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Sample records for waves guide cns

  1. Electromagnetic ultrasonic guided waves

    CERN Document Server

    Huang, Songling; Li, Weibin; Wang, Qing

    2016-01-01

    This book introduces the fundamental theory of electromagnetic ultrasonic guided waves, together with its applications. It includes the dispersion characteristics and matching theory of guided waves; the mechanism of production and theoretical model of electromagnetic ultrasonic guided waves; the effect mechanism between guided waves and defects; the simulation method for the entire process of electromagnetic ultrasonic guided wave propagation; electromagnetic ultrasonic thickness measurement; pipeline axial guided wave defect detection; and electromagnetic ultrasonic guided wave detection of gas pipeline cracks. This theory and findings on applications draw on the author’s intensive research over the past eight years. The book can be used for nondestructive testing technology and as an engineering reference work. The specific implementation of the electromagnetic ultrasonic guided wave system presented here will also be of value for other nondestructive test developers.

  2. Guided-Wave Optical Biosensors

    Science.gov (United States)

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

    2007-01-01

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

  3. Guided Wave Travel Time Tomography for Bends

    NARCIS (Netherlands)

    Volker, A.W.F.; Zon, A.T. van

    2012-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method

  4. Guided wave travel time tomography for bends

    NARCIS (Netherlands)

    Volker, A.W.F.; Bloom, J.G.P.

    2010-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method

  5. Synthetic phase tuning of guided waves.

    Science.gov (United States)

    Wooh, S C; Shi, Y

    2001-01-01

    A novel method has been developed to generate and manipulate multi-mode guided waves. This technique uses a linear phased array whose elements are activated according to a prescribed time delay profile obtained from the dispersion curves. It is shown that a desired guided wave mode can be tuned by synthetically constructing a virtual wave from individually acquired waveform data. In addition to the development of such a synthetic phase tuning (SPT) technique, a pseudo pulse-echo (PPE) operation scheme is also developed for nondestructive testing. Experimental results are compared with those obtained by more traditional techniques using variable angle wedges and array transducers. It was shown that the new technique is convenient, robust, and flexible in utilizing multi-mode guided waves for nondestructive evaluation (NDE). It is a dynamic method that can produce desired guided wave modes propagating in the desired direction without any mechanical alignment. The advantages and limitations of the technique are addressed.

  6. A structured interview guide for global impressions: increasing reliability and scoring accuracy for CNS trials

    Directory of Open Access Journals (Sweden)

    Targum Steven D

    2013-01-01

    Full Text Available Abstract Background The clinical global impression of severity (CGI-S scale is a frequently used rating instrument for the assessment of global severity of illness in Central Nervous System (CNS trials. Although scoring guidelines have been proposed to anchor these scores, the collection of sufficient documentation to support the derived score is not part of any standardized interview procedure. It is self evident that the absence of a standardized, documentary format can affect inter-rater reliability and may adversely affect the accuracy of the resulting data. Method We developed a structured interview guide for global impressions (SIGGI and evaluated the instrument in a 2-visit study of ambulatory patients with Major Depressive Disorder (MDD or schizophrenia. Blinded, site-independent raters listened to audio recorded SIGGI interviews administered by site-based CGI raters. We compared SIGGI-derived CGI-S scores between the two separate site-based raters and the site-independent raters. Results We found significant intraclass correlations (p = 0.001 on all SIGGI-derived CGI-S scores between two separate site-based CGI raters with each other (r = 0.768 and with a blinded, site-independent rater (r = 0.748 and r = 0.706 respectively and significant Pearson’s correlations between CGI-S scores with all MADRS validity comparisons for MDD and PANSS comparisons for schizophrenia (p- 0.001 in all cases. Compared to site-based raters, the site-independent raters gave identical “dual” CGI-S scores to 67.6% and 68.2% of subjects at visit 1 and 77.1% at visit 2. Conclusion We suggest that the SIGGI may improve the inter-rater reliability and scoring precision of the CGI-S and have broad applicability in CNS clinical trials.

  7. Multimode interferometer for guided matter waves.

    Science.gov (United States)

    Andersson, Erika; Calarco, Tommaso; Folman, Ron; Andersson, Mauritz; Hessmo, Björn; Schmiedmayer, Jörg

    2002-03-11

    Atoms can be trapped and guided with electromagnetic fields, using nanofabricated structures. We describe the fundamental features of an interferometer for guided matter waves, built of two combined Y-shaped beam splitters. We find that such a device is expected to exhibit high contrast fringes even in a multimode regime, analogous to a white light interferometer.

  8. Guided wave sensing of polyelectrolyte multilayers

    DEFF Research Database (Denmark)

    Horvath, R.; Pedersen, H.C.; Cuisinier, F.J.G.

    2006-01-01

    A planar optical waveguide configuration is proposed to monitor the buildup of thick polyelectrolyte multilayers on the surface of the waveguide in aqueous solutions. Instead of detecting the layer by the electromagnetic evanescent field the polyelectrolyte layer acts as an additional waveguiding...... film that is sensed by guided waves instead of evanescent waves. This leads to a considerably improved sensitivity and dynamic range....

  9. Periodicity effects on compound guided waves

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

    2016-09-01

    Surface waves of different types can be compounded when a homogeneous layer is sandwiched between two half spaces filled with dissimilar periodically non-homogeneous dielectric materials and the intermediate layer is sufficiently thin. We solved the boundary-value problem for compound waves guided by a layer of a homogeneous and isotropic (metal or dielectric) material sandwiched between a structurally chiral material (SCM) and a periodically multi-layered isotropic dielectric material. We found that the periodicity of the SCM is crucial to excite a multiplicity of compound guided waves with strong coupling between the two interfaces.

  10. Programming of inhomogeneous resonant guided wave networks.

    Science.gov (United States)

    Feigenbaum, Eyal; Burgos, Stanley P; Atwater, Harry A

    2010-12-06

    Photonic functions are programmed by designing the interference of local waves in inhomogeneous resonant guided wave networks composed of power-splitting elements arranged at the nodes of a nonuniform waveguide network. Using a compact, yet comprehensive, scattering matrix representation of the network, the desired photonic function is designed by fitting structural parameters according to an optimization procedure. This design scheme is demonstrated for plasmonic dichroic and trichroic routers in the infrared frequency range.

  11. Wave-Based Subsurface Guide Star

    Energy Technology Data Exchange (ETDEWEB)

    Lehman, S K

    2011-07-26

    Astronomical or optical guide stars are either natural or artificial point sources located above the Earth's atmosphere. When imaged from ground-based telescopes, they are distorted by atmospheric effects. Knowing the guide star is a point source, the atmospheric distortions may be estimated and, deconvolved or mitigated in subsequent imagery. Extending the guide star concept to wave-based measurement systems to include acoustic, seismo-acoustic, ultrasonic, and radar, a strong artificial scatterer (either acoustic or electromagnetic) may be buried or inserted, or a pre-existing or natural sub-surface point scatterer may be identified, imaged, and used as a guide star to determine properties of the sub-surface volume. That is, a data collection is performed on the guide star and the sub-surface environment reconstructed or imaged using an optimizer assuming the guide star is a point scatterer. The optimization parameters are the transceiver height and bulk sub-surface background refractive index. Once identified, the refractive index may be used in subsequent reconstructions of sub-surface measurements. The wave-base guide star description presented in this document is for a multimonostatic ground penetrating radar (GPR) but is applicable to acoustic, seismo-acoustic, and ultrasonic measurement systems operating in multimonostatic, multistatic, multibistatic, etc., modes.

  12. Guided Circumferential Waves in Layered Poroelastic Cylinders

    Directory of Open Access Journals (Sweden)

    Shah S.A.

    2016-12-01

    Full Text Available The present paper investigates the propagation of time harmonic circumferential waves in a two-dimensional hollow poroelastic cylinder with an inner shaft (shaft-bearing assembly. The hollow poroelastic cylinder and inner shaft are assumed to be infinite in axial direction. The outer surface of the cylinder is stress free and at the interface, between the inner shaft and the outer cylinder, it is assumed to be free sliding and the interfacial shear stresses are zero, also the normal stress and radial displacements are continuous. The frequency equation of guided circumferential waves for a permeable and an impermeable surface is obtained. When the angular wave number vanish the frequency equation of guided circumferential waves for a permeable and an impermeable surface degenerates and the dilatational and shear waves are uncoupled. Shear waves are independent of the nature of surface. The frequency equation of a permeable and an impermeable surface for bore-piston assembly is obtained as a particular case of the model under consideration when the outer radius of the hollow poroelastic cylinder tends to infinity. Results of previous studies are obtained as a particular case of the present study. Nondimensional frequency as a function of wave number is presented graphically for two types of models and discussed. Numerical results show that, in general, the first modes are linear for permeable and impermeable surfaces and the frequency of a permeable surface is more than that of an impermeable surface.

  13. Adaptive dispersion compensation for guided wave imaging

    Science.gov (United States)

    Hall, James S.; Michaels, Jennifer E.

    2012-05-01

    Ultrasonic guided waves offer the promise of fast and reliable methods for interrogating large, plate-like structures. Distributed arrays of permanently attached, inexpensive piezoelectric transducers have thus been proposed as a cost-effective means to excite and measure ultrasonic guided waves for structural health monitoring (SHM) applications. Guided wave data recorded from a distributed array of transducers are often analyzed and interpreted through the use of guided wave imaging algorithms, such as conventional delay-and-sum imaging or the more recently applied minimum variance imaging. Both imaging algorithms perform reasonably well using signal envelopes, but can exhibit significant performance improvements when phase information is used. However, the use of phase information inherently requires knowledge of the dispersion relations, which are often not known to a sufficient degree of accuracy for high quality imaging since they are very sensitive to environmental conditions such as temperature, pressure, and loading. This work seeks to perform improved imaging with phase information by leveraging adaptive dispersion estimates obtained from in situ measurements. Experimentally obtained data from a distributed array is used to validate the proposed approach.

  14. Guided-mode resonant wave plates.

    Science.gov (United States)

    Magnusson, Robert; Shokooh-Saremi, Mehrdad; Johnson, Eric G

    2010-07-15

    We introduce half-wave and quarter-wave retarders based on the dispersion properties of guided-mode resonance elements. We design the wave plates using numerical electromagnetic models joined with the particle swarm optimization method. The wave plates operate in reflection. We provide computed results for reflectance and phase in the telecommunication spectral region near 1.55 microm wavelength. A surface-relief grating etched in glass and overcoated with silicon yields a half-wave plate with nearly equal amplitudes of the TE and TM polarization components and pi phase difference across a bandwidth exceeding 50 nm. Wider operational bandwidths are obtainable with more complex designs involving glass substrates and mixed silicon/hafnium dioxide resonant gratings. The results indicate a potential new approach to fashion optical retarders.

  15. Guided wave propagation in multilayered piezoelectric structures

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A general formulation of the method of the reverberation-ray matrix (MRRM) based on the state space formalism and plane wave expansion technique is presented for the analysis of guided waves in multilayered piezoelectric structures. Each layer of the structure is made of an arbitrarily anisotropic piezoelectric material. Since the state equation of each layer is derived from the three-dimensional theory of linear piezoelectricity, all wave modes are included in the formulation. Within the framework of the MRRM, the phase relation is properly established by excluding exponentially growing functions, while the scattering relation is also appropriately set up by avoiding matrix inversion operation. Consequently, the present MRRM is unconditionally numerically stable and free from computational limitations to the total number of layers, the thickness of individual layers, and the frequency range. Numerical examples are given to illustrate the good performance of the proposed formulation for the analysis of the dispersion characteristic of waves in layered piezoelectric structures.

  16. Ultrasonic guided wave tomography for ice detection.

    Science.gov (United States)

    Zhao, Xiang; Rose, Joseph L

    2016-04-01

    Of great concern for many structures, particularly critical sections of rotary and fixed wing aircrafts, is the ability to detect ice either on grounded or in-flight vehicles. As a consequence, some work is reported here that could be useful for a variety of different industries where ice formation is an important problem. This paper presents experimental validations of a probability-based reconstruction algorithm (PRA) on ice detection of plate-like structures. The ice detection tests are performed for three different specimens: a single layer aluminum plate with a circular ice sensing array, a titanium plate with a sparse rectangular ice sensing array, and a carbon-fiber-reinforced titanium plate with an embedded ice sensing array mounted on a carbon fiber back plate. Cases from the simple to the more challenging exemplify that special modes can be used to differentiate ice from water, a sparse rectangular array could also be used for ice detection, and an ice sensing array could be further used to detect the ice on the sensor free side, a very useful application of ice sensing for aircraft wings, for example. Ice detection images for the respective cases are reconstructed to investigate the feasibility of ice sensing with ultrasonic guided wave tomography technology. The results show that the PRA based ultrasonic guided wave tomography method successfully detected and showed ice spots correctly for all three cases. This corroborates the fact that ultrasonic guided wave imaging technology could be a potential useful ice sensing tool in plate-like structures.

  17. Phased annular array transducers for ultrasonic guided wave applications

    Science.gov (United States)

    Yan, Fei; Borigo, Cody; Liang, Yue; Koduru, Jaya P.; Rose, Joseph L.

    2011-04-01

    Mode and frequency control always plays an important role in ultrasonic guided wave applications. In this paper, theoretical understanding of guided wave excitations of axisymmetric sources on plate structures is established. It is shown that a wave number spectrum can be used to investigate the guided wave excitations of an axisymmetric source. The wave number spectrum is calculated from a Hankel transform of the axial source loading profile. On the basis of the theoretical understanding, phased annular array transducers are developed as a powerful tool for guided wave mode and frequency control. By applying appropriate time delays to phase the multiple elements of an annular array transducer, guided wave mode and frequency tuning can be achieved fully electronically. The phased annular array transducers have been successfully used for various applications. Example applications presented in this paper include phased annular arrays for guided wave beamforming and a novel ultrasonic vibration modal analysis technique for damage detection.

  18. Guided wave topological imaging of isotropic plates.

    Science.gov (United States)

    Rodriguez, S; Deschamps, M; Castaings, M; Ducasse, E

    2014-09-01

    Topological imaging is a recent method. So far, it has been applied to bulk waves, and high resolution has been demonstrated for imaging scatterers even with a single ultrasonic insonification of the inspected medium. This method consists of (i) emitting waves and measuring the response of the medium; (ii) solving two propagation problems: the direct problem, where the experimental source is simulated, and the adjoint problem, where the source is the time-reversed difference between the measured wave field and that obtained from the direct problem; (iii) computing the image by simply multiplying both wave fields together in the frequency domain, and integrating over the frequency. The speed of the method depends only on the cost of the field computations that are performed in the defect-free medium. The present work deals with the application of topological imaging to plate guided waves. Combining modal theory and Fourier analysis, the computations are performed in a very short time. In the investigated cases, two-dimensional in-plane imaging is based on propagation of the single S0 Lamb mode. Despite very high dispersion of that mode, scatterers are accurately located and the spatial resolution is equal to about one wavelength.

  19. Helical path separation for guided wave tomography

    Energy Technology Data Exchange (ETDEWEB)

    Huthwaite, P.; Seher, M. [Department of Mechanical Engineering, Imperial College, London, SW7 2AZ (United Kingdom)

    2015-03-31

    The pipe wall loss caused by corrosion can be quantified across an area by transmitting guided Lamb waves through the region and measuring the resulting signals. Typically the dispersive relationship for these waves, resulting in the wave velocity being a function of thickness, is exploited which enables the wall thickness to be determined from a velocity reconstruction. The accuracy and quality of this reconstruction is commonly limited by the angle of view available from the transducer arrays. These arrays are often attached as a pair of ring arrays either side of the inspected region, and due to the cyclic nature of the pipe, waves are able to travel in an inifinite number of helical paths between any two transducers. The first arrivals can be separated relatively easily by time gating, but by using just these components the angle of view is strongly restricted. To improve the viewing angle, it is necessary to separate the wavepackets. This paper provides an outline of a separation approach: initially the waves are backpropagated to their source to align the different signals, then a filtering technique is applied to select the desired components. The technique is applied to experimental data and demonstrated to robustly separate the signals.

  20. Transforming guided waves with metamaterial waveguide cores

    Science.gov (United States)

    Viaene, S.; Ginis, V.; Danckaert, J.; Tassin, P.

    2016-04-01

    Metamaterials make use of subwavelength building blocks to enhance our control on the propagation of light. To determine the required material properties for a given functionality, i.e., a set of desired light flows inside a metamaterial device, metamaterial designs often rely on a geometrical design tool known as transformation optics. In recent years, applications in integrated photonics motivated several research groups to develop two-dimensional versions of transformation optics capable of routing surface waves along graphene-dielectric and metal-dielectric interfaces. Although guided electromagnetic waves are highly relevant to applications in integrated optics, no consistent transformation-optical framework has so far been developed for slab waveguides. Indeed, the conventional application of transformation optics to dielectric slab waveguides leads to bulky three-dimensional devices with metamaterial implementations both inside and outside of the waveguide's core. In this contribution, we develop a transformationoptical framework that still results in thin metamaterial waveguide devices consisting of a nonmagnetic metamaterial core of varying thickness [Phys. Rev. B 93.8, 085429 (2016)]. We numerically demonstrate the effectiveness and versatility of our equivalence relations with three crucial functionalities: a beam bender, a beam splitter and a conformal lens. Our devices perform well on a qualitative (comparison of fields) and quantitative (comparison of transmitted power) level compared to their bulky counterparts. As a result, the geometrical toolbox of transformation optics may lead to a plethora of integrated metamaterial devices to route guided waves along optical chips.

  1. Delamination Detection Using Guided Wave Phased Arrays

    Science.gov (United States)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara

    2016-01-01

    This paper presents a method for detecting multiple delaminations in composite laminates using non-contact phased arrays. The phased arrays are implemented with a non-contact scanning laser Doppler vibrometer (SLDV). The array imaging algorithm is performed in the frequency domain where both the guided wave dispersion effect and direction dependent wave properties are considered. By using the non-contact SLDV array with a frequency domain imaging algorithm, an intensity image of the composite plate can be generated for delamination detection. For the proof of concept, a laboratory test is performed using a non-contact phased array to detect two delaminations (created through quasi-static impact test) at different locations in a composite plate. Using the non-contact phased array and frequency domain imaging, the two impact-induced delaminations are successfully detected. This study shows that the non-contact phased array method is a potentially effective method for rapid delamination inspection in large composite structures.

  2. Ultrasonic guided wave nondestructive evaluation using generalized anisotropic interface waves

    Science.gov (United States)

    Gardner, Michael D.

    The motivation for this work is a goal to inspect interfaces between thick layers of materials that can be anisotropic. The specific application is a thick composite bonded to a metal substrate. The interface is inspected for disbonds between the metal and composite. The large thickness allows the problem to be modeled as a half space. The theory behind guided waves in plates is presented. This theory includes the calculation and analysis of dispersion curves and the resulting wave structure. It is noted that for high frequency-thickness values, certain modes will converge to the half-space waves, e.g. the Rayleigh wave and the Stoneley wave. Points of high energy, especially shear energy, at the interface are desirable for interfacial inspection. Therefore, the wave structure for all modes and frequencies is searched for ideal inspection points. Interface waves are inherently good modes to use for interface inspection. Results from the dispersion curves and wave structures are verified in the finite element model software package called Abaqus. It is confirmed that the group speeds and wave structures of the modes match the predicted values. A theoretical development of interface waves is given wherein Rayleigh, Stoneley, and generalized interface waves are discussed. This is applied to both isotropic and anisotropic materials. It is shown that the Stoneley wave only exists for a certain range of material parameters. Because the Stoneley wave is the interface wave between two solid half spaces, it might appear that only certain pairs of solids would allow for inspection via interface wave. However, it is shown that for perturbations of the Stoneley-wave-valid material properties, interface waves which leak energy away from the interface can still propagate. They can also be used for inspection. Certain choices of materials will leak less energy and will therefore allow for longer inspection distances. The solutions to the isotropic leaky wave problem exist on

  3. Ultrasonic guided wave focusing by a generalized phased array

    Science.gov (United States)

    Zhang, Bixing; Xie, Fuli; Dong, Hefeng; Gong, Junjie

    2013-01-01

    Ultrasonic guided wave focusing by a generalized phased array is studied based on dispersion curves in a multi-layered medium. The different phase of the guided waves with different frequency is added on the excitation signal on each element of the transducer array for focusing. This can be realized by designing a proper excitation pulse based on the dispersion curves of the guided waves for each of the transducer array elements. The numerical simulation results show that the guided waves with different modes, different frequency components, and from different elements of the transducer array can all be focused at the target and focusing is achieved.

  4. GUIDED CIRCUMFERENTIAL WAVES IN DOUBLE-WALLED CARBON NANOTUBES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A model of guided circumferential waves propagating in double-walled carbon nanotubes is built by the theory of wave propagation in continuum mechanics, while the van der Waals force between the inner and outer nanotube has been taken into account in the model. The dispersion curves of the guided circumferential wave propagation are studied, and some dispersion characteristics are illustrated by comparing with those of single-walled carbon nanotubes. It is found that in double-walled carbon nanotubes, the guided circumferential waves will propagate in more dispersive ways. More interactions between neighboring wave modes may take place. In particular, it has been found that a couple of wave modes may disappear at a certain frequency and that, while a couple of wave modes disappear, another new couple of wave modes are excited at the same wave number.

  5. Field trials results of guided wave tomography

    Science.gov (United States)

    Volker, Arno; van Zon, Tim; van der Leden, Edwin

    2015-03-01

    Corrosion is one of the industries major issues regarding the integrity of assets. Guided wave travel time tomography is a method capable of providing an absolute wall thickness map. This method is currently making the transition from the laboratory to the field. For this purpose a dedicated data acquisition system and special purpose EMAT sensor rings have been developed. The system can be deployed for permanent monitoring and inspections. Field trials have been conducted on various pipes with different diameters, containing either liquid or gas. The main focus has been on pipe supports. The results demonstrate the successful operation of the technology in the field. Expected corrosion damage was clearly visible on the produced results enabling asset owner to make calculated decisions on the pipelines safety, maintenance and operations.

  6. Guided wave opto-acoustic device

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Shock wave loading of a magnetic guide

    Science.gov (United States)

    Kindt, L.

    2011-10-01

    The atom laser has long been a holy grail within atom physics and with the creation of an atom laser we hope to bring a similar revolution in to the field of atom optics. With the creation of the Bose-Einstein Condensate (BEC) in 1995 the path to an atom laser was initiated. An atom laser is continues source of BEC. In a Bose condensate all the atoms occupy the same quantum state and can be described by the same wave function and phase. With an atom laser the De Broglie wavelength of atoms can be much smaller than the wavelength of light. Due to the ultimate control over the atoms the atom laser is very interesting for atom optics, lithography, metrology, etching and deposition of atoms on a surface. All previous atom lasers have been created from atoms coupled out from an existing Bose-Einstein Condensate. There are different approaches but common to them all is that the duration of the output of the atom laser is limited by the size of the initial BEC and they all have a low flux. This leaves the quest to build a continuous high flux atom laser. An alternative approach to a continuous BEC beam is to channel a continuous ultra cold atomic beam into a magnetic guide and then cool this beam down to degeneracy. Cooling down a continuous beam of atoms faces three large problems: The collision rate has to be large enough for effective rethermalization, since evaporative cooling in 2D is not as effective as in 3D and a large thermal conductivity due to atoms with a high angular momentum causes heating downstream in the guide. We have built a 4 meter magnetic guide that is placed on a downward slope with a magnetic barrier in the end. In the guide we load packets of ultra cold rubidium atoms with a frequency rate large enough for the packets to merge together to form a continuous atomic beam. The atomic beam is supersonic and when the beam reaches the end barrier it will return and collide with itself. The collisions lowers the velocity of the beam into subsonic

  8. Recent developments in guided wave travel time tomography

    NARCIS (Netherlands)

    Zon, A.T. van; Volker, A.W.F.

    2014-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography had been developed to create a map of the wall thickness using the travel times of guided waves

  9. Microwave & Magnetic (M2) Proteomics Reveals CNS-Specific Protein Expression Waves that Precede Clinical Symptoms of Experimental Autoimmune Encephalomyelitis

    Science.gov (United States)

    Raphael, Itay; Mahesula, Swetha; Purkar, Anjali; Black, David; Catala, Alexis; Gelfond, Jonathon A. L.; Forsthuber, Thomas G.; Haskins, William E.

    2014-09-01

    Central nervous system-specific proteins (CSPs), transported across the damaged blood-brain-barrier (BBB) to cerebrospinal fluid (CSF) and blood (serum), might be promising diagnostic, prognostic and predictive protein biomarkers of disease in individual multiple sclerosis (MS) patients because they are not expected to be present at appreciable levels in the circulation of healthy subjects. We hypothesized that microwave & magnetic (M2) proteomics of CSPs in brain tissue might be an effective means to prioritize putative CSP biomarkers for future immunoassays in serum. To test this hypothesis, we used M2 proteomics to longitudinally assess CSP expression in brain tissue from mice during experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Confirmation of central nervous system (CNS)-infiltrating inflammatory cell response and CSP expression in serum was achieved with cytokine ELISPOT and ELISA immunoassays, respectively, for selected CSPs. M2 proteomics (and ELISA) revealed characteristic CSP expression waves, including synapsin-1 and α-II-spectrin, which peaked at day 7 in brain tissue (and serum) and preceded clinical EAE symptoms that began at day 10 and peaked at day 20. Moreover, M2 proteomics supports the concept that relatively few CNS-infiltrating inflammatory cells can have a disproportionally large impact on CSP expression prior to clinical manifestation of EAE.

  10. Optimal synthesis of tunable elastic wave-guides

    DEFF Research Database (Denmark)

    Evgrafov, Anton; Rupp, Cory J.; Dunn, Martin L.

    2008-01-01

    Topology optimization, or control in the coefficients of partial differential equations, has been successfully utilized for designing wave-guides with precisely tailored functionalities. For many applications it would be desirable to have the possibility of drastically altering the wave......-guiding properties of a device “on the fly,” in a controllable manner as an influence of some external input. This would enable wave-guides with highly non-linear input–output mappings, such as for example controllable wave switches. In this paper, we propose using finite elastic pre-straining for the purpose...

  11. Optimization of ultrasonic transducers for selective guided wave actuation

    Science.gov (United States)

    Miszczynski, Mateusz; Packo, Pawel; Zbyrad, Paulina; Stepinski, Tadeusz; Uhl, Tadeusz; Lis, Jerzy; Wiatr, Kazimierz

    2016-04-01

    The application of guided waves using surface-bonded piezoceramic transducers for nondestructive testing (NDT) and Structural Health Monitoring (SHM) have shown great potential. However, due to difficulty in identification of individual wave modes resulting from their dispersive and multi-modal nature, selective mode excitement methods are highly desired. The presented work focuses on an optimization-based approach to design of a piezoelectric transducer for selective guided waves generation. The concept of the presented framework involves a Finite Element Method (FEM) model in the optimization process. The material of the transducer is optimized in topological sense with the aim of tuning piezoelectric properties for actuation of specific guided wave modes.

  12. Ultrasonic guided wave mechanics for composite material structural health monitoring

    Science.gov (United States)

    Gao, Huidong

    The ultrasonic guided wave based method is very promising for structural health monitoring of aging and modern aircraft. An understanding of wave mechanics becomes very critical for exploring the potential of this technology. However, the guided wave mechanics in complex structures, especially composite materials, are very challenging due to the nature of multi-layer, anisotropic, and viscoelastic behavior. The purpose of this thesis is to overcome the challenges and potentially take advantage of the complex wave mechanics for advanced sensor design and signal analysis. Guided wave mechanics is studied in three aspects, namely wave propagation, excitation, and damage sensing. A 16 layer quasi-isotropic composite with a [(0/45/90/-45)s]2 lay up sequence is used in our study. First, a hybrid semi-analytical finite element (SAFE) and global matrix method (GMM) is used to simulate guided wave propagation in composites. Fast and accurate simulation is achieved by using SAFE for dispersion curve generation and GMM for wave structure calculation. Secondly, the normal mode expansion (NME) technique is used for the first time to study the wave excitation characteristics in laminated composites. A clear and simple definition of wave excitability is put forward as a result of NME analysis. Source influence for guided wave excitation is plotted as amplitude on a frequency and phase velocity spectrum. This spectrum also provides a guideline for transducer design in guided wave excitation. The ultrasonic guided wave excitation characteristics in viscoelastic media are also studied for the first time using a modified normal mode expansion technique. Thirdly, a simple physically based feature is developed to estimate the guided wave sensitivity to damage in composites. Finally, a fuzzy logic decision program is developed to perform mode selection through a quantitative evaluation of the wave propagation, excitation and sensitivity features. Numerical simulation algorithms are

  13. Metal wires for terahertz wave guiding.

    Science.gov (United States)

    Wang, Kanglin; Mittleman, Daniel M

    2004-11-18

    Sources and systems for far-infrared or terahertz (1 THz = 10(12) Hz) radiation have received extensive attention in recent years, with applications in sensing, imaging and spectroscopy. Terahertz radiation bridges the gap between the microwave and optical regimes, and offers significant scientific and technological potential in many fields. However, waveguiding in this intermediate spectral region still remains a challenge. Neither conventional metal waveguides for microwave radiation, nor dielectric fibres for visible and near-infrared radiation can be used to guide terahertz waves over a long distance, owing to the high loss from the finite conductivity of metals or the high absorption coefficient of dielectric materials in this spectral range. Furthermore, the extensive use of broadband pulses in the terahertz regime imposes an additional constraint of low dispersion, which is necessary for compatibility with spectroscopic applications. Here we show how a simple waveguide, namely a bare metal wire, can be used to transport terahertz pulses with virtually no dispersion, low attenuation, and with remarkable structural simplicity. As an example of this new waveguiding structure, we demonstrate an endoscope for terahertz pulses.

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

    OpenAIRE

    2015-01-01

    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 19th 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 natu...

  15. Damage detection in submerged plates using ultrasonic guided waves

    Indian Academy of Sciences (India)

    Sandeep Sharma; Abhijit Mukherjee

    2014-10-01

    This paper describes a non-contact and non-invasive health monitoring strategy for submerged plate structures using guided waves. The structure under consideration is immersed in water and subjected to longitudinal ultrasonic waves at specific angles of incidence using a cylindrical piezoelectric transducer using the surrounding water as coupling medium. Suitable ultrasonic guided wave modes with optimum scanning capabilities have been generated and identified in submerged plate system. Finally, the propagation of selected modes through submerged notched plates is investigated. Sensitivity of leaky waves to the notches has been studied. The methodology would help in identifying damages in the submerged plate structures.

  16. Recent Advances in Millimeter-Wave NRD-Guide Circuits

    Science.gov (United States)

    Yoneyama, Tsukasa

    Though millimeter wave applications have attracted much attention in recent years, they have not yet been put to practical use. The major reason for the failure may be a large transmission loss peculiar to the short wavelength. In order to overcome the inconvenience, it may be promising to introduce the technology of millimeter-wave NRD-guide circuits. In this technology, not only NRD-guide but also Gunn diodes and Schottky diodes play the important role in high bit-rate millimeter-wave applications. A variety of practical millimeter wave wireless systems have been proposed and fabricated. Performances and applications of them are discussed in detail as well.

  17. Guided-wave acousto-optics interactions, devices, and applications

    CERN Document Server

    1990-01-01

    The field of integrated- or guided-wave optics has experienced significant and continuous growth since its inception in the late 1960s. There has been a considerable increase in research and development activity in this field worldwide and some significant advances in the realization of working in­ tegrated optic devices and modules have been made in recent years. In fact, there have already been some commercial manufacturing and technical ap­ plications of such devices and modules. The guided-wave-acoustooptics involving Bragg interactions between guided optical waves and surface acoustic waves is one of the areas of in­ tegrated-optics that has reached some degree of scientific and technological maturity. This topical volume is devoted to an in-depth treatment of this emerging branch of science and technology. Presented in this volume are concise treatments on bulk-wave acoustooptics, guided-wave optics, and surface acoustic waves, and detailed studies of guided-wave acoustooptic Bragg diffraction in thr...

  18. Phased array tuning for optimal ultrasonic guided wave mode selection

    Science.gov (United States)

    Bostron, J. H.; Rose, J. L.; Moose, C. A.

    2014-02-01

    Ultrasonic guided waves have become widely used in a variety of nondestructive evaluation applications due to their efficiency in defect detection, ability to inspect hidden areas, and other reasons. With a thorough understanding of guided wave mechanics, researchers can predict which guided wave modes will have a high probability of success in a particular nondestructive evaluation application. However, work continues to find optimal mode and frequency selection. An "optimal" mode could give the highest sensitivity to defects or the greatest penetration power, increasing inspection efficiency. In this work, we consider the use of guided interface waves for bond evaluation. A phased comb array transducer is used to sweep in the phase velocity - frequency space in an effort to determine optimal modes.

  19. Simulation of guided wave propagation near numerical Brillouin zones

    Science.gov (United States)

    Kijanka, Piotr; Staszewski, Wieslaw J.; Packo, Pawel

    2016-04-01

    Attractive properties of guided waves provides very unique potential for characterization of incipient damage, particularly in plate-like structures. Among other properties, guided waves can propagate over long distances and can be used to monitor hidden structural features and components. On the other hand, guided propagation brings substantial challenges for data analysis. Signal processing techniques are frequently supported by numerical simulations in order to facilitate problem solution. When employing numerical models additional sources of errors are introduced. These can play significant role for design and development of a wave-based monitoring strategy. Hence, the paper presents an investigation of numerical models for guided waves generation, propagation and sensing. Numerical dispersion analysis, for guided waves in plates, based on the LISA approach is presented and discussed in the paper. Both dispersion and modal amplitudes characteristics are analysed. It is shown that wave propagation in a numerical model resembles propagation in a periodic medium. Consequently, Lamb wave propagation close to numerical Brillouin zone is investigated and characterized.

  20. 3D Guided Wave Motion Analysis on Laminated Composites

    Science.gov (United States)

    Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

    2013-01-01

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

  1. ST Quartz Acoustic Wave Sensors with Sectional Guiding Layers

    Directory of Open Access Journals (Sweden)

    Glen McHale

    2008-07-01

    Full Text Available We report the effect of removing a section of guiding layer from the propagation paths of ST-quartz Love wave sensors; this offers the ease of fabrication of a polymer guiding layer whilst retaining the native surface of the quartz which may then be used for the attachment of a sensitizing layer. Data is presented for the rigid and viscous loading, which indicates a small reduction in mass sensitivity compared to a Love wave device. Biosensing capabilities of these discontinuous ‘sectional’ guiding layer devices are demonstrated using protein adsorption from solution.

  2. Circular sensing networks for guided waves based structural health monitoring

    Science.gov (United States)

    Wandowski, T.; Malinowski, P. H.; Ostachowicz, W. M.

    2016-01-01

    In this paper, results of damage localization performed for four sensing network configurations are compared. Process of damage localization is based on guided waves propagation phenomenon. Guided waves are excited using piezoelectric transducer and received by scanning laser vibrometer. Different excitation frequencies are also investigated. In experimental investigations two types of piezoelectric transducers are used as guided waves exciters. Frequency-magnitude characteristics of symmetric and antisymmetric modes are created for both types of transducers. These characteristics allow a choice of an excitation frequency for efficient generation of selected wave mode. The amplitude of second mode in this case has negligibly small value. Finally, sensing networks in the form of circle with three different diameters are realized based on piezoelectric transducers. Damage localization algorithm is prepared in MATLAB® environment as well as in C++.

  3. Theoretical analysis of a Love wave biosensor in liquid with a viscoelastic wave guiding layer

    Science.gov (United States)

    Wu, Huiyan; Xiong, Xiangming; Zu, Hongfei; Wang, James H.-C.; Wang, Qing-Ming

    2017-02-01

    The Love mode surface acoustic wave biosensor is considered as one of the most promising probing methods in biomedical research and diagnosis, which has been applied to detect the mechano-biological behaviors of cells attached to the surface of the device. Recent studies have reported the structural and functional optimization of Love wave biosensors for reducing propagation loss and improving sensitivity; however, the relevant device performance needs to be analyzed in depth in terms of device structure, electromechanical properties of piezoelectric crystal substrates, viscoelastic properties of wave guiding layers, and the effect of liquid loading. In this study, a 36° YX-LiTaO3 based Love wave sensor with a parylene-C wave guiding layer is considered as a cell-based biosensor. A theoretical model is proposed to describe the Love wave propagation in the wave guiding layer and penetration in the liquid medium. Decay length δ for the Love wave penetration in liquid is found to be in the order of ˜50 nm, which agrees well with experimental observations. In addition, the effects of the viscoelastic wave guiding layer and liquid medium on the effective electromechanical coupling coefficient K2 of the sensor, the propagation loss PL, and sensor response to mass loading (mass sensitivity) are investigated. The numerical results indicate that the maximum propagation velocity is found at h/λ = 0, where h is the thickness of the wave guiding layer and λ is the wavelength; and the optimal coupling coefficient and mass sensitivity can be obtained at h/λ = 0.045 and h/λ = ˜0.06 in a vacuum or ˜0.058 in water, respectively. For a good combination of these device performance parameters, it is suggested that the optimal wave guiding layer thickness in a Love wave biosensor is at the vicinity of h/λ = ˜0.05 in a vacuum and ˜0.048 in liquid (water).

  4. Investigation of guided waves propagation in pipe buried in sand

    Energy Technology Data Exchange (ETDEWEB)

    Leinov, Eli; Cawley, Peter; Lowe, Michael J.S. [NDE Group, Department of Mechanical Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

    2014-02-18

    The inspection of pipelines by guided wave testing is a well-established method for the detection of corrosion defects in pipelines, and is currently used routinely in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipes buried in soil, test ranges tend to be significantly compromised because of attenuation of the waves caused by energy radiating into the soil. Moreover, the variability of soil conditions dictates different attenuation characteristics, which in-turn results in different, unpredictable, test ranges. We investigate experimentally the propagation and attenuation characteristics of guided waves in pipes buried in fine sand using a well characterized full scale experimental apparatus. The apparatus consists of an 8 inch-diameter, 5.6-meters long steel pipe embedded over 3 meters of its length in a rectangular container filled with fine sand, and an air-bladder for the application of overburden pressure. Longitudinal and torsional guided waves are excited in the pipe and recorded using a transducer ring (Guided Ultrasonics Ltd). Acoustic properties of the sand are measured independently in-situ and used to make model predictions of wave behavior in the buried pipe. We present the methodology and the systematic measurements of the guided waves under a range of conditions, including loose and compacted sand. It is found that the application of overburden pressure modifies the compaction of the sand and increases the attenuation, and that the measurement of the acoustic properties of sand allows model prediction of the attenuation of guided waves in buried pipes with a high level of confidence.

  5. Synthesis and characterization of plasmonic resonant guided wave networks.

    Science.gov (United States)

    Burgos, Stanley P; Lee, Ho W; Feigenbaum, Eyal; Briggs, Ryan M; Atwater, Harry A

    2014-06-11

    Composed of optical waveguides and power-splitting waveguide junctions in a network layout, resonant guided wave networks (RGWNs) split an incident wave into partial waves that resonantly interact within the network. Resonant guided wave networks have been proposed as nanoscale distributed optical networks (Feigenbaum and Atwater, Phys. Rev. Lett. 2010, 104, 147402) that can function as resonators and color routers (Feigenbaum et al. Opt. Express 2010, 18, 25584-25595). Here we experimentally characterize a plasmonic resonant guided wave network by demonstrating that a 90° waveguide junction of two v-groove channel plasmon polariton (CPP) waveguides operates as a compact power-splitting element. Combining these plasmonic power splitters with CPP waveguides in a network layout, we characterize a prototype plasmonic nanocircuit composed of four v-groove waveguides in an evenly spaced 2 × 2 configuration, which functions as a simple, compact optical logic device at telecommunication wavelengths, routing different wavelengths to separate transmission ports due to the resulting network resonances. The resonant guided wave network exhibits the full permutation of Boolean on/off values at two output ports and can be extended to an eight-port configuration, unlike other photonic crystal and plasmonic add/drop filters, in which only two on/off states are accessible.

  6. Corrosion monitoring using high-frequency guided waves

    Science.gov (United States)

    Fromme, P.

    2016-04-01

    Corrosion can develop due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural integrity. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic wedge transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted for wall thickness reduction due to milling of the steel structure. From the measured signal changes due to the wave mode interference the reduced wall thickness was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  7. Efficient way to convert propagating waves into guided waves via gradient wire structures.

    Science.gov (United States)

    Chu, Hong Chen; Luo, Jie; Lai, Yun

    2016-08-01

    We propose a method for the design of gradient wire structures that are capable of converting propagating waves into guided waves along the wire. The conversion process is achieved by imposing an additional wave vector to the scattered waves via the gradient wire structure, such that the wave vector of scattered waves is beyond the wave number in the background medium. Thus, the scattered waves turn into evanescent waves. We demonstrate that two types of gradient wire structures, with either a gradient permittivity and a fixed radius, or a gradient radius and a fixed permittivity, can both be designed to realize such a wave conversion effect. The principle demonstrated in our work has potential applications in various areas including nanophotonics, silicone photonics, and plasmonics.

  8. Guided waves in cladded composite tubes

    Science.gov (United States)

    Kohl, Thomas

    1989-01-01

    The objectives of this program are as follows: modelling of dynamics of composite tubular space structure truss members; and utilization of ultrasonic waves as probes for material and defect characterization. This discussion is presented in viewgraph format.

  9. Sensors Based on Spectroscopy of Guided Waves

    Science.gov (United States)

    Homola, Jiří

    The last two decades have witnessed remarkable progress in the develpment of affinity biosensors and their applications in areas such as environmental protection, biotechnology, medical diagnostics, drug screening, food safety, and security. An affinity biosensor consists of a transducer and a biological recognition element which is able to interact with a selected analyte. Various optical methods have been exploited in biosensors including fluorescence spectroscopy, interferometry (reflectometric white light interferometry, modal interferometry in optical waveguide structures), and spectroscopy of guided modes of optical waveguides. Optical biosensors based on spectroscopy of guided modes of optical waveguides - grating coupler, resonant mirror, and surface plasmon resonance (SPR) - rely on the measurement of binding-induced refractive index changes and thus are label-free technologies. This paper reviews fundamentals of optical sensors based on spectroscopy of guided modes of optical waveguides and their applications.

  10. Guided wave coupling in integrated-optic gratings - Normal incidence

    Science.gov (United States)

    van Roey, J.; Denturck, B.; Lagasse, P. E.

    1984-10-01

    The coupling between the different guided modes of an integrated-optic waveguide grating filter is analyzed. A numerical method based on a finite-difference scheme for the solution of this coupling problem in the case of normal incidence is presented. This allows one to study the influence of the grating profile on the coupling between guided or radiated waves. The exact numerical results are compared with approximate formulas for the coupling coefficient.

  11. Guided waves in a monopile of an offshore wind turbine.

    Science.gov (United States)

    Zernov, V; Fradkin, L; Mudge, P

    2011-01-01

    We study the guided waves in a structure which consists of two overlapping steel plates, with the overlapping section grouted. This geometry is often encountered in support structures of large industrial offshore constructions, such as wind turbine monopiles. It has been recognized for some time that the guided wave technology offers distinctive advantages for the ultrasonic inspections and health monitoring of structures of this extent. It is demonstrated that there exist advantageous operational regimes of ultrasonic transducers guaranteeing a good inspection range, even when the structures are totally submerged in water, which is a consideration when the wind turbines are deployed off shore.

  12. Guided Waves in Wind Turbine Monopiles Immersed in Water

    Science.gov (United States)

    Zernov, V.; Pradkin, L.; Mudge, P.

    2010-02-01

    We study the guided waves in a structure which consists of two overlapping steel plates, with the overlapping section grouted. This geometry is often encountered in support structures of large industrial off-shore constructions, such as wind turbine monopiles. It has been recognized for some time that the guided wave technology offers distinctive advantages for the ultrasonic inspections and health monitoring of structures of this extent. It is demonstrated that there exist advantageous operational regimes of relevant ultrasonic transducers which result in significant improvement of the inspection range, even when the structures are totally submerged in water.

  13. SU-8 Guiding Layer for Love Wave Devices

    OpenAIRE

    Roach, P; Atherton, S; Doy, N.; McHale, G.; Newton, MI

    2007-01-01

    SU-8 is a technologically important photoresist used extensively for the fabrication of microfluidics and MEMS, allowing high aspect ratio structures to be produced. In this work we report the use of SU-8 as a Love wave sensor guiding layer which allows the possibility of integrating a guiding layer with flow cell during fabrication. Devices were fabricated on ST-cut quartz substrates with a single-single finger design such that a surface skimming bulk wave (SSBW) at 97.4 MHz was excited. SU-...

  14. Characterization of mechanical and geometrical properties of a tube with axial and circumferential guided waves.

    Science.gov (United States)

    Yeh, Cheng-Hung; Yang, Che-Hua

    2011-05-01

    Guided waves propagating in cylindrical tubes are frequently applied for the characterization of material or geometrical properties of tubes. In a tube, guided waves can propagate in the axial direction and called axial guided waves, or in the circumferential direction called circumferential guided waves. Dispersion spectra for the axial and circumferential guided waves share some common behaviors and however exhibit some particular behaviors of their own. This study provides an investigation with theoretical modeling, experimental measurements, and a simplex-based inversion procedure to explore the similarity and difference between the axial guided waves and circumferential guided waves, aiming at providing useful information while axial and circumferential guided waves are applied in the area of material characterization. The sensitivity to the radius curvature for the circumferential guided waves dispersion spectra is a major point that makes circumferential guided waves different from axial guided waves. For the purpose of material characterization, both axial and circumferential guided waves are able to extract an elastic moduli and wall-thickness information from the dispersion spectra, however, radius information can only be extracted from the circumferential guided waves spectra. Copyright © 2010 Elsevier B.V. All rights reserved.

  15. Monitoring of fatigue crack growth using guided ultrasonic waves

    Science.gov (United States)

    Masserey, B.; Kostson, E.; Fromme, P.

    2010-04-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi layer components are connected, possibly leading to the development of fatigue cracks. Guided ultrasonic waves propagating along a structure allow in principle for the efficient non-destructive testing of large plate-like structures, such as aircraft wings. This contribution presents a study of the detection and monitoring of fatigue crack growth using both low frequency and higher frequency guided ultrasonic wave modes. Two types of structures were used, single layer aluminum tensile specimens, and multi layer structures consisting of two adhesively bonded aluminum plate-strips. Fatigue experiments were carried out and it was shown that fatigue crack detection and growth monitoring at a fastener hole during cyclic loading using both guided wave types is possible. The sensitivity and repeatability of the measurements were ascertained, having the potential for fatigue crack detection at critical and difficult to access fastener locations. Good agreement was observed between the experimental results and predictions from full three-dimensional numerical simulations of the scattering of the low frequency guided ultrasonic wave at the fastener hole and crack. The robustness of the methodology for practical in-situ ultrasonic monitoring of fatigue crack growth is discussed.

  16. SU-8 Guiding Layer for Love Wave Devices

    Directory of Open Access Journals (Sweden)

    Michael I. Newton

    2007-11-01

    Full Text Available SU-8 is a technologically important photoresist used extensively for thefabrication of microfluidics and MEMS, allowing high aspect ratio structures to beproduced. In this work we report the use of SU-8 as a Love wave sensor guiding layerwhich allows the possibility of integrating a guiding layer with flow cell during fabrication.Devices were fabricated on ST-cut quartz substrates with a single-single finger design suchthat a surface skimming bulk wave (SSBW at 97.4 MHz was excited. SU-8 polymer layerswere successively built up by spin coating and spectra recorded at each stage; showing afrequency decrease with increasing guiding layer thickness. The insertion loss andfrequency dependence as a function of guiding layer thickness was investigated over thefirst Love wave mode. Mass loading sensitivity of the resultant Love wave devices wasinvestigated by deposition of multiple gold layers. Liquid sensing using these devices wasalso demonstrated; water-glycerol mixtures were used to demonstrate sensing of density-viscosity and the physical adsorption and removal of protein was also assessed usingalbumin and fibrinogen as model proteins.

  17. Guided wave inspection and monitoring of railway track

    CSIR Research Space (South Africa)

    Loveday, PW

    2012-04-01

    Full Text Available for guided wave ultrasound, which offers the potential to interrogate a large length of rail from a single position. Continuously welded rail is installed in tension but temperature changes can result in rail buckling if the tension is insufficient or fatigue...

  18. Dispersion of guided waves in composite laminates and sandwich panels

    Science.gov (United States)

    Schaal, Christoph; Mal, Ajit

    2015-03-01

    In composite structures, damages are often invisible from the surface and can grow to reach a critical size, potentially causing catastrophic failure of the entire structure. Thus safe operation of these structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost-effective method for structural health monitoring in advanced structures. Guided waves allow for long monitoring ranges and are very sensitive to defects within their propagation path. In this work, the relevant properties of guided Lamb waves for damage detection in composite structures are investigated. An efficient numerical approach is used to determine their dispersion characteristics, and these results are compared to those from laboratory experiments. The experiments are based on a pitch-catch method, in which a pair of movable transducers is placed on one surface of the structure to induce and detect guided Lamb waves. The specific cases considered include an aluminum plate and an aluminum honeycomb sandwich panel with woven composite face sheets. In addition, a disbond of the interface between one of the face sheets and the honeycomb core of the sandwich panel is also considered, and the dispersion characteristics of the two resultant waveguides are determined. Good agreement between numerical and experimental dispersion results is found, and suggestions on the applicability of the pitch-catch system for structural health monitoring are made.

  19. High frequency guided wave propagation in monocrystalline silicon wafers

    Science.gov (United States)

    Pizzolato, Marco; Masserey, Bernard; Robyr, Jean-Luc; Fromme, Paul

    2017-04-01

    Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. The cutting process can introduce micro-cracks in the thin wafers and lead to varying thickness. High frequency guided ultrasonic waves are considered for the structural monitoring of the wafers. The anisotropy of the monocrystalline silicon leads to variations of the wave characteristics, depending on the propagation direction relative to the crystal orientation. Full three-dimensional Finite Element simulations of the guided wave propagation were conducted to visualize and quantify these effects for a line source. The phase velocity (slowness) and skew angle of the two fundamental Lamb wave modes (first anti-symmetric mode A0 and first symmetric mode S0) for varying propagation directions relative to the crystal orientation were measured experimentally. Selective mode excitation was achieved using a contact piezoelectric transducer with a custom-made wedge and holder to achieve a controlled contact pressure. The out-of-plane component of the guided wave propagation was measured using a noncontact laser interferometer. Good agreement was found with the simulation results and theoretical predictions based on nominal material properties of the silicon wafer.

  20. Cure monitoring using ultrasonic guided waves in wires.

    Science.gov (United States)

    Vogt, T; Lowe, M; Cawley, P

    2003-09-01

    The possibility of using ultrasonic guided waves for monitoring the cure process of epoxy resins is investigated. The two techniques presented use a wire waveguide which is partly embedded in the resin. The first technique is based on the measurement of attenuation due to leakage of bulk waves into the resin surrounding the waveguide. The second technique measures the reflection of the guided wave that occurs at the point where the waveguide enters the resin. Both the attenuation and the reflection coefficient change significantly during cure, and the numerical methods to relate these to the material properties of the curing resin are presented in this paper. The results from the modeling are experimentally verified and show good agreement. The applicability of each testing method is discussed, and typical cure-monitoring curves are presented.

  1. Cure monitoring using ultrasonic guided waves in wires

    Science.gov (United States)

    Vogt, T.; Lowe, M.; Cawley, P.

    2003-09-01

    The possibility of using ultrasonic guided waves for monitoring the cure process of epoxy resins is investigated. The two techniques presented use a wire waveguide which is partly embedded in the resin. The first technique is based on the measurement of attenuation due to leakage of bulk waves into the resin surrounding the waveguide. The second technique measures the reflection of the guided wave that occurs at the point where the waveguide enters the resin. Both the attenuation and the reflection coefficient change significantly during cure, and the numerical methods to relate these to the material properties of the curing resin are presented in this paper. The results from the modeling are experimentally verified and show good agreement. The applicability of each testing method is discussed, and typical cure-monitoring curves are presented.

  2. Guided wave modes in porous cylinders: experimental results.

    Science.gov (United States)

    Wisse, C J; Smeulders, D M J; van Dongen, M E H; Chao, G

    2002-09-01

    In this paper guided wave modes in porous media are investigated. A water-saturated porous cylinder is mounted in the test section of a shock tube. Between the porous sample and the wall of the shock tube a water-filled annulus exists. For very small annulus width, bulk waves are generated and one-dimensional modeling is sufficient. Otherwise two-dimensional effects become important and multiple guided wave modes occur. Using a newly developed traversable positioning system in the shock tube, the frequency-dependent phase velocities and damping coefficients in the 1-120 kHz frequency range were measured. Prony's method was used for data processing. Agreement was found between the experimental data and the two-dimensional modeling of the shock tube which was based on Biot's theory.

  3. Guided wave propagation in porous unidirectional carbon fiber reinforced plastic

    Science.gov (United States)

    Dobmann, Nicolas; Bach, Martin

    2017-02-01

    Networks of piezoelectric transducers mounted on aircraft structures for Acousto Ultrasonics (AU) purposes are designed to be applied during the service life of the aircraft. The approach to integrate these sensor networks already during the manufacture of carbon fiber reinforced plastic (CFRP) host structures prompts ideas to achieve an additional benefit by their application for cure monitoring, thus extending their use to the manufacturing chain. This benefit could be extended even further if guided waves generated by AU sensor networks could be used for porosity testing extensively applied for CFRP aircraft structures. In light of this, an experimental study was conducted to investigate effects of porosity on the propagation of guided waves in a basic configuration of unidirectional CFRP. Several samples were manufactured at different porosity levels by variation of the processing pressure. Wave fields were acquired using an ultrasonic scanning device. In the present work, phase velocities are chosen as best measurable and quantifiable propagation feature and the approach for the analysis of phase velocities in porosity samples is outlined. First results are presented and discussed regarding the influence of porosity on guided wave phase velocity and basic applicability for porosity testing of aircraft structures.

  4. Fully Coupled Electromechanical Elastodynamic Model for Guided Wave Propagation Analysis

    CERN Document Server

    Borkowski, Luke; Chattopadhyay, Aditi

    2013-01-01

    Physics-based computational models play a key role in the study of wave propagation for structural health monitoring (SHM) and the development of improved damage detection methodologies. Due to the complex nature of guided waves, accurate and efficient computation tools are necessary to investigate the mechanisms responsible for dispersion, coupling, and interaction with damage. In this paper, a fully coupled electromechanical elastodynamic model for wave propagation in a heterogeneous, anisotropic material system is developed. The final framework provides the full three dimensional displacement and electrical potential fields for arbitrary plate and transducer geometries and excitation waveform and frequency. The model is validated theoretically and proven computationally efficient. Studies are performed with surface bonded piezoelectric sensors to gain insight into the physics of experimental techniques used for SHM. Collocated actuation of the fundamental Lamb wave modes is modeled over a range of frequenc...

  5. Scattering of Plane Guided Waves Obliquely Incident on Straight Features

    Science.gov (United States)

    Wilcox, P. D.; Velichko, A.; Drinkwater, B. W.; Croxford, A. J.; Todd, M. D.

    2011-06-01

    A semi-analytical finite element model is developed to study the scattering of plane guided waves obliquely incident on a straight geometric feature. The model is first used to investigate the reflection of the S0 mode from a free edge and the results are compared to those of bulk waves reflecting from a free boundary. The model is then used to predict the transmission of the S0 mode past an adhesively-bonded stiffener. The results obtained are in excellent agreement with experimental measurements.

  6. Ultrasonic Guided Wave Propagation through Welded Lap Joints

    Directory of Open Access Journals (Sweden)

    Audrius Jankauskas

    2016-12-01

    Full Text Available The objective of the research presented here is the investigation of ultrasonic guided wave (UGW propagation through the lap joint welded plates used in the construction of a storage tank floors. The investigations have been performed using numerical simulation by finite element method (FEM and tested by measurement of the transmission losses of the guided waves transmitted through the welded lap joints. Propagation of the symmetric S0 mode in the welded stainless steel plates in the cases of different lap joint overlap width, operation frequency, and additional plate bonding caused by corrosion were investigated. It was shown that the transmission losses of the S0 mode can vary in the range of 2 dB to 8 dB depending on the ratio between lap joint width and wavelength. It was also demonstrated that additional bonding in the overlap zone caused by corrosion can essentially reduce transmission losses.

  7. Monitoring early age cementitious materials using ultrasonic guided waves

    Science.gov (United States)

    Borgerson, Jacob L.

    The evaluation of early age concrete is critical for reducing construction times and ensuring quality. In this study, the use of ultrasonic guided waves for monitoring the development of early age cementitious materials is investigated. A torsional wave is transmitted and received through a waveguide that is embedded in early age mortar or concrete. As the cementitious material sets and hardens, the received wave(s) change, indicating the transition from a semifluid to a solid state. This thesis proposes two systems. The first system is a through-transmission system; a wave is transmitted on one end of an embedded waveguide using a sensor arrangement and then it is received on the opposite end of the rod with another sensor. This approach monitors the attenuation of the fundamental torsional wave mode, resulting from the leakage of energy from the cylindrical steel rod to the surrounding cementitious material. The evolution of the material's properties is related to the energy leakage or attenuation of the guided wave. The second system is a pulse-echo system; a wave is transmitted on one end of a partially embedded waveguide via a sensor arrangement that also receives the reflected signals. This approach monitors both the reflection from the end of the rod and the reflection from the point where the waveguide enters the material. The development of the cementitious material's mechanical properties is related to both the energy leaked into the surrounding material and the energy reflected at the point of entry. The ability of this method to only require access to one side of the specimen makes it attractive for monitoring early age cementitious materials in the field. Experiments were performed on mixtures with varying water-cement ratios (w/c = 0.40, 0.50, and 0.60), chemical admixtures (accelerant and retardant), mineral admixtures (silica fume and fly ash), and coarse aggregate (pea gravel). The time of setting and compressive strength of the various mixtures

  8. Quantitative Diagnostics of Multilayered Composite Structures with Ultrasonic Guided Waves

    Science.gov (United States)

    2014-09-01

    the material. The excitation signal applied to the transmitter was a 12 cycles of sinusoidal toneburst with a frequency of 210 kHz. An improved image...were launched from the outer surfaces of the test specimens by using acrylic coupling shoes . In this way, the guided wave energy was launched through...the tip section of the shoe and subsequently propagating along the surface of the test specimen. Time domain signal processing was applied to analyze

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

    Science.gov (United States)

    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.

  10. An ultrasonic guided wave method to estimate applied biaxial loads

    Science.gov (United States)

    Shi, Fan; Michaels, Jennifer E.; Lee, Sang Jun

    2012-05-01

    Guided waves propagating in a homogeneous plate are known to be sensitive to both temperature changes and applied stress variations. Here we consider the inverse problem of recovering homogeneous biaxial stresses from measured changes in phase velocity at multiple propagation directions using a single mode at a specific frequency. Although there is no closed form solution relating phase velocity changes to applied stresses, prior results indicate that phase velocity changes can be closely approximated by a sinusoidal function with respect to angle of propagation. Here it is shown that all sinusoidal coefficients can be estimated from a single uniaxial loading experiment. The general biaxial inverse problem can thus be solved by fitting an appropriate sinusoid to measured phase velocity changes versus propagation angle, and relating the coefficients to the unknown stresses. The phase velocity data are obtained from direct arrivals between guided wave transducers whose direct paths of propagation are oriented at different angles. This method is applied and verified using sparse array data recorded during a fatigue test. The additional complication of the resulting fatigue cracks interfering with some of the direct arrivals is addressed via proper selection of transducer pairs. Results show that applied stresses can be successfully recovered from the measured changes in guided wave signals.

  11. Guided Wave Tomography Based on Full-Waveform Inversion.

    Science.gov (United States)

    Rao, Jing; Ratassepp, Madis; Fan, Zheng

    2016-02-29

    In this paper, a guided wave tomography method based on Full Waveform Inversion (FWI) is developed for accurate and high resolu- tion reconstruction of the remaining wall thickness in isotropic plates. The forward model is computed in the frequency domain by solving a full-wave equation in a two-dimensional acoustic model, accounting for higher order eects such as diractions and multiple scattering. Both numerical simulations and experiments were carried out to obtain the signals of a dispersive guided mode propagating through defects. The inversion was based on local optimization of a waveform mist func- tion between modeled and measured data, and was applied iteratively to discrete frequency components from low to high frequencies. The resulting wave velocity maps were then converted to thickness maps by the dispersion characteristics of selected guided modes. The results suggest that the FWI method is capable to reconstruct the thickness map of a irregularly shaped defect accurately on a 10 mm thick plate with the thickness error within 0.5 mm.

  12. Enhanced Signal Processing and Characterization Using Guided Waves

    Science.gov (United States)

    Catton, P.; Haig, A.; Sanderson, R.; Weston, M.; Mudge, P.

    2010-02-01

    In the past, inspection by ultrasonic guided waves (also called `Long Range Ultrasonic Testing', or LRUT) has been used as a tool for rapidly screening pipeline for the presence of corrosion, where a loss to the original cross sectional area of greater than around 9% can be detected, and located with an axial resolution of a few inches. Recent advances have shown that this qualitative screening method has the potential to be transformed into a more quantitative NDT technique. This is achieved by using a phased-array technique to focus guided waves at areas of interest identified by an initial screening test, and allows the ability of estimating the circumferential extent and position of localized defects. It is possible to sequentially focus the guided waves at incremental positions along the length of the pipe as well as around the circumference, but the inspection time increases with the number of required focus positions. To address this practical limitation, the present work investigates techniques to greatly reduce the inspection duration. Full Matrix Capture and broadband excitation approaches are discussed and initial results are presented, illustrating the feasibility of such methods.

  13. Mode control of guided wave in magnetic hollow cylinder using electromagnetic acoustic transducer array

    Energy Technology Data Exchange (ETDEWEB)

    Furusawa, Akiniri; Kojima, Fumio; Morikawa, Atsushi [Dept. of Systems Science, Graduate School of System Informatics, Kobe University, Kobe (Japan)

    2015-03-15

    The aim of this work is to demonstrate a method for exciting and receiving torsional and longitudinal mode guided waves with an electromagnetic acoustic transducer (EMAT) ring array. First of all, a three-dimensional guided wave simulator is developed in order to numerically analyze the propagation of the guided wave. The finite difference time domain method is used for the simulator. Second, two guided wave testing systems using an EMAT ring array are provided: one is for torsional mode (T-mode) guided wave and the other is for longitudinal mode (L-mode). The EMATs used in the both systems are the same in design. A method to generate and receive the T- and L-mode guided waves with the same EMAT is proposed. Finally, experimental and numerical results are compared and discussed. The results of experiments and simulation agree well, showing the potential of the EMAT ring array as a mode controllable guided wave transmitter and receiver.

  14. Propagation characteristics of ultrasonic guided waves in continuously welded rail

    Science.gov (United States)

    Yao, Wenqing; Sheng, Fuwei; Wei, Xiaoyuan; Zhang, Lei; Yang, Yuan

    2017-07-01

    Rail defects cause numerous railway accidents. Trains are derailed and serious consequences often occur. Compared to traditional bulk wave testing, ultrasonic guided waves (UGWs) can provide larger monitoring ranges and complete coverage of the waveguide cross-section. These advantages are of significant importance for the non-destructive testing (NDT) of the continuously welded rail, and the technique is therefore widely used in high-speed railways. UGWs in continuous welded rail (CWR) and their propagation characteristics have been discussed in this paper. Finite element methods (FEMs) were used to accomplish a vibration modal analysis, which is extended by a subsequent dispersion analysis. Wave structure features were illustrated by displacement profiles. It was concluded that guided waves have the ability to detect defects in the rail via choice of proper mode and frequency. Additionally, thermal conduction that is caused by temperature variation in the rail is added into modeling and simulation. The results indicated that unbalanced thermal distribution may lead to the attenuation of UGWs in the rail.

  15. Guided Wave Delamination Detection and Quantification With Wavefield Data Analysis

    Science.gov (United States)

    Tian, Zhenhua; Campbell Leckey, Cara A.; Seebo, Jeffrey P.; Yu, Lingyu

    2014-01-01

    Unexpected damage can occur in aerospace composites due to impact events or material stress during off-nominal loading events. In particular, laminated composites are susceptible to delamination damage due to weak transverse tensile and inter-laminar shear strengths. Developments of reliable and quantitative techniques to detect delamination damage in laminated composites are imperative for safe and functional optimally-designed next-generation composite structures. In this paper, we investigate guided wave interactions with delamination damage and develop quantification algorithms by using wavefield data analysis. The trapped guided waves in the delamination region are observed from the wavefield data and further quantitatively interpreted by using different wavenumber analysis methods. The frequency-wavenumber representation of the wavefield shows that new wavenumbers are present and correlate to trapped waves in the damage region. These new wavenumbers are used to detect and quantify the delamination damage through the wavenumber analysis, which can show how the wavenumber changes as a function of wave propagation distance. The location and spatial duration of the new wavenumbers can be identified, providing a useful means not only for detecting the presence of delamination damage but also allowing for estimation of the delamination size. Our method has been applied to detect and quantify real delamination damage with complex geometry (grown using a quasi-static indentation technique). The detection and quantification results show the location, size, and shape of the delamination damage.

  16. SH-guided waves in layered piezoelectric/piezomagnetic plates

    Institute of Scientific and Technical Information of China (English)

    Guoquan Nie; Zijun An; Jinxi Liu

    2009-01-01

    The propagation of shear horizontal (SH) guided waves in a coupled plate consisting of a piezoelectric layer and a piezomagnetic layer is studied. Both the layers are transversely isotropic and perfectly bonded along the interface. The upper and the lower surfaces of the plate are assumed to be mechanically free, electrically open and magnetically dosed. Two different cases are considered. One is that the bulk shear wave velocity of piezoelectric material is larger than that of piezomagnetic material. The other is that the bulk shear wave velocity of piezomagnetic material is larger than that of piezoelectric material. The dispersion relation is obtained while the phase velocity is among the bulk shear wave velocity of two different layers. The numerical results show that the phase velocity approaches the smaller bulk shear wave velocity of the material in the system with the increase in the wave number for different modes. The thickness ratio and the properties of the piezoelectric material have great effect on the dispersion behaviors. The results of this paper can offer some funda-mental theory to the application of piezoelectric/piezomagnetic composites or structures.

  17. Biological decontamination of surfaces using guided ionization waves

    Science.gov (United States)

    Jarrige, Julien; Zaepffel, Clement

    2016-09-01

    Atmospheric pressure plasma jets have received an increasing attention these last ten years in various domains, including biomedical applications and decontamination. Among these technologies, guided ionization waves (also called ``plasma bullets'') are very promising because of their ability to produce a highly non-equilibrium plasma. Reactive species can be generated in the open air over a long distance during the propagation of the wave (typically: several cm), while the background gas remains at ambient temperature. A non-thermal plasma system has been developed and tested for the biological decontamination of surfaces. It consists of a dielectric barrier discharge in a helium flow driven by high voltage pulses. The propagation of the ionization wave and the spatial distribution of the species have been characterized by high speed imaging and optical emission spectroscopy. The influence of the discharge parameters on the plasma properties is investigated. Results of decontamination on several bacteria are shown, and the decontamination efficiency is compared with the plasma properties.

  18. Wave Mode Discrimination of Coded Ultrasonic Guided Waves Using Two-Dimensional Compressed Pulse Analysis.

    Science.gov (United States)

    Malo, Sergio; Fateri, Sina; Livadas, Makis; Mares, Cristinel; Gan, Tat-Hean

    2017-07-01

    Ultrasonic guided waves testing is a technique successfully used in many industrial scenarios worldwide. For many complex applications, the dispersive nature and multimode behavior of the technique still poses a challenge for correct defect detection capabilities. In order to improve the performance of the guided waves, a 2-D compressed pulse analysis is presented in this paper. This novel technique combines the use of pulse compression and dispersion compensation in order to improve the signal-to-noise ratio (SNR) and temporal-spatial resolution of the signals. The ability of the technique to discriminate different wave modes is also highlighted. In addition, an iterative algorithm is developed to identify the wave modes of interest using adaptive peak detection to enable automatic wave mode discrimination. The employed algorithm is developed in order to pave the way for further in situ applications. The performance of Barker-coded and chirp waveforms is studied in a multimodal scenario where longitudinal and flexural wave packets are superposed. The technique is tested in both synthetic and experimental conditions. The enhancements in SNR and temporal resolution are quantified as well as their ability to accurately calculate the propagation distance for different wave modes.

  19. Seismic structure of the oceanic lithosphere inferred from guided wave

    Science.gov (United States)

    Shito, A.; Suetsugu, D.; Furumura, T.; Sugioka, H.; Ito, A.

    2012-12-01

    Characteristic seismic waves are observed by seismological experiment using Broad-Band Ocean Bottom Seismometers (BBOBSs) conducted in the northwestern Pacific from 2007 to 2008 and from 2010 to 2011. The seismic waves have low frequency onset (phases (2.5-10 Hz). The high frequency later phases have large amplitude and long duration for both P and S waves. The seismic waves are observed commonly at the BBOBS array from events in the subducting Pacific plate. To investigate generation and propagation mechanisms of the seismic wave will help us to understand the seismic structure and the origin of the oceanic lithosphere. High frequency phases travelling efficiently through the oceanic lithosphere more than 3000 km are well known phenomenon. These phases were previously called as Po/So waves. Po/So waves were observed as early as 1935, and were studied actively from the 1970s to 1990s. However, the mechanism of generation and propagation of the phases are still controversial. The guided waves propagating in subducting plate are also common phenomenon in the subduction zone. The waves are generally characterized by separation of low frequency and high frequency components. In order to explain the separation, Martin and Rietbrock [2003] considered the trapping of waves in the waveguide formed by thin low velocity former oceanic crust at the top of the plate. However, large amplitude and long duration of the high frequency component cannot be achieved by the model. From the analysis of waveform observed at the eastern seaboard of northern Japan and numerical simulation of seismic wave propagation, Furumura and Kennet [2005] demonstrate that the guided wave travelling in the subducting plate is produced by multiple forward scattering of high-frequency seismic waves due to small-scale random heterogeneity in the plate structure. We apply the method proposed by Furumura and Kennett [2005] to reproduce the seismograms recorded by the BBOBS array. We conduct 2D numerical

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

    Science.gov (United States)

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

    2015-06-01

    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 19th 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.

  1. Light waves guided by a single curved metallic surface.

    Science.gov (United States)

    Krammer, H

    1978-01-15

    Propagation of TE-waves along a single curved metallic surface with radius of curvature much larger than wavelength is investigated both theoretically and experimentally. Approximate analytic expressions for the field configuration yield that power concentrates in a small region near the metal. The attenuation constant per unit angle of bend (radian) is given by the real part of the inverse of the refractive index, independent of the radius of curvature and of the mode number. In agreement with theory experiments with 10-microm radiation showed that low loss guiding can be realized.

  2. Guided wave inspection and monitoring of railway track

    CSIR Research Space (South Africa)

    Loveday, PW

    2012-07-01

    Full Text Available The two major rail applications of guided waves being researched, axial load measurement and defect detection, are reviewed in this section. The different system level approaches are described. 2.1 Axial Load Measurement The measurement of thermal... of California in San Diego [8]. The presence of double harmonic and internal resonance phenomena are described in [9]. A schematic of the experiment is shown in Fig. 1. 4 Fig. 1 Axial load measurement set up at UCSD (courtesy of Prof. F. Lanza di...

  3. High performance guided-wave asynchronous heralded single photon source

    OpenAIRE

    Alibart, Olivier; Ostrowsky, Daniel Barry; Baldi, Pascal; Tanzilli, Sébastien

    2005-01-01

    International audience; We report on a guided wave heralded photon source based on the creation of non-degenerate photon pairs by spontaneous parametric down conversion in a Periodically Poled Lithium Niobate waveguide. Using the signal photon at 1310 nm as a trigger, a gated detection process permits announcing the arrival of single photons at 1550 nm at the output of a single mode optical fiber with a high probability of 0.38. At the same time the multi-photon emission probability is reduce...

  4. Guided wave photonics fundamentals and applications with Matlab

    CERN Document Server

    Binh, Le Nguyen

    2012-01-01

    IntroductionHistorical Overview of Integrated Optics and PhotonicsWhy Analysis of Optical Guided-wave Devices?Principal ObjectivesChapters OverviewSingle Mode Planar Optical WaveguidesFormation of Planar Single Mode Waveguide ProblemsApproximate Analytical Methods of SolutionAPPENDIX A: Maxwell Equations in Dielectric MediaAPPENDIX B: Exact Analysis of Clad-linear Optical WaveguidesAPPENDIX C: Wentzel-Kramers-Brilluoin Method, Turning Points and Connection FormulaeAPPENDIX D: Design and Simulation of Planar Optical Waveguides3D Integrated Optical WaveguidesMarcatili's Method| Effective Index M

  5. Optical Fiber Tweezers Fabricated by Guided Wave Photo-Polymerization

    Directory of Open Access Journals (Sweden)

    Rita S. Rodrigues Ribeiro

    2015-06-01

    Full Text Available In this work the use of guided wave photo-polymerization for the fabrication of novel polymeric micro tips for optical trapping is demonstrated. It is shown that the selective excitation of linear polarized modes, during the fabrication process, has a direct impact on the shape of the resulting micro structures. Tips are fabricated with modes LP02 and LP21 and their shapes and output intensity distribution are compared. The application of the micro structures as optical tweezers is demonstrated with the manipulation of yeast cells.

  6. Slow light hierarchy and tunable switching in fractal wave guide

    Science.gov (United States)

    Nandy, Atanu; Chakrabarti, Arunava

    2017-05-01

    An exact analytical description of unraveling hierarchical distribution of slow optical modes in the context of propagation of classical waves through a fractal wave guide is reported using the scale invariance of the underlying geometry in the tight-binding formalism. The flat photonic modes are localized with finite support in the fractal system and getting trapped over clusters of increasing spans displaying the existence of multitude of localization area. The onset of localization can in principal be delayed in space by a suitable choice of the frequency of the incoming radiation. The length scale at which the onset of localization for each bounded optical mode occurs can be tuned at will following real space renormalization group method. Scanning over arbitrary small range of frequency may lead to the possibility of inter-modal switching behavior.

  7. Anomalous refraction of guided waves via embedded acoustic metasurfaces

    Science.gov (United States)

    Zhu, Hongfei; Semperlotti, Fabio

    2016-04-01

    We illustrate the design of acoustic metasurfaces based on geometric tapers and embedded in thin-plate structures. The metasurface is an engineered discontinuity that enables anomalous refraction of guided wave modes according to the Generalized Snell's Law. Locally-resonant geometric torus-like tapers are designed in order to achieve metasurfaces having discrete phase-shift profiles that enable a high level of control of refraction of the wavefronts. Results of numerical simulations show that anomalous refraction can be achieved on transmitted anti-symmetric modes (A0) either when using a symmetric (S0) or anti-symmetric (A0) incident wave, where the former case clearly involves mode conversion mechanisms.

  8. Sparsity based defect imaging in pipes using guided waves

    Science.gov (United States)

    Golato, Andrew; Santhanam, Sridhar; Ahmad, Fauzia; Amin, Moeness G.

    2016-05-01

    Pipes are used for the transport of fluids and gases in urban and industrial settings, such as buried pipelines to transport water, oil, and other resources. To ensure reliable operation, it is essential that an inspection system be in place to identify and localize damage/defects in the pipes. Unfortunately, many of the typical nondestructive evaluation techniques are inadequate due to limited pipe access; often, only the beginning and end sections of the pipe are physically accessible. As such, this problem is well suited to the use of ultrasonic guided-wave based structural health monitoring. With a limited number of transducers, ultrasonic guided waves can be used to interrogate long lengths of pipes. In this paper, we propose a damage detection and localization scheme that relies upon the inherent sparsity of defects in the pipes. A sparse array of transducers, deployed in accessible areas of the pipes, is utilized in pitch-catch mode to record signals scattered by defects in the pipe. Both the direct path scattering off the defect, and the helical modes, which are paths that spiral around the circumference of the pipe before or after interaction with the defect, are recorded. A Lamb wave based signal model is formulated that accounts for this multipath approach. The signal model is then inverted via group sparse reconstruction, in order to produce an image of the scene. The model accounts for the specificities of Lamb wave propagation through the pipe. Performance validation of the proposed approach is provided using simulated data for an aluminum pipe.

  9. In Situ Guided Wave Structural Health Monitoring System

    Science.gov (United States)

    Zhao, George; Tittmann, Bernhard R.

    2011-01-01

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

  10. Detection of a longitudinal defect in a pipe based on guided circumferential waves techniques

    Institute of Scientific and Technical Information of China (English)

    LI Longtao; HE Cunfu; WU Bin

    2005-01-01

    Based on elasticity theory, the multi-modes and disperse characteristics of guided circumferential waves in a pipe were investigated theoretically and experimentally, the disperse curves of guided circumferential waves were gotten by numerical calculations. The relationships between the angle of beam transducer, frequency and guided circumferential modes were analyzed by our guided wave experiment system. Then single guided circumferential mode was excited in the pipe (O.D 88.8 mm, I.D 80.8 mm). An artificial longitudinal defect (25 × 1 × 0.7 mm)on the surface of the pipe was detected by use of the single guided circumferential wave. The results show that single guided circumferential mode can be excited in the pipe by choosing special frequency and special angle beam transducer, similar to the excitation of Lamb wave in a plate, and it can be used to find the longitudinal defect on a pipe surface.

  11. Guided Waves in a Multi-Layered Cylindrical Elastic Solid Medium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bi-Xing; CUI Han-Yin; XIAO Bo-Xun; ZHANG Cheng-Guang

    2007-01-01

    We investigate the guided waves in a multi-layered cylindrical elastic solid medium. The dispersion function of guided waves is usually complex and the dispersion curves of all modes are not conveniently obtained. Here we present an effective method to obtain the dispersion curves of all modes. First, the dispersion function of the guided waves is transformed into a real function. The dispersion curves are then calculated for all the modes of the guided waves by the bisection method. The modes with the orders n= 0, 1, and 2 are analysed in two- and three-layer media. The existence condition of Stoneley wave is discussed. The modes of the guided waves are also investigated in a two-layer medium, in which the velocity of shear wave in the outer layer is less than that in the inner layer.

  12. Guided Wave and Damage Detection in Composite Laminates Using Different Fiber Optic Sensors

    OpenAIRE

    Fucai Li; Hideaki Murayama; Kazuro Kageyama; Takehiro Shirai

    2009-01-01

    Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber r...

  13. Time reversal method for guided wave inspection in pipes

    Institute of Scientific and Technical Information of China (English)

    Fei DENG; Bin WU; Cunfu HE

    2008-01-01

    The application of the time reversal method in pipe-like structures based on finite element method (FEM) is investigated. A steel pipe model measuring 70 mm × 3.5 mm is used to analyze the reflection coef-ficient of the L(0,2) mode with the time reversal process. Simulation results show that the time reversal array method is beneficial to the improvement of the signal-to-noise ratio of a guided wave inspection system. As the intercepting window is widened, more energy is included in re-emitted signals, which leads to a large reflection coefficient of the L(0,2) mode. In parallel, a circumferential locating method based on the time reversal method is described. The time reversal process used for guided wave inspection leads to the temporal and spatial focusing. When the time reversal signals are re-emitted, the angular profile obtained at the axial loca-tion of the defect can be used to determine the circumfer-ential location of the defect. Except for a pipe with one defect, the circumferential locating method has been veri-fied on another pipe model with two defects. Meanwhile, the elements number of the time reversal array has been discussed for enhancing the discrimination of the defect circumferential location.

  14. Guided Wave Annular Array Sensor Design for Improved Tomographic Imaging

    Science.gov (United States)

    Koduru, Jaya Prakash; Rose, Joseph L.

    2009-03-01

    Guided wave tomography for structural health monitoring is fast emerging as a reliable tool for the detection and monitoring of hotspots in a structure, for any defects arising from corrosion, crack growth etc. To date guided wave tomography has been successfully tested on aircraft wings, pipes, pipe elbows, and weld joints. Structures practically deployed are subjected to harsh environments like exposure to rain, changes in temperature and humidity. A reliable tomography system should take into account these environmental factors to avoid false alarms. The lack of mode control with piezoceramic disk sensors makes it very sensitive to traces of water leading to false alarms. In this study we explore the design of annular array sensors to provide mode control for improved structural tomography, in particular, addressing the false alarm potential of water loading. Clearly defined actuation lines in the phase velocity dispersion curve space are calculated. A dominant in-plane displacement point is found to provide a solution to the water loading problem. The improvement in the tomographic images with the annular array sensors in the presence of water traces is clearly illustrated with a series of experiments. An annular array design philosophy for other problems in NDE/SHM is also discussed.

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

    Science.gov (United States)

    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.

  16. Visualization of Guided Wave Propagation with Laser Doppler Vibrometer Scanning on Curved Surfaces

    Science.gov (United States)

    Hayashi, T.; Kojika, Y.; Kataoka, K.; Takikawa, M.

    2008-02-01

    In guided wave inspection for pipes, defect characterization is performed by echoes from defects. However, since detected signals become very complex due to mode conversion and multiple reflections, wave mechanics in a pipe with defects are not well studied. In this study, therefore, visualization technique for guided waves in a pipe is developed. In order to visualize guided wave propagation in a pipe, we need to scan an ultrasonic probe and measure ultrasonic waves at many points on a surface of a pipe. Position and posture of a laser doppler vibrometer are controlled by a robot arm, and ultrasonic vibration is detected at arbitrary points from arbitrary laser beam direction. Using the laser scanning technique, reflected guided waves from a shallow round defect was observed in the visualization results. From the defect, reflected waves propagated spirally in the oblique direction. From the view point of guided wave, the spiral waves were very high order modes that have not been measured in guided wave inspection. This result shows that such high order guided wave modes should be useful for defect characterization as well as low order modes.

  17. Numerical studies of nonlinear ultrasonic guided waves in uniform waveguides with arbitrary cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Peng; Fan, Zheng, E-mail: ZFAN@ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Zhou, Yu [Advanced Remanufacturing and Technology Center (ARTC), 3 Clean Tech Loop, CleanTech Two, Singapore 637143 (Singapore)

    2016-07-15

    Nonlinear guided waves have been investigated widely in simple geometries, such as plates, pipe and shells, where analytical solutions have been developed. This paper extends the application of nonlinear guided waves to waveguides with arbitrary cross sections. The criteria for the existence of nonlinear guided waves were summarized based on the finite deformation theory and nonlinear material properties. Numerical models were developed for the analysis of nonlinear guided waves in complex geometries, including nonlinear Semi-Analytical Finite Element (SAFE) method to identify internal resonant modes in complex waveguides, and Finite Element (FE) models to simulate the nonlinear wave propagation at resonant frequencies. Two examples, an aluminum plate and a steel rectangular bar, were studied using the proposed numerical model, demonstrating the existence of nonlinear guided waves in such structures and the energy transfer from primary to secondary modes.

  18. Predictive simulation of guide-wave structural health monitoring

    Science.gov (United States)

    Giurgiutiu, Victor

    2017-04-01

    This paper presents an overview of recent developments on predictive simulation of guided wave structural health monitoring (SHM) with piezoelectric wafer active sensor (PWAS) transducers. The predictive simulation methodology is based on the hybrid global local (HGL) concept which allows fast analytical simulation in the undamaged global field and finite element method (FEM) simulation in the local field around and including the damage. The paper reviews the main results obtained in this area by researchers of the Laboratory for Active Materials and Smart Structures (LAMSS) at the University of South Carolina, USA. After thematic introduction and research motivation, the paper covers four main topics: (i) presentation of the HGL analysis; (ii) analytical simulation in 1D and 2D; (iii) scatter field generation; (iv) HGL examples. The paper ends with summary, discussion, and suggestions for future work.

  19. Evanescent light-matter Interactions in Atomic Cladding Wave Guides

    CERN Document Server

    Stern, Liron; Goykhman, Ilya; Levy, Uriel

    2012-01-01

    Alkali vapors, and in particular rubidium, are being used extensively in several important fields of research such as slow and stored light non-linear optics3 and quantum computation. Additionally, the technology of alkali vapors plays a major role in realizing myriad industrial applications including for example atomic clocks magentometers8 and optical frequency stabilization. Lately, there is a growing effort towards miniaturizing traditional centimeter-size alkali vapor cells. Owing to the significant reduction in device dimensions, light matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for non-linear interactions. Here, taking advantage of the mature Complimentary Metal-Oxide-Semiconductor (CMOS) compatible platform of silicon photonics, we construct an efficient and flexible platform for tailored light vapor interactions on a chip. Specifically, we demonstrate light matter interactions in an atomic cladding wave guide (ACWG), consisting of CMOS ...

  20. Guided Waves within the Alpine Fault, central Westland, New Zealand

    Science.gov (United States)

    Eccles, J. D.; Gulley, A. K.; Boese, C. M.; Malin, P.; Townend, J.; Sutherland, R.

    2013-12-01

    Fault Zone Guided waves (FZGWs), seismic energy trapped within the low-velocity ';damage zone', have been observed for the first time within the Alpine Fault of New Zealand. This major transpressional fault accommodates up to 75% of relative motion between the Australian and Pacific plates. Two three-component, 2 Hz, borehole seismometers were installed as part of the first phase of the Deep Fault Drilling Project (DFDP-1) which drilled two shallow (101 m and 151 m) boreholes into the central Alpine Fault principal slip zone at Gaunt Creek, central Westland. These seismometers, part of the DFDP-1 borehole observatory, were installed within the mylonitic cataclasites of the hanging wall and the granitic cataclasite sequence of the footwall, within 20 m of what are thought to be the principal slip surfaces. Seismic data quality is high, revealing high rates of local microseismic activity with approximately fifty proximal events (P-S times array also reveals the strong structural control on incident seismic energy. Recent deployments of borehole and surface seismic networks to observe microseismic activity show somewhat diffuse patterns of seismicity and retain ambiguity as to the location and character of the Alpine Fault principal slip zone at depth. The locations of the events that generated FZGWs indicate the location and connectivity of the main Alpine Fault zone, which is segmented at a catchment scale at the surface. Initial modelling of the FZGWs also gives an estimate of fault zone properties at depth. Paleoseismic evidence indicates the Alpine Fault, capable of producing Mw > 8, is late in its seismic cycle and, despite previously appearing relatively aseismic on timescales of instrumentation, the observation of Fault Zone Guided Waves confirms that episodic, low magnitude seismic activity actually occurs on the main Alpine Fault zone (or strongly linked faults) both as single events and microseismic swarms.

  1. Simultaneous excitation system for efficient guided wave structural health monitoring

    Science.gov (United States)

    Hua, Jiadong; Michaels, Jennifer E.; Chen, Xin; Lin, Jing

    2017-10-01

    Many structural health monitoring systems utilize guided wave transducer arrays for defect detection and localization. Signals are usually acquired using the ;pitch-catch; method whereby each transducer is excited in turn and the response is received by the remaining transducers. When extensive signal averaging is performed, the data acquisition process can be quite time-consuming, especially for metallic components that require a low repetition rate to allow signals to die out. Such a long data acquisition time is particularly problematic if environmental and operational conditions are changing while data are being acquired. To reduce the total data acquisition time, proposed here is a methodology whereby multiple transmitters are simultaneously triggered, and each transmitter is driven with a unique excitation. The simultaneously transmitted waves are captured by one or more receivers, and their responses are processed by dispersion-compensated filtering to extract the response from each individual transmitter. The excitation sequences are constructed by concatenating a series of chirps whose start and stop frequencies are randomly selected from a specified range. The process is optimized using a Monte-Carlo approach to select sequences with impulse-like autocorrelations and relatively flat cross-correlations. The efficacy of the proposed methodology is evaluated by several metrics and is experimentally demonstrated with sparse array imaging of simulated damage.

  2. 1D profiling using highly dispersive guided waves

    Science.gov (United States)

    Volker, Arno; Brandenburg, Martijn

    2017-02-01

    Corrosion is one of the industries major issues regarding the integrity of assets. Currently inspections are conducted at regular intervals to ensure a sufficient integrity level of these assets. There are many situations where the actual defect location is not accessible, e.g., a pipe support or a partially buried pipe. Last year an approach was presented using a phase inversion of guided waves that propagated around the circumference of a pipe. This approach works well for larger corrosion spots, but shows significant under-sizing of small spots due to lack of sufficient phase rotation. In this paper the use of arrival time and amplitude loss of higher order circumferential passes is evaluated. Using higher order passes increases sensitivity for sizing smaller defects. Different defect profiles are assumed and the change in arrival time and amplitude loss are calculated using a wave equation based approach for different defect widths and depths. This produces a differential travel time and amplitude change map as function of defect depth and defect width. The actually measured travel time change and amplitude change produces two contours in these maps. Calculating the intersection point gives the defect dimensions. The contours for amplitude loss and travel time change are quite orthogonal, this yields a good discrimination between deep and shallow defects. The approach is evaluated using experimental data from different pipes contain artificial and real defects.

  3. Coupling characteristics between five-layer slab wave-guides including left-handed materials

    Institute of Scientific and Technical Information of China (English)

    SHEN Lu-fa; WANG Zi-hua

    2008-01-01

    To obtain the coupling characteristics between slab wave-guides including lift-handed material, we modify the coupledwave equations by using Maxwell's equations. First, we obtain new-couplid wave equations and new-coupling coefficient.Second, the coupling between two identical five-layer slab wave-guides where their cores are left-haaded material, but theircladdings are right-handed materials is studied. The coupling coefficient for even TE mode which is more complex than thatof the riglt-handed material slab wave guides, is obtained.

  4. An analytical filter design method for guided wave phased arrays

    Science.gov (United States)

    Kwon, Hyu-Sang; Kim, Jin-Yeon

    2016-12-01

    This paper presents an analytical method for designing a spatial filter that processes the data from an array of two-dimensional guided wave transducers. An inverse problem is defined where the spatial filter coefficients are determined in such a way that a prescribed beam shape, i.e., a desired array output is best approximated in the least-squares sense. Taking advantage of the 2π-periodicity of the generated wave field, Fourier-series representation is used to derive closed-form expressions for the constituting matrix elements. Special cases in which the desired array output is an ideal delta function and a gate function are considered in a more explicit way. Numerical simulations are performed to examine the performance of the filters designed by the proposed method. It is shown that the proposed filters can significantly improve the beam quality in general. Most notable is that the proposed method does not compromise between the main lobe width and the sidelobe levels; i.e. a narrow main lobe and low sidelobes are simultaneously achieved. It is also shown that the proposed filter can compensate the effects of nonuniform directivity and sensitivity of array elements by explicitly taking these into account in the formulation. From an example of detecting two separate targets, how much the angular resolution can be improved as compared to the conventional delay-and-sum filter is quantitatively illustrated. Lamb wave based imaging of localized defects in an elastic plate using a circular array is also presented as an example of practical applications.

  5. The Effect of General Corrosion on the Guided Wave Inspection of the Pipeline

    OpenAIRE

    Zhang Jin Heng; Li Chang; Yang Yang

    2016-01-01

    The guided wave method can inspect pipelines very quickly and widely. For instance, it can inspect the overall pipelines by digging several detection pits or removing part of coating material to set the array ring. However, it will make the guided wave attenuate more seriously and make the signals hard to identify when setting the array ring on the general corrosion. In this study, the wave propagation will be discussed when the general corrosion is under the array ring and the severe localiz...

  6. Guided Waves in Structures for SHM The Time - domain Spectral Element Method

    CERN Document Server

    Ostachowicz, Wieslaw; Krawczuk, Marek; Zak, Arkadiusz

    2011-01-01

    Presents the state of the art in the modelling, analysis and experimental investigation of elastic wave propagation using a technique of rapidly increasing interest and development Addressing an important issue in the field of guided-wave-based damage identification and structural health monitoring,Guided Waves in Structures for SHM presents the modelling, analysis and experimental investigation of elastic wave propagation in engineering structures made of isotropic or composite materials. The authors begin by summarising present-day knowledge on elastic wave propagation in solids, focusing on

  7. A wave guide model of lightning currents and their electromagnetic field

    Science.gov (United States)

    Volland, H.

    1980-01-01

    Lightning channels are considered as resonant wave guides in which only standing resonant wave modes can be excited. Two types of discharging currents develop. Type 1 is an aperiodic wave; type 2 is a damped oscillation. The electromagnetic radiation field of both types of currents is calculated and compared with the observation.

  8. A Guided Wave Sensor Enabling Simultaneous Wavenumber-Frequency Analysis for Both Lamb and Shear-Horizontal Waves.

    Science.gov (United States)

    Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J

    2017-03-01

    Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. We demonstrate that polyvinylidene difluoride (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.

  9. Guided wave and damage detection in composite laminates using different fiber optic sensors.

    Science.gov (United States)

    Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

    2009-01-01

    Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH(0)) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

  10. Guided Wave and Damage Detection in Composite Laminates Using Different Fiber Optic Sensors

    Directory of Open Access Journals (Sweden)

    Fucai Li

    2009-05-01

    Full Text Available Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG and Doppler effect-based fiber optic (FOD sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH0 guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

  11. Third harmonic generation of shear horizontal guided waves propagation in plate-like structures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei Bin [School of Aerospace Engineering, Xiamen University, Xiamen (China); Xu, Chun Guang [School of Mechanical Engineering, Beijing Institute of Technology, Beijing (China); Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-04-15

    The use of nonlinear ultrasonics wave has been accepted as a promising tool for monitoring material states related to microstructural changes, as it has improved sensitivity compared to conventional non-destructive testing approaches. In this paper, third harmonic generation of shear horizontal guided waves propagating in an isotropic plate is investigated using the perturbation method and modal analysis approach. An experimental procedure is proposed to detect the third harmonics of shear horizontal guided waves by electromagnetic transducers. The strongly nonlinear response of shear horizontal guided waves is measured. The accumulative growth of relative acoustic nonlinear response with an increase of propagation distance is detected in this investigation. The experimental results agree with the theoretical prediction, and thus providing another indication of the feasibility of using higher harmonic generation of electromagnetic shear horizontal guided waves for material characterization.

  12. Development of an electromagnetic acoustic transducer (EMAT) for the noncontact excitation of guided ultrasonic waves

    Science.gov (United States)

    Fromme, P.

    2015-03-01

    Fatigue damage can develop in aerospace structures at locations of stress concentration, such as fasteners. For the safe operation of the aircraft fatigue cracks need to be detected before reaching a critical length. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Noncontact excitation of guided waves was achieved using electromagnetic acoustic transducers (EMAT). The transducer development for the specific excitation of the A0 Lamb wave mode is explained. The radial and angular dependency of the excited guided wave pulses at different frequencies were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed and reasonably good agreement with the measured transducer performance was achieved. The developed transducers were employed for defect detection in aluminum components using fully noncontact guided wave measurements. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer. These results provide the basis for the defect characterization in aerospace structures using noncontact guided wave sensors.

  13. Phased array focusing with guided waves in a viscoelastic coated hollow cylinder.

    Science.gov (United States)

    Luo, Wei; Rose, Joseph L

    2007-04-01

    Guided wave phased array focusing has shown many advantages in long-range pipeline inspection, such as, longer inspection distance, greater wave penetration power and higher detection resolution. Viscoelastic coatings applied to a large percentage of pipes for protection purposes created some challenges in terms of focusing feasibility and inspection ability. Previous studies were all based on bare pipe models. In this work, guided wave phased array focusing in viscoelastic coated pipes is studied for the first time. Work was carried out with both numerical and experimental methods. A three-dimensional finite element model was developed for quantitatively and systematically modeling guided waves in pipes with different viscoelastic materials. A method of transforming measured coating properties to finite element method inputs was created in order to create a physically based model of guided waves in coated pipes. Guided wave focusing possibilities in viscoelastic coated pipes and the effects from coatings were comprehensively studied afterwards. A comparison of focusing and nonfocusing inspections was also studied quantitatively in coated pipe showing that focusing increased the wave energy and consequently the inspection ability tremendously. This study provides an important base line and guidance for guided wave propagation and focusing in a real field pipeline under various coating and environmental conditions.

  14. Mode Conversion Behavior of Guided Wave in a Pipe Inspection System Based on a Long Waveguide.

    Science.gov (United States)

    Sun, Feiran; Sun, Zhenguo; Chen, Qiang; Murayama, Riichi; Nishino, Hideo

    2016-10-19

    To make clear the mode conversion behavior of S0-mode lamb wave and SH0-plate wave converting to the longitudinal mode guided wave and torsional mode guided wave in a pipe, respectively, the experiments were performed based on a previous built pipe inspection system. The pipe was wound with an L-shaped plate or a T-shaped plate as the waveguide, and the S0-wave and SH0-wave were excited separately in the waveguide. To carry out the objective, a meander-line coil electromagnetic acoustic transducer (EMAT) for S0-wave and a periodic permanent magnet (PPM) EMAT for SH0-wave were developed and optimized. Then, several comparison experiments were conducted to compare the efficiency of mode conversion. Experimental results showed that the T(0,1) mode, L(0,1) mode, and L(0,2) mode guided waves can be successfully detected when converted from the S0-wave or SH0-wave with different shaped waveguides. It can also be inferred that the S0-wave has a better ability to convert to the T(0,1) mode, while the SH0-wave is easier to convert to the L(0,1) mode and L(0,2) mode, and the L-shaped waveguide has a better efficiency than T-shaped waveguide.

  15. Mode Conversion Behavior of Guided Wave in a Pipe Inspection System Based on a Long Waveguide

    Directory of Open Access Journals (Sweden)

    Feiran Sun

    2016-10-01

    Full Text Available To make clear the mode conversion behavior of S0-mode lamb wave and SH0-plate wave converting to the longitudinal mode guided wave and torsional mode guided wave in a pipe, respectively, the experiments were performed based on a previous built pipe inspection system. The pipe was wound with an L-shaped plate or a T-shaped plate as the waveguide, and the S0-wave and SH0-wave were excited separately in the waveguide. To carry out the objective, a meander-line coil electromagnetic acoustic transducer (EMAT for S0-wave and a periodic permanent magnet (PPM EMAT for SH0-wave were developed and optimized. Then, several comparison experiments were conducted to compare the efficiency of mode conversion. Experimental results showed that the T(0,1 mode, L(0,1 mode, and L(0,2 mode guided waves can be successfully detected when converted from the S0-wave or SH0-wave with different shaped waveguides. It can also be inferred that the S0-wave has a better ability to convert to the T(0,1 mode, while the SH0-wave is easier to convert to the L(0,1 mode and L(0,2 mode, and the L-shaped waveguide has a better efficiency than T-shaped waveguide.

  16. Large scale implementation of guided wave based broken rail monitoring

    Science.gov (United States)

    Burger, Francois A.; Loveday, Philip W.; Long, Craig S.

    2015-03-01

    A guided wave ultrasound system has been developed over the past 17 years to detect breaks in continuously welded rail track. Installation of the version 4 system on an 840 km long heavy duty freight line was conducted between January 2013 and June 2014. The system operates in pitch - catch mode with alternate transmit and receive transducers spaced approximately 1km apart. If the acoustic signal is not received at the receive station an alarm is triggered to indicate a break in the rail between the transmit station and the receive station. The system is permanently installed, powered by solar panels and issues broken rail alarms using the GSM network where available, and digital radio technology in other areas. A total of 931 stations were installed and the entire length of rail is interrogated every fifteen minutes. The system operates reliably although some problems involving unreliable GSM communication and theft of solar panels have been experienced. In the first two months of operation four broken rails were detected and train operation was halted temporarily for repairs.

  17. Ultrasonic Guided Waves in Piezoelectric Layered Composite with Different Interfacial Properties

    Directory of Open Access Journals (Sweden)

    Xiao Chen

    2011-01-01

    Full Text Available Combining the propagation model of guided waves in a multilayered piezoelectric composite with the interfacial model of rigid, slip, and weak interfaces, the generalized dispersion characteristic equations of guided waves propagating in a piezoelectric layered composite with different interfacial properties are derived. The effects of the slip, weak, and delamination interfaces in different depths on the dispersion properties of the lowest-order mode ultrasonic guided wave are analyzed. The theory would be used to characterize the interfacial properties of piezoelectric layered composite nondestructively.

  18. Phased array beamforming and imaging in composite laminates using guided waves

    Science.gov (United States)

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

    2016-04-01

    This paper presents the phased array beamforming and imaging using guided waves in anisotropic composite laminates. A generic phased array beamforming formula is presented, based on the classic delay-and-sum principle. The generic formula considers direction-dependent guided wave properties induced by the anisotropic material properties of composites. Moreover, the array beamforming and imaging are performed in frequency domain where the guided wave dispersion effect has been considered. The presented phased array method is implemented with a non-contact scanning laser Doppler vibrometer (SLDV) to detect multiple simulated defects at different locations in an anisotropic composite plate. The array is constructed of scan points in a small area rapidly scanned by the SLDV. Using the phased array method, multiple simulated defects at different locations are successfully detected. Our study shows that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  19. Spatially Coherent Optical Velocimeter Array for Rapid Guided-wave NDE Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The pace and progress of new sensor technology development continues to lag far behind the broad ranging potential offered by guided wave NDE. In response to NASA...

  20. Ultrasonic Guided Wave Simulation Toolbox for Virtual Inspection of Composites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Ultrasonic guided wave nondestructive evaluation (NDE) techniques are being used to detect flaws and damage in fracture critical structures such as composites. In...

  1. High-frequency guided ultrasonic waves to monitor corrosion thickness loss

    Science.gov (United States)

    Fromme, Paul; Bernhard, Fabian; Masserey, Bernard

    2017-02-01

    Corrosion due to adverse environmental conditions can occur for a range of industrial structures, e.g., ships and offshore oil platforms. Pitting corrosion and generalized corrosion can lead to the reduction of the strength and thus degradation of the structural integrity. The nondestructive detection and monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided ultrasonic waves propagating along the structure. Using standard ultrasonic transducers with single sided access to the structure, the two fundamental Lamb wave modes were selectively generated simultaneously, penetrating through the complete thickness of the structure. The wave propagation and interference of the guided wave modes depends on the thickness of the structure. Numerical simulations were performed using a 2D Finite Difference Method (FDM) algorithm in order to visualize the guided wave propagation and energy transfer across the plate thickness. Laboratory experiments were conducted and the wall thickness reduced initially uniformly by milling of the steel structure. Further measurements were conducted using accelerated corrosion in salt water. From the measured signal change due to the wave mode interference, the wall thickness reduction was monitored and good agreement with theoretical predictions was achieved. Corrosion can lead to non-uniform thickness reduction and the influence of this on the propagation of the high frequency guided ultrasonic waves was investigated. The wave propagation in a steel specimen with varying thickness was measured experimentally and the influence on the wave propagation characteristics quantified.

  2. Load-Differential Features for Automated Detection of Fatigue Cracks Using Guided Waves (Preprint)

    Science.gov (United States)

    2011-11-01

    Quantitative NDE Conference Proceeding. This document contains color. 14. ABSTRACT Guided wave structural health monitoring (SHM) is being used to assess...REFERENCES 1. J. E. Michaels, A. J. Croxford and P. D. Wilcox , “Imaging algorithms for locating damage via in situ ultrasonic sensors,” in Proc...717-731 (2005). 5. G. Konstantinidis, B. W. Drinkwater and P. D. Wilcox “The temperature stability of guided wave structural health monitoring

  3. Numerical Simulation of Monitoring Corrosion in Reinforced Concrete Based on Ultrasonic Guided Waves

    OpenAIRE

    Zheng, Zhupeng; Lei, Ying; Xue, Xin

    2014-01-01

    Numerical simulation based on finite element method is conducted to predict the location of pitting corrosion in reinforced concrete. Simulation results show that it is feasible to predict corrosion monitoring based on ultrasonic guided wave in reinforced concrete, and wavelet analysis can be used for the extremely weak signal of guided waves due to energy leaking into concrete. The characteristic of time-frequency localization of wavelet transform is adopted in the corrosion monitoring of re...

  4. A Love Wave Reflective Delay Line with Polymer Guiding Layer for Wireless Sensor Application

    OpenAIRE

    Shitang He; Wen Wang

    2008-01-01

    This paper presents an optimal design for a Love wave reflective delay line on 41o YX LiNbO3 with a polymer guiding layer for wireless sensor applications. A theoretical model was established to describe the Love wave propagation along the larger piezoelectric substrate with polymer waveguide, and the lossy mechanism from the viscoelastic waveguide was discussed, which results in the optimal guiding layer thickness. Coupling of modes (COM) was used to determine the optimal design parameters o...

  5. Torsional guided wave-based debonding detection in honeycomb sandwich beams

    Science.gov (United States)

    Zhu, Kaige; Qing, Xinlin P.; Liu, Bin

    2016-11-01

    Debonding is one of the most dangerous damages in honeycomb sandwich structures, which causes stiffness reduction and is invisible from the surface. Guided wave-based non-destructive evaluation is a promising approach with high sensitivity and high efficiency for debonding detection. A torsional guided wave method is proposed to inspect debonding damage in honeycomb sandwich beams, which is proved to be better in damage location for the beams in the paper than the flexural wave used before. The honeycomb heterogeneity effect on the interaction between guided waves and debonding are first investigated by finite element methods. Then the ability of torsional waves to determine debonding locations and sizes is discussed in detail. Finally, in order to verify the proposed method, experiments are carried out to inspect debonding damage with two sizes.

  6. Impulse Turbine with 3D Guide Vanes for Wave Energy Conversion

    Institute of Scientific and Technical Information of China (English)

    Manabu TAKAO; Toshiaki SETOGUCHI; Kenji KANEKO; Shuichi NAGATA

    2006-01-01

    In this study, in order to achieve further improvement of the performance of an impulse turbine with fixed guide vanes for wave energy conversion, the effect of guide vane shape on the performance was investigated by experiment. The investigation was performed by model testing under steady flow condition. As a result, it was found that the efficiency of the turbine with 3D guide vanes are slightly superior to that of the turbine with 2D guide vanes because of the increase of torque by means of 3D guide vane, though pressure drop across the turbine for the 3D case is slightly higher than that for the 2D case.

  7. Phased annular array transducers for omnidirectional guided wave mode control in isotropic plate like structures

    Science.gov (United States)

    Koduru, Jaya P.; Momeni, Sepandarmaz; Rose, Joseph L.

    2013-12-01

    Ultrasonic guided waves are fast emerging as a reliable tool for continuous structural health monitoring. Their multi-modal nature along with their long range propagation characteristics offer several possibilities for interrogating structures. Transducers commonly used to generate guided waves in structures excite multiple modes at any frequency; their complex scattering and reflection from defects and boundaries often complicates the extraction of useful information. Often it is desirable to control the guided wave modes propagating in a structure to take advantage of their unique properties for different applications. Earlier attempts at guided wave mode control involved developing fixed wavelength linear and annular array transducers. Their only disadvantage is that the transducer is limited to a particular wavelength and a change in wavelength necessitates a change in the transducer. In this paper, we propose the development of an annular array transducer that can generate mode controlled omnidirectional guided waves by independently controlling the amplitude and phase of the array elements. A simplified actuator model that approximates the transducer loading on the structure to a constant pressure load under the array elements is assumed and an optimization problem is set up to compute the excitation voltage and phase of the elements. A five element annular array transducer is designed utilizing 1-3 type piezocomposite materials. The theoretical computations are experimentally verified on an aluminum plate like structure by exciting A0 and S0 guided wave modes.

  8. High precision ultrasonic guided wave technique for inspection of power transmission line

    Science.gov (United States)

    Cheng, Jun; Qiu, Jinhao; Ji, Hongli; Wang, Enrong; Takagi, Toshiyuki; Uchimoto, Tetsuya

    2017-01-01

    Due to the merits of high inspection speed and long detecting distance, Ultrasonic Guided Wave(UGW) method has been commonly applied to the on-line maintenance of power transmission line. However, the guided wave propagation in this structure is very complicated, leading to the unfavorable defect localization accuracy. Aiming at this situation, a high precision UGW technique for inspection of local surface defect in power transmission line is proposed. The technique is realized by adopting a novel segmental piezoelectric ring transducer and transducer mounting scheme, combining with the comprehensive characterization of wave propagation and circumferential defect positioning with multiple piezoelectric elements. Firstly, the propagation path of guided waves in the multi-wires of transmission line under the proposed technique condition is investigated experimentally. Next, the wave velocities are calculated by dispersion curves and experiment test respectively, and from comparing of the two results, the guided wave mode propagated in transmission line is confirmed to be F(1,1) mode. Finally, the axial and circumferential positioning of local defective wires in transmission line are both achieved, by using multiple piezoelectric elements to surround the stands and send elastic waves into every single wire. The proposed research can play a role of guiding the development of highly effective UGW method and detecting system for multi-wire transmission line.

  9. Noncontact excitation of guided waves (A0 mode) using an electromagnetic acoustic transducer (EMAT)

    Science.gov (United States)

    Fromme, Paul

    2016-02-01

    Fatigue damage can develop in aircraft structures at locations of stress concentration, such as fasteners, and has to be detected before reaching a critical size to ensure safe aircraft operation. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Electromagnetic acoustic transducers (EMAT) for the noncontact excitation of guided ultrasonic waves were developed. The transducer development for the specific excitation of the A0 Lamb wave mode with an out-of-plane Lorentz force is explained. The achieved radial and angular dependency of the excited guided wave pulses were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed. The application of the developed transducers for defect detection in aluminum components using fully noncontact guided wave measurements was demonstrated. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer.

  10. Second order harmonic guided wave mutual interactions in plate: Vector analysis, numerical simulation, and experimental results

    Science.gov (United States)

    Hasanian, Mostafa; Lissenden, Cliff J.

    2017-08-01

    The extraordinary sensitivity of nonlinear ultrasonic waves to the early stages of material degradation makes them excellent candidates for nondestructive material characterization. However, distinguishing weak material nonlinearity from instrumentation nonlinearity remains problematic for second harmonic generation approaches. A solution to this problem is to mix waves having different frequencies and to let their mutual interaction generate sum and difference harmonics at frequencies far from those of the instrumentation. Mixing of bulk waves and surface waves has been researched for some time, but mixing of guided waves has not yet been investigated in depth. A unique aspect of guided waves is their dispersive nature, which means we need to assure that a wave can propagate at the sum or difference frequency. A wave vector analysis is conducted that enables selection of primary waves traveling in any direction that generate phase matched secondary waves. We have tabulated many sets of primary waves and phase matched sum and difference harmonics. An example wave mode triplet of two counter-propagating collinear shear horizontal waves that interact to generate a symmetric Lamb wave at the sum frequency is simulated using finite element analysis and then laboratory experiments are conducted. The finite element simulation eliminates issues associated with instrumentation nonlinearities and signal-to-noise ratio. A straightforward subtraction method is used in the experiments to identify the material nonlinearity induced mutual interaction and show that the generated Lamb wave propagates on its own and is large enough to measure. Since the Lamb wave has different polarity than the shear horizontal waves the material nonlinearity is clearly identifiable. Thus, the mutual interactions of shear horizontal waves in plates could enable volumetric characterization of material in remote regions from transducers mounted on just one side of the plate.

  11. Guided wave diagnosis in composite grid structure with embedded FBG sensors

    Science.gov (United States)

    Amano, Masataro; Arai, Takeo; Takeda, Nobuo

    2007-04-01

    The authors tried to construct a structural health monitoring (SHM) system to identify damage in composite grid structure called Advanced Grid Structure (AGS) by using two types of guided waves, compressional and flexural waves, propagating along ribs of AGS. Fiber Bragg grating (FBG) sensors network embedded in AGS is utilized as their receivers. AGS is defined as trussed structures whose ribs are made of Carbon fiber reinforced plastic (CFRP). AGS has often been applied to aerospace structures because it is structurally effective and redundant. The authors had reported one possible method of SHM of AGS by monitoring of static strain distribution with embedded FBG sensors network in AGS. In this paper, we propose another possible method of SHM of AGS. We utilized two types of guided waves, compressional and flexural waves, for damage diagnosis. First, we verified our proposed system experimentally. The results confirmed that FBG sensors could measure both elastic waves and two types of guided waves were generated with the proposed system. Then, some basic characteristics of compressional and flexural wave propagations were clarified experimentally to find that compressional wave has directionality and flexural wave has isotropy. Based on the characteristics, the authors proposed two types of damage diagnosis methods with compressional and flexural waves, respectively. Moreover, those proposed methods were applied to two specific damage types, rib crack and debonding between ribs and skin. The specific damage diagnosis methods were verified experimentally to find that damages could be detected by those methods.

  12. Effect of pressurization on helical guided wave energy velocity in fluid-filled pipes.

    Science.gov (United States)

    Dubuc, Brennan; Ebrahimkhanlou, Arvin; Salamone, Salvatore

    2017-03-01

    The effect of pressurization stresses on helical guided waves in a thin-walled fluid-filled pipe is studied by modeling leaky Lamb waves in a stressed plate bordered by fluid. Fluid pressurization produces hoop and longitudinal stresses in a thin-walled pipe, which corresponds to biaxial in-plane stress in a plate waveguide model. The effect of stress on guided wave propagation is accounted for through nonlinear elasticity and finite deformation theory. Emphasis is placed on the stress dependence of the energy velocity of the guided wave modes. For this purpose, an expression for the energy velocity of leaky Lamb waves in a stressed plate is derived. Theoretical results are presented for the mode, frequency, and directional dependent variations in energy velocity with respect to stress. An experimental setup is designed for measuring variations in helical wave energy velocity in a thin-walled water-filled steel pipe at different levels of pressure. Good agreement is achieved between the experimental variations in energy velocity for the helical guided waves and the theoretical leaky Lamb wave solutions.

  13. Reflection of semi-guided plane waves at angled thin-film transitions

    NARCIS (Netherlands)

    Çivitci, Fehmi; Hammer, Manfred; Hoekstra, Hugo J.W.M.

    2013-01-01

    The propagation of thin-film guided, in-plane unguided plane optical waves, and their partial or total reflection at transitions between regions with different film thickness, is considered. The properties of reflected and refracted waves can be predicted reasonably by readily available Helmholtz- a

  14. Ultrasonic nonlinear guided wave inspection of microscopic damage in a composite structure

    Science.gov (United States)

    Zhang, Li; Borigo, Cody; Owens, Steven; Lissenden, Clifford; Rose, Joseph; Hakoda, Chris

    2017-02-01

    Sudden structural failure is a severe safety threat to many types of military and industrial composite structures. Because sudden structural failure may occur in a composite structure shortly after macroscale damage initiates, reliable early diagnosis of microdamage formation in the composite structure is critical to ensure safe operation and to reduce maintenance costs. Ultrasonic guided waves have been widely used for long-range defect detection in various structures. When guided waves are generated under certain excitation conditions, in addition to the traditional linear wave mode (known as the fundamental harmonic wave mode), a number of nonlinear higher-order harmonic wave modes are also be generated. Research shows that the nonlinear parameters of a higher-order harmonic wave mode could have excellent sensitivity to microstructural changes in a material. In this work, we successfully employed a nonlinear guided wave structural health monitoring (SHM) method to detect microscopic impact damage in a 32-layer carbon/epoxy fiber-reinforced composite plate. Our effort has demonstrated that, utilizing appropriate transducer design, equipment, excitation signals, and signal processing techniques, nonlinear guided wave parameter measurements can be reliably used to monitor microdamage initiation and growth in composite structures.

  15. Full resonant transmission of semi-guided planar waves through slab waveguide steps at oblique incidence

    CERN Document Server

    Hammer, Manfred; Förstner, Jens

    2015-01-01

    Sheets of slab waveguides with sharp corners are investigated. By means of rigorous numerical experiments, we look at oblique incidence of semi-guided plane waves. Radiation losses vanish beyond a certain critical angle of incidence. One can thus realize lossless propagation through 90-degree corner configurations, where the remaining guided waves are still subject to pronounced reflection and polarization conversion. A system of two corners can be viewed as a structure akin to a Fabry-Perot-interferometer. By adjusting the distance between the two partial reflectors, here the 90-degree corners, one identifies step-like configurations that transmit the semi-guided plane waves without radiation losses, and virtually without reflections. Simulations of semi-guided beams with in-plane wide Gaussian profiles show that the effect survives in a true 3-D framework.

  16. Finite element modeling of guided wave scattering at delaminations in composite panels

    Science.gov (United States)

    Murat, B. I. S.; Fromme, P.

    2016-04-01

    Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., 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, delaminations can occur, reducing the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The guided ultrasonic wave (A0 Lamb wave mode) scattering at delaminations was modelled using full three-dimensional Finite Element (FE) simulations. The influence of the delamination size was systematically investigated from a parameter study. The angular dependency of the scattered guided wave amplitude was calculated using a baseline subtraction method. A significant influence of the delamination width on the guided wave scattering was found. The sensitivity of guided waves for the detection of barely visible impact damage in composite panels has been predicted.

  17. Guided wave phased array sensor tuning for improved defect detection and characterization

    Science.gov (United States)

    Philtron, Jason H.; Rose, Joseph L.

    2014-03-01

    Ultrasonic guided waves are finding increased use in a variety of Nondestructive Evaluation and Structural Health Monitoring applications due to their efficiency in defect detection using a sensor at a single location to inspect a large area of a structure and an ability to inspect hidden and coated areas for example. With a thorough understanding of guided wave mechanics, researchers can predict which guided wave modes will have a high probability of success in a particular nondestructive evaluation application. For example, in a sample problem presented here to access bond integrity, researchers may choose to use a guided wave mode which has high in-plane displacement, stress, or other feature at the interface. However, since material properties used for modeling work may not be precise for the development of dispersion curves, in many cases guided wave mode and frequency selection should be adjusted for increased inspection efficiency in the field. In this work, a phased array comb transducer is used to sweep over phase velocity - frequency space to tune mode excitation for improved defect characterization performance. A thin polycarbonate layer bonded to a thick metal plate is considered with a contaminated surface prior to bonding. Physicallybased features are used to correlate wave signals with defect detection. Features assessed include arrival time and the frequency of maximum amplitude. A pseudo C-scan plot is presented which can be used to simplify data analysis. Excellent results are obtained.

  18. Time delay controlled annular array transducers for omnidirectional guided wave mode control in plate like structures

    Science.gov (United States)

    Koduru, Jaya P.; Rose, Joseph L.

    2014-10-01

    Guided waves in plate like structures offer several modes with unique characteristics that can be taken advantage for nondestructive inspection applications. Conditions relating to the structure under inspection like the surrounding media, liquid loading, coatings etc require the use of special modes for successful inspection. Therefore, transducers that can excite mode controlled guided waves are essential for defect detection and discrimination in structures. Array transducers with annular elements can generate omnidirectional guided waves in plate like structures. However, the wave modes excited are limited to a particular wavelength governed by the element spacing. This limitation on the annular array transducers can be overcome by controlling the phase at each element relative to one another. In this work, annular array transducer construction techniques are theoretically examined and the optimum phase delays between the annular elements to excite a desired guided wave mode are calculated. A five element comb type annular array transducer is fabricated utilizing 1-3 type piezocomposite material. The mode control capability of the transducer is experimentally verified by selectively exciting the A0 and S0 guided wave modes in an aluminum plate like structure.

  19. Guided-wave tomography imaging plate defects by laser-based ultrasonic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Pil; Lim, Ju Young; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Pusan (Korea, Republic of)

    2014-12-15

    Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

  20. A study on laser-based ultrasonic technique by the use of guided wave tomographic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junpil, E-mail: jpp@pusan.ac.kr; Lim, Juyoung, E-mail: jpp@pusan.ac.kr [Graduate school, School of Mechanical Engineering, Pusan National University (Korea, Republic of); Cho, Younho [School of Mechanical Engineering, Pusan National University (Korea, Republic of); Krishnaswamy, Sridhar [Center for Quality Engineering and Failure Prevention, Northwestern University, Evanston, IL (United States)

    2015-03-31

    Guided wave tests are impractical for investigating specimens with limited accessibility and coarse surfaces or geometrically complicated features. A non-contact setup with a laser ultrasonic transmitter and receiver is the classic attractive for guided wave inspection. The present work was done to develop a non-contact guided-wave tomography technique by laser ultrasonic technique in a plate-like structure. A method for Lam wave generation and detection in an aluminum plate with a pulse laser ultrasonic transmitter and a Michelson interferometer receiver has been developed. In the images obtained by laser scanning, the defect shape and area showed good agreement with the actual defect. The proposed approach can be used as a non-contact-based online inspection and monitoring technique.

  1. Analysis of guided wave propagation in a tapered composite panel

    Science.gov (United States)

    Wandowski, Tomasz; Malinowski, Pawel; Moll, Jochen; Radzienski, Maciej; Ostachowicz, Wieslaw

    2015-03-01

    Many studies have been published in recent years on Lamb wave propagation in isotropic and (multi-layered) anisotropic structures. In this paper, adiabatic wave propagation phenomenon in a tapered composite panel made out of glass fiber reinforced polymers (GFRP) will be considered. Such structural elements are often used e.g. in wind turbine blades and aerospace structures. Here, the wave velocity of each wave mode does not only change with frequency and the direction of wave propagation. It further changes locally due to the varying cross-section of the GFRP panel. Elastic waves were excited using a piezoelectric transducer. Full wave-field measurements using scanning Laser Doppler vibrometry have been performed. This approach allows the detailed analysis of elastic wave propagation in composite specimen with linearly changing thickness. It will be demonstrated here experimentally, that the wave velocity changes significantly due to the tapered geometry of the structure. Hence, this work motivates the theoretical and experimental analysis of adiabatic mode propagation for the purpose of Non-Destructive Testing and Structural Health Monitoring.

  2. Guided Wave Propagation Study on Laminated Composites by Frequency-Wavenumber Technique

    Science.gov (United States)

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

    2014-01-01

    Toward the goal of delamination detection and quantification in laminated composites, this paper examines guided wave propagation and wave interaction with delamination damage in laminated carbon fiber reinforced polymer (CFRP) composites using frequency-wavenumber (f-kappa) analysis. Three-dimensional elastodynamic finite integration technique (EFIT) is used to acquire simulated time-space wavefields for a CFRP composite. The time-space wavefields show trapped waves in the delamination region. To unveil the wave propagation physics, the time-space wavefields are further analyzed by using two-dimensional (2D) Fourier transforms (FT). In the analysis results, new f-k components are observed when the incident guided waves interact with the delamination damage. These new f-kappa components in the simulations are experimentally verified through data obtained from scanning laser Doppler vibrometer (SLDV) tests. By filtering the new f-kappa components, delamination damage is detected and quantified.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Il [Kangwon National University, Chuncheon (Korea, Republic of); Choi, Bok Kyoung [Maritime Security Research Center, KIOST, Ansan (Korea, Republic of)

    2014-12-15

    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.

  4. Study of guided wave transmission through complex junction in sodium cooled reactor

    Energy Technology Data Exchange (ETDEWEB)

    Elie, Q.; Le Bourdais, F.; Jezzine, K.; Baronian, V. [Non Destructive Testing Department at the French Atomic Energy Commission (CEA), Saclay, 91191 Gif sur Yvette CEDEX, (France)

    2015-07-01

    Ultrasonic guided wave techniques are seen as suitable candidates for the inspection of welded structures within sodium cooled fast reactors (SFR), as the long range propagation of guided waves without amplitude attenuation can overcome the accessibility problem due to the liquid sodium. In the context of the development of the Advanced Sodium Test Reactor for Industrial Demonstration (ASTRID), the French Atomic Commission (CEA) investigates non-destructive testing techniques based on guided wave propagation. In this work, guided wave NDT methods are applied to control the integrity of welds located in a junction-type structure welded to the main vessel. The method presented in this paper is based on the analysis of scattering matrices peculiar to each expected defect, and takes advantage of the multi-modal and dispersive characteristics of guided wave generation. In a simulation study, an algorithm developed using the CIVA software is presented. It permits selecting appropriate incident modes to optimize detection and identification of expected flawed configurations. In the second part of this paper, experimental results corresponding to a first validation step of the simulation results are presented. The goal of the experiments is to estimate the effectiveness of the incident mode selection in plates. The results show good agreement between experience and simulation. (authors)

  5. Three-dimensional analytical solution for transient guided wave propagation in liquid-filled pipe systems.

    Science.gov (United States)

    Tang, Liguo; Wu, Zhaojun; Liu, Shengxing; Yang, Wuyi

    2012-08-01

    The objective of this study is to investigate the three-dimensional (3-D) analytical solution for transient guided wave propagation in liquid-filled pipe systems using the eigenfunction expansion method (EEM). The eigenfunctions corresponding to finite liquid-filled pipe systems with a traction-free lateral boundary and rigid smooth end boundaries are obtained. Additionally, the orthogonality of the eigenfunctions is proved in detail. Subsequently, the exact 3-D analytical transient response of finite liquid-filled pipe systems to external body forces is constructed using the EEM, based on which, the approximate 3-D analytical transient response of the systems to external surface forces is derived. Furthermore, the analytical solution for transient guided wave propagation in finite liquid-filled pipe systems is extended explicitly and concisely to infinite liquid-filled pipe systems. Several numerical examples are given to illustrate the analysis of the spatial and frequency distributions of the radial and axial displacement amplitudes of various guided wave modes; the numerical examples also simulate the transient displacement of the pipe wall and the transient pressure of the internal liquid from the present solution. The present solution can provide some theoretical guidelines for the guided wave nondestructive evaluation of liquid-filled pipes and the guided wave technique for downhole data transfer.

  6. Angular-profile tuning of guided waves in hollow cylinders using a circumferential phased array.

    Science.gov (United States)

    Li, Jian; Rose, Joseph L

    2002-12-01

    Angular-profile tuning of guided waves in hollow cylinders is implemented by using partial loading of the elements in a circumferentially placed phased array. Each partial loading element generates nonaxisymmetric guided waves in a pipe. In earlier work, numerical calculations and experiments have shown that, for nonaxisymmetric guided waves, circumferential distribution of particle displacements (i.e., the angular profile) changes with propagation distance, frequency, and mode. To change the angular profile at a certain distance, either frequency or mode has to be changed for a single partial loading element. This is not the case, however, for a circumferential phased array. The total angular profile of a circumferential array is the superposition of contributions from all elements. If given the knowledge of the angular profile for a single element, the total guided wave angular profile can be controlled and thus focused at any specific circumferential location by a circumferentially placed phased array with adjustable voltage level and phase inputs. This angular profile tuning technique can be used for implementing a circumferential scan with focused, guided wave beams, which leads to the detection of smaller defects as a result of stronger focused beams. Algorithms and specific nondestructive evaluation (NDE) applications for pipe inspection using this technique are discussed.

  7. A Magnetic Flux Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables

    Directory of Open Access Journals (Sweden)

    Jiang Xu

    2012-01-01

    Full Text Available Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables.

  8. Using the gauge condition to simplify the elastodynamic analysis of guided wave propagation

    Directory of Open Access Journals (Sweden)

    Md Yeasin BHUIYAN

    2016-09-01

    Full Text Available In this article, gauge condition in elastodynamics is explored more to revive its potential capability of simplifying wave propagation problems in elastic medium. The inception of gauge condition in elastodynamics happens from the Navier-Lame equations upon application of Helmholtz theorem. In order to solve the elastic wave problems by potential function approach, the gauge condition provides the necessary conditions for the potential functions. The gauge condition may be considered as the superposition of the separate gauge conditions of Lamb waves and shear horizontal (SH guided waves respectively, and thus, it may be resolved into corresponding gauges of Lamb waves and SH waves. The manipulation and proper choice of the gauge condition does not violate the classical solutions of elastic waves in plates; rather, it simplifies the problems. The gauge condition allows to obtain the analytical solution of complicated problems in a simplified manner.

  9. Consolidating guided wave simulations and experimental data: a dictionary learning approach

    Science.gov (United States)

    Alguri, K. Supreet; Harley, Joel B.

    2016-04-01

    Modeling and simulating guided wave propagation in complex, geometric structures is a topic of significant interest in structural health monitoring. These models have the potential to benefit damage detection, localization, and characterization in structures where traditional algorithms fail. Numerical modelling (for example, using finite element or semi-analytical finite element methods) is a popular approach for simulating complex wave behavior. Yet, using these models to improve experimental data analysis remains difficult. Numerical simulations and experimental data rarely match due to uncertainty in the properties of the structures and the guided waves traveling within them. As a result, there is a significant need to reduce this uncertainty by incorporating experimental data into the models. In this paper, we present a dictionary learning framework to address this challenge. Specifically, use dictionary learning to combine numerical wavefield simulations with 24 simulated guided wave measurements with different frequency-dependent velocity characteristics (emulating an experimental system) to make accurate, global predictions about experimental wave behavior. From just 24 measurements, we show that we can predict and extrapolate guided wave behavior with accuracies greater than 92%.

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

    Science.gov (United States)

    Shen, Yanfeng

    2017-04-01

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

  11. Guided wave propagation in single and double layer hollow cylinders embedded in infinite media.

    Science.gov (United States)

    Jia, Hua; Jing, Mu; Joseph, L Rose

    2011-02-01

    Millions of miles of pipes are being used for the transportation, distribution, and local use of petroleum products, gas, water, and chemicals. Most of the pipes are buried in soil, leading to the significance of the study on the subject of guided wave propagation in pipes with soil influence. Previous investigations of ultrasonic guided wave propagation in an elastic hollow cylinder and in an elastic hollow cylinder coated with a viscoelastic material have led to the development of inspection techniques for bare and coated pipes. However, the lack of investigation on guided wave propagation in hollow cylinders embedded in infinite media like soil has hindered the development of pipe inspection methods. Therefore the influence of infinite media on wave propagation is explored in this paper. Dispersion curves and wave structures of both axisymmetric and nonaxisymmetric wave modes are developed. Due to the importance of the convergence of numerical calculations, the requirements of thickness and element number of the finite soil layer between hollow cylinder and infinite element layer are discussed, and an optimal combination is obtained in this paper. Wave structures are used for the mode identification in the non-monotonic region caused by the viscoelastic properties of coating and infinite media.

  12. Combination of nonlinear ultrasonics and guided wave tomography for imaging the micro-defects.

    Science.gov (United States)

    Li, Weibin; Cho, Younho

    2016-02-01

    The use of guided wave tomography has become an attractive alternative to convert ultrasonic wave raw data to visualized results for quantitative signal interpretation. For more accurate life prediction and efficient management strategies for critical structural components, there is a demand of imaging micro-damages in early stage. However, there is rarely investigation on guided wave tomographic imaging of micro-defects. One of the reasons for this might be that it becomes challenging to monitor tiny signal difference coefficient in a reliable manner for wave propagation in the specimens with micro-damages. Nonlinear acoustic signal whose frequency differs from that of the input signal can be found in the specimens with micro-damages. Therefore, the combination of guided wave tomography and nonlinear acoustic response induced by micro-damages could be a feasibility study for imaging micro-damages. In this paper, the nonlinear Rayleigh surface wave tomographic method is investigated to locate and size micro-corrosive defect region in an isotropic solid media. The variations of acoustic nonlinear responses of ultrasonic waves in the specimens with and without defects are used in guided wave tomographic algorithm to construct the images. The comparisons between images obtained by experimental signals and real defect region induced by hydrogen corrosion are presented in this paper. Results show that the images of defect regions with different shape, size and location are successfully obtained by this novel technique, while there is no visualized result constructed by conventional linear ultrasonic tomographic one. The present approach shows a potential for inspecting, locating and imaging micro-defects by nonlinear Rayleigh surface wave tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. On the effects of geometry on guided electromagnetic waves

    Directory of Open Access Journals (Sweden)

    Tucker Robin W.

    2007-01-01

    Full Text Available The method of moving (Cartan coframes is used to analyze the influence of geometry on the behavior of electromagnetic fields in confining guides and the effect of such fields on their ultra-relativistic sources. Such issues are of relevance to a number of topical problems in accelerator science where the need to control the motion of high current-density micro-meter size bunches of relativistic radiating charge remains a technical and theoretical challenge. By dimensionally reducing the exterior equations for the sources and fields on spacetime using symmetries exhibited by the confining guides one achieves a unifying view that offers natural perturbative approaches for dealing with smooth non-uniform and curved guides. The issue of the back-reaction of radiation fields on the sources is approached in terms of a simple charged relativistic fluid model. .

  14. INS/CNS/GNSS integrated navigation technology

    CERN Document Server

    Quan, Wei; Gong, Xiaolin; Fang, Jiancheng

    2015-01-01

    This book not only introduces the principles of INS, CNS and GNSS, the related filters and semi-physical simulation, but also systematically discusses the key technologies needed for integrated navigations of INS/GNSS, INS/CNS, and INS/CNS/GNSS, respectively. INS/CNS/GNSS integrated navigation technology has established itself as an effective tool for precise positioning navigation, which can make full use of the complementary characteristics of different navigation sub-systems and greatly improve the accuracy and reliability of the integrated navigation system. The book offers a valuable reference guide for graduate students, engineers and researchers in the fields of navigation and its control. Dr. Wei Quan, Dr. Jianli Li, Dr. Xiaolin Gong and Dr. Jiancheng Fang are all researchers at the Beijing University of Aeronautics and Astronautics.

  15. Guided wave technology for a telecom wavelength heralded single photon source

    CERN Document Server

    Alibart, O; Ostrowsky, D B; Baldi, P; Alibart, Olivier; Tanzilli, Sebastien; Ostrowsky, Daniel Barry; Baldi, Pascal

    2004-01-01

    We report on a guided wave heralded photon source based on the creation of non-degenerate photon pairs by spontaneous parametric down conversion in a Periodically Poled Lithium Niobate waveguide. Using the signal photon at 1310 nm as a trigger, a gated detection process permits announcing the arrival of single photons at 1550 nm at the output of a single mode optical fiber with the best probability to date of 0.38. The multi-photon emission probability is reduced by a factor of 10 compared to poissonian light sources. Relying on guided wave technologies such as integrated optics and fiber optics components, our source offers stability, compactness and efficiency and can serve as a paradigm for guided wave devices applied to quantum communication and computation using existing telecom networks.

  16. A Love Wave Reflective Delay Line with Polymer Guiding Layer for Wireless Sensor Application.

    Science.gov (United States)

    Wang, Wen; He, Shitang

    2008-12-05

    This paper presents an optimal design for a Love wave reflective delay line on 41(o) YX LiNbO₃ with a polymer guiding layer for wireless sensor applications. A theoretical model was established to describe the Love wave propagation along the larger piezoelectric substrate with polymer waveguide, and the lossy mechanism from the viscoelastic waveguide was discussed, which results in the optimal guiding layer thickness. Coupling of modes (COM) was used to determine the optimal design parameters of the reflective delay line structured by single phase unidirectional transducers (SPUDTs) and shorted grating reflectors. Using the network analyzer, the fabricated Love wave reflective delay line was characterized, high signal noise ratio (S/N), sharp reflection peaks, and few spurious noise between the peaks were found, and the measured result agrees well with the simulated one. Also, the optimal guiding layer thickness of 1.5~1.8μm was extracted experimentally, and it is consistent with the theoretical analysis.

  17. Influence of Guided Waves in Tibia on Non-linear Scattering of Contrast Agents.

    Science.gov (United States)

    Wang, Diya; Zhong, Hui; Zhai, Yu; Hu, Hong; Jin, Bowen; Wan, Mingxi

    2016-02-01

    The aim of this study was to elucidate the linear and non-linear responses of ultrasound contrast agent (UCA) to frequency-dispersive guided waves from the tibia cortex, particularly two individual modes, S0 (1.23 MHz) and A1 (2.06 MHz). The UCA responses to guided waves were illustrated through the Marmottant model derived from measured guided waves, and then verified by continuous infusion experiments in a vessel-tibia flow phantom. These UCA responses were further evaluated by the enhanced ratio of peak values and the resolutions of UCA backscattered echoes. Because of the individual modes S0 and A1 in the tibia, the peak values of the UCA backscattered echoes were enhanced by 83.57 ± 7.35% (p < 0.05) and 80.77 ± 6.60% (p < 0.01) in the UCA subharmonic frequency and subharmonic imaging, respectively. However, corresponding resolutions were 0.78 ± 0.07 (p < 0.05) and 0.72 ± 0.12 (p < 0.01) times those without guided wave disturbances, respectively. Even though the resolution was partly degenerated, the subharmonic detection sensitivity of UCA was improved by the guided waves. Thus, UCA responses to the double-frequency guided waves should be further explored to benefit the detection of capillary perfusion in tissue layers near the bone cortex, particularly for perfusion imaging in the free flaps and skeletal muscles.

  18. Time-frequency analysis of guided ultrasonic waves used for assessing integrity of rock bolts

    Science.gov (United States)

    Stepinski, Tadeusz

    2017-04-01

    The purpose of this paper is to demonstrate application of the time-frequency analysis (TFA) for processing guided ultrasonic waves measured by means of a specially designed ultrasonic rock bolt tester during nondestructive inspection of rock bolts. A pulse-echo method is adopted in the instrument as the most appropriate for the in-field applications. This paper presents methods for analysis of the measured guided ultrasonic waves using the TFA. The proposed TFA methodology is first demonstrated on the simulated signals and then verified using the experimental signals gathered from grouted prepared rock bolts provided with artificial defects simulating grout discontinuities.

  19. Feasibility of detecting cracks in rail track at long range using guided wave ultrasound

    CSIR Research Space (South Africa)

    Loveday, PW

    2014-01-01

    Full Text Available ,” Journal of Sound and Vibration, vol. 185, no. 3, pp. 531–543, Aug. 1995. 5 P. W. Loveday and C. S. Long, “Field measurement of guided wave modes in rail track,” in Review of Progress in Quantitative Nondestructive Evaluation, vol. 32, pp230-237, 2013. 6... on Computational and Applied Mechanics Somerset West 14 – 16 January 2014 Feasibility of Detecting Cracks in Rail Track at Long Range using Guided Wave Ultrasound Philip W. Loveday*, Craig S. Long CSIR Material Science and Manufacturing, South Africa...

  20. Monitoring ageing of alkali resistant glass fiber reinforced cement (GRC) using guided ultrasonic waves

    Science.gov (United States)

    Eiras, J. N.; Amjad, U.; Mahmoudabadi, E.; Payá, J.; Bonilla, M.; Kundu, T.

    2013-04-01

    Glass fiber reinforced cement (GRC) is a Portland cement based composite with alkali resistant (AR) glass fibers. The main drawback of this material is the ageing of the reinforcing fibers with time and especially in presence of humidity in the environment. Until now only destructive methods have been used to evaluate the durability of GRC. In this study ultrasonic guided wave inspection of plate shaped specimens has been carried out. The results obtained here show that acoustic signatures are capable of discerning ageing in GRC. Therefore, the ultrasonic guided wave based inspection technique is a promising method for the nondestructive evaluation of the durability of the GRC.

  1. Spinor-electron wave guided modes in coupled quantum wells structures by solving the Dirac equation

    Energy Technology Data Exchange (ETDEWEB)

    Linares, Jesus [Area de Optica, Departamento de Fisica Aplicada, Facultade de Fisica, Escola Universitaria de Optica e Optometria, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia (Spain)], E-mail: suso.linares.beiras@usc.es; Nistal, Maria C. [Area de Optica, Departamento de Fisica Aplicada, Facultade de Fisica, Escola Universitaria de Optica e Optometria, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia (Spain)

    2009-05-04

    A quantum analysis based on the Dirac equation of the propagation of spinor-electron waves in coupled quantum wells, or equivalently coupled electron waveguides, is presented. The complete optical wave equations for Spin-Up (SU) and Spin-Down (SD) spinor-electron waves in these electron guides couplers are derived from the Dirac equation. The relativistic amplitudes and dispersion equations of the spinor-electron wave-guided modes in a planar quantum coupler formed by two coupled quantum wells, or equivalently by two coupled slab electron waveguides, are exactly derived. The main outcomes related to the spinor modal structure, such as the breaking of the non-relativistic degenerate spin states, the appearance of phase shifts associated with the spin polarization and so on, are shown.

  2. Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning

    Science.gov (United States)

    Karppinen, Pasi; Salmi, Ari; Moilanen, Petro; Karppinen, Timo; Zhao, Zuomin; Myllylä, Risto; Timonen, Jussi; Hæggström, Edward

    2013-04-01

    Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.

  3. High-frequency guided ultrasonic waves for hidden defect detection in multi-layer aircraft structures

    Science.gov (United States)

    Masserey, B.; Raemy, C.; Fromme, P.

    2012-05-01

    Aerospace structures contain multi-layer components subjected to cyclic loading conditions; fatigue cracks and disbonds can develop, often at fastener holes. High-frequency guided waves have the potential for non-destructive damage detection at critical and difficult to access locations from a stand-off distance. Using commercially available ultrasonic transducers, high frequency guided waves were generated that penetrate through the complete thickness of a model structure, consisting of two adhesively bonded aluminum plates. The wave propagation along the specimen was measured and quantified using a laser interferometer. The wave propagation and scattering at internal defects was simulated using Finite Element (FE) models and good agreement with the measurement results found. The detection sensitivity using standard pulse-echo measurements was verified and the influence of the stand-off distance predicted from the FE simulation results.

  4. An ultrasonic guided wave approach for the inspection of overhead transmission line cables

    DEFF Research Database (Denmark)

    Kappatos, Vasileios; Yücel, Mehmet K.; Legg, Mathew

    2017-01-01

    Inspection of overhead transmission line cables is performed using various non-destructive testing techniques, such as visual, temperature, and eddy current-based inspection; yet each of these techniques have their respective shortcomings and safety concerns. The use of ultrasonic guided waves...... as a non-destructive testing technique is well established for simple geometries such as plates, pipes, and rods. However, its application for multi-wire cables is still in development. In this study, ultrasonic guided waves excited by a shear mode transducer collar are utilised as a defect detection...... technique for untensioned aluminium conductor steel reinforced cable specimens. The identification and analysis of wave propagation for a broad range of frequencies is performed using a laser scanning vibrometer, and the effect of defect size on wave propagation is studied. Signal processing algorithms...

  5. Mode perturbation method for optimal guided wave mode and frequency selection.

    Science.gov (United States)

    Philtron, J H; Rose, J L

    2014-09-01

    With a thorough understanding of guided wave mechanics, researchers can predict which guided wave modes will have a high probability of success in a particular nondestructive evaluation application. However, work continues to find optimal mode and frequency selection for a given application. This "optimal" mode could give the highest sensitivity to defects or the greatest penetration power, increasing inspection efficiency. Since material properties used for modeling work may be estimates, in many cases guided wave mode and frequency selection can be adjusted for increased inspection efficiency in the field. In this paper, a novel mode and frequency perturbation method is described and used to identify optimal mode points based on quantifiable wave characteristics. The technique uses an ultrasonic phased array comb transducer to sweep in phase velocity and frequency space. It is demonstrated using guided interface waves for bond evaluation. After searching nearby mode points, an optimal mode and frequency can be selected which has the highest sensitivity to a defect, or gives the greatest penetration power. The optimal mode choice for a given application depends on the requirements of the inspection.

  6. User guide – COE Calculation Tool for Wave Energy Converters

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez; Kofoed, Jens Peter; Jensen, Niels Ejner Helstrup

    Aalborg University together with Energinet.dk and Julia F. Chozas Consulting Engineer, have released a freely available online spreadsheet to evaluate the Levelised Cost of Energy (LCOE) for wave energy projects. The open-access tool calculates the LCOE based on the power production of a Wave...... Energy Converter (WEC) at a particular location. Production data may derive from laboratory testing, numerical modelling or from sea trials. The tool has been developed as a transparent and simple model that evaluates WEC’s economic feasibility in a range of locations, while scaling WEC’s features...

  7. On the development and testing of a guided ultrasonic wave array for structural integrity monitoring

    OpenAIRE

    Fromme, P.; Wilcox, P. D.; Lowe, M. J. S.; Canvley, P.

    2006-01-01

    The prototype of a guided ultrasonic wave array for the structural integrity monitoring of large, plate-like structures has been designed, built, and tested. The development of suitably small transducers for the excitation and measurement of the first antisymmetric Lamb wave mode A(0) is described. The array design consists of a ring of 32 transducers, permanently bonded to the structure with a protective membrane, in a compact housing with the necessary multiplexing electronics. Using a phas...

  8. The features of the guided wave excitation and propagation at testing of pipes

    Science.gov (United States)

    Myshkin, Yu V.; Muravieva, O. V.

    2017-08-01

    The generalized integral solutions of the problem connected with excitation and propagation of torsional waves by electromagnetic-acoustic transducers in unloaded pipes and under conditions of loading on contact viscoelastic media, taking into account excitation parameters (frequency and geometry of the transducers), geometry, viscosity and elastic characteristics of pipe material and surrounding media, are presented. The amplitude of angular displacements of the torsional waves in pipes is estimated from the point of choice of frequency band, scanning distance and sensitivity estimation in guided wave testing of the pipes with various types and sizes. The numerical and experimental estimation of influence of the surrounding media viscoelastic characteristics on attenuation of the torsional T(0,1), longitudinal L(0,1) and flexural F(1,1) waves in the pipe is performed. The model of acoustic path of the guided wave technique on multiple reflections for testing the pipes with fixed sizes is presented and the guided wave technique sensitivity to defects depending on quantity of the received reflections, clamping force of the acoustic transducer and unwanted mode amplitude which is restricting the sensitivity to the defects is estimated.

  9. Discretized energy minimization in a wave guide with point sources

    Science.gov (United States)

    Propst, G.

    1994-01-01

    An anti-noise problem on a finite time interval is solved by minimization of a quadratic functional on the Hilbert space of square integrable controls. To this end, the one-dimensional wave equation with point sources and pointwise reflecting boundary conditions is decomposed into a system for the two propagating components of waves. Wellposedness of this system is proved for a class of data that includes piecewise linear initial conditions and piecewise constant forcing functions. It is shown that for such data the optimal piecewise constant control is the solution of a sparse linear system. Methods for its computational treatment are presented as well as examples of their applicability. The convergence of discrete approximations to the general optimization problem is demonstrated by finite element methods.

  10. Warped Wigner-Hough Transform for Defect Reflection Enhancement in Ultrasonic Guided Wave Monitoring

    Directory of Open Access Journals (Sweden)

    Luca De Marchi

    2012-01-01

    Full Text Available To improve the defect detectability of Lamb wave inspection systems, the application of nonlinear signal processing was investigated. The approach is based on a Warped Frequency Transform (WFT to compensate the dispersive behavior of ultrasonic guided waves, followed by a Wigner-Ville time-frequency analysis and the Hough Transform to further improve localization accuracy. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested by analyzing numerically simulated Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented for real-world structural health monitoring applications.

  11. CNS development: an overview

    Science.gov (United States)

    Nowakowski, R. S.; Hayes, N. L.

    1999-01-01

    The basic principles of the development of the central nervous system (CNS) are reviewed, and their implications for both normal and abnormal development of the brain are discussed. The goals of this review are (a) to provide a set of concepts to aid in understanding the variety of complex processes that occur during CNS development, (b) to illustrate how these concepts contribute to our knowledge of the normal anatomy of the adult brain, and (c) to provide a basis for understanding how modifications of normal developmental processes by traumatic injury, by environmental or experiential influences, or by genetic variations may lead to modifications in the resultant structure and function of the adult CNS.

  12. Guided wave propagation along the surface of a one-dimensional solid-fluid phononic crystal

    Science.gov (United States)

    Moiseyenko, Rayisa P.; Declercq, Nico F.; Laude, Vincent

    2013-09-01

    We consider an arbitrary periodic corrugated surface of a semi-infinite elastic solid that is immersed in a fluid, forming a one-dimensional phononic crystal. We study the existence and the polarization of guided waves that propagate along the interface. A coupled elastic-acoustic variational model is devised to obtain the dispersion of guided waves, which is implemented with a finite element method. It is found that the deeply corrugated interface supports a family of interface waves whose phase velocity decreases as the corrugation depth increases. Among these interface waves, some display an evanescent decay in the fluid that is reminiscent of the Scholte-Stoneley wave, while others propagate in the solid without causing significant pressure variation in the fluid, or cause localized pressure variations only inside the corrugation openings. The obtained results open the way for the study of conversions between bulk and surface waves in solid-fluid phononic crystals, and their use for wave confinement at the surface.

  13. Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

    NARCIS (Netherlands)

    Pahlavan, P.L.; De Soares Silva e Melo Mota, M.; Blacquière, G.

    2016-01-01

    Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the effe

  14. Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

    NARCIS (Netherlands)

    Pahlavan, P.L.; De Soares Silva e Melo Mota, M.; Blacquière, G.

    2016-01-01

    Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the

  15. Measurements of shock-induced guided and surface acoustic waves along boreholes in poroelastic materials

    NARCIS (Netherlands)

    Chao, G.; Smeulders, D.M.J.; Van Dongen, M.E.H.

    2006-01-01

    Acoustic experiments on the propagation of guided waves along water-filled boreholes in water-saturated porous materials are reported. The experiments were conducted using a shock tube technique. An acoustic funnel structure was placed inside the tube just above the sample in order to enhance the ex

  16. Ultrasonic guided wave propagation across waveguide transitions: energy transfer and mode conversion.

    Science.gov (United States)

    Puthillath, Padmakumar; Galan, Jose M; Ren, Baiyang; Lissenden, Cliff J; Rose, Joseph L

    2013-05-01

    Ultrasonic guided wave inspection of structures containing adhesively bonded joints requires an understanding of the interaction of guided waves with geometric and material discontinuities or transitions in the waveguide. Such interactions result in mode conversion with energy being partitioned among the reflected and transmitted modes. The step transition between an aluminum layer and an aluminum-adhesive-aluminum multi-layer waveguide is analyzed as a model structure. Dispersion analysis enables assessment of (i) synchronism through dispersion curve overlap and (ii) wavestructure correlation. Mode-pairs in the multi-layer waveguide are defined relative to a prescribed mode in a single layer as being synchronized and having nearly perfect wavestructure matching. Only a limited number of mode-pairs exist, and each has a unique frequency range. A hybrid model based on semi-analytical finite elements and the normal mode expansion is implemented to assess mode conversion at a step transition in a waveguide. The model results indicate that synchronism and wavestructure matching is associated with energy transfer through the step transition, and that the energy of an incident wave mode in a single layer is transmitted almost entirely to the associated mode-pair, where one exists. This analysis guides the selection of incident modes that convert into transmitted modes and improve adhesive joint inspection with ultrasonic guided waves.

  17. Experimental Validation of a Fast Forward Model for Guided Wave Tomography of Pipe Elbows.

    Science.gov (United States)

    Brath, Alex J; Simonetti, Francesco; Nagy, Peter B; Instanes, Geir

    2017-05-01

    Ultrasonic guided wave tomography (GWT) methods for the detection of corrosion and erosion damage in straight pipe sections are now well advanced. However, successful application of GWT to pipe bends has not yet been demonstrated due to the computational burden associated with the complex forward model required to simulate guided wave propagation through the bend. In a previous paper [Brath et al., IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 61, pp. 815-829, 2014], we have shown that the speed of the forward model can be increased by replacing the 3-D pipe bend with a 2-D rectangular domain in which guided wave propagation is formulated based on an artificially inhomogeneous and elliptically anisotropic (INELAN) acoustic model. This paper provides further experimental validation of the INLEAN model by studying the traveltime shifts caused by the introduction of shallow defects on the elbow of a pipe bend. Comparison between experiments and simulations confirms that a defect can be modeled as a phase velocity perturbation to the INLEAN velocity field with accuracy that is within the experimental error of the measurements. In addition, it is found that the sensitivity of traveltime measurements to the presence of damage decreases as the damage position moves from the interior side of the bend (intrados) to the exterior one (extrados). This effect is due to the nonuniform ray coverage obtainable when transmitting the guided wave signals with one ring array of sources on one side of the elbow and receiving with a second array on the other side.

  18. Guided UT wave inspection of insulated feedwater piping using magnetostrictive sensors

    Science.gov (United States)

    Brophy, J. W.; Brett, Colin R.

    1996-11-01

    Due to failures in power plant feedwater piping, inspection of these components has become a priority item. The major reason for the failures is wall loss due to flow-accelerated corrosion on the inside diameter (ID) of the pipes. It can be very costly to use standard nondestructive testing (NDT) techniques for a comprehensive inspection due to the need to remove large areas of insulation. Guided UT waves can travel through the pipe over long distances and detect cross- sectional changes in the pipe wall with minimal insulation removal. This makes the guided UT wave an excellent candidate for locating significant wall loss due to corrosion and pitting. Southwest Research Institute (SwRI) has developed a simple and robust technology for generating and receiving guided UT waves based on magnetorestrictive sensors. Signals are generated and detected in the pipe via multi-turn coils acting as transmitters and receivers. Insulation removal is only required where the coils are attached to the pipe and this allows many meters of pipe to be inspected from a single location. Guided UT waves detect cross-sectional changes from corrosion on both the ID and outside diameter of the pipe and can also be used to map weld locations. This paper describes SwRIs systems and the preliminary results from testing on a feedwater pipe mockup containing simulated flow-accelerated corrosion.

  19. Guided wave-based identification of multiple cracks in beams using a Bayesian approach

    Science.gov (United States)

    He, Shuai; Ng, Ching-Tai

    2017-02-01

    A guided wave damage identification method using a model-based approach is proposed to identify multiple cracks in beam-like structures. The guided wave propagation is simulated using spectral finite element method and a crack element is proposed to take into account the mode conversion effect. The Bayesian model class selection algorithm is employed to determine the crack number and then the Bayesian statistical framework is used to identify the crack parameters and the associated uncertainties. In order to improve the efficiency and ensure the reliability of identification, the Transitional Markov Chain Monte Carlo (TMCMC) method is implemented in the Bayesian approach. A series of numerical case studies are carried out to assess the performance of the proposed method, in which the sensitivity of different guided wave modes and effect of different levels of measurement noise in identifying different numbers of cracks is studied in detail. The proposed method is also experimentally verified using guided wave data obtained from laser vibrometer. The results show that the proposed method is able to accurately identify the number, locations and sizes of the cracks, and also quantify the associated uncertainties. In addition the proposed method is robust under measurement noise and different situations of the cracks.

  20. Diffractive beam shaping, tracking and coupling for wave-guided optical waveguides (WOWs)

    DEFF Research Database (Denmark)

    Villangca, Mark Jayson; Bañas, Andrew Rafael; Aabo, Thomas

    2014-01-01

    We have previously proposed and demonstrated the targeted-light delivery capability of wave-guided optical waveguides (WOWs). The full strength of this structure-mediated paradigm can be harnessed by addressing multiple WOWs and manipulating them to work in tandem. We propose the use of diffractive...

  1. Low-velocity fault-zone guided waves: Numerical investigations of trapping efficiency

    Science.gov (United States)

    Li, Y.-G.; Vidale, J.E.

    1996-01-01

    Recent observations have shown that shear waves trapped within low-velocity fault zones may be the most sensitive measure of fault-zone structure (Li et al., 1994a, 1994b). Finite-difference simulations demonstrate the effects of several types of complexity on observations of fault-zone trapped waves. Overlying sediments with a thickness more than one or two fault-zone widths and fault-zone step-overs more than one or two fault widths disrupt the wave guide. Fault kinks and changes in fault-zone width with depth leave readily observable trapped waves. We also demonstrate the effects of decreased trapped wave excitation with increasing hypocentral offset from the fault and the effects of varying the contrast between the velocity in the fault zone and surrounding hard rock. Careful field studies may provide dramatic improvements in our knowledge of fault-zone structure.

  2. CNS infections in Greenland

    DEFF Research Database (Denmark)

    Nordholm, Anne Christine; Søborg, Bolette; Andersson, Mikael

    2017-01-01

    BACKGROUND: Indigenous Arctic people suffer from high rates of infectious diseases. However, the burden of central nervous system (CNS) infections is poorly documented. This study aimed to estimate incidence rates and mortality of CNS infections among Inuits and non-Inuits in Greenland...... and in Denmark. METHODS: We conducted a nationwide cohort study using the populations of Greenland and Denmark 1990-2012. Information on CNS infection hospitalizations and pathogens was retrieved from national registries and laboratories. Incidence rates were estimated as cases per 100,000 person......-years. Incidence rate ratios were calculated using log-linear Poisson-regression. Mortality was estimated using Kaplan-Meier curves and Log Rank test. RESULTS: The incidence rate of CNS infections was twice as high in Greenland (35.6 per 100,000 person years) as in Denmark (17.7 per 100,000 person years...

  3. Ultrasonic guided wave based damage imaging by time-reversal method in frequency-wavenumber domain

    Science.gov (United States)

    Xu, C. G.; Xu, B. Q.; Luo, Y.; Xu, G. D.; Lu, L. Z.

    2017-05-01

    More attention has been drawn to ultrasonic guided waves (UGW) based damage detection method for its advantages of wide range inspection of large scale structures. However, complex propagation characteristics of guided waves as well as traditional contact ultrasonic transducers limit its application for the practical damage detection. By combining Scanning Laser Doppler vibrometer (SLDV) technology, Time-Reversal method in frequency-wavenumber domain (f-k RTM) can compensate for the dispersive nature of Lamb waves, localize multiple damage sites and identify their sizes without time consuming numerical calculation. In this work, we adopt f-k RTM for damage detection in plate-like structure. Instead of SLDV in experiment, 3D finite element numerical method is adopted to obtain scattered ultrasonic guided wavefield data with high spatial resolution. The direct path waves were extracted to obtain the incident wavefield while the scattered signals were used to calculate the scattering wave field. Damage imaging can also be achieved by introducing crosscorrelation imaging condition. Imaging results show that the method is very effective for crack localization and boundary shape-recognition. Numerical simulation results and imaging algorithm laid the foundation for the method applied in experiment and practice.

  4. Defect Detection in Multi-Layered Structures Using High Frequency Guided Waves

    Science.gov (United States)

    Masserey, B.; Kostson, E.; Fromme, P.

    2011-06-01

    Aircraft structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along the structure allow for the efficient non-destructive testing of components, such as aircraft wings. However, the sensitivity for the detection of small defects has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. High frequency ultrasonic wave propagation along the structure and the sensitivity to disbonds and small defects in the metallic layers was investigated and verified experimentally. Preliminary fatigue experiments were carried out and the sensitivity of the guided waves to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated. The measurement setup has the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

  5. Simulation of guided waves in complex piping geometries using the elastodynamic finite integration technique.

    Science.gov (United States)

    Rudd, Kevin E; Leonard, Kevin R; Bingham, Jill P; Hinders, Mark K

    2007-03-01

    Although many technologies exist for inspecting piping systems, they are most successful on straight pipes and are often unable to accommodate the added complexities of pipe elbows, bends, twists, and branches, particularly if the region of interest is inaccessible. This paper presents a numerical technique based on the elastodynamic finite integration technique for simulating guided elastic wave propagation in piping systems. Comparisons show agreement between experimental and simulated data, and guided wave interaction with flaws, focusing, and propagation in pipe bends are presented. These examples demonstrate the ability of the simulation method to be used to study elastic wave propagation in piping systems which include three-dimensional pipe bends, and suggest its potential as a design tool for designing pipe inspection hardware and ultrasonic signal processing algorithms.

  6. Prediction and near-field observation of skull-guided acoustic waves

    CERN Document Server

    Estrada, Héctor; Razansky, Daniel

    2016-01-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field properties unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  7. Amplitude controlled array transducers for mode selection and beam steering of guided waves in plates

    Science.gov (United States)

    Kannajosyula, H.; Lissenden, C. J.; Rose, J. L.

    2013-01-01

    We present a method for mode selection of guided wave modes and beam steering using purely amplitude variation across a one dimensional linear array of transducers. The method is distinct from apodization of phased array transducers that involves amplitude variation in addition to time delays and merely aims to improve the spectral characteristics of the transducer. The relationship between amplitude variation and the pitch of the array is derived by considering the resulting transduction as analogous to a spatio-temporal filter approach. It is also shown analytically and through numerical examples that the proposed method results in bidirectional guided waves when the steering angle is zero. Further, for non-zero steering angles, the waves travel in four directions, including the desired direction. Experimental studies are suggested.

  8. S-polarized nonlinear surface and guided waves in an asymmetric layered structure

    Energy Technology Data Exchange (ETDEWEB)

    Mihalache, D.; Totia, H.

    1983-08-01

    An exact solution of Maxwell's equations is found, corresponding to s-polarized nonlinear surface and guided waves in an asymmetric layered structure. The system under consideration consists of a film with dielectric constant epsilon/sub 2/ bounded at the negative-z side by a linear medium with dielectric constant epsilon/sub 1/ and at the positive -z side by a nonlinear substrate characterized by the diagonal dielectric tensor epsilon/sub 11/ = epsilon/sub 22/ = epsilon/sub 33/ = epsilon/sub 0/ + ..cap alpha.. absolute value of E-vector/sup 2/, ..cap alpha.. > 0 (a selffocussing medium). We predict bistable states of s-polarized nonlinear surface and guided waves provided that the power flow in the wave is the control parameter.

  9. Guided Wave Based Crack Detection in the Rivet Hole Using Global Analytical with Local FEM Approach

    Directory of Open Access Journals (Sweden)

    Md Yeasin Bhuiyan

    2016-07-01

    Full Text Available In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage in the plate structure gives rise to the non-axisymmetric scattering of Lamb wave, as well as shear horizontal (SH wave, although the incident Lamb wave source (primary source is axisymmetric. The damage in the plate acts as a non-axisymmetric secondary source of Lamb wave and SH wave. The scattering of Lamb and SH waves are captured using wave damage interaction coefficient (WDIC. The scatter cubes of complex-valued WDIC are formed that can describe the 3D interaction (frequency, incident direction, and azimuth direction of Lamb waves with the damage. The scatter cubes are fed into the exact analytical framework to produce the time domain signal. This analysis enables us to obtain the optimum design parameters for better detection of the cracks in a multiple-rivet-hole problem. The optimum parameters provide the guideline of the design of the sensor installation to obtain the most noticeable signals that represent the presence of cracks in the rivet hole.

  10. Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces

    Science.gov (United States)

    Zhu, Hongfei; Semperlotti, Fabio

    2016-07-01

    The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A0) either when using a symmetric (S0) or antisymmetric (A0) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation.

  11. Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces.

    Science.gov (United States)

    Zhu, Hongfei; Semperlotti, Fabio

    2016-07-15

    The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A_{0}) either when using a symmetric (S_{0}) or antisymmetric (A_{0}) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation.

  12. WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation

    Science.gov (United States)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

    This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.

  13. Near-to-far field transformations for radiative and guided waves

    CERN Document Server

    Yang, Jianji; Lalanne, Philippe

    2015-01-01

    Light emitters or scatterers embedded in stratified media may couple energy to both free space and guided modes of the stratified structure. For a thorough analysis of such structures, it is important to evaluate the angular intensity distribution of both the free-space-propagative and guided waves. In this work, we propose an original method based on Lorentz-reciprocity theorem and on the computation of the near-field around the emitters or scatterers, to efficiently calculate the free-space and guided radiation diagrams with a high accuracy. We also provide an open-source code that may be used with virtually any Maxwells solver. The numerical tool may help to engineer various devices, such as light-emitting diodes or nanoantennas to achieve directional and efficient radiative spontaneous decays in free space and guided optics.

  14. Propagating modes in a periodic wave guide in the semi-classical limit

    Energy Technology Data Exchange (ETDEWEB)

    Faure, Frederic [LPMMC, Maison des Magisteres Jean Perrin, CNRS, BP 166, Grenoble (France)]. E-mail: frederic.faure@ujf-grenoble.fr

    2002-02-15

    It is well known that the number of propagating modes in a uniform wave guide is the transverse section divided by the wavelength {lambda} (for a two-dimensional (2D) wave guide). In this paper we study the number of propagating modes N{sub modes} in the limit of small {lambda}, in the case where the section is non-constant but periodic. Using results of a study done by Asch and Knauf (Asch J and Knauf A 1998 Nonlinearity 11 175-200), we show that for small {lambda}, N{sub modes} grows like {mu}{sub b}/{lambda} where {mu}{sub b} is the measure of the ballistic classical trajectories inside the guide. In the case of an ergodic wave guide, where there are no ballistic trajectories but only diffusive trajectories, we show that N{sub modes} grows like {radical}D/{radical}{lambda}where D is the diffusion constant. These results are generalized for any Hamiltonian periodic in one direction, and numerical results with the kicked Harper model are given. N{sub modes} can be related to the Landauer conductance. (author)

  15. Monitoring of hidden damage in multi-layered aerospace structures using high-frequency guided waves

    Science.gov (United States)

    Semoroz, A.; Masserey, B.; Fromme, P.

    2011-04-01

    Aerospace structures contain multi-layered components connected by fasteners, where fatigue cracks and disbonds or localized lack of sealant can develop due to cyclic loading conditions and stress concentration. High frequency guided waves propagating along such a structure allow for the efficient non-destructive testing of large components, such as aircraft wings. The type of multi-layered model structure investigated in this contribution consists of two aluminium plates adhesively bonded with an epoxy based sealant layer. Using commercially available transducer equipment, specific high frequency guided ultrasonic wave modes that penetrate through the complete thickness of the structure were excited. The wave propagation along the structure was measured experimentally using a laser interferometer. Two types of hidden damage were considered: a localized lack of sealant and small surface defects in the metallic layer facing the sealant. The detection sensitivity using standard pulse-echo measurement equipment has been quantified and the detection of small hidden defects from significant stand-off distances has been shown. Fatigue experiments were carried out and the potential of high frequency guided waves for the monitoring of fatigue crack growth at a fastener hole during cyclic loading was discussed.

  16. Prediction and near-field observation of skull-guided acoustic waves.

    Science.gov (United States)

    Estrada, Hector; Rebling, Johannes; Razansky, Daniel

    2017-03-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull.. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  17. Application of a Magnetostrictive Guided wave Technique to Monitor the Evolution of Defect Signals

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Yong-Moo; Oh, Se-Beom; Lee, Duck-Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that wave patterns are clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaw. Of course, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Therefore, the different frequency components of the guided waves will travel at different speeds and the shape of the received signal will changed as it propagates along the pipe. Once the magnetostrictive sensors are attached in the pipe permanently and the signal shape and phase can be compared to the signals before and after, we can monitor the evolution of the flow for the given period. We developed a program to subtract the guided wave signal. The program has a capability of adjusting the time scale and can minimize the noise level after subtraction. By applying the newly developed program, a notch with 2% of CSA can be detected with increased accuracy with noise reduction.

  18. San Andreas Fault damage at SAFOD viewed with fault-guided waves

    Science.gov (United States)

    Li, Yong-Gang; Malin, Peter E.

    2008-04-01

    Highly damaged rocks within the San Andreas fault zone at Parkfield form a low-velocity waveguide for seismic waves, giving rise to fault-guided waves. Prominent fault-guided waves have been observed at the San Andreas Fault Observatory at Depth (SAFOD) site, including a surface array across the fault zone and a borehole seismograph placed in the SAFOD well at a depth of ~2.7 km below ground. The resulting observations are modeled here using 3-D finite-difference methods. To fit the amplitude, frequency, and travel-time characteristics of the data, the models require a downward tapering, 30-40-m wide fault-core embedded in a 100-200-m wide jacket. Compared with the intact wall rocks, the core velocities are reduced by ~40% and jacket velocities by ~25%. Based on the depths of earthquakes generating guided waves, we estimate that the low-velocity waveguide along the fault at SAFOD extends at least to depths of ~7 km, more than twice the depth reported in pervious studies.

  19. Damage detection tomography based on guided waves in composite structures using a distributed sensor network

    Science.gov (United States)

    Memmolo, Vittorio; Maio, Leandro; Boffa, Natalino Daniele; Monaco, Ernesto; Ricci, Fabrizio

    2016-01-01

    Structural health monitoring (SHM) based on guided waves allows assessing the health of a structure due to the sensitivity to the occurrence of delamination. However, wave propagation presents several complexities for effective damage identification in composite structures. An efficient implementation of a guided wave-based SHM system requires an accurate analysis of collected data to obtain a useful detection. This paper is concerned with the identification of small emerging delaminations in composite structural components using a sparse array of surface ultrasonic transducers. An ultrasonic-guided wave tomography technique focused on impact damage detection in composite plate-like structures is presented. A statistical damage index approach is adopted to interpret the recorded signals, and a subsequent graphic interpolation is implemented to reconstruct the damage appearance. Experimental tests carried out on a typical composite structure demonstrated the effectiveness of the developed technique with the aim to investigate the presence and location of damage using simple imaging reports and a limited number of measurements. A traditional ultrasonic inspection (C-scan) is used to assess the methodology.

  20. Prediction and near-field observation of skull-guided acoustic waves

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

    2017-06-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  1. Design of guided Bloch surface wave resonance bio-sensors with high sensitivity

    Science.gov (United States)

    Kang, Xiu-Bao; Wen, Li-Wei; Wang, Zhi-Guo

    2017-01-01

    The sensing performance of bio-sensors based on guided Bloch surface wave (BSW) resonance (GBR) is studied. GBR is realized by coupling the propagating electromagnetic wave with BSW on one side of a one-dimensional photonic crystal slab via the grating on the other side. The sensitivity of the designed bio-sensors is proportional to the grating constant when the wavelength spectrum is analyzed, and inversely proportional to the normal wave vector of the incident electromagnetic wave when the angular spectrum is resolved. For a GBR bio-sensor designed to operate near 70° angle of incidence from air, the angular sensitivity is very high, reaching 128 deg RIU-1. The sensitivity can be substantially increased by designing bio-sensors for operating at larger angles of incidence.

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

    Science.gov (United States)

    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.

  3. Lossless directional guiding of light in dielectric nanosheets using Dyakonov surface waves.

    Science.gov (United States)

    Takayama, Osamu; Artigas, David; Torner, Lluis

    2014-06-01

    Guiding light at the nanoscale is usually accomplished using surface plasmons. However, plasmons propagating at the surface of a metal sustain propagation losses. A different type of surface excitation is the Dyakonov surface wave. These waves, which exist in lossless media, were predicted more than two decades ago but observed only recently. Dyakonov surface waves exist when at least one of the two media forming the surface exhibits a suitable anisotropy of refractive indexes. Although propagating only within a narrow range of directions, these waves can be used to create modes supported by ultrathin films that confine light efficiently within film thicknesses well below the cutoff thickness required in standard waveguides. Here, we show that 10 nm and 20 nm dielectric nanosheets of aluminium oxide clad between an anisotropic crystal (lithium triborate) and different liquids support Dyakonov-like modes. The direction of light propagation can be controlled by modulating the refractive index of the cladding. The possibility of guiding light in nanometre-thick films with no losses and high directionality makes Dyakonov wave modes attractive for planar photonic devices in schemes similar to those currently employing long-range plasmons.

  4. Numerical characterisation of guided wave scattering due to welds in rails

    CSIR Research Space (South Africa)

    Long, CS

    2012-04-01

    Full Text Available railway integrity monitoring system,? in Proceedings of SPIE, 2000, vol. 3988, pp. 330-338. 2. P. W. Loveday, ?Analysis of piezoelectric ultrasonic transducers attached to waveguides using waveguide finite elements.,? IEEE transactions on ultrasonics...0 Lamb wave from a rectangular notch in a plate,? J. Acoust. Soc. Am., vol. 111, no. 1, pp. 64-74, 2002. 7. K. Jezzine and A. Lh?mery, ?Simulation of guided wave inspection based on the reciprocity principle and the semi-analytical finite element...

  5. Traveling Wave-Guide Channels of a New Coupled Integrable Dispersionless System

    Institute of Scientific and Technical Information of China (English)

    Abbagari Souleymanou; Victor K. Kuetche; Thomas B. Bouetou; Timoleon C. Kofane

    2012-01-01

    In the wake of the recent investigation of new coupled integrable dispersionless equations by means of the Darboux transformation [Zhaqilao, et al., Chin. Phys; B 18 (2009) 1780], we carry out the initial value analysis of the previous system using the fourth-order Runge-Kutta's computational scheme. As a result, while depicting its phase portraits accordingly, we show that the above dispersionless system actually supports two kinds of solutions amongst which the localized traveling wave-guide channels. In addition, paying particular interests to such localized structures, we construct the bilinear transformation of the current system from which scattering amongst the above waves can be deeply studied.

  6. ISIS Topside-Sounder Plasma-Wave Investigations as Guides to Desired Virtual Wave Observatory (VWO) Data Search Capabilities

    Science.gov (United States)

    Benson, Robert F.; Fung, Shing F.

    2008-01-01

    Many plasma-wave phenomena, observed by space-borne radio sounders, cannot be properly explained in terms of wave propagation in a cold plasma consisting of mobile electrons and infinitely massive positive ions. These phenomena include signals known as plasma resonances. The principal resonances at the harmonics of the electron cyclotron frequency, the plasma frequency, and the upper-hybrid frequency are well explained by the warm-plasma propagation of sounder-generated electrostatic waves, Other resonances have been attributed to sounder-stimulated plasma instability and non-linear effects, eigenmodes of cylindrical electromagnetic plasma oscillations, and plasma memory processes. Data from the topside sounders of the International Satellites for Ionospheric Studies (ISIS) program played a major role in these interpretations. A data transformation and preservation effort at the Goddard Space Flight Center has produced digital ISIS topside ionograms and a metadata search program that has enabled some recent discoveries pertaining to the physics of these plasma resonances. For example, data records were obtained that enabled the long-standing question (several decades) of the origin of the plasma resonance at the fundamental electron cyclotron frequency to be explained [Muldrew, Radio Sci., 2006]. These data-search capabilities, and the science enabled by them, will be presented as a guide to desired data search capabilities to be included in the Virtual Wave Observatory (VWO).

  7. High frequency guided waves for hidden fatigue crack growth monitoring in multi-layer aerospace structures

    Science.gov (United States)

    Chan, Henry; Fromme, Paul

    2015-03-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi-layered components are connected, possibly leading to the development of fatigue cracks. High frequency guided waves propagating along the structure allow for the non-destructive testing of such components, e.g., aircraft wings. However, the sensitivity for the detection of small, potentially hidden, fatigue cracks has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminium plate-strips. Fatigue experiments were carried out. The sensitivity of the high frequency guided wave modes to monitor fatigue crack growth at a fastener hole during cyclic loading was investigated, using both standard pulse-echo equipment and laser interferometry. The sensitivity and repeatability of the measurements were ascertained, having the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance.

  8. Limited-view ultrasonic guided wave tomography using an adaptive regularization method

    Science.gov (United States)

    Rao, Jing; Ratassepp, Madis; Fan, Zheng

    2016-11-01

    Ultrasonic guided waves are useful to assess the integrity of a structure from a remote location. Recently, tomography techniques have been developed to quantitatively estimate the thickness map of plate-like structures based on the dispersion characteristics of guided waves. In many applications only limited locations are available to place transducers. The missing viewing angles lead to artifacts which can degrade the image quality. To address this problem, this paper applies the regularization method to synthesize the missing components. The regularization technique is performed by an adaptive threshold approach to the limited view reconstruction. The effectiveness of this method combined with the full waveform inversion method is demonstrated by using numerical simulations as well as experiments on an irregularly shaped defect and two flat-bottom defects. The results indicate that the additional components obtained from the regularization method can significantly reduce the artifacts, leading to better reconstruction accuracy.

  9. Axial guided wave technique for rapid inspection of the "Noodle" regions in a stiffened composite component

    Science.gov (United States)

    Manogharan, Prabhakaran; Rajagopal, Prabhu; Balasubramaniam, Krishnan

    2015-03-01

    Composite structures are used in a wide variety of applications. The use of stiffened composites is common in aerospace box-like components and provides the additional stiffness required. Examples of such stiffened structural geometries include airfoils, fuselage, wing box, tail section, etc. The inspection of the radius filler "Noodle" that fills the interface between skin and stiffener has been of great concern to the aerospace composites industry. This paper describes the 3D FEM models of the ultrasonic axially propagating guided wave modes. Additionally, the models were used for understanding their confinement in the Noodle region, their leakage to the remaining sections of the component and their interaction with defects of different types, sizes and their locations along Noodle region. The ultrasonic guided wave modes that propagate along the length of the Noodle were identified using the 3D finite element model. These simulations were validated using graphite-epoxy test coupons and components from aerospace industry.

  10. Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor.

    Science.gov (United States)

    Rabani, Amir

    2016-10-12

    The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications.

  11. Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor

    Directory of Open Access Journals (Sweden)

    Amir Rabani

    2016-10-01

    Full Text Available The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications.

  12. Guided Wave Sensing In a Carbon Steel Pipe Using a Laser Vibrometer System

    Science.gov (United States)

    Ruíz Toledo, Abelardo; Salazar Soler, Jordi; Chávez Domínguez, Juan Antonio; García Hernández, Miguel Jesús; Turó Peroy, Antoni

    2010-05-01

    Non-Destructive Evaluation (NDE) techniques have achieved a great development during the last decades as a valuable tool for material characterization, manufacturing control and structural integrity tests. Among these tools, the guided wave technology has been rapidly extended because it reduces inspection time and costs compared to the ordinary point by point testing in large structures, as well as because of the possibility of inspecting under insulation and coating conditions. This fast development has motivated the creation of several inspection and material characterization systems including different technologies which can be combined with this technique. Different measurements systems based on laser techniques have been presented in order to inspect pipes, plates and diverse structures. Many of them are experimental systems of high cost and complexity which combine the employment of a laser for generation of waves in the structure and an interferometer for detection. Some of them employ air-coupled ultrasound generation transducers, with high losses in air and which demand high energy for exciting waves in materials of high stiffness. The combined employment of a commercial vibrometer system for Lamb wave sensing in plates has been successfully shown in the literature. In this paper we present a measurement system based on the combined employment of a piezoelectric wedge transducer and a laser vibrometer to sense guided acoustic waves in carbon steel pipes. The measurement system here presented is mainly compounded of an angular wedge transducer, employed to generate the guided wave and a commercial laser vibrometer used in the detection process. The wedge transducer is excited by means of a signal function generator whose output signal has been amplified with a power signal amplifier. A high precision positioning system is employed to place the laser beam at different points through the pipe surface. The signal detected by the laser vibrometer system is

  13. Waves guided by density ducts in magnetoplasma in the nonresonant region of the whistler frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Es’kin, V. A.; Zaboronkova, T. M.; Kudrin, A. V., E-mail: kud@rf.unn.ru; Ostafiychuk, O. M. [Lobachevskii State University of Nizhni Novgorod (Russian Federation)

    2015-03-15

    Guidance of azimuthally symmetric waves by cylindrical density ducts in magnetoplasma in the nonresonant region of the whistler frequency range is investigated. It is demonstrated that eigenmodes existing at the studied frequencies in ducts with enhanced plasma density allow simplified description that makes analysis of the features of their guided propagation much easier. The results of calculation of the dispersion characteristics and field structure of the whistler modes supported by such ducts are presented.

  14. Computer-generated guided-wave holography: application to beam splitting.

    Science.gov (United States)

    Saarinen, J; Huttunen, J; Vasara, A; Turunen, J

    1992-02-15

    The use of guided-wave synthetic holograms in integrated optics is extended beyond the conventional Fresnel lens and Bragg grating technology. As an example, beam splitters based on Fourier-domain holograms are proposed as an alternative to the usual channel waveguide devices. We demonstrate fanout to six with +/-5% (+/-0.2-dB) uniformity error using a binary phase grating and fanout to eight with +/-20% (+/-0.8-dB) uniformity error using a multilevel grating.

  15. A fully guided-wave squeezing experiment for fiber quantum networks

    OpenAIRE

    Kaiser, Florian; Fedrici, Bruno; Zavatta, Alessandro; D'Auria, Virginia; Tanzilli, Sébastien

    2016-01-01

    International audience; Squeezed light is a fundamental resource for quantum communication. In view of its real-world applications, the realization of easy-to-operate experimental systems compatible with existing fiber networks is a crucial step. To comply with these requirements, we demonstrate the feasibility of a squeezing experiment at a telecom wavelength realized, for the first time, in an entirely guided-wave fashion. In our work, the state generation relies on waveguide non-linear opt...

  16. Reduction of Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers

    CERN Document Server

    Elser, D; Gloeckl, O; Korn, A; Leuchs, G; Lorenz, S; Marquardt, C; Marquardt, Ch.

    2005-01-01

    Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. This excess noise affects the performance of various experiments operating at the quantum noise limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic crystal fiber in a broad frequency range using cavity sound dynamics. We compare the noise spectrum to the one of a standard fiber and observe a roughly 10-fold noise reduction in the frequency range up to 200 MHz.

  17. Guided shear horizontal surface acoustic wave sensors for chemical and biochemical detection in liquids.

    Science.gov (United States)

    Josse, F; Bender, F; Cernose, R W

    2001-12-15

    The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO3 substrates are investigated for high-sensitivity chemical and biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high-sensitivity detectors. The device sensitivity to mass and viscoelastic loading is increased using a thin guiding layer on the device surface. Because of their relatively low shear wave velocity, various polymers including poly(methyl methacrylate) (PMMA) and cyanoethyl cellulose (cured or cross-linked) are investigated as the guiding layers to trap the acoustic energy near the sensing surface. The devices have been tested in biosensing and chemical sensing experiments. Suitable design principles for these applications are discussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquid environments, acoustic loss, and sensor signal distortion. In biosensing experiments, using near-optimal PMMA thickness of approximately 2 microm, mass sensitivity greater than 1500 Hz/(ng/mm2) is demonstrated, resulting in a minimum detection limit less than 20 pg/mm2. For chemical sensor experiments, it is found that optimal waveguide thickness must be modified to account for the chemically sensitive layer which also acts to guide the SH-SAW. A detection limit of 780 (3 x peak-to-peak noise) or 180 ppb (3 x rms noise) is estimated from the present measurements for some organic compounds in water.

  18. Defect detection of pipes using Lyapunov dimension of Duffing oscillator based on ultrasonic guided waves

    Science.gov (United States)

    Wu, Jing; Wang, Yu; Zhang, Weiwei; Nie, Zhenhua; Lin, Rong; Ma, Hongwei

    2017-01-01

    This study proposes a novel small defect detection approach for steel pipes using the Lyapunov dimension (D) of the Duffing chaotic system based on ultrasonic guided waves. In this paper, inspection model is constructed by inputting the measured guided wave signal into the Duffing equation as the external turbulent driving force term and then Dis calculated. The properties of the Duffing system's noise immunity are first demonstrated theoretically based on the Lyapunov exponents. By comparing Dof the Duffing inspection system between the conditions of the inputted pure noise and the guided wave signal, the amplitude of the periodic force (F), the important parameter of the Duffing inspection system, could be determined. The values of other parameters of the Duffing inspection system are subsequently determined according to the numerical investigation. Furthermore, a time-moving window function is constructed to scan along the measured signal to locate the defect. And the small defect echo signal polluted by the noise is illustrated to prove the availability of the proposed method. Both numerical and experimental results show that the proposed approach can be used to improve the sensitivity of small defect detection and locate the small defect in pipes.

  19. Transverse and Oblique Long Bone Fracture Evaluation by Low Order Ultrasonic Guided Waves: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Ying Li

    2017-01-01

    Full Text Available Ultrasonic guided waves have recently been used in fracture evaluation and fracture healing monitoring. An axial transmission technique has been used to quantify the impact of the gap breakage width and fracture angle on the amplitudes of low order guided wave modes S0 and A0 under a 100 kHz narrowband excitation. In our two dimensional finite-difference time-domain (2D-FDTD simulation, the long bones are modeled as three layers with a soft tissue overlay and marrow underlay. The simulations of the transversely and obliquely fractured long bones show that the amplitudes of both S0 and A0 decrease as the gap breakage widens. Fixing the crack width, the increase of the fracture angle relative to the cross section perpendicular to the long axis enhances the amplitude of A0, while the amplitude of S0 shows a nonmonotonic trend with the decrease of the fracture angle. The amplitude ratio between the S0 and A0 modes is used to quantitatively evaluate the fracture width and angles. The study suggests that the low order guided wave modes S0 and A0 have potentials for transverse and oblique bone fracture evaluation and fracture healing monitoring.

  20. Dynamics and guided waves in a smart Timoshenko beam with lateral contraction

    Science.gov (United States)

    Park, I.; Kim, S.; Lee, U.

    2013-07-01

    Surface-bonded wafer-type piezoelectric transducers (PZTs) have been widely used to excite or measure ultrasonic guided waves for the structural health monitoring of thin-walled structures. For successful prediction of the dynamics and ultrasonic guided waves, it is essential to use very reliable computational models for the PZT-bonded multi-layer smart structures. In this paper, the spectral element model is developed for two-layer smart beams which consist of a metallic base beam layer and a PZT layer. Axial-bending-shear-contraction coupled equations of motion and boundary conditions are derived by using Hamilton’s principle with Lagrange multipliers based on the Timoshenko beam theory and Mindlin-Herrmann rod theory. The high accuracy of this spectral element model is verified in due course and the effects of a lateral contraction on the dynamics and guided wave characteristics of the example smart beams are investigated by using this spectral element model. In addition, the constraint forces at the interface between the base beam and the PZT layer are also investigated via Lagrange multipliers.

  1. Design and performance of optimal detectors for guided wave structural health monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Dib, G.; Udpa, L.

    2016-01-01

    Ultrasonic guided wave measurements in a long term structural health monitoring system are affected by measurement noise, environmental conditions, transducer aging and malfunction. This results in measurement variability which affects detection performance, especially in complex structures where baseline data comparison is required. This paper derives the optimal detector structure, within the framework of detection theory, where a guided wave signal at the sensor is represented by a single feature value that can be used for comparison with a threshold. Three different types of detectors are derived depending on the underlying structure’s complexity: (i) Simple structures where defect reflections can be identified without the need for baseline data; (ii) Simple structures that require baseline data due to overlap of defect scatter with scatter from structural features; (iii) Complex structure with dense structural features that require baseline data. The detectors are derived by modeling the effects of variabilities and uncertainties as random processes. Analytical solutions for the performance of detectors in terms of the probability of detection and false alarm are derived. A finite element model is used to generate guided wave signals and the performance results of a Monte-Carlo simulation are compared with the theoretical performance. initial results demonstrate that the problems of signal complexity and environmental variability can in fact be exploited to improve detection performance.

  2. Implementing guided wave mode control by use of a phased transducer array.

    Science.gov (United States)

    Li, J; Rose, J L

    2001-05-01

    A multi-channel time-delay system has been built and applied to a transducer array for implementing guided wave mode control. The time-delay system has a capability of sending high energy controllable tone-burst signals from eight independent channels with arbitrary time delays from 0 to 30 microseconds with resolution of 0.025 microsecond. Software time delays are also provided for summing up received signals of each channel. Theoretical discussions indicate the impact of the time delay capability on the bandwidth and sensitivity improvement of a transducer array for guided wave generation. Determination of both physical and software time delay values is based on a knowledge of dispersion curves and element spacing. Based on reference signals, a non-knowledge-based automatic time-delay searching algorithm was introduced for guided wave mode selection. Experiments were conducted with a phased comb transducer array mounted on a carbon steel pipe. The experimental results show that signal to noise ratio has been greatly improved by use of the time-delay system. Some other benefits of the phased array, including unidirection generation and mode control flexibility, are discussed.

  3. Load-differential features for automated detection of fatigue cracks using guided waves

    Science.gov (United States)

    Chen, Xin; Lee, Sang Jun; Michaels, Jennifer E.; Michaels, Thomas E.

    2012-05-01

    Guided wave structural health monitoring (SHM) is being considered to assess the integrity of plate-like structures for many applications. Prior research has investigated how guided wave propagation is affected by applied loads, which induce anisotropic changes in both dimensions and phase velocity. In addition, it is well-known that applied tensile loads open fatigue cracks and thus enhance their detectability using ultrasonic methods. Here we describe load-differential methods in which signals recorded from different loads at the same damage state are compared without using previously obtained damage-free data. Changes in delay-and-sum images are considered as a function of differential loads and damage state. Load-differential features are extracted from these images that capture the effects of loading as fatigue cracks are opened. Damage detection thresholds are adaptively set based upon the load-differential behavior of the various features, which enables implementation of an automated fatigue crack detection process. The efficacy of the proposed approach is examined using data from a fatigue test performed on an aluminum plate specimen that is instrumented with a sparse array of surface-mounted ultrasonic guided wave transducers.

  4. Standard practice for guided wave testing of above ground steel pipework using piezoelectric effect transduction

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This practice provides a procedure for the use of guided wave testing (GWT), also previously known as long range ultrasonic testing (LRUT) or guided wave ultrasonic testing (GWUT). 1.2 GWT utilizes ultrasonic guided waves, sent in the axial direction of the pipe, to non-destructively test pipes for defects or other features by detecting changes in the cross-section and/or stiffness of the pipe. 1.3 GWT is a screening tool. The method does not provide a direct measurement of wall thickness or the exact dimensions of defects/defected area; an estimate of the defect severity however can be provided. 1.4 This practice is intended for use with tubular carbon steel or low-alloy steel products having Nominal Pipe size (NPS) 2 to 48 corresponding to 60.3 to 1219.2 mm (2.375 to 48 in.) outer diameter, and wall thickness between 3.81 and 25.4 mm (0.15 and 1 in.). 1.5 This practice covers GWT using piezoelectric transduction technology. 1.6 This practice only applies to GWT of basic pipe configuration. This inc...

  5. Investigation of guided wave propagation in pipes fully and partially embedded in concrete.

    Science.gov (United States)

    Leinov, Eli; Lowe, Michael J S; Cawley, Peter

    2016-12-01

    The application of long-range guided-wave testing to pipes embedded in concrete results in unpredictable test-ranges. The influence of the circumferential extent of the embedding-concrete around a steel pipe on the guided wave propagation is investigated. An analytical model is used to study the axisymmetric fully embedded pipe case, while explicit finite-element and semi-analytical finite-element simulations are utilised to investigate a partially embedded pipe. Model predictions and simulations are compared with full-scale guided-wave tests. The transmission-loss of the T(0,1)-mode in an 8 in. steel pipe fully embedded over an axial length of 0.4 m is found to be in the range of 32-36 dB while it reduces by a factor of 5 when only 50% of the circumference is embedded. The transmission-loss in a fully embedded pipe is mainly due to attenuation in the embedded section while in a partially embedded pipe it depend strongly on the extent of mode-conversion at entry to the embedded-section; low loss modes with energy concentrated in the region of the circumference not-covered with concrete have been identified. The results show that in a fully embedded pipe, inspection beyond a short distance will not be possible, whereas when the concrete is debonded over a fraction of the pipe circumference, inspection of substantially longer lengths may be possible.

  6. A Love Wave Reflective Delay Line with Polymer Guiding Layer for Wireless Sensor Application

    Directory of Open Access Journals (Sweden)

    Shitang He

    2008-12-01

    Full Text Available This paper presents an optimal design for a Love wave reflective delay line on 41o YX LiNbO3 with a polymer guiding layer for wireless sensor applications. A theoretical model was established to describe the Love wave propagation along the larger piezoelectric substrate with polymer waveguide, and the lossy mechanism from the viscoelastic waveguide was discussed, which results in the optimal guiding layer thickness. Coupling of modes (COM was used to determine the optimal design parameters of the reflective delay line structured by single phase unidirectional transducers (SPUDTs and shorted grating reflectors. Using the network analyzer, the fabricated Love wave reflective delay line was characterized, high signal noise ratio (S/N, sharp reflection peaks, and few spurious noise between the peaks were found, and the measured result agrees well with the simulated one. Also, the optimal guiding layer thickness of 1.5~1.8μm was extracted experimentally, and it is consistent with the theoretical analysis.

  7. Ultrasonic Guided Wave Method For Crack Detection In Buried Plastic Pipe

    Directory of Open Access Journals (Sweden)

    Wan Hamat Wan Sofian

    2016-01-01

    Full Text Available Plastic pipe are widely used in many fields for the fluid or gaseous product conveyance but basic components of a plastic material made it very sensitive to damage, which requires techniques for detecting damage reliable and efficient. Ultrasonic guided wave is a sensitive method based on propagation of low-frequency excitation in solid structures for damage detection. Ultrasonic guided wave method are performed to investigate the effect of crack to the frequency signal using Fast Fourier Transform (FFT analysis. This paper researched to determine performance of ultrasonic guided wave method in order to detect crack in buried pipeline. It was found that for an uncrack pipe, FFT analysis shows one peak which is the operating frequency by the piezoelectric actuator itself while the FFT analysis for single cracked pipe shows two peak which is the operating frequency by the piezoelectric actuator itself and the resultant frequency from the crack. For multi cracked pipe, the frequency signal shows more than two peak depend the number of crack. The results presented here may facilitate improvements in the accuracy and precision of pipeline crack detection.

  8. Observation of atomic speckle and Hanbury Brown-Twiss correlations in guided matter waves.

    Science.gov (United States)

    Dall, R G; Hodgman, S S; Manning, A G; Johnsson, M T; Baldwin, K G H; Truscott, A G

    2011-01-01

    Speckle patterns produced by multiple independent light sources are a manifestation of the coherence of the light field. Second-order correlations exhibited in phenomena such as photon bunching, termed the Hanbury Brown-Twiss effect, are a measure of quantum coherence. Here we observe for the first time atomic speckle produced by atoms transmitted through an optical waveguide, and link this to second-order correlations of the atomic arrival times. We show that multimode matter-wave guiding, which is directly analogous to multimode light guiding in optical fibres, produces a speckled transverse intensity pattern and atom bunching, whereas single-mode guiding of atoms that are output-coupled from a Bose-Einstein condensate yields a smooth intensity profile and a second-order correlation value of unity. Both first- and second-order coherence are important for applications requiring a fully coherent atomic source, such as squeezed-atom interferometry.

  9. Detection of CFRP Composite Manufacturing Defects Using a Guided Wave Approach

    Science.gov (United States)

    Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.; Yuan, Fuh-Gwo

    2015-01-01

    NASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered

  10. Flavonoids and the CNS

    DEFF Research Database (Denmark)

    Jäger, Anna Katharina; Saaby, Lasse

    2011-01-01

    , sulphatation or glucuronidation. Both the aglycones and the conjugates can pass the blood-brain barrier. In the CNS several flavones bind to the benzodiazepine site on the GABA(A)-receptor resulting in sedation, anxiolytic or anti-convulsive effects. Flavonoids of several classes are inhibitors of monoamine...

  11. On the processing of highly nonlinear solitary waves and guided ultrasonic waves for structural health monitoring and nondestructive evaluation

    Science.gov (United States)

    Bagheri, Abdollah

    The in-situ measurement of thermal stress in civil and mechanical structures may prevent structural anomalies such as unexpected buckling. In the first half of the dissertation, we present a study where highly nonlinear solitary waves (HNSWs) were utilized to measure axial stress in slender beams. HNSWs are compact non-dispersive waves that can form and travel in nonlinear systems such as one-dimensional chains of particles. The effect of the axial stress acting in a beam on the propagation of HNSWs was studied. We found that certain features of the solitary waves enable the measurement of the stress. In general, most guided ultrasonic waves (GUWs)-based health monitoring approaches for structural waveguides are based on the comparison of testing data to baseline data. In the second half of the dissertation, we present a study where some baseline-free signal processing algorithms were presented and applied to numerical and experimental data for the structural health monitoring (SHM) of underwater or dry structures. The algorithms are based on one or more of the following: continuous wavelet transform, empirical mode decomposition, Hilbert transform, competitive optimization algorithm, probabilistic methods. Moreover, experimental data were also processed to extract some features from the time, frequency, and joint time-frequency domains. These features were then fed to a supervised learning algorithm based on artificial neural networks to classify the types of defect. The methods were validated using the numerical model of a plate and a pipe, and the experimental study of a plate in water. In experiment, the propagation of ultrasonic waves was induced by means of laser pulses or transducer and detected with an array of immersion transducers. The results demonstrated that the algorithms are effective, robust against noise, and able to localize and classify the damage.

  12. Efficient methods to model the scattering of ultrasonic guided waves in 3D

    Science.gov (United States)

    Moreau, L.; Velichko, A.; Wilcox, P. D.

    2010-03-01

    The propagation of ultrasonic guided waves and their interaction with a defect is of interest to the nondestructive testing community. There is no general solution to the scattering problem and it is still an ongoing research topic. Due to the complexity of guided wave scattering problems, most existing models are related to the 2D case. However, thanks to the increase in computer calculation power, specific 3D problems can also be studied, with the help of numerical or semi-analytical methods. This paper describes two efficient methods aimed at modeling 3D scattering problems. The first method is the use of the Huygens' principle to reduce the size of finite element models. This principle allows the area of interest to be restricted to the very near field of the defect, for both the generation of the incident field and the modal decomposition of the scattered field. The second method consists of separating the 3D problem into two 2D problems for which the solutions are calculated and used to approximate the 3D solution. This can be used at low frequency-thickness products, where Lamb waves have a similar behavior to bulk waves. These two methods are presented briefly and compared on simple scattering cases.

  13. Local numerical modelling of ultrasonic guided waves in linear and nonlinear media

    Science.gov (United States)

    Packo, Pawel; Radecki, Rafal; Kijanka, Piotr; Staszewski, Wieslaw J.; Uhl, Tadeusz; Leamy, Michael J.

    2017-04-01

    Nonlinear ultrasonic techniques provide improved damage sensitivity compared to linear approaches. The combination of attractive properties of guided waves, such as Lamb waves, with unique features of higher harmonic generation provides great potential for characterization of incipient damage, particularly in plate-like structures. Nonlinear ultrasonic structural health monitoring techniques use interrogation signals at frequencies other than the excitation frequency to detect changes in structural integrity. Signal processing techniques used in non-destructive evaluation are frequently supported by modeling and numerical simulations in order to facilitate problem solution. This paper discusses known and newly-developed local computational strategies for simulating elastic waves, and attempts characterization of their numerical properties in the context of linear and nonlinear media. A hybrid numerical approach combining advantages of the Local Interaction Simulation Approach (LISA) and Cellular Automata for Elastodynamics (CAFE) is proposed for unique treatment of arbitrary strain-stress relations. The iteration equations of the method are derived directly from physical principles employing stress and displacement continuity, leading to an accurate description of the propagation in arbitrarily complex media. Numerical analysis of guided wave propagation, based on the newly developed hybrid approach, is presented and discussed in the paper for linear and nonlinear media. Comparisons to Finite Elements (FE) are also discussed.

  14. Fidelity of a Finite Element Model for Longitudinal Wave Propagation in Thick Cylindrical Wave Guides

    Energy Technology Data Exchange (ETDEWEB)

    Puckett, Anthony D. [Colorado State Univ., Fort Collins, CO (United States)

    2000-09-01

    The ability to model wave propagation in circular cylindrical bars of finite length numerically or analytically has many applications. In this thesis the capability of an explicit finite element method to model longitudinal waves in cylindrical rods with circular cross-sections is explored. Dispersion curves for the first four modes are compared to the analytical solution to determine the accuracy of various element sizes and time steps. Values for the time step and element size are determined that retain accuracy while minimizing computational time. The modeling parameters are validated by calculating a signal propagated with a broadband input force. Limitations on the applicability are considered along with modeling parameters that should be applicable to more general geometries.

  15. On guided circumferential waves in soft electroactive tubes under radially inhomogeneous biasing fields

    Science.gov (United States)

    Wu, Bin; Su, Yipin; Chen, Weiqiu; Zhang, Chuanzeng

    2017-02-01

    Soft electroactive (EA) tube actuators and many other cylindrical devices have been proposed recently in literature, which show great advantages over those made from conventional hard solid materials. However, their practical applications may be limited because these soft EA devices are prone to various failure modes. In this paper, we present an analysis of the guided circumferential elastic waves in soft EA tube actuators, which has potential applications in the in-situ nondestructive evaluation (NDE) or online structural health monitoring (SHM) to detect structural defects or fatigue cracks in soft EA tube actuators and in the self-sensing of soft EA tube actuators based on the concept of guided circumferential elastic waves. Both circumferential SH and Lamb-type waves in an incompressible soft EA cylindrical tube under inhomogeneous biasing fields are considered. The biasing fields, induced by the application of an electric voltage difference to the electrodes on the inner and outer cylindrical surfaces of the EA tube in addition to an axial pre-stretch, are inhomogeneous in the radial direction. Dorfmann and Ogden's theory of nonlinear electroelasticity and the associated linear theory for small incremental motion constitute the basis of our analysis. By means of the state-space formalism for the incremental wave motion along with the approximate laminate technique, dispersion relations are derived in a particularly efficient way. For a neo-Hookean ideal dielectric model, the proposed approach is first validated numerically. Numerical examples are then given to show that the guided circumferential wave propagation characteristics are significantly affected by the inhomogeneous biasing fields and the geometrical parameters. Some particular phenomena such as the frequency veering and the nonlinear dependence of the phase velocity on the radial electric voltage are discussed. Our numerical findings demonstrate that it is feasible to use guided circumferential

  16. Three-dimensional coupled-wave theory for the guided mode resonance in photonic crystal slabs: TM-like polarization.

    Science.gov (United States)

    Yang, Yi; Peng, Chao; Liang, Yong; Li, Zhengbin; Noda, Susumu

    2014-08-01

    A general coupled-wave theory is presented for the guided resonance in photonic crystal (PhC) slabs with TM-like polarization. Numerical results based on our model are presented with finite-difference time-domain validations. The proposed analysis facilitates comprehensive understanding of the physics of guided resonance in PhC slabs and provides guidance for its applications.

  17. Imaging ultrasonic dispersive guided wave energy in long bones using linear radon transform.

    Science.gov (United States)

    Tran, Tho N H T; Nguyen, Kim-Cuong T; Sacchi, Mauricio D; Le, Lawrence H

    2014-11-01

    Multichannel analysis of dispersive ultrasonic energy requires a reliable mapping of the data from the time-distance (t-x) domain to the frequency-wavenumber (f-k) or frequency-phase velocity (f-c) domain. The mapping is usually performed with the classic 2-D Fourier transform (FT) with a subsequent substitution and interpolation via c = 2πf/k. The extracted dispersion trajectories of the guided modes lack the resolution in the transformed plane to discriminate wave modes. The resolving power associated with the FT is closely linked to the aperture of the recorded data. Here, we present a linear Radon transform (RT) to image the dispersive energies of the recorded ultrasound wave fields. The RT is posed as an inverse problem, which allows implementation of the regularization strategy to enhance the focusing power. We choose a Cauchy regularization for the high-resolution RT. Three forms of Radon transform: adjoint, damped least-squares, and high-resolution are described, and are compared with respect to robustness using simulated and cervine bone data. The RT also depends on the data aperture, but not as severely as does the FT. With the RT, the resolution of the dispersion panel could be improved up to around 300% over that of the FT. Among the Radon solutions, the high-resolution RT delineated the guided wave energy with much better imaging resolution (at least 110%) than the other two forms. The Radon operator can also accommodate unevenly spaced records. The results of the study suggest that the high-resolution RT is a valuable imaging tool to extract dispersive guided wave energies under limited aperture.

  18. Temperature dependent E and G measurement of materials using ultrasonic guided waves

    Science.gov (United States)

    Periyannan, Suresh; Balasubramaniam, Krishnan

    2014-02-01

    A novel technique for measuring the moduli of elastic isotropic material as a function of temperature, using ultrasonic guided wave modes is presented here. These techniques can be used for measure the Young's modulus (E) and Shear Modulus (G) of material. Here, the L (0, 1) wave mode is used for measuring E and T(0,1) mode for G. The scope of measurement is made from room temperature to maximum utility temperature of material. In this work, the material is required in the form of a waveguide with an ultrasonic guided wave generator at one end and an embodiment (such as a notch or a bend) at the other end for obtaining reflected signals. The transducer is kept at room temperature while the end (along with the embodiment) is kept inside a heating device such as a temperature controlled furnace. The time of flight difference (δTOF), as a function of temperature, between the guided wave reflections from the embodiment and the end of the waveguide, is used to measure the material properties. The technique is based on the fact that, in addition to elongation of the waveguide, the sound speed in the materials also varies with temperature and is measurable from changes in the time of flight of signals. In addition, the ambient temperature of the waveguide end is measured using a calibrated thermocouple. Several materials were tested and the data was compared with values obtained from literature. For instance, Inconel -690 waveguide with embodiment of a 'L' bend was evaluated from 45°C to 1100°C at a frequency of 0.5 MHz L(0, 1) and T(0, 1) modes. The comparison between the literature values and the measured values were found to be in agreement with a regression correlation factor R=0.999 or better, for both E and G measurements. Advantages of the method over conventional methods of such measurements will also be discussed.

  19. Requirements for an Integrated UAS CNS Architecture

    Science.gov (United States)

    Templin, Fred; Jain, Raj; Sheffield, Greg; Taboso, Pedro; Ponchak, Denise

    2017-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is investigating revolutionary and advanced universal, reliable, always available, cyber secure and affordable Communication, Navigation, Surveillance (CNS) options for all altitudes of UAS operations. In Spring 2015, NASA issued a Call for Proposals under NASA Research Announcements (NRA) NNH15ZEA001N, Amendment 7 Subtopic 2.4. Boeing was selected to conduct a study with the objective to determine the most promising candidate technologies for Unmanned Air Systems (UAS) air-to-air and air-to-ground data exchange and analyze their suitability in a post-NextGen NAS environment. The overall objectives are to develop UAS CNS requirements and then develop architectures that satisfy the requirements for UAS in both controlled and uncontrolled air space. This contract is funded under NASAs Aeronautics Research Mission Directorates (ARMD) Aviation Operations and Safety Program (AOSP) Safe Autonomous Systems Operations (SASO) project and proposes technologies for the Unmanned Air Systems Traffic Management (UTM) service. Communications, Navigation and Surveillance (CNS) requirements must be developed in order to establish a CNS architecture supporting Unmanned Air Systems integration in the National Air Space (UAS in the NAS). These requirements must address cybersecurity, future communications, satellite-based navigation APNT, and scalable surveillance and situational awareness. CNS integration, consolidation and miniaturization requirements are also important to support the explosive growth in small UAS deployment. Air Traffic Management (ATM) must also be accommodated to support critical Command and Control (C2) for Air Traffic Controllers (ATC). This document therefore presents UAS CNS requirements that will guide the architecture.

  20. Visualization of thermally induced delamination by means of guided waves processing

    Science.gov (United States)

    Radzienski, Maciej; Kudela, Pawel; Ostachowicz, Wieslaw

    2013-04-01

    The aim of this paper is to present a method for visualization thermally induced delamination in composite material based on guided wave propagation phenomenon. Tested specimen was submitted to short time period high temperature source, which generated thermal degradation. In particular, delamination in material occurred. This procedure simulates some real case scenarios damage like one cased by atmospheric discharge striking wind turbine blade. Proposed method utilizes processing of full wavefield data acquired by the Scanning Doppler Laser Vibrometer. Registered wavefield images are transformed to wavenumber domain where the wave propagation pattern is removed. In this way after transformation signal back to space domain it contains only information about changes in wave propagation and may be used for damage visualization. However, attenuation of waves cause that visualized anomalies has lower amplitudes with increased distance from the actuator. The proposed enhancement of signal processing algorithm enables quantification of the size of the damage. The enhancement is a technique for compensation of the wave attenuation so that the effects of structural damages have the same influence regardless of the location.

  1. Sparse and Dispersion-Based Matching Pursuit for Minimizing the Dispersion Effect Occurring when Using Guided Wave for Pipe Inspection

    Directory of Open Access Journals (Sweden)

    Javad Rostami

    2017-06-01

    Full Text Available Ultrasonic guided wave is an effective tool for structural health monitoring of structures for detecting defects. In practice, guided wave signals are dispersive and contain multiple modes and noise. In the presence of overlapped wave-packets/modes and noise together with dispersion, extracting meaningful information from these signals is a challenging task. Handling such challenge requires an advanced signal processing tool. The aim of this study is to develop an effective and robust signal processing tool to deal with the complexity of guided wave signals for non-destructive testing (NDT purpose. To achieve this goal, Sparse Representation with Dispersion Based Matching Pursuit (SDMP is proposed. Addressing the three abovementioned facts that complicate signal interpretation, SDMP separates overlapped modes and demonstrates good performance against noise with maximum sparsity. With the dispersion taken into account, an overc-omplete and redundant dictionary of basic atoms based on a narrowband excitation signal is designed. As Finite Element Method (FEM was used to predict the form of wave packets propagating along structures, these atoms have the maximum resemblance with real guided wave signals. SDMP operates in two stages. In the first stage, similar to Matching Pursuit (MP, the approximation improves by adding, a single atom to the solution set at each iteration. However, atom selection criterion of SDMP utilizes the time localization of guided wave reflections that makes a portion of overlapped wave-packets to be composed mainly of a single echo. In the second stage of the algorithm, the selected atoms that have frequency inconsistency with the excitation signal are discarded. This increases the sparsity of the final representation. Meanwhile, leading to accurate approximation, as discarded atoms are not representing guided wave reflections, it simplifies extracting physical meanings for defect detection purpose. To verify the

  2. Sparse and Dispersion-Based Matching Pursuit for Minimizing the Dispersion Effect Occurring when Using Guided Wave for Pipe Inspection.

    Science.gov (United States)

    Rostami, Javad; Tse, Peter W T; Fang, Zhou

    2017-06-06

    Ultrasonic guided wave is an effective tool for structural health monitoring of structures for detecting defects. In practice, guided wave signals are dispersive and contain multiple modes and noise. In the presence of overlapped wave-packets/modes and noise together with dispersion, extracting meaningful information from these signals is a challenging task. Handling such challenge requires an advanced signal processing tool. The aim of this study is to develop an effective and robust signal processing tool to deal with the complexity of guided wave signals for non-destructive testing (NDT) purpose. To achieve this goal, Sparse Representation with Dispersion Based Matching Pursuit (SDMP) is proposed. Addressing the three abovementioned facts that complicate signal interpretation, SDMP separates overlapped modes and demonstrates good performance against noise with maximum sparsity. With the dispersion taken into account, an overc-omplete and redundant dictionary of basic atoms based on a narrowband excitation signal is designed. As Finite Element Method (FEM) was used to predict the form of wave packets propagating along structures, these atoms have the maximum resemblance with real guided wave signals. SDMP operates in two stages. In the first stage, similar to Matching Pursuit (MP), the approximation improves by adding, a single atom to the solution set at each iteration. However, atom selection criterion of SDMP utilizes the time localization of guided wave reflections that makes a portion of overlapped wave-packets to be composed mainly of a single echo. In the second stage of the algorithm, the selected atoms that have frequency inconsistency with the excitation signal are discarded. This increases the sparsity of the final representation. Meanwhile, leading to accurate approximation, as discarded atoms are not representing guided wave reflections, it simplifies extracting physical meanings for defect detection purpose. To verify the effectiveness of SDMP for

  3. CNS Tumors in Neurofibromatosis.

    Science.gov (United States)

    Campian, Jian; Gutmann, David H

    2017-07-20

    Neurofibromatosis (NF) encompasses a group of distinct genetic disorders in which affected children and adults are prone to the development of benign and malignant tumors of the nervous system. The purpose of this review is to discuss the spectrum of CNS tumors arising in individuals with NF type 1 (NF1) and NF type 2 (NF2), their pathogenic etiologies, and the rational treatment options for people with these neoplasms. This article is a review of preclinical and clinical data focused on the treatment of the most common CNS tumors encountered in children and adults with NF1 and NF2. Although children with NF1 are at risk for developing low-grade gliomas of the optic pathway and brainstem, individuals with NF2 typically manifest low-grade tumors affecting the cranial nerves (vestibular schwannomas), meninges (meningiomas), and spinal cord (ependymomas). With the identification of the NF1 and NF2 genes, molecularly targeted therapies are beginning to emerge, as a result of a deeper understanding of the mechanisms underlying NF1 and NF2 protein function. As we enter into an era of precision oncology, a more comprehensive awareness of the factors that increase the risk of developing CNS cancers in affected individuals, coupled with a greater appreciation of the cellular and molecular determinants that maintain tumor growth, will undoubtedly yield more effective therapies for these cancer predisposition syndromes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Huthwaite, P.; Ribichini, R.; Lowe, M. J. S.; Cawley, P. [Department of Mechanical Engineering, Imperial College, London, SW7 2AZ (United Kingdom)

    2014-02-18

    Guided wave tomography offers a method to accurately quantify wall thickness losses in pipes and vessels caused by corrosion. This is achieved using ultrasonic waves transmitted over distances of approximately 1–2m, which are measured by an array of transducers and then used to reconstruct a map of wall thickness throughout the inspected region. To achieve accurate estimations of remnant wall thickness, it is vital that a suitable Lamb mode is chosen. This paper presents a detailed evaluation of the fundamental modes, S{sub 0} and A{sub 0}, which are of primary interest in guided wave tomography thickness estimates since the higher order modes do not exist at all thicknesses, to compare their performance using both numerical and experimental data while considering a range of challenging phenomena. The sensitivity of A{sub 0} to thickness variations was shown to be superior to S{sub 0}, however, the attenuation from A{sub 0} when a liquid loading was present was much higher than S{sub 0}. A{sub 0} was less sensitive to the presence of coatings on the surface of than S{sub 0}.

  5. Parametric Study of Defect Detection in Pipes with Bend Using Guided Ultrasonic Waves

    Directory of Open Access Journals (Sweden)

    Jack Tan Jin

    2016-01-01

    Full Text Available The propagation behaviour of guided ultrasonic waves in a steel pipe with welded bend is studied by finite element simulation. The effectiveness of the longitudinal L(0,2 and torsional T(0,1 guided waves in detecting circumferential cut near the weld is investigated. In order to identify the presence of the defect, the reflection strength due to the cut is studied. The geometry of the weld is constructed based on common V-bevel butt joints and the anisotropy of the 316L stainless steel weld is included to correctly predict the scattering of ultrasonic waves. The finite element model is built to allow high accuracy. Detection of small circumferential cut (up to 60° circumferential extent can be achieved with longitudinal L(0,2 mode. Detection of moderate to large circumferential cut can be achieved by torsional T(0,1 or longitudinal L(0,2 modes, with T(0,1 mode preferred due to its less mode conversion to higher order modes.

  6. Detection of disbonds in a honeycomb composite structure using guided waves

    Science.gov (United States)

    Baid, Harsh; Banerjee, Sauvik; Joshi, Shiv; Mal, Siddhartha

    2008-03-01

    Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure and if undetected, may cause sudden and catastrophic failure of the entire structure. An example of such a defects critical structural component is the "honeycomb composite" in which thin composite skins are bonded with adhesives to the two faces of extremely lightweight and relatively thick metallic honeycombs. These components are often used in aircraft and aerospace structures due to their high strength to weight ratio. Unfortunately, the bond between the honeycomb and the skin may degrade with age and service loads leading to separation of the load-bearing skin from the honeycomb (called "disbonds") and compromising the safety of the structure. This paper is concerned with the noninvasive detection of disbonds using ultrasonic guided waves. Laboratory experiments are carried out on a composite honeycomb specimen containing localized disbonded regions. Ultrasonic waves are launched into the specimen using a broadband PZT transducer and are detected by a distributed array of identical transducers located on the surface of the specimen. The guided wave components of the signals are shown to be very strongly influenced by the presence of a disbond. The experimentally observed results are being used to develop an autonomous scheme to locate the disbonds and to estimate their size.

  7. Hybrid local FEM/global LISA modeling of damped guided wave propagation in complex composite structures

    Science.gov (United States)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2016-09-01

    This paper presents a new hybrid modeling technique for the efficient simulation of guided wave generation, propagation, and interaction with damage in complex composite structures. A local finite element model is deployed to capture the piezoelectric effects and actuation dynamics of the transmitter, while the global domain wave propagation and interaction with structural complexity (structure features and damage) are solved utilizing a local interaction simulation approach (LISA). This hybrid approach allows the accurate modeling of the local dynamics of the transducers and keeping the LISA formulation in an explicit format, which facilitates its readiness for parallel computing. The global LISA framework was extended through the 3D Kelvin-Voigt viscoelasticity theory to include anisotropic damping effects for composite structures, as an improvement over the existing LISA formulation. The global LISA framework was implemented using the compute unified device architecture running on graphic processing units. A commercial preprocessor is integrated seamlessly with the computational framework for grid generation and material property allocation to handle complex structures. The excitability and damping effects are successfully captured by this hybrid model, with experimental validation using the scanning laser doppler vibrometry. To demonstrate the capability of our hybrid approach for complex structures, guided wave propagation and interaction with a delamination in a composite panel with stiffeners is presented.

  8. Hybrid local FEM/global LISA modeling of guided wave propagation and interaction with damage in composite structures

    Science.gov (United States)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2015-03-01

    This paper presents a hybrid modeling technique for the efficient simulation of guided wave propagation and interaction with damage in composite structures. This hybrid approach uses a local finite element model (FEM) to compute the excitability of guided waves generated by piezoelectric transducers, while the global domain wave propagation, wave-damage interaction, and boundary reflections are modeled with the local interaction simulation approach (LISA). A small-size multi-physics FEM with non-reflective boundaries (NRB) was built to obtain the excitability information of guided waves generated by the transmitter. Frequency-domain harmonic analysis was carried out to obtain the solution for all the frequencies of interest. Fourier and inverse Fourier transform and frequency domain convolution techniques are used to obtain the time domain 3-D displacement field underneath the transmitter under an arbitrary excitation. This 3-D displacement field is then fed into the highly efficient time domain LISA simulation module to compute guided wave propagation, interaction with damage, and reflections at structural boundaries. The damping effect of composite materials was considered in the modified LISA formulation. The grids for complex structures were generated using commercial FEM preprocessors and converted to LISA connectivity format. Parallelization of the global LISA solution was achieved through Compute Unified Design Architecture (CUDA) running on Graphical Processing Unit (GPU). The multi-physics local FEM can reliably capture the detailed dimensions and local dynamics of the piezoelectric transducers. The global domain LISA can accurately solve the 3-D elastodynamic wave equations in a highly efficient manner. By combining the local FEM with global LISA, the efficient and accurate simulation of guided wave structural health monitoring procedure is achieved. Two numerical case studies are presented: (1) wave propagation in a unidirectional CFRP composite plate

  9. Depolarized guided acoustic wave Brillouin scattering in hollow-core photonic crystal fibers

    CERN Document Server

    Zhong, Wenjia Elser née; Elser, Dominique; Heim, Bettina; Marquardt, Christoph; Leuchs, Gerd

    2015-01-01

    By performing quantum-noise-limited optical heterodyne detection, we observe polarization noise in light after propagation through a hollow-core photonic crystal fiber (PCF). We compare the noise spectrum to the one of a standard fiber and find an increase of noise even though the light is mainly transmitted in air in a hollow-core PCF. Combined with our simulation of the acoustic vibrational modes in the hollow-core PCF, we are offering an explanation for the polarization noise with a variation of guided acoustic wave Brillouin scattering (GAWBS). Here, instead of modulating the strain in the fiber core as in a solid core fiber, the acoustic vibrations in hollow-core PCF influence the effective refractive index by modulating the geometry of the photonic crystal structure. This induces polarization noise in the light guided by the photonic crystal structure.

  10. Deep rock damage in the San Andreas Fault revealed by P- and S-type fault-zone-guided waves

    Science.gov (United States)

    Ellsworth, William L.; Malin, Peter E.

    2011-01-01

    Damage to fault-zone rocks during fault slip results in the formation of a channel of low seismic-wave velocities. Within such channels guided seismic waves, denoted by Fg, can propagate. Here we show with core samples, well logs and Fg-waves that such a channel is crossed by the SAFOD (San Andreas Fault Observatory at Depth) borehole at a depth of 2.7 km near Parkfield, California, USA. This laterally extensive channel extends downwards to at least half way through the seismogenic crust, more than about 7 km. The channel supports not only the previously recognized Love-type- (FL) and Rayleigh-type- (FR) guided waves, but also a new fault-guided wave, which we name FF. As recorded 2.7 km underground, FF is normally dispersed, ends in an Airy phase, and arrives between the P- and S-waves. Modelling shows that FF travels as a leaky mode within the core of the fault zone. Combined with the drill core samples, well logs and the two other types of guided waves, FF at SAFOD reveals a zone of profound, deep, rock damage. Originating from damage accumulated over the recent history of fault movement, we suggest it is maintained either by fracturing near the slip surface of earthquakes, such as the 1857 Fort Tejon M 7.9, or is an unexplained part of the fault-creep process known to be active at this site.

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

    Science.gov (United States)

    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.

  12. Guided acoustic and optical waves in silicon-on-insulator for Brillouin scattering and optomechanics

    Science.gov (United States)

    Sarabalis, Christopher J.; Hill, Jeff T.; Safavi-Naeini, Amir H.

    2016-10-01

    We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W-1m-1 for backward and forward Brillouin scattering, respectively.

  13. SAFE-3D analysis of a piezoelectric transducer to excite guided waves in a rail web

    CSIR Research Space (South Africa)

    Ramatlo, DA

    2016-10-01

    Full Text Available stream_source_info Ramatlo_2016_ABSTRACT.pdf.txt stream_content_type text/plain stream_size 2038 Content-Encoding ISO-8859-1 stream_name Ramatlo_2016_ABSTRACT.pdf.txt Content-Type text/plain; charset=ISO-8859-1 AIP... Conference Proceedings, 1706, 020005, 26-31 July 2015, Minneapolis, Minnesota SAFE-3D Analysis of a Piezoelectric Transducer to Excite Guided Waves in a Rail Web Dineo A. Ramatlo1, 2, Craig S. Long2 , Philip W. Loveday2 and Daniel N. Wilke1 1...

  14. Collapse of the wave field in a one-dimensional system of weakly coupled light guides

    Science.gov (United States)

    Balakin, A. A.; Litvak, A. G.; Mironov, V. A.; Skobelev, S. A.

    2016-12-01

    The analytical and numerical study of the radiation self-action in a system of coupled light guides is fulfilled on the basis of the discrete nonlinear Schrödinger equation (DNSE). We develop a variational method for qualitative study of DNSE and classify self-action modes. We show that the diffraction of narrow (in grating scale) wave beams weakens in discrete media and, consequently, the "collapse" of the one-dimensional wave field with power exceeding the critical value occurs. This results in the ability to self-channel radiation in the central fiber. Qualitative analytical results were confirmed by numerical simulation of DNSE, which also shows the stability of the collapse mode.

  15. On the existence of guided acoustic waves at rectangular anisotropic edges.

    Science.gov (United States)

    Pupyrev, Pavel D; Lomonosov, Alexey M; Nikodijevic, Aleksandar; Mayer, Andreas P

    2016-09-01

    The existence of acoustic waves with displacements localized at the tip of an isotropic elastic wedge was rigorously proven by Kamotskii, Zavorokhin and Nazarov. This proof, which is based on a variational approach, is extended to rectangular anisotropic wedges. For two high-symmetry configurations of rectangular edges in elastic media with tetragonal symmetry, a criterion is derived that allows identifying the boundary between the regions of existence for wedge modes of even and odd symmetry in regions of parameter space, where even- and odd-symmetry modes do not exist simultaneously. Furthermore, rectangular edges with non-equivalent surfaces are analyzed, and it is shown that at rectangular edges of cubic elastic media with one (110) surface and one (001) surface, a tip-localized guided wave always exists, apart from special cases that are characterized.

  16. Lithium niobate guided-wave beam former for steering phased-array antennas.

    Science.gov (United States)

    Armenise, M N; Passaro, V M; Noviello, G

    1994-09-10

    We present the theoretical investigation, design, and simulation of a novel guided-wave optical processor for L-band-transmission beam forming in a linear array of phased active antennas. The proposed configuration includes two contradirectional surface acoustic-wave transducers, and it is based on a Y-cut, X-propagating Ti:LiNbO(3) planar waveguide supporting the lowest-order modes of both polarizations (TE(0) and TM(0)) at the free-space wavelength λ = 0.85 µm. A detailed comparison between the processor we propose and other optical and electronic architectures reported in the literature is carried out, exhibiting a number of significant advantages in terms of weight, total chip size, and power consumption, when the number of antenna elements is greater than 50.

  17. Interaction of Guided Lamb Waves with Delaminations and Discontinuities in Composite Plate-Like Structures

    Science.gov (United States)

    Balasubramaniam, Krishnan; Ramadas, C.; Padiyar, Janardhan; Krishnamurthy, C. V.

    2011-06-01

    Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in-service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub-laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T-joint. During the interaction of Ao mode with structural discontinuity in a T-joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T-joint have been worked out using D-scan and B-scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non- Contact Ultrasound (NCU) technique.

  18. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection.

    Science.gov (United States)

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-04-22

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH₀) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C.

  19. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection

    Directory of Open Access Journals (Sweden)

    Maria Kogia

    2016-04-01

    Full Text Available Guided Wave Testing (GWT using novel Electromagnetic Acoustic Transducers (EMATs is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH0 waves for GWT with optimal high temperature properties (up to 500 °C has been developed. Thermal and Computational Fluid Dynamic (CFD simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C.

  20. Guided Waves in Asymmetric Hyperbolic Slab Waveguides. The TM Mode Case

    CERN Document Server

    Lyashko, Ekaterina I

    2016-01-01

    Nonlinear guided wave modes in an asymmetric slab waveguide formed by an isotropic dielectric layer placed on a linear or nonlinear substrate and covered by a hyperbolic material are investigated. Optical axis is normal to the slab plane. The dispersion relations for TM waves are found. It is shown that there are additional cut-off frequencies for each TM mode. The effects of the nonlinearity on the dispersion relations are investigated and discussed. There are the modes, which are corresponded with situation where the peak of electric field is localized in the nonlinear substrate. These modes are absent in the linear waveguide. To excite these modes the power must exceed certain threshold value.

  1. Decoupling of Pacific subduction zone guided waves beneath central Japan: Evidence for thin slab

    Science.gov (United States)

    Padhy, Simanchal; Furumura, Takashi; Maeda, Takuto

    2014-11-01

    The fine-scale seismic structure of the northeast Japan subduction zone is studied based on waveform analyses of moderate-sized (M4.5-6), deep-focus earthquakes (h >350 km) and the finite difference method (FDM) simulation of high-frequency (up to 8 Hz) wave propagation. Strong regional S wave attenuation anomalies for specific source-receiver paths connecting the cluster of events occurring in central part of the Sea of Japan recorded at fore arc stations in northern and central Japanese Islands (Honshu) are used to model the deeper structure of the subducting Pacific Plate, where recent teleseismic tomography has shown evidence for a possible slab tear westward beneath the Sea of Japan. The character of the observed anomalous S wave attenuation and the following high-frequency coda can be captured with the two-dimensional (2-D) FDM simulation of seismic waves in heterogeneous plate model, incorporating the thinning of the plate at depth, which is also compared with other possible causes of dramatic attenuation of high-frequency S wave due to low-Q or much weaker heterogeneities in the slab. The results of simulation clearly demonstrate that the dramatic loss of high-frequency S wavefield from the plate into the surrounding mantle occurred due to the variation in the plate geometry (i.e., thinning of the plate) at depth near the source rather than due to variation in physical properties, such as due to the lowered-Q and weaker heterogeneities in the plate. The presence of such a thin zone defocuses the high-frequency slab-guided S wave energy from the subducting plate into the surrounding mantle and acts as a geometric antiwaveguide. Based on the sequence of simulation results obtained, we propose thinning of Pacific Plate at depth subducting beneath northeastern Japan, localized to central part of Honshu, in agreement with the observations.

  2. Pipe wall damage detection by electromagnetic acoustic transducer generated guided waves in absence of defect signals.

    Science.gov (United States)

    Vasiljevic, Milos; Kundu, Tribikram; Grill, Wolfgang; Twerdowski, Evgeny

    2008-05-01

    Most investigators emphasize the importance of detecting the reflected signal from the defect to determine if the pipe wall has any damage and to predict the damage location. However, often the small signal from the defect is hidden behind the other arriving wave modes and signal noise. To overcome the difficulties associated with the identification of the small defect signal in the time history plots, in this paper the time history is analyzed well after the arrival of the first defect signal, and after different wave modes have propagated multiple times through the pipe. It is shown that the defective pipe can be clearly identified by analyzing these late arriving diffuse ultrasonic signals. Multiple reflections and scattering of the propagating wave modes by the defect and pipe ends do not hamper the defect detection capability; on the contrary, it apparently stabilizes the signal and makes it easier to distinguish the defective pipe from the defect-free pipe. This paper also highlights difficulties associated with the interpretation of the recorded time histories due to mode conversion by the defect. The design of electro-magnetic acoustic transducers used to generate and receive the guided waves in the pipe is briefly described in the paper.

  3. Guided wave structural health monitoring with an array of novel piezoelectric transducers

    Science.gov (United States)

    Lesky, A.; Lissenden, C. J.

    2014-02-01

    Multi-element, conformable piezoelectric strip transducers have been designed and fabricated for structural health monitoring using ultrasonic guided waves. The piezoelectric fiber composite elements function as a strip transducer to activate a planar wave. A mockup of a storage tank or pressure vessel has been constructed from a steel shell and a hexagonal array of strip transducers. A hot spot to which artificial damage has been induced is monitored with the strip transducers. In addition, conventional piezoelectric disks have also been affixed to the shell in a circular pattern for the purpose of comparison. Different operating conditions are represented by the presence of water inside the shell and temperature variations between 20 and 35°C. The strip transducers have been designed to excite the S1 Lamb wave mode at the dilatational wave speed, which is oblivious to the presence of liquid loaded boundary conditions. An artificial defect simulated a surface breaking fatigue crack. Preliminary results are presented for baseline and damaged conditions using transmission and reflection coefficients as a damage-sensitive feature. At the request of the Proceedings Editor, and all authors of the paper, an updated version of this article was published on 8 April 2014. The Corrigendum attached to the corrected article PDF file explains the changes made to the original paper.

  4. Air-coupled guided wave detection and wavenumber filtering to full-field representation of delamination in composite plates

    Science.gov (United States)

    Testoni, N.; De Marchi, L.; Marzani, A.

    2014-03-01

    Delamination faults in composite plates are considered dangerous as they can cause catastrophic failure before being visually assessed. Effects of delaminations are particularly relevant in guided waves scattering, local resonances and mode conversion. Detecting and analyzing these phenomena is relevant for plate characterization. In this work, leaky guided waves are used to detect delamination in composite plates. To such purpose, a hybrid ultrasonic set-up and a dedicated signal processing are proposed. An air-probe with a proper lift-off is used to detect the leakage in terms of air pressure wave over the plate surface. A piezoelectric transducer is used to generate acoustic guided waves in the composite plate. Multiple acquisitions are averaged to increase the SNR for each position of the air-probe. Curvelet Transform (CT) domain processing of the projection coefficients of the acquired elastic wave is exploited to decompose waves that are overlapped both in the time/space and in the frequency/wavenumber domain. In fact, CT is a special member of the family of multiscale and multidimensional transforms whose spatial and temporal localization is very well suited for processing signals which are sparse in the above mentioned domains. In this work this sparsity is exploited to emphasize the information of leaky guided waves scattered by the delamination by removing from the data the information related to the incident wave field. As an application, the presence of a delamination generated by a 21 Joule impact performed on a 4.9 mm thickness composite laminate was detected contactless by exploiting guided wave leakage.

  5. Ultrasonic guided wave characterization and damage detection in foam-core sandwich panel using PWAS and LDV

    Science.gov (United States)

    Chakraborty, Nibir; Roy Mahapatra, D.; Srinivasan, Gopalakrishnan

    2012-04-01

    Lamb wave type guided wave propagation in foam core sandwich structures and detectability of damages using spectral analysis method are reported in this paper. An experimental study supported by theoretical evaluation of the guided wave characteristics is presented here that shows the applicability of Lamb wave type guided ultrasonic wave for detection of damage in foam core sandwich structures. Sandwich beam specimens were fabricated with 10 mm thick foam core and 0.3 mm thick aluminum face sheets. Thin piezoelectric patch actuators and sensors are used to excite and sense guided wave. Group velocity dispersion curves and frequency response of sensed signal are obtained experimentally. The nature of damping present in the sandwich panel is monitored by measuring the sensor signal amplitude at various different distances measured from the center of the linear phased array. Delaminations of increasing width are created and detected experimentally by pitch-catch interrogation with guided waves and wavelet transform of the sensed signal. Signal amplitudes are analyzed for various different sizes of damages to differentiate the damage size/severity. A sandwich panel is also fabricated with a planer dimension of 600 mm x 400 mm. Release film delamination is introduced during fabrication. Non-contact Laser Doppler Vibrometer (LDV) is used to scan the panel while exciting with a surface bonded piezoelectric actuator. Presence of damage is confirmed by the reflected wave fringe pattern obtained from the LDV scan. With this approach it is possible to locate and monitor the damages by tracking the wave packets scattered from the damages.

  6. Ultrasonic guided wave bondline evaluation of thick metallic structures with viscoelastic coatings and the demonstration of a novel mode sweep technique

    Science.gov (United States)

    Bostron, Jason

    Ultrasonic guided waves are becoming more widely used in nondestructive evaluation applications due to their efficiency in defect detection, ability to inspect hidden areas, and other reasons. This dissertation addresses two main topics: ultrasonic guided wave bond evaluation of thin and thick coatings on thick metallic structures, and the use of a novel phased array technique for optimal guided wave mode and frequency selection. (Abstract shortened by UMI.).

  7. Final Report: Guided Acoustic Wave Monitoring of Corrosion in Recovery Boiler Tubing

    Energy Technology Data Exchange (ETDEWEB)

    Chinn, D J; Quarry, M J; Rose, J L

    2005-03-31

    Corrosion of tubing used in black-liquor recovery boilers is a major concern in all pulp and paper mills. Extensive corrosion in recovery boiler tubes can result in a significant safety and environmental hazard. Considerable plant resources are expended to inspect recovery boiler tubing. Currently, visual and ultrasonic inspections are primarily used during the annual maintenance shutdown to monitor corrosion rates and cracking of tubing. This Department of Energy, Office of Industrial Technologies project is developing guided acoustic waves for use on recovery boiler tubing. The feature of this acoustic technique is its cost-effectiveness in inspecting long lengths of tubes from a single inspection point. A piezoelectric or electromagnetic transducer induces guided waves into the tubes. The transducer detects fireside defects from the cold side or fireside of the tube. Cracking and thinning on recovery boiler tubes have been detected with this technique in both laboratory and field applications. This technique appears very promising for recovery boiler tube application, potentially expediting annual inspection of tube integrity.

  8. Low-frequency vibration modulation of guided waves to image nonlinear scatterers for structural health monitoring

    Science.gov (United States)

    Jiao, J. P.; Drinkwater, B. W.; Neild, S. A.; Wilcox, P. D.

    2009-06-01

    Guided wave structural health monitoring offers the prospect of continuous interrogation of large plate-like structures with a sparse network of permanently attached sensors. Currently, the most common approach is to monitor changes in the received signals by subtraction from a reference signal obtained when the structure was known to be defect-free. In this paper a comparison is made between this defect-free subtraction approach and a technique in which low-frequency vibration modulation of guided wave signals is used to detect nonlinear scatterers. The modulation technique potentially overcomes the need for the defect-free reference measurement as the subtraction is now made between different parts of an externally applied low-frequency vibration. Linear defects were simulated by masses bonded onto a plate and nonlinear scatterers were simulated by loading a similar mass against the plate. The experimental results show that the defect-free subtraction technique performs well in detecting the bonded mass whereas the modulation technique is able to discriminate between the bonded and loaded masses. Furthermore, because the modulation technique does not require a defect-free reference, it is shown to be relatively independent of temperature effects, a significant problem for reference based subtraction techniques.

  9. Guided wave radiation from a point source in the proximity of a pipe bend

    Science.gov (United States)

    Brath, A. J.; Simonetti, F.; Nagy, P. B.; Instanes, G.

    2014-02-01

    Throughout the oil and gas industry corrosion and erosion damage monitoring play a central role in managing asset integrity. Recently, the use of guided wave technology in conjunction with tomography techniques has provided the possibility of obtaining point-by-point maps of wall thickness loss over the entire volume of a pipeline section between two ring arrays of ultrasonic transducers. However, current research has focused on straight pipes while little work has been done on pipe bends which are also the most susceptible to developing damage. Tomography of the bend is challenging due to the complexity and computational cost of the 3-D elastic model required to accurately describe guided wave propagation. To overcome this limitation, we introduce a 2-D anisotropic inhomogeneous acoustic model which represents a generalization of the conventional unwrapping used for straight pipes. The shortest-path ray-tracing method is then applied to the 2-D model to compute ray paths and predict the arrival times of the fundamental flexural mode, A0, excited by a point source on the straight section of pipe entering the bend and detected on the opposite side. Good agreement is found between predictions and experiments performed on an 8" diameter (D) pipe with 1.5 D bend radius. The 2-D model also reveals the existence of an acoustic lensing effect which leads to a focusing phenomenon also confirmed by the experiments. The computational efficiency of the 2-D model makes it ideally suited for tomography algorithms.

  10. Design of a high efficiency relativistic backward wave oscillator with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoze; Song, Wei; Tan, Weibing; Zhang, Ligang; Su, Jiancang; Zhu, Xiaoxin; Hu, Xianggang; Shen, Zhiyuan; Liang, Xu; Ning, Qi [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2016-07-15

    A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. A trapezoidal resonant reflector is used to reduce the modulation field in the resonant reflector to avoid overmodulation of the electron beam which will lead to a large momentum spread and then low conversion efficiency. The envelope of the inner radius of the slow wave structure (SWS) increases stepwise to keep conformal to the trajectory of the electron beam which will alleviate the bombardment of the electron on the surface of the SWS. The length of period of the SWS is reduced gradually to make a better match between phase velocity and electron beam, which decelerates continually and improves the RF current distribution. Meanwhile the modulation field is reduced by the introduction of nonuniform SWS also. The particle in cell simulation results reveal that a microwave with a power of 1.8 GW and a frequency of 14.7 GHz is generated with an efficiency of 47% when the diode voltage is 620 kV, the beam current 6.1 kA, and the guiding magnetic field 0.95 T.

  11. Ultrasonic torsional guided wave sensor for flow front monitoring inside molds.

    Science.gov (United States)

    Visvanathan, Karthik; Balasubramaniam, Krishnan

    2007-01-01

    Measuring the extent of flow of viscous fluids inside opaque molds has been a very important parameter in determining the quality of products in the manufacturing process such as injection molding and resin transfer molding. Hence, in this article, an ultrasonic torsional guided wave sensor has been discussed for monitoring the movement of flow front during filling of resins in opaque molds. A pair of piezoelectric normal shear transducers were used for generating and receiving the fundamental ultrasonic torsional guided wave mode in thin copper wires. The torsional mode was excited at one end of the wire, while the flowing viscous fluid progressively wet the other free end of the wire. The time of flight of the transient reflections of this fundamental mode from the air-fluid interface, where the wire enters the resin, was used to measure the position of the fluid flow front. Experiments were conducted on four fluids with different viscosity values. Two postprocessing algorithms were developed for enhancing the transient reflected signal and for suppressing the unwanted stationary signals. The algorithms were tested for cases where the reflected signals showed a poor signal to noise ratio.

  12. Effects of temperature variations on guided waves propagating in composite structures

    Science.gov (United States)

    Shoja, Siavash; Berbyuk, Viktor; Boström, Anders

    2016-04-01

    Effects of temperature on guided waves propagating in composite materials is a well-known problem which has been investigated in many studies. The majority of the studies is focused on effects of high temperature. Understanding the effects of low temperature has major importance in composite structures and components which are operating in cold climate conditions such as e.g. wind turbines operating in cold climate regions. In this study first the effects of temperature variations on guided waves propagating in a composite plate is investigated experimentally in a cold climate chamber. The material is a common material used to manufacture rotor blades of wind turbines. The temperature range is 25°C to -25°C and effects of temperature variations on amplitude and phase shift of the received signal are investigated. In order to apply the effects of lowering the temperature on the received signal, the Baseline Signal Stretch (BSS) method is modified and used. The modification is based on decomposing the signal into symmetric and asymmetric modes and applying two different stretch factors on each of them. Finally the results obtained based on the new method is compared with the results of application of BSS with one stretch factor and experimental measurements. Comparisons show that an improvement is obtained using the BSS with the mode decomposition method at temperature variations of more than 25°C.

  13. Defects detection in typical positions of bend pipes using low-frequency ultrasonic guided wave

    Institute of Scientific and Technical Information of China (English)

    罗更生; 谭建平; 汪亮; 许焰

    2015-01-01

    In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE (finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.

  14. Guided wave propagation in a honeycomb composite sandwich structure in presence of a high density core.

    Science.gov (United States)

    Sikdar, Shirsendu; Banerjee, Sauvik

    2016-09-01

    A coordinated theoretical, numerical and experimental study is carried out in an effort to interpret the characteristics of propagating guided Lamb wave modes in presence of a high-density (HD) core region in a honeycomb composite sandwich structure (HCSS). Initially, a two-dimensional (2D) semi-analytical model based on the global matrix method is used to study the response and dispersion characteristics of the HCSS with a soft core. Due to the complex structural characteristics, the study of guided wave (GW) propagation in HCSS with HD-core region inherently poses many challenges. Therefore, a numerical simulation of GW propagation in the HCSS with and without the HD-core region is carried out, using surface-bonded piezoelectric wafer transducer (PWT) network. From the numerical results, it is observed that the presence of HD-core significantly decreases both the group velocity and the amplitude of the received GW signal. Laboratory experiments are then conducted in order to verify the theoretical and numerical results. A good agreement between the theoretical, numerical and experimental results is observed in all the cases studied. An extensive parametric study is also carried out for a range of HD-core sizes and densities in order to study the effect due to the change in size and density of the HD zone on the characteristics of propagating GW modes. It is found that the amplitudes and group velocities of the GW modes decrease with the increase in HD-core width and density.

  15. Genetic algorithms-based inversion of multimode guided waves for cortical bone characterization

    Science.gov (United States)

    Bochud, N.; Vallet, Q.; Bala, Y.; Follet, H.; Minonzio, J.-G.; Laugier, P.

    2016-10-01

    Recent progress in quantitative ultrasound has exploited the multimode waveguide response of long bones. Measurements of the guided modes, along with suitable waveguide modeling, have the potential to infer strength-related factors such as stiffness (mainly determined by cortical porosity) and cortical thickness. However, the development of such model-based approaches is challenging, in particular because of the multiparametric nature of the inverse problem. Current estimation methods in the bone field rely on a number of assumptions for pairing the incomplete experimental data with the theoretical guided modes (e.g. semi-automatic selection and classification of the data). The availability of an alternative inversion scheme that is user-independent is highly desirable. Thus, this paper introduces an efficient inversion method based on genetic algorithms using multimode guided waves, in which the mode-order is kept blind. Prior to its evaluation on bone, our proposal is validated using laboratory-controlled measurements on isotropic plates and bone-mimicking phantoms. The results show that the model parameters (i.e. cortical thickness and porosity) estimated from measurements on a few ex vivo human radii are in good agreement with the reference values derived from x-ray micro-computed tomography. Further, the cortical thickness estimated from in vivo measurements at the third from the distal end of the radius is in good agreement with the values delivered by site-matched high-resolution x-ray peripheral computed tomography.

  16. Development of a Fully Automated Guided Wave System for In-Process Cure Monitoring of CFRP Composite Laminates

    Science.gov (United States)

    Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.; Yaun, Fuh-Gwo

    2016-01-01

    A guided wave-based in-process cure monitoring technique for carbon fiber reinforced polymer (CFRP) composites was investigated at NASA Langley Research Center. A key cure transition point (vitrification) was identified and the degree of cure was monitored using metrics such as amplitude and time of arrival (TOA) of guided waves. Using an automated system preliminarily developed in this work, high-temperature piezoelectric transducers were utilized to interrogate a twenty-four ply unidirectional composite panel fabricated from Hexcel (Registered Trademark) IM7/8552 prepreg during cure. It was shown that the amplitude of the guided wave increased sharply around vitrification and the TOA curve possessed an inverse relationship with degree of cure. The work is a first step in demonstrating the feasibility of transitioning the technique to perform in-process cure monitoring in an autoclave, defect detection during cure, and ultimately a closed-loop process control to maximize composite part quality and consistency.

  17. Full 3D dispersion curve solutions for guided waves in generally anisotropic media

    Science.gov (United States)

    Hernando Quintanilla, F.; Lowe, M. J. S.; Craster, R. V.

    2016-02-01

    Dispersion curves of guided waves provide valuable information about the physical and elastic properties of waves propagating within a given waveguide structure. Algorithms to accurately compute these curves are an essential tool for engineers working in non-destructive evaluation and for scientists studying wave phenomena. Dispersion curves are typically computed for low or zero attenuation and presented in two or three dimensional plots. The former do not always provide a clear and complete picture of the dispersion loci and the latter are very difficult to obtain when high values of attenuation are involved and arbitrary anisotropy is considered in single or multi-layered systems. As a consequence, drawing correct and reliable conclusions is a challenging task in the modern applications that often utilize multi-layered anisotropic viscoelastic materials. These challenges are overcome here by using a spectral collocation method (SCM) to robustly find dispersion curves in the most complicated cases of high attenuation and arbitrary anisotropy. Solutions are then plotted in three-dimensional frequency-complex wavenumber space, thus gaining much deeper insight into the nature of these problems. The cases studied range from classical examples, which validate this approach, to new ones involving materials up to the most general triclinic class for both flat and cylindrical geometry in multi-layered systems. The apparent crossing of modes within the same symmetry family in viscoelastic media is also explained and clarified by the results. Finally, the consequences of the centre of symmetry, present in every crystal class, on the solutions are discussed.

  18. Multipole expansion of Green's function for guided waves in a transversely isotropic plate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Heung Son; Kim, Yoon Young [Seoul National University, Seoul (Korea, Republic of)

    2015-05-15

    The multipole expansion of Green's function in a transversely isotropic plate is derived based on the eigenfunction expansion method. For the derivation, Green's function is expressed in a bilinear form composed of the regular and singular Lamb-type (or shear-horizontal) wave eigenfunctions. The specific form of the derived Green's function facilitates the handling of general scattering problems in an elastic plate when numerical methods such as the methods of the null-field integral equations are employed. In the derivation, the integral transform of an arbitrary guided wave field is first constructed by the Lamb-type and shear horizontal wave eigenfunctions that work as the kernel functions. After showing that the thickness-dependent parts of the eigenfunctions are orthogonal to each other in the transformed space, Green's function is explicitly derived by using the orthogonality. As an application of the derived Green's function, a scattering problem is solved by the transition matrix method.

  19. Investigation on empowering one direction emission of guided waves to avoid undesired reflections from other pipe attachments

    Science.gov (United States)

    Tse, Peter W.; Zhou, Fang

    2016-02-01

    An in-service pipe always contains elbows and joints at the ends of the pipe. Since the emitted guided waves from a transducer array is bi-directional, any attachments located at both ends of the pipe will cause reflections. For building pipes that are partially covered by wall, the transducer array must be installed near one end of the pipe. If there is elbow or joint connected to that end of the pipe, high reflections generated from the elbow or joint are inevitable. Such reflections may interfere the detection of reflections caused by true defect exists along the pipe body. Hence, to minimize such undesired interference, one must employs some smart devices or algorithms so that it can reduce the emission of guided wave from one direction but enhance the emission from the other direction. To achieve such purpose, two identical transducer arrays must be installed on the same pipe but with a smartly and specially calculated distance apart from the mounting locations of these two arrays. The distance is to ensure there is a proper time delay for emitting the second array after the emission of the first array. The designed processes are listed as follow. Firstly, two identical transducer arrays that could emit L(0,1) guided waves were mounted on a pipe with a specific distance apart from their mounting locations. The distance was determined after calculating the necessary time delay. Secondly, the guided waves generated from the two arrays are combined together to create the desired superimposing effect. With the help of simulation and finite element analysis, such single direction guided wave was successfully generated and tested. By accurately adjusted the time delay, results showed that it is possible to minimize the emitted guided waves in one direction and then empower the guided waves in another direction. Hence, the reflections generated from elbows and joints at one end of the pipe has been minimized, whilst, the emission of guided wave in the other direction

  20. CNS regulation of appetite.

    Science.gov (United States)

    Harrold, Joanne A; Dovey, Terry M; Blundell, John E; Halford, Jason C G

    2012-07-01

    This article reviews the regulation of appetite from a biopsychological perspective. It considers psychological experiences and peripheral nutritional systems (both episodic and tonic) and addresses their relationship with the CNS networks that process and integrate their input. Whilst such regulatory aspects of obesity focus on homeostatic control mechanisms, in the modern environment hedonic aspects of appetite are also critical. Enhanced knowledge of the complexity of appetite regulation and the mechanisms that sustain obesity indicate the challenge presented by management of the obesity epidemic. Nonetheless, effective control of appetite expression remains a critical therapeutic target for weight management. Currently, strategies which utilise a combination of agents to target both homeostatic and hedonic control mechanisms represent the most promising approaches. This article is part of a Special Issue entitled 'Central Control of Food Intake'. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Self-action of Bessel wave packets in a system of coupled light guides and formation of light bullets

    Energy Technology Data Exchange (ETDEWEB)

    Balakin, A. A., E-mail: balakin.alexey@yandex.ru; Mironov, V. A.; Skobelev, S. A., E-mail: sk.sa1981@gmail.com [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2017-01-15

    The self-action of two-dimensional and three-dimensional Bessel wave packets in a system of coupled light guides is considered using the discrete nonlinear Schrödinger equation. The features of the self-action of such wave fields are related to their initial strong spatial inhomogeneity. The numerical simulation shows that for the field amplitude exceeding a critical value, the development of an instability typical of a medium with the cubic nonlinearity is observed. Various regimes are studied: the self-channeling of a wave beam in one light guide at powers not strongly exceeding a critical value, the formation of the “kaleidoscopic” picture of a wave packet during the propagation of higher-power radiation along a stratified medium, the formation of light bullets during competition between self-focusing and modulation instabilities in the case of three-dimensional wave packets, etc. In the problem of laser pulse shortening, the situation is considered when the wave-field stratification in the transverse direction dominates. This process is accompanied by the self-compression of laser pulses in well enough separated light guides. The efficiency of conversion of the initial Bessel field distribution to two flying parallel light bullets is about 50%.

  2. Constraining the hydration of the subducting Nazca plate beneath Northern Chile using subduction zone guided waves

    Science.gov (United States)

    Garth, Tom; Rietbrock, Andreas

    2017-09-01

    Guided wave dispersion is observed from earthquakes at 180-280 km depth recorded at stations in the fore-arc of Northern Chile, where the 44 Ma Nazca plate subducts beneath South America. Characteristic P-wave dispersion is observed at several stations in the Chilean fore-arc with high frequency energy (>5 Hz) arriving up to 3 s after low frequency (first motion dispersion observed at multiple stations, or the extended P-wave coda observed in arrivals from intermediate depth events within the Nazca plate. These signals can however be accurately accounted for if dipping low velocity fault zones are included within the subducting lithospheric mantle. A grid search over possible LVL and faults zone parameters (width, velocity contrast and separation distance) was carried out to constrain the best fitting model parameters. Our results imply that fault zone structures of 0.5-1.0 km thickness, and 5-10 km spacing, consistent with observations at the outer rise are present within the subducted slab at intermediate depths. We propose that these low velocity fault zone structures represent the hydrated structure within the lithospheric mantle. They may be formed initially by normal faults at the outer rise, which act as a pathway for fluids to penetrate the deeper slab due to the bending and unbending stresses within the subducting plate. Our observations suggest that the lithospheric mantle is 5-15% serpentinised, and therefore may transport approximately 13-42 Tg/Myr of water per meter of arc. The guided wave observations also suggest that a thin LVL (∼1 km thick) interpreted as un-eclogitised subducted oceanic crust persists to depths of at least 220 km. Comparison of the inferred seismic velocities with those predicted for various MORB assemblages suggest that this thin LVL may be accounted for by low velocity lawsonite-bearing assemblages, suggesting that some mineral-bound water within the oceanic crust may be transported well beyond the volcanic arc. While older

  3. Innate Interferons Regulate CNS Inflammation

    DEFF Research Database (Denmark)

    Dieu, Ruthe; Khorooshi, Reza M. H.; Mariboe, Anne

    Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) whose pathology is characterised by demyelination and axonal damage. This results from interplay between CNS-resident glia, infiltrating leukocytes and a plethora of cytokines and chemokines. Currently, ...

  4. Generalized poroviscoelastic model based on effective Biot theory and its application to borehole guided wave analysis

    Science.gov (United States)

    Liu, Xu; Greenhalgh, Stewart; Zhou, Bing; Heinson, Graham

    2016-12-01

    A method using modified attenuation factor function is suggested to determine the parameters of the generalized Zener model approximating the attenuation factor function. This method is applied to constitute the poroviscoelastic model based on the effective Biot theory which considers the attenuative solid frame of reservoir. In the poroviscoelastic model, frequency-dependent bulk modulus and shear modulus of solid frame are represented by generalized Zener models. As an application, the borehole logging dispersion equations from Biot theory are extended to include effects from the intrinsic body attenuation in formation media in full-frequency range. The velocity dispersions of borehole guided waves are calculated to investigate the influence from attenuative bore fluid, attenuative solid frame of the formation and impermeable bore wall.

  5. Near-to-eye electroholography via guided-wave acousto-optics for augmented reality

    Science.gov (United States)

    Jolly, Sundeep; Savidis, Nickolaos; Datta, Bianca; Smalley, Daniel; Bove, V. Michael

    2017-03-01

    Near-to-eye holographic displays act to directly project wavefronts into a viewer's eye in order to recreate 3-D scenes for augmented or virtual reality applications. Recently, several solutions for near-to-eye electroholography have been proposed based on digital spatial light modulators in conjunction with supporting optics, such as holographic waveguides for light delivery; however, such schemes are limited by the inherent low space-bandwidth product available with current digital SLMs. In this paper, we depict a fully monolithic, integrated optical platform for transparent near-to-eye holographic display requiring no supporting optics. Our solution employs a guided-wave acousto-optic spatial light modulator implemented in lithium niobate in conjunction with an integrated Bragg-regime reflection volume hologram.

  6. Efficient baseline gathering and damage detection in guided wave structural health monitoring

    Science.gov (United States)

    Croxford, A. J.; Putkis, O.; Wilcox, P. D.

    2013-01-01

    Guided wave structural health monitoring (SHM) has been proposed as a technique to allow permanently attached sensors to provide information about the state of a structure. Typical approaches rely on gathering information about the baseline state of the structure and using this data with subtraction to highlight changes to the system. This relies on the baseline data accurately representing the conditions that the system will experience. In reality this is difficult to ensure and may result in either large periods out of service or poor performance. In addition the size of the baseline set can become prohibitively large. This paper describes an alternative approach that produces an efficient continuously evolving baseline. The paper considers how damage detection performance can be characterized within this framework and presents a series of metrics to do this. The result is a new way of considering the baseline problem with practical applications to the long term inspection of structures.

  7. Quantitative Evaluation of Defect Based on Ultrasonic Guided Wave and CHMM

    Directory of Open Access Journals (Sweden)

    Chen Le

    2016-01-01

    Full Text Available The axial length of pipe defects is not linear with the reflection coefficient, which is difficult to identify the axial length of the defect by the reflection coefficient method. Continuous Hidden Markov Model (CHMM is proposed to accurately classify the axial length of defects, achieving the objective of preliminary quantitative evaluation. Firstly, wavelet packet decomposition method is used to extract the characteristic information of the guided wave signal, and Kernel Sliced Inverse Regression (KSIR method is used to reduce the dimension of feature set. Then, a variety of CHMM models are trained for classification. Finally, the trained models are used to identify the artificial corrosion defects on the outer surface of the pipe. The results show that the CHMM model has better robustness and can accurately identify the axial defects.

  8. Guided wave technique for non-destructive testing of StifPipe

    Science.gov (United States)

    Amjad, Umar; Yadav, Susheel K.; Nguyen, Chi H.; Ehsani, Mohammad; Kundu, Tribikram

    2015-03-01

    The newly-developed StifPipe® is an effective technology for repair and strengthening of existing pipes and culverts. The wall of this pipe consists of a lightweight honeycomb core with carbon or glass fiber reinforced polymer (FRP) applied to the skin. The presence of the hollow honeycomb introduces challenges in the nondestructive testing (NDT) of this pipe. In this study, it is investigated if guided waves, excited by PZT (Lead ZirconateTitanate) transducer can detect damages in the honeycomb layer of the StifPipe®. Multiple signal processing techniques are used for in-depth study and understanding of the recorded signals. The experimental technique for damage detection in StifPipe® material is described and the obtained results are presented in this paper.

  9. Ultrasonic Guided-Wave Scan System Used to Characterize Microstructure and Defects in Ceramic Composites

    Science.gov (United States)

    Roth, Don J.; Cosgriff, Laura M.; Martin, Richard E.; Verrilli, Michael J.; Bhatt, Ramakrishna T.

    2004-01-01

    Ceramic matrix composites (CMCs) are being developed for advanced aerospace propulsion applications to save weight, improve reuse capability, and increase performance. However, mechanical and environmental loads applied to CMCs can cause discrete flaws and distributed microdamage, significantly reducing desirable physical properties. Such microdamage includes fiber/matrix debonding (interface failure), matrix microcracking, fiber fracture and buckling, oxidation, and second phase formation. A recent study (ref. 1) of the durability of a C/SiC CMC discussed the requirement for improved nondestructive evaluation (NDE) methods for monitoring degradation in these materials. Distributed microdamage in CMCs has proven difficult to characterize nondestructively because of the complex microstructure and macrostructure of these materials. This year, an ultrasonic guided-wave scan system developed at the NASA Glenn Research Center was used to characterize various microstructural and flaw conditions in SiC/SiC (silicon carbide fiber in silicon carbide matrix) and C/SiC (carbon fiber in silicon carbide matrix) CMC samples.

  10. Relativistic nonlinearity and wave-guide propagation of rippled laser beam in plasma

    Indian Academy of Sciences (India)

    R K Khanna; K Baheti

    2001-06-01

    In the present paper we have investigated the self-focusing behaviour of radially symmetrical rippled Gaussian laser beam propagating in a plasma. Considering the nonlinearity to arise from relativistic phenomena and following the approach of Akhmanov et al, which is based on the WKB and paraxial-ray approximation, the self-focusing behaviour has been investigated in some detail. The effect of the position and width of the ripple on the self-focusing of laser beam has been studied for arbitrary large magnitude of nonlinearity. Results indicate that the medium behaves as an oscillatory wave-guide. The self-focusing is found to depend on the position parameter of ripple as well as on the beam width. Values of critical power has been calculated for different values of the position parameter of ripple. Effects of axially and radially inhomogeneous plasma on self-focusing behaviour have been investigated and presented here.

  11. Wave-guided Optical Waveguides tracked and coupled using dynamic diffractive optics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Villangca, Mark Jayson; Bañas, Andrew Rafael

    With light’s miniscule momentum, shrinking robotics down to the micro- and nano-scale regime creates opportunities for exploiting optical forces and near-field light delivery in advanced actuation and control atthe smallest physical dimensions. Advancing light-driven nano- or micro-actuation requ......With light’s miniscule momentum, shrinking robotics down to the micro- and nano-scale regime creates opportunities for exploiting optical forces and near-field light delivery in advanced actuation and control atthe smallest physical dimensions. Advancing light-driven nano- or micro......-actuation requires the optimization of optical forces and optical torques that, in turn, requires the optimization of the underlying light-matter interaction [1]. We have previously proposed and demonstrated micro-targeted light-delivery and the opto-mechanical capabilities of so-called wave-guided optical...

  12. Resonant-state expansion for wave guides with a Sellmeier dispersion

    CERN Document Server

    Doost, M B

    2015-01-01

    The resonant-state expansion (RSE), a rigorous perturbative method developed in electrodynamics for non-dispersive optical systems is further developed to treat wave guides with a Sellmeier dispersion. For media which can be described by these types of dispersion over the relevant frequency range, such as optical glass, the perturbed problem can be solved by diagonalising a second-order eigenvalue problem. In the case of a single resonance at zero frequency, this is simplified to a generalised eigenvalue problem. Results are presented using analytically solvable planar waveguides and parameters of BK7 glass, for a perturbation in the waveguide width. The efficiency of using either an exact dispersion over all frequencies or an approximate dispersion over a narrow frequency range is compared.

  13. Optimal design of a piezoelectric transducer for exciting guided wave ultrasound in rails

    Science.gov (United States)

    Ramatlo, Dineo A.; Wilke, Daniel N.; Loveday, Philip W.

    2017-02-01

    An existing Ultrasonic Broken Rail Detection System installed in South Africa on a heavy duty railway line is currently being upgraded to include defect detection and location. To accomplish this, an ultrasonic piezoelectric transducer to strongly excite a guided wave mode with energy concentrated in the web (web mode) of a rail is required. A previous study demonstrated that the recently developed SAFE-3D (Semi-Analytical Finite Element - 3 Dimensional) method can effectively predict the guided waves excited by a resonant piezoelectric transducer. In this study, the SAFE-3D model is used in the design optimization of a rail web transducer. A bound-constrained optimization problem was formulated to maximize the energy transmitted by the transducer in the web mode when driven by a pre-defined excitation signal. Dimensions of the transducer components were selected as the three design variables. A Latin hypercube sampled design of experiments that required a total of 500 SAFE-3D analyses in the design space was employed in a response surface-based optimization approach. The Nelder-Mead optimization algorithm was then used to find an optimal transducer design on the constructed response surface. The radial basis function response surface was first verified by comparing a number of predicted responses against the computed SAFE-3D responses. The performance of the optimal transducer predicted by the optimization algorithm on the response surface was also verified to be sufficiently accurate using SAFE-3D. The computational advantages of SAFE-3D in optimal transducer design are noteworthy as more than 500 analyses were performed. The optimal design was then manufactured and experimental measurements were used to validate the predicted performance. The adopted design method has demonstrated the capability to automate the design of transducers for a particular rail cross-section and frequency range.

  14. Evaluation of barely visible indentation damage (BVID) in CF/EP sandwich composites using guided wave signals

    Science.gov (United States)

    Mustapha, Samir; Ye, Lin; Dong, Xingjian; Alamdari, Mehrisadat Makki

    2016-08-01

    Barely visible indentation damage after quasi-static indentation in sandwich CF/EP composites was assessed using ultrasonic guided wave signals. Finite element analyses were conducted to investigate the interaction between guided waves and damage, further to assist in the selection process of the Lamb wave sensitive modes for debonding identification. Composite sandwich beams and panels structures were investigated. Using the beam structure, a damage index was defined based on the change in the peak magnitude of the captured wave signals before and after the indentation, and the damage index was correlated with the residual deformation (defined as the depth of the dent), that was further correlated with the amount of crushing within the core. Both A0 and S0 Lamb wave modes showed high sensitivity to the presence of barely visible indentation damage with residual deformation of 0.2 mm. Furthermore, barely visible indentation damage was assessed in composite sandwich panels after indenting to 3 and 5 mm, and the damage index was defined, based on (a) the peak magnitude of the wave signals before and after indentation or (b) the mismatch between the original and reconstructed wave signals based on a time-reversal algorithm, and was subsequently applied to locate the position of indentation.

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

    Science.gov (United States)

    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.

  16. Photon pair generation by intermodal spontaneous four wave mixing in birefringent, weakly guiding optical fibers

    CERN Document Server

    Garay-Palmett, K; Dominguez-Serna, F; Ortiz-Ricardo, E; Monroy-Ruz, J; Ramirez, H Cruz; Ramirez-Alarcon, R; U'Ren, A B

    2016-01-01

    We present a theoretical and experimental study of the generation of photon pairs through the process of spontaneous four wave mixing (SFWM) in a few-mode, birefringent fiber. Under these conditions, multiple SFWM processes are in fact possible, each associated with a different combination of transverse modes for the four waves involved. We show that in the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized modes, the departure from circular symmetry due to the fiber birefringence translates into conservation rules which retain elements from azimuthal and rectangular symmetries: both OAM and parity must be conserved for a process to be viable. We have implemented a SFWM source based on a "bow-tie" birefringent fiber, and have measured for a collection of pump wavelengths the SFWM spectra of each of the signal and idler photons in coincidence with its partner photon. We have used this information, together with knowledge of the transverse modes into which the ...

  17. A spacing compensation factor for the optimization of guided wave annular array transducers.

    Science.gov (United States)

    Borigo, Cody; Rose, Joseph L; Yan, Fei

    2013-01-01

    Transducer arrays can be utilized in ultrasonic guided wave applications to achieve preferential excitation of particular points on a dispersion curve. These arrays are designed according to the principles of wave interference and the influence of the wavelength excitation spectrum. This paper develops the relationships between the peak wavelength in the excitation spectra and the element spacing of linear comb and annular arrays. The excitation spectra are developed by applying Fourier and Hankel transforms to the spatial loading distribution functions of the comb and annular arrays, respectively. Although the peak wavelength of excitation of a comb array is typically assumed to be equal to the element spacing, it is shown that this can be an inaccurate assumption for annular arrays. The ratio of element spacing to the peak wavelength in the excitation spectrum is termed the spacing compensation factor, and is dependent on the number of array elements and the inner radius. It is determined that the compensation factor is negligible for comb arrays but is crucial for annular arrays in order to achieve optimal mode selection. Finite element analyses and experimental data are used to verify the calculations and demonstrate the significance of the compensation factor.

  18. Increasing the acquisition speed of a multi-channel guided wave system via simultaneous coded excitations

    Science.gov (United States)

    Hua, Jiadong; Michaels, Jennifer E.; Chen, Xin; Lin, Jing

    2017-02-01

    Many guided wave systems that are being evaluated for nondestructive evaluation or structural health monitoring utilize multiple transducers. Data are typically acquired by exciting each transducer in turn and recording received signals on the remaining transducers either simultaneously or separately. For either case, it can be very slow to acquire data because of the multiple transmission cycles combined with a slow repetition rate and extensive signal averaging. This long acquisition time brings another disadvantage by increasing the risk of environmental changes occurring during the complete acquisition process. For example, applied loads and temperature could change over the several seconds that are frequently required to acquire data. To increase the acquisition speed, it is proposed here to simultaneously trigger multiple transmitters, and each transmitter is driven with a unique, coded excitation. The simultaneously transmitted waves are captured by one or more receivers, and their responses are processed by dispersive matched filtering to separately extract the contribution from each transmitter. Results are shown for signals obtained from a spatially distribution array mounted on an aluminum plate.

  19. Beam pattern improvement by compensating array nonuniformities in a guided wave phased array

    Science.gov (United States)

    Kwon, Hyu-Sang; Lee, Seung-Seok; Kim, Jin-Yeon

    2013-08-01

    This paper presents a simple data processing algorithm which can improve the performance of a uniform circular array based on guided wave transducers. The algorithm, being intended to be used with the delay-and-sum beamformer, effectively eliminates the effects of nonuniformities that can significantly degrade the beam pattern. Nonuniformities can arise intrinsically from the array geometry when the circular array is transformed to a linear array for beam steering and extrinsically from unequal conditions of transducers such as element-to-element variations of sensitivity and directivity. The effects of nonuniformities are compensated by appropriately imposing weight factors on the elements in the projected linear array. Different cases are simulated, where the improvements of the beam pattern, especially the level of the highest sidelobe, are clearly seen, and related issues are discussed. An experiment is performed which uses A0 mode Lamb waves in a steel plate, to demonstrate the usefulness of the proposed method. The discrepancy between theoretical and experimental beam patterns is explained by accounting for near-field effects.

  20. On the development and testing of a guided ultrasonic wave array for structural integrity monitoring.

    Science.gov (United States)

    Fromme, Paul; Wilcox, Paul D; Lowe, Michael J S; Cawley, Peter

    2006-04-01

    The prototype of a guided ultrasonic wave array for the structural integrity monitoring of large, plate-like structures has been designed, built, and tested. The development of suitably small transducers for the excitation and measurement of the first antisymmetric Lamb wave mode Ao is described. The array design consists of a ring of 32 transducers, permanently bonded to the structure with a protective membrane, in a compact housing with the necessary multiplexing electronics. Using a phased addition algorithm with dispersion compensation and deconvolution in the wavenumber domain, a good dynamic range can be achieved with a limited number of transducers. Limitations in the transducer design and manufacture restricted the overall dynamic range achieved to 27 dB. Laboratory measurements for a steel plate containing various defects have been performed. The results for standard defects are compared to theoretical predictions and the sensitivity of the array device for defect detection has been established. Simulated corrosion pitting and a defect cut with an angle grinder simulating general corrosion were detected.

  1. Analysis of annular phased array transducers for ultrasonic guided wave mode control

    Science.gov (United States)

    Kannajosyula, H.; Lissenden, C. J.; Rose, J. L.

    2013-08-01

    Exact and asymptotic analyses of annular phased array transducers (PAT) for elastic guided wave mode selection are presented. For the purpose of analysis, the transducer-substrate interaction is formulated in terms of a three-dimensional analogy to filters as applied one-dimensionally in areas such as signal processing and control theory. This enables the deduction of most of the properties of the annular array purely from the Fourier analysis of any actuating function that represents the loading due to the transducer. A generalized mathematical model of the actuating function due to the annular PAT is constructed. The Fourier spectrum is analyzed for resonances in the wavenumber domain. Formulas for phase and time delays are presented. The phenomena of outgoing and incoming waves are also studied. Numerical analysis of the wavenumber spectrum for the annular PAT with a finite number of elements is performed to further illustrate the results deduced from exact and asymptotic analyses. Finite element simulations are presented to further verify the phenomena predicted through the wavenumber spectrum analysis.

  2. Stability of the Guiding Dike in Yangtze Estuary Under the Wave Load

    Institute of Scientific and Technical Information of China (English)

    YAN Shu-wang; LIU Run; FAN Qi-jin; XIE Shi-leng

    2005-01-01

    During the construction of the guiding dike in the Yangtze Estuary, some of the caisson structures sank into the soil for 1~5 m or slid about 20 m away from the original place when a strong storm attacked this area. Dynamic triaxial tests were carried out to simulate the behavior of foundation soils under wave loading. The test results show that the excessive settlement and lateral movement of the caissons are due to the weakening of the soft clay strength during the strong storm. The test results also show that the ability of the soft clay to resist the wave force will be greatly increased when the soft soil samples are suitably improved. Based on the test results, an improvement method combining vertical drains with surcharge loading was proposed to strengthen the foundation soil. On the improved soil foundation, the dike has been reconstructed and undergone several strong storms without any damage. A finite element approach has been developed for analyzing the settlement and stability of the dike under the action of strong storm.

  3. Monitoring of hidden fatigue crack growth in multi-layer aircraft structures using high frequency guided waves

    Science.gov (United States)

    Chan, H.; Masserey, B.; Fromme, P.

    2015-03-01

    Varying loading conditions of aircraft structures result in stress concentration at fastener holes, where multi-layered components are connected, potentially leading to the development of hidden fatigue cracks in inaccessible layers. High frequency guided waves propagating along the structure allow for the structural health monitoring (SHM) of such components, e.g., aircraft wings. Experimentally the required guided wave modes can be easily excited using standard ultrasonic wedge transducers. However, the sensitivity for the detection of small, potentially hidden, fatigue cracks has to be ascertained. The type of multi-layered model structure investigated consists of two adhesively bonded aluminum plate-strips with a sealant layer. Fatigue experiments were carried out and the growth of fatigue cracks at the fastener hole in one of the metallic layers was monitored optically during cyclic loading. The influence of the fatigue cracks of increasing size on the scattered guided wave field was evaluated. The sensitivity and repeatability of the high frequency guided wave modes to detect and monitor the fatigue crack growth was investigated, using both standard pulse-echo equipment and a laser interferometer. The potential for hidden fatigue crack growth monitoring at critical and difficult to access fastener locations from a stand-off distance was ascertained. The robustness of the methodology for practical in situ ultrasonic monitoring of fatigue crack growth is discussed.

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

    Science.gov (United States)

    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.

  5. Flavonoids and the CNS

    Directory of Open Access Journals (Sweden)

    Anna K. Jäger

    2011-02-01

    Full Text Available Flavonoids are present in almost all terrestrial plants, where they provide UV-protection and colour. Flavonoids have a fused ring system consisting of an aromatic ring and a benzopyran ring with a phenyl substituent. The flavonoids can be divided into several classes depending on their structure. Flavonoids are present in food and medicinal plants and are thus consumed by humans. They are found in plants as glycosides. Before oral absorption, flavonoids undergo deglycosylation either by lactase phloridzin hydrolase or cytosolic β-glucocidase. The absorbed aglycone is then conjugated by methylation, sulphatation or glucuronidation. Both the aglycones and the conjugates can pass the blood-brain barrier. In the CNS several flavones bind to the benzodiazepine site on the GABAA-receptor resulting in sedation, anxiolytic or anti-convulsive effects. Flavonoids of several classes are inhibitors of monoamine oxidase A or B, thereby working as anti-depressants or to improve the conditions of Parkinson’s patients. Flavanols, flavanones and anthocyanidins have protective effects preventing inflammatory processes leading to nerve injury. Flavonoids seem capable of influencing health and mood.

  6. The Effect of General Corrosion on the Guided Wave Inspection of the Pipeline

    Directory of Open Access Journals (Sweden)

    Zhang Jin Heng

    2016-01-01

    Full Text Available The guided wave method can inspect pipelines very quickly and widely. For instance, it can inspect the overall pipelines by digging several detection pits or removing part of coating material to set the array ring. However, it will make the guided wave attenuate more seriously and make the signals hard to identify when setting the array ring on the general corrosion. In this study, the wave propagation will be discussed when the general corrosion is under the array ring and the severe localized corrosion is inside the general corrosion via experiment and finite element method. The results showed that the excitation energy will be lower when the array ring set on the pipe surface with the general corrosion. By two-dimensional Fourier transform analysis, its non-uniform contact surface will increase asymmetric modal and mix signals. The energy attenuation will increase when the corrosion depth is deepened or the inspection frequency is risen. For example, the 2 mm deep general corrosion will attenuate −1.09 dB/m at 20 kHz and attenuate −3.01 dB/m at 40 kHz; the 4 mm deep general corrosion will attenuation −5.76 dB/m at 20 kHz and attenuation −23.19 dB/m at 40 kHz. However, the coherent signals which were caused by the general corrosion will decay with increasing frequency. For example, the coherent signals of 2 mm deep general corrosion are −23.67 dB at 20 kHz and −35.44 dB at 40 kHz; then, the 20 mm long and 3.5 mm deep localized corrosion which signal is −26.34 dB at 20 kHz and −26.94 dB at 40 kHz will be detected easily at high frequency. It can provide detectors to understand the impact when the array ring set on the area of general corrosion and the way to distinguish the localized corrosion which is inside the area of general corrosion.

  7. Instantaneous Wave-free Ratio versus Fractional Flow Reserve to Guide PCI.

    Science.gov (United States)

    Götberg, Matthias; Christiansen, Evald H; Gudmundsdottir, Ingibjörg J; Sandhall, Lennart; Danielewicz, Mikael; Jakobsen, Lars; Olsson, Sven-Erik; Öhagen, Patrik; Olsson, Hans; Omerovic, Elmir; Calais, Fredrik; Lindroos, Pontus; Maeng, Michael; Tödt, Tim; Venetsanos, Dimitrios; James, Stefan K; Kåregren, Amra; Nilsson, Margareta; Carlsson, Jörg; Hauer, Dario; Jensen, Jens; Karlsson, Ann-Charlotte; Panayi, Georgios; Erlinge, David; Fröbert, Ole

    2017-03-18

    Background The instantaneous wave-free ratio (iFR) is an index used to assess the severity of coronary-artery stenosis. The index has been tested against fractional flow reserve (FFR) in small trials, and the two measures have been found to have similar diagnostic accuracy. However, studies of clinical outcomes associated with the use of iFR are lacking. We aimed to evaluate whether iFR is noninferior to FFR with respect to the rate of subsequent major adverse cardiac events. Methods We conducted a multicenter, randomized, controlled, open-label clinical trial using the Swedish Coronary Angiography and Angioplasty Registry for enrollment. A total of 2037 participants with stable angina or an acute coronary syndrome who had an indication for physiologically guided assessment of coronary-artery stenosis were randomly assigned to undergo revascularization guided by either iFR or FFR. The primary end point was the rate of a composite of death from any cause, nonfatal myocardial infarction, or unplanned revascularization within 12 months after the procedure. Results A primary end-point event occurred in 68 of 1012 patients (6.7%) in the iFR group and in 61 of 1007 (6.1%) in the FFR group (difference in event rates, 0.7 percentage points; 95% confidence interval [CI], -1.5 to 2.8%; P=0.007 for noninferiority; hazard ratio, 1.12; 95% CI, 0.79 to 1.58; P=0.53); the upper limit of the 95% confidence interval for the difference in event rates fell within the prespecified noninferiority margin of 3.2 percentage points. The results were similar among major subgroups. The rates of myocardial infarction, target-lesion revascularization, restenosis, and stent thrombosis did not differ significantly between the two groups. A significantly higher proportion of patients in the FFR group than in the iFR group reported chest discomfort during the procedure. Conclusions Among patients with stable angina or an acute coronary syndrome, an iFR-guided revascularization strategy was

  8. Structural Diagnostics of CFRP Composite Aircraft Components by Ultrasonic Guided Waves and Built-In Piezoelectric Transducers

    Energy Technology Data Exchange (ETDEWEB)

    Matt, Howard M. [Univ. of California, San Diego, CA (United States)

    2006-01-01

    To monitor in-flight damage and reduce life-cycle costs associated with CFRP composite aircraft, an autonomous built-in structural health monitoring (SHM) system is preferred over conventional maintenance routines and schedules. This thesis investigates the use of ultrasonic guided waves and piezoelectric transducers for the identification and localization of damage/defects occurring within critical components of CFRP composite aircraft wings, mainly the wing skin-to-spar joints. The guided wave approach for structural diagnostics was demonstrated by the dual application of active and passive monitoring techniques. For active interrogation, the guided wave propagation problem was initially studied numerically by a semi-analytical finite element method, which accounts for viscoelastic damping, in order to identify ideal mode-frequency combinations sensitive to damage occurring within CFRP bonded joints. Active guided wave tests across three representative wing skin-to-spar joints at ambient temperature were then conducted using attached Macro Fiber Composite (MFC) transducers. Results from these experiments demonstrate the importance of intelligent feature extraction for improving the sensitivity to damage. To address the widely neglected effects of temperature on guided wave base damage identification, analytical and experimental analyses were performed to characterize the influence of temperature on guided wave signal features. In addition, statistically-robust detection of simulated damage in a CFRP bonded joint was successfully achieved under changing temperature conditions through a dimensionally-low, multivariate statistical outlier analysis. The response of piezoceramic patches and MFC transducers to ultrasonic Rayleigh and Lamb wave fields was analytically derived and experimentally validated. This theory is useful for designing sensors which possess optimal sensitivity toward a given mode-frequency combination or for predicting the frequency dependent

  9. Environmental Causes of CNS Maldevelopment

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2004-04-01

    Full Text Available Developmental processes and the effects of toxic agents in the environment that alter CNS growth and maturation are reviewed by a researcher in the Department of OB/GYN, University of Rochester Medical Center, Rochester, NY.

  10. Model assisted probability of detection for a guided waves based SHM technique

    Science.gov (United States)

    Memmolo, V.; Ricci, F.; Maio, L.; Boffa, N. D.; Monaco, E.

    2016-04-01

    Guided wave (GW) Structural Health Monitoring (SHM) allows to assess the health of aerostructures thanks to the great sensitivity to delamination and/or debondings appearance. Due to the several complexities affecting wave propagation in composites, an efficient GW SHM system requires its effective quantification associated to a rigorous statistical evaluation procedure. Probability of Detection (POD) approach is a commonly accepted measurement method to quantify NDI results and it can be effectively extended to an SHM context. However, it requires a very complex setup arrangement and many coupons. When a rigorous correlation with measurements is adopted, Model Assisted POD (MAPOD) is an efficient alternative to classic methods. This paper is concerned with the identification of small emerging delaminations in composite structural components. An ultrasonic GW tomography focused to impact damage detection in composite plate-like structures recently developed by authors is investigated, getting the bases for a more complex MAPOD analysis. Experimental tests carried out on a typical wing composite structure demonstrated the effectiveness of modeling approach in order to detect damages with the tomographic algorithm. Environmental disturbances, which affect signal waveforms and consequently damage detection, are considered simulating a mathematical noise in the modeling stage. A statistical method is used for an effective making decision procedure. A Damage Index approach is implemented as metric to interpret the signals collected from a distributed sensor network and a subsequent graphic interpolation is carried out to reconstruct the damage appearance. A model validation and first reliability assessment results are provided, in view of performance system quantification and its optimization as well.

  11. Dispersion curve veering of longitudinal guided waves propagating inside prestressed seven-wire strands

    Science.gov (United States)

    Treyssède, Fabien

    2016-04-01

    Elastic guided waves are of interest for the non-destructive evaluation of cables. Such structures are usually helical, multiwired and highly prestressed, which greatly complicates the understanding of wave propagation from a theoretical point of view. A remarkable feature is the occurrence of a missing frequency band in experimental time-frequency diagrams, sometimes referred to as notch frequency in the literature. The central frequency of this band increases under tensile loads. Recently, a numerical model has been proposed to compute the dispersion curves of prestressed helical seven-wire waveguides. Results have shown that the notch frequency indeed corresponds to a curve veering phenomenon between two longitudinal-like modes and that the increase of the notch under tensile loads is mainly due to interwire contact mechanisms. The main goal of this paper is to highlight the origin of this curve veering phenomenon, which is still unexplained up to the author's knowledge. This paper also provides further results which allow us to clarify the accuracy of numerical solutions as well as the influence of contact assumptions. First, the static part of the model, necessary to compute the prestress state including contact effects, is checked from reference analytical solutions. Owing to the importance of contact, the accuracy of results is discussed both in statics and in dynamics. The influence of slip contact conditions is outlined. Then, some numerical tests are conducted by varying the Poisson coefficient and the helix lay angle. These tests allows us to find out that the radial displacement constraint imposed on peripheral wires by the central one in the contact regions constitutes the main source of curve veering. More precisely, it is shown that a similar curve veering does occur for an uncoupled single peripheral wire when constrained by a radially blocked motion localized in its contact zone. Indeed, such a localized boundary condition completely breaks the

  12. Observation of ultrasonic guided wave propagation behaviours in pre-stressed multi-wire structures.

    Science.gov (United States)

    Liu, Xiucheng; Wu, Bin; Qin, Fei; He, Cunfu; Han, Qiang

    2017-01-01

    Ultrasonic guided wave (UGW) is a promising technique for nondestructive testing of pre-stressed multi-wire structures, such as steel strand and wire rope. The understanding of the propagation behaviours of UGW in these structures is a priority to applications. In the present study, first the properties of the UGW missing frequency band in the pre-stressed seven-wire steel strand is experimentally examined. The high correlation between the observed results and the previously published findings proves the feasibility of the magnetostrictive sensor (MsS) based testing method. The evolution of missing frequency band of UGW in slightly tensioned steel strand is discussed. Two calibration equations representing the relationship between the missing band parameters and the tensile force are given to derive a new tensile force measurement method, which is capable of measuring an incremental of stress of approximately 3MPa. Second, the effects of tensile force on the UGW propagation behaviours in three types of complicated steel wire ropes are alternatively investigated based on the short time Fourier transform (STFT) results of the received direct transmission wave (DTW) signals. The observed inherent missing frequency band of the longitudinal mode UGW in the pre-stressed steel wire rope and its shifting to a higher frequency range as the increases of the applied tensile force are reported for the first time. The influence of applied tensile force on the amplitude of the DTW signal and the unique UGW energy jump behaviour observed in a wire rope of 16.0mm, 6×Fi(29)+IWRC are also investigated, despite the fact that they cannot yet be explained.

  13. Surface-plasmon-polariton wave propagation guided by a metal slab in a sculptured nematic thin film

    CERN Document Server

    Faryad, Muhammad

    2010-01-01

    Surface-plasmon-polariton~(SPP) wave propagation guided by a metal slab in a periodically nonhomogeneous sculptured nematic thin film~(SNTF) was studied theoretically. The morphologically significant planes of the SNTF on both sides of the metal slab could either be aligned or twisted with respect to each other. The canonical boundary-value problem was formulated, solved for SPP-wave propagation, and examined to determine the effect of slab thickness on the multiplicity and the spatial profiles of SPP waves. Decrease in slab thickness was found to result in more intense coupling of two metal/SNTF interfaces. But when the metal slab becomes thicker, the coupling between the two interfaces reduces and SPP waves localize to one of the two interfaces. The greater the coupling between the two metal/SNTF interfaces, the smaller is the phase speed.

  14. Left/right asymmetry in Dyakonov-Tamm-wave propagation guided by a topological insulator and a structurally chiral material

    Science.gov (United States)

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

    2016-11-01

    The propagation of Dyakonov-Tamm waves guided by the planar interface of an isotropic topological insulator and a structurally chiral material, both assumed to be nonmagnetic, was investigated by numerically solving the associated canonical boundary-value problem. The topologically insulating surface states of the topological insulator were quantitated via a surface admittance {γ }{{TI}}, which significantly affects the phase speeds and the spatial profiles of the Dyakonov-Tamm waves. Most significantly, it is possible that a Dyakonov-Tamm wave propagates co-parallel to a vector {u} in the interface plane, but no Dyakonov-Tamm wave propagates anti-parallel to {u}. The left/right asymmetry, which vanishes for {γ }{{TI}}=0, is highly attractive for one-way on-chip optical communication.

  15. The development of radiation hardened robot for nuclear facility; development of ultrasonic guided wave evaluation technology for the in-service/post-repair inspection of steam generator tubings

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Youn Ho [Inje University, Kimhae (Korea)

    2002-04-01

    The Potential of Ultrasonic Guided Waves which can propagate along the geometry of structures was explored for the inspection of such various components of nuclear power plants as tubings, pipings and plate-like structures etc. In this project, the fundamental research on the various aspects of guided wave modal characteristics was carried out to provide physically based guidelines which are essential to implement the guided waves as a promising inspection tool in the near future. The efforts for guided wave research include both theoretical and experimental works to make it possible to transfer the technology to power industry beyond the scope of pure academic subject. In the theoretical works, the softwares for the dispersion curves and wave structures of both layered structures and cylindrical ones were developed in the aims of mode identification and determination of probe design parameters. 40 refs., 92 figs., 14 tabs. (Author)

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

    Science.gov (United States)

    Ren, Baiyang

    Composite materials, especially carbon fiber reinforced polymers (CFRP), have been widely used in the aircraft industry because of their high specific strength and stiffness, resistance to corrosion and good fatigue life. Due to their highly anisotropic material properties and laminated structures, joining methods like bolting and riveting are no longer appropriate for joining CFRP since they initiate defects during the assembly and severely compromise the integrity of the structure; thus new techniques for joining CFRP are highly demanded. Adhesive bonding is a promising method because it relieves stress concentration, reduces weight and provides smooth surfaces. Additionally, it is a low-cost alternative to the co-cured method which is currently used to manufacture components of aircraft fuselage. Adhesive defects, disbonds at the interface between adherend and adhesive layer, are focused on in this thesis because they can be initialized by either poor surface preparation during the manufacturing or fatigue loads during service. Aircraft need structural health monitoring (SHM) systems to increase safety and reduce loss, and adhesive bonds usually represent the hotspots of the assembled structure. There are many nondestructive evaluation (NDE) methods for bond inspection. However, these methods cannot be readily integrated into an SHM system because of the bulk size and weight of the equipment and requirement of accessibility to one side of the bonded joint. The first objective of this work is to develop instruments, actuators, sensors and a data acquisition system for SHM of bond lines using ultrasonic guided waves which are well known to be able to cover large volume of the structure and inaccessible regions. Different from widely used guided wave sensors like PZT disks, the new actuators, piezoelectric fiber composite (PFC) phased array transducers0 (PAT), can control the modal content of the excited waves and the new sensors, polyvinylidene fluoride (PVDF

  17. The matching pursuit approach based on the modulated Gaussian pulse for efficient guided-wave damage inspection

    Science.gov (United States)

    Hong, Jin-Chul; Sun, Kyung Ho; Kim, Yoon Young

    2005-08-01

    The success of the guided-wave damage inspection technology depends not only on the generation and measurement of desired waveforms but also on the signal processing of the measured waves, but less attention has been paid to the latter. This research aims to develop an efficient signal processing technique especially suitable for the current guided-wave technology. To achieve this objective, the use of a two-stage matching pursuit approach based on the Gabor dictionary is proposed. Instead of truncated sine pulses commonly used in waveguide inspection, Gabor pulses, the modulated Gaussian pulses, are chosen as the elastic energy carrier to facilitate the matching pursuit algorithm. To extract meaningful waves out of noisy signals, a two-stage matching pursuit strategy is developed, which consists of the following: rough approximations with a set of predetermined parameters characterizing the Gabor pulse, and fine adjustments of the parameters by optimization. The parameters estimated from measured longitudinal elastic waves can be then directly used to assess not only the location but also the size of a crack in a rod. For the estimation of the crack size, in particular, Love's theory is incorporated in the matching pursuit analysis. Several experiments were conducted to verify the validity of the proposed approach in damage assessment.

  18. Acoustic guided waves in cylindrical solid-fluid structures: Modeling with a sweeping frequency finite element method and experimental validation

    Science.gov (United States)

    Liu, Yang; D'Angelo, Ralph M.; Sinha, Bikash K.; Zeroug, Smaine

    2017-02-01

    Modeling and understanding the complex elastic-wave physics prevalent in solid-fluid cylindrically-layered structures is of importance in many NDE fields, and most pertinently in the domain of well integrity evaluation of cased holes in the oil and gas industry. Current sonic measurements provide viable techniques for well integrity evaluation yet their practical effectiveness is hampered by the current lack of knowledge of acoustic wave fields particularly in complicated cased-hole geometry where for instance two or more nested steel strings are present in the borehole. In this article, we propose and implement a Sweeping Frequency Finite Element Method (SFFEM) for acoustic guided waves simulation in complex geometries that include double steel strings cemented to each other and to the formation and where the strings may be non-concentric. Transient dynamic finite element models are constructed with sweeping frequency signals being applied as the excitation sources. The sources and receivers disposition simulate current sonic measurement tools deployed in the oilfield. Synthetic wavetrains are recorded and processed with modified matrix pencil method to isolate both the dispersive and non-dispersive propagating guided wave modes. Scaled experiments of fluid-filled double strings with dimensions mimicking the real ones encountered in the field have also been carried out to generate reference data. A comparison of the experimental and numerical results indicates that the SFFEM is capable of accurately reproducing the rich and intricate higher-order multiple wave fields observed experimentally in the fluid-filled double string geometries.

  19. Sodium vapor cell laser guide star experiments for continuous wave model validation

    Science.gov (United States)

    Pedreros Bustos, Felipe; Holzlöhner, Ronald; Budker, Dmitry; Lewis, Steffan; Rochester, Simon

    2016-07-01

    Recent numerical simulations and experiments on sodium Laser Guide Star (LGS) have shown that a continuous wave (CW) laser with circular polarization and re-pumping should maximize the fluorescent photon return flux to the wavefront sensor for adaptive optics applications. The orientation and strength of the geomagnetic field in the sodium layer also play an important role affecting the LGS return ux. Field measurements of the LGS return flux show agreement with the CW LGS model, however, fluctuations in the sodium column abundance and geomagnetic field intensity, as well as atmospheric turbulence, induce experimental uncertainties. We describe a laboratory experiment to measure the photon return flux from a sodium vapor cell illuminated with a 589 nm CW laser beam, designed to approximately emulate a LGS under controlled conditions. Return flux measurements are carried out controlling polarization, power density, re-pumping, laser linewidth, and magnetic field intensity and orientation. Comparison with the numerical CW simulation package Atomic Density Matrix are presented and discussed.

  20. Rapid guided wave delamination detection and quantification in composites using global-local sensing

    Science.gov (United States)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara

    2016-08-01

    This paper presents a rapid guided ultrasonic wave inspection approach through global inspection by phased array beamforming and local damage evaluation via wavenumber analysis. The global-local approach uses a hybrid system consisting of a PZT wafer and a non-contact laser vibrometer. The overall inspection is performed in two steps. First, a phased array configured by a small number of measurements performs beamforming and beamsteering over the entire plate in order to detect and locate the presence of the damage. A local area is identified as target damage area for the second step. Then a high density wavefield measurement is taken over the target damage area and a spatial wavenumber imaging is performed to quantitatively evaluate the damage. The two-step inspection has been applied to locate and quantify impact-induced delamination damage in a carbon fiber reinforced polymer composite plate. The detected delamination location, size and shape agree well with those of an ultrasonic C-scan. For the test case studied in this work the global-local approach reduced the total composite inspection (damage detection and characterization) time by ∼97% compared to using a full scan approach.

  1. A detailed study of guided wave propagation in a viscoelastic multilayered anisotropic plate

    Energy Technology Data Exchange (ETDEWEB)

    Taupin, L; Lhemery, A [CEA, institut LIST, centre de Saclay, bat. 611, point courrier 120, F-91191 Gif-sur-Yvette cedex (France); Inquiete, G, E-mail: alain.lhemery@cea.fr [EADS - Innovation Works, 12, rue Pasteur, BP76, F-92152 Suresnes cedex (France)

    2011-01-01

    Guided waves (GW) are very attractive in nondestructive technique applications (eg. Structural Health Monitoring) because of their ability to propagate at long range. In a structure made of composite materials, their propagation is complex due to material anisotropy and to their dispersive and multi-modal nature. Interpreting measurements of GW in such a structure requires a sound grasp of their behaviour. Here, the Semi-Analytical Finite Element (SAFE) method is used for studying GW propagation in viscoelastic multilayered anisotropic plates. Beside classical post-processing techniques used to compute the displacement, dispersion and slowness curves, the Poynting vector is also obtained, allowing us to study energy propagation in complex plate structures. Then, GW propagation in multilayered viscoelastic composite (C-epoxy) plates is studied; different stacking sequences typical of those used to build aeronautical parts are considered. Phase, energy velocities and attenuation are studied for different propagation directions and frequencies. It appears that symmetries of GW behaviour are complex: the axes of symmetry depicting this behaviour do not coincide with those of stacking sequences and depend on frequency. Modes appearing above the first cut-off frequency have such a complex behaviour that they cannot be used in practical applications.

  2. Evaluation of weld defects in stainless steel 316L pipe using guided wave

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Joon Hyun [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of); Lee, Jin Kyung [Dept. of Mechanical Engineering, Dongeui University, Busan (Korea, Republic of)

    2015-02-15

    Stainless steel is a popular structural materials for liquid-hydrogen storage containers and piping components for transporting high-temperature fluids because of its superior material properties such as high strength and high corrosion resistance at elevated temperatures. In general, tungsten inert gas (TIG) arc welding is used for bonding stainless steel. However, it is often reported that the thermal fatigue cracks or initial defects in stainless steel after welding decreases the reliability of the material. The objective of this paper is to clarify the characteristics of ultrasonic guided wave propagation in relation to a change in the initial crack length in the welding zone of stainless steel. For this purpose, three specimens with different artificial defects of 5 mm, 10 mm, and 20 mm in stainless steel welds were prepared. By considering the thickness of s stainless steel pipe, special attention was given to both the L(0,1) mode and L(0,2) mode in this study. It was clearly found that the L(0,2) mode was more sensitive to defects than the L(0,1) mode. Based on the results of the L(0,1) and L(0,2) mode analyses, the magnitude ratio of the two modes was more effective than studying each mode when evaluating defects near the welded zone of stainless steel because of its linear relationship with the length of the artificial defect.

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

    Science.gov (United States)

    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.

  4. Microwave pre-heating of natural rubber using a rectangular wave guide (MODE: TE10

    Directory of Open Access Journals (Sweden)

    Doo-ngam, N.

    2007-11-01

    Full Text Available This paper presents an application of microwave radiation for pre-heating of natural rubbercompounding with various sulphur contents. The natural rubber-compounding was pre-heated by microwave radiation using a rectangular wave guide system (MODE: TE10 operating at frequency of 2.45 GHz in which the power can vary from 0 to 1500 W. In the present work, the influence of power input, sample thickness, and sulphur content were examined after applying microwave radiation to the rubber samples. Results are discussed regarding the thermal properties, 3-D network, dielectric properties and chemical structures. From the result, firstly, it was found that microwave radiation can be applied to pre-heating natural rubber-compounding before the vulcanization process. Secondly, microwave radiation was very useful for pre-heating natural rubber-compounding that has a thickness greater than 5mm. Thirdly, crosslinking in natural rubber-compounding may occurs after pre-heating by microwave radiation though Fourier Transform Infrared Spectroscopy(FTIR. Finally, there a little effect of sulphur content on temperature profiles after applying microwave radiation to the natural rubber-compounding. Moreover, natural rubber-compounding without carbon black showed a lower heat absorption compared with natural rubbercompounding filled carbon black. This is due to the difference in dielectric loss factor. This preliminary result will be useful information in terms of microwave radiation for pre-heating natural rubber-compounding and rubber processing in industry.

  5. Guided lamb wave electroacoustic devices on micromachined AlN/Al plates.

    Science.gov (United States)

    Di Pietrantonio, Fabio; Benetti, Massimiliano; Cannatà, Domenico; Beccherelli, Romeo; Verona, Enrico

    2010-05-01

    An electroacoustic micro-device based on the propagation of guided acoustic Lamb waves in AlN/Al plate is described. The AlN thin film is deposited by sputtering technique, optimized to achieve a high degree of orientation (rocking curve full-width at half-maximum /sp lap/ 3.5 degrees ) of the c-axis perpendicular to the plate surface. The AlN plate is micromachined using anisotropic reactive ion etching (RIE), followed by isotropic RIE to remove the silicon underlayer. Simulation results for the dispersion phase velocity curves and the electromechanical coupling coefficient (K(2)) are obtained by the matrix method and by the finite element method and compared with experimental data. A delay line is implemented on the structure and tested for the propagation of the first symmetrical Lamb mode (s(0)) at the frequency of 1.22 GHz. Measurements have shown that the structure is suitable for implementation of arrays of electroacoustic devices on a single chip for application to both sensing devices and signal processing systems.

  6. Influence of resonant transducer variations on long range guided wave monitoring of rail track

    Science.gov (United States)

    Loveday, Philip W.; Long, Craig S.

    2016-02-01

    The ability of certain guided wave modes to propagate long distances in continuously welded rail track is exploited in permanently installed monitoring systems. Previous work demonstrated that reflections from thermite welds could be measured at distances of the order of 1 km from a transducer array. The availability of numerous thermite welds is useful during the development of a monitoring system as real defects are not available. Measurements of reflections from welds were performed over an eleven month period with two permanently installed transducers. Phased array processing was performed and the true location of a weld is indicated by a strong reflection but there is generally also a smaller, spurious replica reflection, at the same distance but in the incorrect direction. In addition, the relative reflection from different welds appears to change over time. The influence of differences between the two resonant transducers was investigated using a model. It was found that estimating the attenuation in either direction and scaling the reflections in either direction decreased the variability in the reflection measurements. Transducer interaction effects, where the transducer closer to the weld records a greater reflection than the second transducer were observed and can be used to determine the direction of a weld. This feature was used to demonstrate a simple alternative to phased array processing that can be used with resonant transducers.

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

    Science.gov (United States)

    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.

  8. MMS observations of plasma wave and electron energization in the electron diffusion region of asymmetric reconnection with strong guide field

    Science.gov (United States)

    Xiao, Chijie; Zhao, Siqi; Shi, Mijie; Pu, Zuyin; Wang, Xiaogang

    2016-10-01

    Here we report an asymmetric reconnection event with strong guide field observed by Magnetospheric Multiscale Mission (MMS) on the dayside magnetopause. In this event there are multiple wave modes, such as electron Alfvenic mode, broadband waves between the lower-hybrid and electron cyclotron frequencies, exist in the vicinity of the electron diffusion region and the separatrix. And the electron velocity distribution functions show that bi-stream electrons with low energy (processes are investigated and comparison with some 3D numerical simulation results. This work was supported by NSFC (Grants 41274168 and 11375053).

  9. A Signal Processing Approach with a Smooth Empirical Mode Decomposition to Reveal Hidden Trace of Corrosion in Highly Contaminated Guided Wave Signals for Concrete-Covered Pipes.

    Science.gov (United States)

    Rostami, Javad; Chen, Jingming; Tse, Peter W

    2017-02-07

    Ultrasonic guided waves have been extensively applied for non-destructive testing of plate-like structures particularly pipes in past two decades. In this regard, if a structure has a simple geometry, obtained guided waves' signals are easy to explain. However, any small degree of complexity in the geometry such as contacting with other materials may cause an extra amount of complication in the interpretation of guided wave signals. The problem deepens if defects have irregular shapes such as natural corrosion. Signal processing techniques that have been proposed for guided wave signals' analysis are generally good for simple signals obtained in a highly controlled experimental environment. In fact, guided wave signals in a real situation such as the existence of natural corrosion in wall-covered pipes are much more complicated. Considering pipes in residential buildings that pass through concrete walls, in this paper we introduced Smooth Empirical Mode Decomposition (SEMD) to efficiently separate overlapped guided waves. As empirical mode decomposition (EMD) which is a good candidate for analyzing non-stationary signals, suffers from some shortcomings, wavelet transform was adopted in the sifting stage of EMD to improve its outcome in SEMD. However, selection of mother wavelet that suits best for our purpose plays an important role. Since in guided wave inspection, the incident waves are well known and are usually tone-burst signals, we tailored a complex tone-burst signal to be used as our mother wavelet. In the sifting stage of EMD, wavelet de-noising was applied to eliminate unwanted frequency components from each IMF. SEMD greatly enhances the performance of EMD in guided wave analysis for highly contaminated signals. In our experiment on concrete covered pipes with natural corrosion, this method not only separates the concrete wall indication clearly in time domain signal, a natural corrosion with complex geometry that was hidden and located inside the

  10. An investigation of student understanding of wave phenomena at a boundary as a guide to the development and assessment of instructional materials on mechanical waves

    Science.gov (United States)

    Kryjevskaia, Lioudmila N.

    This dissertation reports on an in-depth investigation of student understanding of wave phenomena at a boundary. The research and curriculum development were conducted in the contexts of the introductory calculus-based physics course and special courses for preservice and inservice teachers. Research methods included pretests, post-tests, and informal observations and discussions with students. Several student difficulties with wave behavior at a boundary and the cause and effect relationship between wavelength, frequency, and propagation speed were identified. The results from this investigation have guided the development of two sets of instructional materials designed to address the conceptual and reasoning difficulties that were identified. The first is a sequence of tutorials intended to supplement standard lecture and laboratory instruction on mechanical waves in a traditional introductory course. The second consists of a module on mechanical waves designed for use in inquiry-oriented courses for preservice and inservice teachers. Ongoing assessment of both sets of materials indicates that they are effective in addressing many of the student difficulties that were found to be persistent. Such difficulties, when not addressed, may hinder student understanding of more advanced topics such as interference and diffraction of waves.

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

    CERN Document Server

    Gao, Zhen; Zhang, Baile

    2016-01-01

    We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices.

  12. Multi-site delamination detection and quantification in composites through guided wave based global-local sensing

    Science.gov (United States)

    Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

    2017-02-01

    This paper presents a guided wave based global-local sensing method for rapid detection and quantification of multi-site delamination damage in large composite panels. The global-local approach uses a hybrid system consisting of a piezoelectric transducer (PZT) for generating guided waves and a non-contact scanning laser Doppler vibrometer (SLDV) for acquiring guided wave data. The global-local method is performed in two steps. First, a phased array configured of a small number of SLDV scan points (for example 10×10 points in a rectangular grid array) performs inspection over the entire plate to detect and locate damage. Local areas are identified as potential damage regions for the second step. Then high density wavefield measurements are taken over the identified areas and wavefield analysis is performed to quantitatively evaluate the damage. For the proof of concept in case with multi-site damage, the global-local approach is demonstrated on a carbon fiber reinforced polymer (CFRP) composite plate with two sites of impact-induced delamination damage. In the first step, the locations of two delamination sites are detected by the phased array method. In the second step, the delamination size and shape are evaluated using wavefield analysis. The detected delamination location, size and shape agree well with those of ultrasonic C-scan and the method led to a 93% reduction in inspection time compared to a full SLDV dense grid scan.

  13. Deconvolution imaging of weak reflective pipe defects using guided-wave signals captured by a scanning receiver.

    Science.gov (United States)

    Sun, Zeqing; Sun, Anyu; Ju, Bing-Feng

    2017-02-01

    Guided-wave echoes from weak reflective pipe defects are usually interfered by coherent noise and difficult to interpret. In this paper, a deconvolution imaging method is proposed to reconstruct defect images from synthetically focused guided-wave signals, with enhanced axial resolution. A compact transducer, circumferentially scanning around the pipe, is used to receive guided-wave echoes from discontinuities at a distance. This method achieves a higher circumferential sampling density than arrayed transducers-up to 72 sampling spots per lap for a pipe with a diameter of 180 mm. A noise suppression technique is used to enhance the signal-to-noise ratio. The enhancement in both signal-to-noise ratio and axial resolution of the method is experimentally validated by the detection of two kinds of artificial defects: a pitting defect of 5 mm in diameter and 0.9 mm in maximum depth, and iron pieces attached to the pipe surface. A reconstructed image of the pitting defect is obtained with a 5.87 dB signal-to-noise ratio. It is revealed that a high circumferential sampling density is important for the enhancement of the inspection sensitivity, by comparing the images reconstructed with different down-sampling ratios. A modified full width at half maximum is used as the criterion to evaluate the circumferential extent of the region where iron pieces are attached, which is applicable for defects with inhomogeneous reflection intensity.

  14. Instantaneous wave-free ratio to guide coronary revascularization: physiological framework, validation and differences with fractional flow reserve.

    Science.gov (United States)

    de Waard, Guus A; Di Mario, Carlo; Lerman, Amir; Serruys, Patrick W; van Royen, Niels

    2017-02-14

    Determining the optimal treatment strategy for revascularization of coronary artery stenosis involves the use of fractional flow reserve (FFR). To improve the low clinical uptake of physiological lesion assessment to guide revascularization, the instantaneous wave-free period (iFR) was proposed as a simpler alternative to FFR that does not require adenosine administration. iFR is calculated as the ratio of blood pressure distal and proximal to a coronary artery stenosis during the diastolic wave- free period. The wave-free period is a part of the cardiac cycle where generation of new pressure wavefronts does not occur and resting microvascular resistance is relatively minimized. iFR indicates the hemodynamic severity of a stenosis, by assessing the extent to which the epicardial stenosis depletes the microcirculatory, autoregulatory reserve. The introduction of iFR and the potential to assess hemodynamic stenosis severity without the need for administration of potent vasodilators such as adenosine, sparked an interesting debate about the fundamentals of human coronary physiology. Outcomes of two randomized clinical trials investigating iFR are pending. These studies are designed to evaluate whether iFR guided revascularisation is non-inferior to an FFR guided approach. The purpose of this review article is to discuss the physiological concepts underlying iFR, examine the existing validation studies and discuss the advantages and disadvantages of iFR as compared to FFR.

  15. Non-Hermiticity-Induced Wave Confinement and Guiding in Loss-Gain-Loss Three-Layer Systems

    CERN Document Server

    Savoia, Silvio; Galdi, Vincenzo

    2016-01-01

    Following up on previous studies on parity-time-symmetric gain-loss bi-layers, and inspired by formal analogies with plasmonic waveguides, we study non-Hermiticity-induced wave confinement and guiding phenomena that can occur in loss-gain-loss three-layers. By revisiting previous well-established "gain-guiding" concepts, we investigate analytically and numerically the dispersion and confinement properties of guided modes that can be supported by this type of structures, by assuming realistic dispersion models and parameters for the material constituents. As key outcomes, we identify certain modes with specific polarization and symmetry that exhibit particularly desirable characteristics, in terms of quasi-real propagation constant and sub-wavelength confinement. Moreover, we elucidate the effects of material dispersion and parameters, and highlight the potential advantages by comparison with the previously studied gain-loss bi-layer configurations. Our results provide additional perspectives on light control ...

  16. Performance of Wells TUrbine with Guide Vanes for Wave Energy COnversion

    Institute of Scientific and Technical Information of China (English)

    ManabuTakao; ShenYu; 等

    1996-01-01

    In order to improve the performance of a wells turbine the effect of guide vanes with various gaps between turbine rotor and guide vane has been clarified by model testing and numerical simulation.The results have been compared with those of the case without guide vanes,It is found that the overall Characteritics are considerably improved by the inlet guide vanes.Furthermore,a suitable choice of design factor for the gap has been suggested.

  17. Increased range of ultrasonic guided wave testing of overhead transmission line cables using dispersion compensation.

    Science.gov (United States)

    Legg, Mathew; Yücel, Mehmet K; Kappatos, Vassilios; Selcuk, Cem; Gan, Tat-Hean

    2015-09-01

    Overhead Transmission Line (OVTL) cables can experience structural defects and are, therefore, inspected using Non-Destructive Testing (NDT) techniques. Ultrasonic Guided Waves (UGW) is one NDT technique that has been investigated for inspection of these cables. For practical use, it is desirable to be able to inspect as long a section of cable as possible from a single location. This paper investigates increasing the UGW inspection range on Aluminium Conductor Steel Reinforced (ACSR) cables by compensating for dispersion using dispersion curve data. For ACSR cables, it was considered to be difficult to obtain accurate dispersion curves using modelling due to the complex geometry and unknown coupling between wire strands. Group velocity dispersion curves were, therefore, measured experimentally on an untensioned, 26.5m long cable and a method of calculating theoretical dispersion curves was obtained. Attenuation and dispersion compensation were then performed for a broadband Maximum Length Sequence (MLS) excitation signal. An increase in the Signal to Noise Ratio (SNR) of about 4-8dB compared to that of the dispersed signal was obtained. However, the main benefit was the increased ability to resolve the individual echoes from the end of the cable and an introduced defect in the form of a cut, which was 7 to at least 13dB greater than that of the dispersed signal. Five echoes were able to be clearly detected using MLS excitation signal, indicating the potential for an inspection range of up to 130m in each direction. To the best of the authors knowledge, this is the longest inspection range for ACSR cables reported in the literature, where typically cables, which were only one or two meter long, have been investigated previously. Narrow band tone burst and Hann windowed tone burst excitation signal also showed increased SNR and ability to resolve closely spaced echoes. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Advanced signal processing methods applied to guided waves for wire rope defect detection

    Science.gov (United States)

    Tse, Peter W.; Rostami, Javad

    2016-02-01

    Steel wire ropes, which are usually composed of a polymer core and enclosed by twisted wires, are used to hoist heavy loads. These loads are different structures that can be clamshells, draglines, elevators, etc. Since the loading of these structures is dynamic, the ropes are working under fluctuating forces in a corrosive environment. This consequently leads to progressive loss of the metallic cross-section due to abrasion and corrosion. These defects can be seen in the forms of roughened and pitted surface of the ropes, reduction in diameter, and broken wires. Therefore, their deterioration must be monitored so that any unexpected damage or corrosion can be detected before it causes fatal accident. This is of vital importance in the case of passenger transportation, particularly in elevators in which any failure may cause a catastrophic disaster. At present, the widely used methods for thorough inspection of wire ropes include visual inspection and magnetic flux leakage (MFL). Reliability of the first method is questionable since it only depends on the operators' eyes that fails to determine the integrity of internal wires. The later method has the drawback of being a point by point and time-consuming inspection method. Ultrasonic guided wave (UGW) based inspection, which has proved its capability in inspecting plate like structures such as tubes and pipes, can monitor the cross-section of wire ropes in their entire length from a single point. However, UGW have drawn less attention for defect detection in wire ropes. This paper reports the condition monitoring of a steel wire rope from a hoisting elevator with broken wires as a result of corrosive environment and fatigue. Experiments were conducted to investigate the efficiency of using magnetostrictive based UGW for rope defect detection. The obtained signals were analyzed by two time-frequency representation (TFR) methods, namely the Short Time Fourier Transform (STFT) and the Wavelet analysis. The location of

  19. CNS Anticancer Drug Discovery and Development Conference White Paper.

    Science.gov (United States)

    Levin, Victor A; Tonge, Peter J; Gallo, James M; Birtwistle, Marc R; Dar, Arvin C; Iavarone, Antonio; Paddison, Patrick J; Heffron, Timothy P; Elmquist, William F; Lachowicz, Jean E; Johnson, Ted W; White, Forest M; Sul, Joohee; Smith, Quentin R; Shen, Wang; Sarkaria, Jann N; Samala, Ramakrishna; Wen, Patrick Y; Berry, Donald A; Petter, Russell C

    2015-11-01

    Following the first CNS Anticancer Drug Discovery and Development Conference, the speakers from the first 4 sessions and organizers of the conference created this White Paper hoping to stimulate more and better CNS anticancer drug discovery and development. The first part of the White Paper reviews, comments, and, in some cases, expands on the 4 session areas critical to new drug development: pharmacological challenges, recent drug approaches, drug targets and discovery, and clinical paths. Following this concise review of the science and clinical aspects of new CNS anticancer drug discovery and development, we discuss, under the rubric "Accelerating Drug Discovery and Development for Brain Tumors," further reasons why the pharmaceutical industry and academia have failed to develop new anticancer drugs for CNS malignancies and what it will take to change the current status quo and develop the drugs so desperately needed by our patients with malignant CNS tumors. While this White Paper is not a formal roadmap to that end, it should be an educational guide to clinicians and scientists to help move a stagnant field forward. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. A Signal Processing Approach with a Smooth Empirical Mode Decomposition to Reveal Hidden Trace of Corrosion in Highly Contaminated Guided Wave Signals for Concrete-Covered Pipes

    Directory of Open Access Journals (Sweden)

    Javad Rostami

    2017-02-01

    Full Text Available Ultrasonic guided waves have been extensively applied for non-destructive testing of plate-like structures particularly pipes in past two decades. In this regard, if a structure has a simple geometry, obtained guided waves’ signals are easy to explain. However, any small degree of complexity in the geometry such as contacting with other materials may cause an extra amount of complication in the interpretation of guided wave signals. The problem deepens if defects have irregular shapes such as natural corrosion. Signal processing techniques that have been proposed for guided wave signals’ analysis are generally good for simple signals obtained in a highly controlled experimental environment. In fact, guided wave signals in a real situation such as the existence of natural corrosion in wall-covered pipes are much more complicated. Considering pipes in residential buildings that pass through concrete walls, in this paper we introduced Smooth Empirical Mode Decomposition (SEMD to efficiently separate overlapped guided waves. As empirical mode decomposition (EMD which is a good candidate for analyzing non-stationary signals, suffers from some shortcomings, wavelet transform was adopted in the sifting stage of EMD to improve its outcome in SEMD. However, selection of mother wavelet that suits best for our purpose plays an important role. Since in guided wave inspection, the incident waves are well known and are usually tone-burst signals, we tailored a complex tone-burst signal to be used as our mother wavelet. In the sifting stage of EMD, wavelet de-noising was applied to eliminate unwanted frequency components from each IMF. SEMD greatly enhances the performance of EMD in guided wave analysis for highly contaminated signals. In our experiment on concrete covered pipes with natural corrosion, this method not only separates the concrete wall indication clearly in time domain signal, a natural corrosion with complex geometry that was hidden and

  1. Efficient wideband guided-wave acoustooptic Bragg diffraction using phased surface acoustic wave array in LiNbO(3) waveguides.

    Science.gov (United States)

    Nguyen, L T; Tsai, C S

    1977-05-01

    Efficient wideband guided-wave acoustooptic Bragg diffraction has been demonstrated using a phased surface acoustic wave array in Y-cut LiNbO(3) waveguides. The results of measurement made on the devices which employ the first-order acoustic beam steering from six-element phased-SAWs of relatively small total acoustic aperture, at the center frequency of 325 MHz, have shown that accurate tracking of the Bragg condition is achievable for a frequency band of more than 250 MHz. In one of the deflectors that employ a larger total acoustic aperture, only 68 mW of electric drive power or 3.5 mW of acoustic power was required to diffract 50% of the light over a bandwidth of 112 MHz. This bandwidth is a nearly sixfold increase over that of the deflector that employs a single SAW of identical aperture. The quality of both deflected and undeflected light beams was very good.

  2. Genetic models for CNS inflammation

    DEFF Research Database (Denmark)

    Owens, T; Wekerle, H; Antel, J

    2001-01-01

    The use of transgenic technology to over-express or prevent expression of genes encoding molecules related to inflammation has allowed direct examination of their role in experimental disease. This article reviews transgenic and knockout models of CNS demyelinating disease, focusing primarily on ...

  3. Basic Concepts of CNS Development.

    Science.gov (United States)

    Nowakowski, R. S.

    1987-01-01

    The goals of this review are to: (1) provide a set of concepts to aid in the understanding of complex processes which occur during central nervous system (CNS) development; (2) illustrate how they contribute to our knowlege of adult brain anatomy; and (3) delineate how modifications of normal developmental processes may affect the structure and…

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

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhen; Gao, Fei [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Zhang, Baile, E-mail: blzhang@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore, Singapore 637371 (Singapore)

    2016-01-25

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

  5. Observation of skull-guided acoustic waves in a water-immersed murine skull using optoacoustic excitation

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

    2017-02-01

    The skull bone, a curved solid multilayered plate protecting the brain, constitutes a big challenge for the use of ultrasound-mediated techniques in neuroscience. Ultrasound waves incident from water or soft biological tissue are mostly reflected when impinging on the skull. To this end, skull properties have been characterized for both high-intensity focused ultrasound (HIFU) operating in the narrowband far-field regime and optoacoustic imaging applications. Yet, no study has been conducted to characterize the near-field of water immersed skulls. We used the thermoelastic effect with a 532 nm pulsed laser to trigger a wide range of broad-band ultrasound modes in a mouse skull. In order to capture the waves propagating in the near-field, a thin hydrophone was scanned in close proximity to the skull's surface. While Leaky pseudo-Lamb waves and grazing-angle bulk water waves are clearly visible in the spatio-temporal data, we were only able to identify skull-guided acoustic waves after dispersion analysis in the wavenumber-frequency space. The experimental data was found to be in a reasonable agreement with a flat multilayered plate model.

  6. Surface-plasmon-polariton waves guided by the uniformly moving planar interface of a metal film and dielectric slab

    CERN Document Server

    Mackay, Tom G

    2010-01-01

    We explored the effects of relative motion on the excitation of surface-plasmon-polariton (SPP) waves guided by the planar interface of a metal film and a dielectric slab, both materials being isotropic and homogeneous. Electromagnetic phasors in moving and non-moving reference frames were related directly using the corresponding Lorentz transformations. Our numerical studies revealed that, in the case of a uniformly moving dielectric slab, the angle of incidence for SPP-wave excitation is highly sensitive to (i) the ratio $\\beta$ of the speed of motion to speed of light in free space and (ii) the direction of motion. When the direction of motion is parallel to the plane of incidence, the SPP wave is excited by $p$-polarized (but not $s$-polarized) incident plane waves for low and moderate values of $\\beta$, while at higher values of $\\beta$ the total reflection regime breaks down. When the direction of motion is perpendicular to the plane of incidence, the SPP wave is excited by $p$-polarized incident plane ...

  7. Modal approach for the full simulation of nondestructive tests by elastic guided waves; Approche modale pour la simulation globale de controles non-destructifs par ondes elastiques guidees

    Energy Technology Data Exchange (ETDEWEB)

    Jezzine, K

    2006-11-15

    Tools for simulating nondestructive tests by elastic guided waves are developed. Two overall formulations based on modal formalism and reciprocity are derived depending on whether transmission and reception are separated or not. They relate phenomena of guided wave radiation by a transducer, their propagation, their scattering by a non-uniformity of the guide or a defect and their reception. Receiver electrical output is expressed as a product of terms relating to each phenomenon that can be computed separately. Their computation uses developments based on the semi-analytical finite elements method, dealing with guides of arbitrary cross-section and cracks normal to the guide axis. Simulation tools are used to study means for selecting a single mode using a transducer positioned on the guide section, such a selection making easier the interpretation of the results of testing by guided waves. Two methods of mode selection are proposed, based on the use of two specific frequencies (which existence depends on guide geometry and mode symmetry). Mimicking the normal stress distribution of the mode at one of these two frequencies or the other makes it possible to radiate solely or predominantly the mode chosen. Examinations are simulated in configurations using a single or two separated transducers positioned on the section of various guide geometries and cracks of various shapes. The interest and performances of the two methods of mode selection are studied in these configurations. (author)

  8. Effect of front guide nozzle shape on the flow characteristics in an augmentation channel of a direct drive turbine for wave power generation

    Institute of Scientific and Technical Information of China (English)

    Deepak; PRASAD; Mohammed; Asid; ZULLAH; Mohammed; Rafiuddin; AHMED; Young-Ho; LEE

    2010-01-01

    There is an increasing interest in cross flow turbines(also known as Banki turbines) for small and low head applications because of their simple structure as well as low capital and maintenance costs.The present work aims at implementing the direct drive turbine(DDT) of cross flow type for wave power generation.A numerical wave tank was used to simulate the waves and after obtaining the desired wave properties;the augmentation channel plus the front guide nozzle and rear chamber were integrated to the numerical wave tank.The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet.The inlet which was modeled as a plate wall moved sinusoidally with the general function x = asinω t.The augmentation channel consisted of a front nozzle,rear nozzle and an internal fluid region which represented the turbine housing.The front and rear nozzles were geometrically the same.Three different front guide nozzle configurations were studied:a standard guide nozzle which was originally attached to the augmentation channel and two other front guide nozzles of different geometries.The purpose of this study is to observe how the front guide nozzle shape influences the flow downstream,mainly in the augmenta-tion channel,water power and the first stage energy conversion.The analysis was performed using a commercial CFD code ANSYS-CFX.The results of the flow in the augmentation channel for the three front guide nozzles are presented in this paper.

  9. Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

    Directory of Open Access Journals (Sweden)

    Yosef London

    2017-04-01

    Full Text Available An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified, and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.

  10. Enhanced Photocatalytic Activity of Bismuth Precursor by Rapid Phase and Surface Transformation Using Structure-Guided Combustion Waves.

    Science.gov (United States)

    Lee, Kang Yeol; Hwang, Hayoung; Kim, Tae Ho; Choi, Wonjoon

    2016-02-10

    The development of an efficient method for manipulating phase and surface transformations would facilitate the improvement of catalytic materials for use in a diverse range of applications. Herein, we present the first instance of a submicrosecond time frame direct phase and surface transformation of Bi(NO3)3 rods to nanoporous β-Bi2O3 rods via structure-guided combustion waves. Hybrid composites of the prepared Bi(NO3)3·H2O rods and organic fuel were fabricated by a facile preparation method. The anisotropic propagation of combustion waves along the interfacial boundaries of Bi(NO3)3·H2O rods induced direct phase transformation to β-Bi2O3 rods in the original structure due to the rapid pyrolysis, while the release of gas molecules enabled the formation of nanoporous structures on the surfaces of rods. The developed β-Bi2O3 rods showed improved photocatalytic activity for the photodegradation of rhodamine B in comparison with Bi(NO3)3·H2O rods and α-Bi2O3 rods due to the more suitable interdistance and the large contact areas of the porous surfaces. This new method of using structure-guided combustion waves for phase and surface transformation may contribute to the development of new catalysts as well as the precise manipulation of diverse micronanostructured materials.

  11. Omni-directional guided wave transducer arrays for the rapid inspection of large areas of plate structures.

    Science.gov (United States)

    Wilcox, Paul D

    2003-06-01

    Omni-directional guided wave array transducers contain a circular pattern of elements that individually behave as omni-directional point transmitters or receivers. The data set acquired from such an array contains time-domain signals from each permutation of transmitter and receiver. A phased addition algorithm is developed that allows an omni-directional, B-scan image of the surrounding plate to be synthesized from any geometry of array. Numerically simulated data from a single reflector is used to test the performance of the algorithm. The results from an array containing a fully populated circular area of elements (Type I array) are found to be good, but those from an array containing a single ring of elements (Type II array) contain many large side-lobes. An enhancement to the basic-phased addition algorithm is presented that uses deconvolution to suppress these side-lobes. The deconvolution algorithm enables a Type II array to equal the performance of a Type I array of the same overall diameter. The effect of diameter on angular resolution is investigated. Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the So Lamb wave mode in a 5-mm thick aluminium plate are processed with both algorithms and the results are discussed.

  12. Guided-wave-based damage detection in a composite T-joint using 3D scanning laser Doppler vibrometer

    Science.gov (United States)

    Kolappan Geetha, Ganesh; Roy Mahapatra, D.; Srinivasan, Gopalakrishnan

    2012-04-01

    Composite T-joints are commonly used in modern composite airframe, pressure vessels and piping structures, mainly to increase the bending strength of the joint and prevents buckling of plates and shells, and in multi-cell thin-walled structures. Here we report a detailed study on the propagation of guided ultrasonic wave modes in a composite T-joint and their interactions with delamination in the co-cured co-bonded flange. A well designed guiding path is employed wherein the waves undergo a two step mode conversion process, one is due to the web and joint filler on the back face of the flange and the other is due to the delamination edges close to underneath the accessible surface of the flange. A 3D Laser Doppler Vibrometer is used to obtain the three components of surface displacements/velocities of the accessible face of the flange of the T-joint. The waves are launched by a piezo ceramic wafer bonded on to the back surface of the flange. What is novel in the proposed method is that the location of any change in material/geometric properties can be traced by computing a frequency domain power flow along a scan line. The scan line can be chosen over a grid either during scan or during post-processing of the scan data off-line. The proposed technique eliminates the necessity of baseline data and disassembly of structure for structural interrogation.

  13. Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

    Science.gov (United States)

    London, Yosef; Diamandi, Hilel Hagai; Zadok, Avi

    2017-04-01

    An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified, and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.

  14. General Information about Primary CNS Lymphoma

    Science.gov (United States)

    ... Research Primary CNS Lymphoma Treatment (PDQ®)–Patient Version General Information About Primary CNS Lymphoma Go to Health ... start in the eye (called ocular lymphoma). Enlarge Anatomy of the lymph system, showing the lymph vessels ...

  15. A Source-Model Technique for analysis of wave guiding along chains of metallic nanowires in layered media.

    Science.gov (United States)

    Szafranek, Dana; Leviatan, Yehuda

    2011-12-05

    A method for determining the modes that can be guided along infinite chains of metallic nanowires when they are embedded, as in most realistic set-ups, in layered media is presented. The method is based on a rigorous full-wave frequency-domain Source-Model Technique (SMT). The method allows efficient determination of the complex propagation constants and the surface-plasmon type modal fields. Sample results are presented for silver nanowires with circular and triangle-like cross-sections lying in an air-Si-glass layered structure.

  16. An l p -norm approach to robust probabilistic inspection of plate-like structure defects with guided waves

    Science.gov (United States)

    Li, Dan; Yu, Hao; Xu, Feng; Liu, Da Peng; Qiu Zhang, Jian; Ta, De an

    2017-10-01

    In this paper, an l p -norm approach to robust probabilistic inspection of plate-like structure defects with guided waves is proposed. Analytical results show that the more the outliers in the measurements, the smaller p is preferred. Moreover, the relationship between our and the conventional signal difference coefficient (SDC) is also provided. While the experimental results verify the analytical ones, it is also shown that our approach has a good tolerance for impulsive noise interference, namely the unexpected artifacts in the reconstructed tomographic image caused by the impulsive interference are eliminated.

  17. Schrödinger operator in the limit of shrinking wave-guide cross section and singularity scaled twisting

    OpenAIRE

    Gianesello, Céline

    2011-01-01

    17 pages; Motivated by the method of self-similar variables for the study of the large time behavior of the heat equation in twisted wave-guides whose non circular cross-section and the support of twisting diminushing simutaneously to zero. Since in this limit the strength of the twisting increases to infinity and its support shrinks to the point, we show that the corresponding Schrödinger operator converges in a suitable norm-resolvent sense to a one-dimensional harmonic oscillator on the re...

  18. Estimation of permeability tensor and dielectric permittivity of ferrites using a wave guide method under a dc magnetic field

    Directory of Open Access Journals (Sweden)

    Tsiachristos I.

    2014-07-01

    Full Text Available Using a vector network analyzer equipped with a calibrated rectangular wave guide the electric permittivity and the element of the magnetic permeability tensor for Y3Fe5O12, ZnFe2O4 and NiFe2O4 are measured. The electric permittivity can be estimated from the body resonances (d = nλ/2 if a sufficient long sample is used. The estimation of the magnetic permeability tensors’ parameters can be estimated comparing the experimental results with computer simulations using the magnetic properties of the materials as derived from the magnetic measurements.

  19. Post-Processing of the Full Matrix of Ultrasonic Transmit-Receive Array Data for Guided Wave Pipe Inspection

    Science.gov (United States)

    Velichko, A.; Wilcox, P. D.

    2009-03-01

    The paper describes a method for processing data from a guided wave transducer array on a pipe. The raw data set from such an array contains the full matrix of time-domain signals from each transmitter-receiver combination. It is shown that for certain configurations of an array the total focusing method can be applied which allows the array to be focused at every point on a pipe surface in both transmission and reception. The effect of array configuration parameters on the sensitivity of the proposed method to the random and coherent noise is discussed. Experimental results are presented using electromagnetic acoustic transducers (EMAT) for exciting and detecting the S0 Lamb wave mode in a 12 inch steel pipe at 200 kHz excitation frequency. The results show that using the imaging algorithm a 2-mm-diameter (0.08 wavelength) half-thickness hole can be detected.

  20. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

    Science.gov (United States)

    This work aims to extract and characterize fibrous, rod-like and spherical cellulose nanoparticles (CNs) from cottonseed hull and to investigate the structure-morphology-rheology relationships. The rheological behavior of poly(vinyl alcohol) (PVA)/CNs suspensions was also examined to guide the solve...

  1. Ionotropic glutamate receptors & CNS disorders.

    Science.gov (United States)

    Bowie, Derek

    2008-04-01

    Disorders of the central nervous system (CNS) are complex disease states that represent a major challenge for modern medicine. Although aetilogy is often unknown, it is established that multiple factors such as defects in genetics and/or epigenetics, the environment as well as imbalance in neurotransmitter receptor systems are all at play in determining an individual's susceptibility to disease. Gene therapy is currently not available and therefore, most conditions are treated with pharmacological agents that modify neurotransmitter receptor signaling. Here, I provide a review of ionotropic glutamate receptors (iGluRs) and the roles they fulfill in numerous CNS disorders. Specifically, I argue that our understanding of iGluRs has reached a critical turning point to permit, for the first time, a comprehensive re-evaluation of their role in the cause of disease. I illustrate this by highlighting how defects in AMPA receptor (AMPAR) trafficking are important to fragile X mental retardation and ectopic expression of kainate receptor (KAR) synapses contributes to the pathology of temporal lobe epilepsy. Finally, I discuss how parallel advances in studies of other neurotransmitter systems may allow pharmacologists to work towards a cure for many CNS disorders rather than developing drugs to treat their symptoms.

  2. Scattering of guided SH_wave by a partly debonded circular cylinder in a traction free plate

    Institute of Scientific and Technical Information of China (English)

    WANG; Xiaomin

    2001-01-01

    [1]Ying, C.F., Truell, R., Scattering of plane longitudinal wave by a spherical obstacle in an isotropically elastic solid, J.Appl.Phys., 1956, 27(9): 1086.[2]Norris, A.N., Yang, Y., Shear wave scattering from a debonded fiber, in Elastic Waves and Ultrasonic Nondestructive Evaluation (eds.Datta, S.K., Achenbach, J.D., Rajapakes, Y.S.), Amsterdam: Elsevier Science Publishers, 1990, 437-440.[3]Sinclair, A.N., Anddison, R.C., Acoustic diffraction spectrum of a SiC fiber in a solid elastic medium, J.Acoust.Soc.Am., 1993, 94(2): 1126.[4]Huang, W., Brisuda, S., Rokhlin, S.I., Ultrasonic wave scattering from fiber_matrix interphases, J.Acoust.Soc.Am., 1995, 97(2): 807.[5]Huang, W., Wang, Y.J., Rokhlin, S.I., Oblique scattering of an elastic wave from a mutilayered cylinder in a solid: Transfer_matrix approach, J.Acoust.Soc.Am., 1996, 99(5): 2742.[6]Lu, Y., Guided antiplane shear wave propagation in layers reinforced by periodically spaced cylinders, J.Acoust.Soc.Am., 1996, 99(4): 1937.[7]Rokhlin, S.I., Diffraction of Lamb waves by a finite crack in an elastic layer, J.Acoust.Soc.Am., 1980, 67(4): 1157.[8]Rokhlin, S.I., Resonance phenomena of Lamb waves scattering by a finite crack in a solid layer, J.Acoust.Soc.Am., 1981, 69(4): 922.[9]Abduljabbar, Z., Datta, S.K., Shah, A.H., Diffraction of horizontally polarized shear waves by normal cracks in a plate, J.Appl.Phys., 1983, 54(2): 461.[10]Rokhlin, S.I., Lamb wave interaction with lap_shear adhesive joints: theory and experiment, J.Acoust.Soc.Am., 1991, 89(6): 2758.[11]Al_Nassar, Y.N., Datta, S.K., Shah, A.H., Scattering of Lamb waves by a normal rectangular strip of weldment, Ultrasonics, 1991, 29(2): 125.[12]Alleyne, D.N., Cawley, P., The interaction of Lamb waves with defects, IEEE Trans.Ultrason Ferroelectr.Frequency Control, 1992, 39(3): 381.[13]Nielsen, E.D., Scattering by a cylindrical post of complex permittivity in a waveguide, IEEE Trans.on Microwave Theory and

  3. A unified formulation for guided-wave propagation in multi-layered mixed anisotropic-isotropic hybrid aerospace composites

    Science.gov (United States)

    Barazanchy, Darun; Giurgiutiu, Victor

    2016-04-01

    A unified approach was formulated to predict guided-wave propagation in a material regardless its degree of anisotropy, thereby having one solution method for both isotropic and anisotropic material. The unified approach was based on the coupled eigenvalue problem derived from Chirstoffels equation for a lamina. The eigenvalue problem yielded a set of eigenvalues, and corresponding eigenvectors that were used to obtain the stress-displacement matrix. The dispersion curves were obtained by applying the traction free boundary conditions to the stress-displacement matrix, and searching for sign changes in the complex determinant of the matrix. To search for sign changes, hence the velocity-wavenumber pairs which yielded a solution to the problem, the real and imaginary part of the complex determinant had to change sign simultaneously. A phase angle approach was, therefore, developed and successfully applied. A refinement algorithm was applied to refine the accuracy of the solution without increasing the computational time significantly. A high accuracy was required to calculated the correct partial-wave participation factors. The obtained partial-wave participation factors were used to calculate the modeshape through the thickness for each velocity-wavenumber pair. To identify the different wave types, A0, S0, SHS0, SHA0, a modeshape identification was applied successfully. The unified approach was evaluated for hybrid aerospace composites. In addition, the two most common solution methods: (i) the global matrix method; and (ii) the transfer matrix method were applied, and a comparative study between the different methods was performed.

  4. On ultrasound waves guided by bones with coupled soft tissues: a mechanism study and in vitro calibration.

    Science.gov (United States)

    Chen, Jiangang; Su, Zhongqing

    2014-07-01

    The influence of soft tissues coupled with cortical bones on precision of quantitative ultrasound (QUS) has been an issue in the clinical bone assessment in conjunction with the use of ultrasound. In this study, the effect arising from soft tissues on propagation characteristics of guided ultrasound waves in bones was investigated using tubular Sawbones phantoms covered with a layer of mimicked soft tissue of different thicknesses and elastic moduli, and an in vitro porcine femur in terms of the axial transmission measurement. Results revealed that presence of soft tissues can exert significant influence on the propagation of ultrasound waves in bones, leading to reduced propagation velocities and attenuated wave magnitudes compared with the counterparts in a free bone in the absence of soft tissues. However such an effect is not phenomenally dependent on the variations in thickness and elastic modulus of the coupled soft tissues, making it possible to compensate for the coupling effect regardless of the difference in properties of the soft tissues. Based on an in vitro calibration, this study proposed quantitative compensation for the effect of soft tissues on ultrasound waves in bones, facilitating development of high-precision QUS.

  5. Detecting delaminations and disbondings on full-scale wing composite panel by guided waves based SHM system

    Science.gov (United States)

    Monaco, E.; Boffa, N. D.; Memmolo, V.; Ricci, F.; Maio, L.

    2016-04-01

    A full-scale lower wing panel made of composite material has been designed, manufactured and sensorised within the European Funded research project named SARISTU. The authors contributed to the whole development of the system, from design to implementation as well as to the impacts campaign phase where Barely Visible and Visible Damages (BVID and VID) are to be artificially induced on the panel by a pneumatic impact machine. This work summarise part of the experimental results related to damages production, their assessment by C-SCAN as reference NDT method as well as damage detection of delimitations by a guided waves based SHM. The SHM system is made by customized piezoelectric patches secondary bonded on the wing plate acting both as guided waves sources and receivers. The paper will deal mostly with the experimental impact campaign and the signal analyses carried out to extract the metrics more sensitive to damages induced. Image reconstruction of the damages dimensions and shapes will be also described based mostly on the combination of metrics maps over the plate partial surfaces. Finally a comparison of damages maps obtained by the SHM approach and those obtained by "classic" C-SCAN will be presented analyzing briefly pros and cons of the two different approached as a combination to the most effective structural maintenance scenario of a commercial aircraft.

  6. Simulation of acoustic guided wave propagation in cortical bone using a semi-analytical finite element method.

    Science.gov (United States)

    Pereira, Daniel; Haiat, Guillaume; Fernandes, Julio; Belanger, Pierre

    2017-04-01

    Axial transmission techniques have been extensively studied for cortical bone quality assessment. However, the modeling of ultrasonic guided waves propagation in such a complex medium remains challenging. The aim of this paper is to develop a semi-analytical finite element method to simulate the propagation of guided waves in an irregular, multi-layer, and heterogeneous bone cross-section modeled with anisotropic and viscoelastic material properties. The accuracy of the simulations was verified against conventional time-domain three-dimensional finite element. The method was applied in the context of axial transmission in bone to investigate the feasibility of first arrival signal (FAS) to monitor degradation of intracortical properties at low frequency. Different physiopathological conditions for the intracortical region, varying from healthy to osteoporotic, were monitored through FAS velocity using a 10-cycle tone burst excitation centered at 32.5 kHz. The results show that the variation in FAS velocity is mainly associated with four of the eight modes supported by the waveguide, varying with velocity values between 550 and 700 m/s along the different scenarios. Furthermore, the FAS velocity is shown to be associated with the group velocity of the mode with the highest relative amplitude contribution at each studied scenario. However, because of the evolution of the mode with the highest contribution, the FAS velocity is shown to be limited to discriminate intracortical bone properties at low frequency.

  7. Guiding and confinement of interface acoustic waves in solid-fluid pillar-based phononic crystals

    Science.gov (United States)

    Razip Wee, M. F. Mohd; Addouche, Mahmoud; Siow, Kim S.; Zain, A. R. Md; Elayouch, Aliyasin; Chollet, Franck; Khelif, Abdelkrim

    2016-12-01

    Pillar-based phononic crystals exhibit some unique wave phenomena due to the interaction between surface acoustic modes of the substrate and local resonances supported by pillars. In this paper, we extend the investigations by taking into account the presence of a liquid medium. We particularly demonstrate that local resonances dramatically decrease the phase velocity of Scholte-Stoneley wave, which leads to a slow wave at the solid/fluid interface. Moreover, we show that increasing the height of pillars introduces a new set of branches of interface modes and drastically affects the acoustic energy localization. Indeed, while some modes display a highly confined pressure between pillars, others exponentially decay in the fluid or only propagate in the solid without disturbing the fluid pressure. These theoretical results, performed by finite element method, highlight a new acoustic wave confinement suitable in various applications such as acoustophoresis, lab on chip and microfluidics.

  8. Guiding and confinement of interface acoustic waves in solid-fluid pillar-based phononic crystals

    Directory of Open Access Journals (Sweden)

    M. F. Mohd Razip Wee

    2016-12-01

    Full Text Available Pillar-based phononic crystals exhibit some unique wave phenomena due to the interaction between surface acoustic modes of the substrate and local resonances supported by pillars. In this paper, we extend the investigations by taking into account the presence of a liquid medium. We particularly demonstrate that local resonances dramatically decrease the phase velocity of Scholte-Stoneley wave, which leads to a slow wave at the solid/fluid interface. Moreover, we show that increasing the height of pillars introduces a new set of branches of interface modes and drastically affects the acoustic energy localization. Indeed, while some modes display a highly confined pressure between pillars, others exponentially decay in the fluid or only propagate in the solid without disturbing the fluid pressure. These theoretical results, performed by finite element method, highlight a new acoustic wave confinement suitable in various applications such as acoustophoresis, lab on chip and microfluidics.

  9. Vacuum-deposited wave-guiding layers on STW resonators based on LiTaO(3) substrate as love wave sensors for chemical and biochemical sensing in liquids.

    Science.gov (United States)

    Barié, Nicole; Stahl, Ullrich; Rapp, Michael

    2010-05-01

    A promising approach to apply the Love wave concept to commercially available low-loss surface acoustic wave (SAW) devices of the type Murata SAF 380 is presented. Thin wave-guiding layers of variable thickness are coated on the piezoelectric substrate of the devices. Two different layer materials were used: sputtered SiO(2) and a new polymer in this field, paryleneC (poly-[2-chloro-p-xylylene]). Insertion loss, resonance frequency, frequency changes during protein precipitation and noise of the devices are discussed as a function of the thickness of the wave-guiding layer. It is demonstrated that the application of an optimized wave-guiding layer increases the sensitivity. When using SiO(2) as wave-guiding layer, an optimum layer thickness of 4 microm leads to a detection limit of 1.7 pg/mm(2). Therefore, the detection limit is improved by factor 7.7 as compared to uncoated SAW devices. Parylene-coated devices reach a detection limit of 2.9 pg/mm(2) at an optimum layer thickness of 0.5 microm. This corresponds to an improvement by factor 4.3. As the SAW devices used in this study are commercially available at low costs, applying appropriate wave-guiding layers permits an application as chemical or biochemical sensors with excellent sensitivities. Moreover, parylene-coated devices combine the sensitivity increase by excitation of Love waves with an excellent protective effect against corrosive attacks by the surrounding medium. Therefore, these sensors are most suitable for biosensing in conducting buffer solutions.

  10. Wave-front error breakdown in laser guide star multi-object adaptive optics validated on-sky by Canary

    Science.gov (United States)

    Martin, O. A.; Gendron, É.; Rousset, G.; Gratadour, D.; Vidal, F.; Morris, T. J.; Basden, A. G.; Myers, R. M.; Correia, C. M.; Henry, D.

    2017-01-01

    Context. Canary is the multi-object adaptive optics (MOAO) on-sky pathfinder developed in the perspective of multi-object spectrograph on extremely large telescopes (ELTs). In 2013, Canary was operated on-sky at the William Herschel telescope (WHT), using three off-axis natural guide stars (NGS) and four off-axis Rayleigh laser guide stars (LGS), in open-loop, with the on-axis compensated turbulence observed with a H-band imaging camera and a Truth wave-front sensor (TS) for diagnostic purposes. Aims: Our purpose is to establish a reliable and accurate wave-front error breakdown for LGS MOAO. This will enable a comprehensive analysis of Canary on-sky results and provide tools for validating simulations of MOAO systems for ELTs. Methods: To evaluate the MOAO performance, we compared the Canary on-sky results running in MOAO, in single conjugated adaptive optics (SCAO) and in ground layer adaptive optics (GLAO) modes, over a large set of data acquired in 2013. We provide a statistical study of the seeing. We also evaluated the wave-front error breakdown from both analytic computations, one based on a MOAO system modelling and the other on the measurements from the Canary TS. We have focussed especially on the tomographic error and we detail its vertical error decomposition. Results: We show that Canary obtained 30.1%, 21.4% and 17.1% H-band Strehl ratios in SCAO, MOAO and GLAO respectively, for median seeing conditions with 0.66'' of total seeing including 0.59'' at the ground. Moreover, we get 99% of correlation over 4500 samples, for any AO modes, between two analytic computations of residual phase variance. Based on these variances, we obtain a reasonable Strehl-ratio (SR) estimation when compared to the measured IR image SR. We evaluate the gain in compensation for the altitude turbulence brought by MOAO when compared to GLAO.

  11. Radiation therapy of CNS lymphoma

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Yutaka; Wako, Tadashi (Shinshu Univ., Matsumoto, Nagano (Japan). Faculty of Medicine)

    1983-08-01

    Six cases of the CNS malignant lymphoma occurring among 165 cases seen between 1975 -- 1981 were reviewed. Two cases had primary brain mass lesions and one case had a secondary brain mass in the systemic remission period. Two cases had primary extradural spinal mass lesions and one case had a secondary extradural spinal mass in the systemic relapse period. All patients were treated with radiotherapy. Irradiation fields, doses and those effects were discussed. Whole brain irradiation more than 40 Gy was recommended for brain lesion. Prognosis of the secondary case without systemic remission was poor.

  12. Simple equations guide high-frequency surface-wave investigation techniques

    Science.gov (United States)

    Xia, J.; Xu, Y.; Chen, C.; Kaufmann, R.D.; Luo, Y.

    2006-01-01

    We discuss five useful equations related to high-frequency surface-wave techniques and their implications in practice. These equations are theoretical results from published literature regarding source selection, data-acquisition parameters, resolution of a dispersion curve image in the frequency-velocity domain, and the cut-off frequency of high modes. The first equation suggests Rayleigh waves appear in the shortest offset when a source is located on the ground surface, which supports our observations that surface impact sources are the best source for surface-wave techniques. The second and third equations, based on the layered earth model, reveal a relationship between the optimal nearest offset in Rayleigh-wave data acquisition and seismic setting - the observed maximum and minimum phase velocities, and the maximum wavelength. Comparison among data acquired with different offsets at one test site confirms the better data were acquired with the suggested optimal nearest offset. The fourth equation illustrates that resolution of a dispersion curve image at a given frequency is directly proportional to the product of a length of a geophone array and the frequency. We used real-world data to verify the fourth equation. The last equation shows that the cut-off frequency of high modes of Love waves for a two-layer model is determined by shear-wave velocities and the thickness of the top layer. We applied this equation to Rayleigh waves and multi-layer models with the average velocity and obtained encouraging results. This equation not only endows with a criterion to distinguish high modes from numerical artifacts but also provides a straightforward means to resolve the depth to the half space of a layered earth model. ?? 2005 Elsevier Ltd. All rights reserved.

  13. Ultrasound-guided needling combined with shock-wave therapy for the treatment of calcifying tendonitis of the shoulder.

    Science.gov (United States)

    Krasny, C; Enenkel, M; Aigner, N; Wlk, M; Landsiedl, F

    2005-04-01

    We carried out a prospective, randomised controlled trial on two groups of 40 patients with painful calcific tendonitis and a mean age of 48.4 years (32.5 to 67.3). All were to undergo arthroscopic removal of the calcific deposit within six months after randomisation. The 40 patients in group I received ultrasound-guided needling followed by high-energy shock-wave therapy and the 40 in group II had shock-wave therapy alone. In both groups one treatment consisting of 2500 impulses of shock waves with an energy flux density of 0.36 mJ/mm(2) was applied. The clinical and radiological outcome was assessed using the 100-point Constant shoulder scoring system and standardised radiographs. The mean follow-up was 4.1 months and no patient was lost to follow-up. Both groups had significant improvement in their Constant shoulder score. Radiographs showed disappearance of the calcific deposit in 60.0% of the shoulders in group I and in 32.5% of group II (p tendonitis, giving significantly higher rates of elimination of the calcium deposits, better clinical results and reduction in the need for surgery.

  14. 超声导波检测技术的发展、应用与挑战%Development,applications and challenges in ultrasonic guided waves testing technology

    Institute of Scientific and Technical Information of China (English)

    何存富; 吴斌; 郑明方; 吕炎; 邓鹏; 赵华民; 刘秀成; 宋国荣; 刘增华; 焦敬品

    2016-01-01

    回顾了近三十年的超声导波技术发展及应用,阐述了导波的频散现象及其求解方法,深入分析了导波激励的力学加载原理和模态选择原则。论述了导波的传感激励方法与装置,并比较了各种激励接收方法的特点与应用场合。对超声导波在板类、管类和复合材料中的应用进行了评述,并从提高缺陷检测能力的角度,介绍了时间反转法和相控阵法在超声导波技术中的应用。最后总结了当前导波技术面临的机遇与挑战。%This paper gives an overview of the development and application of guided waves technique for NDT&E in recent 30 years. Firstly,the fundamental concepts of guided waves propagation and their characteristics are explained,and the mechanical loading principles and mode selection principles for guided wave excitation is analyzed thoroughly.Secondly,the transducer excitation method and its apparatus for ultrasonic guided waves are introduced,then the features and applications are discussed among different excitation methods.Thirdly,ultrasonic guided wave applications in plates,tubes and composite materials are described,meanwhile,the time reversal and the phased array method are introduced to improve the capability of defect detection.Finally,the challenges and opportunities in of guided ultrasonic waves in future are outlined.

  15. Quantization of a particle guided by its own pilot-wave

    Science.gov (United States)

    Perrard, Stéphane; Labousse, Matthieu; Fort, Emmanuel; Couder, Yves

    2013-11-01

    The association of a particle and a wave can be obtained even at a macroscopic scale, using a simple experimental set up. A liquid bath is set into vertical oscillation so that any drop deposit on it has never the time to break the air layer under it. The drop is always ejected from the bath by the vibration and can then live for hours. The impact generates waves at the surface of the bath which can propel the drop. It becomes a walker, the self-propelled entity formed by a bouncing droplet and its associated surface wave. This system has already shown surprising wave-particle duality as single particle diffraction or Bohr-Sommerfeld quantization of level when the drop is submitted to a transverse force. We now study its motion when the walker is submitted to a central force, which can be tuned at will. In particular, I will present our results in the case of a 2D harmonic potential well. In the case of a strong coupling between the waves and the bouncing drop, the walker exhibit a discrete set of state where the angular momentum and the spatial extend of each level are quantized. Disordered trajectories also appear, as an intermittency between the pure eigenmodes through transitions between them.

  16. Guided Acoustic and Optical Waves in Silicon-on-Insulator for Brillouin Scattering and Optomechanics

    Science.gov (United States)

    2016-08-01

    environment, they also isolate devices from heat-dissipating thermal linkages and on-chip electronics. The intuition of “index-guided” confinement of...coupling. Consider the optical guided modes for 100 nm wide fins spaced 40 nm apart in 340 nm thick silicon shown in Figure 2(b). For these

  17. A finite element analysis of the time-delay periodic ring arrays for guided wave generation and reception in hollow cylinders.

    Science.gov (United States)

    Zhu, W

    2001-09-01

    A new guided wave transducer model, time-delay periodic ring arrays (TDPRAs), is proposed and investigated in this paper for guided cylindrical wave generation and reception in hollow cylinders with application interests focusing on non-destructive testing (NDT) of piping/tubing. A finite element simulation has been performed for axisymmetric guided-mode excitation and reception with TDPRAs. By arranging a proper configuration of the time-delay profile and the electric-connection pattern of a ring array, unidirectional excitation and reception of guided waves can be achieved. The numerical results are obtained for the first three axisymmetrical modes and are compared with respect to generation efficiency and mode selectivity. Parametric influences on the performance of TDPRAs are discussed, combining a 2-D phase velocity-frequency spectrum approach with the mode dispersion and displacement structure analyses. The identification of converted modes in guided cylindrical wave reflections with a flexible TDPRA receiver has also been studied through sample notch reflection.

  18. Effects of geometrical parameters on wrinkling of thin-walled rectangular aluminum alloy wave-guide tubes in rotary-draw bending

    Institute of Scientific and Technical Information of China (English)

    Tian Shan; Liu Yuli; Yang He

    2013-01-01

    Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes,and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes.In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes,a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABAQUS/Explicit,and its reliability was validated by experiments.Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out.The results show that inner flange wrinkling is the main wrinkling way to rectangular wave-guide tubes in rotary-draw bending processes,but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller.Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h,while both b and h affect inner flange wrinkling greatly.Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.

  19. User guide - COE calculation tool for wave energy converters. Draft version 1

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Chozas, J.; Kofoed, J.P. [Aalborg Univ., Aalborg (Denmark); Helstrup Jensen, N.E. [Energinet.dk, Fredericia (Denmark)

    2013-08-15

    Aalborg University together with Energinet.dk and Julia F. Chozas Consulting Engineer, have released a freely available online spreadsheet to evaluate the Levelised Cost of Energy (LCOE) for wave energy projects. The open-access tool calculates the LCOE based on the power production of a Wave Energy Converter (WEC) at a particular location. Production data may derive from laboratory testing, numerical modelling or from sea trials. The tool has been developed as a transparent and simple model that evaluates WEC's economic feasibility in a range of locations, while scaling WEC's features to the selected site. (Author)

  20. Temperature effects on the propagation characteristics of Love waves along multi-guide layers of Sio2/Su-8 on St-90°X quartz.

    Science.gov (United States)

    Xu, Fangqian; Wang, Wen; Hou, Jiaoli; Liu, Minghua

    2012-01-01

    Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent temperature coefficient of frequency (Tcf) of the fabricated Love wave devices with guide layers of SU-8/SiO(2) on ST-90°X quartz substrate is evaluated experimentally as only 2.16 ppm.

  1. Spontaneous Parametric Down-Conversion and Dynamical Casimir Effect for Surface Plasmon Polaritons and Guided Waves

    Directory of Open Access Journals (Sweden)

    Hižnjakov V.

    2015-01-01

    Full Text Available The features of biphotons states generated via spontaneous four-wave mixing in nanofibers with a variable cross-section are studied. The spectral amplitude of the biphoton field is calculated and the effects of interference and phase modulation of the biphoton field in such structures is discussed.

  2. Coherent versus incoherent dynamics in InAs quantum-dot active wave guides

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, W.; Hvam, Jørn Märcher;

    2001-01-01

    Coherent dynamics measured by time-resolved four-wave mixing is compared to incoherent population dynamics measured by differential transmission spectroscopy on the ground-state transition at room temperature of two types of InAs-based quantum dots with different confinement energies. The measure...

  3. Analytical modeling of contact acoustic nonlinearity of guided waves and its application to evaluating severity of fatigue damage

    Science.gov (United States)

    Wang, Kai; Su, Zhongqing

    2016-04-01

    Targeting quantitative estimate of fatigue damage, a dedicated analytical model was developed based on the modal decomposition method and the variational principle. The model well interprets the contact acoustic nonlinearity induced by a "breathing" crack in a two-dimensional scenario, and the nonlinear characteristics of guided ultrasonic waves (GUWs) (e.g., reflection, transmission, mode conversion and high-order generation) when GUWs traversing the crack. Based on the model, a second-order reflection index was defined. Using the index, a fatigue damage evaluation framework was established, showing demonstrated capacity of estimating the severity of fatigue damage in a quantitative manner. The approach, in principle, does not entail a benchmarking process against baseline signals pre-acquired from pristine counterparts. The results obtained using the analytical modeling were compared with those from finite element simulation, showing good coincidence. Limitations of the model were also discussed.

  4. Effect of localized microstructural evolution on higher harmonic generation of guided wave modes

    Science.gov (United States)

    Choi, Gloria; Liu, Yang; Yao, Xiaochu; Lissenden, Cliff J.

    2015-03-01

    Higher harmonic generation of ultrasonic waves has the potential to be used to detect precursors to macroscale damage of phenomenon like fatigue due to microstructural evolution contributing to nonlinear material behavior. Aluminum plates having various plastic zone sizes were plastically deformed to different levels. The fundamental shear horizontal mode was then generated in the plate samples via a magnetostrictive transducer. After propagating through the plastic zone the primary wave mode (SH0) and its third harmonic (sh0) were received by a second transducer. Results of a parallel numerical study using the S1-s2 Lamb mode pair, where sensitivity to changes in third order elastic constants were investigated, are described within the context of the experimental results. Specimens used within both studies are geometrically similar and have double edge notches for dog bone samples that introduce localized plastic deformation. Through both studies, the size of the plastic zone with respect to the propagation distance and damage intensity influence the higher harmonics.

  5. Damage detection in multilayered fiber-metal laminates using guided-wave phased array

    Energy Technology Data Exchange (ETDEWEB)

    Maghsoodi, Ameneh; Ohadi, Abdolrezap; Sadighi, Mojtaba; Amindavar, Hamidreza [Amirkabir University, Tehran (Iran, Islamic Republic of)

    2016-05-15

    This study employs the Lamb wave method to detect damage in Fiber-metal laminates (FMLs). The method is based on quasiisotropic behavior approximation and beam forming techniques. Delay and sum and minimum variance distorsionless response beam formers are applied to a uniform linear phased array. The simulation in finite element software is conducted to evaluate the performance of the presented procedure. The two types of damage studied are the following: (1) Delamination between fiber-epoxy and metal layers and (2) crack on the metal layer. The present study has the following important contributions: (1) Health monitoring of multi-damaged FMLs using Lamb waves and beam forming technique, (2) detection of damage type, (3) detection of damage size by 1D phased array, and (4) identification of damages that occurred very close to the laminate edges or close to each other.

  6. Multimodal sparse reconstruction in guided wave imaging of defects in plates

    Science.gov (United States)

    Golato, Andrew; Santhanam, Sridhar; Ahmad, Fauzia; Amin, Moeness G.

    2016-07-01

    A multimodal sparse reconstruction approach is proposed for localizing defects in thin plates in Lamb wave-based structural health monitoring. The proposed approach exploits both the sparsity of the defects and the multimodal nature of Lamb wave propagation in plates. It takes into account the variation of the defects' aspect angles across the various transducer pairs. At low operating frequencies, only the fundamental symmetric and antisymmetric Lamb modes emanate from a transmitting transducer. Asymmetric defects scatter these modes and spawn additional converted fundamental modes. Propagation models are developed for each of these scattered and spawned modes arriving at the various receiving transducers. This enables the construction of modal dictionary matrices spanning a two-dimensional array of pixels representing potential defect locations in the region of interest. Reconstruction of the region of interest is achieved by inverting the resulting linear model using the group sparsity constraint, where the groups extend across the various transducer pairs and the different modes. The effectiveness of the proposed approach is established with finite-element scattering simulations of the fundamental Lamb wave modes by crack-like defects in a plate. The approach is subsequently validated with experimental results obtained from an aluminum plate with asymmetric defects.

  7. Use of Guided Acoustic Waves to Assess the Effects of Thermal-Mechanical Cycling on Composite Stiffness

    Science.gov (United States)

    Seale, Michael D.; Madaras, Eric I.

    2000-01-01

    The introduction of new, advanced composite materials into aviation systems requires it thorough understanding of the long-term effects of combined thermal and mechanical loading. As part of a study to evaluate the effects of thermal-mechanical cycling, it guided acoustic (Lamb) wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the velocity dispersion curve. A series of 16 and 32-ply composite laminates were subjected to it thermal-mechanical loading profile in load frames equipped with special environmental chambers. The composite systems studied were it graphite fiber reinforced amorphous thermoplastic polyimide and it graphite fiber reinforced bismaleimide thermoset. The samples were exposed to both high and low temperature extremes its well as high and low strain profiles. The bending and out-of-plane stiffnesses for composite sample that have undergone over 6,000 cycles of thermal-mechanical loading are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 20% at 4,936 loading cycles for the graphite/thermoplastic samples and up to 64% at 4,706 loading cycles for the graphite/thermoset samples.

  8. Gas-phase hydrogen/deuterium exchange in a traveling wave ion guide for the examination of protein conformations.

    Science.gov (United States)

    Rand, Kasper D; Pringle, Steven D; Murphy, James P; Fadgen, Keith E; Brown, Jeff; Engen, John R

    2009-12-15

    Accumulating evidence suggests that solution-phase conformations of small globular proteins and large molecular protein assemblies can be preserved for milliseconds after electrospray ionization. Thus, the study of proteins in the gas phase on this time scale is highly desirable. Here we demonstrate that a traveling wave ion guide (TWIG) of a Synapt mass spectrometer offers a highly suitable environment for rapid and efficient gas-phase hydrogen/deuterium exchange (HDX). Gaseous ND(3) was introduced into either the source TWIG or the TWIG located just after the ion mobility cell, such that ions underwent HDX as they passed through the ND(3) on the way to the time-of-flight analyzer. The extent of deuterium labeling could be controlled by varying the quantity of ND(3) or the speed of the traveling wave. The gas-phase HDX of model peptides corresponded to labeling of primarily fast exchanging sites due to the short labeling times (ranging from 0.1 to 10 ms). In addition to peptides, gas-phase HDX of ubiquitin, cytochrome c, lysozyme, and apomyoglobin were examined. We conclude that HDX of protein ions in a TWIG is highly sensitive to protein conformation, enables the detection of conformers present on submilliseconds time scales, and can readily be combined with ion mobility spectrometry.

  9. Ambulatory ECG-based T-wave alternans monitoring for risk assessment and guiding medical therapy: mechanisms and clinical applications.

    Science.gov (United States)

    Verrier, Richard L; Ikeda, Takanori

    2013-01-01

    Identification of individuals at risk for sudden cardiac death (SCD), the main cause of adult mortality in developed countries, remains a major challenge. The main contemporary noninvasive marker, left ventricular ejection fraction (LVEF), has not proved adequately reliable, as the majority of individuals who die suddenly have relatively preserved cardiac mechanical function. Monitoring of T-wave alternans (TWA), a beat-to-beat fluctuation in ST-segment or T-wave morphology, on ambulatory electrocardiogram (AECG) is an attractive approach on both scientific and clinical grounds. Specifically, TWA's capacity to assess risk for malignant arrhythmias has been shown to rest on sound electrophysiologic principles and AECG-based TWA monitoring can be performed in the flow of routine clinical evaluation. This review addresses: (1) electrophysiologic and ionic mechanisms underlying TWA's predictivity, (2) principles and practical aspects of AECG-based TWA monitoring, (3) clinical evidence supporting this approach to SCD risk stratification, and (4) current and potential applications in guiding medical therapy.

  10. Photon-pair generation by intermodal spontaneous four-wave mixing in birefringent, weakly guiding optical fibers

    Science.gov (United States)

    Garay-Palmett, K.; Cruz-Delgado, D.; Dominguez-Serna, F.; Ortiz-Ricardo, E.; Monroy-Ruz, J.; Cruz-Ramirez, H.; Ramirez-Alarcon, R.; U'Ren, A. B.

    2016-03-01

    We present a theoretical and experimental study of the generation of photon pairs through the process of spontaneous four-wave mixing (SFWM) in a few-mode, birefringent fiber. Under these conditions, multiple SFWM processes are in fact possible, each associated with a different combination of transverse modes for the four waves involved. We show that in the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized modes, the departure from circular symmetry due to the fiber birefringence translates into conservation rules, which retain elements from azimuthal and rectangular symmetries: both OAM and parity must be conserved for a process to be viable. We have implemented a SFWM source based on a bowtie birefringent fiber, and have measured for a collection of pump wavelengths the SFWM spectra of each of the signal and idler photons in coincidence with its partner photon. We have used this information, together with knowledge of the transverse modes into which the signal and idler photons are emitted, as input for a genetic algorithm, which accomplishes two tasks: (i) the identification of the particular SFWM processes that are present in the source, and (ii) the characterization of the fiber used.

  11. Ultrasonic Guided Wave Technology for Non-Invasive Assessment of Corrosion-Induced Damage in Piping for Pollution Prevention in DOD Fuel Storage Facilities

    Science.gov (United States)

    2011-08-01

    put on in a three step process per manufacturer’s recommendation. A relatively thin coat of bitumen mastic was applied to the entire pipe surface...Figure. Summary of Ultrasonic Guided Wave Results The Signal peak height from each data trace was extracted and then plotted versus percent CSAL in

  12. Corrosion Induced Loss of Capacity and Development of a Guided Wave Condition Assessment Method for Multistrand Anchor Systems Used in Corps Projects

    Science.gov (United States)

    2014-08-01

    2 33 monitoring, x- ray diffraction, infrared thermography, and impulse radar . This report also mentioned guided waves as a promising technology...End View Imager Code ( MATLAB IMAGE PROCESSING #2 code).................. 59 Appendix B: Axial Scanner Theory and Operation...12 Figure 8. Tracing deformation with string measurement to locate the failure point in unbroken wires

  13. Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a structurally chiral material

    CERN Document Server

    Chiadini, Francesco; Scaglione, Antonio; Lakhtakia, Akhlesh

    2015-01-01

    Multiple compound surface plasmon-polariton (SPP) waves can be guided by a structure consisting of a sufficiently thick layer of metal sandwiched between a homogeneous isotropic dielectric (HID) material and a dielectric structurally chiral material (SCM). The compound SPP waves are strongly bound to both metal/dielectric interfaces when the thickness of the metal layer is comparable to the skin depth but just to one of the two interfaces when the thickness is much larger. The compound SPP waves differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. Some compound SPP waves are not greatly affected by the choice of the direction of propagation in the transverse plane but others are, depending on metal thickness. For fixed metal thickness, the number of compound SPP waves depends on the relative permittivity of the HID material, which can be useful for sensing applications.

  14. Metallothionein expression and roles in the CNS

    DEFF Research Database (Denmark)

    Penkowa, Milena

    2002-01-01

    -I+II) are regulated and expressed coordinately and are currently the best characterized MT isoforms. This review will focus on the expression and roles of MT-I+II in the CNS. MT-I+II are implicated in diverse physiological and pathophysiological functions, such as metal ion metabolism, regulation of the CNS...

  15. User's guide for a large signal computer model of the helical traveling wave tube

    Science.gov (United States)

    Palmer, Raymond W.

    1992-01-01

    The use is described of a successful large-signal, two-dimensional (axisymmetric), deformable disk computer model of the helical traveling wave tube amplifier, an extensively revised and operationally simplified version. We also discuss program input and output and the auxiliary files necessary for operation. Included is a sample problem and its input data and output results. Interested parties may now obtain from the author the FORTRAN source code, auxiliary files, and sample input data on a standard floppy diskette, the contents of which are described herein.

  16. Preliminary design of high-power wave-guide/transmission system for multimegawatt CW requirements of 100 MeV proton LINAC

    Indian Academy of Sciences (India)

    Purushottam Shrivastava; Y D Wanmode; P R Hannurkar

    2002-11-01

    Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR 1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and design specifications-considerations for these stringent requirements.

  17. Characterization of compressed earth blocks using low frequency guided acoustic waves.

    Science.gov (United States)

    Ben Mansour, Mohamed; Ogam, Erick; Fellah, Z E A; Soukaina Cherif, Amel; Jelidi, Ahmed; Ben Jabrallah, Sadok

    2016-05-01

    The objective of this work was to analyze the influence of compaction pressure on the intrinsic acoustic parameters (porosity, tortuosity, air-flow resistivity, viscous, and thermal characteristic lengths) of compressed earth blocks through their identification by solving an inverse acoustic wave transmission problem. A low frequency acoustic pipe (60-6000 Hz of length 22 m, internal diameter 3.4 cm) was used for the experimental characterization of the samples. The parameters were identified by the minimization of the difference between the transmissions coefficients data obtained in the pipe with that from an analytical interaction model in which the compressed earth blocks were considered as having rigid frames. The viscous and thermal effects in the pores were accounted for by employing the Johnson-Champoux-Allard-Lafarge model. The results obtained by inversion for high-density compressed earth blocks showed some discordance between the model and experiment especially for the high frequency limit of the acoustic characteristics studied. This was as a consequence of applying high compaction pressure rendering them very highly resistive therefore degrading the signal-to-noise ratios of the transmitted waves. The results showed that the airflow resistivity was very sensitive to the degree of the applied compaction pressure used to form the blocks.

  18. Charge transfer to a dielectric target by guided ionization waves using electric field measurements

    Science.gov (United States)

    Slikboer, Elmar; Garcia-Caurel, Enric; Guaitella, Olivier; Sobota, Ana

    2017-03-01

    A kHz-operated atmospheric pressure plasma jet is investigated by measuring charge transferred to a dielectric electro-optic surface (BSO crystal) allowing for the measurement of electric field by exploiting the Pockels effect. The electric field values, distribution of the surface discharge and amount of deposited charge are obtained for various parameters, including gas flow, applied voltage, target distance and the length of the capillary from ground to the end. A newly formed surface discharge emerges at the target when enough charge is deposited at the impact point and electric fields are high enough, i.e. 200 pC and 9 ± 2 kV cm‑1. The maximum amount of charge transferred by a single ionization wave (‘plasma bullet’) is 350 ± 40 pC. Due to the emerging new surface discharge behind the impact point, the total charge deposited on the surface of the dielectric target can increase up to 950 pC. The shape of the secondary discharge on the target is found to be mainly driven by gas flow, while the applied voltage allows us to utilize longer distances within the boundaries set by this gas mixing. Finally the ionization wave is found to lose charge along its propagation on the inner walls of the capillary. The loss is estimated to be approximately 7.5 pC mm‑1 of travel distance inside the capillary.

  19. The training on propagation of guided electromagnetic waves from the point of view of LSM LSE modes; La ensenanza de las ondas electromagneticas guiadas desde el punto de vista de los modos LSM y LSE

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, J.

    1997-09-01

    In this work, LSM and LSE modes are proposed as a didactic alternative for modeling the propagation of guided electromagnetic waves. Our considerations can be applied to the most common electromagnetic waves guiding systems: empty metallic waveguides, metallic waveguides partially filled with dielectrics, dielectric sheet waveguides and 3-D dielectric waveguides. In all cases, our interest is focussed on modes with a defined polarization; therefore the teaching activity can be treated from the scalar wave approximation point of view. (Author)

  20. Sparse SVD Method for High-Resolution Extraction of the Dispersion Curves of Ultrasonic Guided Waves.

    Science.gov (United States)

    Xu, Kailiang; Minonzio, Jean-Gabriel; Ta, Dean; Hu, Bo; Wang, Weiqi; Laugier, Pascal

    2016-10-01

    The 2-D Fourier transform analysis of multichannel signals is a straightforward method to extract the dispersion curves of guided modes. Basically, the time signals recorded at several positions along the waveguide are converted to the wavenumber-frequency space, so that the dispersion curves (i.e., the frequency-dependent wavenumbers) of the guided modes can be extracted by detecting peaks of energy trajectories. In order to improve the dispersion curve extraction of low-amplitude modes propagating in a cortical bone, a multiemitter and multireceiver transducer array has been developed together with an effective singular vector decomposition (SVD)-based signal processing method. However, in practice, the limited number of positions where these signals are recorded results in a much lower resolution in the wavenumber axis than in the frequency axis. This prevents a clear identification of overlapping dispersion curves. In this paper, a sparse SVD (S-SVD) method, which combines the signal-to-noise ratio improvement of the SVD-based approach with the high wavenumber resolution advantage of the sparse optimization, is presented to overcome the above-mentioned limitation. Different penalty constraints, i.e., l1 -norm, Frobenius norm, and revised Cauchy norm, are compared with the sparse characteristics. The regularization parameters are investigated with respect to the convergence property and wavenumber resolution. The proposed S-SVD method is investigated using synthetic wideband signals and experimental data obtained from a bone-mimicking phantom and from an ex-vivo human radius. The analysis of the results suggests that the S-SVD method has the potential to significantly enhance the wavenumber resolution and to improve the extraction of the dispersion curves.

  1. Ultrasound-Guided Breast Biopsy

    Science.gov (United States)

    ... Professions Site Index A-Z Ultrasound-Guided Breast Biopsy An ultrasound-guided breast biopsy uses sound waves ... Guided Breast Biopsy? What is Ultrasound-Guided Breast Biopsy? Lumps or abnormalities in the breast are often ...

  2. On-line structural integrity monitoring and defect diagnosis of steam generators using analysis of guided acoustic waves

    Science.gov (United States)

    Lu, Baofu

    2005-11-01

    Integrity monitoring and flaw diagnostics of flat beams and tubular structures was investigated in this research using guided acoustic signals. The primary objective was to study the feasibility of using imbedded sensors for monitoring steam generator and heat exchanger tubing. A piezo-sensor suite was deployed to activate and collect Lamb wave signals that propagate along metallic specimens. The dispersion curves of Lamb waves along plate and tubular structures were generated through numerical analysis. Several advanced techniques were explored to extract representative features from acoustic time series. Among them, the Hilbert-Huang transform (HHT) is a recently developed technique for the analysis of non-linear and transient signals. A moving window method was introduced to generate the local peak characters from acoustic time series, and a zooming window technique was developed to localize the structural flaws. The dissertation presents the background of the analysis of acoustic signals acquired from piezo-electric transducers for structural defect monitoring. A comparison of the use of time-frequency techniques, including the Hilbert-Huang transform, is presented. It also presents the theoretical study of Lamb wave propagation in flat beams and tubular structures, and the need for mode separation in order to effectively perform defect diagnosis. The results of an extensive experimental study of detection, location, and isolation of structural defects in flat aluminum beams and brass tubes are presented. The time-frequency analysis and pattern recognition techniques were combined for classifying structural defects in brass tubes. Several types of flaws in brass tubes were tested, both in the air and in water. The techniques also proved to be effective under background/process noise. A detailed theoretical analysis of Lamb wave propagation was performed and simulations were carried out using the finite element software system ABAQUS. This analytical study

  3. Ultrasound-Guided Extracorporeal Shock Wave Lithotripsy of Pancreatic Ductal Stones: Six Years’ Experience

    Directory of Open Access Journals (Sweden)

    Werner Johanns

    1996-01-01

    Full Text Available Extracorporeal shock wave lithotripsy (ESWL and endoscopic sphincterotomy (EST was performed in 35 patients suffering from pancreatic duct stones. Calculi disintegration and resolution of obstruction were achieved in all cases. Completely stone-free ducts were achieved in 16 patients (46% while some peripheral asymptomatic stone material remained in 19 (54%. Dilation of the main pancreatic duct was reduced in 29 patients (83%. Twelve patients (34% became completely asymptomatic and 17 (49% reported a marked reduction of pain. Pancreatogenic steatorrhea ceased and 18 patients (51% gained weight. Pathological glucose tolerance returned to normal in one patient. No major complications were observed. The combination of ESWL and EST is a successful, nonoperative, new treatment in pancreatic stone disease.

  4. Low-frequency guided waves in a fluid-filled borehole: Simultaneous effects of generation and scattering due to multiple fractures

    Science.gov (United States)

    Minato, Shohei; Ghose, Ranajit

    2017-03-01

    Low-frequency, axially-symmetric guided waves which propagate along a fluid-filled borehole (tube waves) are studied in order to characterize the hydraulic fractures intersecting the borehole. We formulate a new equation for the total tube wavefield, which includes simultaneous effects of (1) tube-wave scattering (reflection and transmission) due to wave propagation across hydraulic fractures, and (2) tube-wave generation due to incident plane P waves. The fracture is represented by the nonwelded interface boundary conditions. We use an appropriate form of the representation theorem in order to correctly handle the multiple scattering due to nonwelded interfaces. Our approach can implement any model that has so far been developed. We consider a recent model which includes simultaneous effects of fluid viscosity, dynamic fluid flow, and fracture compliance. The derived equation offers a number of important insights. We recognize that the effective generation amplitude contains the simultaneous effect of both tube-wave generation and scattering. This leads to a new physical understanding indicating that the tube waves are scattered immediately after generation. We show that this scattering is nonlinear with respect to interface compliance. This physical mechanism can be implicitly accounted for by considering more realistic boundary conditions. We also illustrate the application of the new equation in order to predict the complex signature of the total tube wavefield, including generation and scattering at multiple hydraulic fractures. A new formulation for focusing analyses is also derived in order to image and characterize the hydraulic fractures. The obtained results and discussions are important for interpretation, modeling, and imaging using low-frequency guided waves, in the presence of multiple fractures along a cylindrical inclusion.

  5. Adjoint analysis of the source and path sensitivities of basin-guided waves

    Science.gov (United States)

    Day, Steven M.; Roten, Daniel; Olsen, Kim B.

    2012-05-01

    Simulations of earthquake rupture on the southern San Andreas Fault (SAF) reveal large amplifications in the San Gabriel and Los Angeles Basins (SGB and LAB) apparently associated with long-range path effects. Geometrically similar excitation patterns can be recognized repeatedly in different SAF simulations (e.g. Love wave-like energy with predominant period around 4 s, channelled southwestwardly from the SGB into LAB), yet the amplitudes with which these distinctive wavefield patterns are excited change, depending upon source details (slip distribution, direction and velocity of rupture). We describe a method for rapid calculation of the sensitivity of such predicted wavefield features to perturbations of the source kinematics, using a time-reversed (adjoint) wavefield simulation. The calculations are analogous to those done in adjoint tomography, and the same time-reversed calculation also yields path-sensitivity kernels that give further insight into the excitation mechanism. For rupture on the southernmost 300 km of SAF, LAB excitation is greatest for slip concentrated between the northern Coachella Valley and the transverse ranges, propagating to the NE and with rupture velocities between 3250 and 3500 m s-1 along that fault segment; that is, within or slightly above the velocity range (between Rayleigh and S velocities) that is energetically precluded in the limit of a sharp rupture front, highlighting the potential value of imposing physical constraints (such as from spontaneous rupture models) on source parametrizations. LAB excitation is weak for rupture to the SW and for ruptures in either direction located north of the transverse transverse ranges, whereas Ventura Basin (VTB) is preferentially excited by NE ruptures situated north of the transverse ranges. Path kernels show that LAB excitation is mediated by surface waves deflected by the velocity contrast along the southern margin of the transverse ranges, having most of their energy in basement rock

  6. A Helical Undulator Wave-guide Inverse Free-Electron Laser

    Science.gov (United States)

    Rosenzweig, J.; Bodzin, N.; Frigola, P.; Joshi, C.; Musumeci, P.; Pellegrini, C.; Tochitsky, S.; Travish, G.

    2004-12-01

    With recent success in high gradient, high-energy gain IFEL experiments at the UCLA Neptune Laboratory, future experiments are now being contemplated. The Neptune IFEL was designed to use a tightly focused, highly diffracting, near-TW peak power 10 micron laser. This choice of laser focusing, driven by power-handling limitations of the optics near the interaction region, led to design and use of a very complex undulator, and to sensitivity to both laser misalignment and focusing errors. As these effects limited the performance of the IFEL experiment, a next generation experiment at Neptune has been studied which avoids the use of a highly diffractive laser beam through use of a waveguide. We discuss here the choice of low-loss waveguide, guided mode characteristics and likely power limitations. We also examine a preferred undulator design, which is chosen to be helical in order to maximize the acceleration achieved for a given power. With the limitations of these laser and undulator choices in mind, we show the expected performance of the IFEL using 1D simulations. Three-dimensional effects are examined, in the context of use of a solenoid for focusing and acceleration enhancement.

  7. 冷冻水管道腐蚀缺陷超声导波检测%Ultrasonic Guided Wave for Chilled Water Pipelines Corrosion Testing

    Institute of Scientific and Technical Information of China (English)

    马柯; 张胜军; 曹建群

    2013-01-01

    采用超声导波检测方法,对中央空调冷冻水管道腐蚀缺陷进行了检测.对导波反射回波信号进行标定,拆除保温层对疑似缺陷进行验证,计算缺陷处管道周向腐蚀减薄率,并分析了影响缺陷回波信号的因素.结果表明,超声导波检测能够实现腐蚀缺陷的快速检测与定位;波包在支管与大小头处发生模态转换与发散,使得其后的区域成为检测盲区;导波信号在管道外壁腐蚀层的吸收作用下迅速衰减,沿长度方向的反射回波强度迅速下降.%Corrosion defects in central air-condition chilled water pipelines were tested using ultrasonic guided wave.Reflection signals were marked and suspected defects were verified after removal of the insulating layer.The corrosion rate of the defects in the circumferential direction was calculated,and different factors affecting the reflection signals were studied.The results show that the ultrasonic guided wave method can test and locate the corrosion defects rapidly.Guided wave modes transform and wave packets disperse in the branch and adjustable tube,so the testing results in the areas behind such structures are invalid.Guided wave weakens rapidly due to the corrosion layer's absorb leading to the decline of reflection signals along pipelines.

  8. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

    Science.gov (United States)

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-11-01

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

  9. Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode.

    Science.gov (United States)

    Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

    2015-11-16

    Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

  10. WAVE2-Abi2 complex controls growth cone activity and regulates the multipolar-bipolar transition as well as the initiation of glia-guided migration.

    Science.gov (United States)

    Xie, Min-Jue; Yagi, Hideshi; Kuroda, Kazuki; Wang, Chen-Chi; Komada, Munekazu; Zhao, Hong; Sakakibara, Akira; Miyata, Takaki; Nagata, Koh-Ichi; Oka, Yuichiro; Iguchi, Tokuichi; Sato, Makoto

    2013-06-01

    Glia-guided migration (glia-guided locomotion) during radial migration is a characteristic yet unique mode of migration. In this process, the directionality of migration is predetermined by glial processes and not by growth cones. Prior to the initiation of glia-guided migration, migrating neurons transform from multipolar to bipolar, but the molecular mechanisms underlying this multipolar-bipolar transition and the commencement of glia-guided migration are not fully understood. Here, we demonstrate that the multipolar-bipolar transition is not solely a cell autonomous event; instead, the interaction of growth cones with glial processes plays an essential role. Time-lapse imaging with lattice assays reveals the importance of vigorously active growth cones in searching for appropriate glial scaffolds, completing the transition, and initiating glia-guided migration. These growth cone activities are regulated by Abl kinase and Cdk5 via WAVE2-Abi2 through the phosphorylation of tyrosine 150 and serine 137 of WAVE2. Neurons that do not display such growth cone activities are mispositioned in a more superficial location in the neocortex, suggesting the significance of growth cones for the final location of the neurons. This process occurs in spite of the "inside-out" principle in which later-born neurons are situated more superficially.

  11. Crack propagation monitoring in a full-scale aircraft fatigue test based on guided wave-Gaussian mixture model

    Science.gov (United States)

    Qiu, Lei; Yuan, Shenfang; Bao, Qiao; Mei, Hanfei; Ren, Yuanqiang

    2016-05-01

    For aerospace application of structural health monitoring (SHM) technology, the problem of reliable damage monitoring under time-varying conditions must be addressed and the SHM technology has to be fully validated on real aircraft structures under realistic load conditions on ground before it can reach the status of flight test. In this paper, the guided wave (GW) based SHM method is applied to a full-scale aircraft fatigue test which is one of the most similar test status to the flight test. To deal with the time-varying problem, a GW-Gaussian mixture model (GW-GMM) is proposed. The probability characteristic of GW features, which is introduced by time-varying conditions is modeled by GW-GMM. The weak cumulative variation trend of the crack propagation, which is mixed in time-varying influence can be tracked by the GW-GMM migration during on-line damage monitoring process. A best match based Kullback-Leibler divergence is proposed to measure the GW-GMM migration degree to reveal the crack propagation. The method is validated in the full-scale aircraft fatigue test. The validation results indicate that the reliable crack propagation monitoring of the left landing gear spar and the right wing panel under realistic load conditions are achieved.

  12. A base-sequence-modulated Golay code improves the excitation and measurement of ultrasonic guided waves in long bones.

    Science.gov (United States)

    Song, Xiaojun; Ta, Dean; Wang, Weiqi

    2012-11-01

    Researchers are interested in using ultrasonic guided waves (GWs) to assess long bones. However, GWs suffer high attenuation when they propagate in long bones, resulting in a low SNR. To overcome this limitation, this paper introduces a base-sequence-modulated Golay code (BSGC) to produce larger amplitude and improve the SNR in the ultrasound evaluation of long bones. A 16-bit Golay code was used for excitation in computer simulation. The decoded GWs and the traditional GWs, which were generated by a single pulse, agreed well after decoding the received signals, and the SNR was improved by 26.12 dB. In the experiments using bovine bones, the BSGC excitation produced the amplitudes which were at least 237 times greater than those produced by a single pulse excitation. The BSGC excitation also allowed the GWs to be received over a longer distance between two transducers. The results suggest the BSGC excitation has the potential to measure GWs and assess long bones.

  13. Features of wave generation by a source moving along a one-dimensional flexible guide lying on an elastic-inertial foundation

    Science.gov (United States)

    Erofeev, V. I.; Kolesov, D. A.; Lisenkova, E. E.

    2016-11-01

    A self-consistent dynamic problem is posed for a system including a one-dimensional flexible guide (a string), elastic-inertial foundation (an array of oscillators), and moving oscillating load. The effect of the foundation parameters on the dispersion characteristics (frequency, phase velocity, and group velocity as functions of the wavenumber) of transverse waves propagating along the string has been analyzed. It has been shown that taking into account the foundation inertia leads to the presence of two critical (cutoff) frequencies. Regularities of wave generation by a source moving along the string have been analyzed.

  14. HIV-1 target cells in the CNS

    OpenAIRE

    Joseph, Sarah B.; Arrildt, Kathryn T.; Sturdevant, Christa B.; Swanstrom, Ronald

    2014-01-01

    HIV-1 replication in the central nervous system (CNS) is typically limited by the availability of target cells. HIV-1 variants that are transmitted and dominate the early stages of infection almost exclusively use the CCR5 coreceptor and are well adapted to entering, and thus infecting, cells expressing high CD4 densities similar to those found on CD4+ T cells. While the “immune privileged” CNS is largely devoid of CD4+ T cells, macrophage and microglia are abundant throughout ...

  15. CNS toxoplasmosis in an immunocompetent individual

    OpenAIRE

    2015-01-01

    Toxoplasmosis is a serious and life-threatening disease in humans with a high prevalence in immunocompromised persons. The disease has a wide spectrum, depending on the immune status of the person. A CNS manifestation of toxoplasmosis in an immunocompetent person is very rare and often undetected. Our case of CNS toxoplasmosis in an immunocompetent person emphasizes the radiological diagnosis, which was further confirmed by advanced microbiology technique.

  16. CNS toxoplasmosis in an immunocompetent individual

    Directory of Open Access Journals (Sweden)

    Rajoo Ramachandran, MBBS, MD

    2014-01-01

    Full Text Available Toxoplasmosis is a serious and life-threatening disease in humans with a high prevalence in immunocompromised persons. The disease has a wide spectrum, depending on the immune status of the person. A CNS manifestation of toxoplasmosis in an immunocompetent person is very rare and often undetected. Our case of CNS toxoplasmosis in an immunocompetent person emphasizes the radiological diagnosis, which was further confirmed by advanced microbiology technique.

  17. Wave

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many t...

  18. Knowledge-Based, Central Nervous System (CNS) Lead Selection and Lead Optimization for CNS Drug Discovery.

    Science.gov (United States)

    Ghose, Arup K; Herbertz, Torsten; Hudkins, Robert L; Dorsey, Bruce D; Mallamo, John P

    2012-01-18

    The central nervous system (CNS) is the major area that is affected by aging. Alzheimer's disease (AD), Parkinson's disease (PD), brain cancer, and stroke are the CNS diseases that will cost trillions of dollars for their treatment. Achievement of appropriate blood-brain barrier (BBB) penetration is often considered a significant hurdle in the CNS drug discovery process. On the other hand, BBB penetration may be a liability for many of the non-CNS drug targets, and a clear understanding of the physicochemical and structural differences between CNS and non-CNS drugs may assist both research areas. Because of the numerous and challenging issues in CNS drug discovery and the low success rates, pharmaceutical companies are beginning to deprioritize their drug discovery efforts in the CNS arena. Prompted by these challenges and to aid in the design of high-quality, efficacious CNS compounds, we analyzed the physicochemical property and the chemical structural profiles of 317 CNS and 626 non-CNS oral drugs. The conclusions derived provide an ideal property profile for lead selection and the property modification strategy during the lead optimization process. A list of substructural units that may be useful for CNS drug design was also provided here. A classification tree was also developed to differentiate between CNS drugs and non-CNS oral drugs. The combined analysis provided the following guidelines for designing high-quality CNS drugs: (i) topological molecular polar surface area of <76 Å(2) (25-60 Å(2)), (ii) at least one (one or two, including one aliphatic amine) nitrogen, (iii) fewer than seven (two to four) linear chains outside of rings, (iv) fewer than three (zero or one) polar hydrogen atoms, (v) volume of 740-970 Å(3), (vi) solvent accessible surface area of 460-580 Å(2), and (vii) positive QikProp parameter CNS. The ranges within parentheses may be used during lead optimization. One violation to this proposed profile may be acceptable. The

  19. A method for the measurement of dispersion curves of circumferential guided waves radiating from curved shells: experimental validation and application to a femoral neck mimicking phantom.

    Science.gov (United States)

    Nauleau, Pierre; Minonzio, Jean-Gabriel; Chekroun, Mathieu; Cassereau, Didier; Laugier, Pascal; Prada, Claire; Grimal, Quentin

    2016-07-07

    Our long-term goal is to develop an ultrasonic method to characterize the thickness, stiffness and porosity of the cortical shell of the femoral neck, which could enhance hip fracture risk prediction. To this purpose, we proposed to adapt a technique based on the measurement of guided waves. We previously evidenced the feasibility of measuring circumferential guided waves in a bone-mimicking phantom of a circular cross-section of even thickness. The goal of this study is to investigate the impact of the complex geometry of the femoral neck on the measurement of guided waves. Two phantoms of an elliptical cross-section and one phantom of a realistic cross-section were investigated. A 128-element array was used to record the inter-element response matrix of these waveguides. This experiment was simulated using a custom-made hybrid code. The response matrices were analyzed using a technique based on the physics of wave propagation. This method yields portions of dispersion curves of the waveguides which were compared to reference dispersion curves. For the elliptical phantoms, three portions of dispersion curves were determined with a good agreement between experiment, simulation and theory. The method was thus validated. The characteristic dimensions of the shell were found to influence the identification of the circumferential wave signals. The method was then applied to the signals backscattered by the superior half of constant thickness of the realistic phantom. A cut-off frequency and some portions of modes were measured, with a good agreement with the theoretical curves of a plate waveguide. We also observed that the method cannot be applied directly to the signals backscattered by the lower half of varying thicknesses of the phantom. The proposed approach could then be considered to evaluate the properties of the superior part of the femoral neck, which is known to be a clinically relevant site.

  20. Environmental cues from CNS, PNS, and ENS cells regulate CNS progenitor differentiation

    DEFF Research Database (Denmark)

    Brännvall, Karin; Corell, Mikael; Forsberg-Nilsson, Karin;

    2008-01-01

    Cellular origin and environmental cues regulate stem cell fate determination. Neuroepithelial stem cells form the central nervous system (CNS), whereas neural crest stem cells generate the peripheral (PNS) and enteric nervous system (ENS). CNS neural stem/progenitor cell (NSPC) fate determination...

  1. An invertebrate model for CNS drug discovery

    DEFF Research Database (Denmark)

    Al-Qadi, Sonia; Schiøtt, Morten; Hansen, Steen Honoré

    2015-01-01

    BACKGROUND: ABC efflux transporters at the blood brain barrier (BBB), namely the P-glycoprotein (P-gp), restrain the development of central nervous system (CNS) drugs. Consequently, early screening of CNS drug candidates is pivotal to identify those affected by efflux activity. Therefore, simple,...... barriers. CONCLUSION: Findings suggest a conserved mechanism of brain efflux activity between insects and vertebrates, confirming that this model holds promise for inexpensive and high-throughput screening relative to in vivo models, for CNS drug discovery......., high-throughput and predictive screening models are required. The grasshopper (locust) has been developed as an invertebrate in situ model for BBB permeability assessment, as it has shown similarities to vertebrate models. METHODS: Transcriptome profiling of ABC efflux transporters in the locust brain......BACKGROUND: ABC efflux transporters at the blood brain barrier (BBB), namely the P-glycoprotein (P-gp), restrain the development of central nervous system (CNS) drugs. Consequently, early screening of CNS drug candidates is pivotal to identify those affected by efflux activity. Therefore, simple...

  2. MOLECULAR (RE-)CLASSIFICATION OF CNS-PRIMITIVE NEUROECTODERMAL TUMORS

    OpenAIRE

    Kool, Marcel; Sturm, Dominik; Northcott, Paul A.; Jones, David T. W.; Korshunov, Andrey; Lichter, Peter; Pfister, Stefan

    2014-01-01

    BACKGROUND: According to the current WHO classification of CNS tumors, childhood CNS primitive neuro-ectodermal tumors (CNS-PNETs; WHO °IV) are poorly differentiated embryonal tumors with early onset and aggressive clinical behavior. Histological diagnosis can be complicated by morphological heterogeneity and divergent differentiation. Recent studies suggest the existence of molecular subgroups of CNS-PNETs sharing biological characteristics with other childhood CNS tumors. Here, we aimed at ...

  3. New perspectives on using brain imaging to study CNS stimulants.

    Science.gov (United States)

    Lukas, Scott E

    2014-12-01

    While the recent application of brain imaging to study CNS stimulants has offered new insights into the fundamental factors that contribute to their use and abuse, many gaps remain. Brain circuits that mediate pleasure, dependence, craving and relapse are anatomically, neurophysiologically and neurochemically distinct from one another, which has guided the search for correlates of stimulant-seeking and taking behavior. However, unlike other drugs of abuse, metrics for tolerance and physical dependence on stimulants are not obvious. The dopamine theory of stimulant abuse does not sufficiently explain this disorder as serotonergic, GABAergic and glutamagergic circuits are clearly involved in stimulant pharmacology and so tracking the source of the "addictive" processes must adopt a more multimodal, multidisciplinary approach. To this end, both anatomical and functional magnetic resonance imaging (MRI), MR spectroscopy (MRS) and positron emission tomography (PET) are complementary and have equally contributed to our understanding of how stimulants affect the brain and behavior. New vistas in this area include nanotechnology approaches to deliver small molecules to receptors and use MRI to resolve receptor dynamics. Anatomical and blood flow imaging has yielded data showing that cognitive enhancers might be useful adjuncts in treating CNS stimulant dependence, while MRS has opened opportunities to examine the brain's readiness to accept treatment as GABA tone normalizes after detoxification. A desired outcome of the above approaches is being able to offer evidence-based rationales for treatment approaches that can be implemented in a more broad geographic area, where access to brain imaging facilities may be limited. This article is part of the Special Issue entitled 'CNS Stimulants'.

  4. Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a periodically multilayered isotropic dielectric material

    CERN Document Server

    Chiadini, Francesco; Scaglione, Antonio; Lakhtakia, Akhlesh

    2015-01-01

    Multiple p- and s-polarized compound surface plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic dielectric (HID) material and a periodic multilayered isotropic dielectric (PMLID) material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p-polarization state, is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID material, and the period and the composition of the PMLID material. Some of these are p polarized, the others being s polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The...

  5. Statistical threshold determination method through noise map generation for two dimensional amplitude and time-of-flight mapping of guided waves

    Science.gov (United States)

    Yenn Chong, See; Lee, Jung-Ryul; Yik Park, Chan

    2013-03-01

    Conventional threshold crossing technique generally encounters the difficulty in setting a common threshold level in the extraction of the respective time-of-flights (ToFs) and amplitudes from the guided waves obtained at many different points by spatial scanning. Therefore, we propose a statistical threshold determination method through noise map generation to automatically process numerous guided waves having different propagation distances. First, a two-dimensional (2-D) noise map is generated using one-dimensional (1-D) WT magnitudes at time zero of the acquired waves. Then, the probability density functions (PDFs) of Gamma distribution, Weibull distribution and exponential distribution are used to model the measured 2-D noise map. Graphical goodness-of-fit measurements are used to find the best fit among the three theoretical distributions. Then, the threshold level is automatically determined by selecting the desired confidence level of the noise rejection in the cumulative distribution function of the best fit PDF. Based on this threshold level, the amplitudes and ToFs are extracted and mapped into a 2-D matrix array form. The threshold level determined by the noise statistics may cross the noise signal after time zero. These crossings are represented as salt-and-pepper noise in the ToF and amplitude maps but finally removed by the 1-D median filter. This proposed method was verified in a thick stainless steel hollow cylinder where guided waves were acquired in an area of 180 mm×126 mm of the cylinder by using a laser ultrasonic scanning system and an ultrasonic sensor. The Gamma distribution was estimated as the best fit to the verification experimental data by the proposed algorithm. The statistical parameters of the Gamma distribution were used to determine the threshold level appropriate for most of the guided waves. The ToFs and amplitudes of the first arrival mode were mapped into a 2-D matrix array form. Each map included 447 noisy points out of 90

  6. An energy-based sparse representation of ultrasonic guided-waves for online damage detection of pipelines under varying environmental and operational conditions

    Science.gov (United States)

    Eybpoosh, Matineh; Berges, Mario; Noh, Hae Young

    2017-01-01

    This work addresses the main challenges in real-world application of guided-waves for damage detection of pipelines, namely their complex nature and sensitivity to environmental and operational conditions (EOCs). Different propagation characteristics of the wave modes, their distinctive sensitivities to different types and ranges of EOCs, and to different damage scenarios, make the interpretation of diffuse-field guided-wave signals a challenging task. This paper proposes an unsupervised feature-extraction method for online damage detection of pipelines under varying EOCs. The objective is to simplify diffuse-field guided-wave signals to a sparse subset of the arrivals that contains the majority of the energy carried by the signal. We show that such a subset is less affected by EOCs compared to the complete time-traces of the signals. Moreover, it is shown that the effects of damage on the energy of this subset suppress those of EOCs. A set of signals from the undamaged state of a pipe are used as reference records. The reference dataset is used to extract the aforementioned sparse representation. During the monitoring stage, the sparse subset, representing the undamaged pipe, will not accurately reconstruct the energy of a signal from a damaged pipe. In other words, such a sparse representation of guided-waves is sensitive to occurrence of damage. Therefore, the energy estimation errors are used as damage-sensitive features for damage detection purposes. A diverse set of experimental analyses are conducted to verify the hypotheses of the proposed feature-extraction approach, and to validate the detection performance of the damage-sensitive features. The empirical validation of the proposed method includes (1) detecting a structural abnormality in an aluminum pipe, under varying temperature at different ranges, (2) detecting multiple small damages of different types, at different locations, in a steel pipe, under varying temperature, (3) detecting a structural

  7. Oblique incidence of semi-guided waves on step-like folds in planar dielectric slabs: Lossless vertical interconnects in 3D integrated photonic circuits

    Science.gov (United States)

    Hildebrandt, Andre; Alhaddad, Samer; Hammer, Manfred; Förstner, Jens

    2016-02-01

    Semi-guided light propagation across linear folds of slab waveguides is being considered. Radiation losses vanish beyond certain critical angles of incidence, as can be understood by arguments resembling Snell's law. One thus realizes lossless propagation through 90-degree corner configurations, where the remaining guided waves are still subject to pronounced reflection and polarization conversion. A step-like system of two of these sharp corners can then be viewed as a system akin to a Fabry-Perot interferometer, with two partial reflectors at a distance given by the vertical separation of the slab cores. The respective resonance effect enables full transmission of semiguided, laterally plane waves through the step structures. One obtains a configuration that optically connects guiding layers at different elevation levels in a 3-D integrated optical chip, without radiation losses, over large distances, and reasonably broadband. We show rigorous quasi-analytical results for typical high-contrast Si/SiO2 structures. Although the full-transmission effect requires a symmetric system, here realized by slab waveguides with a silicon core sandwiched between thick silica substrate and cover layers, simulations for configurations with air cover show that a certain asymmetry can well be afforded.

  8. Guided Lamb wave based 2-D spiral phased array for structural health monitoring of thin panel structures

    Science.gov (United States)

    Yoo, Byungseok

    2011-12-01

    In almost all industries of mechanical, aerospace, and civil engineering fields, structural health monitoring (SHM) technology is essentially required for providing the reliable information of structural integrity of safety-critical structures, which can help reduce the risk of unexpected and sometimes catastrophic failures, and also offer cost-effective inspection and maintenance of the structures. State of the art SHM research on structural damage diagnosis is focused on developing global and real-time technologies to identify the existence, location, extent, and type of damage. In order to detect and monitor the structural damage in plate-like structures, SHM technology based on guided Lamb wave (GLW) interrogation is becoming more attractive due to its potential benefits such as large inspection area coverage in short time, simple inspection mechanism, and sensitivity to small damage. However, the GLW method has a few critical issues such as dispersion nature, mode conversion and separation, and multiple-mode existence. Phased array technique widely used in all aspects of civil, military, science, and medical industry fields may be employed to resolve the drawbacks of the GLW method. The GLW-based phased array approach is able to effectively examine and analyze complicated structural vibration responses in thin plate structures. Because the phased sensor array operates as a spatial filter for the GLW signals, the array signal processing method can enhance a desired signal component at a specific direction while eliminating other signal components from other directions. This dissertation presents the development, the experimental validation, and the damage detection applications of an innovative signal processing algorithm based on two-dimensional (2-D) spiral phased array in conjunction with the GLW interrogation technique. It starts with general backgrounds of SHM and the associated technology including the GLW interrogation method. Then, it is focused on the

  9. Delusional Disorder Arising From a CNS Neoplasm.

    Science.gov (United States)

    Stupinski, John; Kim, Jihye; Francois, Dimitry

    2017-01-01

    Erotomania arising from a central nervous system (CNS) neoplasm has not been previously described. Here, we present the first known case, to our knowledge, of erotomania with associated persecutory delusions arising following diagnosis and treatment of a left frontal lobe brain tumor.

  10. Immune regulation and CNS autoimmune disease

    DEFF Research Database (Denmark)

    Antel, J P; Owens, T

    1999-01-01

    The central nervous system is a demonstrated target of both clinical and experimental immune mediated disorders. Immune regulatory mechanisms operative at the levels of the systemic immune system, the blood brain barrier, and within the CNS parenchyma are important determinants of the intensity a...

  11. Myelin-reactive antibodies initiate T cell-mediated CNS autoimmune disease by opsonization of endogenous antigen.

    Science.gov (United States)

    Kinzel, Silke; Lehmann-Horn, Klaus; Torke, Sebastian; Häusler, Darius; Winkler, Anne; Stadelmann, Christine; Payne, Natalie; Feldmann, Linda; Saiz, Albert; Reindl, Markus; Lalive, Patrice H; Bernard, Claude C; Brück, Wolfgang; Weber, Martin S

    2016-07-01

    In the pathogenesis of central nervous system (CNS) demyelinating disorders, antigen-specific B cells are implicated to act as potent antigen-presenting cells (APC), eliciting waves of inflammatory CNS infiltration. Here, we provide the first evidence that CNS-reactive antibodies (Ab) are similarly capable of initiating an encephalitogenic immune response by targeting endogenous CNS antigen to otherwise inert myeloid APC. In a transgenic mouse model, constitutive production of Ab against myelin oligodendrocyte glycoprotein (MOG) was sufficient to promote spontaneous experimental autoimmune encephalomyelitis (EAE) in the absence of B cells, when mice endogenously contained MOG-recognizing T cells. Adoptive transfer studies corroborated that anti-MOG Ab triggered activation and expansion of peripheral MOG-specific T cells in an Fc-dependent manner, subsequently causing EAE. To evaluate the underlying mechanism, anti-MOG Ab were added to a co-culture of myeloid APC and MOG-specific T cells. At otherwise undetected concentrations, anti-MOG Ab enabled Fc-mediated APC recognition of intact MOG; internalized, processed and presented MOG activated naïve T cells to differentiate in an encephalitogenic manner. In a series of translational experiments, anti-MOG Ab from two patients with an acute flare of CNS inflammation likewise facilitated detection of human MOG. Jointly, these observations highlight Ab-mediated opsonization of endogenous CNS auto-antigen as a novel disease- and/or relapse-triggering mechanism in CNS demyelinating disorders.

  12. Non-linearly phased 2-D array transducers arranged on a cylindrical-polar grid for real time guided wave mode control and steering

    Science.gov (United States)

    Kannajosyula, H.; Lissenden, C. J.; Rose, J. L.

    2012-05-01

    Ultrasonic guided wave mode control and steering using phased array transducers (PATs) is studied. A PAT with elements arranged on a cylindrical-polar grid is proposed to overcome the problem of large side-lodes associated with a rectangular grid PAT. The PAT is visualized as a spatio-temporal filter to calculate phase delays. Wavenumber bands resulting from the radial rows enable constructive interfere only in the vicinity of the desired wavenumber and angle of propagation. Finite element simulations are presented to study PAT performance.

  13. Optimum design of phononic crystal perforated plate structures for widest bandgap of fundamental guided wave modes and maximized in-plane stiffness

    Science.gov (United States)

    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. Electromagnetic Field Behavior in Dispersive Isotropic Negative Phase Velocity/Negative Refractive Index Guided Wave Structures Compatible with Millimeter-Wave Monolithic Integrated Circuits

    Directory of Open Access Journals (Sweden)

    Clifford M. Krowne

    2007-01-01

    Full Text Available A microstrip configuration has been loaded with a dispersive isotropic left-handed medium (LHM substrate and studied regarding its high frequency millimeter-wave behavior near 100 GHz. This has been accomplished using a full-wave integral-equation anisotropic Green's function code configured to run for isotropy. Never before seen electromagnetic field distributions are produced, unlike anything found in normal media devices, using this ab initio solver. These distributions are made in the cross-sectional dimension, with the field propagating in the perpendicular direction. It is discovered that the LHM distributions are so radically different from ordinary media used as a substrate that completely new electronic devices based upon the new physics become a real possibility. The distinctive dispersion diagram for the dispersive medium, consisting of unit cells with split ring resonator-rod combinations, is provided over the upper millimeter-wave frequency regime.

  15. MAG, myelin and overcoming growth inhibition in the CNS

    National Research Council Canada - National Science Library

    McKerracher, Lisa; Rosen, Kenneth M

    2015-01-01

    While neurons in the central nervous system (CNS) have the capacity to regenerate their axons after injury, they fail to do so, in part because regeneration is limited by growth inhibitory proteins present in CNS myelin...

  16. Considerations for an Integrated UAS CNS Architecture

    Science.gov (United States)

    Templin, Fred L.; Jain, Raj; Sheffield, Greg; Taboso-Bellesteros, Pedro; Ponchak, Denise

    2017-01-01

    The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is investigating revolutionary and advanced universal, reliable, always available, cyber secure and affordable Communication, Navigation, Surveillance (CNS) options for all altitudes of UAS operations. In Spring 2015, NASA issued a Call for Proposals under NASA Research Announcements (NRA) NNH15ZEA001N, Amendment 7 Subtopic 2.4. Boeing was selected to conduct a study with the objective to determine the most promising candidate technologies for Unmanned Air Systems (UAS) air-to-air and air-to-ground data exchange and analyze their suitability in a post-NextGen NAS environment. The overall objectives are to develop UAS CNS requirements and then develop architectures that satisfy the requirements for UAS in both controlled and uncontrolled air space. This contract is funded under NASAs Aeronautics Research Mission Directorates (ARMD) Aviation Operations and Safety Program (AOSP) Safe Autonomous Systems Operations (SASO) project and proposes technologies for the Unmanned Air Systems Traffic Management (UTM) service.There is a need for accommodating large-scale populations of Unmanned Air Systems (UAS) in the national air space. Scale obviously impacts capacity planning for Communication, Navigation, and Surveillance (CNS) technologies. For example, can wireless communications data links provide the necessary capacity for accommodating millions of small UASs (sUAS) nationwide? Does the communications network provide sufficient Internet Protocol (IP) address space to allow air traffic control to securely address both UAS teams as a whole as well as individual UAS within each team? Can navigation and surveillance approaches assure safe route planning and safe separation of vehicles even in crowded skies?Our objective is to identify revolutionary and advanced CNS alternatives supporting UASs operating at all altitudes and in all airspace while accurately navigating in the absence of

  17. Estimation of femoral bone density from trabecular direct wave and cortical guided wave ultrasound velocities measured at the proximal femur in vivo

    DEFF Research Database (Denmark)

    Barkmann, Reinhard; Dencks, Stefanie; Bremer, Alexander

    2008-01-01

    Bone mineral density (BMD) of the proximal femur is a predictor of hip fracture risk. We developed a Quantitative Ultrasound (QUS) scanner for measurements at this site with similar performance (FemUS). In this study we tested if ultrasound velocities of direct waves through trabecular bone...... echoes reflected from the skin of the leg to yield speed-of-sound (SOS) of different wave components. Data were cross-calibrated and pooled (62 women). Bivariate correlations and a multivariate model were calculated for the estimation of femur BMD. BMD correlated both with trabecular and cortical SOS...

  18. Unilateral versus bilateral ultrasound-guided transversus abdominis plane blocks during ureteric shock wave lithotripsy: A prospective randomized trial

    Directory of Open Access Journals (Sweden)

    Ali Mohamed Ali Elnabtity

    2016-01-01

    Conclusion: Ultrasound-guided unilateral TAP block is as safe and effective analgesic technique as bilateral TAP blocks during unilateral ureteric SWL. It can be used as the sole analgesic technique during ureteric SWL.

  19. 导波检测技术在“抚-鲅”线上的应用%Application of Ultrasonic Guided Wave Detection Technology in Fushun-Bayuquan Pipe

    Institute of Scientific and Technical Information of China (English)

    牛迎战; 张利民; 林猛

    2014-01-01

    The uitrasonic guided wave technology for pipeline defect detection has been applied in industrial field. In this paper, the development history and basic theory of the ultrasonic guided wave technology were introduced. Concrete application of the guided wave inspection technology in defect detection of Fushun-Bayuquan pipe was discussed. Testing conclusion was verified by in-situ observation, which showed that application of the guided wave inspection technology in pipeline defect detection was successful. At last, development trend of the ultrasonic guided wave inspection technology was prospected.%用导波技术对管道缺陷检测进入工业现场应用阶段。介绍了超声导波技术的发展历史及基本理论。表述了导波检测技术“抚-鲅”线缺陷检测中的具体应用过程,检测缺陷结论经现场观测验证准确。表明管道缺陷导波检测技术在“抚-鲅”线上的应用成功。幵指出随着超声导波技术的发展,其在管道缺陷检测工程中将得到广泛的应用。

  20. VIIP: Central Nervous System (CNS) Modeling

    Science.gov (United States)

    Vera, Jerry; Mulugeta, Lealem; Nelson, Emily; Raykin, Julia; Feola, Andrew; Gleason, Rudy; Samuels, Brian; Ethier, C. Ross; Myers, Jerry

    2015-01-01

    Current long-duration missions to the International Space Station and future exploration-class missions beyond low-Earth orbit expose astronauts to increased risk of Visual Impairment and Intracranial Pressure (VIIP) syndrome. It has been hypothesized that the headward shift of cerebrospinal fluid (CSF) and blood in microgravity may cause significant elevation of intracranial pressure (ICP), which in turn may then induce VIIP syndrome through interaction with various biomechanical pathways. However, there is insufficient evidence to confirm this hypothesis. In this light, we are developing lumped-parameter models of fluid transport in the central nervous system (CNS) as a means to simulate the influence of microgravity on ICP. The CNS models will also be used in concert with the lumped parameter and finite element models of the eye described in the related IWS works submitted by Nelson et al., Feola et al. and Ethier et al.

  1. microRNAs in CNS disorders

    DEFF Research Database (Denmark)

    Kocerha, Jannet; Kauppinen, Sakari; Wahlestedt, Claes

    2009-01-01

    In recent years, there has been a shift in the conventional paradigms for transcriptional and translational regulation as extensive sequencing efforts have yielded new insights into the landscape of the human genome and transcriptome. Hundreds of non-coding regulatory RNA molecules called microRNAs...... (miRNAs) have been identified in the mammalian central nervous system (CNS) and are reported to mediate pivotal roles in many aspects of neuronal functions. Disruption of miRNA-based post-transcriptional regulation has been implicated in a range of CNS disorders as one miRNA is predicted to impact...... the expression of numerous downstream mRNA targets. The intricate molecular networks mediated by an miRNA form a robust mechanism for rapid and potent responses to cellular events throughout the development of the human brain. Recent studies have identified a molecular and ultimately pathogenic role for a subset...

  2. Interneuron progenitor transplantation to treat CNS dysfunction

    Directory of Open Access Journals (Sweden)

    Muhammad O Chohan

    2016-08-01

    Full Text Available Due to the inadequacy of endogenous repair mechanisms diseases of the nervous system remain a major challenge to scientists and clinicians. Stem cell based therapy is an exciting and viable strategy that has been shown to ameliorate or even reverse symptoms of CNS dysfunction in preclinical animal models. Of particular importance has been the use of GABAergic interneuron progenitors as a therapeutic strategy. Born in the neurogenic niches of the ventral telencephalon, interneuron progenitors retain their unique capacity to disperse, integrate and induce plasticity in adult host circuitries following transplantation. Here we discuss the potential of interneuron based transplantation strategies as it relates to CNS disease therapeutics. We also discuss mechanisms underlying their therapeutic efficacy and some of the challenges that face the field.

  3. A Guided Self-Consistent-Field Method for Excited-State Wave Function Optimization: Applications to Ligand-Field Transitions in Transition-Metal Complexes.

    Science.gov (United States)

    Peng, Bo; Van Kuiken, Benjamin E; Ding, Feizhi; Li, Xiaosong

    2013-09-10

    A guided self-consistent field (SCF) method is presented in this paper. This method uses the eigenspace update-and-following idea to improve the SCF method for optimizing wave functions that are higher-energy solutions to the Roothaan-Hall equation. In this method, the eigenvectors of the previous SCF step are used to prediagonalize the current Fock/Kohn-Sham matrix, preserving the ordering of orbital occupations. When the subject of interest is an excited state of the same spin symmetry as the ground state, the initial guess of excited wave function is improved with a preconditioning step. The preconditioning step is an SCF iteration applied to the β spin manifold if the initial guess is generated by orbital permutation in the α spin manifold. This simple preconditioning step gives rise to more-stable SCF convergence using the algorithm presented herein. The guided SCF method is used to optimize ligand-field excited states in tetrahedral transition-metal complexes, and calculate ΔSCF excitation energies. The calculated ligand-field transition energies are compared with those obtained from orbital energy differences, linear response time-dependent density functional theory, and experiments. The excitation energies obtained using the method presented in this work show a significant improvement over orbital energy differences and linear response method.

  4. Modeling of guided circumferential SH and Lamb-type waves in open waveguides with semi-analytical finite element and Perfectly Matched Layer method

    Science.gov (United States)

    Matuszyk, Paweł J.

    2017-01-01

    The circumferential guided waves (CGW) are of increasing interest for non-destructive inspecting pipes or other cylindrical structures. If such structures are buried underground, these modes can also deliver some valuable information about the surrounding medium or the quality of the contact between the pipe and the embedding medium. Toward this goal, the detailed knowledge of the dispersive characteristics of CGW is required; henceforth, the robust numerical method has to be established, which allows for the extensive study of the propagation of these modes under different loading conditions. Mathematically, this is the problem of the propagation of guided waves in an open waveguide. This problem differs significantly from the corresponding problem of a closed waveguide both in physical and numerical aspect. The paper presents a combination of semi-analytical finite element method with Perfectly Matched Layer technique for a class of coupled acoustics/elasticity problems with application to modeling of CGW. We discuss different aspects of our algorithm and validate the proposed approach against other established methods available in the literature. The presented numerical examples positively verify the robustness of the proposed method.

  5. Generation of cumulative second-harmonic ultrasonic guided waves with group velocity mismatching: Numerical analysis and experimental validation

    Science.gov (United States)

    Xiang, Yanxun; Zhu, Wujun; Deng, Mingxi; Xuan, Fu-Zhen; Liu, Chang-Jun

    2016-11-01

    The generation of second-harmonic Lamb waves in a homogeneous, isotropic, stress-free elastic plate is analytically and experimentally investigated. The numerical analyses show that whether the matching condition of the group velocity is satisfied or not, the integrated amplitude of a second-harmonic Lamb wave accumulates with the propagation distance when both the finite duration of the primary Lamb wave tone burst and the phase velocity matching are given. The theoretical analyses are validated by experimental measurements of an aluminium plate. Our conclusions are different from those of the previous works that reported that the group velocity matching is required for the generation of the cumulative second-harmonic Lamb waves with the finite duration of tone bursts.

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

    Science.gov (United States)

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

    2012-04-01

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

  7. Core-pumped gain-guided index-antiguided continuous wave lasing in dispersion-engineered erbium-doped fiber.

    Science.gov (United States)

    Chen, Nan-Kuang; Jian, Lian-Jiun

    2012-08-01

    We demonstrate core-pumped gain-guided index-antiguided fiber lasers using a 22 cm long dispersion-engineered erbium-doped fiber. The erbium-doped fiber is dispersion-engineered using optical liquid to replace the most part of silica cladding so that the index of core turns out to be higher (lower) than that of new cladding at pump (lasing) wavelength, respectively. The pump light is confined to propagate in core based on an index-guiding mechanism to efficiently excite the gain medium running through the fiber whereas the cw lasing is constructed in a long, small-core waveguide under a gain-guided, index-antiguided situation.

  8. Lidocaine-induced CNS toxicity--a case report.

    Science.gov (United States)

    Chiang, Y Y; Tseng, K F; Lih, Y W; Tsai, T C; Liu, C T; Leung, H K

    1996-12-01

    Lidocaine is the first local anesthetic of the amide type to be introduced to clinical practice. It is a versatile drug and in anesthesia, is the most commonly used local anesthetic because of its aptness of potency, rapid onset, moderate duration of action and topical activity. It is relatively safe and useful in many other clinical settings. Unfortunately, systemic intoxication and psychotic reaction associated with its use often occur because of its popularity and wider safety margin, for which guide in use is often ignored and overdose becomes commonplace. Moreover, due to its universality in use seldom reports have recently dealt with lidocaine, particularly regarding its toxic reaction. Here, we present a case of lidocaine intoxication occurring during circumcision for a reviewal of the problem. A healthy young male, weighing 65 kg, underwent circumcision for phimosis under penile block with 2% lidocaine which totaled 600 mg. Twenty minutes after injection the patient developed headache, tinnitus, visual and auditory disturbances. Muscle twitching over the mouth angles, trismus and rigidity of extremities were also noted. Later in the course he became restless, agitative, hallucinative, talkative, and verbose with repetitious words. The whole course of the disorder lasted about 5 h. It was believed that lidocaine-induced CNS intoxication, manifested by psychotic reaction broke out. Treatment with thiopental was not very impressive. Also, we took this opportunity to discuss and review the toxic reaction associated with the use of lidocaine, its risk factors, mechanism, treatment and prevention. The complicated associations of lidocaine-induced CNS toxic reaction with central control of behavior and the neurotransmitter systems (adrenergic, dopaminergic and serotonin) were also touched.

  9. Photoacoustic reflection artifact reduction using photoacoustic-guided focused ultrasound: comparison between plane-wave and element-by-element synthetic backpropagation approach

    Science.gov (United States)

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2017-01-01

    Reflection artifacts caused by acoustic inhomogeneities constitute a major problem in epi-mode biomedical photoacoustic imaging. Photoacoustic transients from the skin and superficial optical absorbers traverse into the tissue and reflect off echogenic structures to generate reflection artifacts. These artifacts cause difficulties in the interpretation of images and reduce contrast and imaging depth. We recently developed a method called PAFUSion (photoacoustic-guided focused ultrasound) to circumvent the problem of reflection artifacts in photoacoustic imaging. We already demonstrated that the photoacoustic signals can be backpropagated using synthetic aperture pulse-echo data for identifying and reducing reflection artifacts in vivo. In this work, we propose an alternative variant of PAFUSion in which synthetic backpropagation of photoacoustic signals is based on multi-angled plane-wave ultrasound measurements. We implemented plane-wave and synthetic aperture PAFUSion in a handheld ultrasound/photoacoustic imaging system and demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on a human finger using both approaches. Our results suggest that, while both approaches are equivalent in terms of artifact reduction efficiency, plane-wave PAFUSion requires less pulse echo acquisitions when the skin absorption is the main cause of reflection artifacts. PMID:28736669

  10. SINS/CNS Nonlinear Integrated Navigation Algorithm for Hypersonic Vehicle

    Directory of Open Access Journals (Sweden)

    Yong-jun Yu

    2015-01-01

    Full Text Available Celestial Navigation System (CNS has characteristics of accurate orientation and strong autonomy and has been widely used in Hypersonic Vehicle. Since the CNS location and orientation mainly depend upon the inertial reference that contains errors caused by gyro drifts and other error factors, traditional Strap-down Inertial Navigation System (SINS/CNS positioning algorithm setting the position error between SINS and CNS as measurement is not effective. The model of altitude azimuth, platform error angles, and horizontal position is designed, and the SINS/CNS tightly integrated algorithm is designed, in which CNS altitude azimuth is set as measurement information. GPF (Gaussian particle filter is introduced to solve the problem of nonlinear filtering. The results of simulation show that the precision of SINS/CNS algorithm which reaches 130 m using three stars is improved effectively.

  11. Electrophysiological CNS-processes related to associative learning in humans.

    Science.gov (United States)

    Christoffersen, Gert R J; Schachtman, Todd R

    2016-01-01

    The neurophysiology of human associative memory has been studied with electroencephalographic techniques since the 1930s. This research has revealed that different types of electrophysiological processes in the human brain can be modified by conditioning: sensory evoked potentials, sensory induced gamma-band activity, periods of frequency-specific waves (alpha and beta waves, the sensorimotor rhythm and the mu-rhythm) and slow cortical potentials. Conditioning of these processes has been studied in experiments that either use operant conditioning or repeated contingent pairings of conditioned and unconditioned stimuli (classical conditioning). In operant conditioning, the appearance of a specific brain process is paired with an external stimulus (neurofeedback) and the feedback enables subjects to obtain varying degrees of control of the CNS-process. Such acquired self-regulation of brain activity has found practical uses for instance in the amelioration of epileptic seizures, Autism Spectrum Disorders (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). It has also provided communicative means of assistance for tetraplegic patients through the use of brain computer interfaces. Both extra and intracortically recorded signals have been coupled with contingent external feedback. It is the aim for this review to summarize essential results on all types of electromagnetic brain processes that have been modified by classical or operant conditioning. The results are organized according to type of conditioned EEG-process, type of conditioning, and sensory modalities of the conditioning stimuli.

  12. Preliminary research on overmoded high-power millimeter-wave Cerenkov generator with dual-cavity reflector in low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Hu; Wu, Ping [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an, Shaanxi 710024 (China); Chen, Changhua; Ning, Hui; Tan, Weibing; Teng, Yan; Shi, Yanchao; Song, Zhimin; Cao, Yibing; Du, Zhaoyu [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an, Shaanxi 710024 (China)

    2015-12-15

    This paper presents preliminary research on a V-band overmoded Cerenkov generator with dual-cavity reflector operating in a low guiding magnetic field. It is found that the fluctuation of the electron envelope in the low guiding magnetic field can be predicted using an equivalent coaxial model of a foilless diode, and a dual-cavity reflector based on the model matching method can provide strong reflection at the front end of the overmoded structures so that any microwave power that leaks into the diode region can be effectively suppressed. Numerical simulations indicate that the control of the beam envelope and the use of the dual-cavity reflector ease generator operation in the low guiding magnetic field. In the experimental research, the fluctuation of the annular electron beam with the outer radius of 7.5 mm measures approximately 0.7 mm, which is in good agreement with the theoretical results. The disturbance caused by power leaking from the overmoded slow wave structure is eliminated by the dual-cavity reflector. With accurate fabrication and assembly processes, an operating frequency of 61.6 GHz is attained by the fifth harmonic heterodyne method, and the output power is measured to be approximately 123 MW by the far-field measurement method at a diode voltage of 445 kV, a beam current of 4.45 kA, and under a guiding magnetic field of 1.45 T. The output mode is measured using an array of neon flash bulbs, and the pulse shortening phenomenon is both observed and analyzed.

  13. Rotational spectroscopy and three-wave mixing of 4-carvomenthenol: A technical guide to measuring chirality in the microwave regime

    Energy Technology Data Exchange (ETDEWEB)

    Shubert, V. Alvin; Schmitz, David; Medcraft, Chris; Krin, Anna [Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg (Germany); The Center for Free-Electron Laser Science, 22761 Hamburg (Germany); Patterson, David; Doyle, John M. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Schnell, Melanie, E-mail: melanie.schnell@mpsd.mpg.de [Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg (Germany); The Center for Free-Electron Laser Science, 22761 Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, 22761 Hamburg (Germany)

    2015-06-07

    We apply chirality sensitive microwave three-wave mixing to 4-carvomenthenol, a molecule previously uncharacterized with rotational spectroscopy. We measure its rotational spectrum in the 2-8.5 GHz range and observe three molecular conformers. We describe our method in detail, from the initial step of spectral acquisition and assignment to the final step of determining absolute configuration and enantiomeric excess. Combining fitted rotational constants with dipole moment components derived from quantum chemical calculations, we identify candidate three-wave mixing cycles which were further tested using a double resonance method. Initial optimization of the three-wave mixing signal is done by varying the duration of the second excitation pulse. With known transition dipole matrix elements, absolute configuration can be directly determined from a single measurement.

  14. Obstructive hydrocephalus due to CNS toxocariasis.

    Science.gov (United States)

    Choi, Jae-Hwan; Cho, Jae-Wook; Lee, Jae-Hyeok; Lee, Sang Weon; Kim, Hak-Jin; Choi, Kwang-Dong

    2013-06-15

    A 46-year-old man developed intermittent headache, diplopia, and visual obscuration for two months. Funduscopic examination showed optic disk swelling in both eyes. Brain MRI exhibited hydrocephalus and leptomeningeal enhancement at the prepontine cistern, left cerebellopontine angle cistern and bilateral cerebral hemisphere, and hemosiderin deposition along the cerebellar folia. CSF analysis revealed an elevated opening pressure with xanthochromic appearance and small amount of red blood cells. Antibody titer against Toxocariasis using ELISA was elevated both in blood and CSF. Obstructive hydrocephalus and hemosiderin deposition in this case may result from the active inflammatory process due to CNS toxocariasis within the subarachnoid space.

  15. Evaluation of CNS activity of Bramhi Ghrita

    Directory of Open Access Journals (Sweden)

    Achliya G

    2005-01-01

    Full Text Available OBJECTIVE: To eavaluate the CNS activity of Bramhi Ghrita, a polyherbal formulation containing Bacopa monneri, Evolvulus alsinoids, Acorus calamus, Saussurea lappa and cow′s ghee. MATERIALS AND METHODS: The effect of Bramhi Ghrita on motor coordination, behavior, sleep, convulsions, locomotion and analgesia was evaluated in mice using standard procedures. RESULTS: The formulation exhibited reduced alertness, spontaneous locomotor activity and reactivity. It also antagonized the behavioral effects of d-amphetamine, potentiated the pentobarbitone-induced sleep and increased the pain threshold. Bramhi Ghrita protected mice from maximum electroshock and pentylene tetrazole-induced convulsions.

  16. Electromagnetic wave propagation in metamaterials: a visual guide to Fresnel-Kummer surfaces and their singular points

    CERN Document Server

    Favaro, Alberto

    2016-01-01

    The propagation of light through bianisotropic materials is studied in the geometrical optics approximation. For that purpose, we use the quartic general dispersion equation specified by the Tamm-Rubilar tensor, which is cubic in the electromagnetic response tensor of the medium. A collection of different and remarkable Fresnel (wave) surfaces is gathered, and unified via the projective geometry of Kummer surfaces.

  17. General Design for CARR Neutron Guide System

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    A neutron guide system has been designed and partly installed at the China Advanced Research Reactor (CARR) to transport cold neutrons from the cold neutron source (CNS) to several instruments,which are situated in a separate guide hall of 30 m×60 m.

  18. Immune cell trafficking from the brain maintains CNS immune tolerance.

    Science.gov (United States)

    Mohammad, Mohammad G; Tsai, Vicky W W; Ruitenberg, Marc J; Hassanpour, Masoud; Li, Hui; Hart, Prue H; Breit, Samuel N; Sawchenko, Paul E; Brown, David A

    2014-03-01

    In the CNS, no pathway dedicated to immune surveillance has been characterized for preventing the anti-CNS immune responses that develop in autoimmune neuroinflammatory disease. Here, we identified a pathway for immune cells to traffic from the brain that is associated with the rostral migratory stream (RMS), which is a forebrain source of newly generated neurons. Evaluation of fluorescently labeled leukocyte migration in mice revealed that DCs travel via the RMS from the CNS to the cervical LNs (CxLNs), where they present antigen to T cells. Pharmacologic interruption of immune cell traffic with the mononuclear cell-sequestering drug fingolimod influenced anti-CNS T cell responses in the CxLNs and modulated experimental autoimmune encephalomyelitis (EAE) severity in a mouse model of multiple sclerosis (MS). Fingolimod treatment also induced EAE in a disease-resistant transgenic mouse strain by altering DC-mediated Treg functions in CxLNs and disrupting CNS immune tolerance. These data describe an immune cell pathway that originates in the CNS and is capable of dampening anti-CNS immune responses in the periphery. Furthermore, these data provide insight into how fingolimod treatment might exacerbate CNS neuroinflammation in some cases and suggest that focal therapeutic interventions, outside the CNS have the potential to selectively modify anti-CNS immunity.

  19. Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

    Science.gov (United States)

    El Emam, Dalia Sabry; Farag, Rania Kamel; Abouelkheir, Hossam Youssef

    2016-01-01

    Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure. PMID:28127465

  20. Investigation on the use of artificial neural networks to overcome the effects of environmental and operational changes on guided waves monitoring

    Science.gov (United States)

    El Mountassir, M.; Yaacoubi, S.; Dahmene, F.

    2015-07-01

    Intelligent feature extraction and advanced signal processing techniques are necessary for a better interpretation of ultrasonic guided waves signals either in structural health monitoring (SHM) or in nondestructive testing (NDT). Such signals are characterized by at least multi-modal and dispersive components. In addition, in SHM, these signals are closely vulnerable to environmental and operational conditions (EOCs), and can be severely affected. In this paper we investigate the use of Artificial Neural Network (ANN) to overcome these effects and to provide a reliable damage detection method with a minimal of false indications. An experimental case of study (full scale pipe) is presented. Damages sizes have been increased and their shapes modified in different steps. Various parameters such as the number of inputs and the number of hidden neurons were studied to find the optimal configuration of the neural network.

  1. Guided Wave Detection on Expressway Guardrail Post Based on ISMP%基于ISMP的高速公路护栏立柱导波检测

    Institute of Scientific and Technical Information of China (English)

    柳伟续; 李晓霞; 唐志峰; 吕福在; 申瑞君

    2015-01-01

    超声导波在高速公路护栏立柱检测中存在信噪比低、回波中特征信号不明显等问题,为此,提出一种改进的子空间匹配追踪算法( ISMP),利用回波信号的先验信息在过完备Chirp原子库上得到每次迭代的强相关原子集,经过迭代得到待匹配信号的最佳时频原子,从而实现对立柱回波信号的特征提取。通过对中心频率为128 kHz的检测信号进行算法验证,结果表明,ISMP可以有效提取出回波信号的特征原子,所得检测长度与实际测量误差小于1%,满足工程检测要求。%For the low signal to noise ratio, unconspicuous echo characteristic signal and other issues encountered in ultrasonic guided waves inspection of highway guardrail posts,an Improved Subspace Matching Pursuit( ISMP) algorithm is presented,which obtains the correlated atomic sets for each iteration from over-complete chirp atom library by the priori information of echo signal and achieves echo signal feature extraction by iterating to get the best time-frequency atom of the signal to be matched. The algorithm is verified by the guided wave inspection signal whose center frequency is 128 kHz. The results show that ISMP can effectively extract the characteristic atoms from echo signal, and the actual measurement error is less than 1% . It can meet the requirements of project detection.

  2. Application of ultrasonic guided waves to the characterization of texture in metal sheets of cubic and hexagonal crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan.

    1990-10-08

    Ultrasonic techniques have recently been applied to the texture characterization in polycrystalline aggregates of hexagonal crystals. The basis of this application lies in the relations between the elastic constants {bar C}{sub ij} of the aggregates, which can be inferred from ultrasonic wave velocity measurements, and the orientation distribution coefficients. This communication present such relations for aggregates which possess orthotopic material symmetry and hexagonal crystal symmetry for Voigt, Reuss, and Hill averaging methods in a unified and concise representation.

  3. Which method is more effective in treatment of calcific tendinitis in the shoulder? Prospective randomized comparison between ultrasound-guided needling and extracorporeal shock wave therapy.

    Science.gov (United States)

    Kim, Yang-Soo; Lee, Hyo-Jin; Kim, Yoon-vin; Kong, Chae-Gwan

    2014-11-01

    Ultrasound (US)-guided needling with subacromial corticosteroid injection is more effective than extracorporeal shock wave therapy (ESWT) for function restoration and pain relief in patients with calcific tendinitis of the shoulder. Fifty-four patients diagnosed with unilateral painful calcific tendinitis were randomly allocated to a US needling or ESWT group. The US needling group underwent US-guided needling and received a subacromial corticosteroid injection. The ESWT group received ESWT 3 times a week. All patients were prospectively evaluated; American Shoulder and Elbow Surgeons, Simple Shoulder Test, and visual analog scale for pain scores were recorded before the procedure and at 6 weeks, 12 weeks, 6 months, 12 months, and the last follow-up. The size and morphology of the deposits were evaluated by radiography. The average follow-up period was 23.0 months. At last follow-up, the mean size of the deposits was significantly different between the 2 groups (P = .001); it decreased to 0.5 mm from 14.8 mm in the US needling group and to 5.6 mm from 11.0 mm in the ESWT group. There were also significant improvements in clinical outcomes in both groups after treatment (P .05). Both treatment modalities for calcific tendinitis improved clinical outcomes and eliminated calcium deposits. US-guided needling treatment, however, was more effective in function restoration and pain relief in the short term. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  4. Ultrasonic Guided Wave Technology for Non-invasive Assessment of Corrosion-induced Damage in Piping for Pollution Prevention in DOD Fuel Storage Facilities. Cost and Performance Report. Version 2

    Science.gov (United States)

    2011-09-01

    INTRODUCTION .........................................................................................................3 1.1 BACKGROUND... INTRODUCTION The Oil Pollution Act (OPA) of 1990 sets up operational and maintenance requirements for DOD and civilian fuel/oil storage and transport...5.2.3 Design and layout of technology The ultrasonic guided wave measurement system started with bonding magnetostrictive metal strips to the pipe

  5. Robust regeneration of CNS axons through a track depleted of CNS glia.

    Science.gov (United States)

    Moon, L D; Brecknell, J E; Franklin, R J; Dunnett, S B; Fawcett, J W

    2000-01-01

    Transected CNS axons do not regenerate spontaneously but may do so if given an appropriate environment through which to grow. Since molecules associated with CNS macroglia are thought to be inhibitory to axon regeneration, we have tested the hypothesis that removing these cell types from an area of brain will leave an environment more permissive for axon regeneration. Adult rats received unilateral knife cuts of the nigrostriatal tract and ethidium bromide (EB) was used to create a lesion devoid of astrocytes, oligodendrocytes, intact myelin sheaths, and NG2 immunoreactive cells from the site of the knife cut to the ipsilateral striatum (a distance of 6 mm). The regenerative response and the EB lesion environment was examined with immunostaining and electron microscopy at different timepoints following surgery. We report that large numbers of dopaminergic nigral axons regenerated for over 4 mm through EB lesions. At 4 days postlesion dopaminergic sprouting was maximal and the axon growth front had reached the striatum, but there was no additional growth into the striatum after 7 days. Regenerating axons did not leave the EB lesion to form terminals in the striatum, there was no recovery of function, and the end of axon growth correlated with increasing glial immunoreactivity around the EB lesion. We conclude that the removal of CNS glia promotes robust axon regeneration but that this becomes limited by the reappearance of nonpermissive CNS glia. These results suggest, first, that control of the glial reaction is likely to be an important feature in brain repair and, second, that reports of axon regeneration must be interpreted with caution since extensive regeneration can occur simply as a result of a major glia-depleting lesion, rather than as the result of some other specific intervention.

  6. High temperature ultrasonic transducers for the generation of guided waves for non-destructive evaluation of pipes

    Energy Technology Data Exchange (ETDEWEB)

    Sinding, K.; Searfass, C.; Malarich, N.; Reinhardt, B.; Tittmann, B. R. [Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-02-18

    Applications for non-destructive evaluation and structural health monitoring of steam generators require ultrasonic transducers capable of withstanding the high temperatures of the pipes and heat exchangers. These applications require a strong coupling of the transducer to the heat exchanger’s complex geometry at the elevated temperatures. Our objective is to use spray-on piezo-electrics for depositing comb transducers onto the curved surfaces. This paper shows results for composite transducers such as lead zirconate titanate/ bismuth titanate and bismuth titanate/ lithium niobate. The comb transducers were prepared by precision laser ablation. The feasibility of producing second harmonic waves in rods with these spay-on comb transducers was demonstrated and paves the way toward measuring material degradation early-on before crack initiation occurs.

  7. High temperature ultrasonic transducers for the generation of guided waves for non-destructive evaluation of pipes

    Science.gov (United States)

    Sinding, K.; Searfass, C.; Malarich, N.; Reinhardt, B.; Tittmann, B. R.

    2014-02-01

    Applications for non-destructive evaluation and structural health monitoring of steam generators require ultrasonic transducers capable of withstanding the high temperatures of the pipes and heat exchangers. These applications require a strong coupling of the transducer to the heat exchanger's complex geometry at the elevated temperatures. Our objective is to use spray-on piezo-electrics for depositing comb transducers onto the curved surfaces. This paper shows results for composite transducers such as lead zirconate titanate/ bismuth titanate and bismuth titanate/ lithium niobate. The comb transducers were prepared by precision laser ablation. The feasibility of producing second harmonic waves in rods with these spay-on comb transducers was demonstrated and paves the way toward measuring material degradation early-on before crack initiation occurs.

  8. CNS Involvement in the Non-Hodgkin's Lymhoma

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang Ok; Kim, Gwi Eon; Park, Chang Yun; Kim, Byung Soo [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    1983-06-15

    Two cases of primary malignant lymphoma of the brain and six cases of secondary CNS lymphoma seen at Yonsei cancer center, radiotherapy department for recent 4 years are presented. Primary lymphomas revealed single tumor mass on corpus callosum area and secondary lymphoma were intracranial (3 cases) or leptomeningeal type (3 cases). Histology of primary lymphoma were reticulum cell sarcoma and secondary lymphomas were either diffuse histiocytic or diffuse poorly differentiated lymphocytic lymphoma. All patients showed good response to radiation. Two patients with primary CNS lymphoma and two of six secondary CNS lymphoma are alive after radiotherapy (34, 31, 26, 12 months). But the prognosis of secondary CNS lymphoma is grave, because of progressive systemic disease. Incidence, risk factors, diagnosis and therapeutic management of CNS involvement are also discussed.

  9. A philosophy for CNS radiotracer design.

    Science.gov (United States)

    Van de Bittner, Genevieve C; Ricq, Emily L; Hooker, Jacob M

    2014-10-21

    Decades after its discovery, positron emission tomography (PET) remains the premier tool for imaging neurochemistry in living humans. Technological improvements in radiolabeling methods, camera design, and image analysis have kept PET in the forefront. In addition, the use of PET imaging has expanded because researchers have developed new radiotracers that visualize receptors, transporters, enzymes, and other molecular targets within the human brain. However, of the thousands of proteins in the central nervous system (CNS), researchers have successfully imaged fewer than 40 human proteins. To address the critical need for new radiotracers, this Account expounds on the decisions, strategies, and pitfalls of CNS radiotracer development based on our current experience in this area. We discuss the five key components of radiotracer development for human imaging: choosing a biomedical question, selection of a biological target, design of the radiotracer chemical structure, evaluation of candidate radiotracers, and analysis of preclinical imaging. It is particularly important to analyze the market of scientists or companies who might use a new radiotracer and carefully select a relevant biomedical question(s) for that audience. In the selection of a specific biological target, we emphasize how target localization and identity can constrain this process and discuss the optimal target density and affinity ratios needed for binding-based radiotracers. In addition, we discuss various PET test-retest variability requirements for monitoring changes in density, occupancy, or functionality for new radiotracers. In the synthesis of new radiotracer structures, high-throughput, modular syntheses have proved valuable, and these processes provide compounds with sites for late-stage radioisotope installation. As a result, researchers can manage the time constraints associated with the limited half-lives of isotopes. In order to evaluate brain uptake, a number of methods are available

  10. Tuning up the developing auditory CNS.

    Science.gov (United States)

    Sanes, Dan H; Bao, Shaowen

    2009-04-01

    Although the auditory system has limited information processing resources, the acoustic environment is infinitely variable. To properly encode the natural environment, the developing central auditory system becomes somewhat specialized through experience-dependent adaptive mechanisms that operate during a sensitive time window. Recent studies have demonstrated that cellular and synaptic plasticity occurs throughout the central auditory pathway. Acoustic-rearing experiments can lead to an over-representation of the exposed sound frequency, and this is associated with specific changes in frequency discrimination. These forms of cellular plasticity are manifest in brain regions, such as midbrain and cortex, which interact through feed-forward and feedback pathways. Hearing loss leads to a profound re-weighting of excitatory and inhibitory synaptic gain throughout the auditory CNS, and this is associated with an over-excitability that is observed in vivo. Further behavioral and computational analyses may provide insights into how theses cellular and systems plasticity effects underlie the development of cognitive functions such as speech perception.

  11. Endocannabinoids and synaptic function in the CNS.

    Science.gov (United States)

    Hashimotodani, Yuki; Ohno-Shosaku, Takako; Kano, Masanobu

    2007-04-01

    Marijuana affects neural functions through the binding of its active component (Delta(9)-THC) to cannabinoid receptors in the CNS. Recent studies have elucidated that endogenous ligands for cannabinoid receptors, endocannabinoids, serve as retrograde messengers at central synapses. Endocannabinoids are produced on demand in activity-dependent manners and released from postsynaptic neurons. The released endocannabinoids travel backward across the synapse, activate presynaptic CB1 cannabinoid receptors, and modulate presynaptic functions. Retrograde endocannabinoid signaling is crucial for certain forms of short-term and long-term synaptic plasticity at excitatory or inhibitory synapses in many brain regions, and thereby contributes to various aspects of brain function including learning and memory. Molecular identities of the CB1 receptor and enzymes involved in production and degradation of endocannabinoids have been elucidated. Anatomical studies have demonstrated unique distributions of these molecules around synapses, which provide morphological bases for the roles of endocannabinoids as retrograde messengers. CB1-knockout mice exhibit various behavioral abnormalities and multiple defects in synaptic plasticity, supporting the notion that endocannabinoid signaling is involved in various aspects of neural function. In this review article, the authors describe molecular mechanisms of the endocannabinoid-mediated synaptic modulation and its possible physiological significance.

  12. Monitoring the CNS pathology in aspartylglucosaminuria mice.

    Science.gov (United States)

    Tenhunen, K; Uusitalo, A; Autti, T; Joensuu, R; Kettunen, M; Kauppinen, R A; Ikonen, S; LaMarca, M E; Haltia, M; Ginns, E I; Jalanko, A; Peltonen, L

    1998-12-01

    Aspartylglucosaminuria (AGU) is a recessively inherited lysosomal storage disorder caused by the deficiency of the aspartylglucosaminidase (AGA) enzyme. The hallmark of AGU is slowly progressing mental retardation but the progression of brain pathology has remained uncharacterized in humans. Here we describe the long-term follow-up of mice carrying a targeted AGU-mutation in both alleles. Immunohistochemistry, histology, electron microscopy, quantitative magnetic resonance imaging (MRI) and behavioral studies were carried out to evaluate the CNS affection of the disease during development. The lysosomal storage vacuoles of the AGA -/- mice were most evident in central brain regions where MRI also revealed signs of brain atrophy similar to that seen in the older human patients. By immunohistochemistry and MRI examinations, a subtle delay of myelination was observed in AGA -/- mice. The life span of the AGA -/- mice was not shortened. Similar to the slow clinical course observed in human patients, the AGA -/- mice have behavioral symptoms that emerge at older age. Thus, the AGU knock-out mice represent an accurate model for AGU, both histopathologically and phenotypically.

  13. Amides from Piper capense with CNS activity

    DEFF Research Database (Denmark)

    Pedersen, Mikael Egebjerg; Metzler, Bjørn; Stafford, Gary Ivan

    2009-01-01

    Piper capense L.f. (Piperaceae) is used traditionally in South Africa as a sleep inducing remedy. Bioassay-guided fractionation of the roots of P. capense led to the isolation of piperine (1) and 4,5-dihydropiperine (2), which showed moderate affinity for the benzodiazepine site on the GABA...

  14. 基于导波的弯管裂纹缺陷的检测%Detection of Cracks in Elbow Pipes Using Guided Waves

    Institute of Scientific and Technical Information of China (English)

    周邵萍; 张蒲根; 吕文超; 郝占峰

    2015-01-01

    为了探究超声导波在90°弯头所引起的模态转换对检测造成的影响,采用试验和模拟的方法来研究导波在90°弯头中的传播特性,利用周向均布的长度伸缩型压电片激发导波L(0,2)模态,对弯头及弯头两端直管道上的周向裂纹缺陷进行位置识别;并对比直管道检测结果,研究弯头对导波模态转换的影响。采用小波分析对试验信号进行降噪处理,试验结果表明, L(0,2)模态导波穿过弯头后发生模态转换,产生弯曲模态F(1,2)。弯头处裂纹缺陷的检测敏感性与其所在位置有关,弯头外侧的检测敏感性最高;且检测敏感性与激发频率有一定关系,在较高的激发频率(120~130 kHz)下,弯头两端直管道上裂纹缺陷检测的敏感性最高;当激发频率处于较低频率(80 kHz)时,导波对弯头内侧缺陷检测的敏感度最高。因此提出采用不同激发频率的导波对带有弯头的管道系统进行综合检测的方法。利用数值模拟的方法对导波在弯头处的传播特性进行研究,模拟结果与试验结论相吻合。%The 90° elbow can generate complex mode conversions when ultrasonic guided wave passing through, thus makes it difficult to inspect defects in elbow and beyond elbow. The detection of circumferential cracks of different areas in elbow pipes are investigated in experiments and simulations using the guided waves in mode of L(0, 2) which are excited by a piezoelectric transducer. The effect of elbow to guided wave inspection is researched by comparing the result of straight pipe inspection. The signal is denoised by using three-level discrete wavelet decomposition and reconstruction which mother wavelet is db1. The experimental results show that the circumferential cracks can be determined in axial position for both elbow and bend straight side by the reflected echo of defects in the pipes. The detection sensitivity depends on the location of the

  15. Temperature Effects on the Propagation Characteristics of Love Waves along Multi-Guide Layers of Sio2/Su-8 on St-90°X Quartz

    Directory of Open Access Journals (Sweden)

    Fangqian Xu

    2012-05-01

    Full Text Available Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent temperature coefficient of frequency (Tcf of the fabricated Love wave devices with guide layers of SU-8/SiO2 on ST-90°X quartz substrate is evaluated experimentally as only 2.16 ppm.

  16. LINGO-1 and its role in CNS repair.

    Science.gov (United States)

    Mi, Sha; Sandrock, Alfred; Miller, Robert H

    2008-01-01

    LINGO-1 is selectively expressed in the CNS on both oligodendrocyte precursor cells (OPCs) and neurons. Its expression is developmentally regulated in the normal CNS, as well as up-regulated in human or rat models of neuropathologies. LINGO-1 functions as a negative regulator of oligodendrocyte differentiation and myelination, neuronal survival and axonal regeneration. Across diverse animal CNS disease models, targeted LINGO-1 inhibition was found to promote neuron and oligodendrocyte survival, axon regeneration, oligodendrocyte differentiation, remyelination and improved functional recovery. The targeted inhibition of LINGO-1 therefore presents a novel therapeutic approach for the treatment of neurological diseases.

  17. 3rd ENRI International Workshop on ATM/CNS

    CERN Document Server

    2014-01-01

    The Electronic Navigation Research Institute (ENRI) held its third International Workshop on ATM / CNS in 2013 with the theme of "Drafting the future sky". There is worldwide activity taking place in the research and development of modern air traffic management (ATM) and its enabling technologies in Communication, Navigation and Surveillance (CNS). Pioneering work is necessary to contribute to the global harmonization of air traffic management and control. At this workshop, leading experts in  research, industry and academia from around the world met to share their ideas and approaches on ATM/CNS related topics.

  18. A rare case of CNS tuberculosis with pregnancy

    Directory of Open Access Journals (Sweden)

    Sanjay Singh

    2015-06-01

    Full Text Available Whereas pelvic tuberculosis leading to infertility is quite common in female population of developing countries, Central Nervous System (CNS tuberculosis (TB with pregnancy is a rare entity. Most of the information on this subject is based on sporadic case reports only. Most of the earlier reports suggest very high adverse outcome of CNS Tuberculosis in pregnancy. We are presenting a case of CNS Tuberculosis which was diagnosed timely and managed appropriately in our institute with a favourable outcome, thus highlighting the importance of early diagnosis and treatment. [Int J Reprod Contracept Obstet Gynecol 2015; 4(3.000: 911-914

  19. CNS Vasculitis Associated with Waldenström Macroglobulinemia

    Science.gov (United States)

    Riangwiwat, Tanawan; Wu, Chris Y.; Santos-Ocampo, Alberto S.; Liu, Randal J.

    2016-01-01

    Waldenström macroglobulinemia (WM) is an indolent B cell lymphoproliferative disorder with monoclonal IgM secretion. We present a patient with WM who presented with multifocal acute cortical ischemic strokes and was found to have central nervous system (CNS) vasculitis. Workup was negative for cryoglobulins and hyperviscosity syndrome. Immunosuppression with intravenous steroids and cyclophosphamide stabilized the patient's mental status and neurologic deficits. On followup over 7 years, patient gained independence from walking aids and experienced no recurrences of CNS vasculitis. To our knowledge, CNS vasculitis in a WM patient, in the absence of cryoglobulins, has not been reported. Immunosuppression is the preferred treatment. PMID:27818812

  20. CNS Vasculitis Associated with Waldenström Macroglobulinemia

    Directory of Open Access Journals (Sweden)

    Tanawan Riangwiwat

    2016-01-01

    Full Text Available Waldenström macroglobulinemia (WM is an indolent B cell lymphoproliferative disorder with monoclonal IgM secretion. We present a patient with WM who presented with multifocal acute cortical ischemic strokes and was found to have central nervous system (CNS vasculitis. Workup was negative for cryoglobulins and hyperviscosity syndrome. Immunosuppression with intravenous steroids and cyclophosphamide stabilized the patient’s mental status and neurologic deficits. On followup over 7 years, patient gained independence from walking aids and experienced no recurrences of CNS vasculitis. To our knowledge, CNS vasculitis in a WM patient, in the absence of cryoglobulins, has not been reported. Immunosuppression is the preferred treatment.

  1. Convulsant bicuculline modifies CNS muscarinic receptor affinity

    Directory of Open Access Journals (Sweden)

    Rodríguez de Lores Arnaiz Georgina

    2006-04-01

    Full Text Available Abstract Background Previous work from this laboratory has shown that the administration of the convulsant drug 3-mercaptopropionic acid (MP, a GAD inhibitor, modifies not only GABA synthesis but also binding of the antagonist [3H]-quinuclidinyl benzilate ([3H]-QNB to central muscarinic receptors, an effect due to an increase in affinity without modifications in binding site number. The cholinergic system has been implicated in several experimental epilepsy models and the ability of acetylcholine to regulate neuronal excitability in the neocortex is well known. To study the potential relationship between GABAergic and cholinergic systems with seizure activity, we analyzed the muscarinic receptor after inducing seizure by bicuculline (BIC, known to antagonize the GABA-A postsynaptic receptor subtype. Results We analyzed binding of muscarinic antagonist [3H]-QNB to rat CNS membranes after i.p. administration of BIC at subconvulsant (1.0 mg/kg and convulsant (7.5 mg/kg doses. Subconvulsant BIC dose failed to develop seizures but produced binding alteration in the cerebellum and hippocampus with roughly 40% increase and 10% decrease, respectively. After convulsant BIC dose, which invariably led to generalized tonic-clonic seizures, binding increased 36% and 15% to cerebellar and striatal membranes respectively, but decreased 12% to hippocampal membranes. Kd value was accordingly modified: with the subconvulsant dose it decreased 27% in cerebellum whereas it increased 61% in hippocampus; with the convulsant dose, Kd value decreased 33% in cerebellum but increased 85% in hippocampus. No change in receptor number site was found, and Hill number was invariably close to unity. Conclusion Results indicate dissimilar central nervous system area susceptibility of muscarinic receptor to BIC. Ligand binding was modified not only by a convulsant BIC dose but also by a subconvulsant dose, indicating that changes are not attributable to the seizure process

  2. Loss of Coupling Distinguishes GJB1 Mutations Associated with CNS Manifestations of CMT1X from Those Without CNS Manifestations

    Science.gov (United States)

    Abrams, Charles K.; Goman, Mikhail; Wong, Sarah; Scherer, Steven S.; Kleopa, Kleopas A.; Peinado, Alejandro; Freidin, Mona M.

    2017-01-01

    CMT1X, an X-linked inherited neuropathy, is caused by mutations in GJB1, which codes for Cx32, a gap junction protein expressed by Schwann cells and oligodendrocytes. Many GJB1 mutations cause central nervous system (CNS) abnormality in males, including stable subclinical signs and, less often, short-duration episodes characterized by motor difficulties and altered consciousness. However, some mutations have no apparent CNS effects. What distinguishes mutations with and without CNS manifestations has been unclear. Here we studied a total of 14 Cx32 mutations, 10 of which are associated with florid episodic CNS clinical syndromes in addition to peripheral neuropathy. The other 4 mutations exhibit neuropathy without clinical or subclinical CNS abnormalities. These “PNS-only” mutations (Y151C, V181M, R183C and L239I) form gap junction plaques and produce levels of junctional coupling similar to those for wild-type Cx32. In contrast, mutants with CNS manifestations (F51L, E102del, V139M, R142Q, R142W, R164W T55I, R164Q and C168Y) either form no morphological gap junction plaques or, if they do, produce little or no detectable junctional coupling. Thus, PNS and CNS abnormalities may involve different aspects of connexin function. PMID:28071741

  3. The Wave Energy Sector

    DEFF Research Database (Denmark)

    2017-01-01

    This Handbook for Ocean Wave Energy aims at providing a guide into the field of ocean wave energy utilization. The handbook offers a concise yet comprehensive overview of the main aspects and disciplines involved in the development of wave energy converters (WECs). The idea for the book has been ...

  4. Investigation of standing wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided Focused Ultrasound (MRgFUS) phased array: An experimental and simulation study

    OpenAIRE

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2011-01-01

    Standing wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30 cm diameter with 15 cm radius of curvature, low frequency (230 kHz), hemispherical transcranial Magnetic Resonance guided Focused Ultrasound (MRgFUS) phased-array. Experimental and simulation studies were conducted with changing aperture size and f-number configurations of the phased array, and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to stand...

  5. Fetal MRI in Prenatal Diagnosis of CNS Abnormalities

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2009-02-01

    Full Text Available The value of fetal MRI (fMRI compared to ultrasound in the prenatal detection of CNS abnormalities and impact on counseling were determined in 25 pregnant women examined at University of Dusseldorf, Germany.

  6. CNS drug design: balancing physicochemical properties for optimal brain exposure.

    Science.gov (United States)

    Rankovic, Zoran

    2015-03-26

    The human brain is a uniquely complex organ, which has evolved a sophisticated protection system to prevent injury from external insults and toxins. Designing molecules that can overcome this protection system and achieve optimal concentration at the desired therapeutic target in the brain is a specific and major challenge for medicinal chemists working in CNS drug discovery. Analogous to the now widely accepted rule of 5 in the design of oral drugs, the physicochemical properties required for optimal brain exposure have been extensively studied in an attempt to similarly define the attributes of successful CNS drugs and drug candidates. This body of work is systematically reviewed here, with a particular emphasis on the interplay between the most critical physicochemical and pharmacokinetic parameters of CNS drugs as well as their impact on medicinal chemistry strategies toward molecules with optimal brain exposure. A summary of modern CNS pharmacokinetic concepts and methods is also provided.

  7. Pharmacokinetic, Pharmacogenetic, and Other Factors Influencing CNS Penetration of Antiretrovirals

    Directory of Open Access Journals (Sweden)

    Jacinta Nwamaka Nwogu

    2016-01-01

    Full Text Available Neurological complications associated with the human immunodeficiency virus (HIV are a matter of great concern. While antiretroviral (ARV drugs are the cornerstone of HIV treatment and typically produce neurological benefit, some ARV drugs have limited CNS penetration while others have been associated with neurotoxicity. CNS penetration is a function of several factors including sieving role of blood-brain and blood-CSF barriers and activity of innate drug transporters. Other factors are related to pharmacokinetics and pharmacogenetics of the specific ARV agent or mediated by drug interactions, local inflammation, and blood flow. In this review, we provide an overview of the various factors influencing CNS penetration of ARV drugs with an emphasis on those commonly used in sub-Saharan Africa. We also summarize some key associations between ARV drug penetration, CNS efficacy, and neurotoxicity.

  8. CNS Structural Anomalies in Iranian Children with Global Developmental Delay

    Directory of Open Access Journals (Sweden)

    Gholam Reza ZAMANI

    2013-02-01

    Full Text Available How to Cite This Article: Zamani GH, Shervin Badv R, Niksirat A, Alizadeh H. CNS Structural Anomalies in Iranian Children with Global Developmental Delay. Iran J Child Neurol. 2013 Winter; 7 (1:25-28. ObjectiveCentral Nervous system (CNS malformations are one of the most important causes of global developmental delay (GDD in Children. About one percent of infants with GDD have an inherited metabolic disorder and 3-10 percent have a chromosomal disorder. This study aimed to survey the frequency of brain structural anomalies and their subtypes among the variety of etiologic factors in children with GDD in our patients.Materials & MethodsThis study used the results of neuroimaging studies [unenhanced brain Magnetic Resonance Imaging (MRI] of all children who had been referred for evaluation of GDD to outpatient Clinic of Pediatric neurology at Children’s Medical Center affiliated to Tehran University of Medical Science between September 2009 and September 2010.ResultsIn this study, unenhanced brain MRI was performed on 405 children, of which80 cases (20 percent had brain structural anomalies. In 8.7 percent of the cases, previous history of brain structural disorders existed in other children of the family and 20 percent of mothers had inadequate consumption of folate during pregnancy.ConclusionBased on the results of this study, unenhanced cranial MRI seems to be a fundamental part of evaluation in all children with GDD. Adequate folate consumption as prophylaxis as well as genetic counseling can be worthy for high-risk mothers who have previous history of CNS anomaly or miscarriage to avoid repeated CNS anomalies in their next pregnancies. References1. Fenichel M. Clinical Pediatric Neurology: A Signs and Symptoms Approach. 6th ed. Philadelphia: Saunders; 2009. p. 119-52.2. A guide to investigation of children with developmental delay in East Anglia 2005Available from:http://www. phgfoundation.org/file/2366.3. Williams J. Global developmental

  9. Número e espaçamento entre hastes de guia de onda para medida da umidade do solo com TDR Number and spacing between wave guide rods for measurement of soil water content with TDR

    Directory of Open Access Journals (Sweden)

    Eugênio F. Coelho

    2003-08-01

    feasibility of the use of wave guides of two and three rods with different spacings. Disturbed soil samples were packed in PVC tube segments of 0.075 m diameter. Two sets of 24 have guides were constructed. One of this sets had a capacitor. In each set one half of the wave guides had two rods and the other half contained three rods. The rod spacing varied from 0.009 to 0.022 m. Soil water content data from gravimetry and soil bulk dielectric constant values from Trase System analyzer were collected during drying process with water content values ranging from 0.31 to 0.13 m³ m-3. Five mathematical models were fitted to water content and bulk dielectric constant data. The Malicki's model was the most adequate for estimating soil water content as a function of bulk dielectric constant. The wave guides with three rods 0.017 m apart from each other showed the best performance. The three-rod wave-guides without capacitor performed better for water content determination than the two-rod wave-guides without capacitor. The three-rod wave-guides without capacitor performed better than three-rod wave-guides with capacitor.

  10. CNS Involvement in AML Patient Treated with 5-Azacytidine

    Directory of Open Access Journals (Sweden)

    Diamantina Vasilatou

    2014-01-01

    Full Text Available Central nervous system (CNS involvement in acute myeloid leukemia (AML is a rare complication of the disease and is associated with poor prognosis. Sometimes the clinical presentation can be unspecific and the diagnosis can be very challenging. Here we report a case of CNS infiltration in a patient suffering from AML who presented with normal complete blood count and altered mental status.

  11. An instructive case of CNS histoplasmosis in an immunocompetent host.

    Science.gov (United States)

    Ramireddy, Sweeya; Wanger, Audrey; Ostrosky, Luis

    2012-01-01

    Histoplasma capsulatum is a dimorphic endemic fungus which infects both immunocompetent and immunocompromised hosts. Isolated CNS histoplasmosis is a rare presentation with increased risk in individuals with impaired cellular immunity, however not all patients with this condition are immunocompromised. We report a case of isolated CNS histoplasmosis in an otherwise healthy immunocompetent patient who was initially treated with Liposomal Amphotericin B followed by oral Voriconazole and later Itraconazole with significant improvement in clinical status.

  12. Insights into the Physiological Role of CNS Regeneration Inhibitors

    Directory of Open Access Journals (Sweden)

    Katherine Therese Baldwin

    2015-06-01

    Full Text Available The growth inhibitory nature of injured adult mammalian central nervous system (CNS tissue constitutes a major barrier to robust axonal outgrowth and functional recovery following trauma or disease. Prototypic CNS regeneration inhibitors are broadly expressed in the healthy and injured brain and spinal cord and include myelin-associated glycoprotein (MAG, the reticulon family member NogoA, oligodendrocyte myelin glycoprotein (OMgp, and chondroitin sulfate proteoglycans (CSPGs. These structurally diverse molecules strongly inhibit neurite outgrowth in vitro, and have been most extensively studied in the context of nervous system injury in vivo. The physiological role of CNS regeneration inhibitors in the naïve, or uninjured, CNS remains less well understood, but has received growing attention in recent years and is the focus of this review. CNS regeneration inhibitors regulate myelin development and axon stability, consolidate neuronal structure shaped by experience, and limit activity-dependent modification of synaptic strength. Altered function of CNS regeneration inhibitors is associated with neuropsychiatric disorders, suggesting crucial roles in brain development and health.

  13. The role of inflammation in CNS injury and disease.

    Science.gov (United States)

    Lucas, Sian-Marie; Rothwell, Nancy J; Gibson, Rosemary M

    2006-01-01

    For many years, the central nervous system (CNS) was considered to be 'immune privileged', neither susceptible to nor contributing to inflammation. It is now appreciated that the CNS does exhibit features of inflammation, and in response to injury, infection or disease, resident CNS cells generate inflammatory mediators, including proinflammatory cytokines, prostaglandins, free radicals and complement, which in turn induce chemokines and adhesion molecules, recruit immune cells, and activate glial cells. Much of the key evidence demonstrating that inflammation and inflammatory mediators contribute to acute, chronic and psychiatric CNS disorders is summarised in this review. However, inflammatory mediators may have dual roles, with detrimental acute effects but beneficial effects in long-term repair and recovery, leading to complications in their application as novel therapies. These may be avoided in acute diseases in which treatment administration might be relatively short-term. Targeting interleukin (IL)-1 is a promising novel therapy for stroke and traumatic brain injury, the naturally occurring antagonist (IL-1ra) being well tolerated by rheumatoid arthritis patients. Chronic disorders represent a greater therapeutic challenge, a problem highlighted in Alzheimer's disease (AD); significant data suggested that anti-inflammatory agents might reduce the probability of developing AD, or slow its progression, but prospective clinical trials of nonsteroidal anti-inflammatory drugs or cyclooxygenase inhibitors have been disappointing. The complex interplay between inflammatory mediators, ageing, genetic background, and environmental factors may ultimately regulate the outcome of acute CNS injury and progression of chronic neurodegeneration, and be critical for development of effective therapies for CNS diseases.

  14. Utility of FDG-PETCT and magnetic resonance spectroscopy in differentiating between cerebral lymphoma and non-malignant CNS lesions in HIV-infected patients

    Energy Technology Data Exchange (ETDEWEB)

    Westwood, Thomas D., E-mail: tdwestwood@googlemail.com [Department of Radiology, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Hogan, Celia, E-mail: celiahogan@hotmail.com [Monsall Unit, Department of Infectious Diseases and Tropical Medicine, North Manchester General Hospital, Pennine Acute Hospitals NHS Trust (United Kingdom); Julyan, Peter J., E-mail: Peter.Julyan@christie.nhs.uk [Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Coutts, Glyn, E-mail: Glyn.Coutts@christie.nhs.uk [Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Bonington, Suzie, E-mail: suzi.bonington@christie.nhs.uk [Department of Radiology, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Carrington, Bernadette, E-mail: Bernadette.Carrington@christie.nhs.uk [Department of Radiology, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Taylor, Ben, E-mail: Ben.taylor@christie.nhs.uk [Department of Radiology, The Christie NHS Foundation Trust, Wilmslow Road, Manchester (United Kingdom); Khoo, Saye, E-mail: S.H.Khoo@liverpool.ac.uk [Department of Infectious Diseases and Tropical Medicine, Royal Liverpool Hospital, Liverpool (United Kingdom); Bonington, Alec, E-mail: Alec.Bonington@pat.nhs.uk [Monsall Unit, Department of Infectious Diseases and Tropical Medicine, North Manchester General Hospital, Pennine Acute Hospitals NHS Trust (United Kingdom)

    2013-08-15

    Background and purpose: In HIV infected patients, MRI cannot reliably differentiate between central nervous system (CNS) lymphoma and non-malignant CNS lesions, particularly cerebral toxoplasmosis (CTOX). This study prospectively investigates the utility of FDG PET-CT and magnetic resonance spectroscopy (MRS) in discriminating CNS lymphoma from non-malignant CNS lesions in HIV infected patients, and assesses the ability of FDG PET-CT to guide the use of early brain biopsy. Methods: 10 HIV patients with neurological symptoms and contrast enhancing lesions on MRI were commenced on anti-toxoplasmosis therapy before undergoing FDG PET-CT and MRS. Brain biopsies were sought in those with FDG PET-CT suggestive of CNS lymphoma, and in those with a negative FDG PET-CT scan who failed to respond to therapy. Final diagnosis was based on histology or treatment response. Results: Two patients were confirmed to have CNS lymphoma and FDG PET-CT was consistent with this diagnosis in both. Six patients had cerebral toxoplasmosis in all of whom FDG PET-CT was consistent with non-malignant disease. One patient had progressive multifocal leukoencephalopathy (PML), FDG PET-CT was equivocal. One patient had a haemorrhagic brain metastasis and FDG PET-CT wrongly suggested non-malignant disease. MRS was performed successfully in eight subjects: three results were suggestive of CNS lymphoma (one true positive, two false positive), four suggested CTOX (two false negative, two true negative), one scan was equivocal. Conclusion: FDG PET-CT correctly identified all cases of CNS lymphoma and CTOX, supporting its use in this situation. MRS was unhelpful in our cohort.

  15. 螺旋杆结构中弹性导波频散特性研究%Disperdsion of elastic guided wave in helical rods

    Institute of Scientific and Technical Information of China (English)

    周方俊; 王悦民; 申传俊; 孙丰瑞

    2013-01-01

    为获取弹性导波在螺旋结构中的传播规律,建立了螺旋坐标系下的弹性力学基本方程,得到了螺旋结构中半解析有限元形式的弹性波频散方程.频散计算结果验证了在钢绞线外层螺旋圆杆中弹性导波的L(0,1),T(0,1)和F(1,1)等模态存在频率截止,并进一步计算了圆柱螺旋弹簧和螺旋天线结构的频散中的相速度和能速度曲线.结果表明:a.不同螺旋结构的频散曲线中普遍存在着频率截止和模态分支现象;b.所推导的螺旋坐标系下的弹性力学方程可以满足对螺旋结构的弹性导波频散分析计算;c.钢绞线外层螺旋圆杆的弹性导波能速度频散曲线在中间频段部分与直杆上频散曲线的对应频段部分的特征相近,圆柱螺旋弹簧与同旋绕比的圆环结构之间的能速度频散特征相近;d.不同螺旋天线的结构形式差别较大,其弹性导波频散特性须要根据具体结构特点作具体分析.%To find rules of guided wave in helix, the elasticity governing equations in helical coordinate system was inextensible expressed and a semi-analytical finite element method was applied to calculate dispersion equation of circular helical rod. The dispersion computation results proved that cut-off frequency occured on lower modes of elastic guided wave in outer rod of steel strand, such as L(0,1) , T(0,1) and F(1,1). Then the phase velocity and energy velocity dispersion curves were numerically calculated for helical cylinder spring and helical antenna. The result shows that; a. cut-off frequency and mode separation in dispersion curves appear generally on different helical structure; b. the equations deduced in helical coordinate system is available for the dispersion calculation and analysis; c. Energy velocity dispersion curve between cylinder helical spring and cylinder loop is similar in middle section, so all similar between outer rod of steel strand and cylinder rod; d. Different helical

  16. Propagation of sound waves in ducts

    DEFF Research Database (Denmark)

    Jacobsen, Finn

    2000-01-01

    Plane wave propagation in ducts with rigid walls, radiation from ducts, classical four-pole theory for composite duct systems, and three-dimentional waves in wave guides of various cross-sectional shape are described....

  17. Corrosion Behavior of Ferritic/Martensitic Steels CNS-I and Modified CNS-II in Supercritical Water

    Institute of Scientific and Technical Information of China (English)

    YANG Ying; YAN Qing-zhi; YANG Ya-feng; ZHANG Le-fu; GE Chang-chun

    2012-01-01

    The corrosion behaviors of CNS-I and modified CNS-II were evaluated by exposing to superciritical water (SCW) at 550℃ and 25 MPa with a dissolved oxygen concentration of 200× 10 ^-9 for up to 1 000 h. Detailed corrosion results of these two alloys were provided, including the growth rate of the oxide scales, microstructure of the oxide scales, distribution of phases and alloying elements. The mass gains of CNS-I and modified CNS-II were 609.73 mg/dm2 and 459.42 mg/dm2 , respectively, after exposing to SCW for 1 000 h. A duplex oxide scale with an outer porous magnetite layer and an inner relatively dense magnetite/spinel-mixed layer was identified on CNS-I and modified CNS-II after the test. The oxide scales were rather porous at the beginning of the test but the porosity decreased with increase of the exposure duration. It was found that Fe was enriched in the outer oxide layer, Cr was enriched in the inner oxide layer and O existed at a very high concnetration in the whole oxide scale. Other alloying elements such as Mo, W, Mn were depleted from the outer oxide layer and showed slightly enrichment in the inner oxide layer. The distributution of Ni was different from other elements, it was enriched in the interface bewteen the base metal and the oxide scale and depleted in the outer and inner oxide layers.

  18. Propagation of sound waves in ducts

    DEFF Research Database (Denmark)

    Jacobsen, Finn

    2000-01-01

    Plane wave propagation in ducts with rigid walls, radiation from ducts, classical four-pole theory for composite duct systems, and three-dimentional waves in wave guides of various cross-sectional shape are described.......Plane wave propagation in ducts with rigid walls, radiation from ducts, classical four-pole theory for composite duct systems, and three-dimentional waves in wave guides of various cross-sectional shape are described....

  19. Wave-guided optical waveguides

    DEFF Research Database (Denmark)

    Palima, Darwin; Bañas, Andrew Rafael; Vizsnyiczai, George

    2012-01-01

    This work primarily aims to fabricate and use two photon polymerization (2PP) microstructures capable of being optically manipulated into any arbitrary orientation. We have integrated optical waveguides into the structures and therefore have freestanding waveguides, which can be positioned anywhe...... bridge the diffraction barrier. This structure-mediated paradigm may be carried forward to open new possibilities for exploiting beams from far-field optics down to the subwavelength domain....

  20. Investigation of standing-wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided focused ultrasound (MRgFUS) phased array: an experimental and simulation study.

    Science.gov (United States)

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2012-02-01

    Standing-wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30-cm diameter with 15-cm radius of curvature, low-frequency (230 kHz), hemispherical transcranial magnetic resonance-guided focused ultrasound phased array. Experimental and simulation studies were conducted with changing aperture size and f -number configurations of the phased array and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and antinodes of standing wave produced by the small-aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing-wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number.