WorldWideScience

Sample records for sub-millimeter wave frequency

  1. Solar Flash Sub-Millimeter Wave Range Spectrum Part Radiation Modeling

    Directory of Open Access Journals (Sweden)

    V. Yu. Shustikov

    2015-01-01

    Full Text Available Currently, solar flares are under observation on the RT-7.5 radio telescope of BMSTU. This telescope operates in a little-studied range of the spectrum, at wavelengths of 3.2 and 2.2 mm (93 and 140 GHz, thereby providing unique information about parameters of the chromosphere plasma and zone of the temperature minimum. Observations on various instruments provided relatively small amount of data on the radio emission flare at frequencies close to 93 GHz, and at frequency of 140 GHz such observations were not carried out. For these reasons, data collected from the RT-7.5 radio telescope are of high value (Shustikov et al., 2012.This work describes modeling and gives interpretation of the reason for raising flux density spectrum of sub-millimeter radio frequency emission using as an example the GOES flare of class M 5.3 occurred on 04.07.2012 in the active region 11515. This flare was observed on the RT-7.5 radio telescope of BMSTU and was described by Shustikov et al. (2012 and by Smirnova et al. (2013, where it has been suggested that the reason for raising radio frequency emission is a bremsstrahlung of the thermal electrons in the hot plasma of the solar chromosphere. Rough estimates of the plasma temperature at the flare source were obtained.This paper proposes model calculations of the flux density spectrum of the sub-millimeter radio emission based on the gyrosynchrotron Fleischman-Kuznetsov code (Fleishman & Kuznetsov, 2010. Section 1 briefly describes observational data, tools and processing methods used in the work. Section 2 shows results of modeling the flare radio emission. Section 3 discusses results and conclusions.Numerical modeling the sub-millimeter part of the spectrum of the radio flux density for the GOES flare of class M5.3 has been carried out. This flare occurred in the active region 11515 on 04.07.2012. Modeling was based on the observations on the BMSTU’s RT-7.5 radio telescope.The paper draws conclusion based on the

  2. Rapid Sintering of Silica Xerogel Ceramic Derived from Sago Waste Ash Using Sub-millimeter Wave Heating with a 300 GHz CW Gyrotron

    Science.gov (United States)

    Aripin, Haji; Mitsudo, Seitaro; Sudiana, I. Nyoman; Tani, Shinji; Sako, Katsuhide; Fujii, Yutaka; Saito, Teruo; Idehara, Toshitaka; Sabchevski, Sliven

    2011-06-01

    In this paper, we present and discuss experimental results from a microwave sintering of a silica-glass ceramic, produced from a silica xerogel extracted from a sago waste ash. As a radiation source for the microwave heating a sub-millimeter wave gyrotron (Gyrotron FU CW I) with an output frequency of 300 GHz has been used. The powders of silica xerogel have been dry pressed and then sintered at temperatures ranging from 300°C to 1500°C. The influence of the sintering temperature on the technological properties such as porosity and bulk density was studied in detail. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy have been used in order to study the structure of the produced silica glass-ceramics. It has been found that the silica xerogel crystallizes at a temperature of 800°C, which is about 200°C lower than the one observed in the conventional process. The silica xerogel samples sintered by their irradiation with a sub-millimeter wave at 900°C for 18 minutes are fully crystallized into a silica glass-ceramic with a density of about 2.2 g/cm3 and cristobalite as a major crystalline phase. The results obtained in this study allow one to conclude that the microwave sintering with sub-millimeter waves is an appropriate technological process for production of silica glass-ceramics from a silica xerogel and is characterized with such advantages as shorter times of the thermal cycle, lower sintering temperatures and higher quality of the final product.

  3. A low-cost fabrication method for sub-millimeter wave GaAs Schottky diode

    Science.gov (United States)

    Jenabi, Sarvenaz; Deslandes, Dominic; Boone, Francois; Charlebois, Serge A.

    2017-10-01

    In this paper, a submillimeter-wave Schottky diode is designed and simulated. Effect of Schottky layer thickness on cut-off frequency is studied. A novel microfabrication process is proposed and implemented. The presented microfabrication process avoids electron-beam (e-beam) lithography which reduces the cost. Also, this process provides more flexibility in selection of design parameters and allows significant reduction in the device parasitic capacitance. A key feature of the process is that the Schottky contact, the air-bridges, and the transmission lines, are fabricated in a single lift-off step. This process relies on a planarization method that is suitable for trenches of 1-10 μm deep and is tolerant to end-point variations. The fabricated diode is measured and results are compared with simulations. A very good agreement between simulation and measurement results are observed.

  4. Sub-millimeter-Wave Equivalent Circuit Model for External Parasitics in Double-Finger HEMT Topologies

    Science.gov (United States)

    Karisan, Yasir; Caglayan, Cosan; Sertel, Kubilay

    2018-02-01

    We present a novel distributed equivalent circuit that incorporates a three-way-coupled transmission line to accurately capture the external parasitics of double-finger high electron mobility transistor (HEMT) topologies up to 750 GHz. A six-step systematic parameter extraction procedure is used to determine the equivalent circuit elements for a representative device layout. The accuracy of the proposed approach is validated in the 90-750 GHz band through comparisons between measured data (via non-contact probing) and full-wave simulations, as well as the equivalent circuit response. Subsequently, a semi-distributed active device model is incorporated into the proposed parasitic circuit to demonstrate that the three-way-coupled transmission line model effectively predicts the adverse effect of parasitic components on the sub-mmW performance in an amplifier setting.

  5. Design of a ×4 subharmonic sub-millimeter wave diode mixer, based on an analytic expression for small-signal conversion admittance parameters

    DEFF Research Database (Denmark)

    Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Krozer, Viktor

    2013-01-01

    Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description of the s......Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description...

  6. Analysis of the Sub-Millimeter Rotational Spectrum of Urea

    Science.gov (United States)

    Thomas, Jessica R.; Fosnight, Alyssa M.; Medvedev, Ivan R.

    2013-06-01

    Urea, ((NH_{2})_{2}CO), has broad presence in biological species. As a byproduct of human metabolism, this molecule is commonly tested for in blood to diagnose different pathologies. Furthermore, urea is seen in interstellar medium and its detection could yield valuable insight into the mechanisms governing star formation. Despite the prevalence of urea, an absence exists in recorded frequencies of this molecule. The new generation of the sub-millimeter telescopes, such as ALMA, HERSCHEL, and SOFIA, allows detection of interstellar molecular spectra at unprecedented spatial and spectral resolutions. The knowledge of the precise frequencies of spectra transitions present in interstellar molecular clouds would alleviate the problem of spectral congestion and aid in molecular identification. This paper reports the most recent investigation of the submillimeter/terahertz gas phase spectrum of urea. Up until now, only the microwave laboratory spectrum of urea's vibrational ground state has been available. This paper reports the high-resolution spectra of urea in the sub-millimeter range, and extends the spectroscopic assignment of the rotational transitions in the vibrational ground state. Additionally, the assignment of the first vibrational state and tentative assignments of two additional vibrational states have been made.

  7. A Sub-millimeter, Inductively Powered Neural Stimulator

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    Daniel K. Freeman

    2017-11-01

    Full Text Available Wireless neural stimulators are being developed to address problems associated with traditional lead-based implants. However, designing wireless stimulators on the sub-millimeter scale (<1 mm3 is challenging. As device size shrinks, it becomes difficult to deliver sufficient wireless power to operate the device. Here, we present a sub-millimeter, inductively powered neural stimulator consisting only of a coil to receive power, a capacitor to tune the resonant frequency of the receiver, and a diode to rectify the radio-frequency signal to produce neural excitation. By replacing any complex receiver circuitry with a simple rectifier, we have reduced the required voltage levels that are needed to operate the device from 0.5 to 1 V (e.g., for CMOS to ~0.25–0.5 V. This reduced voltage allows the use of smaller receive antennas for power, resulting in a device volume of 0.3–0.5 mm3. The device was encapsulated in epoxy, and successfully passed accelerated lifetime tests in 80°C saline for 2 weeks. We demonstrate a basic proof-of-concept using stimulation with tens of microamps of current delivered to the sciatic nerve in rat to produce a motor response.

  8. High-Sensitivity AGN Polarimetry at Sub-Millimeter Wavelengths

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    Ivan Martí-Vidal

    2017-10-01

    Full Text Available The innermost regions of radio loud Active Galactic Nuclei (AGN jets are heavily affected by synchrotron self-absorption, due to the strong magnetic fields and high particle densities in these extreme zones. The only way to overcome this absorption is to observe at sub-millimeter wavelengths, although polarimetric observations at such frequencies have so far been limited by sensitivity and calibration accuracy. However, new generation instruments such as the Atacama Large mm/sub-mm Array (ALMA overcome these limitations and are starting to deliver revolutionary results in the observational studies of AGN polarimetry. Here we present an overview of our state-of-the-art interferometric mm/sub-mm polarization observations of AGN jets with ALMA (in particular, the gravitationally-lensed sources PKS 1830−211 and B0218+359, which allow us to probe the magneto-ionic conditions at the regions closest to the central black holes.

  9. Black Holes and Sub-millimeter Dimensions

    CERN Document Server

    Argyres, Philip C; March-Russell, John David; Argyres, Philip C.; Dimopoulos, Savas; March-Russell, John

    1998-01-01

    Recently, a new framework for solving the hierarchy problem was proposed which does not rely on low energy supersymmetry or technicolor. The fundamental Planck mass is at a TeV and the observed weakness of gravity at long distances is due the existence of new sub-millimeter spatial dimensions. In this letter, we study how the properties of black holes are altered in these theories. Small black holes---with Schwarzschild radii smaller than the size of the new spatial dimensions---are quite different. They are bigger, colder, and longer-lived than a usual $(3+1)$-dimensional black hole of the same mass. Furthermore, they primarily decay into harmless bulk graviton modes rather than standard-model degrees of freedom. We discuss the interplay of our scenario with the holographic principle. Our results also have implications for the bounds on the spectrum of primordial black holes (PBHs) derived from the photo-dissociation of primordial nucleosynthesis products, distortion of the diffuse gamma-ray spectrum, overcl...

  10. EXPLORING THE RELATION BETWEEN (SUB-)MILLIMETER RADIATION AND {gamma}-RAY EMISSION IN BLAZARS WITH PLANCK AND FERMI

    Energy Technology Data Exchange (ETDEWEB)

    Leon-Tavares, J.; Tornikoski, M.; Laehteenmaeki, A. [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FIN-02540 Kylmaelae (Finland); Valtaoja, E. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20100 Turku (Finland); Giommi, P.; Polenta, G.; Gasparrini, D.; Cutini, S., E-mail: leon@kurp.hut.fi [ASI Science Data Center, ASDC c/o ESRIN, via G. Galilei, 00044 Frascati (Italy)

    2012-07-20

    The coexistence of Planck and Fermi satellites in orbit has enabled the exploration of the connection between the (sub-)millimeter and {gamma}-ray emission in a large sample of blazars. We find that the {gamma}-ray emission and the (sub-)mm luminosities are correlated over five orders of magnitude, L{sub {gamma}}{proportional_to}L{sub (sub-)mm}. However, this correlation is not significant at some frequency bands when simultaneous observations are considered. The most significant statistical correlations, on the other hand, arise when observations are quasi-simultaneous within two months. Moreover, we find that sources with an approximate spectral turnover in the middle of the mm-wave regime are more likely to be strong {gamma}-ray emitters. These results suggest a physical relation between the newly injected plasma components in the jet and the high levels of {gamma}-ray emission.

  11. Magnetostatic wave oscillator frequencies

    Science.gov (United States)

    Sethares, J. C.; Stiglitz, M. R.; Weinberg, I. J.

    1981-03-01

    The frequencies of magnetostatic wave (MSW) oscillators employing three principal modes of propagation, surface (MSSW), forward (MSFVW), and backward (MSBVW) volume waves, have been investigated. Previous (MSW) oscillator papers dealt with MSSW. Oscillators were fabricated using LPE-YIG MSW delay lines in a feedback loop of a 2-4 GHz amplifier. Wide and narrow band transducers were employed. Oscillator frequency as a function of biasing field is in agreement with a theoretical analysis. The analysis predicts frequency in terms of material parameters, biasing field, and transducer geometry. With wide band transducers a comb of frequencies is generated. Narrow band transducers for MSSW and MSFVW select a single mode; and MSBVW selects two modes. Spurious modes, attributed to instrumentation, are more than 20 dB below the main response, and bandwidths are less than 0.005 percent. No other spurious modes are observed. MSW oscillators produce clean electronically tunable signals and appear attractive in frequency agile systems.

  12. Estimation of physiological sub-millimeter displacement with CW Doppler radar.

    Science.gov (United States)

    Jia Xu; Xiaomeng Gao; Padasdao, Bryson E; Boric-Lubecke, Olga

    2015-01-01

    Doppler radar physiological sensing has been studied for non-contact detection of vital signs including respiratory and heartbeat rates. This paper presents the first micrometer resolution Wi-Fi band Doppler radar for sub-millimeter physiological displacement measurement. A continuous-wave Doppler radar working at 2.4GHz is used for the measurement. It is intended for estimating small displacements on the body surface resulting from physiological activity. A mechanical mover was used as target, and programmed to conduct sinusoidal motions to simulate pulse motions. Measured displacements were compared with a reference system, which indicates a superior performance in accuracy for having absolute errors less than 10μm, and relative errors below 4%. It indicates the feasibility of highly accurate non-contact monitoring of physiological movements using Doppler radar.

  13. Signal to Noise Ratio Maximization in Quiet Zone Acquisitions for Range Assessment at Sub-millimeter Wavelengths

    Directory of Open Access Journals (Sweden)

    A. Muñoz-Acevedo

    2012-06-01

    Full Text Available This paper proposes a quiet zone probing approach which deals with low dynamic range quiet zone acquisitions. Lack of dynamic range is a feature of millimeter and sub-millimeter wavelength technologies. It is consequence of the gradually smaller power generated by the instrumentation, that follows a f^α law with frequency, being α≥1 variable depending on the signal source’s technology. The proposed approach is based on an optimal data reduction scenario which redounds in a maximum signal to noise ratio increase for the signal pattern, with minimum information losses. After theoretical formulation, practical applications of the technique are proposed.

  14. Status of MUSIC, the MUltiwavelength Sub/millimeter Inductance Camera

    Science.gov (United States)

    Golwala, Sunil R.; Bockstiegel, Clint; Brugger, Spencer; Czakon, Nicole G.; Day, Peter K.; Downes, Thomas P.; Duan, Ran; Gao, Jiansong; Gill, Amandeep K.; Glenn, Jason; Hollister, Matthew I.; LeDuc, Henry G.; Maloney, Philip R.; Mazin, Benjamin A.; McHugh, Sean G.; Miller, David; Noroozian, Omid; Nguyen, Hien T.; Sayers, Jack; Schlaerth, James A.; Siegel, Seth; Vayonakis, Anastasios K.; Wilson, Philip R.; Zmuidzinas, Jonas

    2012-09-01

    We present the status of MUSIC, the MUltiwavelength Sub/millimeter Inductance Camera, a new instrument for the Caltech Submillimeter Observatory. MUSIC is designed to have a 14', diffraction-limited field-of-view instrumented with 2304 detectors in 576 spatial pixels and four spectral bands at 0.87, 1.04, 1.33, and 1.98 mm. MUSIC will be used to study dusty star-forming galaxies, galaxy clusters via the Sunyaev-Zeldovich effect, and star formation in our own and nearby galaxies. MUSIC uses broadband superconducting phased-array slot-dipole antennas to form beams, lumpedelement on-chip bandpass filters to define spectral bands, and microwave kinetic inductance detectors to sense incoming light. The focal plane is fabricated in 8 tiles consisting of 72 spatial pixels each. It is coupled to the telescope via an ambient-temperature ellipsoidal mirror and a cold reimaging lens. A cold Lyot stop sits at the image of the primary mirror formed by the ellipsoidal mirror. Dielectric and metal-mesh filters are used to block thermal infrared and out-ofband radiation. The instrument uses a pulse tube cooler and 3He/ 3He/4He closed-cycle cooler to cool the focal plane to below 250 mK. A multilayer shield attenuates Earth's magnetic field. Each focal plane tile is read out by a single pair of coaxes and a HEMT amplifier. The readout system consists of 16 copies of custom-designed ADC/DAC and IF boards coupled to the CASPER ROACH platform. We focus on recent updates on the instrument design and results from the commissioning of the full camera in 2012.

  15. An alma survey of sub-millimeter galaxies in the extended Chandra deep field south: Sub-millimeter properties of color-selected galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Decarli, R.; Walter, F.; Hodge, J. A.; Rix, H.-W.; Schinnerer, E. [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Smail, I.; Swinbank, A. M.; Karim, A.; Simpson, J. M. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Chapman, S. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Coppin, K. E. K. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Cox, P. [IRAM, 300 rue de la piscine, F-38406 Saint-Martin d' Hères (France); Dannerbauer, H. [Universität Wien, Institut für Astrophysik, Türenschanzstrasse 17, A-1180 Wien (Austria); Greve, T. R. [University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT (United Kingdom); Ivison, R. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Knudsen, K. K.; Lindroos, L. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala SE-439 92 (Sweden); Van der Werf, P. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Weiß, A., E-mail: decarli@mpia.de [Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2014-01-10

    We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ∼20''-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECDFS) Sub-millimeter Survey. We select various classes of galaxies (K-selected, star-forming sBzK galaxies, extremely red objects, and distant red galaxies) according to their optical/near-infrared fluxes. We find clear, >10σ detections in the stacked images of all these galaxy classes. We include in our stacking analysis Herschel/SPIRE data to constrain the dust spectral energy distribution of these galaxies. We find that their dust emission is well described by a modified blackbody with T {sub dust} ≈ 30 K and β = 1.6 and infrared luminosities of (5-11) × 10{sup 11} L {sub ☉} or implied star formation rates of 75-140 M {sub ☉} yr{sup –1}. We compare our results with those of previous studies based on single-dish observations at 870 μm and find that our flux densities are a factor 2-3 higher than previous estimates. The discrepancy is observed also after removing sources individually detected in ALESS maps. We report a similar discrepancy by repeating our analysis on 1.4 GHz observations of the whole ECDFS. Hence, we find tentative evidence that galaxies that are associated in projected and redshift space with sub-mm bright sources are brighter than the average population. Finally, we put our findings in the context of the cosmic star formation rate density as a function of redshift.

  16. CORRELATIONS IN THE (SUB)MILLIMETER BACKGROUND FROM ACT Multiplication-Sign BLAST

    Energy Technology Data Exchange (ETDEWEB)

    Hajian, Amir; Battaglia, Nick; Bond, J. Richard [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Viero, Marco P.; Bock, James J. [California Institute of Technology, Pasadena, CA 91125 (United States); Addison, Graeme [Department of Astrophysics, Oxford University, Oxford, OX1 3RH (United Kingdom); Aguirre, Paula [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica, Casilla 306, Santiago 22 (Chile); Appel, John William; Duenner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hincks, Adam D. [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Das, Sudeep; Dunkley, Joanna [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Devlin, Mark J.; Dicker, Simon R. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); Hughes, John P. [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854-8019 (United States); Halpern, Mark [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Hasselfield, Matthew [Laboratoire APC, Universite Paris Diderot, 75205 Paris (France); Hilton, Matt [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041 (South Africa); and others

    2012-01-01

    We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at 250, 350, and 500 {mu}m (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope (BLAST); and at 1380 and 2030 {mu}m (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope (ACT). The overlapping observations cover 8.6 deg{sup 2} in an area relatively free of Galactic dust near the south ecliptic pole. The ACT bands are sensitive to radiation from the cosmic microwave background, to the Sunyaev-Zel'dovich effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline and also detect correlations between the ACT and BLAST maps at over 25{sigma} significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at 4{sigma}, and using a model for the DSFG evolution and number counts, we successfully fit all of our spectra with a linear clustering model and a bias that depends only on redshift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints on future models.

  17. The SCUBA-2 Cosmology Legacy Survey: ALMA Resolves the Bright-end of the Sub-millimeter Number Counts

    NARCIS (Netherlands)

    Simpson, J. M.; Smail, Ian; Swinbank, A. M.; Chapman, S. C.; Geach, J. E.; Ivison, R. J.; Thomson, A. P.; Aretxaga, I.; Blain, A. W.; Cowley, W. I.; Chen, Chian-Chou; Coppin, K. E. K.; Dunlop, J. S.; Edge, A. C.; Farrah, D.; Ibar, E.; Karim, A.; Knudsen, K. K.; Meijerink, R.; Michałowski, M. J.; Scott, D.; Spaans, M.; van der Werf, P. P.

    We present high-resolution 870 μm Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1 degree2 850 μm maps from the SCUBA-2 Cosmology Legacy Survey, and are representative of the

  18. Fabrication of an absorber-coupled MKID detector and readout for sub-millimeter and far-infrared astronomy

    Science.gov (United States)

    Brown, Ari-David; Hsieh, Wen-Ting; Moseley, S. Harvey; Stevenson, Thomas R.; U-yen, Kongpop; Wollack, Edward J.

    2010-07-01

    We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and farinfrared astronomy. Each detector array is comprised of λ/2 stepped impedance resonators, a 1.5μm thick silicon membrane, and 380μm thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

  19. Fabrication of an Absorber-Coupled MKID Detector and Readout for Sub-Millimeter and Far-Infrared Astronomy

    Science.gov (United States)

    Brown, Ari-David; Hsieh, Wen-Ting; Moseley, S. Harvey; Stevenson, Thomas R.; U-yen, Kongpop; Wollack, Edward J.

    2010-01-01

    We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and farinfrared astronomy. Each detector array is comprised of lambda/2 stepped impedance resonators, a 1.5µm thick silicon membrane, and 380µm thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

  20. Low frequency piezoresonance defined dynamic control of terahertz wave propagation.

    Science.gov (United States)

    Dutta, Moumita; Betal, Soutik; Peralta, Xomalin G; Bhalla, Amar S; Guo, Ruyan

    2016-11-30

    Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

  1. cluster-in-a-box: Statistical model of sub-millimeter emission from embedded protostellar clusters

    Science.gov (United States)

    Kristensen, Lars E.; Bergin, Edwin A.

    2016-10-01

    Cluster-in-a-box provides a statistical model of sub-millimeter emission from embedded protostellar clusters and consists of three modules grouped in two scripts. The first (cluster_distribution) generates the cluster based on the number of stars, input initial mass function, spatial distribution and age distribution. The second (cluster_emission) takes an input file of observations, determines the mass-intensity correlation and generates outflow emission for all low-mass Class 0 and I sources. The output is stored as a FITS image where the flux density is determined by the desired resolution, pixel scale and cluster distance.

  2. The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths

    Science.gov (United States)

    Matthews, L. D.; Crew, G. B.; Doeleman, S. S.; Lacasse, R.; Saez, A. F.; Alef, W.; Akiyama, K.; Amestica, R.; Anderson, J. M.; Barkats, D. A.; Baudry, A.; Broguière, D.; Escoffier, R.; Fish, V. L.; Greenberg, J.; Hecht, M. H.; Hiriart, R.; Hirota, A.; Honma, M.; Ho, P. T. P.; Impellizzeri, C. M. V.; Inoue, M.; Kohno, Y.; Lopez, B.; Martí-Vidal, I.; Messias, H.; Meyer-Zhao, Z.; Mora-Klein, M.; Nagar, N. M.; Nishioka, H.; Oyama, T.; Pankratius, V.; Perez, J.; Phillips, N.; Pradel, N.; Rottmann, H.; Roy, A. L.; Ruszczyk, C. A.; Shillue, B.; Suzuki, S.; Treacy, R.

    2018-01-01

    The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub)millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u–v coverage and north–south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics.

  3. Taiwanese antennas for the Sub-Millimeter Array: a progress report

    Science.gov (United States)

    Raffin, Phillippe A.; Liu, Ching-Tang; Cervera, Mathieu; Chang, Chi-Ling; Chen, Ming-Tang; Lee, Cheng-Ching; Lee, Typhoon; Lo, Kwok-Yung; Ma, Rwei-Ping; Martin, Robert N.; Martin-Cocher, Pierre; Ong, Ching-Long; Park, Yong-Sun; Tsai, Rong-Den; Wu, Enboa; Yang, Shun-Cheng; Yang, Tien-Szu

    2000-07-01

    The Academia Sinica, Institute for Astronomy and Astrophysics (ASIAA) is building two antennas to be added to the six antennas of the Sub-Millimeter Array (SMA) of the Smithsonian Astrophysical Observatory (SAO). The antennas have been designed at SAO and are currently under construction at Mauna Kea. ASIAA's two antennas are made in Taiwan from parts manufactured locally and imported from Europe and from the USA. This report will focus on the manufacturing and testing of 2 major components: the alidade and the reflector. We will emphasize the work done on the composite parts used in the 6- meter reflectors, namely the carbon fiber tubes for the backup structure, the carbon fiber legs of the quadrupod and the composite central hub. We will discuss the modal testing and pointing tests of the antennas. Finally this report will show how the Taiwanese industry was able to respond to the high manufacturing standards required to build sub-millimeter antennas. The design and manufacturing capabilities of the Aeronautical Research Laboratories and China Shipbuilding Corporation have made possible the construction of the telescopes in Taiwan.

  4. Extending the LHC reach for new physics with sub-millimeter displaced vertices

    Science.gov (United States)

    Ito, Hayato; Jinnouchi, Osamu; Moroi, Takeo; Nagata, Natsumi; Otono, Hidetoshi

    2017-08-01

    Particles with a sub-millimeter decay length appear in many models of physics beyond the Standard Model. However, their longevity has been often ignored in their LHC searches and they have been regarded as promptly-decaying particles. In this letter, we show that, by requiring displaced vertices on top of the event selection criteria used in the ordinary search strategies for promptly-decaying particles, we can considerably extend the LHC reach for particles with a decay length of ≳ 100 μm. We discuss a way of reconstructing sub-millimeter displaced vertices by exploiting the same technique used for the primary vertex reconstruction on the assumption that the metastable particles are always pair-produced and their decay products contain high-pT jets. We show that, by applying a cut based on displaced vertices on top of standard kinematical cuts for the search of new particles, the LHC reach can be significantly extended if the decay length is ≳ 100 μm. In addition, we may measure the lifetime of the target particle through the reconstruction of displaced vertices, which plays an important role in understanding the new physics behind the metastable particles.

  5. Short wave breaking effects on low frequency waves

    NARCIS (Netherlands)

    Daly, C.; Roelvink, J.A.; Van Dongeren, A.; Van Thiel de Vries, J.S.M.; McCall, R.T.

    2010-01-01

    The effect of short wave breaking on low frequency waves is investigated using two breaker formulations implemented in a time-dependent numerical model (XBeach): (1) an advective-deterministic approach (ADA) and (2) the probabilistic breaker formulation of Roelvink (1993). Previous research has

  6. High-frequency Rayleigh-wave method

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  7. The wave buoy analogy - estimating high-frequency wave excitations

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam

    2008-01-01

    The paper deals with the wave buoy analogy where a ship is considered as a wave buoy, so that measured ship responses are used as a basis to estimate wave spectra and associated sea state parameters. The study presented follows up on a previous paper, Nielsen [Nielsen UD. Response-based estimation...... of sea state parameters — influence of filtering. Ocean Engineering 2007;34:1797–810.], where time series of ship responses were generated from a known wave spectrum for the purpose of the inverse process — the estimation of the underlying wave excitations. Similar response generations and vice versa...... be estimated reasonably well, even considering high-frequency wave components of a wind sea wave spectrum....

  8. Diffusion in and around alginate and chitosan films with embedded sub-millimeter voids

    Energy Technology Data Exchange (ETDEWEB)

    Patra, Subhajit; Bal, Dharmendra Kumar; Ganguly, Somenath, E-mail: snganguly@che.iitkgp.ernet.in

    2016-02-01

    Hydrogel scaffolds from biopolymers have potential use in the controlled release of drugs, and as 3-D structure for the formation of tissue matrix. This article describes the solute release behavior of alginate and chitosan films with embedded voids of sub-millimeter dimensions. Nitrogen gas was bubbled in a fluidic arrangement to generate bubbles, prior to the crosslinking. The crosslinked gel was dried in a vacuum oven, and subsequently, soaked in Vitamin B-12 solution. The dimensions of the voids immediately after the cross-linking of gel, and also after complete drying were obtained using a digital microscope and scanning electron microscope respectively. The porosity of the gel was measured gravimetrically. The release of Vitamin B-12 in PBS buffer on a shaker was studied. The release experiments were repeated at an elevated temperature of 37 °C in the presence of lysozyme. The diffusion coefficient within the gel layer and the mass transfer coefficient at the interface with the bulk-liquid were estimated using a mathematical model. For comparison, the experiment was repeated with a film that does not have any embedded void. The enhancement in diffusion coefficient due to the presence of voids is discussed in this article. - Highlights: • Formation of sub-millimeter voids in biopolymer films using fluidic arrangement • The retention of self-assembled bubbles in films after crosslinking, and drying • The enhancement observed in release of model drug with introduction of voids • The diffusion coefficients in and around biopolymer films from model regression • Use of classical model in explaining release profiles from dual porosity media.

  9. High Frequency Guided Wave Virtual Array SAFT

    Science.gov (United States)

    Roberts, R.; Pardini, A.; Diaz, A.

    2003-03-01

    The principles of the synthetic aperture focusing technique (SAFT) are generalized for application to high frequency plate wave signals. It is shown that a flaw signal received in long-range plate wave propagation can be analyzed as if the signals were measured by an infinite array of transducers in an unbounded medium. It is shown that SAFT-based flaw sizing can be performed with as few as three or less actual measurement positions.

  10. Generalized Nonlinear Wave Equation in Frequency Domain

    DEFF Research Database (Denmark)

    Guo, Hairun; Zeng, Xianglong; Bache, Morten

    2013-01-01

    We interpret the forward Maxwell equation with up to third order induced polarizations and get so called nonlinear wave equation in frequency domain (NWEF), which is based on Maxwell wave equation and using slowly varying spectral amplitude approximation. The NWEF is generalized in concept...... as it directly describes the electric field dynamics rather than the envelope dynamics and because it concludes most current-interested nonlinear processes such as three-wave mixing, four-wave-mixing and material Raman effects. We give two sets of NWEF, one is a 1+1D equation describing the (approximated) planar...... wave propagation in nonlinear bulk material and the other corresponds to the propagation in a waveguide structure....

  11. VizieR Online Data Catalog: Sub-millimeter spectra of 2-hydroxyacetonitrile (Margules+, 2017)

    Science.gov (United States)

    Margules, L.; McGuire, B. A.; Senent, M. L.; Motiyenko, R. A.; Remijan, A.; Guillemin, J. C.

    2017-02-01

    Measured frequencies and residuals from the global fit of the submillimeter-wave data for 2-hydroxyacetonitrile and files used for SPFIT. Detailled explanations on SPFIT could be found at https://www.astro.uni-koeln.de/cdms/pickett (4 data files).

  12. Controlled production of sub-millimeter liquid core hydrogel capsules for parallelized 3D cell culture.

    Science.gov (United States)

    Doméjean, Hugo; de la Motte Saint Pierre, Mathieu; Funfak, Anette; Atrux-Tallau, Nicolas; Alessandri, Kevin; Nassoy, Pierre; Bibette, Jérôme; Bremond, Nicolas

    2016-12-20

    Liquid core capsules having a hydrogel membrane are becoming a versatile tool for three-dimensional culture of micro-organisms and mammalian cells. Making sub-millimeter capsules at a high rate, via the breakup of a compound jet in air, opens the way to high-throughput screening applications. However, control of the capsule size monodispersity, especially required for quantitative bioassays, was still lacking. Here, we report how the understanding of the underlying hydrodynamic instabilities that occur during the process can lead to calibrated core-shell bioreactors. The requirements are: i) damping the shear layer instability that develops inside the injector arising from the co-annular flow configuration of liquid phases having contrasting viscoelastic properties; ii) controlling the capillary instability of the compound jet by superposing a harmonic perturbation onto the shell flow; iii) avoiding coalescence of drops during jet fragmentation as well as during drop flight towards the gelling bath; iv) ensuring proper engulfment of the compound drops into the gelling bath for building a closed hydrogel shell. We end up with the creation of numerous identical compartments in which cells are able to form multicellular aggregates, namely spheroids. In addition, we implement an intermediate composite hydrogel layer, composed of alginate and collagen, allowing cell adhesion and thus the formation of epithelia or monolayers of cells.

  13. The status of MUSIC: the multiwavelength sub-millimeter inductance camera

    Science.gov (United States)

    Sayers, Jack; Bockstiegel, Clint; Brugger, Spencer; Czakon, Nicole G.; Day, Peter K.; Downes, Thomas P.; Duan, Ran P.; Gao, Jiansong; Gill, Amandeep K.; Glenn, Jason; Golwala, Sunil R.; Hollister, Matthew I.; Lam, Albert; LeDuc, Henry G.; Maloney, Philip R.; Mazin, Benjamin A.; McHugh, Sean G.; Miller, David A.; Mroczkowski, Anthony K.; Noroozian, Omid; Nguyen, Hien Trong; Schlaerth, James A.; Siegel, Seth R.; Vayonakis, Anastasios; Wilson, Philip R.; Zmuidzinas, Jonas

    2014-08-01

    The Multiwavelength Sub/millimeter Inductance Camera (MUSIC) is a four-band photometric imaging camera operating from the Caltech Submillimeter Observatory (CSO). MUSIC is designed to utilize 2304 microwave kinetic inductance detectors (MKIDs), with 576 MKIDs for each observing band centered on 150, 230, 290, and 350 GHz. MUSIC's field of view (FOV) is 14' square, and the point-spread functions (PSFs) in the four observing bands have 45'', 31'', 25'', and 22'' full-widths at half maximum (FWHM). The camera was installed in April 2012 with 25% of its nominal detector count in each band, and has subsequently completed three short sets of engineering observations and one longer duration set of early science observations. Recent results from on-sky characterization of the instrument during these observing runs are presented, including achieved map- based sensitivities from deep integrations, along with results from lab-based measurements made during the same period. In addition, recent upgrades to MUSIC, which are expected to significantly improve the sensitivity of the camera, are described.

  14. Rapid Asymmetric Inflation and Early Cosmology in Theories with Sub-Millimeter Dimensions

    CERN Document Server

    Arkani-Hamed, N; Kaloper, Nemanja; March-Russell, John David; Arkani-Hamed, Nima; Dimopoulos, Savas; Kaloper, Nemanja; March-Russell, John

    2000-01-01

    It was recently pointed out that the fundamental Planck mass could be close to the TeV scale with the observed weakness of gravity at long distances being due the existence of new sub-millimeter spatial dimensions. In this picture the standard model fields are localized to a $(3+1)$-dimensional wall or ``3-brane''. We show that in such theories there exist attractive models of inflation that occur while the size of the new dimensions are still small. We show that it is easy to produce the required number of efoldings, and further that the density perturbations $\\delta\\rho/\\rho$ as measured by COBE can be easily reproduced, both in overall magnitude and in their approximately scale-invariant spectrum. In the minimal approach, the inflaton field is just the moduli describing the size of the internal dimensions, the role of the inflationary potential being played by the stabilizing potential of the internal space. We show that under quite general conditions, the inflationary era is followed by an epoch of contra...

  15. Improved wedge method for the measurement of sub-millimeter slice thicknesses in magnetic resonance imaging.

    Science.gov (United States)

    Kanazawa, Tsutomu; Ohkubo, Masaki; Kondo, Tatsuya; Miyazawa, Takayuki; Inagawa, Shoichi

    2017-12-01

    The standard method for measuring the slice thickness of magnetic resonance images uses the inclined surface of a wedge (wedge method); it is sensitive to small increases in noise because of the differentiation of the edge response function (ERF) required. The purpose of this study was to improve the wedge method by fitting a curve to the ERF. The curve-fit function was obtained by convolving an ideal ERF (a ramp function) with a Gaussian function to represent ERF blurring. Measurements of 5- and 3-mm slice thicknesses were performed on a 3T scanner using the conventional wedge method, the improved wedge method, and another standard method using an inclined slab (slab method). Subsequently, 0.5- and 0.25-mm slice thicknesses from multiple slices acquired using a three-dimensional sequence were measured using the improved wedge method. When measuring 5-mm slices, the differences in measurements obtained using the improved wedge method and the conventional slab and wedge methods were very small: <0.6% of the 5-mm slice thickness. The difference was ≤1.7% for 3-mm slices. For 0.5- and 0.25-mm slices, the mean values obtained using the improved wedge method were 0.543 ± 0.007 mm and 0.247 ± 0.015 mm, with a 1.2 and 5.9% coefficient of variation across slices, respectively. The improved wedge method is valid and potentially applicable to the measurement of sub-millimeter slice thicknesses.

  16. A sub-millimeter resolution detector module for small-animal PET applications

    Science.gov (United States)

    Sacco, I.; Dohle, R.; Fischer, P.; Gola, A.; Piemonte, C.; Ritzert, M.

    2017-01-01

    We present a gamma detection module optimized for very high resolution PET applications, able to resolve arrays of scintillating crystals with sub-millimeter pitch. The detector is composed of a single ceramic substrate (LTCC): it hosts four flip-chip mounted PETA5 ASICs on the bottom side and an array of SiPM sensors on the top surface, fabricated in HD-RGB technology by FBK. Each chip has 36 channels, for a maximum of 144 readout channels on a sensitive area of about 32 mm × 32 mm. The module is MR-compatible. The thermal decoupling of the readout electronics from the photon sensors is obtained with an efficient internal liquid channel, integrated within the ceramic substrate. Two modules have been designed, based on different SiPM topologies: • Light spreader-based: an array of 12 × 12 SiPMs, with an overall pitch of 2.5 mm, is coupled with a scintillators array using a 1 mm thick glass plate. The light from one crystal is spread over a group of SiPMs, which are read out in parallel using PETA5 internal neighbor logic. • Interpolating SiPM-based: ISiPMs are intrinsic position-sensitive sensors. The photon diodes in the array are connected to one of the four available outputs so that the center of gravity of any bunch of detected photons can be reconstructed using a proper weight function of the read out amplitudes. An array of ISiPMs, each 7.5 mm× 5 mm sized, is directly coupled with the scintillating crystals. Both modules can clearly resolve LYSO arrays with a pitch of only 0.833 mm. The detector can be adjusted for clinical PET, where it has already shown ToF resolution of about 230 ps CRT at FWHM. The module designs, their features and results are described.

  17. A Novel Design of Micromachined Horn Antenna for Millimeter and Sub-millimeter Applications

    Directory of Open Access Journals (Sweden)

    A.Ansari

    2007-04-01

    Full Text Available A novel design of micromachined horn antenna is presented. Horn excited with a quasi-Yagi antenna. In this paper micromachining process of this antenna, and simulation results of a horn structure operate around 330GHz using Agilent High Frequency Structure Simulator (HFSS software is presented. The results indicate a gain around 10dB, directivity 10.5dB and resonant dipole impedance 48.3Ω for horn antenna. The micromachined horn antenna is a high-efficiency antenna suitable for applications in millimeter-wave imaging systems, remote-sensing, and radio astronomy.

  18. A Multiwavelength Study of the Intracluster Medium and the Characterization of the Multiwavelength Sub/millimeter Inductance Camera

    Science.gov (United States)

    Siegel, Seth Robert

    -arrays of slot dipole antennas for beam formation, on-chip lumped element filters for band definition, and Microwave Kinetic Inductance Detectors (MKIDs) for transduction of incoming light to electric signal. MKIDs are superconducting micro-resonators coupled to a feedline. Incoming light breaks apart Cooper pairs in the superconductor, causing a change in the quality factor and frequency of the resonator. This is read out as amplitude and phase modulation of a microwave probe signal centered on the resonant frequency. By tuning each resonator to a slightly different frequency and sending out a superposition of probe signals, hundreds of detectors can be read out on a single feedline. This natural capability for large scale, frequency domain multiplexing combined with relatively simple fabrication makes MKIDs a promising low temperature detector for future kilopixel sub/millimeter instruments. There is also considerable interest in using MKIDs for optical through near-infrared spectrophotometry due to their fast microsecond response time and modest energy resolution. In order to optimize the MKID design to obtain suitable performance for any particular application, it is critical to have a well-understood physical model for the detectors and the sources of noise to which they are susceptible. MUSIC has collected many hours of on-sky data with over 1000 MKIDs. This work studies the performance of the detectors in the context of one such physical model. Chapter 2 describes the theoretical model for the responsivity and noise of MKIDs. Chapter 3 outlines the set of measurements used to calibrate this model for the MUSIC detectors. Chapter 4 presents the resulting estimates of the spectral response, optical efficiency, and on-sky loading. The measured detector response to Uranus is compared to the calibrated model prediction in order to determine how well the model describes the propagation of signal through the full instrument. Chapter 5 examines the noise present in the

  19. Frequency and wavelength prediction of ultrasonic induced liquid surface waves.

    Science.gov (United States)

    Mahravan, Ehsan; Naderan, Hamid; Damangir, Ebrahim

    2016-12-01

    A theoretical investigation of parametric excitation of liquid free surface by a high frequency sound wave is preformed, using potential flow theory. Pressure and velocity distributions, resembling the sound wave, are applied to the free surface of the liquid. It is found that for impinging wave two distinct capillary frequencies will be excited: One of them is the same as the frequency of the sound wave, and the other is equal to the natural frequency corresponding to a wavenumber equal to the horizontal wavenumber of the sound wave. When the wave propagates in vertical direction, mathematical formulation leads to an equation, which has resonance frequency equal to half of the excitation frequency. This can explain an important contradiction between the frequency and the wavelength of capillary waves in the two cases of normal and inclined interaction of the sound wave and the free surface of the liquid. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. A sub-millimeter resolution PET detector module using a multi-pixel photon counter array

    Science.gov (United States)

    Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B.; Tai, Yuan-Chuan

    2010-05-01

    A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 × 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 × 0.8 × 3 mm3 and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 × 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and ±5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when ±10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing

  1. Lamb wave structural health monitoring using frequency-wavenumber analysis

    Science.gov (United States)

    Tian, Zhenhua; Yu, Lingyu

    2013-01-01

    Lamb waves have shown great potential for structural health monitoring (SHM) in plate-like structures. Their attractive features include sensitivity to a variety of damage types and the capability of traveling relatively long distance. However, Lamb waves are dispersive and multimodal. Moreover, the propagating Lamb waves may include incident, reflected and converted waves. Various wave modes make the interpretation of Lamb wave signal very difficult. This paper presents studies on Lamb wave propagation using frequency-wavenumber analysis. By using two-dimensional Fourier transform (2-D FT), the time-space wavefield can be transformed into frequency-wavenumber domain, where various wave modes and waves propagating in different directions can be clearly discerned. By a frequency-wavenumber filtering strategy, the desired wave modes or wave propagation at certain direction can be extracted and further utilized for the purpose of SHM. The frequency-wavenumber analysis and its applications to Lamb wave SHM are illustrated through two experimental investigations. One is Lamb wave propagation in a plate half immersed in water and the other is Lamb wave mode decomposition by using two-dimensional frequency-wavenumber filtering strategy. Lamb waves are excited by piezoelectric wafer sensor and measured by scanning laser Doppler vibrometer. Various wave modes were visualized and successfully decomposed.

  2. SUB-MILLIMETER TELESCOPE CO (2-1) OBSERVATIONS OF NEARBY STAR-FORMING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xue-Jian; Gu, Qiusheng [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Wang, Zhong [Harvard-Smithsonian Center for Astrophysics, MS 66, 60 Garden Street, Cambridge, MA 02138 (United States); Wang, Junzhi [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Zhang, Zhi-Yu, E-mail: xjjiang@nju.edu.cn [The UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)

    2015-01-20

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M {sub *} galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV – r, and WISE color W3 – W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M {sub *} ≤10{sup 10} M {sub ☉}, the H I fraction (f {sub H} {sub I} ≡ M {sub H} {sub I}/M {sub *}) is significantly higher than that of more massive galaxies, while the H{sub 2} gas fraction (f{sub H{sub 2}} ≡ M{sub H{sub 2}}/M {sub *}) remains nearly unchanged. (2) Compared to f{sub H{sub 2}}, f {sub H} {sub I} correlates better with both M {sub *} and NUV – r. (3) A new parameter, WISE color W3 – W2 (12-4.6 μm), is introduced, which is similar to NUV – r in tracing star formation activity, and we find that W3 – W2 has a tighter anti-correlation with log f{sub H{sub 2}} than the anti-correlation of (NUV – r)-f {sub H} {sub I}, (NUV – r)-f{sub H{sub 2}}, and (W3 – W2)-f {sub H} {sub I}. This indicates that W3 – W2 can trace the H{sub 2} fraction in galaxies. For the gas ratio M{sub H{sub 2}}/M {sub H} {sub I} , only in the intermediate-M {sub *} galaxies it appears to depend on M {sub *} and NUV – r. We find a tight correlation between the molecular gas mass M{sub H{sub 2}} and 12 μm (W3) luminosities (L {sub 12} {sub μm}), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H{sub 2} mass for star-forming galaxies.

  3. BIOLOGICAL EFFECTS OF HIGH-FREQUENCY ELECTROMAGNETIC WAVES

    Science.gov (United States)

    In this report the author discusses the influence of high-frequency electromagnetic waves on living matter, especially in the field of microwaves. He...of electromagnetic waves . Symptoms of damage are listed and methods of protection discussed.

  4. Development Of A Multicolor Sub/millimeter Camera Using Microwave Kinetic Inductance Detectors

    Science.gov (United States)

    Schlaerth, James A.; Czakon, N. G.; Day, P. K.; Downes, T. P.; Duan, R.; Glenn, J.; Golwala, S. R.; Hollister, M. I.; LeDuc, H. G.; Maloney, P. R.; Mazin, B. A.; Noroozian, O.; Sayers, J.; Siegel, S.; Vayonakis, A.; Zmuidzinas, J.

    2011-01-01

    Microwave Kinetic Inductance Detectors (MKIDs) are superconducting resonators useful for detecting light from the millimeter-wave to the X-ray. These detectors are easily multiplexed, as the resonances can be tuned to slightly different frequencies, allowing hundreds of detectors to be read out simultaneously using a single feedline. The Multicolor Submillimeter Inductance Camera, MUSIC, will use 2304 antenna-coupled MKIDs in multicolor operation, with bands centered at wavelengths of 0.85, 1.1, 1.3 and 2.0 mm, beginning in 2011. Here we present the results of our demonstration instrument, DemoCam, containing a single 3-color array with 72 detectors and optics similar to MUSIC. We present sensitivities achieved at the telescope, and compare to those expected based upon laboratory tests. We explore the factors that limit the sensitivity, in particular electronics noise, antenna efficiency, and excess loading. We discuss mitigation of these factors, and how we plan to improve sensitivity to the level of background-limited performance for the scientific operation of MUSIC. Finally, we note the expected mapping speed and contributions of MUSIC to astrophysics, and in particular to the study of submillimeter galaxies. This research has been funded by grants from the National Science Foundation, the Gordon and Betty Moore Foundation, and the NASA Graduate Student Researchers Program.

  5. Nonlinear multi-frequency electromagnetic wave propagation phenomena

    Science.gov (United States)

    Valovik, Dmitry V.

    2017-11-01

    A generalisation of the concept of monochromatic electromagnetic waves guided by layered waveguide structures filled with non-linear medium is introduced. This generalisation leads to guided waves of a novel type: a non-linear multi-frequency guided wave. The existence of such waves, in particular guide structures, is proven using the perturbation method. Numerical experiments are presented for non-linear 1- and 2-frequency guided waves in plane and cylindrical (with a circular cross-section) waveguides. Numerically, a novel non-linear effect is found for particular cases of non-linear multi-frequency guided waves. The suggested generalisation gives not only a unified approach to treat various electromagnetic wave propagation problems but also paves the way to study non-linear interactions of guided waves.

  6. Low-frequency fluid waves in fractures and pipes

    Energy Technology Data Exchange (ETDEWEB)

    Korneev, Valeri

    2010-09-01

    Low-frequency analytical solutions have been obtained for phase velocities of symmetrical fluid waves within both an infinite fracture and a pipe filled with a viscous fluid. Three different fluid wave regimes can exist in such objects, depending on the various combinations of parameters, such as fluid density, fluid viscosity, walls shear modulus, channel thickness, and frequency. Equations for velocities of all these regimes have explicit forms and are verified by comparisons with the exact solutions. The dominant role of fractures in rock permeability at field scales and the strong amplitude and frequency effects of Stoneley guided waves suggest the importance of including these wave effects into poroelastic theories.

  7. Hacking for astronomy: can 3D printers and open-hardware enable low-cost sub-/millimeter instrumentation?

    Science.gov (United States)

    Ferkinhoff, Carl

    2014-07-01

    There have been several exciting developments in the technologies commonly used n in the hardware hacking community. Advances in low cost additive-manufacturing processes (i.e. 3D-printers) and the development of openhardware projects, which have produced inexpensive and easily programmable micro-controllers and micro-computers (i.e. Arduino and Raspberry Pi) have opened a new door for individuals seeking to make their own devices. Here we describe the potential for these technologies to reduce costs in construction and development of submillimeter/millimeter astronomical instrumentation. Specifically we have begun a program to measure the optical properties of the custom plastics used in 3D-printers as well as the printer accuracy and resolution to assess the feasibility of directly printing sub- /millimeter transmissive optics. We will also discuss low cost designs for cryogenic temperature measurement and control utilizing Arduino and Raspberry Pi.

  8. Cutoff frequencies for Alfven waves in the solar atmosphere

    Science.gov (United States)

    Perera, B. L. Harsha Kalpanie

    Propagation of linear Alfven waves in the isothermal and non-isothermal solar atmosphere is investigated numerically and analytically. It is shown that the two wave variables, the velocity and magnetic field perturbations, behave differently and that there is a range of wave frequencies for which the wave behavior changes from propagating to non-propagating. The so-called transition and turning points corresponding to this change are determined analytically, and their locations in the atmosphere are calculated and verified against the numerical results. The transition and turning points are then used to introduce cutoff frequencies, which are different for different wave variables. The main result is that there isn't a unique cutoff frequency for Alfven waves. Instead, a number of cutoff frequencies can be introduced depending upon the method used to define them, as well as on the choice of the wave variable used to describe the waves. Relevance of the obtained results to recent observations of Alfven waves in the solar atmosphere is also discussed. A concept of global cutoff frequencies is also introduced by using Leighton's, Hille's and Kneser's oscillation theorems, as well as the Sturm comparison theorems. The oscillation theorems have been applied to bounded and unbounded Alfven wave equations for both the velocity and magnetic field wave variables. The obtained results demonstrated that the global cutoff frequency and the local cutoff frequency are two different physical concepts. Furthermore, the latter exists if and only if the wave frequency is greater than the former. These analytical results have been verified using numerical solutions of the linear Alfven wave equations. The original ideal MHD equations were modified by taking into account the displacement current, and several oscillations theorems were applied to the resulting wave equations. As expected, only oscillatory solutions were found. The results presented in this PhD dissertation give strong

  9. Damping and Frequency Shift of Large Amplitude Electron Plasma Waves

    DEFF Research Database (Denmark)

    Thomsen, Kenneth; Juul Rasmussen, Jens

    1983-01-01

    The initial evolution of large-amplitude one-dimensional electron waves is investigated by applying a numerical simulation. The initial wave damping is found to be strongly enhanced relative to the linear damping and it increases with increasing amplitude. The temporal evolution of the nonlinear...... damping rate γ(t) shows that it increases with time within the initial phase of propagation, t≲π/ωB (ωB is the bounce frequency), whereafter it decreases and changes sign implying a regrowth of the wave. The shift in the wave frequency δω is observed to be positive for t≲π/ωB; then δω changes sign...

  10. Body waves separation in the time-frequency domain

    Science.gov (United States)

    Herrera, R. H.; Tary, J.; Van der Baan, M.

    2013-12-01

    Arrival times of body waves generated by small magnitude microseismic events are usually very close and their limited bandwidth can cause even partial overlap in the time and frequency domains. The separation of P and S waves is then a challenging task that if solved could bring more insights about nature and location of the generating source. Differences in arrival times and frequency content of P and S waves can be seen by using time-frequency decomposition. The traditional time-frequency representation based on the Fourier Transform is limited by its trade-off between time and frequency resolutions, while other alternatives like the Wavelet Transform are still limited by the Heisenberg box. A new derivation of the Continuous Wavelet Transform, called Synchrosqueezing, stretches these boundaries using a mixture of the reassignment method with instantaneous frequency, giving a better frequency representation with improved time localization. Furthermore, all the individual components of the signal are separated in the time domain. This means that we are able to isolate the waveforms of a complex microseismic trace. Each spectral component can then be matched with a body wave plus its associated coda. Proper parameters have to be selected prior to the computation, such as the central frequency and bandwidth of the mother wavelet. We thus include a signal characterization first to find the best matching mother wavelet. In this paper we use the Synchrosqueezing transform to perform the time frequency representation of short brittle events recorded during microseismic experiments. Decomposition results for these examples show that the Synchrosqueezing transform outperforms the Short-Time Fourier Transform. The different components of each body waves (first arrival, coda, frequency components) can then be identified in the time-frequency plane. For some microseismic events, a first P-wave arrival is followed by another arrival at lower frequency that could be a P-wave

  11. Modulation of radio frequency signals by ULF waves

    Directory of Open Access Journals (Sweden)

    C. L. Waters

    2007-06-01

    Full Text Available The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1–100 mHz plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B0, giving an e×B0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.

  12. Modulation of radio frequency signals by ULF waves

    Directory of Open Access Journals (Sweden)

    C. L. Waters

    2007-06-01

    Full Text Available The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1–100 mHz plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B0, giving an e×B0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.

  13. Effect of wave frequency and directional spread on shoreline runup

    Science.gov (United States)

    Guza, R. T.; Feddersen, Falk

    2012-06-01

    Wave breaking across the surf zone elevates the mean water level at the shoreline (setup), and drives fluctuations about the mean (runup). Runup often is divided into sea-swell (0.04-0.3 Hz) and lower frequency infragravity (0.00-0.04 Hz) components. With energetic incident waves, runup is dominated by infragravity frequencies, and total water levels (combined setup and runup) can exceed 3 m, significantly contributing to coastal flooding and erosion. Setup and runup observations on sandy beaches are scattered about empirical parameterizations based on near-shoreline beach slope and deep water wave height and wavelength. Accurate parameterizations are needed to determine flooding and erosion risk to coastal ecosystems and communities. Here, numerical simulations with the Boussinesq wave model funwaveC are shown to statistically reproduce typical empirical setup and runup parameterizations. Furthermore, the model infragravity runup Rs(ig) strongly depends on the incident wave directional and frequency spread (about the mean direction and peak frequency). Realistic directional spread variations change Rs(ig) equivalent to a factor of two variation in incident wave height. The modeled Rs(ig) is shown to vary systematically with a new, non-dimensional spreading parameter that involves peak frequency, frequency spread, and directional spread. This suggests a new parameterization for Rs(ig) potentially useful to predict coastal flooding and erosion.

  14. Frequency References for Gravitational Wave Missions

    Science.gov (United States)

    Preston, Alix; Thrope, J. I.; Donelan, D.; Miner, L.

    2012-01-01

    The mitigation of laser frequency noise is an important aspect of interferometry for LISA-like missions. One portion of the baseline mitigation strategy in LISA is active stabilization utilizing opto-mechanical frequency references. The LISA optical bench is an attractive place to implement such frequency references due to its environmental stability and its access to primary and redundant laser systems. We have made an initial investigation of frequency references constructed using the techniques developed for the LISA and LISA Pathfinder optical benches. Both a Mach-Zehnder interferometer and triangular Fabry-Perot cavity have been successfully bonded to a Zerodur baseplate using the hydroxide bonding method. We will describe the construction of the bench along with preliminary stability results.

  15. Detecting high-frequency gravitational waves with optically levitated sensors.

    Science.gov (United States)

    Arvanitaki, Asimina; Geraci, Andrew A

    2013-02-15

    We propose a tunable resonant sensor to detect gravitational waves in the frequency range of 50-300 kHz using optically trapped and cooled dielectric microspheres or microdisks. The technique we describe can exceed the sensitivity of laser-based gravitational wave observatories in this frequency range, using an instrument of only a few percent of their size. Such a device extends the search volume for gravitational wave sources above 100 kHz by 1 to 3 orders of magnitude, and could detect monochromatic gravitational radiation from the annihilation of QCD axions in the cloud they form around stellar mass black holes within our galaxy due to the superradiance effect.

  16. Ultralow Frequency Waves In Saturn's Magnetosphere: More Than Ion Cyclotron Waves

    Science.gov (United States)

    Crary, Frank; Dols, Vincent; Usanova, Maria; Meeks, Zachary; Simon, Sven

    2017-04-01

    Electromagnetic waves near the oxygen/water group cyclotron frequency are an ubiquitous feature of Saturn's inner magnetosphere. These left-circularly polarized, transverse waves are generated by the anisotropic velocity distribution of recently produced ions, and reflect the ion production rate. The properties and distribution of these emissions have been previous studies and related to the distribution of neutrals in the system (Leisner et al., 2006; Crary et al., 2013; Meeks et al., 2016.) In addition to these waves, other, related mode have been observed by the Cassini spacecraft. The waves near the W+ (water group) cyclotron frequency sometimes have a compressional component and/or accompanying emission the first (2f) harmonic (implying the waves are oblique rather than parallel propagating. Neither of these properties is predicted by the classic theory of wave growth from a ring-beam distribution. In addition, ion cyclotron waves are also observed near the gyrofrequency of a 32 AMU ion, suggesting production of O2+. While observed, O2+ is a very low abundance species outside of 4 Saturn radii, and in the regions where these waves are present. Finally, strong but linearly polarized waves are sometimes observed near the orbit of Enceladus. The association between these waves and W+ ion cyclotron waves is unclear. We will present the measurements of these ULF waves, their frequency of occurrence with respect to position and time, and discuss their implications for plasma production in Saturn's magnetosphere.

  17. Experimental Limits on Gravitational Waves in the MHz frequency Range

    Energy Technology Data Exchange (ETDEWEB)

    Lanza, Robert Jr. [Univ. of Chicago, IL (United States)

    2015-03-01

    This thesis presents the results of a search for gravitational waves in the 1-11MHz frequency range using dual power-recycled Michelson laser interferometers at Fermi National Accelerator Laboratory. An unprecedented level of sensitivity to gravitational waves in this frequency range has been achieved by cross-correlating the output fluctuations of two identical and colocated 40m long interferometers. This technique produces sensitivities better than two orders of magnitude below the quantum shot-noise limit, within integration times of less than 1 hour. 95% confidence level upper limits are placed on the strain amplitude of MHz frequency gravitational waves at the 10-21 Hz-1/2 level, constituting the best direct limits to date at these frequencies. For gravitational wave power distributed over this frequency range, a broadband upper limit of 2.4 x 10-21Hz-1/2 at 95% confidence level is also obtained. This thesis covers the detector technology, the commissioning and calibration of the instrument, the statistical data analysis, and the gravitational wave limit results. Particular attention is paid to the end-to-end calibration of the instrument’s sensitivity to differential arm length motion, and so to gravitational wave strain. A detailed statistical analysis of the data is presented as well.

  18. Frequency clusters in self-excited dust density waves

    Science.gov (United States)

    Menzel, Kristoffer O.; Arp, Oliver; Piel, Alexander

    2010-11-01

    Self-excited dust density waves were studied under microgravity conditions. Their non-sinusoidal shape and high degrees of modulation suggests that nonlinear effects play an important role in their spatio-temporal dynamics. The resulting complex wave pattern is analyzed in great detail by means of the Hilbert transform, which provides instantaneous wave attributes, such as the phase and the frequency. Our analysis showed that the spatial frequency distribution of the DDWs is usually not constant over the dust cloud. In contrast, the wave field is divided into regions of different but almost constant frequencies [1]. The boundaries of these so-called frequency clusters coincide with the locations of phase defects in the wave field. It is found that the size of the clusters depends on the strength of spatial gradients in the plasma parameters. We attribute the formation of frequency clusters to synchronization phenomena as a consequence of the nonlinear character of the wave.[1] K. O. Menzel, O. Arp, A.Piel, Phys. Rev. Lett. 104, 235002 (2010)

  19. Pulsar timing arrays: closing in on low- frequency gravitational waves

    Science.gov (United States)

    Sampson, Laura

    2017-01-01

    Just like electromagnetic radiation, gravitational waves come in a wide spectrum of frequencies. Different frequencies give us access to different physical information about our universe. By taking advantage of the phenomenal stability of the spin rate of millisecond pulsars, pulsar timing arrays will allow us to detect gravitational waves in the nanohertz band. The most likely source in this band is supermassive black hole binaries, formed when galaxies merge, and so the detection of these gravitational waves gives us a new tool to learn about the merger history of galaxies and the environment in galactic cores. I will discuss the exciting astrophysics we can learn using pulsar timing arrays, as well as the prospects and expected timeline for gravitational wave detection in this new frequency regime.

  20. Micro-Spec: An Ultra-Compact, High-Sensitivity Spectrometer for Far-Infrared and Sub-Millimeter Astronomy

    Science.gov (United States)

    Cataldo, Giuseppe; Hsieh, Wen-Ting; Huang, Wei-Chung; Moseley, S. Harvey; Stevenson, Thomas R.; Wollack, Edward J.

    2013-01-01

    High-performance, integrated spectrometers operating in the far-infrared and sub-millimeter promise to be powerful tools for the exploration of the epochs of reionization and initial galaxy formation. These devices, using high-efficiency superconducting transmission lines, can achieve the performance of a meter-scale grating spectrometer in an instrument implemented on a four-inch silicon wafer. Such a device, when combined with a cryogenic telescope in space, provides an enabling capability for studies of the early universe. Here, the optical design process for Micro-Spec (mu-Spec) is presented, with particular attention given to its two-dimensional diffractive region, where the light of different wavelengths is focused on the different detectors. The method is based on the stigmatization and minimization of the light path function in this bounded region, which results in an optimized geometrical configuration. A point design with an efficiency of approx. 90% has been developed for initial demonstration, and can serve as the basis for future instruments. Design variations on this implementation are also discussed, which can lead to lower efficiencies due to diffractive losses in the multimode region.

  1. High-frequency matrix converter with square wave input

    Science.gov (United States)

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  2. The millimeter and sub-millimeter rotational spectrum of triple 13C-substituted ethyl cyanide

    Science.gov (United States)

    Pienkina, A. O.; Margulès, L.; Motiyenko, R. A.; Müller, H. S. P.; Guillemin, J.-C.

    2017-05-01

    Context. A recently published astronomical detection of all three doubly 13C-substituted ethyl cyanides toward Sgr B2(N2) motivated us to investigate triple 13C isotopic species that are expected to be also present in the ISM. Aims: We aim to present an experimental study of the rotational spectrum of triple 13C-substituted ethyl cyanide, 13CH313CH213CN, in the frequency range 150-990 GHz. We want to use the determined spectroscopic parameters for searching for 13CH313CH213CN in ALMA data. The main objective of this work is to provide accurate frequency predictions to search for this molecule in the Galactic center source Sagittarius B2(N) and to facilitate its detection in space. Methods: The laboratory rotational spectrum of 13CH313CH213CN has been recorded with the Lille's fast DDS solid-state spectrometer between 150 GHz and 990 GHz. Results: More than 4000 rotational transitions were identified in the laboratory. The quantum numbers reach J = 115 and Ka = 39. Watson's Hamiltonian in the A and S reductions were used to analyze the spectra. Accurate spectroscopic parameters were determined. The rotational spectra of the 13C containing species CH3CH2CN have been assigned, thus allowing the determination of the rotational and centrifugal distortion constants Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A2

  3. Computation of High-Frequency Waves with Random Uncertainty

    KAUST Repository

    Malenova, Gabriela

    2016-01-06

    We consider the forward propagation of uncertainty in high-frequency waves, described by the second order wave equation with highly oscillatory initial data. The main sources of uncertainty are the wave speed and/or the initial phase and amplitude, described by a finite number of random variables with known joint probability distribution. We propose a stochastic spectral asymptotic method [1] for computing the statistics of uncertain output quantities of interest (QoIs), which are often linear or nonlinear functionals of the wave solution and its spatial/temporal derivatives. The numerical scheme combines two techniques: a high-frequency method based on Gaussian beams [2, 3], a sparse stochastic collocation method [4]. The fast spectral convergence of the proposed method depends crucially on the presence of high stochastic regularity of the QoI independent of the wave frequency. In general, the high-frequency wave solutions to parametric hyperbolic equations are highly oscillatory and non-smooth in both physical and stochastic spaces. Consequently, the stochastic regularity of the QoI, which is a functional of the wave solution, may in principle below and depend on frequency. In the present work, we provide theoretical arguments and numerical evidence that physically motivated QoIs based on local averages of |uE|2 are smooth, with derivatives in the stochastic space uniformly bounded in E, where uE and E denote the highly oscillatory wave solution and the short wavelength, respectively. This observable related regularity makes the proposed approach more efficient than current asymptotic approaches based on Monte Carlo sampling techniques.

  4. RoboWeedSupport-Semi-Automated Unmanned Aerial System for Cost Efficient High Resolution in Sub-Millimeter Scale Acquisition of Weed Images

    OpenAIRE

    Simon L. Madsen; Mads Dyrmann; Morten S. Laursen; Rasmus N. Jørgensen

    2017-01-01

    Recent advances in the Unmanned Aerial System (UAS) safety and perception systems enable safe low altitude autonomous terrain following flights recently demonstrated by the consumer DJI Mavic PRO and Phamtom 4 Pro drones. This paper presents the first prototype system utilizing this functionality in form of semi-automated UAS based collection of crop/weed images where the embedded perception system ensures a significantly safer and faster gathering of weed images with sub-millimeter resolutio...

  5. Scattering of radio frequency waves by turbulence in fusion plasmas

    Science.gov (United States)

    Ram, Abhay K.

    2016-10-01

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments and incoherent fluctuations due to turbulence are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. While the effect of fluctuations on RF waves has not been quantified experimentally, there are telltale signs, arising from differences between results from simulations and from experiments, that fluctuations can modify the spectrum of RF waves. Any effect on RF waves in the scrape-off layer can have important experimental consequences. For example, electron cyclotron waves are expected to stabilize the deleterious neoclassical tearing mode (NTM) in ITER. Spectral and polarization changes due to scattering will modify the spatial location and profile of the current driven by the RF waves, thereby affecting the control of NTMs. Pioneering theoretical studies and complementary computer simulations have been pursued to elucidate the impact of fluctuations on RF waves. From the full complement of Maxwell's equations for cold, magnetized plasmas, it is shown that the Poynting flux in the wake of filaments develops spatial structure due to diffraction and shadowing. The uniformity of power flow into the plasma is affected by side-scattering, modifications to the wave spectrum, and coupling to plasma waves other than the incident RF wave. The Snell's law and the Fresnel equations have been reformulated within the context of magnetized plasmas. They are distinctly different from their counterparts in scalar dielectric media, and reveal new and important physical insight into the scattering of RF waves. The Snell's law and Fresnel equations are the basis for the Kirchhoff approximation necessary to determine properties of the scattered waves. Furthermore, this theory is also relevant for studying back

  6. Accelerating wave propagation modeling in the frequency domain using Python

    Science.gov (United States)

    Jo, Sang Hoon; Park, Min Jun; Ha, Wan Soo

    2017-04-01

    Python is a dynamic programming language adopted in many science and engineering areas. We used Python to simulate wave propagation in the frequency domain. We used the Pardiso matrix solver to solve the impedance matrix of the wave equation. Numerical examples shows that Python with numpy consumes longer time to construct the impedance matrix using the finite element method when compared with Fortran; however we could reduce the time significantly to be comparable to that of Fortran using a simple Numba decorator.

  7. Frequency-dependent attenuation of Love waves and its estimation

    Energy Technology Data Exchange (ETDEWEB)

    Xiao-Ping Li [Karlsruhe Univ. (T.H.) (Germany)

    1995-12-31

    Absorption analysis of Love channel waves plays an important role in in-seam seismic exploration, because the usefulness of this method in a particular locality depends on the rate at which Love-type channel waves are attenuated during the passage through the coal seam. In the absence of any evidence of reflections, it is always important to know at what range such features would have been detected in case of their presence. Obviously this is determined by the number of factor, for example, the distance and especially the absorption. By introducing the complex propagation functions into the known dispersion relation of Love waves for a simple symmetric homogeneous three-layered linear elastic model, the frequency-dependent attenuation relation can be explicitly given assuming that the quality factor of the coal (Q{sub {beta}1}) and the country rock (Q{sub {beta}2}) is constant, The attenuation coefficient of the Love waves becomes a non-linear function of the frequency because of the velocity dispersion. In this case the spectral ratio method can not be applied since it can only estimate the frequency-independent component Q. Therefore, a modification of the spectral ratio method is presented to inverse the frequency-dependent Q of Love-waves. (author). 7 refs., 3 figs

  8. Performance evaluation of a sub-millimeter spatial resolution PET detector module using a digital silicon photomultiplier coupled LGSO array

    Science.gov (United States)

    Leem, Hyun Tae; Choi, Yong; Kim, Kyu Bom; Lee, Sangwon; Yamamoto, Seiichi; Yeom, Jung-Yeol

    2017-02-01

    In positron emission tomography (PET) for breast, brain and small animal imaging, the spatial resolution of a PET detector is crucial to obtain high quality PET images. In this study, a PET detector for sub-millimeter spatial resolution imaging purpose was assembled using 4×4 pixels of a digital silicon photomultiplier (dSiPM, DPC-3200-22-44, Philips) coupled with a 15×15 LGSO array with BaSO4 reflector, and a 1 mm thick acrylic light guide for light distribution between the dSiPM pixels. The active area of each dSiPM pixel was 3.2×3.9 mm2 and the size of each LGSO scintillator element was 0.7×0.7×6 mm3. In this paper, we experimentally demonstrated the performance of the PET detector by measuring the energy resolution, 2D flood map, peak to valley (P/V) ratio, and coincidence resolving time (CRT). All measurements were performed at a temperature of 10±1 ℃. The average energy resolution was 15.6% (without correcting for saturation effects) at 511 keV and the best CRT was 242±5 ps. The 2D flood map obtained with an energy window of 400-600 keV demonstrated clear identification of all pixels, and the average P/V ratio of the X- and Y-directions were 7.31 and 7.81, respectively. This study demonstrated that the PET detector could be suitable for application in high resolution PET while achieving good timing resolution.

  9. Active bacteriophage biocontrol and therapy on sub-millimeter scales towards removal of unwanted bacteria from foods and microbiomes

    Directory of Open Access Journals (Sweden)

    Stephen T. Abedon

    2017-08-01

    Full Text Available Bacteriophages can be used as antibacterial agents as a form of biological control, e.g., such as phage therapy. With active treatment, phages must “actively” produce new virions, in situ, to attain “inundative” densities, i.e., sufficient titers to eradicate bacteria over reasonable timeframes. Passive treatment, by contrast, can be accomplished using phages that are bactericidal but incapable of generating new phage virions in situ during their interaction with target bacteria. These ideas of active versus passive treatment come from theoretical considerations of phage therapy pharmacology, particularly as developed in terms of phage application to well-mixed cultures consisting of physically unassociated bacteria. Here I extend these concepts to bacteria which instead are physically associated. These are bacteria as found making up cellular arrangements or bacterial microcolonies—collectively, clonal bacterial “clumps”. I consider circumstances where active phage replication would be required to effect desired levels of bacterial clearance, but populations of bacteria nevertheless are insufficiently prevalent to support phage replication to bacteria-inundative densities across environments. Clumped bacteria, however, may still support active treatment at more local, i.e., sub-millimeter, within-clump spatial scales, and potential consequences of this are explored mathematically. Application is to the post-harvest biocontrol of foodborne pathogens, and potentially also to precise microbiome editing. Adequate infection performance by phages in terms of timely burst sizes, that is, other than just adsorption rates and bactericidal activity, thus could be important for treatment effectiveness even if bacterial densities overall are insufficient to support active treatment across environments. Poor phage replication during treatment of even low bacterial numbers, such as given food refrigeration during treatment, consequently could

  10. Performance evaluation of a sub-millimeter spatial resolution PET detector module using a digital silicon photomultiplier coupled LGSO array

    Energy Technology Data Exchange (ETDEWEB)

    Leem, Hyun Tae [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Choi, Yong, E-mail: ychoi@sogang.ac.kr [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Kim, Kyu Bom; Lee, Sangwon [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Yamamoto, Seiichi [Department of Medical Technology, Nagoya University Graduate School of Medicine, Nagoya (Japan); Yeom, Jung-Yeol, E-mail: jungyeol@korea.ac.kr [School of Biomedical Engineering, Korea University, Seoul (Korea, Republic of)

    2017-02-21

    In positron emission tomography (PET) for breast, brain and small animal imaging, the spatial resolution of a PET detector is crucial to obtain high quality PET images. In this study, a PET detector for sub-millimeter spatial resolution imaging purpose was assembled using 4×4 pixels of a digital silicon photomultiplier (dSiPM, DPC-3200-22-44, Philips) coupled with a 15×15 LGSO array with BaSO{sub 4} reflector, and a 1 mm thick acrylic light guide for light distribution between the dSiPM pixels. The active area of each dSiPM pixel was 3.2×3.9 mm{sup 2} and the size of each LGSO scintillator element was 0.7×0.7×6 mm{sup 3}. In this paper, we experimentally demonstrated the performance of the PET detector by measuring the energy resolution, 2D flood map, peak to valley (P/V) ratio, and coincidence resolving time (CRT). All measurements were performed at a temperature of 10±1 ℃. The average energy resolution was 15.6% (without correcting for saturation effects) at 511 keV and the best CRT was 242±5 ps. The 2D flood map obtained with an energy window of 400–600 keV demonstrated clear identification of all pixels, and the average P/V ratio of the X- and Y-directions were 7.31 and 7.81, respectively. This study demonstrated that the PET detector could be suitable for application in high resolution PET while achieving good timing resolution.

  11. High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

    Directory of Open Access Journals (Sweden)

    G. Thejappa

    2004-01-01

    Full Text Available Short wavelength ion sound waves (2-4kHz are detected in association with the Langmuir waves (~15-30kHz in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

  12. High-Frequency Electrostatic Wave Generation and Transverse Ion Acceleration by Low Alfvenic Wave Components of BBELF Turbulence

    Science.gov (United States)

    Singh, Nagendra; Khazanov, George; Mukhter, Ali

    2006-01-01

    Satellite observations in the auroral plasma have revealed that extremely low frequency (ELF) waves play a dominant role in the acceleration of electrons and ions in the auroral plasma. The electromagnetic components of the ELF (EMELF) waves are the electromagnetic ion cyclotron (EMIC) waves below the cyclotron frequency of the lightest ion species in a multi-ion plasma. Shear Alfv6n waves (SAWS) constitute the lowest frequency components of the ELF waves below the ion cyclotron frequency of the heaviest ion. The -2 mechanism for the transfer of energy from such EMELF waves to ions affecting transverse ion heating still remains a matter of debate. A very ubiquitous fe8ture of ELF waves now observed in several rocket and satellite experiments is that they occur in conjunction with high-frequency electrostatic waves. The frequency spectrum of the composite wave turbulence extends from the low frequency of the Alfvenic waves to the high frequency of proton plasma frequency and/or the lower hybrid frequency. The spectrum does not show any feature organized by the ion cyclotron frequencies and their harmonics. Such broadband waves consisting of both the EM and ES waves are now popularly referred as BBELF waves. We present results here from 2.5-D particle-in-cell simulations showing that the ES components are directly generated by cross- field plasma instabilities driven by the drifts of the ions and electrons in the EM component of the BBELF waves.

  13. Structure-Optical Property Correlations of Arsenic Sulfide Glasses in Visible, Infrared, and Sub-millimeter Regions

    Energy Technology Data Exchange (ETDEWEB)

    McCloy, John S.; Riley, Brian J.; Sundaram, S. K.; Qiao, Hong (Amy); Crum, Jarrod V.; Johnson, Bradley R.

    2010-06-01

    Optical properties and structural aspects of AsxS100-x glasses from visible to terahertz wavelengths were explored. A series of annealed, bulk AsxS100-x glasses (x = 30 to 42) were made and their refractive indices determined at terahertz, infrared, and visible frequencies using a combination of a quasi-optical backwards wave oscillator spectrometer for terahertz measurements and a prism coupler for visible and infrared measurements. It was found that refractive index at all frequencies increases with arsenic composition up to 40 atomic % arsenic then decreases with additional arsenic. Structure in x-ray diffraction patterns support the notion of a minimum volume at 40 atomic %, while the average covalent coordination number indicates the rigidity percolation threshold is reached there. At As concentrations > 40 atomic %, the network becomes over-constrained, the molar volume increases.

  14. Quantitative subsurface analysis using frequency modulated thermal wave imaging

    Science.gov (United States)

    Subhani, S. K.; Suresh, B.; Ghali, V. S.

    2018-01-01

    Quantitative depth analysis of the anomaly with an enhanced depth resolution is a challenging task towards the estimation of depth of the subsurface anomaly using thermography. Frequency modulated thermal wave imaging introduced earlier provides a complete depth scanning of the object by stimulating it with a suitable band of frequencies and further analyzing the subsequent thermal response using a suitable post processing approach to resolve subsurface details. But conventional Fourier transform based methods used for post processing unscramble the frequencies with a limited frequency resolution and contribute for a finite depth resolution. Spectral zooming provided by chirp z transform facilitates enhanced frequency resolution which can further improves the depth resolution to axially explore finest subsurface features. Quantitative depth analysis with this augmented depth resolution is proposed to provide a closest estimate to the actual depth of subsurface anomaly. This manuscript experimentally validates this enhanced depth resolution using non stationary thermal wave imaging and offers an ever first and unique solution for quantitative depth estimation in frequency modulated thermal wave imaging.

  15. Low-Frequency Gravitational Wave Searches Using Spacecraft Doppler Tracking

    Directory of Open Access Journals (Sweden)

    Armstrong J. W.

    2006-01-01

    Full Text Available This paper discusses spacecraft Doppler tracking, the current-generation detector technology used in the low-frequency (~millihertz gravitational wave band. In the Doppler method the earth and a distant spacecraft act as free test masses with a ground-based precision Doppler tracking system continuously monitoring the earth-spacecraft relative dimensionless velocity $2 Delta v/c = Delta u/ u_0$, where $Delta u$ is the Doppler shift and $ u_0$ is the radio link carrier frequency. A gravitational wave having strain amplitude $h$ incident on the earth-spacecraft system causes perturbations of order $h$ in the time series of $Delta u/ u_0$. Unlike other detectors, the ~1-10 AU earth-spacecraft separation makes the detector large compared with millihertz-band gravitational wavelengths, and thus times-of-flight of signals and radio waves through the apparatus are important. A burst signal, for example, is time-resolved into a characteristic signature: three discrete events in the Doppler time series. I discuss here the principles of operation of this detector (emphasizing transfer functions of gravitational wave signals and the principal noises to the Doppler time series, some data analysis techniques, experiments to date, and illustrations of sensitivity and current detector performance. I conclude with a discussion of how gravitational wave sensitivity can be improved in the low-frequency band.

  16. Coherent Thz Frequency Radiation from Shock Waves: a New Ultrafast Strain Wave Detection Mechanism

    Science.gov (United States)

    Reed, Evan J.; Armstrong, Michael R.; Kim, Ki-Yong; Glownia, James H.

    2007-12-01

    We discover that strain waves of THz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering AlN/GaN heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time-dependence of the strain wave with potentially unprecedented nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude THz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals. We have performed proof of principle experiments that demonstrate THz signals that correlate with strain wave propagation times across Al thin films.

  17. Gravitational Waves and the Maximum Spin Frequency of Neutron Stars

    NARCIS (Netherlands)

    Patruno, A.; Haskell, B.; D'Angelo, C.

    2012-01-01

    In this paper, we re-examine the idea that gravitational waves are required as a braking mechanism to explain the observed maximum spin frequency of neutron stars. We show that for millisecond X-ray pulsars, the existence of spin equilibrium as set by the disk/magnetosphere interaction is sufficient

  18. A frequency selective acoustic transducer for directional Lamb wave sensing.

    Science.gov (United States)

    Senesi, Matteo; Ruzzene, Massimo

    2011-10-01

    A frequency selective acoustic transducer (FSAT) is proposed for directional sensing of guided waves. The considered FSAT design is characterized by a spiral configuration in wavenumber domain, which leads to a spatial arrangement of the sensing material producing output signals whose dominant frequency component is uniquely associated with the direction of incoming waves. The resulting spiral FSAT can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. The analytical expression of the shape of the spiral FSAT is obtained through the theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. Testing is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The discrete array approximates the continuous spiral FSAT geometry, and provides the flexibility to test several configurations. The experimental results demonstrate the strong frequency dependent directionality of the spiral FSAT and suggest its application for frequency selective acoustic sensors, to be employed for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health. © 2011 Acoustical Society of America

  19. Resonant interactions between cometary ions and low frequency electromagnetic waves

    Science.gov (United States)

    Thorne, Richard M.; Tsurutani, Bruce T.

    1987-01-01

    The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

  20. Millimeter-wave interconnects for microwave-frequency quantum machines

    Science.gov (United States)

    Pechal, Marek; Safavi-Naeini, Amir H.

    2017-10-01

    Superconducting microwave circuits form a versatile platform for storing and manipulating quantum information. A major challenge to further scalability is to find approaches for connecting these systems over long distances and at high rates. One approach is to convert the quantum state of a microwave circuit to optical photons that can be transmitted over kilometers at room temperature with little loss. Many proposals for electro-optic conversion between microwave and optics use optical driving of a weak three-wave mixing nonlinearity to convert the frequency of an excitation. Residual absorption of this optical pump leads to heating, which is problematic at cryogenic temperatures. Here we propose an alternative approach where a nonlinear superconducting circuit is driven to interconvert between microwave-frequency (7 ×109 Hz) and millimeter-wave-frequency photons (3 ×1011 Hz). To understand the potential for quantum state conversion between microwave and millimeter-wave photons, we consider the driven four-wave mixing quantum dynamics of nonlinear circuits. In contrast to the linear dynamics of the driven three-wave mixing converters, the proposed four-wave mixing converter has nonlinear decoherence channels that lead to a more complex parameter space of couplings and pump powers that we map out. We consider physical realizations of such converter circuits by deriving theoretically the upper bound on the maximum obtainable nonlinear coupling between any two modes in a lossless circuit, and synthesizing an optimal circuit based on realistic materials that saturates this bound. Our proposed circuit dissipates less than 10-9 times the energy of current electro-optic converters per qubit. Finally, we outline the quantum link budget for optical, microwave, and millimeter-wave connections, showing that our approach is viable for realizing interconnected quantum processors for intracity or quantum data center environments.

  1. Nonlinear low-frequency wave aspect of foreshock density holes

    Directory of Open Access Journals (Sweden)

    N. Lin

    2008-11-01

    Full Text Available Recent observations have uncovered short-duration density holes in the Earth's foreshock region. There is evidence that the formation of density holes involves non-linear growth of fluctuations in the magnetic field and plasma density, which results in shock-like boundaries followed by a decrease in both density and magnetic field. In this study we examine in detail a few such events focusing on their low frequency wave characteristics. The propagation properties of the waves are studied using Cluster's four point observations. We found that while these density hole-structures were convected with the solar wind, in the plasma rest frame they propagated obliquely and mostly sunward. The wave amplitude grows non-linearly in the process, and the waves are circularly or elliptically polarized in the left hand sense. The phase velocities calculated from four spacecraft timing analysis are compared with the velocity estimated from δE/δB. Their agreement justifies the plane electromagnetic wave nature of the structures. Plasma conditions are found to favor firehose instabilities. Oblique Alfvén firehose instability is suggested as a possible energy source for the wave growth. Resonant interaction between ions at certain energy and the waves could reduce the ion temperature anisotropy and thus the free energy, thereby playing a stabilizing role.

  2. Nonlinear low-frequency wave aspect of foreshock density holes

    Directory of Open Access Journals (Sweden)

    N. Lin

    2008-11-01

    Full Text Available Recent observations have uncovered short-duration density holes in the Earth's foreshock region. There is evidence that the formation of density holes involves non-linear growth of fluctuations in the magnetic field and plasma density, which results in shock-like boundaries followed by a decrease in both density and magnetic field. In this study we examine in detail a few such events focusing on their low frequency wave characteristics. The propagation properties of the waves are studied using Cluster's four point observations. We found that while these density hole-structures were convected with the solar wind, in the plasma rest frame they propagated obliquely and mostly sunward. The wave amplitude grows non-linearly in the process, and the waves are circularly or elliptically polarized in the left hand sense. The phase velocities calculated from four spacecraft timing analysis are compared with the velocity estimated from δEB. Their agreement justifies the plane electromagnetic wave nature of the structures. Plasma conditions are found to favor firehose instabilities. Oblique Alfvén firehose instability is suggested as a possible energy source for the wave growth. Resonant interaction between ions at certain energy and the waves could reduce the ion temperature anisotropy and thus the free energy, thereby playing a stabilizing role.

  3. Kinetic Scale Structure of Low-frequency Waves and Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    López, Rodrigo A.; Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States); Araneda, Jaime A., E-mail: rlopezh@umd.edu, E-mail: yoonp@umd.edu [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)

    2017-08-10

    The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.

  4. Propagation of radio frequency waves through density fluctuations

    Science.gov (United States)

    Valvis, S. I.; Papagiannis, P.; Papadopoulos, A.; Hizanidis, K.; Glytsis, E.; Bairaktaris, F.; Zisis, A.; Tigelis, I.; Ram, A. K.

    2017-10-01

    On their way to the core of a tokamak plasma, radio frequency (RF) waves, excited in the vacuum region, have to propagate through a variety of density fluctuations in the edge region. These fluctuations include coherent structures, like blobs that can be field aligned or not, as well as turbulent and filamentary structures. We have been studying the effect of fluctuations on RF propagation using both theoretical (analytical) and computational models. The theoretical results are being compared with those obtained by two different numerical codes ``a Finite Difference Frequency Domain code and the commercial COMSOL package. For plasmas with arbitrary distribution of coherent and turbulent fluctuations, we have formulated an effective dielectric permittivity of the edge plasma. This permittivity tensor is then used in numerical simulations to study the effect of multi-scale turbulence on RF waves. We not only consider plane waves but also Gaussian beams in the electron cyclotron and lower hybrid range of frequencies. The analytical theory and results from simulations on the propagation of RF waves will be presented. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium and by DoE Grant DE-FG02-91ER-54109.

  5. Dispersion of Own Frequency of Ion-Dipole by Supersonic Transverse Wave in Solid

    Directory of Open Access Journals (Sweden)

    Minasyan V.

    2010-10-01

    Full Text Available First, we predict an existence of transverse electromagnetic field formed by supersonic transverse wave in solid. This electromagnetic wave acquires frequency and speed of sound, and it propagates along of direction propagation of supersonic wave. We also show that own frequency of ion-dipole depends on frequency of supersonic transverse wave.

  6. Controlling Energy Radiations of Electromagnetic Waves via Frequency Coding Metamaterials.

    Science.gov (United States)

    Wu, Haotian; Liu, Shuo; Wan, Xiang; Zhang, Lei; Wang, Dan; Li, Lianlin; Cui, Tie Jun

    2017-09-01

    Metamaterials are artificial structures composed of subwavelength unit cells to control electromagnetic (EM) waves. The spatial coding representation of metamaterial has the ability to describe the material in a digital way. The spatial coding metamaterials are typically constructed by unit cells that have similar shapes with fixed functionality. Here, the concept of frequency coding metamaterial is proposed, which achieves different controls of EM energy radiations with a fixed spatial coding pattern when the frequency changes. In this case, not only different phase responses of the unit cells are considered, but also different phase sensitivities are also required. Due to different frequency sensitivities of unit cells, two units with the same phase response at the initial frequency may have different phase responses at higher frequency. To describe the frequency coding property of unit cell, digitalized frequency sensitivity is proposed, in which the units are encoded with digits "0" and "1" to represent the low and high phase sensitivities, respectively. By this merit, two degrees of freedom, spatial coding and frequency coding, are obtained to control the EM energy radiations by a new class of frequency-spatial coding metamaterials. The above concepts and physical phenomena are confirmed by numerical simulations and experiments.

  7. Radar and Laser Sensors for High Frequency Ocean Wave Measurement.

    Science.gov (United States)

    Kennedy, C. R.

    2016-02-01

    Experimental measurement of air-sea fluxes invariably take place using shipbourne instrumentation and simultaneous measurement of wave height and direction is desired. A number of researchers have shown that range measuring sensors combined with inertial motion compensation can be successful on board stationary or very slowly moving ships. In order to measure wave characteristics from ships moving at moderate to full speed the sensors are required to operate at higher frequency so as to overcome the Doppler shift caused by ship motion. This work presents results from some preliminary testing of laser, radar and ultrasonic range sensors in the laboratory and on board ship. The characteristics of the individual sensors are discussed and comparison of the wave spectra produced by each is presented.

  8. Low-frequency gravitational-wave science frontiers

    Science.gov (United States)

    Hughes, Scott

    2017-01-01

    With LIGO detecting stellar mass black holes and (soon) other stellar mass compact objects, and with LISA Pathfinder demonstrating important elements of the technology needed to fly a gravitational-wave antenna in space, the case for a low-frequency, space-based gravitational-wave detector - LISA - is stronger than ever. In this talk, I will survey the landscape of low-frequency gravitational-wave astronomy. The LISA frequency band from afew ×10-5 Hz to about 1 Hz is one which is rich with known sources whose measurement will enable new astronomical and physical measurements of important systems. It is also a band with great potential discovery space. In this talk, I will survey the known knowns and known unknowns in the LISA band, describing the frontiers that we can study in advance of the mission, and the frontiers that LISA measurements will unveil. I will also talk about the possible unknown unknowns where surprising discoveries may lurk.

  9. 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.

  10. Electromagnetic waves near the proton cyclotron frequency: Stereo observations

    Energy Technology Data Exchange (ETDEWEB)

    Jian, L. K. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Wei, H. Y.; Russell, C. T. [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095 (United States); Luhmann, J. G. [Space Science Laboratory, University of California, Berkeley, CA 94720 (United States); Klecker, B. [Max-Planck-Institut für Extraterrestrische Physik, D-85741 Garching (Germany); Omidi, N. [Solana Scientific Inc., Solana Beach, CA 92075 (United States); Isenberg, P. A. [Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 (United States); Goldstein, M. L.; Figueroa-Viñas, A. [Heliophysics Science Division, NASA Goddard Space Flight Center, MD 20771 (United States); Blanco-Cano, X., E-mail: lan.jian@nasa.gov [Instituto de Geofisica, Universidad Nacional Autónoma de México, Coyoacán D.F. (Mexico)

    2014-05-10

    Transverse, near-circularly polarized, parallel-propagating electromagnetic waves around the proton cyclotron frequency were found sporadically in the solar wind throughout the inner heliosphere. They could play an important role in heating and accelerating the solar wind. These low-frequency waves (LFWs) are intermittent but often occur in prolonged bursts lasting over 10 minutes, named 'LFW storms'. Through a comprehensive survey of them from Solar Terrestrial Relations Observatory A using dynamic spectral wave analysis, we have identified 241 LFW storms in 2008, present 0.9% of the time. They are left-hand (LH) or right-hand (RH) polarized in the spacecraft frame with similar characteristics, probably due to Doppler shift of the same type of waves or waves of intrinsically different polarities. In rare cases, the opposite polarities are observed closely in time or even simultaneously. Having ruled out interplanetary coronal mass ejections, shocks, energetic particles, comets, planets, and interstellar ions as LFW sources, we discuss the remaining generation scenarios: LH ion cyclotron instability driven by greater perpendicular temperature than parallel temperature or by ring-beam distribution, and RH ion fire hose instability driven by inverse temperature anisotropy or by cool ion beams. The investigation of solar wind conditions is compromised by the bias of the one-dimensional Maxwellian fit used for plasma data calibration. However, the LFW storms are preferentially detected in rarefaction regions following fast winds and when the magnetic field is radial. This preference may be related to the ion cyclotron anisotropy instability in fast wind and the minimum in damping along the radial field.

  11. Waves in a short cable at low frequencies, or just hand-waving?

    CERN Document Server

    Kish, L B; Granqvist, C G; Smulko, J M

    2015-01-01

    We address the question of low-frequency signals in a short cable, which are often considered as waves in engineering calculations. Such an assumption violates several laws of physics, but exact calculations can be carried out via linear network theory.

  12. Frequency selection for coda wave interferometry in concrete structures.

    Science.gov (United States)

    Fröjd, Patrik; Ulriksen, Peter

    2017-09-01

    This study contributes to the establishment of frequency recommendations for use in coda wave interferometry structural health monitoring (SHM) systems for concrete structures. To this end, codas with widely different central frequencies were used to detect boreholes with different diameters in a large concrete floor slab, and to track increasing damage in a small concrete beam subjected to bending loads. SHM results were obtained for damage that can be simulated by drilled holes on the scale of a few mm or microcracks due to bending. These results suggest that signals in the range of 50-150kHz are suitable in large concrete structures where it is necessary to account for the high attenuation of high-frequency signals. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Dual-frequency continuous wave optical parametric oscillator

    Science.gov (United States)

    Sun, Bingjie; Wang, Xin; Yang, Suhui; Li, Kun

    2018-01-01

    This article shows a dual-frequency OPO with multi-grating (28.5-31.5 μm) periodically poled MgO:LiNbO3 (MgO:PPLN) pumped by a dual-frequency continuous wave at 1.064 μm. The wavelengths of idler and signal varying versus temperature at different periods of inverted domains were numerical simulated. It proves that as the temperature rises, or as the poling period increases, the idler wavelength shortens and signal wavelength lengthens. The pump is a 30 W dual-frequency fiber laser MOPA with beat note frequency varying from 125 MHz to 175 MHz. The pump threshold of the bow-tie ring cavity OPO was 3 W. An average dual-frequency idler output power of 2.6 W was obtained when the pump power was 17.2 W at 45 °C. The idler wavelength was 3.4 μm when the poling period was 30.5 μm. The idler wavelength could be tuned from 2.9 μm to 3.9 μm by changing the temperature and the poling period, and the beat note frequency was proved to be equal to that of the pump.

  14. Wave propagation in reconfigurable broadband gain metamaterials at microwave frequencies

    Science.gov (United States)

    Fan, Yifeng; Nagarkoti, Deepak S.; Rajab, Khalid Z.; Hao, Yang; Zhang, Hao Chi; Cui, Tie Jun

    2016-05-01

    The wave dispersion characteristics for loop array-based metamaterials were analyzed, based on the general transmission line model of a one-dimensional host medium interacting with a chain of coupled loops. By relating the wave propagation constant and the effective parameters of the coupled host medium, we showed that an active medium embedded with non-Foster loaded loop array can be designed to exhibit broadband negative material parameters with positive gain. Accounting for all interactions, the stability of the active medium was investigated, further yielding necessary design specifications for the non-Foster loads. Subsequently, an experimental demonstration was provided to verify the theoretical analysis, showing that stable reconfigurable broadband gain metamaterials at microwave frequencies can be obtained with proper negative impedance converter design.

  15. Evaluation of a wave-vector-frequency-domain method for nonlinear wave propagation

    Science.gov (United States)

    Jing, Yun; Tao, Molei; Clement, Greg T.

    2011-01-01

    A wave-vector-frequency-domain method is presented to describe one-directional forward or backward acoustic wave propagation in a nonlinear homogeneous medium. Starting from a frequency-domain representation of the second-order nonlinear acoustic wave equation, an implicit solution for the nonlinear term is proposed by employing the Green’s function. Its approximation, which is more suitable for numerical implementation, is used. An error study is carried out to test the efficiency of the model by comparing the results with the Fubini solution. It is shown that the error grows as the propagation distance and step-size increase. However, for the specific case tested, even at a step size as large as one wavelength, sufficient accuracy for plane-wave propagation is observed. A two-dimensional steered transducer problem is explored to verify the nonlinear acoustic field directional independence of the model. A three-dimensional single-element transducer problem is solved to verify the forward model by comparing it with an existing nonlinear wave propagation code. Finally, backward-projection behavior is examined. The sound field over a plane in an absorptive medium is backward projected to the source and compared with the initial field, where good agreement is observed. PMID:21302985

  16. Evaluation of a wave-vector-frequency-domain method for nonlinear wave propagation.

    Science.gov (United States)

    Jing, Yun; Tao, Molei; Clement, Greg T

    2011-01-01

    A wave-vector-frequency-domain method is presented to describe one-directional forward or backward acoustic wave propagation in a nonlinear homogeneous medium. Starting from a frequency-domain representation of the second-order nonlinear acoustic wave equation, an implicit solution for the nonlinear term is proposed by employing the Green's function. Its approximation, which is more suitable for numerical implementation, is used. An error study is carried out to test the efficiency of the model by comparing the results with the Fubini solution. It is shown that the error grows as the propagation distance and step-size increase. However, for the specific case tested, even at a step size as large as one wavelength, sufficient accuracy for plane-wave propagation is observed. A two-dimensional steered transducer problem is explored to verify the nonlinear acoustic field directional independence of the model. A three-dimensional single-element transducer problem is solved to verify the forward model by comparing it with an existing nonlinear wave propagation code. Finally, backward-projection behavior is examined. The sound field over a plane in an absorptive medium is backward projected to the source and compared with the initial field, where good agreement is observed.

  17. Cluster observations of high-frequency waves in the exterior cusp

    Directory of Open Access Journals (Sweden)

    Y. Khotyaintsev

    2004-07-01

    Full Text Available We study wave emissions, in the frequency range from above the lower hybrid frequency up to the plasma frequency, observed during one of the Cluster crossings of a high-beta exterior cusp region on 4 March 2003. Waves are localized near narrow current sheets with a thickness a few times the ion inertial length; currents are strong, of the order of 0.1-0.5μA/m2 (0.1-0.5mA/m2 when mapped to ionosphere. The high frequency part of the waves, frequencies above the electron-cyclotron frequency, is analyzed in more detail. These high frequency waves can be broad-band, can have spectral peaks at the plasma frequency or spectral peaks at frequencies below the plasma frequency. The strongest wave emissions usually have a spectral peak near the plasma frequency. The wave emission intensity and spectral character change on a very short time scale, of the order of 1s. The wave emissions with strong spectral peaks near the plasma frequency are usually seen on the edges of the narrow current sheets. The most probable generation mechanism of high frequency waves are electron beams via bump-on-tail or electron two-stream instability. Buneman and ion-acoustic instability can be excluded as a possible generation mechanism of waves. We suggest that high frequency waves are generated by electron beams propagating along the separatrices of the reconnection region.

  18. THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES THE REST-FRAME FAR-INFRARED EMISSION OF SUB-MILLIMETER GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, J. M.; Smail, Ian; Swinbank, A. M.; Chen, Chian-Chou; Danielson, A. L. R.; Edge, A. C.; Ma, C.-J. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Almaini, O.; Conselice, C.; Hartley, W. G.; Lani, C. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Blain, A. W. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Bremer, M. N.; Coppin, K. E. K. [School of Physics, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Dunlop, J. S.; Ivison, R. J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford HIll, Edinburgh EH9 3HJ (United Kingdom); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Geach, J. E. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Karim, A., E-mail: j.m.simpson@dur.ac.uk [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); and others

    2015-01-20

    We present high-resolution (0.''3) Atacama Large Millimeter Array 870 μm imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10 kpc scales. We derive a median intrinsic angular size of FWHM = 0.''30 ± 0.''04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (S/N) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. A stacking analysis of the SMGs detected at S/N <10 shows they have sizes consistent with the 870 μm bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ∼250 μm sizes of SMGs are consistent with studies of resolved {sup 12}CO (J = 3-2 to 7-6) emission lines, but that sizes derived from 1.4 GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 M {sub ☉} yr{sup –1} kpc{sup –2}, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.

  19. An improved wave-vector frequency-domain method for nonlinear wave modeling.

    Science.gov (United States)

    Jing, Yun; Tao, Molei; Cannata, Jonathan

    2014-03-01

    In this paper, a recently developed wave-vector frequency-domain method for nonlinear wave modeling is improved and verified by numerical simulations and underwater experiments. Higher order numeric schemes are proposed that significantly increase the modeling accuracy, thereby allowing for a larger step size and shorter computation time. The improved algorithms replace the left-point Riemann sum in the original algorithm by the trapezoidal or Simpson's integration. Plane waves and a phased array were first studied to numerically validate the model. It is shown that the left-point Riemann sum, trapezoidal, and Simpson's integration have first-, second-, and third-order global accuracy, respectively. A highly focused therapeutic transducer was then used for experimental verifications. Short high-intensity pulses were generated. 2-D scans were conducted at a prefocal plane, which were later used as the input to the numerical model to predict the acoustic field at other planes. Good agreement is observed between simulations and experiments.

  20. Resent developments in high-frequency surface-wave techniques

    Science.gov (United States)

    Xia, J.; Pan, Y.; Zeng, C.

    2012-12-01

    High-frequency Rayleigh-wave methods, such as Multi-channel Analysis of Surface Waves (MASW), are getting increasingly attention in the near-surface geophysics and geotechnique community in the last 20 years because of their non-invasive, non-destructive, efficient, and low-cost advantages and their success in environmental and engineering applications. They are viewed by near-surface geophysics community as the one of most promise techniques in the future. However, they face unique problems related to extremely irregular velocity variations in near-surface geology or man-made constructions, for example, highway, foundation, dam, levee, jetty, etc., which are not solvable by techniques or algorithms widely used in earthquake seismology or oil/gas seismic exploration. We present solutions to the problems associated with near-surface materials that possess velocity inverse and high Poisson's ratio. Calculation of dispersion curves by existing algorithms may fail for some special velocity models due to velocity inverse (a high-velocity layer on the top of a low-velocity layer). Two velocity models are most common in near-surface applications. One is a low-velocity half space model and the other a high-velocity topmost layer. The former model results in a complex matrix that no roots can be found in the real number domain, which implies that no phase velocities can be calculated in certain frequency ranges based on current exist algorithms. A solution is to use the real part of the root of the complex number. It is well-known that phase velocities approach about 91% of the shear (S)-wave velocity of the topmost layer when wavelengths are much shorter than the thickness of the topmost layer. The later model, however, results in that phase velocities in a high-frequency range calculated using the current algorithms approach a velocity associated with the S-wave velocity of the second layer NOT the topmost layer. A solution to this problem is to use a two-layer model to

  1. Attenuation Characteristics of High Frequency Seismic Waves in Southern India

    Science.gov (United States)

    Sivaram, K.; Utpal, Saikia; Kanna, Nagaraju; Kumar, Dinesh

    2017-07-01

    We present a systematic study of seismic attenuation and its related Q structure derived from the spectral analysis of P-, S-waves in the southern India. The study region is separated into parts of EDC (Eastern Dharwar Craton), Western Dharwar Craton (WDC) and Southern Granulite Terrain (SGT). The study is carried out in the frequency range 1-20 Hz, using a single-station spectral ratio technique. We make use of about 45 earthquakes, recorded in a network of about 32 broadband 3-component seismograph-stations, having magnitudes ( M L) varying from 1.6 to 4.5, to estimate the average seismic body wave attenuation quality factors; Q P and Q S. Their estimated average values are observed to be fitting to the power law form of Q = Q 0 f n . The averaged power law relations for Southern Indian region (as a whole) are obtained as Q P = (95 ± 1.12) f (1.32±0.01); Q S = (128 ± 1.84) f (1.49±0.01). Based on the stations and recorded local earthquakes, for parts of EDC, WDC and SGT, the average power law estimates are obtained as: Q P = (97 ± 5) f (1.40±0.03), Q S = (116 ± 1.5) f (1.48±0.01) for EDC region; Q P = (130 ± 7) f (1.20±0.03), Q S = (103 ± 3) f (1.49±0.02) for WDC region; Q P = (68 ± 2) f (1.4±0.02), Q S = (152 ± 6) f (1.48±0.02) for SGT region. These estimates are weighed against coda Q ( Q C) estimates, using the coda decay technique, which is based on a weak backscattering of S-waves. A major observation in the study of body wave analysis is the low body wave Q ( Q 0 0.5) and Q S/ Q P ≫ 1, suggesting lateral stretches of dominant scattering mode of seismic wave propagation. This primarily could be attributed to possible thermal anomalies and spread of partially fluid-saturated rock-masses in the crust and upper mantle of the southern Indian region, which, however, needs further laboratory studies. Such physical conditions might partly be correlated to the active seismicity and intraplate tectonism, especially in SGT and EDC regions, as per the

  2. Influence of high frequency electric field on the dispersion of ion-acoustic waves in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Turky, A.; Cercek, M.; Tavzes, R.

    1981-01-01

    The modification of the ion-acoustic wave dispersion under the action of a high frequency electric field was studied experimentally, the wave propagating along and against the plasma stream. The frequency of the field amounted to approximately half the electron plasma frequency. It was found that the phase velocity of the ion wave and the plasma drift velocity decrease as the effective high frequency field power increases.

  3. Scanning SQUID microscopy as a new tool for sub-millimeter scale magnetostratigraphy: An application to unveil the growth process of marine ferromanganese crusts and its future potential

    Science.gov (United States)

    Oda, H.; Noguchi, A.; Yamamoto, Y.; Usui, A.; Sato, M.; Kawai, J.

    2016-12-01

    Scanning SQUID microscope, a new developing tool for paleomagnetists, enables us to map magnetic field on surfaces of geological samples or thin sections at sub-millimeter scale and provides opportunity to conduct magnetostratigraphy with an unprecedented resolution. In the presentation, we show an example of sub-millimeter scale magnetostratigraphy with a newly developed scanning SQUID (superconducting quantum interference device) microscope (SSM) at Geological Survey, AIST (Kawai et al., 2016; Oda et al., submitted). Marine ferromanganese crusts grow very slowly throughout the global ocean by direct precipitation typically on seamounts for more than several tens of millions of years, which can be considered as archives of paleoclimate and paleoceanography.In order to uncover the history of paleoenvironment recorded in the ferromanganese cursts, it is very important to provide their reliable age models and growth rates. Previous studies have shown universal applicability of magnetostratigraphy in estimating growth ages of ferromanganese crust (Oda et al., 2011; Noguchi et al., in press). A thin section of a ferromanganese crust sample from Takuyo-Daigo seamount in northwest Pacific was used for the mapping of magnetic field with the SSM, where minimum amount of dust and sediment are expected to come from continents. The result shows that average growth rate of the ferromanganese crust from this seamount is 3.56 ± mm/m.y., which is within 17.6% of that deduced from the 10Be/9Be dating method (2.93 ±0.15 mm/m.y.). Although the mechanism of remanent magnetization acquisition for ferromanganese crusts need to be investigated further, the magnetic stripes parallel to the growth pattern observed on optical and backscattered electron images promises the future possibilities to provide a quick tool to estimate ages and growth rates for ferromanganese crusts. Finally, it can be concluded that SSM could be a fundamental tool for paleomagnetists in providing avenue to

  4. TU-H-CAMPUS-TeP2-03: High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Izaguirre, E; Pokhrel, S; Knewtson, T [University of Tennessee Medical Science Center, Memphis, TN (United States); University of Missouri, Columbia, MO (United States); Hedrick, S [Provision Center for Proton Therapy, Knoxville, TN (United States)

    2016-06-15

    Purpose: Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research. Methods: We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has green output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison. Results: The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples. Conclusion: The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell

  5. SU-F-T-642: Sub Millimeter Accurate Setup of More Than Three Vertebrae in Spinal SBRT with 6D Couch

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X; Zhao, Z; Yang, J; Yang, J; McAleer, M; Brown, P; Li, J; Ghia, A [MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To assess the initial setup accuracy in treating more than 3 vertebral body levels in spinal SBRT using a 6D couch. Methods: We retrospectively analyzed last 20 spinal SBRT patients (4 cervical, 9 thoracic, 7 lumbar/sacrum) treated in our clinic. These patients in customized immobilization device were treated in 1 or 3 fractions. Initial setup used ExacTrac and Brainlab 6D couch to align target within 1 mm and 1 degree, following by a cone beam CT (CBCT) for verification. Our current standard practice allows treating a maximum of three continuous vertebrae. Here we assess the possibility to achieve sub millimeter setup accuracy for more than three vertebrae by examining the residual error in every slice of CBCT. The CBCT had a range of 17.5 cm, which covered 5 to 9 continuous vertebrae depending on the patient and target location. In the study, CBCT from the 1st fraction treatment was rigidly registered with the planning CT in Pinnacle. The residual setup error of a vertebra was determined by expanding the vertebra contour on the planning CT to be large enough to enclose the corresponding vertebra on CBCT. The margin of the expansion was considered as setup error. Results: Out of the 20 patients analyzed, initial setup accuracy can be achieved within 1 mm for a span of 5 or more vertebrae starting from T2 vertebra to inferior vertebra levels. 2 cervical and 2 upper thoracic patients showed the cervical spine was difficult to achieve sub millimeter accuracy for multi levels without a customized immobilization headrest. Conclusion: If the curvature of spinal columns can be reproduced in customized immobilization device during treatment as simulation, multiple continuous vertebrae can be setup within 1 mm with the use of a 6D couch.

  6. 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.

  7. Iterative procedures for wave propagation in the frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seongjai [Rice Univ., Houston, TX (United States); Symes, W.W.

    1996-12-31

    A parallelizable two-grid iterative algorithm incorporating a domain decomposition (DD) method is considered for solving the Helmholtz problem. Since a numerical method requires choosing at least 6 to 8 grid points per wavelength, the coarse-grid problem itself is not an easy task for high frequency applications. We solve the coarse-grid problem using a nonoverlapping DD method. To accelerate the convergence of the iteration, an artificial damping technique and relaxation parameters are introduced. Automatic strategies for finding efficient parameters are discussed. Numerical results are presented to show the effectiveness of the method. It is numerically verified that the rate of convergence of the algorithm depends on the wave number sub-linearly and does not deteriorate as the mesh size decreases.

  8. Frequency modulated continuous wave lidar performance model for target detection

    Science.gov (United States)

    Du Bosq, Todd W.; Preece, Bradley L.

    2017-05-01

    The desire to provide the warfighter both ranging and reflected intensity information is increasing to meet expanding operational needs. LIDAR imaging systems can provide the user with intensity, range, and even velocity information of a scene. The ability to predict the performance of LIDAR systems is critical for the development of future designs without the need to conduct time consuming and costly field studies. Performance modeling of a frequency modulated continuous wave (FMCW) LIDAR system is challenging due to the addition of the chirped laser source and waveform mixing. The FMCW LIDAR model is implemented in the NV-IPM framework using the custom component generation tool. This paper presents an overview of the FMCW Lidar, the customized LIDAR components, and a series of trade studies using the LIDAR model.

  9. Binary pulsars as detectors of ultralow-frequency gravitational waves

    Science.gov (United States)

    Kopeikin, Sergei M.

    1997-10-01

    Fundamental limits on the energy density Ωg of the ultralow-frequency primordial gravitational wave background (GWB) radiation which can be obtained from the measurement of secular variations of orbital parameters of binary pulsars are explored. For analytical convenience we choose the simple timing model comprised of the binary system with a pulsar on a circular orbit and a remote observer on the Earth whose motion about the barycenter of the Solar System is assumed to be known with sufficient accuracy. The primordial gravitational waves bring about stochastic noise fluctuations in the times of arrival of the pulsar pulses which include (as our analysis shows) both nonstationary and stationary components. The latter part of the noise is supposed to have spectral power ~Ωg/f5, where f is the frequency of a gravitational wave intersecting or passing near the line of sight and Ωg is the energy density of the GWB radiation. An analytical technique of processing observational data in the time domain is worked out to determine the functional dependence of the pulsar timing residuals and variances of spin and orbital parameters of the binary pulsar with time. This technique enables us to prove that the procedure of fitting the pulsar's spin and orbital parameters acts not only as a low frequency filter of the background noise but also eliminates the nonstationary component of the noise so that the post-fit timing residuals contain only a stationary component. In order to keep the calculations manageable we idealize the observations by assuming that they are uniformly spaced and extend over an integral number of orbital revolutions N which is taken so large that any sum over all observation points can be approximated by an integral over the observing period T. The integrals one meets in calculations are divergent because of the existence of an algebraic singularity in the spectrum of the stochastic gravitational wave background as the frequency approaches the point f=0

  10. Effect of High-Frequency Sea Waves on Wave Period Retrieval from Radar Altimeter and Buoy Data

    Directory of Open Access Journals (Sweden)

    Xifeng Wang

    2016-09-01

    Full Text Available Wave periods estimated from satellite altimetry data behave differently from those calculated from buoy data, especially in low-wind conditions. In this paper, the geometric mean wave period T a is calculated from buoy data, rather than the commonly used zero-crossing wave period T z . The geometric mean wave period uses the fourth moment of the wave frequency spectrum and is related to the mean-square slope of the sea surface measured using altimeters. The values of T a obtained from buoys and altimeters agree well (root mean square difference: 0.2 s only when the contribution of high-frequency sea waves is estimated by a wavenumber spectral model to complement the buoy data, because a buoy cannot obtain data from waves having wavelengths that are shorter than the characteristic dimension of the buoy.

  11. Ground roll wave suppression based on wavelet frequency division and radial trace transform

    Science.gov (United States)

    Wang, Wan-Li; Yang, Wu-Yang; Wei, Xin-Jian; He, Xin

    2017-03-01

    Ground roll waves interfere with seismic data. The suppression of ground roll waves based on the division of wavelet frequencies considers the low-frequency characteristics of ground roll waves. However, this method will not be effective when the ground roll wave and the effective signal have the same frequency bands because of overlapping. The radial trace transform (RTT) considers the apparent velocity difference between the effective signal and the ground roll wave to suppress the latter, but affects the low-frequency components of the former. This study proposes a ground roll wave suppression method by combining the wavelet frequency division and the RTT based on the difference between the ground roll wave velocity and the effective signal and their energy difference in the wavelet domain, thus making full use of the advantages of both methods. First, we decompose the seismic data into different frequency bands through wavelet transform. Second, the RTT and low-cut filtering are applied to the low-frequency band, where the ground roll waves are appearing. Third, we reconstruct the seismic record without ground roll waves by using the inverse RTT and the remaining frequency bands. The proposed method not only improves the ground roll wave suppression, but also protects the signal integrity. The numerical simulation and real seismic data processing results suggest that the proposed method has a strong ability to denoise while preserving the amplitude.

  12. Semiannual Status Report. [excitation of electromagnetic waves in the whistler frequency range

    Science.gov (United States)

    1994-01-01

    During the last six months, we have continued our study of the excitation of electromagnetic waves in the whistler frequency range and the role that these waves will play in the acceleration of electrons and ions in the auroral region. A paper entitled 'Electron Beam Excitation of Upstream Waves in the Whistler Mode Frequency Range' was listed in the Journal of Geophysical Research. In this paper, we have shown that an anisotropic electron beam (or gyrating electron beam) is capable of generating both left-hand and right-hand polarized electromagnetic waves in the whistler frequency range. Since right-hand polarized electromagnetic waves can interact with background electrons and left-hand polarized waves can interact with background ions through cyclotron resonance, it is possible that these beam generated left-hand and right-hand polarized electromagnetic waves can accelerate either ions or electrons (or both), depending on the physical parameters under consideration. We are currently carrying out a comprehensive study of the electromagnetic whistler and lower hybrid like waves observed in the auroral zone using both wave and particle data. Our first task is to identify these wave modes and compare it with particle observations. Using both the DE-1 particle and wave measurements, we can positively identify those electromagnetics lower hybrid like waves as fast magnetosonic waves and the upper cutoff of these waves is the local lower hybrid frequency. From the upper cutoff of the frequency spectrum, one can infer the particle density and the result is in very good agreement with the particle data. Since these electromagnetic lower hybrid like waves can have frequencies extended down to the local ion cyclotron frequency, it practically confirms that they are not whistler waves.

  13. Passive Wireless Hydrogen Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the continued development of passive orthogonal frequency coded (OFC) surface acoustic wave (SAW) based hydrogen sensors for NASA application...

  14. Dual frequency MM-wave radar for antitank helicopter

    Science.gov (United States)

    Jehle, F. X.; Meinel, H.

    1986-07-01

    Helicopters are gaining increasing significance for air close support, airborne landing, tank unit interdiction and both helicopter and tank engagement missions. To support these mission phases, sensors are required for obstacle warning, navigation, and moving and fixed target indication for weapon designation. The majority of the present systems use optical and infrared sensors; some of them apply laser systems. These sensor systems are subject to considerable limitations with respect to their capability of penetrating bad weather zones, fog, and battlefield environment (dust, smoke, man-made fog etc.). The design concept of a dual-frequency radar operating in millimeter wave range which avoids these drawbacks and complements existing sensors is presented. It consists of a 60 GHz radar subsystem for obstacle warning including the detection of wires up to a range of approximately 500 m; due to the selection of a frequency in the absorption line of oxygen resulting in a high atmospheric attenuation (16 dB/km), the susceptibility to interception and thus also to interference electronic countermeasures can be maintained at a very low level. A 50 GHz radar subsystem (attenuation as low as 0.3 dB/km) with its range of approximately 5 km against targets of interest is used for navigation, fixed and moving target indication as well as weapon designation. Due to the combination of the two subsystems (50/60 GHz), high-value components (antenna, scanner, receiver assemblies, control and indicator units) can be used jointly for both subsystems, so that the special features of each subsystem become available at reasonable expenses.

  15. Effect of near-surface topography on high-frequency Rayleigh-wave propagation

    Science.gov (United States)

    Wang, Limin; Xu, Yixian; Xia, Jianghai; Luo, Yinhe

    2015-05-01

    Rayleigh waves, which are formed due to interference of P- and Sv-waves near the free surface, propagate along the free surface and vanish exponentially in the vertical direction. Their propagation is strongly influenced by surface topography. Due to the high resolution and precision requirements of near-surface investigations, the high-frequency Rayleigh waves are usually used for near-surface structural detecting. Although there are some numerical studies on high-frequency Rayleigh-wave propagation on topographic free surface, detailed analysis of characters of high-frequency Rayleigh-wave propagation on topographic free surface remains untouched. Hence, research of propagation of Rayleigh waves on complex topographic surface becomes critical for Rayleigh-wave methods in near-surface applications. To study the propagation of high-frequency Rayleigh waves on topographic free surface, two main topographic models are designed in this study. One of the models contains a depressed topographic surface, and another contains an uplifted topographic surface. We numerically simulate the propagation of high-frequency Rayleigh waves on these two topographic surfaces by finite-difference method. Soon afterwards, we analyze the propagation character of high-frequency Rayleigh waves on such topographic models, and compare the variations on its energy and frequency before and after passing the topographic region. At last, we discuss the relationship between the variations and topographical steepness of each model. Our numerical results indicate that influence of depressed topography for high-frequency Rayleigh waves is more distinct than influence of uplifted topography. Rayleigh waves produce new scattering body waves during passing the depressed topography with reduction of amplitude and loss of high-frequency components. Moreover, the steeper the depressed topography is, the more energy of Rayleigh waves is lost. The uplifted topography with gentle slope produces similar

  16. Diamond Heat-Spreader for Submillimeter-Wave Frequency Multipliers

    Science.gov (United States)

    Lin, Robert H.; Schlecht, Erich T.; Chattopadhyay, Goutam; Gill, John J.; Mehdi, Imran; Siegel, Peter H.; Ward, John S.; Lee, Choonsup; Thomas, Bertrand C.; Maestrini, Alain

    2010-01-01

    The planar GaAs Shottky diode frequency multiplier is a critical technology for the local oscillator (LO) for submillimeter- wave heterodyne receivers due to low mass, tenability, long lifetime, and room-temperature operation. The use of a W-band (75-100 GHz) power amplifier followed by a frequency multiplier is the most common for submillimeter-wave sources. Its greatest challenge is to provide enough input power to the LO for instruments onboard future planetary missions. Recently, JPL produced 800 mW at 92.5 GHz by combining four MMICs in parallel in a balanced configuration. As more power at W-band is available to the multipliers, their power-handling capability be comes more important. High operating temperatures can lead to degradation of conversion efficiency or catastrophic failure. The goal of this innovation is to reduce the thermal resistance by attaching diamond film as a heat-spreader on the backside of multipliers to improve their power-handling capability. Polycrystalline diamond is deposited by hot-filament chemical vapor deposition (CVD). This diamond film acts as a heat-spreader to both the existing 250- and 300-GHz triplers, and has a high thermal conductivity (1,000-1,200 W/mK). It is approximately 2.5 times greater than copper (401 W/mK) and 20 times greater than GaAs (46 W/mK). It is an electrical insulator (resistivity approx. equals 10(exp 15) Ohms-cm), and has a low relative dielectric constant of 5.7. Diamond heat-spreaders reduce by at least 200 C at 250 mW of input power, compared to the tripler without diamond, according to thermal simulation. This superior thermal management provides a 100-percent increase in power-handling capability. For example, with this innovation, 40-mW output power has been achieved from a 250-GHz tripler at 350-mW input power, while the previous triplers, without diamond, suffered catastrophic failures. This breakthrough provides a stepping-stone for frequency multipliers-based LO up to 3 THz. The future work

  17. Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, V. E.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2017-03-15

    Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron–ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.

  18. Tidally-modulated high frequency internal waves in Gautami-Godavari estuary, East coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, B.; Murty, T.V.R.; Sadhuram, Y.; Sarma, V.V.S.S.; Murty, V.S.N.; Prasad, K.V.S.R.

    of Internal waves (IWs) and to infer their generation mechanism Based on the stability criteria, two High Frequency (HF) significant modes in the Internal Wave (IW) field at frequencies 96.67 cph (10 m depth) and 71.15 cph (14 m depth) have been identified...

  19. Nonlinear-optical up and down frequency-converting backward-wave metasensors and metamirrors

    CERN Document Server

    Popov, Alexander K; Myslivets, Sergey A; Shalaev, Mikhail I; Slabko, Vitaly V

    2013-01-01

    A concept of a family of unique backward-wave photonic devices, such as frequency up and down converting nonlinear-optical mirrors, sensors, modulators, filters and amplifiers is proposed. Novel materials are considered, which support coexistence of ordinary and backward waves and thus enable enhanced nonlinear-optical frequency-conversion processes. Particular properties of short-pulse regime are investigated.

  20. The oblique behavior of low-frequency electromagnetic waves excited by newborn cometary ions

    Science.gov (United States)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1989-01-01

    The free energy in oxygen or hydrogen ions freshly created in the solar wind stimulates low-frequency electromagnetic waves whose growth does not always maximize at parallel propagation. Exploration of the wave vector plane discloses the frequent occurrence of islets of oblique growth unconnected to the unstable parallel modes. Contour plots of the growth rate, real frequency, polarization, and magnetic compression characterize the oblique wave behavior for large values of the initial pitch angle of the cometary particles. Although wave-particle (Landau and cyclotron) resonances feed most of the surveyed oblique instabilities, some are seemingly fluidlike. The results, obtained from the numerical solution of the kinetic dispersion and wave equations, imply that newborn ions can easily excite significant oblique hydromagnetic wave activity. Cometary environments provide the adopted plasma model, but the study is helpful in the interpretation of other low-frequency wave observations in space.

  1. Atmospheric and Fog Effects on Ultra-Wide Band Radar Operating at Extremely High Frequencies

    Directory of Open Access Journals (Sweden)

    Nezah Balal

    2016-05-01

    Full Text Available The wide band at extremely high frequencies (EHF above 30 GHz is applicable for high resolution directive radars, resolving the lack of free frequency bands within the lower part of the electromagnetic spectrum. Utilization of ultra-wideband signals in this EHF band is of interest, since it covers a relatively large spectrum, which is free of users, resulting in better resolution in both the longitudinal and transverse dimensions. Noting that frequencies in the millimeter band are subjected to high atmospheric attenuation and dispersion effects, a study of the degradation in the accuracy and resolution is presented. The fact that solid-state millimeter and sub-millimeter radiation sources are producing low power, the method of continuous-wave wideband frequency modulation becomes the natural technique for remote sensing and detection. Millimeter wave radars are used as complementary sensors for the detection of small radar cross-section objects under bad weather conditions, when small objects cannot be seen by optical cameras and infrared detectors. Theoretical analysis for the propagation of a wide “chirped” Frequency-Modulated Continuous-Wave (FMCW radar signal in a dielectric medium is presented. It is shown that the frequency-dependent (complex refractivity of the atmospheric medium causes distortions in the phase of the reflected signal, introducing noticeable errors in the longitudinal distance estimations, and at some frequencies may also degrade the resolution.

  2. Gram Schmidt Based Greedy Hybrid Precoding for Frequency Selective Millimeter Wave MIMO Systems

    OpenAIRE

    Alkhateeb, Ahmed; Heath Jr., Robert W.

    2016-01-01

    Hybrid analog/digital precoding allows millimeter wave MIMO systems to leverage large antenna array gains while permitting low cost and power consumption hardware. Most prior work has focused on hybrid precoding for narrow-band mmWave systems. MmWave systems, however, will likely operate on wideband channels with frequency selectivity. Therefore, this paper considers frequency selective hybrid precoding with RF beamforming vectors taken from a quantized codebook. For this system, a low-comple...

  3. Low-frequency dilatational wave propagation through unsaturated porous media containing two immiscible fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lo, W.-C.; Sposito, G.; Majer, E.

    2007-02-01

    An analytical theory is presented for the low-frequency behavior of dilatational waves propagating through a homogeneous elastic porous medium containing two immiscible fluids. The theory is based on the Berryman-Thigpen-Chin (BTC) model, in which capillary pressure effects are neglected. We show that the BTC model equations in the frequency domain can be transformed, at sufficiently low frequencies, into a dissipative wave equation (telegraph equation) and a propagating wave equation in the time domain. These partial differential equations describe two independent modes of dilatational wave motion that are analogous to the Biot fast and slow compressional waves in a single-fluid system. The equations can be solved analytically under a variety of initial and boundary conditions. The stipulation of 'low frequency' underlying the derivation of our equations in the time domain is shown to require that the excitation frequency of wave motions be much smaller than a critical frequency. This frequency is shown to be the inverse of an intrinsic time scale that depends on an effective kinematic shear viscosity of the interstitial fluids and the intrinsic permeability of the porous medium. Numerical calculations indicate that the critical frequency in both unconsolidated and consolidated materials containing water and a nonaqueous phase liquid ranges typically from kHz to MHz. Thus engineering problems involving the dynamic response of an unsaturated porous medium to low excitation frequencies (e.g. seismic wave stimulation) should be accurately modeled by our equations after suitable initial and boundary conditions are imposed.

  4. Electromagnetic cyclotron waves near the proton cyclotron frequency in the solar wind

    Science.gov (United States)

    Jian, Lan K.; Boardsen, Scott; Moya, Pablo; Stevens, Michael; Alexander, Robert; Vinas, Adolfo

    2015-04-01

    Strong narrow-band electromagnetic waves around the proton cyclotron frequency (fpc) have been found sporadically in the solar wind from 0.3 to 0.7 AU during MESSENGER spacecraft’s cruise phase. These waves are transverse and circularly polarized, and they propagate in directions quasi-parallel to the magnetic field. The wave power decreases quadratically with heliocentric distance, faster than the trend if assuming the conservation of Poynting flux for wave packets, suggesting there is energy dissipation from the waves, which could contribute to the heating and acceleration of solar wind plasma. Although the wave frequency is a few times of fpc in the spacecraft frame, it is a fraction of fpc in the solar wind plasma frame after removing the Doppler shift effect. In this frequency range, the waves can be left-hand (LH) polarized ion cyclotron waves or right-hand (RH) polarized magnetosonic waves. Because the waves are LH or RH polarized in the spacecraft frame with otherwise nearly identical characteristics, they could be due to Doppler shift of a same type of waves or a mixture of waves with intrinsically different polarizations. Through the assistance of audification, we have studied the long-lasting wave events in 2005 using high-cadence magnetic field data from the Wind mission. Statistically, in contrast with general solar wind, the protons at these waves are distributed closer to the proton instability thresholds, while the alpha particles at these waves are distributed further away from the alpha instability thresholds. For selected events of extensive waves, the ion distribution is analyzed in detail. A mixture of temperature anisotropies for core protons, beam protons, and alpha particles, as well as proton beam drift are often found in such events. We conduct linear wave dispersion analysis using these ion moments to examine whether these waves can be explained by the local generation of kinetic instabilities such as the LH ion cyclotron, the RH

  5. A Novel Multimode Waveguide Coupler for Accurate Power Measurement of Traveling Wave Tube Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2014-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.

  6. High-frequency waves in the corona due to null points

    Science.gov (United States)

    Santamaria, I. C.; Khomenko, E.; Collados, M.; de Vicente, A.

    2017-06-01

    This work aims to understand the behavior of non-linear waves in the vicinity of a coronal null point. In previous works we have shown that high-frequency waves are generated in such a magnetic configuration. This paper studies those waves in detail in order to provide a plausible explanation of their generation. We demonstrate that slow magneto-acoustic shock waves generated in the chromosphere propagate through the null point and produce a train of secondary shocks that escape along the field lines. A particular combination of the shock wave speeds generates waves at a frequency of 80 mHz. We speculate that this frequency may be sensitive to the atmospheric parameters in the corona and therefore can be used to probe the structure of this solar layer. Movies attached to Figs 2 and 4 are available at http://www.aanda.org

  7. Localization of Ultra-Low Frequency Waves in Multi-Ion Plasmas of the Planetary Magnetosphere

    Directory of Open Access Journals (Sweden)

    Eun-Hwa Kim

    2015-12-01

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

  8. Atomic-Scale Time and Space Resolution of Terahertz Frequency Acoustic Waves

    Science.gov (United States)

    Reed, Evan J.; Armstrong, Michael R.; Kim, Ki-Yong; Glownia, James H.

    2008-07-01

    Using molecular dynamics simulations and analytics, we find that strain waves of terahertz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering AlN/GaN heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time dependence of the strain wave with potentially subpicosecond, nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude terahertz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals.

  9. A Novel HBT Frequency Doubler Design for Millimeter-Wave Applications

    DEFF Research Database (Denmark)

    Johansen, Tom Keinicke; Krozer, Viktor; Vidkjær, Jens

    2006-01-01

    In this paper we presents a novel HBT frequency doubler design for millimeter-wave application. A HBT frequency doubler theory is described which leads to accurate design equations for optimal performance. The developed theory shows that an optimal HBT frequency doubler can be achieved using...

  10. The Importance of Pressure Sampling Frequency in Models for Determination of Critical Wave Loadingson Monolithic Structures

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Andersen, Thomas Lykke; Meinert, Palle

    2008-01-01

    This paper discusses the influence of wave load sampling frequency on calculated sliding distance in an overall stability analysis of a monolithic caisson. It is demonstrated by a specific example of caisson design that for this kind of analyses the sampling frequency in a small scale model could...... be as low as 100 Hz in model scale. However, for design of structure elements like the wave wall on the top of a caisson the wave load sampling frequency must be much higher, in the order of 1000 Hz in the model. Elastic-plastic deformations of foundation and structure were not included in the analysis....

  11. Intrauterine manipulation does not adversely influence the direction and frequency of endometrial waves.

    Science.gov (United States)

    van Gestel, Iris; Ijland, Marga M; Willekes, Christine; Evers, Johannes L H; Hoogland, Henk J

    2008-11-01

    To investigate whether intrauterine manipulation affects the direction or alters the frequency of endometrial wavelike activity. Prospective observational study. University hospital-based fertility clinic. Thirty-six patients undergoing intrauterine insemination (IUI). Ultrasound observation before and after IUI. Endometrial wave type and endometrial wave frequency before and after IUI. There was no difference in the direction and frequency of endometrial waves before and after IUI in 36 patients. Although the induction of uterine contractions by intrauterine manipulation has been suggested in the literature, the present study shows no contractions or induction of unfavorable (fundus to cervix) endometrial wavelike activity in 36 patients undergoing IUI.

  12. Frequency-dependent attenuation of seismic waves in the Pannonian basin

    Science.gov (United States)

    Süle, Bálint

    2017-04-01

    The attenuation of S waves have been estimated for the territory of Hungary (central Pannonian basin). Waveforms of 310 local eartquakes (0.8 < ML < 4.8) were analyzed. The events were recorded at hipocentral distances between 20 and 100 km. For estimating the frequency-dependent attenuation of S waves (OS) the coda normalization method was applied in the frequency range from 1.5 to 24 Hz. The results show strong attenuation of S waves along the ray paths. By fitting a power-law frequency dependence model the relation QS = 92 ṡ f0.93 is obtained.

  13. A current drive by using the fast wave in frequency range higher than two timeslower hybrid resonance frequency on tokamaks

    Directory of Open Access Journals (Sweden)

    Kim Sun Ho

    2017-01-01

    Full Text Available An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.

  14. Sub-millimeter T2 weighted fMRI at 7 T: comparison of 3D-GRASE and 2D SE-EPI.

    Science.gov (United States)

    Kemper, Valentin G; De Martino, Federico; Vu, An T; Poser, Benedikt A; Feinberg, David A; Goebel, Rainer; Yacoub, Essa

    2015-01-01

    Functional magnetic resonance imaging (fMRI) allows studying human brain function non-invasively up to the spatial resolution of cortical columns and layers. Most fMRI acquisitions rely on the blood oxygenation level dependent (BOLD) contrast employing T(*) 2 weighted 2D multi-slice echo-planar imaging (EPI). At ultra-high magnetic field (i.e., 7 T and above), it has been shown experimentally and by simulation, that T2 weighted acquisitions yield a signal that is spatially more specific to the site of neuronal activity at the cost of functional sensitivity. This study compared two T2 weighted imaging sequences, inner-volume 3D Gradient-and-Spin-Echo (3D-GRASE) and 2D Spin-Echo EPI (SE-EPI), with evaluation of their imaging point-spread function (PSF), functional specificity, and functional sensitivity at sub-millimeter resolution. Simulations and measurements of the imaging PSF revealed that the strongest anisotropic blurring in 3D-GRASE (along the second phase-encoding direction) was about 60% higher than the strongest anisotropic blurring in 2D SE-EPI (along the phase-encoding direction). In a visual paradigm, the BOLD sensitivity of 3D-GRASE was found to be superior due to its higher temporal signal-to-noise ratio (tSNR). High resolution cortical depth profiles suggested that the contrast mechanisms are similar between the two sequences, however, 2D SE-EPI had a higher surface bias owing to the higher T(*) 2 contribution of the longer in-plane EPI echo-train for full field of view compared to the reduced field of view of zoomed 3D-GRASE.

  15. Low frequency electromagnetic radiation from gravitational waves generated by neutron stars

    Science.gov (United States)

    Jones, Preston; Gretarsson, Andri; Singleton, Douglas

    2017-12-01

    We investigate the possibility of observing very low frequency (VLF) electromagnetic radiation produced from the vacuum by gravitational waves. We review the calculations leading to the possibility of vacuum conversion of gravitational waves into electromagnetic waves and show how this process evades the well-known prohibition against particle production from gravitational waves. Using Newman-Penrose scalars, we estimate the luminosity of this proposed electromagnetic counterpart radiation coming from gravitational waves produced by neutron star oscillations. The detection of electromagnetic counterpart radiation would provide an indirect way of observing gravitational radiation with future spacecraft missions, especially lunar orbiting probes.

  16. Parametric interaction of optical waves in metamaterials under low-frequency pumping

    Science.gov (United States)

    Kasumova, R. J.; Amirov, Sh Sh; Shamilova, Sh A.

    2017-07-01

    The influence of phase effects under three-wave parametric interaction and low-frequency pumping in metamaterials is studied in the case of a negative refractive index at a signal-wave frequency. It is found that the efficiency of the backward signalwave amplification is the higher, the greater the ratio of the intensities of the idler and signal waves at the input to the metamaterial. An increase in the idler wave intensity at the input by five times, as compared to the signal-wave intensity, leads to a nonlinear increase in the signal-wave amplification by almost 20 times. According to the analytic expressions obtained in the constant-intensity approximation, the choice of the optimal parameters for the pump intensity, total length of the metamaterial and phase detuning will facilitate the implementation of regimes of effective amplification and generation of the signal wave. A comparison is made with the results obtained in the constant-field approximation, and a numerical estimate of the expected efficiency of the frequency conversion is presented. Control of frequency and pump power is shown to make possible the smooth tuning of the parametric converter frequency. The developed method can be used to design frequency converters based on nonlinear metamaterials.

  17. A causal and fractional all-frequency wave equation for lossy media.

    Science.gov (United States)

    Holm, Sverre; Näsholm, Sven Peter

    2011-10-01

    This work presents a lossy partial differential acoustic wave equation including fractional derivative terms. It is derived from first principles of physics (mass and momentum conservation) and an equation of state given by the fractional Zener stress-strain constitutive relation. For a derivative order α in the fractional Zener relation, the resulting absorption α(k) obeys frequency power-laws as α(k) ∝ ω(1+α) in a low-frequency regime, α(k) ∝ ω(1-α/2) in an intermediate-frequency regime, and α(k) ∝ ω(1-α) in a high-frequency regime. The value α=1 corresponds to the case of a single relaxation process. The wave equation is causal for all frequencies. In addition the sound speed does not diverge as the frequency approaches infinity. This is an improvement over a previously published wave equation building on the fractional Kelvin-Voigt constitutive relation. © 2011 Acoustical Society of America

  18. Test the mergers of the primordial black holes by high frequency gravitational-wave detector

    Science.gov (United States)

    Li, Xin; Wang, Li-Li; Li, Jin

    2017-09-01

    The black hole could have a primordial origin if its mass is less than 1M_⊙. The mergers of these black hole binaries generate stochastic gravitational-wave background (SGWB). We investigate the SGWB in high frequency band 108-10^{10} Hz. It can be detected by high frequency gravitational-wave detector. Energy density spectrum and amplitude of the SGWB are derived. The upper limit of the energy density spectrum is around 10^{-7}. Also, the upper limit of the amplitude ranges from 10^{-31.5} to 10^{-29.5}. The fluctuation of spacetime origin from gravitational wave could give a fluctuation of the background electromagnetic field in a high frequency gravitational-wave detector. The signal photon flux generated by the SGWB in the high frequency band 108-10^{10} Hz is derived, which ranges from 1 to 10^2 s^{-1}. The comparison between the signal photon flux generated by relic gravitational waves (RGWs) and the SGWB is also discussed in this paper. It is shown that the signal photon flux generated by the RGW, which is predicted by the canonical single-field slow-roll inflation models, is sufficiently lower than the one generated by the SGWB in the high frequency band 108-10^{10} Hz. Our results indicate that the SGWB in the high frequency band 108-10^{10} Hz is more likely to be detected by the high frequency gravitational-wave detector.

  19. Testing General Relativity with Low-Frequency, Space-Based Gravitational-Wave Detectors.

    Science.gov (United States)

    Gair, Jonathan R; Vallisneri, Michele; Larson, Shane L; Baker, John G

    2013-01-01

    We review the tests of general relativity that will become possible with space-based gravitational-wave detectors operating in the ∼ 10-5 - 1 Hz low-frequency band. The fundamental aspects of gravitation that can be tested include the presence of additional gravitational fields other than the metric; the number and tensorial nature of gravitational-wave polarization states; the velocity of propagation of gravitational waves; the binding energy and gravitational-wave radiation of binaries, and therefore the time evolution of binary inspirals; the strength and shape of the waves emitted from binary mergers and ringdowns; the true nature of astrophysical black holes; and much more. The strength of this science alone calls for the swift implementation of a space-based detector; the remarkable richness of astrophysics, astronomy, and cosmology in the low-frequency gravitational-wave band make the case even stronger.

  20. Testing General Relativity with Low-Frequency, Space-Based Gravitational-Wave Detectors

    Directory of Open Access Journals (Sweden)

    John G. Baker

    2013-09-01

    Full Text Available We review the tests of general relativity that will become possible with space-based gravitational-wave detectors operating in the ∼ 10^{-5} – 1 Hz low-frequency band. The fundamental aspects of gravitation that can be tested include the presence of additional gravitational fields other than the metric; the number and tensorial nature of gravitational-wave polarization states; the velocity of propagation of gravitational waves; the binding energy and gravitational-wave radiation of binaries, and therefore the time evolution of binary inspirals; the strength and shape of the waves emitted from binary mergers and ringdowns; the true nature of astrophysical black holes; and much more. The strength of this science alone calls for the swift implementation of a space-based detector; the remarkable richness of astrophysics, astronomy, and cosmology in the low-frequency gravitational-wave band make the case even stronger.

  1. Low-Frequency Electrostatic Ion Surface Waves in Magnetized Electron-Positron Plasmas

    Science.gov (United States)

    Cho, Sang-Hoon; Lee, Hee J.

    The dispersion relations of a surface ion wave propagating on the interface between a warm electron-positron plasma and vacuum when a static magnetic field is directed either normal to the interface (x-wave) or parallel to the wave vector (z-wave) are solved analytically, and the influence of the magnetic field on the ion surface wave is investigated in detail using some numerical work. It is shown that ion surface waves do not exist if the magnetic field is large enough to make the ion gyrofrequency greater than the ion plasma frequency. The attenuation constant of x-waves is more attenuated than that of z-waves and the x-wave is more attenuated as the parameter normalized ion gyrofrequency ζ increases toward 1, but this tendency is reversed for the z-wave. The z-wave does not exist for k2λD2< (ζ/(1-ζ))(p + 1) while the x-wave exists over the whole range of k, where the fractional number p is the ratio between the unperturbed positron and the electron number density. Additionally, we compare the ion surface wave properties of electron-positron plasma with conventional electron-ion plasma.

  2. Time-domain analysis of frequency dependent inertial wave forces on cylinders

    DEFF Research Database (Denmark)

    Krenk, Steen

    2013-01-01

    Mono-pile structures are attractive for small well-head platforms and foundation of offshore wind turbines at moderate water depth. Their diameter of several meters makes them prone to simultaneous occurrence of frequency-dependent inertial forces and non-linear drag. The present paper presents a...... a simple time-domain procedure for the inertial force, in which the frequency dependence is represented via a simple explicit time filter on the wave particle acceleration or velocity. The frequency dependence of the inertia coefficient is known analytically as a function of the wave......-number, and the relevant range of waves shorter than about six times the diameter typically corresponds to deep water waves. This permits a universal non-dimensional frequency representation, that is converted to rational form to provide the relevant filter equation. Simple time-domain simulations demonstrate...

  3. Multipath propagation of low‐frequency radio waves inferred from high‐resolution array analysis

    National Research Council Canada - National Science Library

    Füllekrug, Martin; Smith, Nathan; Mezentsev, Andrew; Watson, Robert; Astin, Ivan; Gaffet, Stéphane; Evans, Adrian; Rycroft, Michael

    2015-01-01

    .... Here we report a thorough high‐resolution analysis of radio waves from low‐frequency (∼20–150 kHz) radio communication transmitters which are recorded with a small aperture array of radio receivers during the day...

  4. Flute mode waves near the lower hybrid frequency excited by ion rings in velocity space

    Science.gov (United States)

    Cattell, C.; Hudson, M.

    1982-01-01

    Discrete emissions at the lower hybrid frequency are often seen on the S3-3 satellite. Simultaneous observation of perpendicularly heated ions suggests that these ions may provide the free energy necessary to drive the instability. Studies of the dispersion relation for flute modes excited by warm ion rings in velocity space show that waves are excited with real frequencies near the lower hybrid frequency and with growth rates ranging from about 0.01 to 1 times the ion cyclotron frequency. Numerical results are therefore consistent with the possibility that the observed ions are the free energy source for the observed waves.

  5. Whistler Mode Waves Below Lower Hybrid Resonance Frequency: Generation and Spectral Features

    Science.gov (United States)

    Shklyar, D. R.; Balikhin, M. A.

    2017-10-01

    Equatorial noise in the frequency range below the lower hybrid resonance frequency, whose structure is shaped by high proton cyclotron harmonics, has been observed by the Cluster spacecraft. We develop a model of this wave phenomenon which assumes (as, in general, has been suggested long ago) that the observed spectrum is excited due to loss cone instability of energetic ions in the equatorial region of the magnetosphere. The wavefield is represented as a sum of constant frequency wave packets which cross a number of cyclotron resonances while propagating in a highly oblique mode along quite specific trajectories. The growth (damping) rate of these wave packets varies both in sign and magnitude along the raypath, making the wave net amplification, but not the growth rate, the main characteristic of the wave generation process. The growth rates and the wave amplitudes along the ray paths, determined by the equations of geometrical optics, have been calculated for a 3-D set of wave packets with various frequencies, initial L shells, and initial wave normal angles at the equator. It is shown that the dynamical spectrum resulting from the proposed model qualitatively matches observations.

  6. Electromagnetic Waves with Frequencies Near the Local Proton Gryofrequency: ISEF-3 1 AU Observations

    Science.gov (United States)

    Tsurutani, B.

    1993-01-01

    Low Frequency electromagnetic waves with periods near the local proton gyrofrequency have been detected near 1 AU by the magnetometer onboard ISEE-3. For these 1 AU waves two physical processes are possible: solar wind pickup of nuetral (interstellar?) particles and generation by relativistic electron beams propagating from the Sun.

  7. Frequency Invariant Uniform Circular Array for Wideband mm-Wave Channel Characterization

    DEFF Research Database (Denmark)

    Zhang, Fengchun; Fan, Wei; Pedersen, Gert F.

    2016-01-01

    A new approach for designing frequency invariant (FI) uniform circular array (UCA) is proposed, and its application to wideband multipath estimation at millimeter wave bands is studied. Both numerical simulations and channel sounding results at mm-Wave bands are provided to demonstrate...

  8. Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons

    OpenAIRE

    Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zong, Q.-G.; Zhou, X.-Z.; Zheng, Huinan; Wang, Yuming; Wang, Shui; Hao, Y.-X.; Gao, Zhonglei; He, Zhaoguo; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Blake, J. B.

    2015-01-01

    Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance ha...

  9. A new mechanism for THz-frequency radiation generation: Nonlinear strain waves in piezoelectrics

    Science.gov (United States)

    Reed, Evan; Armstrong, Michael

    2007-03-01

    Using molecular dynamics simulations and analytics, we show that extremely large strain amplitude THz frequency acoustic waves can spontaneously form in crystalline GaN at the front of a shock wave and generate THz frequency radiation at an interface with AlN or another piezoelectric material. This new mechanism for the generation of THz radiation can be realized using a table-top ultrafast laser and has fundamentally different limiting properties than existing nonlinear optical ultrafast techniques for THz generation.

  10. Quantum-state-preserving Frequency Conversion Using Four-wave Mixing

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Reddy, Dileep V.; McKinstrie, Colin J.

    2013-01-01

    We investigate the applicability of temporal multiplexing using four-wave mixing Bragg scattering for quantum frequency conversion. Various pump shapes are considered and we find that a large selectivity is possible for all the pump shapes.......We investigate the applicability of temporal multiplexing using four-wave mixing Bragg scattering for quantum frequency conversion. Various pump shapes are considered and we find that a large selectivity is possible for all the pump shapes....

  11. Phase-frequency calibration of a sine wave oscillator using ...

    African Journals Online (AJOL)

    A method of measuring phase changes within the positive feedback loop of a sine wave oscillator without terminating the oscillations is presented. This involves the use of a reference network, outside the loop, which is an exact replica of the positive feedback network of the oscillator. Such phase changes produce new ...

  12. Rayleigh Wave Velocity Measurements Using Broad Band Frequency Sources.

    Science.gov (United States)

    1981-07-01

    Heukelom 4I and Foster 1960, Chang and Ballard 1973, Ballard and McLean 1975). The procedure for measuring the Rayleigh wave velocity has consisted... Heukelom , W., and Foster, C. R. 1960. "Dynamic Testing of Pavements," Journal, Soil Mechanics and Foundations Division, American Society of Civil Engineers

  13. Non-linear high-frequency waves in the magnetosphere

    Indian Academy of Sciences (India)

    electric field. Keywords. Magnetosphere; bipolar; sawtooth wave-forms. PACS Nos 52.35.Mw; 52.35.Qz; 90.30.Tz. 1. Introduction. Recent observations by the GEOTAIL [1], POLAR [2] and FAST [3] spacecrafts have in- dicated the presence of broadband electrostatic noise (BEN) in the Earth's magnetosphere. Several ...

  14. On the role of high frequency waves in ocean altimetry

    Science.gov (United States)

    Vandemark, Douglas C.

    This work mines a coastal and open ocean air-sea interaction field experiment data set where the goals are to refine satellite retrieval of wind, wind stress, and sea level using a microwave radar altimeter. The data were collected from a low-flying aircraft using a sensor suite designed to measure the surface waves, radar backscatter, the atmospheric flow, and turbulent fluxes within the marine boundary layer. This uncommon ensemble provides the means to address several specific altimeter-related topics. First, we examine and document the impact that non wind-driven gravity wave variability, e.g. swell, has upon the commonly-invoked direct relationship between altimeter backscatter and near surface wind speed. The demonstrated impact is larger in magnitude and more direct than previously suggested. The study also isolates the wind-dependence of short-scale slope variance and suggests its magnitude is somewhat lower than shown elsewhere while a second-order dependence on long waves is also evident. A second study assesses the hypothesis that wind-aligned swell interacts with the atmospheric boundary flow leading to a depressed level of turbulence. Cases of reduced drag coefficient at moderate wind speeds were in evidence within the data set, and buoy observations indicate that swell was present and a likely control during these events. Coincidentally, short-scale wave roughness was also depressed suggesting decreased wind stress. Attempts to confirm the theory failed, however, due to numerous limitations in the quantity and quality of the data in hand. A lesson learned is that decoupling atmospheric stability and wave impacts in field campaigns requires both a very large amount of data as well as vertical resolution of fluxes within the first 10--20 m of the surface.

  15. A first approach to model the low-frequency wave activity in the plasmasphere

    Directory of Open Access Journals (Sweden)

    R. André

    Full Text Available A comprehensive empirical model of waves is developed in the objective to simulate wave-particle interactions involved in the loss and acceleration of radiation belt electrons. Three years of measured magnetic wave field components from the Plasma Wave Instrument on board the DE-1 satellite are used to model the amplitude spectral density of the magnetic wave field of each type of emission observed in the equatorial regions of the plasmasphere: VLF transmitter emissions, chorus emissions, plasmaspheric hiss emissions and equatorial emissions below ~ 200 Hz. Each model is a function of the wave frequency f , the MLT, L and Mlat parameters, and the Kp values. The performances of the plasmaspheric hiss and chorus models are tested on amplitude spectra recorded on board the OGO-5 and GEOS-1 satellites.

    Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities; instruments and techniques

  16. A first approach to model the low-frequency wave activity in the plasmasphere

    Directory of Open Access Journals (Sweden)

    R. André

    2002-07-01

    Full Text Available A comprehensive empirical model of waves is developed in the objective to simulate wave-particle interactions involved in the loss and acceleration of radiation belt electrons. Three years of measured magnetic wave field components from the Plasma Wave Instrument on board the DE-1 satellite are used to model the amplitude spectral density of the magnetic wave field of each type of emission observed in the equatorial regions of the plasmasphere: VLF transmitter emissions, chorus emissions, plasmaspheric hiss emissions and equatorial emissions below ~ 200 Hz. Each model is a function of the wave frequency f , the MLT, L and Mlat parameters, and the Kp values. The performances of the plasmaspheric hiss and chorus models are tested on amplitude spectra recorded on board the OGO-5 and GEOS-1 satellites.Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities; instruments and techniques

  17. A statistical survey of ultralow-frequency wave power and polarization in the Hermean magnetosphere.

    Science.gov (United States)

    James, Matthew K; Bunce, Emma J; Yeoman, Timothy K; Imber, Suzanne M; Korth, Haje

    2016-09-01

    We present a statistical survey of ultralow-frequency wave activity within the Hermean magnetosphere using the entire MErcury Surface, Space ENvironment, GEochemistry, and Ranging magnetometer data set. This study is focused upon wave activity with frequencies Wave activity is mapped to the magnetic equatorial plane of the magnetosphere and to magnetic latitude and local times on Mercury using the KT14 magnetic field model. Wave power mapped to the planetary surface indicates the average location of the polar cap boundary. Compressional wave power is dominant throughout most of the magnetosphere, while azimuthal wave power close to the dayside magnetopause provides evidence that interactions between the magnetosheath and the magnetopause such as the Kelvin-Helmholtz instability may be driving wave activity. Further evidence of this is found in the average wave polarization: left-handed polarized waves dominate the dawnside magnetosphere, while right-handed polarized waves dominate the duskside. A possible field line resonance event is also presented, where a time-of-flight calculation is used to provide an estimated local plasma mass density of ∼240 amu cm-3.

  18. Using ultra-low frequency waves and their characteristics to diagnose key physics of substorm onset

    Science.gov (United States)

    Rae, I. J.; Murphy, K. R.; Watt, Clare E. J.; Mann, Ian R.; Yao, Zhonghua; Kalmoni, Nadine M. E.; Forsyth, Colin; Milling, David K.

    2017-12-01

    Substorm onset is marked in the ionosphere by the sudden brightening of an existing auroral arc or the creation of a new auroral arc. Also present is the formation of auroral beads, proposed to play a key role in the detonation of the substorm, as well as the development of the large-scale substorm current wedge (SCW), invoked to carry the current diversion. Both these phenomena, auroral beads and the SCW, have been intimately related to ultra-low frequency (ULF) waves of specific frequencies as observed by ground-based magnetometers. We present a case study of the absolute and relative timing of Pi1 and Pi2 ULF wave bands with regard to a small substorm expansion phase onset. We find that there is both a location and frequency dependence for the onset of ULF waves. A clear epicentre is observed in specific wave frequencies concurrent with the brightening of the substorm onset arc and the presence of "auroral beads". At higher and lower wave frequencies, different epicentre patterns are revealed, which we conclude demonstrate different characteristics of the onset process; at higher frequencies, this epicentre may demonstrate phase mixing, and at intermediate and lower frequencies these epicentres are characteristic of auroral beads and cold plasma approximation of the "Tamao travel time" from near-earth neutral line reconnection and formation of the SCW.

  19. Effects of anisotropy on the frequency spectrum of gravity waves observed by MST radar

    Science.gov (United States)

    Liu, C. H.

    1986-01-01

    In the investigation of gravity waves using mesosphere-stratosphere-troposphere radar data, model gravity-wave spectra have been used. In these model spectra, one usually assumes azimuthal symmetry. The effect of spectral anisotropy on the observed spectrum is studied here. It is shown that for a general Garrett-Munk-type spectrum, the anisotropy does not affect the frequency spectrum observed by the vertically beamed radar. For the oblique beam, however, the observed frequency spectrum is changed. A general gravity wave spectrum including azimuthal anisotropy is considered.

  20. Mid-frequency sound propagation through internal waves at short range with synoptic oceanographic observations.

    Science.gov (United States)

    Rouseff, Daniel; Tang, Dajun; Williams, Kevin L; Wang, Zhongkang; Moum, James N

    2008-09-01

    Preliminary results are presented from an analysis of mid-frequency acoustic transmission data collected at range 550 m during the Shallow Water 2006 Experiment. The acoustic data were collected on a vertical array immediately before, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave's position as a function of time is developed. Experimental results show a new acoustic path is generated as the internal wave passes above the acoustic source.

  1. Photon wave function formalism for analysis of Mach–Zehnder interferometer and sum-frequency generation

    Energy Technology Data Exchange (ETDEWEB)

    Ritboon, Atirach, E-mail: atirach.3.14@gmail.com [School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom); Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai 90112 (Thailand); Daengngam, Chalongrat, E-mail: chalongrat.d@psu.ac.th [Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai 90112 (Thailand); Pengpan, Teparksorn, E-mail: teparksorn.p@psu.ac.th [Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai 90112 (Thailand)

    2016-08-15

    Biakynicki-Birula introduced a photon wave function similar to the matter wave function that satisfies the Schrödinger equation. Its second quantization form can be applied to investigate nonlinear optics at nearly full quantum level. In this paper, we applied the photon wave function formalism to analyze both linear optical processes in the well-known Mach–Zehnder interferometer and nonlinear optical processes for sum-frequency generation in dispersive and lossless medium. Results by photon wave function formalism agree with the well-established Maxwell treatments and existing experimental verifications.

  2. Gravitational lens models based on submillimeter array imaging of Herschel -selected strongly lensed sub-millimeter galaxies at z > 1.5

    Energy Technology Data Exchange (ETDEWEB)

    Bussmann, R. S.; Gurwell, M. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Pérez-Fournon, I. [Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Amber, S. [Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA (United Kingdom); Calanog, J.; De Bernardis, F.; Wardlow, J. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Dannerbauer, H. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Université Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); Fu, Hai [Department of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242 (United States); Harris, A. I. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Krips, M. [Institut de RadioAstronomie Millimétrique, 300 Rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d' Hères (France); Lapi, A. [Department Fisica, Univ. Tor Vergata, Via Ricerca Scientifica 1, 00133 Rome, Italy and SISSA, Via Bonomea 265, 34136 Trieste (Italy); Maiolino, R. [Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Ave., Cambridge CB3 OHE (United Kingdom); Omont, A. [Institut d' Astrophysique de Paris, UMR 7095, CNRS, UPMC Univ. Paris 06, 98bis boulevard Arago, F-75014 Paris (France); Riechers, D. [Department of Astronomy, Space Science Building, Cornell University, Ithaca, NY 14853-6801 (United States); Baker, A. J. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States); Birkinshaw, M. [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Bock, J. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); and others

    2013-12-10

    Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S {sub 500} > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r {sub half}) and far-infrared luminosities (L {sub FIR}) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z {sub lens} > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L {sub FIR} (median L {sub FIR} = 7.9 × 10{sup 12} L {sub ☉}) and two decades in FIR luminosity surface density (median Σ{sub FIR} = 6.0 × 10{sup 11} L {sub ☉} kpc{sup –2}). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.

  3. Low-frequency electromagnetic waves driven by gyrotropic gyrating ion beams

    Science.gov (United States)

    Sharma, O. P.; Patel, V. L.

    1986-01-01

    The origin of left- and right-hand-polarized low-frequency waves in space plasmas is analyzed. It has been shown that a gyrotropic gyrating ion beam, a ring in velocity space, can excite electromagnetic modes in the plasma near the beam gyrofrequency. It excites left-hand-polarized shear Alfven waves and their harmonics via the coupling of Alfven modes with the beam modes. It can also excite right-hand-polarized fast-mode magnetosonic waves and their harmonics as well. The excitation is possible for beam ions heavier than the plasma ions. The growth rate varies as one-third power of the beam density and decreases with the angle of wave propagation with respect to the ambient magnetic field. The nonlocality has a stabilizing effect on the instability. The predicted values of the wave frequencies compare reasonably well with those observed in satellite data.

  4. The Characteristics of Frequency Spectrum of Radiated Electromagnetic Waves with AC Discharge Progress in Liquid Nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Park, K.S.; Yoon, D.H.; Lee, S.H.; Kim, K.C.; Lee, K.S. [Yeungnam University, Gyeongsan (Korea); Lee, H.D. [LG Industrial Systems Co., Ltd., Cheongju (Korea); Kim, C.M. [Kyungwoon University, Kumi (Korea); Choi, B.J. [Sorabol College, Gyeongju (Korea)

    2003-03-01

    In this paper, a relationship between AC discharge progress and the radiated electromagnetic waves was investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The frequency spectrum of the radiated electromagnetic waves were measured at the atmospheric pressure in liquid nitrogen(LN{sub 2}) during partial discharges progressed by AC high voltage in nonuniform electric field. From the results of this study, a new method was introduced for measurement and analysis of the radiated electromagnetic waves with discharge progress in LN{sub 2}. Besides, according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting partial discharge and estimating discharge progress could be possible. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of electric insulations about superconducting and cryogenic power equipments. (author). 14 refs., 7 figs.

  5. Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons.

    Science.gov (United States)

    Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zong, Q-G; Zhou, X-Z; Zheng, Huinan; Wang, Yuming; Wang, Shui; Hao, Y-X; Gao, Zhonglei; He, Zhaoguo; Baker, D N; Spence, H E; Reeves, G D; Blake, J B; Wygant, J R

    2015-12-22

    Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance has not yet been determined definitively. Here we report a unique radiation belt event with intense ULF waves but no detectable VLF chorus waves. Our results demonstrate that the ULF waves moved the inner edge of the outer radiation belt earthward 0.3 Earth radii and enhanced the relativistic electron fluxes by up to one order of magnitude near the slot region within about 10 h, providing strong evidence for the radial diffusion of radiation belt relativistic electrons.

  6. Simultaneous multi-band channel sounding at mm-Wave frequencies

    DEFF Research Database (Denmark)

    Müller, Robert; Häfner, Stephan; Dupleich, Diego

    2016-01-01

    and verification of those novel technologies required an understanding of the propagation effects at mm-Wave which enabled by channel sounding measurements and analysis. Due to the variety of considered frequency bands and the necessity of spatial resolved measurements for e.g. testing of beamforming approaches......The vision of multi Gbit/s data rates in future mobile networks requires the change to millimeter wave (mm-Wave) frequencies for increasing bandwidth. As a consequence, new technologies have to be deployed to tackle the drawbacks of higher frequency bands, e.g. increased path loss. Development......, which comprises the microwave band at 10 GHz and the mm-Wave band at 30 GHz. Preliminary analysis results are presented....

  7. Time-frequency analysis of spike-wave discharges using a modified wavelet transform

    NARCIS (Netherlands)

    Bosnyakova, D.Y.; Gabova, A.V.; Kuznetsova, G.D.; Obukhov, Y.; Midzyanovskaya, I.S.; Salonin, D.V.; Rijn, C.M. van; Coenen, A.M.L.; Tuomisto, L.M.; Luijtelaar, E.L.J.M. van

    2006-01-01

    The continuous Morlet wavelet transform was used for the analysis of the time-frequency pattern of spike-wave discharges (SWD) as can be recorded in a genetic animal model of absence epilepsy (rats of the WAG/Rij strain). We developed a new wavelet transform that allows to obtain the time-frequency

  8. One hertz seismic attenuation for low frequency gravitational waves interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Mantovani, Maddalena [Universita di Siena Via Roma 56-53100 Siena (Italy)]. E-mail: mantovan@ego-gw.it; DeSalvo, Riccardo [California Institute of Technology 18-34, Pasadena, CA 91125 (United States)

    2005-12-01

    This article describes a mechanical vertical attenuation system capable to provide large attenuation factors above 1Hz. This system is derived from, and improves, the passive Geometric Anti-Spring seismic attenuation filters minimizing their vertical resonant frequency by means of a tunable electromagnetic spring mounted in parallel with the main spring. The tunable spring is also used to compensate thermal drift in the new arrangement. We found an unexplained deviation from the 1/f{sup 2} transfer function at resonant frequencies below {approx}100mHz.

  9. Quantum-limited detection of millimeter waves using superconducting tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Mears, C.A.

    1991-09-01

    The quasiparticle tunneling current in a superconductor-insulator- superconductor (SIS) tunnel junction is highly nonlinear. Such a nonlinearity can be used to mix two millimeter wave signals to produce a signal at a much lower intermediate frequency. We have constructed several millimeter and sub-millimeter wave SIS mixers in order to study high frequency response of the quasiparticle tunneling current and the physics of high frequency mixing. We have made the first measurement of the out-of-phase tunneling currents in an SIS tunnel junction. We have developed a method that allows us to determine the parameters of the high frequency embedding circuit by studying the details of the pumped I-V curve. We have constructed a 80--110 GHz waveguide-based mixer test apparatus that allows us to accurately measure the gain and added noise of the SIS mixer under test. Using extremely high quality tunnel junctions, we have measured an added mixer noise of 0.61 {plus minus} 0.36 quanta, which is within 25 percent of the quantum limit imposed by the Heisenberg uncertainty principle. This measured performance is in excellent agreement with that predicted by Tucker's theory of quantum mixing. We have also studied quasioptically coupled millimeter- and submillimeter-wave mixers using several types of integrated tuning elements. 83 refs.

  10. Quantum-limited detection of millimeter waves using superconducting tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Mears, Carl Atherton [Univ. of California, Berkeley, CA (United States)

    1991-09-01

    The quasiparticle tunneling current in a superconductor-insulator- superconductor (SIS) tunnel junction is highly nonlinear. Such a nonlinearity can be used to mix two millimeter wave signals to produce a signal at a much lower intermediate frequency. We have constructed several millimeter and sub-millimeter wave SIS mixers in order to study high frequency response of the quasiparticle tunneling current and the physics of high frequency mixing. We have made the first measurement of the out-of-phase tunneling currents in an SIS tunnel junction. We have developed a method that allows us to determine the parameters of the high frequency embedding circuit by studying the details of the pumped I-V curve. We have constructed a 80--110 GHz waveguide-based mixer test apparatus that allows us to accurately measure the gain and added noise of the SIS mixer under test. Using extremely high quality tunnel junctions, we have measured an added mixer noise of 0.61 ± 0.36 quanta, which is within 25 percent of the quantum limit imposed by the Heisenberg uncertainty principle. This measured performance is in excellent agreement with that predicted by Tucker`s theory of quantum mixing. We have also studied quasioptically coupled millimeter- and submillimeter-wave mixers using several types of integrated tuning elements. 83 refs.

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

    Science.gov (United States)

    Ivry, Yachin; Wang, Nan; Durkan, Colm

    2014-03-01

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

  12. Finite-frequency sensitivity kernels of seismic waves to fault zone structures

    Science.gov (United States)

    Allam, A. A.; Tape, C.; Ben-Zion, Y.

    2015-12-01

    We analyse the volumetric sensitivity of fault zone seismic head and trapped waves by constructing finite-frequency sensitivity (Fréchet) kernels for these phases using a suite of idealized and tomographically derived velocity models of fault zones. We first validate numerical calculations by waveform comparisons with analytical results for two simple fault zone models: a vertical bimaterial interface separating two solids of differing elastic properties, and a `vertical sandwich' with a vertical low velocity zone surrounded on both sides by higher velocity media. Establishing numerical accuracy up to 12 Hz, we compute sensitivity kernels for various phases that arise in these and more realistic models. In contrast to direct P body waves, which have little or no sensitivity to the internal fault zone structure, the sensitivity kernels for head waves have sharp peaks with high values near the fault in the faster medium. Surface wave kernels show the broadest spatial distribution of sensitivity, while trapped wave kernels are extremely narrow with sensitivity focused entirely inside the low-velocity fault zone layer. Trapped waves are shown to exhibit sensitivity patterns similar to Love waves, with decreasing width as a function of frequency and multiple Fresnel zones of alternating polarity. In models that include smoothing of the boundaries of the low velocity zone, there is little effect on the trapped wave kernels, which are focused in the central core of the low velocity zone. When the source is located outside a shallow fault zone layer, trapped waves propagate through the surrounding medium with body wave sensitivity before becoming confined. The results provide building blocks for full waveform tomography of fault zone regions combining high-frequency head, trapped, body, and surface waves. Such an imaging approach can constrain fault zone structure across a larger range of scales than has previously been possible.

  13. Damping of Mechanical Waves with Styrene/Butadiene Rubber Filled with Polystyrene Particle: Effects of Particles Size and Wave Frequency

    Directory of Open Access Journals (Sweden)

    M. Haghgo

    2007-08-01

    Full Text Available Utilizing polymeric materials for damping mechanical waves is of great importance in various fields of applications such as military camouflage, prevention of structural vibrational energy transfer, and noise attenuation. This ability originates from segmental dynamics of chain-like polymer molecules. Damping properties of styrene-butadiene rubbercontaining 10 wt% of monosize polystyrene particles with different diameters (from 80 nm to 500 μm was investigated in the frequency range of vibration, sound, and ultrasound via dynamic mechanical thermal analysis, normalsound adsorption test, and ultrasound attenuation coefficient measurement. The obtained results indicated that for different systems, containing different sizes of polystyrene particles, the area under the damping curve does not show significant change comparing to the neat SBR in the frequency range studied. However, addition of polystyrene particles, specifically nanosized particles, resulted in emergence of a secondary glass transition temperature which could be attributed to the modified dynamics of a layer of matrix molecules near the surface of PS particles. In the range of sound frequency, 0.5 to 6.3 kHz, the maximum damping was observed for the system containing polystyrene nanoparticles. However the single damping curve of neat SBR was separated into two or even three distinct curves owing to the presence of the particles. The maximum damping in the ultrasound frequency range was found for the system containing 0.5 mm polystyrene particles. This is attributed to different contributions from matrix chains dynamics and the reflection of mechanical waves from particles-matrix interface at different frequency ranges. On other words, the increase in the glass transition temperature of the elastomeric matrix phase with increasing the mechanical wave frequency causes a reduction in the contribution from matrix chains dynamics while the contribution due to diffraction from dispersed

  14. Tobacco smoking produces widespread dominant brain wave alpha frequency increases.

    Science.gov (United States)

    Domino, Edward F; Ni, Lisong; Thompson, Michael; Zhang, Huilei; Shikata, Hiroki; Fukai, Hiromi; Sakaki, Takeshi; Ohya, Ippei

    2009-12-01

    The major pharmacological ingredient in tobacco smoke is nicotine, a mild stimulant known to alter brain electrical activity. The objective of this study was to determine if tobacco smoking in humans produces localized or widespread neocortical dominant alpha electroencephalographic (EEG) frequency increases consistent with nicotine stimulation of the brainstem activating system in animals. Twenty-two male volunteer non-deprived tobacco smokers were studied. They were asked not to smoke for at least 1h before the experiment in mid-morning as part of their usual smoking schedule. In the laboratory, they sham smoked and then smoked their favorite tobacco cigarette. Two experimental sessions (#1 and #2) were conducted, separated by a one to two month interval. In both sessions, there were minor statistically significant increases in the dominant alpha frequencies after sham smoking. In both sessions, after the subjects smoked a favorite tobacco cigarette there was a significant generalized increase in dominant alpha EEG frequencies in most scalp recording sites. This study demonstrates that tobacco smoking produces widespread bilateral neocortical increases in dominant alpha EEG frequencies consistent with the stimulant effects of nicotine on the brainstem reticular activating system.

  15. Frequency Management for Electromagnetic Continuous Wave Conductivity Meters

    Directory of Open Access Journals (Sweden)

    Przemyslaw Mazurek

    2016-04-01

    Full Text Available Ground conductivity meters use electromagnetic fields for the mapping of geological variations, like the determination of water amount, depending on ground layers, which is important for the state analysis of embankments. The VLF band is contaminated by numerous natural and artificial electromagnetic interference signals. Prior to the determination of ground conductivity, the meter’s working frequency is not possible, due to the variable frequency of the interferences. Frequency management based on the analysis of the selected band using track-before-detect (TBD algorithms, which allows dynamical frequency changes of the conductivity of the meter transmitting part, is proposed in the paper. Naive maximum value search, spatio-temporal TBD (ST-TBD, Viterbi TBD and a new algorithm that uses combined ST-TBD and Viterbi TBD are compared. Monte Carlo tests are provided for the numerical analysis of the properties for a single interference signal in the considered band, and a new approach based on combined ST-TBD and Viterbi algorithms shows the best performance. The considered algorithms process spectrogram data for the selected band, so DFT (Discrete Fourier Transform could be applied for the computation of the spectrogram. Real–time properties, related to the latency, are discussed also, and it is shown that TBD algorithms are feasible for real applications.

  16. Traveling-Wave Tube Amplifier for THz Frequencies

    DEFF Research Database (Denmark)

    Kotiranta, Mikko; Krozer, Viktor; Zhurbenko, Vitaliy

    The lack of a compact and powerful terahertz source has been hindering the application of terahertz radiation in many fields. Frequency multipliers can be used in conjunction with an electronic solid-state source to obtain power levels up to around 1 mW. A higher power may be generated with vacuu...

  17. Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock

    Directory of Open Access Journals (Sweden)

    A. P. Dimmock

    2013-08-01

    Full Text Available Low frequency waves in the foot of a supercritical quasi-perpendicular shock front have been observed since the very early in situ observations of the terrestrial bow shock (Guha et al., 1972. The great attention that has been devoted to these type of waves since the first observations is explained by the key role attributed to them in the processes of energy redistribution in the shock front by various theoretical models. In some models, these waves play the role of the intermediator between the ions and electrons. It is assumed that they are generated by plasma instability that exist due to the counter-streaming flows of incident and reflected ions. In the second type of models, these waves result from the evolution of the shock front itself in the quasi-periodic process of steepening and overturning of the magnetic ramp. However, the range of the observed frequencies in the spacecraft frame are not enough to distinguish the origin of the observed waves. It also requires the determination of the wave vectors and the plasma frame frequencies. Multipoint measurements within the wave coherence length are needed for an ambiguous determination of the wave vectors. In the main multi-point missions such as ISEE, AMPTE, Cluster and THEMIS, the spacecraft separation is too large for such a wave vector determination and therefore only very few case studies are published (mainly for AMPTE UKS AMPTE IRM pair. Here we present the observations of upstream low frequency waves by the Cluster spacecraft which took place on 19 February 2002. The spacecraft separation during the crossing of the bow shock was small enough to determine the wave vectors and allowed the identification of the plasma wave dispersion relation for the observed waves. Presented results are compared with whistler wave dispersion and it is shown that contrary to previous studies based on the AMPTE data, the phase velocity in the shock frame is directed downstream. The consequences of this

  18. Charged particle behavior in localized ultralow frequency waves: Theory and observations

    Science.gov (United States)

    Li, Li; Zhou, Xu-Zhi; Zong, Qiu-Gang; Rankin, Robert; Zou, Hong; Liu, Ying; Chen, Xing-Ran; Hao, Yi-Xin

    2017-06-01

    The formation and variability of the Van Allen radiation belts are highly influenced by charged particles accelerated via drift-resonant interactions with ultralow frequency (ULF) waves. In the prevailing theory of drift resonance, the ULF wave amplitude is assumed independent of magnetic longitude. This assumption is not generally valid in Earth's magnetosphere, as supported by numerous observations that point to the localized nature of ULF waves. Here we introduce a longitude dependence of the ULF wave amplitude, achieved via a von Mises function, into the theoretical framework of ULF wave-particle drift resonance. To validate the revised theory, the predicted particle signatures are compared with observational data through a best fit procedure. It is demonstrated that incorporation of nonlocal effects in drift-resonance theory provides an improved understanding of charged particle behavior in the inner magnetosphere through the intermediary of ULF waves.

  19. Inhibition of Salmonella typhi growth using extremely low frequency electromagnetic (ELF-EM) waves at resonance frequency.

    Science.gov (United States)

    Fadel, M A; Mohamed, S A; Abdelbacki, A M; El-Sharkawy, A H

    2014-08-01

    Typhoid is a serious disease difficult to be treated with conventional drugs. The aim of this study was to demonstrate a new method for the control of Salmonella typhi growth, through the interference with the bioelectric signals generated from the microbe during cell division by extremely low frequency electromagnetic waves (ELF-EMW-ELF-EM) at resonance frequency. Isolated Salmonella typhi was subjected to square amplitude modulated waves (QAMW) with different modulation frequencies from two generators with constant carrier frequency of 10 MHz, amplitude of 10 Vpp, modulating depth ± 2 Vpp and constant field strength of 200 V m(-1) at 37°C. Both the control and exposed samples were incubated at the same conditions during the experiment. The results showed that there was highly significant inhibition effect for Salm. typhi exposed to 0·8 Hz QAMW for a single exposure for 75 min. Dielectric relaxation, TEM and DNA results indicated highly significant changes in the molecular structure of the DNA and cellular membrane resulting from the exposure to the inhibiting EM waves. It was concluded that finding out the inhibiting resonance frequency of ELF-EM waves that deteriorates Salm. typhi growth will be promising method for the treatment of Salm. typhi infection either in vivo or in vitro. This new non-invasive technique for treatment of bacterial infections is of considerable interest for the use in medical and biotechnological applications. © 2014 The Society for Applied Microbiology.

  20. The possible role of high-frequency waves in heating solar coronal loops

    Science.gov (United States)

    Porter, Lisa J.; Klimchuk, James A.; Sturrock, Peter A.

    1994-01-01

    We investigate the role of high-frequency waves in the heating of solar active region coronal loops. We assume a uniform background magnetic field, and we introduce a density stratification in a direction perpendicular to this field. We focus on ion compressive viscosity as the damping mechanism of the waves. We incorporate viscosity self-consistently into the equations, and we derive a dispersion relation by adopting a slab model, where the density inside the slab is greater than that outside. Such a configuration supports two types of modes: surface waves and trapped body waves. In order to determine under what conditions these waves may contribute to the heating of active regions, we solve our dispersion relation for a range of densities, temperatures, magnetic field strengths, density ratios, wavevector magnitudes, wavevector ratios, and slab widths. We find that surface waves exhibit very small damping, but body waves can potentially damp at rates needed to balance radiative losses. However, the required frequencies of these body waves are very high. For example, the wave frequency must be at least 5.0/s for a slab density of 10(exp 9,5)/cc, a slab temperature of 10(exp 6,5) K, a field strength of 100 G, and a density ratio of 5. For a slab density of 10(exp 10)/cc, this frequency increases to 8.8/s. Although these frequencies are very high, there in no observational evidence to rule out their existence, and they may be generated both below the corona and at magnetic reconnection sites in the corona. However, we do find that, for slab densities of 10(exp 10)/cc or less, the dissipation of high-frequency waves will be insufficient to balance the radiative losses if the magnetic field strength exceeds roughly 200 G. Because the magnetic field is known to exceed 200 G in many active region loops, particularly low-lying loops and loops emanating from sunspots, it is unlikely that high-frequency waves can provide sufficient heating in these regions.

  1. Identification and classification of very low frequency waves on a coral reef flat

    Science.gov (United States)

    Gawehn, Matthijs; van Dongeran, Ap; van Rooijen, Arnold; Storlazzi, Curt; Cheriton, Olivia; Reniers, Ad

    2016-01-01

    Very low frequency (VLF, 0.001–0.005 Hz) waves are important drivers of flooding of low-lying coral reef-islands. In particular, VLF wave resonance is known to drive large wave runup and subsequent overwash. Using a 5 month data set of water levels and waves collected along a cross-reef transect on Roi-Namur Island in the Republic of the Marshall Islands, the observed VLF motions were categorized into four different classes: (1) resonant, (2) (nonresonant) standing, (3) progressive-growing, and (4) progressive-dissipative waves. Each VLF class is set by the reef flat water depth and, in the case of resonance, the incident-band offshore wave period. Using an improved method to identify VLF wave resonance, we find that VLF wave resonance caused prolonged (∼0.5–6.0 h), large-amplitude water surface oscillations at the inner reef flat ranging in wave height from 0.14 to 0.83 m. It was induced by relatively long-period, grouped, incident-band waves, and occurred under both storm and nonstorm conditions. Moreover, observed resonant VLF waves had nonlinear, bore-like wave shapes, which likely have a larger impact on the shoreline than regular, sinusoidal waveforms. As an alternative technique to the commonly used Fast Fourier Transformation, we propose the Hilbert-Huang Transformation that is more computationally expensive but can capture the wave shape more accurately. This research demonstrates that understanding VLF waves on reef flats is important for evaluating coastal flooding hazards.

  2. Modeling surf zone tracer plumes: 1. Waves, mean currents, and low-frequency eddies

    Science.gov (United States)

    Feddersen, Falk; Clark, David B.; Guza, R. T.

    2011-11-01

    A model that accurately simulates surf zone waves, mean currents, and low-frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion. In this paper, a wave-resolving time-dependent Boussinesq model is compared with waves and currents observed during five surf zone dye release experiments. In a companion paper, Clark et al. (2011) compare a coupled tracer model to the dye plume observations. The Boussinesq model uses observed bathymetry and incident random, directionally spread waves. For all five releases, the model generally reproduces the observed cross-shore evolution of significant wave height, mean wave angle, bulk directional spread, mean alongshore current, and the frequency-dependent sea surface elevation spectra and directional moments. The largest errors are near the shoreline where the bathymetry is most uncertain. The model also reproduces the observed cross-shore structure of rotational velocities in the infragravity (0.004 surf zone. The model-data agreement for sea swell waves, low-frequency eddies, and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion.

  3. Delta waves differently modulate high frequency components of EEG oscillations in various unconsciousness levels.

    Science.gov (United States)

    Molaee-Ardekani, Behnam; Senhadji, Lotfi; Shamsollahi, Mohammad-Bagher; Wodey, Eric; Vosoughi-Vahdat, Bijan

    2007-01-01

    In this paper we investigate the modulation properties of high frequency EEG activities by delta waves during various depth of anesthesia. We show that slow and fast delta waves (0-2 Hz and 2-4 Hz respectively) and high frequency components of the EEG (8-20 Hz) are correlated with each other and there is a kind of phase locking between them that varies with depth of anesthesia. Our analyses show that maximum amplitudes of high frequency components of the EEG signal are appeared in different phases of slow and fast delta waves when the concentration of Desflurane and Propofol anesthetic agents varies in a patient. There are some slight differences in using slow and fast components of delta waves. For instance, when depth of anesthesia changes, biphasic responses of the EEG have more influences on results of the fast delta wave method. In addition, this method obtains more robust and less noisy results compared with the slow delta wave method. Since phase angle between fast EEG oscillations and delta waves indicates the status of information processing in the brain and it changes in various unconsciousness levels, it may improve the performance of other classic methods of determining depth of anesthesia.

  4. Pressure induced by the interaction of water waves with nearly equal frequencies and nearly opposite directions

    Directory of Open Access Journals (Sweden)

    L. Pellet

    2017-05-01

    Full Text Available We present second-order expressions for the free-surface elevation, velocity potential and pressure resulting from the interaction of surface waves in water of arbitrary depth. When the surface waves have nearly equal frequencies and nearly opposite directions, a second-order pressure can be felt all the way to the sea bottom. There are at least two areas of applications: reflective structures and microseisms. Microseisms generated by water waves in the ocean are small vibrations of the ground resulting from pressure oscillations associated with the coupling of ocean surface gravity waves and the sea floor. They are recorded on land-based seismic stations throughout the world and they are divided into primary and secondary types, as a function of spectral content. Secondary microseisms are generated by the interaction of surface waves with nearly equal frequencies and nearly opposite directions. The efficiency of microseism generation thus depends in part on ocean wave frequency and direction. Based on the second-order expressions for the dynamic pressure, a simple theoretical analysis that quantifies the degree of nearness in amplitude, frequency, and incidence angle, which must be reached to observe the phenomenon, is presented.

  5. High-frequency guided ultrasonic waves for hidden defect detection in multi-layered aircraft structures.

    Science.gov (United States)

    Masserey, Bernard; Raemy, Christian; Fromme, Paul

    2014-09-01

    Aerospace structures often contain multi-layered metallic components where hidden defects such as fatigue cracks and localized disbonds can develop, necessitating non-destructive testing. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete thickness were generated in a model structure consisting of two adhesively bonded aluminium plates. Interference occurs between the wave modes during propagation along the structure, resulting in a frequency dependent variation of the energy through the thickness with distance. The wave propagation along the specimen was measured experimentally using a laser interferometer. Good agreement with theoretical predictions and two-dimensional finite element simulations was found. Significant propagation distance with a strong, non-dispersive main wave pulse was achieved. The interaction of the high frequency guided ultrasonic waves with small notches in the aluminium layer facing the sealant and on the bottom surface of the multilayer structure was investigated. Standard pulse-echo measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulations. The results demonstrated the potential of high frequency guided waves for hidden defect detection at critical and difficult to access locations in aerospace structures from a stand-off distance. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  6. Low frequency axisymmetric longitudinal guided waves in eccentric annular cylinders.

    Science.gov (United States)

    Pattanayak, Roson Kumar; Manogharan, Prabhakaran; Balasubramaniam, Krishnan; Rajagopal, Prabhu

    2015-06-01

    This paper studies the effect of axially uniform eccentricity on the modal structures and velocities of the lower order axisymmetric guided wave mode L(0,2) in circular tubes or pipes. The semi-analytical finite element method is mainly used, supported by fully three-dimensional finite element models and validated using experiments. The studies show that even a small eccentricity in the pipe can cause a loss in the L(0,2) mode axisymmetry, leading to its confinement in the thinned side of the pipe cross-section and also a reduction in mode velocities. The physics of this phenomenon is related to the feature-guiding and mode confinement effects noted in recent years in the literature, particularly studies on waveguides with local cross-section variations and curvature.

  7. The role of localised Ultra-Low Frequency waves in energetic electron precipitation

    Science.gov (United States)

    Rae, J.; Murphy, K. R.; Watt, C.; Mann, I. R.; Ozeke, L.; Halford, A. J.; Sibeck, D. G.; Clilverd, M. A.; Rodger, C. J.; Degeling, A. W.; Singer, H. J.

    2016-12-01

    Electromagnetic waves play pivotal roles in radiation belt dynamics through a variety of different means. Typically, Ultra-Low Frequency (ULF) waves have historically been invoked for radial diffusive transport leading to both acceleration and loss of outer radiation belt electrons. Very-Low Frequency (VLF) and Extremely-Low Frequency (ELF) waves are generally thought to provide a mechanism for localized acceleration and loss through precipitation into the ionosphere. In this study we present a new mechanism for electron loss through precipitation into the ionosphere due to direct modulation of the loss cone via localized compressional ULF waves. Observational evidence is presented demonstrating that modulation of the equatorial loss cone can occur via localized compressional wave activity. We then perform statistical computations of the probability distribution to determine how likely a given magnetic perturbation would produce a given percentage change in the bounce loss-cone (BLC). We discuss the ramifications of the action of coherent, localized compressional ULF waves on drifting electron populations; their precipitation response can be a complex interplay between electron energy, the shape of the phase space density profile at pitch angles close to the loss cone, ionospheric decay timescales, and the time-dependence of the electron source. We present a case study of compressional wave activity in tandem with riometer and balloon-borne electron precipitation across keV-MeV energies to demonstrate that the experimental measurements can be explained by our new enhanced loss cone mechanism. We determine that the two pivotal components not usually considered are localized ULF wave fields and ionospheric decay timescales. We conclude that ULF wave modulation of the loss cone is a viable candidate for direct precipitation of radiation belt electrons without any additional requirement for gyroresonant wave-particle interaction. Additional mechanisms would be

  8. Frequencies of wave packets of whistler-mode chorus inside its source region: a case study

    Directory of Open Access Journals (Sweden)

    O. Santolik

    2008-06-01

    Full Text Available Whistler-mode chorus is a structured wave emission observed in the Earth's magnetosphere in a frequency range from a few hundreds of Hz to several kHz. We investigate wave packets of chorus using high-resolution measurements recorded by the WBD instrument on board the four Cluster spacecraft. A night-side chorus event observed during geomagnetically disturbed conditions is analyzed. We identify lower and upper frequencies for a large number of individual chorus wave packets inside the chorus source region. We investigate how these observations are related to the central position of the chorus source which has been previously estimated from the Poynting flux measurements. We observe typical frequency bandwidths of chorus of approximately 10% of the local electron cyclotron frequency. Observed time scales are around 0.1 s for the individual wave packets. Our results indicate a lower occurrence probability for lower frequencies in the vicinity of the central position of the source compared to measurements recorded closer to the outer boundaries of the source. This is in agreement with recent research based on the backward wave oscillator theory.

  9. Test the mergers of the primordial black holes by high frequency gravitational-wave detector

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin; Wang, Li-Li; Li, Jin [Chongqing University, Department of Physics, Chongqing (China)

    2017-09-15

    The black hole could have a primordial origin if its mass is less than 1M {sub CircleDot}. The mergers of these black hole binaries generate stochastic gravitational-wave background (SGWB). We investigate the SGWB in high frequency band 10{sup 8}-10{sup 10} Hz. It can be detected by high frequency gravitational-wave detector. Energy density spectrum and amplitude of the SGWB are derived. The upper limit of the energy density spectrum is around 10{sup -7}. Also, the upper limit of the amplitude ranges from 10{sup -31.5} to 10{sup -29.5}. The fluctuation of spacetime origin from gravitational wave could give a fluctuation of the background electromagnetic field in a high frequency gravitational-wave detector. The signal photon flux generated by the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz is derived, which ranges from 1 to 10{sup 2} s{sup -1}. The comparison between the signal photon flux generated by relic gravitational waves (RGWs) and the SGWB is also discussed in this paper. It is shown that the signal photon flux generated by the RGW, which is predicted by the canonical single-field slow-roll inflation models, is sufficiently lower than the one generated by the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz. Our results indicate that the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz is more likely to be detected by the high frequency gravitational-wave detector. (orig.)

  10. Atoms in the counter-propagating frequency-modulated waves: splitting, cooling, confinement

    Science.gov (United States)

    Romanenko, Victor I.; Kornilovska, Nataliya V.

    2017-09-01

    We show that the counter-propagating frequency-modulated (FM) waves of the same intensity can split an orthogonal atomic beam into two beams. We calculate the temperature of the atomic ensemble for the case when the atoms are grouped around zero velocity in the direction of the waves propagation. The high-intensity laser radiation with a properly chosen carrier frequency can form a one-dimensional trap for atoms. We carry out the numerical simulation of the atomic motion (two-level model of the atom-field interaction) using parameters appropriate for sodium atoms and show that sub-Doppler cooling can be reached. We suppose that such a cooling is partly based on the cooling without spontaneous emission in polychromatic waves [H. Metcalf, Phys. Rev. A 77, 061401 (2008)]. We calculate the state of the atom in the field by the Monte Carlo wave-function method and describe its mechanical motion by the classical mechanics.

  11. Waves on fluid-loaded shells and their resonance frequency spectrum

    DEFF Research Database (Denmark)

    Bao, X.L.; Uberall, H.; Raju, P.K.

    2005-01-01

    Technical requirements for elastic (metal) cylindrical shells include the knowledge of their natural frequency spectrum. These shells may be empty and fluid-immersed, or fluid-filled in an ambient medium of air, or doubly fluid-loaded inside and out. They may support circumferential waves......, or axially propagating waves both in the shell material, and in the fluid loading. Previous results by Bao et al. (J. Acoust. Soc. Am. 105 (1999) 2704) were obtained for the circumferential-wave dispersion curves on doubly loaded aluminum shells; the present study extends this to fluid-filled shells in air....... For practical applications, steel shells are most important and we have here obtained corresponding results for these. To find the natural frequencies of cylindrical shells, one may invoke the principle of phase matching where resonating standing waves are formed around the circumference, or in the axial...

  12. Low-frequency surface waves on semi-bounded magnetized quantum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Afshin, E-mail: a.moradi@kut.ac.ir [Department of Engineering Physics, Kermanshah University of Technology, Kermanshah (Iran, Islamic Republic of)

    2016-08-15

    The propagation of low-frequency electrostatic surface waves on the interface between a vacuum and an electron-ion quantum plasma is studied in the direction perpendicular to an external static magnetic field which is parallel to the interface. A new dispersion equation is derived by employing both the quantum magnetohydrodynamic and Poisson equations. It is shown that the dispersion equations for forward and backward-going surface waves are different from each other.

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

    Science.gov (United States)

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

    2012-08-01

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

  14. An improved dual-frequency technique for the remote sensing of ocean currents and wave spectra

    Science.gov (United States)

    Schuler, D. L.; Eng, W. P.

    1984-01-01

    A two frequency microwave radar technique for the remote sensing of directional ocean wave spectra and surface currents is investigated. This technique is conceptually attractive because its operational physical principle involves a spatial electromagnetic scattering resonance with a single, but selectable, long gravity wave. Multiplexing of signals having different spacing of the two transmitted frequencies allows measurements of the entire long wave ocean spectrum to be carried out. A new scatterometer is developed and experimentally tested which is capable of making measurements having much larger signal/background values than previously possible. This instrument couples the resonance technique with coherent, frequency agility radar capabilities. This scatterometer is presently configured for supporting a program of surface current measurements.

  15. Two-frequency /Delta k/ microwave scatterometer measurements of ocean wave spectra from an aircraft

    Science.gov (United States)

    Johnson, J. W.; Jones, W. L.; Weissman, D. E.

    1981-01-01

    A technique for remotely sensing the large-scale gravity wave spectrum on the ocean surface using a two frequency (Delta k) microwave scatterometer has been demonstrated from stationary platforms and proposed from moving platforms. This measurement takes advantage of Bragg type resonance matching between the electromagnetic wavelength at the difference frequency and the length of the large-scale surface waves. A prominent resonance appears in the cross product power spectral density (PSD) of the two backscattered signals. Ku-Band aircraft scatterometer measurements were conducted by NASA in the North Sea during the 1979 Maritime Remote Sensing (MARSEN) experiment. Typical examples of cross product PSD's computed from the MARSEN data are presented. They demonstrate strong resonances whose frequency and bandwidth agree with the surface characteristics and the theory. Directional modulation spectra of the surface reflectivity are compared to the gravity wave spectrum derived from surface truth measurements.

  16. Large-scale transmission-type multifunctional anisotropic coding metasurfaces in millimeter-wave frequencies

    Science.gov (United States)

    Cui, Tie Jun; Wu, Rui Yuan; Wu, Wei; Shi, Chuan Bo; Li, Yun Bo

    2017-10-01

    We propose fast and accurate designs to large-scale and low-profile transmission-type anisotropic coding metasurfaces with multiple functions in the millimeter-wave frequencies based on the antenna-array method. The numerical simulation of an anisotropic coding metasurface with the size of 30λ × 30λ by the proposed method takes only 20 min, which however cannot be realized by commercial software due to huge memory usage in personal computers. To inspect the performance of coding metasurfaces in the millimeter-wave band, the working frequency is chosen as 60 GHz. Based on the convolution operations and holographic theory, the proposed multifunctional anisotropic coding metasurface exhibits different effects excited by y-polarized and x-polarized incidences. This study extends the frequency range of coding metasurfaces, filling the gap between microwave and terahertz bands, and implying promising applications in millimeter-wave communication and imaging.

  17. On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

    Science.gov (United States)

    Jensen, Eric J.

    2016-01-01

    Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

  18. Full-wave analysis of the high frequency characteristics of the sine waveguide slow-wave structure

    Science.gov (United States)

    Lei, Xia; Wei, Yanyu; Wang, Yuanyuan; Zhou, Qing; Wu, Gangxiong; Ding, Chong; Li, Qian; Zhang, Luqi; Jiang, Xuebing; Gong, Yubin; Wang, Wenxiang

    2017-08-01

    A theoretical model for calculation of the high frequency characteristics of the sine waveguide slow-wave structure (SWS) is proposed. The formulas of dispersion and interaction impedances of the hybrid modes are obtained by combining the Helmholtz equation with the appropriate boundary conditions. Using the full wave analysis method, it is proved that the periodic structures with a half-period shift followed leads to a pairwise closing of passbands characteristic of adjacent mode. The sine waveguide SWS for 0.22THz traveling wave tube (TWT) is chosen as an illustrative example to verify the validity of the theoretical model, and the calculation results of the dispersion curve and interaction impedance curve are consistent with the HFSS simulation results. In addition, the influences of dimensions of sine waveguide on the high frequency characteristics of +1st spatial harmonic wave are investigated by numerical calculation. The study indicates that the appropriate SWS parameters are helpful for improving the bandwidth and increasing output power of TWT.

  19. Full-wave analysis of the high frequency characteristics of the sine waveguide slow-wave structure

    Directory of Open Access Journals (Sweden)

    Xia Lei

    2017-08-01

    Full Text Available A theoretical model for calculation of the high frequency characteristics of the sine waveguide slow-wave structure (SWS is proposed. The formulas of dispersion and interaction impedances of the hybrid modes are obtained by combining the Helmholtz equation with the appropriate boundary conditions. Using the full wave analysis method, it is proved that the periodic structures with a half-period shift followed leads to a pairwise closing of passbands characteristic of adjacent mode. The sine waveguide SWS for 0.22THz traveling wave tube (TWT is chosen as an illustrative example to verify the validity of the theoretical model, and the calculation results of the dispersion curve and interaction impedance curve are consistent with the HFSS simulation results. In addition, the influences of dimensions of sine waveguide on the high frequency characteristics of +1st spatial harmonic wave are investigated by numerical calculation. The study indicates that the appropriate SWS parameters are helpful for improving the bandwidth and increasing output power of TWT.

  20. First results of low frequency electromagnetic wave detector of TC-2/Double Star program

    Directory of Open Access Journals (Sweden)

    J. B. Cao

    2005-11-01

    Full Text Available LFEW is a low frequency electromagnetic wave detector mounted on TC-2, which can measure the magnetic fluctuation of low frequency electromagnetic waves. The frequency range is 8 Hz to 10 kHz. LFEW comprises a boom-mounted, three-axis search coil magnetometer, a preamplifier and an electronics box that houses a Digital Spectrum Analyzer. LFEW was calibrated at Chambon-la-Forêt in France. The ground calibration results show that the performance of LFEW is similar to that of STAFF on TC-1. The first results of LFEW show that it works normally on board, and that the AC magnetic interference of the satellite platform is very small. In the plasmasphere, LFEW observed the ion cyclotron waves. During the geomagnetic storm on 8 November 2004, LFEW observed a wave burst associated with the oxygen ion cyclotron waves. This observation shows that during geomagnetic storms, the oxygen ions are very active in the inner magnetosphere. Outside the plasmasphere, LFEW observed the chorus on 3 November 2004. LFEW also observed the plasmaspheric hiss and mid-latitude hiss both in the Southern Hemisphere and Northern Hemisphere on 8 November 2004. The hiss in the Southern Hemisphere may be the reflected waves of the hiss in the Northern Hemisphere.

  1. Phase-locking in Multi-Frequency Brillouin Oscillator via Four Wave Mixing

    CERN Document Server

    Buettner, Thomas F S; Hudson, Darren D; Pant, Ravi; Poulton, Christopher G; Judge, Alexander C; Eggleton, Benjamin J

    2014-01-01

    Stimulated Brillouin scattering (SBS) and Kerr-nonlinear four wave-mixing (FWM) are among the most important and widely studied nonlinear effects in optical fibres. At high powers SBS can be cascaded producing multiple Stokes waves spaced by the Brillouin frequency shift. Here, we investigate the complex nonlinear interaction of the cascade of Stokes waves, generated in a Fabry-Perot chalcogenide fibre resonator through the combined action of SBS and FWM. We demonstrate the existence of parameter regimes, in which pump and Stokes waves attain a phase-locked steady state. Real-time measurements of 40ps pulses with 8GHz repetition rate are presented, confirming short-and long-term stability. Numerical simulations qualitatively agree with experiments and show the significance of FWM in phase-locking of pump and Stokes waves. Our findings can be applied for the design of novel picosecond pulse sources with GHz repetition rate for optical communication systems.

  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. Wave intensifications near the electron cyclotron frequency within the polar cusp

    Science.gov (United States)

    Farrell, W. M.; Gurnett, D. A.; Menietti, J. D.; Wong, H. K.; Lin, C. S.

    1990-01-01

    As DE 1 flew through the polar cusp, enhanced narrowband electrostatic waves were sometimes observed just above the electron cyclotron frequency. Here, wave and particle measurements from three representative cusp transits are presented in order to characterize these signals and understand the conditions that favor their generation. It was found that the form of the local cusp electron velocity distribution had a direct influence on the wave spectral character. A preliminary study indicates that electron beams in the cusp can generate the enhanced signals, although generation by an anisotropic warm component cannot be ruled out.

  4. Portable, Real-time Tissue Functional Imaging Using Frequency Domain and Continuous Wave Diffuse Optics

    OpenAIRE

    Mohammad Mirzaei Zarandi, Soroush

    2014-01-01

    The aim of this research is to develop and build a low cost portable integrated frequency-domain and continuous wave (CW) system for real-time spectroscopic imaging of human tissue. This system measures four tissue chromophore concentrations (water, lipid, deoxygenated, and oxygenated hemoglobin) using eight near-infrared wavelengths ranging from 660nm to 980nm, in real-time. The frequency domain (FD) module measures the phase and amplitude of photon density waves from 50-500 MHz with an oper...

  5. Particle simulation of radio frequency waves with fully-kinetic ions and gyrokinetic electrons

    Science.gov (United States)

    Lin, Jingbo; Zhang, Wenlu; Liu, Pengfei; Lin, Zhihong; Dong, Chao; Cao, Jintao; Li, Ding

    2018-01-01

    A toroidal particle-in-cell (PIC) code, suitable for investigating nonlinear phenomena in radio frequency (RF) heating and current drive, is developed and verified thereafter through a series of fidelity tests for field solvers and single particle motions in toroidal geometry, where simulation results show good coincidence with analytical prediction. The RF capability is then demonstrated through the integrated benchmarks with linear lower hybrid wave and ion Bernstein wave theory in cylindrical geometry, where the analytic result is easily available. The frequency and mode structure in the simulations agree well with the theoretical prediction.

  6. P Wave and S Wave Acoustic Velocities of Partial Molten Peridotite at Mantle P-T and MHz Frequencies

    Science.gov (United States)

    Weidner, D. J.; Li, L.; Whitaker, M. L.; Triplett, R.

    2016-12-01

    The speed that acoustic waves travel in a partially molten peridotite are crucial parameters to detect not only the presence of melt in the Earth's deep interior, but also understand many issues about the structure and dynamics of the mantle. Technical challenges have hindered such measurements in the laboratory. Here we report the experimental results on the ultrasonic acoustic wave velocities in a partial molten peridotite using multi-anvil high pressure apparatus located at beamline BM6 Advance Photon Source. We use the newly installed ultrasonic equipment using the pulse-echo-overlap method coupled with D-DIA device. X-ray radiography is used to measure sample length at high P-T. The X-ray diffraction spectrum is used to determine the pressure and sample conditions. Precise measurements of P and S wave velocities are obtained at 60 and 35 MHz respectively and are nearly simultaneous. We use a double reflector method to enable measurement of elastic wave velocities of cold-pressed polycrystalline sample which is sintered in situ at high P-T. Experiments were carried out up to 3 GPa and 1500 oC. Our preliminary results indicate that the KLB1 peridotite sample experienced a few percent decrease of both p and s wave velocities as partial melting occurs. The data define a small decrease in the bulk modulus as well as the shear modulus upon melting. This implies that dynamic melting is a significant process at megahertz frequencies.

  7. Floquet engineering of long-range p -wave superconductivity: Beyond the high-frequency limit

    Science.gov (United States)

    Li, Zeng-Zhao; Lam, Chi-Hang; You, J. Q.

    2017-10-01

    It has been shown that long-range p -wave superconductivity in a Kitaev chain can be engineered via an ac field with a high frequency [M. Benito et al., Phys. Rev. B 90, 205127 (2014), 10.1103/PhysRevB.90.205127]. For its experimental realization, however, theoretical understanding of Floquet engineering with a broader range of driving frequencies becomes important. In this paper, focusing on the ac-driven tunneling interactions of a Kitaev chain, we investigate effects from the leading correction to the high-frequency limit on the emergent p -wave superconductivity. Importantly, we find new engineered long-range p -wave pairing interactions that can significantly alter the ones in the high-frequency limit at long interaction ranges. We also find that the leading correction additionally generates nearest-neighbor p -wave pairing interactions with a renormalized pairing energy, long-range tunneling interactions, and, in particular, multiple pairs of Floquet Majorana edge states that are destroyed in the high-frequency limit.

  8. Modeling of low-frequency seismic waves in a shallow sea using the staggered grid difference method

    Science.gov (United States)

    Lu, Zaihua; Zhang, Zhihong; Gu, Jiannong

    2017-09-01

    Elastic waves in the seabed generated by low-frequency noise radiating from ships are known as ship seismic waves and can be used to detect and identify ships. To obtain the propagation characteristics of ship seismic waves, an algorithm for calculating seismic waves at the seafloor is presented based on the staggered-grid finite difference method. The accuracy of the algorithm was tested by comparison with analytical solutions. Numerical simulation of seismic waves generated by a low-frequency point sound source in a typical shallow sea environment was carried out. Using various source frequencies and locations in the numerical simulation, we show that the seismic waves in the near field are composed mostly of transmitted S-waves and interface waves while transmitted P-waves are weak near the seafloor. However, in the far field, the wave components of the seismic wave are mainly normal modes and interface waves, with the latter being relatively strong in the waveforms. As the source frequency decreases, the normal modes become smaller and the interface waves dominate the time series of the seismic waves.

  9. Photonic integrated single-sideband modulator / frequency shifter based on surface acoustic waves

    DEFF Research Database (Denmark)

    Barretto, Elaine Cristina Saraiva; Hvam, Jørn Märcher

    2010-01-01

    Optical frequency shifters are essential components of many systems. In this paper, a compact integrated optical frequency shifter is designed making use of the combination of surface acoustic waves and Mach-Zehnder interferometers. It has a very simple operation setup and can be fabricated...... in standard semiconductor materials. The performance of the device is analyzed in detail, and by using multi-branch interferometers, the sensitivity of the device to fabrication tolerances can be drastically reduced....

  10. Electron Scattering by High-Frequency Whistler Waves at Earth's Bow Shock

    Science.gov (United States)

    Oka, M.; Wilson, L. B., III; Phan, T. D.; Hull, A. J.; Amano, T.; Hoshino, M.; Argall, M. R.; Le Contel, O.; Agapitov, O.; Gersham, D. J.; hide

    2017-01-01

    Electrons are accelerated to non-thermal energies at shocks in space and astrophysical environments. While different mechanisms of electron acceleration have been proposed, it remains unclear how non-thermal electrons are produced out of the thermal plasma pool. Here, we report in situ evidence of pitch-angle scattering of non-thermal electrons by whistler waves at Earths bow shock. On 2015 November 4, the Magnetospheric Multiscale (MMS) mission crossed the bow shock with an Alfvn Mach number is approximately 11 and a shock angle of approximately 84deg. In the ramp and overshoot regions, MMS revealed bursty enhancements of non-thermal (0.52 keV) electron flux, correlated with high-frequency (0.2 - 0.4 Omega(sub ce), where Omega(sub ce) is the cyclotron frequency) parallel-propagating whistler waves. The electron velocity distribution (measured at 30 ms cadence) showed an enhanced gradient of phase-space density at and around the region where the electron velocity component parallel to the magnetic field matched the resonant energy inferred from the wave frequency range. The flux of 0.5 keV electrons (measured at 1ms cadence) showed fluctuations with the same frequency. These features indicate that non-thermal electrons were pitch-angle scattered by cyclotron resonance with the high-frequency whistler waves. However, the precise role of the pitch-angle scattering by the higher-frequency whistler waves and possible nonlinear effects in the electron acceleration process remains unclear.

  11. Electron Scattering by High-frequency Whistler Waves at Earth’s Bow Shock

    Science.gov (United States)

    Oka, M.; Wilson, L. B., III; Phan, T. D.; Hull, A. J.; Amano, T.; Hoshino, M.; Argall, M. R.; Le Contel, O.; Agapitov, O.; Gershman, D. J.; Khotyaintsev, Y. V.; Burch, J. L.; Torbert, R. B.; Pollock, C.; Dorelli, J. C.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W.; Ergun, R. E.; Strangeway, R. J.; Russell, C. T.; Lindqvist, P. A.

    2017-06-01

    Electrons are accelerated to non-thermal energies at shocks in space and astrophysical environments. While different mechanisms of electron acceleration have been proposed, it remains unclear how non-thermal electrons are produced out of the thermal plasma pool. Here, we report in situ evidence of pitch-angle scattering of non-thermal electrons by whistler waves at Earth’s bow shock. On 2015 November 4, the Magnetospheric Multiscale (MMS) mission crossed the bow shock with an Alfvén Mach number ˜11 and a shock angle ˜84°. In the ramp and overshoot regions, MMS revealed bursty enhancements of non-thermal (0.5-2 keV) electron flux, correlated with high-frequency (0.2-0.4 {{{Ω }}}{ce}, where {{{Ω }}}{ce} is the cyclotron frequency) parallel-propagating whistler waves. The electron velocity distribution (measured at 30 ms cadence) showed an enhanced gradient of phase-space density at and around the region where the electron velocity component parallel to the magnetic field matched the resonant energy inferred from the wave frequency range. The flux of 0.5 keV electrons (measured at 1 ms cadence) showed fluctuations with the same frequency. These features indicate that non-thermal electrons were pitch-angle scattered by cyclotron resonance with the high-frequency whistler waves. However, the precise role of the pitch-angle scattering by the higher-frequency whistler waves and possible nonlinear effects in the electron acceleration process remains unclear.

  12. Detecting the thickness mode frequency in a concrete plate using backward wave propagation.

    Science.gov (United States)

    Bjurström, Henrik; Ryden, Nils

    2016-02-01

    Material stiffness and plate thickness are the two key parameters when performing quality assurance/quality control on pavement structures. In order to estimate the plate thickness non-destructively, the Impact Echo (IE) method can be utilized to extract the thickness resonance frequency. An alternative to IE for estimating the thickness resonance frequency of a concrete plate, and to subsequently enable thickness determination, is presented in this paper. The thickness resonance is often revealed as a sharp peak in the frequency spectrum when contact receivers are used in seismic testing. Due to a low signal-to-noise ratio, IE is not ideal when using non-contact microphone receivers. In studying the complex Lamb wave dispersion curves at a frequency infinitesimally higher than the thickness frequency, it is seen that two counter-directed waves occur at the same frequency but with phase velocities in opposite directions. Results show that it is possible to detect the wave traveling with a negative phase velocity using both accelerometers and air-coupled microphones as receivers. This alternative technique can possibly be used in non-contact scanning measurements based on air-coupled microphones.

  13. Structured waves near the plasma frequency observed in three auroral rocket flights

    Directory of Open Access Journals (Sweden)

    M. Samara

    2006-11-01

    Full Text Available We present observations of waves at and just above the plasma frequency (fpe from three high frequency electric field experiments on three recent rockets launched to altitudes of 300–900 km in active aurora. The predominant observed HF waves just above fpe are narrowband, short-lived emissions with amplitudes ranging from <1 mV/m to 20 mV/m, often associated with structured electron density. The nature of these HF waves, as determined from frequency-time spectrograms, is highly variable: in some cases, the frequency decreases monotonically with time as in the "HF-chirps" previously reported (McAdams and LaBelle, 1999, but in other cases rising frequencies are observed, or features which alternately rise and fall in frequency. They exhibit two timescales of amplitude variation: a short timescale, typically 50–100 ms, associated with individual discrete features, and a longer timescale associated with the general decrease in the amplitudes of the emissions as the rocket moves away from where the condition f~fpe holds. The latter timescale ranges from 0.6 to 6.0 s, corresponding to distances of 2–7 km, assuming the phenomenon to be stationary and using the rocket velocity to convert time to distance.

  14. Excitation of Lamb waves over a large frequency-thickness product range for corrosion detection

    Science.gov (United States)

    Zeng, Liang; Luo, Zhi; Lin, Jing; Hua, Jiadong

    2017-09-01

    For corrosion detection, it is often desirable that a Lamb wave mode is highly sensitive to surface thinning and enjoys some degree of mode purity at a particular frequency. In view of this, this paper aims to generate a variety of Lamb wave modes over broad frequency bands to ensure an abundant supply of candidates for corrosion detection, and further, establish a strategy to find appropriate operation points efficiently and effectively. Firstly, a short-duration laser pulse is applied to generate Lamb waves over a large frequency-thickness product range. The selection of symmetric modes or anti-symmetric modes is obtained by addition or subtraction of signals captured by two identical transducers which are symmetrically coupled on both sides of the plate. Subsequently, the S0 mode at a non-dispersive frequency bandwidth is employed to improve the accuracy of the transmitter-receiver distance. Based on those, three selection criteria including mode separability, amplitude ratio and corrosion sensitivity, are presented to efficiently determine the suitable operation points (i.e., mode types and frequencies). The experimental results show that the simulated corrosion could be correctly detected and accurately localized at the chosen modes and frequencies.

  15. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    Science.gov (United States)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  16. Controlling the transmission of ultrahigh frequency bulk acoustic waves in silicon by 45° mirrors.

    Science.gov (United States)

    Wang, Shengxiang; Gao, Jiaming; Carlier, Julien; Campistron, Pierre; NDieguene, Assane; Guo, Shishang; Matar, Olivier Bou; Dorothee, Debavelaere-Callens; Nongaillard, Bertrand

    2011-07-01

    In this paper, we present a feasible microsystem in which the direction of localized ultrahigh frequency (∼1GHz) bulk acoustic wave can be controlled in a silicon wafer. Deep etching technology on the silicon wafer makes it possible to achieve high aspect ratio etching patterns which can be used to control bulk acoustic wave to transmit in the directions parallel to the surface of the silicon wafer. Passive 45° mirror planes obtained by wet chemical etching were employed to reflect the bulk acoustic wave. Zinc oxide (ZnO) thin film transducers were deposited by radio frequency sputtering with a thickness of about 1μm on the other side of the wafer, which act as emitter/receptor after aligned with the mirrors. Two opponent vertical mirrors were inserted between the 45° mirrors to guide the transmission of the acoustic waves. The propagation of the bulk acoustic wave was studied with simulations and the characterization of S(21) scattering parameters, indicating that the mirrors were efficient to guide bulk acoustic waves in the silicon wafer. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Performance Analysis of Multiple Wave Energy Converters Placed on a Floating Platform in the Frequency Domain

    Directory of Open Access Journals (Sweden)

    Hyebin Lee

    2018-02-01

    Full Text Available Wind-wave hybrid power generation systems have the potential to become a significant source of affordable renewable energy. However, their strong interactions with both wind- and wave-induced forces raise a number of technical challenges for modelling. The present study undertakes a numerical investigation on multi-body hydrodynamic interaction between a wind-wave hybrid floating platform and multiple wave energy converters (WECs in a frequency domain. In addition to the exact responses of the platform and the WECs, the power take-off (PTO mechanism was taken into account for analysis. The coupled hydrodynamic coefficients and wave exciting forces were obtained from WAMIT, the 3D diffraction/radiation solver based on the boundary element method. The overall performance of the multiple WECs is presented and compared with the performance of a single isolated WEC. The analysis showed significant differences in the dynamic responses of the WECs when the multi-body interaction was considered. In addition, the PTO damping effect made a considerable difference to the responses of the WECs. However, the platform response was only minimally affected by PTO damping. With regard to energy capture, the interaction effect of the designed multiple WEC array layout is evaluated. The WEC array configuration showed both constructive and destructive effects in accordance with the incident wave frequency and direction.

  18. Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Analysis and interpretation

    Science.gov (United States)

    Neubauer, Fritz M.; Glassmeier, Karl-Heinz; Coates, A. J.; Johnstone, A. D.

    1993-01-01

    The propagation and polarization characteristic of low-frequency electromagnetic wave fields near comet P/Grigg-Skjellerup (P/GS) are analyzed using magnetic field and plasma observations obtained by the Giotto magnetometer experiment and the Johnstone plasma analyzer during the encounter at the comet on July 10, 1992. The results have been physically interpreted.

  19. A Frequency-Domain Model for a Novel Wave Energy Converter

    NARCIS (Netherlands)

    Wei, Yanji; Yu, Zhiheng; Barradas Berglind, Jose de Jesus; van Rooij, Marijn; Prins, Wouter; Jayawardhana, Bayu; Vakis, Antonis I.

    2017-01-01

    In this work, we develop a frequency-domain model for the novel Ocean Grazer (OG) wave energy converter (WEC), with the intention to study the hydrodynamic behavior of its array of floater elements individually connected to power take-off (PTO) systems. To investigate these hydrodynamic

  20. Remote sensing planetary waves in the midlatitude mesosphere using low frequency transmitter signals

    Directory of Open Access Journals (Sweden)

    E. D. Schmitter

    2011-07-01

    Full Text Available Very low and low radio frequency (VLF/LF propagation responds sensitively to the electron density distribution in the lower ionosphere (upper mesosphere. Whereas propagation paths crossing subpolar and polar regions are frequently affected by forcing from above by particle precipitations, mid- and lowlatitude paths let forcing from below be more prominent. Our observations (2009–2011 show, that the low frequency propagation conditions along the midlatitude path from Sicily to Germany (52° N 8° E using the NSY 45.9 kHz transmitter (37° N 14° E prove to be a good proxy of mesosphere planetary wave activity along the propagation path. High absorption events with VLF/LF propagation correlate to the well known winter time D-layer anomaly observed with high frequency (HF radio waves. VLF/LF propagation calculations are presented which show that the radio signal amplitude variations can be modeled by planetary wave modulated collison frequency and electron density profiles. The other way around wave pressure amplitudes can be inferred from the VLF/LF data.

  1. Ultrahigh-frequency surface acoustic wave generation for acoustic charge transport in silicon

    NARCIS (Netherlands)

    Büyükköse, S.; Vratzov, B.; van der Veen, Johan (CTIT); Santos, P.V.; van der Wiel, Wilfred Gerard

    2013-01-01

    We demonstrate piezo-electrical generation of ultrahigh-frequency surface acoustic waves on silicon substrates, using high-resolution UV-based nanoimprint lithography, hydrogen silsequioxane planarization, and metal lift-off. Interdigital transducers were fabricated on a ZnO layer sandwiched between

  2. Ultracold atoms in radio-frequency dressed potentials beyond the rotating-wave approximation

    DEFF Research Database (Denmark)

    Hofferberth, S.; Fischer, B.; Schumm, Thorsten

    2007-01-01

    We study dressed Bose-Einstein condensates in an atom chip radio-frequency trap. We show that in this system sufficiently strong dressing can be achieved to cause the widely used rotating-wave approximation (RWA) to break down. We present a full calculation of the atom-field coupling which shows...

  3. Quantum frequency translation by four-wave mixing in a fiber: low-conversion regime

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; McKinstrie, C. J.; Raymer, M. G.

    2012-01-01

    In this paper we consider frequency translation enabled by Bragg scattering, a four-wave mixing process. First we introduce the theoretical background of the Green function formalism and the Schmidt decomposition. Next the Green functions for the low-conversion regime are derived perturbatively...

  4. High-frequency precursors to P-wave arrivals in New Zealand : implications for slab structure

    NARCIS (Netherlands)

    Hilst, R.D. van der; Snieder, R.K.

    1996-01-01

    This report revisits the very early high-frequency slab phases from earthquakes in the Kermadec slab (between −25°S and −37°S) that arrive as a precursor to the P wave onset at stations in New Zealand. The analysis of short-period digital records for station SNZO (South Karori New Zealand) for the

  5. Frequency-Domain Green's Functions for Radar Waves in Heterogeneous 2.5D Media

    Science.gov (United States)

    Green’s functions for radar waves propagating in heterogeneous media may be calculated in the frequency domain using a hybrid of two numerical methods. The model is defined in the Cartesian coordinate system, and its electromagnetic properties may vary in the x and z directions, ...

  6. A Frequency-Domain Model for a Novel Wave Energy Converter

    NARCIS (Netherlands)

    Wei, Yanji; Yu, Zhiheng; Barradas Berglind, Jose de Jesus; van Rooij, Marijn; Prins, Wouter; Jayawardhana, Bayu; Vakis, Antonis I.

    In this work, we develop a frequency-domain model for the novel Ocean Grazer (OG) wave energy converter (WEC), with the intention to study the hydrodynamic behavior of its array of floater elements individually connected to power take-off (PTO) systems. To investigate these hydrodynamic

  7. Biological effects of THz electromagnetic waves on frequencies of active cell metabolites at a molecular level

    OpenAIRE

    Vyacheslav F. Kirichuk; Alexander A. Tsymbal

    2013-01-01

    A reaction of biomolecules had been studied, including an effect of albumin molecules on THz electromagnetic waves on frequencies of active cell metabolites (nitrogen oxide 150.176-150.664 GHz and atmospheric oxygen 129.0 GHz). Change of conformational molecule state had been displayed.

  8. Amplification of a high-frequency electromagnetic wave by a relativistic plasma

    Science.gov (United States)

    Yoon, Peter H.

    1990-01-01

    The amplification of a high-frequency transverse electromagnetic wave by a relativistic plasma component, via the synchrotron maser process, is studied. The background plasma that supports the transverse wave is considered to be cold, and the energetic component whose density is much smaller than that of the background component has a loss-cone feature in the perpendicular momentum space and a finite field-aligned drift speed. The ratio of the background plasma frequency squared to the electron gyrofrequency squared is taken to be sufficiently larger than unity. Such a parameter regime is relevant to many space and astrophysical situations. A detailed study of the amplification process is carried out over a wide range of physical parameters including the loss-cone index, the ratio of the electron mass energy to the temperature of the energetic component, the field-aligned drift speed, the normalized density, and the wave propagation angle.

  9. Low-frequency pressure wave propagation in liquid-filled, flexible tubes. (A)

    DEFF Research Database (Denmark)

    Bjørnø, Leif; Bjelland, C.

    1992-01-01

    A model has been developed for propagation of low-frequency pressure waves in viscoelastic tubes with distensibility of greater importance than compressibility of the liquid. The dispersion and attenuation are shown to be strongly dependent on the viscoelastic properties of the tube wall...... the model and are compared with results of experimental pressure wave propagation in the liquid-filled, flexible tube. A good agreement between experimental data and theoretical predictions is found........ The complex, frequency-dependent moduli of relevant tube materials have been measured in a series of experiments using three different experimental procedures, and the data obtained are compared. The three procedures were: (1) ultrasonic wave propagation, (2) transversal resonance in bar samples, and (3...

  10. High-Frequency Gravitational Wave research and application to exoplanet studies

    Science.gov (United States)

    Baker, R. M. L., Jr.

    2017-10-01

    A discussion of the history of High-Frequency Gravitational Wave (HFGW) research is first presented. Over the years until modern times, starting with the first mention of Gravitational Waves by Poincaré in 1905 and the definition of HFGWs in 1961 by Robert L. Forward, the discussion continues concerning the international research efforts to detect HFGWs. The article highlights the accomplishments of HFGW researchers in China, Russia, Ukraine, England, Australia, Japan, Germany, Spain, Italy, and the United States. Comparisons are made with Low-Frequency Gravitational Wave (LFGW) research, especially concerning the Laser Interferometer Gravitational Observatory or LIGO. In fine, there are presented several interesting perspectives concerning cosmology, the speed of time and, especially, exoplanet applications of HFGWs.

  11. Tunable odd-frequency triplet pairing states and skyrmion modes in chiral p-wave superconductor.

    Science.gov (United States)

    Lou, Yu-Feng; Wen, Lin; Zha, Guo-Qiao; Zhou, Shi-Ping

    2017-08-29

    Bogliubov-de Gennes equations are solved self-consistently to investigate the properties of bound states in chiral p-wave superconductive disks. It shows that either an s-wave or the mixed d- and s-wave state with odd-frequency and spin-triplet symmetry is induced at the vortex core, depending both on the chirality of the pairing states and on the vortex topology. It is also found that the odd-frequency triplet even parity (OTE) bound state can be manipulated with a local non-magnetic potential. Interestingly, with an appropriate potential amplitude, the zero-energy OTE bound state can be stabilized at a distance from the vortex core and from the local potential. Possible existences of the Majorana fermion modes are expected if the particle-hole symmetry property is applied to the zero-energy OTE bound state. Moreover, skyrmion modes with an integer topological charge have been found to exist.

  12. A variable-frequency structural health monitoring system based on omnidirectional shear horizontal wave piezoelectric transducers

    Science.gov (United States)

    Huan, Qiang; Miao, Hongchen; Li, Faxin

    2018-02-01

    Structural health monitoring (SHM) is of great importance for engineering structures as it may detect the early degradation and thus avoid life and financial loss. Guided wave based inspection is very useful in SHM due to its capability for long distance and wide range monitoring. The fundamental shear horizontal (SH0) wave based method should be most promising since SH0 is the unique non-dispersive wave mode in plate-like structures. In this work, a sparse array SHM system based on omnidirectional SH wave piezoelectric transducers (OSH-PT) was proposed and the multi data fusion method was used for defect inspection in a 2 mm thick aluminum plate. Firstly, the performances of three types OSH-PTs was comprehensively compared and the thickness-poled d15 mode OSH-PT used in this work was demonstrated obviously superior to the other two. Then, the signal processing method and imaging algorithm for this SHM system was presented. Finally, experiments were carried out to examine the performance of the proposed SHM system in defect localization and imaging. Results indicated that this SHM system can locate a through hole as small as 0.12λ (4 mm) in diameter (where λ is the wavelength corresponding to the central operation frequency) under frequencies from 90 to 150 kHz. It can also locate multiple defects accurately based on the baseline subtraction method. Obviously, this SHM system can detect larger areas with sparse sensors because of the adopted single mode, non-dispersive and low frequency SH0 wave which can propagate long distance with small attenuation. Considering its good performances, simple data processing and sparse array, this SH0 wave-based SHM system is expected to greatly promote the applications of guided wave inspection.

  13. Influence of multiple ion species on low-frequency electromagnetic wave instabilities. [in solar wind

    Science.gov (United States)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1989-01-01

    The effect of multiple (singly ionized) coexisting newborn ion species on the stability of low-frequency electromagnetic waves was investigated using a plasma model in which solar wind magnetoplasma is made up of isotropic Maxwellian electron and proton populations with a common number density of 4.95/cu cm and temperatures equal to 17.2 eV and 6.9 eV, respectively. It is shown that the effect of multiple ions on wave growth, for given background magnetoplasma conditions and relative densities, depends not only on their mass but also on the physical nature of the wave modes. If the ion masses are disparate, each one of the coexisting ion beams tends to stimulate instabilities without undue influence from the other species. If the masses of newborn ions are similar, they can strongly catalyze wave growth of fluidlike nonresonant modes, but bring about weak growth enhancements in cyclotron resonant instabilities.

  14. Biophysical control of the growth of Agrobacterium tumefaciens using extremely low frequency electromagnetic waves at resonance frequency.

    Science.gov (United States)

    Fadel, M Ali; El-Gebaly, Reem H; Mohamed, Shaimaa A; Abdelbacki, Ashraf M M

    2017-12-09

    Isolated Agrobacterium tumefaciens was exposed to different extremely low frequencies of square amplitude modulated waves (QAMW) from two generators to determine the resonance frequency that causes growth inhibition. The carrier was 10 MHz sine wave with amplitude ±10 Vpp which was modulated by a second wave generator with a modulation depth of ± 2Vpp and constant field strength of 200 V/m at 28 °C. The exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min inhibited the bacterial growth by 49.2%. In addition, the tested antibiotics became more effective against A. tumefaciens after the exposure. Furthermore, results of DNA, dielectric relaxation and TEM showed highly significant molecular and morphological changes due to the exposure to 1.0 Hz QAMW for 90 min. An in-vivo study has been carried out on healthy tomato plants to test the pathogenicity of A. tumefaciens before and after the exposure to QAMW at the inhibiting frequency. Symptoms of crown gall and all pathological symptoms were more aggressive in tomato plants treated with non-exposed bacteria, comparing with those treated with exposed bacteria. We concluded that, the exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min modified its cellular activity and DNA structure, which inhibited the growth and affected the microbe pathogenicity. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Second harmonic generation at fatigue cracks by low-frequency Lamb waves: Experimental and numerical studies

    Science.gov (United States)

    Yang, Yi; Ng, Ching-Tai; Kotousov, Andrei; Sohn, Hoon; Lim, Hyung Jin

    2018-01-01

    This paper presents experimental and theoretical analyses of the second harmonic generation due to non-linear interaction of Lamb waves with a fatigue crack. Three-dimensional (3D) finite element (FE) simulations and experimental studies are carried out to provide physical insight into the mechanism of second harmonic generation. The results demonstrate that the 3D FE simulations can provide a reasonable prediction on the second harmonic generated due to the contact nonlinearity at the fatigue crack. The effect of the wave modes on the second harmonic generation is also investigated in detail. It is found that the magnitude of the second harmonic induced by the interaction of the fundamental symmetric mode (S0) of Lamb wave with the fatigue crack is much higher than that by the fundamental anti-symmetric mode (A0) of Lamb wave. In addition, a series of parametric studies using 3D FE simulations are conducted to investigate the effect of the fatigue crack length to incident wave wavelength ratio, and the influence of the excitation frequency on the second harmonic generation. The outcomes show that the magnitude and directivity pattern of the generated second harmonic depend on the fatigue crack length to incident wave wavelength ratio as well as the ratio of S0 to A0 incident Lamb wave amplitude. In summary, the findings of this study can further advance the use of second harmonic generation in damage detection.

  16. Ion sense of polarization of the electromagnetic wave field in the electron whistler frequency band

    Directory of Open Access Journals (Sweden)

    B. Lundin

    2002-08-01

    Full Text Available It is shown that the left-hand (or ion-type sense of polarization can appear in the field interference pattern of two plane electron whistler waves. Moreover, it is demonstrated that the ion-type polarized wave electric fields can be accompanied by the presence at the same observation point of electron-type polarized wave magnetic fields. The registration of ion-type polarized fields with frequencies between the highest ion gyrofrequency and the electron gyrofrequency in a cold, overdense plasma is a sufficient indication for the existence of an interference wave pattern, which can typically occur near artificial or natural reflecting magnetospheric plasma regions, inside waveguides (as in helicon discharges, for example, in fields resonantly emitted by beams of charged particles or, in principle, in some self-sustained, nonlinear wave field structures. A comparison with the conventional spectral matrix data processing approach is also presented in order to facilitate the calculations of the analyzed polarization parameters.Key words. Ionosphere (wave propagation Radio science (waves in plasma Space plasma physics (general or miscellaneous

  17. Ion sense of polarization of the electromagnetic wave field in the electron whistler frequency band

    Directory of Open Access Journals (Sweden)

    B. Lundin

    Full Text Available It is shown that the left-hand (or ion-type sense of polarization can appear in the field interference pattern of two plane electron whistler waves. Moreover, it is demonstrated that the ion-type polarized wave electric fields can be accompanied by the presence at the same observation point of electron-type polarized wave magnetic fields. The registration of ion-type polarized fields with frequencies between the highest ion gyrofrequency and the electron gyrofrequency in a cold, overdense plasma is a sufficient indication for the existence of an interference wave pattern, which can typically occur near artificial or natural reflecting magnetospheric plasma regions, inside waveguides (as in helicon discharges, for example, in fields resonantly emitted by beams of charged particles or, in principle, in some self-sustained, nonlinear wave field structures. A comparison with the conventional spectral matrix data processing approach is also presented in order to facilitate the calculations of the analyzed polarization parameters.

    Key words. Ionosphere (wave propagation Radio science (waves in plasma Space plasma physics (general or miscellaneous

  18. Global particle in cell simulation of radio frequency waves in tokamak ∖fs20

    Science.gov (United States)

    Kuley, Animesh; Lin, Z.; Bao, J.; Lau, C.; Sun, G. Y.

    2016-10-01

    We are looking into a new nonlinear kinetic simulation model to study the radio frequency heating and current drive of fusion plasmas using toroidal code GTC. In this model ions are considered as fully kinetic (FK) particles using Vlasov equation and the electrons are treated as drift kinetic (DK) particles using drift kinetic equation. We have benchmarked this numerical model to verify the linear physics of normal modes, conversion of slow and fast waves and its propagation in the core region of the tokamak using the Boozer coordinates. In the nonlinear simulation of ion Bernstein wave (IBW) in a tokamak, parametric decay instability (PDI) is observed where a large amplitude pump wave decays into an IBW sideband and an ion cyclotron quasi-mode (ICQM). The ICQM induces an ion perpendicular heating, with a heating rate proportional to the pump wave intensity. Finally, in the electromagnetic LH simulation, nonlinear wave trapping of electrons is verified and plasma current is nonlinearly driven. Presently we are working on the development of new PIC simulation model using cylindrical coordinates to address the RF wave propagation from the edge of the tokamak to the core region and the parametric instabilities associated with this RF waves. We have verified the cyclotron integrator using Boris push method.

  19. Anomalous high-frequency wave activity flux preceding anomalous changes in the Northern polar jet

    Science.gov (United States)

    Nakamura, Mototaka; Kadota, Minoru; Yamane, Shozo

    2010-05-01

    Anomalous forcing by quasi-geostrophic (QG) waves has been reported as an important forcing factor in the Northern Annular Mode (NAM) in recent literatures. In order to shed a light on the dynamics of the NAM from a different angle, we have examined anomalous behavior of the winter jets in the upper troposphere and stratosphere by focusing our diagnosis on not the anomalous geopotential height (Z) itself, but on the anomalous change in the Z (dZ) between two successive months and preceding transient QG wave activity flux during the cold season. We calculated EOFs of dZ between two successive months at 150hPa for a 46-year period, from 1958 to 2003, using the monthly mean NCEP reanalysis data. We then formed anomaly composites of changes in Z and the zonal velocity (U), as well as the preceding and following wave activity flux, Z, U, and temperature at various heights, for both positive and negative phases of the first EOF. For the wave forcing fields, we adopted the diagnostic system for the three-dimensional QG transient wave activity flux in the zonally-varying three-dimensional mean flow developed by Plumb (1986) with a slight modification in its application to the data. Our choice of the Plumb86 is based on the fact that the winter mean flow in the Northern Hemisphere is characterized by noticeable zonal asymmetry, and has a symbiotic relationship with waves in the extra-tropics. The Plumb86 flux was calculated for high-frequency (period of 2 to 7 days) and low-frequency (period of 10 to 20 days) waves with the ultra-low-frequency (period of 30 days or longer) flow as the reference state for each time frame of the 6 hourly NCEP reanalysis data from 1958 to 2003. By replacing the mean flow with the ultra-low-frequency flow in the application of the Plumb86 formula, the flux fields were calculated as time series at 6 hour intervals. The time series of the wave activity flux was then averaged for each month. The patterns of composited anomalous dZ and dU clearly

  20. Frequency dependent attenuation of seismic waves for Delhi and surrounding area, India

    Directory of Open Access Journals (Sweden)

    Babita Sharma

    2015-06-01

    Full Text Available The attenuation properties of Delhi & surrounding region have been investigated using 62 local earthquakes recorded at nine stations. The frequency dependent quality factors Qa (using P-waves and Qb (using S-waves have been determined using the coda normalization method. Quality factor of coda-waves (Qc has been estimated using the single backscattering model in the frequency range from 1.5 Hz to 9 Hz. Wennerberg formulation has been used to estimate Qi (intrinsic attenuation parameter and Qs (scattering attenuation parameter for the region. The values Qa, Qb, Qc, Qi and Qs estimated are frequency dependent in the range of 1.5Hz-9Hz. Frequency dependent relations are estimated as Qa=52f1.03, Qb=98f1.07 and Qc=158f0.97. Qc estimates lie in between the values of Qi and Qs but closer to Qi at all central frequencies. Comparison between Qi and Qs shows that intrinsic absorption is predominant over scattering for Delhi and surrounding region. 

  1. Wave-number-frequency spectrum for turbulence from a random sweeping hypothesis with mean flow.

    Science.gov (United States)

    Wilczek, M; Narita, Y

    2012-12-01

    We derive the energy spectrum in wave-number-frequency space for turbulent flows based on Kraichnan's idealized random sweeping hypothesis with additional mean flow, which yields the instantaneous energy spectrum multiplied by a Gaussian frequency distribution. The model spectrum has two adjustable parameters, the mean flow velocity and the sweeping velocity, and has the property that the power-law index of the wave-number spectrum translates to the frequency spectrum, invariant for arbitrary choices of the mean velocity and sweeping velocity. The model spectrum incorporates both Taylor's frozen-in flow approximation and the random sweeping approximation in a natural way and can be used to distinguish between these two effects when applied to real time-resolved multipoint turbulence data. Evaluated in real space, its properties with respect to space-time velocity correlations are discussed, and a comparison to the recently introduced elliptic model is drawn.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ivry, Yachin, E-mail: ivry@mit.edu, E-mail: cd229@eng.cam.ac.uk; Wang, Nan; Durkan, Colm, E-mail: ivry@mit.edu, E-mail: cd229@eng.cam.ac.uk [Nanoscience Centre, University of Cambridge, 11 JJ Thomson Avenue, Cambridge CB3 0FF (United Kingdom)

    2014-03-31

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

  3. Optical Synthesis of Terahertz and Millimeter-Wave Frequencies with Discrete Mode Diode Lasers

    CERN Document Server

    O'Brien, Stephen; Bitauld, David; Brandonisio, Nicola; Amann, Andreas; Phelan, Richard; Kelly, Brian; O'Gorman, James

    2010-01-01

    It is shown that optical synthesis of terahertz and millimeter-wave frequencies can be achieved using two-mode and mode-locked discrete mode diode lasers. These edge-emitting devices incorporate a spatially varying refractive index profile which is designed according to the spectral output desired of the laser. We first demonstrate a device which supports two primary modes simultaneously with high spectral purity. In this case sinusoidal modulation of the optical intensity at terahertz frequencies can be obtained. Cross saturation of the material gain in quantum well lasers prevents simultaneous lasing of two modes with spacings in the millimeter-wave region. We show finally that by mode-locking of devices that are designed to support a minimal set of four primary modes, we obtain a sinusoidal modulation of the optical intensity in this frequency region.

  4. Deriving inertial wave characteristics from surface drifter velocities: Frequency variability in the Tropical Pacific

    Science.gov (United States)

    Poulain, Pierre-Marie; Luther, Douglas S.; Patzert, William C.

    1992-11-01

    Two techniques have been developed for estimating statistics of inertial oscillations from satellite-tracked drifters. These techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space coordinates that are a function of time. Application of these techniques to tropical surface drifter data collected during the NORPAX, EPOCS, and TOGA programs reveals a latitude-dependent, statistically significant "blue shift" of inertial wave frequency. The latitudinal dependence of the blue shift is similar to predictions based on "global" internal wave spectral models, with a superposition of frequency shifting due to modification of the effective local inertial frequency by the presence of strongly sheared zonal mean currents within 12° of the equator.

  5. Theoretical and experimental study of the light deflection by a frequency modulated ultrasonic wave

    Science.gov (United States)

    Guessoum, A.; Laouar, N.; Ferria, K.

    2017-12-01

    A formula that describes angular excursion variation of an acousto-optical deflector is theoretically demonstrated and experimentally confirmed. This deflector is obtained using a laser beam interaction with a frequency modulated ultrasonic sinusoidal wave in a liquid medium. The obtained results show that each diffracted order position varies sinusoidally around its central position, in the same rhythm as the modulating signal. Moreover, the scanning frequency of the diffraction order increases linearly according to the modulating signal frequency. Furthermore, the increase in the frequency excursion leads to the increase of the angular excursion. All the theoretical results are confirmed experimentally. Finally, the frequency modulation index has been easily obtained with good precision using experimental measurements of the diffracted order angular excursion.

  6. Cut-off frequencies of circumferential horizontal shear waves in various functionally graded cylinder shells.

    Science.gov (United States)

    Shen, Xiaoqin; Ren, Dawei; Cao, Xiaoshan; Wang, Ji

    2017-11-06

    In this study, cut-off frequencies of the circumferential SH waves in functionally graded piezoelectric-piezomagnetic material (FGPPM) cylinder shells with traction free, electrical and magnetic open boundary conditions are investigated analytically. The Wentzel-Kramers-Brillouin (WKB) method is employed for solving differential equations with variable coefficients for general cases. For comparison, Bessel functions and Kummer functions are used for solving cut-off frequency problems in homogenous and ideal FGPPM cylinder shells. It is shown that the WKB solution for the cut-off frequencies has good precise. The set of cut-off frequencies is a series of approximate arithmetic progressions, for which the difference is a function of the density and the effective elastic parameter. The relationship between the difference and the gradient coefficient is described. These results provide theoretical guidance for the non-destructive evaluation of curved shells based on the cut-off frequencies. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Electromagnetic waves with frequencies near the local proton gyrofrequency: ISEE-3 1 AU observations

    Science.gov (United States)

    Tsurutani, Bruce T.; Arballo, John K.; Mok, John; Smith, Edward J.; Mason, Glenn M.; Tan, Lun C.

    1994-01-01

    Low Frequency (LF) electromagnetic waves with periods near the local proton gyrofrequency have been detected in interplanetary space by the magnetometer onboard International-Sun-Earth-Explorer-3 (ISEE-3). Transverse peak-to-peak amplitudes as large as delta vector B/absolute value of B approximately 0.4 have been noted with compressional components (Delta absolute value of B/absolute value of B) typically less than or = 0.1. Generally, the waves have even smaller amplitudes, or are not detectable within the solar wind turbulence. The waves are elliptically/linearly polarized and are often, but not always, found to propagate nearly along vector B(sub zero). Both right- and left-hand polarizations in the spacecraft-frame have been detected. The waves are observed during all orientations of the interplanetary magnetic field, with the Parker spiral orientation being the most common case. Because the waves are detected at and near the local proton cyclotron frequency, the generation mechanism must almost certainly be solar wind pickup of freshly created hydrogen ions. Possible sources for the hydrogen are the Earth's atmosphere, coronal mass ejections from the Sun, comets and interstellar neutral atoms. At this time it is not obvious which potential source is the correct one. Statistical tests employing over one year of ISEE-3 data will be done in the near future to eliminate/confirm some of these possibilities.

  8. Intensity statistics of very high frequency sound scattered from wind-driven waves.

    Science.gov (United States)

    Walstead, Sean P; Deane, Grant B

    2016-05-01

    The interaction of vhf 100-1000 kHz underwater sound with the ocean surface is explored. The bistatic forward scatter of 300 kHz sound is measured in a wind driven wave channel. Fluctuations in arrival amplitude are described by the scintillation index (SI) which is a measure of arrival intensity variance. SI initially increases with wind speed but eventually saturates to a value of 0.5 when the root-mean-square (rms) roughness is 0.5 mm. An adjusted scintillation index (SI*) is suggested that accounts for the multiple arrivals and properly saturates to a value of 1. Fluctuations in arrival time do not saturate and increase proportionately to the dominant surface wave component. Forward scattering is modeled at frequencies ranging from 50 to 2000 kHz using the Helmholtz-Kirchhoff integral with surface wave realizations derived from wave gauge data. The amplitude and temporal statistics of the simulated scattering agree well with measured data. Intensity saturation occurs at lower wind speeds for higher frequency sound. Both measured and modeled vhf sound is characterized by many surface arrivals at saturation. Doppler shifts associated with wave motion are expected to vary rapidly for vhf sound however further analysis is required.

  9. A micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications

    Science.gov (United States)

    Wingqvist, G.; Arapan, L.; Yantchev, V.; Katardjiev, I.

    2009-03-01

    Micromachined thin film plate acoustic wave resonators (FPARs) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2 µm thick aluminium nitride (AlN) membranes have been successfully demonstrated (Yantchev and Katardjiev 2007 IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54 87-95). The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900 MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is the non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm K-1 to -25 ppm K-1. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.

  10. Ultra low frequency waves at Venus: Observations by the Venus Express spacecraft

    Science.gov (United States)

    Fränz, M.; Echer, E.; Marques de Souza, A.; Dubinin, E.; Zhang, T. L.

    2017-10-01

    The generation of waves with low frequencies (below 100 mHz) has been observed in the environment of most bodies in the solar system and well studied at Earth. These waves can be generated either upstream of the body in the solar wind by ionization of planetary exospheres or ions reflected from a bow shock or in the magnetosheath closer to the magnetic barrier. For Mars and Venus the waves may have special importance since they can contribute to the erosion of the ionopause and by that enhance atmospheric escape. While over the past years many case studies on wave phenomena observed at Venus have been published most statistical studies have been based on magnetic observations only. On the other hand the generation mechanisms and transport of these waves through the magnetosphere can only be quantified using both magnetic and particle observations. We use the long time observations of Venus Express (2006-2014) to determine the predominant processes and transport parameters. First we demonstrate the analysis methods in four case studies, then we present a statistical analysis by determining transport ratios from the complete Venus Express dataset. We find that Alfvenic waves are very dominant (>80%) in the solar wind and in the core magnetosheath. Fast waves are observed mainly at the bow shock (around 40%) but also at the magnetic barrier where they may be most important for the energy transfer into the ionosphere. Their occurrence in the magnetotail may be an artifact of the detection of individual plasma jets in this region. Slow mode waves are rarely dominating but occur with probability of about 10% at the bow shock and in the pile-up-region. Mirror mode waves have probability <20% in the magnetosheath slightly increasing towards the pile-up-boundary.

  11. Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps

    Directory of Open Access Journals (Sweden)

    Katarzyna Krupa

    2012-01-01

    Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.

  12. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    Science.gov (United States)

    Jackson, F. C.

    1980-01-01

    Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

  13. Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children

    Science.gov (United States)

    Astill, Rebecca G.; Piantoni, Giovanni; Raymann, Roy J. E. M.; Vis, Jose C.; Coppens, Joris E.; Walker, Matthew P.; Stickgold, Robert; Van Der Werf, Ysbrand D.; Van Someren, Eus J. W.

    2014-01-01

    Background and Aim: The role of sleep in the enhancement of motor skills has been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children. Hypothesis: We hypothesized sleep-dependence of skill enhancement and an association of interindividual differences in skill and sleep characteristics. Methods: 30 children (19 females, 10.7 ± 0.8 years of age; mean ± SD) performed finger sequence tapping tasks in a repeated-measures design spanning 4 days including 1 polysomnography (PSG) night. Initial and delayed performance were assessed over 12 h of wake; 12 h with sleep; and 24 h with wake and sleep. For the 12 h with sleep, children were assigned to one of three conditions: modulation of slow waves and spindles was attempted using acoustic perturbation, and compared to yoked and no-sound control conditions. Analyses: Mixed effect regression models evaluated the association of sleep, its macrostructure and spindles and slow wave parameters with initial and delayed speed and accuracy. Results and Conclusions: Children enhance their accuracy only over an interval with sleep. Unlike previously reported in adults, children enhance their speed independent of sleep, a capacity that may to be lost in adulthood. Individual differences in the dominant frequency of spindles and slow waves were predictive for performance: children performed better if they had less slow spindles, more fast spindles and faster slow waves. On the other hand, overnight enhancement of accuracy was most pronounced in children with more slow spindles and slower slow waves, i.e., the ones with an initial lower performance. Associations of spindle and slow wave characteristics with initial performance may confound interpretation of their involvement in overnight enhancement. Slower frequencies of characteristic sleep events may mark slower learning and immaturity of networks involved in motor skills. PMID:25426055

  14. Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children

    Directory of Open Access Journals (Sweden)

    Rebecca G Astill

    2014-11-01

    Full Text Available Background and Aim. The role of sleep in the enhancement of motor skills has been been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children. Hypothesis. We hypothesized sleep-dependence of skill enhancement and an association of interindividual differences in skill and sleep characteristics. Methods. 30 children (19 females, 10.7±0.8 years of age; mean±SD performed finger sequence tapping tasks in a repeated-measures design spanning 4 days including 1 polysomnography night. Initial and delayed performance were assessed over 12 hours of wake; 12 hours with sleep; and 24 hours with wake and sleep. For the 12 hours with sleep, children were assigned to one of three conditions: modulation of slow waves and spindles was attempted using acoustic perturbation, and compared to yoked and no-sound control conditions. Analyses. Mixed effect regression models evaluated the association of sleep, its macrostructure and spindles and slow wave parameters with initial and delayed speed and accuracy.Results and Conclusions. Children enhance their accuracy only over an interval with sleep. Unlike previously reported in adults, children enhance their speed independent of sleep, a capacity that may to be lost in adulthood. Individual differences in the dominant frequency of spindles and slow waves were predictive for performance: children performed better if they had less slow spindles, more fast spindles and faster slow waves. On the other hand, overnight enhancement of accuracy was most pronounced in children with more slow spindles and slower slow waves, i.e. the ones with an initial lower performance. Associations of spindle and slow wave characteristics with initial performance may confound interpretation of their involvement in overnight enhancement. Slower frequencies of characteristic sleep events may mark slower learning and immaturity of networks involved in

  15. Nonlinear wave equation in frequency domain: accurate modeling of ultrafast interaction in anisotropic nonlinear media

    DEFF Research Database (Denmark)

    Guo, Hairun; Zeng, Xianglong; Zhou, Binbin

    2013-01-01

    We interpret the purely spectral forward Maxwell equation with up to third-order induced polarizations for pulse propagation and interactions in quadratic nonlinear crystals. The interpreted equation, also named the nonlinear wave equation in the frequency domain, includes quadratic and cubic...... nonlinearities, delayed Raman effects, and anisotropic nonlinearities. The full potential of this wave equation is demonstrated by investigating simulations of solitons generated in the process of ultrafast cascaded second-harmonic generation. We show that a balance in the soliton delay can be achieved due...

  16. Squeezed light for the interferometric detection of high-frequency gravitational waves

    Science.gov (United States)

    Schnabel, R.; Harms, J.; Strain, K. A.; Danzmann, K.

    2004-03-01

    The quantum noise of the light field is a fundamental noise source in interferometric gravitational-wave detectors. Injected squeezed light is capable of reducing the quantum noise contribution to the detector noise floor to values that surpass the so-called standard quantum limit (SQL). In particular, squeezed light is useful for the detection of gravitational waves at high frequencies where interferometers are typically shot-noise limited, although the SQL might not be beaten in this case. We theoretically analyse the quantum noise of the signal-recycled laser interferometric gravitational-wave detector GEO 600 with additional input and output optics, namely frequency-dependent squeezing of the vacuum state of light entering the dark port and frequency-dependent homodyne detection. We focus on the frequency range between 1 kHz and 10 kHz, where, although signal recycled, the detector is still shot-noise limited. It is found that the GEO 600 detector with present design parameters will benefit from frequency-dependent squeezed light. Assuming a squeezing strength of -6 dB in quantum noise variance, the interferometer will become thermal noise limited up to 4 kHz without further reduction of bandwidth. At higher frequencies the linear noise spectral density of GEO 600 will still be dominated by shot noise and improved by a factor of 106dB/20dB ap 2 according to the squeezing strength assumed. The interferometer might reach a strain sensitivity of 6 × 10-23 above 1 kHz (tunable) with a bandwidth of around 350 Hz. We propose a scheme to implement the desired frequency-dependent squeezing by introducing an additional optical component into GEO 600's signal-recycling cavity.

  17. Lower frequency companions for the Advanced LIGO gravitational wave interferometric detectors: an observational opportunity?

    Energy Technology Data Exchange (ETDEWEB)

    DeSalvo, Riccardo [California Institute of Technology, LIGO Project, Pasadena, CA 91125 (United States)

    2004-03-07

    Recent x-ray and optical observations provide evidence for a population of intermediate mass black holes with masses of tens to thousands of solar masses. Dynamical braking in high stellar density regions may 'catalyze' the inspiral of heavy mass objects down to the million-year time scale. Black-hole binaries, with the masses implied by the observations, will plunge below 100 Hz. It may be technologically possible to build ground-based low frequency gravitational wave interferometric detectors optimized to detect these events and install them next to Advanced LIGO (AdL), within the existing LIGO facilities. This additional interferometer, operated coherently with AdL and Virgo, would greatly enhance the effectiveness of the existing interferometers by generating a wealth of triggers for potentially frequent but otherwise undetectable heavy mass inspirals. AdL would study, at higher frequency, the triggered, ultra-relativistic phases (merging and ringdown) of these inspirals. Comparisons are made between the expected detection performances of AdL in its proposed wide band tuning, as well as AdL in its best low frequency tuning, with a low frequency gravitational wave interferometric detector that is mechanically and optically optimized for operation at the lowest possible frequency. Finally, the synergies of tandem operation of AdL and the proposed low frequency interferometer have been considered.

  18. Shallow PS-logging by high frequency wave; Koshuha wo mochiita senbu PS kenso

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, A.; Miyazawa, M.; Azuma, H. [OYO Corp., Tokyo (Japan)

    1996-05-01

    This paper describes the following matters on down-hole PS logging in shallow subsurface. Determining an elastic wave velocity structure in shallow subsurface with high accuracy by using down-hole PS logging requires reduction of errors in reading travel time. Therefore, a high-frequency vibration source was fabricated with an objective to raise frequencies of waves used for the measurement. Measurements were made on two holes, A and B, at a measurement interval of 0.5 m, whereas at the hole A a measurement was performed simultaneously by using a normal type (low-frequency) vibration source. A spectral analysis on the waveform record revealed that the frequencies with each vibration source were 127 Hz and 27 Hz for the hole A, 115 Hz for the hole B, and the S/N ratio was all the same for both holes. When the high-frequency vibration source was used, the velocity was determined at accuracy of 5% over the whole length of the shallow section. When the low-frequency vibration source was used, sections with the velocity determining error greater than 5% were found, and it was not possible to derive the velocity structure in the shallow subsurface in fine segments. 3 refs., 8 figs., 2 tabs.

  19. Effect of antiferromagnetic interfacial coupling on spin-wave resonance frequency of multi-layer film

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Rong-ke, E-mail: rkqiu@163.com; Cai, Wei

    2017-08-15

    Highlights: • A quantum approach is developed to study the SWR of a bicomponent multi-layer films. • The comparison of the SWR in films with FM and AFM interfacial coupling has been made. • The present results show the method to enhance and adjust the SWR frequency of films. - Abstract: We investigate the spin-wave resonance (SWR) frequency in a bicomponent bilayer and triple-layer films with antiferromagnetic or ferromagnetic interfacial couplings, as function of interfacial coupling, surface anisotropy, interface anisotropy, thickness and external magnetic field, using the linear spin-wave approximation and Green’s function technique. The microwave properties for multi-layer magnetic film with antiferromagnetic interfacial coupling is different from those for multi-layer magnetic film with ferromagnetic interfacial coupling. For the bilayer film with antiferromagnetic interfacial couplings, as the lower (upper) surface anisotropy increases, only the SWR frequencies of the odd (even) number modes increase. The lower (upper) surface anisotropy does not affect the SWR frequencies of the even (odd) number modes{sub .} For the multi-layer film with antiferromagnetic interfacial coupling, the SWR frequency of modes m = 1, 3 and 4 decreases while that of mode m = 2 increases with increasing thickness of the film within a proper parameter region. The present results could be useful in enhancing our fundamental understanding and show the method to enhance and adjust the SWR frequency of bicomponent multi-layer magnetic films with antiferromagnetic or ferromagnetic interfacial coupling.

  20. Dispersion relations for low-frequency waves in a warm, underdense, two-fluid plasma

    Science.gov (United States)

    Kakuwa, Jun

    2017-10-01

    Analytical forms of dispersion relations for three lower-frequency waves in a two-fluid plasma are presented. In underdense plasmas, ωp2≲Ωce 2, that is, low density or strongly magnetized plasmas, where ωp and Ωce are respectively the plasma frequency and the electron cyclotron frequency, the displacement current can become important in higher-frequency (non-magnetohydrodynamic) region. Focusing on only three branches that become magnetohydrodynamic waves in the low-frequency limit, we derive dispersion relations applicable to both underdense and overdense plasmas by the full set of equations of two-fluid plasmas including the displacement current. It is shown that our analytical results well agree with the exact numerical ones in all frequency ranges when the following conditions are satisfied: normal (i.e., not pair) plasma; low plasma β, and not extremely small electron to ion temperature ratio, me/mi≪Te/Ti, while more exact dispersion relations are needed to perform polarization analysis.

  1. Spin-wave resonance frequency in ferromagnetic thin film with interlayer exchange coupling and surface anisotropy

    Science.gov (United States)

    Zhang, Shuhui; Rong, Jianhong; Wang, Huan; Wang, Dong; Zhang, Lei

    2018-01-01

    We have investigated the dependence of spin-wave resonance(SWR) frequency on the surface anisotropy, the interlayer exchange coupling, the ferromagnetic layer thickness, the mode number and the external magnetic field in a ferromagnetic superlattice film by means of the linear spin-wave approximation and Green's function technique. The SWR frequency of the ferromagnetic thin film is shifted to higher values corresponding to those of above factors, respectively. It is found that the linear behavior of SWR frequency curves of all modes in the system is observed as the external magnetic field is increasing, however, SWR frequency curves are nonlinear with the lower and the higher modes for different surface anisotropy and interlayer exchange coupling in the system. In addition, the SWR frequency of the lowest (highest) mode is shifted to higher (lower) values when the film thickness is thinner. The interlayer exchange coupling is more important for the energetically higher modes than for the energetically lower modes. The surface anisotropy has a little effect on the SWR frequency of the highest mode, when the surface anisotropy field is further increased.

  2. Self-injection-locking of a CW-OPO by intracavity frequency-doubling the idler wave.

    Science.gov (United States)

    Lee, D H; Klein, M; Meyn, J P; Grob, P; Wallenstein, R; Boller, K

    1999-08-30

    We report on the observation of self-injection-locking of the signal wave of an optical parametric oscillator (OPO) with the intracavity frequency doubled idler wave. The two-mirror OPO is based on a periodically poled LiNbO3 (PPLN) crystal and pumped with a grating stabilized, continuous-wave (CW) single-frequency diode master-oscillator power-amplifier (MOPA) system. Simultaneous quasi-phase-matching (QPM) of OPO and second harmonic generation (SHG) is provided in the same crystal which carries two different domain gratings. The beat of the signal wave and the frequency-doubled idler wave is suppressed within a 500-kHz wide frequency range centered around zero as expected for self-injection- locking. The measurements prove the feasibility of optically phase-stabilized by-three-division of an optical frequency with CW-OPOs using cascaded nonlinearities.

  3. 2.5-D frequency-domain viscoelastic wave modelling using finite-element method

    Science.gov (United States)

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

    2017-10-01

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

  4. Dispersion curves of viscoelastic plane waves and Rayleigh surface wave in high frequency range with fractional derivatives

    Science.gov (United States)

    Usuki, Tsuneo

    2013-09-01

    The moduli of conventional elastic structural materials are extended to one of the viscoelastic materials through a modification whereby the dynamic moduli converge to the static moduli of elasticity as the fractional order approaches zero. By plotting phase velocity curves and group velocity curves of plane waves and Rayleigh surface wave for a viscoelastic material (polyvinyl chloride foam), the influence of the fractional order of viscoelasticity is examined. The phase and group velocity curves in the high frequency range were derived for longitudinal, transverse, and Rayleigh waves inherent to the viscoelastic material. In addition, the equation for the phase velocity was mathematically derived on the complex plane, too, and graphically illustrated. A phenomenon was found that, at the moment when the fractional order of the time derivative reaches an integer value 1, the curve on the complex plane becomes completely different, exhibiting snap-through behavior. We examined the mechanism of the snap-through mathematically. Numerical calculation examples were solved, and good agreement was confirmed between the numerical calculation and the analytical expression mentioned above. From the results of the numerical example, regularities were derived for the absolute value of the complex phase and group velocities on the complex plane.

  5. Ring-plane traveling-wave tube slow-wave circuit design simulations at V-Band frequencies

    Science.gov (United States)

    Kory, Carol L.; Wilson, Jeffrey D.

    1995-01-01

    The V-Band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for intersatellite communications. As a first effort to develop a high-efficiency V-band TWT, variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite the high-power capabilities of the ring-plane TWT, disadvantages of low bandwidth and high voltage requirements have until now prevented its acceptance outside the laboratory. In this paper, we use the three-dimensional electromagnetic simulation code MAFIA to investigate methods of increasing the bandwidth and lowering the operating voltage. Dispersion, impedance, and attenuation calculations for various geometric variations and loading distributions were performed. Based on the results of the variations, a circuit termed the finned-ladder TWT slowwave circuit was designed and is compared here to the scaled ring-plane prototype and the conventional ferruled coupled-cavity TWT circuit over the V-band frequency range.

  6. High-harmonic electron bunching in the field of a signal wave and the use of this effect in cyclotron masers with frequency multiplication

    Directory of Open Access Journals (Sweden)

    I. V. Bandurkin

    2005-01-01

    Full Text Available A method of organizing electron-wave interaction at the multiplied frequency of the signal wave is proposed. This type of electron-wave interaction provides multiplied-frequency electron bunching, which leads to formation of an intense harmonic of the electron current at a selected multiplied frequency of the signal wave. This effect is attractive for the use in klystron-type cyclotron masers with frequency multiplication as a way to increase the output frequency and improve the selectivity.

  7. Modeling and experiments with low-frequency pressure wave propagation in liquid-filled, flexible tubes

    DEFF Research Database (Denmark)

    Bjelland, C; Bjarnø, Leif

    1992-01-01

    A model for wave propagation in a liquid-filled viscoelastic tube with arrays of receivers inside, is being used to analyze the influence of noise generated by in-line vibrational noise sources. In this model, distensibility is of greater importance than compressibility of the liquid...... accelerometers and arrays of hydrophones inside are compared to the theoretical model for wave propagation. A good agreement between experimental data and theoretical predictions is found........ The dispersion and attenuation is shown to be strongly dependent on the viscoelastic properties of the tube wall. The complex, frequency-dependent moduli of relevant tube materials have been measured in stress wave transfer function experiments. The moduli are used in the model to produce realistic dispersion...

  8. A Sparse Stochastic Collocation Technique for High-Frequency Wave Propagation with Uncertainty

    KAUST Repository

    Malenova, G.

    2016-09-08

    We consider the wave equation with highly oscillatory initial data, where there is uncertainty in the wave speed, initial phase, and/or initial amplitude. To estimate quantities of interest related to the solution and their statistics, we combine a high-frequency method based on Gaussian beams with sparse stochastic collocation. Although the wave solution, uϵ, is highly oscillatory in both physical and stochastic spaces, we provide theoretical arguments for simplified problems and numerical evidence that quantities of interest based on local averages of |uϵ|2 are smooth, with derivatives in the stochastic space uniformly bounded in ϵ, where ϵ denotes the short wavelength. This observable related regularity makes the sparse stochastic collocation approach more efficient than Monte Carlo methods. We present numerical tests that demonstrate this advantage.

  9. Comparison of Signals from Gravitational Wave Detectors with Instantaneous Time-Frequency Maps

    Science.gov (United States)

    Stroeer, A.; Blackburn, L.; Camp, J.

    2011-01-01

    Gravitational wave astronomy relies on the use of multiple detectors, so that coincident detections may distinguish real signals from instrumental artifacts, and also so that relative timing of signals can provide the sky position of sources. We show that the comparison of instantaneous time-frequency and time-amplitude maps provided by the Hilbert-Huang Transform (HHT) can be used effectively for relative signal timing of common signals, to discriminate between the case of identical coincident signals and random noise coincidences and to provide a classification of signals based on their time-frequency trajectories. The comparison is done with a X(sup 2) goodness-offit method which includes contributions from both the instantaneous amplitude and frequency components of the HHT to match two signals in the time domain. This approach naturally allows the analysis of waveforms with strong frequency modulation.

  10. Analysis of dispersion and attenuation of surface waves in poroelastic media in the exploration-seismic frequency band

    Science.gov (United States)

    Zhang, Y.; Xu, Y.; Xia, J.

    2011-01-01

    We analyse dispersion and attenuation of surface waves at free surfaces of possible vacuum/poroelastic media: permeable-'open pore', impermeable-'closed pore' and partially permeable boundaries, which have not been previously reported in detail by researchers, under different surface-permeable, viscous-damping, elastic and fluid-flowing conditions. Our discussion is focused on their characteristics in the exploration-seismic frequency band (a few through 200 Hz) for near-surface applications. We find two surface-wave modes exist, R1 waves for all conditions, and R2 waves for closed-pore and partially permeable conditions. For R1 waves, velocities disperse most under partially permeable conditions and least under the open-pore condition. High-coupling damping coefficients move the main dispersion frequency range to high frequencies. There is an f1 frequency dependence as a constant-Q model for attenuation at high frequencies. R1 waves for the open pore are most sensitive to elastic modulus variation, but least sensitive to tortuosities variation. R1 waves for partially permeable surface radiate as non-physical waves (Im(k) attenuation are diffusive of f1/2 frequency dependence, as P2 waves. It is found that for partially permeable surfaces, the attenuation displays -f1 frequency dependence as frequency increasing. High surface permeability, low-coupling damping coefficients, low Poisson's ratios, and low tortuosities increase the slope of the -f1 dependence. When the attenuation coefficients reach 0, R2 waves for partially permeable surface begin to radiate as non-physical waves. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.

  11. Computational helioseismology in the frequency domain: acoustic waves in axisymmetric solar models with flows

    Science.gov (United States)

    Gizon, Laurent; Barucq, Hélène; Duruflé, Marc; Hanson, Chris S.; Leguèbe, Michael; Birch, Aaron C.; Chabassier, Juliette; Fournier, Damien; Hohage, Thorsten; Papini, Emanuele

    2017-04-01

    Context. Local helioseismology has so far relied on semi-analytical methods to compute the spatial sensitivity of wave travel times to perturbations in the solar interior. These methods are cumbersome and lack flexibility. Aims: Here we propose a convenient framework for numerically solving the forward problem of time-distance helioseismology in the frequency domain. The fundamental quantity to be computed is the cross-covariance of the seismic wavefield. Methods: We choose sources of wave excitation that enable us to relate the cross-covariance of the oscillations to the Green's function in a straightforward manner. We illustrate the method by considering the 3D acoustic wave equation in an axisymmetric reference solar model, ignoring the effects of gravity on the waves. The symmetry of the background model around the rotation axis implies that the Green's function can be written as a sum of longitudinal Fourier modes, leading to a set of independent 2D problems. We use a high-order finite-element method to solve the 2D wave equation in frequency space. The computation is embarrassingly parallel, with each frequency and each azimuthal order solved independently on a computer cluster. Results: We compute travel-time sensitivity kernels in spherical geometry for flows, sound speed, and density perturbations under the first Born approximation. Convergence tests show that travel times can be computed with a numerical precision better than one millisecond, as required by the most precise travel-time measurements. Conclusions: The method presented here is computationally efficient and will be used to interpret travel-time measurements in order to infer, e.g., the large-scale meridional flow in the solar convection zone. It allows the implementation of (full-waveform) iterative inversions, whereby the axisymmetric background model is updated at each iteration.

  12. Modeling of high‐frequency seismic‐wave scattering and propagation using radiative transfer theory

    Science.gov (United States)

    Zeng, Yuehua

    2017-01-01

    This is a study of the nonisotropic scattering process based on radiative transfer theory and its application to the observation of the M 4.3 aftershock recording of the 2008 Wells earthquake sequence in Nevada. Given a wide range of recording distances from 29 to 320 km, the data provide a unique opportunity to discriminate scattering models based on their distance‐dependent behaviors. First, we develop a stable numerical procedure to simulate nonisotropic scattering waves based on the 3D nonisotropic scattering theory proposed by Sato (1995). By applying the simulation method to the inversion of M 4.3 Wells aftershock recordings, we find that a nonisotropic scattering model, dominated by forward scattering, provides the best fit to the observed high‐frequency direct S waves and S‐wave coda velocity envelopes. The scattering process is governed by a Gaussian autocorrelation function, suggesting a Gaussian random heterogeneous structure for the Nevada crust. The model successfully explains the common decay of seismic coda independent of source–station locations as a result of energy leaking from multiple strong forward scattering, instead of backscattering governed by the diffusion solution at large lapse times. The model also explains the pulse‐broadening effect in the high‐frequency direct and early arriving S waves, as other studies have found, and could be very important to applications of high‐frequency wave simulation in which scattering has a strong effect. We also find that regardless of its physical implications, the isotropic scattering model provides the same effective scattering coefficient and intrinsic attenuation estimates as the forward scattering model, suggesting that the isotropic scattering model is still a viable tool for the study of seismic scattering and intrinsic attenuation coefficients in the Earth.

  13. Frequency-dependent responses in third generation gravitational-wave detectors

    Science.gov (United States)

    Essick, Reed; Vitale, Salvatore; Evans, Matthew

    2017-10-01

    Interferometric gravitational-wave detectors are dynamic instruments. Changing gravitational-wave strains influence the trajectories of null geodesics and therefore modify the interferometric response. These effects will be important when the associated frequencies are comparable to the round-trip light travel time down the detector arms. The arms of advanced detectors currently in operation are short enough that the strain can be approximated as static, but planned 3rd generation detectors, with arms an order of magnitude longer, will need to account for these effects. We investigate the impact of neglecting the frequency-dependent detector response for compact binary coalescences and show that it can introduce large systematic biases in localization, larger than the statistical uncertainty for 1.4 -1.4 M⊙ neutron star coalescences at z ≲1.7 . Analysis of 3rd generation detectors therefore must account for these effects.

  14. Inverted pendulum as low-frequency pre-isolation for advanced gravitational wave detectors

    Energy Technology Data Exchange (ETDEWEB)

    Takamori, A. [University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan); Raffai, P. [Eoetvoes Lorand University, Budapest 1117 (Hungary)], E-mail: praffai@bolyai.elte.hu; Marka, S. [Columbia University in the City of New York, New York, NY 10027 (United States); DeSalvo, R.; Sannibale, V.; Tariq, H. [California Institute of Technology, Pasadena, CA 91125 (United States); Bertolini, A. [Deutsches Elektronen-Synchrotron, Hamburg 22607 (Germany); Cella, G. [Dipartmento di Fisica, Universita di Pisa, Pisa (Italy); Viboud, N. [Institut National des Sciences Apliquee at Lyon, Lyon (France); Numata, K. [University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan); Takahashi, R.; Fukushima, M. [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2007-11-21

    We have developed advanced seismic attenuation systems for Gravitational Wave (GW) detectors. The design consists of an Inverted Pendulum (IP) holding stages of Geometrical Anti-Spring Filters (GASF) and pendula, which isolate the test mass suspension from ground noise. The ultra-low-frequency IP suppresses the horizontal seismic noise, while the GASF suppresses the vertical ground vibrations. The three legs of the IP are supported by cylindrical maraging steel flexural joints. The IP can be tuned to very low frequencies by carefully adjusting its load. As a best result, we have achieved an ultra low, {approx}12 mHz pendulum frequency for the system prototype made for Advanced LIGO (Laser Interferometer Gravitational Wave Observatory). The measured quality factor, Q, of this IP, ranging from Q{approx}2500 (at 0.45 Hz) to Q{approx}2 (at 12 mHz), is compatible with structural damping, and is proportional to the square of the pendulum frequency. Tunable counterweights allow for precise center-of-percussion tuning to achieve the required attenuation up to the first leg internal resonance ({approx}60 Hz for advanced LIGO prototype). All measurements are in good agreement with our analytical models. We therefore expect good attenuation in the low-frequency region, from {approx}0.1to {approx}50 Hz, covering the micro-seismic peak. The extremely soft IP requires minimal control force, which simplifies any needed actuation.

  15. Spectral element method for elastic and acoustic waves in frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Linlin; Zhou, Yuanguo; Wang, Jia-Min; Zhuang, Mingwei [Institute of Electromagnetics and Acoustics, and Department of Electronic Science, Xiamen, 361005 (China); Liu, Na, E-mail: liuna@xmu.edu.cn [Institute of Electromagnetics and Acoustics, and Department of Electronic Science, Xiamen, 361005 (China); Liu, Qing Huo, E-mail: qhliu@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC, 27708 (United States)

    2016-12-15

    Numerical techniques in time domain are widespread in seismic and acoustic modeling. In some applications, however, frequency-domain techniques can be advantageous over the time-domain approach when narrow band results are desired, especially if multiple sources can be handled more conveniently in the frequency domain. Moreover, the medium attenuation effects can be more accurately and conveniently modeled in the frequency domain. In this paper, we present a spectral-element method (SEM) in frequency domain to simulate elastic and acoustic waves in anisotropic, heterogeneous, and lossy media. The SEM is based upon the finite-element framework and has exponential convergence because of the use of GLL basis functions. The anisotropic perfectly matched layer is employed to truncate the boundary for unbounded problems. Compared with the conventional finite-element method, the number of unknowns in the SEM is significantly reduced, and higher order accuracy is obtained due to its spectral accuracy. To account for the acoustic-solid interaction, the domain decomposition method (DDM) based upon the discontinuous Galerkin spectral-element method is proposed. Numerical experiments show the proposed method can be an efficient alternative for accurate calculation of elastic and acoustic waves in frequency domain.

  16. Low frequency energy scavenging using sub-wave length scale acousto-elastic metamaterial

    Directory of Open Access Journals (Sweden)

    Riaz U. Ahmed

    2014-11-01

    Full Text Available This letter presents the possibility of energy scavenging (ES utilizing the physics of acousto-elastic metamaterial (AEMM at low frequencies (<∼3KHz. It is proposed to use the AEMM in a dual mode (Acoustic Filter and Energy Harvester, simultaneously. AEMM’s are typically reported for filtering acoustic waves by trapping or guiding the acoustic energy, whereas this letter shows that the dynamic energy trapped inside the soft constituent (matrix of metamaterials can be significantly harvested by strategically embedding piezoelectric wafers in the matrix. With unit cell AEMM model, we experimentally asserted that at lower acoustic frequencies (< ∼3 KHz, maximum power in the micro Watts (∼35µW range can be generated, whereas, recently reported phononic crystal based metamaterials harvested only nano Watt (∼30nW power against 10KΩ resistive load. Efficient energy scavengers at low acoustic frequencies are almost absent due to large required size relevant to the acoustic wavelength. Here we report sub wave length scale energy scavengers utilizing the coupled physics of local, structural and matrix resonances. Upon validation of the argument through analytical, numerical and experimental studies, a multi-frequency energy scavenger (ES with multi-cell model is designed with varying geometrical properties capable of scavenging energy (power output from ∼10µW – ∼90µW between 0.2 KHz and 1.5 KHz acoustic frequencies.

  17. Spectral element method for elastic and acoustic waves in frequency domain

    Science.gov (United States)

    Shi, Linlin; Zhou, Yuanguo; Wang, Jia-Min; Zhuang, Mingwei; Liu, Na; Liu, Qing Huo

    2016-12-01

    Numerical techniques in time domain are widespread in seismic and acoustic modeling. In some applications, however, frequency-domain techniques can be advantageous over the time-domain approach when narrow band results are desired, especially if multiple sources can be handled more conveniently in the frequency domain. Moreover, the medium attenuation effects can be more accurately and conveniently modeled in the frequency domain. In this paper, we present a spectral-element method (SEM) in frequency domain to simulate elastic and acoustic waves in anisotropic, heterogeneous, and lossy media. The SEM is based upon the finite-element framework and has exponential convergence because of the use of GLL basis functions. The anisotropic perfectly matched layer is employed to truncate the boundary for unbounded problems. Compared with the conventional finite-element method, the number of unknowns in the SEM is significantly reduced, and higher order accuracy is obtained due to its spectral accuracy. To account for the acoustic-solid interaction, the domain decomposition method (DDM) based upon the discontinuous Galerkin spectral-element method is proposed. Numerical experiments show the proposed method can be an efficient alternative for accurate calculation of elastic and acoustic waves in frequency domain.

  18. Identification of low-frequency kinetic wave modes in the Earth's ion foreshock

    Directory of Open Access Journals (Sweden)

    X. Blanco-Cano

    1997-03-01

    Full Text Available In this work we use ion and magnetic field data from the AMPTE-UKS mission to study the characteristics of low frequency (ωr « Ωp waves observed upstream of the Earth's bow shock. We test the application of various plasma-field correlations and magnetic ratios derived from linear Vlasov theory to identify the modes in this region. We evaluate (for a parameter space consistent with the ion foreshock the Alfvén ratio, the parallel compressibility, the cross-helicity, the noncoplanar ratio, the magnetic compression and the polarization for the two kinetic instabilities that can be generated in the foreshock by the interaction of hot diffuse ions with the solar wind: the left-hand resonant and the right-hand resonant ion beam instabilities. Comparison of these quantities with the observed plasma-field correlations and various magnetic properties of the waves observed during 10 intervals on 30 October 1984, where the waves are associated with diffuse ions, allows us to identify regions with Alfvénic waves and regions where the predominant mode is the right-hand resonant instability. In all the cases the waves are transverse, propagating at angles ≤ 33° and are elliptically polarized. Our results suggest that while the observed Alfvén waves are generated locally by hot diffuse ions, the right-handed waves may result from the superposition of waves generated by two different types of beam distribution (i.e. cold beam and diffuse ions. Even when there was good agreement between the values of observed transport ratios and the values given by the theory, some discrepancies were found. This shows that the observed waves are different from the theoretical modes and that mode identification based only on polarization quantities does not give a complete picture of the waves' characteristics and can lead to mode identification of waves whose polarization may agree with theoretical predictions even when other properties can diverge from those of the

  19. Identification of low-frequency kinetic wave modes in the Earth's ion foreshock

    Directory of Open Access Journals (Sweden)

    X. Blanco-Cano

    Full Text Available In this work we use ion and magnetic field data from the AMPTE-UKS mission to study the characteristics of low frequencyr « Ωp waves observed upstream of the Earth's bow shock. We test the application of various plasma-field correlations and magnetic ratios derived from linear Vlasov theory to identify the modes in this region. We evaluate (for a parameter space consistent with the ion foreshock the Alfvén ratio, the parallel compressibility, the cross-helicity, the noncoplanar ratio, the magnetic compression and the polarization for the two kinetic instabilities that can be generated in the foreshock by the interaction of hot diffuse ions with the solar wind: the left-hand resonant and the right-hand resonant ion beam instabilities. Comparison of these quantities with the observed plasma-field correlations and various magnetic properties of the waves observed during 10 intervals on 30 October 1984, where the waves are associated with diffuse ions, allows us to identify regions with Alfvénic waves and regions where the predominant mode is the right-hand resonant instability. In all the cases the waves are transverse, propagating at angles ≤ 33° and are elliptically polarized. Our results suggest that while the observed Alfvén waves are generated locally by hot diffuse ions, the right-handed waves may result from the superposition of waves generated by two different types of beam distribution (i.e. cold beam and diffuse ions. Even when there was good agreement between the values of observed transport ratios and the values given by the theory, some discrepancies were found. This shows that the observed waves are different from the theoretical modes and that mode identification based only on polarization quantities does not give a complete picture of the waves' characteristics and can lead to mode identification of waves whose polarization may agree with theoretical predictions even when

  20. One dimensional full wave analysis of slow-to-fast mode conversion in lower hybrid frequencies

    Science.gov (United States)

    Jia, Guo-Zhang; Gao, Zhe

    2014-12-01

    The linear conversion from the slow wave to the fast wave in the lower hybrid range of frequencies is analyzed numerically by using the set of field equations describing waves in a cold plane-stratified plasma. The equations are solved as a two-point boundary value problem, where the polarizations of each mode are set consistently in the boundary conditions. The scattering coefficients and the field patterns are obtained for various density profiles. It is shown that, for large density scale length, the results agree well with the traditional cognitions. In contrast, the reflected component and the probable transmitted-converted component from the conversion region, which are neglected in the usual calculations, become significant when the scale length is smaller than the wavelength of the mode. The inclusion of these new components will improve the accuracy of the simulated propagation and deposition for the injected rf power when the conversion process is involved within a sharp-varying density profile. Meanwhile, the accessibility of the incident slow wave for the low frequency case is also affected by the scale length of the density profile.

  1. Signal photon flux generated by high-frequency relic gravitational waves

    CERN Document Server

    Li, Xin; Wen, Hao

    2015-01-01

    The power spectrum of primordial tensor perturbations $\\mathcal{P}_t$ increases rapidly in high frequency region if the spectral index $n_t>0$. It is shown that the amplitude of relic gravitational wave $h_t$($5\\times10^9$Hz) varies from $10^{-36}$ to $10^{-25}$ while $n_t$ varies from $-6.25\\times 10^{-3}$ to $0.87$. High frequency gravitational waves detector that is proposed by F.-Y. Li detects gravitational waves through observing the perturbed photon flux that is generated by interaction between the relic gravitational waves and electromagnetic system. It is shown that the perturbative photon flux $N_x^1$($5\\times10^9$Hz) varies from $1.40\\times10^{-4}\\rm s^{-1}$ to $2.85\\times10^{7}\\rm s^{-1}$ while $n_t$ varies from $-6.25\\times 10^{-3}$ to $0.87$. Correspondingly, the ratio of the transverse perturbative photon flux $N_x^1$ to the background photon flux varies from $10^{-28}$ to $10^{-16}$.

  2. Links between extremely high frequency electromagnetic waves and their biological manifestations

    Directory of Open Access Journals (Sweden)

    Anton Emil

    2015-01-01

    Full Text Available In this mini-review, we describe some of the latest facts regarding the generation of condensed base phonons by biological entities, initially described by the renowned contemporary physicist, Nobel laureate, Herbert Fröhlich, who proposed a new biophysical interaction mechanism between extremely high frequency electromagnetic waves and the biological environment. As we will show, this extremely low intensity millimeter therapy crystallizes as an important new method, universal and effective in the management of diseases with different etiologies. Moreover, the existence of internal electromagnetic fields generated by biological entities, as well as external electromagnetic fields, are essential for understanding the electromagnetic-biological effect. In fact, it is estimated that at present millimeter-wave therapy is used for the management of more than 120 diseases in cardiology, neurology, oncology, gynecology, urology, gastroenterology, surgery, pharmacology and pediatrics. However, so far there is still no consensus regarding the interaction between extremely high frequency/extremely low intensity electromagnetic waves and the biological environment at its different levels of organization. Thus, the present paper was intended to contribute to the development for the theory of millimeter-wave interaction with living biological entities.

  3. Frequency degeneracy of acoustic waves in two-dimensional phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Darinskii, A N [Institute of Crystallography RAS, Leninskiy pr. 59, Moscow, 119333 (Russian Federation); Le Clezio, E [Universite Francois Rabelais de Tours, ENI Val de Loire, LUSSI, FRE CNRS 2448, rue de la Chocolaterie, BP3410, 41034 Blois (France); Feuillard, G [Universite Francois Rabelais de Tours, ENI Val de Loire, LUSSI, FRE CNRS 2448, rue de la Chocolaterie, BP3410, 41034 Blois (France)

    2007-12-15

    Degeneracies of acoustic wave spectra in 2D phononic crystals (PC) and PC slabs are studied. A PC structure is constituted of parallel steel rods immersed into water and forming the quadratic lattice. Given the projection k{sub z} of the wave vector on the direction of rods, the bulk wave spectrum of the infinite PC is a set of frequency surfaces f{sub i}(k{sub x}, k{sub y}), i = 1,2,..., where k{sub x,y} are the components of the wave vector in the plane perpendicular to the rods. An investigation is performed of the shape of frequency surfaces in the vicinity of points (k{sub dx}, k{sub dy}), where these surfaces fall into contact. In addition, the evolution of the degeneracy with changing rod radius and cross-section shape is examined. Degeneracy in the spectrum of leaky modes propagating along a single waveguide in a PC slab is also investigated.

  4. Climate change and heat and cold wave frequencies for different locations in Europe

    Science.gov (United States)

    Parey, Sylvie; Thu Huong Hoang, Thi; Dacunha-Castelle, Didier

    2014-05-01

    Heat and cold waves are important meteorological events related to electricity production and consumption. Therefore, we developed a stochastic model for temperature able to correctly reproduce extreme events and this tool can be used to downscale climate model simulations. As a matter of fact, the stochastic model simulates the residues after removing trends and seasonalities in the mean and the variance of temperature time-series. Thus, once the model has been calibrated on an observed time-series, future time series can be re-constructed from the modelled residues and the trends and seasonalities given by any climate model simulation, suitably corrected. This technique allows increasing the number of temperature time-series in order to infer the significance of possible changes. When applied to study the frequency changes of heat or cold waves of different lengths, from 1 day to more than 15 days, preliminary results have shown that the changes are significant only for very long heat or cold waves in the near future. This first analysis will be extended to further locations in Europe and future time periods, using the CMIP5 simulation results of different climate models, in order to check the robustness of such results and to further investigate possible changes in the frequencies of heat and cold waves. The presentation will thus describe the used methodology and detail the main results obtained when applied for different temperature time-series.

  5. Frequency conversion through spontaneous degenerate four wave mixing in large mode area hybrid photonic crystal fibers

    DEFF Research Database (Denmark)

    Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Olausson, Christina Bjarnal Thulin

    2014-01-01

    Frequency conversion through spontaneous degenerate four wave mixing (FWM) is investigated in large mode area hybrid photonic crystal fibers. Different FWM processes are observed, phasematching between fiber modes of orthogonal polarization, intermodal phasematching across bandgaps, and intramoda...... phasematching within the same transmission band as the one containing the pump laser. Furthermore first and second order Raman scattering is observed. The interplay between the different FWM processes and Raman scattering are investigated....

  6. Nanoliter-droplet acoustic streaming via ultra high frequency surface acoustic waves.

    Science.gov (United States)

    Shilton, Richie J; Travagliati, Marco; Beltram, Fabio; Cecchini, Marco

    2014-08-06

    The relevant length scales in sub-nanometer amplitude surface acoustic wave-driven acoustic streaming are demonstrated. We demonstrate the absence of any physical limitations preventing the downscaling of SAW-driven internal streaming to nanoliter microreactors and beyond by extending SAW microfluidics up to operating frequencies in the GHz range. This method is applied to nanoliter scale fluid mixing. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Monolithic watt-level millimeter-wave diode-grid frequency tripler array

    Science.gov (United States)

    Hwu, R. J.; Luhmann, N. C., Jr.; Rutledge, D. B.; Hancock, B.; Lieneweg, U.

    1988-01-01

    In order to provide watt-level CW output power throughout the millimeter and submillimeter wave region, thousands of solid-state diodes have been monolithically integrated using a metal grid to produce a highly efficient frequency multiplier. Devices considered include GaAs Schottky diodes, thin MOS diodes, and GaAs Barrier-Intrinsic-N(+)diodes. The performance of the present compact low-cost device has been theoretically and experimentally validated.

  8. Chirp Z transform based enhanced frequency resolution for depth resolvable non stationary thermal wave imaging

    Science.gov (United States)

    Suresh, B.; Subhani, Sk.; Vijayalakshmi, A.; Vardhan, V. H.; Ghali, V. S.

    2017-01-01

    This paper proposes a novel post processing modality to enhance depth resolution in frequency modulated thermal wave imaging using chirp Z transform. It explores the spectral zooming feature of the proposed modality to enhance depth resolution and validates it through the experimentation carried over a carbon fiber reinforced plastic and mild steel specimens. Further, defect detection capability of the proposed modality has been compared with that of the other contemporary modalities by taking the defect signal to noise ratio into consideration.

  9. Frequency Modulated Continuous Wave RADAR for Objects Mapping in Enclosed Spaces Using Smartphones and Arduino Components

    Science.gov (United States)

    Bar-Magen Numhauser, Jonathan; Zalevsky, Zeev

    2017-06-01

    Based on previous studies and using mobile portable device, we were able to realize a portable system capable of detecting metallic objects in a room surrounded by walls while also extracting the approximate position of such objects. Our hardware included only a smartphone device connected to several Arduino components and we were applying frequency-modulated continuous-wave electronics in each of the Arduino devices.

  10. Enhanced Next Generation Millimeter-Wave Multicarrier System with Generalized Frequency Division Multiplexing

    Directory of Open Access Journals (Sweden)

    Hidekazu Shimodaira

    2016-01-01

    Full Text Available Orthogonal Frequency Division Multiplexing (OFDM is a popular multicarrier technique used to attain high spectral efficiencies. It also has other advantages such as multipath tolerance and ease of implementation. However, OFDM based systems suffer from high Peak-to-Average Power Ratio (PAPR problem. Because of the nonlinearity of the power amplifiers, the high PAPR causes significant distortion in the transmitted signal for millimeter-wave (mmWave systems. To alleviate the high PAPR problem, this paper utilizes Generalized Frequency Division Multiplexing (GFDM which can achieve high spectral efficiency as well as low PAPR. In this paper, we show the performance of GFDM using the IEEE 802.11ad multicarrier frame structures. IEEE 802.11ad is considered one of the most successful industry standards utilizing unlicensed mmWave frequency band. In addition, this paper indicates the feasibility of using GFDM for the future standards such as IEEE 802.11ay. This paper studies the performance improvements in terms of PAPR reduction for GFDM. Based on the performance results, the optimal numbers of subcarriers and subsymbols are calculated for PAPR reduction while minimizing the Bit Error Rate (BER performance degradation. Moreover, transmitter side ICI (Intercarrier Interference reduction is introduced to reduce the receiver load.

  11. The effects of frequency on the elastic wave velocity in rocks at high temperatures under pressure

    Science.gov (United States)

    Matsushima, S.

    1986-04-01

    P- and S-wave velocities in nepheline basalt, Hamada, as well as diabase, Maryland, were measured experimentally to 1000°C and 2.5 GPa. A remarkable frequency dependence of large velocity-decrease was observed for both P- and S-waves at temperatures above 500°C. Remarkable velocity-characteristics, which cannot be explained by the existing theories, were: (1) Velocities were decreased considerably at 1-3 MHz. Above 3 MHz, samples showed elastic behavior like that of a perfect solid, and below 1 MHz, velocity-decrease decayed gradually. (2) Both P- and S-wave velocities decreased in the same way and almost to the same degree. (3) The higher the temperature, the more remarkably velocities decreased, at least up to the experimental limit temperature. A hypothesis of the relaxation of stress waves by the fluid-flow in the inclusions is proposed. Examples of geophysical applications are given for the attenuation and travel-time anomalies in the volcanic region and the P- and S-wave velocity-decrease in the upper mantle beneath continents.

  12. 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.

  13. Mechanical properties of viscoelastic media by local frequency estimation of divergence-free wave fields.

    Science.gov (United States)

    Clayton, Erik H; Okamoto, Ruth J; Bayly, Philip V

    2013-02-01

    Magnetic resonance elastography (MRE) is an imaging modality with which mechanical properties can be noninvasively measured in living tissue. Magnetic resonance elastography relies on the fact that the elastic shear modulus determines the phase velocity and, hence the wavelength, of shear waves which are visualized by motion-sensitive MR imaging. Local frequency estimation (LFE) has been used to extract the local wavenumber from displacement wave fields recorded by MRE. LFE -based inversion is attractive because it allows material parameters to be estimated without explicitly invoking the equations governing wave propagation, thus obviating the need to numerically compute the Laplacian. Nevertheless, studies using LFE have not explicitly addressed three important issues: (1) tissue viscoelasticity; (2) the effects of longitudinal waves and rigid body motion on estimates of shear modulus; and (3) mechanical anisotropy. In the current study we extend the LFE technique to (1) estimate the (complex) viscoelastic shear modulus in lossy media; (2) eliminate the effects of longitudinal waves and rigid body motion; and (3) determine two distinct shear moduli in anisotropic media. The extended LFE approach is demonstrated by analyzing experimental data from a previously-characterized, isotropic, viscoelastic, gelatin phantom and simulated data from a computer model of anisotropic (transversely isotropic) soft material.

  14. Water-waves frequency upshift of the spectral mean due to wind forcing

    Science.gov (United States)

    Eeltink, Debbie; Chabchoub, Amin; Brunetti, Maura; Kasparian, Jerome; Kimmoun, Olivier; Branger, Hubert

    2017-04-01

    The effect of wind forcing on monochromatic modulated water waves was investigated both numerically and experimentally in the context of the Modified Non-Linear Schrödinger (MNLS) equation framework. While wind is usually associated with a frequency downshift of the dominant spectral peak, we show that it may induce an upshift of the spectral mean due to an asymmetric amplification of the spectrum. Here the weighted average spectral mean is equal to the ratio of the momentum of the envelope to its norm and it detects any asymmetries in the spectrum (Segur et al. 2005). Wind can however indirectly induce frequency downshifts, by promoting dissipative effects like wave breaking. We highlight that the definition of the up- and downshift in terms of peak frequency or average frequency is critical for a relevant discussion. In our model, the wind input consists of a leading order forcing term that amplifies all frequencies equally and induces a broadening of the spectrum, and a higher order asymmetric term (Brunetti et al. 2014; Brunetti & Kasparian 2014) that amplifies higher frequencies more than lower ones and induces a permanent upshift of the spectral mean. The effect of MNLS + wind is exactly opposite to MNLS + viscosity, where the lower order viscosity terms damp the whole spectrum, while the higher order viscosity terms damp higher frequencies more than lower ones and thus causes a permanent downshift, as evidenced by Carter & Govan (2016). We corroborated the model with wave tank experiments conducted in the IRPHE/Pytheas large wind-wave facility located in Marseille, France. Wave data analysis show the temporary downshift in the spectral peak sense caused by the wind, and the temporary upshift in the spectral mean sense characteristic of the MNLS. As the tank-length was limited, we used long-range simulations to obtain upshift in the spectral mean sense caused by the wind. The limit of the model is reached when breaking events occur. We acknowledge financial

  15. Alpha-wave frequency characteristics in health and insomnia during sleep.

    Science.gov (United States)

    Schwabedal, Justus T C; Riedl, Maik; Penzel, Thomas; Wessel, Niels

    2016-06-01

    Appearances of alpha waves in the sleep electrencephalogram indicate physiological, brief states of awakening that lie in between wakefulness and sleep. These microstates may also cause the loss in sleep quality experienced by individuals suffering from insomnia. To distinguish such pathological awakenings from physiological ones, differences in alpha-wave characteristics between transient awakening and wakefulness observed before the onset of sleep were studied. In polysomnographic datasets of sleep-healthy participants (n = 18) and patients with insomnia (n = 10), alpha waves were extracted from the relaxed, wake state before sleep onset, wake after sleep-onset periods and arousals of sleep. In these, alpha frequency and variability were determined as the median and standard deviation of inverse peak-to-peak intervals. Before sleep onset, patients with insomnia showed a decreased alpha variability compared with healthy participants (P sleep onset, both groups showed patterns of decreased alpha frequency that was lower for wake after sleep-onset periods of shorter duration. For patients with insomnia, alpha variability increased for short wake after sleep-onset periods. Major differences between the two groups were encountered during arousal. In particular, the alpha frequency in patients with insomnia rebounded to wake levels, while the frequency in healthy participants remained at the reduced level of short wake after sleep-onset periods. Reductions in alpha frequency during wake after sleep-onset periods may be related to the microstate between sleep and wakefulness that was described for such brief awakenings. Reduced alpha variability before sleep may indicate a dysfunction of the alpha generation mechanism in insomnia. Alpha characteristics may also prove valuable in the study of other sleep and attention disorders. © 2016 European Sleep Research Society.

  16. Frequency variations of gravity waves interacting with a time-varying tide

    Directory of Open Access Journals (Sweden)

    C. M. Huang

    2013-10-01

    Full Text Available Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative accelerations induce frequency increases (decreases with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

  17. Frequency variations of gravity waves interacting with a time-varying tide

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.M.; Zhang, S.D.; Yi, F.; Huang, K.M.; Gan, Q.; Gong, Y. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan, Hubei (China); Zhang, Y.H. [Nanjing Univ. of Information Science and Technology (China). College of Hydrometeorolgy

    2013-11-01

    Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when aGW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal-GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

  18. Observations of wave transformation over a fringing coral reef and the importance of low-frequency waves and offshore water levels to runup, overwash, and coastal flooding

    Science.gov (United States)

    Cheriton, Olivia; Storlazzi, Curt; Rosenberger, Kurt

    2016-01-01

    Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

  19. Validation of HFCS-I on Calculation of High-Frequency Parameters of Helical Slow-Wave Structures

    Science.gov (United States)

    Zhu, Xiaofang; Yang, Zhonghai; Li, Bin; Li, Jianqing; Xu, Li

    2010-02-01

    To validate HFCS-I, a newly developed design tool for high frequency circuits of microwave tubes, the high-frequency parameters (including dispersion, interaction impedance and attenuation constant) of a typical helical slow-wave structure (SWS) for millimetre wave travelling-wave tube are calculated by HFCS-I and MAFIA. Both the direct calculation method and the Non-Resonant Perturbation (NRP) technique are adopted to get the interaction impedance. The obtained high-frequency parameters from HFCS-I and MAFIA are compared in detail and the consistency has proved the reliability and validity of HFCS-I.

  20. Quasi-B-mode generated by high-frequency gravitational waves and corresponding perturbative photon fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fangyu, E-mail: cqufangyuli@hotmail.com [Institute of Gravitational Physics, Department of Physics, Chongqing University, Chongqing 400044 (China); Wen, Hao [Institute of Gravitational Physics, Department of Physics, Chongqing University, Chongqing 400044 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Fang, Zhenyun [Institute of Gravitational Physics, Department of Physics, Chongqing University, Chongqing 400044 (China); Wei, Lianfu; Wang, Yiwen; Zhang, Miao [Quantum Optoelectronics Laboratory, Southwest Jiaotong University, Chengdu 610031 (China)

    2016-10-15

    Interaction of very low-frequency primordial (relic) gravitational waves (GWs) to cosmic microwave background (CMB) can generate B-mode polarization. Here, for the first time we point out that the electromagnetic (EM) response to high-frequency GWs (HFGWs) would produce quasi-B-mode distribution of the perturbative photon fluxes. We study the duality and high complementarity between such two B-modes, and it is shown that such two effects are from the same physical origin: the tensor perturbation of the GWs and not the density perturbation. Based on this quasi-B-mode in HFGWs and related numerical calculation, it is shown that the distinguishing and observing of HFGWs from the braneworld would be quite possible due to their large amplitude, higher frequency and very different physical behaviors between the perturbative photon fluxes and background photons, and the measurement of relic HFGWs may also be possible though face to enormous challenge.

  1. Quasi-B-mode generated by high-frequency gravitational waves and corresponding perturbative photon fluxes

    Directory of Open Access Journals (Sweden)

    F.Y. Fangyu Li

    2016-10-01

    Full Text Available Interaction of very low-frequency primordial (relic gravitational waves (GWs to cosmic microwave background (CMB can generate B-mode polarization. Here, for the first time we point out that the electromagnetic (EM response to high-frequency GWs (HFGWs would produce quasi-B-mode distribution of the perturbative photon fluxes. We study the duality and high complementarity between such two B-modes, and it is shown that such two effects are from the same physical origin: the tensor perturbation of the GWs and not the density perturbation. Based on this quasi-B-mode in HFGWs and related numerical calculation, it is shown that the distinguishing and observing of HFGWs from the braneworld would be quite possible due to their large amplitude, higher frequency and very different physical behaviors between the perturbative photon fluxes and background photons, and the measurement of relic HFGWs may also be possible though face to enormous challenge.

  2. Dual-frequency continuous-wave terahertz transmission imaging of nonmelanoma skin cancers

    Science.gov (United States)

    Joseph, Cecil S.; Yaroslavsky, Anna N.; Lagraves, Julie L.; Goyette, Thomas M.; Giles, Robert H.

    2010-02-01

    Continuous wave terahertz imaging has the potential for diagnosing and delineating skin cancers. While contrast has been observed between cancerous and normal tissue at terahertz frequencies, the source mechanism behind this contrast is not clearly understood.1Transmission measurements of 240μm thick sections of nonmelanoma skin cancer were taken at two frequencies of 1.39 THz and 1.63 THz that lie within and outside the tryptophan absorption band, respectively. Two CO2 pumped Far-Infrared molecular gas lasers were used for illuminating the tissue while the transmitted signals were detected using a liquid Helium cooled Silicon bolometer. At both THz frequencies 2-dimensional THz transmission images of nonmelanoma skin cancers were acquired with better than 0.5mm spatial resolution. The resulting images were compared to the sample histology and showed a correlation between cancerous tissue and decreased transmission. The results of the imaging experiments will be presented and discussed.

  3. Optimal Vagus Nerve Stimulation Frequency for Suppression of Spike-and-Wave Seizures in Rats.

    Science.gov (United States)

    Jiao, Jianhang; Harreby, Kristian R; Sevcencu, Cristian; Jensen, Winnie

    2016-06-01

    Vagus nerve stimulation (VNS) is used as an adjunctive therapy for drug-resistant epilepsy and results in a 50% seizure reduction in up to 50% of treated patients. The VNS frequency used in the clinic today is in the range of 10-30 Hz. The evidence for choosing the stimulation frequency is limited, and little knowledge is available on the effect of other VNS frequencies. Deep brain, trigeminal nerve, or spinal cord stimulation studies have suggested the use of stimulation frequencies above 80 Hz for seizure control. Therefore, our objective for the present study was to investigate if VNS using frequencies higher than those currently used in the clinic could be more effective in attenuating seizures. Spike-and-wave (SW) discharges were induced in 11 rats, which then were subjected to VNS sessions applied at the frequencies of 10, 30, 80, 130, and 180 Hz combined with control intervals without stimulation. The anticonvulsive effect of VNS was evaluated by comparing the normalized mean power (nMP) and frequency (nMSF) of the SW discharges derived from intracortical recordings collected during the stimulation and control intervals. Compared with the control intervals, all the tested VNS frequencies significantly reduced the nMP (in the range of 9-21%). However, we found that 130 and 180 Hz VNS induced a 50% larger attenuation of seizures than that achieved by 30 Hz VNS. In addition, we found that 80, 130, and 180 Hz VNS induced a significant reduction of the nMSF, that is by 5, 7, and 8%, respectively. These results suggest that a VNS stimulation frequency in the range of 130-180 Hz may be more effective in inhibiting seizures than the 30 Hz VNS applied in the clinic today. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  4. Computational studies on scattering of radio frequency waves by density filaments in fusion plasmas

    Science.gov (United States)

    Ioannidis, Zisis C.; Ram, Abhay K.; Hizanidis, Kyriakos; Tigelis, Ioannis G.

    2017-10-01

    In modern magnetic fusion devices, such as tokamaks and stellarators, radio frequency (RF) waves are commonly used for plasma heating and current profile control, as well as for certain diagnostics. The frequencies of the RF waves range from ion cyclotron frequency to the electron cyclotron frequency. The RF waves are launched from structures, like waveguides and current straps, placed near the wall in a very low density, tenuous plasma region of a fusion device. The RF electromagnetic fields have to propagate through this scrape-off layer before coupling power to the core of the plasma. The scrape-off layer is characterized by turbulent plasmas fluctuations and by blobs and filaments. The variations in the edge density due to these fluctuations and filaments can affect the propagation characteristics of the RF waves—changes in density leading to regions with differing plasma permittivity. Analytical full-wave theories have shown that scattering by blobs and filaments can alter the RF power flow into the core of the plasma in a variety of ways, such as through reflection, refraction, diffraction, and shadowing [see, for example, Ram and Hizanidis, Phys. Plasmas 23, 022504 (2016), and references therein]. There are changes in the wave vectors and the distribution of power-scattering leading to coupling of the incident RF wave to other plasma waves, side-scattering, surface waves, and fragmentation of the Poynting flux in the direction towards the core. However, these theoretical models are somewhat idealized. In particular, it is assumed that there is step-function discontinuity in the density between the plasma inside the filament and the background plasma. In this paper, results from numerical simulations of RF scattering by filaments using a commercial full-wave code are described. The filaments are taken to be cylindrical with the axis of the cylinder aligned along the direction of the ambient magnetic field. The plasma inside and outside the filament is

  5. Time-Frequency-Wavenumber Analysis of Surface Waves Using the Continuous Wavelet Transform

    Science.gov (United States)

    Poggi, V.; Fäh, D.; Giardini, D.

    2013-03-01

    A modified approach to surface wave dispersion analysis using active sources is proposed. The method is based on continuous recordings, and uses the continuous wavelet transform to analyze the phase velocity dispersion of surface waves. This gives the possibility to accurately localize the phase information in time, and to isolate the most significant contribution of the surface waves. To extract the dispersion information, then, a hybrid technique is applied to the narrowband filtered seismic recordings. The technique combines the flexibility of the slant stack method in identifying waves that propagate in space and time, with the resolution of f- k approaches. This is particularly beneficial for higher mode identification in cases of high noise levels. To process the continuous wavelet transform, a new mother wavelet is presented and compared to the classical and widely used Morlet type. The proposed wavelet is obtained from a raised-cosine envelope function (Hanning type). The proposed approach is particularly suitable when using continuous recordings (e.g., from seismological-like equipment) since it does not require any hardware-based source triggering. This can be subsequently done with the proposed method. Estimation of the surface wave phase delay is performed in the frequency domain by means of a covariance matrix averaging procedure over successive wave field excitations. Thus, no record stacking is necessary in the time domain and a large number of consecutive shots can be used. This leads to a certain simplification of the field procedures. To demonstrate the effectiveness of the method, we tested it on synthetics as well on real field data. For the real case we also combine dispersion curves from ambient vibrations and active measurements.

  6. On the dispersion law of low-frequency electron whistler waves in a multi-ion plasma

    Directory of Open Access Journals (Sweden)

    B. V. Lundin

    2008-06-01

    Full Text Available A new and simple dispersion law for extra-low-frequency electron whistler waves in a multi-ion plasma is derived. It is valid in a plasma with finite ratio ωc/ωpe of electron gyro-to-plasma frequency and is suitable for wave frequencies much less than ωpe but well above the gyrofrequencies of most heavy ions. The resultant contribution of the ions to the dispersion law is expressed by means of the lower hybrid resonance frequency, the highest ion cutoff frequency and the relative content of the lightest ion. In a frequency domain well above the ions' gyrofrequencies, this new dispersion law merges with the "modified electron whistler dispersion law" determined in previous works by the authors. It is shown that it fits well to the total cold plasma electron whistler dispersion law, for different orientations of the wave vectors and different ion constituents, including negative ions or negatively charged dust grains.

  7. Manipulating waves by distilling frequencies: a tunable shunt-enabled rainbow trap

    Science.gov (United States)

    Cardella, Davide; Celli, Paolo; Gonella, Stefano

    2016-08-01

    In this work, we propose and test a strategy for tunable, broadband wave attenuation in electromechanical waveguides with shunted piezoelectric inclusions. Our strategy is built upon the vast pre-existing literature on vibration attenuation and bandgap generation in structures featuring periodic arrays of piezo patches, but distinguishes itself for several key features. First, we demystify the idea that periodicity is a requirement for wave attenuation and bandgap formation. We further embrace the idea of ‘organized disorder’ by tuning the circuits as to resonate at distinct neighboring frequencies. In doing so, we create a tunable ‘rainbow trap’ (Tsakmakidis et al 2007 Nature 450 397-401) capable of attenuating waves with broadband characteristics, by distilling (sequentially) seven frequencies from a traveling wavepacket. Finally, we devote considerable attention to the implications in terms of packet distortion of the spectral manipulation introduced by shunting. This work is also meant to serve as a didactic tool for those approaching the field of shunted piezoelectrics, and attempts to provide a different perspective, with abundant details, on how to successfully design an experimental setup involving resistive-inductive shunts.

  8. The Impact of Bars and Spiral Density Waves on the Relative Frequencies of Supernovae

    Science.gov (United States)

    Aramyan, L. S.; Hakobyan, A. A.; Petrosian, A. R.; Barkhudaryan, L. V.; Karapetyan, A. G.; Adibekyan, V.; Turatto, M.

    2017-07-01

    We present the results of the analysis of the impact of bars and spiral density waves on the relative frequencies of supernovae (SNe). We find that for early -type Grand-Design (GD) and non-Grand-Design (NGD) galaxies, the NIa/NCC ratios, i.e., one of the tracers of specific star formation rate (sSFR), are not significantly different between barred and unbarred hosts. At the same time, for both barred and unbarred early-type galaxies, the NIa /NCC ratio in NGD hosts is significantly higher than that in GD, and for late-type galaxies no any significant difference exists between the N Ia/NCC ratios. Thus, in contrast to bars, the spiral density waves significantly enhance the relative frequencies of SNe in early-type GD galaxies, while not in late-type hosts. This result is actual also for galaxies when barred and unbarred categories are separated. Hence, the sSFR might be enhanced by density waves in early-type galaxies only.

  9. Millimeter Wave Systems for Airports and Short-Range Aviation Communications: A Survey of the Current Channel Models at mmWave Frequencies

    Science.gov (United States)

    Khatun, Mahfuza; Mehrpouyan, Hani; Matolak, David; Guvenc, Ismail

    2017-01-01

    Millimeter-wave (mmWave) communications will play a key role in enhancing the throughput, reliability, and security of next generation wireless networks. These advancements are achieved through the large bandwidth available in this band and through the use of highly directional links that will be used to overcome the large pathloss at these frequencies. Although the terrestrial application of mmWave systems is advancing at a rapid pace, the use of mmWave communication systems in aviation systems or airports is still in its infancy. This can be attributed to the challenges related to radio technology and lack of development, and characterization of mmWave wireless channels for the aviation field and the airport environment. Consequently, one of our goals is to develop methodologies that support mmWave air to ground links, and various links at airports, by applying new localization schemes that allow for application of highly directional links that can be deployed over longer distances despite the high path loss at mmWave frequencies. However, a very thorough understanding of the mmWave channel models are needed to enable such new applications. To this end, in this paper, we present a survey of the current channel models in the mmWave band. The 3-dimensional statistical channel model is also reviewed and its parameters and typical characteristics for this model are identified and computed through simulation for the Boise metropolitan area.

  10. High frequency computation in wave equations and optimal design for a cavity

    Science.gov (United States)

    Lai, Jun

    Two types of problems are studied in this thesis. One part of the thesis is devoted to high frequency computation. Motivated by fast multiscale Gaussian wavepacket transforms and multiscale Gaussian beam methods which were originally designed for initial value problems of wave equations in the high frequency regime, we develop fast multiscale Gaussian beam methods for wave equations in bounded convex domains in the high frequency regime. To compute the wave propagation in bounded convex domains, we have to take into account reflecting multiscale Gaussian beams, which are accomplished by enforcing reflecting boundary conditions during beam propagation and carrying out suitable reflecting beam summation. To propagate multiscale beams efficiently, we prove that the ratio of the squared magnitude of beam amplitude and the beam width is roughly conserved, and accordingly we propose an effective indicator to identify significant beams. We also prove that the resulting multiscale Gaussian beam methods converge asymptotically. Numerical examples demonstrate the accuracy and efficiency of the method. The second part of the thesis studies the reduction of backscatter radar cross section (RCS) for a cavity embedded in the ground plane. One approach for RCS reduction is through the coating material. Assume the bottom of the cavity is coated by a thin, multilayered radar absorbing material (RAM) with possibly different permittivities. The objective is to minimize the backscatter RCS by the incidence of a plane wave over a single or a set of incident angles and frequencies. By formulating the scattering problem as a Helmholtz equation with artificial boundary condition, the gradient with respect to the material permittivities is determined efficiently by the adjoint state method, which is integrated into a nonlinear optimization scheme. Numerical example shows the RCS may be significantly reduced. Another approach is through shape optimization. By introducing a transparent

  11. Numerical study of sub-millimeter Gunn oscillations in InP and GaN vertical diodes: Dependence on bias, doping, and length

    Science.gov (United States)

    García, S.; Íñiguez-de-la-Torre, I.; Pérez, S.; Mateos, J.; González, T.

    2013-08-01

    In this work, we report on Monte Carlo simulations of InP and GaN vertical Gunn diodes to optimize their oscillation frequency and DC to AC conversion efficiency. We show that equivalent operating conditions are achieved by the direct application of a sinusoidal AC voltage superimposed to the DC bias and by the simulation of the intrinsic device coupled with the consistent solution of a parallel RLC resonant circuit connected in series. InP diodes with active region about 1 μm offer a conversion efficiency up to 5.5% for frequencies around 225 GHz. By virtue of the larger saturation velocity, for a given diode length, oscillation frequencies in GaN diodes are higher than for InP structures. Current oscillations at frequencies as high as 675 GHz, with 0.1% efficiency, are predicted at the sixth generation band in a 0.9 μm-long GaN diode, corroborating the suitability of GaN to operate near the THz band. At the first generation band, structures with notch, in general, provide lower oscillation frequencies and efficiencies in comparison with the same structures without notch. However, a higher number of generation bands are originated in notched diodes, thus, typically reaching larger frequencies. Self-heating effects reduce the performance, but in GaN diodes the efficiency is not significantly degraded.

  12. Sub-harmonic frequency lock-in and vortex shedding synchronization due to regular and irregular surface waves.

    Science.gov (United States)

    Gunnoo, Hans; Abcha, Nizar; Bennis, Anne-claire; Levacher, Daniel

    2017-04-01

    The influence of both regular and irregular surface waves on a turbulent Von Karman vortex street has been investigated experimentally with the help of the phase modulation of the signals. The experiments have been performed in a hydrodynamic flume, where the Von Karman Street created behind a vertical cylinder is created by a steady current. The surface waves propagating upstream are excited by a computer controlled wave maker. It is found that the regular surface wave can give rise to different regimes of vortex shedding in the Von Karman Street: Sub-harmonic frequency lock-in arise if the frequency of the wave is approximately two times that of the vortex shedding frequency. We also observed another regime called harmonic frequency lock-in when the shedding frequency coincides with the frequency of the surface wave. Phase synchronization can also be obtained with irregular surface waves. In this case, the peak frequency of the applied surface wave spectrum is twice that of the vortex shedding frequency. The relationship between the vortex shedding frequency and the amplitude of the surface waves has been studied. It was found that an increase in the amplitude of the applied waves causes the shedding frequency to decrease and tends to half of the frequency of the applied wave. For a more detailed study of this effect, Hilbert transformation is applied. Using this transformation, the continuous phases of the surface waves fw and that of the Von Karman vortex street fk are calculated. The relation between the phases combination F= 2fk- fwand the surface wave amplitude is studied. It was found that the time-evolution of F has a step-like shape. The time interval of F having a slope around 0, corresponds to synchronization-like effect. This explains the changes obtained in the spectrum of the turbulent vortex shedding with an increase in the amplitude of the irregular surface waves. We then decided to compare the evolution of the scouring and the sandy patterns

  13. Low-frequency wave propagation in an elastic plate loaded by a two-layer fluid

    DEFF Research Database (Denmark)

    Indeitsev, Dmitrij; Sorokin, Sergey

    2012-01-01

    In several technical applications, for example, in the Arctic off-shore oil industry, it is necessary to predict waveguide properties of floating elastic plates in contact with a relatively thin layer of water, which has a non-uniform density distribution across its depth. The issue of particular...... of salty water. The former one produces fluid loading at the plate, whereas the latter one is bounded by the sea bottom. We employ classical asymptotic methods to identify significant regimes of wave motion in the compound three-component waveguide. The roles of parameters involved in the problem...... concern is propagation of low-frequency waves in such a coupled waveguide. In the present paper, we assume that an inhomogeneous fluid may be modelled as two homogeneous, inviscid and incompressible layers with slightly different densities. The lighter layer of fresh water lies on top of the heavier layer...

  14. Frequency-domain bridging multiscale method for wave propagation simulations in damaged structures

    Science.gov (United States)

    Casadei, F.; Ruzzene, M.

    2010-03-01

    Efficient numerical models are essential for the simulation of the interaction of propagating waves with localized defects. Classical finite elements may be computationally time consuming, especially when detailed discretizations are needed around damage regions. A multi-scale approach is here propose to bridge a fine-scale mesh defined on a limited region around the defect and a coarse-scale discretization of the entire domain. This "bridging" method is formulated in the frequency domain in order to further reduce the computational cost and provide a general framework valid for different types of structures. Numerical results presented for propagating elastic waves in 1D and 2D damaged waveguides illustrate the proposed technique and its advantages.

  15. Low-frequency waves in a high-beta collisionless plasma Polarization, compressibility and helicity

    Science.gov (United States)

    Gary, S. P.

    1986-01-01

    This paper considers the linear theory of waves near and below the ion cyclotron frequency in an isothermal electron-ion Vlasov plasma which is isotropic, homogeneous and magnetized. Numerical solutions of the full dispersion equation for the magnetosonic/whistler and Alfven/ion cyclotron modes at beta(i) = 1.0 are presented, and the polarizations, compressibilities, helicities, ion Alfven ratios and ion cross-helicities are exhibited and compared. At sufficiently large beta(i) and theta, the angle of propagation with respect to the magnetic field, the real part of the polarization of the Alfven/ion cyclotron wave changes sign, so that, for such parameters, this mode is no longer left-hand polarized. The Alfven/ion cyclotron mode becomes more compressive as the wavenumber increases, whereas the magnetosonic/whistler becomes more compressive with increasing theta.

  16. TEMPERATURE ANISOTROPY IN THE PRESENCE OF ULTRA LOW FREQUENCY WAVES IN THE TERRESTRIAL FORESHOCK

    Energy Technology Data Exchange (ETDEWEB)

    Selzer, L. A.; Hnat, B.; Osman, K. T.; Nakariakov, V. M. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Eastwood, J. P. [Space and Atmospheric Physics, The Blackett Laboratory, Imperial College London, London (United Kingdom); Burgess, D., E-mail: L.A.Selzer@warwick.ac.uk [School of Physics and Astronomy, Queen Mary University of London (United Kingdom)

    2014-06-10

    We report the first study of the correlation between elevated solar wind core plasma temperatures and temperature anisotropy in the terrestrial foreshock. Plasma temperature is enhanced near the fire hose marginal stability threshold in the presence of ultra low frequency (ULF) large amplitude magnetic perturbations, which are intrinsically right-hand circularly polarized. Direct comparison of contemporaneous anisotropic temperatures in the upstream solar wind and the foreshock suggests that the net heating of plasma is mediated via increase of the parallel temperature in the foreshock region where the ULF waves are present. We consider the possibility that a mechanism based on Landau damping, where solar wind plasma temperature parallel to the background magnetic field is increased by interaction with oblique compressible fast magneto-acoustic ULF waves, influences temperature anisotropy.

  17. Temperature Anisotropy in the Presence of Ultra Low Frequency Waves in the Terrestrial Foreshock

    Science.gov (United States)

    Selzer, L. A.; Hnat, B.; Osman, K. T.; Nakariakov, V. M.; Eastwood, J. P.; Burgess, D.

    2014-06-01

    We report the first study of the correlation between elevated solar wind core plasma temperatures and temperature anisotropy in the terrestrial foreshock. Plasma temperature is enhanced near the fire hose marginal stability threshold in the presence of ultra low frequency (ULF) large amplitude magnetic perturbations, which are intrinsically right-hand circularly polarized. Direct comparison of contemporaneous anisotropic temperatures in the upstream solar wind and the foreshock suggests that the net heating of plasma is mediated via increase of the parallel temperature in the foreshock region where the ULF waves are present. We consider the possibility that a mechanism based on Landau damping, where solar wind plasma temperature parallel to the background magnetic field is increased by interaction with oblique compressible fast magneto-acoustic ULF waves, influences temperature anisotropy.

  18. Frequency domain response of a parametrically excited riser under random wave forces

    Science.gov (United States)

    Lei, Song; Zhang, Wen-Shou; Lin, Jia-Hao; Yue, Qian-Jin; Kennedy, D.; Williams, F. W.

    2014-01-01

    Floating Production, Drilling, Storage and Offloading units represent a new technology with a promising future in the offshore oil industry. An important role is played by risers, which are installed between the subsea wellhead and the Tension Leg Deck located in the middle of the moon-pool in the hull. The inevitable heave motion of the floating hull causes a time-varying axial tension in the riser. This time dependent tension may have an undesirable influence on the lateral deflection response of the riser, with random wave forces in the frequency domain. To investigate this effect, a riser is modeled as a Bernoulli-Euler beam. The axial tension is expressed as a static part, along with a harmonic dynamic part. By linearizing the wave drag force, the riser's lateral deflection is obtained through a partial differential equation containing a time-dependent coefficient. Applying the Galerkin method, the equation is reduced to an ordinary differential equation that can be solved using the pseudo-excitation method in the frequency domain. Moreover, the Floquet-Liapunov theorem is used to estimate the stability of the vibration system in the space of parametric excitation. Finally, stability charts are obtained for some numerical examples, the correctness of the proposed method is verified by comparing with Monte-Carlo simulation and the influence of the parametric excitation on the frequency domain responses of the riser is discussed.

  19. Fractional biharmonic operator equation model for arbitrary frequency-dependent scattering attenuation in acoustic wave propagation.

    Science.gov (United States)

    Chen, Wen; Fang, Jun; Pang, Guofei; Holm, Sverre

    2017-01-01

    This paper proposes a fractional biharmonic operator equation model in the time-space domain to describe scattering attenuation of acoustic waves in heterogeneous media. Compared with the existing models, the proposed fractional model is able to describe arbitrary frequency-dependent scattering attenuation, which typically obeys an empirical power law with an exponent ranging from 0 to 4. In stark contrast to an extensive and rapidly increasing application of the fractional derivative models for wave absorption attenuation in the literature, little has been reported on frequency-dependent scattering attenuation. This is largely because the order of the fractional Laplacian is from 0 to 2 and is infeasible for scattering attenuation. In this study, the definition of the fractional biharmonic operator in space with an order varying from 0 to 4 is proposed, as well as a fractional biharmonic operator equation model of scattering attenuation which is consistent with arbitrary frequency power-law dependency and obeys the causal relation under the smallness approximation. Finally, the correlation between the fractional order and the ratio of wavelength to the diameter of the scattering heterogeneity is investigated and an expression on exponential form is also provided.

  20. Generation of High-Frequency P and S Wave Energy by Rock Fracture During a Buried Explosion

    Science.gov (United States)

    2015-07-20

    speed digital cameras, and monitored the resultant seismic waves using a laser vibrometer (as an ultra-high-frequency seismometer). We originally... laser vibrometers to record particle velocities in the resultant P and S waves. Since no mechanical data was available for candy- glass, we measured...plates photographing them using high-speed digital cameras, and monitoring the resultant seismic waves using laser vibrometers (as an array of

  1. Differential evolution algorithm for nonlinear inversion of high-frequency Rayleigh wave dispersion curves

    Science.gov (United States)

    Song, Xianhai; Li, Lei; Zhang, Xueqiang; Huang, Jianquan; Shi, Xinchun; Jin, Si; Bai, Yiming

    2014-10-01

    to nonlinear inversion of high-frequency surface wave data should be considered good not only in terms of the accuracy but also in terms of the convergence speed.

  2. Comparison of intermediate- and low-frequency shock wave lithotripsy for pediatric kidney stones.

    Science.gov (United States)

    Kaygısız, Onur; Kılıçarslan, Hakan; Mert, Ahmet; Coşkun, Burhan; Kordan, Yakup

    2017-07-29

    The aim of the study to compare low and intermediate shock wave frequency rates in terms of success and complications for treating pediatric kidney stones. This retrospective study was performed on 58 consecutive pediatric patients (24 girls, 34 boys) who underwent shock wave lithotripsy (SWL) for kidney stones with an electrohydraulic lithotripter between April 2014 and March 2016. In the first year, all children underwent SWL with a frequency of 90 SWs/min as an intermediate frequency (Group 90), and in the second year all children were treated by SWL using 60 SWs/min as a low frequency (Group 60). The mean age of the patients was 5.87 ± 4.5 years. There were no significant differences in age, gender, stone characteristics and SWL energy level between the groups. Stone-free status was achieved in 14, 6 and 4 children in group 60; and in 10, 6 and 4 children in group 90 after one, two and three sessions, respectively. The stone-free rates were 80 and 74.1% after SWL and 90 and 88.9% after additional treatment in groups 60 and 90, respectively. The total median shock pulses were 2000 and 3600 in groups 60 and 90, respectively (p = 0.115). Efficiency quotients were 51.93 and 44.47 in groups 60 and 90, respectively. The mean total anesthesia times and complication rates did not differ between the groups. The low and intermediate frequency of SWL provided similar stone clearance in pediatric renal stones with similar anesthesia times. However, low SWL tended to need fewer shock pulses (2000/3600) for stone clearance, but the trend was not significant.

  3. Method for generation of THz frequency radiation and sensing of large amplitude material strain waves in piezoelectric materials

    Science.gov (United States)

    Reed, Evan J.; Armstrong, Michael R.

    2010-09-07

    Strain waves of THz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. Such radiation is of detectable amplitude and contains sufficient information to determine the time-dependence of the strain wave with unprecedented subpicosecond, nearly atomic time and space resolution.

  4. A frequency-modulated continuous-wave reflectometer for the Lithium Tokamak Experiment

    Science.gov (United States)

    Kubota, S.; Majeski, R.; Peebles, W. A.; Bell, R. E.; Boyle, D. P.; Kaita, R.; Kozub, T.; Lucia, M.; Merino, E.; Nguyen, X. V.; Rhodes, T. L.; Schmitt, J. C.

    2017-05-01

    The frequency-modulated continuous-wave reflectometer on LTX (Lithium Tokamak Experiment) and the data analysis methods used for determining electron density profiles are described. The diagnostic uses a frequency range of 13.1-33.5 GHz, for covering a density range of 0.21-1.4 ×1013 cm-3 (in O-mode polarization) with a time resolution down to 8 μs. The design of the diagnostic incorporates the concept of an "optimized" source frequency sweep, which minimizes the large variation in the intermediate frequency signal due to a long dispersive transmission line. The quality of the raw data is dictated by the tuning characteristics of the microwave sources, as well as the group delay ripple in the transmission lines, which can generate higher-order nonlinearities in the frequency sweep. Both effects are evaluated for our diagnostic and best practices are presented for minimizing "artifacts" generated in the signals. The quality of the reconstructed profiles is also improved using two additional data analysis methods. First, the reflectometer data are processed as a radar image, where clutter due to echoes from the wall and backscattering from density fluctuations can be easily identified and removed. Second, a weighed least-squares lamination algorithm POLAN (POLynomial ANalysis) is used to reconstruct the electron density profile. Examples of density profiles in LTX are presented, along with comparisons to measurements from the Thomson scattering and the λ = 1 mm interferometer diagnostics.

  5. Switchable Multi-Frequency MMIC Oscillator for the 60 GHz Millimeter Wave Band

    Science.gov (United States)

    Taillefer, Eddy; Kitazawa, Shoichi; Ueba, Masazumi

    We propose a proof-of-concept of a switchable multi-frequency MMIC (monolithic microwave integrated circuit) oscillator device, operating in the 60GHz millimeter wave band, which is implemented in GaAs p-HEMT transistor technology. Oscillators that can switch between two frequencies have been designed, fabricated and evaluated. The oscillator uses a cross-coupled FET topology, combined with a bent asymmetric coplanar stripline for the resonator, and a switched-capacitor for the frequency switching components. The oscillator generates two oscillations at ƒ/2 and ƒ where ƒ is the target frequency of around 60GHz. The switchable oscillator has been demonstrated for the range of frequency from 44GHz to 68.9GHz. Moreover, the designed oscillator exhibits a wide-band negative resistance property that allows fabricating switchable oscillators covering the 50 to 75GHz V-band. An evaluated switchable oscillator delivers -17.09dBm and -13.72dBm output power at 62.45GHz and 64.78GHz, for a supplied power of 40.6mW and 39.1mW, respectively.

  6. Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko

    CERN Document Server

    Richter, I; Auster, H -U; Fruehauff, D; Goetz, C; Heinisch, P; Perschke, C; Motschmann, U; Stoll, B; Altwegg, K; Burch, J; Carr, C; Cupido, E; Eriksson, A; Henri, P; Goldstein, R; Lebreton, J -P; Mokashi, P; Nemeth, Z; Nilsson, H; Rubin, M; Szegoe, K; Tsurutani, B T; Vallat, C; Volwerk, M; Glassmeier, K -H

    2015-01-01

    We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low activity state. Quasi-coherent, large-amplitude ($\\delta B/B \\sim 2$), compressional magnetic field oscillations at $\\sim$ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied comet-interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pick-up ion driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

  7. Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

    Energy Technology Data Exchange (ETDEWEB)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Lin, Y.; Wright, J. C.; Wukitch, S. J. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Jaeger, E. F. [XCEL Engineering, Inc., Oak Ridge, Tennessee 37830 (United States); Green, D. L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Harvey, R. W. [CompX, Del Mar, California 92014 (United States)

    2012-08-15

    Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D-{sup 3}He plasmas. The measured mode converted wave intensity in the D-{sup 3}He mode conversion regime was found to be a factor of {approx}50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.

  8. The Sine Wave Tuning method: Robust PID controller design in the frequency domain

    Directory of Open Access Journals (Sweden)

    Š. Bucz

    2015-12-01

    Full Text Available The paper presents a novel robust PID controller design method for nominal performance specified in terms of maximum overshoot and settling time. The PID controller design provides guaranteed gain margin GM. The parameter of the tuning rules is a suitably chosen point of the plant frequency response obtained by a sine-wave signal with excitation frequency ωn. Then, the designed controller moves this point into the phase crossover with the required gain margin GM. The couple (ωn;GM is specified with respect to closed-loop performance requirements in terms of ηmax (maximum overshoot and ts (settling time according to developed parabolic dependences. The new approach has been verified on a vast batch of benchmark examples; subsequently, the developed algorithm has been extended to robust PID controller design for plants with unstable zero and unstructured uncertainties.

  9. Minimum Lens Size Supporting the Leaky-Wave Nature of Slit Dipole Antenna at Terahertz Frequency

    Directory of Open Access Journals (Sweden)

    Niamat Hussain

    2016-01-01

    Full Text Available We designed a slit dipole antenna backed by an extended hemispherical silicon lens and investigated the minimum lens size in which the slit dipole antenna works as a leaky-wave antenna. The slit dipole antenna consists of a planar feeding structure, which is a center-fed and open-ended slot line. A slit dipole antenna backed by an extended hemispherical silicon lens is investigated over a frequency range from 0.2 to 0.4 THz with the center frequency at 0.3 THz. The numerical results show that the antenna gain responses exhibited an increased level of sensitivity to the lens size and increased linearly with increasing lens radius. The lens with the radius of 1.2λo is found to be the best possible minimum lens size for a slit dipole antenna on an extended hemispherical silicon lens.

  10. Calculation of high frequency ultrasonic signals for shear wave insonification in solid material.

    Science.gov (United States)

    Schmitz, V; Langenberg, K J; Chakhlov, S

    2004-04-01

    The goal of the theoretical part is to simulate an automatic ultrasonic inspection with contact technique shear wave probes, where the high frequency signals are captured and used to perform a reconstruction based on the synthetic aperture focusing method "SAFT". Therefore the ultrasonic probe, the scanning path and the defects are parameters in a CAD model. The scattering behavior of the defect is calculated by the Kirchhoff approximation in its elastodynamic version. The result of the simulation--the high frequency data--and the result of the SAFT-reconstructions are compared with experimental results on a steel test block with side drilled and flat bottom holes. The model is validated by the experiment. One of the applications of the model is to identify multiple reflections.

  11. Electrostatic ion cyclotron waves in a plasma with an ion beam and counterstreaming bulk electrons - Waves in the zero-frequency band. [in aurora

    Science.gov (United States)

    Singh, N.; Conrad, J. R.; Schunk, R. W.

    1985-01-01

    A common feature of the auroral plasma in the region above field-aligned (parallel) potential drops are electrostatic hydrogen cyclotron (EHC) waves. The present paper has the objective to show that wave excitation in the zero-frequency band can occur when the ion beams and the current-carrying bulk electrons counterstream. The instability mechanism involves the Landau interaction of the slow (negative energy) ion-beam-cyclotron waves with the drifting electrons and also with the target (background) ions. Only the latter resonant interaction between the beam and the target ions was considered by Okuda and Nishikawa (1984). In this study, it is shown that an electron drift makes an additional unstable contribution to the waves in the zero-frequency band, including those discussed by Okuda and Nishikawa.

  12. Low-Frequency Gravitational-Wave Science with eLISA/ NGO

    Science.gov (United States)

    Amaro-Seoane, Pau; Aoudia, Sofiane; Babak, Stanislav; Binetruy, Pierre; Berti, Emanuele; Bohe, Alejandro; Caprini, Chiara; Colpi, Monica; Cornish, Neil J.; Danzmann, Karsten; hide

    2011-01-01

    We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultracompact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA's high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime.

  13. Low-frequency gravitational-wave science with eLISA/NGO

    CERN Document Server

    Amaro-Seoane, Pau; Babak, Stanislav; Binetruy, Pierre; Berti, Emanuele; Bohe, Alejandro; Caprini, Chiara; Colpi, Monica; Cornish, Neil J; Danzmann, Karsten; Dufaux, Jean-Francois; Gair, Jonathan; Jennrich, Oliver; Jetzer, Philippe; Klein, Antoine; Lang, Ryan N; Lobo, Alberto; Littenberg, Tyson; McWilliams, Sean T; Nelemans, Gijs; Petiteau, Antoine; Porter, Edward K; Schutz, Bernard F; Sesana, Alberto; Stebbins, Robin; Sumner, Tim; Vallisneri, Michele; Vitale, Stefano; Volonteri, Marta; Ward, Henry

    2012-01-01

    We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultracompact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA's high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime.

  14. Dispersion Relations and Polarizations of Low-frequency Waves in Two-fluid Plasmas

    CERN Document Server

    Zhao, Jinsong

    2015-01-01

    Analytical expressions for the dispersion relations and polarizations of low-frequency waves in magnetized plasmas based on two-fluid model are obtained. The properties of waves propagating at different angles (to the ambient magnetic field $\\mathbf{B}_{0}$) and \\beta (the ratio of the plasma to magnetic pressures) values are investigated. It is shown that two linearly polarized waves, namely the fast and Alfv\\'{e}n modes in the low-\\beta $\\left( \\beta \\ll 1\\right)$ plasmas, the fast and slow modes in the \\beta \\sim 1 plasmas, and the Alfv\\'{e}n and slow modes in the high-\\beta $\\left( \\beta \\gg 1\\right)$ plasmas, become circularly polarized at the near-parallel (to $\\mathbf{B}_{0}$) propagation. The negative magnetic-helicity of the Alfv\\'{e}n mode occurs only at small or moderate angles in the low-\\beta plasmas, and the ion cross-helicity of the slow mode is nearly the same as that of the Alfv\\'{e}n mode in the high-\\beta plasmas. It also shown the electric polarization $\\delta E_{z}/\\delta E_{y}$ decreases...

  15. Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media

    Science.gov (United States)

    Ellefsen, K.J.; Croize, D.; Mazzella, A.T.; McKenna, J.R.

    2009-01-01

    Green's functions for radar waves propagating in heterogeneous 2.5D media might be calculated in the frequency domain using a hybrid method. The model is defined in the Cartesian coordinate system, and its electromagnetic properties might vary in the x- and z-directions, but not in the y-direction. Wave propagation in the x- and z-directions is simulated with the finite-difference method, and wave propagation in the y-direction is simulated with an analytic function. The absorbing boundaries on the finite-difference grid are perfectly matched layers that have been modified to make them compatible with the hybrid method. The accuracy of these numerical Greens functions is assessed by comparing them with independently calculated Green's functions. For a homogeneous model, the magnitude errors range from -4.16% through 0.44%, and the phase errors range from -0.06% through 4.86%. For a layered model, the magnitude errors range from -2.60% through 2.06%, and the phase errors range from -0.49% through 2.73%. These numerical Green's functions might be used for forward modeling and full waveform inversion. ?? 2009 Society of Exploration Geophysicists. All rights reserved.

  16. On the effect of topography on surface wave propagation in the ambient noise frequency range

    Science.gov (United States)

    Köhler, Andreas; Weidle, Christian; Maupin, Valérie

    2012-04-01

    Due to the increasing popularity of analyzing empirical Green's functions obtained from ambient seismic noise, more and more regional tomographical studies based on short-period surface waves are published. Results could potentially be biased in mountainous regions where topography is not small compared to the wavelength and penetration depth of the considered waves. We investigate the effect of topography on the propagation of short-period Rayleigh waves empirically by means of synthetic data using a spectral element code and a 3-D model with real topography. We show that topography along a profile through the studied area can result in an underestimation of phase velocities of up to about 0.7% at the shortest investigated period (3 s). Contrary to the expectation that this bias results from the increased surface distance along topography, we find that this error can be estimated by local topographic contrasts in the vicinity of the receiver alone. We discuss and generalize our results by considering topographic profiles through other mountain ranges and find that southern Norway is a good proxy to assess the topography effect. Nevertheless, topographic bias on phase velocity measurements is in general not large enough to significantly affect recovered velocity variations in the ambient noise frequency range.

  17. Wave propagation in relaxed micromorphic continua: modeling metamaterials with frequency band-gaps

    Science.gov (United States)

    Madeo, A.; Neff, P.; Ghiba, I. D.; Placidi, L.; Rosi, G.

    2015-09-01

    In this paper, the relaxed micromorphic model proposed in Ghiba et al. (Math Mech Solids, 2013), Neff et al. (Contin Mech Thermodyn, 2013) has been used to study wave propagation in unbounded continua with microstructure. By studying dispersion relations for the considered relaxed medium, we are able to disclose precise frequency ranges (band-gaps) for which propagation of waves cannot occur. These dispersion relations are strongly nonlinear so giving rise to a macroscopic dispersive behavior of the considered medium. We prove that the presence of band-gaps is related to a unique elastic coefficient, the so-called Cosserat couple modulus μ c , which is also responsible for the loss of symmetry of the Cauchy force stress tensor. This parameter can be seen as the trigger of a bifurcation phenomenon since the fact of slightly changing its value around a given threshold drastically changes the observed response of the material with respect to wave propagation. We finally show that band-gaps cannot be accounted for by classical micromorphic models as well as by Cosserat and second gradient ones. The potential fields of application of the proposed relaxed model are manifold, above all for what concerns the conception of new engineering materials to be used for vibration control and stealth technology.

  18. Microfluidic pumping through miniaturized channels driven by ultra-high frequency surface acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Shilton, Richie J., E-mail: richard.shilton@iit.it [Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa (Italy); Travagliati, Marco [Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa (Italy); NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127 Pisa (Italy); Beltram, Fabio [NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127 Pisa (Italy); Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa (Italy); Cecchini, Marco, E-mail: marco.cecchini@nano.cnr.it [NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127 Pisa (Italy)

    2014-08-18

    Surface acoustic waves (SAWs) are an effective means to pump fluids through microchannel arrays within fully portable systems. The SAW-driven acoustic counterflow pumping process relies on a cascade phenomenon consisting of SAW transmission through the microchannel, SAW-driven fluid atomization, and subsequent coalescence. Here, we investigate miniaturization of device design, and study both SAW transmission through microchannels and the onset of SAW-driven atomization up to the ultra-high-frequency regime. Within the frequency range from 47.8 MHz to 754 MHz, we show that the acoustic power required to initiate SAW atomization remains constant, while transmission through microchannels is most effective when the channel widths w ≳ 10 λ, where λ is the SAW wavelength. By exploiting the enhanced SAW transmission through narrower channels at ultra-high frequencies, we discuss the relevant frequency-dependent length scales and demonstrate the scaling down of internal flow patterns and discuss their impact on device miniaturization strategies.

  19. Study of transmission line attenuation in broad band millimeter wave frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Hitesh Kumar B. [ITER-India, IPR, Gandhinagar, Gujarat (India); Austin, M. E. [Institute for Fusion Studies, the University of Texas at Austin, Austin, Texas (United States); Ellis, R. F. [Laboratory for Plasma and Fusion Energy Studies, University of Maryland, College Park, Maryland 20742 (United States)

    2013-10-15

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  20. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

    Science.gov (United States)

    El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

    2017-06-26

    Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

  1. Study of transmission line attenuation in broad band millimeter wave frequency range.

    Science.gov (United States)

    Pandya, Hitesh Kumar B; Austin, M E; Ellis, R F

    2013-10-01

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  2. High-frequency gravitational waves from magnetars and gamma-ray bursts

    CERN Document Server

    Wen, Hao; Li, Jin; Fang, Zhenyun

    2016-01-01

    Extremely powerful astrophysical electromagnetic (EM) system could lead to significant energy-momentum tensor as possible source of high-frequency gravitational waves (HFGWs). Here based on properties of magnetars and gamma-ray bursts (GRBs), we address 'Gamma-HFGWs' caused by ultra-strong EM radiations (in the radiation-dominated phase of GRBs fireball) interacting with super-high magnetar surface magnetic fields (10^{11}Tesla). By certain parameters of distance and power, the Gamma-HFGWs would have amplitude of 10^{-41} at 10^{20}Hz, and such very high frequency effectively compensate their weak amplitude and thus would cause perturbed EM waves of 10^{-20}Watt/m^2 in proposed HFGW detection system based on EM response to GWs. Particularly, predicted Gamma-HFGWs can possess distinctive pulse-like envelopes with characteristic shapes, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could involve in possible astrophysical EM sources o...

  3. High-frequency torsional Alfvén waves as an energy source for coronal heating

    Science.gov (United States)

    Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N.

    2017-03-01

    The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12-42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m-2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m-2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind.

  4. Magnetic Cyclotron Waves near the Proton Cyclotron Frequency in the Solar Wind: Wind and ACE Observations in 2005

    Science.gov (United States)

    Broiles, T. W.; Jian, L.; Stevens, M. L.; Gary, S. P.; Lepri, S. T.; Vinas, A. F.; Moya, P. S.; Alexander, R.

    2016-12-01

    Strong narrow-band electromagnetic waves near the proton cyclotron frequency (fpc) have been observed extensively in the solar wind throughout the inner heliosphere. They are transverse and near-circularly polarized, and propagate in directions quasi-parallel or anti-parallel to the magnetic field. Their frequency is a few times of fpc in the spacecraft frame and a fraction of fpc in the plasma frame after removing the Doppler shift effect. These waves are left-hand (LH) or right-hand (RH) polarized in the spacecraft frame with otherwise similar characteristics except LH ones appear more often and have higher wave power. Intrinsically they can be LH polarized Alfven-cyclotron waves or RH polarized magnetosonic waves. Through the assistance of audification, we have studied the long-lasting wave events near fpc in 2005 using the high-cadence magnetic field data and well-calibrated plasma data from the Wind mission. A mixture of temperature anisotropies for core protons, beam protons, and alpha particles, as well as proton beam drift are often found for selected events of extensive waves. The wave dispersion analysis using these ion moments indicate these waves are likely to be associated with unstable Alfven-cyclotron anisotropy instability or ion beam instability, and suggest there is a mixture of Alfven-cyclotron waves and magnetosonic waves in the solar wind. Using the conjunction of Wind and ACE spacecraft when they were within 50 Earth radii of each other, we study how often the two spacecraft observe the same waves and whether there is noticeable heating for heavy ions associated with these waves.

  5. The Peoples Republic of China High-Frequency Gravitational Wave Research Program

    Science.gov (United States)

    Baker, Robert M. L.

    2009-03-01

    For the past decade the Peoples Republic of China has been increasingly active in the pursuit of High-Frequency Gravitational Wave (HFGW) research. Much of their progress has been during 2008. An epochal achievement was the publication of the theoretical analysis of the Li-Baker HFGW detector in the European Physical Journal C (Li, et al., 2008), "Perturbative Photon Fluxes Generated by High-Frequency Gravitational Waves and Their Physical Effects"). Many Chinese scientists and graduate students have participated in these HFGW studies and their contributions are briefly discussed. Some of the key scientists and their institutions are as follows: first from Chongqing University: Zhenyun Fang, Director of the Institute of Theoretical Physics, Xing gang Wu, The Institute of Theoretical Physics, Nan Yang, The Institute of Gravitational Physics; Jun Luo, Huazhong University of Science and Technology (HUST), Wuhan, China, the Head of Gravitational Laboratory, Yang Zhang, University of Science and Technology of China, Associate Dean of the College of Sciences, Biao Li, Institute of Electronic Engineering of China Academy of Engineering Physics (CAEP), Chief of Microwave Antenna Division, Chuan-Ming Zhou, Technology Committee of Institute of Electronic Engineering of the CAEP, Jie Zhou, Institute of Electronic Engineering of the CAEP, Chief of the Signal Processing Division; Weijia Wen, Department of Physics, The Hong Kong University of Science and Technology. This Chinese HFGW team includes two parts: (1) Theoretical study and (2) Experimental investigation. These two parts have closed relations, and many cross projects, including cooperation between the American GravWave and Chinese HFGW teams. Referring to financial support, The Institute of Electronic Engineering (i.e., Microwave Laboratory) has already (June 2008) provided support more than three million Yuan for the HFGW detection project and this activity is discussed.

  6. The propagation characteristics of electromagnetic waves through plasma in the near-field region of low-frequency loop antenna

    Energy Technology Data Exchange (ETDEWEB)

    Liu, DongLin, E-mail: donglinliu@stu.xidian.edu.cn; Li, XiaoPing; Xie, Kai; Liu, ZhiWei [School of Aerospace Science and Technology, Xidian University, Xi' an 710071 (China)

    2015-10-15

    A high-speed vehicle flying through the atmosphere between 100 and 20 km may suffer from a “communication blackout.” In this paper, a low frequency system with an on-board loop antenna to receive signals is presented as a potential blackout mitigation method. Because the plasma sheath is in the near-field region of the loop antenna, the traditional scattering matrix method that is developed for the far-field region may overestimate the electromagnetic (EM) wave's attenuation. To estimate the EM wave's attenuation in the near-field region, EM interference (EMI) shielding theory is introduced. Experiments are conducted, and the results verify the EMI shielding theory's effectiveness. Simulations are also conducted with different plasma parameters, and the results obtained show that the EM wave's attenuation in the near-field region is far below than that in the far-field region. The EM wave's attenuation increases with the increase in electron density and decreases with the increase in collision frequency. The higher the frequency, the larger is the EM wave's attenuation. During the entire re-entry phase of a RAM-C module, the EM wave's attenuations are below 10 dB for EM waves with a frequency of 1 MHz and below 1 dB for EM waves with a frequency of 100 kHz. Therefore, the low frequency systems (e.g., Loran-C) may provide a way to transmit some key information to high-speed vehicles even during the communication “blackout” period.

  7. Insights into performance of pattern search algorithms for high-frequency surface wave analysis

    Science.gov (United States)

    Song, Xianhai; Li, Duanyou; Gu, Hanming; Liao, Yonglong; Ren, Dachun

    2009-08-01

    Inversion of high-frequency surface wave dispersion curves is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this paper, we implemented an investigation to fully exploit and utilize the potentiality of pattern search algorithms and to further enhance their performance for surface wave analysis. We first investigate effects of different inversion strategies, initial mesh size and final mesh size, expansion factor, and contraction factor, as well as inclusion of noise in surface wave data on the performance of the approaches, by three synthetic earth models. Then, a comparative analysis with genetic algorithms is made to further highlight the advantages of the proposed inverse procedure. Finally, the insights issued from this analysis are verified by a real-world example from Henan, China. Results from both synthetic and field data demonstrate: (a) generalized pattern search (GPS) algorithm with the maximal positive basis set 2 N vectors works better than GPS algorithm with the minimal positive basis set N+1 vectors; (b) if one gets a suitable initial mesh size by taking some experimentation, then setting expansion factor Λ=1 (i.e., not allow expansions) and contraction factor θ=1/2 can greatly enhance the performance of pattern search algorithms. This is particularly true as the algorithm converges and final mesh size should go to zero; and (c) pattern search algorithms possess stronger immunity with respect to noise and should be considered good not only in terms of accuracy but also in terms of computation effort, especially when compared to the application of genetic algorithms to Rayleigh wave inversion.

  8. Effects of corrugation shape on frequency band-gaps for longitudinal wave motion in a periodic elastic layer

    DEFF Research Database (Denmark)

    Sorokin, Vladislav

    2016-01-01

    The paper concerns determining frequency band-gaps for longitudinal wave motion in a periodic waveguide. The waveguide may be considered either as an elastic layer with variable thickness or as a rod with variable cross section. As a result, widths and locations of all frequency band......, harmonic in the corrugation series. The revealed insights into the mechanism of band-gap formation can be used to predict locations and widths of all frequency band-gaps featured by any corrugation shape. These insights are general and can be valid also for other types of wave motion in periodic structures...

  9. Frequency content of sea surface height variability from internal gravity waves to mesoscale eddies

    Science.gov (United States)

    Savage, Anna C.; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Alford, Matthew H.; Buijsman, Maarten C.; Thomas Farrar, J.; Sharma, Hari; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis

    2017-03-01

    High horizontal-resolution (1/12.5° and 1/25°) 41-layer global simulations of the HYbrid Coordinate Ocean Model (HYCOM), forced by both atmospheric fields and the astronomical tidal potential, are used to construct global maps of sea surface height (SSH) variability. The HYCOM output is separated into steric and nonsteric and into subtidal, diurnal, semidiurnal, and supertidal frequency bands. The model SSH output is compared to two data sets that offer some geographical coverage and that also cover a wide range of frequencies—a set of 351 tide gauges that measure full SSH and a set of 14 in situ vertical profilers from which steric SSH can be calculated. Three of the global maps are of interest in planning for the upcoming Surface Water and Ocean Topography (SWOT) two-dimensional swath altimeter mission: (1) maps of the total and (2) nonstationary internal tidal signal (the latter calculated after removing the stationary internal tidal signal via harmonic analysis), with an average variance of 1.05 and 0.43 cm2, respectively, for the semidiurnal band, and (3) a map of the steric supertidal contributions, which are dominated by the internal gravity wave continuum, with an average variance of 0.15 cm2. Stationary internal tides (which are predictable), nonstationary internal tides (which will be harder to predict), and nontidal internal gravity waves (which will be very difficult to predict) may all be important sources of high-frequency "noise" that could mask lower frequency phenomena in SSH measurements made by the SWOT mission.

  10. On the source-frequency dependence of fracture-orientation estimates from shear-wave transmission experiments

    Science.gov (United States)

    Santos, Leo K.; de Figueiredo, J. J. S.; Omoboya, Bode; Schleicher, Jörg; Stewart, Robert R.; Dyaur, Nikolay

    2015-03-01

    Shear-wave propagation through anisotropic fractured or cracked media can provide valuable information about these fracture swarms and their orientations. The main goal of this work is to recover information about fracture orientation based on the shear waveforms (S-waveforms). For this study, we carried out ultrasonic S-wave measurements in a synthetic physical model made of epoxy resin (isotropic matrix proxy), with small cylindrical rubber strips as inclusions (artificial cracks) inserted in it to simulate a homogeneous anisotropic medium. In these experiments, we used low, intermediate, and high frequency shear-wave sources, with frequencies 90, 431, and 840 kHz. We integrated and interpreted the resulting S-wave seismograms, cross-correlation panels and anisotropic parameter-analysis curves. We were able to estimate the crack orientation in single-orientation fracture zones. The high frequency peaks associated with scattered S-waves provided interpretable information about the fracture orientations when the propagation direction was parallel to the fracture plane. The analysis was possible utilizing results from frequency-versus-polarization-angle curves. Moreover, we applied a bandpass filtering process to the intermediate and high frequency seismograms in order to obtain low frequency seismograms. A spectral analysis using frequency-wavenumber (F-K) spectra supports this filtering process. The results obtained using an analysis of cross-correlograms and the Thomsen parameter γ extracted from filtered high-frequency data were quite similar to those obtained using a low-frequency source. This highlighted the possibility of using less expensive high-frequency sources to recover information about the fracture set.

  11. Full wavefield decomposition of high-frequency secondary microseisms reveals distinct arrival azimuths for Rayleigh and Love waves

    Science.gov (United States)

    Gal, M.; Reading, A. M.; Ellingsen, S. P.; Koper, K. D.; Burlacu, R.

    2017-06-01

    In the secondary microseism band (0.1-1.0 Hz) the theoretical excitation of Rayleigh waves (Rg/LR), through oceanic wave-wave interaction, is well understood. For Love waves (LQ), the excitation mechanism in the secondary microseism band is less clear. We explore high-frequency secondary microseism excitation between 0.35 and 1 Hz by analyzing a full year (2013) of records from a three-component seismic array in Pilbara (PSAR), Australia. Our recently developed three-component waveform decomposition algorithm (CLEAN-3C) fully decomposes the beam power in slowness space into multiple point sources. This method allows for a directionally dependent power estimation for all separable wave phases. In this contribution, we compare quantitatively microseismic energy recorded on vertical and transverse components. We find the mean power representation of Rayleigh and Love waves to have differing azimuthal distributions, which are likely a result of their respective generation mechanisms. Rayleigh waves show correlation with convex coastlines, while Love waves correlate with seafloor sedimentary basins. The observations are compared to the WAVEWATCH III ocean model, implemented at the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), which describes the spatial and temporal characteristics of microseismic source excitation. We find Love wave energy to originate from raypaths coinciding with seafloor sedimentary basins where strong Rayleigh wave excitation is predicted by the ocean model. The total power of Rg waves is found to dominate at 0.35-0.6 Hz, and the Rayleigh/Love wave power ratio strongly varies with direction and frequency.

  12. Nonlinear effects associated with the finite frequency pump kinetic Alfvén wave and turbulent spectrum in solar wind

    Science.gov (United States)

    Sharma, R. P.; Modi, K. V.

    2014-07-01

    The paper contains a numerical simulation of the nonlinear coupling between the kinetic Alfvén wave and the ion acoustic wave for an intermediate β-plasma ( m e/ m i≪ β≪1). For this study, we have introduced the nonlinear ponderomotive force (due to the finite frequency ( ω 0acoustic wave. The main aim of the present paper is to study the nonlinear effects associated with the different driving finite frequencies ( ω 0pump kinetic Alfvén wave on the formation of localized structures and a turbulent spectrum applicable to the solar wind around 1 AU. As a result, we found that the different driving frequencies of the pump kinetic Alfvén wave affect the formation of the localized structures. We have also studied the turbulent scaling which follows (˜ k -3.6) for ω 0/ ω ci≈0.2, (˜ k -3.4) for ω 0/ ω ci≈0.3 and (˜ k -3.2) for ω 0/ ω ci≈0.4, at small scales. Further, we have also found that different finite driving frequencies of the pump kinetic Alfvén wave affect the turbulence scaling at small scales, which may affect the heating of the plasma particles in solar wind. The present study is correlated with the observation made by the Cluster spacecraft for the solar wind around 1 AU.

  13. High-frequency guided ultrasonic waves for the detection of hidden defects in multi-layer aerospace structures

    Science.gov (United States)

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

    2012-04-01

    High-frequency guided ultrasonic waves allow for the non-destructive testing of aerospace structures. This type of structure often contains multi-layer components subjected to cyclic loading conditions, where fatigue cracks and localized disbonds can develop. Using standard ultrasonic transducers, high frequency guided wave modes were generated in a model structure consisting of two adhesively bonded aluminum plates. This type of waves propagates along the structure and penetrates through the complete thickness. The wave propagation along the specimen was measured experimentally using a laser interferometer. Good agreement with 2D finite element simulations was found. Two types of hidden defects were considered: localized lacks of sealant and small defects in the aluminum layer facing the sealant. The interaction of the high frequency guided waves with the hidden defects was investigated. Standard pulseecho measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulation results. The high frequency guided waves have the potential for fatigue crack growth monitoring at critical and difficult to access fastener locations in aerospace structures from a stand-off distance.

  14. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    Science.gov (United States)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-08-01

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-3He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  15. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    Tsujii, N., E-mail: tsujii@k.u-tokyo.ac.jp [Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561 (Japan); Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Jaeger, E. F. [XCEL Engineering, Inc., Oak Ridge, Tennessee 37830 (United States); Green, D. L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Harvey, R. W. [CompX, Del Mar, California 92014 (United States)

    2015-08-15

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-{sup 3}He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  16. The linear variable differential transformer (LVDT) position sensor for gravitational wave interferometer low-frequency controls

    CERN Document Server

    Tariq, H; Vetrano, F; Wang Chen Yang; Bertolini, A; Calamai, G; DeSalvo, R; Gennai, A; Holloway, L E; Losurdo, G; Marka, S; Mazzoni, M; Paoletti, F; Passuello, D; Sannibale, V; Stanga, R

    2002-01-01

    Low-power, ultra-high-vacuum compatible, non-contacting position sensors with nanometer resolution and centimeter dynamic range have been developed, built and tested. They have been designed at Virgo as the sensors for low-frequency modal damping of Seismic Attenuation System chains in Gravitational Wave interferometers and sub-micron absolute mirror positioning. One type of these linear variable differential transformers (LVDTs) has been designed to be also insensitive to transversal displacement thus allowing 3D movement of the sensor head while still precisely reading its position along the sensitivity axis. A second LVDT geometry has been designed to measure the displacement of the vertical seismic attenuation filters from their nominal position. Unlike the commercial LVDTs, mostly based on magnetic cores, the LVDTs described here exert no force on the measured structure.

  17. Dual Channel S-Band Frequency Modulated Continuous Wave Through-Wall Radar Imaging

    Directory of Open Access Journals (Sweden)

    Ying-Chun Li

    2018-01-01

    Full Text Available This article deals with the development of a dual channel S-Band frequency-modulated continuous wave (FMCW system for a through-the-wall imaging (TWRI system. Most existing TWRI systems using FMCW were developed for synthetic aperture radar (SAR which has many drawbacks such as the need for several antenna elements and movement of the system. Our implemented TWRI system comprises a transmitting antenna and two receiving antennas, resulting in a significant reduction of the number of antenna elements. Moreover, a proposed algorithm for range-angle-Doppler 3D estimation based on a 3D shift invariant structure is utilized in our implemented dual channel S-band FMCW TWRI system. Indoor and outdoor experiments were conducted to image the scene beyond a wall for water targets and person targets, respectively. The experimental results demonstrate that high-quality imaging can be achieved under both experimental scenarios.

  18. The linear variable differential transformer (LVDT) position sensor for gravitational wave interferometer low-frequency controls

    Energy Technology Data Exchange (ETDEWEB)

    Tariq, Hareem E-mail: htariq@ligo.caltech.edu; Takamori, Akiteru; Vetrano, Flavio; Wang Chenyang; Bertolini, Alessandro; Calamai, Giovanni; DeSalvo, Riccardo; Gennai, Alberto; Holloway, Lee; Losurdo, Giovanni; Marka, Szabolcs; Mazzoni, Massimo; Paoletti, Federico; Passuello, Diego; Sannibale, Virginio; Stanga, Ruggero

    2002-08-21

    Low-power, ultra-high-vacuum compatible, non-contacting position sensors with nanometer resolution and centimeter dynamic range have been developed, built and tested. They have been designed at Virgo as the sensors for low-frequency modal damping of Seismic Attenuation System chains in Gravitational Wave interferometers and sub-micron absolute mirror positioning. One type of these linear variable differential transformers (LVDTs) has been designed to be also insensitive to transversal displacement thus allowing 3D movement of the sensor head while still precisely reading its position along the sensitivity axis. A second LVDT geometry has been designed to measure the displacement of the vertical seismic attenuation filters from their nominal position. Unlike the commercial LVDTs, mostly based on magnetic cores, the LVDTs described here exert no force on the measured structure.

  19. The frequency and damping of ion acoustic waves in collisional and collisionless two-species plasma

    Energy Technology Data Exchange (ETDEWEB)

    Berger, R L; Valeo, E J

    2004-07-15

    The dispersion properties of ion acoustic waves (IAW) are sensitive to the strength of ion-ion collisions in multi-species plasma in which the different species usually have differing charge-to-mass ratios. The modification of the frequency and damping of the fast and slow acoustic modes in a plasma composed of light (low Z) and heavy (high Z) ions is considered. In the fluid limit where the light ion scattering mean free path, {lambda}{sub th} is smaller than the acoustic wavelength, {lambda} = 2{pi}/k, the interspecies friction and heat flow carried by the light ions scattering from the heavy ions causes the damping. In the collisionless limit, k{lambda}{sub lh} >> 1, Landau damping by the light ions provides the dissipation. In the intermediate regime when k{lambda}{sub lh} {approx} 1, the damping is at least as large as the sum of the collisional and Landau damping.

  20. The Frequency and Damping of Ion Acoustic Waves in Collisional and Collisionless Two-species Plasma

    Energy Technology Data Exchange (ETDEWEB)

    R.L. Berger; E.J. Valeo

    2004-08-18

    The dispersion properties of ion acoustic waves (IAW) are sensitive to the strength of ion-ion collisions in multi-species plasma in which the different species usually have differing charge-to-mass ratios. The modification of the frequency and damping of the fast and slow acoustic modes in a plasma composed of light (low Z) and heavy (high Z) ions is considered. In the fluid limit where the light ion scattering mean free path, {lambda}{sub th} is smaller than the acoustic wavelength, {lambda} = 2{pi}/k, the interspecies friction and heat flow carried by the light ions scattering from the heavy ions causes the damping. In the collisionless limit, k{lambda}{sub th} >> 1, Landau damping by the light ions provides the dissipation. In the intermediate regime when k{lambda}{sub th} {approx} 1, the damping is at least as large as the sum of the collisional and Landau damping.

  1. ULTRA HIGH FREQUENCY WAVES EFFECT UPON ASSIMILATORY PIGMENTS IN OAK SEEDLINGS

    OpenAIRE

    C. Goiceanu; I. Creanga; Ispas, A.; D.D. Sandu; D.E. Creanga; I.I. Bara

    2003-01-01

    The influenc e of ultra high fre que ncy ra diation in forestry arbor se e dlings wa s studie d by spec tra l me thod. Chlorophy ll pigm e nt c onte nts, ve ry im porta nt for photosy nthe sis phe nome na , we re found to be dim inishe d in pe dunc ula te oa k see dlings a fter da ily e xposure tim es of: 1;2; 3; 4; 6 a nd 8 hours, a t ultra high frequency waves with 400 M H z fre que ncy a nd 1 mW /cm 2 powe r de nsity. N on-therma l effect seem s to underline th putative m olecu...

  2. Nonlinear standing waves, resonance phenomena, and frequency characteristics of distributed systems

    Science.gov (United States)

    Rudenko, O. V.

    2009-01-01

    This review is dedicated to resonator oscillations under conditions of a strongly expressed nonlinearity under which steep shock fronts emerge in the wave profiles. Models and approximated methods for their analysis for quadratic and cubic nonlinear media are examined, as well as for nonlinearity when taking into account the mobility of boundaries. The forms of the profiles are calculated both for a steady-state oscillation regime and during the establishment of the profiles. Dissipative losses and selective losses at specially chosen frequencies are considered. An analysis of nonlinear Q-factor is given. The possibility of increasing the acoustic energy accumulated in the cavity of the resonator is discussed. Special attention is given to various physical phenomena that are exhibited only in nonlinear acoustic fields.

  3. Blood-brain barrier disruption by continuous-wave radio frequency radiation.

    Science.gov (United States)

    Sirav, Bahriye; Seyhan, Nesrin

    2009-01-01

    The increasing use of cellular phones and the increasing number of associated base stations are becoming a widespread source of non ionizing electromagnetic radiation. Some biological effects are likely to occur even at low-level EM fields. This study was designed to investigate the effects of 900 and 1,800 MHz Continuous Wave Radio Frequency Radiation (CW RFR) on the permeability of Blood Brain Barrier (BBB) of rats. Results have shown that 20 min RFR exposure of 900 and 1,800 MHz induces an effect and increases the permeability of BBB of male rats. There was no change in female rats. The scientific evidence on RFR safety or harm remains inconclusive. More studies are needed to demonstrate the effects of RFR on the permeability of BBB and the mechanisms of that breakdown.

  4. Low-frequency shock waves in a magnetized superthermal dusty plasma

    Science.gov (United States)

    Chahal, B. S.; Ghai, Yashika; Saini, N. S.

    2017-09-01

    The characteristics of low-frequency shocks in a magnetized dusty plasma comprising of negatively charged dust fluid, kappa-distributed electrons and ions have been investigated. Using the reductive perturbation method, the nonlinear Korteweg de-Vries-Burgers (KdV-B) equation which governs the dynamics of the dust acoustic (DA) shock waves is derived. The characteristics of shock structures are studied under the influence of various plasma parameters, viz. superthermality of ions, magnetic field, electron-to-dust-density ratio, kinematic viscosity, ion-to-electron-temperature ratio and obliqueness. The combined effects of these physical parameters significantly influence the characteristics of DA shock structures. It is observed that only negative potential shocks exist in a plasma environment comprising of dust fluid and superthermal electrons and ions such as that of Saturn's magnetosphere.

  5. [The effect of high-frequency current and ultrasonic wave on selected indicators of body weight].

    Science.gov (United States)

    Kiełczewska, Magdalena; Szymczyk, Jerzy; Leszczyńsk, Ryszard; Błaszczyk, Jan

    2015-03-01

    Effective change the appearance of the body through available both invasive and non-invasive methods such as treatment has been documented in numerous clinical trials. Liposuction and lipoplasty are currently the most widely used methods of reducing fat deposits. Technological advances made has become increasingly popular use of invasive procedures using energy fields and high-frequency ultrasonic wave. It is now one of the most effective and safe methods of treatment, based on the principle of mechanical and thermal stimulation of the physiological processes leading to the reduction of locally accumulated fat. The aim of the study was to evaluate the behavior of selected parameters of body weight in patients undergoing fat reduction BTL Exilis device. IThe study included a 50-group of women who are patients of the Specialist Outpatient Clinic Al-Med in Kolobrzeg. Taken twice the measurement of body weight, waist circumference and thickness measurement of skinfolds before the first treatment, and after a series of treatments. Treatment consisted of 4 sessions while maintaining the 10-day interval between treatments. In the study a statistically significant reduction in the studied parameters such as actual body weight, waist circumference, fat mass and thickness of the skinfolds were showed. The effect of treatment with the energy field of highfrequency ultrasonic wave in a reduction in the size of fat body mass and improving the contour shape. Willingness to continue participation examined in this type of surgery proves positive reception of therapy and its effectiveness. © 2015 MEDPRESS.

  6. Study of Temperature Wave Propagation in Superfluid Helium Focusing on Radio-Frequency Cavity Cooling

    CERN Document Server

    Koettig, T; Avellino, S; Junginger, T; Bremer, J

    2015-01-01

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches of superconducting radio-frequency cavities. Local hot spots at the cavity surface initiate temperature waves in the surrounding superfluid helium that acts as cooling fluid at typical temperatures in the range of 1.6 K to 2 K. The temperature wave is characterised by the properties of superfluid helium such as the second sound velocity. For high heat load densities second sound velocities greater than the standard literature values are observed. This fast propagation has been verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound is linked to OST signals. The aim of this study is to improve the understanding of the OST signal especially the incident angle dependency. The characterised OSTs are used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resolution was proven to b...

  7. Broadband Enhancement of Optical Frequency Comb Using Cascaded Four-Wave Mixing in Photonic Crystal Fiber

    Directory of Open Access Journals (Sweden)

    Tawfig Eltaif

    2017-01-01

    Full Text Available A cascaded intensity modulator (IM and phase modulator (PM are used to modulate a continuous-wave (CW laser and generate an optical frequency comb (OFC. Thus, the generated comb is utilized as an initial seed and combined with another CW-laser to generate four-wave mixing (FWM in photonic crystal fiber (PCF. Results show that an initial flat 30 GHz OFC of 29, 55 lines within power fluctuation of 0.8 dB and 2 dB, respectively, can be achieved by setting the ratio of the DC bias to amplitude of sinusoidal signal at 0.1 and setting the modulation indices of both IM and PM at 10. Moreover, the 1st order of FWM created through 14 m of PCF has over 68 and 94 lines with fluctuation of 0.8 dB and 2 dB, respectively. Hence, the generated wavelengths of 1st left and right order of FWM can be tuned in a range from ~1500 nm to ~1525 nm and ~1590 nm to ~1604 nm, respectively.

  8. Potential health effects of standing waves generated by low frequency noise

    Directory of Open Access Journals (Sweden)

    Stanislav Ziaran

    2013-01-01

    Full Text Available The main aim is to present the available updated knowledge regarding the potential health effects of standing waves generated by low frequency noise (LFN from an open window in a moving car where the negative effects of LFN induced by heating components and/or heating, ventilation and air-conditioning are assessed. Furthermore, the assessment of noise in chosen enclosed spaces, such as rooms, offices, and classrooms, or other LFN sources and their effect on the human being were investigated. These types of noise are responsible for disturbance during relaxation, sleep, mental work, education, and concentration, which may reflect negatively on the comfort and health of the population and on the mental state of people such as scientific staff and students. The assessment points out the most exposed areas, and analyzes the conditions of standing wave generation in these rooms caused by outdoor and/or indoor sources. Measurements were made for three different enclosed spaces (office, flat, and passenger car and sources (traffic specific noise at intersections, noise induced by pipe vibration, and aerodynamic noise and their operating conditions. For the detection of LFN, the A-weighted sound pressure level and vibration were measured and a fast Fourier transform analysis was used. The LFN sources are specified and the direct effects on the human are reported. Finally, this paper suggests the possibilities for the assessment of LFN and some possible measures that can be taken to prevent or reduce them.

  9. Insights in P- and S-wave relative traveltime tomography from analysing finite-frequency Fréchet kernels

    Science.gov (United States)

    Maupin, Valérie; Kolstrup, Marianne Lanzky

    2015-09-01

    Regional body-wave tomography, also called ACH tomography, is the inversion of relative traveltime residuals of teleseismic body waves measured at regional networks. We analyse the characteristics of the finite-frequency Fréchet kernels for P and S waves for this kind of tomography. Using a simplified geometry enables us to use the complete Green's function in the expression of the Fréchet kernels and analyse elements, which are usually neglected, like the importance of the near-field terms and the P-wave traveltime sensitivity to shear wave velocity variations. By comparing the kernels of the relative residuals and absolute ones, we show that relative residuals have a reduced sensitivity to heterogeneities of large dimensions, and that this reduction is a generalization of the fact that the average model is not recovered in ACH tomography. This sensitivity reduction affects equally short- and long-period residuals. We show in addition the presence of a sensitivity reduction at large depth for the long-period waves. Kernels and reflectivity impulse responses of the crust are used to analyse if crustal corrections should be made frequency-dependent in finite-frequency regional tomography. We find that in most cases the frequency dependence due to reverberations is substantial, and that in many realistic network configurations ray theory is unlikely to be well appropriate to compute crustal corrections for the long-period waves. We also find that the lateral dimensions of the crust affecting the traveltimes is frequency dependent and reaches, at long periods, 50 km for sedimentary basins and 100 km for Moho depth.

  10. W-Band Millimeter-Wave Vector Signal Generation Based on Precoding-Assisted Random Photonic Frequency Tripling Scheme Enabled by Phase Modulator

    National Research Council Canada - National Science Library

    Li, Xinying; Xu, Yuming; Xiao, Jiangnan; Yu, Jianjun

    2016-01-01

    We propose W-band photonic millimeter-wave (mm-wave) vector signal generation employing a precoding-assisted random frequency tripling scheme enabled by a single phase modulator cascaded with a wavelength selective switch (WSS...

  11. Temporal and spatial evolution characteristics of disturbance wave in a hypersonic boundary layer due to single-frequency entropy disturbance.

    Science.gov (United States)

    Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing; Shi, Jianqiang

    2014-01-01

    By using a high-order accurate finite difference scheme, direct numerical simulation of hypersonic flow over an 8° half-wedge-angle blunt wedge under freestream single-frequency entropy disturbance is conducted; the generation and the temporal and spatial nonlinear evolution of boundary layer disturbance waves are investigated. Results show that, under the freestream single-frequency entropy disturbance, the entropy state of boundary layer is changed sharply and the disturbance waves within a certain frequency range are induced in the boundary layer. Furthermore, the amplitudes of disturbance waves in the period phase are larger than that in the response phase and ablation phase and the frequency range in the boundary layer in the period phase is narrower than that in these two phases. In addition, the mode competition, dominant mode transformation, and disturbance energy transfer exist among different modes both in temporal and in spatial evolution. The mode competition changes the characteristics of nonlinear evolution of the unstable waves in the boundary layer. The development of the most unstable mode along streamwise relies more on the motivation of disturbance waves in the upstream than that of other modes on this motivation.

  12. Electromagnetic fluctuation spectra of collective oscillations in magnetized Maxwellian equal mass plasmas for low-frequency waves

    Energy Technology Data Exchange (ETDEWEB)

    Vafin, S.; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- & Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Scholl of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of)

    2016-05-15

    Recently, the general electromagnetic fluctuation theory for magnetized plasmas has been used to study the steady-state fluctuation spectra and the total intensity of low-frequency collective weakly damped modes for parallel wave vectors in Maxwellian plasmas. Now, we address the same question with respect to an arbitrary direction of the wave-vector. Here, we analyze this problem for equal mass plasmas. These plasmas are a very good tool to study various plasma phenomena, as they considerably facilitate the theoretical consideration and at the same time provide with their clear physical picture. Finally, we compare our results in the limiting case of parallel wave vectors with the previous study.

  13. Continuous-wave single-frequency 295 nm laser source by a frequency-quadrupled optically pumped semiconductor laser.

    Science.gov (United States)

    Kaneda, Yushi; Fallahi, Mahmoud; Hader, Jörg; Moloney, Jerome V; Koch, Stephan W; Kunert, Bernardette; Stoltz, Wolfgang

    2009-11-15

    Up to 136 mW of cw single-frequency output at 295 nm was obtained from a frequency-quadrupled optically pumped semiconductor laser. The highly strained InGaAs quantum-well semiconductor laser operates at 1178 nm in a single frequency. The single-frequency intracavity-doubled 589 nm output is further converted to 295 nm in an external resonator using beta-BaB(2)O(4).

  14. A Novel Unit Cell for Active Switches in the Millimeter-Wave Frequency Range

    Science.gov (United States)

    Müller, Daniel; Scherer, Gunnar; Lewark, Ulrich J.; Massler, Hermann; Wagner, Sandrine; Tessmann, Axel; Leuther, Arnulf; Zwick, Thomas; Kallfass, Ingmar

    2018-02-01

    This paper presents a novel transistor unit cell which is intended to realize compact active switches in the high millimeter-wave frequency range. The unit cell consists of the combination of shunt and common gate transistor within a four-finger transistor cell, achieving gain in the amplifying state as well as good isolation in the isolating state. Gate width-dependent characteristics of the unit cell as well as the design of actual switch implementations are discussed in detail. To verify the concept, two switches, a single pole double throw (SPDT) switch and single pole quadruple throw (SP4T) switch, intended for the WR3 frequency range (220-325 GHz) were manufactured and characterized. The measured gain at 250 GHz is 4.6 and 2.2 dB for the SPDT and SP4T switch, respectively. An isolation of more than 24 dB for the SPDT switch and 12.8 dB for the SP4T switch was achieved.

  15. Radiation from an electron beam in magnetized plasma: excitation of a whistler mode wave packet by interacting, higher-frequency, electrostatic-wave eigenmodes

    Science.gov (United States)

    Brenning, N.; Axnäs, I.; Koepke, M.; Raadu, M. A.; Tennfors, E.

    2017-12-01

    Infrequent, bursty, electromagnetic, whistler-mode wave packets, excited spontaneously in the laboratory by an electron beam from a hot cathode, appear transiently, each with a time duration τ around ∼1 μs. The wave packets have a center frequency f W that is broadly distributed in the range 7 MHz electrostatic (es) plasma oscillations at values of f hf, 200 MHz < f hf < 500 MHz, that are hypothesized to match eigenmode frequencies of an axially localized hf es field in a well-defined region attached to the cathode. Features of these es-eigenmodes that are studied include: the mode competition at times of transitions from one dominating es-eigenmode to another, the amplitude and spectral distribution of simultaneously occurring es-eigenmodes that do not lead to a transition, and the correlation of these features with the excitation of whistler mode waves. It is concluded that transient coupling of es-eigenmode pairs at f hf such that | {{{f}}}1,{{h}{{f}}}-{{{f}}}2,{{h}{{f}}}| = {f}{{W}}< {f}{{g}{{e}}} can explain both the transient lifetime and the frequency spectra of the whistler-mode wave packets (f W) as observed in lab. The generalization of the results to bursty whistler-mode excitation in space from electron beams, created on the high potential side of double layers, is discussed.

  16. Atomization off thin water films generated by high-frequency substrate wave vibrations

    Science.gov (United States)

    Collins, David J.; Manor, Ofer; Winkler, Andreas; Schmidt, Hagen; Friend, James R.; Yeo, Leslie Y.

    2012-11-01

    Generating aerosol droplets via the atomization of thin aqueous films with high frequency surface acoustic waves (SAWs) offers several advantages over existing nebulization methods, particularly for pulmonary drug delivery, offering droplet sizes in the 1-5-μm range ideal for effective pulmonary therapy. Nevertheless, the physics underlying SAW atomization is not well understood, especially in the context of thin liquid film formation and spreading and how this affects the aerosol production. Here, we demonstrate that the film geometry, governed primarily by the applied power and frequency of the SAW, indeed plays a crucial role in the atomization process and, in particular, the size of the atomized droplets. In contrast to the continuous spreading of low surface energy liquids atop similar platforms, high surface energy liquids such as water, in the present case, are found to undergo transient spreading due to the SAW to form a quasisteady film whose height is determined by self-selection of the energy minimum state associated with the acoustic resonance in the film and whose length arises from a competition between acoustic streaming and capillary effects. This is elucidated from a fundamental model for the thin film spreading behavior under SAW excitation, from which we show good agreement between the experimentally measured and theoretically predicted droplet dimension, both of which consistently indicate a linear relationship between the droplet diameter and the mechanical power coupled into the liquid by the SAW (the latter captured by an acoustic Weber number to the two thirds power, and the reciprocal of the SAW frequency).

  17. Transmission of high frequency sound waves through a slug flow jet

    Science.gov (United States)

    Parthasarathy, S. P.; Vijayaraghavan, A.

    1980-01-01

    An analysis has been performed of sound waves which propagate in a pipe with gas flow. At the pipe exit these waves are partially reflected and the remainder are diffracted. The analysis is carried out by resolving the sound at the exit into its Fourier components and then continuing the solution, which is a combination of elementary plane waves, beyond the exit. These waves are of two types: homogeneous waves which propagate to infinity, and inhomogeneous waves with complex wave numbers which decay. The reflected waves are evaluated from the inhomogeneous waves. At the boundary of the jet, refraction of the elementary plane waves is accounted for and the far field sound is evaluated by the method of stationary phase. Comparisons of the theoretical calculations are made with experimental results and with calculations of other theories.

  18. Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors

    Science.gov (United States)

    Erkmen, Baris I.; Barber, Zeb W.; Dahl, Jason

    2014-01-01

    Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramér-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal

  19. Measurement of Frequency, Temperature, RF Field Dependence of Surface Resistance of Superconductors Using a Half Wave Cavity

    Science.gov (United States)

    Park, Hyekyoung; Delayen, Jean

    2017-01-01

    A theory of surface resistance of superconductor was rigorously formulated by Bardeen, Cooper, Schrieffer more than 50 years ago. Since then the accelerator community has been used the theory as a guideline to improve the surface resistance of the superconducting cavity. It has been observed that the surface resistance is dependent on frequency, temperature and rf field strength, and surface preparation. To verify these dependences, a well-controlled study is required. Although many different types of cavities have been tested, the typical superconducting cavities are built for specific frequencies of their application. They do not provide data other than at its own frequency. A superconducting half wave cavity is a cavity that enables us to collect the surface resistance data across frequencies of interest for particle accelerators and evaluate preparation techniques. This paper will present the design of the half wave cavity, its electromagnetic mode characteristics and experimental results. Research supported by NSF Award PHY-1416051.

  20. Time-frequency mapping of the positional characteristics of single- and multimode wave beam at the lengthy atmospheric path output

    Science.gov (United States)

    Arsenyan, Tatiana; Babanin, Eugeniy; Kapranov, Vitaliy; Stryungis, Rinat; Suhareva, Natalia; Tugaenko, Vjatcheslav

    2017-10-01

    The comparative experimental analysis of the single-mode and multimode positional characteristics of the wave beams at the lengthy atmospheric path output was carried out and the results are presented. As the main instrument the method of nonlinear time-frequency mapping was chosen usingWigner function apparatus. The characteristic time-frequency spectra under the conditions of strong, intermediate and weak turbulence of the atmospheric path were defined.

  1. On the dispersion law of low-frequency electron whistler waves in a multi-ion plasma

    Directory of Open Access Journals (Sweden)

    B. V. Lundin

    2008-06-01

    Full Text Available A new and simple dispersion law for extra-low-frequency electron whistler waves in a multi-ion plasma is derived. It is valid in a plasma with finite ratio ωcpe of electron gyro-to-plasma frequency and is suitable for wave frequencies much less than ωpe but well above the gyrofrequencies of most heavy ions. The resultant contribution of the ions to the dispersion law is expressed by means of the lower hybrid resonance frequency, the highest ion cutoff frequency and the relative content of the lightest ion. In a frequency domain well above the ions' gyrofrequencies, this new dispersion law merges with the "modified electron whistler dispersion law" determined in previous works by the authors. It is shown that it fits well to the total cold plasma electron whistler dispersion law, for different orientations of the wave vectors and different ion constituents, including negative ions or negatively charged dust grains.

  2. Quantitative evaluation of atrial radio frequency ablation using intracardiac shear-wave elastography.

    Science.gov (United States)

    Kwiecinski, Wojciech; Provost, Jean; Dubois, Rémi; Sacher, Frédéric; Haïssaguerre, Michel; Legros, Mathieu; Nguyen-Dinh, An; Dufait, Rémi; Tanter, Mickaël; Pernot, Mathieu

    2014-11-01

    Radio frequency catheter ablation (RFCA) is a well-established clinical procedure for the treatment of atrial fibrillation (AF) but suffers from a low single-procedure success rate. Recurrence of AF is most likely attributable to discontinuous or nontransmural ablation lesions. Yet, despite this urgent clinical need, there is no clinically available imaging modality that can reliably map the lesion transmural extent in real time. In this study, the authors demonstrated the feasibility of shear-wave elastography (SWE) to map quantitatively the stiffness of RFCA-induced thermal lesions in cardiac tissues in vitro and in vivo using an intracardiac transducer array. SWE was first validated in ex vivo porcine ventricular samples (N = 5). Both B-mode imaging and SWE were performed on normal cardiac tissue before and after RFCA. Areas of the lesions were determined by tissue color change with gross pathology and compared against the SWE stiffness maps. SWE was then performed in vivo in three sheep (N = 3). First, the stiffness of normal atrial tissues was assessed quantitatively as well as its variation during the cardiac cycle. SWE was then performed in atrial tissue after RFCA. A large increase in stiffness was observed in ablated ex vivo regions (average shear modulus across samples in normal tissue: 22 ± 5 kPa, average shear-wave speed (ct): 4.5 ± 0.4 m s(-1) and in determined ablated zones: 99 ± 17 kPa, average ct: 9.0 ± 0.5 m s(-1) for a mean shear modulus increase ratio of 4.5 ± 0.9). In vivo, a threefold increase of the shear modulus was measured in the ablated regions, and the lesion extension was clearly visible on the stiffness maps. By its quantitative and real-time capabilities, Intracardiac SWE is a promising intraoperative imaging technique for the evaluation of thermal ablation during RFCA.

  3. Nonlinear frequency shift on an electron plasma wave: hysteresis, nonlocality and multidimensional effects in an inhomogeneous plasma

    Science.gov (United States)

    Benisti, Didier

    2017-10-01

    We provide a general derivation of the nonlinear frequency shift, δω , for a sinusoidal electron plasma wave (EPW) that varies slowly enough for neo-adiabatic theory to apply. We first consider the situation when the EPW monotonously grows and then monotonously decays in a homogeneous plasma. In this situation, we show a hysteresis in the wave frequency, which does not converge back to its linear value as the wave decays to small amplitudes. We then address the derivation of δω for an EPW that keeps growing in a one-dimensional (1-D) inhomogeneous plasma. We show that, usually, the frequency shift does not only depend on the local EPW amplitude and wavenumber. It also depends on the whole history of the density variations, as experienced by the wave. In a multidimensional inhomogeneous plasma, the values assumed by δω are usually different from those derived in 1-D because, due to the transverse electron motion, one must account for the hysteresis in δω in addition to plasma inhomogeneity. Hence, unless the EPW keeps growing in a homogeneous 1-D plasma, one cannot derive δω a priori as a function of the local wave amplitude and wavenumber. Due to the nonlocality in the action distribution function, δω depends on the whole history of the variations of the EPW amplitude and plasma density.

  4. Applications of High-Frequency Gravitational Waves to the Global War on Terror

    Science.gov (United States)

    Baker, Robert M. L.

    2010-01-01

    Applications of high-frequency gravitational waves or HFGWs to the global war on terror are now realistic because technology developed by GravWave® LLC and other institutions overseas can lead to devices, some already constructed, that can generate and detect HFGWs. In fact, three HFGW detectors have been built outside the United States and an ultra high-sensitive Li-Baker HFGW Detector has been proposed. HFGW generators have been proposed theoretically by the Russians, Germans, Italians and Chinese. Because of their unique characteristics, such as their ability to pass through all material without attenuation, HFGWs could be utilized for uninterruptible, very low-probability-of-intercept (LPI), high-bandwidth communications among and between anti-terrorist assets. One such communications system, which can be constructed from off-the-shelf elements, is discussed. The HFGW generation device or transmitter alternative selected is based upon bands of piezoelectric crystal, film-bulk acoustic resonators or FBARs energized by conventional Magnetrons. The system is theoretically capable of transmitting and detecting, through use of the Li-Baker HFGW detector, a signal generated on the opposite side of the Earth. Although HFGWs do not interact with and are not absorbed by ordinary matter, their presence can be detected by their distortion of spacetime as measured by the Laser Interferometer Gravitational Observatory (LIGO), Virgo, GEO600, et al., by detection photons generated from electromagnetic beams having the same frequency, direction and phase as the HFGWs in a superimposed magnetic field (Li-Baker HFGW Detector), by the change in polarization HFGWs produce in a microwave guide (Birmingham University Detector) and by other such instruments. Potential theoretical applications, which may or may not be practical yet theoretically possible, are propulsion, including "moving" space objects such as missiles, anti-missiles and warheads in flight; surveillance through

  5. Relation between frequency of seismic wave and resolution of tomography; Danseiha tomography kaiseki ni okeru shuhasu to bunkaino no kankei

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, M.; Watanabe, T.; Ashida, Y.; Sassa, K. [Kyoto University, Kyoto (Japan). Faculty of Engineering

    1997-05-27

    With regard to the elastic wave exploration, discussions have been given on the relationship between frequency and resolution in P-wave velocity tomography using the initial travel time. The discussions were carried out by using a new analysis method which incorporates the concept of Fresnel volume into tomography analysis. The following two arrangements were used in the calculation: a cross hole arrangement, in which seismic source and vibration receiving points were arranged so as to surround the three directions of a region extending 250 m in the horizontal direction and 500 m in the vertical direction, and observation is performed between two wells, and a permeation VSP arrangement in which the seismic source is installed on the ground surface and receiving points installed in wells. Restructuring was performed on the velocity structure by using a total of 819 observation travel times. This method has derived results of the restructuring according to frequencies of the seismic source used for the exploration. The resolution shown in the result of the restructuring has become higher as elastic waves with higher frequency are used, and the size of the structure identified from the restructuring result has decreased. This fact reveals that sufficient considerations must be given on frequencies of elastic waves used according to size of objects to be explored. 4 refs., 4 figs.

  6. Longitudinal Surveys of Australian Youth (LSAY) 2006 Cohort: Wave 6 (2011)--Frequency Tables. Technical Report 75B

    Science.gov (United States)

    National Centre for Vocational Education Research (NCVER), 2012

    2012-01-01

    The Longitudinal Surveys of Australian Youth (LSAY) program studies the progress of several groups of young Australians as they move from school into post-secondary education and work. This series of documents provides supporting information for the LSAY data set of the 2006 cohort at wave 6 (2011). This document presents the frequency tables for…

  7. Power and chirp effects on the frequency stability of resonant dispersive waves generated in photonic crystal fibres.

    Science.gov (United States)

    Cao, Tao; Liu, Mingchen; Xu, Chang; Yan, Jikun; Shen, Chaochao; Liu, Shaozhen; Peng, Hao; Peng, Jiahui; Sokolov, Alexei V

    2018-01-09

    Optimization of laser output parameters vs. f-to-2f beating signals can be mutually contradicting, when an octave-spanning supercontinuum is employed for f-to-2f measurements. We show that resonant dispersive waves will solve this issue, thanks to their frequency stability against changes in laser power and chirping.

  8. High-frequency internal waves and thick bottom mixed layers observed by gliders in the Gulf Stream

    Science.gov (United States)

    Todd, Robert E.

    2017-06-01

    Autonomous underwater gliders are conducting high-resolution surveys within the Gulf Stream along the U.S. East Coast. Glider surveys reveal two mechanisms by which energy is extracted from the Gulf Stream as it flows over the Blake Plateau, a portion of the outer continental shelf between Florida and North Carolina where bottom depths are less than 1000 m. Internal waves with vertical velocities exceeding 0.1 m s-1 and frequencies just below the local buoyancy frequency are routinely found over the Blake Plateau, particularly near the Charleston Bump, a prominent topographic feature. These waves are likely internal lee waves generated by the subinertial Gulf Stream flow over the irregular bathymetry of the outer continental shelf. Bottom mixed layers with O(100) m thickness are also frequently encountered; these thick bottom mixed layers likely form in the lee of topography due to enhanced turbulence generated by O(1) m s-1 near-bottom flows.

  9. Development and beam test of a continuous wave radio frequency quadrupole accelerator

    Science.gov (United States)

    Ostroumov, P. N.; Mustapha, B.; Barcikowski, A.; Dickerson, C.; Kolomiets, A. A.; Kondrashev, S. A.; Luo, Y.; Paskvan, D.; Perry, A.; Schrage, D.; Sharamentov, S. I.; Sommer, R.; Toter, W.; Zinkann, G.

    2012-11-01

    The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ). While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW) RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS). Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0.75βλ was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE) copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O5+ ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

  10. Development and beam test of a continuous wave radio frequency quadrupole accelerator

    Directory of Open Access Journals (Sweden)

    P. N. Ostroumov

    2012-11-01

    Full Text Available The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ. While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS. Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0.75βλ was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O^{5+} ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

  11. Design and cold model experiment of a continuous-wave deuteron radio-frequency quadrupole

    Science.gov (United States)

    Fu, Q.; Zhu, K.; Lu, Y. R.; Easton, M. J.; Gao, S. L.; Wang, Z.; Jia, F. J.; Li, H. P.; Gan, P. P.; He, Y.

    2017-12-01

    A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University. It is a very compact high-current RFQ, operating at 162.5 MHz in continuous-wave mode. By optimizing the beam dynamics design, our simulations reached 98% transmission efficiency for acceleration of the 50-mA deuteron beam from 50 keV to 1 MeV, with an intervane voltage of 60 kV and a length of 1.809 m. This RFQ adopts a window-type structure, with low power consumption and sufficient mode separation, with no stabilizing rods required. Its magnetic coupling windows have been optimized by both electromagnetic simulation and the construction of an equivalent circuit model. The empirical equation based on the circuit model provides a new way to evaluate the effect of the window size on the frequency. In addition, an aluminum model of the full-length RFQ has been built and tested, and the results show good agreement with the simulations. During the tuning process, the magnetic coupling effect between quadrants was found to be unique to the window-type RFQ. We also propose a method to estimate the effects of different degrees of electric field unflatness on the beam transmission. For the cooling system design, the results of thermostructural analysis, verified by comparing results from ansys and cst, show that the special cooling channels provide a high cooling efficiency around the magnetic coupling windows. The maximal deformation of the structure was approximately 75 μ m . The beam-loading effect caused by a high current, and the coupler design, are also discussed.

  12. Finite-frequency wave propagation through outer rise fault zones and seismic measurements of upper mantle hydration

    Science.gov (United States)

    Miller, Nathaniel; Lizarralde, Daniel

    2016-01-01

    Effects of serpentine-filled fault zones on seismic wave propagation in the upper mantle at the outer rise of subduction zones are evaluated using acoustic wave propagation models. Modeled wave speeds depend on azimuth, with slowest speeds in the fault-normal direction. Propagation is fastest along faults, but, for fault widths on the order of the seismic wavelength, apparent wave speeds in this direction depend on frequency. For the 5–12 Hz Pn arrivals used in tomographic studies, joint-parallel wavefronts are slowed by joints. This delay can account for the slowing seen in tomographic images of the outer rise upper mantle. At the Middle America Trench, confining serpentine to fault zones, as opposed to a uniform distribution, reduces estimates of bulk upper mantle hydration from ~3.5 wt % to as low as 0.33 wt % H2O.

  13. Observations of a free-energy source for intense electrostatic waves. [in upper atmosphere near upper hybrid resonance frequency

    Science.gov (United States)

    Kurth, W. S.; Frank, L. A.; Gurnett, D. A.; Burek, B. G.; Ashour-Abdalla, M.

    1980-01-01

    Significant progress has been made in understanding intense electrostatic waves near the upper hybrid resonance frequency in terms of the theory of multiharmonic cyclotron emission using a classical loss-cone distribution function as a model. Recent observations by Hawkeye 1 and GEOS 1 have verified the existence of loss-cone distributions in association with the intense electrostatic wave events, however, other observations by Hawkeye and ISEE have indicated that loss cones are not always observable during the wave events, and in fact other forms of free energy may also be responsible for the instability. Now, for the first time, a positively sloped feature in the perpendicular distribution function has been uniquely identified with intense electrostatic wave activity. Correspondingly, we suggest that the theory is flexible under substantial modifications of the model distribution function.

  14. Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation

    National Research Council Canada - National Science Library

    Koji Suizu; Kaoru Koketsu; Takayuki Shibuya; Toshihiro Tsutsui; Takuya Akiba; Kodo Kawase

    2009-01-01

    .... The fact limits efficient and wide tunable THz-wave generation. Here, we show that Cherenkov radiation with waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-wave source...

  15. Frequency Sensitivity to Cavity Geometry Errors of HIE-ISOLDE High-Beta QuarterWave Resonator

    CERN Document Server

    Zhang, P; Venturini Delsolaro, W

    2014-01-01

    Quarter-Wave Resonators (QWRs) are to be used in the linac upgrade in the framework of HIE-ISOLDE project. The QWRs are made of copper with niobium sputtered on the RF surface. The resonant frequency of the cavity is 101.28 MHz at 4.5 K. The resonant frequency changes due to cavity geometry variation. Thus the manufacturing tolerance has been set to 0.1 mm for the copper substrate. The frequency sensitivity to different geometry changes has been evaluated in this report.

  16. Brahan Project High Frequency Radar Ocean Measurements: Currents, Winds, Waves and Their Interactions

    OpenAIRE

    Belinda Lipa; Donald Barrick; Andres Alonso-Martirena; Maria Fernandes; Maria Inmaculada Ferrer; Bruce Nyden

    2014-01-01

    We describe radar measurements of waves, currents and winds made on the coast of northern Scotland during two 2013/14 winter storms, giving methods, results and interpretation. Wave parameters (height, period, direction and short-wave/wind direction) were derived and compared with measurements made by a neighboring buoy and local weather stations. Wind direction and current velocity maps were produced and the interactions of winds and currents discussed. Significant oscillations in wave param...

  17. The Utilization of High-Frequency Gravitational Waves for Global Communications

    Directory of Open Access Journals (Sweden)

    Robert M L Baker

    2012-10-01

    Full Text Available For over 1000 years electromagnetic radiation has been utilized for long-distance communication. Smoke signals, heliographs, telegraphs, telephones and radio have all served our previous communication needs. Nevertheless, electromagnetic radiation has one major difficulty: it is easily absorbed. In this paper we consider a totally different radiation, a radiation that is not easily absorbed: gravitational radiation. Such radiation, like gravity itself, is not absorbed by earth, water or any material substance. In particular we discuss herein means to generate and detect high-frequency gravitational waves or HFGWs, and how they can be utilized for communication. There are two barriers to their practical utilization: they are extremely difficult to generate (a large power required to generate very weak GWs and it is extremely difficult to detect weak GWs. We intend to demonstrate theoretically in this paper their phase-coherent generation utilizing an array of in-phase microelectro-mechanical systems or MEMS resonator elements in which the HFGW flux is proportional to the square of the number of elements. This process solves the transmitter difficulty. Three HFGW detectors have previously been built; but their sensitivity is insufficient for meaningful HFGW reception; greater sensitivity is necessary. A new Li-Baker HFGW detector, discussed herein, is based upon a different measurement technique than the other detectors and is predicted to achieve a sensitivity to satisfy HFGW communication needs.

  18. Detection and Characterization of Flaws in Sprayed on Foam Insulation with Pulsed Terahertz Frequency Electromagnetic Waves

    Science.gov (United States)

    Winfree, William P.; Madaras, Eric I.

    2005-01-01

    The detection and repair of flaws such as voids and delaminations in the sprayed on foam insulation of the external tank reduces the probability of foam debris during shuttle ascent. The low density of sprayed on foam insulation along with it other physical properties makes detection of flaws difficult with conventional techniques. An emerging technology that has application for quantitative evaluation of flaws in the foam is pulsed electromagnetic waves at terahertz frequencies. The short wavelengths of these terahertz pulses make them ideal for imaging flaws in the foam. This paper examines the application of terahertz pulses for flaw detection in foam characteristic of the foam insulation of the external tank. Of particular interest is the detection of voids and delaminations, encapsulated in the foam or at the interface between the foam and a metal backing. The technique is shown to be capable of imaging small voids and delaminations through as much as 20 cm of foam. Methods for reducing the temporal responses of the terahertz pulses to improve flaw detection and yield quantitative characterizations of the size and location of the flaws are discussed.

  19. Real-time optical monitoring of radio-frequency tissue fusion by continuous wave transmission spectroscopy.

    Science.gov (United States)

    Floume, Timmy; Syms, Richard R A; Darzi, Ara W; Hanna, George B

    2008-01-01

    Radio-frequency (RF) tissue fusion is a novel method of tissue approximation that can seal tissue without the need for sutures or staples, based on the combined effects of heat and pressure on the apposed tissue surfaces. RF delivery must be controlled and optimized to obtain a reproducible, reliable seal. We use real-time optical measurements to improve understanding of the tissue modifications induced by RF fusion. The main macroscopic transformations are thermal denaturation and dehydration. Light propagation in tissue is a function of both and therefore should provide interesting insight into the dynamic of occurring phenomena. Quantification by continuous wave technique has proven challenging. We proposed an algorithm based on the measurement of the absolute transmittance of the tissue, making use of the modified Beer-Lambert law. The experimental method and the data algorithm are demonstrated by RF fusion of porcine small bowel. The proposed optical measurement modality is well adapted to modern surgical instrumentation used for minimally invasive procedures.

  20. 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.

  1. Herbal extracts modulate the amplitude and frequency of slow waves in circular smooth muscle of mouse small intestine.

    Science.gov (United States)

    Storr, M; Sibaev, A; Weiser, D; Kelber, O; Schirra, J; Goke, B; Allescher, H D

    2004-01-01

    Herbal preparations like STW 5 (Iberogast) are widely used drugs in the treatment of dyspepsia and motility-related disorders of the gastrointestinal tract. STW 5 is a phytotherapeutic agent consisting of a fixed mixture of 9 individual plant extracts. The electrophysiological mechanisms of action of STW 5 remain obscure. The aim of the present study was to investigate whether herbal extracts influence electrophysiological parameters of the small intestine. For this purpose, the resting membrane potential (RMP) and the slow wave rhythmicity of smooth muscle cells of mouse small intestine were observed. Intracellular recordings of smooth muscle cells of the circular muscle layer of mouse small intestine were performed using standard microelectrode techniques. After dissection of the mucosa, the small intestine was placed in an organ bath and a microelectrode was applied on a circular smooth muscle cell. The RMP and the amplitude of slow waves were measured in millivolts. The RMP of smooth muscle cells was -59 +/- 1.3 mV. This RMP was significantly depolarized by STW 5 (9.6 +/- 1.6 mV); the depolarizing effects can be mainly attributed to the constituents of matricariae flos, angelicae radix and chelidonii herba. The basal frequency of small intestinal slow waves was 39.5 +/- 1.4 min(-1) and the amplitude was 23.1 +/- 0.9 mV. STW 5 significantly reduced the amplitude and frequency of the slow waves (11.7 +/- 0.8 mV; 33.5 +/- 3.4 min(-1)). This effect on slow waves represents the sum of the effects of the 9 phytoextracts. Whereas angelicae radix and matricariae flos completely blocked slow wave activity, Iberis amara increased the frequency and amplitude, chelidonii herba reduced the frequency and amplitude of the slow waves, mentae piperitae folium reduced the frequency and left amplitude unchanged and liquiritae radix, carvi fructus and melissae folium had no effects. Herbal extracts cause changes in smooth muscle RMP and slow wave rhythmicity, up to reversible

  2. Van Allen Probes observations of unusually low frequency whistler mode waves observed in association with moderate magnetic storms: Statistical study.

    Science.gov (United States)

    Cattell, C A; Breneman, A W; Thaller, S A; Wygant, J R; Kletzing, C A; Kurth, W S

    2015-09-28

    We show the first evidence for locally excited chorus at frequencies below 0.1  f ce (electron cyclotron frequency) in the outer radiation belt. A statistical study of chorus during geomagnetic storms observed by the Van Allen Probes found that frequencies are often dramatically lower than expected. The frequency at peak power suddenly stops tracking the equatorial 0.5  f ce and f / f ce decreases rapidly, often to frequencies well below 0.1  f ce (in situ and mapped to equator). These very low frequency waves are observed both when the satellites are close to the equatorial plane and at higher magnetic latitudes. Poynting flux is consistent with generation at the equator. Wave amplitudes can be up to 20 to 40 mV/m and 2 to 4 nT. We conclude that conditions during moderate to large storms can excite unusually low frequency chorus, which is resonant with more energetic electrons than typical chorus, with critical implications for understanding radiation belt evolution.

  3. Effects of frequency and temperature- and strain-wave form on thermal fatigue strength of type 316 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Tsunenari, Toshiyasu; Horikawa, Takeshi; Okada, Tomonobu; Take, Koji; Miyashita, Takuya (Kawasaki Heavy Industries Ltd., Akashi, Hyogo (Japan). Technical Inst.)

    1983-06-01

    The effects of frequency and temperature- and strain-wave form on thermal fatigue strength were examined by conducting out-of-phase and in-phase thermal fatigue tests with three kinds of temperature-wave forms (fast heating and fast cooling, slow heating and slow cooling, slow heating and fast cooling) under temperature cycling between 350 - 650/sup 0/C and by isothermal low-cycle fatigue tests at 650/sup 0/C under cyclic frequencies of 0.5 -- 0.039 cpm. The following results were obtained. (1) The effect of frequency on fatigue life in out-of-phase thermal fatigue was as small as in isothermal low-cycle fatigue, whereas in in-phase thermal fatigue it was much greater and the fatigue life reduction was more remarkable in low frequency. (2) The effect of temperature- and strain-wave form on thermal fatigue life was still smaller than the effect of frequency on out-of-phase thermal fatigue life. (3) The fracture mode of out-of-phase thermal fatigue was the transgranular type even at the lowest frequency tested, but that of in-phase thermal fatigue changed to the intergranular type at low frequency. (4) Out-of-phase and in-phase thermal fatigue data obtained at the test condition of such an extremely low frequency as 0.039 cpm were found to coincide well with ..delta..epsilon sub(PC) - N sub(PC) and ..delta..epsilon sub(CP) - N sub(CP) relations, respectively.

  4. Imaging a soil fragipan using a high-frequency multi-channel analysis of surface wave method

    Science.gov (United States)

    Lu, Zhiqu; Wilson, Glenn V.

    2017-08-01

    The objective of this study was to noninvasively image fragipan layers using a high-frequency multi-channel analysis of surface wave (HF-MASW) method. The HF-MASW method is developed to measure the soil profile in terms of the shear wave velocity at depths up to a few meters in the vadose zone. The present MASW method uses an accelerometer as a vibration sensor to detect Rayleigh wave propagation generated by an electrodynamic shaker operating in a frequency-sweeping mode in three overlapped frequency bands. With the method, a subsurface image was obtained, i.e., the soil properties in terms of shear wave velocity of a vertical cross-section of the test site were measured, visualized, and evaluated. From the contrast of the image, the presence, depth, and extent of a fragipan were identified. The HF-MASW result was compared with field observations of a soil pit face and a 2-dimensional image obtained by penetration tests. They were in good agreement. The study demonstrated the capability of the HF-MASW technique for detection and imaging soil subsurface hard layers such as fragipan.

  5. Modulation Model of High Frequency Band Radar Backscatter by the Internal Wave Based on the Third-Order Statistics

    Directory of Open Access Journals (Sweden)

    Pengzhen Chen

    2017-05-01

    Full Text Available Modulation model of radar backscatters is an important topic in the remote sensing of oceanic internal wave by synthetic aperture radar (SAR. Previous studies related with the modulation models were analyzed mainly based on the hypothesis that ocean surface waves are Gaussian distributed. However, this is not always true for the complicated ocean environment. Research has showed that the measurements are usually larger than the values predicted by modulation models for the high frequency radars (X-band and above. In this paper, a new modulation model was proposed which takes the third-order statistics of the ocean surface into account. It takes the situation into consideration that the surface waves are Non-Gaussian distributed under some conditions. The model can explain the discrepancy between the measurements and the values calculated by the traditional models in theory. Furthermore, it can accurately predict the modulation for the higher frequency band. The model was verified by the experimental measurements recorded in a wind wave tank. Further discussion was made about applicability of this model that it performs better in the prediction of radar backscatter modulation compared with the traditional modulation model for the high frequency band radar or under lager wind speeds.

  6. Overly persistent circulation in climate models contributes to overestimated frequency and duration of heat waves and cold spells

    Science.gov (United States)

    Plavcová, Eva; Kyselý, Jan

    2016-05-01

    The study examines links of summer heat waves and winter cold spells in Central Europe to atmospheric circulation and specifically its persistence in an ensemble of regional climate models (RCMs). We analyse 13 RCMs driven by the ERA-40 reanalysis and compare them against observations over reference period 1971-2000. Using objective classification of circulation types and an efficiency coefficient with a block resampling test, we identify circulation types significantly conducive to heat waves and cold spells. We show that the RCMs have a stronger tendency to group together days with very high or low temperature and tend to simulate too many heat waves and cold spells, especially those lasting 5 days and more. Circulation types conducive to heat waves in summer are characterized by anticyclonic, southerly and easterly flow, with increasing importance of warm advection during heat waves. Winter cold spells are typically associated with easterly and anticyclonic flow, and the onset of cold spells tends to be linked to northerly and cyclonic flow with cold advection. The RCMs are generally able to reproduce the links between circulation and heat waves or cold spells, including the radiation-to-advection effect for heat waves and the opposite advection-to-radiation effect for cold spells. They capture relatively well also changes of mean temperature anomalies during sequences of given circulation types, namely the tendency towards temperature increase (decrease) during those types conducive to heat waves (cold spells). Since mean lengths of all circulation supertypes are overestimated in the RCMs, we conclude that the overly persistent circulation in climate models contributes to the overestimated frequency of long heat waves and cold spells. As these biases are rather general among the examined RCMs and similar drawbacks are likely to be manifested in climate model simulations for the twenty-first century, the results also suggest that climate change scenarios for

  7. Observations of Low-Frequency Magnetic Waves due to Newborn Interstellar Pickup Ions Using ACE, Ulysses, and Voyager Data

    Science.gov (United States)

    Smith, Charles W.; Aggarwal, Poornima; Argall, Matthew R.; Burlaga, Leonard F.; Bzowski, Maciej; Cannon, Bradford E.; Gary, S. Peter; Fisher, Meghan K.; Gilbert, Jason A.; Hollick, Sophia J.; Isenberg, Philip A.; Joyce, Colin J.; Murphy, Neil; Nuno, Raquel G.; Pine, Zackary B.; Richardson, John D.; Schwadron, Nathan A.; Skoug, Ruth M.; Sokół, Justyna M.; Taylor, David K.; Vasquez, Bernard J.

    2017-09-01

    Wave excitation by newborn interstellar pickup ions (PUIs) plays a significant role in theories that attempt to describe IBEX and Voyager observations in the solar wind and heliosheath. The same dynamic processes can be far-reaching and extend into the inner heliosphere to at least 1AU and likely to smaller heliocentric distances. While the high-resolution magnetic field measurements required to study these waves are not yet available in the heliosheath, we have studied a range of available observations and found evidence of waves due to interstellar PUIs using ACE (1998-2015 at 1 AU), Ulysses (1996-2006 at 2 to 5 AU, high and low latitudes) and Voyager (1978-1979 and 2 to 6 AU) observations. Efforts to extend the Voyager observations to 35 AU are ongoing. We have examined these data sets and report on observations of low-frequency waves that result from newborn interstellar pickup H+ and He+ ions. Although not as common as theory originally predicted, we presently have identified 524 independent occurrences. Our conclusion from studying these waves is that they are seen only when the ambient turbulence is sufficiently weak. The instability that generates these waves requires a slow accumulation of wave energy over several to tens of hours to achieve observable wave amplitudes. In regions where the turbulence is moderate to strong, the turbulence absorbs the wave energy before it can reach observable levels and transports the energy to the dissipation scales where it heats the background thermal particles. Only intervals with the weakest turbulence will permit energy accumulation over this time scale. These conditions are most often, but not exclusively, achieved in solar wind rarefaction regions.

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

    Science.gov (United States)

    Chan, Henry; Masserey, Bernard; Fromme, Paul

    2015-02-01

    Especially for ageing aircraft the development of fatigue cracks at fastener holes due to stress concentration and varying loading conditions constitutes a significant maintenance problem. High frequency guided waves offer a potential compromise between the capabilities of local bulk ultrasonic measurements with proven defect detection sensitivity and the large area coverage of lower frequency guided ultrasonic waves. High frequency guided waves have energy distributed through all layers of the specimen thickness, allowing in principle hidden (2nd layer) fatigue damage monitoring. For the integration into structural health monitoring systems the sensitivity for the detection of hidden fatigue damage in inaccessible locations of the multi-layered components from a stand-off distance has to be ascertained. The multi-layered model structure investigated consists of two aluminium plate-strips with an epoxy sealant layer. During cyclic loading fatigue crack growth at a fastener hole was monitored. Specific guided wave modes (combination of fundamental A0 and S0 Lamb modes) were selectively excited above the cut-off frequencies of higher modes using a standard ultrasonic wedge transducer. Non-contact laser measurements close to the defect were performed to qualify the influence of a fatigue crack in one aluminium layer on the guided wave scattering. Fatigue crack growth monitoring using laser interferometry showed good sensitivity and repeatability for the reliable detection of small, quarter-elliptical cracks. Standard ultrasonic pulse-echo equipment was employed to monitor hidden fatigue damage from a stand-off distance without access to the damaged specimen layer. Sufficient sensitivity for the detection of fatigue cracks located in the inaccessible aluminium layer was verified, allowing in principle practical in situ ultrasonic monitoring of fatigue crack growth.

  9. The Life-Cycle of High Frequency Internal Waves in a Continental Shelf Sea: Generation, Propagation and Dissipation".

    Science.gov (United States)

    Domina, A.; Palmer, M.; Sharples, J.; Vlasenko, V.; Green, M.

    2016-02-01

    High-frequency internal waves (HFIW) are particularly important to internal mixing in the shelf seas, where they contain an enhanced fraction of the available baroclinic energy. The origin, generation mechanism, propagation and spatial distribution of these waves are unfortunately still poorly understood since they are difficult to measure and simulate, and are therefore not represented in the vast majority of ocean and climate models. In this study we aim to increase our understanding of HFIW dynamics in shelf seas through a combination of observational (moorings, gliders, OMGs) and modelling methods (MITgcm), and test the hypothesis that "Solitary waves are responsible for driving a large fraction of the vertical diffusivity at the shelf edge and adjacent shelf region". Our analysis of two separate sites, both situated 20km from the continental shelf break, shows that the energetics (KE and APE) of low frequency internal waves (IWs) are of similar magnitude with subtle differences explained through variable local and remote forcing. Baroclinic energy distribution at high frequencies is shown to be near constant at both sites, independent of low frequency forcing. There is however a significant difference in energy levels between sites, one being enhanced by 60%. A new high-resolution (50m horizontal) MITgcm configuration is validated using the observed IW characteristics and employed to identify the generation and propagation of IWs in the Celtic Sea. We identify how energy is transferred to higher frequencies and subsequently identify likely mixing hotspots on the Celtic Sea. These predictions are then compared to turbulence data collected using an Ocean Microstructure Glider and VMP to assess the impact of the identified IW characteristics on internal mixing. Lastly, we force the model with different density structures to assess the likely impact of changing climate forcing scenarios on IW generation and internal mixing on the continental shelf.

  10. Intrinsic and scattering attenuation of high-frequency S-waves in the central part of the External Dinarides

    Science.gov (United States)

    Majstorović, Josipa; Belinić, Tena; Namjesnik, Dalija; Dasović, Iva; Herak, Davorka; Herak, Marijan

    2017-09-01

    The central part of the External Dinarides (CED) is a geologically and tectonically complex region formed in the collision between the Adriatic microplate and the European plate. In this study, the contributions of intrinsic and scattering attenuation ( Q i - 1 and Q sc - 1 , respectively) to the total S-wave attenuation were calculated for the first time. The multiple lapse-time window analysis (MLTWA method), based on the assumptions of multiple isotropic scattering in a homogeneous medium with uniformly distributed scatterers, was applied to seismograms of 450 earthquakes recorded at six seismic stations. Selected events have hypocentral distances between 40 and 90 km with local magnitudes between 1.5 and 4.7. The analysis was performed over 11 frequency bands with central frequencies between 1.5 and 16 Hz. Results show that the seismic albedo of the studied area is less than 0.5 and Q i - 1 > Q sc - 1 at all central frequencies and for all stations. These imply that the intrinsic attenuation dominates over scattering attenuation in the whole study area. Calculated total S-wave and expected coda wave attenuation for CED are in a very good agreement with the ones measured in previous studies using the coda normalization and the coda-Q methods. All estimated attenuation factors decrease with increasing frequency. The intrinsic attenuation for CED is among the highest observed elsewhere, which could be due to the highly fractured and fluid-filled carbonates in the upper crust. The scattering and the total S-wave attenuation for CED are close to the average values obtained in other studies performed worldwide. In particular, good agreement of frequency dependence of total attenuation in CED and in the regions that contributed most strong-motion records for ground motion prediction equations used in PSHA in Croatia indicates that those were well chosen and applicable to this area as far as their attenuation properties are concerned.

  11. Effects of Underground Cavities on the Frequency Spectrum of Seismic Shear Waves

    OpenAIRE

    Lancioni, G.; Bernetti, R.; Quagliarini, E.; Tonti, L.

    2014-01-01

    A numerical method is proposed to study the scattering of seismic shear waves induced by the presence of underground cavities in homogeneous soils. The method is based on the superposition of two solutions: the solution of the free-wave propagation problem in a uniform half-space, easily determined analytically, and the solution of the wave scattering problem due to the cave presence, evaluated numerically by means of an ad hoc code implemented by using the ANSYS Parametric ...

  12. Parametric decay instability of an obliquely propagating ordinary wave in the electron cyclotron frequency range

    Science.gov (United States)

    Gusakov, E. Z.; Popov, A. Yu.

    2018-01-01

    The possibility of the low-power-threshold parametric decay of an obliquely propagating ordinary wave to an upper hybrid wave and a low-hybrid wave is analysed under conditions of nonmonotonic plasma density profile in a magnetic trap. The instability threshold and growth rate are derived explicitly. The analytical results are illustrated under the conditions typical of the ordinary mode fundamental electron cyclotron resonance heating harmonic experiments at the FTU tokamak.

  13. Passive Wireless Hydrogen Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the development of passive surface acoustic wave (SAW) based hydrogen sensors for NASA application to distributed wireless hydrogen leak...

  14. Brahan Project High Frequency Radar Ocean Measurements: Currents, Winds, Waves and Their Interactions

    Directory of Open Access Journals (Sweden)

    Belinda Lipa

    2014-12-01

    Full Text Available We describe radar measurements of waves, currents and winds made on the coast of northern Scotland during two 2013/14 winter storms, giving methods, results and interpretation. Wave parameters (height, period, direction and short-wave/wind direction were derived and compared with measurements made by a neighboring buoy and local weather stations. Wind direction and current velocity maps were produced and the interactions of winds and currents discussed. Significant oscillations in wave parameters were observed, which appear to be due to forcing by tidal current velocity variations. The oscillations in waveheight are explained using hydrodynamic analysis and derived amplitudes are compared with radar measurements.

  15. Frequency-domain theory of laser infrared photothermal radiometric detection of thermal waves generated by diffuse-photon-density wave fields in turbid media.

    Science.gov (United States)

    Mandelis, Andreas; Feng, Chris

    2002-02-01

    A three-dimensional theory of the frequency-domain thermal-wave field generated inside a turbid medium with optical and thermal properties of human tissue is presented. The optical source is treated as a three-dimensional harmonically modulated diffuse-photon-density wave (DPDW) field in the diffusion approximation of the radiative transfer theory. Unlike earlier Green-function-based theoretical models, exact boundary conditions are used based on the requirement that there should be no diffuse photon intensity entering the turbid medium from the outside. Explicit analytical expressions for the DPDW field and for the dependent thermal-wave field are obtained in the spatial Hankel-transform domain. The formalism is further extended to the calculation of the infrared photothermal radiometric signal arising from the nonradiatively generated thermal-wave distribution in turbid media with instantaneous nonradiative deexcitation as well as in media with nonzero fluorescence relaxation lifetimes. Numerical inversions have been performed and presented as examples of selected special cases of the theory. It is found that the present theory with exact DPDW-field boundary conditions is valid throughout the entire domain of the turbid medium, with the exception of the very near-surface ballistic photon "skin layer" (7-50 microm). Photothermal radiometric signals were found to be more reliably predicted than DPDW signals within this layer, due to the depth-integration nature of this detection methodology.

  16. Evaluation of cross-connected waveguides as transfer standards of transmission at high millimetre-wave frequencies

    Science.gov (United States)

    Ridler, Nick; Clarke, Roland; Huang, Hui; Zinal, Sherko

    2016-08-01

    At the present time, transfer and verification standards of transmission coefficient (or, equivalently, transmission loss) are not readily available at high millimetre-wave frequencies (i.e. at frequencies ranging typically from 100 GHz to 300 GHz). In recent years, cross-connected waveguide devices have been proposed to provide calculable standards of transmission loss at these frequencies. This paper investigates the viability of these cross-connected waveguides as transfer standards of transmission for inter-laboratory measurement comparison exercises. This relates to their potential use in activities such as international key comparison exercises and measurement audit programmes. A trial inter-laboratory comparison involving four laboratories using two cross-connected waveguides in the WR-05 waveguide size (covering frequencies from 140 GHz to 220 GHz) is described and includes an analysis of the measurement results obtained during the comparison exercise.

  17. An Empirical Outdoor-to-Indoor Path Loss Model from below 6 GHz to cm-Wave Frequency Bands

    DEFF Research Database (Denmark)

    Rodriguez Larrad, Ignacio; Nguyen, Huan Cong; Kovács, István Z.

    2017-01-01

    This letter presents an empirical multi-frequency outdoor-to-indoor path loss model. The model is based on measurements performed on the exact same set of scenarios for different frequency bands ranging from traditional cellular allocations below 6 GHz (0.8, 2, 3.5 and 5.2 GHz), up to cm-wave...... frequencies (10, 18 and 28 GHz). The model has applicability similar to the typical 3GPP and ITU-R outdoor-to-indoor simplified models, including the multi-frequency formulation recently included in the 3GPP TR 38.900. This letter highlights some of the details behind these simplified models and provides...... additional modeling for internal multi-wall attenuation and associated shadow fading....

  18. Forming of space charge wave with broad frequency spectrum in helical relativistic two-stream electron beams

    DEFF Research Database (Denmark)

    Lysenko, Alexander V.; Volk, Iurii I.; Serozhko, A.

    2017-01-01

    We elaborate a quadratic nonlinear theory of plural interactions of growing space charge wave (SCW) harmonics during the development of the two-stream instability in helical relativistic electron beams. It is found that in helical two-stream electron beams the growth rate of the two......-stream instability increases with the beam entrance angle. An SCW with the broad frequency spectrum, in which higher harmonics have higher amplitudes, forms when the frequency of the first SCW harmonic is much less than the critical frequency of the two-stream instability. For helical electron beams the spectrum...... expands with the increase of the beam entrance angle. Moreover, we obtain that utilizing helical electron beams in multiharmonic two-stream superheterodyne free-electron lasers leads to the improvement of their amplification characteristics, the frequency spectrum broadening in multiharmonic signal...

  19. Gravitational Wave (GW Classification, Space GW Detection Sensitivities and AMIGO (Astrodynamical Middle-frequency Interferometric GW Observatory

    Directory of Open Access Journals (Sweden)

    Ni Wei-Tou

    2018-01-01

    Full Text Available After first reviewing the gravitational wave (GW spectral classification. we discuss the sensitivities of GW detection in space aimed at low frequency band (100 nHz–100 mHz and middle frequency band (100 mHz–10 Hz. The science goals are to detect GWs from (i Supermassive Black Holes; (ii Extreme-Mass-Ratio Black Hole Inspirals; (iii Intermediate-Mass Black Holes; (iv Galactic Compact Binaries; (v Stellar-Size Black Hole Binaries; and (vi Relic GW Background. The detector proposals have arm length ranging from 100 km to 1.35×109 km (9 AU including (a Solar orbiting detectors and (b Earth orbiting detectors. We discuss especially the sensitivities in the frequency band 0.1-10 μHz and the middle frequency band (0.1 Hz–10 Hz. We propose and discuss AMIGO as an Astrodynamical Middlefrequency Interferometric GW Observatory.

  20. Low-frequency permittivity of spin-density wave in (TMTSF)2PF6 at low temperatures

    DEFF Research Database (Denmark)

    Nad, F.; Monceau, P.; Bechgaard, K.

    1995-01-01

    Conductivity and permittivity epsilon of(TMTSF)(2)PF6 have been measured at low frequencies of (10(2)-10(7) Hz) at low temperatures below the spin-density wave (SDW) transition temperature T-p. The temperature dependence of the conductivity shows a deviation from thermally activated behavior at T...... less than or equal to 2 K and a transition to hopping type conductivity. The frequency dependences of Re epsilon = epsilon' and Im epsilon = epsilon '' show log f scaling as it is typical for various disordered systems. The temperature dependence of epsilon' exhibits a maximum which shifts to lower...... evidence for a transition of the SDW conductor into a glassy-like state at low temperatures similarly to the case of charge density waves....

  1. Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator

    CERN Document Server

    Yang, Yong; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan; Yang, Lan; Chormaic, Síle Nic

    2016-01-01

    Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \\textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

  2. [Comparative evaluation of the efficiency of the effect of very high frequency electromagnetic waves on platelet functional activity].

    Science.gov (United States)

    Kirichuk, V F; Maĭborodin, A V; Volin, M V; Krenitskiĭ, A P; Tupikin, V D

    2001-01-01

    A comparative analysis was made of the effect of two kinds of EMI MMD-radiation: EMI MMD-waves, generated by a vehicle "Jav-1 M" (42.2 and 53.5 HHz), and EMI MMD-waves exerting influence with frequencies of molecular spectrum of radiation and nitric oxide absorption (150.176-150.644 HHz), obtained with a specially created generator, with respect to their influence on the functional ability of platelets of unstable angina pectoris patients. It was shown that in vitro EMI MMD-fluctuations with frequencies of molecular spectrum of radiation and nitric oxide absorption exert a stronger inhibiting influence on the functional activity of platelets of unstable angina pectoris patients. Features of the action of various kinds of EMI MMD-effect on the activative-high-speed characteristics of platelet aggregation are shown.

  3. The Relative Frequency of Rossby Wave Train Triggering Mechanisms Associated with Downstream Development Over Europe

    Science.gov (United States)

    2014-06-01

    TCs in the Southern Hemisphere . As this research is focused on Northern Hemisphere RWTs, Southern Hemisphere triggering mechanisms will not be...requirements for the degree of MASTER OF SCIENCE IN METEOROLOGY AND PHYSICAL OCEANOGRAPHY from the NAVAL POSTGRADUATE SCHOOL June 2014...Department of Meteorology iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT Rossby wave trains (RWTs) are coherent envelopes of baroclinic waves

  4. Method and apparatus for extraction of low-frequency artifacts from brain waves for alertness detection

    Science.gov (United States)

    Clapp, Ned E.; Hively, Lee M.

    1997-01-01

    Methods and apparatus automatically detect alertness in humans by monitoring and analyzing brain wave signals. Steps include: acquiring the brain wave (EEG or MEG) data from the subject, digitizing the data, separating artifact data from raw data, and comparing trends in f-data to alertness indicators, providing notification of inadequate alertness.

  5. Stress depended changes in activityof gp red blood cells receptors and its correction by therahertz waves at nitric oxide frequency

    Directory of Open Access Journals (Sweden)

    Kirichuk V.F.

    2011-09-01

    Full Text Available The effect of electromagnetic radiation in the terahertz range frequencies of molecular spectrum of emission and absorption of nitric oxide 150.176–150.664 GHz for the restoration of the impaired carbohydrate component and functional activity glikoproteid receptors of erythrocytes of white rats in a state of acute imm obilization stress. Shown that exposure to electromagnetic waves at these frequencies is the normalization of the increased content of b-D-galactose in the carbohydrate component and the restoration of the impaired activity of the receptors glikoproteid erythrocytes

  6. Multi-frequency force-detected electron spin resonance in the millimeter-wave region up to 150 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Ohmichi, E., E-mail: ohmichi@harbor.kobe-u.ac.jp; Tokuda, Y.; Tabuse, R.; Tsubokura, D.; Okamoto, T. [Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan); Ohta, H. [Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan)

    2016-07-15

    In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn{sup 2+} impurities(∼0.2%) in MgO.

  7. Statistical Channel Model with Multi-Frequency and Arbitrary Antenna Beamwidth for Millimeter-Wave Outdoor Communications

    OpenAIRE

    Samimi, Mathew K.; Rappaport, Theodore S.

    2015-01-01

    This paper presents a 3-dimensional millimeter-wave statistical channel impulse response model from 28 GHz and 73 GHz ultrawideband propagation measurements. An accurate 3GPP-like channel model that supports arbitrary carrier frequency, RF bandwidth, and antenna beamwidth (for both omnidirectional and arbitrary directional antennas), is provided. Time cluster and spatial lobe model parameters are extracted from empirical distributions from field measurements. A step-by-step modeling procedure...

  8. Observation of High-Frequency Electrostatic Waves in the Vicinity of the Reconnection Ion Diffusion Region by the Spacecraft of the Magnetospheric Multiscale (MMS) Mission

    Science.gov (United States)

    Zhou, M.; Ashour-Abdalla, M.; Berchem, J.; Walker, R. J.; Liang, H.; El-Alaoui, M.; Goldstein, M. L.; Lindqvist, P.-A.; Marklund, G.; Khotyaintsev, Y. V.; hide

    2016-01-01

    We report Magnetospheric Multiscale observations of high-frequency electrostatic waves in the vicinity of the reconnection ion diffusion region on the dayside magnetopause. The ion diffusion region is identified during two magnetopause crossings by the Hall electromagnetic fields, the slippage of ions with respect to the magnetic field, and magnetic energy dissipation. In addition to electron beam modes that have been previously detected at the separatrix on the magnetospheric side of the magnetopause, we report, for the first time, the existence of electron cyclotron harmonic waves at the magnetosheath separatrix. Broadband waves between the electron cyclotron and electron plasma frequencies, which were probably generated by electron beams, were found within the magnetopause current sheet. Contributions by these high-frequency waves to the magnetic energy dissipation were negligible in the diffusion regions as compared to those of lower-frequency waves.

  9. Increasing the density of modes in an optical frequency comb by cascaded four-wave mixing in a nonlinear optical fiber

    Science.gov (United States)

    Karki, Khadga J.

    2017-10-01

    Here, it is shown that when two optical frequency combs with identical mode spacing but different offset frequencies copropagate through a nonlinear optical fiber, four-wave mixing between them generates new modes. Although the spacings between the new modes depend on the difference of the offset frequencies, they appear irregular because of the large number of possible four-wave-mixing processes. However, when the difference in the offset frequencies is an integer fraction of the mode spacing of the original combs, the cascaded four-wave mixing generates a new comb with a fixed mode spacing given by the difference in the offset frequencies. This process can be used to substantially increase the mode density of a frequency comb. The method can be used in conjunction with new sources of frequency combs, such as quantum cascade lasers and microresonators, which have large mode spacing of tens of GHz. Decreasing the mode spacing of such sources is likely to increase their applicability.

  10. High-frequency sound waves to eliminate a horizon in the mixmaster universe.

    Science.gov (United States)

    Chitre, D. M.

    1972-01-01

    From the linear wave equation for small-amplitude sound waves in a curved space-time, there is derived a geodesiclike differential equation for sound rays to describe the motion of wave packets. These equations are applied in the generic, nonrotating, homogeneous closed-model universe (the 'mixmaster universe,' Bianchi type IX). As for light rays described by Doroshkevich and Novikov (DN), these sound rays can circumnavigate the universe near the singularity to remove particle horizons only for a small class of these models and in special directions. Although these results parallel those of DN, different Hamiltonian methods are used for treating the Einstein equations.

  11. Generalized Generators of Very-High-Frequency Gravitational Waves Including Ring Devices

    Science.gov (United States)

    Woods, R. C.; Baker, R. M. L.

    2009-03-01

    A number of researchers have previously proposed methods of generating very-high frequency gravitational waves (VHFGWs) using various interactions and mechanisms. These included mechanical devices, electromagnetic actuators, film bulk acoustic resonators (FBARs) using magnetron excitation, and nuclear explosions. In most cases the generated VHFGW power is a minute fraction of the input power needed to create the required excitation. Only on using a nuclear interaction is the output power significant; however, this appears not to be a practical generation method that can potentially achieve wide usage, at least in the near future. When a number of sources interfere constructively the amplitudes add in direct proportion to the number of radiation-element pairs or sources, N, and the radiation pattern narrows correspondingly in proportion to 1/N. Thus, the generated radiation flux (power per unit cross-sectional area) is proportional to the square of the number of sources or radiation element pairs, N2. Therefore, far greater GW power is obtained by using a larger number of smaller sources (consisting of mass pairs) excited (or "jerked") in phase rather than by using a smaller number of large excited (jerked) masses. The present paper examines the consequences of this scaling law to find how to optimize the generation of VHFGW power from a general set of jerked masses so that the result derives from the combination of all the individual excitations. Extreme cases that can be readily achieved using conventional known technology are firstly to jerk a set of atomic nuclei in phase, and secondly to jerk a set of electrons in phase. The former case uses most of the available mass and the second case sacrifices the excitations available from the masses of the corresponding nuclei. Specific devices, consisting of a ring or tube formed of rings of infra-red-excited molecules or electrons, are suggested. Algebraic and numerical estimates are given of the corresponding VHFGW

  12. New prototype of acousto-optical radio-wave spectrometer with parallel frequency processing for astrophysical applications

    Science.gov (United States)

    Shcherbakov, Alexandre S.; Chavez Dagostino, Miguel; Arellanes, Adan O.; Aguirre Lopez, Arturo

    2016-09-01

    We develop a multi-band spectrometer with a few spatially parallel optical arms for the combined processing of their data flow. Such multi-band capability has various applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar possibility is based on designing each optical arm individually via exploiting different materials for acousto-optical cells operating within various regimes, frequency ranges and light wavelengths from independent light sources. Individual beam shapers provide both the needed incident light polarization and the required apodization to increase the dynamic range of a system. After parallel acousto-optical processing, data flows are united by the joint CCD matrix on the stage of the combined electronic data processing. At the moment, the prototype combines still three bands, i.e. includes three spatial optical arms. The first low-frequency arm operates at the central frequencies 60-80 MHz with frequency bandwidth 40 MHz. The second arm is oriented to middle-frequencies 350-500 MHz with frequency bandwidth 200-300 MHz. The third arm is intended for ultra-high-frequency radio-wave signals about 1.0-1.5 GHz with frequency bandwidth <300 MHz. To-day, this spectrometer has the following preliminary performances. The first arm exhibits frequency resolution 20 KHz; while the second and third arms give the resolution 150-200 KHz. The numbers of resolvable spots are 1500- 2000 depending on the regime of operation. The fourth optical arm at the frequency range 3.5 GHz is currently under construction.

  13. Passive Wireless Cryogenic Liquid Level Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the continued development of passive wireless surface acoustic wave (SAW) based liquid level sensors for NASA application to cryogenic liquid...

  14. Passive Wireless Cryogenic Liquid Level Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the development of passive wireless surface acoustic wave (SAW) based liquid level sensors for NASA application to cryogenic liquid level...

  15. Miniaturized MMIC-Based Millimeter-Wave Frequency Synthesizers for Space Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — MMIC technology provides the technology base to reduce the size and weight of microwave and millimeter wave (MMW) equipment on board airborne and space-based...

  16. Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children

    NARCIS (Netherlands)

    Astill, R.G.; Piantoni, G.; Raymann, R.J.E.M; Vis, J.C.; Coppens, J.E.; Walker, M.P.; Stickgold, R.; van der Werf, Y.D.; van Someren, E.J.W.

    2014-01-01

    Background and Aim: The role of sleep in the enhancement of motor skills has been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children.

  17. The Influence of Stack Position and Acoustic Frequency on the Performance of Thermoacoustic Refrigerator with the Standing Wave

    Science.gov (United States)

    Kajurek, Jakub; Rusowicz, Artur; Grzebielec, Andrzej

    2017-12-01

    Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

  18. Broadband-tunable LP$_{01}$ mode frequency shifting by Raman coherence waves in H$_2$-filled hollow-core PCF

    CERN Document Server

    Bauerschmidt, S T; Abdolvand, Amir; Russell, Philip S J

    2015-01-01

    When a laser pump beam of sufficient intensity is incident on a Raman-active medium such as hydrogen gas, a strong Stokes signal, red-shifted by the Raman transition frequency {\\Omega}$_R$, is generated. This is accompanied by the creation of a "coherence wave" of synchronized molecular oscillations with wavevector {\\Delta}{\\beta} determined by the optical dispersion. Within its lifetime, this coherence wave can be used to shift by {\\Omega}$_R$ the frequency of a third "mixing" signal, provided phase-matching is satisfied, i.e., {\\Delta}{\\beta} is matched. Conventionally this can be arranged using non-collinear beams or higher-order waveguide modes. Here we report collinear phase-matched frequency shifting of an arbitrary mixing signal using only the fundamental LP$_{01}$ modes of a hydrogen-filled hollow-core PCF. This is made possible by the S-shaped dispersion curve that occurs around the pressure-tunable zero dispersion point. Phase-matched frequency shifting by 125 THz is possible from the UV to the near...

  19. Development of a low frequency shear horizontal piezoelectric transducer for the generation of plane SH waves

    Science.gov (United States)

    Boivin, Guillaume; Viens, Martin; Belanger, Pierre

    2016-02-01

    The shear horizontal guided wave fundamental mode (SH0) has the particularity of being the only non-dispersive plate guided wave mode. This characteristic makes this ultrasonic guided wave mode very attractive in non-destructive testing, facilitating signal processing for long range inspections. It is, however, difficult to generate only a single guided wave mode when using piezoelectric transduction. This work aims to develop a piezoelectric transducer capable of generating a virtually pure plane zeroth order shear horizontal wave. The chosen material was the PZT-5H for its dominant d15 piezoelectric constant, which makes it a perfect candidate for SH-wave generation. The transducer dimensions were optimised using an analytical model based on the Huygens' principle of superposition and the dipole pattern of a shear point source. A 3D multiphysics finite element model was then used to validate the analytical model results. Experimental validation was finally conducted with a laser Doppler vibrometer (LDV) system. Excellent agreement between the analytical model, finite element model and experimental validation was seen.

  20. The identification of solar wind waves at discrete frequencies and the role of the spectral analysis techniques

    Science.gov (United States)

    Di Matteo, S.; Villante, U.

    2017-05-01

    The occurrence of waves at discrete frequencies in the solar wind (SW) parameters has been reported in the scientific literature with some controversial results, mostly concerning the existence (and stability) of favored sets of frequencies. On the other hand, the experimental results might be influenced by the analytical methods adopted for the spectral analysis. We focused attention on the fluctuations of the SW dynamic pressure (PSW) occurring in the leading edges of streams following interplanetary shocks and compared the results of the Welch method (WM) with those of the multitaper method (MTM). The results of a simulation analysis demonstrate that the identification of the wave occurrence and the frequency estimate might be strongly influenced by the signal characteristics and analytical methods, especially in the presence of multicomponent signals. In SW streams, PSW oscillations are routinely detected in the entire range f ≈ 1.2-5.0 mHz; nevertheless, the WM/MTM agreement in the identification and frequency estimate occurs in ≈50% of events and different sets of favored frequencies would be proposed for the same set of events by the WM and MTM analysis. The histogram of the frequency distribution of the events identified by both methods suggests more relevant percentages between f ≈ 1.7-1.9, f ≈ 2.7-3.4, and f ≈ 3.9-4.4 (with a most relevant peak at f ≈ 4.2 mHz). Extremely severe thresholds select a small number (14) of remarkable events, with a one-to-one correspondence between WM and MTM: interestingly, these events reveal a tendency for a favored occurrence in bins centered at f ≈ 2.9 and at f ≈ 4.2 mHz.

  1. Electrosmog. Effects of high-frequency electromagnetic waves on health. Pt. 1. Elektrosmog. Gesundheitliche Wirkungen hochfrequenter elektromagnetischer Wellen. T. 1

    Energy Technology Data Exchange (ETDEWEB)

    Matthes, R. (Bundesamt fuer Strahlenschutz, Oberschleissheim (Germany). Inst. fuer Strahlenhygiene)

    1993-10-01

    (1) The concept of Electrosmog concerns technically electromagnetic waves and fields of variable frequency and intensity. In our environment, high frequency fields come almost entirely from man-made sources. (2) High frequency electromagnetic fields can cause physical effects either directly or indirectly - eg through conductive materials. Thermal effects are the most prominent. The action of force mediated by the field can cause the loadig of there electric charges in the body. (3) The amount of energy absorbed by a fabric can be calculated from the intensity of the yield and the conductivity of the material. (4) In-vitro studies have suggested that high frequency fields affect the cell membranes and can cause changes in their permeability, enzyme activity and immune responses; although there are no proven results blaming high frequency fields for such mutations, and effects on cell proliferation have not been ascertained. (5) A basic limit of O-4 W/kg has been set internationally for work-related exposure, according to public health considerations, and the limit for the general public is 0.08 W/kg. (6) These basic limits are generally kept as a minimum requirement, and generally exposure is a hot lower. When high frequency equipment is in use nearby, measures must be taken to ensure that sefety limits are upheld and injury avoided, to the eyes in particular. (orig./MG)

  2. Sympathetically-induced changes in microvascular cerebral blood flow and in the morphology of its low-frequency waves.

    Science.gov (United States)

    Deriu, F; Roatta, S; Grassi, C; Urciuoli, R; Micieli, G; Passatore, M

    1996-06-10

    The effect of bilateral cervical sympathetic nerve stimulation on microvascular cerebral blood flow, recorded at various depths in the parietal lobe and in ponto-mesencephalic areas, was investigated by laser-Doppler flowmetry in normotensive rabbits. These areas were chosen as representative of the vascular beds supplied by the carotid and vertebro-basilar systems, which exhibit different degrees of sympathetic innervation, the former being richer than the latter. Sympathetic stimulation at 30 imp/s affects cerebral blood flow in 77% of the parietal lobe and in 43% of the ponto-mesencephalic tested areas. In both cases the predominant effect was a reduction in blood flow (14.7 +/- 5.1% and 4.1 +/- 2.4%, respectively). The extent of the reduction in both areas was less if the stimulation frequency was decreased. Sometimes mean cerebral blood flow showed a small and transient increase, mainly in response to low-frequency stimulation. The morphology was analysed of low-frequency spontaneous oscillations in cerebral blood flow, attributed to vasomotion. Present in 41% of the tested areas (frequency 4-12 cycles/min, peak-to-peak amplitude 10-40% of mean value), these waves decreased in amplitude and increased in frequency during sympathetic stimulation, irrespective of changes in mean flow. The possibility has been proposed that the sympathetic action on low-frequency spontaneous oscillations may contribute to the protective influence that this system is known to exert on the blood-brain barrier in hypertension.

  3. High efficiency off-axis current drive by high frequency fast waves

    Science.gov (United States)

    Prater, R.; Pinsker, R. I.; Moeller, C. P.; Porkolab, M.; Vdovin, V.

    2014-02-01

    Modeling work shows that current drive can be done off-axis with high efficiency, as required for FNSF and DEMO, by using very high harmonic fast waves ("helicons" or "whistlers"). The modeling indicates that plasmas with high electron beta are needed in order for the current drive to take place off-axis, making DIII-D a highly suitable test vehicle for this process. The calculations show that the driven current is not very sensitive to the launched value of n∥, a result that can be understood from examination of the evolution of n∥ as the waves propagate in the plasma. Because of this insensitivity, relatively large values (˜3) of n∥ can be launched, thereby avoiding some of the problems with mode conversion in the boundary found in some previous experiments. Use of a traveling wave antenna provides a very narrow n∥ spectrum, which also helps avoid mode conversion.

  4. Photonic Implementation of 4-QAM/QPSK Electrical Modulation at Millimeter-Wave Frequency

    DEFF Research Database (Denmark)

    Yu, Xianbin; Jensen, Jesper Bevensee; Tafur Monroy, Idelfonso

    2008-01-01

    We propose a photonic method for generating millimeter-wave 4-QAM/QPSK modulated signals. The method is based on optical phase modulation by multilevel electrical signals and optical carrier-suppression. Simulation results are presented for 2.5 Gsymbol/s 4-QAM and QPSK signals at a 36 GHz carrier....... Furthermore, this method can be extended to generate millimeter-wave m-PSK signals and can be incorporated into broadband radio-over-fiber systems to support wireless/ wireline converged access network....

  5. Dynamic thermal wave response and propagation through building structures using infinite elements in time and frequency domain

    Science.gov (United States)

    Kazakov, Konstantin S.; Stoynova, Iliana Y.

    2017-07-01

    This paper is devoted to a new approach the dynamic termal response and the factor of termal wave propagation through of complex building structure to be evaluated using infinite elements. The far field of such structures is discretized by decay or mapped infinite elements. These elements are appropriate for complex building structures, subjected to termal wave propagation and solved in time or frequency domain. Such infinite elements can be treated as new modified forms of the recently proposed by the first author infinite elements with united shape functions. In the research the time domain form of the equations is demonstrated and used in the numerical example. Only 2D horizontal type infinite elements is used, but by similar techniques 2D vertical and 2D corner infinite elements can also be formulated. The application of the proposed elements in the Finite element method is demonstrated in brief.

  6. Theoretical study of collinear optical frequency comb generation under multi-wave, transient stimulated Raman scattering in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Smetanin, S N [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2014-11-30

    Using mathematical modelling we have studied the conditions of low-threshold collinear optical frequency comb generation under transient (picosecond) stimulated Raman scattering (SRS) and parametric four-wave coupling of SRS components in crystals. It is shown that Raman-parametric generation of an octave-spanning optical frequency comb occurs most effectively under intermediate, transient SRS at a pump pulse duration exceeding the dephasing time by five-to-twenty times. We have found the optimal values of not only the laser pump pulse duration, but also of the Raman crystal lengths corresponding to highly efficient generation of an optical frequency comb from the second anti-Stokes to the fourth Stokes Raman components. For the KGd(WO{sub 4}){sub 2} (high dispersion) and Ba(NO{sub 3}){sub 2} (low dispersion) crystals pumped at a wavelength of 1.064 μm and a pulse duration five or more times greater than the dephasing time, the optimum length of the crystal was 0.3 and 0.6 cm, respectively, which is consistent with the condition of the most effective Stokes – anti-Stokes coupling ΔkL ≈ 15, where Δk is the wave detuning from phase matching of Stokes – anti-Stokes coupling, determined by the refractive index dispersion of the SRS medium. (nonlinear optical phenomena)

  7. First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva, A.; Anderson, S. B.; Anderson, W. G.; Antier, S.; Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; AultONeal, K.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bawaj, M.; Bazzan, M.; Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.; Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.; Calloni, E.; Camp, J. B.; Canizares, P.; Cannon, K. C.; Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Carney, M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chatterjee, D.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, H.-P.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani, G.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.; Clark, J. A.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L. R.; Constancio, M.; Conti, L.; Cooper, S. J.; Corban, P.; Corbitt, T. R.; Corley, K. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davis, D.; Daw, E. J.; Day, B.; De, S.; DeBra, D.; Deelman, E.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devenson, J.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Duncan, J.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fong, H.; Forsyth, P. W. F.; Forsyth, S. S.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gabel, M.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar, S. G.; Garufi, F.; Gaudio, S.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannuksela, O. A.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J.-M.; Isi, M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.; Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, W.; Kim, W. S.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koch, P.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia, A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.; Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Liu, J.; Lo, R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lovelace, G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macfoy, S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña Hernandez, I.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matas, A.; Matichard, F.; Matone, L.; Mavalvala, N.; Mayani, R.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McCuller, L.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Mejuto-Villa, E.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minazzoli, O.; Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muniz, E. A. M.; Murray, P. G.; Napier, K.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Nery, M.; Neunzert, A.; Newport, J. M.; Newton, G.; Ng, K. K. Y.; Nguyen, T. T.; Nichols, D.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ormiston, R.; Ortega, L. F.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pace, A. E.; Page, J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pang, B.; Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell, J.; Prasad, J.; Pratt, J. W. W.; Predoi, V.; Prestegard, T.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Ramirez, K. E.; Rapagnani, P.; Raymond, V.; Razzano, M.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Ricker, P. M.; Rieger, S.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romel, C. L.; Romie, J. H.; Rosińska, D.; Ross, M. P.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Rynge, M.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Scheuer, J.; Schmidt, E.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schulte, B. W.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.; Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shao, L.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.; Son, E. J.; Sonnenberg, J. A.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, R.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Taylor, J. A.; Taylor, R.; Theeg, T.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.; Tso, R.; Tuyenbayev, D.; Ueno, K.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahi, K.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walet, R.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, J. Z.; Wang, M.; Wang, Y.-F.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wessel, E. K.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Wofford, J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, Hang; Yu, Haocun; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zelenova, T.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.-H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.; Anderson, D. P.; LIGO Scientific Collaboration; Virgo Collaboration

    2017-12-01

    We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7 [1 /√{Hz }] . At the frequency of best strain sensitivity, near 100 Hz, we set 90% confidence upper limits of 1.8 ×1 0-25. At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9 ×1 0-24. At 55 Hz we can exclude sources with ellipticities greater than 1 0-5 within 100 pc of Earth with fiducial value of the principal moment of inertia of 1038 kg m2 .

  8. Confluent Heun functions and the physics of black holes: Resonant frequencies, Hawking radiation and scattering of scalar waves

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, H.S., E-mail: horacio.santana.vieira@hotmail.com [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, CEP 58051-970, João Pessoa, PB (Brazil); Centro de Ciências, Tecnologia e Saúde, Universidade Estadual da Paraíba, CEP 58233-000, Araruna, PB (Brazil); Bezerra, V.B., E-mail: valdir@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, CEP 58051-970, João Pessoa, PB (Brazil)

    2016-10-15

    We apply the confluent Heun functions to study the resonant frequencies (quasispectrum), the Hawking radiation and the scattering process of scalar waves, in a class of spacetimes, namely, the ones generated by a Kerr–Newman–Kasuya spacetime (dyon black hole) and a Reissner–Nordström black hole surrounded by a magnetic field (Ernst spacetime). In both spacetimes, the solutions for the angular and radial parts of the corresponding Klein–Gordon equations are obtained exactly, for massive and massless fields, respectively. The special cases of Kerr and Schwarzschild black holes are analyzed and the solutions obtained, as well as in the case of a Schwarzschild black hole surrounded by a magnetic field. In all these special situations, the resonant frequencies, Hawking radiation and scattering are studied. - Highlights: • Charged massive scalar field in the dyon black hole and massless scalar field in the Ernst spacetime are analyzed. • The confluent Heun functions are applied to obtain the solution of the Klein–Gordon equation. • The resonant frequencies are obtained. • The Hawking radiation and the scattering process of scalar waves are examined.

  9. Algorithm for extracting multiple object waves without Fourier transform from a single image recorded by spatial frequency-division multiplexing and its application to digital holography

    Science.gov (United States)

    Tahara, Tatsuki; Akamatsu, Takanori; Arai, Yasuhiko; Shimobaba, Tomoyoshi; Ito, Tomoyoshi; Kakue, Takashi

    2017-11-01

    We propose a novel algorithm that does not require any Fourier transform to extract multiple object waves in a single image recorded with spatial frequency-division multiplexing. Smoothing is utilized to extract the desired object-wave information from a spatially multiplexed image. Numerical and experimental results show its validity and applicability for image and Fresnel digital holography. Our investigations clarify the speeding up of both the object-wave extractions and multiple object-image reconstructions quantitatively.

  10. Comparison of High, Intermediate, and Low Frequency Shock Wave Lithotripsy for Urinary Tract Stone Disease: Systematic Review and Network Meta-Analysis.

    Science.gov (United States)

    Kang, Dong Hyuk; Cho, Kang Su; Ham, Won Sik; Lee, Hyungmin; Kwon, Jong Kyou; Choi, Young Deuk; Lee, Joo Yong

    2016-01-01

    To perform a systematic review and network meta-analysis of randomized controlled trials (RCTs) to determine the optimal shock wave lithotripsy (SWL) frequency range for treating urinary stones, i.e., high-frequency (100-120 waves/minute), intermediate-frequency (80-90 waves/minute), and low-frequency (60-70 waves/minute) lithotripsy. Relevant RCTs were identified from electronic databases for meta-analysis of SWL success and complication rates. Using pairwise and network meta-analyses, comparisons were made by qualitative and quantitative syntheses. Outcome variables are provided as odds ratios (ORs) with 95% confidence intervals (CIs). Thirteen articles were included in the qualitative and quantitative synthesis using pairwise and network meta-analyses. On pairwise meta-analyses, comparable inter-study heterogeneity was observed for the success rate. On network meta-analyses, the success rates of low- (OR 2.2; 95% CI 1.5-2.6) and intermediate-frequency SWL (OR 2.5; 95% CI 1.3-4.6) were higher than high-frequency SWL. Forest plots from the network meta-analysis showed no significant differences in the success rate between low-frequency SWL versus intermediate-frequency SWL (OR 0.87; 95% CI 0.51-1.7). There were no differences in complication rate across different SWL frequency ranges. By rank-probability testing, intermediate-frequency SWL was ranked highest for success rate, followed by low-frequency and high-frequency SWL. Low-frequency SWL was also ranked highest for low complication rate, with high- and intermediate-frequency SWL ranked lower. Intermediate- and low-frequency SWL have better treatment outcomes than high-frequency SWL when considering both efficacy and complication.

  11. Comparison of High, Intermediate, and Low Frequency Shock Wave Lithotripsy for Urinary Tract Stone Disease: Systematic Review and Network Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    Dong Hyuk Kang

    Full Text Available To perform a systematic review and network meta-analysis of randomized controlled trials (RCTs to determine the optimal shock wave lithotripsy (SWL frequency range for treating urinary stones, i.e., high-frequency (100-120 waves/minute, intermediate-frequency (80-90 waves/minute, and low-frequency (60-70 waves/minute lithotripsy.Relevant RCTs were identified from electronic databases for meta-analysis of SWL success and complication rates. Using pairwise and network meta-analyses, comparisons were made by qualitative and quantitative syntheses. Outcome variables are provided as odds ratios (ORs with 95% confidence intervals (CIs.Thirteen articles were included in the qualitative and quantitative synthesis using pairwise and network meta-analyses. On pairwise meta-analyses, comparable inter-study heterogeneity was observed for the success rate. On network meta-analyses, the success rates of low- (OR 2.2; 95% CI 1.5-2.6 and intermediate-frequency SWL (OR 2.5; 95% CI 1.3-4.6 were higher than high-frequency SWL. Forest plots from the network meta-analysis showed no significant differences in the success rate between low-frequency SWL versus intermediate-frequency SWL (OR 0.87; 95% CI 0.51-1.7. There were no differences in complication rate across different SWL frequency ranges. By rank-probability testing, intermediate-frequency SWL was ranked highest for success rate, followed by low-frequency and high-frequency SWL. Low-frequency SWL was also ranked highest for low complication rate, with high- and intermediate-frequency SWL ranked lower.Intermediate- and low-frequency SWL have better treatment outcomes than high-frequency SWL when considering both efficacy and complication.

  12. First low frequency all-sky search for continuous gravitational wave signals

    NARCIS (Netherlands)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Phythian-Adams, A.T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.T.; Aguiar, O. D.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Amariutei, D. V.; Andersen, M.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Ashton, G.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, R.D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Bartlett, J.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, M.J.; Birney, R.; Biscans, S.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, C. D.; Bloemen, A.L.S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, J.G.; Bojtos, P.; Bond, T.C; Bondu, F.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Branco, V.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, A.D.; Brown, D.; Brown, D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Bustillo, J. Calderon; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Diaz, J. Casanueva; Casentini, C.; Caudill, S.; Cavaglia, M.; Cavalier, F.; Cavalieri, R.; Celerier, C.; Cella, G.; Cepeda, C. B.; Baiardi, L. Cerboni; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, D. S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Qian; Chua, S. E.; Chung, E.S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P. -F.; Colla, A.; Collette, C. G.; Colombini, M.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, A.C.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, A.L.; Cuoco, E.; Dal Canton, T.; Damjanic, M. D.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Debra, D.; Debreczeni, G.; Degallaix, J.; De laurentis, M.; Deleglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.A.; Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Dia, M. C.; Di Fiore, L.; Giovanni, M.G.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Dominguez, E.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Edwards, M.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.; Eichholz, J. M.; Eikenberry, S. S.; Essick, R. C.; Etzel, T.; Evans, T. M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fournier, J. -D.; Franco, S; Frasca, S.; Frasconi, F.; Frede, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Gergely, L. A.; Germain, V.; Ghosh, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gleason, J. R.; Goetz, E.; Goetz, R.; Gondan, L.; Gonzalez, Idelmis G.; Gonzalez, J.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Lee-Gosselin, M.; Gossler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.M.; Greco, G.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C. J.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Buffoni-Hall, R.; Hall, E. D.; Hammer, D. X.; Hammond, G.L.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, P.J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C. -J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hoelscher-Obermaier, J.; Hofman, D.; Hollitt, S. E.; Holt, K.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Islas, G.; Isler, J. C.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacobson, M. B.; Jang, D.H.; Jaranowski, P.; Jawahar, S.; Ji, Y.; Jimenez-Forteza, F.; Johnson, W.; Jones, I.D.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalogera, V.; Kandhasamy, S.; Kang, G.H.; Kanner, J. B.; Karki, S.; Karlen, J. L.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kefelian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kerrigan, J.; Key, J. S.; Khalili, F. Y.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J. T.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Krolak, A.; Krueger, C.; Kuehn, G.; Kumar, A.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C.H.; Lee, K.H.; Lee, M.H.; Lee, J. P.; Lee, J. P.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Lin, A. C.; Littenberg, T. B.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lubinski, M. J.; Luck, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; Macarthur, J.; Macdonald, E. P.; MacDonald, T.T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Madden-Fong, D. X.; Magana-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mangini, N. M.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marka, S.; Ma, H.Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R.M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meinders, M.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B.C.; Moraru, D.; Gutierrez Moreno, M.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, A.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P.G.; Mytidis, A.; Nagy, M. F.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Gutierrez-Neri, M.; Newton-Howes, G.; Nguyen, T. T.; Nielsen, A. B.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J.; Oh, S. H.; Ohme, F.; Okounkova, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ortega, W. E.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Padilla, C. T.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pan, Y.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Papa, M. A.; Paris, H. R.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patrick, Z.; Pedraza, M.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poeld, J. H.; Poggiani, R.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Purrer, M.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Racz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rodger, A. S.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosins, D.; Rowan, S.; Rud, A.; Ruggi, P.; Ryan, K.A.; Sachdev, P.S.; Sadecki, T.; Sadeghian, L.; Saleem, M.; Salemi, F.; Sammut, L.; Sanchez, E.; Sandberg, V.; Sanders, J. R.; Santiago-Prieto, I.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, P.; Schnabel, R.B.; Schofield, R. M. S.; Schonbeck, A.; Schreiber, K.E.C.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, M.S.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Sevigny, A.; Shaddock, D. A.; Shaffery, P.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, António Dias da; Simakov, D.; Singer, A; Singer, L. P.; Singh, R.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, R. J. E.; Smith, N.D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Steplewski, S.; Stevenson-Moore, P.; Stone, J.R.; Strain, K. A.; Straniero, N.; Strauss, N. A.; Strigin, S. E.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepanczyk, M. J.; Tacca, M.D.; Talukder, D.; Tanner, D. B.; Tap, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, W.R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Trifiro, D.; Tringali, M. C.; Tse, M.; Turconi, M.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; Van Bakel, N.; Van Beuzekom, Martin; Van den Brand, J. F. J.; Van Den Broeck, C.F.F.; van der Schaaf, L.; van der Sluys, M. V.; Eijningen, J. V.; Eggel, A. A. V.; Vardaro, M.; Vass, S.; Vasuth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P.J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Vicere, A.; Vinet, J. -Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, MT; Wade, L. E.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L. -W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.M.; Wessels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Williams, K. J.; Williams, L.; Williams, D.R.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yvert, M.; Zadrozny, A.; Zangrando, L.; Zanolin, M.; Zendri, J. -P.; Zhang, Fan; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.

    2016-01-01

    Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of 10−23/√Hz at 100 Hz, the product of observable volume and measurement time

  13. Absolute parametric instability of low-frequency waves in a 2D ...

    Indian Academy of Sciences (India)

    Using the separation method, absolute parametric instability (API) of electrostatic waves in a magnetized pumped warm plasma is investigated. In this case the effect of static strong magnetic field is considered. The problem of strong magnetic field is solved in two-dimensional (2D) nonuniform plane plasma. Equations ...

  14. Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children

    NARCIS (Netherlands)

    Astill, Rebecca G; Piantoni, Giovanni; Raymann, Roy J E M; Vis, Jose C; Coppens, Joris E; Walker, Matthew P; Stickgold, Robert; Van Der Werf, Ysbrand D; Van Someren, Eus J W

    2014-01-01

    Background and Aim: The role of sleep in the enhancement of motor skills has been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children. Hypothesis: We hypothesized sleep-dependence of skill enhancement

  15. Fast Iterative Solution of the Time-Harmonic Elastic Wave Equation at Multiple Frequencies

    NARCIS (Netherlands)

    Baumann, M.M.

    2018-01-01

    Seismic Full-Waveform Inversion is an imaging technique to better understand the earth's subsurface. Therefore, the reflection intensity of sound waves is measured in a field experiment and is matched with the results from a computer simulation in a least-squares sense. From a computational

  16. Effects of density fluctuations on nonlinear evolution of low-frequency Alfven waves in solar wind plasmas

    Science.gov (United States)

    Nariyuki, Y.; Seough, J.

    2015-12-01

    It is well known that low-frequency Alfven waves are unstable to parametric instabilities, in which these waves are nonlinearly coupled with density fluctuations [e.g, Nariyuki+Hada, JGR, 2007 and references therein]. In solar wind plasmas, low-frequency fluctuations with non-zero cross-helicity are frequently observed [e.g., Bruno+Carbone, Living Rev. Solar Phys. (2013) and references therein]. When the absolute values of normalized cross helicities are close to the unity, the fluctuations may be composed of uni-directionally (anti-sunward) propagating Alfven waves. The derivative nonlinear Schrodinger equation (DNLS) has been known as the mode of modulational instabilities of unidirectional Alfven waves [Mio et al, JPSJ, 1976; Mjolhus, JPP, 1976]. In the DNLS, the density fluctuations are assumed to be the quasi-static state, which is determined according to the ponderomotive force of envelope-modulated Alfven waves. The DNLS was extended to include the obliquely propagating, compressional component of magnetic field by Mjolhus and Wyller (JPP, 1988). The kinetically modified DNLS (KDNLS) has also been discussed by many authors [Rogister, POF, 1971; Mjolhus and Wyller, Phys. Scr, 1986; JPP, 1988; Spangler, POF B, 1989; 1990; Medvedev+Diamond, POP, 1996; Nariyuki et al, POP, 2013]. On the other hand, ion acoustic modes [Hada, 1993], large scale inhomogeneity of plasmas [Buti et al, APJ, 1999; Nariyuki, POP, 2015] and random density fluctuations [Ruderman, POP, 2002] can also affect nonlinear evolution of Alfven waves. At the present time, combined effects of these effects are not fully understood. In this presentation, we discuss two models: one of them is the model including both ion kinetic effects and ion acoustic mode and another is the model including finite thermal effects and random density fluctuations. In the former case, ion kinetic effects on both longitudinal [Nariyuki+Hada, JPSJ, 2007] and transverse modulational instabilities are discussed, while the

  17. Optical coherence tomography of scattering media using frequency-modulated continuous-wave techniques with tunable near-infrared laser

    Science.gov (United States)

    Haberland, Udo; Jansen, Peter; Blazek, Vladimir; Schmitt, Hans J.

    1997-05-01

    A new near-infrared coherent imaging technique that can reveal scattering bodies embedded in highly scattering media is presented. Its underlying principle is extended from frequency modulated continuous wave radar systems. This technique has advantages over low coherence tomography as it does not require the reference mirror to be scanned. The tunable laser is characterized and the system's performance is demonstrated on images recorded from solid scattering phantoms. Furthermore a combination of our chirp-tomography (C-OCT) and laser Doppler perfusion imaging (LDPI) is demonstrated. The influence of moving scatterers on the tomographic images are discussed.

  18. Chemical Ni-C Bonding in Ni-CNT Composite by a Microwave Welding Method and Its Induced High-frequency Radar Frequency Electromagnetic Wave Absorption.

    Science.gov (United States)

    Sha, Linna; Gao, Peng; Wu, Tingting; Chen, Yujin

    2017-11-01

    In this work, a microwave welding method has been used for the construction of chemical Ni-C bonding at the interface between carbon nanotubes (CNTs) and metal Ni in order to provide a different surface electron distribution, which determined the electromagnetic (EM) wave absorption properties based on a surface plasmon resonance (SPR) mechanism. Through a serial of detailed examinations, such as XRD, SEM, TEM, HRTEM, XPS and Raman spectrum etc., the as-expected chemical Ni-C bonding between CNTs and metal Ni has been confirmed. And the BET and surface Zeta potential measurements uncovered the great evolution of structure and electronic density compared with CNTs, metal Ni and Ni-CNT composite without Ni-C bonding. Correspondingly, except the EM absorption due to CNTs and metal Ni in the composite, another wide and strong EM absorption band ranging from 10 GHz to 18 GHz was found, which was induced by the Ni-C bonded interface. The absorption bandwidth with reflection loss less than -10 dB is up to 6.5 GHz (in the frequency range of 10.1-16.6 GHz). With a thinner thickness and more exposed Ni-C interfaces, the Ni-CNT composite displayed a minimum reflection loss, which means that more than 99% EM wave energy attenuated by the absorber.

  19. Plasma filamentation and shock wave enhancement in microwave rockets by combining low-frequency microwaves with external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Masayuki, E-mail: m.takahashi@al.t.u-tokyo.ac.jp [Department of Aeronautics and Astronautics, The University of Tokyo, Bunkyo-ku 113-8656 (Japan); Ohnishi, Naofumi [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2016-08-14

    A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasma increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.

  20. Absorption and emission of extraordinary-mode electromagnetic waves near cyclotron frequency in nonequilibrium plasmas

    Science.gov (United States)

    Wu, C. S.; Lin, C. S.; Wong, H. K.; Tsai, S. T.; Zhou, R. L.

    1981-01-01

    An investigation is presented of two cases: (1) weakly relativistic electrons with a loss-cone type distribution, and (2) electrons with a drift velocity parallel to the ambient magnetic field. Numerical computations are given for physical parameters close to those in the polar region of the earth magnetosphere and laboratory experiments, with attention to the fast extraordinary-mode radiation whose frequency is near that of the electron cyclotron frequency. The fast extraordinary mode can escape from a strong field region to the weaker field region and may therefore be measured outside the plasma. It is found that the X mode radiation can be amplified by means of a cyclotron maser effect when the electrons have a loss-cone distribution, and it is concluded that, when the electron energy is sufficiently high, the X mode cutoff frequency may be lower than the cyclotron frequency.

  1. Research on the FDTD method of scattering effects of obliquely incident electromagnetic waves in time-varying plasma sheath on collision and plasma frequencies

    Science.gov (United States)

    Chen, Wei; Guo, Li-xin; Li, Jiang-ting

    2017-04-01

    This study analyzes the scattering characteristics of obliquely incident electromagnetic (EM) waves in a time-varying plasma sheath. The finite-difference time-domain algorithm is applied. According to the empirical formula of the collision frequency in a plasma sheath, the plasma frequency, temperature, and pressure are assumed to vary with time in the form of exponential rise. Some scattering problems of EM waves are discussed by calculating the radar cross section (RCS) of the time-varying plasma. The laws of the RCS varying with time are summarized at the L and S wave bands.

  2. High efficiency off-axis current drive by high frequency fast waves

    Energy Technology Data Exchange (ETDEWEB)

    Prater, R.; Pinsker, R. I.; Moeller, C. P. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Porkolab, M.; Vdovin, V. [Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)

    2014-02-12

    Modeling work shows that current drive can be done off-axis with high efficiency, as required for FNSF and DEMO, by using very high harmonic fast waves (“helicons” or “whistlers”). The modeling indicates that plasmas with high electron beta are needed in order for the current drive to take place off-axis, making DIII-D a highly suitable test vehicle for this process. The calculations show that the driven current is not very sensitive to the launched value of n{sub ∥}, a result that can be understood from examination of the evolution of n{sub ∥} as the waves propagate in the plasma. Because of this insensitivity, relatively large values (∼3) of n{sub ∥} can be launched, thereby avoiding some of the problems with mode conversion in the boundary found in some previous experiments. Use of a traveling wave antenna provides a very narrow n{sub ∥} spectrum, which also helps avoid mode conversion.

  3. 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...... times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for the UK is estimated at 25% of current demand; a lot less, but a very substantial amount nonetheless....

  4. Design of InP DHBT power amplifiers at millimeter-wave frequencies using interstage matched cascode technique

    DEFF Research Database (Denmark)

    Yan, Lei; Johansen, Tom Keinicke

    2013-01-01

    In this paper, the design of InP DHBT based millimeter-wave(mm-wave) power amplifiers(PAs) using an interstage matched cascode technique is presented. The output power of a traditional cascode is limited by the early saturation of the common-base(CB) device. The interstage matched cascode can...... be employed to improve the power handling ability through optimizing the input impedance of the CB device. The minimized power mismatch between the CB and the common-emitter(CE) devices results in an improved saturated output power. To demonstrate the technique for power amplifier designs at mm......-wave frequencies, a single-branch cascode based PA using single-finger devices and a two-way combined based PA using three-finger devices are fabricated. The single-branch design shows a measured power gain of 9.2dB and a saturated output power of 12.3dBm at 67.2GHz and the two-way combined design shows a power...

  5. Estimation of the whole-body averaged SAR of grounded human models for plane wave exposure at respective resonance frequencies.

    Science.gov (United States)

    Hirata, Akimasa; Yanase, Kazuya; Laakso, Ilkka; Chan, Kwok Hung; Fujiwara, Osamu; Nagaoka, Tomoaki; Watanabe, Soichi; Conil, Emmanuelle; Wiart, Joe

    2012-12-21

    According to the international guidelines, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric of basic restriction for radio-frequency whole-body exposure. It is well known that the WBA-SAR largely depends on the frequency of the incident wave for a given incident power density. The frequency at which the WBA-SAR becomes maximal is called the 'resonance frequency'. Our previous study proposed a scheme for estimating the WBA-SAR at this resonance frequency based on an analogy between the power absorption characteristic of human models in free space and that of a dipole antenna. However, a scheme for estimating the WBA-SAR in a grounded human has not been discussed sufficiently, even though the WBA-SAR in a grounded human is larger than that in an ungrounded human. In this study, with the use of the finite-difference time-domain method, the grounded condition is confirmed to be the worst-case exposure for human body models in a standing posture. Then, WBA-SARs in grounded human models are calculated at their respective resonant frequencies. A formula for estimating the WBA-SAR of a human standing on the ground is proposed based on an analogy with a quarter-wavelength monopole antenna. First, homogenized human body models are shown to provide the conservative WBA-SAR as compared with anatomically based models. Based on the formula proposed here, the WBA-SARs in grounded human models are approximately 10% larger than those in free space. The variability of the WBA-SAR was shown to be ±30% even for humans of the same age, which is caused by the body shape.

  6. SPH Simulation of Acoustic Waves: Effects of Frequency, Sound Pressure, and Particle Spacing

    Directory of Open Access Journals (Sweden)

    Y. O. Zhang

    2015-01-01

    Full Text Available Acoustic problems consisting of multiphase systems or with deformable boundaries are difficult to describe using mesh-based methods, while the meshfree, Lagrangian smoothed particle hydrodynamics (SPH method can handle such complicated problems. In this paper, after solving linearized acoustic equations with the standard SPH theory, the feasibility of the SPH method in simulating sound propagation in the time domain is validated. The effects of sound frequency, maximum sound pressure amplitude, and particle spacing on numerical error and time cost are then subsequently discussed based on the sound propagation simulation. The discussion based on a limited range of frequency and sound pressure demonstrates that the rising of sound frequency increases simulation error, and the increase is nonlinear, whereas the rising sound pressure has limited effects on the error. In addition, decreasing the particle spacing reduces the numerical error, while simultaneously increasing the CPU time. The trend of both changes is close to linear on a logarithmic scale.

  7. Low-frequency electrostatic waves in the ionospheric E-region: a comparison of rocket observations and numerical simulations

    Directory of Open Access Journals (Sweden)

    L. Dyrud

    2006-11-01

    Full Text Available Low frequency electrostatic waves in the lower parts of the ionosphere are studied by a comparison of observations by instrumented rockets and of results from numerical simulations. Particular attention is given to the spectral properties of the waves. On the basis of a good agreement between the observations and the simulations, it can be argued that the most important nonlinear dynamics can be accounted for in a 2-D numerical model, referring to a plane perpendicular to a locally homogeneous magnetic field. It does not seem necessary to take into account turbulent fluctuations or motions in the neutral gas component. The numerical simulations explain the observed strongly intermittent nature of the fluctuations: secondary instabilities develop on the large scale gradients of the largest amplitude waves, and the small scale dynamics is strongly influenced by these secondary instabilities. We compare potential variations obtained at a single position in the numerical simulations with two point potential-difference signals, where the latter is the adequate representation for the data obtained by instrumented rockets. We can demonstrate a significant reduction in the amount of information concerning the plasma turbulence when the latter signal is used for analysis. In particular we show that the bicoherence estimate is strongly affected. The conclusions have implications for studies of low frequency ionospheric fluctuations in the E and F regions by instrumented rockets, and also for other methods relying on difference measurements, using two probes with large separation. The analysis also resolves a long standing controversy concerning the supersonic phase velocities of these cross-field instabilities being observed in laboratory experiments.

  8. Survey of low-frequency electromagnetic waves stimulated by two coexisting newborn ion species

    Science.gov (United States)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1988-01-01

    Parallel electromagnetic instabilities generated by coexisting newborn hydrogen and oxygen ions are studied for different orientations of the interplanetary magnetic field with respect to the solar wind velocity. The wave growth dependence on the densities and temperatures of the newborn species is investigated. The results indicate that in most domains of the Brillouin plane each ion beam can excite resonant instabilities without undue influence from the other newborn ion species. Although comparable resonant instabilities are more efficiently generated by the lighter newborn ions in ion-rich environments, the growth stimulated by the heavier species can withstand large beam density decreases.

  9. Mapping of wave packets in direct fragmentation via pump-probe frequency integrated fluorescence spectroscopy

    DEFF Research Database (Denmark)

    Engel, Volker; Henriksen, Niels Engholm

    2000-01-01

    We consider femtosecond excitation of a molecule to a dissociative electronic state. The quantum dynamics is recorded via delayed excitation to a higher electronic state and measurement of the total fluorescence from this state detected as a function of delay time. It is shown that the signal can...... be used to determine the probability density distribution of the outgoing wave packet describing the fragmentation. This, in particular, applies to the case of fragment detection since then the time-dependent signal directly measures the probability flux at a fixed value of the dissociation coordinate...

  10. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles

    DEFF Research Database (Denmark)

    El-Ella, Haitham; Ahmadi, Sepehr; Wojciechowski, Adam

    2017-01-01

    Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the deri...

  11. Waves of change: immunomodulation of the innate immune response by low frequency electromagnetic field exposure

    NARCIS (Netherlands)

    Golbach, L.A.

    2015-01-01

      In this thesis we investigated possible modulatory roles of low frequency electromagnetic fields (LF EMFs) exposure on the innate immune system. Recent decades have seen a huge increase in the use of electronic devices that nowadays enable us to communicate with distant family, enjoy music

  12. The standing wave phenomenon in radio telescopes - Frequency modulation of the WSRT primary beam

    NARCIS (Netherlands)

    Popping, A.; Braun, R.

    Context. Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity, particularly when "mosaicing" over multiple telescope pointings. Aims. We hope to overcome these limitations by constructing a frequency-resolved,

  13. Impacts of short-time scale water column variability on broadband high-frequency acoustic wave propagation

    Science.gov (United States)

    Eickmeier, Justin

    Acoustical oceanography is one way to study the ocean, its internal layers, boundaries and all processes occurring within using underwater acoustics. Acoustical sensing techniques allows for the measurement of ocean processes from within that logistically or financially preclude traditional in-situ measurements. Acoustic signals propagate as pressure wavefronts from a source to a receiver through an ocean medium with variable physical parameters. The water column physical parameters that change acoustic wave propagation in the ocean include temperature, salinity, current, surface roughness, seafloor bathymetry, and vertical stratification over variable time scales. The impacts of short-time scale water column variability on acoustic wave propagation include coherent and incoherent surface reflections, wavefront arrival time delay, focusing or defocusing of the intensity of acoustic beams and refraction of acoustic rays. This study focuses on high-frequency broadband acoustic waves, and examines the influence of short-time scale water column variability on broadband high-frequency acoustics, wavefronts, from 7 to 28 kHz, in shallow water. Short-time scale variability is on the order of seconds to hours and the short-spatial scale variability is on the order of few centimeters. Experimental results were collected during an acoustic experiment along 100 m isobaths and data analysis was conducted using available acoustic wave propagation models. Three main topics are studied to show that acoustic waves are viable as a remote sensing tool to measure oceanographic parameters in shallow water. First, coherent surface reflections forming striation patterns, from multipath receptions, through rough surface interaction of broadband acoustic signals with the dynamic sea surface are analyzed. Matched filtered results of received acoustic waves are compared with a ray tracing numerical model using a sea surface boundary generated from measured water wave spectra at the time of

  14. A Novel Ku-Band/Ka-Band and Ka-Band/E-Band Multimode Waveguide Couplers for Power Measurement of Traveling-Wave Tube Amplifier Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2015-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler, fabricated from two dissimilar frequency band waveguides, is capable of isolating power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT) amplifier. Test results from proof-of-concept demonstrations are presented for a Ku-band/Ka-band MDC and a Ka-band/E-band MDC. In addition to power measurements at harmonic frequencies, a potential application of the MDC is in the design of a satellite borne beacon source for atmospheric propagation studies at millimeter-wave (mm-wave) frequencies (Ka-band and E-band).

  15. Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

    Science.gov (United States)

    Stefan, V. Alexander; IAPS-team Team

    2017-10-01

    The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

  16. Design and modeling of InP DHBT power amplifiers at millimeter-wave frequencies

    DEFF Research Database (Denmark)

    Yan, Lei; Johansen, Tom K.

    2012-01-01

    In this paper, the design and modeling of InP DHBT based millimeter-wave(mm-wave) power amplifiers is described. This includes the modeling of InP DHBT devices and layout parasitics. An EM-circuit co-simulation approach is described to allow all parasitics to be modeled for accurate circuit...... performance evaluation. A single-branch cascode based PA using single-finger InP DHBT devices shows a measured power gain of 9.2dB and a saturated output power of 12.3dBm at 67.2GHz. The output power at 1dB compression is 9.0dBm. A similar two-way combined cascode based PA using three-finger devices...... demonstrates a power gain of 4.5dB with a saturated output power of 14.2dBm at 69.2GHz. © 2012 European Microwave Assoc....

  17. Preliminary results of high-frequency surface wave tomography along MASE line

    Science.gov (United States)

    Iglesias, A.; Clayton, R. W.; Pacheco, J.; Singh, S. K.; Pérez-Campos, X.; Valdés-González, C.

    2006-12-01

    The MASE array is a line of 100 broadband seismic stations, perpendicular to the Middle American Trench, , that traverses Mexico from the Pacific coast to a point close to the Gulf of Mexico. We present preliminary results of a group-velocity tomographic inversion along the line and of an inversion of local dispersion curves reconstructed from the tomographic images. The MASE array was complemented with data from seismological stations operated by the Mexican Seismological Service (SSN), to make the images more 3D. In order to compute the tomographic maps, we determine group-velocity dispersion curves for Rayleigh waves (5-50s) from a set of ~50 well located earthquakes recorded by MASE and SSN stations. These dispersion curves map average group velocities between each earthquake-station combination. We construct a .125 x .125 km grid over central and south Mexico. At each element, the observed group velocity for each period is inverted to obtain a group-velocity value. Using the images for several periods, we construct a local dispersion curve for each MASE station. Finally, these local dispersion curves are individually inverted using a layered homogeneous medium and a simulated annealing algorithm to obtain an S-wave velocity crustal structure. Results show variations in crustal thicjness along the MASE line, as well as indication of a mantle wedge under the Mexcian Volcanic Belt.

  18. Effect of radio frequency waves of electromagnetic field on the tubulin.

    Science.gov (United States)

    Taghi, Mousavi; Gholamhosein, Riazi; Saeed, Rezayi-Zarchi

    2013-09-01

    Microtubules (MTs) are macromolecular structures consisting of tubulin heterodimers and present in almost every eukaryotic cell. MTs fulfill all conditions for generation of electromagnetic field and are electrically polar due to the electrical polarity of a tubulin heterodimer. The calculated static electric dipole moment of about 1000 Debye makes them capable of being aligned parallel to the applied electromagnetic field direction. In the present study, the tubulin heterodimers were extracted and purified from the rat brains. MTs were obtained by polymerization in vitro. Samples of microtubules were adsorbed in the absence and in the presence of electromagnetic fields with radio frequency of 900 Hz. Our results demonstrate the effect of electromagnetic field with 900 Hz frequency to change the structure of MTs. In this paper, a related patent was used that will help to better understand the studied subject.

  19. Single-frequency tunable long-wave infrared OP-GaAs OPO for gas sensing

    Science.gov (United States)

    Armougom, J.; Clément, Q.; Melkonian, J.-M.; Dherbecourt, J.-B.; Raybaut, M.; Grisard, A.; Lallier, E.; Gérard, B.; Faure, B.; Souhaité, G.; Godard, A.

    2017-02-01

    We report on the first single-frequency nanosecond optical parametric oscillator (OPO) emitting in the longwave infrared, and use it to perform standoff detection of ammonia vapor by differential spectrometry. The OPO is based on orientation-patterned GaAs (OP-GaAs) pumped by a pulsed single-frequency Tm:YAP microlaser. Single-longitudinal mode emission is obtained owing to a nested cavity OPO (NesCOPO) scheme. The OPO is tuned over 700 nm around 10.4 μm, allowing to measure the absorption spectrum of ammonia across several lines at atmospheric pressure. The potential of this OPO for standoff detection of hazardous gases is also discussed.

  20. Applications of a plane wave based room correction system for low frequencies using multiple loudspeakers

    DEFF Research Database (Denmark)

    Celestinos, Adrian; Nielsen, Sofus Birkedal

    2008-01-01

    When low frequency sound is radiated inside small listening spaces by loudspeakers, large uniformities occur over the sound field. This is due to the multiple reflection and diffraction of sound on the walls and different objects in the room. A developed system named Controlled Acoustically Bass...... System (CABS) produces uniform sound field at low frequencies. This is performed by utilizing loudspeakers at the front wall and extra loudspeakers at the opposite wall, processed to remove the rear-wall reflection of a rectangular room. Effectiveness of CABS on different room scenarios has been...... evaluated by using a computer simulation program based on the Finite Difference Time Domain Method (FDTD). CABS has been simulated in a small car cabin and in an irregular room. Non-ideal placement of loudspeakers in CABS have been evaluated. The influence of utilizing CABS with different types...

  1. Differences in EEG delta frequency characteristics and patterns in slow-wave sleep between dementia patients and controls: a pilot study.

    Science.gov (United States)

    Bonanni, Enrica; Di Coscio, Elisa; Maestri, Michelangelo; Carnicelli, Luca; Tsekou, Hara; Economou, Nicholas Tiberio; Paparrigopoulos, Thomas; Bonakis, Anastasios; Papageorgiou, Sokratis G; Vassilopoulos, Dimitris; Soldatos, Constantin R; Murri, Luigi; Ktonas, Periklis Y

    2012-02-01

    To evaluate the modifications of EEG activity during slow-wave sleep in patients with dementia compared with healthy elderly subjects, using spectral analysis and period-amplitude analysis. Five patients with dementia and 5 elderly control subjects underwent night polysomnographic recordings. For each of the first three nonrapid eye movement-rapid eye movement sleep cycles, a well-defined slow-wave sleep portion was chosen. The delta frequency band (0.4-3.6 Hz) in these portions was analyzed with both spectral analysis and period-amplitude analysis. Spectral analysis showed an increase in the delta band power in the dementia group, with a decrease across the night observed only in the control group. For the dementia group, period-amplitude analysis showed a decrease in well-defined delta waves of frequency lower than 1.6 Hz and an increase in such waves of frequency higher than 2 Hz, in incidence and amplitude. Our study showed (1) a loss of the dynamics of delta band power across the night sleep, in dementia, and (2) a different distribution of delta waves during slow-wave sleep in dementia compared with control subjects. This kind of computer-based analysis can highlight the presence of a pathologic delta activity during slow-wave sleep in dementia and may support the hypothesis of a dynamic interaction between sleep alteration and cognitive decline.

  2. Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations

    Directory of Open Access Journals (Sweden)

    A. K. Sinha

    2002-01-01

    Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not

  3. Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations

    Directory of Open Access Journals (Sweden)

    A. K. Sinha

    Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not

  4. Adiabatic radio-frequency potentials for the coherent manipulation of matter waves

    DEFF Research Database (Denmark)

    Lesanovsky, Igor; Schumm, Thorsten; Hofferberth, S.

    2006-01-01

    Adiabatic dressed state potentials are created when magnetic substates of trapped atoms are coupled by a radio-frequency field. We discuss their theoretical foundations a