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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

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.

Analysis of group-velocity dispersion of high-frequency Rayleigh waves for near-surface applications

USGS Publications Warehouse

Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.

2011-01-01

The Multichannel Analysis of Surface Waves (MASW) method is an efficient tool to obtain the vertical shear (S)-wave velocity profile using the dispersive characteristic of Rayleigh waves. Most MASW researchers mainly apply Rayleigh-wave phase-velocity dispersion for S-wave velocity estimation with a few exceptions applying Rayleigh-wave group-velocity dispersion. Herein, we first compare sensitivities of fundamental surface-wave phase velocities with group velocities with three four-layer models including a low-velocity layer or a high-velocity layer. Then synthetic data are simulated by a finite difference method. Images of group-velocity dispersive energy of the synthetic data are generated using the Multiple Filter Analysis (MFA) method. Finally we invert a high-frequency surface-wave group-velocity dispersion curve of a real-world example. Results demonstrate that (1) the sensitivities of group velocities are higher than those of phase velocities and usable frequency ranges are wider than that of phase velocities, which is very helpful in improving inversion stability because for a stable inversion system, small changes in phase velocities do not result in a large fluctuation in inverted S-wave velocities; (2) group-velocity dispersive energy can be measured using single-trace data if Rayleigh-wave fundamental-mode energy is dominant, which suggests that the number of shots required in data acquisition can be dramatically reduced and the horizontal resolution can be greatly improved using analysis of group-velocity dispersion; and (3) the suspension logging results of the real-world example demonstrate that inversion of group velocities generated by the MFA method can successfully estimate near-surface S-wave velocities. ?? 2011 Elsevier B.V.

Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre

PubMed Central

Beugnot, Jean-Charles; Lebrun, Sylvie; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

2014-01-01

Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of Brillouin light scattering from surface acoustic waves. These Rayleigh-type surface waves travel the wire surface at a specific velocity of 3,400 m s−1 and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics. PMID:25341638

Investigation of phononic crystals for dispersive surface acoustic wave ozone sensors

NASA Astrophysics Data System (ADS)

Westafer, Ryan S.

The object of this research was to investigate dispersion in surface phononic crystals (PnCs) for application to a newly developed passive surface acoustic wave (SAW) ozone sensor. Frequency band gaps and slow sound already have been reported for PnC lattice structures. Such engineered structures are often advertised to reduce loss, increase sensitivity, and reduce device size. However, these advances have not yet been realized in the context of surface acoustic wave sensors. In early work, we computed SAW dispersion in patterned surface structures and we confirmed that our finite element computations of SAW dispersion in thin films and in one dimensional surface PnC structures agree with experimental results obtained by laser probe techniques. We analyzed the computations to guide device design in terms of sensitivity and joint spectral operating point. Next we conducted simulations and experiments to determine sensitivity and limit of detection for more conventional dispersive SAW devices and PnC sensors. Finally, we conducted extensive ozone detection trials on passive reflection mode SAW devices, using distinct components of the time dispersed response to compensate for the effect of temperature. The experimental work revealed that the devices may be used for dosimetry applications over periods of several days.

Producing data-based sensitivity kernels from convolution and correlation in exploration geophysics.

NASA Astrophysics Data System (ADS)

Chmiel, M. J.; Roux, P.; Herrmann, P.; Rondeleux, B.

2016-12-01

Many studies have shown that seismic interferometry can be used to estimate surface wave arrivals by correlation of seismic signals recorded at a pair of locations. In the case of ambient noise sources, the convergence towards the surface wave Green's functions is obtained with the criterion of equipartitioned energy. However, seismic acquisition with active, controlled sources gives more possibilities when it comes to interferometry. The use of controlled sources makes it possible to recover the surface wave Green's function between two points using either correlation or convolution. We investigate the convolutional and correlational approaches using land active-seismic data from exploration geophysics. The data were recorded on 10,710 vertical receivers using 51,808 sources (seismic vibrator trucks). The sources spacing is the same in both X and Y directions (30 m) which is known as a "carpet shooting". The receivers are placed in parallel lines with a spacing 150 m in the X direction and 30 m in the Y direction. Invoking spatial reciprocity between sources and receivers, correlation and convolution functions can thus be constructed between either pairs of receivers or pairs of sources. Benefiting from the dense acquisition, we extract sensitivity kernels from correlation and convolution measurements of the seismic data. These sensitivity kernels are subsequently used to produce phase-velocity dispersion curves between two points and to separate the higher mode from the fundamental mode for surface waves. Potential application to surface wave cancellation is also envisaged.

On the modeling of wave-enhanced turbulence nearshore

NASA Astrophysics Data System (ADS)

Moghimi, Saeed; Thomson, Jim; Özkan-Haller, Tuba; Umlauf, Lars; Zippel, Seth

2016-07-01

A high resolution k-ω two-equation turbulence closure model, including surface wave forcing was employed to fully resolve turbulence dissipation rate profiles close to the ocean surface. Model results were compared with observations from Surface Wave Instrument Floats with Tracking (SWIFTs) in the nearshore region at New River Inlet, North Carolina USA, in June 2012. A sensitivity analysis for different physical parameters and wave and turbulence formulations was performed. The flux of turbulent kinetic energy (TKE) prescribed by wave dissipation from a numerical wave model was compared with the conventional prescription using the wind friction velocity. A surface roughness length of 0.6 times the significant wave height was proposed, and the flux of TKE was applied at a distance below the mean sea surface that is half of this roughness length. The wave enhanced layer had a total depth that is almost three times the significant wave height. In this layer the non-dimensionalized Terray scaling with power of - 1.8 (instead of - 2) was applicable.

A phased antenna array for surface plasmons

PubMed Central

Dikken, Dirk Jan W.; Korterik, Jeroen P.; Segerink, Frans B.; Herek, Jennifer L.; Prangsma, Jord C.

2016-01-01

Surface plasmon polaritons are electromagnetic waves that propagate tightly bound to metal surfaces. The concentration of the electromagnetic field at the surface as well as the short wavelength of surface plasmons enable sensitive detection methods and miniaturization of optics. We present an optical frequency plasmonic analog to the phased antenna array as it is well known in radar technology and radio astronomy. Individual holes in a thick gold film act as dipolar emitters of surface plasmon polaritons whose phase is controlled individually using a digital spatial light modulator. We show experimentally, using a phase sensitive near-field microscope, that this optical system allows accurate directional emission of surface waves. This compact and flexible method allows for dynamically shaping the propagation of plasmons and holds promise for nanophotonic applications employing propagating surface plasmons. PMID:27121099

Ultrasound for non-invasive fluid droplet detection inside a sealed container

NASA Astrophysics Data System (ADS)

Glass, S. W.; Good, M. S.; Roy, S.; Luzi, F.

2017-02-01

Ultrasound has long been known to be capable of measuring water level. Zero-degree ultrasound transducers may be used to send an L-wave through the fluid and receive a reflected signal from the fluid/gas interface surface. The level of the fluid is proportional to the sound wave time of flight to traverse the water path. This approach may even be used from outside the fluid containment wall by sending the wave through the tank or pipe bottom. The approach, however, does not work well if there is only a thin layer of fluid consisting of one or two millimeters or even only a few droplets. Surface waves are also known to be sensitive to the presence or absence of fluid on a surface. A surface wave may be transmitted a significant distance by a transmitting transducer and then received by a similar transducer. If the surface along the wave path is wet with even a few droplets of fluid, the surface wave may be significantly attenuated. Generating and measuring such a surface wave from the opposite side of a tank or pipe containment wall and separating the near-wall surface wave from the far-wall surface wave, however, is more challenging. The feasibility of an approach for producing a surface wave on the opposite side of a steel plate to sense the presence or absence of fluid is discussed. This approach is supported by 2-D finite element modeling of the measurement configuration and by empirical demonstration of the technique's sensitivity. This technique was developed for measurement of a very small amount of fluid that may condense within a used nuclear fuel canister after it cools for several years. Early detection of fluid would provide advance warning of potential degradation to internal components in time for mitigation or management of the waste inside that container. Other potential applications include non-intrusive detection of trace liquids within any sealed container, within inaccessible plena of aircrafts or within other inaccessible complex welded skin structures.

Initial Steps Toward Next-Generation, Waveform-Based, Three-Dimensional Models and Metrics to Improve Nuclear Explosion Monitoring in the Middle East

DTIC Science & Technology

2008-09-30

propagation effects by splitting apart the longer period surface waves from the shorter period, depth-sensitive Pnl waves. Problematic, or high-error... Pnl waves. Problematic, or high-error, stations and paths were further analyzed to identify systematic errors with unknown sensor responses and...frequency Pnl components and slower, longer period surface waves. All cut windows are fit simultaneously, allowing equal weighting of phases that may be

Surface-Wave Relocation of Remote Continental Earthquakes

NASA Astrophysics Data System (ADS)

Kintner, J. A.; Ammon, C. J.; Cleveland, M.

2017-12-01

Accurate hypocenter locations are essential for seismic event analysis. Single-event location estimation methods provide relatively imprecise results in remote regions with few nearby seismic stations. Previous work has demonstrated that improved relative epicentroid precision in oceanic environments is obtainable using surface-wave cross correlation measurements. We use intermediate-period regional and teleseismic Rayleigh and Love waves to estimate relative epicentroid locations of moderately-sized seismic events in regions around Iran. Variations in faulting geometry, depth, and intermediate-period dispersion make surface-wave based event relocation challenging across this broad continental region. We compare and integrate surface-wave based relative locations with InSAR centroid location estimates. However, mapping an earthquake sequence mainshock to an InSAR fault deformation model centroid is not always a simple process, since the InSAR observations are sensitive to post-seismic deformation. We explore these ideas using earthquake sequences in western Iran. We also apply surface-wave relocation to smaller magnitude earthquakes (3.5 < M < 5.0). Inclusion of smaller-magnitude seismic events in a relocation effort requires a shift in bandwidth to shorter periods, which increases the sensitivity of relocations to surface-wave dispersion. Frequency-domain inter-event phase observations are used to understand the time-domain cross-correlation information, and to choose the appropriate band for applications using shorter periods. Over short inter-event distances, the changing group velocity does not strongly degrade the relative locations. For small-magnitude seismic events in continental regions, surface-wave relocation does not appear simple enough to allow broad routine application, but using this method to analyze individual earthquake sequences can provide valuable insight into earthquake and faulting processes.

High-resolution shear-wave reflection profiling to image offset in unconsolidated near-surface sediments

NASA Astrophysics Data System (ADS)

Bailey, Bevin L.

S-wave reflection profiling has many theoretical advantages, when compared to P-wave profiling, such as high-resolution potential, greater sensitivities to lithologic changes and insensitivity to the water table and pore fluids, and could be particularly useful in near-surface settings. However, S-wave surveys can be plagued by processing pitfalls unique to near-surface studies such as interference of Love waves with reflections, and the stacking of Love waves as coherent noise, leading to possible misinterpretations of the subsurface. Two lines of S-wave data are processed and used to locate previously unknown faults in Quaternary sediments in a region where earthquake activity poses a threat to surface structures. This study provides clear examples of processing pitfalls such as Love waves with hyperbolic appearances on shot gathers, and a CMP section with coherent noise that is easily misinterpreted as reflections. This study demonstrates pros and cons of using SH reflection data in the near surface.

A simple approach to the joint inversion of seismic body and surface waves applied to the southwest U.S.

NASA Astrophysics Data System (ADS)

West, Michael; Gao, Wei; Grand, Stephen

2004-08-01

Body and surface wave tomography have complementary strengths when applied to regional-scale studies of the upper mantle. We present a straight-forward technique for their joint inversion which hinges on treating surface waves as horizontally-propagating rays with deep sensitivity kernels. This formulation allows surface wave phase or group measurements to be integrated directly into existing body wave tomography inversions with modest effort. We apply the joint inversion to a synthetic case and to data from the RISTRA project in the southwest U.S. The data variance reductions demonstrate that the joint inversion produces a better fit to the combined dataset, not merely a compromise. For large arrays, this method offers an improvement over augmenting body wave tomography with a one-dimensional model. The joint inversion combines the absolute velocity of a surface wave model with the high resolution afforded by body waves-both qualities that are required to understand regional-scale mantle phenomena.

Laser-based ultrasonics by dual-probe interferometer detection and narrow-band ultrasound generation

NASA Astrophysics Data System (ADS)

Huang, Jin

1993-01-01

Despite the advantages of laser-based ultrasonic (LBU) systems, the overall sensitivity of LBU systems needs to be improved for practical applications. Progress is reported to achieve better LBU detection accuracy and sensitivity for applications with surface waves and Lamb waves. A novel dual-probe laser interferometer has been developed to measure the same signal at two points. The dual-probe interferometer is a modification of a conventional single-probe interferometer in that the reference beam is guided to a second detecting point on the specimen surface to form a differential measurement mode, which measure the difference of the displacements at the two points. This dual-probe interferometer is particularly useful for accurate measurements of the speed and attenuation of surface waves and Lamb waves. The dual-probe interferometer has been applied to obtain accurate measurements of the surface wave speed and attenuation on surfaces of increasing surface roughness. It has also been demonstrated that with an appropriate signal processing method, namely, the power cepstrum method, the dual-probe interferometer is applicable to measure the local surface wave speed even when the probe separation is so small that the two waveforms in the interferometer output signal overlap in the time domain. Narrow-band signal generation and detection improve the sensitivity of LBU systems. It is proposed to use a diffraction grating to form an array of illuminating strips which form a source of narrowband surface and Lamb waves. The line-array of thermoelastic sources generates narrow-band signals whose frequency and bandwidth can be easily controlled. The optimum line-array parameters, such as width, spacing and the number of lines in the array have been derived theoretically and verified experimentally. Narrow-band signal generation with optimum parameters has been demonstrated. The enhanced LBU system with dual-probe detection and narrowband signal generation has been successfully applied to the detection of cracks emanating from rivet holes in aircraft fuselage panel samples. A compact fiber-optic dual-probe interferometer has also been developed and applied to the above mentioned problem of crack detection. Results agree well with those obtained with a bulk LBU system.

Hydrogenated amorphous silicon nitride photonic crystals for improved-performance surface electromagnetic wave biosensors.

PubMed

Sinibaldi, Alberto; Descrovi, Emiliano; Giorgis, Fabrizio; Dominici, Lorenzo; Ballarini, Mirko; Mandracci, Pietro; Danz, Norbert; Michelotti, Francesco

2012-10-01

We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

Enhanced Sensitivity of Wireless Chemical Sensor Based on Love Wave Mode

NASA Astrophysics Data System (ADS)

Wang, Wen; Oh, Haekwan; Lee, Keekeun; Yang, Sangsik

2008-09-01

A 440 MHz wireless and passive Love-wave-based chemical sensor was developed for CO2 detection. The developed device was composed of a reflective delay line patterned on 41° YX LiNbO3 piezoelectric substrate, a poly(methyl methacrylate) (PMMA) waveguide layer, and Teflon AF 2400 sensitive film. A theoretical model is presented to describe wave propagation in Love wave devices with large piezoelectricity and to allow the design of an optimized structure. In wireless device testing using a network analyzer, infusion of CO2 into the testing chamber induced large phase shifts of the reflection peaks owing to the interaction between the sensing film and the test gas (CO2). Good linearity and repeatability were observed at CO2 concentrations of 0-350 ppm. The obtained sensitivity from the Love wave device was approximately 7.07° ppm-1. The gas response properties of the fabricated Love-wave sensor in terms of linearity and sensitivity were provided, and a comparison to surface acoustic wave devices was also discussed.

Surface Generated Acoustic Wave Biosensors for the Detection of Pathogens: A Review

PubMed Central

Rocha-Gaso, María-Isabel; March-Iborra, Carmen; Montoya-Baides, Ángel; Arnau-Vives, Antonio

2009-01-01

This review presents a deep insight into the Surface Generated Acoustic Wave (SGAW) technology for biosensing applications, based on more than 40 years of technological and scientific developments. In the last 20 years, SGAWs have been attracting the attention of the biochemical scientific community, due to the fact that some of these devices - Shear Horizontal Surface Acoustic Wave (SH-SAW), Surface Transverse Wave (STW), Love Wave (LW), Flexural Plate Wave (FPW), Shear Horizontal Acoustic Plate Mode (SH-APM) and Layered Guided Acoustic Plate Mode (LG-APM) - have demonstrated a high sensitivity in the detection of biorelevant molecules in liquid media. In addition, complementary efforts to improve the sensing films have been done during these years. All these developments have been made with the aim of achieving, in a future, a highly sensitive, low cost, small size, multi-channel, portable, reliable and commercially established SGAW biosensor. A setup with these features could significantly contribute to future developments in the health, food and environmental industries. The second purpose of this work is to describe the state-of-the-art of SGAW biosensors for the detection of pathogens, being this topic an issue of extremely importance for the human health. Finally, the review discuses the commercial availability, trends and future challenges of the SGAW biosensors for such applications. PMID:22346725

Photonic surface waves on metamaterial interfaces

NASA Astrophysics Data System (ADS)

Takayama, O.; Bogdanov, A. A.; Lavrinenko, A. V.

2017-11-01

A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. Research on surface waves has been flourishing in the last few decades due to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on near-field techniques, contributing to the establishment of nanophotonics as a field of research. Up to now, a wide variety of surface waves has been investigated in numerous material and structure settings. This article reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of surface wave, we discuss the material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods.

Spread spectrum communication link using surface wave devices

NASA Technical Reports Server (NTRS)

Hunsinger, B. J.; Fugit, B. B.

1971-01-01

A fast lock-up, 8-MHz bandwidth 8,000 bit per second data rate spread spectrum communication link breadboard is described that is implemented using surface wave devices as the primary signal generators and signal processing elements. It uses surface wave tapped delay lines in the transmitter to generate the signals and in the receiver to detect them. The breadboard provides a measured processing gain for Gaussian noise of 31.5 dB which is within one dB of the theoretical optimum. This development demonstrates that spread spectrum receivers implemented with surface wave devices have sensitivities and complexities comparable to those of serial correlation receivers, but synchronization search times which are two to three orders of magnitude smaller.

Bloch surface wave structures for high sensitivity detection and compact waveguiding

NASA Astrophysics Data System (ADS)

Khan, Muhammad Umar; Corbett, Brian

2016-01-01

Resonant propagating waves created on the surface of a dielectric multilayer stack, called Bloch surface waves (BSW), can be designed for high sensitivity monitoring of the adjacent refractive index as an alternative platform to the metal-based surface plasmon resonance (SPR) sensing. The resonant wavelength and polarization can be designed by engineering of the dielectric layers unlike the fixed resonance of SPR, while the wide bandwidth low loss of dielectrics permits sharper resonances, longer propagation lengths and thus their use in waveguiding devices. The transparency of the dielectrics allows the excitation and monitoring of surface-bound fluorescent molecules. We review the recent developments in this technology. We show the advantages that can be obtained by using high index contrast layered structures. Operating at 1550 nm wavelengths will allow the BSW sensors to be implemented in the silicon photonics platform where active waveguiding can be used in the realization of compact planar integrated circuits for multi-parameter sensing.

Improving the accurate assessment of a layered shear-wave velocity model using joint inversion of the effective Rayleigh wave and Love wave dispersion curves

NASA Astrophysics Data System (ADS)

Yin, X.; Xia, J.; Xu, H.

2016-12-01

Rayleigh and Love waves are two types of surface waves that travel along a free surface.Based on the assumption of horizontal layered homogenous media, Rayleigh-wave phase velocity can be defined as a function of frequency and four groups of earth parameters: P-wave velocity, SV-wave velocity, density and thickness of each layer. Unlike Rayleigh waves, Love-wave phase velocities of a layered homogenous earth model could be calculated using frequency and three groups of earth properties: SH-wave velocity, density, and thickness of each layer. Because the dispersion of Love waves is independent of P-wave velocities, Love-wave dispersion curves are much simpler than Rayleigh wave. The research of joint inversion methods of Rayleigh and Love dispersion curves is necessary. (1) This dissertation adopts the combinations of theoretical analysis and practical applications. In both lateral homogenous media and radial anisotropic media, joint inversion approaches of Rayleigh and Love waves are proposed to improve the accuracy of S-wave velocities.A 10% random white noise and a 20% random white noise are added to the synthetic dispersion curves to check out anti-noise ability of the proposed joint inversion method.Considering the influences of the anomalous layer, Rayleigh and Love waves are insensitive to those layers beneath the high-velocity layer or low-velocity layer and the high-velocity layer itself. Low sensitivities will give rise to high degree of uncertainties of the inverted S-wave velocities of these layers. Considering that sensitivity peaks of Rayleigh and Love waves separate at different frequency ranges, the theoretical analyses have demonstrated that joint inversion of these two types of waves would probably ameliorate the inverted model.The lack of surface-wave (Rayleigh or Love waves) dispersion data may lead to inaccuracy S-wave velocities through the single inversion of Rayleigh or Love waves, so this dissertation presents the joint inversion method of Rayleigh and Love waves which will improve the accuracy of S-wave velocities. Finally, a real-world example is applied to verify the accuracy and stability of the proposed joint inversion method. Keywords: Rayleigh wave; Love wave; Sensitivity analysis; Joint inversion method.

Comparison of embedded, surface bonded and reusable piezoelectric transducers for monitoring of concrete structures

NASA Astrophysics Data System (ADS)

Sabet Divsholi, Bahador; Yang, Yaowen

2011-04-01

Piezoelectric lead zirconate titanate (PZT) transducers have been used for health monitoring of various structures over the last two decades. There are three methods to install the PZT transducers to structures, namely, surface bonded, reusable setup and embedded PZTs. The embedded PZTs and reusable PZT setups can be used for concrete structures during construction. On the other hand, the surface bonded PZTs can be installed on the existing structures. In this study, the applicability and limitations of each installation method are experimentally studied. A real size concrete structure is cast, where the surface bonded, reusable setup and embedded PZTs are installed. Monitoring of concrete hydration and structural damage is conducted by the electromechanical impedance (EMI), wave propagation and wave transmission techniques. It is observed that embedded PZTs are suitable for monitoring the hydration of concrete by using both the EMI and the wave transmission techniques. For damage detection in concrete structures, the embedded PZTs can be employed using the wave transmission technique, but they are not suitable for the EMI technique. It is also found that the surface bonded PZTs are sensitive to damage when using both the EMI and wave propagation techniques. The reusable PZT setups are able to monitor the hydration of concrete. However they are less sensitive in damage detection in comparison to the surface bonded PZTs.

Neutron whispering gallery

NASA Astrophysics Data System (ADS)

Nesvizhevsky, Valery V.; Voronin, Alexei Yu.; Cubitt, Robert; Protasov, Konstantin V.

2010-02-01

The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms and neutrons. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. Here, we present for the first time the quantum whispering-gallery effect for cold neutrons. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to the recently discovered gravitationally bound quantum states of neutrons . These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state. Deeply bound whispering-gallery states are long-living and weakly sensitive to surface potential; highly excited states are short-living and very sensitive to the wall potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects.

Acousto-optical Transducer with Surface Plasmons

NASA Astrophysics Data System (ADS)

Kolomenskii, A. A.; Surovic, E.; Schuessler, H. A.

2018-04-01

The surface plasmon resonance (SPR) is a sensitive technique for the detection of changes in dielectric parameters in close proximity to a metal film supporting surface plasmon waves. Here we study the application of the SPR effect to an efficient conversion of an acoustic signal into an optical one. Such a transducer potentially has a large bandwidth and good sensitivity. When an acoustic wave is incident onto a receiving plate positioned within the penetration depth of the surface plasmons, it creates displacements of the surface of the plate and, thus, modulates the dielectric properties in the proximity of the gold film. This modulation, in turn, modifies the light reflection under surface plasmon resonance conditions. We simulate characteristics of this acousto-optical transducer with surface plasmons and provide sets of parameters at the optical wavelength of 800 nm and 633 nm for its realization.

Non-perturbational surface-wave inversion: A Dix-type relation for surface waves

USGS Publications Warehouse

Haney, Matt; Tsai, Victor C.

2015-01-01

We extend the approach underlying the well-known Dix equation in reflection seismology to surface waves. Within the context of surface wave inversion, the Dix-type relation we derive for surface waves allows accurate depth profiles of shear-wave velocity to be constructed directly from phase velocity data, in contrast to perturbational methods. The depth profiles can subsequently be used as an initial model for nonlinear inversion. We provide examples of the Dix-type relation for under-parameterized and over-parameterized cases. In the under-parameterized case, we use the theory to estimate crustal thickness, crustal shear-wave velocity, and mantle shear-wave velocity across the Western U.S. from phase velocity maps measured at 8-, 20-, and 40-s periods. By adopting a thin-layer formalism and an over-parameterized model, we show how a regularized inversion based on the Dix-type relation yields smooth depth profiles of shear-wave velocity. In the process, we quantitatively demonstrate the depth sensitivity of surface-wave phase velocity as a function of frequency and the accuracy of the Dix-type relation. We apply the over-parameterized approach to a near-surface data set within the frequency band from 5 to 40 Hz and find overall agreement between the inverted model and the result of full nonlinear inversion.

Charge management for gravitational-wave observatories using UV LEDs

NASA Astrophysics Data System (ADS)

Pollack, S. E.; Turner, M. D.; Schlamminger, S.; Hagedorn, C. A.; Gundlach, J. H.

2010-01-01

Accumulation of electrical charge on the end mirrors of gravitational-wave observatories can become a source of noise limiting the sensitivity of such detectors through electronic couplings to nearby surfaces. Torsion balances provide an ideal means for testing gravitational-wave technologies due to their high sensitivity to small forces. Our torsion pendulum apparatus consists of a movable plate brought near a plate pendulum suspended from a nonconducting quartz fiber. A UV LED located near the pendulum photoejects electrons from the surface, and a UV LED driven electron gun directs photoelectrons towards the pendulum surface. We have demonstrated both charging and discharging of the pendulum with equivalent charging rates of ˜105e/s, as well as spectral measurements of the pendulum charge resulting in a white noise level equivalent to 3×105e/Hz.

The detection of organophosphonates by polymer films on a surface acoustic wave device and a micromirror fiber optic sensor

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

Hughes, R.C.; Ricco, A.J.; Butler, M.A.

There is a need for sensitive detection of organophosphonates by, inexpensive, portable instruments. Two kinds of chemical sensors, based on surface acoustic wave (SAW) devices and fiber optic micromirrors, show promise for such sensing systems. Chemically sensitive coatings are required for detection and data for thin films of the polymer polysiloxane are reported for both kinds of physical transducers. Both kinds of sensor are shown to be capable of detecting concentrations of diisopropylmethylphosphonate (DIMP) down to 1 ppM.

High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.

PubMed

Xin, Xin; Zhong, Nianbing; Liao, Qiang; Cen, Yanyan; Wu, Ruohua; Wang, Zhengkun

2017-05-15

We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l) -1 in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO 2 . The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Crack Detection in Plates Using Coupled Rayleigh-Like Waves

NASA Astrophysics Data System (ADS)

Masserey, B.; Fromme, P.

2008-02-01

The use of coupled Rayleigh-like waves in aluminum plates with a view towards the non-destructive inspection of aircraft structures has been investigated experimentally and theoretically. Rayleigh-like waves transfer energy between both plate surfaces with a characteristic distance called the beatlength. A simple, analytical model and finite difference calculations are used to describe the reflection of Rayleigh-like waves at surface defects. Good agreement has been achieved with experimental results using either standard pulse-echo or laser interferometer measurements. The sensitivity for the detection and localization of small defects on both plate surfaces has been found to be very good. Selecting appropriate excitation frequency and position, a significant part of the energy of the Rayleigh-like wave can be transmitted past surface features, allowing the remote detection of defects in areas where access is restricted.

Photonics surface waves on metamaterials interfaces.

PubMed

Takayama, Osamu; Bogdanov, Andrey; Lavrinenko, Andrei V

2017-09-12

A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. The research on surface waves has been flourishing in last few decades thanks to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on the near-field techniques, contributing to the establishment of the nanophotonics as a field of research. Up to present, a wide variety of surface waves has been investigated in numerous material and structure settings. This paper reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of the surface waves, we discuss material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods. © 2017 IOP Publishing Ltd.

Charge management for gravitational-wave observatories using UV LEDs

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

Pollack, S. E.; Turner, M. D.; Schlamminger, S.

Accumulation of electrical charge on the end mirrors of gravitational-wave observatories can become a source of noise limiting the sensitivity of such detectors through electronic couplings to nearby surfaces. Torsion balances provide an ideal means for testing gravitational-wave technologies due to their high sensitivity to small forces. Our torsion pendulum apparatus consists of a movable plate brought near a plate pendulum suspended from a nonconducting quartz fiber. A UV LED located near the pendulum photoejects electrons from the surface, and a UV LED driven electron gun directs photoelectrons towards the pendulum surface. We have demonstrated both charging and discharging ofmore » the pendulum with equivalent charging rates of {approx}10{sup 5}e/s, as well as spectral measurements of the pendulum charge resulting in a white noise level equivalent to 3x10{sup 5}e/{radical}(Hz).« less

Unified Application of Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

2010-01-01

Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack. The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

Unified Application Vapor Screen Flow Visualization and Pressure Sensitive Paint Measurement Techniques to Vortex- and Shock Wave-Dominated Flow Fields

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

2008-01-01

Laser vapor screen (LVS) flow visualization and pressure sensitive paint (PSP) techniques were applied in a unified approach to wind tunnel testing of slender wing and missile configurations dominated by vortex flows and shock waves at subsonic, transonic, and supersonic speeds. The off-surface cross-flow patterns using the LVS technique were combined with global PSP surface static pressure mappings to characterize the leading-edge vortices and shock waves that coexist and interact at high angles of attack (alpha). The synthesis of LVS and PSP techniques was also effective in identifying the significant effects of passive surface porosity and the presence of vertical tail surfaces on the flow topologies. An overview is given of LVS and PSP applications in selected experiments on small-scale models of generic slender wing and missile configurations in the NASA Langley Research Center (NASA LaRC) Unitary Plan Wind Tunnel (UPWT) and 8-Foot Transonic Pressure Tunnel (8-Foot TPT).

Acoustic sensors as a biophysical tool for probing cell attachment and cell/surface interactions.

PubMed

Saitakis, Michael; Gizeli, Electra

2012-02-01

Acoustic biosensors offer the possibility to analyse cell attachment and spreading. This is due to the offered speed of detection, the real-time non-invasive approach and their high sensitivity not only to mass coupling, but also to viscoelastic changes occurring close to the sensor surface. Quartz crystal microbalance (QCM) and surface acoustic wave (Love-wave) systems have been used to monitor the adhesion of animal cells to various surfaces and record the behaviour of cell layers under various conditions. The sensors detect cells mostly via their sensitivity in viscoelasticity and mechanical properties. Particularly, the QCM sensor detects cytoskeletal rearrangements caused by specific drugs affecting either actin microfilaments or microtubules. The Love-wave sensor directly measures cell/substrate bonds via acoustic damping and provides 2D kinetic and affinity parameters. Other studies have applied the QCM sensor as a diagnostic tool for leukaemia and, potentially, for chemotherapeutic agents. Acoustic sensors have also been used in the evaluation of the cytocompatibility of artificial surfaces and, in general, they have the potential to become powerful tools for even more diverse cellular analysis.

Contactless ultrasonic device to measure surface acoustic wave velocities versus temperature.

PubMed

Hubert, C; Nadal, M H; Ravel-Chapuis, G; Oltra, R

2007-02-01

A complete optical experimental setup for generating and detecting surface acoustic waves [Rayleigh waves (RWs)] in metals versus temperature up to the melting point is described. The RWs were excited by a pulsed Nd:YAG laser and detected by a high sensitivity subangstrom heterodyne interferometer. A special furnace was used to heat the sample using infrared radiation with a regulation of the sample temperature less than 0.1 K. First measurements on an aluminum alloy sample are presented to validate the setup.

Graphene oxide as sensitive layer in Love-wave surface acoustic wave sensors for the detection of chemical warfare agent simulants.

PubMed

Sayago, Isabel; Matatagui, Daniel; Fernández, María Jesús; Fontecha, José Luis; Jurewicz, Izabela; Garriga, Rosa; Muñoz, Edgar

2016-02-01

A Love-wave device with graphene oxide (GO) as sensitive layer has been developed for the detection of chemical warfare agent (CWA) simulants. Sensitive films were fabricated by airbrushing GO dispersions onto Love-wave devices. The resulting Love-wave sensors detected very low CWA simulant concentrations in synthetic air at room temperature (as low as 0.2 ppm for dimethyl-methylphosphonate, DMMP, a simulant of sarin nerve gas, and 0.75 ppm for dipropylene glycol monomethyl ether, DPGME, a simulant of nitrogen mustard). High responses to DMMP and DPGME were obtained with sensitivities of 3087 and 760 Hz/ppm respectively. Very low limit of detection (LOD) values (9 and 40 ppb for DMMP and DPGME, respectively) were calculated from the achieved experimental data. The sensor exhibited outstanding sensitivity, good linearity and repeatability to all simulants tested. The detection mechanism is here explained in terms of hydrogen bonding formation between the tested CWA simulants and GO. Copyright © 2015 Elsevier B.V. All rights reserved.

In Situ Guided Wave Structural Health Monitoring System

NASA Technical Reports Server (NTRS)

Zhao, George; Tittmann, Bernhard R.

2011-01-01

Aircraft engine rotating equipment operates at high temperatures and stresses. Noninvasive inspection of microcracks in those components poses a challenge for nondestructive evaluation. A low-cost, low-profile, high-temperature ultrasonic guided wave sensor was developed that detects cracks in situ. The transducer design provides nondestructive evaluation of structures and materials. A key feature of the sensor is that it withstands high temperatures and excites strong surface wave energy to inspect surface and subsurface cracks. The sol-gel bismuth titanate-based surface acoustic wave (SAW) sensor can generate efficient SAWs for crack inspection. The sensor is very thin (submillimeter) and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. The sensor can be implemented on structures of various shapes. With a spray-coating process, the sensor can be applied to the surface of large curvatures. It has minimal effect on airflow or rotating equipment imbalance, and provides good sensitivity.

Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

NASA Astrophysics Data System (ADS)

Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

2017-08-01

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

Three-Dimensional Sensitivity Kernels of Z/H Amplitude Ratios of Surface and Body Waves

NASA Astrophysics Data System (ADS)

Bao, X.; Shen, Y.

2017-12-01

The ellipticity of Rayleigh wave particle motion, or Z/H amplitude ratio, has received increasing attention in inversion for shallow Earth structures. Previous studies of the Z/H ratio assumed one-dimensional (1D) velocity structures beneath the receiver, ignoring the effects of three-dimensional (3D) heterogeneities on wave amplitudes. This simplification may introduce bias in the resulting models. Here we present 3D sensitivity kernels of the Z/H ratio to Vs, Vp, and density perturbations, based on finite-difference modeling of wave propagation in 3D structures and the scattering-integral method. Our full-wave approach overcomes two main issues in previous studies of Rayleigh wave ellipticity: (1) the finite-frequency effects of wave propagation in 3D Earth structures, and (2) isolation of the fundamental mode Rayleigh waves from Rayleigh wave overtones and converted Love waves. In contrast to the 1D depth sensitivity kernels in previous studies, our 3D sensitivity kernels exhibit patterns that vary with azimuths and distances to the receiver. The laterally-summed 3D sensitivity kernels and 1D depth sensitivity kernels, based on the same homogeneous reference model, are nearly identical with small differences that are attributable to the single period of the 1D kernels and a finite period range of the 3D kernels. We further verify the 3D sensitivity kernels by comparing the predictions from the kernels with the measurements from numerical simulations of wave propagation for models with various small-scale perturbations. We also calculate and verify the amplitude kernels for P waves. This study shows that both Rayleigh and body wave Z/H ratios provide vertical and lateral constraints on the structure near the receiver. With seismic arrays, the 3D kernels afford a powerful tool to use the Z/H ratios to obtain accurate and high-resolution Earth models.

A Novel Approach to Constrain Near-Surface Seismic Wave Speed Based on Polarization Analysis

NASA Astrophysics Data System (ADS)

Park, S.; Ishii, M.

2016-12-01

Understanding the seismic responses of cities around the world is essential for the risk assessment of earthquake hazards. One of the important parameters is the elastic structure of the sites, in particular, near-surface seismic wave speed, that influences the level of ground shaking. Many methods have been developed to constrain the elastic structure of the populated sites or urban basins, and here, we introduce a new technique based on analyzing the polarization content or the three-dimensional particle motion of seismic phases arriving at the sites. Polarization analysis of three-component seismic data was widely used up to about two decades ago, to detect signals and identify different types of seismic arrivals. Today, we have good understanding of the expected polarization direction and ray parameter for seismic wave arrivals that are calculated based on a reference seismic model. The polarization of a given phase is also strongly sensitive to the elastic wave speed immediately beneath the station. This allows us to compare the observed and predicted polarization directions of incoming body waves and infer the near-surface wave speed. This approach is applied to High-Sensitivity Seismograph Network in Japan, where we benchmark the results against the well-log data that are available at most stations. There is a good agreement between our estimates of seismic wave speeds and those from well logs, confirming the efficacy of the new method. In most urban environments, where well logging is not a practical option for measuring the seismic wave speeds, this method can provide a reliable, non-invasive, and computationally inexpensive estimate of near-surface elastic properties.

Whispering gallery states of neutrons and anti-hydrogen atoms and their applications to fundamental and surface physics

NASA Astrophysics Data System (ADS)

Nesvizhevsky, Valery

2013-03-01

The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It is intensively used and explored due to its numerous crucial applications. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for neutrons and (anti)atoms. For (anti)matter waves, it includes a new feature: a massive particle is settled in quantum states, with parameters depending on its mass. In this talk, we present the first observation of the quantum whispering-gallery effect for matter particles (cold neutrons) 1-2. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to recently discovered gravitational quantum states of neutrons3. These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a quantum state. Deeply bound long-living states are weakly sensitive to surface potential; highly excited short-living states are very sensitive to the wall nuclear potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects. Analogous phenomena could be measured with atoms and anti-atoms 4-5.

Surface waves magnitude estimation from ionospheric signature of Rayleigh waves measured by Doppler sounder and OTH radar.

PubMed

Occhipinti, Giovanni; Aden-Antoniow, Florent; Bablet, Aurélien; Molinie, Jean-Philippe; Farges, Thomas

2018-01-24

Surface waves emitted after large earthquakes are known to induce atmospheric infrasonic waves detectable at ionospheric heights using a variety of techniques, such as high frequency (HF) Doppler, global positioning system (GPS), and recently over-the-horizon (OTH) radar. The HF Doppler and OTH radar are particularly sensitive to the ionospheric signature of Rayleigh waves and are used here to show ionospheric perturbations consistent with the propagation of Rayleigh waves related to 28 and 10 events, with a magnitude larger than 6.2, detected by HF Doppler and OTH radar respectively. A transfer function is introduced to convert the ionospheric measurement into the correspondent ground displacement in order to compare it with classic seismometers. The ground vertical displacement, measured at the ground by seismometers, and measured at the ionospheric altitude by HF Doppler and OTH radar, is used here to compute surface wave magnitude. The ionospheric surface wave magnitude (M s iono ) proposed here introduces a new way to characterize earthquakes observing the signature of surface Rayleigh waves in the ionosphere. This work proves that ionospheric observations are useful seismological data to better cover the Earth and to explore the seismology of the Solar system bodies observing the ionosphere of other planets.

Alpha-fetoprotein detection by using a localized surface plasmon coupled fluorescence fiber-optic biosensor

NASA Astrophysics Data System (ADS)

Chang, Ying-Feng; Chen, Ran-Chou; Li, Ying-Chang; Yu, Chih-Jen; Hsieh, Bao-Yu; Chou, Chien

2007-11-01

Alpha-fetoprotein (AFP) detection by using a localized surface plasmon coupled fluorescence (LSPCF) fiber-optic biosensor is setup and experimentally demonstrated. It is based on gold nanoparticle (GNP) and coupled with localized surface plasmon wave on the surface of GNP. In this experiment, the fluorophores are labeled on anti-AFP which are bound to protein A conjugated GNP. Thus, LSPCF is excited with high efficiency in the near field of localized surface plasmon wave. Therefore, not only the sensitivity of LSPCF biosensor is enhanced but also the specific selectivity of AFP is improved. Experimentally, the ability of real time measurement in the range of AFP concentration from 0.1ng/ml to 100ng/ml was detected. To compare with conventional methods such as enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA), the LSPCF fiber-optic biosensor performs higher or comparable detection sensitivity, respectively.

Making the most of CZ seismics: Improving shallow critical zone characterization using surface-wave analysis

NASA Astrophysics Data System (ADS)

Pasquet, S.; Wang, W.; Holbrook, W. S.; Bodet, L.; Carr, B.; Flinchum, B. A.

2017-12-01

Estimating porosity and saturation in the shallow subsurface over large lateral scales is vitally important for understanding the development and evolution of the Critical Zone (CZ). Because elastic properties (P- and S-wave velocities) are particularly sensitive to porosity and saturation, seismic methods (in combination with petrophysical models) are effective tools for mapping CZ architecture and processes. While many studies employ P-wave refraction methods, fewer use the surface waves that are typically also recorded in those same surveys. Here we show the value of exploiting surface waves to extract supplementary shear-wave velocity (Vs) information in the CZ. We use a new, user-friendly, open-source MATLAB-based package (SWIP) to invert surface-wave data and estimate lateral variations of Vs in the CZ. Results from synthetics show that this approach enables the resolution of physical property variations in the upper 10-15 m below the surface with lateral scales of about 5 m - a vast improvement compared to P-wave tomography alone. A field example at a Yellowstone hydrothermal system also demonstrates the benefits of including Vs in the petrophysical models to estimate not only porosity but also saturation, thus highlighting subsurface gas pathways. In light of these results, we strongly suggest that surface-wave analysis should become a standard approach in CZ seismic surveys.

Development and comparative investigation of Ag-sensitive layer based SAW and QCM sensors for mercury sensing applications.

PubMed

Kabir, K M Mohibul; Sabri, Ylias M; Kandjani, Ahmad Esmaielzadeh; Ippolito, Samuel J; Bhargava, Suresh K

2016-04-21

Piezoelectric acoustic wave devices integrated with noble metal surfaces provide exciting prospects for the direct measurement of toxic gas species such as mercury (Hg) in the atmosphere. Even though gold (Au) based acoustic wave sensors have been utilized extensively for detecting Hg, the potential of using other metal surfaces such as silver (Ag) is yet to be thoroughly studied. Here, we developed Ag sensitive layer-based surface acoustic wave (SAW) and quartz crystal microbalance (QCM) sensors and focused on their comparative analysis for Hg sensing applications with parameters such as the sensor sensitivity, selectivity, adsorption/desorption isotherm and Hg diffusion into the surface thoroughly studied. The SAW sensor was fabricated with nickel (Ni) interdigitated transducer (IDT) electrodes and a Ag thin film on the delay line of the device. In the case of the QCM sensor, the electrodes were constructed of Ag thin film and simultaneously employed as a sensitive layer. Mercury sensing experiments were conducted for a range of concentrations between 24-365 ppbv without/with the presence of some common industrial interfering gas species (i.e. ammonia, acetaldehyde, ethyl mercaptan, dimethyl disulphide, methyl ethyl ketone and humidity) at various operating temperatures in the range of 35-95 °C. The SAW sensor was found to possess up to 70 times higher response magnitudes than its QCM counterpart at 35 °C while up to 30 and 23 times higher response magnitudes were observed for the SAW sensor at elevated temperatures of 75 and 95 °C, respectively. Furthermore, the SAW sensor showed good selectivity (>89%) toward Hg(0) vapor in the presence of all the interferents tested at an operating temperature of 75 °C while the QCM sensor exhibited significant cross-sensitivity when ethyl mercaptan was introduced along with Hg(0) vapor. Overall, it is indicative that Ag-based acoustic wave sensors do have great potential for Hg sensing applications, given that right operating conditions are applied.

Influence of the carrier-envelope phase of few-cycle pulses on ponderomotive surface-plasmon electron acceleration.

PubMed

Irvine, S E; Dombi, P; Farkas, Gy; Elezzabi, A Y

2006-10-06

Control over basic processes through the electric field of a light wave can lead to new knowledge of fundamental light-matter interaction phenomena. We demonstrate, for the first time, that surface-plasmon (SP) electron acceleration can be coherently controlled through the carrier-envelope phase (CEP) of an excitation optical pulse. Analysis indicates that the physical origin of the CEP sensitivity arises from the electron's ponderomotive interaction with the oscillating electromagnetic field of the SP wave. The ponderomotive electron acceleration mechanism provides sensitive (nJ energies), high-contrast, single-shot CEP measurement capability of few-cycle laser pulses.

A study on the prenatal zone of ultrasonic guided waves in plates

NASA Astrophysics Data System (ADS)

Thomas, Tibin; Balasubramaniam, Krishnan

2017-02-01

Low frequency guided wave based inspection is an extensively used method for asset management with the advantage of wide area coverage from a single location at the cost of spatial resolution. With the advent of high frequency guided waves, short range inspections with high spatial resolution for monitoring corrosion under pipe supports and tank annular plates has gained widespread interest and acceptance. One of the major challenges in the application of high frequency guided waves in a short range inspection is to attain the desired modal displacements with respect to the application. In this paper, an investigation on the generation and formation of fundamental S0 mode is carried out through numerical simulation and experiments to establish a prenatal zone for guided waves. The effect of frequency, thickness of the plate and frequency-thickness (f*d) is studied. The investigation reveals the existence of a rudimentary form with similar modal features to the fully developed mode. This study helps in the design and development of a high frequency guided wave generator for particular applications which demands waves with very less sensitivity to the surface and loading during the initial phase which immediately evolves to a more sensitive wave towards the surface on propagation for the detection of shallow defects.

Optical Tamm states in one-dimensional superconducting photonic crystal

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

El Abouti, O.; El Boudouti, E. H.; IEMN, UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq

2016-08-15

In this study, we investigate localized and resonant optical waves associated with a semi-infinite superlattice made out of superconductor-dielectric bilayers and terminated with a cap layer. Both transverse electric and transverse magnetic waves are considered. These surface modes are analogous to the so-called Tamm states associated with electronic states found at the surface of materials. The surface guided modes induced by the cap layer strongly depend on whether the superlattice ends with a superconductor or a dielectric layer, the thickness of the surface layer, the temperature of the superconductor layer as well as on the polarization of the waves. Differentmore » kinds of surface modes are found and their properties examined. These structures can be used to realize the highly sensitive photonic crystal sensors.« less

Time and space analysis of turbulence of gravity surface waves

NASA Astrophysics Data System (ADS)

Mordant, Nicolas; Aubourg, Quentin; Viboud, Samuel; Sommeria, Joel

2016-11-01

Wave turbulence is a statistical state made of a very large number of nonlinearly interacting waves. The Weak Turbulence Theory was developed to describe such a situation in the weakly nonlinear regime. Although, oceanic data tend to be compatible with the theory, laboratory data fail to fulfill the theoretical predictions. A space-time resolved measurement of the waves have proven to be especially fruitful to identify the mechanism at play in turbulence of gravity-capillary waves. We developed an image processing algorithm to measure the motion of the surface of water with both space and time resolution. We first seed the surface with slightly buoyant polystyrene particles and use 3 cameras to reconstruct the surface. Our stereoscopic algorithm is coupled to PIV so that to obtain both the surface deformation and the velocity of the water surface. Such a coupling is shown to improve the sensitivity of the measurement by one order of magnitude. We use this technique to probe the existence of weakly nonlinear turbulence excited by two small wedge wavemakers in a 13-m diameter wave flume. We observe a truly weakly nonlinear regime of isotropic wave turbulence. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No 647018-WATU).

FEM Analysis of Sezawa Mode SAW Sensor for VOC Based on CMOS Compatible AlN/SiO₂/Si Multilayer Structure.

PubMed

Aslam, Muhammad Zubair; Jeoti, Varun; Karuppanan, Saravanan; Malik, Aamir Farooq; Iqbal, Asif

2018-05-24

A Finite Element Method (FEM) simulation study is conducted, aiming to scrutinize the sensitivity of Sezawa wave mode in a multilayer AlN/SiO₂/Si Surface Acoustic Wave (SAW) sensor to low concentrations of Volatile Organic Compounds (VOCs), that is, trichloromethane, trichloroethylene, carbon tetrachloride and tetrachloroethene. A Complimentary Metal-Oxide Semiconductor (CMOS) compatible AlN/SiO₂/Si based multilayer SAW resonator structure is taken into account for this purpose. In this study, first, the influence of AlN and SiO₂ layers’ thicknesses over phase velocities and electromechanical coupling coefficients ( k ²) of two SAW modes (i.e., Rayleigh and Sezawa) is analyzed and the optimal thicknesses of AlN and SiO₂ layers are opted for best propagation characteristics. Next, the study is further extended to analyze the mass loading effect on resonance frequencies of SAW modes by coating a thin Polyisobutylene (PIB) polymer film over the AlN surface. Finally, the sensitivity of the two SAW modes is examined for VOCs. This study concluded that the sensitivity of Sezawa wave mode for 1 ppm of selected volatile organic gases is twice that of the Rayleigh wave mode.

Easy-to-Fabricate and High-Sensitivity LSPR Type Specific Protein Detection Sensor Using AAO Nano-Pore Size Control

PubMed Central

Kim, Sae-Wan; Lee, Jae-Sung; Lee, Sang-Won; Kang, Byoung-Ho; Kwon, Jin-Beom; Kim, Ok-Sik; Kim, Ju-Seong; Kim, Eung-Soo; Kwon, Dae-Hyuk; Kang, Shin-Won

2017-01-01

In this study, we developed a pore size/pore area-controlled optical biosensor-based anodic aluminum oxide (AAO) nanostructure. As the pore size of AAO increases, the unit cell of AAO increases, which also increases the non-pore area to which the antibody binds. The increase in the number of antibodies immobilized on the surface of the AAO enables effective detection of trace amounts of antigen, because increased antigen-antibody bonding results in a larger surface refractive index change. High sensitivity was thus achieved through amplification of the interference wave of two vertically-incident reflected waves through the localized surface plasmon resonance phenomenon. The sensitivity of the fabricated sensor was evaluated by measuring the change in wavelength with the change in the refractive index of the device surface, and sensitivity was increased with increasing pore-size and non-pore area. The sensitivity of the fabricated sensor was improved and up to 11.8 ag/mL serum amyloid A1 antigen was detected. In addition, the selectivity of the fabricated sensor was confirmed through a reaction with a heterogeneous substance, C-reactive protein antigen. By using hard anodization during fabrication of the AAO, the fabrication time of the device was reduced and the AAO chip was fabricated quickly and easily. PMID:28406469

Propagation of thickness-twist waves in a piezoelectric ceramic plate with unattached electrodes.

PubMed

Qian, Zheng-Hua; Kishimoto, Kikuo; Yang, Jiashi

2009-06-01

We analyze the propagation of thickness-twist waves in an unbounded piezoelectric ceramic plate with air gaps between the plate surfaces and two electrodes. These waves are also called anti-plane or shear-horizontal waves with one displacement component only. An exact solution is obtained from the equations of the linear theory of piezoelectricity. Dispersion relations of the waves are obtained and plotted. Results show that the wave frequency or speed is sensitive to the air gap thickness. This effect can be used to manipulate the behavior of the waves and has implications in acoustic wave devices.

Application of nonlinear deterministic decomposition to the prediction and energy dissipation of long-crested irregular ocean surface waves

NASA Astrophysics Data System (ADS)

Meza Conde, Eustorgio

The Hybrid Wave Model (HWM) is a deterministic nonlinear wave model developed for the computation of wave properties in the vicinity of ocean wave measurements. The HWM employs both Mode-Coupling and Phase Modulation Methods to model the wave-wave interactions in an ocean wave field. Different from other nonlinear wave models, the HWM decouples the nonlinear wave interactions from ocean wave field measurements and decomposes the wave field into a set of free-wave components. In this dissertation the HWM is applied to the prediction of wave elevation from pressure measurements and to the quantification of energy during breaking of long-crested irregular surface waves. 1.A transient wave train was formed in a two-dimensional wave flume by sequentially generating a series of waves from high to low frequencies that superposed at a downstream location. The predicted wave elevation using the HWM based on the pressure measurement of a very steep transient wave train is in excellent agreement with the corresponding elevation measurement, while that using Linear Wave Theory (LWT) has relatively large discrepancies. Furthermore, the predicted elevation using the HWM is not sensitive to the choice of the cutoff frequency, while that using LWT is very sensitive. 2.Several transient wave trains containing an isolated plunging or spilling breaker at a prescribed location were generated in a two-dimensional wave flume using the same superposition technique. Surface elevation measurements of each transient wave train were made at locations before and after breaking. Applying the HWM nonlinear deterministic decomposition to the measured elevation, the free-wave components comprising the transient wave train were derived. By comparing the free-wave spectra before and after breaking it is found that energy loss was almost exclusively from wave components at frequencies higher than the spectral peak frequency. Even though the wave components near the peak frequency are the largest, they do not significantly gain or lose energy after breaking. It was also observed that wave components of frequencies significantly below or near the peak frequency gain a small portion of energy lost by the high-frequency waves. These findings may have important implications to the ocean wave energy budget.

Surface Acoustic Wave Nebulisation Mass Spectrometry for the Fast and Highly Sensitive Characterisation of Synthetic Dyes in Textile Samples

NASA Astrophysics Data System (ADS)

Astefanei, Alina; van Bommel, Maarten; Corthals, Garry L.

2017-10-01

Surface acoustic wave nebulisation (SAWN) mass spectrometry (MS) is a method to generate gaseous ions compatible with direct MS of minute samples at femtomole sensitivity. To perform SAWN, acoustic waves are propagated through a LiNbO3 sampling chip, and are conducted to the liquid sample, which ultimately leads to the generation of a fine mist containing droplets of nanometre to micrometre diameter. Through fission and evaporation, the droplets undergo a phase change from liquid to gaseous analyte ions in a non-destructive manner. We have developed SAWN technology for the characterisation of organic colourants in textiles. It generates electrospray-ionisation-like ions in a non-destructive manner during ionisation, as can be observed by the unmodified chemical structure. The sample size is decreased by tenfold to 1000-fold when compared with currently used liquid chromatography-MS methods, with equal or better sensitivity. This work underscores SAWN-MS as an ideal tool for molecular analysis of art objects as it is non-destructive, is rapid, involves minimally invasive sampling and is more sensitive than current MS-based methods. [Figure not available: see fulltext.

Surface Acoustic Wave Monitor for Deposition and Analysis of Ultra-Thin Films

NASA Technical Reports Server (NTRS)

Hines, Jacqueline H. (Inventor)

2015-01-01

A surface acoustic wave (SAW) based thin film deposition monitor device and system for monitoring the deposition of ultra-thin films and nanomaterials and the analysis thereof is characterized by acoustic wave device embodiments that include differential delay line device designs, and which can optionally have integral reference devices fabricated on the same substrate as the sensing device, or on a separate device in thermal contact with the film monitoring/analysis device, in order to provide inherently temperature compensated measurements. These deposition monitor and analysis devices can include inherent temperature compensation, higher sensitivity to surface interactions than quartz crystal microbalance (QCM) devices, and the ability to operate at extreme temperatures.

Surface acoustic-wave piezoelectric crystal aerosol mass microbalance

NASA Technical Reports Server (NTRS)

Bowers, W. D.; Chuan, R. L.

1989-01-01

The development of a particulate mass-sensing instrument based on a quartz-crystal microbalance and enhanced with the new surface acoustic-wave (SAW) technology is reported. Mass sensitivity comparisons of a 158-MHz SAW piezoelectric microbalance and a conventional 10-MHz quartz-crystal microbalance show that the SAW crystal is 266 times more sensitive, in good agreement with the theoretical value of 250. The frequency stability of a single SAW resonator is 6 parts in 10 to the 8th over 1 min. The response to temperature changes is found to be very linear over the range +30 to -30 C. A strong response to 15 ppm SO2 has been demonstrated on a chemically coated SAW crystal.

Quantitative Estimation of Seismic Velocity Changes Using Time-Lapse Seismic Data and Elastic-Wave Sensitivity Approach

NASA Astrophysics Data System (ADS)

Denli, H.; Huang, L.

2008-12-01

Quantitative monitoring of reservoir property changes is essential for safe geologic carbon sequestration. Time-lapse seismic surveys have the potential to effectively monitor fluid migration in the reservoir that causes geophysical property changes such as density, and P- and S-wave velocities. We introduce a novel method for quantitative estimation of seismic velocity changes using time-lapse seismic data. The method employs elastic sensitivity wavefields, which are the derivatives of elastic wavefield with respect to density, P- and S-wave velocities of a target region. We derive the elastic sensitivity equations from analytical differentiations of the elastic-wave equations with respect to seismic-wave velocities. The sensitivity equations are coupled with the wave equations in a way that elastic waves arriving in a target reservoir behave as a secondary source to sensitivity fields. We use a staggered-grid finite-difference scheme with perfectly-matched layers absorbing boundary conditions to simultaneously solve the elastic-wave equations and the elastic sensitivity equations. By elastic-wave sensitivities, a linear relationship between relative seismic velocity changes in the reservoir and time-lapse seismic data at receiver locations can be derived, which leads to an over-determined system of equations. We solve this system of equations using a least- square method for each receiver to obtain P- and S-wave velocity changes. We validate the method using both surface and VSP synthetic time-lapse seismic data for a multi-layered model and the elastic Marmousi model. Then we apply it to the time-lapse field VSP data acquired at the Aneth oil field in Utah. A total of 10.5K tons of CO2 was injected into the oil reservoir between the two VSP surveys for enhanced oil recovery. The synthetic and field data studies show that our new method can quantitatively estimate changes in seismic velocities within a reservoir due to CO2 injection/migration.

Picosecond ultrasonic study of surface acoustic waves on periodically patterned layered nanostructures.

PubMed

Colletta, Michael; Gachuhi, Wanjiru; Gartenstein, Samuel A; James, Molly M; Szwed, Erik A; Daly, Brian C; Cui, Weili; Antonelli, George A

2018-07-01

We have used the ultrafast pump-probe technique known as picosecond ultrasonics to generate and detect surface acoustic waves on a structure consisting of nanoscale Al lines on SiO 2 on Si. We report results from ten samples with varying pitch (1000-140 nm) and SiO 2 film thickness (112 nm or 60 nm), and compare our results to an isotropic elastic calculation and a coarse-grained molecular dynamics simulation. In all cases we are able to detect and identify a Rayleigh-like surface acoustic wave with wavelength equal to the pitch of the lines and frequency in the range of 5-24 GHz. In some samples, we are able to detect additional, higher frequency surface acoustic waves or independent modes of the Al lines with frequencies close to 50 GHz. We also describe the effects of probe beam polarization on the measurement's sensitivity to the different surface modes. Copyright © 2018 Elsevier B.V. All rights reserved.

Asymmetry of wind waves studied in a laboratory tank

NASA Astrophysics Data System (ADS)

Ileykin, L. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.

1995-03-01

Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.

Asymmetry of wind waves studied in a laboratory tank

NASA Astrophysics Data System (ADS)

Leykin, I. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.

Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.

Assessment of precipitation in alloy steel using nonlinear Rayleigh surface waves

NASA Astrophysics Data System (ADS)

Thiele, Sebastian; Matlack, Kathryn H.; Kim, Jin-Yeon; Qu, Jianmin; Wall, James J.; Jacobs, Laurence J.

2014-02-01

Nonlinear ultrasonic waves have shown to be sensitive to various microstructural changes in metals including coherent precipitates; these precipitates introduce a strain field in the lattice structure. The thermal aging of certain alloy steels leads to the formation of coherent precipitates, which pin dislocations and contribute to the generation of a second harmonic component. A precipitate hardenable material namely 17-4 PH stainless steel is thermally treated in this research to obtain different precipitation stages, and then the influence of precipitates on the acoustic nonlinearity parameter is assessed. Conclusions about the microstrucutural changes in the material are drawn based on the results from a nonlinear Rayleigh surface wave measurement and complementary thermo-electric power, hardness and ultrasonic velocity measurements. The results show that the nonlinear parameter is sensitive to coherent precipitates in the material and moreover that precipitation characteristics can be characterized based on the obtained experimental data.

Enhancing the sensitivity of three-axis detectable surface acoustic wave gyroscope by using a floating thin piezoelectric membrane

NASA Astrophysics Data System (ADS)

Lee, Munhwan; Lee, Keekeun

2017-06-01

A new type of surface acoustic wave (SAW) gyroscope was developed on a floating thin piezoelectric membrane to enhance sensitivity and reliability by removing a bulk noise effect and by importing a higher amplitude of SAW. The developed device constitutes a two-port SAW resonator with a metallic dot array between two interdigital transducers (IDTs), and a one-port SAW delay line. The bulk silicon was completely etched away, leaving only a thin piezoelectric membrane with a thickness of one wavelength. A voltage controlled oscillator (VCO) was connected to a SAW resonator to activate the SAW resonator, while the SAW delay line was connected to the oscilloscope to monitor any variations caused by the Coriolis force. When the device was rotated, a secondary wave was generated, changing the amplitude of the SAW delay line. The highest sensitivity was observed in a device with a full acoustic wavelength thickness of the membrane because most of the acoustic field is confined within an acoustic wavelength thickness from the top surface; moreover, the thin-membrane-based gyroscope eliminates the bulk noise effect flowing along the bulk substrate. The obtained sensitivity and linearity of the SAW gyroscope were ˜27.5 µV deg-1 s-1 and ˜4.3%, respectively. Superior directivity was observed. The device surface was vacuum-sealed using poly(dimethylsiloxane) (PDMS) bonding to eliminate environmental interference. A three-axis detectable gyroscope was also implemented by placing three gyrosensors with the same configuration at right angles to each other on a printed circuit board.

Percentage Contributions from Atmospheric and Surface Features to Computed Brightness Temperatures

NASA Technical Reports Server (NTRS)

Jackson, Gail Skofronick

2006-01-01

Over the past few years, there has become an increasing interest in the use of millimeter-wave (mm-wave) and sub-millimeter-wave (submm-wave) radiometer observations to investigate the properties of ice particles in clouds. Passive radiometric channels respond to both the integrated particle mass throughout the volume and field of view, and to the amount, location, and size distribution of the frozen (and liquid) particles with the sensitivity varying for different frequencies and hydrometeor types. One methodology used since the 1960's to discern the relationship between the physical state observed and the brightness temperature (TB) is through the temperature weighting function profile. In this research, the temperature weighting function concept is exploited to analyze the sensitivity of various characteristics of the cloud profile, such as relative humidity, ice water path, liquid water path, and surface emissivity. In our numerical analysis, we compute the contribution (in Kelvin) from each of these cloud and surface characteristics, so that the sum of these various parts equals the computed TB. Furthermore, the percentage contribution from each of these characteristics is assessed. There is some intermingling/contamination of the contributions from various components due to the integrated nature of passive observations and the absorption and scattering between the vertical layers, but all in all the knowledge gained is useful. This investigation probes the sensitivity over several cloud classifications, such as cirrus, blizzards, light snow, anvil clouds, and heavy rain. The focus is on mm-wave and submm-wave frequencies, however discussions of the effects of cloud variations to frequencies as low as 10 GHz and up to 874 GHz will also be presented. The results show that nearly 60% of the TB value at 89 GHz comes from the earth's surface for even the heaviest blizzard snow rates. On the other hand, a significant percentage of the TB value comes from the snow in the cloud for 166, and 183 plus or minus 7 GHz for the heavy and medium snow rates. For submm-wave channels, there is no contribution from the surface because these channels cannot probe through clouds, nor normal water vapor amounts in clear air regions. This work is extremely valuable in physically-based retrieval algorithm development research.

Rejection of atrial sensing artifacts by a pacing lead with short tip-to-ring spacing.

PubMed

Nash, A; Fröhlig, G; Taborsky, M; Stammwitz, E; Maru, F; Bouwens, L H M; Celiker, C

2005-01-01

The ability of a new pacing lead design, with a 10 mm tip-to-ring spacing, to facilitate rejection of sensed far field R-waves and myopotentials was evaluated. Measurements were performed in 66 patients. The occurrence of far field R-wave sensing and myopotential sensing was determined by means of the surface ECG and the ECG markers provided by the pacemaker. At an atrial sensitivity of 0.25 mV and an atrial blanking of 50 ms far field R-wave sensing was observed in 12 patients (18.2%) and at an atrial sensitivity of 1.0 mV no far-field R-wave sensing was observed. Myopotentials were sensed in 3 patients. In all patients the measured P-wave amplitude was at least twice the estimated amplitude of the far field R-wave at an atrial blanking of 50 ms. The results from this study show that a small tip-to-ring spacing allows for programming of a high atrial sensitivity and short atrial blanking with an acceptably low risk for atrial artifact sensing.

Modeling guided wave excitation in plates with surface mounted piezoelectric elements: coupled physics and normal mode expansion

NASA Astrophysics Data System (ADS)

Ren, Baiyang; Lissenden, Cliff J.

2018-04-01

Guided waves have been extensively studied and widely used for structural health monitoring because of their large volumetric coverage and good sensitivity to defects. Effectively and preferentially exciting a desired wave mode having good sensitivity to a certain defect is of great practical importance. Piezoelectric discs and plates are the most common types of surface-mounted transducers for guided wave excitation and reception. Their geometry strongly influences the proportioning between excited modes as well as the total power of the excited modes. It is highly desirable to predominantly excite the selected mode while the total transduction power is maximized. In this work, a fully coupled multi-physics finite element analysis, which incorporates the driving circuit, the piezoelectric element and the wave guide, is combined with the normal mode expansion method to study both the mode tuning and total wave power. The excitation of circular crested waves in an aluminum plate with circular piezoelectric discs is numerically studied for different disc and adhesive thicknesses. Additionally, the excitation of plane waves in an aluminum plate, using a stripe piezoelectric element is studied both numerically and experimentally. It is difficult to achieve predominant single mode excitation as well as maximum power transmission simultaneously, especially for higher order modes. However, guidelines for designing the geometry of piezoelectric elements for optimal mode excitation are recommended.

A size selective porous silicon grating-coupled Bloch surface and sub-surface wave biosensor.

PubMed

Rodriguez, Gilberto A; Ryckman, Judson D; Jiao, Yang; Weiss, Sharon M

2014-03-15

A porous silicon (PSi) grating-coupled Bloch surface and sub-surface wave (BSW/BSSW) biosensor is demonstrated to size selectively detect the presence of both large and small molecules. The BSW is used to sense large immobilized analytes at the surface of the structure while the BSSW that is confined inside but near the top of the structure is used to sensitively detect small molecules. Functionality of the BSW and BSSW modes is theoretically described by dispersion relations, field confinements, and simulated refractive index shifts within the structure. The theoretical results are experimentally verified by detecting two different small chemical molecules and one large 40 base DNA oligonucleotide. The PSi-BSW/BSSW structure is benchmarked against current porous silicon technology and is shown to have a 6-fold higher sensitivity in detecting large molecules and a 33% improvement in detecting small molecules. This is the first report of a grating-coupled BSW biosensor and the first report of a BSSW propagating mode. © 2013 Published by Elsevier B.V.

Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Park, C.B.

1999-01-01

The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pavement) and its effect on seismic-wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh-wave phase velocity of a layered-earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high-frequency range when using the Levenberg-Marquardt and singular-value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.Iterative solutions to the weighted equation by the Levenberg-Marquardt and singular-value decomposition techniques are derived to estimate near-surface shear-wave velocity. Synthetic and real examples demonstrate the calculation efficiency and stability of the inverse procedure. The inverse results of the real example are verified by borehole S-wave velocity measurements.

Development and application of gravity-capillary wave fourier analysis for the study of air-sea interaction physics

NASA Astrophysics Data System (ADS)

MacKenzie Laxague, Nathan Jean

Short ocean waves play a crucial role in the physical coupling between the ocean and the atmosphere. This is particularly true for gravity-capillary waves, waves of a scale (O(0.01-0.1) m) such that they are similarly restored to equilibrium by gravitational and interfacial tension (capillary) effects. These waves are inextricably linked to the turbulent boundary layer processes which characterize near-interfacial flows, acting as mediators of the momentum, gas, and heat fluxes which bear greatly on surface material transport, tropical storms, and climatic processes. The observation of these waves and the fluid mechanical phenomena which govern their behavior has long posed challenges to the would-be observer. This is due in no small part to the delicacy of centimeter-scale waves and the sensitivity of their properties to disruption via tactile measurement. With the ever-growing interest in satellite remote sensing, direct observations of short wave characteristics are needed along coastal margins. These zones are characterized by a diversity of physical processes which can affect the short-scale sea surface topography that is directly sensed via radar backscatter. In a related vein, these observations are needed to more fully understand the specific hydrodynamic relationship between young, wind-generated gravity-capillary waves and longer gravity waves. Furthermore, understanding of the full oceanic current profile is hampered by a lack of observations in the near-surface domain (z = O(0.01-0.1) m), where flows can differ greatly from those at depth. Here I present the development of analytical techniques for describing gravity-capillary ocean surface waves in order to better understand their role in the mechanical coupling between the atmosphere and ocean. This is divided amongst a number of research topics, each connecting short ocean surface waves to a physical forcing process via the transfer of momentum. One involves the examination of the sensitivity of short ocean surface waves to atmospheric forcing. Another is the exploration of long wave-short wave interactions and their effects on air-sea interaction vis-a-vis hydrodynamic modulation. The third and final topic is the characterization of the gravity-capillary regime of the wavenumber-frequency spectrum for the purpose of retrieving near-surface, wind-driven current. All of these fit as part of the desire to more fully describe the mechanism by which momentum is transferred across the air-sea interface and to discuss the consequences of this flux in the very near-surface layer of the ocean. Gravity-capillary waves are found to have an outsize share of ocean surface roughness, with short wave spectral peaks showing a connection to turbulent atmospheric stress. Short wave modulation is found to occur strongest at high wavenumbers at the lowest wind speeds, with peak modulation occurring immediately downwind of the long wave crest. Furthermore, short scale roughness enhancement is found to occur upwind of the long wave crest for increasing wind forcing magnitude. Observations of the near-surface current profile show that flows retrieved via this method agree well with the results of camera-tracked dye. Application of this method to data collected in the mouth of the Columbia River (MCR) indicates the presence of a near-surface current component that departs considerably from the tidal flow and orients into the wind stress direction. These observations demonstrate that wind speed-based parameterizations may not be sufficient to estimate wind drift and hold implications for the way in which surface material (e.g., debris or spilled oil) transport is estimated when atmospheric stress is of relatively high magnitude or is steered off the mean wind direction.

Wave turbulence in a two-layer fluid: Coupling between free surface and interface waves

NASA Astrophysics Data System (ADS)

Falcon, Eric; Issenmann, Bruno; Laroche, Claude

2017-11-01

We experimentally study gravity-capillary wave turbulence on the interface between two immiscible fluids of close density with free upper surface. We locally measure the wave height at the interface between both fluids by means of a highly sensitive laser Doppler vibrometer. We show that the inertial range of the capillary wave turbulence regime is significantly extended when the upper fluid depth is increased: The crossover frequency between the gravity and capillary wave turbulence regimes is found to decrease whereas the dissipative cut-off frequency of the spectrum is found to increase. We explain these observations by the progressive decoupling between waves propagating at the interface and the ones at the free surface, using the full dispersion relation of gravity-capillary waves in a two-layer fluid of finite depths. The cut-off evolution is due to the disappearance of parasitic capillaries responsible for the main wave dissipation for a single fluid. B. Issenmann, C. Laroche & E. Falcon, EPL 116, 64005 (2016) published online 16 feb. 2017. This work has been partially supported by CNRS (1-year postdoctoral funding), ANR Turbulon 12-BS04-0005, and ANR Dysturb 2017.

LITHO1.0: An Updated Crust and Lithosphere Model of the Earth

DTIC Science & Technology

2010-09-01

wc arc uncertain what causes the remainder of the discrepancy. The measurement discrepancies are much smaller than the signal in the data, and the...short-period group velocity data measured with a new technique which are sensitive to lid properties as well as crustal thickness and average...most progress was made on surface-wave measurements . We use a cluster analysis technique to measure surface-wave group velocity from lOmHz to 40mHz

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity

NASA Astrophysics Data System (ADS)

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Ghasemi, Amir Hossein Baradaran; Afshar, Amir; Mohseni, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ˜5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices.

A contactless ultrasonic surface wave approach to characterize distributed cracking damage in concrete.

PubMed

Ham, Suyun; Song, Homin; Oelze, Michael L; Popovics, John S

2017-03-01

We describe an approach that utilizes ultrasonic surface wave backscatter measurements to characterize the volume content of relatively small distributed defects (microcrack networks) in concrete. A simplified weak scattering model is used to demonstrate that the scattered wave field projected in the direction of the surface wave propagation is relatively insensitive to scatterers that are smaller than the propagating wavelength, while the scattered field projected in the opposite direction is more sensitive to sub-wavelength scatterers. Distributed microcracks in the concrete serve as the small scatterers that interact with a propagating surface wave. Data from a finite element simulation were used to demonstrate the viability of the proposed approach, and also to optimize a testing configuration to collect data. Simulations were validated through experimental measurements of ultrasonic backscattered surface waves from test samples of concrete constructed with different concentrations of fiber filler (0.0, 0.3 and 0.6%) to mimic increasing microcrack volume density and then samples with actual cracking induced by controlled thermal cycles. A surface wave was induced in the concrete samples by a 50kHz ultrasonic source operating 10mm above the surface at an angle of incidence of 9°. Silicon-based miniature MEMS acoustic sensors located a few millimeters above the concrete surface both behind and in front of the sender were used to detect leaky ultrasonic surface waves emanating from concrete. A normalized backscattered energy parameter was calculated from the signals. Statistically significant differences in the normalized backscattered energy were observed between concrete samples with varying levels of simulated and actual cracking damage volume. Copyright © 2016 Elsevier B.V. All rights reserved.

A Theoretical Study of Love Wave Sensors Based on ZnO–Glass Layered Structures for Application to Liquid Environments

PubMed Central

Caliendo, Cinzia; Hamidullah, Muhammad

2016-01-01

The propagation of surface acoustic Love modes along ZnO/glass-based structures was modeled and analysed with the goal of designing a sensor able to detect changes in the environmental parameters, such as liquid viscosity changes and minute amounts of mass supported in the viscous liquid medium. Love mode propagation was modeled by numerically solving the system of coupled electro-mechanical field equations and Navier–Stokes equations. The phase and group velocities and the attenuation of the acoustic wave propagating along the 30° tilted c-axis ZnO/glass structure contacting a viscous non-conductive liquid were calculated for different ZnO guiding layer thicknesses, added mass thicknesses, and liquid viscosity and density. The three sensor responses, i.e., the wave phase and group velocity, and attenuation changes are calculated for different environmental parameters and related to the sensor velocity and attenuation sensitivities. The resulted sensitivities to liquid viscosity and added mass were optimized by adjusting the ZnO guiding layer thickness corresponding to a sensitivity peak. The present analysis is valuable for the manufacture and application of the ZnO-glass structure Love wave sensors for the detection of liquid properties, such as viscosity, density and mass anchored to the sensor surface. PMID:27918419

Novel Shear-horizontal Surface Acoustic Wave Based Immunosensors Using SiO2Waveguiding Layers And Flow Injection Analysis.

PubMed

Guo, X S; Chen, Y Q; Yang, X L; Wang, L R

2005-01-01

Surface acoustic wave (SAW) devices based on shear-horizontal (SH) waves can be used as mass-sensitive immunosensors. This paper presents a novel SH-SAW sensor to detect anti-immunoglobulin (IgG) molecules by means of the antibody-antigen binding mechanism. The sensor system comprising dual delay lines was fabricated on 36° Y-X LiTaO3substrate. A SiO2layer was used as love mode waveguiding layers, well as insulating and chemically resistant protective layer. Moreover, flow injection analysis (FIA) method was used for continuous detection the protein molecules. The protein A was immobilized on the optional surface of the gold layer, then coupled with IgG to adsorb the antigens to be measured in the protein solution. The operational frequency of the system changed due to the interaction of antibody-antigen binding. The experimental result demonstrates the sensor has stable frequency response to the mass loading effect of the various anti-IgG concentrations with the sensitivity up to 3.3ng/ml/Hz.

The effect of bathymetric filtering on nearshore process model results

USGS Publications Warehouse

Plant, N.G.; Edwards, K.L.; Kaihatu, J.M.; Veeramony, J.; Hsu, L.; Holland, K.T.

2009-01-01

Nearshore wave and flow model results are shown to exhibit a strong sensitivity to the resolution of the input bathymetry. In this analysis, bathymetric resolution was varied by applying smoothing filters to high-resolution survey data to produce a number of bathymetric grid surfaces. We demonstrate that the sensitivity of model-predicted wave height and flow to variations in bathymetric resolution had different characteristics. Wave height predictions were most sensitive to resolution of cross-shore variability associated with the structure of nearshore sandbars. Flow predictions were most sensitive to the resolution of intermediate scale alongshore variability associated with the prominent sandbar rhythmicity. Flow sensitivity increased in cases where a sandbar was closer to shore and shallower. Perhaps the most surprising implication of these results is that the interpolation and smoothing of bathymetric data could be optimized differently for the wave and flow models. We show that errors between observed and modeled flow and wave heights are well predicted by comparing model simulation results using progressively filtered bathymetry to results from the highest resolution simulation. The damage done by over smoothing or inadequate sampling can therefore be estimated using model simulations. We conclude that the ability to quantify prediction errors will be useful for supporting future data assimilation efforts that require this information.

Lightweight dew-/frost-point hygrometer based on a surface-acoustic-wave sensor for balloon-borne atmospheric water vapor profile sounding

NASA Astrophysics Data System (ADS)

Hansford, Graeme M.; Freshwater, Ray A.; Eden, Louise; Turnbull, Katharine F. V.; Hadaway, David E.; Ostanin, Victor P.; Jones, Roderic L.

2006-01-01

The design of a very lightweight dew-/frost-point hygrometer for balloon-borne atmospheric water vapor profiling is described. The instrument is based on a surface-acoustic-wave sensor. The low instrument weight is a key feature, allowing flights on meteorological balloons which brings many more flight opportunities. The hygrometer shows consistently good performance in the troposphere and while water vapor measurements near the tropopause and in the stratosphere are possible with the current instrument, the long-time response in these regions hampers realistic measurements. The excellent intrinsic sensitivity of the surface-acoustic-wave sensor should permit considerable improvement in the hygrometer performance in the very dry regions of the atmosphere.

Development of attenuation and diffraction corrections for linear and nonlinear Rayleigh surface waves radiating from a uniform line source

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

Jeong, Hyunjo, E-mail: hjjeong@wku.ac.kr; Cho, Sungjong; Zhang, Shuzeng

2016-04-15

In recent studies with nonlinear Rayleigh surface waves, harmonic generation measurements have been successfully employed to characterize material damage and microstructural changes, and found to be sensitive to early stages of damage process. A nonlinearity parameter of Rayleigh surface waves was derived and frequently measured to quantify the level of damage. The accurate measurement of the nonlinearity parameter generally requires making corrections for beam diffraction and medium attenuation. These effects are not generally known for nonlinear Rayleigh waves, and therefore not properly considered in most of previous studies. In this paper, the nonlinearity parameter for a Rayleigh surface wave ismore » defined from the plane wave displacement solutions. We explicitly define the attenuation and diffraction corrections for fundamental and second harmonic Rayleigh wave beams radiated from a uniform line source. Attenuation corrections are obtained from the quasilinear theory of plane Rayleigh wave equations. To obtain closed-form expressions for diffraction corrections, multi-Gaussian beam (MGB) models are employed to represent the integral solutions derived from the quasilinear theory of the full two-dimensional wave equation without parabolic approximation. Diffraction corrections are presented for a couple of transmitter-receiver geometries, and the effects of making attenuation and diffraction corrections are examined through the simulation of nonlinearity parameter determination in a solid sample.« less

Investigation of Various Surface Acoustic Wave Design Configurations for Improved Sensitivity

NASA Astrophysics Data System (ADS)

Manohar, Greeshma

Surface acoustic wave sensors have been a focus of active research for many years. Its ability to respond for surface perturbation is a basic principle for its sensing capability. Sensitivity to surface perturbation changes with every inter-digital transducer (IDT) design parameters, substrate selection, metallization choice and technique, delay line length and working environment. In this thesis, surface acoustic wave (SAW) sensors are designed and characterized to improve sensitivity and reduce loss. To quantify the improvements with a specific design configuration, the sensors are employed to measure temperature. Four SAW sensors design configurations, namely bi-directional, split electrode, single phase unidirectional transducer (SPUDT) and metal grating on delay line (shear transvers wave sensors) are designed and then fabricated in Nanotechnology Research and Education Center (NREC) facility using traditional MEMS fabrication processes Additionally, sensors are then coated with guiding layer SU8-2035 of 40µm using spin coating and SiO 2 of 6µm using plasma enhanced chemical vapor deposition (PECVD) process. Sensors are later diced and tested for every 5°C increment using network analyzer for temperature ranging from 30°C±0.5°C to 80°C±0.5°C. Data acquired from network analyzer is analyzed using plot of logarithmic magnitude, phase and frequency shift. Furthermore, to investigate the effect of metallization technique on the sensor performance, sensors are also fabricated on substrates that were metallized at a commercial MEMS foundry. All in-house and outside sputtered sensor configurations are compared to investigate quality of sputtered metal on wafer. One with better quality sputtered metal is chosen for further study. Later sensors coated with SU8 and SiO2 as guiding layer are compared to investigate effect of each waveguide on sensors and determine which waveguide offers better performance. The results showed that company sputtered sensors have higher sensitivity compared to in-house sputtered wafers. Furthermore after comparing SU8 and SiO2 coated sensors in the same instrumental and environmental condition, it was observed that SU8 coated di-directional and single phase unidirectional transducer (SPUDT) sensors showed best response.

Antarctic icequakes triggered by the 2010 Maule earthquake in Chile

NASA Astrophysics Data System (ADS)

Peng, Zhigang; Walter, Jacob I.; Aster, Richard C.; Nyblade, Andrew; Wiens, Douglas A.; Anandakrishnan, Sridhar

2014-09-01

Seismic waves from distant, large earthquakes can almost instantaneously trigger shallow micro-earthquakes and deep tectonic tremor as they pass through Earth's crust. Such remotely triggered seismic activity mostly occurs in tectonically active regions. Triggered seismicity is generally considered to reflect shear failure on critically stressed fault planes and is thought to be driven by dynamic stress perturbations from both Love and Rayleigh types of surface seismic wave. Here we analyse seismic data from Antarctica in the six hours leading up to and following the 2010 Mw 8.8 Maule earthquake in Chile. We identify many high-frequency seismic signals during the passage of the Rayleigh waves generated by the Maule earthquake, and interpret them as small icequakes triggered by the Rayleigh waves. The source locations of these triggered icequakes are difficult to determine owing to sparse seismic network coverage, but the triggered events generate surface waves, so are probably formed by near-surface sources. Our observations are consistent with tensile fracturing of near-surface ice or other brittle fracture events caused by changes in volumetric strain as the high-amplitude Rayleigh waves passed through. We conclude that cryospheric systems can be sensitive to large distant earthquakes.

A finite element model of a MEMS-based surface acoustic wave hydrogen sensor.

PubMed

El Gowini, Mohamed M; Moussa, Walied A

2010-01-01

Hydrogen plays a significant role in various industrial applications, but careful handling and continuous monitoring are crucial since it is explosive when mixed with air. Surface Acoustic Wave (SAW) sensors provide desirable characteristics for hydrogen detection due to their small size, low fabrication cost, ease of integration and high sensitivity. In this paper a finite element model of a Surface Acoustic Wave sensor is developed using ANSYS12© and tested for hydrogen detection. The sensor consists of a YZ-lithium niobate substrate with interdigital electrodes (IDT) patterned on the surface. A thin palladium (Pd) film is added on the surface of the sensor due to its high affinity for hydrogen. With increased hydrogen absorption the palladium hydride structure undergoes a phase change due to the formation of the β-phase, which deteriorates the crystal structure. Therefore with increasing hydrogen concentration the stiffness and the density are significantly reduced. The values of the modulus of elasticity and the density at different hydrogen concentrations in palladium are utilized in the finite element model to determine the corresponding SAW sensor response. Results indicate that with increasing the hydrogen concentration the wave velocity decreases and the attenuation of the wave is reduced.

Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods.

PubMed

Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

2014-01-01

Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident light, we have demonstrated that maximum sensitivity of glucose detection down to 7.1 × 10(-8) refractive index units could be achieved with optimal deposition parameters of silver nanorods.

Optical sensing of analytes in aqueous solutions with a multiple surface-plasmon-polariton-wave platform

PubMed Central

Swiontek, Stephen E.; Pulsifer, Drew P.; Lakhtakia, Akhlesh

2013-01-01

The commonly used optical sensor based on surface plasmon-polariton wave phenomenon can sense just one chemical, because only one SPP wave can be guided by the interface of a metal and a dielectric material contained in the sensor. Multiple analytes could be detected and/or the sensing reliability for a single analyte could be enhanced, if multiple SPP-wave modes could be excited on a single metal/dielectric interface. For that to happen, the partnering dielectric material must be periodically non-homogeneous. Using a chiral sculptured thin film (CSTF) as that material in a SPP-wave platform, we show that the angular locations of multiple SPP-wave modes shift when the void regions of the CSTF are infiltrated with a fluid. The sensitivities realized in the proof-of-concept experiments are comparable to state-of-research values. PMID:23474988

Active micromixer using surface acoustic wave streaming

DOEpatents

Branch,; Darren W. , Meyer; Grant D. , Craighead; Harold, G [Ithaca, NY

2011-05-17

An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

Design of the sample cell in near-field surface-enhanced Raman scattering by finite difference time domain method

NASA Astrophysics Data System (ADS)

Li, Yaqin; Jian, Guoshu; Wu, Shifa

2006-11-01

The rational design of the sample cell may improve the sensitivity of surface-enhanced Raman scattering (SERS) detection in a high degree. Finite difference time domain (FDTD) simulations of the configuration of Ag film-Ag particles illuminated by plane wave and evanescent wave are performed to provide physical insight for design of the sample cell. Numerical solutions indicate that the sample cell can provide more "hot spots' and the massive field intensity enhancement occurs in these "hot spots'. More information on the nanometer character of the sample can be got because of gradient-field Raman (GFR) of evanescent wave.

Investigating the impact of surface wave breaking on modeling the trajectories of drifters in the northern Adriatic Sea during a wind-storm event

USGS Publications Warehouse

Carniel, S.; Warner, J.C.; Chiggiato, J.; Sclavo, M.

2009-01-01

An accurate numerical prediction of the oceanic upper layer velocity is a demanding requirement for many applications at sea and is a function of several near-surface processes that need to be incorporated in a numerical model. Among them, we assess the effects of vertical resolution, different vertical mixing parameterization (the so-called Generic Length Scale -GLS- set of k-??, k-??, gen, and the Mellor-Yamada), and surface roughness values on turbulent kinetic energy (k) injection from breaking waves. First, we modified the GLS turbulence closure formulation in the Regional Ocean Modeling System (ROMS) to incorporate the surface flux of turbulent kinetic energy due to wave breaking. Then, we applied the model to idealized test cases, exploring the sensitivity to the above mentioned factors. Last, the model was applied to a realistic situation in the Adriatic Sea driven by numerical meteorological forcings and river discharges. In this case, numerical drifters were released during an intense episode of Bora winds that occurred in mid-February 2003, and their trajectories compared to the displacement of satellite-tracked drifters deployed during the ADRIA02-03 sea-truth campaign. Results indicted that the inclusion of the wave breaking process helps improve the accuracy of the numerical simulations, subject to an increase in the typical value of the surface roughness z0. Specifically, the best performance was obtained using ??CH = 56,000 in the Charnok formula, the wave breaking parameterization activated, k-?? as the turbulence closure model. With these options, the relative error with respect to the average distance of the drifter was about 25% (5.5 km/day). The most sensitive factors in the model were found to be the value of ??CH enhanced with respect to a standard value, followed by the adoption of wave breaking parameterization and the particular turbulence closure model selected. ?? 2009 Elsevier Ltd.

On Pulsating and Cellular Forms of Hydrodynamic Instability in Liquid-Propellant Combustion

NASA Technical Reports Server (NTRS)

Margolis, Stephen B.; Sacksteder, Kurt (Technical Monitor)

1998-01-01

An extended Landau-Levich model of liquid-propellant combustion, one that allows for a local dependence of the burning rate on the (gas) pressure at the liquid-gas interface, exhibits not only the classical hydrodynamic cellular instability attributed to Landau but also a pulsating hydrodynamic instability associated with sufficiently negative pressure sensitivities. Exploiting the realistic limit of small values of the gas-to-liquid density ratio p, analytical formulas for both neutral stability boundaries may be obtained by expanding all quantities in appropriate powers of p in each of three distinguished wave-number regimes. In particular, composite analytical expressions are derived for the neutral stability boundaries A(sub p)(k), where A, is the pressure sensitivity of the burning rate and k is the wave number of the disturbance. For the cellular boundary, the results demonstrate explicitly the stabilizing effect of gravity on long-wave disturbances, the stabilizing effect of viscosity (both liquid and gas) and surface tension on short-wave perturbations, and the instability associated with intermediate wave numbers for negative values of A(sub p), which is characteristic of many hydroxylammonium nitrate-based liquid propellants over certain pressure ranges. In contrast, the pulsating hydrodynamic stability boundary is insensitive to gravitational and surface-tension effects but is more sensitive to the effects of liquid viscosity because, for typical nonzero values of the latter, the pulsating boundary decreases to larger negative values of A(sub p) as k increases through O(l) values. Thus, liquid-propellant combustion is predicted to be stable (that is, steady and planar) only for a range of negative pressure sensitivities that lie below the cellular boundary that exists for sufficiently small negative values of A(sub p) and above the pulsating boundary that exists for larger negative values of this parameter.

A Variable-resolution Surface Wave Dispersion Study of Eurasia, North Africa, and Surrounding Regions

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

Pasyanos, M E

This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, andmore » have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant correlations. We don't find any similar correlation between the longest period surface waves and hot spots.« less

North Atlantic storm driving of extreme wave heights in the North Sea

NASA Astrophysics Data System (ADS)

Bell, R. J.; Gray, S. L.; Jones, O. P.

2017-04-01

The relationship between storms and extreme ocean waves in the North Sea is assessed using a long-period wave data set and storms identified in the Interim ECMWF Re-Analysis (ERA-Interim). An ensemble sensitivity analysis is used to provide information on the spatial and temporal forcing from mean sea-level pressure and surface wind associated with extreme ocean wave height responses. Extreme ocean waves in the central North Sea arise due to intense extratropical cyclone winds from either the cold conveyor belt (northerly-wind events) or the warm conveyor belt (southerly-wind events). The largest wave heights are associated with northerly-wind events which tend to have stronger wind speeds and occur as the cold conveyor belt wraps rearward round the cyclone to the cold side of the warm front. The northerly-wind events provide a larger fetch to the central North Sea to aid wave growth. Southerly-wind events are associated with the warm conveyor belts of intense extratropical cyclones that develop in the left upper tropospheric jet exit region. Ensemble sensitivity analysis can provide early warning of extreme wave events by demonstrating a relationship between wave height and high pressure to the west of the British Isles for northerly-wind events 48 h prior. Southerly-wind extreme events demonstrate sensitivity to low pressure to the west of the British Isles 36 h prior.

Liquid density analysis of sucrose and alcoholic beverages using polyimide guided Love-mode acoustic wave sensors

NASA Astrophysics Data System (ADS)

Turton, Andrew; Bhattacharyya, Debabrata; Wood, David

2006-02-01

A liquid density sensor using Love-mode acoustic waves has been developed which is suitable for use in the food and drinks industries. The sensor has an open flat surface allowing immersion into a sample and simple cleaning. A polyimide waveguide layer allows cheap and simple fabrication combined with a robust chemically resistant surface. The low shear modulus of polyimide allows thin guiding layers giving a high sensitivity. A dual structure with a smooth reference device exhibiting viscous coupling with the wave, and a patterned sense area to trap the liquid causing mass loading, allows discrimination of the liquid density from the square root of the density-viscosity product (ρη)0.5. Frequency shift and insertion loss change were proportional to (ρη)0.5 with a non-linear response due to the non-Newtonian nature of viscous liquids at high frequencies. Measurements were made with sucrose solutions up to 50% and different alcoholic drinks. A maximum sensitivity of 0.13 µg cm-3 Hz-1 was achieved, with a linear frequency response to density. This is the highest liquid density sensitivity obtained for acoustic mode sensors to the best of our knowledge.

A high-sensitivity fiber-optic evanescent wave sensor with a three-layer structure composed of Canada balsam doped with GeO2.

PubMed

Zhong, Nianbing; Zhao, Mingfu; Zhong, Lianchao; Liao, Qiang; Zhu, Xun; Luo, Binbin; Li, Yishan

2016-11-15

In this paper, we present a high-sensitivity polymer fiber-optic evanescent wave (FOEW) sensor with a three-layer structure that includes bottom, inter-, and surface layers in the sensing region. The bottom layer and inter-layer are POFs composed of standard cladding and the core of the plastic optical fiber, and the surface layer is made of dilute Canada balsam in xylene doped with GeO2. We examine the morphology of the doped GeO2, the refractive index and composition of the surface layer and the surface luminous properties of the sensing region. We investigate the effects of the content and morphology of the GeO2 particles on the sensitivity of the FOEW sensors by using glucose solutions. In addition, we examine the response of sensors incubated with staphylococcal protein A plus mouse IgG isotype to goat anti-mouse IgG solutions. Results indicate very good sensitivity of the three-layer FOEW sensor, which showed a 3.91-fold improvement in the detection of the target antibody relative to a conventional sensor with a core-cladding structure, and the novel sensor showed a lower limit of detection of 0.2ng/l and a response time around 320s. The application of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, biomedical and biochemical analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity.

PubMed

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Baradaran Ghasemi, Amir Hossein; Afshar, Amir; Mohseni Armaki, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ∼5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Surface-acoustic-wave (SAW) flow sensor

NASA Astrophysics Data System (ADS)

Joshi, Shrinivas G.

1991-03-01

The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

Surface-acoustic-wave (SAW) flow sensor.

PubMed

Joshi, S G

1991-01-01

The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 degrees rotated Y-cut lithium niobate substrate and heated to 55 degrees C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cm(3)/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves, propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

P- and S-Wave Speeds of the Very Upper Crust Estimated by a New Technique Based Upon Body-Wave Polarization

NASA Astrophysics Data System (ADS)

Park, S.; Ishii, M.

2017-12-01

Various seismic imaging methods have been developed, such as traveltime, waveform, and noise tomography, improving our knowledge of the subsurface structure and evolution. Near-surface structure, in particular, is crucial in understanding earthquake and volcano hazards. Seismic speed is directly related to the level of ground shaking, and monitoring its temporal change is valuable in volcanic hazard assessment. Here, we introduce a novel technique to constrain seismic wave speed of the very upper crust based upon the polarization measurements of teleseismic body-wave arrivals. The technique relates the orientation of recorded body waves to the wave speed immediately beneath a seismic instrument. We develop a counter-intuitive relationship that the P-wave polarization direction is only sensitive to subsurface shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. This approach is applied to the High-Sensitivity Seismograph Network in Japan, where the results are benchmarked against the borehole well data available at most stations. There is a good agreement between polarization-based estimates and the well measurements at as shallow as 100 m, confirming the efficacy of the new method in resolving the shallow structure. The lateral variation of wave speeds shows that sedimentary basins and mountainous regions are characterized by low and high wave speeds, respectively. It also correlates with volcano locations and geological units of different ages. Moreover, the analysis is expanded into 3D by examining the frequency dependence, where some preliminary results using broadband data are presented. These 2D and 3D wave speed estimates can be used to identify zones of high seismic risk by comparison with population distribution. This technique requires minimal computation resources and can be applied to any single three-component seismograph. It opens a new path to a reliable, non-invasive, and inexpensive earthquake hazard assessment in any environment where a drilling or a field experiment using vibro-trucks or explosives is not a practical option for measuring the near-surface seismic wave speeds. It can also provide means of monitoring changes that occur within the very upper crust such as from volcanic or hydrological phenomena.

Optical transfer function in corneal topography for clinical contrast sensitivity analysis

NASA Astrophysics Data System (ADS)

Bende, Thomas; Jean, Benedikt J.; Oltrup, Theo

2000-06-01

Customized ablation aiming to optimize visual acuity in refractive surgery requires objective data on corneal surface, like the contrast sensitivity. Fast ray tracing, using the high resolution 3-D elevation data in conjunction with Snell's law describe the diffraction of the incident rays and the resulting image on a 'virtual retina.' A retroprojection leads to a 'surface quality map.' For objective contrast sensitivity measurement a sinus (or cos) wave of different frequencies is used for a calculated projection in analogy to the clinical contrast sensitivity charts. The projection on the individual cornea surface is analyzed for the Modular Transfer Function (MTF) and the Phase Shift Function (PSF) as a function of frequencies. PSF, not yet clinically used, is a parameter to determine even minimal corneal tilt. The resulting corneal aberration map (CAM) as described here and applied to a 4.5 D PRK (OZD equals 6.5 mm) reveals that the area of minimal aberration measures only 4.2 mm. The CAM can likewise be used to describe the 'quality' of a laser system's ablation pattern based upon the area of minimal optical aberrations. The CAM only describes surface aberration with high resolution, an advantage over wave front sensing which measures all accumulated optical aberrations including the changing ones of the lens during accommodation and the transient ones due to lens aging and early cataract formation.

Nonlinear ultrasonic assessment of stress corrosion cracking damage in sensitized 304 stainless steel

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

Morlock, Florian, E-mail: fmorlock3@gatech.edu; Jacobs, Laurence J., E-mail: fmorlock3@gatech.edu; Kim, Jin-Yeon, E-mail: fmorlock3@gatech.edu

2015-03-31

This research uses nonlinear Rayleigh surface waves to characterize stress corrosion cracking (SCC) damage in welded 304 Stainless Steel (304 SS). 304 SS is widely used in reactor pressure vessels, where a corrosive environment in combination with applied stress due to high internal pressures can cause SCC. Welds and the nearby heat affected zones (HAZ) in the vessel material are especially sensitive to SCC damage. SCC damage results in microstructural changes such as dislocation formation and microcrack initiation that in the long term lead to reduced structural integrity and material failure. Therefore, the early detection of SCC is crucial tomore » ensure safe operation. It has been shown that the microstructural changes caused by SCC can generate higher harmonic waves when excited harmonically. This research considers different levels of SCC damage induced in samples of welded 304 SS by applying stress to a specimen held in a corrosive medium (Sodium Thiosulfate). A nonlinear Rayleigh surface wave is introduced in the material and the fundamental and the second harmonic waves are measured using wedge detection. The nonlinearity parameter that relates the fundamental and the second harmonic amplitudes, is computed to quantify the SCC damage in each sample. These results are used to demonstrate the feasibility of using nonlinear Rayleigh waves to characterize SCC damage.« less

Finite-difference modeling and dispersion analysis of high-frequency love waves for near-surface applications

USGS Publications Warehouse

Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.; Liu, J.

2010-01-01

Love-wave propagation has been a topic of interest to crustal, earthquake, and engineering seismologists for many years because it is independent of Poisson's ratio and more sensitive to shear (S)-wave velocity changes and layer thickness changes than are Rayleigh waves. It is well known that Love-wave generation requires the existence of a low S-wave velocity layer in a multilayered earth model. In order to study numerically the propagation of Love waves in a layered earth model and dispersion characteristics for near-surface applications, we simulate high-frequency (>5 Hz) Love waves by the staggered-grid finite-difference (FD) method. The air-earth boundary (the shear stress above the free surface) is treated using the stress-imaging technique. We use a two-layer model to demonstrate the accuracy of the staggered-grid modeling scheme. We also simulate four-layer models including a low-velocity layer (LVL) or a high-velocity layer (HVL) to analyze dispersive energy characteristics for near-surface applications. Results demonstrate that: (1) the staggered-grid FD code and stress-imaging technique are suitable for treating the free-surface boundary conditions for Love-wave modeling, (2) Love-wave inversion should be treated with extra care when a LVL exists because of a lack of LVL information in dispersions aggravating uncertainties in the inversion procedure, and (3) energy of high modes in a low-frequency range is very weak, so that it is difficult to estimate the cutoff frequency accurately, and "mode-crossing" occurs between the second higher and third higher modes when a HVL exists. ?? 2010 Birkh??user / Springer Basel AG.

Strategies to Enhance the Model Update in Regions of Weak Sensitivities for Use in Full Waveform Inversion

NASA Astrophysics Data System (ADS)

Nuber, André; Manukyan, Edgar; Maurer, Hansruedi

2014-05-01

Conventional methods of interpreting seismic data rely on filtering and processing limited portions of the recorded wavefield. Typically, either reflections, refractions or surface waves are considered in isolation. Particularly in near-surface engineering and environmental investigations (depths less than, say 100 m), these wave types often overlap in time and are difficult to separate. Full waveform inversion is a technique that seeks to exploit and interpret the full information content of the seismic records without the need for separating events first; it yields models of the subsurface at sub-wavelength resolution. We use a finite element modelling code to solve the 2D elastic isotropic wave equation in the frequency domain. This code is part of a Gauss-Newton inversion scheme which we employ to invert for the P- and S-wave velocities as well as for density in the subsurface. For shallow surface data the use of an elastic forward solver is essential because surface waves often dominate the seismograms. This leads to high sensitivities (partial derivatives contained in the Jacobian matrix of the Gauss-Newton inversion scheme) and thus large model updates close to the surface. Reflections from deeper structures may also include useful information, but the large sensitivities of the surface waves often preclude this information from being fully exploited. We have developed two methods that balance the sensitivity distributions and thus may help resolve the deeper structures. The first method includes equilibrating the columns of the Jacobian matrix prior to every inversion step by multiplying them with individual scaling factors. This is expected to also balance the model updates throughout the entire subsurface model. It can be shown that this procedure is mathematically equivalent to balancing the regularization weights of the individual model parameters. A proper choice of the scaling factors required to balance the Jacobian matrix is critical. We decided to normalise the columns of the Jacobian based on their absolute column sum, but defining an upper threshold for the scaling factors. This avoids particularly small and therefore insignificant sensitivities being over-boosted, which would produce unstable results. The second method proposed includes adjusting the inversion cell size with depth. Multiple cells of the forward modelling grid are merged to form larger inversion cells (typical ratios between forward and inversion cells are in the order of 1:100). The irregular inversion grid is adapted to the expected resolution power of full waveform inversion. Besides stabilizing the inversion, this approach also reduces the number of model parameters to be recovered. Consequently, the computational costs and the memory consumption are reduced significantly. This is particularly critical when Gauss-Newton type inversion schemes are employed. Extensive tests with synthetic data demonstrated that both methods stabilise the inversion and improve the inversion results. The two methods have some redundancy, which can be seen when both are applied simultaneously, that is, when scaling of the Jacobian matrix is applied to an irregular inversion grid. The calculated scaling factors are quite balanced and span a much smaller range than in the case of a regular inversion grid.

An oxygen pressure sensor using surface acoustic wave devices

NASA Technical Reports Server (NTRS)

Leighty, Bradley D.; Upchurch, Billy T.; Oglesby, Donald M.

1993-01-01

Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.

Color constancy: enhancing von Kries adaption via sensor transformations

NASA Astrophysics Data System (ADS)

Finlayson, Graham D.; Drew, Mark S.; Funt, Brian V.

1993-09-01

Von Kries adaptation has long been considered a reasonable vehicle for color constancy. Since the color constancy performance attainable via the von Kries rule strongly depends on the spectral response characteristics of the human cones, we consider the possibility of enhancing von Kries performance by constructing new `sensors' as linear combinations of the fixed cone sensitivity functions. We show that if surface reflectances are well-modeled by 3 basis functions and illuminants by 2 basis functions then there exists a set of new sensors for which von Kries adaptation can yield perfect color constancy. These new sensors can (like the cones) be described as long-, medium-, and short-wave sensitive; however, both the new long- and medium-wave sensors have sharpened sensitivities -- their support is more concentrated. The new short-wave sensor remains relatively unchanged. A similar sharpening of cone sensitivities has previously been observed in test and field spectral sensitivities measured for the human eye. We present simulation results demonstrating improved von Kries performance using the new sensors even when the restrictions on the illumination and reflectance are relaxed.

Development and applications of a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System

NASA Astrophysics Data System (ADS)

Warner, J. C.; Armstrong, B. N.; He, R.; Zambon, J. B.; Olabarrieta, M.; Voulgaris, G.; Kumar, N.; Haas, K. A.

2012-12-01

Understanding processes responsible for coastal change is important for managing both our natural and economic coastal resources. Coastal processes respond from both local scale and larger regional scale forcings. Understanding these processes can lead to significant insight into how the coastal zone evolves. Storms are one of the primary driving forces causing coastal change from a coupling of wave and wind driven flows. Here we utilize a numerical modeling approach to investigate these dynamics of coastal storm impacts. We use the Coupled Ocean - Atmosphere - Wave - Sediment Transport (COAWST) Modeling System that utilizes the Model Coupling Toolkit to exchange prognostic variables between the ocean model ROMS, atmosphere model WRF, wave model SWAN, and the Community Sediment Transport Modeling System (CSTMS) sediment routines. The models exchange fields of sea-surface temperature, ocean currents, water levels, bathymetry, wave heights, lengths, periods, bottom orbital velocities, and atmospheric surface heat and momentum fluxes, atmospheric pressure, precipitation, and evaporation. Data fields are exchanged using regridded flux conservative sparse matrix interpolation weights computed from the SCRIP spherical coordinate remapping interpolation package. We describe the modeling components and the model field exchange methods. As part of the system, the wave and ocean models run with cascading, refined, spatial grids to provide increased resolution, scaling down to resolve nearshore wave driven flows simulated by the vortex force formulation, all within selected regions of a larger, coarser-scale coastal modeling system. The ocean and wave models are driven by the atmospheric component, which is affected by wave dependent ocean-surface roughness and sea surface temperature which modify the heat and momentum fluxes at the ocean-atmosphere interface. We describe the application of the modeling system to several regions of multi-scale complexity to identify the significance of larger scale forcing cascading down to smaller scales and to investigate the interactions of the coupled system with increasing degree of model-model interactions. Three examples include the impact of Hurricane Ivan in 2004 in the Gulf of Mexico, Hurricane Ida in 2009 that evolved into a tropical storm on the US East coast, and passage of strong cold fronts across the US southeast. Results identify that hurricane intensity is extremely sensitive to sea-surface temperature, with a reduction in intensity when the atmosphere is coupled to the ocean model due to rapid cooling of the ocean from the surface through the mixed layer. Coupling of the ocean to the atmosphere also results in decreased boundary layer stress and coupling of the waves to the atmosphere results in increased sea-surface stress. Wave results are sensitive to both ocean and atmospheric coupling due to wave-current interactions with the ocean and wave-growth from the atmospheric wind stress. Sediment resuspension at regional scale during the hurricane is controlled by shelf width and wave propagation during hurricane approach. Results from simulation of passage of cold fronts suggest that synoptic meteorological systems can strongly impact surf zone and inner shelf response, therefore act as a strong driver for long term littoral sediment transport. We will also present some of the challenges faced to develop the modeling system.

Increasing the Sensitivity of Surface Acoustic Wave (SAW) Chemical Sensors and other Chemical Sensing Investigations

DTIC Science & Technology

2010-03-01

are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S...device recovers to a neutral state [8]. 2.1.2 Sensing Methods There are many methods of using acoustic waves for sensing applications. Some of the

Graphene-Based Long-Period Fiber Grating Surface Plasmon Resonance Sensor for High-Sensitivity Gas Sensing

PubMed Central

Wei, Wei; Nong, Jinpeng; Zhang, Guiwen; Tang, Linlong; Jiang, Xiao; Chen, Na; Luo, Suqin; Lan, Guilian; Zhu, Yong

2016-01-01

A graphene-based long-period fiber grating (LPFG) surface plasmon resonance (SPR) sensor is proposed. A monolayer of graphene is coated onto the Ag film surface of the LPFG SPR sensor, which increases the intensity of the evanescent field on the surface of the fiber and thereby enhances the interaction between the SPR wave and molecules. Such features significantly improve the sensitivity of the sensor. The experimental results demonstrate that the sensitivity of the graphene-based LPFG SPR sensor can reach 0.344 nm%−1 for methane, which is improved 2.96 and 1.31 times with respect to the traditional LPFG sensor and Ag-coated LPFG SPR sensor, respectively. Meanwhile, the graphene-based LPFG SPR sensor exhibits excellent response characteristics and repeatability. Such a SPR sensing scheme offers a promising platform to achieve high sensitivity for gas-sensing applications. PMID:28025483

Integrated immunoassay using tuneable surface acoustic waves and lensfree detection.

PubMed

Bourquin, Yannyk; Reboud, Julien; Wilson, Rab; Zhang, Yi; Cooper, Jonathan M

2011-08-21

The diagnosis of infectious diseases in the Developing World is technologically challenging requiring complex biological assays with a high analytical performance, at minimal cost. By using an opto-acoustic immunoassay technology, integrating components commonly used in mobile phone technologies, including surface acoustic wave (SAW) transducers to provide pressure driven flow and a CMOS camera to enable lensfree detection technique, we demonstrate the potential to produce such an assay. To achieve this, antibody functionalised microparticles were manipulated on a low-cost disposable cartridge using the surface acoustic waves and were then detected optically. Our results show that the biomarker, interferon-γ, used for the diagnosis of diseases such as latent tuberculosis, can be detected at pM concentrations, within a few minutes (giving high sensitivity at a minimal cost). This journal is © The Royal Society of Chemistry 2011

A Surface Wave Dispersion Study of the Middle East and North Africa for Monitoring the Comprehensive Nuclear-Test-Ban Treaty

NASA Astrophysics Data System (ADS)

Pasyanos, M. E.; Walter, W. R.; Hazler, S. E.

- We present results from a large-scale study of surface-wave group velocity dispersion across the Middle East, North Africa, southern Eurasia and the Mediterranean. Our database for the region is populated with seismic data from regional events recorded at permanent and portable broadband, three-component digital stations. We have measured the group velocity using a multiple narrow-band filter on deconvolved displacement data. Overall, we have examined more than 13,500 seismograms and made good quality dispersion measurements for 6817 Rayleigh- and 3806 Love-wave paths. We use a conjugate gradient method to perform a group-velocity tomography. Our current results include both Love- and Rayleigh-wave inversions across the region for periods from 10 to 60 seconds. Our findings indicate that short-period structure is sensitive to slow velocities associated with large sedimentary features such as the Mediterranean Sea and Persian Gulf. We find our long-period Rayleigh-wave inversion is sensitive to crustal thickness, such as fast velocities under the oceans and slow along the relatively thick Zagros Mts. and Turkish-Iranian Plateau. We also find slow upper mantle velocities along known rift systems. Accurate group velocity maps can be used to construct phase-matched filters along any given path. The filters can improve weak surface wave signals by compressing the dispersed signal. The signals can then be used to calculate regionally determined MS measurements, which we hope can be used to extend the threshold of mb:MS discriminants down to lower magnitude levels. Other applications include using the group velocities in the creation of a suitable background model for forming station calibration maps, and using the group velocities to model the velocity structure of the crust and upper mantle.

Finite-frequency sensitivity kernels for global seismic wave propagation based upon adjoint methods

NASA Astrophysics Data System (ADS)

Liu, Qinya; Tromp, Jeroen

2008-07-01

We determine adjoint equations and Fréchet kernels for global seismic wave propagation based upon a Lagrange multiplier method. We start from the equations of motion for a rotating, self-gravitating earth model initially in hydrostatic equilibrium, and derive the corresponding adjoint equations that involve motions on an earth model that rotates in the opposite direction. Variations in the misfit function χ then may be expressed as , where δlnm = δm/m denotes relative model perturbations in the volume V, δlnd denotes relative topographic variations on solid-solid or fluid-solid boundaries Σ, and ∇Σδlnd denotes surface gradients in relative topographic variations on fluid-solid boundaries ΣFS. The 3-D Fréchet kernel Km determines the sensitivity to model perturbations δlnm, and the 2-D kernels Kd and Kd determine the sensitivity to topographic variations δlnd. We demonstrate also how anelasticity may be incorporated within the framework of adjoint methods. Finite-frequency sensitivity kernels are calculated by simultaneously computing the adjoint wavefield forward in time and reconstructing the regular wavefield backward in time. Both the forward and adjoint simulations are based upon a spectral-element method. We apply the adjoint technique to generate finite-frequency traveltime kernels for global seismic phases (P, Pdiff, PKP, S, SKS, depth phases, surface-reflected phases, surface waves, etc.) in both 1-D and 3-D earth models. For 1-D models these adjoint-generated kernels generally agree well with results obtained from ray-based methods. However, adjoint methods do not have the same theoretical limitations as ray-based methods, and can produce sensitivity kernels for any given phase in any 3-D earth model. The Fréchet kernels presented in this paper illustrate the sensitivity of seismic observations to structural parameters and topography on internal discontinuities. These kernels form the basis of future 3-D tomographic inversions.

The Influence of depth and surface waves on marine current turbine performance

NASA Astrophysics Data System (ADS)

Lust, Ethan; Flack, Karen; Luznik, Luksa; van Benthem, Max; Walker, Jessica

2013-11-01

Performance characteristics are presented for a 1/25th scale marine current turbine operating in calm conditions and in the presence of intermediate and deep water waves. The two-bladed turbine has radius of 0.4 m and a maximum blade pitch of 17°. The hydrofoil is a NACA63-618 which was selected to be Reynolds number independent for lift in the operational range (ReC = 2 - 4 × 105) . The experiments were performed in the 116 m tow-tank at the United States Naval Academy at depths of 0.8D and 1.75D measured from the blade tip to the mean free surface. Overall average values for power and thrust coefficient were found to be insensitive to wave form and weakly sensitive to turbine depth. Waves yield a small increase in turbine performance which can be explained by Stokes drift. Variations on performance parameters are on the same order of magnitude as the average value especially near the mean free surface and in the presence of high energy waves. Office of Naval Research.

Portable evanescent wave fiber biosensor for highly sensitive detection of Shigella

NASA Astrophysics Data System (ADS)

Xiao, Rui; Rong, Zhen; Long, Feng; Liu, Qiqi

2014-11-01

A portable evanescent wave fiber biosensor was developed to achieve the rapid and highly sensitive detection of Shigella. In this study, a DNA probe was covalently immobilized onto fiber-optic biosensors that can hybridize with a fluorescently labeled complementary DNA. The sensitivity of detection for synthesized oligonucleotides can reach 10-10 M. The surface of the sensor can be regenerated with 0.5% sodium dodecyl sulfate solution (pH 1.9) for over 30 times without significant deterioration of performance. The total analysis time for a single sample, including the time for measurement and surface regeneration, was less than 6 min. We employed real-time polymerase chain reaction (PCR) and compared the results of both methods to investigate the actual Shigella DNA detection capability of the fiber-optic biosensor. The fiber-optic biosensor could detect as low as 102 colony-forming unit/mL Shigella. This finding was comparable with that by real-time PCR, which suggests that this method is a potential alternative to existing detection methods.

Guided-Wave Optical Biosensors

PubMed Central

Passaro, Vittorio M. N.; Dell'Olio, Francesco; Casamassima, Biagio; De Leonardis, Francesco

2007-01-01

Guided-wave optical biosensors are reviewed in this paper. Advantages related to optical technologies are presented and integrated architectures are investigated in detail. Main classes of bio receptors and the most attractive optical transduction mechanisms are discussed. The possibility to use Mach-Zehnder and Young interferometers, microdisk and microring resonators, surface plasmon resonance, hollow and antiresonant waveguides, and Bragg gratings to realize very sensitive and selective, ultra-compact and fast biosensors is discussed. Finally, CMOS-compatible technologies are proved to be the most attractive for fabrication of guided-wave photonic biosensors.

Optical fiber interferometer for the study of ultrasonic waves in composite materials

NASA Technical Reports Server (NTRS)

Claus, R. O.; Zewekh, P. S.; Turner, T. M.; Wade, J. C.; Rogers, R. T.; Garg, A. O.

1981-01-01

The possibility of acoustic emission detection in composites using embedded optical fibers as sensing elements was investigated. Optical fiber interferometry, fiber acoustic sensitivity, fiber interferometer calibration, and acoustic emission detection are reported. Adhesive bond layer dynamical properties using ultrasonic interface waves, the design and construction of an ultrasonic transducer with a two dimensional Gaussian pressure profile, and the development of an optical differential technique for the measurement of surface acoustic wave particle displacements and propagation direction are also examined.

Investigation of hurricane Ivan using the coupled ocean-atmosphere-wave-sediment transport (COAWST) model

USGS Publications Warehouse

Zambon, Joseph B.; He, Ruoying; Warner, John C.

2014-01-01

The coupled ocean–atmosphere–wave–sediment transport (COAWST) model is used to hindcast Hurricane Ivan (2004), an extremely intense tropical cyclone (TC) translating through the Gulf of Mexico. Sensitivity experiments with increasing complexity in ocean–atmosphere–wave coupled exchange processes are performed to assess the impacts of coupling on the predictions of the atmosphere, ocean, and wave environments during the occurrence of a TC. Modest improvement in track but significant improvement in intensity are found when using the fully atmosphere–ocean-wave coupled configuration versus uncoupled (e.g., standalone atmosphere, ocean, or wave) model simulations. Surface wave fields generated in the fully coupled configuration also demonstrates good agreement with in situ buoy measurements. Coupled and uncoupled model-simulated sea surface temperature (SST) fields are compared with both in situ and remote observations. Detailed heat budget analysis reveals that the mixed layer temperature cooling in the deep ocean (on the shelf) is caused primarily by advection (equally by advection and diffusion).

Complex Rayleigh Waves Produced by Shallow Sedimentary Basins and their Potential Effects on Mid-Rise Buildings

NASA Astrophysics Data System (ADS)

Kohler, M. D.; Castillo, J.; Massari, A.; Clayton, R. W.

2017-12-01

Earthquake-induced motions recorded by spatially dense seismic arrays in buildings located in the northern Los Angeles basin suggest the presence of complex, amplified surface wave effects on the seismic demand of mid-rise buildings. Several moderate earthquakes produced large-amplitude, seismic energy with slow shear-wave velocities that cannot be explained or accurately modeled by any published 3D seismic velocity models or by Vs30 values. Numerical experiments are conducted to determine if sedimentary basin features are responsible for these rarely modeled and poorly documented contributions to seismic demand computations. This is accomplished through a physics-based wave propagation examination of the effects of different sedimentary basin geometries on the nonlinear response of a mid-rise structural model based on an existing, instrumented building. Using two-dimensional finite-difference predictive modeling, we show that when an earthquake focal depth is near the vertical edge of an elongated and relatively shallow sedimentary basin, dramatically amplified and complex surface waves are generated as a result of the waveguide effect introduced by this velocity structure. In addition, for certain source-receiver distances and basin geometries, body waves convert to secondary Rayleigh waves that propagate both at the free-surface interface and along the depth interface of the basin that show up as multiple large-amplitude arrivals. This study is motivated by observations from the spatially dense, high-sample-rate acceleration data recorded by the Community Seismic Network, a community-hosted strong-motion network, currently consisting of hundreds of sensors located in the southern California area. The results provide quantitative insight into the causative relationship between a sedimentary basin shape and the generation of Rayleigh waves at depth, surface waves at the free surface, scattered seismic energy, and the sensitivity of building responses to each of these.

Characterization of Infrastructure Materials using Nonlinear Ultrasonics

NASA Astrophysics Data System (ADS)

Liu, Minghe

In order to improve the safety, reliability, cost, and performance of civil and mechanical structures/components, it is necessary to develop techniques that are capable of characterizing and quantifying the amount of distributed damage in engineering materials before any detectable discontinuities (cracks, delaminations, voids, etc.) appear. In this dissertation, novel nonlinear ultrasonic NDE methods are developed and applied to characterize cumulative damage such as fatigue damage in metallic materials and degradation of cement-based materials due to chemical reactions. First, nonlinear Rayleigh surface waves are used to measure the near-surface residual stresses in shot-peened aluminum alloy (AA 7075) samples. Results show that the nonlinear Rayleigh wave is very sensitive to near-surface residual stresses, and has the potential to quantitatively detect them. Second, a novel two-wave mixing method is theoretically developed and numerically verified. This method is then successfully applied to detect the fatigue damage in aluminum alloy (AA 6061) samples subjected to monotonic compression. In addition to its high sensitivity to fatigue damage, this collinear wave mixing method allows the measurement over a specific region of interest in the specimen, and this capability makes it possible to obtain spatial distribution of fatigue damage through the thickness direction of the sample by simply timing the transducers. Third, the nonlinear wave mixing method is used to characterize the degradation of cement-based materials caused by alkali-silica reaction (ASR). It is found that the nonlinear ultrasonic method is sensitive to detect ASR damage at very early stage, and has the potential to identify the different damage stages. Finally, a micromechanics-based chemo-mechanical model is developed which relates the acoustic nonlinearity parameter to ASR damage. This model provides a way to quantitatively predict the changes in the acoustic nonlinearity parameter due to ASR damage, which can be used to guide experimental measurements for nondestructive evaluation of ASR damage.

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

NASA Astrophysics Data System (ADS)

Syracuse, E. M.; Zhang, H.; Maceira, M.

2017-10-01

We present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body wave first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region. Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. Without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.

VLP seismicity from resonant modes of acoustic-gravity waves in a conduit-crack system filled with multiphase magma

NASA Astrophysics Data System (ADS)

Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.

2016-12-01

Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) seismic signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP seismicity using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack system filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing system, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack system that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous boundary layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes from seismic observations of VLP events.

Seismic tomography of northeastern Tibetan Plateau from body wave arrival times and surface wave dispersion data

NASA Astrophysics Data System (ADS)

Fang, H.; Yao, H.; Zhang, H.

2017-12-01

Reliable crustal and upper mantle structure is important to understand expansion of material from the Tibetan plateau to its northeastern margin. Previous studies have used either ambient noise tomography or body wave traveltime tomography to obtain the crustal velocity models in northeastern Tibetan Plateau. However, clear differences appear in these models obtained using different datasets. Here we propose to jointly invert local and teleseismic body wave arrival times and surface wave dispersion data from ambient noise cross correlation to obtain a unified P and S wavespeed model of the crust and upper mantle in NE Tibetan Plateau. Following Fang et al. (2016), we adopt the direct inversion strategy for surface wave data (Fang et al., 2015), which eliminates the need to construct the phase/group velocity maps and allows the straightforward incorporation of surface wave dispersion data into the body wave inversion framework. For body wave data including both local and teleseismic arrival times, we use the fast marching method (Rawlinson et al., 2004) in order to trace multiple seismic phases simultaneously. The joint inversion method takes advantage of the complementary strengths of different data types, with local body wave data constraining more on the P than S wavespeed in the crust, surface wave data most sensitive to S wavespeed in the crust and upper mantle, teleseismic body wave data resolving the upper mantle structure. A series of synthetic tests will be used to show the robustness and superiority of the joint inversion method. Besides, the inverted model will be validated by waveform simulation and comparison with other studies, like receiver function imaging. The resultant P and S wavespeed models, as well as the derived Vp/Vs model, will be essential to understand the regional tectonics of the northeastern Tibetan Plateau, and to address the related geodynamic questions of the Tibetan Plateau formation and expansion.

All-optical photoacoustic microscopy (AOPAM) system for remote characterization of biological tissues

NASA Astrophysics Data System (ADS)

Sampathkumar, Ashwin; Chitnis, Parag V.; Silverman, Ronald H.

2014-03-01

Conventional photoacoustic microscopy (PAM) employs light pulses to produce a photoacoustic (PA) effect and detects the resulting acoustic waves using an ultrasound transducer acoustically coupled to the target. The resolution of conventional PAM is limited by the sensitivity and bandwidth of the ultrasound transducer. We investigated a versatile, all-optical PAM (AOPAM) system for characterizing in vivo as well as ex vivo biological specimens. The system employs non-contact interferometric detection of PA signals that overcomes limitations of conventional PAM. A 532-nm pump laser with a pulse duration of 5 ns excites the PA effect in tissue. Resulting acoustic waves produce surface displacements that are sensed using a 532-nm continuous-wave (CW) probe laser in a Michelson interferometer with a 1- GHz bandwidth. The pump and probe beams are coaxially focused using a 50X objective giving a diffraction-limited spot size of 0.48 μm. The phase-encoded probe beam is demodulated using homodyne methods. The detected timedomain signal is time reversed using k-space wave-propagation methods to produce a spatial distribution of PA sources in the target tissue. A minimum surface-displacement sensitivity of 0.19 pm was measured. PA-induced surface displacements are very small; therefore, they impose stringent detection requirements and determine the feasibility of implementing an all-optical PAM in biomedical applications. 3D PA images of ex vivo porcine retina specimens were generated successfully. We believe the AOPAM system potentially is well suited for assessing retinal diseases and other near-surface biomedical applications such as sectionless histology and evaluation of skin burns and pressure or friction ulcers.

Development of a high-sensitivity strain measurement system based on a SH SAW sensor

NASA Astrophysics Data System (ADS)

Oh, Haekwan; Lee, Keekeun; Eun, Kyoungtae; Choa, Sung-Hoon; Yang, Sang Sik

2012-02-01

A strain measurement system based on a shear horizontal surface acoustic wave (SH SAW) was developed. The developed system is composed of a SAW microsensor, a printed circuit board (PCB), an adhesive and a strain gauge. When a compression force is applied to the PCB by the strain gauge, the PCB is bent so that external strain energy can be evenly delivered to the microsensor without any detachment of the sensor from the board. When a stretching force is applied to the PCB under the condition that one side of the PCB is fixed and the other side is modulated, the actual length of the SAW delay line between the two interdigital transducers (IDTs) is increased. The increase in the delay line length causes a change in the time for the propagating SAW to reach the output IDT. If strain energy is applied to the piezoelectric substrate, the substrate density is changed, which then changes the propagation velocity of the SAW. Coupling-of-modes modeling was conducted prior to fabrication to determine the optimal device parameters. Depending on the strain, the frequency difference was linearly modulated. The obtained sensitivity for stretching was 17.3 kHz/% for the SH wave mode and split electrode. And the obtained sensitivity for bending was 46.1 kHz/% for the SH wave mode and split electrode. The SH wave showed about 15% higher sensitivity than the Rayleigh wave, and the dog-bone PCB showed about 8% higher sensitivity than the rectangular PCB. The obtained sensitivity was about five times higher than that of existing SAW-based strain sensors.

Joint Inversion of Body-Wave Arrival Times and Surface-Wave Dispersion Data in the Wavelet Domain Constrained by Sparsity Regularization

NASA Astrophysics Data System (ADS)

Zhang, H.; Fang, H.; Yao, H.; Maceira, M.; van der Hilst, R. D.

2014-12-01

Recently, Zhang et al. (2014, Pure and Appiled Geophysics) have developed a joint inversion code incorporating body-wave arrival times and surface-wave dispersion data. The joint inversion code was based on the regional-scale version of the double-difference tomography algorithm tomoDD. The surface-wave inversion part uses the propagator matrix solver in the algorithm DISPER80 (Saito, 1988) for forward calculation of dispersion curves from layered velocity models and the related sensitivities. The application of the joint inversion code to the SAFOD site in central California shows that the fault structure is better imaged in the new model, which is able to fit both the body-wave and surface-wave observations adequately. Here we present a new joint inversion method that solves the model in the wavelet domain constrained by sparsity regularization. Compared to the previous method, it has the following advantages: (1) The method is both data- and model-adaptive. For the velocity model, it can be represented by different wavelet coefficients at different scales, which are generally sparse. By constraining the model wavelet coefficients to be sparse, the inversion in the wavelet domain can inherently adapt to the data distribution so that the model has higher spatial resolution in the good data coverage zone. Fang and Zhang (2014, Geophysical Journal International) have showed the superior performance of the wavelet-based double-difference seismic tomography method compared to the conventional method. (2) For the surface wave inversion, the joint inversion code takes advantage of the recent development of direct inversion of surface wave dispersion data for 3-D variations of shear wave velocity without the intermediate step of phase or group velocity maps (Fang et al., 2014, Geophysical Journal International). A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. We will test the new joint inversion code at the SAFOD site to compare its performance over the previous code. We will also select another fault zone such as the San Jacinto Fault Zone to better image its structure.

Modal content based damage indicators and phased array transducers for structural health monitoring of aircraft structures using ultrasonic guided waves

NASA Astrophysics Data System (ADS)

Ren, Baiyang

Composite materials, especially carbon fiber reinforced polymers (CFRP), have been widely used in the aircraft industry because of their high specific strength and stiffness, resistance to corrosion and good fatigue life. Due to their highly anisotropic material properties and laminated structures, joining methods like bolting and riveting are no longer appropriate for joining CFRP since they initiate defects during the assembly and severely compromise the integrity of the structure; thus new techniques for joining CFRP are highly demanded. Adhesive bonding is a promising method because it relieves stress concentration, reduces weight and provides smooth surfaces. Additionally, it is a low-cost alternative to the co-cured method which is currently used to manufacture components of aircraft fuselage. Adhesive defects, disbonds at the interface between adherend and adhesive layer, are focused on in this thesis because they can be initialized by either poor surface preparation during the manufacturing or fatigue loads during service. Aircraft need structural health monitoring (SHM) systems to increase safety and reduce loss, and adhesive bonds usually represent the hotspots of the assembled structure. There are many nondestructive evaluation (NDE) methods for bond inspection. However, these methods cannot be readily integrated into an SHM system because of the bulk size and weight of the equipment and requirement of accessibility to one side of the bonded joint. The first objective of this work is to develop instruments, actuators, sensors and a data acquisition system for SHM of bond lines using ultrasonic guided waves which are well known to be able to cover large volume of the structure and inaccessible regions. Different from widely used guided wave sensors like PZT disks, the new actuators, piezoelectric fiber composite (PFC) phased array transducers0 (PAT), can control the modal content of the excited waves and the new sensors, polyvinylidene fluoride (PVDF) arrays, which can extract modal information from the received waves. Also, the PATs and array sensors have broad frequency bandwidth and can easily excite and receive high order guided wave modes which are not possible using PZT disks. Currently, many guided wave SHM techniques employ the fundamental guided wave modes below the first cut-off frequency because of their low dispersion in this frequency range. Such a practice ignores the possibility of using higher order modes which sometimes have much better sensitivity to defects. A frequency domain finite element model is created in this work to study the behavior of the interaction between guided waves and a disbond. The sensitivities of modes are classified into three levels, namely, good sensitivity, intermediate sensitivity and no sensitivity. The novel damage indicators, wave modal amplitude and wave modal composition, are proposed to increase the sensitivity to disbonds. The effects of environmental operational conditions (EOC) are presenting great challenges to reliable SHM practice because they may influence the wave amplitude and time of flight. The use of fundamental modes shows poor sensitivity to the disbond; but the use of higher order modes shows good sensitivity. The experiments demonstrate that the new damage indicators have excellent sensitivity to disbonds even with elevated temperatures and have the capability to characterize the size of a disbond. Additionally, the detection of other types of defects like notches on aluminum plates and disbonds in adhesively bonded aluminum plate are also demonstrated using the proposed damage indicators. The use of the new damage indicators for SHM applications relies on the capability of resolving the modal content of wave signals which is enabled only by using PFC PATs and polyvinylidene fluoride (PVDF) array sensors.

Effect of wave-current interaction on wind-driven circulation in narrow, shallow embayments

USGS Publications Warehouse

Signell, Richard P.; Beardsley, Robert C.; Graber, H. C.; Capotondi, A.

1990-01-01

The effect of wind waves on the steady wind-driven circulation in a narrow, shallow bay is investigated with a two-dimensional (y, z) circulation model and the Grant and Madsen [1979] bottom-boundary layer model, which includes wave-current interaction. A constant wind stress is applied in the along-channel x direction to a channel with a constant cross-sectional profile h(y). The wind-induced flushing of shallow bays is shown to be sensitive to both the shape of the cross section and the effects of surface waves. The flushing increases with increasing , where h′ is the standard deviation of cross-channel depth and  is the mean depth. This is consistent with the findings of Hearn et al. [1987]. The flushing decreases, however, with the inclusion of surface wave effects which act to increase the bottom drag felt by the currents. Increasing effective bottom friction reduces the strength of the circulation, while the along-bay surface slope, bottom stress and the structure of current profiles remain nearly unchanged. An implication of the circulation dependence on wave-current interaction is that low-frequency oscillatory winds may drive a mean circulation when the wave field changes with wind direction.x

Interactions between self-assembled monolayers and an organophosphonate: A detailed study using surface acoustic wave-based mass analysis, polarization modulation-FTIR spectroscopy, and ellipsometry

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

Crooks, R.M.; Yang, H.C.; McEllistrem, L.J.

Self-assembled monolayers (SAMs) having surfaces terminated in the following functional groups: -CH{sub 3}, -OH, -COOH, and (COO{sup -}){sub 2}Cu{sup 2+} (MUA-Cu{sup 2+}) have been prepared and examined as potential chemically sensitive interfaces. Mass measurements made using surface acoustic wave (SAW) devices indicate that these surfaces display different degrees of selectivity and sensitivity to a range of analytes. The response of the MUA-Cu{sup 2+} SAM to the nerve-agent simulant diisopropyl methylphosphonate (DIMP) is particularly intriguing. Exposure of this surface to 50%-of-saturation DIMP yields a surface concentration equivalent to about 20 DIMP monolayers. Such a high surface concentration in equilibrium with amore » much lower-than-saturation vapor pressure has not previously been observed. Newly developed analytical tools have made it possible to measure the infrared spectrum of the chemically receptive surface during analyte dosing. Coupled with in-situ SAW/ellipsometry measurements, which permit simultaneous measurement of mass and thickness with nanogram and Angstrom resolution, respectively, it has been possibly to develop a model for the surface chemistry leading to the unusual behavior of this system. The results indicate that DIMP interacts strongly with surface-confined Cu{sup 2+} adduct that nucleates growth of semi-ordered crystallites having substantially lower vapor pressure than the liquid.« less

Proposed Ultra-High Sensitivity High-Frequency Gravitational Wave Detector

NASA Astrophysics Data System (ADS)

Baker, Robert M. L.; Stephenson, Gary V.; Li, Fangyu

2008-01-01

The paper discusses the proposed improvement of a High-Frequency Relic Gravitational Wave (HFRGW) detector designed by Li, Baker, Fang, Stephenson and Chen in order to greatly improve its sensitivity. The improved detector is inspired by the Laser Interferometer Gravitational Observatory or LIGO, but is sensitive to the high-frequency end of the gravitational-wave spectrum. As described in prior papers it utilizes the Gertsenshtein effect, which introduces the conversion of gravitational waves to electromagnetic (EM) waves in the presence of a static magnetic field. Such a conversion, if it leads to photons moving in a direction perpendicular to the plane of the EM waves and the magnetic field, will allow for ultra-high sensitivity HFRGW detection. The use of sensitive microwave, single photon detectors such as a circuit QED and/or the Rydberg Atom Cavity Detector, or off-the-shelf detectors, could lead to such detection. When the EM-detection photons are focused at the microwave detectors by fractal-membrane reflectors sensitivity is also improved. Noise sources external to the HFRGW detector will be eliminated by placing a tight mosaic of superconducting tiles (e.g., YBCO) and/or fractal membranes on the interior surface of the detector's cryogenic containment vessel in order to provide a perfect Faraday cage. Internal thermal noise will be eliminated by means of a microwave absorbing (or reflecting) interior enclosure shaped to conform to a high-intensity continuous microwave Gaussian beam (GB), will reduce any background photon flux (BPF) noise radiated normal to the GB's axis. Such BPF will be further attenuated by a series of microwave absorbing baffles forming tunnels to the sensitive microwave detectors on each side of the GB and at right angles to the static magnetic field. A HFGW detector of bandwidth of 1 KHz to 10 KHz or less in the GHz band has been selected. It is concluded that the utilization of the new ultra-high-sensitivity microwave detectors, together with the increased microwave power and magnet intensity will allow for a detection of high-frequency gravitational waves (HFGWs) exhibiting amplitudes, A, of the time-varying spacetime strains on the order of 10-30 to 10-34.

Sensitivity analysis of seismic waveforms to upper-mantle discontinuities using the adjoint method

NASA Astrophysics Data System (ADS)

Koroni, Maria; Bozdağ, Ebru; Paulssen, Hanneke; Trampert, Jeannot

2017-09-01

Using spectral-element simulations of wave propagation, we investigated the sensitivity of seismic waveforms, recorded on transverse components, to upper-mantle discontinuities in 1-D and 3-D background models. These sensitivity kernels, or Fréchet derivatives, illustrate the spatial sensitivity to model parameters, of which those for shear wave speed and the surface topography of internal boundaries are discussed in this paper. We focus on the boundaries at 400 and 670 km depth of the mantle transition zone. SS precursors have frequently been used to infer the topography of upper-mantle discontinuities. These seismic phases are underside reflections off these boundaries and are usually analysed in the distance range of 110°-160°. This distance range is chosen to minimize the interference from other waves. We show sensitivity kernels for consecutive time windows at three characteristic epicentral distances within the 110°-160° range. The sensitivity kernels are computed with the adjoint method using synthetic data. From our simulations we can draw three main conclusions: (i) The exact Fréchet derivatives show that in all time windows, and also in those centred on the SS precursors, there is interference from other waves. This explains the difficulty reported in the literature to correct for 3-D shear wave speed perturbations, even if the 3-D structure is perfectly known. (ii) All studies attempting to map the topography of the 400 and 670 km discontinuities to date assume that the traveltimes of SS precursors can be linearly decomposed into a 3-D elastic structure and a topography part. We recently showed that such a linear decomposition is not possible for SS precursors, and the sensitivity kernels presented in this paper explain why. (iii) In agreement with previous work, we show that other parts of the seismograms have greater sensitivity to upper-mantle discontinuities than SS precursors, especially multiply bouncing S waves exploiting the S-wave triplications due to the mantle transition zone. These phases can potentially improve the inference of global topographic variations of the upper-mantle discontinuities in the context of full waveform inversion in a joint inversion for (an)elastic parameters and topography.

Development of a satellite SAR image spectra and altimeter wave height data assimilation system for ERS-1

NASA Technical Reports Server (NTRS)

Hasselmann, Klaus; Hasselmann, Susanne; Bauer, Eva; Bruening, Claus; Lehner, Susanne; Graber, Hans; Lionello, Piero

1988-01-01

The applicability of ERS-1 wind and wave data for wave models was studied using the WAM third generation wave model and SEASAT altimeter, scatterometer and SAR data. A series of global wave hindcasts is made for the surface stress and surface wind fields by assimilation of scatterometer data for the full 96-day SEASAT and also for two wind field analyses for shorter periods by assimilation with the higher resolution ECMWF T63 model and by subjective analysis methods. It is found that wave models respond very sensitively to inconsistencies in wind field analyses and therefore provide a valuable data validation tool. Comparisons between SEASAT SAR image spectra and theoretical SAR spectra derived from the hindcast wave spectra by Monte Carlo simulations yield good overall agreement for 32 cases representing a wide variety of wave conditions. It is concluded that SAR wave imaging is sufficiently well understood to apply SAR image spectra with confidence for wave studies if supported by realistic wave models and theoretical computations of the strongly nonlinear mapping of the wave spectrum into the SAR image spectrum. A closed nonlinear integral expression for this spectral mapping relation is derived which avoids the inherent statistical errors of Monte Carlo computations and may prove to be more efficient numerically.

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

NASA Astrophysics Data System (ADS)

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

2016-07-01

A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

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

Ambroziński, Łukasz; AGH University of Science and Technology, Krakow 30059; Pelivanov, Ivan, E-mail: ivanp3@uw.edu

A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking softmore » biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.« less

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

Haker, C.D.; Rix, G.J.; Lai, C.G.

The seismic stability of municipal solid waste (MSW) landfills is often a significant consideration in landfill design. However, until recently, the dynamic properties of the waste material itself, which govern the seismic response of MSW landfills, have often been approximated or assumed. Tests to determine the dynamic properties of the material directly have been limited. Measurements of seismic surface waves were used to determine the dynamic properties of MSW, which are the initial tangent shear modulus and low-strain hysteretic damping ratio. Surface wave tests were performed at three MSW landfills to determine their shear modulus and damping ratio profiles. Surfacemore » wave tests are ideal for measuring the near-surface shear modulus and damping profiles of MSW landfills because the tests are non-invasive, an advantage for testing environmentally sensitive waste material. Factors which influence the dynamic properties of waste including density, confinement, age, and placement techniques are used to interpret the measured shear modulus and damping ratio profiles.« less

Interfaces and thin films as seen by bound electromagnetic waves.

PubMed

Knoll, W

1998-01-01

This contribution summarizes the use of plasmon surface polaritons and guided optical waves for the characterization of interfaces and thin organic films. After a short introduction to the theoretical background of evanescent wave optics, examples are given that show how this interfacial "light" can be employed to monitor thin coatings at a solid/air or solid/liquid interface. Examples are given for a very sensitive thickness determination of samples ranging from self-assembled monolayers, to multilayer assemblies prepared by the Langmuir/Blodgett/Kuhn technique or by the alternate polyelectrolyte deposition. These are complemented by the demonstration of the potential of the technique to also monitor time-dependent processes in a kinetic mode. Here, we put an emphasis on the combination set-up of surface plasmon optics with electrochemical techniques, allowing for the on-line characterization of various surface functionalization strategies, e.g. for (bio-) sensor purposes.

Long-Wavelength Elastic Wave Propagation Across Naturally Fractured Rock Masses

NASA Astrophysics Data System (ADS)

Mohd-Nordin, Mohd Mustaqim; Song, Ki-Il; Cho, Gye-Chun; Mohamed, Zainab

2014-03-01

Geophysical site investigation techniques based on elastic waves have been widely used to characterize rock masses. However, characterizing jointed rock masses by using such techniques remains challenging because of a lack of knowledge about elastic wave propagation in multi-jointed rock masses. In this paper, the roughness of naturally fractured rock joint surfaces is estimated by using a three-dimensional (3D) image-processing technique. The classification of the joint roughness coefficient (JRC) is enhanced by introducing the scan line technique. The peak-to-valley height is selected as a key indicator for JRC classification. Long-wavelength P-wave and torsional S-wave propagation across rock masses containing naturally fractured joints are simulated through the quasi-static resonant column (QSRC) test. In general, as the JRC increases, the S-wave velocity increases within the range of stress levels considered in this paper, whereas the P-wave velocity and the damping ratio of the shear wave decrease. In particular, the two-dimensional joint specimen underestimates the S-wave velocity while overestimating the P-wave velocity. This suggests that 3D joint surfaces should be implicated to obtain the reliable elastic wave velocity in jointed rock masses. The contact characteristic and degree of roughness and waviness of the joint surface are identified as a factor influencing P-wave and S-wave propagation in multi-jointed rock masses. The results indicate a need for a better understanding of the sensitivity of contact area alterations to the elastic wave velocity induced by changes in normal stress. This paper's framework can be a reference for future research on elastic wave propagation in naturally multi-jointed rock masses.

Deep-Focusing Time-Distance Helioseismology

NASA Technical Reports Server (NTRS)

Duvall, T. L., Jr.; Jensen, J. M.; Kosovichev, A. G.; Birch, A. C.; Fisher, Richard R. (Technical Monitor)

2001-01-01

Much progress has been made by measuring the travel times of solar acoustic waves from a central surface location to points at equal arc distance away. Depth information is obtained from the range of arc distances examined, with the larger distances revealing the deeper layers. This method we will call surface-focusing, as the common point, or focus, is at the surface. To obtain a clearer picture of the subsurface region, it would, no doubt, be better to focus on points below the surface. Our first attempt to do this used the ray theory to pick surface location pairs that would focus on a particular subsurface point. This is not the ideal procedure, as Born approximation kernels suggest that this focus should have zero sensitivity to sound speed inhomogeneities. However, the sensitivity is concentrated below the surface in a much better way than the old surface-focusing method, and so we expect the deep-focusing method to be more sensitive. A large sunspot group was studied by both methods. Inversions based on both methods will be compared.

Impact of density information on Rayleigh surface wave inversion results

NASA Astrophysics Data System (ADS)

Ivanov, Julian; Tsoflias, Georgios; Miller, Richard D.; Peterie, Shelby; Morton, Sarah; Xia, Jianghai

2016-12-01

We assessed the impact of density on the estimation of inverted shear-wave velocity (Vs) using the multi-channel analysis of surface waves (MASW) method. We considered the forward modeling theory, evaluated model sensitivity, and tested the effect of density information on the inversion of seismic data acquired in the Arctic. Theoretical review, numerical modeling and inversion of modeled and real data indicated that the density ratios between layers, not the actual density values, impact the determination of surface-wave phase velocities. Application on real data compared surface-wave inversion results using: a) constant density, the most common approach in practice, b) indirect density estimates derived from refraction compressional-wave velocity observations, and c) from direct density measurements in a borehole. The use of indirect density estimates reduced the final shear-wave velocity (Vs) results typically by 6-7% and the use of densities from a borehole reduced the final Vs estimates by 10-11% compared to those from assumed constant density. In addition to the improved absolute Vs accuracy, the resulting overall Vs changes were unevenly distributed laterally when viewed on a 2-D section leading to an overall Vs model structure that was more representative of the subsurface environment. It was observed that the use of constant density instead of increasing density with depth not only can lead to Vs overestimation but it can also create inaccurate model structures, such as a low-velocity layer. Thus, optimal Vs estimations can be best achieved using field estimates of subsurface density ratios.

Ultrasonic infrared thermal wave nondestructive evaluation for crack detection of several aerospace materials

NASA Astrophysics Data System (ADS)

Xu, Weichao; Shen, Jingling; Zhang, Cunlin; Tao, Ning; Feng, Lichun

2008-03-01

The applications of ultrasonic infrared thermal wave nondestructive evaluation for crack detection of several materials, which often used in aviation alloy. For instance, steel and carbon fiber. It is difficult to test cracks interfacial or vertical with structure's surface by the traditional nondestructive testing methods. Ultrasonic infrared thermal wave nondestructive testing technology uses high-power and low-frequency ultrasonic as heat source to excite the sample and an infrared video camera as a detector to detect the surface temperature. The ultrasonic emitter launch pulses of ultrasonic into the skin of the sample, which causes the crack interfaces to rub and dissipate energy as heat, and then caused local increase in temperature at one of the specimen surfaces. The infrared camera images the returning thermal wave reflections from subsurface cracks. A computer collects and processes the thermal images according to different properties of samples to get the satisfied effect. In this paper, a steel plate with fatigue crack we designed and a juncture of carbon fiber composite that has been used in a space probe were tested and get satisfying results. The ultrasonic infrared thermal wave nondestructive detection is fast, sensitive for cracks, especially cracks that vertical with structure's surface. It is significative for nondestructive testing in manufacture produce and application of aviation, cosmography and optoelectronics.

A high figure of merit localized surface plasmon sensor based on a gold nanograting on the top of a gold planar film

NASA Astrophysics Data System (ADS)

Zhang, Zu-Yin; Wang, Li-Na; Hu, Hai-Feng; Li, Kang-Wen; Ma, Xun-Peng; Song, Guo-Feng

2013-10-01

We investigate the sensitivity and figure of merit (FOM) of a localized surface plasmon (LSP) sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon sensor is 317 nm/RIU, and the FOM is predicted to be above 8, which is very high for a localized surface plasmon sensor. By employing the rigorous coupled-wave analysis (RCWA) method, we analyze the distribution of the magnetic field and find that the sensing property of our proposed system is attributed to the interactions between the localized surface plasmon around the gold nanostrips and the surface plasmon polarition on the surface of the gold planar metallic film. These findings are important for developing high FOM localized surface plasmon sensors.

Field test investigation of high sensitivity fiber optic seismic geophone

NASA Astrophysics Data System (ADS)

Wang, Meng; Min, Li; Zhang, Xiaolei; Zhang, Faxiang; Sun, Zhihui; Li, Shujuan; Wang, Chang; Zhao, Zhong; Hao, Guanghu

2017-10-01

Seismic reflection, whose measured signal is the artificial seismic waves ,is the most effective method and widely used in the geophysical prospecting. And this method can be used for exploration of oil, gas and coal. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of geophones at the surface. Compared to traditional geophones such as electric, magnetic, mechanical and gas geophone, optical fiber geophones have many advantages. Optical fiber geophones can achieve sensing and signal transmission simultaneously. With the development of fiber grating sensor technology, fiber bragg grating (FBG) is being applied in seismic exploration and draws more and more attention to its advantage of anti-electromagnetic interference, high sensitivity and insensitivity to meteorological conditions. In this paper, we designed a high sensitivity geophone and tested its sensitivity, based on the theory of FBG sensing. The frequency response range is from 10 Hz to 100 Hz and the acceleration of the fiber optic seismic geophone is over 1000pm/g. sixteen-element fiber optic seismic geophone array system is presented and the field test is performed in Shengli oilfield of China. The field test shows that: (1) the fiber optic seismic geophone has a higher sensitivity than the traditional geophone between 1-100 Hz;(2) The low frequency reflection wave continuity of fiber Bragg grating geophone is better.

A Robust Definition for the Turbulent Langmuir Number

NASA Astrophysics Data System (ADS)

Christensen, K. H.; Breivik, O.; Sutherland, G.; Belcher, S. E.; Gargett, A.

2016-02-01

The turbulent Langmuir number combines the water side friction velocity and the surface value of the Stokes drift, and is central to parameterizations of mixing by Langmuir turbulence. Making a direct comparison between such parameterizations and observations is difficult since the surface Stokes drift is sensitive to both the spectral tail and the directional spread of the waves. We propose a new definition for the turbulent Langmuir number based on low order moments of the one-dimensional frequency spectrum, hence eliminating most of the uncertainties associated with the diagnostic spectral tail. Comparison is made between the old and the new definitions using both observed and modeled wave spectra. The new definition has a higher variation around the mean and is better at resolving typical oceanic conditions. In addition, it is backwards compatible with the old definition for monochromatic waves, which means that scalings based on large eddy simulations with monochromatic wave forcing are still valid.

The sea surface currents as a potential factor in the estimation and monitoring of wave energy potential

NASA Astrophysics Data System (ADS)

Zodiatis, George; Galanis, George; Nikolaidis, Andreas; Stylianoy, Stavros; Liakatas, Aristotelis

2015-04-01

The use of wave energy as an alternative renewable is receiving attention the last years under the shadow of the economic crisis in Europe and in the light of the promising corresponding potential especially for countries with extended coastline. Monitoring and studying the corresponding resources is further supported by a number of critical advantages of wave energy compared to other renewable forms, like the reduced variability and the easier adaptation to the general grid, especially when is jointly approached with wind power. Within the framework, a number of countries worldwide have launched research and development projects and a significant number of corresponding studies have been presented the last decades. However, in most of them the impact of wave-sea surface currents interaction on the wave energy potential has not been taken into account neglecting in this way a factor of potential importance. The present work aims at filling this gap for a sea area with increased scientific and economic interest, the Eastern Mediterranean Sea. Based on a combination of high resolution numerical modeling approach with advanced statistical tools, a detailed analysis is proposed for the quantification of the impact of sea surface currents, which produced from downscaling the MyOcean-FO regional data, to wave energy potential. The results although spatially sensitive, as expected, prove beyond any doubt that the wave- sea surface currents interaction should be taken into account for similar resource analysis and site selection approaches since the percentage of impact to the available wave power may reach or even exceed 20% at selected areas.

Shock-wave propagation and cavitation bubble oscillation by Nd:YAG laser ablation of a metal in water.

PubMed

Chen, Xiao; Xu, Rong-Qing; Chen, Jian-Ping; Shen, Zhong-Hua; Jian, Lu; Ni, Xiao-Wu

2004-06-01

A highly sensitive fiber-optic sensor based on optical beam deflection is applied for investigating the propagation of a laser-induced plasma shock wave, the oscillation of a cavitation bubble diameter, and the development of a bubble-collapse-induced shock wave when a Nd:YAG laser pulse is focused upon an aluminum surface in water. By the sequence of experimental waveforms detected at different distances, the attenuation properties of the plasma shock wave and of the bubble-collapse-induced shock wave are obtained. Besides, based on characteristic signals, both the maximum and the minimum bubble radii at each oscillation cycle are determined, as are the corresponding oscillating periods.

Method and apparatus for monitoring and measuring the surface tension of a fluid using fiber optics

DOEpatents

Abraham, Bernard M.; Ketterson, John B.; Bohanon, Thomas M.; Mikrut, John M.

1994-01-01

A non-contact method and apparatus for measuring and monitoring the surface of a fluid using fiber optics and interferometric detection to permit measurement mechanical characteristics' fluid surfaces. The apparatus employs an alternating electric field gradient for generating a capillary wave on the surface of the fluid. A fiber optic coupler and optical fiber directs a portion of a laser beam onto the surface of the fluid, another portion of the laser beam onto the photo sensor, and directs light reflected from the surface of the fluid onto the photo sensor. The output of the photo sensor is processed and coupled to a phase sensitive detector to permit measurement of phase shift between the drive signal creating the capillary wave and the detected signal. This phase shift information is then used to determine mechanical properties of the fluid surface such as surface tension, surface elasticity, and surface inhomogeneity. The resulting test structure is easily made compact, portable, and easy to align and use.

Enhanced Sensitivity of a Surface Acoustic Wave Gyroscope

NASA Astrophysics Data System (ADS)

Zhang, Yanhua; Wang, Wen

2009-10-01

In this paper, we present an optimal design and performance evaluation of a surface acoustic wave (SAW) gyroscope. It consists of a two-port SAW resonator (SAWR) and a SAW sensor (SAWS) structured using a delay line pattern. The SAW resonator provides a stable reference vibration and creates a standing wave, and the vibrating metallic dot array at antinodes of the standing wave induces the second SAW in the normal direction by the Coriolis force, and the SAW sensor is used to detect the secondary SAW. By using the coupling of modes (COM), the SAW resonator was simulated, and the effects of the design parameters on the frequency response of the device were investigated. Also, a theoretical analysis was performed to investigate the effect of metallic dots on the frequency response of the SAW device. The measured frequency response S21 of the fabricated 80 MHz two-port SAW resonator agrees well with the simulated result, that is, a low insertion loss (˜5 dB) and a single steep resonance peak were observed. In the gyroscopic experiments using a rate table, optimal metallic dot thickness was determined, and the sensitivity of the fabricated SAW gyroscope with an optimal metallic dot thickness of ˜350 nm was determined to be 3.2 µV deg-1 s-1.

Enhanced Sensitivity of Novel Surface Acoustic Wave Microelectromechanical System-Interdigital Transducer Gyroscope

NASA Astrophysics Data System (ADS)

Wang, Wen; Oh, Haekwan; Lee, Keekeun; Yoon, Sungjin; Yang, Sangsik

2009-06-01

In this paper, we present a novel microelectromechanical system-interdigital transducer (MEMS-IDT) surface acoustic wave (SAW) gyroscope with an 80 MHz central frequency on a 128° YX LiNbO3 wafer. The developed MEMS-IDT gyroscope is composed of a two-port SAW resonator, a dual delay line oscillator, and metallic dots. The SAW resonator provides a stable standing wave, and the vibrating metallic dot at an antinode of the standing wave induces the second SAW in the normal direction of its vibrating axis. The dual delay line oscillator detects the Coriolis force by comparing the resonant frequencies between two oscillators through the interference effect. The coupling of mode (COM) modeling was used to extract the optimal design parameters prior to fabrication. In the electrical testing by the network analyzer, the fabricated SAW resonator and delay lines showed low insertion loss and similar operation frequencies between a resonator and delay lines. When the device was rotated, the resonant frequency differences between two oscillators linearly varied owing to the Coriolis force. The obtained sensitivity was approximately 119 Hz deg-1 s-1 in the angular rate range of 0-1000 deg/s. Satisfactory linearity and superior directivity were also observed in the test.

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.

Scattering-Type Surface-Plasmon-Resonance Biosensors

NASA Technical Reports Server (NTRS)

Wang, Yu; Pain, Bedabrata; Cunningham, Thomas; Seshadri, Suresh

2005-01-01

Biosensors of a proposed type would exploit scattering of light by surface plasmon resonance (SPR). Related prior biosensors exploit absorption of light by SPR. Relative to the prior SPR biosensors, the proposed SPR biosensors would offer greater sensitivity in some cases, enough sensitivity to detect bioparticles having dimensions as small as nanometers. A surface plasmon wave can be described as a light-induced collective oscillation in electron density at the interface between a metal and a dielectric. At SPR, most incident photons are either absorbed or scattered at the metal/dielectric interface and, consequently, reflected light is greatly attenuated. The resonance wavelength and angle of incidence depend upon the permittivities of the metal and dielectric. An SPR sensor of the type most widely used heretofore includes a gold film coated with a ligand a substance that binds analyte molecules. The gold film is thin enough to support evanescent-wave coupling through its thickness. The change in the effective index of refraction at the surface, and thus the change in the SPR response, increases with the number of bound analyte molecules. The device is illuminated at a fixed wavelength, and the intensity of light reflected from the gold surface opposite the ligand-coated surface is measured as a function of the angle of incidence. From these measurements, the angle of minimum reflection intensity is determined

Highly sensitive evanescent wave combination tapered fiber optic fluorosensor for protein detection

NASA Astrophysics Data System (ADS)

Nardone, Vincent; Kapoor, Rakesh

2008-02-01

In this paper we are reporting the development of a highly sensitive evanescent wave combination tapered fiber optic fluorosensor. We have demonstrated detection of 5 pM Bovine Serum Albumin (BSA) protein using these fiber optic sensors. The sensor can be easily adopted for detection of other proteins. Six identical probes were prepared and affinity pure Goat anti-BSA antibodies were immobilized on the probe surface. We could detect signal from all the probes kept in 5 pM to 1 nM BSA solution while no signal was detected from the probes kept in 20 nM labeled ESA solution.

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

DOE PAGES

Syracuse, Ellen Marie; Zhang, Haijiang; Maceira, Monica

2017-07-11

Here, we present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body waves first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region.more » Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. In conclusion, without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.« less

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

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

Syracuse, Ellen Marie; Zhang, Haijiang; Maceira, Monica

Here, we present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body waves first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region.more » Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. In conclusion, without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.« less

Coupled atmosphere-ocean-wave simulations of a storm event over the Gulf of Lion and Balearic Sea

USGS Publications Warehouse

Renault, Lionel; Chiggiato, Jacopo; Warner, John C.; Gomez, Marta; Vizoso, Guillermo; Tintore, Joaquin

2012-01-01

The coastal areas of the North-Western Mediterranean Sea are one of the most challenging places for ocean forecasting. This region is exposed to severe storms events that are of short duration. During these events, significant air-sea interactions, strong winds and large sea-state can have catastrophic consequences in the coastal areas. To investigate these air-sea interactions and the oceanic response to such events, we implemented the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System simulating a severe storm in the Mediterranean Sea that occurred in May 2010. During this event, wind speed reached up to 25 m.s-1 inducing significant sea surface cooling (up to 2°C) over the Gulf of Lion (GoL) and along the storm track, and generating surface waves with a significant height of 6 m. It is shown that the event, associated with a cyclogenesis between the Balearic Islands and the GoL, is relatively well reproduced by the coupled system. A surface heat budget analysis showed that ocean vertical mixing was a major contributor to the cooling tendency along the storm track and in the GoL where turbulent heat fluxes also played an important role. Sensitivity experiments on the ocean-atmosphere coupling suggested that the coupled system is sensitive to the momentum flux parameterization as well as air-sea and air-wave coupling. Comparisons with available atmospheric and oceanic observations showed that the use of the fully coupled system provides the most skillful simulation, illustrating the benefit of using a fully coupled ocean-atmosphere-wave model for the assessment of these storm events.

SAW Humidity Sensor Sensitivity Enhancement via Electrospraying of Silver Nanowires

PubMed Central

Sayar Irani, Farid; Tunaboylu, Bahadir

2016-01-01

In this research, we investigated the influence of the surface coatings of silver nanowires on the sensitivity of surface acoustic wave (SAW) humidity sensors. Silver nanowires, with poly(vinylpyrrolidone) (PVP), which is a hydrophilic capping agent, were chemically synthesized, with an average length of 15 µm and an average diameter of 60 nm. Humidity sensors, with 433 MHz frequency dual-port resonator Rayleigh-SAW devices, were coated by silver nanowires (AgNWs) using the electrospray coating method. It was demonstrated that increasing thickness of coated AgNW on the surfaces of SAW devices results in increased sensitivity. The highest frequency shift (262 kHz) in these SAW devices was obtained with an injection of 0.5 mL of the AgNW solution with a concentration of 0.5 mg/mL at an injection rate of 1 mL/h. It also showed the highest humidity sensitivity among the other prepared SAW devices. PMID:27916870

3D shear wave velocity structure revealed with ambient noise tomography on a DAS array

NASA Astrophysics Data System (ADS)

Zeng, X.; Thurber, C. H.; Wang, H. F.; Fratta, D.

2017-12-01

An 8700-m Distributed Acoustic Sensing (DAS) cable was deployed at Brady's Hot Springs, Nevada in March 2016 in a 1.5 by 0.5 km study area. The layout of the DAS array was designed with a zig-zag geometry to obtain relatively uniform areal and varied angular coverage, providing very dense coverage with a one-meter channel spacing. This array continuously recorded signals of a vibroseis truck, earthquakes, and traffic noise during the 15-day deployment. As shown in a previous study (Zeng et al., 2017), ambient noise tomography can be applied to DAS continuous records to image shear wave velocity structure in the near surface. To avoid effects of the vibroseis truck operation, only continuous data recorded during the nighttime was used to compute noise cross-correlation functions for channel pairs within a given linear segment. The frequency band of whitening was set at 5 to 15 Hz and the length of the cross-correlation time window was set to 60 second. The phase velocities were determined using the multichannel analysis of surface waves (MASW) methodology. The phase velocity dispersion curve was then used to invert for shear wave velocity profiles. A preliminarily velocity model at Brady's Hot Springs (Lawrence Livermore National Laboratory, 2015) was used as the starting model and the sensitivity kernels of Rayleigh wave group and phase velocities were computed with this model. As the sensitivity kernel shows, shear wave velocity in the top 200 m can be constrained with Rayleigh wave group and phase velocities in our frequency band. With the picked phase velocity data, the shear wave velocity structure can be obtained via Occam's inversion (Constable et al., 1987; Lai 1998). Shear wave velocity gradually increases with depth and it is generally faster than the Lawrence Livermore National Laboratory (2015) model. Furthermore, that model has limiting constraints at shallow depth. The strong spatial variation is interpreted to reflect the different sediments and sediment thicknesses in the near surface. Shear wave velocities in the northeast corner of the tested area is high whereas loose soil reduces shear wave velocities in the central part of the tested area. This spatial variation pattern is very similar to the results obtained with the ambient noise tomography using the 238-geophone array used the experiment.

Preliminary Analysis of an Oscillating Surge Wave Energy Converter with Controlled Geometry: Preprint

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

Tom, Nathan; Lawson, Michael; Yu, Yi-Hsiang

The aim of this paper is to present a novel wave energy converter device concept that is being developed at the National Renewable Energy Laboratory. The proposed concept combines an oscillating surge wave energy converter with active control surfaces. These active control surfaces allow for the device geometry to be altered, which leads to changes in the hydrodynamic properties. The device geometry will be controlled on a sea state time scale and combined with wave-to-wave power-take-off control to maximize power capture, increase capacity factor, and reduce design loads. The paper begins with a traditional linear frequency domain analysis of themore » device performance. Performance sensitivity to foil pitch angle, the number of activated foils, and foil cross section geometry is presented to illustrate the current design decisions; however, it is understood from previous studies that modeling of current oscillating wave energy converter designs requires the consideration of nonlinear hydrodynamics and viscous drag forces. In response, a nonlinear model is presented that highlights the shortcomings of the linear frequency domain analysis and increases the precision in predicted performance.« less

Robust laser-based detection of Lamb waves using photo-EMF sensors

NASA Astrophysics Data System (ADS)

Klein, Marvin B.; Bacher, Gerald D.

1998-03-01

Lamb waves are easily generated and detected using laser techniques. It has been shown that both symmetric and antisymmetric modes can be produced, using single-spot and phased array generation. Detection has been demonstrated with Michelson interferometers, but these instruments can not function effectively on rough surfaces. By contrast, the confocal Fabry-Perot interferometer can interrogate rough surfaces, but generally is not practical for operation below 300 kHz. In this paper we will present Lamb wave data on a number of parts using a robust, adaptive receiver based on photo-emf detection. This receiver has useful sensitivity down to at least 100 kHz, can process speckled beams and can be easily configured to measure both out-of-plane and in- plane motion with a single probe beam.

Ambient Noise Tomography at Regional and Local Scales in Southern California using Rayleigh Wave Phase Dispersion and Ellipticity

NASA Astrophysics Data System (ADS)

Berg, E.; Lin, F. C.; Qiu, H.; Wang, Y.; Allam, A. A.; Clayton, R. W.; Ben-Zion, Y.

2017-12-01

Rayleigh waves extracted from cross-correlations of ambient seismic noise have proven useful in imaging the shallow subsurface velocity structure. In contrast to phase velocities, which are sensitive to slightly deeper structure, Rayleigh wave ellipticity (H/V ratios) constrains the uppermost crust. We conduct Rayleigh wave ellipticity and phase dispersion measurements in Southern California between 6 and 18 second periods, computed from multi-component ambient noise cross-correlations using 315 stations across the region in 2015. Because of the complimentary sensitivity of phase velocity and H/V, this method enables simple and accurate resolution of near-surface geological features from the surface to 20km depth. We compare the observed H/V ratios and phase velocities to predictions generated from the current regional models (SCEC UCVM), finding strong correspondence where the near-surface structure is well-resolved by the models. This includes high H/V ratios in the LA Basin, Santa Barbara Basin and Salton Trough; and low ratios in the San Gabriel, San Jacinto and southern Sierra Nevada mountains. Disagreements in regions such as the Western Transverse Ranges, Salton Trough, San Jacinto and Elsinore fault zones motivate further work to improve the community models. A new updated 3D isotropic model of the area is derived via a joint inversion of Rayleigh phase dispersions and H/V ratios. Additionally, we examine azimuthal dependence of the H/V ratio to ascertain anisotropy patterns for each station. Clear 180º periodicity is observed for many stations suggesting strong shallow anisotropy across the region including up to 20% along the San Andreas fault, 15% along the San Jacinto Fault and 25% in the LA Basin. To better resolve basin structures, we apply similar techniques to three dense linear geophone arrays in the San Gabriel and San Bernardino basins. The three arrays are composed by 50-125 three-component 5Hz geophones deployed for one month each with 15-25km apertures to image basin structure, important for seismic hazard analysis and ground motion predictions. Clear Rayleigh and Love wave signals are extracted. We determine Love wave dispersion and Rayleigh wave H/V and phase dispersion measurements. The preliminary basin models from inverting surface wave measurements will be presented.

Bifurcation-enhanced ultrahigh sensitivity of a buckled cantilever

PubMed Central

An, Sangmin; Kim, Bongsu; Kwon, Soyoung; Moon, Geol; Lee, Manhee

2018-01-01

Buckling, first introduced by Euler in 1744 [Euler L (1744) Opera Omnia I 24:231], a sudden mechanical sideways deflection of a structural member under compressive stress, represents a bifurcation in the solution to the equations of static equilibrium. Although it has been investigated in diverse research areas, such a common nonlinear phenomenon may be useful to devise a unique mechanical sensor that addresses the still-challenging features, such as the enhanced sensitivity and polarization-dependent detection capability. We demonstrate the bifurcation-enhanced sensitive measurement of mechanical vibrations using the nonlinear buckled cantilever tip in ambient conditions. The cantilever, initially buckled with its tip pinned, flips its buckling near the bifurcation point (BP), where the buckled tip becomes softened. The enhanced mechanical sensitivity results from the increasing fluctuations, unlike the typical linear sensors, which facilitate the noise-induced buckling-to-flipping transition of the softened cantilever. This allows the in situ continuous or repeated single-shot detection of the surface acoustic waves of different polarizations without any noticeable wear of the tip. We obtained the sensitivity above 106 V(m/s)−1, a 1,000-fold enhancement over the conventional seismometers. Our results lead to development of mechanical sensors of high sensitivity, reproducibility, and durability, which may be applied to detect, e.g., the directional surface waves on the laboratory as well as the geological scale. PMID:29511105

Data Analysis Techniques for Ligo Detector Characterization

NASA Astrophysics Data System (ADS)

Valdes Sanchez, Guillermo A.

Gravitational-wave astronomy is a branch of astronomy which aims to use gravitational waves to collect observational data about astronomical objects and events such as black holes, neutron stars, supernovae, and processes including those of the early universe shortly after the Big Bang. Einstein first predicted gravitational waves in the early century XX, but it was not until Septem- ber 14, 2015, that the Laser Interferometer Gravitational-Wave Observatory (LIGO) directly ob- served the first gravitational waves in history. LIGO consists of two twin detectors, one in Livingston, Louisiana and another in Hanford, Washington. Instrumental and sporadic noises limit the sensitivity of the detectors. Scientists conduct Data Quality studies to distinguish a gravitational-wave signal from the noise, and new techniques are continuously developed to identify, mitigate, and veto unwanted noise. This work presents the application of data analysis techniques, such as Hilbert-Huang trans- form (HHT) and Kalman filtering (KF), in LIGO detector characterization. We investigated the application of HHT to characterize the gravitational-wave signal of the first detection, we also demonstrated the functionality of HHT identifying noise originated from light being scattered by perturbed surfaces, and we estimated thermo-optical aberration using KF. We put particular attention to the scattering origin application, for which a tool was developed to identify disturbed surfaces originating scattering noise. The results reduced considerably the time to search for the scattering surface and helped LIGO commissioners to mitigate the noise.

Monitoring of surface-fatigue crack propagation in a welded steel angle structure using guided waves and principal component analysis

NASA Astrophysics Data System (ADS)

Lu, Mingyu; Qu, Yongwei; Lu, Ye; Ye, Lin; Zhou, Limin; Su, Zhongqing

2012-04-01

An experimental study is reported in this paper demonstrating monitoring of surface-fatigue crack propagation in a welded steel angle structure using Lamb waves generated by an active piezoceramic transducer (PZT) network which was freely surface-mounted for each PZT transducer to serve as either actuator or sensor. The fatigue crack was initiated and propagated in welding zone of a steel angle structure by three-point bending fatigue tests. Instead of directly comparing changes between a series of specific signal segments such as S0 and A0 wave modes scattered from fatigue crack tips, a variety of signal statistical parameters representing five different structural status obtained from marginal spectrum in Hilbert-huang transform (HHT), indicating energy progressive distribution along time period in the frequency domain including all wave modes of one wave signal were employed to classify and distinguish different structural conditions due to fatigue crack initiation and propagation with the combination of using principal component analysis (PCA). Results show that PCA based on marginal spectrum is effective and sensitive for monitoring the growth of fatigue crack although the received signals are extremely complicated due to wave scattered from weld, multi-boundaries, notch and fatigue crack. More importantly, this method indicates good potential for identification of integrity status of complicated structures which cause uncertain wave patterns and ambiguous sensor network arrangement.

Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave

NASA Astrophysics Data System (ADS)

Chang, Sheng-Yi; Hsieh, Tung-Sheng; Chen, Wei-Ru; Chen, Jin-Chung; Chou, Chien

2017-08-01

A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW's oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave.

PubMed

Chang, Sheng-Yi; Hsieh, Tung-Sheng; Chen, Wei-Ru; Chen, Jin-Chung; Chou, Chien

2017-08-01

A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW’s oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

Ultrasonic surface measurements at the Porta Nigra, Trier, and the Neptungrotte, Park Sanssouci Potsdam

NASA Astrophysics Data System (ADS)

Meier, Thomas; Auras, Michael; Fehr, Moritz; Köhn, Daniel

2015-04-01

Ultrasonic measurements along profiles at the surface of an object are well suited to characterize non-destructively weathering of natural stone near the surface. Ultrasonic waveforms of surface measurements in the frequency range between 10 kHz and 300 kHz are often dominated by the Rayleigh wave - a surface wave that is mainly sensitive to the velocity and attenuation of S-waves in the upper 0.3 cm to 3 cm. The frequency dependence of the Rayleigh wave velocity may be used to analyze variations of the material properties with depth. Applications of ultrasonic surface measurements are shown for two buildings: the Roman Porta Nigra in Trier from the 3rd century AD and the Neptungrotte at Park Sanssouci in Potsdam designed by von Knobelsdorff in the 18th century. Both buildings belong to the world cultural heritage and restorations are planned for the near future. It is interesting to compare measurements at these two buildings because they show the applicability of ultrasonic surface measurements to different natural stones. The Porta Nigra is made of local sandstones whereas the facades of the Neptungrotte are made of Carrara and Kauffunger marble. 71 and 46 surface measurements have been carried out, respectively. At both buildings, Rayleigh-wave group velocities show huge variations. At the Porta Nigra they vary between ca. 0.4 km/s and 1.8 km/s and at the Neptungrotte between ca. 0.7 km/s and 3.0 km/s pointing to alterations in the Rayleigh- and S-wave velocities of more than 50 % due to weathering. Note that velocities of elastic waves may increase e.g. because of the formation of black crusts like at the Porta Nigra or they may be strongly reduced due to weathering. The accuracy of the ultrasonic surface measurements, its reproducibility, and the influence of varying water saturation are discussed. Options for the analysis of ultrasonic waveforms are presented ranging from dispersion analysis to full waveform inversions for one-dimensional and two-dimensional models of the outermost layers of the object under investigation. Furthermore, results of non-destructive ultrasonic surface measurements are compared to results of destructive investigation techniques.

A guided wave dispersion compensation method based on compressed sensing

NASA Astrophysics Data System (ADS)

Xu, Cai-bin; Yang, Zhi-bo; Chen, Xue-feng; Tian, Shao-hua; Xie, Yong

2018-03-01

The ultrasonic guided wave has emerged as a promising tool for structural health monitoring (SHM) and nondestructive testing (NDT) due to their capability to propagate over long distances with minimal loss and sensitivity to both surface and subsurface defects. The dispersion effect degrades the temporal and spatial resolution of guided waves. A novel ultrasonic guided wave processing method for both single mode and multi-mode guided waves dispersion compensation is proposed in this work based on compressed sensing, in which a dispersion signal dictionary is built by utilizing the dispersion curves of the guided wave modes in order to sparsely decompose the recorded dispersive guided waves. Dispersion-compensated guided waves are obtained by utilizing a non-dispersion signal dictionary and the results of sparse decomposition. Numerical simulations and experiments are implemented to verify the effectiveness of the developed method for both single mode and multi-mode guided waves.

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.

Joint body and surface wave tomography applied to the Toba caldera complex (Indonesia)

NASA Astrophysics Data System (ADS)

Jaxybulatov, Kairly; Koulakov, Ivan; Shapiro, Nikolai

2016-04-01

We developed a new algorithm for a joint body and surface wave tomography. The algorithm is a modification of the existing LOTOS code (Koulakov, 2009) developed for local earthquake tomography. The input data for the new method are travel times of P and S waves and dispersion curves of Rayleigh and Love waves. The main idea is that the two data types have complementary sensitivities. The body-wave data have good resolution at depth, where we have enough crossing rays between sources and receivers, whereas the surface waves have very good near-surface resolution. The surface wave dispersion curves can be retrieved from the correlations of the ambient seismic noise and in this case the sampled path distribution does not depend on the earthquake sources. The contributions of the two data types to the inversion are controlled by the weighting of the respective equations. One of the clearest cases where such approach may be useful are volcanic systems in subduction zones with their complex magmatic feeding systems that have deep roots in the mantle and intermediate magma chambers in the crust. In these areas, the joint inversion of different types of data helps us to build a comprehensive understanding of the entire system. We apply our algorithm to data collected in the region surrounding the Toba caldera complex (north Sumatra, Indonesia) during two temporary seismic experiments (IRIS, PASSCAL, 1995, GFZ, LAKE TOBA, 2008). We invert 6644 P and 5240 S wave arrivals and ~500 group velocity dispersion curves of Rayleigh and Love waves. We present a series of synthetic tests and real data inversions which show that joint inversion approach gives more reliable results than the separate inversion of two data types. Koulakov, I., LOTOS code for local earthquake tomographic inversion. Benchmarks for testing tomographic algorithms, Bull. seism. Soc. Am., 99(1), 194-214, 2009, doi:10.1785/0120080013

US Drought-Heat Wave Relationships in Past Versus Current Climates

NASA Astrophysics Data System (ADS)

Cheng, L.; Hoerling, M. P.; Eischeid, J.; Liu, Z.

2017-12-01

This study explores the relationship between droughts and heat waves over various regions of the contiguous United States that are distinguished by so-called energy-limited versus water-limited climatologies. We first examine the regional sensitivity of heat waves to soil moisture variability under 19th century climate conditions, and then compare to sensitivities under current climate that has been subjected to human-induced change. Our approach involves application of the conditional statistical framework of vine copula. Vine copula is known for its flexibility in reproducing various dependence structures exhibited by climate variables. Here we highlight its feature for evaluating the importance of conditional relationships between variables and processes that capture underlying physical factors involved in their interdependence during drought/heat waves. Of particular interest is identifying changes in coupling strength between heat waves and land surface conditions that may yield more extreme events as a result of land surface feedbacks. We diagnose two equilibrium experiments a coupled climate model (CESM1), one subjected to Year-1850 external forcing and the other to Year-2000 radiative forcing. We calculate joint heat wave/drought relationships for each climate state, and also calculate their change as a result of external radiative forcing changes across this 150-yr period. Our results reveal no material change in the dependency between heat waves and droughts, aside from small increases in coupling strength over the Great Plains. Overall, hot U.S. summer droughts of 1850-vintage do not become hotter in the current climate -- aside from the warming contribution of long-term climate change, in CESM1. The detectability of changes in hotter droughts as a consequence of anthropogenic forced changes in this single effect, i.e. coupling strength between soil moisture and hot summer temperature, is judged to be low at this time.

Numerical simulation of evaluation of surface breaking cracks by array-lasers generated narrow-band SAW

NASA Astrophysics Data System (ADS)

Dong, Li-Ming; Ni, Chen-Yin; Shen, Zhong-Hua; Ni, Xiao-Wu

2011-09-01

Most of the factors limiting the extensive application of laser-based ultrasonic for nondestructive evaluation of surface breaking crack are its poor sensitivity, low efficiency relative to conventional contact ultrasonic methods and limit on the dimension of the cracks. For this reason, a new technique that multiplepulse narrow-band ultrasound generated by laser arrays has been proposed. It is found that crack detection dependent on spectrum of narrow-band ultrasound generated by laser arrays can be operated with low amplitude requirements. In this paper, the narrow-band ultrasound generated by pulse laser arrays interacting with surface breaking cracks has been simulated in detail by the finite element method (FEM) according to the thermoelastic theory. The pulsed array lasers were assumed to be transient heat source, and the surface acoustic wave (SAW) which propagating on the top of the plate was computed based on thermoelastic theory. Then the frequency spectrums of both reflected waves by crack and transmission ones through crack were compared with the direct waves. Results demonstrate that multiple-frequency components of the narrow-band ultrasound were varied with change of the depth of surface breaking cracks significantly, which provides the possibility for precise evaluation of surface breaking cracks.

Element sensitive reconstruction of nanostructured surfaces with finite elements and grazing incidence soft X-ray fluorescence.

PubMed

Soltwisch, Victor; Hönicke, Philipp; Kayser, Yves; Eilbracht, Janis; Probst, Jürgen; Scholze, Frank; Beckhoff, Burkhard

2018-03-29

The geometry of a Si3N4 lamellar grating was investigated experimentally with reference-free grazing-incidence X-ray fluorescence analysis. While simple layered systems are usually treated with the matrix formalism to determine the X-ray standing-wave field, this approach fails for laterally structured surfaces. Maxwell solvers based on finite elements are often used to model electrical field strengths for any 2D or 3D structures in the optical spectral range. We show that this approach can also be applied in the field of X-rays. The electrical field distribution obtained with the Maxwell solver can subsequently be used to calculate the fluorescence intensities in full analogy to the X-ray standing-wave field obtained by the matrix formalism. Only the effective 1D integration for the layer system has to be replaced by a 2D integration of the finite elements, taking into account the local excitation conditions. We will show that this approach is capable of reconstructing the geometric line shape of a structured surface with high elemental sensitivity. This combination of GIXRF and finite-element simulations paves the way for a versatile characterization of nanoscale-structured surfaces.

A Fatigue Crack Size Evaluation Method Based on Lamb Wave Simulation and Limited Experimental Data

PubMed Central

He, Jingjing; Ran, Yunmeng; Liu, Bin; Yang, Jinsong; Guan, Xuefei

2017-01-01

This paper presents a systematic and general method for Lamb wave-based crack size quantification using finite element simulations and Bayesian updating. The method consists of construction of a baseline quantification model using finite element simulation data and Bayesian updating with limited Lamb wave data from target structure. The baseline model correlates two proposed damage sensitive features, namely the normalized amplitude and phase change, with the crack length through a response surface model. The two damage sensitive features are extracted from the first received S0 mode wave package. The model parameters of the baseline model are estimated using finite element simulation data. To account for uncertainties from numerical modeling, geometry, material and manufacturing between the baseline model and the target model, Bayesian method is employed to update the baseline model with a few measurements acquired from the actual target structure. A rigorous validation is made using in-situ fatigue testing and Lamb wave data from coupon specimens and realistic lap-joint components. The effectiveness and accuracy of the proposed method is demonstrated under different loading and damage conditions. PMID:28902148

Short-Period Surface Wave Based Seismic Event Relocation

NASA Astrophysics Data System (ADS)

White-Gaynor, A.; Cleveland, M.; Nyblade, A.; Kintner, J. A.; Homman, K.; Ammon, C. J.

2017-12-01

Accurate and precise seismic event locations are essential for a broad range of geophysical investigations. Superior location accuracy generally requires calibration with ground truth information, but superb relative location precision is often achievable independently. In explosion seismology, low-yield explosion monitoring relies on near-source observations, which results in a limited number of observations that challenges our ability to estimate any locations. Incorporating more distant observations means relying on data with lower signal-to-noise ratios. For small, shallow events, the short-period (roughly 1/2 to 8 s period) fundamental-mode and higher-mode Rayleigh waves (including Rg) are often the most stable and visible portion of the waveform at local distances. Cleveland and Ammon [2013] have shown that teleseismic surface waves are valuable observations for constructing precise, relative event relocations. We extend the teleseismic surface wave relocation method, and apply them to near-source distances using Rg observations from the Bighorn Arche Seismic Experiment (BASE) and the Earth Scope USArray Transportable Array (TA) seismic stations. Specifically, we present relocation results using short-period fundamental- and higher-mode Rayleigh waves (Rg) in a double-difference relative event relocation for 45 delay-fired mine blasts and 21 borehole chemical explosions. Our preliminary efforts are to explore the sensitivity of the short-period surface waves to local geologic structure, source depth, explosion magnitude (yield), and explosion characteristics (single-shot vs. distributed source, etc.). Our results show that Rg and the first few higher-mode Rayleigh wave observations can be used to constrain the relative locations of shallow low-yield events.

Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system

USGS Publications Warehouse

Olabarrieta, Maitane; Warner, John C.; Armstrong, Brandy N.; Zambon, Joseph B.; He, Ruoying

2012-01-01

The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system was used to investigate atmosphere–ocean–wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor’Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor’easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor’Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness-based parameterization (OOST) provided the best results for wind and wave growth prediction. However, the best agreement between the measured (CODAR) and computed surface currents and storm surge values was obtained with the wave steepness-based roughness parameterization (TY2001), although the differences obtained with respect to DGHQ were not significant. The influence of sea surface temperature (SST) fields on the atmospheric boundary layer dynamics was examined; in particular, we evaluated how the SST affects wind wave generation, surface currents and storm surges. The integrated hydrograph and integrated wave height, parameters that are highly correlated with the storm damage potential, were found to be highly sensitive to the ocean surface roughness parameterization.

Detection of swine-origin influenza A (H1N1) viruses using a paired surface plasma waves biosensor

NASA Astrophysics Data System (ADS)

Su, Li-Chen; Chang, Ying-Feng; Li, Ying-Chang; Hsieh, Jo-Ping; Lee, Cheng-Chung; Chou, Chien

2010-08-01

In order to enhance the sensitivity of conventional rapid test technique for the detection of swine-origin influenza A (H1N1) viruses (S-OIVs), we used a paired surface plasma waves biosensor (PSPWB) based on SPR in conjunction with an optical heterodyne technique. Experimentally, PSPWB showed a 125-fold improvement at least in the S-OIV detection as compared to conventional enzyme linked immunosorbent assay. Moreover, the detection limit of the PSPWB for the S-OIV detection was enhanced 250-fold in buffer at least in comparison with that of conventional rapid influenza diagnostic test.

Direct Measurement of Wave Kernels in Time-Distance Helioseismology

NASA Technical Reports Server (NTRS)

Duvall, T. L., Jr.

2006-01-01

Solar f-mode waves are surface-gravity waves which propagate horizontally in a thin layer near the photosphere with a dispersion relation approximately that of deep water waves. At the power maximum near 3 mHz, the wavelength of 5 Mm is large enough for various wave scattering properties to be observable. Gizon and Birch (2002,ApJ,571,966)h ave calculated kernels, in the Born approximation, for the sensitivity of wave travel times to local changes in damping rate and source strength. In this work, using isolated small magnetic features as approximate point-sourc'e scatterers, such a kernel has been measured. The observed kernel contains similar features to a theoretical damping kernel but not for a source kernel. A full understanding of the effect of small magnetic features on the waves will require more detailed modeling.

Sensitivity of Tsunami Waves and Coastal Inundation/Runup to Seabed Displacement Models: Application to the Cascadia Subduction zone

NASA Astrophysics Data System (ADS)

Jalali Farahani, R.; Fitzenz, D. D.; Nyst, M.

2015-12-01

Major components of tsunami hazard modeling include earthquake source characterization, seabed displacement, wave propagation, and coastal inundation/run-up. Accurate modeling of these components is essential to identify the disaster risk exposures effectively, which would be crucial for insurance industry as well as policy makers to have tsunami resistant design of structures and evacuation planning (FEMA, 2008). In this study, the sensitivity and variability of tsunami coastal inundation due to Cascadia megathrust subduction earthquake are studied by considering the different approaches for seabed displacement model. The first approach is the analytical expressions that were proposed by Okada (1985, 1992) for the surface displacements and strains of rectangular sources. The second approach was introduced by Meade (2006) who introduced analytical solutions for calculating displacements, strains, and stresses on triangular sources. In this study, the seabed displacement using triangular representation of geometrically complex fault surfaces is compared with the Okada rectangular representations for the Cascadia subduction zone. In the triangular dislocation algorithm, the displacement is calculated using superposition of two angular dislocations for each of the three triangle legs. The triangular elements could give a better and gap-free representation of the fault surfaces. In addition, the rectangular representation gives large unphysical vertical displacement along the shallow-depth fault edge that generates unrealistic short-wavelength waves. To study the impact of these two different algorithms on the final tsunami inundation, the initial tsunami wave as well as wave propagation and the coastal inundation are simulated. To model the propagation of tsunami waves and coastal inundation, 2D shallow water equations are modeled using the seabed displacement as the initial condition for the numerical model. Tsunami numerical simulation has been performed on high-resolution bathymetric/topographic computational grids to identify accurate tsunami impact and flooding limits for the west of USA.

Non-destructive evaluation of coating thickness using guided waves

NASA Astrophysics Data System (ADS)

Ostiguy, Pierre-Claude; Quaegebeur, Nicolas; Masson, Patrice

2015-04-01

Among existing strategies for non-destructive evaluation of coating thickness, ultrasonic methods based on the measurement of the Time-of-Flight (ToF) of high frequency bulk waves propagating through the thickness of a structure are widespread. However, these methods only provide a very localized measurement of the coating thickness and the precision on the results is largely affected by the surface roughness, porosity or multi-layered nature of the host structure. Moreover, since the measurement is very local, inspection of large surfaces can be time consuming. This article presents a robust methodology for coating thickness estimation based on the generation and measurement of guided waves. Guided waves have the advantage over ultrasonic bulk waves of being less sensitive to surface roughness, and of measuring an average thickness over a wider area, thus reducing the time required to inspect large surfaces. The approach is based on an analytical multi-layer model and intercorrelation of reference and measured signals. The method is first assessed numerically for an aluminum plate, where it is demonstrated that coating thickness can be measured within a precision of 5 micrometers using the S0 mode at frequencies below 500 kHz. Then, an experimental validation is conducted and results show that coating thicknesses in the range of 10 to 200 micrometers can be estimated within a precision of 10 micrometers of the exact coating thickness on this type of structure.

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.

Fast, high sensitivity dewpoint hygrometer

NASA Technical Reports Server (NTRS)

Hoenk, Michael E. (Inventor)

1998-01-01

A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature. The effect of this response is to heat or cool the surface moisture-sensitive device, which shifts the equilibrium with respect to evaporation and condensation at the surface of the device. The equilibrium temperature under feedback control is a measure of dewpoint or frostpoint.

Ocean-atmosphere dynamics during Hurricane Ida and Nor'Ida: An application of the coupled ocean-;atmosphere–wave–sediment transport (COAWST) modeling system

USGS Publications Warehouse

Olabarrieta, Maitane; Warner, John C.; Armstrong, Brandy N.; Zambon, Joseph B.; He, Ruoying

2012-01-01

The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system was used to investigate atmosphere–ocean–wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor'Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor'easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor'Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness-based parameterization (OOST) provided the best results for wind and wave growth prediction. However, the best agreement between the measured (CODAR) and computed surface currents and storm surge values was obtained with the wave steepness-based roughness parameterization (TY2001), although the differences obtained with respect to DGHQ were not significant. The influence of sea surface temperature (SST) fields on the atmospheric boundary layer dynamics was examined; in particular, we evaluated how the SST affects wind wave generation, surface currents and storm surges. The integrated hydrograph and integrated wave height, parameters that are highly correlated with the storm damage potential, were found to be highly sensitive to the ocean surface roughness parameterization.

Full skin quantitative optical coherence elastography achieved by combining vibration and surface acoustic wave methods

NASA Astrophysics Data System (ADS)

Li, Chunhui; Guan, Guangying; Huang, Zhihong; Wang, Ruikang K.; Nabi, Ghulam

2015-03-01

By combining with the phase sensitive optical coherence tomography (PhS-OCT), vibration and surface acoustic wave (SAW) methods have been reported to provide elastography of skin tissue respectively. However, neither of these two methods can provide the elastography in full skin depth in current systems. This paper presents a feasibility study on an optical coherence elastography method which combines both vibration and SAW in order to give the quantitative mechanical properties of skin tissue with full depth range, including epidermis, dermis and subcutaneous fat. Experiments are carried out on layered tissue mimicking phantoms and in vivo human forearm and palm skin. A ring actuator generates vibration while a line actuator were used to excited SAWs. A PhS-OCT system is employed to provide the ultrahigh sensitive measurement of the generated waves. The experimental results demonstrate that by the combination of vibration and SAW method the full skin bulk mechanical properties can be quantitatively measured and further the elastography can be obtained with a sensing depth from ~0mm to ~4mm. This method is promising to apply in clinics where the quantitative elasticity of localized skin diseases is needed to aid the diagnosis and treatment.

A joint method to retrieve directional ocean wave spectra from SAR and wave spectrometer data

NASA Astrophysics Data System (ADS)

Ren, Lin; Yang, Jingsong; Zheng, Gang; Wang, Juan

2016-07-01

This paper proposes a joint method to simultaneously retrieve wave spectra at different scales from spaceborne Synthetic Aperture Radar (SAR) and wave spectrometer data. The method combines the output from the two different sensors to overcome retrieval limitations that occur in some sea states. The wave spectrometer sensitivity coefficient is estimated using an effective significant wave height (SWH), which is an average of SAR-derived and wave spectrometer-derived SWH. This averaging extends the area of the sea surface sampled by the nadir beam of the wave spectrometer to improve the accuracy of the estimated sensitivity coefficient in inhomogeneous sea states. Wave spectra are then retrieved from SAR data using wave spectrometer-derived spectra as first guess spectra to complement the short waves lost in SAR data retrieval. In addition, the problem of 180° ambiguity in retrieved spectra is overcome using SAR imaginary cross spectra. Simulated data were used to validate the joint method. The simulations demonstrated that retrieved wave parameters, including SWH, peak wave length (PWL), and peak wave direction (PWD), agree well with reference parameters. Collocated data from ENVISAT advanced SAR (ASAR), the airborne wave spectrometer STORM, the PHAROS buoy, and the European Centre for Medium-Range Weather Forecasting (ECMWF) were then used to verify the proposed method. Wave parameters retrieved from STORM and two ASAR images were compared to buoy and ECMWF wave data. Most of the retrieved parameters were comparable to reference parameters. The results of this study show that the proposed joint retrieval method could be a valuable complement to traditional methods used to retrieve directional ocean wave spectra, particularly in inhomogeneous sea states.

ZnO thin film as MSG for sensitive biosensor

NASA Astrophysics Data System (ADS)

Iftimie, N.; Savin, A.; Steigmann, R.; Faktorova, D.; Salaoru, I.

2016-08-01

In this paper, we investigate the cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles were grown on ITO/glass substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air. Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating in sub-wavelength regime. Before testing the transducer with metamaterials lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

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.

Analysis of liquid-phase chemical detection using guided shear horizontal-surface acoustic wave sensors.

PubMed

Li, Zhonghui; Jones, Yolanda; Hossenlopp, Jeanne; Cernosek, Richard; Josse, Fabien

2005-07-15

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36 degrees rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the four-layer model. Contributions from mass loading and coating viscoelasticity changes to the sensor response are evaluated, taking into account the added mass, swelling, and plasticization. Chemically sensitive polymers are investigated in the detection of low concentrations (1-60 ppm) of toluene, ethylbenzene, and xylenes in water. A low-ppb level detection limit is estimated from the present experimental measurements. Sensor properties are investigated by varying the sensor geometries, coating thickness combinations, coating properties, and curing temperature for operation in liquid environments. Partition coefficients for polymer-aqueous analyte pairs are used to explain the observed trend in sensitivity for the polymers PMMA, poly(isobutylene), poly(epichlorohydrin), and poly(ethyl acrylate) used in this work.

Method and apparatus for monitoring and measuring the surface tension of a fluid using fiber optics

DOEpatents

Abraham, B.M.; Ketterson, J.B.; Bohanon, T.M.; Mikrut, J.M.

1994-04-12

A non-contact method and apparatus are described for measuring and monitoring the surface of a fluid using fiber optics and interferometric detection to permit measurement of mechanical characteristics of fluid surfaces. The apparatus employs an alternating electric field gradient for generating a capillary wave on the surface of the fluid. A fiber optic coupler and optical fiber directs a portion of a laser beam onto the surface of the fluid, another portion of the laser beam onto the photo sensor, and directs light reflected from the surface of the fluid onto the photo sensor. The output of the photo sensor is processed and coupled to a phase sensitive detector to permit measurement of phase shift between the drive signal creating the capillary wave and the detected signal. This phase shift information is then used to determine mechanical properties of the fluid surface such as surface tension, surface elasticity, and surface inhomogeneity. The resulting test structure is easily made compact, portable, and easy to align and use. 4 figures.

Real-time protein aggregation monitoring with a Bloch surface wave-based approach

NASA Astrophysics Data System (ADS)

Santi, Sara; Barakat, Elsie; Descrovi, Emiliano; Neier, Reinhard; Herzig, Hans Peter

2014-05-01

The misfolding and aggregation of amyloid proteins has been associated with incurable diseases such as Alzheimer's or Parkinson's disease. In the specific case of Alzheimer's disease, recent studies have shown that cell toxicity is caused by soluble oligomeric forms of aggregates appearing in the early stages of aggregation, rather than by insoluble fibrils. Research on new strategies of diagnosis is imperative to detect the disease prior to the onset of clinical symptoms. Here, we propose the use of an optical method for protein aggregation dynamic studies using a Bloch surface wave based approach. A one dimension photonic crystal made of a periodic stack of silicon oxide and silicon nitride layers is used to excite a Bloch surface wave, which is sensitive to variation of the refractive index of an aqueous solution. The aim is to detect the early dynamic events of protein aggregation and fibrillogenesis of the amyloid-beta peptide Aβ42, which plays a central role in the onset of the Alzheimer's disease. The detection principle relies on the refractive index changes caused by the depletion of the Aβ42 monomer concentration during oligomerization and fibrillization. We demonstrate the efficacy of the Bloch surface wave approach by monitoring in real-time the first crucial steps of Aβ42 oligomerization.

High resolution SAW elastography for ex-vivo porcine skin specimen

NASA Astrophysics Data System (ADS)

Zhou, Kanheng; Feng, Kairui; Wang, Mingkai; Jamera, Tanatswa; Li, Chunhui; Huang, Zhihong

2018-02-01

Surface acoustic wave (SAW) elastography has been proven to be a non-invasive, non-destructive method for accurately characterizing tissue elastic properties. Current SAW elastography technique tracks generated surface acoustic wave impulse point by point which are a few millimeters away. Thus, reconstructed elastography has low lateral resolution. To improve the lateral resolution of current SAW elastography, a new method was proposed in this research. A M-B scan mode, high spatial resolution phase sensitive optical coherence tomography (PhS-OCT) system was employed to track the ultrasonically induced SAW impulse. Ex-vivo porcine skin specimen was tested using this proposed method. A 2D fast Fourier transform based algorithm was applied to process the acquired data for estimating the surface acoustic wave dispersion curve and its corresponding penetration depth. Then, the ex-vivo porcine skin elastogram was established by relating the surface acoustic wave dispersion curve and its corresponding penetration depth. The result from the proposed method shows higher lateral resolution than that from current SAW elastography technique, and the approximated skin elastogram could also distinguish the different layers in the skin specimen, i.e. epidermis, dermis and fat layer. This proposed SAW elastography technique may have a large potential to be widely applied in clinical use for skin disease diagnosis and treatment monitoring.

Surface acoustic waves in one-dimensional piezoelectric-metallic phononic crystal: Effect of a cap layer.

PubMed

Alami, M; El Boudouti, E H; Djafari-Rouhani, B; El Hassouani, Y; Talbi, A

2018-06-18

We study the propagation of transverse acoustic waves associated with the surface of a semi-infinite superlattice (SL) composed of piezoelectric-metallic layers and capped with a piezoelectric layer. We present closed-form expressions for localized surface waves, the so-called Bleustein-Gulyaev (BG) waves depending on whether the cap layer is open-circuited or short-circuited. These expressions are obtained by means of the Green's function method which enables to deduce also the densities of states. These theoretical results are illustrated by a few numerical applications to SLs made of piezoelectric layers of hexagonal symmetry belonging to the 6 mm class such as PZT4 and ZnO in contact with metallic layers such as Fe, Al, Au, Cu and boron-doped-diamond. We demonstrate a rule about the existence of surface modes when considering two complementary semi-infinite SLs obtained by the cleavage of an infinite SL along a plane parallel to the piezoelectric layers. Indeed, when the surface layers are open-circuited, one obtains one surface mode per gap, this mode is associated with one of the two complementary SLs. However, when the surface layers are short-circuited, this rule is not fulfilled and one can obtain zero, one or two modes inside each gap of the two complementary SLs depending on the position of the plane where the cleavage is produced. We show that in addition to the BG surface waves localized at the surface of the cap layer, there may exist true guided waves and pseudo-guided waves (i.e. leaky waves) induced by the cap layer either inside the gaps or inside the bands of the SL respectively. Also, we highlight the possibility of existence of interface modes between the SL and a cap layer as well as an interaction between these modes and the BG surface mode when both modes fall in the same band gaps of the SL. The strength of the interaction depends on the width of the cap layer. Finally, we show that the electromechanical coupling coefficient (ECC) is very sensitive to the cap layer thickness, in particular we calculate and discuss the behavior of the ECC as a function of the adlayer thickness for the low velocity surface modes of the SL which exhibit the highest ECC values. The effect of the nature of the metallic layers inside the SL on the ECC is also investigated. The different surface modes discussed in this work should have applications in sensing applications. Copyright © 2018. Published by Elsevier B.V.

Mechanism linking T-wave alternans to the genesis of cardiac fibrillation.

PubMed

Pastore, J M; Girouard, S D; Laurita, K R; Akar, F G; Rosenbaum, D S

1999-03-16

Although T-wave alternans has been closely associated with vulnerability to ventricular arrhythmias, the cellular processes underlying T-wave alternans and their role, if any, in the mechanism of reentry remain unclear. -T-wave alternans on the surface ECG was elicited in 8 Langendorff-perfused guinea pig hearts during fixed-rate pacing while action potentials were recorded simultaneously from 128 epicardial sites with voltage-sensitive dyes. Alternans of the repolarization phase of the action potential was observed above a critical threshold heart rate (HR) (209+/-46 bpm) that was significantly lower (by 57+/-36 bpm) than the HR threshold for alternation of action potential depolarization. The magnitude (range, 2.7 to 47.0 mV) and HR threshold (range, 171 to 272 bpm) of repolarization alternans varied substantially between cells across the epicardial surface. T-wave alternans on the surface ECG was explained primarily by beat-to-beat alternation in the time course of cellular repolarization. Above a critical HR, membrane repolarization alternated with the opposite phase between neighboring cells (ie, discordant alternans), creating large spatial gradients of repolarization. In the presence of discordant alternans, a small acceleration of pacing cycle length produced a characteristic sequence of events: (1) unidirectional block of an impulse propagating against steep gradients of repolarization, (2) reentrant propagation, and (3) the initiation of ventricular fibrillation. Repolarization alternans at the level of the single cell accounts for T-wave alternans on the surface ECG. Discordant alternans produces spatial gradients of repolarization of sufficient magnitude to cause unidirectional block and reentrant ventricular fibrillation. These data establish a mechanism linking T-wave alternans of the ECG to the pathogenesis of sudden cardiac death.

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.

The UKC2 regional coupled prediction system

NASA Astrophysics Data System (ADS)

Castillo, Juan; Lewis, Huw; Graham, Jennifer; Saulter, Andrew; Arnold, Alex; Fallmann, Joachim; Martinez de la Torre, Alberto; Blyth, Eleanor; Bricheno, Lucy

2017-04-01

It is hypothesized that more accurate prediction and warning of natural hazards, such as of the impacts of severe weather through the environment, requires a more integrated approach to forecasting. This approach also delivers research benefits through providing tools with which to explore the known interactions and feedbacks between different physical and biogeochemical components of the environment across sky, sea and land. This hypothesis is being tested in a UK regional context at km-scale through the UK Environmental Prediction Project. This presentation will provide an introduction to the UKC2 UK Environmental Prediction research system. This incorporates models of the atmosphere (Met Office Unified Model), land surface (JULES), shelf-sea ocean (NEMO) and ocean waves (WAVEWATCH III). These components are coupled (via OASIS3-MCT libraries) at unprecedentedly high resolution across the UK and the wider north-west European regional domain. A research framework has been established to explore the representation of feedback processes in coupled and uncoupled modes, providing a unique new research tool for UK environmental science. The presentation will highlight work undertaken to review and improve the computational cost of running these systems for efficient research application. Research will be presented highlighting case study evaluation on the sensitivity of the ocean and surface waves to the representation of feedbacks to the atmosphere, and on the sensitivity of weather systems and boundary layer cloud development to the exchange of heat and momentum at the ocean surface modified through sea surface temperature and wave-induced roughness. The presentation will discuss plans for future development through UKC3 and beyond.

Full-waveform inversion of surface waves in exploration geophysics

NASA Astrophysics Data System (ADS)

Borisov, D.; Gao, F.; Williamson, P.; Tromp, J.

2017-12-01

Full-waveform inversion (FWI) is a data fitting approach to estimate high-resolution properties of the Earth from seismic data by minimizing the misfit between observed and calculated seismograms. In land seismics, the source on the ground generates high-amplitude surface waves, which generally represent most of the energy recorded by ground sensors. Although surface waves are widely used in global seismology and engineering studies, they are typically treated as noise within the seismic exploration community since they mask deeper reflections from the intervals of exploration interest. This is mainly due to the fact that surface waves decay exponentially with depth and for a typical frequency range (≈[5-50] Hz) sample only the very shallow part of the subsurface, but also because they are much more sensitive to S-wave than P-wave velocities. In this study, we invert surface waves in the hope of using them as additional information for updating the near surface. In a heterogeneous medium, the main challenge of surface wave inversion is associated with their dispersive character, which makes it difficult to define a starting model for conventional FWI which can avoid cycle-skipping. The standard approach to dealing with this is by inverting the dispersion curves in the Fourier (f-k) domain to generate locally 1-D models, typically for the shear wavespeeds only. However this requires that the near-surface zone be more or less horizontally invariant over a sufficient distance for the spatial Fourier transform to be applicable. In regions with significant topography, such as foothills, this is not the case, so we revert to the time-space domain, but aim to minimize the differences of envelopes in the early stages of the inversion to resolve the cycle-skipping issue. Once the model is good enough, we revert to the classic waveform-difference inversion. We first present a few synthetic examples. We show that classical FWI might be trapped in a local minimum even for relatively simple scenario, while FWI with envelopes is stable and can converge using an inaccurate starting model. We also perform resolution analysis using a checkerboard test. We then present a field example. The final shear wavespeed model is compared to the results from the inversion of dispersion curves.

Mapping the upper mantle beneath North American continent with joint inversion of surface-wave phase and amplitude

NASA Astrophysics Data System (ADS)

Yoshizawa, K.; Hamada, K.

2017-12-01

A new 3-D S-wave model of the North American upper mantle is constructed from a large number of inter-station phase and amplitude measurements of surface waves. A fully nonlinear waveform fitting method by Hamada and Yoshizawa (2015, GJI) is applied to USArray for measuring inter-station phase speeds and amplitude ratios of the fundamental-mode Rayleigh and Love waves. We employed the seismic events from 2007 - 2014 with Mw 6.0 or greater, and collected a large-number of inter-station phase speed data (about 130,000 for Rayleigh and 85,000 for Love waves) and amplitude ratio data (about 75,000 for Rayleigh waves) in a period range from 30 to 130 s for fundamental-mode surface waves. Typical inter-station distances are mostly in a range between 300 and 800 km, which can be of help in enhancing the lateral resolution of a regional tomography model. We first invert Rayleigh-wave phase speeds and amplitudes simultaneously for phase speed maps as well as local amplification factors at receiver locations. The isotropic 3-D S-wave model constructed from these phase speed maps incorporating both phase and amplitude data exhibits better recovery of the strength of velocity perturbations. In particular, local tectonic features characterized by strong velocity gradients, such as Rio Grande Rift, Colorado Plateau and New Madrid Seismic Zone, are more enhanced than conventional models derived from phase information only. The results indicate that surface-wave amplitude, which is sensitive to the second derivative of phase speeds, can be of great help in retrieving small-scale heterogeneity in the upper mantle. We also obtain a radial anisotropy model from the simultaneous inversions of Rayleigh and Love waves (without amplitude information). The model has shown faster SH wave speed anomalies than SV above the depth of 100 km, particularly in tectonically active regions in the western and central U.S., representing the effects of current and former tectonic processes on anisotropic properties in the continental lithosphere.

The GNSS Reflectometry Response to the Ocean Surface

NASA Astrophysics Data System (ADS)

Chang, Paul; Jelenak, Zorana; Soisuvarn, Seubson; Said, Faozi

2016-04-01

Global Navigation Satellite System - Reflectometry (GNSS-R) exploits signals of opportunity from the Global Navigation Satellite System (GNSS). GNSS transmitters continuously transmit navigation signals at L-band toward the earth's surface. The scattered power reflected off the earth's surface can be sensed by specially designed GNSS-R receivers. The reflected signal can then be used to glean information about the surface of the earth, such as ocean surface roughness, snow depth, sea ice extent, and soil moisture. The use of GNSS-R for ocean wind retrievals was first demonstrated from aircraft. On July 8 2014, the TechDemoSat-1 satellite (TDS-1) was launched by Surrey Satellite Technology, Ltd as a technology risk reduction mission into sun-synchronous orbit. This paper investigates the GNSS-R measurements collected by the Space GNSS Receiver-Remote Sensing Instrument (SGR-ReSI) on board the TDS-1 satellite. The sensitivity of the SGR-ReSI measurements to the ocean surface winds and waves are characterized. The effects of sea surface temperature, wind direction, and rain are also investigated. The SGR-ReSI measurements exhibited sensitivity through the entire range of wind speeds sampled in this dataset, up to 35 m/s. A significant dependence on the larger waves was observed for winds < 6 m/s. Additionally, an interesting dependence on SST was observed where the slope of the SGR-ReSI measurements is positive for winds < 5 m/s and reverses for winds > 5 m/s. There appeared to be very little wind direction signal, and investigation of the rain impacts found no apparent sensitivity in the data. These results are shown through the analysis of global statistics and examination of a few case studies. This released SGR-ReSI dataset provided the first opportunity to comprehensively investigate the sensitivity of satellite-based GNSS-R measurements to various ocean surface parameters. The upcoming NASA's Cyclone Global Navigation Satellite System (CYGNSS) satellite constellation will utilize a similar receiver to SGI-ReSI and thus this data provides valuable pre-launch knowledge for the CYGNSS mission.

Heterodyne lock-in thermography of early demineralized in dental tissues

NASA Astrophysics Data System (ADS)

Wang, Fei; Liu, Jun-yan; Mohummad, Oliullah; Wang, Xiao-chun; Wang, Yang

2017-12-01

Heterodyne lock-in thermography (HeLIT) is a highly sensitive method to detect early demineralized in dental tissues, which is based on nonlinear photothermal phenomena of dental tissues. In this paper, the nonlinear photothermal phenomena of dental tissues was introduced, and then the system of HeLIT was developed. The relationship between laser modulated parameters (modulated frequency and laser intensity) and heterodyne lock-in thermal wave signal was investigated. The comparison between HeLIT and homodyne lock-in thermography (HoLIT) for detecting the different types of dental caries (smooth surface caries, proximal surface caries and occlusal surface caries) were carried out. Experimental results illustrate that the HeLIT has the merits of high sensitivity and high specificity in detecting different types of early caries.

Separation of density and viscosity influence on liquid-loaded surface acoustic wave devices

NASA Astrophysics Data System (ADS)

Herrmann, F.; Hahn, D.; Büttgenbach, S.

1999-05-01

Love-mode sensors are reported for separate measurement of liquid density and viscosity. They combine the general merits of Love-mode devices, e.g., ease of sensitivity adjustment and robustness, with a highly effective procedure of separate determination of liquid density and viscosity. A model is proposed to describe the frequency response of the devices to liquid loading. Moreover, design rules are given for further optimization and sensitivity enhancement.

Shear-horizontal surface acoustic wave phononic device with high density filling material for ultra-low power sensing applications

NASA Astrophysics Data System (ADS)

Richardson, M.; Sankaranarayanan, S. K. R. S.; Bhethanabotla, V. R.

2014-06-01

Finite element simulations of a phononic shear-horizontal surface acoustic wave (SAW) sensor based on ST 90°-X Quartz reveal a dramatic reduction in power consumption. The phononic sensor is realized by artificially structuring the delay path to form an acoustic meta-material comprised of a periodic microcavity array incorporating high-density materials such as tantalum or tungsten. Constructive interference of the scattered and secondary reflected waves at every microcavity interface leads to acoustic energy confinement in the high-density regions translating into reduced power loss. Tantalum filled cavities show the best performance while tungsten inclusions create a phononic bandgap. Based on our simulation results, SAW devices with tantalum filled microcavities were fabricated and shown to significantly decrease insertion loss. Our findings offer encouraging prospects for designing low power, highly sensitive portable biosensors.

Bifocal Fresnel Lens Based on the Polarization-Sensitive Metasurface

NASA Astrophysics Data System (ADS)

Markovich, Hen; Filonov, Dmitrii; Shishkin, Ivan; Ginzburg, Pavel

2018-05-01

Thin structured surfaces allow flexible control over propagation of electromagnetic waves. Focusing and polarization state analysis are among functions, required for effective manipulation of radiation. Here a polarization sensitive Fresnel zone plate lens is proposed and experimentally demonstrated for GHz spectral range. Two spatially separated focal spots for orthogonal polarizations are obtained by designing metasurface pattern, made of overlapping tightly packed cross and rod shaped antennas with a strong polarization selectivity. Optimized subwavelength pattern allows multiplexing two different lenses with low polarization crosstalk on the same substrate and provides a control over focal spots of the lens only by changing of the polarization state of the incident wave. More than a wavelength separation between the focal spots was demonstrated for a broad spectral range, covering half a decade in frequency. The proposed concept could be straightforwardly extended for THz and visible spectra, where polarization-sensitive elements utilize localized plasmon resonance phenomenon.

Lamb mode selection for accurate wall loss estimation via guided wave tomography

NASA Astrophysics Data System (ADS)

Huthwaite, P.; Ribichini, R.; Lowe, M. J. S.; Cawley, P.

2014-02-01

Guided wave tomography offers a method to accurately quantify wall thickness losses in pipes and vessels caused by corrosion. This is achieved using ultrasonic waves transmitted over distances of approximately 1-2m, which are measured by an array of transducers and then used to reconstruct a map of wall thickness throughout the inspected region. To achieve accurate estimations of remnant wall thickness, it is vital that a suitable Lamb mode is chosen. This paper presents a detailed evaluation of the fundamental modes, S0 and A0, which are of primary interest in guided wave tomography thickness estimates since the higher order modes do not exist at all thicknesses, to compare their performance using both numerical and experimental data while considering a range of challenging phenomena. The sensitivity of A0 to thickness variations was shown to be superior to S0, however, the attenuation from A0 when a liquid loading was present was much higher than S0. A0 was less sensitive to the presence of coatings on the surface of than S0.

THz holography in reflection using a high resolution microbolometer array.

PubMed

Zolliker, Peter; Hack, Erwin

2015-05-04

We demonstrate a digital holographic setup for Terahertz imaging of surfaces in reflection. The set-up is based on a high-power continuous wave (CW) THz laser and a high-resolution (640 × 480 pixel) bolometer detector array. Wave propagation to non-parallel planes is used to reconstruct the object surface that is rotated relative to the detector plane. In addition we implement synthetic aperture methods for resolution enhancement and compare Fourier transform phase retrieval to phase stepping methods. A lateral resolution of 200 μm and a relative phase sensitivity of about 0.4 rad corresponding to a depth resolution of 6 μm are estimated from reconstructed images of two specially prepared test targets, respectively. We highlight the use of digital THz holography for surface profilometry as well as its potential for video-rate imaging.

Newtonian noise and ambient ground motion for gravitational wave detectors

NASA Astrophysics Data System (ADS)

Beker, M. G.; van den Brand, J. F. J.; Hennes, E.; Rabeling, D. S.

2012-06-01

Fluctuations of the local gravitational field as a result of seismic and atmospheric displacements will limit the sensitivity of ground based gravitational wave detectors at frequencies below 10 Hz. We discuss the implications of Newtonian noise for future third generation gravitational wave detectors. The relevant seismic wave fields are predominately of human origin and are dependent on local infrastructure and population density. Seismic studies presented here show that considerable seismic noise reduction is possible compared to current detector locations. A realistic seismic amplitude spectral density of a suitably quiet site should not exceed 0.5 nm/(Hz/f)2 above 1 Hz. Newtonian noise models have been developed both analytically and by finite element analysis. These show that the contribution to Newtonian noise from surface waves due to distance sources significantly reduces with depth. Seismic displacements from local sources and body waves then become the dominant contributors to the Newtonian fluctuations.

Shallow seismic source parameter determination using intermediate-period surface wave amplitude spectra

NASA Astrophysics Data System (ADS)

Fox, Benjamin D.; Selby, Neil D.; Heyburn, Ross; Woodhouse, John H.

2012-09-01

Estimating reliable depths for shallow seismic sources is important in both seismo-tectonic studies and in seismic discrimination studies. Surface wave excitation is sensitive to source depth, especially at intermediate and short-periods, owing to the approximate exponential decay of surface wave displacements with depth. A new method is presented here to retrieve earthquake source parameters from regional and teleseismic intermediate period (100-15 s) fundamental-mode surface wave recordings. This method makes use of advances in mapping global dispersion to allow higher frequency surface wave recordings at regional and teleseismic distances to be used with more confidence than in previous studies and hence improve the resolution of depth estimates. Synthetic amplitude spectra are generated using surface wave theory combined with a great circle path approximation, and a grid of double-couple sources are compared with the data. Source parameters producing the best-fitting amplitude spectra are identified by minimizing the least-squares misfit in logarithmic amplitude space. The F-test is used to search the solution space for statistically acceptable parameters and the ranges of these variables are used to place constraints on the best-fitting source. Estimates of focal mechanism, depth and scalar seismic moment are determined for 20 small to moderate sized (4.3 ≤Mw≤ 6.4) earthquakes. These earthquakes are situated across a wide range of geographic and tectonic locations and describe a range of faulting styles over the depth range 4-29 km. For the larger earthquakes, comparisons with other studies are favourable, however existing source determination procedures, such as the CMT technique, cannot be performed for the smaller events. By reducing the magnitude threshold at which robust source parameters can be determined, the accuracy, especially at shallow depths, of seismo-tectonic studies, seismic hazard assessments, and seismic discrimination investigations can be improved by the application of this methodology.

Phase-sensitive detection of acoustically stimulated electromagnetic response in steel

NASA Astrophysics Data System (ADS)

Yamada, Hisato; Yotsuji, Junichi; Ikushima, Kenji

2018-07-01

The signal amplitude and the phase of acoustically stimulated electromagnetic (ASEM) response have been investigated in steel. In the ASEM method, magnetization is temporally modulated with the radio frequency (rf) of irradiated ultrasonic waves through magnetomechanical coupling. The first-harmonic components of the induced rf dipolar magnetic fields are detected using a resonant loop antenna. The signal amplitude of ASEM waves is determined by the magnitude of local piezomagnetic coefficients on an acoustically excited spot. Here, we divided the ASEM waves into the “in-phase” and “quadrature” components by phase-sensitive detection (PSD). On the basis of the linear response theory, we provided the theoretical formalism of ASEM response by introducing local complex piezomagnetic coefficients, d loc = d‧ + id‧‧. We investigated the magnetic field (H) dependence of the individual components on the different surface conditions of steel plates. The in-phase component [∝ d‧(H)] shows a hysteresis loop on the machined surface of a steel plate, in which d‧(H) switches sign at two finite field values, ±H 0. The inversion of magnetization associated with the applied static fields is thus definitely observed in the PSD measurements. In addition, we measured the hysteresis behaviors on a steel surface with a thin mill scale (iron oxide layers). The hysteresis loop broadens and a significant contribution of the quadrature component [∝ d‧‧(H)] is found. We discuss the origin of the hysteresis behaviors of d‧ and d‧‧ using the Debye relaxation model.

Reflective measurement of water concentration using millimeter wave illumination

NASA Astrophysics Data System (ADS)

Sung, Shijun; Bennett, David; Taylor, Zachary; Bajwa, Neha; Tewari, Priyamvada; Maccabi, Ashkan; Culjat, Martin; Singh, Rahul; Grundfest, Warren

2011-04-01

THz and millimeter wave technology have shown the potential to become a valuable medical imaging tool because of its sensitivity to water and safe, non-ionizing photon energy. Using the high dielectric constant of water in these frequency bands, reflectionmode THz sensing systems can be employed to measure water content in a target with high sensitivity. This phenomenology may lead to the development of clinical systems to measure the hydration state of biological targets. Such measurements may be useful in fast and convenient diagnosis of conditions whose symptoms can be characterized by changes in water concentration such as skin burns, dehydration, or chemical exposure. To explore millimeter wave sensitivity to hydration, a reflectometry system is constructed to make water concentration measurements at 100 GHz, and the minimum detectable water concentration difference is measured. This system employs a 100 GHz Gunn diode source and Golay cell detector to perform point reflectivity measurements of a wetted polypropylene towel as it dries on a mass balance. A noise limited, minimum detectable concentration difference of less than 0.5% by mass can be detected in water concentrations ranging from 70% to 80%. This sensitivity is sufficient to detect hydration changes caused by many diseases and pathologies and may be useful in the future as a diagnostic tool for the assessment of burns and other surface pathologies.

Enhanced sensitivity of surface acoustic wave-based rate sensors incorporating metallic dot arrays.

PubMed

Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

2014-02-26

A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz∙deg∙s(-1)) and good linearity were observed.

Enhanced Sensitivity of Surface Acoustic Wave-Based Rate Sensors Incorporating Metallic Dot Arrays

PubMed Central

Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

2014-01-01

A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz·deg·s−1) and good linearity were observed. PMID:24577520

Modeling, design, packing and experimental analysis of liquid-phase shear-horizontal surface acoustic wave sensors

NASA Astrophysics Data System (ADS)

Pollard, Thomas B

Recent advances in microbiology, computational capabilities, and microelectromechanical-system fabrication techniques permit modeling, design, and fabrication of low-cost, miniature, sensitive and selective liquid-phase sensors and lab-on-a-chip systems. Such devices are expected to replace expensive, time-consuming, and bulky laboratory-based testing equipment. Potential applications for devices include: fluid characterization for material science and industry; chemical analysis in medicine and pharmacology; study of biological processes; food analysis; chemical kinetics analysis; and environmental monitoring. When combined with liquid-phase packaging, sensors based on surface-acoustic-wave (SAW) technology are considered strong candidates. For this reason such devices are focused on in this work; emphasis placed on device modeling and packaging for liquid-phase operation. Regarding modeling, topics considered include mode excitation efficiency of transducers; mode sensitivity based on guiding structure materials/geometries; and use of new piezoelectric materials. On packaging, topics considered include package interfacing with SAW devices, and minimization of packaging effects on device performance. In this work novel numerical models are theoretically developed and implemented to study propagation and transduction characteristics of sensor designs using wave/constitutive equations, Green's functions, and boundary/finite element methods. Using developed simulation tools that consider finite-thickness of all device electrodes, transduction efficiency for SAW transducers with neighboring uniform or periodic guiding electrodes is reported for the first time. Results indicate finite electrode thickness strongly affects efficiency. Using dense electrodes, efficiency is shown to approach 92% and 100% for uniform and periodic electrode guiding, respectively; yielding improved sensor detection limits. A numerical sensitivity analysis is presented targeting viscosity using uniform-electrode and shear-horizontal mode configurations on potassium-niobate, langasite, and quartz substrates. Optimum configurations are determined yielding maximum sensitivity. Results show mode propagation-loss and sensitivity to viscosity are correlated by a factor independent of substrate material. The analysis is useful for designing devices meeting sensitivity and signal level requirements. A novel, rapid and precise microfluidic chamber alignment/bonding method was developed for SAW platforms. The package is shown to have little effect on device performance and permits simple macrofluidic interfacing. Lastly, prototypes were designed, fabricated, and tested for viscosity and biosensor applications; results show ability to detect as low as 1% glycerol in water and surface-bound DNA crosslinking.

High-resolution all-optical photoacoustic imaging system for remote interrogation of biological specimens

NASA Astrophysics Data System (ADS)

Sampathkumar, Ashwin

2014-05-01

Conventional photoacoustic imaging (PAI) employs light pulses to produce a photoacoustic (PA) effect and detects the resulting acoustic waves using an ultrasound transducer acoustically coupled to the target tissue. The resolution of conventional PAI is limited by the sensitivity and bandwidth of the ultrasound transducer. We have developed an all-optical versatile PAI system for characterizing ex vivo and in vivo biological specimens. The system employs noncontact interferometric detection of the acoustic signals that overcomes limitations of conventional PAI. A 532-nm pump laser with a pulse duration of 5 ns excited the PA effect in tissue. Resulting acoustic waves produced surface displacements that were sensed using a 532-nm continuous-wave (CW) probe laser in a Michelson interferometer with a GHz bandwidth. The pump and probe beams were coaxially focused using a 50X objective giving a diffraction-limited spot size of 0.48 μm. The phase-encoded probe beam was demodulated using a homodyne interferometer. The detected time-domain signal was time reversed using k-space wave-propagation methods to produce a spatial distribution of PA sources in the target tissue. Performance was assessed using PA images of ex vivo rabbit lymph node specimens and human tooth samples. A minimum peak surface displacement sensitivity of 0.19 pm was measured. The all-optical PAI (AOPAI) system is well suited for assessment of retinal diseases, caries lesion detection, skin burns, section less histology and pressure or friction ulcers.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

New Polymer Coatings for Chemically Selective Mass Sensors

NASA Technical Reports Server (NTRS)

Sims, S. C.; Wright, Cassandra; Cobb, J.; McCalla, T.; Revelle, R.; Morris, V. R.; Pollack, S. K.

1997-01-01

There is a current need to develop sensitive and chemically specific sensors for the detection of nitric acid for in-situ measurements in the atmosphere. Polymer coatings have been synthesized and tested for their sensitivity and selectivity to nitric acid. A primary requirement for these polymers is detectability down to the parts per trillion range. The results of studies using these polymers as coatings for quartz crystal microbalances (QCM) and surface acoustic wave (SAW) devices will be presented.

S-Wave Velocity Models Under the Saudi Arabian Portable Broadband Deployment: Evidence for Lithospheric Erosion Beneath the Arabian Shield

NASA Astrophysics Data System (ADS)

Julià, J.; Ammon, C. J.; Herrmann, R. B.

2002-12-01

Models of crustal evolution strongly rely on our knowledge on the mineralogical composition of subsurface rocks, as well as pressure and temperature conditions. Direct sampling of subsurface rocks is often not possible, so that constraints have to be placed from indirect estimates of rock properties. Detailed seismic imaging of subsurface rocks has the potential for providing such constraints, and probe the extent at depth of surface geologic observations. In this study, we provide detailed S-wave velocity profiles for the crust and uppermost mantle beneath the Saudi Arabian Portable Broadband Deployment stations. Seismic velocities have been estimated from the joint inversion of receiver functions and fundamental mode group velocities. Receiver functions are sensitive to S-wave velocity contrasts and vertical travel times, and surface-wave dispersion is sensitive to vertical S-wave velocity averages, so that their combination bridge resolution gaps associated with each individual data set. Our resulting models correlate well with surface geology observations in the Arabian Shield and characterize its terranes at depth: the Asir terrane consists of a 10-km thick upper crust of 3.3~km/s overlying a lower crust with shear-wave velocities of 3.7-3.8 km/s; the Afif terrane is made of a 20-km thick upper crust with average velocity of 3.6 km/s and a lower crust with a shear-velocity of about 3.8~km/s; the Nabitah mobile belt has a gradational, 15-km thick upper crust up to 3.6 km/s overlying a gradational lower crust with velocities up to 4.0 km/s. The crust-mantle transition is sharper in terranes of continental affinity and more gradational beneath terranes of oceanic affinity. In the uppermost mantle, our models suggest a thin lid between up to 50-60 km depth overlying a low velocity zone beneath station TAIF, located close to a region of upwelling mantle material. Temperatures in the lid are estimated to be about 1000 C, which are in good agreement with independent xenolith data, and suggest that the lithosphere could be eroded to a thickness as little as 50~km under this station.

A new type of glucose biosensor based on surface acoustic wave resonator using Mn-doped ZnO multilayer structure.

PubMed

Luo, Jingting; Luo, Pingxiang; Xie, Min; Du, Ke; Zhao, Bixia; Pan, Feng; Fan, Ping; Zeng, Fei; Zhang, Dongping; Zheng, Zhuanghao; Liang, Guangxing

2013-11-15

This work reports a high-performance Mn-doped ZnO multilayer structure Love mode surface acoustic wave (SAW) biosensor for the detection of blood sugar. The biosensor was functionalized via immobilizing glucose oxidase onto a pH-sensitive polymer which was attached on Mn-doped ZnO biosensor. The fabricated SAW glucose biosensor is highly sensitive, accurate and fast with good anti-interference. The sensitivity of the SAW glucose biosensor is 7.184 MHz/mM and the accuracy is 6.96 × 10(-3)mM, which is sensitive and accurate enough for glucose monitoring. A good degree of reversibility and stability of the glucose sensor is also demonstrated, which keeps a constant differential frequency shift up to 32 days. Concerning the time response to human serum, the glucose sensor shows a value of 4.6 ± 0.4 min when increasing glucose concentrations and 7.1 ± 0.6 min when decreasing, which is less than 10 min and reach the fast response requirement for medical applications. The Mn-doped ZnO Love mode SAW biosensor can be fully integrated with CMOS Si chips and developed as a portable, passive and wireless real time detection system for blood sugar monitoring in human serum. Copyright © 2013 Elsevier B.V. All rights reserved.

A high-performance lab-on-a-chip liquid sensor employing surface acoustic wave resonance

NASA Astrophysics Data System (ADS)

Kustanovich, K.; Yantchev, V.; Kirejev, V.; Jeffries, G. D. M.; Lobovkina, T.; Jesorka, A.

2017-11-01

We demonstrate herein a new concept for lab-on-a-chip in-liquid sensing, through integration of surface acoustic wave resonance (SAR) in a one-port configuration with a soft polymer microfluidic delivery system. In this concept, the reflective gratings of a one-port surface acoustic wave (SAW) resonator are employed as mass loading-sensing elements, while the SAW transducer is protected from the measurement environment. We describe the design, fabrication, implementation, and characterization using liquid medium. The sensor operates at a frequency of 185 MHz and has demonstrated a comparable sensitivity to other SAW in-liquid sensors, while offering quality factor (Q) value in water of about 250, low impedance and fairly low susceptibility to viscous damping. For proof of principle, sensing performance was evaluated by means of binding 40 nm neutravidin-coated SiO2 nanoparticles to a biotin-labeled lipid bilayer deposited over the reflectors. Frequency shifts were determined for every step of the affinity assay. Demonstration of this integrated technology highlights the potential of SAR technology for in-liquid sensing.

Rayleigh-Wave Group-Velocity Tomography of Saudi Arabia

NASA Astrophysics Data System (ADS)

Tang, Zheng; Mai, P. Martin; Chang, Sung-Joon; Zahran, Hani

2017-04-01

We use surface-wave tomography to investigate the lithospheric structure of the Arabian plate, which is traditionally divided into the Arabian shield in the west and the Arabian platform in the east. The Arabian shield is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks. The Arabian platform is primarily covered by very thick Paleozoic, Mesozoic and Cenozoic sediments. We develop high-resolution tomographic images from fundamental-mode Rayleigh-wave group-velocities across Saudi Arabia, utilizing the teleseismic data recorded by the permanent Saudi National Seismic Network (SNSN). Our study extends previous efforts on surface wave work by increasing ray path density and improving spatial resolution. Good quality dispersion measurements for roughly 3000 Rayleigh-wave paths have been obtained and utilized for the group-velocity tomography. We have applied the Fast Marching Surface Tomography (FMST) scheme of Rawlinson (2005) to obtain Rayleigh-wave group-velocity images for periods from 8 s to 40 s on a 0.8° 0.8° grid and at resolutions approaching 2.5° based on the checkerboard tests. Our results indicate that short-period group-velocity maps (8-15 s) correlate well with surface geology, with slow velocities delineating the main sedimentary features including the Arabian platform, the Persian Gulf and Mesopotamia. For longer periods (20-40 s), the velocity contrast is due to the differences in crustal thickness and subduction/collision zones. The lower velocities are sensitive to the thicker continental crust beneath the eastern Arabia and the subduction/collision zones between the Arabian and Eurasian plate, while the higher velocities in the west infer mantle velocity.

Inversion of high frequency surface waves with fundamental and higher modes

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Park, C.B.; Tian, G.

2003-01-01

The phase velocity of Rayleigh-waves of a layered earth model is a function of frequency and four groups of earth parameters: compressional (P)-wave velocity, shear (S)-wave velocity, density, and thickness of layers. For the fundamental mode of Rayleigh waves, analysis of the Jacobian matrix for high frequencies (2-40 Hz) provides a measure of dispersion curve sensitivity to earth model parameters. S-wave velocities are the dominant influence of the four earth model parameters. This thesis is true for higher modes of high frequency Rayleigh waves as well. Our numerical modeling by analysis of the Jacobian matrix supports at least two quite exciting higher mode properties. First, for fundamental and higher mode Rayleigh wave data with the same wavelength, higher modes can "see" deeper than the fundamental mode. Second, higher mode data can increase the resolution of the inverted S-wave velocities. Real world examples show that the inversion process can be stabilized and resolution of the S-wave velocity model can be improved when simultaneously inverting the fundamental and higher mode data. ?? 2002 Elsevier Science B.V. All rights reserved.

Quantitative examination of demineralized and remineralized dental lesions using photothermal radiometry and modulated luminescence

NASA Astrophysics Data System (ADS)

Hellen, Adam; Mandelis, Andreas; Finer, Yoav; Amaechi, Bennett

2010-02-01

The development of photothermal techniques to detect thermal waves in biological tissue has occurred with a concomitant advancement in the extraction of material thermophysical properties and knowledge regarding the internal structure of a medium. Human molars (n=37) were subjected to demineralization in acid gel (pH 4.5, 10 days), followed by incubation in different fluoride-containing remineralization solutions. PTR-LUM frequency scans (1 Hz - 1 kHz) were performed prior to and during demineralization and remineralization treatments. Transverse Micro-Radiography (TMR) analysis followed at treatment conclusion. A coupled diffuse-photon-density-wave and thermal-wave theoretical model was used to quantitatively evaluate changes in thermal and optical properties of sound, demineralized and remineralized enamel. Amplitude increase and phase lag decrease in demineralized samples were consistent with higher scatter of the diffuse-photon density field and thermal wave confinement to near-surface regions. A remineralized sample illustrates a complex interplay between surface and subsurface processes, confining the thermal-wave centroid toward the dominating layer. PTR-LUM sensitivity to changes in tooth mineralization coupled with optical and thermal property extraction illustrates the technique's potential for non-destructive evaluation of multi-layered turbid media.

Approximate Stokes Drift Profiles and their use in Ocean Modelling

NASA Astrophysics Data System (ADS)

Breivik, Oyvind; Bidlot, Jea-Raymond; Janssen, Peter A. E. M.; Mogensen, Kristian

2016-04-01

Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons against parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. Of the two Stokes drift profiles explored here, the profile based on the Phillips spectrum is by far the best. In particular, the shear near the surface is almost identical to that influenced by the f-5 tail of spectral wave models. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. The ECWMF coupled atmosphere-wave-ocean ensemble forecast system now includes these wave effects in the ocean model component (NEMO).

Dyakonov surface waves at the interface between hexagonal-boron-nitride and isotropic material

NASA Astrophysics Data System (ADS)

Zhu, B.; Ren, G.; Gao, Y.; Wang, Q.; Wan, C.; Wang, J.; Jian, S.

2016-12-01

In this paper we analyze the propagation of Dyakonov surface waves (DSWs) at the interface between hexagonal-boron-nitride (h-BN) and isotropic dielectric material. Various properties of DSWs supported at the dielectric-elliptic and dielectric-hyperbolic types of interfaces have been theoretically investigated, including the real effective index, propagation length, the angular existence domain (AED) and the composition ratio of evanescent field components in an h-BN crystal and isotropic dielectric material, respectively. The analysis in this paper reveals that h-BN could be a promising anisotropic material to observe the propagation of DSWs and may have potential diverse applications, such as high sensitivity stress sensing or optical sensing of analytes infiltrating dielectric materials.

Eastern North American finite-frequency, compressional and shear tomographic models

NASA Astrophysics Data System (ADS)

Savage, B.; Shen, Y.

2017-12-01

The Eastern North American margin and continental interior is imaged using a finite-frequency, tomographic method. Each of the P and S teleseismic body wave date sets consists of over 80,000 usable measurements recorded on the Transportable Array (TA). Sensitivity kernels are computed from a 1D model with grid spacing of 50 x 50 x 25 km. Measurements are performed automatically at three individual frequency bands, allowing a more effective use of the available broadband data. Imaged shear and compressional wave speeds show similar long-wavelength features of reduced wave speeds along the continent-ocean margin and increased wave speeds within the stable interior. Wave speeds throughout the model are highly variable at the scale of 100 to 200 km. Large wave speed reductions are present near New England, the Mid-Atlantic states, and the Gulf Coast states; these variations are present in previous models. Interestingly, the strongly reduced wave speeds near South Carolina are absent at depths greater than of 150 km within this model and recent teleseismic body-wave models. This result is contrary to a variety of surface wave models which contain an intense, reduced wave speed anomaly extending past 250 km depth and interpreted as a mantle upwelling associated with edge driven convection. An anomaly along the West Virginia-Virginia border, associated with volcanism and mantle upwelling, is also present, tightly constrained, and extends to 200 km depth. Moreover, the interior of the continent contains significant, regional wave speed variations. Variation of this style is present in other surface and body wave models and is not consistent with a massive, homogeneous continent with no internal variations. These internal continental variations suggest a compositional influence as temperature, melt and water are thought to have minimal effect. Unlike surface wave models that include a distinct continental base around 175 km, teleseismic body wave models, including this one, do not show this base. However, this model does include the deep, positive wave speed anomaly within the mantle transition zone interpreted as a slab fragment, agreeing with previous models.

Joint Inversion of Phase and Amplitude Data of Surface Waves for North American Upper Mantle

NASA Astrophysics Data System (ADS)

Hamada, K.; Yoshizawa, K.

2015-12-01

For the reconstruction of the laterally heterogeneous upper-mantle structure using surface waves, we generally use phase delay information of seismograms, which represents the average phase velocity perturbation along a ray path, while the amplitude information has been rarely used in the velocity mapping. Amplitude anomalies of surface waves contain a variety of information such as anelastic attenuation, elastic focusing/defocusing, geometrical spreading, and receiver effects. The effects of elastic focusing/defocusing are dependent on the second derivative of phase velocity across the ray path, and thus, are sensitive to shorter-wavelength structure than the conventional phase data. Therefore, suitably-corrected amplitude data of surface waves can be useful for improving the lateral resolution of phase velocity models. In this study, we collect a large-number of inter-station phase velocity and amplitude ratio data for fundamental-mode surface waves with a non-linear waveform fitting between two stations of USArray. The measured inter-station phase velocity and amplitude ratios are then inverted simultaneously for phase velocity maps and local amplification factor at receiver locations in North America. The synthetic experiments suggest that, while the phase velocity maps derived from phase data only reflect large-scale tectonic features, those from phase and amplitude data tend to exhibit better recovery of the strength of velocity perturbations, which emphasizes local-scale tectonic features with larger lateral velocity gradients; e.g., slow anomalies in Snake River Plain and Rio Grande Rift, where significant local amplification due to elastic focusing are observed. Also, the spatial distribution of receiver amplification factor shows a clear correlation with the velocity structure. Our results indicate that inter-station amplitude-ratio data can be of help in reconstructing shorter-wavelength structures of the upper mantle.

Joint inversion of apparent resistivity and seismic surface and body wave data

NASA Astrophysics Data System (ADS)

Garofalo, Flora; Sauvin, Guillaume; Valentina Socco, Laura; Lecomte, Isabelle

2013-04-01

A novel inversion algorithm has been implemented to jointly invert apparent resistivity curves from vertical electric soundings, surface wave dispersion curves, and P-wave travel times. The algorithm works in the case of laterally varying layered sites. Surface wave dispersion curves and P-wave travel times can be extracted from the same seismic dataset and apparent resistivity curves can be obtained from continuous vertical electric sounding acquisition. The inversion scheme is based on a series of local 1D layered models whose unknown parameters are thickness h, S-wave velocity Vs, P-wave velocity Vp, and Resistivity R of each layer. 1D models are linked to surface-wave dispersion curves and apparent resistivity curves through classical 1D forward modelling, while a 2D model is created by interpolating the 1D models and is linked to refracted P-wave hodograms. A priori information can be included in the inversion and a spatial regularization is introduced as a set of constraints between model parameters of adjacent models and layers. Both a priori information and regularization are weighted by covariance matrixes. We show the comparison of individual inversions and joint inversion for a synthetic dataset that presents smooth lateral variations. Performing individual inversions, the poor sensitivity to some model parameters leads to estimation errors up to 62.5 %, whereas for joint inversion the cooperation of different techniques reduces most of the model estimation errors below 5% with few exceptions up to 39 %, with an overall improvement. Even though the final model retrieved by joint inversion is internally consistent and more reliable, the analysis of the results evidences unacceptable values of Vp/Vs ratio for some layers, thus providing negative Poisson's ratio values. To further improve the inversion performances, an additional constraint is added imposing Poisson's ratio in the range 0-0.5. The final results are globally improved by the introduction of this constraint further reducing the maximum error to 30 %. The same test was performed on field data acquired in a landslide-prone area close by the town of Hvittingfoss, Norway. Seismic data were recorded on two 160-m long profiles in roll-along mode using a 5-kg sledgehammer as source and 24 4.5-Hz vertical geophones with 4-m separation. First-arrival travel times were picked at every shot locations and surface wave dispersion curves extracted at 8 locations for each profile. 2D resistivity measurements were carried out on the same profiles using Gradient and Dipole-Dipole arrays with 2-m electrode spacing. The apparent resistivity curves were extracted at the same location as for the dispersion curves. The data were subsequently jointly inverted and the resulting model compared to individual inversions. Although models from both, individual and joint inversions are consistent, the estimation error is smaller for joint inversion, and more especially for first-arrival travel times. The joint inversion exploits different sensitivities of the methods to model parameters and therefore mitigates solution nonuniqueness and the effects of intrinsic limitations of the different techniques. Moreover, it produces an internally consistent multi-parametric final model that can be profitably interpreted to provide a better understanding of subsurface properties.

Wide Band Low Noise Love Wave Magnetic Field Sensor System.

PubMed

Kittmann, Anne; Durdaut, Phillip; Zabel, Sebastian; Reermann, Jens; Schmalz, Julius; Spetzler, Benjamin; Meyners, Dirk; Sun, Nian X; McCord, Jeffrey; Gerken, Martina; Schmidt, Gerhard; Höft, Michael; Knöchel, Reinhard; Faupel, Franz; Quandt, Eckhard

2018-01-10

We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/[Formula: see text], a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. A range of additional measures to further increase the sensitivity are investigated with simulations.

Determining the near-surface current profile from measurements of the wave dispersion relation

NASA Astrophysics Data System (ADS)

Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen

2017-11-01

The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.

A reusable evanescent wave immunosensor for highly sensitive detection of bisphenol A in water samples

NASA Astrophysics Data System (ADS)

Xiao-Hong, Zhou; Lan-Hua, Liu; Wei-Qi, Xu; Bao-Dong, Song; Jian-Wu, Sheng; Miao, He; Han-Chang, Shi

2014-04-01

This paper proposed a compact and portable planar waveguide evanescent wave immunosensor (EWI) for highly sensitive detection of BPA. The incident light is coupled into the planar waveguide chip via a beveled angle through undergoing total internal reflection, where the evanescent wave field forms and excites the binding fluorophore-tagged antibodies on the chip surface. Typical calibration curves obtained for BPA has detection limits of 0.03 μg/L. Linear response for BPA ranged from 0.124 μg/L-9.60 μg/L with 50% inhibition concentration for BPA of 1.09 +/- 0.25 μg/L. The regeneration of the planar optical waveguide chip allows the performance of more than 300 assay cycles within an analysis time of about 20 min for each assay cycle. By application of effective pretreatment procedure, the recoveries of BPA in real water samples gave values from 88.3% +/- 8.5% to 103.7% +/- 3.5%, confirming its application potential in the measurement of BPA in reality.

Sensitivity of acoustic nonlinearity parameter to the microstructural changes in cement-based materials

NASA Astrophysics Data System (ADS)

Kim, Gun; Kim, Jin-Yeon; Kurtis, Kimberly E.; Jacobs, Laurence J.

2015-03-01

This research experimentally investigates the sensitivity of the acoustic nonlinearity parameter to microcracks in cement-based materials. Based on the second harmonic generation (SHG) technique, an experimental setup using non-contact, air-coupled detection is used to receive the consistent Rayleigh surface waves. To induce variations in the extent of microscale cracking in two types of specimens (concrete and mortar), shrinkage reducing admixture (SRA), is used in one set, while a companion specimen is prepared without SRA. A 50 kHz wedge transducer and a 100 kHz air-coupled transducer are implemented for the generation and detection of nonlinear Rayleigh waves. It is shown that the air-coupled detection method provides more repeatable fundamental and second harmonic amplitudes of the propagating Rayleigh waves. The obtained amplitudes are then used to calculate the relative nonlinearity parameter βre, the ratio of the second harmonic amplitude to the square of the fundamental amplitude. The experimental results clearly demonstrate that the nonlinearity parameter (βre) is highly sensitive to the microstructural changes in cement-based materials than the Rayleigh phase velocity and attenuation and that SRA has great potential to avoid shrinkage cracking in cement-based materials.

Non-contact feature detection using ultrasonic Lamb waves

DOEpatents

Sinha, Dipen N [Los Alamos, NM

2011-06-28

Apparatus and method for non-contact ultrasonic detection of features on or within the walls of hollow pipes are described. An air-coupled, high-power ultrasonic transducer for generating guided waves in the pipe wall, and a high-sensitivity, air-coupled transducer for detecting these waves, are disposed at a distance apart and at chosen angle with respect to the surface of the pipe, either inside of or outside of the pipe. Measurements may be made in reflection or transmission modes depending on the relative position of the transducers and the pipe. Data are taken by sweeping the frequency of the incident ultrasonic waves, using a tracking narrow-band filter to reduce detected noise, and transforming the frequency domain data into the time domain using fast Fourier transformation, if required.

Apparatus for measuring surface movement of an object that is subjected to external vibrations

DOEpatents

Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1997-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Method and apparatus for measuring surface movement of a solid object that is subjected to external vibrations

DOEpatents

Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1995-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Method and apparatus for measuring surface movement of an object using a polarizing interfeometer

DOEpatents

Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1995-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Method and apparatus for measuring surface movement of an object using a polarizing interferometer

DOEpatents

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-05-09

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figs.

Method and apparatus for measuring surface movement of a solid object that is subjected to external vibrations

DOEpatents

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-04-25

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figs.

Apparatus for measuring surface movement of an object that is subjected to external vibrations

DOEpatents

Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1997-04-22

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figs.

Precise optical observation of 0.5-GPa shock waves in condensed materials

NASA Astrophysics Data System (ADS)

Nagayama, Kunihito; Mori, Yasuhito

1999-06-01

Precision optical observation method was developed to study impact-generated high-pressure shock waves in condensed materials. The present method makes it possible to sensitively detect the shock waves of the relatively low shock stress around 0.5 GPa. The principle of the present method is based on the use of total internal reflection by triangular prisms placed on the free surface of a target assembly. When a plane shock wave arrives at the free surface, the light reflected from the prisms extinguishes instantaneously. The reason is that the total internal reflection changes to the reflection depending on micron roughness of the free surface after the shock arrival. The shock arrival at the bottom face of the prisms can be detected here by two kinds of methods, i.e., a photographic method and a gauge method. The photographic method is an inclined prism method of using a high-speed streak camera. The shock velocity and the shock tilt angle can be estimated accurately from an obtained streak photograph. While in the gauge method, an in-material PVDF stress gauge is combined with an optical prism-pin. The PVDF gauge records electrically the stress profile behind the shockwave front, and the Hugoniot data can be precisely measured by combining the prism pin with the PVDF gauge.

The radio power reflected from rough and undulating ionospheric surfaces

NASA Astrophysics Data System (ADS)

Whitehead, J. D.; From, W. R.; Smith, L. G.

1984-08-01

It is shown for both rough and undulating surfaces that the mean radio power reflected by the ionosphere averaged over a sufficiently long time is exactly the same as for a smooth flat surface at the same height provided the sounder is equally sensitive for echoes from all directions. When making radio wave absorption measurements under spread conditions the total integrated power over the whole time the direct echoes are being received must be used but the distance attenuation factor must be calculated from the time of arrival of the first echo.

Source amplitudes of NTS explosions inferred from Rayleigh waves at Albuquerque and Tucson. Topical report

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

Bache, T.C.; Rodi, W.L.; Mason, B.F.

1978-06-01

Comparing observed and synthetic seismograms, source amplitudes of NTS explosions are inferred from Rayleigh wave recordings from the WWSSN stations at Albuquerque, New Mexico (ALQ) and Tucson, Arizona (TUC). The potential influence of source complexities, particularly surface spallation and related phenomena, is studied in detail. As described in earlier work by Bache, Rodi and Harkrider, the earth model for the synthetic were converted from observations at ALQ and TUC. The agreement of observed and synthetic seismograms is quite good and is sensitive to important features of the source.

High-resolution angle-resolved photoemission study of electronic structure and charge-density wave formation in HoTe3

NASA Astrophysics Data System (ADS)

Liu, Guodong; Wang, Chenlu; Zhang, Yan; Hu, Bingfeng; Mou, Daixiang; Yu, Li; Zhao, Lin; Zhou, Xingjiang; Wang, Nanlin; Chen, Chuangtian; Xu, Zuyan

We performed high-resolution angle-resolved photoemission spectroscopy (ARPES) measurement on high quality crystal of HoTe3, an intriguing quasi-two-dimensional rare-earth-element tritelluride charge-density-wave (CDW) compound. The main features of the electronic structure in this compound are established by employing a quasi-CW laser (7eV) and a helium discharging lamp (21.22 eV) as excitation light sources. It reveals many bands back folded according to the CDW periodicity and two incommensurate CDW gaps created by perpendicular Fermi surface (FS) nesting vectors. A large gap is found to open in well nested regions of the Fermi surface sheets, whereas other Fermi surface sections with poor nesting remain ungapped. In particular, some peculiar features are identified by using our ultra-high resolution and bulk sensitive laser-ARPES.

Using Adjoint Methods to Improve 3-D Velocity Models of Southern California

NASA Astrophysics Data System (ADS)

Liu, Q.; Tape, C.; Maggi, A.; Tromp, J.

2006-12-01

We use adjoint methods popular in climate and ocean dynamics to calculate Fréchet derivatives for tomographic inversions in southern California. The Fréchet derivative of an objective function χ(m), where m denotes the Earth model, may be written in the generic form δχ=int Km(x) δln m(x) d3x, where δln m=δ m/m denotes the relative model perturbation. For illustrative purposes, we construct the 3-D finite-frequency banana-doughnut kernel Km, corresponding to the misfit of a single traveltime measurement, by simultaneously computing the 'adjoint' wave field s† forward in time and reconstructing the regular wave field s backward in time. The adjoint wave field is produced by using the time-reversed velocity at the receiver as a fictitious source, while the regular wave field is reconstructed on the fly by propagating the last frame of the wave field saved by a previous forward simulation backward in time. The approach is based upon the spectral-element method, and only two simulations are needed to produce density, shear-wave, and compressional-wave sensitivity kernels. This method is applied to the SCEC southern California velocity model. Various density, shear-wave, and compressional-wave sensitivity kernels are presented for different phases in the seismograms. We also generate 'event' kernels for Pnl, S and surface waves, which are the Fréchet kernels of misfit functions that measure the P, S or surface wave traveltime residuals at all the receivers simultaneously for one particular event. Effectively, an event kernel is a sum of weighted Fréchet kernels, with weights determined by the associated traveltime anomalies. By the nature of the 3-D simulation, every event kernel is also computed based upon just two simulations, i.e., its construction costs the same amount of computation time as an individual banana-doughnut kernel. One can think of the sum of the event kernels for all available earthquakes, called the 'misfit' kernel, as a graphical representation of the gradient of the misfit function. With the capability of computing both the value of the misfit function and its gradient, which assimilates the traveltime anomalies, we are ready to use a non-linear conjugate gradient algorithm to iteratively improve velocity models of southern California.

Projected Changes on the Global Surface Wave Drift Climate towards the END of the Twenty-First Century

NASA Astrophysics Data System (ADS)

Carrasco, Ana; Semedo, Alvaro; Behrens, Arno; Weisse, Ralf; Breivik, Øyvind; Saetra, Øyvind; Håkon Christensen, Kai

2016-04-01

The global wave-induced current (the Stokes Drift - SD) is an important feature of the ocean surface, with mean values close to 10 cm/s along the extra-tropical storm tracks in both hemispheres. Besides the horizontal displacement of large volumes of water the SD also plays an important role in the ocean mix-layer turbulence structure, particularly in stormy or high wind speed areas. The role of the wave-induced currents in the ocean mix-layer and in the sea surface temperature (SST) is currently a hot topic of air-sea interaction research, from forecast to climate ranges. The SD is mostly driven by wind sea waves and highly sensitive to changes in the overlaying wind speed and direction. The impact of climate change in the global wave-induced current climate will be presented. The wave model WAM has been forced by the global climate model (GCM) ECHAM5 wind speed (at 10 m height) and ice, for present-day and potential future climate conditions towards the end of the end of the twenty-first century, represented by the Intergovernmental Panel for Climate Change (IPCC) CMIP3 (Coupled Model Inter-comparison Project phase 3) A1B greenhouse gas emission scenario (usually referred to as a ''medium-high emissions'' scenario). Several wave parameters were stored as output in the WAM model simulations, including the wave spectra. The 6 hourly and 0.5°×0.5°, temporal and space resolution, wave spectra were used to compute the SD global climate of two 32-yr periods, representative of the end of the twentieth (1959-1990) and twenty-first (1969-2100) centuries. Comparisons of the present climate run with the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-40 reanalysis are used to assess the capability of the WAM-ECHAM5 runs to produce realistic SD results. This study is part of the WRCP-JCOMM COWCLIP (Coordinated Ocean Wave Climate Project) effort.

Assessment of the importance of the current-wave coupling in the shelf ocean forecasts

NASA Astrophysics Data System (ADS)

Jordà, G.; Bolaños, R.; Espino, M.; Sánchez-Arcilla, A.

2006-10-01

The effects of wave-current interactions on shelf ocean forecasts is investigated in the framework of the MFSTEP (Mediterranean Forecasting System Project Towards Enviromental Predictions) project. A one way sequential coupling approach is adopted to link the wave model (WAM) to the circulation model (SYMPHONIE). The coupling of waves and currents has been done considering four main processes: wave refraction due to currents, surface wind drag and bo€ttom drag modifications due to waves, and the wave induced mass flux. The coupled modelling system is implemented in the southern Catalan shelf (NW Mediterranean), a region with characteristics similar to most of the Mediterranean shelves. The sensitivity experiments are run in a typical operational configuration. The wave refraction by currents seems to be not very relevant in a microtidal context such as the western Mediterranean. The main effect of waves on current forecasts is through the modification of the wind drag. The Stokes drift also plays a significant role due to its spatial and temporal characteristics. Finally, the enhanced bottom friction is just noticeable in the inner shelf.

Investigation of contact acoustic nonlinearities on metal and composite airframe structures via intensity based health monitoring.

PubMed

Romano, P Q; Conlon, S C; Smith, E C

2013-01-01

Nonlinear structural intensity (NSI) and nonlinear structural surface intensity (NSSI) based damage detection techniques were improved and extended to metal and composite airframe structures. In this study, the measurement of NSI maps at sub-harmonic frequencies was completed to provide enhanced understanding of the energy flow characteristics associated with the damage induced contact acoustic nonlinearity mechanism. Important results include NSI source localization visualization at ultra-subharmonic (nf/2) frequencies, and damage detection results utilizing structural surface intensity in the nonlinear domain. A detection metric relying on modulated wave spectroscopy was developed and implemented using the NSSI feature. The data fusion of the intensity formulation provided a distinct advantage, as both the single interrogation frequency NSSI and its modulated wave extension (NSSI-MW) exhibited considerably higher sensitivities to damage than using single-sensor (strain or acceleration) nonlinear detection metrics. The active intensity based techniques were also extended to composite materials, and results show both NSSI and NSSI-MW can be used to detect damage in the bond line of an integrally stiffened composite plate structure with high sensitivity. Initial damage detection measurements made on an OH-58 tailboom (Penn State Applied Research Laboratory, State College, PA) indicate the techniques can be transitioned to complex airframe structures achieving high detection sensitivities with minimal sensors and actuators.

A SAW-based chemical sensor for detecting sulfur-containing organophosphorus compounds using a two-step self-assembly and molecular imprinting technology.

PubMed

Pan, Yong; Yang, Liu; Mu, Ning; Shao, Shengyu; Wang, Wen; Xie, Xiao; He, Shitang

2014-05-19

This paper presents a new effective approach for the sensitive film deposition of surface acoustic wave (SAW) chemical sensors for detecting organophosphorus compounds such as O-ethyl-S-2-diisopropylaminoethyl methylphosphonothiolate (VX) containing sulfur at extremely low concentrations. To improve the adsorptive efficiency, a two-step technology is proposed for the sensitive film preparation on the SAW delay line utilizing gold electrodes. First, mono[6-deoxy-6-[(mercaptodecamethylene)thio

A SAW-Based Chemical Sensor for Detecting Sulfur-Containing Organophosphorus Compounds Using a Two-Step Self-Assembly and Molecular Imprinting Technology

PubMed Central

Pan, Yong; Yang, Liu; Mu, Ning; Shao, Shengyu; Wang, Wen; Xie, Xiao; He, Shitang

2014-01-01

This paper presents a new effective approach for the sensitive film deposition of surface acoustic wave (SAW) chemical sensors for detecting organophosphorus compounds such as O-ethyl-S-2-diisopropylaminoethyl methylphosphonothiolate (VX) containing sulfur at extremely low concentrations. To improve the adsorptive efficiency, a two-step technology is proposed for the sensitive film preparation on the SAW delay line utilizing gold electrodes. First, mono[6-deoxy-6-[(mercaptodecamethylene)thio

Applications of a nanocomposite-inspired in-situ broadband ultrasonic sensor to acousto-ultrasonics-based passive and active structural health monitoring.

PubMed

Liu, Menglong; Zeng, Zhihui; Xu, Hao; Liao, Yaozhong; Zhou, Limin; Zhang, Zhong; Su, Zhongqing

2017-07-01

A novel nanocomposite-inspired in-situ broadband ultrasonic sensor previously developed, with carbon black as the nanofiller and polyvinylidene fluoride as the matrix, was networked for acousto-ultrasonic wave-based passive and active structural health monitoring (SHM). Being lightweight and small, this kind of sensor was proven to be capable of perceiving strain perturbation in virtue of the tunneling effect in the formed nanofiller conductive network when acousto-ultrasonic waves traverse the sensor. Proof-of-concept validation was implemented, to examine the sensor performance in responding to acousto-ultrasonic waves in a broad frequency regime: from acoustic emission (AE) of lower frequencies to guided ultrasonic waves (GUWs) of higher frequencies. Results have demonstrated the high fidelity, ultrafast response and high sensitivity of the sensor to acousto-ultrasonic waves up to 400kHz yet with an ultra-low magnitude (of the order of micro-strain). The sensor is proven to possess sensitivity and accuracy comparable with commercial piezoelectric ultrasonic transducers, whereas with greater flexibility in accommodating curved structural surfaces. Application paradigms of using the sensor for damage evaluation have spotlighted the capability of the sensor in compromising "sensing cost" with "sensing effectiveness" for passive AE- or active GUW-based SHM. Copyright © 2017 Elsevier B.V. All rights reserved.

Receiver function HV ratio: a new measurement for reducing non-uniqueness of receiver function waveform inversion

NASA Astrophysics Data System (ADS)

Chong, Jiajun; Chu, Risheng; Ni, Sidao; Meng, Qingjun; Guo, Aizhi

2018-02-01

It is known that a receiver function has relatively weak constraint on absolute seismic wave velocity, and that joint inversion of the receiver function with surface wave dispersion has been widely applied to reduce the trade-off of velocity with 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 receiver function 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.

Noncontact holographic detection for photoacoustic tomography

NASA Astrophysics Data System (ADS)

Buj, Christian; Münter, Michael; Schmarbeck, Benedikt; Horstmann, Jens; Hüttmann, Gereon; Brinkmann, Ralf

2017-10-01

A holographic method for high-speed, noncontact photoacoustic tomography is introduced and evaluated. Relative changes of the object's topography, induced by the impact of thermoelastic pressure waves, were determined at nanometer sensitivity without physical contact. The object's surface was illuminated with nanosecond laser pulses and imaged with a high-speed CMOS camera. From two interferograms measured before and after excitation of the acoustic wave, surface displacement was calculated and then used as the basis for a tomographic reconstruction of the initial pressure caused by optical absorption. The holographic detection scheme enables variable sampling rates of the photoacoustic signal of up to 50 MHz. The total acquisition times for complete volumes with 230 MVoxel is far below 1 s. Measurements of silicone and porcine skin tissue phantoms with embedded artificial absorbers, which served as a model for human subcutaneous vascular networks, were possible. Three-dimensional reconstructions of the absorbing structures show details with a diameter of 310 μm up to a depth of 2.5 mm. Theoretical limitations and the experimental sensitivity, as well as the potential for in vivo imaging depending on the detection repetition rate, are analyzed and discussed.

Dynamics of avalanche-generated impulse waves: three-dimensional hydrodynamic simulations and sensitivity analysis

NASA Astrophysics Data System (ADS)

Chisolm, Rachel E.; McKinney, Daene C.

2018-05-01

This paper studies the lake dynamics for avalanche-triggered glacial lake outburst floods (GLOFs) in the Cordillera Blanca mountain range in Ancash, Peru. As new glacial lakes emerge and existing lakes continue to grow, they pose an increasing threat of GLOFs that can be catastrophic to the communities living downstream. In this work, the dynamics of displacement waves produced from avalanches are studied through three-dimensional hydrodynamic simulations of Lake Palcacocha, Peru, with an emphasis on the sensitivity of the lake model to input parameters and boundary conditions. This type of avalanche-generated wave is an important link in the GLOF process chain because there is a high potential for overtopping and erosion of the lake-damming moraine. The lake model was evaluated for sensitivity to turbulence model and grid resolution, and the uncertainty due to these model parameters is significantly less than that due to avalanche boundary condition characteristics. Wave generation from avalanche impact was simulated using two different boundary condition methods. Representation of an avalanche as water flowing into the lake generally resulted in higher peak flows and overtopping volumes than simulating the avalanche impact as mass-momentum inflow at the lake boundary. Three different scenarios of avalanche size were simulated for the current lake conditions, and all resulted in significant overtopping of the lake-damming moraine. Although the lake model introduces significant uncertainty, the avalanche portion of the GLOF process chain is likely to be the greatest source of uncertainty. To aid in evaluation of hazard mitigation alternatives, two scenarios of lake lowering were investigated. While large avalanches produced significant overtopping waves for all lake-lowering scenarios, simulations suggest that it may be possible to contain waves generated from smaller avalanches if the surface of the lake is lowered.

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.

Comparison of sensor structures for the signal amplification of surface plasmon resonance immunoassay using enzyme precipitation

NASA Astrophysics Data System (ADS)

Yang, Chih-Tsung; Thierry, Benjamin

2015-12-01

Surface plasmon resonance (SPR) biosensing has been successfully applied for the label-free detection of a broad range of bioanalytes ranging from bacteria, cell, exosome, protein and nucleic acids. When it comes to the detection of small molecules or analytes found at low concentration, amplification schemes are desirable to enhance binding signals and in turn increase sensitivity. A number of SPR signal amplification schemes have been developed and validated; however, little effort has been devoted to understanding the effect of the SPR sensor structures on the amplification of binding signals and therefore on the overall sensing performance. The physical phenomenon of long-range SPR (LRSPR) relies on the propagation of coupled surface plasmonic waves on the opposite sides of a nanoscale-thick noble metal film suspended between two dielectrics with similar refractive indices. Importantly, as compared with commonly used conventional SPR (cSPR), LRSPR is not only characterized by a longer penetration depth of the plasmonic waves in the analyzed medium but also by a greater sensitivity to bulk refractive index changes. In this work, an immunoassay signal amplification platform based on horseradish peroxidase (HRP) catalyzed precipitation was utilized to investigate the sensing performance with regards to cSPR and LRSPR. The enzymatic precipitation of 3, 3'-diaminobenzidine tetrahydrochloride (DAB)/H2O2 was used to amplify SPR signals. The structure-function relationship of cSPR and LRSPR sensors is presented for both standard refractometric measurements and the enzymatic precipitation scheme. Experimental data shows that despite its inherent higher sensitivity to bulk refractive index changes and higher figure of merit, LRSPR was characterized by a lower angular sensitivity in the model enzymatic amplification scheme used here.

Waves on Seas of Mars and Titan: Wind-Tunnel Experiments on Wind-Wave Generation in Extraterrestrial Atmospheres

NASA Technical Reports Server (NTRS)

Lorenz, R. D.; Kraal, E. R.; Eddlemon, E. E.; Cheney, J.; Greeley, R.

2004-01-01

The generation of waves by winds across Earth's water oceans is a topic of enduring fascination. However, the physics of the problem are rather forbidding and thus the relationships between real-world windspeed and sea state tend to be empirical. Such empirical relations are of limited utility in environments where the physical parameters are different, such as the surfaces of other planets. These environments have only recently come to oceanographers attention, with the discovery of ancient shorelines and lakes on Mars, and the prospects for and recent evidence of lakes and seas of liquid hydrocarbons on Saturn's moon Titan. We are aware of only one other published experimental wind-water tunnel study where the fluid parameters have been varied. This used artificially-generated mm-scale waves at 3.8-7.6 Hz in water, glycerol solutions (higher viscosity) and surfactant solutions (lower surface tension). Lower viscosity solutions had higher wave growth rates: surprisingly, higher surface tension led to more rapid wave growth. The liquid density was not appreciably varied, and 1 bar air was used throughout.We used the MARSWIT (Mars Wind Tunnel) operated by ASU at NASA Ames. A fiberglass tray (5 cm x 120 cm x 75 cm) was installed in the tunnel, with an approx. 1:5 ramp to prevent strong flow separation. The tray was filled to a depth of about 4 cm. Sensors were clamped to the tray itself or held by a steel and aluminium frame just above the water level. A towel was draped on the water surface at the downwind end of the tray to act as a damper to suppress wave reflection. Position-sensitive infrared (IR) reflection sensors (Sharp GP12D02) and ultrasonic rangers (Devantech DF-04) used in mobile robotics were used as water level sensors. The tray was observed with a video camera, whose output could be viewed on a monitor and recorded on VHS tape.

Phase-sensitive terahertz spectroscopy with backward-wave oscillators in reflection mode.

PubMed

Pronin, A V; Goncharov, Yu G; Fischer, T; Wosnitza, J

2009-12-01

In this article we describe a method which allows accurate measurements of the complex reflection coefficient r = absolute value(r) x exp(i phi(R)) of a solid at frequencies of 1-50 cm(-1) (30 GHz-1.5 THz). Backward-wave oscillators are used as sources for monochromatic coherent radiation tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a Michelson interferometer. This method is particular useful for nontransparent samples, where phase-sensitive transmission measurements are not possible. The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as the complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeabilities different from unity at the measurement frequencies (for example, colossal-magnetoresistance materials and metamaterials). Measuring both the phase-sensitive transmission and the phase-sensitive reflection allows for a straightforward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

Phase-sensitive terahertz spectroscopy with backward-wave oscillators in reflection mode

NASA Astrophysics Data System (ADS)

Pronin, A. V.; Goncharov, Yu. G.; Fischer, T.; Wosnitza, J.

2009-12-01

In this article we describe a method which allows accurate measurements of the complex reflection coefficient r̂=|r̂|ṡexp(iφR) of a solid at frequencies of 1-50 cm-1 (30 GHz-1.5 THz). Backward-wave oscillators are used as sources for monochromatic coherent radiation tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a Michelson interferometer. This method is particular useful for nontransparent samples, where phase-sensitive transmission measurements are not possible. The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as the complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeabilities different from unity at the measurement frequencies (for example, colossal-magnetoresistance materials and metamaterials). Measuring both the phase-sensitive transmission and the phase-sensitive reflection allows for a straightforward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

Grating-patterned FeCo coated surface acoustic wave device for sensing magnetic field

NASA Astrophysics Data System (ADS)

Wang, Wen; Jia, Yana; Xue, Xufeng; Liang, Yong; Du, Zhaofu

2018-01-01

This study addresses the theoretical and experimental investigations of grating-patterned magnetostrictive FeCo coated surface acoustic wave (SAW) device for sensing magnetic field. The proposed sensor is composed of a configuration of differential dual-delay-line oscillators, and a magnetostrictive FeCo grating array deposited along the SAW propagation path of the sensing device, which suppresses effectively the hysteresis effect by releasing the internal binding force in FeCo. The magnetostrictive strain and ΔE effect from the FeCo coating modulates the SAW propagation characteristic, and the corresponding shift in differential oscillation frequency was utilized to evaluate the measurant. A theoretical model is performed to investigate the wave propagation in layered structure of FeCo/LiNbO3 in the effect of magnetostrictive, and allowing determining the optimal structure. The experimental results indicate that higher sensitivity, excellent linearity, and lower hysteresis error over the typical FeCo thin-film coated sensor were achieved from the grating-patterned FeCo coated sensor successfully.

Hydrodynamic Instability in an Extended Landau/Levich Model of Liquid-Propellant Combustion

NASA Technical Reports Server (NTRS)

Margolis, Stephen B.; Sackesteder, Kurt (Technical Monitor)

1998-01-01

The classical Landau/Levich models of liquid propellant combustion, which serve as seminal examples of hydrodynamic instability in reactive systems, have been combined and extended to account for a dynamic dependence, absent in the original formulations, of the local burning rate on the local pressure and/or temperature fields. The resulting model admits an extremely rich variety of both hydrodynamic and reactive/diffusive instabilities that can be analyzed in various limiting parameter regimes. In the present work, a formal asymptotic analysis, based on the realistic smallness of the gas-to-liquid density ratio, is developed to investigate the combined effects of gravity, surface tension and viscosity on the hydrodynamic instability of the propagating liquid/gas interface. In particular, a composite asymptotic expression, spanning three distinguished wavenumber regimes, is derived for both cellular and pulsating hydrodynamic neutral stability boundaries A(sub p)(k), where A(sub p) is the pressure sensitivity of the burning rate and k is the disturbance wavenumber. For the case of cellular (Landau) instability, the results demonstrate explicitly the stabilizing effect of gravity on long-wave disturbances, the stabilizing effect of viscosity and surface tension on short-wave perturbations, and the instability associated with intermediate wavenumbers for critical negative values of A(sub p). In the limiting case of weak gravity, it is shown that cellular hydrodynamic instability in this context is a long-wave instability phenomenon, whereas at normal gravity, this instability is first manifested through O(l) wavenumber disturbances. It is also demonstrated that, in the large wavenumber regime, surface tension and both liquid and gas viscosity all produce comparable stabilizing effects in the large-wavenumber regime, thereby providing significant modifications to previous analyses of Landau instability in which one or more of these effects were neglected. In contrast, the pulsating hydrodynamic stability boundary is found to be insensitive to gravitational and surface-tension effects, but is more sensitive to the effects of liquid viscosity, which is a significant stabilizing effect for O(l) and higher wavenumbers. Liquid-propellant combustion is predicted to be stable (i.e., steady and planar) only for a range of negative pressure sensitivities that lie between the two types of hydrodynamic stability boundaries.

Catastrophic instabilities of modified DA-DC hybrid surface waves in a semi-bounded plasma system

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

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

We find the catastrophic instabilities and derive the growth rates for the dust-cyclotron resonance (DCR) and dust-rotation resonance (DRR) modes of the modified dust-acoustic and dust-cyclotron (DA-DC) hybrid surface waves propagating at the plasma–vacuum interface where the plasma is semi-bounded and composed of electrons and rotating dust grains. The effects of magnetic field and dust rotation frequency on the DCR- and DDR-modes are also investigated. We find that the dust rotation frequency enhances the growth rate of DCR-mode and the effect of dust rotation on this resonance mode decreases with an increase of the wave number. We also find thatmore » an increase of magnetic field strength enhances the DCR growth rate, especially, for the short wavelength regime. In the case of DRR-mode, the growth rate is found to be decreased less sensitively with an increase of the wave number compared with the case of DCR, but much significantly enhanced by an increase of dust rotation frequency. The DRR growth rate also decreases with an increase of the magnetic field strength, especially in the long wavelength regime. Interestingly, we find that catastrophic instabilities occur for both DCR- and DRR-modes of the modified DA-DC hybrid surface waves when the rotational frequency is close to the dust-cyclotron frequency. Both modes can also be excited catastrophically due to the cooperative interaction between the DCR-mode and the DRR-mode.« less

The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride.

PubMed

Kim, Kris S; Trajanoski, Daniel; Ho, Kevin; Gilburd, Leonid; Maiti, Aniket; van der Velden, Luuk; de Beer, Sissi; Walker, Gilbert C

2017-07-06

In order to apply the ability of hexagonal boron nitride (hBN) to confine energy in the form of hyperbolic phonon polariton (HPhP) modes in photonic-electronic devices, approaches to finely control and leverage the sensitivity of these propagating waves must be investigated. Here, we show that by surrounding hBN with materials of lower/higher dielectric responses, such as air and silicon, lower/higher surface momenta of HPhPs can be achieved. Furthermore, an alternative method for preparing thin hBN crystals with minimum contamination is presented, which provides opportunities to study the sensitivity of the damping mechanism of HPhPs on adsorbed materials. Infrared scanning near-field optical microscopy (IR-SNOM) results suggest that the reflections at the upper and lower hBN interfaces are primary causes of the damping of HPhPs, and that the damping coefficients of propagating waves are highly sensitive to adjacent layers, suggesting opportunities for sensor applications.

Surface acoustic wave resonators

NASA Astrophysics Data System (ADS)

Avitabile, Gianfranco; Roselli, Luca; Atzeni, Carlo; Manes, Gianfranco

1991-10-01

The development of surface acoustic wave (SAW) resonators is reviewed with attention given to the design of a simulation package for CAD-assisted SAW resonator design. Basic design configurations and operation parameters are set forth for the SAW resonators including the phase of the reflection factor, evaluation of the stopband center frequency, stopband width, and the free propagation speed. The use of synchronous designs is shown to reduce device sensitivity to variations in the technological process but generate higher insertion losses. The existence of transverse modes and propagation losses is shown to affect the rejection of spurious modes and the achievement of low insertion losses. Several SAW resonators are designed and fabricated with the CAD process, and the resonators in the VHF-UHF bands perform in a manner predicted by simulated results.

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.

Low Insertion Loss and Highly Sensitive SH-SAW Sensors Based on 36° YX LiTaO 3 Through the Incorporation of Filled Microcavities

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

Richardson, Mandek; Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.

2015-02-01

Reduction in power consumption and improvement in mass sensitivity are important considerations for surface acoustic wave (SAW) devices used in various sensing applications. Detection of minute quantities of a particular species (clinical sensing) and power requirements (wireless sensing) are two key metrics that must be optimized. In this paper, a 3-D finite element model (FEM) was employed to compare insertion loss (IL) and mass sensitivity of SAW sensors having microcavities filled with ZnO and nanocrystalline diamond to a standard two-port SAW design. Initial simulation results show that ZnO filled cavities (depth = 5 mu m) were most effective at reducingmore » power loss Delta IL = (6.03 dB) by increasing particle displacement (acousto-electric to mechanical transduction) at the output transducer. A 100-pg/cm(2) load was applied to the sensing area of each device to evaluate mass sensitivity. Our simulations suggest that ZnO filled cavities with shallow depth (2.5 mu m) have the greatest sensitivity. The FEM simulations are used to understand the acoustic wave propagation in microcavity-based SAW sensors. The observed enhancement in mass sensitivity and power transfer is attributed to waveguiding effects and constructive interference of the scattered acoustic waves from the microcavities. Devices fabricated with microcavities similar to 1 mu m deep decreased IL by 3.306 dB compared with a standard SAW device. Additional simulations were conducted for each device configuration using the same depth in order to make a direct comparison between measured and simulated results. Our findings offer encouraging prospects for designing low IL highly sensitive microcavity-based SAW biosensors.« less

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Development of Interference Lithography Capability Using a Helium Cadmium Ultraviolet Multimode Laser for the Fabrication of Sub-Micron-Structured Optical Materials

DTIC Science & Technology

2011-03-01

into separate parts, transmitted into different directions , and then recombined upon a surface to produce interference. The concern with this type of...photoresist (PR), is a radiation sensitive compound that is classified as positive or negative, depending on how it responds to radiation . Each is designed...emerging waves, and are referred to as diffraction gratings. Upon reflection from these kinds of gratings, light scattered from the periodic surface

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.

Note on the directional properties of meter-scale gravity waves

NASA Astrophysics Data System (ADS)

Peureux, Charles; Benetazzo, Alvise; Ardhuin, Fabrice

2018-01-01

The directional distribution of the energy of young waves is bimodal for frequencies above twice the peak frequency; i.e., their directional distribution exhibits two peaks in different directions and a minimum between. Here we analyze in detail a typical case measured with a peak frequency fp = 0.18 Hz and a wind speed of 10.7 m s-1 using a stereo-video system. This technique allows for the separation of free waves from the spectrum of the sea-surface elevation. The latter indeed tend to reduce the contrast between the two peaks and the background. The directional distribution for a given wavenumber is nearly symmetric, with the angle distance between the two peaks growing with frequency, reaching 150° at 35 times the peak wavenumber kp and increasing up to 45 kp. When considering only free waves, the lobe ratio, the ratio of oblique peak energy density over energy in the wind direction, increases linearly with the non-dimensional wavenumber k/kp, up to a value of 6 at k/kp ≃ 22, and possibly more for shorter components. These observations extend to shorter components' previous measurements, and have important consequences for wave properties sensitive to the directional distribution, such as surface slopes, Stokes drift or microseism sources.

Development of a nearshore oscillating surge wave energy converter with variable geometry

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

Tom, N. M.; Lawson, M. J.; Yu, Y. H.

This paper presents an analysis of a novel wave energy converter concept that combines an oscillating surge wave energy converter (OSWEC) with control surfaces. The control surfaces allow for a variable device geometry that enables the hydrodynamic properties to be adapted with respect to structural loading, absorption range and power-take-off capability. The device geometry is adjusted on a sea state-to-sea state time scale and combined with wave-to-wave manipulation of the power take-off (PTO) to provide greater control over the capture efficiency, capacity factor, and design loads. This work begins with a sensitivity study of the hydrodynamic coefficients with respect tomore » device width, support structure thickness, and geometry. A linear frequency domain analysis is used to evaluate device performance in terms of absorbed power, foundation loads, and PTO torque. Previous OSWEC studies included nonlinear hydrodynamics, in response a nonlinear model that includes a quadratic viscous damping torque that was linearized via the Lorentz linearization. Inclusion of the quadratic viscous torque led to construction of an optimization problem that incorporated motion and PTO constraints. Results from this study found that, when transitioning from moderate-to-large sea states the novel OSWEC was capable of reducing structural loads while providing a near constant power output.« less

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

NASA Astrophysics Data System (ADS)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-05-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

NASA Astrophysics Data System (ADS)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-06-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Design and simulation study of high frequency response for surface acoustic wave device by using CST software

NASA Astrophysics Data System (ADS)

Zakaria, M. R.; Hashim, U.; Amin, Mohd Hasrul I. M.; Ayub, R. Mat; Hashim, M. N.; Adam, T.

2015-05-01

This paper focuses on the enhancement and improvement of the Surface Acoustic Wave (SAW) device performance. Due to increased demand in the international market for biosensor product, the product must be emphasized in terms of quality. However, within the technological advances, demand for device with low cost, high efficiency and friendly-user preferred. Surface Acoustic Wave (SAW) device with the combination of pair electrode know as Interdigital Transducer (IDT) was fabricated on a piezoelectric substrate. The design of Interdigital Transducer (IDT) parameter is changes in several sizes and values for which it is able to provide greater efficiency in sensing sensitivity by using process simulation with CST STUDIO Suite software. In addition, Interdigital Transducer (IDT) parameters also changed to be created the products with a smaller size and easy to handle where it also reduces the cost of this product. Parameter values of an Interdigital Transducer (IDT) will be changed in the design is the total number of fingers pair, finger length, finger width and spacing, aperture and also the thickness of the Interdigital Transducer (IDT). From the result, the performance of the sensor is improved significantly after modification is done.

Helioseismic measurements in the solar envelope using group velocities of surface waves

NASA Astrophysics Data System (ADS)

Vorontsov, S. V.; Baturin, V. A.; Ayukov, S. V.; Gryaznov, V. K.

2014-07-01

At intermediate- and high-degree l, solar p and f modes can be considered as surface waves. Using variational principle, we derive an integral expression for the group velocities of the surface waves in terms of adiabatic eigenfunctions of normal modes, and address the benefits of using group-velocity measurements as a supplementary diagnostic tool in solar seismology. The principal advantage of using group velocities, when compared with direct analysis of the oscillation frequencies, comes from their smaller sensitivity to the uncertainties in the near-photospheric layers. We address some numerical examples where group velocities are used to reveal inconsistencies between the solar models and the seismic data. Further, we implement the group-velocity measurements to the calibration of the specific entropy, helium abundance Y, and heavy-element abundance Z in the adiabatically stratified part of the solar convective envelope, using different recent versions of the equation of state. The results are in close agreement with our earlier measurements based on more sophisticated analysis of the solar oscillation frequencies. These results bring further support to the downward revision of the solar heavy-element abundances in recent spectroscopic measurements.

Evanescent wave cavity ring-down spectroscopy (EW-CRDS) as a probe of macromolecule adsorption kinetics at functionalized interfaces.

PubMed

O'Connell, Michael A; de Cuendias, Anne; Gayet, Florence; Shirley, Ian M; Mackenzie, Stuart R; Haddleton, David M; Unwin, Patrick R

2012-05-01

Evanescent wave cavity ring-down spectroscopy (EW-CRDS) has been employed to study the interfacial adsorption kinetics of coumarin-tagged macromolecules onto a range of functionalized planar surfaces. Such studies are valuable in designing polymers for complex systems where the degree of interaction between the polymer and surface needs to be tailored. Three tagged synthetic polymers with different functionalities are examined: poly(acrylic acid) (PAA), poly(3-sulfopropyl methacrylate, potassium salt) (PSPMA), and a mannose-modified glycopolymer. Adsorption transients at the silica/water interface are found to be characteristic for each polymer, and kinetics are deduced from the initial rates. The chemistry of the adsorption interfaces has been varied by, first, manipulation of silica surface chemistry via the bulk pH, followed by surfaces modified by poly(L-glutamic acid) (PGA) and cellulose, giving five chemically different surfaces. Complementary atomic force microscopy (AFM) imaging has been used for additional surface characterization of adsorbed layers and functionalized interfaces to allow adsorption rates to be interpreted more fully. Adsorption rates for PSPMA and the glycopolymer are seen to be highly surface sensitive, with significantly higher rates on cellulose-modified surfaces, whereas PAA shows a much smaller rate dependence on the nature of the adsorption surface.

Surface elastic wave detectors

NASA Technical Reports Server (NTRS)

Lawson, R. L.

1971-01-01

The potential applications of acoustic surface wave technology to multiplex communication systems such as data-bus, are examined. The goals are primarily to characterize certain aspects of surface wave trapped delay lines, surface wave modulation techniques, and surface wave applications that are relevant to the evaluation of surface wave devices in multiplex systems. The results indicate that there is a potential for the application of surface wave technology in data-bus type systems.

Surface wave chemical detector using optical radiation

DOEpatents

Thundat, Thomas G.; Warmack, Robert J.

2007-07-17

A surface wave chemical detector comprising at least one surface wave substrate, each of said substrates having a surface wave and at least one measurable surface wave parameter; means for exposing said surface wave substrate to an unknown sample of at least one chemical to be analyzed, said substrate adsorbing said at least one chemical to be sensed if present in said sample; a source of radiation for radiating said surface wave substrate with different wavelengths of said radiation, said surface wave parameter being changed by said adsorbing; and means for recording signals representative of said surface wave parameter of each of said surface wave substrates responsive to said radiation of said different wavelengths, measurable changes of said parameter due to adsorbing said chemical defining a unique signature of a detected chemical.

Estimates of Rayleigh-to-Love wave ratio in microseisms by co-located Ring Laser and STS-2

NASA Astrophysics Data System (ADS)

Tanimoto, Toshiro; Hadziioannou, Céline; Igel, Heiner; Wassermann, Joachim; Schreiber, Ulrich; Gebauer, André

2015-04-01

In older studies of microseisms (seismic noise), it was often assumed that microseisms, especially the secondary microseisms (0.1-0.3 Hz), mainly consist of Rayleigh waves. However, it has become clear that there exists a large amount of Love-wave energy mixed in it (e.g., Nishida et al., 2008). However, its confirmation is not necessarily straightforward and often required an array of seismographs. In this study, we take advantage of two co-located instruments, a Ring Laser and an STS-2 type seismograph, at Wettzell (WET), Germany (Schreiber et al., 2009). The Ring Laser records rotation (its vertical component) and is thus only sensitive to Love waves. The vertical component of STS-2 seismograph is only sensitive to Rayleigh waves. Therefore, a combination of the two instruments provides a unique opportunity to separate Rayleigh waves and Love waves in microseisms. The question we address in this paper is the ratio of Rayleigh waves to Love waves in microseisms. For both instruments, we analyze data from 2009 to 2014. Our basic approach is to create stacked vertical acceleration spectra for Rayleigh waves from STS-2 and stacked transverse acceleration spectra for Love waves from Ring Laser. The two spectra at Earth's surface can then be compared directly by their amplitudes. The first step in our analysis is a selection of time portions (each six-hour long) that are least affected by earthquakes. We do this by examining the GCMT (Global Centroid Moment Tensor) catalogue and also checking the PSDs for various frequency ranges. The second step is to create stacked (averaged) Fourier spectra from those selected time portions. The key is to use the same time portions for the STS-2 and the Ring Laser data so that the two can be directly compared. The vertical spectra from STS-2 are converted to acceleration spectra. The Ring Laser rotation spectra are first obtained in the unit of radians/sec (rotation rate). But as the Ring Laser spectra are dominated by fundamental-mode Love waves, the rotation spectra can be converted to transverse (SH) acceleration by multiplying them by the factor 2xCp where Cp is the Love-wave phase velocity. We used a seismic model by Fichtner et al. (2013) at WET to estimate Love-wave phase velocity. This conversion from rotation to transverse acceleration was first extensively used by Igel et al. (2005) for the analysis of lower frequency Love waves and the same relation holds for our spectral data. The two spectra provide the ratio of surface amplitudes. In the frequency range of secondary microseisms (0.10-0.35 Hz), they are comparable; near the spectral peak (~0.20 Hz), Rayleigh waves are about 20 percent larger in amplitudes but outside this peak region, Love waves have comparable or slightly larger amplitudes than Rayleigh waves. Therefore, the secondary microseisms at WET consist of similar contributions from Rayleigh waves and Love waves.

Towards the Wetness Characterization of Soil Subsurface Using Fibre Optic Distributed Acoustic Sensing

NASA Astrophysics Data System (ADS)

Ciocca, F.; Bodet, L.; Simon, N.; Karaulanov, R.; Clarke, A.; Abesser, C.; Krause, S.; Chalari, A.; Mondanos, M.

2017-12-01

Active seismic methods combined with detectors deployed at the soil surface, such as vertical collinear geophones, have revealed great potential for hydrogeophysical characterization of the soil vadose zone. In particular, recent findings have highlighted a clear dependence of both P-waves arrival times and surface-wave dispersion on the local degree of soil saturation, visible at laboratory as well as at field scale. In this study, we investigate the sensitivity of a fibre optic Distributed Acoustic Sensor (DAS) to different soil saturation. In vertical seismic applications, DAS have proven to offer equal and often better performance compared to the geophones, with the advantage that a fibre optic cable, whose length can reach 40 km, replaces the array of geophones as sensing element. We present the response to active seismic tests of 20 m of fibre optic cable buried in a poorly permeable bare soil. Tests were conducted in different moments of the year, with saturation monitored by means of independent dielectric probes. Body-wave travel times as well as surface-wave dispersion are compared. Finally, we discuss the possibility to determine a site-specific relation between the Poisson ratio and the soil saturation. This research has been performed in the framework of the British National Environmental Research Council (NERC) funded Distributed intelligent Heat Pulse System (DiHPS) project and of the Marie Curie H2020 Research and Innovation Staff Exchange (RISE) consortium Hi-Freq.

Biological implications of the hydrodynamics of swimming at or near the surface and in shallow water.

PubMed

Blake, R W

2009-03-01

The origins and effects of wave drag at and near the surface and in shallow water are discussed in terms of the dispersive waves generated by streamlined technical bodies of revolution and by semi-aquatic and aquatic animals with a view to bearing on issues regarding the design and function of autonomous surface and underwater vehicles. A simple two-dimensional model based on energy flux, allowing assessment of drag and its associated wave amplitude, is applied to surface swimming in Lesser Scaup ducks and is in good agreement with measured values. It is argued that hydrodynamic limitations to swimming at speeds associated with the critical Froude number ( approximately 0.5) and hull speed do not necessarily set biological limitations as most behaviours occur well below the hull speed. From a comparative standpoint, the need for studies on the hull displacement of different forms is emphasized. For forms in surface proximity, drag is a function of both Froude and Reynolds numbers. Whilst the depth dependence of wave drag is not particularly sensitive to Reynolds number, its magnitude is, with smaller and slower forms subject to relatively less drag augmentation than larger, faster forms that generate additional resistance due to ventilation and spray. A quasi-steady approach to the hydrodynamics of swimming in shallow water identifies substantial drag increases relative to the deeply submerged case at Froude numbers of about 0.9 that could limit the performance of semi-aquatic and aquatic animals and autonomous vehicles. A comparative assessment of fast-starting trout and upside down catfish shows that the energy losses of fast-starting fish are likely to be less for fish in surface proximity in deep water than for those in shallow water. Further work on unsteady swimming in both circumstances is encouraged. Finally, perspectives are offered as to how autonomous surface and underwater vehicles in surface proximity and shallow water could function to avoid prohibitive hydrodynamic resistance, thereby increasing their operational life.

On the Piezoelectric Detection of Guided Ultrasonic Waves

PubMed Central

2017-01-01

In order to quantify the wave motion of guided ultrasonic waves, the characteristics of piezoelectric detectors, or ultrasonic transducers and acoustic emission sensors, have been evaluated systematically. Such guided waves are widely used in structural health monitoring and nondestructive evaluation, but methods of calibrating piezoelectric detectors have been inadequate. This study relied on laser interferometry for the base displacement measurement of bar waves, from which eight different guided wave test set-ups are developed with known wave motion using piezoelectric transmitters. Both plates and bars of 12.7 and 6.4 mm thickness were used as wave propagation media. The upper frequency limit was 2 MHz. Output of guided wave detectors were obtained on the test set-ups and their receiving sensitivities were characterized and averaged. While each sensitivity spectrum was noisy for a detector, the averaged spectrum showed a good convergence to a unique receiving sensitivity. Twelve detectors were evaluated and their sensitivity spectra determined in absolute units. Generally, these showed rapidly dropping sensitivity with increasing frequency due to waveform cancellation on their sensing areas. This effect contributed to vastly different sensitivities to guided wave and to normally incident wave for each one of the 12 detectors tested. Various other effects are discussed and recommendations on methods of implementing the approach developed are provided. PMID:29156579

A reusable evanescent wave immunosensor for highly sensitive detection of bisphenol A in water samples

PubMed Central

Xiao-hong, Zhou; Lan-hua, Liu; Wei-qi, Xu; Bao-dong, Song; Jian-wu, Sheng; Miao, He; Han-chang, Shi

2014-01-01

This paper proposed a compact and portable planar waveguide evanescent wave immunosensor (EWI) for highly sensitive detection of BPA. The incident light is coupled into the planar waveguide chip via a beveled angle through undergoing total internal reflection, where the evanescent wave field forms and excites the binding fluorophore-tagged antibodies on the chip surface. Typical calibration curves obtained for BPA has detection limits of 0.03 μg/L. Linear response for BPA ranged from 0.124 μg/L–9.60 μg/L with 50% inhibition concentration for BPA of 1.09 ± 0.25 μg/L. The regeneration of the planar optical waveguide chip allows the performance of more than 300 assay cycles within an analysis time of about 20 min for each assay cycle. By application of effective pretreatment procedure, the recoveries of BPA in real water samples gave values from 88.3% ± 8.5% to 103.7% ± 3.5%, confirming its application potential in the measurement of BPA in reality. PMID:24699239

Materials, methods and devices to detect and quantify water vapor concentrations in an atmosphere

DOEpatents

Allendorf, Mark D; Robinson, Alex L

2014-12-09

We have demonstrated that a surface acoustic wave (SAW) sensor coated with a nanoporous framework material (NFM) film can perform ultrasensitive water vapor detection at concentrations in air from 0.05 to 12,000 ppmv at 1 atmosphere pressure. The method is extendable to other MEMS-based sensors, such as microcantilevers, or to quartz crystal microbalance sensors. We identify a specific NFM that provides high sensitivity and selectivity to water vapor. However, our approach is generalizable to detection of other species using NFM to provide sensitivity and selectivity.

Mass sensing AlN sensors for waste water monitoring

NASA Astrophysics Data System (ADS)

Porrazzo, R.; Potter, G.; Lydecker, L.; Foraida, Z.; Gattu, S.; Tokranova, N.; Castracane, J.

2014-08-01

Monitoring the presence of nanomaterials in waste water from semiconductor facilities is a critical task for public health organizations. Advanced semiconductor technology allows the fabrication of sensitive piezoelectric-based mass sensors with a detection limit of less than 1.35 ng/cm2 of nanomaterials such as nanoparticles of alumina, amorphous silica, ceria, etc. The interactions between acoustic waves generated by the piezoelectric sensor and nanomaterial mass attached to its surface define the sensing response as a shift in the resonant frequency. In this article the development and characterization of a prototype AlN film bulk acoustic resonator (FBAR) are presented. DC reactive magnetron sputtering was used to create tilted c-axis oriented AlN films to generate shear waves which don't propagate in liquids thus minimizing the acoustic losses. The high acoustic velocity of AlN over quartz allows an increase in resonance frequency in comparison with a quartz crystal microbalance (QCM) and results in a higher frequency shift per mass change, and thus greater sensitivity. The membrane and electrodes were fabricated using state of the art semiconductor technology. The device surface functionalization was performed to demonstrate selectivity towards a specific nanomaterial. As a result, the devices were covered with a "docking" layer that allows the nanomaterials to be selectively attached to the surface. This was achieved using covalent modification of the surface, specifically targeting ZnO nanoparticles. Our functionalization approach was tested using two different types of nanoparticles, and binding specificity was confirmed with various analytical techniques.

[INVITED] Porphyrin-nanoassembled fiber-optic gas sensor fabrication: Optimization of parameters for sensitive ammonia gas detection

NASA Astrophysics Data System (ADS)

Korposh, Sergiy; Kodaira, Suguru; Selyanchyn, Roman; Ledezma, Francisco H.; James, Stephen W.; Lee, Seung-Woo

2018-05-01

Highly sensitive fiber-optic ammonia gas sensors were fabricated via layer-by-layer deposition of poly(diallyldimethylammonium chloride) (PDDA) and tetrakis(4-sulfophenyl)porphine (TSPP) onto the surface of the core of a hard-clad multimode fiber that was stripped of its polymer cladding. The effects of film thickness, length of sensing area, and depth of evanescent wave penetration were investigated to clearly understand the sensor performance. The sensitivity of the fiber-optic sensor to ammonia was linear in the concentration range of 0.5-50 ppm and the response and recovery times were less than 3 min, with a limit of detection of 0.5 ppm, when a ten-cycle PDDA/TSPP film was assembled on the surface of the core along a 1 cm-long stripped section of the fiber. The sensor's response towards ammonia was also checked under different relative humidity conditions and a simple statistical data treatment approach, principal component analysis, demonstrated the feasibility of ammonia sensing in environmental relative humidity ranging from dry 7% to highly saturated 80%. Penetration depths of the evanescent wave for the optimal sensor configuration were estimated to be 30 and 33 nm at wavelengths of 420 and 706 nm, which are in a good agreement with the thickness of the 10-cycle deposited film (ca. 30 nm).

Chemical-free lysis and fractionation of cells by use of surface acoustic waves for sensitive protein assays.

PubMed

Salehi-Reyhani, Ali; Gesellchen, Frank; Mampallil, Dileep; Wilson, Rab; Reboud, Julien; Ces, Oscar; Willison, Keith R; Cooper, Jonathan M; Klug, David R

2015-02-17

We exploit the mechanical action of surface acoustic waves (SAW) to differentially lyse human cancer cells in a chemical-free manner. The extent to which cells were disrupted is reported for a range of SAW parameters, and we show that the presence of 10 μm polystyrene beads is required to fully rupture cells and their nuclei. We show that SAW is capable of subcellular fractionation through the chemical-free isolation of nuclei from whole cells. The concentration of protein was assessed in lysates with a sensitive microfluidic antibody capture (MAC) chip. An antibody-based sandwich assay in a microfluidic microarray format was used to detect unlabeled human tumor suppressor protein p53 in crude lysates, without any purification step, with single-molecule resolution. The results are digital, enabling sensitive quantification of proteins with a dynamic range >4 orders of magnitude. For the conditions used, the efficiency of SAW-induced mechanical lysis was determined to be 12.9% ± 0.7% of that for conventional detergent-based lysis in yielding detectable protein. A range of possible loss mechanisms that could lead to the drop in protein yield are discussed. Our results show that the methods described here are amenable to an integrated point-of-care device for the assessment of tumor protein expression in fine needle aspirate biopsies.

Desorption atmospheric pressure photoionization and direct analysis in real time coupled with travelling wave ion mobility mass spectrometry.

PubMed

Räsänen, Riikka-Marjaana; Dwivedi, Prabha; Fernández, Facundo M; Kauppila, Tiina J

2014-11-15

Ambient mass spectrometry (MS) is a tool for screening analytes directly from sample surfaces. However, background impurities may complicate the spectra and therefore fast separation techniques are needed. Here, we demonstrate the use of travelling wave ion mobility spectrometry in a comparative study of two ambient MS techniques. Desorption atmospheric pressure photoionization (DAPPI) and direct analysis in real time (DART) were coupled with travelling wave ion mobility mass spectrometry (TWIM-MS) for highly selective surface analysis. The ionization efficiencies of DAPPI and DART were compared. Test compounds were: bisphenol A, benzo[a]pyrene, ranitidine, cortisol and α-tocopherol. DAPPI-MS and DART-TWIM-MS were also applied to the analysis of chloroquine from dried blood spots, and α-tocopherol from almond surface, and DAPPI-TWIM-MS was applied to analysis of pharmaceuticals and multivitamin tablets. DAPPI was approximately 100 times more sensitive than DART for bisphenol A and 10-20 times more sensitive for the other compounds. The limits of detection were between 30-290 and 330-8200 fmol for DAPPI and DART, respectively. Also, from the authentic samples, DAPPI ionized chloroquine and α-tocopherol more efficiently than DART. The mobility separation enabled the detection of species with low signal intensities, e.g. thiamine and cholecalciferol, in the DAPPI-TWIM-MS analysis of multivitamin tablets. DAPPI ionized the studied compounds of interest more efficiently than DART. For both DAPPI and DART, the mobility separation prior to MS analysis reduced the amount of chemical noise in the mass spectrum and significantly increased the signal-to-noise ratio for the analytes. Copyright © 2014 John Wiley & Sons, Ltd.

Bloch surface waves confined in one dimension with a single polymeric nanofibre

NASA Astrophysics Data System (ADS)

Wang, Ruxue; Xia, Hongyan; Zhang, Douguo; Chen, Junxue; Zhu, Liangfu; Wang, Yong; Yang, Erchan; Zang, Tianyang; Wen, Xiaolei; Zou, Gang; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

2017-02-01

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor-memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes.

Quantum Control of a Nitrogen-Vacancy Center using Surface Acoustic Waves in the Resolved Sideband Limit

NASA Astrophysics Data System (ADS)

Golter, David; Oo, Thein; Amezcua, Maira; Wang, Hailin

Micro-electromechanical systems research is producing increasingly sophisticated tools for nanophononic applications. Such technology is well-suited for achieving chip-based, integrated acoustic control of solid-state quantum systems. We demonstrate such acoustic control in an important solid-state qubit, the diamond nitrogen-vacancy (NV) center. Using an interdigitated transducer to generate a surface acoustic wave (SAW) field in a bulk diamond, we observe phonon-assisted sidebands in the optical excitation spectrum of a single NV center. This exploits the strong strain sensitivity of the NV excited states. The mechanical frequencies far exceed the relevant optical linewidths, reaching the resolved-sideband regime. This enables us to use the SAW field for driving Rabi oscillations on the phonon-assisted optical transition. These results stimulate the further integration of SAW-based technologies with the NV center system.

Anomalous hydrodynamics and normal fluids in rapidly rotating Bose-Einstein condensates.

PubMed

Bourne, A; Wilkin, N K; Gunn, J M F

2006-06-23

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a "normal fluid," allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches--perhaps related to those observed at JILA.

Relative humidity sensor based on surface plasmon resonance of D-shaped fiber with polyvinyl alcohol embedding Au grating

NASA Astrophysics Data System (ADS)

Yan, Haitao; Han, Daofu; Li, Ming; Lin, Bo

2017-01-01

This paper presents the design, fabrication, and characterization of a D-shaped fiber coated with polyvinyl alcohol (PVA) embedding an Au grating-based relative humidity (RH) sensor. The Au grating is fabricated on a D-shaped fiber to match the wave-vector and excite the surface plasmon, and the PVA is embedded in the Au grating as a sensitive cladding film. The refractive index of PVA changes with the ambient humidity. Measurements in a controlled environment show that the RH sensor can achieve a sensitivity of 5.4 nm per relative humidity unit in the RH range from 0% to 70% RH. Moreover, the surface plasmon resonance can be realized and used for RH sensing at the C band of optical fiber communication instead of the visible light band due to the metallic grating microstructure on the D-shaped fiber.

Low-Level Detection of a Bacillus Anthracis Simulant using Love-Wave Biosensors on 36 Degree YX LiTaO3

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

BRANCH,DARREN W.; BROZIK,SUSAN M.

Crucial to low-level detection of biowarfare agents in aqueous environments is the mass sensitivity optimization of Love-wave acoustic sensors. The present work is an experimental study of 36{sup o} YX cut LiTaO{sub 3} based Love-wave devices for detection of pathogenic spores in aqueous conditions. Given that the detection limit (DL) of Love-wave based sensors is a strong function of the overlying waveguide, two waveguide materials have been investigated, which are polyimide and polystyrene. To determine the mass sensitivity of Love-wave sensor, bovine serum albumin (BSA) protein was injected into the Love-wave test cell while recording magnitude and phase shift acrossmore » each sensor. Polyimide had the lowest mass detection limit with an estimated value of 1-2 ng/cm{sup 2}, as compared to polystyrene where DL = 2.0 ng/cm{sup 2}. Suitable chemistries were used to orient antibodies on the Love-wave sensor using adsorbed protein G. The thickness of each biofilm was measured using ellipsometry from which the surface concentrations were calculated. The monoclonal antibody BD8 with a high degree of selectivity for anthrax spores was used to capture the non-pathogenic simulant B. thuringiensis B8 spores. Bacillus Subtilis spores were used as a negative control to determine whether significant non-specific binding would occur. Spore aliquots were prepared using an optical counting method, which permitted removal of background particles for consistent sample preparation. This work demonstrates that Love-wave devices can be used to detect B. anthracis simulant below reported infectious levels.« less

Prospects for Jovian seismological observations following the impact of comet Shoemaker-Levy 9

NASA Technical Reports Server (NTRS)

Deming, Drake

1994-01-01

The impact of each fragment of comet SL-9 will produce a downward-propagating pressure wave which will travel at the sound speed through the jovian interior. Since the sound speed increases with depth, most of the energy in the pressure pulse will be strongly refracted and return to the surface, as recently computed by Marley (1994). This wave may in principle be observable as it propagates into the stratosphere, using sufficiently sensitive thermal infrared imaging. If so, it will provide a unique opportunity to constrain models of the jovian interior. This paper extends Marley's calculations to include the effect of the limited spatial resolution which will be characteristic of real observations. The wave pattern on the disk will consist of closely spaced regions of alternating temperature increases and decreases. Spatial averaging will significantly reduce the observed amplitude for resolutions attainable using earth-based telescopes, but the waves should remain above the detection limit.

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

PubMed

Francis, Laurent A; Friedt, Jean-Michel; Zhou, Cheng; Bertrand, Patrick

2006-06-15

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

X-ray diffraction and surface acoustic wave analysis of BST/Pt/TiO{sub 2}/SiO{sub 2}/Si thin films

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

Mseddi, Souhir; Hedi Ben Ghozlen, Mohamed; Njeh, Anouar

2011-11-15

High dielectric constant and electrostriction property of (Ba, Sr)Ti0{sub 3} (BST) thin films result in an increasing interest for dielectric devices and microwave acoustic resonator. Barium strontium titanate (Ba{sub 0.645}Sr{sub 0.355}TiO{sub 3}) films of about 300 nm thickness are grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrates by rf magnetron sputtering deposition techniques. X-ray diffraction is applied for the microstructural characterization. The BST films exhibit a cubic perovskite structure with a dense and smooth surface. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in the BST films. Young's modulus E and the Poisson ratio {nu}more » of TiO{sub 2,} Pt and BST films in different propagation directions are derived from the measured dispersion curves. Estimation of BST elastics constants are served in SAW studies. Impact of stratification process on SAW, propagating along [100] and [110] directions of silicon substrate, has been interpreted on the basis of ordinary differential equation (ODE) and stiffness matrix method (SMM). A good agreement is observed between experimental and calculated dispersion curves. The performed calculations are strongly related to the implemented crystallographic data of each layer. Dispersion curves are found to be sensitive to the SAW propagation direction and the stratification process for the explored frequency ranges 50-250 MHz, even though it corresponds to a wave length clearly higher than the whole films thickness.« less

Dispersion Energy Analysis of Rayleigh and Love Waves in the Presence of Low-Velocity Layers in Near-Surface Seismic Surveys

NASA Astrophysics Data System (ADS)

Mi, Binbin; Xia, Jianghai; Shen, Chao; Wang, Limin

2018-03-01

High-frequency surface-wave analysis methods have been effectively and widely used to determine near-surface shear (S) wave velocity. To image the dispersion energy and identify different dispersive modes of surface waves accurately is one of key steps of using surface-wave methods. We analyzed the dispersion energy characteristics of Rayleigh and Love waves in near-surface layered models based on numerical simulations. It has been found that if there is a low-velocity layer (LVL) in the half-space, the dispersion energy of Rayleigh or Love waves is discontinuous and ``jumping'' appears from the fundamental mode to higher modes on dispersive images. We introduce the guided waves generated in an LVL (LVL-guided waves, a trapped wave mode) to clarify the complexity of the dispersion energy. We confirm the LVL-guided waves by analyzing the snapshots of SH and P-SV wavefield and comparing the dispersive energy with theoretical values of phase velocities. Results demonstrate that LVL-guided waves possess energy on dispersive images, which can interfere with the normal dispersion energy of Rayleigh or Love waves. Each mode of LVL-guided waves having lack of energy at the free surface in some high frequency range causes the discontinuity of dispersive energy on dispersive images, which is because shorter wavelengths (generally with lower phase velocities and higher frequencies) of LVL-guided waves cannot penetrate to the free surface. If the S wave velocity of the LVL is higher than that of the surface layer, the energy of LVL-guided waves only contaminates higher mode energy of surface waves and there is no interlacement with the fundamental mode of surface waves, while if the S wave velocity of the LVL is lower than that of the surface layer, the energy of LVL-guided waves may interlace with the fundamental mode of surface waves. Both of the interlacements with the fundamental mode or higher mode energy may cause misidentification for the dispersion curves of surface waves.

Bloch Surface Waves Biosensors for High Sensitivity Detection of Soluble ERBB2 in a Complex Biological Environment.

PubMed

Sinibaldi, Alberto; Sampaoli, Camilla; Danz, Norbert; Munzert, Peter; Sonntag, Frank; Centola, Fabio; Occhicone, Agostino; Tremante, Elisa; Giacomini, Patrizio; Michelotti, Francesco

2017-08-17

We report on the use of one-dimensional photonic crystals to detect clinically relevant concentrations of the cancer biomarker ERBB2 in cell lysates. Overexpression of the ERBB2 protein is associated with aggressive breast cancer subtypes. To detect soluble ERBB2, we developed an optical set-up which operates in both label-free and fluorescence modes. The detection approach makes use of a sandwich assay, in which the one-dimensional photonic crystals sustaining Bloch surface waves are modified with monoclonal antibodies, in order to guarantee high specificity during the biological recognition. We present the results of exemplary protein G based label-free assays in complex biological matrices, reaching an estimated limit of detection of 0.5 ng/mL. On-chip and chip-to-chip variability of the results is addressed too, providing repeatability rates. Moreover, results on fluorescence operation demonstrate the capability to perform high sensitive cancer biomarker assays reaching a resolution of 0.6 ng/mL, without protein G assistance. The resolution obtained in both modes meets international guidelines and recommendations (15 ng/mL) for ERBB2 quantification assays, providing an alternative tool to phenotype and diagnose molecular cancer subtypes.

Perturbational and nonperturbational inversion of Rayleigh-wave velocities

USGS Publications Warehouse

Haney, Matt; Tsai, Victor C.

2017-01-01

The inversion of Rayleigh-wave dispersion curves is a classic geophysical inverse problem. We have developed a set of MATLAB codes that performs forward modeling and inversion of Rayleigh-wave phase or group velocity measurements. We describe two different methods of inversion: a perturbational method based on finite elements and a nonperturbational method based on the recently developed Dix-type relation for Rayleigh waves. In practice, the nonperturbational method can be used to provide a good starting model that can be iteratively improved with the perturbational method. Although the perturbational method is well-known, we solve the forward problem using an eigenvalue/eigenvector solver instead of the conventional approach of root finding. Features of the codes include the ability to handle any mix of phase or group velocity measurements, combinations of modes of any order, the presence of a surface water layer, computation of partial derivatives due to changes in material properties and layer boundaries, and the implementation of an automatic grid of layers that is optimally suited for the depth sensitivity of Rayleigh waves.

A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

DTIC Science & Technology

2015-09-30

We aim at understanding the impact of tidal , seasonal, and mesoscale variability of the internal wave field and how it influences the surface waves ...Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves

A total internal reflection-fluorescence correlation spectroscopy setup with pulsed diode laser excitation

NASA Astrophysics Data System (ADS)

Weger, Lukas; Hoffmann-Jacobsen, Kerstin

2017-09-01

Fluorescence correlation spectroscopy (FCS) measures fluctuations in a (sub-)femtoliter volume to analyze the diffusive behavior of fluorescent particles. This highly sensitive method has proven to be useful for the analysis of dynamic biological systems as well as in chemistry, physics, and material sciences. It is routinely performed with commercial fluorescence microscopes, which provide a confined observation volume by the confocal technique. The evanescent wave of total internal reflectance (TIR) is used in home-built systems to permit a surface sensitive FCS analysis. We present a combined confocal and TIR-FCS setup which uses economic low-power pulsed diode lasers for excitation. Excitation and detection are coupled to time-correlated photon counting hardware. This allows simultaneous fluorescence lifetime and FCS measurements in a surface-sensitive mode. Moreover, the setup supports fluorescence lifetime correlation spectroscopy at surfaces. The excitation can be easily switched between TIR and epi-illumination to compare the surface properties with those in liquid bulk. The capabilities of the presented setup are demonstrated by measuring the diffusion coefficients of a free dye molecule, a labeled polyethylene glycol, and a fluorescent nanoparticle in confocal as well as in TIR-FCS.

Surface-Wave Pulse Routing around Sharp Right Angles

NASA Astrophysics Data System (ADS)

Gao, Z.; Xu, H.; Gao, F.; Zhang, Y.; Luo, Y.; Zhang, B.

2018-04-01

Surface-plasmon polaritons (SPPs), or localized electromagnetic surface waves propagating on a metal-dielectric interface, are deemed promising information carriers for future subwavelength terahertz and optical photonic circuitry. However, surface waves fundamentally suffer from scattering loss when encountering sharp corners in routing and interconnection of photonic signals. Previous approaches enabling scattering-free surface-wave guidance around sharp corners are limited to either volumetric waveguide environments or extremely narrow bandwidth, being unable to guide a surface-wave pulse (SPP wave packet) on an on-chip platform. Here, in a surface-wave band-gap crystal implemented on a single metal surface, we demonstrate in time-domain routing a surface-wave pulse around multiple sharp right angles without perceptible scattering. Our work not only offers a solution to on-chip surface-wave pulse routing along an arbitrary path, but it also provides spatiotemporal information on the interplay between surface-wave pulses and sharp corners, both of which are desirable in developing high-performance large-scale integrated photonic circuits.

On the influence of ocean waves on simulated GNSS-R delay-doppler maps

NASA Astrophysics Data System (ADS)

Clarizia, M. P.; di Bisceglie, M.; Galdi, C.; Gommenginger, C.; Srokosz, M.

2012-04-01

Global Navigation Satellite System-Reflectometry (GNSS-R), is an established technique that exploits GNSS signals of opportunity reflected from the surface of the ocean, to look primarily at the ocean surface roughness. The strength of this technique, and the primary motivation to carry it forward, is in the fact that GNSS signals are available globally, all the time and over the long term, and could help dramatically improve the monitoring of ocean wind and waves. GNSS-R offers the prospect of high density global measurements of directional sea surface roughness, which are essential for scientific purposes (i.e. quantifying the air-sea exchanges of gases), operational weather and ocean forecasting (i.e. prediction of high winds, dangerous sea states, risk of flooding and storm surges) and to support important climate-relevant Earth Observation techniques (IR SST, or surface salinity retrieval). The retrieval of ocean roughness from GNSS-R data has now been demonstrated with a reasonable level of accuracy from both airborne [1] and spaceborne [2] platforms. In both cases, Directional Mean Square Slopes (DMSS) of the ocean surface have been retrieved from GNSS-R data, in the form of Delay-Doppler Maps (DDMs), using an established theoretical scattering model by Zavorotny and Voronovich (Z-V) [3]. The need for a better assessment of the way the ocean waves influence the scattering of GPS signals has recently led to a different approach, consisting of simulating the scattering of such signals, using a more sophisticated large-scale scattering model than Z-V, and explicit simulations of realistic seas. Initial results produced from these simulations have been recently published in [4], where the emphasis has been put on the effects of different sea states on Radar Cross Section (RCS) and Polarization Ratio (PR) in space domain. Linear wind wave surfaces have been simulated using the Elfouhaily wind wave spectrum [5], for different wind speeds and directions, and with or without a superimposed swell. Then, the scattering from such surfaces has been computed using the innovative Facet Approach (FA), which approximates the surface through a number of rectangular facets, differently oriented, and calculates the surface scattering as the ensemble of the signals scattered from all the facets. Here we proceed with the next step of the GPS-Reflectometry simulator, through investigation of the results in Delay- Doppler (DD) domain. Changes and variations of the DDMs, computed using the FA scattering model, are investigated for a variety of wind and wave conditions of the underlying sea surfaces simulated. Results are analysed for changing wind speed and direction of the waves, presence of a swell component superimposed on wind waves, and changing parameters (wavelength, amplitude, direction) of the swell, revealing some degree of sensitivity of these maps to different sea states. The effect of polarization is also taken into account, through an analysis of PR in DD domain. Finally, an initial investigation into the effect of nonlinearities on the sea surface in DD domain is carried out, by looking at DDMs of the signal scattered from non linear non gaussian sea surfaces explicitly simulated.

Effects of Sea-Surface Waves and Ocean Spray on Air-Sea Momentum Fluxes

NASA Astrophysics Data System (ADS)

Zhang, Ting; Song, Jinbao

2018-04-01

The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer (MABL) at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

Long-period ground motions at near-regional distances caused by the PL wave from, inland earthquakes: Observation and numerical simulation of the 2004 Mid-Niigata, Japan, Mw6.6 earthquake

NASA Astrophysics Data System (ADS)

Furumura, T.; Kennett, B. L. N.

2017-12-01

We examine the development of large, long-period ground motions at near-regional distances (D=50-200 km) generated by the PL wave from large, shallow inland earthquakes, based on the analysis of strong motion records and finite-difference method (FDM) simulations of seismic wave propagation. PL wave can be represented as leaking modes of the crustal waveguide and are commonly observed at regional distances between 300 to 1000 km as a dispersed, long-period signal with a dominant period of about 20 s. However, observations of recent earthquakes at the dense K-NET and KiK-net strong motion networks in Japan demonstrate the dominance of the PL wave at near-regional (D=50-200 km) distances as, e.g., for the 2004 Mid Niigata, Japan, earthquake (Mw6.6; h=13 km). The observed PL wave signal between P and S wave shows a large, dispersed wave packet with dominant period of about T=4-10 s with amplitude almost comparable to or larger than the later arrival of the S and surface waves. Thus, the early arrivals of the long-period PL wave immediately after P wave can enhance resonance with large-scale constructions such as high-rise buildings and large oil-storage tanks etc. with potential for disaster. Such strong effects often occurred during the 2004 Mid Niigata earthquakes and other large earthquakes which occurred nearby the Kanto (Tokyo) basin. FDM simulation of seismic wave propagation employing realistic 3-D sedimentary structure models demonstrates the process by which the PL wave develops at near-regional distances from shallow, crustal earthquakes by constructive interference of the P wave in the long-period band. The amplitude of the PL wave is very sensitive to low-velocity structure in the near-surface. Lowered velocities help to develop large SV-to-P conversion and weaken the P-to-SV conversion at the free surface. Both effects enhance the multiple P reflections in the crustal waveguide and prevent the leakage of seismic energy into the mantle. However, a very thick (>3 km) cover of sediment above the source disrupts the coherent reflections to form the PL wave. This explains the weak close-range PL wave from the 2007 Off Niigata earthquake (Mw=6.6; h=16 km), which occurred near-by the 2004 event but located beneath the deep Echigo basin.

Monitoring corrosion of rebar embedded in mortar using guided ultrasonic waves

NASA Astrophysics Data System (ADS)

Ervin, Benjamin Lee

This thesis investigates the use of guided mechanical waves for monitoring uniform and localized corrosion in steel reinforcing bars embedded in concrete. The main forms of structural deterioration from uniform corrosion in reinforced concrete are the destruction of the bond between steel and concrete, the loss of steel cross-sectional area, and the loss of concrete cross-sectional area from cracking and spalling. Localized corrosion, or pitting, leads to severe loss of steel cross-sectional area, creating a high risk of bar tensile failure and unintended transfer of loads to the surrounding concrete. Reinforcing bars were used to guide the waves, rather than bulk concrete, allowing for longer inspection distances due to lower material absorption, scattering, and divergence. Guided mechanical waves in low frequency ranges (50-200 kHz) and higher frequency ranges (2-8 MHz) were monitored in reinforced mortar specimens undergoing accelerated uniform corrosion. The frequency ranges chosen contain wave modes with varying amounts of interaction, i.e. displacement profile, at the material interface. Lower frequency modes were shown to be sensitive to the accumulation of corrosion product and the level of bond between the surrounding mortar and rebar. This allows for the onset of corrosion and bond deterioration to be monitored. Higher frequency modes were shown to be sensitive to changes in the bar profile surface, allowing for the loss of cross-sectional area to be monitored. Guided mechanical waves in the higher frequency range were also used to monitor reinforced mortar specimens undergoing accelerated localized corrosion. The high frequency modes were sensitive to the localized attack. Also promising was the unique frequency spectrum response for both uniform and localized corrosion, allowing the two corrosion types to be differentiated from through-transmission evaluation. The isolated effects of the reinforcing ribs, simulated debonding, simulated pitting, water surrounding, and mortar surrounding were also investigated using guided mechanical waves. Results are presented and discussed within the framework of a corrosion process degradation model and service life. A thorough review and discussion of the corrosion process, modeling the propagation of corrosion, nondestructive methods for monitoring corrosion in reinforced concrete, and guided mechanical waves have also been presented.

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.

Transverse electromagnetic horn antenna with resistively-loaded exterior surfaces

DOEpatents

Aurand, John F.

1999-01-01

An improved transverse electromagnetic (TEM) horn antenna comprises a resistive loading material on the exterior surfaces of the antenna plates. The resistive loading material attenuates or inhibits currents on the exterior surfaces of the TEM horn antenna. The exterior electromagnetic fields are of opposite polarity in comparison to the primary and desired interior electromagnetic field, thus inherently cause partial cancellation of the interior wave upon radiation or upon reception. Reducing the exterior fields increases the radiation efficiency of the antenna by reducing the cancellation of the primary interior field (supported by the interior surface currents). This increases the transmit gain and receive sensitivity of the TEM horn antenna, as well as improving the transient (time-domain) response.

Beyond Single Images: Combining the Geosciences in Geothermal Exploration

NASA Astrophysics Data System (ADS)

Malin, P. E.

2012-12-01

Geothermal exploration routinely includes a variety of field surveys, the interpretations of which are usually done separately and then combined in some ad hoc way. Instead, because these data share numerous constraints, combining them in a systematic, quantitative way is far preferable. Aside from the shared geological background, a "joint" analysis can dampen errors and noise in one data set by less sensitive responses in another. In this presentation case histories from several surveys will be used to illustrate these points. By way of background, an example of this type of integrated approach is the improvement in earthquake location when P-wave data are supplemented with S-wave data. These two waves share the effects of the S-wave velocity structure through its shear modulus, which the S-wave measures independent of the P-wave. Using only P-waves travel times for event location is thus equivalent to making the acoustic approximation for the elastic rock velocities. When earthquake location combines both phases, not only is this approximation improved, but errors in picking these times are reduced as well. The case histories include 1) mapping fracture orientations -primarily using seismic shear wave splitting and magnetotelluric polarization directions, but supplemented with surface geology and 2) deriving combined porosity and permeability from seismic velocity and resistivity. Shear wave splitting is routinely used to detect fracture orientation since S-waves propagate faster parallel to their direction. However shear wave splitting can also be caused by other features such as 2-D layering. Magnetotelluric polarizations can be the result of fracture orientation, but also with 3-D structural effects. However, combined, the non-fracture related effects are notably different between the two data types. As a result, detecting similar polarization effects in both makes the case for aligned fractures strong. In a similar vein, porosity and permeability play different roles in determining the relationships between seismic velocities and electrical conductivities. Velocities are more sensitive to rocks with different lithology and porosity while electrical conductivities are more sensitive to rocks with different permeability. Change in seismic velocity due to rock density or lithology have less of an effect on electrical conductivity as compared to a similar change in seismic velocity due to porosity. Similarly, a large fluctuation in electrical conductivity is more logically attributed to variation in permeability. The joint quantitative analysis of such data sets includes using, for example, simple linear and more advanced inversion schemes. Combining their inversion creates a subsurface map that is more robust than with either method alone. The combination of sensitivities helps constrain local fluctuations in these properties as well as background noise. The final test is of course in the drilling, recent results of which support the approach described here.

Theoretical analyses of localized surface plasmon resonance spectrum with nanoparticles imprinted polymers

NASA Astrophysics Data System (ADS)

Li, Hong; Peng, Wei; Wang, Yanjie; Hu, Lingling; Liang, Yuzhang; Zhang, Xinpu; Yao, Wenjuan; Yu, Qi; Zhou, Xinlei

2011-12-01

Optical sensors based on nanoparticles induced Localized Surface Plasmon Resonance are more sensitive to real-time chemical and biological sensing, which have attracted intensive attentions in many fields. In this paper, we establish a simulation model based on nanoparticles imprinted polymer to increase sensitivity of the LSPR sensor by detecting the changes of Surface Plasmon Resonance signals. Theoretical analysis and numerical simulation of parameters effects to absorption peak and light field distribution are highlighted. Two-dimensional simulated color maps show that LSPR lead to centralization of the light energy around the gold nanoparticles, Transverse Magnetic wave and total reflection become the important factors to enhance the light field in our simulated structure. Fast Fourier Transfer analysis shows that the absorption peak of the surface plasmon resonance signal resulted from gold nanoparticles is sharper while its wavelength is bigger by comparing with silver nanoparticles; a double chain structure make the amplitude of the signals smaller, and make absorption wavelength longer; the absorption peak of enhancement resulted from nanopore arrays has smaller wavelength and weaker amplitude in contrast with nanoparticles. These simulation results of the Localized Surface Plasmon Resonance can be used as an enhanced transduction mechanism for enhancement of sensitivity in recognition and sensing of target analytes in accordance with different requirements.

Polarization-based material classification technique using passive millimeter-wave polarimetric imagery.

PubMed

Hu, Fei; Cheng, Yayun; Gui, Liangqi; Wu, Liang; Zhang, Xinyi; Peng, Xiaohui; Su, Jinlong

2016-11-01

The polarization properties of thermal millimeter-wave emission capture inherent information of objects, e.g., material composition, shape, and surface features. In this paper, a polarization-based material-classification technique using passive millimeter-wave polarimetric imagery is presented. Linear polarization ratio (LPR) is created to be a new feature discriminator that is sensitive to material type and to remove the reflected ambient radiation effect. The LPR characteristics of several common natural and artificial materials are investigated by theoretical and experimental analysis. Based on a priori information about LPR characteristics, the optimal range of incident angle and the classification criterion are discussed. Simulation and measurement results indicate that the presented classification technique is effective for distinguishing between metals and dielectrics. This technique suggests possible applications for outdoor metal target detection in open scenes.

Feasibility of near-unstable cavities for future gravitational wave detectors

NASA Astrophysics Data System (ADS)

Wang, Haoyu; Dovale-Álvarez, Miguel; Collins, Christopher; Brown, Daniel David; Wang, Mengyao; Mow-Lowry, Conor M.; Han, Sen; Freise, Andreas

2018-01-01

Near-unstable cavities have been proposed as an enabling technology for future gravitational wave detectors, as their compact structure and large beam spots can reduce the coating thermal noise of the interferometer. We present a tabletop experiment investigating the behavior of an optical cavity as it is parametrically pushed to geometrical instability. We report on the observed degeneracies of the cavity's eigenmodes as the cavity becomes unstable and the resonance conditions become hyper-sensitive to mirror surface imperfections. A simple model of the cavity and precise measurements of the resonant frequencies allow us to characterize the stability of the cavity and give an estimate of the mirror astigmatism. The significance of these results for gravitational wave detectors is discussed, and avenues for further research are suggested.

Vertical shear-wave velocity profiles generated from spectral analysis of surface waves : field examples

DOT National Transportation Integrated Search

2003-04-01

Surface wave (Rayleigh wave) seismic data were acquired at six separate bridge sites in southeast Missouri. Each acquired surface wave data set was processed (spectral analysis of surface waves; SASW) and transformed into a site-specific vertical she...

Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations

USGS Publications Warehouse

Forghani-Arani, Farnoush; Willis, Mark; Snieder, Roel; Haines, Seth S.; Behura, Jyoti; Batzle, Mike; Davidson, Michael

2014-01-01

Surface-wave dispersion analysis is useful for estimating near-surface shear-wave velocity models, designing receiver arrays, and suppressing surface waves. Here, we analyze whether passive seismic noise generated during hydraulic-fracturing operations can be used to extract surface-wave dispersion characteristics. Applying seismic interferometry to noise measurements, we extract surface waves by cross-correlating several minutes of passive records; this approach is distinct from previous studies that used hours or days of passive records for cross-correlation. For comparison, we also perform dispersion analysis for an active-source array that has some receivers in common with the passive array. The active and passive data show good agreement in the dispersive character of the fundamental-mode surface-waves. For the higher mode surface waves, however, active and passive data resolve the dispersive properties at different frequency ranges. To demonstrate an application of dispersion analysis, we invert the observed surface-wave dispersion characteristics to determine the near-surface, one-dimensional shear-wave velocity.

Scattered surface wave energy in the seismic coda

USGS Publications Warehouse

Zeng, Y.

2006-01-01

One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.

Application of interface waves for near surface damage detection in hybrid structures

NASA Astrophysics Data System (ADS)

Jahanbin, M.; Santhanam, S.; Ihn, J.-B.; Cox, A.

2017-04-01

Guided waves are acoustic waves that are guided by boundaries. Depending on the structural geometry, guided waves can either propagate between boundaries, known as plate waves, or propagate on the surface of the objects. Many different types of surface waves exist based on the material property of the boundary. For example Rayleigh wave in solid - air, Scholte wave in solid - liquid, Stoneley in solid - solid interface and many other different forms like Love wave on inhomogeneous surfaces, creeping waves, etc. This research work is demonstrating the application of surface and interface waves for detection of interfacial damages in hybrid bonded structures.

U-Shaped and Surface Functionalized Polymer Optical Fiber Probe for Glucose Detection.

PubMed

Azkune, Mikel; Ruiz-Rubio, Leire; Aldabaldetreku, Gotzon; Arrospide, Eneko; Pérez-Álvarez, Leyre; Bikandi, Iñaki; Zubia, Joseba; Vilas-Vilela, Jose Luis

2017-12-25

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

Observation of Mountain Lee Waves with MODIS NIR Column Water Vapor

NASA Technical Reports Server (NTRS)

Lyapustin, A.; Alexander, M. J.; Ott, L.; Molod, A.; Holben, B.; Susskind, J.; Wang, Y.

2014-01-01

Mountain lee waves have been previously observed in data from the Moderate Resolution Imaging Spectroradiometer (MODIS) "water vapor" 6.7 micrometers channel which has a typical peak sensitivity at 550 hPa in the free troposphere. This paper reports the first observation of mountain waves generated by the Appalachian Mountains in the MODIS total column water vapor (CWV) product derived from near-infrared (NIR) (0.94 micrometers) measurements, which indicate perturbations very close to the surface. The CWV waves are usually observed during spring and late fall or some summer days with low to moderate CWV (below is approx. 2 cm). The observed lee waves display wavelengths from3-4 to 15kmwith an amplitude of variation often comparable to is approx. 50-70% of the total CWV. Since the bulk of atmospheric water vapor is confined to the boundary layer, this indicates that the impact of thesewaves extends deep into the boundary layer, and these may be the lowest level signatures of mountain lee waves presently detected by remote sensing over the land.

Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods

NASA Astrophysics Data System (ADS)

Meo, Michele; Polimeno, Umberto; Zumpano, Giuseppe

2008-05-01

Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.

Particle transport model sensitivity on wave-induced processes

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Ricker, Marcel; Krüger, Oliver; Breivik, Oyvind; Stanev, Emil; Schrum, Corinna

2017-04-01

Different effects of wind waves on the hydrodynamics in the North Sea are investigated using a coupled wave (WAM) and circulation (NEMO) model system. The terms accounting for the wave-current interaction are: the Stokes-Coriolis force, the sea-state dependent momentum and energy flux. The role of the different Stokes drift parameterizations is investigated using a particle-drift model. Those particles can be considered as simple representations of either oil fractions, or fish larvae. In the ocean circulation models the momentum flux from the atmosphere, which is related to the wind speed, is passed directly to the ocean and this is controlled by the drag coefficient. However, in the real ocean, the waves play also the role of a reservoir for momentum and energy because different amounts of the momentum flux from the atmosphere is taken up by the waves. In the coupled model system the momentum transferred into the ocean model is estimated as the fraction of the total flux that goes directly to the currents plus the momentum lost from wave dissipation. Additionally, we demonstrate that the wave-induced Stokes-Coriolis force leads to a deflection of the current. During the extreme events the Stokes velocity is comparable in magnitude to the current velocity. The resulting wave-induced drift is crucial for the transport of particles in the upper ocean. The performed sensitivity analyses demonstrate that the model skill depends on the chosen processes. The results are validated using surface drifters, ADCP, HF radar data and other in-situ measurements in different regions of the North Sea with a focus on the coastal areas. The using of a coupled model system reveals that the newly introduced wave effects are important for the drift-model performance, especially during extremes. Those effects cannot be neglected by search and rescue, oil-spill, transport of biological material, or larva drift modelling.

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

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

Gao, Zhen; Gao, Fei; Zhang, Baile, E-mail: blzhang@ntu.edu.sg

2016-01-25

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find usemore » in the design of integrated surface-wave devices with suppressed crosstalk.« less

Time-domain full-waveform inversion of Rayleigh and Love waves in presence of free-surface topography

NASA Astrophysics Data System (ADS)

Pan, Yudi; Gao, Lingli; Bohlen, Thomas

2018-05-01

Correct estimation of near-surface seismic-wave velocity when encountering lateral heterogeneity and free surface topography is one of the challenges to current shallow seismic. We propose to use time-domain full-waveform inversion (FWI) of surface waves, including both Rayleigh and Love waves, to solve this problem. We adopt a 2D time-domain finite-difference method with an improved vacuum formulation (IVF) to simulate shallow-seismic Rayleigh wave in presence of free-surface topography. We modify the IVF for SH-wave equation for the simulation of Love wave in presence of topographic free surface and prove its accuracy by benchmark tests. Checkboard model tests are performed in both cases when free-surface topography is included or neglected in FWI. Synthetic model containing a dipping planar free surface and lateral heterogeneity was then tested, in both cases of considering and neglecting free-surface topography. Both checkerboard and synthetic models show that Rayleigh- and Love-wave FWI have similar ability of reconstructing near-surface structures when free-surface topography is considered, while Love-wave FWI could reconstruct near-surface structures better than Rayleigh-wave when free-surface topography is neglected.

Development of optical WGM resonators for biosensors

NASA Astrophysics Data System (ADS)

Brice, I.; Pirktina, A.; Ubele, A.; Grundsteins, K.; Atvars, A.; Viter, R.; Alnis, J.

2017-12-01

Whispering Gallery Mode (WGM) resonators are very sensitive to nanoparticles attaching to the surface. We simulate this process using COMSOL Wave Optics module. Our spherical WGM resonators are produced by melting a tip of an optical fiber and we measure optical Q factors in the 105 range. Molecular oxygen lines of the air in the 760 nm region are used as reference markers when looking for the shifts of the WGM resonance lines. We demonstrate WGM microresonator surface coating with a layer of ZnO nanorods as well as with polystyrene microspheres. Coatings produce increased contact surface. Additional layer of antigens/antibodies will be coated to make high-specificity biosensors.

Inversion of Surface Wave Phase Velocities for Radial Anisotropy to an Depth of 1200 km

NASA Astrophysics Data System (ADS)

Xing, Z.; Beghein, C.; Yuan, K.

2012-12-01

This study aims to evaluate three dimensional radial anisotropy to an depth of 1200 km. Radial anisotropy describes the difference in velocity between horizontally polarized Rayleigh waves and vertically polarized Love waves. Its presence in the uppermost 200 km mantle has well been documented by different groups, and has been regarded as an indicator of mantle convection which aligns the intrinsically anisotropic minerals, largely olivine, to form large scale anisotropy. However, there is no global agreement on whether anisotropy exists in the region below 200 km. Recent models also associate a fast vertically polarized shear wave with vertical upwelling mantle flow. The data used in this study is the globally isotropic phase velocity models of fundamental and higher mode Love and Rayleigh waves (Visser, 2008). The inclusion of higher mode surface wave phase velocity provides sensitivities to structure at depth that extends to below the transition zone. While the data is the same as used by Visser (2008), a quite different parameterization is applied. All the six parameters - five elastic parameters A, C, F, L, N and density - are now regarded as independent, which rules out possible biased conclusions induced by scaling relation method used in several previous studies to reduce the number of parameters partly due to limited computing resources. The data need to be modified by crustal corrections (Crust2.0) as we want to look at the mantle structure only. We do this by eliminating the perturbation in surface wave phase velocity caused by the difference in crustal structure with respect to the referent model PREM. Sambridge's Neighborhood Algorithm is used to search the parameter space. The introduction of such a direct search technique pales the traditional inversion method, which requires regularization or some unnecessary priori restriction on the model space. On the contrary, the new method will search the full model space, providing probability density function of each anisotropic parameter and the corresponding resolution.

Experimental observation of standing interfacial waves induced by surface waves in muddy water

NASA Astrophysics Data System (ADS)

Maxeiner, Eric; Dalrymple, Robert A.

2011-09-01

A striking feature has been observed in a laboratory wave tank with a thin layer of clear water overlying a layer of mud. A piston-type wave maker is used to generate long monochromatic surface waves in a tank with a layer of kaolinite clay at the bottom. The wave action on the mud causes the clay particles to rise from the bottom into the water column, forming a lutocline. As the lutocline approaches the water surface, a set of standing interfacial waves form on the lutocline. The interfacial wave directions are oriented nearly orthogonal to the surface wave direction. The interfacial waves, which sometimes cover the entire length and width of the tank, are also temporally subharmonic as the phase of the interfacial wave alternates with each passing surface wave crest. These interfacial waves are the result of a resonant three-wave interaction involving the surface wave train and the two interfacial wave trains. The interfacial waves are only present when the lutocline is about 3 cm of the water surface and they can be sufficiently nonlinear as to exhibit superharmonics and a breaking-type of instability.

Surface Acoustic Wave Devices as Chemical Vapor Sensors

DTIC Science & Technology

2009-03-26

x105cm/s) (x10−6cm1/2g1/2) (pF/cm) (ppm/oC) Quartz ST 3.158 0.13 1.34 0.88 0.0011 0.5 ∼ 0 X Lithium Niobate -Y 3.488 0 0.83 0.56 0.048 4.6 94 X Gallium ...sensitivity, followed by lithium niobate and gallium arsenide in ratios of 7.4:5.9:4.8, re- spectively. Thus, even though lithium niobate has the superior...Acoustic Wave (SAW) Sensor for 2,4-Dinitro Toluene (DNT) Vapour Detection,” Sensors and Actuators B: Chemical, vol. 101, no. 3, pp. 328–334, 2004. 8

Three-component ambient noise beamforming in the Parkfield area

NASA Astrophysics Data System (ADS)

Löer, Katrin; Riahi, Nima; Saenger, Erik H.

2018-06-01

We apply a three-component beamforming algorithm to an ambient noise data set recorded at a seismic array to extract information about both isotropic and anisotropic surface wave velocities. In particular, we test the sensitivity of the method with respect to the array geometry as well as to seasonal variations in the distribution of noise sources. In the earth's crust, anisotropy is typically caused by oriented faults or fractures and can be altered when earthquakes or human activities cause these structures to change. Monitoring anisotropy changes thus provides time-dependent information on subsurface processes, provided they can be distinguished from other effects. We analyse ambient noise data at frequencies between 0.08 and 0.52 Hz recorded at a three-component array in the Parkfield area, California (US), between 2001 November and 2002 April. During this time, no major earthquakes were identified in the area and structural changes are thus not expected. We compute dispersion curves of Love and Rayleigh waves and estimate anisotropy parameters for Love waves. For Rayleigh waves, the azimuthal source coverage is too limited to perform anisotropy analysis. For Love waves, ambient noise sources are more widely distributed and we observe significant and stable surface wave anisotropy for frequencies between 0.2 and 0.4 Hz. Synthetic data experiments indicate that the array geometry introduces apparent anisotropy, especially when waves from multiple sources arrive simultaneously at the array. Both the magnitude and the pattern of apparent anisotropy, however, differ significantly from the anisotropy observed in Love wave data. Temporal variations of anisotropy parameters observed at frequencies below 0.2 Hz and above 0.4 Hz correlate with changes in the source distribution. Frequencies between 0.2 and 0.4 Hz, however, are less affected by these variations and provide relatively stable results over the period of study.

On the generation of internal wave modes by surface waves

NASA Astrophysics Data System (ADS)

Harlander, Uwe; Kirschner, Ian; Maas, Christian; Zaussinger, Florian

2016-04-01

Internal gravity waves play an important role in the ocean since they transport energy and momentum and the can lead to mixing when they break. Surface waves and internal gravity waves can interact. On the one hand, long internal waves imply a slow varying shear current that modifies the propagation of surface waves. Surface waves generated by the atmosphere can, on the other hand, excite internal waves by nonlinear interaction. Thereby a surface wave packet consisting of two close frequencies can resonate with a low frequency internal wave (Phillips, 1966). From a theoretical point of view, the latter has been studied intensively by using a 2-layer model, i.e. a surface layer with a strong density contrast and an internal layer with a comparable weak density contrast (Ball, 1964; Craig et al., 2010). In the present work we analyse the wave coupling for a continuously stratified fluid using a fully non-linear 2D numerical model (OpenFoam) and compare this with laboratory experiments (see Lewis et al. 1974). Surface wave modes are used as initial condition and the time development of the dominant surface and internal waves are studied by spectral and harmonic analysis. For the simple geometry of a box, the results are compared with analytical spectra of surface and gravity waves. Ball, F.K. 1964: Energy transfer between external and internal gravity waves. J. Fluid Mech. 19, 465. Craig, W., Guyenne, P., Sulem, C. 2010: Coupling between internal and surface waves. Natural Hazards 57, 617-642. Lewis, J.E., Lake, B.M., Ko, D.R.S 1974: On the interaction of internal waves and surfacr gravity waves, J. Fluid Mech. 63, 773-800. Phillips, O.M. 1966: The dynamics of the upper ocean, Cambridge University Press, 336pp.

Surface waves in the western Taiwan coastal plain from an aftershock of the 1999 Chi-Chi, Taiwan, earthquake

USGS Publications Warehouse

Wang, G.-Q.; Tang, G.-Q.; Boore, D.M.; Van Ness, Burbach; Jackson, C.R.; Zhou, X.-Y.; Lin, Q.-L.

2006-01-01

Significant surface waves were recorded in the western coastal plain (WCP) of Taiwan during the 1999 Chi-Chi, Taiwan, earthquake and its series of aftershocks. We study in detail the surface waves produced by one aftershock (20 September 1999, 18hr 03m 41.16sec, M 6.2) in this paper. We take the Chelungpu-Chukou fault to be the eastern edge of the WCP because it marks a distinct lateral contrast in seismic wave velocities in the upper few kilometers of the surface. For many records from stations within the WCP, body waves and surface waves separate well in both the time domain and the period domain. Long-period (e.g., >2 sec) ground motions in the plain are dominated by surface waves. Significant prograde Rayleigh wave particle motions were observed in the WCP. The observed peak ground velocities are about 3-5 times larger than standard predictions in the central and western part of the plain. Observed response spectra at 3 sec, 4 sec, and 5 sec at the center of the plain can be 15 times larger than standard predictions and 10 times larger than the predictions of Joyner (2000) based on surface wave data from the Los Angeles basin. The strong surface waves were probably generated at the boundary of the WCP and then propagated toward the west, largely along radial directions relative to the epicenter. The geometry of the boundary may have had a slight effect on propagation directions of surface waves. Group velocities of fundamental mode Rayleigh and Love waves are estimated using the multiple filter analysis (MFA) technique and are refined with phase matched filtering (PMF). Group velocities of fundamental mode surface waves range from about 0.7 km/sec to 1.5 km/sec for the phases at periods from 3 sec to 10 sec. One important observation from this study is that the strongest surface waves were recorded in the center of the plain. The specific location of the strongest motions depends largely on the period of surface waves rather than on specific site conditions or plain structures. Accordingly, we conjecture that surface waves could be generated in a wide area close to boundaries of low-velocity sedimentary wave guides. In the case studied in this article the area can be as wide as 30 km (from the Chelungpu fault to the center of the plain). Surface waves converted by P and S waves at different locations would overlap each other and add constructively along their propagation paths. As a result, the surface waves would get stronger and stronger. Beyond a certain distance to the boundary, no more surface waves would be generated. Consequently, no more local surface waves would be superimposed into the invasive surface waves, and the surface waves would tend to decay in amplitude with distance.

Quantitative measurement and real-time tracking of high intensity focused ultrasound using phase-sensitive optical coherence tomography: Feasibility study.

PubMed

Le, Nhan; Song, ShaoZhen; Nabi, Ghulam; Wang, Ruikang; Huang, Zhihong

2016-09-01

Phase-sensitive optical coherence tomography (PhS-OCT) is proposed, as a new high intensity focused ultrasound (HIFU) imaging guidance to detect and track HIFU focus inside 1% agar samples in this work. The experiments studied the effect of varying HIFU power on the induction of shear wave, which can be implemented as a new technique to monitor focused ultrasound surgery (FUS). A miniature HIFU transducer (1.02 MHz, 20 mm aperture diameter, 15 mm radius of curvature) was produced in-house, pressure-field mapped, and calibrated. The transducer was then embedded inside a 1% agar phantom, which was placed under PhS-OCT for observation, under various HIFU power settings (acoustic power, and number of cycles per pulse). Shear wave was induced on the sample surface by HIFU and was captured in full under PhS-OCT. The lowest HIFU acoustic power output for the detection of shear wave was found to be 0.36 W (1.02 MHz, 100 cycles/pulse), or with the number of cycles/pulse as low as 20 (1.02 MHz, 0.98 W acoustic power output). A linear relationship between acoustic power output and the maximum shear wave displacement was found in the first study. The second study explores a non-linear correlation between the (HIFU) numbers of cycles per pulse, and the maximum shear wave displacement. PhS-OCT demonstrates excellent tracking and detection of HIFU-induced shear wave. The results could benefit other imaging techniques in tracking and guiding HIFU focus. Further studies will explore the relationship between the physical transducer characteristics and the HIFU-induced shear wave.

Theoretical Study of Monolayer and Double-Layer Waveguide Love Wave Sensors for Achieving High Sensitivity.

PubMed

Li, Shuangming; Wan, Ying; Fan, Chunhai; Su, Yan

2017-03-22

Love wave sensors have been widely used for sensing applications. In this work, we introduce the theoretical analysis of the monolayer and double-layer waveguide Love wave sensors. The velocity, particle displacement and energy distribution of Love waves were analyzed. Using the variations of the energy repartition, the sensitivity coefficients of Love wave sensors were calculated. To achieve a higher sensitivity coefficient, a thin gold layer was added as the second waveguide on top of the silicon dioxide (SiO₂) waveguide-based, 36 degree-rotated, Y-cut, X-propagating lithium tantalate (36° YX LiTaO₃) Love wave sensor. The Love wave velocity was significantly reduced by the added gold layer, and the flow of wave energy into the waveguide layer from the substrate was enhanced. By using the double-layer structure, almost a 72-fold enhancement in the sensitivity coefficient was achieved compared to the monolayer structure. Additionally, the thickness of the SiO₂ layer was also reduced with the application of the gold layer, resulting in easier device fabrication. This study allows for the possibility of designing and realizing robust Love wave sensors with high sensitivity and a low limit of detection.

X-ray diffraction and X-ray standing-wave study of the lead stearate film structure

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

Blagov, A. E.; Dyakova, Yu. A.; Kovalchuk, M. V.

2016-05-15

A new approach to the study of the structural quality of crystals is proposed. It is based on the use of X-ray standing-wave method without measuring secondary processes and considers the multiwave interaction of diffraction reflections corresponding to different harmonics of the same crystallographic reflection. A theory of multiwave X-ray diffraction is developed to calculate the rocking curves in the X-ray diffraction scheme under consideration for a long-period quasi-one-dimensional crystal. This phase-sensitive method is used to study the structure of a multilayer lead stearate film on a silicon substrate. Some specific structural features are revealed for the surface layer ofmore » the thin film, which are most likely due to the tilt of the upper layer molecules with respect to the external normal to the film surface.« less

Bloch surface waves confined in one dimension with a single polymeric nanofibre

PubMed Central

Wang, Ruxue; Xia, Hongyan; Zhang, Douguo; Chen, Junxue; Zhu, Liangfu; Wang, Yong; Yang, Erchan; Zang, Tianyang; Wen, Xiaolei; Zou, Gang; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

2017-01-01

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor–memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes. PMID:28155871

Detection of bioagents using a shear horizontal surface acoustic wave biosensor

DOEpatents

Larson, Richard S; Hjelle, Brian; Hall, Pam R; Brown, David C; Bisoffi, Marco; Brozik, Susan M; Branch, Darren W; Edwards, Thayne L; Wheeler, David

2014-04-29

A biosensor combining the sensitivity of surface acoustic waves (SAW) generated at a frequency of 325 MHz with the specificity provided by antibodies and other ligands for the detection of viral agents. In a preferred embodiment, a lithium tantalate based SAW transducer with silicon dioxide waveguide sensor platform featuring three test and one reference delay lines was used to adsorb antibodies directed against Coxsackie virus B4 or the negative-stranded category A bioagent Sin Nombre virus (SNV). Rapid detection of increasing concentrations of viral particles was linear over a range of order of magnitude for both viruses, and the sensor's selectivity for its target was not compromised by the presence of confounding Herpes Simplex virus type 1 The biosensor was able to delect SNV at doses lower than the load of virus typically found in a human patient suffering from hantavirus cardiopulmonary syndrome (HCPS).

Anomalous Hydrodynamics and Normal Fluids in Rapidly Rotating Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Bourne, A.; Wilkin, N. K.; Gunn, J. M. F.

2006-06-01

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a “normal fluid,” allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches—perhaps related to those observed at JILA.

Modeling Encapsulated Microbubble Dynamics at High Pressure Amplitudes

NASA Astrophysics Data System (ADS)

Heyse, Jan F.; Bose, Sanjeeb; Iaccarino, Gianluca

2017-11-01

Encapsulated microbubbles are commonly used in ultrasound contrast imaging and are of growing interest in therapeutic applications where local cavitation creates temporary perforations in cell membranes allowing for enhanced drug delivery. Clinically used microbubbles are encapsulated by a shell commonly consisting of protein, polymer, or phospholipid; the response of these bubbles to externally imposed ultrasound waves is sensitive to the compressibility of the encapsulating shell. Existing models approximate the shell compressibility via an effective surface tension (Marmottant et al. 2005). We present simulations of microbubbles subjected to high amplitude ultrasound waves (on the order of 106 Pa) and compare the results with the experimental measurements of Helfield et al. (2016). Analysis of critical points (corresponding to maximum and minimum expansion) in the governing Rayleigh-Plesset equation is used to make estimates of the parameters used to characterize the effective surface tension of the encapsulating shell. Stanford Graduate Fellowship.

Shock Wave / Boundary Layer Interaction Experiment on Control Surface

DTIC Science & Technology

2007-06-01

attachment points to the cold structure of the capsule (see Figure 16, left). Vibrational and acoustical loads are relevant for electronic components. Noise...thermal detector subsystems. Table 1: Summary of infrared technologies considered. Thermal Detectors Quantum Detectors Bolometer Pyrometer InGaAs...holes but a decrease in sensitivity at lower temperature results. Pyrometers are suitable for high temperature measurement, but they respond only to

SENSITIVITY OF HELIOSEISMIC TRAVEL TIMES TO THE IMPOSITION OF A LORENTZ FORCE LIMITER IN COMPUTATIONAL HELIOSEISMOLOGY

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

Moradi, Hamed; Cally, Paul S., E-mail: hamed.moradi@monash.edu

The rapid exponential increase in the Alfvén wave speed with height above the solar surface presents a serious challenge to physical modeling of the effects of magnetic fields on solar oscillations, as it introduces a significant Courant-Friedrichs-Lewy time-step constraint for explicit numerical codes. A common approach adopted in computational helioseismology, where long simulations in excess of 10 hr (hundreds of wave periods) are often required, is to cap the Alfvén wave speed by artificially modifying the momentum equation when the ratio between the Lorentz and hydrodynamic forces becomes too large. However, recent studies have demonstrated that the Alfvén wave speedmore » plays a critical role in the MHD mode conversion process, particularly in determining the reflection height of the upwardly propagating helioseismic fast wave. Using numerical simulations of helioseismic wave propagation in constant inclined (relative to the vertical) magnetic fields we demonstrate that the imposition of such artificial limiters significantly affects time-distance travel times unless the Alfvén wave-speed cap is chosen comfortably in excess of the horizontal phase speeds under investigation.« less

Calibration of the QCM/SAW Cascade Impactor for Measurement of Ozone

NASA Technical Reports Server (NTRS)

Williams, Cassandra K.; Peterson, C. B.; Morris, V. R.

1997-01-01

The Quartz Crystal Microbalance Surface Acoustic Wave (QCM/SAW) cascade impactor is an instrument designed to collect size-fractionated distributions of aerosols on a series of quartz crystals and employ SAW devices coated with chemical sensors for gas detection. We are calibrating the cascade impactor in our laboratory for future deployment for in-situ experiments to measure ozone. Experiments have been performed to characterize the QCM and SAW mass loading, saturation limits, mass frequency relationships, and sensitivity. The characteristics of mass loading, saturation limits, mass-frequency relationships, sensitivity, and the loss of ozone on different materials have been quantified.

Topology optimization of two-dimensional elastic wave barriers

NASA Astrophysics Data System (ADS)

Van hoorickx, C.; Sigmund, O.; Schevenels, M.; Lazarov, B. S.; Lombaert, G.

2016-08-01

Topology optimization is a method that optimally distributes material in a given design domain. In this paper, topology optimization is used to design two-dimensional wave barriers embedded in an elastic halfspace. First, harmonic vibration sources are considered, and stiffened material is inserted into a design domain situated between the source and the receiver to minimize wave transmission. At low frequencies, the stiffened material reflects and guides waves away from the surface. At high frequencies, destructive interference is obtained that leads to high values of the insertion loss. To handle harmonic sources at a frequency in a given range, a uniform reduction of the response over a frequency range is pursued. The minimal insertion loss over the frequency range of interest is maximized. The resulting design contains features at depth leading to a reduction of the insertion loss at the lowest frequencies and features close to the surface leading to a reduction at the highest frequencies. For broadband sources, the average insertion loss in a frequency range is optimized. This leads to designs that especially reduce the response at high frequencies. The designs optimized for the frequency averaged insertion loss are found to be sensitive to geometric imperfections. In order to obtain a robust design, a worst case approach is followed.

Furnace control apparatus using polarizing interferometer

DOEpatents

Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1995-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Polarizing optical interferometer having a dual use optical element

DOEpatents

Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-04-04

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Process control system using polarizing interferometer

DOEpatents

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1994-02-15

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Polarizing optical interferometer having a dual use optical element

DOEpatents

Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1995-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Process control system using polarizing interferometer

DOEpatents

Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

1994-01-01

A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Furnace control apparatus using polarizing interferometer

DOEpatents

Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

1995-03-28

A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

Characteristics of Quasi-Biennial Oscillation simulation in the Meteorological Research Institute earth system model

NASA Astrophysics Data System (ADS)

Yoshida, K.; Naoe, H.

2016-12-01

Whether climate models drive Quasi-Biennial Oscillation (QBO) appropriately is important to assess QBO impact on climate change such as global warming and solar related variation. However, there were few models generating QBO in the Coupled Model Intercomparison Project Phase 5 (CMIP5). This study focuses on dynamical structure of the QBO and its sensitivity to background wind pattern and model configuration. We present preliminary results of experiments designed by "Towards Improving the QBO in Global Climate Models (QBOi)", which is derived from the Stratosphere-troposphere processes and their role in climate (SPARC), in the Meteorological Research Institute earth system model, MRI-ESM2. The simulations were performed in present-day climate condition, repeated annual cycle condition with various CO2 level and sea surface temperatures, and QBO hindcast. In the present climate simulation, zonal wind in the equatorial stratosphere generally exhibits realistic behavior of the QBO. Equatorial zonal wind variability associated with QBO is overestimated in upper stratosphere and underestimated in lower stratosphere. In the MRI-ESM2, the QBO behavior is mainly driven by gravity wave drag parametrization (GWDP) introduced in Hines (1997). Comparing to reanalyses, shortage of resolved wave forcing is found especially in equatorial lower stratosphere. These discrepancies can be attributed to difference in wave forcing, background wind pattern and model configuration. We intend to show results of additional sensitivity experiments to examine how model configuration and background wind pattern affect resolved wave source, wave propagation characteristics, and QBO behavior.

Calculation of Seismic Waves from Explosions with Tectonic Stresses and Topography

NASA Astrophysics Data System (ADS)

Stevens, J. L.; O'Brien, M.

2017-12-01

We investigate the effects of explosion depth, tectonic stresses and topography on seismic waves from underground nuclear explosions. We perform three-dimensional nonlinear calculations of an explosion at several depths in the topography of the North Korean test site. We also perform a large number of two-dimensional axisymmetric calculations of explosions at depths from 150 to 1000 meters in four earth structures, with compressive and tensile tectonic stresses and with no tectonic stresses. We use the representation theorem to propagate the results of these calculations and calculate seismic waves at regional and teleseismic distances. We find that P-waves are not strongly affected by any of these effects because the initial downgoing P-wave is unaffected by interaction with the free surface. Surface waves, however, are strongly affected by all of these effects. There is an optimal depth at which surface waves are maximized at the base of a mountain and at or slightly below normal containment depth. At deeper depths, increasing overburden pressure reduces the surface waves. At shallower depths, interaction with the free surface reduces the surface waves. For explosions inside a mountain, displacement of the sides of the mountain reduces surface waves. Compressive prestress reduces surface waves substantially, while tensile prestress increases surface waves. The North Korean explosions appear to be at an optimal depth, in a region of extension, and beneath a mountain, all of which increase surface wave amplitudes.

Laser mode conversion into a surface plasma wave in a metal coated optical fiber

NASA Astrophysics Data System (ADS)

Liu, C. S.; Kumar, Gagan; Tripathi, V. K.

2006-07-01

An optical fiber, coated with thin metal film, supports two distinct kinds of waves, viz., body waves that propagate through the fiber as transverse magnetic (TM) and transverse electric modes, and surface plasma waves that propagate on metal free space interface. When the metal has a ripple of suitable wave number q, a body wave of frequency ω and propagation constant kz induces a current at ω ,kz+q in the ripple region that resonantly derives a surface plasma wave. When the metal surface has metallic particles attached to it and molecules are adsorbed on them, the surface plasma wave undergoes surface enhanced Raman scattering with them. The scattered signals propagate backward as a TM body wave and can be detected.

A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters

NASA Astrophysics Data System (ADS)

Ren, Luchuan

2015-04-01

A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters Luchuan Ren, Jianwei Tian, Mingli Hong Institute of Disaster Prevention, Sanhe, Heibei Province, 065201, P.R. China It is obvious that the uncertainties of the maximum tsunami wave heights in offshore area are partly from uncertainties of the potential seismic tsunami source parameters. A global sensitivity analysis method on the maximum tsunami wave heights to the potential seismic source parameters is put forward in this paper. The tsunami wave heights are calculated by COMCOT ( the Cornell Multi-grid Coupled Tsunami Model), on the assumption that an earthquake with magnitude MW8.0 occurred at the northern fault segment along the Manila Trench and triggered a tsunami in the South China Sea. We select the simulated results of maximum tsunami wave heights at specific sites in offshore area to verify the validity of the method proposed in this paper. For ranking importance order of the uncertainties of potential seismic source parameters (the earthquake's magnitude, the focal depth, the strike angle, dip angle and slip angle etc..) in generating uncertainties of the maximum tsunami wave heights, we chose Morris method to analyze the sensitivity of the maximum tsunami wave heights to the aforementioned parameters, and give several qualitative descriptions of nonlinear or linear effects of them on the maximum tsunami wave heights. We quantitatively analyze the sensitivity of the maximum tsunami wave heights to these parameters and the interaction effects among these parameters on the maximum tsunami wave heights by means of the extended FAST method afterward. The results shows that the maximum tsunami wave heights are very sensitive to the earthquake magnitude, followed successively by the epicenter location, the strike angle and dip angle, the interactions effect between the sensitive parameters are very obvious at specific site in offshore area, and there exist differences in importance order in generating uncertainties of the maximum tsunami wave heights for same group parameters at different specific sites in offshore area. These results are helpful to deeply understand the relationship between the tsunami wave heights and the seismic tsunami source parameters. Keywords: Global sensitivity analysis; Tsunami wave height; Potential seismic tsunami source parameter; Morris method; Extended FAST method

Ultrasensitive Biosensors Using Enhanced Fano Resonances in Capped Gold Nanoslit Arrays

PubMed Central

Lee, Kuang-Li; Huang, Jhih-Bin; Chang, Jhih-Wei; Wu, Shu-Han; Wei, Pei-Kuen

2015-01-01

Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU. PMID:25708955

Finite-frequency sensitivity kernels for head waves

NASA Astrophysics Data System (ADS)

Zhang, Zhigang; Shen, Yang; Zhao, Li

2007-11-01

Head waves are extremely important in determining the structure of the predominantly layered Earth. While several recent studies have shown the diffractive nature and the 3-D Fréchet kernels of finite-frequency turning waves, analogues of head waves in a continuous velocity structure, the finite-frequency effects and sensitivity kernels of head waves are yet to be carefully examined. We present the results of a numerical study focusing on the finite-frequency effects of head waves. Our model has a low-velocity layer over a high-velocity half-space and a cylindrical-shaped velocity perturbation placed beneath the interface at different locations. A 3-D finite-difference method is used to calculate synthetic waveforms. Traveltime and amplitude anomalies are measured by the cross-correlation of synthetic seismograms from models with and without the velocity perturbation and are compared to the 3-D sensitivity kernels constructed from full waveform simulations. The results show that the head wave arrival-time and amplitude are influenced by the velocity structure surrounding the ray path in a pattern that is consistent with the Fresnel zones. Unlike the `banana-doughnut' traveltime sensitivity kernels of turning waves, the traveltime sensitivity of the head wave along the ray path below the interface is weak, but non-zero. Below the ray path, the traveltime sensitivity reaches the maximum (absolute value) at a depth that depends on the wavelength and propagation distance. The sensitivity kernels vary with the vertical velocity gradient in the lower layer, but the variation is relatively small at short propagation distances when the vertical velocity gradient is within the range of the commonly accepted values. Finally, the depression or shoaling of the interface results in increased or decreased sensitivities, respectively, beneath the interface topography.

Reaction of water with MgO(100) surfaces: Part III. X-ray standing wave studies

NASA Astrophysics Data System (ADS)

Liu, P.; Kendelewicz, T.; Nelson, E. J.; Brown, G. E.

1998-09-01

Clean MgO(100) surfaces cleaved in vacuum and exposed to water vapor or bulk water were studied using the X-ray standing wave (XSW) technique in back reflection mode and surface sensitive, element specific O KLL and Mg KLL Auger electron yield detection. The effects of surface charging were mitigated, but not entirely eliminated, by using a low-energy electron flood gun. Simulation of the XSW signal showed that the effect of surface charging on the XSW data could be minimized with careful experimental design. We demonstrate that the XSW method can be applied to studies of insulating surfaces, and our results for MgO(100) surfaces exposed to water vapor or bulk water indicate the following: (1) the vacuum-cleaved clean surface undergoes no surface reconstruction or significant relaxation perpendicular to the surface; (2) Mg-OH distances on surfaces exposed to water vapor or bulk water measured perpendicular to the (100) surface are the same as in bulk MgO; and (3) the z-position of the surface Mg atoms does not change within the estimated error [±2% of the (200) spacing] after the surface is fully hydroxylated. Our results for the clean, vacuum-cleaved surface disagree with results from impact collision ion-scattering spectroscopy and surface-extended electron-loss fine structure for MgO(100), which indicate 15 and 17% inward relaxation, respectively, and they support results from low-energy electron diffraction, reflection high-energy electron diffraction, and photoelectron diffraction that show little, if any, relaxation or rumpling of the surface.

Molecular genetics of root gravitropism and waving in Arabidopsis thaliana

NASA Technical Reports Server (NTRS)

Sedbrook, J.; Boonsirichai, K.; Chen, R.; Hilson, P.; Pearlman, R.; Rosen, E.; Rutherford, R.; Batiza, A.; Carroll, K.; Schulz, T.;

Excitation of high-frequency surface waves with long duration in the Valley of Mexico

NASA Astrophysics Data System (ADS)

Iida, Masahiro

1999-04-01

During the 1985 Michoacan earthquake (Ms = 8.1), large-amplitude seismograms with extremely long duration were recorded in the lake bed zone of Mexico City. We interpret high-frequency seismic wave fields in the three geotechnical zones (the hill, the transition, and the lake bed zones) in the Valley of Mexico on the basis of a systematic analysis for borehole strong motion recordings. We make identification of wave types for real seismograms. First, amplitude ratios between surface and underground seismograms indicate that predominant periods of the surface seismograms are largely controlled by the wave field incident into surficial layers in the Valley of Mexico. We interpret recorded surface waves as fundamental-mode Love waves excited in the Mexican Volcanic Belt by calculating theoretical amplification for different-scale structures. Second, according to a cross-correlation analysis, the hill and transition seismograms are mostly surface waves. In the lake bed zone, while early portions are noisy body waves, late portions are mostly surface waves. Third, using two kinds of surface arrays with different station intervals, we investigate high-frequency surface-wave propagation in the lake bed zone. The wave propagation is very complicated, depending upon the time section and the frequency band. Finally, on the basis of a statistical time series model with an information criterion, we separate S- and surface-wave portions from lake bed seismograms. Surface waves are dominant and are recognized even in the early time section. Thus high-frequency surface waves with long duration in the Valley of Mexico are excited by the Mexican Volcanic Belt.

Modeling the Warming Impact of Urban Land Expansion on Hot Weather Using the Weather Research and Forecasting Model: A Case Study of Beijing, China

NASA Astrophysics Data System (ADS)

Liu, Xiaojuan; Tian, Guangjin; Feng, Jinming; Ma, Bingran; Wang, Jun; Kong, Lingqiang

2018-06-01

The impacts of three periods of urban land expansion during 1990-2010 on near-surface air temperature in summer in Beijing were simulated in this study, and then the interrelation between heat waves and urban warming was assessed. We ran the sensitivity tests using the mesoscaleWeather Research and Forecasting model coupled with a single urban canopy model, as well as high-resolution land cover data. The warming area expanded approximately at the same scale as the urban land expansion. The average regional warming induced by urban expansion increased but the warming speed declined slightly during 2000-2010. The smallest warming occurred at noon and then increased gradually in the afternoon before peaking at around 2000 LST—the time of sunset. In the daytime, urban warming was primarily caused by the decrease in latent heat flux at the urban surface. Urbanization led to more ground heat flux during the day and then more release at night, which resulted in nocturnal warming. Urban warming at night was higher than that in the day, although the nighttime increment in sensible heat flux was smaller. This was because the shallower planetary boundary layer at night reduced the release efficiency of near-surface heat. The simulated results also suggested that heat waves or high temperature weather enhanced urban warming intensity at night. Heat waves caused more heat to be stored in the surface during the day, greater heat released at night, and thus higher nighttime warming. Our results demonstrate a positive feedback effect between urban warming and heat waves in urban areas.

Laboratory modeling of air-sea interaction under severe wind conditions

NASA Astrophysics Data System (ADS)

Troitskaya, Yuliya; Vasiliy, Kazakov; Nicolay, Bogatov; Olga, Ermakova; Mikhail, Salin; Daniil, Sergeev; Maxim, Vdovin

2010-05-01

Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. The idea on saturation (and even reduction) of the coefficient of aerodynamic resistance of the sea surface at hurricane wind speed was first suggested by Emanuel (1995) on the basis of theoretical analysis of sensitivity of maximum wind speed in a hurricane to the ratio of the enthalpy and momentum exchange coefficients. Both field (Powell, Vickery, Reinhold, 2003, French et al, 2007, Black, et al, 2007) and laboratory (Donelan et al, 2004) experiments confirmed that at hurricane wind speed the sea surface drag coefficient is significantly reduced in comparison with the parameterization obtained at moderate to strong wind conditions. Two groups of possible theoretical mechanisms for explanation of the effect of the sea surface drag reduction can be specified. In the first group of models developed by Kudryavtsev & Makin (2007) and Kukulka,Hara Belcher (2007), the sea surface drag reduction is explained by peculiarities of the air flow over breaking waves. Another approach more appropriate for the conditions of developed sea exploits the effect of sea drops and sprays on the wind-wave momentum exchange (Andreas, 2004; Makin, 2005; Kudryavtsev, 2006). The main objective of this work is investigation of factors determining momentum exchange under high wind speeds basing on the laboratory experiment in a well controlled environment. The experiments were carried out in the Thermo-Stratified WInd-WAve Tank (TSWIWAT) of the Institute of Applied Physics. The parameters of the facility are as follows: airflow 0 - 25 m/s (equivalent 10-m neutral wind speed U10 up to 60 m/s), dimensions 10m x 0.4m x 0.7 m, temperature stratification of the water layer. Simultaneous measurements of the airflow velocity profiles and wind waves were carried out in the wide range of wind velocities. Airflow velocity profile was measured by WindSonic ultrasonic wind sensor. The water elevation was measured by the three-channel wave-gauge. Top and side views of the water surface were fixed by CCD-camera. Wind friction velocity and surface drag coefficients were retrieved from the measurements by the profile method. Obtained values are in good agreement with the data of measurements by Donelan et al (2004). The directional frequency-wave-number spectra of surface waves were retrieved by the wavelet directional method (Donelan et al, 1996). The obtained dependencies of parameters of the wind waves indicate existing of two regimes of the waves with the critical wind speed Ucr about 30 m/s. For U10Ucr the dependencies of peak wave period, peak wavelength, significant wave height on the wind speed tend to saturation, in the same time the peak wave slope has the maximum at approximately Ucr and then decreases with the tendency to saturation. The surface drag also tends to saturation for U10>Ucr similarly to (Donelan et al, 2004). Video filming indicates onset of wave breaking with white-capping and spray generation at wind speeds approximately equal to Ucr. We compared the obtained experimental dependencies with the predictions of the quasi-linear model of the turbulent boundary layer over the waved water surface (Reutov&Troitskaya, 1995). Comparing shows that theoretical predictions give low estimates for the measured drag coefficient and wave fields. Taking into account momentum flux associated with the spray generation yields theoretical estimations in good agreement with the experimental data. Basing on the experimental data a possible physical mechanism of the drag is suggested. Tearing of the wave crests at severe wind conditions leads to the effective smoothing (decreasing wave slopes) of the water surface, which in turn reduces the aerodynamic roughness of the water surface. Quantitative agreement of the experimental data and theoretical estimations od the surface drag occurs if spray and drop momentum flux is taken into account. This study was supported by Russian Foundation for basic research (project code 07-05-00565, 10-05-00339). References Andreas E. L. Spray stress revised, J. Phys. Oceanogr., 2004, v.34, p.1429--1440. Black P.G., et al, Bulletin of the American Meteorological Society, 2007, v. 88, №3, p.357-374. Donelan M.A., et al, J. Phys. Oceanogr., 26, 1901-1914, 1996 Donelan M.A., et al, Geophys. Res. Lett., 2004, v.31, L18306. Emanuel, K.A. , J. Atmos. Sci/, 1995, v.52, p.3969-3976. Fairall C.W., et al, J. Climate, 2003, v.16, № 4, p.571-591. French, J. R., et al, J. Atmos. Sci., 2007, v.64, p.1089-1102. Garratt J.R., Mon. Weather Rev., 1977, v.105, p.915-929. Kudryavtsev V. N., J. Geophys. Res., 2006, v.111, C07020. Kudryavtsev V., Makin V. , Boundary-Layer Meteorol., 2007, v.125, p. 289--303. Kukulka, T., T. Hara, and S. E. Belcher., J. Phys. Oceanogr., 37, 1811-1828, 2007 Makin V. K. ,Boundary Layer Meteorol., 2005, v. 115, №1, p.169-176. Powell, M.D., Vickery P.J., Reinhold T.A., Nature, 2003, v.422, p.279-283. Reutov V.P., Troitskaya Yu.I. ,. Izvestiya RAN, FAO, 31, 825-834, 1995

Utilization of high-frequency Rayleigh waves in near-surface geophysics

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Park, C.B.; Ivanov, J.; Tian, G.; Chen, C.

2004-01-01

Shear-wave velocities can be derived from inverting the dispersive phase velocity of the surface. The multichannel analysis of surface waves (MASW) is one technique for inverting high-frequency Rayleigh waves. The process includes acquisition of high-frequency broad-band Rayleigh waves, efficient and accurate algorithms designed to extract Rayleigh-wave dispersion curves from Rayleigh waves, and stable and efficient inversion algorithms to obtain near-surface S-wave velocity profiles. MASW estimates S-wave velocity from multichannel vertical compoent data and consists of data acquisition, dispersion-curve picking, and inversion.

Probing Dynamically Tunable Localized Surface Plasmon Resonances of Film-Coupled Nanoparticles by Evanescent Wave Excitation

PubMed Central

Mock, Jack J.; Hill, Ryan T.; Tsai, Yu-Ju; Chilkoti, Ashutosh; Smith, David R.

2012-01-01

The localized surface plasmon resonance (LSPR) spectrum associated with a gold nanoparticle (NP) coupled to a gold film exhibits extreme sensitivity to the nano-gap region where the fields are tightly localized. The LSPR of an ensemble of film-coupled NPs can be observed using an illumination scheme similar to that used to excite the surface plasmon resonance (SPR) of a thin metallic film; however, in the present system, the light is used to probe the highly sensitive distance-dependent LSPR of the gaps between NPs and film rather than the delocalized SPR of the film. We show that the SPR and LSPR spectral contributions can be readily distinguished, and we compare the sensitivities of both modes to displacements in the average gap between a collection of NPs and the gold film. The distance by which the NPs are suspended in solution above the gold film is fixed via a thin molecular spacer layer, and can be further modulated by subjecting the NPs to a quasistatic electric field. The observed LSPR spectral shifts triggered by the applied voltage can be correlated with Angstrom scale displacements of the NPs, suggesting the potential for chip-scale or flow-cell plasmonic nanoruler devices with extreme sensitivity. PMID:22429053

Voxel-based measurement sensitivity of spatially resolved near-infrared spectroscopy in layered tissues

NASA Astrophysics Data System (ADS)

Niwayama, Masatsugu

2018-03-01

We quantitatively investigated the measurement sensitivity of spatially resolved spectroscopy (SRS) across six tissue models: cerebral tissue, a small animal brain, the forehead of a fetus, an adult brain, forearm muscle, and thigh muscle. The optical path length in the voxel of the model was analyzed using Monte Carlo simulations. It was found that the measurement sensitivity can be represented as the product of the change in the absorption coefficient and the difference in optical path length in two states with different source-detector distances. The results clarified the sensitivity ratio between the surface layer and the deep layer at each source-detector distance for each model and identified changes in the deep measurement area when one of the detectors was close to the light source. A comparison was made with the results from continuous-wave spectroscopy. The study also identified measurement challenges that arise when the surface layer is inhomogeneous. Findings on the measurement sensitivity of SRS at each voxel and in each layer can support the correct interpretation of measured values when near-infrared oximetry or functional near-infrared spectroscopy is used to investigate different tissue structures.

Observation of low-frequency acoustic surface waves in the nocturnal boundary layer.

PubMed

Talmadge, Carrick L; Waxler, Roger; Di, Xiao; Gilbert, Kenneth E; Kulichkov, Sergey

2008-10-01

A natural terrain surface, because of its porosity, can support an acoustic surface wave that is a mechanical analog of the familiar vertically polarized surface wave in AM radio transmission. At frequencies of several hundred hertz, the acoustic surface wave is attenuated over distances of a few hundred meters. At lower frequencies (e.g., below approximately 200 Hz) the attenuation is much less, allowing surface waves to propagate thousands of meters. At night, a low-frequency surface wave is generally present at long ranges even when downward refraction is weak. Thus, surface waves represent a ubiquitous nighttime transmission mode that exists even when other transmission modes are weak or absent. Data from recent nighttime field experiments and theoretical calculations are presented, demonstrating the persistence of the surface wave under different meteorological conditions. The low-frequency surface wave described here is the "quasiharmonical" tail observed previously in nighttime measurements but not identified by S. Kulichkov and his colleagues (Chunchuzov, I. P. et al. 1990. "On acoustical impulse propagation in a moving inhomogeneous atmospheric layer," J. Acoust. Soc. Am. 88, 455-461).

LANDSAT-D investigations in snow hydrology

NASA Technical Reports Server (NTRS)

Dozier, J. (Principal Investigator)

1982-01-01

The sample LANDSAT-4 TM tape (7 bands) of NE Arkansas/Tennessee area was received and displayed. Snow reflectance in all 6 TM reflective bands, i.e. 1, 2, 3, 4, 5, and 7 was simulated, using Wiscombe and Warren's (1980) delta-Eddington model. Snow reflectance in bands 4, 5, and 7 appear sensitive to grain size. One of the objectives is to interpret surface optical grain size of snow, for spectral extension of albedo. While TM data of the study area are not received, simulation results are encouraging. It also appears that the TM filters resemble a "square-wave" closely enough to permit assuming a square-wave in calculations. Integrated band reflectance over the actual response functions was simulated, using sensor data supplied by Santa Barbara Research Center. Differences between integrating over the actual response functions and the equivalent square wave were negligible.

Theoretical study of surface plasmon resonance sensors based on 2D bimetallic alloy grating

NASA Astrophysics Data System (ADS)

Dhibi, Abdelhak; Khemiri, Mehdi; Oumezzine, Mohamed

2016-11-01

A surface plasmon resonance (SPR) sensor based on 2D alloy grating with a high performance is proposed. The grating consists of homogeneous alloys of formula MxAg1-x, where M is gold, copper, platinum and palladium. Compared to the SPR sensors based a pure metal, the sensor based on angular interrogation with silver exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which provides a big detection accuracy, whereas the sensor based on gold exhibits the broadest dips and the highest sensitivity. The detection accuracy of SPR sensor based a metal alloy is enhanced by the increase of silver composition. In addition, the composition of silver which is around 0.8 improves the sensitivity and the quality of SPR sensor of pure metal. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensor based on a metal alloy not only has a high sensitivity and a high detection accuracy, but also exhibits a good linearity and a good quality.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

PubMed Central

Yaman, Yesim Tugce; Abaci, Serdar

2016-01-01

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability. PMID:27231912

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.

Rayleigh wave ellipticity across the Iberian Peninsula and Morocco

NASA Astrophysics Data System (ADS)

Gómez García, Clara; Villaseñor, Antonio

2015-04-01

Spectral amplitude ratios between horizontal and vertical components (H/V ratios) from seismic records are useful to evaluate site effects, predict ground motion and invert for S velocity in the top several hundred meters. These spectral ratios can be obtained from both ambient noise and earthquakes. H/V ratios from ambient noise depend on the content and predominant wave types: body waves, Rayleigh waves, a mixture of different waves, etc. The H/V ratio computed in this way is assumed to measure Rayleigh wave ellipticity since ambient vibrations are dominated by Rayleigh waves. H/V ratios from earthquakes are able to determine the local crustal structure at the vicinity of the recording station. These ratios obtained from earthquakes are based on surface wave ellipticity measurements. Although long period (>20 seconds) Rayleigh H/V ratio is not currently used because of large scatter has been reported and uncertainly about whether these measurements are compatible with traditional phase and group velocity measurements, we will investigate whether it is possible to obtain stable estimates after collecting statistics for many earthquakes. We will use teleseismic events from shallow earthquakes (depth ≤ 40 km) between 2007 January 1 and 2012 December 31 with M ≥ 6 and we will compute H/V ratios for more than 400 stations from several seismic networks across the Iberian Peninsula and Morocco for periods between 20 and 100 seconds. Also H/V ratios from cross-correlations of ambient noise in different components for each station pair will be computed. Shorter period H/V ratio measurements based on ambient noise cross-correlations are strongly sensitive to near-surface structure, rather than longer period earthquake Rayleigh waves. The combination of ellipticity measurements based on earthquakes and ambient noise will allow us to perform a joint inversion with Rayleigh wave phase velocity. Upper crustal structure is better constrained by the joint inversion compared to inversions based on phase velocities alone.

Propagation of Gaussian wave packets in complex media and application to fracture characterization

NASA Astrophysics Data System (ADS)

Ding, Yinshuai; Zheng, Yingcai; Zhou, Hua-Wei; Howell, Michael; Hu, Hao; Zhang, Yu

2017-08-01

Knowledge of the subsurface fracture networks is critical in probing the tectonic stress states and flow of fluids in reservoirs containing fractures. We propose to characterize fractures using scattered seismic data, based on the theory of local plane-wave multiple scattering in a fractured medium. We construct a localized directional wave packet using point sources on the surface and propagate it toward the targeted subsurface fractures. The wave packet behaves as a local plane wave when interacting with the fractures. The interaction produces multiple scattering of the wave packet that eventually travels up to the surface receivers. The propagation direction and amplitude of the multiply scattered wave can be used to characterize fracture density, orientation and compliance. Two key aspects in this characterization process are the spatial localization and directionality of the wave packet. Here we first show the physical behaviour of a new localized wave, known as the Gaussian Wave Packet (GWP), by examining its analytical solution originally formulated for a homogenous medium. We then use a numerical finite-difference time-domain (FDTD) method to study its propagation behaviour in heterogeneous media. We find that a GWP can still be localized and directional in space even over a large propagation distance in heterogeneous media. We then propose a method to decompose the recorded seismic wavefield into GWPs based on the reverse-time concept. This method enables us to create a virtually recorded seismic data using field shot gathers, as if the source were an incident GWP. Finally, we demonstrate the feasibility of using GWPs for fracture characterization using three numerical examples. For a medium containing fractures, we can reliably invert for the local parameters of multiple fracture sets. Differing from conventional seismic imaging such as migration methods, our fracture characterization method is less sensitive to errors in the background velocity model. For a layered medium containing fractures, our method can correctly recover the fracture density even with an inaccurate velocity model.

Formation and propagation of Love waves in a surface layer with a P-wave source. Technical report

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

Florence, A.L.; Miller, S.A.

The objective of this research is to investigate experimentally, and support with theoretical calculations, the formation and propagation of Love waves from a P-wave source due to scattering at material heterogeneities. The P-wave source is a spherical piezoelectric crystal cast in a surface layer of rock simulant overlaying a higher impedance granite substrate. Excitation of the piezoelectric crystal with a known voltage applies a spherical compressional pulse of known amplitude to the surrounding medium. Lateral heterogeneities cast in the surface layer convert incident P-wave energy into shear waves. The horizontally polarized shear waves (SH waves) trapped in the surface layermore » wave guide are the Love waves we will measure at the surface.« less

Tapping of Love waves in an isotropic surface waveguide by surface-to-bulk wave transduction.

NASA Technical Reports Server (NTRS)

Tuan, H.-S.; Chang, C.-P.

1972-01-01

A theoretical study of tapping a Love wave in an isotropic microacoustic surface waveguide is given. The surface Love wave is tapped by partial transduction into a bulk wave at a discontinuity. It is shown that, by careful design of the discontinuity, the converted bulk wave power and the radiation pattern may be controlled. General formulas are derived for the calculation of these important characteristics from a relatively general surface contour deformation.

Characterization of the surface wave variability in the California Current region from satellite altimetry.

NASA Astrophysics Data System (ADS)

Villas Boas, A. B.; Gille, S. T.; Mazloff, M. R.

2016-02-01

Surface gravity waves play a crucial role in upper-ocean dynamics, and they are an important mechanism by which the ocean exchanges energy with the overlying atmosphere. Surface waves are largely wind forced and can also be modulated by ocean currents via nonlinear wave-current interactions, leading to either an amplification or attenuation of the wave amplitude. Even though individual waves cannot be detected by present satellite altimeters, surface waves have the potential to produce a sea-state bias in altimeter measurements and can impact the sea-surface-height spectrum at high wavenumbers or frequencies. Knowing the wave climatology is relevant for the success of future altimeter missions, such as the Surface Water and Ocean Topography (SWOT). We analyse the seasonal, intra-annual and interannual variability of significant wave heights retrieved from over two decades of satellite altimeter data and assess the extent to which the variability of the surface wave field in the California Current region is modulated by the local wind and current fields.

Influence of handling-relevant factors on the behaviour of a novel calculus-detection device.

PubMed

Meissner, Grit; Oehme, Bernd; Strackeljan, Jens; Kocher, Thomas

2005-03-01

The aim of periodontal therapy is always the complete debridement of root surfaces with the removal of calculus and without damaging cementum. We have recently demonstrated the feasibility of a surface recognition device that discriminates dental surfaces by mathematical analysis of reflected ultrasound waves. This principle should enable the construction of calculus detecting ultrasonic device. Pre-clinical test results are presented here. An impulse generator, coupled to a conventional piezo-driven ultrasonic scaler, sends signals to the cementum via the tip of an ultrasound device. The oscillation signal reflected from the surface contains the information necessary to analyse its characteristics. In order to discriminate different surfaces, learning sets were generated from 70 extracted teeth using standardized tip angle/lateral force combinations. The complete device was then used to classify root surfaces unknown to the system. About 80% of enamel and cementum was correctly identified in vivo (sensitivity: 75%, specificity: 82%). The surface discrimination method was not influenced by the application conditions examined. A new set of 200 tests on 10 teeth was correctly recognized in 82% of the cases (sensitivity: 87%, specificity: 76%). It was shown in vitro that the tooth surface recognition system is able to function correctly, independent of the lateral forces and the tip angle of the instrument. Copyright 2005 Blackwell Munksgaard.

The effects of the theoretical formalism and data selection on mantle models derived from waveform tomography

NASA Astrophysics Data System (ADS)

Mégnin, Charles; Romanowicz, Barbara

1999-08-01

Most global tomographic models to date are derived using a combination of surface wave (or normal-mode) data and body wave traveltime data. The traveltime approach limits the number of phases available for inversion by requiring them to be isolated on the seismogram. This may ultimately result in limiting the resolution of 3-D structure, at least in some depth ranges in the mantle. In a previous study, we successfully derived a degree 12 whole-mantle SH-velocity tomographic model (SAW12D) using exclusively waveform data. In that inversion, a normal-mode formalism suitable for body waveforms, the non-linear asymptotic coupling theory (NACT), was combined with a body wave windowing scheme, referred to as the `individual wavepacket' (IW) technique, which allows one to assign individual weights to different body wave energy packets. We here compare the relative merits of this choice of theoretical formalism and windowing scheme at different depth ranges in the mantle. Choosing as the reference a model obtained using 7500 transverse-component body wave and 8000 surface wave seismograms and the NACT and IW approaches, we discuss the relative performance of the path average approximation (PAVA), a zeroth-order theoretical approximation appropriate for single-mode surface waves, relative to NACT, and compare the IW windowing scheme with a more standard `full window' (FW) approach, in which a single time window is considered from the first body wave arrival to the fundamental-mode surface waves. The combination PAVA/FW is often used in global tomography to supplement the traveltime data. We show that although the quality of the image derived under the PAVA/FW formalism is very similar to that derived under NACT/IW in the first 300 km of the upper mantle, where the resolution is dominated by surface waves, it deteriorates at greater depths. Images of the lower mantle are shown to be strongly sensitive to the theoretical formalism. In contrast, the resolution of structure near the core-mantle boundary depends mostly on the windowing scheme. This is because this resolution is controlled by low-amplitude phases such as S_diff, which are downweighted in the FW scheme. Whilst the image obtained in D'' using the combination NACT/IW is in good agreement with images obtained by other authors using both waveforms and traveltimes, we show that, when using FW, uppermost mantle structure can be mapped into D''. This result is confirmed by synthetic tests performed on a composite of the upper-mantle geodynamic model 3SMAC. We also show, based on synthetic tests, that for structures in the upper mantle with sharp boundaries, differences are observed between NACT and PAVA. Whilst a combination of traveltimes and surface wave data is adequate for resolving relatively smooth features in the mantle, our results show that by potentially increasing the achievable sampling, the waveform approach shows great promise for future high-resolution tomographic modelling of mantle structure, if cast in an appropriate theoretical framework.

Frequency lock-in and phase synchronization of vortex shedding behind circular cylinder due to surface waves

NASA Astrophysics Data System (ADS)

Gunnoo, Hans; Abcha, Nizar; Ezersky, Alexander

2016-02-01

The influence of harmonic surface wave on non-regular Karman Vortex Street is investigated. In our experiments, Karman Street arises behind a vertical circular cylinder in a water flow and harmonic surface waves propagating upstream. It is found that surface waves can modify regimes of shedding in Karman Street: frequency lock-in and synchronization of vortex shedding can arise. Intensive surface waves can excite symmetric vortex street instead of chess-like street, and completely suppress shedding behind the cylinder. It is shown experimentally that such effects occur if frequency of harmonic surface wave is approximately twice higher than the frequency of vortex shedding. Region of frequency lock-in is found on the plane amplitude-frequency of surface wave.

4-D permafrost thaw observations from ambient road traffic noise and a very dense distributed fiber optic sensing array

NASA Astrophysics Data System (ADS)

Lindsey, N.; Dou, S.; Martin, E. R.; Wagner, A. M.; Ajo Franklin, J. B.

2017-12-01

How does frozen soil thaw? The answer to this question affects hydrology, ecology, climate, and human infrastructure. We are using the local ambient noise field from a road recorded on a distributed fiber optic acoustic sensing (DAS) array to monitor the evolution in seismic parameters related to the top-down permafrost thaw process in the upper 10 m. Our field experiment demonstrates the advantages of "Large N" ambient noise studies using DAS, particularly to probe near surface critical zone dynamics. Over 60 days beginning in August 2016, we made continuous seismic recordings with a >4000 channel trenched fiber optic DAS dataset above a controlled permafrost warming demonstration experiment in Fairbanks, AK. The warming experiment accelerated the state of permafrost degradation by approximately two decades in a small 15 m x 20 m area, deepening the permafrost table from 4 m to 5.5 m. Continuous seismic DAS recording of high frequency surface waves (5-30 Hz) generated by vehicles traveling along a nearby road enables our investigation of hypothesized shear wave speed and attenuation changes, which lab measurements suggest may result from decreasing shear modulus and increasing saturation. We develop daily auto- and crosscorrelation function estimates using combinations of horizontal inline, collinear, and crossline DAS sensor orientations and vertical component geophone data, and then invert for maps of Love and Rayleigh wave speed that are sensitive to the upper 30 m. Many issues related to the accuracy, stability, and repeatability of the recovered empirical Green's tensor, as well as the sensitivity of the DAS sensor network will be considered.

Cell separation using tilted-angle standing surface acoustic waves

PubMed Central

Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2014-01-01

Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼97%. We illustrate that taSSAW is capable of effectively separating particles–cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological–biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice. PMID:25157150

Cell separation using tilted-angle standing surface acoustic waves.

PubMed

Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2014-09-09

Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼ 99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼ 97%. We illustrate that taSSAW is capable of effectively separating particles-cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological-biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice.

Molecular interferometric imaging study of molecular interactions

NASA Astrophysics Data System (ADS)

Zhao, Ming; Wang, Xuefeng; Nolte, David

2008-02-01

Molecular Interferometric Imaging (MI2) is a sensitive detection platform for direct optical detection of immobilized biomolecules. It is based on inline common-path interferometry combined with far-field optical imaging. The substrate is a simple thermal oxide on a silicon surface with a thickness at or near the quadrature condition that produces a π/2 phase shift between the normal-incident wave reflected from the top oxide surface and the bottom silicon surface. The presence of immobilized or bound biomolecules on the surface produces a relative phase shift that is converted to a far-field intensity shift and is imaged by a reflective microscope onto a CCD camera. Shearing interferometry is used to remove the spatial 1/f noise from the illumination to achieve shot-noise-limited detection of surface dipole density profiles. The lateral resolution of this technique is diffraction limited at 0.4 micron, and the best longitudinal resolution is 10 picometers. The minimum detectable mass at the metrology limit is 2 attogram, which is 8 antibody molecules of size 150 kDa. The corresponding scaling mass sensitivity is 5 fg/mm compared with 1 pg/mm for typical SPR sensitivity. We have applied MI2 to immunoassay applications, and real-time binding kinetics has been measured for antibody-antigen reactions. The simplicity of the substrate and optical read-out make MI2 a promising analytical assay tool for high-throughput screening and diagnostics.

Teleseismic surface wave study of S-wave velocity structure in Southern California

NASA Astrophysics Data System (ADS)

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

2002-12-01

We report on a 3D S-wave velocity structure derived from teleseismic Rayleigh and Love waves using TriNet broadband seismic data. Phase velocity maps, constructed between 20 and 55 mHz for Rayleigh waves and between 25 and 45 mHz for Love waves, were inverted for S-wave velocity structure at depth. Our starting model is SCEC 2.2, which has detailed crustal structure, but laterally homogeneous upper mantle structure. Depth resolution from the data set is good from the surface to approximately 100 km, but deteriorates rapidly beyond this depth. Our 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. Various regions in Southern California have different seismic-velocity signatures in terms of fast and slow S-wave velocities: In the Southern Sierra, both the crust and mantle are slow. In the Mojave desert, mid-crustal depths tend to show slow velocities, which are already built into SCEC 2.2. In the Transverse Ranges, the lower crust and mantle are both fast. Our Love wave results require much faster crustal velocity than those in SCEC 2.2 in this region. In the Peninsular ranges, both the crust and mantle are fast with mantle fast velocity extending to about 70 km. This is slightly more shallow than the depth extent under the Transverse Ranges, yet it is surprisingly deep. Under the Salton Sea, the upper crust is very slow and the upper mantle is also slow. However, these two slow velocity layers are separated by faster velocity lower crust which creates a distinct contrast with respect to the adjacent slow velocity regions. Existence of such a relatively fast layer, sandwiched by slow velocities, are related to features in phase velocity maps, especially in the low frequency Love wave phase velocity map (25 mHz) and the high frequency Rayleigh wave phase velocity maps (above 40 mHz). Such a feature may be related to partial melting processes under the Salton Sea.

Development of a New Surface Acoustic Wave Based Gyroscope on a X-112°Y LiTaO3 Substrate

PubMed Central

Wang, Wen; Liu, Jiuling; Xie, Xiao; Liu, Minghua; He, Shitang

2011-01-01

A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT) and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg−1 s at angular rates of up to 1,000 deg s−1 and good linearity are observed. PMID:22346678

Development of a new surface acoustic wave based gyroscope on a X-112°Y LiTaO3 substrate.

PubMed

Wang, Wen; Liu, Jiuling; Xie, Xiao; Liu, Minghua; He, Shitang

2011-01-01

A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT) and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg(-1) s at angular rates of up to 1,000 deg s(-1) and good linearity are observed.

Sunspot seismology: accounting for magnetohydrodynamic wave processes using imaging spectropolarimetry

NASA Astrophysics Data System (ADS)

Rajaguru, S. P.

Effects of acoustic wave absorption, mode conversion and transmission by a sunspot on the helioseismic inferences are widely discussed, yet accounting for them has proved difficult for lack of a consistent framework within helioseismic modelling. Here, following a discussion of problems and issues that the near-surface magnetohydrodynamics hosts through a complex interplay of radiative transfer, measurement issues, and MHD wave processes, I present some possibilities entirely from observational analyses based on imaging spectropolarimetry. In particular, I present some results on wave evolution as a function of observation height and inclination of magnetic field to the vertical, derived from a high-cadence imaging spectropolarimetric observation of a sunspot and its surroundings using the instrument IBIS (NSO/Sac Peak, USA). These observations were made in magnetically sensitive (Fe I 6173 Å) and insensitive (Fe I 7090 Å) upper photospheric absorption lines. Wave travel time contributions from within the photospheric layers of a sunspot estimated here would then need to be removed from the inversion modelling procedure, that does not have the provision to account for them.

Nostradamus: The radar that wanted to be a seismometer

NASA Astrophysics Data System (ADS)

Occhipinti, Giovanni; Dorey, Philippe; Farges, Thomas; Lognonné, Philippe

2010-09-01

Surface waves emitted after large earthquakes are known to induce, by dynamic coupling, atmospheric infrasonic waves propagating upward through the neutral and ionized atmosphere. Those waves have been detected in the past at ionospheric heights using a variety of techniques, such as HF Doppler sounding or GPS receivers. The HF Doppler technique, particularly sensitive to the ionospheric signature of Rayleigh waves is used here to show ionospheric perturbations consistent with the propagation of Rayleigh wave phases R1 and R2 following the Sumatra earthquake on the 28 March 2005 (M = 8.6). This is in our knowledge the first time that the phase R2 is detected by ionospheric sounding. In addition, we prove here that the ionospheric signature of R2 is also observed by over-the-horizon (OTH) Radar. The latter was never used before to detect seismic signature in the ionosphere. Adding the OTH Radar to the list of the “ionospheric seismometers” we discuss and compare the performances of the three different instruments mentioned above, namely HF Doppler sounding, GPS receivers and OTH radar.

Development of chipless, wireless current sensor system based on giant magnetoimpedance magnetic sensor and surface acoustic wave transponder.

PubMed

Kondalkar, Vijay V; Li, Xiang; Park, Ikmo; Yang, Sang Sik; Lee, Keekeun

2018-02-05

A chipless, wireless current sensor system was developed using a giant magnetoimpedance (GMI) magnetic sensor and one-port surface acoustic wave (SAW) reflective delay line for real-time power monitoring in a current-carrying conductor. The GMI sensor has a high-quality crystalline structure in each layer, which contributes to a high sensitivity and good linearity in a magnetic field of 3-16 Oe. A 400 MHz RF energy generated from the interdigital transducer (IDT)-type reflector on the one-port SAW delay line was used as an activation source for the GMI magnetic sensor. The one-port SAW delay line replaces the presently existing transceiver system, which is composed of thousands of transistors, thus enabling chipless and wireless operation. We confirmed a large variation in the amplitude of the SAW reflection peak with a change in the impedance of the GMI sensor caused by the current flow through the conductor. Good linearity and sensitivity of ~0.691 dB/A were observed for currents in the range 1-12 A. Coupling of Mode (COM) modeling and impedance matching analysis were also performed to predict the device performance in advance and these were compared with the experimental results.

Electron density measurements from the shot noise collected on the STEREO/WAVES antennas

NASA Astrophysics Data System (ADS)

Zouganelis, Ioannis; Bale, Stuart; Bougeret, J.-L.; Maksimovic, Milan

One of the most reliable techniques for in situ measuring the electron density and temperature in space plasmas is the quasi-thermal noise spectroscopy. When a passive electric antenna is immersed in a stable plasma, the thermal motion of the ambient particles produces electrostatic fluctuations, which can be adequately measured with a sensitive wave receiver connected to a wire dipole antenna. Unfortunately, on STEREO, the S/WAVES design does not let us use this high accuracy technique because the antennas have a large surface area and the resulting shot noise spectrum in the solar wind dominates the power at lower frequencies. We can use, instead, the electron shot noise to infer the plasma density. For this, we use well calibrated Wind particle data to deduce the base capacitance of the S/WAVES instrument in a special configuration when the STEREO-B spacecraft was just downstream of Wind. The electron plasma density deduced is then compared to the S/PLASTIC ion density and its accuracy is estimated of up to 10

Recurrence in truncated Boussinesq models for nonlinear waves in shallow water

NASA Technical Reports Server (NTRS)

Elgar, Steve; Freilich, M. H.; Guza, R. T.

1990-01-01

The rapid spatial recurrence of weakly nonlinear and weakly dispersive progressive shallow-water waves is examined using a numerical integration technique on the discretized and truncated form of the Boussinesq equations. This study primarily examines recurrence in wave fields with Ursell number O(1) and characterizes the sensitivity of recurrence to initial spectral shape and number of allowed frequency modes. It is shown that the rapid spatial recurrence is not an inherent property of the considered Boussinesq systems for evolution distances of 10-50 wavelengths. The main result of the study is that highly truncated Boussinesq models of resonant shallow-water ocean surface gravity waves predict rapid multiple recurrence cycles, but that this is an artifact dependent on the number of allowed modes. For initial conditions consisting of essentially all energy concentrated in a single mode, damping of the recurrence cycles increases as the number of low-power background modes increases. When more than 32 modes are allowed, the recurrence behavior is relatively insensitive to the number of allowed modes.

Approximate Stokes Drift Profiles and their use in Ocean Modelling

NASA Astrophysics Data System (ADS)

Breivik, O.; Biblot, J.; Janssen, P. A. E. M.

2016-02-01

Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons with parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. I will show some results from the coupled atmosphere-wave-ocean ensemble forecast system of ECMWF where these wave effects are now included in the ocean model component.

Excitation of Love waves in a thin film layer by a line source.

NASA Technical Reports Server (NTRS)

Tuan, H.-S.; Ponamgi, S. R.

1972-01-01

The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.

Reconstructing surface wave profiles from reflected acoustic pulses using multiple receivers.

PubMed

Walstead, Sean P; Deane, Grant B

2014-08-01

Surface wave shapes are determined by analyzing underwater reflected acoustic signals collected at multiple receivers. The transmitted signals are of nominal frequency 300 kHz and are reflected off surface gravity waves that are paddle-generated in a wave tank. An inverse processing algorithm reconstructs 50 surface wave shapes over a length span of 2.10 m. The inverse scheme uses a broadband forward scattering model based on Kirchhoff's diffraction formula to determine wave shapes. The surface reconstruction algorithm is self-starting in that source and receiver geometry and initial estimates of wave shape are determined from the same acoustic signals used in the inverse processing. A high speed camera provides ground-truth measurements of the surface wave field for comparison with the acoustically derived surface waves. Within Fresnel zone regions the statistical confidence of the inversely optimized surface profile exceeds that of the camera profile. Reconstructed surfaces are accurate to a resolution of about a quarter-wavelength of the acoustic pulse only within Fresnel zones associated with each source and receiver pair. Multiple isolated Fresnel zones from multiple receivers extend the spatial extent of accurate surface reconstruction while overlapping Fresnel zones increase confidence in the optimized profiles there.

Lamb waves increase sensitivity in nondestructive testing

NASA Technical Reports Server (NTRS)

Di Novi, R.

1967-01-01

Lamb waves improve sensitivity and resolution in the detection of small defects in thin plates and small diameter, thin-walled tubing. This improvement over shear waves applies to both longitudinal and transverse flaws in the specimens.

SAW Sensors for Chemical Vapors and Gases

PubMed Central

Devkota, Jagannath; Ohodnicki, Paul R.; Greve, David W.

2017-01-01

Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future. PMID:28397760

SAW Sensors for Chemical Vapors and Gases

DOE PAGES

Devkota, Jagannath; Ohodnicki, Paul R.; Greve, David W.

2017-04-08

Here, surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identifymore » new opportunities and needs for additional research in this area moving into the future.« less

SAW Sensors for Chemical Vapors and Gases.

PubMed

Devkota, Jagannath; Ohodnicki, Paul R; Greve, David W

2017-04-08

Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future.

Pressure-sensitive paint measurements on a supersonic high-sweep oblique wing model. [conducted in the NASA Ames 9- by 7-ft Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

McLachlan, B. G.; Bell, J. H.; Park, H.; Kennelly, R. A.; Schreiner, J. A.; Smith, S. C.; Strong, J. M.; Gallery, J.; Gouterman, M.

1995-01-01

The pressure-sensitive paint method was used in the test of a high-sweep oblique wing model, conducted in the NASA Ames 9- by 7-ft Supersonic Wind Tunnel. Surface pressure data was acquired from both the luminescent paint and conventional pressure taps at Mach numbers between M = 1.6 and 2.0. In addition, schlieren photographs of the outer flow were used to determine the location of shock waves impinging on the model. The results show that the luminescent pressure-sensitive paint can capture both global and fine features of the static surface pressure field. Comparison with conventional pressure tap data shows good agreement between the two techniques, and that the luminescent paint data can be used to make quantitative measurements of the pressure changes over the model surface. The experiment also demonstrates the practical considerations and limitations that arise in the application of this technique under supersonic flow conditions in large-scale facilities, as well as the directions in which future research is necessary in order to make this technique a more practical wind-tunnel testing tool.

Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

PubMed

Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

2015-09-29

Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

Increased sensitivity of prolonged P-wave during exercise stress test in detection of angiographically documented coronary artery disease.

PubMed

Wsol, Agnieszka; Wydra, Wioletta; Chmielewski, Marek; Swiatowiec, Andrzej; Kuch, Marek

2017-01-01

A retrospective study was designed to investigate P-wave duration changes in exercise stress test (EST) for the prediction of angiographically documented substantial coronary artery disease (CAD). We analyzed 265 cases of patients, who underwent EST and subsequently coronary angiography. Analysis of P-wave duration was performed in leads II, V5 at rest, and in the recovery period. The sensitivity and specificity for the isolated ST-segment depression were only 31% and 76%, respectively. The combination of ST-depression with other exercise-induced clinical and electrocardio-graphic abnormalities (chest pain, ventricular arrhythmia, hypotension, left bundle branch block) was characterized by 41% sensitivity and 69% specificity. The combination of abnormal recovery P-wave duration (≥ 120 ms) with ST-depression and other exercise-induced abnormalities had 83% sensitivity but only 20% specificity. Combined analysis of increased delta P-wave duration, ST-depression and other exercise-induced abnormalities had 69% sensitivity and 42% specificity. Sensitivity and specificity of the increase in delta P-wave duration for left CAD was 69% and 47%, respectively, and for 3-vessel CAD 70% and 50%, respectively. The presence of arterial hypertension negatively influenced the prog-nostic value of P-wave changes in the stress test. The results of the study show that an addition of P-wave duration changes assessment to ST-depression analysis and other exercise-induced abnormalities increase sensitivity of EST, especially for left CAD and 3-vessel coronary disease. We have also provided evidence for the negative influence of the presence of arterial hypertension on the predictive value of P-wave changes in the stress test. (Cardiol J 2017; 24, 2: 159-166).

Estimation of near-surface shear-wave velocities and quality factors using multichannel analysis of surface-wave methods

NASA Astrophysics Data System (ADS)

Xia, Jianghai

2014-04-01

This overview article gives a picture of multichannel analysis of high-frequency surface (Rayleigh and Love) waves developed mainly by research scientists at the Kansas Geological Survey, the University of Kansas and China University of Geosciences (Wuhan) during the last eighteen years by discussing dispersion imaging techniques, inversion systems, and real-world examples. Shear (S)-wave velocities of near-surface materials can be derived from inverting the dispersive phase velocities of high-frequency surface waves. Multichannel analysis of surface waves—MASW used phase information of high-frequency Rayleigh waves recorded on vertical component geophones to determine near-surface S-wave velocities. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that inversion with higher modes and the fundamental mode simultaneously can increase model resolution and an investigation depth. Multichannel analysis of Love waves—MALW used phase information of high-frequency Love waves recorded on horizontal (perpendicular to the direction of wave propagation) component geophones to determine S-wave velocities of shallow materials. Because of independence of compressional (P)-wave velocity, the MALW method has some attractive advantages, such as 1) Love-wave dispersion curves are simpler than Rayleigh wave's; 2) dispersion images of Love-wave energy have a higher signal to noise ratio and more focused than those generated from Rayleigh waves; and 3) inversion of Love-wave dispersion curves is less dependent on initial models and more stable than Rayleigh waves.

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

NASA Astrophysics Data System (ADS)

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

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

Absorption and Modification of Lower Hybrid Waves in the Scrape Off Layer

NASA Astrophysics Data System (ADS)

Parker, R.; Wallace, G.; Shiraiwa, S.; Baek, S.-G.; Faust, I.

2015-11-01

Loss of current drive efficiency of lower hybrid waves at high density in Alcator C-Mod current drive experiments has been attributed, at least in part, to interactions in the SOL. While ray-tracing calculations indicate that collisional absorption and modification of n|| during reflections in the SOL can be significant, their validity can be called into question owing to steep SOL gradients. In order to further quantify these losses, full-wave calculations using a plane-stratified SOL model have been carried out. The results show that the loss resulting from reflections in the SOL can be substantial, with collisional losses accounting for a loss of up to 50% per bounce of the incident wave power. The loss is sensitive to the SOL parameters with the strongest collisional absorption occurring in the case of steep temperature and weak density gradients. Modification of n|| can also be significant when the density gradient and normal to the flux surfaces are not aligned. These effects are less severe for the fast wave since its penetration into the SOL is significantly less than that of the slow wave. Work supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

Hindcasting of Storm Surges, Currents, and Waves at Lower Delaware Bay during Hurricane Isabel

NASA Astrophysics Data System (ADS)

Salehi, M.

2017-12-01

Hurricanes are a major threat to coastal communities and infrastructures including nuclear power plants located in low-lying coastal zones. In response, their sensitive elements should be protected by smart design to withstand against drastic impact of such natural phenomena. Accurate and reliable estimate of hurricane attributes is the first step to that effort. Numerical models have extensively grown over the past few years and are effective tools in modeling large scale natural events such as hurricane. The impact of low probability hurricanes on the lower Delaware Bay is investigated using dynamically coupled meteorological, hydrodynamic, and wave components of Delft3D software. Efforts are made to significantly reduce the computational overburden of performing such analysis for the industry, yet keeping the same level of accuracy at the area of study (AOS). The model is comprised of overall and nested domains. The overall model domain includes portion of Atlantic Ocean, Delaware, and Chesapeake bays. The nested model domain includes Delaware Bay, its floodplain, and portion of the continental shelf. This study is portion of a larger modeling effort to study the impact of low probability hurricanes on sensitive infrastructures located at the coastal zones prone to hurricane activity. The AOS is located on the east bank of Delaware Bay almost 16 miles upstream of its mouth. Model generated wind speed, significant wave height, water surface elevation, and current are calibrated for hurricane Isabel (2003). The model calibration results agreed reasonably well with field observations. Furthermore, sensitivity of surge and wave responses to various hurricane parameters was tested. In line with findings from other researchers, accuracy of wind field played a major role in hindcasting the hurricane attributes.

Multiple focused EMAT designs for improved surface breaking defect characterization

NASA Astrophysics Data System (ADS)

Thring, C. B.; Fan, Y.; Edwards, R. S.

2017-02-01

Ultrasonic Rayleigh waves can be employed for the detection of surface breaking defects such as rolling contact fatigue and stress corrosion cracking. Electromagnetic Acoustic Transducers (EMATs) are well suited to this technique as they can directly generate Rayleigh waves within the sample without the requirement for wedges, and they are robust and inexpensive compared to laser ultrasonics. Three different EMAT coil types have been developed, and these are compared to assess their ability to detect and characterize small (down to 0.5 mm depth, 1 mm diameter) surface breaking defects in aluminium. These designs are: a pair of linear meander coils used in a pseudo-pulse-echo mode, a pair of focused meander coils also used in pseudo-pulse-echo mode, and a pair of focused racetrack coils used in pitch-catch mode. The linear meander coils are able to detect most of the defects tested, but have a much lower signal to noise ratio and give limited sizing information. The focused meander coils and the focused racetrack coils can detect all defects tested, but have the advantage that they can also characterize the defect sizes on the sample surface, and have a stronger sensitivity at their focal point. Measurements using all three EMAT designs are presented and compared for high resolution imaging of surface-breaking defects.

Air-ground interface: Surface waves, surface impedance and acoustic-to-seismic coupling coefficient

NASA Technical Reports Server (NTRS)

Daigle, Gilles; Embleton, Tony

1990-01-01

In atmospheric acoustics, the subject of surface waves has been an area of discussion for many years. The existence of an acoustic surface wave is now well established theoretically. The mathematical solution for spherical wave propagation above an impedance boundary includes the possibility of a contribution that possesses all the standard properties for a surface wave. Surface waves exist when the surface is sufficiently porous, relative to its acoustical resistance, that it can influence the airborne particle velocity near the surface and reduce the phase velocity of sound waves in air at the surface. This traps some of the sound energy in the air to remain near the surface as it propagates. Above porous grounds, the existence of surface waves has eluded direct experimental confirmation (pulse experiments have failed to show a separate arrival expected from the reduced phase speed) and indirect evidence for its existence has appeared contradictory. The experimental evidence for the existence of an acoustical surface wave above porous boundaries is reviewed. Recent measurements including pulse experiments are also described. A few years ago the acoustic impedance of a grass-covered surface was measured in the frequency range 30 to 300 Hz. Here, further measurements on the same site are discussed. These measurements include core samples, a shallow refractive survey to determine the seismic velocities, and measurements of the acoustic-to-seismic coupling coefficient.

Non-invasive thermal profiling of silicon wafer surface during RTP using acoustic and signal processing techniques

NASA Astrophysics Data System (ADS)

Syed, Ahmed Rashid

Among the great physical challenges faced by the current front-end semiconductor equipment manufacturers is the accurate and repeatable surface temperature measurement of wafers during various fabrication steps. Close monitoring of temperature is essential in that it ensures desirable device characteristics to be reliably reproduced across various wafer lots. No where is the need to control temperature more pronounced than it is during Rapid Thermal Processing (RTP) which involves temperature ramp rates in excess of 200°C/s. This dissertation presents an elegant and practical approach to solve the wafer surface temperature estimation problem, in context of RTP, by deploying hardware that acquires the necessary data while preserving the integrity and purity of the wafer. In contrast to the widely used wafer-contacting (and hence contaminating) methods, such as bonded thermocouples, or environment sensitive schemes, such as light-pipes and infrared pyrometry, the proposed research explores the concept of utilizing Lamb (acoustic) waves to detect changes in wafer surface temperature, during RTP. Acoustic waves are transmitted to the wafer via an array of quartz rods that normally props the wafer inside an RTP chamber. These waves are generated using piezoelectric transducers affixed to the bases of the quartz rods. The group velocity of Lamb waves traversing the wafer surface undergoes a monotonic decrease with rise in wafer temperature. The correspondence of delay in phase of the received Lamb waves and the ambient temperature, along all direct paths between sending and receiving transducers, yields a psuedo real-time thermal image of the wafer. Although the custom built hardware-setup implements the above "proof-of-concept" scheme by transceiving acoustic signals at a single frequency, the real-world application will seek to enhance the data acquistion. rate (>1000 temperature measurements per seconds) by sending and receiving Lamb waves at multiple frequencies (by employing broadband quartz rod-transducer assembles). Experimental results, as predicted by prior rigorous simulations, prove that the temperature measurement accuracy obtained through several dynamic runs using the above specified approach, is better than +/-2°C. Furthermore, these results are highly repeatable and independent of wafer treatment conditions, thereby extolling the versatility and immunity of the new method from environmental conditions.

Second order harmonic guided wave mutual interactions in plate: Vector analysis, numerical simulation, and experimental results

NASA Astrophysics Data System (ADS)

Hasanian, Mostafa; Lissenden, Cliff J.

2017-08-01

The extraordinary sensitivity of nonlinear ultrasonic waves to the early stages of material degradation makes them excellent candidates for nondestructive material characterization. However, distinguishing weak material nonlinearity from instrumentation nonlinearity remains problematic for second harmonic generation approaches. A solution to this problem is to mix waves having different frequencies and to let their mutual interaction generate sum and difference harmonics at frequencies far from those of the instrumentation. Mixing of bulk waves and surface waves has been researched for some time, but mixing of guided waves has not yet been investigated in depth. A unique aspect of guided waves is their dispersive nature, which means we need to assure that a wave can propagate at the sum or difference frequency. A wave vector analysis is conducted that enables selection of primary waves traveling in any direction that generate phase matched secondary waves. We have tabulated many sets of primary waves and phase matched sum and difference harmonics. An example wave mode triplet of two counter-propagating collinear shear horizontal waves that interact to generate a symmetric Lamb wave at the sum frequency is simulated using finite element analysis and then laboratory experiments are conducted. The finite element simulation eliminates issues associated with instrumentation nonlinearities and signal-to-noise ratio. A straightforward subtraction method is used in the experiments to identify the material nonlinearity induced mutual interaction and show that the generated Lamb wave propagates on its own and is large enough to measure. Since the Lamb wave has different polarity than the shear horizontal waves the material nonlinearity is clearly identifiable. Thus, the mutual interactions of shear horizontal waves in plates could enable volumetric characterization of material in remote regions from transducers mounted on just one side of the plate.

Emergence of multiple synchronization modes in hydrodynamically-coupled cilia

NASA Astrophysics Data System (ADS)

Guo, Hanliang; Kanso, Eva

2016-11-01

Motile cilia and flagella exhibit different phase coordinations. For example, closely swimming spermatozoa are observed to synchronize together; bi-flagellates Chlamydomonas regulate the flagella in a "breast-stroke" fashion; cilia on the surface of Paramecium beat in a fixed phase lag in an orchestrated wave like fashion. Experimental evidence suggests that phase coordinations can be achieved solely via hydrodynamical interactions. However, the exact mechanisms behind it remain illusive. Here, adapting a "geometric switch" model, we observe different synchronization modes in pairs of hydrodynamically-coupled cilia by changing physical parameters such as the strength of the cilia internal motor and the separation distance between cilia. Interestingly, we find regions in the parameter space where the coupled cilia reach stable phase coordinations and regions where the phase coordinations are sensitive to perturbations. We also find that leaning into the fluid reduces the sensitivity to perturbations, and produces stable phase coordination that is neither in-phase nor anti-phase, which could explain the origin of metachronal waves in large cilia populations.

High-resolution surface wave tomography of the European crust and uppermost mantle from ambient seismic noise

NASA Astrophysics Data System (ADS)

Lu, Yang; Stehly, Laurent; Paul, Anne; AlpArray Working Group

2018-05-01

Taking advantage of the large number of seismic stations installed in Europe, in particular in the greater Alpine region with the AlpArray experiment, we derive a new high-resolution 3-D shear-wave velocity model of the European crust and uppermost mantle from ambient noise tomography. The correlation of up to four years of continuous vertical-component seismic recordings from 1293 broadband stations (10° W-35° E, 30° N-75° N) provides Rayleigh wave group velocity dispersion data in the period band 5-150 s at more than 0.8 million virtual source-receiver pairs. Two-dimensional Rayleigh wave group velocity maps are estimated using adaptive parameterization to accommodate the strong heterogeneity of path coverage. A probabilistic 3-D shear-wave velocity model, including probability densities for the depth of layer boundaries and S-wave velocity values, is obtained by non-linear Bayesian inversion. A weighted average of the probabilistic model is then used as starting model for the linear inversion step, providing the final Vs model. The resulting S-wave velocity model and Moho depth are validated by comparison with previous geophysical studies. Although surface-wave tomography is weakly sensitive to layer boundaries, vertical cross-sections through our Vs model and the associated probability of presence of interfaces display striking similarities with reference controlled-source (CSS) and receiver-function sections across the Alpine belt. Our model even provides new structural information such as a ˜8 km Moho jump along the CSS ECORS-CROP profile that was not imaged by reflection data due to poor penetration across a heterogeneous upper crust. Our probabilistic and final shear wave velocity models have the potential to become new reference models of the European crust, both for crustal structure probing and geophysical studies including waveform modeling or full waveform inversion.

Land surface and atmospheric conditions associated with heat waves over the Chickasaw Nation in the South Central United States

NASA Astrophysics Data System (ADS)

Lee, Eungul; Bieda, Rahama; Shanmugasundaram, Jothiganesh; Basara Richter, Heather

2016-06-01

Exposure to extreme heat was reconstructed based on regional land-atmosphere processes from 1979 to 2010 in the South Central U.S. The study region surrounds the Chickasaw Nation (CN), a predominantly Native American population with a highly prevalent burden of climate-sensitive chronic diseases. Land surface and atmospheric conditions for summer heat waves were analyzed during spring (March-April-May, MAM) and summer (June-July-August, JJA) based on the Climate and Ocean: Variability, Predictability, and Change maximum temperature definition for heat wave frequency (HWF). The spatial-temporal pattern of HWF was determined using empirical orthogonal function (EOF) analysis and the corresponding principle component time series of the first EOF of HWF. Statistically significant analyses of observed conditions indicated that sensible heat increased and latent heat fluxes decreased with high HWF in the South Central U.S. The largest positive correlations of sensible heat flux to HWF and the largest negative correlations of latent heat flux to HWF were specifically observed over the CN. This is a significantly different energy transfer regime due to less available soil moisture during the antecedent MAM and JJA. The higher sensible heat from dry soil could cause significant warming from the near surface (>2.0°C) to the lower troposphere (>1.5°C), and accumulated boundary layer heat could induce the significant patterns of higher geopotential height and enhance anticyclonic circulations (negative vorticity anomaly) at the midtroposphere. Results suggested a positive land-atmosphere feedback associated with heat waves and called attention to the need for region-specific climate adaptation planning.

Land surface and atmospheric conditions associated with heat waves in the South Central United States

NASA Astrophysics Data System (ADS)

Lee, Eungul; Bieda, Rahama; Shanmugasundaram, Jothiganesh; Richter, Heather

2017-04-01

Exposure to extreme heat was reconstructed based on regional land-atmosphere processes from 1979 to 2010 in the South Central U.S. The study region surrounds the Chickasaw Nation (CN), a predominantly Native American population with a highly prevalent burden of climate-sensitive chronic diseases. Land surface and atmospheric conditions for summer heat waves were analyzed during spring (March-April-May, MAM) and summer (June-July-August, JJA) based on the Climate and Ocean: Variability, Predictability, and Change maximum temperature definition for heat wave frequency (HWF). The spatial-temporal pattern of HWF was determined using empirical orthogonal function (EOF) analysis and the corresponding principle component time series of the first EOF of HWF. Statistically significant analyses of observed conditions indicated that sensible heat increased and latent heat fluxes decreased with high HWF in the South Central U.S. The largest positive correlations of sensible heat flux to HWF and the largest negative correlations of latent heat flux to HWF were specifically observed over the CN. This is a significantly different energy transfer regime due to less available soil moisture during the antecedent MAM and JJA. The higher sensible heat from dry soil could cause significant warming from the near surface (> 2.0°C) to the lower troposphere (> 1.5°C), and accumulated boundary layer heat could induce the significant patterns of higher geopotential height and enhance anticyclonic circulations (negative vorticity anomaly) at the midtroposphere. Results suggested a positive land-atmosphere feedback associated with heat waves and called attention to the need for region-specific climate adaptation planning.

Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of light

NASA Astrophysics Data System (ADS)

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Affeldt, C.; Aguiar, O. D.; Ajith, P.; Allen, B.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Ast, S.; Aston, S. M.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballmer, S.; Bao, Y.; Barayoga, J. C.; Barker, D.; Barr, B.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Batch, J.; Bauchrowitz, J.; Behnke, B.; Bell, A. S.; Bell, C.; Bergmann, G.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bond, C.; Bork, R.; Born, M.; Bose, S.; Bowers, J.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brinkmann, M.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Buckland, K.; Brückner, F.; Buchler, B. C.; Buonanno, A.; Burguet-Castell, J.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Campsie, P.; Cannon, K.; Cao, J.; Capano, C. D.; Carbone, L.; Caride, S.; Castiglia, A. D.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chen, X.; Chen, Y.; Cho, H.-S.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, C. T. Y.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Constancio Junior, M.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cumming, A.; Cunningham, L.; Dahl, K.; Damjanic, M.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Daveloza, H.; Davies, G. S.; Daw, E. J.; Dayanga, T.; Deleeuw, E.; Denker, T.; Dent, T.; Dergachev, V.; Derosa, R.; Desalvo, R.; Dhurandhar, S.; di Palma, I.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drasco, S.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eikenberry, S. S.; Engel, R.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fairhurst, S.; Fang, Q.; Farr, B. F.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Finn, L. S.; Fisher, R. P.; Foley, S.; Forsi, E.; Fotopoulos, N.; Frede, M.; Frei, M. A.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Garcia, J.; Gehrels, N.; Gelencser, G.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Graef, C.; Graff, P. B.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guido, C.; Gustafson, E. K.; Gustafson, R.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Haris, K.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heintze, M. C.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hough, J.; Howell, E. J.; Huang, V.; Huerta, E. A.; Hughey, B.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jesse, E.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, Y.-M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kozak, D.; Kozameh, C.; Kremin, A.; Kringel, V.; Krishnan, B.; Kucharczyk, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuper, B. J.; Kurdyumov, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Leong, J. R.; Levine, B.; Lhuillier, V.; Lin, A. C.; Litvine, V.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lormand, M.; Lough, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; MacArthur, J.; MacDonald, E.; Machenschalk, B.; Macinnis, M.; MacLeod, D. M.; Magaña-Sandoval, F.; Mageswaran, M.; Mailand, K.; Manca, G.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martin, I. W.; Martin, R. M.; Martinov, D.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazzolo, G.; McAuley, K.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Miller, J.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mokler, F.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nanda Kumar, D.; Nash, T.; Nayak, R.; Necula, V.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Pan, Y.; Pankow, C.; Papa, M. A.; Paris, H.; Parkinson, W.; Pedraza, M.; Penn, S.; Peralta, C.; Perreca, A.; Phelps, M.; Pickenpack, M.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Pöld, J.; Postiglione, F.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Privitera, S.; Prokhorov, L. G.; Puncken, O.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Ramet, C.; Raymond, V.; Reed, C. M.; Reed, T.; Reid, S.; Reitze, D. H.; Riesen, R.; Riles, K.; Roberts, M.; Robertson, N. A.; Robinson, E. L.; Roddy, S.; Rodriguez, C.; Rodriguez, L.; Rodruck, M.; Rollins, J. G.; Romie, J. H.; Röver, C.; Rowan, S.; Rüdiger, A.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sergeev, A.; Shaddock, D. A.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Son, E. J.; Sorazu, B.; Souradeep, T.; Stefszky, M.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Szeifert, G.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Torres, C. V.; Torrie, C. I.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vallisneri, M.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vecchio, A.; Veitch, P. J.; Veitch, J.; Venkateswara, K.; Verma, S.; Vincent-Finley, R.; Vitale, S.; Vo, T.; Vorvick, C.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, J.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Wiseman, A. G.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Zanolin, M.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2013-08-01

Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity.

Excitation of multiple surface-plasmon-polariton waves using a compound surface-relief grating

NASA Astrophysics Data System (ADS)

Faryad, Muhammad; Lakhtakia, Akhlesh

2012-01-01

The excitation of multiple surface-plasmon-polariton waves, all of the same frequency but different polarization states, phase speeds, spatial profiles and degrees of localization, by a compound surface-relief grating formed by a metal and a rugate filter, both of finite thickness, was studied using the rigorous coupled-wave approach. Each period of the compound surface-relief grating was chosen to have an integral number of periods of two different simple surface-relief gratings. The excitation of different SPP waves was inferred from the absorptance peaks that were independent of the thickness of the rugate filter. The excitation of each SPP wave could be attributed to either a simple surface-relief grating present in the compound surface-relief grating or to the compound surface-relief grating itself. However, the excitation of SPP waves was found to be less efficient with the compound surface-relief grating than with a simple surface-relief grating.

Feasibility of detecting near-surface feature with Rayleigh-wave diffraction

USGS Publications Warehouse

Xia, J.; Nyquist, Jonathan E.; Xu, Y.; Roth, M.J.S.; Miller, R.D.

2007-01-01

Detection of near-surfaces features such as voids and faults is challenging due to the complexity of near-surface materials and the limited resolution of geophysical methods. Although multichannel, high-frequency, surface-wave techniques can provide reliable shear (S)-wave velocities in different geological settings, they are not suitable for detecting voids directly based on anomalies of the S-wave velocity because of limitations on the resolution of S-wave velocity profiles inverted from surface-wave phase velocities. Therefore, we studied the feasibility of directly detecting near-surfaces features with surface-wave diffractions. Based on the properties of surface waves, we have derived a Rayleigh-wave diffraction traveltime equation. We also have solved the equation for the depth to the top of a void and an average velocity of Rayleigh waves. Using these equations, the depth to the top of a void/fault can be determined based on traveltime data from a diffraction curve. In practice, only two diffraction times are necessary to define the depth to the top of a void/fault and the average Rayleigh-wave velocity that generates the diffraction curve. We used four two-dimensional square voids to demonstrate the feasibility of detecting a void with Rayleigh-wave diffractions: a 2??m by 2??m with a depth to the top of the void of 2??m, 4??m by 4??m with a depth to the top of the void of 7??m, and 6??m by 6??m with depths to the top of the void 12??m and 17??m. We also modeled surface waves due to a vertical fault. Rayleigh-wave diffractions were recognizable for all these models after FK filtering was applied to the synthetic data. The Rayleigh-wave diffraction traveltime equation was verified by the modeled data. Modeling results suggested that FK filtering is critical to enhance diffracted surface waves. A real-world example is presented to show how to utilize the derived equation of surface-wave diffractions. ?? 2006 Elsevier B.V. All rights reserved.

Azimuthally Anisotropic Global Adjoint Tomography

NASA Astrophysics Data System (ADS)

Bozdag, E.; Orsvuran, R.; Lefebvre, M. P.; Lei, W.; Peter, D. B.; Ruan, Y.; Smith, J. A.; Komatitsch, D.; Tromp, J.

2017-12-01

Earth's upper mantle shows significant evidence of anisotropy as a result of its composition and deformation. After the first-generation global adjoint tomography model, GLAD-M15 (Bozdag et al. 2016), which has transverse isotropy confined to upper mantle, we continue our iterations including surface-wave azimuthal anisotropy with an emphasis on the upper mantle. We are focusing on four elastic parameters that surface waves are known to be most sensitive to, namely, vertically and horizontally polarized shear waves and the density-normalised anisotropic parameters Gc' & Gs'. As part of the current anisotropic inversions, which will lead to our "second-generation" global adjoint tomography model, we have started exploring new misfits based on a double-difference approach (Yuan et al. 2016). We define our misfit function in terms of double-difference multitaper measurements, where each waveform is normalized by its number of pairs in the period ranges 45-100 s & 90-250 s. New measurements result in better balanced gradients while extracting more information underneath clusters of stations, such as USArray. Our initial results reveals multi-scale anisotorpic signals depending on ray (kernel) coverage close to continental-scale resolution in areas with dense coverage, consistent with previous studies.

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.

Evaluation of a scale-model experiment to investigate long-range acoustic propagation

NASA Technical Reports Server (NTRS)

Parrott, Tony L.; Mcaninch, Gerry L.; Carlberg, Ingrid A.

1987-01-01

Tests were conducted to evaluate the feasibility of using a scale-model experiment situated in an anechoic facility to investigate long-range sound propagation over ground terrain. For a nominal scale factor of 100:1, attenuations along a linear array of six microphones colinear with a continuous-wave type of sound source were measured over a wavelength range from 10 to 160 for a nominal test frequency of 10 kHz. Most tests were made for a hard model surface (plywood), but limited tests were also made for a soft model surface (plywood with felt). For grazing-incidence propagation over the hard surface, measured and predicted attenuation trends were consistent for microphone locations out to between 40 and 80 wavelengths. Beyond 80 wavelengths, significant variability was observed that was caused by disturbances in the propagation medium. Also, there was evidence of extraneous propagation-path contributions to data irregularities at more remote microphones. Sensitivity studies for the hard-surface and microphone indicated a 2.5 dB change in the relative excess attenuation for a systematic error in source and microphone elevations on the order of 1 mm. For the soft-surface model, no comparable sensitivity was found.

Photonic Crystal Fiber-Based Surface Plasmon Resonance Sensor with Selective Analyte Channels and Graphene-Silver Deposited Core

PubMed Central

Rifat, Ahmmed A.; Mahdiraji, G. Amouzad; Chow, Desmond M.; Shee, Yu Gang; Ahmed, Rajib; Adikan, Faisal Rafiq Mahamd

2015-01-01

We propose a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) with selectively filled analyte channels. Silver is used as the plasmonic material to accurately detect the analytes and is coated with a thin graphene layer to prevent oxidation. The liquid-filled cores are placed near to the metallic channel for easy excitation of free electrons to produce surface plasmon waves (SPWs). Surface plasmons along the metal surface are excited with a leaky Gaussian-like core guided mode. Numerical investigations of the fiber’s properties and sensing performance are performed using the finite element method (FEM). The proposed sensor shows maximum amplitude sensitivity of 418 Refractive Index Units (RIU−1) with resolution as high as 2.4 × 10−5 RIU. Using the wavelength interrogation method, a maximum refractive index (RI) sensitivity of 3000 nm/RIU in the sensing range of 1.46–1.49 is achieved. The proposed sensor is suitable for detecting various high RI chemicals, biochemical and organic chemical analytes. Additionally, the effects of fiber structural parameters on the properties of plasmonic excitation are investigated and optimized for sensing performance as well as reducing the sensor’s footprint. PMID:25996510

On the surface-to-bulk mode conversion of Rayleigh waves.

NASA Technical Reports Server (NTRS)

Chang, C.-P.; Tuan, H.-S.

1973-01-01

Surface-to-bulk wave conversion phenomena occurring at a discontinuity characterized by a surface contour deformation are shown to be usable as a means for tapping Rayleigh waves in a nonpiezoelectric solid. A boundary perturbation technique is used in the treatment of the mode conversion problem. A systematic procedure is presented for calculating not only the first-order scattered waves, which include the reflected surface wave and the converted bulk wave, but also the higher order terms.

Numerical simulation and experimental research on interaction of micro-defects and laser ultrasonic signal

NASA Astrophysics Data System (ADS)

Guo, Hualing; Zheng, Bin; Liu, Hui

2017-11-01

In the present research, the mechanism governing the interaction between laser-generated ultrasonic wave and the micro-defects on an aluminum plate has been studied by virtue of numerical simulation as well as practical experiments. Simulation results indicate that broadband ultrasonic waves are caused mainly by surface waves, and that the surface waves produced by micro-defects could be utilized for the detection of micro-defects because these waves reflect as much information of the defects as possible. In the research, a laser-generated ultrasonic wave testing system with a surface wave probe has been established for the detection of micro-defects, and the surface waves produced by the defects with different depths on an aluminum plate have been tested by using the system. The interaction between defect depth and the maximum amplitude of the surface wave and that between defect depth and the center frequency of the surface wave have also been analyzed in detail. Research results indicate that, when the defect depth is less than half of the wavelength of the surface wave, the maximum amplitude and the center frequency of the surface wave are in linear proportion to the defect depth. Sound consistency of experimental results with theoretical simulation indicates that the system as established in the present research could be adopted for the quantitative detection of micro-defects.

Comparison of Travel-Time and Amplitude Measurements for Deep-Focusing Time-Distance Helioseismology

NASA Astrophysics Data System (ADS)

Pourabdian, Majid; Fournier, Damien; Gizon, Laurent

2018-04-01

The purpose of deep-focusing time-distance helioseismology is to construct seismic measurements that have a high sensitivity to the physical conditions at a desired target point in the solar interior. With this technique, pairs of points on the solar surface are chosen such that acoustic ray paths intersect at this target (focus) point. Considering acoustic waves in a homogeneous medium, we compare travel-time and amplitude measurements extracted from the deep-focusing cross-covariance functions. Using a single-scattering approximation, we find that the spatial sensitivity of deep-focusing travel times to sound-speed perturbations is zero at the target location and maximum in a surrounding shell. This is unlike the deep-focusing amplitude measurements, which have maximum sensitivity at the target point. We compare the signal-to-noise ratio for travel-time and amplitude measurements for different types of sound-speed perturbations, under the assumption that noise is solely due to the random excitation of the waves. We find that, for highly localized perturbations in sound speed, the signal-to-noise ratio is higher for amplitude measurements than for travel-time measurements. We conclude that amplitude measurements are a useful complement to travel-time measurements in time-distance helioseismology.

Preparation and Properties of Surface-Coated HMX with Viton and Graphene Oxide

NASA Astrophysics Data System (ADS)

Wang, Jingyu; Ye, Baoyun; An, Chongwei; Wu, Bidong; Li, Hequn; Wei, Yanju

2016-07-01

To improve the safety performance of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) particles, the new carbon material graphene oxide (GO) and Viton were used to coat HMX via a solvent-slurry process. For comparison, the HMX/Viton/graphite (HMX/Viton/G) and HMX/Viton composites were also prepared by the same process. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC) were employed to characterize the morphology, composition, and thermal decomposition of samples. The impact sensitivity and shock wave sensitivity of HMX-based composites were also measured and analyzed. The results of SEM, XRD, and XPS indicate that the cladding layer of HMX-based composites is successfully constructed. HMX/Viton/GO composites exhibit better thermal stability compared to HMX and HMX/Viton. The results show that both impact and shock wave sensitivities of HMX/Viton/GO composites are much lower than that of HMX/Viton. In addition, GO sheets exhibit a better desensitizing effect than G sheets. These combined properties suggest that nano-GO has good compatibility with explosives and can be utilized as a desensitizer in HMX particles.

Antiferromagnetic spin current rectifier

NASA Astrophysics Data System (ADS)

Khymyn, Roman; Tiberkevich, Vasil; Slavin, Andrei

2017-05-01

It is shown theoretically, that an antiferromagnetic dielectric with bi-axial anisotropy, such as NiO, can be used for the rectification of linearly-polarized AC spin current. The AC spin current excites two evanescent modes in the antiferromagnet, which, in turn, create DC spin current flowing back through the antiferromagnetic surface. Spin diode based on this effect can be used in future spintronic devices as direct detector of spin current in the millimeter- and submillimeter-wave bands. The sensitivity of such a spin diode is comparable to the sensitivity of modern electric Schottky diodes and lies in the range 102-103 V/W for 30 ×30 nm2 structure.

Development of PZT-excited stroboscopic shearography for full-field nondestructive evaluation.

PubMed

Asemani, Hamidreza; Park, Jinwoo; Lee, Jung-Ryul; Soltani, Nasser

2017-05-01

Nondestructive evaluation using shearography requires a way to stress the inspection target. This technique is able to directly measure the displacement gradient distribution on the object surface. Shearography visualizes the internal structural damages as the anomalous pattern in the shearograpic fringe pattern. A piezoelectric (PZT) excitation system is able to generate loadings in the vibrational, acoustic, and ultrasonic regimes. In this paper, we propose a PZT-excited stroboscopic shearography. The PZT excitation could generate vibrational loading, a stationary wavefield, and a nonstationary propagation wave to fulfill the external loading requirement of shearography. The sweeping of the PZT excitation frequency, the formation of a standing wave, and a small shearing to suppress the incident wave were powerful controllable tools to detect the defects. The sweeping of the PZT excitation frequency enabled us to determine one of the defect-sensitive frequencies almost in real time. In addition, because the defect sensitive frequencies always existed in wide and plural ranges, the risk of the defect being overlooked by the inspector could be alleviated. The results of evaluation using stroboscopic shearography showed that an artificial 20 mm-diameter defect could be visualized at the excitation frequencies of 5-8 kHz range and 12.5-15.5 kHz range. This technique provided full field reliable and repeatable inspection results. Additionally, the proposed method overcame the important drawback of the time-averaged shearography, being required to identify the resonance vibration frequency sensitive to the defect.

Seismic Wave Propagation

NASA Astrophysics Data System (ADS)

Wu, Xianyun; Wu, Ru-Shan

A seismic wave is a mechanical disturbance or energy packet that can propagate from point to point in the Earth. Seismic waves can be generated by a sudden release of energy such as an earthquake, volcanic eruption, or chemical explosion. There are several types of seismic waves, often classified as body waves, which propagate through the volume of the Earth, and surface waves, which travel along the surface of the Earth. Compressional and shear waves are the two main types of body wave and Rayleigh and Love waves are the most common forms of surface wave.

Gravitational astrophysics

NASA Astrophysics Data System (ADS)

Hendry, Martin; Woan, Graham

2007-02-01

Like the surface of a busy swimming pool, spacetime is awash with waves generated by the local and distant motions of mass and, in principle, much of this activity can be reconstructed by analysing the waveforms. However, instrumentation with a reasonable chance of directly detecting these gravitational waves has only become available within the past year, with the LIGO detectors now running at design sensitivity. Here we review the burgeoning field of observational gravitational astrophysics: using gravitational wave detectors as telescopes to help answer a wide range of astrophysical questions from neutron-star physics to cosmology. The next generation of ground-based telescopes should be able to make extensive gravitational observations of some of the more energetic events in our local universe. Looking only slightly further ahead, the space-based LISA observatory will reveal the gravitational universe in phenomenal detail, supplying high-quality data on perhaps thousands of sources, and tackling some of the most fascinating questions in contemporary astronomy.

Evanescent wave absorbance based fiber optic biosensor for label-free detection of E. coli at 280 nm wavelength.

PubMed

Bharadwaj, Reshma; Sai, V V R; Thakare, Kamini; Dhawangale, Arvind; Kundu, Tapanendu; Titus, Susan; Verma, Pradeep Kumar; Mukherji, Soumyo

2011-03-15

A novel label-free technique for the detection of pathogens based on evanescent wave absorbance (EWA) changes at 280 nm from a U-bent optical fiber sensor is demonstrated. Bending a decladded fiber into a U-shaped structure enhances the penetration depth of evanescent waves and hence sensitivity of the probe. We show that the enhanced EWA response from such U-bent probes, caused by the inherent optical absorbance properties of bacterial cells or biomolecules specifically bound to the sensor surface, can be exploited for the detection of pathogens. A portable optical set-up with a UV light emitting diode, a spectrometer and U-bent fiber optic probe of 200 μm core diameter, 0.75 mm bend radius and effective probe length of 1cm demonstrated an ability to detect less than 1000 cfu/ml. Copyright © 2011. Published by Elsevier B.V.

Vibrational spectra of individual millimeter-size membrane patches using miniature infrared waveguides.

PubMed Central

Plunkett, S E; Jonas, R E; Braiman, M S

1997-01-01

We have used miniature planar IR waveguides, consisting of Ge strips 30-50 microm thick and 2 mm wide, as evanescent-wave sensors to detect the mid-(IR) evanescent-wave absorbance spectra of small areas of biomolecular monolayers and multilayers. Examples include picomolar quantities of an integral transmembrane protein (bacteriorhodopsin) and lipid (dimyristoyl phosphatidylcholine). IR bands due to the protein and lipid components of the plasma membrane of individual 1.5-mm-diameter devitellinized Xenopus laevis oocytes, submerged in buffer and sticking to the waveguide surface, were also detected. A significant improvement in sensitivity was observed, as compared to previous sizes and geometries of evanescent-wave sensors (e.g., commercially available internal reflection elements or tapered optical fibers). These measurements suggest the feasibility of using such miniature supported planar IR waveguides to observe structural changes in transmembrane proteins functioning in vivo in single cells. PMID:9336219

Radiative-photochemical response of the mesosphere to dynamical forcing

NASA Technical Reports Server (NTRS)

Frederick, J. E.

1981-01-01

Combination of the chemical continuity equation for odd oxygen with the second law of thermodynamics yields analytic solutions which describe the coupled behavior of temperature and ozone perturbations in response to an externally specified forcing. The results appear in a form which allows easy physical interpretation of the coupling between radiative and photochemical processes. When the forcing is chosen to mimic a planetary scale wave, the theory shows that photochemical acceleration of radiative damping reduces the amplitude of the temperature perturbation by an amount which increases with the wave period. Although ozone fluctuations are anti-correlated with those in temperature, minima in ozone do not coincide exactly in longitude with temperature maxima. The percentage variation in ozone increases upward and is always larger than that in temperature at the same pressure. This demonstrates that variations in ozone on constant pressure surfaces may serve as a sensitive indicator of wave activity in the mesosphere.

Modeling transport and deposition of the Mekong River sediment

USGS Publications Warehouse

Xue, Zuo; He, Ruoying; Liu, J. Paul; Warner, John C.

2012-01-01

A Coupled Wave–Ocean–SedimentTransport Model was used to hindcast coastal circulation and fine sedimenttransport on the Mekong shelf in southeastern Asian in 2005. Comparisons with limited observations showed that the model simulation captured the regional patterns and temporal variability of surface wave, sea level, and suspended sediment concentration reasonably well. Significant seasonality in sedimenttransport was revealed. In summer, a large amount of fluvial sediments was delivered and deposited near the MekongRiver mouth. In the following winter, strong ocean mixing, and coastal current lead to resuspension and southwestward dispersal of a small fraction of previously deposited sediments. Model sensitivity experiments (with reduced physics) were performed to investigate the impact of tides, waves, and remotely forced ambient currents on the transport and dispersal of the fluvial sediment. Strong wave mixing and downwelling-favorable coastal current associated with the more energetic northeast monsoon in the winter season are the main factors controlling the southwestward along-shelf transport.

Highly Efficient Wave-Front Reshaping of Surface Waves with Dielectric Metawalls

NASA Astrophysics Data System (ADS)

Dong, Shaohua; Zhang, Yu; Guo, Huijie; Duan, Jingwen; Guan, Fuxin; He, Qiong; Zhao, Haibin; Zhou, Lei; Sun, Shulin

2018-01-01

Controlling the wave fronts of surface waves (including surface-plamon polaritons and their equivalent counterparts) at will is highly important in photonics research, but the available mechanisms suffer from the issues of low efficiency, bulky size, and/or limited functionalities. Inspired by recent studies of metasurfaces that can freely control the wave fronts of propagating waves, we propose to use metawalls placed on a plasmonic surface to efficiently reshape the wave fronts of incident surface waves (SWs). Here, the metawall is constructed by specifically designed meta-atoms that can reflect SWs with desired phases and nearly unit amplitudes. As a proof of concept, we design and fabricate a metawall in the microwave regime (around 12 GHz) that can anomalously reflect the SWs following the generalized Snell's law with high efficiency (approximately 70%). Our results, in excellent agreement with full-wave simulations, provide an alternative yet efficient way to control the wave fronts of SWs in different frequency domains. We finally employ full-wave simulations to demonstrate a surface-plasmon-polariton focusing effect at telecom wavelength based on our scheme.

Theoretical aspects of studies of oxide and semiconductor surfaces using low energy positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.; Weiss, A. H.

2011-01-01

This paper presents the results of a theoretical study of positron surface and bulk states and annihilation characteristics of surface trapped positrons at the oxidized Cu(100) single crystal and at both As- and Ga-rich reconstructed GaAs(100) surfaces. The variations in atomic structure and chemical composition of the topmost layers of the surfaces associated with oxidation and reconstructions and the charge redistribution at the surfaces are found to affect localization and spatial extent of the positron surface-state wave functions. The computed positron binding energy, work function, and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the surfaces. Theoretical positron annihilation probabilities with relevant core electrons computed for the oxidized Cu(100) surface and the As- and Ga-rich reconstructed GaAs(100) surfaces are compared with experimental ones estimated from the positron annihilation induced Auger peak intensities measured from these surfaces.

High-frequency guided ultrasonic waves for hidden defect detection in multi-layered aircraft structures.

PubMed

Masserey, Bernard; Raemy, Christian; Fromme, Paul

2014-09-01

Aerospace structures often contain multi-layered metallic components where hidden defects such as fatigue cracks and localized disbonds can develop, necessitating non-destructive testing. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete thickness were generated in a model structure consisting of two adhesively bonded aluminium plates. Interference occurs between the wave modes during propagation along the structure, resulting in a frequency dependent variation of the energy through the thickness with distance. The wave propagation along the specimen was measured experimentally using a laser interferometer. Good agreement with theoretical predictions and two-dimensional finite element simulations was found. Significant propagation distance with a strong, non-dispersive main wave pulse was achieved. The interaction of the high frequency guided ultrasonic waves with small notches in the aluminium layer facing the sealant and on the bottom surface of the multilayer structure was investigated. Standard pulse-echo measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulations. The results demonstrated the potential of high frequency guided waves for hidden defect detection at critical and difficult to access locations in aerospace structures from a stand-off distance. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes with surface and nonlocal effects

NASA Astrophysics Data System (ADS)

Zhen, Ya-Xin

2017-02-01

In this paper, the transverse wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes is investigated based on nonlocal elasticity theory with consideration of surface effect. The governing equation is formulated utilizing nonlocal Euler-Bernoulli beam theory and Kelvin-Voigt model. Explicit wave dispersion relation is developed and wave phase velocities and frequencies are obtained. The effect of the fluid flow velocity, structural damping, surface effect, small scale effects and tube diameter on the wave propagation properties are discussed with different wave numbers. The wave frequency increases with the increase of fluid flow velocity, but decreases with the increases of tube diameter and wave number. The effect of surface elasticity and residual surface tension is more significant for small wave number and tube diameter. For larger values of wave number and nonlocal parameters, the real part of frequency ratio raises.

TM surface wave diffraction by a truncated dielectric slab recessed in a perfectly conducting surface. [considering flush mounted space shuttle antenna

NASA Technical Reports Server (NTRS)

Pathak, P. H.; Kouyoumjian, R. G.

1974-01-01

The diffraction of a TM sub o surface wave by a terminated dielectric slab which is flush mounted in a perfectly conducting surface is studied. The incident surface wave gives rise to waves reflected and diffracted by the termination; these reflected and diffracted fields may be expressed in terms of the geometrical theory of diffraction by introducing surface wave reflection and diffraction coefficients which are associated with the termination. In this investigation, the surface wave reflection and diffraction coefficients have been deduced from a formally exact solution to this canonical problem. The solution is obtained by a combination of the generalized scattering matrix technique and function theoretic methods.

Optical Production and Detection of Ultrasonic Waves in Metals for Nondestructive Testing

NASA Technical Reports Server (NTRS)

Morrison, R. A.

1972-01-01

Ultrasonic waves were produced by striking the surface of a metal with the focused one-joule pulse of a Q-switched ruby laser. Rayleigh (surface) waves and longitudinal waves were detected with conventional transducers. Optical methods of detection were tested and developed. Rayleigh waves were produced with an oscillator and transducer. They were optically detected on curved polished surfaces, and on unpolished surfaces. The technique uses a knife edge to detect small angle changes of the surface as the wave pulse passes the illuminated spot. Optical flaw detection using pulse echo and attenuation is demonstrated.

Observation of the seismic anisotropy effects on free oscillations below 4 mHz

NASA Astrophysics Data System (ADS)

Hu, X.; Liu, L.

2009-12-01

We present observations of significant fundamental spheroidal-toroidal mode coupling at frequencies below 4 mHz in the early part of vertical component records from seismic stations on near-equatorial source-receiver propagation paths and in Antarctica after the 26 December 2004 and 28 March 2005 great Sumatra earthquakes. When seismic surface waves propagate along the equator, the particle motion of Love waves runs parallels to the Earth’s rotation axis, and the particle motion of Rayleigh waves runs perpendicular to it, thus the Coriolis force has no vertical deflection effect on Love waves and no transverse deflection effect on the Rayleigh waves. Coriolis coupling can be naturally minimized at a station on a nearequatorial source-receiver propagation path. In Antarctica, especially near the South Pole, the vertical deflection of toroidial motion is very weak but there are lateral gradients in the anisotropic properties of upper mantle. Therefore, we can find a chance to directly observe seismic anisotropy coupling below 4 mHz without the disturbance of Coriolis coupling at Antarctic station, and at the seismic station locate close to the Earth’s equator when the epicenter also locates close to the equator. Our observations of strong anomalous toroidal-spheroidal coupling at these stations provide direct evidence to confirm the theory that the azimuthal anisotropy has pronounced effects on the quasi-toroidal mode excitations at the frequencies below 4 mHz, which can convince the skeptics that anisotropy really is visible in the low-frequency normal mode data. Strong anisotropic coupling is usually observed at stations having the geometric nodes for the spheroidal fundamentals, giving the association of quasi-toroidal excitation with the geometric effect. The presence of significant anisotropy coupling below 4 mHz depends not only on anisotropic depth, anisotropic identities and orientations but also on radiation nodes for Rayleigh waves and geometry nodes for spheroidal fundamentals. The quasi-toroidal modes below 4 mHz have significant sensitivity throughout most of the mantle, extending into the lower mantle, and therefore, it is likely that the resolution of locating the depth of origin of azimuthal anisotropy in the mantle will be improved by joint inversions that take advantage of the partly complementary depth resolution of anisotropy coupling measurements, quasi-Love surface-wave measurements, body wave splitting measurements and surface-wave dispersion measurements.

Development of an ultrasonic inspection robot using an electromagnetic acoustic transducer for a Lamb wave and an SH-plate wave.

PubMed

Murayama, Riichi; Makiyama, Shunnichi; Kodama, Mitutoshi; Taniguchi, Yasutoshi

2004-04-01

For inspection of a storage tank and pipeline in service, the application of an automatic inspection system (nondestructive inspection robot) is desirable, because manual inspection is difficult to perfectly and exactly perform due to the enormous amount of inspection needed. However, an ultrasonic nondestructive inspection robot with a piezoelectric oscillator needs to touch only the material surface to be directly inspected using a coupling medium. That is, the material surface and the sensor must always be held by constant pressure in the vertical direction on the material side. Actually, it is difficult to overcome these problems; thus an ultrasonic inspection robot could not be widely applied. We then tried to develop an ultrasonic inspection robot with an electromagnetic acoustic transducer (EMAT) which did not require a coupling medium to inspect the circumferential pipe parts. We developed a special EMAT that could transmit and receive alternately a Lamb wave with high sensitivity and a SH-plate wave without influence by the welded part. The method by which the inspection robot turned around the direction of the steel pipe surroundings was executed by observing the tape pasted in the direction of the steel pipe surroundings with an installed CCD camera. In this report, the basic mechanism of this inspection robot and an examination of results are described.

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

Roberts, Jesse D.; Grace Chang; Jason Magalen

A n indust ry standard wave modeling tool was utilized to investigate model sensitivity to input parameters and wave energy converter ( WEC ) array deploym ent scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that b oth wave height and near - bottom orbital velocity we re subject to the largest pote ntial variations, each decreas ed in sensitivity as transmission coefficient increase d , as number and spacing of WEC devices decrease d , and as the deploymentmore » location move d offshore. Wave direction wa s affected consistently for all parameters and wave perio d was not affected (or negligibly affected) by varying model parameters or WEC configuration .« less

Surface acoustic wave hydrogen sensor

NASA Technical Reports Server (NTRS)

Bhethanabotla, Venkat R. (Inventor); Bhansali, Shekhar (Inventor)

2006-01-01

The present invention provides a delay line SAW device fabricated on a lithium niobate substrate and coated with a bilayer of nanocrystalline or other nanomaterials such as nanoparticles or nanowires of palladiumn and metal free pthalocyanine which will respond to hydrogen gas in near real time, at low (room) temperature, without being affected by CO, O.sub.2, CH.sub.4 and other gases, in air ambient or controlled ambient, providing sensitivity to low ppm levels.

Love-to-Rayleigh Conversions and Seismic Anisotropy in Cascadia

NASA Astrophysics Data System (ADS)

Rieger, Duayne Matthew

Seismic anisotropy is often attributed to the development of lattice-preferred orientation (LPO) of olivine crystals in peridotite, induced by the dislocation creep component of mantle deformation (Karato et al., 2008; Ribe, 1992). Mantle-flow-induced seismic anisotropy is often modeled in the simple form of hexagonal symmetry, where the anisotropic volume is uniaxially fast or slow. This relationship between seismic anisotropy and mantle deformation allows for the mapping of mantle dynamics using measurements of seismic anisotropy. Presently, methods of measuring seismic anisotropy in Earth's mantle include shear-wave splitting and surface-wave tomography. These methods are tuned to seismically fast axes laying in the horizontal or surface-tangent plane and are limited in discerning clipping seismic fast axes. This is a shortcoming. It is reasonable to suspect the presence of dipping seismic fast axes induced by mantle flow in several tectonic regimes such as subduction zones. The slab rollback model of the subduction zone system has been argued to exhibit trench-parallel subslab anisotropy due to the lateral evacuation of the subslab mantle material (Hall et al., 2000; Russo and Silver, 1994). This model has been emboldened by the dominance of trench-parallel shear-wave-splitting measurements in the subslab mantle of global subduction zones. This model has significant geodynamic implications, requiring viscous decoupling between the subslab mantle and the sub-ducting slab. The Cascadian subduction zone is of particular scientific interest. While experiencing slab rollback (Zandt and Humphreys, 2008), trench-perpendicular shear-wave-splitting measurements are observed in the subslab mantle of Cascadia (Currie et al., 2004; Eakin et al., 2010; Long and Silver, 2008; 2009). This suggests either viscous coupling resulting in slab-entrained flow or the presence of an alternate relationship between finite strain in the mantle and seismic anisotropy. The ability to discern a clipping anisotropic axis would help gain insight into the mantle dynamics of regions such as Cascadia. Lateral gradients of seismic anisotropy in Earth's upper mantle induce coupling among Earth's spheroidal and toroidal normal modes. This coupling can manifest as observable surface-wave polarization anomalies resulting from Love to Rayleigh wave conversions. These Love to Rayleigh conversions are known in the literature as Quasi-Love (QL) waves (Park and Yu, 1992) and are sensitive to both the strike and the dip of an anisotropic symmetry axis. In this dissertation I investigate the phenomenology of QL surface-wave scattering, including its sensitivity to the type and orientation of seismic anisotropy. I then apply my findings to observations of QL wave scattering in Cascada in order to further constrain subslab mantle anisotropy in the region. First, I make initial observations and confirm the presence of QL scattering in Cascada and the western U.S. using data recorded on USArray. I then move on to develop an algorithm to model efficiently QL wave scattering in the presence of 3-dimensional anisotropic structure. Using this forward-modeling algorithm, I investigate the dependence of QL wave scattering on the type and orientation of seismic Anisotropy. I find that P and S anisotropies exhibit independent effects on scattering. Scattering due to S anisotropy is stronger than that due to P anisotropy for all orientations and dominates in the observed scattering pattern. Both the phase and amplitude of the QL wave is dependent on the orientation (strike and dip) of the symmetry axis relative to the incident propagation azimuth of the source-receiver great-circle path. Due to this, the orientation of the anisotropic symmetry axis provides a distinct signature which is observable in the variation of QL wave scattering with wave-propagation azimuth. Finally, using data recorded on USArray, I observe the variation in QL wave scattering with propagation azimuth. I then attempt to forward-model the observed behavior using the algorithm developed earlier. The best-fitting model suggests coherent trench-perpendicular mantle anisotropy with an eastward dip in the sublsab mantle of the Cascadian subduction zone. The resulting anisotropic model adds confidence to the entrained subslab mantle-flow model for Cascadia and further refutes the 3-D return-flow model associated with slab rollback.

U-bent plastic optical fiber based plasmonic biosensor for nucleic acid detection

NASA Astrophysics Data System (ADS)

Gowri, A.; Sai, V. V. R.

2017-05-01

This study presents the development of low cost, rapid and highly sensitive plasmonic sandwich DNA biosensor using U-bent plastic optical fiber (POF) probes with high evanescent wave absorbance sensitivity and gold nanoparticles (AuNP) as labels. Plastic optical fiber (PMMA core and fluorinated polymer as cladding) offer ease in machinability and handling due to which optimum U-bent geometry (with fiber and bend diameter of 0.5 and 1.5 mm respectively) for high sensitivity could be achieved. A sensitive fiber optic DNA biosensor is realized by (i) modifying the PMMA surface using ethylenediamine (EDA) in order to maximize the immobilization of capture oligonucleotides (ONs) and (ii) conjugating probe ONs to AuNP labels of optimum size ( 35 nm) with high extinction coefficient and optimal ON surface density. The sandwich hybridization assay on U-bent POF probes results in increase in optical absorbance through the probe with increase in target ON concentration due to the presence of increased number of AuNPs. The absorbance of light passing through the U-bent probe due to the presence of AuNP labels on its surface as result of sandwich DNA hybridization is measured using a halogen lamp and a fiber optic spectrometer. A picomolar limit of detection of target ON (0.2 pM or 1 pg/ml or 5 attomol in 25 μL) is achieved with this biosensing scheme, indicating its potential for the development of a highly sensitive DNA biosensor.

Apparatus for checking the direction of polarization of shear-wave ultrasonic transducers

DOEpatents

Karplus, Henry H. B.

1980-01-01

An apparatus for checking the direction of polarization of shear-wave ultrasonic transducers comprises a first planar surface for mounting the shear-wave transducer, a second planar surface inclined at a predetermined angle to the first surface to generate longitudinal waves by mode conversion, and a third planar surface disposed at a second predetermined angle to the first for mounting a longitudinal-wave ultrasonic transducer. In an alternate embodiment, two second planar surfaces at the predetermined angle are placed at an angle to each other. The magnitude of the shear wave is a function of the angle between the direction of polarization of the transducer and the mode-conversion surface.

Apparatus for checking the direction of polarization of shear-wave ultrasonic transducers

DOEpatents

Karplus, H.H.B.; Forster, G.A.

An apparatus for checking the direction of polarization of shear-wave ultrasonic transducers comprises a first planar surface for mounting the shear-wave transducer, a second planar surface inclined at a predetermined angle to the first surface to generate longitudinal waves by mode conversion, and a third planar surface disposed at a second predetermined angle to the first for mounting a longitudinal-wave ultransonic transducer. In an alternate embodiment, two second planar surfaces at the predetermined angle are placed at an angle to each other. The magnitude of the shear wave is a function of the angle between the direction of polarization of the transducer and the mode-conversion surface.

Viscoelastic representation of surface waves in patchy saturated poroelastic media

NASA Astrophysics Data System (ADS)

Zhang, Yu; Xu, Yixian; Xia, Jianghai; Ping, Ping; Zhang, Shuangxi

2014-08-01

Wave-induced flow is observed as the dominated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation in patchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range (0.1-1,000 Hz). The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent viscoelastic media. The simulation of surface wave propagation within mesoscopic patches requires solving Biot's differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Biot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase viscoelastic differential equations.

Plasmonic fiber-optic vector magnetometer

NASA Astrophysics Data System (ADS)

Zhang, Zhaochuan; Guo, Tuan; Zhang, Xuejun; Xu, Jian; Xie, Wenping; Nie, Ming; Wu, Qiang; Guan, Bai-Ou; Albert, Jacques

2016-03-01

A compact fiber-optic vector magnetometer based on directional scattering between polarized plasmon waves and ferro-magnetic nanoparticles is demonstrated. The sensor configuration reported in this work uses a short section of tilted fiber Bragg grating (TFBG) coated with a nanometer scale gold film and packaged with a magnetic fluid (Fe3O4) inside a capillary. The transmission spectrum of the sensor provides a fine comb of narrowband resonances that overlap with a broader absorption of the surface plasmon resonance (SPR). The wavelength of the SPR attenuation in transmission shows high sensitivity to slight perturbations by magnetic fields, due to the strong directional scattering between the SPR attenuated cladding modes and the magnetic fluid near the fiber surface. Both the orientation (2 nm/deg) and the intensity (1.8 nm/mT) of magnetic fields can be determined unambiguously from the TFBG spectrum. Temperature cross sensitivity can be referenced out by monitoring the wavelength of the core mode resonance simultaneously.

A Room Temperature Nitric Oxide Gas Sensor Based on a Copper-Ion-Doped Polyaniline/Tungsten Oxide Nanocomposite

PubMed Central

Wang, Shih-Han; Shen, Chi-Yen; Su, Jian-Ming; Chang, Shiang-Wen

2015-01-01

The parts-per-billion-level nitric oxide (NO) gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu2+/PANI/WO3) film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu2+/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases. PMID:25811223

Cleanroom Contaminant Monitor

NASA Technical Reports Server (NTRS)

1997-01-01

Under a Small Business Innovation Research (SBIR) contract from Kennedy Space Center (KSC), Femtometrics, Inc. developed the Real-Time Non-Volatile Residue (NVR) monitor. Criteria established by KSC called for a technology that could regulate the accumulation of nonvolatile residues in cleanroom environments. The company accommodated the Center's need with an advanced, highly sensitive surface acoustic wave (SAW) microsensor capable of detecting sub-monolayer deposition in cleanrooms where aerospace systems are assembled. Years earlier, Femtometrics responded to and received SBIR contracts from Langley Research Center for highly sensitive aerosol detectors for environmental researchers. Stimulated by the SBIR wins, the company set about to develop the SAW resonator technology. A new type of sensor has evolved from the research, one that has the ability to measure a range of chemical vapors by applying chemical-specific coating on the sensing surface. Commercial applications of the Real-Time NVR include Class 1 cleanrooms at semiconductor and hard-disk manufacturing plants.

Theory of Electromagnetic Surface Waves in Plasma with Smooth Boundaries

NASA Astrophysics Data System (ADS)

Kuzelev, M. V.

2018-05-01

A theory of nonpotential surface waves in plasma with smooth boundaries is developed. The complex frequencies of surface waves for plasma systems of different geometries and different profiles of the plasma density are calculated. Expressions for the rates of collisionless damping of surface waves due to their resonance interaction with local plasma waves of continuous spectrum are obtained. The influence of collisions in plasma is also considered.

Adapting detection sensitivity based on evidence of irregular sinus arrhythmia to improve atrial fibrillation detection in insertable cardiac monitors.

PubMed

Pürerfellner, Helmut; Sanders, Prashanthan; Sarkar, Shantanu; Reisfeld, Erin; Reiland, Jerry; Koehler, Jodi; Pokushalov, Evgeny; Urban, Luboš; Dekker, Lukas R C

2017-10-03

Intermittent change in p-wave discernibility during periods of ectopy and sinus arrhythmia is a cause of inappropriate atrial fibrillation (AF) detection in insertable cardiac monitors (ICM). To address this, we developed and validated an enhanced AF detection algorithm. Atrial fibrillation detection in Reveal LINQ ICM uses patterns of incoherence in RR intervals and absence of P-wave evidence over a 2-min period. The enhanced algorithm includes P-wave evidence during RR irregularity as evidence of sinus arrhythmia or ectopy to adaptively optimize sensitivity for AF detection. The algorithm was developed and validated using Holter data from the XPECT and LINQ Usability studies which collected surface electrocardiogram (ECG) and continuous ICM ECG over a 24-48 h period. The algorithm detections were compared with Holter annotations, performed by multiple reviewers, to compute episode and duration detection performance. The validation dataset comprised of 3187 h of valid Holter and LINQ recordings from 138 patients, with true AF in 37 patients yielding 108 true AF episodes ≥2-min and 449 h of AF. The enhanced algorithm reduced inappropriately detected episodes by 49% and duration by 66% with <1% loss in true episodes or duration. The algorithm correctly identified 98.9% of total AF duration and 99.8% of total sinus or non-AF rhythm duration. The algorithm detected 97.2% (99.7% per-patient average) of all AF episodes ≥2-min, and 84.9% (95.3% per-patient average) of detected episodes involved AF. An enhancement that adapts sensitivity for AF detection reduced inappropriately detected episodes and duration with minimal reduction in sensitivity. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Cardiology

Surface waves generated by shallow underwater explosions

NASA Technical Reports Server (NTRS)

Falade, A.; Holt, M.

1978-01-01

Surface water waves generated by surface and near surface point explosions are calculated. Taking the impulse distribution imparted at the water surface by the explosion as the overriding mechanism for transferring energy of the explosive to surface wave motion, the linearized theory of Kranzer and Keller is used to obtain the wave displacement in the far field. The impulse distribution is obtained by integrating the pressure wave over an appropriate time interval on a horizontal surface just beneath the undisturbed water surface. For surface explosions, a modified form of the similarity method first used by Collins and Holt is used to obtain the flow field. In the case of submerged explosions, the flow field is estimated by making necessary modifications to Sedov's similarity solution to account for the venting that accompanies the interaction of the leading (blast) wave with the ocean surface. Surface waves generated by a charge at six depths of placement (0.15 m, 0.30 m, 0.61 m, 0.91 m, 1.37 m, 3.05 m) are considered in addition to surface explosions. The results seem to support the existence of an upper critical depth phenomenon (of the type already established for chemical explosions) for point (nuclear) explosions.

Distributed feedback acoustic surface wave oscillator

NASA Technical Reports Server (NTRS)

Elachi, C. (Inventor)

1977-01-01

An acoustic surface wave oscillator is constructed from a semiconductor piezoelectric acoustic surface wave amplifier by providing appropriate perturbations at the piezoelectric boundary. The perturbations cause Bragg order reflections that maintain acoustic wave oscillation under certain conditions of gain and feedback.

Numerical modeling of the effects of wave energy converter characteristics on nearshore wave conditions

DOE PAGES

Chang, G.; Ruehl, K.; Jones, C. A.; ...

2015-12-24

Modeled nearshore wave propagation was investigated downstream of simulated wave energy converters (WECs) to evaluate overall near- and far-field effects of WEC arrays. Model sensitivity to WEC characteristics and WEC array deployment scenarios was evaluated using a modified version of an industry standard wave model, Simulating WAves Nearshore (SWAN), which allows the incorporation of device-specific WEC characteristics to specify obstacle transmission. The sensitivity study illustrated that WEC device type and subsequently its size directly resulted in wave height variations in the lee of the WEC array. Wave heights decreased up to 30% between modeled scenarios with and without WECs formore » large arrays (100 devices) of relatively sizable devices (26 m in diameter) with peak power generation near to the modeled incident wave height. Other WEC types resulted in less than 15% differences in modeled wave height with and without WECs, with lesser influence for WECs less than 10 m in diameter. Wave directions and periods were largely insensitive to changes in parameters. Furthermore, additional model parameterization and analysis are required to fully explore the model sensitivity of peak wave period and mean wave direction to the varying of the parameters.« less

Simulations of Variability and Waves at Cloud Altitudes Using a Venus Middle Atmosphere General Circulation Model

NASA Astrophysics Data System (ADS)

Parish, H. F.; Mitchell, J.

2017-12-01

We have developed a Venus general circulation model, the Venus Middle atmosphere Model (VMM), to simulate the atmosphere from just below the cloud deck 40 km altitude to around 100 km altitude. Our primary goal is to assess the influence of waves on the variability of winds and temperatures observed around Venus' cloud deck. Venus' deep atmosphere is not simulated directly in the VMM model, so the effects of waves propagating upwards from the lower atmosphere is represented by forcing at the lower boundary of the model. Sensitivity tests allow appropriate amplitudes for the wave forcing to be determined by comparison with Venus Express and probe measurements and allow the influence of waves on the cloud-level atmosphere to be investigated. Observations at cloud altitudes are characterized by waves with a wide variety of periods and wavelengths, including gravity waves, thermal tides, Rossby waves, and Kelvin waves. These waves may be generated within the cloud deck by instabilities, or may propagate up from the deep atmosphere. Our development of the VMM is motivated by the fact that the circulation and dynamics between the surface and the cloud levels are not well measured and wind velocities below 40 km altitude cannot be observed remotely, so we focus on the dynamics at cloud levels and above. Initial results from the VMM with a simplified radiation scheme have been validated by comparison with Pioneer Venus and Venus Express observations and show reasonable agreement with the measurements.

Wave propagation through an inhomogeneous slab sandwiched by the piezoelectric and the piezomagnetic half spaces.

PubMed

Jiao, Fengyu; Wei, Peijun; Li, Li

2017-01-01

Wave propagation through a gradient slab sandwiched by the piezoelectric and the piezomagnetic half spaces are studied in this paper. First, the secular equations in the transverse isotropic piezoelectric/piezomagnetic half spaces are derived from the general dynamic equation. Then, the state vectors at piezoelectric and piezomagnetic half spaces are related to the amplitudes of various possible waves. The state transfer equation of the functionally graded slab is derived from the equations of motion by the reduction of order, and the transfer matrix of the functionally gradient slab is obtained by solving the state transfer equation with the spatial-varying coefficient. Finally, the continuous interface conditions are used to lead to the resultant algebraic equations. The algebraic equations are solved to obtain the amplitude ratios of various waves which are further used to obtain the energy reflection and transmission coefficients of various waves. The numerical results are shown graphically and are validated by the energy conservation law. Based on the numerical results on the fives of gradient profiles, the influences of the graded slab on the wave propagation are discussed. It is found that the reflection and transmission coefficients are obviously dependent upon the gradient profile. The various surface waves are more sensitive to the gradient profile than the bulk waves. Copyright © 2016 Elsevier B.V. All rights reserved.

Global lake evaporation accelerated by changes in surface energy allocation in a warmer climate

NASA Astrophysics Data System (ADS)

Wang, Wei; Lee, Xuhui; Xiao, Wei; Liu, Shoudong; Schultz, Natalie; Wang, Yongwei; Zhang, Mi; Zhao, Lei

2018-06-01

Lake evaporation is a sensitive indicator of the hydrological response to climate change. Variability in annual lake evaporation has been assumed to be controlled primarily by the incoming surface solar radiation. Here we report simulations with a numerical model of lake surface fluxes, with input data based on a high-emissions climate change scenario (Representative Concentration Pathway 8.5). In our simulations, the global annual lake evaporation increases by 16% by the end of the century, despite little change in incoming solar radiation at the surface. We attribute about half of this projected increase to two effects: periods of ice cover are shorter in a warmer climate and the ratio of sensible to latent heat flux decreases, thus channelling more energy into evaporation. At low latitudes, annual lake evaporation is further enhanced because the lake surface warms more slowly than the air, leading to more long-wave radiation energy available for evaporation. We suggest that an analogous change in the ratio of sensible to latent heat fluxes in the open ocean can help to explain some of the spread among climate models in terms of their sensitivity of precipitation to warming. We conclude that an accurate prediction of the energy balance at the Earth's surface is crucial for evaluating the hydrological response to climate change.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Akutsu, T.; Allen, B.; Allocca, A.; Altin, P. A.; Ananyeva, A.; Anderson, S. B.; Anderson, W. G.; Ando, M.; Appert, S.; Arai, K.; Araya, A.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Asada, H.; Ascenzi, S.; Ashton, G.; Aso, Y.; Ast, M.; Aston, S. M.; Astone, P.; Atsuta, S.; Aufmuth, P.; Aulbert, C.; Avila-Alvarez, A.; Awai, K.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baiotti, L.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Belgin, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, H.-P.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conti, L.; Cooper, S. J.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco, E.; Canton, T. Dal; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Davis, D.; Daw, E. J.; Day, B.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Fiore, L. Di; Giovanni, M. Di; Girolamo, T. Di; Lieto, A. Di; Pace, S. Di; Palma, I. Di; Virgilio, A. Di; Doctor, Z.; Doi, K.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Eda, K.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Etienne, Z.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fernández Galiana, A.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fong, H.; Forsyth, S. S.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov, V. V.; Fujii, Y.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hagiwara, A.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Hayama, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hirose, E.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Ioka, K.; Isa, H. N.; Isac, J.-M.; Isi, M.; Isogai, T.; Itoh, Y.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kagawa, T.; Kajita, T.; Kakizaki, M.; Kalaghatgi, C. V.; Kalogera, V.; Kamiizumi, M.; Kanda, N.; Kandhasamy, S.; Kanemura, S.; Kaneyama, M.; Kang, G.; Kanner, J. B.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Kataoka, Y.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawai, N.; Kawamura, S.; Kéfélian, F.; Keitel, D.; Kelley, D. B.; Kennedy, R.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, H.; Kim, J. C.; Kim, J.; Kim, W.; Kim, Y.-M.; Kimbrell, S. J.; Kimura, N.; King, E. J.; King, P. J.; Kirchhoff, R.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koch, P.; Koehlenbeck, S. M.; Kojima, Y.; Kokeyama, K.; Koley, S.; Komori, K.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kotake, K.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, Rahul; Kumar, Rakesh; Kuo, L.; Kuroda, K.; Kutynia, A.; Kuwahara, Y.; Lackey, B. D.; Landry, M.; Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.; Lehmann, J.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Liu, J.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macfoy, S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mano, S.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marchio, M.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Matsumoto, N.; Matsushima, F.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGrath, C.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Michimura, Y.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Miyamoto, A.; Miyamoto, T.; Miyoki, S.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morii, W.; Morisaki, S.; Moriwaki, Y.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muniz, E. A. M.; Murray, P. G.; Mytidis, A.; Nagano, S.; Nakamura, K.; Nakamura, T.; Nakano, H.; Nakano, Masaya; Nakano, Masayuki; Nakao, K.; Napier, K.; Nardecchia, I.; Narikawa, T.; Naticchioni, L.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Nery, M.; Neunzert, A.; Newport, J. M.; Newton, G.; Nguyen, T. T.; Ni, W.-T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. 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S.; Wu, G.; Yam, W.; Yamamoto, H.; Yamamoto, K.; Yamamoto, T.; Yancey, C. C.; Yano, K.; Yap, M. J.; Yokoyama, J.; Yokozawa, T.; Yoon, T. H.; Yu, Hang; Yu, Haocun; Yuzurihara, H.; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zeidler, S.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.

2018-04-01

We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-20 deg^2 requires at least three detectors of sensitivity within a factor of ˜ 2 of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA.

PubMed

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Man, N; Mandic, V; Mangano, V; Mano, S; Mansell, G L; Manske, M; Mantovani, M; Marchesoni, F; Marchio, M; Marion, F; Márka, S; Márka, Z; Markosyan, A S; Maros, E; Martelli, F; Martellini, L; Martin, I W; Martynov, D V; Mason, K; Masserot, A; Massinger, T J; Masso-Reid, M; Mastrogiovanni, S; Matichard, F; Matone, L; Matsumoto, N; Matsushima, F; Mavalvala, N; Mazumder, N; McCarthy, R; McClelland, D E; McCormick, S; McGrath, C; McGuire, S C; McIntyre, G; McIver, J; McManus, D J; McRae, T; McWilliams, S T; Meacher, D; Meadors, G D; Meidam, J; Melatos, A; Mendell, G; Mendoza-Gandara, D; Mercer, R A; Merilh, E L; Merzougui, M; Meshkov, S; Messenger, C; Messick, C; Metzdorff, R; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Michimura, Y; Middleton, H; Mikhailov, E E; Milano, L; Miller, A L; Miller, A; Miller, B B; Miller, J; Millhouse, M; Minenkov, Y; Ming, J; Mirshekari, S; Mishra, C; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Miyakawa, O; Miyamoto, A; Miyamoto, T; Miyoki, S; Moggi, A; Mohan, M; Mohapatra, S R P; Montani, M; Moore, B C; Moore, C J; Moraru, D; Moreno, G; Morii, W; Morisaki, S; Moriwaki, Y; Morriss, S R; Mours, B; Mow-Lowry, C M; Mueller, G; Muir, A W; Mukherjee, Arunava; Mukherjee, D; Mukherjee, S; Mukund, N; Mullavey, A; Munch, J; Muniz, E A M; Murray, P G; Mytidis, A; Nagano, S; Nakamura, K; Nakamura, T; Nakano, H; Nakano, Masaya; Nakano, Masayuki; Nakao, K; Napier, K; Nardecchia, I; Narikawa, T; Naticchioni, L; Nelemans, G; Nelson, T J N; Neri, M; Nery, M; Neunzert, A; Newport, J M; Newton, G; Nguyen, T T; Ni, W-T; Nielsen, A B; Nissanke, S; Nitz, A; Noack, A; Nocera, F; Nolting, D; Normandin, M E N; Nuttall, L K; Oberling, J; Ochsner, E; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohashi, M; Ohishi, N; Ohkawa, M; Ohme, F; Okutomi, K; Oliver, M; Ono, K; Ono, Y; Oohara, K; Oppermann, P; Oram, Richard J; O'Reilly, B; O'Shaughnessy, R; Ottaway, D J; Overmier, H; Owen, B J; Pace, A E; Page, J; Pai, A; Pai, S A; Palamos, J R; Palashov, O; Palomba, C; Pal-Singh, A; Pan, H; Pankow, C; Pannarale, F; Pant, B C; Paoletti, F; Paoli, A; Papa, M A; Paris, H R; Parker, W; Pascucci, D; Pasqualetti, A; Passaquieti, R; Passuello, D; Patricelli, B; Pearlstone, B L; Pedraza, M; Pedurand, R; Pekowsky, L; Pele, A; Peña Arellano, F E; Penn, S; Perez, C J; Perreca, A; Perri, L M; Pfeiffer, H P; Phelps, M; Piccinni, O J; Pichot, M; Piergiovanni, F; Pierro, V; Pillant, G; Pinard, L; Pinto, I M; Pitkin, M; Poe, M; Poggiani, R; Popolizio, P; Post, A; Powell, J; Prasad, J; Pratt, J W W; Predoi, V; Prestegard, T; Prijatelj, M; Principe, M; Privitera, S; Prodi, G A; Prokhorov, L G; Puncken, O; Punturo, M; Puppo, P; Pürrer, M; Qi, H; Qin, J; Qiu, S; Quetschke, V; Quintero, E A; Quitzow-James, R; Raab, F J; Rabeling, D S; Radkins, H; Raffai, P; Raja, S; Rajan, C; Rakhmanov, M; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Read, J; Regimbau, T; Rei, L; Reid, S; Reitze, D H; Rew, H; Reyes, S D; Rhoades, E; Ricci, F; Riles, K; Rizzo, M; Robertson, N A; Robie, R; Robinet, F; Rocchi, A; Rolland, L; Rollins, J G; Roma, V J; Romano, R; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Sago, N; Saijo, M; Saito, Y; Sakai, K; Sakellariadou, M; Salconi, L; Saleem, M; Salemi, F; Samajdar, A; Sammut, L; Sampson, L M; Sanchez, E J; Sandberg, V; Sanders, J R; Sasaki, Y; Sassolas, B; Sathyaprakash, B S; Sato, S; Sato, T; Saulson, P R; Sauter, O; Savage, R L; Sawadsky, A; Schale, P; Scheuer, J; Schmidt, E; Schmidt, J; Schmidt, P; Schnabel, R; Schofield, R M S; Schönbeck, A; Schreiber, E; Schuette, D; Schutz, B F; Schwalbe, S G; Scott, J; Scott, S M; Sekiguchi, T; Sekiguchi, Y; Sellers, D; Sengupta, A S; Sentenac, D; Sequino, V; Sergeev, A; Setyawati, Y; Shaddock, D A; Shaffer, T J; Shahriar, M S; Shapiro, B; Shawhan, P; Sheperd, A; Shibata, M; Shikano, Y; Shimoda, T; Shoda, A; Shoemaker, D H; Shoemaker, D M; Siellez, K; Siemens, X; Sieniawska, M; Sigg, D; Silva, A D; Singer, A; Singer, L P; Singh, A; Singh, R; Singhal, A; Sintes, A M; Slagmolen, B J J; Smith, B; Smith, J R; Smith, R J E; Somiya, K; Son, E J; Sorazu, B; Sorrentino, F; Souradeep, T; Spencer, A P; Srivastava, A K; Staley, A; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Stevenson, S P; Stone, R; Strain, K A; Straniero, N; Stratta, G; Strigin, S E; Sturani, R; Stuver, A L; Sugimoto, Y; Summerscales, T Z; Sun, L; Sunil, S; Sutton, P J; Suzuki, T; Swinkels, B L; Szczepańczyk, M J; Tacca, M; Tagoshi, H; Takada, S; Takahashi, H; Takahashi, R; Takamori, A; Talukder, D; Tanaka, H; Tanaka, K; Tanaka, T; Tanner, D B; Tápai, M; Taracchini, A; Tatsumi, D; Taylor, R; Telada, S; Theeg, T; Thomas, E G; Thomas, M; Thomas, P; Thorne, K A; Thrane, E; Tippens, T; Tiwari, S; Tiwari, V; Tokmakov, K V; Toland, K; Tomaru, T; Tomlinson, C; Tonelli, M; Tornasi, Z; Torrie, C I; Töyrä, D; Travasso, F; Traylor, G; Trifirò, D; Trinastic, J; Tringali, M C; Trozzo, L; Tse, M; Tso, R; Tsubono, K; Tsuzuki, T; Turconi, M; Tuyenbayev, D; Uchiyama, T; Uehara, T; Ueki, S; Ueno, K; Ugolini, D; Unnikrishnan, C S; Urban, A L; Ushiba, T; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; van Bakel, N; van Beuzekom, M; van den Brand, J F J; Van Den Broeck, C; Vander-Hyde, D C; van der Schaaf, L; van Heijningen, J V; van Putten, M H P M; van Veggel, A A; Vardaro, M; Varma, V; Vass, S; Vasúth, M; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Venugopalan, G; Verkindt, D; Vetrano, F; Viceré, A; Viets, A D; Vinciguerra, S; Vine, D J; Vinet, J-Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Voss, D V; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L E; Wade, M; Wakamatsu, T; Walker, M; Wallace, L; Walsh, S; Wang, G; Wang, H; Wang, M; Wang, Y; Ward, R L; Warner, J; Was, M; Watchi, J; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Wen, L; Weßels, P; Westphal, T; Wette, K; Whelan, J T; Whiting, B F; Whittle, C; Williams, D; Williams, R D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M H; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Woehler, J; Worden, J; Wright, J L; Wu, D S; Wu, G; Yam, W; Yamamoto, H; Yamamoto, K; Yamamoto, T; Yancey, C C; Yano, K; Yap, M J; Yokoyama, J; Yokozawa, T; Yoon, T H; Yu, Hang; Yu, Haocun; Yuzurihara, H; Yvert, M; Zadrożny, A; Zangrando, L; Zanolin, M; Zeidler, S; Zendri, J-P; Zevin, M; Zhang, L; Zhang, M; Zhang, T; Zhang, Y; Zhao, C; Zhou, M; Zhou, Z; Zhu, S J; Zhu, X J; Zucker, M E; Zweizig, J

2018-01-01

We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and [Formula: see text] credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-[Formula: see text] requires at least three detectors of sensitivity within a factor of [Formula: see text] of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces.

PubMed

Colombi, Andrea; Ageeva, Victoria; Smith, Richard J; Clare, Adam; Patel, Rikesh; Clark, Matt; Colquitt, Daniel; Roux, Philippe; Guenneau, Sebastien; Craster, Richard V

2017-07-28

Recent years have heralded the introduction of metasurfaces that advantageously combine the vision of sub-wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. An important topic within metasurfaces is the tailored rainbow trapping and selective spatial frequency separation of electromagnetic and acoustic waves using graded metasurfaces. This frequency dependent trapping and spatial frequency segregation has implications for energy concentrators and associated energy harvesting, sensing and wave filtering techniques. Different demonstrations of acoustic and electromagnetic rainbow devices have been performed, however not for deep elastic substrates that support both shear and compressional waves, together with surface Rayleigh waves; these allow not only for Rayleigh wave rainbow effects to exist but also for mode conversion from surface into shear waves. Here we demonstrate experimentally not only elastic Rayleigh wave rainbow trapping, by taking advantage of a stop-band for surface waves, but also selective mode conversion of surface Rayleigh waves to shear waves. These experiments performed at ultrasonic frequencies, in the range of 400-600 kHz, are complemented by time domain numerical simulations. The metasurfaces we design are not limited to guided ultrasonic waves and are a general phenomenon in elastic waves that can be translated across scales.

On mantle heterogeneity and anisotropy as mapped by inversion of global surface wave data

NASA Astrophysics Data System (ADS)

Khan, A.; Boschi, L.; Connolly, J.; Deschamps, F.

2008-12-01

We jointly invert Love and Rayleigh wave dispersion curves for the Earth's mantle composition, thermal state, P and S wave anisotropy at different locations on the Earth, based on self-consistent thermodynamic calculations. The method consists of four parts: 1. The composition of the Earth is modeled by the chemical system CaO-FeO-MgO- Al2O3-SiO2. Given these parameters and a geotherm (also an unknown), we calculate stable mineral modes, elastic properties, bulk density at the prevailing physical conditions using Gibbs free energy minimisation. Voigt-Reuss-Hill averaging is subsequently emplouyed to compute radial isotropic P and S wave velocity profiles in the elastic limit. 2. Anisotropic P and S wave velocities are determined from the isotropic ones by employing the relations ξ=(Vsh/Vsv)2, φ = (Vpv/Vph)2, η=F/(2A-L), Vs=(2Vsv2+Vsh2)/3 and Vp=(Vpv2+4Vph2)/5. The former three parameters are the standard anisotropy parameters, that we also invert for. 4. From these radial profiles, i.e. of Vsv, Vsh, Vph, Vpv and ρ, sunthetic Love and Rayleigh wave dispersion curves are calculated. The dispersion curves, which comprise fundamental and overtones up to 5th (Love) and 6th (Rayleigh) order have been extracted from global surface wave velocity maps. Given the above scheme, the data are at each location are jointly inverted using a Markov Chain Monte Carlo algorithm, from which a range of compositions, temperatures and radial profiles of anisotropy parameters, fitting data within uncertainties, are obtained. Our method has several advantages over standard approaches, in that no scaling relationships between Vs and Vp and ρ and Vs have to be introduced, implying that the full sensitivity of Rayleigh and Love waves to the parameters Vs, Vp and ρ is accounted for. In this particular study we investigate 5 locations distributed across the globe and reveal mantle chemical and thermal differences at these locations.

ZnO nanomaterials based surface acoustic wave ethanol gas sensor.

PubMed

Wu, Y; Li, X; Liu, J H; He, Y N; Yu, L M; Liu, W H

2012-08-01

ZnO nanomaterials based surface acoustic wave (SAW) gas sensor has been investigated in ethanol environment at room temperature. The ZnO nanomaterials have been prepared through thermal evaporation of high-purity zinc powder. The as-prepared ZnO nanomaterials have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray Diffraction (XRD) techniques. The results indicate that the obtained ZnO nanomaterials, including many types of nanostructures such as nanobelts, nanorods, nanowires as well as nanosheets, are wurtzite with hexagonal structure and well-crystallized. The SAW sensor coated with the nanostructured ZnO materials has been tested in ethanol gas of various concentrations at room temperature. A network analyzer is used to monitor the change of the insertion loss of the SAW sensor when exposed to ethanol gas. The insertion loss of the SAW sensor varies significantly with the change of ethanol concentration. The experimental results manifest that the ZnO nanomaterials based SAW ethanol gas sensor exhibits excellent sensitivity and good short-term reproducibility at room temperature.

Application of Excitation from Multiple Locations on a Simplified High-Lift System

NASA Technical Reports Server (NTRS)

Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

2004-01-01

A series of active flow control experiments were recently conducted on a simplified high-lift system. The purpose of the experiments was to explore the prospects of eliminating all but simply hinged leading and trailing edge flaps, while controlling separation on the supercritical airfoil using multiple periodic excitation slots. Excitation was provided by three. independently controlled, self-contained, piezoelectric actuators. Low frequency excitation was generated through amplitude modulation of the high frequency carrier wave, the actuators' resonant frequencies. It was demonstrated, for the first time, that pulsed modulated signal from two neighboring slots interact favorably to increase lift. Phase sensitivity at the low frequency was measured, even though the excitation was synthesized from the high-frequency carrier wave. The measurements were performed at low Reynolds numbers and included mean and unsteady surface pressures, surface hot-films, wake pressures and particle image velocimetry. A modest (6%) increase in maximum lift (compared to the optimal baseline) was obtained due t o the activation of two of the three actuators.

Detection of coffee flavour ageing by solid-phase microextraction/surface acoustic wave sensor array technique (SPME/SAW).

PubMed

Barié, Nicole; Bücking, Mark; Stahl, Ullrich; Rapp, Michael

2015-06-01

The use of polymer coated surface acoustic wave (SAW) sensor arrays is a very promising technique for highly sensitive and selective detection of volatile organic compounds (VOCs). We present new developments to achieve a low cost sensor setup with a sampling method enabling the highly reproducible detection of volatiles even in the ppb range. Since the VOCs of coffee are well known by gas chromatography (GC) research studies, the new sensor array was tested for an easy assessable objective: coffee ageing during storage. As reference method these changes were traced with a standard GC/FID set-up, accompanied by sensory panellists. The evaluation of GC data showed a non-linear characteristic for single compound concentrations as well as for total peak area values, disabling prediction of the coffee age. In contrast, the new SAW sensor array demonstrates a linear dependency, i.e. being capable to show a dependency between volatile concentration and storage time. Copyright © 2014 Elsevier Ltd. All rights reserved.

Flexible surface acoustic wave strain sensor based on single crystalline LiNbO3 thin film

NASA Astrophysics Data System (ADS)

Xu, Hongsheng; Dong, Shurong; Xuan, Weipeng; Farooq, Umar; Huang, Shuyi; Li, Menglu; Wu, Ting; Jin, Hao; Wang, Xiaozhi; Luo, Jikui

2018-02-01

A flexible surface acoustic wave (SAW) strain sensor in the frequency range of 162-325 MHz was developed based on a single crystalline LiNbO3 thin film with dual resonance modes, namely, the Rayleigh mode and the thickness shear mode (TSM). This SAW sensor could handle a wide strain range up to ±3500 μɛ owing to its excellent flexibility, which is nearly six times the detecting range of bulk piezoelectric substrate based SAW strain sensors. The sensor exhibited a high sensitivity of 193 Hz/ μɛ with a maximum hysteresis less than 1.5%. The temperature coefficients of frequency, for Rayleigh and TSM modes, were -85 and -59 ppm/ °C , respectively. No visible deterioration was observed after cyclic bending for hundreds of times, showing its desirable stability and reliability. By utilizing the dual modes, the strain sensor with a self-temperature calibrated capability can be achieved. The results demonstrate that the sensor is an excellent candidate for strain sensing.

Rapid determination of floral aroma compounds of lilac blossom by fast gas chromatography combined with surface acoustic wave sensor.

PubMed

Oh, Se Yeon; Shin, Hyun Du; Kim, Sung Jean; Hong, Jongki

2008-03-07

A novel analytical method using fast gas chromatography combined with surface acoustic wave sensor (GC/SAW) has been developed for the detection of volatile aroma compounds emanated from lilac blossom (Syringa species: Syringa vulgaris variginata and Syringa dilatata). GC/SAW could detect and quantify various fragrance emitted from lilac blossom, enabling to provide fragrance pattern analysis results. The fragrance pattern analysis could easily characterize the delicate differences in aromas caused by the substantial difference of chemical composition according to different color and shape of petals. Moreover, the method validation of GC/SAW was performed for the purpose of volatile floral actual aroma analysis, achieving a high reproducibility and excellent sensitivity. From the validation results, GC/SAW could serve as an alternative analytical technique for the analysis of volatile floral actual aroma of lilac. In addition, headspace solid-phase microextraction (HS-SPME) GC-MS was employed to further confirm the identification of fragrances emitted from lilac blossom and compared to GC/SAW.

Regional Detection of Decoupled Explosions, Yield Estimation from Surface Waves, Two-Dimensional Source Effects, Three-Dimensional Earthquake Modeling and Automated Magnitude Measures

DTIC Science & Technology

1980-07-01

41 3.2 EXPERIMENTAL DETERMINATION OF THE DEPENDENCE OF RAYLEIGH WAVE AMPLITUDE ON PROPERTIES OF THE SOURCE MATERIAL ...Surface Wave Observations ...... ................ 48 3.3.3 Surface Wave Dependence on Source Material Properties ..... ................ .. 51 SYSTEMS...with various aspects of the problem of estimating yield from single station recordings of surface waves. The material in these four summaries has been

Determination of optimum "multi-channel surface wave method" field parameters.

DOT National Transportation Integrated Search

2012-12-01

Multi-channel surface wave methods (especially the multi-channel analyses of surface wave method; MASW) are routinely used to : determine the shear-wave velocity of the subsurface to depths of 100 feet for site classification purposes. Users are awar...

Lagrangian particle drift and surface deformation in a rotating wave on a free liquid surface

NASA Astrophysics Data System (ADS)

Fontana, Paul W.; Francois, Nicolas; Xia, Hua; Punzmann, Horst; Shats, Michael

2017-11-01

A nonlinear model of a rotating wave on the free surface of a liquid is presented. The flow is assumed to be inviscid and irrotational. The wave is constructed as a superposition of two perpendicular, monochromatic standing Stokes waves and is standing-wave-like, but with ``antinodes'' or cells consisting of rotating surface gradients of alternating polarity. Lagrangian fluid particle trajectories show a rotational drift about each cell in the direction of wave rotation, corresponding to a rotating Stokes drift. Each cell therefore has a circulating flow and localized angular momentum even though the Eulerian flow is irrotational. Meanwhile, the wave sets up a static displacement of the free surface, making a trough in each cell. This static surface gradient provides a centripetal force that may account for additional rotation seen in experiments.

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

NASA Astrophysics Data System (ADS)

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

2012-04-01

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

Resonant generation of internal waves on the soft sea bed by a surface water wave

NASA Astrophysics Data System (ADS)

Wen, Feng

1995-08-01

The nonlinear response of an initially flat sea bed to a monochromatic surface progressive wave was studied using the multiple scale perturbation method. Two opposite-traveling subliminal internal ``mud'' waves are selectively excited and form a resonant triad with the surface wave. The amplitudes of the internal waves grow on a time scale much longer than the period of the surface wave. It was found that the sea bed response is critically dependent on the density ratio of water and soil, depth of water, and depth and viscosity of the saturated soil. The result of instability analysis is in qualitative agreement with the result of a wave flume experiment.

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

USGS Publications Warehouse

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

2008-01-01

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

Evaluation of Relative Sensitivity of SAW and Flexural Plate Wave Devices for Atmospheric Sensing

NASA Technical Reports Server (NTRS)

White, Richard M.; Black, Justin; Chen, Bryan

1998-01-01

The objective of this project is to evaluate the suitability of the ultrasonic flexural plate wave (FPW) device as the detector in a gas chromatograph (GC). Of particular interest is the detection of nitrous oxide (N2O). From experimental results we conclude analyte detection is achieved through two mechanisms: changes in gas density, and mass loading of the device membrane due to the sorption of gas molecules. Reducing the dead volume of the FPW chamber increased the FPW response. A comparison of the FPW response to that of the surface acoustic wave (SAW) detector provided with the GC (made by MSI, Microsensor Technologies, Inc.), shows that for unseparated N2O in N2, the FPW exhibits a sensitivity that is at least 550 times greater than that of the SAW device. A Porapak Q column was found to separate N2O from its carrier gas, N2 or He. With the Porapak Q column, a coated FPW detected 1 ppm N2O in N2 or He, with a response magnitude of 7 Hz. A coated SAW exhibited a response of 25 Hz to pure N2O. The minimal detectable N2O concentrations of the sensors were not evaluated.

Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.; Lock, James A.

1991-01-01

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented.

Characteristics of finite amplitude stationary gravity waves in the atmosphere of Venus

NASA Technical Reports Server (NTRS)

Young, Richard E.; Walterscheid, Richard L.; Schubert, Gerald; Pfister, Leonhard; Houben, Howard; Bindschadler, Duane L.

1994-01-01

This paper extends the study of stationary gravity waves generated near the surface of Venus reported previously by Young et al. to include finite amplitude effects associated with large amplitude waves. Waves are forced near the surface of Venus by periodic forcing. The height-dependent profiles of static stability and mean wind in the Venus atmosphere play a very important role in the evolution of the nonlinear behavior of the waves, just as they do in the linear wave solutions. Certain wave properties are qualitatively consistent with linear wave theory, such as wave trapping, resonance, and wave evanescence for short horizontal wavelenghts. However, the finite amplitude solutions also exhibit many other interesting features. In particular, for forcing amplitudes representative of those that could be expected in mountainous regions such as Aphrodite Terra, waves generated near the surface can reach large amplitudes at and above cloud levels, with clear signatures in the circulation pattern. At still higher levels, the waves can reach large enough amplitude to break, unless damping rates above the clouds are sufficient to limit wave amplitude growth. Well below cloud levels the waves develop complex flow patterns as the result of finite amplitude wave-wave interactions, and waves are generated having considerably shorter horizontal wavelenghts than that associated with the forcing near the surface. Nonlinear interactions can excite waves that are resonant with the background wind and static stability fields even when the primary surface forcing does not, and these waves can dominate the wave spectrum near cloud levels. A global map of Venus topographic slopes derived from Magellan altimetry data shows that slopes of magnitude comparable to or exceeding that used to force the model are ubiquitous over the surface.

Solitary wave solutions and their interactions for fully nonlinear water waves with surface tension in the generalized Serre equations

NASA Astrophysics Data System (ADS)

Dutykh, Denys; Hoefer, Mark; Mitsotakis, Dimitrios

2018-04-01

Some effects of surface tension on fully nonlinear, long, surface water waves are studied by numerical means. The differences between various solitary waves and their interactions in subcritical and supercritical surface tension regimes are presented. Analytical expressions for new peaked traveling wave solutions are presented in the dispersionless case of critical surface tension. Numerical experiments are performed using a high-accurate finite element method based on smooth cubic splines and the four-stage, classical, explicit Runge-Kutta method of order 4.

Multivariate classification with random forests for gravitational wave searches of black hole binary coalescence

NASA Astrophysics Data System (ADS)

Baker, Paul T.; Caudill, Sarah; Hodge, Kari A.; Talukder, Dipongkar; Capano, Collin; Cornish, Neil J.

2015-03-01

Searches for gravitational waves produced by coalescing black hole binaries with total masses ≳25 M⊙ use matched filtering with templates of short duration. Non-Gaussian noise bursts in gravitational wave detector data can mimic short signals and limit the sensitivity of these searches. Previous searches have relied on empirically designed statistics incorporating signal-to-noise ratio and signal-based vetoes to separate gravitational wave candidates from noise candidates. We report on sensitivity improvements achieved using a multivariate candidate ranking statistic derived from a supervised machine learning algorithm. We apply the random forest of bagged decision trees technique to two separate searches in the high mass (≳25 M⊙ ) parameter space. For a search which is sensitive to gravitational waves from the inspiral, merger, and ringdown of binary black holes with total mass between 25 M⊙ and 100 M⊙ , we find sensitive volume improvements as high as 70±13%-109±11% when compared to the previously used ranking statistic. For a ringdown-only search which is sensitive to gravitational waves from the resultant perturbed intermediate mass black hole with mass roughly between 10 M⊙ and 600 M⊙ , we find sensitive volume improvements as high as 61±4%-241±12% when compared to the previously used ranking statistic. We also report how sensitivity improvements can differ depending on mass regime, mass ratio, and available data quality information. Finally, we describe the techniques used to tune and train the random forest classifier that can be generalized to its use in other searches for gravitational waves.

The geometry and volume of melt beneath Ethiopia

NASA Astrophysics Data System (ADS)

Kendall, J. M.; Hammond, J. O. S.

2016-12-01

A range of seismic measurements can be used to map melt distribution in the crust and uppermost mantle. These include seismic P- and S-wave velocities derived from surface- and body-wave tomography, Vp/Vs ratios obtained from receiver functions, and estimates of seismic anisotropy and attenuation. The most obvious melt parameter that seismic data might be sensitive to is volume fraction. However, such data are more sensitive to the aspect ratio of melt inclusions, which is controlled by the melt wetting angle or in other words the shape of the melt inclusion. To better understand this we perform numerical modelling, varying the shape and amount of melt, to show how various seismic phases are effected by melt. To consider the effects on seismic anisotropy we assume that the melt can be stored in pockets of melt that are either horizontally or vertically aligned (e.g., sills versus dykes). We then consider a range of seismic observations from the rifting environment of Ethiopia. Recent studies of P- and S-wave tomography, Rayleigh and Love waves, and Pn or wide angle P-wave refractions provide provide complimentary constraints on melt volume, orientation and inclusion aspect ratio. Furthermore, receiver functions and shear-wave splitting in body waves show strong anisotropy in this region and can be used to constrain the strike of vertically-aligned partial melt. We show that melt in the mantle beneath Ethiopia is likely stored in low aspect ratio disk-like inclusions, suggesting melt is not in textural equilibrium. We estimate that 2-7% vertically aligned melt is stored beneath the Main Ethiopian Rift, >6% horizontally and vertically aligned melt is stored beneath the Afar-region of the Red Sea Rift and 1-6% horizontally aligned melt is stored beneath the Danakil microplate. This supports ideas of strong shear-derived segregation of melt in narrow parts of the rift and large volumes of melt beneath Afar.

Distributed Acoustic Sensing (DAS) Array near a Highway for Traffic Monitoring and Near-Surface Shear-Wave Velocity Profiles

NASA Astrophysics Data System (ADS)

Wang, H. F.; Fratta, D.; Lancelle, C.; Ak, E. Ms; Lord, N. E.

2017-12-01

Monitoring traffic is important for many technical reasons. It allows for better design of future roads and assessment of the state of current roads. The number, size, weight, and speed of vehicles control deterioration rate. Also, real-time information supplies data to intelligent information systems to help control traffic. Recently there have been studies looking at monitoring traffic seismically as vibrations from traffic are not sensitive to weather and poor visibility. Furthermore, traffic noise can be used to image S-wave velocity distribution in the near surface by capturing and interpreting Rayleigh and Love waves (Nakata, 2016; Zeng et al. 2016). The capability of DAS for high spatial sampling (1 m), temporal sampling (up to 10 kHz), and distributed nature (tens of kilometers) allows for a closer look at the traffic as it passes and how the speed of the vehicle may change over the length of the array. The potential and difficulties of using DAS for these objectives were studied using two DAS arrays. One at Garner Valley in Southern California (a 700-meter array adjacent to CA Highway 74) and another in Brady Hot Springs, Nevada (an 8700-meter array adjacent to Interstate 80). These studies experimentally evaluated the use of DAS data for monitoring traffic and assessing the use of traffic vibration as non-localized sources for seismic imaging. DAS arrays should also be resilient to issues with lighting conditions that are problematic for video monitoring and it may be sensitive to the weight of a vehicle. This study along a major interstate provides a basis for examining DAS' potential and limitations as a key component of intelligent highway systems.

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2013-09-30

SPH Model for Water Waves and Other Free Surface Flows ...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...proving to be a competent modeling scheme for free surface flows in three dimensions including the complex flows of the surf zone. As the GPU

Asymmetries in surface waves and reflection/transmission characteristics associated with topological insulators

NASA Astrophysics Data System (ADS)

Mackay, Tom G.; Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

2017-08-01

Three numerical studies were undertaken involving the interactions of plane waves with topological insulators. In each study, the topologically insulating surface states of the topological insulator were represented through a surface admittance. Canonical boundary-value problems were solved for the following cases: (i) Dyakonov surface-wave propagation guided by the planar interface of a columnar thin film and an isotropic dielectric topological insulator; (ii) Dyakonov-Tamm surface-wave propagation guided by the planar interface of a structurally chiral material and an isotropic dielectric topological insulator; and (iii) reflection and transmission due to the planar interface of a topologically insulating columnar thin film and vacuum. The nonzero surface admittance resulted in asymmetries in the wave speeds and decay constants of the surface waves in studies (i) and (ii). The nonzero surface admittance resulted in asymmetries in the reflectances and transmittances in study (iii).

Anodized aluminum pressure sensitive paint for unsteady aerodynamic applications

NASA Astrophysics Data System (ADS)

Sakaue, Hirotaka

2003-06-01

A comprehensive study of anodized aluminum pressure sensitive paint (AA-PSP) is documented. The study consisted of the development of AA-PSP and its application to unsteady aerodynamic fields at atmospheric conditions. Luminophore application mechanism and two-component application on anodized aluminum was studied for the development. Two-component application includes hydrophobic-coated AA-PSP and bi-luminophore system. It was found that the polarity of solvents and the surface charge of anodized aluminum determine the optimized luminophore application. As a result, a wide variation of luminophore can be applied on anodized aluminum. To apply both components on anodized aluminum, optimum solvent polarities for each component should match. AA-PSP performances, such as pressure sensitivity, temperature dependency, signal level, and aging were improved by the luminophore application mechanism and two-component application. AA-PSPs demonstrate the capability of measuring surface pressures on unsteady aerodynamic fields. For an application to the Purdue Mach 4 Quiet Flow Ludwieg Tube, surface pressures on the order of a hundred Pascals were measured for approximately 200ms. The measurement uncertainty of the pressure was on the order of 5%. The main uncertainty source comes from fitting the adsorption control model to calibration points. The results compared qualitatively well to CFD calculations. A miniature fluidic oscillator was used to demonstrate the capability of measuring oscillating unsteady aerodynamic fields with 6.4kHz primary frequency. Flow oscillation images as well as pressure maps of various phases were captured by AA-PSP with PtTFPP as a luminophore (AA-PSPPtTFPP ). Main uncertainty source comes from fitting the adsorption control model to calibration points and from the pulse width of illumination. The measurement uncertainty of the pressure was 4.68%. AA-PSPPtTFPP was applied to a high-amplified acoustic fielding in a standing wave tube. The maximum pressure change created was 171dB (1.04psi). Sinusoidal pressure wave images inside a standing wave tube were captured at various phases. From these images, the integrated pressure map was obtained. In this case, measurement uncertainty was 3.64% and was due mainly to the pulse width and from fitting of the adsorption controlled model. Comparison with theoretical model is necessary to validate the integrated map as a streaming pattern.

Aerodynamic heating in transitional hypersonic boundary layers: Role of second-mode instability

NASA Astrophysics Data System (ADS)

Zhu, Yiding; Chen, Xi; Wu, Jiezhi; Chen, Shiyi; Lee, Cunbiao; Gad-el-Hak, Mohamed

2018-01-01

The evolution of second-mode instabilities in hypersonic boundary layers and its effects on aerodynamic heating are investigated. Experiments are conducted in a Mach 6 wind tunnel using fast-response pressure sensors, fluorescent temperature-sensitive paint, and particle image velocimetry. Calculations based on parabolic stability equations and direct numerical simulations are also performed. It is found that second-mode waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region that rapidly heats the fluid passing through it. As the second-mode waves decay downstream, the dilatation-induced aerodynamic heating decreases while its shear-induced counterpart keeps growing. The latter brings about a second growth of the surface temperature when transition is completed.

Band gaps and localization of surface water waves over large-scale sand waves with random fluctuations

NASA Astrophysics Data System (ADS)

Zhang, Yu; Li, Yan; Shao, Hao; Zhong, Yaozhao; Zhang, Sai; Zhao, Zongxi

2012-06-01

Band structure and wave localization are investigated for sea surface water waves over large-scale sand wave topography. Sand wave height, sand wave width, water depth, and water width between adjacent sand waves have significant impact on band gaps. Random fluctuations of sand wave height, sand wave width, and water depth induce water wave localization. However, random water width produces a perfect transmission tunnel of water waves at a certain frequency so that localization does not occur no matter how large a disorder level is applied. Together with theoretical results, the field experimental observations in the Taiwan Bank suggest band gap and wave localization as the physical mechanism of sea surface water wave propagating over natural large-scale sand waves.

Note: Force- and torque-detection of high frequency electron spin resonance using a membrane-type surface-stress sensor

NASA Astrophysics Data System (ADS)

Takahashi, Hideyuki; Ishimura, Kento; Okamoto, Tsubasa; Ohmichi, Eiji; Ohta, Hitoshi

2018-03-01

We developed a practical useful method for force- and torque-detected electron spin resonance (FDESR/TDESR) spectroscopy in the millimeter wave frequency region. This method uses a commercially available membrane-type surface-stress (MSS) sensor. The MSS is composed of a silicon membrane supported by four beams in which piezoresistive paths are integrated for detecting the deformation of the membrane. Although this device has a lower spin sensitivity than a microcantilever, it offers several distinct advantages, including mechanical strength, ease of use, and versatility. These advantages make this device suitable for practical applications that require FDESR/TDESR.

A study of rain effects on radar scattering from water waves

NASA Technical Reports Server (NTRS)

Bliven, Larry F.; Giovanangeli, Jean-Paul; Norcross, George

1988-01-01

Results are presented from a laboratory investigation of microwave power return due to rain-generated short waves on a wind wave surface. The wind wave tank, sensor, and data processing methods used in the study are described. The study focuses on the response of a 36-GHz radar system, orientated 30 deg from nadir and pointing upwind, to surface waves generated by various combinations of rain and wind. The results show stronger radar signal levels due to short surface waves generated by rain impacting the wind wave surface, supporting the results of Moore et al. (1979) for a 14-GHz radar.

Waveform tomography of crustal structure in the south San Francisco Bay region

USGS Publications Warehouse

Pollitz, F.F.; Fletcher, J.P.

2005-01-01

We utilize a scattering-based seismic tomography technique to constrain crustal tructure around the southern San Francisco Bay region (SFBR). This technique is based on coupled traveling wave scattering theory, which has usually been applied to the interpretation of surface waves in large regional-scale studies. Using fully three-dimensional kernels, this technique is here applied to observed P, S, and surface waves of intermediate period (3-4 s dominant period) observed following eight selected regional events. We use a total of 73 seismograms recorded by a U.S. Geological Survey short-period seismic array in the western Santa Clara Valley, the Berkeley Digital Seismic Network, and the Northern California Seismic Network. Modifications of observed waveforms due to scattering from crustal structure include (positive or negative) amplification, delay, and generation of coda waves. The derived crustal structure explains many of the observed signals which cannot be explained with a simple layered structure. There is sufficient sensitivity to both deep and shallow crustal structure that even with the few sources employed in the present study, we obtain shallow velocity structure which is reasonably consistent with previous P wave tomography results. We find a depth-dependent lateral velocity contrast across the San Andreas fault (SAF), with higher velocities southwest of the SAF in the shallow crust and higher velocities northeast of the SAF in the midcrust. The method does not have the resolution to identify very slow sediment velocities in the upper approximately 3 km since the tomographic models are smooth at a vertical scale of about 5 km. Copyright 2005 by the American Geophysical Union.

Organic-vapor detection using carbon-nanotubes nanocomposite microacoustic sensors

NASA Astrophysics Data System (ADS)

Penza, M.; Tagliente, M. A.; Aversa, P.; Cassano, G.

2005-06-01

We have developed highly sensitive microacoustic vapor sensors based on surface acoustic waves (SAWs) ST,X quartz 315 and 433 MHz two-port resonator oscillators. A nanocomposite film of single-walled carbon nanotubes (SWCNTs) embedded in a cadmium arachidate (CdA) amphiphilic matrix was prepared by Langmuir-Blodgett technique with a fixed SWCNTs weight filler-content as nanostructured and nanosensing interface, for vapor detection at room temperature. The structural properties and surface morphology of the nanocomposite have been examined by X-ray Specular Reflectivity and Field-Emission Gun Scanning Electron Microscopy, respectively. The measured acoustic sensing characteristics indicate that the SAW sensitivity to polar and nonpolar tested organic molecules (ethanol, ethylacetate, and toluene) of the SWCNTs/CdA nanocomposite is up to two times higher than that of unembedded CdA device; also the SWCNTs/CdA nanocomposite vapor sensitivity results significantly enhanced with respect to traditional organic molecular cavities materials and increases with SAW oscillating frequency with a linear dependence in the frequency change response up to a very low sub-ppm limit of detection.

Statistical properties of nonlinear one-dimensional wave fields

NASA Astrophysics Data System (ADS)

Chalikov, D.

2005-06-01

A numerical model for long-term simulation of gravity surface waves is described. The model is designed as a component of a coupled Wave Boundary Layer/Sea Waves model, for investigation of small-scale dynamic and thermodynamic interactions between the ocean and atmosphere. Statistical properties of nonlinear wave fields are investigated on a basis of direct hydrodynamical modeling of 1-D potential periodic surface waves. The method is based on a nonstationary conformal surface-following coordinate transformation; this approach reduces the principal equations of potential waves to two simple evolutionary equations for the elevation and the velocity potential on the surface. The numerical scheme is based on a Fourier transform method. High accuracy was confirmed by validation of the nonstationary model against known solutions, and by comparison between the results obtained with different resolutions in the horizontal. The scheme allows reproduction of the propagation of steep Stokes waves for thousands of periods with very high accuracy. The method here developed is applied to simulation of the evolution of wave fields with large number of modes for many periods of dominant waves. The statistical characteristics of nonlinear wave fields for waves of different steepness were investigated: spectra, curtosis and skewness, dispersion relation, life time. The prime result is that wave field may be presented as a superposition of linear waves is valid only for small amplitudes. It is shown as well, that nonlinear wave fields are rather a superposition of Stokes waves not linear waves. Potential flow, free surface, conformal mapping, numerical modeling of waves, gravity waves, Stokes waves, breaking waves, freak waves, wind-wave interaction.

A note on specific variability of long surface gravity waves and drag coefficient in coastal upwelling zone

NASA Astrophysics Data System (ADS)

Krzyścin, Janusz

1990-01-01

In this paper we solve analytically wave kinematic equations and the wave energy transport equation, for basic long surface gravity wave in the coastal upwelling zone. Using Gent and Taylor's (1978) parameterization of drag coefficient (which includes interaction between long surface waves and the air flow) we find variability of this coefficient due to wave amplification and refraction caused by specific surface water current in the region. The drag coefficient grows towards the shore. The growth is faster for stronger current. When the angle between waves and the current is less than 90° the growth is mainly connected with the waves steepness, but when the angle is larger, it is caused by relative growth of the wave phase velocity.

Surface spin-electron acoustic waves in magnetically ordered metals

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

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru; Kuz'menkov, L. S., E-mail: lsk@phys.msu.ru

2016-05-09

Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma, we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area, the dispersion branches are located close to each other. In this area, there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuirmore » waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the spin-electron acoustic waves.« less

Observation of `third sound' in superfluid 3He

NASA Astrophysics Data System (ADS)

Schechter, A. M. R.; Simmonds, R. W.; Packard, R. E.; Davis, J. C.

1998-12-01

Waves on the surface of a fluid provide a powerful tool for studying the fluid itself and the surrounding physical environment. For example, the wave speed is determined by the force per unit mass at the surface, and by the depth of the fluid: the decreasing speed of ocean waves as they approach the shore reveals the changing depth of the sea and the strength of gravity. Other examples include propagating waves in neutron-star oceans and on the surface of levitating liquid drops. Although gravity is a common restoring force, others exist, including the electrostatic force which causes a thin liquid film to adhere to a solid. Usually surface waves cannot occur on such thin films because viscosity inhibits their motion. However, in the special case of thin films of superfluid 4He, surface waves do exist and are called `third sound'. Here we report the detection of similar surface waves in thin films of superfluid 3He. We describe studies of the speed of these waves, the properties of the surface force, and the film's superfluid density.

Wave-Induced Momentum Flux over Wind-driven Surface Waves

NASA Astrophysics Data System (ADS)

Yousefi, Kianoosh; Veron, Fabrice; Buckley, Marc; Husain, Nyla; Hara, Tetsu

2017-11-01

In recent years, the exchange of momentum between the atmosphere and the ocean has been the subject of several investigations. Although the role of surface waves on the air-sea momentum flux is now well established, detailed quantitative measurements of wave-induced momentum fluxes are lacking. In the current study, using a combined Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) system, we obtained laboratory measurements of the airflow velocity above surface waves for wind speeds ranging from 0.86 to 16.63 m s-1. The mean, turbulent, and wave-coherent velocity fields are then extracted from instantaneous measurements. Wave-induced stress can, therefore, be estimated. In strongly forced cases in high wind speeds, the wave-induced stress near the surface is a significant fraction of the total stress. At lower wind speeds and larger wave ages, the wave-induced stress is positive very close to the surface, below the critical height and decreases to a negative value further above the critical height. This indicates a shift in the direction of the wave-coherent momentum flux across the critical layer. NSF OCE1458977, NSF OCE1634051.

Numerical modeling of surface wave development under the action of wind

NASA Astrophysics Data System (ADS)

Chalikov, Dmitry

2018-06-01

The numerical modeling of two-dimensional surface wave development under the action of wind is performed. The model is based on three-dimensional equations of potential motion with a free surface written in a surface-following nonorthogonal curvilinear coordinate system in which depth is counted from a moving surface. A three-dimensional Poisson equation for the velocity potential is solved iteratively. A Fourier transform method, a second-order accuracy approximation of vertical derivatives on a stretched vertical grid and fourth-order Runge-Kutta time stepping are used. Both the input energy to waves and dissipation of wave energy are calculated on the basis of earlier developed and validated algorithms. A one-processor version of the model for PC allows us to simulate an evolution of the wave field with thousands of degrees of freedom over thousands of wave periods. A long-time evolution of a two-dimensional wave structure is illustrated by the spectra of wave surface and the input and output of energy.

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces.

PubMed

Sidabras, Jason W; Varanasi, Shiv K; Mett, Richard R; Swarts, Steven G; Swartz, Harold M; Hyde, James S

2014-10-01

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg(2+) doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

PubMed Central

Sidabras, Jason W.; Varanasi, Shiv K.; Mett, Richard R.; Swarts, Steven G.; Swartz, Harold M.; Hyde, James S.

2014-01-01

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg2+ doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown. PMID:25362434

A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

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

Sidabras, Jason W.; Varanasi, Shiv K.; Hyde, James S.

2014-10-15

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is eithermore » surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg{sup 2+} doped polystyrene 1.1 mm thick on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.« less