Science.gov

Sample records for plate wave device

  1. Modeling and Imaging Flexural Plate Wave Devices

    SciTech Connect

    Adkins, D.R.; Butler, M.A.; Chu, A.S.; Schubert, W.K.

    1999-07-09

    Sandia National Laboratories is developing a new form of flexural plate wave device (FPW) for sensor applications. In this device, Lorentz forces cause out of plane vibrations in a silicon nitride membrane. Current induced in transducer lines on the membrane provides information about the amplitude and phase of these surface vibrations. By tracking the large amplitude vibrations that occur at resonant frequencies, it is possible to infer information about loading on the membrane. In fabricating FPWs, it is important to understand the impact that minor defects can have on operation. Through modeling and testing, they are developing resilient designs that provide large amplitude signals with a high tolerance to defects. A finite element model has been developed to perform design trade-off studies, and results from the model are being verified with a unique measurement system that can image Angstrom scale displacements at vibrational frequencies up to 800 kHz. Results from FPW modeling and imaging efforts are presented in this paper.

  2. Improved equivalent circuits for acoustic plate wave devices.

    PubMed

    Zaitsev, B D; Kuznetsova, I E; Joshi, S G

    2002-05-01

    This paper presents improved equivalent circuits for the analysis and design of acoustic plate wave devices. The method uses a mixed equivalent circuit for the interdigital transducer consisting of both active and passive sections placed on the surface of a piezoelectric plate. The values of the various circuit elements are obtained by carrying out a best fit between theoretical and experimental frequency dependence of the real and imaginary parts of transducer input impedance. Knowledge of the equivalent circuit parameters allows one to optimize design of the devices. The method has been successfully employed for the design of one-port shear-horizontal wave resonators on Y-X lithium niobate plates. The proposed method can also be utilized for determining acoustic wave velocity with high accuracy.

  3. Surface Micromachined Flexural Plate Wave Device Integrable on Silicon

    SciTech Connect

    Clem, P.G.; Dimos, D.; Garino, T.J.; Martin, S.J.; Mitchell, M.A.; Olson, W.R.; Ruffner, J.A.; Schubert, W.K.; Tuttle, B.A.

    1999-01-01

    Small, reliable chemical sensors are needed for a wide range of applications, such as weapon state-of-health monitoring, nonproliferation activities, and manufacturing emission monitoring. Significant improvements in present surface acoustic wave sensors could be achieved by developing a flexural plate-wave (FPW) architecture, in which acoustic waves are excited in a thin sensor membrane. Further enhancement of device performance could be realized by integrating a piezoelectric thin film on top of the membrane. These new FPW-piezoelectric thin film devices would improve sensitivity, reduce size, enhance ruggedness and reduce the operating frequency so that the FPW devices would be compatible with standard digital microelectronics. Development of these piezoelectric thin film // FPW devices requires integration of (1) acoustic sensor technology, (2) silicon rnicromachining techniques to fabricate thin membranes, and (3) piezoelectric thin films. Two piezoelectric thin film technologies were emphasized in this study: Pb(Zr,Ti)O{sub 3} (PZT) and AlN. PZT thin films were of sufficient quality such that the first high frequency SAW measurements on PZT thin films were measured during the course of this study. Further, reasonable ferroelectric properties were obtained from PZT films deposited on Si surface micromachined FPW device membranes. Fundamental understanding of the effect of nanodimension interfacial layers on AlN thin film domain configurations and piezoelectric response was developed. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Department of Energy under contract DE-AC04-94AL85000.

  4. Method and apparatus for actively controlling a micro-scale flexural plate wave device

    DOEpatents

    Dohner, Jeffrey L.

    2001-01-01

    An actively controlled flexural plate wave device provides a micro-scale pump. A method of actively controlling a flexural plate wave device produces traveling waves in the device by coordinating the interaction of a magnetic field with actively controlled currents. An actively-controlled flexural plate wave device can be placed in a fluid channel and adapted for use as a micro-scale fluid pump to cool or drive micro-scale systems, for example, micro-chips, micro-electrical-mechanical devices, micro-fluid circuits, or micro-scale chemical analysis devices.

  5. Wave-plate structures, power selective optical filter devices, and optical systems using same

    SciTech Connect

    Koplow, Jeffrey P

    2012-07-03

    In an embodiment, an optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes first and second substantially zero-order, zero-wave plates arranged in series with and oriented at an angle relative to each other. The first and second zero-wave plates are configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. Each zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

  6. Gradient Index Devices for the Full Control of Elastic Waves in Plates

    PubMed Central

    Jin, Yabin; Torrent, Daniel; Pennec, Yan; Pan, Yongdong; Djafari-Rouhani, Bahram

    2016-01-01

    In this work, we present a method for the design of gradient index devices for elastic waves in plates. The method allows the design of devices to control the three fundamental modes, despite the fact that their dispersion relation is managed by different elastic constants. It is shown that by means of complex graded phononic crystals and thickness variations it is possible to independently design the three refractive indexes of these waves, allowing therefore their simultaneous control. The effective medium theory required for this purpose is presented, and the method is applied to the design of the Luneburg and Maxwell lenses as well as to the design of a flat gradient index lens. Finally, numerical simulations are used to demonstrate the performance of the method in a broadband frequency region. PMID:27075601

  7. Gradient Index Devices for the Full Control of Elastic Waves in Plates.

    PubMed

    Jin, Yabin; Torrent, Daniel; Pennec, Yan; Pan, Yongdong; Djafari-Rouhani, Bahram

    2016-04-14

    In this work, we present a method for the design of gradient index devices for elastic waves in plates. The method allows the design of devices to control the three fundamental modes, despite the fact that their dispersion relation is managed by different elastic constants. It is shown that by means of complex graded phononic crystals and thickness variations it is possible to independently design the three refractive indexes of these waves, allowing therefore their simultaneous control. The effective medium theory required for this purpose is presented, and the method is applied to the design of the Luneburg and Maxwell lenses as well as to the design of a flat gradient index lens. Finally, numerical simulations are used to demonstrate the performance of the method in a broadband frequency region.

  8. 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.

  9. Acoustic wave device using plate modes with surface-parallel displacement

    DOEpatents

    Martin, S.J.; Ricco, A.J.

    1988-04-29

    Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes therebetween. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them. 6 figs.

  10. Acoustic wave device using plate modes with surface-parallel displacement

    DOEpatents

    Martin, Stephen J.; Ricco, Antonio J.

    1992-01-01

    Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes therebetween. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them.

  11. Acoustic wave device using plate modes with surface-parallel displacement

    DOEpatents

    Martin, S.J.; Ricco, A.J.

    1992-05-26

    Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes there between. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them. 6 figs.

  12. Development of Magnetically Excited Flexural Plate Wave Devices for Implementation as Physical, Chemical, and Acoustic Sensors, and as Integrated Micro-Pumps for Sensored Systems

    NASA Astrophysics Data System (ADS)

    Schubert, W. K.; Mitchell, M. A.; Graf, D. C.; Shul, R. J.

    2002-05-01

    The magnetically excited flexural plate wave (mag-FPW) device has great promise as a versatile sensor platform. FPW's can have better sensitivity at lower operating frequencies than surface acoustic wave (SAW) devices. Lower operating frequency simplifies the control electronics and makes integration of sensor with electronics easier. Magnetic rather than piezoelectric excitation of the FPW greatly simplifies the device structure and processing by eliminating the need for piezoelectric thin films, also simplifying integration issues. The versatile mag-FPW resonator structure can potentially be configured to fulfill a number of critical functions in an autonomous sensored system. As a physical sensor, the device can be extremely sensitive to temperature, fluid flow, strain, acceleration and vibration. By coating the membrane with self-assembled monolayers (SAMs), or polymer films with selective absorption properties (originally developed for SAW sensors), the mass sensitivity of the FPW allows it to be used as biological or chemical sensors. Yet another critical need in autonomous sensor systems is the ability to pump fluid. FPW structures can be configured as micro-pumps. This report describes work done to develop mag-FPW devices as physical, chemical, and acoustic sensors, and as micro-pumps for both liquid and gas-phase analytes to enable new integrated sensing platform.

  13. Ion plated electronic tube device

    DOEpatents

    Meek, T.T.

    1983-10-18

    An electronic tube and associated circuitry which is produced by ion plating techniques. The process is carried out in an automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  14. Wave propagation in metamaterial lattice sandwich plates

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Wen, Jihong; Yin, Jianfei; Yu, Dianlong

    2016-04-01

    This paper designed a special acoustic metamaterial 3D Kagome lattice sandwich plate. Dispersion properties and vibration responses of both traditional plate and metamaterial plate are investigated based on FEA methods. The traditional plate does not have low-frequency complete bandgaps, but the metamaterial plate has low-frequency complete bandgap (at 620Hz) coming from the symmetrical local cantilever resonators. The bandgap frequency is approximate to the first-order natural frequency of the oscillator. Complex wave modes are analyzed. The dispersion curves of longitudinal waves exist in the flexural bandgap. The dispersion properties demonstrate the metamaterial design is advantageous to suppress the low-frequency flexural wave propagation in lattice sandwich plate. The flexural vibrations near the bandgap are also suppressed efficiently. The longitudinal excitation stimulates mainly longitudinal waves and lots of low-frequency flexural vibration modes are avoided. Furthermore, the free edge effects in metamaterial plate provide new method for damping optimizations. The influences of damping on vibrations of the metamaterial sandwich plate are studied. Damping has global influence on the wave propagation; stronger damping will induce more vibration attenuation. The results enlighten us damping and metamaterial design approaches can be unite in the sandwich plates to suppress the wave propagations.

  15. Titanium Carbide Bipolar Plate for Electrochemical Devices

    SciTech Connect

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    1998-05-08

    Titanium carbide comprises a corrosion resistant, electrically conductive, non-porous bipolar plate for use in an electrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  16. Titanium carbide bipolar plate for electrochemical devices

    DOEpatents

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    2000-07-04

    A corrosion resistant, electrically conductive, non-porous bipolar plate is made from titanium carbide for use in an eletrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  17. Retardation Measurements of Infrared PVA Wave plate

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Z, H.; W, D.; D, Y.; Z, Z.; S, J.

    The wave plate made of Polyvinyl Alcohol PVA plastic film has several advantages such as its lower cost and insensitivity to temperature and incidence angle so it has been used in the Solar Multi-Channel Telescope SMCT in China But the important parameter retardations of PVA wave plates in the near infrared wavelength have never been provided In this paper a convenient and high precise instrument to get the retardations of discrete wavelengths or a continuous function of wavelength in near infrared is developed In this method the retardations of wave plates have been determined through calculating the maximum and minimum of light intensity The instrument error has been shown Additionally we can get the continuous direction of wavelength retardations in the ultraviolet visible or infrared spectral in another way

  18. Millimeter Wave Nonreciprocal Devices.

    DTIC Science & Technology

    1983-01-03

    gradients of the dc bias field saturation magnetization , or magnetic anisotrophy can control mode properties of magnetostatic waves (MSW) propagating in...measures microwave magnetic field patterns of magnetostatic waves in LPE- YIG thin films has been developed. The probe’s sensing element is either a... magnetic resonance mode of a YIG sphere. Theoretical analyses show that there is a critical ratio between the -4-Ai p. , , . , l!~ mj radius of the

  19. Guided waves in a jointed composite plate

    SciTech Connect

    Karunasena, W.; Shah, A.H. ); Datta, S.K. )

    1994-03-01

    Reflection of guided waves by a thin region of bonding material at the interface between two composite plates has been investigated in this paper. The study is motivated by the need to develop a quantitative ultrasonic technique to characterize properties of joints between two plates, which may be laminated and anisotropic. Although there have been some recent studies that have examined the reflection and transmission of surface waves at the interface between two plates, they consider the two plates to be semi-infinite in thickness. Thus the mode conversion of waves into higher guided modes of the plates are not taken into account. In this paper, a model study of the interaction of the [ital A][sub 0] and [ital S][sub 0] guided wave modes with the joint material is presented. It is shown that as the frequency increases the coefficient of reflection shows resonant peaks at the cutoff frequencies of higher guided modes. These peaks become increasingly pronounced as the thickness of the joint increases. Another interesting feature is that the reflection coefficients have minima at a frequency that depends on the thickness and the properties of the joint material. These features can be used to determine the relevant properties of the joint.

  20. AE Source Orientation by Plate Wave Analysis

    NASA Technical Reports Server (NTRS)

    Gorman, Michael R.; Prosser, William H.

    1991-01-01

    Lead breaks (Hsu-Neilsen source) were used to generate simulated acoustic emission signals in an aluminum plate at angles of 0, 30, 60, and 90 degrees with respect to the plane of the plate. This was accomplished by breaking the lead on slots cut into the plate at the respective angles. The out-of-plane and in-plane displacement components of the resulting signals were detected by broad band transducers and digitized. Analysis of the waveforms showed them to consist of the extensional and flexural plate modes. The amplitude of both components of the two modes was dependent on the source orientation angle. This suggests that plate wave analysis may be used to determine the source orientation of acoustic emission sources.

  1. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  2. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  3. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, Stephen J.; Butler, Michael A.; Frye, Gregory C.; Smith, James H.

    1998-01-01

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed.

  4. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, S.J.; Butler, M.A.; Frye, G.C.; Smith, J.H.

    1998-11-17

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane is disclosed. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed. 15 figs.

  5. Ocean Wave Energy Harvesting Devices

    DTIC Science & Technology

    2008-01-01

    on the near-zero friction ferrofluid bearings, fabricated a low frequency linear generator, and integrated the generator to a floating platform to...device, this is a good assumption since the parasitic frictional loss is reduced by using the ferrofluid lubricant. The above formulations define the...exceeds 20:1. Coils Yoke plate Coil cartridge Ferrofluid ki. 4. Teledtine linear generator design. The red arrow lines are the magnetic flux loop

  6. Technology Transfer of Plate Wave NDE to Ultrasonic Rotary Actuation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.

    1995-01-01

    Plate waves have been the subject of NDE research and applications. These waves, also known as guided waves of Lamb waves, are formed in two distinct modes--symmetric and antisymmetric --depending on their vibration characteristics in relation to the plate geometry. Experiments have corroborated the predictions for various plate wave modes, allowing the elastic properties of composite materials and adhesive bonded joints to be determined.

  7. Lamb waves propagation in layered piezoelectric/piezomagnetic plates.

    PubMed

    Ezzin, Hamdi; Ben Amor, Morched; Ben Ghozlen, Mohamed Hédi

    2017-04-01

    A dynamic solution is presented for the propagation of harmonic waves in magneto-electro-elastic plates composed of piezoelectric BaTiO3(B) and magnetostrictive CoFe2O4(F) material. The state-vector approach is employed to derive the propagator matrix which connects the field variables at the upper interface to those at the lower interface of each layer. The ordinary differential approach is employed to determine the wave propagating characteristics in the plate by imposing the traction-free boundary condition on the top and bottom surfaces of the layered plate. The dispersion curves of the piezoelectric-piezomagnetic plate are shown for different thickness ratios. The numerical results show clearly the influence of different stacking sequences as well as thickness ratio on dispersion curves and on magneto-electromechanical coupling factor. These findings could be relevant to the analysis and design of high-performance surface acoustic wave (SAW) devices constructed from piezoelectric and piezomagnetic materials.

  8. Numerical calculation of the operation wavelength range of a polarization controller based on rotatable wave plates

    NASA Astrophysics Data System (ADS)

    Park, Hee Su; Sharma, Aditya

    2016-12-01

    We calculate the operation wavelength range of polarization controllers based on rotating wave plates such as paddle-type optical fiber devices. The coverages over arbitrary polarization conversion or arbitrary birefringence compensation are numerically estimated. The results present the acceptable phase retardation range of polarization controllers composed of two quarter-wave plates or a quarter-half-quarter-wave plate combination, and thereby determines the operation wavelength range of a given design. We further prove that a quarter-quarter-half-wave-plate combination is also an arbitrary birefringence compensator as well as a conventional quarter-half-quarter-wave-plate combination, and show that the two configurations have the identical range of acceptable phase retardance within the uncertainty of our numerical method.

  9. Focusing on Plates: Controlling Guided Waves using Negative Refraction.

    PubMed

    Philippe, Franck D; Murray, Todd W; Prada, Claire

    2015-06-08

    Elastic waves are guided along finite structures such as cylinders, plates, or rods through reflection, refraction, and mode conversion at the interfaces. Such wave propagation is ubiquitous in the world around us, and studies of elastic waveguides first emerged in the later part of the 19(th) century. Early work on elastic waveguides revealed the presence of backward propagating waves, in which the phase velocity and group velocity are anti-parallel. While backward wave propagation exists naturally in very simple finite elastic media, there has been remarkably little attention paid to this phenomenon. Here we report the development of a tunable acoustic lens in an isotropic elastic plate showing negative refraction over a finite acoustic frequency bandwidth. As compared to engineered acoustic materials such as phononic crystals and metamaterials, the design of the acoustic lens is very simple, with negative refraction obtained through thickness changes rather than internal periodicity or sub-wavelength resonant structures. A new class of acoustic devices, including resonators, filters, lenses, and cloaks, may be possible through topography optimization of elastic waveguide structures to exploit the unique properties of backward waves.

  10. Wave interaction with dual circular porous plates

    NASA Astrophysics Data System (ADS)

    Mondal, Arpita; Gayen, R.

    2015-12-01

    In this paper we investigated the reflection and the transmission of a system of two symmetric circular-arc-shaped thin porous plates submerged in deep water within the context of linear theory. The hypersingular integral equation technique has been used to analyze the problem mathematically. The integral equations are formulated by applying Green's integral theorem to the fundamental potential function and the scattered potential function into a suitable fluid region, and then using the boundary condition on the porous plate surface. These are solved approximately using an expansion-cum-collocation method using the behaviour of the potential functions at the tips of the plates. This method ultimately produces a very good numerical approximation for the reflection and the transmission coefficients and hydrodynamic force components. The numerical results are depicted graphically against the wave number for a variety of layouts of the arc. Some results are compared with known results for similar configurations of dual rigid plate systems available in the literature with good agreement.

  11. Multi-reflective acoustic wave device

    DOEpatents

    Andle, Jeffrey C.

    2006-02-21

    An acoustic wave device, which utilizes multiple localized reflections of acoustic wave for achieving an infinite impulse response while maintaining high tolerance for dampening effects, is disclosed. The device utilized a plurality of electromechanically significant electrodes disposed on most of the active surface. A plurality of sensors utilizing the disclosed acoustic wave mode device are also described.

  12. Focusing and waveguiding of Lamb waves in micro-fabricated piezoelectric phononic plates.

    PubMed

    Chiou, Meng-Jhen; Lin, Yu-Ching; Ono, Takahito; Esashi, Masayoshi; Yeh, Sih-Ling; Wu, Tsung-Tsong

    2014-09-01

    This paper presents results on the numerical and experimental studies of focusing and waveguiding of the lowest anti-symmetric Lamb wave in micro-fabricated piezoelectric phononic plates. The phononic structure was based on an AT-cut quartz plate and consisted of a gradient-index phononic crystal (GRIN PC) lens and a linear phononic plate waveguide. The band structures of the square-latticed AT-cut quartz phononic crystal plates with different filling ratios were analyzed using the finite element method. The design of a GRIN PC plate lens which is attached with a linear phononic plate waveguide is proposed. In designing the waveguide, propagation modes in square-latticed PC plates with different waveguide widths were studied and the results were served for the experimental design. In the micro-fabrication, deep reactive ion etching (Deep-RIE) process with a laboratory-made etcher was utilized to fabricate both the GRIN PC plate lens and the linear phononic waveguide on an 80 μm thick AT-cut quartz plate. Interdigital transducers were fabricated directly on the quartz plate to generate the lowest anti-symmetric Lamb waves. A vibro-meter was used to detect the wave fields and the measured results on the focusing and waveguiding of the piezoelectric GRIN PC lens and waveguide are in good accordance with the numerical predictions. The results of this study may serve as a basis for developing an active micro plate lens and related devices.

  13. A dual plate thermoplastic recording device for holographic interferometry

    NASA Technical Reports Server (NTRS)

    Umstatter, Holly L.; Craig, James E.; Trolinger, James D.; Lee, George

    1986-01-01

    The development of a dual plate holographic interferometer using thermoplastic recording devices is described. The operational characteristics of the thermoplastic devices are investigated and optimized for fringe contrast and signal-to-noise ratio. The dual plate device was demonstrated in a transonic wind tunnel at NASA Ames Research Center. The interferograms derived from the thermoplastic device are compared with those derived from conventional photographic emulsions. The fringe contrast achieved with the optimized thermoplastic device is equivalent to the contrast achieved with conventional techniques.

  14. Multi-octave metamaterial reflective half-wave plate for millimeter and sub-millimeter wave applications.

    PubMed

    Pisano, Giampaolo; Maffei, Bruno; Ade, Peter A R; de Bernardis, Paolo; de Maagt, Peter; Ellison, Brian; Henry, Manju; Ng, Ming Wah; Schortt, Brian; Tucker, Carole

    2016-12-20

    The quasi-optical modulation of linear polarization at millimeter and sub-millimeter wavelengths can be achieved by using rotating half-wave plates (HWPs) in front of polarization-sensitive detectors. Large operational bandwidths are required when the same device is meant to work simultaneously across different frequency bands. Previous realizations of half-wave plates, ranging from birefringent multi-plates to mesh-based devices, have achieved bandwidths of the order of 100%. Here we present the design and experimental characterization of a reflective HWP able to work across bandwidths of the order of 150%. The working principle of the novel device is completely different from any previous realization, and it is based on the different phase-shift experienced by two orthogonal polarizations reflecting, respectively, off an electric conductor and an artificial magnetic conductor.

  15. Acoustoelastic lamb wave propagation in a homogeneous, isotropic aluminum plate

    SciTech Connect

    Gandhi, Navneet; Michaels, Jennifer E.; Lee, Sang Jun

    2011-06-23

    The effect of stress on Lamb wave propagation is relevant to both nondestructive evaluation and structural health monitoring because of changes in received signals due to both the associated strain and the acoustoelastic effect. A homogeneous plate that is initially isotropic becomes anisotropic under uniaxial stress, and dispersion of propagating waves becomes directionally dependent. The problem is similar to Lamb wave propagation in an anisotropic plate, except the fourth order tensor in the resulting wave equation does not have the same symmetry as that for the unstressed anisotropic plate, and the constitutive equation relating incremental stress to incremental strain is more complicated. Here we consider the theory of acoustoelastic Lamb wave propagation and show how dispersion curves shift anisotropically for an aluminum plate under uniaxial tension. Theoretical predictions of changes in phase velocity as a function of propagation direction are compared to experimental results for a single wave mode.

  16. Resonant metalenses for flexural waves in plates.

    PubMed

    Colombi, Andrea

    2016-11-01

    The dispersion curves of a cluster of closely spaced rods supported by a thin plate are characterised by subwavelength bandgaps and slow group velocities induced by local resonance effects. A recent analytical study [Williams, Roux, Rupin, and Kuperman (2015). Phys. Rev. B 91, 104307], has shown how the slow velocity branch depends, amongst other parameters, on the height of the rods that make up the cluster. Such metamaterial, offering easy-to-tune spatial velocity gradients, is a perfect candidate for building gradient index lenses such as Luneburg, Maxwell, and 90° rotating. Here theoretical results are combined with numerical simulations to design and test metalenses for flexural waves. The lenses are obtained by tuning the height of the cluster of rods such that they provide the required refractive index profile. Snapshots and videos from three-dimensional numerical simulations in a narrow band centered at ∼4 kHz are used to analyse the performances of three types of gradient index metalens (Luneburg, Maxwell, and 90° rotating).

  17. Design of a Variable Thickness Plate to Focus Bending Waves

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Lin, Sz-Chin Steven; Cabell, Randolph H.; Huang, Tony Jun

    2012-01-01

    This paper describes the design of a thin plate whose thickness is tailored in order to focus bending waves to a desired location on the plate. Focusing is achieved by smoothly varying the thickness of the plate to create a type of lens, which focuses structural-borne energy. Damping treatment can then be positioned at the focal point to efficiently dissipate energy with a minimum amount of treatment. Numerical simulations of both bounded and unbounded plates show that the design is effective over a broad frequency range, focusing traveling waves to the same region of the plate regardless of frequency. This paper also quantifies the additional energy dissipated by local damping treatment installed on a variable thickness plate relative to a uniform plate.

  18. Architectures and Devices for Millimeter Wave Imaging

    DTIC Science & Technology

    2009-02-01

    Architectures and Devices for Millimeter Wave Imaging by David A. Wikner , Joseph N. Mait, and Mark Mirotznik ARL-TR-4733 February 2009...4733 February 2009 Architectures and Devices for Millimeter Wave Imaging David A. Wikner and Joseph N. Mait Sensors and Electron Devices...PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 6. AUTHOR(S) David A. Wikner , Joseph N. Mait, and Mark Mirotznik 5f. WORK UNIT NUMBER

  19. Omnidirectional refractive devices for flexural waves based on graded phononic crystals

    SciTech Connect

    Torrent, Daniel Pennec, Yan; Djafari-Rouhani, Bahram

    2014-12-14

    Different omnidirectional refractive devices for flexural waves in thin plates are proposed and numerically analyzed. Their realization is explained by means phononic crystal plates, where a previously developed homogenization theory is employed for the design of graded index refractive devices. These devices consist of a circular cluster of inclusions with a properly designed gradient in their radius. With this approach, the Luneburg and Maxwell lenses and a family of beam splitters for flexural waves are proposed and analyzed. Results show that these devices work properly in a broadband frequency region, being therefore an efficient approach for the design of refractive devices specially interesting for nano-scale applications.

  20. Shock wave strength reduction by passive control using perforated plates

    NASA Astrophysics Data System (ADS)

    Doerffer, Piotr; Szulc, Oskar

    2007-05-01

    Strong, normal shock wave, terminating a local supersonic area on an airfoil, not only limits aerodynamic performance but also becomes a source of a high-speed impulsive helicopter noise. The application of a passive control system (a cavity covered by a perforated plate) on a rotor blade should reduce the noise created by a moving shock. This article covers the numerical implementation of the Bohning/Doerffer transpiration law into the SPARC code and includes an extended validation against the experimental data for relatively simple geometries of transonic nozzles. It is a first step towards a full simulation of a helicopter rotor equipped with a noise reducing passive control device in hover and in forward flight conditions.

  1. Longitudinal wave motion in width-constrained auxetic plates

    NASA Astrophysics Data System (ADS)

    Lim, Teik-Cheng

    2016-05-01

    This paper investigates the longitudinal wave velocity in auxetic plates in comparison to conventional ones, in which the plate is constrained from motion in the width direction. By taking into account the thickness change of the plate and its corresponding change in density, the developed wave velocity is casted not only as a function of Young’s modulus and density, but also in terms of Poisson’s ratio and longitudinal strain. Results show that density and thickness variations compensate for one another when the Poisson’s ratio is positive, but add up when the Poisson’s ratio is negative. Results also reveal that the classical model of longitudinal wave velocity for the plate is accurate when the Poisson’s ratio is about 1/3; at this Poisson’s ratio the influence from density and thickness variations cancel each other. Comparison between the current corrected model and the density-corrected Rayleigh-Lamb model reveals a number of consistent trends, while the discrepancies are elucidated. If the plate material possesses a negative Poisson’s ratio, the deviation of the actual wave velocity from the classical model becomes significant; auxeticity suppresses and enhances the wave velocity in compressive and tensile impacts, respectively. Hence the use of the corrected model is proposed when predicting longitudinal waves in width-constrained auxetic plates, and auxetic materials can be harnessed for effectively controlling wave velocities in thin-walled structures.

  2. Spin wave nonreciprocity for logic device applications

    PubMed Central

    Jamali, Mahdi; Kwon, Jae Hyun; Seo, Soo-Man; Lee, Kyung-Jin; Yang, Hyunsoo

    2013-01-01

    The utilization of spin waves as eigenmodes of the magnetization dynamics for information processing and communication has been widely explored recently due to its high operational speed with low power consumption and possible applications for quantum computations. Previous proposals of spin wave Mach-Zehnder devices were based on the spin wave phase, a delicate entity which can be easily disrupted. Here, we propose a complete logic system based on the spin wave amplitude utilizing the nonreciprocal spin wave behavior excited by microstrip antennas. The experimental data reveal that the nonreciprocity of magnetostatic surface spin wave can be tuned by the bias magnetic field. Furthermore, engineering of the device structure could result in a high nonreciprocity factor for spin wave logic applications. PMID:24196318

  3. Propagation of thickness-twist waves through a joint between two semi-infinite piezoelectric plates.

    PubMed

    Yang, Jiashi; Chen, Ziguang; Hu, Yuantai

    2007-04-01

    We study the propagation of thickness-twist waves through a joint between two semi-infinite piezoelectric plates of crystals with 6-mm symmetry or polarized ceramics. An exact solution from the three-dimensional equations of piezoelectricity is obtained. The solution shows the cutoff of certain waves and the presence of localized electromechanical fields near the joint. The results are of fundamental importance to the understanding and design of resonators and other devices made from plates of these materials, in particular thin film resonators of ZnO and AlN.

  4. Plated lamination structures for integrated magnetic devices

    SciTech Connect

    Webb, Bucknell C.

    2014-06-17

    Semiconductor integrated magnetic devices such as inductors, transformers, etc., having laminated magnetic-insulator stack structures are provided, wherein the laminated magnetic-insulator stack structures are formed using electroplating techniques. For example, an integrated laminated magnetic device includes a multilayer stack structure having alternating magnetic and insulating layers formed on a substrate, wherein each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by an insulating layer, and a local shorting structure to electrically connect each magnetic layer in the multilayer stack structure to an underlying magnetic layer in the multilayer stack structure to facilitate electroplating of the magnetic layers using an underlying conductive layer (magnetic or seed layer) in the stack as an electrical cathode/anode for each electroplated magnetic layer in the stack structure.

  5. Radial Shock Wave Devices Generate Cavitation

    PubMed Central

    Császár, Nikolaus B. M.; Angstman, Nicholas B.; Milz, Stefan; Sprecher, Christoph M.; Kobel, Philippe; Farhat, Mohamed; Furia, John P.; Schmitz, Christoph

    2015-01-01

    Background Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT) devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues. Methods and Findings We used laser fiber optic probe hydrophone (FOPH) measurements, high-speed imaging and x-ray film analysis to compare fundamental elements of the energy signatures of two rESWT devices (Swiss DolorClast; Electro Medical Systems, Nyon, Switzerland; D-Actor 200; Storz Medical, Tägerwillen, Switzerland) and a vibrating massage device (Vibracare; G5/General Physiotherapy, Inc., Earth City, MO, USA). To assert potential bioeffects of these treatment modalities we investigated the influence of rESWT and vibrating massage devices on locomotion ability of Caenorhabditis elegans (C. elegans) worms. Results FOPH measurements demonstrated that both rESWT devices generated acoustic waves with comparable pressure and energy flux density. Furthermore, both rESWT devices generated cavitation as evidenced by high-speed imaging and caused mechanical damage on the surface of x-ray film. The vibrating massage device did not show any of these characteristics. Moreover, locomotion ability of C. elegans was statistically significantly impaired after exposure to radial extracorporeal shock waves but was unaffected after exposure of worms to the vibrating massage device. Conclusions The results of the present study indicate that both energy signature and bioeffects of rESWT devices are fundamentally different from those of vibrating massage devices. Clinical Relevance Prior ESWT studies have shown that tissues treated with sufficient quantities of acoustic sound waves undergo cavitation build-up, mechanotransduction, and ultimately, a biological alteration that “kick-starts” the healing response. Due to their different treatment indications and contra-indications rESWT devices cannot be equated to vibrating

  6. Ultrasonic plate waves in wood-based composite panels

    NASA Astrophysics Data System (ADS)

    Tucker, Brian James

    Two key shortcomings of current ultrasonic nondestructive evaluation (NDE) techniques for plywood, medium density fiberboard (MDF), and oriented strandboard are the reliance on empirical correlations and the neglect of valuable waveform information. The research reported herein examined the feasibility of using fundamental physical relationships along with advanced signal analysis to evaluate material properties and locate defects in wood-based composite panels. Dispersion curves were constructed exhibiting the variation of ultrasonic flexural plate wave phase velocity with frequency. Based on shear deformation plate wave theory, flexural and transverse shear rigidity values for a variety of wood-based composite panels were obtained from the dispersion curves. Axial rigidity values were obtained directly from extensional plate wave phase velocity. Excellent agreement (within 5%) of flexural rigidity values was obtained between NDE and mechanical testing for thin panels (less than or equal to 6.4 mm). Transverse shear rigidity values were obtained from NDE, but no reliable mechanical results were obtained for comparison. Tensile and compressive axial rigidity values obtained from NDE were from 12% to 31% and from 22% to 41% higher than mechanical tension and compression test results, respectively. These differences between NDE and axial mechanical testing results are likely due to load-rate effects. Nondestructive rigidity results for thicker panels using the setup described herein were either unreliable or not interpretable due to highly attenuated signals and/or violation of plate wave assumptions. Shear deformation laminated plate theory was used to predict flexural and axial laminate rigidity values of wood-based laminates from NDE measurements to within 3% and 25%, respectively. Plate wave NDE was also used to successfully locate a 60-mm square delaminated area within a 6.4-mm thick MDF laminate. This fundamental research advances the state-of-the-art of wood

  7. Standing wave acoustic levitation on an annular plate

    NASA Astrophysics Data System (ADS)

    Kandemir, Mehmet Hakan; Çalışkan, Mehmet

    2016-11-01

    In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

  8. Scattering of ultrasonic wave by cracks in a plate

    NASA Technical Reports Server (NTRS)

    Liu, S. W.; Datta, S. K.

    1993-01-01

    A hybrid numerical method combining finite elements and the boundary integral representation is used to investigate the transient scattering of ultrasonic waves by a crack in a plate. The incident wave models the guided waves generated by a steel ball impact on the plate. Two surface-breaking cracks and one subsurface crack are studied here. The results show that the location and depth of cracks have measurable effects on the surface responses in time and frequency domains. Also, the scattered fields have distinct differences in the three cases.

  9. Envelope solitons of acoustic plate modes and surface waves.

    PubMed

    Mayer, Andreas P; Kovalev, Alexander S

    2003-06-01

    The problem of the existence of evelope solitons in elastic plates and at solid surfaces covered by an elastic film is revisited with special attention paid to nonlinear long-wave short-wave interactions. Using asymptotic expansions and multiple scales, conditions for the existence of envelope solitons are established and it is shown how their parameters can be expressed in terms of the elastic moduli and mass densities of the materials involved. In addition to homogeneous plates, weak periodic modulation of the plate's material parameters are also considered. In the case of wave propagation in an elastic plate, modulations of weakly nonlinear carrier waves are governed by a coupled system of partial differential equations consisting of evolution equations for the complex amplitude of the carrier wave (the nonlinear Schrödinger equation for envelope solitons and the Mills-Trullinger equations for gap solitons), and the wave equation for long-wavelength acoustic plate modes. In contrast to this situation, envelope solitons of surface acoustic waves in a layered structure are normally described by the nonlinear Schrödinger equation alone. However, at higher orders of the carrier wave amplitude, the envelope soliton is found to be accompanied by a quasistatic long-wavelength strain field, which may be localized at the surface with penetration depth into the substrate of the order of the inverse amplitude or which may radiate energy into the bulk. A new set of modulation equations is derived for the resonant case of the carrier wave's group velocity being equal to the phase velocity of long-wavelength Rayleigh waves of the uncoated substrate.

  10. Ocean Wave Energy Harvesting Devices

    DTIC Science & Technology

    2007-04-01

    coupled to a suitable buoy platform. 2. The approach of designing a device which meets the requirements for mounting on dogfish and generating...used on the tail of a marine life such as dogfish to harvest energy as it swims. The output power can be used to trickle charge battery packs to power...to be mounted to a dogfish to harvest energy from its motion. Due to the small fish size (approximate 40-50 inches, 25 pounds), the device was

  11. Waves in periodic dissipative laminate metamaterial generated by plate impact

    NASA Astrophysics Data System (ADS)

    Navarro, Pedro Franco; Benson, David J.; Nesterenko, Vitali F.

    2017-01-01

    We investigated numerically the nature of high amplitude stress waves generated by plate impact on Al/W viscoplastic laminates with different cell sizes. Weakly attenuating localized travelling waves, closely resembling solitary waves, quickly form near the impacted surface at relatively short duration of incoming pulse. They have properties similar to solitary solutions of the Korteweg-de Vries equation with the dispersive and nonlinear parameters connected to laminate properties. The peak temperature in the localized stress wave is dramatically different than the temperature corresponding to the shock wave at the same pressure, reflecting different paths of loading. Increase of the duration of the incoming pulse results in a train of solitary pulses or in oscillatory stationary shock like stress waves. The leading front of the shock like stress wave is closely described by the rising part of solitary stress wave.

  12. Stress waves in isotropic elastic plate excited by circular transducer

    NASA Technical Reports Server (NTRS)

    Williams, J. H., Jr.; Lee, S. S.; Karagulle, H.

    1986-01-01

    Steady state harmonic stress waves in an isotropic elastic plate excited on one face by a circular transducer are analyzed theoretically. The transmitting transducer transforms an electrical voltage into a uniform normal stress at the top of the plate. To solve the boundary value problem,the radiation into a half-space is considered. The receiving transducer produces an electrical voltage proportional to the average spatially integrated normal stress over its face due to an incident wave. A numerical procedure is given to evaluate the frequency response at a receiving point due to a multiply reflected wave in the near field. Its stability and convergence are discussed. Parameterization plots which determine the particular wave whose frequency response has maximum magnitude compared with other multiple reflected waves are given for a range of values of dimensionless parameters. The effects of changes in the values of the parameters are discussed.

  13. Directional cloaking of flexural waves in a plate with a locally resonant metamaterial.

    PubMed

    Colombi, Andrea; Roux, Philippe; Guenneau, Sebastien; Rupin, Matthieu

    2015-04-01

    This paper deals with the numerical design of a directional invisibility cloak for backward scattered elastic waves propagating in a thin plate (A0 Lamb waves). The directional cloak is based on a set of resonating beams that are attached perpendicular to the plate and are arranged at a sub-wavelength scale in ten concentric rings. The exotic effective properties of this locally resonant metamaterial ensure coexistence of bandgaps and directional cloaking for certain beam configurations over a large frequency band. The best directional cloaking was obtained when the resonators' length decreases from the central to the outermost ring. In this case, flexural waves experience a vanishing index of refraction when they cross the outer layers, leading to a frequency bandgap that protects the central part of the cloak. Numerical simulation shows that there is no back-scattering in these configurations. These results might have applications in the design of seismic-wave protection devices.

  14. Wave propagation in a plate after impact by a projectile

    NASA Technical Reports Server (NTRS)

    El-Raheb, M.; Wagner, P.

    1987-01-01

    The wave propagation in a circular plate after impact by a cylindrical projectile is studied. In the vicinity of impact, the pressure is computed numerically. An intense pressure pulse is generated that peaks 0.2 microns after impact, then drops sharply to a plateau. The response of the plate is determined adopting a modal solution of Mindlin's equations. Velocity and acceleration histories display both propagating and dispersive features.

  15. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, Carol

    2010-06-08

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  16. Millimeter wave transmission systems and related devices

    NASA Technical Reports Server (NTRS)

    Hebert, L. M.

    1984-01-01

    A survey was made of the state-of-the-art in millimeter (20 GHz to 300 GHz) wave transmission systems and related devices. The survey includes summaries of analytical studies and theoretical results that were obtained for various transmission line structures. This material was supplemented by further analysis where appropriate. The transmission line structures are evaluated in terms of electrical performance, ease of manufacture, usefulness for building other devices and compatibility with solid state devices. Descriptions of waveguide transmission lines which have commonly been used in the microwave frequency range are provided along with special attention given to the problems that these guides face when their use is extended into the millimeter wave range. Also, guides which have been introduced specifically to satisfy the requirements of millimeter wave transmission are discussed in detail.

  17. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, legal representative, Carol

    2010-11-23

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  18. PLATE WAVE RESONANCE WITH AIR-COUPLED ULTRASONICS

    SciTech Connect

    Bar, H. N.; Dayal, V.; Barnard, D.; Hsu, D. K.

    2010-02-22

    Air-coupled ultrasonic transducers can excite plate waves in metals and composites. The coincidence effect, i.e., the wave vector of plate wave coincides with projection of exciting airborne sound vector, leads to a resonance which strongly amplifies the sound transmission through the plate. The resonance depends on the angle of incidence and the frequency. In the present study, the incidence angle for maximum transmission (theta{sub max}) is measured in plates of steel, aluminum, carbon fiber reinforced composites and honeycomb sandwich panels. The variations of (theta{sub max}) with plate thickness are compared with theoretical values in steel, aluminum and quasi-isotropic carbon fiber composites. The enhanced transmission of air-coupled ultrasound at oblique incidence can substantially improve the probability of flaw detection in plates and especially in honeycomb structures. Experimental air-coupled ultrasonic scan of subtle flaws in CFRP laminates showed definite improvement of signal-to-noise ratio with oblique incidence at theta{sub max}.

  19. Edge waves and resonances in two-dimensional phononic crystal plates

    NASA Astrophysics Data System (ADS)

    Hsu, Jin-Chen; Hsu, Chih-Hsun

    2015-05-01

    We present a numerical study on phononic band gaps and resonances occurring at the edge of a semi-infinite two-dimensional (2D) phononic crystal plate. The edge supports localized edge waves coupling to evanescent phononic plate modes that decay exponentially into the semi-infinite phononic crystal plate. The band-gap range and the number of edge-wave eigenmodes can be tailored by tuning the distance between the edge and the semi-infinite 2D phononic lattice. As a result, a phononic band gap for simultaneous edge waves and plate waves is created, and phononic cavities beside the edge can be built to support high-frequency edge resonances. We design an L3 edge cavity and analyze its resonance characteristics. Based on the band gap, high quality factor and strong confinement of resonant edge modes are achieved. The results enable enhanced control over acoustic energy flow in phononic crystal plates, which can be used in designing micro and nanoscale resonant devices and coupling of edge resonances to other types of phononic or photonic crystal cavities.

  20. Gas sensing with surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Martin, S. J.; Schweizer, K. S.; Ricco, A. J.; Zipperian, T. E.

    1985-03-01

    The use of a ZnO-on-Si surface acoustic wave (SAW) resonator as a gas sensor is discussed. In particular, the sensitivity of the device to organic vapors is examined. The planar nature of the SAW device, in which the acoustic energy is confined to within roughly one acoustic wavelength of the surface, makes the device extremely sensitive to surface perturbations. This characteristic has been exploited in the construction of SAW gas sensors in which the surface wave propagation characteristics are altered by species adsorbed from the ambient gas. The porous nature of the sputtered ZnO film, in conjunction with the microbalance capability of the SAW device, gives the sensor the ability to distinguish molecules on the basis of both size and mass.

  1. Amplitude-dependent Lamb wave dispersion in nonlinear plates.

    PubMed

    Packo, Pawel; Uhl, Tadeusz; Staszewski, Wieslaw J; Leamy, Michael J

    2016-08-01

    The paper presents a perturbation approach for calculating amplitude-dependent Lamb wave dispersion in nonlinear plates. Nonlinear dispersion relationships are derived in closed form using a hyperelastic stress-strain constitutive relationship, the Green-Lagrange strain measure, and the partial wave technique integrated with a Lindstedt-Poincaré perturbation approach. Solvability conditions are derived using an operator formalism with inner product projections applied against solutions to the adjoint problem. When applied to the first- and second-order problems, these solvability conditions lead to amplitude-dependent, nonlinear dispersion corrections for frequency as a function of wavenumber. Numerical simulations verify the predicted dispersion shifts for an example nonlinear plate. The analysis and identification of amplitude-dependent, nonlinear Lamb wave dispersion complements recent research focusing on higher harmonic generation and internally resonant waves, which require precise dispersion relationships for frequency-wavenumber matching.

  2. Active cloaking of flexural waves in thin plates

    NASA Astrophysics Data System (ADS)

    Futhazar, Gregory; Parnell, William J.; Norris, Andrew N.

    2015-11-01

    An active cloak consists of a set of discrete multipole sources distributed in space. When the source positions and amplitudes are carefully specified the active field destructively interferes with an incident time harmonic wave so as to nullify the total field in some finite domain and ensure that in the far field only the incident wave is present, i.e. the active field is non-radiating. Here it is shown how to efficiently determine the source coefficients explicitly in the context of flexural waves in thin plates. The work is carried out in the context of Kirchhoff plate theory, using the Rayleigh-Green theorem to derive the unique source amplitudes for a given incident flexural wave.

  3. Dynamic interfacial trapping of flexural waves in structured plates

    PubMed Central

    Craster, R. V.; Movchan, A. B.; Movchan, N. V.; Jones, I. S.

    2016-01-01

    The paper presents new results on the localization and transmission of flexural waves in a structured plate containing a semi-infinite two-dimensional array of rigid pins. In particular, localized waves are identified and studied at the interface boundary between the homogeneous part of the flexural plate and the part occupied by rigid pins. A formal connection has been made with the dispersion properties of flexural Bloch waves in an infinite doubly periodic array of rigid pins. Special attention is given to regimes corresponding to standing waves of different types as well as Dirac-like points that may occur on the dispersion surfaces. A single half-grating problem, hitherto unreported in the literature, is also shown to bring interesting solutions. PMID:27118892

  4. Higher order acoustoelastic Lamb wave propagation in stressed plates.

    PubMed

    Pei, Ning; Bond, Leonard J

    2016-11-01

    Modeling and experiments are used to investigate Lamb wave propagation in the direction perpendicular to an applied stress. Sensitivity, in terms of changes in velocity, for both symmetrical and anti-symmetrical modes was determined. Codes were developed based on analytical expressions for waves in loaded plates and they were used to give wave dispersion curves. The experimental system used a pair of compression wave transducers on variable angle wedges, with set separation, and variable frequency tone burst excitation, on an aluminum plate 0.16 cm thick with uniaxial applied loads. The loads, which were up to 600 με, were measured using strain gages. Model results and experimental data are in good agreement. It was found that the change in Lamb wave velocity, due to the acoustoelastic effect, for the S1 mode exhibits about ten times more sensitive, in terms of velocity change, than the traditional bulk wave measurements, and those performed using the fundamental Lamb modes. The data presented demonstrate the potential for the use of higher order Lamb modes for online industrial stress measurement in plate, and that the higher sensitivity seen offers potential for improved measurement systems.

  5. Gasoline identifier based on SH0 plate acoustic waves.

    PubMed

    Kuznetsova, Iren E; Zaitsev, Boris D; Seleznev, Eugenii P; Verona, Enrico

    2016-08-01

    The present paper is devoted to the development of gasoline identifier based on zero order shear-horizontal (SH0) acoustic wave propagating in piezoelectric plate. It has been found that the permittivity of gasoline is increased when its octane number rises. The development of such identifier is experimentally demonstrated to be possible.

  6. A theoretical analysis in the time-domain of wave reflection on a bone plate

    NASA Astrophysics Data System (ADS)

    Grimal, Quentin; Naïli, Salah

    2006-11-01

    This paper presents an original method for simulating ultrasonic wave reflection on a fluid-loaded plate. Geometrical and material parameters used are relevant to the "axial transmission technique" (ATT) setup. Devices based on the ATT are used for the assessment of cortical bone strength (estimate of a fracture risk). In this work, the cortical bone layer is represented as a plate of infinite extent surrounded by fluid (soft tissues). A line source and a receiver are placed in the fluid. Transient waves generated upon reflection at the plate-fluid interfaces are addressed. Analytic Green's functions are derived with the generalized ray/Cagniard-de Hoop method. The acoustic response is obtained upon convolution of Green's functions with a given source pulse. The method associates each wave amplitude in the time-domain (lateral waves, reflected body waves, etc.) to a specific term of the final solution. The method is ideally suited to a detailed analysis of the ultrasonic signal for various geometrical and mechanical parameters. The results presented highlight the potential of the method for the understanding of wave phenomena involved in the ATT and similar setups. They also bring new elements that reinforce our theoretical knowledge of the ATT.

  7. Broadband Lamb wave trapping in cellular metamaterial plates with multiple local resonances.

    PubMed

    Zhao, De-Gang; Li, Yong; Zhu, Xue-Feng

    2015-03-20

    We have investigated the Lamb wave propagation in cellular metamaterial plates constructed by bending-dominated and stretch-dominated unit-cells with the stiffness differed by orders of magnitude at an ultralow density. The simulation results show that ultralight metamaterial plates with textured stubs deposited on the surface can support strong local resonances for both symmetric and anti-symmetric modes at low frequencies, where Lamb waves at the resonance frequencies are highly localized in the vibrating stubs. The resonance frequency is very sensitive to the geometry of textured stubs. By reasonable design of the geometry of resonant elements, we establish a simple loaded-bar model with the array of oscillators having a gradient relative density (or weight) that can support multiple local resonances, which permits the feasibility of a broadband Lamb wave trapping. Our study could be potentially significant in designing ingenious weight-efficient acoustic devices for practical applications, such as shock absorption, cushioning, and vibrations traffic, etc.

  8. Stable operating regime for traveling wave devices

    DOEpatents

    Carlsten, Bruce E.

    2000-01-01

    Autophase stability is provided for a traveling wave device (TWD) electron beam for amplifying an RF electromagnetic wave in walls defining a waveguide for said electromagnetic wave. An off-axis electron beam is generated at a selected energy and has an energy noise inherently arising from electron gun. The off-axis electron beam is introduced into the waveguide. The off-axis electron beam is introduced into the waveguide at a second radius. The waveguide structure is designed to obtain a selected detuning of the electron beam. The off-axis electron beam has a velocity and the second radius to place the electron beam at a selected distance from the walls defining the waveguide, wherein changes in a density of the electron beam due to the RF electromagnetic wave are independent of the energy of the electron beam to provide a concomitant stable operating regime relative to the energy noise.

  9. Characterization and Scaling of Heave Plates for Ocean Wave Energy Converters

    NASA Astrophysics Data System (ADS)

    Rosenberg, Brian; Mundon, Timothy

    2016-11-01

    Ocean waves present a tremendous, untapped source of renewable energy, capable of providing half of global electricity demand by 2040. Devices developed to extract this energy are known as wave energy converters (WECs) and encompass a wide range of designs. A somewhat common archetype is a two-body point-absorber, in which a surface float reacts against a submerged "heave" plate to extract energy. Newer WEC's are using increasingly complex geometries for the submerged plate and an emerging challenge in creating low-order models lies in accurately determining the hydrodynamic coefficients (added mass and drag) in the corresponding oscillatory flow regime. Here we present experiments in which a laboratory-scale heave plate is sinusoidally forced in translation (heave) and rotation (pitch) to characterize the hydrodynamic coefficients as functions of the two governing nondimensional parameters, Keulegan-Carpenter number (amplitude) and Reynolds number. Comparisons against CFD simulations are offered. As laboratory-scale physical model tests remain the standard for testing wave energy devices, effects and implications of scaling (with respect to a full-scale device) are also investigated.

  10. Application of Lamb waves for the characterization of composite plates

    SciTech Connect

    Agostini, Valentina; Delsanto, Pier P.; Olivero, Dimitri; Baboux, Jean-C.; Monnier, Thomas

    1999-12-02

    In order to detect and evaluate flaws in thin composite structures, such as skins on aircraft wings or sail boat bodies, Lamb waves are the preferred tool of ultrasonic excitation. In the framework of a European Brite EuRam project, we have been involved in the problem of damage assessment in smart composite plates. Our goal is to predict the system signature and to identify optimal signal extraction routines. Given the wave frequency, thickness and physical properties of the materials, we simulate, using the Local Interaction Simulation Approach (LISA), the propagation of Lamb waves in carbon fiber reinforced plates and their interaction with defects and compare the numerical results with the experimental data.

  11. Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase-change Metasurface

    PubMed Central

    Wang, Dacheng; Zhang, Lingchao; Gu, Yinghong; Mehmood, M. Q.; Gong, Yandong; Srivastava, Amar; Jian, Linke; Venkatesan, T.; Qiu, Cheng-Wei; Hong, Minghui

    2015-01-01

    Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices. PMID:26442614

  12. Nonlinear Viscous Waves Produced by AN Impulsively Moving Plate.

    NASA Astrophysics Data System (ADS)

    Yang, Shih-An.

    1989-12-01

    The free-surface flow generated by an impulsively accelerating, surface-piercing, vertical plate has been studied numerically as well as experimentally. The two -dimensional, unsteady Navier-Stokes equations are discretized using the finite-analytic scheme which incorporates the analytic solution into the locally linearized differential equations. The continuity equation and the dynamic boundary conditions on normal and tangential stresses at the free surface are applied to determine the pressure and two velocity components at the free surface. The kinematic boundary condition on the free surface provides the movement of the free surface. A series of experiments is carried out in an open channel with a constant water depth. The flat vertical plate is fixed on a towing carriage which is set off by suddenly dropping a weight bucket through a connecting steel cable in a pulley system. The free-surface profile ahead of the plate and the pressure distribution on the plate surface are measured. The agreement of the free -surface profile and the pressure distribution between the numerical results and the experimental measurements is fairly good. The mathematical singularity, which is predicted by the potential-flow theory, at the contact line between the plate and the free surface is not observed in the physical experiments. The flow field around the moving contact line is studied by applying the present numerical code. The contact angle between the free surface and the vertical plate is found to be very close to that formed by the free surface of a fluid contained in a rectangular tank which moves with the same constant acceleration. The velocity of the moving contact line is thereby derived as a function of the acceleration of the plate based on the principle of the conservation of mass. The propagation of waves produced by a moving plate along the channel is also investigated numerically. The propagation speed of generated waves is close to that of shallow-water waves

  13. Guided wave phased array beamforming and imaging in composite plates.

    PubMed

    Yu, Lingyu; Tian, Zhenhua

    2016-05-01

    This paper describes phased array beamforming using guided waves in anisotropic composite plates. A generic phased array algorithm is presented, in which direction dependent guided wave parameters and the energy skew effect are considered. This beamforming at an angular direction is achieved based on the classic delay-and-sum principle by applying phase delays to signals received at array elements and adding up the delayed signals. The phase delays are determined with the goal to maximize the array output at the desired direction and minimize it otherwise. For array characterization, the beam pattern of rectangular grid arrays in composite plates is derived. In addition to the beam pattern, the beamforming factor in terms of wavenumber distribution is defined to provide intrinsic explanations for phased array beamforming. The beamforming and damage detection in a composite plate are demonstrated using rectangular grid arrays made by a non-contact scanning laser Doppler vibrometer. Detection images of the composite plate with multiple surface defects at various directions are obtained. The results show that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  14. Guiding of elastic waves in a two-dimensional graded phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Guo, Yuning; Hettich, Mike; Dekorsy, Thomas

    2017-01-01

    The guiding of elastic waves in a two-dimensional graded phononic crystal plate is investigated. This effect is induced by the resonance coupling of attachments and matrix in a silicon pillar-substrate system and the resonance frequencies of guided surface modes can be tuned by tailoring the geometry and material properties of the pillars. The resonance frequencies increase with radius and Young’s modulus, and decrease with height and density of the pillars, which provides several possibilities for the guiding of elastic waves. These devices show the capability of spatially selecting different frequencies into designed channels, thus acting as a phononic multi-channel filter.

  15. Plate damage identification using wave propagation and impedance methods.

    SciTech Connect

    Wait, J. R.; Park, G. H.; Sohn, H.; Farrar, C. R.

    2004-01-01

    This paper illustrates an integrated approach for identifying structural damage in an aluminum plate. Piezoelectric (PZT) materials are used to actuatehense the dynamic response of the structure. Two damage identification techniques are integrated in this study, including Lamb wave propagations and impedance methods. In Lamb wave propagations, one PZT launches an elastic wave through the structure, and responses are measured by an array of PZT sensors. The changes in both wave attenuation and reflection are used to detect and locate the damage. The impedance method monitors the variations in structural mechanical impedance, which is coupled with the electrical impedance of the PZT. Both methods operate in high frequency ranges at which there are measurable changes in structural responses even for incipient damage such as small cracks or loose connections. This paper summarizes two methods used for damage identification, experimental procedures, and additional issues that can be used as a guideline for future investigations.

  16. Elastic guided waves in plates with surface roughness. II. Experiments

    SciTech Connect

    Lobkis, O.I.; Chimenti, D.E.

    1997-07-01

    In this artice are reported fundamental experimental measurements on guided waves in plates with surface roughness; the experimental data are critically compared to theoretical calculations presented in Part I. All experiments, in either immersion or contact coupling mode, are modeled by the theory developed in I that exploits the phase-screen approximation. In this theory the effect of the rough surface on the received signal, on a local scale, is assumed to be restricted to the signal phase. The comparisons between experiment and predictions show good agreement in most regimes, despite the rather simplifying approximations contained in the calculation. The model is shown to fail only when the guided wave vector is close to a branch point, that is when the guided wave phase velocity approaches the compressional or shear wavespeeds of the plate. Near these values the internal partial waves comprising the guided wave strike the surfaces at grazing incidence or are evanescent, and a simple phase-screen model cannot account for this behavior. Elsewhere in the guided wave spectrum, agreement is quite good. Of practical significance is the finding that the rough-surface damping contrast can be maximized by configuring the experimental conditions to measure just below and well above the compressional critical angle. Aluminum samples, prepared by indenting or sandblasting and independently profiled to determine rms roughness, are measured in immersion and in contact transduction, the latter with wedge couplers and line sources. The influence of the roughness in immersion experiments is strongly affected by whether the upper or lower plate surface is rough, but only in the interaction zone between specular and nonspecular reflection components. {copyright} {ital 1997 Acoustical Society of America.}

  17. Sensitivity of higher order acoustoelastic Lamb wave in stressed plates

    NASA Astrophysics Data System (ADS)

    Pei, Ning; Bond, Leonard J.

    2017-02-01

    Residual stress can occur during various metal working processes including rolling, forging and welding. Such stress can impact the performance of the material, including generating cracking and corrosion. To better control residual stresses, the initial distribution of stresses in materials must be known. Ultrasonic methods can be used as a good tool for non-destructive residual stress characterization and this can be achieved at modest cost. One approach is to employ Lamb waves the acoustoelastic effect for thin plate materials. This paper reports a study in which a numerical model is used to investigate Lamb wave dispersion curves for plates under load. The numerical result shows that the sensitivity of different modes varies and that the S1 mode is the most sensitivity to the effects of load, as compared with S0, A0 and A1 modes. If a local load of 100 MPa is applied the change in velocity for the S1 mode can be as large to 40 m/s, which is about 6 times more than the effect on traditional bulk waves. This makes the S1 mode potentially a good option for residual stress characterization in thin plates industry application.

  18. Shock Waves Impacting Composite Material Plates: The Mutual Interaction

    NASA Astrophysics Data System (ADS)

    Andreopoulos, Yiannis

    2013-02-01

    High-performance, fiber-reinforced polymer composites have been extensively used in structural applications in the last 30 years because of their light weight combined with high specific stiffness and strength at a rather low cost. The automotive industry has adopted these materials in new designs of lightweight vehicles. The mechanical response and characterization of such materials under transient dynamic loading caused with shock impact induced by blast is not well understood. Air blast is associated with a fast traveling shock front with high pressure across followed by a decrease in pressure behind due to expansion waves. The time scales associated with the shock front are typically 103 faster than those involved in the expansion waves. Impingement of blast waves on structures can cause a reflection of the wave off the surface of the structure followed by a substantial transient aerodynamic load, which can cause significant deformation and damage of the structure. These can alter the overpressure, which is built behind the reflected shock. In addition, a complex aeroelastic interaction between the blast wave and the structure develops that can induce reverberation within an enclosure, which can cause substantial overpressure through multiple reflections of the wave. Numerical simulations of such interactions are quite challenging. They usually require coupled solvers for the flow and the structure. The present contribution provides a physics-based analysis of the phenomena involved, a critical review of existing computational techniques together with some recent results involving face-on impact of shock waves on thin composite plates.

  19. Wave energy devices with compressible volumes.

    PubMed

    Kurniawan, Adi; Greaves, Deborah; Chaplin, John

    2014-12-08

    We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power take-off (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000 m(3) and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s.

  20. Wave energy devices with compressible volumes

    PubMed Central

    Kurniawan, Adi; Greaves, Deborah; Chaplin, John

    2014-01-01

    We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power take-off (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000 m3 and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s. PMID:25484609

  1. Research on metal-plated cellulose nitrate flakes and their infrared / millimeter wave characteristics

    NASA Astrophysics Data System (ADS)

    Ye, Shu-qin; Zhu, Chen-guang; Wang, Li-hong; Ou'yang, De-hua; Pan, Gong-pei

    2016-10-01

    Copper-plated and silver-plated cellulose nitrate flakes, which were prepared by using chemical plating technology, were used to jam infrared detector and millimeter-wave radar. It was tested for the conductivity and infrared jamming performance of plating and also the RCS (Radar Cross Section) performance of millimeter-wave radar. Test results showed that the prepared metal-plated cellulose nitrate flakes have obvious conductivity, and infrared total radiation energy of silver plating and copper plating had approximately increased 32% and 21% respectively. Through determination, the millimeter-wave reflecting property and RCS of silver-plated cellulose nitrate flakes were higher than that of copper-plated cellulose nitrate flakes. Therefore, silver-plated cellulose nitrate flakes can be used as an effective infrared / millimeter wave composite jamming material.

  2. Low frequency guided plate wave propagation in fiber reinforced composites

    SciTech Connect

    Lih, S.S.; Mal, A.K.; Bar-Cohen, Y.

    1995-12-31

    The behavior of low frequency guided waves in composite laminates was studied theoretically and experimentally. The objective of this study is to develop a contact-coupling ultrasonic method of determining of the stiffness constants of composite materials. The solution for the low frequency guided wave modes was derived from exact and approximate plate theories. A parametric study was curried out to examine the influence of variations in the elastic stiffness constants on the guided wave modes. A comparison was made between the measured and calculated group velocities to corroborate the theoretical calculations. The experimental setup consisted of a contact coupled pair of transmitting and receiving transducers using pulsed waves and a broadband ultrasonic system. Graphite/epoxy laminates were tested by transmitting the wave along various angles of propagation with the fibers. The received signals were analyzed to determine the group velocity of the low frequency wave modes. Test results have shown a very, good agreement of the calculated and measured elastic constants.

  3. Waves in Periodic Dissipative Laminate Metamaterial Generated by Plate Impact

    NASA Astrophysics Data System (ADS)

    Franco Navarro, Pedro; Benson, David; Nesterenko, Vitali

    2015-06-01

    Waves generated by plate impact loading of Al/W laminates with different size of cell were investigated numerically depending on the impactor/cell mass ratio. The materials model took into account viscoplastic behavior of materials. It was observed that this mass ratio has a direct impact on the structure of stress pulses traveling through the composite. At the small impactor/cell mass ratio travelling waves closely resembling solitary waves were quickly formed near the impacted surface. They propagate as quasistationary weakly attenuating localized pulses. The properties of these pulses were satisfactory described based on a theoretical model using dispersive and nonlinear parameters of the materials similar to solitary solutions for the Korteweg-de Vries equation (KdV). The temperature at given pressure at the maximum is dramatically different then the temperature corresponding to the shock wave at the same pressure reflecting a different paths of loading. Increase of impactor/cell mass ratio results in the train of solitary like pulses which number increased with the increase of the impactor/cell mass ratio. At large impactor/cell mass ratio oscillatory stationary shock waves were formed. The leading front of these stationary shock waves was closely described by a solitary like pulse observed at small impactor/cell mass ratio. One of the authors (PFN) was supported by UCMexus Fellowship

  4. Interaction of guided waves with delaminations in composite plate structures

    NASA Astrophysics Data System (ADS)

    Gupta, Saurabh; Yu, Xudong; Fan, Zheng; Rajagopal, Prabhu

    2017-02-01

    This paper addresses a gap in the literature on the 3-dimensional scattering of the fundamental symmetric Lamb mode S0 from delimitations in composite plates. We study the scattering of low-frequency S0 Lamb mode from a delamination in a stiffened 4-ply CFRP composite plate with [0/0]S ply orientation. Far field scattering coefficients for the S0 Lamb mode are plotted as a function of circumferential position around the delamination using 3D FE simulations. Results show that the delamination size has less influence on S0 Lamb wave scattering in the low-frequency regime where the S0 mode is non-dispersive. Further analysis was done using two-dimensional FE simulation for different ply-layup orientations with S0 Lamb mode. This study shows that ply-layup orientation and through-thickness delamination location in fiber composite laminate have a significant influence on S0 Lamb mode interaction. We also analyzed the interaction of A0 Lamb mode for a few cases. This work will be useful for practical Lamb wave based inspection of composite plate structures.

  5. Surface acoustic wave devices for sensor applications

    NASA Astrophysics Data System (ADS)

    Bo, Liu; Xiao, Chen; Hualin, Cai; Mohammad, Mohammad Ali; Xiangguang, Tian; Luqi, Tao; Yi, Yang; Tianling, Ren

    2016-02-01

    Surface acoustic wave (SAW) devices have been widely used in different fields and will continue to be of great importance in the foreseeable future. These devices are compact, cost efficient, easy to fabricate, and have a high performance, among other advantages. SAW devices can work as filters, signal processing units, sensors and actuators. They can even work without batteries and operate under harsh environments. In this review, the operating principles of SAW sensors, including temperature sensors, pressure sensors, humidity sensors and biosensors, will be discussed. Several examples and related issues will be presented. Technological trends and future developments will also be discussed. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the China Postdoctoral Science Foundation (CPSF).

  6. Metal-mesh achromatic half-wave plate for use at submillimeter wavelengths.

    PubMed

    Pisano, Giampaolo; Savini, Giorgio; Ade, Peter A R; Haynes, Vic

    2008-11-20

    A metal-mesh achromatic half-wave plate (HWP) has been designed, manufactured, and tested for potential use in millimeter and submillimeter astronomical instruments. The prototype device presented here is based on a 12-grid Shatrow [IEEE Trans. Antennas Propag. 43, 109 (1995)] recipe to operate over the frequency range of 120-180 GHz. Transmission line modeling and finite-element analysis [Ansoft HFSS website: http://www.ansoft.com/hfss/] were used to optimize the design geometrical parameters in terms of the device transmission, reflection, absorption, phase-shift, and cross-polarization as a function of frequency. The resulting prototype device was constructed and characterized using incoherent radiation from a polarizing Fourier transform spectrometer to explore its frequency and polarization behavior. These measurements are shown to be in excellent agreement with the models. Lists of the achieved HWP performance characteristics are reported.

  7. Scattering of guided waves at delaminations in composite plates.

    PubMed

    Murat, Bibi I S; Khalili, Pouyan; Fromme, Paul

    2016-06-01

    Carbon fiber laminate composites are increasingly employed for aerospace structures as they offer advantages, such as a good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, fiber and matrix breakage or delaminations can occur, reducing the load carrying capacity of the structure. Efficient nondestructive testing and structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The scattering of the A0 Lamb wave mode at delaminations was investigated using a full three-dimensional (3D) finite element (FE) analysis. The influence of the delamination geometry (size and depth) was systematically evaluated. In addition to the depth dependency, a significant influence of the delamination width due to sideways reflection of the guided waves within the delamination area was found. Mixed-mode defects were simulated using a combined model of delamination with localized material degradation. The guided wave scattering at cross-ply composite plates with impact damage was measured experimentally using a non-contact laser interferometer. Good agreement between experiments and FE predictions using the mixed-mode model for an approximation of the impact damage was found.

  8. Spinning wave plate design for retinal birefringence scanning

    NASA Astrophysics Data System (ADS)

    Irsch, K.; Gramatikov, B. I.; Wu, Y.-K.; Guyton, D. L.

    2009-02-01

    To enhance foveal fixation detection while bypassing the deleterious effects of corneal birefringence in retinal birefringence scanning (RBS), we developed a new RBS design introducing a double-pass spinning half wave plate (HWP) and a fixed double-pass retarder into the optical system. Utilizing the measured corneal birefringence from a data set of 300 human eyes, an algorithm and a related computer program, based on Mueller-Stokes matrix calculus, were developed in MATLAB for optimizing the properties of both wave plates. Foveal fixation detection was optimized with the HWP spun 9/16 as fast as the circular scan, with the fixed retarder having a retardance of 45° and fast axis at 90°. With this new RBS design, a significant statistical improvement of 7.3 times in signal strength, i.e. FFT power, was achieved for the available data set compared with the previous RBS design. The computer-model-optimized RBS design has the potential not only for eye alignment screening, but also for remote fixation sensing and eye tracking applications.

  9. Generalized concept of shear horizontal acoustic plate mode and Love wave sensors

    NASA Astrophysics Data System (ADS)

    McHale, Glen

    2003-11-01

    An approach to mass and liquid sensitivity for both the phase velocity and insertion loss of shear mode acoustic wave sensors based on the dispersion equations for layered systems is outlined. The approach is sufficiently general to allow for viscoelastic guiding layers. An equation for the phase velocity and insertion loss sensitivities is given which depends on the slope of the complex phase velocity dispersion curves. This equation contains the equivalent of the Sauerbrey and Kanazawa equations for loading of a quartz crystal microbalance by rigid mass and Newtonian liquids, respectively, and also describes surface loading by viscoelastic layers. The theoretical approach can be applied to a four-layer system, with any of the four layers being viscoelastic, so that mass deposition from a liquid can also be modelled. The theoretical dispersion equation based approach to layer-guided shear horizontal acoustic wave modes on finite substrates presented in this work provides a unified view of Love wave and shear horizontal acoustic plate mode (SH-APM) devices, which have been generally regarded as distinct in sensor research. It is argued that SH-APMs with guiding layers possessing shear acoustic speeds lower than that of the substrate and Love waves are two branches of solution of the same dispersion equation. The layer guided SH-APMs have a phase velocity higher than that of the substrate and the Love waves a phase velocity lower than that of the substrate. Higher-order Love wave modes are continuations of the layer-guided SH-APMs. The generalized concept of SH-APMs and Love waves provides a basis for understanding the change in sensitivity with higher-frequency operation and the relationship between multiple modes in Love wave sensors. It also explains why a relatively thick layer of a high-loss polymer can be used as a waveguide layer and so extends the range of materials that can be considered experimentally. Moreover, it is predicted that a new type of sensor, a

  10. Broadband Lamb Wave Trapping in Cellular Metamaterial Plates with Multiple Local Resonances

    PubMed Central

    Zhao, De-Gang; Li, Yong; Zhu, Xue-Feng

    2015-01-01

    We have investigated the Lamb wave propagation in cellular metamaterial plates constructed by bending-dominated and stretch-dominated unit-cells with the stiffness differed by orders of magnitude at an ultralow density. The simulation results show that ultralight metamaterial plates with textured stubs deposited on the surface can support strong local resonances for both symmetric and anti-symmetric modes at low frequencies, where Lamb waves at the resonance frequencies are highly localized in the vibrating stubs. The resonance frequency is very sensitive to the geometry of textured stubs. By reasonable design of the geometry of resonant elements, we establish a simple loaded-bar model with the array of oscillators having a gradient relative density (or weight) that can support multiple local resonances, which permits the feasibility of a broadband Lamb wave trapping. Our study could be potentially significant in designing ingenious weight-efficient acoustic devices for practical applications, such as shock absorption, cushioning, and vibrations traffic, etc. PMID:25790858

  11. Fatigue crack detection in a plate girder using Lamb waves

    NASA Astrophysics Data System (ADS)

    Greve, D. W.; Oppenheim, I. J.; Wu, Wei; Zheng, Peng

    2007-04-01

    We report on the application of wafer-type PZT transducers to the detection of flaws in steel plate girders. In these experiments one transducer is used to emit a pulse and the second receives the pulse and reflections from nearby boundaries, flaws, or discontinuities (pitch-catch mode). In this application there will typically be numerous reflections observed in the undamaged structure. A major challenge is to recognize new reflections caused by fatigue cracks in the presence of these background reflections. A laboratory specimen plate girder was fabricated at approximately half scale, 910 mm deep with an h/t ratio of 280 for the web and a b/t ratio of 16 for the flanges, and with transverse stiffeners fabricated with a web gap at the tension flange. Two wafer-type transducers were mounted on the web approximately 175 mm from the crack location, one on each side of the stiffener. The transducers were operated in pitch-catch mode, excited by a windowed sinusoid to create a narrowband transient excitation. The transducer location relative to the crack corresponded to a total included angle of roughly 30 degrees in the path reflecting from the crack. Cyclic loading was applied to develop a distortion-induced fatigue crack in the web at the web gap location. After appearance of the crack, ultrasonic measurements were performed at a range of center frequencies below the cutoff frequency of the A1 Lamb wave mode. Subsequently the crack was extended mechanically to simulate crack growth under primary longitudinal (bending) stress and the measurements were repeated. Direct differencing of the signals showed arrivals at times corresponding to reflection from the crack location, growing in amplitude as the crack was lengthened mechanically. These results demonstrate the utility of Lamb waves for crack detection even in the presence of numerous background reflections.

  12. Guided wave propagation in metallic and resin plates loaded with water on single surface

    NASA Astrophysics Data System (ADS)

    Hayashi, Takahiro; Inoue, Daisuke

    2016-02-01

    Our previous papers reported dispersion curves for leaky Lamb waves in a water-loaded plate and wave structures for several typical modes including quasi-Scholte waves [1,2]. The calculations were carried out with a semi-analytical finite element (SAFE) method developed for leaky Lamb waves. This study presents SAFE calculations for transient guided waves including time-domain waveforms and animations of wave propagation in metallic and resin water-loaded plates. The results show that non-dispersive and non-attenuated waves propagating along the interface between the fluid and the plate are expected for effective non-destructive evaluation of such fluid-loaded plates as storage tanks and transportation pipes. We calculated transient waves in both steel and polyvinyl chloride (PVC) plates loaded with water on a single side and input dynamic loading from a point source on the other water-free surface as typical examples of metallic and resin plates. For a steel plate, there exists a non-dispersive and non-attenuated mode, called the quasi-Scholte wave, having an almost identical phase velocity to that of water. The quasi-Scholte wave has superior generation efficiency in the low frequency range due to its broad energy distribution across the plate, whereas it is localized near the plate-water interface at higher frequencies. This means that it has superior detectability of inner defects. For a PVC plate, plural non-attenuated modes exist. One of the non-attenuated modes similar to the A0 mode of the Lamb wave in the form of a group velocity dispersion curve is promising for the non-destructive evaluation of the PVC plate because it provides prominent characteristics of generation efficiency and low dispersion.

  13. Sensitivity of surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Filipiak, Jerzy; Zubko, Konrad

    2001-08-01

    The SAW devices are widely used as filters, delay lines, resonators and gas sensors. It is possible to use it as mechanical force. The paper describes sensitivity of acceleration sensor based on SAW using the Rayleigh wave propagation. Since characteristic of acceleration SAW sensors are largely determined by piezoelectric materials, it is very important to select substrate with required characteristics. Researches and numerical modeling based on simply sensor model include piezoelectric beam with unilateral free end. An aggregated mass is connected to the one. The dimension and aggregated mass are various. In this case a buckling stress and sensitivity are changed. Sensitivity in main and perpendicular axis are compare for three sensor based on SiO2, LiNbO3, Li2B4O7. Influences of phase velocity, electro-mechanical coupling constant and density on sensitivity are investigated. Some mechanical parameters of the substrates in dynamic work mode are researched using sensor model and Rayleigh model of vibrations without vibration damping. The model is useful because it simply determines dependencies between sensor parameters and substrate parameters. Differences between measured and evaluated quantities are less than 5 percent. Researches based on sensor modes, which fulfilled mechanical specifications similarly to aircraft navigation.

  14. Lamb wave scattering by a surface-breaking crack in a plate

    NASA Technical Reports Server (NTRS)

    Datta, S. K.; Al-Nassar, Y.; Shah, A. H.

    1991-01-01

    An NDE method based on finite-element representation and modal expansion has been developed for solving the scattering of Lamb waves in an elastic plate waveguide. This method is very powerful for handling discontinuities of arbitrary shape, weldments of different orientations, canted cracks, etc. The advantage of the method is that it can be used to study the scattering of Lamb waves in anisotropic elastic plates and in multilayered plates as well.

  15. Wavelet Spectral Finite Elements for Wave Propagation in Composite Plates with Damages - Years 3-4

    DTIC Science & Technology

    2014-05-23

    spectral element to obtain all the lamb wave modes. Validated the element with the conventional finite elements -Formulated the wavelet spectral...efforts -Formulated Wavelet Spectral element for a healthy composite plates and used the formulated spectral element to obtain all the lamb wave modes...modeling of Lamb wave propagation in healthy composite plates through experimental measurements and conventional FEM; 3. Implemented ‘baseline-free

  16. Sensitivity comparisons of layered Rayleigh wave and Love wave acoustic devices

    NASA Astrophysics Data System (ADS)

    Pedrick, Michael K.; Tittmann, Bernhard R.

    2007-04-01

    Due to their high sensitivity, layered Surface Acoustic Wave (SAW) devices are ideal for various film characterization and sensor applications. Two prominent wave types realized in these devices are Rayleigh waves consisting of coupled Shear Vertical and Longitudinal displacements and Love waves consisting of Shear Horizontal displacements. Theoretical calculations of sensitivity of SAW devices to pertubations in wave propagation are limited to idealized scenarios. Derivations of sensitivity to mass change in an overlayer are often based on the effect of rigid body motion of the overlayer on the propagation of one of the aforementioned wave types. These devices often utilize polymer overlayers for enhanced sensitivity. The low moduli of such overlayers are not sufficiently stiff to accommodate the rigid body motion assumption. This work presents device modeling based on the Finite Element Method. A coupled-field model allows for a complete description of device operation including displacement profiles, frequency, wave velocity, and insertion loss through the inclusion of transmitting and receiving IDTs. Geometric rotations and coordinate transformations allow for the modeling of different crystal orientations in piezoelectric substrates. The generation of Rayleigh and Love Wave propagation was realized with this model by examining propagation in ST Quartz both normal to and in the direction of the X axis known to support Love Waves and Rayleigh Waves, respectively. Sensitivities of layered SAW devices to pertubations in mass, layer thickness, and mechanical property changes of a Polymethyl methacrylate (PMMA) and SU-8 overlayers were characterized and compared. Experimental validation of these models is presented.

  17. Acoustic wave based MEMS devices for biosensing applications.

    PubMed

    Voiculescu, Ioana; Nordin, Anis Nurashikin

    2012-03-15

    This paper presents a review of acoustic-wave based MEMS devices that offer a promising technology platform for the development of sensitive, portable, real-time biosensors. MEMS fabrication of acoustic wave based biosensors enables device miniaturization, power consumption reduction and integration with electronic circuits. For biological applications, the biosensors are integrated in a microfluidic system and the sensing area is coated with a biospecific layer. When a bioanalyte interacts with the sensing layer, mass and viscosity variations of the biospecific layer can be detected by monitoring changes in the acoustic wave properties such as velocity, attenuation, resonant frequency and delay time. Few types of acoustic wave devices could be integrated in microfluidic systems without significant degradation of the quality factor. The acoustic wave based MEMS devices reported in the literature as biosensors and presented in this review are film bulk acoustic wave resonators (FBAR), surface acoustic waves (SAW) resonators and SAW delay lines. Different approaches to the realization of FBARs, SAW resonators and SAW delay lines for various biochemical applications are presented. Methods of integration of the acoustic wave MEMS devices in the microfluidic systems and functionalization strategies will be also discussed.

  18. Plate Wave Transmission/reflection at Geometric Obstructions: Experiment

    NASA Astrophysics Data System (ADS)

    Reusser, R. S.; Chimenti, D. E.; Holland, S. D.; Roberts, R. A.

    2010-02-01

    This paper reports on the experimental examination of the transmission and reflection characteristics of arbitrarily shaped geometric obstructions in problems of plate wave propagation, such as joints, stiffeners, thickness transitions, and bends. The motivation for this work is noise source location in structures, the specific application being the location of air leaks in spacecraft skins, funded by NASA. In this work, it has been demonstrated that leaks can be located at a distance using array-based sensors which determine direction of signal propagation at the sensor location. The limiting factor in practice is the influence of geometric obstructions between the leak and sensor. This work reports a quantitative examination of the transmission properties of various obstructions such as stiffening ribs. Surface motions arising from a distance source are recorded over a local array of spatial positions using a scanned laser vibrometer. Spatial Fourier analysis is then applied to determine the individual contributions of the constituent mode types to the measured signals. Transmission properties of intervening geometric obstructions are determined by comparison to unobstructed signals. Comparisons to theoretical predictions of transmission characteristics will be presented for selected cases.

  19. Propagation of electromagnetic wave packets in iron-yttrium garnet plates and films

    SciTech Connect

    Visatskas, A.V.; Ivashka, V.P.; Meshkauskas, I.I.

    1987-10-01

    The propagation of wave packets and harmonic waves in iron-yttrium garnet (YIG) polycrystalline plates and single-crystalline films is studied. The basic parameters of the waves are determined with the use of the equations for a flat waveguide and also the equations of magnetostatics. The theoretical results agree well with the experimental results.

  20. Leaky lamb waves of a piezoelectric plate subjected to conductive fluid loading: an experimental study.

    PubMed

    Lee, Yung-Chun; Kuo, Shi Hoa

    2006-09-01

    This paper proposes a novel experimental method for measuring the propagating characteristics of leaky Lamb waves in a piezoelectric plate surrounded by a fluid. It is a differential type of measurement and is very sensitive to the velocity change and wave attenuation of leaky Lamb waves induced by fluid-loading effects. Experimental measurements on an X-cut LiNbO3 plate immersed in a dielectric and conductive fluid have been carried out. The velocity change and wave attenuation of the leaky Lamb waves caused by dielectric and conductive loadings of the fluid have been experimentally determined. The measured data have been compared with the theoretical ones that are calculated from a partial wave analysis. For the wave velocity, very good agreements between the experimental and theoretical results are observed. For the wave attenuation, there are some discrepancies, but an important characteristic in the relationship between wave attenuation and fluid conductivity as predicted by the theory have been verified experimentally.

  1. Evaluation of Thickness Reduction in a Thin Plate Using a Non-Contact Guided Wave Technique

    SciTech Connect

    Song, Won-Joon; Park, Ik-Keun; Kim, Tae-Hyung; Kim, Hyun-Mook; Kim, Yong-Kwon; Cho, Yong-Sang

    2006-03-06

    Ultrasonic guided waves are widely being studied and successfully applied to various non-destructive tests with the advantage of a long range inspection. Recently, non-contact methods are also adopted and combined with the guided wave techniques. In this paper, an advanced technique for the nondestructive detection of thinning defects simulating hidden corrosion in thin plates using non-contact guided waves is presented. The proposed approach uses EMAT(Electro-Magnetic Acoustic Transducer) for the non-contact generation and detection of guided plate waves in aluminum plates. Interesting features of the dispersive behavior in selected wave modes are used for the detection of plate thinning. The experimental results show that the mode cutoff measurements provide a qualitative measurement of thinning defects and change in the mode group velocity can be used as quantitative parameter of thinning depth measurement.

  2. Traveling wave device for combining or splitting symmetric and asymmetric waves

    DOEpatents

    Möbius, Arnold; Ives, Robert Lawrence

    2005-07-19

    A traveling wave device for the combining or splitting of symmetric and asymmetric traveling wave energy includes a feed waveguide for traveling wave energy, the feed waveguide having an input port and a launching port, a reflector for coupling wave energy between the feed waveguide and a final waveguide for the collection and transport of wave energy to or from the reflector. The power combiner has a launching port for symmetrical waves which includes a cylindrical section coaxial to the feed waveguide, and a launching port for asymmetric waves which includes a sawtooth rotated about a central axis.

  3. Analysis of second-harmonic generation by primary ultrasonic guided wave propagation in a piezoelectric plate.

    PubMed

    Deng, Mingxi; Xiang, Yanxun

    2015-08-01

    The effect of second-harmonic generation (SHG) by primary ultrasonic guided wave propagation is analyzed, where the nonlinear elastic, piezoelectric, and dielectric properties of the piezoelectric plate material are considered simultaneously. The formal solution of the corresponding second-harmonic displacement field is presented. Theoretical and numerical investigations clearly show that the SHG effect of primary guided wave propagation is highly sensitive to the electrical boundary conditions of the piezoelectric plate. The results obtained may provide a means through which the SHG efficiency of ultrasonic guided wave propagation can effectively be regulated by changing the electrical boundary conditions of the piezoelectric plate.

  4. [Determination of optical axis of quartz wave plate based on spectroscopic ellipsometer].

    PubMed

    Zhang, Bei-Bei; Han, Pei-Gao; Fu, Shi-Rong; Zhu, Jiu-Kai; Yan, Ke-Zhu

    2013-01-01

    The optical axis is one of the most important parameters in the application of wave plates. In the transmission mode of spectroscopic ellipsometer, taking the advantage of Jones matrix to analyse the phase difference of P and S directions in the process of spinning wave plate, a new method for the determination of optical axis of quartz wave plate was designed. The method has characteristics of simple light path structure and high efficiency in the judging of the optical axis, and this method thus got a good practicability.

  5. Experimental studies on the deformation and rupture of thin metal plates subject to underwater shock wave loading

    NASA Astrophysics Data System (ADS)

    Chen, Pengwan; Liu, Han; Zhang, Shaolong; Liu, Haibo; Chen, Ang; Guo, Baoqiao

    2015-09-01

    In this paper, the dynamic deformation and rupture of thin metal plates subject to underwater shock wave loading are studied by using high-speed 3D digital image correlation (3D-DIC). An equivalent device consist of a gas gun and a water anvil tube was used to supplying an exponentially decaying pressure in lieu of explosive detonation which acted on the panel specimen. The thin metal plate is clamped on the end of the shock tube by a flange. The deformation and rupture process of the metal plates subject to underwater shock waves are recorded by two high-speed cameras. The shape, displacement fields and strain fields of the metal plates under dynamic loading are obtained by using VIC-3D digital image correlation software. The strain gauges also were used to monitor the structural response on the selected position for comparison. The DIC data and the strain gauges results show a high level of correlation, and 3D-DIC is proven to be an effective method to measure 3D full-field dynamic response of structures under underwater impact loading. The effects of pre-notches on the failure modes of thin circular plate were also discussed.

  6. Simulating wave-turbulence on thin elastic plates with arbitrary boundary conditions

    NASA Astrophysics Data System (ADS)

    van Rees, Wim M.; Mahadevan, L.

    2016-11-01

    The statistical characteristics of interacting waves are described by the theory of wave turbulence, with the study of deep water gravity wave turbulence serving as a paradigmatic physical example. Here we consider the elastic analog of this problem in the context of flexural waves arising from vibrations of a thin elastic plate. Such flexural waves generate the unique sounds of so-called thunder machines used in orchestras - thin metal plates that make a thunder-like sound when forcefully shaken. Wave turbulence in elastic plates is typically investigated numerically using spectral simulations with periodic boundary conditions, which are not very realistic. We will present the results of numerical simulations of the dynamics of thin elastic plates in physical space, with arbitrary shapes, boundary conditions, anisotropy and inhomogeneity, and show first results on wave turbulence beyond the conventionally studied rectangular plates. Finally, motivated by a possible method to measure ice-sheet thicknesses in the open ocean, we will further discuss the behavior of a vibrating plate when floating on an inviscid fluid.

  7. Wavelet Spectral Finite Elements for Wave Propagation in Composite Plates

    DTIC Science & Technology

    2011-07-31

    experimentally validated at the Clarkson University. Composite plates were fabricated using aerospace grade carbon fiber prepregs . A scanning laser vibrometer...implemented at Clarkson. Composite plates were fabricated using aerospace grade carbon fiber prepregs . A scanning laser vibrometer was used to record out-of...validation of the developed model is performed at Clarkson University (Dr Ratan Jha?s group). Composite plates were fabricated using aerospace grade carbon

  8. Assessment of accumulated fatigue damage in solid plates using nonlinear Lamb wave approach

    NASA Astrophysics Data System (ADS)

    Deng, Mingxi; Pei, Junfeng

    2007-03-01

    The feasibility of using the nonlinear effect of primary Lamb wave propagation for assessing accumulated fatigue damage in solid plates is theoretically analyzed. After the aluminum sheets are subjected to tension-tension fatigue loading for different numbers of loading cycles, they are subjected to ultrasonic tests near the driving frequency where Lamb waves have a strong nonlinearity. This is followed by the measurement of the amplitude-frequency curves for second harmonics of the considered Lamb waves. The experimental results show that the effect of second-harmonic generation by Lamb wave propagation is very sensitive to the accumulation of fatigue damage of solid plates.

  9. Applications of surface acoustic and shallow bulk acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Campbell, Colin K.

    1989-10-01

    Surface acoustic wave (SAW) device coverage includes delay lines and filters operating at selected frequencies in the range from about 10 MHz to 11 GHz; modeling with single-crystal piezoelectrics and layered structures; resonators and low-loss filters; comb filters and multiplexers; antenna duplexers; harmonic devices; chirp filters for pulse compression; coding with fixed and programmable transversal filters; Barker and quadraphase coding; adaptive filters; acoustic and acoustoelectric convolvers and correlators for radar, spread spectrum, and packet radio; acoustooptic processors for Bragg modulation and spectrum analysis; real-time Fourier-transform and cepstrum processors for radar and sonar; compressive receivers; Nyquist filters for microwave digital radio; clock-recovery filters for fiber communications; fixed-, tunable-, and multimode oscillators and frequency synthesizers; acoustic charge transport; and other SAW devices for signal processing on gallium arsenide. Shallow bulk acoustic wave device applications include gigahertz delay lines, surface-transverse-wave resonators employing energy-trapping gratings, and oscillators with enhanced performance and capability.

  10. Design principles for wave plate metasurfaces using plasmonic L-shaped nanoantennas

    NASA Astrophysics Data System (ADS)

    Tahir, Asad A.; Schulz, Sebastian A.; De Leon, Israel; Boyd, Robert W.

    2017-03-01

    Plasmonic L-shaped antennas are an important building block of metasurfaces and have been used to fabricate ultra-thin wave plates. In this work we present principles that can be used to design wave plates at a wavelength of choice and for diverse application requirements using arrays of L-shaped plasmonic antennas. We derive these design principles by studying the behavior of the vast parameter space of these antenna arrays. We show that there are two distinct regimes: a weak inter-particle coupling and a strong inter-particle coupling regime. We describe the behavior of the antenna array in each regime with regards to wave plate functionality, without resorting to approximate theoretical models. Our work is the first to explain these design principles and serves as a guide for designing wave plates for specific application requirements using plasmonic L-shaped antenna arrays.

  11. Dynamical decoupling with tailored wave plates for long-distance communication using polarization qubits

    NASA Astrophysics Data System (ADS)

    Roy Bardhan, Bhaskar; Brown, Katherine L.; Dowling, Jonathan P.

    2013-11-01

    We address the issue of dephasing effects in flying polarization qubits propagating through optical fiber by using the method of dynamical decoupling. The control pulses are implemented with half-wave plates suitably placed along the realistic lengths of the single-mode optical fiber. The effects of the finite widths of the wave plates on the polarization rotation are modeled using tailored refractive index profiles inside the wave plates. We show that dynamical decoupling is effective in preserving the input qubit state with the fidelity close to unity when the polarization qubit is subject to the random birefringent noise in the fiber, as well the rotational imperfections (flip-angle errors) due to the finite width of the wave plates.

  12. Discrete control of resonant wave energy devices.

    PubMed

    Clément, A H; Babarit, A

    2012-01-28

    Aiming at amplifying the energy productive motion of wave energy converters (WECs) in response to irregular sea waves, the strategies of discrete control presented here feature some major advantages over continuous control, which is known to require, for optimal operation, a bidirectional power take-off able to re-inject energy into the WEC system during parts of the oscillation cycles. Three different discrete control strategies are described: latching control, declutching control and the combination of both, which we term latched-operating-declutched control. It is shown that any of these methods can be applied with great benefit, not only to mono-resonant WEC oscillators, but also to bi-resonant and multi-resonant systems. For some of these applications, it is shown how these three discrete control strategies can be optimally defined, either by analytical solution for regular waves, or numerically, by applying the optimal command theory in irregular waves. Applied to a model of a seven degree-of-freedom system (the SEAREV WEC) to estimate its annual production on several production sites, the most efficient of these discrete control strategies was shown to double the energy production, regardless of the resource level of the site, which may be considered as a real breakthrough, rather than a marginal improvement.

  13. Time-frequency characterization of lamb waves for material evaluation and damage inspection of plates

    NASA Astrophysics Data System (ADS)

    Frank Pai, P.; Deng, Haoguang; Sundaresan, Mannur J.

    2015-10-01

    Guided wave-based technique is one major approach for damage inspection of structures. To detect a small damage, an elastic wave's wavelength needs to be in the order of the damage size and hence the frequency needs to be high. Unfortunately, high-frequency wave dynamics always involves complicated wave reflection, refraction and diffraction, and it is difficult to separate them in order to perform detailed examination and system identification. This paper investigates dynamic characteristics of Lamb waves in plates in order to be used for material evaluation and damage inspection of thin-walled structures. A one-dimensional finite-element modeling and analysis technique is developed for computing dispersion curves and all symmetric and antisymmetric modes of Lamb waves in isotropic and multi-layer plates. Moreover, the conjugate-pair decomposition (CPD) method is introduced for time-frequency analysis of propagating Lamb waves. Results show that, under a k-cycle sine-burst excitation at a plate's edge, the time-varying frequency of a surface point's response can reveal the Lamb wave propagating inside the plate being a symmetric or an antisymmetric mode. The frequency of the measured wave packet increases from the wave front to the trailing edge if it is a symmetric mode, and the frequency decreases from the wave front to the trailing edge if it is an antisymmetric mode. Moreover, interaction of two different wave packets results in a peak in the time-frequency curve. These characteristics can be used for accurate separation of wave packets and identification of different wave speeds to enable fast and accurate material evaluation and damage inspection. Transient finite-element analysis of Lamb waves in finite plates with crack/delamination show that k-cycle sine-burst probing waves are good agents for guided wave-based damage inspection of structures. Although crack and delamination introduce different waves into and complicate the probing wave packet, time

  14. Time-frequency beamforming for nondestructive evaluations of plate using ultrasonic Lamb wave

    NASA Astrophysics Data System (ADS)

    Han, Je-Heon; Kim, Yong-Joe

    2015-03-01

    The objective of this study is to detect structural defect locations in a plate by exciting the plate with a specific ultrasonic Lamb wave and recording reflective wave signals using a piezoelectric transducer array. For the purpose of eliminating the effects of the direct excitation signals as well as the boundary-reflected wave signals, it is proposed to improve a conventional MUSIC beamforming procedure by processing the measured signals in the time-frequency domain. In addition, a normalized, damped, cylindrical 2-D steering vector is proposed to increase the spatial resolution of time-frequency MUSIC power results. A cross-shaped array is selected to further improve the spatial resolution and to avoid mirrored virtual image effects. Here, it is experimentally demonstrated that the proposed time-frequency MUSIC beamforming procedure can be used to identify structural defect locations on an aluminum plate by distinguishing the defect-induced waves from the excitation-generated and boundary-reflected waves.

  15. Acoustoelastic Lamb Wave Propagation in Biaxially Stressed Plates (Preprint)

    DTIC Science & Technology

    2012-03-01

    particularly as compared to most bulk wave NDE methods, Lamb wave are particularly sensitive to changes in the propagation environment, such as... Wilcox , and J. E. Michaels, “Efficient temperature compensation strategies for guided wave structural health monitoring,” Ultrasonics, 50, pp. 517...Liu, “Effects of residual stress on guided waves in layered media,” Rev. Prog. Quant. NDE , 17, D. O. Thompson and D. E. Chimenti (Eds.), Plenum Press

  16. Elastic guided waves in plates with surface roughness. I. Model calculation

    SciTech Connect

    Lobkis, O.I.; Chimenti, D.E.

    1997-07-01

    This paper reports analytical research on the effect of surface roughness on ultrasonic guided waves in plates. The theoretical model is constructed by exploiting the phase-screen assumption that takes advantage of the Kirchhoff approximation, where, on a local scale, the roughness degrades only the signal phase. The effect of the rough surface on the guided wave is treated by decomposing the wave modes into their constituent partial waves and considering individually the effect of the roughness on the partial wave components as they reflect from the plate surfaces. An approximate dispersion relation is derived for the traction-free rough waveguide that is formally identical to the conventional Lamb wave equation, but incorporating the roughness parameter as a complex plate thickness. A more accurate version of the model calculation is generalized to fluid-immersed plates having only a single rough surface either on the same, or opposite, side of the plate as the incident ultrasonic field. Calculations of the reflection coefficients in the presence of roughness serve to illustrate the phenomena for the case of the guided waves. {copyright} {ital 1997 Acoustical Society of America.}

  17. Acoustic radiation from bending waves of a plate

    NASA Astrophysics Data System (ADS)

    Ingard, K. Uno; Akay, A.

    1987-01-01

    An account is given of the behavior of a plate that is driven by a traveling force distribution, in which the amplitude of the force, rather than the displacement, is independent of the radiation load. A modified definition of radiation efficiency is proposed. Attention is given to the effect of internal damping in the plate, the effects of viscothermal losses, and the propagational, temperature, and viscous modes. It is noted with respect to viscothermal effects that, at the coincidence frequency, the contributions to the reactive part of load impedance on the plate from the viscothermal boundary layer and the viscothermal losses in the bulk of the surrounding fluid almost cancel each other out.

  18. Propagation of Lamb waves in an immersed periodically grooved plate: experimental detection of the scattered converted backward waves.

    PubMed

    Harhad, Nadia; El-Kettani, Mounsif Ech-Cherif; Djelouah, Hakim; Izbicki, Jean-Louis; Predoi, Mihai Valentin

    2014-03-01

    Guided waves propagation in immersed plates with irregular surfaces has potential application to detection and assessment of the extent, depth and pattern of the irregularity. The complexity of the problem, due to the large number of involved parameters, has limited the number of existing studies. The simplest case of irregularities of practical interest is the two-dimensional corrosion profile. Even this case is in general so complex, that one can extract several amplitude dominant periodic surfaces only by using a Fourier spectrum of the surface. Guided waves in plates, with one or both free surfaces having periodic perturbations of different shapes, have been presented in specialized literature. In this paper is studied the propagation of Lamb waves in an aluminum plate with a periodic grooved surface on only one side and immersed in water. The interaction between an incident Lamb wave and the grating gives rise to retro-converted waves. Preliminary numerical simulation by the finite element method is performed in order to obtain key parameters for the experiments. It is shown that retro-converted waves radiating into the water are detectable although their amplitudes are small. The phonon relation is verified for the leaky Lamb modes. The damping coefficients of the leaky Lamb modes in the grooved immersed plate are evaluated.

  19. Propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom

    NASA Astrophysics Data System (ADS)

    Lee, Kang Il; Choi, Bok Kyoung

    2014-12-01

    The present study aims to investigate the propagation of ultrasonic guided waves in an acrylic plate as a cortical-bone-mimicking phantom. The velocities of the guided waves in a 5-mm-thick acrylic plate were measured by using the axial transmission technique. A pure A0 Lamb mode could be successfully launched in the 5-mm-thick acrylic plate through a time reversal process of Lamb waves, consistent with the fact that the time reversal process can automatically compensate for the dispersive nature of Lamb waves. The experimental velocities of the slow guided wave (SGW) and the time-reversed Lamb wave were found to be in reasonable agreement with the theoretical group velocity of the A0 Lamb mode, suggesting that both the SGW and the time-reversed Lamb wave excited in the 5-mm-thick acrylic plate correspond to the A0 Lamb mode. These results suggest that the time reversal process of Lamb waves can be usefully applied to noninvasive characterization of long cortical bones.

  20. Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates.

    PubMed

    Tian, Zhenhua; Yu, Lingyu

    2017-01-05

    The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region near the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Moreover, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.

  1. Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates

    NASA Astrophysics Data System (ADS)

    Tian, Zhenhua; Yu, Lingyu

    2017-01-01

    The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region near the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Moreover, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.

  2. Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates

    PubMed Central

    Tian, Zhenhua; Yu, Lingyu

    2017-01-01

    The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region near the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Moreover, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics. PMID:28054601

  3. Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates

    DOE PAGES

    Tian, Zhenhua; Yu, Lingyu

    2017-01-05

    The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region nearmore » the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Furthermore, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.« less

  4. An infrared achromatic quarter-wave plate designed based on simulated annealing algorithm

    NASA Astrophysics Data System (ADS)

    Pang, Yajun; Zhang, Yinxin; Huang, Zhanhua; Yang, Huaidong

    2017-03-01

    Quarter-wave plates are primarily used to change the polarization state of light. Their retardation usually varies depending on the wavelength of the incident light. In this paper, the design and characteristics of an achromatic quarter-wave plate, which is formed by a cascaded system of birefringent plates, are studied. For the analysis of the combination, we use Jones matrix method to derivate the general expressions of the equivalent retardation and the equivalent azimuth. The infrared achromatic quarter-wave plate is designed based on the simulated annealing (SA) algorithm. The maximum retardation variation and the maximum azimuth variation of this achromatic waveplate are only about 1.8 ° and 0.5 ° , respectively, over the entire wavelength range of 1250-1650 nm. This waveplate can change the linear polarized light into circular polarized light with a less than 3.2% degree of linear polarization (DOLP) over that wide wavelength range.

  5. Prolonged acousto-optic interaction with Lamb waves in crystalline plates

    PubMed

    Parygin; Vershoubskiy; Mozhaev; Weihnacht

    2000-03-01

    The propagation and acousto-optic interaction of Lamb modes in an anisotropic plate of tellurium dioxide (TeO2) are studied numerically and analytically. In the case of a Y-cut X-propagating TeO2 plate, the very high elastic anisotropy of the crystal greatly modifies the dispersion curves, giving rise to their multiple oscillations. The existence ranges of backward Lamb modes increase with the mode order contrary to the case of isotropic plates. The quasi-collinear light scattering by Lamb waves is considered. Owing to the structure of Lamb wave field, a simultaneous light diffraction at two different optical frequencies can take place while Lamb waves are excited only at the single frequency. It is demonstrated with the Z-cut (110)-propagating plate that a small change in the acoustic frequency can result in a significant shift in the frequency of the scattered light.

  6. Electric Field Tunable Microwave and MM-wave Ferrite Devices

    DTIC Science & Technology

    2010-04-30

    Electric Field Tunable Microwave and MM-wave Ferrite Devices (N00014-06-01-0167) Period of Performance: May 1, 2006-April 30, 2010 Principal...modes as a function of E. The coupling was strong and ranged from 1 to 30 MHz/(kV/cm). Ferrite - ferroelectric composites were used in microwave and...2005, focused on ME effects at microwave and millimeter wave frequencies in ferrite -ferroelectric composites. Studies were performed on basic

  7. Electrochemical Device Comprising Composite Bipolar Plate and Method of Using the Same

    NASA Technical Reports Server (NTRS)

    Mittelsteadt, Cortney K. (Inventor); Braff, William A. (Inventor)

    2013-01-01

    An electrochemical device and methods of using the same. In one embodiment, the electrochemical device may be used as a fuel cell and/or as an electrolyzer and includes a membrane electrode assembly (MEA), an anodic gas diffusion medium in contact with the anode of the MEA, a cathodic gas diffusion medium in contact with the cathode, a first bipolar plate in contact with the anodic gas diffusion medium, and a second bipolar plate in contact with the cathodic gas diffusion medium. Each of the bipolar plates includes an electrically-conductive, chemically-inert, non-porous, liquid-permeable, substantially gas-impermeable membrane in contact with its respective gas diffusion medium, as well as a fluid chamber and a non-porous an electrically-conductive plate.

  8. Electrochemical Device Comprising Composite Bipolar Plate and Method of Using the Same

    NASA Technical Reports Server (NTRS)

    Mittelsteadt, Cortney K. (Inventor); Braff, William A. (Inventor)

    2017-01-01

    An electrochemical device and methods of using the same. In one embodiment, the electrochemical device may be used as a fuel cell and/or as an electrolyzer and includes a membrane electrode assembly (MEA), an anodic gas diffusion medium in contact with the anode of the MEA, a cathodic gas diffusion medium in contact with the cathode, a first bipolar plate in contact with the anodic gas diffusion medium, and a second bipolar plate in contact with the cathodic gas diffusion medium. Each of the bipolar plates includes an electrically-conductive, chemically-inert, non-porous, liquid-permeable, substantially gas-impermeable membrane in contact with its respective gas diffusion medium, as well as a fluid chamber and a non-porous an electrically-conductive plate.

  9. Unusual energy properties of leaky backward Lamb waves in a submerged plate.

    PubMed

    Nedospasov, I A; Mozhaev, V G; Kuznetsova, I E

    2017-05-01

    It is found that leaky backward Lamb waves, i.e. waves with negative energy-flux velocity, propagating in a plate submerged in a liquid possess extraordinary energy properties distinguishing them from any other type of waves in isotropic media. Namely, the total time-averaged energy flux along the waveguide axis is equal to zero for these waves due to opposite directions of the longitudinal energy fluxes in the adjacent media. This property gives rise to the fundamental question of how to define and calculate correctly the energy velocity in such an unusual case. The procedure of calculation based on incomplete integration of the energy flux density over the plate thickness alone is applied. The derivative of the angular frequency with respect to the wave vector, usually referred to as the group velocity, happens to be close to the energy velocity defined by this mean in that part of the frequency range where the backward mode exists in the free plate. The existence region of the backward mode is formally increased for the submerged plate in comparison to the free plate as a result of the liquid-induced hybridization of propagating and nonpropagating (evanescent) Lamb modes. It is shown that the Rayleigh's principle (i.e. equipartition of total time-averaged kinetic and potential energies for time-harmonic acoustic fields) is violated due to the leakage of Lamb waves, in spite of considering nondissipative media.

  10. Surface acoustic wave coding for orthogonal frequency coded devices

    NASA Technical Reports Server (NTRS)

    Malocha, Donald (Inventor); Kozlovski, Nikolai (Inventor)

    2011-01-01

    Methods and systems for coding SAW OFC devices to mitigate code collisions in a wireless multi-tag system. Each device producing plural stepped frequencies as an OFC signal with a chip offset delay to increase code diversity. A method for assigning a different OCF to each device includes using a matrix based on the number of OFCs needed and the number chips per code, populating each matrix cell with OFC chip, and assigning the codes from the matrix to the devices. The asynchronous passive multi-tag system includes plural surface acoustic wave devices each producing a different OFC signal having the same number of chips and including a chip offset time delay, an algorithm for assigning OFCs to each device, and a transceiver to transmit an interrogation signal and receive OFC signals in response with minimal code collisions during transmission.

  11. Optimization of magnetically accelerated, ultra-high velocity aluminum flyer plates for use in plate impact, shock wave experiments.

    SciTech Connect

    Cochrane, Kyle Robert; Knudson, Marcus D.; Slutz, Stephen A.; Lemke, Raymond William; Davis, J. P.; Harjes, Henry Charles III; Giunta, Anthony Andrew; Bliss, David Emery

    2005-05-01

    The intense magnetic field produced by the 20 MA Z accelerator is used as an impulsive pressure source to accelerate metal flyer plates to high velocity for the purpose of performing plate impact, shock wave experiments. This capability has been significantly enhanced by the recently developed pulse shaping capability of Z, which enables tailoring the rise time to peak current for a specific material and drive pressure to avoid shock formation within the flyer plate during acceleration. Consequently, full advantage can be taken of the available current to achieve the maximum possible magnetic drive pressure. In this way, peak magnetic drive pressures up to 490 GPa have been produced, which shocklessly accelerated 850 {micro}m aluminum (6061-T6) flyer plates to peak velocities of 34 km/s. We discuss magnetohydrodynamic (MHD) simulations that are used to optimize the magnetic pressure for a given flyer load and to determine the shape of the current rise time that precludes shock formation within the flyer during acceleration to peak velocity. In addition, we present results pertaining to plate impact, shock wave experiments in which the aluminum flyer plates were magnetically accelerated across a vacuum gap and impacted z-cut, {alpha}-quartz targets. Accurate measurements of resulting quartz shock velocities are presented and analyzed through high-fidelity MHD simulations enhanced using optimization techniques. Results show that a fraction of the flyer remains at solid density at impact, that the fraction of material at solid density decreases with increasing magnetic pressure, and that the observed abrupt decrease in the quartz shock velocity is well correlated with the melt transition in the aluminum flyer.

  12. Theoretical Analysis of Electromechanical Coupling Coefficient of Lamb Waves in ZnO/Si Multilayered Piezoelectric Plates

    NASA Astrophysics Data System (ADS)

    Yung-Yu Chen,

    2010-07-01

    Lamb wave devices have been widely used in electro-acoustic and microfluidic devices. In order to improve their performances, the phase velocity dispersion and electromechanical coupling coefficient (ECC) of the Lamb wave should be calculated exactly during designing. Accordingly, this paper aims at analyzing exactly Lamb waves in multilayered piezoelectric plates with distinct electrode arrangements. First, the formulae of effective permittivity were derived based on the transfer matrix method and further was employed to calculate the phase velocity dispersion. The ZnO/Si multilayered plate was taken as the calculation example. The ECCs under distinct electrical boundary conditions were calculated by the Green’s function method. Finally, the influences of the silicon thickness on the phase velocity dispersion and ECC are further discussed. Results show that the coupling coefficients deeply depends on the electrode arrangement, and the S0 mode with the electrode arrangements of type D is a better due to its larger velocity and higher coupling coefficient. Moreover, the ECC can be enlarged by reducing the nonpiezoelectric membrane thickness.

  13. Theoretical Analysis of Electromechanical Coupling Coefficient of Lamb Waves in ZnO/Si Multilayered Piezoelectric Plates

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Yu

    2010-07-01

    Lamb wave devices have been widely used in electro-acoustic and microfluidic devices. In order to improve their performances, the phase velocity dispersion and electromechanical coupling coefficient (ECC) of the Lamb wave should be calculated exactly during designing. Accordingly, this paper aims at analyzing exactly Lamb waves in multilayered piezoelectric plates with distinct electrode arrangements. First, the formulae of effective permittivity were derived based on the transfer matrix method and further was employed to calculate the phase velocity dispersion. The ZnO/Si multilayered plate was taken as the calculation example. The ECCs under distinct electrical boundary conditions were calculated by the Green's function method. Finally, the influences of the silicon thickness on the phase velocity dispersion and ECC are further discussed. Results show that the coupling coefficients deeply depends on the electrode arrangement, and the S0 mode with the electrode arrangements of type D is a better due to its larger velocity and higher coupling coefficient. Moreover, the ECC can be enlarged by reducing the nonpiezoelectric membrane thickness.

  14. Guided wave opto-acoustic device

    DOEpatents

    Jarecki, Jr., Robert L.; Rakich, Peter Thomas; Camacho, Ryan; Shin, Heedeuk; Cox, Jonathan Albert; Qiu, Wenjun; Wang, Zheng

    2016-02-23

    The various technologies presented herein relate to various hybrid phononic-photonic waveguide structures that can exhibit nonlinear behavior associated with traveling-wave forward stimulated Brillouin scattering (forward-SBS). The various structures can simultaneously guide photons and phonons in a suspended membrane. By utilizing a suspended membrane, a substrate pathway can be eliminated for loss of phonons that suppresses SBS in conventional silicon-on-insulator (SOI) waveguides. Consequently, forward-SBS nonlinear susceptibilities are achievable at about 3000 times greater than achievable with a conventional waveguide system. Owing to the strong phonon-photon coupling achievable with the various embodiments, potential application for the various embodiments presented herein cover a range of radiofrequency (RF) and photonic signal processing applications. Further, the various embodiments presented herein are applicable to applications operating over a wide bandwidth, e.g. 100 MHz to 50 GHz or more.

  15. Reflection of Lamb waves obliquely incident on the free edge of a plate.

    PubMed

    Santhanam, Sridhar; Demirli, Ramazan

    2013-01-01

    The reflection of obliquely incident symmetric and anti-symmetric Lamb wave modes at the edge of a plate is studied. Both in-plane and Shear-Horizontal (SH) reflected wave modes are spawned by an obliquely incident in-plane Lamb wave mode. Energy reflection coefficients are calculated for the reflected wave modes as a function of frequency and angle of incidence. This is done by using the method of orthogonal mode decomposition and by enforcing traction free conditions at the plate edge using the method of collocation. A PZT sensor network, affixed to an Aluminum plate, is used to experimentally verify the predictions of the analysis. Experimental results provide support for the analytically determined results.

  16. An experimental study of nonlinear waves produced by an accelerating plate

    NASA Astrophysics Data System (ADS)

    Yang, S. A.; Chwang, Allen T.

    1992-11-01

    The free-surface flow generated by an impulsively accelerating, surface-piercing, vertical plate has been studied experimentally in an open channel of constant depth. The flat vertical plate is fixed on a towing carriage that is set off by suddenly dropping a weight bucket through a connecting steel cable in a pulley system. The free-surface profile in front of the plate and the pressure distribution on the plate surface are measured for three different accelerations of the plate. A capacitance-type wave gauge is used to measure the variations of the water surface, while a variable reluctance pressure transducer is used to measure the pressure on the plate surface. The acceleration of the plate is obtained by means of an accelerometer. All response voltage outputs are recorded on an IBM PC-XT personal computer with a data-acquisition electrical board. Experimental measurements are compared with the numerical, viscous-flow results of Yang and Chwang (IIHR Report No. 332; Iowa Institute of Hydraulic Research, The University of Iowa, 1989) and the analytical, inviscid-flow solution of Chwang [Phys. Fluids 26, 383 (1983)]. The agreement of the free-surface profile and the pressure distribution between the numerical results and the present experimental measurements is fairly good. However, the inviscid-flow solution overpredicts the wave amplitude and the pressure distribution on the plate. In the physical experiments, the water surface is observed to rise in front of the vertical plate where the potential-flow theory becomes singular.

  17. Solitary SH waves in two-layered traction-free plates

    NASA Astrophysics Data System (ADS)

    Djeran-Maigre, Irini; Kuznetsov, Sergey

    2008-01-01

    A solitary wave, resembling a soliton wave, is observed when analyzing the linear problem of polarized shear (SH) surface acoustic waves propagating in elastic orthotropic two-layered traction-free plates. The analysis is performed by applying a special complex formalism and the Modified Transfer Matrix (MTM) method. Conditions for the existence of solitary SH waves are obtained. Analytical expressions for the phase speed of the solitary wave are derived. To cite this article: I. Djeran-Maigre, S. Kuznetsov, C. R. Mecanique 336 (2008).

  18. Nonlinear viscous waves produced by an impulsively moving plate

    NASA Astrophysics Data System (ADS)

    Yang, S. A.; Chwang, Allen T.

    1989-09-01

    The free surface flow generated by an impulsively accelerating, surface piercing, vertical plate are studied numerically as well as experimentally. The 2-D, unsteady Navier-Stokes equations are discretized using the finite analytic scheme which incorporates the analytic solution into the locally linearized differential equations. The continuity equation and the dynamic boundary conditions on normal and tangential stresses at the free surface are applied to determine the pressure and two velocity components at the free surface. The kinematic boundary condition on the free surface provides the movement of the free surface. A series of experiments is carried out. The flat vertical plate is fixed on a towing carriage which is set off by suddenly dropping a weight bucket through a connecting steel cable in a pulley system. A data acquisition system is used for controlling the sampling process and for recording the signal output. The agreement of the free surface profile and the pressure distribution between the numerical results and the experimental measurements is fairly good. The mathematical singularity, which is predicted by the potential flow theory, at the contact line between the plate and the free surface is not observed in the physical experiments. The water surface in front of the vertical plate simply rises up during the initial stage of the acceleration of the plate.

  19. Underwater Shock Wave Research Applied to Therapeutic Device Developments

    NASA Astrophysics Data System (ADS)

    Takayama, K.; Yamamoto, H.; Shimokawa, H.

    2013-07-01

    The chronological development of underwater shock wave research performed at the Shock Wave Research Center of the Institute of Fluid Science at the Tohoku University is presented. Firstly, the generation of planar underwater shock waves in shock tubes and their visualization by using the conventional shadowgraph and schlieren methods are described. Secondly, the generation of spherical underwater shock waves by exploding lead azide pellets weighing from several tens of micrograms to 100 mg, that were ignited by irradiating with a Q-switched laser beam, and their visualization by using double exposure holographic interferometry are presented. The initiation, propagation, reflection, focusing of underwater shock waves, and their interaction with various interfaces, in particular, with air bubbles, are visualized quantitatively. Based on such a fundamental underwater shock wave research, collaboration with the School of Medicine at the Tohoku University was started for developing a shock wave assisted therapeutic device, which was named an extracorporeal shock wave lithotripter (ESWL). Miniature shock waves created by irradiation with Q-switched HO:YAG laser beams are studied, as applied to damaged dysfunctional nerve cells in the myocardium in a precisely controlled manner, and are effectively used to design a catheter for treating arrhythmia.

  20. 3D analysis of interaction of Lamb waves with defects in loaded steel plates.

    PubMed

    Kazys, R; Mazeika, L; Barauskas, R; Raisutis, R; Cicenas, V; Demcenko, A

    2006-12-22

    The objective of the research presented here is the investigation of the interaction of guided waves with welds, defects and other non-uniformities in steel plates loaded by liquid. The investigation has been performed using numerical simulation for 2D and 3D cases by the finite differences method, finite element method and measurement of 3D distributions of acoustic fields. Propagation of the S(0) mode in a steel plate and its interaction with non-uniformities was investigated. It was shown that using the measured leaky wave signals in the water loading of the steel plate and by application of signal processing, the 3D ultrasonic field structure inside and outside of the plate can be reconstructed. The presence of leaky wave signals over the defect caused by the mode conversion of Lamb waves has been proved using the numerical modelling and experimental investigations. The developed signal and data processing enables to visualise dynamics of ultrasonic fields over the plate, and also to estimate spatial positions of defects inside the steel plates.

  1. The study of surface acoustic wave charge transfer device

    NASA Technical Reports Server (NTRS)

    Papanicolaou, N.; Lin, H. C.

    1978-01-01

    A surface acoustic wave-charge transfer device, consisting of an n-type silicon substrate, a thermally grown silicon dioxide layer, and a sputtered film of piezoelectric zinc oxide is proposed as a means of circumventing problems associated with charge-coupled device (CCD) applications in memory, signal processing, and imaging. The proposed device creates traveling longitudinal electric fields in the silicon and replaces the multiphase clocks in CCD's. The traveling electric fields create potential wells which carry along charges stored there. These charges may be injected into the wells by light or by using a p-n junction as in conventional CCD's.

  2. Surface acoustic wave vapor sensors based on resonator devices

    NASA Astrophysics Data System (ADS)

    Grate, Jay W.; Klusty, Mark

    1991-05-01

    Surface acoustic wave (SAW) devices fabricated in the resonator configuration have been used as organic vapor sensors and compared with delay line devices more commonly used. The experimentally determined mass sensitivities of 200, 300, and 400 MHz resonators and 158 MHz delay lines coated with Langmuir-Blodgett films of poly(vinyl tetradecanal) are in excellent agreement with theoretical predictions. The response of LB- and spray-coated sensors to various organic vapors were determined, and scaling laws for mass sensitivities, vapor sensitivities, and detection limits are discussed. The 200 MHz resonators provide the lowest noise levels and detection limits of all the devices examined.

  3. Design of multi-stopband metamaterial plates for absorption of broadband elastic waves and vibration

    NASA Astrophysics Data System (ADS)

    Peng, Hao; Pai, P. F.

    2015-03-01

    This paper presents the modeling technique, working mechanism and design guidelines for acoustic multi-stopband metamaterial plates for broadband elastic wave absorption and vibration suppression. The metamaterial plate is designed by integrating two-DOF (degree of freedom) mass-spring subsystems with an isotropic plate to act as vibration absorbers. For an infinite metamaterial plate without damping, a unit cell is modeled using the extended Hamilton's principle, and two stopbands are obtained by dispersion analysis on the averaged three-DOF model. For a finite metamaterial plate with boundary conditions and damping, shear-deformable conforming plate elements are used to model the whole plate, and stopbands and their dynamic effects are investigated by frequency response analysis and transient analysis by direct numerical integration. Influences of absorbers' resonant frequencies and damping ratios, plate's boundary conditions and dimensions, and working plate-absorber modes are thoroughly investigated. Results show that the metamaterial plate is essentially based on the concept of conventional vibration absorbers. The local resonance of the two-DOF subsystems generates two stopbands, and the inertial forces generated by the resonant vibrations of absorbers straighten the plate and attenuate/stop wave propagation. Each stopband's bandwidth can be increased by increasing the absorber mass and/or reducing the isotropic plate's unit cell mass. Moreover, a high damping ratio for the secondary absorber can combine the two stopbands into one wide stopband for vibration suppression, and a low damping ratio for the primary absorber warrants absorbers' quick response to steady and/or transient excitations.

  4. Control of Rayleigh-like waves in thick plate Willis metamaterials

    NASA Astrophysics Data System (ADS)

    Diatta, André; Achaoui, Younes; Brûlé, Stéphane; Enoch, Stefan; Guenneau, Sébastien

    2016-12-01

    Recent advances in control of anthropic seismic sources in structured soil led us to explore interactions of elastic waves propagating in plates (with soil parameters) structured with concrete pillars buried in the soil. Pillars are 2 m in diameter, 30 m in depth and the plate is 50 m in thickness. We study the frequency range 5 to 10 Hz, for which Rayleigh wave wavelengths are smaller than the plate thickness. This frequency range is compatible with frequency ranges of particular interest in earthquake engineering. It is demonstrated in this paper that two seismic cloaks' configurations allow for an unprecedented flow of elastodynamic energy associated with Rayleigh surface waves. The first cloak design is inspired by some approximation of ideal cloaks' parameters within the framework of thin plate theory. The second, more accomplished but more involved, cloak design is deduced from a geometric transform in the full Navier equations that preserves the symmetry of the elasticity tensor but leads to Willis' equations, well approximated by a homogenization procedure, as corroborated by numerical simulations. The two cloaks's designs are strickingly different, and the superior efficiency of the second type of cloak emphasizes the necessity for rigour in transposition of existing cloaks's designs in thin plates to the geophysics setting. Importantly, we focus our attention on geometric transforms applied to thick plates, which is an intermediate case between thin plates and semi-infinite media, not studied previously. Cloaking efficiency (reduction of the disturbance of the wave wavefront and its amplitude behind an obstacle) and protection (reduction of the wave amplitude within the center of the cloak) are studied for ideal and approximated cloaks' parameters. These results represent a preliminary step towards designs of seismic cloaks for surface Rayleigh waves propagating in sedimentary soils structured with concrete pillars.

  5. Electromechanical model for actuating liquids in a two-plate droplet microfluidic device.

    PubMed

    Chatterjee, Debalina; Shepherd, Heather; Garrell, Robin L

    2009-05-07

    Both conducting and insulating liquids can be actuated in two-plate droplet ("digital") microfluidic devices. Droplet movement is accomplished by applying a voltage across electrodes patterned beneath the dielectric-coated top and bottom plates. This report presents a general electromechanical model for calculating the forces on insulating and conducting liquids in two-plate devices. The devices are modeled as an equivalent circuit in which the dielectric layers and ambient medium (air or oil) are described as capacitors, while the liquid being actuated is described as a resistor and capacitor in parallel. The experimental variables are the thickness and dielectric constant of each layer in the device, the gap between plates, the applied voltage and frequency, and the conductivity of the liquid. The model has been used to calculate the total force acting on droplets of liquids that have been studied experimentally, and to explain the relative ease with which liquids of different conductivities can be actuated. The contributions of the electrowetting (EW) and dielectrophoretic (DEP) forces to droplet actuation have also been calculated. While for conductive liquids the EW force dominates, for dielectric liquids, both DEP and EW contribute, and the DEP force may dominate. The general utility of the model is that it can be used to predict the operating conditions needed to actuate particular liquids in devices of known geometry, and to optimize the design and operating conditions to enable movement of virtually any liquid.

  6. Quasi-Rayleigh waves in butt-welded thick steel plate

    SciTech Connect

    Kamas, Tuncay E-mail: victorg@sc.edu Giurgiutiu, Victor E-mail: victorg@sc.edu Lin, Bin E-mail: victorg@sc.edu

    2015-03-31

    This paper discusses theoretical and experimental analyses of weld guided surface acoustic waves (SAW) through the guided wave propagation (GWP) analyses. The GWP analyses have been carried out by utilizing piezoelectric wafer active sensors (PWAS) for in situ structural inspection of a thick steel plate with butt weld as the weld bead is ground flush. Ultrasonic techniques are commonly used for validation of welded structures in many in-situ monitoring applications, e.g. in off-shore structures, in nuclear and pressure vessel industries and in a range of naval applications. PWAS is recently employed in such ultrasonic applications as a resonator as well as a transducer. Quasi-Rayleigh waves a.k.a. SAW can be generated in relatively thick isotropic elastic plate having the same phase velocity as Rayleigh waves whereas Rayleigh waves are a high frequency approximation of the first symmetric (S0) and anti-symmetric (A0) Lamb wave modes. As the frequency becomes very high the S0 and the A0 wave speeds coalesce, and both have the same value. This value is exactly the Rayleigh wave speed and becomes constant along the frequency i.e. Rayleigh waves are non-dispersive guided surface acoustic waves. The study is followed with weld-GWP tests through the pitch-catch method along the butt weld line. The tuning curves of quasi-Rayleigh wave are determined to show the tuning and trapping effect of the weld bead that has higher thickness than the adjacent plates on producing a dominant quasi-Rayleigh wave mode. The significant usage of the weld tuned and guided quasi-Rayleigh wave mode is essentially discussed for the applications in the in-situ inspection of relatively thick structures with butt weld such as naval offshore structures. The paper ends with summary, conclusions and suggestions for future work.

  7. Surface acoustic wave devices for harsh environment wireless sensing

    DOE PAGES

    Greve, David W.; Chin, Tao -Lun; Zheng, Peng; ...

    2013-05-24

    In this study, langasite surface acoustic wave devices can be used to implement harsh environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensormore » with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity.« less

  8. Surface acoustic wave devices for harsh environment wireless sensing

    SciTech Connect

    Greve, David W.; Chin, Tao -Lun; Zheng, Peng; Ohodnicki, Paul; Baltrus, John; Oppenheim, Irving J.

    2013-05-24

    In this study, langasite surface acoustic wave devices can be used to implement harsh environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity.

  9. Surface Acoustic Wave Devices for Harsh Environment Wireless Sensing

    PubMed Central

    Greve, David W.; Chin, Tao-Lun; Zheng, Peng; Ohodnicki, Paul; Baltrus, John; Oppenheim, Irving J.

    2013-01-01

    Langasite surface acoustic wave devices can be used to implement harsh-environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity. PMID:23708273

  10. Multiple-frequency surface acoustic wave devices as sensors

    NASA Astrophysics Data System (ADS)

    Ricco, Antonio J.; Martin, Stephen J.

    We have designed, fabricated, and tested a multiple-frequency acoustic wave (MUFAW) device on ST-cut quartz with nominal surface acoustic wave (SAW) center frequencies of 16, 40, 100, and 250 MHz. The four frequencies are obtained by patterning four sets of input and output interdigital transducers of differing periodicities on a single substrate. Such a device allows the frequency dependence of AW sensor perturbations to be examined, aiding in the elucidation of the operative interaction mechanism(s). Initial measurements of the SAW response to the vacuum deposition of a thin nickel film show the expected frequency dependence of mass sensitivity in addition to the expected frequency independence of the magnitude of the acoustoelectric effect. By measuring changes in both wave velocity and attenuation at multiple frequencies, extrinsic perturbations such as temperature and pressure changes are readily differentiated from one another and from changes in surface mass.

  11. Stress waves in an isotropic elastic plate excited by a circular transducer

    NASA Technical Reports Server (NTRS)

    Karagulle, H.; Williams, J. H., Jr.; Lee, S. S.

    1985-01-01

    Steady state harmonic stress waves in an isotropic elastic plate excited on one face by a circular transducer are analyzed theoretically. The transmitting transducer transforms an electrical voltage into a uniform normal stress at the top of the plate. To solve the boundary value problem, the radiation into a half-space is considered. The receiving transducer produces an electrical voltage proportional to the average spatially integrated normal stress over its face due to an incident wave. A numerical procedure is given to evaluate the frequency response at a receiving point due to a multiply reflected wave in the near field. Its stability and convergence are discussed. Parameterization plots which determine the particular wave whose frequency response has maximum magnitude compared with other multiple reflected waves are given for a range of values of dimensionless parameters. The effects of changes in the values of the parameters are discussed.

  12. Fabrication of Achromatic Infrared Wave Plate by Direct Imprinting Process on Chalcogenide Glass

    NASA Astrophysics Data System (ADS)

    Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

    2012-07-01

    An achromatic infrared wave plate was fabricated by forming a subwavelength grating on the chalcogenide glass using direct imprint lithography. A low toxic chalcogenide glass (Sb-Ge-Sn-S system) substrate was imprinted with a grating of 1.63-µm depth, a fill factor of 0.7, and 3-µm period using glassy carbon as a mold at 253 °C and 3.8 MPa. Phase retardation of the element reached around 30° at 8.5-10.5 µm wavelengths, and the transmittance exceeded that of a flat substrate over 8 µm wavelength. Fabrication of the mid-infrared wave plate is thereby less expensive than that of conventional crystalline wave plates.

  13. Analysis of particle penetration into aluminum plate using underwater shock wave

    SciTech Connect

    Tanaka, S.; Hokamoto, K.; Itoh, S.

    2007-12-12

    Some techniques using underwater shock waves have been developed for several material processing applications: explosive welding, shock compaction, and shock synthesis. In this research, a new technique was developed for surface modification of an aluminum plate. Diamond particles were accelerated by an underwater shock wave and penetrated into an aluminum plate, creating a surface coating of diamond on the aluminum plate. In the observation of the cross-section of the recovered Al-diamond composite, a rich diamond layer was confirmed at about 200 {mu}m depth. XRD and wear measurements were conducted for the recovered Al-diamond composite. We also report on the optical observation of the underwater shock wave in this paper.

  14. An automatic system for measurement of retardation of wave plates based on phase-shifted method

    NASA Astrophysics Data System (ADS)

    Gao, Zhishan; Yan, Ming

    2005-02-01

    A practical system is described to measure the retardation of wave plates with phase-shifted method. The tested wave plate is put in and the original angle between the axis of it and the analyzer is random, not 45 degree. For the measurement is made rapidly and automatically, a standard wave plate act as a compensator, the stepping motor is used to drive the analyzer to realize phase shifting and a grating encoder is used to measure its rotating angle. At the same time, while the beam comes out from the analyzer, the photoelectric detector gets its intensity, and then the signals is magnified, filtered and sent to computer through its serial port. The results show the system has the advantages of costing little time and high accuracy.

  15. Acoustic and Cavitation Fields of Shock Wave Therapy Devices

    NASA Astrophysics Data System (ADS)

    Chitnis, Parag V.; Cleveland, Robin O.

    2006-05-01

    Extracorporeal shock wave therapy (ESWT) is considered a viable treatment modality for orthopedic ailments. Despite increasing clinical use, the mechanisms by which ESWT devices generate a therapeutic effect are not yet understood. The mechanistic differences in various devices and their efficacies might be dependent on their acoustic and cavitation outputs. We report acoustic and cavitation measurements of a number of different shock wave therapy devices. Two devices were electrohydraulic: one had a large reflector (HMT Ossatron) and the other was a hand-held source (HMT Evotron); the other device was a pneumatically driven device (EMS Swiss DolorClast Vet). Acoustic measurements were made using a fiber-optic probe hydrophone and a PVDF hydrophone. A dual passive cavitation detection system was used to monitor cavitation activity. Qualitative differences between these devices were also highlighted using a high-speed camera. We found that the Ossatron generated focused shock waves with a peak positive pressure around 40 MPa. The Evotron produced peak positive pressure around 20 MPa, however, its acoustic output appeared to be independent of the power setting of the device. The peak positive pressure from the DolorClast was about 5 MPa without a clear shock front. The DolorClast did not generate a focused acoustic field. Shadowgraph images show that the wave propagating from the DolorClast is planar and not focused in the vicinity of the hand-piece. All three devices produced measurable cavitation with a characteristic time (cavitation inception to bubble collapse) that varied between 95 and 209 μs for the Ossatron, between 59 and 283 μs for the Evotron, and between 195 and 431 μs for the DolorClast. The high-speed camera images show that the cavitation activity for the DolorClast is primarily restricted to the contact surface of the hand-piece. These data indicate that the devices studied here vary in acoustic and cavitation output, which may imply that the

  16. Micro and nano devices in passive millimetre wave imaging systems

    NASA Astrophysics Data System (ADS)

    Appleby, R.

    2013-06-01

    The impact of micro and nano technology on millimetre wave imaging from the post war years to the present day is reviewed. In the 1950s whisker contacted diodes in mixers and vacuum tubes were used to realise both radiometers and radars but required considerable skill to realise the performance needed. Development of planar semiconductor devices such as Gunn and Schottky diodes revolutionised mixer performance and provided considerable improvement. The next major breakthrough was high frequency transistors based on gallium arsenide which were initially used at intermediate frequencies but later after further development at millimeter wave frequencies. More recently Monolithic Microwave Integrated circuits(MMICs) offer exceptional performance and the opportunity for innovative design in passive imaging systems. In the future the use of micro and nano technology will continue to drive system performance and we can expect to see integration of antennae, millimetre wave and sub millimetre wave circuits and signal processing.

  17. Propagation of flexural waves in inhomogeneous plates exhibiting hysteretic nonlinearity: Nonlinear acoustic black holes.

    PubMed

    Gusev, Vitalyi E; Ni, Chenyin; Lomonosov, Alexey; Shen, Zhonghua

    2015-08-01

    Theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous material on flexural wave in the plates of continuously varying thickness is developed. For the wedges with thickness increasing as a power law of distance from its edge strong modifications of the wave dynamics with propagation distance are predicted. It is found that nonlinear absorption progressively disappearing with diminishing wave amplitude leads to complete attenuation of acoustic waves in most of the wedges exhibiting black hole phenomenon. It is also demonstrated that black holes exist beyond the geometrical acoustic approximation. Applications include nondestructive evaluation of micro-inhomogeneous materials and vibrations damping.

  18. Far-field subwavelength imaging for ultrasonic elastic waves in a plate using an elastic hyperlens

    NASA Astrophysics Data System (ADS)

    Lee, Hyung Jin; Kim, Hoe Woong; Kim, Yoon Young

    2011-06-01

    Subwavelength imaging was experimentally performed for ultrasonic elastic waves by using an angularly stratified plat, an elastic plate hyperlens. It consists of alternating layers of aluminum and air, exhibiting a large contrast in elastic stiffness. A specially configured experimental setup is used to locate two sources within half the wavelength at 100 kHz. To explain the observed phenomenon, the homogenization of the elasticity coefficients of the stratified structure is employed. Because of the strong cylindrical anisotropy, an equifrequency contour becomes nearly flat along the angular wave vector so that evanescent waves involved with high angular resolution are converted to propagating waves.

  19. Planar shear horizontal guided wave inspection of a plate using piezoelectric fiber transducers

    NASA Astrophysics Data System (ADS)

    Soorgee, M. H.; Lissenden, C. J.; Rose, J. L.; Yousefi-Koma, A.

    2013-01-01

    Fundamental Shear Horizontal (SH0) guided waves have been simulated using finite element software in order to locate a crack in a plate structure. Long but narrow piezoelectric fiber composite strips have been considered as transducers to excite and receive SH guided waves. A segmented transducer, which enables piecewise sensing, has been shown by finite element analysis to be capable of locating a tiny through-thickness crack. The main benefits are that SH waves could be used to inspect fluid loaded structures and that it is possible to detect a crack oriented parallel to the wave vector.

  20. Interaction of Higher Order Modes Cluster (HOMC) guided waves with notch-like defects in plates

    NASA Astrophysics Data System (ADS)

    Sri Harsha Reddy, K.; Rajagopal, Prabhu; Balasubramaniam, Krishnan; Hill, Samuel; Dixon, Steve

    2017-02-01

    Guided ultrasonic waves are widely used for long range inspection. Higher Order Modes Cluster (HOMC), discovered at the author's research group [1-3] consist of multiple higher order guided wave modes that travel together as a single wave-packet and without appreciable dispersion for distances in the range of meters. These waves not only propagate along the length of the structure but also cover the entire thickness, and in view of the higher frequencies, they can offer improved resolution over conventional low-frequency guided waves. This paper studies the sensitivity of axial plate HOMC to notch-like defects, evaluated by calculating wave reflection co-efficient. The studies are carried out using finite element models validated by experiments. Analysis is presented for better understanding of wave-defect interaction. Advantages and limitations for practical realization of the above approach are also discussed.

  1. Surface wave phase velocities from 2-D surface wave tomography studies in the Anatolian plate

    NASA Astrophysics Data System (ADS)

    Arif Kutlu, Yusuf; Erduran, Murat; Çakır, Özcan; Vinnik, Lev; Kosarev, Grigoriy; Oreshin, Sergey

    2014-05-01

    We study the Rayleigh and Love surface wave fundamental mode propagation beneath the Anatolian plate. To examine the inter-station phase velocities a two-station method is used along with the Multiple Filter Technique (MFT) in the Computer Programs in Seismology (Herrmann and Ammon, 2004). The near-station waveform is deconvolved from the far-station waveform removing the propagation effects between the source and the station. This method requires that the near and far stations are aligned with the epicentre on a great circle path. The azimuthal difference of the earthquake to the two-stations and the azimuthal difference between the earthquake and the station are restricted to be smaller than 5o. We selected 3378 teleseismic events (Mw >= 5.7) recorded by 394 broadband local stations with high signal-to-noise ratio within the years 1999-2013. Corrected for the instrument response suitable seismogram pairs are analyzed with the two-station method yielding a collection of phase velocity curves in various period ranges (mainly in the range 25-185 sec). Diffraction from lateral heterogeneities, multipathing, interference of Rayleigh and Love waves can alter the dispersion measurements. In order to obtain quality measurements, we select only smooth portions of the phase velocity curves, remove outliers and average over many measurements. We discard these average phase velocity curves suspected of suffering from phase wrapping errors by comparing them with a reference Earth model (IASP91 by Kennett and Engdahl, 1991). The outlined analysis procedure yields 3035 Rayleigh and 1637 Love individual phase velocity curves. To obtain Rayleigh and Love wave travel times for a given region we performed 2-D tomographic inversion for which the Fast Marching Surface Tomography (FMST) code developed by N. Rawlinson at the Australian National University was utilized. This software package is based on the multistage fast marching method by Rawlinson and Sambridge (2004a, 2004b). The

  2. Effects of adhesive, host plate, transducer and excitation parameters on time reversibility of ultrasonic Lamb waves.

    PubMed

    Agrahari, J K; Kapuria, S

    2016-08-01

    To develop an effective baseline-free damage detection strategy using the time-reversal process (TRP) of Lamb waves in thin walled structures, it is essential to develop a good understanding of the parameters that affect the amplitude dispersion and consequently the time reversibility of the Lamb wave signal. In this paper, the effects of adhesive layer between the transducers and the host plate, the tone burst count of the excitation signal, the plate thickness, and the piezoelectric transducer thickness on the time reversibility of Lamb waves in metallic plates are studied using experiments and finite element simulations. The effect of adhesive layer on the forward propagation response and frequency tuning has been also studied. The results show that contrary to the general expectation, the quality of the reconstruction of the input signal after the TRP may increase with the increase in the adhesive layer thickness at certain frequency ranges. Similarly, an increase in the tone burst count resulting in a narrowband signal does not necessarily enhance the time reversibility at all frequencies, contrary to what has been reported earlier. For a given plate thickness, a thinner transducer yields a better reconstruction, but for a given transducer thickness, the similarity of the reconstructed signal may not be always higher for a thicker plate. It is important to study these effects to achieve the best quality of reconstruction in undamaged plates, for effective damage detection.

  3. Inverse mirror plasma experimental device (IMPED) - a magnetized linear plasma device for wave studies

    NASA Astrophysics Data System (ADS)

    Bose, Sayak; Chattopadhyay, P. K.; Ghosh, J.; Sengupta, S.; Saxena, Y. C.; Pal, R.

    2015-04-01

    In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n <= 1%, Luniform ~ 120 cm at argon filling pressure of ~10-4 mbar and axial magnetic field of B = 1090 G.

  4. Interaction of surface water waves with a vertical elastic plate: a hypersingular integral equation approach

    NASA Astrophysics Data System (ADS)

    Chakraborty, Rumpa; Mondal, Arpita; Gayen, R.

    2016-10-01

    In this paper, we present an alternative method to investigate scattering of water waves by a submerged thin vertical elastic plate in the context of linear theory. The plate is submerged either in deep water or in the water of uniform finite depth. Using the condition on the plate, together with the end conditions, the derivative of the velocity potential in the direction of normal to the plate is expressed in terms of a Green's function. This expression is compared with that obtained by employing Green's integral theorem to the scattered velocity potential and the Green's function for the fluid region. This produces a hypersingular integral equation of the first kind in the difference in potential across the plate. The reflection coefficients are computed using the solution of the hypersingular integral equation. We find good agreement when the results for these quantities are compared with those for a vertical elastic plate and submerged and partially immersed rigid plates. New results for the hydrodynamic force on the plate, the shear stress and the shear strain of the vertical elastic plate are also evaluated and represented graphically.

  5. Phase Velocity Method for Guided Wave Measurements in Composite Plates

    NASA Astrophysics Data System (ADS)

    Moreno, E.; Galarza, N.; Rubio, B.; Otero, J. A.

    Carbon Fiber Reinforced Polymer is a well-recognized material for aeronautic applications. Its plane structure has been widely used where anisotropic characteristics should be evaluated with flaw detection. A phase velocity method of ultrasonic guided waves based on a pitch-catch configuration is presented for this purpose. Both shear vertical (SV) and shear horizontal (SH) have been studied. For SV (Lamb waves) the measurements were done at different frequencies in order to evaluate the geometrical dispersion and elastic constants. The results for SV are discussed with an orthotropic elastic model. Finally experiments with lamination flaws are presented.

  6. Propagation of thickness shear waves in a periodically corrugated quartz crystal plate and its application exploration in acoustic wave filters.

    PubMed

    Li, Peng; Cheng, Li

    2017-02-07

    The propagation of thickness shear waves in a periodically corrugated quartz crystal plate is investigated in the present paper using a power series expansion technique. In the proposed simulation model, an equivalent continuity of shear stress moment is introduced as an approximation to handle sectional interfaces with abrupt thickness changes. The Bloch theory is applied to simulate the band structures for three different thickness variation patterns. It is shown that the power series expansion method exhibits good convergence and accuracy, in agreement with results by finite element method (FEM). A broad stop band can be obtained in the power transmission spectra owing to the trapped thickness shear modes excited by the thickness variation, whose physical mechanism is totally different from the well-known Bragg scattering effect and is insensitive to the structural periodicity. Based on the observed energy trapping phenomenon, an acoustic wave filter is proposed in a quartz plate with sectional decreasing thickness, which inhibits wave propagation in different regions.

  7. Acoustic field of a ballistic shock wave therapy device.

    PubMed

    Cleveland, Robin O; Chitnis, Parag V; McClure, Scott R

    2007-08-01

    Shock wave therapy (SWT) refers to the use of focused shock waves for treatment of musculoskeletal indications including plantar fascitis and dystrophic mineralization of tendons and joint capsules. Measurements were made of a SWT device that uses a ballistic source. The ballistic source consists of a handpiece within which compressed air (1-4 bar) is used to fire a projectile that strikes a metal applicator placed on the skin. The projectile generates stress waves in the applicator that transmit as pressure waves into tissue. The acoustic fields from two applicators were measured: one applicator was 15 mm in diameter and the surface slightly convex and the second was 12 mm in diameter the surface was concave. Measurements were made in a water tank and both applicators generated a similar pressure pulse consisting of a rectangular positive phase (4 micros duration and up to 8 MPa peak pressure) followed by a predominantly negative tail (duration of 20 micros and peak negative pressure of -6 MPa), with many oscillations. The rise times of the waveforms were around 1 micros and were shown to be too long for the pulses to be considered shock waves. Measurements of the field indicated that region of high pressure was restricted to the near-field (20-40 mm) of the source and was consistent with the Rayleigh distance. The measured acoustic field did not display focusing supported by calculations, which demonstrated that the radius of curvature of the concave surface was too large to effect a focusing gain. Other SWT devices use electrohydraulic, electromagnetic and piezoelectric sources that do result in focused shock waves. This difference in the acoustic fields means there is potentially a significant mechanistic difference between a ballistic source and other SWT devices.

  8. Combined spectral estimator for phase velocities of multimode Lamb waves in multilayer plates.

    PubMed

    Ta, De-an; Liu, Zhen-qing; Liu, Xiao

    2006-12-22

    A novel combined spectral estimate (CSE) method for differentiation and estimation the phase velocities of multimode Lamb waves whose wave numbers are much close or overlap one another in multiplayer plates is presented in this paper, which based on auto-regressive (AR) model and 2-D FFT. Simulated signals in brass plate were processed by 2-D FFT and CSE. And experiments are performed by using two conventional angle probes as emitter and receiver on the same surface of three-layered aluminum/xpoxy/aluminum plates, which include symmetrical and unsymmetrical plates. The multimode Lamb waves are excited in these laminates, and the received signal is processed by 2-D FFT and CSE, respectively. The results showed that the phase velocities of multimode signals whose wave numbers are much closed cannot be differentiated by 2-D FFT, but CSE has strong spatial resolution. Compared the measured phase velocities with the theoretical values, the error is smaller than 2% on the whole. It promises to be a useful method in experimental signals processing of multimode Lamb waves.

  9. Nonlinear guided waves in plates: a numerical perspective.

    PubMed

    Chillara, Vamshi Krishna; Lissenden, Cliff J

    2014-08-01

    Harmonic generation from non-cumulative fundamental symmetric (S0) and antisymmetric (A0) modes in plate is studied from a numerical standpoint. The contribution to harmonic generation from material nonlinearity is shown to be larger than that from geometric nonlinearity. Also, increasing the magnitude of the higher order elastic constants increases the amplitude of second harmonics. Second harmonic generation from non-phase-matched modes illustrates that group velocity matching is not a necessary condition for harmonic generation. Additionally, harmonic generation from primary mode is continuous and once generated, higher harmonics propagate independently. Lastly, the phenomenon of mode-interaction to generate sum and difference frequencies is demonstrated.

  10. Edge waves in plates with resonators: an elastic analogue of the quantum valley Hall effect

    NASA Astrophysics Data System (ADS)

    Pal, Raj Kumar; Ruzzene, Massimo

    2017-02-01

    We investigate elastic periodic structures characterized by topologically nontrivial bandgaps supporting backscattering suppressed edge waves. These edge waves are topologically protected and are obtained by breaking inversion symmetry within the unit cell. Examples for discrete one and two-dimensional lattices elucidate the concept and illustrate parallels with the quantum valley Hall effect. The concept is implemented on an elastic plate featuring an array of resonators arranged according to a hexagonal topology. The resulting continuous structures have non-trivial bandgaps supporting edge waves at the interface between two media with different topological invariants. The topological properties of the considered configurations are predicted by unit cell and finite strip dispersion analyses. Numerical simulations demonstrate edge wave propagation for excitation at frequencies belonging to the bulk bandgaps. The considered plate configurations define a framework for the implementation of topological concepts on continuous elastic structures of potential engineering relevance.

  11. Energy device powered by the motion of water beneath waves

    SciTech Connect

    Smith, E.J.

    1983-02-01

    A device for extracting both kinetic and potential energy from the motion beneath waves over a considerable depth comprising a power member or sail guided to reciprocate with the movement of the water. The power sail is connected to and operates a power device such as an electric generator or pump. A second member, or sail, is located in geometric position relative to the power sail to reflect energy back to the power sail. Sensors, servo systems, and computers may be used to optimize power output. Multiple units can be arranged in ''farms'' to furnish megawatts of power.

  12. Frequency dependent directivity of guided waves excited by circular transducers in anisotropic composite plates.

    PubMed

    Glushkov, Evgeny; Glushkova, Natalia; Eremin, Artem; Lammering, Rolf; Neumann, Mirko

    2012-08-01

    Lamb wave propagation in fiber-reinforced composite plates is featured by a pronounced directivity of wave energy transfer along the fibers from a point surface source. In the case of non-point (sized) source, the main lobe of radiation diagram may turn with frequency up to the orthogonal to the fibers direction. This effect has been theoretically studied and physically explained in the context of semi-analytical integral-equation based mathematical model. The present paper gives its experimental verification.

  13. Laser-Ultrasonic Investigation on Lamb Waves in Two-Dimensional Phononic Crystal Plates

    NASA Astrophysics Data System (ADS)

    Wang, Jing Shi; Cheng, Ying; Xu, Xiao Dong; Liu, Xiao Jun

    2015-06-01

    In this paper, laser-ultrasonic non-destructive testing is used to investigate the propagation of Lamb waves in two-dimensional phononic crystal plates. The bandgaps are experimentally observed for low-order Lamb wave modes. The influence of crucial parameters such as the periodical arrangement of scatterers on bandgaps is discussed in detail. The finite element simulations further agree well with the results of the laser-ultrasonic investigation.

  14. Fraunhofer diffraction of the plane wave by a multilevel (quantized) spiral phase plate.

    PubMed

    Kotlyar, Victor V; Kovalev, Alexey A

    2008-01-15

    We obtain an analytical expression in the form of a finite sum of plane waves that describes the paraxial scalar Fraunhofer diffraction of a limited plane wave by a multilevel (quantized) spiral phase plate (SPP) bounded by a polygonal aperture. For several topological charges of the SPP we numerically obtain the minimal number of SPP sectors for which the RMS between the Fraunhofer diffraction patterns for multilevel and continuous SPP does not exceed 2%.

  15. Scattering of Lamb waves in a composite plate

    NASA Technical Reports Server (NTRS)

    Bratton, Robert; Datta, Subhendu; Shah, Arvind

    1991-01-01

    A combined analytical and finite element technique is developed to gain a better understanding of the scattering of elastic waves by defects. This hybrid method is capable of predicting scattered displacements from arbitrary shaped defects as well as inclusions of different material. The continuity of traction and displacements at the boundaries of the two areas provided the necessary equations to find the nodal displacements and expansion coefficients. Results clearly illustrate the influence of increasing crack depth on the scattered signal.

  16. The environmental interactions of tidal and wave energy generation devices

    SciTech Connect

    Frid, Chris; Andonegi, Eider; Judd, Adrian; Rihan, Dominic; Rogers, Stuart I.; Kenchington, Ellen

    2012-01-15

    Global energy demand continues to grow and tidal and wave energy generation devices can provide a significant source of renewable energy. Technological developments in offshore engineering and the rising cost of traditional energy means that offshore energy resources will be economic in the next few years. While there is now a growing body of data on the ecological impacts of offshore wind farms, the scientific basis on which to make informed decisions about the environmental effects of other offshore energy developments is lacking. Tidal barrages have the potential to cause significant ecological impacts particularly on bird feeding areas when they are constructed at coastal estuaries or bays. Offshore tidal stream energy and wave energy collectors offer the scope for developments at varying scales. They also have the potential to alter habitats. A diversity of designs exist, including floating, mid-water column and seabed mounted devices, with a variety of moving-part configurations resulting in a unique complex of potential environmental effects for each device type, which are discussed to the extent possible. - Highlights: Black-Right-Pointing-Pointer We review the environmental impacts of tidal barrages and fences, tidal stream farms and wave energy capture devices. Black-Right-Pointing-Pointer Impacts on habitats, species and the water column, and effects of noise and electromagnetic fields are considered. Black-Right-Pointing-Pointer Tidal barrages can cause significant impacts on bird feeding areas when constructed at coastal estuaries or bays. Black-Right-Pointing-Pointer Wave energy collectors can alter water column and sea bed habitats locally and over large distances.

  17. Guided-Wave Optic Devices for Integrated Optic Information Processing.

    DTIC Science & Technology

    1984-08-08

    integrating miniature optical components such as laser light sources, modulators, switches, deflectors , lenses, prisms, and detectors in a common substrate...ZnO composite waveguides, and 2 . Planar Guided-Wave Magneto- Optic Bragg Diffraction and Devices in YIG-GGG Waveguides. Some very significant progress... optical wavelength. We have recently obtained further theoretical results. ( 2 ) For example, as shown in Fig. l(a) and 1(b), the topographical

  18. Theory of Evanescent-Wave Johnson Noise in Qubit Devices

    DTIC Science & Technology

    2015-05-28

    metallic electrodes and leads. This random motion has both thermal and quantum components, though in most devices presently under investigation, the...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 evanescent wave, Johnson noise, decoherence, metal surface REPORT DOCUMENTATION PAGE 11...ultimate source of these fluctuations is the random electric currents that are strongest in the metallic electrodes and leads. This random motion has both

  19. Impacts of wave energy conversion devices on local wave climate: observations and modelling from the Perth Wave Energy Project

    NASA Astrophysics Data System (ADS)

    Hoeke, Ron; Hemer, Mark; Contardo, Stephanie; Symonds, Graham; Mcinnes, Kathy

    2016-04-01

    As demonstrated by the Australian Wave Energy Atlas (AWavEA), the southern and western margins of the country possess considerable wave energy resources. The Australia Government has made notable investments in pre-commercial wave energy developments in these areas, however little is known about how this technology may impact local wave climate and subsequently affect neighbouring coastal environments, e.g. altering sediment transport, causing shoreline erosion or accretion. In this study, a network of in-situ wave measurement devices have been deployed surrounding the 3 wave energy converters of the Carnegie Wave Energy Limited's Perth Wave Energy Project. This data is being used to develop, calibrate and validate numerical simulations of the project site. Early stage results will be presented and potential simulation strategies for scaling-up the findings to larger arrays of wave energy converters will be discussed. The intended project outcomes are to establish zones of impact defined in terms of changes in local wave energy spectra and to initiate best practice guidelines for the establishment of wave energy conversion sites.

  20. New Biosensor Using Shear Horizontal Surface Acoustic Wave Device

    NASA Astrophysics Data System (ADS)

    Kondoh, Jun; Matsui, Yoshikazu; Shiokawa, Showko

    1993-05-01

    This paper describes a new biosensor to detect an enzyme reaction in liquid using surface acoustic wave (SAW) devices fabricated on 36°-rotated Y-cut, X-propagating LiTaO3. The sensing wave on the substrate is a predominantly shear-horizontal-mode SAW (SH-SAW) and is affected by a strong acoustoelectric interaction between the piezoelectric potential and electrical properties of the materials in the adjacent liquid. As an example of an electrical property, pH change associated with an enzyme reaction leads to measurable perturbation in the wave-propagation characteristic. Taking advantage of this phenomenon we realized a SAW biosensor which consists of an immobilized urease membrane on the surface. Also, highly sensitive detection for the urea solution was obtained in our preliminary experiments.

  1. SAW devices based on novel surface wave excitations

    NASA Astrophysics Data System (ADS)

    Therrien, Joel; Dai, Lian

    2015-03-01

    Surface Acoustic Wave (SAW) devices have applications in radio frequency and microwave filtering as well as highly sensitive sensors. Current SAW design employs the use of an array of electrode pairs, referred to as Inter-Digitated Transducers (IDTs) for creating and receiving surface waves on piezoelectric substrates. The pitch of the electrode pairs along with the properties of the substrate determine the operating frequency. The number of electrode pairs determine the bandwidth of the emitted waves. We will present a novel configuration that eliminates the need for the IDTs and replaces with with a single circular electrode located inside a larger ground ring. This configuration induces drumhead modes. We will show that the resonant frequencies follow the zeros of Bessel functions of the first kind. Applications in RF filtering and mass sensing will be presented.

  2. Scattering of impact wave by a crack in composite plate

    NASA Technical Reports Server (NTRS)

    Ju, T. H.; Datta, S. K.; Shah, A. H.

    1990-01-01

    The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate with and without delamination cracks are investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour enclosing completely the crack. This combined method leads to a set of linear unsymmetric complex matrix equations which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high order finite elements have been used. Also, both the six node singular elements and eight node transition elements are used around the crack tips to model the crack-tip singularity. It is shown that from the numerical results for surface responses both depth and length of this crack can be identified.

  3. Performance optimization of a pneumatic wave energy conversion device

    NASA Astrophysics Data System (ADS)

    Surko, S. W.

    1982-08-01

    The purpose of this study was, for the first time, to optimize the performance of a pneumatic wave energy conversion device. The experiments of Jolly and Newmaster (1979) and Trop and Casey (1980) left a capture chamber and turbine for further investigation. To optimize the system performance the turbine had to be first analyzed so that its power performance curves could be determined. These curves were needed to help define the possible overall performance of the system, and for the impedance matching of the system necessary for performance optimization. With this knowledge, an appropriate generator was purchased and a generator-turbine linkage designed and built. The completed system was then analyzed in the 380 ft wave tank at the U.S. Naval Academy to establish its optimum performance. From the research it is clear that pneumatic wave energy conversion is a promising concept. With several hundred of these devices situated some 100 km off the coast of the Pacific Northwest each device would be producing from 50 to 200 kW which would be transferred back to shore.

  4. Numerical investigation of a standing-wave thermoacoustic device

    NASA Astrophysics Data System (ADS)

    Dar Ramdane, M. Z.; Khorsi, A.

    2015-05-01

    The thermoacoustic effect concerns conversion of energy between a gas and a solid in the presence of acoustic waves. Although the working principle is well understood, the optimal design of thermoacoustic devices remains a challenge. The present work aims to perform a numerical simulation of a simple standing-wave thermoacoustic device. The analysis of the flow and the prediction of the heat transfer are performed by solving the non-linear unsteady Navier-Stokes equations using the finite volume method implemented in the commercial code ANSYS-CFX. The goal of this work is to study the effect of the stack temperature gradient, on the acoustic pressure and the produced acoustic power. This stack temperature gradient generates the thermoacoustic instability in standing-wave thermoacoustic resonator. The obtained results show an increase of the acoustic pressure and the acoustic power while increasing in the stack temperature gradient. The thermodynamic cycles of the thermoacoustic device are illustrated and observed for the different stack temperature gradients.

  5. Plate-type elastic metamaterials for low-frequency broadband elastic wave attenuation.

    PubMed

    Li, Yinggang; Zhu, Ling; Chen, Tianning

    2017-01-01

    In this paper, we numerically and experimentally demonstrate the low-frequency broadband elastic wave attenuation and vibration suppression by using plate-type elastic metamaterial, which is constituted of periodic double-sides stepped resonators deposited on a two-dimensional phononic plate with steel matrix. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are calculated by using the finite element method. In contrast to the typical phononic plates consisting of periodic stepped resonators deposited on a homogeneous steel plate, the proposed elastic metamaterial can yield large band gap in the low-frequency range, resulting in the low-frequency broadband elastic wave attenuation. The formation mechanisms of the band gap as well as the effects of material and geometrical parameters on the band gap are further explored numerically. Numerical results show that, the formation mechanism of opening the low-frequency band gap is attributed to the coupling between the local resonant Lamb modes of two-dimensional phononic plate and the resonant modes of the stepped resonators. The band gap can be significantly modulated by the material and geometrical parameters. The properties of broadband gaps of the proposed subwavelength scale elastic metamaterials can potentially be applied to vibration and noise reduction in the audio regime as well as broadband elastic wave confinement and modulation in ultrasonic region.

  6. Solution of Transcendental and Algebraic Equations with Application to Wave Propagation in Elastic Plates.

    DTIC Science & Technology

    1981-08-07

    ACKNOWLEDGMENTS The author gratefully acknowledges Anthony J. Rudgers for his con- tinuing expert guidance, and for critically checking the entire...Flexural and Extensional Waves in an Unloaded Thick Plate," NRL Report 8372 (submitted for publication). Anthony J. Rudgers , "Acoustical reflection

  7. Influence of the external electric field on propagation of Lamb waves in piezoelectric plates.

    PubMed

    Burkov, Sergei I; Zolotova, Olga P; Sorokin, Boris P

    2011-01-01

    The influence of the electric field on the properties of the Lamb and SH-waves in piezoelectric Bi(12)GeO(20) and La(3)Ga(5)SiO1(4) crystal plates has been investigated. Using basic equations and boundary conditions, the formulas for computer simulation have been obtained. The effect of acoustic modes hybridization has been considered.

  8. Diffraction of a plane, finite-radius wave by a spiral phase plate.

    PubMed

    Kotlyar, V V; Khonina, S N; Kovalev, A A; Soifer, V A; Elfstrom, H; Turunen, J

    2006-06-01

    We derive analytical expressions containing a hypergeometric function to describe the Fresnel and Fraunhofer diffraction of a plane wave of circular and ringlike cross section by a spiral phase plate (SPP) of an arbitrary integer order. Experimental diffraction patterns generated by an SPP fabricated in resist through direct e-beam writing are in good agreement with the theoretical intensity distribution.

  9. The simulation of Lamb waves in a cracked plate using the scaled boundary finite element method.

    PubMed

    Gravenkamp, Hauke; Prager, Jens; Saputra, Albert A; Song, Chongmin

    2012-09-01

    The scaled boundary finite element method is applied to the simulation of Lamb waves for ultrasonic testing applications. With this method, the general elastodynamic problem is solved, while only the boundary of the domain under consideration has to be discretized. The reflection of the fundamental Lamb wave modes from cracks of different geometry in a steel plate is modeled. A test problem is compared with commercial finite element software, showing the efficiency and convergence of the scaled boundary finite element method. A special formulation of this method is utilized to calculate dispersion relations for plate structures. For the discretization of the boundary, higher-order elements are employed to improve the efficiency of the simulations. The simplicity of mesh generation of a cracked plate for a scaled boundary finite element analysis is illustrated.

  10. Traveling-wave device with mass flux suppression

    DOEpatents

    Swift, Gregory W.; Backhaus, Scott N.; Gardner, David L.

    2000-01-01

    A traveling-wave device is provided with the conventional moving pistons eliminated. Acoustic energy circulates in a direction through a fluid within a torus. A side branch may be connected to the torus for transferring acoustic energy into or out of the torus. A regenerator is located in the torus with a first heat exchanger located on a first side of the regenerator downstream of the regenerator relative to the direction of the circulating acoustic energy; and a second heat exchanger located on an upstream side of the regenerator. The improvement is a mass flux suppressor located in the torus to minimize time-averaged mass flux of the fluid. In one embodiment, the device further includes a thermal buffer column in the torus to thermally isolate the heat exchanger that is at the operating temperature of the device.

  11. Experimental study of the acoustoelastic Lamb wave in thin plates

    NASA Astrophysics Data System (ADS)

    Pei, Ning; Bond, Leonard J.

    2016-02-01

    Many factors can cause residual stresses in industry, like rolling, welding and coating. Residual stresses can have both benefits and shortcomings on components, so it is important to find the residual stresses out and enhance its benefits part and get rid of its harmful part. There are many methods for residual stresses detection and ultrasonic method turns out to be a good one for it is nondestructive, relative cheap and portable. The critically refracted longitudinal (LCR) wave is widely used for it is regarded most sensitive to stress and less sensitive to texture which can influence detection results. Ultrasonic methods for residual stresses detection are based on time of flight (TOF) measurement, but because the measurement should reach nanosecond to show stress change, there are many other factors that can influence TOF, like temperature, texture of the components and even the thickness of the couplant. So increasing the TOF's sensitivity to stress is very important. In this paper the relationships between velocity and frequency are studied experimentally[6] for different Lamb modes, under various stress loadings. The result shows that the sensitivity of different modes various a lot, the A1 mode is the most sensitivity, compared to S0, S1 and A0 modes; if the force is added to 100 MPa, the change stress of A1 mode can be as large to 80 m/s, which is about 10 times more sensitive than the traditional bulk wave. This makes it as a good choice for residual stress detection.

  12. Magneto-thermo-elastokinetics of geometrically nonlinear laminated composite plates. Part 2: vibration and wave propagation

    NASA Technical Reports Server (NTRS)

    Qin, Zhanming; Hasanyan, Davresh; Librescu, Liviu; Ambur, Damodar R.

    2005-01-01

    In Part 1 of this paper, the governing equations of geometrically nonlinear, anisotropic composite plates incorporating magneto-thermo-elastic effects have been derived. In order to gain insight into the implications of a number of geometrical and physical features of the system. three special cases are investigated: (i) free vibration of a plate strip immersed in a transversal magnetic field; (ii) free vibration of the plate strip immersed in an axial magnetic field; (iii) magneto-elastic wave propagations of an infinite plate. Within each of these cases, a prescribed uniform thermal field is considered. Special coupling characteristics between the magnetic and elastic fields are put into evidence. Extensive numerical investigations are conducted and pertinent conclusions which highlight the various effects induced by the magneto-elastic couplings and the finite electroconductivity, are outlined.

  13. Design for the optical retardation in broadband zero-order half-wave plates.

    PubMed

    Liu, Jin; Cai, Yi; Chen, Hongyi; Zeng, Xuanke; Zou, Da; Xu, Shixiang

    2011-04-25

    This paper presents a novel design for broadband zero-order half-wave plates to eliminate the first-order or up to second-order wavelength-dependent birefringent phase retardation (BPR) with 2 or 3 different birefringent materials. The residual BPRs of the plates increase monotonously with the wavelength deviation from a selected wavelength, so the plates are applicable to the broadband light pulses which gather most of the light energy around their central wavelengths. The model chooses the materials by the birefringent dispersion coefficient and evaluates the performances of the plates by the weighted average of the absolute value of residual BPR in order to emphasize the contributions of the incident spectral components whose possess higher energies.

  14. Low-cost simulation of guided wave propagation in notched plate-like structures

    NASA Astrophysics Data System (ADS)

    Glushkov, E.; Glushkova, N.; Eremin, A.; Giurgiutiu, V.

    2015-09-01

    The paper deals with the development of low-cost tools for fast computer simulation of guided wave propagation and diffraction in plate-like structures of variable thickness. It is focused on notched surface irregularities, which are the basic model for corrosion damages. Their detection and identification by means of active ultrasonic structural health monitoring technologies assumes the use of guided waves generated and sensed by piezoelectric wafer active sensors as well as the use of laser Doppler vibrometry for surface wave scanning and visualization. To create a theoretical basis for these technologies, analytically based computer models of various complexity have been developed. The simplest models based on the Euler-Bernoulli beam and Kirchhoff plate equations have exhibited a sufficiently wide frequency range of reasonable coincidence with the results obtained within more complex integral equation based models. Being practically inexpensive, they allow one to carry out a fast parametric analysis revealing characteristic features of wave patterns that can be then made more exact using more complex models. In particular, the effect of resonance wave energy transmission through deep notches has been revealed within the plate model and then validated by the integral equation based calculations and experimental measurements.

  15. 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.

  16. HeatWave: the next generation of thermography devices

    NASA Astrophysics Data System (ADS)

    Moghadam, Peyman; Vidas, Stephen

    2014-05-01

    Energy sustainability is a major challenge of the 21st century. To reduce environmental impact, changes are required not only on the supply side of the energy chain by introducing renewable energy sources, but also on the demand side by reducing energy usage and improving energy efficiency. Currently, 2D thermal imaging is used for energy auditing, which measures the thermal radiation from the surfaces of objects and represents it as a set of color-mapped images that can be analysed for the purpose of energy efficiency monitoring. A limitation of such a method for energy auditing is that it lacks information on the geometry and location of objects with reference to each other, particularly across separate images. Such a limitation prevents any quantitative analysis to be done, for example, detecting any energy performance changes before and after retrofitting. To address these limitations, we have developed a next generation thermography device called Heat Wave. Heat Wave is a hand-held 3D thermography device that consists of a thermal camera, a range sensor and color camera, and can be used to generate precise 3D model of objects with augmented temperature and visible information. As an operator holding the device smoothly waves it around the objects of interest, Heat Wave can continuously track its own pose in space and integrate new information from the range and thermal and color cameras into a single, and precise 3D multi-modal model. Information from multiple viewpoints can be incorporated together to improve the accuracy, reliability and robustness of the global model. The approach also makes it possible to reduce any systematic errors associated with the estimation of surface temperature from the thermal images.

  17. Diffraction of Harmonic Flexural Waves in a Cracked Elastic Plate Carrying Electrical Current

    NASA Technical Reports Server (NTRS)

    Ambur, Damodar R.; Hasanyan, Davresh; Librescu, iviu; Qin, Zhanming

    2005-01-01

    The scattering effect of harmonic flexural waves at a through crack in an elastic plate carrying electrical current is investigated. In this context, the Kirchhoffean bending plate theory is extended as to include magnetoelastic interactions. An incident wave giving rise to bending moments symmetric about the longitudinal z-axis of the crack is applied. Fourier transform technique reduces the problem to dual integral equations, which are then cast to a system of two singular integral equations. Efficient numerical computation is implemented to get the bending moment intensity factor for arbitrary frequency of the incident wave and of arbitrary electrical current intensity. The asymptotic behaviour of the bending moment intensity factor is analysed and parametric studies are conducted.

  18. The influence of temperature variations on ultrasonic guided waves in anisotropic CFRP plates.

    PubMed

    Putkis, O; Dalton, R P; Croxford, A J

    2015-07-01

    Carbon Fibre Reinforced Polymer (CFRP) materials are lightweight and corrosion-resistant and therefore are increasingly used in aerospace, automotive and construction industries. In Structural Health Monitoring (SHM) applications of CFRP materials, ultrasonic guided waves potentially offer large area inspection or inspection from a remote location. This paper addresses the effect of temperature variation on guided wave propagation in highly anisotropic CFRP materials. Temperature variations cause changes in guided wave velocity that can in turn compromise the baseline subtraction procedures employed by many SHM systems for damage detection. A simple model that describes the dependence of elastic properties of the CFRP plates on temperature is presented in this paper. The model can be used to predict anisotropic velocity changes and baseline subtraction performance under varying thermal conditions. The results produced by the model for unidirectional and 0/90 CFRP plates are compared with experimental measurements.

  19. Interaction of acoustic waves generated by coupled plate

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1990-01-01

    When two substructures are coupled, the acoustic field generated by the motion of each of the substructures will interact with the motion of the other substructure. This would be the case of a structure enclosing an acoustic cavity. A technique to model the interaction of the generated sound fields from the two components of a coupled structure, and the influence of this interaction on the vibration of the structural components is presented. Using a mobility power flow approach, each element of the substructure is treated independently both when developing the structural response and when determining the acoustic field generated by this component. The presence of the other substructural components is introduced by assuming these components to be rigid baffles. The excitation of one of the substructures is assumed to be by an incident acoustic wave which is dependent of the motion of the substructure. The sound field generated by the motion of the substructure is included in the solution of the response.

  20. Propagating plane harmonic waves through finite length plates of variable thickness using finite element techniques

    NASA Technical Reports Server (NTRS)

    Clark, J. H.; Kalinowski, A. J.; Wagner, C. A.

    1983-01-01

    An analysis is given using finite element techniques which addresses the propagaton of a uniform incident pressure wave through a finite diameter axisymmetric tapered plate immersed in a fluid. The approach utilized in developing a finite element solution to this problem is based upon a technique for axisymmetric fluid structure interaction problems. The problem addressed is that of a 10 inch diameter axisymmetric fixed plate totally immersed in a fluid. The plate increases in thickness from approximately 0.01 inches thick at the center to 0.421 inches thick at a radius of 5 inches. Against each face of the tapered plate a cylindrical fluid volume was represented extending five wavelengths off the plate in the axial direction. The outer boundary of the fluid and plate regions were represented as a rigid encasement cylinder as was nearly the case in the physical problem. The primary objective of the analysis is to determine the form of the transmitted pressure distribution on the downstream side of the plate.

  1. Propagation of flexural and membrane waves with fluid loaded NASTRAN plate and shell elements

    NASA Technical Reports Server (NTRS)

    Kalinowski, A. J.; Wagner, C. A.

    1983-01-01

    Modeling of flexural and membrane type waves existing in various submerged (or in vacuo) plate and/or shell finite element models that are excited with steady state type harmonic loadings proportioned to e(i omega t) is discussed. Only thin walled plates and shells are treated wherein rotary inertia and shear correction factors are not included. More specifically, the issue of determining the shell or plate mesh size needed to represent the spatial distribution of the plate or shell response is of prime importance towards successfully representing the solution to the problem at hand. To this end, a procedure is presented for establishing guide lines for determining the mesh size based on a simple test model that can be used for a variety of plate and shell configurations such as, cylindrical shells with water loading, cylindrical shells in vacuo, plates with water loading, and plates in vacuo. The procedure for doing these four cases is given, with specific numerical examples present only for the cylindrical shell case.

  2. Scattering of flexural waves from a hole in a thin plate with an internal beam.

    PubMed

    Climente, A; Norris, Andrew N; Sánchez-Dehesa, José

    2015-01-01

    The scattering of flexural waves by a hole in a thin plate traversed by a beam is modeled here by coupling the Kirchhoff-Love and the Euler-Bernoulli theories. A closed form expression is obtained for the transfer matrix (T-matrix) relating the incident wave to the scattered cylindrical waves. For this purpose, a general method has been developed, based on an analogous impedance method for acoustic waves, for calculating the T-matrix for flexural wave scattering problems. The T-matrix for the problem considered displays a simple structure, composed of distinct sub-matrices which decouple the inside and the outside fields. The conservation of energy principle and numerical comparisons with a commercial finite element simulator have been used to prove the theory.

  3. Island-ground single-plate electro-wetting on dielectric device for digital microfluidic systems

    NASA Astrophysics Data System (ADS)

    Cui, Weiwei; Zhang, Menglun; Zhang, Daihua; Pang, Wei; Zhang, Hao

    2014-07-01

    In this paper, we present a single-plate electro-wetting on dielectric (SEWOD) device by integrating an island-ground electrode (IG), which is surrounded by the driving electrodes and looks like an island. Both experiments and theoretical analysis have been conducted to investigate the performance of the IG-SEWOD device. The driving voltage of a fabricated IG-SEWOD has been measured to be 15 V, which is half of that of a floating SEWOD. The digital dynamic properties of the EWOD device are greatly enhanced due to the "double locking" effect and rapid residual charges elimination provided by the IG. The proposed EWOD device shows great potential in constructing advanced microfluidics platforms for bio-chemical detection and disease diagnosis.

  4. Shock Wave Based Biolistic Device for DNA and Drug Delivery

    NASA Astrophysics Data System (ADS)

    Nakada, Mutsumi; Menezes, Viren; Kanno, Akira; Hosseini, S. Hamid R.; Takayama, Kazuyoshi

    2008-03-01

    A shock wave assisted biolistic (biological ballistic) device has been developed to deliver DNA/drug-coated micro-projectiles into soft living targets. The device consists of an Nd:YAG laser, an optical setup to focus the laser beam and, a thin aluminum (Al) foil (typically 100 µm thick) which is a launch pad for the micro-projectiles. The DNA/drug-coated micro-particles to be delivered are deposited on the anterior surface of the foil and the posterior surface of the foil is ablated using the laser beam with an energy density of about 32×109 W/cm2. The ablation launches a shock wave through the foil that imparts an impulse to the foil surface, due to which the deposited particles accelerate and acquire sufficient momentum to penetrate soft targets. The device has been tested for particle delivery by delivering 1 µm size tungsten particles into liver tissues of experimental rats and in vitro test models made of gelatin. The penetration depths of about 90 and 800 µm have been observed in the liver and gelatin targets, respectively. The device has been tested for in vivo DNA [encoding β-glucuronidase (GUS) gene] transfer by delivering plasmid DNA-coated, 1-µm size gold (Au) particles into onion scale, tobacco leaf and soybean seed cells. The GUS activity was detected in the onion, tobacco and soybean cells after the DNA delivery. The present device is totally non-intrusive in nature and has a potential to get miniaturized to suit the existing medical procedures for DNA and/or drug delivery.

  5. Contribution of Antisymmetric and Symmetric Waves to the Reflection of Sound in a Fluid by a Thick, Homogeneous Plate.

    DTIC Science & Technology

    1980-10-23

    SOUND IN A FLUID BY A THICK, HOMOGENEOUS PLATE INTRODUCTION In a recent report Rudgers [11 describes the acoustical behavior of thick, fluid-loaded...symmetric waves to the plate-fluid interactions studied by Rudgers (1]. In the present report, the role of antisymmetric and symmetric waves is analyzed...defined by Rudgers (4]. The structural response function of the two types of waves in combination is related to the response functions of the two types

  6. Calculation of electromechanical coupling coefficient of Lamb waves in multilayered plates.

    PubMed

    Fan, Li; Zhang, Shu-Yi; Zheng, Kai; Lin, Wei; Gao, Hui-Dong

    2006-12-22

    Two methods have been always used to calculate the electromechanical coupling coefficient of a Lamb wave in a multilayered plate: one is an approximate method using the acoustic velocity difference under different electric boundary conditions and the other is the Green's function method. The Green's function method is more accurate but more complicated, because an 8N-order matrix is used for calculating the electromechanical coupling coefficient of the Lamb wave in an N-layered plate, which induces great computation loads and some calculation deviations. In this paper, a transfer matrix method is used for calculating the electromechanical coupling coefficient of Lamb waves in a multilayered plate, in which only an 8-order matrix is needed regardless of the number of layers of the plate. The results show that the transfer matrix method can obtain the same accuracy as those by the Green's function method, but the computation load and deviation are greatly decreased by avoiding the use of a high order matrix used in the Green's function method.

  7. Wireless device for activation of an underground shock wave absorber

    NASA Astrophysics Data System (ADS)

    Chikhradze, M.; Akhvlediani, I.; Bochorishvili, N.; Mataradze, E.

    2011-10-01

    The paper describes the mechanism and design of the wireless device for activation of energy absorber for localization of blast energy in underground openings. The statistics shows that the greatest share of accidents with fatal results associate with explosions in coal mines due to aero-methane and/or air-coal media explosion. The other significant problem is terrorist or accidental explosions in underground structures. At present there are different protective systems to reduce the blast energy. One of the main parts of protective Systems is blast Identification and Registration Module. The works conducted at G. Tsulukidze Mining Institute of Georgia enabled to construct the wireless system of explosion detection and mitigation of shock waves. The system is based on the constant control on overpressure. The experimental research continues to fulfill the system based on both threats, on the constant control on overpressure and flame parameters, especially in underground structures and coal mines. Reaching the threshold value of any of those parameters, the system immediately starts the activation. The absorber contains a pyrotechnic device ensuring the discharge of dispersed water. The operational parameters of wireless device and activation mechanisms of pyrotechnic element of shock wave absorber are discussed in the paper.

  8. On the propagation mechanism of a detonation wave in a round tube with orifice plates

    NASA Astrophysics Data System (ADS)

    Ciccarelli, G.; Cross, M.

    2016-09-01

    This study deals with the investigation of the detonation propagation mechanism in a circular tube with orifice plates. Experiments were performed with hydrogen air in a 10-cm-inner-diameter tube with the second half of the tube filled with equally spaced orifice plates. A self-sustained Chapman-Jouguet (CJ) detonation wave was initiated in the smooth first half of the tube and transmitted into the orifice-plate-laden second half of the tube. The details of the propagation were obtained using the soot-foil technique. Two types of foils were used between obstacles, a wall-foil placed on the tube wall, and a flat-foil (sooted on both sides) placed horizontally across the diameter of the tube. When placed after the first orifice plate, the flat foil shows symmetric detonation wave diffraction and failure, while the wall foil shows re-initiation via multiple local hot spots created when the decoupled shock wave interacts with the tube wall. At the end of the tube, where the detonation propagated at an average velocity much lower than the theoretical CJ value, the detonation propagation is much more asymmetric with only a few hot spots on the tube wall leading to local detonation initiation. Consecutive foils also show that the detonation structure changes after each obstacle interaction. For a mixture near the detonation propagation limit, detonation re-initiation occurs at a single wall hot spot producing a patch of small detonation cells. The local overdriven detonation wave is short lived, but is sufficient to keep the global explosion front propagating. Results associated with the effect of orifice plate blockage and spacing on the detonation propagation mechanism are also presented.

  9. Dispersion of Lamb waves under a periodic metal grating in aluminum nitride plates.

    PubMed

    Naumenko, Natalya F

    2014-09-01

    Dispersion of Lamb waves propagating in AlN plates with a periodic Al grating on the top surface and an Al electrode on the bottom surface is investigated using the numerical technique SDA-FEM-SDA, which combines finite element modeling (FEM) analysis of the electrode region with spectral-domain analysis (SDA) of the adjacent multi-layered half-spaces. Characteristics of zero-order and higher-order Lamb waves are presented as functions of plate thickness and spectral frequency, which varies in the first Brillouin zone. The structures of typical Lamb waves are examined via visualization of the instantaneous displacement fields in the AlN plate confined between the grating and the bottom electrode. The mechanism of building hybrid modes, which arise from intermode coupling between the counter-propagating Lamb waves of different symmetry and order, is illustrated by two examples of modes propagating with wavelengths λ = 3p and λ = 4p, where p is the pitch of the grating.

  10. Modeling and measurement of angle-beam wave propagation in a scatterer-free plate

    NASA Astrophysics Data System (ADS)

    Dawson, Alexander J.; Michaels, Jennifer E.; Michaels, Thomas E.

    2017-02-01

    Wavefield imaging has been shown to be a powerful tool for improving the understanding and characterization of wave propagation and scattering in plates. The complete measurement of surface displacement over a 2-D grid provided by wavefield imaging has the potential to serve as a useful means of validating ultrasonic models. Here, a preliminary study of ultrasonic angle-beam wave propagation in a scatterer-free plate using a combination of wavefield measurements and 2-D finite element models is described. Both wavefield imaging and finite element analysis are used to study the propagation of waves at a refracted angle of 56.8° propagating in a 6.35 mm thick aluminum plate. Wavefield imaging is performed using a laser vibrometer mounted on an XYZ scanning stage, which is programmed to move point-to-point on a rectilinear grid to acquire waveform data. The commercial finite element software package, PZFlex, which is specifically designed to handle large, complex ultrasonic problems, is used to create a 2-D cross-sectional model of the transducer and plate. For model validation, vertical surface displacements from both the wavefield measurements and the PZFlex finite element model are compared and found to be in excellent agreement. The validated PZFlex model is then used to explain the mechanism of Rayleigh wave generation by the angle-beam wedge. Since the wavefield measurements are restricted to the specimen surface, the cross-sectional PZFlex model is able to provide insights the wavefield data cannot. This study illustrates how information obtained from ultrasonic experiments and modeling results can be combined to improve understanding of angle-beam wave generation and propagation.

  11. Surface acoustic wave devices including Langmuir-Blodgett films (Review)

    NASA Astrophysics Data System (ADS)

    Plesskii, V. P.

    1991-06-01

    Recent theoretical and experimental research related to the use of Langmuir-Blodgett (LB) films in surface acoustic wave (SAW) devices is reviewed. The sensitivity of the different cuts of quartz and lithium niobate to inertial loading is investigated, and it is shown that some cuts in lithium niobate are twice as sensitive to mass loading than the commonly used YZ-cut. The large variety of organic compounds suitable for the production of LB films makes it possible to create SAW sensors reacting selectively to certain substances. The existing SAW sensors based on LB films are characterized by high sensitivity and fast response.

  12. A serial sample loading system: interfacing multiwell plates with microfluidic devices.

    PubMed

    Rane, Tushar D; Zec, Helena C; Wang, Tza-Huei

    2012-10-01

    There is an increasing demand for novel high-throughput screening (HTS) technologies in the pharmaceutical and biotechnological industries. The robotic sample-handling techniques currently used in these industries, although fast, are still limited to operating in multiwell plates with the sample volumes per reaction in the microliter regime. Digital microfluidics offers an alternative for reduction in sample volume consumption for HTS but lacks a reliable technique for transporting a large number of samples to the microfluidic device. In this report, we develop a technique for serial delivery of sample arrays to a microfluidic device from multiwell plates, through a single sample inlet. Under this approach, a serial array of sample plugs, separated by an immiscible carrier fluid, is loaded into a capillary and delivered to a microfluidic device. Similar approaches have been attempted in the past, however, either with a slower sample loading device such as a syringe pump or vacuum-based sample loading with limited driving pressure. We demonstrated the application of our positive-pressure-based serial sample loading (SSL) system to load a series of sample plugs into a capillary. The adaptability of the SSL system to generate sample plugs with a variety of volumes in a predictable manner was also demonstrated.

  13. A Serial Sample Loading System: Interfacing Multi-well plates with Microfluidic Devices

    PubMed Central

    Rane, Tushar D.; Zec, Helena; Wang, Jeff Tza-Huei

    2013-01-01

    There is an increasing demand for novel high-throughput screening (HTS) technologies in the pharmaceutical and biotechnological industries. The robotic sample handling techniques currently used in these industries, although fast, are still limited to operating in multi-well plates with the sample volumes per reaction in the microliter regime. Digital microfluidics offers an alternative for reduction in sample volume consumption for HTS but lacks a reliable technique for transporting large number of samples to the microfluidic device. In this report, we develop a technique for serial delivery of sample arrays to a microfluidic device from multi-well plates, through a single sample inlet. Under this approach, a serial array of sample plugs, separated by an immiscible carrier fluid, is loaded into a capillary and delivered to a microfluidic device. Similar approaches have been attempted in the past, however, either with a slower sample loading device like syringe pump or vacuum based sample loading with limited driving pressure. We demonstrated the application of our positive pressure based ‘Serial Sample Loading’ (SSL) system to load a series of sample plugs into a capillary. The adaptability of the SSL system to generate sample plugs with a variety of volumes in a predictable manner was also demonstrated. PMID:22885789

  14. Characterising fatigue crack in an aluminium plate using guided elastic waves

    NASA Astrophysics Data System (ADS)

    Zhou, Chao; Su, Zhongqing; Cheng, Li

    2011-04-01

    Integrity of in-service engineering structures is prone to fatigue damage over their lifespan. Majority of the currently existing elastic-wave-based damage identification techniques have been developed and validated for damage at macroscopic levels, by canvassing linear properties of elastic waves such as attenuation, transmission, reflection and mode conversion. However the real damage in engineering structures often initiates from fatigue crack, presenting highly nonlinear characteristics under cyclic loads. It is of great significance but vast challenge to detect fatigue damage of small dimension at its initial stage. In this study, traditional elastic-wave-based damage identification techniques were first employed with an attempt to detect fatigue crack initiated from a notch in an aluminium plate with the assistance of a signal correlation analysis, to observe the deficiency of the approach. Then the higher-order harmonic wave generation was used to exploit the nonlinear characteristics of acousto-ultrasonic waves (Lamb waves), whereby the fatigue damage was characterised. Results show that nonlinear characteristics of acousto-ultrasonic waves can facilitate more effective detection of fatigue damage than linear signal features such as wave reflection, transmission or mode conversion.

  15. Ultra-wideband ladder filters using zero-th shear mode plate wave in ultrathin LiNbO3 plate with apodized interdigital transducers

    NASA Astrophysics Data System (ADS)

    Kadota, Michio; Tanaka, Shuji

    2016-07-01

    There are two kinds of plate waves propagating in a thin plate, Lamb and shear horizontal (SH) waves. The former has a velocity higher than 15,000 m/s when the plate is very thin. On the contrary, 0th SH (SH0) mode plate wave in an ultrathin LiNbO3 plate has an electro-mechanical coupling factor larger than 50%. Authors fabricated an ultra-wideband T-type ladder filter with a relative bandwidth (BW) of 41% using the SH0 mode plate wave. Although the BW of the filter fully covers the digital TV band in Japan, it does not have sufficient margin at the lower and higher end of BW. Besides, periodic small ripples due to transverse mode in pass-band of the filter were observed. In this study π-type ladder filters were fabricated by changing the pitch ratio of interdigital transducer (IDT) of parallel and series arm resonators (PR(IDT)) to control the BW, and by apodizing IDTs to improve the periodic small ripples due to transverse mode. Ultra-wideband filters without periodic small transverse mode with ultrawide bandwidth from 41 to 49% were fabricated. The BWs fully cover ultrawide digital television bands in Japan and U.S.A. These filters with an ultrawide BW and a steep characteristic show the possibility to be applied to a reported cognitive radio system and other communication systems requiring an ultrawide BW.

  16. Vectorial approach to Huygens's principle for plane waves: circular aperture and zone plates.

    PubMed

    Romero, Julio A; Hernández, Luis

    2006-05-01

    A vectorial equation that describes the Huygens principle was reported, and an expression for the secondary-spherical-wave energy density was found. With a vectorial formulation, we performed an exact calculation for the relative axial intensity of the wave diffracted by an illuminated circular aperture. The off-axis intensity in Fresnel's and Fraunhofer's approximations was calculated. The zone plate was also studied by vectorial formulation. We showed that with increasing number of rings, the intensity maxima magnify as (2n + 2)(2), their full widths decrease, their positions remain unchanged, and secondary maxima appear, in a behavior similar to that for diffraction gratings.

  17. Lamb waves in two-dimensional phononic crystal plate with anisotropic inclusions.

    PubMed

    Yao, Yuanwei; Wu, Fugen; Hou, Zhilin; Xin, Zhang

    2011-07-01

    An analysis is given to the band structure of the two-dimensional phononic crystal plate constituted of a square array of elastic anisotropic, circular Pb cylinders embedded in elastic isotropic epoxy. The numerical results show that the band gap can be tuned by rotating the anisotropic material orientation. It is found that the influence of anisotropy on band gap of Lamb wave is clearly different from that on the band gap of bulk waves. The thickness of the system under study is a sensitive parameter to affect the influence of anisotropic materials on the normalized gap width.

  18. Damage localization in metallic plate structures using edge-reflected lamb waves

    NASA Astrophysics Data System (ADS)

    Ebrahimkhanlou, A.; Dubuc, B.; Salamone, S.

    2016-08-01

    This paper presents a model-based guided ultrasonic waves imaging algorithm, in which multiple ultrasonic echoes caused by reflections from the plate’s boundaries are leveraged to enhance imaging performance. An analytical model is proposed to estimate the envelope of scattered waves. Correlation between the estimated and experimental data is used to generate images. The proposed method is validated through experimental tests on an aluminum plate instrumented with three low profile piezoelectric transducers. Different damage conditions are simulated including through-thickness holes. Results are compared with two other imaging localization methods, that is, delay and sum and minimum variance.

  19. Achromatic half-wave plate for submillimeter instruments in cosmic microwave background astronomy: experimental characterization.

    PubMed

    Pisano, Giampaolo; Savini, Giorgio; Ade, Peter A R; Haynes, Vic; Gear, Walter K

    2006-09-20

    An achromatic half-wave plate (HWP) to be used in millimeter cosmic microwave background (CMB) polarization experiments has been designed, manufactured, and tested. The design is based on the 5-plates Pancharatnam recipe and it works in the frequency range 85-185 GHz. A model has been used to predict the transmission, reflection, absorption, and phase shift as a function of frequency. The HWP has been tested by using coherent radiation from a back-wave oscillator to investigate its modulation efficiency and with incoherent radiation from a polarizing Fourier transform spectrometer (FTS) to explore its frequency behavior. The FTS measurements have been fitted with an optical performance model which is in excellent agreement with the data. A detailed analysis of the data also allows a precise determination of the HWP fast and slow axes in the frequency band of operation. A list of the HWP performance characteristics is reported including estimates of its cross polarization.

  20. Numerical modeling of wave propagation processes in micropolar rods and thin plates

    NASA Astrophysics Data System (ADS)

    Varygina, M.

    2016-10-01

    Mathematical models of micropolar rods and thin plates are considered. Constitutive equations of the models are written in symmetric hyperbolic form. To illustrate wave propagation processes in micropolar media, computational algorithm is developed. It is based on two-cyclic splitting method in combination with monotone finite-difference ENO scheme. Computations of problems on action of instant concentrated and impulse distributed loads are performed.

  1. Generalized thermoelastic wave propagation in circumferential direction of transversely isotropic cylindrical curved plates

    NASA Astrophysics Data System (ADS)

    Sharma, J. N.; Pathania, Vijayata

    2005-03-01

    The propagation of thermoelastic waves along circumferential direction in homogeneous, transversely isotropic, cylindrical curved plates has been investigated in the context of theories of thermoelasticity. This type of study is important for ultrasonic non-destructive inspection of large-diameter pipes, which helps in the health monitoring of ailing infrastructure. Longitudinal stress-corrosion cracks are usually temperature dependent and can be detected more efficiently by inducing circumferential waves; hence the study of generalized thermoelastic wave propagation in the circumferential direction in a pipe wall is essential. Mathematical modeling of the problem of obtaining dispersion curves for curved transversely isotropic thermally conducting elastic plates leads to coupled differential equations. The model has been simplified by using the Helmholtz decomposition technique and the resulting equations have been solved by using separation of variable method to obtain the secular equations in isolated mathematical conditions for the plates with stress-free or rigidly fixed, thermally insulated and isothermal boundary surfaces. The closed form solutions are also obtained under different situations and conditions. The longitudinal shear motion and axially symmetric shear vibration modes get decoupled from the rest of the motion and are not affected by thermal variations, whereas for the non-axially symmetric case of plane strain vibrations, these modes remain coupled and are affected by temperature changes. Moreover, these vibration modes are found to be dispersive and dissipative in character. In order to illustrate theoretical development, numerical solutions are obtained and presented graphically for a zinc plate. The obtained results are also compared with those available in the literature in case of waves in cylindrical shell/circular annulus in the absence of thermomechanical coupling and thermal relaxation times.

  2. Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

    NASA Astrophysics Data System (ADS)

    Shen, Li; Wu, Jiu Hui; Liu, Zhangyi; Fu, Gang

    2015-11-01

    In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

  3. A novel rheo-optical device for studying complex fluids in a double shear plate geometry

    NASA Astrophysics Data System (ADS)

    Boitte, Jean-Baptiste; Vizcaïno, Claude; Benyahia, Lazhar; Herry, Jean-Marie; Michon, Camille; Hayert, Murielle

    2013-01-01

    A new rheo-optical shearing device was designed to investigate the structural evolution of complex material under shear flow. Seeking to keep the area under study constantly within the field of vision, it was conceived to produce shear flow by relying on the uniaxial translation of two parallel plates. The device features three modes of translation motion: step strain (0.02-320), constant shear rate (0.01-400 s-1), and oscillation (0.01-20 Hz) flow. Because the temperature is controlled by using a Peltier module coupled with a water cooling system, temperatures can range from 10 to 80 °C. The sample is loaded onto a user-friendly plate on which standard glasses can be attached with a depression vacuum pump. The principle innovation of the proposed rheo-optical shearing device lies in the fact that this suction system renders the microscopy glasses one with the plates, thereby ensuring their perfect planarity and parallelism. The gap width between the two plates can range from 0 to 5 mm. The device was designed to fit on any inverted confocal laser scanning microscope. In terms of controlled deformation, the conception and technical solutions achieve a high level of accuracy. Moreover, user-friendly software has been developed to control both shear flow parameters and temperature. The validation of specifications as well as the three modes of motion was carried out, first of all without a sample, and then by tracking fluorescent particles in a model system, in our case a micro-gel. Real values agreed well with those we targeted. In addition, an experiment with bread dough deformation under shear flow was initiated to gain some insight into the potential use of our device. These results show that the RheOptiCAD® promises to be a useful tool to better understand, from both a fundamental and an industrial point of view, the rheological behavior of the microstructure of complex fluids under controlled thermo-mechanical parameters in the case of food and non

  4. Lamb wave dispersion in a PZT/metal/PZT sandwich plate with imperfect interface

    NASA Astrophysics Data System (ADS)

    Kurt, Ilkay; Akbarov, Surkay D.; Sezer, Semih

    2016-07-01

    The Lamb wave dispersion in a PZT/Metal/PZT sandwich plate is investigated by employing the exact linear equations of electro-elastic waves in piezoelectric materials within the scope of the plane-strain state. It is assumed that at the interfaces between the piezoelectric face layers and metal core layer, shear-spring and normal-spring type imperfect conditions are satisfied. The degree of this imperfectness is estimated through the corresponding shear-spring and normal-spring type parameters which appear in the contact condition characterizing the transverse and normal displacements' discontinuity. The corresponding dispersion equation is derived, and as a result of the numerical solution to this equation, the dispersion curves are constructed for the first and second lowest modes in the cases where the material of the face layers is PZT and the material of the middle layer is Steel (St). Consequently, for the PZT/St/PZT sandwich plate, the study of the influence of the problem parameters such as the piezoelectric and dielectric constants, layer thickness ratios, non-dimensional shear-spring, and normal-spring type parameters, is carried out. In particular, it is established that the imperfectness of the contact between the layers of the plate causes a decrease in the values of the wave propagation velocity.

  5. Laser-launched flyer plate and confined laser ablation for shock wave loading: Validation and applications

    NASA Astrophysics Data System (ADS)

    Paisley, Dennis L.; Luo, Sheng-Nian; Greenfield, Scott R.; Koskelo, Aaron C.

    2008-02-01

    We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2-7mrad (with an average of 4±1mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.

  6. Method for in-situ nondestructive measurement of Young's modulus of plate structures

    NASA Technical Reports Server (NTRS)

    Huang, Jerry Qixin (Inventor); Perez, Robert J. (Inventor); DeLangis, Leo M. (Inventor)

    2003-01-01

    A method for determining stiffness of a composite laminate plate entails disposing a device for generating an acoustical pulse against a surface of the plate and disposing a detecting device against the same surface spaced a known distance from the pulse-generating device, and using the pulse-generating device to emit a pulse so as to create an extensional wave in the plate. The detecting device is used to determine a time of flight of the wave over the known distance, and the wave velocity is calculated. A Young's modulus of the plate is determined based on the wave velocity. Methods for both anisotropic and quasi-isotropic laminates are disclosed.

  7. Determination of ultrasonic wave velocities and phase velocity dispersion curves of an Inconel 600 plate using resonant ultrasound spectroscopy and leaky Lamb waves.

    PubMed

    Kim, Young H; Song, Sung-Jin; Kwon, Sung-Duk; Cheong, Yong-Moo; Jung, Hyun-Kyu

    2004-04-01

    A plate of Inconel 600 was interrogated using the resonant ultrasound spectroscopy (RUS) and the reflected leaky Lamb waves (LLW). It was found that the plate used in the present work has anisotropy in its material properties by the RUS. The longitudinal and the transverse wave velocities of the Inconel 600 plate were determined by the RUS, ultrasonic pulse-echo method and cut-off frequencies of the LLWs. The wave velocities in the direction of thickness determined by the RUS under the assumption of the orthotropic symmetry were quite similar to those obtained by other methods, the pulse-echo method and from cut-off frequencies. The reflected LLW from the plate was measured with varying the incident angle. The dispersion curves obtained from the reflected LLWs show good agreement with the theoretical calculation in general. The mismatches may be caused by anisotropy of the plate.

  8. Effect of skew angle on second harmonic guided wave measurement in composite plates

    NASA Astrophysics Data System (ADS)

    Cho, Hwanjeong; Choi, Sungho; Lissenden, Cliff J.

    2017-02-01

    Waves propagating in anisotropic media are subject to skewing effects due to the media having directional wave speed dependence, which is characterized by slowness curves. Likewise, the generation of second harmonics is sensitive to micro-scale damage that is generally not detectable from linear features of ultrasonic waves. Here, the effect of skew angle on second harmonic guided wave measurement in a transversely isotropic lamina and a quasi-isotropic laminate are numerically studied. The strain energy density function for a nonlinear transversely isotropic material is formulated in terms of the Green-Lagrange strain invariants. The guided wave mode pairs for cumulative second harmonic generation in the plate are selected in accordance with the internal resonance criteria - i.e., phase matching and non-zero power flux. Moreover, the skew angle dispersion curves for the mode pairs are obtained from the semi-analytical finite element method using the derivative of the slowness curve. The skew angles of the primary and secondary wave modes are calculated and wave propagation simulations are carried out using COMSOL. Numerical simulations revealed that the effect of skew angle mismatch can be significant for second harmonic generation in anisotropic media. The importance of skew angle matching on cumulative second harmonic generation is emphasized and the accompanying issue of the selection of internally resonant mode pairs for both a unidirectional transversely isotropic lamina and a quasi-isotropic laminate is demonstrated.

  9. Preparation of micro gold devices on poly(dimethylsiloxane) chips with region-selective electroless plating.

    PubMed

    Hao, Zhenxia; Chen, Hengwu; Ma, Dan

    2009-10-15

    A novel protocol for fabrication of micro gold devices on poly(dimethylsiloxane) (PDMS) substrates was developed on the basis of region-selective electroless plating. The layout of a micro gold device was first photochemically patterned onto the PDMS surface through a UV induced poly(acrylic acid) (PAA) grafting process. The carboxylic moieties on the grafted PAA served as the scaffold for a series of wet chemical reactions that led to the immobilization of gold nanoparticles in the UV-exposed region, where electroless plating then occurred under the catalysis of the nanoparticles. Gold devices fabricated with such a protocol could tolerate the Scotch tape test and survive in a repeated bending-straightening test. They also showed good stability in acidic and alkaline solutions, possessed almost the same electrochemical properties as a standard gold disk electrode, and allowed thiol-compounds to form a perfect self-assembled monolayer on their surfaces. The fabricated micro gold electrode was demonstrated to be suitable as the integrated amperometric detection element in a full PDMS micro electrophoresis chip.

  10. A millimeter-wave integrated-circuit antenna based on the Fresnel zone plate

    NASA Astrophysics Data System (ADS)

    Gouker, Mark A.; Smith, Glenn S.

    1992-05-01

    A moderate-gain, easily constructed, millimeter-wave IC antenna based on the Fresnel zone plate has been developed. The gain and beamwidth of the antenna can be varied by adjusting the diameter and focal length of the zone plate. A theory is developed which accurately predicts the on-axis gain, beamwidth, and sidelobe levels of antennas with zone-plate focal lengths greater than 8-9 lambda. Graphs are presented to aid in the design of other IC zone-plate antennas. The performance of the antenna without the reflector and lambda/4 spacer was investigated. The gain of the antenna with nothing behind the zone plate is found to approach that of the fully configured antenna with the lambda/4 spacer and reflector. The reflection from the open rings which is responsible for this phenomenon is enhanced as the dielectric constant of the substrate is increased. Thus, on substrates with high permittivity the reflector and lambda/4 spacer may not be necessary.

  11. Ultrasonic guided wave detection of scatterers on large clad steel plates

    NASA Astrophysics Data System (ADS)

    Gong, Peng; Harley, Joel B.; Berges, Mario; Junker, Warren R.; Greve, David W.; Oppenheim, Irving J.

    2016-04-01

    "Clad steel" refers to a thick carbon steel structural plate bonded to a corrosion resistant alloy (CRA) plate, such as stainless steel or titanium, and is widely used in industry to construct pressure vessels. The CRA resists the chemically aggressive environment on the interior, but cannot prevent the development of corrosion losses and cracks that limit the continued safe operation of such vessels. At present there are no practical methods to detect such defects from the exposed outer surface of the thick carbon steel plate, often necessitating removing such vessels from service and inspecting them visually from the interior. In previous research, sponsored by industry to detect and localize damage in pressurized piping systems under operational and environmental changes, we investigated a number of data-driven signal processing methods to extract damage information from ultrasonic guided wave pitch-catch records. We now apply those methods to relatively large clad steel plate specimens. We study a sparse array of wafer-type ultrasonic transducers adhered to the carbon steel surface, attempting to localize mass scatterers grease-coupled to the stainless steel surface. We discuss conditions under which localization is achieved by relatively simple first-arrival methods, and other conditions for which data-driven methods are needed; we also discuss observations of plate-like mode properties implied by these results.

  12. Properties of Guided Waves in Composite Plates, and Implications for NDE

    NASA Astrophysics Data System (ADS)

    Lowe, M. J. S.; Neau, G.; Deschamps, M.

    2004-02-01

    Guided waves are potentially very useful for the rapid NDE of plate structures. In the aerospace industry in particular, they have been proposed for the structural health monitoring of carbon fibre skin panels, in either an active or a passive configuration. In an active configuration a guided wave is deliberately generated and then later received after it has travelled through the structure; in a passive configuration an acoustic emission sensor is used to listen to sound created by the structure itself. The successful development of these ideas depends on a good knowledge of the properties of the guided waves, yet it has been found that the properties of guided waves in such materials are very much more complicated than those in a simple metal skin. The complications include steering of the direction of the group velocity by the anisotropy of the plate, and attenuation because of damping of the matrix material and scattering by the fibres. The authors have studied these phenomena both analytically and experimentally. This paper presents an overview of the findings and identifies the key implications for practical developments of structural health monitoring techniques.

  13. Lattice Theory of Face-Shear and Thickness-Twist Waves in Body-Centered Cubic Crystal Plates.

    DTIC Science & Technology

    An analytical study is made of face-shear and thickness-twist waves propagating along the (100) and (110) directions of a body - centered cubic lattice...in the (100) direction of simple-cubic and face-centered cubic plates. In the (100) direction of the body - centered cubic plate, the situation is quite

  14. A hybrid wave propagation and statistical energy analysis on the mid-frequency vibration of built-up plate systems

    NASA Astrophysics Data System (ADS)

    Ma, Yongbin; Zhang, Yahui; Kennedy, David

    2015-09-01

    Based on the concept of the hybrid finite element (FE) analysis and statistical energy analysis (SEA), a new hybrid method is developed for the mid-frequency vibration of a system comprising rectangular thin plates. The wave propagation method based on symplectic analysis is used to describe the vibration of the deterministic plate component. By enforcing the displacement continuity and equilibrium of force at the connection interface, the dynamic coupling between the deterministic plate component and the statistical plate component described by SEA is established. Furthermore, the hybrid solution formulation for the mid-frequency vibration of the system built up by plates is proposed. The symplectic analytical wave describing the deterministic plate component eliminates the boundary condition limitation of the traditional analytical wave propagation method and overcomes the numerical instability of numerical wave propagation methods. Numerical examples compare results from the proposed method with those from the hybrid FE-SEA method and the Monte Carlo method. The comparison illustrates that the proposed method gives good predictions for the mid-frequency behavior of the system considered here with low computational time. In addition, a constant proportionality coefficient between the system coupling power and the energy difference between the plate components can be found, when external forces are applied at different locations on a line perpendicular to the wave propagation direction. Based on this finding, two fast solution techniques are developed for the energy response of the system, and are validated by numerical examples.

  15. The capacitive division image readout: a novel imaging device for microchannel plate detectors

    NASA Astrophysics Data System (ADS)

    Lapington, J. S.; Conneely, T. M.; Leach, S. A.; Moore, L.

    2013-09-01

    The Capacitive Division Image Readout (C-DIR) is a simple and novel image readout for photon counting detectors offering major performance advantages. C-DIR is a charge centroiding device comprising three elements; (i) a resistive anode providing event charge localization, event current return path and electrical isolation from detector high voltage, (ii) a dielectric substrate which capacitively couples the event transient signal to the third element, (iii) the readout device; an array of capacitively coupled electrodes which divides the signal among the readout charge measurement nodes. The resistive anode and dielectric substrate constitute the rear interface of the detector and capacitively couple the signal to the external C-DIR readout device. The C-DIR device is a passive, multilayer printed circuit board type device comprising a matrix of isolated electrodes whose geometries define the capacitive network. C-DIR is manufactured using conventional PCB geometries and is straightforward and economical to construct. C-DIR's robustness and simplicity belie its performance advantages. Its capacitive nature avoids partition noise, the Poisson noise associated with collection of discrete charges. The dominant noise limiting position resolution is electronic noise. However C-DIR also presents a low input capacitance to the readout electronics, minimising this noise component thus maximising spatial resolution. Optimisation of the C-DIR pattern-edge geometry can provide ~90% linear dynamic range. We present data showing image resolution and linearity of the C-DIR device in a microchannel plate detector and describe various electronic charge measurement scheme designed to exploit the full performance potential of the C-DIR device.

  16. Device for the control of oxygen concentration in multiwell cell culture plates.

    PubMed

    Oppegard, Shawn C; Eddington, David T

    2009-01-01

    Oxygen is a key modulator of many cellular pathways but current devices permitting in vitro oxygen modulation fail to meet the needs of many researchers. In this study, a microfabricated insert for multiwell formats has been developed to control the gas concentration of each well independent of the global incubator's condition. The platform consists of a polydimethylsiloxane (PDMS) insert that nests into a standard multiwell plate and serves as a passive network with a gas permeable membrane aimed to deliver gas to adherent cell cultures. Preliminary data demonstrate that the insert is effective in controlling the oxygen concentration at the cell surface inside a well with equilibration times in minutes rather than hours for conventional technologies. A wide variety of oxygen profiles can be attained based on the device design, such as the cyclic profile achieved in this study, and even gradients in local oxygen concentration to mimic those found in vivo for more biomimetic cellular models.

  17. Well Plate-Based Perfusion Culture Device for Tissue and Tumor Microenvironment Replication

    PubMed Central

    Zhang, W.; Gu, Y.; Hao, Y.; Sun, Q.; Konior, K.; Wang, H.

    2015-01-01

    There are significant challenges in developing in vitro human tissue and tumor models that can be used to support new drug development and evaluate personalized therapeutics. The challenges include: (1) working with primary cells which are often difficult to maintain ex vivo, (2) mimicking native microenvironments from which primary cells are harvested, and (3) lack of culture devices that can support these microenvironments to evaluate drug responses in a high-throughput manner. Here we report a versatile well plate-based perfusion culture device that was designed, fabricated and used to: (1) ascertain the role of perfusion in facilitating the expansion of human multiple myeloma cells and evaluate drug response of the cells, (2) preserve the physiological phenotype of primary murine osteocytes by reconstructing the 3D cellular network of osteocytes, and (3) circulate primary murine T cells through a layer of primary murine intestine epithelial cells to recapitulate the interaction of the immune cells with the epithelial cells. Through these diverse case studies, we demonstrate the device’s design features to support: (1) the convenient and spatiotemporal placement of cells and biomaterials into the culture wells of the device; (2) the replication of tissues and tumor microenvironments using perfusion, stromal cells, and/or biomaterials; (3) the circulation of non-adherent cells through the culture chambers; and (4) conventional tissue and cell characterization by plate reading, histology, and flow cytometry. Future challenges are identified and discussed from the perspective of manufacturing the device and making its operation for routine and wide use. PMID:26021852

  18. Scattering of Lamb waves by cracks in a composite graphite fiber-reinforced epoxy plate

    NASA Technical Reports Server (NTRS)

    Bratton, Robert; Datta, Subhendu K.; Shah, Arvind

    1990-01-01

    Recent investigations of space construction techniques have explored the used of composite materials in the construction of space stations and platforms. These composites offer superior strength to weight ratio and are thermally stable. For example, a composite material being considered is laminates of graphite fibers in an epoxy matrix. The overall effective elastic constants of such a medium can be calculated from fiber and matrix properties by using an effective modulus theory as shown in Datta, el. al. The investigation of propagation and scattering of elastic waves in composite materials is necessary in order to develop an ability to characterize cracks and predict the reliability of composite structures. The objective of this investigation is the characterization of a surface breaking crack by ultrasonic techniques. In particular, the use of Lamb waves for this purpose is studied here. The Lamb waves travel through the plate, encountering a crack, and scatter. Of interest is the modeling of the scattered wave in terms of the Lamb wave modes. The direct problem of propagation and scattering of Lamb waves by a surface breaking crack has been analyzed. This would permit an experimentalist to characterize the crack by comparing the measured response to the analytical model. The plate is assumed to be infinite in the x and y directions with a constant thickness in the z direction. The top and bottom surfaces are traction free. Solving the governing wave equations and using the stress-free boundary conditions results in the dispersion equation. This equation yields the guided modes in the homogeneous plate. The theoretical model is a hybrid method that combines analytical and finite elements techniques to describe the scattered displacements. A finite region containing the defects is discretized by finite elements. Outside the local region, the far field solution is expressed as a Fourier summation of the guided modes obtained from the dispersion equation

  19. Detecting cavitation in vivo from shock-wave therapy devices

    NASA Astrophysics Data System (ADS)

    Matula, Thomas J.; Yu, Jinfei; Bailey, Michael R.

    2005-04-01

    Extracorporeal shock-wave therapy (ESWT) has been used as a treatment for plantar faciitis, lateral epicondylitis, shoulder tendonitis, non-unions, and other indications where conservative treatments have been unsuccessful. However, in many areas, the efficacy of SW treatment has not been well established, and the mechanism of action, particularly the role of cavitation, is not well understood. Research indicates cavitation plays an important role in other ultrasound therapies, such as lithotripsy and focused ultrasound surgery, and in some instances, cavitation has been used as a means to monitor or detect a biological effect. Although ESWT can generate cavitation easily in vitro, it is unknown whether or not cavitation is a significant factor in vivo. The purpose of this investigation is to use diagnostic ultrasound to detect and monitor cavitation generated by ESWT devices in vivo. Diagnostic images are collected at various times during and after treatment. The images are then post-processed with image-processing algorithms to enhance the contrast between bubbles and surrounding tissue. The ultimate goal of this research is to utilize cavitation as a means for optimizing shock wave parameters such as amplitude and pulse repetition frequency. [Work supported by APL internal funds and NIH DK43881 and DK55674.

  20. Advanced, High Power, Next Scale, Wave Energy Conversion Device

    SciTech Connect

    Mekhiche, Mike; Dufera, Hiz; Montagna, Deb

    2012-10-29

    The project conducted under DOE contract DE‐EE0002649 is defined as the Advanced, High Power, Next Scale, Wave Energy Converter. The overall project is split into a seven‐stage, gated development program. The work conducted under the DOE contract is OPT Stage Gate III work and a portion of Stage Gate IV work of the seven stage product development process. The project effort includes Full Concept Design & Prototype Assembly Testing building on our existing PowerBuoy technology to deliver a device with much increased power delivery. Scaling‐up from 150kW to 500kW power generating capacity required changes in the PowerBuoy design that addressed cost reduction and mass manufacturing by implementing a Design for Manufacturing (DFM) approach. The design changes also focused on reducing PowerBuoy Installation, Operation and Maintenance (IO&M) costs which are essential to reducing the overall cost of energy. In this design, changes to the core PowerBuoy technology were implemented to increase capability and reduce both CAPEX and OPEX costs. OPT conceptually envisaged moving from a floating structure to a seabed structure. The design change from a floating structure to seabed structure would provide the implementation of stroke‐ unlimited Power Take‐Off (PTO) which has a potential to provide significant power delivery improvement and transform the wave energy industry if proven feasible.

  1. Identification of thin elastic isotropic plate parameters applying Guided Wave Measurement and Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Pabisek, Ewa; Waszczyszyn, Zenon

    2015-12-01

    A new hybrid computational system for material identification (HCSMI) is presented, developed for the identification of homogeneous, elastic, isotropic plate parameters. Attention is focused on the construction of dispersion curves, related to Lamb waves. The main idea of the system HCSMI lies in separation of two essential basic computational stages, corresponding to direct or inverse analyses. In the frame of the first stage an experimental dispersion curve DCexp is constructed, applying Guided Wave Measurement (GWM) technique. Then, in the other stage, corresponding to the inverse analysis, an Artificial Neural Network (ANN) is trained 'off line'. The substitution of results of the first stage, treated as inputs of the ANN, gives the values of identified plate parameters. In such a way no iteration is needed, unlike to the classical approach. In such an approach, the "distance" between the approximate experimental curves DCexp and dispersion curves DCnum obtained in the direct analysis, is iteratively minimized. Two case studies are presented, corresponding either to measurements in laboratory tests or those related to pseudo-experimental noisy data of computer simulations. The obtained results prove high numerical efficiency of HCSMI, applied to the identification of aluminum plate parameters.

  2. [Analysis of bactericidal material generated by electrical devices advertising bactericidal ability against bacteria on the agar gel plates].

    PubMed

    Nishimura, Hidekazu

    2012-11-01

    Several Japanese companies sell electrical devices advertised as effective in inactivating viruses and killing bacteria by releasing special materials, e.g., Plasmacluster ions, Nanoe particle and minus ions, into the air. These companies claim that their devices killed bacteria on plates in their own experiments. We tested device effectiveness using the same experiments from the Plasmacluster ioniser SHARP Co., Japan, the Nanoe generator Panasonic Co., Japan, and the Vion KING JIM Co., Japan, to test their advertising claims. Bactericidal ability on agar plate was tested, using Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, and Enterococcus faecalis as follows: the medium containing a certain amount of each bacterium was put onto an agar plate and smeared. Plates were kept in a closed chamber (inner volume 14.4 m3) or a glove box (inner volume 0.2 m), with one of the devices run for 2 hours. Plates not exposed to any device were used as controls. Each plate was retrieved and put in an incubator to count the number of bacterial colonies formed on the plate. There was no significant difference in the number of colonies on plates exposed to devices compared to control, in the number for all devices, or in all bacteria tested in experiments in the 14.4 m3 chamber. These results strongly suggest that these devices have almost no bactericidal effect, at least in space exceeding this volume. Colony formation was suppressed in the glove box in all devices and in all bacteria tested except P. aeruginosa, although the degree of suppression differed among experiments. The colony formation suppression mechanism was analyzed, and indicated that:colony formation did not change even after the removal of Plasmacluster ions, Nanoe particles, or negative ions from the air, while colony formation was decreased drastically by the removal of ozone from space, which was revealed to be generated inevitably during device operation. These results strongly suggest that the

  3. Lamb waves propagation in a novel metal-matrix phononic crystals plate

    NASA Astrophysics Data System (ADS)

    Li, Suobin; Chen, Tianning; Wang, Xiaopeng; Xi, Yanhui

    2016-09-01

    In this paper, the propagation properties of Lamb waves in a novel phononic crystals (PCs) plate composed of a square array of double-sided composite taper stubs, which are deposited on a 2D locally resonant PC plate that composes of an array of rubber fillers embedded in the steel plate is studied. It is shown that the spring-mass system of the resonator will be decoupled by introducing the rubber filler, and then the out-of-plane band gap (BG) and the in-plane BG can be adjusted into the same lowest frequency range, respectively (the out-of-plane BG is adjusted by the rubber filler and the in-plane BG is adjusted by the taper stub). As a result, the frequency range of the generated complete BG is between 59-93 Hz due to the overlap between the in-plane and out-of-plane BG. Compared with the classic double-sided stubbed PC plate, the relative bandwidth of the BG is enlargement by a factor of 5.5 and the location of the BG is reduced by a factor of 5.5 in the proposed structure. It provides an effective way for metal-matrix PCs to obtain complete BGs in low-frequency range (below 100 Hz), which has potential for the reduction of the vibration at low frequency in practical case.

  4. Adaptive beamforming for array imaging of plate structures using lamb waves.

    PubMed

    Engholm, Marcus; Stepinski, Tadeusz

    2010-12-01

    Lamb waves are considered a promising tool for the monitoring of plate structures. Large areas of plate structures can be monitored using active arrays employing beamforming techniques. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard delay-and-sum (DAS) beamforming while reducing the effects of multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two-dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared with the standard DAS beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better side lobe and mode suppression capabilities. Known issues of the MVDR approach, such as signal cancellation in highly correlated environments and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.

  5. Non-Contact Determination of Antisymmetric Plate Wave Velocity in Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.

    1996-01-01

    A 13 mJ NdYAG 1064 nm, 4 ns, laser pulse was employed to produce ultrasonic plate waves in 20 percent porous SiC/SiC composite tensile specimens of three different architectures. An air coupled 0.5 MHz transducer was used to detect and collect the waveforms which contained first antisymmetric plate wave pulses for determining the shear wave velocity (VS). These results were compared to VS values determined on the same specimens with 0.5 MHz ultrasonic transducers with contact coupling. Averages of four noncontact determinations on each of 18 specimens were compared to averages of four contact values. The noncontact VS's fall in the same range as the contact. The standard deviations for the noncontact VS's averaged 2.8 percent. The standard deviations for the contact measurements averaged 2.3 percent, indicating similar reproducibility. Repeated laser pulsing at the same location always lead to deterioration of the ulu-"nic signal. The signal would recover in about 24 hr in air however, indicating that no permanent damage was produced.

  6. Numerical design optimization of an EMAT for A0 Lamb wave generation in steel plates

    NASA Astrophysics Data System (ADS)

    Seher, Matthias; Huthwaite, Peter; Lowe, Mike; Nagy, Peter; Cawley, Peter

    2014-02-01

    An electromagnetic acoustic transducer (EMAT) for A0 Lamb wave generation on steel plates is developed to operate at 0.50 MHz-mm. A key objective of the development is to maximize the excitation and reception of the A0 mode, while minimizing those of the S0 mode. The chosen EMAT design consists of an induction coil and a permanent magnet. A finite element (FE) model of the EMAT is developed, coupling the electromagnetic and elastodynamic phenomena. An optimization process using a genetic algorithm is implemented, employing the magnet diameter and liftoff distance from the plate as design parameters and using the FE model to calculate the fitness. The optimal design suggested by the optimization process is physically implemented and the experimental measurements are compared to the FE simulation results. In a further step, the variations of the design parameters are studied numerically and the proposed EMAT design exhibits a robust behavior to small changes of the design parameters.

  7. Blind inversion method using Lamb waves for the complete elastic property characterization of anisotropic plates.

    PubMed

    Vishnuvardhan, J; Krishnamurthy, C V; Balasubramaniam, Krishnan

    2009-02-01

    A novel blind inversion method using Lamb wave S(0) and A(0) mode velocities is proposed for the complete determination of elastic moduli, material symmetries, as well as principal plane orientations of anisotropic plates. The approach takes advantage of genetic algorithm, introduces the notion of "statistically significant" elastic moduli, and utilizes their sensitivities to velocity data to reconstruct the elastic moduli. The unknown material symmetry and the principal planes are then evaluated using the method proposed by Cowin and Mehrabadi [Q. J. Mech. Appl. Math. 40, 451-476 (1987)]. The blind inversion procedure was verified using simulated ultrasonic velocity data sets on materials with transversely isotropic, orthotropic, and monoclinic symmetries. A modified double ring configuration of the single transmitter and multiple receiver compact array was developed to experimentally validate the blind inversion approach on a quasi-isotropic graphite-epoxy composite plate. This technique finds application in the area of material characterization and structural health monitoring of anisotropic platelike structures.

  8. Excitation and focusing of Lamb waves in a multilayered anisotropic plate.

    PubMed

    Chapuis, Bastien; Terrien, Nicolas; Royer, Daniel

    2010-01-01

    The radiation of Lamb waves by an axisymmetric source on the surface of an anisotropic plate is investigated. An analytical expression of the Green's function, valid in the far field domain, is derived. This approximation shows that the anisotropy of the propagation medium induces a focusing of Lamb modes in some directions, which correspond to minima of the slowness. Numerical simulations and experiments demonstrate that for the fundamental A(0) and S(0) modes, this phenomenon, analog to the phonon focusing effect, can be very strong in materials such as composite fiber-reinforced polymers. This effect due to the plate anisotropy must be correctly taken into account, for example, in order to develop systems for in situ structural health monitoring. The choice of the most appropriate Lamb mode, the excitation frequency, and the design of the array of piezoelectric disks used as transmitters and receivers depends on such considerations.

  9. Reverberation-ray matrix analysis for wave propagation in multiferroic plates with imperfect interfacial bonding.

    PubMed

    Zhu, Jun; Chen, Weiqiu; Ye, Guiru

    2012-01-01

    The dispersion behavior of waves in multiferroic plates with imperfect interfacial bonding has been investigated via the method of reverberation-ray matrix, which is directly established from the three-dimensional equations of magneto-electro-elasticity in the form of state space formalism. A generalized spring-layer model is employed to characterize the interfacial imperfection. By introducing a dual system of local coordinates for each single layer, the numerical instability usually encountered in the state space method can be avoided. Based on the proposed method, a typical sandwich plate made of piezoelectric and piezomagnetic phases is considered in numerical examples to calculate the dispersion curves and mode shapes. It is demonstrated that the results obtained by the present method is unconditionally stable as compared to the traditional state space method. The influence of different interfacial bonding conditions on the dispersion characteristics and corresponding mode shapes is investigated.

  10. Slow strain waves in blocky geological media from GPS and seismological observations on the Amurian plate

    NASA Astrophysics Data System (ADS)

    Bykov, Victor G.; Trofimenko, Sergey V.

    2016-12-01

    Based on the statistical analysis of spatiotemporal distribution of earthquake epicenters and perennial geodetic observation series, new evidence is obtained for the existence of slow strain waves in the Earth. The results of our investigation allow us to identify the dynamics of seismicity along the northern boundary of the Amurian plate as a wave process. Migration of epicenters of weak earthquakes (2 ≤  M ≤ 4) is initiated by the east-west propagation of a strain wave front at an average velocity of 1000 km yr-1. We have found a synchronous quasi-periodic variation of seismicity in equally spaced clusters with spatial periods of 3.5 and 7.26° comparable with the length of slow strain waves. The geodetic observations at GPS sites in proximity to local active faults show that in a number of cases, the GPS site coordinate seasonal variations exhibit a significant phase shift, whereas the time series of these GPS sites differ significantly from a sinusoid. Based on experimental observation data and the developed model of crustal block movement, we have shown that there is one possible interpretation for this fact that the trajectory of GPS station position disturbance is induced by migration of crustal deformation in the form of slow waves.

  11. Surface-Wave Imaging of the Juan de Fuca Plate and Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The Juan de Fuca plate over the past four years has been the location of the onshore-offshore Cascadia Initiative (CI) array. These data present a rare opportunity to image the evolution of the crust and mantle of an entire plate from the ridge through the subduction zone. The Cascadia subduction zone is capable of up to a M9 megathrust earthquake; seismic imaging provides a major constraint on the thermal structure and hydration state of the plate, which in turn constrain models of seismogenesis. We utilize a multi-channel cross-correlation analysis to estimate the phase-velocity of Rayleigh waves traversing the CI from teleseismic earthquakes recorded over the first three years of the deployment, to image the structure of the Juan de Fuca plate and the Cascadia arc and forearc. Our initial results are dominated by the transition from high-velocity oceanic to low-velocity continental lithosphere across the margin, high velocities in the region of the subducting slab, and low velocities beneath the arc. All of these areas produce reasonable standard deviation in the velocity estimates. These images confirm the robustness of our methodology, despite the different noise characteristics of the onshore sites and the ocean bottom seismometers (OBS). Among the OBS sites there are additional differences between those deployed in deep water on oceanic crust and those in shallow water on the continental shelf. Compliance and tilt corrections have a significant effect at some stations and are taken into account accordingly. These results will be combined with recent results from offshore receiver functions and estimates of short-period Rayleigh wave dispersion from ambient noise to constrain the crust and mantle structure in a joint inversion.

  12. Polarization characterization of PZT disks and of embedded PZT plates by thermal wave methods

    SciTech Connect

    Eydam, Agnes Suchaneck, Gunnar Gerlach, Gerald; Esslinger, Sophia; Schönecker, Andreas; Neumeister, Peter

    2014-11-05

    In this work, the thermal wave method was applied to characterize PZT disks and embedded PZT plates with regard to the polarization magnitude and spatial homogeneity. The samples were exposed to periodic heating by means of a laser beam and the pyroelectric response was determined. Thermal relaxation times (single time constants or distributions of time constants) describe the heat losses of the PZT samples to the environment. The resulting pyroelectric current spectrum was fitted to the superposition of thermal relaxation processes. The pyroelectric coefficient gives insight in the polarization distribution. For PZT disks, the polarization distribution in the surface region showed a characteristic decrease towards the electrodes.

  13. Scattering of guided waves from complex defects in plates in pipes

    NASA Astrophysics Data System (ADS)

    Velichko, A.; Wilcox, P. D.

    2013-01-01

    Guided ultrasonic waves are successfully employed for rapid screening of plate-like structures and pipelines. Imaging techniques allow to identify and localize areas of the structure with possible defects. However, inverse problem of defect characterization and sizing still represents a considerable challenge. In this paper the efficient FE model is used to simulate the scattering response from various corrosion defects with complex realistic depth and surface profiles. The data is then analyzed in order to determine the defect geometrical parameters (lateral size, depth, etc). The results of analysis are presented and its implications to practical remote defect characterization are discussed.

  14. Sub-wavelength quarter-wave plate based on plasmonic patch antennas

    NASA Astrophysics Data System (ADS)

    Zhao, Hang; Yang, Yuanqing; Li, Qiang; Qiu, Min

    2013-12-01

    A quarter-wave plate using plasmonic patch antennas has been investigated. The nanostructures can convert linear polarized light into circular polarized light in the visible range (633 nm). By further exploiting the dimer patch antenna structure composed of different metals, directional emission (with a directivity of 4.8) of circular polarized light (with a conversion efficiency of 27.8%) in an oblique direction with respect to the incident light is enabled. Compared with previous designs, the proposed structures are ultra-thin, and are more suitable for integration applications.

  15. Visualization of Acoustic Waves Propagating within a Single Anisotropic Crystalline Plate

    SciTech Connect

    Chiaki Miyasaka; Kenneth L. Telschow; Jeffry T. Sadler; Roman. Gr. Maev

    2007-04-01

    High frequency acoustic waves propagating within a thin anisotropic plate were imaged using a hybrid system consisting of an acoustic lens (Frequency: 200MHz; Point Focus) for point excitation on one side and a laser displacement interferometer for point detection on the opposite side. The laser beam spot was about 5µm diameter on the surface and the sample was scanned to provide an image of the lateral spatial distribution of the resultant displacement. Theoretical prediction of the resultant displacement was performed using the Angular Spectrum Analysis approach for propagation through the [100] oriented silicon. Comparison of the theoretical predictions with experimental measurements is presented.

  16. Underwater Sound Levels at a Wave Energy Device Testing Facility in Falmouth Bay, UK.

    PubMed

    Garrett, Joanne K; Witt, Matthew J; Johanning, Lars

    2016-01-01

    Passive acoustic monitoring devices were deployed at FaBTest in Falmouth Bay, UK, a marine renewable energy device testing facility during trials of a wave energy device. The area supports considerable commercial shipping and recreational boating along with diverse marine fauna. Noise monitoring occurred during (1) a baseline period, (2) installation activity, (3) the device in situ with inactive power status, and (4) the device in situ with active power status. This paper discusses the preliminary findings of the sound recording at FabTest during these different activity periods of a wave energy device trial.

  17. Measurement of velocity variations along a wave path in the through-thickness direction in a plate.

    PubMed

    Kawashima, Katsuhiro

    2005-01-01

    In this paper there is given a method to predict ultrasonic wave velocity variations along a wave path in the through-thickness direction in a plate from thickness resonance spectra. Thickness resonance spectra are numerically calculated and two simple rules used to predict the entire ultrasonic wave velocity variation are derived. In the calculation, the wave path is assumed to be straight along the thickness direction and the velocity variation is assumed to be either as a parabolic curve dependence or a linear dependence with respect to the distance from the surface and to be symmetric with respect to the plate center. To see if the numerical calculation method is reliable, thickness resonance frequencies of a sample with three-layers were measured by EMAT (electromagnetic acoustic transducer) with a good agreement between the measured and the calculated frequencies. This method can be applied to the ultrasonic measurement of material characteristics, internal stress or various other properties of plate materials.

  18. Rectification of Lamb wave propagation in thin plates with piezo-dielectric periodic structures

    NASA Astrophysics Data System (ADS)

    Iwasaki, Yuhei; Tsuruta, Kenji; Ishikawa, Atsushi

    2016-07-01

    Based on a heterostructured plate consisting of piezoelectric-ceramic/epoxy-resin composites with different periodicities, we design a novel acoustic diode for the symmetrical/asymmetrical (S/A) mode of Lamb wave at audible ranges. The acoustic diode is constructed with two parts, i.e., the mode conversion part and the mode selection part, and the mode conversion mechanism at the interface is applied to the mode hybridization from S to S+A and for the mode conversion from A to S. The phonon band structures for each part are calculated and optimized so that the mode selection is realized for a specific mode at the junction. Finite-element simulations prove that the proposed acoustic diode achieves efficient rectification at audio frequency ranges for both S and A mode incidences of the Lamb wave.

  19. Shear wave velocity structure of the Anatolian Plate and surrounding regions using Ambient Noise Tomography

    NASA Astrophysics Data System (ADS)

    Delph, J. R.; Beck, S. L.; Zandt, G.; Biryol, C. B.; Ward, K. M.

    2013-12-01

    The Anatolian Plate consists of various lithospheric terranes amalgamated during the closure of the Tethys Ocean, and is currently extruding to the west in response to a combination of the collision of the Arabian plate in the east and the roll back of the Aegean subduction zone in the west. We used Ambient Noise Tomography (ANT) at periods <= 40s to investigate the crust and uppermost mantle structure of the Anatolian Plate. We computed a total of 13,779 unique cross-correlations using one sample-per-second vertical component broadband seismic data from 215 stations from 8 different networks over a period of 7 years to compute fundamental-mode Rayleigh wave dispersion curves following the method of Benson et al. (2007). We then inverted the dispersion data to calculate phase velocity maps for 11 periods from 8 s - 40 s throughout Anatolia and the Aegean regions (Barmin et al. 2001). Using smoothed Moho values derived from Vanacore et al. (2013) in our starting models, we inverted our dispersion curves using a linear least-squares iterative inversion scheme (Herrmann & Ammon 2004) to produce a 3-D shear-wave velocity model of the crust and uppermost mantle throughout Anatolia and the Aegean. We find a good correlation between our seismic shear wave velocities and paleostructures (suture zones) and modern deformation (basin formation and fault deformation). The most prominent crustal velocity contrasts occur across intercontinental sutures zones, resulting from the juxtaposition of the compositionally different basements of the amalgamated terranes. At shallow depths, seismic velocity contrasts correspond closely with surficial features. The Thrace, Cankiri and Tuz Golu basins, and accretionary complexes related to the closure of the Neotethys are characterized by slow shear wave velocities, while the Menderes and Kirsehir Massifs, Pontides, and Istanbul Zone are characterized by fast velocities. We find that the East Anatolia Plateau has slow shear-wave velocities

  20. Mass sensitivity of layered shear-horizontal surface acoustic wave devices for sensing applications

    NASA Astrophysics Data System (ADS)

    Kalantar-Zadeh, Kourosh; Trinchi, Adrian; Wlodarski, Wojtek; Holland, Anthony; Galatsis, Kosmas

    2001-11-01

    Layered Surface Acoustic Wave (SAW) devices that allow the propagation of Love mode acoustic waves will be studied in this paper. In these devices, the substrate allows the propagation of Surface Skimming Bulks Waves (SSBWs). By depositing layers, that the speed of Shear Horizontal (SH) acoustic wave propagation is less than that of the substrate, the propagation mode transforms to Love mode. Love mode devices which will be studied in this paper, have SiO2 and ZnO acoustic guiding layers. As Love mode of propagation has no movement of particles component normal to the active sensor surface, they can be employed for the sensing applications in the liquid media.

  1. A study of time harmonic guided Lamb waves and their caustics in composite plates.

    PubMed

    Karmazin, Alexander; Kirillova, Evgenia; Seemann, Wolfgang; Syromyatnikov, Pavel

    2013-01-01

    Spatial steady-state Lamb wave propagation in an anisotropic composite plate excited by harmonic surface sources is modeled using a Green's matrix representation in a frequency-wavenumber domain. An approach based on a residue integration technique for two dimensional wavenumber integrals for the computation of displacements outside an excitation source is presented in this paper. In the far-field zone of the excitation source, the method of stationary phase is used, which gives an asymptotic expansion of the displacement vector as a sum of cylindrical waves. Near caustic directions, a far-field solution is computed in terms of Airy functions. The results obtained applying residue integration technique and asymptotic expansion are found to be coinciding with the results of the computation by using the adaptive quadratures. Moreover, these approaches agree well with experimental data. Then, the advantages and disadvantages of the various methods applied for modeling of Lamb wave propagation are discussed in this paper. Focussing and other properties of Lamb waves are studied using numerical examples.

  2. Characteristics of second harmonic generation of Lamb waves in nonlinear elastic plates.

    PubMed

    Müller, Martin F; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J

    2010-04-01

    This paper investigates the characteristics of the second harmonic generation of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal generation of a symmetric second harmonic mode by an antisymmetric primary mode is possible. These solutions also demonstrate that modes showing internal resonance-nonzero power flux to the second harmonic mode, plus phase velocity matching-are most useful for measurements. In addition, when using finite wave packets, which is the case in most experimental measurements, group velocity matching is required for a cumulative increase in the second harmonic amplitude with propagation distance. Finally, five mode types (which are independent of material properties) that satisfy all three requirements for this cumulative increase in second harmonic amplitude-nonzero power flux, plus phase and group velocity matching-are identified. These results are important for the development of an experimental procedure to measure material nonlinearity with Lamb waves.

  3. Rayleigh–Lamb wave propagation on a fractional order viscoelastic plate

    PubMed Central

    Meral, F. Can; Royston, Thomas J.; Magin, Richard L.

    2011-01-01

    A previous study of the authors published in this journal focused on mechanical wave motion in a viscoelastic material representative of biological tissue [Meral et al., J. Acoust. Soc. Am. 126, 3278–3285 (2009)]. Compression, shear and surface wave motion in and on a viscoelastic halfspace excited by surface and sub-surface sources were considered. It was shown that a fractional order Voigt model, where the rate-dependent damping component that is dependent on the first derivative of time is replaced with a component that is dependent on a fractional derivative of time, resulted in closer agreement with experiment as compared with conventional (integer order) models, such as those of Voigt and Zener. In the present study, this analysis is extended to another configuration and wave type: out-of-plane response of a viscoelastic plate to harmonic anti-symmetric Lamb wave excitation. Theoretical solutions are compared with experimental measurements for a polymeric tissue mimicking phantom material. As in the previous configurations the fractional order modeling assumption improves the match between theory and experiment over a wider frequency range. Experimental complexities in the present study and the reliability of the different approaches for quantifying the shear viscoelastic properties of the material are discussed. PMID:21361459

  4. Measurement-device-independent quantum key distribution with q-plate

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Shang-Hong, Zhao; Ying, Sun

    2015-12-01

    The original measurement-device-independent quantum key distribution is reviewed and a modified protocol using rotation invariant photonic state is proposed. A hybrid encoding approach combined polarization qubit with orbit angular momentum qubit is adopted to overcome the polarization misalignment associated with random rotations in long-distance quantum key distribution. The initial encoding and final decoding of information in our MDI-QKD implementation protocol can be conveniently performed in the polarization space, while the transmission is done in the rotation invariant hybrid space. Our analysis indicates that both the secure key rate and transmission distance can be improved with our modified protocol owing to the lower quantum bit error rate. Furthermore, our hybrid encoding approach only needs to insert four q-plates in practical experiment and to overcome the polarization misalignment problem mentioned above without including any feedback control.

  5. Roll-to-plate fabrication of microfluidic devices with rheology-modified thiol-ene resins

    NASA Astrophysics Data System (ADS)

    Senkbeil, Silja; Aho, Johanna; Yde, Leif; Lindvold, Lars R.; Stensborg, Jan F.; Rantanen, Jukka; Lafleur, Josiane P.; Kutter, Jörg P.

    2016-07-01

    In this paper, the replication possibilities of microfluidic channels by UV-roll-to-plate fabrication were investigated and a study of rheology-modified thiol-ene for the application in such a UV-roll-to-plate setup was conducted. The system allows the manufacture of channels with aspect ratios of 2:1 and a maximal channel depth of 90 μm as well as the sealing of the finished devices with patterning and sealing speeds of up to 19 m min-1. By adding fumed silica nanoparticles to the uncured resins, it was possible to alter the rheological behavior of the resin system to fabricate shallow microfluidic channels with 40  ×  95 μm cross-sectional dimensions. Moreover, deeper (90 μm) channels can be fabricated with highly viscous resins based on thiol-terminated oligomers. As a demonstration, capillary electrophoresis chips were prepared and tested for a simple separation of two fluorescent dyes.

  6. Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

    NASA Technical Reports Server (NTRS)

    Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

    2006-01-01

    Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell-lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a-Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two "control plates" are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (gladwater) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

  7. Guided-Wave TeO2 Acousto-Optic Devices

    DTIC Science & Technology

    1991-01-12

    In this research program, Guided-wave TeO2 Acousto - Optic Devices, the properties of surface acoustic waves on tellurium dioxide single crystal...surfaces has been studied for its potential applications as acousto - optic signal processing devices. Personal computer based numerical method has been...interaction with laser beams. Use of the acousto - optic probe, the surface acoustic wave velocity and field distribution have been obtained and compared

  8. Feature guided waves (FGW) in fiber reinforced composite plates with 90° transverse bends

    NASA Astrophysics Data System (ADS)

    Yu, Xudong; Ratassepp, Madis; Fan, Zheng; Manogharan, Prabhakaran; Rajagopal, Prabhu

    2016-02-01

    Fiber reinforced composite materials have been increasingly used in high performance structures such as aircraft and large wind turbine blades. 90◦ composite bends are common in reinforcing structural elements, which are prone to defects such as delamination, crack, fatigue, etc. Current techniques are based on local inspection which makes the whole bend area scanning time consuming and tedious. This paper explores the feasibility of using feature guided waves (FGW) for rapid screening of 90◦ composite laminated bends. In this study, the behavior of the bend-guided wave in the anisotropic composite material is investigated through modal studies by applying the Semi-Analytical Finite Element (SAFE) method, also 3D Finite Element (FE) simulations are performed to visualize the results and to obtain cross validation. To understand the influence of the anisotropy, three-dimensional dispersion surfaces of the guided modes in flat laminated plates are obtained, showing the dependence of the phase velocity with the frequency and the fiber orientation. S H0-like and S 0-like bend-guided modes are identified with energy concentrated in the bend region, limiting energy radiation into adjacent plates and thus achieving increased inspection length. Finally, parametric studies are carried out to further investigate the properties of these two bend-guided modes, demonstrating the variation of the group velocity, the energy concentration, and the attenuation with the frequency.

  9. The Half Wave Plate Rotator for the BLAST-TNG Balloon-Borne Telescope

    NASA Astrophysics Data System (ADS)

    Setiawan, Hananiel; Ashton, Peter; Novak, Giles; Angilè, Francesco E.; Devlin, Mark J.; Galitzki, Nicholas; Ade, Peter; Doyle, Simon; Pascale, Enzo; Pisano, Giampaolo; Tucker, Carole E.

    2016-01-01

    The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is an experiment designed to map magnetic fields in molecular clouds in order to study their role in the star formation process. The telescope will be launched aboard a high-altitude balloon in December 2016 for a 4-week flight from McMurdo station in Antarctica. BLAST-TNG will measure the polarization of submillimeter thermal emission from magnetically aligned interstellar dust grains, using large format arrays of kinetic inductance detectors operating in three bands centered at 250, 350, and 500 microns, with sub-arcminute angular resolution. The optical system includes an achromatic Half Wave Plate (HWP), mounted in a Half Wave Plate rotator (HWPr). The HWP and HWPr will operate at 4 K temperature to reduce thermal noise in our measurements, so it was crucial to account for the effects of thermal contraction at low temperature in the HWPr design. It was also equally important for the design to meet torque requirements while minimizing the power from friction and conduction dissipated at the 4 K stage. We also discuss our plan for cold testing the HWPr using a repurposed cryostat with a Silicon Diode thermometer read out by an EDAS-CE Ethernet data acquisition system.

  10. Vibrational response prediction of a pneumatic tyre using an orthotropic two-plate wave model

    NASA Astrophysics Data System (ADS)

    Muggleton, J. M.; Mace, B. R.; Brennan, M. J.

    2003-07-01

    A wave model to predict the vibrational response of a pneumatic tyre subject to line force excitation is presented. The tread and sidewalls are each modelled as thin, flat orthotropic plates with in-plane tension, which are joined together by a translational stiffness, and to a rigid rim. The dynamic response of the tyre to harmonic excitation is decomposed into spatial harmonics around the circumference, and waves in the meridional direction. At low frequencies (<100 Hz), the response is stiffness-like, and is controlled by the sidewall properties and tension effects resulting from the tyre pressure. In the mid-frequency range (100-500 Hz), a resonant response is observed, associated with modes both across and around the tyre. At high frequencies (>500 Hz), the response tends towards that of an infinite orthotropic plate. Experiments have been conducted on an inflated tyre fitted to a wheel rim to confirm the theoretical findings. The results show reasonable agreement with the predictions, the model accurately reflecting the phenomenological behaviour.

  11. Effects of Z-pins on Lamb waves in composite plates

    NASA Astrophysics Data System (ADS)

    Swenson, Eric D.; Kapoor, Hitesh; Soni, Som R.

    2010-04-01

    This experimental research investigates the effects of adding z-pins to a carbon fiber reinforced plate (CFRP) on Lamb wave propagation, such as mode conversion and reflections. The motivation for this study is derived from the current and expected future use of z-pins in aircraft structures coupled with the requirement to design structural health monitoring (SHM) systems for detecting damage in regions of composite structures with z-pins. This experimental study is conducted on two 4.8 mm thick CFRP test articles, where one plate has a 20 by 279 mm2 band of z-pins and the other does not. The z-pins have an average diameter of 0.28 mm and are inserted through the thickness of the panel with an area density of 4% before curing. A three-dimensional (3D) laser Doppler vibrometer (LDV) was employed to collect velocity measurements over a 1 mm uniformly-spaced grid of 17,899 scan points. Time-sequenced 3D LDV scans are presented to show that adding this relatively small amount of z-pins to a 4.8 mm thick CFRP has few measureable effects on Lamb wave propagation.

  12. Transmission of Lamb waves and resonance at an adhesive butt joint of plates.

    PubMed

    Mori, Naoki; Biwa, Shiro

    2016-12-01

    The transmission behavior of Lamb waves and the possible occurrence of resonance at an adhesive butt joint of plates are studied experimentally. To this purpose, two 2.5-mm thick aluminum alloy plates are bonded at their edges using cyanoacrylate-based adhesive. Bonded plate specimens with different joint conditions are prepared by changing the bonding procedure. The measurements are performed for the transmission characteristics of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb modes for the frequency range of 0.4-0.6MHz below the cut-off frequency of the higher-order modes. The experimental results show that the transmission coefficients of the S0 and A0 modes exhibit different frequency-dependent characteristics depending on the joint condition. Furthermore, for the incidence of the S0 mode at the center frequency of 1MHz, the transmitted S0 mode in weakly bonded specimens shows a long oscillation tail due to the resonance effect. The experimental results are discussed in the light of the theoretical results based on the spring-type interface model. The interfacial stiffnesses identified from the transmission coefficients are shown to be correlated with the bonding condition of the joint and give reasonable estimates of the resonance frequencies of weakly bonded specimens.

  13. Crack Imaging and Quantification in Aluminum Plates with Guided Wave Wavenumber Analysis Methods

    NASA Technical Reports Server (NTRS)

    Yu, Lingyu; Tian, Zhenhua; Leckey, Cara A. C.

    2015-01-01

    Guided wavefield analysis methods for detection and quantification of crack damage in an aluminum plate are presented in this paper. New wavenumber components created by abrupt wave changes at the structural discontinuity are identified in the frequency-wavenumber spectra. It is shown that the new wavenumbers can be used to detect and characterize the crack dimensions. Two imaging based approaches, filter reconstructed imaging and spatial wavenumber imaging, are used to demonstrate how the cracks can be evaluated with wavenumber analysis. The filter reconstructed imaging is shown to be a rapid method to map the plate and any existing damage, but with less precision in estimating crack dimensions; while the spatial wavenumber imaging provides an intensity image of spatial wavenumber values with enhanced resolution of crack dimensions. These techniques are applied to simulated wavefield data, and the simulation based studies show that spatial wavenumber imaging method is able to distinguish cracks of different severities. Laboratory experimental validation is performed for a single crack case to confirm the methods' capabilities for imaging cracks in plates.

  14. Shear wave velocity structure of the Anatolian Plate: anomalously slow crust in southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Delph, Jonathan R.; Biryol, C. Berk; Beck, Susan L.; Zandt, George; Ward, Kevin M.

    2015-07-01

    The Anatolian Plate is composed of different lithospheric blocks and ribbon continents amalgamated during the closure of the Paleotethys Ocean and Neotethys Ocean along a subduction margin. Using ambient noise tomography, we investigate the crustal and uppermost mantle shear wave velocity structure of the Anatolian Plate. A total of 215 broad-band seismic stations were used spanning 7 yr of recording to compute 13 778 cross-correlations and obtain Rayleigh wave dispersion measurements for periods between 8 and 40 s. We then perform a shear wave inversion to calculate the seismic velocity structure of the crust and uppermost mantle. Our results show that the overall crustal shear wave velocities of the Anatolian crust are low (˜3.4 km s-1), indicative of a felsic overall composition. We find that prominent lateral seismic velocity gradients correlate with Tethyan suture zones, supporting the idea that the neotectonic structures of Turkey are exploiting the lithospheric weaknesses associated with the amalgamation of Anatolia. Anomalously slow shear wave velocities (˜3.15 km s-1 at 25 km) are located in the western limb of the Isparta Angle in southwestern Turkey. In the upper crust, we find that these low shear wave velocities correlate well with the projected location of a carbonate platform unit (Bey Dağlari) beneath the Lycian Nappe complex. In the lower crust and upper mantle of this region, we propose that the anomalously slow velocities are due to the introduction of aqueous fluids related to the underplating of accretionary material from the underthrusting of a buoyant, attenuated continental fragment similar to the Eratosthenes seamount. We suggest that this fragment controlled the location of the formation of the Subduction-Transform Edge Propagator fault in the eastern Aegean Sea during rapid slab rollback of the Aegean Arc in early Miocene times. Lastly, we observe that the uppermost mantle beneath continental Anatolia is generally slow (˜4.2 km s-1

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  16. Highly temperature-dependent performance of a polyvinylidene fluoride Lamb wave device

    NASA Astrophysics Data System (ADS)

    Toda, Kohji; Ikenohira, Kazuo

    1980-11-01

    A Lamb wave device using a polyvinylidene flouride film is described. The transducer of the device consists of interdigital electrodes and a uniform counter-electrode. The performance of the device is highly temperature dependent. The attenuation of the Lamb wave on the film increases with higher frequencies. The attenuation decreases with increasing temperature, while the conversion efficiency of the transducer is nearly constant for the temperature change. The output of the device changes significantly under the influence of irradiation from a black body, and the device is very sensitive in the infrared region.

  17. Parametric Decay of Pump Waves into two Linear Modes in SINP MaPLE Device

    SciTech Connect

    Biswas, Subir; Pal, Rabindranath

    2010-11-23

    Parametric decay of incident waves of ion cyclotron frequency range into linear modes is observed in experiment performed in the SINP MaPLE device where nitrogen plasma produced by ECR discharge. Along with a mode in drift wave frequency range, sideband of the incident waves are observed when amplitude of the exciter signal goes above a threshold value. Sideband of the second harmonic is also seen. Preliminary studies point towards excitation of ion Bernstein wave. Details of the experimental results are presented.

  18. Realizing full visible spectrum metamaterial half-wave plates with patterned metal nanoarray/insulator/metal film structure.

    PubMed

    Dai, Yanmeng; Ren, Wenzhen; Cai, Hongbing; Ding, Huaiyi; Pan, Nan; Wang, Xiaoping

    2014-04-07

    Abrupt phase shift introduced by plasmonic resonances has been frequently used to design subwavelength wave plates for optical integration. Here, with the sandwich structure consisting of a top periodic patterned silver nanopatch, an in-between insulator layer and a bottom thick Au film, we realize a broadband half-wave plate which is capable to cover entire visible light spectrum ranging from 400 to 780 nm. Moreover, when the top layer is replaced with a periodic array of composite super unit cell comprised of two nanopatches with different sizes, the operation bandwidth can be further improved to exceed an octave (400-830 nm). In particular, we demonstrate that the designed half-wave plate can be used efficiently to rotate the polarization state of an ultra-fast light pulse with reserved pulse width. Our result offers a new strategy to design and construct broadband high efficiency phase-response based optical components using patterned metal nanoarray/insulator/metal structure.

  19. Anisotropy of Lamb and SH waves propagation in langasite single crystal plates under the influence of dc electric field.

    PubMed

    Burkov, S I; Zolotova, O P; Sorokin, B P

    2012-03-01

    Paper is presented the results of computer simulation. Effect of the homogeneous dc electric field influence on the propagation of zero and first order Lamb and SH waves in piezoelectric langasite single crystal plates for a lot of cuts and directions have been calculated. Crystalline directions and cuts with maximal and minimal influence of dc electric field have indicated. Effect of hybridization of plate modes has been discussed.

  20. Surface acoustic wave devices as passive buried sensors

    NASA Astrophysics Data System (ADS)

    Friedt, J.-M.; Rétornaz, T.; Alzuaga, S.; Baron, T.; Martin, G.; Laroche, T.; Ballandras, S.; Griselin, M.; Simonnet, J.-P.

    2011-02-01

    Surface acoustic wave (SAW) devices are currently used as passive remote-controlled sensors for measuring various physical quantities through a wireless link. Among the two main classes of designs—resonator and delay line—the former has the advantage of providing narrow-band spectrum informations and hence appears compatible with an interrogation strategy complying with Industry-Scientific-Medical regulations in radio-frequency (rf) bands centered around 434, 866, or 915 MHz. Delay-line based sensors require larger bandwidths as they consists of a few interdigitated electrodes excited by short rf pulses with large instantaneous energy and short response delays but is compatible with existing equipment such as ground penetrating radar (GPR). We here demonstrate the measurement of temperature using the two configurations, particularly for long term monitoring using sensors buried in soil. Although we have demonstrated long term stability and robustness of packaged resonators and signal to noise ratio compatible with the expected application, the interrogation range (maximum 80 cm) is insufficient for most geology or geophysical purposes. We then focus on the use of delay lines, as the corresponding interrogation method is similar to the one used by GPR which allows for rf penetration distances ranging from a few meters to tens of meters and which operates in the lower rf range, depending on soil water content, permittivity, and conductivity. Assuming propagation losses in a pure dielectric medium with negligible conductivity (snow or ice), an interrogation distance of about 40 m is predicted, which overcomes the observed limits met when using interrogation methods specifically developed for wireless SAW sensors, and could partly comply with the above-mentioned applications. Although quite optimistic, this estimate is consistent with the signal to noise ratio observed during an experimental demonstration of the interrogation of a delay line buried at a depth of 5

  1. Acoustic scattering from a finite plate: generation of guided Lamb waves S(0), A(0) and A.

    PubMed

    Cité, N; Chati, F; Décultot, D; Léon, F; Maze, G

    2012-06-01

    In the domain of renewable energies, marine current turbines constitute one of the possibilities of producing electrical energy. Naked-eye inspection, or with the aid of video monitoring systems of these machines to ensure their perfect working order, can be difficult in a turbid environment. Acoustic methods are conceivable. The study focuses on the blades of these machines, by considering rectangular plates. The propagation of Lamb waves in a plate is studied by analyzing experimental time signals obtained from acoustic scattering. These signals are analyzed employing the ray theory. In vacuum, the flexural wave is the A(0) Lamb wave, whilst in water this wave splits in a bifurcation: the A wave with a phase velocity always smaller than the sound speed in water, and the A(0) wave with a phase velocity always higher than the sound speed in water. In the central bandpass of the transducers used in the experiments, mainly the A and S(0) waves exist. However, signals observed in the third harmonic bandpass of the transducers are also analyzed. In order to complement these results, resonance frequencies of the plate studied are calculated taking into account the boundary conditions and compared with the resonance frequencies of the experimental spectra.

  2. Laser-Generated Lamb Waves Propagation in Multilayered Plates Composed of Viscoelastic Fiber-reinforced Composite Materials

    NASA Astrophysics Data System (ADS)

    Sun, Hong-xiang; Zhang, Shu-yi; Yuan, Shou-qi; Guan, Yi-jun; Ge, Yong

    2016-07-01

    The propagation characteristics of laser-generated Lamb waves in multilayered fiber-reinforced composite plates with different fiber orientations and number of layers have been investigated quantitatively. Considering the viscoelasticity of the composite materials, we have set up finite element models for simulating the laser-generated Lamb waves in two types of the multilayered composite plates. In the first type, different fiber orientations are adopted. In the second one, different number of layers are considered. The results illustrate the occurrence of attenuation and dispersion, which is induced by the viscoelasticity and multilayer structure, respectively.

  3. Experimental and theoretical study of Rayleigh-Lamb waves in a plate containing a surface-breaking crack

    NASA Technical Reports Server (NTRS)

    Paffenholz, Joseph; Fox, Jon W.; Gu, Xiaobai; Jewett, Greg S.; Datta, Subhendu K.

    1990-01-01

    Scattering of Rayleigh-Lamb waves by a normal surface-breaking crack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scattering of waves generated by this impact source by the crack is subsequently solved by employing a Green's function integral expression for the scattered field coupled with a finite element representation of the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implication for practical applications are discussed.

  4. Parallel generation of multiple first-order vector beams with a polarization grating and a q-plate device

    NASA Astrophysics Data System (ADS)

    Badham, Katherine; Moreno, Ignacio; Sánchez-López, María M.; Davis, Jeffrey A.; Hashimoto, Nobuyuki; Kurihara, Makoto; Albero, Jorge; Cottrell, Don M.

    2016-12-01

    Vector beams, usually generated using q-plates, are of interest because their polarization state varies spatially. In general, the q-plate performance is examined by illuminating the device and detecting the output beam with polarization states on the 6 cardinal points on the zero-order Poincaré sphere, requiring a total of 36 separate measurements. In this work we present a powerful technique to generate arbitrary vector beams in parallel, thus reducing the number of measurements required. We begin with a programmable polarization diffraction grating capable to generate an arbitrary number of diffraction orders with defined polarization states selected at will. Then we combine this grating with a segmented q-plate device with q = 1/2 value. Using this combination, the parallel generation of six arbitrary first-order vector beams is achieved in a single shot. Therefore, the analysis of these beams can be greatly reduced.

  5. Non-linear control of the ''clam'' wave energy device. Final report

    SciTech Connect

    Not Available

    1983-09-01

    A promising wave energy device being currently investigated is the ''clam'' device. The clam extracts energy by pumping air through a specially designed (Wells) turbine. Although operation of the Wells turbine does not require a rectified air flow, some additional control will be necessary to optimize the phase of the clam motion for good efficiencies. An examination of the equation of motion in the time domain suggests the possibility of non-linear phase control by mechanical, power take-off, or pneumatic latching. Latching can be shown to increase the efficiency of the device in the longer wavelengths of the wave spectrum, i.e. those of high incident wave power.

  6. Microwave and millimeter-wave resonant-tunneling devices

    NASA Technical Reports Server (NTRS)

    Sollner, T. C. L. Gerhard; Le, Han Quang; Brown, E. L.

    1988-01-01

    Resonant-tunneling devices in microelectronic component form, whose structure is the electron analog of a Fabry-Perot resonator, encompass oscillators, self-oscillating mixers, and harmonic multipliers. The negative differential resistance characteristic of these devices has been obtained at room temperature, and resonant-tunneling transistors capable of operation in the THz-frequency range appear to be feasible. Three-terminal resonant-tunneling device development is in its infancy, as is that of devices for digital applications.

  7. Exploring the resonant vibration of thin plates: Reconstruction of Chladni patterns and determination of resonant wave numbers.

    PubMed

    Tuan, P H; Wen, C P; Chiang, P Y; Yu, Y T; Liang, H C; Huang, K F; Chen, Y F

    2015-04-01

    The Chladni nodal line patterns and resonant frequencies for a thin plate excited by an electronically controlled mechanical oscillator are experimentally measured. Experimental results reveal that the resonant frequencies can be fairly obtained by means of probing the variation of the effective impedance of the exciter with and without the thin plate. The influence of the extra mass from the central exciter is confirmed to be insignificant in measuring the resonant frequencies of the present system. In the theoretical aspect, the inhomogeneous Helmholtz equation is exploited to derive the response function as a function of the driving wave number for reconstructing experimental Chladni patterns. The resonant wave numbers are theoretically identified with the maximum coupling efficiency as well as the maximum entropy principle. Substituting the theoretical resonant wave numbers into the derived response function, all experimental Chladni patterns can be excellently reconstructed. More importantly, the dispersion relationship for the flexural wave of the vibrating plate can be determined with the experimental resonant frequencies and the theoretical resonant wave numbers. The determined dispersion relationship is confirmed to agree very well with the formula of the Kirchhoff-Love plate theory.

  8. Modeling of wave propagation in plate structures using three-dimensional spectral element method for damage detection

    NASA Astrophysics Data System (ADS)

    Peng, Haikuo; Meng, Guang; Li, Fucai

    2009-03-01

    This paper presents the application of three-dimensional (3-D) spectral element method (SEM) to wave propagation problems in plate structures for the purpose of damage detection. The excellent characteristic of the SEM is that the mass matrix is diagonal because of the choice of Lagrange interpolation function supported on the Gauss-Lobatto-Legendre (GLL) points in conjunction with the GLL integration rule. Therefore, numerical calculation can be significantly efficient in comparison with the classical finite element method (FEM). By taking advantage of this characteristic, a 3-D spectral finite elements (SFEs)-based model is developed to simulate the wave propagation in plate structures. Lamb waves, propagating in aluminum plates with and without a crack are investigated. Responses from 3-D SFEs- and 2-D SFEs-based models are compared. Different Lamb wave modes are generated using different excitation approaches and, subsequently, characteristics of those modes are analyzed. The results demonstrate that the proposed model can offer efficient and realistic simulation for Lamb wave propagation in plate structures, so as to detect damages in those structures.

  9. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    DOE PAGES

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; ...

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore » channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

  10. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    SciTech Connect

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.

  11. Development of an Inductively Coupled Thermometer for a Cryogenic Half-Wave Plate

    NASA Astrophysics Data System (ADS)

    Madurowicz, Alexander; Kusaka, Akito

    2017-01-01

    The current state of Cosmic Microwave Background (CMB) research has focused much attention on the measurement of polarization. In an effort to modulate the CMB polarization while also minimizing photon noise due to thermal emission, we are developing a sapphire half-wave plate (HWP) cooled to 50 K rotating at 2 Hz on a superconducting magnetic levitating bearing. In order to measure the temperature of the rotor without making physical contact, we designed an inductively coupled cryogenic thermometer. The complex impedance of the circuit has a resonant peak when driven around 1 MHz. The width of this resonance is dependent on the value of the resistor, which varies with temperature and functions as a thermometer once calibrated. In this talk, we will present results from stationary measurements of this impedance and discuss the temperature accuracy of this thermometer, as well as a preliminary circuit design to measure this impedance during the HWP rotation.

  12. Texture in steel plates revealed by laser ultrasonic surface acoustic waves velocity dispersion analysis.

    PubMed

    Yin, Anmin; Wang, Xiaochen; Glorieux, Christ; Yang, Quan; Dong, Feng; He, Fei; Wang, Yanlong; Sermeus, Jan; Van der Donck, Tom; Shu, Xuedao

    2017-02-24

    A photoacoustic, laser ultrasonics based approach in an Impulsive Stimulated Scattering (ISS) implementation was used to investigate the texture in polycrystalline metal plates. The angular dependence of the 'polycrystalline' surface acoustic wave (SAW) velocity measured along regions containing many grains was experimentally determined and compared with simulated results that were based on the angular dependence of the 'single grain' SAW velocity within single grains and the grain orientation distribution. The polycrystalline SAW velocities turn out to vary with texture. The SAW velocities and their angular variations for {110} texture were found to be larger than that the ones for {111} texture or the strong γ fiber texture. The SAW velocities for {001} texture were larger than for {111} texture, but with almost the same angular dependence. The results infer the feasibility to apply angular SAW angular dispersion measurements by laser ultrasonics for on-line texture monitoring.

  13. Systematics of an ambient-temperature, rapidly-rotating half-wave plate

    NASA Astrophysics Data System (ADS)

    Essinger-Hileman, T.; Kusaka, A.; Appel, J. W.; Gallardo, P.; Irwin, K. D.; Jarosik, N.; Nolta, M. R.; Page, L. A.; Parker, L. P.; Raghunathan, S.; Sievers, J. L.; Simon, S. M.; Staggs, S. T.; Visnjic, K.

    2016-07-01

    In these proceedings, we summarize our in-field evaluation of temperature-to-polarization leakage associated with the use of a continuously-rotating, ambient-temperature half-wave plate (HWP) on the Atacama B-Mode Search (ABS) experiment. Using two seasons of data, we demonstrate scalar leakage of ˜ 0.01%. This is consistent with model expectations and an order of magnitude better than any previously-reported leakage. We constrain higher-order dipole and quadrupole leakage terms to be < 0.06% (95% confidence). Without any mitigation from scan cross-linking or boresight rotation, this corresponds to an upper limit on systematic errors in the tensor-to-scalar ratio r ;S 0.01. The HWP significantly reduces temperature-to-polarization leakage systematic errors for ABS and shows the promise of fast polarization modulation with HWPs for future experiments. Full details can be found in Ref. 1.

  14. A New Omni-Directional EMAT for Ultrasonic Lamb Wave Tomography Imaging of Metallic Plate Defects

    PubMed Central

    Huang, Songling; Wei, Zheng; Zhao, Wei; Wang, Shen

    2014-01-01

    This paper proposes a new omni-directional electromagnetic acoustic transducer (EMAT) for the ultrasonic Lamb wave (ULW) tomography imaging (TI) of defects in metallic plates. The proposed EMAT is composed of a permanent magnet and a coil with a contra-flexure structure. This new EMAT coil structure is used for omni-directional ULW transmission and reception and ULW TI for the first time. The theoretical background and the working principles of this EMAT are presented and analyzed. The experimental results of its use on a 3 mm thick aluminum plate indicate that the EMAT with a contra-flexure coil (CFC) can transmit and receive a pure single A0 mode ULW with a high signal-to-noise ratio (SNR). Thus, the extraction of the projection data used for ULW TI may be performed accurately. The circumferential consistency of the projection data is only slightly influenced by the distortion of the eddy current field that is induced by the new CFC with an irregular shape. When the new EMAT array is used for ULW TI using the cross-hole method and SIRT arithmetic, a desirable imaging quality can be achieved, and the estimated size of an artificial corrosion defect agreed well with its actual value. The relation between the reconstruction resolution and the number of the new EMATs used is analyzed. More TI experiments are carried out when the aluminum plate defect is in two different locations relative to the EMAT array, for the further investigation of the performances of the new EMATs. PMID:24561398

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

    USGS Publications Warehouse

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

    1991-01-01

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

  16. Generation, Diffraction and Radiation of Subsonic Flexural Waves on Membranes and Plates: Observations of Structural and Acoustical Wavefields.

    NASA Astrophysics Data System (ADS)

    Matula, Thomas John

    Electromagnetic acoustic wave transducers (EMATs) are described for generating low-frequency tone bursts on metalized membranes in air and elastic plates in water. Bursts on the membrane have phase velocities much less than the speed of sound in the surrounding air and are accompanied by plane evanescent waves. The frequency and time-domain responses of the EMAT and the dependence on gap spacing between the coupling coil and the membrane were studied. Wave -number selective optical and capacitive probes were used to measure the wave properties. Versions of these transducers are insensitive to long wavelength motion of the membrane. Diffraction of the burst by a sharp edge in air was observed as a function of the gap between the membrane and a razor edge. The scattered pressure decreases exponentially with increasing gap as expected from an approximate analysis of edge diffraction of evanescent waves. In related work an EMAT is used to generate 28 kHz tone bursts of bending waves on an aluminum plate. The bursts propagate down into water where the surrounding wavefield is probed. Observations described indicate that there occurs a branching of energy as the wave crosses the air-water interface. Radiation from subsonic flexural plate waves due to the discontinuity in fluid -loading is observed. It is partially analogous to the transition radiation of fast charged particles crossing a dielectric interface. The angular radiation pattern resembles that of a line quadrupole. Near the interface there exists an interference between the two energy branches in water that produces a series of pressure nulls. The pressure nulls are associated with a pi phase change in the wavefield and are indicators of wavefront dislocations. A computation of the wavefield in an unbounded fluid due to a line-moment excitation of a plate is comparable with the null pattern observed but differs in certain details.

  17. High-frequency programmable acoustic wave device realized through ferroelectric domain engineering

    NASA Astrophysics Data System (ADS)

    Ivry, Yachin; Wang, Nan; Durkan, Colm

    2014-03-01

    Surface acoustic wave devices are extensively used in contemporary wireless communication devices. We used atomic force microscopy to form periodic macroscopic ferroelectric domains in sol-gel deposited lead zirconate titanate, where each ferroelectric domain is composed of many crystallites, each of which contains many microscopic ferroelastic domains. We examined the electro-acoustic characteristics of the apparatus and found a resonator behavior similar to that of an equivalent surface or bulk acoustic wave device. We show that the operational frequency of the device can be tailored by altering the periodicity of the engineered domains and demonstrate high-frequency filter behavior (>8 GHz), allowing low-cost programmable high-frequency resonators.

  18. Power selective optical filter devices and optical systems using same

    DOEpatents

    Koplow, Jeffrey P

    2014-10-07

    In an embodiment, a power selective optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes at least one substantially zero-order, zero-wave plate. The zero-order, zero-wave plate is configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. The zero-order, zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

  19. Application of surface acoustic wave devices to radio telemetry

    NASA Technical Reports Server (NTRS)

    Strasilla, U.

    1983-01-01

    Three experimental Surface Acoustic Wave Resonators (SAWR) are developed and evaluated. A desired center frequency is obtained by correct spacing of the Inter-Digital Transducers (IDT). Transmitting and receiving IDT's must be close for adequate coupling and a sufficient number of reflectors are required to create a high quality standing wave. A review of oscillator theory is given and current technology evaluated.

  20. Ultrathin Terahertz Quarter-wave plate based on Split Ring Resonator and Wire Grating hybrid Metasurface

    PubMed Central

    Nouman, Muhammad Tayyab; Hwang, Ji Hyun; Jang, Jae-Hyung

    2016-01-01

    Planar metasurface based quarter-wave plates offer various advantages over conventional waveplates in terms of compactness, flexibility and simple fabrication; however they offer very narrow bandwidth of operation. Here, we demonstrate a planar terahertz (THz) metasurface capable of linear to circular polarization conversion and vice versa in a wide frequency range. The proposed metasurface is based on horizontally connected split ring resonators and is realized on an ultrathin (0.05λ) zeonor substrate. The fabricated quarter waveplate realizes linear to circular polarization conversion in two broad frequency bands comprising 0.64–0.82 THz and 0.96–1.3 THz with an insertion loss ranging from −3.9 to −10 dB. By virtue of ultrathin sub wavelength thickness, the proposed waveplate design is well suited for application in near field THz optical systems. Additionally, the proposed metasurface design offers novel transmission phase characteristics that present further opportunities to realize dynamic polarization control of incident waves. PMID:27958358

  1. Ultrathin Terahertz Quarter-wave plate based on Split Ring Resonator and Wire Grating hybrid Metasurface

    NASA Astrophysics Data System (ADS)

    Nouman, Muhammad Tayyab; Hwang, Ji Hyun; Jang, Jae-Hyung

    2016-12-01

    Planar metasurface based quarter-wave plates offer various advantages over conventional waveplates in terms of compactness, flexibility and simple fabrication; however they offer very narrow bandwidth of operation. Here, we demonstrate a planar terahertz (THz) metasurface capable of linear to circular polarization conversion and vice versa in a wide frequency range. The proposed metasurface is based on horizontally connected split ring resonators and is realized on an ultrathin (0.05λ) zeonor substrate. The fabricated quarter waveplate realizes linear to circular polarization conversion in two broad frequency bands comprising 0.64–0.82 THz and 0.96–1.3 THz with an insertion loss ranging from ‑3.9 to ‑10 dB. By virtue of ultrathin sub wavelength thickness, the proposed waveplate design is well suited for application in near field THz optical systems. Additionally, the proposed metasurface design offers novel transmission phase characteristics that present further opportunities to realize dynamic polarization control of incident waves.

  2. Characterizing Atacama B-mode Search Detectors with a Half-Wave Plate

    NASA Astrophysics Data System (ADS)

    Simon, S. M.; Appel, J. W.; Campusano, L. E.; Choi, S. K.; Crowley, K. T.; Essinger-Hileman, T.; Gallardo, P.; Ho, S. P.; Kusaka, A.; Nati, F.; Palma, G. A.; Page, L. A.; Raghunathan, S.; Staggs, S. T.

    2016-08-01

    The Atacama B-Mode Search (ABS) instrument is a cryogenic (˜ 10 K) crossed-Dragone telescope located at an elevation of 5190 m in the Atacama Desert in Chile that observed for three seasons between February 2012 and October 2014. ABS observed the cosmic microwave background (CMB) at large angular scales (40<ℓ <500) to limit the B-mode polarization spectrum around the primordial B-mode peak from inflationary gravity waves at ℓ ˜ 100. The ABS focal plane consists of 480 transition-edge sensor (TES) bolometers. They are coupled to orthogonal polarizations from a planar ortho-mode transducer and observe at 145 GHz. ABS employs an ambient-temperature, rapidly rotating half-wave plate (HWP) to mitigate systematic effects and move the signal band away from atmospheric 1 / f noise, allowing for the recovery of large angular scales. We discuss how the signal at the second harmonic of the HWP rotation frequency can be used for data selection and for monitoring the detector responsivities.

  3. Unsteady heat-flux measurements of second-mode instability waves in a hypersonic flat-plate boundary layer

    NASA Astrophysics Data System (ADS)

    Kegerise, Michael A.; Rufer, Shann J.

    2016-08-01

    In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

  4. Apparatus for in-situ nondestructive measurement of Young's modulus of plate structures

    NASA Technical Reports Server (NTRS)

    Huang, Jerry Qixin (Inventor); Perez, Robert J. (Inventor); DeLangis, Leo M. (Inventor)

    2005-01-01

    A method and apparatus for determining stiffness of a plate-like structure including a monolithic or composite laminate plate entails disposing a device for generating an acoustical pulse against a surface of the plate and disposing a detecting device against the same surface spaced a known distance from the pulse-generating device, and using the pulse-generating device to emit a pulse so as to create an extensional wave in the plate. The detecting device is used to determine a time of flight of the wave over the known distance, and the wave velocity is calculated. A Young's modulus of the plate is determined by a processor based on the wave velocity. Methods and apparatus for evaluating both isotropic plates and anisotropic laminates are disclosed.

  5. Ultrasonic inspection apparatus and method using a focused wave device

    DOEpatents

    Gieske, John H.; Roach, Dennis P.; Walkington, Phillip D.

    2001-01-01

    An ultrasonic pulse echo inspection apparatus and method for detecting structural failures. A focus lens is coupled to the transducer to focus the ultrasonic signal on an area to be inspected and a stop is placed in the focus lens to block selected ultrasonic waves. Other waves are not blocked and are transmitted through the structure to arrive at interfaces therein concurrently to produce an echo response with significantly less distortion.

  6. Numerical simulations of a pulsed detonation wave augmentation device

    NASA Technical Reports Server (NTRS)

    Cambier, Jean-Luc; Adelman, Henry; Menees, Gene P.

    1993-01-01

    We present here the concept of a hybrid engine for Single Stage To Orbit (SSTO) air-breathing hypersonic vehicle. This concept relies on the use of pulsed detonation waves, both for thrust generation and mixing/combustion augmentation. We describe the principles behind the engine concept, which we call the Pulsed Detonation Wave Augmentor (PDWA). We demonstrate the principles of operation for two possible configurations through numerical simulations. We also attempt a first approximation to engine design, and propose various applications.

  7. The effect of shock wave impingement on thin, woven glass fiber reinforced, polymer composite plates

    NASA Astrophysics Data System (ADS)

    Jahnke, Douglas M.

    deformation of the test specimen. The technique has been validated by comparing the results obtained in a static experiment with the results measured by laser displacement sensors. Additional validation of dynamically obtained strain measurements was carried out by using a 13 mm (1/2") thick in-house fabricated composite specimen with embedded strain gauges and piezoelectric sensors. Surface mounted sensors due to the large inertia forces experienced by a test specimen tend to detach from it almost immediately after the shock impact, so very little useful data could be collected. The present work has created a strong foundation in testing methodology and baseline results in studying the effects of shock wave impingement on FRP composites. It was found that the maximum deformation of the plate occurs immediate after the shock impact and much before the whole loading cycle is completed. The results of permanent deformation have been normalized by using the impulse of the loading force. Additional work has been focused on the energy exchange between the incoming shock wave and the specimen. Understanding how much energy is associated with the shock reflection, transmission, absorption, or passed through is critical to designing protective systems using FRP composites.

  8. Evolution of the oceanic lithosphere inferred from Po/So waves traveling in the Philippine Sea Plate

    NASA Astrophysics Data System (ADS)

    Shito, Azusa; Suetsugu, Daisuke; Furumura, Takashi

    2015-07-01

    Po/So waves are characterized by their high-frequency content and long-duration travel over great distances (up to 3000km) through the oceanic lithosphere. Po/So waves are developed by the multiple forward scattering of P and S waves due to small-scale stochastic random heterogeneities. To study the nature of these heterogeneities, Po/So waves are analyzed in the Philippine Sea Plate, which consists of three regions with different lithospheric ages. In the Philippine Sea Plate, Po/So waves propagate in the youngest region (15 Ma) and propagate more effectively in older regions. We investigate the mechanism of this propagation efficiency using numerical finite difference method simulations of 2-D seismic wave propagation. The results of this study demonstrate that the increase in propagation efficiency of Po/So waves depends on the age of the oceanic lithosphere, and this relationship can be qualitatively explained by thickening of the oceanic lithosphere including small-scale heterogeneities and a reduction in the intrinsic attenuation. These small-scale heterogeneities may form continuously in oceanic lithosphere from the time of its formation at a spreading ridge, via the solidification of melts distributed in the asthenosphere.

  9. Numerical Simulation of Nonlinear Lamb Waves Used in a Thin Plate for Detecting Buried Micro-Cracks

    PubMed Central

    Wan, Xiang; Zhang, Qing; Xu, Guanghua; Tse, Peter W.

    2014-01-01

    Compared with conventional linear ultrasonic inspection methods, which are sensitive only to severe defects, nonlinear ultrasonic inspection methods are better for revealing micro-cracks in thin plates. However, most nonlinear ultrasonic inspection methods have only been experimentally investigated using bulk or Rayleigh waves. Numerical studies, especially numerical simulations of Lamb ultrasonic waves, have seldom been reported. In this paper, the interaction between nonlinear S0 mode Lamb waves and micro-cracks of various lengths and widths buried in a thin metallic plate was simulated using the finite element method (FEM). The numerical results indicate that after interacting with a micro-crack, a new wave-packet was generated in addition to the S0 mode wave-packet. The second harmonics of the S0 mode Lamb waves and the new wave-packet were caused by nonlinear acoustic effects at the micro-crack. An amplitude ratio indicator is thus proposed for the early detection of buried micro-cracks. PMID:24834908

  10. Numerical simulation of nonlinear Lamb waves used in a thin plate for detecting buried micro-cracks.

    PubMed

    Wan, Xiang; Zhang, Qing; Xu, Guanghua; Tse, Peter W

    2014-05-15

    Compared with conventional linear ultrasonic inspection methods, which are sensitive only to severe defects, nonlinear ultrasonic inspection methods are better for revealing micro-cracks in thin plates. However, most nonlinear ultrasonic inspection methods have only been experimentally investigated using bulk or Rayleigh waves. Numerical studies, especially numerical simulations of Lamb ultrasonic waves, have seldom been reported. In this paper, the interaction between nonlinear S0 mode Lamb waves and micro-cracks of various lengths and widths buried in a thin metallic plate was simulated using the finite element method (FEM). The numerical results indicate that after interacting with a micro-crack, a new wave-packet was generated in addition to the S0 mode wave-packet. The second harmonics of the S0 mode Lamb waves and the new wave-packet were caused by nonlinear acoustic effects at the micro-crack. An amplitude ratio indicator is thus proposed for the early detection of buried micro-cracks.

  11. High-Q cross-plate phononic crystal resonator for enhanced acoustic wave localization and energy harvesting

    NASA Astrophysics Data System (ADS)

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-05-01

    A high-Q cross-plate phononic crystal resonator (Cr-PCR) coupled with an electromechanical Helmholtz resonator (EMHR) is proposed to improve acoustic wave localization and energy harvesting. Owing to the strongly directional wave-scattering effect of the cross-plate corners, strong confinement of acoustic waves emerges. Consequently, the proposed Cr-PCR structure exhibits ∼353.5 times higher Q value and ∼6.1 times greater maximum pressure amplification than the phononic crystal resonator (Cy-PCR) (consisting of cylindrical scatterers) of the same size. Furthermore, the harvester using the proposed Cr-PCR and the EMHR has ∼22 times greater maximum output-power volume density than the previous harvester using Cy-PCR and EMHR structures.

  12. Numerical study and topology optimization of 1D periodic bimaterial phononic crystal plates for bandgaps of low order Lamb waves.

    PubMed

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, Mohammad

    2015-03-01

    The optimum topology of bimaterial phononic crystal (PhCr) plates with one-dimensional (1D) periodicity to attain maximum relative bandgap width of low order Lamb waves is computationally investigated. The evolution of optimized topology with respect to filling fraction of constituents, alternatively stiff scattering inclusion, is explored. The underlying idea is to develop PhCr plate structures with high specific bandgap efficiency at particular filling fraction, or further with multiscale functionality through gradient of optimized PhCr unitcell all over the lattice array. Multiobjective genetic algorithm (GA) is employed in this research in conjunction with finite element method (FEM) for topology optimization of silicon-tungsten PhCr plate unitcells. A specialized FEM model is developed and verified for dispersion analysis of plate waves and calculation of modal response. Modal band structure of regular PhCr plate unitcells with centric scattering layer is studied as a function of aspect ratio and filling fraction. Topology optimization is then carried out for a few aspect ratios, with and without prescribed symmetry, over various filling fractions. The efficiency of obtained solutions is verified as compared to corresponding regular centric PhCr plate unitcells. Moreover, being inspired by the obtained optimum topologies, definite and easy to produce topologies are proposed with enhanced bandgap efficiency as compared to centric unitcells. Finally a few cases are introduced to evaluate the frequency response of finite PhCr plate structures produced by achieved topologies and also to confirm the reliability of calculated modal band structures. Cases made by consecutive unitcells of different filling fraction are examined in order to attest the bandgap efficiency and multiscale functionality of such graded PhCr plate structures.

  13. A submicron device to rectify a square-wave angular velocity.

    PubMed

    Moradian, A; Miri, M F

    2011-02-01

    We study a system composed of two thick dielectric disks separated by a thin layer of an electrolyte solution. Initially both plates have the same surface charge distribution. The surface charge distribution has no rotational symmetry. We show that the top plate experiences a torque [Formula: see text]([Formula: see text]) if it rotates about its axis by an angle [Formula: see text] . The torque can be controlled by varying the electrolyte concentration, the separation and the surface charge density of the plates. For a specific example of charged rods attached to the plates, we find [Formula: see text]([Formula: see text]) [Formula: see text] sin(4[Formula: see text]) . We also study the dynamics of the system. We consider the case where the angular velocity of the bottom disk is a square-wave signal. We find that the average angular velocity of the top disk is not zero.

  14. The propagation of RF wave in a tandem mirror plasma propulsion device

    NASA Technical Reports Server (NTRS)

    Yang, T. F.; Peng, S.; Chang-Diaz, F. R.

    1990-01-01

    The propagation of RF waves launched in the end and the central cell of the tandem mirror propulsion device has been investigated both theoretically and experimentally. It was found that the amplitude of the wave excited in the plasma peaked while approaching the resonance, but then damped out, indicating strong absorption of the wave by the plasma. The absorption took place near the axis and the midplane of the device. The experimental results confirmed the theoretical prediction of the resonance effect. A very important discovery of this experiment was the broadening of the ICRF Fourier spectrum in the presence of the plasma.

  15. Advanced, High Power, Next Scale, Wave Energy Conversion Device

    SciTech Connect

    Hart, Philip R.

    2011-09-27

    This presentation from the Water Peer Review highlights one of the program's marine and hyrokinetics device design projects to scale up the current Ocean Power Technology PowerBuoy from 150kW to 500kW.

  16. On-chip temperature-compensated Love mode surface acoustic wave device for gravimetric sensing

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Flewitt, A. J.

    2014-11-01

    Love mode surface acoustic wave (SAW) sensors have been recognized as one of the most sensitive devices for gravimetric sensors in liquid environments such as bio sensors. Device operation is based upon measuring changes in the transmitted (S21) frequency and phase of the first-order Love wave resonance associated with the device upon on attachment of mass. However, temperature variations also cause a change in the first order S21 parameters. In this work, shallow grooved reflectors and a "dotted" single phase unidirectional interdigitated transducer (D-SPUDT) have been added to the basic SAW structure, which promote unidirectional Love wave propagation from the device's input interdigitated transducers. Not only does this enhance the first-order S21 signal but also it allows propagation of a third-order Love wave. The attenuation coefficient of the third-order wave is sufficiently great that, whilst there is a clear reflected S11 signal, the third-order wave does not propagate into the gravimetric sensing area of the device. As a result, whilst the third-order S11 signal is affected by temperature changes, it is unaffected by mass attachment in the sensing area. It is shown that this signal can be used to remove temperature effects from the first-order S21 signal in real time. This allows gravimetric sensing to take place in an environment without the need for any other temperature measurement or temperature control; this is a particular requirement of gravimetric biosensors.

  17. Power absorption by arrays of interacting vertical axisymmetric wave-energy devices

    SciTech Connect

    Mavrakos, S.A.; Kalofonos, A.

    1996-12-31

    The paper deals with the evaluation of the optimum wave-power absorption characteristics of arrays of interacting wave-energy devices. The hydrodynamic interference effects among the devices are exactly accounted for using a method that can solve the problem to any desired accuracy. The method is based on single body hydrodynamic characteristics that are properly combined through the physical idea of multiple scattering to account for interaction effects. Extensive numerical results for a variety of different array arrangements and individual device geometries are presented and comparisons are made to predictions based on approximate theories, the accuracy of which is critically assessed.

  18. Double-layer PVDF transducer and V(z) measurement system for measuring leaky Lamb waves in a piezoelectric plate.

    PubMed

    Lee, Yung-Chun; Kuo, Shi Hoa

    2007-03-01

    This paper presents a new experimental measurement method for leaky Lamb waves propagating in a piezoelectric plate immersed in a conductive fluid. The measurement system is a low-frequency version of lens-less acoustic microscopy which has been developed based on a line-focus double-layer PVDF transducer. The transducer and its defocusing measurement system can perform V(z) measurements on a sample plate immersed in a fluid, and therefore can obtain the leaky Lamb wave velocities with high accuracy. An X-cut LiNbO(3) plate is investigated with this experimental measurement system to find out its fluid-loading effects, especially the conductive loading effects by water of various conductivities. Angular dependence of this conductive loading effect along different propagating directions on the X-cut LiNbO(3) plate is measured. It is found out the conductive loading effects are strongly dependent on the piezoelectric coupling factor. Theoretical calculations based on partial wave theory have also been carried out and compared with experimental data. Good agreements have been observed.

  19. Dynamics of a mechanical frequency up-converted device for wave energy harvesting

    NASA Astrophysics Data System (ADS)

    Lin, Zheng; Zhang, Yongliang

    2016-04-01

    This paper proposes a novel mechanical impact-driven frequency up-converted device for wave energy harvesting, which could bridge a gap between waves of frequency 0.03-1 Hz and electrical generators of operation frequency hundreds hertz. The device mainly consists of a cylindrical buoy, beams and teeth. A mathematical model for the dynamics of such a device is presented, which incorporates the fluid-structure interaction between the wave and the buoy, and the structural interactions between the beams and the teeth. The momentum balance method and the coefficient of restitution are employed, which give rise to piecewise nonlinear equations governing the motions of the buoy and the beams. Experimental tests carried out in a wave flume validate the model and prove the effectiveness of frequency up-converted method in wave energy harvesting. The characteristics of frequency up-converted transformation from buoy motion to beams oscillation for wave energy harvesting are probed, and the effects of beam Young's modulus, beam number, wave period and wave height on strain power of the beams are explored.

  20. Hybrid yttrium iron garnet-ferromagnet structures for spin-wave devices

    SciTech Connect

    Papp, A.; Porod, W. Csaba, G.

    2015-05-07

    We study coupled ferromagnetic layers, which could facilitate low loss, sub 100 nm wavelength spin-wave propagation and manipulation. One of the layers is a low-loss garnet film (such as yttrium iron garnet (YIG)) that enables long-distance, coherent spin-wave propagation. The other layer is made of metal-based (Permalloy, Co, and CoFe) magnetoelectronic structures that can be used to generate, manipulate, and detect the spin waves. Using micromagnetic simulations, we analyze the interactions between the spin waves in the YIG and the metallic nanomagnet structures and demonstrate the components of a scalable spin-wave based signal processing device. We argue that such hybrid-metallic ferromagnet structures can be the basis of potentially high-performance, ultra low-power computing devices.

  1. Modeling Transmission and Reflection Mueller Matrices of Dielectric Half-Wave Plates

    NASA Astrophysics Data System (ADS)

    Salatino, Maria; de Bernardis, Paolo; Masi, Silvia

    2017-02-01

    We present a simple analytical model describing multiple reflections in dielectric and optically active waveplates, for both normal and slant incidence, including absorption. We compute from first principles the transmission and reflection Mueller matrices of the waveplate. The model is used to simulate the performance of a Stokes polarimeter for mm-waves, in the framework of current attempts to precisely measure the linear polarization of the Cosmic Microwave Background (CMB). We study the spectral response of these optical devices, taking into account band and angle averaging effects and confirm the presence of a much richer spectral dependence than in an ideal phase retarder. We also present the matrix elements for the reflection matrix, which is useful to estimate systematic effects in some polarimeter configurations. The formulas we have derived can be used to quickly simulate the performance of future CMB polarimeters.

  2. Control of Tollmien-Schlichting Waves on a Flat Plate Using a Piezoelectric-Driven Oscillating Surface

    NASA Astrophysics Data System (ADS)

    Dell'Orso, Haley; Tuna, Burak; Memauro, Edward; Amitay, Michael

    2014-11-01

    Micro-air vehicles operate in the regime of low Reynolds numbers where the drag associated with skin friction is significant. One proposed method for drag reduction is to control the transition from laminar to turbulent flow by using active surface modification to either excite or suppress instabilities within the flow. To do so, the Piezoelectric-Driven Oscillating Surface (PDOS) actuator was developed and quantified. Two PDOS actuators were placed on a flat plate at two stream wise locations in a low Reynolds number flow. The upstream PDOS was actuated at a characteristic frequency appropriate to phase-lock Tollmien-Schlichting waves within the flow while the downstream PDOS was actuated at the anti-phase to reduce the magnitude of the T-S waves. Particle image velocimetry data were obtained along the centerline of the flat plate at different streamwise locations. Data showed that the upstream PDOS successfully locked-in to the instabilities in the flow and the growth of T-S waves was recorded over the increasing streamwise locations from the leading edge of the flat plate. Finally, the anti-phase (at the proper amplitude) was applied using the downstream PDOS and yielded substantial attenuation of the magnitude of the T-S waves.

  3. Plate-like structure health monitoring based on ultrasonic guided wave technology by using bonded piezoelectric ceramic wafers

    NASA Astrophysics Data System (ADS)

    Liu, Zenghua; Zhao, Jichen; He, Cunfu; Wu, Bin

    2008-11-01

    Piezoelectric ceramic wafers are applied for the excitation and detection of ultrasonic guided waves to determine the health state of plate-like structures. Two PZT wafers, whose diameter is 11mm and thickness is 0.4mm respectively, are bonded permanently on the surface of a 1mm thick aluminum plate. One of these wafers is actuated by sinusoidal tone burst at various frequencies ranging from 100kHz to 500kHz, the other one is used as a receiver for acquiring ultrasonic guided wave signals. According to the amplitudes and shapes of these received signals, guided wave modes and their proper frequency range by using these wafers are determined. For the improvement of the signal-to-noise ratio, the Daubechies wavelet of order 40 is used for signal denoising as the mother wavelet. Furthermore, the detection of an artificial cylindrical through-hole defect is achieved by using S0 at 300kHz. Experimental results show that it is feasible and effective to detect defects in plate-like structures based on ultrasonic guided wave technology by using bonded piezoelectric ceramic wafers.

  4. Surface Acoustic Wave Devices as Chemical Vapor Sensors

    DTIC Science & Technology

    2009-03-26

    Plasma-Enhanced Chemical Vapor Deposited Surfaces,” Advanced Materials, 2006. 45. S . C. Huang, K. D. Caldwell , J. N. Lin, H . K. Wang, and J. N. Herron...exposure, 45 s develop, titanium. 59 Figure 4.4: SEM image of one of the devices from Series 3. 4.2 Testing AFRL- Designed SAW Devices Through...Approach for the Detection of Explosives,” Jour- nal of Hazardous Materials,, vol. 144, pp. 15–28, June 2007. 4. M. H . Ervin, S . J. Kilpatrick, C

  5. Shallow Bulk Acoustic Wave (SBAW) Devices and Oscillators.

    DTIC Science & Technology

    1982-11-01

    millimeter adapter for the automatic network analyzer. The two phase-locked sources would be implemented as SBAW phase-locked oscillators at 7 GHz, followed ...GHz device was designed with the parameters shown in Fig. 4-18s to be replicated as devices using a Shipley resist on AT quartz, followed by ion milling...Width 0.4 um Aperture Width 100 x Number of Fingers/Transducer 1001 Center-to-Center Separation of Transducers 1000 1m Distance Between Transducers 200

  6. Integratable quarter-wave plates enable one-way angular momentum conversion.

    PubMed

    Liang, Yao; Zhang, Fengchun; Gu, Jiahua; Huang, Xu Guang; Liu, Songhao

    2016-04-22

    Nanophotonic waveguides are the building blocks of integrated photonics. To date, while quarter-wave plates (QWPs) are widely used as common components for a wide range of applications in free space, there are almost no reports of Integratable QWPs being able to manipulate the angular momentum (AM) of photons inside nanophotonic waveguides. Here, we demonstrate two kinds of Integratable QWPs respectively based on the concept of abrupt phase change and birefringence effect. The orientation of the equivalent optical axis of an Integratable QWP is designable. Remarkably, a combination of two integratable QWPs with different equivalent optical axes leads to an integrated system that performances one-way AM conversion. Moreover, this system can be used as a point source that can excite different patterns on a metal surface via directional excitation of surface plasmon polaritons (SPP). These results allow for the control of AM of light in nanophotonic waveguides, which are crucial for various applications with limited physical space, such as on-chip bio-sensing and integrated quantum information processing.

  7. Integratable quarter-wave plates enable one-way angular momentum conversion

    PubMed Central

    Liang, Yao; Zhang, Fengchun; Gu, Jiahua; Huang, Xu Guang; Liu, Songhao

    2016-01-01

    Nanophotonic waveguides are the building blocks of integrated photonics. To date, while quarter-wave plates (QWPs) are widely used as common components for a wide range of applications in free space, there are almost no reports of Integratable QWPs being able to manipulate the angular momentum (AM) of photons inside nanophotonic waveguides. Here, we demonstrate two kinds of Integratable QWPs respectively based on the concept of abrupt phase change and birefringence effect. The orientation of the equivalent optical axis of an Integratable QWP is designable. Remarkably, a combination of two integratable QWPs with different equivalent optical axes leads to an integrated system that performances one-way AM conversion. Moreover, this system can be used as a point source that can excite different patterns on a metal surface via directional excitation of surface plasmon polaritons (SPP). These results allow for the control of AM of light in nanophotonic waveguides, which are crucial for various applications with limited physical space, such as on-chip bio-sensing and integrated quantum information processing. PMID:27102332

  8. Robust sky light polarization detection with an S-wave plate in a light field camera.

    PubMed

    Zhang, Wenjing; Zhang, Xuanzhe; Cao, Yu; Liu, Haibo; Liu, Zejin

    2016-05-01

    The sky light polarization navigator has many advantages, such as low cost, no decrease in accuracy with continuous operation, etc. However, current celestial polarization measurement methods often suffer from low performance when the sky is covered by clouds, which reduce the accuracy of navigation. In this paper we introduce a new method and structure based on a handheld light field camera and a radial polarizer, composed of an S-wave plate and a linear polarizer, to detect the sky light polarization pattern across a wide field of view in a single snapshot. Each micro-subimage has a special intensity distribution. After extracting the texture feature of these subimages, stable distribution information of the angle of polarization under a cloudy sky can be obtained. Our experimental results match well with the predicted properties of the theory. Because the polarization pattern is obtained through image processing, rather than traditional methods based on mathematical computation, this method is less sensitive to errors of pixel gray value and thus has better anti-interference performance.

  9. Optically switchable and axially symmetric half-wave plate based on photoaligned liquid crystal films

    NASA Astrophysics Data System (ADS)

    Lin, C.-C.; Huang, T.-C.; Chu, C.-C.; Hsiao, Vincent K. S.

    2016-07-01

    We demonstrate an optically switchable half-wave plate (HWP) composed of a photoaligned and axially symmetric liquid crystal (ASLC) film containing two azobenzene derivatives, methyl red (MR) and 4-butyl-4‧-methoxyazobenzene (BMAB). MR is responsible for photoalignment, and BMAB is used for optical tuning and switching the state of polarization (SOP) of probe beam (633 nm He-Ne laser) passing through the MR/BMAB doped ASLC film. The photoaligned ASLC film is first fabricated using a line-shaped laser beam (532 nm) exposure applied on a rotating LC sample. The fabricated ASLC film can passively change the linearly polarized light. Under UV light exposure, the formation of cis-BMAB (bend-like shape) within the film disrupts the LC molecules, switches the LC orientation, and further changes the SOP of the probe beam. Under laser irradiation (532 nm), the formation of trans-BMAB (rod-like shape) reverts the LC orientation back and simultaneously generates cis-MR, helping anchor the LC in the previously photoaligned orientation. The photoaligned MR/BMAB-doped LC HWP can change the linear SOP under alternating UV and visible light exposure.

  10. Systematic effects from an ambient-temperature, continuously rotating half-wave plate

    NASA Astrophysics Data System (ADS)

    Essinger-Hileman, T.; Kusaka, A.; Appel, J. W.; Choi, S. K.; Crowley, K.; Ho, S. P.; Jarosik, N.; Page, L. A.; Parker, L. P.; Raghunathan, S.; Simon, S. M.; Staggs, S. T.; Visnjic, K.

    2016-09-01

    We present an evaluation of systematic effects associated with a continuously rotating, ambient-temperature half-wave plate (HWP) based on two seasons of data from the Atacama B-Mode Search (ABS) experiment located in the Atacama Desert of Chile. The ABS experiment is a microwave telescope sensitive at 145 GHz. Here we present our in-field evaluation of celestial (Cosmic Microwave Background (CMB) plus galactic foreground) temperature-to-polarization leakage. We decompose the leakage into scalar, dipole, and quadrupole leakage terms. We report a scalar leakage of ˜0.01%, consistent with model expectations and an order of magnitude smaller than other CMB experiments have been reported. No significant dipole or quadrupole terms are detected; we constrain each to be <0.07% (95% confidence), limited by statistical uncertainty in our measurement. Dipole and quadrupole leakage at this level lead to systematic error on r ≲ 0.01 before any mitigation due to scan cross-linking or boresight rotation. The measured scalar leakage and the theoretical level of dipole and quadrupole leakage produce systematic error of r < 0.001 for the ABS survey and focal-plane layout before any data correction such as so-called deprojection. This demonstrates that ABS achieves significant beam systematic error mitigation from its HWP and shows the promise of continuously rotating HWPs for future experiments.

  11. Systematic effects from an ambient-temperature, continuously rotating half-wave plate.

    PubMed

    Essinger-Hileman, T; Kusaka, A; Appel, J W; Choi, S K; Crowley, K; Ho, S P; Jarosik, N; Page, L A; Parker, L P; Raghunathan, S; Simon, S M; Staggs, S T; Visnjic, K

    2016-09-01

    We present an evaluation of systematic effects associated with a continuously rotating, ambient-temperature half-wave plate (HWP) based on two seasons of data from the Atacama B-Mode Search (ABS) experiment located in the Atacama Desert of Chile. The ABS experiment is a microwave telescope sensitive at 145 GHz. Here we present our in-field evaluation of celestial (Cosmic Microwave Background (CMB) plus galactic foreground) temperature-to-polarization leakage. We decompose the leakage into scalar, dipole, and quadrupole leakage terms. We report a scalar leakage of ∼0.01%, consistent with model expectations and an order of magnitude smaller than other CMB experiments have been reported. No significant dipole or quadrupole terms are detected; we constrain each to be <0.07% (95% confidence), limited by statistical uncertainty in our measurement. Dipole and quadrupole leakage at this level lead to systematic error on r ≲ 0.01 before any mitigation due to scan cross-linking or boresight rotation. The measured scalar leakage and the theoretical level of dipole and quadrupole leakage produce systematic error of r < 0.001 for the ABS survey and focal-plane layout before any data correction such as so-called deprojection. This demonstrates that ABS achieves significant beam systematic error mitigation from its HWP and shows the promise of continuously rotating HWPs for future experiments.

  12. Lamb wave dispersion and anisotropy profiling of composite plates via non-contact air-coupled and laser ultrasound

    NASA Astrophysics Data System (ADS)

    Harb, M. S.; Yuan, F. G.

    2015-03-01

    Conventional ultrasound inspection has been a standard non-destructive testing method for providing an in-service evaluation and noninvasive means of probing the interior of a structure. In particular, measurement of the propagation characteristics of Lamb waves allows inspection of plates that are typical components in aerospace industry. A rapid, complete non-contact hybrid approach for excitation and detection of Lamb waves is presented and applied for non-destructive evaluation of composites. An air-coupled transducer (ACT) excites ultrasonic waves on the surface of a composite plate, generating different propagating Lamb wave modes and a laser Doppler vibrometer (LDV) is used to measure the out-of-plane velocity of the plate. This technology, based on direct waveform imaging, focuses on measuring dispersive curves for A0 mode in a composite laminate and its anisotropy. A two-dimensional fast Fourier transform (2D-FFT) is applied to out-of-plane velocity data captured experimentally using LDV to go from the time-spatial domain to frequency-wavenumber domain. The result is a 2D array of amplitudes at discrete frequencies and wavenumbers for A0 mode in a given propagation direction along the composite. The peak values of the curve are then used to construct frequency wavenumber and phase velocity dispersion curves, which are also obtained directly using Snell's law and the incident angle of the excited ultrasonic waves. A high resolution and strong correlation between numerical and experimental results are observed for dispersive curves with Snell's law method in comparison to 2D-FFT method. Dispersion curves as well as velocity curves for the composite plate along different directions of wave propagation are measured. The visual read-out of the dispersion curves at different propagation directions as well as the phase velocity curves provide profiling and measurements of the composite anisotropy. The results proved a high sensitivity of the air-coupled and laser

  13. Note: Device for underwater laboratory simulation of unconfined blast waves.

    PubMed

    Courtney, Elijah; Courtney, Amy; Courtney, Michael

    2015-06-01

    Shock tubes simulate blast waves to study their effects in air under laboratory conditions; however, few experimental models exist for simulating underwater blast waves that are needed for facilitating experiments in underwater blast transmission, determining injury thresholds in marine animals, validating numerical models, and exploring mitigation strategies for explosive well removals. This method incorporates an oxy-acetylene driven underwater blast simulator which creates peak blast pressures of about 1860 kPa. Shot-to-shot consistency was fair, with an average standard deviation near 150 kPa. Results suggest that peak blast pressures from 460 kPa to 1860 kPa are available by adjusting the distance from the source.

  14. Note: Device for underwater laboratory simulation of unconfined blast waves

    NASA Astrophysics Data System (ADS)

    Courtney, Elijah; Courtney, Amy; Courtney, Michael

    2015-06-01

    Shock tubes simulate blast waves to study their effects in air under laboratory conditions; however, few experimental models exist for simulating underwater blast waves that are needed for facilitating experiments in underwater blast transmission, determining injury thresholds in marine animals, validating numerical models, and exploring mitigation strategies for explosive well removals. This method incorporates an oxy-acetylene driven underwater blast simulator which creates peak blast pressures of about 1860 kPa. Shot-to-shot consistency was fair, with an average standard deviation near 150 kPa. Results suggest that peak blast pressures from 460 kPa to 1860 kPa are available by adjusting the distance from the source.

  15. Light-Millimeter Wave Interactions in Semiconductor Devices

    DTIC Science & Technology

    1990-01-30

    bias will result in better transient performance [4-91. can be applied to rather high bias voltage. When examining the traditional techniques of...millimeter wave antenna for nents. imaging array applications." Electromagentics , vol. 3. pp. 209-215. 1983. 151 C. P. Wen. "Coplanar waveguidc: A...heterodyne detection," Opt. Lett., vol. 8, pp. 419-421, 1983 21. S. Ben . E, Biglieri and V. Castellri, " Digital Transmission Theory," pp. 211-220, Addison

  16. Space manufacturing of surface acoustic wave devices, appendix D

    NASA Technical Reports Server (NTRS)

    Sardella, G.

    1973-01-01

    Space manufacturing of transducers in a vibration free environment is discussed. Fabrication of the masks, and possible manufacturing of the surface acoustic wave components aboard a space laboratory would avoid the inherent ground vibrations and the frequency limitation imposed by a seismic isolator pad. The manufacturing vibration requirements are identified. The concepts of space manufacturing are analyzed. A development program for manufacturing transducers is recommended.

  17. Performance Optimization of a Pneumatic Wave Energy Conversion Device.

    DTIC Science & Technology

    1982-08-26

    The edges of the internal plexi - glass turbine casing was rounded off to reduce turbulence in the air flow. The turbine was now read-F for the second...As a wave approaches shore it interacts with the sea floor and loses energy due to bottom friction and irrotationalities. The deep water condition...heavier parts had increased the internal friction of the system, and to see if the turbine could handle the effects of greater air flow. For this

  18. Applications of Shock Wave Research to Developments of Therapeutic Devices.

    NASA Astrophysics Data System (ADS)

    Takayama, Kazuyoshi

    2007-06-01

    Underwater shock wave research applied to medicine started in 1980 by exploding micro lead azide pellets in water. Collaboration with urologists in the School of Medicine, Tohoku University at the same time was directed to disintegration of kidney stones by controlling shock waves. We initially proposed a miniature truncated ellipsoidal cavity for generating high-pressures enough to disintegrate the stone but gave up the idea, when encountering the Dornie Systems' invention of an extracorporeal shock wave lithotripter (ESWL). Then we confirmed its effectiveness by using 10 mg silver azide pellets and constructed our own lithotripter, which was officially approved for a clinical use in 1987. Tissue damage during ESWL was attributable to bubble collapse and we convinced it could be done in a controlled fashion. In 1996, we used 160 mJ pulsed Ho:YAG laser beam focusing inside a catheter for shock generation and applied it to the revascularization of cerebral embolism, which is recently expanded to the treatment of pulmonary infarction. Micro water jets discharged in air were so effective to dissect soft tissues preserving small blood vessels. Animal experiments are successfully performed with high frequency water jets driven by an actuator-assisted micro-pump. A metal foil is deformed at high speed by a Q-switched Nd:YAG laser beam loading. We used this technique to project micro-particles or dry drugs attached on its reverse side and extended it to a laser ablation assisted dry drug delivery or DNA introductory system.

  19. Mode-selective excitation and detection of ultrasonic guided waves for delamination detection in laminated aluminum plates.

    PubMed

    Shelke, Amit; Kundu, Tribikram; Amjad, Umar; Hahn, Katrin; Grill, Wolfgang

    2011-03-01

    Selective modes of guided Lamb waves are generated in a laminated aluminum plate for damage detection using a broadband piezoelectric transducer structured with a rigid electrode. Appropriate excitation frequencies and modes for inspection are selected from theoretical and experimental dispersion curves. Dispersion curves are obtained experimentally by short time Fourier transform of the transient signals. Sensitivity of antisymmetric and symmetric modes for delamination detection are investigated. The antisymmetric mode is found to be more reliable for delamination detection. Unlike other studies, in which the attenuation of the propagating waves is related to the extent of the internal damage, in this investigation, the changes in the time-of-flight (TOF) of guided Lamb waves are related to the damage progression. The mode conversion phenomenon of Lamb waves during progressive delamination is investigated. Close matching between the theoretical and experimentally derived dispersion curves and TOF assures the reliability of the results presented here.

  20. Temperature effects on the band gaps of Lamb waves in a one-dimensional phononic-crystal plate (L).

    PubMed

    Cheng, Y; Liu, X J; Wu, D J

    2011-03-01

    This study investigates the temperature-tuned band gaps of Lamb waves in a one-dimensional phononic-crystal plate, which is formed by alternating strips of ferroelectric ceramic Ba(0.7)Sr(0.3)TiO(3) and epoxy. The sensitive and continuous temperature-tunability of Lamb wave band gaps is demonstrated using the analyses of the band structures and the transmission spectra. The width and position of Lamb wave band gaps shift prominently with variation of temperature in the range of 26 °C-50 °C. For example, the width of the second band gap increases from 0.066 to 0.111 MHz as the temperature is increased from 26 °C to 50 °C. The strong shift promises that the structure could be suitable for temperature-tuned multi-frequency Lamb wave filters.

  1. Observation of a spark channel generated in water with shock wave assistance in plate-to-plate electrode configuration

    SciTech Connect

    Stelmashuk, V.

    2014-01-15

    When a high voltage pulse with an amplitude of 30 kV is applied to a pair of disk electrodes at a time when a shock wave is passing between them, an electrical spark is generated. The dynamic changes in the spark morphology are studied here using a high-speed framing camera. The primary result of this work is the provision of experimental evidence of plasma instability that was observed in the channel of the electric spark.

  2. Propagation of SH waves in a piezoelectric/piezomagnetic plate: Effects of interfacial imperfection couplings and the related physical mechanisms

    NASA Astrophysics Data System (ADS)

    Wei, Hong-Xing; Li, Yong-Dong; Xiong, Tao; Guan, Yong

    2016-09-01

    The problem of dispersive SH wave in a piezoelectric/piezomagnetic plate that contains an imperfect interface is considered in the present work. An imperfection coupling model is adopted to describe the magnetic, electric and mechanical imperfections on the interface. A transcendental dispersion equation is derived and numerically solved to get the phase velocity. The validity of the numerical procedure is verified in a degenerated case. The effects of the coupled interfacial imperfections on the dispersion behavior of SH waves are discussed in detail and the related underlying physical mechanisms are explained.

  3. Diffraction of plane waves by finite-radius spiral phase plates of integer and fractional topological charge.

    PubMed

    Garcia-Gracia, Hipolito; Gutiérrez-Vega, Julio C

    2009-04-01

    A detailed analysis of the plane-wave diffraction by a finite-radius circular spiral phase plate (SPP) with integer and fractional topological charge and with variable transmission coefficients inside and outside of the plate edge is presented. We characterize the effect of varying the transmission coefficients and the parameters of the SPP on the propagated field. The vortex structure for integer and fractional phase step of the SPPs with and without phase apodization at the plate edge is also analyzed. The consideration of the interference between the light crossing the SPP and the light that undergoes no phase alteration at the aperture plane reveals new and interesting phenomena associated to this classical problem.

  4. Measurement of Underwater Operational Noise Emitted by Wave and Tidal Stream Energy Devices.

    PubMed

    Lepper, Paul A; Robinson, Stephen P

    2016-01-01

    The increasing international growth in the development of marine and freshwater wave and tidal energy harvesting systems has been followed by a growing requirement to understand any associated underwater impact. Radiated noise generated during operation is dependent on the device's physical properties, the sound-propagation environment, and the device's operational state. Physical properties may include size, distribution in the water column, and mechanics/hydrodynamics. The sound-propagation environment may be influenced by water depth, bathymetry, sediment type, and water column acoustic properties, and operational state may be influenced by tidal cycle and wave height among others This paper discusses some of the challenges for measurement of noise characteristics from these devices as well as a case study of the measurement of radiated noise from a full-scale wave energy converter.

  5. Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate

    SciTech Connect

    Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

    2014-12-09

    This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

  6. Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate

    NASA Astrophysics Data System (ADS)

    Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

    2014-12-01

    This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

  7. Determining the values of second-order surface nonlinearities by measurements with wave plates of different retardations.

    PubMed

    Valev, Ventsislav K; Foerier, Stijn; Verbiest, Thierry

    2009-06-01

    We measured the second harmonic generation response of a thin film consisting of chiral molecules with four wave plates having different retardation coefficients. By means of the fitting procedure described in a previously reported formalism, we demonstrated that a single set of tensor components of second order surface nonlinearities fits all the data. Our results provide clear experimental evidence for the validity of this method, which can find applications in the studies of chiral structures and achiral anisotropic materials.

  8. Design and manufacturing of a piezoelectric traveling-wave pumping device.

    PubMed

    Hernandez, Camilo; Bernard, Yves; Razek, Adel

    2013-09-01

    In this article, we present the design and construction of a micropump exhibiting a nontraditional pumping principle whose design is achievable at very low scales. The operation is based on the action of a mechanical traveling wave deforming the bottom wall of a flexible channel containing a fluid. The paper treats for the first time the influence of the traveling wave parameters on the performance of the pump with the help of finite element simulations. The results obtained from the simulation are subsequently used for the dimensioning of the linear ultrasonic traveling wave actuator that drives the device. Finally, a very simple channel-reservoirs structure was conceived to test the device. At this point, several measurements of flow rate and back pressure were carried out to estimate the performance of the prototype for different values of wave amplitude. The article finishes with a comparison between the numerical and experimental results and a brief section of discussion and conclusions.

  9. Lamb wave band gaps in one-dimensional radial phononic crystal plates with periodic double-sided corrugations

    NASA Astrophysics Data System (ADS)

    Li, Yinggang; Chen, Tianning; Wang, Xiaopeng; Li, Suobin

    2015-11-01

    In this paper, we present the theoretical investigation of Lamb wave propagation in one-dimensional radial phononic crystal (RPC) plates with periodic double-sided corrugations. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are studied by using the finite element method based on two-dimensional axial symmetry models in cylindrical coordinates. Numerical results show that the proposed RPC plates with periodic double-sided corrugations can yield several band gaps with a variable bandwidth for Lamb waves. The formation mechanism of band gaps in the double-sided RPC plates is attributed to the coupling between the Lamb modes and the in-phase and out-phases resonant eigenmodes of the double-sided corrugations. We investigate the evolution of band gaps in the double-sided RPC plates with the corrugation heights on both sides arranged from an asymmetrical distribution to a symmetrical distribution gradually. Significantly, with the introduction of symmetric double-sided corrugations, the antisymmetric Lamb mode is suppressed by the in-phase resonant eigenmodes of the double-sided corrugations, resulting in the disappearance of the lowest band gap. Furthermore, the effects of the geometrical parameters on the band gaps are further explored numerically.

  10. Weak etalon effect in wave plates can introduce significant FM-to-AM modulations in complex laser systems.

    PubMed

    Dangpeng, Xu; Jianjun, Wang; Mingzhong, Li; Honghuan, Lin; Rui, Zhang; Ying, Deng; Qinghua, Deng; Xiaodong, Huang; Mingzhe, Wang; Lei, Ding; Jun, Tang

    2010-03-29

    The conversion of frequency modulation to amplitude modulation (FM-to-AM) effect is harmful to the high power laser facility based on the phase modulation technique. The FM-to-AM effect of phase modulation pulse induced by the weak etalon effect in wave plates was investigated theoretically and experimentally. A bulk phase modulator with a modulation frequency of 9.2GHz was employed. The numerical simulation results show that the FM-to-AM effect with a temporal modulation depth of 2.5% and 29.7% on the top of the pulse shape was induced by the weak etalon effect in half-wave plate with thickness of 1mm and residual reflectance ratio of 0.5% for 1 pass and 12 passes respectively. On the same condition, the temporal modulation depth is 3.0% and 23.4% respectively in the experiment. The results are in good agreement with numerical simulation results. To our knowledge, it is the first time to introduce the weak etalon effect in wave plates for a complex phase modulation laser system.

  11. Fast characterization of aluminum plates with TV-holography measurements of the frequency spectrum of multimode, quasi- monochromatic Lamb waves.

    PubMed

    Deán-Ben, X Luís; Trillo, Cristina; Doval, Angel F; Fernández, José L

    2011-06-01

    We introduce a novel approach for measuring the frequency spectrum of Lamb waves and, subsequently, for obtaining the thickness and the bulk wave velocities of isotropic, homogeneous plates. It is based on Fourier transforming a set of spatial and temporal samples of the acoustic displacement but, in contrast to the traditional approach that employs dense temporal sampling and a reduced set of spatial sampling locations, our data set is a sequence of 2-D high-resolution maps of the instantaneous out-of-plane displacement obtained with TV holography. We have devised three variants to obtain a set of points of the wavenumber-frequency space, based, respectively, on the spatial (1-D or 2-D) and on the spatio-temporal (3-D) Fourier transforms. The whole process to obtain these points can be easily automated and substantial time savings can be achieved, compared with other full-field techniques that require human intervention or with pointwise scanned probes. Experimental demonstration of the three variants with quasimonochromatic multimode Lamb waves in aluminum plates is presented. The characteristic parameters of the plates are calculated by fitting the theoretical model to the experimental points of the frequency spectrum. The analysis of the uncertainties shows that the accuracy of the method is only slightly lower than the accuracy of a previously reported method based on measuring the wavelength of single-modes, for which the data acquisition procedure is much slower.

  12. Thermal Quantum Annealing on the D-Wave device

    NASA Astrophysics Data System (ADS)

    Mishra, Anurag; Vinci, Walter; Albash, Tameem; Warburton, Paul; Lidar, Daniel

    2014-03-01

    We report on new experimental results supporting previous work concluding that the D-Wave processor implements quantum annealing. We introduce techniques adopted to the D-Wave programmable annealer to correct for systematic fabrication and control errors. Correcting for systematic errors allows us to explore the behavior of the annealer at low energy scales, which were previously inaccessible. We describe the behavior of the annealer as we investigate the effect of thermal noise on the programmed Ising Hamiltonian. Thermal noise becomes dominant when we scale down the overall energy of the final-time Ising Hamiltonian, or increase the total annealing time. We found three qualitatively different thermal noise regimes; a high energy scale where ground state statistics dominates, a moderate noise regime regime where low lying excited states contribute, and a high thermal noise regime where the system dynamics are dominated by thermalization effects. The qualitative results are robust to increasing the size (number of qubits) of the benchmark Hamiltonian. We additionally investigated auto-correlations in the final state statistics.

  13. Giga-Hertz Electromagnetic Wave Science and Devices for Advanced Battlefield Communications

    DTIC Science & Technology

    2010-12-15

    Microwave Assisted Magnetic Reversal”, MMM Conference, Washington D. C. (2010 19. “Hexagonal barium ferrite thin film-based millimeter wave phase...International Conference on Microwave Magnetics, Boston, June 1-4, 2010. (Contributed talk) 25. “Hexagonal barium ferrite -based millimeter wave notch...Wafer Microwave Devices, Study of Material Properties in the the GHz range Z. Celinski University of Colorado - Colorado Springs Regents of the Univ

  14. Surface-acoustic-wave device incorporating conducting Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Holcroft, B.; Roberts, G. G.; Barraud, A.; Richard, J.

    1987-04-01

    Surface-acoustic-wave devices incorporating conducting Langmuir-Blodgett films are reported for the first time. Excellent characteristics have been obtained using a mixed valence charge transfer salt of a substituted pyridinium tetracyanoquinodimethane. The control afforded by the deposition technique has enabled the fractional change in surface wave velocity due to the electrical effects to be distinguished from those due to mass loading. The resistivity of the organic surface layer is measured to be 2 ohm-cm.

  15. Device connectivity: the next big wave in diabetes.

    PubMed

    Walsh, John; Roberts, Ruth; Morris, Richard; Heinemann, Lutz

    2015-05-01

    Patients with diabetes have to take numerous factors/data into their therapeutic decisions in daily life. Connecting the devices they are using by feeding the data generated into a database/app is supposed to help patients to optimize their glycemic control. As this is not established in practice, the different roadblocks have to be discussed to open the road. That large telecommunication companies are now entering this market might be a big help in pushing this forward. Smartphones offer an ideal platform for connectivity solutions.

  16. Bendable ZnO thin film surface acoustic wave devices on polyethylene terephthalate substrate

    SciTech Connect

    He, Xingli; Guo, Hongwei; Chen, Jinkai; Wang, Wenbo; Xuan, Weipeng; Xu, Yang E-mail: jl2@bolton.ac.uk; Luo, Jikui E-mail: jl2@bolton.ac.uk

    2014-05-26

    Bendable surface acoustic wave (SAW) devices were fabricated using high quality c-axis orientation ZnO films deposited on flexible polyethylene terephthalate substrates at 120 °C. Dual resonance modes, namely, the zero order pseudo asymmetric (A{sub 0}) and symmetric (S{sub 0}) Lamb wave modes, have been obtained from the SAW devices. The SAW devices perform well even after repeated flexion up to 2500 με for 100 times, demonstrating its suitability for flexible electronics application. The SAW devices are also highly sensitive to compressive and tensile strains, exhibiting excellent anti-strain deterioration property, thus, they are particularly suitable for sensing large strains.

  17. High-frequency programmable acoustic wave device realized through ferroelectric domain engineering

    SciTech Connect

    Ivry, Yachin E-mail: cd229@eng.cam.ac.uk; Wang, Nan; Durkan, Colm E-mail: cd229@eng.cam.ac.uk

    2014-03-31

    Surface acoustic wave devices are extensively used in contemporary wireless communication devices. We used atomic force microscopy to form periodic macroscopic ferroelectric domains in sol-gel deposited lead zirconate titanate, where each ferroelectric domain is composed of many crystallites, each of which contains many microscopic ferroelastic domains. We examined the electro-acoustic characteristics of the apparatus and found a resonator behavior similar to that of an equivalent surface or bulk acoustic wave device. We show that the operational frequency of the device can be tailored by altering the periodicity of the engineered domains and demonstrate high-frequency filter behavior (>8 GHz), allowing low-cost programmable high-frequency resonators.

  18. Shallow structure and surface wave propagation characteristics of the Juan de Fuca plate from seismic ambient noise

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Shen, W.; Ritzwoller, M. H.

    2013-12-01

    Ambient noise cross-correlation analysis has been widely used to investigate the continental lithosphere, but the method has been applied much less to study the oceanic lithosphere due to the relative shortage of continuous ocean bottom seismic measurements. The Cascadia Initiative experiment possesses a total of 62 ocean bottom seismometers that spans much of the Juan de Fuca plate and provides data to investigate both the structure and evolution of the oceanic lithosphere near the Juan De Fuca ridge and the characteristics of surface waves and overtones propagating within the oceanic lithosphere. We produce ambient noise cross correlations for the first year of Cascadia OBS data for both the vertical and the horizontal components. The observed empirical Green's functions are first used to test the hypothesis that the near-ridge phase speeds can be described by a simple age-dependent formula, which we invert for an age-dependent shear wave speed model (Figure 1a). A shallow low shear velocity zone with a velocity minimum at about 20km depth is observed in Vsv and the lithosphere thickens with age faster than predicted by a half-space conductive cooling model (Figure 1b). To further understand the oceanic surface waves, we analyze the first higher mode Rayleigh waves that propagate within the Juan De Fuca plate and emerge on the North American continent and investigate the existence of radial anisotropy beneath the ridge by exploring the Rayleigh and Love wave Green's functions. The results of the study are summarized with the age-dependent shear velocity model along with some preliminary observations of both Love wave and higher mode Rayleigh waves.

  19. Gas sensor technology at Sandia National Laboratories: Catalytic gate, Surface Acoustic Wave and Fiber Optic Devices

    SciTech Connect

    Hughes, R.C.; Moreno, D.J.; Jenkins, M.W.; Rodriguez, J.L.

    1993-10-01

    Sandia`s gas sensor program encompasses three separate electronic platforms: Acoustic Wave Devices, Fiber Optic Sensors and sensors based on silicon microelectronic devices. A review of most of these activities was presented recently in a article in Science under the title ``Chemical Microsensors.`` The focus of the program has been on understanding and developing the chemical sensor coatings that are necessary for using these electronic platforms as effective chemical sensors.

  20. Square wave voltages-induced ON states of organic resistive memory devices

    NASA Astrophysics Data System (ADS)

    Qin, Jiajun; Chu, Ming; Peng, Huan; Zhang, Jiawei; Hou, Xiaoyuan

    2016-10-01

    In organic resistive memory device field, alternating current (AC) has seldom been studied systematically. In the present work, square wave voltage pulses are considered to obtain memory switching to the ON state with voltage amplitude lower than the threshold voltage of the device, even with less time. The ON states induced by such AC depend on both frequency and amplitude. A possible mechanism related to filamentary formation was proposed to explain the AC induced effect.

  1. Contactless remote induction of shear waves in soft tissues using a transcranial magnetic stimulation device

    NASA Astrophysics Data System (ADS)

    Grasland-Mongrain, Pol; Miller-Jolicoeur, Erika; Tang, An; Catheline, Stefan; Cloutier, Guy

    2016-03-01

    This study presents the first observation of shear waves induced remotely within soft tissues. It was performed through the combination of a transcranial magnetic stimulation device and a permanent magnet. A physical model based on Maxwell and Navier equations was developed. Experiments were performed on a cryogel phantom and a chicken breast sample. Using an ultrafast ultrasound scanner, shear waves of respective amplitudes of 5 and 0.5 μm were observed. Experimental and numerical results were in good agreement. This study constitutes the framework of an alternative shear wave elastography method.

  2. Application of Normal Mode Expansion to AE Waves in Finite Plates

    NASA Technical Reports Server (NTRS)

    Gorman, M. R.; Prosser, W. H.

    1997-01-01

    Breckenridge et al. (1975), Hsu (1985) and Pao (1978) adapted approaches from seismology to calculate the response at the surface of an infinite half-space and an infinite plate. These approaches have found use in calibrating acoustic emission (AE) transducers. However, it is difficult to extend this theoretical approach to AE testing of practical structures. Weaver and Pao (1982) considered a normal mode solution to the Lamb equations. Hutchinson (1983) pointed out the potential relevance of Mindlin's plate theory (1951) to AE. Pao (1982) reviewed Medick s (1961) classical plate theory for a point source, but rejected it as useful for AE and no one seems to have investigated its relevance to AE any further. Herein, a normal mode solution to the classical plate bending equation was investigated for its applicability to AE. The same source-time function chosen by Weaver and Pao is considered. However, arbitrary source and receiver positions are chosen relative to the boundaries of the plate. This is another advantage of the plate theory treatment in addition to its simplicity. The source does not have to be at the center of the plate as in the axisymmetric treatment. The plate is allowed to remain finite and reflections are predicted. The importance of this theory to AE is that it can handle finite plates, realistic boundary conditions, and can be extended to composite materials.

  3. Exponential stabilization of magnetoelastic waves in a Mindlin-Timoshenko plate by localized internal damping

    NASA Astrophysics Data System (ADS)

    Grobbelaar-Van Dalsen, Marié

    2015-08-01

    This article is a continuation of our earlier work in Grobbelaar-Van Dalsen (Z Angew Math Phys 63:1047-1065, 2012) on the polynomial stabilization of a linear model for the magnetoelastic interactions in a two-dimensional electrically conducting Mindlin-Timoshenko plate. We introduce nonlinear damping that is effective only in a small portion of the interior of the plate. It turns out that the model is uniformly exponentially stable when the function , that represents the locally distributed damping, behaves linearly near the origin. However, the use of Mindlin-Timoshenko plate theory in the model enforces a restriction on the region occupied by the plate.

  4. Derivation of acoustoelastic Lamb wave dispersion curves in anisotropic plates at the initial and natural frames of reference.

    PubMed

    C Kubrusly, Alan; M B Braga, Arthur; von der Weid, Jean Pierre

    2016-10-01

    The propagation speed of ultrasonic waves in pre-stressed media can be evaluated either at the natural or initial frames of reference. In this paper general equations that can be applied to the partial wave technique are presented in order to obtain the dispersion spectra of acoustoelastic Lamb waves in anisotropic plates in either frame of reference. Employing these equations, dispersion curves for the fundamental modes in a pre-stressed transversely isotropic aluminum plate were numerically obtained in both reference frames under longitudinal and transverse loading with the material transverse axis along each of the Cartesian directions, as well as the propagation along a non-principal direction. Results confirm that due to the material natural anisotropy, the speed variation depends not only on the pre-stress direction but also on the material orientation as well as on the polarization of the propagating mode. Similar to bulk waves, the relationship between the speed at the natural and initial frames is a function of the load direction.

  5. Mechanism of operation and design considerations for surface acoustic wave device vapor sensors

    NASA Astrophysics Data System (ADS)

    Wohltjen, H.

    1984-04-01

    Surface acoustic wave (SAW) devices offer many attractive features for application as vapor phase chemical microsensors. This paper describes the characteristics of SAW devices and techniques by which they can be employed as vapor sensors. The perturbation of SAW amplitude and velocity by polymeric coating films was investigated both theoretically and experimentally. High sensitivity can be achieved when the device is used as the resonating element in a delay line oscillator circuit. A simple equation has been developed from theoretical considerations which offers reasonably accurate quantitative predictions of SAW Device frequency shifts when subjected to a given mass loading. In this mode the SAW device behaves in a fashion very similar to conventional bulk wave quartz crystal microbalance except that the sensitivity can be several orders of magnitude higher and the device size can be several orders of magnitude smaller. Detection of mass changes of less than 1 femtogram by a SAW device having a surface area of 0.0001 square cm. is theoretically possible.

  6. Precision positioning device

    DOEpatents

    McInroy, John E.

    2005-01-18

    A precision positioning device is provided. The precision positioning device comprises a precision measuring/vibration isolation mechanism. A first plate is provided with the precision measuring mean secured to the first plate. A second plate is secured to the first plate. A third plate is secured to the second plate with the first plate being positioned between the second plate and the third plate. A fourth plate is secured to the third plate with the second plate being positioned between the third plate and the fourth plate. An adjusting mechanism for adjusting the position of the first plate, the second plate, the third plate, and the fourth plate relative to each other.

  7. Optimal control of wave energy devices with various power-take-off mechanisms

    SciTech Connect

    Nichols, N.K.; Crossley, A.

    1996-12-31

    The aims of this research are to develop and test methods for analyzing and computing optimal control strategies for maximizing the useful power generated from wave energy converters incorporating realistic power-take-off and control mechanisms. Previously, strategies for maximizing energy absorbed by wave devices have been investigated, but these studies have assumed an ideal conversion rate using perfectly efficient turbomachinery with no constraints imposed by the generator capacity. In this paper various turbine characteristics and control mechanisms incorporating nonlinear losses are modelled, the qualitative properties of the optimal control strategy for maximizing average power delivered at the turbine shaft are analyzed, computational techniques for determining numerical solutions to the optimal control problem are established and the results are tested on a fully developed hydrodynamic model of a wave energy device.

  8. Analysis of the coupling between shear horizontal plate waves and liquids: Application to the measurement of the shear rigidity modulus of glycerol solutions

    NASA Astrophysics Data System (ADS)

    Teston, F.; Feuillard, G.; Tessier, L.; Tran Hu Hue, L. P.; Lethiecq, M.

    2000-01-01

    This article presents an acoustic wave viscometer based on the shear horizontal acoustic plate mode excited by interdigital transducers on a ST-cut quartz substrate. A theoretical model, which is an extension of the plate effective permittivity function taking into account the presence of liquids, is developed in order to predict the phase and attenuation variations versus the viscosity of liquid. These results are discussed and compared to those of models from the literature such as variational or perturbation methods. The measured results for aqueous solutions of glycerol show linear dependence between the phase and attenuation variations and the square root of liquid viscosity, and are consistent with the theoretical results. The device can be used for viscosity measurements up to 1000 mPa s. For higher viscosities, the viscoelastic behavior of the solution appears and the shear rigidity modulus must be taken into account. The value of μ∞=2.5×109N m2 has been obtained for glycerol by fitting the theoretical curves to the experimental points.

  9. Layered surface acoustic wave devices for film characterization and sensor applications

    NASA Astrophysics Data System (ADS)

    Pedrick, Michael K.

    2007-05-01

    This work has introduced novel applications for Layered Surface Acoustic Wave (SAW) devices along with concepts for enhanced sensitivity via refined modeling techniques. The derivation of Love Wave and Rayleigh wave propagation pertinent to SAW substrates with thin film overlayers was explored. Novel aspects were presented for Finite Element analysis of Layered SAW sensors. This included coordinate transformations of model geometries to coincide with crystallographic orientations known to generate Surface Skimming Bulk Waves (SSBW) and various Rayleigh wave types of propagation in ST Quartz, 90° rotated ST Quartz, and 77° Y rotated Lithium Tantalate. This work has shown for the first time, FEM prediction of SSBW, Generalized SAW and High Velocity SAW waves. Rayleigh damping properties were extended to develop a Finite element model capable of predicting Layered SAW response to glass transition in a polymer film. The ability to monitor localized mechanical behavior in a PMMA film was explored with Love Waves generated by 90° rotated ST Quartz and Shear Vertical (SV)-SAWs generated by 77° Y rotated Lithium Tantalate. Similar trends were found experimentally as compared to the Finite element models. The capability of Love Wave devices for monitoring polymer film curing behavior was investigated. The ability to qualitatively assess the bond quality between film and substrate was also demonstrated based on the characteristics of the transmitted frequency response. The results of these developments have laid the ground work for developing diagnostic tools to better characterize film behavior in practical applications. Several sensor applications for Layered SAW devices were discussed. The Shear Horizontal displacement of the Love Wave device was exploited to demonstrate the capability of such a sensor for ice detection. A clear distinction between air, water, and ice loading was found with Love Waves whereas SV-SAWs were unable to distinguish between liquid and ice

  10. Possible nano-spintronics devices with graphene as electron wave guides

    NASA Astrophysics Data System (ADS)

    Kusakabe, Koichi

    2009-03-01

    Another application of graphene to semiconductor spintronics devices is proposed theoretically. We have designed possible methods for fabrication of nano-scale device structures utilizing graphene as electron wave guides. Important techniques should be 1) formation of strong covalent bonding between a part of substrate and graphene, 2) creation of nano-sized superstructure with sharp edges inducing the grapheme edge states[1] by controlling interface between external electrodes and graphene, and 3) creation of nano-sized quantum structures based on the spinodal nano-decomposition. Several test simulations on the electronic states of proposed structures and theoretical estimation of functionality of graphene as an electron wave guide for semiconductor spintronics devices are presented. [1] M. Fujita, K. Wakabayashi, K. Nakada and K. Kusakabe, J. Phys. Soc. Jpn. 65, 1920 (1996).

  11. Time reversal focusing of elastic waves in plates for an educational demonstration.

    PubMed

    Heaton, Christopher; Anderson, Brian E; Young, Sarah M

    2017-02-01

    The purpose of this research is to develop a visual demonstration of time reversal focusing of vibrations in a thin plate. Various plate materials are tested to provide optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the vibration coupling efficiency from a shaker to the plate are quantified to illustrate why a given plate provides the best spatially confined focus as well as the highest focal amplitude possible. A single vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing. Table salt is sprinkled onto the plate surface to allow visualization of the high amplitude, spatially localized time reversal focus; the salt is thrown upward only at the focal position. Spatial mapping of the vibration focusing on the plate using the SLDV is correlated to the visual salt jumping demonstration. The time reversal focusing is also used to knock over an object when the object is placed at the focal position; some discussion of optimal objects to use for this demonstration are given.

  12. Ridge asymmetry and deep aqueous alteration at the trench observed from Rayleigh wave tomography of the Juan de Fuca plate

    NASA Astrophysics Data System (ADS)

    Bell, Samuel; Ruan, Youyi; Forsyth, Donald W.

    2016-10-01

    Using Rayleigh wave tomography of noise-removed ocean bottom seismometer data from the Cascadia Initiative, we illuminate the structure of the upper mantle beneath the Juan de Fuca plate. Beneath the Juan de Fuca ridge, there is strong asymmetry, with a pronounced low-velocity zone in the 25-65 km depth range. Extending to the west from the spreading axis, this anomaly has velocities low enough to indicate the presence of melt. The asymmetry in velocity structure and the much greater abundance of seamounts on the west flank of the ridge suggest that dynamic, buoyant upwelling is important, perhaps triggered by thermal or compositional anomalies beneath Axial Seamount. In contrast, there is no evidence for asymmetry in the axial zone or lower than expected velocities beneath the Gorda ridge. On the eastern flank of the Juan de Fuca ridge, the shear velocity in the 25-65 depth range is higher than expected; the lithosphere appears to be colder and thicker than predicted by standard plate cooling models, perhaps caused by the downwelling counterpart of the upwelling on the west side of the ridge. Close to the trench, there is a sharp decrease in shear velocity. We interpret this as aqueous alteration caused by hydrothermal circulation through deep normal faults associated with bending of the plate. Beneath the Astoria and Nitinat fans, where abyssal plain sediment is thickest, the velocity decrease is much smaller, which is consistent with a thick sediment cap that prevents hydrothermal alteration of the plate.

  13. Multi-Mode Electromagnetic Ultrasonic Lamb Wave Tomography Imaging for Variable-Depth Defects in Metal Plates

    PubMed Central

    Huang, Songling; Zhang, Yu; Wang, Shen; Zhao, Wei

    2016-01-01

    This paper proposes a new cross-hole tomography imaging (CTI) method for variable-depth defects in metal plates based on multi-mode electromagnetic ultrasonic Lamb waves (LWs). The dispersion characteristics determine that different modes of LWs are sensitive to different thicknesses of metal plates. In this work, the sensitivities to thickness variation of A0- and S0-mode LWs are theoretically studied. The principles and procedures for the cooperation of A0- and S0-mode LW CTI are proposed. Moreover, the experimental LW imaging system on an aluminum plate with a variable-depth defect is set up, based on A0- and S0-mode EMAT (electromagnetic acoustic transducer) arrays. For comparison, the traditional single-mode LW CTI method is used in the same experimental platform. The imaging results show that the computed thickness distribution by the proposed multi-mode method more accurately reflects the actual thickness variation of the defect, while neither the S0 nor the A0 single-mode method was able to distinguish thickness variation in the defect region. Moreover, the quantification of the defect’s thickness variation is more accurate with the multi-mode method. Therefore, theoretical and practical results prove that the variable-depth defect in metal plates can be successfully quantified and visualized by the proposed multi-mode electromagnetic ultrasonic LW CTI method. PMID:27144571

  14. Analysis and experimental verification of electroacoustic wave energy harvesting in a coupled piezoelectric plate-harvester system

    NASA Astrophysics Data System (ADS)

    Darabi, Amir; Leamy, Michael J.

    2017-03-01

    This paper introduces an analytical framework for predicting wave energy harvested by a circular piezoelectric disk attached to a thin plate. An harmonic point source excitation generates waves that are then incident on a piezoelectric disk—summing responses due to all such excitation enables general forcing profiles to be considered. The analysis approach decomposes the coupled system into two subdomains, one being the piezoelectric disk, and the other an infinite plate for which a Green's function is readily available. Interaction forces between the two subdomains couple the problems and lead to a closed-form solution for the propagation, transmission, and reflection of waves over the entire domain. In addition, the voltage generated by the harvester is calculated using coupled electromechanical equations. The analysis approach is first validated by comparing predicted response quantities to those computed using numerical simulations, documenting good agreement. The system is then studied in the frequency domain and the optimum harvester resistance is found for generating the most electrical power. Representative experiments are carried out to demonstrate the validity of the analytical approach and verify the harvested power versus resistance trend.

  15. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device.

    PubMed

    Heywood, Sarah L; Glavin, Boris A; Beardsley, Ryan P; Akimov, Andrey V; Carr, Michael W; Norman, James; Norton, Philip C; Prime, Brian; Priestley, Nigel; Kent, Anthony J

    2016-08-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1-12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies.

  16. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device

    PubMed Central

    Heywood, Sarah L.; Glavin, Boris A.; Beardsley, Ryan P.; Akimov, Andrey V.; Carr, Michael W.; Norman, James; Norton, Philip C.; Prime, Brian; Priestley, Nigel; Kent, Anthony J.

    2016-01-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies. PMID:27477841

  17. Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device

    NASA Astrophysics Data System (ADS)

    Heywood, Sarah L.; Glavin, Boris A.; Beardsley, Ryan P.; Akimov, Andrey V.; Carr, Michael W.; Norman, James; Norton, Philip C.; Prime, Brian; Priestley, Nigel; Kent, Anthony J.

    2016-08-01

    We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies.

  18. Solitary wave-based delamination detection in composite plates using a combined granular crystal sensor and actuator

    NASA Astrophysics Data System (ADS)

    Kim, Eunho; Restuccia, Francesco; Yang, Jinkyu; Daraio, Chiara

    2015-12-01

    We experimentally and numerically investigate a diagnostic method for detecting hidden delamination in composite panels, using highly nonlinear solitary waves. Solitary waves are a type of nonlinear waves with strong energy intensity and non-distortive nature, which can be controllably generated in one-dimensional granular crystals. In this study, we use granular crystals as a combined sensor and actuator to detect hidden delamination in carbon fiber reinforced polymer (CFRP) composite panels. Specifically, we locally excite a CFRP composite specimen using the granular crystal as an actuator and measure the reflected waves that carry the specimen’s diagnostic information using the same device as a sensor. We first investigate the effect of the panel’s boundary conditions on the response of the reflected solitary waves. We then investigate the interactions of a solitary wave with delamination hidden in the CFRP composite specimen. Lastly, we define a damage index based on the solitary waves’ responses to identify the location of the hidden delamination in the CFRP composite panel. The solitary wave-based diagnostic method can provide unique merits, such as portable and fast sensing of composites’ hidden damage, thereby with the potential of being used for hot spot monitoring of composite-based structures.

  19. Modal density and modal distribution of bending wave vibration fields in ribbed plates.

    PubMed

    Dickow, Kristoffer Ahrens; Brunskog, Jonas; Ohlrich, Mogens

    2013-10-01

    Plates reinforced by ribs or joists are common elements in lightweight building structures, as well as in other engineering structures such as vehicles, ships, and aircraft. These structures, however, are often not well suited for simple structural acoustic prediction models such as statistical energy analysis. One reason is that the modal density is not uniformly distributed due to the spatial periodicity introduced by the ribs. This phenomenon is investigated in the present paper, using a modal model of a ribbed plate. The modal model uses the Fourier sine modes, and the coupling between the plate and ribs is incorporated using Hamilton's principle. This model is then used to investigate the modal density of the considered spatially periodic structure, and a grouping of the modes in different dominating directions is proposed. Suggestions are also given regarding how to proceed towards a simplified prediction model for ribbed plates.

  20. The Propagation of Time Harmonic Rayleigh - Lamb Waves in a Bimaterial Plate

    DTIC Science & Technology

    1989-11-07

    analysis is to study the modal contributions to these fields. For an infinite homogeneous plate the only field present should be the incident field...coefficients, an analysis of the stress and displacement fields in either plate can be undertaken. Of particular interest is the fraction of the incident...choices for N were determined from a sensitivity analysis of the output to varying N. Results of this analysis are presented in tables I and II, where

  1. Thick plate bending wave transmission using a mobility power flow approach

    NASA Technical Reports Server (NTRS)

    Mccollum, M. D.; Cuschieri, J. M.

    1990-01-01

    The mobility power flow (MPF) approach is used in this paper to describe the flexural behavior of an L-shaped plate structure consisting of thick plates with rotary inertia and shear deformation effects included in the analysis. The introduction of the thick plate effects significantly increases the complexity of the structural mobility functions used in the definitions of the power flow terms; however, because of the substructuring that is used in the MPF approach, the complexity of the problem is significantly reduced as compared to solving for the global structure. Additionally, with the MPF approach the modal behavior is described. The MPF analysis of the L-shaped plate is performed for the case of point force excitation on one plate, with the two plates being identical in both size and thickness. The results of this analysis are compared to results from the finite-element analysis (FEA) and the statistical energy analysis (SEA) and show very good agreement in the low- and high-frequency regimes, respectively.

  2. Flow-Field Measurement of Device-Induced Embedded Streamwise Vortex on a Flat Plate

    NASA Technical Reports Server (NTRS)

    Yao, Chung-Sheng; Lin, John C.; Allan, Brian G.

    2002-01-01

    Detailed flow-field measurements were performed downstream of a single vortex generator (VG) using an advanced Stereo Digital Particle Image Velocimetry system. Thc passive flow-control devices examined consisted of a low-profile VG with a device height, h, approximately equal to 20 percent of the boundary-layer thickness, sigma, and a conventional VG with h is approximately sigma. Flow-field data were taken at twelve cross-flow planes downstream of the VG to document and quantify the evolution of embedded streamwise vortex. The effects of device angle of attack on vortex development downstream were compared between the low-profile VG and the conventional VG. Key parameters including vorticity, circulation, trajectory, and half-life radius - describing concentration, strength, path, and size, respectively--of the device-induced streamwise vortex were extracted from the flow-field data. The magnitude of maximum vorticity increases as angle of attack increases for the low-profile VG, but the trend is reversed for the conventional VG, probably due to flow stalling around the larger device at higher angles of attack. Peak vorticity and circulation for the low-profile VG decays exponentially and inversely proportional to the distance downstream from the device. The device-height normalized vortex trajectories for the low-profile VG, especially in the lateral direction, follow the general trends of the conventional VG. The experimental database was used to validate the predictive capability of computational fluid dynamics (CFD). CFD accurately predicts the vortex circulation and path; however, improvements are needed for predicting the vorticity strength and vortex size.

  3. Surface acoustic wave nebulization device with dual interdigitated transducers improves SAWN-MS performance.

    PubMed

    Huang, Yue; Heron, Scott R; Clark, Alicia M; Edgar, J Scott; Yoon, Sung Hwan; Kilgour, David P A; Turecek, Frantisek; Aliseda, Alberto; Goodlett, David R

    2016-06-01

    We compared mass spectrometric (MS) performance of surface acoustic wave nebulization (SAWN) generated by a single interdigitated transducer (IDT) designed to produce a progressive wave (PW) to one with a dual IDT that can in theory generate standing waves (SW). Given that devices using dual IDTs had been shown to produce fewer large size droplets on average, we hypothesized they would improve MS performance by improving the efficiency of desolvation. Indeed, the SW-SAWN chip provided an improved limit of detection of 1 femtomole of peptide placed on chip making it 100× more sensitive than the PW design. However, as measured by high-speed image recording and phase Doppler particle analyzer measurements, there was only a 26% increase in the small diameter (1-10 µm) droplets produced from the new device, precluding a conclusion that the decrease in droplet size was solely responsible for the improvement in MS signal/noise. Given that the dual IDT design produced a more instantaneous plume than the PW design, the more likely contributor to improved MS signal/noise was concluded to be a higher ion flux entering the mass spectrometer for the dual IDT designs. Notably, the dual IDT device allowed production of much higher quality protein mass spectra up to about 20 kDa, compared with the single IDT device. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles.

    PubMed

    Shields, C Wyatt; Cruz, Daniela F; Ohiri, Korine A; Yellen, Benjamin B; Lopez, Gabriel P

    2016-03-06

    Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

  5. Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

    PubMed Central

    Shields, C. Wyatt; Cruz, Daniela F.; Ohiri, Korine A.; Yellen, Benjamin B.; Lopez, Gabriel P.

    2016-01-01

    Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly. PMID:27022681

  6. Finite element method analysis of surface acoustic wave devices with microcavities for detection of liquids

    NASA Astrophysics Data System (ADS)

    Senveli, Sukru U.; Tigli, Onur

    2013-12-01

    This paper introduces the use of finite element method analysis tools to investigate the use of a Rayleigh type surface acoustic wave (SAW) sensor to interrogate minute amounts of liquids trapped in microcavities placed on the delay line. Launched surface waves in the ST-X quartz substrate couple to the liquid and emit compressional waves. These waves form a resonant cavity condition and interfere with the surface waves in the substrate. Simulations show that the platform operates in a different mechanism than the conventional mass loading of SAW devices. Based on the proposed detection mechanism, it is able to distinguish between variations of 40% and 90% glycerin based on phase relations while using liquid volumes smaller than 10 pl. Results from shallow microcavities show high correlation with sound velocity parameter of the liquid whereas deeper microcavities display high sensitivities with respect to glycerin concentration. Simulated devices yield a maximum sensitivity of -0.77°/(% glycerin) for 16 μm wavelength operation with 8 μm deep, 24 μm wide, and 24 μm long microcavities.

  7. Micro-Fresnel Zone Plate Optical Devices Using Densely Accumulated Ray Points

    NASA Technical Reports Server (NTRS)

    Choi, Sang H. (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2011-01-01

    An embodiment generally relates to an optical device suitable for use with an optical medium for the storage and retrieval of data. The optical device includes an illumination means for providing a beam of optical radiation of wavelength .lamda. and an optical path that the beam of optical radiation follows. The optical device also includes a diffractive optical element defined by a plurality of annular sections. The plurality of annular sections having a first material alternately disposed with a plurality of annular sections comprising a second material. The diffractive optical element generates a plurality of focal points and densely accumulated ray points with phase contrast phenomena and the optical medium is positioned at a selected focal point or ray point of the diffractive optical element.

  8. Multiple damage identification and imaging in an aluminum plate using effective Lamb wave response automatic extraction technology

    NASA Astrophysics Data System (ADS)

    Ouyang, Qinghua; Zhou, Li; Liu, Xiaotong

    2016-04-01

    In order to identify multiple damage in the structure, a method of multiple damage identification and imaging based on the effective Lamb wave response automatic extraction algorithm is proposed. In this method, the detected key area in the structure is divided into a number of subregions, and then, the effective response signals including the structural damage information are automatically extracted from the entire Lamb wave responses which are received by the piezoelectric sensors. Further, the damage index values of every subregion based on the correlation coefficient are calculated using the effective response signals. Finally, the damage identification and imaging are performed using the reconstruction algorithm for probabilistic inspection of damage (RAPID) technique. The experimental research was conducted using an aluminum plate. The experimental results show that the method proposed in this research can quickly and effectively identify the single damage or multiple damage and image the damages clearly in detected area.

  9. Band gaps of lamb waves in one-dimensional piezoelectric composite plates: effect of substrate and boundary conditions.

    PubMed

    Zou, Xin-Ye; Liang, Bin; Chen, Qian; Cheng, Jian-Chun

    2009-02-01

    We theoretically study the band structures of Lamb waves in one-dimensional phononic crystal plates consisting of piezoelectric ceramics placed periodically in epoxy with epoxy or piezoelectric ceramic substrate by the virtual plane wave expansion method. The dependences of the widths and starting frequencies of first band gaps (FBG) on the substrate's thickness, the filling fraction, and the lattice spacing are calculated for different materials of substrate under different electric boundary conditions, i.e., short circuit (SC) and open circuit (OC). The FBG width decreases gradually as the substrate's thickness increases and the FBG starting frequency increases progressively as the thickness increases on the whole. The FBG widths and starting frequencies with SC are always larger than with OC. Our research shows that it is possible to control the width and starting frequency of the FBG in the engineering according to need by choosing suitable values of the substrate's thickness, the filling fraction, and the lattice spacing.

  10. Properties of Maser-generated Alfvén wave in a Large Laboratory Device

    NASA Astrophysics Data System (ADS)

    Zhu, Ziyan; Dorfman, Seth; Carter, Troy; Morales, George; Clark, Mary; Rossi, Giovanni

    2016-10-01

    This research is motivated by the investigations of the natural Alfvén wave maser, which refers to the resonant amplification of Alfvén wave in the earth-surrounding plasmas. A resonant cavity that results from applying a locally non-uniform magnetic field to a plasma source region between the anode and cathode of the Large Plasma Device creates the maser. In this research, a lanthanum hexaboride (LaB6)) cathode is used as the plasma source. Above an excitation threshold, selective amplification produces a highly coherent, large amplitude Alfvén wave that propagates out of the resonator through a semitransparent mesh anode into the plasma column where the magnetic field is uniform. The excitation threshold depends on the discharge voltage, and it increases as background magnetic field strength increases; this threshold influences the maser behaviors, including amplitude modulations. The maser with LaB6 source has m = 1 mode and exhibits a right-handed rotation, which is consistent with the electron diamagnetic drift rotation, supporting the possibility of a drift Alfvén wave maser. To distinguish between drift and shear Alfvén waves, a new experiment with the maser cavity excited by a driving circuit was performed. This allows us to access low frequencies (compared to ω*) that cannot be spontaneously driven. The dispersion relation of this driven maser is under investigation. The experimental results will motivate future Alfvén wave study in laboratory devices and thus help better understand space plasma physics such as testing the theory of Alfvén-wave-induced heating of stellar atmosphere. Work supported by the U.S. Department of Energy Office of Science.

  11. Sensor Measurement Strategies for Monitoring Offshore Wind and Wave Energy Devices

    NASA Astrophysics Data System (ADS)

    O'Donnell, Deirdre; Srbinovsky, Bruno; Murphy, Jimmy; Popovici, Emanuel; Pakrashi, Vikram

    2015-07-01

    While the potential of offshore wind and wave energy devices is well established and accepted, operations and maintenance issues are still not very well researched or understood. In this regard, scaled model testing has gained popularity over time for such devices at various technological readiness levels. The dynamic response of these devices are typically measured by different instruments during such scaled tests but agreed sensor choice, measurement and placement guidelines are still not in place. This paper compared the dynamic responses of some of these sensors from a scaled ocean wave testing to highlight the importance of sensor measurement strategies. The possibility of using multiple, cheaper sensors of seemingly inferior performance as opposed to the deployment of a small number of expensive and accurate sensors are also explored. An energy aware adaptive sampling theory is applied to highlight the possibility of more efficient computing when large volumes of data are available from the tested structures. Efficient sensor measurement strategies are expected to have a positive impact on the development of an device at different technological readiness levels while it is expected to be helpful in reducing operation and maintenance costs if such an approach is considered for the devices when they are in operation.

  12. Finite element modelling of surface acoustic wave device based corrugated microdiaphragms

    NASA Astrophysics Data System (ADS)

    Dissanayake, Don W.; Al-Sarawi, Said; Lu, Tien-Fu; Abbott, Derek

    2009-09-01

    This paper presents modelling and analysis of microdiaphragms that are designed for implantable micropump applications. Microdiaphragms are considered to be a major component of micropumps. A securely operated, electrostatically actuated, fully passive micropump is designed using a novel method, which is based on surface acoustic wave (SAW) devices and wireless transcutaneous radio frequency (RF) communication. The device is capable of extracting the required power from the RF signal itself, like RFID (ID: identification device) tags; hence the need of a battery and active electronics is negated. Moreover, a SAW correlator is used for secure interrogation of the device. As a result, the device responds only to a unique RF signal, which has the same code as was implanted in the SAW correlator. Finite element analysis (FEA) based on code from ANSYS Inc. is carried out to model the microdiaphragm, and a Rayleigh-Ritz method based analytical model is developed to investigate the validity of the FEA results. During the FEA, a three-dimensional model of the diaphragm is developed and various kinds of corrugation profiles are considered for enhancing the device performance. A coupled-field analysis is carried out to model the electrostatics-solid interaction between the corrugated microdiaphragm and the SAW device. In modelling microdiaphragms, selection of appropriate material properties and element types, application of accurate constraints, and selection of suitable mesh parameters are carefully considered.

  13. The Biological Sensor for Detection of Bacterial Cells in Liquid Phase Based on Plate Acoustic Wave

    NASA Astrophysics Data System (ADS)

    Borodina, Irina; Zaitsev, Boris; Shikhabudinov, Alexander; Guliy, Olga; Ignatov, Oleg; Teplykh, Andrey

    The interactions "bacterial cells - bacteriophages", "bacterial cells - antibodies" and "bacterial cells - mini- antibodies" directly in liquid phase were experimentally investigated with a help of acoustic sensor. The acoustic sensor under study represents two-channel delay line based on the plate of Y-X lithium niobate. One channel of delay line was electrically shorted, the second channel was electrically open. The liquid container was glued on plate surface between transducers of delay line. The dependencies of the change in phase and insertion loss on concentration of bacteriophages, antibodies, and mini- antibodies were obtained for both channels of delay line.

  14. Tailoring the Blast Exposure Conditions in the Shock Tube for Generating Pure, Primary Shock Waves: The End Plate Facilitates Elimination of Secondary Loading of the Specimen.

    PubMed

    Kuriakose, Matthew; Skotak, Maciej; Misistia, Anthony; Kahali, Sudeepto; Sundaramurthy, Aravind; Chandra, Namas

    2016-01-01

    The end plate mounted at the mouth of the shock tube is a versatile and effective implement to control and mitigate the end effects. We have performed a series of measurements of incident shock wave velocities and overpressures followed by quantification of impulse values (integral of pressure in time domain) for four different end plate configurations (0.625, 2, 4 inches, and an open end). Shock wave characteristics were monitored by high response rate pressure sensors allocated in six positions along the length of 6 meters long 229 mm square cross section shock tube. Tests were performed at three shock wave intensities, which was controlled by varying the Mylar membrane thickness (0.02, 0.04 and 0.06 inch). The end reflector plate installed at the exit of the shock tube allows precise control over the intensity of reflected waves penetrating into the shock tube. At the optimized distance of the tube to end plate gap the secondary waves were entirely eliminated from the test section, which was confirmed by pressure sensor at T4 location. This is pronounced finding for implementation of pure primary blast wave animal model. These data also suggest only deep in the shock tube experimental conditions allow exposure to a single shock wave free of artifacts. Our results provide detailed insight into spatiotemporal dynamics of shock waves with Friedlander waveform generated using helium as a driver gas and propagating in the air inside medium sized tube. Diffusion of driver gas (helium) inside the shock tube was responsible for velocity increase of reflected shock waves. Numerical simulations combined with experimental data suggest the shock wave attenuation mechanism is simply the expansion of the internal pressure. In the absence of any other postulated shock wave decay mechanisms, which were not implemented in the model the agreement between theory and experimental data is excellent.

  15. Tailoring the Blast Exposure Conditions in the Shock Tube for Generating Pure, Primary Shock Waves: The End Plate Facilitates Elimination of Secondary Loading of the Specimen

    PubMed Central

    Misistia, Anthony; Kahali, Sudeepto; Sundaramurthy, Aravind; Chandra, Namas

    2016-01-01

    The end plate mounted at the mouth of the shock tube is a versatile and effective implement to control and mitigate the end effects. We have performed a series of measurements of incident shock wave velocities and overpressures followed by quantification of impulse values (integral of pressure in time domain) for four different end plate configurations (0.625, 2, 4 inches, and an open end). Shock wave characteristics were monitored by high response rate pressure sensors allocated in six positions along the length of 6 meters long 229 mm square cross section shock tube. Tests were performed at three shock wave intensities, which was controlled by varying the Mylar membrane thickness (0.02, 0.04 and 0.06 inch). The end reflector plate installed at the exit of the shock tube allows precise control over the intensity of reflected waves penetrating into the shock tube. At the optimized distance of the tube to end plate gap the secondary waves were entirely eliminated from the test section, which was confirmed by pressure sensor at T4 location. This is pronounced finding for implementation of pure primary blast wave animal model. These data also suggest only deep in the shock tube experimental conditions allow exposure to a single shock wave free of artifacts. Our results provide detailed insight into spatiotemporal dynamics of shock waves with Friedlander waveform generated using helium as a driver gas and propagating in the air inside medium sized tube. Diffusion of driver gas (helium) inside the shock tube was responsible for velocity increase of reflected shock waves. Numerical simulations combined with experimental data suggest the shock wave attenuation mechanism is simply the expansion of the internal pressure. In the absence of any other postulated shock wave decay mechanisms, which were not implemented in the model the agreement between theory and experimental data is excellent. PMID:27603017

  16. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Astrophysics Data System (ADS)

    Boyd, Ronald D.; Turknett, Jerry C.; Smith, Alvin

    1989-08-01

    The effects of enhancement devices on flow boiling heat transfer in circular coolant channels, which are heated over a fraction of their perimeters, are studied. The variations were examined in both the mean and local (axial, and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls. Improvements were initiated in the present data reduction analysis. These efforts should lead to the development of heat transfer correlations which include effects of single side heat flux and enhancement device configuration. It is hoped that a stage will be set for the study of heat transfer and pressure drop in single sided heated systems under zero gravity conditions.

  17. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Technical Reports Server (NTRS)

    Boyd, Ronald D.; Turknett, Jerry C.; Smith, Alvin

    1989-01-01

    The effects of enhancement devices on flow boiling heat transfer in circular coolant channels, which are heated over a fraction of their perimeters, are studied. The variations were examined in both the mean and local (axial, and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls. Improvements were initiated in the present data reduction analysis. These efforts should lead to the development of heat transfer correlations which include effects of single side heat flux and enhancement device configuration. It is hoped that a stage will be set for the study of heat transfer and pressure drop in single sided heated systems under zero gravity conditions.

  18. The Beynon Gabor zone plate: a new tool for de Broglie matter waves and hard X-rays? An off axis and focus intensity investigation.

    PubMed

    Greve, Martin M; Vial, Alexandre M; Stamnes, Jakob J; Holst, Bodil

    2013-11-18

    Optical elements based on Fresnel zones are used in a range of applications, from X-ray telescopy to microscopy and recently also in the manipulation of de Broglie matter waves. In 1992 Beynon and co-workers presented a binary Gabor type zone plate (henceforth referred to as the Beynon Gabor zone plate). Because this zone plate has no higher order foci, it is in principle a very attractive candidate for focusing of de Broglie matter waves and in some cases X-rays. So far the Beynon Gabor zone plate investigations presented in the literature have concentrated on the intensity distribution along the optical axis and in the focal plane. Here we present a detailed numerical investigation of the Beynon Gabor zone plate, including an investigation of the off-optical axis, off focal plane intensity distribution for point source illumination. We show that at integer fractions of the focal length, the beam becomes nearly toroidal (doughnut-shaped). This offers potentially interesting new possibilities for de Broglie matter wave and X-ray optics, for example in STED-like applications. We further show that the increased intensity at the focal point predicted in the literature for a particular Beynon Gabor zone plate transmission function configuration is an artifact due to the lack of sampling nodes. We support our calculations with experimental measurements in the visible light range, using a Beynon Gabor zone plate fabricated with electron beam lithography.

  19. Refractive index matched half-wave plate with a nematic liquid crystal for three-dimensional laser metrology applications

    NASA Astrophysics Data System (ADS)

    Piecek, W.; Jaroszewicz, L. R.; Miszczyk, E.; Raszewski, Z.; Mrukiewicz, M.; Perkowski, P.; Nowinowski-Kruszelnicki, E.; Zieliński, J.; Olifierczuk, M.; Kędzierski, J.; Sun, X. W.; Garbat, K.; Kowiorski, K.; Morawiak, P.; Mazur, R.; Tkaczyk, J.

    2016-12-01

    There exists a need in a quality and accuracy of a three-dimensional laser metrology operating in numerically controlled automatic machines. For this purpose, one sends three laser beams mutually perpendicular. These three beams of the wavelength λ = 0.6328 μm are generated by the same laser and are directed along three independent, orthogonal, mutually perpendicular, optical paths with a given light polarization plain. Using these beams, constituting the frame of coordinates, three independent laser rangefinders are able to determine spatial coordinates of a working tool or a workpiece. To form these optical pulses, a special refractive index matched Half-Wave Plate with nematic Liquid Crystal (LCHWP) was applied. The presented half-wave plate is based on a single Twisted Nematic (TN) cell (with the twist angle Φ = π/2) of a rather high cell gap d 15 μm filled with a newly developed High-Birefringence Nematic Liquid Crystal Mixture (HBLCM) of optical anisotropy as high as Δn 0.40 at λ = 0.6328 μm, where the Mauguin limit above 5.00 Δnd >> λ/2 = 0.32 is fulfilled.

  20. Determination of plate wave velocities and diffuse field decay rates with braod-band acousto-ultrasonic signals

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.

    1993-01-01

    Lowest symmetric and lowest antisymmetric plate wave modes were excited and identified in broad-band acousto-ultrasonic (AU) signals collected from various high temperature composite materials. Group velocities have been determined for these nearly nondispersive modes. An algorithm has been developed and applied to determine phase velocities and hence dispersion curves for the frequency ranges of the broad-band pulses. It is demonstrated that these data are sensitive to changes in the various stiffness moduli of the materials, in agreement by analogy, with the theoretical and experimental results of Tang and Henneke on fiber reinforced polymers. Diffuse field decay rates have been determined in the same specimen geometries and AU configuration as for the plate wave measurements. These decay rates are of value in assessing degradation such as matrix cracking in ceramic matrix composites. In addition, we verify that diffuse field decay rates respond to fiber/matrix interfacial shear strength and density in ceramic matrix composites. This work shows that velocity/stiffness and decay rate measurements can be obtained in the same set of AU experiments for characterizing materials and in specimens with geometries useful for mechanical measurements.

  1. Re-thinking Reading in the Context of a New Wave of Electronic Reading Devices

    NASA Astrophysics Data System (ADS)

    Kratky, Andreas

    We are currently witnessing a new wave of digital reading devices that will probably significantly change the way we read and publish. This is not the first digital revolution of aspects of cultural production and perception. This paper compares the previous digital revolutions of the music, film and publishing industries and attempts a prognosis of coming changes in the way we will work with digital texts. As a conclusion a new notion of interface design for the emerging reading ecology is proposed.

  2. Low-loss unidirectional transducer for high frequency surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Biryukov, S. V.; Martin, G.; Schmidt, H.; Wall, B.

    2011-10-01

    A multi-track unidirectional transducer for surface acoustic wave devices is presented. This transducer consists of periodic cells containing in each of the multiple tracks, only two electrodes and two gaps with quarter period width. So the structure has maximal possible dimensions of its elements for a cell period equal to one wavelength. In spite of current technological limitations this permits to implement unidirectional transducers in GHz range. In contrast to known structures with active tracks only, the structure contains alternating both active transducer tracks and passive reflector tracks with different apertures comparable to surface acoustic wave (SAW) wavelength. The tracks strongly interact due to diffraction of waves excited by such electrode structure on a piezoelectric substrate. A structure analysis by means of finite element method shows that complete unidirectionality can be reached. First experimental results are given.

  3. Fabrication of two-color annular hybrid wave plate for three-dimensional super-resolution microscopy

    NASA Astrophysics Data System (ADS)

    Kumagai, Hiroshi; Iketaki, Yoshinori; Jahn, Kornel; Bokor, Nador

    2016-03-01

    In super-resolution microscopy, we use fluorescence depletion, where an erase beam quenches a molecule in the S1 state generated by a pump beam, and then prevents fluorescence from the S1 state. When a tight doughnut shaped erase beam with is focused on the dyed sample together with a Gaussian pump beam, the remaining fluorescence spot in the focal plane becomes smaller than the diffraction-limited size. Applying destructive interference to the erase beam, erase beam has a minute three-dimensional dark spot surrounded by the light near the focal region. Since this spot introduces fluorescence depletion along the optical axis as in the focal plane, we can achieve three-dimensional super-resolution microscopy. However, to overcome the diffraction limit, an extremely precise optical alignment is required for projecting the focused pump beam into the dark spot of the erase beam. To resolve this technical issue, we fabricated a two-color annular hybrid wave plate (TAHWP) by combining two multi-order wave quartz plates. Although the pump and erase beams co-axially pass through the plate; the pump beam retains its original Gaussian shape, while the erase beam undergoes destructive interference. Inserting the TAHWP into a commercial scanning laser microscope, a three-dimensional spherical fluorescence spot with a volume of (~100 nm)3 can be created. Beside eliminating alignment problems and yielding a compact setup, the TAHWP makes our proposed method very suitable for commercial microscope systems. In this study, we report about detailed fabrication procedure and three-dimensional image properties given by the TAHWP.

  4. Potentiality of semiconducting diamond as the base material of millimeter-wave and terahertz IMPATT devices

    NASA Astrophysics Data System (ADS)

    Acharyya, Aritra; Banerjee, Suranjana; Banerjee, J. P.

    2014-03-01

    An attempt is made in this paper to explore the potentiality of semiconducting type-IIb diamond as the base material of double-drift region (DDR) impact avalanche transit time (IMPATT) devices operating at both millimetre-wave (mm-wave) and terahertz (THz) frequencies. A rigorous large-signal (L-S) simulation based on the non-sinusoidal voltage excitation (NSVE) model developed earlier by the authors is used in this study. At first, a simulation study based on avalanche response time reveals that the upper cut-off frequency for DDR diamond IMPATTs is 1.5 THz, while the same for conventional DDR Si IMPATTs is much smaller, i.e. 0.5 THz. The L-S simulation results show that the DDR diamond IMPATT device delivers a peak RF power of 7.79 W with an 18.17% conversion efficiency at 94 GHz; while at 1.5 THz, the peak power output and conversion efficiency decrease to 6.19 mW and 8.17% respectively, taking 50% voltage modulation. A comparative study of DDR IMPATTs based on diamond and Si shows that the former excels over the later as regards high frequency and high power performance at both mm-wave and THz frequency bands. The effect of band to band tunneling on the L-S properties of DDR diamond and Si IMPATTs has also been studied at different mm-wave and THz frequencies.

  5. Excitation of Electron Acoustic Waves in Plasmas of the SINP-MaPLE Device

    NASA Astrophysics Data System (ADS)

    Chowdhury, Satyajit; Biswas, Subir; Chakrabrati, Nikhil; Pal, Rabindranath

    2016-10-01

    Electron acoustic wave (EAW) is the low frequency branch of the undamped electrostatic plasma wave and has low phase velocity. In order to overcome Landau damping the EAW needs a non-Maxwellian electron velocity distribution with a flat region near the phase velocity, or equivalently, a plasma with two temperature electron species with a relative velocity between them. The ECR produced plasmas of the MaPLE device at Saha Institute of Nuclear Physics provide such characteristics as observed by retarded field energy analyzer and single Langmuir probe. Experiments are carried out to exploit this feature by putting a negatively biased mesh launcher inside the plasma and energizing it with sinusoidal voltages from a function generator with frequencies varying near the ion plasma frequency. Circular mesh probes along the axis of the device serve as detectors for wave propagation. Experimental results show EAWs are indeed launched and propagate along the magnetic field direction. The dispersion curve experimentally obtained shows the phase velocity matching satisfactorily with the estimated theoretical values. Changing the bias on the launcher the electron distribution function is varied, which, in turn, controls the wave amplitude. Detailed experimental results will be presented. Department of Atomic Energy, Govt. of India.

  6. Scattering of Rayleigh-Lamb waves by a surface breaking crack in an elastic plate.

    PubMed

    Flores-López, Miguel A; Gregory, R Douglas

    2006-04-01

    This work studies the problem of scattering of Rayleigh-Lamb waves by a thin surface-breaking crack. The problem is solved by the projection method, which exploits some orthogonality relations deduced from the reciprocal theorem. Numerical results obtained by the projection method are compared with the results obtained using a finite element method reported by other authors for the case of a flat crack, finding good agreement. From the numerical results it is observed that, as the wave number of the incident wave, so for instance, is smaller, the reflected and transmitted energy corresponding to the converted mode, A0 in this case, are almost equal to each other. An explanation for this result is given, based on the asymptotic nature of the modes S0 and A0 for small wave numbers.

  7. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Astrophysics Data System (ADS)

    Boyd, Ronald D., Sr.

    1989-02-01

    A research program to study the effect of enhancement devices on flow boiling heat transfer in coolant channels, which are heated either from the top side or uniformly, is discussed. Freon 11 is the working fluid involved. The specific objectives are: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls, (2) examine the effect channel diameter (and the length-to-diameter aspect ratio) variations for the smooth wall channel, and (3) develop an improved data reduction analysis.

  8. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Technical Reports Server (NTRS)

    Boyd, Ronald D., Sr.

    1989-01-01

    A research program to study the effect of enhancement devices on flow boiling heat transfer in coolant channels, which are heated either from the top side or uniformly, is discussed. Freon 11 is the working fluid involved. The specific objectives are: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape and spiral finned walls, (2) examine the effect channel diameter (and the length-to-diameter aspect ratio) variations for the smooth wall channel, and (3) develop an improved data reduction analysis.

  9. AlScN thin film based surface acoustic wave devices with enhanced microfluidic performance

    NASA Astrophysics Data System (ADS)

    Wang, W. B.; Fu, Y. Q.; Chen, J. J.; Xuan, W. P.; Chen, J. K.; Wang, X. Z.; Mayrhofer, P.; Duan, P. F.; Bittner, A.; Schmid, U.; Luo, J. K.

    2016-07-01

    This paper reports the characterization of scandium aluminum nitride (Al1-x Sc x N, x  =  27%) films and discusses surface acoustic wave (SAW) devices based on them. Both AlScN and AlN films were deposited on silicon by sputtering and possessed columnar microstructures with (0 0 0 2) crystal orientation. The AlScN/Si SAW devices showed improved electromechanical coupling coefficients (K 2, ~2%) compared with pure AlN films (<0.5%). The performance of the two types of devices was also investigated and compared, using acoustofluidics as an example. The AlScN/Si SAW devices achieved much lower threshold powers for the acoustic streaming and pumping of liquid droplets, and the acoustic streaming and pumping velocities were 2  ×  and 3  ×  those of the AlN/Si SAW devices, respectively. Mechanical characterization showed that the Young’s modulus and hardness of the AlN film decreased significantly when Sc was doped, and this was responsible for the decreased acoustic velocity and resonant frequency, and the increased temperature coefficient of frequency, of the AlScN SAW devices.

  10. Finite Element Analysis of Bulk-Acoustic-Wave Devices: Model Setup and Applications.

    PubMed

    Thalhammer, Robert; Larson, John

    2016-04-20

    In this work, the principles of finite element modeling for the electro-acoustic simulation of bulk-acoustic- wave devices will be summarized. We will outline model setup including governing equations and boundary conditions, as well as its efficient computer implementation. Particular emphasis will be given to tailoring the model dimension to the specific requirements of the desired investigation. As 3D simulations still require a major effort, it will be illustrated that various aspects of device physics and design can be addressed already by fast and efficient 2D simulations. Multiple theoretical and experimental evidence will be presented to demonstrate the validity of the modeling concepts. Based on various examples it will be sketched how to benefit from numerical simulations for understanding fundamental effects, designing devices for actual products, and exploring novel technologies.

  11. Collisional damping of helicon waves in a high density hydrogen linear plasma device

    SciTech Connect

    Caneses, Juan F.; Blackwell, Boyd D.

    2016-09-28

    In this paper, we investigate the propagation and damping of helicon waves along the length (~50 cm) of a helicon-produced 20 kW hydrogen plasma ( ~1-2 1019 m-3, ~1-6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50-200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (~10 G and ~ 10-15 cm) propagating away from the antenna region which become collisionally absorbed within 40 to 50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based on experimental measurements. By comparing theory and experiment, we show that for the conditions associated with this paper classical collisions are sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in our device (MAGPIE).

  12. Collisional damping of helicon waves in a high density hydrogen linear plasma device

    NASA Astrophysics Data System (ADS)

    Caneses, Juan F.; Blackwell, Boyd D.

    2016-10-01

    In this paper, we investigate the propagation and damping of helicon waves along the length (50 cm) of a helicon-produced 20 kW hydrogen plasma ({{n}\\text{e}}˜ 1-2 × 1019 m-3, {{T}\\text{e}}˜ 1-6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50-200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (4-8 G and {λz}˜ 10-15 cm) propagating away from the antenna region which become collisionally absorbed within 40-50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based on experimental measurements. Theoretical calculations are consistent with experiment and indicate that for conditions where Coulomb collisions are dominant classical collisionality is sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in helicon based linear plasma devices.

  13. Spontaneous excitation of waves by an intense ion beam on the Large Plasma Device

    NASA Astrophysics Data System (ADS)

    Tripathi, Shreekrishna; van Compernolle, Bart; Gekelman, Walter; Pribyl, Patrick; Heidbrink, William

    2016-10-01

    A hydrogen ion beam (15 keV, 10 A) has been injected into a large magnetized plasma (n 1010 -1013 cm-3, Te = 5.0 - 15.0 eV, B = 0.6 - 1.8 kG, He+ and H+ ions, 19 m long, 0.6 m diameter) for performing fast-ion studies on the Large Plasma Device (LAPD). The beam forms a helical orbit (pitch-angle 7° -55°), propagates with an Alfvénic speed (beam-speed/Alfvén-speed = 0.2 - 3.0), and significantly enhances the electron temperature and density when injected during the plasma afterglow. We report results on spontaneous generation of Alfvén waves and electrostatic waves in the lower-hybrid range of frequencies by the beam. Roles of normal and anomalous Doppler-shifted ion-cyclotron resonances in destabilizing the Alfvén waves were examined by measuring the phase-speed of waves and relevant parameters of the plasma using a variety of diagnostic tools (retarding-field energy analyzer, three-axis magnetic-loop, Dipole, and Langmuir probes). Conditions for the maximum growth of these waves were determined by varying the parameters of the beam and ambient plasma and examining the mode-structures in the fluctuation-spectra. Work jointly supported by US DOE and NSF and performed at the Basic Plasma Science Facility, UCLA.

  14. Collisional damping of helicon waves in a high density hydrogen linear plasma device

    DOE PAGES

    Caneses, Juan F.; Blackwell, Boyd D.

    2016-09-28

    In this paper, we investigate the propagation and damping of helicon waves along the length (~50 cm) of a helicon-produced 20 kW hydrogen plasma ( ~1-2 1019 m-3, ~1-6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50-200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (~10 G and ~ 10-15 cm) propagating away from the antenna region which become collisionally absorbed within 40 to 50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based onmore » experimental measurements. By comparing theory and experiment, we show that for the conditions associated with this paper classical collisions are sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in our device (MAGPIE).« less

  15. Factors Affecting Energy Absorption of a Plate during Shock Wave Impact Using a Damage Material Model

    DTIC Science & Technology

    2010-08-07

    August 7, 2010 Institution : Mississippi State University Major Field: Civil and Environmental Engineering Major Professor: Dr. Philip Gullett...Temperature was a tertiary influence on the plate response. However, only the AM60 had temperature dependant stress-strain characterization. Better 62...Blast, and Burn Injuries. Washington, D.C.: Walter Reed Army Institute of Research, Walter Reed Army Medical Center, 1991. Box, G.E., W.G. Hunter

  16. Experimental Structural Dynamic Response of Plate Specimens Due to Sonic Loads in a Progressive Wave Tube

    NASA Technical Reports Server (NTRS)

    Betts, Juan F.

    2001-01-01

    The objective of the current study was to assess the repeatability of experiments at NASA Langley's Thermal Acoustic Fatigue Apparatus (TAFA) facility and to use these experiments to validate numerical models. Experiments show that power spectral density (PSD) curves were repeatable except at the resonant frequencies, which tended to vary between 5 Hz to 15 Hz. Results show that the thinner specimen had more variability in the resonant frequency location than the thicker sample, especially for modes higher than the first mode in the frequency range. Root Mean Square (RMS) tended to be more repeatable. The RMS behaved linearly through the SPL range of 135 to 153 dB. Standard Deviations (STDs) of the results tended to be relatively low constant up to about 147 dB. The RMS results were more repeatable than the PDS results. The STD results were less than 10% of the RMS results for both the 0.125 in (0.318 cm) and 0.062 in (0.1588 cm) thick plate. The STD of the PSD results were around 20% to 100% of the mean PSD results for non-resonant and resonant frequencies, respectively, for the 0.125 in (0.318 cm) thicker plate and between 25% to 125% of the mean PSD results, for nonresonant and resonant frequencies, respectively, for the thinner plate.

  17. Mode-splitting and quasi-degeneracies in circular plate vibration problems: The example of free vibrations of the stator of a traveling wave ultrasonic motor

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwin; Krousgrill, Charles M.

    2012-12-01

    In systems with rotational symmetry, bending modes occur in doubly-degenerate pairs with two independent vibration modes for each repeated natural frequency. In circular plates, the standing waves of two such degenerate bending modes can be superposed with a 1/4 period separation in time to yield a traveling wave response. This is the principle of a traveling wave ultrasonic motor (TWUM), in which a traveling bending wave in a stator drives the rotor through a friction contact. The stator contains teeth to increase the speed at the contact region, and these affect the rotational symmetry of the plate. When systems with rotational symmetry are modified either in their geometry, or by spatially varying their properties or boundary conditions, some mode-pairs split into singlet modes having distinct frequencies. In addition, coupling between some pairs of distinct unperturbed modes also causes quasi-degeneracies in the perturbed modes, which leads their frequency curves to approach and veer away in some regions of the parameter space. This paper discusses the effects of tooth geometry on the behavior of plate modes under free vibration. It investigates mode splitting and quasi-degeneracies and derives analytic expressions to predict these phenomena, using variational methods and a degenerate perturbation scheme for the solution to the plate's discrete eigenvalue problem; these expressions are confirmed by solving the discrete eigenvalue problem of the plate with teeth.

  18. Mechanical-Stress Induced Nd:YAG Active Quarter-Wave Plate

    NASA Astrophysics Data System (ADS)

    Ohmi, Masato; Akatsuka, Masanori; Ishikawa, Koji; Naito, Kenta; Yonezawa, Yoshiyuki; Yamanaka, Masanobu; Izawa, Yasukazu; Nakai, Sadao

    1994-09-01

    A quarter-wave retardation was obtained by mechanically induced stress in a Nd:YAG laser rod and a laser gain of 1.15 at 1064 nm was obtained by pumping with a quasi-CW 300 W laser-diode array at 808 nm. The laser rod was held in a brass heatsink in which the mechanical stress was induced horizontally by means of screws. The effective quarter-wave area was measured to be 1 mm (vertical)×2 mm (horizontal) in the center of the 4 mm-diameter Nd:YAG rod by means of a newly constructed polarimeter.

  19. Acoustic field characterization of the Duolith: Measurements and modeling of a clinical shock wave therapy device

    PubMed Central

    Perez, Camilo; Chen, Hong; Matula, Thomas J.; Karzova, Maria; Khokhlova, Vera A.

    2013-01-01

    Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from −2 to −11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabolotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled. PMID:23927207

  20. Determination of the physical properties of room temperature ionic liquids using a Love wave device.

    PubMed

    Ouali, F Fouzia; Doy, Nicola; McHale, Glen; Hardacre, Christopher; Ge, Rile; Allen, Ray W K; MacInnes, Jordan M; Newton, Michael I

    2011-09-01

    In this work, we have shown that a 100 MHz Love wave device can be used to determine whether room temperature ionic liquids (RTILs) are Newtonian fluids and have developed a technique that allows the determination of the density-viscosity product, ρη, of a Newtonian RTIL. In addition, a test for a Newtonian response was established by relating the phase change to insertion loss change. Five concentrations of a water-miscible RTIL and seven pure RTILs were measured. The changes in phase and insertion loss were found to vary linearly with the square root of the density-viscosity product for values up to (ρη)(1/2) ~ 10 kg m(-2) s(-1/2). The square root of the density-viscosity product was deduced from the changes in either phase or insertion loss using glycerol as a calibration liquid. In both cases, the deduced values of ρη agree well with those measured using viscosity and density meters. Miniaturization of the device, beyond that achievable with the lower-frequency quartz crystal microbalance approach, to measure smaller volumes is possible. The ability to fabricate Love wave and other surface acoustic wave sensors using planar metallization technologies gives potential for future integration into lab-on-a-chip analytical systems for characterizing ionic liquids.

  1. A Microfluidic Love-Wave Biosensing Device for PSA Detection Based on an Aptamer Beacon Probe.

    PubMed

    Zhang, Feng; Li, Shuangming; Cao, Kang; Wang, Pengjuan; Su, Yan; Zhu, Xinhua; Wan, Ying

    2015-06-11

    A label-free and selective aptamer beacon-based Love-wave biosensing device was developed for prostate specific antigen (PSA) detection. The device consists of the following parts: LiTaO3 substrate with SiO2 film as wave guide layer, two set of inter-digital transducers (IDT), gold film for immobilization of the biorecongniton layer and a polydimethylsiloxane (PDMS) microfluidic channels. DNA aptamer, or "artificial antibody", was used as the specific biorecognition probe for PSA capture. Some nucleotides were added to the 3'-end of the aptamer to form a duplex with the 3'-end, turning the aptamer into an aptamer-beacon. Taking advantage of the selective target-induced assembly changes arising from the "aptamer beacon", highly selective and specific detection of PSA was achieved. Furthermore, PDMS microfluidic channels were designed and fabricated to realize automated quantitative sample injection. After optimization of the experimental conditions, the established device showed good performance for PSA detection between 10 ng/mL to 1 μg/mL, with a detection limit of 10 ng/mL. The proposed sensor might be a promising alternative for point of care diagnostics.

  2. Effective Shear Modulus for Flexural and Extensional Waves in an Unloaded Thick Plate.

    DTIC Science & Technology

    1980-09-29

    various texts (see e.g. Timo- shenko and Goodier [6] ). The relationships between the elements of the stress tensor o and the strain tensor e are given by...Extensional Vibrations of Plates," Trans. ASME, Ser. E, J. Appl. Mech. 23, 277-283 (1956). 6. S.P. Timoshenko and J.N. Goodier , Theory of Elasticity, 3d ed...private communication), David Taylor Naval Shin Research & Development Center, 1980. D2. R. D. Mindlin, "Influence of Rotatory inertia and Shear on

  3. Recent developments in Fresnel zone plate antennas at microwave/millimeter wave

    NASA Astrophysics Data System (ADS)

    Wiltse, James C.

    1998-10-01

    The Fresnel zone plate antenna is an example of an optical analogy that has been transferred to microwave/millimeter wavelength use. The latter case has seen extensive research and application, and in the past dozen years more than seventy relevant papers have been published on a worldwide basis. These studies have dealt with either lens or reflector designs, and have quantified many parameters, such as gain, antenna patterns, efficiency, bandwidth, and structural options. The most recent designs have dealt with high efficiency or dual band configurations. This report will summarize the many advances of the past few years, and will provide some parametric design tradeoffs.

  4. Growth and characterization of zinc oxide and PZT films for micromachined acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Yoon, Sang Hoon

    The ability to detect the presence of low concentrations of harmful substances, such as biomolecular agents, warfare agents, and pathogen cells, in our environment and food chain would greatly advance our safety, provide more sensitive tools for medical diagnostics, and protect against terrorism. Acoustic wave (AW) devices have been widely studied for such applications due to several attractive properties, such as rapid response, reliability, portability, ease of use, and low cost. The principle of these sensors is based on a fundamental feature of the acoustic wave that is generated and detected by a piezoelectric material. The performance of the device, therefore, greatly depends on the properties of piezoelectric thin film. The required properties include a high piezoelectric coefficient and high electromechanical coefficients. The surface roughness and the mechanical properties, such as Young's modulus and hardness, are also factors that can affect the wave propagation of the device. Since the film properties are influenced by the structure of the material, understanding thin film structure is very important for the design of high-performance piezoelectric MEMS devices for biosensor applications. In this research, two piezoelectric thin film materials were fabricated and investigated. ZnO films were fabricated by CSD (Chemical Solution Deposition) and sputtering, and PZT films were fabricated by CSD only. The process parameters for solution derived ZnO and PZT films, such as the substrate type, the effect of the chelating agent, and heat treatment, were studied to find the relationship between process parameters and thin film structure. In the case of the sputtered ZnO films, the process gas types and their ratio, heat treatment in situ, and post deposition were investigated. The key results of systematic experiments show that the combined influence of chemical modifiers and substrates in chemical solution deposition have an effect on the crystallographic

  5. A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument

    NASA Astrophysics Data System (ADS)

    Bryan, Sean; Ade, Peter; Amiri, Mandana; Benton, Steven; Bihary, Richard; Bock, James; Bond, J. Richard; Chiang, H. Cynthia; Contaldi, Carlo; Crill, Brendan; Dore, Olivier; Elder, Benjamin; Filippini, Jeffrey; Fraisse, Aurelien; Gambrel, Anne; Gandilo, Natalie; Gudmundsson, Jon; Hasselfield, Matthew; Halpern, Mark; Hilton, Gene; Holmes, Warren; Hristov, Viktor; Irwin, Kent; Jones, William; Kermish, Zigmund; Lawrie, Craig; MacTavish, Carrie; Mason, Peter; Megerian, Krikor; Moncelsi, Lorenzo; Montroy, Thomas; Morford, Tracy; Nagy, Johanna; Netterfield, C. Barth; Padilla, Ivan; Rahlin, Alexandra S.; Reintsema, Carl; Riley, Daniel C.; Ruhl, John; Runyan, Marcus; Saliwanchik, Benjamin; Shariff, Jamil; Soler, Juan; Trangsrud, Amy; Tucker, Carole; Tucker, Rebecca; Turner, Anthony; Wen, Shyang; Wiebe, Donald; Young, Edward

    2016-01-01

    We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1∘. The system performed well in Spider during its successful 16 day flight.

  6. Comparison of birefringent electric split-ring resonator and meanderline structures as quarter-wave plates at terahertz frequencies.

    PubMed

    Strikwerda, Andrew C; Fan, Kebin; Tao, Hu; Pilon, Daniel V; Zhang, Xin; Averitt, Richard D

    2009-01-05

    We have fabricated a quarter-wave plate from a single layer of birefringent electric split-ring resonators (ELC). For comparison, an appropriately scaled double layer meanderline structure was fabricated. At the design frequency of 639 GHz, the ELC structure achieves 99.9% circular polarization while the meanderline achieves 99.6%. The me-anderline displays a larger bandwidth of operation, attaining over 99% circular polarization from 615 - 743 GHz, while the ELC achieves 99% from 626 - 660 GHz. However, both are broad enough for use with CW sources making ELCs a more attractive choice due to the ease of fabrication. Both samples are free standing with a total thickness of 70 microm for the meanderline structure and a mere 20 microm for the ELC highlighting the large degree of birefringence exhibited with metamaterial structures.

  7. A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument.

    PubMed

    Bryan, Sean; Ade, Peter; Amiri, Mandana; Benton, Steven; Bihary, Richard; Bock, James; Bond, J Richard; Chiang, H Cynthia; Contaldi, Carlo; Crill, Brendan; Dore, Olivier; Elder, Benjamin; Filippini, Jeffrey; Fraisse, Aurelien; Gambrel, Anne; Gandilo, Natalie; Gudmundsson, Jon; Hasselfield, Matthew; Halpern, Mark; Hilton, Gene; Holmes, Warren; Hristov, Viktor; Irwin, Kent; Jones, William; Kermish, Zigmund; Lawrie, Craig; MacTavish, Carrie; Mason, Peter; Megerian, Krikor; Moncelsi, Lorenzo; Montroy, Thomas; Morford, Tracy; Nagy, Johanna; Netterfield, C Barth; Padilla, Ivan; Rahlin, Alexandra S; Reintsema, Carl; Riley, Daniel C; Ruhl, John; Runyan, Marcus; Saliwanchik, Benjamin; Shariff, Jamil; Soler, Juan; Trangsrud, Amy; Tucker, Carole; Tucker, Rebecca; Turner, Anthony; Wen, Shyang; Wiebe, Donald; Young, Edward

    2016-01-01

    We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1(∘). The system performed well in Spider during its successful 16 day flight.

  8. Development of a Highly Portable Plate Loading Device and In Situ Modulus Measurements in Weak Rock Masses

    NASA Astrophysics Data System (ADS)

    Kallu, Raj R.; Keffeler, Evan R.; Watters, Robert J.; Warren, Sean N.

    2016-02-01

    In recent years, underground mines in Nevada are increasingly exploiting in weak mineralized zones at greater depths that are intensely fractured and highly altered. The mechanical behavior of these rock masses ranges between weak rock and very stiff soil. A common limitation for design of underground mining excavations in these types of rock masses is absence of in situ geotechnical data. This limitation is generally overcome by estimating in situ mechanical behavior from empirical relationships so that the continuum-based numerical methods can be used to evaluate ground support designs. Because of the cost, time, and specialized equipment involved, historically in situ tests have not been performed in these underground mines. Predictive rock mass modulus relationships that are currently available in the literature are derived from field testing of predominantly good-quality rock masses. Consequently, there is limited confidence in using these models for rock masses with Rock Mass Ratings less than 45. In order to overcome some of these limitations, a portable plate loading device (PPLD) was designed and fabricated. The PPLD allows one to perform low cost and relatively quick in situ deformability tests to be performed on weak rock masses in underground mines. Test procedures and data reduction methods were developed to limit potential sources of error associated with the PPLD test. A total of fourteen plate loading tests were performed in weak rock masses at two different active underground mines in Nevada, USA. The resulting the test data were compared to eight published empirical rock mass modulus relationships to determine which, if any, of these relationships are sufficiently accurate for estimating modulus in similar geotechnical conditions. Only two of these relationships were found to be sufficient for first-order estimations of in situ modulus.

  9. Three-mode coupling of symmetric and antisymmetric Lamb waves in plates with finite corrugations.

    PubMed

    Asfar, Omar; Morvan, Bruno; Izbicki, Jean-Louis

    2015-03-01

    Coupled-mode equations governing the amplitudes of the higher-order symmetric Lamb modes S1 and S2 with the antisymmetric mode A2 in an infinite elastic plate with sinusoidal surface corrugation over a finite length are obtained via multiple-scales analysis. This phenomenon of threemode coupling is observed when the wavenumbers k(s1) and k(s2) of the symmetric modes and k(A2) of the antisymmetric mode satisfy the simultaneous resonance conditions k(s1) - k(A2) = k(w) and k(A2) - k(s2) = k(w), where k(w) is the wavenumber of the sinusoidal corrugation. Near resonance, the coupled amplitude equations are solved exactly as an initial-value problem and it is seen that the modes are transmitted through the grating without reflection. Complete conversion from the symmetric modes into the antisymmetric mode is observed at periodic intervals along the grating when the resonance conditions are exactly satisfied. The effect of detuning away from resonance also shows propagation without reflection with periodic energy exchange. In the latter case, the modes couple without complete conversion. This phenomenon of mode conversion is confirmed by the results of an experiment on an aluminum plate with a triangular grating excited with the S2 symmetric mode at 2.7 MHz.

  10. Printed circuit board impedance matching step for microwave (millimeter wave) devices

    DOEpatents

    Pao, Hsueh-Yuan; Aguirre, Jerardo; Sargis, Paul

    2013-10-01

    An impedance matching ground plane step, in conjunction with a quarter wave transformer section, in a printed circuit board provides a broadband microwave matching transition from board connectors or other elements that require thin substrates to thick substrate (>quarter wavelength) broadband microwave (millimeter wave) devices. A method of constructing microwave and other high frequency electrical circuits on a substrate of uniform thickness, where the circuit is formed of a plurality of interconnected elements of different impedances that individually require substrates of different thicknesses, by providing a substrate of uniform thickness that is a composite or multilayered substrate; and forming a pattern of intermediate ground planes or impedance matching steps interconnected by vias located under various parts of the circuit where components of different impedances are located so that each part of the circuit has a ground plane substrate thickness that is optimum while the entire circuit is formed on a substrate of uniform thickness.

  11. Analysis and Synthesis of Leaky-Wave Devices in Planar Technology

    NASA Astrophysics Data System (ADS)

    Martinez Ros, Alejandro Javier

    The work developed along this doctoral thesis has been focused on the analysis and synthesis of microwave devices in planar technology. In particular, several types of devices based on the radiation mechanism of leaky waves have been studied. Typically, the radiation properties in leaky-wave devices are determined by the complex propagation constant of the leaky mode, wherein the phase constant is responsible for the pointing angle and the leakage rate for the intensity of the radiated fields. In this manner, by controlling both amplitude and phase of the leaky mode, an effective control over the device's radiation diagram can be obtained. Moreover, with the purpose of efficiently obtaining the leaky mode's radiation properties as function of the main geometrical parameters of the structure, several modal tools based on the transverse resonance analysis of the structure have been performed. In order to demonstrate this simultaneous control over the complex propagation constant in planar technology, several types of leaky-wave devices, including antennas (LWAs), multiplexors and near-field focusing systems, have been designed and manufactured in the technology of substrate integrated waveguide (SIW). This recently proposed technology, allows the design of devices based on classical waveguide technology with standard manufacturing techniques used for printed circuit board (PCB) designs. In this way, most of the parts that form a communication system can be integrated into a single substrate, thus reducing its cost and providing a more robust and compact device, which has less losses compared to other planar technologies such as the microstrip. El trabajo llevado a cabo durante la realizacion de esta tesis doctoral, se ha centrado en el analisis y sintesis de dispositivos de microondas en tecnologia planar. En concreto, se han estudiado diferentes tipos de dispositivos basados en radiacion por ondas de fuga "leaky waves", en los cuales las propiedades de radiacion

  12. Modeling seismic wave propagation across the European plate: structural models and numerical techniques, state-of-the-art and prospects

    NASA Astrophysics Data System (ADS)

    Morelli, Andrea; Danecek, Peter; Molinari, Irene; Postpischl, Luca; Schivardi, Renata; Serretti, Paola; Tondi, Maria Rosaria

    2010-05-01

    Together with the building and maintenance of observational and data banking infrastructures - i.e. an integrated organization of coordinated sensor networks, in conjunction with connected data banks and efficient data retrieval tools - a strategic vision for bolstering the future development of geophysics in Europe should also address the essential issue of improving our current ability to model coherently the propagation of seismic waves across the European plate. This impacts on fundamental matters, such as correctly locating earthquakes, imaging detailed earthquake source properties, modeling ground shaking, inferring geodynamic processes. To this extent, we both need detailed imaging of shallow and deep earth structure, and accurate modeling of seismic waves by numerical methods. Our current abilities appear somewhat limited, but emerging technologies may enable soon a significant leap towards better accuracy and reliability. To contribute to this debate, we present here the state-of-the-art of knowledge of earth structure and numerical wave modeling in the European plate, as the result of a comprehensive study towards the definition of a continental-scale reference model. Our model includes a description of crustal structure (EPcrust) merging information deriving from previous studies - large-scale compilations, seismic prospection, receiver functions, inversion of surface wave dispersion measurements and Green functions from noise correlation. We use a simple description of crustal structure, with laterally-varying sediment and cristalline layers thickness, density, and seismic parameters. This a priori crustal model improves the overall fit to observed Bouguer anomaly maps over CRUST2.0. The new crustal model is then used as a constraint in the inversion for mantle shear wave speed, based on fitting Love and Rayleigh surface wave dispersion. The new mantle model sensibly improves over global S models in the imaging of shallow asthenospheric (slow) anomalies

  13. Model-Based IN SITU Parameter Estimation of Ultrasonic Guided Waves in AN Isotropic Plate

    NASA Astrophysics Data System (ADS)

    Hall, James S.; Michaels, Jennifer E.

    2010-02-01

    Most ultrasonic systems employing guided waves for flaw detection require information such as dispersion curves, transducer locations, and expected propagation loss. Degraded system performance may result if assumed parameter values do not accurately reflect the actual environment. By characterizing the propagating environment in situ at the time of test, potentially erroneous a priori estimates are avoided and performance of ultrasonic guided wave systems can be improved. A four-part model-based algorithm is described in the context of previous work that estimates model parameters whereby an assumed propagation model is used to describe the received signals. This approach builds upon previous work by demonstrating the ability to estimate parameters for the case of single mode propagation. Performance is demonstrated on signals obtained from theoretical dispersion curves, finite element modeling, and experimental data.

  14. Non-Reflecting Regions for Finite Difference Methods in Modeling of Elastic Wave Propagation in Plates

    NASA Technical Reports Server (NTRS)

    Kishoni, Doron; Taasan, Shlomo

    1994-01-01

    Solution of the wave equation using techniques such as finite difference or finite element methods can model elastic wave propagation in solids. This requires mapping the physical geometry into a computational domain whose size is governed by the size of the physical domain of interest and by the required resolution. This computational domain, in turn, dictates the computer memory requirements as well as the calculation time. Quite often, the physical region of interest is only a part of the whole physical body, and does not necessarily include all the physical boundaries. Reduction of the calculation domain requires positioning an artificial boundary or region where a physical boundary does not exist. It is important however that such a boundary, or region, will not affect the internal domain, i.e., it should not cause reflections that propagate back into the material. This paper concentrates on the issue of constructing such a boundary region.

  15. Transversal and longitudinal mode selections in double-corrugation coaxial slow-wave devices

    SciTech Connect

    Ge Xingjun; Zhong Huihuang; Qian Baoliang; Liu Lie; Liu Yonggui; Li Limin; Shu Ting; Zhang Jiande

    2009-06-15

    To reduce the dimensions of relativistic backward wave oscillators (RBWOs) operating in the low frequency regime of less than 2 GHz, the theory of transversal and longitudinal mode selections are introduced in this paper. The transversal mode selection is achieved using the property of ''surface wave'' of the coaxial slow-wave structure (SWS) to excite the quasi transverse electromagnetic (quasi-TEM) mode without the higher transverse magnetic (TM) modes and it is proved that the coaxial SWS may decrease the transversal dimension of the SWS sections. In addition, the S-parameter method is employed to investigate the longitudinal resonant characteristic of the finite-length SWS, and the scheme of longitudinal mode selection is put forward. It is proposed that the introduction of a well-designed coaxial extractor to slow-wave devices can help to achieve the longitudinal mode selection and reduce the period number of the SWS, which not only can make the devices more compact, but also can avoid the destructive competition between various longitudinal modes, therefore can enhance the efficiency and stabilize the frequency. To sum up, the physical mechanisms of transversal and longitudinal mode selections ensure that the microwave is produced with a single mode and a narrow band. Based on the above discussion, a compact L-band coaxial RBWO is investigated and optimized in detail with the particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). In simulation, the L-band coaxial RBWO, driven by a 700 kV, 11 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave of quasi-TEM mode is generated with an average power of 2.66 GW, a frequency of 1.6 GHz, and power conversion efficiency of 34.5% in durations of 30-60 ns.

  16. Channelling of elastic waves in an eight-ply fiber composite plate

    NASA Astrophysics Data System (ADS)

    Green, E. Rhian; Green, W. A.

    2000-05-01

    The paper is concerned with the channeling of elastic waves propagating in an eight-ply quasi-isotropic laminate arising from impulsive line sources of dislocation located at each of the seven interfaces in turn. The laminate is composed of identical layers of fiber composite material which is modeled as a transversely isotropic continuum with the axis of transverse isotropy along the fiber direction. The line sources set up a straight crested wave travelling along the laminate in the direction normal to the load line and the elastodynamic equations within each layer are solved by taking Laplace transforms with respect to time and Fourier transforms with response to the co-ordinate in the propagation direction. The resulting system of six first order differential equations in each layer are solved to obtain the transforms of the displacement and stress components throughout the laminate. The time history of any displacement or stress component at any location may then be recovered by numerical inversion of the double transform. This numerical inversion involves a summation over the normal modes of Rayleigh-Lamb waves and in an earlier paper, it has been shown that for some locations of the line source, the contribution to the upper surface normal displacement from the fundamental mode is swamped by contributions from some of the higher modes. Here, details are presented of the displacement variation through the laminate associated with the different Rayleigh-Lamb modes showing how the disturbance is channelled in some layers for specific locations of the source line.

  17. Analysis of Electro-Optic Materials Properties on Guided Wave Devices

    DTIC Science & Technology

    1992-12-16

    AD-A262 787 APPLIED RESEARCH, INC, ANALYSIS OF ELECTRO - OPTIC MATERIALS PROPERTIES ON GUIDED WAVE DEVICES FINAL REPORT DTI 6700 ODYSSEY DR HUNTSVILLE...ALABAMA 35814-1220 s IMAR1893 APPROVED FOR PUKIC RE’.EASE DISTRIBUTION UNLIMlITED Applied Research Inc. ARI/92iR-048Z ANALYSIS OF ELECTRO - OPTIC MATERIALS...uNiT ATTN: Dr. 2aul Ashley-AMSMI-RD-~WS--CM ELEMENT NO 4 NO IAr SSiON No t1I TI TLE iciup SeawIfy 0Mft*G’I Analysis of Electro - optic Materials

  18. In situ high-temperature characterization of AlN-based surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Aubert, Thierry; Bardong, Jochen; Legrani, Ouarda; Elmazria, Omar; Badreddine Assouar, M.; Bruckner, Gudrun; Talbi, Abdelkrim

    2013-07-01

    We report on in situ electrical measurements of surface acoustic wave delay lines based on AlN/sapphire structure and iridium interdigital transducers between 20 °C and 1050 °C under vacuum conditions. The devices show a great potential for temperature sensing applications. Burnout is only observed after 60 h at 1050 °C and is mainly attributed to the agglomeration phenomena undergone by the Ir transducers. However, despite the vacuum conditions, a significant oxidation of the AlN film is observed, pointing out the limitation of the considered structure at least at such extreme temperatures. Original structures overcoming this limitation are then proposed and discussed.

  19. Guided lamb waves and L-SAFT processing technique for enhanced detection and imaging of corrosion defects in plates with small depth-to-wavelength ratio.

    PubMed

    Sicard, René; Chahbaz, Ahmad; Goyette, Jacques

    2004-10-01

    The Lamb synthetic aperture focusing technique (L-SAFT) imaging algorithm in the Fourier domain is used to produce Lamb wave imaging in plates while considering the wave dispersive properties. This artificial focusing technique produces easy-to-interpret, modified B-scan type images of Lamb wave inspection results. The high level of sensitivity of Lamb waves combined with the L-SAFT algorithm allows one to detect and to produce images of corrosion defects with small depth-to-wavelength ratio. This paper briefly presents the formulated L-SAFT algorithm used for Lamb waves and, in more details, some experimental results obtained on simulated and real corrosion pits, demonstrating the benefit of combining L-SAFT with pulse-echo Lamb wave inspection. The obtained images of the real corrosion defects showed detection of pits with a depth-to-wavelength ratio of approximately 2/11.

  20. Development and Demonstration of a Device to Determine Thrust by Measuring the Force on a Target Plate in the Exhaust of a Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Chavers, Greg; Chang-Diaz, Franklin

    2004-01-01

    A device has been developed to measure the force on a target plate by an impacting beam of charged and neutral particles. This device, an impact thrust stand, was developed to allow thrusters at low TRL, levels to be easily tested without the expense of developing a flight prototype of the thruster to be placed on a conventional thrust stand. The impact thrust stand was developed for the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) but has been tested and calibrated using several devices including Hall thrusters. The calibration and comparison of the impact thrust stand against conventional thrust stands will be discussed in this paper.

  1. High-frequency surface acoustic wave device based on thin-film piezoelectric interdigital transducers

    SciTech Connect

    Sarin Kumar, A.K.; Paruch, P.; Triscone, J.-M.; Daniau, W.; Ballandras, S.; Pellegrino, L.; Marre, D.; Tybell, T.

    2004-09-06

    Using high-quality epitaxial c-axis Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} films grown by off-axis magnetron sputtering onto metallic (001) Nb-doped SrTiO{sub 3} substrates, a nonconventional thin-film surface acoustic wave device based on periodic piezoelectric transducers was realized. The piezoelectric transducers consist of a series of ferroelectric domains with alternating polarization states. The artificial modification of the ferroelectric domain structure is performed by using an atomic force microscope tip as a source of electric field, allowing local switching of the polarization. Devices with 1.2 and 0.8 {mu}m wavelength, defined by the modulation period of the polarization, and corresponding to central frequencies in the range 1.50-3.50 GHz have been realized and tested.

  2. Acoustofluidics and whole-blood manipulation in surface acoustic wave counterflow devices.

    PubMed

    Travagliati, Marco; Shilton, Richie J; Pagliazzi, Marco; Tonazzini, Ilaria; Beltram, Fabio; Cecchini, Marco

    2014-11-04

    On-chip functional blocks for sample preprocessing are necessary elements for the implementation of fully portable micrototal analysis systems (μTAS). We demonstrate and characterize the microparticle and whole-blood manipulation capabilities of surface acoustic wave (SAW) driven counterflow micropumps. The motion of suspended cells in this system is governed by the two dominant acoustic forces associated with the scattered SAW (of wavelength λf): acoustic-radiation force and acoustic-streaming Stokesian drag force. We show that by reducing the microchannel height (h) beyond a threshold value the balance of these forces is shifted toward the acoustic-radiation force and that this yields control of two different regimes of microparticle dynamics. In the regime dominated by the acoustic radiation force (h ≲ λf), microparticles are collected in the seminodes of the partial standing sound-wave arising from reflections off microchannel walls. This enables the complete separation of plasma and corpuscular components of whole blood in periodical predetermined positions without any prior sample dilution. Conversely, in the regime dominated by acoustic streaming (h ≫ λf), the microbeads follow vortical streamlines in a pattern characterized by three different phases during microchannel filling. This makes it possible to generate a cell-concentration gradient within whole-blood samples, a behavior not previously reported in any acoustic-streaming device. By careful device design, a new class of SAW pumping devices is presented that allows the manipulation and pretreatment of whole-blood samples for portable and integrable biological chips and is compatible with hand-held battery-operated devices.

  3. Separation of biological cells in a microfluidic device using surface acoustic waves (SAWs)

    NASA Astrophysics Data System (ADS)

    Ai, Ye; Marrone, Babetta L.

    2014-03-01

    In this study, a surface acoustic wave (SAW)-based microfluidic device has been developed to separate heterogeneous particle or cell mixtures in a continuous flow using acoustophoresis. The microfluidic device is comprised of two components, a SAW transducer and a microfluidic channel made of polydimethylsiloxane (PDMS). The SAW transducer was fabricated by patterning two pairs of interdigital electrodes on a lithium niobate (LiNbO3) piezoelectric substrate. When exciting the SAW transducer by AC signals, a standing SAW is generated along the cross-section of the channel. Solid particles immersed in the standing SAW field are accordingly pushed to the pressure node arising from the acoustic radiation force acting on the particles, referring to the acoustic particle-focusing phenomenon. Acoustic radiation force highly depends on the particle properties, resulting in different acoustic responses for different types of cells. A numerical model, coupling the piezoelectric effect in the solid substrate and acoustic pressure in the fluid, was developed to provide a better understanding of SAW-based particle manipulation. Separation of two types of fluorescent particles has been demonstrated using the developed SAW-based microfluidic device. An efficient separation of E. coli bacteria from peripheral blood mononuclear cell (PBMC) samples has also been successfully achieved. The purity of separated E. coli bacteria and separated PBMCs were over 95% and 91%, respectively, obtained by a flow cytometric analysis. The developed microfluidic device can efficiently separate E. coli bacteria from biological samples, which has potential applications in biomedical analysis and clinical diagnosis.

  4. Simulations of Thermal Quantum Annealing on the D-Wave Device

    NASA Astrophysics Data System (ADS)

    Albash, Tameem; Vinci, Walter; Mishra, Anurag; Warburton, Paul; Lidar, Daniel

    2014-03-01

    We report on classical and quantum simulations to model the open-system dynamics of the D-Wave programmable annealer as we increase the thermal noise level on the device. We consider three models for the device: (1) the evolution is described by a classical simulated annealer acting on the final-time Ising Hamiltonian; (2) the evolution is described by an O(3) model with a time-dependent Hamiltonian; (3) the evolution is described by a quantum adiabatic Markovian master equation with a time dependent Hamiltonian. We increase the thermal noise level by either decreasing the overall energy scale of the final-time Ising Hamiltonian or by increasing the total annealing time. Using a benchmark Ising Hamiltonian, we show that all three models give distinct predictions for the behavior of the system as the noise level on the device is increased. The only model that captures the results of the device over the entire range of noise levels studied is the quantum master equation, ruling out the two classical models considered here.

  5. Numerical Simulation of Inlet Bleed with Circular Holes on Plate Under Shock-Wave/Boundary-Layer Interactions

    NASA Technical Reports Server (NTRS)

    Chyu, Wei J.; Rimlinger, Mark J.; Shih, Tom I.-P.

    1994-01-01

    A numerical study was performed to investigate the shock-wave/boundary-layer interactions on a flat plate with bleed through one or more circular holes that vent into a plenum. The bleed-hole patterns considered for the study include in-line multiple holes and staggered multiple-row holes that are configured to simulate the patterns used in inlet bleed systems of high performance aircraft. The focus of the study was to examine how the bleed through multiple holes affect bleed rate and the pressure and Mach number distributions. Since the bleed performance was found sensitive to the change in bleed conditions, a computational procedure was developed to give a good turnaround computational time for parametric studies involving changes in bleed hole geometry and the structure of shock-wave/boundary-layer flowfield. The procedure includes the grid-generation methodology and the flow simulation with solutions from the Navier-Stokes equations. The computational techniques permit analysis of complex bleed systems and make possible the investigation of a broader range of design variables associated with inlet bleed operation.

  6. Clinical comparison of Zero-profile interbody fusion device and anterior cervical plate interbody fusion in treating cervical spondylosis

    PubMed Central

    Yan, Bin; Nie, Lin

    2015-01-01

    Objective: the aim of the study was to compare the clinical effect of Zero-profile interbody fusion device (Zero-P) with anterior cervical plate interbody fusion system (PCB) in treating cervical spondylosis. Methods: a total of 98 patients with cervical spondylosis (110 segments) in February 2011 to January 2013 were included in our hospital. All participants were randomly divided into observation group and control group with 49 cases in each group. The observation group was treated with Zero-P, while the control group received PCB treatment. Comparison of the two groups in neurological function score (JOA), pain visual analogue scale (VAS), the neck disability index (NDI), quality of life score (SF-36) and cervical curvature (Cobb angle) change were recorded and analyzed before and after treatment. Results: The observation group was found with 90% excellent and good rate, which was higher than that of the control group (80%). Dysphagia rate in observational group was 16.33% (8/49), which was significantly less than that in control group (46.94%). Operation time and bleeding volume in the observation group was less than those in control group. Postoperative improvements of JOA score, VAS score, and NDI in observational group were also significantly better than that in control group (P<0.05). Conclusion: The clinical effect of Zero-P and PCB for the treatment of cervical spondylosis was quite fair, but Zero-P showed a better therapeutic effect with improvement of life quality. PMID:26550337

  7. Interfacial slip on a transverse-shear mode acoustic wave device

    NASA Astrophysics Data System (ADS)

    Ellis, Jonathan S.; Hayward, Gordon L.

    2003-12-01

    This article describes a mathematical relationship between the slip parameter α and the slip length b for a slip boundary condition applied to the transverse-shear model for a quartz-crystal acoustic wave device. The theory presented here reduces empirical determination of slip to a one-parameter fit. It shows that the magnitude and phase of the slip parameter, which describes the relative motion of the surface and liquid in the transverse-shear model, can be linked to the slip length. Furthermore, the magnitude and phase of the slip parameter are shown to depend on one another. An experiment is described to compare the effects of liquid-surface affinity on the resonant properties of a transverse-shear mode wave device by applying different polar and nonpolar liquids to surfaces of different polarity. The theory is validated with slip values determined from the transverse-shear model and compared to slip length values from literature. Agreement with literature values of slip length is within one order of magnitude.

  8. Note: Experimental study on feasibility of a flexural traveling wave piezoelectric device for biomedical micro-electromechanical system.

    PubMed

    Marinozzi, F; Bini, F

    2014-06-01

    The aim of this paper is to experimentally show that polyvinylidene fluoride biaxially oriented in bimorph configuration is a suitable flexural traveling wave device. Piezoelectric ceramic is promising, however the lack biocompatibility is the main drawback for biomedical micro-electromechanical system. A prototype of 20 mm diameter was designed, constructed, and tested via an optical method. A first investigation was performed on two standing waves which were excited to generate the traveling wave. The findings of amplitude and phase have revealed a B31 vibration mode at 7.2 kHz and a maximum amplitude of roughly 40 nm. The flexural traveling wave was confirmed experimentally.

  9. On Locally Deformed Stratified Media : Applications To Rough Surfaces And Guided Wave Devices With Corrugated Boundaries

    NASA Astrophysics Data System (ADS)

    Petit, R.; Hugonin, J. P.

    1984-12-01

    In 1977, we published two papers on the diffraction of electromagnetic waves at a locally deformed flat boundary surface and at a locally deformed plane wave-guide. Since this time, an important theoretical and numerical study of locally deformed stratified media has been carried out in our lab. This study has been summarized three years ago in the J.O.S.A. and it has been presented last year as a thesis dissertation. But both the J.O.S.A. paper and the thesis are difficult to read for non specialists because the involved mathematics are rather subtle and, at least, tedious for experimenters. In other words, an important work has been done, which seems to be unknown to most of "practical people". We thought that a SPIE meeting is a good opportunity to cure this regrettable situation. A computer program is now available which probably might be very useful for those working on rough dielectric surfaces and on guided wave devices with corrugated boundaries. We would like to present to engineers the possibilities and the limits of this big computer code called hereafter Program (P)

  10. Implementing wavelet inverse-transform processor with surface acoustic wave device.

    PubMed

    Lu, Wenke; Zhu, Changchun; Liu, Qinghong; Zhang, Jingduan

    2013-02-01

    The objective of this research was to investigate the implementation schemes of the wavelet inverse-transform processor using surface acoustic wave (SAW) device, the length function of defining the electrodes, and the possibility of solving the load resistance and the internal resistance for the wavelet inverse-transform processor using SAW device. In this paper, we investigate the implementation schemes of the wavelet inverse-transform processor using SAW device. In the implementation scheme that the input interdigital transducer (IDT) and output IDT stand in a line, because the electrode-overlap envelope of the input IDT is identical with the one of the output IDT (i.e. the two transducers are identical), the product of the input IDT's frequency response and the output IDT's frequency response can be implemented, so that the wavelet inverse-transform processor can be fabricated. X-112(0)Y LiTaO(3) is used as a substrate material to fabricate the wavelet inverse-transform processor. The size of the wavelet inverse-transform processor using this implementation scheme is small, so its cost is low. First, according to the envelope function of the wavelet function, the length function of the electrodes is defined, then, the lengths of the electrodes can be calculated from the length function of the electrodes, finally, the input IDT and output IDT can be designed according to the lengths and widths for the electrodes. In this paper, we also present the load resistance and the internal resistance as the two problems of the wavelet inverse-transform processor using SAW devices. The solutions to these problems are achieved in this study. When the amplifiers are subjected to the input end and output end for the wavelet inverse-transform processor, they can eliminate the influence of the load resistance and the internal resistance on the output voltage of the wavelet inverse-transform processor using SAW device.

  11. Numerical modelling of seismic wave propagation along the plate contact of the Hellenic Subduction Zone-the influence of a deep subduction channel

    NASA Astrophysics Data System (ADS)

    Essen, Katja; Braatz, Mandy; Ceranna, Lars; Friederich, Wolfgang; Meier, Thomas

    2009-12-01

    We model seismic wave propagation from intermediate depth earthquakes in a subduction zone using a 2-D Chebyshev pseudospectral method. Particular attention is directed to the influence of a deep, low-viscosity subduction channel on top of the plate contact where metamorphic rocks may be exhumed by forced return flow. The study is motivated by observations of complicated dispersive and high-amplitude P- and S-wave trains in the forearc of the Hellenic Subduction Zone. The basic model is a subducted slab with a thin oceanic crust forming a low-velocity layer. Our model setup closely follows recent results on the structure of the Hellenic Subduction Zone obtained from receiver functions and surface wave studies. They exhibit an abrupt change of the dip of the downgoing slab at about 70 km depth. The subduction channel is modelled as a thin, wedge-shaped layer of intermediate seismic velocity above a slower oceanic crust and below a faster overlying mantle wedge. We also look into the effects of a continuous phase transition from basalt to eclogite in the subducted oceanic crust and near-surface crustal structures. In all models, wave propagation is characterized by dispersive guided channel waves trapped in the low-velocity subducted crust. They produce high-amplitude arrivals in the forearc. A fast guided wave train (gP) originates from the direct P wave and a slower one (gS) from the direct S wave. Guided waves are radiated into the overlying mantle where the dip of the slab is abruptly changing. Seismogram sections for models without a subduction channel typically show two spatially separated guided wave trains, one following the oceanic crust and one travelling more steeply towards the forearc high. A subduction channel above the plate contact enhances the radiation effect of gP waves at the slab bend due to the weaker velocity contrast and inhibits the separation of the wave trains. In models with additional near-surface crustal structures the wave field is

  12. The properties of thickness-twist (TT) wave modes in a rotated Y-cut quartz plate with a functionally graded material top layer.

    PubMed

    Wang, Bin; Qian, Zhenghua; Li, Nian; Sarraf, Hamid

    2016-01-01

    We propose the use of thickness-twist (TT) wave modes of an AT-cut quartz crystal plate resonator for measurement of material parameters, such as stiffness, density and material gradient, of a functionally graded material (FGM) layer on its surface, whose material property varies exponentially in thickness direction. A theoretical analysis of dispersion relations for TT waves is presented using Mindlin's plate theory, with displacement mode shapes plotted, and the existence of face-shear (FS) wave modes discussed. Through numerical examples, the effects of material parameters (stiffness, density and material gradient) on dispersion curves, cutoff frequencies and mode shapes are thoroughly examined, which can act as a theoretical reference for measurements of unknown properties of FGM layer.

  13. Near-field radiative heat transfer between metasurfaces: A full-wave study based on two-dimensional grooved metal plates

    NASA Astrophysics Data System (ADS)

    Dai, Jin; Dyakov, Sergey A.; Bozhevolnyi, Sergey I.; Yan, Min

    2016-09-01

    Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two two-dimensional grooved metal plates by a full-wave scattering approach. The enhancement originates from both transverse-magnetic spoof surface-plasmon polaritons and a series of transverse-electric bonding- and anti-bonding-waveguide modes at surfaces. The RHT spectrum is frequency selective and highly geometrically tailorable. Our simulation also reveals thermally excited nonresonant surface waves in constituent metallic materials may play a prevailing role for RHT at an extremely small separation between two metal plates, rendering metamaterial modes insignificant for the energy-transfer process.

  14. Relationship between compressional-wave velocity and porosity of sediments along subduction plate interface

    NASA Astrophysics Data System (ADS)

    Yamaguchi, M.; Hashimoto, Y.

    2012-12-01

    Evolution of physical properties of sediments along subduction interface has effects on wedge strength, wedge geometry, dewatering and dehydration processes, and seismic behavior. Sediments have initially more than 70% of porosity prior to subduction. Through underthrusting and accretion, porosity of sediments decreases by compaction and cementation to be lithified sediments. The purpose of this study is to understand evolution of physical properties from a state before subduction to a state within a wedge using a relationship between compressional-wave velocity and porosity. In this study, we obtained new data for sediments from a reference site in IODP NanTroSEIZE, Expedition 333. In addition to that, we have complied velocity-porosity relationships for the samples and also for previous studies from NanTroSEIZE (off Kumano) (Hashimoto et al., 2010, 2011), ODP Leg 190 (off Shikoku) (Hoffman and Tobin, 2004) and ODP Leg 170 (off Costa Rica) (Gettemy and Tobin, 2003). Velocity measurement procedure in this study to obtain new data is as following: Two pumps were used to control pore fluid pressure and confining pressure. The pore pressure of 1000kPa was kept under drained conditions. Confining (effective) pressure was increased stepwise in the measurements. Velocity measurements were conducted under isotropic pressure conditions. Confining pressure was pressurized in tens seconds and kept for more than 8 hours for next step to obtain equilibrium conditions between effective pressure and sediments strain. Lead zirconate titanate (PZT) shear wave transducers (500kHz) were used in a source-receiver pair to measure wave speed. Porosity and P-wave velocity ranges about 27 - 75% and 1.4 - 2.2 km/s in this study, respectively. In the comparison in Vp-porosity relationships between sedimetns from reference sites and others, sediments were classified into two, simply compacted sediments (reference site and slope sediments) and wedge sediments. Different trends in Vp

  15. Vanadium dioxide devices for terahertz wave modulation: a study of wire grid structures.

    PubMed

    Parrott, Edward P J; Han, Chunrui; Yan, Fei; Humbert, Georges; Bessaudou, Annie; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

    2016-05-20

    Vandium dioxide (VO2) shows promise as the basis for a terahertz wave modulator due to its phase transition properties. Its insulator-metal-transition (IMT) can be induced either through temperature changes, optically or electronically. Recently, a metal-VO2 wire grid structure was proposed which was able to increase the modulation depth (MD) from 0.65 to 0.9, suggesting that these simple metallic structures could greatly increase the difference in terahertz transmission for the insulating and metallic states of VO2 based structures. In this paper, we have found that the increase in MD decreases with increasing VO2 conductivity in the metallic state, resulting in a maximum modulation depth of approximately 0.95 for wire grid structures that preserves a high transmission in the insulating state. Surprisingly, we find that deposition of VO2 on top of metallic structures results in reduced performance. However, we find that devices based upon VO2 alone can achieve unexpectedly high performance. In this work we present a device with a switchable wire-grid polariser effect over a broadband frequency range (from 0.3 to 2 THz). To our knowledge this is the first such broadband metamaterial based solely on VO2. The ability to switch on a metamaterial property like this to produce a polarisation effect is very useful for future terahertz optical devices such as rotators and waveplates.

  16. Creation of cavitation activity in a microfluidic device through acoustically driven capillary waves.

    PubMed

    Tandiono; Ohl, Siew-Wan; Ow, Dave Siak-Wei; Klaseboer, Evert; Wong, Victor V T; Camattari, Andrea; Ohl, Claus-Dieter

    2010-07-21

    We present a study on achieving intense acoustic cavitation generated by ultrasonic vibrations in polydimethylsiloxane (PDMS) based microfluidic devices. The substrate to which the PDMS is bonded was forced into oscillation with a simple piezoelectric transducer attached at 5 mm from the device to a microscopic glass slide. The transducer was operated at 100 kHz with driving voltages ranging between 20 V and 230 V. Close to the glass surface, pressure and vibration amplitudes of up to 20 bar and 400 nm were measured respectively. It is found that this strong forcing leads to the excitation of nonlinear surface waves when gas-liquid interfaces are present in the microfluidic channels. Also, it is observed that nuclei leading to intense inertial cavitation are generated by the entrapment of gas pockets at those interfaces. Subsequently, cavitation bubble clusters with void fractions of more than 50% are recorded with high-speed photography at up to 250,000 frames/s. The cavitation clusters can be sustained through the continuous injection of gas using a T-junction in the microfluidic device.

  17. Vanadium dioxide devices for terahertz wave modulation: a study of wire grid structures

    NASA Astrophysics Data System (ADS)

    Parrott, Edward P. J.; Han, Chunrui; Yan, Fei; Humbert, Georges; Bessaudou, Annie; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

    2016-05-01

    Vandium dioxide (VO2) shows promise as the basis for a terahertz wave modulator due to its phase transition properties. Its insulator-metal-transition (IMT) can be induced either through temperature changes, optically or electronically. Recently, a metal-VO2 wire grid structure was proposed which was able to increase the modulation depth (MD) from 0.65 to 0.9, suggesting that these simple metallic structures could greatly increase the difference in terahertz transmission for the insulating and metallic states of VO2 based structures. In this paper, we have found that the increase in MD decreases with increasing VO2 conductivity in the metallic state, resulting in a maximum modulation depth of approximately 0.95 for wire grid structures that preserves a high transmission in the insulating state. Surprisingly, we find that deposition of VO2 on top of metallic structures results in reduced performance. However, we find that devices based upon VO2 alone can achieve unexpectedly high performance. In this work we present a device with a switchable wire-grid polariser effect over a broadband frequency range (from 0.3 to 2 THz). To our knowledge this is the first such broadband metamaterial based solely on VO2. The ability to switch on a metamaterial property like this to produce a polarisation effect is very useful for future terahertz optical devices such as rotators and waveplates.

  18. An exact analysis of surface acoustic waves in a plate of functionally graded materials.

    PubMed

    Gao, Liming; Wang, Ji; Zhong, Zheng; Du, Jianke

    2009-12-01

    Some traditional applications of structures and devices with homogeneous materials are being gradually replaced by functionally graded materials (FGM) with spatial variation of properties. The analysis of SAW propagating in FGM structures will be different primarily due to variations of material properties and resulting differential equations with variable coefficients. To provide an effective method and accurate results for the analysis of SAWs in FGM structures, we employed the Frobenius method as the only available method for a detailed analysis of SAW in materials with property variations in a linear pattern. Analytical examples are presented to demonstrate the effectiveness of the method and the effect of FGM on changes of surface displacements in SAW propagation.

  19. Vortex generation and wave-vortex interaction over a concave plate with roughness and suction

    NASA Technical Reports Server (NTRS)

    Bertolotti, Fabio

    1993-01-01

    The generation and amplification of vortices by surface homogeneities, both in the form of surface waviness and of wall-normal velocity, is investigated using the nonlinear parabolic stability equations. Transients and issues of algebraic growth are avoided through the use of a similarity solution as initial condition for the vortex. In the absence of curvature, the vortex decays as the square root of 1/x when flowing over streamwise aligned riblets of constant height, and grows as the square root of x when flowing over a corresponding streamwise aligned variation of blowing/suction transpiration velocity. However, in the presence of wall inhomogeneities having both streamwise and spanwise periodicity, the growth of the vortex can be much larger. In the presence of curvature, the vortex develops into a Gortler vortex. The 'direct' and 'indirect' interaction mechanisms possible in wave-vortex interaction are presented. The 'direct' interaction does not lead to strong resonance with the flow conditions investigated. The 'indirect' interaction leads to K-type transition.

  20. An optimal modeling of multidimensional wave digital filtering network for free vibration analysis of symmetrically laminated composite FSDT plates

    NASA Astrophysics Data System (ADS)

    Tseng, Chien-Hsun

    2015-02-01

    The technique of multidimensional wave digital filtering (MDWDF) that builds on traveling wave formulation of lumped electrical elements, is successfully implemented on the study of dynamic responses of symmetrically laminated composite plate based on the first order shear deformation theory. The philosophy applied for the first time in this laminate mechanics relies on integration of certain principles involving modeling and simulation, circuit theory, and MD digital signal processing to provide a great variety of outstanding features. Especially benefited by the conservation of passivity gives rise to a nonlinear programming problem (NLP) for the issue of numerical stability of a MD discrete system. Adopting the augmented Lagrangian genetic algorithm, an effective optimization technique for rapidly achieving solution spaces of NLP models, numerical stability of the MDWDF network is well received at all time by the satisfaction of the Courant-Friedrichs-Levy stability criterion with the least restriction. In particular, optimum of the NLP has led to the optimality of the network in terms of effectively and accurately predicting the desired fundamental frequency, and thus to give an insight into the robustness of the network by looking at the distribution of system energies. To further explore the application of the optimum network, more numerical examples are engaged in efforts to achieve a qualitative understanding of the behavior of the laminar system. These are carried out by investigating various effects based on different stacking sequences, stiffness and span-to-thickness ratios, mode shapes and boundary conditions. Results are scrupulously validated by cross referencing with early published works, which show that the present method is in excellent agreement with other numerical and analytical methods.

  1. The effect of nanocomposite polymeric layer on the radiation of antisymmetric zero-order Lamb wave in a piezoelectric plate contacting with liquid

    NASA Astrophysics Data System (ADS)

    Kuznetsova, I. E.; Zaitsev, B. D.; Borodina, I. A.; Shikhabudinov, A. M.; Teplykh, A. A.; Manga, E.; Feuillard, G.

    2013-06-01

    A nanocomposite polymeric layer is proposed to be used for increasing the efficiency of ultrasound radiation into the liquid by antisymmetric zero-order (A0) Lamb waves propagating in piezoelectric plates. The theoretical and experimental investigations of the influence of the nanocomposite polymeric layers on the efficiency and radiation angle of acoustic wave into liquid were carried out. It has been theoretically shown that the use of the layer of the polyethylene of low density with nanoparticles of cadmium sulfide of concentration 25% between the plate of 128YX LiNbO3 and water medium allows to increase the radiation attenuation on ˜1 dB/λ if the ratio of the thicknesses of the layer and plate is equal to 0.16 at the frequency of 1.3 MHz. The experimental data were in a good agreement with theoretical results. It has been also shown that the presence of nanocomposite film leads to the increase of the radiation angle of bulk acoustic wave in liquid and allows the effective operation of the radiator not only in the sweet water but also in salt one. The obtained results may be used for the development of effective radiators/receivers of acoustic waves in liquids for flow meters and for underwater communication systems.

  2. Ultrasonic probe deployment device for increased wave transmission and rapid area scan inspections

    DOEpatents

    DiMambro, Joseph [Placitas, NM; Roach, Dennis P [Albuquerque, NM; Rackow, Kirk A [Albuquerque, NM; Nelson, Ciji L [Albuquerque, NM; Dasch, Cameron J [Boomfield Hills, MI; Moore, David G [Albuquerque, NM

    2012-01-03

    An ultrasonic probe deployment device in which an ultrasound-transmitting liquid forms the portion of the ultrasonic wave path in contact with the surface being inspected (i.e., the inspection surface). A seal constrains flow of the liquid, for example preventing the liquid from surging out and flooding the inspection surface. The seal is not rigid and conforms to variations in the shape and unevenness of the inspection surface, thus forming a seal (although possibly a leaky seal) around the liquid. The probe preferably is held in place to produce optimum ultrasonic focus on the area of interest. Use of encoders can facilitate the production of C-scan area maps of the material being inspected.

  3. Ultrasonic probe deployment device for increased wave transmission and rapid area scan inspections

    DOEpatents

    DiMambro, Joseph; Roach, Dennis P; Rackow, Kirk A; Nelson, Ciji L; Dasch, Cameron J; Moore, David G

    2013-02-12

    An ultrasonic probe deployment device in which an ultrasound-transmitting liquid forms the portion of the ultrasonic wave path in contact with the surface being inspected (i.e., the inspection surface). A seal constrains flow of the liquid, for example preventing the liquid from surging out and flooding the inspection surface. The seal is not rigid and conforms to variations in the shape and unevenness of the inspection surface, thus forming a seal (although possibly a leaky seal) around the liquid. The probe preferably is held in place to produce optimum ultrasonic focus on the area of interest. Use of encoders can facilitate the production of C-scan area maps of the material being inspected.

  4. Resonant excitation of waves by a spiraling ion beam on the large plasma device

    NASA Astrophysics Data System (ADS)

    Tripathi, Shreekrishna

    2015-11-01

    The resonant interaction between energetic-ions and plasma waves is a fundamental topic of importance in the space, controlled magnetic-fusion, and laboratory plasma physics. We report new results on the spontaneous generation of traveling shear Alfvén waves and high-harmonic beam-modes in the lower-hybrid range of frequencies by an intense ion beam. In particular, the role of Landau and Doppler-shifted ion-cyclotron resonances (DICR) in extracting the free-energy from the ion-beam and destabilizing Alfvén waves was explored on the Large Plasma Device (LAPD). In these experiments, single and dual-species magnetized plasmas (n ~1010 -1012 cm-3, Te ~ 5.0-10.0 eV, B = 0.6-1.8 kG, He+ and H+ ions, 19.0 m long, 0.6 m diameter) were produced and a spiraling hydrogen ion beam (5-15 keV, 2-10 A, beam-speed/Alfvén-speed = 0.2-1.5, J ~ 50-150 mA/cm2, pitch-angle ~53°) was injected into the plasma. The interaction of the beam with the plasma was diagnosed using a retarding-field energy analyzer, three-axis magnetic-loop, and Langmuir probes. The resonance conditions for the growth of shear Alfvén waves were examined by varying the parameters of the ion-beam and ambient plasma. The experimental results demonstrate that the DICR process is particularly effective in exciting left-handed polarized shear Alfvén waves that propagate in the direction opposite to the ion beam. The high-harmonic beam modes were detected in the vicinity of the spiraling ion beam and contained more than 80 harmonics of Doppler-shifted gyro-frequency of the beam. Work jointly supported by US DOE and NSF and performed at the Basic Plasma Science Facility, UCLA.

  5. Seismic Tomography of the Southern California Plate Boundary Region from Noise-Based Rayleigh and Love Waves

    NASA Astrophysics Data System (ADS)

    Zigone, Dimitri; Ben-Zion, Yehuda; Campillo, Michel; Roux, Philippe

    2015-05-01

    We use cross-correlations of ambient seismic noise between pairs of 158 broadband and short-period sensors to investigate velocity structure over the top 5-10 km of the crust in the Southern California plate boundary region around the San Jacinto Fault Zone (SJFZ). From the 9-component correlation tensors associated with all station pairs we derive dispersion curves of Rayleigh and Love wave group velocities. The dispersion results are inverted first for Rayleigh and Love waves group velocity maps on a 1.5 × 1.5 km2 grid that includes portions of the SJFZ, the San Andreas Fault (SAF), and the Elsinore fault. We then invert these maps to 3D shear wave velocities in the top ~7 km of the crust. The distributions of the Rayleigh and Love group velocities exhibit 2θ azimuthal anisotropy with fast directions parallel to the main faults and rotations in complex areas. The reconstructed 3D shear velocity model reveals complex shallow structures correlated with the main geological units, and strong velocity contrasts across various fault sections along with low-velocity damage zones and basins. The SJFZ is marked by a clear velocity contrast with higher V s values on the NE block for the section SE of the San Jacinto basin and a reversed contrast across the section between the San Jacinto basin and the SAF. Velocity contrasts are also observed along the southern parts on the SAF and the Elsinore fault, with a faster southwest block in both cases. The region around the Salton Trough is associated with a significant low-velocity zone. Strong velocity reductions following flower-shape with depth are observed extensively around both the SJFZ and the SAF, and are especially prominent in areas of geometrical complexity. In particular, the area between the SJFZ and the SAF is associated with an extensive low-velocity zone correlated with diffuse seismicity at depth, and a similar pattern including correlation with deep diffuse seismicity is observed on a smaller scale in the

  6. The Characterization of Surface Acoustic Wave Devices Based on AlN-Metal Structures

    PubMed Central

    Shu, Lin; Peng, Bin; Li, Chuan; Gong, Dongdong; Yang, Zhengbing; Liu, Xingzhao; Zhang, Wanli

    2016-01-01

    We report in this paper on the study of surface acoustic wave (SAW) resonators based on an AlN/titanium alloy (TC4) structure. The AlN/TC4 structure with different thicknesses of AlN films was simulated, and the acoustic propagating modes were discussed. Based on the simulation results, interdigital transducers with a periodic length of 24 μm were patterned by lift-off photolithography techniques on the AlN films/TC4 structure, while the AlN film thickness was in the range 1.5–3.5 μm. The device performances in terms of quality factor (Q-factor) and electromechanical coupling coefficient (k2) were determined from the measure S11 parameters. The Q-factor and k2 were strongly dependent not only on the normalized AlN film thickness but also on the full-width at half-maximum (FWHM) of AlN (002) peak. The dispersion curve of the SAW phase velocity was analyzed, and the experimental results showed a good agreement with simulations. The temperature behaviors of the devices were also presented and discussed. The prepared SAW resonators based on AlN/TC4 structure have potential applications in integrated micromechanical sensing systems. PMID:27077864

  7. Polydimethylsiloxane-LiNbO3 surface acoustic wave micropump devices for fluid control into microchannels.

    PubMed

    Girardo, Salvatore; Cecchini, Marco; Beltram, Fabio; Cingolani, Roberto; Pisignano, Dario

    2008-09-01

    This paper presents prototypical microfluidic devices made by hybrid microchannels based on piezoelectric LiNbO(3) and polydimethylsiloxane. This system enables withdrawing micropumping by acoustic radiation in microchannels. The withdrawing configuration, integrated on chip, is here quantitatively investigated for the first time, and found to be related to the formation and coalescence dynamics of droplets within the microchannel, primed by surface acoustic waves. The growth dynamics of droplets is governed by the water diffusion on LiNbO(3), determining the advancement of the fluid front. Observed velocities are up to 2.6 mm s(-1) for 30 dBm signals applied to the interdigital transducer, corresponding to tens of nl s(-1), and the micropumping dynamics is described by a model taking into account an acoustic power exponentially decaying upon travelling along the microchannel. This straighforward and flexible micropumping approach is particularly promising for the withdrawing of liquids in lab-on-chip devices performing cycling transport of fluids and biochemical reactions.

  8. The propagation characteristics of the plate modes of acoustic emission waves in thin aluminum plates and thin graphite/epoxy composite plates and tubes. Ph.D. Thesis - Johns Hopkins Univ., 1991

    NASA Technical Reports Server (NTRS)

    Prosser, William H.

    1991-01-01

    Acoustic emission was interpreted as modes of vibration in plates. Classical plate theory was used to predict dispersion curves for the two fundamental modes and to calculate the shapes of flexural waveforms produced by vertical step function loading. There was good agreement between theoretical and experimental results for aluminum. Composite materials required the use of a higher order plate theory (Reissner-Mindlin) to get good agreement with the measured velocities. Four composite plates with different laminate stacking sequences were studied. The dispersion curves were determined from phase spectra of the time dependent waveforms. Plate modes were shown to be useful for determining the direction of source motion. Aluminum plates were loaded by breaking a pencil lead against their surface. By machining slots at angles to the plane of a plate, the direction in which the force acted was varied. Changing the source motion direction produced regular variations in the waveforms. To demonstrate applicability beyond simple plates, waveforms produced by lead breaks on a thin walled composite tube were also shown to be interpretable as plate modes. The tube design was based on the type of struts proposed for Space Station Freedom's trussed structures.

  9. Modelling of Optical Guided Wave Devices in Lithium Niobate Using Test Structures for Process Characterization

    NASA Astrophysics Data System (ADS)

    Wooten, Eddie Lynn

    This dissertation presents a study of the modelling of optical guided wave devices in LiNbO_3 with emphasis on experimental verification of the models. The goals are to identify the main sources of error in the modelling process, construct a model capable of achieving qualitative and quantitative accuracy, and develop a method of determining the correct set of input parameters to the model for a given fabrication process. The investigation is limited to mode interference type devices and the switching voltage is used as a basis for comparison. The finite element method is used for calculation of optical modes in waveguides with graded refractive index profiles. The integral equation method is used for calculation of the static electric field due to electrodes in a three layer anisotropic structure. It is proposed that the main source of error in the modelling process is not in the model itself, but in determining the correct input parameters to the model. The investigation of the input parameters focusses on a priori knowledge of the parameters and the sensitivity of the model to each parameter. The five parameters responsible for the largest errors in Ti:LiNbO_3 devices are identified as the Ti diffusion coefficients, the peak index change in the waveguides, the electrooptic coefficient, and the buffer layer dielectric constant. A method is presented for determining each of the selected parameters using a set of test devices fabricated on a single chip. The test set includes a planar waveguide, Mach-Zehnder modulators, and symmetrically perturbed directional couplers. Several sets of these devices have been fabricated using different fabrication conditions. The parameter values determined using this method compare favorably to those reported in the literature. The diffusion of Ti for x-cut crystals is found to be highly anisotropic, with the lateral diffusion length being about twice as large as the diffusion depth. The dependence of the diffusion lengths on

  10. Spin wave resonance and relaxation in microwave magnetic multilayer structures and devices

    NASA Astrophysics Data System (ADS)

    Wu, Cheng

    The continuous and increasing demand for higher frequency magnetic microwave structures triggered a tremendous development in the field of magnetization dynamics over the past decade. In order to develop smaller and faster devices, more efforts are required to achieve a better understanding of the complex magnetization precessional dynamics, the magnetization anisotropy, and the sources of spin scattering at the nanoscale. This thesis presents measurements of magnetic precession and relaxation dynamics in multilayer ferromagnetic films of CoFe/PtMn/CoFe in both frequency and time domain. First, we conducted the ferromagnetic resonance (FMR) measurements for samples with the ferromagnetic CoFe layer thicknesses varying from 10 A to 500 A. The magnetic anisotropic parameters were determined by rotating the field aligned axis with respect to the spectral field in the configurations of both in-plane and out-of-plane. Moreover, we identified a high-order standing spin wave in our spectra and found a "critical angle" in the multilayer samples. We included an effective surface anisotropy field to describe our results. This allows us to determine the exchange interaction stiffness in the CoFe layers. Next, we performed pump-probe Magneto-Optical Kerr Effect experiments in the multilayer films. Three precession modes were observed in the Voigt geometry. The modes are assigned to the exchange-dominated spin wave excitations and the non-homogeneous dipole mode. We developed a comprehensive model of the magnetic eigenmodes and their coupling to light to gain accurate values of the exchange, bulk and surface anisotropy constants. The results are consistent with those from the FMR measurements. Finally, the measured resonance linewidths of CoFe/PtMn/CoFe films were analyzed by the thickness dependence of the CoFe layers. We discussed the contribution of the Gilbert damping, two magnon scattering, as well as surface and interface to the FMR linewidth and concluded the two magnon

  11. Advances in nonlinear characterization of millimetre-wave devices for telecommunications

    NASA Astrophysics Data System (ADS)

    Parker, Anthony E.

    2007-12-01

    Field Effect Transistors exhibit a variety of complicated dynamic and nonlinear interactions that affect millimetre-wave devices used for telecommunications. The dynamics include self heating, bias dependent change in trapped charge, and variations due to impact ionization. These are feedback mechanisms that contribute to intermodulation as a memory effect does. A FET is better viewed as a nonlinear system with feedback, bias dependent rates, and high-order nonlinear conductance and charge storage with specific terminal to terminal interaction. Identifying and characterizing FET dynamics and linearity is a key step in the design process. Extraction of true intrinsic characteristics is an important first step to understanding the physics of trapping and heating within the device. Standard measurement techniques tend to derive access networks with an emphasis on scaling with layout geometry. The intrinsic device is then modelled as whatever is left after de-embedding the measurements. As such, the intrinsic model exhibits significant frequency dispersions and behaviour that is not easily related to the operation of the transistor. A correct determination of the access network reveals that the dispersions within the intrinsic data are related to physical process, such as heating and trapping. Recent work has been carried out to accurately implement trapping within a circuit simulator. This is key to correct prediction of intermodulation and bias dependence effects generated by a FET. It is shown that heating significantly affects trapping and is an important factor in the transient rate dependence of the characteristics. The implementation of trapping within a circuit model, and its consequences on linearity are explored.

  12. Application of Wave Propagation and Vibration-based Structural Health Monitoring Techniques to Friction Stir Welded Plate and Sandwich Honeycomb Panel

    NASA Astrophysics Data System (ADS)

    Sundararaman, S.; White, J. R.; Adams, D. E.; Jata, K. V.

    2007-03-01

    Wave propagation and vibration-based structural health monitoring methodologies are presented to detect, locate and quantify dent/crack, thermal debond, and corrosion damage in a solid aluminum friction stir weld plate and a sandwich honeycomb thermal protection panel. A wave propagation based method can identify small defects because propagating waves typically consist of small wavelengths while a vibration-based scheme is better equipped to quantify damage over wide areas of large structures. Near-real time online diagnostics is achieved by using localized sensing (wave propagation) and distributed sensing (vibration-based) in an active measurement array. Sensor/actuator arrays have been developed to implement these techniques and portable health management systems have been developed based on the combination of damage detection algorithms, active sensing, and graphical user interfaces. Propagating waves are shown to have a heightened sensitivity to damage located at the anti-nodes of a friction stir wed plate forced by low frequency environmental vibrations. Measurement of the input forcing in the vibration-based method is shown to enable damage quantification.

  13. Structure of the Lithosphere-Asthenosphere System Beneath the Juan de Fuca Plate: Results of Body Wave Imaging Using Cascadia Initiative Data

    NASA Astrophysics Data System (ADS)

    Byrnes, J. S.; Toomey, D. R.; Hooft, E. E. E.

    2014-12-01

    The plate-scale deployment of ocean bottom seismometers (OBS) as part of the Cascadia Initiative (CI) of NSF provides a unique opportunity to study the structure and dynamics of the lithosphere-asthenosphere system beneath an entire oceanic plate, from its birth at a spreading center to its subduction beneath a continent. Here we present tomographic images of the seismic structure of oceanic upper mantle beneath the Juan de Fuca (JdF) and Gorda plates derived from body wave delay times. The results constrain structural anomalies beneath the JdF and Gorda spreading centers, the Blanco and Mendocino transform faults, near ridge hotspots such as Axial Seamount, and the upper mantle structure beneath the subducting oceanic lithosphere. We measured delay times of teleseismic P and S wave phases for the first two years of the CI. Our tomographic analysis assumes both isotropic and anisotropic starting models and accounts for finite-frequency effects and three-dimensional ray bending. Preliminary results indicate that the upper mantle structure beneath the JdF spreading center is asymmetric, with lower shear wave velocities beneath the Pacific plate (also the direction of ridge migration). On a regional scale, regions of lower seismic velocities beneath the JdF and Gorda spreading centers correlate with shallower ridge depths. Beneath the southern Gorda plate a low velocity anomaly is detected, which is absent to the north; this anomaly is bounded to the south by the Mendocino transform. Ongoing work includes analysis of the third year of CI data, which will improve resolution of structure and allow better definition of anomalies in the vicinity of the Blanco transform. In addition, we will combine ocean and continental data to obtain images of the Cascadia subduction zone.

  14. Surface wave Tomography on the Indian Plate under La Réunion Island from RHUM-RUM experiment data

    NASA Astrophysics Data System (ADS)

    Mazzullo, Alessandro; Stutzmann, Eleonore; Montagner, Jean-Paul; Barruol, Guilhem; Sigloch, Karin; Maurya, Satish

    2016-04-01

    The island of La Reunion has been created by one of the most active volcanoes in the world, but the origin at depth of the mantle upwelling beneath the hotspot is still controversial. More particularly the interaction between the plume and the ridge is not known. In the framework of the RHUM-RUM project, an array of 57 french and german ocean bottom seismometers (OBS) has been deployed during one year (2012-2013) over an area of 2000 km x 2000 km centered on La Reunion Island. 15 land stations have also been installed in Madagascar, the Comoros and Mozambique. This dataset has been used to obtain a high resolution tomographic model of the South West indian area. For each earthquake-station path, Rayleigh wave fundamental mode phase velocity has been measured using the roller-coaster method in the period range 30-250 seconds. The total dataset consists of 3500 paths. This dataset has then been regionalized and inverted versus depth using a simulated annealing method in which the number and shape of the splines that describe the S-wave velocity model are variable. The model lateral resolution is about 500 km. We observe a good correlation between the tomographic model and surface tectonics down to about 100 km depth. At 50 km depth, a slow velocity anomaly is found beneath the hot-spot of Réunion-Mauritius islands. This slow anomaly is extended along the Rodrigues ridge up to the Indian central ridge which confirms a connection between the plume and the ridge. At greater depth (150 km) a large slow velocity anomaly is observed beneath the Réunion hot-spot elongated in the direction of the African plate motion, that may be related to the spreading of hot plume material. We also observe slow velocities beneath the hot-spots of Marion, Crozet and Kerguelen. Finally, under Comoros archipelago, the slow velocity anomaly may be the signature of the termination of the East African rift.

  15. An efficient model to predict guided wave radiation by finite-sized sources in multilayered anisotropic plates with account of caustics

    NASA Astrophysics Data System (ADS)

    Stévenin, M.; Lhémery, A.; Grondel, S.

    2016-01-01

    Elastic guided waves (GW) are used in various non-destructive testing (NDT) methods to inspect plate-like structures, generated by finite-sized transducers. Thanks to GW long range propagation, using a few transducers at permanent positions can provide a full coverage of the plate. Transducer diffraction effects take place, leading to complex radiated fields. Optimizing transducers positioning makes it necessary to accurately predict the GW field radiated by a transducer. Fraunhofer-like approximations applied to GW in isotropic homogeneous plates lead to fast and accurate field computation but can fail when applied to multi-layered anisotropic composite plates, as shown by some examples given. Here, a model is proposed for composite plates, based on the computation of the approximate Green's tensor describing modal propagation from a source point, with account of caustics typically seen when strong anisotropy is concerned. Modal solutions are otherwise obtained by the Semi-Analytic Finite Element method. Transducer diffraction effects are accounted for by means of an angular integration over the transducer surface as seen from the calculation point, that is, over energy paths involved, which are mode-dependent. The model is validated by comparing its predictions with those computed by means of a full convolution integration of the Green's tensor with the source over transducer surface. Examples given concern disk and rectangular shaped transducers commonly used in NDT.

  16. Low-noise dc superconducting quantum interference devices for gravity wave detection

    NASA Astrophysics Data System (ADS)

    Jin, Insik

    I have designed, built and tested a low noise dc Superconducting QUantum Interference Device (SQUID) system which is intended primarily for use in a 50 mK omnidirectional gravity wave antenna. The SQUID system has three SQUIDs on a single chip: one SQUID is the sensor, another SQUID is the main readout, and the last is a spare readout. For good impedance matching between the sensor SQUID and the input circuit, I use a thin-film transformer. This thin-film transformer gives an input inductance of about 1 muH, which is good for many applications. A SQUID system in a gravity wave antenna must operate continuously for at least 6 months with high reliability. To meet these requirements, I fabricated dc SQUID chips from Nb-Al/AlOsbx-Nb trilayers. I tested the SQUID chips in a liquid helium bath and a dilution refrigerator in the temperature range of 4.2 K to 90 mK. I have designed and tested an eddy-current damping filter as a distributed microwave filter to damp out microwave resonances in strip-line input coils coupled to SQUIDs. The filter chip consists of a Au/Cu-dot array. The filter chip was coupled to the SQUID using a flip-chip arrangement on the SQUID chip. I found that the filter reduced noise bumps and removed distortion from the current-voltage curves. To flux-lock the SQUID system, I developed 2-stage SQUID feedback loops. I investigated two cascade SQUID systems in which I feed the feedback signal into the sensor SQUID and couple the ac modulation signal to the readout SQUID. I found that the noise spectrum with 2-SQUID feedback operation recovers the noise spectrum of the sensor SQUID with about 9% higher noise.

  17. Finite elements modelling of scattering problems for flexural waves in thin plates: Application to elliptic invisibility cloaks, rotators and the mirage effect

    SciTech Connect

    Farhat, M.; Guenneau, S.; Enoch, S.

    2011-03-20

    We propose a finite elements algorithm to solve a fourth order partial differential equation governing the propagation of time-harmonic bending waves in thin elastic plates. Specially designed perfectly matched layers are implemented to deal with the infinite extent of the plates. These are deduced from a geometric transform in the biharmonic equation. To numerically illustrate the power of elastodynamic transformations, we analyze the elastic response of an elliptic invisibility cloak surrounding a clamped obstacle in the presence of a cylindrical excitation i.e. a concentrated point force. Elliptic cloaking for flexural waves involves a density and an orthotropic Young's modulus which depend on the radial and azimuthal positions, as deduced from a coordinates transformation for circular cloaks in the spirit of Pendry et al. [Science 312, 1780 (2006)], but with a further stretch of a coordinate axis. We find that a wave radiated by a concentrated point force located a couple of wavelengths away from the cloak is almost unperturbed in magnitude and in phase. However, when the point force lies within the coating, it seems to radiate from a shifted location. Finally, we emphasize the versatility of transformation elastodynamics with the design of an elliptic cloak which rotates the wavevector of a flexural wave within its core.

  18. Phase-Sensitive Reflective Imaging Device in the mm-wave and Terahertz Regions

    NASA Astrophysics Data System (ADS)

    Gallerano, Gian Piero; Doria, Andrea; Germini, Marzia; Giovenale, Emilio; Messina, Giovanni; Spassovsky, Ivan P.

    2009-12-01

    Two Free Electron Laser sources have been developed at ENEA-Frascati for a variety of applications: A Compact Free Electron Laser (C-FEL) that provides coherent radiation in the frequency range between 90 and 150 GHz Gallerano et al. (Infrared Phys. and Techn. 40:161, 1999), and a second source, FEL-CATS, which utilizes a peculiar radio-frequency structure to generate coherent emission in the range 0.4 to 0.7 THz Doria et al. (Phys. Rev. Lett 93:264801, 2004). The high peak power of several kW in 15 to 50 ps pulses, makes these sources particularly suitable for the assessment of exposure limits in biological systems and for long range detection. In this paper we present a phase-sensitive reflective imaging device in the mm-wave and THz regions, which has proven to be a valuable tool in the biological Ramundo-Orlando et al. (Bioelectromagnetics 28:587-598, 2007), environmental Doria et al. (2005) and art conservation fields Gallerano et al. (2008). Different setups have been tested at different levels of spatial resolution to image objects from a few centimeter square to larger sizes. Images have been compared to identify and characterize the contrast mechanism.

  19. Self-regulating Drift wave -- Zonal Flow turbulence in a linear plasma device

    NASA Astrophysics Data System (ADS)

    Xie, Jinlin; Chen, Ran; Hu, Guanghai; Jin, Xiaoli; Li, Hong; Liu, Wandong; Yu, Changxuan

    2012-10-01

    Here we report new and interesting results about the DW-ZF system in a linear plasma device with much better control environments to illustrate important Zonal flow physics: (1) The three-dimensional spectral features of the LFZF have been provided. In particular, it is identified that the LFZF damping is dominated by ion-neutral collision in our case. Also experimental evidence of the shearing effect of ZF on DW has been given. (2) A zonal flow dominated state of the DW-ZF system has been achieved. Theoretically, it has been predicted that a significant portion of the turbulence energy can be stored in the Zonal Flows for the case of low collisionality plasmas. In our experiments we achieve a zonal flow dominated state, in which the maximum ratio of the ZF energy to the total turbulence energy is about 80%, which seems to support the hypothesis of zonostropic state in geostrophic turbulence. (3) The self-regulating dynamics in the DW-ZF system is clearly elucidated. The evolution of the energy partition ratio of drift-wave turbulence and zonal flow is investigated with varying magnetic field strength, which is found consistent with the general prey-predator model.

  20. Determination of thickness and elastic constants of aluminum plates from full-field wavelength measurements of single-mode narrowband Lamb waves.

    PubMed

    Deán, J Luis; Trillo, Cristina; Doval, Angel F; Fernández, José L

    2008-09-01

    A method based on fitting the theoretical dispersion curves of Lamb waves to experimental data is presented to determine the thickness and two independent elastic constants of aluminum plates a few millimeters thick. The waves are generated by means of the wedge method using a narrowband source, selecting the wedge angle and the acoustic frequency f so that mainly one mode is excited. A self-developed pulsed electronic speckle pattern interferometry system renders a two dimensional map of the out-of-plane acoustic displacement field at the plate surface, which allows an accurate measurement of the acoustic wavelength lambda(1). For any mode, the relation between lambda(1) and f depends on the three unknown parameters, so at least three experimental measurements (lambda(1i),f(i)) with different frequencies and/or different modes are required to calculate them. The suitability of different Lamb modes to determine each parameter when the others are known is studied, as well as the conditions that the experimental set of values must fulfill to calculate all three parameters. Numerous Lamb modes at different frequencies are generated in each plate, and a fitting is made based on the minimization of the error function, resulting in an accuracy better than 1%.

  1. Gain and far-field patterns for phase-correcting Fresnel zone plate antennas at millimeter-wave and terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Wiltse, James C.

    2007-04-01

    The Fresnel zone plate lens antenna, which provides advantages compared to a normal paraboloidal or spherical lens, has been extensively investigated in the millimeter-wave and terahertz regions. The advantages include reduced weight, volume, and attenuation and simplicity of design. The principal disadvantage is that the zone plate sometimes provides reduced gain compared to a true lens. Particularly at high millimeter-wave or terahertz frequencies the low loss of the zone plate more than compensates for the reduced directivity. This paper investigates the gains and far-field patterns for a number of cases and gives both the analysis and numerical results for the examples. These cases have dealt with large-angle designs, where the focal length (F) and diameter (D) are comparable (F/D = 0.3 to 2.5), unlike the typical optical examples. The antenna patterns are found to have beamwidths and first sidelobes that are similar to what one would obtain with a standard lens, given the same aperture illumination. Appropriate feed designs are also described. For best aperture efficiency the illumination taper is about 10 dB, and this gives first sidelobe levels of about -24dB for a circular aperture. Far-out average sidelobes are not as low as for a true lens, and this is where the gain is affected.

  2. Millimeter-Wave Imaging of Person-Borne Improvised Explosive Devices

    NASA Astrophysics Data System (ADS)

    Fernandes, Justin Leigh

    With the recent rise in casualties and threat of casulties resulting from person-borne improvised explosive devices (PBIEDs) there is an urgent need for building imaging systems to perform standoff and portal detection of such threats. An optimum system that fulfills the requirements of PBIED detection must be low cost and have a high probability of detection with low probability of false alarm. A standoff detection system must also be portable while a portal imaging system can be stationary. Currently there are a variety of modalities being researched to perform standoff detection of PBIED's including: backscatter X-ray imaging, infrared imaging, optical detection, terahertz imaging, video analytics, and millimeter-wave (MMW) imaging. MMW imaging is a perferable modality for full body imaging of PBIEDs for many reasons. MMWs can propagate through the atmosphere and clothing with very little attenuation, while at the same time do not cause damage to human skin tissue. MMWs are small enough to build physical and synthetic aperture systems small enough to have a realistic physical system footprint while also providing excellent cross-range resolution. Present technology is available to generate very wideband coherent MMWsignals, which can be used to generate very high resolution images of targets at both standoff (> 15 meters) and portal (< 1 meter) distances. Due to the large expense of building MMW imaging systems there is a large need to accurately model such systems numerically. With a forward model complex geometries, novel sensor and system configurations can be tested with minimal cost and overhead. Models also allow researchers to carry out extremely precise and repeatable analyses that have the ability to give extraordinary insight to scattering processes. The finite difference method in the frequency domain (FDFD) is a forward model which yields itself as an excellent method to analyze the scattering at MMW frequencies. However, due to the matrix inversion

  3. Multiple-frequency acoustic wave devices for chemical sensing and materials characterization in both gas and liquid phase

    DOEpatents

    Martin, Stephen J.; Ricco, Antonio J.

    1993-01-01

    A chemical sensor (1) includes two or more pairs of interdigital electrodes (10) having different periodicities. Each pair is comprised of a first electrode (10a) and a second electrode (10b). The electrodes are patterned on a surface of a piezoelectric substrate (12). Each pair of electrodes may launch and receive various acoustic waves (AW), including a surface acoustic wave (SAW), and may also launch and receive several acoustic plate modes (APMs). The frequencies associated with each are functions of the transducer periodicity as well as the velocity of the particular AW in the chosen substrate material. An AW interaction region (13) exists between each pair of electrodes. Circuitry (20, 40) is used to launch, receive, and monitor the propagation characteristics of the AWs and may be configured in an intermittent measurement fashion or in a continuous measurement fashion. Perturbations to the AW velocity and attenuation are recorded at several frequencies and provide the sensor response.

  4. Nonlinear Excitation of Acoustic Modes by Large Amplitude Alfvén waves in the Large Plasma Device (LAPD)

    NASA Astrophysics Data System (ADS)

    Dorfman, S. E.; Carter, T. A.; Pribyl, P.; Tripathi, S.; Van Compernolle, B.; Vincena, S. T.; Sydora, R. D.

    2013-12-01

    Alfvén waves, a fundamental mode of magnetized plasmas, are ubiquitous in space plasmas. While the linear behavior of these waves has been extensively studied [1], non-linear effects are important in many real systems, including the solar corona and solar wind. In particular, a parametric decay process in which a large amplitude Alfvén wave decays into an ion acoustic wave and backward propagating Alfvén wave may play an important role in the coronal heating problem. Specifically, the decay of large-amplitude Alfvén waves propagating outward from the photosphere could lead to heating of the corona by the daughter ion acoustic modes [2]. As direct observational evidence of parametric decay is limited [3], laboratory experiments may play an important role in validating simple theoretical predictions and aiding in the interpretation of space measurements. Recent counter-propagating Alfvén wave experiments in the Large Plasma Device (LAPD) have recorded the first laboratory observation of the Alfvén-acoustic mode coupling at the heart of this parametric decay instability [4]. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force. Strong damping observed after the pump Alfvén waves are turned off is under investigation; a novel ion acoustic wave launcher is under development to launch the mode directly for damping studies. New experiments also aim to identify decay instabilities from a single large-amplitude Alfvén wave. In conjunction with these experiments, gyrokinetic simulation efforts are underway to scope out the relevant parameter space. [1] W. Gekelman, et. al., Phys. Plasmas 18, 055501 (2011). [2] F

  5. Development of GaAs-Based Monolithic Surface Acoustic Wave Devices for Chemical Sensing and RF Filter Applications

    SciTech Connect

    Baca, A.G.; Casalnuovo, S.A.; Drummond, T.J.; Frye, G.C.; Heller, E.J.; Hietala, V.M.; Klem, J.F.

    1998-12-24

    Since their invention in the mid-1960's, surface acoustic wave (SAW) devices have become popular for a wide variety of applications. SAW devices represent a low-cost and compact method of achieving a variety of electronic signal processing functions at high frequencies, such as RF filters for TV or mobile wireless communications [1]. SAW devices also provide a convenient platform in chemical sensing applications, achieving extremely high sensitivity to vapor phase analytes in part-per-billion concentrations [2]. Although the SAW acoustic mode can be created on virtually any crystalline substrate, the development of SAW technology has historically focused on the use of piezoelectric materials, such as various orientations of either quartz or lithium niobate, allowing the devices to be fabricated simply and inexpensively. However, the III-V compound semiconductors, and GaAs in particular, are also piezoelectric as a result of their partially covalent bonding and support the SAW acoustic mode, allowing for the convenient fabrication of SAW devices. In addition, GaAs microelectronics has, in the past decade, matured commercially in numerous RF wireless technologies. In fact, GaAs was recognized long ago as a potential candidate for the monolithic integration of SAW devices with microelectronics, to achieve compact RF signal processing functions [3]. The details of design and fabrication of SAW devices can be found in a variety of references [1].

  6. Need for and evaluation of hail protection devices for solar flat plate collectors. Final report, June 1978-March 1980

    SciTech Connect

    Armstrong, P R; Cox, M; de Winter, F

    1980-03-01

    A brief summary of the hail risk work previously done under this contract is given, and a summary evaluation of hail impact resistance standards currently being developed is presented. Simulated hail impact test data, field data, and the impact resistance of commercially available glazings are discussed. The use of screens for protection against hail and the threat of vandalism to solar flat plate collectors are discussed. (WHK)

  7. P-wave locking in the postventricular atrial refractory period of cardiac resynchronization devices. Management with the Biotronik system.

    PubMed

    Barold, S S; Stroobandt, R X; Herweg, B; Kucher, A

    2012-06-01

    Electrical desynchronization in cardiac resynchronization therapy (CRT) occurs when sinus P waves are continually locked in the postventricular atrial refractory period (PVARP). This process is characterized by sequences of a P wave as an atrial event in the PVARP followed by a conducted and sensed ventricular event. Such sequences are more common in patients with a prolonged PR interval, often initiated by premature ventricular complexes (PVC) and terminated by PVCs or slowing of the sinus rate. Specific algorithms automatically identify a recurring pattern of P wave locking in the PVARP, whereupon they shorten the PVARP temporarily until atrial tracking is restored with the programmed sensed AV interval. The Biotronik family of Lumax CRT devices use an AV control window which is not an algorithm that "unlocks" P waves trapped in the PVARP. Rather, it prevents P waves from becoming trapped in the PVARP. A ventricular sensed event occurring within the AV control interval does not start a PVARP so that P wave locking cannot occur when the AV conduction time is shorter than the AV control interval.

  8. Development of Highly Sensitive Bulk Acoustic Wave Device Biosensor Arrays for Screening and Early Detection of Prostate Cancer

    DTIC Science & Technology

    2009-01-01

    Acoustic Wave Device Biosensor Arrays for Screening and Early Detection of Prostate Cancer PRINCIPAL INVESTIGATOR: Anthony J. Dickherber, Ph.D...Arrays for Screening and Early Detection of Prostate Cancer 5b. GRANT NUMBER W81XWH-07-1-0099 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...of developing a cost-effective, highly sensitive and highly selective sensor array for the detection of early cancer proliferation. First I report

  9. Millimeter wave imaging at up to 40 frames per second using an optoelectronic photo-injected Fresnel zone plate lens antenna

    NASA Astrophysics Data System (ADS)

    Robertson, Duncan A.; Gallacher, Thomas F.; Søndenâ, Rune; Macfarlane, David G.

    2016-05-01

    Optoelectronic methods are promising for rapid and highly reconfigurable beam steering across the microwave to the terahertz range. In particular, the photo-injected Fresnel zone plate antenna (piFZPA) offers high speed, wide angle, precise beam steering with good beam quality, to enable video rate millimeter wave imagery with no moving parts. We present a piFZPA demonstrator based on a commercial digital light projector (DLP) and high power laser which achieves steering rates up to 17,500 beams per second at 94 and 188 GHz. We also demonstrate radar imaging at 94 GHz at frame rates of 40 Hz (2D PPI) and 7 Hz (3D volumetric).

  10. Charge coupled devices vs. microchannel plates in the extreme and far ultraviolet - A comparison based on the latest laboratory measurements

    NASA Technical Reports Server (NTRS)

    Vallerga, J.; Lampton, M.

    1988-01-01

    While microchannel plates (MCPs) have been established as imaging photon counters in the EUV and FUV for some years, CCDs are associated with low light level sensing at visible and near-IR wavelengths. Attention is presently given to recent proposals for CCDs' use as EUV and FUV detectors with quantum efficiencies sometimes exceeding those of MCPs; quantum resolution, format size, dynamic range, and long-term stability are also used as bases of comparison, for the cases of both space-based astronomical and spectroscopic applications.

  11. High performance AlScN thin film based surface acoustic wave devices with large electromechanical coupling coefficient

    SciTech Connect

    Wang, Wenbo; He, Xingli; Ye, Zhi E-mail: jl2@bolton.ac.uk; Wang, Xiaozhi; Mayrhofer, Patrick M.; Gillinger, Manuel; Bittner, Achim; Schmid, Ulrich

    2014-09-29

    AlN and AlScN thin films with 27% scandium (Sc) were synthesized by DC magnetron sputtering deposition and used to fabricate surface acoustic wave (SAW) devices. Compared with AlN-based devices, the AlScN SAW devices exhibit much better transmission properties. Scandium doping results in electromechanical coupling coefficient, K{sup 2}, in the range of 2.0% ∼ 2.2% for a wide normalized thickness range, more than a 300% increase compared to that of AlN-based SAW devices, thus demonstrating the potential applications of AlScN in high frequency resonators, sensors, and high efficiency energy harvesting devices. The coupling coefficients of the present AlScN based SAW devices are much higher than that of the theoretical calculation based on some assumptions for AlScN piezoelectric material properties, implying there is a need for in-depth investigations on the material properties of AlScN.

  12. Recent advances in particle and droplet manipulation for lab-on-a-chip devices based on surface acoustic waves.

    PubMed

    Wang, Zhuochen; Zhe, Jiang

    2011-04-07

    Manipulation of microscale particles and fluid liquid droplets is an important task for lab-on-a-chip devices for numerous biological researches and applications, such as cell detection and tissue engineering. Particle manipulation techniques based on surface acoustic waves (SAWs) appear effective for lab-on-a-chip devices because they are non-invasive, compatible with soft lithography micromachining, have high energy density, and work for nearly any type of microscale particles. Here we review the most recent research and development of the past two years in SAW based particle and liquid droplet manipulation for lab-on-a-chip devices including particle focusing and separation, particle alignment and patterning, particle directing, and liquid droplet delivery.

  13. Optimum design of phononic crystal perforated plate structures for widest bandgap of fundamental guided wave modes and maximized in-plane stiffness

    NASA Astrophysics Data System (ADS)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, Mohammad; Ng, Ching-Tai

    2016-04-01

    This paper presents a topology optimization of single material phononic crystal plate (PhP) to be produced by perforation of a uniform background plate. The primary objective of this optimization study is to explore widest exclusive bandgaps of fundamental (first order) symmetric or asymmetric guided wave modes as well as widest complete bandgap of mixed wave modes (symmetric and asymmetric). However, in the case of single material porous phononic crystals the bandgap width essentially depends on the resultant structural integration introduced by achieved unitcell topology. Thinner connections of scattering segments (i.e. lower effective stiffness) generally lead to (i) wider bandgap due to enhanced interfacial reflections, and (ii) lower bandgap frequency range due to lower wave speed. In other words higher relative bandgap width (RBW) is produced by topology with lower effective stiffness. Hence in order to study the bandgap efficiency of PhP unitcell with respect to its structural worthiness, the in-plane stiffness is incorporated in optimization algorithm as an opposing objective to be maximized. Thick and relatively thin Polysilicon PhP unitcells with square symmetry are studied. Non-dominated sorting genetic algorithm NSGA-II is employed for this multi-objective optimization problem and modal band analysis of individual topologies is performed through finite element method. Specialized topology initiation, evaluation and filtering are applied to achieve refined feasible topologies without penalizing the randomness of genetic algorithm (GA) and diversity of search space. Selected Pareto topologies are presented and gradient of RBW and elastic properties in between the two Pareto front extremes are investigated. Chosen intermediate Pareto topology, even not extreme topology with widest bandgap, show superior bandgap efficiency compared with the results reported in other works on widest bandgap topology of asymmetric guided waves, available in the literature

  14. Focusing, refraction, and asymmetric transmission of elastic waves in solid metamaterials with aligned parallel gaps.

    PubMed

    Su, Xiaoshi; Norris, Andrew N

    2016-06-01

    Gradient index (GRIN), refractive, and asymmetric transmission devices for elastic waves are designed using a solid with aligned parallel gaps. The gaps are assumed to be thin so that they can be considered as parallel cracks separating elastic plate waveguides. The plates do not interact with one another directly, only at their ends where they connect to the exterior solid. To formulate the transmission and reflection coefficients for SV- and P-waves, an analytical model is established using thin plate theory that couples the waveguide modes with the waves in the exterior body. The GRIN lens is designed by varying the thickness of the plates to achieve different flexural wave speeds. The refractive effect of SV-waves is achieved by designing the slope of the edge of the plate array, and keeping the ratio between plate length and flexural wavelength fixed. The asymmetric transmission of P-waves is achieved by sending an incident P-wave at a critical angle, at which total conversion to SV-wave occurs. An array of parallel gaps perpendicular to the propagation direction of the reflected waves stop the SV-wave but let P-waves travel through. Examples of focusing, steering, and asymmetric transmission devices are discussed.

  15. Character of the Caribbean-Gônave-North America plate boundaries in the upper mantle based on shear-wave splitting

    NASA Astrophysics Data System (ADS)

    Benford, B.; Tikoff, B.; DeMets, C.

    2012-12-01

    We present new shear-wave splitting measurements of SKS, SKKS, PKS, and sSKS phases from eight stations in the northern Caribbean. Prior to this work, shear-wave splitting analysis of the northern Caribbean boundary was only evaluated at a station in Puerto Rico. Stations that lie within several tens of kilometers of microplate boundaries have mean fast polarization directions parallel to the boundary and have delay times greater than 1 s. Stations more than several tens of kilometers away from microplate boundaries show no evidence for an anisotropic upper mantle. Stations in Cuba and Jamaica have fast axes oriented ˜100° with delay times of ˜1.5 s, indicating that the east-striking left-lateral strike-slip faults that define the north and south boundaries of the Gônave microplate continue into the upper mantle. A station located in Antigua, where the North America plate subducts beneath the Caribbean plate, has a high degree of splitting with the fast axis parallel to the trench. Based on our results, the deformation related to the presence of microplates in the northern Caribbean extends into the upper mantle.

  16. Combined plate motion and density driven flow in the asthenosphere beneath Saudi Arabia: Evidence from shear-wave splitting and seismic anisotropy

    SciTech Connect

    Hansen, S; Schwartz, S

    2006-02-08

    A comprehensive study of mantle anisotropy along the Red Sea and across Saudi Arabia was performed by analyzing shear-wave splitting recorded by stations from three different seismic networks: the largest, most widely distributed array of stations examined across Saudi Arabia to date. Stations near the Gulf of Aqaba display fast orientations that are aligned parallel to the Dead Sea Transform Fault, most likely related to the strike-slip motion between Africa and Arabia. However, most of our observations across Saudi Arabia are statistically the same, showing a consistent pattern of north-south oriented fast directions with delay times averaging about 1.4 s. Fossilized anisotropy related to the Proterozoic assembly of the Arabian Shield may contribute to the pattern but is not sufficient to fully explain the observations. We feel that the uniform anisotropic signature across Saudi Arabia is best explained by a combination of plate and density driven flow in the asthenosphere. By combining the northeast oriented flow associated with absolute plate motion with the northwest oriented flow associated with the channelized Afar plume along the Red Sea, we obtain a north-south oriented resultant that matches our splitting observations and supports models of active rifting processes. This explains why the north-south orientation of the fast polarization direction is so pervasive across the vast Arabian Plate.

  17. Microwave and millimeter-wave power generation in silicon carbide avalanche devices

    NASA Technical Reports Server (NTRS)

    Mehdi, I.; Haddad, G. I.; Mains, R. K.

    1988-01-01

    Numerical simulations were performed to investigate the typical power-generating capabilities of SiC IMPATT diodes. Using available material parameters, SiC double-drift IMPATT diodes were simulated at 10, 35, 60, and 94 GHz, and the operating characteristics of these devices were compared to those of Si and GaAs devices. Compared to the Si and GaAs IMPATT performances in the pulsed mode, the SiC IMPATT performance was found to be far superior. The performance of SiC devices in the CW mode was also superior to that of GaAs devices, especially at lower frequencies. At a high frequency (94 GHz), the performance of the SiC device was found to be comparable to that of Si devices.

  18. A comparison of Pd and Au electrodes-based LiNbO3 surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Mohammad, Mohammad Ali; Wang, Dan-Yang; Tian, Xiang-Guang; Tao, Lu-Qi; Yang, Yi; Ren, Tian-Ling

    2016-11-01

    We report the comparison of electrode metals for LiNbO3 surface acoustic wave (SAW) devices. Palladium (Pd) was systematically studied as a SAW electrode metal for the first time, compared with gold (Au). Simulations were first conducted to gain an understanding of the differences of the materials and the metallization ratio. Two sets of identical SAW devices were then fabricated using Au and Pd as electrodes with different electrode widths and same SAW period. The insertion losses, types of resonance mode, the resonance frequencies, peak amplitudes, quality factors and trends with different metallization ratios were systematically compared and analyzed. We found that Pd electrode devices only exhibit the parallel resonance frequency and have higher resonance frequency for both the first-order and third-order harmonics. Au electrode devices tend to have a smooth response and a quality factor two times higher than Pd. Both Pd and Au electrode devices have nearly identical electromechanical coupling coefficients, and the quality factor and third-order harmonics both improve with increasing metallization ratio.

  19. Development and experimental verification of a finite element method for accurate analysis of a surface acoustic wave device

    NASA Astrophysics Data System (ADS)

    Mohibul Kabir, K. M.; Matthews, Glenn I.; Sabri, Ylias M.; Russo, Salvy P.; Ippolito, Samuel J.; Bhargava, Suresh K.

    2016-03-01

    Accurate analysis of surface acoustic wave (SAW) devices is highly important due to their use in ever-growing applications in electronics, telecommunication and chemical sensing. In this study, a novel approach for analyzing the SAW devices was developed based on a series of two-dimensional finite element method (FEM) simulations, which has been experimentally verified. It was found that the frequency response of the two SAW device structures, each having slightly different bandwidth and center lobe characteristics, can be successfully obtained utilizing the current density of the electrodes via FEM simulations. The two SAW structures were based on XY Lithium Niobate (LiNbO3) substrates and had two and four electrode finger pairs in both of their interdigital transducers, respectively. Later, SAW devices were fabricated in accordance with the simulated models and their measured frequency responses were found to correlate well with the obtained simulations results. The results indicated that better match between calculated and measured frequency response can be obtained when one of the input electrode finger pairs was set at zero volts and all the current density components were taken into account when calculating the frequency response of the simulated SAW device structures.

  20. Phase velocities and attentuations of shear, Lamb, and Rayleigh waves in plate-like tissues submerged in a fluid (L)

    PubMed Central

    Nenadic, Ivan Z.; Urban, Matthew W.; Bernal, Miguel; Greenleaf, James F.

    2011-01-01

    In the past several decades, the fields of ultrasound and magnetic resonance elastography have shown promising results in noninvasive estimates of mechanical properties of soft tissues. These techniques often rely on measuring shear wave velocity due to an external or internal source of force and relating the velocity to viscoelasticity of the tissue. The mathematical relationship between the measured velocity and material properties of the myocardial wall, arteries, and other organs with non-negligible boundary conditions is often complicated and computationally expensive. A simple relationship between the Lamb–Rayleigh dispersion and the shear wave dispersion is derived for both the velocity and attenuation. The relationship shows that the shear wave velocity is around 20% higher than the Lamb–Rayleigh velocity and that the shear wave attenuation is about 20% lower than the Lamb–Rayleigh attenuation. Results of numerical simulations in the frequency range 0–500 Hz are presented. PMID:22225009