with the crustal structures predict by the flat slab subduction model. We interpret these lateral crustal structure variations reflect the tectonic evolution of the Yangtze Craton and Cathaysia Block prior the Mesozoic and the post-orogenic magmatism due to the breaking up of the subducted flat slab and subsequent slab rollback in the South China. The observed variations of the crustal structures not only reveal the lateral crustal inhomogeneity, but also provide constraints on the geodynamic evolution of the South China.

Lithospheric Velocity Structure of the Anatolain plateau-Caucasus-Caspian Regions

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

Gok, R; Mellors, R J; Sandvol, E

Anatolian Plateau-Caucasus-Caspian region is an area of complex structure accompanied by large variations in seismic wave velocities. Despite the complexity of the region little is known about the detailed lithospheric structure. Using data from 29 new broadband seismic stations in the region, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Love and Rayleigh surface waves dispersion curves have been derived from event-based analysis and ambient-noise correlation. We jointly inverted the receiver functions with the surface wave dispersion curves to determine absolute shear wave velocity and important discontinuities such as sedimentary layer, Moho, lithospheric-asthenospheric boundary. Wemore » combined these new station results with Eastern Turkey Seismic Experiment results (29 stations). Caspian Sea and Kura basin underlained by one of the thickest sediments in the world. Therefore, short-period surface waves are observed to be very slow. The strong crustal multiples in receiver functions and the slow velocities in upper crust indicate the presence of thick sedimentary unit (up to 20 km). Crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located.« less

Structures of Xishan village landslide in Li County, Sichuan, China, inferred from high-frequency receiver functions of local earthquakes

NASA Astrophysics Data System (ADS)

Wei, Z.; Chu, R.

2017-12-01

Teleseismic receiver function methods are widely used to study the deep structural information beneath the seismic station. However, teleseismic waveforms are difficult to extract the high-frequency receiver function, which are insufficient to constrain the shallow structure because of the inelastic attenuation effect of the earth. In this study, using the local earthquake waveforms collected from 3 broadband stations deployed on the Xishan village landslide in Li County in Sichuan Province, we used the high-frequency receiver function method to study the shallow structure beneath the landslide. We developed the Vp-k (Vp/Vs) staking method of receiver functions, and combined with the H-k stacking and waveform inversion methods of receiver functions to invert the landslide's thickness, S-wave velocity and average Vp/Vs ratio beneath these stations, and compared the thickness with the borehole results. Our results show small-scale lateral variety of velocity structure, a 78-143m/s lower S-wave velocity in the bottom layer and 2.4-3.1 Vp/Vs ratio in the landslide. The observed high Vp/Vs ratio and low S-wave velocity in the bottom layer of the landslide are consistent with low electrical resistivity and water-rich in the bottom layer, suggesting a weak shear strength and potential danger zone in landslide h1. Our study suggest that the local earthquake receiver function can obtain the shallow velocity structural information and supply some seismic constrains for the landslide catastrophe mitigation.

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

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

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

DOE PAGES

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.; ...

2017-01-30

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

New trial wave function for the nuclear cluster structure of nuclei

NASA Astrophysics Data System (ADS)

Zhou, Bo

2018-04-01

A new trial wave function is proposed for nuclear cluster physics, in which an exact solution to the long-standing center-of-mass problem is given. In the new approach, the widths of the single-nucleon Gaussian wave packets and the widths of the relative Gaussian wave functions describing correlations of nucleons or clusters are treated as variables in the explicit intrinsic wave function of the nuclear system. As an example, this new wave function was applied to study the typical {^{20}Ne} (α+{{^{16}}O}) cluster system. By removing exactly the spurious center-of-mass effect in a very simple way, the energy curve of {^{20}Ne} was obtained by variational calculations with the width of the α cluster, the width of the {{^{16}}O} cluster, and the size parameter of the nucleus. These are considered the three crucial variational variables in describing the {^{20}Ne} (α+{{^{16}}O}) cluster system. This shows that the new wave function can be a very interesting new tool for studying many-body and cluster effects in nuclear physics.

Parameter Governing of Wave Resonance in Water Chamber and Its Application

NASA Astrophysics Data System (ADS)

Husain, F.; Alie, M. Z. M.; Rahman, T.

2018-04-01

It has become known that the oscillating water column (OWC) device is very popular as one of wave energy extraction facilities installed in coastal and ocean structures. However, it has not been clarified sufficiently how to obtain an effective cross section design of the structure until now. This paper describes theoretical procedure to yield effective cross section of water chamber type of sea wall, which is similar to the OWC type structure in relation to wave period or wave length. The water chamber type sea wall has a water chamber partitioned by a curtain wall installed in front of part of the structure. This type of sea wall also can be applied to extract wave power same as of OWC function. When the wave conditions on site are known, the dimensions especially the breadth of water chamber type sea wall can be determined.

Fine crustal and uppermost mantle S-wave velocity structure beneath the Tengchong volcanic area inferred from receiver function and surface-wave dispersion: constraints on magma chamber distribution

NASA Astrophysics Data System (ADS)

Li, Mengkui; Zhang, Shuangxi; Wu, Tengfei; Hua, Yujin; Zhang, Bo

2018-03-01

The Tengchong volcanic area is located in the southeastern margin of the collision zone between the Indian and Eurasian Plates. It is one of the youngest intraplate volcano groups in mainland China. Imaging the S-wave velocity structure of the crustal and uppermost mantle beneath the Tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity. In this study, we analyze teleseismic data from nine broadband seismic stations in the Tengchong Earthquake Monitoring Network. We then image the crustal and uppermost mantle S-wave velocity structure by joint analysis of receiver functions and surface-wave dispersion. The results reveal widely distributed low-velocity zones. We find four possible magma chambers in the upper-to-middle crust and one in the uppermost mantle. The chamber in the uppermost mantle locates in the depth range from 55 to 70 km. The four magma chambers in the crust occur at different depths, ranging from the depth of 7 to 25 km in general. They may be the heat sources for the high geothermal activity at the surface. Based on the fine crustal and uppermost mantle S-wave velocity structure, we propose a model for the distribution of the magma chambers.

Protective longitudinal paths linking child competence to behavioral problems among African American siblings.

PubMed

Brody, Gene H; Kim, Sooyeon; Murry, Velma McBride; Brown, Anita C

2004-01-01

A 4-wave longitudinal design was used to examine protective links from child competence to behavioral problems in first- (M=10.97 years) and second- (M=8.27 years) born rural African American children. At 1-year intervals, teachers assessed child behavioral problems, mothers reported their psychological functioning, and both mothers and children reported parenting practices. Structural equation modeling indicated that child competence was linked with residualized positive changes in mothers' psychological functioning from Wave 1 to Wave 2. Mothers' psychological functioning and child competence at Wave 2 forecast involved-supportive parenting at Wave 3, which was associated negatively with externalizing and internalizing problems at Wave 4. The importance of replicating processes leading to outcomes among children in the same study is discussed.

Modeling and Circumventing the Effect of Sediments and Water Column on Receiver Functions

NASA Astrophysics Data System (ADS)

Audet, P.

2017-12-01

Teleseismic P-wave receiver functions are routinely used to resolve crust and mantle structure in various geologic settings. Receiver functions are approximations to the Earth's Green's functions and are composed of various scattered phase arrivals, depending on the complexity of the underlying Earth structure. For simple structure, the dominant arrivals (converted and back-scattered P-to-S phases) are well separated in time and can be reliably used in estimating crustal velocity structure. In the presence of sedimentary layers, strong reverberations typically produce high-amplitude oscillations that contaminate the early part of the wave train and receiver functions can be difficult to interpret in terms of underlying structure. The effect of a water column also limits the interpretability of under-water receiver functions due to the additional acoustic wave propagating within the water column that can contaminate structural arrivals. We perform numerical modeling of teleseismic Green's functions and receiver functions using a reflectivity technique for a range of Earth models that include thin sedimentary layers and overlying water column. These modeling results indicate that, as expected, receiver functions are difficult to interpret in the presence of sediments, but the contaminating effect of the water column is dependent on the thickness of the water layer. To circumvent these effects and recover source-side structure, we propose using an approach based on transfer function modeling that bypasses receiver functions altogether and estimates crustal properties directly from the waveforms (Frederiksen and Delayney, 2015). Using this approach, reasonable assumptions about the properties of the sedimentary layer can be included in forward calculations of the Green's functions that are convolved with radial waveforms to predict vertical waveforms. Exploration of model space using Monte Carlo-style search and least-square waveform misfits can be performed to estimate any model parameter of interest, including those of the sedimentary or water layer. We show how this method can be applied to OBS data using broadband stations from the Cascadia Initiative to recover oceanic plate structure.

Quantum Monte Carlo for electronic structure: Recent developments and applications

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

Rodriquez, Maria Milagos Soto

Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined bymore » the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C 2H and C 2H 2. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is included.« less

Topologically-protected one-way leaky waves in nonreciprocal plasmonic structures

NASA Astrophysics Data System (ADS)

Hassani Gangaraj, S. Ali; Monticone, Francesco

2018-03-01

We investigate topologically-protected unidirectional leaky waves on magnetized plasmonic structures acting as homogeneous photonic topological insulators. Our theoretical analyses and numerical experiments aim at unveiling the general properties of these exotic surface waves, and their nonreciprocal and topological nature. In particular, we study the behavior of topological leaky modes in stratified structures composed of a magnetized plasma at the interface with isotropic conventional media, and we show how to engineer their propagation and radiation properties, leading to topologically-protected backscattering-immune wave propagation, and highly directive and tunable radiation. Taking advantage of the non-trivial topological properties of these leaky modes, we also theoretically demonstrate advanced functionalities, including arbitrary re-routing of leaky waves on the surface of bodies with complex shapes, as well as the realization of topological leaky-wave (nano)antennas with isolated channels of radiation that are completely independent and separately tunable. Our findings help shedding light on the behavior of topologically-protected modes in open wave-guiding structures, and may open intriguing directions for future antenna generations based on topological structures, at microwaves and optical frequencies.

High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region

DTIC Science & Technology

2009-09-30

region is part of the Alpine-Himalayan collision belt and is an area of complex structure accompanied by large variations in seismic wave velocities...velocity structure is developed using teleseismic receiver functions and surface waves. Joint inversion of surface wave group dispersion curves...Caucasus and the thinnest is in the Arabian Plate. Thin crust is also observed near the Caspian. The lithospheric mantle in the Greater Caucasus and the

Developing Regionalized Models of Lithospheric Thickness and Velocity Structure Across Eurasia and the Middle East from Jointly Inverting P-Wave and S-Wave Receiver Functions with Rayleigh Wave Group and Phase Velocities

DTIC Science & Technology

2010-09-01

lithospheric velocity structure for a wide variety of tectonic regions throughout Eurasia and the Middle East. We expect the regionalized models will improve...constructed by combining the 1D joint inversion models within each tectonic region and validated through regional waveform modeling. The velocity models thus...important differences in lithospheric structure between the cratonic regions of Eastern Europe and the tectonic regions of Western Europe and the

Covariant extension of the GPD overlap representation at low Fock states

DOE PAGES

Chouika, N.; Mezrag, C.; Moutarde, H.; ...

2017-12-26

Here, we present a novel approach to compute generalized parton distributions within the lightfront wave function overlap framework. We show how to systematically extend generalized parton distributions computed within the DGLAP region to the ERBL one, fulfilling at the same time both the polynomiality and positivity conditions. We exemplify our method using pion lightfront wave functions inspired by recent results of non-perturbative continuum techniques and algebraic nucleon lightfront wave functions. We also test the robustness of our algorithm on reggeized phenomenological parameterizations. This approach paves the way to a better understanding of the nucleon structure from non-perturbative techniques and tomore » a unification of generalized parton distributions and transverse momentum dependent parton distribution functions phenomenology through lightfront wave functions.« less

Pseudopotential plane-wave calculation of the structural properties of yttrium

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

Wang, Y.; Chou, M.Y.

1991-11-01

The structural properties of hexagonal-close-packed yttrium are studied by using the plane-wave basis within the pseudopotential method and local-density-functional approximation. By employing a soft'' pseudopotential proposed by Troullier and Martins, satisfactory convergence is achieved with a plane-wave energy cutoff of 30--40 Ry for this early-transition-metal element. The overall results for the structural properties are in good agreement with experiment. It is found that the charge overlap between core and valence electrons has a substantial effect on the accuracy of the calculated structural properties. Two different calculations are performed with and without the outer-core 4{ital p} orbital included as a valencemore » state. In addition, as found in some other local-density calculations, the uncertainty in the results due to different exchange-correlation energy functionals may not be negligible in transition metals.« less

Acoustic metamaterials: From local resonances to broad horizons

PubMed Central

Ma, Guancong; Sheng, Ping

2016-01-01

Within a time span of 15 years, acoustic metamaterials have emerged from academic curiosity to become an active field driven by scientific discoveries and diverse application potentials. This review traces the development of acoustic metamaterials from the initial findings of mass density and bulk modulus frequency dispersions in locally resonant structures to the diverse functionalities afforded by the perspective of negative constitutive parameter values, and their implications for acoustic wave behaviors. We survey the more recent developments, which include compact phase manipulation structures, superabsorption, and actively controllable metamaterials as well as the new directions on acoustic wave transport in moving fluid, elastic, and mechanical metamaterials, graphene-inspired metamaterials, and structures whose characteristics are best delineated by non-Hermitian Hamiltonians. Many of the novel acoustic metamaterial structures have transcended the original definition of metamaterials as arising from the collective manifestations of constituent resonating units, but they continue to extend wave manipulation functionalities beyond those found in nature. PMID:26933692

Electron acoustic nonlinear structures in planetary magnetospheres

NASA Astrophysics Data System (ADS)

Shah, K. H.; Qureshi, M. N. S.; Masood, W.; Shah, H. A.

2018-04-01

In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ( r , q ) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ( r , q ) distribution. It has been found that the flatness parameter r , tail parameter q , and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.

Nutrient loading and consumers: Agents of change in open-coast macrophyte assemblages

PubMed Central

Nielsen, Karina J.

2003-01-01

Human activities are significantly altering nutrient regimes and the abundance of consumers in coastal ecosystems. A field experiment in an open-coast, upwelling ecosystem showed that small increases in nutrients increased the biomass and evenness of tide pool macrophytes where consumer abundance and nutrient loading rates were low. Consumers, when abundant, had negative effects on the diversity and biomass of macrophytes. Nutrient loading increases and consumers are less abundant and efficient as wave exposure increases along open coastlines. Experimentally reversing the natural state of nutrient supply and consumer pressure at a wave-protected site to match wave-exposed sites caused the structure of the macrophyte assemblage to converge on that found naturally in wave-exposed pools. The increases in evenness and abundance were driven by increases in structurally complex functional groups. In contrast, increased nutrient loading in semienclosed marine or estuarine ecosystems is typically associated with declines in macrophyte diversity because of increases in structurally simple and opportunistic functional groups. If nutrient concentration of upwelled waters changes with climatic warming or increasing frequency of El Niños, as predicted by some climate models, these results suggest that macrophyte abundance and evenness along wave-swept open-coasts will also change. Macrophytes represent a significant fraction of continental shelf production and provide important habitat for many marine species. The combined effects of shifting nutrient regimes and overexploitation of consumers may have unexpected consequences for the structure and functioning of open-coast communities. PMID:12796509

Nutrient loading and consumers: agents of change in open-coast macrophyte assemblages.

PubMed

Nielsen, Karina J

2003-06-24

Human activities are significantly altering nutrient regimes and the abundance of consumers in coastal ecosystems. A field experiment in an open-coast, upwelling ecosystem showed that small increases in nutrients increased the biomass and evenness of tide pool macrophytes where consumer abundance and nutrient loading rates were low. Consumers, when abundant, had negative effects on the diversity and biomass of macrophytes. Nutrient loading increases and consumers are less abundant and efficient as wave exposure increases along open coastlines. Experimentally reversing the natural state of nutrient supply and consumer pressure at a wave-protected site to match wave-exposed sites caused the structure of the macrophyte assemblage to converge on that found naturally in wave-exposed pools. The increases in evenness and abundance were driven by increases in structurally complex functional groups. In contrast, increased nutrient loading in semienclosed marine or estuarine ecosystems is typically associated with declines in macrophyte diversity because of increases in structurally simple and opportunistic functional groups. If nutrient concentration of upwelled waters changes with climatic warming or increasing frequency of El Niños, as predicted by some climate models, these results suggest that macrophyte abundance and evenness along wave-swept open-coasts will also change. Macrophytes represent a significant fraction of continental shelf production and provide important habitat for many marine species. The combined effects of shifting nutrient regimes and overexploitation of consumers may have unexpected consequences for the structure and functioning of open-coast communities.

Ionizing gas breakdown waves in strong electric fields.

NASA Technical Reports Server (NTRS)

Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

1972-01-01

A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

On the interplay between cosmological shock waves and their environment

NASA Astrophysics Data System (ADS)

Martin-Alvarez, Sergio; Planelles, Susana; Quilis, Vicent

2017-05-01

Cosmological shock waves are tracers of the thermal history of the structures in the Universe. They play a crucial role in redistributing the energy within the cosmic structures and are also amongst the main ingredients of galaxy and galaxy cluster formation. Understanding this important function requires a proper description of the interplay between shocks and the different environments where they can be found. In this paper, an Adaptive Mesh Refinement (AMR) Eulerian cosmological simulation is analysed by means of a shock-finding algorithm that allows to generate shock wave maps. Based on the population of dark matter halos and on the distribution of density contrast in the simulation, we classify the shocks in five different environments. These range from galaxy clusters to voids. The shock distribution function and the shocks power spectrum are studied for these environments dynamics. We find that shock waves on different environments undergo different formation and evolution processes, showing as well different characteristics. We identify three different phases of formation, evolution and dissipation of these shock waves, and an intricate migration between distinct environments and scales. Shock waves initially form at external, low density regions and are merged and amplified through the collapse of structures. Shock waves and cosmic structures follow a parallel evolution. Later on, shocks start to detach from them and dissipate. We also find that most of the power that shock waves dissipate is found at scales of k ˜0.5 Mpc^{-1}, with a secondary peak at k ˜8 Mpc^{-1}. The evolution of the shocks power spectrum confirms that shock waves evolution is coupled and conditioned by their environment.

Shoreline-crossing shear-velocity structure of the Juan de Fuca plate and Cascadia subduction zone from surface waves and receiver functions

NASA Astrophysics Data System (ADS)

Janiszewski, Helen; Gaherty, James; Abers, Geoffrey; Gao, Haiying

2017-04-01

The Cascadia subduction zone (CSZ) is the site of the onshore-offshore Cascadia Initiative, which deployed seismometers extending from the Juan de Fuca ridge to the subduction zone and onshore beyond the volcanic arc. This array allows the unique opportunity to seismically image the evolution and along-strike variation of the crust and mantle of the entire CSZ. We compare teleseismic receiver functions, ambient-noise Rayleigh-wave phase velocities in the 10-20 s period band, and earthquake-source Rayleigh-wave phase velocities from 20-100 s, to determine shear-velocity structure in the upper 200 km. Receiver functions from both onshore and shallow-water offshore sites provide constraints on crustal and plate interface structure. Spectral-domain fitting of ambient-noise empirical Green's functions constrains shear velocity of the crust and shallow mantle. An automated multi-channel cross-correlation analysis of teleseismic Rayleigh waves provides deeper lithosphere and asthenosphere constraints. The amphibious nature of the array means it is essential to examine the effect of noise variability on data quality. Ocean bottom seismometers (OBS) are affected by tilt and compliance noise. Removal of this noise from the vertical components of the OBS is essential for the teleseismic Rayleigh waves; this stabilizes the output phase velocity maps particularly along the coastline where observations are predominately from shallow water OBS. Our noise-corrected phase velocity maps reflect major structures and tectonic transitions including the transition from high-velocity oceanic lithosphere to low-velocity continental lithosphere, high velocities associated with the subducting slab, and low velocities beneath the ridge and arc. We interpret the resulting shear-velocity model in the context of temperature and compositional variation in the incoming plate and along the strike of the CSZ.

Shoreline-Crossing Shear-Velocity Structure of the Juan de Fuca Plate and Cascadia Subduction Zone from Surface Waves and Receiver Functions

NASA Astrophysics Data System (ADS)

Janiszewski, H. A.; Gaherty, J. B.; Abers, G. A.; Gao, H.

2016-12-01

The Cascadia subduction zone (CSZ) is the site of the onshore-offshore Cascadia Initiative, which deployed seismometers extending from the Juan de Fuca ridge to the subduction zone and onshore beyond the volcanic arc. This array allows the unique opportunity to seismically image the evolution and along-strike variation of the crust and mantle of the entire CSZ. We compare teleseismic receiver functions, ambient-noise Rayleigh-wave phase velocities in the 10-20 s period band, and earthquake-source Rayleigh-wave phase velocities from 20-100 s, to determine shear-velocity structure in the upper 200 km. Receiver functions from both onshore and shallow-water offshore sites provide constraints on crustal and plate interface structure. Spectral-domain fitting of ambient-noise empirical Green's functions constrains shear velocity of the crust and shallow mantle. An automated multi-channel cross-correlation analysis of teleseismic Rayleigh waves provides deeper lithosphere and asthenosphere constraints. The amphibious nature of the array means it is essential to examine the effect of noise variability on data quality. Ocean bottom seismometers (OBS) are affected by tilt and compliance noise. Removal of this noise from the vertical components of the OBS is essential for the teleseismic Rayleigh waves; this stabilizes the output phase velocity maps particularly along the coastline where observations are predominately from shallow water OBS. Our noise-corrected phase velocity maps reflect major structures and tectonic transitions including the transition from high-velocity oceanic lithosphere to low-velocity continental lithosphere, high velocities associated with the subducting slab, and low velocities beneath the ridge and arc. We interpret the resulting shear-velocity model in the context of temperature and compositional variation in the incoming plate and along the strike of the CSZ.

Spatio-Temporal Evolutions of Non-Orthogonal Equatorial Wave Modes Derived from Observations

NASA Astrophysics Data System (ADS)

Barton, C.; Cai, M.

2015-12-01

Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. Historically, their activity is diagnosed mainly in the wavenumber-frequency domain. Recently, many studies have projected observational data onto parabolic cylinder functions (PCF), which represent the meridional structure of individual wave modes, to attain time-dependent spatial wave structures. In this study, we propose a methodology that seeks to identify individual wave modes in instantaneous fields of observations by determining their projections on PCF modes according to the equatorial wave theory. The new method has the benefit of yielding a closed system with a unique solution for all waves' spatial structures, including IG waves, for a given instantaneous observed field. We have applied our method to the ERA-Interim reanalysis dataset in the tropical stratosphere where the wave-mean flow interaction mechanism for the quasi-biennial oscillation (QBO) is well-understood. We have confirmed the continuous evolution of the selection mechanism for equatorial waves in the stratosphere from observations as predicted by the theory for the QBO. This also validates the proposed method for decomposition of observed tropical wave fields into non-orthogonal equatorial wave modes.

Quantum-shutter approach to tunneling time scales with wave packets

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

Yamada, Norifumi; Garcia-Calderon, Gaston; Villavicencio, Jorge

2005-07-15

The quantum-shutter approach to tunneling time scales [G. Garcia-Calderon and A. Rubio, Phys. Rev. A 55, 3361 (1997)], which uses a cutoff plane wave as the initial condition, is extended to consider certain type of wave packet initial conditions. An analytical expression for the time-evolved wave function is derived. The time-domain resonance, the peaked structure of the probability density (as the function of time) at the exit of the barrier, originally found with the cutoff plane wave initial condition, is studied with the wave packet initial conditions. It is found that the time-domain resonance is not very sensitive to themore » width of the packet when the transmission process occurs in the tunneling regime.« less

Lattice-matched double dip-shaped BAlGaN/AlN quantum well structures for ultraviolet light emission devices

NASA Astrophysics Data System (ADS)

Park, Seoung-Hwan; Ahn, Doyeol

2018-05-01

Ultraviolet light emission characteristics of lattice-matched BxAlyGa1-x-y N/AlN quantum well (QW) structures with double AlGaN delta layers were investigated theoretically. In contrast to conventional single dip-shaped QW structure where the reduction effect of the spatial separation between electron and hole wave functions is negligible, proposed double dip-shaped QW shows significant enhancement of the ultraviolet light emission intensity from a BAlGaN/AlN QW structure due to the reduced spatial separation between electron and hole wave functions. The emission peak of the double dip-shaped QW structure is expected to be about three times larger than that of the conventional rectangular AlGaN/AlN QW structure.

Lithospheric structure beneath Eastern Africa from joint inversion of receiver functions and Rayleigh wave velocities

NASA Astrophysics Data System (ADS)

Dugda, Mulugeta Tuji

Crust and upper mantle structure beneath eastern Africa has been investigated using receiver functions and surface wave dispersion measurements to understand the impact of the hotspot tectonism found there on the lithospheric structure of the region. In the first part of this thesis, I applied H-kappa stacking of receiver functions, and a joint inversion of receiver functions and Rayleigh wave group velocities to determine the crustal parameters under Djibouti. The two methods give consistent results. The crust beneath the GEOSCOPE station ATD has a thickness of 23+/-1.5 km and a Poisson's ratio of 0.31+/-0.02. Previous studies give crustal thickness beneath Djibouti to be between 8 and 10 km. I found it necessary to reinterprete refraction profiles for Djibouti from a previous study. The crustal structure obtained for ATD is similar to adjacent crustal structure in many other parts of central and eastern Afar. The high Poisson's ratio and Vp throughout most of the crust indicate a mafic composition, suggesting that the crust in Afar consists predominantly of new igneous rock emplaced during the late synrift stage where extension is accommodated within magmatic segments by diking. In the second part of this thesis, the seismic velocity structure of the crust and upper mantle beneath Ethiopia and Djibouti has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities to obtain new constraints on the thermal structure of the lithosphere. Crustal structure from the joint inversion for Ethiopia and Djibouti is similar to previously published models. Beneath the Main Ethiopian Rift (MER) and Afar, the lithospheric mantle has a maximum shear wave velocity of 4.1-4.2 km/s and extends to a depth of at most 50 km. In comparison to the lithosphere away from the East African Rift System in Tanzania, where the lid extends to depths of ˜100-125 km and has a maximum shear velocity of 4.6 km/s, the mantle lithosphere under the Ethiopian Plateau appears to have been thinned by ˜30-50 km and the maximum shear wave velocity reduced by ˜0.3 km/s. Results from a 1D conductive thermal model suggest that the shear velocity structure of the lithosphere beneath the Ethiopian Plateau can be explained by a plume model, if a plume rapidly thinned the lithosphere by ˜30--50 km at the time of the flood basalt volcanism (c. 30 Ma), and if warm plume material has remained beneath the lithosphere since then. About 45-65% of the 1-1.5 km of plateau uplift in Ethiopia can be attributed to the thermally perturbed lithospheric structure. In the final part of this thesis, the shear-wave velocity structure of the crust and upper mantle beneath Kenya has been obtained from a joint inversion of receiver functions, and Rayleigh wave group and phase velocities. The crustal structure from the joint inversion is consistent with crustal structure published previously by different authors. The lithospheric mantle beneath the East African Plateau in Kenya is similar to the lithosphere under the East African Plateau in Tanzania. Beneath the Kenya Rift, the lithosphere extends to a depth of at most ˜75 km. The lithosphere under the Kenya Plateau is not perturbed when compared to the highly perturbed lithosphere beneath the Ethiopian Plateau. On the other hand, the lithosphere under the Kenya Rift is perturbed as compared to the Kenya Plateau or the rest of the East African Plateau, but is not as perturbed as the lithosphere beneath the Main Ethiopian Rift or the Afar. Although Kenya and Ethiopia have similar uplift and rifting histories, they have different volcanic histories. Much of Ethiopia has been affected by the Afar Flood Basalt volcanism, which may be the cause of this difference in lithospheric structure between these two regions.

Evolution of wave function in a dissipative system

NASA Technical Reports Server (NTRS)

Yu, Li-Hua; Sun, Chang-Pu

1994-01-01

For a dissipative system with Ohmic friction, we obtain a simple and exact solution for the wave function of the system plus the bath. It is described by the direct product in two independent Hilbert space. One of them is described by an effective Hamiltonian, the other represents the effect of the bath, i.e., the Brownian motion, thus clarifying the structure of the wave function of the system whose energy is dissipated by its interaction with the bath. No path integral technology is needed in this treatment. The derivation of the Weisskopf-Wigner line width theory follows easily.

Body-wave traveltime and amplitude shifts from asymptotic travelling wave coupling

USGS Publications Warehouse

Pollitz, F.

2006-01-01

We explore the sensitivity of finite-frequency body-wave traveltimes and amplitudes to perturbations in 3-D seismic velocity structure relative to a spherically symmetric model. Using the approach of coupled travelling wave theory, we consider the effect of a structural perturbation on an isolated portion of the seismogram. By convolving the spectrum of the differential seismogram with the spectrum of a narrow window taper, and using a Taylor's series expansion for wavenumber as a function of frequency on a mode dispersion branch, we derive semi-analytic expressions for the sensitivity kernels. Far-field effects of wave interactions with the free surface or internal discontinuities are implicitly included, as are wave conversions upon scattering. The kernels may be computed rapidly for the purpose of structural inversions. We give examples of traveltime sensitivity kernels for regional wave propagation at 1 Hz. For the direct SV wave in a simple crustal velocity model, they are generally complicated because of interfering waves generated by interactions with the free surface and the Mohorovic??ic?? discontinuity. A large part of the interference effects may be eliminated by restricting the travelling wave basis set to those waves within a certain range of horizontal phase velocity. ?? Journal compilation ?? 2006 RAS.

Modelling Of Anticipated Damage Ratio On Breakwaters Using Fuzzy Logic

NASA Astrophysics Data System (ADS)

Mercan, D. E.; Yagci, O.; Kabdasli, S.

2003-04-01

In breakwater design the determination of armour unit weight is especially important in terms of the structure's life. In a typical experimental breakwater stability study, different wave series composed of different wave heights; wave period and wave steepness characteristics are applied in order to investigate performance the structure. Using a classical approach, a regression equation is generated for damage ratio as a function of characteristic wave height. The parameters wave period and wave steepness are not considered. In this study, differing from the classical approach using a fuzzy logic, a relationship between damage ratio as a function of mean wave period (T_m), wave steepness (H_s/L_m) and significant wave height (H_s) was further generated. The system's inputs were mean wave period (T_m), wave steepness (H_s/L_m) and significant wave height (H_s). For fuzzification all input variables were divided into three fuzzy subsets, their membership functions were defined using method developed by Mandani (Mandani, 1974) and the rules were written. While for defuzzification the centroid method was used. In order to calibrate and test the generated models an experimental study was conducted. The experiments were performed in a wave flume (24 m long, 1.0 m wide and 1.0 m high) using 20 different irregular wave series (P-M spectrum). Throughout the study, the water depth was 0.6 m and the breakwater cross-sectional slope was 1V/2H. In the armour layer, a type of artificial armour unit known as antifer cubes were used. The results of the established fuzzy logic model and regression equation model was compared with experimental data and it was determined that the established fuzzy logic model gave a more accurate prediction of the damage ratio on this type of breakwater. References Mandani, E.H., "Application of Fuzzy Algorithms for Control of Simple Dynamic Plant", Proc. IEE, vol. 121, no. 12, December 1974.

Utilization of Model Predictive Control to Balance Power Absorption Against Load Accumulation

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

Abbas, Nikhar; Tom, Nathan M

2017-06-03

Wave energy converter (WEC) control strategies have been primarily focused on maximizing power absorption. The use of model predictive control strategies allows for a finite-horizon, multiterm objective function to be solved. This work utilizes a multiterm objective function to maximize power absorption while minimizing the structural loads on the WEC system. Furthermore, a Kalman filter and autoregressive model were used to estimate and forecast the wave exciting force and predict the future dynamics of the WEC. The WEC's power-take-off time-averaged power and structural loads under a perfect forecast assumption in irregular waves were compared against results obtained from the Kalmanmore » filter and autoregressive model to evaluate model predictive control performance.« less

Utilization of Model Predictive Control to Balance Power Absorption Against Load Accumulation: Preprint

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

Abbas, Nikhar; Tom, Nathan

Wave energy converter (WEC) control strategies have been primarily focused on maximizing power absorption. The use of model predictive control strategies allows for a finite-horizon, multiterm objective function to be solved. This work utilizes a multiterm objective function to maximize power absorption while minimizing the structural loads on the WEC system. Furthermore, a Kalman filter and autoregressive model were used to estimate and forecast the wave exciting force and predict the future dynamics of the WEC. The WEC's power-take-off time-averaged power and structural loads under a perfect forecast assumption in irregular waves were compared against results obtained from the Kalmanmore » filter and autoregressive model to evaluate model predictive control performance.« less

Relation between exercise central haemodynamic response and resting cardiac structure and function in young healthy men.

PubMed

Babcock, Matthew C; Lefferts, Wesley K; Heffernan, Kevin S

2017-07-01

Left ventricular (LV) structure and function are predictors of cardiovascular (CV) morbidity and mortality and are related to resting peripheral haemodynamic load in older adults. The central haemodynamic response to exercise may reveal associations with LV structure and function not detected by traditional peripheral (brachial) measures in a younger population. To examine correlations between acute exercise-induced changes in central artery stiffness and wave reflections and measures of resting LV structure and function. Sixteen healthy men (age 26 ± 6 year; BMI 25·3 ± 2·7 kg m -2 ) had measures of central haemodynamic load measured before/after a 30-s Wingate anaerobic test (WAT). Common carotid artery stiffness and reflected wave intensity were assessed via wave intensity analysis as a regional pulse wave velocity (PWV) and negative area (NA), respectively. Resting LV structure (LV mass) and function [midwall fractional shortening (mFS)] were assessed using M-mode echocardiography in the parasternal short-axis view. There was a significant association between mFS and WAT-mediated change in carotid systolic BP (r = -0·57, P = 0·011), logNA (r = -0·58, P = 0·009) and PWV (r = -0·44, P = 0·045). There were no significant associations between resting mFS and changes in brachial systolic BP (r = -0·26, P>0·05). There were no associations between resting LV mass and changes in any haemodynamic variable (P>0·05). Exercise-induced increases in central haemodynamic load reveal associations with lower resting LV function in young healthy men undetected by traditional peripheral haemodynamics. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Current-wave spectra coupling project. Volume III. Cumulative distribution of forces on structures subjected to the combined action of currents and random waves for potential OTEC sites: (A) Keahole Point, Hawaii, 100 year hurricane; (B) Punta Tuna, Puerto Rico, 100 year hurricane; (C) New Orleans, Louisiana, 100 year hurricane; (D) West Coast of Florida, 100 year hurricane. [CUFOR code

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

Venezian, G.; Bretschneider, C.L.

1980-08-01

This volume details a new methodology to analyze statistically the forces experienced by a structure at sea. Conventionally a wave climate is defined using a spectral function. The wave climate is described using a joint distribution of wave heights and periods (wave lengths), characterizing actual sea conditions through some measured or estimated parameters like the significant wave height, maximum spectral density, etc. Random wave heights and periods satisfying the joint distribution are then generated. Wave kinetics are obtained using linear or non-linear theory. In the case of currents a linear wave-current interaction theory of Venezian (1979) is used. The peakmore » force experienced by the structure for each individual wave is identified. Finally, the probability of exceedance of any given peak force on the structure may be obtained. A three-parameter Longuet-Higgins type joint distribution of wave heights and periods is discussed in detail. This joint distribution was used to model sea conditions at four potential OTEC locations. A uniform cylindrical pipe of 3 m diameter, extending to a depth of 550 m was used as a sample structure. Wave-current interactions were included and forces computed using Morison's equation. The drag and virtual mass coefficients were interpolated from published data. A Fortran program CUFOR was written to execute the above procedure. Tabulated and graphic results of peak forces experienced by the structure, for each location, are presented. A listing of CUFOR is included. Considerable flexibility of structural definition has been incorporated. The program can easily be modified in the case of an alternative joint distribution or for inclusion of effects like non-linearity of waves, transverse forces and diffraction.« less

Crustal structure of northern Egypt from joint inversion of receiver functions and surface wave dispersion velocities

NASA Astrophysics Data System (ADS)

Badawy, Ahmed; Hegazi, Mona; Gaber, Hanan; Korrat, Ibrahim

2018-05-01

In this study, we used a combined inversion of body wave receiver functions and surface wave dispersion measurements to provide constraints on the crustal structure of northern Egypt. The two techniques are complementary to each other: receiver functions (RFs) are sensitive to shear-wave velocity contrasts, while surface wave dispersion (SWD) measurements are sensitive to finite variations of shear-wave velocity with depth. A database of 122 teleseismic events digitally recorded by the Egyptian National Seismological Network (ENSN) stations has been used as well. To enhance the resulting RFs at each ENSN station, the H-k stacking method was applied. A joint inversion process between the resulting receiver functions and the surface wave dispersion curves was applied as well. We have produced three averaged velocity structure models for distinct geographic and tectonic provinces namely Sinai, eastern desert, and western desert from east to the west respectively. These models will deeply help in estimation the epicenter distance of earthquake, focal mechanism solutions, and earthquake hazard analysis in northern Egypt. An obvious image of the subsurface structure has been determined which shows that generally the crustal structure of northern Egypt consists of three layers covered with a sequence of sediments that differs in thickness from across the region except in the Sharm area where the sedimentary cover is absent. The obtained results indicate that crustal thickness differs from east to west and reaches its maximum value of about 36 km at Siwa station (SWA) in the western desert and its minimum value of about 28 km at Sharm station (SHR) of the southern tip of the Sinai Peninsula. The Vp/Vs ratio varies between 1.71 and 2.07 in northern Egypt. Generally, the high values (1.93) of (Vp/Vs) at SWA station may reflect the well-known rich aquifer with fully saturated sediments of the Swia Oasis in the Western Desert. Moreover, the highest value (2.07) of (Vp/Vs) at BNS station may be attributed to the widespread recently discovered hydrocarbon fields at the Beni-Suef Basin along the Eastern Desert. Finally, an integrated geophysical and hydrological study of the dimensions and physical properties of the aquifer and hydrocarbon fields at SWA and BNS stations to confirm if they are sufficient to produce the elevated Vp/Vs ratios or not become essential and highly recommended.

Crustal structure of northern Egypt from joint inversion of receiver functions and surface wave dispersion velocities

NASA Astrophysics Data System (ADS)

Badawy, Ahmed; Hegazi, Mona; Gaber, Hanan; Korrat, Ibrahim

2018-01-01

In this study, we used a combined inversion of body wave receiver functions and surface wave dispersion measurements to provide constraints on the crustal structure of northern Egypt. The two techniques are complementary to each other: receiver functions (RFs) are sensitive to shear-wave velocity contrasts, while surface wave dispersion (SWD) measurements are sensitive to finite variations of shear-wave velocity with depth. A database of 122 teleseismic events digitally recorded by the Egyptian National Seismological Network (ENSN) stations has been used as well. To enhance the resulting RFs at each ENSN station, the H-k stacking method was applied. A joint inversion process between the resulting receiver functions and the surface wave dispersion curves was applied as well. We have produced three averaged velocity structure models for distinct geographic and tectonic provinces namely Sinai, eastern desert, and western desert from east to the west respectively. These models will deeply help in estimation the epicenter distance of earthquake, focal mechanism solutions, and earthquake hazard analysis in northern Egypt. An obvious image of the subsurface structure has been determined which shows that generally the crustal structure of northern Egypt consists of three layers covered with a sequence of sediments that differs in thickness from across the region except in the Sharm area where the sedimentary cover is absent. The obtained results indicate that crustal thickness differs from east to west and reaches its maximum value of about 36 km at Siwa station (SWA) in the western desert and its minimum value of about 28 km at Sharm station (SHR) of the southern tip of the Sinai Peninsula. The Vp/Vs ratio varies between 1.71 and 2.07 in northern Egypt. Generally, the high values (1.93) of (Vp/Vs) at SWA station may reflect the well-known rich aquifer with fully saturated sediments of the Swia Oasis in the Western Desert. Moreover, the highest value (2.07) of (Vp/Vs) at BNS station may be attributed to the widespread recently discovered hydrocarbon fields at the Beni-Suef Basin along the Eastern Desert. Finally, an integrated geophysical and hydrological study of the dimensions and physical properties of the aquifer and hydrocarbon fields at SWA and BNS stations to confirm if they are sufficient to produce the elevated Vp/Vs ratios or not become essential and highly recommended.

Imaging performance of an isotropic negative dielectric constant slab.

PubMed

Shivanand; Liu, Huikan; Webb, Kevin J

2008-11-01

The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant slab is studied. Resonance in the plane-wave transfer function produces a high spatial frequency ripple that could be useful in fabricating periodic structures. A cost function based on the plane-wave transfer function provides a useful metric to evaluate the planar slab lens performance, and using this, the optimal slab dielectric constant can be determined.

Entanglement entropy of critical spin liquids.

PubMed

Zhang, Yi; Grover, Tarun; Vishwanath, Ashvin

2011-08-05

Quantum spin liquids are phases of matter whose internal structure is not captured by a local order parameter. Particularly intriguing are critical spin liquids, where strongly interacting excitations control low energy properties. Here we calculate their bipartite entanglement entropy that characterizes their quantum structure. In particular we calculate the Renyi entropy S(2) on model wave functions obtained by Gutzwiller projection of a Fermi sea. Although the wave functions are not sign positive, S(2) can be calculated on relatively large systems (>324 spins) using the variational Monte Carlo technique. On the triangular lattice we find that entanglement entropy of the projected Fermi sea state violates the boundary law, with S(2) enhanced by a logarithmic factor. This is an unusual result for a bosonic wave function reflecting the presence of emergent fermions. These techniques can be extended to study a wide class of other phases.

Epicenter Location of Regional Seismic Events Using Love Wave and Rayleigh Wave Ambient Seismic Noise Green's Functions

NASA Astrophysics Data System (ADS)

Levshin, A. L.; Barmin, M. P.; Moschetti, M. P.; Mendoza, C.; Ritzwoller, M. H.

2011-12-01

We describe a novel method to locate regional seismic events based on exploiting Empirical Green's Functions (EGF) that are produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long time-series of ambient noise recorded at the two stations. The EGFs principally contain Rayleigh waves on the vertical-vertical cross-correlations and Love waves on the transverse-transverse cross-correlations. Earlier work (Barmin et al., "Epicentral location based on Rayleigh wave empirical Green's functions from ambient seismic noise", Geophys. J. Int., 2011) showed that group time delays observed on Rayleigh wave EGFs can be exploited to locate to within about 1 km moderate sized earthquakes using USArray Transportable Array (TA) stations. The principal advantage of the method is that the ambient noise EGFs are affected by lateral variations in structure similarly to the earthquake signals, so the location is largely unbiased by 3-D structure. However, locations based on Rayleigh waves alone may be biased by more than 1 km if the earthquake depth is unknown but lies between 2 km and 7 km. This presentation is motivated by the fact that group time delays for Love waves are much less affected by earthquake depth than Rayleigh waves; thus exploitation of Love wave EGFs may reduce location bias caused by uncertainty in event depth. The advantage of Love waves to locate seismic events, however, is mitigated by the fact that Love wave EGFs have a smaller SNR than Rayleigh waves. Here, we test the use of Love and Rayleigh wave EGFs between 5- and 15-sec period to locate seismic events based on the USArray TA in the western US. We focus on locating aftershocks of the 2008 M 6.0 Wells earthquake, mining blasts in Wyoming and Montana, and small earthquakes near Norman, OK and Dallas, TX, some of which may be triggered by hydrofracking or injection wells.

Control of Spin Wave Dynamics in Spatially Twisted Magnetic Structures

DTIC Science & Technology

2017-06-27

realize high-performance spintronic and magnetic storage devices. 15. SUBJECT TERMS nano- electronics , spin, wave, magnetic, multi-functional, device 16... electronics has required us to develop high-performance and multi-functional electronic devices driven with extremely low power consumption...Spintronics”, simultaneously utilizing the charge and the spin of electrons , provides us with solutions to essential problems for semiconductor-based

Empirical transfer functions: Application to the determination of outermost core velocity structure using teleseismic SmKS phases

NASA Astrophysics Data System (ADS)

Eaton, D. W.; Alexandrakis, C.

2007-05-01

Teleseismic SmKS waves propagate as S-waves in the mantle and compressional (K) waves in the core, with m-1 underside bounce points at the core-mantle boundary. For long-period or broadband recordings at epicentral distances of 115-135°, higher-order SmKS waves (3 ≤ m < ∞) are not often discernible as distinct pulses. Instead, they are typically manifested as a weakly dispersive waveform that lags SKKS by ~ 12-32s. In a ray-theoretical representation of this process, there is a strong geometrical similarity between the coalescence of SmKS turning waves to form a composite arrival and the interference of mantle S waves to form teleseismic Love waves. SmKS waves can thus be viewed as a type of pseudo-interface wave, the dispersive properties of which depend strongly on the fine-scale velocity structure of the outermost core. In order to analyze SmKS arrivals, we have developed an empirical transfer-function (ETF) technique that uses SKKS as a reference phase. An ETF is a wave-shaping filter that transforms the observed SKKS pulse into the observed SmKS pulse. We obtain this filter by windowing the respective pulses and applying frequency- domain Wiener deconvolution. Each ETF contains SmKS-SKKS differential arrival-time, phase-shift and relative-amplitude information; it also implicitly removes the source-time function and instrument response, thus facilitating the merging of results from different stations and events. Here, we apply this approach to global observations of SmKS phases and invert the results to yield a new velocity model for the outermost core region.

THz emission of donor and acceptor doped GaAs/AlGaAs quantum well structures with inserted thin AlAs monolayer

NASA Astrophysics Data System (ADS)

van Dommelen, Paphavee; Daengngam, Chalongrat; Kalasuwan, Pruet

2018-04-01

In this paper, we explore THz range optical intersubband transition energies in a donor doped quantum well of a GaAs/AlGaAs system as a function of the insertion position of an AlAs monolayer in the GaAs quantum well. In simulated models, the optical transition energies between electron subband levels 1 and 2 were higher in the doped structure than in the undoped structure. This may be because the envelope wave function of the second electron subband strongly overlapped the envelope wave function of the first electron subband and influenced the optical intersubband transition between the two levels in the THz range. At different levels of bias voltage at the Schottky barrier on the donor doped structure, the electric field in the growth direction of the structure linearly increased the further away the AlAs monolayer was placed from the reference position. We also simulated the optical transition energies between acceptor energy levels of the acceptor doped structure as a function of the insertion position of the AlAs monolayer. The acceptor doped structure induced THz range emission whereas the undoped structure induced mid-IR emission.

An intelligent signal processing and pattern recognition technique for defect identification using an active sensor network

NASA Astrophysics Data System (ADS)

Su, Zhongqing; Ye, Lin

2004-08-01

The practical utilization of elastic waves, e.g. Rayleigh-Lamb waves, in high-performance structural health monitoring techniques is somewhat impeded due to the complicated wave dispersion phenomena, the existence of multiple wave modes, the high susceptibility to diverse interferences, the bulky sampled data and the difficulty in signal interpretation. An intelligent signal processing and pattern recognition (ISPPR) approach using the wavelet transform and artificial neural network algorithms was developed; this was actualized in a signal processing package (SPP). The ISPPR technique comprehensively functions as signal filtration, data compression, characteristic extraction, information mapping and pattern recognition, capable of extracting essential yet concise features from acquired raw wave signals and further assisting in structural health evaluation. For validation, the SPP was applied to the prediction of crack growth in an alloy structural beam and construction of a damage parameter database for defect identification in CF/EP composite structures. It was clearly apparent that the elastic wave propagation-based damage assessment could be dramatically streamlined by introduction of the ISPPR technique.

Sensitivity of Rayleigh wave ellipticity and implications for surface wave inversion

NASA Astrophysics Data System (ADS)

Cercato, Michele

2018-04-01

The use of Rayleigh wave ellipticity has gained increasing popularity in recent years for investigating earth structures, especially for near-surface soil characterization. In spite of its widespread application, the sensitivity of the ellipticity function to the soil structure has been rarely explored in a comprehensive and systematic manner. To this end, a new analytical method is presented for computing the sensitivity of Rayleigh wave ellipticity with respect to the structural parameters of a layered elastic half-space. This method takes advantage of the minor decomposition of the surface wave eigenproblem and is numerically stable at high frequency. This numerical procedure allowed to retrieve the sensitivity for typical near surface and crustal geological scenarios, pointing out the key parameters for ellipticity interpretation under different circumstances. On this basis, a thorough analysis is performed to assess how ellipticity data can efficiently complement surface wave dispersion information in a joint inversion algorithm. The results of synthetic and real-world examples are illustrated to analyse quantitatively the diagnostic potential of the ellipticity data with respect to the soil structure, focusing on the possible sources of misinterpretation in data inversion.

The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures

NASA Astrophysics Data System (ADS)

Wang, Hongmei; Zhang, Yafei; Xu, Huaizhe

2007-01-01

The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures, which is significant but has been frequently omitted in previous theoretical methods, has been reported in this paper. The analytical expressions of the longitudinal energies of quasibound levels (LEQBL) and the lifetimes of quasibound levels (LQBL) in symmetrical double-barrier (SDB) structures have been derived as a function of transverse wave vector and longitudinal magnetic fields perpendicular to interfaces. Based on our derived analytical expressions, the LEQBL and LQBL dependence upon transverse wave vector and longitudinal magnetic fields has been explored numerically for a SDB structure. Model calculations show that the LEQBL decrease monotonically and the LQBL shorten with increasing transverse wave vector, and each original LEQBL splits to a series of sub-LEQBL which shift nearly linearly toward the well bottom and the lifetimes of quasibound level series (LQBLS) shorten with increasing Landau-level indices and magnetic fields.

Exploring the Alfven-Wave Acceleration of Auroral Electrons in the Laboratory

NASA Astrophysics Data System (ADS)

Schroeder, James William Ryan

Inertial Alfven waves occur in plasmas where the Alfven speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfven waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfven waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfven waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfven waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfven waves, the measured portion of the distribution function oscillates at the Alfven wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfven wave antennas. The oscillation of the distribution function is described by a purely Alfvenic model when the Alfven wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvenic and non-Alfvenic effects. Indications of a nonlinear interaction between electrons and inertial Alfven waves are present in recent data.

A terahertz in-line polarization converter based on through-via connected double layer slot structures

PubMed Central

Woo, Jeong Min; Hussain, Sajid; Jang, Jae-Hyung

2017-01-01

A terahertz (THz) in-line polarization converter that yields a polarization conversion ratio as high as 99.9% is demonstrated at 1 THz. It has double-layer slot structures oriented in orthogonal directions that are electrically connected by 1/8-wavelngth-long through-via holes beside the slot structures. The slots on the front metal-plane respond to the incident THz wave with polarization orthogonal to the slots and generates a circulating surface current around the slots. The surface current propagates along a pair of through-via holes that function as a two-wire transmission line. The propagating current generates a surface current around the backside slot structures oriented orthogonal to the slot structures on the front metal layer. The circulating current generates a terahertz wave polarized orthogonal to the backside slot structures and the 90° polarization conversion is completed. The re-radiating THz wave with 90° converted polarization propagates in the same direction as the incident THz wave. PMID:28211498

Crustal structure of Precambrian terranes in the southern African subcontinent with implications for secular variation in crustal genesis

NASA Astrophysics Data System (ADS)

Kachingwe, Marsella; Nyblade, Andrew; Julià, Jordi

2015-07-01

New estimates of crustal thickness, Poisson's ratio and crustal shear wave velocity have been obtained for 39 stations in Angola, Botswana, the Democratic Republic of Congo, Malawi, Mozambique, Namibia, Rwanda, Tanzania and Zambia by modelling P-wave receiver functions using the H-κ stacking method and jointly inverting the receiver functions with Rayleigh-wave phase and group velocities. These estimates, combined with similar results from previous studies, have been examined for secular trends in Precambrian crustal structure within the southern African subcontinent. In both Archean and Proterozoic terranes we find similar Moho depths [38-39 ± 3 km SD (standard deviation)], crustal Poisson's ratio (0.26 ± 0.01 SD), mean crustal shear wave velocity (3.7 ± 0.1 km s-1 SD), and amounts of heterogeneity in the thickness of the mafic lower crust, as defined by shear wave velocities ≥4.0 km s-1. In addition, the amount of variability in these crustal parameters is similar within each individual age grouping as between age groupings. Thus, the results provide little evidence for secular variation in Precambrian crustal structure, including between Meso- and Neoarchean crust. This finding suggests that (1) continental crustal has been generated by similar processes since the Mesoarchean or (2) plate tectonic processes have reworked and modified the crust through time, erasing variations in structure resulting from crustal genesis.

A new wave front shape-based approach for acoustic source localization in an anisotropic plate without knowing its material properties.

PubMed

Sen, Novonil; Kundu, Tribikram

2018-07-01

Estimating the location of an acoustic source in a structure is an important step towards passive structural health monitoring. Techniques for localizing an acoustic source in isotropic structures are well developed in the literature. Development of similar techniques for anisotropic structures, however, has gained attention only in the recent years and has a scope of further improvement. Most of the existing techniques for anisotropic structures either assume a straight line wave propagation path between the source and an ultrasonic sensor or require the material properties to be known. This study considers different shapes of the wave front generated during an acoustic event and develops a methodology to localize the acoustic source in an anisotropic plate from those wave front shapes. An elliptical wave front shape-based technique was developed first, followed by the development of a parametric curve-based technique for non-elliptical wave front shapes. The source coordinates are obtained by minimizing an objective function. The proposed methodology does not assume a straight line wave propagation path and can predict the source location without any knowledge of the elastic properties of the material. A numerical study presented here illustrates how the proposed methodology can accurately estimate the source coordinates. Copyright © 2018 Elsevier B.V. All rights reserved.

On the Mathematical Modeling of Single and Multiple Scattering of Ultrasonic Guided Waves by Small Scatterers: A Structural Health Monitoring Measurement Model

NASA Astrophysics Data System (ADS)

Strom, Brandon William

In an effort to assist in the paradigm shift from schedule based maintenance to conditioned based maintenance, we derive measurement models to be used within structural health monitoring algorithms. Our models are physics based, and use scattered Lamb waves to detect and quantify pitting corrosion. After covering the basics of Lamb waves and the reciprocity theorem, we develop a technique for the scattered wave solution. The first application is two-dimensional, and is employed in two different ways. The first approach integrates a traction distribution and replaces it by an equivalent force. The second approach is higher order and uses the actual traction distribution. We find that the equivalent force version of the solution technique holds well for small pits at low frequencies. The second application is three-dimensional. The equivalent force caused by the scattered wave of an arbitrary equivalent force is calculated. We obtain functions for the scattered wave displacements as a function of equivalent forces, equivalent forces as a function of incident wave, and scattered wave amplitudes as a function of incident amplitude. The third application uses self-consistency to derive governing equations for the scattered waves due to multiple corrosion pits. We decouple the implicit set of equations and solve explicitly by using a recursive series solution. Alternatively, we solve via an undetermined coefficient method which results in an interaction operator and solution via matrix inversion. The general solution is given for N pits including mode conversion. We show that the two approaches are equivalent, and give a solution for three pits. Various approximations are advanced to simplify the problem while retaining the leading order physics. As a final application, we use the multiple scattering model to investigate resonance of Lamb waves. We begin with a one-dimensional problem and progress to a three-dimensional problem. A directed graph enables interpretation of the interaction operator, and we show that a series solution converges due to loss of energy in the system. We see that there are four causes of resonance and plot the modulation depth as a function of spacing between the pits.

Crustal Structure of Iraq from Receiver Functions and Surface Wave Dispersion

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

Gok, R; Mahdi, H; Al-Shukri, H

2006-08-31

We report the crustal structure of Iraq, located in the northeastern Arabian plate, estimated by joint inversion of P-wave receiver functions and surface wave group velocity dispersion. Receiver functions were computed from teleseismic recordings at two temporary broadband seismic stations in Mosul (MSL) and Baghdad (BHD), separated by approximately 360 km. Group velocity dispersion curves at the sites were derived from continental-scale tomography of Pasyanos (2006). The inversion results show that the crustal thicknesses are 39 km at MSL and 43 km at BHD. Both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km atmore » station MSL and 7 km at BHD, agreeing well with the existing models. Ignoring the sediments, the crustal velocities and thicknesses are remarkably similar between the two stations, suggesting that the crustal structure of the proto-Arabian Platform in northern Iraq was uniform before subsidence and deposition of the sediments in the Cenozoic. Deeper low velocity sediments at BHD are expected to result in higher ground motions for earthquakes.« less

3D Structure of Iran and Surrounding Areas From The Simultaneous Inversion of Complementary Geophysical Observations

NASA Astrophysics Data System (ADS)

Ammon, C. J.; Maceira, M.; Cleveland, M.

2010-12-01

We present a three-dimensional seismic-structure model of the Arabian-Eurasian collision zone obtained via simultaneous, joint inversion of surface-wave dispersion measurements, teleseismic P-wave receiver functions, and gravity observations. We use a simple, approximate relationship between density and seismic velocities so that the three data sets may be combined in a single inversion. The sensitivity of the different data sets are well known: surface waves provide information on the smooth variations in elastic properties, receiver functions provide information on abrupt velocity contrasts, and gravity measurements provide information on broad-wavenumber shallow density variations and long-wavenumber components of deeper density structures. The combination of the data provides improved resolution of shallow-structure variations, which in turn help produce the smooth features at depth with less contamination from the strong heterogeneity often observed in the upper crust. We also explore geologically based smoothness constraints to help resolve sharp features in the underlying shallow 3D structure. Our focus is on the region surrounding Iran from east Turkey and Iraq in the west, to Pakistan and Afghanistan in the east. We use Bouguer gravity anomalies derived from the global gravity model extracted from the GRACE satellite mission. Surface-wave dispersion velocities in the period range between 7 and 150 s are taken from previously published tomographic maps for the region. Preliminary results show expected strong variations in the Caspian region as well as the deep sediment regions of the Persian Gulf. Regions constrained with receiver-function information generally show sharper crust-mantle boundary structure than that obtained by inversion of the surface waves alone (with thin layers and smoothing constraints). Final results of the simultaneous inversion will help us to better understand one of the most prominent examples of continental collision. Such models also provide an important starting model for time-consuming and fully 3D inversions.

Orthogonality of embedded wave functions for different states in frozen-density embedding theory

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

Zech, Alexander; Wesolowski, Tomasz A.; Aquilante, Francesco

2015-10-28

Other than lowest-energy stationary embedded wave functions obtained in Frozen-Density Embedding Theory (FDET) [T. A. Wesolowski, Phys. Rev. A 77, 012504 (2008)] can be associated with electronic excited states but they can be mutually non-orthogonal. Although this does not violate any physical principles — embedded wave functions are only auxiliary objects used to obtain stationary densities — working with orthogonal functions has many practical advantages. In the present work, we show numerically that excitation energies obtained using conventional FDET calculations (allowing for non-orthogonality) can be obtained using embedded wave functions which are strictly orthogonal. The used method preserves the mathematicalmore » structure of FDET and self-consistency between energy, embedded wave function, and the embedding potential (they are connected through the Euler-Lagrange equations). The orthogonality is built-in through the linearization in the embedded density of the relevant components of the total energy functional. Moreover, we show formally that the differences between the expectation values of the embedded Hamiltonian are equal to the excitation energies, which is the exact result within linearized FDET. Linearized FDET is shown to be a robust approximation for a large class of reference densities.« less

Characterizing the propagation evolution of wave patterns and vortex structures in astigmatic transformations of Hermite-Gaussian beams

NASA Astrophysics Data System (ADS)

Chen, Y. F.; Chang, C. C.; Lee, C. Y.; Tung, J. C.; Liang, H. C.; Huang, K. F.

2018-01-01

Theoretical wave functions are analytically derived to characterize the propagation evolution of the Hermite-Gaussian (HG) beams transformed by a single-lens astigmatic mode converter with arbitrary angle. The derived wave functions are related to the combination of the rotation transform and the antisymmetric fractional Fourier transform. The derived formula is systematically validated by using an off-axis diode-pumped solid-state laser to generate various high-order HG beams for mode conversions. In addition to validation, the creation and evolution of vortex structures in the transformed HG beams are numerically manifested. The present theoretical analyses can be used not only to characterize the evolution of the transformed beams but to design the optical vortex beams with various forms.

Self-consistent adjoint analysis for topology optimization of electromagnetic waves

NASA Astrophysics Data System (ADS)

Deng, Yongbo; Korvink, Jan G.

2018-05-01

In topology optimization of electromagnetic waves, the Gâteaux differentiability of the conjugate operator to the complex field variable results in the complexity of the adjoint sensitivity, which evolves the original real-valued design variable to be complex during the iterative solution procedure. Therefore, the self-inconsistency of the adjoint sensitivity is presented. To enforce the self-consistency, the real part operator has been used to extract the real part of the sensitivity to keep the real-value property of the design variable. However, this enforced self-consistency can cause the problem that the derived structural topology has unreasonable dependence on the phase of the incident wave. To solve this problem, this article focuses on the self-consistent adjoint analysis of the topology optimization problems for electromagnetic waves. This self-consistent adjoint analysis is implemented by splitting the complex variables of the wave equations into the corresponding real parts and imaginary parts, sequentially substituting the split complex variables into the wave equations with deriving the coupled equations equivalent to the original wave equations, where the infinite free space is truncated by the perfectly matched layers. Then, the topology optimization problems of electromagnetic waves are transformed into the forms defined on real functional spaces instead of complex functional spaces; the adjoint analysis of the topology optimization problems is implemented on real functional spaces with removing the variational of the conjugate operator; the self-consistent adjoint sensitivity is derived, and the phase-dependence problem is avoided for the derived structural topology. Several numerical examples are implemented to demonstrate the robustness of the derived self-consistent adjoint analysis.

Shear-wave velocity structure of the Tongariro Volcanic Centre, New Zealand: Fast Rayleigh and slow Love waves indicate strong shallow anisotropy

NASA Astrophysics Data System (ADS)

Godfrey, Holly J.; Fry, Bill; Savage, Martha K.

2017-04-01

Models of the velocity structure of volcanoes can help define possible magma pathways and contribute to calculating more accurate earthquake locations, which can help with monitoring volcanic activity. However, shear-wave velocity of volcanoes is difficult to determine from traditional seismic techniques, such as local earthquake tomography (LET) or refraction/reflection surveys. Here we use the recently developed technique of noise cross correlation of continuous seismic data to investigate the subsurface shear-wave velocity structure of the Tongariro Volcanic Centre (TgVC) of New Zealand, focusing on the active Ruapehu and Tongariro Volcanoes. We observe both the fundamental and first higher-order modes of Rayleigh and Love waves within our noise dataset, made from stacks of 15 min cross-correlation functions. We manually pick group velocity dispersion curves from over 1900 correlation functions, of which we consider 1373 to be high quality. We subsequently invert a subset of the fundamental mode Rayleigh- and Love-wave dispersion curves both independently and jointly for one dimensional shear-wave velocity (Vs) profiles at Ruapehu and Tongariro Volcanoes. Vs increases very slowly at a rate of approximately 0.2 km/s per km depth beneath Ruapehu, suggesting that progressive hydrothermal alteration mitigates the effects of compaction driven velocity increases. At Tongariro, we observe larger Vs increases with depth, which we interpret as different layers within Tongariro's volcanic system above altered basement greywacke. Slow Vs, on the order of 1-2 km/s, are compatible with P-wave velocities (using a Vp/Vs ratio of 1.7) from existing velocity profiles of areas within the TgVC, and the observations of worldwide studies of shallow volcanic systems that used ambient noise cross-correlation methods. Most of the measured group velocities of fundamental mode Love-waves across the TgVC are 0.1-0.4 km/s slower than those of fundamental mode Rayleigh-waves in the frequency range of 0.25-1 Hz. First-higher mode Love-waves are similarly slower than first-higher mode Rayleigh waves. This is incompatible with synthetic dispersion curves we calculate using isotropic, layered velocity models appropriate for Ruapehu and Tongariro, in which Love waves travel more quickly than Rayleigh waves of the same period. The Love-Rayleigh discrepancy is likely due to structures such as dykes or cracks in the vertical plane having increased influence on surface-wave propagation. However, several measurements at Ruapehu have Love-wave group velocities that are faster than Rayleigh-wave group velocities. The differences between the Love- and Rayleigh-wave dispersion curves also vary with the azimuth of the interstation path across Ruapehu and Tongariro Volcanoes. Significant azimuthal dependence of both Love and Rayleigh-wave velocities are also observed. This suggests azimuthal anisotropy within the volcanic structures, which coupled with radial anisotropy, makes the Vs structures of Ruapehu and Tongariro Volcanoes anisotropic with orthorhombic or lower order symmetry. We suggest that further work to determine three-dimensional volcanic structures should include provisions for such anisotropy.

Bumps of the wave structure function in non-Kolmogorov turbulence

NASA Astrophysics Data System (ADS)

Qiao, Chunhong; Lu, Lu; Zhang, Pengfei; Wang, Haitao; Huang, Honghua; Fan, Chengyu

2015-10-01

The analytical expressions for wave structure function of plane and spherical waves are derived both in the viscous dissipation and inertial range. Due to previously research, there is a discrepancy between theoretical results and the experimental datum in viscous dissipation range. In this paper, only considering the inertial range, taking plane waves for example, we give a comparison of results of WSF calculated by the analytical formula obtained in this paper and the numerical calculations of the definition at the fixed parameter (i.e., the generalized exponent α), it can be seen that the two results are in agreement with each other exactly. Based on non-Kolmogorov power spectrum, new characteristics for wave structure function (WSF) have been found for plane and spherical wave models when the different ratio of inner scale l0 and outer scale of turbulence L0 is obtained. In outer scale assumed finite case (i.e., L0 =1m), WSF obtains the maximum when α approximates to 3.3 both for plane and spherical wave models. In outer scale assumed infinite case (i.e., L0 = ∞), the WSF can be sorted into three parts, including two rapid-rising regions (i.e., 3.0 < α < 3.3 and 3.8 < α < 4.0 ) and one gently rising region (i.e., 3.3 < α < 3.8 ).Further, the changes of scaled WSF versus the ratio of separation distance and inner scale ( p/ l0 ) are investigated under mentioned above conditions for two models. In L0 = 1m case, both for plane and spherical waves, the value of α determines the bump position of WSF. In L0 = ∞ case, the bump of scaled WSF disappears when the generalized exponent has large values. The changings of scaled WSF monotonically increase as α increased when the generalized exponent is larger than11/3 for two models. Besides, the properties of spherical waves are similar to plane waves, except which the values of WSF and the scaled WSF are smaller than plane ones.

Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping

NASA Astrophysics Data System (ADS)

Chen, K.; Strigari, F.; Sundermann, M.; Hu, Z.; Fisk, Z.; Bauer, E. D.; Rosa, P. F. S.; Sarrao, J. L.; Thompson, J. D.; Herrero-Martin, J.; Pellegrin, E.; Betto, D.; Kummer, K.; Tanaka, A.; Wirth, S.; Severing, A.

2018-01-01

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4 ,5 edges of Cd- and Sn-doped CeCoIn5. The 4 f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In1-xCdx) 5 suggests that the 4 f -conduction-electron (c f ) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In1-ySny) 5 compresses the 4 f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4 f and conduction electrons, even conveying information about direction dependencies.

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.

New soliton solution to the longitudinal wave equation in a magneto-electro-elastic circular rod

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.; Manafian, Jalil

2018-03-01

This paper examines the effectiveness of an integration scheme which called the extended trial equation method (ETEM) in exactly solving a well-known nonlinear equation of partial differential equations (PDEs). In this respect, the longitudinal wave equation (LWE) that arises in mathematical physics with dispersion caused by the transverse Poisson's effect in a magneto-electro-elastic (MEE) circular rod, which a series of exact traveling wave solutions for the aforementioned equation is formally extracted. Explicit new exact solutions are derived in different form such as dark solitons, bright solitons, solitary wave, periodic solitary wave, rational function, and elliptic function solutions of the longitudinal wave equation. The movements of obtained solutions are shown graphically, which helps to understand the physical phenomena of this longitudinal wave equation. Many other such types of nonlinear equations arising in non-destructive evaluation of structures made of the advanced MEE material can also be solved by this method.

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.

Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma

NASA Astrophysics Data System (ADS)

Panwar, A.; Ryu, C. M.; Bains, A. S.

2014-12-01

A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c , κ h , cold to hot electron temperature ratio σ, angle of propagation and ion cyclotron frequency ωci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.

Electron cyclotron thruster new modeling results preparation for initial experiments

NASA Technical Reports Server (NTRS)

Hooper, E. Bickford

1993-01-01

The following topics are discussed: a whistler-based electron cyclotron resonance heating (ECRH) thruster; cross-field coupling in the helicon approximation; wave propagation; wave structure; plasma density; wave absorption; the electron distribution function; isothermal and adiabatic plasma flow; ECRH thruster modeling; a PIC code model; electron temperature; electron energy; and initial experimental tests. The discussion is presented in vugraph form.

Wave energy and swimming performance shape coral reef fish assemblages

PubMed Central

Fulton, C.J; Bellwood, D.R; Wainwright, P.C

2005-01-01

Physical factors often have an overriding influence on the distribution patterns of organisms, and can ultimately shape the long-term structure of communities. Although distribution patterns in sessile marine organisms have frequently been attributed to functional characteristics interacting with wave-induced water motion, similar evidence for mobile organisms is lacking. Links between fin morphology and swimming performance were examined in three diverse coral reef fish families from two major evolutionary lineages. Among-habitat variation in morphology and performance was directly compared with quantitative values of wave-induced water motion from seven coral reef habitats of different depth and wave exposure on the Great Barrier Reef. Fin morphology was strongly correlated with both field and experimental swimming speeds in all three families. The range of observed swimming speeds coincided closely with the magnitude of water velocities commonly found on coral reefs. Distribution patterns in all three families displayed highly congruent relationships between fin morphology and wave-induced water motion. Our findings indicate a general functional relationship between fin morphology and swimming performance in labriform-swimming fishes, and provide quantitative evidence that wave energy may directly influence the assemblage structure of coral reef fishes through interactions with morphology and swimming performance. PMID:15888415

Interface waves in multilayered plates.

PubMed

Li, Bing; Li, Ming-Hang; Lu, Tong

2018-04-01

In this paper, the characteristic equation of interface waves in multilayered plates is derived. With a reasonable assumption undertaken for the potential functions of longitudinal and shear waves in the nth layer medium, the characteristic equation of interface waves in the N-layered plate is derived and presented in a determinant form. The particle displacement and stress components are further presented in explicit forms. The dispersion curves and wave structures of interface waves in both a three-layered Al-Steel-Ti and a four-layered Steel-Al-Steel-Ti plate are displayed subsequently. It is observed in dispersion curves that obvious dispersion occurs on the low frequency band, whereas the phase velocities converge to the corresponding true Stoneley wave mode velocities at high frequency, and the number of interface wave modes equals the number of interfaces in multilayered plates (if all individual interfaces satisfy the existence condition of Stoneley waves). The wave structures reveal that the displacement components of interface waves are relatively high at interfaces, and the amplitude distribution varies from frequency to frequency. In the end, a similarly structured three-layered Al-Steel-Ti plate is tested. In this experiment, theoretical group velocity and experimental group velocity are compared. According to the discussion and comparison, the predicted group velocities are in good agreement with the experimental results. Thus, the theory of interface wave in multilayered plates is proved. As a result, the proposed theoretical approach represents a leap forward in the understanding of how to promote the characteristic study and practical applications of interface waves in multilayered structures.

Derivative expansion of wave function equivalent potentials

NASA Astrophysics Data System (ADS)

Sugiura, Takuya; Ishii, Noriyoshi; Oka, Makoto

2017-04-01

Properties of the wave function equivalent potentials introduced by the HAL QCD collaboration are studied in a nonrelativistic coupled-channel model. The derivative expansion is generalized, and then applied to the energy-independent and nonlocal potentials. The expansion coefficients are determined from analytic solutions to the Nambu-Bethe-Salpeter wave functions. The scattering phase shifts computed from these potentials are compared with the exact values to examine the convergence of the expansion. It is confirmed that the generalized derivative expansion converges in terms of the scattering phase shift rather than the functional structure of the non-local potentials. It is also found that the convergence can be improved by tuning either the choice of interpolating fields or expansion scale in the generalized derivative expansion.

Love-type waves in functionally graded piezoelectric material (FGPM) sandwiched between initially stressed layer and elastic substrate

NASA Astrophysics Data System (ADS)

Saroj, Pradeep K.; Sahu, S. A.; Chaudhary, S.; Chattopadhyay, A.

2015-10-01

This paper investigates the propagation behavior of Love-type surface waves in three-layered composite structure with initial stress. The composite structure has been taken in such a way that a functionally graded piezoelectric material (FGPM) layer is bonded between initially stressed piezoelectric upper layer and an elastic substrate. Using the method of separation of variables, frequency equation for the considered wave has been established in the form of determinant for electrical open and short cases on free surface. The bisection method iteration technique has been used to find the roots of the dispersion relations which give the modes for electrical open and short cases. The effects of gradient variation of material constant and initial stress on the phase velocity of surface waves are discussed. Dependence of thickness on each parameter of the study has been shown explicitly. Study has been also done to show the existence of cut-off frequency. Graphical representation has been done to exhibit the findings. The obtained results are significant for the investigation and characterization of Love-type waves in FGPM-layered media.

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.

Crustal shear wave velocity structure in the northeastern Tibet based on the Neighbourhood algorithm inversion of receiver functions

NASA Astrophysics Data System (ADS)

Wu, Zhenbo; Xu, Tao; Liang, Chuntao; Wu, Chenglong; Liu, Zhiqiang

2018-03-01

The northeastern (NE) Tibet records and represents the far-field deformation response of the collision between the Indian and Eurasian plates in the Cenozoic time. Over the past two decades, studies have revealed the existence of thickened crust in the NE Tibet, but the thickening mechanism is still in debate. We deployed a passive-source seismic profile with 22 temporary broad-band seismic stations in the NE Tibet to investigate the crustal shear wave velocity structure in this region. We selected 288 teleseismic events located in the west Pacific subduction zone near Japan with similar ray path to calculate P-wave receiver functions. Neighbourhood algorithm method is applied to invert the shear wave velocity beneath stations. The inversion result shows a low-velocity zone (LVZ) is roughly confined to the Songpan-Ganzi block and Kunlun mountains and extends to the southern margin of Gonghe basin. Considering the low P-wave velocity revealed by the wide-angle reflection-refraction seismic experiment and high ratio of Vp/Vs based on H-κ grid searching of the receiver functions in this profile, LVZ may be attributed to partial melting induced by temperature change. This observation appears to be consistent with the crustal ductile deformation in this region derived from other geophysical investigations.

Evidence for mafic lower crust in Tanzania, East Africa, from joint inversion of receiver functions and Rayleigh wave dispersion velocities

NASA Astrophysics Data System (ADS)

Julià, Jordi; Ammon, Charles J.; Nyblade, Andrew A.

2005-08-01

The S-wave velocity structure of Precambrian terranes in Tanzania, East Africa is modelled by jointly inverting receiver functions and surface wave dispersion velocities from the 1994-1995 Tanzania broad-band seismic experiment. The study region, which consists of an Archean craton surrounded by Proterozoic mobile belts, forms a unique setting for evaluating Precambrian crustal evolution. Our results show a uniform crustal structure across the region, with a 10-15 km thick upper crust with VS= 3.4-3.5 km s-1, overlying a gradational lower crust with S-wave velocities up to 4.1 km s-1 at 38-42 km depth. The upper-mantle lid displays uniform S-wave velocities of 4.5-4.7 km s-1 to depths of 100-150 km and overlays a prominent low-velocity zone. This low-velocity zone is required by the dispersion and receiver function data, but its depth interval is uncertain. The high crustal velocities within the lowermost crust characterize the entire region and suggest that mafic lithologies are present in both Archean and Proterozoic terranes. The ubiquitous mafic lower crust can be attributed to underplating associated with mafic dyke emplacement. This finding suggests that in East Africa there has been little secular variation in Precambrian crustal development.

3D Numerical Simulation of the Wave and Current Loads on a Truss Foundation of the Offshore Wind Turbine During the Extreme Typhoon Event

NASA Astrophysics Data System (ADS)

Lin, C. W.; Wu, T. R.; Chuang, M. H.; Tsai, Y. L.

2015-12-01

The wind in Taiwan Strait is strong and stable which offers an opportunity to build offshore wind farms. However, frequently visited typhoons and strong ocean current require more attentions on the wave force and local scour around the foundation of the turbine piles. In this paper, we introduce an in-house, multi-phase CFD model, Splash3D, for solving the flow field with breaking wave, strong turbulent, and scour phenomena. Splash3D solves Navier-Stokes Equation with Large-Eddy Simulation (LES) for the fluid domain, and uses volume of fluid (VOF) with piecewise linear interface reconstruction (PLIC) method to describe the break free-surface. The waves were generated inside the computational domain by internal wave maker with a mass-source function. This function is designed to adequately simulate the wave condition under observed extreme events based on JONSWAP spectrum and dispersion relationship. Dirichlet velocity boundary condition is assigned at the upper stream boundary to induce the ocean current. At the downstream face, the sponge-layer method combined with pressure Dirichlet boundary condition is specified for dissipating waves and conducting current out of the domain. Numerical pressure gauges are uniformly set on the structure surface to obtain the force distribution on the structure. As for the local scour around the foundation, we developed Discontinuous Bi-viscous Model (DBM) for the development of the scour hole. Model validations were presented as well. The force distribution under observed irregular wave condition was extracted by the irregular-surface force extraction (ISFE) method, which provides a fast and elegant way to integrate the force acting on the surface of irregular structure. From the Simulation results, we found that the total force is mainly induced by the impinging waves, and the force from the ocean current is about 2 order of magnitude smaller than the wave force. We also found the dynamic pressure, wave height, and the projection area of the structure are the main factors to the total force. Detailed results and discussion are presented as well.

Multiconfiguration Pair-Density Functional Theory: A New Way To Treat Strongly Correlated Systems.

PubMed

Gagliardi, Laura; Truhlar, Donald G; Li Manni, Giovanni; Carlson, Rebecca K; Hoyer, Chad E; Bao, Junwei Lucas

2017-01-17

The electronic energy of a system provides the Born-Oppenheimer potential energy for internuclear motion and thus determines molecular structure and spectra, bond energies, conformational energies, reaction barrier heights, and vibrational frequencies. The development of more efficient and more accurate ways to calculate the electronic energy of systems with inherently multiconfigurational electronic structure is essential for many applications, including transition metal and actinide chemistry, systems with partially broken bonds, many transition states, and most electronically excited states. Inherently multiconfigurational systems are called strongly correlated systems or multireference systems, where the latter name refers to the need for using more than one ("multiple") configuration state function to provide a good zero-order reference wave function. This Account describes multiconfiguration pair-density functional theory (MC-PDFT), which was developed as a way to combine the advantages of wave function theory (WFT) and density functional theory (DFT) to provide a better treatment of strongly correlated systems. First we review background material: the widely used Kohn-Sham DFT (which uses only a single Slater determinant as reference wave function), multiconfiguration WFT methods that treat inherently multiconfigurational systems based on an active space, and previous attempts to combine multiconfiguration WFT with DFT. Then we review the formulation of MC-PDFT. It is a generalization of Kohn-Sham DFT in that the electron kinetic energy and classical electrostatic energy are calculated from a reference wave function, while the rest of the energy is obtained from a density functional. However, there are two main differences with respent to Kohn-Sham DFT: (i) The reference wave function is multiconfigurational rather than being a single Slater determinant. (ii) The density functional is a function of the total density and the on-top pair density rather than being a function of the spin-up and spin-down densities. In work carried out so far, the multiconfigurational wave function is a multiconfiguration self-consistent-field wave function. The new formulation has the advantage that the reference wave function has the correct spatial and spin symmetry and can describe bond dissociation (of both single and multiple bonds) and electronic excitations in a formally and physically correct way. We then review the formulation of density functionals in terms of the on-top pair density. Finally we review successful applications of the theory to bond energies and bond dissociation potential energy curves of main-group and transition metal bonds, to barrier heights (including pericyclic reactions), to proton affinities, to the hydrogen bond energy of water dimer, to ground- and excited-state charge transfer, to valence and Rydberg excitations of molecules, and to singlet-triplet splittings of radicals. We find that that MC-PDFT can give accurate results not only with complete-active-space multiconfiguration wave functions but also with generalized-active-space multiconfiguration wave functions, which are practical for larger numbers of active electrons and active orbitals than are complete-active-space wave functions. The separated-pair approximation, which is a special case of generalized active space self-consistent-field theory, is especially promising. MC-PDFT, because it requires much less computer time and storage than pure WFT methods, has the potential to open larger and more complex strongly correlated systems to accurate simulation.

Mapping of spin wave propagation in a one-dimensional magnonic crystal

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

Ordóñez-Romero, César L., E-mail: cloro@fisica.unam.mx; Lazcano-Ortiz, Zorayda; Aguilar-Huerta, Melisa

2016-07-28

The formation and evolution of spin wave band gaps in the transmission spectrum of a magnonic crystal have been studied. A time and space resolved magneto inductive probing system has been used to map the spin wave propagation and evolution in a geometrically structured yttrium iron garnet film. Experiments have been carried out using (1) a chemically etched magnonic crystal supporting the propagation of magnetostatic surface spin waves, (2) a short microwave pulsed excitation of the spin waves, and (3) direct spin wave detection using a movable magneto inductive probe connected to a synchronized fast oscilloscope. The results show thatmore » the periodic structure not only modifies the spectra of the transmitted spin waves but also influences the distribution of the spin wave energy inside the magnonic crystal as a function of the position and the transmitted frequency. These results comprise an experimental confirmation of Bloch′s theorem in a spin wave system and demonstrate good agreement with theoretical observations in analogue phononic and photonic systems. Theoretical prediction of the structured transmission spectra is achieved using a simple model based on microwave transmission lines theory. Here, a spin wave system illustrates in detail the evolution of a much more general physical concept: the band gap.« less

Statistical properties and correlation functions for drift waves

NASA Technical Reports Server (NTRS)

Horton, W.

1986-01-01

The dissipative one-field drift wave equation is solved using the pseudospectral method to generate steady-state fluctuations. The fluctuations are analyzed in terms of space-time correlation functions and modal probability distributions. Nearly Gaussian statistics and exponential decay of the two-time correlation functions occur in the presence of electron dissipation, while in the absence of electron dissipation long-lived vortical structures occur. Formulas from renormalized, Markovianized statistical turbulence theory are given in a local approximation to interpret the dissipative turbulence.

Linking Wave Forcing to Coral Cover and Structural Complexity Across Coral Reef Flats

NASA Astrophysics Data System (ADS)

Harris, D. L.; Rovere, A.; Parravicini, V.; Casella, E.

2015-12-01

The hydrodynamic regime is a significant component in the geomorphic and ecological development of coral reefs. The energy gradients and flow conditions generated by the breaking and transformation of waves across coral reef crests and flats drive changes in geomorphic structure, and coral growth form and distribution. One of the key aspects in regulating the wave energy propagating across reef flats is the rugosity or roughness of the benthic substrate. Rugosity and structural complexity of coral reefs is also a key indicator of species diversity, ecological functioning, and reef health. However, the links between reef rugosity, coral species distribution and abundance, and hydrodynamic forcing are poorly understood. In this study we examine this relationship by using high resolution measurement of waves in the surf zone and coral reef benthic structure.Pressure transducers (logging at 4 Hz) were deployed in cross reef transects at two sites (Tiahura and Ha'apiti reef systems) in Moorea, French Polynesia with wave characteristics determined on a wave by wave basis. A one dimensional hydrodynamic model (XBeach) was calibrated from this data to determine wave processes on the reef flats under average conditions. Transects of the reef benthic structure were conducted using photographic analysis and the three dimensional reef surface was constructed using structure from motion procedures. From this analysis reef rugosity, changes in coral genus and growth form, and across reef shifts in benthic community were determined. The results show clear changes in benthic assemblages along wave energy gradients with some indication of threshold values of wave induced bed shear stress above which live coral cover was reduced. Reef rugosity was shown to be significantly along the cross-reef transect which has important implications for accurate assessment of wave dissipation across coral reef flats. Links between reef rugosity and coral genus were also observed and may indicate that some coral species are crucial in maintaining the structural diversity of coral reefs.

Deep structure of the Alborz Mountains by joint inversion of P receiver functions and dispersion curves

NASA Astrophysics Data System (ADS)

Rastgoo, Mehdi; Rahimi, Habib; Motaghi, Khalil; Shabanian, Esmaeil; Romanelli, Fabio; Panza, Giuliano F.

2018-04-01

The Alborz Mountains represent a tectonically and seismically active convergent boundary in the Arabia - Eurasia collision zone, in western Asia. The orogenic belt has undergone a long-lasted tectono-magmatic history since the Cretaceous. The relationship between shallow and deep structures in this complex tectonic domain is not straightforward. We present a 2D velocity model constructed by the assemblage of 1D shear wave velocity (Vs) models from 26 seismic stations, mainly distributed along the southern flank of the Alborz Mountains. The shear wave velocity structure has been estimated beneath each station using joint inversion of P-waves receiver functions and Rayleigh wave dispersion curves. A substantiation of the Vs inversion results sits on the modeling of Bouguer gravity anomaly data. Our velocity and density models show low velocity/density anomalies in uppermost mantle of western and central Alborz at a depth range of ∼50-100 km. In deeper parts of the uppermost mantle (depth range of 100-150 km), a high velocity/density anomaly is located beneath most of the Mountain range. The spatial pattern of these low and high velocity/density structures in the upper mantle is interpreted as the result of post collisional delamination of lower part of the western and central Alborz lithosphere.

Experimental and theoretical study of Rayleigh-Lamb wave propagation

NASA Technical Reports Server (NTRS)

Rogers, Wayne P.; Datta, Subhendu K.; Ju, T. H.

1990-01-01

Many space structures, such as the Space Station Freedom, contain critical thin-walled components. The structural integrity of thin-walled plates and shells can be monitored effectively using acoustic emission and ultrasonic testing in the Rayleigh-Lamb wave frequency range. A new PVDF piezoelectric sensor has been developed that is well suited to remote, inservice nondestructive evaluation of space structures. In the present study the new sensor was used to investigate Rayleigh-Lamb wave propagation in a plate. The experimental apparatus consisted of a glass plate (2.3 m x 25.4 mm x 5.6 mm) with PVDF sensor (3 mm diam.) mounted at various positions along its length. A steel ball impact served as a simulated acoustic emission source, producing surface waves, shear waves and longitudinal waves with dominant frequencies between 1 kHz and 200 kHz. The experimental time domain wave-forms were compared with theoretical predictions of the wave propagation in the plate. The model uses an analytical solution for the Green's function and the measured response at a single position to predict response at any other position in the plate. Close agreement was found between the experimental and theoretical results.

Tight-binding analysis of Si and GaAs ultrathin bodies with subatomic wave-function resolution

NASA Astrophysics Data System (ADS)

Tan, Yaohua P.; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy B.; Klimeck, Gerhard

2015-08-01

Empirical tight-binding (ETB) methods are widely used in atomistic device simulations. Traditional ways of generating the ETB parameters rely on direct fitting to bulk experiments or theoretical electronic bands. However, ETB calculations based on existing parameters lead to unphysical results in ultrasmall structures like the As-terminated GaAs ultrathin bodies (UTBs). In this work, it is shown that more transferable ETB parameters with a short interaction range can be obtained by a process of mapping ab initio bands and wave functions to ETB models. This process enables the calibration of not only the ETB energy bands but also the ETB wave functions with corresponding ab initio calculations. Based on the mapping process, ETB models of Si and GaAs are parameterized with respect to hybrid functional calculations. Highly localized ETB basis functions are obtained. Both the ETB energy bands and wave functions with subatomic resolution of UTBs show good agreement with the corresponding hybrid functional calculations. The ETB methods can then be used to explain realistically extended devices in nonequilibrium that cannot be tackled with ab initio methods.

Probability and Quantum Paradigms: the Interplay

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

Kracklauer, A. F.

Since the introduction of Born's interpretation of quantum wave functions as yielding the probability density of presence, Quantum Theory and Probability have lived in a troubled symbiosis. Problems arise with this interpretation because quantum probabilities exhibit features alien to usual probabilities, namely non Boolean structure and non positive-definite phase space probability densities. This has inspired research into both elaborate formulations of Probability Theory and alternate interpretations for wave functions. Herein the latter tactic is taken and a suggested variant interpretation of wave functions based on photo detection physics proposed, and some empirical consequences are considered. Although incomplete in a fewmore » details, this variant is appealing in its reliance on well tested concepts and technology.« less

Probability and Quantum Paradigms: the Interplay

NASA Astrophysics Data System (ADS)

Kracklauer, A. F.

2007-12-01

Since the introduction of Born's interpretation of quantum wave functions as yielding the probability density of presence, Quantum Theory and Probability have lived in a troubled symbiosis. Problems arise with this interpretation because quantum probabilities exhibit features alien to usual probabilities, namely non Boolean structure and non positive-definite phase space probability densities. This has inspired research into both elaborate formulations of Probability Theory and alternate interpretations for wave functions. Herein the latter tactic is taken and a suggested variant interpretation of wave functions based on photo detection physics proposed, and some empirical consequences are considered. Although incomplete in a few details, this variant is appealing in its reliance on well tested concepts and technology.

Dynamical Effects in Metal-Organic Frameworks: The Microporous Materials as Shock Absorbers

NASA Astrophysics Data System (ADS)

Banlusan, Kiettipong; Strachan, Alejandro

2017-06-01

Metal-organic frameworks (MOFs) are a class of nano-porous crystalline solids consisting of inorganic units coordinated to organic linkers. The unique molecular structures and outstanding properties with ultra-high porosity and tunable chemical functionality by various choices of metal clusters and organic ligands make this class of materials attractive for many applications. The complex and quite unique responses of these materials to mechanical loading including void collapse make them attractive for applications in energy absorption and storage. We will present using large-scale molecular dynamics simulations to investigate shock propagation in zeolitic imidazolate framework ZIF-8 and MOF-5. We find that for shock strengths above a threshold a two-wave structure develops with a leading elastic precursor followed by a second wave of structural collapse to relax the stress. Structural transition of MOFs in response to shock waves corresponds to the transition between two Hugoniot curves, and results in abrupt change in temperature. The pore-collapse wave propagates at slower velocity than the leading wave and weakens it, resulting in shock attenuation. Increasing piston speed results in faster propagation of pore-collapse wave, but the leading elastic wave remains unchanged below the overdriven regime. We discuss how the molecular structure of the MOFs and shock propagation direction affect the response of the materials and their ability to weaken shocks. Office of Naval Research, MURI 2012 02341 01.

Three-Dimensional Velocity Structure in Southern California from Teleseismic Surface Waves and Body Waves.

NASA Astrophysics Data System (ADS)

Prindle-Sheldrake, K. L.; Tanimoto, T.

2003-12-01

Analysis of teleseismic waves generated by large earthquakes worldwide across the Southern California TriNet Seismic Broadband Array has yielded high quality measurements of both surface waves and body waves. Rayleigh waves and Love waves were previously analyzed using a spectral fitting technique (Tanimoto. and Prindle-Sheldrake, GRL 2002; Prindle-Sheldrake and Tanimoto, submitted to JGR), producing a three-dimensional S-wave velocity structure. Features in our velocity structure show some regional contrasts with respect to the starting model (SCEC 2.2), which has detailed crustal structure, but laterally homogeneous upper mantle structure. The most prominent of which is a postulated fast velocity anomaly located west of the Western Transverse Ranges that could be related to a rotated remnant plate from Farallon subduction. Analysis indicates that, while Rayleigh wave data are mostly sensitive to mantle structure, Love wave data require some modifications of crustal structure from SCEC 2.2 model. Recent advances in our velocity structure focus on accommodation of finite frequency effect, and the addition of body waves to the data. Thus far, 118 events have been analyzed for body waves. A simple geometrical approach is used to represent the finite frequency effect in phase velocity maps. Due to concerns that, for seismic phases between 10-100 seconds, structure away from the ray theoretical is also sampled by a propagating surface wave, we have adopted a technique which examines a normal mode formula in its asymptotic limit (Tanimoto, GRL 2003 in press). An ellipse, based on both distance from source to receiver and wavelength, can be used to approximate the effect on the structure along the ray path and adjacent structure. Three models were tested in order to select the appropriate distribution within the ellipse; the first case gives equal weight to all blocks within the ellipse; case 2 incorporates a Gaussian function which falls off perpendicular to the ray path, allowing the amplitude to peak at the receiver; case 3 is the same as case 2, yet removes the effect of the peak at the receiver. A major improvement is that the locale under consideration has expanded due to the effect of ray paths spreading over a larger area than the ray theoretical. Comparison of the three techniques yields very similar results, and all techniques show an exceptional correlation to the ray theoretical phase velocity maps. After analyzing our data in terms of the finite frequency effect, we find that little change has occurred as a result of employing this technique other than expanding our region of study. P-wave measurements were obtained from the data set for 118 events. Preliminary results show systematic patterns. We have successfully measured 30 S-wave events which we plan to incorporate into our velocity structure. Our goal is to proceed with a joint inversion of P-waves, S-waves and Surface waves for a collective Southern California velocity structure.

Site-effect estimations for Taipei Basin based on shallow S-wave velocity structures

NASA Astrophysics Data System (ADS)

Chen, Ying-Chi; Huang, Huey-Chu; Wu, Cheng-Feng

2016-03-01

Shallow S-wave velocities have been widely used for earthquake ground-motion site characterization. Thus, the S-wave velocity structures of Taipei Basin, Taiwan were investigated using array records of microtremors at 15 sites (Huang et al., 2015). In this study, seven velocity structures are added to the database describing Taipei Basin. Validity of S-wave velocity structures are first examined using the 1D Haskell method and well-logging data at the Wuku Sewage Disposal Plant (WK) borehole site. Basically, the synthetic results match well with the observed data at different depths. Based on S-wave velocity structures at 22 sites, theoretical transfer functions at five different formations of the sedimentary basin are calculated. According to these results, predominant frequencies for these formations are estimated. If the S-wave velocity of the Tertiary basement is assumed to be 1000 m/s, the predominant frequencies of the Quaternary sediments are between 0.3 Hz (WUK) and 1.4 Hz (LEL) in Taipei Basin while the depths of sediments between 0 m (i.e. at the edge of the basin) and 616 m (i.e. site WUK) gradually increase from southeast to northwest. Our results show good agreement with available geological and geophysical information.

Control of circular polarization of electroluminescence in spin light-emitting diodes based on InGaAs/GaAs/δ〈Mn〉 heterostructures

NASA Astrophysics Data System (ADS)

Malysheva, E. I.; Dorokhin, M. V.; Demina, P. B.; Zdoroveyshchev, A. V.; Rykov, A. V.; Ved', M. V.; Danilov, Yu. A.

2017-11-01

Circularly polarized luminescence of light-emitting InGaAs/GaAs structures with a delta-doped Mn layer in a GaAs barrier was studied. The structural parameters were varied by different ways, among them are homogeneous and delta-doping with acceptor impurity, and removal of donor doping from the technological process. As it was found, the magnitude and polarity of the degree of circular polarization of luminescence strongly depend on the technological mode chosen. Simultaneous modeling of wave functions of structures highlights a good agreement between the parameters of circularly polarized luminescence and spatial distribution of wave functions of heavy holes relative to the Mn delta-layer.

Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

NASA Astrophysics Data System (ADS)

Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

2017-12-01

Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

Lithosphere structure in Madagascar as revealed from receiver functions and surface waves analysis.

NASA Astrophysics Data System (ADS)

Rindraharisaona, E. J.; Tilmann, F. J.; Yuan, X.; Dreiling, J.; Priestley, K. F.; Barruol, G.; Wysession, M. E.

2017-12-01

The geological history of Madagascar makes it an ideal place to study the lithospheric structure and its evolution. It comprises Archean to Proterozoic units on the central eastern part, which is surrounded by a Triassic to Jurassic basin formation in the west and Cretaceous volcanics along the coasts. Quaternary volcanic rocks have been embedded in crystalline and sedimentary rocks. The aim of the present work is to characterize the crustal structure and determine the imprint of the dominant geodynamic events that have affected Madagascar: the Pan-African orogeny, the breakup of Gondwanaland and Neogene tectonic activity. From 2011 to 2014 different temporary seismic arrays were deployed in Madagascar. We based the current study mostly on SELASOMA project, which is composed of 50 seismic stations that were installed traversing southern Madagascar from the west to the east, sampling the different geological units. To measured seismic dispersion curves, one a wide period ranges using ambient noise, Rayleigh and Love surface waves. To compute the average crustal Vp/Vs ratio internal crustal structure and discontinuities in the mantle, we use both P- and S-waves receiver functions. To better resolve of the crustal structure, we jointly inverted P-wave receiver functions and Rayleigh wave group velocity.The crustal extension during the Carboniferous to Cenozoic has thinned the igneous crust down to 15 km in the western Morondava basin by removing much of the lower crust, while the thickness of the upper crust is nearly identical in the sedimentary basin and under Proterozoic and Archaean rocks of the eastern two thirds of Southern Madagascar. In general, the Archean crust is thicker than the Proterozoic, because mafic component is missing in the Proterozoic domain while it forms the bottom of the Archean crust. The lithosphere thickness in the southern part of Madagascar is estimated to be between 90 and 125 km.

Propagation of ultrasonic Love waves in nonhomogeneous elastic functionally graded materials.

PubMed

Kiełczyński, P; Szalewski, M; Balcerzak, A; Wieja, K

2016-02-01

This paper presents a theoretical study of the propagation behavior of ultrasonic Love waves in nonhomogeneous functionally graded elastic materials, which is a vital problem in the mechanics of solids. The elastic properties (shear modulus) of a semi-infinite elastic half-space vary monotonically with the depth (distance from the surface of the material). The Direct Sturm-Liouville Problem that describes the propagation of Love waves in nonhomogeneous elastic functionally graded materials is formulated and solved by using two methods: i.e., (1) Finite Difference Method, and (2) Haskell-Thompson Transfer Matrix Method. The dispersion curves of phase and group velocity of surface Love waves in inhomogeneous elastic graded materials are evaluated. The integral formula for the group velocity of Love waves in nonhomogeneous elastic graded materials has been established. The effect of elastic non-homogeneities on the dispersion curves of Love waves is discussed. Two Love wave waveguide structures are analyzed: (1) a nonhomogeneous elastic surface layer deposited on a homogeneous elastic substrate, and (2) a semi-infinite nonhomogeneous elastic half-space. Obtained in this work, the phase and group velocity dispersion curves of Love waves propagating in the considered nonhomogeneous elastic waveguides have not previously been reported in the scientific literature. The results of this paper may give a deeper insight into the nature of Love waves propagation in elastic nonhomogeneous functionally graded materials, and can provide theoretical guidance for the design and optimization of Love wave based devices. Copyright © 2015 Elsevier B.V. All rights reserved.

An open-source framework for analyzing N-electron dynamics. II. Hybrid density functional theory/configuration interaction methodology.

PubMed

Hermann, Gunter; Pohl, Vincent; Tremblay, Jean Christophe

2017-10-30

In this contribution, we extend our framework for analyzing and visualizing correlated many-electron dynamics to non-variational, highly scalable electronic structure method. Specifically, an explicitly time-dependent electronic wave packet is written as a linear combination of N-electron wave functions at the configuration interaction singles (CIS) level, which are obtained from a reference time-dependent density functional theory (TDDFT) calculation. The procedure is implemented in the open-source Python program detCI@ORBKIT, which extends the capabilities of our recently published post-processing toolbox (Hermann et al., J. Comput. Chem. 2016, 37, 1511). From the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions, the framework exploits the multideterminental structure of the hybrid TDDFT/CIS wave packet to compute fundamental one-electron quantities such as difference electronic densities, transient electronic flux densities, and transition dipole moments. The hybrid scheme is benchmarked against wave function data for the laser-driven state selective excitation in LiH. It is shown that all features of the electron dynamics are in good quantitative agreement with the higher-level method provided a judicious choice of functional is made. Broadband excitation of a medium-sized organic chromophore further demonstrates the scalability of the method. In addition, the time-dependent flux densities unravel the mechanistic details of the simulated charge migration process at a glance. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Upper Crustal Structure of Taiwan Constrained by the Ellipticity of the Noise-derived Rayleigh Waves

NASA Astrophysics Data System (ADS)

Chien, C. C.; Chen, Y. N.; Gung, Y.; Liang, W. T.

2016-12-01

In the last decade, the noise interferometry has been a popular technique, and widely applied to constraint the crust and uppermost mantle structure, bringing in revolutionary resolution in area with dense seismic network, including Taiwan. However, limited by the available frequency band of the noise-derived surface waves, the near surface (<5km) structure is much less resolved as compared to the rest of the crust in Taiwan. Such limitation may be lifted by using the ZH ratio of Rayleigh waves, because, for the same period, the ZH ratio of Rayleigh waves is much more sensitive to the shallower structure than those provided by the corresponding phase or group velocities. In this study, aiming to better constraint the seismic structure of the shallow crust of Taiwan, we measure the ZH ratios of the Rayleigh waves derived by noise interferometry. Continuous records from two major seismic networks in Taiwan are used. In total, data from 63 short period stations and 48 broadband stations are used to derived the four combinations (ZZ, ZR, RZ, RR) of cross-correlation functions (CCF). We then measure the ZH ratios of the derived Rayleigh waves. We present the measured results, invert for the local 1-D structure for sites with stable measurements. We then compare the results with the published tomographic models and discuss their geological implications.

Adaptation of the projector-augmented-wave formalism to the treatment of orbital-dependent exchange-correlation functionals

NASA Astrophysics Data System (ADS)

Xu, Xiao; Holzwarth, N. A. W.

2011-10-01

This paper presents the formulation and numerical implementation of a self-consistent treatment of orbital-dependent exchange-correlation functionals within the projector-augmented-wave method of Blöchl [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.50.17953 50, 17953 (1994)] for electronic structure calculations. The methodology is illustrated with binding energy curves for C in the diamond structure and LiF in the rock salt structure, by comparing results from the Hartree-Fock (HF) formalism and the optimized effective potential formalism in the so-called KLI approximation [Krieger, Li, and Iafrate, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.45.101 45, 101 (1992)] with those of the local density approximation. While the work here uses pure Fock exchange only, the formalism can be extended to treat orbital-dependent functionals more generally.

The Precambrian crustal structure of East Africa

NASA Astrophysics Data System (ADS)

Young, A. J.; Tugume, F.; Nyblade, A.; Julia, J.; Mulibo, G.

2011-12-01

We present new results on crustal structure from East Africa from analyzing P wave receiver functions. The data for this study come from temporary AfricaArray broadband seismic stations deployed between 2007 and 2011 in Uganda, Tanzania and Zambia. Receiver functions have been computed using an iterative deconvolution method. Crustal structure has been imaged using the H-k stacking method and by jointly inverting the receiver functions and surface wave phase and group velocities. The results show remarkably uniform crust throughout the Archean and Proterozoic terrains that comprise the Precambrian tectonic framework of the region. Crustal thickness for most terrains is between 37 and 40 km, and Poisson's ratio is between 0.25 and 0.27. Results from the joint inversion yield average crustal Vs values of 3.6 to 3.7 km/s. For most terrains, a thin (1-5 km) thick high velocity (Vs>4.0 km/s) is found at the base of the crust.

Tunable optical and excitonic properties of phosphorene via oxidation

NASA Astrophysics Data System (ADS)

Sadki, S.; Drissi, L. B.

2018-06-01

The optical properties and excitonic wave function of phosphorene oxides (PO) are studied using the first principle many-body Green function and the Bethe–Salpeter equation formalism. In this work, the optical properties are determined using ab initio calculations of the dielectric function. At the long wavelength limit q of EM wave (i.e. ), the dielectric function, the absorption spectrum, the lectivity, the electron energy loss spectra (EELS) and the wave function are calculated. The results show an excitonic binding energy of 818 meV with a bright exciton located in the armchair direction in pristine phosphorene. For PO, the arrangement of the oxygen atoms significantly influences the optical properties. In particular, the absorption spectrum is extended along the solar spectrum, with a high absorption coefficient observed in the dangling structures. The maximum lectivity values are observed for the high energies of the light spectrum. Moreover, the first EELS peak is located in the visible region in all the structures except for one configuration that exhibits the same behavior as pure phosphorene. Finally, the exciton effect reveals that all PO conformers have a dark exciton state, which is suitable for long-lived applications.

Understanding Effects of Traumatic Insults on Brain Structure and Function

DTIC Science & Technology

2016-08-01

42 Fig. 33 The supersonic shock wave at the various distances from its launch. The liposome is located at 117.4 nm. The...For instance, although the pressure front of a shock wave travels at supersonic speeds (the speed of sound in water is 1,497 m/s), the shock wave... supersonic shock wave at the various distances from its launch. The liposome is located at 117.4 nm. The Mach number is 1.49. b) The pressure profile at t

Orbital dependent functionals: An atom projector augmented wave method implementation

NASA Astrophysics Data System (ADS)

Xu, Xiao

This thesis explores the formulation and numerical implementation of orbital dependent exchange-correlation functionals within electronic structure calculations. These orbital-dependent exchange-correlation functionals have recently received renewed attention as a means to improve the physical representation of electron interactions within electronic structure calculations. In particular, electron self-interaction terms can be avoided. In this thesis, an orbital-dependent functional is considered in the context of Hartree-Fock (HF) theory as well as the Optimized Effective Potential (OEP) method and the approximate OEP method developed by Krieger, Li, and Iafrate, known as the KLI approximation. In this thesis, the Fock exchange term is used as a simple well-defined example of an orbital-dependent functional. The Projected Augmented Wave (PAW) method developed by P. E. Blochl has proven to be accurate and efficient for electronic structure calculations for local and semi-local functions because of its accurate evaluation of interaction integrals by controlling multiple moments. We have extended the PAW method to treat orbital-dependent functionals in Hartree-Fock theory and the Optimized Effective Potential method, particularly in the KLI approximation. In the course of study we develop a frozen-core orbital approximation that accurately treats the core electron contributions for above three methods. The main part of the thesis focuses on the treatment of spherical atoms. We have investigated the behavior of PAW-Hartree Fock and PAW-KLI basis, projector, and pseudopotential functions for several elements throughout the periodic table. We have also extended the formalism to the treatment of solids in a plane wave basis and implemented PWPAW-KLI code, which will appear in future publications.

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions

NASA Astrophysics Data System (ADS)

Jerke, Jonathan; Poirier, Bill

2018-03-01

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy—i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted—as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions.

PubMed

Jerke, Jonathan; Poirier, Bill

2018-03-14

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy-i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted-as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Synconset Waves and Chains: Spiking Onsets in Synchronous Populations Predict and Are Predicted by Network Structure

PubMed Central

Raghavan, Mohan; Amrutur, Bharadwaj; Narayanan, Rishikesh; Sikdar, Sujit Kumar

2013-01-01

Synfire waves are propagating spike packets in synfire chains, which are feedforward chains embedded in random networks. Although synfire waves have proved to be effective quantification for network activity with clear relations to network structure, their utilities are largely limited to feedforward networks with low background activity. To overcome these shortcomings, we describe a novel generalisation of synfire waves, and define ‘synconset wave’ as a cascade of first spikes within a synchronisation event. Synconset waves would occur in ‘synconset chains’, which are feedforward chains embedded in possibly heavily recurrent networks with heavy background activity. We probed the utility of synconset waves using simulation of single compartment neuron network models with biophysically realistic conductances, and demonstrated that the spread of synconset waves directly follows from the network connectivity matrix and is modulated by top-down inputs and the resultant oscillations. Such synconset profiles lend intuitive insights into network organisation in terms of connection probabilities between various network regions rather than an adjacency matrix. To test this intuition, we develop a Bayesian likelihood function that quantifies the probability that an observed synfire wave was caused by a given network. Further, we demonstrate it's utility in the inverse problem of identifying the network that caused a given synfire wave. This method was effective even in highly subsampled networks where only a small subset of neurons were accessible, thus showing it's utility in experimental estimation of connectomes in real neuronal-networks. Together, we propose synconset chains/waves as an effective framework for understanding the impact of network structure on function, and as a step towards developing physiology-driven network identification methods. Finally, as synconset chains extend the utilities of synfire chains to arbitrary networks, we suggest utilities of our framework to several aspects of network physiology including cell assemblies, population codes, and oscillatory synchrony. PMID:24116018

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

DOE PAGES

Chen, K.; Strigari, F.; Sundermann, M.; ...

2018-01-17

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

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

Chen, K.; Strigari, F.; Sundermann, M.

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Development of a hybrid wave based-transfer matrix model for sound transmission analysis.

PubMed

Dijckmans, A; Vermeir, G

2013-04-01

In this paper, a hybrid wave based-transfer matrix model is presented that allows for the investigation of the sound transmission through finite multilayered structures placed between two reverberant rooms. The multilayered structure may consist of an arbitrary configuration of fluid, elastic, or poro-elastic layers. The field variables (structural displacements and sound pressures) are expanded in terms of structural and acoustic wave functions. The boundary and continuity conditions in the rooms determine the participation factors in the pressure expansions. The displacement of the multilayered structure is determined by the mechanical impedance matrix, which gives a relation between the pressures and transverse displacements at both sides of the structure. The elements of this matrix are calculated with the transfer matrix method. First, the hybrid model is numerically validated. Next a comparison is made with sound transmission loss measurements of a hollow brick wall and a sandwich panel. Finally, numerical simulations show the influence of structural damping, room dimensions and plate dimensions on the sound transmission loss of multilayered structures.

The application of the constants of motion to nonlinear stationary waves in complex plasmas: a unified fluid dynamic viewpoint

NASA Astrophysics Data System (ADS)

McKenzie, J. F.; Dubinin, E.; Sauer, K.; Doyle, T. B.

2004-08-01

Perturbation reductive procedures, as used to analyse various weakly nonlinear plasma waves (solitons and periodic waves), normally lead to the dynamical system being described by KdV, Burgers' or a nonlinear Schrödinger-type equation, with properties that can be deduced from an array of mathematical techniques. Here we develop a fully nonlinear theory of one-dimensional stationary plasma waves, which elucidates the common nature of various diverse wave phenomena. This is accomplished by adopting an essentially fluid dynamic viewpoint. In this unified treatment the constants of the motion (for mass, momentum and energy) lead naturally to the construction of the wave structure equations. It is shown, for example, that electrostatic, Hall magnetohydrodynamic and ion cyclotron acoustic nonlinear waves all obey first-order differential equations of the same generic type for the longitudinal flow field of the wave. The equilibrium points, which define the soliton amplitude, are given by the compressive and/or rarefactive roots of a total plasma ‘energy’ or ‘momentum’ function characterizing the wave type. This energy function, which is an algebraic combination of the Bernoulli momentum and energy functions for the longitudinal flow field, is the fluid dynamic counterpart of the pseudo-potentials, which are characteristic of system structure equations formulated in other than fluid variables. Another general feature of the structure equation is the phenomenon of choked flow, which occurs when the flow speed becomes sonic. It is this trans-sonic property that limits the soliton amplitudes and defines the critical collective Mach numbers of the waves. These features are also obtained in multi-component plasmas where, for example, in a bi-ion plasma, momentum exchanges between protons and heavier ions are mediated by the Maxwell magnetic stresses. With a suitable generalization of the concept of a sonic point in a bi-ion system and the corresponding choked flow feature, the wave structures, although now more complicated, can also be understood within this overall fluid framework. Particularly useful tools in this context are the momentum hodograph (an algebraic relation between the bi-ion speeds and the electron speed, or magnetic field, which follows from the conservation of mass, momentum and charge-neutrality) and a generalized Bernoulli energy density for each species. Analysis shows that the bi-ion solitons are essentially compressive, but contain the remarkable feature of the presence of a proton rarefactive core. A new type of soliton, called an ‘oscilliton’ because embedded spatial oscillations are superimposed on the classical soliton, is also described and discussed. A necessary condition for the existence of this type of wave is that the linear phase velocity must exhibit an extremum where the phase speed matches the group speed. The remarkable properties of this wave are illustrated for the case of both whistler waves and bi-ion waves where, for the latter, the requisite condition is met near the cross-over frequencies. In the case of the whistler oscilliton, which propagates at speeds in excess of one half of the Alfvén speed (based on the electrons), an analytic solution has been constructed through a phase-portrait integral of the system in which the proton and electron dynamics must be placed on the same footing. The relevance of the different wave structures to diverse space environments is briefly discussed in relation to recently available high-time and spatial resolution data from satellite observations.

Fundamental physical theories: Mathematical structures grounded on a primitive ontology

NASA Astrophysics Data System (ADS)

Allori, Valia

In my dissertation I analyze the structure of fundamental physical theories. I start with an analysis of what an adequate primitive ontology is, discussing the measurement problem in quantum mechanics and theirs solutions. It is commonly said that these theories have little in common. I argue instead that the moral of the measurement problem is that the wave function cannot represent physical objects and a common structure between these solutions can be recognized: each of them is about a clear three-dimensional primitive ontology that evolves according to a law determined by the wave function. The primitive ontology is what matter is made of while the wave function tells the matter how to move. One might think that what is important in the notion of primitive ontology is their three-dimensionality. If so, in a theory like classical electrodynamics electromagnetic fields would be part of the primitive ontology. I argue that, reflecting on what the purpose of a fundamental physical theory is, namely to explain the behavior of objects in three-dimensional space, one can recognize that a fundamental physical theory has a particular architecture. If so, electromagnetic fields play a different role in the theory than the particles and therefore should be considered, like the wave function, as part of the law. Therefore, we can characterize the general structure of a fundamental physical theory as a mathematical structure grounded on a primitive ontology. I explore this idea to better understand theories like classical mechanics and relativity, emphasizing that primitive ontology is crucial in the process of building new theories, being fundamental in identifying the symmetries. Finally, I analyze what it means to explain the word around us in terms of the notion of primitive ontology in the case of regularities of statistical character. Here is where the notion of typicality comes into play: we have explained a phenomenon if the typical histories of the primitive ontology give rise to the statistical regularities we observe.

Lithospheric Structure of the Arabian Shield From the Joint Inversion of Receiver Function and Surface-Wave Dispersion Observations

DTIC Science & Technology

2007-01-01

dashed lines correspond to observations and predictions, respectively. 9 Inversion results corresponding to the stations located within the Asir t~er- 17...wave velocity models ............................................................. A-2 A3 Asir terrane S-wave velocity models...island-arc terranes ( Asir , Hijaz and Midyan), and to the east, one terrane of continental affinity (Afif) and one terrane of possible continental

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.

Quantitative modeling of coupled piezo-elastodynamic behavior of piezoelectric actuators bonded to an elastic medium for structural health monitoring: a review.

PubMed

Huang, Guoliang; Song, Fei; Wang, Xiaodong

2010-01-01

Elastic waves, especially guided waves, generated by a piezoelectric actuator/sensor network, have shown great potential for on-line health monitoring of advanced aerospace, nuclear, and automotive structures in recent decades. Piezoelectric materials can function as both actuators and sensors in these applications due to wide bandwidth, quick response and low costs. One of the most fundamental issues surrounding the effective use of piezoelectric actuators is the quantitative evaluation of the resulting elastic wave propagation by considering the coupled piezo-elastodynamic behavior between the actuator and the host medium. Accurate characterization of the local interfacial stress distribution between the actuator and the host medium is the key issue for the problem. This paper presents a review of the development of analytical, numerical and hybrid approaches for modeling of the coupled piezo-elastodynamic behavior. The resulting elastic wave propagation for structural health monitoring is also summarized.

Crust and upper mantle shear wave structure of Northeast Algeria from Rayleigh wave dispersion analysis

NASA Astrophysics Data System (ADS)

Radi, Zohir; Yelles-Chaouche, Abdelkrim; Corchete, Victor; Guettouche, Salim

2017-09-01

We resolve the crust and upper mantle structure beneath Northeast Algeria at depths of 0-400 km, using inversion of fundamental mode Rayleigh wave. Our data set consists of 490 earthquakes recorded between 2007 and 2014 by five permanent broadband seismic stations in the study area. Applying a combination of different filtering technics and inversion method shear wave velocities structure were determined as functions of depth. The resolved changes in Vs at 50 km depth are in perfect agreement with crustal thickness estimates, which reflect the study area's orogenic setting, partly overlying the collision zone between the African and Eurasian plates. The inferred Moho discontinuity depths are close to those estimated for other convergent areas. In addition, there is good agreement between our results and variations in orientations of regional seismic anisotropy. At depths of 80-180 km, negative Vs anomalies at station CBBR suggest the existence of a failed subduction slab.

Tidal waves within the thermosphere. [emphasizing wave dissipation and diffusion

NASA Technical Reports Server (NTRS)

Volland, H.; Mayr, H. G.

1974-01-01

The eigenfunctions of the atmosphere (the Hough functions within the lower atmosphere below about 100 km) change their structure and their propagation characteristics within the thermosphere due to dissipation effects such as heat conduction, viscosity, and ion drag. Wave dissipation can be parameterized to a first-order approximation by a complex frequency, the imaginary term of which simulates an effective ion drag force. It is shown how the equivalent depth, the attenuation, and the vertical wavelength of the predominant symmetric diurnal tidal modes change with height as functions of effective ion drag. The boundary conditions of tidal waves are discussed, and asymptotic solutions for the wave parameters like pressure, density, temperature, and wind generated by a heat input proportional to the mean pressure are given. Finally, diffusion effects upon the minor constituents within the thermosphere are described.

The Microphysics Explorer (MPEX) Mission: A Small Explorer Mission to Investigate the Role of Small Scale Non-Linear Time Domain Structures (TDS) and Waves in the Energization of Electrons and Energy Flow in Space Plasmas.

NASA Astrophysics Data System (ADS)

Wygant, J. R.

2016-12-01

Evidence has accumulated that most energy conversion structures in space plasmas are characterized by intense small-scale size electric fields with strong parallel components, which are prime suspects in the rapid and efficient bulk acceleration of electrons. The proposed MPEX mission will provide, for the first time, 1 ms measurements of electrons capable of resolving the acceleration process due to these small-scale structures. These structures include Time Domain Structures (TDS) which are often organized into wave trains of hundreds of discrete structures propagating along magnetic fields lines. Recent measurements in the near Earth tail on auroral field lines indicate these wave trains are associated with electron acceleration in layers of strong energy flow in the form of particle energy flux and Poynting flux. Also coincident are kinetic Alfven waves which may be capable of driving the time domain structures or directly accelerating electrons. Other waves that may be important include lower hybrid wave packets, electron cyclotron waves, and large amplitude whistler waves. High time resolution field measurements show that such structures occur within dayside and tail reconnection regions, at the bow shock, at interplanetary shocks, and at other structures in the solar wind. The MPEX mission will be a multiphase mission with apogee boosts, which will explore all these regions. An array of electron ESAs will provide a 1 millisecond measurement of electron flux variations with nearly complete pitch angle coverage over a programmable array of selected energy channels. The electric field detector will provide measurement a fully 3-D measurement of the electric field with the benefit of an extremely large ratio of boom length to spacecraft radius and an improved sensor design. 2-D ion distribution functions will be provided by ion mass spectrometer and energetic electrons will be measured by a solid-state telescope.

Infrasonic induced ground motions

NASA Astrophysics Data System (ADS)

Lin, Ting-Li

On January 28, 2004, the CERI seismic network recorded seismic signals generated by an unknown source. Our conclusion is that the acoustic waves were initiated by an explosive source near the ground surface. The meteorological temperature and effective sound speed profiles suggested existence of an efficient near-surface waveguide that allowed the acoustic disturbance to propagate to large distances. An explosion occurring in an area of forest and farms would have limited the number of eyewitnesses. Resolution of the source might be possible by experiment or by detailed analysis of the ground motion data. A seismo-acoustic array was built to investigate thunder-induced ground motions. Two thunder events with similar N-wave waveforms but different horizontal slownesses are chosen to evaluate the credibility of using thunder as a seismic source. These impulsive acoustic waves excited P and S reverberations in the near surface that depend on both the incident wave horizontal slowness and the velocity structure in the upper 30 meters. Nineteen thunder events were chosen to further investigate the seismo-acoustic coupling. The consistent incident slowness differences between acoustic pressure and ground motions suggest that ground reverberations were first initiated somewhat away from the array. Acoustic and seismic signals were used to generate the time-domain transfer function through the deconvolution technique. Possible non-linear interaction for acoustic propagation into the soil at the surface was observed. The reverse radial initial motions suggest a low Poisson's ratio for the near-surface layer. The acoustic-to-seismic transfer functions show a consistent reverberation series of the Rayleigh wave type, which has a systematic dispersion relation to incident slownesses inferred from the seismic ground velocity. Air-coupled Rayleigh wave dispersion was used to quantitatively constrain the near-surface site structure with constraints afforded by near-surface body wave refraction and Rayleigh wave dispersion data. Theoretical standard high-frequency and air-coupled Rayleigh wave dispersion calculated by the inferred site structure match the observed dispersion curves. Our study suggests that natural or controlled air-borne pressure sources can be used to investigate the near-surface site structures for earthquake shaking hazard studies.

Systematic structure of the neutron drip-line {sup 22}C nucleus

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

Ismail, Atef; Cheong, Lee Yen; Yahya, Noorhana

2014-10-24

In the present work we systematically discuss the nuclear structure of the the heaviest particle-bound carbon isotope, {sup 22}C. The ground state wave function of the carbon isotope is calculated using the {sup 20}C core plus two-valence neutron based on a phenomenological mean-field MF potential. We apply the deduced wave function to provide the nuclear matter density which is necessary in the calculations of the total reaction cross section. Calculations show that there is a reasonable good description of the experimental binding energy BE and root-mean square RMS radius. The exotic structure and configuration of the ground state carbon isotopemore » is explained and a consistent explanation on the two-neutron halo (Borromean) nucleus is given.« less

The FLAME-slab method for electromagnetic wave scattering in aperiodic slabs

NASA Astrophysics Data System (ADS)

Mansha, Shampy; Tsukerman, Igor; Chong, Y. D.

2017-12-01

The proposed numerical method, "FLAME-slab," solves electromagnetic wave scattering problems for aperiodic slab structures by exploiting short-range regularities in these structures. The computational procedure involves special difference schemes with high accuracy even on coarse grids. These schemes are based on Trefftz approximations, utilizing functions that locally satisfy the governing differential equations, as is done in the Flexible Local Approximation Method (FLAME). Radiation boundary conditions are implemented via Fourier expansions in the air surrounding the slab. When applied to ensembles of slab structures with identical short-range features, such as amorphous or quasicrystalline lattices, the method is significantly more efficient, both in runtime and in memory consumption, than traditional approaches. This efficiency is due to the fact that the Trefftz functions need to be computed only once for the whole ensemble.

Mapping Shear Zones, Faults, and Crustal Deformation Fabric With Receiver Functions

NASA Astrophysics Data System (ADS)

Schulte-Pelkum, V.; Mahan, K. H.

2014-12-01

Dipping faults, shear zones, and pervasive anisotropic crustal fabric due to deformation are all capable of generating strong near-station mode conversions of teleseismic body waves, even for weak (a few percent) velocity anisotropy. These conversions can be found using the receiver function technique. Dipping foliation and dipping isotropic velocity contrasts can occur in isolation or together in deformed crust. Both generate receiver function arrivals that have a characteristic periodicity with azimuth. Different fixed azimuthal phase shifts between radial and tangential component receiver functions distinguish dipping or tilted structure and fabric from horizontal axis anisotropy. We demonstrate a method that uses these characteristics to map geologically relevant information such as strike and depth of foliation of dipping isotropic velocity contrasts and of horizontal symmetry axis anisotropy contrasts. The method uses waveforms without matching them via forward modeling, which makes choices such as slow versus fast axis symmetry and isotropic dip versus anisotropic axis tilt unnecessary. It also does not use shear wave splitting of the converted waves, which is more difficult to isolate. We show results from the continental U.S. and Canada and from the collision zones in the Himalaya and Tibetan Plateau and Taiwan. We discuss interpretation of our results in the light of recent laboratory measurements of deformed crustal rocks and contributions to the seismic signal from individual minerals such as micas, amphiboles, and quartz. Our observations are connected to geological ground truth by using structural maps and sample anisotropy determined using electron backscatter diffraction from exhumed deep crust in the Athabasca granulite province to predict the seismic signal from present-day deep crust. We also discuss the reconciliation of measurements from anisotropic receiver functions, surface waves, and split shear waves.

Receiver Functions From Regional and Near-Teleseismic P Waves

NASA Astrophysics Data System (ADS)

Park, J.; Levin, V.

2001-05-01

P waves from regional-distance earthquakes are complex and reverberatory, as would be expected from a combination of head waves, post-critical crustal reflections and shallow-incident P from the upper mantle. Although developed to analyze steeply-incident teleseismic P waves, receiver function analysis can also retrieve information about crustal structure from regional and near-teleseismic P. Using a new method to estimate receiver functions, based on multiple-taper spectral analysis, regional-distance RFs for GSN stations RAYN and ANTO show broad agreement with teleseismic RFs. At RAYN the moveout of the Moho-converted Ps phase, relative to direct P, follows well the predictions of the IASP91 earth model. The Moho-converted Ps phase shows complexity associated with the transition-zone triplication near Δ =20o and constant delay (zero moveout) as Δ -> 0, consistent with conversion from Pn. Similar behavior is seen for ANTO for events that arrive from the west. For eastern backazimuths the ANTO RFs show features whose moveout is negative as Δ -> 0. This moveout is poorly fit by reverberations in flat layers or by direct scattering from a dipping interface, but is consistent with a topographic scatterer 20--30 km eastward of the ANTO site. Regional receiver functions may therefore be useful in judging whether teleseismic RFs at a particular station are suitable candidates for a 1-D velocity structure inversion. Synthetic seismograms of regional P phases, computed with a locked-mode reflectivity approach, confirm broad features of the RAYN and ANTO regional receiver functions.

Identification of damage in composite structures using Gaussian mixture model-processed Lamb waves

NASA Astrophysics Data System (ADS)

Wang, Qiang; Ma, Shuxian; Yue, Dong

2018-04-01

Composite materials have comprehensively better properties than traditional materials, and therefore have been more and more widely used, especially because of its higher strength-weight ratio. However, the damage of composite structures is usually varied and complicated. In order to ensure the security of these structures, it is necessary to monitor and distinguish the structural damage in a timely manner. Lamb wave-based structural health monitoring (SHM) has been proved to be effective in online structural damage detection and evaluation; furthermore, the characteristic parameters of the multi-mode Lamb wave varies in response to different types of damage in the composite material. This paper studies the damage identification approach for composite structures using the Lamb wave and the Gaussian mixture model (GMM). The algorithm and principle of the GMM, and the parameter estimation, is introduced. Multi-statistical characteristic parameters of the excited Lamb waves are extracted, and the parameter space with reduced dimensions is adopted by principal component analysis (PCA). The damage identification system using the GMM is then established through training. Experiments on a glass fiber-reinforced epoxy composite laminate plate are conducted to verify the feasibility of the proposed approach in terms of damage classification. The experimental results show that different types of damage can be identified according to the value of the likelihood function of the GMM.

High lateral resolution exploration using surface waves from noise records

NASA Astrophysics Data System (ADS)

Chávez-García, Francisco José Yokoi, Toshiaki

2016-04-01

Determination of the shear-wave velocity structure at shallow depths is a constant necessity in engineering or environmental projects. Given the sensitivity of Rayleigh waves to shear-wave velocity, subsoil structure exploration using surface waves is frequently used. Methods such as the spectral analysis of surface waves (SASW) or multi-channel analysis of surface waves (MASW) determine phase velocity dispersion from surface waves generated by an active source recorded on a line of geophones. Using MASW, it is important that the receiver array be as long as possible to increase the precision at low frequencies. However, this implies that possible lateral variations are discarded. Hayashi and Suzuki (2004) proposed a different way of stacking shot gathers to increase lateral resolution. They combined strategies used in MASW with the common mid-point (CMP) summation currently used in reflection seismology. In their common mid-point with cross-correlation method (CMPCC), they cross-correlate traces sharing CMP locations before determining phase velocity dispersion. Another recent approach to subsoil structure exploration is based on seismic interferometry. It has been shown that cross-correlation of a diffuse field, such as seismic noise, allows the estimation of the Green's Function between two receivers. Thus, a virtual-source seismic section may be constructed from the cross-correlation of seismic noise records obtained in a line of receivers. In this paper, we use the seismic interferometry method to process seismic noise records obtained in seismic refraction lines of 24 geophones, and analyse the results using CMPCC to increase the lateral resolution of the results. Cross-correlation of the noise records allows reconstructing seismic sections with virtual sources at each receiver location. The Rayleigh wave component of the Green's Functions is obtained with a high signal-to-noise ratio. Using CMPCC analysis of the virtual-source seismic lines, we are able to identify lateral variations of phase velocity inside the seismic line, and increase the lateral resolution compared with results of conventional analysis.

Love and Rayleigh wave dispersion from regional Ambient Noise Tomography in the Eastern Alps of Europe

NASA Astrophysics Data System (ADS)

Behm, Michael; Nakata, Nori; Bianchi, Irene; Bokelmann, Götz

2014-05-01

ALPASS is an international passive seismic monitoring experiment aimed at understanding the upper mantle structure in the in the European Eastern Alps. Data were collected from May 2005 to June 2006 at about 50 locations with an average spacing of 20 km, and have been used for teleseismic travel time tomography and receiver function analysis in previous studies. We combine the ALPASS data from 23 broadband stations with additional data from the temporary CBP (Carpathian Basin Project) network (15 stations), and present results from ambient noise tomography applied to the region covering the easternmost part of the Alps and its transition to the adjacent tectonic provinces (Vienna Basin, Bohemian Massif, Dinarides). By turning each station into a virtual source, we are able to recover surface waves in the frequency range of 0.05 - 0.5 Hz, which are sensitive to depths of approximately 2 - 15 kilometers. The three-component recordings allow distinguishing between Rayleigh waves on the vertical/radial components and Love waves on the transverse component. On average, the Love waves have higher apparent velocity by about 15%. Owing to dense receiver spacing and high S/N ratio of the obtained interferograms, we are able to derive a large set of dispersion curves. The complicated 3D structure of the investigated region calls for a tomographic approach to transform these dispersion curves to be representative of local 1D structures. The results correlate well with surface geology and provide the input to inversion for the vertical shear-wave velocity distribution. Compared to data from active source experiments, we derive lower average shear wave velocities. This observation is comparable to receiver functions analysis which show a high Vp/Vs ratio for the area of the Molasse basin, where the shear wave velocities retrieved from the surface wave inversion are in particular low.

Simulation tools for guided wave based structural health monitoring

NASA Astrophysics Data System (ADS)

Mesnil, Olivier; Imperiale, Alexandre; Demaldent, Edouard; Baronian, Vahan; Chapuis, Bastien

2018-04-01

Structural Health Monitoring (SHM) is a thematic derived from Non Destructive Evaluation (NDE) based on the integration of sensors onto or into a structure in order to monitor its health without disturbing its regular operating cycle. Guided wave based SHM relies on the propagation of guided waves in plate-like or extruded structures. Using piezoelectric transducers to generate and receive guided waves is one of the most widely accepted paradigms due to the low cost and low weight of those sensors. A wide range of techniques for flaw detection based on the aforementioned setup is available in the literature but very few of these techniques have found industrial applications yet. A major difficulty comes from the sensitivity of guided waves to a substantial number of parameters such as the temperature or geometrical singularities, making guided wave measurement difficult to analyze. In order to apply guided wave based SHM techniques to a wider spectrum of applications and to transfer those techniques to the industry, the CEA LIST develops novel numerical methods. These methods facilitate the evaluation of the robustness of SHM techniques for multiple applicative cases and ease the analysis of the influence of various parameters, such as sensors positioning or environmental conditions. The first numerical tool is the guided wave module integrated to the commercial software CIVA, relying on a hybrid modal-finite element formulation to compute the guided wave response of perturbations (cavities, flaws…) in extruded structures of arbitrary cross section such as rails or pipes. The second numerical tool is based on the spectral element method [2] and simulates guided waves in both isotropic (metals) and orthotropic (composites) plate like-structures. This tool is designed to match the widely accepted sparse piezoelectric transducer array SHM configuration in which each embedded sensor acts as both emitter and receiver of guided waves. This tool is under development and will be adapted to simulate complex real-life structures such as curved composite panels with stiffeners. This communication will present these numerical tools and their main functionalities.

Qualitative numerical studies of the modification of the pitch angle distribution of test particles by alfvènic wave activity

NASA Astrophysics Data System (ADS)

Keilbach, D.; Drews, C.; Berger, L.; Marsch, E.; Wimmer-Schweingruber, R. F.

2017-12-01

Using a test particle approach we have investigated, how an oxygen pickup ion torus velocity distribution is modified by continuous and intermittent alfvènic waves on timescales, where the gyro trajectory of each particle can be traced.We have therefore exposed the test particles to mono frequent waves, which expanded through the whole simulation in time and space. The general behavior of the pitch angle distribution is found to be stationary and a nonlinear function of the wave frequency, amplitude and the initial angle between wave elongation and field-perpendicular particle velocity vector. The figure shows the time-averaged pitch angle distributions as a function of the Doppler shifted wave frequency (where the Doppler shift was calculated with respect to the particles initial velocity) for three different wave amplitudes (labeled in each panel). The background field is chosen to be 5 nT and the 500 test particles were initially distributed on a torus with 120° pitch angle at a solar wind velocity of 450 km/s. Each y-slice of the histogram (which has been normalized to it's respective maximum) represents an individual run of the simulation.The frequency-dependent behavior of the test particles is found to be classifiable into the regimes of very low/high frequencies and frequencies close to first order resonance. We have found, that only in the latter regime the particles interact strongly with the wave, where in the time averaged histograms a branch structure is found, which was identified as a trace of particles co-moving with the wave phase. The magnitude of pitch angle change of these particles is as well as the frequency margin, where the branch structure is found, an increasing function with the wave amplitude.We have also investigated the interaction with mono frequent intermittent waves. Exposed to such waves a torus distribution is scattered in pitch angle space, whereas the pitch angle distribution is broadened systematically over time similar to pitch angle diffusion.The framework of our simulations is a first step toward understanding wave particle interactions at the most basic level and is readily expandable to e.g. the inclusion of multiple wave frequencies, intermittent wave activity, gradients in the background magnetic field or collisions with solar wind particles.

Developing Regionalized Models of Lithospheric Thickness and Velocity Structure Across Eurasia and the Middle East from Jointly Inverting P-Wave and S-Wave Receiver Functions with Rayleigh Wave Group and Phase Velocities

DTIC Science & Technology

2011-09-01

modeling of regional waveforms at station ANTO , in UNIFIED region #14. The velocity models (left) and the corresponding predictions (middle and right) are...models, Geophy. J. Int. 118: 245–254. Rychert, C. A. and P. M. Shearer (2009). A global view of the lithosphere-asthenosphere boundary, Science 324 : 495

Rayleigh-Bloch waves trapped by a periodic perturbation: exact solutions

NASA Astrophysics Data System (ADS)

Merzon, A.; Zhevandrov, P.; Romero Rodríguez, M. I.; De la Paz Méndez, J. E.

2018-06-01

Exact solutions describing the Rayleigh-Bloch waves for the two-dimensional Helmholtz equation are constructed in the case when the refractive index is a sum of a constant and a small amplitude function which is periodic in one direction and of finite support in the other. These solutions are quasiperiodic along the structure and exponentially decay in the orthogonal direction. A simple formula for the dispersion relation of these waves is obtained.

Steering of SH wave propagation in electrorheological elastomer with a structured meta-slab by tunable phase discontinuities

NASA Astrophysics Data System (ADS)

Xu, Yanlong; Li, Yi; Cao, Liyun; Yang, Zhichun; Zhou, Xiaoling

2017-09-01

The generalized Snell's law (GSL) with phase discontinuity proposed based on the concept of a metasurface, which can be used to control arbitrarily the reflection and refraction of waves, attracts a growing attention in these years. The concept of abnormally deflecting the incident wave has been applied to the elastic field very recently. However, most of the studies on metasurfaces are based on passive materials, which restricts the frequency or the deflected angles always working in a single state. Here, we steer elastic SH wave propagation in an electrorheological (ER) elastomer with a structured meta-slab composed of geometrically periodic wave guides by exposing the slab to the programmed electric fields. The dependence of phase velocities of SH waves on the applied electric fields can make the phase shift under the form of a special function along the slab, which will control the refraction angles of the transmitted SH waves by the GSL. Accordingly we design the meta-slab theoretically and conduct corresponding numerical simulations. The results demonstrate that the structured meta-slab under the programmed external electric fields can deflect SH wave flexibly with tunable refraction angles and working frequencies, and can focus SH wave with tunable focal lengths. The present study will broaden the scope of applying adaptive materials to design metasurfaces with tunability.

Progress on the development of FullWave, a Hot and Cold Plasma Parallel Full Wave Code

NASA Astrophysics Data System (ADS)

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

2017-10-01

FullWave is being developed at FAR-TECH, Inc. to simulate RF waves in hot inhomogeneous magnetized plasmas without making small orbit approximations. FullWave is based on a meshless formulation in configuration space on non-uniform clouds of computational points (CCP) adapted to better resolve plasma resonances, antenna structures and complex boundaries. The linear frequency domain wave equation is formulated using two approaches: for cold plasmas the local cold plasma dielectric tensor is used (resolving resonances by particle collisions), while for hot plasmas the conductivity kernel is calculated. The details of FullWave and some preliminary results will be presented, including: 1) a monitor function based on analytic solutions of the cold-plasma dispersion relation; 2) an adaptive CCP based on the monitor function; 3) construction of the finite differences for approximation of derivatives on adaptive CCP; 4) results of 2-D full wave simulations in the cold plasma model in tokamak geometry using the formulated approach for ECRH, ICRH and Lower Hybrid range of frequencies. Work is supported by the U.S. DOE SBIR program.

Coupled Waves on a Periodically Supported Timoshenko Beam

NASA Astrophysics Data System (ADS)

HECKL, MARIA A.

2002-05-01

A mathematical model is presented for the propagation of structural waves on an infinitely long, periodically supported Timoshenko beam. The wave types that can exist on the beam are bending waves with displacements in the horizontal and vertical directions, compressional waves and torsional waves. These waves are affected by the periodic supports in two ways: their dispersion relation spectra show passing and stopping bands, and coupling of the different wave types tends to occur. The model in this paper could represent a railway track where the beam represents the rail and an appropriately chosen support type represents the pad/sleeper/ballast system of a railway track. Hamilton's principle is used to calculate the Green function matrix of the free Timoshenko beam without supports. The supports are incorporated into the model by combining the Green function matrix with the superposition principle. Bloch's theorem is applied to describe the periodicity of the supports. This leads to polynomials with several solutions for the Bloch wave number. These solutions are obtained numerically for different combinations of wave types. Two support types are examined in detail: mass supports and spring supports. More complex support types, such as mass/spring systems, can be incorporated easily into the model.

Identification and Characterization of Molecular Bonding Structures by ab initio Quasi-Atomic Orbital Analyses.

PubMed

West, Aaron C; Duchimaza-Heredia, Juan J; Gordon, Mark S; Ruedenberg, Klaus

2017-11-22

The quasi-atomic analysis of ab initio electronic wave functions in full valence spaces, which was developed in preceding papers, yields oriented quasi-atomic orbitals in terms of which the ab initio molecular wave function and energy can be expressed. These oriented quasi-atomic orbitals are the rigorous ab initio counterparts to the conceptual bond forming atomic hybrid orbitals of qualitative chemical reasoning. In the present work, the quasi-atomic orbitals are identified as bonding orbitals, lone pair orbitals, radical orbitals, vacant orbitals and orbitals with intermediate character. A program determines the bonding characteristics of all quasi-atomic orbitals in a molecule on the basis of their occupations, bond orders, kinetic bond orders, hybridizations and local symmetries. These data are collected in a record and provide the information for a comprehensive understanding of the synergism that generates the bonding structure that holds the molecule together. Applications to a series of molecules exhibit the complete bonding structures that are embedded in their ab initio wave functions. For the strong bonds in a molecule, the quasi-atomic orbitals provide quantitative ab initio amplifications of the Lewis dot symbols. Beyond characterizing strong bonds, the quasi-atomic analysis also yields an understanding of the weak interactions, such as vicinal, hyperconjugative and radical stabilizations, which can make substantial contributions to the molecular bonding structure.

Lithospheric Structure of Arabia from the Joint Inversion of P- and S-wave Receiver Functions and Dispersion Velocities

NASA Astrophysics Data System (ADS)

Julia, Jordi; Al-Amri, Abdullah; Pasyanos, Michael; Rodgers, Arthur; Matzel, Eric; Nyblade, Andrew

2013-04-01

Seismic imaging of the lithosphere under the Arabian shield and platform is critical to help answer important geologic questions of regional and global interest. The Arabian Shield can be regarded as an amalgamation of several arcs and microplates of Proterozoic age that culminated in the accretion of the Arabian portion of Gondwana during the Pan-African event at ~550 Ma and the role of important geologic features observed on the surface - such as the lineaments and shear zones separating the Proterozoic terrains in the shield - is not completely understood. Also, current models of Precambrian crustal evolution predict that Proterozoic terranes are underlain by fertile (FeO-rich) cratonic roots that should promote the production of mafic magmas and underplating of the Arabian shield terranes, and the shield contains Tertiary and Quaternary volcanic rocks related to the early stages of the Red Sea formation that might also be related to plume-related lithospheric "erosion". In order to better understand these relationships, we are developing new velocity models of litospheric structure for the Arabian shield and platform from the joint inversion of up to four seismic data sets: P-wave receiver functions, S-wave receiver functions, dispersion velocities from surface-waves, and dispersion velocities from ambient-noise cross-correlations. The joint inversion combines constraints on crustal thickness from P-wave receiver functions, constraints on lithospheric thickness from S-wave receiver functions and constraints on S-velocity and S-velocity gradients from dispersion velocities to produce detailed S-velocity profiles under single recording stations. We will present S-velocity profiles for a number of permanent stations operated by the Saudi Geological Survey and the King ing Abdulaziz Center for Science and Technology as well as stations from past temporary deployments and discuss the implications of the velocity models regarding composition and tectonics of the Arabian shield and platform.

Log-amplitude variance and wave structure function: A new perspective for Gaussian beams

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

Miller, W.B.; Ricklin, J.C.; Andrews, L.C.

1993-04-01

Two naturally linked pairs of nondimensional parameters are identified such that either pair, together with wavelength and path length, completely specifies the diffractive propagation environment for a lowest-order paraxial Gaussian beam. Both parameter pairs are intuitive, and within the context of locally homogeneous and isotropic turbulence they reflect the long-recognized importance of the Fresnel zone size in the behavior of Rytov propagation statistics. These parameter pairs, called, respectively, the transmitter and receiver parameters, also provide a change in perspective in the analysis of optical turbulence effects on Gaussian beams by unifying a number of behavioral traits previously observed or predicted,more » and they create an environment in which the determination of limiting interrelationships between beam forms is especially simple. The fundamental nature of the parameter pairs becomes apparent in the derived analytical expressions for the log-amplitude variance and the wave structure function. These expressions verify general optical turbulence-related characteristics predicted for Gaussian beams, provide additional insights into beam-wave behavior, and are convenient tools for beam-wave analysis. 22 refs., 10 figs., 2 tabs.« less

WASH and WAVE actin regulators of the Wiskott-Aldrich syndrome protein (WASP) family are controlled by analogous structurally related complexes.

PubMed

Jia, Da; Gomez, Timothy S; Metlagel, Zoltan; Umetani, Junko; Otwinowski, Zbyszek; Rosen, Michael K; Billadeau, Daniel D

2010-06-08

We recently showed that the Wiskott-Aldrich syndrome protein (WASP) family member, WASH, localizes to endosomal subdomains and regulates endocytic vesicle scission in an Arp2/3-dependent manner. Mechanisms regulating WASH activity are unknown. Here we show that WASH functions in cells within a 500 kDa core complex containing Strumpellin, FAM21, KIAA1033 (SWIP), and CCDC53. Although recombinant WASH is constitutively active toward the Arp2/3 complex, the reconstituted core assembly is inhibited, suggesting that it functions in cells to regulate actin dynamics through WASH. FAM21 interacts directly with CAPZ and inhibits its actin-capping activity. Four of the five core components show distant (approximately 15% amino acid sequence identify) but significant structural homology to components of a complex that negatively regulates the WASP family member, WAVE. Moreover, biochemical and electron microscopic analyses show that the WASH and WAVE complexes are structurally similar. Thus, these two distantly related WASP family members are controlled by analogous structurally related mechanisms. Strumpellin is mutated in the human disease hereditary spastic paraplegia, and its link to WASH suggests that misregulation of actin dynamics on endosomes may play a role in this disorder.

Independent Controls of Differently-Polarized Reflected Waves by Anisotropic Metasurfaces

PubMed Central

Ma, Hui Feng; Wang, Gui Zhen; Kong, Gu Sheng; Cui, Tie Jun

2015-01-01

We propose a kind of anisotropic planar metasurface, which has capacity to manipulate the orthogonally-polarized electromagnetic waves independently in the reflection mode. The metasurface is composed of orthogonally I-shaped structures and a metal-grounded plane spaced by a dielectric isolator, with the thickness of about 1/15 wavelength. The normally incident linear-polarized waves will be totally reflected by the metal plane, but the reflected phases of x- and y-polarized waves can be controlled independently by the orthogonally I-shaped structures. Based on this principle, we design four functional devices using the anisotropic metasurfaces to realize polarization beam splitting, beam deflection, and linear-to-circular polarization conversion with a deflection angle, respectively. Good performances have been observed from both simulation and measurement results, which show good capacity of the anisotropic metasurfaces to manipulate the x- and y-polarized reflected waves independently. PMID:25873323

Lithospheric structure below seismic stations in Cuba from the joint inversion of Rayleigh surface waves dispersion and receiver functions

NASA Astrophysics Data System (ADS)

González, O'Leary; Moreno, Bladimir; Romanelli, Fabio; Panza, Giuliano F.

2012-05-01

The joint inversion of Rayleigh wave group velocity dispersion and receiver functions has been used to study the crust and upper mantle structure at eight seismic stations in Cuba. Receiver functions have been computed from teleseismic recordings of earthquakes at epicentral (angular) distances in the range from 30° to 90° and Rayleigh wave group velocity dispersion relations have been taken from earlier surface wave tomographic studies in the Caribbean area. The thickest crust (˜30 km) below Cuban stations is found at Cascorro (CCC) and Maisí (MAS) whereas the thinnest crust (˜18 km) is found at stations Río Carpintero (RCC) and Guantánamo Bay (GTBY), in the southeastern part of Cuba; this result is in agreement with the southward gradual thinning of the crust revealed by previous studies. In the crystalline crust, the S-wave velocity varies between ˜2.8 and ˜3.9 km s-1 and, at the crust-mantle transition zone, the shear wave velocity varies from ˜4.0 and ˜4.3 km s-1. The lithospheric thickness varies from ˜65 km, in the youngest lithosphere, to ˜150 km in the northeastern part of the Cuban island, below Maisí (MAS) and Moa (MOA) stations. Evidence of a subducted slab possibly belonging to the Caribbean plate is present below the stations Las Mercedes (LMG), RCC and GTBY whereas earlier subducted slabs could explain the results obtained below the Soroa (SOR), Manicaragua (MGV) and Cascorro (CCC) station.

Implementation of density functional theory method on object-oriented programming (C++) to calculate energy band structure using the projector augmented wave (PAW)

NASA Astrophysics Data System (ADS)

Alfianto, E.; Rusydi, F.; Aisyah, N. D.; Fadilla, R. N.; Dipojono, H. K.; Martoprawiro, M. A.

2017-05-01

This study implemented DFT method into the C++ programming language with object-oriented programming rules (expressive software). The use of expressive software results in getting a simple programming structure, which is similar to mathematical formula. This will facilitate the scientific community to develop the software. We validate our software by calculating the energy band structure of Silica, Carbon, and Germanium with FCC structure using the Projector Augmented Wave (PAW) method then compare the results to Quantum Espresso calculation’s results. This study shows that the accuracy of the software is 85% compared to Quantum Espresso.

Calculation of broadband time histories of ground motion: Comparison of methods and validation using strong-ground motion from the 1994 Northridge earthquake

USGS Publications Warehouse

Hartzell, S.; Harmsen, S.; Frankel, A.; Larsen, S.

1999-01-01

This article compares techniques for calculating broadband time histories of ground motion in the near field of a finite fault by comparing synthetics with the strong-motion data set for the 1994 Northridge earthquake. Based on this comparison, a preferred methodology is presented. Ground-motion-simulation techniques are divided into two general methods: kinematic- and composite-fault models. Green's functions of three types are evaluated: stochastic, empirical, and theoretical. A hybrid scheme is found to give the best fit to the Northridge data. Low frequencies ( 1 Hz) are calculated using a composite-fault model with a fractal subevent size distribution and stochastic, bandlimited, white-noise Green's functions. At frequencies below 1 Hz, theoretical elastic-wave-propagation synthetics introduce proper seismic-phase arrivals of body waves and surface waves. The 3D velocity structure more accurately reproduces record durations for the deep sedimentary basin structures found in the Los Angeles region. At frequencies above 1 Hz, scattering effects become important and wave propagation is more accurately represented by stochastic Green's functions. A fractal subevent size distribution for the composite fault model ensures an ??-2 spectral shape over the entire frequency band considered (0.1-20 Hz).

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

Erkaev, N. V.; Semenov, V. S.; Biernat, H. K.

Hall magnetohydrodynamic model is investigated for current sheet flapping oscillations, which implies a gradient of the normal magnetic field component. For the initial undisturbed current sheet structure, the normal magnetic field component is assumed to have a weak linear variation. The profile of the electric current velocity is described by hyperbolic functions with a maximum at the center of the current sheet. In the framework of this model, eigenfrequencies are calculated as functions of the wave number for the ''kink'' and ''sausage'' flapping wave modes. Because of the Hall effects, the flapping eigenfrequency is larger for the waves propagating alongmore » the electric current, and it is smaller for the opposite wave propagation with respect to the current. The asymmetry of the flapping wave propagation, caused by Hall effects, is pronounced stronger for thinner current sheets. This is due to the Doppler effect related to the electric current velocity.« less

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

Pasyanos, M; Gok, R; Zor, E

We investigate the crustal and upper mantle structure of eastern Turkey where the Anatolian, Arabian and Eurasian Plates meet and form a complex tectonic structure. The Bitlis suture is a continental collision zone between the Anatolian plateau and the Arabian plate. Broadband data available through the Eastern Turkey Seismic Experiment (ETSE) provided a unique opportunity for studying the high resolution velocity structure. Zor et al. found an average 46 km thick crust in Anatolian plateau using six-layered grid search inversion of the ETSE receiver functions. Receiver functions are sensitive to the velocity contrast of interfaces and the relative travel timemore » of converted and reverberated waves between those interfaces. The interpretation of receiver function alone with many-layered parameterization may result in an apparent depth-velocity tradeoff. In order to improve previous velocity model, we employed the joint inversion method with many layered parameterization of Julia et al. (2000) to the ETSE receiver functions. In this technique, the receiver function and surface-wave observations are combined into a single algebraic equation and each data set is weighted by an estimate of the uncertainty in the observations. We consider azimuthal changes of receiver functions and have stacked them into different groups. We calculated the receiver functions using iterative time-domain deconvolution technique and surface wave group velocity dispersion curves between 10-100 sec. We are making surface wave dispersion measurements at the ETSE stations and have incorporated them into a regional group velocity model. Preliminary results indicate a strong trend in the long period group velocity in the northeast. This indicates slow upper mantle velocities in the region consistent with Pn, Sn and receiver function results. We started with both the 1-D model that is obtained with the 12 tones dam explosion shot data recorded by ETSE network and the existing receiver function inversion results. In fact, we observe that the inversion results are independent at the starting model and converges well to the same final model. We don't observe a significant change at the first order discontinuities of model (e.g. Moho depth), but we obtain better defined depths to low velocity layers.« less

Seismic velocity structure of the crust and upper mantle beneath the Texas-Gulf of Mexico margin from joint inversion of Ps and Sp receiver functions and surface wave dispersion

NASA Astrophysics Data System (ADS)

Agrawal, M.; Pulliam, J.; Sen, M. K.

2013-12-01

The seismic structure beneath Texas Gulf Coast Plain (GCP) is determined via velocity analysis of stacked common conversion point (CCP) Ps and Sp receiver functions and surface wave dispersion. The GCP is a portion of a ocean-continental transition zone, or 'passive margin', where seismic imaging of lithospheric Earth structure via passive seismic techniques has been rare. Seismic data from a temporary array of 22 broadband stations, spaced 16-20 km apart, on a ~380-km-long profile from Matagorda Island, a barrier island in the Gulf of Mexico, to Johnson City, Texas were employed to construct a coherent image of the crust and uppermost mantle. CCP stacking was applied to data from teleseismic earthquakes to enhance the signal-to-noise ratios of converted phases, such as Ps phases. An inaccurate velocity model, used for time-to-depth conversion in CCP stacking, may produce higher errors, especially in a region of substantial lateral velocity variations. An accurate velocity model is therefore essential to constructing high quality depth-domain images. To find accurate velocity P- and S-wave models, we applied a joint modeling approach that searches for best-fitting models via simulated annealing. This joint inversion approach, which we call 'multi objective optimization in seismology' (MOOS), simultaneously models Ps receiver functions, Sp receiver functions and group velocity surface wave dispersion curves after assigning relative weights for each objective function. Weights are computed from the standard deviations of the data. Statistical tools such as the posterior parameter correlation matrix and posterior probability density (PPD) function are used to evaluate the constraints that each data type places on model parameters. They allow us to identify portions of the model that are well or poorly constrained.

TaRh2B2 and NbRh2B2: Superconductors with a chiral noncentrosymmetric crystal structure.

PubMed

Carnicom, Elizabeth M; Xie, Weiwei; Klimczuk, Tomasz; Lin, Jingjing; Górnicka, Karolina; Sobczak, Zuzanna; Ong, Nai Phuan; Cava, Robert J

2018-05-01

It is a fundamental truth in solid compounds that the physical properties follow the symmetry of the crystal structure. Nowhere is the effect of symmetry more pronounced than in the electronic and magnetic properties of materials-even the projection of the bulk crystal symmetry onto different crystal faces is known to have a substantial impact on the surface electronic states. The effect of bulk crystal symmetry on the properties of superconductors is widely appreciated, although its study presents substantial challenges. The effect of a lack of a center of symmetry in a crystal structure, for example, has long been understood to necessitate that the wave function of the collective electron state that gives rise to superconductivity has to be more complex than usual. However, few nonhypothetical materials, if any, have actually been proven to display exotic superconducting properties as a result. We introduce two new superconductors that in addition to having noncentrosymmetric crystal structures also have chiral crystal structures. Because the wave function of electrons in solids is particularly sensitive to the host material's symmetry, crystal structure chirality is expected to have a substantial effect on their superconducting wave functions. Our two experimentally obtained chiral noncentrosymmetric superconducting materials have transition temperatures to superconductivity that are easily experimentally accessible, and our basic property characterization suggests that their superconducting properties may be unusual. We propose that their study may allow for a more in-depth understanding of how chirality influences the properties of superconductors and devices that incorporate them.

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

Thein, Pyi Soe, E-mail: pyisoethein@yahoo.com; Pramumijoyo, Subagyo; Wilopo, Wahyu

In this study, we investigated the strong ground motion characteristics under Palu City, Indonesia. The shear wave velocity structures evaluated by eight microtremors measurement are the most applicable to determine the thickness of sediments and average shear wave velocity with Vs ≤ 300 m/s. Based on subsurface underground structure models identified, earthquake ground motion was estimated in the future Palu-Koro earthquake by using statistical green’s function method. The seismic microzonation parameters were carried out by considering several significant controlling factors on ground response at January 23, 2005 earthquake.

Fermionic spectral functions in backreacting p-wave superconductors at finite temperature

NASA Astrophysics Data System (ADS)

Giordano, G. L.; Grandi, N. E.; Lugo, A. R.

2017-04-01

We investigate the spectral function of fermions in a p-wave superconducting state, at finite both temperature and gravitational coupling, using the AdS/CF T correspondence and extending previous research. We found that, for any coupling below a critical value, the system behaves as its zero temperature limit. By increasing the coupling, the "peak-dip-hump" structure that characterizes the spectral function at fixed momenta disappears. In the region where the normal/superconductor phase transition is first order, the presence of a non-zero order parameter is reflected in the absence of rotational symmetry in the fermionic spectral function at the critical temperature.

Three dimensional dust-acoustic solitary waves in an electron depleted dusty plasma with two-superthermal ion-temperature

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

Borhanian, J.; Shahmansouri, M.

2013-01-15

A theoretical investigation is carried out to study the existence and characteristics of propagation of dust-acoustic (DA) waves in an electron-depleted dusty plasma with two-temperature ions, which are modeled by kappa distribution functions. A three-dimensional cylindrical Kadomtsev-Petviashvili equation governing evolution of small but finite amplitude DA waves is derived by means of a reductive perturbation method. The influence of physical parameters on solitary wave structure is examined. Furthermore, the energy integral equation is used to study the existence domains of the localized structures. It is found that the present model can be employed to describe the existence of positive asmore » well as negative polarity DA solitary waves by selecting special values for parameters of the system, e.g., superthermal index of cold and/or hot ions, cold to hot ion density ratio, and hot to cold ion temperature ratio. This model may be useful to understand the excitation of nonlinear DA waves in astrophysical objects.« less

Polarization control in flexible interference lithography for nano-patterning of different photonic structures with optimized contrast.

PubMed

He, Jianfang; Fang, Xiaohui; Lin, Yuanhai; Zhang, Xinping

2015-05-04

Half-wave plates were introduced into an interference-lithography scheme consisting of three fibers that were arranged into a rectangular triangle. Such a flexible and compact geometry allows convenient tuning of the polarizations of both the UV laser source and each branch arm. This not only enables optimization of the contrast of the produced photonic structures with expected square lattices, but also multiplies the nano-patterning functions of a fixed design of fiber-based interference lithography. The patterns of the photonic structures can be thus tuned simply by rotating a half-wave plate.

Non-Linear Seismic Velocity Estimation from Multiple Waveform Functionals and Formal Assessment of Constraints

DTIC Science & Technology

2011-09-01

tectonically active regions such as the Middle East. For example, we previously applied the code to determine the crust and upper mantle structure...Objective Optimization (MOO) for Multiple Datasets The primary goal of our current project is to develop a tool for estimating crustal structure that...be used to obtain crustal velocity structures by modeling broadband waveform, receiver function, and surface wave dispersion data. The code has been

Early network activity propagates bidirectionally between hippocampus and cortex.

PubMed

Barger, Zeke; Easton, Curtis R; Neuzil, Kevin E; Moody, William J

2016-06-01

Spontaneous activity in the developing brain helps refine neuronal connections before the arrival of sensory-driven neuronal activity. In mouse neocortex during the first postnatal week, waves of spontaneous activity originating from pacemaker regions in the septal nucleus and piriform cortex propagate through the neocortex. Using high-speed Ca(2+) imaging to resolve the spatiotemporal dynamics of wave propagation in parasagittal mouse brain slices, we show that the hippocampus can act as an additional source of neocortical waves. Some waves that originate in the hippocampus remain restricted to that structure, while others pause at the hippocampus-neocortex boundary and then propagate into the neocortex. Blocking GABAergic neurotransmission decreases the likelihood of wave propagation into neocortex, whereas blocking glutamatergic neurotransmission eliminates spontaneous and evoked hippocampal waves. A subset of hippocampal and cortical waves trigger Ca(2+) waves in astrocytic networks after a brief delay. Hippocampal waves accompanied by Ca(2+) elevation in astrocytes are more likely to propagate into the neocortex. Finally, we show that two structures in our preparation that initiate waves-the hippocampus and the piriform cortex-can be electrically stimulated to initiate propagating waves at lower thresholds than the neocortex, indicating that the intrinsic circuit properties of those regions are responsible for their pacemaker function. © 2015 Wiley Periodicals, Inc.

Mechanical and Thermophysical Properties of Cubic Rock-Salt AlN Under High Pressure

NASA Astrophysics Data System (ADS)

Lebga, Noudjoud; Daoud, Salah; Sun, Xiao-Wei; Bioud, Nadhira; Latreche, Abdelhakim

2018-03-01

Density functional theory, density functional perturbation theory, and the Debye model have been used to investigate the structural, elastic, sound velocity, and thermodynamic properties of AlN with cubic rock-salt structure under high pressure, yielding the equilibrium structural parameters, equation of state, and elastic constants of this interesting material. The isotropic shear modulus, Pugh ratio, and Poisson's ratio were also investigated carefully. In addition, the longitudinal, transverse, and average elastic wave velocities, phonon contribution to the thermal conductivity, and interesting thermodynamic properties were predicted and analyzed in detail. The results demonstrate that the behavior of the elastic wave velocities under increasing hydrostatic pressure explains the hardening of the corresponding phonons. Based on the elastic stability criteria under pressure, it is found that AlN with cubic rock-salt structure is mechanically stable, even at pressures up to 100 GPa. Analysis of the Pugh ratio and Poisson's ratio revealed that AlN with cubic rock-salt structure behaves in brittle manner.

Dynamic response of some tentative compliant wall structures to convected turbulence fields

NASA Technical Reports Server (NTRS)

Nijim, H. H.; Lin, Y. K.

1977-01-01

Some tentative compliant wall structures designed for possible skin friction drag reduction are investigated. Among the structural models considered is a ribbed membrane backed by polyurethane or PVS plastisol. This model is simplified as a beam placed on a viscoelastic foundation as well as on a set of evenly spaced supports. The total length of the beam may be either finite or infinite, and the supports may be either rigid or elastic. Another structural model considered is a membrane mounted over a series of pretensioned wires, also evenly spaced, and the entire membrane is backed by an air cavity. The forcing pressure field is idealized as a frozen random pattern convected downstream at a characteristic velocity. The results are given in terms of the frequency response functions of the system, the spectral density of the structural motion, and the spectral density of the boundary layer pressure including the effect of structural motion. These results are used in a parametric study of structural configurations capable of generating favorable wave lengths, wave amplitudes, and wave speeds in the structural motion for potential drag reduction.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

USGS Publications Warehouse

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

2012-01-01

Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from and . Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Association between smoking status and the parameters of vascular structure and function in adults: results from the EVIDENT study.

PubMed

Recio-Rodriguez, Jose I; Gomez-Marcos, Manuel A; Patino Alonso, Maria C; Martin-Cantera, Carlos; Ibañez-Jalon, Elisa; Melguizo-Bejar, Amor; Garcia-Ortiz, Luis

2013-12-01

The present study analyses the relation between smoking status and the parameters used to assess vascular structure and function. This cross-sectional, multi-centre study involved a random sample of 1553 participants from the EVIDENT study. The smoking status, peripheral augmentation index and ankle-brachial index were measured in all participants. In a small subset of the main population (265 participants), the carotid intima-media thickness and pulse wave velocity were also measured. After controlling for the effect of age, sex and other risk factors, present smokers have higher values of carotid intima-media thickness (p = 0.011). Along the same lines, current smokers have higher values of pulse wave velocity and lower mean values of ankle-brachial index but without statistical significance in both cases. Among the parameters of vascular structure and function analysed, only the IMT shows association with the smoking status, after adjusting for confounders.

Association between smoking status and the parameters of vascular structure and function in adults: results from the EVIDENT study

PubMed Central

2013-01-01

Background The present study analyses the relation between smoking status and the parameters used to assess vascular structure and function. Methods This cross-sectional, multi-centre study involved a random sample of 1553 participants from the EVIDENT study. Measurements: The smoking status, peripheral augmentation index and ankle-brachial index were measured in all participants. In a small subset of the main population (265 participants), the carotid intima-media thickness and pulse wave velocity were also measured. Results After controlling for the effect of age, sex and other risk factors, present smokers have higher values of carotid intima-media thickness (p = 0.011). Along the same lines, current smokers have higher values of pulse wave velocity and lower mean values of ankle-brachial index but without statistical significance in both cases. Conclusions Among the parameters of vascular structure and function analysed, only the IMT shows association with the smoking status, after adjusting for confounders. PMID:24289208

Imaging of the internal structure of comet 67P/Churyumov-Gerasimenko from radiotomography CONSERT Data (Rosetta Mission) through a full 3D regularized inversion of the Helmholtz equations on functional spaces

NASA Astrophysics Data System (ADS)

Barriot, Jean-Pierre; Serafini, Jonathan; Sichoix, Lydie; Benna, Mehdi; Kofman, Wlodek; Herique, Alain

We investigate the inverse problem of imaging the internal structure of comet 67P/ Churyumov-Gerasimenko from radiotomography CONSERT data by using a coupled regularized inversion of the Helmholtz equations. A first set of Helmholtz equations, written w.r.t a basis of 3D Hankel functions describes the wave propagation outside the comet at large distances, a second set of Helmholtz equations, written w.r.t. a basis of 3D Zernike functions describes the wave propagation throughout the comet with avariable permittivity. Both sets are connected by continuity equations over a sphere that surrounds the comet. This approach, derived from GPS water vapor tomography of the atmosphere,will permit a full 3D inversion of the internal structure of the comet, contrary to traditional approaches that use a discretization of space at a fraction of the radiowave wavelength.

Numerical investigation of nonlinear interactions between multimodal guided waves and delamination in composite structures

NASA Astrophysics Data System (ADS)

Shen, Yanfeng

2017-04-01

This paper presents a numerical investigation of the nonlinear interactions between multimodal guided waves and delamination in composite structures. The elastodynamic wave equations for anisotropic composite laminate were formulated using an explicit Local Interaction Simulation Approach (LISA). The contact dynamics was modeled using the penalty method. In order to capture the stick-slip contact motion, a Coulomb friction law was integrated into the computation procedure. A random gap function was defined for the contact pairs to model distributed initial closures or openings to approximate the nature of rough delamination interfaces. The LISA procedure was coded using the Compute Unified Device Architecture (CUDA), which enables the highly parallelized computation on powerful graphic cards. Several guided wave modes centered at various frequencies were investigated as the incident wave. Numerical case studies of different delamination locations across the thickness were carried out. The capability of different wave modes at various frequencies to trigger the Contact Acoustic Nonlinearity (CAN) was studied. The correlation between the delamination size and the signal nonlinearity was also investigated. Furthermore, the influence from the roughness of the delamination interfaces was discussed as well. The numerical investigation shows that the nonlinear features of wave delamination interactions can enhance the evaluation capability of guided wave Structural Health Monitoring (SHM) system. This paper finishes with discussion, concluding remarks, and suggestions for future work.

A Survey of Synoptic Waves over West Africa

NASA Astrophysics Data System (ADS)

Cheng, Yuan-Ming; Thorncroft, Chris D.; Kiladis, George N.

2017-04-01

Motivated by the pronounced wave-to-wave variability in African easterly wave (AEW) circulation, the three-dimensional structure of synoptic waves over West Africa is revisited with an Empirical Orthogonal Function (EOF) approach to isolate the dominant wave pattern. In this talk we present results of EOF analyses conducted with brightness temperature (Tb) derived from satellite observation and meridional wind at multiple levels from reanalysis data to examine the characteristics and variability of synoptic waves. The structure of waves is extracted by projecting the wind fields and Tb onto the principle components associated with EOF patterns of appropriately filtered parameters. The Tb EOF shows a confined AEW circulation centered around 7.5°N and a distinct evolution of convection within the wave in line with previous research. However, in striking contrast to the confined flow pattern in the Tb EOF, the EOF of 700-hPa meridional wind is distinguished by a meridionally broad AEW circulation. While the peak in circulation is centered around 10°N, there is marked cross-equatorial flow that is associated with an antisymmetric geopotential signature across the equator. This suggests the presence of a mixed Rossby-gravity wave (MRG) structure consistent with Matsuno's shallow water theory. Granted that the vast majority of studies on MRGs focus on the central and western Pacific region, this "hybrid" between AEWs and MRGs over West Africa and Atlantic sector has received little attention and more work regarding the nature and causes of its wave structure and behavior is needed. In addition, an upper-level synoptic wave is captured by EOFs of 200-hPa meridional wind. The kinematic fields reveal a continental-scale wave straddling the equator that resembles an MRG. This upper-level MRG appears to develop in situ over the Horn of Africa and intensifies as it moves across the continent. The associated lower-level structure shows an AEW-like circulation but with a larger spatial extent. This finding motivates the need for more in-depth investigations of synoptic wave variability over the region including an assessment of the direction of causality between the upper-level MRG and the lower-level AEW. This study highlights the various synoptic wave structures over West Africa and their interaction with AEWs. The results suggest the variability of AEW activity could be modulated by, in addition to the large-scale environment, other synoptic waves in the region. We will pursue the EOF approach to shed light on the characteristics and causes of the variability in synoptic wave activity over West Africa.

Determination of wave-function functionals: The constrained-search variational method

NASA Astrophysics Data System (ADS)

Pan, Xiao-Yin; Sahni, Viraht; Massa, Lou

2005-09-01

In a recent paper [Phys. Rev. Lett. 93, 130401 (2004)], we proposed the idea of expanding the space of variations in variational calculations of the energy by considering the approximate wave function ψ to be a functional of functions χ , ψ=ψ[χ] , rather than a function. A constrained search is first performed over all functions χ such that the wave-function functional ψ[χ] satisfies a physical constraint or leads to the known value of an observable. A rigorous upper bound to the energy is then obtained via the variational principle. In this paper we generalize the constrained-search variational method, applicable to both ground and excited states, to the determination of arbitrary Hermitian single-particle operators as applied to two-electron atomic and ionic systems. We construct analytical three-parameter ground-state functionals for the H- ion and the He atom through the constraint of normalization. We present the results for the total energy E , the expectations of the single-particle operators W=∑irin , n=-2,-1,1,2 , W=∑iδ(ri) , and W=∑iδ(ri-r) , the structure of the nonlocal Coulomb hole charge ρc(rr') , and the expectations of the two particle operators u2,u,1/u,1/u2 , where u=∣ri-rj∣ . The results for all the expectation values are remarkably accurate when compared with the 1078-parameter wave function of Pekeris, and other wave functions that are not functionals. We conclude by describing our current work on how the constrained-search variational method in conjunction with quantal density-functional theory is being applied to the many-electron case.

Fault zone reverberations from cross-correlations of earthquake waveforms and seismic noise

NASA Astrophysics Data System (ADS)

Hillers, Gregor; Campillo, Michel

2016-03-01

Seismic wavefields interact with low-velocity fault damage zones. Waveforms of ballistic fault zone head waves, trapped waves, reflected waves and signatures of trapped noise can provide important information on structural and mechanical fault zone properties. Here we extend the class of observable fault zone waves and reconstruct in-fault reverberations or multiples in a strike-slip faulting environment. Manifestations of the reverberations are significant, consistent wave fronts in the coda of cross-correlation functions that are obtained from scattered earthquake waveforms and seismic noise recorded by a linear fault zone array. The physical reconstruction of Green's functions is evident from the high similarity between the signals obtained from the two different scattered wavefields. Modal partitioning of the reverberation wavefield can be tuned using different data normalization techniques. The results imply that fault zones create their own ambiance, and that the here reconstructed reverberations are a key seismic signature of wear zones. Using synthetic waveform modelling we show that reverberations can be used for the imaging of structural units by estimating the location, extend and magnitude of lateral velocity contrasts. The robust reconstruction of the reverberations from noise records suggests the possibility to resolve the response of the damage zone material to various external and internal loading mechanisms.

Semiconductor Quantum Electron Wave Transport, Diffraction, and Interference: Analysis, Device, and Measurement.

NASA Astrophysics Data System (ADS)

Henderson, Gregory Newell

Semiconductor device dimensions are rapidly approaching a fundamental limit where drift-diffusion equations and the depletion approximation are no longer valid. In this regime, quantum effects can dominate device response. To increase further device density and speed, new devices must be designed that use these phenomena to positive advantage. In addition, quantum effects provide opportunities for a new class of devices which can perform functions previously unattainable with "conventional" semiconductor devices. This thesis has described research in the analysis of electron wave effects in semiconductors and the development of methods for the design, fabrication, and characterization of quantum devices based on these effects. First, an exact set of quantitative analogies are presented which allow the use of well understood optical design and analysis tools for the development of electron wave semiconductor devices. Motivated by these analogies, methods are presented for modeling electron wave grating diffraction using both an exact rigorous coupled-wave analysis and approximate analyses which are useful for grating design. Example electron wave grating switch and multiplexer designs are presented. In analogy to thin-film optics, the design and analysis of electron wave Fabry-Perot interference filters are also discussed. An innovative technique has been developed for testing these (and other) electron wave structures using Ballistic Electron Emission Microscopy (BEEM). This technique uses a liquid-helium temperature scanning tunneling microscope (STM) to perform spectroscopy of the electron transmittance as a function of electron energy. Experimental results show that BEEM can resolve even weak quantum effects, such as the reflectivity of a single interface between materials. Finally, methods are discussed for incorporating asymmetric electron wave Fabry-Perot filters into optoelectronic devices. Theoretical and experimental results show that such structures could be the basis for a new type of electrically pumped mid - to far-infrared semiconductor laser.

Structure of the Los Angeles Basin from Ambient Noise and Receiver Function Analysis

NASA Astrophysics Data System (ADS)

Clayton, R. W.; Ma, Y.; Cochran, E. S.

2015-12-01

We show the results from the LASSIE seismic experiment, which consists of a dense (1-km spacing) linear array of broadband stations deployed across the LA basin for approximately two months. Two common methods - ambient noise and receiver function (RF) - are applied to determine the velocity and structure of the basin. The basin RFs are complicated, however, the dense array enhances the lateral coherence of the signals and allows the structure to be imaged. The basement shape is clearly shown in the migrated image of the PpPs phase. The Ps conversion at the basement is the largest signal (including the direct wave) in the first 3 s. However, the Ps phase does not form as clear an image compared with the PpPs phase, possibly due to a requirement of more accurate velocity model. The surface wave signals from the ambient noise cross-correlations between LASSIE and surrounding SCSN stations are used for velocity inversion. A linear Dix-type inversion (Haney and Tsai, 2015, Geophysics) is applied to the extracted dispersion curves. The 1-10 s period Rayleigh wave and the 1-8 s period Love wave dispersion curves provide excellent constraints on top 5 km SV and top 3 km SH velocity structures respectively. Strong anisotropy (SV > SH) is observed for the top 1 km, and we plan to use this result to infer the fracture orientation and density of the shallow sedimentary rocks.

Quantitative Modeling of Coupled Piezo-Elastodynamic Behavior of Piezoelectric Actuators Bonded to an Elastic Medium for Structural Health Monitoring: A Review

PubMed Central

Huang, Guoliang; Song, Fei; Wang, Xiaodong

2010-01-01

Elastic waves, especially guided waves, generated by a piezoelectric actuator/sensor network, have shown great potential for on-line health monitoring of advanced aerospace, nuclear, and automotive structures in recent decades. Piezoelectric materials can function as both actuators and sensors in these applications due to wide bandwidth, quick response and low costs. One of the most fundamental issues surrounding the effective use of piezoelectric actuators is the quantitative evaluation of the resulting elastic wave propagation by considering the coupled piezo-elastodynamic behavior between the actuator and the host medium. Accurate characterization of the local interfacial stress distribution between the actuator and the host medium is the key issue for the problem. This paper presents a review of the development of analytical, numerical and hybrid approaches for modeling of the coupled piezo-elastodynamic behavior. The resulting elastic wave propagation for structural health monitoring is also summarized. PMID:22319319

Structure of the Lithosphere and Upper Mantle Across the Arabian Peninsula

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

Al-Amri, A; Rodgers, A

2007-01-05

Analysis of modern broadband (BB) waveform data allows for the inference of seismic velocity structure of the crust and upper mantle using a variety of techniques. This presentation will report inferences of seismic structure of the Arabian Plate using BB data from various networks. Most data were recorded by the Saudi Arabian National Digital Seismic Network (SANDSN) which consists of 38 (26 BB, 11 SP) stations, mostly located on the Arabian Shield. Additional data were taken from the 1995-7 Saudi Arabian IRIS-PASSCAL Deployment (9 BB stations) and other stations across the Peninsula. Crustal structure, inferred from teleseismic P-wave receiver functions,more » reveals thicker crust in the Arabian Platform (40-45 km) and the interior of the Arabian Shield (35-40 km) and thinner crust along the Red Sea coast. Lithospheric thickness inferred from teleseismic S-wave receiver functions reveals very thin lithosphere (40-80 km) along the Red Sea coast which thickens rapidly toward the interior of the Arabian Shield (100-120 km). We also observe a step of 20-40 km in lithospheric thickness across the Shield-Platform boundary. Seismic velocity structure of the upper mantle inferred from teleseismic P- and S-wave travel time tomography reveals large differences between the Shield and Platform, with the Shield being underlain by slower velocities, {+-}3% for P-waves and {+-}6% for S-waves. Seismic anisotropy was inferred from shear-wave splitting, using teleseismic SKS waveforms. Results reveal a splitting time of approximately 1.4 seconds, with the fast axis slightly east of north. The shear-wave splitting results are consistent across the Peninsula, with a slight clockwise rotation parallel for stations near the Gulf of Aqaba. In summary, these results allow us to make several conclusions about the tectonic evolution and current state of the Arabian Plate. Lithospheric thickness implies that thinning near the Red Sea has accompanied the rupturing of the Arabian-Nubian continental lithosphere. The step in the lithospheric thickness across the Shield-Platform boundary likely reveals a pre-existing difference in the lithospheric structure prior to accretion of the terranes composing the eastern Arabian Shield. Tomographic imaging of upper mantle velocities implies a single large-scale thermal anomaly underlies the Arabian Shield and is associated with Cenozoic uplift and volcanism.« less

Composite fermion basis for two-component Bose gases

NASA Astrophysics Data System (ADS)

Meyer, Marius; Liabotro, Ola

The composite fermion (CF) construction is known to produce wave functions that are not necessarily orthogonal, or even linearly independent, after projection. While usually not a practical issue in the quantum Hall regime, we have previously shown that it presents a technical challenge for rotating Bose gases with low angular momentum. These are systems where the CF approach yield surprisingly good approximations to the exact eigenstates of weak short-range interactions, and so solving the problem of linearly dependent wave functions is of interest. It can also be useful for studying CF excitations for fermions. Here we present several ways of constructing a basis for the space of ``simple CF states'' for two-component rotating Bose gases in the lowest Landau level, and prove that they all give a basis. Using the basis, we study the structure of the lowest-lying state using so-called restricted wave functions. We also examine the scaling of the overlap between the exact and CF wave functions at the maximal possible angular momentum for simple states. This work was financially supported by the Research Council of Norway.

Construction of CASCI-type wave functions for very large active spaces.

PubMed

Boguslawski, Katharina; Marti, Konrad H; Reiher, Markus

2011-06-14

We present a procedure to construct a configuration-interaction expansion containing arbitrary excitations from an underlying full-configuration-interaction-type wave function defined for a very large active space. Our procedure is based on the density-matrix renormalization group (DMRG) algorithm that provides the necessary information in terms of the eigenstates of the reduced density matrices to calculate the coefficient of any basis state in the many-particle Hilbert space. Since the dimension of the Hilbert space scales binomially with the size of the active space, a sophisticated Monte Carlo sampling routine is employed. This sampling algorithm can also construct such configuration-interaction-type wave functions from any other type of tensor network states. The configuration-interaction information obtained serves several purposes. It yields a qualitatively correct description of the molecule's electronic structure, it allows us to analyze DMRG wave functions converged for the same molecular system but with different parameter sets (e.g., different numbers of active-system (block) states), and it can be considered a balanced reference for the application of a subsequent standard multi-reference configuration-interaction method.

A 3-D crustal and uppermost mantle model of the western US from receiver functions and surface wave dispersion derived from ambient noise and teleseismic earthquakes

NASA Astrophysics Data System (ADS)

Shen, W.; Schulte-Pelkum, V.; Ritzwoller, M. H.

2011-12-01

The joint inversion of surface wave dispersion and receiver functions was proven feasible on a station by station basis more than a decade ago. Joint application to a large number of stations across a broad region such as western US is more challenging, however, because of the different resolutions of the two methods. Improvements in resolution in surface wave studies derived from ambient noise and array-based methods applied to earthquake data now allow surface wave dispersion and receiver functions to be inverted simultaneously across much of the Earthscope/USArray Transportable Array (TA), and we have developed a Monte-Carlo procedure for this purpose. As a proof of concept we applied this procedure to a region containing 186 TA stations in the intermountain west, including a variety of tectonic settings such as the Colorado Plateau, the Basin and Range, the Rocky Mountains, and the Great Plains. This work has now been expanded to encompass all TA stations in the western US. Our approach includes three main components. (1) We enlarge the Earthscope Automated Receiver Survey (EARS) receiver function database by adding more events within a quality control procedure. A back-azimuth-independent receiver function and its associated uncertainties are constructed using a harmonic stripping algorithm. (2) Rayleigh wave dispersion curves are generated from the eikonal tomography applied to ambient noise cross-correlation data and Helmoholtz tomography applied to teleseismic surface wave data to yield dispersion maps from 8 sec to 80 sec period. (3) We apply a Metropolis Monte Carlo algorithm to invert for the average velocity structure beneath each station. Simple kriging is applied to interpolate to the discrete results into a continuous 3-D model. This method has now been applied to over 1,000 TA stations in the western US. We show that the receiver functions and surface wave dispersion data can be reconciled beneath more than 80% of the stations using a smooth parameterization of both crustal and uppermost mantle structure. After the inversion, a 3-D model for the crust and uppermost mantle to a depth of 150 km is constructed for this region. Compared with using surface wave data alone, uncertainty in crustal thickness is much lower and as a result, the lower crustal velocity is better constrained given a smaller depth-velocity trade-off. The new 3-D model including Moho depth with attendant uncertainties provides the basis for further analysis on radial anisotropy and geodynamics in the western US, and also forms a starting point for other seismological studies such as body wave tomography and receiver function CCP analysis.

Propagation of gaseous detonation waves in a spatially inhomogeneous reactive medium

NASA Astrophysics Data System (ADS)

Mi, XiaoCheng; Higgins, Andrew J.; Ng, Hoi Dick; Kiyanda, Charles B.; Nikiforakis, Nikolaos

2017-05-01

Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulation. The inhomogeneity is introduced via step functions in the reaction progress variable, with the local value of energy release correspondingly increased so as to maintain the same average energy density in the medium and thus a constant Chapman-Jouguet (CJ) detonation velocity. A one-step Arrhenius rate governs the rate of energy release in the reactive zones. The resulting dynamics of a detonation propagating in such systems with one-dimensional layers and two-dimensional squares are simulated using a Godunov-type finite-volume scheme. The resulting wave dynamics are analyzed by computing the average wave velocity and one-dimensional averaged wave structure. In the case of sufficiently inhomogeneous media wherein the spacing between reactive zones is greater than the inherent reaction zone length, average wave speeds significantly greater than the corresponding CJ speed of the homogenized medium are obtained. If the shock transit time between reactive zones is less than the reaction time scale, then the classical CJ detonation velocity is recovered. The spatiotemporal averaged structure of the waves in these systems is analyzed via a Favre-averaging technique, with terms associated with the thermal and mechanical fluctuations being explicitly computed. The analysis of the averaged wave structure identifies the super-CJ detonations as weak detonations owing to the existence of mechanical nonequilibrium at the effective sonic point embedded within the wave structure. The correspondence of the super-CJ behavior identified in this study with real detonation phenomena that may be observed in experiments is discussed.

Crust structure beneath Jilin Province and Liaoning Province in China based on seismic ambient noise tomography

NASA Astrophysics Data System (ADS)

Pang, Guanghua; Feng, Jikun; Lin, Jun

2016-11-01

We imaged the crust structure beneath Jilin Province and Liaoning Province in China with fundamental mode Rayleigh waves recorded by 60 broadband stations deployed in the region. Surface-wave empirical Green's functions were retrieved from cross-correlations of inter-station data and phase velocity dispersions were measured using a frequency-time analysis method. Dispersion measurements were then utilized to construct 2D phase velocity maps for periods between 5 and 35 s. Subsequently, the phase-dispersion curves extracted from each cell of the 2D phase velocity maps were inverted to determine the 3D shear wave velocity structures of the crust. The phase velocity maps at different periods reflected the average velocity structures corresponding to different depth ranges. The maps in short periods, in particular, were in excellent agreement with known geological features of the surface. In addition to imaging shear wave velocity structures of the volcanoes, we show that obvious low-velocity anomalies imaged in the Changbaishan-Tianchi Volcano, the Longgang-Jinlongdingzi Volcano, and the system of the Dunmi Fault crossing the Jingbohu Volcano, all of which may be due to geothermal anomalies.

Towards a Full Waveform Ambient Noise Inversion

NASA Astrophysics Data System (ADS)

Sager, K.; Ermert, L. A.; Boehm, C.; Fichtner, A.

2015-12-01

Noise tomography usually works under the assumption that the inter-station ambient noise correlation is equal to a scaled version of the Green's function between the two receivers. This assumption, however, is only met under specific conditions, for instance, wavefield diffusivity and equipartitioning, zero attenuation, etc., that are typically not satisfied in the Earth. This inconsistency inhibits the exploitation of the full waveform information contained in noise correlations regarding Earth structure and noise generation. To overcome this limitation we attempt to develop a method that consistently accounts for noise distribution, 3D heterogeneous Earth structure and the full seismic wave propagation physics in order to improve the current resolution of tomographic images of the Earth. As an initial step towards a full waveform ambient noise inversion we develop a preliminary inversion scheme based on a 2D finite-difference code simulating correlation functions and on adjoint techniques. With respect to our final goal, a simultaneous inversion for noise distribution and Earth structure, we address the following two aspects: (1) the capabilities of different misfit functionals to image wave speed anomalies and source distribution and (2) possible source-structure trade-offs, especially to what extent unresolvable structure could be mapped into the inverted noise source distribution and vice versa.

EVOLUTION OF FAST MAGNETOACOUSTIC PULSES IN RANDOMLY STRUCTURED CORONAL PLASMAS

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

Yuan, D.; Li, B.; Pascoe, D. J.

2015-02-01

We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one-dimensional numerical simulations of fast wave pulses propagating perpendicular to a constant magnetic field in a low-β plasma with a random density profile across the field. Both linear and nonlinear regimes are considered. We study how the evolution of the pulse amplitude and width depends on their initial values and the parameters of the random structuring. Acting as a dispersive medium, a randomly structured plasma causes amplitude attenuation and width broadening of the fast wavemore » pulses. After the passage of the main pulse, secondary propagating and standing fast waves appear. Width evolution of both linear and nonlinear pulses can be well approximated by linear functions; however, narrow pulses may have zero or negative broadening. This arises because narrow pulses are prone to splitting, while broad pulses usually deviate less from their initial Gaussian shape and form ripple structures on top of the main pulse. Linear pulses decay at an almost constant rate, while nonlinear pulses decay exponentially. A pulse interacts most efficiently with a random medium with a correlation length of about half of the initial pulse width. This detailed model of fast wave pulses propagating in highly structured media substantiates the interpretation of EIT waves as fast magnetoacoustic waves. Evolution of a fast pulse provides us with a novel method to diagnose the sub-resolution filamentation of the solar atmosphere.« less

Ultrasonic wave-based structural health monitoring embedded instrument.

PubMed

Aranguren, G; Monje, P M; Cokonaj, Valerijan; Barrera, Eduardo; Ruiz, Mariano

2013-12-01

Piezoelectric sensors and actuators are the bridge between electronic and mechanical systems in structures. This type of sensor is a key element in the integrity monitoring of aeronautic structures, bridges, pressure vessels, wind turbine blades, and gas pipelines. In this paper, an all-in-one system for Structural Health Monitoring (SHM) based on ultrasonic waves is presented, called Phased Array Monitoring for Enhanced Life Assessment. This integrated instrument is able to generate excitation signals that are sent through piezoelectric actuators, acquire the received signals in the piezoelectric sensors, and carry out signal processing to check the health of structures. To accomplish this task, the instrument uses a piezoelectric phased-array transducer that performs the actuation and sensing of the signals. The flexibility and strength of the instrument allow the user to develop and implement a substantial part of the SHM technique using Lamb waves. The entire system is controlled using configuration software and has been validated through functional, electrical loading, mechanical loading, and thermal loading resistance tests.

Pore-Scale Modeling of Pore Structure Effects on P-Wave Scattering Attenuation in Dry Rocks

PubMed Central

Li, Tianyang; Qiu, Hao; Wang, Feifei

2015-01-01

Underground rocks usually have complex pore system with a variety of pore types and a wide range of pore size. The effects of pore structure on elastic wave attenuation cannot be neglected. We investigated the pore structure effects on P-wave scattering attenuation in dry rocks by pore-scale modeling based on the wave theory and the similarity principle. Our modeling results indicate that pore size, pore shape (such as aspect ratio), and pore density are important factors influencing P-wave scattering attenuation in porous rocks, and can explain the variation of scattering attenuation at the same porosity. From the perspective of scattering attenuation, porous rocks can safely suit to the long wavelength assumption when the ratio of wavelength to pore size is larger than 15. Under the long wavelength condition, the scattering attenuation coefficient increases as a power function as the pore density increases, and it increases exponentially with the increase in aspect ratio. For a certain porosity, rocks with smaller aspect ratio and/or larger pore size have stronger scattering attenuation. When the pore aspect ratio is larger than 0.5, the variation of scattering attenuation at the same porosity is dominantly caused by pore size and almost independent of the pore aspect ratio. These results lay a foundation for pore structure inversion from elastic wave responses in porous rocks. PMID:25961729

Rayleigh wave behavior in functionally graded magneto-electro-elastic material

NASA Astrophysics Data System (ADS)

Ezzin, Hamdi; Mkaoir, Mohamed; Amor, Morched Ben

2017-12-01

Piezoelectric-piezomagnetic functionally graded materials, with a gradual change of the mechanical and electromagnetic properties have greatly applying promises. Based on the ordinary differential equation and stiffness matrix methods, a dynamic solution is presented for the propagation of the wave on a semi-infinite piezomagnetic substrate covered with a functionally graded piezoelectric material (FGPM) layer. The materials properties are assumed to vary in the direction of the thickness according to a known variation law. The phase and group velocity of the Rayleigh wave is numerically calculated for the magneto-electrically open and short cases, respectively. The effect of gradient coefficients on the phase velocity, group velocity, coupled magneto-electromechanical factor, on the stress fields, the magnetic potential and the mechanical displacement are discussed, respectively. Illustration is achieved on the hetero-structure PZT-5A/CoFe2O4; the obtained results are especially useful in the design of high-performance acoustic surface devices and accurately prediction of the Rayleigh wave propagation behavior.

Spectra, current flow, and wave-function morphology in a model PT -symmetric quantum dot with external interactions

NASA Astrophysics Data System (ADS)

Tellander, Felix; Berggren, Karl-Fredrik

2017-04-01

In this paper we use numerical simulations to study a two-dimensional (2D) quantum dot (cavity) with two leads for passing currents (electrons, photons, etc.) through the system. By introducing an imaginary potential in each lead the system is made symmetric under parity-time inversion (PT symmetric). This system is experimentally realizable in the form of, e.g., quantum dots in low-dimensional semiconductors, optical and electromagnetic cavities, and other classical wave analogs. The computational model introduced here for studying spectra, exceptional points (EPs), wave-function symmetries and morphology, and current flow includes thousands of interacting states. This supplements previous analytic studies of few interacting states by providing more detail and higher resolution. The Hamiltonian describing the system is non-Hermitian; thus, the eigenvalues are, in general, complex. The structure of the wave functions and probability current densities are studied in detail at and in between EPs. The statistics for EPs is evaluated, and reasons for a gradual dynamical crossover are identified.

Seismic Velocity Assessment In The Kachchh Region, India, From Multiple Waveform Functionals

NASA Astrophysics Data System (ADS)

Ghosh, R.; Sen, M. K.; Mandal, P.; Pulliam, J.; Agrawal, M.

2014-12-01

The primary goal of this study is to estimate well constrained crust and upper mantle seismic velocity structure in the Kachchh region of Gujarat, India - an area of active interest for earthquake monitoring purposes. Several models based on 'stand-alone' surface wave dispersion and receiver function modeling exist in this area. Here we jointly model the receiver function, surface wave dispersion and, S and shear-coupled PL wavetrains using broadband seismograms of deep (150-700 km), moderate to-large magnitude (5.5-6.8) earthquakes recorded teleseismically at semi-permanent seismograph stations in the Kachchh region, Gujarat, India. While surface wave dispersion and receiver function modeling is computationally fast, full waveform modeling makes use of reflectivity synthetic seismograms. An objective function that measures misfit between all three data is minimized using a very fast simulated annealing (VFSA) approach. Surface wave and receiver function data help reduce the model search space which is explored extensively for detailed waveform fitting. Our estimated crustal and lithospheric thicknesses in this region vary from 32 to 41 km and 70 to 80 km, respectively, while crustal P and S velocities from surface to Moho discontinuity vary from 4.7 to 7.0 km/s and 2.7 to 4.1 km/s, respectively. Our modeling clearly reveals a zone of crustal as well as an asthenospheric upwarping underlying the Kachchh rift zone relative to the surrounding unrifted area. We believe that this feature plays a key role in the seismogenesis of lower crustal earthquakes occurring in the region through the emanation of volatile CO2 into the hypocentral zones liberating from the crystallization of carbonatite melts in the asthenosphere. Such a crust-mantle structure might be related to the plume-lithosphere interaction during the Deccan/Reunion plume episode (~65 Ma).

Accurately predicting the structure, density, and hydrostatic compression of crystalline β-1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane based on its wave-function-based potential

NASA Astrophysics Data System (ADS)

Song, H.-J.; Huang, F.

2011-09-01

A wave-function-based intermolecular potential of the β phase 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) molecule has been constructed from first principles using the Williams-Stone-Misquitta method and the symmetry-adapted perturbation theory. Using the potential and its derivatives, we have accurately predicted not only the structure and lattice energy of the crystalline β-HMX at 0 K, but also its densities at temperatures of 0-403 K within an accuracy of 1% of density. The calculated densities at pressures within 0-6 GPa excellently agree with the results from the experiments on hydrostatic compression.

Dependence of the atomic level Green-Kubo stress correlation function on wavevector and frequency: molecular dynamics results from a model liquid.

PubMed

Levashov, V A

2014-09-28

We report on a further investigation of a new method that can be used to address vibrational dynamics and propagation of stress waves in liquids. The method is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the atomic level stress correlation functions. This decomposition, as was demonstrated previously for a model liquid studied in molecular dynamics simulations, reveals the presence of stress waves propagating over large distances and a structure that resembles the pair density function. In this paper, by performing the Fourier transforms of the atomic level stress correlation functions, we elucidate how the lifetimes of the stress waves and the ranges of their propagation depend on their frequency, wavevector, and temperature. These results relate frequency and wavevector dependence of the generalized viscosity to the character of propagation of the shear stress waves. In particular, the results suggest that an increase in the value of the frequency dependent viscosity at low frequencies with decrease of temperature is related to the increase in the ranges of propagation of the stress waves of the corresponding low frequencies. We found that the ranges of propagation of the shear stress waves of frequencies less than half of the Einstein frequency extend well beyond the nearest neighbor shell even above the melting temperature. The results also show that the crossover from quasilocalized to propagating behavior occurs at frequencies usually associated with the Boson peak.

Exact travelling wave solutions for a diffusion-convection equation in two and three spatial dimensions

NASA Astrophysics Data System (ADS)

Elwakil, S. A.; El-Labany, S. K.; Zahran, M. A.; Sabry, R.

2004-04-01

The modified extended tanh-function method were applied to the general class of nonlinear diffusion-convection equations where the concentration-dependent diffusivity, D( u), was taken to be a constant while the concentration-dependent hydraulic conductivity, K( u) were taken to be in a power law. The obtained solutions include rational-type, triangular-type, singular-type, and solitary wave solutions. In fact, the profile of the obtained solitary wave solutions resemble the characteristics of a shock-wave like structure for an arbitrary m (where m>1 is the power of the nonlinear convection term).

Anisotropic Lithospheric layering in the North American craton, revealed by Bayesian inversion of short and long period data

NASA Astrophysics Data System (ADS)

Roy, C.; Calo, M.; Bodin, T.; Romanowicz, B. A.

2016-12-01

Competing hypotheses for the formation and evolution of continents are highly under debate, including the theory of underplating by hot plumes or accretion by shallow subduction in continental or arc settings. In order to support these hypotheses, documenting structural layering in the cratonic lithosphere becomes especially important. Studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at 100-140 km depths, which is too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. This leads to the conclusion that 1) the cratonic lithosphere may be thinner than expected, contradicting tomographic and other geophysical or geochemical inferences, or 2) that the receiver function studies detect a mid-lithospheric discontinuity rather than the LAB. Recent studies (Bodin et al., 2015, Calo et al. 2016) confirmed the presence of a structural boundary under the north American craton at 100-140 km depths by taking advantage of the power of a trans-dimensional Monte Carlo Markov chain (TMCMC). They generated probabilistic 1D radially shear wave velocity profiles for selected stations in North America by jointly inverting 2 different data types (PS Receiver Functions, surface wave dispersion for Love and Rayleigh waves), which sample different volumes of the Earth and have different sensitivities to structure. The resulting 1D profiles include both isotropic and anisotropic discontinuities in the upper mantle (above 350 km depth). Here we extend this approach and include the vp/vs ratio as an unknown in the TMCMC algorithm to avoid artificial layers induced by multiples of the receiver functions. Additionally, we include SKS waveforms in the joint inversion and invert for azimuthal anisotropy to verify if layering in the anisotropic structure of the stable part of the North American continent involves significant changes in the direction of azimuthal anisotropy as suggested by Yuan and Romanowicz (2010). We recently demonstrated the power of this approach in the case of two stations located in different tectonic settings (Bodin et al., 2016. Here we extend this approach to a broader range of settings within the north American continent.

Advanced numerical technique for analysis of surface and bulk acoustic waves in resonators using periodic metal gratings

NASA Astrophysics Data System (ADS)

Naumenko, Natalya F.

2014-09-01

A numerical technique characterized by a unified approach for the analysis of different types of acoustic waves utilized in resonators in which a periodic metal grating is used for excitation and reflection of such waves is described. The combination of the Finite Element Method analysis of the electrode domain with the Spectral Domain Analysis (SDA) applied to the adjacent upper and lower semi-infinite regions, which may be multilayered and include air as a special case of a dielectric material, enables rigorous simulation of the admittance in resonators using surface acoustic waves, Love waves, plate modes including Lamb waves, Stonely waves, and other waves propagating along the interface between two media, and waves with transient structure between the mentioned types. The matrix formalism with improved convergence incorporated into SDA provides fast and robust simulation for multilayered structures with arbitrary thickness of each layer. The described technique is illustrated by a few examples of its application to various combinations of LiNbO3, isotropic silicon dioxide and silicon with a periodic array of Cu electrodes. The wave characteristics extracted from the admittance functions change continuously with the variation of the film and plate thicknesses over wide ranges, even when the wave nature changes. The transformation of the wave nature with the variation of the layer thicknesses is illustrated by diagrams and contour plots of the displacements calculated at resonant frequencies.

On a new class of completely integrable nonlinear wave equations. II. Multi-Hamiltonian structure

NASA Astrophysics Data System (ADS)

Nutku, Y.

1987-11-01

The multi-Hamiltonian structure of a class of nonlinear wave equations governing the propagation of finite amplitude waves is discussed. Infinitely many conservation laws had earlier been obtained for these equations. Starting from a (primary) Hamiltonian formulation of these equations the necessary and sufficient conditions for the existence of bi-Hamiltonian structure are obtained and it is shown that the second Hamiltonian operator can be constructed solely through a knowledge of the first Hamiltonian function. The recursion operator which first appears at the level of bi-Hamiltonian structure gives rise to an infinite sequence of conserved Hamiltonians. It is found that in general there exist two different infinite sequences of conserved quantities for these equations. The recursion relation defining higher Hamiltonian structures enables one to obtain the necessary and sufficient conditions for the existence of the (k+1)st Hamiltonian operator which depends on the kth Hamiltonian function. The infinite sequence of conserved Hamiltonians are common to all the higher Hamiltonian structures. The equations of gas dynamics are discussed as an illustration of this formalism and it is shown that in general they admit tri-Hamiltonian structure with two distinct infinite sets of conserved quantities. The isothermal case of γ=1 is an exceptional one that requires separate treatment. This corresponds to a specialization of the equations governing the expansion of plasma into vacuum which will be shown to be equivalent to Poisson's equation in nonlinear acoustics.

Global seismic attenuation imaging using full-waveform inversion: a comparative assessment of different choices of misfit functionals

NASA Astrophysics Data System (ADS)

Karaoǧlu, Haydar; Romanowicz, Barbara

2018-02-01

We present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3-D imaging of shear wave attenuation in the earth's upper mantle at the global scale, using long-period full-waveform data. The synthetic tests are conducted with simple hypothetical upper-mantle models that contain Qμ anomalies centred at different depths and locations, with or without additional seismic velocity anomalies. To build synthetic waveform data sets, we performed simulations of 50 events in the hypothetical (target) models, using the spectral element method, filtered in the period range 60-400 s. The selected events are chosen among 273 events used in the development of radially anisotropic model SEMUCB-WM1 and recorded at 495 stations worldwide. The synthetic Z-component waveforms correspond to paths and time intervals (fundamental mode and overtone Rayleigh waves) that exist in the real waveform data set. The inversions for shear attenuation structure are carried out using a Gauss-Newton optimization scheme in which the gradient and Hessian are computed using normal mode perturbation theory. The three different misfit functionals considered are based on time domain waveform (WF) and waveform envelope (E-WF) differences, as well as spectral amplitude ratios (SA), between observed and predicted waveforms. We evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved S-wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3-D Qμ structure. We observed that the performance of WF is poorer than the other two misfit functionals in recovering attenuation structure, unless anelastic dispersion effects are taken into account in the calculation of partial derivatives. WF also turns out to be more sensitive to seismic noise than E-WF and SA. Overall, SA performs best for attenuation imaging. Our tests show that it is important to account for 3-D elastic effects (focusing) before inverting for Qμ. Additionally, we show that including high signal-to-noise ratio overtone wave packets is necessary to resolve Qμ structure at depths greater than 250 km.

Multiple Volume Scattering in Random Media and Periodic Structures with Applications in Microwave Remote Sensing and Wave Functional Materials

NASA Astrophysics Data System (ADS)

Tan, Shurun

The objective of my research is two-fold: to study wave scattering phenomena in dense volumetric random media and in periodic wave functional materials. For the first part, the goal is to use the microwave remote sensing technique to monitor water resources and global climate change. Towards this goal, I study the microwave scattering behavior of snow and ice sheet. For snowpack scattering, I have extended the traditional dense media radiative transfer (DMRT) approach to include cyclical corrections that give rise to backscattering enhancements, enabling the theory to model combined active and passive observations of snowpack using the same set of physical parameters. Besides DMRT, a fully coherent approach is also developed by solving Maxwell's equations directly over the entire snowpack including a bottom half space. This revolutionary new approach produces consistent scattering and emission results, and demonstrates backscattering enhancements and coherent layer effects. The birefringence in anisotropic snow layers is also analyzed by numerically solving Maxwell's equation directly. The effects of rapid density fluctuations in polar ice sheet emission in the 0.5˜2.0 GHz spectrum are examined using both fully coherent and partially coherent layered media emission theories that agree with each other and distinct from incoherent approaches. For the second part, the goal is to develop integral equation based methods to solve wave scattering in periodic structures such as photonic crystals and metamaterials that can be used for broadband simulations. Set upon the concept of modal expansion of the periodic Green's function, we have developed the method of broadband Green's function with low wavenumber extraction (BBGFL), where a low wavenumber component is extracted and results a non-singular and fast-converging remaining part with simple wavenumber dependence. We've applied the technique to simulate band diagrams and modal solutions of periodic structures, and to construct broadband Green's functions including periodic scatterers.

Density functional theory calculations of 95Mo NMR parameters in solid-state compounds.

PubMed

Cuny, Jérôme; Furet, Eric; Gautier, Régis; Le Pollès, Laurent; Pickard, Chris J; d'Espinose de Lacaillerie, Jean-Baptiste

2009-12-21

The application of periodic density functional theory-based methods to the calculation of (95)Mo electric field gradient (EFG) and chemical shift (CS) tensors in solid-state molybdenum compounds is presented. Calculations of EFG tensors are performed using the projector augmented-wave (PAW) method. Comparison of the results with those obtained using the augmented plane wave + local orbitals (APW+lo) method and with available experimental values shows the reliability of the approach for (95)Mo EFG tensor calculation. CS tensors are calculated using the recently developed gauge-including projector augmented-wave (GIPAW) method. This work is the first application of the GIPAW method to a 4d transition-metal nucleus. The effects of ultra-soft pseudo-potential parameters, exchange-correlation functionals and structural parameters are precisely examined. Comparison with experimental results allows the validation of this computational formalism.

P wave dispersion and maximum P wave duration are independently associated with rapid renal function decline.

PubMed

Su, Ho-Ming; Tsai, Wei-Chung; Lin, Tsung-Hsien; Hsu, Po-Chao; Lee, Wen-Hsien; Lin, Ming-Yen; Chen, Szu-Chia; Lee, Chee-Siong; Voon, Wen-Chol; Lai, Wen-Ter; Sheu, Sheng-Hsiung

2012-01-01

The P wave parameters measured by 12-lead electrocardiogram (ECG) are commonly used as noninvasive tools to assess for left atrial enlargement. There are limited studies to evaluate whether P wave parameters are independently associated with decline in renal function. Accordingly, the aim of this study is to assess whether P wave parameters are independently associated with progression to renal end point of ≥25% decline in estimated glomerular filtration rate (eGFR). This longitudinal study included 166 patients. The renal end point was defined as ≥25% decline in eGFR. We measured two ECG P wave parameters corrected by heart rate, i.e. corrected P wave dispersion (PWdisperC) and corrected P wave maximum duration (PWdurMaxC). Heart function and structure were measured from echocardiography. Clinical data, P wave parameters, and echocardiographic measurements were compared and analyzed. Forty-three patients (25.9%) reached renal end point. Kaplan-Meier curves for renal end point-free survival showed PWdisperC > median (63.0 ms) (log-rank P = 0.004) and PWdurMaxC > median (117.9 ms) (log-rank P<0.001) were associated with progression to renal end point. Multivariate forward Cox-regression analysis identified increased PWdisperC (hazard ratio [HR], 1.024; P = 0.001) and PWdurMaxC (HR, 1.029; P = 0.001) were independently associated with progression to renal end point. Our results demonstrate that increased PWdisperC and PWdurMaxC were independently associated with progression to renal end point. Screening patients by means of PWdisperC and PWdurMaxC on 12 lead ECG may help identify a high risk group of rapid renal function decline.

Seismic structure of the Slave craton crust

NASA Astrophysics Data System (ADS)

Barantseva, O.; Vinnik, L. P.; Farra, V.; van der Hilst, R. D.; Artemieva, I. M.; Montagner, J. P.

2017-12-01

We present P- and S-receiver functions for 20 stations along a 200-km-long NNW-SSE seismological profile across the Slave craton, and estimate the average crustal Vp/Vs ratio which is indicative of rock composition. We observe high Vp/Vs ratio ( 1.85-2.00) for the bulk crust and elevated Vp values at a depth range from 20-30 km to 40 km. High Vp values (>7.0 km/s) suggest mafic composition of the lower crust. In case of dry lower crustal rocks, the Vp/Vs ratio is expected to range from 1.6 to 1.8, which is lower than the observed values of 1.9-2.0. Laboratory studies show that Vp/Vs 1.9-2.0 can be explained by the presence of numerous cracks saturated with an incompressible fluid. Our results are at odds with the structure of the cratonic crust in many regions worldwide, and may suggest a unique geodynamic evolution of the Slave crust. Possible explanations for the observed crustal structure include the presence of an underplated mafic material, possibly related to intraplate magmatism or paleosubduction. Receiver functions are highly sensitive to the change of acoustic impedance and S-wave velocities, but do not resolve the internal seismic structure with a high precision. We extend our study of the crustal structure by using ambient noise tomography (ANT). We measure Rayleigh wave dispersion from Green's functions that are estimated from one-year noise cross-correlation (NCF). The phase velocity maps are inverted for 1D wave speed profiles which are then combined to form 2D and 3D models of the crust of the Slave Province. The combined results of RF analyses and ANT are interpreted in terms of crustal structure, composition, and evolution.

Ion-acoustic and electron-acoustic type nonlinear waves in dusty plasmas

NASA Astrophysics Data System (ADS)

Volosevich, A.-V.; Meister, C.-V.

2003-04-01

In the present work, two three-dimensional nonlinear theoretical models of electrostatic solitary waves are investigated within the frame of magnetohydrodynamics. Both times, a multi-component plasma is considered, which consists of hot electrons with a rather flexible distribution function, hot ions with Boltzmann-type distribution, and (negatively as well as positively charged) dust. Additionally, cold ion beams are taken into account in the model to study ion-acoustic structures (IAS), and cold electron beams are included into the model to investigate electron-acoustic structures (EAS). The numerical results of the considered theoretical models allow to make the following conclusions: 1) Electrostatic structures with negative potential (of rarefaction type) are formed both in the IAS model and in the EAS model, but structures with negative potential (of compressional type) are formed in the IAS model only. 2) The intervals of various plasma parameters (velocities of ion and electron beams, temperatures, densities of the plasma components, ions' masses), for which the existence of IAS and EAS solitary waves and structures is possible, are calculated. 3) Further, the parameters of the electrostatic structures (wave amplitudes, scales along and perpendicular to the magnetic field, velocities) are estimated. 4) The application of the present numerical simulation for multi-component plasmas to various astrophysical systems under different physical conditions is discussed.

Theoretical atomic physics code development I: CATS: Cowan Atomic Structure Code

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

Abdallah, J. Jr.; Clark, R.E.H.; Cowan, R.D.

An adaptation of R.D. Cowan's Atomic Structure program, CATS, has been developed as part of the Theoretical Atomic Physics (TAPS) code development effort at Los Alamos. CATS has been designed to be easy to run and to produce data files that can interface with other programs easily. The CATS produced data files currently include wave functions, energy levels, oscillator strengths, plane-wave-Born electron-ion collision strengths, photoionization cross sections, and a variety of other quantities. This paper describes the use of CATS. 10 refs.

Determination of Shear Wave Velocity Structure in the Rio Grande Rift Through Receiver Function and Surface Wave Analysis. Appendix B

DTIC Science & Technology

1991-08-01

source and receiver responses for constant ray parameter, Bull. Seism. Soc. Am. 67, 1029-1050, 1977. Langston, C. A., Structure under Mount Rainier ...the 106 petrologic processes taking place within the rift. APPENDIX LIST OF COMPUTER PROGRAMS USED IN THESIS. 107 I 108 PROGRAM: RAY3D AUTHOR: Dr. T.J...Lab. Rep., LA-8676-T, 218 pp., 1981. Baldridge, W. S., Petrology an,3 petrogenesis of Plio- Pleistocene basaltic rocks from the central Rio Grand

Balancing the Power-to-Load Ratio for a Novel Variable Geometry Wave Energy Converter with Nonideal Power Take-Off in Regular Waves: Preprint

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

Tom, Nathan M; Yu, Yi-Hsiang; Wright, Alan D

This work attempts to balance power absorption against structural loading for a novel variable geometry wave energy converter. The variable geometry consists of four identical flaps that will be opened in ascending order starting with the flap closest to the seafloor and moving to the free surface. The influence of a pitch motion constraint on power absorption when utilizing a nonideal power take-off (PTO) is examined and found to reduce the losses associated with bidirectional energy flow. The power-to-load ratio is evaluated using pseudo-spectral control to determine the optimum PTO torque based on a multiterm objective function. The pseudo-spectral optimalmore » control problem is extended to include load metrics in the objective function, which may now consist of competing terms. Separate penalty weights are attached to the surge-foundation force and PTO control torque to tune the optimizer performance to emphasize either power absorption or load shedding. PTO efficiency is not included in the objective function, but the penalty weights are utilized to limit the force and torque amplitudes, thereby reducing losses associated with bidirectional energy flow. Results from pseudo-spectral control demonstrate that shedding a portion of the available wave energy can provide greater reductions in structural loads and reactive power.« less

Inverse medium scattering from periodic structures with fixed-direction incoming waves

NASA Astrophysics Data System (ADS)

Gibson, Peter; Hu, Guanghui; Zhao, Yue

2018-07-01

This paper is concerned with inverse time-harmonic acoustic and electromagnetic scattering from an infinite biperiodic medium (diffraction grating) in three dimensions. In the acoustic case, we prove that the near-field data of fixed-direction plane waves incited at multiple frequencies uniquely determine a refractive index function which depends on two variables. An analogous uniqueness result holds for time-harmonic Maxwell’s system if the inhomogeneity is periodic in one direction and remains invariant along the other two directions. Uniqueness for recovering (non-periodic) compactly supported contrast functions are also presented.

QEDMOD: Fortran program for calculating the model Lamb-shift operator

NASA Astrophysics Data System (ADS)

Shabaev, V. M.; Tupitsyn, I. I.; Yerokhin, V. A.

2018-02-01

We present Fortran package QEDMOD for computing the model QED operator hQED that can be used to account for the Lamb shift in accurate atomic-structure calculations. The package routines calculate the matrix elements of hQED with the user-specified one-electron wave functions. The operator can be used to calculate Lamb shift in many-electron atomic systems with a typical accuracy of few percent, either by evaluating the matrix element of hQED with the many-electron wave function, or by adding hQED to the Dirac-Coulomb-Breit Hamiltonian.

Study of Rayleigh-Love coupling from Spatial Gradient Observation

NASA Astrophysics Data System (ADS)

Lin, C. J.; Hosseini, K.; Donner, S.; Vernon, F.; Wassermann, J. M.; Igel, H.

2017-12-01

We present a new method to study Rayleigh-Love coupling. Instead of using seismograms solely, where ground motion is recorded as function of time, we incorporate with rotation and strain, also called spatial gradient where ground is represented as function of distance. Seismic rotation and strain are intrinsic different observable wavefield so are helpful to indentify wave type and wave propagation. A Mw 7.5 earthquake on 29 March 2015 occurred in Kokopo, Papua New Guinea recorded by a dense seismic array at PFO, California are used to obtaint seismic spatial gradient. We firstly estimate time series of azimuthal direction and phase velocity of SH wave and Rayleigh wave by analyzing collocated seismograms and rotations. This result also compares with frequency wavenumber methods using a nearby ANZA seismic array. We find the direction of Rayleigh wave fits well with great-circle back azimuth during wave propagation, while the direction of Love wave deviates from that, especially when main energy of Rayleigh wave arrives. From the analysis of cross-correlation between areal strain and vertical rotation, it reveals that high coherence, either positive or negative, happens at the same time when Love wave deparate from great-circle path. We also find the observed azimuth of Love wave and polarized particle motion of Rayleigh wave fits well with the fast direction of Rayleigh wave, for the period of 50 secs. We conclude the cause of deviated azimuth of Love wave is due to Rayleigh-Love coupling, as surface wave propagates through the area with anisotropic structure.

Acute effects of 30 minutes of exposure to a smartphone call on in vitro platelet function

PubMed Central

Lippi, Giuseppe; Danese, Elisa; Brocco, Giorgio; Gelati, Matteo; Salvagno, Gian Luca; Montagnana, Martina

2017-01-01

Background Significant concerns are now regularly raised about the safety of excessive mobile phone use. This study was aimed to assess the acute effects of radiofrequency waves emitted by a commercial smartphone on platelet function. Materials and methods Two sequential citrated blood samples were collected from 16 healthy volunteers recruited from laboratory staff. The first sample was placed in a plastic rack, 1 cm distant from a commercial smartphone receiving a 30-min call and emitting 900 MHz radiofrequency waves. The second sample was placed in another plastic rack, isolated from radiofrequency wave sources, for the same period. The platelet count and the mean platelet volume were then assessed in all blood samples, whereas platelet function was evaluated using the platelet function analyser-100 (PFA-100). Results A 30-min exposure of citrated blood to smartphone radiofrequency waves induced significant prolongation of collagen-epinephrine aggregation (median increase, 10%) and a considerable increase of mean platelet volume (median increase, 5%), whereas collagen-adenosine diphosphate aggregation and platelet count remained unchanged. Discussion This study demonstrates that smartphone radiofrequency waves induce significant perturbation of platelet structure and function, thus providing further support to concerns regarding excessive use of mobile phones. Caution should also be taken with regards to blood products containing platelets, which should be kept far away from mobile phones and smartphones throughout the production pipeline and storage period. PMID:27177410

Acute effects of 30 minutes of exposure to a smartphone call on in vitro platelet function.

PubMed

Lippi, Giuseppe; Danese, Elisa; Brocco, Giorgio; Gelati, Matteo; Salvagno, Gian Luca; Montagnana, Martina

2017-05-01

Significant concerns are now regularly raised about the safety of excessive mobile phone use. This study was aimed to assess the acute effects of radiofrequency waves emitted by a commercial smartphone on platelet function. Two sequential citrated blood samples were collected from 16 healthy volunteers recruited from laboratory staff. The first sample was placed in a plastic rack, 1 cm distant from a commercial smartphone receiving a 30-min call and emitting 900 MHz radiofrequency waves. The second sample was placed in another plastic rack, isolated from radiofrequency wave sources, for the same period. The platelet count and the mean platelet volume were then assessed in all blood samples, whereas platelet function was evaluated using the platelet function analyser-100 (PFA-100). A 30-min exposure of citrated blood to smartphone radiofrequency waves induced significant prolongation of collagen-epinephrine aggregation (median increase, 10%) and a considerable increase of mean platelet volume (median increase, 5%), whereas collagen-adenosine diphosphate aggregation and platelet count remained unchanged. This study demonstrates that smartphone radiofrequency waves induce significant perturbation of platelet structure and function, thus providing further support to concerns regarding excessive use of mobile phones. Caution should also be taken with regards to blood products containing platelets, which should be kept far away from mobile phones and smartphones throughout the production pipeline and storage period.

Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

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

Solis-Najera, S. E., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Neria-Pérez, J. A., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Medina, L., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx

Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot’s model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot’smore » waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.« less

Pseudo-spectral control of a novel oscillating surge wave energy converter in regular waves for power optimization including load reduction

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

Tom, Nathan M.; Yu, Yi -Hsiang; Wright, Alan D.

The aim of this study is to describe a procedure to maximize the power-to-load ratio of a novel wave energy converter (WEC) that combines an oscillating surge wave energy converter with variable structural components. The control of the power-take-off torque will be on a wave-to-wave timescale, whereas the structure will be controlled statically such that the geometry remains the same throughout the wave period. Linear hydrodynamic theory is used to calculate the upper and lower bounds for the time-averaged absorbed power and surge foundation loads while assuming that the WEC motion remains sinusoidal. Previous work using pseudo-spectral techniques to solvemore » the optimal control problem focused solely on maximizing absorbed energy. This work extends the optimal control problem to include a measure of the surge foundation force in the optimization. The objective function includes two competing terms that force the optimizer to maximize power capture while minimizing structural loads. A penalty weight was included with the surge foundation force that allows control of the optimizer performance based on whether emphasis should be placed on power absorption or load shedding. Results from pseudo-spectral optimal control indicate that a unit reduction in time-averaged power can be accompanied by a greater reduction in surge-foundation force.« less

Pseudo-spectral control of a novel oscillating surge wave energy converter in regular waves for power optimization including load reduction

DOE PAGES

Tom, Nathan M.; Yu, Yi -Hsiang; Wright, Alan D.; ...

2017-04-18

The aim of this study is to describe a procedure to maximize the power-to-load ratio of a novel wave energy converter (WEC) that combines an oscillating surge wave energy converter with variable structural components. The control of the power-take-off torque will be on a wave-to-wave timescale, whereas the structure will be controlled statically such that the geometry remains the same throughout the wave period. Linear hydrodynamic theory is used to calculate the upper and lower bounds for the time-averaged absorbed power and surge foundation loads while assuming that the WEC motion remains sinusoidal. Previous work using pseudo-spectral techniques to solvemore » the optimal control problem focused solely on maximizing absorbed energy. This work extends the optimal control problem to include a measure of the surge foundation force in the optimization. The objective function includes two competing terms that force the optimizer to maximize power capture while minimizing structural loads. A penalty weight was included with the surge foundation force that allows control of the optimizer performance based on whether emphasis should be placed on power absorption or load shedding. Results from pseudo-spectral optimal control indicate that a unit reduction in time-averaged power can be accompanied by a greater reduction in surge-foundation force.« less

Ion flux oscillations associated with a radially polarized transverse Pc 5 magnetic pulsation

NASA Technical Reports Server (NTRS)

Takahashi, K.; Mcentire, R. W.; Lui, A. T. Y.; Potemra, T. A.

1990-01-01

The AMPTE CCE spacecraft observed a transverse Pc 5 magnetic pulsation (period of about 200 s) at 2155-2310 UT on November 20, 1985, at a radial distance of 5.7 - 7.0 earth radii, at a magnetic latitude of 1.2 - 19 deg, and near 1300 magnetic local time. The magnetic pulsation exhibits properties consistent with a standing Alfven wave with a second-harmonic standing structure along the ambient magnetic field. The amplitude and the phase of the flux pulsation are found to be a function of the particle detector look direction and the particle energy. The observed energy dependence of the shift is interpreted as the result of a drift-bounce resonance of the ions with the wave. From this interpretation it follows that the wave propagated westward with an azimuthal wave number of approximately 100. Thus the study demonstrates that particle data can be useful for determining the spatial structure of some types of ULF waves.

Structure of the Nucleon and its Excitations

NASA Astrophysics Data System (ADS)

Kamleh, Waseem; Leinweber, Derek; Liu, Zhan-wei; Stokes, Finn; Thomas, Anthony; Thomas, Samuel; Wu, Jia-jun

2018-03-01

The structure of the ground state nucleon and its finite-volume excitations are examined from three different perspectives. Using new techniques to extract the relativistic components of the nucleon wave function, the node structure of both the upper and lower components of the nucleon wave function are illustrated. A non-trivial role for gluonic components is manifest. In the second approach, the parity-expanded variational analysis (PEVA) technique is utilised to isolate states at finite momenta, enabling a novel examination of the electric and magnetic form factors of nucleon excitations. Here the magnetic form factors of low-lying odd-parity nucleons are particularly interesting. Finally, the structure of the nucleon spectrum is examined in a Hamiltonian effective field theory analysis incorporating recent lattice-QCD determinations of low-lying two-particle scattering-state energies in the finite volume. The Roper resonance of Nature is observed to originate from multi-particle coupled-channel interactions while the first radial excitation of the nucleon sits much higher at approximately 1.9 GeV.

Thin Lithosphere Beneath the Ethiopian Plateau Revealed by a Joint Inversion of Rayleigh Wave Group Velocities and Receiver Functions

NASA Astrophysics Data System (ADS)

Dugda, Mulugeta T.; Nyblade, Andrew A.; Julia, Jordi

2007-08-01

The seismic velocity structure of the crust and upper mantle beneath Ethiopia and Djibouti has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities to obtain new constraints on the thermal structure of the lithosphere. Most of the data for this study come from the Ethiopia broadband seismic experiment, conducted between 2000 and 2002. Shear velocity models obtained from the joint inversion show crustal structure that is similar to previously published models, with crustal thicknesses of 35 to 44 km beneath the Ethiopian Plateau, and 25 to 35 km beneath the Main Ethiopian Rift (MER) and the Afar. The lithospheric mantle beneath the Ethiopian Plateau has a maximum shear wave velocity of about 4.3 km/s and extends to a depth of ˜70-80 km. Beneath the MER and Afar, the lithospheric mantle has a maximum shear wave velocity of 4.1-4.2 km/s and extends to a depth of at most 50 km. In comparison to the lithosphere away from the East African Rift System in Tanzania, where the lid extends to depths of ˜100-125 km and has a maximum shear velocity of 4.6 km/s, the mantle lithosphere under the Ethiopian Plateau appears to have been thinned by ˜30-50 km and the maximum shear wave velocity reduced by ˜0.3 km/s. Results from a 1D conductive thermal model suggest that the shear velocity structure of the Ethiopian Plateau lithosphere can be explained by a plume model, if a plume rapidly thinned the lithosphere by ˜30-50 km at the time of the flood basalt volcanism (c. 30 Ma), and if warm plume material has remained beneath the lithosphere since then. About 45-65% of the 1-1.5 km of plateau uplift in Ethiopia can be attributed to the thermally perturbed lithospheric structure.

Anisotropic Lithospheric layering in the North American craton, revealed by Bayesian inversion of short and long period data

NASA Astrophysics Data System (ADS)

Roy, Corinna; Calo, Marco; Bodin, Thomas; Romanowicz, Barbara

2016-04-01

Competing hypotheses for the formation and evolution of continents are highly under debate, including the theory of underplating by hot plumes or accretion by shallow subduction in continental or arc settings. In order to support these hypotheses, documenting structural layering in the cratonic lithosphere becomes especially important. Recent studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at 100-140 km depths, which is too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. This leads to the conclusion that 1) the cratonic lithosphere may be thinner than expected, contradicting tomographic and other geophysical or geochemical inferences, or 2) that the receiver function studies detect a mid-lithospheric discontinuity rather than the LAB. On the other hand, several recent studies documented significant changes in the direction of azimuthal anisotropy with depth that suggest layering in the anisotropic structure of the stable part of the North American continent. In particular, Yuan and Romanowicz (2010) combined long period surface wave and overtone data with core refracted shear wave (SKS) splitting measurements in a joint tomographic inversion. A question that arises is whether the anisotropic layering observed coincides with that obtained from receiver function studies. To address this question, we use a trans-dimensional Markov-chain Monte Carlo (MCMC) algorithm to generate probabilistic 1D radially and azimuthal anisotropic shear wave velocity profiles for selected stations in North America. In the algorithm we jointly invert short period (Ps Receiver Functions, surface wave dispersion for Love and Rayleigh waves) and long period data (SKS waveforms). By including three different data types, which sample different volumes of the Earth and have different sensitivities to 
structure, we overcome the problem of incompatible interpretations of models provided by only one data set. The resulting 1D profiles include both isotropic and anisotropic discontinuities in the upper mantle (above 350 km depth). The huge advantage of our procedure is the avoidance of any intermediate processing steps such as numerical deconvolution or the calculation of splitting parameters, which can be very sensitive to noise. Additionally, the number of layers, as well as the data noise and the presence of anisotropy are treated as unknowns in the transdimensional Monte Carlo Markov chain algorithm. We recently demonstrated the power of this approach in the case of two stations located in different tectonic settings (Bodin et al., 2015, submitted). Here we extend this approach to a broader range of settings within the north American continent.

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

Verma, U. P.; Nayak, V.

Quantum mechanical first principle calculations have been performed to study the electronic and structural properties of TiN and TiAs in zinc blende (ZB) and rock salt (RS) structures. The full-potential linearized augmented plane wave (FP-LAPW) method has been used within the framework of density functional theory (DFT). The exchange correlation functional has been solved employing generalized gradient approximation (GGA). Our predicted results for lattice constants are in good agreement with the earlier findings. The electronic band structures of TiX are metallic in both the phases.

Method for the Direct Solve of the Many-Body Schrödinger Wave Equation

NASA Astrophysics Data System (ADS)

Jerke, Jonathan; Tymczak, C. J.; Poirier, Bill

We report on theoretical and computational developments towards a computationally efficient direct solve of the many-body Schrödinger wave equation for electronic systems. This methodology relies on two recent developments pioneered by the authors: 1) the development of a Cardinal Sine basis for electronic structure calculations; and 2) the development of a highly efficient and compact representation of multidimensional functions using the Canonical tensor rank representation developed by Belykin et. al. which we have adapted to electronic structure problems. We then show several relevant examples of the utility and accuracy of this methodology, scaling with system size, and relevant convergence issues of the methodology. Method for the Direct Solve of the Many-Body Schrödinger Wave Equation.

Density functional study of molecular interactions in secondary structures of proteins.

PubMed

Takano, Yu; Kusaka, Ayumi; Nakamura, Haruki

2016-01-01

Proteins play diverse and vital roles in biology, which are dominated by their three-dimensional structures. The three-dimensional structure of a protein determines its functions and chemical properties. Protein secondary structures, including α-helices and β-sheets, are key components of the protein architecture. Molecular interactions, in particular hydrogen bonds, play significant roles in the formation of protein secondary structures. Precise and quantitative estimations of these interactions are required to understand the principles underlying the formation of three-dimensional protein structures. In the present study, we have investigated the molecular interactions in α-helices and β-sheets, using ab initio wave function-based methods, the Hartree-Fock method (HF) and the second-order Møller-Plesset perturbation theory (MP2), density functional theory, and molecular mechanics. The characteristic interactions essential for forming the secondary structures are discussed quantitatively.

Parallel pumping of a ferromagnetic nanostripe: Confinement quantization and off-resonant driving

NASA Astrophysics Data System (ADS)

Yarbrough, P. M.; Livesey, K. L.

2018-01-01

The parametric excitation of spin waves in a rectangular, ferromagnetic nanowire in the parallel pump configuration and with an applied field along the long axis of the wire is studied theoretically, using a semi-classical and semi-analytic Hamiltonian approach. We find that as a function of static applied field strength, there are jumps in the pump power needed to excite thermal spin waves. At these jumps, there is the possibility to non-resonantly excite spin waves near kz = 0. Spin waves with negative or positive group velocity and with different standing wave structures across the wire width can be excited by tuning the applied field. By using a magnetostatic Green's function that depends on both the nanowire's width and thickness—rather than just its aspect ratio—we also find that the threshold field strength varies considerably for nanowires with the same aspect ratio but of different sizes. Comparisons between different methods of calculations are made and the advantages and disadvantages of each are discussed.

3D Crust and Uppermost Mantle Structure beneath Tian Shan Region from ambient noise and earthquake surface waves

NASA Astrophysics Data System (ADS)

Xiao, X.; Wen, L.

2017-12-01

As a typical active intracontinental mountain range in Central Asia, Tian Shan Mt serves as the prototype in studying geodynamic processes and mechanism of intracontinental mountain building. We study 3D crust and the uppermost mantle structure beneath Tian Shan region using ambient noise and earthquake surface waves. Our dataset includes vertical component records of 62 permanent broadband seismic stations operated by the Earthquake Administration of China. Firstly, we calculate two-year stacked Cross-Correlation Functions (CCFs) of ambient noise records between the stations. The CCFs are treated as the Empirical Green's Functions (EGFs) of each station pair, from which we measured phase velocities of fundamental-mode Rayleigh wave in the period of 3-40 s using a frequency-time analysis method. Secondly, we collect surface wave data from tele-seismic events with Mw > 5.5 and depth shallower than 200 km and measure phase velocities of the fundamental-mode of Rayleigh wave in the period of 30-150 s using a two-station method. Finally, we combine the phase velocity measurements from ambient noise and earthquake surface waves, obtain lateral isotropic phase velocity maps at different periods based on tomography and invert a 3D Vsv model of crust and uppermost mantle down to about 150 km using a Monte Carlo Inversion method. We will discuss our inversion results in detail, as well as their implications to the tectonics in the region.

Slow Feature Analysis on Retinal Waves Leads to V1 Complex Cells

PubMed Central

Dähne, Sven; Wilbert, Niko; Wiskott, Laurenz

2014-01-01

The developing visual system of many mammalian species is partially structured and organized even before the onset of vision. Spontaneous neural activity, which spreads in waves across the retina, has been suggested to play a major role in these prenatal structuring processes. Recently, it has been shown that when employing an efficient coding strategy, such as sparse coding, these retinal activity patterns lead to basis functions that resemble optimal stimuli of simple cells in primary visual cortex (V1). Here we present the results of applying a coding strategy that optimizes for temporal slowness, namely Slow Feature Analysis (SFA), to a biologically plausible model of retinal waves. Previously, SFA has been successfully applied to model parts of the visual system, most notably in reproducing a rich set of complex-cell features by training SFA with quasi-natural image sequences. In the present work, we obtain SFA units that share a number of properties with cortical complex-cells by training on simulated retinal waves. The emergence of two distinct properties of the SFA units (phase invariance and orientation tuning) is thoroughly investigated via control experiments and mathematical analysis of the input-output functions found by SFA. The results support the idea that retinal waves share relevant temporal and spatial properties with natural visual input. Hence, retinal waves seem suitable training stimuli to learn invariances and thereby shape the developing early visual system such that it is best prepared for coding input from the natural world. PMID:24810948

Structure of the spatial periphery of the {sup 11}Li and {sup 11}Be isobars

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

Galanina, L. I., E-mail: galan-lidiya@mail.ru; Zelenskaya, N. S.

2016-07-15

On the basis of the shell model with an extended basis, the structure of {sup 9}Li-{sup 9}Be to {sup 11}Li-{sup 11}Be nuclei is examined with allowance for the competition of {sup jj} coupling and Majorana exchange forces via considering the sequential addition of neutrons, and the respective wave functions are determined. A formalism for calculating the spectroscopic factor for a dineutron and for individual neutrons in nuclei whose wave functions incorporate the mixing of shell configurations is developed. The reactions {sup 9}Li(t, p){sup 11}Li and {sup 9}Be(t, p){sup 11}Be treated with allowance for the mechanisms of dineutron stripping and amore » sequential transfer of two neutrons are considered as an indicator of the proposed structure of lithium and berylliumisotopes. The parameters of the optical potentials, the wave functions for the bound states of transferred particles, and the interaction potentials corresponding to them are determined from a comparison of the theoretical angular distribution of protons from the reaction {sup 9}Be(t, p){sup 11}Be with its experimental counterpart. It is shown that a dineutron periphery of size about 6.4 fm is present in the {sup 11}Li nucleus and that a single-neutron periphery of size about 8 fm is present in the {sup 11}Be nucleus.« less

Test of high-resolution 3D P-wave velocity model of Poland by back-azimuthal sections of teleseismic receiver function

NASA Astrophysics Data System (ADS)

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

2015-04-01

Geological and seismic structure under area of Poland is well studied by over one hundred thousand boreholes, over thirty deep seismic refraction and wide angle reflection profiles and by vertical seismic profiling, magnetic, gravity, magnetotelluric and thermal methods. Compilation of these studies allowed to create a high-resolution 3D P-wave velocity model down to 60 km depth in the area of Poland (Polkowski et al. 2014). Model also provides details about the geometry of main layers of sediments (Tertiary and Quaternary, Cretaceous, Jurassic, Triassic, Permian, old Paleozoic), consolidated/crystalline crust (upper, middle and lower) and uppermost mantle. This model gives an unique opportunity for calculation synthetic receiver function and compering it with observed receiver function calculated for permanent and temporary seismic stations. Modified ray-tracing method (Langston, 1977) can be used directly to calculate the response of the structure with dipping interfaces to the incoming plane wave with fixed slowness and back-azimuth. So, 3D P-wave velocity model has been interpolated to 2.5D P-wave velocity model beneath each seismic station and back-azimuthal sections of components of receiver function have been calculated. Vp/Vs ratio is assumed to be 1.8, 1.67, 1.73, 1.77 and 1.8 in the sediments, upper/middle/lower consolidated/crystalline crust and uppermost mantle, respectively. Densities were calculated with combined formulas of Berteussen (1977) and Gardner et al. (1974). Additionally, to test a visibility of the lithosphere-asthenosphere boundary phases at receiver function sections models have been extended to 250 km depth based on P4-mantle model (Wilde-Piórko et al., 2010). National Science Centre Poland provided financial support for this work by NCN grant DEC-2011/02/A/ST10/00284 and by NCN grant UMO-2011/01/B/ST10/06653.

Interplay between arterial stiffness and diastolic function: a marker of ventricular-vascular coupling.

PubMed

Zito, Concetta; Mohammed, Moemen; Todaro, Maria Chiara; Khandheria, Bijoy K; Cusmà-Piccione, Maurizio; Oreto, Giuseppe; Pugliatti, Pietro; Abusalima, Mohamed; Antonini-Canterin, Francesco; Vriz, Olga; Carerj, Scipione

2014-11-01

We evaluated the interplay between left ventricular diastolic function and large-artery stiffness in asymptomatic patients at increased risk of heart failure and no structural heart disease (Stage A). We divided 127 consecutive patients (mean age 49 ± 17 years) with risk factors for heart failure who were referred to our laboratory to rule out structural heart disease into two groups according to presence (Group 1, n = 35) or absence (Group 2, n = 92) of grade I left ventricular diastolic dysfunction. Doppler imaging with high-resolution echo-tracking software was used to measure intima-media thickness (IMT) and stiffness of carotid arteries. Group 1 had significantly higher mean age, blood pressure, left ventricular mass index, carotid IMT and arterial stiffness than Group 2 (P < 0.05). Overall, carotid stiffness indices (β-stiffness index, augmentation index and elastic modulus) and 'one-point' pulse wave velocity each showed inverse correlation with E-wave velocity, E' velocity and E/A ratio, and direct correlation with A-wave velocity, E-wave deceleration time and E/E' ratio (P < 0.05). Arterial compliance showed negative correlations with the echocardiographic indices of left ventricular diastolic function (P < 0.05). On logistic regression analysis, age, hypertension, SBP, pulse pressure, left ventricular mass index, carotid IMT and stiffness parameters were associated with grade I left ventricular diastolic dysfunction (P < 0.05 for each). However, on multivariate logistic analysis, only 'one-point' pulse wave velocity and age were independent predictors (P = 0.038 and P = 0.016, respectively). An independent association between grade I left ventricular diastolic dysfunction and increased arterial stiffness is demonstrated at the earliest stage of heart failure. Hence, assessment of vascular function, beyond cardiac function, should be included in a comprehensive clinical evaluation of these patients.

Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter

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

Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter: Preprint

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

Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

Structure of Kinetic Alfvén Waves of Small Transverse Scale

NASA Astrophysics Data System (ADS)

Morales, G. J.; Maggs, J. E.

1996-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension R transverse to the confining magnetic field is comparable to cs / Ω_i. The radial structure of the wave azimuthal magnetic field consists of 3 regions: a Bessel function behavior for r < R, a near null at r ~ R, and a driven Airy pattern for r >> R. The pattern spreads at an angle given by tan θ = (ω/Ω_i)(c_s/V_A)/(2 \\cdot 6), where ω is the modulation frequency and VA the Alfvén speed. This arises because there is a maximum value at finite k_⊥ for the ratio of the perpendicular to parallel group velocity, which differs from the cone spreading(G.J. Morales, R.S. Loritsch, and J.E. Maggs, Phys. Plasmas) 1, 3765 (1994) associated with inertial Alfvén waves. Sponsored by ONR

Introduction to Density Functional Theory: Calculations by Hand on the Helium Atom

ERIC Educational Resources Information Center

Baseden, Kyle A.; Tye, Jesse W.

2014-01-01

Density functional theory (DFT) is a type of electronic structure calculation that has rapidly gained popularity. In this article, we provide a step-by-step demonstration of a DFT calculation by hand on the helium atom using Slater's X-Alpha exchange functional on a single Gaussian-type orbital to represent the atomic wave function. This DFT…

The effects of core-reflected waves on finite fault inversions with teleseismic body wave data

NASA Astrophysics Data System (ADS)

Qian, Yunyi; Ni, Sidao; Wei, Shengji; Almeida, Rafael; Zhang, Han

2017-11-01

Teleseismic body waves are essential for imaging rupture processes of large earthquakes. Earthquake source parameters are usually characterized by waveform analyses such as finite fault inversions using only turning (direct) P and SH waves without considering the reflected phases from the core-mantle boundary (CMB). However, core-reflected waves such as ScS usually have amplitudes comparable to direct S waves due to the total reflection from the CMB and might interfere with the S waves used for inversion, especially at large epicentral distances for long duration earthquakes. In order to understand how core-reflected waves affect teleseismic body wave inversion results, we develop a procedure named Multitel3 to compute Green's functions that contain turning waves (direct P, pP, sP, direct S, sS and reverberations in the crust) and core-reflected waves (PcP, pPcP, sPcP, ScS, sScS and associated reflected phases from the CMB). This ray-based method can efficiently generate synthetic seismograms for turning and core-reflected waves independently, with the flexibility to take into account the 3-D Earth structure effect on the timing between these phases. The performance of this approach is assessed through a series of numerical inversion tests on synthetic waveforms of the 2008 Mw7.9 Wenchuan earthquake and the 2015 Mw7.8 Nepal earthquake. We also compare this improved method with the turning-wave only inversions and explore the stability of the new procedure when there are uncertainties in a priori information (such as fault geometry and epicentre location) or arrival time of core-reflected phases. Finally, a finite fault inversion of the 2005 Mw8.7 Nias-Simeulue earthquake is carried out using the improved Green's functions. Using enhanced Green's functions yields better inversion results as expected. While the finite source inversion with conventional P and SH waves is able to recover large-scale characteristics of the earthquake source, by adding PcP and ScS phases, the inverted slip model and moment rate function better match previous results incorporating field observations, geodetic and seismic data.

Multi-spectral Metasurface for Different Functional Control of Reflection Waves.

PubMed

Huang, Cheng; Pan, Wenbo; Ma, Xiaoliang; Luo, Xiangang

2016-03-22

Metasurface have recently generated much interest due to its strong manipulation of electromagnetic wave and its easy fabrication compared to bulky metamaterial. Here, we propose the design of a multi-spectral metasurface that can achieve beam deflection and broadband diffusion simultaneously at two different frequency bands. The metasurface is composed of two-layered metallic patterns backed by a metallic ground plane. The top-layer metasurface utilizes the cross-line structures with two different dimensions for producing 0 and π reflection phase response, while the bottom-layer metasurface is realized by a topological morphing of the I-shaped patterns for creating the gradient phase distribution. The whole metasurface is demonstrated to independently control the reflected waves to realize different functions at two bands when illuminated by a normal linear-polarized wave. Both simulation and experimental results show that the beam deflection is achieved at K-band with broadband diffusion at X-Ku band.

Multi-spectral Metasurface for Different Functional Control of Reflection Waves

PubMed Central

Huang, Cheng; Pan, Wenbo; Ma, Xiaoliang; Luo, Xiangang

2016-01-01

Metasurface have recently generated much interest due to its strong manipulation of electromagnetic wave and its easy fabrication compared to bulky metamaterial. Here, we propose the design of a multi-spectral metasurface that can achieve beam deflection and broadband diffusion simultaneously at two different frequency bands. The metasurface is composed of two-layered metallic patterns backed by a metallic ground plane. The top-layer metasurface utilizes the cross-line structures with two different dimensions for producing 0 and π reflection phase response, while the bottom-layer metasurface is realized by a topological morphing of the I-shaped patterns for creating the gradient phase distribution. The whole metasurface is demonstrated to independently control the reflected waves to realize different functions at two bands when illuminated by a normal linear-polarized wave. Both simulation and experimental results show that the beam deflection is achieved at K-band with broadband diffusion at X-Ku band. PMID:27001206

Faraday waves under time-reversed excitation.

PubMed

Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas

2013-03-01

Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.

Evaluating the Potential for Marine and Hydrokinetic Devices to Act As Artificial Reefs or Fish Aggregating Devices

NASA Astrophysics Data System (ADS)

Kramer, S.; Nelson, P.

2016-02-01

Wave energy converters (WECs) and tidal energy converters (TECs) are only beginning to be deployed along the U.S. West Coast and in Hawai'i, and a better understanding of their ecological effects on fish, particularly on special status fish is needed to facilitate project siting, design and environmental permitting. The structures of WECs and TECs placed on to the seabed, such as anchors and foundations, may function as artificial reefs that attract reef associated fishes, while the midwater and surface structures, such as mooring lines, buoys, and wave or tidal power devices, may function as fish aggregating devices (FADs). We evaluated these potential ecological interactions by comparing them to surrogate structures, such as artificial reefs, natural reefs, kelp vegetation, floating and sunken debris, oil and gas platforms, anchored FADs deployed to enhance fishing opportunities, net cages used for mariculture, and piers and marinas. We also conducted guided discussions with scientists and resource managers to provide unpublished observations. Our findings indicate the structures of WECs and TECs placed on or near the seabed in coastal waters of the U.S. West Coast and Hawai`i likely will function as small scale artificial reefs and attract potentially high densities of reef associated fishes and the midwater and surface structures of WECs placed in the tropical waters of Hawai`i likely will function as de facto FADs.

An estimate of equatorial wave energy flux at 9- to 90-day periods in the Central Pacific

NASA Technical Reports Server (NTRS)

Eriksen, Charles C.; Richman, James G.

1988-01-01

Deep fluctuations in current along the equator in the Central Pacific are dominated by coherent structures which correspond closely to narrow-band propagating equatorial waves. Currents were measured roughly at 1500 and 3000 m depths at five moorings between 144 and 148 deg W from January 1981 to March 1983, as part of the Pacific Equatorial Ocean Dynamics program. In each frequency band resolved, a single complex empirical orthogonal function accounts for half to three quarters of the observed variance in either zonal or meridional current. Dispersion for equatorial first meridional Rossby and Rossby gravity waves is consistent with the observed vertical-zonal coherence structure. The observations indicate that energy flux is westward and downward in long first meridional mode Rossby waves at periods 45 days and longer, and eastward and downward in short first meridional mode Rossby waves and Rossby-gravity waves at periods 30 days and shorter. A local minimum in energy flux occurs at periods corresponding to a maximum in upper-ocean meridional current energy contributed by tropical instability waves. Total vertical flux across the 9- to 90-day period range is 2.5 kW/m.

Noise-based body-wave seismic tomography in an active underground mine.

NASA Astrophysics Data System (ADS)

Olivier, G.; Brenguier, F.; Campillo, M.; Lynch, R.; Roux, P.

2014-12-01

Over the last decade, ambient noise tomography has become increasingly popular to image the earth's upper crust. The seismic noise recorded in the earth's crust is dominated by surface waves emanating from the interaction of the ocean with the solid earth. These surface waves are low frequency in nature ( < 1 Hz) and not usable for imaging smaller structures associated with mining or oil and gas applications. The seismic noise recorded at higher frequencies are typically from anthropogenic sources, which are short lived, spatially unstable and not well suited for constructing seismic Green's functions between sensors with conventional cross-correlation methods. To examine the use of ambient noise tomography for smaller scale applications, continuous data were recorded for 5 months in an active underground mine in Sweden located more than 1km below surface with 18 high frequency seismic sensors. A wide variety of broadband (10 - 3000 Hz) seismic noise sources are present in an active underground mine ranging from drilling, scraping, trucks, ore crushers and ventilation fans. Some of these sources generate favorable seismic noise, while others are peaked in frequency and not usable. In this presentation, I will show that the noise generated by mining activity can be useful if periods of seismic noise are carefully selected. Although noise sources are not temporally stable and not evenly distributed around the sensor array, good estimates of the seismic Green's functions between sensors can be retrieved for a broad frequency range (20 - 400 Hz) when a selective stacking scheme is used. For frequencies below 100 Hz, the reconstructed Green's functions show clear body-wave arrivals for almost all of the 153 sensor pairs. The arrival times of these body-waves are picked and used to image the local velocity structure. The resulting 3-dimensional image shows a high velocity structure that overlaps with a known ore-body. The material properties of the ore-body differ from the host rock and is likely the cause of the observed high velocity structure. For frequencies above 200 Hz, the seismic waves are multiply scattered by the tunnels and excavations and used to determine the scattering properties of the medium. The results of this study should be useful for future imaging and exploration projects in mining and oil and gas industries.

Elucidating the role of surface passivating ligand structural parameters in hole wave function delocalization in semiconductor cluster molecules.

PubMed

Teunis, Meghan B; Nagaraju, Mulpuri; Dutta, Poulami; Pu, Jingzhi; Muhoberac, Barry B; Sardar, Rajesh; Agarwal, Mangilal

2017-09-28

This article describes the mechanisms underlying electronic interactions between surface passivating ligands and (CdSe) 34 semiconductor cluster molecules (SCMs) that facilitate band-gap engineering through the delocalization of hole wave functions without altering their inorganic core. We show here both experimentally and through density functional theory calculations that the expansion of the hole wave function beyond the SCM boundary into the ligand monolayer depends not only on the pre-binding energetic alignment of interfacial orbitals between the SCM and surface passivating ligands but is also strongly influenced by definable ligand structural parameters such as the extent of their π-conjugation [π-delocalization energy; pyrene (Py), anthracene (Anth), naphthalene (Naph), and phenyl (Ph)], binding mode [dithiocarbamate (DTC, -NH-CS 2 - ), carboxylate (-COO - ), and amine (-NH 2 )], and binding head group [-SH, -SeH, and -TeH]. We observe an unprecedentedly large ∼650 meV red-shift in the lowest energy optical absorption band of (CdSe) 34 SCMs upon passivating their surface with Py-DTC ligands and the trend is found to be Ph- < Naph- < Anth- < Py-DTC. This shift is reversible upon removal of Py-DTC by triethylphosphine gold(i) chloride treatment at room temperature. Furthermore, we performed temperature-dependent (80-300 K) photoluminescence lifetime measurements, which show longer lifetime at lower temperature, suggesting a strong influence of hole wave function delocalization rather than carrier trapping and/or phonon-mediated relaxation. Taken together, knowledge of how ligands electronically interact with the SCM surface is crucial to semiconductor nanomaterial research in general because it allows the tuning of electronic properties of nanomaterials for better charge separation and enhanced charge transfer, which in turn will increase optoelectronic device and photocatalytic efficiencies.

Picture of the global field of quasi-monochromatic gravity waves observed by stratospheric balloons and MST radars

NASA Technical Reports Server (NTRS)

Yamanaka, M. D.

1989-01-01

In MAP observations, it was found that: (1) gravity waves in selected or filtered portions of data are fit for monochromatic structures, whereas (2) those in fully continuous and resolved observations take universal continuous spectra. It is possible to explain (2) by dispersion of quasi-monochromatic (or slowly varying) wave packets observed locally as (1), since the medium atmosphere is unsteady and nonuniform. Complete verification of the wave-mean flow interactions by tracking individual wave packets seems hopeless, because the wave induced flow cannot be distinguished from the basic flow independent of the waves. Instead, the primitive picture is looked at before MAP, that is, the atmosphere is just like an entertainment stage illuminated by cocktail lights of quasi-monochromatic gravity waves. The wave parameters are regarded as functions of time and spatial coordinates. The observational evidences (1) and (2) suggest that the wave parameter field is rather homogeneous, which can be explained by interference of quasi-monochromatic wave packets.

The crustal thickness and lithospheric structure of active and inactive volcanic arc terrains in Fiji and Tonga

NASA Astrophysics Data System (ADS)

Chen, J.; Wiens, D.; Wei, S. S.; Zha, Y.; Julià, J.; Cai, C.; Chen, Y. J.

2015-12-01

In order to investigate the crustal thickness and lithospheric structure beneath active and inactive volcanic arcs in Fiji and Tonga, we analyzed receiver functions from teleseismic P waves as well as Rayleigh waves from teleseismic earthquakes and ambient noise. The data were recorded by stations from three previous temporary seismic arrays deployed on the islands during 1993-1995, 2001-2002, and 2009-2010. Receiver functions were calculated with an iterative deconvolution in the time domain. We used an H-k stacking method to get preliminary Moho depth estimates under the island arcs, after assuming constant seismic average crustal P velocity. We also determined the shear wave velocity structure beneath each station from a 1-D combined inversion of receiver functions and Rayleigh wave phase velocity dispersion curves from ambient noise cross correlation at 8s - 20s and teleseismic surface waves at 20s-90s. The joint inversion models reveal that the Moho beneath the main islands of the Fiji plateau is 26-31 km deep, whereas the crust under the outer islands - including the Lau Ridge - is generally thinner, with Moho depths of 21-23.5 km. The thinnest crust (16 km) is found beneath Moala Island located between the Fiji Platform and the Lau Ridge. Crustal thickness beneath several Tonga islands is about 18-20 km. A relatively high velocity lithosphere (Vs of 4.4 - 4.5 km/s) extends to only about 60 km depth beneath the outer Fiji Islands and Lau Ridge, but to depths of 90 km underneath the main islands of the Fiji Plateau. The much thicker crust and lithosphere of the Fiji plateau relative to the Lau Ridge and Tonga Arc reflects its much longer geological history of arc crust building, going back to the early Miocene.

A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitating Fluxes

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.

2002-01-01

Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.

A New Algorithm with Plane Waves and Wavelets for Random Velocity Fields with Many Spatial Scales

NASA Astrophysics Data System (ADS)

Elliott, Frank W.; Majda, Andrew J.

1995-03-01

A new Monte Carlo algorithm for constructing and sampling stationary isotropic Gaussian random fields with power-law energy spectrum, infrared divergence, and fractal self-similar scaling is developed here. The theoretical basis for this algorithm involves the fact that such a random field is well approximated by a superposition of random one-dimensional plane waves involving a fixed finite number of directions. In general each one-dimensional plane wave is the sum of a random shear layer and a random acoustical wave. These one-dimensional random plane waves are then simulated by a wavelet Monte Carlo method for a single space variable developed recently by the authors. The computational results reported in this paper demonstrate remarkable low variance and economical representation of such Gaussian random fields through this new algorithm. In particular, the velocity structure function for an imcorepressible isotropic Gaussian random field in two space dimensions with the Kolmogoroff spectrum can be simulated accurately over 12 decades with only 100 realizations of the algorithm with the scaling exponent accurate to 1.1% and the constant prefactor accurate to 6%; in fact, the exponent of the velocity structure function can be computed over 12 decades within 3.3% with only 10 realizations. Furthermore, only 46,592 active computational elements are utilized in each realization to achieve these results for 12 decades of scaling behavior.

Subwavelength diffractive acoustics and wavefront manipulation with a reflective acoustic metasurface

NASA Astrophysics Data System (ADS)

Wang, Wenqi; Xie, Yangbo; Popa, Bogdan-Ioan; Cummer, Steven A.

2016-11-01

Acoustic metasurfaces provide useful wavefront shaping capabilities, such as beam steering, acoustic focusing, and asymmetric transmission, in a compact structure. Most acoustic metasurfaces described in the literature are transmissive devices and focus their performance on steering sound beam of the fundamental diffractive order. In addition, the range of incident angles studied is usually below the critical incidence predicted by generalized Snell's law of reflection. In this work, we comprehensively analyze the wave interaction with a generic periodic phase-modulating structure in order to predict the behavior of all diffractive orders, especially for cases beyond critical incidence. Under the guidance of the presented analysis, a broadband reflective metasurface is designed based on an expanded library of labyrinthine acoustic metamaterials. Various local and nonlocal wavefront shaping properties are experimentally demonstrated, and enhanced absorption of higher order diffractive waves is experimentally shown for the first time. The proposed methodology provides an accurate approach for predicting practical diffracted wave behaviors and opens a new perspective for the study of acoustic periodic structures. The designed metasurface extends the functionalities of acoustic metasurfaces and paves the way for the design of thin planar reflective structures for broadband acoustic wave manipulation and extraordinary absorption.

RELATIVE ACTIN NUCLEATION PROMOTION EFFICIENCY BY WASP AND WAVE PROTEINS IN ENDOTHELIAL CELLS

PubMed Central

Kang, Hyeran; Wang, Jingjing; Longley, Sarah J.; Tang, Jay X.; Shaw, Sunil K.

2010-01-01

The mammalian genome encodes multiple WASP1 (Wiskott-Aldrich Syndrome Protein)/WAVE (WASP-family Verprolin homologous) proteins. Members of this family interact with the Arp (actin related protein) 2/3 complex to promote growth of a branched actin network near the plasma membrane or the surface of moving cargos. Arp2/3 mediated branching can further lead to formation of comet tails (actin rockets). Despite their similar domain structure, different WASP/WAVE family members fulfill unique functions that depend on their subcellular location and activity levels. We measured the relative efficiency of actin nucleation promotion of full length WASP/WAVE proteins in a cytoplasmic extract from primary human umbilical vein endothelial cells (HUVEC). In this assay WAVE2 and WAVE3 complexes showed higher nucleation efficiency than WAVE1 and N-WASP, indicating distinct cellular controls for different family members. Previously, WASP and N-WASP were the only members that were known to stimulate comet formation. We observed that in addition to N-WASP, WAVE3 also induced short actin tails, and the other WAVEs induced formation of asymmetric actin shells. Differences in shape and structure of actin-based growth may reflect varying ability of WASP/WAVE proteins to break symmetry of the actin shell, possibly by differential recruitment of actin bundling or severing (pruning or debranching) factors. PMID:20816932

Seismic Barrier Protection of Critical Infrastructure from Earthquakes

DTIC Science & Technology

2017-05-01

structure composed of opposing boreholes or trenches to mitigate seismic waves from diffracting and traveling in the vertical plane. Computational...dams, etc., pose significant risk to civilians while adding tremendous cost and recovery time to regain their functionality. Lower energy earthquakes...the most destructive are surface waves (Rayleigh, Love, shear) which can travel great distances in the far field from the earthquake hypocenter and

First measurement of the beam asymmetry in photoproduction off the proton near threshold

NASA Astrophysics Data System (ADS)

Levi Sandri, P.; Mandaglio, G.; De Leo, V.; Bartalini, O.; Bellini, V.; Bocquet, J.-P.; Capogni, M.; Curciarello, F.; Didelez, J.-P.; D'Angelo, A.; Di Salvo, R.; Fantini, A.; Franco, D.; Gervino, G.; Ghio, F.; Girolami, B.; Giusa, A.; Lapik, A.; Lleres, A.; Mammoliti, F.; Manganaro, M.; Moricciani, D.; Mushkarenkov, A.; Nedorezov, V.; Randieri, C.; Rebreyend, D.; Rudnev, N.; Russo, G.; Schaerf, C.; Sperduto, M.-L.; Sutera, M.-C.; Turinge, A.; Vegna, V.; Zonta, I.

2015-07-01

The beam asymmetry in photoproduction off the proton was measured at the GrAAL polarised photon beam with incoming photon energies of 1.461 and 1.480 GeV. For both energies the asymmetry as a function of the meson production angle shows a clear structure, more pronounced at the lowest one, with a change of sign around . The observed behaviour is compatible with P-wave D-wave (or S-wave F-wave) interference, the closer to threshold the stronger. The results are compared to the existing state-of-the-art calculations that fail to account for the data.

Ultrasound finite element simulation sensitivity to anisotropic titanium microstructures

NASA Astrophysics Data System (ADS)

Freed, Shaun; Blackshire, James L.; Na, Jeong K.

2016-02-01

Analytical wave models are inadequate to describe complex metallic microstructure interactions especially for near field anisotropic property effects and through geometric features smaller than the wavelength. In contrast, finite element ultrasound simulations inherently capture microstructure influences due to their reliance on material definitions rather than wave descriptions. To better understand and quantify heterogeneous crystal orientation effects to ultrasonic wave propagation, a finite element modeling case study has been performed with anisotropic titanium grain structures. A parameterized model has been developed utilizing anisotropic spheres within a bulk material. The resulting wave parameters are analyzed as functions of both wavelength and sphere to bulk crystal mismatch angle.

Auto Correlation Analysis of Coda Waves from Local Earthquakes for Detecting Temporal Changes in Shallow Subsurface Structures: the 2011 Tohoku-Oki, Japan Earthquake

NASA Astrophysics Data System (ADS)

Nakahara, Hisashi

2015-02-01

For monitoring temporal changes in subsurface structures I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Use of coda waves requires earthquakes resulting in decreased time resolution for monitoring. Nonetheless, it may be possible to monitor subsurface structures in sufficient time resolutions in regions with high seismicity. In studying the 2011 Tohoku-Oki, Japan earthquake (Mw 9.0), for which velocity changes have been previously reported, I try to validate the method. KiK-net stations in northern Honshu are used in this analysis. For each moderate earthquake normalized auto correlation functions of surface records are stacked with respect to time windows in the S-wave coda. Aligning the stacked, normalized auto correlation functions with time, I search for changes in phases arrival times. The phases at lag times of <1 s are studied because changes at shallow depths are focused. Temporal variations in the arrival times are measured at the stations based on the stretching method. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. The amounts of the phase delays are 10 % on average with the maximum of about 50 % at some stations. The deconvolution analysis using surface and subsurface records at the same stations is conducted for validation. The results show the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percent, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable in detecting larger changes. In spite of these disadvantages, this analysis is still attractive because it can be applied to many records on the surface in regions where no boreholes are available.

Riccati parameterized self-similar waves in two-dimensional graded-index waveguide

NASA Astrophysics Data System (ADS)

Kumar De, Kanchan; Goyal, Amit; Raju, Thokala Soloman; Kumar, C. N.; Panigrahi, Prasanta K.

2015-04-01

An analytical method based on gauge-similarity transformation technique has been employed for mapping a (2+1)- dimensional variable coefficient coupled nonlinear Schrödinger equations (vc-CNLSE) with dispersion, nonlinearity and gain to standard NLSE. Under certain functional relations we construct a large family of self-similar waves in the form of bright similaritons, Akhmediev breathers and rogue waves. We report the effect of dispersion on the intensity of the solitary waves. Further, we illustrate the procedure to amplify the intensity of self-similar waves using isospectral Hamiltonian approach. This approach provides an efficient mechanism to generate analytically a wide class of tapering profiles and widths by exploiting the Riccati parameter. Equivalently, it enables one to control efficiently the self-similar wave structures and hence their evolution.

Adsorbate Diffusion on Transition Metal Nanoparticles

DTIC Science & Technology

2015-01-01

different sizes and shapes using density functional theory calculations. We show that nanoparticles bind adsorbates more strongly than the...structure theoretical methods, a quantitative study with accurate density functional theory (DFT) calculations is still missing. Here, we perform a...functional theory . The projector augmented wave (PAW) potentials29,30 were used for electron- ion interactions and the generalized gradient approximation

Label-free imaging of the native, living cellular nanoarchitecture using partial-wave spectroscopic microscopy

PubMed Central

Almassalha, Luay M.; Bauer, Greta M.; Chandler, John E.; Gladstein, Scott; Cherkezyan, Lusik; Stypula-Cyrus, Yolanda; Weinberg, Samuel; Zhang, Di; Thusgaard Ruhoff, Peder; Roy, Hemant K.; Subramanian, Hariharan; Chandel, Navdeep S.; Szleifer, Igal; Backman, Vadim

2016-01-01

The organization of chromatin is a regulator of molecular processes including transcription, replication, and DNA repair. The structures within chromatin that regulate these processes span from the nucleosomal (10-nm) to the chromosomal (>200-nm) levels, with little known about the dynamics of chromatin structure between these scales due to a lack of quantitative imaging technique in live cells. Previous work using partial-wave spectroscopic (PWS) microscopy, a quantitative imaging technique with sensitivity to macromolecular organization between 20 and 200 nm, has shown that transformation of chromatin at these length scales is a fundamental event during carcinogenesis. As the dynamics of chromatin likely play a critical regulatory role in cellular function, it is critical to develop live-cell imaging techniques that can probe the real-time temporal behavior of the chromatin nanoarchitecture. Therefore, we developed a live-cell PWS technique that allows high-throughput, label-free study of the causal relationship between nanoscale organization and molecular function in real time. In this work, we use live-cell PWS to study the change in chromatin structure due to DNA damage and expand on the link between metabolic function and the structure of higher-order chromatin. In particular, we studied the temporal changes to chromatin during UV light exposure, show that live-cell DNA-binding dyes induce damage to chromatin within seconds, and demonstrate a direct link between higher-order chromatin structure and mitochondrial membrane potential. Because biological function is tightly paired with structure, live-cell PWS is a powerful tool to study the nanoscale structure–function relationship in live cells. PMID:27702891

Brønsted acidity of protic ionic liquids: a modern ab initio valence bond theory perspective.

PubMed

Patil, Amol Baliram; Mahadeo Bhanage, Bhalchandra

2016-09-21

Room temperature ionic liquids (ILs), especially protic ionic liquids (PILs), are used in many areas of the chemical sciences. Ionicity, the extent of proton transfer, is a key parameter which determines many physicochemical properties and in turn the suitability of PILs for various applications. The spectrum of computational chemistry techniques applied to investigate ionic liquids includes classical molecular dynamics, Monte Carlo simulations, ab initio molecular dynamics, Density Functional Theory (DFT), CCSD(t) etc. At the other end of the spectrum is another computational approach: modern ab initio Valence Bond Theory (VBT). VBT differs from molecular orbital theory based methods in the expression of the molecular wave function. The molecular wave function in the valence bond ansatz is expressed as a linear combination of valence bond structures. These structures include covalent and ionic structures explicitly. Modern ab initio valence bond theory calculations of representative primary and tertiary ammonium protic ionic liquids indicate that modern ab initio valence bond theory can be employed to assess the acidity and ionicity of protic ionic liquids a priori.

Derivation of force field parameters for SnO2-H2O surface systems from plane-wave density functional theory calculations.

PubMed

Bandura, A V; Sofo, J O; Kubicki, J D

2006-04-27

Plane-wave density functional theory (DFT-PW) calculations were performed on bulk SnO2 (cassiterite) and the (100), (110), (001), and (101) surfaces with and without H2O present. A classical interatomic force field has been developed to describe bulk SnO2 and SnO2-H2O surface interactions. Periodic density functional theory calculations using the program VASP (Kresse et al., 1996) and molecular cluster calculations using Gaussian 03 (Frisch et al., 2003) were used to derive the parametrization of the force field. The program GULP (Gale, 1997) was used to optimize parameters to reproduce experimental and ab initio results. The experimental crystal structure and elastic constants of SnO2 are reproduced reasonably well with the force field. Furthermore, surface atom relaxations and structures of adsorbed H2O molecules agree well between the ab initio and force field predictions. H2O addition above that required to form a monolayer results in consistent structures between the DFT-PW and classical force field results as well.

Dynamics of Proton Spin: Role of qqq Force

NASA Astrophysics Data System (ADS)

Mitra, A. N.

The analytic structure of the qqq wave function, obtained recently in the high momentum regime of QCD, is employed for the formulation of baryonic transition amplitudes via quark loops. A new aspect of this study is the role of a direct (Y -shaped, Mercedes-Benz type) qqq force in generating the qqq wave function The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. The dynamics of this 3-body force shows up through a characteristic singularity in the hypergeometric differential equation for the 3D wave function ϕ, corresponding to a negative eigenvalue of the spin operator iσ1·σ2 × σ3 which is an integral part of the qqq force. As a first application of this wave function to the problem of the proton spin anomaly, the two-gluon contribution to the anomaly yields an estimate of the right sign, although somewhat smaller in magnitude.

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.

Spatial coherence resonance and spatial pattern transition induced by the decrease of inhibitory effect in a neuronal network

NASA Astrophysics Data System (ADS)

Tao, Ye; Gu, Huaguang; Ding, Xueli

2017-10-01

Spiral waves were observed in the biological experiment on rat brain cortex with the application of carbachol and bicuculline which can block inhibitory coupling from interneurons to pyramidal neurons. To simulate the experimental spiral waves, a two-dimensional neuronal network composed of pyramidal neurons and inhibitory interneurons was built. By decreasing the percentage of active inhibitory interneurons, the random-like spatial patterns change to spiral waves and to random-like spatial patterns or nearly synchronous behaviors. The spiral waves appear at a low percentage of inhibitory interneurons, which matches the experimental condition that inhibitory couplings of the interneurons were blocked. The spiral waves exhibit a higher order or signal-to-noise ratio (SNR) characterized by spatial structure function than both random-like spatial patterns and nearly synchronous behaviors, which shows that changes of the percentage of active inhibitory interneurons can induce spatial coherence resonance-like behaviors. In addition, the relationship between the coherence degree and the spatial structures of the spiral waves is identified. The results not only present a possible and reasonable interpretation to the spiral waves observed in the biological experiment on the brain cortex with disinhibition, but also reveal that the spiral waves exhibit more ordered degree in spatial patterns.

Superluminal and negative delay times in isotropic-anisotropic one-dimensional photonic crystal

NASA Astrophysics Data System (ADS)

Ouchani, N.; El Moussaouy, A.; Aynaou, H.; El Hassouani, Y.; El Boudouti, E. H.; Djafari-Rouhani, B.

2017-11-01

In this work, we investigate the possibility of superluminal and negative delay times for electromagnetic wave propagation in a linear and passive periodic structure consisting of alternating isotropic and anisotropic media. This phenomenon is due to the birefringence of the anisotropic layers of the structure. By adjusting the orientations of these layers, the delay times of transmitted waves can be controlled from subluminality to superluminality and vice versa. Numerical results indicate that the apparent superluminal propagation of light occurs inside the photonic band-gaps when the principal axes of the anisotropic layers are parallel or perpendicular to the fixed axes. For other orientations of these layers, tunneling and superluminal regimes appear inside the photonic bandgaps and in the allowed bands for frequencies close to the transmission minima. The effect of the number of unit cells of the photonic crystal structure on the propagation of light with superluminal and negative delay times is also investigated. We show that the structure exhibits the Hartman effect in which the tunneling delay time of the electromagnetic wave through the photonic band-gap of the structure converges asymptotically to a finite value with increasing the number of layers. The Green's function approach has been used to derive the transmission and reflection coefficients, the density of states, and the delay times of electromagnetic waves propagating through the structure. The control of the magnitude and the sign of the delay time of light propagation represent a key point in slow and fast light technologies. The proposed structure in this study represents a new system for controlling the delay times of wave propagation without a need of active or non-linear media as well as lossy or asymmetric periodic structures.

Structural, elastic, electronic, optical and thermoelectric properties of the Zintl-phase Ae3AlAs3 (Ae = Sr, Ba)

NASA Astrophysics Data System (ADS)

Benahmed, A.; Bouhemadou, A.; Alqarni, B.; Guechi, N.; Al-Douri, Y.; Khenata, R.; Bin-Omran, S.

2018-05-01

First-principles calculations were performed to investigate the structural, elastic, electronic, optical and thermoelectric properties of the Zintl-phase Ae3AlAs3 (Ae = Sr, Ba) using two complementary approaches based on density functional theory. The pseudopotential plane-wave method was used to explore the structural and elastic properties whereas the full-potential linearised augmented plane wave approach was used to study the structural, electronic, optical and thermoelectric properties. The calculated structural parameters are in good consistency with the corresponding measured ones. The single-crystal and polycrystalline elastic constants and related properties were examined in details. The electronic properties, including energy band dispersions, density of states and charge-carrier effective masses, were computed using Tran-Blaha modified Becke-Johnson functional for the exchange-correlation potential. It is found that both studied compounds are direct band gap semiconductors. Frequency-dependence of the linear optical functions were predicted for a wide photon energy range up to 15 eV. Charge carrier concentration and temperature dependences of the basic parameters of the thermoelectric properties were explored using the semi-classical Boltzmann transport model. Our calculations unveil that the studied compounds are characterised by a high thermopower for both carriers, especially the p-type conduction is more favourable.

Spectroscopy of Sound Transmission in Solid Samples

ERIC Educational Resources Information Center

Campbell, Dean J.; Peterson, Joshua P.; Fitzjarrald, Tamara J.

2013-01-01

These laboratory experiments are designed to familiarize students with concepts of spectroscopy by using sound waves. Topics covered in these experiments include the structure of nitinol alloys and polymer chain stiffness as a function of structure and temperature. Generally, substances that are stiffer or have higher symmetry at the molecular…

If It's Resonance, What is Resonating?

ERIC Educational Resources Information Center

Kerber, Robert C.

2006-01-01

The phenomenon under the name "resonance," which, is based on the mathematical analogy between mechanical resonance and the behavior of wave functions in quantum mechanical exchange phenomena was described. The resonating system does not have a structure intermediate between those involved in the resonance, but instead a structure which is further…

Application of magnetoelastic materials in spatiotemporally modulated phononic crystals for nonreciprocal wave propagation

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Attarzadeh, M. A.; Nouh, M.; Karami, M. Amin

2018-01-01

In this paper, a physical platform is proposed to change the properties of phononic crystals in space and time in order to achieve nonreciprocal wave transmission. The utilization of magnetoelastic materials in elastic phononic systems is studied. Material properties of magnetoelastic materials change significantly with an external magnetic field. This property is used to design systems with a desired wave propagation pattern. The properties of the magnetoelastic medium are changed in a traveling wave pattern, which changes in both space and time. A phononic crystal with such a modulation exhibits one-way wave propagation behavior. An extended transfer matrix method (TMM) is developed to model a system with time varying properties. The stop band and the pass band of a reciprocal and a nonreciprocal bar are found using this method. The TMM is used to find the transfer function of a magnetoelastic bar. The obtained results match those obtained via the theoretical Floquet-Bloch approach and numerical simulations. It is shown that the stop band in the transfer function of a system with temporal varying property for the forward wave propagation is different from the same in the backward wave propagation. The proposed configuration enables the physical realization of a class of smart structures that incorporates nonreciprocal wave propagation.

Soliton-cnoidal interactional wave solutions for the reduced Maxwell-Bloch equations

NASA Astrophysics Data System (ADS)

Huang, Li-Li; Qiao, Zhi-Jun; Chen, Yong

2018-02-01

Based on nonlocal symmetry method, localized excitations and interactional solutions are investigated for the reduced Maxwell-Bloch equations. The nonlocal symmetries of the reduced Maxwell-Bloch equations are obtained by the truncated Painleve expansion approach and the Mobious invariant property. The nonlocal symmetries are localized to a prolonged system by introducing suitable auxiliary dependent variables. The extended system can be closed and a novel Lie point symmetry system is constructed. By solving the initial value problems, a new type of finite symmetry transformations is obtained to derive periodic waves, Ma breathers and breathers travelling on the background of periodic line waves. Then rich exact interactional solutions are derived between solitary waves and other waves including cnoidal waves, rational waves, Painleve waves, and periodic waves through similarity reductions. In particular, several new types of localized excitations including rogue waves are found, which stem from the arbitrary function generated in the process of similarity reduction. By computer numerical simulation, the dynamics of these localized excitations and interactional solutions are discussed, which exhibit meaningful structures.

Self-consistent construction of virialized wave dark matter halos

NASA Astrophysics Data System (ADS)

Lin, Shan-Chang; Schive, Hsi-Yu; Wong, Shing-Kwong; Chiueh, Tzihong

2018-05-01

Wave dark matter (ψ DM ), which satisfies the Schrödinger-Poisson equation, has recently attracted substantial attention as a possible dark matter candidate. Numerical simulations have, in the past, provided a powerful tool to explore this new territory of possibility. Despite their successes in revealing several key features of ψ DM , further progress in simulations is limited, in that cosmological simulations so far can only address formation of halos below ˜2 ×1011 M⊙ and substantially more massive halos have become computationally very challenging to obtain. For this reason, the present work adopts a different approach in assessing massive halos by constructing wave-halo solutions directly from the wave distribution function. This approach bears certain similarities with the analytical construction of the particle-halo (cold dark matter model). Instead of many collisionless particles, one deals with one single wave that has many noninteracting eigenstates. The key ingredient in the wave-halo construction is the distribution function of the wave power, and we use several halos produced by structure formation simulations as templates to determine the wave distribution function. Among different models, we find the fermionic King model presents the best fits and we use it for our wave-halo construction. We have devised an iteration method for constructing the nonlinear halo and demonstrate its stability by three-dimensional simulations. A Milky Way-sized halo has also been constructed, and the inner halo is found to be flatter than the NFW profile. These wave-halos have small-scale interferences both in space and time producing time-dependent granules. While the spatial scale of granules varies little, the correlation time is found to increase with radius by 1 order of magnitude across the halo.

The Role of Stress Exposure and Family Functioning in Internalizing Outcomes of Urban Families

PubMed Central

Henry, David B.; Tolan, Patrick H.; Strachan, Martha K.

2013-01-01

Although research suggests that stress exposure and family functioning are associated with internalizing problems in adolescents and caregivers, surprisingly few studies have investigated the mechanisms that underlie this association. To determine whether family functioning buffers the development of internalizing problems in stress-exposed families, we assessed the relation between stress exposure, family functioning, and internalizing symptoms among a large sample of inner-city male youth and their caregivers living in poverty across five waves of data collection. We hypothesized that stress exposure and family functioning would predict development of subsequent youth and caregiver internalizing problems and that family functioning would moderate this relation, with higher functioning families demonstrating greater resiliency to stress exposure. We used a longitudinal, prospective design to evaluate whether family functioning (assessed at waves one through four) activated or buffered the effects of stress exposure (assessed at wave one) on subsequent internalizing symptoms (assessed at waves four and five). Stress from Developmental Transitions and family functioning were significant predictors of depressive symptoms and anxiety in youth; however, family functioning did not moderate the relation. Family functioning mediated the relation between stress from Daily Hassles and internalizing outcomes suggesting that poor parenting practices, low structure, and low emotional cohesion activate depression and anxiety in youth exposed to chronic and frequent everyday stressors. Surprisingly, only family functioning predicted depressive symptoms in caregivers. Results validate the use of a comprehensive, multi-informant assessment of stress when investigating internalizing outcomes in youth and support using family-based interventions in the treatment and prevention of internalizing. PMID:25601821

The Role of Stress Exposure and Family Functioning in Internalizing Outcomes of Urban Families.

PubMed

Sheidow, Ashli J; Henry, David B; Tolan, Patrick H; Strachan, Martha K

2014-11-01

Although research suggests that stress exposure and family functioning are associated with internalizing problems in adolescents and caregivers, surprisingly few studies have investigated the mechanisms that underlie this association. To determine whether family functioning buffers the development of internalizing problems in stress-exposed families, we assessed the relation between stress exposure, family functioning, and internalizing symptoms among a large sample of inner-city male youth and their caregivers living in poverty across five waves of data collection. We hypothesized that stress exposure and family functioning would predict development of subsequent youth and caregiver internalizing problems and that family functioning would moderate this relation, with higher functioning families demonstrating greater resiliency to stress exposure. We used a longitudinal, prospective design to evaluate whether family functioning (assessed at waves one through four) activated or buffered the effects of stress exposure (assessed at wave one) on subsequent internalizing symptoms (assessed at waves four and five). Stress from Developmental Transitions and family functioning were significant predictors of depressive symptoms and anxiety in youth; however, family functioning did not moderate the relation. Family functioning mediated the relation between stress from Daily Hassles and internalizing outcomes suggesting that poor parenting practices, low structure, and low emotional cohesion activate depression and anxiety in youth exposed to chronic and frequent everyday stressors. Surprisingly, only family functioning predicted depressive symptoms in caregivers. Results validate the use of a comprehensive, multi-informant assessment of stress when investigating internalizing outcomes in youth and support using family-based interventions in the treatment and prevention of internalizing.

Crustal and upper mantle S-wave velocity structures across the Taiwan Strait from ambient seismic noise and teleseismic Rayleigh wave analyses

NASA Astrophysics Data System (ADS)

Huang, Y.; Yao, H.; Wu, F. T.; Liang, W.; Huang, B.; Lin, C.; Wen, K.

2013-12-01

Although orogeny seems to have stopped in western Taiwan large and small earthquakes do occur in the Taiwan Strait. Limited studies have focused on this region before and were barely within reach for comprehensive projects like TAICRUST and TAIGER for logistical reasons; thus, the overall crustal structures of the Taiwan Strait remain unknown. Time domain empirical Green's function (TDEGF) from ambient seismic noise to determine crustal velocity structure allows us to study an area using station pairs on its periphery. This research aims to resolve 1-D average crustal and upper mantle S-wave velocity (Vs) structures alone paths of several broadband station-pairs across the Taiwan Strait; 5-120 s Rayleigh wave phase velocity dispersion data derived by combining TDEGF and traditional surface wave two-station method (TS). The average Vs structures show significant differences in the upper 15 km as expected. In general, the highest Vs are observed in the coastal area of Mainland China and the lowest Vs appear along the southwest offshore of the Taiwan Island; they differ by about 0.6-1.1 km/s. For different parts of the Strait, the Vs are lower in the middle by about 0.1-0.2 km/s relative to those in the northern and southern parts. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island.

Numerical simulations (2D) on the influence of pre-existing local structures and seismic source characteristics in earthquake-volcano interactions

NASA Astrophysics Data System (ADS)

Farías, Cristian; Galván, Boris; Miller, Stephen A.

2017-09-01

Earthquake triggering of hydrothermal and volcanic systems is ubiquitous, but the underlying processes driving these systems are not well-understood. We numerically investigate the influence of seismic wave interaction with volcanic systems simulated as a trapped, high-pressure fluid reservoir connected to a fluid-filled fault system in a 2-D poroelastic medium. Different orientations and earthquake magnitudes are studied to quantify dynamic and static stress, and pore pressure changes induced by a seismic event. Results show that although the response of the system is mainly dominated by characteristics of the radiated seismic waves, local structures can also play an important role on the system dynamics. The fluid reservoir affects the seismic wave front, distorts the static overpressure pattern induced by the earthquake, and concentrates the kinetic energy of the incoming wave on its boundaries. The static volumetric stress pattern inside the fault system is also affected by the local structures. Our results show that local faults play an important role in earthquake-volcanic systems dynamics by concentrating kinetic energy inside and acting as wave-guides that have a breakwater-like behavior. This generates sudden changes in pore pressure, volumetric expansion, and stress gradients. Local structures also influence the regional Coulomb yield function. Our results show that local structures affect the dynamics of volcanic and hydrothermal systems, and should be taken into account when investigating triggering of these systems from nearby or distant earthquakes.

Convection and Easterly Wave Structure Observed in the Eastern Pacific Warm-Pool during EPIC-2001

NASA Technical Reports Server (NTRS)

Peterson, Walter A.; Cifelli, R.; Boccippio, D.; Rutledge, S. A.; Fairall, C. W.; Arnold, James E. (Technical Monitor)

2002-01-01

During September-October 2001, the East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC-2001) ITCZ field campaign focused on studies of deep convection in the warm-pool region of the East Pacific. In addition to the TAO mooring array, observational platforms deployed during the field phase included the NOAA ship RN Ronald H. Brown, the NSF ship RN Horizon, and the NOAA P-3 and NCAR C-130 aircraft. This study combines C-band Doppler radar, rawinsonde, and surface heat flux data collected aboard the RN Brown to describe ITCZ convective structure and rainfall statistics in the eastern Pacific as a function of 3-5 day easterly wave phase. Three distinct easterly wave passages occurred during EPIC-2001. Wind and thermodynamic data reveal that the wave trough axes exhibited positively correlated U and V winds and a slight westward phase tilt with height. A relatively strong (weak) northeasterly deep tropospheric shear followed the trough (ridge) axis. Temperature and humidity perturbations exhibited mid-to upper level cooling (warming) and drying (moistening) in the northerly (trough and southerly) phase. At low levels warming (cooling) occurred in the northerly (southerly) phase with little change in the relative humidity, though mixed layer mixing ratios were larger during the northerly phase. When composited, radar, sounding, lightning and surface heat flux observations suggest the following systematic behavior as a function of wave phase: approximately zero to one quarter wavelength ahead of (behind) the wave trough in northerly (southerly) flow, larger (smaller) CAPE, lower (higher) CIN, weaker (stronger) tropospheric shear, higher (lower) conditional mean rain rates, higher (lower) lightning flash densities, and more (less) robust convective vertical structure occurred. Latent and sensible heat fluxes reached a minimum in the northerly phase and then increased through the trough, reaching a peak during the ridge phase (leading the peak in CAPE). From a radar echo coverage perspective, larger areas of light rain and slightly larger (10%) area averaged rain rates occurred in the vicinity of, and just behind, the trough axes in southerly flow. Importantly, the transition in convective structure observed across the trough axis when considered with the relatively small change in area mean rain rates suggests the presence of a transition in the vertical structure of diabatic heating across the easterly waves examined. The inferred transition in heating structure is supported by radar diagnosed divergence profiles that exhibit convective (stratiform) characteristics ahead of (behind) the trough.

Discontinuity-free edge-diffraction model for characterization of focused wave fields.

PubMed

Sedukhin, Andrey G

2010-03-01

A model of discontinuity-free edge diffraction is proposed that is valid in the framework of the scalar Debye approximation and describes the formation process and approximate structure of the stationary diffracted field of a monochromatic converging spherical wave of limited angular opening throughout the whole space about the focus. The field is represented semianalytically in terms of the sum of a direct quasi-spherical wave and two edge quasi-conical waves of the zeroth and first order. The angular spectrum amplitudes of all these waves have smooth continuous variations of the real and imaginary parts in polar angle and radius, the separable nonanalytic functions defining the polar-angle variations of the amplitudes being found by optimization techniques.

Controlled simulation of optical turbulence in a temperature gradient air chamber

NASA Astrophysics Data System (ADS)

Toselli, Italo; Wang, Fei; Korotkova, Olga

2016-05-01

Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation with controlled strength of the refractive-index fluctuations. The temperature gradients are generated by a sequence of heat guns with controlled individual strengths. The temperature structure functions are measured in two directions transverse to propagation path with the help of a thermocouple array and used for evaluation of the corresponding refractive-index structure functions of optical turbulence.

Improving the shear wave velocity structure beneath Bucharest (Romania) using ambient vibrations

NASA Astrophysics Data System (ADS)

Manea, Elena Florinela; Michel, Clotaire; Poggi, Valerio; Fäh, Donat; Radulian, Mircea; Balan, Florin Stefan

2016-11-01

Large earthquakes from the intermediate-depth Vrancea seismic zone are known to produce in Bucharest ground motion characterized by predominant long periods. This phenomenon has been interpreted as the combined effect of both seismic source properties and site response of the large sedimentary basin. The thickness of the unconsolidated Quaternary deposits beneath the city is more than 200 m, the total depth of sediments is more than 1000 m. Complex basin geometry and the low seismic wave velocities of the sediments are primarily responsible for the large amplification and long duration experienced during earthquakes. For a better understanding of the geological structure under Bucharest, a number of investigations using non-invasive methods have been carried out. With the goal to analyse and extract the polarization and dispersion characteristics of the surface waves, ambient vibrations and low-magnitude earthquakes have been investigated using single station and array techniques. Love and Rayleigh dispersion curves (including higher modes), Rayleigh waves ellipticity and SH-wave fundamental frequency of resonance (f0SH) have been inverted simultaneously to estimate the shear wave velocity structure under Bucharest down to a depth of about 8 km. Information from existing borehole logs was used as prior to reduce the non-uniqueness of the inversion and to constrain the shallow part of the velocity model (<300 m). In this study, we use data from a 35-km diameter array (the URS experiment) installed by the National Institute for Earth Physics and by the Karlsruhe Institute of Technology during 10 months in the period 2003-2004. The array consisted of 32 three-component seismological stations, deployed in the urban area of Bucharest and adjacent zones. The large size of the array and the broad-band nature of the available sensors gave us the possibility to characterize the surface wave dispersion at very low frequencies (0.05-1 Hz) using frequency-wavenumber techniques. This is essential to explore and resolve the deeper portions of the basin. The horizontal to vertical spectral ratio (H/V) curves provide important additional information about the structure and are here characterized by two major peaks. The first is attributed to the fundamental frequency of the basin, while the second can be interpreted as a mixture of the second higher mode of Rayleigh waves and other types of waves such as SH waves. This hypothesis has been verified by comparing the H/V curves with the SH-wave transfer function from the retrieved velocity structure. We could also approximate the SH transfer function with H/V ratios of earthquake recordings, providing additional verification of the robustness of the proposed velocity model. The Cretaceous bedrock depth was then inverted at each URS station from the fundamental frequency of resonance and using this model. A 3-D geophysical model for Bucharest has been constructed based on the integration of the inverted velocity profiles and the available geological information using a geographic information system.

Bio-wave change photo-voltages of the solar cells at same changed rate by probability effect of spacetime structure

NASA Astrophysics Data System (ADS)

Cao, Dayong

In our experiment, when light (of ``lamp LED'' 3W, 20cm away from the solar cells) simultaneous radiated on four solar cells, they would produce their photo-voltages which are called as background photo-voltages. And then, the author used thought wave to remotely (wireless) act on the four solar cells and increase four background photo-voltages at the same rates which is about 64%. After that, Adding the other light (of ``lamp CFL'') to simultaneous radiate on the four solar cells to changed their background photo-voltages. But there are different changed rates which will appear in the general experiments because the luminous sensitivities of the solar cell are different and the photo-voltages is a nonlinear function. The probability effects of the spacetime structure (of Confined Structural non-Newtonian Fluids) of brain wave (because the wave is spacetime) to change a balance structure between Electron Clouds and electron holes of P-N Junction, and change the background photo-voltages of the solar cells. In the experiments, the consciousness effect, and the relationship between brain wave and consciousness effect will be considered. After the decade of the brain research and the ``BRAIN'' Initiative, a decade of the consciousness need be taken. http://meetings.aps.org/Meeting/APR16/Session/M13.8 AEEA.

The NESH/Abi-3-based WAVE2 complex is functionally distinct from the Abi-1-based WAVE2 complex.

PubMed

Sekino, Saki; Kashiwagi, Yuriko; Kanazawa, Hitoshi; Takada, Kazuki; Baba, Takashi; Sato, Seiichi; Inoue, Hiroki; Kojima, Masaki; Tani, Katsuko

2015-10-01

Abl interactor (Abi) family proteins play significant roles in actin cytoskeleton organization through participation in the WAVE complex. Mammals possess three Abi proteins: Abi-1, Abi-2, and NESH/Abi-3. Abi-1 and Abi-2 were originally identified as Abl tyrosine kinase-binding proteins. It has been disclosed that Abi-1 acts as a bridge between c-Abl and WAVE2, and c-Abl-mediated WAVE2 phosphorylation promotes actin remodeling. We showed previously that NESH/Abi-3 is present in the WAVE2 complex, but neither binds to c-Abl nor promotes c-Abl-mediated phosphorylation of WAVE2. In this study, we characterized NESH/Abi-3 in more detail, and compared its properties with those of Abi-1 and Abi-2. NESH/Abi-3 was ectopically expressed in NIH3T3 cells, in which Abi-1, but not NESH/Abi-3, is expressed. The expression of NESH/Abi-3 caused degradation of endogenous Abi-1, which led to the formation of a NESH/Abi-3-based WAVE2 complex. When these cells were plated on fibronectin-coated dishes, the translocation of WAVE2 to the plasma membrane was significantly reduced and the formation of peripheral lamellipodial structures was disturbed, suggesting that the NESH/Abi-3-based WAVE2 complex was unable to help produce lamellipodial protrusions. Next, Abi-1, Abi-2, or NESH/Abi-3 was expressed in v-src-transformed NIH3T3 cells. Only in NESH/Abi-3-expressed cells did treatment with an Abl kinase inhibitor, imatinib mesylate, or siRNA-mediated knockdown of c-Abl promote the formation of invadopodia, which are ventral membrane protrusions with extracellular matrix degradation activity. Structural studies showed that a linker region between the proline-rich regions and the Src homology 3 (SH3) domain of Abi-1 is crucial for its interaction with c-Abl and c-Abl-mediated phosphorylation of WAVE2. The NESH/Abi-3-based WAVE2 complex is functionally distinct from the Abi-1-based one, and NESH/Abi-3 may be involved in the formation of ventral protrusions under certain conditions.

Plasticity of brain wave network interactions and evolution across physiologic states

PubMed Central

Liu, Kang K. L.; Bartsch, Ronny P.; Lin, Aijing; Mantegna, Rosario N.; Ivanov, Plamen Ch.

2015-01-01

Neural plasticity transcends a range of spatio-temporal scales and serves as the basis of various brain activities and physiologic functions. At the microscopic level, it enables the emergence of brain waves with complex temporal dynamics. At the macroscopic level, presence and dominance of specific brain waves is associated with important brain functions. The role of neural plasticity at different levels in generating distinct brain rhythms and how brain rhythms communicate with each other across brain areas to generate physiologic states and functions remains not understood. Here we perform an empirical exploration of neural plasticity at the level of brain wave network interactions representing dynamical communications within and between different brain areas in the frequency domain. We introduce the concept of time delay stability (TDS) to quantify coordinated bursts in the activity of brain waves, and we employ a system-wide Network Physiology integrative approach to probe the network of coordinated brain wave activations and its evolution across physiologic states. We find an association between network structure and physiologic states. We uncover a hierarchical reorganization in the brain wave networks in response to changes in physiologic state, indicating new aspects of neural plasticity at the integrated level. Globally, we find that the entire brain network undergoes a pronounced transition from low connectivity in Deep Sleep and REM to high connectivity in Light Sleep and Wake. In contrast, we find that locally, different brain areas exhibit different network dynamics of brain wave interactions to achieve differentiation in function during different sleep stages. Moreover, our analyses indicate that plasticity also emerges in frequency-specific networks, which represent interactions across brain locations mediated through a specific frequency band. Comparing frequency-specific networks within the same physiologic state we find very different degree of network connectivity and link strength, while at the same time each frequency-specific network is characterized by a different signature pattern of sleep-stage stratification, reflecting a remarkable flexibility in response to change in physiologic state. These new aspects of neural plasticity demonstrate that in addition to dominant brain waves, the network of brain wave interactions is a previously unrecognized hallmark of physiologic state and function. PMID:26578891

Wave Number Selection for Incompressible Parallel Jet Flows Periodic in Space

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

1997-01-01

The temporal instability of a spatially periodic parallel flow of an incompressible inviscid fluid for various jet velocity profiles is studied numerically using Floquet Analysis. The transition matrix at the end of a period is evaluated by direct numerical integration. For verification, a method based on approximating a continuous function by a series of step functions was used. Unstable solutions were found only over a limited range of wave numbers and have a band type structure. The results obtained are analogous to the behavior observed in systems exhibiting complexity at the edge of order and chaos.

Gap junction-mediated calcium waves define communication networks among murine postnatal neural progenitor cells.

PubMed

Lacar, Benjamin; Young, Stephanie Z; Platel, Jean-Claude; Bordey, Angélique

2011-12-01

In the postnatal neurogenic niche, two populations of astrocyte-like cells (B cells) persist, one acting as neural progenitor cells (NPCs, B1 cells) and one forming a structural boundary between the neurogenic niche and the striatum (B2 cells, niche astrocytes). Despite being viewed as two distinct entities, we found that B1 and B2 cells express the gap junction protein connexin 43 and display functional coupling involving 50-60 cells. Using neonatal electroporation to label slowly cycling radial glia-derived B1 cells, which send a basal process onto blood vessels, we further confirmed dye coupling between NPCs. To assess the functionality of the coupling, we used calcium imaging in a preparation preserving the three-dimensional architecture of the subventricular zone. Intercellular calcium waves were observed among B cells. These waves travelled bidirectionally between B1 and B2 cells and propagated on blood vessels. Inter-B-cell calcium waves were absent in the presence of a gap junction blocker but persisted with purinergic receptor blockers. These findings show that privileged microdomains of communication networks exist among NPCs and niche astrocytes. Such functional coupling between these two cell types suggests that niche astrocytes do not merely have a structural role, but may play an active role in shaping the behavior of NPCs. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Ambient Noise Interferometry and Surface Wave Array Tomography: Promises and Problems

NASA Astrophysics Data System (ADS)

van der Hilst, R. D.; Yao, H.; de Hoop, M. V.; Campman, X.; Solna, K.

2008-12-01

In the late 1990ies most seismologists would have frowned at the possibility of doing high-resolution surface wave tomography with noise instead of with signal associated with ballistic source-receiver propagation. Some may still do, but surface wave tomography with Green's functions estimated through ambient noise interferometry ('sourceless tomography') has transformed from a curiosity into one of the (almost) standard tools for analysis of data from dense seismograph arrays. Indeed, spectacular applications of ambient noise surface wave tomography have recently been published. For example, application to data from arrays in SE Tibet revealed structures in the crust beneath the Tibetan plateau that could not be resolved by traditional tomography (Yao et al., GJI, 2006, 2008). While the approach is conceptually simple, in application the proverbial devil is in the detail. Full reconstruction of the Green's function requires that the wavefields used are diffusive and that ambient noise energy is evenly distributed in the spatial dimensions of interest. In the field, these conditions are not usually met, and (frequency dependent) non-uniformity of the noise sources may lead to incomplete reconstruction of the Green's function. Furthermore, ambient noise distributions can be time-dependent, and seasonal variations have been documented. Naive use of empirical Green's functions may produce (unknown) bias in the tomographic models. The degrading effect on EGFs of the directionality of noise distribution forms particular challenges for applications beyond isotropic surface wave inversions, such as inversions for (azimuthal) anisotropy and attempts to use higher modes (or body waves). Incomplete Green's function reconstruction can (probably) not be prevented, but it may be possible to reduce the problem and - at least - understand the degree of incomplete reconstruction and prevent it from degrading the tomographic model. We will present examples of Rayleigh wave inversions and discuss strategies to mitigate effects of incomplete Green's function reconstruction on tomographic images.

Structure of the nucleon's low-lying excitations

NASA Astrophysics Data System (ADS)

Chen, Chen; El-Bennich, Bruno; Roberts, Craig D.; Schmidt, Sebastian M.; Segovia, Jorge; Wan, Shaolong

2018-02-01

A continuum approach to the three valence-quark bound-state problem in quantum field theory is used to perform a comparative study of the four lightest (I =1 /2 ,JP=1 /2±) baryon isospin doublets in order to elucidate their structural similarities and differences. Such analyses predict the presence of nonpointlike, electromagnetically active quark-quark (diquark) correlations within all baryons; and in these doublets, isoscalar-scalar, isovector-pseudovector, isoscalar-pseudoscalar, and vector diquarks can all play a role. In the two lightest (1 /2 ,1 /2+) doublets, however, scalar and pseudovector diquarks are overwhelmingly dominant. The associated rest-frame wave functions are largely S -wave in nature; and the first excited state in this 1 /2+ channel has the appearance of a radial excitation of the ground state. The two lightest (1 /2 ,1 /2-) doublets fit a different picture: accurate estimates of their masses are obtained by retaining only pseudovector diquarks; in their rest frames, the amplitudes describing their dressed-quark cores contain roughly equal fractions of even- and odd-parity diquarks; and the associated wave functions are predominantly P -wave in nature, but possess measurable S -wave components. Moreover, the first excited state in each negative-parity channel has little of the appearance of a radial excitation. In quantum field theory, all differences between positive- and negative-parity channels must owe to chiral symmetry breaking, which is overwhelmingly dynamical in the light-quark sector. Consequently, experiments that can validate the contrasts drawn herein between the structure of the four lightest (1 /2 ,1 /2±) doublets will prove valuable in testing links between emergent mass generation and observable phenomena and, plausibly, thereby revealing dynamical features of confinement.

Effects of Prolonged Spaceflight on Atrial Size, Atrial Electrophysiology, and Risk of Atrial Fibrillation.

PubMed

Khine, Htet W; Steding-Ehrenborg, Katarina; Hastings, Jeffrey L; Kowal, Jamie; Daniels, James D; Page, Richard L; Goldberger, Jeffery J; Ng, Jason; Adams-Huet, Beverley; Bungo, Michael W; Levine, Benjamin D

2018-05-01

The prevalence of atrial fibrillation (AF) in active astronauts is ≈5%, similar to the general population but at a younger age. Risk factors for AF include left atrial enlargement, increased number of premature atrial complexes, and certain parameters on signal-averaged electrocardiography, such as P-wave duration, root mean square voltage for the terminal 20 ms of the signal-averaged P wave, and P-wave amplitude. We aimed to evaluate changes in atrial structure, supraventricular beats, and atrial electrophysiology to determine whether spaceflight could increase the risk of AF. Thirteen astronauts underwent cardiac magnetic resonance imaging to assess atrial structure and function before and after 6 months in space and high-resolution Holter monitoring for multiple 48-hour time periods before flight, during flight, and on landing day. Left atrial volume transiently increased after 6 months in space (12±18 mL; P =0.03) without changing atrial function. Right atrial size remained unchanged. No changes in supraventricular beats were noted. One astronaut had a large increase in supraventricular ectopic beats but none developed AF. Filtered P-wave duration did not change over time, but root mean square voltage for the terminal 20 ms decreased on all fight days except landing day. No changes in P-wave amplitude were seen in leads II or V 1 except landing day for lead V 1 . Six months of spaceflight may be sufficient to cause transient changes in left atrial structure and atrial electrophysiology that increase the risk of AF. However, there was no definite evidence of increased supraventricular arrhythmias and no identified episodes of AF. © 2018 American Heart Association, Inc.

Computational Modeling of Bloch Surface Waves in One-Dimensional Periodic and Aperiodic Multilayer Structures

NASA Astrophysics Data System (ADS)

Koju, Vijay

Photonic crystals and their use in exciting Bloch surface waves have received immense attention over the past few decades. This interest is mainly due to their applications in bio-sensing, wave-guiding, and other optical phenomena such as surface field enhanced Raman spectroscopy. Improvement in numerical modeling techniques, state of the art computing resources, and advances in fabrication techniques have also assisted in growing interest in this field. The ability to model photonic crystals computationally has benefited both the theoretical as well as experimental communities. It helps the theoretical physicists in solving complex problems which cannot be solved analytically and helps to acquire useful insights that cannot be obtained otherwise. Experimentalists, on the other hand, can test different variants of their devices by changing device parameters to optimize performance before fabrication. In this dissertation, we develop two commonly used numerical techniques, namely transfer matrix method, and rigorous coupled wave analysis, in C++ and MATLAB, and use two additional software packages, one open-source and another commercial, to model one-dimensional photonic crystals. Different variants of one-dimensional multilayered structures such as perfectly periodic dielectric multilayers, quasicrystals, aperiodic multilayer are modeled, along with one-dimensional photonic crystals with gratings on the top layer. Applications of Bloch surface waves, along with new and novel aperiodic dielectric multilayer structures that support Bloch surface waves are explored in this dissertation. We demonstrate a slow light configuration that makes use of Bloch Surface Waves as an intermediate excitation in a double-prism tunneling configuration. This method is simple compared to the more usual techniques for slowing light using the phenomenon of electromagnetically induced transparency in atomic gases or doped ionic crystals operated at temperatures below 4K. Using a semi-numerical approach, we show that a 1D photonic crystal, a multilayer structure composed of alternating layers of TiO2 and SiO2 , can be used to slow down light by a factor of up to 400. The results also show that better control of the speed of light can be achieved by changing the number of bilayers and the air-gap thickness appropriately. The existence of Bloch surface waves in periodic dielectric multilayer structures with a surface defect is well-known. Not yet recognized is that quasi-crystals and aperiodic dielectric multilayers can also support Bloch-like surface waves. We numerically show the excitation of Bloch-like surface waves in Fibonacci quasi-crystals, Thue-Morse aperiodic dielectric multilayers using the prism coupling method. We report improved surface electric field intensity and penetration depth of Bloch-like surface waves in the air side in such structures compared to their periodic counterparts. Bloch surface waves have also demonstrated significant potential in the field of bios-ensing technology. We further extend our study into a new type of multilayer structure based on Maximal-length sequence, which is a pseudo random sequence. We study the characteristics of Bloch surface waves in a 32 layered Maximal-length sequence multilayer and perform angular, as well as spectral sensitivity analysis for refractive index change detection. We demonstrate numerically that Maximal-length sequence multilayers significantly enhance the sensitivity of Bloch surface waves. Another type of structure that support Bloch surface waves are dielectric multilayer structures with a grating profile on the top-most layer. The grating profile adds an additional degree of freedom to the phase matching conditions for Bloch surface wave excitation. In such structures, the conditions for Bloch surface wave coupling can also be achieved by rotating both polar and azimuthal angles. The generation of Bloch surface waves as a function of azimuthal angle have similar characteristics to conventional grating coupled Bloch surface waves. However, azimuthal generated Bloch surface waves have enhanced angular sensitivity compared to conventional polar angle coupled modes, which makes them appropriate for detecting tiny variations in surface refractive index due to the addition of nano-particles such as protein molecules.

Crustal seismic structure beneath the southwest Yunnan region from joint inversion of body-wave and surface wave data

NASA Astrophysics Data System (ADS)

Luo, Y.; Thurber, C. H.; Zeng, X.; Zhang, L.

2016-12-01

Data from 71 broadband stations of a dense transportable array deployed in southwest Yunnan makes it possible to improve the resolution of the seismic model in this region. Continuous waveforms from 12 permanent stations of the China National Seismic Network were also used in this study. We utilized one-year continuous vertical component records to compute ambient noise cross-correlation functions (NCF). More than 3,000 NCFs were obtained and used to measure group velocities between 5 and 25 seconds with the frequency-time analysis method. This frequency band is most sensitive to crustal seismic structure, especially the upper and middle crust. The group velocity at short-period shows a clear azimuthal anisotropy with a north-south fast direction. The fast direction is consistent with previous seismic results revealed from shear wave splitting. More than 2,000 group velocity measurements were employed to invert the surface wave dispersion data for group velocity maps. We applied a finite difference forward modeling algorithm with an iterative inversion. A new body-wave and surface wave joint inversion algorithm (Fang et al., 2016) was utilized to improve the resolution of both P and S models. About 60,000 P wave and S wave arrivals from 1,780 local earthquakes, which occurred from May 2011 to December 2013 with magnitudes larger than 2.0, were manually picked. The new high-resolution seismic structure shows good consistency with local geological features, e.g. Tengchong Volcano. The earthquake locations also were refined with our new velocity model.

Building Quakes: Detection of Weld Fractures in Buildings using High-Frequency Seismic Techniques

NASA Astrophysics Data System (ADS)

Heckman, V.; Kohler, M. D.; Heaton, T. H.

2009-12-01

Catastrophic fracture of welded beam-column connections in buildings was observed in the Northridge and Kobe earthquakes. Despite the structural importance of such connections, it can be difficult to locate damage in structural members underneath superficial building features. We have developed a novel technique to locate fracturing welds in buildings in real time using high-frequency information from seismograms. Numerical and experimental methods were used to investigate an approach for detecting the brittle fracture of welds of beam-column connections in instrumented steel moment-frame buildings through the use of time-reversed Green’s functions and wave propagation reciprocity. The approach makes use of a prerecorded catalogue of Green’s functions for an instrumented building to detect high-frequency failure events in the building during a later earthquake by screening continuous data for the presence of one or more of the events. This was explored experimentally by comparing structural responses of a small-scale laboratory structure under a variety of loading conditions. Experimentation was conducted on a polyvinyl chloride frame model structure with data recorded at a sample rate of 2000 Hz using piezoelectric accelerometers and a 24-bit digitizer. Green’s functions were obtained by applying impulsive force loads at various locations along the structure with a rubber-tipped force transducer hammer. We performed a blind test using cross-correlation techniques to determine if it was possible to use the catalogue of Green’s functions to pinpoint the absolute times and locations of subsequent, induced failure events in the structure. A finite-element method was used to simulate the response of the model structure to various source mechanisms in order to determine the types of elastic waves that were produced as well as to obtain a general understanding of the structural response to localized loading and fracture.

The inverse problem of acoustic wave scattering by an air-saturated poroelastic cylinder.

PubMed

Ogam, Erick; Fellah, Z E A; Baki, Paul

2013-03-01

The efficient use of plastic foams in a diverse range of structural applications like in noise reduction, cushioning, and sleeping mattresses requires detailed characterization of their permeability and deformation (load-bearing) behavior. The elastic moduli and airflow resistance properties of foams are often measured using two separate techniques, one employing mechanical vibration methods and the other, flow rates of fluids based on fluid mechanics technology, respectively. A multi-parameter inverse acoustic scattering problem to recover airflow resistivity (AR) and mechanical properties of an air-saturated foam cylinder is solved. A wave-fluid saturated poroelastic structure interaction model based on the modified Biot theory and plane-wave decomposition using orthogonal cylindrical functions is employed to solve the inverse problem. The solutions to the inverse problem are obtained by constructing the objective functional given by the total square of the difference between predictions from the model and scattered acoustic field data acquired in an anechoic chamber. The value of the recovered AR is in good agreement with that of a slab sample cut from the cylinder and characterized using a method employing low frequency transmitted and reflected acoustic waves in a long waveguide developed by Fellah et al. [Rev. Sci. Instrum. 78(11), 114902 (2007)].

Modeling resting-state functional networks when the cortex falls asleep: local and global changes.

PubMed

Deco, Gustavo; Hagmann, Patric; Hudetz, Anthony G; Tononi, Giulio

2014-12-01

The transition from wakefulness to sleep represents the most conspicuous change in behavior and the level of consciousness occurring in the healthy brain. It is accompanied by similarly conspicuous changes in neural dynamics, traditionally exemplified by the change from "desynchronized" electroencephalogram activity in wake to globally synchronized slow wave activity of early sleep. However, unit and local field recordings indicate that the transition is more gradual than it might appear: On one hand, local slow waves already appear during wake; on the other hand, slow sleep waves are only rarely global. Studies with functional magnetic resonance imaging also reveal changes in resting-state functional connectivity (FC) between wake and slow wave sleep. However, it remains unclear how resting-state networks may change during this transition period. Here, we employ large-scale modeling of the human cortico-cortical anatomical connectivity to evaluate changes in resting-state FC when the model "falls asleep" due to the progressive decrease in arousal-promoting neuromodulation. When cholinergic neuromodulation is parametrically decreased, local slow waves appear, while the overall organization of resting-state networks does not change. Furthermore, we show that these local slow waves are structured macroscopically in networks that resemble the resting-state networks. In contrast, when the neuromodulator decrease further to very low levels, slow waves become global and resting-state networks merge into a single undifferentiated, broadly synchronized network. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

The picosecond structure of ultra-fast rogue waves

NASA Astrophysics Data System (ADS)

Klein, Avi; Shahal, Shir; Masri, Gilad; Duadi, Hamootal; Sulimani, Kfir; Lib, Ohad; Steinberg, Hadar; Kolpakov, Stanislav A.; Fridman, Moti

2018-02-01

We investigated ultrafast rogue waves in fiber lasers and found three different patterns of rogue waves: single- peaks, twin-peaks, and triple-peaks. The statistics of the different patterns as a function of the pump power of the laser reveals that the probability for all rogue waves patterns increase close to the laser threshold. We developed a numerical model which prove that the ultrafast rogue waves patterns result from both the polarization mode dispersion in the fiber and the non-instantaneous nature of the saturable absorber. This discovery reveals that there are three different types of rogue waves in fiber lasers: slow, fast, and ultrafast, which relate to three different time-scales and are governed by three different sets of equations: the laser rate equations, the nonlinear Schrodinger equation, and the saturable absorber equations, accordingly. This discovery is highly important for analyzing rogue waves and other extreme events in fiber lasers and can lead to realizing types of rogue waves which were not possible so far such as triangular rogue waves.

Study of Linear and Nonlinear Wave Excitation

NASA Astrophysics Data System (ADS)

Chu, Feng; Berumen, Jorge; Hood, Ryan; Mattingly, Sean; Skiff, Frederick

2013-10-01

We report an experimental study of externally excited low-frequency waves in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional. Wave excitation in the drift wave frequency range is accomplished by low-percentage amplitude modulation of the RF plasma source. Laser-induced fluorescence is adopted to study ion-density fluctuations in phase space. The laser is chopped to separate LIF from collisional fluorescence. A single negatively-biased Langmuir probe is used to detect ion-density fluctuations in the plasma. A ring array of Langmuir probes is also used to analyze the spatial and spectral structure of the excited waves. We apply coherent detection with respect to the wave frequency to obtain the ion distribution function associated with externally generated waves. Higher-order spectra are computed to evaluate the nonlinear coupling between fluctuations at various frequencies produced by the externally generated waves. Parametric decay of the waves is observed. This work is supported by U.S. DOE Grant No. DE-FG02-99ER54543.

Structure of the North Anatolian Fault Zone from the Autocorrelation of Ambient Seismic Noise

NASA Astrophysics Data System (ADS)

Taylor, George; Rost, Sebastian; Houseman, Gregory

2016-04-01

In recent years the technique of cross-correlating the ambient seismic noise wavefield at two seismometers to reconstruct empirical Green's Functions for the determination of Earth structure has been a powerful tool to study the Earth's interior without earthquakes or man-made sources. However, far less attention has been paid to using auto-correlations of seismic noise to reveal body wave reflections from interfaces in the subsurface. In principle, the Green's functions thus derived should be comparable to the Earth's impulse response to a co-located source and receiver. We use data from a dense seismic array (Dense Array for Northern Anatolia - DANA) deployed across the northern branch of the North Anatolian Fault Zone (NAFZ) in the region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike-slip system that extends ~1200 km across northern Turkey and continues to pose a high level of seismic hazard, in particular to the mega-city of Istanbul. We construct body wave images for the entire crust and the shallow upper mantle over the ~35 km by 70 km footprint of the 70-station DANA array. Using autocorrelations of the vertical component of ground motion, P-wave reflections can be retrieved from the wavefield to constrain crustal structure. We show that clear P-wave reflections from the crust-mantle boundary (Moho) can be retrieved using the autocorrelation technique, indicating topography on the Moho on horizontal scales of less than 10 km. Offsets in crustal structure can be identified that seem to be correlated with the surface expression of the northern branch of the fault zone, indicating that the NAFZ reaches the upper mantle as a narrow structure. The southern branch has a less clear effect on crustal structure. We also see evidence of several discontinuities in the mid-crust in addition to an upper mantle reflector that we interpret to represent the Hales discontinuity.

Structural power flow measurement

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

Falter, K.J.; Keltie, R.F.

Previous investigations of structural power flow through beam-like structures resulted in some unexplained anomalies in the calculated data. In order to develop structural power flow measurement as a viable technique for machine tool design, the causes of these anomalies needed to be found. Once found, techniques for eliminating the errors could be developed. Error sources were found in the experimental apparatus itself as well as in the instrumentation. Although flexural waves are the carriers of power in the experimental apparatus, at some frequencies longitudinal waves were excited which were picked up by the accelerometers and altered power measurements. Errors weremore » found in the phase and gain response of the sensors and amplifiers used for measurement. A transfer function correction technique was employed to compensate for these instrumentation errors.« less

Ab Initio study on structural, electronic, magnetic and dielectric properties of LSNO within Density Functional Perturbation Theory

NASA Astrophysics Data System (ADS)

Petersen, John; Bechstedt, Friedhelm; Furthmüller, Jürgen; Scolfaro, Luisa

LSNO (La2-xSrxNiO4) is of great interest due to its colossal dielectric constant (CDC) and rich underlying physics. While being an antiferromagnetic insulator, localized holes are present in the form of stripes in the Ni-O planes which are commensurate with the inverse of the Sr concentration. The stripes are a manifestation of charge density waves with period approximately 1/x and spin density waves with period approximately 2/x. Here, the spin ground state is calculated via LSDA + U with the PAW method implemented in VASP. Crystal structure and the effective Hubbard U parameter are optimized before calculating ɛ∞ within the independent particle approximation. ɛ∞ and the full static dielectric constant (including the lattice polarizability) ɛ0 are calculated within Density Functional Perturbation Theory.

A complete active space valence bond method with nonorthogonal orbitals

NASA Astrophysics Data System (ADS)

Hirao, Kimihiko; Nakano, Haruyuki; Nakayama, Kenichi

1997-12-01

A complete active space self-consistent field (SCF) wave function is transformed into a valence bond type representation built from nonorthogonal orbitals, each strongly localized on a single atom. Nonorthogonal complete active space SCF orbitals are constructed by Ruedenberg's projected localization procedure so that they have maximal overlaps with the corresponding minimum basis set of atomic orbitals of the free-atoms. The valence bond structures which are composed of such nonorthogonal quasiatomic orbitals constitute the wave function closest to the concept of the oldest and most simple valence bond method. The method is applied to benzene, butadiene, hydrogen, and methane molecules and compared to the previously proposed complete active space valence bond approach with orthogonal orbitals. The results demonstrate the validity of the method as a powerful tool for describing the electronic structure of various molecules.

Decay width of hadronic molecule structure for quarks

NASA Astrophysics Data System (ADS)

Chen, Xiaozhao; Lü, Xiaofu

2018-06-01

Based on the general form of the Bethe-Salpeter wave functions for the bound states consisting of two vector fields, we obtain the general formulas for the decay widths of molecular states composed of two heavy vector mesons with arbitrary spin and parity into a heavy meson plus a light meson. In this approach, our attention is still focused on the internal structure of heavy vector mesons in the molecular state. According to the molecule state model of exotic meson, we give the generalized Bethe-Salpeter wave function of molecular state as a four-quark state. Then the observed Y (3940 ) state is considered as a molecular state consisting of two heavy vector mesons D*0D¯*0 and the strong Y (3940 )→J /ψ ω decay width is calculated. The numerical result is consistent with the experimental values.

Entanglement entropies and fermion signs of critical metals

NASA Astrophysics Data System (ADS)

Kaplis, N.; Krüger, F.; Zaanen, J.

2017-04-01

The fermion sign problem is often viewed as a sheer inconvenience that plagues numerical studies of strongly interacting electron systems. Only recently has it been suggested that fermion signs are fundamental for the universal behavior of critical metallic systems and crucially enhance their degree of quantum entanglement. In this work we explore potential connections between emergent scale invariance of fermion sign structures and scaling properties of bipartite entanglement entropies. Our analysis is based on a wave-function Ansatz that incorporates collective, long-range backflow correlations into fermionic Slater determinants. Such wave functions mimic the collapse of a Fermi liquid at a quantum critical point. Their nodal surfaces, a representation of the fermion sign structure in many-particle configurations space, show fractal behavior up to a length scale ξ that diverges at a critical backflow strength. We show that the Hausdorff dimension of the fractal nodal surface depends on ξ , the number of fermions and the exponent of the backflow. For the same wave functions we numerically calculate the second Rényi entanglement entropy S2. Our results show a crossover from volume scaling, S2˜ℓθ (θ =2 in d =2 dimensions), to the characteristic Fermi-liquid behavior S2˜ℓ lnℓ on scales larger than ξ . We find that volume scaling of the entanglement entropy is a robust feature of critical backflow fermions, independent of the backflow exponent and hence the fractal dimension of the scale invariant sign structure.

Spiraling Light with Magnetic Metamaterial Quarter-Wave Turbines.

PubMed

Zeng, Jinwei; Luk, Ting S; Gao, Jie; Yang, Xiaodong

2017-09-19

Miniaturized quarter-wave plate devices empower spin to orbital angular momentum conversion and vector polarization formation, which serve as bridges connecting conventional optical beam and structured light. Enabling the manipulability of additional dimensions as the complex polarization and phase of light, quarter-wave plate devices are essential for exploring a plethora of applications based on orbital angular momentum or vector polarization, such as optical sensing, holography, and communication. Here we propose and demonstrate the magnetic metamaterial quarter-wave turbines at visible wavelength to produce radially and azimuthally polarized vector vortices from circularly polarized incident beam. The magnetic metamaterials function excellently as quarter-wave plates at single wavelength and maintain the quarter-wave phase retardation in broadband, while the turbine blades consist of multiple polar sections, each of which contains homogeneously oriented magnetic metamaterial gratings near azimuthal or radial directions to effectively convert circular polarization to linear polarization and induce phase shift under Pancharatnum-Berry's phase principle. The perspective concept of multiple polar sections of magnetic metamaterials can extend to other analogous designs in the strongly coupled nanostructures to accomplish many types of light phase-polarization manipulation and structured light conversion in the desired manner.

Intermolecular shielding contributions studied by modeling the 13C chemical-shift tensors of organic single crystals with plane waves

PubMed Central

Johnston, Jessica C.; Iuliucci, Robbie J.; Facelli, Julio C.; Fitzgerald, George; Mueller, Karl T.

2009-01-01

In order to predict accurately the chemical shift of NMR-active nuclei in solid phase systems, magnetic shielding calculations must be capable of considering the complete lattice structure. Here we assess the accuracy of the density functional theory gauge-including projector augmented wave method, which uses pseudopotentials to approximate the nodal structure of the core electrons, to determine the magnetic properties of crystals by predicting the full chemical-shift tensors of all 13C nuclides in 14 organic single crystals from which experimental tensors have previously been reported. Plane-wave methods use periodic boundary conditions to incorporate the lattice structure, providing a substantial improvement for modeling the chemical shifts in hydrogen-bonded systems. Principal tensor components can now be predicted to an accuracy that approaches the typical experimental uncertainty. Moreover, methods that include the full solid-phase structure enable geometry optimizations to be performed on the input structures prior to calculation of the shielding. Improvement after optimization is noted here even when neutron diffraction data are used for determining the initial structures. After geometry optimization, the isotropic shift can be predicted to within 1 ppm. PMID:19831448

Endothelial cells use dynamic actin to facilitate lymphocyte transendothelial migration and maintain the monolayer barrier

PubMed Central

Mooren, Olivia L.; Li, Jinmei; Nawas, Julie; Cooper, John A.

2014-01-01

The vascular endothelium is a highly dynamic structure, and the integrity of its barrier function is tightly regulated. Normally impenetrable to cells, the endothelium actively assists lymphocytes to exit the bloodstream during inflammation. The actin cytoskeleton of the endothelial cell (EC) is known to facilitate transmigration, but the cellular and molecular mechanisms are not well understood. Here we report that actin assembly in the EC, induced by Arp2/3 complex under control of WAVE2, is important for several steps in the process of transmigration. To begin transmigration, ECs deploy actin-based membrane protrusions that create a cup-shaped docking structure for the lymphocyte. We found that docking structure formation involves the localization and activation of Arp2/3 complex by WAVE2. The next step in transmigration is creation of a migratory pore, and we found that endothelial WAVE2 is needed for lymphocytes to follow a transcellular route through an EC. Later, ECs use actin-based protrusions to close the gap behind the lymphocyte, which we discovered is also driven by WAVE2. Finally, we found that ECs in resting endothelial monolayers use lamellipodial protrusions dependent on WAVE2 to form and maintain contacts and junctions between cells. PMID:25355948

Optical Measurement of In-plane Waves in Mechanical Metamaterials Through Digital Image Correlation

NASA Astrophysics Data System (ADS)

Schaeffer, Marshall; Trainiti, Giuseppe; Ruzzene, Massimo

2017-02-01

We report on a Digital Image Correlation-based technique for the detection of in-plane elastic waves propagating in structural lattices. The experimental characterization of wave motion in lattice structures is currently of great interest due its relevance to the design of novel mechanical metamaterials with unique/unusual properties such as strongly directional behaviour, negative refractive indexes and topologically protected wave motion. Assessment of these functionalities often requires the detection of highly spatially resolved in-plane wavefields, which for reticulated or porous structural assemblies is an open challenge. A Digital Image Correlation approach is implemented that tracks small displacements of the lattice nodes by centring image subsets about the lattice intersections. A high speed camera records the motion of the points by properly interleaving subse- quent frames thus artificially enhancing the available sampling rate. This, along with an imaging stitching procedure, enables the capturing of a field of view that is sufficiently large for subsequent processing. The transient response is recorded in the form of the full wavefields, which are processed to unveil features of wave motion in a hexagonal lattice. Time snapshots and frequency contours in the spatial Fourier domain are compared with numerical predictions to illustrate the accuracy of the recorded wavefields.

Theoretical aspects of tidal and planetary wave propagation at thermospheric heights

NASA Technical Reports Server (NTRS)

Volland, H.; Mayr, H. G.

1977-01-01

A simple semiquantitative model is presented which allows analytic solutions of tidal and planetary wave propagation at thermospheric heights. This model is based on perturbation approximation and mode separation. The effects of viscosity and heat conduction are parameterized by Rayleigh friction and Newtonian cooling. Because of this simplicity, one gains a clear physical insight into basic features of atmospheric wave propagation. In particular, we discuss the meridional structures of pressure and horizontal wind (the solutions of Laplace's equation) and their modification due to dissipative effects at thermospheric heights. Furthermore, we solve the equations governing the height structure of the wave modes and arrive at a very simple asymptotic solution valid in the upper part of the thermosphere. That 'system transfer function' of the thermosphere allows one to estimate immediately the reaction of the thermospheric wave mode parameters such as pressure, temperature, and winds to an external heat source of arbitrary temporal and spatial distribution. Finally, the diffusion effects of the minor constituents due to the global wind circulation are discussed, and some results of numerical calculations are presented.

Reflected wave manipulation by inhomogeneous impedance via varying-depth acoustic liners

NASA Astrophysics Data System (ADS)

Guo, Jingwen; Zhang, Xin; Fang, Yi; Fattah, Ryu

2018-05-01

Acoustic liners, consisting of a perforated panel affixed to a honeycomb core with a rigid back plate, are widely used for noise attenuation purpose. In this study, by exploiting inhomogeneous impedance properties, we report an experimental and numerical study on a liner-type acoustic metasurface, which possesses the functionality of both reflected wave manipulation and sound energy attenuation simultaneously. To realize the inhomogeneous acoustic impedance, an acoustic metasurface constructed by varying-depth acoustic liners is designed and fabricated. The reflected sound pressure fields induced by the metasurface are obtained in both experiments and simulations. A complete characterization of this metasurface is performed, including the effects of depth gradient, incident angle, and incident frequency. Anomalous reflection, apparent negative reflection, and conversion from an incident wave to a surface wave with strong energy dissipation are achieved by the structure. Moreover, our proposed structure can overcome the single frequency performance limitation that exists in conventional metasurfaces and performs well in a broadband frequency range. The proposed acoustic metasurface offers flexibility in controlling the direction of sound wave propagation with energy dissipation property and holds promise for various applications of noise reduction.

Sound transmission in porcine thorax through airway insonification.

PubMed

Peng, Ying; Dai, Zoujun; Mansy, Hansen A; Henry, Brian M; Sandler, Richard H; Balk, Robert A; Royston, Thomas J

2016-04-01

Many pulmonary injuries and pathologies may lead to structural and functional changes in the lungs resulting in measurable sound transmission changes on the chest surface. Additionally, noninvasive imaging of externally driven mechanical wave motion in the chest (e.g., using magnetic resonance elastography) can provide information about lung structural property changes and, hence, may be of diagnostic value. In the present study, a comprehensive computational simulation (in silico) model was developed to simulate sound wave propagation in the airways, lung, and chest wall under normal and pneumothorax conditions. Experiments were carried out to validate the model. Here, sound waves with frequency content from 50 to 700 Hz were introduced into airways of five porcine subjects via an endotracheal tube, and transmitted waves were measured by scanning laser Doppler vibrometry at the chest wall surface. The computational model predictions of decreased sound transmission with pneumothorax were consistent with experimental measurements. The in silico model can also be used to visualize wave propagation inside and on the chest wall surface for other pulmonary pathologies, which may help in developing and interpreting diagnostic procedures that utilize sound and vibration.

Sound transmission in porcine thorax through airway insonification

PubMed Central

Dai, Zoujun; Mansy, Hansen A.; Henry, Brian M.; Sandler, Richard H.; Balk, Robert A.; Royston, Thomas J.

2015-01-01

Many pulmonary injuries and pathologies may lead to structural and functional changes in the lungs resulting in measurable sound transmission changes on the chest surface. Additionally, noninvasive imaging of externally driven mechanical wave motion in the chest (e.g., using magnetic resonance elastography) can provide information about lung structural property changes and, hence, may be of diagnostic value. In the present study, a comprehensive computational simulation (in silico) model was developed to simulate sound wave propagation in the airways, lung, and chest wall under normal and pneumothorax conditions. Experiments were carried out to validate the model. Here, sound waves with frequency content from 50 to 700 Hz were introduced into airways of five porcine subjects via an endotracheal tube, and transmitted waves were measured by scanning laser Doppler vibrometry at the chest wall surface. The computational model predictions of decreased sound transmission with pneumothorax were consistent with experimental measurements. The in silico model can also be used to visualize wave propagation inside and on the chest wall surface for other pulmonary pathologies, which may help in developing and interpreting diagnostic procedures that utilize sound and vibration. PMID:26280512

Analysis of wave motion in one-dimensional structures through fast-Fourier-transform-based wavelet finite element method

NASA Astrophysics Data System (ADS)

Shen, Wei; Li, Dongsheng; Zhang, Shuaifang; Ou, Jinping

2017-07-01

This paper presents a hybrid method that combines the B-spline wavelet on the interval (BSWI) finite element method and spectral analysis based on fast Fourier transform (FFT) to study wave propagation in One-Dimensional (1D) structures. BSWI scaling functions are utilized to approximate the theoretical wave solution in the spatial domain and construct a high-accuracy dynamic stiffness matrix. Dynamic reduction on element level is applied to eliminate the interior degrees of freedom of BSWI elements and substantially reduce the size of the system matrix. The dynamic equations of the system are then transformed and solved in the frequency domain through FFT-based spectral analysis which is especially suitable for parallel computation. A comparative analysis of four different finite element methods is conducted to demonstrate the validity and efficiency of the proposed method when utilized in high-frequency wave problems. Other numerical examples are utilized to simulate the influence of crack and delamination on wave propagation in 1D rods and beams. Finally, the errors caused by FFT and their corresponding solutions are presented.

A projection-free method for representing plane-wave DFT results in an atom-centered basis

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

Dunnington, Benjamin D.; Schmidt, J. R., E-mail: schmidt@chem.wisc.edu

2015-09-14

Plane wave density functional theory (DFT) is a powerful tool for gaining accurate, atomic level insight into bulk and surface structures. Yet, the delocalized nature of the plane wave basis set hinders the application of many powerful post-computation analysis approaches, many of which rely on localized atom-centered basis sets. Traditionally, this gap has been bridged via projection-based techniques from a plane wave to atom-centered basis. We instead propose an alternative projection-free approach utilizing direct calculation of matrix elements of the converged plane wave DFT Hamiltonian in an atom-centered basis. This projection-free approach yields a number of compelling advantages, including strictmore » orthonormality of the resulting bands without artificial band mixing and access to the Hamiltonian matrix elements, while faithfully preserving the underlying DFT band structure. The resulting atomic orbital representation of the Kohn-Sham wavefunction and Hamiltonian provides a gateway to a wide variety of analysis approaches. We demonstrate the utility of the approach for a diverse set of chemical systems and example analysis approaches.« less

Backward spoof surface wave in plasmonic metamaterial of ultrathin metallic structure.

PubMed

Liu, Xiaoyong; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

2016-02-04

Backward wave with anti-parallel phase and group velocities is one of the basic properties associated with negative refraction and sub-diffraction image that have attracted considerable interest in the context of photonic metamaterials. It has been predicted theoretically that some plasmonic structures can also support backward wave propagation of surface plasmon polaritons (SPPs), however direct experimental demonstration has not been reported, to the best of our knowledge. In this paper, a specially designed plasmonic metamaterial of corrugated metallic strip has been proposed that can support backward spoof SPP wave propagation. The dispersion analysis, the full electromagnetic field simulation and the transmission measurement of the plasmonic metamaterial waveguide have clearly validated the backward wave propagation with dispersion relation possessing negative slope and opposite directions of group and phase velocities. As a further verification and application, a contra-directional coupler is designed and tested that can route the microwave signal to opposite terminals at different operating frequencies, indicating new application opportunities of plasmonic metamaterial in integrated functional devices and circuits for microwave and terahertz radiation.

System identification based on deconvolution and cross correlation: An application to a 20‐story instrumented building in Anchorage, Alaska

USGS Publications Warehouse

Wen, Weiping; Kalkan, Erol

2017-01-01

Deconvolution and cross‐correlation techniques are used for system identification of a 20‐story steel, moment‐resisting frame building in downtown Anchorage, Alaska. This regular‐plan midrise structure is instrumented with a 32‐channel accelerometer array at 10 levels. The impulse response functions (IRFs) and correlation functions (CFs) are computed based on waveforms recorded from ambient vibrations and five local and regional earthquakes. The earthquakes occurred from 2005 to 2014 with moment magnitudes between 4.7 and 6.2 over a range of azimuths at epicenter distances of 13.3–183 km. The building’s fundamental frequencies and mode shapes are determined using a complex mode indicator function based on singular value decomposition of multiple reference frequency‐response functions. The traveling waves, identified in IRFs with a virtual source at the roof, and CFs are used to estimate the intrinsic attenuation associated with the fundamental modes and shear‐wave velocity in the building. Although the cross correlation of the waveforms at various levels with the corresponding waveform at the first floor provides more complicated wave propagation than that from the deconvolution with virtual source at the roof, the shear‐wave velocities identified by both techniques are consistent—the largest difference in average values is within 8%. The median shear‐wave velocity from the IRFs of five earthquakes is 191  m/s for the east–west (E‐W), 205  m/s for the north–south (N‐S), and 176  m/s for the torsional responses. The building’s average intrinsic‐damping ratio is estimated to be 3.7% and 3.4% in the 0.2–1 Hz frequency band for the E‐W and N‐S directions, respectively. These results are intended to serve as reference for the undamaged condition of the building, which may be used for tracking changes in structural integrity during and after future earthquakes.

A New Comprehensive Model for Crustal and Upper Mantle Structure of the European Plate

NASA Astrophysics Data System (ADS)

Morelli, A.; Danecek, P.; Molinari, I.; Postpischl, L.; Schivardi, R.; Serretti, P.; Tondi, M. R.

2009-12-01

We present a new comprehensive model of crustal and upper mantle structure of the whole European Plate — from the North Atlantic ridge to Urals, and from North Africa to the North Pole — describing seismic speeds (P and S) and density. Our description of crustal structure merges information from previous studies: large-scale compilations, seismic prospection, receiver functions, inversion of surface wave dispersion measurements and Green functions from noise correlation. We use a simple description of crustal structure, with laterally-varying sediment and cristalline layers thickness and seismic parameters. Most original information refers to P-wave speed, from which we derive S speed and density from scaling relations. This a priori crustal model by itself improves the overall fit to observed Bouguer anomaly maps, as derived from GRACE satellite data, over CRUST2.0. The new crustal model is then used as a constraint in the inversion for mantle shear wave speed, based on fitting Love and Rayleigh surface wave dispersion. In the inversion for transversely isotropic mantle structure, we use group speed measurements made on European event-to-station paths, and use a global a priori model (S20RTS) to ensure fair rendition of earth structure at depth and in border areas with little coverage from our data. The new mantle model sensibly improves over global S models in the imaging of shallow asthenospheric (slow) anomalies beneath the Alpine mobile belt, and fast lithospheric signatures under the two main Mediterranean subduction systems (Aegean and Tyrrhenian). We map compressional wave speed inverting ISC travel times (reprocessed by Engdahl et al.) with a non linear inversion scheme making use of finite-difference travel time calculation. The inversion is based on an a priori model obtained by scaling the 3D mantle S-wave speed to P. The new model substantially confirms images of descending lithospheric slabs and back-arc shallow asthenospheric regions, shown in other more local high-resolution tomographic studies, but covers the whole range of the European Plate. We also obtain three-dimensional mantle density structure by inversion of GRACE Bouguer anomalies locally adjusting density and the scaling relation between seismic wave speeds and density. We validate the new comprehensive model through comparison of recorded seismograms with numerical simulations based on SPECFEM3D. This work is a contribution towards the definition of a reference earth model for Europe. To this extent, in order to improve model dissemination and comparison, we propose the adoption of a common exchange format for tomographic earth models based on JSON, a lightweight data-interchange format supported by most high-level programming languages. We provide tools for manipulating and visualising models, described in this standard format, in Google Earth and GEON IDV.

Superoscillating electron wave functions with subdiffraction spots

NASA Astrophysics Data System (ADS)

Remez, Roei; Tsur, Yuval; Lu, Peng-Han; Tavabi, Amir H.; Dunin-Borkowski, Rafal E.; Arie, Ady

2017-03-01

Almost one and a half centuries ago, Abbe [Arch. Mikrosk. Anat. 9, 413 (1873), 10.1007/BF02956173] and shortly after Lord Rayleigh [Philos. Mag. Ser. 5 8, 261 (1879), 10.1080/14786447908639684] showed that, when an optical lens is illuminated by a plane wave, a diffraction-limited spot with radius 0.61 λ /sinα is obtained, where λ is the wavelength and α is the semiangle of the beam's convergence cone. However, spots with much smaller features can be obtained at the focal plane when the lens is illuminated by an appropriately structured beam. Whereas this concept is known for light beams, here, we show how to realize it for a massive-particle wave function, namely, a free electron. We experimentally demonstrate an electron central spot of radius 106 pm, which is more than two times smaller than the diffraction limit of the experimental setup used. In addition, we demonstrate that this central spot can be structured by adding orbital angular momentum to it. The resulting superoscillating vortex beam has a smaller dark core with respect to a regular vortex beam. This family of electron beams having hot spots with arbitrarily small features and tailored structures could be useful for studying electron-matter interactions with subatomic resolution.

A double expansion method for the frequency response of finite-length beams with periodic parameters

NASA Astrophysics Data System (ADS)

Ying, Z. G.; Ni, Y. Q.

2017-03-01

A double expansion method for the frequency response of finite-length beams with periodic distribution parameters is proposed. The vibration response of the beam with spatial periodic parameters under harmonic excitations is studied. The frequency response of the periodic beam is the function of parametric period and then can be expressed by the series with the product of periodic and non-periodic functions. The procedure of the double expansion method includes the following two main steps: first, the frequency response function and periodic parameters are expanded by using identical periodic functions based on the extension of the Floquet-Bloch theorem, and the period-parametric differential equation for the frequency response is converted into a series of linear differential equations with constant coefficients; second, the solutions to the linear differential equations are expanded by using modal functions which satisfy the boundary conditions, and the linear differential equations are converted into algebraic equations according to the Galerkin method. The expansion coefficients are obtained by solving the algebraic equations and then the frequency response function is finally determined. The proposed double expansion method can uncouple the effects of the periodic expansion and modal expansion so that the expansion terms are determined respectively. The modal number considered in the second expansion can be reduced remarkably in comparison with the direct expansion method. The proposed double expansion method can be extended and applied to the other structures with periodic distribution parameters for dynamics analysis. Numerical results on the frequency response of the finite-length periodic beam with various parametric wave numbers and wave amplitude ratios are given to illustrate the effective application of the proposed method and the new frequency response characteristics, including the parameter-excited modal resonance, doubling-peak frequency response and remarkable reduction of the maximum frequency response for certain parametric wave number and wave amplitude. The results have the potential application to structural vibration control.

Non-contact thickness measurement using UTG

NASA Technical Reports Server (NTRS)

Bui, Hoa T. (Inventor)

1996-01-01

A measurement structure for determining the thickness of a specimen without mechanical contact but instead employing ultrasonic waves including an ultrasonic transducer and an ultrasonic delay line connected to the transducer by a retainer or collar. The specimen, whose thickness is to be measured, is positioned below the delay line. On the upper surface of the specimen a medium such as a drop of water is disposed which functions to couple the ultrasonic waves from the delay line to the specimen. A receiver device, which may be an ultrasonic thickness gauge, receives reflected ultrasonic waves reflected from the upper and lower surface of the specimen and determines the thickness of the specimen based on the time spacing of the reflected waves.

The role of coral reef rugosity in dissipating wave energy and coastal protection

NASA Astrophysics Data System (ADS)

Harris, Daniel; Rovere, Alessio; Parravicini, Valeriano; Casella, Elisa

2016-04-01

Coral reefs are the most effective natural barrier in dissipating wave energy through breaking and bed friction. The attenuation of wave energy by coral reef flats is essential in the protection and stability of coral reef aligned coasts and reef islands. However, the effectiveness of wave energy dissipation by coral reefs may be diminished under future climate change scenarios with a potential reduction of coral reef rugosity due to increased stress environmental stress on corals. The physical roughness or rugosity of coral reefs is directly related to ecological diversity, reef health, and hydrodynamic roughness. However, the relationship between physical roughness and hydrodynamic roughness is not well understood despite the crucial role of bed friction in dissipating wave energy in coral reef aligned coasts. We examine the relationship between wave energy dissipation across a fringing reef in relation to the cross-reef ecological zonation and the benthic hydrodynamic roughness. Waves were measured by pressure transducers in a cross-reef transect on the reefs flats and post processed on a wave by wave basis to determine wave statistics such as significant wave height and wave period. Results from direct wave measurement were then used to calibrate a 1D wave dissipation model that incorporates dissipation functions due to bed friction and wave breaking. This model was used to assess the bed roughness required to produce the observed wave height dissipation during propagation from deep water and across the coral reef flats. Changes in wave dissipation was also examined under future scenarios of sea level rise and reduced bed roughness. Three dimensional models of the benthic reef structure were produced through structure-from-motion photogrammetry surveys. Reef rugosity was then determined from these surveys and related to the roughness results from the calibrated model. The results indicate that applying varying roughness coefficients as the benthic ecological assemblage changes produces the most accurate assessment of wave energy dissipation across the reef flat. However, the modelled results of bed roughness (e.g. 0.01 for the fore-reef slope) were different to the directly measured rugosity values (0.05 for the fore-reef slope) from three dimension structure-from-motion surveys. In spite of this, the modelled and directly measured values of roughness are similar considering the difficulties outlined in previous research when relating the coral reef structural complexity to a single value of hydrodynamic roughness. Bed roughness was shown to be a secondary factor behind wave breaking in dissipating wave energy. However, without bed friction waves could be an order of magnitude higher in the back-reef environment. Bed friction is also increasingly important in wave dissipation at higher sea levels as wave energy dissipation due to wave breaking is reduced at greater depths. This shows that maintaining a structurally diverse and healthy reef is crucial under future sea level rise scenarios in order to maintain the protection of coastal environments. These results also indicate that significant geomorphic change in coastal environments will occur due to reduced wave dissipation at higher sea levels unless reefs are capable of keeping up with forecasted sea level rise.

Origin of chaos near three-dimensional quantum vortices: A general Bohmian theory

NASA Astrophysics Data System (ADS)

Tzemos, Athanasios C.; Efthymiopoulos, Christos; Contopoulos, George

2018-04-01

We provide a general theory for the structure of the quantum flow near three-dimensional (3D) nodal lines, i.e., one-dimensional loci where the 3D wave function becomes equal to zero. In suitably defined coordinates (comoving with the nodal line) the generic structure of the flow implies the formation of 3D quantum vortices. We show that such vortices are accompanied by nearby invariant lines of the comoving quantum flow, called X lines, which are normally hyperbolic. Furthermore, the stable and unstable manifolds of the X lines produce chaotic scatterings of nearby quantum (Bohmian) trajectories, thus inducing an intricate form of the quantum current in the neighborhood of each 3D quantum vortex. Generic formulas describing the structure around 3D quantum vortices are provided, applicable to an arbitrary choice of 3D wave function. We also give specific numerical examples as well as a discussion of the physical consequences of chaos near 3D quantum vortices.

Origin of chaos near three-dimensional quantum vortices: A general Bohmian theory.

PubMed

Tzemos, Athanasios C; Efthymiopoulos, Christos; Contopoulos, George

2018-04-01

We provide a general theory for the structure of the quantum flow near three-dimensional (3D) nodal lines, i.e., one-dimensional loci where the 3D wave function becomes equal to zero. In suitably defined coordinates (comoving with the nodal line) the generic structure of the flow implies the formation of 3D quantum vortices. We show that such vortices are accompanied by nearby invariant lines of the comoving quantum flow, called X lines, which are normally hyperbolic. Furthermore, the stable and unstable manifolds of the X lines produce chaotic scatterings of nearby quantum (Bohmian) trajectories, thus inducing an intricate form of the quantum current in the neighborhood of each 3D quantum vortex. Generic formulas describing the structure around 3D quantum vortices are provided, applicable to an arbitrary choice of 3D wave function. We also give specific numerical examples as well as a discussion of the physical consequences of chaos near 3D quantum vortices.

Nonlinear guided wave propagation in prestressed plates.

PubMed

Pau, Annamaria; Lanza di Scalea, Francesco

2015-03-01

The measurement of stress in a structure presents considerable interest in many fields of engineering. In this paper, the diagnostic potential of nonlinear elastic guided waves in a prestressed plate is investigated. To do so, an analytical model is formulated accounting for different aspects involved in the phenomenon. The fact that the initial strains can be finite is considered using the Green Lagrange strain tensor, and initial and final configurations are not merged, as it would be assumed in the infinitesimal strain theory. Moreover, an appropriate third-order expression of the strain energy of the hyperelastic body is adopted to account for the material nonlinearities. The model obtained enables to investigate both the linearized case, which gives the variation of phase and group velocity as a function of the initial stress, and the nonlinear case, involving second-harmonic generation as a function of the initial state of stress. The analysis is limited to Rayleigh-Lamb waves propagating in a plate. Three cases of initial prestress are considered, including prestress in the direction of the wave propagation, prestress orthogonal to the direction of wave propagation, and plane isotropic stress.

Three-Dimensional Passive-Source Reverse-Time Migration of Converted Waves: The Method

NASA Astrophysics Data System (ADS)

Li, Jiahang; Shen, Yang; Zhang, Wei

2018-02-01

At seismic discontinuities in the crust and mantle, part of the compressional wave energy converts to shear wave, and vice versa. These converted waves have been widely used in receiver function (RF) studies to image discontinuity structures in the Earth. While generally successful, the conventional RF method has its limitations and is suited mostly to flat or gently dipping structures. Among the efforts to overcome the limitations of the conventional RF method is the development of the wave-theory-based, passive-source reverse-time migration (PS-RTM) for imaging complex seismic discontinuities and scatters. To date, PS-RTM has been implemented only in 2D in the Cartesian coordinate for local problems and thus has limited applicability. In this paper, we introduce a 3D PS-RTM approach in the spherical coordinate, which is better suited for regional and global problems. New computational procedures are developed to reduce artifacts and enhance migrated images, including back-propagating the main arrival and the coda containing the converted waves separately, using a modified Helmholtz decomposition operator to separate the P and S modes in the back-propagated wavefields, and applying an imaging condition that maintains a consistent polarity for a given velocity contrast. Our new approach allows us to use migration velocity models with realistic velocity discontinuities, improving accuracy of the migrated images. We present several synthetic experiments to demonstrate the method, using regional and teleseismic sources. The results show that both regional and teleseismic sources can illuminate complex structures and this method is well suited for imaging dipping interfaces and sharp lateral changes in discontinuity structures.

Generator Coordinate Method Analysis of Xe and Ba Isotopes

NASA Astrophysics Data System (ADS)

Higashiyama, Koji; Yoshinaga, Naotaka; Teruya, Eri

Nuclear structure of Xe and Ba isotopes is studied in terms of the quantum-number projected generator coordinate method (GCM). The GCM reproduces well the energy levels of high-spin states as well as low-lying states. The structure of the low-lying states is analyzed through the GCM wave functions.

Quantization of Chirikov Map and Quantum KAM Theorem.

NASA Astrophysics Data System (ADS)

Shi, Kang-Jie

KAM theorem is one of the most important theorems in classical nonlinear dynamics and chaos. To extend KAM theorem to the regime of quantum mechanics, we first study the quantum Chirikov map, whose classical counterpart provides a good example of KAM theorem. Under resonance condition 2pihbar = 1/N, we obtain the eigenstates of the evolution operator of this system. We find that the wave functions in the coherent state representation (CSR) are very similar to the classical trajectories. In particular, some of these wave functions have wall-like structure at the locations of classical KAM curves. We also find that a local average is necessary for a Wigner function to approach its classical limit in the phase space. We then study the general problem theoretically. Under similar conditions for establishing the classical KAM theorem, we obtain a quantum extension of KAM theorem. By constructing successive unitary transformations, we can greatly reduce the perturbation part of a near-integrable Hamiltonian system in a region associated with a Diophantine number {rm W}_{o}. This reduction is restricted only by the magnitude of hbar.. We can summarize our results as follows: In the CSR of a nearly integrable quantum system, associated with a Diophantine number {rm W}_ {o}, there is a band near the corresponding KAM torus of the classical limit of the system. In this band, a Gaussian wave packet moves quasi-periodically (and remain close to the KAM torus) for a long time, with possible diffusion in both the size and the shape of its wave packet. The upper bound of the tunnelling rate out of this band for the wave packet can be made much smaller than any given power of hbar, if the original perturbation is sufficiently small (but independent of hbar). When hbarto 0, we reproduce the classical KAM theorem. For most near-integrable systems the eigenstate wave function in the above band can either have a wall -like structure or have a vanishing amplitude. These conclusions agree with the numerical results of the quantum Chirikov map.

Accessing the uncertainties of seismic velocity and anisotropy structure of Northern Great Plains using a transdimensional Bayesian approach

NASA Astrophysics Data System (ADS)

Gao, C.; Lekic, V.

2017-12-01

Seismic imaging utilizing complementary seismic data provides unique insight on the formation, evolution and current structure of continental lithosphere. While numerous efforts have improved the resolution of seismic structure, the quantification of uncertainties remains challenging due to the non-linearity and the non-uniqueness of geophysical inverse problem. In this project, we use a reverse jump Markov chain Monte Carlo (rjMcMC) algorithm to incorporate seismic observables including Rayleigh and Love wave dispersion, Ps and Sp receiver function to invert for shear velocity (Vs), compressional velocity (Vp), density, and radial anisotropy of the lithospheric structure. The Bayesian nature and the transdimensionality of this approach allow the quantification of the model parameter uncertainties while keeping the models parsimonious. Both synthetic test and inversion of actual data for Ps and Sp receiver functions are performed. We quantify the information gained in different inversions by calculating the Kullback-Leibler divergence. Furthermore, we explore the ability of Rayleigh and Love wave dispersion data to constrain radial anisotropy. We show that when multiple types of model parameters (Vsv, Vsh, and Vp) are inverted simultaneously, the constraints on radial anisotropy are limited by relatively large data uncertainties and trade-off strongly with Vp. We then perform joint inversion of the surface wave dispersion (SWD) and Ps, Sp receiver functions, and show that the constraints on both isotropic Vs and radial anisotropy are significantly improved. To achieve faster convergence of the rjMcMC, we propose a progressive inclusion scheme, and invert SWD measurements and receiver functions from about 400 USArray stations in the Northern Great Plains. We start by only using SWD data due to its fast convergence rate. We then use the average of the ensemble as a starting model for the joint inversion, which is able to resolve distinct seismic signatures of geological structures including the trans-Hudson orogen, Wyoming craton and Yellowstone hotspot. Various analyses are done to access the uncertainties of the seismic velocities and Moho depths. We also address the importance of careful data processing of receiver functions by illustrating artifacts due to unmodelled sediment reverberations.

Design and fabrication of integrated micro/macrostructure for 3D functional gradient systems based on additive manufacturing

NASA Astrophysics Data System (ADS)

Yin, Ming; Xie, Luofeng; Jiang, Weifeng; Yin, Guofu

2018-05-01

Functional gradient systems have important applications in many areas. Although a 2D dielectric structure that serves as the gradient index medium for controlling electromagnetic waves is well established, it may not be suitable for application in 3D case. In this paper, we present a method to realize functional gradient systems with 3D integrated micro/macrostructure. The homogenization of the structure is studied in detail by conducting band diagram analysis. The analysis shows that the effective medium approximation is valid even when periodicity is comparable to wavelength. The condition to ensure the polarization-invariant, isotropic, and frequency-independent property is investigated. The scheme for the design and fabrication of 3D systems requiring spatial material property distribution is presented. By using the vat photopolymerization process, a large overall size of macrostructure at the system level and precise fine features of microstructure at the unit cell level are realized, thus demonstrating considerable scalability of the system for wave manipulation.

Study on acceleration processes of the radiation belt electrons through interaction with sub-packet chorus waves in parallel propagation

NASA Astrophysics Data System (ADS)

Hiraga, R.; Omura, Y.

2017-12-01

By recent observations, chorus waves include fine structures such as amplitude fluctuations (i.e. sub-packet structure), and it has not been verified in detail yet how energetic electrons are efficiently accelerated under the wave features. In this study, we firstly focus on the acceleration process of a single electron: how it experiences the efficient energy increase by interaction with sub-packet chorus waves in parallel propagation along the Earth's magnetic field. In order to reproduce the chorus waves as seen by the latest observations by Van Allen Probes (Foster et al. 2017), the wave model amplitude in our simulation is structured such that when the wave amplitude nonlinearly grows to reach the optimum amplitude, it starts decreasing until crossing the threshold. Once it crosses the threshold, the wave dissipates and a new wave rises to repeat the nonlinear growth and damping in the same manner. The multiple occurrence of this growth-damping cycle forms a saw tooth-like amplitude variation called sub-packet. This amplitude variation also affects the wave frequency behavior which is derived by the chorus wave equations as a function of the wave amplitude (Omura et al. 2009). It is also reasonable to assume that when a wave packet diminishes and the next wave rises, it has a random phase independent of the previous wave. This randomness (discontinuity) in phase variation is included in the simulation. Through interaction with such waves, dynamics of energetic electrons were tracked. As a result, some electrons underwent an efficient acceleration process defined as successive entrapping, in which an electron successfully continues to surf the trapping potential generated by consecutive wave packets. When successive entrapping occurs, an electron trapped and de-trapped (escape the trapping potential) by a single wave packet falls into another trapping potential generated by the next wave sub-packet and continuously accelerated. The occurrence of successive entrapping is influenced by some factors such as the magnitude of wave amplitude or inhomogeneity of the Earth's dipole magnetic field. In addition, an energy range of electrons is also a major factor. In this way, it has been examined in detail how and under which conditions electrons are efficiently accelerated in the formation process of the radiation belts.

Towards Full-Waveform Ambient Noise Inversion

NASA Astrophysics Data System (ADS)

Sager, K.; Ermert, L. A.; Boehm, C.; Fichtner, A.

2016-12-01

Noise tomography usually works under the assumption that the inter-station ambient noise correlation is equal to a scaled version of the Green function between the two receivers. This assumption, however, is only met under specific conditions, e.g. wavefield diffusivity and equipartitioning, or the isotropic distribution of both mono- and dipolar uncorrelated noise sources. These assumptions are typically not satisfied in the Earth. This inconsistency inhibits the exploitation of the full waveform information contained in noise correlations in order to constrain Earth structure and noise generation. To overcome this limitation, we attempt to develop a method that consistently accounts for the distribution of noise sources, 3D heterogeneous Earth structure and the full seismic wave propagation physics. This is intended to improve the resolution of tomographic images, to refine noise source location, and thereby to contribute to a better understanding of noise generation. We introduce an operator-based formulation for the computation of correlation functions and apply the continuous adjoint method that allows us to compute first and second derivatives of misfit functionals with respect to source distribution and Earth structure efficiently. Based on these developments we design an inversion scheme using a 2D finite-difference code. To enable a joint inversion for noise sources and Earth structure, we investigate the following aspects: The capability of different misfit functionals to image wave speed anomalies and source distribution. Possible source-structure trade-offs, especially to what extent unresolvable structure can be mapped into the inverted noise source distribution and vice versa. In anticipation of real-data applications, we present an extension of the open-source waveform modelling and inversion package Salvus, which allows us to compute correlation functions in 3D media with heterogeneous noise sources at the surface.

S-wave velocity structure in the Nankai accretionary prism derived from Rayleigh admittance

NASA Astrophysics Data System (ADS)

Tonegawa, Takashi; Araki, Eiichiro; Kimura, Toshinori; Nakamura, Takeshi; Nakano, Masaru; Suzuki, Kensuke

2017-04-01

Two cabled seafloor networks with 22 and 29 stations (DONET 1 and 2: Dense Oceanfloor Network System for Earthquake and Tsunamis) have been constructed on the accretionary prism at the Nankai subduction zone of Japan since March 2010. The observation periods of DONET 1 and 2 exceed more than 5 years and 10 months, respectively. Each station contains broadband seismometers and absolute and differential pressure gauges. In this study, using Rayleigh waves of microseisms and earthquakes, we calculate the Rayleigh admittance (Ruan et al., 2014, JGR) at the seafloor for each station, i.e., an amplitude transfer function from pressure to displacement, particularly for the frequencies of 0.1-0.2 Hz (ambient noise) and 0.04-0.1 Hz (earthquake signal), and estimate S-wave velocity (Vs) structure beneath stations in DONET 1 and 2. We calculated the displacement seismogram by removing the instrument response from the velocity seismogram for each station. The pressure record observed at the differential pressure gauge was used in this study because of a high resolution of the pressure observation. In addition to Rayleigh waves of microseisms, we collected waveforms of Rayleigh waves for earthquakes with an epicentral distance of 15-90°, M>5.0, and focal depth shallower than 50 km. In the frequency domain, we smoothed the transfer function of displacement/pressure with the Parzen window of ±0.01 Hz. In order to determine one-dimensional Vs profiles, we performed a nonlinear inversion technique, i.e., simulated annealing. As a result, Vs profiles obtained at stations near the land show simple Vs structure, i.e., Vs increases with depth. However, some profiles located at the toe of the acceretionary prism have a low-velocity zone (LVZ) at a depth of 5-7 km within the accretinary sediment. The velocity reduction is approximately 5-20 %. Park et al. (2010) reported such a large reduction in P-wave velocity in the region of DONET 1 (eastern network and southeast of the Kii Peninsula), but our result shows the LVZ in the regions of both DONET 1 and 2 (2: western network and southwest of the Kii Peninsula). Similar features could also be obtained by using Rayleigh waves of earthquake-signals only. This indicates lateral variation of Vs structure at the toe of the Nankai accretionary prism.

Nonreciprocity of spin waves in magnonic crystals created by surface acoustic waves in structures with yttrium iron garnet

NASA Astrophysics Data System (ADS)

Kryshtal, R. G.; Medved, A. V.

2015-12-01

Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW - magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW - magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW - magnonic crystals are promising for signal processing in the GHz range.

Tympanal travelling waves in migratory locusts.

PubMed

Windmill, James F C; Göpfert, Martin C; Robert, Daniel

2005-01-01

Hearing animals, including many vertebrates and insects, have the capacity to analyse the frequency composition of sound. In mammals, frequency analysis relies on the mechanical response of the basilar membrane in the cochlear duct. These vibrations take the form of a slow vibrational wave propagating along the basilar membrane from base to apex. Known as von Békésy's travelling wave, this wave displays amplitude maxima at frequency-specific locations along the basilar membrane, providing a spatial map of the frequency of sound--a tonotopy. In their structure, insect auditory systems may not be as sophisticated at those of mammals, yet some are known to perform sound frequency analysis. In the desert locust, this analysis arises from the mechanical properties of the tympanal membrane. In effect, the spatial decomposition of incident sound into discrete frequency components involves a tympanal travelling wave that funnels mechanical energy to specific tympanal locations, where distinct groups of mechanoreceptor neurones project. Notably, observed tympanal deflections differ from those predicted by drum theory. Although phenomenologically equivalent, von Békésy's and the locust's waves differ in their physical implementation. von Békésy's wave is born from interactions between the anisotropic basilar membrane and the surrounding incompressible fluids, whereas the locust's wave rides on an anisotropic membrane suspended in air. The locust's ear thus combines in one structure the functions of sound reception and frequency decomposition.

Fetal Echocardiography/Your Unborn Baby's Heart

MedlinePlus

... heart for the doctor to evaluate. The sound waves can also detect blood flow throughout the baby's heart. This enables the doctor to evaluate the structure and function of the fetal heart. Who needs one? Fetal ...

Wave function for harmonically confined electrons in time-dependent electric and magnetostatic fields.

PubMed

Zhu, Hong-Ming; Chen, Jin-Wang; Pan, Xiao-Yin; Sahni, Viraht

2014-01-14

We derive via the interaction "representation" the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field-the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement - the uniform electron gas - the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKT wave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide examples of the application of the GKT wave function.

Instantaneous Frequency Analysis on Nonlinear EMIC Emissions: Arase Observation

NASA Astrophysics Data System (ADS)

Shoji, M.; Yoshizumi, M.; Omura, Y.; Kasaba, Y.; Ishisaka, K.; Matsuda, S.; Kasahara, Y.; Yagitani, S.; Matsuoka, A.; Teramoto, M.; Takashima, T.; Shinohara, I.

2017-12-01

In the inner magnetosphere, electromagnetic ion cyclotron (EMIC) waves cause nonlinear interactions with energetic protons. The waves drastically modify the proton distribution function, resulting in the particle loss in the radiation belt. Arase spacecraft, launched in late 2016, observed a nonlinear EMIC falling tone emission in the high magnetic latitude (MLAT) region of the inner magnetosphere. The wave growth with sub-packet structures of the falling tone emission is found by waveform data from PWE/EFD instrument. The evolution of the instantaneous frequency of the electric field of the EMIC falling tone emission is analyzed by Hilbert-Huang transform (HHT). We find several sub-packets with rising frequency in the falling tone wave. A self-consistent hybrid simulation suggested the complicate frequency evolution of the EMIC sub-packet emissions in the generation region. The intrinsic mode functions of Arase data derived from HHT are compared with the simulation data. The origin of the falling tone emission in the high MLAT region is also discussed.

Adhesive joint evaluation by ultrasonic interface and lamb waves

NASA Technical Reports Server (NTRS)

Rokhlin, S. I.

1986-01-01

Some results on the application of interface and Lamb waves for the study of curing of thin adhesive layers were summarized. In the case of thick substrates (thickness much more than the wave length) the interface waves can be used. In this case the experimental data can be inverted and the shear modulus of the adhesive film may be explicitly found based on the measured interface wave velocity. It is shown that interface waves can be used for the study of curing of structural adhesives as a function of different temperatures and other experimental conditions. The kinetics of curing was studied. In the case of thin substrates the wave phenomena are much more complicated. It is shown that for successful measurements proper selection of experimental conditions is very important. This can be done based on theoretical estimations. For correctly selected experimental conditions the Lamb waves may be a sensitive probe of adhesive bond quality and may be used or cure monitoring.

Compressive and rarefactive double layers in non-uniform plasma with q-nonextensive distributed electrons

NASA Astrophysics Data System (ADS)

Shan, S. Ali; Saleem, H.

2018-05-01

Electrostatic solitary waves and double layers (DLs) formed by the coupled ion acoustic (IA) and drift waves have been investigated in non-uniform plasma using q-nonextensive distribution function for the electrons and assuming ions to be cold Ti< Te. It is found that both compressive and rarefactive nonlinear structures (solitary waves and DLs) are possible in such a system. The steeper gradients are supportive for compressive solitary (and double layers) and destructive for rarefactive ones. The q-nonextensivity parameter q and the magnitudes of gradient scale lengths of density and temperature have significant effects on the amplitude of the double layers (and double layers) as well as on the speed of these structures. This theoretical model is general which has been applied here to the F-region ionosphere for illustration.

Evaluation of concrete cover by surface wave technique: Identification procedure

NASA Astrophysics Data System (ADS)

Piwakowski, Bogdan; Kaczmarek, Mariusz; Safinowski, Paweł

2012-05-01

Concrete cover degradation is induced by aggressive agents in ambiance, such as moisture, chemicals or temperature variations. Due to degradation usually a thin (a few millimeters thick) surface layer has porosity slightly higher than the deeper sound material. The non destructive evaluation of concrete cover is vital to monitor the integrity of concrete structures and prevent their irreversible damage. In this paper the methodology applied by the classical technique used for ground structure recovery called Multichanel Analysis of Surface Waves is discussed as the NDT tool in civil engineering domain to characterize the concrete cover. In order to obtain the velocity as a function of sample depth the dispersion of surface waves is used as an input for solving inverse problem. The paper describes the inversion procedure and provides the practical example of use of developed system.

Cardiovascular Structure and Function in Children With Middle Aortic Syndrome and Renal Artery Stenosis.

PubMed

Rumman, Rawan K; Slorach, Cameron; Hui, Wei; Matsuda-Abedini, Mina; Langlois, Valerie; Radhakrishnan, Seetha; Lorenzo, Armando J; Amaral, Joao; Mertens, Luc; Parekh, Rulan S

2017-12-01

Middle aortic syndrome (MAS) is a narrowing of the abdominal aorta, often in conjunction with renal artery stenosis (RAS). Structure and function of the cardiovascular system are not well understood. In a prospective cross-sectional study, 35 children with MAS or RAS or both (MAS/RAS) were compared with 140 age-, sex-, and body surface area-matched healthy children. Vascular assessment included carotid intima-media thickness and carotid distensibility using B-mode ultrasound and central and peripheral pulse wave velocities using applanation tonometry. Left ventricular structure and function were assessed by 2-dimensional and speckle-tracking echocardiography. Children with MAS or RAS were 12.5±3.0 years old at enrollment, and 50% were men. Carotid intima-media thickness (0.54±0.10 versus 0.44±0.05 mm; P <0.001) and central pulse wave velocities (5.58±1.83 versus 5.00±0.90 m/s; P =0.01) were significantly higher in children with disease compared with healthy children; however, after adjustment for systolic blood pressure z score, only carotid intima-media thickness remained significantly higher in the MAS/RAS group compared with the controls (β=0.07 [0.03, 0.10]). Peripheral pulse wave velocities and carotid distensibility were normal. Children with disease had significantly increased left ventricular mass and changes in diastolic function (lower E/a ratio and lower e' velocities). Systolic parameters, including ejection fraction, global longitudinal and circumferential strain, were similar to controls. Our findings demonstrate that children with MAS or RAS have evidence of carotid and left ventricular remodeling, without peripheral arterial involvement, which suggests a localized disease process. Left ventricular systolic function is preserved; however, subtle changes in diastolic function are observed. Carotid vessel changes are consistent with a 5- to 10-year aging, which underscores the importance of blood pressure control. © 2017 American Heart Association, Inc.

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

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

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

DOE PAGES

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; ...

2017-05-24

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

A broadband gyrotron backward-wave oscillator with tapered interaction structure and magnetic field

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

Li, G. D.; Chang, P. C.; Chiang, W. Y.

2015-11-15

The gyro-monotron and gyrotron backward-wave oscillator (gyro-BWO) are the two oscillator versions of gyrotrons. While serving different functions, they are also radically different in the RF field formation mechanisms. The gyro-monotron RF field profile is essentially fixed by the resonant interaction structure, while the gyro-BWO possesses an extra degree of freedom in that the axial RF field profile is self-determined by the beam-wave interaction in a waveguide structure. The present study examines ways to utilize the latter feature for bandwidth broadening with a tapered magnetic field, while also employing a tapered waveguide to enhance the interaction efficiency. We begin withmore » a mode competition analysis, which suggests the theoretical feasibility of broadband frequency tuning in single-mode operation. It is then shown in theory that, by controlling the RF field profile with an up- or down-tapered magnetic field, the gyro-BWO is capable of efficient operation with a much improved tunable bandwidth.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

NASA Astrophysics Data System (ADS)

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; van Driel, Tim B.; Chollet, Matthieu; Glownia, James M.; Song, Sanghoon; Zhu, Diling; Pace, Elisabetta; Matar, Samir F.; Nielsen, Martin M.; Benfatto, Maurizio; Gaffney, Kelly J.; Collet, Eric; Cammarata, Marco

2017-05-01

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.

Electronic Structures of Free-Standing Nanowires made from Indirect Bandgap Semiconductor Gallium Phosphide

PubMed Central

Liao, Gaohua; Luo, Ning; Chen, Ke-Qiu; Xu, H. Q.

2016-01-01

We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)—a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the bands show anti-crossing structures, while the bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the conduction bands, while the maximum of the valence bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest conduction bands and the highest valence bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. PMID:27307081

Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

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

Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr; Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr

2016-04-18

Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized formore » deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.« less

Algebraic calculations for spectrum of superintegrable system from exceptional orthogonal polynomials

NASA Astrophysics Data System (ADS)

Hoque, Md. Fazlul; Marquette, Ian; Post, Sarah; Zhang, Yao-Zhong

2018-04-01

We introduce an extended Kepler-Coulomb quantum model in spherical coordinates. The Schrödinger equation of this Hamiltonian is solved in these coordinates and it is shown that the wave functions of the system can be expressed in terms of Laguerre, Legendre and exceptional Jacobi polynomials (of hypergeometric type). We construct ladder and shift operators based on the corresponding wave functions and obtain their recurrence formulas. These recurrence relations are used to construct higher-order, algebraically independent integrals of motion to prove superintegrability of the Hamiltonian. The integrals form a higher rank polynomial algebra. By constructing the structure functions of the associated deformed oscillator algebras we derive the degeneracy of energy spectrum of the superintegrable system.

Adolescents with Classical Polycystic Ovary Syndrome Have Alterations in the Surrogate Markers of Cardiovascular Disease but Not in the Endothelial Function. The Possible Benefits of Metformin.

PubMed

Fruzzetti, Franca; Ghiadoni, Lorenzo; Virdis, Agostino; De Negri, Ferdinando; Perini, Daria; Bucci, Fiorella; Giannarelli, Chiara; Gadducci, Angiolo; Taddei, Stefano

2016-10-01

To study whether adolescents with the classical form of polycystic ovary syndrome (PCOS) have alterations in metabolic and vascular structure and function. The effect of metformin was evaluated. Controlled study. University outpatient clinic. Eighteen nonobese adolescents with PCOS were enrolled. Seventeen healthy age-matched adolescents were recruited as control subjects. The metabolic profile and the endothelial structure and function were evaluated. Hormonal and lipid profile, blood pressure (BP) measurement, fasting glucose and insulin levels, C-reactive protein (CRP), homocysteine, tissue-type plasminogen activator, plasminogen activator inhibitor-1 (PAI-1), and plasmin-antiplasmin complexes (PAP) were measured. Flow mediated dilation (FMD), central pulse wave velocity (PWV), radial artery pulse wave, and common carotid intima-media thickness (IMT) were also assessed. Girls with PCOS were also studied 6 months after treatment with metformin (850 mg twice per day). Adolescents with PCOS were insulin resistant and/or hyperinsulinemic and they had higher BP values and levels of CRP and PAI-1 than the control subjects. The levels of tissue-type plasminogen activator and PAP were similar in both groups. FMD, PWV, and IMT were also similar. Metformin significantly (P < .05) reduced insulin, BP, CRP, and PAI-1 levels. The PAP levels significantly (P < .05) increased. Radial artery pulse wave was significantly reduced after metformin treatment. No modifications in FMD, PWV, and IMT were observed. Adolescents with classical PCOS have alterations in some surrogate markers of cardiovascular risk and they are ameliorated by metformin. No deterioration of vascular structure and function has been detected, probably because of the short duration of exposure to the disease. Copyright © 2016 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

Relationship of carotid arterial functional and structural changes to left atrial volume in untreated hypertension.

PubMed

Jaroch, Joanna; Rzyczkowska, Barbara; Bociąga, Zbigniew; Vriz, Olga; Driussi, Caterina; Loboz-Rudnicka, Maria; Dudek, Krzysztof; Łoboz-Grudzień, Krystyna

2016-04-01

The contribution of arterial functional and structural changes to left ventricular (LV) diastolic dysfunction has been the area of recent research. There are some studies on the relationship between arterial stiffness (a.s.) and left atrial (LA) remodelling as a marker of diastolic burden. Little is known about the association of arterial structural changes and LA remodelling in hypertension (H). The aim of this study was to examine the relationship between carotid a.s. and intima-media thickness (IMT) and LA volume in subjects with H. The study included 245 previously untreated hypertensives (166 women and 79 men, mean age 53.7 ± 11.8 years). Each patient was subjected to echocardiography with measurement of LA volume, evaluation of left ventricular hypertrophy (LVH) and LV systolic/diastolic function indices, integrated assessment of carotid IMT and echo-tracking of a.s. and wave reflection parameters. Univariate regression analysis revealed significant correlations between indexed LA volume and selected clinical characteristics, echocardiographic indices of LVH and LV diastolic/systolic function and a.s./wave reflection parameters. The following parameters were identified as independent determinants of indexed LA volume on multivariate regression analysis: diastolic blood pressure (beta = -0.229, P < 0.001), left ventricular mass index (LVMI; beta = 0.258, P < 0.001), E/e’ index (ratio of early mitral flow wave velocity – E to early diastolic mitral annular velocity – e’; beta = 0.266, P = 0.001), augmentation index (AI; beta = 0.143, P = 0.008) and body mass index (BMI; beta = 0.132, P = 0.017). No correlations between indexed LA volume and IMT were found. There is a significant relationship between carotid arterial stiffness but not intima-media thickness and LA volume in patients with untreated hypertension.

Chronic hypoxia alters maternal uterine and fetal hemodynamics in the full-term pregnant guinea pig.

PubMed

Turan, Sifa; Aberdeen, Graham W; Thompson, Loren P

2017-10-01

Placental hypoxia is associated with maternal hypertension, placental insufficiency, and fetal growth restriction. In the pregnant guinea pig, prenatal hypoxia during early gestation inhibits cytotrophoblast invasion of spiral arteries, increases maternal blood pressure, and induces fetal growth restriction. In this study the impact of chronic maternal hypoxia on fetal heart structure was evaluated using four-dimensional echocardiography with spatiotemporal image correlation and tomographic ultrasound, and uterine and umbilical artery resistance/pulsatility indexes and fetal heart function were evaluated using pulsed-wave Doppler ultrasound. Pregnant guinea pigs were exposed to normoxia ( n = 7) or hypoxia (10.5% O 2 , n = 9) at 28-30 days gestation, which was maintained until full term (65 days). At full term, fetal heart structure and outflow tracts were evaluated in the four-chamber view. Fetal heart diastolic function was assessed by E wave-to-A wave diastolic filling ratios (E/A ratios) of both ventricles and systolic function by the myocardial performance index (or Tie) of left ventricles of normoxic ( n = 21) and hypoxic ( n = 17) fetuses. There were no structural abnormalities in fetal hearts. However, hypoxia induced asymmetric fetal growth restriction and increased the placental/fetal weight compared with normoxic controls. Hypoxia increased Doppler resistance and pulsatility indexes in the uterine, but not umbilical, arteries, had no effect on the Tie index, and increased the E/A ratio in left, but not right, ventricles. Thus, prolonged hypoxia, starting at midgestation, increases uterine artery resistance and generates fetal growth restriction at full term. Furthermore, the enhanced cardiac diastolic filling with no changes in systolic function or umbilical artery resistance suggests that the fetal guinea pig systemic circulation undergoes a compensated, adaptive response to prolonged hypoxia exposure. Copyright © 2017 the American Physiological Society.

Tropical Cyclogenesis in a Tropical Wave Critical Layer: Easterly Waves

NASA Technical Reports Server (NTRS)

Dunkerton, T. J.; Montgomery, M. T.; Wang, Z.

2009-01-01

The development of tropical depressions within tropical waves over the Atlantic and eastern Pacific is usually preceded by a "surface low along the wave" as if to suggest a hybrid wave-vortex structure in which flow streamlines not only undulate with the waves, but form a closed circulation in the lower troposphere surrounding the low. This structure, equatorward of the easterly jet axis, is identified herein as the familiar critical layer of waves in shear flow, a flow configuration which arguably provides the simplest conceptual framework for tropical cyclogenesis resulting from tropical waves, their interaction with the mean flow, and with diabatic processes associated with deep moist convection. The recirculating Kelvin cat's eye within the critical layer represents a sweet spot for tropical cyclogenesis in which a proto-vortex may form and grow within its parent wave. A common location for storm development is given by the intersection of the wave's critical latitude and trough axis at the center of the cat's eye, with analyzed vorticity centroid nearby. The wave and vortex live together for a time, and initially propagate at approximately the same speed. In most cases this coupled propagation continues for a few days after a tropical depression is identified. For easterly waves, as the name suggests, the propagation is westward. It is shown that in order to visualize optimally the associated Lagrangian motions, one should view the flow streamlines, or stream function, in a frame of reference translating horizontally with the phase propagation of the parent wave. In this co-moving frame, streamlines are approximately equivalent to particle trajectories. The closed circulation is quasi-stationary, and a dividing streamline separates air within the cat's eye from air outside.

Dynamic of solitary wave solutions in some nonlinear pseudoparabolic models and Dodd-Bullough-Mikhailov equation

NASA Astrophysics Data System (ADS)

Ilhan, O. A.; Bulut, H.; Sulaiman, T. A.; Baskonus, H. M.

2018-02-01

In this study, the modified exp ( - Φ (η )) -expansion function method is used in constructing some solitary wave solutions to the Oskolkov-Benjamin-Bona-Mahony-Burgers, one-dimensional Oskolkov equations and the Dodd-Bullough-Mikhailov equation. We successfully construct some singular solitons and singular periodic waves solutions with the hyperbolic, trigonometric and exponential function structures to these three nonlinear models. Under the choice of some suitable values of the parameters involved, we plot the 2D and 3D graphics to some of the obtained solutions in this study. All the obtained solutions in this study verify their corresponding equation. We perform all the computations in this study with the help of the Wolfram Mathematica software. The obtained solutions in this study may be helpful in explaining some practical physical problems.

P- and S-wave Receiver Function Imaging with Scattering Kernels

NASA Astrophysics Data System (ADS)

Hansen, S. M.; Schmandt, B.

2017-12-01

Full waveform inversion provides a flexible approach to the seismic parameter estimation problem and can account for the full physics of wave propagation using numeric simulations. However, this approach requires significant computational resources due to the demanding nature of solving the forward and adjoint problems. This issue is particularly acute for temporary passive-source seismic experiments (e.g. PASSCAL) that have traditionally relied on teleseismic earthquakes as sources resulting in a global scale forward problem. Various approximation strategies have been proposed to reduce the computational burden such as hybrid methods that embed a heterogeneous regional scale model in a 1D global model. In this study, we focus specifically on the problem of scattered wave imaging (migration) using both P- and S-wave receiver function data. The proposed method relies on body-wave scattering kernels that are derived from the adjoint data sensitivity kernels which are typically used for full waveform inversion. The forward problem is approximated using ray theory yielding a computationally efficient imaging algorithm that can resolve dipping and discontinuous velocity interfaces in 3D. From the imaging perspective, this approach is closely related to elastic reverse time migration. An energy stable finite-difference method is used to simulate elastic wave propagation in a 2D hypothetical subduction zone model. The resulting synthetic P- and S-wave receiver function datasets are used to validate the imaging method. The kernel images are compared with those generated by the Generalized Radon Transform (GRT) and Common Conversion Point stacking (CCP) methods. These results demonstrate the potential of the kernel imaging approach to constrain lithospheric structure in complex geologic environments with sufficiently dense recordings of teleseismic data. This is demonstrated using a receiver function dataset from the Central California Seismic Experiment which shows several dipping interfaces related to the tectonic assembly of this region. Figure 1. Scattering kernel examples for three receiver function phases. A) direct P-to-s (Ps), B) direct S-to-p and C) free-surface PP-to-s (PPs).

Microstructural correlates of infant functional development: example of the visual pathways.

PubMed

Dubois, Jessica; Dehaene-Lambertz, Ghislaine; Soarès, Catherine; Cointepas, Yann; Le Bihan, Denis; Hertz-Pannier, Lucie

2008-02-20

The development of cognitive functions during childhood relies on several neuroanatomical maturation processes. Among these processes is myelination of the white matter pathways, which speeds up electrical conduction. Quantitative indices of such structural processes can be obtained in vivo with diffusion tensor imaging (DTI), but their physiological significance remains uncertain. Here, we investigated the microstructural correlates of early functional development by combining DTI and visual event-related potentials (VEPs) in 15 one- to 4-month-old healthy infants. Interindividual variations of the apparent conduction speed, computed from the latency of the first positive VEP wave (P1), were significantly correlated with the infants' age and DTI indices measured in the optic radiations. This demonstrates that fractional anisotropy and transverse diffusivity are structural markers of functionally efficient myelination. Moreover, these indices computed along the optic radiations showed an early wave of maturation in the anterior region, with the posterior region catching up later in development, which suggests two asynchronous fronts of myelination in both the geniculocortical and corticogeniculate fibers. Thus, in addition to microstructural information, DTI provides noninvasive exquisite information on the functional development of the brain in human infants.

Enhanced NMR Discrimination of Pharmaceutically Relevant Molecular Crystal Forms through Fragment-Based Ab Initio Chemical Shift Predictions.

PubMed

Hartman, Joshua D; Day, Graeme M; Beran, Gregory J O

2016-11-02

Chemical shift prediction plays an important role in the determination or validation of crystal structures with solid-state nuclear magnetic resonance (NMR) spectroscopy. One of the fundamental theoretical challenges lies in discriminating variations in chemical shifts resulting from different crystallographic environments. Fragment-based electronic structure methods provide an alternative to the widely used plane wave gauge-including projector augmented wave (GIPAW) density functional technique for chemical shift prediction. Fragment methods allow hybrid density functionals to be employed routinely in chemical shift prediction, and we have recently demonstrated appreciable improvements in the accuracy of the predicted shifts when using the hybrid PBE0 functional instead of generalized gradient approximation (GGA) functionals like PBE. Here, we investigate the solid-state 13 C and 15 N NMR spectra for multiple crystal forms of acetaminophen, phenobarbital, and testosterone. We demonstrate that the use of the hybrid density functional instead of a GGA provides both higher accuracy in the chemical shifts and increased discrimination among the different crystallographic environments. Finally, these results also provide compelling evidence for the transferability of the linear regression parameters mapping predicted chemical shieldings to chemical shifts that were derived in an earlier study.

Enhanced NMR Discrimination of Pharmaceutically Relevant Molecular Crystal Forms through Fragment-Based Ab Initio Chemical Shift Predictions

PubMed Central

2016-01-01

Chemical shift prediction plays an important role in the determination or validation of crystal structures with solid-state nuclear magnetic resonance (NMR) spectroscopy. One of the fundamental theoretical challenges lies in discriminating variations in chemical shifts resulting from different crystallographic environments. Fragment-based electronic structure methods provide an alternative to the widely used plane wave gauge-including projector augmented wave (GIPAW) density functional technique for chemical shift prediction. Fragment methods allow hybrid density functionals to be employed routinely in chemical shift prediction, and we have recently demonstrated appreciable improvements in the accuracy of the predicted shifts when using the hybrid PBE0 functional instead of generalized gradient approximation (GGA) functionals like PBE. Here, we investigate the solid-state 13C and 15N NMR spectra for multiple crystal forms of acetaminophen, phenobarbital, and testosterone. We demonstrate that the use of the hybrid density functional instead of a GGA provides both higher accuracy in the chemical shifts and increased discrimination among the different crystallographic environments. Finally, these results also provide compelling evidence for the transferability of the linear regression parameters mapping predicted chemical shieldings to chemical shifts that were derived in an earlier study. PMID:27829821

Edge effect on a vacancy state in semi-infinite graphene

NASA Astrophysics Data System (ADS)

Deng, Hai-Yao; Wakabayashi, Katsunori

2014-09-01

The edge effect on a single vacancy state of semi-infinite graphene (SIG) has been studied using Green's function method within the tight-binding model. In the case of infinite graphene, it is known that a vacancy induces a zero-energy resonance state, whose wave function decays inversely with distance (R) from the vacancy and is not normalizable. However, for SIG with an armchair edge, we find that the corresponding wave function decays as R-2 and hence becomes normalizable owing to the intervalley interference caused by the armchair edge. For SIG with a zigzag edge, the vacancy state depends on the sublattice of the vacancy. When the vacancy and the edge belong to different sublattices, the vacancy has no effect on the zero-energy vacancy state. In contrast, when the vacancy is located on the same sublattice as the edge, the resonance state disappears but the wave function at zero energy is strongly distorted near the vacancy. Our results reveal that the presence of edges crucially changes the vacancy state in graphene, and thus such a state can be used to probe the edge structure.

Dispersion relation for electromagnetic propagation in stochastic dielectric and magnetic helical photonic crystals

NASA Astrophysics Data System (ADS)

Avendaño, Carlos G.; Reyes, Arturo

2017-03-01

We theoretically study the dispersion relation for axially propagating electromagnetic waves throughout a one-dimensional helical structure whose pitch and dielectric and magnetic properties are spatial random functions with specific statistical characteristics. In the system of coordinates rotating with the helix, by using a matrix formalism, we write the set of differential equations that governs the expected value of the electromagnetic field amplitudes and we obtain the corresponding dispersion relation. We show that the dispersion relation depends strongly on the noise intensity introduced in the system and the autocorrelation length. When the autocorrelation length increases at fixed fluctuation and when the fluctuation augments at fixed autocorrelation length, the band gap widens and the attenuation coefficient of electromagnetic waves propagating in the random medium gets larger. By virtue of the degeneracy in the imaginary part of the eigenvalues associated with the propagating modes, the random medium acts as a filter for circularly polarized electromagnetic waves, in which only the propagating backward circularly polarized wave can propagate with no attenuation. Our results are valid for any kind of dielectric and magnetic structures which possess a helical-like symmetry such as cholesteric and chiral smectic-C liquid crystals, structurally chiral materials, and stressed cholesteric elastomers.

Acoustic wave propagation in heterogeneous structures including experimental validation

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Dahl, Milo D.

1989-01-01

A finite element model was developed to solve for the acoustic pressure and energy fields in a heterogeneous suppressor. The derivations from the governing equations assumed that the material properties could vary with position resulting in a heterogeneous variable property two-dimensional wave equation. This eliminated the necessity of finding the boundary conditions between different materials. For a two-media region consisting of part air and part bulk absorber, a model was used to describe the bulk absorber properties in two directions. Complex metallic structures inside the air duct are simulated by simply changing element properties from air to the structural material in a pattern to describe the desired shapes. To verify the numerical theory, experiments were conducted without flow in a rectangular duct with a single folded cavity mounted above the duct and absorbing material mounted inside a cavity. Changes in a nearly plane wave sound field were measured on the wall opposite the absorbing cavity. Fairly good agreement was found in the standing wave pattern upstream of the absorber and in the decay of pressure level opposite the absorber, as a function of distance along the duct. The finite element model provides a convenient method for evaluating the acoustic properties of bulk absorbers.

Imaging the square of the correlated two-electron wave function of a hydrogen molecule

DOE PAGES

Waitz, M.; Bello, R. Y.; Metz, D.; ...

2017-12-22

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in whichmore » electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Finally, our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.« less

Imaging the square of the correlated two-electron wave function of a hydrogen molecule.

PubMed

Waitz, M; Bello, R Y; Metz, D; Lower, J; Trinter, F; Schober, C; Keiling, M; Lenz, U; Pitzer, M; Mertens, K; Martins, M; Viefhaus, J; Klumpp, S; Weber, T; Schmidt, L Ph H; Williams, J B; Schöffler, M S; Serov, V V; Kheifets, A S; Argenti, L; Palacios, A; Martín, F; Jahnke, T; Dörner, R

2017-12-22

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in which electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.

Imaging the square of the correlated two-electron wave function of a hydrogen molecule

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

Waitz, M.; Bello, R. Y.; Metz, D.

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in whichmore » electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Finally, our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.« less

Instabilities and subharmonic resonances of subsonic heated round jets, volume 2. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Ng, Lian Lai

1990-01-01

When a jet is perturbed by a periodic excitation of suitable frequency, a large-scale coherent structure develops and grows in amplitude as it propagates downstream. The structure eventually rolls up into vortices at some downstream location. The wavy flow associated with the roll-up of a coherent structure is approximated by a parallel mean flow and a small, spatially periodic, axisymmetric wave whose phase velocity and mode shape are given by classical (primary) stability theory. The periodic wave acts as a parametric excitation in the differential equations governing the secondary instability of a subharmonic disturbance. The (resonant) conditions for which the periodic flow can strongly destabilize a subharmonic disturbance are derived. When the resonant conditions are met, the periodic wave plays a catalytic role to enhance the growth rate of the subharmonic. The stability characteristics of the subharmonic disturbance, as a function of jet Mach number, jet heating, mode number and the amplitude of the periodic wave, are studied via a secondary instability analysis using two independent but complementary methods: (1) method of multiple scales, and (2) normal mode analysis. It is found that the growth rates of the subharmonic waves with azimuthal numbers beta = 0 and beta = 1 are enhanced strongly, but comparably, when the amplitude of the periodic wave is increased. Furthermore, compressibility at subsonic Mach numbers has a moderate stabilizing influence on the subharmonic instability modes. Heating suppresses moderately the subharmonic growth rate of an axisymmetric mode, and it reduces more significantly the corresponding growth rate for the first spinning mode. Calculations also indicate that while the presence of a finite-amplitude periodic wave enhances the growth rates of subharmonic instability modes, it minimally distorts the mode shapes of the subharmonic waves.

The journey from forensic to predictive materials science using density functional theory

DOE PAGES

Schultz, Peter A.

2017-09-12

Approximate methods for electronic structure, implemented in sophisticated computer codes and married to ever-more powerful computing platforms, have become invaluable in chemistry and materials science. The maturing and consolidation of quantum chemistry codes since the 1980s, based upon explicitly correlated electronic wave functions, has made them a staple of modern molecular chemistry. Here, the impact of first principles electronic structure in physics and materials science had lagged owing to the extra formal and computational demands of bulk calculations.

The journey from forensic to predictive materials science using density functional theory

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

Schultz, Peter A.

Approximate methods for electronic structure, implemented in sophisticated computer codes and married to ever-more powerful computing platforms, have become invaluable in chemistry and materials science. The maturing and consolidation of quantum chemistry codes since the 1980s, based upon explicitly correlated electronic wave functions, has made them a staple of modern molecular chemistry. Here, the impact of first principles electronic structure in physics and materials science had lagged owing to the extra formal and computational demands of bulk calculations.

Rayleigh surface acoustic wave as an efficient heating system for biological reactions: investigation of microdroplet temperature uniformity.

PubMed

Roux-Marchand, Thibaut; Beyssen, Denis; Sarry, Frederic; Elmazria, Omar

2015-04-01

When a microdroplet is put on the Rayleigh surface acoustic wave path, longitudinal waves are radiated into the liquid and induce several phenomena such as the wellknown surface acoustic wave streaming. At the same time, the temperature of the microdroplet increases as it has been shown. In this paper, we study the temperature uniformity of a microdroplet heated by Rayleigh surface acoustic wave for discrete microfluidic applications such as biological reactions. To precisely ascertain the temperature uniformity and not interfere with the biological reaction, we used an infrared camera. We then tested the temperature uniformity as a function of three parameters: the microdroplet volume, the Rayleigh surface acoustic wave frequency, and the continuous applied radio frequency power. Based on these results, we propose a new device structure to develop a future lab on a chip based on reaction temperatures.

Wave-function-renormalization effects in resonantly enhanced tunneling

NASA Astrophysics Data System (ADS)

Lörch, N.; Pepe, F. V.; Lignier, H.; Ciampini, D.; Mannella, R.; Morsch, O.; Arimondo, E.; Facchi, P.; Florio, G.; Pascazio, S.; Wimberger, S.

2012-05-01

We study the time evolution of ultracold atoms in an accelerated optical lattice. For a Bose-Einstein condensate with a narrow quasimomentum distribution in a shallow optical lattice the decay of the survival probability in the ground band has a steplike structure. In this regime we establish a connection between the wave-function-renormalization parameter Z introduced by P. Facchi, H. Nakazato, and S. Pascazio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.2699 86, 2699 (2001)] to characterize nonexponential decay and the phenomenon of resonantly enhanced tunneling, where the decay rate is peaked for particular values of the lattice depth and the accelerating force.

Lithospheric structure of the Arabian Shield from the joint inversion of receiver functions and surface-wave group velocities

NASA Astrophysics Data System (ADS)

Julià, Jordi; Ammon, Charles J.; Herrmann, Robert B.

2003-08-01

We estimate lithospheric velocity structure for the Arabian Shield by jointly modeling receiver functions and fundamental-mode group velocities from events recorded by the 1995-1997 Saudi Arabian Portable Broadband Deployment. Receiver functions are primarily sensitive to shear-wave velocity contrasts and vertical travel times, and surface-wave dispersion measurements are sensitive to vertical shear-wave velocity averages, so that their combination bridge resolution gaps associated with each individual data set. Our resulting models correlate well with the observed surface geology; the Asir terrane to the West consists of a 10-km-thick upper crust of 3.3 km/s overlying a lower crust of 3.7-3.8 km/s; in the Afif terrane to the East, the upper crust is 20 km thick and has an average velocity of 3.6 km/s, and the lower crust is about 3.8 km/s; separating the terranes, the Nabitah mobile belt is made of a gradational upper crust up to 3.6 km/s at 15 km overlying an also gradational lower crust up to 4.0 km/s. The crust-mantle transition is found to be sharp in terranes of continental affinity (east) and gradual in terranes of oceanic affinity (west). The upper mantle shear velocities range from 4.3 to 4.6 km/s. Temperatures around 1000 °C are obtained from our velocity models for a thin upper mantle lid observed beneath station TAIF, and suggest that the lithosphere could be as thin as 50-60 km under this station.

Preliminary Results of Crustal Structure beneath the Wabash Valley Seismic Zone Using Teleseismic Receiver Functions and Ambient Noise Tomography

NASA Astrophysics Data System (ADS)

Zhu, L.; Aziz Zanjani, A.; Hu, S.; Liu, Y.; Herrmann, R. B.; Conder, J. A.

2015-12-01

As part of a on-going EarthScope FlexArray project, we deployed 45 broadband seismographs in a 300-km-long linear profile across the Wabash Valley Seismic Zone (WVSZ). Here we present preliminary results of crustal structure beneath WVSZ based on teleseismic receiver functions and ambient noise tomography. We combined waveform data of the temporary stations in 2014 with those of permanent seismic stations and the transportable array stations in our study area since 2011. We found 656 teleseismic events with clear P-wave signals and obtained 2657 good-quality receiver functions of 84 stations using a time-domain iterative deconvolution method. We estimated crustal thickness and Vp/Vs ratio beneath each station using the H-κ stacking method. A high-resolution crustal structural image along the linear profile was obtained using the Common-Conversion-Point (CCP) stacking method. We also measured Rayleigh-wave phase and group velocities from 5 to 50 s by cross-correlating ambient noises between stations and did joint-inversion of receiver functions and surface wave dispersions for S-velocity structures beneath selected stations. The results show that the average crustal thickness in the region is 47 km with a gentle increase of crustal thickness from southeast to northwest. A mid-crustal interface is identified in the CCP image that also deepens from 15 km in the southeastern end to >20 km in the northwest. The CCP image shows that the low-velocity sedimentary layer along the profile is broad and is thickest (~10 km) near the center of the Wabash Valley. Beneath the center of the Valley there is a 40-km-wide positive velocity discontinuity at a depth of 40 km in the lower crust that might be the top of a rift pillow in this failed continental rift. Further results using 3D joint inversion and CCP migration will be presented at the meeting.

Attenuation and source properties at the Coso Geothermal area, California

USGS Publications Warehouse

Hough, S.E.; Lees, J.M.; Monastero, F.

1999-01-01

We use a multiple-empirical Green's function method to determine source properties of small (M -0.4 to 1.3) earthquakes and P- and S-wave attenuation at the Coso Geothermal Field, California. Source properties of a previously identified set of clustered events from the Coso geothermal region are first analyzed using an empirical Green's function (EGF) method. Stress-drop values of at least 0.5-1 MPa are inferred for all of the events; in many cases, the corner frequency is outside the usable bandwidth, and the stress drop can only be constrained as being higher than 3 MPa. P- and S-wave stress-drop estimates are identical to the resolution limits of the data. These results are indistinguishable from numerous EGF studies of M 2-5 earthquakes, suggesting a similarity in rupture processes that extends to events that are both tiny and induced, providing further support for Byerlee's Law. Whole-path Q estimates for P and S waves are determined using the multiple-empirical Green's function (MEGF) method of Hough (1997), whereby spectra from clusters of colocated events at a given station are inverted for a single attenuation parameter, ??, with source parameters constrained from EGF analysis. The ?? estimates, which we infer to be resolved to within 0.01 sec or better, exhibit almost as much scatter as a function of hypocentral distance as do values from previous single-spectrum studies for which much higher uncertainties in individual ?? estimates are expected. The variability in ?? estimates determined here therefore suggests real lateral variability in Q structure. Although the ray-path coverage is too sparse to yield a complete three-dimensional attenuation tomographic image, we invert the inferred ?? value for three-dimensional structure using a damped least-squares method, and the results do reveal significant lateral variability in Q structure. The inferred attenuation variability corresponds to the heat-flow variations within the geothermal region. A central low-Q region corresponds well with the central high-heat flow region; additional detailed structure is also suggested.

Upper crustal structure of Madeira Island revealed from ambient noise tomography

NASA Astrophysics Data System (ADS)

Matos, Catarina; Silveira, Graça; Matias, Luís; Caldeira, Rita; Ribeiro, M. Luísa; Dias, Nuno A.; Krüger, Frank; Bento dos Santos, Telmo

2015-06-01

We present the first image of the Madeira upper crustal structure, using ambient seismic noise tomography. 16 months of ambient noise, recorded in a dense network of 26 seismometers deployed across Madeira, allowed reconstructing Rayleigh wave Green's functions between receivers. Dispersion analysis was performed in the short period band from 1.0 to 4.0 s. Group velocity measurements were regionalized to obtain 2D tomographic images, with a lateral resolution of 2.0 km in central Madeira. Afterwards, the dispersion curves, extracted from each cell of the 2D group velocity maps, were inverted as a function of depth to obtain a 3D shear wave velocity model of the upper crust, from the surface to a depth of 2.0 km. The obtained 3D velocity model reveals features throughout the island that correlates well with surface geology and island evolution.

Transport characteristics of a ZnMgO/ZnO hetero junction and the effect of temperature and Mg content

NASA Astrophysics Data System (ADS)

Uslu, Salih; Yarar, Zeki

2017-02-01

The Ensemble Monte Carlo method is used to calculate the transport characteristics of two dimensional electron gas (2DEG) at a ZnMgO/ZnO hetero structure. The spontaneous and piezoelectric polarizations are considered and there is no intentional doping in either material. Numerical Schrödinger and Poisson equations are solved self consistently to obtain the scattering rates of various scattering mechanisms. The density of carriers, each energy sub bands, potential profile and corresponding wave functions are obtained from the self consistent calculations. The self consistent sub band wave functions of acoustic and optic phonon scattering and interface roughness scattering are used in Monte Carlo method to obtain transport characteristics at ZnMgO/ZnO junction. Two dimensional electron gas confined to ZnMgO/ZnO hetero structure is studied and the effect of temperature and Mg content are investigated.

Dynamic Structure Factor: An Introduction

NASA Astrophysics Data System (ADS)

Sturm, K.

1993-02-01

The doubly differential cross-section for weak inelastic scattering of waves or particles by manybody systems is derived in Born approximation and expressed in terms of the dynamic structure factor according to van Hove. The application of this very general scheme to scattering of neutrons, x-rays and high-energy electrons is discussed briefly. The dynamic structure factor, which is the space and time Fourier transform of the density-density correlation function, is a property of the many-body system independent of the external probe and carries information on the excitation spectrum of the system. The relation of the electronic structure factor to the density-density response function defined in linear-response theory is shown using the fluctuation-dissipation theorem. This is important for calculations, since the response function can be calculated approximately from the independent-particle response function in self-consistent field approximations, such as the random-phase approximation or the local-density approximation of the density functional theory. Since the density-density response function also determines the dielectric function, the dynamic structure can be expressed by the dielectric function.

Whole-Retina Reduced Electrophysiological Activity in Mice Bearing Retina-Specific Deletion of Vesicular Acetylcholine Transporter.

PubMed

Bedore, Jake; Martyn, Amanda C; Li, Anson K C; Dolinar, Eric A; McDonald, Ian S; Coupland, Stuart G; Prado, Vania F; Prado, Marco A; Hill, Kathleen A

2015-01-01

Despite rigorous characterization of the role of acetylcholine in retinal development, long-term effects of its absence as a neurotransmitter are unknown. One of the unanswered questions is how acetylcholine contributes to the functional capacity of mature retinal circuits. The current study investigates the effects of disrupting cholinergic signalling in mice, through deletion of vesicular acetylcholine transporter (VAChT) in the developing retina, pigmented epithelium, optic nerve and optic stalk, on electrophysiology and structure of the mature retina. A combination of electroretinography, optical coherence tomography imaging and histological evaluation assessed retinal integrity in mice bearing retina- targeted (embryonic day 12.5) deletion of VAChT (VAChTSix3-Cre-flox/flox) and littermate controls at 5 and 12 months of age. VAChTSix3-Cre-flox/flox mice did not show any gross changes in nuclear layer cellularity or synaptic layer thickness. However, VAChTSix3-Cre-flox/flox mice showed reduced electrophysiological response of the retina to light stimulus under scotopic conditions at 5 and 12 months of age, including reduced a-wave, b-wave, and oscillatory potential (OP) amplitudes and decreased OP peak power and total energy. Reduced a-wave amplitude was proportional to the reduction in b-wave amplitude and not associated with altered a-wave 10%-90% rise time or inner and outer segment thicknesses. This study used a novel genetic model in the first examination of function and structure of the mature mouse retina with disruption of cholinergic signalling. Reduced amplitude across the electroretinogram wave form does not suggest dysfunction in specific retinal cell types and could reflect underlying changes in the retinal and/or extraretinal microenvironment. Our findings suggest that release of acetylcholine by VAChT is essential for the normal electrophysiological response of the mature mouse retina.

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.

Auto correlation analysis of coda waves from local earthquakes for detecting temporal changes in shallow subsurface structures - The 2011 Tohoku-Oki, Japan, earthquake -

NASA Astrophysics Data System (ADS)

Nakahara, H.

2013-12-01

For monitoring temporal changes in subsurface structures, I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Because the use of coda waves requires earthquakes, time resolution for monitoring decreases. But at regions with high seismicity, it may be possible to monitor subsurface structures in sufficient time resolutions. Studying the 2011 Tohoku-Oki (Mw 9.0), Japan, earthquake for which velocity changes have been already reported by previous studies, I try to validate the method. KiK-net stations in northern Honshu are used in the analysis. For each moderate earthquake, normalized auto correlation functions of surface records are stacked with respect to time windows in S-wave coda. Aligning the stacked normalized auto correlation functions with time, I search for changes in arrival times of phases. The phases at lag times of less than 1s are studied because changes at shallow depths are focused. Based on the stretching method, temporal variations in the arrival times are measured at the stations. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. Amounts of the phase delays are in the order of 10% on average with the maximum of about 50% at some stations. For validation, the deconvolution analysis using surface and subsurface records at the same stations are conducted. The results show that the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percents, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable to detect larger changes. In spite of these disadvantages, this analysis is still attractive because it can be applied to many records on the surface in regions where no boreholes are available. Acknowledgements: Seismograms recorded by KiK-net managed by National Research Institute for Earth Science and Disaster Prevention (NIED) were used in this study. This study was partially supported by JST J-RAPID program and JSPS KAKENHI Grant Numbers 24540449 and 23540449.

Velocity Structure of the Subducted Yakutat Terrane, Alaska: Insights from Guided Waves

NASA Astrophysics Data System (ADS)

Coulson, S.; Garth, T.; Rietbrock, A.

2017-12-01

Subduction zone guided wave arrivals from intermediate depth earthquakes provide insight into the fine scale velocity structure of the subducting oceanic crust as it dehydrates. These observations can be used to determine the average velocity and thickness of the crustal low velocity layer (LVL) at depth, allowing inferences to be drawn about composition and degree of hydration. We constrain guided wave dispersion by comparing waveforms recorded in the subduction forearc with simulated waveforms, produced using a 2D finite difference waveform propagation model. The structure of the Aleutian arc is complex due to the accretion of the Yakutat Terrane (YT) to the east, which is partially coupled with the subducting Pacific plate. An unusually thick LVL associated with the YT has been inferred down to 140 km depth by receiver function studies and travel time tomography. Focussing on a profile running NNW-SSE close to Anchorage, we constrain slab geometry using global and local catalogues, as well as the curvature inferred from receiver functions (Kim et al., 2014). P-wave arrivals from 41 earthquakes (2012-2015) show significant guided wave dispersion on at least one station; high frequency (>1-3 Hz) energy is delayed by up to 2-3 seconds. Choosing the clearest dispersion observations, we systematically vary both LVL width and P-wave velocity, to find the lowest misfit between the observed and synthetic waveforms. Multiple modelled events show the thickness of the LVL associated with subducted YT to be 6-10 km, significantly thinner than inferred by receiver function studies. Most events are accounted for by an LVL velocity contrast of 12.5-15% with overriding mantle material, however, observations of the deepest event in the northern corner of the YT require a velocity contrast of 6%. Lower velocities in the shallower slab (70-120 km) cannot be accounted for by reacted or unreacted MORB or gabbro compositions. We postulate the presence of interbedded sediments within the YT reducing the bulk velocity of the LVL. Increased velocities seen at the northern edge of the YT can be explained by reacted MORB or gabbro assemblages. This may be explained by a lack of interbedded sediments in this part of the YT, or the warmer conditions at the edge of the subducted terrane causing a faster pace of metamorphic reaction in this part of the slab.

Short-range density functional correlation within the restricted active space CI method

NASA Astrophysics Data System (ADS)

Casanova, David

2018-03-01

In the present work, I introduce a hybrid wave function-density functional theory electronic structure method based on the range separation of the electron-electron Coulomb operator in order to recover dynamic electron correlations missed in the restricted active space configuration interaction (RASCI) methodology. The working equations and the computational algorithm for the implementation of the new approach, i.e., RAS-srDFT, are presented, and the method is tested in the calculation of excitation energies of organic molecules. The good performance of the RASCI wave function in combination with different short-range exchange-correlation functionals in the computation of relative energies represents a quantitative improvement with respect to the RASCI results and paves the path for the development of RAS-srDFT as a promising scheme in the computation of the ground and excited states where nondynamic and dynamic electron correlations are important.

Analysis of STM images with pure and CO-functionalized tips: A first-principles and experimental study

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Okabayashi, Norio; Peronio, Angelo; Giessibl, Franz J.; Paulsson, Magnus

2017-08-01

We describe a first-principles method to calculate scanning tunneling microscopy (STM) images, and compare the results to well-characterized experiments combining STM with atomic force microscopy (AFM). The theory is based on density functional theory with a localized basis set, where the wave functions in the vacuum gap are computed by propagating the localized-basis wave functions into the gap using a real-space grid. Constant-height STM images are computed using Bardeen's approximation method, including averaging over the reciprocal space. We consider copper adatoms and single CO molecules adsorbed on Cu(111), scanned with a single-atom copper tip with and without CO functionalization. The calculated images agree with state-of-the-art experiments, where the atomic structure of the tip apex is determined by AFM. The comparison further allows for detailed interpretation of the STM images.

Facing the Corporate University: The New Wave of Student Movements in Europe

ERIC Educational Resources Information Center

Fernández, Joseba

2014-01-01

The transformation of the historical functions and goals of the European university is producing the transition from mass university to what has been called "corporate university". With this goal, I will examine how the new functions of the university are aimed at providing services and precarious workers to the labor structure of…

Impact Of Coral Structures On Wave Directional Spreading Across A Shallow Reef Flat - Lizard Island, Northern Great Barrier Reef

NASA Astrophysics Data System (ADS)

Leon, J. X.; Baldock, T.; Callaghan, D. P.; Hoegh-guldberg, O.; Mumby, P.; Phinn, S. R.; Roelfsema, C. M.; Saunders, M. I.

2013-12-01

Coral reef hydrodynamics operate at several and overlapping spatial-temporal scales. Waves have the most important forcing function on shallow (< 5 m) reefs as they drive most ecological and biogeochemical processes by exerting direct physical stress, directly mixing water (temperature and nutrients) and transporting sediments, nutrients and plankton. Reef flats are very effective at dissipating wave energy and providing an important ecosystem service by protecting highly valued shorelines. The effectiveness of reef flats to dissipate wave energy is related to the extreme hydraulic roughness of the benthos and substrate composition. Hydraulic roughness is usually obtained empirically from frictional-dissipation calculations, as detailed field measurements of bottom roughness (e.g. chain-method or profile gauges) is a very labour and time-consuming task. In this study we measured the impact of coral structures on wave directional spreading. Field data was collected during October 2012 across a reef flat on Lizard Island, northern Great Barrier Reef. Wave surface levels were measured using an array of self-logging pressure sensors. A rapid in situ close-range photogrammetric method was used to create a high-resolution (0.5 cm) image mosaic and digital elevation model. Individual coral heads were extracted from these datasets using geo-morphometric and object-based image analysis techniques. Wave propagation was modelled using a modified version of the SWAN model which includes the measured coral structures in 2m by 1m cells across the reef. The approach followed a cylinder drag approach, neglecting skin friction and inertial components. Testing against field data included bed skin friction. Our results show, for the first time, how the variability of the reef benthos structures affects wave dissipation across a shallow reef flat. This has important implications globally for coral reefs, due to the large extent of their area occupied by reef flats, particularly, as global-scale degradation in coral reef health is causing a lowering of reef carbonate production that might lead to a decrease in reef structure and roughness.

Wave-filter-based approach for generation of a quiet space in a rectangular cavity

NASA Astrophysics Data System (ADS)

Iwamoto, Hiroyuki; Tanaka, Nobuo; Sanada, Akira

2018-02-01

This paper is concerned with the generation of a quiet space in a rectangular cavity using active wave control methodology. It is the purpose of this paper to present the wave filtering method for a rectangular cavity using multiple microphones and its application to an adaptive feedforward control system. Firstly, the transfer matrix method is introduced for describing the wave dynamics of the sound field, and then feedforward control laws for eliminating transmitted waves is derived. Furthermore, some numerical simulations are conducted that show the best possible result of active wave control. This is followed by the derivation of the wave filtering equations that indicates the structure of the wave filter. It is clarified that the wave filter consists of three portions; modal group filter, rearrangement filter and wave decomposition filter. Next, from a numerical point of view, the accuracy of the wave decomposition filter which is expressed as a function of frequency is investigated using condition numbers. Finally, an experiment on the adaptive feedforward control system using the wave filter is carried out, demonstrating that a quiet space is generated in the target space by the proposed method.

Convergence of quasiparticle self-consistent G W calculations of transition-metal monoxides

NASA Astrophysics Data System (ADS)

Das, Suvadip; Coulter, John E.; Manousakis, Efstratios

2015-03-01

Finding an accurate ab initio approach for calculating the electronic properties of transition-metal oxides has been a problem for several decades. In this paper, we investigate the electronic structure of the transition-metal monoxides MnO, CoO, and NiO in their undistorted rocksalt structure within a fully iterated quasiparticle self-consistent G W (QPsc G W ) scheme. We study the convergence of the QPsc G W method, i.e., how the quasiparticle energy eigenvalues and wave functions converge as a function of the QPsc G W iterations, and we compare the converged outputs obtained from different starting wave functions. We find that the convergence is slow and that a one-shot G0W0 calculation does not significantly improve the initial eigenvalues and states. It is important to notice that in some cases the "path" to convergence may go through energy band reordering which cannot be captured by the simple initial unperturbed Hamiltonian. When we reach a fully iterated solution, the converged density of states, band gaps, and magnetic moments of these oxides are found to be only weakly dependent on the choice of the starting wave functions and in reasonably good agreement with the experiment. Finally, this approach provides a clear picture of the interplay between the various orbitals near the Fermi level of these simple transition-metal monoxides. The results of these accurate ab initio calculations can provide input for models aiming at describing the low-energy physics in these materials.

Arterial stiffness estimation based photoplethysmographic pulse wave analysis

NASA Astrophysics Data System (ADS)

Huotari, Matti; Maatta, Kari; Kostamovaara, Juha

2010-11-01

Arterial stiffness is one of the indices of vascular healthiness. It is based on pulse wave analysis. In the case we decompose the pulse waveform for the estimation and determination of arterial elasticity. Firstly, optically measured with photoplethysmograph and then investigating means by four lognormal pulse waveforms for which we can find very good fit between the original and summed decomposed pulse wave. Several studies have demonstrated that these kinds of measures predict cardiovascular events. While dynamic factors, e.g., arterial stiffness, depend on fixed structural features of the vascular wall. Arterial stiffness is estimated based on pulse wave decomposition analysis in the radial and tibial arteries. Elucidation of the precise relationship between endothelial function and vascular stiffness awaits still further study.

A data-driven approach of load monitoring on laminated composite plates using support vector machine

NASA Astrophysics Data System (ADS)

Gwon, Y. S.; Fekrmandi, H.

2018-03-01

In this study, the surface response to excitation method (SuRE) is investigated using a data-driven method for load monitoring on a laminated composite plate structure. The SuRE method is an emerging approach in ultrasonic wavebased structural health monitoring (SHM) field. In this method, a range of high-frequency, surface-guided waves are excited on the structure using piezoceramic elements. The waves propagate on the structure and interact with internal or surface damages. Initially, a baseline data of the intact structure is created by measuring the frequency transfer function between the excitation and sensing point. The integrity of structure is evaluated by monitoring changes in the frequency spectrums. The SuRE method has effectively been used for a variety of SHM applications including the detection of loose bolts, delamination in composite structures, internal corrosion in pipelines, and load and impact monitoring. Data obtained using the SuRE method was used for identifying the location of the applied load on a laminated composite plate using Support Vector Machine (SVM). A set of two piezoelectric elements were attached on the surface of the plate. A sweep excitation (150-250 kHz) generated surface-guided waves, and the transmitted waves were monitored at the sensory positions. The reference data set was measured simultaneously from the sensors. The plate was subjected to static loads while health monitoring data was being captured using the SuRE method. The confusion matrix indicated that the model classified correctly with up to 99.8% accuracy.

Feature and Statistical Model Development in Structural Health Monitoring

NASA Astrophysics Data System (ADS)

Kim, Inho

All structures suffer wear and tear because of impact, excessive load, fatigue, corrosion, etc. in addition to inherent defects during their manufacturing processes and their exposure to various environmental effects. These structural degradations are often imperceptible, but they can severely affect the structural performance of a component, thereby severely decreasing its service life. Although previous studies of Structural Health Monitoring (SHM) have revealed extensive prior knowledge on the parts of SHM processes, such as the operational evaluation, data processing, and feature extraction, few studies have been conducted from a systematical perspective, the statistical model development. The first part of this dissertation, the characteristics of inverse scattering problems, such as ill-posedness and nonlinearity, reviews ultrasonic guided wave-based structural health monitoring problems. The distinctive features and the selection of the domain analysis are investigated by analytically searching the conditions of the uniqueness solutions for ill-posedness and are validated experimentally. Based on the distinctive features, a novel wave packet tracing (WPT) method for damage localization and size quantification is presented. This method involves creating time-space representations of the guided Lamb waves (GLWs), collected at a series of locations, with a spatially dense distribution along paths at pre-selected angles with respect to the direction, normal to the direction of wave propagation. The fringe patterns due to wave dispersion, which depends on the phase velocity, are selected as the primary features that carry information, regarding the wave propagation and scattering. The following part of this dissertation presents a novel damage-localization framework, using a fully automated process. In order to construct the statistical model for autonomous damage localization deep-learning techniques, such as restricted Boltzmann machine and deep belief network, are trained and utilized to interpret nonlinear far-field wave patterns. Next, a novel bridge scour estimation approach that comprises advantages of both empirical and data-driven models is developed. Two field datasets from the literature are used, and a Support Vector Machine (SVM), a machine-learning algorithm, is used to fuse the field data samples and classify the data with physical phenomena. The Fast Non-dominated Sorting Genetic Algorithm (NSGA-II) is evaluated on the model performance objective functions to search for Pareto optimal fronts.

Suppressive Shields Structural Design and Analysis Handbook

DTIC Science & Technology

1977-11-18

of this disturbance to steepen as it passes through the air until it exhibits nearly discontinuous increases in pressure, density, and temperature ...sure. density, and temperature of the reflected wave are all in- creased above the values in the incident wave. The ove-nressure at the wall surface...limiting thickness of concrete at which per- foration will occur can be obtained from Fig. 3-18 and is a function of the coefficient C1, the fragment weight

Application of a simplified calculation for full-wave microtremor H/ V spectral ratio based on the diffuse field approximation to identify underground velocity structures

NASA Astrophysics Data System (ADS)

Wu, Hao; Masaki, Kazuaki; Irikura, Kojiro; Sánchez-Sesma, Francisco José

2017-12-01

Under the diffuse field approximation, the full-wave (FW) microtremor H/ V spectral ratio ( H/ V) is modeled as the square root of the ratio of the sum of imaginary parts of the Green's function of the horizontal components to that of the vertical one. For a given layered medium, the FW H/ V can be well approximated with only surface waves (SW) H/ V of the "cap-layered" medium which consists of the given layered medium and a new larger velocity half-space (cap layer) at large depth. Because the contribution of surface waves can be simply obtained by the residue theorem, the computation of SW H/ V of cap-layered medium is faster than that of FW H/ V evaluated by discrete wavenumber method and contour integration method. The simplified computation of SW H/ V was then applied to identify the underground velocity structures at six KiK-net strong-motion stations. The inverted underground velocity structures were used to evaluate FW H/ Vs which were consistent with the SW H/ Vs of corresponding cap-layered media. The previous study on surface waves H/ Vs proposed with the distributed surface sources assumption and a fixed Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement with the SW H/ Vs of our study. The consistency between observed and theoretical spectral ratios, such as the earthquake motions of H/ V spectral ratio and spectral ratio of horizontal motions between surface and bottom of borehole, indicated that the underground velocity structures identified from SW H/ V of cap-layered medium were well resolved by the new method.[Figure not available: see fulltext.

Single-Layer Plasmonic Metasurface Half-Wave Plates with Wavelength-Independent Polarization Conversion Angle

DOE PAGES

Liu, Zhaocheng; Li, Zhancheng; Liu, Zhe; ...

2017-06-30

Manipulation of polarization state is of great fundamental importance and plays a crucial role in modern photonic applications such as optical communication, imaging, and sensing. Metamaterials and metasurfaces have attracted increasing interest in this area because they facilitate designer optical response through engineering the composite subwavelength structures. In this paper, we propose a general methods of designing half-wave plate and demonstrate in the near-infrared wavelength range an optically thin plasmonic metasurface half-wave plates that rotate the polarization direction of the linearly polarized incident light with a high degree of linear polarization. Finally, the half-wave plate functionality is realized through arrangingmore » the orientation of the nanoantennas to form an appropriate spatial distribution profile, which behave exactly as in classical half-wave plates but over in a wavelength-independent way.« less

Improving the resolution for Lamb wave testing via a smoothed Capon algorithm

NASA Astrophysics Data System (ADS)

Cao, Xuwei; Zeng, Liang; Lin, Jing; Hua, Jiadong

2018-04-01

Lamb wave testing is promising for damage detection and evaluation in large-area structures. The dispersion of Lamb waves is often unavoidable, restricting testing resolution and making the signal hard to interpret. A smoothed Capon algorithm is proposed in this paper to estimate the accurate path length of each wave packet. In the algorithm, frequency domain whitening is firstly used to obtain the transfer function in the bandwidth of the excitation pulse. Subsequently, wavenumber domain smoothing is employed to reduce the correlation between wave packets. Finally, the path lengths are determined by distance domain searching based on the Capon algorithm. Simulations are applied to optimize the number of smoothing times. Experiments are performed on an aluminum plate consisting of two simulated defects. The results demonstrate that spatial resolution is improved significantly by the proposed algorithm.

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.

Crustal structure in Tengchong Volcano-Geothermal Area, western Yunnan, China

NASA Astrophysics Data System (ADS)

Wang, Chun-Yong; Huangfu, Gang

2004-02-01

Based upon the deep seismic sounding profiles carried out in the Tengchong Volcano-Geothermal Area (TVGA), western Yunnan Province of China, a 2-D crustal P velocity structure is obtained by use of finite-difference inversion and forward travel-time fitting method. The crustal model shows that a low-velocity anomaly zone exists in the upper crust, which is related to geothermal activity. Two faults, the Longling-Ruili Fault and Tengchong Fault, on the profile extend from surface to the lower crust and the Tengchong Fault likely penetrates the Moho. Moreover, based on teleseismic receiver functions on a temporary seismic network, S-wave velocity structures beneath the geothermal field show low S-wave velocity in the upper crust. From results of geophysical survey, the crust of TVGA is characterized by low P-wave and S-wave velocities, low resistivity, high heat-flow value and low Q. The upper mantle P-wave velocity is also low. This suggests presence of magma in the crust derived from the upper mantle. The low-velocity anomaly in upper crust may be related to the magma differentiation. The Tengchong volcanic area is located on the northeast edge of the Indian-Eurasian plate collision zone, away from the eastern boundary of the Indian plate by about 450 km. Based on the results of this paper and related studies, the Tengchong volcanoes can be classified as plate boundary volcanoes.

Scattering images from autocorrelation functions of P-wave seismic velocity images: the case of Tenerife Island (Canary Islands, Spain)

NASA Astrophysics Data System (ADS)

García-Yeguas, A.; Sánchez-Alzola, A.; De Siena, L.; Prudencio, J.; Díaz-Moreno, A.; Ibáñez, J. M.

2018-03-01

We present a P-wave scattering image of the volcanic structures under Tenerife Island using the autocorrelation functions of P-wave vertical velocity fluctuations. We have applied a cluster analysis to total quality factor attenuation ( {Q}_t^{-1} ) and scattering quality factor attenuation ( {Q}_{PSc}^{-1} ) images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2D plane, corresponding to a depth of 2000 m, and check the robustness of the scattering imaging. The results show that scattering patterns are similar to total attenuation patterns in the south of the island. There are two main areas where patterns differ: at Cañadas-Teide-Pico Viejo Complex, high total attenuation and average-to-low scattering values are observed. We interpret the difference as induced by intrinsic attenuation. In the Santiago Ridge Zone (SRZ) region, high scattering values correspond to average total attenuation. In our interpretation, the anomaly is induced by an extended scatterer, geometrically related to the surficial traces of Garachico and El Chinyero historical eruptions and the area of highest seismic activity during the 2004-2008 seismic crises.

Investigating Segmentation in Cascadia: Anisotropic Crustal Structure and Mantle Wedge Serpentinization from Receiver Functions

NASA Astrophysics Data System (ADS)

Krueger, Hannah E.; Wirth, Erin A.

2017-10-01

The Cascadia subduction zone exhibits along-strike segmentation in structure, processes, and seismogenic behavior. While characterization of seismic anisotropy can constrain deformation processes at depth, the character of seismic anisotropy in Cascadia remains poorly understood. This is primarily due to a lack of seismicity in the subducting Juan de Fuca slab, which limits shear wave splitting and other seismological analyses that interrogate the fine-scale anisotropic structure of the crust and mantle wedge. We investigate lower crustal anisotropy and mantle wedge structure by computing P-to-S receiver functions at 12 broadband seismic stations along the Cascadia subduction zone. We observe P-to-SV converted energy consistent with previously estimated Moho depths. Several stations exhibit evidence of an "inverted Moho" (i.e., a downward velocity decrease across the crust-mantle boundary), indicative of a serpentinized mantle wedge. Stations with an underlying hydrated mantle wedge appear prevalent from northern Washington to central Oregon, but sparse in southern Oregon and northern California. Transverse component receiver functions are complex, suggesting anisotropic and/or dipping crustal structure. To constrain the orientation of crustal anisotropy we compute synthetic receiver functions using manual forward modeling. We determine that the lower crust shows variable orientations of anisotropy along-strike, with highly complex anisotropy in northern Cascadia, and generally NW-SE and NE-SW orientations of slow-axis anisotropy in central and southern Cascadia, respectively. The orientations of anisotropy from this work generally agree with those inferred from shear wave splitting of tremor studies at similar locations, lending confidence to this relatively new method of inferring seismic anisotropy from slow earthquakes.

Assessment of Impact of Weight Loss on Left and Right Ventricular Functions and Value of Tissue Doppler Echocardiography in Obese Patients.

PubMed

Yuksel, Isa Oner; Akar Bayram, Nihal; Koklu, Erkan; Ureyen, Cagin Mustafa; Kucukseymen, Selcuk; Arslan, Sakir; Bozkurt, Engin

2016-06-01

In our study, we aimed to evaluate the effect of weight loss on left and right ventricular functions in obese patients. Thirty patients with a BMI greater than 30 kg/m(2) and without any exclusion criteria were included in the study. Left ventricular systolic and diastolic functions were assessed with conventional and tissue Doppler echocardiography (TDE). At the end of 3 months, echocardiographic examination was repeated in patients with weight loss for cardiac function evaluation and it was compared to the baseline echocardiographic parameters. At the end of 3 months of weight loss period, conventional Doppler echocardiography revealed an improvement in diastolic functions with an increase in mitral E-wave, a decrease in mitral A-wave and an increase in E/A ratio. Deceleration time and isovolumetric relaxation time were ascertained shortened and Tei index decreased. TDE showed an increase in left ventricular lateral wall systolic wave (Sm) and E-wave velocity (Em). Mitral septal annular isovolumetric acceleration time (IVA), Sm and Em, were found to be increased, whereas Tei index was ascertained reduced. Right ventricular tissue Doppler examination following weight loss revealed an increase in RV- IVA, RV-Sm, and RV-Em, and a decrease in Tei index. We disclosed that left ventricular structural changes and diastolic dysfunction occur in obese patients, and by weight loss, these abnormalities may be reversible which we demonstrated both by conventional and TDE. In addition, obesity might impair RV function as well, and we observed an enhancement in right ventricular functions by weight loss. © 2016, Wiley Periodicals, Inc.

Retrieving both phase and amplitude information of Green's functions by ambient seismic wave field cross-correlation: A case study with a limestone mine induced seismic event

NASA Astrophysics Data System (ADS)

Kwak, S.; Song, S. G.; Kim, G.; Shin, J. S.

2015-12-01

Recently many seismologists have paid attention to ambient seismic field, which is no more referred as noise and called as Earth's hum, but as useful signal to understand subsurface seismic velocity structure. It has also been demonstrated that empirical Green's functions can be constructed by retrieving both phase and amplitude information from ambient seismic field (Prieto and Beroza 2008). The constructed empirical Green's functions can be used to predict strong ground motions after focal depth and double-couple mechanism corrections (Denolle et al. 2013). They do not require detailed subsurface velocity model and intensive computation for ground motion simulation. In this study, we investigate the capability of predicting long period surface waves by the ambient seismic wave field with a seismic event of Mw 4.0, which occurred with a limestone mine collapse in South Korea on January 31, 2015. This limestone-mine event provides an excellent opportunity to test the efficiency of the ambient seismic wave field in retrieving both phase and amplitude information of Green's functions due to the single force mechanism of the collapse event. In other words, both focal depth and double-couple mechanism corrections are not required for this event. A broadband seismic station, which is about 5.4 km away from the mine event, is selected as a source station. Then surface waves retrieved from the ambient seismic wave field cross-correlation are compared with those generated by the event. Our preliminary results show some potential of the ambient seismic wave field in retrieving both phase and amplitude of Green's functions from a single force impulse source at the Earth's surface. More comprehensive analysis by increasing the time length of stacking may improve the results in further studies. We also aim to investigate the efficiency of retrieving the full empirical Green's functions with the 2007 Mw 4.6 Odaesan earthquake, which is one of the strongest earthquakes occurred in South Korea in the last decade.

Breaking Symmetry in Time-Dependent Electronic Structure Theory to Describe Spectroscopic Properties of Non-Collinear and Chiral Molecules

NASA Astrophysics Data System (ADS)

Goings, Joshua James

Time-dependent electronic structure theory has the power to predict and probe the ways electron dynamics leads to useful phenomena and spectroscopic data. Here we report several advances and extensions of broken-symmetry time-dependent electronic structure theory in order to capture the flexibility required to describe non-equilibrium spin dynamics, as well as electron dynamics for chiroptical properties and vibrational effects. In the first half, we begin by discussing the generalization of self-consistent field methods to the so-called two-component structure in order to capture non-collinear spin states. This means that individual electrons are allowed to take a superposition of spin-1/2 projection states, instead of being constrained to either spin-up or spin-down. The system is no longer a spin eigenfunction, and is known a a spin-symmetry broken wave function. This flexibility to break spin symmetry may lead to variational instabilities in the approximate wave function, and we discuss how these may be overcome. With a stable non-collinear wave function in hand, we then discuss how to obtain electronic excited states from the non-collinear reference, along with associated challenges in their physical interpretation. Finally, we extend the two-component methods to relativistic Hamiltonians, which is the proper setting for describing spin-orbit driven phenomena. We describe the first implementation of the explicit time propagation of relativistic two-component methods and how this may be used to capture spin-forbidden states in electronic absorption spectra. In the second half, we describe the extension of explicitly time-propagated wave functions to the simulation of chiroptical properties, namely circular dichroism (CD) spectra of chiral molecules. Natural circular dichroism, that is, CD in the absence of magnetic fields, originates in the broken parity symmetry of chiral molecules. This proves to be an efficient method for computing circular dichroism spectra for high density-of-states chiral molecules. Next, we explore the impact of allowing nuclear motion on electronic absorption spectra within the context of mixed quantum-classical dynamics. We show that nuclear motion modulates the electronic response, and this gives rise to infrared absorption as well as Raman scattering phenomena in the computed dynamic polarizability. Finally, we explore the accuracy of several perturbative approximations to the equation-of-motion coupled-cluster methods for the efficient and accurate prediction of electronic absorption spectra.

Green's function and Bloch theory for the analysis of the dynamic response of a periodically supported beam to a moving load

NASA Astrophysics Data System (ADS)

Lassoued, R.; Lecheheb, M.; Bonnet, G.

2012-08-01

This paper describes an analytical method for the wave field induced by a moving load on a periodically supported beam. The Green's function for an Euler beam without support is evaluated by using the direct integration. Afterwards, it introduces the supports into the model established by using the superposition principle which states that the response from all the sleeper points and from the external point force add up linearly to give a total response. The periodicity of the supports is described by Bloch's theorem. The homogeneous system thus obtained represents a linear differential equation which governs rail response. It is initially solved in the homogeneous case, and it admits a no null solution if its determinant is null, this permits the establishment the dispersion equation to Bloch waves and wave bands. The Bloch waves and dispersion curves contain all the physics of the dynamic problem and the wave field induced by a dynamic load applied to the system is finally obtained by decomposition into Bloch waves, similarly to the usual decomposition into dynamic modes on a finite structure. The method is applied to obtain the field induced by a load moving at constant velocity on a thin beam supported by periodic elastic supports.

Dysbindin-1, WAVE2 and Abi-1 form a complex that regulates dendritic spine formation.

PubMed

Ito, H; Morishita, R; Shinoda, T; Iwamoto, I; Sudo, K; Okamoto, K; Nagata, K

2010-10-01

Genetic variations in dysbindin-1 (dystrobrevin-binding protein-1) are one of the most commonly reported variations associated with schizophrenia. As schizophrenia could be regarded as a neurodevelopmental disorder resulting from abnormalities of synaptic connectivity, we attempted to clarify the function of dysbindin-1 in neuronal development. We examined the developmental change of dysbindin-1 in rat brain by western blotting and found that a 50 kDa isoform is highly expressed during the embryonic stage, whereas a 40 kDa one is detected at postnatal day 11 and increased thereafter. Immunofluorescent analyses revealed that dysbindin-1 is enriched at the spine-like structure of primary cultured rat hippocampal neurons. We identified WAVE2, but not N-WASP, as a binding partner for dysbindin-1. We also found that Abi-1, a binding molecule for WAVE2 involved in spine morphogenesis, interacts with dysbindin-1. Although dysbindin-1, WAVE2 and Abi-1 form a ternary complex, dysbindin-1 promoted the binding of WAVE2 to Abi-1. RNA interference-mediated knockdown of dysbindin-1 led to the generation of abnormally elongated immature dendritic protrusions. The present results indicate possible functions of dysbindin-1 at the postsynapse in the regulation of dendritic spine morphogenesis through the interaction with WAVE2 and Abi-1.

Unified concept of effective one component plasma for hot dense plasmas

DOE PAGES

Clerouin, Jean; Arnault, Philippe; Ticknor, Christopher; ...

2016-03-17

Orbital-free molecular dynamics simulations are used to benchmark two popular models for hot dense plasmas: the one component plasma (OCP) and the Yukawa model. A unified concept emerges where an effective OCP (EOCP) is constructed from the short-range structure of the plasma. An unambiguous ionization and the screening length can be defined and used for a Yukawa system, which reproduces the long-range structure with finite compressibility. Similarly, the dispersion relation of longitudinal waves is consistent with the screened model at vanishing wave number but merges with the OCP at high wave number. Additionally, the EOCP reproduces the overall relaxation timemore » scales of the correlation functions associated with ionic motion. Lastly, in the hot dense regime, this unified concept of EOCP can be fruitfully applied to deduce properties such as the equation of state, ionic transport coefficients, and the ion feature in x-ray Thomson scattering experiments.« less

Realistic full wave modeling of focal plane array pixels

DOE PAGES

Campione, Salvatore; Warne, Larry K.; Jorgenson, Roy E.; ...

2017-11-01

Here, we investigate full-wave simulations of realistic implementations of multifunctional nanoantenna enabled detectors (NEDs). We focus on a 2x2 pixelated array structure that supports two wavelengths of operation. We design each resonating structure independently using full-wave simulations with periodic boundary conditions mimicking the whole infinite array. We then construct a supercell made of a 2x2 pixelated array with periodic boundary conditions mimicking the full NED; in this case, however, each pixel comprises 10-20 antennas per side. In this way, the cross-talk between contiguous pixels is accounted for in our simulations. We observe that, even though there are finite extent effects,more » the pixels work as designed, each responding at the respective wavelength of operation. This allows us to stress that realistic simulations of multifunctional NEDs need to be performed to verify the design functionality by taking into account finite extent and cross-talk effects.« less

On the correct implementation of Fermi-Dirac statistics and electron trapping in nonlinear electrostatic plane wave propagation in collisionless plasmas

NASA Astrophysics Data System (ADS)

Schamel, Hans; Eliasson, Bengt

2016-05-01

Quantum statistics and electron trapping have a decisive influence on the propagation characteristics of coherent stationary electrostatic waves. The description of these strictly nonlinear structures, which are of electron hole type and violate linear Vlasov theory due to the particle trapping at any excitation amplitude, is obtained by a correct reduction of the three-dimensional Fermi-Dirac distribution function to one dimension and by a proper incorporation of trapping. For small but finite amplitudes, the holes become of cnoidal wave type and the electron density is shown to be described by a ϕ ( x ) 1 / 2 rather than a ϕ ( x ) expansion, where ϕ ( x ) is the electrostatic potential. The general coefficients are presented for a degenerate plasma as well as the quantum statistical analogue to these steady state coherent structures, including the shape of ϕ ( x ) and the nonlinear dispersion relation, which describes their phase velocity.

Ultrasonic velocity testing of steel pipeline welded joints

NASA Astrophysics Data System (ADS)

Carreón, Hector

2017-04-01

In general the ultrasonic techniques have been used to determine the mechanical properties of materials on based of their relationship with metallurgical characteristics. In this research work, the relationship between ultrasonic velocity and phased array and the microstructure of steel pipeline welded joints is investigated. Measurements of ultrasonic wave velocity were made as a function of the location across the weld. Hardness measurements were performated in an attempt to correlate with ultrasonic response. In addition, the coarse and dendritic grain structure of the weld material is extreme and unpredictably anisotropic. Thus, due to the acoustic anisotropy of the crystal itself weld material of studied joints is anisotropic, too. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of conventional ultrasonic phased array techniques becomes desirable.

A 2D Daubechies finite wavelet domain method for transient wave response analysis in shear deformable laminated composite plates

NASA Astrophysics Data System (ADS)

Nastos, C. V.; Theodosiou, T. C.; Rekatsinas, C. S.; Saravanos, D. A.

2018-03-01

An efficient numerical method is developed for the simulation of dynamic response and the prediction of the wave propagation in composite plate structures. The method is termed finite wavelet domain method and takes advantage of the outstanding properties of compactly supported 2D Daubechies wavelet scaling functions for the spatial interpolation of displacements in a finite domain of a plate structure. The development of the 2D wavelet element, based on the first order shear deformation laminated plate theory is described and equivalent stiffness, mass matrices and force vectors are calculated and synthesized in the wavelet domain. The transient response is predicted using the explicit central difference time integration scheme. Numerical results for the simulation of wave propagation in isotropic, quasi-isotropic and cross-ply laminated plates are presented and demonstrate the high spatial convergence and problem size reduction obtained by the present method.

Nonlinear amplification of coherent waves in media with soliton-type refractive index pattern.

PubMed

Bugaychuk, S; Conte, R

2012-08-01

We derive the complex Ginzburg-Landau equation for the dynamical self-diffraction of optical waves in a nonlinear cavity. The case of the reflection geometry of wave interaction as well as a medium that possesses the cubic nonlinearity (including a local and a nonlocal nonlinear responses) and the relaxation is considered. A stable localized spatial structure in the form of a "dark" dissipative soliton is formed in the cavity in the steady state. The envelope of the intensity pattern, as well as of the dynamical grating amplitude, takes the shape of a tanh function. The obtained complex Ginzburg-Landau equation describes the dynamics of this envelope; at the same time, the evolution of this spatial structure changes the parameters of the output waves. New effects are predicted in this system due to the transformation of the dissipative soliton which takes place during the interaction of a pulse with a continuous wave, such as retention of the pulse shape during the transmission of impulses in a long nonlinear cavity, and giant amplification of a seed pulse, which takes energy due to redistribution of the pump continuous energy into the signal.

Passive monitoring of a sea dike during a tidal cycle using sea waves as a seismic noise source

NASA Astrophysics Data System (ADS)

Joubert, Anaëlle; Feuvre, Mathieu Le; Cote, Philippe

2018-05-01

Over the past decade, ambient seismic noise has been used successfully to monitor various geological objects with high accuracy. Recently, it has been shown that surface seismic waves propagating within a sea dike body can be retrieved from the cross-correlation of ambient seismic noise generated by sea waves. We use sea wave impacts to monitor the response of a sea dike during a tidal cycle using empirical Green's functions. These are obtained either by cross-correlation or deconvolution, from signals recorded by sensors installed linearly on the crest of a dike. Our analysis is based on delay and spectral amplitude measurements performed on reconstructed surface waves propagating along the array. We show that localized variations of velocity and attenuation are correlated with changes in water level as a probable consequence of water infiltration inside the structure. Sea dike monitoring is of critical importance for safety and economic reasons, as internal erosion is generally only detected at late stages by visual observations. The method proposed here may provide a solution for detecting structural weaknesses, monitoring progressive internal erosion, and delineating areas of interest for further geotechnical studies, in view to understanding the erosion mechanisms involved.

Localized water reverberation phases and its impact on back-projection images

NASA Astrophysics Data System (ADS)

Yue, H.; Castillo, J.; Yu, C.; Meng, L.; Zhan, Z.

2017-12-01

Coherent radiators imaged by back-projections (BP) are commonly interpreted as part of the rupture process. Nevertheless, artifacts introduced by structure related phases are rarely discriminated from the rupture process. In this study, we adopt the logic of empirical Greens' function analysis (EGF) to discriminate between rupture and structure effect. We re-examine the waveforms and BP images of the 2012 Mw 7.2 Indian Ocean earthquake and an EGF event (Mw 6.2). The P wave codas of both events present similar shape with characteristic period of approximately 10 s, which are back-projected as coherent radiators near the trench. S wave BP doesn't image energy radiation near the trench. We interpret those coda waves as localized water reverberation phases excited near the trench. We perform a 2D waveform modeling using realistic bathymetry model, and find that the sharp near-trench bathymetry traps the acoustic water waves forming localized reverberation phases. These waves can be imaged as coherent near-trench radiators with similar features as that in the observations. We present a set of methodology to discriminate between the rupture and propagation effects in BP images, which can serve as a criterion of subevent identification.

Determining Crust and Upper Mantle Structure by Bayesian Joint Inversion of Receiver Functions and Surface Wave Dispersion at a Single Station: Preparation for Data from the InSight Mission

NASA Astrophysics Data System (ADS)

Jia, M.; Panning, M. P.; Lekic, V.; Gao, C.

2017-12-01

The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission will deploy a geophysical station on Mars in 2018. Using seismology to explore the interior structure of the Mars is one of the main targets, and as part of the mission, we will use 3-component seismic data to constrain the crust and upper mantle structure including P and S wave velocities and densities underneath the station. We will apply a reversible jump Markov chain Monte Carlo algorithm in the transdimensional hierarchical Bayesian inversion framework, in which the number of parameters in the model space and the noise level of the observed data are also treated as unknowns in the inversion process. Bayesian based methods produce an ensemble of models which can be analyzed to quantify uncertainties and trade-offs of the model parameters. In order to get better resolution, we will simultaneously invert three different types of seismic data: receiver functions, surface wave dispersion (SWD), and ZH ratios. Because the InSight mission will only deliver a single seismic station to Mars, and both the source location and the interior structure will be unknown, we will jointly invert the ray parameter in our approach. In preparation for this work, we first verify our approach by using a set of synthetic data. We find that SWD can constrain the absolute value of velocities while receiver functions constrain the discontinuities. By joint inversion, the velocity structure in the crust and upper mantle is well recovered. Then, we apply our approach to real data from an earth-based seismic station BFO located in Black Forest Observatory in Germany, as already used in a demonstration study for single station location methods. From the comparison of the results, our hierarchical treatment shows its advantage over the conventional method in which the noise level of observed data is fixed as a prior.

Geometry of the Arabia-Somalia Plate Boundary into Afar: Preliminary Results from the Seismic Profile Across the Asal Rift (Djibouti)

NASA Astrophysics Data System (ADS)

Vergne, J.; Doubre, C.; Mohamed, K.; Tiberi, C.; Leroy, S.; Maggi, A.

2010-12-01

In the Afar Depression, the Asal-Ghoubbet Rift in Djibouti is a young segment on land at the propagating tip of the Aden Ridge. This segment represents an ideal laboratory to observe the mechanisms of extension and the structural evolutions involved, from the continental break-up to the first stage of oceanic spreading. However, we lack first order information about the crustal and upper mantle structure in this region, which for example prevent detailed numerical modeling of the deformations observed at the surface from GPS or InSAR. Moreover the current permanent network is not well suited to precisely constrain the ratio of seismic/aseismic deformation and to characterize the active deformation and the rifting dynamics. Since November 2009 we have maintained a temporary network of 25 seismic stations deployed along a 150 km-long profile. Because we expect rapid variations of the lithospheric structure across the 10 km-wide central part of the rift, we gradually decreased the inter-stations spacing to less than 1 km in the middle section of the profile. In order to obtain a continuous image of the plate boundary, from the topographic surface to the upper mantle, several techniques and methods will be applied: P and S wave receiver functions, tomographies based on body waves, surface waves and seismic noise correlation, anisotropy, and finally a gravity-seismic joint inversion. We present some preliminary results deduced from the receiver functions applied to the data acquired during the first months of the experiment. We migrate several sets of receiver functions computed in various frequency bands to resolve both mantle interfaces and fine scale structures within the thin crust in the center of the rift. These first images confirm a rapid variation of the Moho depth on both sides of the rift and a very complex lithospheric structure in the central section with several low velocity zones within the top 50km that might correspond to magma lenses.

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

Associations of Novel and Traditional Vascular Biomarkers of Arterial Stiffness: Results of the SAPALDIA 3 Cohort Study.

PubMed

Endes, Simon; Caviezel, Seraina; Schaffner, Emmanuel; Dratva, Julia; Schindler, Christian; Künzli, Nino; Bachler, Martin; Wassertheurer, Siegfried; Probst-Hensch, Nicole; Schmidt-Trucksäss, Arno

There is a lack of evidence concerning associations between novel parameters of arterial stiffness as cardiovascular risk markers and traditional structural and functional vascular biomarkers in a population-based Caucasian cohort. We examined these associations in the second follow-up of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA 3). Arterial stiffness was measured oscillometrically by pulse wave analysis to derive the cardio-ankle vascular index (CAVI), brachial-ankle (baPWV) and aortic pulse wave velocity (aPWV), and amplitude of the forward and backward wave. Carotid ultrasonography was used to measure carotid intima-media thickness (cIMT) and carotid lumen diameter (LD), and to derive a distensibility coefficient (DC). We used multivariable linear regression models adjusted for several potential confounders for 2,733 people aged 50-81 years. CAVI, aPWV and the amplitude of the forward and backward wave were significant predictors of cIMT (p < 0.001). All parameters were significantly associated with LD (p < 0.001), with aPWV and the amplitude of the forward wave explaining the highest proportion of variance (2%). Only CAVI and baPWV were significant predictors of DC (p < 0.001), explaining more than 0.3% of the DC variance. We demonstrated that novel non-invasive oscillometric arterial stiffness parameters are differentially associated with specific established structural and functional local stiffness parameters. Longitudinal studies are needed to follow-up on these cross-sectional findings and to evaluate their relevance for clinical phenotypes.

Optical Rogue Waves in Vortex Turbulence.

PubMed

Gibson, Christopher J; Yao, Alison M; Oppo, Gian-Luca

2016-01-29

We present a spatiotemporal mechanism for producing 2D optical rogue waves in the presence of a turbulent state with creation, interaction, and annihilation of optical vortices. Spatially periodic structures with bound phase lose stability to phase unbound turbulent states in complex Ginzburg-Landau and Swift-Hohenberg models with external driving. When the pumping is high and the external driving is low, synchronized oscillations are unstable and lead to spatiotemporal vortex-mediated turbulence with high excursions in amplitude. Nonlinear amplification leads to rogue waves close to turbulent optical vortices, where the amplitude tends to zero, and to probability density functions (PDFs) with long tails typical of extreme optical events.

Parana Basin Structure from Multi-Objective Inversion of Surface Wave and Receiver Function by Competent Genetic Algorithm

NASA Astrophysics Data System (ADS)

An, M.; Assumpcao, M.

2003-12-01

The joint inversion of receiver function and surface wave is an effective way to diminish the influences of the strong tradeoff among parameters and the different sensitivity to the model parameters in their respective inversions, but the inversion problem becomes more complex. Multi-objective problems can be much more complicated than single-objective inversion in the model selection and optimization. If objectives are involved and conflicting, models can be ordered only partially. In this case, Pareto-optimal preference should be used to select solutions. On the other hand, the inversion to get only a few optimal solutions can not deal properly with the strong tradeoff between parameters, the uncertainties in the observation, the geophysical complexities and even the incompetency of the inversion technique. The effective way is to retrieve the geophysical information statistically from many acceptable solutions, which requires more competent global algorithms. Competent genetic algorithms recently proposed are far superior to the conventional genetic algorithm and can solve hard problems quickly, reliably and accurately. In this work we used one of competent genetic algorithms, Bayesian Optimization Algorithm as the main inverse procedure. This algorithm uses Bayesian networks to draw out inherited information and can use Pareto-optimal preference in the inversion. With this algorithm, the lithospheric structure of Paran"› basin is inverted to fit both the observations of inter-station surface wave dispersion and receiver function.

Wave Function Engineering in CdSe/PbS Core/Shell Quantum Dots.

PubMed

Wieliczka, Brian M; Kaledin, Alexey L; Buhro, William E; Loomis, Richard A

2018-05-25

The synthesis of epitaxial CdSe/PbS core/shell quantum dots (QDs) is reported. The PbS shell grows in a rock salt structure on the zinc blende CdSe core, thereby creating a crystal structure mismatch through additive growth. Absorption and photoluminescence (PL) band edge features shift to lower energies with increasing shell thickness, but remain above the CdSe bulk band gap. Nevertheless, the profiles of the absorption spectra vary with shell growth, indicating that the overlap of the electron and hole wave functions is changing significantly. This leads to over an order of magnitude reduction of absorption near the band gap and a large, tunable energy shift, of up to 550 meV, between the onset of strong absorption and the band edge PL. While the bulk valence and conduction bands adopt an inverse type-I alignment, the observed spectroscopic behavior is consistent with a transition between quasi-type-I and quasi-type-II behavior depending on shell thickness. Three effective mass approximation models support this hypothesis and suggest that the large difference in effective masses between the core and shell results in hole localization in the CdSe core and a delocalization of the electron across the entire QD. These results show the tuning of wave functions and transition energies in CdSe/PbS nanoheterostructures with prospects for use in optoelectronic devices for luminescent solar concentration or multiexciton generation.

Craton Heterogeneity in the South American Lithosphere

NASA Astrophysics Data System (ADS)

Lloyd, S.; Van der Lee, S.; Assumpcao, M.; Feng, M.; Franca, G. S.

2012-04-01

We investigate structure of the lithosphere beneath South America using receiver functions, surface wave dispersion analysis, and seismic tomography. The data used include recordings from 20 temporary broadband seismic stations deployed across eastern Brazil (BLSP02) and from the Chile Ridge Subduction Project seismic array in southern Chile (CRSP). By jointly inverting Moho point constraints, Rayleigh wave group velocities, and regional S and Rayleigh wave forms we obtain a continuous map of Moho depth. The new tomographic Moho map suggests that Moho depth and Moho relief vary slightly with age within the Precambrian crust. Whether or not a correlation between crustal thickness and geologic age can be derived from the pre-interpolation point constraints depends strongly on the selected subset of receiver functions. This implies that using only pre-interpolation point constraints (receiver functions) inadequately samples the spatial variation in geologic age. We also invert for S velocity structure and estimate the depth of the lithosphere-asthenosphere boundary (LAB) in Precambrian South America. The new model reveals a relatively thin lithosphere throughout most of Precambrian South America (< 140 km). Comparing LAB depth with lithospheric age shows they are overall positively correlated, whereby the thickest lithosphere occurs in the relatively small Saõ Francisco craton (200 km). However, within the larger Amazonian craton the younger lithosphere is thicker, indicating that locally even larger cratons are not protected from erosion or reworking of the lithosphere.

The Verriest Lecture: Short-wave-sensitive cone pathways across the life span

PubMed Central

Werner, John S.

2017-01-01

Structurally and functionally, the short-wave-sensitive (S) cone pathways are thought to decline more rapidly with normal aging than the middle- and long-wave-sensitive cone pathways. This would explain the celebrated results by Verriest and others demonstrating that the largest age-related color discrimination losses occur for stimuli on a tritan axis. Here, we challenge convention, arguing from psychophysical data that selective S-cone pathway losses do not cause declines in color discrimination. We show substantial declines in chromatic detection and discrimination, as well as in temporal and spatial vision tasks, that are mediated by S-cone pathways. These functional losses are not, however, unique to S-cone pathways. Finally, despite reduced photon capture by S cones, their postreceptoral pathways provide robust signals for the visual system to renormalize itself to maintain nearly stable color perception across the life span. PMID:26974914

Physics of Electronic Materials

NASA Astrophysics Data System (ADS)

Rammer, Jørgen

2017-03-01

1. Quantum mechanics; 2. Quantum tunneling; 3. Standard metal model; 4. Standard conductor model; 5. Electric circuit theory; 6. Quantum wells; 7. Particle in a periodic potential; 8. Bloch currents; 9. Crystalline solids; 10. Semiconductor doping; 11. Transistors; 12. Heterostructures; 13. Mesoscopic physics; 14. Arithmetic, logic and machines; Appendix A. Principles of quantum mechanics; Appendix B. Dirac's delta function; Appendix C. Fourier analysis; Appendix D. Classical mechanics; Appendix E. Wave function properties; Appendix F. Transfer matrix properties; Appendix G. Momentum; Appendix H. Confined particles; Appendix I. Spin and quantum statistics; Appendix J. Statistical mechanics; Appendix K. The Fermi-Dirac distribution; Appendix L. Thermal current fluctuations; Appendix M. Gaussian wave packets; Appendix N. Wave packet dynamics; Appendix O. Screening by symmetry method; Appendix P. Commutation and common eigenfunctions; Appendix Q. Interband coupling; Appendix R. Common crystal structures; Appendix S. Effective mass approximation; Appendix T. Integral doubling formula; Bibliography; Index.

The direct and inverse problems of an air-saturated poroelastic cylinder submitted to acoustic radiation

NASA Astrophysics Data System (ADS)

Ogam, Erick; Fellah, Z. E. A.

2011-09-01

A wave-fluid saturated poroelastic structure interaction model based on the modified Biot theory (MBT) and plane-wave decomposition using orthogonal cylindrical functions is developed. The model is employed to recover from real data acquired in an anechoic chamber, the poromechanical properties of a soft cellular melamine cylinder submitted to an audible acoustic radiation. The inverse problem of acoustic diffraction is solved by constructing the objective functional given by the total square of the difference between predictions from the MBT interaction model and diffracted field data from experiment. The faculty of retrieval of the intrinsic poromechanical parameters from the diffracted acoustic fields, indicate that a wave initially propagating in a light fluid (air) medium, is able to carry in the absence of mechanical excitation of the specimen, information on the macroscopic mechanical properties which depend on the microstructural and intrinsic properties of the solid phase.

The Association of Myosin IB with Actin Waves in Dictyostelium Requires Both the Plasma Membrane-Binding Site and Actin-Binding Region in the Myosin Tail

PubMed Central

Brzeska, Hanna; Pridham, Kevin; Chery, Godefroy; Titus, Margaret A.; Korn, Edward D.

2014-01-01

F-actin structures and their distribution are important determinants of the dynamic shapes and functions of eukaryotic cells. Actin waves are F-actin formations that move along the ventral cell membrane driven by actin polymerization. Dictyostelium myosin IB is associated with actin waves but its role in the wave is unknown. Myosin IB is a monomeric, non-filamentous myosin with a globular head that binds to F-actin and has motor activity, and a non-helical tail comprising a basic region, a glycine-proline-glutamine-rich region and an SH3-domain. The basic region binds to acidic phospholipids in the plasma membrane through a short basic-hydrophobic site and the Gly-Pro-Gln region binds F-actin. In the current work we found that both the basic-hydrophobic site in the basic region and the Gly-Pro-Gln region of the tail are required for the association of myosin IB with actin waves. This is the first evidence that the Gly-Pro-Gln region is required for localization of myosin IB to a specific actin structure in situ. The head is not required for myosin IB association with actin waves but binding of the head to F-actin strengthens the association of myosin IB with waves and stabilizes waves. Neither the SH3-domain nor motor activity is required for association of myosin IB with actin waves. We conclude that myosin IB contributes to anchoring actin waves to the plasma membranes by binding of the basic-hydrophobic site to acidic phospholipids in the plasma membrane and binding of the Gly-Pro-Gln region to F-actin in the wave. PMID:24747353

A self-adaptive metamaterial beam with digitally controlled resonators for subwavelength broadband flexural wave attenuation

NASA Astrophysics Data System (ADS)

Li, Xiaopeng; Chen, Yangyang; Hu, Gengkai; Huang, Guoliang

2018-04-01

Designing lightweight materials and/or structures for broadband low-frequency noise/vibration mitigation is an issue of fundamental importance both practically and theoretically. In this paper, by leveraging the concept of frequency-dependent effective stiffness control, we numerically and experimentally demonstrate, for the first time, a self-adaptive metamaterial beam with digital circuit controlled mechanical resonators for strong and broadband flexural wave attenuation at subwavelength scales. The digital controllers that are capable of feedback control of piezoelectric shunts are integrated into mechanical resonators in the metamaterial, and the transfer function is semi-analytically determined to realize an effective bending stiffness in a quadratic function of the wave frequency for adaptive band gaps. The digital as well as analog control circuits as the backbone of the system are experimentally realized with the guarantee stability of the whole electromechanical system in whole frequency regions, which is the most challenging problem so far. Our experimental results are in good agreement with numerical predictions and demonstrate the strong wave attenuation in almost a three times larger frequency region over the bandwidth of a passive metamaterial. The proposed metamaterial could be applied in a range of applications in the design of elastic wave control devices.

Low frequency piezoresonance defined dynamic control of terahertz wave propagation

NASA Astrophysics Data System (ADS)

Dutta, Moumita; Betal, Soutik; Peralta, Xomalin G.; Bhalla, Amar S.; Guo, Ruyan

2016-11-01

Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

Low frequency piezoresonance defined dynamic control of terahertz wave propagation.

PubMed

Dutta, Moumita; Betal, Soutik; Peralta, Xomalin G; Bhalla, Amar S; Guo, Ruyan

2016-11-30

Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO 3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

S-wave attenuation of the shallow sediments in the North China basin based on borehole seismograms of local earthquakes

NASA Astrophysics Data System (ADS)

Wang, Sheng; Li, Zhiwei

2018-06-01

S-wave velocity and attenuation structures of shallow sediments play important roles in accurate prediction of strong ground motion. However, it is more difficult to investigate the attenuation than velocity structures. In this study, we developed a new approach for estimating frequency-dependent S-wave attenuation (Q_S^{ - 1}) structures of shallow sediments based on multiple time window analysis of borehole seismograms from local earthquakes. Multiple time windows for separating direct and surface-reflected S-waves in local earthquake waveforms at borehole stations are selected with a global optimization scheme. With respect to different time windows, the transfer functions between direct and surface-reflected S-waves are achieved with a weighted averaging scheme, based on which frequency dependent Q_S^{ - 1} values are obtained. Synthetic tests suggest that the proposed method can restore robust and reliableQ_S^{ - 1} values, especially when the dataset of local earthquakes is not abundant. We utilize this method for local earthquake waveforms at 14 borehole seismic stations in the North China basin, and obtain Q_S^{ - 1} values in 2 ˜ 10 Hz frequency band, as well as average {V_P}, {V_S} and {V_P}/{{}}{V_S} ratio for shallow sediments deep to a few hundred meters. Results suggest that Q_S^{ - 1} values are to 0.01˜0.06, and generally decrease with frequency. The average attenuation structure of shallow sediments within the depth of a few hundred meters beneath 14 borehole stations in the North China basin can be modeled as Q_S^{ - 1} = 0.056{f^{ - 0.61}}. It is generally consistent with the attenuation structure of sedimentary basins in other areas, such as Mississippi Embayment sediments in the United States and Sendai basin in Japan.

Heavy and Heavy-Light Mesons in the Covariant Spectator Theory

NASA Astrophysics Data System (ADS)

Stadler, Alfred; Leitão, Sofia; Peña, M. T.; Biernat, Elmar P.

2018-05-01

The masses and vertex functions of heavy and heavy-light mesons, described as quark-antiquark bound states, are calculated with the Covariant Spectator Theory (CST). We use a kernel with an adjustable mixture of Lorentz scalar, pseudoscalar, and vector linear confining interaction, together with a one-gluon-exchange kernel. A series of fits to the heavy and heavy-light meson spectrum were calculated, and we discuss what conclusions can be drawn from it, especially about the Lorentz structure of the kernel. We also apply the Brodsky-Huang-Lepage prescription to express the CST wave functions for heavy quarkonia in terms of light-front variables. They agree remarkably well with light-front wave functions obtained in the Hamiltonian basis light-front quantization approach, even in excited states.

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function.

PubMed

Levashov, V A

2017-11-14

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function

NASA Astrophysics Data System (ADS)

Levashov, V. A.

2017-11-01

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

On the importance of local orbitals using second energy derivatives for d and f electrons

NASA Astrophysics Data System (ADS)

Karsai, Ferenc; Tran, Fabien; Blaha, Peter

2017-11-01

The all-electron linearized augmented plane wave (LAPW) methods are among the most accurate to solve the Kohn-Sham equations of density functional theory for periodic solids. In the LAPW methods, the unit cell is partitioned into spheres surrounding the atoms, inside which the wave functions are expanded into spherical harmonics, and the interstitial region, where the wave functions are expanded in Fourier series. Recently, Michalicek et al. (2013) reported an analysis of the so-called linearization error, which is inherent to the basis functions inside the spheres, and advocated the use of local orbital basis functions involving the second energy derivative of the radial part (HDLO). In the present work, we report the implementation of such basis functions into the WIEN2k code, and discuss in detail the improvement in terms of accuracy. From our tests, which involve atoms from the whole periodic table, it is concluded that for ground-state properties (e.g., equilibrium volume) the use of HDLO is necessary only for atoms with d or f electrons in the valence and large atomic spheres. For unoccupied states which are not too high above the Fermi energy, HDLO systematically improve the band structure, which may be of importance for the calculation of optical properties.

Generalization of the Kohn-Sham system that can represent arbitrary one-electron density matrices

DOE PAGES

Hubertus J. J. van Dam

2016-04-27

Density functional theory is currently the most widely applied method in electronic structure theory. The Kohn-Sham method, based on a fictitious system of noninteracting particles, is the workhorse of the theory. The particular form of the Kohn-Sham wave function admits only idempotent one-electron density matrices whereas wave functions of correlated electrons in post-Hartree-Fock methods invariably have fractional occupation numbers. Here we show that by generalizing the orbital concept and introducing a suitable dot product as well as a probability density, a noninteracting system can be chosen that can represent the one-electron density matrix of any system, even one with fractionalmore » occupation numbers. This fictitious system ensures that the exact electron density is accessible within density functional theory. It can also serve as the basis for reduced density matrix functional theory. Moreover, to aid the analysis of the results the orbitals may be assigned energies from a mean-field Hamiltonian. This produces energy levels that are akin to Hartree-Fock orbital energies such that conventional analyses based on Koopmans' theorem are available. Lastly, this system is convenient in formalisms that depend on creation and annihilation operators as they are trivially applied to single-determinant wave functions.« less

Effective Collision Strengths for Fine-structure Transitions in Si VII

NASA Astrophysics Data System (ADS)

Sossah, A. M.; Tayal, S. S.

2014-05-01

The effective collision strengths for electron-impact excitation of fine-structure transitions in Si VII are calculated as a function of electron temperature in the range 5000-2,000,000 K. The B-spline Breit-Pauli R-matrix method has been used to calculate collision strengths by electron impact. The target wave functions have been obtained using the multi-configuration Hartree-Fock method with term-dependent non-orthogonal orbitals. The 92 fine-structure levels belonging to the 46 LS states of 2s 22p 4, 2s2p 5, 2p 6, 2s 22p 33s, 2s 22p 33p, 2s 22p 33d, and 2s2p 43s configurations are included in our calculations of oscillator strengths and collision strengths. There are 4186 possible fine-structure allowed and forbidden transitions among the 92 levels. The present excitation energies, oscillator strengths, and collision strengths have been compared with previous theoretical results and available experimental data. Generally, a good agreement is found with the 6 LS-state close-coupling approximation results of Butler & Zeippen and the 44 LS-state distorted wave calculation of Bhatia & Landi.

Arterial stiffness, pressure and flow pulsatility and brain structure and function: the Age, Gene/Environment Susceptibility--Reykjavik study.

PubMed

Mitchell, Gary F; van Buchem, Mark A; Sigurdsson, Sigurdur; Gotal, John D; Jonsdottir, Maria K; Kjartansson, Ólafur; Garcia, Melissa; Aspelund, Thor; Harris, Tamara B; Gudnason, Vilmundur; Launer, Lenore J

2011-11-01

Aortic stiffness increases with age and vascular risk factor exposure and is associated with increased risk for structural and functional abnormalities in the brain. High ambient flow and low impedance are thought to sensitize the cerebral microcirculation to harmful effects of excessive pressure and flow pulsatility. However, haemodynamic mechanisms contributing to structural brain lesions and cognitive impairment in the presence of high aortic stiffness remain unclear. We hypothesized that disproportionate stiffening of the proximal aorta as compared with the carotid arteries reduces wave reflection at this important interface and thereby facilitates transmission of excessive pulsatile energy into the cerebral microcirculation, leading to microvascular damage and impaired function. To assess this hypothesis, we evaluated carotid pressure and flow, carotid-femoral pulse wave velocity, brain magnetic resonance images and cognitive scores in participants in the community-based Age, Gene/Environment Susceptibility--Reykjavik study who had no history of stroke, transient ischaemic attack or dementia (n = 668, 378 females, 69-93 years of age). Aortic characteristic impedance was assessed in a random subset (n = 422) and the reflection coefficient at the aorta-carotid interface was computed. Carotid flow pulsatility index was negatively related to the aorta-carotid reflection coefficient (R = -0.66, P<0.001). Carotid pulse pressure, pulsatility index and carotid-femoral pulse wave velocity were each associated with increased risk for silent subcortical infarcts (hazard ratios of 1.62-1.71 per standard deviation, P<0.002). Carotid-femoral pulse wave velocity was associated with higher white matter hyperintensity volume (0.108 ± 0.045 SD/SD, P = 0.018). Pulsatility index was associated with lower whole brain (-0.127 ± 0.037 SD/SD, P<0.001), grey matter (-0.079 ± 0.038 SD/SD, P = 0.038) and white matter (-0.128 ± 0.039 SD/SD, P<0.001) volumes. Carotid-femoral pulse wave velocity (-0.095 ± 0.043 SD/SD, P = 0.028) and carotid pulse pressure (-0.114 ± 0.045 SD/SD, P = 0.013) were associated with lower memory scores. Pulsatility index was associated with lower memory scores (-0.165 ± 0.039 SD/SD, P<0.001), slower processing speed (-0.118 ± 0.033 SD/SD, P<0.001) and worse performance on tests assessing executive function (-0.155 ± 0.041 SD/SD, P<0.001). When magnetic resonance imaging measures (grey and white matter volumes, white matter hyperintensity volumes and prevalent subcortical infarcts) were included in cognitive models, haemodynamic associations were attenuated or no longer significant, consistent with the hypothesis that increased aortic stiffness and excessive flow pulsatility damage the microcirculation, leading to quantifiable tissue damage and reduced cognitive performance. Marked stiffening of the aorta is associated with reduced wave reflection at the interface between carotid and aorta, transmission of excessive flow pulsatility into the brain, microvascular structural brain damage and lower scores in various cognitive domains.

From cluster structures to nuclear molecules: The role of nodal structure of the single-particle wave functions

NASA Astrophysics Data System (ADS)

Afanasjev, A. V.; Abusara, H.

2018-02-01

The nodal structure of the density distributions of the single-particle states occupied in rod-shaped, hyper- and megadeformed structures of nonrotating and rotating N ˜Z nuclei has been investigated in detail. The single-particle states with the Nilsson quantum numbers of the [N N 0 ]1 /2 (with N from 0 to 5) and [N ,N -1 ,1 ]Ω (with N from 1 to 3 and Ω =1 /2 , 3/2) types are considered. These states are building blocks of extremely deformed shapes in the nuclei with mass numbers A ≤50 . Because of (near) axial symmetry and large elongation of such structures, the wave functions of the single-particle states occupied are dominated by a single basis state in cylindrical basis. This basis state defines the nodal structure of the single-particle density distribution. The nodal structure of the single-particle density distributions allows us to understand in a relatively simple way the necessary conditions for α clusterization and the suppression of the α clusterization with the increase of mass number. It also explains in a natural way the coexistence of ellipsoidal mean-field-type structures and nuclear molecules at similar excitation energies and the features of particle-hole excitations connecting these two types of the structures. Our analysis of the nodal structure of the single-particle density distributions does not support the existence of quantum liquid phase for the deformations and nuclei under study.

Chemical Bonding: The Orthogonal Valence-Bond View

PubMed Central

Sax, Alexander F.

2015-01-01

Chemical bonding is the stabilization of a molecular system by charge- and spin-reorganization processes in chemical reactions. These processes are said to be local, because the number of atoms involved is very small. With multi-configurational self-consistent field (MCSCF) wave functions, these processes can be calculated, but the local information is hidden by the delocalized molecular orbitals (MO) used to construct the wave functions. The transformation of such wave functions into valence bond (VB) wave functions, which are based on localized orbitals, reveals the hidden information; this transformation is called a VB reading of MCSCF wave functions. The two-electron VB wave functions describing the Lewis electron pair that connects two atoms are frequently called covalent or neutral, suggesting that these wave functions describe an electronic situation where two electrons are never located at the same atom; such electronic situations and the wave functions describing them are called ionic. When the distance between two atoms decreases, however, every covalent VB wave function composed of non-orthogonal atomic orbitals changes its character from neutral to ionic. However, this change in the character of conventional VB wave functions is hidden by its mathematical form. Orthogonal VB wave functions composed of orthonormalized orbitals never change their character. When localized fragment orbitals are used instead of atomic orbitals, one can decide which local information is revealed and which remains hidden. In this paper, we analyze four chemical reactions by transforming the MCSCF wave functions into orthogonal VB wave functions; we show how the reactions are influenced by changing the atoms involved or by changing their local symmetry. Using orthogonal instead of non-orthogonal orbitals is not just a technical issue; it also changes the interpretation, revealing the properties of wave functions that remain otherwise undetected. PMID:25906476

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.

Observation of Landau quantization and standing waves in HfSiS

NASA Astrophysics Data System (ADS)

Jiao, L.; Xu, Q. N.; Qi, Y. P.; Wu, S.-C.; Sun, Y.; Felser, C.; Wirth, S.

2018-05-01

Recently, HfSiS was found to be a new type of Dirac semimetal with a line of Dirac nodes in the band structure. Meanwhile, Rashba-split surface states are also pronounced in this compound. Here we report a systematic study of HfSiS by scanning tunneling microscopy/spectroscopy at low temperature and high magnetic field. The Rashba-split surface states are characterized by measuring Landau quantization and standing waves, which reveal a quasilinear dispersive band structure. First-principles calculations based on density-functional theory are conducted and compared with the experimental results. Based on these investigations, the properties of the Rashba-split surface states and their interplay with defects and collective modes are discussed.

Transverse Wave Induced Kelvin–Helmholtz Rolls in Spicules

NASA Astrophysics Data System (ADS)

Antolin, P.; Schmit, D.; Pereira, T. M. D.; De Pontieu, B.; De Moortel, I.

2018-03-01

In addition to their jet-like dynamic behavior, spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze Hinode and IRIS observations of spicules and find different behaviors in terms of their Doppler velocity evolution and collective motion of their sub-structure. Some have a Doppler shift sign change that is rather fixed along the spicule axis, and lack coherence in the oscillatory motion of strand-like structure, matching rotation models, or long-wavelength torsional Alfvén waves. Others exhibit a Doppler shift sign change at maximum displacement and coherent motion of their strands, suggesting a collective magnetohydrodynamic (MHD) wave. By comparing with an idealized 3D MHD simulation combined with radiative transfer modeling, we analyze the role of transverse MHD waves and associated instabilities in spicule-like features. We find that transverse wave induced Kelvin–Helmholtz (TWIKH) rolls lead to coherence of strand-like structure in imaging and spectral maps, as seen in some observations. The rapid transverse dynamics and the density and temperature gradients at the spicule boundary lead to ring-shaped Mg II k and Ca II H source functions in the transverse cross-section, potentially allowing IRIS to capture the Kelvin–Helmholtz instability dynamics. Twists and currents propagate along the spicule at Alfvénic speeds, and the temperature variations within TWIKH rolls, produce the sudden appearance/disappearance of strands seen in Doppler velocity and in Ca II H intensity. However, only a mild intensity increase in higher-temperature lines is obtained, suggesting there is an additional heating mechanism at work in spicules.

Effects of pressure on the magnetic properties of FeO: A diffusion Monte Carlo study

NASA Astrophysics Data System (ADS)

Townsend, Joshua; Shulenburger, Luke; Mattsson, Thomas; Esler, Ken; Cohen, Ronald

While simple in terms of structure and composition, both experimental and computational investigations have demonstrated that FeO has a rich phase diagram of structural phase transformations, electronic spin transitions, insulator-metal transitions, and magnetic ordering transitions, due to the open-shell occupation of the Fe 3d electrons. We investigated the magnetic and electronic structures of FeO under ambient and high pressure conditions using diffusion Quantum Monte Carlo (QMC) within the fixed-node approximation. QMC techniques are especially well suited to the study of strongly correlated systems because they explicitly include correlation into the ground-state wave function. Here we report on the effects of the choice of trial wave function on the ambient pressure lattice distortion due to AFM ordering, as well as the equation of state, spin collapse, and metal-insulator transitions. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE.

Calculation of the electron wave function in a graded-channel double-heterojunction modulation-doped field-effect transistor

NASA Technical Reports Server (NTRS)

Mui, D. S. L.; Patil, M. B.; Morkoc, H.

1989-01-01

Three double-heterojunction modulation-doped field-effect transistor structures with different channel composition are investigated theoretically. All of these transistors have an In(x)Ga(1-x)As channel sandwiched between two doped Al(0.3)Ga(0.7)As barriers with undoped spacer layers. In one of the structures, x varies from 0 from either heterojunction to 0.15 at the center of the channel quadratically; in the other two, constant values of x of 0 and 0.15 are used. The Poisson and Schroedinger equations are solved self-consistently for the electron wave function in all three cases. The results showed that the two-dimensional electron gas (2DEG) concentration in the channel of the quadratically graded structure is higher than the x = 0 one and slightly lower than the x = 0.15 one, and the mean distance of the 2DEG is closer to the center of the channel for this transistor than the other two. These two effects have important implications on the electron mobility in the channel.

Relocating San Miguel Volcanic Seismic Events for Receiver Functions and Tomographic Models

NASA Astrophysics Data System (ADS)

Patlan, E.; Velasco, A. A.; Konter, J.

2009-12-01

The San Miguel volcano lies near the city of San Miguel, El Salvador (13.43N and -88.26W). San Miguel volcano, an active stratovolcano, presents a significant natural hazard for the city of San Miguel. Furthermore, the internal state and activity of volcanoes remains an important component to understanding volcanic hazard. The main technology for addressing volcanic hazards and processes is through the analysis of data collected from the deployment of seismic sensors that record ground motion. Six UTEP seismic stations were deployed around San Miguel volcano from 2007-2008 to define the magma chamber and assess the seismic and volcanic hazard. We utilize these data to develop images of the earth structure beneath the volcano, studying the volcanic processes by identifying different sources, and investigating the role of earthquakes and faults in controlling the volcanic processes. We will calculate receiver functions to determine the thickness of San Miguel volcano internal structure, within the Caribbean plate. Crustal thicknesses will be modeled using calculated receiver functions from both theoretical and hand-picked P-wave arrivals. We will use this information derived from receiver functions, along with P-wave delay times, to map the location of the magma chamber.

A new energy transfer model for turbulent free shear flow

NASA Technical Reports Server (NTRS)

Liou, William W.-W.

1992-01-01

A new model for the energy transfer mechanism in the large-scale turbulent kinetic energy equation is proposed. An estimate of the characteristic length scale of the energy containing large structures is obtained from the wavelength associated with the structures predicted by a weakly nonlinear analysis for turbulent free shear flows. With the inclusion of the proposed energy transfer model, the weakly nonlinear wave models for the turbulent large-scale structures are self-contained and are likely to be independent flow geometries. The model is tested against a plane mixing layer. Reasonably good agreement is achieved. Finally, it is shown by using the Liapunov function method, the balance between the production and the drainage of the kinetic energy of the turbulent large-scale structures is asymptotically stable as their amplitude saturates. The saturation of the wave amplitude provides an alternative indicator for flow self-similarity.

Composite fermions on a torus

NASA Astrophysics Data System (ADS)

Pu, Songyang; Wu, Ying-Hai; Jain, J. K.

2017-11-01

We achieve an explicit construction of the lowest Landau level (LLL) projected wave functions for composite fermions in the periodic (torus) geometry. To this end, we first demonstrate how the vortex attachment of the composite fermion (CF) theory can be accomplished in the torus geometry to produce the "unprojected" wave functions satisfying the correct (quasi)periodic boundary conditions. We then consider two methods for projecting these wave functions into the LLL. The direct projection produces valid wave functions but can be implemented only for very small systems. The more powerful and more useful projection method of Jain and Kamilla fails in the torus geometry because it does not preserve the periodic boundary conditions and thus takes us out of the original Hilbert space. We have succeeded in constructing a modified projection method that is consistent with both the periodic boundary conditions and the general structure of the CF theory. This method is valid for a large class of states of composite fermions, called "proper states," which includes the incompressible ground states at electron filling factors ν =n/2 p n +1 , their charged and neutral excitations, and also the quasidegenerate ground states at arbitrary filling factors of the form ν =ν/*2pν*+1 , where n and p are integers and ν* is the CF filling factor. Comparison with exact results known for small systems for the ground and excited states at filling factors ν =1 /3 , 2/5, and 3/7 demonstrates our LLL-projected wave functions to be extremely accurate representations of the actual Coulomb eigenstates. Our construction enables the study of large systems of composite fermions on the torus, thereby opening the possibility of investigating numerous interesting questions and phenomena.

The "Fermi hole" and the correlation introduced by the symmetrization or the anti-symmetrization of the wave function.

PubMed

Giner, Emmanuel; Tenti, Lorenzo; Angeli, Celestino; Malrieu, Jean-Paul

2016-09-28

The impact of the antisymmetrization is often addressed as a local property of the many-electron wave function, namely that the wave function should vanish when two electrons with parallel spins are in the same position in space. In this paper, we emphasize that this presentation is unduly restrictive: we illustrate the strong non-local character of the antisymmetrization principle, together with the fact that it is a matter of spin symmetry rather than spin parallelism. To this aim, we focus our attention on the simplest representation of various states of two-electron systems, both in atomic (helium atom) and molecular (H 2 and the π system of the ethylene molecule) cases. We discuss the non-local property of the nodal structure of some two-electron wave functions, both using analytical derivations and graphical representations of cuttings of the nodal hypersurfaces. The attention is then focussed on the impact of the antisymmetrization on the maxima of the two-body density, and we show that it introduces strong correlation effects (radial and/or angular) with a non-local character. These correlation effects are analyzed in terms of inflation and depletion zones, which are easily identifiable, thanks to the nodes of the orbitals composing the wave function. Also, we show that the correlation effects induced by the antisymmetrization occur also for anti-parallel spins since all M s components of a given spin state have the same N-body densities. Finally, we illustrate that these correlation effects occur also for the singlet states, but they have strictly opposite impacts: the inflation zones in the triplet become depletion zones in the singlet and vice versa.

A Source Term for Wave Attenuation by Sea Ice in WAVEWATCH III(registered trademark): IC4

DTIC Science & Technology

2017-06-07

energy in the high frequency face of the spectrum, which highlights the fact that frequency dependent attenuation in necessary to replicate the low-pass... frequency space ; M6) and an expanded version of M5 with up to 10 steps. The remainder of this report is structured as follows: a note about the...function period, T = 1/f. Measurements have shown that ice preferentially damps high frequency waves and in this way ice acts as a low pass filter

Contributions to the Fourth Solar Wind Conference. [interplanetary magnetic fields and medium

NASA Technical Reports Server (NTRS)

Acuna, M. H.; Behannon, K. W.; Burlaga, L. F.; Lepping, R.; Ness, N.; Ogilvie, K.; Pizzo, J.

1979-01-01

Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed.

Gravity dual of spin and charge density waves

NASA Astrophysics Data System (ADS)

Jokela, Niko; Järvinen, Matti; Lippert, Matthew

2014-12-01

At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.

Chiral Domain Structure in Superfluid 3He-A Studied by Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Kasai, J.; Okamoto, Y.; Nishioka, K.; Takagi, T.; Sasaki, Y.

2018-05-01

The existence of a spatially varying texture in superfluid 3He is a direct manifestation of the complex macroscopic wave function. The real space shape of the texture, namely, a macroscopic wave function, has been studied extensively with the help of theoretical modeling but has never been directly observed experimentally with spatial resolution. We have succeeded in visualizing the texture by a specialized magnetic resonance imaging. With this new technology, we have discovered that the macroscopic chiral domains, of which sizes are as large as 1 mm, and corresponding chiral domain walls exist rather stably in 3He - A film at temperatures far below the transition temperature.

FUNDUS AUTOFLUORESCENCE IN RUBELLA RETINOPATHY: Correlation With Photoreceptor Structure and Function.

PubMed

Bukowska, Danuta M; Wan, Sue Ling; Chew, Avenell L; Chelva, Enid; Tang, Ivy; Mackey, David A; Chen, Fred K

2017-01-01

To illustrate altered fundus autofluorescence in rubella retinopathy and to investigate their relationships with photoreceptor structure and function using multimodal imaging. The authors report four cases of rubella retinopathy aged 8, 33, 42, and 50 years. All patients had dilated clinical fundus examination; wide-field color photography; blue, green, and near-infrared autofluorescence imaging and spectral domain optical coherence tomography. Two patients also underwent microperimetry and adaptive optics imaging. En face optical coherence tomography, cone mosaic, and microperimetry were coregistered with autofluorescence images. The authors explored the structure-function correlation. All four patients had a "salt-and-pepper" appearance on dilated fundus examination and wide-field color photography. There were variable-sized patches of hypoautofluorescence on both blue and near-infrared excitation in all four patients. Wave-guiding cones were visible and retinal sensitivity was intact over these regions. There was no correlation between hypoautofluorescence and regions of attenuated ellipsoid and interdigitation zones. Hyperautofluorescent lesions were also noted and some of these were pseudo-vitelliform lesions. Patchy hypoautofluorescence on near-infrared excitation can be a feature of rubella retinopathy. This may be due to abnormal melanin production or loss of melanin within retinal pigment epithelium cells harboring persistent rubella virus infection. Preservation of the ellipsoid zone, wave-guiding cones, and retinal sensitivity within hypoautofluorescent lesions suggest that these retinal pigment epithelium changes have only mild impact on photoreceptor cell function.

On the nature of fast sausage waves in coronal loops

NASA Astrophysics Data System (ADS)

Bahari, Karam

2018-05-01

The effect of the parameters of coronal loops on the nature of fast sausage waves are investigated. To do this three models of the coronal loop considered, a simple loop model, a current-carrying loop model and a model with radially structured density called "Inner μ" profile. For all the models the Magnetohydrodynamic (MHD) equations solved analytically in the linear approximation and the restoring forces of oscillations obtained. The ratio of the magnetic tension force to the pressure gradient force obtained as a function of the distance from the axis of the loop. In the simple loop model for all values of the loop parameters the fast sausages wave have a mixed nature of Alfvénic and fast MHD waves, in the current-carrying loop model with thick annulus and low density contrast the fast sausage waves can be considered as purely Alfvénic wave in the core region of the loop, and in the "Inner μ" profile for each set of the parameters of the loop the wave can be considered as a purely Alfvénic wave in some regions of the loop.

Elastic wave field computation in multilayered nonplanar solid structures: a mesh-free semianalytical approach.

PubMed

Banerjee, Sourav; Kundu, Tribikram

2008-03-01

Multilayered solid structures made of isotropic, transversely isotropic, or general anisotropic materials are frequently used in aerospace, mechanical, and civil structures. Ultrasonic fields developed in such structures by finite size transducers simulating actual experiments in laboratories or in the field have not been rigorously studied. Several attempts to compute the ultrasonic field inside solid media have been made based on approximate paraxial methods like the classical ray tracing and multi-Gaussian beam models. These approximate methods have several limitations. A new semianalytical method is adopted in this article to model elastic wave field in multilayered solid structures with planar or nonplanar interfaces generated by finite size transducers. A general formulation good for both isotropic and anisotropic solids is presented in this article. A variety of conditions have been incorporated in the formulation including irregularities at the interfaces. The method presented here requires frequency domain displacement and stress Green's functions. Due to the presence of different materials in the problem geometry various elastodynamic Green's functions for different materials are used in the formulation. Expressions of displacement and stress Green's functions for isotropic and anisotropic solids as well as for the fluid media are presented. Computed results are verified by checking the stress and displacement continuity conditions across the interface of two different solids of a bimetal plate and investigating if the results for a corrugated plate with very small corrugation match with the flat plate results.

WASp family verprolin-homologous protein-2 (WAVE2) and Wiskott-Aldrich syndrome protein (WASp) engage in distinct downstream signaling interactions at the T cell antigen receptor site.

PubMed

Pauker, Maor H; Reicher, Barak; Joseph, Noah; Wortzel, Inbal; Jakubowicz, Shlomi; Noy, Elad; Perl, Orly; Barda-Saad, Mira

2014-12-12

T cell antigen receptor (TCR) engagement has been shown to activate pathways leading to actin cytoskeletal polymerization and reorganization, which are essential for lymphocyte activation and function. Several actin regulatory proteins were implicated in regulating the actin machinery, such as members of the Wiskott-Aldrich syndrome protein (WASp) family. These include WASp and the WASp family verprolin-homologous protein-2 (WAVE2). Although WASp and WAVE2 share several structural features, the precise regulatory mechanisms and potential redundancy between them have not been fully characterized. Specifically, unlike WASp, the dynamic molecular interactions that regulate WAVE2 recruitment to the cell membrane and specifically to the TCR signaling complex are largely unknown. Here, we identify the molecular mechanism that controls the recruitment of WAVE2 in comparison with WASp. Using fluorescence resonance energy transfer (FRET) and novel triple-color FRET (3FRET) technology, we demonstrate how WAVE2 signaling complexes are dynamically regulated during lymphocyte activation in vivo. We show that, similar to WASp, WAVE2 recruitment to the TCR site depends on protein-tyrosine kinase, ZAP-70, and the adaptors LAT, SLP-76, and Nck. However, in contrast to WASp, WAVE2 leaves this signaling complex and migrates peripherally together with vinculin to the membrane leading edge. Our experiments demonstrate that WASp and WAVE2 differ in their dynamics and their associated proteins. Thus, this study reveals the differential mechanisms regulating the function of these cytoskeletal proteins. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

WASp Family Verprolin-homologous Protein-2 (WAVE2) and Wiskott-Aldrich Syndrome Protein (WASp) Engage in Distinct Downstream Signaling Interactions at the T Cell Antigen Receptor Site*

PubMed Central

Pauker, Maor H.; Reicher, Barak; Joseph, Noah; Wortzel, Inbal; Jakubowicz, Shlomi; Noy, Elad; Perl, Orly; Barda-Saad, Mira

2014-01-01

T cell antigen receptor (TCR) engagement has been shown to activate pathways leading to actin cytoskeletal polymerization and reorganization, which are essential for lymphocyte activation and function. Several actin regulatory proteins were implicated in regulating the actin machinery, such as members of the Wiskott-Aldrich syndrome protein (WASp) family. These include WASp and the WASp family verprolin-homologous protein-2 (WAVE2). Although WASp and WAVE2 share several structural features, the precise regulatory mechanisms and potential redundancy between them have not been fully characterized. Specifically, unlike WASp, the dynamic molecular interactions that regulate WAVE2 recruitment to the cell membrane and specifically to the TCR signaling complex are largely unknown. Here, we identify the molecular mechanism that controls the recruitment of WAVE2 in comparison with WASp. Using fluorescence resonance energy transfer (FRET) and novel triple-color FRET (3FRET) technology, we demonstrate how WAVE2 signaling complexes are dynamically regulated during lymphocyte activation in vivo. We show that, similar to WASp, WAVE2 recruitment to the TCR site depends on protein-tyrosine kinase, ZAP-70, and the adaptors LAT, SLP-76, and Nck. However, in contrast to WASp, WAVE2 leaves this signaling complex and migrates peripherally together with vinculin to the membrane leading edge. Our experiments demonstrate that WASp and WAVE2 differ in their dynamics and their associated proteins. Thus, this study reveals the differential mechanisms regulating the function of these cytoskeletal proteins. PMID:25342748

Lithospheric Structure across the Alaskan Cordillera from Surface Waves and Receiver Functions

NASA Astrophysics Data System (ADS)

Ward, K. M.; Lin, F. C.

2017-12-01

The long awaited Transportable Array (TA) deployment in Alaska and western Canada is nearing its final deployment stage. With only one more deployment season, most of the TA station locations have been occupied and begun providing data. These TA stations combined with upgraded existing locations have provided enough high-quality data to begin investigating the crustal and upper mantle structure across the entire Alaskan Cordillera. From a tectonic standpoint, many interesting questions remain unanswered. For example, how does the transition from oceanic-oceanic subduction to continental-oceanic normal subduction to continental-oceanic "flat-slab" subduction to strike-slip conservative plate motion affect the deformation/uplift of the overriding plate and mantle geodynamic characteristics? How does the long and completed terrene accretion process partition stress/strain in the crust? On more local scales, are there any significant mid-crustal magmatic systems as observed in other sections of the American Cordillera, and if so, what is there role in uplift and crustal deformation? Our approach to investigating these questions is though surface wave imaging from ambient noise and earthquake generated sources along with Rayleigh wave ellipticity paired with Ps receiver functions. Our preliminary tomography results agree with previous studies but expand the spatial coverage showing additional detail. Our ellipticity results show a heterogeneous but spatially consistent anisotropic shallow crust. Although the complete TA data set has not yet been collected, we have jointly inverted surface waves with receiver functions for a 3-D shear-wave velocity model across the entire Alaskan Cordillera. Key features of our velocity model include a high-velocity feature in the upper mantle associated with the subducting Pacific plate that extends north of the seismicity used to contour the geometry of the slab and mid-crustal low-velocity zones associated with the active volcanics in the Wrangell mountains and along the Aleutian arc.

Modeling seismic wave propagation across the European plate: structural models and numerical techniques, state-of-the-art and prospects

NASA Astrophysics Data System (ADS)

Morelli, Andrea; Danecek, Peter; Molinari, Irene; Postpischl, Luca; Schivardi, Renata; Serretti, Paola; Tondi, Maria Rosaria

2010-05-01

Together with the building and maintenance of observational and data banking infrastructures - i.e. an integrated organization of coordinated sensor networks, in conjunction with connected data banks and efficient data retrieval tools - a strategic vision for bolstering the future development of geophysics in Europe should also address the essential issue of improving our current ability to model coherently the propagation of seismic waves across the European plate. This impacts on fundamental matters, such as correctly locating earthquakes, imaging detailed earthquake source properties, modeling ground shaking, inferring geodynamic processes. To this extent, we both need detailed imaging of shallow and deep earth structure, and accurate modeling of seismic waves by numerical methods. Our current abilities appear somewhat limited, but emerging technologies may enable soon a significant leap towards better accuracy and reliability. To contribute to this debate, we present here the state-of-the-art of knowledge of earth structure and numerical wave modeling in the European plate, as the result of a comprehensive study towards the definition of a continental-scale reference model. Our model includes a description of crustal structure (EPcrust) merging information deriving from previous studies - large-scale compilations, seismic prospection, receiver functions, inversion of surface wave dispersion measurements and Green functions from noise correlation. We use a simple description of crustal structure, with laterally-varying sediment and cristalline layers thickness, density, and seismic parameters. This a priori crustal model improves the overall fit to observed Bouguer anomaly maps over CRUST2.0. The new crustal model is then used as a constraint in the inversion for mantle shear wave speed, based on fitting Love and Rayleigh surface wave dispersion. The new mantle model sensibly improves over global S models in the imaging of shallow asthenospheric (slow) anomalies beneath the Alpine mobile belt, and fast lithospheric signatures under the two main Mediterranean subduction systems (Aegean and Tyrrhenian). We validate this new model through comparison of recorded seismograms with simulations based on numerical codes (SPECFEM3D). To ease and increase model usage, we also propose the adoption of a common exchange format for tomographic earth models based on JSON, a lightweight data-interchange format supported by most high-level programming languages, and provide tools for manipulating and visualising models, described in this standard format, in Google Earth and GEON IDV. In the next decade seismologists will be able to reap new possibilities offered by exciting progress in general computing power and algorithmic development in computational seismology. Structural models, still based on classical approaches and modeling just few parameters in each seismogram, will benefit from emerging techniques - such as full waveform fitting and fully nonlinear inversion - that are now just showing their potential. This will require extensive availability of supercomputing resources to earth scientists in Europe, as a tool to match the planned new massive data flow. We need to make sure that the whole apparatus, needed to fully exploit new data, will be widely accessible. To maximize the development, so as for instance to enable us to promptly model ground shaking after a major earthquake, we will also need a better coordination framework, that will enable us to share and amalgamate the abundant local information on earth structure - most often available but difficult to retrieve, merge and use. Comprehensive knowledge of earth structure and of best practices to model wave propagation can by all means be considered an enabling technology for further geophysical progress.

Structure of kinetic Alfvén waves with small transverse scale length

NASA Astrophysics Data System (ADS)

Morales, G. J.; Maggs, J. E.

1997-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension a, transverse to the confining magnetic field, is comparable to the ion sound gyroradius cs/Ωi, where cs is the sound speed and Ωi the ion cyclotron frequency. The radial structure of the wave azimuthal magnetic field is found to consist of four regions: a Bessel function behavior for r

Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

NASA Astrophysics Data System (ADS)

Ahmadi, N.; Wilder, F. D.; Usanova, M.; Ergun, R.; Argall, M. R.; Goodrich, K.; Eriksson, S.; Germaschewski, K.; Torbert, R. B.; Lindqvist, P. A.; Le Contel, O.; Khotyaintsev, Y. V.; Strangeway, R. J.; Schwartz, S. J.; Giles, B. L.; Burch, J.

2017-12-01

The Magnetospheric Multiscale (MMS) mission observed electron whistler waves at the center and at the gradients of magnetic holes on the dayside magnetosheath. The magnetic holes are nonlinear mirror structures which are anti-correlated with particle density. We used expanding box Particle-in-cell simulations and produced the mirror instability magnetic holes. We show that the electron whistler waves can be generated at the gradients and the center of magnetic holes in our simulations which is in agreement with MMS observations. At the nonlinear regime of mirror instability, the proton and electron temperature anisotropy are anti-correlated with the magnetic hole. The plasma is unstable to electron whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are dominant, electron temperature anisotropy develops at the edges of the magnetic holes and electrons become isotropic at the magnetic field minimum. We investigate the possible mechanism for enhancing the electron temperature anisotropy and analyze the electron pitch angle distributions and electron distribution functions in our simulations and compare it with MMS observations.

Can Outer Hair Cells Actively Pump Fluid into the Tunnel of Corti?

NASA Astrophysics Data System (ADS)

Zagadou, Brissi Franck; Mountain, David C.

2011-11-01

Non-classical models of the cochlear traveling wave have been introduced in attempt to capture the unique features of the cochlear amplifier (CA). These models include multiple modes of longitudinal coupling. In one approach, it is hypothesized that two wave modes can add their energies to create amplification such as that desired in the CA. The tunnel of Corti (ToC) was later used to represent the second wave mode for the proposed traveling wave amplifier model, and was incorporated in a multi-compartment cochlea model. The results led to the hypothesis that the CA functions as a fluid pump. However, this hypothesis must be consistent with the anatomical structure of the organ of Corti (OC). The fluid must pass between the outer pillar cells before reaching the ToC, and the ToC fluid and the underlying basilar membrane must constitute an appropriate waveguide. We have analyzed an anatomically based 3D finite element model of the ToC of the gerbil. Our results demonstrate that the OC structure is consistent with the hypothesis.

Shallow subsurface structure estimated from dense aftershock records and microtremor observations in Furukawa district, Miyagi, Japan

NASA Astrophysics Data System (ADS)

Goto, Hiroyuki; Mitsunaga, Hitoshi; Inatani, Masayuki; Iiyama, Kahori; Hada, Koji; Ikeda, Takaaki; Takaya, Toshiyasu; Kimura, Sayaka; Akiyama, Ryohei; Sawada, Sumio; Morikawa, Hitoshi

2017-11-01

We conducted single-site and array observations of microtremors in order to revise the shallow subsurface structure of the Furukawa district, Miyagi, Japan, where severe residential damage was reported during the Great Eastern Japan Earthquake of 2011, off the Pacific coast of Tohoku. The phase velocities of Rayleigh waves are estimated from array observations at three sites, and S-wave velocity models are established. The spatial distribution of predominant periods is estimated for the surface layer, on the basis of the spectral ratio of horizontal and vertical components (H/V) of microtremors obtained from single-site observations. We then compared ground motion records from a dense seismometer network with results of microtremor observations, and revised a model of the shallow (~100 m) subsurface structure in the Furukawa district. The model implies that slower near-surface S-wave velocity and deeper basement are to be found in the southern and eastern areas. It was found that the damage in residential structures was concentrated in an area where the average value for the transfer functions in the frequency range of 2 to 4 Hz was large.

Shear wave velocity variation across the Taupo Volcanic Zone, New Zealand, from receiver function inversion

USGS Publications Warehouse

Bannister, S.; Bryan, C.J.; Bibby, H.M.

2004-01-01

The Taupo Volcanic Zone (TVZ), New Zealand is a region characterized by very high magma eruption rates and extremely high heat flow, which is manifest in high-temperature geothermal waters. The shear wave velocity structure across the region is inferred using non-linear inversion of receiver functions, which were derived from teleseismic earthquake data. Results from the non-linear inversion, and from forward synthetic modelling, indicate low S velocities at ???6- 16 km depth near the Rotorua and Reporoa calderas. We infer these low-velocity layers to represent the presence of high-level bodies of partial melt associated with the volcanism. Receiver functions at other stations are complicated by reverberations associated with near-surface sedimentary layers. The receiver function data also indicate that the Moho lies between 25 and 30 km, deeper than the 15 ?? 2 km depth previously inferred for the crust-mantle boundary beneath the TVZ. ?? 2004 RAS.

Preliminary study of crust-upper mantle structure of the Tibetan Plateau by using broadband teleseismic body waveforms

NASA Astrophysics Data System (ADS)

Zhu, Lu-Pei; Zeng, Rong-Sheng; Wu, Francis T.; Owens, Thomas J.; Randall, George E.

1993-05-01

As part of a joint Sino-U.S. research project to study the deep structure of the Tibetan Plateau, 11 broadband digital seismic recorders were deployed on the Plateau for one year of passive seismic recording. In this report we use teleseimic P waveforms to study the seismic velocity structure of crust and upper mantle under three stations by receiver function inversion. The receiver function is obtained by first rotating two horizontal components of seismic records into radial and tangential components and then deconvolving the vertical component from them. The receiver function depends only on the structure near the station because the source and path effects have been removed by the deconvolution. To suppress noise, receiver functions calculated from events clustered in a small range of back-azimuths and epicentral distances are stacked. Using a matrix formalism describing the propagation of elastic waves in laterally homogeneous stratified medium, a synthetic receiver function and differential receiver functions for the parameters in each layer can be calculated to establish a linearized inversion for one-dimensional velocity structure. Preliminary results of three stations, Wen-quan, Golmud and Xigatze (Coded as WNDO, TUNL and XIGA), located in central, northern and southern Plateau are given in this paper. The receiver functions of all three stations show clear P-S converted phases. The time delays of these converted phases relative to direct P arrivals are: WNDO 7.9s (for NE direction) and 8.3s (for SE direction), TUNL 8.2s, XIGA 9.0s. Such long time delays indicate the great thickness of crust under the Plateau. The differences between receiver function of these three station shows the tectonic difference between southern and north-central Plateau. The waveforms of the receiver functions for WNDO and TUNL are very simple, while the receiver function of XIGA has an additional midcrustal converted phase. The S wave velocity structures at these three stations are estimated from inversions of the receiver function. The crustal shear wave velocities at WNDO and TUNL are vertically homogeneous, with value between 3.5 3.6 km/s down to Moho. This value in the lower crust is lower than the normal value for the lower crust of continents, which is consistent with the observed strong Sn attenuation in this region. The velocity structure at XIGA shows a velocity discontinuity at depth of 20 km and high velocity value of 4.0 km/s in the midcrust between 20 30 km depth. Similar results are obtained from a DSS profile in southern Tibet. The velocity under XIGA decreases below a depth of 30 km, reaching the lowest value of 3.2 km/s between 50 55 km. depth. This may imply that the Indian crust underthrusts the low part of Tibetan crust in the southern Plateau, forming a “double crust”. The crustal thickness at each of these sites is: WNDO, 68 km; TUNL, 70 km; XI-GA, 80 km.

The Fundamental Structure and the Reproduction of Spiral Wave in a Two-Dimensional Excitable Lattice.

PubMed

Qian, Yu; Zhang, Zhaoyang

2016-01-01

In this paper we have systematically investigated the fundamental structure and the reproduction of spiral wave in a two-dimensional excitable lattice. A periodically rotating spiral wave is introduced as the model to reproduce spiral wave artificially. Interestingly, by using the dominant phase-advanced driving analysis method, the fundamental structure containing the loop structure and the wave propagation paths has been revealed, which can expose the periodically rotating orbit of spiral tip and the charity of spiral wave clearly. Furthermore, the fundamental structure is utilized as the core for artificial spiral wave. Additionally, the appropriate parameter region, in which the artificial spiral wave can be reproduced, is studied. Finally, we discuss the robustness of artificial spiral wave to defects.

Polymer Morphological Change Induced by Terahertz Irradiation

NASA Astrophysics Data System (ADS)

Hoshina, Hiromichi; Suzuki, Hal; Otani, Chiko; Nagai, Masaya; Kawase, Keigo; Irizawa, Akinori; Isoyama, Goro

2016-06-01

As terahertz (THz) frequencies correspond to those of the intermolecular vibrational modes in a polymer, intense THz wave irradiation affects the macromolecular polymorph, which determines the polymer properties and functions. THz photon energy is quite low compared to the covalent bond energy; therefore, conformational changes can be induced “softly,” without damaging the chemical structures. Here, we irradiate a poly(3-hydroxybutylate) (PHB) / chloroform solution during solvent casting crystallization using a THz wave generated by a free electron laser (FEL). Morphological observation shows the formation of micrometer-sized crystals in response to the THz wave irradiation. Further, a 10-20% increase in crystallinity is observed through analysis of the infrared (IR) absorption spectra. The peak power density of the irradiating THz wave is 40 MW/cm2, which is significantly lower than the typical laser intensities used for material manipulation. We demonstrate for the first time that the THz wave effectively induces the intermolecular rearrangement of polymer macromolecules.

Subwavelength wave manipulation in a thin surface-wave bandgap crystal.

PubMed

Gao, Zhen; Wang, Zhuoyuan; Zhang, Baile

2018-01-01

It has been recently reported that the unit cell of wire media metamaterials can be tailored locally to shape the flow of electromagnetic waves at deep-subwavelength scales [Nat. Phys.9, 55 (2013)NPAHAX1745-247310.1038/nphys2480]. However, such bulk structures have a thickness of at least the order of wavelength, thus hindering their applications in the on-chip compact plasmonic integrated circuits. Here, based upon a Sievenpiper "mushroom" array [IEEE Trans. Microwave Theory Tech.47, 2059 (1999)IETMAB0018-948010.1109/22.798001], which is compatible with standard printed circuit board technology, we propose and experimentally demonstrate the subwavelength manipulation of surface waves on a thin surface-wave bandgap crystal with a thickness much smaller than the wavelength (1/30th of the operating wavelength). Functional devices including a T-shaped splitter and sharp bend are constructed with good performance.

Effect of shock waves on the statistics and scaling in compressible isotropic turbulence

NASA Astrophysics Data System (ADS)

Wang, Jianchun; Wan, Minping; Chen, Song; Xie, Chenyue; Chen, Shiyi

2018-04-01

The statistics and scaling of compressible isotropic turbulence in the presence of large-scale shock waves are investigated by using numerical simulations at turbulent Mach number Mt ranging from 0.30 to 0.65. The spectra of the compressible velocity component, density, pressure, and temperature exhibit a k-2 scaling at different turbulent Mach numbers. The scaling exponents for structure functions of the compressible velocity component and thermodynamic variables are close to 1 at high orders n ≥3 . The probability density functions of increments of the compressible velocity component and thermodynamic variables exhibit a power-law region with the exponent -2 . Models for the conditional average of increments of the compressible velocity component and thermodynamic variables are developed based on the ideal shock relations and are verified by numerical simulations. The overall statistics of the compressible velocity component and thermodynamic variables are similar to one another at different turbulent Mach numbers. It is shown that the effect of shock waves on the compressible velocity spectrum and kinetic energy transfer is different from that of acoustic waves.

Exact result in strong wave turbulence of thin elastic plates

NASA Astrophysics Data System (ADS)

Düring, Gustavo; Krstulovic, Giorgio

2018-02-01

An exact result concerning the energy transfers between nonlinear waves of a thin elastic plate is derived. Following Kolmogorov's original ideas in hydrodynamical turbulence, but applied to the Föppl-von Kármán equation for thin plates, the corresponding Kármán-Howarth-Monin relation and an equivalent of the 4/5 -Kolmogorov's law is derived. A third-order structure function involving increments of the amplitude, velocity, and the Airy stress function of a plate, is proven to be equal to -ɛ ℓ , where ℓ is a length scale in the inertial range at which the increments are evaluated and ɛ the energy dissipation rate. Numerical data confirm this law. In addition, a useful definition of the energy fluxes in Fourier space is introduced and proven numerically to be flat in the inertial range. The exact results derived in this Rapid Communication are valid for both weak and strong wave turbulence. They could be used as a theoretical benchmark of new wave-turbulence theories and to develop further analogies with hydrodynamical turbulence.

Solving the Vlasov equation in two spatial dimensions with the Schrödinger method

NASA Astrophysics Data System (ADS)

Kopp, Michael; Vattis, Kyriakos; Skordis, Constantinos

2017-12-01

We demonstrate that the Vlasov equation describing collisionless self-gravitating matter may be solved with the so-called Schrödinger method (ScM). With the ScM, one solves the Schrödinger-Poisson system of equations for a complex wave function in d dimensions, rather than the Vlasov equation for a 2 d -dimensional phase space density. The ScM also allows calculating the d -dimensional cumulants directly through quasilocal manipulations of the wave function, avoiding the complexity of 2 d -dimensional phase space. We perform for the first time a quantitative comparison of the ScM and a conventional Vlasov solver in d =2 dimensions. Our numerical tests were carried out using two types of cold cosmological initial conditions: the classic collapse of a sine wave and those of a Gaussian random field as commonly used in cosmological cold dark matter N-body simulations. We compare the first three cumulants, that is, the density, velocity and velocity dispersion, to those obtained by solving the Vlasov equation using the publicly available code ColDICE. We find excellent qualitative and quantitative agreement between these codes, demonstrating the feasibility and advantages of the ScM as an alternative to N-body simulations. We discuss, the emergence of effective vorticity in the ScM through the winding number around the points where the wave function vanishes. As an application we evaluate the background pressure induced by the non-linearity of large scale structure formation, thereby estimating the magnitude of cosmological backreaction. We find that it is negligibly small and has time dependence and magnitude compatible with expectations from the effective field theory of large scale structure.

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.

On the Connection Between Microbursts and Nonlinear Electronic Structures in Planetary Radiation Belts

NASA Technical Reports Server (NTRS)

Osmane, Adnane; Wilson, Lynn B., III; Blum, Lauren; Pulkkinen, Tuija I.

2016-01-01

Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave-particle interactions. We show that wave parameters, consistent with large amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (greater than 1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles Theta (sub k)B greater than 50 degrees and phase-speeds v(sub phi) greater than or equal to c/9. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution function of electrons near the magnetic mirror point can result in the generation of double layers and electron solitary holes consistent in scales (of the order of Debye lengths) to nonlinear structures observed in the radiation belts by the Van Allen Probes. Our results indicate a relationship between nonlinear electrostatic and electromagnetic structures in the dynamics of planetary radiation belts and their role in the cyclical production of energetic electrons (E greater than or equal to 100 keV) on kinetic timescales, which is much faster than previously inferred.

Optimal Tikhonov Regularization in Finite-Frequency Tomography

NASA Astrophysics Data System (ADS)

Fang, Y.; Yao, Z.; Zhou, Y.

2017-12-01

The last decade has witnessed a progressive transition in seismic tomography from ray theory to finite-frequency theory which overcomes the resolution limit of the high-frequency approximation in ray theory. In addition to approximations in wave propagation physics, a main difference between ray-theoretical tomography and finite-frequency tomography is the sparseness of the associated sensitivity matrix. It is well known that seismic tomographic problems are ill-posed and regularizations such as damping and smoothing are often applied to analyze the tradeoff between data misfit and model uncertainty. The regularizations depend on the structure of the matrix as well as noise level of the data. Cross-validation has been used to constrain data uncertainties in body-wave finite-frequency inversions when measurements at multiple frequencies are available to invert for a common structure. In this study, we explore an optimal Tikhonov regularization in surface-wave phase-velocity tomography based on minimization of an empirical Bayes risk function using theoretical training datasets. We exploit the structure of the sensitivity matrix in the framework of singular value decomposition (SVD) which also allows for the calculation of complete resolution matrix. We compare the optimal Tikhonov regularization in finite-frequency tomography with traditional tradeo-off analysis using surface wave dispersion measurements from global as well as regional studies.

Mechanically induced intercellular calcium communication in confined endothelial structures.

PubMed

Junkin, Michael; Lu, Yi; Long, Juexuan; Deymier, Pierre A; Hoying, James B; Wong, Pak Kin

2013-03-01

Calcium signaling in the diverse vascular structures is regulated by a wide range of mechanical and biochemical factors to maintain essential physiological functions of the vasculature. To properly transmit information, the intercellular calcium communication mechanism must be robust against various conditions in the cellular microenvironment. Using plasma lithography geometric confinement, we investigate mechanically induced calcium wave propagation in networks of human umbilical vein endothelial cells organized. Endothelial cell networks with confined architectures were stimulated at the single cell level, including using capacitive force probes. Calcium wave propagation in the network was observed using fluorescence calcium imaging. We show that mechanically induced calcium signaling in the endothelial networks is dynamically regulated against a wide range of probing forces and repeated stimulations. The calcium wave is able to propagate consistently in various dimensions from monolayers to individual cell chains, and in different topologies from linear patterns to cell junctions. Our results reveal that calcium signaling provides a robust mechanism for cell-cell communication in networks of endothelial cells despite the diversity of the microenvironmental inputs and complexity of vascular structures. Copyright © 2012 Elsevier Ltd. All rights reserved.

New Insights on the Structure of the Cascadia Subduction Zone from Amphibious Seismic Data

NASA Astrophysics Data System (ADS)

Janiszewski, Helen Anne

A new onshore-offshore seismic dataset from the Cascadia subduction zone was used to characterize mantle lithosphere structure from the ridge to the volcanic arc, and plate interface structure offshore within the seismogenic zone. The Cascadia Initiative (CI) covered the Juan de Fuca plate offshore the northwest coast of the United States with an ocean bottom seismometer (OBS) array for four years; this was complemented by a simultaneous onshore seismic array. Teleseismic data recorded by this array allows the unprecedented imaging of an entire tectonic plate from its creation at the ridge through subduction initiation and back beyond the volcanic arc along the entire strike of the Cascadia subduction zone. Higher frequency active source seismic data also provides constraints on the crustal structure along the plate interface offshore. Two seismic datasets were used to image the plate interface structure along a line extending 100 km offshore central Washington. These are wide-angle reflections from ship-to-shore seismic data from the Ridge-To-Trench seismic cruise and receiver functions calculated from a densely spaced CI OBS focus array in a similar region. Active source seismic observations are consistent with reflections from the plate interface offshore indicating the presence of a P-wave velocity discontinuity. Until recently, there has been limited success in using the receiver function technique on OBS data. I avoid these traditional challenges by using OBS constructed with shielding deployed in shallow water on the continental shelf. These data have quieter horizontals and avoid water- and sediment-multiple contamination at the examined frequencies. The receiver functions are consistently modeled with a velocity structure that has a low velocity zone (LVZ) with elevated P to S-wave velocity ratios at the plate interface. A similar LVZ structure has been observed onshore and interpreted as a combination of elevated pore-fluid pressures or metasediments. This new offshore result indicates that the structure may persist updip indicating the plate interface may be weak. To focus more broadly on the entire subduction system, I calculate phase velocities from teleseismic Rayleigh waves from 20-100 s period across the entire onshore-offshore array. The shear-wave velocity model calculated from these data can provide constrains on the thermal structure of the lithosphere both prior to and during subduction of the Juan de Fuca plate. Using OBS data in this period band requires removal of tilt and compliance noise, two types of water-induced noise that affect long period data. To facilitate these corrections on large seismic arrays such as the CI, an automated quality control routine was developed for selecting noise windows for the calculation of the required transfer functions. These corrections typically involve either averaging out transient signals, which requires the assumption of stationarity of the noise over the long periods of time, or laborious hand selection of noise segments. This new method calculates transfer functions based on daily time series that exclude transient signals, but allows for the investigation of long-term variation over the course of an instrument's deployment. I interpret these new shoreline-crossing phase velocity maps in terms of the tectonics associated with the Cascadia subduction system. Major findings include that oceanic plate cooling models do not explain the velocities observed beneath the Juan de Fuca plate, that slow velocities in the forearc appear to be more prevalent in areas modeled to have experienced high slip in past Cascadia megathrust earthquakes, and along strike variations in phase velocity reflect variations in arc structure and backarc tectonics.

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.

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.

The scotopic electroretinogram of the sugar glider related to histological features of its retina.

PubMed

Akula, James D; Esdaille, Tricia M; Caffé, A Romeo; Naarendorp, Franklin

2011-11-01

The flash electroretinogram (ERG) was used to characterize the scotopic retinal function in a marsupial. Key parameter values of the a- and b-waves of adult male sugar gliders, Petaurus breviceps breviceps, elicited with ganzfeld flashes were determined under dark- and light-adapted conditions. Using standard histological methods, the thicknesses of the major layers of the retina were assessed to provide insight into the nature of the ERG responses. The ERG and histological results were compared to corresponding data for placental C57Bl/6 mice to establish whether the functional retinal specialization that underlies scotopic visual function in a marsupial parallels that of a placental mouse. The sensitivity of the a-wave assessed with the Lamb and Pugh (Invest Ophthalmol Vis Sci 47:5138-5152, 2006) "model" and that of the b-wave assessed with standard methods were lower in the sugar glider compared to the mouse. The thickness of the sugar glider retina was two-third of that of the mouse. The high-intensity flash ERG of the sugar glider substantially differed in shape from that of the mouse reflecting perhaps structural and functional differences between the two species at the level of the inner retina.

Dynamic Scaling of Colloidal Gel Formation at Intermediate Concentrations

DOE PAGES

Zhang, Qingteng; Bahadur, Divya; Dufresne, Eric M.; ...

2017-10-25

Here, we have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scatter- ing (SAXS), x-ray photon correlation spectroscopy (XPCS), and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically-determined gel temperature, T gel, was characterized via the slow-down of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT = T quench - T gel), wave vector, and formation time (t f). We findmore » similar patterns in the slow-down of dynamics that maps the wave-vector-dependent dynamics at a particular ΔT and t f to that at other ΔTs and t fs via an effective scaling temperature, Ts. A single Ts applies to a broad range of ΔT and tf but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than that of the attraction strength between colloids. Finally, we interpret this strong temperature de- pendence in terms of changes in cooperative bonding required to form stable, energetically favored, local structures.« less

Dynamic Scaling of Colloidal Gel Formation at Intermediate Concentrations

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

Zhang, Qingteng; Bahadur, Divya; Dufresne, Eric M.

Here, we have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scatter- ing (SAXS), x-ray photon correlation spectroscopy (XPCS), and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically-determined gel temperature, T gel, was characterized via the slow-down of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT = T quench - T gel), wave vector, and formation time (t f). We findmore » similar patterns in the slow-down of dynamics that maps the wave-vector-dependent dynamics at a particular ΔT and t f to that at other ΔTs and t fs via an effective scaling temperature, Ts. A single Ts applies to a broad range of ΔT and tf but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than that of the attraction strength between colloids. Finally, we interpret this strong temperature de- pendence in terms of changes in cooperative bonding required to form stable, energetically favored, local structures.« less

A novel approach to gravitation from fluid theory: Titius-Bode structures, flat rotation rate of galaxies, and other predictions

NASA Astrophysics Data System (ADS)

Munera, Hector A.

Following the discovery of quantum phenomena at laboratory scale (Couder & Fort 2006), de Broglie pilot wave theory (De Broglie 1962) has been revived under a hydrodynamic guise (Bush 2015). Theoretically, it boils down to solving the transport equations for the energy and linear momentum densities of a postulated fundamental fluid in terms of classical wave equations, which inherently are Lorentz-invariant and scale-invariant. Instead of the conventional harmonic solutions, for astronomical and gravitational problems the novel solutions for the homogeneous wave equation in spherical coordinates are more suitable (Munera et al. 1995, Munera & Guzman 1997, and Munera 2000). Two groups of solutions are particularly relevant: (a) The inherently-quantized helicoidal solutions that may be applicable to describe spiral galaxies, and (b) The non-harmonic solutions with time (t) and distance (r) entangled in the single variable q = Ct/r (C is the two-way local electromagnetic speed). When these functions are plotted against 1/q they manifestly depict quantum effects in the near field, and Newtonian-like gravity in the far-field. The near-field predicts quantized effects similar to ring structures and to Titius-Bode structures, both in our own solar system and in exoplanets, the correlation between predicted and observed structures being typically larger than 99 per cent. In the far-field, some non-harmonic functions have a rate of decrement with distance slower than inverse-square thus explaining the flat rotation rate of galaxies. Additional implications for Trojan orbits, and quantized effects in photon deflection were also noted.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

NASA Astrophysics Data System (ADS)

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK' 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha's Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

The effects of core-reflected waves on finite fault inversion with teleseismic body wave data

NASA Astrophysics Data System (ADS)

Qian, Y.; Ni, S.; Wei, S.

2016-12-01

Reliable estimation of rupture processes for a large earthquake is valuable for post-seismic rescue, tsunami alert, seismotectonic studies, as well as earthquake physics. Finite-fault inversion has been widely accepted to reconstruct the spatial-temporal distribution of rupture processes, which can be obtained by individual or jointly inversion of seismic, geodetic and tsunami data sets. Among the above observations, teleseismic (30° 90°) body waves, usually P and SH waves, have been used extensively in such inversions because their propagation are well understood and readily available for large earthquakes with good coverages of slowness and azimuth. However, finite fault inversion methods usually assume turning P and SH waves without inclusion of core-reflected waves when calculating the synthetic waveforms, which may result in systematic error in finite-fault inversions. For the core-reflected SH wave ScS, it is expected to be strong due to total reflection from Core-Mantle-Boundary. Moreover, the time interval between direct S and ScS could be smaller than the duration of large earthquakes for large epicentral distances. In order to improve the accuracy of finite fault inversion with teleseismic body waves, we develop a procedure named multitel3 to compute Greens' functions that contain both turning waves (P, pP, sP, S, sS et al.) and core-reflected phases (PcP and ScS) and apply it to finite fault inversions. This ray-based method can rapidly calculate teleseismic body wave synthetics with flexibility for path calibration of 3D mantle structure. The new Green's function is plugged into finite fault inversion package to replace the original Green's function with only turning P and SH waves. With the 2008 Mw7.9 Wenchuan earthquake as example, a series of numerical tests conducted on synthetic data are used to assess the performance of our approach. We also explore this new procedure's stability when there are discrepancies between the parameters of input model and the priori information of inverse model, such as strike, dip of finite fault and so on. With the quantified code, we apply it to study rupture process of the 2016 Mw7.8 Sumatra earthquake.

Nuclear spin dependence of time reversal invariance violating effects in neutron scattering

NASA Astrophysics Data System (ADS)

Gudkov, Vladimir; Shimizu, Hirohiko M.

2018-06-01

The spin structure of parity violating and time reversal invariance violating effects in neutron scattering is discussed. The explicit relations between these effects are presented in terms of functions nuclear spins and neutron partial widths of p -wave resonances.

The new wave-ring helical (WRH) slow-wave structure for traveling wave tube amplifiers

NASA Astrophysics Data System (ADS)

Panahi, Nasser; Saviz, S.; Ghorannevis, M.

2017-12-01

In this paper, the new slow-wave structure called wave-ring helix to enhance the power of the traveling wave tubes is introduced. In this new structure, without increasing the length and radius of the helix, the wave motion path can be increased to radiofrequency wave in phase with the electron beam. The results show that in the special frequency range the output power and gain are greater than conventional helix. In this paper, optimization results are presented in cold and hot tests on the new structure. The software CST is used in S-band frequency range.

Angular momentum transport with twisted exciton wave packets

NASA Astrophysics Data System (ADS)

Zang, Xiaoning; Lusk, Mark T.

2017-10-01

A chain of cofacial molecules with CN or CN h symmetry supports excitonic states with a screwlike structure. These can be quantified with the combination of an axial wave number and an azimuthal winding number. Combinations of these states can be used to construct excitonic wave packets that spiral down the chain with well-determined linear and angular momenta. These twisted exciton wave packets can be created and annihilated using laser pulses, and their angular momentum can be optically modified during transit. This allows for the creation of optoexcitonic circuits in which information, encoded in the angular momentum of light, is converted into excitonic wave packets that can be manipulated, transported, and then reemitted. A tight-binding paradigm is used to demonstrate the key ideas. The approach is then extended to quantify the evolution of twisted exciton wave packets in a many-body, multilevel time-domain density functional theory setting. In both settings, numerical methods are developed that allow the site-to-site transfer of angular momentum to be quantified.

A circuit mechanism for the propagation of waves of muscle contraction in Drosophila

PubMed Central

Fushiki, Akira; Zwart, Maarten F; Kohsaka, Hiroshi; Fetter, Richard D; Cardona, Albert; Nose, Akinao

2016-01-01

Animals move by adaptively coordinating the sequential activation of muscles. The circuit mechanisms underlying coordinated locomotion are poorly understood. Here, we report on a novel circuit for the propagation of waves of muscle contraction, using the peristaltic locomotion of Drosophila larvae as a model system. We found an intersegmental chain of synaptically connected neurons, alternating excitatory and inhibitory, necessary for wave propagation and active in phase with the wave. The excitatory neurons (A27h) are premotor and necessary only for forward locomotion, and are modulated by stretch receptors and descending inputs. The inhibitory neurons (GDL) are necessary for both forward and backward locomotion, suggestive of different yet coupled central pattern generators, and its inhibition is necessary for wave propagation. The circuit structure and functional imaging indicated that the commands to contract one segment promote the relaxation of the next segment, revealing a mechanism for wave propagation in peristaltic locomotion. DOI: http://dx.doi.org/10.7554/eLife.13253.001 PMID:26880545

(e, 2e) simple ionization of {{\\rm{H}}}_{3}^{+} by fast electron impact: use of triangular three-center continuum and bound state wave functions

NASA Astrophysics Data System (ADS)

Obeid, S.; Chuluunbaatar, O.; Joulakian, B. B.

2017-07-01

The variation of the multiply differential cross section of the (e, 2e) simple ionization of {{{H}}}3+, with the incident and ejection energy values, as well as the directions of the ejected and scattered electrons, is studied. The calculations have been performed in the frame of the perturbative first Born procedure, which has required the development of equilateral triangular three center bound and continuum state wave functions. The results explore the optimal conditions and the particularities of the triangular targets, such as the appearance of interference patterns in the variation of the four fold differential cross section (FDCS) with the scattering angle for a fixed orientation of the molecule. The comparison between the results obtained by two H3 + ground wave functions, with and without a correlation term r 12, shows that the effect of correlation on the magnitude of the triple differential cross section is not large, but it produces some modification in the structure of the FDCS.

A New Energy Ordering and the Dipole Moment of Gas Phase Glycine via Plane-Wave Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Min, Byeong June

2018-03-01

The abundance of glycine (Gly), the simplest amino acid, in meteorites leads us to the next question about its extraterrestrial origin. However, astronomers have not yet found glycine signature in interstellar medium. Laboratory microwave spectroscopy experiments report the most stable Gly conformer has a dipole moment of 4.5 - 5.45 Debye. Theoretical calculations, so far performed only with Gaussian basis functions, has predicted a dipole moment of about 1 Debye. This discrepancy has baffled astronomers. We study the energetics of glycine and its isomers and conformers via plane-wave density functional theory calculations. The geometric structures of the isomers and their conformers are identified, along with their relative stability and their dipole moment. In the case of glycine, we obtain the most stable conformer with a dipole moment of 5.76 Debye, close to the microwave spectroscopy experiments. If the plane wave energy cutoff is reduced to a lower value ( 400 eV) on purpose, the energy ordering reverses to the case with Gaussian basis calculations.

GW study of topological insulators Bi2Se3, Bi2Te3, and Sb2Te3: Beyond the perturbative one-shot approach

NASA Astrophysics Data System (ADS)

Aguilera, Irene; Friedrich, Christoph; Bihlmayer, Gustav; Blügel, Stefan

2013-07-01

We present GW calculations of the topological insulators Bi2Se3, Bi2Te3, and Sb2Te3 within the all-electron full-potential linearized augmented-plane-wave formalism. Quasiparticle effects produce significant qualitative changes in the band structures of these materials when compared to density functional theory (DFT), especially at the Γ point, where band inversion takes place. There, the widely used perturbative one-shot GW approach can produce unphysical band dispersions, as the quasiparticle wave functions are forced to be identical to the noninteracting single-particle states. We show that a treatment beyond the perturbative approach, which incorporates the off-diagonal GW matrix elements and thus enables many-body hybridization to be effective in the quasiparticle wave functions, is crucial in these cases to describe the characteristics of the band inversion around the Γ point in an appropriate way. In addition, this beyond one-shot GW approach allows us to calculate the values of the Z2 topological invariants and compare them with those previously obtained within DFT.

Pixel level optical-transfer-function design based on the surface-wave-interferometry aperture

PubMed Central

Zheng, Guoan; Wang, Yingmin; Yang, Changhuei

2010-01-01

The design of optical transfer function (OTF) is of significant importance for optical information processing in various imaging and vision systems. Typically, OTF design relies on sophisticated bulk optical arrangement in the light path of the optical systems. In this letter, we demonstrate a surface-wave-interferometry aperture (SWIA) that can be directly incorporated onto optical sensors to accomplish OTF design on the pixel level. The whole aperture design is based on the bull’s eye structure. It composes of a central hole (diameter of 300 nm) and periodic groove (period of 560 nm) on a 340 nm thick gold layer. We show, with both simulation and experiment, that different types of optical transfer functions (notch, highpass and lowpass filter) can be achieved by manipulating the interference between the direct transmission of the central hole and the surface wave (SW) component induced from the periodic groove. Pixel level OTF design provides a low-cost, ultra robust, highly compact method for numerous applications such as optofluidic microscopy, wavefront detection, darkfield imaging, and computational photography. PMID:20721038

Discovery of a general method of solving the Schrödinger and dirac equations that opens a way to accurately predictive quantum chemistry.

PubMed

Nakatsuji, Hiroshi

2012-09-18

Just as Newtonian law governs classical physics, the Schrödinger equation (SE) and the relativistic Dirac equation (DE) rule the world of chemistry. So, if we can solve these equations accurately, we can use computation to predict chemistry precisely. However, for approximately 80 years after the discovery of these equations, chemists believed that they could not solve SE and DE for atoms and molecules that included many electrons. This Account reviews ideas developed over the past decade to further the goal of predictive quantum chemistry. Between 2000 and 2005, I discovered a general method of solving the SE and DE accurately. As a first inspiration, I formulated the structure of the exact wave function of the SE in a compact mathematical form. The explicit inclusion of the exact wave function's structure within the variational space allows for the calculation of the exact wave function as a solution of the variational method. Although this process sounds almost impossible, it is indeed possible, and I have published several formulations and applied them to solve the full configuration interaction (CI) with a very small number of variables. However, when I examined analytical solutions for atoms and molecules, the Hamiltonian integrals in their secular equations diverged. This singularity problem occurred in all atoms and molecules because it originates from the singularity of the Coulomb potential in their Hamiltonians. To overcome this problem, I first introduced the inverse SE and then the scaled SE. The latter simpler idea led to immediate and surprisingly accurate solution for the SEs of the hydrogen atom, helium atom, and hydrogen molecule. The free complement (FC) method, also called the free iterative CI (free ICI) method, was efficient for solving the SEs. In the FC method, the basis functions that span the exact wave function are produced by the Hamiltonian of the system and the zeroth-order wave function. These basis functions are called complement functions because they are the elements of the complete functions for the system under consideration. We extended this idea to solve the relativistic DE and applied it to the hydrogen and helium atoms, without observing any problems such as variational collapse. Thereafter, we obtained very accurate solutions of the SE for the ground and excited states of the Born-Oppenheimer (BO) and non-BO states of very small systems like He, H(2)(+), H(2), and their analogues. For larger systems, however, the overlap and Hamiltonian integrals over the complement functions are not always known mathematically (integration difficulty); therefore we formulated the local SE (LSE) method as an integral-free method. Without any integration, the LSE method gave fairly accurate energies and wave functions for small atoms and molecules. We also calculated continuous potential curves of the ground and excited states of small diatomic molecules by introducing the transferable local sampling method. Although the FC-LSE method is simple, the achievement of chemical accuracy in the absolute energy of larger systems remains time-consuming. The development of more efficient methods for the calculations of ordinary molecules would allow researchers to make these calculations more easily.

The Fundamental Structure and the Reproduction of Spiral Wave in a Two-Dimensional Excitable Lattice

PubMed Central

Qian, Yu; Zhang, Zhaoyang

2016-01-01

In this paper we have systematically investigated the fundamental structure and the reproduction of spiral wave in a two-dimensional excitable lattice. A periodically rotating spiral wave is introduced as the model to reproduce spiral wave artificially. Interestingly, by using the dominant phase-advanced driving analysis method, the fundamental structure containing the loop structure and the wave propagation paths has been revealed, which can expose the periodically rotating orbit of spiral tip and the charity of spiral wave clearly. Furthermore, the fundamental structure is utilized as the core for artificial spiral wave. Additionally, the appropriate parameter region, in which the artificial spiral wave can be reproduced, is studied. Finally, we discuss the robustness of artificial spiral wave to defects. PMID:26900841

Balancing Power Absorption Against Structural Loads With Viscous Drag and Power-Takeoff Efficiency Considerations

DOE PAGES

Tom, Nathan; Yu, Yi-Hsiang; Wright, Alan; ...

2017-11-17

The focus of this paper is to balance power absorption against structural loading for a novel fixed-bottom oscillating surge wave energy converter in both regular and irregular wave environments. The power-to-load ratio will be evaluated using pseudospectral control (PSC) to determine the optimum power-takeoff (PTO) torque based on a multiterm objective function. This paper extends the pseudospectral optimal control problem to not just maximize the time-averaged absorbed power but also include measures for the surge-foundation force and PTO torque in the optimization. The objective function may now potentially include three competing terms that the optimizer must balance. Separate weighting factorsmore » are attached to the surge-foundation force and PTO control torque that can be used to tune the optimizer performance to emphasize either power absorption or load shedding. To correct the pitch equation of motion, derived from linear hydrodynamic theory, a quadratic-viscous-drag torque has been included in the system dynamics; however, to continue the use of quadratic programming solvers, an iteratively obtained linearized drag coefficient was utilized that provided good accuracy in the predicted pitch motion. Furthermore, the analysis considers the use of a nonideal PTO unit to more accurately evaluate controller performance. The PTO efficiency is not directly included in the objective function but rather the weighting factors are utilized to limit the PTO torque amplitudes, thereby reducing the losses resulting from the bidirectional energy flow through a nonideal PTO. Results from PSC show that shedding a portion of the available wave energy can lead to greater reductions in structural loads, peak-to-average power ratio, and reactive power requirement.« less

Upper mantle and transition zone structure beneath Ethiopia: Regional evidence for the African Superplume

NASA Astrophysics Data System (ADS)

Benoit, M. H.; Nyblade, A. A.; Pasyanos, M.; Owens, T. J.

2005-12-01

Throughout much of the Cenozoic, Ethiopia has undergone extensive tectonism, including rifting, volcanism and uplift, and the origin of this tectonism remains enigmatic. While the cause of the tectonism has often been attributed to one or more mantle plumes, recent global tomographic studies suggest that the African Superplume, a broad, through-going mantle upwelling, may be related to the tectonism. To further understand the origin of the tectonism in Ethiopia, we employ a variety of methods, including an S wave travel time body wave tomography, receiver function analysis of the 410 and 660 km discontinuities, and surface wave tomography. Using data from the Ethiopia Broadband Seismic Experiment [2000-2002], we computed new S wave models of the upper mantle seismic velocity structure from 150 - 400 km depth. The S wave model revealed an elongated low wave speed region that is deep (> 300 km) and wide (> 500 km). The location of the low wave speed anomaly aligns with the Afar Depression and Main Ethiopian Rift in the uppermost mantle, but the center of the anomaly shifts to the west with depth. Results from receiver function stacking of the 410 and 660 km discontinuities show a shallow 660 beneath most of Ethiopia, implying that the low wave speed anomaly found in the S wave model likely extends to at least 660 km depth. This result suggests that the low velocity anomaly may be related to the African Superplume. A group velocity surface wave tomographic study of East Africa was also computed using data from permanent and temporary stations from Africa and Arabia. Results of this study reveal low Sn velocities beneath much of the region, and suggest that low elevations found in the region between the Ethiopian and East African Plateaus likely reflect an isostatic response to crustal thinning. If the crust in this region had not been thinned by approximately 10 - 15 km, then it is likely that the high elevation of the Ethiopian and East African Plateaus would be continuous and that these plateaus would not be viewed as separate, distinct regions of uplift. This finding further suggests that a large scale, buoyant feature, such as the African Superplume, exists in the mantle beneath the Ethiopia and East African Plateaus that contributes to the uplift of the region.

Verification and Improvement of the Three-Dimensional Basin Velocity Structure Model in the Osaka Sedimentary Basin, Japan Using Interstation Green's Functions and H/V Spectral Ratios of Microtremors

NASA Astrophysics Data System (ADS)

Asano, K.; Iwata, T.; Sekiguchi, H.; Somei, K.; Nishimura, T.; Miyakoshi, K.; Aoi, S.; Kunugi, T.

2012-12-01

The Osaka sedimentary basin is filled by the Plio-Pleistocene Osaka group, terrace deposits, and alluvium deposits with thickness of 1 to 2 km over the bedrock, and it is surrounded by active fault systems. The Uemachi active fault system underlies the Osaka urban area. In order to predict the strong ground motions for future events of the Uemachi fault and others, the precise basin velocity structure model is indispensable as well as the detailed source fault model. The velocity structure of the Osaka basin has been extensively investigated by using various techniques such as gravity anomaly measurements, reflection surveys, boring explorations, and microtremor measurements. Based on these surveys and ground motion simulations for observed events, the three-dimensional velocity structure models of the Osaka basin have been developed and improved for decades (e.g., Kagawa et al., 1993; Horikawa et al., 2003; Iwata et al., 2008; Iwaki and Iwata, 2011). Now we are trying to verify the velocity structure model of the Osaka basin and to improve it incorporating new data sets. We have conducted two kinds of observations in the Osaka basin. The first observation is continuous microtremor observation. We have temporarily installed three-component velocity sensors at 15 sites covering the Osaka basin to record microtremors continuously for more than one year. The seismic interferometry technique (e.g. Shapiro and Campillo, 2004) is applied to retrieve interstation Green's function for analyzing the wave propagation characteristics inside the sedimentary basin. Both Rayleigh- and Love-wave type signals are identified in 0.1-0.5 Hz from observed interstation Green's functions. The group velocities of Rayleigh and Love waves propagating between two stations are estimated from them using the multiple filter analysis method, and they are compared with the theoretical group-velocities of the model. For example, estimated Love-wave group velocity along a line inside the basin is as low as 350 m/s in 0.2-0.5 Hz. The second observation is a set of short-time (30~60 min) single-station microtremor observations to obtain H/V spectral ratios at sites. We observed microtremor at 100 strong motion stations of Osaka prefecture government, JMA, K-NET, KiK-net, and other institutes. The peak period of H/V ranges from about 1 to 7 s, and it depends on the bedrock depth at the observation site as previously pointed by Miyakoshi et al. (1997). Though the basin velocity model explains the characteristics of observed H/V spectral ratios at most sites, we found discrepancies between observed and predicted H/V peak periods at north part of Osaka bay area and hill area in southeastern part of the basin. By combining the observed constraints from the group velocities, waveform characteristics of interstation Green's functions, and H/V spectral ratios, we will improve the S-wave velocity structure model inside the Osaka basin.

Balancing Power Absorption and Structural Loading for a Novel Fixed-Bottom Wave Energy Converter with Nonideal Power Take-Off in Regular Waves: Preprint

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

Tom, Nathan M; Yu, Yi-Hsiang; Wright, Alan D

In this work, the net power delivered to the grid from a nonideal power take-off (PTO) is introduced followed by a review of the pseudo-spectral control theory. A power-to-load ratio, used to evaluate the pseudo-spectral controller performance, is discussed, and the results obtained from optimizing a multiterm objective function are compared against results obtained from maximizing the net output power to the grid. Simulation results are then presented for four different oscillating wave energy converter geometries to highlight the potential of combing both geometry and PTO control to maximize power while minimizing loads.

A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System

PubMed Central

Lee, Inbok; Zhang, Aoqi; Lee, Changgil; Park, Seunghee

2016-01-01

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths. PMID:27999252

A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System.

PubMed

Lee, Inbok; Zhang, Aoqi; Lee, Changgil; Park, Seunghee

2016-12-16

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths.

A novel embeddable spherical smart aggregate for structural health monitoring: part I. Fabrication and electrical characterization

NASA Astrophysics Data System (ADS)

Kong, Qingzhao; Fan, Shuli; Bai, Xiaolong; Mo, Y. L.; Song, Gangbing

2017-09-01

Recently developed piezoceramic-based transducers, known as smart aggregates (SAs), have shown their applicability and versatility in various applications of structural health monitoring (SHM). The lead zirconate titanate (PZT) patches embedded inside SAs have different modes that are more suitable for generating or receiving different types of stress waves (e.g. P and S waves, each of which has a unique role in SHM). However, due to the geometry of the 2D PZT patch, the embedded SA can only generate or receive the stress wave in a single direction and thus greatly limits its applications. This paper is the first of a series of two companion papers that introduces the authors’ latest work in developing a novel, embeddable spherical smart aggregate (SSA) for the health monitoring of concrete structures. In addition to the 1D guided wave produced by SA, the SSA embedded in concrete structures can generate or receive omni-directional stress waves that can significantly improve the detection aperture and provide additional functionalities in SHM. In the first paper (Part I), the detailed fabrication procedures with the help of 3D printing technology and electrical characterization of the proposed SSA is presented. The natural frequencies of the SSA were experimentally obtained and further compared with the numerical results. In addition, the influence of the components’ thickness (spherical piezoceramic shell and epoxy) and outer radius (spherical piezoceramic shell and protection concrete) on the natural frequencies of the SSA were analytically studied. The results will help elucidate the key parameters that determine the natural frequencies of the SSA. The natural frequencies of the SSA can thus be designed for suitability in the damage detection of concrete structures. In the second paper (Part II), further numerical and experimental verifications on the performance of the proposed SSA in concrete structures will be discussed.