On square-wave-driven stochastic resonance for energy harvesting in a bistable system

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

Su, Dongxu, E-mail: sudx@iis.u-tokyo.ac.jp; Zheng, Rencheng; Nakano, Kimihiko

Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analyticalmore » model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.« less

Modeling Surfzone/Inner-shelf Exchange

DTIC Science & Technology

2013-09-30

goal here is the use a wave-resolving Boussinesq model to figure out how to parameterize the vorticity generation due to short-crested breaking of...individual waves. The Boussinesq model funwaveC used here, developed by the PI and distributed as open-source software, has been val- idated in ONR funded...shading of bottom bathymetry, mooring locations (green squares) and the local co-ordinate system (black arrows). Positive x is directed towards the

Note: A novel method for generating multichannel quasi-square-wave pulses.

PubMed

Mao, C; Zou, X; Wang, X

2015-08-01

A 21-channel quasi-square-wave nanosecond pulse generator was constructed. The generator consists of a high-voltage square-wave pulser and a channel divider. Using an electromagnetic relay as a switch and a 50-Ω polyethylene cable as a pulse forming line, the high-voltage pulser produces a 10-ns square-wave pulse of 1070 V. With a specially designed resistor-cable network, the channel divider divides the high-voltage square-wave pulse into 21 identical 10-ns quasi-square-wave pulses of 51 V, exactly equal to 1070 V/21. The generator can operate not only in a simultaneous mode but also in a delay mode if the cables in the channel divider are different in length.

Discretized energy minimization in a wave guide with point sources

NASA Technical Reports Server (NTRS)

Propst, G.

1994-01-01

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

SQUARE WAVE AMPLIFIER

DOEpatents

Leavitt, M.A.; Lutz, I.C.

1958-08-01

An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

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

PubMed

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

2017-05-09

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

Synchronization of tunable asymmetric square-wave pulses in delay-coupled optoelectronic oscillators.

PubMed

Martínez-Llinàs, Jade; Colet, Pere; Erneux, Thomas

2015-03-01

We consider a model for two delay-coupled optoelectronic oscillators under positive delayed feedback as prototypical to study the conditions for synchronization of asymmetric square-wave oscillations, for which the duty cycle is not half of the period. We show that the scenario arising for positive feedback is much richer than with negative feedback. First, it allows for the coexistence of multiple in- and out-of-phase asymmetric periodic square waves for the same parameter values. Second, it is tunable: The period of all the square-wave periodic pulses can be tuned with the ratio of the delays, and the duty cycle of the asymmetric square waves can be changed with the offset phase while the total period remains constant. Finally, in addition to the multiple in- and out-of-phase periodic square waves, low-frequency periodic asymmetric solutions oscillating in phase may coexist for the same values of the parameters. Our analytical results are in agreement with numerical simulations and bifurcation diagrams obtained by using continuation techniques.

Accurate source location from waves scattered by surface topography: Applications to the Nevada and North Korean test sites

NASA Astrophysics Data System (ADS)

Shen, Y.; Wang, N.; Bao, X.; Flinders, A. F.

2016-12-01

Scattered waves generated near the source contains energy converted from the near-field waves to the far-field propagating waves, which can be used to achieve location accuracy beyond the diffraction limit. In this work, we apply a novel full-wave location method that combines a grid-search algorithm with the 3D Green's tensor database to locate the Non-Proliferation Experiment (NPE) at the Nevada test site and the North Korean nuclear tests. We use the first arrivals (Pn/Pg) and their immediate codas, which are likely dominated by waves scattered at the surface topography near the source, to determine the source location. We investigate seismograms in the frequency of [1.0 2.0] Hz to reduce noises in the data and highlight topography scattered waves. High resolution topographic models constructed from 10 and 90 m grids are used for Nevada and North Korea, respectively. The reference velocity model is based on CRUST 1.0. We use the collocated-grid finite difference method on curvilinear grids to calculate the strain Green's tensor and obtain synthetic waveforms using source-receiver reciprocity. The `best' solution is found based on the least-square misfit between the observed and synthetic waveforms. To suppress random noises, an optimal weighting method for three-component seismograms is applied in misfit calculation. Our results show that the scattered waves are crucial in improving resolution and allow us to obtain accurate solutions with a small number of stations. Since the scattered waves depends on topography, which is known at the wavelengths of regional seismic waves, our approach yields absolute, instead of relative, source locations. We compare our solutions with those of USGS and other studies. Moreover, we use differential waveforms to locate pairs of the North Korea tests from years 2006, 2009, 2013 and 2016 to further reduce the effects of unmodeled heterogeneities and errors in the reference velocity model.

An interpretation of flare-induced and decayless coronal-loop oscillations as interference patterns

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

Hindman, Bradley W.; Jain, Rekha, E-mail: hindman@solarz.colorado.edu

2014-04-01

We present an alternative model of coronal-loop oscillations, which considers that the waves are trapped in a two-dimensional waveguide formed by the entire arcade of field lines. This differs from the standard one-dimensional model which treats the waves as the resonant oscillations of just the visible bundle of field lines. Within the framework of our two-dimensional model, the two types of oscillations that have been observationally identified, flare-induced waves and 'decayless' oscillations, can both be attributed to MHD fast waves. The two components of the signal differ only because of the duration and spatial extent of the source that createsmore » them. The flare-induced waves are generated by strong localized sources of short duration, while the decayless background can be excited by a continuous, stochastic source. Further, the oscillatory signal arising from a localized, short-duration source can be interpreted as a pattern of interference fringes produced by waves that have traveled diverse routes of various pathlengths through the waveguide. The resulting amplitude of the fringes slowly decays in time with an inverse square root dependence. The details of the interference pattern depend on the shape of the arcade and the spatial variation of the Alfvén speed. The rapid decay of this wave component, which has previously been attributed to physical damping mechanisms that remove energy from resonant oscillations, occurs as a natural consequence of the interference process without the need for local dissipation.« less

Directional Limits on Persistent Gravitational Waves Using LIGO S5 Science Data

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Arain, M. A.; Araya, M. C.; Aronsson, M.; Arun, K. G.; Aso, Y.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Beker, M. G.; Belletoile, A.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bigotta, S.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Boccara, C.; Bock, O.; Bodiya, T. P.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Bouhou, B.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coulon, J.-P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Das, K.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Davis, A.; Daw, E. J.; Day, R.; Dayanga, T.; de Rosa, R.; Debra, D.; Degallaix, J.; Del Prete, M.; Dergachev, V.; Derosa, R.; Desalvo, R.; Devanka, P.; Dhurandhar, S.; di Fiore, L.; di Lieto, A.; di Palma, I.; di Paolo Emilio, M.; di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dueck, J.; Dumas, J.-C.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Flasch, K.; Foley, S.; Forrest, C.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Gholami, I.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hall, P.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A. W.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hoyland, D.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh–Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J. B.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, H.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Krause, T.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kullman, J.; Kumar, R.; Kwee, P.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lin, H.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubinski, M.; Lucianetti, A.; Lück, H.; Lundgren, A. D.; Machenschalk, B.; Macinnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Mak, C.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIvor, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Morioka, T.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; Mow–Lowry, C. M.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Pardi, S.; Pareja, M.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radke, T.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Röver, C.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Sammut, L.; Sancho de La Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stein, A. J.; Stein, L. C.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Trummer, J.; Tseng, K.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2011-12-01

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10-50strain2Hz-1 and 5-35×10-49strain2Hz-1sr-1 for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10-25 in the most sensitive frequency range near 160 Hz.

Generation and evolution of mode-locked noise-like square-wave pulses in a large-anomalous-dispersion Er-doped ring fiber laser.

PubMed

Liu, Jun; Chen, Yu; Tang, Pinghua; Xu, Changwen; Zhao, Chujun; Zhang, Han; Wen, Shuangchun

2015-03-09

In a passively mode-locked Erbium-doped fiber laser with large anomalous-dispersion, we experimentally demonstrate the formation of noise-like square-wave pulse, which shows quite different features from conventional dissipative soliton resonance (DSR). The corresponding temporal and spectral characteristics of a variety of operation states, including Q-switched mode-locking, continuous-wave mode-locking and Raman-induced noise-like pulse near the lasing threshold, are also investigated. Stable noise-like square-wave mode-locked pulses can be obtained at a fundamental repetition frequency of 195 kHz, with pulse packet duration tunable from 15 ns to 306 ns and per-pulse energy up to 200 nJ. By reducing the linear cavity loss, stable higher-order harmonic mode-locking had also been observed, with pulse duration ranging from 37 ns at the 21st order harmonic wave to 320 ns at the fundamental order. After propagating along a piece of long telecom fiber, the generated square-wave pulses do not show any obvious change, indicating that the generated noise-like square-wave pulse can be considered as high-energy pulse packet for some promising applications. These experimental results should shed some light on the further understanding of the mechanism and characteristics of noise-like square-wave pulses.

Optimization of one-way wave equations.

USGS Publications Warehouse

Lee, M.W.; Suh, S.Y.

1985-01-01

The theory of wave extrapolation is based on the square-root equation or one-way equation. The full wave equation represents waves which propagate in both directions. On the contrary, the square-root equation represents waves propagating in one direction only. A new optimization method presented here improves the dispersion relation of the one-way wave equation. -from Authors

Measurement and fitting techniques for the assessment of material nonlinearity using nonlinear Rayleigh waves

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

Torello, David; Kim, Jin-Yeon; Qu, Jianmin

2015-03-31

This research considers the effects of diffraction, attenuation, and the nonlinearity of generating sources on measurements of nonlinear ultrasonic Rayleigh wave propagation. A new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects is provided based on analytical models and experimental considerations. A method for extracting the nonlinearity parameter β{sub 11} is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements. Quantitative experiments are conducted to confirm the predictions for the nonlinearity of the piezoelectric source and to demonstrate the effectiveness of the curve-fitting procedure. Thesemore » experiments are conducted on aluminum 2024 and 7075 specimens and a β{sub 11}{sup 7075}/β{sub 11}{sup 2024} measure of 1.363 agrees well with previous literature and earlier work.« less

Medium change based image estimation from application of inverse algorithms to coda wave measurements

NASA Astrophysics Data System (ADS)

Zhan, Hanyu; Jiang, Hanwan; Jiang, Ruinian

2018-03-01

Perturbations worked as extra scatters will cause coda waveform distortions; thus, coda wave with long propagation time and traveling path are sensitive to micro-defects in strongly heterogeneous media such as concretes. In this paper, we conduct varied external loads on a life-size concrete slab which contains multiple existing micro-cracks, and a couple of sources and receivers are installed to collect coda wave signals. The waveform decorrelation coefficients (DC) at different loads are calculated for all available source-receiver pair measurements. Then inversions of the DC results are applied to estimate the associated distribution density values in three-dimensional regions through kernel sensitivity model and least-square algorithms, which leads to the images indicating the micro-cracks positions. This work provides an efficiently non-destructive approach to detect internal defects and damages of large-size concrete structures.

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

NASA Astrophysics Data System (ADS)

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

2012-09-01

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

Multifrequency synthesis and extraction using square wave projection patterns for quantitative tissue imaging.

PubMed

Nadeau, Kyle P; Rice, Tyler B; Durkin, Anthony J; Tromberg, Bruce J

2015-11-01

We present a method for spatial frequency domain data acquisition utilizing a multifrequency synthesis and extraction (MSE) method and binary square wave projection patterns. By illuminating a sample with square wave patterns, multiple spatial frequency components are simultaneously attenuated and can be extracted to determine optical property and depth information. Additionally, binary patterns are projected faster than sinusoids typically used in spatial frequency domain imaging (SFDI), allowing for short (millisecond or less) camera exposure times, and data acquisition speeds an order of magnitude or more greater than conventional SFDI. In cases where sensitivity to superficial layers or scattering is important, the fundamental component from higher frequency square wave patterns can be used. When probing deeper layers, the fundamental and harmonic components from lower frequency square wave patterns can be used. We compared optical property and depth penetration results extracted using square waves to those obtained using sinusoidal patterns on an in vivo human forearm and absorbing tube phantom, respectively. Absorption and reduced scattering coefficient values agree with conventional SFDI to within 1% using both high frequency (fundamental) and low frequency (fundamental and harmonic) spatial frequencies. Depth penetration reflectance values also agree to within 1% of conventional SFDI.

Multifrequency synthesis and extraction using square wave projection patterns for quantitative tissue imaging

PubMed Central

Nadeau, Kyle P.; Rice, Tyler B.; Durkin, Anthony J.; Tromberg, Bruce J.

2015-01-01

Abstract. We present a method for spatial frequency domain data acquisition utilizing a multifrequency synthesis and extraction (MSE) method and binary square wave projection patterns. By illuminating a sample with square wave patterns, multiple spatial frequency components are simultaneously attenuated and can be extracted to determine optical property and depth information. Additionally, binary patterns are projected faster than sinusoids typically used in spatial frequency domain imaging (SFDI), allowing for short (millisecond or less) camera exposure times, and data acquisition speeds an order of magnitude or more greater than conventional SFDI. In cases where sensitivity to superficial layers or scattering is important, the fundamental component from higher frequency square wave patterns can be used. When probing deeper layers, the fundamental and harmonic components from lower frequency square wave patterns can be used. We compared optical property and depth penetration results extracted using square waves to those obtained using sinusoidal patterns on an in vivo human forearm and absorbing tube phantom, respectively. Absorption and reduced scattering coefficient values agree with conventional SFDI to within 1% using both high frequency (fundamental) and low frequency (fundamental and harmonic) spatial frequencies. Depth penetration reflectance values also agree to within 1% of conventional SFDI. PMID:26524682

A multi-channel isolated power supply in non-equipotential circuit

NASA Astrophysics Data System (ADS)

Li, Xiang; Zhao, Bo-Wen; Zhang, Yan-Chi; Xie, Da

2018-04-01

A multi-channel isolation power supply is designed for the problems of different MOSFET or IGBT in the non-equipotential circuit in this paper. It mainly includes the square wave generation circuit, the high-frequency transformer and the three-terminal stabilized circuit. The first part is used to generate the 24V square wave, and as the input of the magnetic ring transformer. In the second part, the magnetic ring transformer consists of one input and three outputs to realize multi-channel isolation output. The third part can output different potential and realize non-equal potential function through the three-terminal stabilized chip. In addition, the multi-channel isolation power source proposed in this paper is Small size, high reliability and low price, and it is convenient for power electronic switches that operate on multiple different potentials. Therefore, the research on power supply of power electronic circuit has practical significance.

The acoustic field of a point source in a uniform boundary layer over an impedance plane

NASA Technical Reports Server (NTRS)

Zorumski, W. E.; Willshire, W. L., Jr.

1986-01-01

The acoustic field of a point source in a boundary layer above an impedance plane is investigated anatytically using Obukhov quasi-potential functions, extending the normal-mode theory of Chunchuzov (1984) to account for the effects of finite ground-plane impedance and source height. The solution is found to be asymptotic to the surface-wave term studies by Wenzel (1974) in the limit of vanishing wind speed, suggesting that normal-mode theory can be used to model the effects of an atmospheric boundary layer on infrasonic sound radiation. Model predictions are derived for noise-generation data obtained by Willshire (1985) at the Medicine Bow wind-turbine facility. Long-range downwind propagation is found to behave as a cylindrical wave, with attention proportional to the wind speed, the boundary-layer displacement thickness, the real part of the ground admittance, and the square of the frequency.

A compact, all-optical, THz wave generator based on self-modulation in a slab photonic crystal waveguide with a single sub-nanometer graphene layer.

PubMed

Asadi, R; Ouyang, Z; Mohammd, M M

2015-07-14

We design a compact, all-optical THz wave generator based on self-modulation in a 1-D slab photonic crystal (PhC) waveguide with a single sub-nanometer graphene layer by using enhanced nonlinearity of graphene. It has been shown that at the bandgap edge of higher bands of a 1-D slab PhC, through only one sub-nanometer graphene layer we can obtain a compact, high modulation factor (about 0.98 percent), self-intensity modulator at a high frequency (about 0.6 THz) and low threshold intensity (about 15 MW per square centimeter), and further a compact, all-optical THz wave generator by integrating the self-modulator with a THz photodiode or photonic mixer. Such a THz source is expected to have a relatively high efficiency compared with conventional sources based on optical methods. The proposed THz source can find wide applications in THz science and technology, e.g., in THz imaging, THz sensors and detectors, THz communication systems, and THz optical integrated logic circuits.

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

NASA Astrophysics Data System (ADS)

Giongo, Gabriel Augusto; Valentin Bageston, José; Prado Batista, Paulo; Wrasse, Cristiano Max; Dornelles Bittencourt, Gabriela; Paulino, Igo; Paes Leme, Neusa Maria; Fritts, David C.; Janches, Diego; Hocking, Wayne; Schuch, Nelson Jorge

2018-02-01

The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR) airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym) located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m2, was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m2 sandwiched between layers above and below with m2 < 0) was found in any of the events, favorable propagation conditions for horizontal propagation of the fronts were found in three cases. In the fourth case, the wave front did not find any duct support and it appeared to dissipate near the zenith, transferring energy and momentum to the medium and, consequently, accelerating the wind in the wave propagation direction (near to south) above the OH peak (88-92 km). The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases.

Pinpointing the North Korea Nuclear tests with body waves scattered by surface topography

NASA Astrophysics Data System (ADS)

Wang, N.; Shen, Y.; Bao, X.; Flinders, A. F.

2017-12-01

On September 3, 2017, North Korea conducted its sixth and by far the largest nuclear test at the Punggye-ri test site. In this work, we apply a novel full-wave location method that combines a non-linear grid-search algorithm with the 3D strain Green's tensor database to locate this event. We use the first arrivals (Pn waves) and their immediate codas, which are likely dominated by waves scattered by the surface topography near the source, to pinpoint the source location. We assess the solution in the search volume using a least-squares misfit between the observed and synthetic waveforms, which are obtained using the collocated-grid finite difference method on curvilinear grids. We calculate the one standard deviation level of the 'best' solution as a posterior error estimation. Our results show that the waveform based location method allows us to obtain accurate solutions with a small number of stations. The solutions are absolute locations as opposed to relative locations based on relative travel times, because topography-scattered waves depend on the geometric relations between the source and the unique topography near the source. Moreover, we use both differential waveforms and traveltimes to locate pairs of the North Korea tests in years 2016 and 2017 to further reduce the effects of inaccuracies in the reference velocity model (CRUST 1.0). Finally, we compare our solutions with those of other studies based on satellite images and relative traveltimes.

A Variable Frequency, Mis-Match Tolerant, Inductive Plasma Source

NASA Astrophysics Data System (ADS)

Rogers, Anthony; Kirchner, Don; Skiff, Fred

2014-10-01

Presented here is a survey and analysis of an inductively coupled, magnetically confined, singly ionized Argon plasma generated by a square-wave, variable frequency plasma source. The helicon-style antenna is driven directly by the class ``D'' amplifier without matching network for increased efficiency while maintaining independent control of frequency and applied power at the feed point. The survey is compared to similar data taken using a traditional exciter--power amplifier--matching network source. Specifically, the flexibility of this plasma source in terms of the independent control of electron plasma temperature and density is discussed in comparison to traditional source arrangements. Supported by US DOE Grant DE-FG02-99ER54543.

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

PubMed

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

2015-05-04

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

A proposed physical analog for a quantum probability amplitude

NASA Astrophysics Data System (ADS)

Boyd, Jeffrey

What is the physical analog of a probability amplitude? All quantum mathematics, including quantum information, is built on amplitudes. Every other science uses probabilities; QM alone uses their square root. Why? This question has been asked for a century, but no one previously has proposed an answer. We will present cylindrical helices moving toward a particle source, which particles follow backwards. Consider Feynman's book QED. He speaks of amplitudes moving through space like the hand of a spinning clock. His hand is a complex vector. It traces a cylindrical helix in Cartesian space. The Theory of Elementary Waves changes direction so Feynman's clock faces move toward the particle source. Particles follow amplitudes (quantum waves) backwards. This contradicts wave particle duality. We will present empirical evidence that wave particle duality is wrong about the direction of particles versus waves. This involves a paradigm shift; which are always controversial. We believe that our model is the ONLY proposal ever made for the physical foundations of probability amplitudes. We will show that our ``probability amplitudes'' in physical nature form a Hilbert vector space with adjoints, an inner product and support both linear algebra and Dirac notation.

Superlensing effect for surface acoustic waves in a pillar-based phononic crystal with negative refractive index

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

Addouche, Mahmoud, E-mail: mamoud.addouche@femto-st.fr; Al-Lethawe, Mohammed A., E-mail: mohammed.abdulridha@femto-st.fr; Choujaa, Abdelkrim, E-mail: achoujaa@femto-st.fr

2014-07-14

We demonstrate super resolution imaging for surface acoustic waves using a phononic structure displaying negative refractive index. This phononic structure is made of a monolithic square lattice of cylindrical pillars standing on a semi-infinite medium. The pillars act as acoustic resonator and induce a surface propagating wave with unusual dispersion. We found, under specific geometrical parameters, one propagating mode that exhibits negative refraction effect with negative effective index close to −1. Furthermore, a flat lens with finite number of pillars is designed to allow the focusing of an acoustic point source into an image with a resolution of (λ)/3 ,more » overcoming the Rayleigh diffraction limit.« less

Vertical coherence and forward scattering from the sea surface and the relation to the directional wave spectrum.

PubMed

Dahl, Peter H; Plant, William J; Dall'Osto, David R

2013-09-01

Results of an experiment to measure vertical spatial coherence from acoustic paths interacting once with the sea surface but at perpendicular azimuth angles are presented. The measurements were part of the Shallow Water 2006 program that took place off the coast of New Jersey in August 2006. An acoustic source, frequency range 6-20 kHz, was deployed at depth 40 m, and signals were recorded on a 1.4 m long vertical line array centered at depth 25 m and positioned at range 200 m. The vertical array consisted of four omni-directional hydrophones and vertical coherences were computed between pairs of these hydrophones. Measurements were made over four source-receiver bearing angles separated by 90°, during which sea surface conditions remained stable and characterized by a root-mean-square wave height of 0.17 m and a mixture of swell and wind waves. Vertical coherences show a statistically significant difference depending on source-receiver bearing when the acoustic frequency is less than about 12 kHz, with results tending to fade at higher frequencies. This paper presents field observations and comparisons of these observations with two modeling approaches, one based on bistatic forward scattering and the other on a rough surface parabolic wave equation utilizing synthetic sea surfaces.

High-frequency matrix converter with square wave input

DOEpatents

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.

Study on THz wave generation from air plasma induced by quasi-square Airy beam

NASA Astrophysics Data System (ADS)

Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin

2018-01-01

Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.

Low frequency AC waveform generator

DOEpatents

Bilharz, Oscar W.

1986-01-01

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Near- and far-field spectroscopic imaging investigation of resonant square-loop infrared metasurfaces.

PubMed

D' Archangel, Jeffrey; Tucker, Eric; Kinzel, Ed; Muller, Eric A; Bechtel, Hans A; Martin, Michael C; Raschke, Markus B; Boreman, Glenn

2013-07-15

Optical metamaterials have unique properties which result from geometric confinement of the optical conductivity. We developed a series of infrared metasurfaces based on an array of metallic square loop antennas. The far-field absorption spectrum can be designed with resonances across the infrared by scaling the geometric dimensions. We measure the amplitude and phase of the resonant mode as standing wave patterns within the square loops using scattering-scanning near-field optical microscopy (s-SNOM). Further, using a broad-band synchrotron-based FTIR microscope and s-SNOM at the Advanced Light Source, we are able to correlate far-field spectra to near-field modes of the metasurface as the resonance is tuned between samples. The results highlight the importance of multi-modal imaging for the design and characterization of optical metamaterials.

Low frequency ac waveform generator

DOEpatents

Bilharz, O.W.

1983-11-22

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Iterative image reconstruction in elastic inhomogenous media with application to transcranial photoacoustic tomography

NASA Astrophysics Data System (ADS)

Poudel, Joemini; Matthews, Thomas P.; Mitsuhashi, Kenji; Garcia-Uribe, Alejandro; Wang, Lihong V.; Anastasio, Mark A.

2017-03-01

Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the photoacoustically induced initial pressure distribution within tissue. The PACT reconstruction problem corresponds to a time-domain inverse source problem, where the initial pressure distribution is recovered from the measurements recorded on an aperture outside the support of the source. A major challenge in transcranial PACT brain imaging is to compensate for aberrations in the measured data due to the propagation of the photoacoustic wavefields through the skull. To properly account for these effects, a wave equation-based inversion method should be employed that can model the heterogeneous elastic properties of the medium. In this study, an iterative image reconstruction method for 3D transcranial PACT is developed based on the elastic wave equation. To accomplish this, a forward model based on a finite-difference time-domain discretization of the elastic wave equation is established. Subsequently, gradient-based methods are employed for computing penalized least squares estimates of the initial source distribution that produced the measured photoacoustic data. The developed reconstruction algorithm is validated and investigated through computer-simulation studies.

The prospects of pulsar timing with new-generation radio telescopes and the Square Kilometre Array

NASA Astrophysics Data System (ADS)

Stappers, B. W.; Keane, E. F.; Kramer, M.; Possenti, A.; Stairs, I. H.

2018-05-01

Pulsars are highly magnetized and rapidly rotating neutron stars. As they spin, the lighthouse-like beam of radio emission from their magnetic poles sweeps across the Earth with a regularity approaching that of the most precise clocks known. This precision combined with the extreme environments in which they are found, often in compact orbits with other neutron stars and white dwarfs, makes them excellent tools for studying gravity. Present and near-future pulsar surveys, especially those using the new generation of telescopes, will find more extreme binary systems and pulsars that are more precise `clocks'. These telescopes will also greatly improve the precision to which we can measure the arrival times of the pulses. The Square Kilometre Array will revolutionize pulsar searches and timing precision. The increased number of sources will reveal rare sources, including possibly a pulsar-black hole binary, which can provide the most stringent tests of strong-field gravity. The improved timing precision will reveal new phenomena and also allow us to make a detection of gravitational waves in the nanohertz frequency regime. It is here where we expect to see the signature of the binary black holes that are formed as galaxies merge throughout cosmological history. This article is part of a discussion meeting issue `The promises of gravitational-wave astronomy'.

Square-Wave Ocular Oscillation and Ataxia in an Anti-GAD-Positive Individual With Hypothyroidism.

PubMed

Brokalaki, Chrysoula; Kararizou, Evangelia; Dimitrakopoulos, Antonis; Evdokimidis, Ioannis; Anagnostou, Evangelos

2015-12-01

Cerebellar ataxia is an uncommon manifestation of hypothyroidism with unknown pathomechanism. The few descriptions of the clinical phenotype range from limb, gait, and trunk ataxia to various ocular motor abnormalities. We evaluated a 62-year-old woman with previously undetected severe hypothyroidism who presented with prominent saccadic intrusions and gait ataxia. She had high titers of antithyroid autoantibodies and anti-glutamic acid decarboxylase (anti-GAD) antibodies. Horizontal eye movement recordings revealed a series of nearly continuous pseudoharmonic square wave jerks (SWJs) constituting a square wave oscillation. Amplitudes reached maximum values of about 4, and wave frequency approached 100 cycles per minute. Thyroxine substitution and corticosteroid administration had little effect on SWJ parameters. The square wave oscillation nearly completely resolved after a single treatment session with intravenous immunoglobulin suggesting a causal link between an autoimmune process and the cerebellar dysfunction. Current concepts of the genesis of saccadic intrusions favor a role for anti-GAD antibodies in the etiology of SWJs.

Mean-square angle-of-arrival difference between two counter-propagating spherical waves in the presence of atmospheric turbulence.

PubMed

Chen, Chunyi; Yang, Huamin; Tong, Shoufeng; Lou, Yan

2015-09-21

The mean-square angle-of-arrival (AOA) difference between two counter-propagating spherical waves in atmospheric turbulence is theoretically formulated. Closed-form expressions for the path weighting functions are obtained. It is found that the diffraction and refraction effects of turbulent cells make negative and positive contributions to the mean-square AOA difference, respectively, and the turbulent cells located at the midpoint of the propagation path have no contributions to the mean-square AOA difference. If the mean-square AOA difference is separated into the refraction and diffraction parts, the refraction part always dominates the diffraction one, and the ratio of the diffraction part to the refraction one is never larger than 0.5 for any turbulence spectrum. Based on the expressions for the mean-square AOA difference, formulae for the correlation coefficient between the angles of arrival of two counter-propagating spherical waves in atmospheric turbulence are derived. Numerical calculations are carried out by considering that the turbulence spectrum has no path dependence. It is shown that the mean-square AOA difference always approximates to the variance of AOA fluctuations. It is found that the correlation coefficient between the angles of arrival in the x or y direction of two counter-propagating spherical waves ranges from 0.46 to 0.5, implying that the instantaneous angles of arrival of two counter-propagating spherical waves in atmospheric turbulence are far from being perfectly correlated even when the turbulence spectrum does not vary along the path.

Funneled focusing of planar acoustic waves utilizing the metamaterial properties of an acoustic lens

NASA Astrophysics Data System (ADS)

Walker, E.; Reyes, D.; Rojas, M. M.; Krokhin, A.; Neogi, A.

2014-02-01

Metamaterial acoustic lenses are acoustic devices based on phononic crystal structures that take advantage of negative or near-zero indices of refraction. These unique properties arise due to either the antiparallel direction of the phase and group velocity or strongly anisotropic dispersion characteristics, usually above the first transmission band. In this study, we utilize an FDTD program to examine two phononic lenses that utilize anisotropic effects available in their second band to collimate and focus acoustic waves from a plane-wave source with a k00 wavevector. The phononic crystals consist of stainless steel rods arranged in a square lattice with water as the ambient material. Results show collimation and focusing in the second band for select frequencies, fc ± 0.005𝑓𝑐.

Relativistic mirrors in laser plasmas (analytical methods)

NASA Astrophysics Data System (ADS)

Bulanov, S. V.; Esirkepov, T. Zh; Kando, M.; Koga, J.

2016-10-01

Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort x-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. We present an overview of theoretical methods used to describe relativistic flying, accelerating, oscillating mirrors emerging in intense laser-plasma interactions.

Characterization of electrophysiological propagation by multichannel sensors

PubMed Central

Bradshaw, L. Alan; Kim, Juliana H.; Somarajan, Suseela; Richards, William O.; Cheng, Leo K.

2016-01-01

Objective The propagation of electrophysiological activity measured by multichannel devices could have significant clinical implications. Gastric slow waves normally propagate along longitudinal paths that are evident in recordings of serosal potentials and transcutaneous magnetic fields. We employed a realistic model of gastric slow wave activity to simulate the transabdominal magnetogastrogram (MGG) recorded in a multichannel biomagnetometer and to determine characteristics of electrophysiological propagation from MGG measurements. Methods Using MGG simulations of slow wave sources in a realistic abdomen (both superficial and deep sources) and in a horizontally-layered volume conductor, we compared two analytic methods (Second Order Blind Identification, SOBI and Surface Current Density, SCD) that allow quantitative characterization of slow wave propagation. We also evaluated the performance of the methods with simulated experimental noise. The methods were also validated in an experimental animal model. Results Mean square errors in position estimates were within 2 cm of the correct position, and average propagation velocities within 2 mm/s of the actual velocities. SOBI propagation analysis outperformed the SCD method for dipoles in the superficial and horizontal layer models with and without additive noise. The SCD method gave better estimates for deep sources, but did not handle additive noise as well as SOBI. Conclusion SOBI-MGG and SCD-MGG were used to quantify slow wave propagation in a realistic abdomen model of gastric electrical activity. Significance These methods could be generalized to any propagating electrophysiological activity detected by multichannel sensor arrays. PMID:26595907

Optimal secondary source position in exterior spherical acoustical holophony

NASA Astrophysics Data System (ADS)

Pasqual, A. M.; Martin, V.

2012-02-01

Exterior spherical acoustical holophony is a branch of spatial audio reproduction that deals with the rendering of a given free-field radiation pattern (the primary field) by using a compact spherical loudspeaker array (the secondary source). More precisely, the primary field is known on a spherical surface surrounding the primary and secondary sources and, since the acoustic fields are described in spherical coordinates, they are naturally subjected to spherical harmonic analysis. Besides, the inverse problem of deriving optimal driving signals from a known primary field is ill-posed because the secondary source cannot radiate high-order spherical harmonics efficiently, especially in the low-frequency range. As a consequence, a standard least-squares solution will overload the transducers if the primary field contains such harmonics. Here, this is avoided by discarding the strongly decaying spherical waves, which are identified through inspection of the radiation efficiency curves of the secondary source. However, such an unavoidable regularization procedure increases the least-squares error, which also depends on the position of the secondary source. This paper deals with the above-mentioned questions in the context of far-field directivity reproduction at low and medium frequencies. In particular, an optimal secondary source position is sought, which leads to the lowest reproduction error in the least-squares sense without overloading the transducers. In order to address this issue, a regularization quality factor is introduced to evaluate the amount of regularization required. It is shown that the optimal position improves significantly the holophonic reconstruction and maximizes the regularization quality factor (minimizes the amount of regularization), which is the main general contribution of this paper. Therefore, this factor can also be used as a cost function to obtain the optimal secondary source position.

Evidence of Biot Slow Waves in Electroseismic Measurementss on Laboratory-Scale

NASA Astrophysics Data System (ADS)

Devi, M. S.

2015-12-01

Electroseismic methods which are the opposite of seismo-electric methods have only been little investigated up to now especially in the near surface scale. These methods can generate the solid-fluid relative movement induced by the electric potential in fluid-filled porous media. These methods are the response of electro-osmosis due to the presence of the electrical double layer. Laboratory experiments and numerical simulations of electroseismic studies have been performed. Electroseismic measurements conducted in micro glass beads saturated with demineralized water. Pair of 37 x 37 mm square aluminium grids with 2 mm of aperture and 4 mm of spacing is used as the electric dipole that connected to the electric power source with the voltage output 150 V. A laser doppler vibrometer is the system used to measure velocity of vibrating objects during measurements by placing a line of reflective paper on the surface of media that scattered back a helium-neon laser. The results in homogeneous media shows that the compressional waves induced by an electric signal. We confirm that the results are not the effects of thermal expansion. We also noticed that there are two kinds of the compressional waves are recorded: fast and slow P-waves. The latter, Biot slow waves, indicate the dominant amplitude. Moreover, we found that the transition frequency (ωc) of Biot slow waves depends on mechanical parameters such as porosity and permeability. The ωc is not affected when varying conductivity of the fluid from 25 - 320 μS/cm, although the amplitude slightly changed. For the results in two layer media by placing a sandstone as a top layer shows that a large amount of transmission seismic waves (apparently as Biot slow waves) rather than converted electromagnetic-to-seismic waves. These properties have also been simulated with full waveform numerical simulations relying on Pride's (1994) using our computer code (Garambois & Dietrich, 2002). If it is true that the electric source in the safe voltage range generates seismic waves dominantly, it may be a reason of electro-osmosis dewatering technique to transport liquids. And this source may be used an alternative as a seismic source in geophysical exploration.

Defects formation and wave emitting from defects in excitable media

NASA Astrophysics Data System (ADS)

Ma, Jun; Xu, Ying; Tang, Jun; Wang, Chunni

2016-05-01

Abnormal electrical activities in neuronal system could be associated with some neuronal diseases. Indeed, external forcing can cause breakdown even collapse in nervous system under appropriate condition. The excitable media sometimes could be described by neuronal network with different topologies. The collective behaviors of neurons can show complex spatiotemporal dynamical properties and spatial distribution for electrical activities due to self-organization even from the regulating from central nervous system. Defects in the nervous system can emit continuous waves or pulses, and pacemaker-like source is generated to perturb the normal signal propagation in nervous system. How these defects are developed? In this paper, a network of neurons is designed in two-dimensional square array with nearest-neighbor connection type; the formation mechanism of defects is investigated by detecting the wave propagation induced by external forcing. It is found that defects could be induced under external periodical forcing under the boundary, and then the wave emitted from the defects can keep balance with the waves excited from external forcing.

Triboelectrification-Enabled Self-Powered Data Storage.

PubMed

Kuang, Shuang Yang; Zhu, Guang; Wang, Zhong Lin

2018-02-01

Data storage by any means usually requires an electric driving power for writing or reading. A novel approach for self-powered, triboelectrification-enabled data storage (TEDS) is presented. Data are incorporated into a set of metal-based surface patterns. As a probe slides across the patterned surface, triboelectrification between the scanning probe and the patterns produces alternatively varying voltage signal in quasi-square wave. The trough and crest of the quasi-square wave signal are coded as binary bits of "0" and "1," respectively, while the time span of the trough and the crest is associated with the number of bits. The storage of letters and sentences is demonstrated through either square-shaped or disc-shaped surface patterns. Based on experimental data and numerical calculation, the theoretically predicted maximum data storage density could reach as high as 38.2 Gbit in -2 . Demonstration of real-time data retrieval is realized with the assistance of software interface. For the TEDS reported in this work, the measured voltage signal is self-generated as a result of triboelectrification without the reliance on an external power source. This feature brings about not only low power consumption but also a much more simplified structure. Therefore, this work paves a new path to a unique approach of high-density data storage that may have widespread applications.

Pattern masking: the importance of remote spatial frequencies and their phase alignment.

PubMed

Huang, Pi-Chun; Maehara, Goro; May, Keith A; Hess, Robert F

2012-02-16

To assess the effects of spatial frequency and phase alignment of mask components in pattern masking, target threshold vs. mask contrast (TvC) functions for a sine-wave grating (S) target were measured for five types of mask: a sine-wave grating (S), a square-wave grating (Q), a missing fundamental square-wave grating (M), harmonic complexes consisting of phase-scrambled harmonics of a square wave (Qp), and harmonic complexes consisting of phase-scrambled harmonics of a missing fundamental square wave (Mp). Target and masks had the same fundamental frequency (0.46 cpd) and the target was added in phase with the fundamental frequency component of the mask. Under monocular viewing conditions, the strength of masking depends on phase relationships among mask spatial frequencies far removed from that of the target, at least 3 times the target frequency, only when there are common target and mask spatial frequencies. Under dichoptic viewing conditions, S and Q masks produced similar masking to each other and the phase-scrambled masks (Qp and Mp) produced less masking. The results suggest that pattern masking is spatial frequency broadband in nature and sensitive to the phase alignments of spatial components.

In-vivo digital wavefront sensing using swept source OCT

PubMed Central

Kumar, Abhishek; Wurster, Lara M.; Salas, Matthias; Ginner, Laurin; Drexler, Wolfgang; Leitgeb, Rainer A.

2017-01-01

Sub-aperture based digital adaptive optics is demonstrated in a fiber based point scanning optical coherence tomography system using a 1060 nm swept source laser. To detect optical aberrations in-vivo, a small lateral field of view of ~150×150 μm2 is scanned on the sample at a high volume rate of 17 Hz (~1.3 kHz B-scan rate) to avoid any significant lateral and axial motion of the sample, and is used as a “guide star” for the sub-aperture based DAO. The proof of principle is demonstrated using a micro-beads phantom sample, wherein a significant root mean square wavefront error (RMS WFE) of 1.48 waves (> 1μm) is detected. In-vivo aberration measurement with a RMS WFE of 0.33 waves, which is ~5 times higher than the Marechal’s criterion of 1/14 waves for the diffraction limited performance, is shown for a human retinal OCT. Attempt has been made to validate the experimental results with the conventional Shack-Hartmann wavefront sensor within reasonable limitations. PMID:28717573

Reconfigurable wave band structure of an artificial square ice

DOE PAGES

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; ...

2016-04-18

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

Reconfigurable wave band structure of an artificial square ice

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

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

Square-Wave Model for a Pendulum with Oscillating Suspension

ERIC Educational Resources Information Center

Yorke, Ellen D.

1978-01-01

Demonstrates that if a sinusoidal oscillation of the point of support of a pendulum is approximated by a square wave, a matrix method may be used to discuss parametric resonance and the stability of the inverted pendulum. (Author/SL)

Research on spacecraft electrical power conversion

NASA Technical Reports Server (NTRS)

Wilson, T. G.

1974-01-01

The steady state characteristics and starting behavior of some widely used self-oscillating magnetically coupled square wave inverters were studied and the development of LC-tuned square wave inverters is reported. An analysis on high amplitude voltage spikes which occur in dc-to-square-wave parallel converters shows the importance of various circuit parameters for inverter design and for the suppression of spikes. A computerized simulation of an inductor energy storage dc-to-dc converter with closed loop regulators and of a preregulating current step-up converter are detailed. Work continued on the computer aided design of two-winding energy storage dc-to-dc converters.

Square wave voltammetry at the dropping mercury electrode: Experimental

USGS Publications Warehouse

Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.

1977-01-01

Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.

Search for Gravitational Waves Associated with γ-ray Bursts Detected by the Interplanetary Network

NASA Astrophysics Data System (ADS)

Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Andersen, M.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J. S.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Augustus, H.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barbet, M.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bauchrowitz, J.; Bauer, Th. S.; Baune, C.; Bavigadda, V.; Behnke, B.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bell, A. S.; Bell, C.; Bergmann, G.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bosi, L.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Buchman, S.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burman, R.; Buskulic, D.; Buy, C.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Celerier, C.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C.; Colombini, M.; Cominsky, L.; Constancio, M.; Conte, A.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Croce, R. P.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, C.; Dahl, K.; Dal Canton, T.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; DeBra, D.; Debreczeni, G.; Degallaix, J.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Dickson, J.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; 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.; Eberle, T.; Edo, T.; Edwards, M.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fazi, D.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Feroz, F.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; 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.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S.; Garufi, F.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Gräf, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C. J.; Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Ha, J.; Hall, E. D.; Hamilton, W.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hart, M.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Holt, K.; Hopkins, P.; Horrom, T.; Hoske, D.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Huerta, E.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Idrisy, A.; Ingram, D. R.; Inta, R.; Islas, G.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; Jang, H.; Jaranowski, P.; Ji, Y.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karlen, J.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Keiser, G. M.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, C.; Kim, K.; Kim, N. G.; Kim, N.; Kim, S.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, A.; Kumar, D. Nanda; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lam, P. K.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, J.; Lee, P. J.; Leonardi, M.; Leong, J. R.; Leonor, I.; Le Roux, A.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B.; Lewis, J.; Li, T. G. F.; Libbrecht, K.; Libson, A.; Lin, A. C.; Littenberg, T. B.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lopez, E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M. J.; Lück, H.; Lundgren, A. P.; Ma, Y.; Macdonald, E. P.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R.; Mageswaran, M.; Maglione, C.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, V.; Mangini, N. M.; Mansell, G.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Mavalvala, N.; May, G.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; McLin, K.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meinders, M.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nielsen, A. B.; Nissanke, S.; Nitz, A. H.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Oh, J. J.; Oh, S. H.; Ohme, F.; Omar, S.; Oppermann, P.; Oram, R.; O'Reilly, B.; Ortega, W.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palashov, O.; Palomba, C.; Pan, H.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Poteomkin, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qin, J.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Ramirez, K.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Recchia, S.; Reed, C. M.; Regimbau, T.; Reid, S.; Reitze, D. H.; Reula, O.; Rhoades, E.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Roddy, S. B.; Rolland, L.; Rollins, J. G.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J. R.; Sankar, S.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Scheuer, J.; Schilling, R.; Schilman, M.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Singh, R.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Son, E. J.; Sorazu, B.; Souradeep, T.; Staley, A.; Stebbins, J.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Stephens, B. C.; Steplewski, S.; Stevenson, S.; Stone, R.; Stops, D.; Strain, K. A.; Straniero, N.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tao, J.; Tarabrin, S. P.; Taylor, R.; Tellez, G.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Tshilumba, D.; Tuennermann, H.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vyachanin, S. P.; Wade, A. R.; Wade, L.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, M.; Wang, X.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Williams, K.; Williams, L.; Williams, R.; Williams, T. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wolovick, N.; Worden, J.; Wu, Y.; Yablon, J.; Yakushin, I.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yoshida, S.; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, Fan; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zucker, M. E.; Zuraw, S.; Zweizig, J.; Aptekar, R. L.; Atteia, J. L.; Cline, T.; Connaughton, V.; Frederiks, D. D.; Golenetskii, S. V.; Hurley, K.; Krimm, H. A.; Marisaldi, M.; Pal'shin, V. D.; Palmer, D.; Svinkin, D. S.; Terada, Y.; von Kienlin, A.; LIGO Scientific Collaboration; Virgo Collaboration; IPN Collaboration

2014-07-01

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10-2M⊙c2 at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by the Interplanetary Network

NASA Technical Reports Server (NTRS)

Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Blackbum, L.; Camp, J. B.; Gehrels, N.; Graff, P. B.;

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network.

PubMed

Aasi, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Acernese, F; Ackley, K; Adams, C; Adams, T; Addesso, P; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Alemic, A; Allen, B; Allocca, A; Amariutei, D; Andersen, M; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J S; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Augustus, H; Aulbert, C; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barbet, M; Barish, B C; Barker, D; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J C; Bauchrowitz, J; Bauer, Th S; Baune, C; Bavigadda, V; Behnke, B; Bejger, M; Beker, M G; Belczynski, C; Bell, A S; Bell, C; Bergmann, G; Bersanetti, D; Bertolini, A; Betzwieser, J; Bilenko, I A; Billingsley, G; Birch, J; Biscans, S; Bitossi, M; Biwer, C; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Bloemen, S; Bock, O; Bodiya, T P; Boer, M; Bogaert, G; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, Sukanta; Bosi, L; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brau, J E; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Buchman, S; Buikema, A; Bulik, T; Bulten, H J; Buonanno, A; Burman, R; Buskulic, D; Buy, C; Cadonati, L; Cagnoli, G; Calderón Bustillo, J; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castaldi, G; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Celerier, C; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chamberlin, S J; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Cho, M; Chow, J H; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Clayton, J H; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Collette, C; Colombini, M; Cominsky, L; Constancio, M; Conte, A; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J-P; Countryman, S; Couvares, P; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Croce, R P; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Cutler, C; Dahl, K; Dal Canton, T; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; DeBra, D; Debreczeni, G; Degallaix, J; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; De Rosa, R; DeRosa, R T; DeSalvo, R; Dhurandhar, S; Díaz, M; Dickson, J; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; 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; Eberle, T; Edo, T; Edwards, M; Effler, A; Eggenstein, H-B; Ehrens, P; Eichholz, J; Eikenberry, S S; Endrőczi, G; Essick, R; Etzel, T; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fazi, D; Fehrmann, H; Fejer, M M; Feldbaum, D; Feroz, F; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Finn, L S; 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; Gair, J R; Gammaitoni, L; Gaonkar, S; Garufi, F; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Gräf, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C J; Gushwa, K; Gustafson, E K; Gustafson, R; Ha, J; Hall, E D; Hamilton, W; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hart, M; Hartman, M T; Haster, C-J; Haughian, K; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hewitson, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Holt, K; Hopkins, P; Horrom, T; Hoske, D; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Huerta, E; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Idrisy, A; Ingram, D R; Inta, R; Islas, G; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; Jang, H; Jaranowski, P; Ji, Y; Jiménez-Forteza, F; Johnson, W W; Jones, D I; Jones, R; Jonker, R J G; Ju, L; Haris, K; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Karlen, J; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Keiser, G M; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, C; Kim, K; Kim, N G; Kim, N; Kim, S; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D B; Kringel, V; Krishnan, B; Królak, A; Kuehn, G; Kumar, A; Kumar, D Nanda; Kumar, P; Kumar, R; Kuo, L; Kutynia, A; Lam, P K; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lazzarini, A; Lazzaro, C; Leaci, P; Leavey, S; Lebigot, E O; Lee, C H; Lee, H K; Lee, H M; Lee, J; Lee, P J; Leonardi, M; Leong, J R; Leonor, I; Le Roux, A; Leroy, N; Letendre, N; Levin, Y; Levine, B; Lewis, J; Li, T G F; Libbrecht, K; Libson, A; Lin, A C; Littenberg, T B; Lockerbie, N A; Lockett, V; Lodhia, D; Loew, K; Logue, J; Lombardi, A L; Lopez, E; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Lubinski, M J; Lück, H; Lundgren, A P; Ma, Y; Macdonald, E P; MacDonald, T; Machenschalk, B; MacInnis, M; Macleod, D M; Magaña-Sandoval, F; Magee, R; Mageswaran, M; Maglione, C; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Manca, G M; Mandel, I; Mandic, V; Mangano, V; Mangini, N M; Mansell, G; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Maros, E; Marque, J; Martelli, F; Martin, I W; Martin, R M; Martinelli, L; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Mavalvala, N; May, G; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McGuire, S C; McIntyre, G; McIver, J; McLin, K; Meacher, D; Meadors, G D; Mehmet, M; Meidam, J; Meinders, M; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Mikhailov, E E; Milano, L; Miller, J; Minenkov, Y; Mingarelli, C M F; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Moggi, A; Mohan, M; Mohapatra, S R P; Moraru, D; Moreno, G; Morgado, N; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Nardecchia, I; Naticchioni, L; Nayak, R K; Necula, V; Nelemans, G; Neri, I; Neri, M; Newton, G; Nguyen, T; Nielsen, A B; Nissanke, S; Nitz, A H; Nocera, F; Nolting, D; Normandin, M E N; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Oh, J J; Oh, S H; Ohme, F; Omar, S; Oppermann, P; Oram, R; O'Reilly, B; Ortega, W; O'Shaughnessy, R; Osthelder, C; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Padilla, C; Pai, A; Palashov, O; Palomba, C; Pan, H; Pan, Y; Pankow, C; Paoletti, F; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Pedraza, M; Pele, A; Penn, S; Perreca, A; Phelps, M; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pinard, L; Pinto, I M; Pitkin, M; Poeld, J; Poggiani, R; Poteomkin, A; Powell, J; Prasad, J; Predoi, V; Premachandra, S; Prestegard, T; Price, L R; Prijatelj, M; Privitera, S; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Pürrer, M; Qin, J; Quetschke, V; Quintero, E; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rakhmanov, M; Ramet, C; Ramirez, K; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Recchia, S; Reed, C M; Regimbau, T; Reid, S; Reitze, D H; Reula, O; Rhoades, E; Ricci, F; Riesen, R; Riles, K; Robertson, N A; Robinet, F; Rocchi, A; Roddy, S B; Rolland, L; Rollins, J G; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Salemi, F; Sammut, L; Sandberg, V; Sanders, J R; Sankar, S; Sannibale, V; Santiago-Prieto, I; Saracco, E; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Scheuer, J; Schilling, R; Schilman, M; Schmidt, P; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sengupta, A S; Sentenac, D; Sequino, V; Sergeev, A; Shaddock, D A; Shah, S; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; Siemens, X; Sigg, D; Simakov, D; Singer, A; Singer, L; Singh, R; Sintes, A M; Slagmolen, B J J; Slutsky, J; Smith, J R; Smith, M R; Smith, R J E; Smith-Lefebvre, N D; Son, E J; Sorazu, B; Souradeep, T; Staley, A; Stebbins, J; Steinke, M; Steinlechner, J; Steinlechner, S; Stephens, B C; Steplewski, S; Stevenson, S; Stone, R; Stops, D; Strain, K A; Straniero, N; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Susmithan, S; Sutton, P J; Swinkels, B; Tacca, M; Talukder, D; Tanner, D B; Tao, J; Tarabrin, S P; Taylor, R; Tellez, G; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tokmakov, K V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Tshilumba, D; Tuennermann, H; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; Vallisneri, M; van Beuzekom, M; van den Brand, J F J; Van Den Broeck, C; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J-Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vyachanin, S P; Wade, A R; Wade, L; Wade, M; Walker, M; Wallace, L; Walsh, S; Wang, M; Wang, X; Ward, R L; Was, M; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; West, M; Westphal, T; Wette, K; Whelan, J T; White, D J; Whiting, B F; Wiesner, K; Wilkinson, C; Williams, K; Williams, L; Williams, R; Williams, T D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M; Winkler, W; Wipf, C C; Wiseman, A G; Wittel, H; Woan, G; Wolovick, N; Worden, J; Wu, Y; Yablon, J; Yakushin, I; Yam, W; Yamamoto, H; Yancey, C C; Yang, H; Yoshida, S; Yvert, M; Zadrożny, A; Zanolin, M; Zendri, J-P; Zhang, Fan; Zhang, L; Zhao, C; Zhu, H; Zhu, X J; Zucker, M E; Zuraw, S; Zweizig, J; Aptekar, R L; Atteia, J L; Cline, T; Connaughton, V; Frederiks, D D; Golenetskii, S V; Hurley, K; Krimm, H A; Marisaldi, M; Pal'shin, V D; Palmer, D; Svinkin, D S; Terada, Y; von Kienlin, A

2014-07-04

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Comparison of techniques for approximating ocean bottom topography in a wave-refraction computer model

NASA Technical Reports Server (NTRS)

Poole, L. R.

1975-01-01

A study of the effects of using different methods for approximating bottom topography in a wave-refraction computer model was conducted. Approximation techniques involving quadratic least squares, cubic least squares, and constrained bicubic polynomial interpolation were compared for computed wave patterns and parameters in the region of Saco Bay, Maine. Although substantial local differences can be attributed to use of the different approximation techniques, results indicated that overall computed wave patterns and parameter distributions were quite similar.

Re-examination of radiofrequency mass spectrometers: Center Director's Discretionary Fund

NASA Technical Reports Server (NTRS)

Carruth, M. R., Jr.

1989-01-01

The three-stage, two-cycle, Bennett mass spectrometers in use in space and ground experiments today are of the same physical configuration as developed by Bennett in 1950. Sine-wave radiofrequency (RF) is also still used. The literature indicates that the electronics and physical manufacturing capabilities of 1950 technology may have limited the use of other improvements at that time. Therefore, a study, experimental and analytical, was undertaken to examine previously rejected RF approaches as well as new ones. The results of this study indicate there are other approaches which use fewer grids and square wave or a combination of square-wave and sine-wave RF. In regard to suppression of harmonics, none performed better than the three-stage, two-cycle, Bennett mass spectrometer. Use of square-wave RF in the Bennett approach can provide a slightly more compact configuration but no increase in throughput.

LANDSAT-D investigations in snow hydrology

NASA Technical Reports Server (NTRS)

Dozier, J. (Principal Investigator)

1982-01-01

Snow reflectance in all 6 TM reflective bands, i.e., 1, 2, 3, 4, 5, and 7 was simulated using a delta-Eddington model. Snow reflectance in bands 4, 5, and 7 appear sensitive to grain size. It appears that the TM filters resemble a ""square-wave'' closely enough that a square-wave can be assumed in calculations. Integrated band reflectance over the actual response functions was calculated using sensor data supplied by Santa Barbara Research Center. Differences between integrating over the actual response functions and the equivalent square wave were negligible. Tables are given which show (1) sensor saturation radiance as a percentage of the solar constant, integrated through the band response function; (2) comparisons of integrations through the sensor response function with integrations over the equivalent square wave; and (3) calculations of integrated reflectance for snow over all reflective TM bands, and water and ice clouds with thickness of 1 mm water equivalent over TM bands 5 and 7. These calculations look encouraging for snow/cloud discrimination with TM bands 5 and 7.

Lamb waves in phononic crystal slabs with square or rectangular symmetries

NASA Astrophysics Data System (ADS)

Brunet, Thomas; Vasseur, Jérôme; Bonello, Bernard; Djafari-Rouhani, Bahram; Hladky-Hennion, Anne-Christine

2008-08-01

We report on both numerical and experimental results showing the occurrence of band gaps for Lamb waves propagating in phononic crystal plates. The structures are made of centered rectangular and square arrays of holes drilled in a silicon plate. A supercell plane wave expansion method is used to calculate the band structures and to predict the position and the magnitude of the gaps. The band structures of phononic crystal slabs are then measured using a laser ultrasonic technique. Lamb waves in the megahertz range and with wave vectors ranging over more than the first two reduced Brillouin zones are investigated.

The prospects of pulsar timing with new-generation radio telescopes and the Square Kilometre Array.

PubMed

Stappers, B W; Keane, E F; Kramer, M; Possenti, A; Stairs, I H

2018-05-28

Pulsars are highly magnetized and rapidly rotating neutron stars. As they spin, the lighthouse-like beam of radio emission from their magnetic poles sweeps across the Earth with a regularity approaching that of the most precise clocks known. This precision combined with the extreme environments in which they are found, often in compact orbits with other neutron stars and white dwarfs, makes them excellent tools for studying gravity. Present and near-future pulsar surveys, especially those using the new generation of telescopes, will find more extreme binary systems and pulsars that are more precise 'clocks'. These telescopes will also greatly improve the precision to which we can measure the arrival times of the pulses. The Square Kilometre Array will revolutionize pulsar searches and timing precision. The increased number of sources will reveal rare sources, including possibly a pulsar-black hole binary, which can provide the most stringent tests of strong-field gravity. The improved timing precision will reveal new phenomena and also allow us to make a detection of gravitational waves in the nanohertz frequency regime. It is here where we expect to see the signature of the binary black holes that are formed as galaxies merge throughout cosmological history.This article is part of a discussion meeting issue 'The promises of gravitational-wave astronomy'. © 2018 The Author(s).

On the reliability and limitations of the SPAC method with a directional wavefield

NASA Astrophysics Data System (ADS)

Luo, Song; Luo, Yinhe; Zhu, Lupei; Xu, Yixian

2016-03-01

The spatial autocorrelation (SPAC) method is one of the most efficient ways to extract phase velocities of surface waves from ambient seismic noise. Most studies apply the method based on the assumption that the wavefield of ambient noise is diffuse. However, the actual distribution of sources is neither diffuse nor stationary. In this study, we examined the reliability and limitations of the SPAC method with a directional wavefield. We calculated the SPAC coefficients and phase velocities from a directional wavefield for a four-layer model and characterized the limitations of the SPAC. We then applied the SPAC method to real data in Karamay, China. Our results show that, 1) the SPAC method can accurately measure surface wave phase velocities from a square array with a directional wavefield down to a wavelength of twice the shortest interstation distance; and 2) phase velocities obtained from real data by the SPAC method are stable and reliable, which demonstrates that this method can be applied to measure phase velocities in a square array with a directional wavefield.

Wave field synthesis, adaptive wave field synthesis and ambisonics using decentralized transformed control: Potential applications to sound field reproduction and active noise control

NASA Astrophysics Data System (ADS)

Gauthier, Philippe-Aubert; Berry, Alain; Woszczyk, Wieslaw

2005-09-01

Sound field reproduction finds applications in listening to prerecorded music or in synthesizing virtual acoustics. The objective is to recreate a sound field in a listening environment. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. Classical WFS, therefore, does not perform well in a real reproduction space such as room. Previous work has suggested that it is physically possible to reproduce a progressive wave field in-room situation using active control approaches. In this paper, a formulation of adaptive wave field synthesis (AWFS) introduces practical possibilities for an adaptive sound field reproduction combining WFS and active control (with WFS departure penalization) with a limited number of error sensors. AWFS includes WFS and closed-loop ``Ambisonics'' as limiting cases. This leads to the modification of the multichannel filtered-reference least-mean-square (FXLMS) and the filtered-error LMS (FELMS) adaptive algorithms for AWFS. Decentralization of AWFS for sound field reproduction is introduced on the basis of sources' and sensors' radiation modes. Such decoupling may lead to decentralized control of source strength distributions and may reduce computational burden of the FXLMS and the FELMS algorithms used for AWFS. [Work funded by NSERC, NATEQ, Université de Sherbrooke and VRQ.] Ultrasound/Bioresponse to

Vertical structure and characteristics of 23-60 day (zonal) oscillations over the tropical latitudes during the winter months of 1986 - Results of equatorial wave campaign-II

NASA Technical Reports Server (NTRS)

Raghavarao, R.; Suhasini, R.; Sridharan, R.; Krishnamurthy, B. V.; Nagpal, O. P.

1990-01-01

Results are presented of the equatorial wave campaign-II, a meteorological rocket study which was part of the Indian Middle Atmosphere Program. The equatorial wave campaign-II was conducted from Shar, India (13.7 deg N, 80.2 deg E) from January 15-February 28, 1986. By means of high altitude balloon and the RH-200 meteorological rocket, winds were measured from ground level up to 60 km altitude once each day during the 45-day period. The oscillation frequencies of the deviations in the east-west component of the winds from their mean at each 1-km height interval are obtained by the maximum entropy method. The phases and amplitudes of these frequencies are determined by use of the least squares method on the wind variation time series. Enhanced wave activity is shown to take place in the troposphere and lower mesosphere. The tropospheric waves observed suggest themselves to be Rossby waves of extratropical origin penetrating to tropical latitudes. The observed stratospheric/mesospheric waves appear to emanate from a source around the stratopause.

Instrument For Simulation Of Piezoelectric Transducers

NASA Technical Reports Server (NTRS)

Mcnichol, Randal S.

1996-01-01

Electronic instrument designed to simulate dynamic output of integrated-circuit piezoelectric acceleration or pressure transducer. Operates in conjunction with external signal-conditioning circuit, generating square-wave signal of known amplitude for use in calibrating signal-conditioning circuit. Instrument also useful as special-purpose square-wave generator in other applications.

Maximizing the Detection Probability of Kilonovae Associated with Gravitational Wave Observations

NASA Astrophysics Data System (ADS)

Chan, Man Leong; Hu, Yi-Ming; Messenger, Chris; Hendry, Martin; Heng, Ik Siong

2017-01-01

Estimates of the source sky location for gravitational wave signals are likely to span areas of up to hundreds of square degrees or more, making it very challenging for most telescopes to search for counterpart signals in the electromagnetic spectrum. To boost the chance of successfully observing such counterparts, we have developed an algorithm that optimizes the number of observing fields and their corresponding time allocations by maximizing the detection probability. As a proof-of-concept demonstration, we optimize follow-up observations targeting kilonovae using telescopes including the CTIO-Dark Energy Camera, Subaru-HyperSuprimeCam, Pan-STARRS, and the Palomar Transient Factory. We consider three simulated gravitational wave events with 90% credible error regions spanning areas from ∼ 30 {\\deg }2 to ∼ 300 {\\deg }2. Assuming a source at 200 {Mpc}, we demonstrate that to obtain a maximum detection probability, there is an optimized number of fields for any particular event that a telescope should observe. To inform future telescope design studies, we present the maximum detection probability and corresponding number of observing fields for a combination of limiting magnitudes and fields of view over a range of parameters. We show that for large gravitational wave error regions, telescope sensitivity rather than field of view is the dominating factor in maximizing the detection probability.

Separation of Migration and Tomography Modes of Full-Waveform Inversion in the Plane Wave Domain

NASA Astrophysics Data System (ADS)

Yao, Gang; da Silva, Nuno V.; Warner, Michael; Kalinicheva, Tatiana

2018-02-01

Full-waveform inversion (FWI) includes both migration and tomography modes. The migration mode acts like a nonlinear least squares migration to map model interfaces with reflections, while the tomography mode behaves as tomography to build a background velocity model. The migration mode is the main response of inverting reflections, while the tomography mode exists in response to inverting both the reflections and refractions. To emphasize one of the two modes in FWI, especially for inverting reflections, the separation of the two modes in the gradient of FWI is required. Here we present a new method to achieve this separation with an angle-dependent filtering technique in the plane wave domain. We first transform the source and residual wavefields into the plane wave domain with the Fourier transform and then decompose them into the migration and tomography components using the opening angles between the transformed source and residual plane waves. The opening angles close to 180° contribute to the tomography component, while the others correspond to the migration component. We find that this approach is very effective and robust even when the medium is relatively complicated with strong lateral heterogeneities, highly dipping reflectors, and strong anisotropy. This is well demonstrated by theoretical analysis and numerical tests with a synthetic data set and a field data set.

Wave refraction diagrams for the Baltimore Canyon region of the mid-Atlantic continental shelf computed by using three bottom topography approximation techniques

NASA Technical Reports Server (NTRS)

Poole, L. R.

1976-01-01

The Langley Research Center and Virginia Institute of Marine Science wave refraction computer model was applied to the Baltimore Canyon region of the mid-Atlantic continental shelf. Wave refraction diagrams for a wide range of normally expected wave periods and directions were computed by using three bottom topography approximation techniques: quadratic least squares, cubic least squares, and constrained bicubic interpolation. Mathematical or physical interpretation of certain features appearing in the computed diagrams is discussed.

A Novel Multilevel DC - AC Converter from Green Energy Power Generators Using Step-Square Waving and PWM Technique

NASA Astrophysics Data System (ADS)

Fajingbesi, F. E.; Midi, N. S.; Khan, S.

2017-06-01

Green energy sources or renewable energy system generally utilize modular approach in their design. This sort of power sources are generally in DC form or in single cases AC. Due to high fluctuation in the natural origin of this energy (wind & solar) source they are stored as DC. DC power however are difficult to transfer over long distances hence DC to AC converters and storage system are very important in green energy system design. In this work we have designed a novel multilevel DC to AC converter that takes into account the modular design of green energy systems. A power conversion efficiency of 99% with reduced total harmonic distortion (THD) was recorded from our simulated system design.

Phase modulation for reduced vibration sensitivity in laser-cooled clocks in space

NASA Technical Reports Server (NTRS)

Klipstein, W.; Dick, G.; Jefferts, S.; Walls, F.

2001-01-01

The standard interrogation technique in atomic beam clocks is square-wave frequency modulation (SWFM), which suffers a first order sensitivity to vibrations as changes in the transit time of the atoms translates to perceived frequency errors. Square-wave phase modulation (SWPM) interrogation eliminates sensitivity to this noise.

Milliwatt dc/dc Inverter

NASA Technical Reports Server (NTRS)

Mclyman, C. W.

1983-01-01

Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

Generation of high-order Bessel vortex beam carrying orbital angular momentum using multilayer amplitude-phase-modulated surfaces in radiofrequency domain

NASA Astrophysics Data System (ADS)

Kou, Na; Yu, Shixing; Li, Long

2017-01-01

A high-order Bessel vortex beam carrying orbital angular momentum (OAM) is generated by using multilayer amplitude-phase-modulated surfaces (APMSs) at 10 GHz. The APMS transmitarray is composed of four-layer conformal square-loop (FCSL) surfaces with both amplitude and phase modulation. The APMS can transform a quasi-spherical wave emitted from the feeding source into a pseudo non-diffractive high-order Bessel vortex beam with OAM. The APMS for a second-order Bessel beam carrying OAM in the n = 2 mode is designed, fabricated, and measured. Full-wave simulation and measurement results confirm that Bessel vortex beams with OAM can be effectively generated using the proposed APMS transmitarray.

Cross-Shore Exchange on Natural Beaches

DTIC Science & Technology

2014-09-01

87   Figure 2.   Wave conditions measured by the ADCP in 13 m water depth of (a) root- mean-square wave height Hrms...horizontal velocity, Umean, measured in the reference level, ∑Tsig,pulse T3−hour ∑Tsig,pulse T3−hour xi (e) local water depth, h, and (f) local root...mean-square wave height normalized by the local water depth, Hrms/h, measured by ADCPin (blue) and ADCPout (red) during the 3HRLTs. Colored lines

Shear Wave Velocity and Site Amplification Factors for 25 Strong-Motion Instrument Stations Affected by the M5.8 Mineral, Virginia, Earthquake of August 23, 2011

USGS Publications Warehouse

Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.; Zangwill, Aliza; Estevez, Ivan; Lai, Lena

2015-01-01

Vertical one-dimensional shear wave velocity (Vs) profiles are presented for 25 strong-motion instrument sites along the Mid-Atlantic eastern seaboard, Piedmont region, and Appalachian region, which surround the epicenter of the M5.8 Mineral, Virginia, Earthquake of August 23, 2011. Testing was performed at sites in Pennsylvania, Maryland, West Virginia, Virginia, the District of Columbia, North Carolina, and Tennessee. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS,30), the average velocity for the entire profile (VS,Z), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The Vs profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. A large trailer-mounted active source was used to shake the ground during the testing and produce the surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

A kilonova as the electromagnetic counterpart to a gravitational-wave source.

PubMed

Smartt, S J; Chen, T-W; Jerkstrand, A; Coughlin, M; Kankare, E; Sim, S A; Fraser, M; Inserra, C; Maguire, K; Chambers, K C; Huber, M E; Krühler, T; Leloudas, G; Magee, M; Shingles, L J; Smith, K W; Young, D R; Tonry, J; Kotak, R; Gal-Yam, A; Lyman, J D; Homan, D S; Agliozzo, C; Anderson, J P; Angus, C R; Ashall, C; Barbarino, C; Bauer, F E; Berton, M; Botticella, M T; Bulla, M; Bulger, J; Cannizzaro, G; Cano, Z; Cartier, R; Cikota, A; Clark, P; De Cia, A; Della Valle, M; Denneau, L; Dennefeld, M; Dessart, L; Dimitriadis, G; Elias-Rosa, N; Firth, R E; Flewelling, H; Flörs, A; Franckowiak, A; Frohmaier, C; Galbany, L; González-Gaitán, S; Greiner, J; Gromadzki, M; Guelbenzu, A Nicuesa; Gutiérrez, C P; Hamanowicz, A; Hanlon, L; Harmanen, J; Heintz, K E; Heinze, A; Hernandez, M-S; Hodgkin, S T; Hook, I M; Izzo, L; James, P A; Jonker, P G; Kerzendorf, W E; Klose, S; Kostrzewa-Rutkowska, Z; Kowalski, M; Kromer, M; Kuncarayakti, H; Lawrence, A; Lowe, T B; Magnier, E A; Manulis, I; Martin-Carrillo, A; Mattila, S; McBrien, O; Müller, A; Nordin, J; O'Neill, D; Onori, F; Palmerio, J T; Pastorello, A; Patat, F; Pignata, G; Podsiadlowski, Ph; Pumo, M L; Prentice, S J; Rau, A; Razza, A; Rest, A; Reynolds, T; Roy, R; Ruiter, A J; Rybicki, K A; Salmon, L; Schady, P; Schultz, A S B; Schweyer, T; Seitenzahl, I R; Smith, M; Sollerman, J; Stalder, B; Stubbs, C W; Sullivan, M; Szegedi, H; Taddia, F; Taubenberger, S; Terreran, G; van Soelen, B; Vos, J; Wainscoat, R J; Walton, N A; Waters, C; Weiland, H; Willman, M; Wiseman, P; Wright, D E; Wyrzykowski, Ł; Yaron, O

2017-11-02

Gravitational waves were discovered with the detection of binary black-hole mergers and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.

A kilonova as the electromagnetic counterpart to a gravitational-wave source

NASA Astrophysics Data System (ADS)

Smartt, S. J.; Chen, T.-W.; Jerkstrand, A.; Coughlin, M.; Kankare, E.; Sim, S. A.; Fraser, M.; Inserra, C.; Maguire, K.; Chambers, K. C.; Huber, M. E.; Krühler, T.; Leloudas, G.; Magee, M.; Shingles, L. J.; Smith, K. W.; Young, D. R.; Tonry, J.; Kotak, R.; Gal-Yam, A.; Lyman, J. D.; Homan, D. S.; Agliozzo, C.; Anderson, J. P.; Angus, C. R.; Ashall, C.; Barbarino, C.; Bauer, F. E.; Berton, M.; Botticella, M. T.; Bulla, M.; Bulger, J.; Cannizzaro, G.; Cano, Z.; Cartier, R.; Cikota, A.; Clark, P.; De Cia, A.; Della Valle, M.; Denneau, L.; Dennefeld, M.; Dessart, L.; Dimitriadis, G.; Elias-Rosa, N.; Firth, R. E.; Flewelling, H.; Flörs, A.; Franckowiak, A.; Frohmaier, C.; Galbany, L.; González-Gaitán, S.; Greiner, J.; Gromadzki, M.; Guelbenzu, A. Nicuesa; Gutiérrez, C. P.; Hamanowicz, A.; Hanlon, L.; Harmanen, J.; Heintz, K. E.; Heinze, A.; Hernandez, M.-S.; Hodgkin, S. T.; Hook, I. M.; Izzo, L.; James, P. A.; Jonker, P. G.; Kerzendorf, W. E.; Klose, S.; Kostrzewa-Rutkowska, Z.; Kowalski, M.; Kromer, M.; Kuncarayakti, H.; Lawrence, A.; Lowe, T. B.; Magnier, E. A.; Manulis, I.; Martin-Carrillo, A.; Mattila, S.; McBrien, O.; Müller, A.; Nordin, J.; O'Neill, D.; Onori, F.; Palmerio, J. T.; Pastorello, A.; Patat, F.; Pignata, G.; Podsiadlowski, Ph.; Pumo, M. L.; Prentice, S. J.; Rau, A.; Razza, A.; Rest, A.; Reynolds, T.; Roy, R.; Ruiter, A. J.; Rybicki, K. A.; Salmon, L.; Schady, P.; Schultz, A. S. B.; Schweyer, T.; Seitenzahl, I. R.; Smith, M.; Sollerman, J.; Stalder, B.; Stubbs, C. W.; Sullivan, M.; Szegedi, H.; Taddia, F.; Taubenberger, S.; Terreran, G.; van Soelen, B.; Vos, J.; Wainscoat, R. J.; Walton, N. A.; Waters, C.; Weiland, H.; Willman, M.; Wiseman, P.; Wright, D. E.; Wyrzykowski, Ł.; Yaron, O.

2017-11-01

Gravitational waves were discovered with the detection of binary black-hole mergers and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.

An Enhanced Method for Scheduling Observations of Large Sky Error Regions for Finding Optical Counterparts to Transients

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

Rana, Javed; Singhal, Akshat; Gadre, Bhooshan

2017-04-01

The discovery and subsequent study of optical counterparts to transient sources is crucial for their complete astrophysical understanding. Various gamma-ray burst (GRB) detectors, and more notably the ground-based gravitational wave detectors, typically have large uncertainties in the sky positions of detected sources. Searching these large sky regions spanning hundreds of square degrees is a formidable challenge for most ground-based optical telescopes, which can usually image less than tens of square degrees of the sky in a single night. We present algorithms for better scheduling of such follow-up observations in order to maximize the probability of imaging the optical counterpart, basedmore » on the all-sky probability distribution of the source position. We incorporate realistic observing constraints such as the diurnal cycle, telescope pointing limitations, available observing time, and the rising/setting of the target at the observatory’s location. We use simulations to demonstrate that our proposed algorithms outperform the default greedy observing schedule used by many observatories. Our algorithms are applicable for follow-up of other transient sources with large positional uncertainties, such as Fermi -detected GRBs, and can easily be adapted for scheduling radio or space-based X-ray follow-up.« less

Experiments of multichannel least-square methods for sound field reproduction inside aircraft mock-up: Objective evaluations

NASA Astrophysics Data System (ADS)

Gauthier, P.-A.; Camier, C.; Lebel, F.-A.; Pasco, Y.; Berry, A.; Langlois, J.; Verron, C.; Guastavino, C.

2016-08-01

Sound environment reproduction of various flight conditions in aircraft mock-ups is a valuable tool for the study, prediction, demonstration and jury testing of interior aircraft sound quality and annoyance. To provide a faithful reproduced sound environment, time, frequency and spatial characteristics should be preserved. Physical sound field reproduction methods for spatial sound reproduction are mandatory to immerse the listener's body in the proper sound fields so that localization cues are recreated at the listener's ears. Vehicle mock-ups pose specific problems for sound field reproduction. Confined spaces, needs for invisible sound sources and very specific acoustical environment make the use of open-loop sound field reproduction technologies such as wave field synthesis (based on free-field models of monopole sources) not ideal. In this paper, experiments in an aircraft mock-up with multichannel least-square methods and equalization are reported. The novelty is the actual implementation of sound field reproduction with 3180 transfer paths and trim panel reproduction sources in laboratory conditions with a synthetic target sound field. The paper presents objective evaluations of reproduced sound fields using various metrics as well as sound field extrapolation and sound field characterization.

Orthogonality catastrophe and fractional exclusion statistics

NASA Astrophysics Data System (ADS)

Ares, Filiberto; Gupta, Kumar S.; de Queiroz, Amilcar R.

2018-02-01

We show that the N -particle Sutherland model with inverse-square and harmonic interactions exhibits orthogonality catastrophe. For a fixed value of the harmonic coupling, the overlap of the N -body ground state wave functions with two different values of the inverse-square interaction term goes to zero in the thermodynamic limit. When the two values of the inverse-square coupling differ by an infinitesimal amount, the wave function overlap shows an exponential suppression. This is qualitatively different from the usual power law suppression observed in the Anderson's orthogonality catastrophe. We also obtain an analytic expression for the wave function overlaps for an arbitrary set of couplings, whose properties are analyzed numerically. The quasiparticles constituting the ground state wave functions of the Sutherland model are known to obey fractional exclusion statistics. Our analysis indicates that the orthogonality catastrophe may be valid in systems with more general kinds of statistics than just the fermionic type.

Orthogonality catastrophe and fractional exclusion statistics.

PubMed

Ares, Filiberto; Gupta, Kumar S; de Queiroz, Amilcar R

2018-02-01

We show that the N-particle Sutherland model with inverse-square and harmonic interactions exhibits orthogonality catastrophe. For a fixed value of the harmonic coupling, the overlap of the N-body ground state wave functions with two different values of the inverse-square interaction term goes to zero in the thermodynamic limit. When the two values of the inverse-square coupling differ by an infinitesimal amount, the wave function overlap shows an exponential suppression. This is qualitatively different from the usual power law suppression observed in the Anderson's orthogonality catastrophe. We also obtain an analytic expression for the wave function overlaps for an arbitrary set of couplings, whose properties are analyzed numerically. The quasiparticles constituting the ground state wave functions of the Sutherland model are known to obey fractional exclusion statistics. Our analysis indicates that the orthogonality catastrophe may be valid in systems with more general kinds of statistics than just the fermionic type.

All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Ajith, P.; Allen, B.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barayoga, J. C. B.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Beck, D.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Belletoile, A.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet–Castell, J.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chaibi, O.; Chalermsongsak, T.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, W.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Del Pozzo, W.; del Prete, M.; Dent, T.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Paolo Emilio, M.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Endrőczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Feroz, F.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Flanigan, M.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Geng, R.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Gray, N.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Ha, T.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Hardt, A.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; James, E.; Jang, Y. J.; Jaranowski, P.; Jesse, E.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kelley, D.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, H.; Kim, K.; Kim, N.; Kim, Y. M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kranz, O.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Leaci, P.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lindquist, P. E.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Luan, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marandi, A.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; McKechan, D. J. A.; McWilliams, S.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Morriss, S. R.; Mosca, S.; Mossavi, K.; Mours, B.; Mow–Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Necula, V.; Nelson, J.; Neri, I.; Newton, G.; Nguyen, T.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pedraza, M.; Peiris, P.; Pekowsky, L.; Penn, S.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Prato, M.; Predoi, V.; 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.; Quetschke, V.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Redwine, K.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J. G.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sainathan, P.; Salemi, F.; Sammut, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Stein, A. J.; Stein, L. C.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Tseng, K.; Tucker, E.; Ugolini, D.; Vahlbruch, H.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, X.; Wang, Z.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhang, W.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2012-06-01

We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration ≲1s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc3 for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range ˜5×10-22Hz-1/2 to ˜1×10-20Hz-1/2. The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.

Wave packet dynamics for a system with position and time-dependent effective mass in an infinite square well

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

Vubangsi, M.; Tchoffo, M.; Fai, L. C.

The problem of a particle with position and time-dependent effective mass in a one-dimensional infinite square well is treated by means of a quantum canonical formalism. The dynamics of a launched wave packet of the system reveals a peculiar revival pattern that is discussed. .

Diagnostic criteria for the characterization of quasireversible electron transfer reactions by cyclic square wave voltammetry.

PubMed

Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A

2014-08-19

Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

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

Gubbiotti, G.; Tacchi, S.; Montoncello, F.

2015-06-29

The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained bymore » dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.« less

A methodology for estimating dog noise in an animal housing facility

NASA Technical Reports Server (NTRS)

Sierens, S. E.; Ingley, H. A.; Besch, E. L.

1977-01-01

A rectangular reverberation chamber was designed, constructed and calibrated for the experimental measurement of the sound power level (acoustic power) of a dog. Calibration of the chamber consisted of comparing the acoustic power measured for a random noise source in the chamber with that for the identical source in a free field environment. Data from dogs indicate that barking noise can be modeled as a square wave pattern with short duration and peak sound power levels in the 500 Hz octave band. A-weighted sound pressure levels of up to 114.7 dBA were absorbed, indicating a potential concern for both animals and man chronically exposed to such environments.

Directional Limits on Persistent Gravitational Waves Using LIGO S5 Science Data

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.;

Earthquake source parameters of repeating microearthquakes at Parkfield, CA, determined using the SAFOD Pilot Hole seismic array

NASA Astrophysics Data System (ADS)

Imanishi, K.; Ellsworth, W. L.

2005-12-01

We determined source parameters of repeating microearthquakes occurring at Parkfield, CA, using the SAFOD Pilot Hole seismic array. To estimate reliable source parameters, we used the empirical Green's function (EGF) deconvolution method which removes the attenuation effects and site responses by taking the spectral amplitude ratio between the spectra of the two colocated events. For earthquakes during the period from December 2002 to October 2003 whose S-P time differences are less than 1 s, we detected 34 events that classified into 14 groups. Moment magnitudes range from -0.3 to 2.1. These data were recorded at a sampling rate of 2 kHz. The dataset includes two SAFOD target repeating earthquakes which occurred on October 2003. In general, the deconvolution procedure is an unstable process, especially for higher frequencies, because small location differences result in the profound effects on the spectral ratio. This leads to large uncertainties in the estimations of corner frequencies. According to Chaverria et al. [2003], the wavetrain recorded in the Pilot Hole is dominated by reflections and conversions and not random coda waves. So, we expect that the spectral ratios of the waves between P and S wave will also reflect the source, as will the waves following S wave. We compared spectral ratios calculated from the direct waves with those from other parts of the wavetrain, and confirmed that they showed similar shapes. Therefore it is possible to obtain a more robust measure of spectral ratio by stacking the ratios calculated from shorter moving windows taken along the record following the direct waves. We further stacked all ratios obtained from each level of the array. The stacked spectral ratios were inverted for corner frequencies assuming the omega-square model. We determined static stress drops from those corner frequencies assuming a circular crack model. We also calculated apparent stresses for each event by considering frequency dependent attenuation, where the average difference between the observed and the calculated omega-square model was assumed to represent the path and site effects. The estimated static stress drops are high, mostly in excess of 10 MPa and with some above 50 MPa. It should be noted that the highest value is near the strength of the rock. Apparent stresses range from 0.4 to 20 MPa, at the high end of the range of those reported by other studies. According to an asperity model [e.g., McGarr, 1981; Johnson & Nadeau, 2002], the small strong asperity patch is surrounded by a much weaker fault that creeps under the influence of tectonic stress. When the asperity patch ruptures, the surrounding area slips as it is dynamically loaded by the stress release of the asperity patch. If so, our estimated source dimensions seem to correspond to the size of the area surrounding the asperity patch, and the stress drops of the asperity might be much higher than our estimations. Although this is consistent with the hypocesis of Nadeau and Johnson [1998], it is unlikely that the stress drops exceed the strength of the rock. We should re-examine the asperity model based on the results obtained in this study.

Application of the Pseudo Wigner-Ville Distribution to the Measurement of the Dispersion of Lamb Modes in Graphite/Epoxy Plates

NASA Technical Reports Server (NTRS)

Prosser, W. H.; Seale, M. D.; Smith, B. T.

1997-01-01

Acoustic waves propagate in thin plates as guided or Lamb modes. The velocities of these modes are dispersive in that they depend not only on the material elastic properties and density, but also on the frequency. Accurate characterization of Lamb wave dispersion is important in many acoustic based nondestructive evaluation techniques. It is necessary for ultrasonic measurements in thin plates to determine elastic properties and for flaw detection and localization. In acoustic emission (AE) testing, if not taken into account, highly dispersive Lamb mode propagation can lead to large errors in source location. In this study, the pseudo Wigner-Ville distribution (PWVD) was used for measurement of group velocity dispersion of Lamb waves in a unidirectional graphite/epoxy (AS4/3502) laminate. The PWVD is one of a number of transforms which provide a time-frequency representation of a digitized time series. Broad band acoustic waves were generated by a pencil lead fracture (Hsu-Neilsen source) and were detected with broad band ultrasonic transducers. The arrival times for the lowest order symmetric (S(sub 0)) and antisymmetric (A(sub 0)) Lamb modes were determined from measurements of the time at which the respective peak amplitudes occurred in the PWVD. Measurements were made at several source-to-detector distances and a least squares fit used to calculate the velocity. Results are presented for propagation along, and perpendicular to, the fiber direction. Theoretical dispersion curves were also calculated and a comparison between theory and experiment demonstrates good agreement.

Comparisons of Source Characteristics between Recent Inland Crustal Earthquake Sequences inside and outside of Niigata-Kobe Tectonic Zone, Japan

NASA Astrophysics Data System (ADS)

Somei, K.; Asano, K.; Iwata, T.; Miyakoshi, K.

2012-12-01

After the 1995 Kobe earthquake, many M7-class inland earthquakes occurred in Japan. Some of those events (e.g., the 2004 Chuetsu earthquake) occurred in a tectonic zone which is characterized as a high strain rate zone by the GPS observation (Sagiya et al., 2000) or dense distribution of active faults. That belt-like zone along the coast in Japan Sea side of Tohoku and Chubu districts, and north of Kinki district, is called as the Niigata-Kobe tectonic zone (NKTZ, Sagiya et al, 2000). We investigate seismic scaling relationship for recent inland crustal earthquake sequences in Japan and compare source characteristics between events occurring inside and outside of NKTZ. We used S-wave coda part for estimating source spectra. Source spectral ratio is obtained by S-wave coda spectral ratio between the records of large and small events occurring close to each other from nation-wide strong motion network (K-NET and KiK-net) and broad-band seismic network (F-net) to remove propagation-path and site effects. We carefully examined the commonality of the decay of coda envelopes between event-pair records and modeled the observed spectral ratio by the source spectral ratio function with assuming omega-square source model for large and small events. We estimated the corner frequencies and seismic moment (ratio) from those modeled spectral ratio function. We determined Brune's stress drops of 356 events (Mw: 3.1-6.9) in ten earthquake sequences occurring in NKTZ and six sequences occurring outside of NKTZ. Most of source spectra obey omega-square source spectra. There is no obvious systematic difference between stress drops of events in NKTZ zone and others. We may conclude that the systematic tendency of seismic source scaling of the events occurred inside and outside of NKTZ does not exist and the average source scaling relationship can be effective for inland crustal earthquakes. Acknowledgements: Waveform data were provided from K-NET, KiK-net and F-net operated by National Research Institute for Earth Science and Disaster Prevention Japan. This study is supported by Multidisciplinary research project for Niigata-Kobe tectonic zone promoted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Probing the critical zone using passive- and active-source estimates of subsurface shear-wave velocities

NASA Astrophysics Data System (ADS)

Callahan, R. P.; Taylor, N. J.; Pasquet, S.; Dueker, K. G.; Riebe, C. S.; Holbrook, W. S.

2016-12-01

Geophysical imaging is rapidly becoming popular for quantifying subsurface critical zone (CZ) architecture. However, a diverse array of measurements and measurement techniques are available, raising the question of which are appropriate for specific study goals. Here we compare two techniques for measuring S-wave velocities (Vs) in the near surface. The first approach quantifies Vs in three dimensions using a passive source and an iterative residual least-squares tomographic inversion. The second approach uses a more traditional active-source seismic survey to quantify Vs in two dimensions via a Monte Carlo surface-wave dispersion inversion. Our analysis focuses on three 0.01 km2 study plots on weathered granitic bedrock in the Southern Sierra Critical Zone Observatory. Preliminary results indicate that depth-averaged velocities from the two methods agree over the scales of resolution of the techniques. While the passive- and active-source techniques both quantify Vs, each method has distinct advantages and disadvantages during data acquisition and analysis. The passive-source method has the advantage of generating a three dimensional distribution of subsurface Vs structure across a broad area. Because this method relies on the ambient seismic field as a source, which varies unpredictably across space and time, data quality and depth of investigation are outside the control of the user. Meanwhile, traditional active-source surveys can be designed around a desired depth of investigation. However, they only generate a two dimensional image of Vs structure. Whereas traditional active-source surveys can be inverted quickly on a personal computer in the field, passive source surveys require significantly more computations, and are best conducted in a high-performance computing environment. We use data from our study sites to compare these methods across different scales and to explore how these methods can be used to better understand subsurface CZ architecture.

Effect of current on spectrum of breaking waves in water of finite depth

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.

1987-01-01

This paper presents an approximate method to compute the mean value, the mean square value and the spectrum of waves in water of finite depth taking into account the effect of wave breaking with or without the presence of current. It is assumed that there exists a linear and Gaussian ideal wave train whose spectrum is first obtained using the wave energy flux balance equation without considering wave breaking. The Miche wave breaking criterion for waves in finite water depth is used to limit the wave elevation and establish an expression for the breaking wave elevation in terms of the elevation and its second time derivative of the ideal waves. Simple expressions for the mean value, the mean square value and the spectrum are obtained. These results are applied to the case in which a deep water unidirectional wave train, propagating normally towards a straight shoreline over gently varying sea bottom of parallel and straight contours, encounters an adverse steady current whose velocity is assumed to be uniformly distributed with depth. Numerical results are obtained and presented in graphical form.

Nonnormality increases variance of gravity waves trapped in a tilted box

NASA Astrophysics Data System (ADS)

Harlander, Uwe; Borcia, Ion Dan; Krebs, Andreas

2017-04-01

We study the prototype problem of internal gravity waves in a square domain tilted with respect to the gravity vector by an angle theta. Only when theta is zero regular normal modes exist, for all other angles wave attractors and singularities dominate the flow. We show that the linear operator of the governing PDE becomes non-normal for nonzero theta giving rise to non-modal transient growth. This growth depends on the underlying norm: for the variance norm significant growth rates can be found whereas for the energy norm, no growth is possible since there is no source for energy (in contrast to shear fows, for which the mean flow feeds the perturbations). We continue by showing that the nonnormality of the system matrix is increasing with theta and reaches a maximum when theta is 45 degree. Moreover, the growth rate is increasing as can be expected from the increasing nonnormality of the matrix. Our results imply that at least the most simple wave attractors can be seen as those initial flow fields that gain most of the variance during a given time period.

40-Hz square-wave stimulation requires less energy to produce muscle contraction: compared with the TASER® X26 conducted energy weapon.

PubMed

Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

2013-07-01

Conducted energy weapons (CEWs) (including the Advanced TASER(®) X26 model produced by TASER International, Inc.) incapacitate individuals by causing muscle contractions. In this study using anesthetized swine, the potential incapacitating effect of primarily monophasic, 19-Hz voltage imposed by the commercial CEW was compared with the effect of voltages imposed by a laboratory device that created 40-Hz square waves. Forces of muscle contraction were measured with the use of strain gauges. Stimulation with 40-Hz square waves required less pulse energy than stimulation with the commercial CEW to produce similar muscle contraction. The square-pulse stimulation, at the higher repetition rate, caused a more complete tetanus at a lower energy. Use of such a simple shape of waveform may be used to make future nonlethal weapon devices more efficient. © 2013 American Academy of Forensic Sciences Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.

Experimental study on an S-band near-field microwave magnetron power transmission system on hundred-watt level

NASA Astrophysics Data System (ADS)

Zhang, Biao; Jiang, Wan; Yang, Yang; Yu, Chengyang; Huang, Kama; Liu, Changjun

2015-11-01

A multi-magnetron microwave source, a metamaterial transmitting antenna, and a large power rectenna array are presented to build a near-field 2.45 GHz microwave power transmission system. The square 1 m2 rectenna array consists of sixteen rectennas with 2048 Schottky diodes for large power microwave rectifying. It receives microwave power and converts them into DC power. The design, structure, and measured performance of a unit rectenna as well as the entail rectenna array are presented in detail. The multi-magnetron microwave power source switches between half and full output power levels, i.e. the half-wave and full-wave modes. The transmission antenna is formed by a double-layer metallic hole array, which is applied to combine the output power of each magnetron. The rectenna array DC output power reaches 67.3 W on a 1.2 Ω DC load at a distance of 5.5 m from the transmission antenna. DC output power is affected by the distance, DC load, and the mode of microwave power source. It shows that conventional low power Schottky diodes can be applied to a microwave power transmission system with simple magnetrons to realise large power microwave rectifying.

Phase-Sensitive Reflective Imaging Device in the mm-wave and Terahertz Regions

NASA Astrophysics Data System (ADS)

Gallerano, Gian Piero; Doria, Andrea; Germini, Marzia; Giovenale, Emilio; Messina, Giovanni; Spassovsky, Ivan P.

2009-12-01

Two Free Electron Laser sources have been developed at ENEA-Frascati for a variety of applications: A Compact Free Electron Laser (C-FEL) that provides coherent radiation in the frequency range between 90 and 150 GHz Gallerano et al. (Infrared Phys. and Techn. 40:161, 1999), and a second source, FEL-CATS, which utilizes a peculiar radio-frequency structure to generate coherent emission in the range 0.4 to 0.7 THz Doria et al. (Phys. Rev. Lett 93:264801, 2004). The high peak power of several kW in 15 to 50 ps pulses, makes these sources particularly suitable for the assessment of exposure limits in biological systems and for long range detection. In this paper we present a phase-sensitive reflective imaging device in the mm-wave and THz regions, which has proven to be a valuable tool in the biological Ramundo-Orlando et al. (Bioelectromagnetics 28:587-598, 2007), environmental Doria et al. (2005) and art conservation fields Gallerano et al. (2008). Different setups have been tested at different levels of spatial resolution to image objects from a few centimeter square to larger sizes. Images have been compared to identify and characterize the contrast mechanism.

Millimeter transient point sources in the SPTpol 100 square degree survey

DOE PAGES

Whitehorn, N.; Natoli, T.; Ade, P. A. R.; ...

2016-10-18

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg 2 patch of sky centered atmore » R.A. 23 h30 m and decl. –55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. As a result, one candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low (p = 0.01) to confirm detection.« less

MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

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

Whitehorn, N.; Haan, T. de; George, E. M.

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg{sup 2} patch of sky centered atmore » R.A. 23{sup h}30{sup m} and decl. −55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. One candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low ( p = 0.01) to confirm detection.« less

Millimeter transient point sources in the SPTpol 100 square degree survey

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

Whitehorn, N.; Natoli, T.; Ade, P. A. R.

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg 2 patch of sky centered atmore » R.A. 23 h30 m and decl. –55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. As a result, one candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low (p = 0.01) to confirm detection.« less

Optimizing an ELF/VLF Phased Array at HAARP

NASA Astrophysics Data System (ADS)

Fujimaru, S.; Moore, R. C.

2013-12-01

The goal of this study is to maximize the amplitude of 1-5 kHz ELF/VLF waves generated by ionospheric HF heating and measured at a ground-based ELF/VLF receiver. The optimization makes use of experimental observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) Observatory in Gakona, Alaska. During these experiments, the amplitude, phase, and propagation delay of the ELF/VLF waves were carefully measured. The HF beam was aimed at 15 degrees zenith angle in 8 different azimuthal directions, equally spaced in a circle, while broadcasting a 3.25 MHz (X-mode) signal that was amplitude modulated (square wave) with a linear frequency-time chirp between 1 and 5 kHz. The experimental observations are used to provide reference amplitudes, phases, and propagation delays for ELF/VLF waves generated at these specific locations. The presented optimization accounts for the trade-off between duty cycle, heated area, and the distributed nature of the source region in order to construct a "most efficient" phased array. The amplitudes and phases generated by modulated heating at each location are combined in post-processing to find an optimal combination of duty cycle, heating location, and heating order.

Optical Counterparts to Gravitational Waves

NASA Astrophysics Data System (ADS)

Beroiz, Martin

The novel field of Gravitational Wave Astronomy has opened a new window to the universe. Never before had we received gravitational waves from the distant celestial bodies carried away by space-time perturbations, until the detection of GW150914 on September 14, 2015. But these signals, however faint, carry very little information about their positions on the sky. The sky localization can have uncertainties that span up to a few hundreds square degrees, which makes locating the sources very difficult. Traditional Astronomy can complement this limitation of gravitational wave detection where optical astronomy is stronger: localization. However, this poses other technological challenges of a different kind. In the era of multi-messenger Astronomy, a low latency response time after detection is crucial in order to have any hope of detecting the optically faint electromagnetic counterparts of the event. The mission of the Transient Optical Robotic Observatory of the South (TOROS), in the context of multi-messenger and time-domain astronomy, is to create a facility ready to respond to gravitational wave detections for prompt follow-up observations searching for optical counterparts. This dissertation discusses the implementation of a software pipeline for the TOROS project and the results obtained during the O1 campaign of Advanced LIGO.

The measurement of acoustic properties of limited size panels by use of a parametric source

NASA Astrophysics Data System (ADS)

Humphrey, V. F.

1985-01-01

A method of measuring the acoustic properties of limited size panels immersed in water, with a truncated parametric array used as the acoustic source, is described. The insertion loss and reflection loss of thin metallic panels, typically 0·45 m square, were measured at normal incidence by using this technique. Results were obtained for a wide range of frequencies (10 to 100 kHz) and were found to be in good agreement with the theoretical predictions for plane waves. Measurements were also made of the insertion loss of aluminium, Perspex and G.R.P. panels for angles of incidence up to 50°. The broad bandwidth available from the parametric source permitted detailed measurements to be made over a wide frequency range using a single transmitting transducer. The small spot sizes obtainable with the parametric source also helped to reduce the significance of diffraction from edges of the panel under test.

An extension of the Lighthill theory of jet noise to encompass refraction and shielding

NASA Technical Reports Server (NTRS)

Ribner, Herbert S.

1995-01-01

A formalism for jet noise prediction is derived that includes the refractive 'cone of silence' and other effects; outside the cone it approximates the simple Lighthill format. A key step is deferral of the simplifying assumption of uniform density in the dominant 'source' term. The result is conversion to a convected wave equation retaining the basic Lighthill source term. The main effect is to amend the Lighthill solution to allow for refraction by mean flow gradients, achieved via a frequency-dependent directional factor. A general formula for power spectral density emitted from unit volume is developed as the Lighthill-based value multiplied by a squared 'normalized' Green's function (the directional factor), referred to a stationary point source. The convective motion of the sources, with its powerful amplifying effect, also directional, is already accounted for in the Lighthill format: wave convection and source convection are decoupled. The normalized Green's function appears to be near unity outside the refraction dominated 'cone of silence', this validates our long term practice of using Lighthill-based approaches outside the cone, with extension inside via the Green's function. The function is obtained either experimentally (injected 'point' source) or numerically (computational aeroacoustics). Approximation by unity seems adequate except near the cone and except when there are shrouding jets: in that case the difference from unity quantifies the shielding effect. Further extension yields dipole and monopole source terms (cf. Morfey, Mani, and others) when the mean flow possesses density gradients (e.g., hot jets).

Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

NASA Astrophysics Data System (ADS)

Zhu, Hui; Chen, Yueyuan; Chu, Daping; Feng, Shiwei; Zhang, Yingqiao; Wang, Pengfei

2016-09-01

The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V 0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V 0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

Narrowing the Search After Gravitational-Wave Detections

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

Now that were able to detect gravitational waves, the next challenge is to spot electromagnetic signatures associated with gravitational-wave events. A team of scientists has proposed a new algorithm that might narrow the search.Artists illustrations of the stellar-merger model for short gamma-ray bursts. In the model, 1) two neutron stars inspiral, 2) they merge and produce a gamma-ray burst, 3) a small fraction of their mass is flung out and radiates as a kilonova, 4) a massive neutron star or black hole with a disk remains after the event. [NASA, ESA, and A. Feild (STScI)]Light from Neutron-Star MergersJust over a year ago, LIGO detected its first gravitational-wave signal: GW150914, produced when two black holes merged. While we didnt expect to see any sort of light-based signal from this merger, we could expect to see transient electromagnetic signatures in the case of a neutron starblack hole merger or a neutron starneutron star merger in the form of a kilonova or a short gamma-ray burst.While we havent yet detected any mergers involving neutron stars, LIGO has the sensitivity to make these detections in the local universe, and we hope to start seeing them soon! Finding the electromagnetic companions to gravitational-wave signals would be the best way to probe the evolution history of the universe and learn what happens when evolved stars collide. So how do we hunt them down?2D localization maps for LIGOs detection of GW150914 (black contours), as well as the footprints of follow-up observations (red for radio, green for optical/IR, blue for X-ray). [Abbott et al. 2016]Pinpointing a VolumeThe two LIGO detectors can already provide rough 2D localization of where the gravitational-wave signal came from, but the region predicted for GW150914 still covered 600 square degrees, which is a pretty hefty patch of sky! In light of this, the simplest follow-up strategy of tiling large survey observations of the entire predicted region is somewhat impractical and time-consuming. Could we possibly take a more targeted approach?The key, say a team of scientists led by Leo Singer (NASA Goddard SFC), is in using 3D estimates of the source location, rather than 2D sky maps: we need to produce distance estimates for the gravitational-wave source as well. Singer and collaborators have developed an algorithm that, from a gravitational-wave signal, can produce a fast full-volume estimate of the probability distribution for its sources location.Volume rendering of the 90% credible region for a simulated gravitational-wave event, superimposed over a galaxy map for the region. Green crosshairs represent the true location of the source; the most massive galaxies inside the credible region are highlighted. Searching only these galaxies could significantly reduce the observing time needed to detect an electromagnetic counterpart. [Singer et al. 2016]We can then easily cross-reference the volume predicted to contain the source against a galaxy catalog to identify the most probable host galaxies for the signal. This approach allows us to target specific galaxies for rapid observations with follow-up campaigns in the search for a counterpart.Targeted EfficiencySinger and collaborators approach would make searching for electromagnetic counterparts to gravitational-wave events a much more efficient process. One particular advantage would be in reducing the number of false positives: for a typical wide-field follow-up campaign searching 100 square degrees, hundreds of contaminatingsupernovae would be in the field. Targeting only 10 x 10 patches around 100 nearby galaxies, however, reduces the background to fewer than 10 contaminatingsupernovae.An additional benefit is that this targeted strategy opens the door of gravitational-wave follow-up to many small-field-of-view, large-aperture telescopes, instead of limiting the task to broad synoptic surveys. This permits the involvement of many more campaigns in the hunt for the important electromagnetic counterparts to gravitational waves.Note: Want to check out the teams data? Its publicly available here!CitationLeo P. Singer et al 2016 ApJL 829 L15. doi:10.3847/2041-8205/829/1/L15

Can JWST Follow Up on Gravitational-Wave Detections?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-02-01

Bitten by the gravitational-wave bug? While we await Thursdays press conference, heres some food for thought: if LIGO were able to detect gravitational waves from compact-object mergers, how could we follow up on the detections? A new study investigates whether the upcoming James Webb Space Telescope (JWST) will be able to observe electromagnetic signatures of some compact-object mergers.Hunting for MergersStudying compact-object mergers (mergers of black holes and neutron stars) can help us understand a wealth of subjects, like high-energy physics, how matter behaves at nuclear densities, how stars evolve, and how heavy elements in the universe were created.The Laser Interferometer Gravitational-Wave Observatory (LIGO) is searching for the signature ripples in spacetime identifying these mergers, but gravitational waves are squirrelly: LIGO will only be able to localize wave sources to tens of square degrees. If we want to find out more about any mergers LIGO discovers in gravitational waves, well need a follow-up search for electromagnetic counterparts with other observatories.The Kilonova KeyOne possible electromagnetic counterpart is kilonovae, explosions that can be produced during a merger of a binary neutron star or a neutron starblack hole system. If the neutron star is disrupted during the merger, some of the hot mass is flung outward and shines brightly by radioactive decay.Kilonovae are especially promising as electromagnetic counterparts to gravitational waves for three reasons:They emit isotropically, so the number of observable mergers isnt limited by relativistic beaming.They shine for a week, giving follow-up observatories time to search for them.The source location can beeasily recovered.The only problem? We dont currently have any sensitive survey instruments in the near-infrared band (where kilonova emission peaks) that can provide coverage over tens of square degrees. Luckily, we will soon have just the thing: JWST, launching in 2018!JWSTs SearchIntegration time needed for JWSTs NIRCam to detect a kilonova at 200 Mpc, as a function of time since the merger. Different curves correspond to different NIRCam filters. Note that the total time for follow-up is overwhelmingly dominated by things like telescope slew time, rather than by this exposure time. [Bartos et al. 2016]In a recent study, a team of authors led by Imre Bartos (Columbia University) evaluatewhether JWST will be capable of catching these kilonovae if LIGO finds gravitational wave signals.Bartos and collaborators calculate that, given the sensitivity of the different filters on JWSTs Near-Infrared Camera, the instrument should easily be able to detect a kilonova 200 Mpc away (a typical distance at which LIGO might be able to find a neutron-star binary). But theres a catch: 10 deg2 is a really big sky area, and it would take JWST an unfeasible amount of time (days!) to fully cover it.The authors suggest insteadusing a targeted search. Since most mergers are expected to be in or near galaxies, JWST could specifically focus the follow-up search on known galaxies within the searcharea. This approach would bring the total search time down to 12.6 hours, which is within the realm of feasibility. And this time could be reduced even further by concentrating on galaxies most likely to host kilonovae, like those with high star-formation rates.The conclusion: if LIGO is able to detect gravitational waves, JWST will provide an excellent means to follow up on the detection in the attempt toidentify the source.CitationI. Bartos et al 2016 ApJ 816 61. doi:10.3847/0004-637X/816/2/61

Imaging the square of the correlated two-electron wave function of a hydrogen molecule

DOE PAGES

Waitz, M.; Bello, R. Y.; Metz, D.; ...

2017-12-22

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in whichmore » electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Finally, our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.« less

Imaging the square of the correlated two-electron wave function of a hydrogen molecule.

PubMed

Waitz, M; Bello, R Y; Metz, D; Lower, J; Trinter, F; Schober, C; Keiling, M; Lenz, U; Pitzer, M; Mertens, K; Martins, M; Viefhaus, J; Klumpp, S; Weber, T; Schmidt, L Ph H; Williams, J B; Schöffler, M S; Serov, V V; Kheifets, A S; Argenti, L; Palacios, A; Martín, F; Jahnke, T; Dörner, R

2017-12-22

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in which electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.

Imaging the square of the correlated two-electron wave function of a hydrogen molecule

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

Waitz, M.; Bello, R. Y.; Metz, D.

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H 2 two-electron wave function in whichmore » electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Finally, our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources.« less

Transformation elastodynamics and cloaking for flexural waves

NASA Astrophysics Data System (ADS)

Colquitt, D. J.; Brun, M.; Gei, M.; Movchan, A. B.; Movchan, N. V.; Jones, I. S.

2014-12-01

The paper addresses an important issue of cloaking transformations for fourth-order partial differential equations representing flexural waves in thin elastic plates. It is shown that, in contrast with the Helmholtz equation, the general form of the partial differential equation is not invariant with respect to the cloaking transformation. The significant result of this paper is the analysis of the transformed equation and its interpretation in the framework of the linear theory of pre-stressed plates. The paper provides a formal framework for transformation elastodynamics as applied to elastic plates. Furthermore, an algorithm is proposed for designing a broadband square cloak for flexural waves, which employs a regularised push-out transformation. Illustrative numerical examples show high accuracy and efficiency of the proposed cloaking algorithm. In particular, a physical configuration involving a perturbation of an interference pattern generated by two coherent sources is presented. It is demonstrated that the perturbation produced by a cloaked defect is negligibly small even for such a delicate interference pattern.

Effective Algorithm for Detection and Correction of the Wave Reconstruction Errors Caused by the Tilt of Reference Wave in Phase-shifting Interferometry

NASA Astrophysics Data System (ADS)

Xu, Xianfeng; Cai, Luzhong; Li, Dailin; Mao, Jieying

2010-04-01

In phase-shifting interferometry (PSI) the reference wave is usually supposed to be an on-axis plane wave. But in practice a slight tilt of reference wave often occurs, and this tilt will introduce unexpected errors of the reconstructed object wave-front. Usually the least-square method with iterations, which is time consuming, is employed to analyze the phase errors caused by the tilt of reference wave. Here a simple effective algorithm is suggested to detect and then correct this kind of errors. In this method, only some simple mathematic operation is used, avoiding using least-square equations as needed in most methods reported before. It can be used for generalized phase-shifting interferometry with two or more frames for both smooth and diffusing objects, and the excellent performance has been verified by computer simulations. The numerical simulations show that the wave reconstruction errors can be reduced by 2 orders of magnitude.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, R.F. Jr.

1994-12-13

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current. 6 figures.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, Jr., Robert F.

1994-01-01

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Spin-wave energy dispersion of a frustrated spin-½ Heisenberg antiferromagnet on a stacked square lattice.

PubMed

Majumdar, Kingshuk

2011-03-23

The effects of interlayer coupling and spatial anisotropy on the spin-wave excitation spectra of a three-dimensional spatially anisotropic, frustrated spin-½ Heisenberg antiferromagnet (HAFM) are investigated for the two ordered phases using second-order spin-wave expansion. We show that the second-order corrections to the spin-wave energies are significant and find that the energy spectra of the three-dimensional HAFM have similar qualitative features to the energy spectra of the two-dimensional HAFM on a square lattice. We also discuss the features that can provide experimental measures for the strength of the interlayer coupling, spatial anisotropy parameter, and magnetic frustration.

Location of acoustic radiators and inversion for energy density using radio-frequency sources and thunder recordings

NASA Astrophysics Data System (ADS)

Anderson, J.; Johnson, J. B.; Arechiga, R. O.; Edens, H. E.; Thomas, R. J.

2011-12-01

We use radio frequency (VHF) pulse locations mapped with the New Mexico Tech Lightning Mapping Array (LMA) to study the distribution of thunder sources in lightning channels. A least squares inversion is used to fit channel acoustic energy radiation with broadband (0.01 to 500 Hz) acoustic recordings using microphones deployed local (< 10 km) to the lightning. We model the thunder (acoustic) source as a superposition of line segments connecting the LMA VHF pulses. An optimum branching algorithm is used to reconstruct conductive channels delineated by VHF sources, which we discretize as a superposition of finely-spaced (0.25 m) acoustic point sources. We consider total radiated thunder as a weighted superposition of acoustic waves from individual channels, each with a constant current along its length that is presumed to be proportional to acoustic energy density radiated per unit length. Merged channels are considered as a linear sum of current-carrying branches and radiate proportionally greater acoustic energy. Synthetic energy time series for a given microphone location are calculated for each independent channel. We then use a non-negative least squares inversion to solve for channel energy densities to match the energy time series determined from broadband acoustic recordings across a 4-station microphone network. Events analyzed by this method have so far included 300-1000 VHF sources, and correlations as high as 0.5 between synthetic and recorded thunder energy were obtained, despite the presence of wind noise and 10-30 m uncertainty in VHF source locations.

Fish-Eye Observing with Phased Array Radio Telescopes

NASA Astrophysics Data System (ADS)

Wijnholds, S. J.

The radio astronomical community is currently developing and building several new radio telescopes based on phased array technology. These telescopes provide a large field-of-view, that may in principle span a full hemisphere. This makes calibration and imaging very challenging tasks due to the complex source structures and direction dependent radio wave propagation effects. In this thesis, calibration and imaging methods are developed based on least squares estimation of instrument and source parameters. Monte Carlo simulations and actual observations with several prototype show that this model based approach provides statistically and computationally efficient solutions. The error analysis provides a rigorous mathematical framework to assess the imaging performance of current and future radio telescopes in terms of the effective noise, which is the combined effect of propagated calibration errors, noise in the data and source confusion.

Exact ghost-free bigravitational waves

NASA Astrophysics Data System (ADS)

Ayón-Beato, Eloy; Higuita-Borja, Daniel; Méndez-Zavaleta, Julio A.; Velázquez-Rodríguez, Gerardo

2018-04-01

We study the propagation of exact gravitational waves in the ghost-free bimetric theory. Our focus is on type-N spacetimes compatible with the cosmological constants provided by the bigravity interaction potential, and particularly in the single class known by allowing at least a Killing symmetry: the AdS waves. They have the advantage of being represented by a generalized Kerr-Schild transformation from AdS spacetime. This entails a notorious simplification in bigravity by allowing to straightforwardly compute any power of its interaction square root matrix, opening the door to explore physically meaningful exact configurations. For these exact gravitational waves the complex dynamical structure of bigravity decomposes into elementary exact massless or massive excitations propagating on AdS. We use a complexified formulation of the Euler-Darboux equations to provide for the first time the general solutions to the massive version of the Siklos equation which rules the resulting AdS-wave dynamics, using an integral representation originally due to Poisson. Inspired by this progress, we tackle the subtle problem of how matter couples to bigravity and, more concretely, if this occurs through a composite metric, which is hard to handle in a general setting. Surprisingly, the Kerr-Schild ansatz brings again a huge simplification in how the related energy-momentum tensors are calculated. This allows us to explicitly characterize AdS waves supported by either a massless free scalar field or a wavefront-homogeneous Maxwell field. Considering the most general allowed Maxwell source instead is a highly nontrivial task, which we accomplish by again exploiting the complexified Euler-Darboux description and taking advantage of the classical Riemann method. In fact, this eventually allows us to find the most general configurations for any matter source.

All Sky Search for Gravitational-Wave Bursts in the Second Joint LIGO-Virgo Run

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.;

LANDSAT-D investigations in snow hydrology

NASA Technical Reports Server (NTRS)

Dozier, J. (Principal Investigator)

1982-01-01

The sample LANDSAT-4 TM tape (7 bands) of NE Arkansas/Tennessee area was received and displayed. Snow reflectance in all 6 TM reflective bands, i.e. 1, 2, 3, 4, 5, and 7 was simulated, using Wiscombe and Warren's (1980) delta-Eddington model. Snow reflectance in bands 4, 5, and 7 appear sensitive to grain size. One of the objectives is to interpret surface optical grain size of snow, for spectral extension of albedo. While TM data of the study area are not received, simulation results are encouraging. It also appears that the TM filters resemble a "square-wave" closely enough to permit assuming a square-wave in calculations. Integrated band reflectance over the actual response functions was simulated, using sensor data supplied by Santa Barbara Research Center. Differences between integrating over the actual response functions and the equivalent square wave were negligible.

Design and performance of heart assist or artificial heart control systems

NASA Technical Reports Server (NTRS)

Webb, J. A., Jr.; Gebben, V. D.

1978-01-01

The factors leading to the design of a controlled driving system for either a heart assist pump or artificial heart are discussed. The system provides square pressure waveform to drive a pneumatic-type blood pump. For assist usage the system uses an R-wave detector circuit that can detect the R-wave of the electrocardiogram in the presence of electrical disturbances. This circuit provides a signal useful for synchronizing an assist pump with the natural heart. It synchronizes a square wave circuit, the output of which is converted into square waveforms of pneumatic pressure suitable for driving both assist device and artificial heart. The pressure levels of the driving waveforms are controlled by means of feedback channels to maintain physiological regulation of the artificial heart's output flow. A more compact system that could achieve similar regulatory characteristics is also discussed.

Ultrashort high-brightness pulses from storage rings

NASA Astrophysics Data System (ADS)

Khan, Shaukat

2017-09-01

The brightness of short-wavelength radiation from accelerator-based sources can be increased by coherent emission in which the radiation intensity scales with the number of contributing electrons squared. This requires a microbunched longitudinal electron distribution, which is the case in free-electron lasers. The brightness of light sources based on electron storage rings was steadily improved, but could profit further from coherent emission. The modulation of the electron energy by a continuous-wave laser field may provide steady-state microbunching in the infrared regime. For shorter wavelengths, the energy modulation can be converted into a temporary density modulation by a dispersive chicane. One particular goal is coherent emission from a very short "slice" within an electron bunch in order to produce ultrashort radiation pulses with high brightness.

Radiative transfer theory for a random distribution of low velocity spheres as resonant isotropic scatterers

NASA Astrophysics Data System (ADS)

Sato, Haruo; Hayakawa, Toshihiko

2014-10-01

Short-period seismograms of earthquakes are complex especially beneath volcanoes, where the S wave mean free path is short and low velocity bodies composed of melt or fluid are expected in addition to random velocity inhomogeneities as scattering sources. Resonant scattering inherent in a low velocity body shows trap and release of waves with a delay time. Focusing of the delay time phenomenon, we have to consider seriously multiple resonant scattering processes. Since wave phases are complex in such a scattering medium, the radiative transfer theory has been often used to synthesize the variation of mean square (MS) amplitude of waves; however, resonant scattering has not been well adopted in the conventional radiative transfer theory. Here, as a simple mathematical model, we study the sequence of isotropic resonant scattering of a scalar wavelet by low velocity spheres at low frequencies, where the inside velocity is supposed to be low enough. We first derive the total scattering cross-section per time for each order of scattering as the convolution kernel representing the decaying scattering response. Then, for a random and uniform distribution of such identical resonant isotropic scatterers, we build the propagator of the MS amplitude by using causality, a geometrical spreading factor and the scattering loss. Using those propagators and convolution kernels, we formulate the radiative transfer equation for a spherically impulsive radiation from a point source. The synthesized MS amplitude time trace shows a dip just after the direct arrival and a delayed swelling, and then a decaying tail at large lapse times. The delayed swelling is a prominent effect of resonant scattering. The space distribution of synthesized MS amplitude shows a swelling near the source region in space, and it becomes a bell shape like a diffusion solution at large lapse times.

Time-domain least-squares migration using the Gaussian beam summation method

NASA Astrophysics Data System (ADS)

Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo

2018-04-01

With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modeling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modeling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a preconditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.

Time-domain least-squares migration using the Gaussian beam summation method

NASA Astrophysics Data System (ADS)

Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo

2018-07-01

With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modelling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modelling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a pre-conditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.

Performance of various branch-point tolerant phase reconstructors with finite time delays and measurement noise

NASA Astrophysics Data System (ADS)

Zetterlind, Virgil E., III; Magee, Eric P.

2002-06-01

This study extends branch point tolerant phase reconstructor research to examine the effect of finite time delays and measurement error on system performance. Branch point tolerant phase reconstruction is particularly applicable to atmospheric laser weapon and communication systems, which operate in extended turbulence. We examine the relative performance of a least squares reconstructor, least squares plus hidden phase reconstructor, and a Goldstein branch point reconstructor for various correction time-delays and measurement noise scenarios. Performance is evaluated using a wave-optics simulation that models a 100km atmospheric propagation of a point source beacon to a transmit/receive aperture. Phase-only corrections are then calculated using the various reconstructor algorithms and applied to an outgoing uniform field. Point Strehl is used as the performance metric. Results indicate that while time delays and measurement noise reduce the performance of branch point tolerant reconstructors, these reconstructors can still outperform least squares implementations in many cases. We also show that branch point detection becomes the limiting factor in measurement noise corrupted scenarios.

Effects of Different Waveforms on the Performance of Active Capillary Dielectric Barrier Discharge Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Dumlao, Morphy C.; Xiao, Dan; Zhang, Daming; Fletcher, John; Donald, William A.

2017-04-01

Active capillary dielectric barrier discharge ionization (DBDI) is emerging as a compact, low-cost, and robust method to form intact ions of small molecules for detection in near real time by portable mass spectrometers. Here, we demonstrate that by using a 10 kHz, 2.5 kVp-p high-voltage square-wave alternating current plasma, active capillary DBDI can consume less than 1 μW of power. In contrast, the power consumed using a sine and triangle alternating current waveform is more than two orders of magnitude higher than that for the square waveform to obtain a similar voltage for plasma generation. Moreover, the plasma obtained using a square waveform can be significantly more homogenous than that obtained using sine and triangle waveforms. Protonated dimethyl methylphosphonate (DMMP) and deprotonated perfluorooctanoic acid (PFOA) can be detected at about the same or higher abundances using square-wave DBDI mass spectrometry compared with the use of sine and triangle waveforms. By use of benzylammonium thermometer ions, the extent of internal energy deposition using square, sine, or triangle waveform excited plasmas are essentially the same at the optimum voltages for ion detection. Using an H-bridge circuit driving a transformer optimized to reduce losses, square-wave active capillary DBDI can be continuously powered for 50 h by common 9 V-battery (PP3).

A Case Study of Array-based Early Warning System for Tsunami Offshore Ventura, California

NASA Astrophysics Data System (ADS)

Xie, Y.; Meng, L.

2017-12-01

Extreme scenarios of M 7.5+ earthquakes on the Red Mountain and Pitas Point faults can potentially generate significant local tsunamis in southern California. The maximum water elevation could be as large as 10 m in the nearshore region of Oxnard and Santa Barbara. Recent development in seismic array processing enables rapid tsunami prediction and early warning based on the back-projection approach (BP). The idea is to estimate the rupture size by back-tracing the seismic body waves recorded by stations at local and regional distances. A simplified source model of uniform slip is constructed and used as an input for tsunami simulations that predict the tsunami wave height and arrival time. We demonstrate the feasibility of this approach in southern California by implementing it in a simulated real-time environment and applying to a hypothetical M 7.7 Dip-slip earthquake scenario on the Pitas Point fault. Synthetic seismograms are produced using the SCEC broadband platform based on the 3D SoCal community velocity model. We use S-wave instead of P-wave to avoid S-minus-P travel times shorter than rupture duration. Two clusters of strong-motion stations near Bakersfield and Palmdale are selected to determine the back-azimuth of the strongest high-frequency radiations (0.5-1 Hz). The back-azimuths of the two clusters are then intersected to locate the source positions. The rupture area is then approximated by enclosing these BP radiators with an ellipse or a polygon. Our preliminary results show that the extent of 1294 square kilometers rupture area and magnitude of 7.6 obtained by this approach is reasonably close to the 1849 square kilometers and 7.7 of the input model. The average slip of 7.3 m is then estimated according to the scaling relation between slip and rupture area, which is close to the actual average dislocation amount, 8.3 m. Finally, a tsunami simulation is conducted to assess the wave height and arrival time. The errors of -3 to +9 s in arrival time and 0.4 m in wave amplitude are reasonably small for early warning purpose. The blind zone for early warning is the region north of the outcrop of Pitas Point faults and has a scale close to the length of the fault, 43 km. The warning time is above 15 min in the nearshore region west of Cojo Bay Beach and south of Oxnard.

Ultrahigh energy neutrino afterglows of nearby long duration gamma-ray bursts

NASA Astrophysics Data System (ADS)

Thomas, Jessymol K.; Moharana, Reetanjali; Razzaque, Soebur

2017-11-01

Detection of ultrahigh energy (UHE, ≳1 PeV ) neutrinos from astrophysical sources will be a major advancement in identifying and understanding the sources of UHE cosmic rays (CRs) in nature. Long duration gamma-ray burst (GRB) blast waves have been considered as potential acceleration sites of UHECRs. These CRs are expected to interact with GRB afterglow photons, which are synchrotron radiation from relativistic electrons coaccelerated with CRs in the blast wave, and naturally produce UHE neutrinos. Fluxes of these neutrinos are uncertain, however, and crucially depend on the observed afterglow modeling. We have selected a sample of 23 long duration GRBs within redshift 0.5 for which adequate electromagnetic afterglow data are available and which could produce high flux of UHE afterglow neutrinos, being nearby. We fit optical, x-ray, and γ -ray afterglow data with an adiabatic blast wave model in a constant density interstellar medium and in a wind environment where the density of the wind decreases as the inverse square of the radius from the center of the GRB. The blast wave model parameters extracted from these fits are then used for calculating UHECR acceleration and p γ interactions to produce UHE neutrino fluxes from these GRBs. We have also explored the detectability of these neutrinos by currently running and upcoming large area neutrino detectors, such as the Pierre Auger Observatory, IceCube Gen-2, and KM3NeT observatories. We find that our realistic flux models from nearby GRBs will be unconstrained in the foreseeable future.

Optical frequency comb generation based on the dual-mode square microlaser and a nonlinear fiber loop

NASA Astrophysics Data System (ADS)

Weng, Hai-Zhong; Han, Jun-Yuan; Li, Qing; Yang, Yue-De; Xiao, Jin-Long; Qin, Guan-Shi; Huang, Yong-Zhen

2018-05-01

A novel approach using a dual-mode square microlaser as the pump source is demonstrated to produce wideband optical frequency comb (OFC). The enhanced nonlinear frequency conversion processes are accomplished in a nonlinear fiber loop, which can reduce the stimulated Brillouin scattering threshold and then generate a dual-mode Brillouin laser with improved optical signal-to-noise ratio. An OFC with 130 nm bandwidth and 76 GHz repetition rate is successfully generated under the four-wave mixing, and the number of the comb lines is enhanced by 26 times compared with the system without fiber loop. In addition, the repetition rate of the comb can be adjusted by changing the injection current of the microlaser. The pulse width of the comb spectrum is also compressed from 3 to 1 ps with an extra amplification-nonlinear process.

Optical NOR logic gate design on square lattice photonic crystal platform

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

D’souza, Nirmala Maria, E-mail: nirmala@cukerala.ac.in; Mathew, Vincent, E-mail: vincent@cukerala.ac.in

We numerically demonstrate a new configuration of all-optical NOR logic gate with square lattice photonic crystal (PhC) waveguide using finite difference time domain (FDTD) method. The logic operations are based on interference effect of optical waves. We have determined the operating frequency range by calculating the band structure for a perfectly periodic PhC using plane wave expansion (PWE) method. Response time of this logic gate is 1.98 ps and it can be operated with speed about 513 GB/s. The proposed device consists of four linear waveguides and a square ring resonator waveguides on PhC platform.

A second-order all-digital phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Tegnelia, C. R.

1974-01-01

A simple second-order digital phase-locked loop has been designed to synchronize itself to a square-wave subcarrier. Analysis and experimental performance are given for both acquisition behavior and steady-state phase error performance. In addition, the damping factor and the noise bandwidth are derived analytically. Although all the data are given for the square-wave subcarrier case, the results are applicable to arbitrary subcarriers that are odd symmetric about their transition region.

Multiple soliton production and the Korteweg-de Vries equation.

NASA Technical Reports Server (NTRS)

Hershkowitz, N.; Romesser, T.; Montgomery, D.

1972-01-01

Compressive square-wave pulses are launched in a double-plasma device. Their evolution is interpreted according to the Korteweg-de Vries description of Washimi and Taniuti. Square-wave pulses are an excitation for which an explicit solution of the Schrodinger equation permits an analytical prediction of the number and amplitude of emergent solitons. Bursts of energetic particles (pseudowaves) appear above excitation voltages greater than an electron thermal energy, and may be mistaken for solitons.

Pulse dynamics of dual-wavelength dissipative soliton resonances and domain wall solitons in a Tm fiber laser with fiber-based Lyot filter.

PubMed

Wang, Pan; Zhao, Kangjun; Xiao, Xiaosheng; Yang, Changxi

2017-11-27

We report on the first demonstration of dual-wavelength square-wave pulses in a thulium-doped fiber laser. Under appropriate cavity parameters, dual-wavelength dissipative soliton resonances (DSRs) and domain wall solitons (DWSs) are successively obtained. Meanwhile, dark pulses generation is achieved at the dual-wavelength DWSs region due to the overlap of the two domain wall pulses. The fiber-based Lyot filter, conducted by inserting PMF between an in-line PBS and a PD-ISO, facilitates the generation of dual-wavelength operation. The polarization-resolved investigation suggests that the cross coupling between two orthogonal polarization components in the high nonlinear fiber plays an important role in the square-wave pulses formation. The investigation may be helpful for further understanding the square-wave pulse formation and has potential in application filed of multi-wavelength pulsed fiber lasers.

Determination of genotoxic effects of methidathion alkaline hydrolysis in human lymphocytes using the micronucleus assay and square-wave voltammetry.

PubMed

Stivaktakis, Polychronis D; Giannakopoulos, Evangelos; Vlastos, Dimitris; Matthopoulos, Demetrios P

2017-02-01

The interaction of pesticides with environmental factors, such as pH, may result in alterations of their physicochemical properties and should be taken into consideration in regard to their classification. This study investigates the genotoxicity of methidathion and its alkaline hydrolysis by-products in cultured human lymphocytes, using the square-wave voltammetry (square wave-adsorptive cathodic stripping voltammetry (SW-AdCSV) technique) and the cytokinesis block micronucleus assay (CBMN assay). According to the SW-AdCSV data the alkaline hydrolysis of methidathion results in two new molecules, one non-electro-active and a second electro-active which is more genotoxic than methidathion itself in cultured human lymphocytes, inducing higher micronuclei frequencies. The present study confirms the SW-AdCSV technique as a voltammetric method which can successfully simulates the electrodynamics of the cellular membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

Feasibility of Wave Energy in Hong Kong

NASA Astrophysics Data System (ADS)

Lu, M.; Hodgson, P.

2014-12-01

Kinetic energy produced by the movement of ocean waves can be harnessed by wave energy converter equipment such as wave turbines to power onshore electricity generators, creating a valuable source of renewable energy. This experiment measures the potential of wave energy in Hoi Ha Wan Marine Park, Hong Kong using a data buoy programmed to send data through wireless internet every five minutes. Wave power (known as 'wave energy flux') is proportional to wave energy periodicity and to the square of wave height, and can be calculated using the equation: P = 0.5 kW/(m3)(s) x Hs2 x Tp P = wave energy flux (wave energy per unit of wave crest length in kW/m) Hs = significant wave height (m) Tp = wave period (seconds) Acoustic Doppler Current Profilers (ADCPs), or ultrasonic sensors, were installed on the seabed at three monitoring locations to measure Significant Wave Heights (Hs), Significant Wave Periods (Tp) and Significant Wave Direction (Wd). Over a twelve month monitoring period, Significant Wave Heights ranged from 0 ~ 8.63m. Yearly averages were 1.051m. Significant Wave Period ranged from 0 ~ 14.9s. Yearly averages were 6.846s. The maximum wave energy amount recorded was 487.824 kW/m. These results implied that electricity sufficient to power a small marine research center could be supplied by a generator running at 30% efficiency or greater. A wave piston driven generator prototype was designed that could meet output objectives without using complex hydraulics, expensive mechanical linkages, or heavy floating buoys that might have an adverse impact on marine life. The result was a design comprising a water piston connected by an air pipe to a rotary turbine powered generator. A specially designed air valve allowed oscillating bidirectional airflow generated in the piston to be converted into unidirectional flow through the turbine, minimizing kinetic energy loss. A 35cm wave with a one second period could generate 139.430W of electricity, with an efficiency of 37.6%.

Generalized thermoelastic wave band gaps in phononic crystals without energy dissipation

NASA Astrophysics Data System (ADS)

Wu, Ying; Yu, Kaiping; Li, Xiao; Zhou, Haotian

2016-01-01

We present a theoretical investigation of the thermoelastic wave propagation in the phononic crystals in the context of Green-Nagdhi theory by taking thermoelastic coupling into account. The thermal field is assumed to be steady. Thermoelastic wave band structures of 3D and 2D are derived by using the plane wave expansion method. For the 2D problem, the anti-plane shear mode is not affected by the temperature difference. Thermoelastic wave bands of the in-plane x-y mode are calculated for lead/silicone rubber, aluminium/silicone rubber, and aurum/silicone rubber phononic crystals. The new findings in the numerical results indicate that the thermoelastic wave bands are composed of the pure elastic wave bands and the thermal wave bands, and that the thermal wave bands can serve as the low boundary of the first band gap when the filling ratio is low. In addition, for the lead/silicone rubber phononic crystals the effects of lattice type (square, rectangle, regular triangle, and hexagon) and inclusion shape (circle, oval, and square) on the normalized thermoelastic bandwidth and the upper/lower gap boundaries are analysed and discussed. It is concluded that their effects on the thermoelastic wave band structure are remarkable.

The Hunt for a Counterpart to GW150914

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-07-01

On 14 September 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) in a pre-operative testing state at the time detected its first sign of gravitational-waves. The LIGO team sprang into action, performing data-quality checks on this unexpected signal. Within two days, they had sent a notification to 63 observing teams at observatories representing the entire electromagnetic spectrum, from radio to gamma-ray wavelengths.Illustration of a binary neutron star merger. The neutron stars 1) inspiral, 2) can produce a short gamma-ray burst, 3) can fling out hot, radioactive material in the form of a kilonova, and 4) form a massive neutron star or black hole with a possible remnant debris disk around it. [NASA/ESA/A. Feild (STScI)]Thus began the very first hunt for an electromagnetic counterpart to a detected gravitational wave signal.What were they looking for?As two compact objects in a binary system merge, the system is expected to emit energy in the form of gravitational waves. If both of the compact objects are black holes, were unlikely to see any electromagnetic radiation in the process, unless the merger is occurring in an (improbable) environment filled with gas and dust.But if one or both of the two compact objects is a neutron star, then there are a number of electromagnetic signatures that could occur due to energetic outflows. If a relativistic jet forms, we could see a short gamma-ray burst and X-ray, optical, and radio afterglows. Sub-relativistic outflows could produce optical and near-infrared signals, or a radio blast wave.Timeline of observations of GW150914, separated by wavelength band, and relative to the time of the gravitational-wave trigger. The top row shows LIGO information releases. The bottom four rows show high-energy, optical, near-infrared, and radio observations, respectively. Click for a closer look! [Abbott et al. 2016]Surprise SignalSince LIGO and Virgo (LIGOs European counterpart), wereprimarily expecting to detect binaries involving neutron stars, they set up a notification system to be able to quickly alert electromagnetic observatories of a gravitational-wave detection. Those observatories would then be able to follow up on the gravitational-wave detectorsrough localization, with the goal of detecting the source by its electromagnetic signature.Given that LIGO had only just come online for testing when GW150914 was detected, its impressive that the pipeline was ready and there were observatories able to follow up so quickly! When the alert went out, 25 teams responded, mobilizing satellites and ground-based telescopes spanning 19 orders of magnitude in electromagnetic wavelength.The Search PartyThe only information the teams were initially given was the localization of the signal to roughly 600 square degrees on the sky. With this starting point, over the next three months, these 25 facilities carefully observed the entirety of the estimated localization area.Footprints of observations in comparison with the initial LIGO localization of GW150914 (black contours). Shown are radio fields (red), optical/infrared fields (green), and X-ray fields (blue circles); not shown are the all-sky Fermi GBM, LAT, INTEGRAL SPI-ACS, and MAXI observations. [Abbott et al. 2016]Some high-energy observatories, like Fermi and INTEGRAL, covered the whole sky. Many optical facilities used a tiling strategy, together covering about 900 square degrees. Still other observatories used a targeted approach, specifically looking at fields that contained a high density of nearby galaxies, in the hopes of detecting signs of a neutron-star merger or a core-collapse supernova.For the transient sources that were found, follow-up spectroscopy and further photometry was performed, to determine if the transient could have been the source of the detected gravitational waves.What Was the Outcome?No electromagnetic counterpart to GW150914 was found. It turns out this isnt surprising; GW150914 was later determined to have been the merger of two black holes, which should not generate an electromagnetic signature.So why report on this? In the publication prepared jointly by LIGO, Virgo, and these 25 teams (with one of the longer author lists youre likely to encounter!), the authors emphasize not the conclusion, but the process leading to it.In spite of the fact that LIGO had not yet even begun its first observing run, the alert system worked, and the community mobilized to cover the entire 600 square degrees of sky with observations and follow-up characterization of candidate sources. If all this can be accomplished for an unexpected signal, imagine how well the system will work for future detections during actual science runs! With any luck, well be identifying the electromagnetic counterparts to gravitational-wave sources soon.CitationB. P. Abbott et al 2016 ApJ 826 L13. doi:10.3847/2041-8205/826/1/L13

Synthesis and evaluation of phase detectors for active bit synchronizers

NASA Technical Reports Server (NTRS)

Mcbride, A. L.

1974-01-01

Self-synchronizing digital data communication systems usually use active or phase-locked loop (PLL) bit synchronizers. The three main elements of PLL synchronizers are the phase detector, loop filter, and the voltage controlled oscillator. Of these three elements, phase detector synthesis is the main source of difficulty, particularly when the received signals are demodulated square-wave signals. A phase detector synthesis technique is reviewed that provides a physically realizable design for bit synchronizer phase detectors. The development is based upon nonlinear recursive estimation methods. The phase detector portion of the algorithm is isolated and analyzed.

Plasma-anode electron gun

NASA Astrophysics Data System (ADS)

Santoru, Joseph; Schumacher, Robert W.; Gregoire, Daniel J.

1994-11-01

The plasma-anode electron gun (PAG) is an electron source in which the thermionic cathode is replaced with a cold, secondary-electron-emitting electrode. Electron emission is stimulated by bombarding the cathode with high-energy ions. Ions are injected into the high-voltage gap through a gridded structure from a plasma source (gas pressure less than or equal to 50 mTorr) that is embedded in the anode electrode. The gridded structure serves as both a cathode for the plasma discharge and as an anode for the PAG. The beam current is modulated at near ground potential by modulating the plasma source, eliminating the need for a high-voltage modulator system. During laboratory tests, the PAG has demonstrated square-wave, 17-microsecond-long beam pulses at 100 kV and 10 A, and it has operated stably at 70 kV and 2.5 A for 210 microsecond pulse lengths without gap closure.

Quantitative sonoelastography for the in vivo assessment of skeletal muscle viscoelasticity

NASA Astrophysics Data System (ADS)

Hoyt, Kenneth; Kneezel, Timothy; Castaneda, Benjamin; Parker, Kevin J.

2008-08-01

A novel quantitative sonoelastography technique for assessing the viscoelastic properties of skeletal muscle tissue was developed. Slowly propagating shear wave interference patterns (termed crawling waves) were generated using a two-source configuration vibrating normal to the surface. Theoretical models predict crawling wave displacement fields, which were validated through phantom studies. In experiments, a viscoelastic model was fit to dispersive shear wave speed sonoelastographic data using nonlinear least-squares techniques to determine frequency-independent shear modulus and viscosity estimates. Shear modulus estimates derived using the viscoelastic model were in agreement with that obtained by mechanical testing on phantom samples. Preliminary sonoelastographic data acquired in healthy human skeletal muscles confirm that high-quality quantitative elasticity data can be acquired in vivo. Studies on relaxed muscle indicate discernible differences in both shear modulus and viscosity estimates between different skeletal muscle groups. Investigations into the dynamic viscoelastic properties of (healthy) human skeletal muscles revealed that voluntarily contracted muscles exhibit considerable increases in both shear modulus and viscosity estimates as compared to the relaxed state. Overall, preliminary results are encouraging and quantitative sonoelastography may prove clinically feasible for in vivo characterization of the dynamic viscoelastic properties of human skeletal muscle.

Measurement of attenuation coefficients of the fundamental and second harmonic waves in water

NASA Astrophysics Data System (ADS)

Zhang, Shuzeng; Jeong, Hyunjo; Cho, Sungjong; Li, Xiongbing

2016-02-01

Attenuation corrections in nonlinear acoustics play an important role in the study of nonlinear fluids, biomedical imaging, or solid material characterization. The measurement of attenuation coefficients in a nonlinear regime is not easy because they depend on the source pressure and requires accurate diffraction corrections. In this work, the attenuation coefficients of the fundamental and second harmonic waves which come from the absorption of water are measured in nonlinear ultrasonic experiments. Based on the quasilinear theory of the KZK equation, the nonlinear sound field equations are derived and the diffraction correction terms are extracted. The measured sound pressure amplitudes are adjusted first for diffraction corrections in order to reduce the impact on the measurement of attenuation coefficients from diffractions. The attenuation coefficients of the fundamental and second harmonics are calculated precisely from a nonlinear least squares curve-fitting process of the experiment data. The results show that attenuation coefficients in a nonlinear condition depend on both frequency and source pressure, which are much different from a linear regime. In a relatively lower drive pressure, the attenuation coefficients increase linearly with frequency. However, they present the characteristic of nonlinear growth in a high drive pressure. As the diffraction corrections are obtained based on the quasilinear theory, it is important to use an appropriate source pressure for accurate attenuation measurements.

Reproducibility of blood oxygen level-dependent signal changes with end-tidal carbon dioxide alterations.

PubMed

Dengel, Donald R; Evanoff, Nicholas G; Marlatt, Kara L; Geijer, Justin R; Mueller, Bryon A; Lim, Kelvin O

2017-11-01

Hypercapnia has been utilized as a stimulus to elicit changes in cerebral blood flow (CBF). However, in many instances it has been delivered in a non-controlled method that is often difficult to reproduce. The purpose of this study was to examine the within- and between-visit reproducibility of blood oxygen level-dependent (BOLD) signal changes to an iso-oxic square wave alteration in end-tidal carbon dioxide partial pressure (P et CO 2 ). Two 3-Tesla (3T) MRI scans were performed on the same visit, with two square wave alterations administered per scan. The protocol was repeated on a separate visit with minimum of 3 days between scanning sessions. P et CO 2 was altered to stimulate changes in cerebral vascular reactivity (CVR), while P et O 2 was held constant. Eleven subjects (six females; mean age 26·5 ± 5·7 years) completed the full testing protocol. Excellent within-visit square wave reproducibility (ICC > 0·75) was observed. Similarly, square waves were reproducible between scanning sessions (ICC > 0·7). This study demonstrates BOLD signal changes in response to alterations in P et CO 2 are reproducible both within- and between-visit MRI scans. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa.

PubMed

Phillipou, Andrea; Rossell, Susan Lee; Castle, David Jonathan; Gurvich, Caroline; Abel, Larry Allen

2014-12-02

The factors contributing to the cause and maintenance of anorexia nervosa (AN) are poorly understood, though increasing interest surrounds the neurobiological underpinnings of the condition. The examination of saccadic eye movements has proven useful in our understanding of the neurobiology of some other psychiatric illnesses, as they utilize identifiable brain circuits. Square wave jerks (SWJs), which describe an involuntary saccade away and back to fixation, have been observed to occur at abnormally high rates in neurodegenerative disorders and some psychiatric illnesses, but have not been examined in AN. Therefore, the aim of this study was to investigate whether individuals with AN and healthy control (HC) individuals differ in SWJ rate during attempted fixation. Square wave jerk frequency was compared across 23 female participants with AN and 22 HC participants matched for age, sex, and premorbid intelligence. Anorexia nervosa participants were found to make SWJs at a significantly higher rate than HC participants. The rate of SWJs in AN was also found to negatively correlate with anxiety. Square wave jerk rate and anxiety were found to correctly classify groups, with an accuracy of 87% for AN participants and 95.5% for HCs. Given our current understanding of saccadic eye movements, the findings suggest a potential role of γ-aminobutyric acid (GABA) in the superior colliculus, frontal eye fields, or posterior parietal cortex in the psychopathology of AN. © ARVO.

Noninvasive hemoglobin measurement using dynamic spectrum

NASA Astrophysics Data System (ADS)

Yi, Xiaoqing; Li, Gang; Lin, Ling

2017-08-01

Spectroscopy methods for noninvasive hemoglobin (Hgb) measurement are interfered by individual difference and particular weak signal. In order to address these problems, we have put forward a series of improvement methods based on dynamic spectrum (DS), including instrument design, spectrum extraction algorithm, and modeling approach. The instrument adopts light sources composed of eight laser diodes with the wavelength range from 600 nm to 1100 nm and records photoplethysmography signals at eight wavelengths synchronously. In order to simplify the optical design, we modulate the light sources with orthogonal square waves and design the corresponding demodulation algorithm, instead of adopting a beam-splitting system. A newly designed algorithm named difference accumulation has been proved to be effective in improving the accuracy of dynamic spectrum extraction. 220 subjects are involved in the clinical experiment. An extreme learning machine calibration model between the DS data and the Hgb levels is established. Correlation coefficient and root-mean-square error of prediction sets are 0.8645 and 8.48 g/l, respectively. The results indicate that the Hgb level can be derived by this approach noninvasively with acceptable precision and accuracy. It is expected to achieve a clinic application in the future.

Experimental Evaluation of the High-Speed Motion Vector Measurement by Combining Synthetic Aperture Array Processing with Constrained Least Square Method

NASA Astrophysics Data System (ADS)

Yokoyama, Ryouta; Yagi, Shin-ichi; Tamura, Kiyoshi; Sato, Masakazu

2009-07-01

Ultrahigh speed dynamic elastography has promising potential capabilities in applying clinical diagnosis and therapy of living soft tissues. In order to realize the ultrahigh speed motion tracking at speeds of over thousand frames per second, synthetic aperture (SA) array signal processing technology must be introduced. Furthermore, the overall system performance should overcome the fine quantitative evaluation in accuracy and variance of echo phase changes distributed across a tissue medium. On spatial evaluation of local phase changes caused by pulsed excitation on a tissue phantom, investigation was made with the proposed SA signal system utilizing different virtual point sources that were generated by an array transducer to probe each component of local tissue displacement vectors. The final results derived from the cross-correlation method (CCM) brought about almost the same performance as obtained by the constrained least square method (LSM) extended to successive echo frames. These frames were reconstructed by SA processing after the real-time acquisition triggered by the pulsed irradiation from a point source. The continuous behavior of spatial motion vectors demonstrated the dynamic generation and traveling of the pulsed shear wave at a speed of one thousand frames per second.

Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.

Functional significance of the pattern of renal sympathetic nerve activation.

PubMed

Dibona, G F; Sawin, L L

1999-08-01

To assess the renal functional significance of the pattern of renal sympathetic nerve activation, computer-generated stimulus patterns (delivered at constant integrated voltage) were applied to the decentralized renal sympathetic nerve bundle and renal hemodynamic and excretory responses determined in anesthetized rats. When delivered at the same integrated voltage, stimulus patterns resembling those observed in in vivo multifiber recordings of renal sympathetic nerve activity (diamond-wave patterns) produced greater renal vasoconstrictor responses than conventional square-wave patterns. Within diamond-wave patterns, increasing integrated voltage by increasing amplitude produced twofold greater renal vasoconstrictor responses than by increasing duration. With similar integrated voltages that were subthreshold for renal vasoconstriction, neither diamond- nor square-wave pattern altered glomerular filtration rate, whereas diamond- but not square-wave pattern reversibly decreased urinary sodium excretion by 25 +/- 3%. At the same number of pulses per second, intermittent stimulation produced faster and greater renal vasoconstriction than continuous stimulation. At the same number of pulses per second, increases in rest period during intermittent stimulation proportionally augmented the renal vasoconstrictor response compared with that observed with continuous stimulation; the maximum augmentation of 55% occurred at a rest period of 500 ms. These results indicate that the pattern of renal sympathetic nerve stimulation (activity) significantly influences the rapidity, magnitude, and selectivity of the renal vascular and tubular responses.

Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion.

PubMed

Shao, Zhihua; Qiao, Xueguang; Rong, Qiangzhou; Su, Dan

2015-08-01

A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

Deconvolution of squared velocity waveform as applied to the study of a noncoherent short-period radiator in the earthquake source

NASA Astrophysics Data System (ADS)

Gusev, A. A.; Pavlov, V. M.

1991-07-01

We consider an inverse problem of determination of short-period (high-frequency) radiator in an extended earthquake source. This radiator is assumed to be noncoherent (i.e., random), it can be described by its power flux or brightness (which depends on time and location over the extended source). To decide about this radiator we try to use temporal intensity function (TIF) of a seismic waveform at a given receiver point. It is defined as (time-varying) mean elastic wave energy flux through unit area. We suggest estimating it empirically from the velocity seismogram by its squaring and smoothing. We refer to this function as “observed TIF”. We believe that one can represent TIF produced by an extended radiator and recorded at some receiver point in the earth as convolution of the two components: (1) “ideal” intensity function (ITIF) which would be recorded in the ideal nonscattering earth from the same radiator; and (2) intensity function which would be recorded in the real earth from unit point instant radiator (“intensity Green's function”, IGF). This representation enables us to attempt to estimate an ITIF of a large earthquake by inverse filtering or deconvolution of the observed TIF of this event, using the observed TIF of a small event (actually, fore-or aftershock) as the empirical IGF. Therefore, the effect of scattering is “stripped off”. Examples of the application of this procedure to real data are given. We also show that if one can determine far-field ITIF for enough rays, one can extract from them the information on space-time structure of the radiator (that is, of brightness function). We apply this theoretical approach to short-period P-wave records of the 1978 Miyagi-oki earthquake ( M=7.6). Spatial and temporal centroids of a short-period radiator are estimated.

High power broadband millimeter wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1999-05-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed using this technology, and have been deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts to 50 kilowatts. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies other technologies will have to be considered particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

High Power Broadband Millimeter Wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1998-04-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed and deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts CW to 10 kilowatts Peak at W band over a 2 GHz bandwidth. Also a 50 kW peak power and 10 kW average power device at Ka band with 2 GHz bandwidth has been developed. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies, other technologies will have to be considered, particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

Simplified method for the calculation of irregular waves in the coastal zone

NASA Astrophysics Data System (ADS)

Leont'ev, I. O.

2011-04-01

A method applicable for the estimation of the wave parameters along a set bottom profile is suggested. It takes into account the principal processes having an influence on the waves in the coastal zone: the transformation, refraction, bottom friction, and breaking. The ability to use a constant mean value of the friction coefficient under conditions of sandy shores is implied. The wave breaking is interpreted from the viewpoint of the concept of the limiting wave height at a given depth. The mean and root-mean-square wave heights are determined by the height distribution function, which transforms under the effect of the breaking. The verification of the method on the basis of the natural data shows that the calculation results reproduce the observed variations of the wave heights in a wide range of conditions, including profiles with underwater bars. The deviations from the calculated values mostly do not exceed 25%, and the mean square error is 11%. The method does not require a preliminary setting and can be implemented in the form of a relatively simple calculator accessible even for an inexperienced user.

EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM

EPA Science Inventory

A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

A highly accurate analytical solution for the surface fields of a short vertical wire antenna lying on a multilayer ground

NASA Astrophysics Data System (ADS)

Parise, M.

2018-01-01

A highly accurate analytical solution is derived to the electromagnetic problem of a short vertical wire antenna located on a stratified ground. The derivation consists of three steps. First, the integration path of the integrals describing the fields of the dipole is deformed and wrapped around the pole singularities and the two vertical branch cuts of the integrands located in the upper half of the complex plane. This allows to decompose the radiated field into its three contributions, namely the above-surface ground wave, the lateral wave, and the trapped surface waves. Next, the square root terms responsible for the branch cuts are extracted from the integrands of the branch-cut integrals. Finally, the extracted square roots are replaced with their rational representations according to Newton's square root algorithm, and residue theorem is applied to give explicit expressions, in series form, for the fields. The rigorous integration procedure and the convergence of square root algorithm ensure that the obtained formulas converge to the exact solution. Numerical simulations are performed to show the validity and robustness of the developed formulation, as well as its advantages in terms of time cost over standard numerical integration procedures.

Acoustophoretic particle motion in a square glass capillary

NASA Astrophysics Data System (ADS)

Barnkob, Rune; Marin, Alvaro; Rossi, Massimiliano; Kähler, Christian J.

2014-11-01

Acoustofluidics applications often use complex resonator geometries and complex acoustic actuation, which complicates the prediction of the acoustic resonances and the induced forces from the acoustic radiation and the acoustic streaming. Recently, it was shown that simultaneous actuation of two perpendicular half-wave resonances in a square channel can lead to acoustic streaming that will spiral small particles towards the pressure nodal center (Antfolk, Anal. Chem. 84, 2012). This we investigate in details experimentally by examining a square glass capillary with a 400- μm microchannel acoustically actuated around its 2-MHz half-wave transverse resonance. The acoustic actuation leads to the formation of a half-wave resonance in both the vertical and horizontal direction of the microchannel. Due to viscous and dissipative losses both resonances have finite widths, but are shifted in frequency due to asymmetric actuation and fabrication tolerances making the channel not perfectly square. We determine the resonance widths and shift by measuring the 3D3C trajectories of large particles whose motion is fully dominated by acoustic radiation forces, while the induced acoustic streaming is determined by measuring smaller particles weakly influenced by the acoustic radiation force. DFG KA 1808/16-1.

Vibration waveform effects on dynamic stabilization of ablative Rayleigh-Taylor instability

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

Piriz, A. R.; Lucchio, L. Di; Rodriguez Prieto, G.

2011-08-15

An analysis of dynamic stabilization of Rayleigh-Taylor instability in an ablation front is performed by considering a general square wave for modulating the vertical acceleration of the front. Such a kind of modulation allows for clarifying the role of thermal conduction in the mechanism of dynamic stabilization. In addition, the study of the effect of different modulations by varying the duration and amplitude of the square wave in each half-period provides insight on the optimum performance of dynamic stabilization.

Response functions for sine- and square-wave modulations of disparity.

NASA Technical Reports Server (NTRS)

Richards, W.

1972-01-01

Depth sensations cannot be elicited by modulations of disparity that are more rapid than about 6 Hz, regardless of the modulation amplitude. Vergence tracking also fails at similar modulation rates, suggesting that this portion of the oculomotor system is limited by the behavior of disparity detectors. For sinusoidal modulations of disparity between 1/2 to 2 deg of disparity, most depth-response functions exhibit a low-frequency decrease that is not observed with square-wave modulations of disparity.

Cyclic Square Wave Voltammetry of Surface-Confined Quasireversible Electron Transfer Reactions.

PubMed

Mann, Megan A; Bottomley, Lawrence A

2015-09-01

The theory for cyclic square wave voltammetry of surface-confined quasireversible electrode reactions is presented and experimentally verified. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. These criteria were experimentally confirmed using two well-established surface-confined analytes. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

Optimal decay rate for the wave equation on a square with constant damping on a strip

NASA Astrophysics Data System (ADS)

Stahn, Reinhard

2017-04-01

We consider the damped wave equation with Dirichlet boundary conditions on the unit square parametrized by Cartesian coordinates x and y. We assume the damping a to be strictly positive and constant for x<σ and zero for x>σ . We prove the exact t^{-4/3}-decay rate for the energy of classical solutions. Our main result (Theorem 1) answers question (1) of Anantharaman and Léautaud (Anal PDE 7(1):159-214, 2014, Section 2C).

Faraday wave patterns on a square cell network

NASA Astrophysics Data System (ADS)

Peña-Polo, Franklin; Vargas, Carlos A.; Vásquez-González, Benjamín; Medina, Abraham; Trujillo, Leonardo; Klapp, Jaime; Sigalotti, Leonardo Di G.

2017-05-01

We present the experimental observations of the Faraday instability when the vibrated liquid is contained in a network of small square cells for exciting frequencies in the range 10≤ F≤ 24 Hz. A sweep of the parameter space has been performed to investigate the amplitudes and frequencies of the driving force for which different patterns form over the network. Regular patterns in the form of square lattices are observed for driving frequencies in the range 10≤ F<14 Hz, while ordered matrices of oscillons are formed for 1423 Hz, disordered periodic patterns appear within individual cells for a small range of amplitudes. In this case, the wave field is dominated by oscillating blobs that interact on the capillary-gravity scale. A Pearson correlation analysis of the recorded videos shows that for all ordered patterns, the surface waves are periodic and correspond to Faraday waves of dominant frequency equal to half the excitation frequency (i.e., f=F/2). In contrast, the oscillons formed for 1423 Hz are not subharmonic and correspond to periodic harmonic waves with f=nF/2 (for n=2,4,\\ldots ). We find that the experimentally determined minimum forcing necessary to destabilize the rest state and generate surface waves is consistent with a recent stability analysis of stationary solutions as derived from a new dispersion relation for time-periodic waves with nonzero forcing and dissipation.

Modeling the 16 September 2015 Chile tsunami source with the inversion of deep-ocean tsunami records by means of the r - solution method

NASA Astrophysics Data System (ADS)

Voronina, Tatyana; Romanenko, Alexey; Loskutov, Artem

2017-04-01

The key point in the state-of-the-art in the tsunami forecasting is constructing a reliable tsunami source. In this study, we present an application of the original numerical inversion technique to modeling the tsunami sources of the 16 September 2015 Chile tsunami. The problem of recovering a tsunami source from remote measurements of the incoming wave in the deep-water tsunameters is considered as an inverse problem of mathematical physics in the class of ill-posed problems. This approach is based on the least squares and the truncated singular value decomposition techniques. The tsunami wave propagation is considered within the scope of the linear shallow-water theory. As in inverse seismic problem, the numerical solutions obtained by mathematical methods become unstable due to the presence of noise in real data. A method of r-solutions makes it possible to avoid instability in the solution to the ill-posed problem under study. This method seems to be attractive from the computational point of view since the main efforts are required only once for calculating the matrix whose columns consist of computed waveforms for each harmonic as a source (an unknown tsunami source is represented as a part of a spatial harmonics series in the source area). Furthermore, analyzing the singular spectra of the matrix obtained in the course of numerical calculations one can estimate the future inversion by a certain observational system that will allow offering a more effective disposition for the tsunameters with the help of precomputations. In other words, the results obtained allow finding a way to improve the inversion by selecting the most informative set of available recording stations. The case study of the 6 February 2013 Solomon Islands tsunami highlights a critical role of arranging deep-water tsunameters for obtaining the inversion results. Implementation of the proposed methodology to the 16 September 2015 Chile tsunami has successfully produced tsunami source model. The function recovered by the method proposed can find practical applications both as an initial condition for various optimization approaches and for computer calculation of the tsunami wave propagation.

Teaching graphical simulations of Fourier series expansion of some periodic waves using spreadsheets

NASA Astrophysics Data System (ADS)

Singh, Iqbal; Kaur, Bikramjeet

2018-05-01

The present article demonstrates a way of programming using an Excel spreadsheet to teach Fourier series expansion in school/colleges without the knowledge of any typical programming language. By using this, a student learns to approximate partial sum of the n terms of Fourier series for some periodic signals such as square wave, saw tooth wave, half wave rectifier and full wave rectifier signals.

The Joint CCSDS-SFCG Modulation Study--A Comparison of Modulation Schemes

NASA Technical Reports Server (NTRS)

Martin, W. L.; Nguyen, T. M.

1994-01-01

This paper compares the various modulation schemes, namely, PCM/PSK/PM, PCM/PM and BPSK. The subcarrier wave form for PCM/PSK/PM can be either square wave or sine wave, and the data format for PCM/PM and BPSK can be wither NRZ or Bi-phase.

Parametric instabilities of the circularly polarized Alfven waves including dispersion. [for solar wind

NASA Technical Reports Server (NTRS)

Wong, H. K.; Goldstein, M. L.

1986-01-01

A class of parametric instabilities of large-amplitude, circularly polarized Alfven waves is considered in which finite frequency (dispersive) effects are included. The dispersion equation governing the instabilities is a sixth-order polynomial which is solved numerically. As a function of K identically equal to k/k-sub-0 (where k-sub-0 and k are the wave number of the 'pump' wave and unstable sound wave, respectively), there are three regionals of instability: a modulation instability at K less than 1, a decay instability at K greater than 1, and a relatively weak and narrow instability at K close to squared divided by v-sub-A squared (where c-sub-s and v-sub-A are the sound and Alfven speeds respectively), the modulational instability occurs when beta is less than 1 (more than 1) for left-hand (right-hand) pump waves, in agreement with the previous results of Sakai and Sonnerup (1983). The growth rate of the decay instability of left-hand waves is greater than the modulational instability at all values of beta. Applications to large-amplitude wave observed in the solar wind, in computer simulations, and in the vicinity of planetary and interplanetary collisionless shocks are discussed.

Numerical investigation of the interaction between a planar shock wave with square and triangular bubbles containing different gases

NASA Astrophysics Data System (ADS)

Igra, Dan; Igra, Ozer

2018-05-01

The interaction between a planar shock wave and square and triangular bubbles containing either SF6, He, Ar, or CO2 is studied numerically. It is shown that, due to the existing large differences in the molecular weight, the specific heat ratio, and the acoustic impedance between these gases, different wave patterns and pressure distribution inside the bubbles are developed during the interaction process. In the case of heavy gases, the velocity of the shock wave propagating along the bubble inner surface is always less than that of the incident shock wave and higher than that of the transmitted shock wave. However, in the case of the light gas (He), the fastest one is the transmitted shock wave and the slowest one is the incident shock wave. The largest pressure jump is witnessed in the SF6 case, while the smallest pressure jump is seen in the helium case. There are also pronounced differences in the deformation of the investigated bubbles; while triangular bubbles filled with either Ar, CO2, or SF6 were deformed to a crescent shape, the helium bubble is deformed to a trapezoidal shape with three pairs of vortices emanating from its surface.

Anodic Oxidation of Etodolac and its Linear Sweep, Square Wave and Differential Pulse Voltammetric Determination in Pharmaceuticals

PubMed Central

Yilmaz, B.; Kaban, S.; Akcay, B. K.

2015-01-01

In this study, simple, fast and reliable cyclic voltammetry, linear sweep voltammetry, square wave voltammetry and differential pulse voltammetry methods were developed and validated for determination of etodolac in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of etodolac at platinum electrode in acetonitrile solution containing 0.1 M lithium perchlorate. The well-defined oxidation peak was observed at 1.03 V. The calibration curves were linear for etodolac at the concentration range of 2.5-50 μg/ml for linear sweep, square wave and differential pulse voltammetry methods, respectively. Intra- and inter-day precision values for etodolac were less than 4.69, and accuracy (relative error) was better than 2.00%. The mean recovery of etodolac was 100.6% for pharmaceutical preparations. No interference was found from three tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Etol, Tadolak and Etodin tablets as pharmaceutical preparation. PMID:26664057

Using Kinect to Measure Wave Spectrum

NASA Astrophysics Data System (ADS)

Fong, J.; Loose, B.; Lovely, A.

2012-12-01

Gas exchange at the air-sea interface is enhanced by aqueous turbulence generated by capillary-gravity waves, affecting the absorption of atmospheric carbon dioxide by the ocean. The mean squared wave slope of these waves correlates strongly with the gas transfer velocity. To measure the energy in capillary-gravity waves, this project aims to use the Microsoft Xbox Kinect to measure the short period wave spectrum. Kinect is an input device for the Xbox 360 with an infrared laser and camera that can be used to map objects at high frequency and spatial resolution, similar to a LiDAR sensor. For air-sea gas exchange, we are interested in the short period gravity waves with a wavenumber of 40 to 100 radians per meter. We have successfully recorded data from Kinect at a sample rate of 30 Hz with 640x480 pixel resolution, consistent with the manufacturer specifications for its scanning capabilities. At 0.5 m distance from the surface, this yields a nominal resolution of approximately 0.7 mm with a theoretical vertical precision of 0.24 mm and a practical 1 σ noise level of 0.91 mm. We have found that Kinect has some limitations in its ability to detect the air-water interface. Clean water proved to be a weaker reflector for the Kinect IR source, whereas a relatively strong signal can be received for liquids with a high concentration of suspended solids. Colloids such as milk and Ca(OH)2 in water proved more suitable media from which height and wave spectra were detectable. Moreover, we will show results from monochromatic as well as wind-wave laboratory studies. With the wave field measurements from Kinect, gas transfer velocities at the air-sea interface can be determined.

AMLSA Algorithm for Hybrid Precoding in Millimeter Wave MIMO Systems

NASA Astrophysics Data System (ADS)

Liu, Fulai; Sun, Zhenxing; Du, Ruiyan; Bai, Xiaoyu

2017-10-01

In this paper, an effective algorithm will be proposed for hybrid precoding in mmWave MIMO systems, referred to as alternating minimization algorithm with the least squares amendment (AMLSA algorithm). To be specific, for the fully-connected structure, the presented algorithm is exploited to minimize the classical objective function and obtain the hybrid precoding matrix. It introduces an orthogonal constraint to the digital precoding matrix which is amended subsequently by the least squares after obtaining its alternating minimization iterative result. Simulation results confirm that the achievable spectral efficiency of our proposed algorithm is better to some extent than that of the existing algorithm without the least squares amendment. Furthermore, the number of iterations is reduced slightly via improving the initialization procedure.

High frequency measurement of P- and S-wave velocities on crystalline rock massif surface - methodology of measurement

NASA Astrophysics Data System (ADS)

Vilhelm, Jan; Slavík, Lubomír

2014-05-01

For the purpose of non-destructive monitoring of rock properties in the underground excavation it is possible to perform repeated high-accuracy P- and S-wave velocity measurements. This contribution deals with preliminary results gained during the preparation of micro-seismic long-term monitoring system. The field velocity measurements were made by pulse-transmission technique directly on the rock outcrop (granite) in Bedrichov gallery (northern Bohemia). The gallery at the experimental site was excavated using TBM (Tunnel Boring Machine) and it is used for drinking water supply, which is conveyed in a pipe. The stable measuring system and its automatic operation lead to the use of piezoceramic transducers both as a seismic source and as a receiver. The length of measuring base at gallery wall was from 0.5 to 3 meters. Different transducer coupling possibilities were tested namely with regard of repeatability of velocity determination. The arrangement of measuring system on the surface of the rock massif causes better sensitivity of S-transducers for P-wave measurement compared with the P-transducers. Similarly P-transducers were found more suitable for S-wave velocity determination then P-transducers. The frequency dependent attenuation of fresh rock massif results in limited frequency content of registered seismic signals. It was found that at the distance between the seismic source and receiver from 0.5 m the frequency components above 40 kHz are significantly attenuated. Therefore for the excitation of seismic wave 100 kHz transducers are most suitable. The limited frequency range should be also taken into account for the shape of electric impulse used for exciting of piezoceramic transducer. The spike pulse generates broad-band seismic signal, short in the time domain. However its energy after low-pass filtration in the rock is significantly lower than the energy of seismic signal generated by square wave pulse. Acknowledgments: This work was partially supported by the Technology Agency of the Czech Republic, project No. TA 0302408

Cancellous bone analysis with modified least squares Prony's method and chirp filter: phantom experiments and simulation.

PubMed

Wear, Keith A

2010-10-01

The presence of two longitudinal waves in porous media is predicted by Biot's theory and has been confirmed experimentally in cancellous bone. When cancellous bone samples are interrogated in through-transmission, these two waves can overlap in time. Previously, the Modified Least-Squares Prony's (MLSP) method was validated for estimation of amplitudes, attenuation coefficients, and phase velocities of fast and slow waves, but tended to overestimate phase velocities by up to about 5%. In the present paper, a pre-processing chirp filter to mitigate the phase velocity bias is derived. The MLSP/chirp filter (MLSPCF) method was tested for decomposition of a 500 kHz-center-frequency signal containing two overlapping components: one passing through a low-density-polyethylene plate (fast wave) and another passing through a cancellous-bone-mimicking phantom material (slow wave). The chirp filter reduced phase velocity bias from 100 m/s (5.1%) to 69 m/s (3.5%) (fast wave) and from 29 m/s (1.9%) to 10 m/s (0.7%) (slow wave). Similar improvements were found for 1) measurements in polycarbonate (fast wave) and a cancellous-bone-mimicking phantom (slow wave), and 2) a simulation based on parameters mimicking bovine cancellous bone. The MLSPCF method did not offer consistent improvement in estimates of attenuation coefficient or amplitude.

Electrical resistivity well-logging system with solid-state electronic circuitry

USGS Publications Warehouse

Scott, James Henry; Farstad, Arnold J.

1977-01-01

An improved 4-channel electrical resistivity well-logging system for use with a passive probe with electrodes arranged in the 'normal' configuration has been designed and fabricated by Westinghouse Electric Corporation to meet technical specifications developed by the U.S. Geological Survey. Salient features of the system include solid-state switching and current regulation in the transmitter circuit to produce a constant-current source square wave, and synchronous solid-state switching and sampling of the potential waveform in the receiver circuit to provide an analog dc voltage proportions to the measured resistivity. Technical specifications and design details are included in this report.

Waves in a Cloudy Vortex

DTIC Science & Technology

2007-02-01

Waves in a Cloudy Vortex DAVID A. SCHECTER Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado MICHAEL T. MONTGOMERY...waves account for precessing tilts and elliptical (triangular, square, etc.) deformations of the vortex core. If the Rossby number of the cyclone ex...ceeds unity, its baroclinic VR waves can efficiently ex- Corresponding author address: Dr. David Schecter, NorthWest Research Associates, 14508 NE 20th

4th Generation ECR Ion Sources

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

Lyneis, Claude M.; Leitner, D.; Todd, D.S.

2008-12-01

The concepts and technical challenges related to developing a 4th generation ECR ion source with an RF frequency greater than 40 GHz and magnetic confinement fields greater than twice Becr will be explored in this paper. Based on the semi-empirical frequency scaling of ECR plasma density with the square of operating frequency, there should be significant gains in performance over current 3rd generation ECR ion sources, which operate at RF frequencies between 20 and 30 GHz. While the 3rd generation ECR ion sources use NbTi superconducting solenoid and sextupole coils, the new sources will need to use different superconducting materialsmore » such as Nb3Sn to reach the required magnetic confinement, which scales linearly with RF frequency. Additional technical challenges include increased bremsstrahlung production, which may increase faster than the plasma density, bremsstrahlung heating of the cold mass and the availability of high power continuous wave microwave sources at these frequencies. With each generation of ECR ion sources, there are new challenges to be mastered, but the potential for higher performance and reduced cost of the associated accelerator continue to make this a promising avenue for development.« less

Quantitative weaknesses of the Marcus-Hush theory of electrode kinetics revealed by Reverse Scan Square Wave Voltammetry: The reduction of 2-methyl-2-nitropropane at mercury microelectrodes

NASA Astrophysics Data System (ADS)

Laborda, Eduardo; Wang, Yijun; Henstridge, Martin C.; Martínez-Ortiz, Francisco; Molina, Angela; Compton, Richard G.

2011-08-01

The Marcus-Hush and Butler-Volmer kinetic electrode models are compared experimentally by studying the reduction of 2-methyl-2-nitropropane in acetonitrile at mercury microelectrodes using Reverse Scan Square Wave Voltammetry. This technique is found to be very sensitive to the electrode kinetics and to permit critical comparison of the two models. The Butler-Volmer model satisfactorily fits the experimental data whereas Marcus-Hush does not quantitatively describe this redox system.

Diagnostic Criteria for the Characterization of Electrode Reactions with Chemically Coupled Reactions Preceding the Electron Transfer by Cyclic Square Wave Voltammetry.

PubMed

Helfrick, John C; Mann, Megan A; Bottomley, Lawrence A

2016-08-18

Theory for cyclic square wave voltammetry of electrode reactions with chemical reactions preceding the electron transfer is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Response functions for dimers and square-symmetric molecules in four-wave-mixing experiments with polarized light

NASA Astrophysics Data System (ADS)

Smith, Eric Ryan; Farrow, Darcie A.; Jonas, David M.

2005-07-01

Four-wave-mixing nonlinear-response functions are given for intermolecular and intramolecular vibrations of a perpendicular dimer and intramolecular vibrations of a square-symmetric molecule containing a doubly degenerate state. A two-dimensional particle-in-a-box model is used to approximate the electronic wave functions and obtain harmonic potentials for nuclear motion. Vibronic interactions due to symmetry-lowering distortions along Jahn-Teller active normal modes are discussed. Electronic dephasing due to nuclear motion along both symmetric and asymmetric normal modes is included in these response functions, but population transfer between states is not. As an illustration, these response functions are used to predict the pump-probe polarization anisotropy in the limit of impulsive excitation.

Polarization switching of sodium guide star laser for brightness enhancement

NASA Astrophysics Data System (ADS)

Fan, Tingwei; Zhou, Tianhua; Feng, Yan

2016-07-01

The efficiency of optical pumping that enhances the brightness of sodium laser guide star with circularly polarized light is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the photon return. With ESO's cw laser guide star system at Paranal as example, numerical simulation for both square-wave and sine-wave polarization modulation is conducted. For the square-wave switching case, the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 40% at 90°. The method can also be applied for remote measurement of magnetic field with available cw guide star laser.

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

NASA Technical Reports Server (NTRS)

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.

Wave-induced fluid flow in random porous media: Attenuation and dispersion of elastic waves

NASA Astrophysics Data System (ADS)

Müller, Tobias M.; Gurevich, Boris

2005-05-01

A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. .

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

NASA Technical Reports Server (NTRS)

Armano, M.; Audley, H.; Auger, G.; Baird, J. T.; Bassan, M.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Thorpe, J. I.

2016-01-01

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 +/- 0.1 fm s(exp -2)/square root of Hz, or (0.54 +/- 0.01) x 10(exp -15) g/square root of Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 +/- 0.3) fm square root of Hz, about 2 orders of magnitude better than requirements. At f less than or equal to 0.5 mHz we observe a low-frequency tail that stays below 12 fm s(exp -2)/square root of Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Comparison between results of solution of Burgers' equation and Laplace's equation by Galerkin and least-square finite element methods

NASA Astrophysics Data System (ADS)

Adib, Arash; Poorveis, Davood; Mehraban, Farid

2018-03-01

In this research, two equations are considered as examples of hyperbolic and elliptic equations. In addition, two finite element methods are applied for solving of these equations. The purpose of this research is the selection of suitable method for solving each of two equations. Burgers' equation is a hyperbolic equation. This equation is a pure advection (without diffusion) equation. This equation is one-dimensional and unsteady. A sudden shock wave is introduced to the model. This wave moves without deformation. In addition, Laplace's equation is an elliptical equation. This equation is steady and two-dimensional. The solution of Laplace's equation in an earth dam is considered. By solution of Laplace's equation, head pressure and the value of seepage in the directions X and Y are calculated in different points of earth dam. At the end, water table is shown in the earth dam. For Burgers' equation, least-square method can show movement of wave with oscillation but Galerkin method can not show it correctly (the best method for solving of the Burgers' equation is discrete space by least-square finite element method and discrete time by forward difference.). For Laplace's equation, Galerkin and least square methods can show water table correctly in earth dam.

Bipolar square-wave current source for transient electromagnetic systems based on constant shutdown time

NASA Astrophysics Data System (ADS)

Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan

2016-03-01

Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.

Bipolar square-wave current source for transient electromagnetic systems based on constant shutdown time.

PubMed

Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan

2016-03-01

Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.

Algorithms for System Identification and Source Location.

NASA Astrophysics Data System (ADS)

Nehorai, Arye

This thesis deals with several topics in least squares estimation and applications to source location. It begins with a derivation of a mapping between Wiener theory and Kalman filtering for nonstationary autoregressive moving average (ARMO) processes. Applying time domain analysis, connections are found between time-varying state space realizations and input-output impulse response by matrix fraction description (MFD). Using these connections, the whitening filters are derived by the two approaches, and the Kalman gain is expressed in terms of Wiener theory. Next, fast estimation algorithms are derived in a unified way as special cases of the Conjugate Direction Method. The fast algorithms included are the block Levinson, fast recursive least squares, ladder (or lattice) and fast Cholesky algorithms. The results give a novel derivation and interpretation for all these methods, which are efficient alternatives to available recursive system identification algorithms. Multivariable identification algorithms are usually designed only for left MFD models. In this work, recursive multivariable identification algorithms are derived for right MFD models with diagonal denominator matrices. The algorithms are of prediction error and model reference type. Convergence analysis results obtained by the Ordinary Differential Equation (ODE) method are presented along with simulations. Sources of energy can be located by estimating time differences of arrival (TDOA's) of waves between the receivers. A new method for TDOA estimation is proposed for multiple unknown ARMA sources and additive correlated receiver noise. The method is based on a formula that uses only the receiver cross-spectra and the source poles. Two algorithms are suggested that allow tradeoffs between computational complexity and accuracy. A new time delay model is derived and used to show the applicability of the methods for non -integer TDOA's. Results from simulations illustrate the performance of the algorithms. The last chapter analyzes the response of exact least squares predictors for enhancement of sinusoids with additive colored noise. Using the matrix inversion lemma and the Christoffel-Darboux formula, the frequency response and amplitude gain of the sinusoids are expressed as functions of the signal and noise characteristics. The results generalize the available white noise case.

Stress Wave E-Rating of Structural Timber—Size and Moisture Content Effects

Treesearch

Xiping Wang

2013-01-01

The objectives of this study were to investigate the influence of cross sectional size and moisture content on stress wave properties of structural timber in various sizes and evaluate the feasibility of using stress wave method to E-rate timber in green conditions. Four different sizes of Douglas-fir (Pseudotsuga menziesii) square timbers were...

Importance of Fluctuations in Light on Plant Photosynthetic Acclimation1[CC-BY

PubMed Central

2017-01-01

The acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on the photosynthetic processes and growth of Arabidopsis (Arabidopsis thaliana). High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern, were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light-grown plants. This, together with elevated levels of proteins associated with electron transport, indicates greater investment in leaf structural components and photosynthetic processes. In contrast, plants grown under fluctuating light had thinner leaves, lower leaf light absorption, but maintained similar photosynthetic rates per unit leaf area to square wave-grown plants. Despite high light use efficiency, plants grown under fluctuating light had a slow growth rate early in development, likely due to the fact that plants grown under fluctuating conditions were not able to fully utilize the light energy absorbed for carbon fixation. Diurnal leaf-level measurements revealed a negative feedback control of photosynthesis, resulting in a decrease in total diurnal carbon assimilated of at least 20%. These findings highlight that growing plants under square wave growth conditions ultimately fails to predict plant performance under realistic light regimes and stress the importance of considering fluctuations in incident light in future experiments that aim to infer plant productivity under natural conditions in the field. PMID:28184008

Oil Slick Observation at Low Incidence Angles in Ku-Band

NASA Astrophysics Data System (ADS)

Panfilova, M. A.; Karaev, V. Y.; Guo, Jie

2018-03-01

On the 20 April 2010 the oil platform Deep Water Horizon in the Gulf of Mexico suffered an explosion during the final phases of drilling an exploratory well. As a result, an oil film covered the sea surface area of several thousand square kilometers. In the present paper the data of the Ku-band Precipitation Radar, which operates at low incidence angles, were used to explore the oil spill event. The two-scale model of the scattering surface was used to describe radar backscatter from the sea surface. The algorithm for retrieval of normalized radar cross section at nadir and the total slope variance of large-scale waves compared to the wavelength of electromagnetic wave (22 mm) was developed for the Precipitation Radar swath. It is shown that measurements at low incidence angles can be used for oil spill detection. This is the first time that the dependence of mean square slope of large-scale waves on wind speed has been obtained for oil slicks from Ku-band data, and compared to mean square slope obtained by Cox and Munk from optical data.

[Study on predicting sugar content and valid acidity of apples by near infrared diffuse reflectance technique].

PubMed

Liu, Yan-de; Ying, Yi-bin; Fu, Xia-ping

2005-11-01

The nondestructive method for quantifying sugar content (SC) and available acid (VA) of intact apples using diffuse near infrared reflectance and optical fiber sensing techniques were explored in the present research. The standard sample sets and prediction models were established by partial least squares analysis (PLS). A total of 120 Shandong Fuji apples were tested in the wave number of 12,500 - 4000 cm(-1) using Fourier transform near infrared spectroscopy. The results of the research indicated that the nondestructive quantification of SC and VA, gave a high correlation coefficient 0.970 and 0.906, a low root mean square error of prediction (RMSEP) 0.272 and 0.056 2, a low root mean square error of calibration (RMSEC) 0.261 and 0.0677, and a small difference between RMSEP and RMSEC 0.011 a nd 0.0115. It was suggested that the diffuse nearinfrared reflectance technique be feasible for nondestructive determination of apple sugar content in the wave number range of 10,341 - 5461 cm(-1) and for available acid in the wave number range of 10,341 - 3818 cm(-1).

Movable-Bed Laboratory Experiments Comparing Radiation Stress and Energy Flux Factor as Predictors of Longshore Transport Rate.

DTIC Science & Technology

1981-04-01

acceleration of gravity H wave height H average wave height Hrms root-mean-square wave height Hs significant wave height IX longshore transport rate in...wave height, H, measured during the tests (and discussed later in Section IV) is equal to Hrms . By rewriting equation (4), S ( Cg cos.) C (7) xy 8 Cg...only for conditions where H equals Hrms * 2. Energy Flux. In literature, the longshore transport rate has been empirically related most frequently to a

Some simple solutions of Schrödinger's equation for a free particle or for an oscillator

NASA Astrophysics Data System (ADS)

Andrews, Mark

2018-05-01

For a non-relativistic free particle, we show that the evolution of some simple initial wave functions made up of linear segments can be expressed in terms of Fresnel integrals. Examples include the square wave function and the triangular wave function. The method is then extended to wave functions made from quadratic elements. The evolution of all these initial wave functions can also be found for the harmonic oscillator by a transformation of the free evolutions.

Seismic noise frequency dependent P and S wave sources

NASA Astrophysics Data System (ADS)

Stutzmann, E.; Schimmel, M.; Gualtieri, L.; Farra, V.; Ardhuin, F.

2013-12-01

Seismic noise in the period band 3-10 sec is generated in the oceans by the interaction of ocean waves. Noise signal is dominated by Rayleigh waves but body waves can be extracted using a beamforming approach. We select the TAPAS array deployed in South Spain between June 2008 and September 2009 and we use the vertical and horizontal components to extract noise P and S waves, respectively. Data are filtered in narrow frequency bands and we select beam azimuths and slownesses that correspond to the largest continuous sources per day. Our procedure automatically discard earthquakes which are localized during short time durations. Using this approach, we detect many more noise P-waves than S-waves. Source locations are determined by back-projecting the detected slowness/azimuth. P and S waves are generated in nearby areas and both source locations are frequency dependent. Long period sources are dominantly in the South Atlantic and Indian Ocean whereas shorter period sources are rather in the North Atlantic Ocean. We further show that the detected S-waves are dominantly Sv-waves. We model the observed body waves using an ocean wave model that takes into account all possible wave interactions including coastal reflection. We use the wave model to separate direct and multiply reflected phases for P and S waves respectively. We show that in the South Atlantic the complex source pattern can be explained by the existence of both coastal and pelagic sources whereas in the North Atlantic most body wave sources are pelagic. For each detected source, we determine the equivalent source magnitude which is compared to the model.

Spin configurations on a decorated square lattice

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

Mert, Gülistan; Mert, H. Şevki

Spin configurations on a decorated square lattice are investigated using Bertaut’s microscopic method. We have obtained collinear and non-collinear (canted) modes for the given wave vectors in the ground state. We have found ferromagnetic and antiferromagnetic commensurate spin configurations. We have found canted incommensurate spin configurations.

Oscillation of a polymer gel entrained with a periodic force.

PubMed

Shiota, Takaya; Ikura, Yumihiko S; Nakata, Satoshi

2013-02-21

The oscillation of a polymer gel induced by the Belousov-Zhabotinsky (BZ) reaction was investigated under an external force composed of a square wave. The oscillation of the BZ reaction entrained to the periodic force and the features of this entrainment changed depending on the period and duty cycle of the square wave. The experimental results suggest that the change in the volume of the gel also gave feedback to the BZ reaction. The mechanism of entrainment is discussed in relation to the compression of the gel and the reaction-diffusion system in the BZ reaction.

Silicon-controlled-rectifier square-wave inverter with protection against commutation failure

NASA Technical Reports Server (NTRS)

Birchenough, A. G.

1971-01-01

The square-wave SCR inverter that was designed, built, and tested includes a circuit to turn off the inverter in case of commutation failure. The basic power stage is a complementary impulse-commutated parallel inverter consisting of only six components. The 400-watt breadboard was tested while operating at + or - 28 volts, and it had a peak efficiency of 95.5 percent at 60 hertz and 91.7 percent at 400 hertz. The voltage regulation for a fixed input was 3 percent at 60 hertz. An analysis of the operation and design information is included.

Relationships among classes of self-oscillating transistor parallel inverters. [dc to square wave converter circuits for power conditioning

NASA Technical Reports Server (NTRS)

Wilson, T. G.; Lee, F. C. Y.; Burns, W. W., III; Owen, H. A., Jr.

1974-01-01

A procedure is developed for classifying dc-to-square-wave two-transistor parallel inverters used in power conditioning applications. The inverters are reduced to equivalent RLC networks and are then grouped with other inverters with the same basic equivalent circuit. Distinction between inverter classes is based on the topology characteristics of the equivalent circuits. Information about one class can then be extended to another class using the basic oscillation theory and the concept of duality. Oscillograms from test circuits confirm the validity of the procedure adopted.

Attenuation and source properties at the Coso Geothermal area, California

USGS Publications Warehouse

Hough, S.E.; Lees, J.M.; Monastero, F.

1999-01-01

We use a multiple-empirical Green's function method to determine source properties of small (M -0.4 to 1.3) earthquakes and P- and S-wave attenuation at the Coso Geothermal Field, California. Source properties of a previously identified set of clustered events from the Coso geothermal region are first analyzed using an empirical Green's function (EGF) method. Stress-drop values of at least 0.5-1 MPa are inferred for all of the events; in many cases, the corner frequency is outside the usable bandwidth, and the stress drop can only be constrained as being higher than 3 MPa. P- and S-wave stress-drop estimates are identical to the resolution limits of the data. These results are indistinguishable from numerous EGF studies of M 2-5 earthquakes, suggesting a similarity in rupture processes that extends to events that are both tiny and induced, providing further support for Byerlee's Law. Whole-path Q estimates for P and S waves are determined using the multiple-empirical Green's function (MEGF) method of Hough (1997), whereby spectra from clusters of colocated events at a given station are inverted for a single attenuation parameter, ??, with source parameters constrained from EGF analysis. The ?? estimates, which we infer to be resolved to within 0.01 sec or better, exhibit almost as much scatter as a function of hypocentral distance as do values from previous single-spectrum studies for which much higher uncertainties in individual ?? estimates are expected. The variability in ?? estimates determined here therefore suggests real lateral variability in Q structure. Although the ray-path coverage is too sparse to yield a complete three-dimensional attenuation tomographic image, we invert the inferred ?? value for three-dimensional structure using a damped least-squares method, and the results do reveal significant lateral variability in Q structure. The inferred attenuation variability corresponds to the heat-flow variations within the geothermal region. A central low-Q region corresponds well with the central high-heat flow region; additional detailed structure is also suggested.

Teaching Graphical Simulations of Fourier Series Expansion of Some Periodic Waves Using Spreadsheets

ERIC Educational Resources Information Center

Singh, Iqbal; Kaur, Bikramjeet

2018-01-01

The present article demonstrates a way of programming using an Excel spreadsheet to teach Fourier series expansion in school/colleges without the knowledge of any typical programming language. By using this, a student learns to approximate partial sum of the n terms of Fourier series for some periodic signals such as square wave, saw tooth wave,…

Parameter identification of JONSWAP spectrum acquired by airborne LIDAR

NASA Astrophysics Data System (ADS)

Yu, Yang; Pei, Hailong; Xu, Chengzhong

2017-12-01

In this study, we developed the first linear Joint North Sea Wave Project (JONSWAP) spectrum (JS), which involves a transformation from the JS solution to the natural logarithmic scale. This transformation is convenient for defining the least squares function in terms of the scale and shape parameters. We identified these two wind-dependent parameters to better understand the wind effect on surface waves. Due to its efficiency and high-resolution, we employed the airborne Light Detection and Ranging (LIDAR) system for our measurements. Due to the lack of actual data, we simulated ocean waves in the MATLAB environment, which can be easily translated into industrial programming language. We utilized the Longuet-Higgin (LH) random-phase method to generate the time series of wave records and used the fast Fourier transform (FFT) technique to compute the power spectra density. After validating these procedures, we identified the JS parameters by minimizing the mean-square error of the target spectrum to that of the estimated spectrum obtained by FFT. We determined that the estimation error is relative to the amount of available wave record data. Finally, we found the inverse computation of wind factors (wind speed and wind fetch length) to be robust and sufficiently precise for wave forecasting.

Get the LED Out.

ERIC Educational Resources Information Center

Jewett, John W., Jr.

1991-01-01

Describes science demonstrations with light-emitting diodes that include electrical concepts of resistance, direct and alternating current, sine wave versus square wave, series and parallel circuits, and Faraday's Law; optics concepts of real and virtual images, photoresistance, and optical communication; and modern physics concepts of spectral…

Direct quantification of test bacteria in synthetic water-polluted samples by square wave voltammetry and chemometric methods.

PubMed

Carpani, Irene; Conti, Paolo; Lanteri, Silvia; Legnani, Pier Paolo; Leoni, Erica; Tonelli, Domenica

2008-02-28

A home-made microelectrode array, based on reticulated vitreous carbon, was used as working electrode in square wave voltammetry experiments to quantify the bacterial load of Escherichia coli ATCC 13706 and Pseudomonas aeruginosa ATCC 27853, chosen as test microorganisms, in synthetic samples similar to drinking water (phosphate buffer). Raw electrochemical signals were analysed with partial least squares regression coupled to variable selection in order to correlate these values with the bacterial load estimated by aerobic plate counting. The results demonstrated the ability of the method to detect even low loads of microorganisms in synthetic water samples. In particular, the model detects the bacterial load in the range 3-2,020 CFU ml(-1) for E. coli and in the range 76-155,556 CFU ml(-1) for P. aeruginosa.

Estimation of fast and slow wave properties in cancellous bone using Prony's method and curve fitting.

PubMed

Wear, Keith A

2013-04-01

The presence of two longitudinal waves in poroelastic media is predicted by Biot's theory and has been confirmed experimentally in through-transmission measurements in cancellous bone. Estimation of attenuation coefficients and velocities of the two waves is challenging when the two waves overlap in time. The modified least squares Prony's (MLSP) method in conjuction with curve-fitting (MLSP + CF) is tested using simulations based on published values for fast and slow wave attenuation coefficients and velocities in cancellous bone from several studies in bovine femur, human femur, and human calcaneus. The search algorithm is accelerated by exploiting correlations among search parameters. The performance of the algorithm is evaluated as a function of signal-to-noise ratio (SNR). For a typical experimental SNR (40 dB), the root-mean-square errors (RMSEs) for one example (human femur) with fast and slow waves separated by approximately half of a pulse duration were 1 m/s (slow wave velocity), 4 m/s (fast wave velocity), 0.4 dB/cm MHz (slow wave attenuation slope), and 1.7 dB/cm MHz (fast wave attenuation slope). The MLSP + CF method is fast (requiring less than 2 s at SNR = 40 dB on a consumer-grade notebook computer) and is flexible with respect to the functional form of the parametric model for the transmission coefficient. The MLSP + CF method provides sufficient accuracy and precision for many applications such that experimental error is a greater limiting factor than estimation error.

Gasdynamics of relativistically expanding gamma-ray burst sources - Kinematics, energetics, magnetic fields, and efficiency

NASA Technical Reports Server (NTRS)

Meszaros, P.; Laguna, P.; Rees, M. J.

1993-01-01

We calculate both analytically and numerically the evolution of highly relativistic fireballs through the stages of free expansion and coasting, and determine the dependence of the thermodynamic and radiation variables in the comoving and laboratory flames. The dynamics and the comoving geometry change at the (lab) expansion factors r/r(0) greater than eta and r/r(0) greater than eta-squared, respectively, where eta = E(0)/M(0)c-squared is the initial Lorentz factor. In the lab, the gas appears concentrated in a thin shell of width r(0) until r/r(0) of less than about eta-squared, and increases linearly after that. Magnetic fields may have been important in the original impulsive event. We discuss their effect on the fireball dynamics and also consider their effects on the radiation emitted when the fireball runs into an external medium and is decelerated. The inverse synchro-Compton mechanism can then yield high radiative efficiency in the reverse shock (and through turbulent instabilities and mixing also in the forward blast wave), producing a burst of nonthermal radiation mainly in the MeV to GeV range. The energy and duration depend on eta, the magnetic field strength, and the external density, and can match the range of properties observed in cosmic gamma-ray bursts.

Design of a three-phase, 15-kilovolt-ampere static inverter for motor-starting a Brayton space power system

NASA Technical Reports Server (NTRS)

Frye, R. J.; Birchenough, A. G.

1971-01-01

The design of a three-phase, 400-Hz, 15-kVA static inverter for motor-starting the 2- to 15-kWe Brayton electrical space power system is described. The inverter operates from a nominal 56-V dc source to provide a 28-V, rms, quasi-square-wave output. The inverter is capable of supplying a 200-A peak current. Integrated circuitry is used to generate the three-phase, 400-Hz reference signals. Performance data for a drive stage that improves switching speed and provides efficient operation over a range of output current and drive supply voltage are presented. A transformerless, transistor output stage is used.

Speckle evolution with multiple steps of least-squares phase removal

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

Chen Mingzhou; Dainty, Chris; Roux, Filippus S.

2011-08-15

We study numerically the evolution of speckle fields due to the annihilation of optical vortices after the least-squares phase has been removed. A process with multiple steps of least-squares phase removal is carried out to minimize both vortex density and scintillation index. Statistical results show that almost all the optical vortices can be removed from a speckle field, which finally decays into a quasiplane wave after such an iterative process.

Resonant fiber optic gyro based on a sinusoidal wave modulation and square wave demodulation technique.

PubMed

Wang, Linglan; Yan, Yuchao; Ma, Huilian; Jin, Zhonghe

2016-04-20

New developments are made in the resonant fiber optic gyro (RFOG), which is an optical sensor for the measurement of rotation rate. The digital signal processing system based on the phase modulation technique is capable of detecting the weak frequency difference induced by the Sagnac effect and suppressing the reciprocal noise in the circuit, which determines the detection sensitivity of the RFOG. A new technique based on the sinusoidal wave modulation and square wave demodulation is implemented, and the demodulation curve of the system is simulated and measured. Compared with the past technique using sinusoidal modulation and demodulation, it increases the slope of the demodulation curve by a factor of 1.56, improves the spectrum efficiency of the modulated signal, and reduces the occupancy of the field-programmable gate array resource. On the basis of this new phase modulation technique, the loop is successfully locked and achieves a short-term bias stability of 1.08°/h, which is improved by a factor of 1.47.

Azimuthal Dependence of the Ground Motion Variability from Scenario Modeling of the 2014 Mw6.0 South Napa, California, Earthquake Using an Advanced Kinematic Source Model

NASA Astrophysics Data System (ADS)

Gallovič, F.

2017-09-01

Strong ground motion simulations require physically plausible earthquake source model. Here, I present the application of such a kinematic model introduced originally by Ruiz et al. (Geophys J Int 186:226-244, 2011). The model is constructed to inherently provide synthetics with the desired omega-squared spectral decay in the full frequency range. The source is composed of randomly distributed overlapping subsources with fractal number-size distribution. The position of the subsources can be constrained by prior knowledge of major asperities (stemming, e.g., from slip inversions), or can be completely random. From earthquake physics point of view, the model includes positive correlation between slip and rise time as found in dynamic source simulations. Rupture velocity and rise time follows local S-wave velocity profile, so that the rupture slows down and rise times increase close to the surface, avoiding unrealistically strong ground motions. Rupture velocity can also have random variations, which result in irregular rupture front while satisfying the causality principle. This advanced kinematic broadband source model is freely available and can be easily incorporated into any numerical wave propagation code, as the source is described by spatially distributed slip rate functions, not requiring any stochastic Green's functions. The source model has been previously validated against the observed data due to the very shallow unilateral 2014 Mw6 South Napa, California, earthquake; the model reproduces well the observed data including the near-fault directivity (Seism Res Lett 87:2-14, 2016). The performance of the source model is shown here on the scenario simulations for the same event. In particular, synthetics are compared with existing ground motion prediction equations (GMPEs), emphasizing the azimuthal dependence of the between-event ground motion variability. I propose a simple model reproducing the azimuthal variations of the between-event ground motion variability, providing an insight into possible refinement of GMPEs' functional forms.

Sines and Cosines. Part 1 of 3

NASA Technical Reports Server (NTRS)

Apostol, Tom M. (Editor)

1992-01-01

Applying the concept of similarities, the mathematical principles of circular motion and sine and cosine waves are presented utilizing both film footage and computer animation in this 'Project Mathematics' series video. Concepts presented include: the symmetry of sine waves; the cosine (complementary sine) and cosine waves; the use of sines and cosines on coordinate systems; the relationship they have to each other; the definitions and uses of periodic waves, square waves, sawtooth waves; the Gibbs phenomena; the use of sines and cosines as ratios; and the terminology related to sines and cosines (frequency, overtone, octave, intensity, and amplitude).

Verification of elastic-wave static displacement in solids. [using ultrasonic techniques on Ge single crystals

NASA Technical Reports Server (NTRS)

Cantrell, J. H., Jr.; Winfree, W. P.

1980-01-01

The solution of the nonlinear differential equation which describes an initially sinusoidal finite-amplitude elastic wave propagating in a solid contains a static-displacement term in addition to the harmonic terms. The static-displacement amplitude is theoretically predicted to be proportional to the product of the squares of the driving-wave amplitude and the driving-wave frequency. The first experimental verification of the elastic-wave static displacement in a solid (the 111 direction of single-crystal germanium) is reported, and agreement is found with the theoretical predictions.

Prospects for gravitational wave astronomy with next generation large-scale pulsar timing arrays

NASA Astrophysics Data System (ADS)

Wang, Yan; Mohanty, Soumya D.

2018-02-01

Next generation radio telescopes, namely the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Square Kilometer Array (SKA), will revolutionize the pulsar timing arrays (PTAs) based gravitational wave (GW) searches. We review some of the characteristics of FAST and SKA, and the resulting PTAs, that are pertinent to the detection of gravitational wave signals from individual supermassive black hole binaries.

Tropopause inversion layer formation and stratosphere-troposphere exchange during idealized baroclinic wave life cycle experiments

NASA Astrophysics Data System (ADS)

Kunkel, Daniel; Wirth, Volkmar; Hoor, Peter

2014-05-01

Recent simulations of baroclinic wave life cycles revealed that the tropopause inversion layer (TIL), commonly situated just above the thermal tropopause, is evident in such experiments and emerges after the onset of wave breaking. Furthermore, bidirectional stratosphere-troposphere exchange (STE) occurs during this non-linear stage of the wave evolution and might be affected by the appearance of the TIL. We study the evolution and the impact of the TIL on STE by using the COSMO model in an idealized mid-latitude channel geometry configuration without physical sub-grid scale parameterizations. We initialize the model with a geostrophically balanced upper level jet stream which is disturbed by an anomaly of potential vorticity to trigger the evolution of the baroclinic waves. Moreover, we use passive tracers of tropospheric or stratospheric origin to identify regions of potential STE. Our results show that the static stability is low in regions of stratosphere to troposphere exchange (STT), while it is high in regions dominated by exchange in the opposite direction (TST). Furthermore, inertia gravity waves, originating from regions with strong ageostrophic wind components, modulate the static stability as well as the vertical shear of the horizontal wind near and above the tropopause. While propagating away from their source, the inertia gravity waves lead to large values of the squared Brunt Vaisala frequency in regions which are simultaneously characterized by low bulk Richardson numbers. Thus, these regions are statically stable and turbulent at the same time and might be crucial for TST, thereby explaining tropospheric mixing ratio changes of e.g. CO across the tropopause which commonly change from tropospheric to stratospheric values a few hundred meters above the local thermal tropopause.

Phase stability in the two-dimensional anisotropic boson Hubbard Hamiltonian

DOE PAGES

Ying, T.; Batrouni, G. G.; Rousseau, V. G.; ...

2013-05-15

The two dimensional square lattice hard-core boson Hubbard model with near neighbor interactions has a ‘checkerboard’ charge density wave insulating phase at half-filling and sufficiently large intersite repulsion. When doped, rather than forming a supersolid phase in which long range charge density wave correlations coexist with a condensation of superfluid defects, the system instead phase separates. However, it is known that there are other lattice geometries and interaction patterns for which such coexistence takes place. In this paper we explore the possibility that anisotropic hopping or anisotropic near neighbor repulsion might similarly stabilize the square lattice supersolid. Lastly, by consideringmore » the charge density wave structure factor and superfluid density for different ratios of interaction strength and hybridization in the ˆx and ˆy directions, we conclude that phase separation still occurs.« less

A study of the stress wave factor technique for the characterization of composite materials

NASA Technical Reports Server (NTRS)

Govada, A. K.; Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.

1985-01-01

This study has investigated the potential of the Stress Wave Factor as an NDT technique for thin composite laminates. The conventional SWF and an alternate method for quantifying the SWF were investigated. Agreement between the initial SWF number, ultrasonic C-scan, inplane displacements as obtained by full field moire interferometry, and the failure location have been observed. The SWF number was observed to be the highest when measured along the fiber direction and the lowest when measured across the fibers. The alternate method for quantifying the SWF used square root of the zeroth moment (square root of M sub o) of the frequency spectrum of the received signal as a quantitative parameter. From this study it therefore appears that the stress wave factor has an excellent potential to monitor damage development in thin composite laminates.

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

NASA Astrophysics Data System (ADS)

Denli, H.; Huang, L.

2008-12-01

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

Ultrasonic tracking of shear waves using a particle filter.

PubMed

Ingle, Atul N; Ma, Chi; Varghese, Tomy

2015-11-01

This paper discusses an application of particle filtering for estimating shear wave velocity in tissue using ultrasound elastography data. Shear wave velocity estimates are of significant clinical value as they help differentiate stiffer areas from softer areas which is an indicator of potential pathology. Radio-frequency ultrasound echo signals are used for tracking axial displacements and obtaining the time-to-peak displacement at different lateral locations. These time-to-peak data are usually very noisy and cannot be used directly for computing velocity. In this paper, the denoising problem is tackled using a hidden Markov model with the hidden states being the unknown (noiseless) time-to-peak values. A particle filter is then used for smoothing out the time-to-peak curve to obtain a fit that is optimal in a minimum mean squared error sense. Simulation results from synthetic data and finite element modeling suggest that the particle filter provides lower mean squared reconstruction error with smaller variance as compared to standard filtering methods, while preserving sharp boundary detail. Results from phantom experiments show that the shear wave velocity estimates in the stiff regions of the phantoms were within 20% of those obtained from a commercial ultrasound scanner and agree with estimates obtained using a standard method using least-squares fit. Estimates of area obtained from the particle filtered shear wave velocity maps were within 10% of those obtained from B-mode ultrasound images. The particle filtering approach can be used for producing visually appealing SWV reconstructions by effectively delineating various areas of the phantom with good image quality properties comparable to existing techniques.

Focal Mechanism of a Catastrophic Earthquake of the Last Rococo Period (1783) in Southern Italy Retrieved by Inverting Historical Information on Damage

NASA Astrophysics Data System (ADS)

Sirovich, L.; Pettenati, F.

2007-05-01

Using geophysical inversion to discover the fault source of a blind earthquake, that took place before the invention of the seismograph, seemed impossible. We demonstrated that sometimes it is possible using our simplified KF model (Sirovich, 1996) through automatic genetic inversion (Gentile et al., 2004 in BSSA; Sirovich and Pettenati, 2004 in JGR), and determined it conclusively by treating the Coalinga 1983, Loma Prieta 1989, and Northridge 1994 earthquakes (Pettenati and Sirovich, 2007 in BSSA). KF is able to simulate the body-wave radiation from a linear source, and eleven source parameters are retrieved: the three nucleation coordinates, the fault-plane solution, the seismic moment, the rupture velocities and lengths along-strike and anti-strike, the shear wave velocity in the half-space. To find the minima on the hypersurface of the residuals in the multi-parameter model space, we use a genetic process with niching since we have already shown that the problem is bimodal for pure dip-slip mechanisms. The objective function of the nonlinear inversion is the sum of the squared residuals (calculated-minus-observed intensity at all sites). Here, we use the very good intensity data provided in the MCS scale by the INGV of Italy for the M 6.9 earthquake of Feb. 5, 1783 (see the Italian intensity data bank on http:emidius.mi.ingv.it/DOM/consultazione.html). The data of 1783 were created by seismologists and historians who interpreted the reports of the time and many other historical sources. Given the limitations of the KF approach, we limited our inversion to a square area of 200 by 200 km around the most heavily damaged zone. 341 surveyed towns and hamlets received intensity degrees by INGV (we discarded 6 of them as statistical outliers according to the classical Chauvenet method). Thus, 335 data were inverted. The match between experimental and synthetic isoseismals is really noteworthy. The found mechanism is almost pure dip-slip and, thus, the problem is bimodal. In fact, two source models score almost the same objective function, and they coincide with the auxiliary planes of the same solution. The best source is: nucleation latitude [degrees] 38.28, longitude 15.95, depth 13.1 km; strike angle 210, dip 31, rake 269(±180); seismic moment 2.7 * 10e19 Nm, 3.1 km/s rupture velocity along-strike (3.3 anti-strike), 22.3 km rupture length along-strike (20.7 anti-strike), 3.9 km/s shear wave velocity in the half-space. The second solution, having the same nucleation coordinates and a one-point difference in the objective function (117 against 116) is: strike angle 30, dip 60, rake 270(±180); seismic moment 2.6 * 10e19 Nm, 3.3 km/s rupture velocity along-strike (3.0 anti-strike), 19.4 km rupture length along-strike (21.9 anti-strike), 3.9 km/s shear wave velocity in the half-space. Note the symmetry with the former solution. In other words, we find one fault source having a low-angle dip toward the Tyrrhenian Sea; its virtual intersection with the topographical surface should be found close to the Jonian coast. On the contrary, its symmetric solution strikes SW, has a high-angle dip toward the Jonian Sea, and the fault should outcrop close to the Tyrrhenian coast. Both sources are compatible with the orientation of the principal tectonic structures in the area, however. The final choice between them will hopefully come from tectonic interpretation. This kind of study seems especially promising for southern Europe where a lot of documents on seismic damage caused by old earthquakes exist.

Point-particle effective field theory I: classical renormalization and the inverse-square potential

NASA Astrophysics Data System (ADS)

Burgess, C. P.; Hayman, Peter; Williams, M.; Zalavári, László

2017-04-01

Singular potentials (the inverse-square potential, for example) arise in many situations and their quantum treatment leads to well-known ambiguities in choosing boundary conditions for the wave-function at the position of the potential's singularity. These ambiguities are usually resolved by developing a self-adjoint extension of the original prob-lem; a non-unique procedure that leaves undetermined which extension should apply in specific physical systems. We take the guesswork out of this picture by using techniques of effective field theory to derive the required boundary conditions at the origin in terms of the effective point-particle action describing the physics of the source. In this picture ambiguities in boundary conditions boil down to the allowed choices for the source action, but casting them in terms of an action provides a physical criterion for their determination. The resulting extension is self-adjoint if the source action is real (and involves no new degrees of freedom), and not otherwise (as can also happen for reasonable systems). We show how this effective-field picture provides a simple framework for understanding well-known renormalization effects that arise in these systems, including how renormalization-group techniques can resum non-perturbative interactions that often arise, particularly for non-relativistic applications. In particular we argue why the low-energy effective theory tends to produce a universal RG flow of this type and describe how this can lead to the phenomenon of reaction catalysis, in which physical quantities (like scattering cross sections) can sometimes be surprisingly large compared to the underlying scales of the source in question. We comment in passing on the possible relevance of these observations to the phenomenon of the catalysis of baryon-number violation by scattering from magnetic monopoles.

Costas loop lock detection in the advanced receiver

NASA Technical Reports Server (NTRS)

Mileant, A.; Hinedi, S.

1989-01-01

The advanced receiver currently being developed uses a Costas digital loop to demodulate the subcarrier. Previous analyses of lock detector algorithms for Costas loops have ignored the effects of the inherent correlation between the samples of the phase-error process. Accounting for this correlation is necessary to achieve the desired lock-detection probability for a given false-alarm rate. Both analysis and simulations are used to quantify the effects of phase correlation on lock detection for the square-law and the absolute-value type detectors. Results are obtained which depict the lock-detection probability as a function of loop signal-to-noise ratio for a given false-alarm rate. The mathematical model and computer simulation show that the square-law detector experiences less degradation due to phase jitter than the absolute-value detector and that the degradation in detector signal-to-noise ratio is more pronounced for square-wave than for sine-wave signals.

Degradation in finite-harmonic subcarrier demodulation

NASA Technical Reports Server (NTRS)

Feria, Y.; Townes, S.; Pham, T.

1995-01-01

Previous estimates on the degradations due to a subcarrier loop assume a square-wave subcarrier. This article provides a closed-form expression for the degradations due to the subcarrier loop when a finite number of harmonics are used to demodulate the subcarrier, as in the case of the buffered telemetry demodulator. We compared the degradations using a square wave and using finite harmonics in the subcarrier demodulation and found that, for a low loop signal-to-noise ratio, using finite harmonics leads to a lower degradation. The analysis is under the assumption that the phase noise in the subcarrier (SC) loop has a Tikhonov distribution. This assumption is valid for first-order loops.

Relationship between cutoff frequency and accuracy in time-interval photon statistics applied to oscillating signals

NASA Astrophysics Data System (ADS)

Rebolledo, M. A.; Martinez-Betorz, J. A.

1989-04-01

In this paper the accuracy in the determination of the period of an oscillating signal, when obtained from the photon statistics time-interval probability, is studied as a function of the precision (the inverse of the cutoff frequency of the photon counting system) with which time intervals are measured. The results are obtained by means of an experiment with a square-wave signal, where the Fourier or square-wave transforms of the time-interval probability are measured. It is found that for values of the frequency of the signal near the cutoff frequency the errors in the period are small.

Ferrocene-Boronic Acid-Fructose Binding Based on Dual-Plate Generator-Collector Voltammetry and Square-Wave Voltammetry.

PubMed

Li, Meng; Xu, Su-Ying; Gross, Andrew J; Hammond, Jules L; Estrela, Pedro; Weber, James; Lacina, Karel; James, Tony D; Marken, Frank

2015-06-10

The interaction of ferrocene-boronic acid with fructose is investigated in aqueous 0.1 m phosphate buffer at pH 7, 8 and 9. Two voltammetric methods, based on 1) a dual-plate generator-collector micro-trench electrode (steady state) and 2) a square-wave voltammetry (transient) method, are applied and compared in terms of mechanistic resolution. A combination of experimental data is employed to obtain new insights into the binding rates and the cumulative binding constants for both the reduced ferrocene-boronic acid (pH dependent and weakly binding) and for the oxidised ferrocene-boronic acid (pH independent and strongly binding).

Nonlinear analysis of a family of LC tuned inverters. [dc to square wave circuits for power conditioning

NASA Technical Reports Server (NTRS)

Lee, F. C. Y.; Wilson, T. G.

1974-01-01

A family of four dc-to-square-wave LC tuned inverters are analyzed using singular point. Limit cycles and waveshape characteristics are given for three modes of oscillation: quasi-harmonic, relaxation, and discontinuous. An inverter in which the avalanche breakdown of the transistor emitter-to-base junction occurs is discussed and the starting characteristics of this family of inverters are presented. The LC tuned inverters are shown to belong to a family of inverters with a common equivalent circuit consisting of only three 'series' elements: a five-segment piecewise-linear current-controlled resistor, linear inductor, and linear capacitor.

Feature Detection and Curve Fitting Using Fast Walsh Transforms for Shock Tracking: Applications

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2017-01-01

Walsh functions form an orthonormal basis set consisting of square waves. Square waves make the system well suited for detecting and representing functions with discontinuities. Given a uniform distribution of 2p cells on a one-dimensional element, it has been proven that the inner product of the Walsh Root function for group p with every polynomial of degree < or = (p - 1) across the element is identically zero. It has also been proven that the magnitude and location of a discontinuous jump, as represented by a Heaviside function, are explicitly identified by its Fast Walsh Transform (FWT) coefficients. These two proofs enable an algorithm that quickly provides a Weighted Least Squares fit to distributions across the element that include a discontinuity. The detection of a discontinuity enables analytic relations to locally describe its evolution and provide increased accuracy. Time accurate examples are provided for advection, Burgers equation, and Riemann problems (diaphragm burst) in closed tubes and de Laval nozzles. New algorithms to detect up to two C0 and/or C1 discontinuities within a single element are developed for application to the Riemann problem, in which a contact discontinuity and shock wave form after the diaphragm bursts.

Canards in a minimal piecewise-linear square-wave burster

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

Desroches, M.; Krupa, M.; Fernández-García, S., E-mail: soledad@us.es

We construct a piecewise-linear (PWL) approximation of the Hindmarsh-Rose (HR) neuron model that is minimal, in the sense that the vector field has the least number of linearity zones, in order to reproduce all the dynamics present in the original HR model with classical parameter values. This includes square-wave bursting and also special trajectories called canards, which possess long repelling segments and organise the transitions between stable bursting patterns with n and n + 1 spikes, also referred to as spike-adding canard explosions. We propose a first approximation of the smooth HR model, using a continuous PWL system, and show that itsmore » fast subsystem cannot possess a homoclinic bifurcation, which is necessary to obtain proper square-wave bursting. We then relax the assumption of continuity of the vector field across all zones, and we show that we can obtain a homoclinic bifurcation in the fast subsystem. We use the recently developed canard theory for PWL systems in order to reproduce the spike-adding canard explosion feature of the HR model as studied, e.g., in Desroches et al., Chaos 23(4), 046106 (2013).« less

Source Mechanism of May 30, 2015 Bonin Islands, Japan Deep Earthquake (Mw7.8) Estimated by Broadband Waveform Modeling

NASA Astrophysics Data System (ADS)

Tsuboi, S.; Nakamura, T.; Miyoshi, T.

2015-12-01

May 30, 2015 Bonin Islands, Japan earthquake (Mw 7.8, depth 679.9km GCMT) was one of the deepest earthquakes ever recorded. We apply the waveform inversion technique (Kikuchi & Kanamori, 1991) to obtain slip distribution in the source fault of this earthquake in the same manner as our previous work (Nakamura et al., 2010). We use 60 broadband seismograms of IRIS GSN seismic stations with epicentral distance between 30 and 90 degrees. The broadband original data are integrated into ground displacement and band-pass filtered in the frequency band 0.002-1 Hz. We use the velocity structure model IASP91 to calculate the wavefield near source and stations. We assume that the fault is squared with the length 50 km. We obtain source rupture model for both nodal planes with high dip angle (74 degree) and low dip angle (26 degree) and compare the synthetic seismograms with the observations to determine which source rupture model would explain the observations better. We calculate broadband synthetic seismograms with these source propagation models using the spectral-element method (Komatitsch & Tromp, 2001). We use new Earth Simulator system in JAMSTEC to compute synthetic seismograms using the spectral-element method. The simulations are performed on 7,776 processors, which require 1,944 nodes of the Earth Simulator. On this number of nodes, a simulation of 50 minutes of wave propagation accurate at periods of 3.8 seconds and longer requires about 5 hours of CPU time. Comparisons of the synthetic waveforms with the observation at teleseismic stations show that the arrival time of pP wave calculated for depth 679km matches well with the observation, which demonstrates that the earthquake really happened below the 660 km discontinuity. In our present forward simulations, the source rupture model with the low-angle fault dipping is likely to better explain the observations.

True amplitude wave equation migration arising from true amplitude one-way wave equations

NASA Astrophysics Data System (ADS)

Zhang, Yu; Zhang, Guanquan; Bleistein, Norman

2003-10-01

One-way wave operators are powerful tools for use in forward modelling and inversion. Their implementation, however, involves introduction of the square root of an operator as a pseudo-differential operator. Furthermore, a simple factoring of the wave operator produces one-way wave equations that yield the same travel times as the full wave equation, but do not yield accurate amplitudes except for homogeneous media and for almost all points in heterogeneous media. Here, we present augmented one-way wave equations. We show that these equations yield solutions for which the leading order asymptotic amplitude as well as the travel time satisfy the same differential equations as the corresponding functions for the full wave equation. Exact representations of the square-root operator appearing in these differential equations are elusive, except in cases in which the heterogeneity of the medium is independent of the transverse spatial variables. Here, we address the fully heterogeneous case. Singling out depth as the preferred direction of propagation, we introduce a representation of the square-root operator as an integral in which a rational function of the transverse Laplacian appears in the integrand. This allows us to carry out explicit asymptotic analysis of the resulting one-way wave equations. To do this, we introduce an auxiliary function that satisfies a lower dimensional wave equation in transverse spatial variables only. We prove that ray theory for these one-way wave equations leads to one-way eikonal equations and the correct leading order transport equation for the full wave equation. We then introduce appropriate boundary conditions at z = 0 to generate waves at depth whose quotient leads to a reflector map and an estimate of the ray theoretical reflection coefficient on the reflector. Thus, these true amplitude one-way wave equations lead to a 'true amplitude wave equation migration' (WEM) method. In fact, we prove that applying the WEM imaging condition to these newly defined wavefields in heterogeneous media leads to the Kirchhoff inversion formula for common-shot data when the one-way wavefields are replaced by their ray theoretic approximations. This extension enhances the original WEM method. The objective of that technique was a reflector map, only. The underlying theory did not address amplitude issues. Computer output obtained using numerically generated data confirms the accuracy of this inversion method. However, there are practical limitations. The observed data must be a solution of the wave equation. Therefore, the data over the entire survey area must be collected from a single common-shot experiment. Multi-experiment data, such as common-offset data, cannot be used with this method as currently formulated. Research on extending the method is ongoing at this time.

Linking source region and ocean wave parameters with the observed primary microseismic noise

NASA Astrophysics Data System (ADS)

Juretzek, C.; Hadziioannou, C.

2017-12-01

In previous studies, the contribution of Love waves to the primary microseismic noise field was found to be comparable to those of Rayleigh waves. However, so far only few studies analysed both wave types present in this microseismic noise band, which is known to be generated in shallow water and the theoretical understanding has mainly evolved for Rayleigh waves only. Here, we study the relevance of different source region parameters on the observed primary microseismic noise levels of Love and Rayleigh waves simultaneously. By means of beamforming and correlation of seismic noise amplitudes with ocean wave heights in the period band between 12 and 15 s, we analysed how source areas of both wave types compare with each other around Europe. The generation effectivity in different source regions was compared to ocean wave heights, peak ocean gravity wave propagation direction and bathymetry. Observed Love wave noise amplitudes correlate comparably well with near coastal ocean wave parameters as Rayleigh waves. Some coastal regions serve as especially effective sources for one or the other wave type. These coincide not only with locations of high wave heights but also with complex bathymetry. Further, Rayleigh and Love wave noise amplitudes seem to depend equally on the local ocean wave heights, which is an indication for a coupled variation with swell height during the generation of both wave types. However, the wave-type ratio varies directionally. This observation likely hints towards a spatially varying importance of different source mechanisms or structural influences. Further, the wave-type ratio is modulated depending on peak ocean wave propagation directions which could indicate a variation of different source mechanism strengths but also hints towards an imprint of an effective source radiation pattern. This emphasizes that the inclusion of both wave types may provide more constraints for the understanding of acting generation mechanisms.

Analog circuit for the measurement of phase difference between two noisy sine-wave signals

NASA Technical Reports Server (NTRS)

Shakkottai, P.; Kwack, E. Y.; Back, L. H.

1989-01-01

A simple circuit was designed to measure the phase difference between two noisy sine waves. It locks over a wide range of frequencies and produces an output proportional to the phase difference of rapidly varying signals. A square wave locked in frequency and phase to the first signal is produced by a phase-locked loop and is amplified by an operational amplifier.

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

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

Dietz, Barbara; Iachello, Francesco; Macek, Michal

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

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

DOE PAGES

Dietz, Barbara; Iachello, Francesco; Macek, Michal

2017-08-07

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

Design of a simple non-destructive detection system using P-wave lasers for determining the soluble solids content of apples.

PubMed

Hua, Shih-Hao; Chen, Chao-Pin; Han, Pin

2017-08-01

The simple and nondestructive detection system studied in this work uses a near-infrared (NIR) detector and parallel-polarized (P-wave) NIR lasers to determine the soluble solids content (SSC) of apples. The P-wave NIR laser in this system is incident into the apple's pulp at the Brewster angle to minimize the interference caused by interfacial reflections. After the apple has been illuminated by four P-wave NIR lasers that correspond to the specified wavelengths of the SSC chemical bonds (880, 940, 980, and 1064 nm), the prediction of correlation (rp2) and the root-mean-square error for prediction (RMSEP) of the SSC are determined via partial least square regression analysis of the reflectance. Our results indicate that the use of P-wave lasers at the Brewster angle (as the angle of incidence) and the above specified wavelengths for the prediction set measurement of the SSC of apples obtained an rp2 of 0.88 and an RMSEP of 0.47°Brix. These rp2 are 6% higher, and the RMSEPs are 9% lower, than those obtained using non-polarized lasers.

High speed point derivative microseismic detector

DOEpatents

Uhl, J.E.; Warpinski, N.R.; Whetten, E.B.

1998-06-30

A high speed microseismic event detector constructed in accordance with the present invention uses a point derivative comb to quickly and accurately detect microseismic events. Compressional and shear waves impinging upon microseismic receiver stations disposed to collect waves are converted into digital data and analyzed using a point derivative comb including assurance of quiet periods prior to declaration of microseismic events. If a sufficient number of quiet periods have passed, the square of a two point derivative of the incoming digital signal is compared to a trip level threshold exceeding the determined noise level to declare a valid trial event. The squaring of the derivative emphasizes the differences between noise and signal, and the valid event is preferably declared when the trip threshold has been exceeded over a temporal comb width to realize a comb over a given time period. Once a trial event has been declared, the event is verified through a spatial comb, which applies the temporal event comb to additional stations. The detector according to the present invention quickly and accurately detects initial compressional waves indicative of a microseismic event which typically exceed the ambient cultural noise level by a small amount, and distinguishes the waves from subsequent larger amplitude shear waves. 9 figs.

High speed point derivative microseismic detector

DOEpatents

Uhl, James Eugene; Warpinski, Norman Raymond; Whetten, Ernest Blayne

1998-01-01

A high speed microseismic event detector constructed in accordance with the present invention uses a point derivative comb to quickly and accurately detect microseismic events. Compressional and shear waves impinging upon microseismic receiver stations disposed to collect waves are converted into digital data and analyzed using a point derivative comb including assurance of quiet periods prior to declaration of microseismic events. If a sufficient number of quiet periods have passed, the square of a two point derivative of the incoming digital signal is compared to a trip level threshold exceeding the determined noise level to declare a valid trial event. The squaring of the derivative emphasizes the differences between noise and signal, and the valid event is preferably declared when the trip threshold has been exceeded over a temporal comb width to realize a comb over a given time period. Once a trial event has been declared, the event is verified through a spatial comb, which applies the temporal event comb to additional stations. The detector according to the present invention quickly and accurately detects initial compressional waves indicative of a microseismic event which typically exceed the ambient cultural noise level by a small amount, and distinguishes the waves from subsequent larger amplitude shear waves.

Volume fraction instability in an oscillating non-Brownian iso-dense suspension.

NASA Astrophysics Data System (ADS)

Roht, Y. L.; Gauthier, G.; Hulin, J. P.; Salin, D.; Chertcoff, R.; Auradou, H.; Ippolito, I.

2017-06-01

The instability of an iso-dense non-Brownian suspension of polystyrene beads of diameter 40 μm dispersed in a water-glycerol mixture submitted to a periodic square wave oscillating flow in a Hele-Shaw cell is studied experimentally. The instability gives rise to stationary bead concentration waves transverse to the flow. It has been observed for average particle volume fractions between 0.25 and 0.4, for periods of the square wave flow variation between 0.4 and 10 s and in finite intervals of the amplitude of the fluid displacement. The study shows that the wavelength λ increases roughly linearly with the amplitude of the oscillatory flow; on the other hand, λ is independent of the particle concentration and of the period of oscillation of the flow although the minimum threshold amplitude for observing the instability increases with the period.

Design and numerical analysis of a THz square porous-core photonic crystal fiber for low flattened dispersion, ultrahigh birefringence.

PubMed

Luo, Jianfeng; Tian, Fengjun; Qu, Hongkun; Li, Li; Zhang, Jianzhong; Yang, Xinhua; Yuan, Libo

2017-08-20

We propose a kind of square porous-core photonic crystal fiber (PCF) for polarization-maintaining terahertz (THz) wave guidance. An asymmetry is introduced by implementing rectangular array air holes in the porous core of the PCF, and ultrahigh birefringence and low effective material loss (EML) can be achieved simultaneously. The properties of THz wave propagation are analyzed numerically in detail. The numerical results indicate that the proposed fiber offers a high birefringence of 0.063 and a low EML of 0.081  cm -1 at 1 THz. Moreover, a very low flattened dispersion profile is observed over a wide frequency domain of 0.85-1.9 THz. The zero flattened dispersion can be controlled. It is predicted that this PCF would be used potentially in polarization maintaining and dispersion management of THz waves.

A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes.

PubMed

Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

2015-03-01

A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm(3)) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

Evaluation of a dense seismic array for acquisition of high quality data in the ACROSS observation

NASA Astrophysics Data System (ADS)

Tsuruga, K.; Kunitomo, T.; Hasada, Y.; Kumazawa, M.; Shigeta, N.; Kasahara, J.

2004-12-01

ACROSS is an active monitoring methodology to detect any subtle temporal change of physical properties in the Earth's interior. We demonstrate the potentiality of the ACROSS observation with a dense sensor array. We have conducted a dense seismic array observation at the distance of 1 km from the ACROSS source since 2003. The array is composed of 36 three-component velocity seismometers buried at 1.8 m deep in an area 25 m square. All the data are recorded accurately referring to a GPS clock. We derived and analyzed a transfer function (TF) from the source to a receiver by the following steps: (1) evaluating a force vector as source characteristics, (2) converting the observed data to the displacement vectors by incorporating all the corrections of the instruments, (3) stacking the observed data for an enough time to suppress the temporal noise, (4) extracting ACROSS signal and evaluating noise level, (5) representing TF in a tensor form with the estimated errors, (6) slant-stacking with variable ray parameters, (7) estimating the travel times and amplitudes of the wave arrivals by Sompi Event Analysis (Hasada et al., 2001) and representing the result by a pulse sequence, and (8) deriving the polarization vector for each arrival to identify all the wave modes. We analyzed TF of SH-wave component from 16 to 20 Hz as an example. We obtained good quality TF with S/N ratio up to 104 by stacking for 12 days at the step (3). The spatial noise originated from the local heterogeneity around the array was eliminated by the step (6). Several arrivals were recognized within the time windows from 0.6 to 1.8 s. The maximum amplitude of event traces was detected at the travel time of 1.064 s with a ray parameter of 7.9x10-4 s/m. We also found the scattered waves probably generated by the heterogeneities around the array. The ACROSS dense array observation would provide a lot of information on the underground heterogeneities. Consequently, we have the important and challenging subjects: (1) optimum designing of ACROSS array to acquire the better data and (2) development of new theoretical method to deal with the variable types of the wave.

Investigating the mechanism of aggregation of colloidal particles during electrophoretic deposition

NASA Astrophysics Data System (ADS)

Guelcher, Scott Arthur

Charged particles deposited near an electrode aggregate to form ordered clusters in the presence of both dc and ac applied electric fields. The aggregation process could have important applications in areas such as coatings technology and ceramics processing. This thesis has sought to identify the phenomena driving the aggregation process. According to the electroosmotic flow developed by Solomentsev et al. (1997), aggregation in dc electric fields is caused by convection in the electroosmotic flow about deposited particles, and it is therefore an electrokinetic phenomenon which scales linearly with the electric field and the zeta-potential of the particles. Trajectories of pairs of particles aggregating to form doublets have been shown to scale linearly with the electric field and the zeta-potential of the particles, as predicted by the electroosmotic flow model. Furthermore, quantitative agreement has been demonstrated between the experimental and calculated trajectories for surface-to-surface separation distances between the particles ranging from one to two radii. The trajectories were calculated from the electroosmotic flow model with no fitting parameters; the only inputs to the model were the mobility of the deposited particles, the zeta- potential of the particles, and the applied electric field, all of which were measured independently. Clustering of colloidal particles deposited near an electrode in ac fields has also been observed, but a suitable model for the aggregation process has not been proposed and quantitative data in the literature are scarce. Trajectories of pairs of particles aggregating to form doublets in an ac field have been shown to scale with the root-mean-square (rms) electric field raised to the power 1.4 over the range of electric fields 10-35 V/cm (100-Hz sine and square waves). The aggregation is also frequency dependent; the doublets aggregate fastest at 30 Hz (square wave) and slowest at 500 Hz (square wave), while the interaction is repulsive at 1 kHz (square wave). The advantage of ac fields is that the process can operated at frequencies sufficiently high to avoid the negative effects of electrochemical reactions.

Quantified Energy Dissipation Rates in the Terrestrial Bow Shock. 2; Waves and Dissipation

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Sibeck, D. G.; Breneman, A. W.; Le Contel, O.; Cully, C.; Turner, D. L.; Angelopoulos, V.; Malaspina, D. M.

2014-01-01

We present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collision-less bow shock using data from the Time History of Events and Macro-Scale Interactions during Sub-Storms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collision-less shocks. In every bow shock crossing examined, we observed both low-frequency (less than 10 hertz) and high-frequency (approximately or greater than10 hertz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding delta B approximately equal to 10 nanoteslas and delta E approximately equal to 300 millivolts per meter, though more typical values were delta B approximately equal to 0.1-1.0 nanoteslas and delta E approximately equal to 10-50 millivolts per meter (2) Poynting fluxes in excess of 2000 microWm(sup -2) (micro-waves per square meter) (typical values were approximately 1-10 microWm(sup -2) (micro-waves per square meter); (3) resistivities greater than 9000 omega meters; and (4) associated energy dissipation rates greater than 10 microWm(sup -3) (micro-waves per cubic meter). The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for approximately 90 percent of the wave burst durations. For approximately 22 percent of these times, the wave-particle interactions needed to only be less than or equal to 0.1 percent efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collision-less shocks.

The New Method of Tsunami Source Reconstruction With r-Solution Inversion Method

NASA Astrophysics Data System (ADS)

Voronina, T. A.; Romanenko, A. A.

2016-12-01

Application of the r-solution method to reconstructing the initial tsunami waveform is discussed. This methodology is based on the inversion of remote measurements of water-level data. The wave propagation is considered within the scope of a linear shallow-water theory. The ill-posed inverse problem in question is regularized by means of a least square inversion using the truncated Singular Value Decomposition method. As a result of the numerical process, an r-solution is obtained. The method proposed allows one to control the instability of a numerical solution and to obtain an acceptable result in spite of ill posedness of the problem. Implementation of this methodology to reconstructing of the initial waveform to 2013 Solomon Islands tsunami validates the theoretical conclusion for synthetic data and a model tsunami source: the inversion result strongly depends on data noisiness, the azimuthal and temporal coverage of recording stations with respect to the source area. Furthermore, it is possible to make a preliminary selection of the most informative set of the available recording stations used in the inversion process.

The Inverse-Square Law with Data Loggers

ERIC Educational Resources Information Center

Bates, Alan

2013-01-01

The inverse-square law for the intensity of light received at a distance from a light source has been verified using various experimental techniques. Typical measurements involve a manual variation of the distance between a light source and a light sensor, usually by sliding the sensor or source along a bench, measuring the source-sensor distance…

Ultrasonic tracking of shear waves using a particle filter

PubMed Central

Ingle, Atul N.; Ma, Chi; Varghese, Tomy

2015-01-01

Purpose: This paper discusses an application of particle filtering for estimating shear wave velocity in tissue using ultrasound elastography data. Shear wave velocity estimates are of significant clinical value as they help differentiate stiffer areas from softer areas which is an indicator of potential pathology. Methods: Radio-frequency ultrasound echo signals are used for tracking axial displacements and obtaining the time-to-peak displacement at different lateral locations. These time-to-peak data are usually very noisy and cannot be used directly for computing velocity. In this paper, the denoising problem is tackled using a hidden Markov model with the hidden states being the unknown (noiseless) time-to-peak values. A particle filter is then used for smoothing out the time-to-peak curve to obtain a fit that is optimal in a minimum mean squared error sense. Results: Simulation results from synthetic data and finite element modeling suggest that the particle filter provides lower mean squared reconstruction error with smaller variance as compared to standard filtering methods, while preserving sharp boundary detail. Results from phantom experiments show that the shear wave velocity estimates in the stiff regions of the phantoms were within 20% of those obtained from a commercial ultrasound scanner and agree with estimates obtained using a standard method using least-squares fit. Estimates of area obtained from the particle filtered shear wave velocity maps were within 10% of those obtained from B-mode ultrasound images. Conclusions: The particle filtering approach can be used for producing visually appealing SWV reconstructions by effectively delineating various areas of the phantom with good image quality properties comparable to existing techniques. PMID:26520761

Shock wave oscillation driven by turbulent boundary layer fluctuations

NASA Technical Reports Server (NTRS)

Plotkin, K. J.

1972-01-01

Pressure fluctuations due to the interaction of a shock wave with a turbulent boundary layer were investigated. A simple model is proposed in which the shock wave is convected from its mean position by velocity fluctuations in the turbulent boundary layer. Displacement of the shock is assumed limited by a linear restoring mechanism. Predictions of peak root mean square pressure fluctuation and spectral density are in excellent agreement with available experimental data.

Design Parameters of a Miniaturized Piezoelectric Underwater Acoustic Transmitter

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

Li, Huidong; Deng, Zhiqun; Yuan, Yong

2012-07-02

The Juvenile Salmon Acoustic Telemetry System (JSATS) project supported by the U.S. Army Corps of Engineers, Portland District, has yielded the smallest acoustic fish tag transmitter commercially available to date. In order to study even smaller fish populations and make the transmitter injectable by needles, the JSATS acoustic micro transmitter needs to be further downsized. As part of the transmitter downsizing effort some of the design parameters of the lead zirconate titanate (PZT) ceramic tube transducer in the transmitter were studied, including the type of PZT, the backing material, the necessary drive voltage, the transmitting bandwidth and the length ofmore » the transducer. It was found that, to satisfy the 156-dB source level requirement of JSATS, a square wave with a 10-volt amplitude is required to drive 'soft' PZT transducers. PZT-5H demonstrated the best source level performance. For Navy types I and II, 16 volts or 18 volts were needed. Ethylene-propylene-diene monomer (EPDM) closed-cell foam was found to be the backing material providing the highest source level. The effect of tube length on the source level is also demonstrated in this paper, providing quantitative information for downsizing of small piezoelectric transmitters.« less

Application of a simplified calculation for full-wave microtremor H/ V spectral ratio based on the diffuse field approximation to identify underground velocity structures

NASA Astrophysics Data System (ADS)

Wu, Hao; Masaki, Kazuaki; Irikura, Kojiro; Sánchez-Sesma, Francisco José

2017-12-01

Under the diffuse field approximation, the full-wave (FW) microtremor H/ V spectral ratio ( H/ V) is modeled as the square root of the ratio of the sum of imaginary parts of the Green's function of the horizontal components to that of the vertical one. For a given layered medium, the FW H/ V can be well approximated with only surface waves (SW) H/ V of the "cap-layered" medium which consists of the given layered medium and a new larger velocity half-space (cap layer) at large depth. Because the contribution of surface waves can be simply obtained by the residue theorem, the computation of SW H/ V of cap-layered medium is faster than that of FW H/ V evaluated by discrete wavenumber method and contour integration method. The simplified computation of SW H/ V was then applied to identify the underground velocity structures at six KiK-net strong-motion stations. The inverted underground velocity structures were used to evaluate FW H/ Vs which were consistent with the SW H/ Vs of corresponding cap-layered media. The previous study on surface waves H/ Vs proposed with the distributed surface sources assumption and a fixed Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement with the SW H/ Vs of our study. The consistency between observed and theoretical spectral ratios, such as the earthquake motions of H/ V spectral ratio and spectral ratio of horizontal motions between surface and bottom of borehole, indicated that the underground velocity structures identified from SW H/ V of cap-layered medium were well resolved by the new method.[Figure not available: see fulltext.

Full duplex fiber link for alternative wired and wireless access based on SSB optical millimeter-wave with 4-PAM signal

NASA Astrophysics Data System (ADS)

Ma, Jianxin; Zhang, Junjie

2015-03-01

A novel full-duplex fiber-wireless link based on single sideband (SSB) optical millimeter (mm)-wave with 10 Gbit/s 4-pulse amplitude modulation (PAM) signal is proposed to provide alternative wired and 40 GHz wireless accesses for the user terminals. The SSB optical mm-wave with 4-PAM signal consists of two tones: one bears the 4-PAM signal and the other is unmodulated with high power. After transmission over the fiber to the hybrid optical network unit (HONU), the SSB optical mm-wave signal can be decomposed by fiber Bragg gratings (FBGs) as the SSB optical mm-wave signal with reduced carrier-to-sideband ratio (the baseband 4-PAM optical signal) and the uplink optical carrier for the wireless (wired) access. This makes the HONU free from the laser source. For the uplink, since the wireless access signal is converted to the baseband by power detection, both the transmitter in the HONU and the receiver in optical line terminal (OLT) are co-shared for both wireless and wired accesses, which makes the full duplex link much simpler. In our scheme, the optical electrical field of the square-root increment level 4-PAM signal assures an equal level spacing receiving for both the downlink wired and wireless accesses. Since the downlink wireless signal is down-converted to the baseband by power detection, RF local oscillator is unnecessary. To confirm the feasibility of our proposed scheme, a simulation full duplex link with 40 GHz SSB optical mm-wave with 10 Gbit/s 4-PAM signal is built. The simulation results show that both down- and up-links for either wired or wireless access can keep good performance even if the link length of the SSMF is extended to 40 km.

Seasonality of P wave microseisms from NCF-based beamforming using ChinArray

NASA Astrophysics Data System (ADS)

Wang, Weitao; Gerstoft, Peter; Wang, Baoshan

2018-06-01

Teleseismic P wave microseisms produce interference signals with high apparent velocity in noise cross-correlation functions (NCFs). Sources of P wave microseisms can be located with NCFs from seismic arrays. Using the vertical-vertical component NCFs from a large-aperture array in southwestern China (ChinArray), we studied the P wave source locations and their seasonality of microseisms at two period bands (8-12 and 4-8 s) with an NCF-based beamforming method. The sources of P, PP and PKPbc waves are located. The ambiguity between P and PP source locations is analysed using averaged significant ocean wave height and sea surface pressure as constraints. The results indicate that the persistent P wave sources are mainly located in the deep oceans such as the North Atlantic, North Pacific and Southern Ocean, in agreement with previous studies. The Gulf of Alaska is found to generate P waves favouring the 8-12 s period band. The seasonality of P wave sources is consistent with the hemispheric storm pattern, which is stronger in local winter. Using the identified sources, arrival times of the interference signals are predicted and agree well with observations. The interference signals exhibit seasonal variation, indicating that body wave microseisms in southwestern China are from multiple seasonal sources.

Shear Wave Generation and Modeling Ground Motion From a Source Physics Experiment (SPE) Underground Explosion

NASA Astrophysics Data System (ADS)

Pitarka, Arben; Mellors, Robert; Rodgers, Arthur; Vorobiev, Oleg; Ezzedine, Souheil; Matzel, Eric; Ford, Sean; Walter, Bill; Antoun, Tarabay; Wagoner, Jeffery; Pasyanos, Mike; Petersson, Anders; Sjogreen, Bjorn

2014-05-01

We investigate the excitation and propagation of far-field (epicentral distance larger than 20 m) seismic waves by analyzing and modeling ground motion from an underground chemical explosion recorded during the Source Physics Experiment (SPE), Nevada. The far-field recorded ground motion is characterized by complex features, such as large azimuthal variations in P- and S-wave amplitudes, as well as substantial energy on the tangential component of motion. Shear wave energy is also observed on the tangential component of the near-field motion (epicentral distance smaller than 20 m) suggesting that shear waves were generated at or very near the source. These features become more pronounced as the waves propagate away from the source. We address the shear wave generation during the explosion by modeling ground motion waveforms recorded in the frequency range 0.01-20 Hz, at distances of up to 1 km. We used a physics based approach that combines hydrodynamic modeling of the source with anelastic modeling of wave propagation in order to separate the contributions from the source and near-source wave scattering on shear motion generation. We found that wave propagation scattering caused by the near-source geological environment, including surface topography, contributes to enhancement of shear waves generated from the explosion source. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-06NA25946/ NST11-NCNS-TM-EXP-PD15.

Distributional Tests for Gravitational Waves from Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Szczepanczyk, Marek; LIGO Collaboration

2017-01-01

Core-Collapse Supernovae (CCSN) are spectacular and violent deaths of massive stars. CCSN are some of the most interesting candidates for producing gravitational-waves (GW) transients. Current published results focus on methodologies to detect single GW unmodelled transients. The advantages of these tests are that they do not require a background for which we have an analytical model. Examples of non-parametric tests that will be compared are Kolmogorov-Smirnov, Mann-Whitney, chi squared, and asymmetric chi squared. I will present methodological results using publicly released LIGO-S6 data recolored to the design sensitivity of Advanced LIGO and that will be time lagged between interferometers sites so that the resulting coincident events are not GW.

A square-wave wavelength modulation system for automatic background correction in carbon furnace atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Bezur, L.; Marshall, J.; Ottaway, J. M.

A square-wave wavelength modulation system, based on a rotating quartz chopper with four quadrants of different thicknesses, has been developed and evaluated as a method for automatic background correction in carbon furnace atomic emission spectrometry. Accurate background correction is achieved for the residual black body radiation (Rayleigh scatter) from the tube wall and Mie scatter from particles generated by a sample matrix and formed by condensation of atoms in the optical path. Intensity modulation caused by overlap at the edges of the quartz plates and by the divergence of the optical beam at the position of the modulation chopper has been investigated and is likely to be small.

Making High-Pass Filters For Submillimeter Waves

NASA Technical Reports Server (NTRS)

Siegel, Peter H.; Lichtenberger, John A.

1991-01-01

Micromachining-and-electroforming process makes rigid metal meshes with cells ranging in size from 0.002 in. to 0.05 in. square. Series of steps involving cutting, grinding, vapor deposition, and electroforming creates self-supporting, electrically thick mesh. Width of holes typically 1.2 times cutoff wavelength of dominant waveguide mode in hole. To obtain sharp frequency-cutoff characteristic, thickness of mesh made greater than one-half of guide wavelength of mode in hole. Meshes used as high-pass filters (dichroic plates) for submillimeter electromagnetic waves. Process not limited to square silicon wafers. Round wafers also used, with slightly more complication in grinding periphery. Grid in any pattern produced in electroforming mandrel. Any platable metal or alloy used for mesh.

Dual-pulses and harmonic patterns of a square-wave soliton in passively mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Zhang, Jing; Jia, Qingsong; Jiang, Huilin

2018-06-01

We demonstrate a square-wave soliton pulse passively mode-locked fiber laser. The mode-locked pulses are achieved by using a nonlinear amplifying loop mirror. Single-pulse operation at a fundamental repetition rate of 3.2 MHz is obtained. The optical spectrum presents the soliton feature of several sidebands. The pulse duration expands with increasing pump power, but the amplitude hardly varies. Pulse breaking occurs and a stable dual-pulse is obtained with a fixed interval of 48 ns. Harmonic mode-locked states can be achieved when the total pump power is higher than 740 mW. The harmonic pulses can also operate in both single-pulse and dual-pulse states.

Babinet's principle and the band structure of surface waves on patterned metal arrays

NASA Astrophysics Data System (ADS)

Edmunds, J. D.; Taylor, M. C.; Hibbins, A. P.; Sambles, J. R.; Youngs, I. J.

2010-05-01

The microwave response of an array of square metal patches and its complementary structure, an array of square holes, has been experimentally studied. The resonant phenomena, which yield either enhanced transmission or reflection, are attributed to the excitation of diffractively coupled surface waves. The band structure of these surface modes has been quantified for both p-(transverse magnetic) and s-(transverse electric) polarized radiation and is found to be dependent on the periodicity of the electric and magnetic fields on resonance. The results are in excellent accord with predictions from finite element method modeling and the electromagnetic form of Babinet's principle [Babinet, C. R. Acad. Sci. 4, 638 (1837)].

Quantifying High Frequency Skill and Relative Cost of Two Physics Packages for an Operational Spectral Wave Model

NASA Astrophysics Data System (ADS)

Edwards, K. L.; Siqueira, S. A.; Rogers, W. E.

2017-12-01

Simulating WAves Nearshore (SWAN) is one of the two phase-averaged spectral models used by the U.S. Navy for forecasting waves. The source term package available during SWAN's first validation for operational use in 2002 is referred to here as "SWAN-ST1". Since then, improvements to the source term package were implemented (SWAN-ST6). One outcome of the new package is better skill within the higher frequencies of the spectrum, where SWAN-ST1 gives non-physical response to changes in wind speed and non-physical response to presence of swell in the lower frequencies. However, SWAN-ST6 is typically 25% more expensive computationally than SWAN-ST1, so it is worthwhile to estimate its benefit to operational cases, where computation time is a primary concern. To validate SWAN-ST6 and quantify its improvement over SWAN-ST1, we apply the model to two geographic regions—the Northern Gulf of Mexico (NGoM) and Southern California (SoCal) coasts. The NGoM case is typified by smaller fetch and smaller swell contribution. We analyze the NGoM case for a year (2010 July-2011 Aug.); and the SoCal application for summer (2016 July-Aug.) and winter (2017 Jan.-Feb.) seasons. We compare results to available buoy data. The wave parameter mean square slope (MSS) is included in this study, since it is sensitive to accuracy (or lack thereof) at higher frequencies, as it is weighted by frequency to the fourth power. Model-data comparisons for the NGoM case show little benefit to using SWAN-ST6; both models highly correlate with observations, a result attributable to a) the lack of swell and b) the fact that the shorter dominant periods in this basin imply that available buoys typically measure very little of the spectral tail (e.g. 2 to 4 times the peak frequency). Model-data comparisons for the SoCal test case show that SWAN-ST6 performs at least as well but most often better than SWAN-ST1. The improvement is almost negligible for the lower order moments, significant wave height and period, which are less sensitive to the spectral tail. However, SWAN-ST6 in the SoCal case dramatically improves the comparisons of MSS relative to SWAN-ST1. Thus, results show that, in cases where the wave climate and frequency range of buoy data permit validation of the spectral tail, skill of MSS prediction is dramatically improved with the new source term package.

Shear Wave Structure of Umbria and Marche, Italy, Strong Motion Seismometer Sites Affected by the 1997-98 Umbria-Marche, Italy, Earthquake Sequence

USGS Publications Warehouse

Kayen, Robert; Scasserra, Giuseppe; Stewart, Jonathan P.; Lanzo, Giuseppe

2008-01-01

A long sequence of earthquakes, eight with magnitudes between 5 and 6, struck the Umbria and Marche regions of central Italy between September 26, 1997 and July 1998. The earthquake swarm caused severe structural damage, particularly to masonry buildings, and resulted in the loss of twelve lives and about 150 injuries. The source of the events was a single seismogenic structure that consists of several faults with a prevailing northwest-southeast strike and crosses the Umbria-Marche border. The focal mechanism of the largest shocks indicates that the events were the product of shallow extensional normal faulting along a NE-SW extension perpendicular to the trend of the Apennines. The network of analog seismometer stations in the Umbria and Marche regions recorded motions of the main September and October 1997 events and a dense array of mobile digital stations, installed since September 29, recorded most of the swarm. The permanent national network Rete Accelerometrica Nazionale (RAN) is administered and maintained by Dipartimento delle Protezione Civile (DPC: Civil Protection Department); the temporary array was managed by Servizio Sismico Nazionale (SSN) in cooperation with small agencies and Universities. ENEA, the operator of many seismometer stations in Umbria, is the public Italian National Agency for New Technologies, Energy and the Environment. Many of the temporary and permanent stations in the Italian seismic network have little or no characterization of seismic velocities. In this study, we investigated 17 Italian sites using an active-source approach that employs low frequency harmonic waves to measure the dispersive nature of surface waves in the ground. We used the Spectral Analysis of Surface Wave (SASW) approach, coupled with an array of harmonic-wave electro-mechanical sources that are driven in-phase to excite the ground. An inversion algorithm using a non-linear least-squares best-fit method is used to compute shear wave velocities for up to 100 meters of the soil column. A draft report was published in the summer of 2008, followed by a comment period, lengthy discussions with Italian colleagues, and improved knowledge of the subsurface at the sites from soil logs. Four of the sites were reprocessed in order to correct issues with phase unwrapping of the field dispersion curves that complicated the velocity profile calculations at the lowest velocity sites. This report presents the final results from the reprocessing effort.

Oscillating square wave Transcranial Direct Current Stimulation (tDCS) delivered during slow wave sleep does not improve declarative memory more than sham: A randomized sham controlled crossover study

PubMed Central

Sahlem, Gregory L.; Badran, Bashar W.; Halford, Jonathan J.; Williams, Nolan R.; Korte, Jeffrey E.; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L.; Runion, Jennifer; Bachman, David L.; Uhde, Thomas W.; Borckardt, Jeffery J.; George, Mark S.

2015-01-01

Background A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current wave form (square in our study, nearly sinusoidal in the original). Objective/Hypothesis Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Methods Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517mA/CM2, and oscillated between zero and maximal current at a frequency of 0.75Hz. Stimulation occurred during five-five minute blocks with one-minute inter-block intervals (25 minutes total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. Results There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1±3.0SD more associations) (sham = 3.8±3.1S.D more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6±2.7 S.D. correctly typed sequences) compared to sham stimulation (2.3± 2.2 S.D. correctly typed sequences)]. Conclusion In this study, we failed to find improvements in declarative or performance memory and could not replicate an earlier study using nearly identical settings. Specifically we failed to find a beneficial effect on either overnight declarative or non-declarative memory consolidation via square-wave oscillating tDCS intervention applied bi-frontally during early NREM sleep. It is unclear if the morphology of the tDCS pulse is critical in any memory related improvements. PMID:25795621

Signal processing method of the diameter measurement system based on CCD parallel light projection method

NASA Astrophysics Data System (ADS)

Song, Qing; Zhu, Sijia; Yan, Han; Wu, Wenqian

2008-03-01

Parallel light projection method for the diameter measurement is to project the workpiece to be measured on the photosensitive units of CCD, but the original signal output from CCD cannot be directly used for counting or measurement. The weak signal with high-frequency noise should be filtered and amplified firstly. This paper introduces RC low-pass filter and multiple feed-back second-order low-pass filter with infinite gain. Additionally there is always dispersion on the light band and the output signal has a transition between the irradiant area and the shadow, because of the instability of the light source intensity and the imperfection of the light system adjustment. To obtain exactly the shadow size related to the workpiece diameter, binary-value processing is necessary to achieve a square wave. Comparison method and differential method can be adopted for binary-value processing. There are two ways to decide the threshold value when using voltage comparator: the fixed level method and the floated level method. The latter has a high accuracy. Deferential method is to output two spike pulses with opposite pole by the rising edge and the failing edge of the video signal related to the differential circuit firstly, then the rising edge of the signal output from the differential circuit is acquired by half-wave rectifying circuit. After traveling through the zero passing comparator and the maintain- resistance edge trigger, the square wave which indicates the measured size is acquired at last. And then it is used for filling through standard pulses and for counting through the counter. Data acquisition and information processing is accomplished by the computer and the control software. This paper will introduce in detail the design and analysis of the filter circuit, binary-value processing circuit and the interface circuit towards the computer.

Millimeter Wave Sensor For On-Line Inspection Of Thin Sheet Dielectrics

DOEpatents

Bakhtiari, Sasan; Gopalsami, Nachappa; Raptis, Apostolos C.

1999-03-23

A millimeter wave sensor is provided for non-destructive inspection of thin sheet dielectric materials. The millimeter wave sensor includes a Gunn diode oscillator (GDO) source generating a mill meter wave electromagnetic energy signal having a single frequency. A heater is coupled to the GDO source for stabilizing the single frequency. A small size antenna is coupled to the GDO source for transmitting the millimeter wave electromagnetic energy signal to a sample material and for receiving a reflected millimeter wave electromagnetic energy signal from the sample material. Ferrite circulator isolators coupled between the GDO source and the antenna separate the millimeter wave electromagnetic energy signal into transmitted and received electromagnetic energy signal components and a detector detects change in both amplitude and phase of the transmitted and received electromagnetic energy signal components. A millimeter wave sensor is provided for non-destructive inspection of thin sheet dielectric materials. The millimeter wave sensor includes a Gunn diode oscillator (GDO) source generating a mill meter wave electromagnetic energy signal having a single frequency. A heater is coupled to the GDO source for stabilizing the single frequency. A small size antenna is coupled to the GDO source for transmitting the millimeter wave electromagnetic energy signal to a sample material and for receiving a reflected millimeter wave electromagnetic energy signal from the sample material. Ferrite circulator isolators coupled between the GDO source and the antenna separate the millimeter wave electromagnetic energy signal into transmitted and received electromagnetic energy signal components and a detector detects change in both amplitude and phase of the transmitted and received electromagnetic energy signal components.

Separation of the low-frequency atmospheric variability into non-Gaussian multidimensional sources by Independent Subspace Analysis

NASA Astrophysics Data System (ADS)

Pires, Carlos; Ribeiro, Andreia

2016-04-01

An efficient nonlinear method of statistical source separation of space-distributed non-Gaussian distributed data is proposed. The method relies in the so called Independent Subspace Analysis (ISA), being tested on a long time-series of the stream-function field of an atmospheric quasi-geostrophic 3-level model (QG3) simulating the winter's monthly variability of the Northern Hemisphere. ISA generalizes the Independent Component Analysis (ICA) by looking for multidimensional and minimally dependent, uncorrelated and non-Gaussian distributed statistical sources among the rotated projections or subspaces of the multivariate probability distribution of the leading principal components of the working field whereas ICA restrict to scalar sources. The rationale of that technique relies upon the projection pursuit technique, looking for data projections of enhanced interest. In order to accomplish the decomposition, we maximize measures of the sources' non-Gaussianity by contrast functions which are given by squares of nonlinear, cross-cumulant-based correlations involving the variables spanning the sources. Therefore sources are sought matching certain nonlinear data structures. The maximized contrast function is built in such a way that it provides the minimization of the mean square of the residuals of certain nonlinear regressions. The issuing residuals, followed by spherization, provide a new set of nonlinear variable changes that are at once uncorrelated, quasi-independent and quasi-Gaussian, representing an advantage with respect to the Independent Components (scalar sources) obtained by ICA where the non-Gaussianity is concentrated into the non-Gaussian scalar sources. The new scalar sources obtained by the above process encompass the attractor's curvature thus providing improved nonlinear model indices of the low-frequency atmospheric variability which is useful since large circulation indices are nonlinearly correlated. The non-Gaussian tested sources (dyads and triads, respectively of two and three dimensions) lead to a dense data concentration along certain curves or surfaces, nearby which the clusters' centroids of the joint probability density function tend to be located. That favors a better splitting of the QG3 atmospheric model's weather regimes: the positive and negative phases of the Arctic Oscillation and positive and negative phases of the North Atlantic Oscillation. The leading model's non-Gaussian dyad is associated to a positive correlation between: 1) the squared anomaly of the extratropical jet-stream and 2) the meridional jet-stream meandering. Triadic sources coming from maximized third-order cross cumulants between pairwise uncorrelated components reveal situations of triadic wave resonance and nonlinear triadic teleconnections, only possible thanks to joint non-Gaussianity. That kind of triadic synergies are accounted for an Information-Theoretic measure: the Interaction Information. The dominant model's triad occurs between anomalies of: 1) the North Pole anomaly pressure 2) the jet-stream intensity at the Eastern North-American boundary and 3) the jet-stream intensity at the Eastern Asian boundary. Publication supported by project FCT UID/GEO/50019/2013 - Instituto Dom Luiz.

The natural diatomite from caldiran-van (Turkey): electroanalytical application to antimigraine compound naratriptan at modified carbon paste electrode.

PubMed

Calışkan, Necla; Sögüt, Eda; Saka, Cafer; Yardım, Yavuz; Sentürk, Zuhre

2010-09-01

This paper is the first report describing the characterization of local diatomite of Caldiran-Van region (Eastern Anatolia, Turkey). Special attention was paid to the ability of its electroanalytical performance at modified electrodes and to the potential application of diatomite-modified electrode. For this purpose, the determination of Naratriptan which is a novel oral triptan (5-hydroxytryptamine receptor agonist) in migraine treatment, by means of a carbon paste electrode modified with 10% (w/w) of diatomite was studied using cyclic and square-wave voltammetry. The experimental conditions that affect the electrode reaction process were studied in terms of pH of the supporting electrolyte, scan rate, accumulation variables, modifier composition and square-wave parameters. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 4.0 at 0.84 V (vs. Ag/AgCl) (a pre-concentration step being carried out with an open circuit at 120 s). The process could be used to determine Naratriptan concentrations in the range 5x10(-7)-9x10(-7) M, with a detection limit of 1.25x10(-7) M (46.5 mug L(-1)). The applicability of the method to spiked human urine samples was illustrated.

Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts

NASA Astrophysics Data System (ADS)

LIGO Scientific Collaboration; Virgo Collaboration; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Ajith, P.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Beker, M. G.; Bell, A. S.; Belletoile, A.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarin, E.; Chaibi, O.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; Dayanga, T.; DeRosa, R.; Debra, D.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Del Prete, M.; Dent, T.; Dergachev, V.; Derosa, R.; Desalvo, R.; Dhillon, V.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; De Paolo Emilio, M.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Diguglielmo, J.; Donovan, F.; Dooley, K. L.; Dorsher, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Endröczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Farr, W.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Flanigan, M.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fridriksson, J. K.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P. J.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Ganija, M. R.; Garcia, J.; Garofoli, J. A.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Geng, R.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Gray, N.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Ha, T.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Homan, J.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; Jang, H.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kamaretsos, I.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B.; Kim, C.; Kim, D.; Kim, H.; Kim, K.; Kim, N.; Kim, Y.-M.; King, P. J.; Kinsey, M.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Krâ´Olak, A.; Kuehn, G.; Kumar, R.; Kwee, P.; Laas-Bourez, M.; Lam, P. K.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Leaci, P.; Lee, C. H.; Lee, H. M.; Leindecker, N.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Luan, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; MacDonald, E.; Machenschalk, B.; Macinnis, M.; MacLeod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marandi, A.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McDaniel, P.; McGuire, S. C.; McIntyre, G.; McIver, J.; McKechan, D. J. A.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menendez, D.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Moesta, P.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Mosca, S.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Nawrodt, R.; Necula, V.; Nelson, J.; Newton, G.; Nishizawa, A.; Nocera, F.; Nolting, D.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pedraza, M.; Peiris, P.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Phelps, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C. R.; Rankins, B.; Rapagnani, P.; Rapoport, S.; Raymond, V.; Re, V.; Redwine, K.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Ryll, H.; Sainathan, P.; Sakosky, M.; Salemi, F.; Samblowski, A.; Sammut, L.; Sancho de La Jordana, L.; Sandberg, V.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schlamminger, S.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Smith, R. J. E.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Stein, A. J.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Tseng, K.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, X.; Wang, Z.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zadroźny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhang, W.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; Akerlof, C.; Boer, M.; Fender, R.; Gehrels, N.; Klotz, A.; Ofek, E. O.; Smith, M.; Sokolowski, M.; Stappers, B. W.; Steele, I.; Swinbank, J.; Wijeres, R. A. M. J.

2012-04-01

Aims: A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods: During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results: For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with ~50% or better probability with a few pointings of wide-field telescopes.

Implementation and Testing of the First Prompt for Electromagnetic Counterparts to Gravitational Wave Transients

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.;

Implementation and Testing of the First Prompt Search for Gravitational Wave Transients with Electromagnetic Counterparts

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.;

The excitation of spiral density waves through turbulent fluctuations in accretion discs - II. Numerical simulations with MRI-driven turbulence

NASA Astrophysics Data System (ADS)

Heinemann, T.; Papaloizou, J. C. B.

2009-07-01

We present fully three-dimensional local simulations of compressible magneto-rotational instability (MRI) turbulence with the object of studying and elucidating the excitation of the non-axisymmetric spiral density waves that are observed to always be present in such simulations. They are potentially important for affecting protoplanetary migration through the action of associated stochastic gravitational forces and producing residual transport in MHD inactive regions through which they may propagate. The simulations we perform are with zero net flux and produce mean activity levels corresponding to the Shakura & Syunyaev α ~ 5 × 10-3, being at the lower end of the range usually considered in accretion disc modelling. We reveal the nature of the mechanism responsible for the excitation of these waves by determining the time-dependent evolution of the Fourier transforms of the participating state variables. The dominant waves are found to have no vertical structure and to be excited during periodically repeating swings in which they change from leading to trailing. The initial phase of the evolution of such a swing is found to be in excellent agreement with that expected from the WKBJ theory developed in a preceding paper by Heinemann & Papaloizou. However, shortly after the attainment of the expected maximum wave amplitude, the waves begin to be damped on account of the formation of weak shocks. As expected from the theory, the waves are seen to shorten in radial wavelength as they propagate. This feature enables non-linear dissipation to continue in spite of amplitude decrease. As a consequence, the waves are almost always seen to be in the non-linear regime. We demonstrate that the important source terms causing excitation of the waves are related to a quantity that reduces to the potential vorticity for small perturbations from the background state with no vertical dependence. We find that the root mean square density fluctuations associated with the waves are positively correlated with both this quantity and the general level of hydromagnetic turbulence. The mean angular momentum transport associated with spiral density waves generated in our simulations is estimated to be a significant fraction of that associated with the turbulent Reynolds stress.

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Gravitational wave as probe of superfluid dark matter

NASA Astrophysics Data System (ADS)

Cai, Rong-Gen; Liu, Tong-Bo; Wang, Shao-Jiang

2018-02-01

In recent years, superfluid dark matter (SfDM) has become a competitive model of emergent modified Newtonian dynamics (MOND) scenario: MOND phenomenons naturally emerge as a derived concept due to an extra force mediated between baryons by phonons as a result of axionlike particles condensed as superfluid at galactic scales; Beyond galactic scales, these axionlike particles behave as normal fluid without phonon-mediated MOND-like force between baryons, therefore SfDM also maintains the usual success of Λ CDM at cosmological scales. In this paper, we use gravitational waves (GWs) to probe the relevant parameter space of SfDM. GWs through Bose-Einstein condensate (BEC) could propagate with a speed slightly deviation from the speed-of-light due to the change in the effective refractive index, which depends on the SfDM parameters and GW-source properties. We find that Five hundred meter Aperture Spherical Telescope (FAST), Square Kilometre Array (SKA) and International Pulsar Timing Array (IPTA) are the most promising means as GW probe of relevant parameter space of SfDM. Future space-based GW detectors are also capable of probing SfDM if a multimessenger approach is adopted.

A three-wavelength multi-channel brain functional imager based on digital lock-in photon-counting technique

NASA Astrophysics Data System (ADS)

Ding, Xuemei; Wang, Bingyuan; Liu, Dongyuan; Zhang, Yao; He, Jie; Zhao, Huijuan; Gao, Feng

2018-02-01

During the past two decades there has been a dramatic rise in the use of functional near-infrared spectroscopy (fNIRS) as a neuroimaging technique in cognitive neuroscience research. Diffuse optical tomography (DOT) and optical topography (OT) can be employed as the optical imaging techniques for brain activity investigation. However, most current imagers with analogue detection are limited by sensitivity and dynamic range. Although photon-counting detection can significantly improve detection sensitivity, the intrinsic nature of sequential excitations reduces temporal resolution. To improve temporal resolution, sensitivity and dynamic range, we develop a multi-channel continuous-wave (CW) system for brain functional imaging based on a novel lock-in photon-counting technique. The system consists of 60 Light-emitting device (LED) sources at three wavelengths of 660nm, 780nm and 830nm, which are modulated by current-stabilized square-wave signals at different frequencies, and 12 photomultiplier tubes (PMT) based on lock-in photon-counting technique. This design combines the ultra-high sensitivity of the photon-counting technique with the parallelism of the digital lock-in technique. We can therefore acquire the diffused light intensity for all the source-detector pairs (SD-pairs) in parallel. The performance assessments of the system are conducted using phantom experiments, and demonstrate its excellent measurement linearity, negligible inter-channel crosstalk, strong noise robustness and high temporal resolution.

Rapid determination of the energy magnitude Me

NASA Astrophysics Data System (ADS)

di Giacomo, D.; Parolai, S.; Bormann, P.; Saul, J.; Grosser, H.; Wang, R.; Zschau, J.

2009-04-01

The magnitude of an earthquake is one of the most used parameters to evaluate the earthquake's damage potential. However, many magnitude scales developed over the past years have different meanings. Among the non-saturating magnitude scales, the energy magnitude Me is related to a well defined physical parameter of the seismic source, that is the radiated seismic energy ES (e.g. Bormann et al., 2002): Me = 2/3(log10 ES - 4.4). Me is more suitable than the moment magnitude Mw in describing an earthquake's shaking potential (Choy and Kirby, 2004). Indeed, Me is calculated over a wide frequency range of the source spectrum and represents a better measure of the shaking potential, whereas Mw is related to the low-frequency asymptote of the source spectrum and is a good measure of the fault size and hence of the static (tectonic) effect of an earthquake. The calculation of ES requires the integration over frequency of the squared P-waves velocity spectrum corrected for the energy loss experienced by the seismic waves along the path from the source to the receivers. To accout for the frequency-dependent energy loss, we computed spectral amplitude decay functions for different frequenciesby using synthetic Green's functions (Wang, 1999) based on the reference Earth model AK135Q (Kennett et al., 1995; Montagner and Kennett, 1996). By means of these functions the correction for the various propagation effects of the recorded P-wave velocity spectra is performed in a rapid and robust way, and the calculation of ES, and hence of Me, can be computed at the single station. We analyse teleseismic broadband P-waves signals in the distance range 20°-98°. We show that our procedure is suitable for implementation in rapid response systems since it could provide stable Me determinations within 10-15 minutes after the earthquake's origin time. Indeed, we use time variable cumulative energy windows starting 4 s after the first P-wave arrival in order to include the earthquake rupture duration, which is calculated according to Bormann and Saul (2008). We tested our procedure for a large dataset composed by about 750 earthquakes globally distributed in the Mw range 5.5-9.3 recorded at the broadband stations managed by the IRIS, GEOFON, and GEOSCOPE global networks, as well as other regional seismic networks. Me and Mw express two different aspects of the seismic source, and a combined use of these two magnitude scales would allow a better assessment of the tsunami and shaking potential of an earthquake.. References Bormann, P., Baumbach, M., Bock, G., Grosser, H., Choy, G. L., and Boatwright, J. (2002). Seismic sources and source parameters, in IASPEI New Manual of Seismological Observatory Practice, P. Bormann (Editor), Vol. 1, GeoForschungsZentrum, Potsdam, Chapter 3, 1-94. Bormann, P., and Saul, J. (2008). The new IASPEI standard broadband magnitude mB. Seism. Res. Lett., 79(5), 699-705. Choy, G. L., and Kirby, S. (2004). Apparent stress, fault maturity and seismic hazard for normal-fault earthquakes at subduction zones. Geophys. J. Int., 159, 991-1012. Kennett, B. L. N., Engdahl, E. R., and Buland, R. (1995). Constraints on seismic velocities in the Earth from traveltimes. Geophys. J. Int., 122, 108-124. Montagner, J.-P., and Kennett, B. L. N. (1996). How to reconcile body-wave and normal-mode reference Earth models?. Geophys. J. Int., 125, 229-248. Wang, R. (1999). A simple orthonormalization method for stable and efficient computation of Green's functions. Bull. Seism. Soc. Am., 89(3), 733-741.

Experimental quantification of nonlinear time scales in inertial wave rotating turbulence

NASA Astrophysics Data System (ADS)

Yarom, Ehud; Salhov, Alon; Sharon, Eran

2017-12-01

We study nonlinearities of inertial waves in rotating turbulence. At small Rossby numbers the kinetic energy in the system is contained in helical inertial waves with time dependence amplitudes. In this regime the amplitude variations time scales are slow compared to wave periods, and the spectrum is concentrated along the dispersion relation of the waves. A nonlinear time scale was extracted from the width of the spectrum, which reflects the intensity of nonlinear wave interactions. This nonlinear time scale is found to be proportional to (U.k ) -1, where k is the wave vector and U is the root-mean-square horizontal velocity, which is dominated by large scales. This correlation, which indicates the existence of turbulence in which inertial waves undergo weak nonlinear interactions, persists only for small Rossby numbers.

Experimental demonstrations in audible frequency range of band gap tunability and negative refraction in two-dimensional sonic crystal.

PubMed

Pichard, Hélène; Richoux, Olivier; Groby, Jean-Philippe

2012-10-01

The propagation of audible acoustic waves in two-dimensional square lattice tunable sonic crystals (SC) made of square cross-section infinitely rigid rods embedded in air is investigated experimentally. The band structure is calculated with the plane wave expansion (PWE) method and compared with experimental measurements carried out on a finite extend structure of 200 cm width, 70 cm depth and 15 cm height. The structure is made of square inclusions of 5 cm side with a periodicity of L = 7.5 cm placed inbetween two rigid plates. The existence of tunable complete band gaps in the audible frequency range is demonstrated experimentally by rotating the scatterers around their vertical axis. Negative refraction is then analyzed by use of the anisotropy of the equi-frequency surface (EFS) in the first band and of a finite difference time domain (FDTD) method. Experimental results finally show negative refraction in the audible frequency range.

Radiated Seismic Energy of Earthquakes in the South-Central Region of the Gulf of California, Mexico

NASA Astrophysics Data System (ADS)

Castro, Raúl R.; Mendoza-Camberos, Antonio; Pérez-Vertti, Arturo

2018-05-01

We estimated the radiated seismic energy (ES) of 65 earthquakes located in the south-central region of the Gulf of California. Most of these events occurred along active transform faults that define the Pacific-North America plate boundary and have magnitudes between M3.3 and M5.9. We corrected the spectral records for attenuation using nonparametric S-wave attenuation functions determined with the whole data set. The path effects were isolated from the seismic source using a spectral inversion. We computed radiated seismic energy of the earthquakes by integrating the square velocity source spectrum and estimated their apparent stresses. We found that most events have apparent stress between 3 × 10-4 and 3 MPa. Model independent estimates of the ratio between seismic energy and moment (ES/M0) indicates that this ratio is independent of earthquake size. We conclude that in general the apparent stress is low (σa < 3 MPa) in the south-central and southern Gulf of California.

Empirical wind model for the middle and lower atmosphere. Part 1: Local time average

NASA Technical Reports Server (NTRS)

Hedin, A. E.; Fleming, E. L.; Manson, A. H.; Schmidlin, F. J.; Avery, S. K.; Franke, S. J.

1993-01-01

The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and longitude (stationary wave 1). The model represents a smoothed compromise between the data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Root mean square differences between data and model are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for zonal wind, and 10 m/s and 4 m/s, respectively, for meridional wind.

The Bolocam Galactic Plane Survey

NASA Technical Reports Server (NTRS)

Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II;

Rapid testing of pulse transformers

NASA Technical Reports Server (NTRS)

Grillo, J.

1980-01-01

Quality-control testing of pulse transformers is speeded up by method for determining rise time and droop. Instead of using oscilloscope and square-wave generator to measure these characteristics directly, method uses voltmeter and sine-wave generator to measure them indirectly in about one-tenth time. Droop and rise time are determined by measuring input/output voltage ratio at just four frequencies.

Relative sideband amplitudes versus modulation index for common functions using frequency and phase modulation. [for design and testing of communication system

NASA Technical Reports Server (NTRS)

Stocklin, F.

1973-01-01

The equations defining the amplitude of sidebands resulting from either frequency modulation or phase modulation by either square wave, sine wave, sawtooth or triangular modulating functions are presented. Spectral photographs and computer generated tables of modulation index vs. relative sideband amplitudes are also included.

The effects of shockwave profile shape and shock obliquity on spallation in Cu and Ta: kinetic and stress-state effects on damage evolution(u)

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

Gray, George T

2010-12-14

Widespread research over the past five decades has provided a wealth of experimental data and insight concerning shock hardening and the spallation response of materials subjected to square-topped shock-wave loading profiles. Less quantitative data have been gathered on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (or triangular-wave) loading profile shock loading on the shock hardening, damage evolution, or spallation response of materials. Explosive loading induces an impulse dubbed a 'Taylor Wave'. This is a significantly different loading history than that achieved by a square-topped impulse in terms of both the pulse duration at a fixed peak pressure,more » and a different unloading strain rate from the peak Hugoniot state achieved. The goal of this research is to quantify the influence of shockwave obliquity on the spallation response of copper and tantalum by subjecting plates of each material to HE-driven sweeping detonation-wave loading and quantify both the wave propagation and the post-mortem damage evolution. This talk will summarize our current understanding of damage evolution during sweeping detonation-wave spallation loading in Cu and Ta and show comparisons to modeling simulations. The spallation responses of Cu and Ta are both shown to be critically dependent on the shockwave profile and the stress-state of the shock. Based on variations in the specifics of the shock drive (pulse shape, peak stress, shock obliquity) and sample geometry in Cu and Ta, 'spall strength' varies by over a factor of two and the details of the mechanisms of the damage evolution is seen to vary. Simplistic models of spallation, such as P{sub min} based on 1-D square-top shock data lack the physics to capture the influence of kinetics on damage evolution such as that operative during sweeping detonation loading. Such considerations are important for the development of predictive models of damage evolution and spallation in metals and alloys.« less

Do cigarette prices motivate smokers to quit? New evidence from the ITC survey

PubMed Central

Ross, Hana; Blecher, Evan; Yan, Lili; Hyland, Andrew

2015-01-01

Aims To examine the importance of cigarette prices in influencing smoking cessation and the motivation to quit. Design We use longitudinal data from three waves of the International Tobacco Control Policy Evaluation Survey (ITC). The study contrasts smoking cessation and motivation to quit among US and Canadian smokers and evaluates how this relationship is modified by cigarette prices, nicotine dependence and health knowledge. Different price measures are used to understand how the ability to purchase cheaper cigarettes may reduce the influence of prices. Our first model examines whether cigarette prices affect motivation to quit smoking using Generalized Estimating Equations to predict cessation stage and a least squares model to predict the change in cessation stage. The second model evaluates quitting behavior over time. The probability of quitting is estimated with Generalized Estimating Equations and a transition model to account for the ‘left-truncation’ of the data. Settings US and Canada. Participants 4352 smokers at Wave 1, 2000 smokers completing all three waves. Measurements Motivation to quit, cigarette prices, nicotine dependence and health knowledge. Findings Smokers living in areas with higher cigarette prices are significantly more motivated to quit. There is limited evidence to suggest that price increases over time may also increase quit motivation. Higher cigarette prices increase the likelihood of actual quitting, with the caveat that results are statistically significant in one out of two models. Access to cheaper cigarette sources does not impede cessation although smokers would respond more aggressively (in terms of cessation) to price increases if cheaper cigarette sources were not available. Conclusions This research provides a unique opportunity to study smoking cessation among adult smokers and their response to cigarette prices in a market where they are able to avoid tax increases by purchasing cigarettes from cheaper sources. Higher cigarette prices appear to be associated with greater motivation to stop smoking, an effect which does not appear to be mitigated by cheaper cigarette sources. The paper supports the use of higher prices as a means of encouraging smoking cessation and motivation to quit. PMID:21059183

Do cigarette prices motivate smokers to quit? New evidence from the ITC survey.

PubMed

Ross, Hana; Blecher, Evan; Yan, Lili; Hyland, Andrew

2011-03-01

To examine the importance of cigarette prices in influencing smoking cessation and the motivation to quit. We use longitudinal data from three waves of the International Tobacco Control Policy Evaluation Survey (ITC). The study contrasts smoking cessation and motivation to quit among US and Canadian smokers and evaluates how this relationship is modified by cigarette prices, nicotine dependence and health knowledge. Different price measures are used to understand how the ability to purchase cheaper cigarettes may reduce the influence of prices. Our first model examines whether cigarette prices affect motivation to quit smoking using Generalized Estimating Equations to predict cessation stage and a least squares model to predict the change in cessation stage. The second model evaluates quitting behavior over time. The probability of quitting is estimated with Generalized Estimating Equations and a transition model to account for the 'left-truncation' of the data. US and Canada. 4352 smokers at Wave 1, 2000 smokers completing all three waves. Motivation to quit, cigarette prices, nicotine dependence and health knowledge. Smokers living in areas with higher cigarette prices are significantly more motivated to quit. There is limited evidence to suggest that price increases over time may also increase quit motivation. Higher cigarette prices increase the likelihood of actual quitting, with the caveat that results are statistically significant in one out of two models. Access to cheaper cigarette sources does not impede cessation although smokers would respond more aggressively (in terms of cessation) to price increases if cheaper cigarette sources were not available. This research provides a unique opportunity to study smoking cessation among adult smokers and their response to cigarette prices in a market where they are able to avoid tax increases by purchasing cigarettes from cheaper sources. Higher cigarette prices appear to be associated with greater motivation to stop smoking, an effect which does not appear to be mitigated by cheaper cigarette sources. The paper supports the use of higher prices as a means of encouraging smoking cessation and motivation to quit. © 2010 The Authors, Addiction © 2010 Society for the Study of Addiction.

Phononic band gap and wave propagation on polyvinylidene fluoride-based acoustic metamaterials

NASA Astrophysics Data System (ADS)

Oltulu, Oral; Simsek, Sevket; Mamedov, Amirullah M.; Ozbay, Ekmel

2016-12-01

In the present work, the acoustic band structure of a two-dimensional phononic crystal (PC) containing an organic ferroelectric (PVDF-polyvinylidene fluoride) and topological insulator (SnTe) was investigated by the plane-wave-expansion (PWE) method. Two-dimensional PC with square lattices composed of SnTe cylindrical rods embedded in the PVDF matrix is studied to find the allowed and stop bands for the waves of certain energy. Phononic band diagram ω = ω(k) for a 2D PC, in which non-dimensional frequencies ωa/2πc (c-velocity of wave) were plotted vs. the wavevector k along the Г-X-M-Г path in the square Brillouin zone shows five stop bands in the frequency range between 10 and 110 kHz. The ferroelectric properties of PVDF and the unusual properties of SnTe as a topological material give us the ability to control the wave propagation through the PC over a wide frequency range of 103-106 Hz. SnTe is a discrete component that allows conducting electricity on its surface but shows insulator properties through its bulk volume. Tin telluride is considered as an acoustic topological insulator as the extension of topological insulators into the field of "topological phononics".

High speed point derivative microseismic detector

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

Uhl, J.E.; Warpinski, N.R.; Whetten, E.B.

A high speed microseismic event detector constructed in accordance with the present invention uses a point derivative comb to quickly and accurately detect microseismic events. Compressional and shear waves impinging upon microseismic receiver stations disposed to collect waves are converted into digital data and analyzed using a point derivative comb including assurance of quiet periods prior to declaration of microseismic events. If a sufficient number of quiet periods have passed, the square of a two point derivative of the incoming digital signal is compared to a trip level threshold exceeding the determined noise level to declare a valid trial event.more » The squaring of the derivative emphasizes the differences between noise and signal, and the valid event is preferably declared when the trip threshold has been exceeded over a temporal comb width to realize a comb over a given time period. Once a trial event has been declared, the event is verified through a spatial comb, which applies the temporal event comb to additional stations. The detector according to the present invention quickly and accurately detects initial compressional waves indicative of a microseismic event which typically exceed the ambient cultural noise level by a small amount, and distinguishes the waves from subsequent larger amplitude shear waves. 9 figs.« less

Correlation of wave propagation modes in helicon plasma with source tube lengths

NASA Astrophysics Data System (ADS)

Niu, Chen; Zhao, Gao; Wang, Yu; Liu, Zhongwei; Chen, Qiang

2017-01-01

Helicon wave plasma demonstrates lots of advantages in high coupling efficiency, high density, and low magnetic field. However, the helicon wave plasma still meets challenges in applications of material deposition, surface treatment, and electromagnetic thrusters owing to the changeable coupled efficiency and the remarkable non-uniformity. In this paper, we explore the wave propagation characterization by the B-dot probe in various lengths of source tubes. We find that in a long source tube the standing wave appears under the antenna zone, while the traveling wave is formed out of the antenna region. The apparent modulation of wave amplitude is formed in upstream rather than in downstream of the antenna. In a short source tube, however, there is only standing wave propagation.

Incidence of microcracks in maxillary first premolars after instrumentation with three different mechanized file systems: a comparative ex vivo study.

PubMed

Kfir, A; Elkes, D; Pawar, A; Weissman, A; Tsesis, I

2017-01-01

The objective of this study is to determine the potential for microcracks in the radicular dentin of first maxillary premolars using three different mechanized endodontic instrumentation systems. Eighty extracted maxillary first premolars with two root canals and no externally visible microcracks were selected. Root canal instrumentation was performed with either the ProTaper file system, the WaveOne primary file, or the self-adjusting file (SAF). Teeth with intact roots served as controls. The roots were cut into segments and examined with an intensive, small-diameter light source that was applied diagonally to the entire periphery of the root slice under ×20 magnification; the presence of microcracks and fractures was recorded. Pearson's chi-square method was used for statistical analysis, and significance was set at p < 0.05. Microcracks were present in 30 and 20 % of roots treated with the ProTaper and WaveOne systems, respectively, while no microcracks were present in the roots treated with the SAF (p = 0.008 and p = 0.035, respectively). Intact teeth presented with cracks in 5 % of the roots. The intensive, small-diameter light source revealed microcracks that could not be detected when using the microscope's light alone. Within the limitations of this study, it could be concluded that mechanized root canal instrumentation with the ProTaper and WaveOne systems in maxillary first premolars causes microcracks in the radicular dentin, while the use of the SAF file causes no such microcracks. Rotary and reciprocating files with large tapers may cause microcracks in the radicular dentin of maxillary first premolars. Less aggressive methods should be considered for these teeth.

ARRIVAL TIME DIFFERENCES BETWEEN GRAVITATIONAL WAVES AND ELECTROMAGNETIC SIGNALS DUE TO GRAVITATIONAL LENSING

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

Takahashi, Ryuichi

In this study we demonstrate that general relativity predicts arrival time differences between gravitational wave (GW) and electromagnetic (EM) signals caused by the wave effects in gravitational lensing. The GW signals can arrive earlier than the EM signals in some cases if the GW/EM signals have passed through a lens, even if both signals were emitted simultaneously by a source. GW wavelengths are much larger than EM wavelengths; therefore, the propagation of the GWs does not follow the laws of geometrical optics, including the Shapiro time delay, if the lens mass is less than approximately 10{sup 5} M {sub ⊙}(more » f /Hz){sup −1}, where f is the GW frequency. The arrival time difference can reach ∼0.1 s ( f /Hz){sup −1} if the signals have passed by a lens of mass ∼8000 M {sub ⊙}( f /Hz){sup −1} with the impact parameter smaller than the Einstein radius; therefore, it is more prominent for lower GW frequencies. For example, when a distant supermassive black hole binary (SMBHB) in a galactic center is lensed by an intervening galaxy, the time lag becomes of the order of 10 days. Future pulsar timing arrays including the Square Kilometre Array and X-ray detectors may detect several time lags by measuring the orbital phase differences between the GW/EM signals in the SMBHBs. Gravitational lensing imprints a characteristic modulation on a chirp waveform; therefore, we can deduce whether a measured arrival time lag arises from intrinsic source properties or gravitational lensing. Determination of arrival time differences would be extremely useful in multimessenger observations and tests of general relativity.« less

Polar Spacecraft Based Comparisons of Intense Electric Fields and Poynting Flux Near and Within the Plasma Sheet-Tail Lobe Boundary to UVI Images: An Energy Source for the Aurora

NASA Technical Reports Server (NTRS)

Wygant, J. R.; Keiling, A.; Cattell, C. A.; Johnson, M.; Lysak, R. L.; Temerin, M.; Mozer, F. S.; Kletzing, C. A.; Scudder, J. D.; Peterson, W.;

Wave propagation in media having negative permittivity and permeability.

PubMed

Ziolkowski, R W; Heyman, E

2001-11-01

Wave propagation in a double negative (DNG) medium, i.e., a medium having negative permittivity and negative permeability, is studied both analytically and numerically. The choices of the square root that leads to the index of refraction and the wave impedance in a DNG medium are determined by imposing analyticity in the complex frequency domain, and the corresponding wave properties associated with each choice are presented. These monochromatic concepts are then tested critically via a one-dimensional finite difference time domain (FDTD) simulation of the propagation of a causal, pulsed plane wave in a matched, lossy Drude model DNG medium. The causal responses of different spectral regimes of the medium with positive or negative refractive indices are studied by varying the carrier frequency of narrowband pulse excitations. The smooth transition of the phenomena associated with a DNG medium from its early-time nondispersive behavior to its late-time monochromatic response is explored with wideband pulse excitations. These FDTD results show conclusively that the square root choice leading to a negative index of refraction and positive wave impedance is the correct one, and that this choice is consistent with the overall causality of the response. An analytical, exact frequency domain solution to the scattering of a wave from a DNG slab is also given and is used to characterize several physical effects. This solution is independent of the choice of the square roots for the index of refraction and the wave impedance, and thus avoids any controversy that may arise in connection with the signs of these constituents. The DNG slab solution is used to critically examine the perfect lens concept suggested recently by Pendry. It is shown that the perfect lens effect exists only under the special case of a DNG medium with epsilon(omega)=mu(omega)=-1 that is both lossless and nondispersive. Otherwise, the closed form solutions for the field structure reveal that the DNG slab converts an incident spherical wave into a localized beam field whose parameters depend on the values of epsilon and mu. This beam field is characterized with a paraxial approximation of the exact DNG slab solution. These monochromatic concepts are again explored numerically via a causal two-dimensional FDTD simulation of the scattering of a pulsed cylindrical wave by a matched, lossy Drude model DNG slab. These FDTD results demonstrate conclusively that the monochromatic electromagnetic power flow through the DNG slab is channeled into beams rather then being focused and, hence, the Pendry perfect lens effect is not realizable with any realistic metamaterial.

Stability Criteria Analysis for Landing Craft Utility

DTIC Science & Technology

2017-12-01

Square meter m/s Meters per Second m/s2 Meters per Second Squared n Vertical Displacement of Sea Water Free Surface n3 Ship’s Heave... Displacement n5 Ship’s Pitch Angle p(ξ) Rayleigh Distribution Probability Function POSSE Program of Ship Salvage Engineering pk...Spectrum Constant γ JONSWAP Wave Spectrum Peak Factor Γ(λ) Gamma Probability Function Δ Ship’s Displacement Δω Small Frequency

The Impact of Moisture on Mountain Waves During T-REX

DTIC Science & Technology

2009-11-01

sensitivity to the upstream wind speed. After re- moving these three outliers, the linear least squares re- gression using the other 21 points yields W( U c )5...The wave amplitudes for the 24 flights normalized by the reference wave amplitude are plotted versus the upstream RH maxima in Fig. 3b. There are four...mountaintop level de- rived from the upwind sondes for 24 UWKA flights. The filled circles represent moist cases as defined in the text. The bold line

Observation of Wave Energy Evolution in Coastal Areas Using HF Radar

DTIC Science & Technology

2009-09-01

the root-mean-square (RMS) wave height Hrms and mean wave period T as a function of the backscatter power ratio of the second- order to first-order...range Hrms $ 0.3/ko (Hs $ 2.26 m; Barrick 1977a), consideration of values outside this constraint did not change a significantly. Also, the apparent...propagation in the region (section 4c ). Analysis of the data showed that the wavelet filtering is consistent with other techniques (e.g., Fourier band

Analysis of Ground Motion from An Underground Chemical Explosion

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

Pitarka, Arben; Mellors, Robert J.; Walter, William R.

Here in this paper we investigate the excitation and propagation of far-field seismic waves from the 905 kg trinitrotoluene equivalent underground chemical explosion SPE-3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far-field ground motion at short and long distances is characterized by substantial shear-wave energy, and large azimuthal variations in P-and S-wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances <50 m suggests they were generated at or very near the source. The relative amplitude of the shear waves grows as the waves propagate away frommore » the source. We analyze and model the shear-wave excitation during the explosion in the 0.01–10 Hz frequency range, at epicentral distances of up to 1 km. We used two simulation techniques. One is based on the empirical isotropic Mueller–Murphy (MM) (Mueller and Murphy, 1971) nuclear explosion source model, and 3D anelastic wave propagation modeling. The second uses a physics-based approach that couples hydrodynamic modeling of the chemical explosion source with anelastic wave propagation modeling. Comparisons with recorded data show the MM source model overestimates the SPE-3 far-field ground motion by an average factor of 4. The observations show that shear waves with substantial high-frequency energy were generated at the source. However, to match the observations additional shear waves from scattering, including surface topography, and heterogeneous shallow structure contributed to the amplification of far-field shear motion. Comparisons between empirically based isotropic and physics-based anisotropic source models suggest that both wave-scattering effects and near-field nonlinear effects are needed to explain the amplitude and irregular radiation pattern of shear motion observed during the SPE-3 explosion.« less

Analysis of Ground Motion from An Underground Chemical Explosion

DOE PAGES

Pitarka, Arben; Mellors, Robert J.; Walter, William R.; ...

2015-09-08

Here in this paper we investigate the excitation and propagation of far-field seismic waves from the 905 kg trinitrotoluene equivalent underground chemical explosion SPE-3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far-field ground motion at short and long distances is characterized by substantial shear-wave energy, and large azimuthal variations in P-and S-wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances <50 m suggests they were generated at or very near the source. The relative amplitude of the shear waves grows as the waves propagate away frommore » the source. We analyze and model the shear-wave excitation during the explosion in the 0.01–10 Hz frequency range, at epicentral distances of up to 1 km. We used two simulation techniques. One is based on the empirical isotropic Mueller–Murphy (MM) (Mueller and Murphy, 1971) nuclear explosion source model, and 3D anelastic wave propagation modeling. The second uses a physics-based approach that couples hydrodynamic modeling of the chemical explosion source with anelastic wave propagation modeling. Comparisons with recorded data show the MM source model overestimates the SPE-3 far-field ground motion by an average factor of 4. The observations show that shear waves with substantial high-frequency energy were generated at the source. However, to match the observations additional shear waves from scattering, including surface topography, and heterogeneous shallow structure contributed to the amplification of far-field shear motion. Comparisons between empirically based isotropic and physics-based anisotropic source models suggest that both wave-scattering effects and near-field nonlinear effects are needed to explain the amplitude and irregular radiation pattern of shear motion observed during the SPE-3 explosion.« less

Mathematical Construction of Magic Squares Utilizing Base-N Arithmetic

ERIC Educational Resources Information Center

O'Brien, Thomas D.

2006-01-01

Magic squares have been of interest as a source of recreation for over 4,500 years. A magic square consists of a square array of n[squared] positive and distinct integers arranged so that the sum of any column, row, or main diagonal is the same. In particular, an array of consecutive integers from 1 to n[squared] forming an nxn magic square is…

Square or sine: finding a waveform with high success rate of eliciting SSVEP.

PubMed

Teng, Fei; Chen, Yixin; Choong, Aik Min; Gustafson, Scott; Reichley, Christopher; Lawhead, Pamela; Waddell, Dwight

2011-01-01

Steady state visual evoked potential (SSVEP) is the brain's natural electrical potential response for visual stimuli at specific frequencies. Using a visual stimulus flashing at some given frequency will entrain the SSVEP at the same frequency, thereby allowing determination of the subject's visual focus. The faster an SSVEP is identified, the higher information transmission rate the system achieves. Thus, an effective stimulus, defined as one with high success rate of eliciting SSVEP and high signal-noise ratio, is desired. Also, researchers observed that harmonic frequencies often appear in the SSVEP at a reduced magnitude. Are the harmonics in the SSVEP elicited by the fundamental stimulating frequency or by the artifacts of the stimuli? In this paper, we compare the SSVEP responses of three periodic stimuli: square wave (with different duty cycles), triangle wave, and sine wave to find an effective stimulus. We also demonstrate the connection between the strength of the harmonics in SSVEP and the type of stimulus.

Influence of modulation frequency in rubidium cell frequency standards

NASA Technical Reports Server (NTRS)

Audoin, C.; Viennet, J.; Cyr, N.; Vanier, J.

1983-01-01

The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.

Elastic least-squares reverse time migration with velocities and density perturbation

NASA Astrophysics Data System (ADS)

Qu, Yingming; Li, Jinli; Huang, Jianping; Li, Zhenchun

2018-02-01

Elastic least-squares reverse time migration (LSRTM) based on the non-density-perturbation assumption can generate false-migrated interfaces caused by density variations. We perform an elastic LSRTM scheme with density variations for multicomponent seismic data to produce high-quality images in Vp, Vs and ρ components. However, the migrated images may suffer from crosstalk artefacts caused by P- and S-waves coupling in elastic LSRTM no matter what model parametrizations used. We have proposed an elastic LSRTM with density variations method based on wave modes separation to reduce these crosstalk artefacts by using P- and S-wave decoupled elastic velocity-stress equations to derive demigration equations and gradient formulae with respect to Vp, Vs and ρ. Numerical experiments with synthetic data demonstrate the capability and superiority of the proposed method. The imaging results suggest that our method promises imaging results with higher quality and has a faster residual convergence rate. Sensitivity analysis of migration velocity, migration density and stochastic noise verifies the robustness of the proposed method for field data.

Robust control algorithms for Mars aerobraking

NASA Technical Reports Server (NTRS)

Shipley, Buford W., Jr.; Ward, Donald T.

1992-01-01

Four atmospheric guidance concepts have been adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. The first two offer improvements to the Analytic Predictor Corrector (APC) to increase its robustness to density variations. The second two are variations of a new Liapunov tracking exit phase algorithm, developed to guide the vehicle along a reference trajectory. These four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness. MARSGRAM is used to develop realistic atmospheres for the study. When square wave density pulses perturb the atmosphere all four controllers are successful. The algorithms are tested against atmospheres where the inbound and outbound density functions are different. Square wave density pulses are again used, but only for the outbound leg of the trajectory. Additionally, sine waves are used to perturb the density function. The new algorithms are found to be more robust than any previously tested and a Liapunov controller is selected as the most robust control algorithm overall examined.

Bandgaps and directional propagation of elastic waves in 2D square zigzag lattice structures

NASA Astrophysics Data System (ADS)

Wang, Yan-Feng; Wang, Yue-Sheng; Zhang, Chuanzeng

2014-12-01

In this paper we propose various types of two-dimensional (2D) square zigzag lattice structures, and we study their bandgaps and directional propagation of elastic waves. The band structures and the transmission spectra of the systems are calculated by using the finite element method. The effects of the geometry parameters of the 2D-zigzag lattices on the bandgaps are investigated and discussed. The mechanism of the bandgap generation is analyzed by studying the vibration modes at the bandgap edges. Multiple wide complete bandgaps are found in a wide porosity range owing to the separation of the degeneracy by introducing bending arms. The bandgaps are sensitive to the geometry parameters of the systems. The deformed displacement fields of the transient response of finite structures subjected to time-harmonic loads are presented to show the directional wave propagation. The research in this paper is relevant to the practical design of cellular structures with enhanced vibro-acoustics performance.

A Study of Regional Wave Source Time Functions of Central Asian Earthquakes

NASA Astrophysics Data System (ADS)

Xie, J.; Perry, M. R.; Schult, F. R.; Wood, J.

2014-12-01

Despite the extensive use of seismic regional waves in seismic event identification and attenuation tomography, very little is known on how seismic sources radiate energy into these waves. For example, whether regional Lg wave has the same source spectrum as that of the local S has been questioned by Harr et al. and Frenkel et al. three decades ago; many current investigators assume source spectra in Lg, Sn, Pg, Pn and Lg coda waves have either the same or very similar corner frequencies, in contrast to local P and S spectra whose corner frequencies differ. The most complete information on how the finite source ruptures radiate energy into regional waves is contained in the time domain source time functions (STFs). To estimate the STFs of regional waves using the empirical Green's function (EGF) method, we have been substantially modifying a semi-automotive computer procedure to cope with the increasingly diverse and inconsistent naming patterns of new data files from the IRIS DMC. We are applying the modified procedure to many earthquakes in central Asia to study the STFs of various regional waves to see whether they have the same durations and pulse shapes, and how frequently source directivity occur. When applicable, we also examine the differences between STFs of local P and S waves and those of regional waves. The result of these analyses will be presented at the meeting.

Excitation of Love waves in a thin film layer by a line source.

NASA Technical Reports Server (NTRS)

Tuan, H.-S.; Ponamgi, S. R.

1972-01-01

The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.

Propagation and Linear Mode Conversion of Magnetosonic and Electromagnetic Ion Cyclotron Waves in the Radiation Belts

NASA Astrophysics Data System (ADS)

Horne, R. B.; Yoshizumi, M.

2017-12-01

Magnetosonic waves and electromagnetic ion cyclotron (EMIC) waves are important for electron acceleration and loss from the radiation belts. It is generally understood that these waves are generated by unstable ion distributions that form during geomagnetically disturbed times. Here we show that magnetosonic waves could be a source of EMIC waves as a result of propagation and a process of linear mode conversion. The converse is also possible. We present ray tracing to show how magnetosonic (EMIC) waves launched with large (small) wave normal angles can reach a location where the wave normal angle is zero and the wave frequency equals the so-called cross-over frequency whereupon energy can be converted from one mode to another without attenuation. While EMIC waves could be a source of magnetosonic waves below the cross-over frequency magnetosonic waves could be a source of hydrogen band waves but not helium band waves.

Power converter

NASA Technical Reports Server (NTRS)

Black, J. M. (Inventor)

1981-01-01

A dc-to-dc converter employs four transistor switches in a bridge to chop dc power from a source, and a voltage multiplying diode rectifying ladder network to rectify and filter the chopped dc power for delivery to a load. The bridge switches are cross coupled in order for diagonally opposite pairs to turn on and off together using RC networks for the cross coupling to achieve the mode of operation of a free running multivibrator, and the diode rectifying ladder is configured to operate in a push-pull mode driven from opposite sides of the multivibrator outputs of the ridge switches. The four transistor switches provide a square-wave output voltage which as a peak-to-peak amplitude that is twice the input dc voltage, and is thus useful as a dc-to-ac inverter.

Investigating the generation of Love waves in secondary microseisms using 3D numerical simulations

NASA Astrophysics Data System (ADS)

Wenk, Stefan; Hadziioannou, Celine; Pelties, Christian; Igel, Heiner

2014-05-01

Longuet-Higgins (1950) proposed that secondary microseismic noise can be attributed to oceanic disturbances by surface gravity wave interference causing non-linear, second-order pressure perturbations at the ocean bottom. As a first approximation, this source mechanism can be considered as a force acting normal to the ocean bottom. In an isotropic, layered, elastic Earth model with plain interfaces, vertical forces generate P-SV motions in the vertical plane of source and receiver. In turn, only Rayleigh waves are excited at the free surface. However, several authors report on significant Love wave contributions in the secondary microseismic frequency band of real data measurements. The reason is still insufficiently analysed and several hypothesis are under debate: - The source mechanism has strongest influence on the excitation of shear motions, whereas the source direction dominates the effect of Love wave generation in case of point force sources. Darbyshire and Okeke (1969) proposed the topographic coupling effect of pressure loads acting on a sloping sea-floor to generate the shear tractions required for Love wave excitation. - Rayleigh waves can be converted into Love waves by scattering. Therefore, geometric scattering at topographic features or internal scattering by heterogeneous material distributions can cause Love wave generation. - Oceanic disturbances act on large regions of the ocean bottom, and extended sources have to be considered. In combination with topographic coupling and internal scattering, the extent of the source region and the timing of an extended source should effect Love wave excitation. We try to elaborate the contribution of different source mechanisms and scattering effects on Love to Rayleigh wave energy ratios by 3D numerical simulations. In particular, we estimate the amount of Love wave energy generated by point and extended sources acting on the free surface. Simulated point forces are modified in their incident angle, whereas extended sources are adapted in their spatial extent, magnitude and timing. Further, the effect of variations in the correlation length and perturbation magnitude of a random free surface topography as well as an internal random material distribution are studied.

Rg-Lg coupling as a Lg-wave excitation mechanism

NASA Astrophysics Data System (ADS)

Ge, Z.; Xie, X.

2003-12-01

Regional phase Lg is predominantly comprised of shear wave energy trapped in the crust. Explosion sources are expected to be less efficient for excitation of Lg phases than earthquakes to the extent that the source can be approximated as isotropic. Shallow explosions generate relatively large surface wave Rg compared to deeper earthquakes, and Rg is readily disrupted by crustal heterogeneity. Rg energy may thus scatter into trapped crustal S-waves near the source region and contribute to low-frequency Lg wave. In this study, a finite-difference modeling plus the slowness analysis are used for investigating the above mentioned Lg-wave excitation mechanism. The method allows us to investigate near source energy partitioning in multiple domains including frequency, slowness and time. The main advantage of this method is that it can be applied at close range, before Lg is actually formed, which allows us to use very fine near source velocity model to simulate the energy partitioning process. We use a layered velocity structure as the background model and add small near source random velocity patches to the model to generate the Rg to Lg coupling. Two types of simulations are conducted, (1) a fixed shallow explosion source vs. randomness at different depths and (2) a fixed shallow randomness vs. explosion sources at different depths. The results show apparent couplings between the Rg and Lg waves at lower frequencies (0.3-1.5 Hz). A shallow source combined with shallow randomness generates the maximum Lg-wave, which is consistent with the Rg energy distribution of a shallow explosion source. The Rg energy and excited Lg energy show a near linear relationship. The numerical simulation and slowness analysis suggest that the Rg to Lg coupling is an effective excitation mechanism for low frequency Lg-waves from a shallow explosion source.

Characteristics of Love and Rayleigh waves in ambient noise: wavetype ratio, source location and seasonal behavior

NASA Astrophysics Data System (ADS)

Juretzek, C.; Perleth, M.; Hadziioannou, C.

2015-12-01

Ambient seismic noise has become an important source of signal for tomography and monitoring purposes. Better understanding of the noise field characteristics is crucial to further improve noise applications. Our knowledge about the common and different origins of Love and Rayleigh waves in the microseism bands is still limited. This applies in particular to constraints on source locations and source mechanisms of Love waves. Here, 3-component beamforming is used to distinguish between the differently polarized wave types present in the noise field recorded at several arrays across Europe. The focus lies on frequencies around the primary and secondary microseismic bands. We compare characteristics of Love and Rayleigh wave noise, such as source directions and frequency content. Further, Love to Rayleigh wave ratios are measured at each array, and a dependence on direction is observed. We constrain the corresponding source regions of both wave types by backprojection. By using a full year of data in 2013, we are able to track the seasonal changes in our observations of Love-to-Rayleigh ratio and source locations.

Rapid Monte Carlo Simulation of Gravitational Wave Galaxies

NASA Astrophysics Data System (ADS)

Breivik, Katelyn; Larson, Shane L.

2015-01-01

With the detection of gravitational waves on the horizon, astrophysical catalogs produced by gravitational wave observatories can be used to characterize the populations of sources and validate different galactic population models. Efforts to simulate gravitational wave catalogs and source populations generally focus on population synthesis models that require extensive time and computational power to produce a single simulated galaxy. Monte Carlo simulations of gravitational wave source populations can also be used to generate observation catalogs from the gravitational wave source population. Monte Carlo simulations have the advantes of flexibility and speed, enabling rapid galactic realizations as a function of galactic binary parameters with less time and compuational resources required. We present a Monte Carlo method for rapid galactic simulations of gravitational wave binary populations.

Nonlinear optical waves with the second Painleve transcendent shape of envelope in Kerr media

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Tepichin Rodriguez, Eduardo; Sanchez Sanchez, Mauro

2004-05-01

Nonlinear optical wave packets with the second Painleve transcendent shape of envelope are revealed in Kerr media, manifesting weakly focusing cubic nonlinearity, square-law dispersion, and linear losses. When the state of nonlinear optical transmission is realized, two possible types of boundary conditions turn out to be satisfied for these wave packets. The propagation of initially unchirped optical wave packets under consideration could be supported by lossless medium in both normal and anomalous dispersion regimes. At the same time initially chirped optical waves with the second Painleve transcendent shape in low-loss medium and need matching the magnitude of optical losses by the dispersion and nonlinear properties of that medium.

Full-wave generalizations of the fundamental Gaussian beam.

PubMed

Seshadri, S R

2009-12-01

The basic full wave corresponding to the fundamental Gaussian beam was discovered for the outwardly propagating wave in a half-space by the introduction of a source in the complex space. There is a class of extended full waves all of which reduce to the same fundamental Gaussian beam in the appropriate limit. For the extended full Gaussian waves that include the basic full Gaussian wave as a special case, the sources are in the complex space on different planes transverse to the propagation direction. The sources are cylindrically symmetric Gaussian distributions centered at the origin of the transverse planes, the axis of symmetry being the propagation direction. For the special case of the basic full Gaussian wave, the source is a point source. The radiation intensity of the extended full Gaussian waves is determined and their characteristics are discussed and compared with those of the fundamental Gaussian beam. The extended full Gaussian waves are also obtained for the oppositely propagating outwardly directed waves in the second half-space. The radiation intensity distributions in the two half-spaces have reflection symmetry about the midplane. The radiation intensity distributions of the various extended full Gaussian waves are not significantly different. The power carried by the extended full Gaussian waves is evaluated and compared with that of the fundamental Gaussian beam.

Oscillating Square Wave Transcranial Direct Current Stimulation (tDCS) Delivered During Slow Wave Sleep Does Not Improve Declarative Memory More Than Sham: A Randomized Sham Controlled Crossover Study.

PubMed

Sahlem, Gregory L; Badran, Bashar W; Halford, Jonathan J; Williams, Nolan R; Korte, Jeffrey E; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L; Runion, Jennifer; Bachman, David L; Uhde, Thomas W; Borckardt, Jeffery J; George, Mark S

2015-01-01

A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current waveform (square in our study, nearly sinusoidal in the original). Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517 mA/cm(2), and oscillated between zero and maximal current at a frequency of 0.75 Hz. Stimulation occurred during five-five minute blocks with 1-min inter-block intervals (25 min total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1 ± 3.0 SD more associations) (sham = 3.8 ± 3.1 SD more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6 ± 2.7 SD correctly typed sequences) compared to sham stimulation (2.3 ± 2.2 SD correctly typed sequences)]. In this study, we failed to find improvements in declarative or performance memory and could not replicate an earlier study using nearly identical settings. Specifically we failed to find a beneficial effect on either overnight declarative or non-declarative memory consolidation via square-wave oscillating tDCS intervention applied bi-frontally during early NREM sleep. It is unclear if the morphology of the tDCS pulse is critical in any memory related improvements. Copyright © 2015 Elsevier Inc. All rights reserved.

Formation and propagation of Love waves in a surface layer with a P-wave source. Technical report

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

Florence, A.L.; Miller, S.A.

The objective of this research is to investigate experimentally, and support with theoretical calculations, the formation and propagation of Love waves from a P-wave source due to scattering at material heterogeneities. The P-wave source is a spherical piezoelectric crystal cast in a surface layer of rock simulant overlaying a higher impedance granite substrate. Excitation of the piezoelectric crystal with a known voltage applies a spherical compressional pulse of known amplitude to the surrounding medium. Lateral heterogeneities cast in the surface layer convert incident P-wave energy into shear waves. The horizontally polarized shear waves (SH waves) trapped in the surface layermore » wave guide are the Love waves we will measure at the surface.« less

Anisoplanatic image propagation along a slanted path under lower atmosphere phase turbulence in the presence of encrypted chaos

NASA Astrophysics Data System (ADS)

Chatterjee, Monish R.; Mohamed, Ali A.

2017-05-01

In recent research, anisoplanatic electromagnetic (EM) wave propagation along a slanted path in the presence of low atmosphere phase turbulence (modified von Karman spectrum or MVKS) has been investigated assuming a Hufnagel-Valley (HV) type structure parameter. Preliminary results indicate a strong dependence on the slant angle especially for long range transmission and relatively strong turbulence. The investigation was further divided into two regimes, viz. (a) one where the EM source consisted of a plane wave modulated with a digitized image, which is propagated along the turbulent path and recovered via demodulation at the receiver; and (b) transmit the plane wave without modulation along the turbulent path through an image transparency and a thin lens designed to gather the received image in the focal plane. In this paper, we reexamine the same problem (part (a) only) in the presence of a chaotic optical carrier where the chaos is generated in the feedback loop of an acousto-optic Bragg cell. The image information is encrypted within the chaos wave, and subsequently propagated along a similar slant path and identical turbulence conditions. The recovered image extracted via heterodyning from the received chaos is compared quantitatively (through image cross-correlations and mean-squared error measures) for the non-chaotic versus the chaotic approaches. Generally, "packaging" the information in chaos improves performance through turbulent propagation, and results are discussed from this perspective. Concurrently, we will also examine the effect of a non-encrypted plane EM wave propagation through a transparency-lens combination. These results are also presented with appropriate comparisons with the cases involving lensless transmission of imagery through corresponding turbulent and non-turbulent layers.

The nightmare scenario: measuring the stochastic gravitational wave background from stalling massive black hole binaries with pulsar timing arrays

NASA Astrophysics Data System (ADS)

Dvorkin, Irina; Barausse, Enrico

2017-10-01

Massive black hole binaries, formed when galaxies merge, are among the primary sources of gravitational waves targeted by ongoing pulsar timing array (PTA) experiments and the upcoming space-based Laser Interferometer Space Antenna (LISA) interferometer. However, their formation and merger rates are still highly uncertain. Recent upper limits on the stochastic gravitational wave background obtained by PTAs are starting to be in marginal tension with theoretical models for the pairing and orbital evolution of these systems. This tension can be resolved by assuming that these binaries are more eccentric or interact more strongly with the environment (gas and stars) than expected, or by accounting for possible selection biases in the construction of the theoretical models. However, another (pessimistic) possibility is that these binaries do not merge at all, but stall at large (˜pc) separations. We explore this extreme scenario by using a semi-analytic galaxy formation model including massive black holes (isolated and in binaries), and show that future generations of PTAs will detect the stochastic gravitational wave background from the massive black hole binary population within 10-15 yr of observations, even in the `nightmare scenario' in which all binaries stall at the hardening radius. Moreover, we argue that this scenario is too pessimistic, because our model predicts the existence of a subpopulation of binaries with small mass ratios (q ≲ 10-3) that should merge within a Hubble time simply as a result of gravitational wave emission. This subpopulation will be observable with large signal-to-noise ratios by future PTAs thanks to next-generation radio telescopes such as Square Kilometre Array or Five-hundred-meter Aperture Spherical Telescope, and possibly by LISA.

Study of diffusion of wave packets in a square lattice under external fields along the discrete nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

de Brito, P. E.; Nazareno, H. N.

2012-09-01

The object of the present work is to analyze the effect of nonlinearity on wave packet propagation in a square lattice subject to a magnetic and an electric field in the Hall configuration, by using the Discrete Nonlinear Schrödinger Equation (DNLSE). In previous works we have shown that without the nonlinear term, the presence of the magnetic field induces the formation of vortices that remain stationary, while a wave packet is introduced in the system. As for the effect of an applied electric field, it was shown that the vortices propagate in a direction perpendicular to the electric field, similar behavior as presented in the classical treatment, we provide a quantum mechanics explanation for that. We have performed the calculations considering first the action of the magnetic field as well as the nonlinearity. The results indicate that for low values of the nonlinear parameter U the vortices remain stationary while preserving the form. For greater values of the parameter the picture gets distorted, the more so, the greater the nonlinearity. As for the inclusion of the electric field, we note that for small U, the wave packet propagates perpendicular to the applied field, until for greater values of U the wave gets partially localized in a definite region of the lattice. That is, for strong nonlinearity the wave packet gets partially trapped, while the tail of it can propagate through the lattice. Note that this tail propagation is responsible for the over-diffusion for long times of the wave packet under the action of an electric field. We have produced short films that show clearly the time evolution of the wave packet, which can add to the understanding of the dynamics.

Rupture Dynamics and Ground Motion from Earthquakes on Rough Faults in Heterogeneous Media

NASA Astrophysics Data System (ADS)

Bydlon, S. A.; Kozdon, J. E.; Duru, K.; Dunham, E. M.

2013-12-01

Heterogeneities in the material properties of Earth's crust scatter propagating seismic waves. The effects of scattered waves are reflected in the seismic coda and depend on the amplitude of the heterogeneities, spatial arrangement, and distance from source to receiver. In the vicinity of the fault, scattered waves influence the rupture process by introducing fluctuations in the stresses driving propagating ruptures. Further variability in the rupture process is introduced by naturally occurring geometric complexity of fault surfaces, and the stress changes that accompany slip on rough surfaces. Our goal is to better understand the origin of complexity in the earthquake source process, and to quantify the relative importance of source complexity and scattering along the propagation path in causing incoherence of high frequency ground motion. Using a 2D high order finite difference rupture dynamics code, we nucleate ruptures on either flat or rough faults that obey strongly rate-weakening friction laws. These faults are embedded in domains with spatially varying material properties characterized by Von Karman autocorrelation functions and their associated power spectral density functions, with variations in wave speed of approximately 5 to 10%. Flat fault simulations demonstrate that off-fault material heterogeneity, at least with this particular form and amplitude, has only a minor influence on the rupture process (i.e., fluctuations in slip and rupture velocity). In contrast, ruptures histories on rough faults in both homogeneous and heterogeneous media include much larger short-wavelength fluctuations in slip and rupture velocity. We therefore conclude that source complexity is dominantly influenced by fault geometric complexity. To examine contributions of scattering versus fault geometry on ground motions, we compute spatially averaged root-mean-square (RMS) acceleration values as a function of fault perpendicular distance for a homogeneous medium and several heterogeneous media characterized by different statistical properties. We find that at distances less than ~6 km from the fault, RMS acceleration values from simulations with homogeneous and heterogeneous media are similar, but at greater distances the RMS values associated with heterogeneous media are larger than those associated with homogeneous media. The magnitude of this divergence increases with the amplitude of the heterogeneities. For instance, for a heterogeneous medium with a 10% standard deviation in material property values relative to mean values, RMS accelerations are ~50% larger than for a homogeneous medium at distances greater than 6 km. This finding is attributed to the scattering of coherent pulses into multiple pulses of decreased amplitude that subsequently arrive at later times. In order to understand the robustness of these results, an extension of our dynamic rupture and wave propagation code to 3D is underway.

A novel design for passive misscromixers based on topology optimization method.

PubMed

Chen, Xueye; Li, Tiechuan

2016-08-01

In this paper, a series of novel passive micromixers, called topological micromixers with reversed flow (TMRFX), are proposed. The reversed flow in the microchannels can enhance chaotic advection and produce better mixing performance. Therefore the maximum of reversed flow is chosen as the objective function of the topology optimization problem. Because the square-wave unit is easier to fabricate and have better mixing performance than many other serpentine micromixers, square-wave structure becomes the original geometry structure. By simulating analysis, the series of TMRFX, namely TMRF, TMRF0.75, TMRF0.5, TMRF0.25, mix better than the square-wave micromixer at various Reynolds numbers (Re), but pressure drops of TMRFX are much higher. Lots of intensive numerical simulations are conducted to prove that TMRF and TMRF0.75 have remarkable advantages on mixing over other micromixers at various Re. The mixing performance of TMRF0.75 is similar to TMRF's. What's more, TMRF have a larger pressure drop than TMRF0.75, which means that TMRF have taken more energy than TMRF0.75. For a wide range of Re (Re ≤ 0.1 and Re ≥ 10), TMRF0.75 delivers a great performance and the mixing efficiency is greater than 95 %. Even in the range of 0.1-10 for the Re, the mixing efficiency of TMRF0.75 is higher than 85 %.

Differentially-charged and sequentially-switched square-wave pulse forming network

DOEpatents

North, George G. [Stockton, CA; Vogilin, George E. [Livermore, CA

1980-04-01

A pulse forming network for delivering a high-energy square-wave pulse to a load, including a series of inductive-capacitive sections wherein the capacitors are differentially charged higher further from the load. Each charged capacitor is isolated from adjacent sections and the load by means of a normally open switch at the output of each section. The switch between the load and the closest section to the load is closed to begin discharge of the capacitor in that section into the load. During discharge of each capacitor, the voltage thereacross falls to a predetermined potential with respect to the potential across the capacitor in the next adjacent section further from the load. When this potential is reached, it is used to close the switch in the adjacent section further from the load and thereby apply the charge in that section to the load through the adjacent section toward the load. Each successive section further from the load is sequentially switched in this manner to continuously and evenly supply energy to the load over the period of the pulse, with the differentially charged capacitors providing higher potentials away from the load to compensate for the voltage drop across the resistance of each inductor. This arrangement is low in cost and yet provides a high-energy pulse in an acceptable square-wave form.

Differentially-charged and sequentially-switched square-wave pulse forming network

DOEpatents

North, G.G.; Vogilin, G.E.

1980-04-01

Disclosed is a pulse forming network for delivering a high-energy square-wave pulse to a load, including a series of inductive-capacitive sections wherein the capacitors are differentially charged higher further from the load. Each charged capacitor is isolated from adjacent sections and the load by means of a normally open switch at the output of each section. The switch between the load and the closest section to the load is closed to begin discharge of the capacitor in that section into the load. During discharge of each capacitor, the voltage thereacross falls to a predetermined potential with respect to the potential across the capacitor in the next adjacent section further from the load. When this potential is reached, it is used to close the switch in the adjacent section further from the load and thereby apply the charge in that section to the load through the adjacent section toward the load. Each successive section further from the load is sequentially switched in this manner to continuously and evenly supply energy to the load over the period of the pulse, with the differentially charged capacitors providing higher potentials away from the load to compensate for the voltage drop across the resistance of each inductor. This arrangement is low in cost and yet provides a high-energy pulse in an acceptable square-wave form. 5 figs.

Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.

PubMed

Barus, C; Romanytsia, I; Striebig, N; Garçon, V

2016-11-01

A Square Wave Voltammetry electrochemical method is proposed to measure phosphate in seawater as pulse techniques offer a higher sensitivity as compared to classical cyclic voltammetry. Chronoamperometry cannot be either adapted for an in situ sensor since this method requires to have controlled convection which will be impossible in a miniaturised sensor. Tests and validation of Square Wave Voltammetry parameters have been performed using an open cell and for the first time with a small volume (<400µL) laboratory prototypes. Two designs of prototypes have been compared. Using high frequency (f=250Hz) allows to obtain a linear behaviour between 0.1 and 1µmolL(-1) with a very low limit of detection of 0.05 µmolL(-1) after 60min of complexation waiting time. In order to obtain a linear regression for a larger concentration range i.e. 0.25-4µmolL(-1), a lower frequency of 2.5Hz is needed. A limit of detection of 0.1µmolL(-1) is obtained in this case after 30min of complexation waiting time for the peak measured at E=0.12V. Changing the position of the molybdenum electrode for the complexation step and moving the detection into another electrochemical cell allow to decrease the reaction time down to 5min. Copyright © 2016 Elsevier B.V. All rights reserved.

Picosecond, tunable, high-brightness hard x-ray inverse Compton source at Duke storage ring

NASA Astrophysics Data System (ADS)

Litvinenko, Vladimir N.; Wu, Ying; Burnham, Bentley; Barnett, Genevieve A.; Madey, John M. J.

1995-09-01

We suggest a state-of-the art x-ray source using a compact electron storage ring with modest energy (less than 1 GeV) and a high power mm-wave as an undulator. A source of this type has x-ray energies and brightness comparable with third generation synchrotron light sources while it can be very compact and fit in a small university or industrial laboratory or hospital. We propose to operate an isochronous mm-wave FEL and a hard x-ray inverse Compton source at the Duke storage ring to test this concept. Resonant FEL conditions for the mm- wave will be provided by the off-axis interaction with an electromagnetic wave. A special optical resonator with holes for the e-beam is proposed for pumping a hard x-ray inverse Compton source with very high brightness. Simulation results of mm-wave FEL operation of the Duke storage ring are discussed. Expected performance of mm-wave FEL and hard x-ray inverse Compton source are presented.

Regional Detection of Decoupled Explosions, Yield Estimation from Surface Waves, Two-Dimensional Source Effects, Three-Dimensional Earthquake Modeling and Automated Magnitude Measures

DTIC Science & Technology

1980-07-01

41 3.2 EXPERIMENTAL DETERMINATION OF THE DEPENDENCE OF RAYLEIGH WAVE AMPLITUDE ON PROPERTIES OF THE SOURCE MATERIAL ...Surface Wave Observations ...... ................ 48 3.3.3 Surface Wave Dependence on Source Material Properties ..... ................ .. 51 SYSTEMS...with various aspects of the problem of estimating yield from single station recordings of surface waves. The material in these four summaries has been

Source process and tectonic implication of the January 20, 2007 Odaesan earthquake, South Korea

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Ali K.; Kim, K. Y.; Fnais, M. S.; Al-Amri, A. M.

2014-04-01

The source process for the 20th of January 2007, Mw 4.5 Odaesan earthquake in South Korea is investigated in the low- and high-frequency bands, using velocity and acceleration waveform data recorded by the Korea Meteorological Administration Seismographic Network at distances less than 70 km from the epicenter. Synthetic Green functions are adopted for the low-frequency band of 0.1-0.3 Hz by using the wave-number integration technique and the one dimensional velocity model beneath the epicentral area. An iterative technique was performed by a grid search across the strike, dip, rake, and focal depth of rupture nucleation parameters to find the best-fit double-couple mechanism. To resolve the nodal plane ambiguity, the spatiotemporal slip distribution on the fault surface was recovered using a non-negative least-square algorithm for each set of the grid-searched parameters. The focal depth of 10 km was determined through the grid search for depths in the range of 6-14 km. The best-fit double-couple mechanism obtained from the finite-source model indicates a vertical strike-slip faulting mechanism. The NW faulting plane gives comparatively smaller root-mean-squares (RMS) error than its auxiliary plane. Slip pattern event provides simple source process due to the effect of Low-frequency that acted as a point source model. Three empirical Green functions are adopted to investigate the source process in the high-frequency band. A set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2.0-4.0 km/s. Although there is a small difference between the RMS errors produced by the two orthogonal nodal planes, the SW dipping plane gives a smaller RMS error than its auxiliary plane. The slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high-frequency analysis; indicating a complex rupture scenario for such moderate-sized earthquake, similar to those reported for large earthquakes.

Early Separation Incentives: An Analysis of Survey Data and Reenlistment Decision-Making Models

DTIC Science & Technology

1993-05-01

Table 8 Analyses of Variance for COL by Race and Gender (Enlisted Personnel) SOURCE 2F TYPE III SS MEAN SQUARE F VALUE PR > F SEX 1 80219.5873...SOURCE TYPEIII MEAN SUARE F VALUE PR >F SEX 1 82779.4582 82779.4582 1.04 0.3074 RACE 4 202214.2787 50553.5697 0.64 0.6362 Note: R-Square= 0.004141 12...Table 10 Analyses of Variance for COL by Race and Gender (Commissioned officers) SOURCE DF TYPE III SS MEAN SQUARE F VALUE PR > F SEX 1 1843343.079

A statistical assessment of seismic models of the U.S. continental crust using Bayesian inversion of ambient noise surface wave dispersion data

NASA Astrophysics Data System (ADS)

Olugboji, T. M.; Lekic, V.; McDonough, W.

2017-07-01

We present a new approach for evaluating existing crustal models using ambient noise data sets and its associated uncertainties. We use a transdimensional hierarchical Bayesian inversion approach to invert ambient noise surface wave phase dispersion maps for Love and Rayleigh waves using measurements obtained from Ekström (2014). Spatiospectral analysis shows that our results are comparable to a linear least squares inverse approach (except at higher harmonic degrees), but the procedure has additional advantages: (1) it yields an autoadaptive parameterization that follows Earth structure without making restricting assumptions on model resolution (regularization or damping) and data errors; (2) it can recover non-Gaussian phase velocity probability distributions while quantifying the sources of uncertainties in the data measurements and modeling procedure; and (3) it enables statistical assessments of different crustal models (e.g., CRUST1.0, LITHO1.0, and NACr14) using variable resolution residual and standard deviation maps estimated from the ensemble. These assessments show that in the stable old crust of the Archean, the misfits are statistically negligible, requiring no significant update to crustal models from the ambient noise data set. In other regions of the U.S., significant updates to regionalization and crustal structure are expected especially in the shallow sedimentary basins and the tectonically active regions, where the differences between model predictions and data are statistically significant.

Finite‐fault Bayesian inversion of teleseismic body waves

USGS Publications Warehouse

Clayton, Brandon; Hartzell, Stephen; Moschetti, Morgan P.; Minson, Sarah E.

2017-01-01

Inverting geophysical data has provided fundamental information about the behavior of earthquake rupture. However, inferring kinematic source model parameters for finite‐fault ruptures is an intrinsically underdetermined problem (the problem of nonuniqueness), because we are restricted to finite noisy observations. Although many studies use least‐squares techniques to make the finite‐fault problem tractable, these methods generally lack the ability to apply non‐Gaussian error analysis and the imposition of nonlinear constraints. However, the Bayesian approach can be employed to find a Gaussian or non‐Gaussian distribution of all probable model parameters, while utilizing nonlinear constraints. We present case studies to quantify the resolving power and associated uncertainties using only teleseismic body waves in a Bayesian framework to infer the slip history for a synthetic case and two earthquakes: the 2011 Mw 7.1 Van, east Turkey, earthquake and the 2010 Mw 7.2 El Mayor–Cucapah, Baja California, earthquake. In implementing the Bayesian method, we further present two distinct solutions to investigate the uncertainties by performing the inversion with and without velocity structure perturbations. We find that the posterior ensemble becomes broader when including velocity structure variability and introduces a spatial smearing of slip. Using the Bayesian framework solely on teleseismic body waves, we find rake is poorly constrained by the observations and rise time is poorly resolved when slip amplitude is low.

P-wave fault-plane solutions and the generation of surface waves by earthquakes in the western United States

NASA Astrophysics Data System (ADS)

Patton, Howard J.

1985-08-01

Surface waves recorded at regional distances are used to study the source mechanisms of seven earthquakes in the western United States with magnitudes between 4.3 and 5.5. The source mechanisms of events in or on the margins of the Basin and Range show T-axis with an azimuth of N85°W +/- 16° and a plunge of 12° +/- 16°. Of the seven events, four have P-wave solutions that are inconsistent with surface-wave observations. Azimuths of the T-axis obtained from the surface-wave mechanisms and from the P-wave solutions differ by up to 45°. These events have dip-slip or oblique-slip mechanisms, and the source depths for three of the events are 5 km or less. Their source mechanisms and small magnitudes make identification of the P-wave first motion difficult due to poor signal-to-noise ratio of the initial P-wave and close arrivals of pP or sP with significant amplitude. We suggest that mis-identification of the P-wave first motion and distortion of the body-wave ray paths due to non-planar structure were sources of error in determining the nodal planes for these events.

Analysis of Dual Rotating Rake Data from the NASA Glenn Advanced Noise Control Fan Duct with Artificial Sources

NASA Technical Reports Server (NTRS)

Dahl, Milo D.; Sutliff, Daniel L.

2014-01-01

The Rotating Rake mode measurement system was designed to measure acoustic duct modes generated by a fan stage. Initially, the mode amplitudes and phases were quantified from a single rake measurement at one axial location. To directly measure the modes propagating in both directions within a duct, a second rake was mounted to the rotating system with an offset in both the axial and the azimuthal directions. The rotating rake data analysis technique was then extended to include the data measured by the second rake. The analysis resulted in a set of circumferential mode levels at each of the two rake microphone locations. Radial basis functions were then least-squares fit to this data to obtain the radial mode amplitudes for the modes propagating in both directions within the duct. Validation experiments have been conducted using artificial acoustic sources. Results are shown for the measurement of the standing waves in the duct from sound generated by one and two acoustic sources that are separated into the component modes propagating in both directions within the duct. Measured reflection coefficients from the open end of the duct are compared to analytical predictions.

Energy-optimal electrical excitation of nerve fibers.

PubMed

Jezernik, Saso; Morari, Manfred

2005-04-01

We derive, based on an analytical nerve membrane model and optimal control theory of dynamical systems, an energy-optimal stimulation current waveform for electrical excitation of nerve fibers. Optimal stimulation waveforms for nonleaky and leaky membranes are calculated. The case with a leaky membrane is a realistic case. Finally, we compare the waveforms and energies necessary for excitation of a leaky membrane in the case where the stimulation waveform is a square-wave current pulse, and in the case of energy-optimal stimulation. The optimal stimulation waveform is an exponentially rising waveform and necessitates considerably less energy to excite the nerve than a square-wave pulse (especially true for larger pulse durations). The described theoretical results can lead to drastically increased battery lifetime and/or decreased energy transmission requirements for implanted biomedical systems.

A Generalized Wave Diagram for Moving Sources

NASA Astrophysics Data System (ADS)

Alt, Robert; Wiley, Sam

2004-12-01

Many introductory physics texts1-5 accompany the discussion of the Doppler effect and the formation of shock waves with diagrams illustrating the effect of a source moving through an elastic medium. Typically these diagrams consist of a series of equally spaced dots, representing the location of the source at different times. These are surrounded by a series of successively smaller circles representing wave fronts (see Fig. 1). While such a diagram provides a clear illustration of the shock wave produced by a source moving at a speed greater than the wave speed, and also the resultant pattern when the source speed is less than the wave speed (the Doppler effect), the texts do not often show the details of the construction. As a result, the key connection between the relative distance traveled by the source and the distance traveled by the wave is not explicitly made. In this paper we describe an approach emphasizing this connection that we have found to be a useful classroom supplement to the usual text presentation. As shown in Fig. 2 and Fig. 3, the Doppler effect and the shock wave can be illustrated by diagrams generated by the construction that follows.

Source location impact on relative tsunami strength along the U.S. West Coast

NASA Astrophysics Data System (ADS)

Rasmussen, L.; Bromirski, P. D.; Miller, A. J.; Arcas, D.; Flick, R. E.; Hendershott, M. C.

2015-07-01

Tsunami propagation simulations are used to identify which tsunami source locations would produce the highest amplitude waves on approach to key population centers along the U.S. West Coast. The reasons for preferential influence of certain remote excitation sites are explored by examining model time sequences of tsunami wave patterns emanating from the source. Distant bathymetric features in the West and Central Pacific can redirect tsunami energy into narrow paths with anomalously large wave height that have disproportionate impact on small areas of coastline. The source region generating the waves can be as little as 100 km along a subduction zone, resulting in distinct source-target pairs with sharply amplified wave energy at the target. Tsunami spectral ratios examined for transects near the source, after crossing the West Pacific, and on approach to the coast illustrate how prominent bathymetric features alter wave spectral distributions, and relate to both the timing and magnitude of waves approaching shore. To contextualize the potential impact of tsunamis from high-amplitude source-target pairs, the source characteristics of major historical earthquakes and tsunamis in 1960, 1964, and 2011 are used to generate comparable events originating at the highest-amplitude source locations for each coastal target. This creates a type of "worst-case scenario," a replicate of each region's historically largest earthquake positioned at the fault segment that would produce the most incoming tsunami energy at each target port. An amplification factor provides a measure of how the incoming wave height from the worst-case source compares to the historical event.

Modulation instability initiated high power all-fiber supercontinuum lasers and their applications

NASA Astrophysics Data System (ADS)

Alexander, Vinay V.; Kulkarni, Ojas P.; Kumar, Malay; Xia, Chenan; Islam, Mohammed N.; Terry, Fred L.; Welsh, Michael J.; Ke, Kevin; Freeman, Michael J.; Neelakandan, Manickam; Chan, Allan

2012-09-01

High average power, all-fiber integrated, broadband supercontinuum (SC) sources are demonstrated. Architecture for SC generation using amplified picosecond/nanosecond laser diode (LD) pulses followed by modulation instability (MI) induced pulse breakup is presented and used to demonstrate SC sources from the mid-IR to the visible wavelengths. In addition to the simplicity in implementation, this architecture allows scaling up of the SC average power by increasing the pulse repetition rate and the corresponding pump power, while keeping the peak power, and, hence, the spectral extent approximately constant. Using this process, we demonstrate >10 W in a mid-IR SC extending from ˜0.8 to 4 μm, >5 W in a near IR SC extending from ˜0.8 to 2.8 μm, and >0.7 W in a visible SC extending from ˜0.45 to 1.2 μm. SC modulation capability is also demonstrated in a mid-IR SC laser with ˜3.9 W in an SC extending from ˜0.8 to 4.3 μm. The entire system and SC output in this case is modulated by a 500 Hz square wave at 50% duty cycle without any external chopping or modulation. We also explore the use of thulium doped fiber amplifier (TDFA) stages for mid-IR SC generation. In addition to the higher pump to signal conversion efficiency demonstrated in TDFAs compared to erbium/ytterbium doped fiber amplifier (EYFA), the shifting of the SC pump from ˜1.5 to ˜2 μm is pursued with an attempt to generate a longer extending SC into the mid-IR. We demonstrate ˜2.5 times higher optical conversion efficiency from pump to SC generation in wavelengths beyond 3.8 μm in the TDFA versus the EYFA based SC systems. The TDFA SC spectrum extends from ˜1.9 to 4.5 μm with ˜2.6 W at 50% modulation with a 250 Hz square wave. A variety of applications in defense, health care and metrology are also demonstrated using the SC laser systems presented in this paper.

Screw withdrawal : a means to evaluate densities of in-situ wood members

Treesearch

Zhiyong Cai; Michael O. Hunt; Robert J. Ross; Lawrence A. Soltis

2003-01-01

Dynamic modulus of elasticity (MOE) of a wood member is defined as the product of its density and square of stress wave speed. The dynamic MOE, which is highly correlated to the static MOE, is commonly used to estimate the load carrying capacity and serviceability of in-situ wood members. The stress wave speed can be estimated using ultrasonic, impact, or vibration...

Imaging and control of interfering wave packets in a dissociating molecule.

PubMed

Skovsen, Esben; Machholm, Mette; Ejdrup, Tine; Thøgersen, Jan; Stapelfeldt, Henrik

2002-09-23

Using two identical 110 femtosecond (fs) optical pulses separated by 310 fs, we launch two dissociative wave packets in I2. We measure the square of the wave function as a function of both the internuclear separation, /Psi(R)/(2), and of the internuclear velocity, /Psi(v(R))/(2), by ionizing the dissociating molecule with an intense 20 fs probe pulse. Strong interference is observed in both /Psi(R)/(2) and in /Psi(v(R))/(2). The interference, and therefore the shape of the wave function, is controlled through the phase difference between the two dissociation pulses in good agreement with calculations.

Determination of the mode composition of long-wave disturbances in a supersonic flow in a hotshot wind tunnel

NASA Astrophysics Data System (ADS)

Tsyryulnikov, I. S.; Kirilovskiy, S. V.; Poplavskaya, T. V.

2016-10-01

In this paper, we describe a new method of mode decomposition of disturbances on the basis of specific features of interaction of long-wave free-stream disturbances with the shock wave and knowing the trends of changing of the conversion factors of various disturbance modes due to variations of the shock wave incidence angle. The range of admissible root-mean-square amplitudes of oscillations of vortex, entropy, and acoustic modes in the free stream generated in IT-302M was obtained by using the pressure fluctuations measured on the model surface and the calculated conversion factors.

Wideband radar cross section reduction using two-dimensional phase gradient metasurfaces

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

Li, Yongfeng; Qu, Shaobo; Wang, Jiafu

2014-06-02

Phase gradient metasurface (PGMs) are artificial surfaces that can provide pre-defined in-plane wave-vectors to manipulate the directions of refracted/reflected waves. In this Letter, we propose to achieve wideband radar cross section (RCS) reduction using two-dimensional (2D) PGMs. A 2D PGM was designed using a square combination of 49 split-ring sub-unit cells. The PGM can provide additional wave-vectors along the two in-plane directions simultaneously, leading to either surface wave conversion, deflected reflection, or diffuse reflection. Both the simulation and experiment results verified the wide-band, polarization-independent, high-efficiency RCS reduction induced by the 2D PGM.

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

PubMed

Sen, Novonil; Kundu, Tribikram

2018-07-01

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

Muscle contraction during electro-muscular incapacitation: A comparison between square-wave pulses and the TASER(®) X26 Electronic control device.

PubMed

Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

2011-01-01

Electronic control devices (including the Advanced TASER(®) X26 model produced by TASER International) incapacitate individuals by causing muscle contractions. To provide information relevant to development of future potential devices, effects of monophasic square waves with different parameters were compared with those of the X26 electronic control device, using two animal models (frogs and swine). Pulse power, electrical pulse charge, pulse duration, and pulse repetition frequency affected muscle contraction. There was no difference in the charge required, between the square waveform and the X26 waveform, to cause approximately the same muscle-contraction response (in terms of the strength-duration curve). Thus, on the basis of these initial studies, the detailed shape of a waveform may not be important in terms of generating electro-muscular incapacitation. More detailed studies, however, may be required to thoroughly test all potential waveforms to be considered for future use in ECDs. 2010 American Academy of Forensic Sciences. Published 2010. This article is a U.S. Government work and is in the public domain in the U.S.A.

3-component beamforming analysis of ambient seismic noise field for Love and Rayleigh wave source directions

NASA Astrophysics Data System (ADS)

Juretzek, Carina; Hadziioannou, Céline

2014-05-01

Our knowledge about common and different origins of Love and Rayleigh waves observed in the microseism band of the ambient seismic noise field is still limited, including the understanding of source locations and source mechanisms. Multi-component array methods are suitable to address this issue. In this work we use a 3-component beamforming algorithm to obtain source directions and polarization states of the ambient seismic noise field within the primary and secondary microseism bands recorded at the Gräfenberg array in southern Germany. The method allows to distinguish between different polarized waves present in the seismic noise field and estimates Love and Rayleigh wave source directions and their seasonal variations using one year of array data. We find mainly coinciding directions for the strongest acting sources of both wave types at the primary microseism and different source directions at the secondary microseism.

Crosswell seismic studies in gas hydrate-bearing sediments: P wave velocity and attenuation tomography

NASA Astrophysics Data System (ADS)

Bauer, K.; Haberland, Ch.; Pratt, R. G.; Ryberg, T.; Weber, M. H.; Mallik Working Group

2003-04-01

We present crosswell seismic data from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. The crosswell seismic measurements were carried out by making use of two 1160 m deep observation wells (Mallik 3L-38 and 4L-38) both 45 m from and co-planar with the 1188 m deep production research well (5L-38). A high power piezo-ceramic source was used to generate sweeped signals with frequencies between 100 and 2000 Hz recorded with arrays of 8 hydrophones per depth level. A depth range between 800 and 1150 m was covered, with shot and receiver spacings of 0.75 m. High quality data could be collected during the survey which allow for application of a wide range of crosswell seismic methods. The initial data analysis included suppression of tube wave energy and picking of first arrivals. A damped least-squares algorithm was used to derive P-wave velocities from the travel time data. Next, t* values were derived from the decay of the amplitude spectra, which served as input parameters for a damped least-squares attenuation tomography. The initial results of the P-wave velocity and attenuation tomography reveal significant features reflecting the stratigraphic environment and allow for detection and eventually quantification of gas hydrate bearing sediments. A prominent correlation between P velocity and attenuation was found for the gas hydrate layers. This contradicts to the apparently more meaningful inverse correlation as it was determined for the gas hydrates at the Blake Ridge but supports the results from the Mallik 2L-38 sonic log data. The P velocities and attenuation values, if combined with other information can be important for the quantitative evaluation of the gas hydrate saturation, and may further constrain petrophysical models of the hydrate bearing sediment formation.

Study of blasting seismic effects of underground powerhouse of pumped storage project in granite condition

NASA Astrophysics Data System (ADS)

Wan, Sheng; Li, Hui

2018-03-01

Though the test of blasting vibration, the blasting seismic wave propagation laws in southern granite pumped storage power project are studied. Attenuation coefficient of seismic wave and factors coefficient are acquired by the method of least squares regression analysis according to Sadaovsky empirical formula, and the empirical formula of seismic wave is obtained. This paper mainly discusses on the test of blasting vibration and the procedure of calculation. Our practice might as well serve as a reference for similar projects to come.

Observation and simulation of flow on soap film induced by concentration gradient

NASA Astrophysics Data System (ADS)

Ohnishi, Mitsuru; Yoshihara, Shoichi; Azuma, Hisao

The behavior of the flow and capillary wave induced on the film surface by the surfactant concentration difference is studied. Flat soap film is used as a model of thin film. The result is applicable to the case of flow by thermal gradient. The Schlieren method is used to observe the flow and the wave on the soap film. It is found that the wave velocities, in the case of a high surface tension difference, are linearly related to the square root of the surface tension difference.

The thermal-wave model: A Schroedinger-like equation for charged particle beam dynamics

NASA Technical Reports Server (NTRS)

Fedele, Renato; Miele, G.

1994-01-01

We review some results on longitudinal beam dynamics obtained in the framework of the Thermal Wave Model (TWM). In this model, which has recently shown the capability to describe both longitudinal and transverse dynamics of charged particle beams, the beam dynamics is ruled by Schroedinger-like equations for the beam wave functions, whose squared modulus is proportional to the beam density profile. Remarkably, the role of the Planck constant is played by a diffractive constant epsilon, the emittance, which has a thermal nature.

Sensitivity of ground motion parameters to local site effects for areas characterised by a thick buried low-velocity layer.

NASA Astrophysics Data System (ADS)

Farrugia, Daniela; Galea, Pauline; D'Amico, Sebastiano; Paolucci, Enrico

2016-04-01

It is well known that earthquake damage at a particular site depends on the source, the path that the waves travel through and the local geology. The latter is capable of amplifying and changing the frequency content of the incoming seismic waves. In regions of sparse or no strong ground motion records, like Malta (Central Mediterranean), ground motion simulations are used to obtain parameters for purposes of seismic design and analysis. As an input to ground motion simulations, amplification functions related to the shallow subsurface are required. Shear-wave velocity profiles of several sites on the Maltese islands were obtained using the Horizontal-to-Vertical Spectral Ratio (H/V), the Extended Spatial Auto-Correlation (ESAC) technique and the Genetic Algorithm. The sites chosen were all characterised by a layer of Blue Clay, which can be up to 75 m thick, underlying the Upper Coralline Limestone, a fossiliferous coarse grained limestone. This situation gives rise to a velocity inversion. Available borehole data generally extends down till the top of the Blue Clay layer therefore the only way to check the validity of the modelled shear-wave velocity profile is through the thickness of the topmost layer. Surface wave methods are characterised by uncertainties related to the measurements and the model used for interpretation. Moreover the inversion procedure is also highly non-unique. Such uncertainties are not commonly included in site response analysis. Yet, the propagation of uncertainties from the extracted dispersion curves to inversion solutions can lead to significant differences in the simulations (Boaga et al., 2011). In this study, a series of sensitivity analyses will be presented with the aim of better identifying those stratigraphic properties which can perturb the ground motion simulation results. The stochastic one-dimensional site response analysis algorithm, Extended Source Simulation (EXSIM; Motazedian and Atkinson, 2005), was used to perform these analyses. The amplification functions were extracted using the programme SITE_AMP (Boore, 2003), which computes amplifications based on the square root of the effective seismic impedance. Sensitivity indices were obtained by changing two parameters (thickness and shear-wave velocity) of the different layers while keeping the others constant. Additional analyses were carried out by producing various profiles within specified boundaries which are able to fit the experimental data. The analyses also show the important role that the shear-wave velocity profiles play in ground motion simulations. The results obtained highlight the importance of the correct knowledge of both the properties of the Upper Coralline Limestone and the Blue Clay, especially the Blue Clay thickness.

Characteristics of microseisms in South China

NASA Astrophysics Data System (ADS)

Xiao, H.; Xue, M.; Pan, M.

2017-12-01

Microseisms are generated by coupling ocean waves and the solid earth, and their main frequencies and sources vary in different regions of the world. We use continuous waveforms from three arrays along the southern coast of China to study the types and sources of microseisms in South China. Using cross-correlation functions and a three-component F-K analysis, we found that the main type of microseisms in this area propagates as surface waves, arriving mainly from the east and southeast. We also found that the surface waves have different characteristics: the Rayleigh waves and Love waves have diverse sources, are frequency dependent and have no obvious seasonal changes. In the 0.2-0.25 Hz frequency band, the Rayleigh and Love waves at the W01, W02 and ST arrays show the influences of common microseisms sources from Taiwan and the Luzon Strait. However, in the 0.27-0.5 Hz frequency band, the energy of the microseisms tends to be governed by the offshore sources near the stations. In addition, the Love waves have broader back azimuths than those of the Rayleigh waves, which may due to the energy transfer between Rayleigh and Love waves in the thick sediment layers.

NW transverse fault system in Southern Bogota, Colombia: New seismologic and structural evidences derived from focal mechanisms and stress field determination

NASA Astrophysics Data System (ADS)

Angel Amaya, J.; Fierro Morales, J.; Ordoñez Potes, M.; Blanco, M.

2012-12-01

We present new seismological, morphotectonic and structural data of the Southern Bogota area. The goals of the study were to characterize the NW transverse fault system and to evaluate its effect on seismic wave's generation and propagation. The data set included epicenters of the RSNC (Red Sismologica Nacional de Colombia) catalog over the period 1993-2012, historical description of seismic events (period 1644-1921), structural field data (scale 1:100000) and remote sensors interpretation. The methodology included the structural analysis of over 476 faults having a known sense of offset by using a least squares iterative inversion outlined by Angelier (1984) to determinate the mean deviatoric principal stress tensor. Preliminary conclusions showed that both propagation medium and direction are determined by the structural and mechanic conditions of the Southern Bogota Shear Zone (SBSZ) defined by Fierro & Angel, (2008) as a NW-SE oblique-slip fault zone within sinistral and normal regimes. Based on both data sources (focal mechanism and field structural data) we attempted to reconstruct the stress field starting with a strike slip faulting stress regime (S2 vertical), the solution yielded a ENE-WSW orientation for horizontal principal stress (S1). It is hypothesized that the NW oblique-slip fault zone may generate and/or propagate seismic waves, as a local source, implying local hazard to Bogota the capital city of Colombia with over 8 million habitants.

Sensitivity of new detection method for ultra-low frequency gravitational waves with pulsar spin-down rate statistics

NASA Astrophysics Data System (ADS)

Yonemaru, Naoyuki; Kumamoto, Hiroki; Takahashi, Keitaro; Kuroyanagi, Sachiko

2018-04-01

A new detection method for ultra-low frequency gravitational waves (GWs) with a frequency much lower than the observational range of pulsar timing arrays (PTAs) was suggested in Yonemaru et al. (2016). In the PTA analysis, ultra-low frequency GWs (≲ 10-10 Hz) which evolve just linearly during the observation time span are absorbed by the pulsar spin-down rates since both have the same effect on the pulse arrival time. Therefore, such GWs cannot be detected by the conventional method of PTAs. However, the bias on the observed spin-down rates depends on relative direction of a pulsar and GW source and shows a quadrupole pattern in the sky. Thus, if we divide the pulsars according to the position in the sky and see the difference in the statistics of the spin-down rates, ultra-low frequency GWs from a single source can be detected. In this paper, we evaluate the potential of this method by Monte-Carlo simulations and estimate the sensitivity, considering only the "Earth term" while the "pulsar term" acts like random noise for GW frequencies 10-13 - 10-10 Hz. We find that with 3,000 milli-second pulsars, which are expected to be discovered by a future survey with the Square Kilometre Array, GWs with the derivative of amplitude of about 3 × 10^{-19} {s}^{-1} can in principle be detected. Implications for possible supermassive binary black holes in Sgr* and M87 are also given.

Pseudospin symmetry of the Dirac equation for a Möbius square plus Mie type potential with a Coulomb-like tensor interaction via SUSYQM

NASA Astrophysics Data System (ADS)

Akpan, N. Ikot; Zarrinkamar, S.; Eno, J. Ibanga; Maghsoodi, E.; Hassanabadi, H.

2014-01-01

We investigate the approximate solution of the Dirac equation for a combination of Möbius square and Mie type potentials under the pseudospin symmetry limit by using supersymmetry quantum mechanics. We obtain the bound-state energy equation and the corresponding spinor wave functions in an approximate analytical manner. We comment on the system via various useful figures and tables.

Kinetic Super-Resolution Long-Wave Infrared (KSR LWIR) Thermography Diagnostic for Building Envelopes: Scott AFB, IL

DTIC Science & Technology

2015-08-18

techniques of measuring energy loss due to enve- lope inefficiencies from the built environment. A multi-sensor hardware device attached to the roof of a...at this installa- tion, recommends specific energy conservation measures (ECMs), and quantifies significant potential return on investment. ERDC/CERL...to several thousand square feet, total building square feet was used as a metric to measure the cost effectiveness of handheld versus mobile

On the parameters influencing air-water gas exchange

NASA Astrophysics Data System (ADS)

JäHne, Bernd; Münnich, Karl Otto; BöSinger, Rainer; Dutzi, Alfred; Huber, Werner; Libner, Peter

1987-02-01

Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k ∝ Sc-⅔ to k ∝ Sc-½indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes.

Sequential deconvolution from wave-front sensing using bivariate simplex splines

NASA Astrophysics Data System (ADS)

Guo, Shiping; Zhang, Rongzhi; Li, Jisheng; Zou, Jianhua; Xu, Rong; Liu, Changhai

2015-05-01

Deconvolution from wave-front sensing (DWFS) is an imaging compensation technique for turbulence degraded images based on simultaneous recording of short exposure images and wave-front sensor data. This paper employs the multivariate splines method for the sequential DWFS: a bivariate simplex splines based average slopes measurement model is built firstly for Shack-Hartmann wave-front sensor; next, a well-conditioned least squares estimator for the spline coefficients is constructed using multiple Shack-Hartmann measurements; then, the distorted wave-front is uniquely determined by the estimated spline coefficients; the object image is finally obtained by non-blind deconvolution processing. Simulated experiments in different turbulence strength show that our method performs superior image restoration results and noise rejection capability especially when extracting the multidirectional phase derivatives.

Diffusion Driven Combustion Waves in Porous Media

NASA Technical Reports Server (NTRS)

Aldushin, A. P.; Matkowsky, B. J.

2000-01-01

Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases the wave velocity. In addition to the reaction and diffusion layers, the uniformly propagating wave structure includes a layer with a pressure gradient, where the gas motion is induced by the production or consumption of the gas in the reaction as well as by thermal expansion of the gas. The width of this zone determines the scale of the combustion wave in the porous medium.

Observations of shallow water marine ambient sound: the low frequency underwater soundscape of the central Oregon coast.

PubMed

Haxel, Joseph H; Dziak, Robert P; Matsumoto, Haru

2013-05-01

A year-long experiment (March 2010 to April 2011) measuring ambient sound at a shallow water site (50 m) on the central OR coast near the Port of Newport provides important baseline information for comparisons with future measurements associated with resource development along the inner continental shelf of the Pacific Northwest. Ambient levels in frequencies affected by surf-generated noise (f < 100 Hz) characterize the site as a high-energy end member within the spectrum of shallow water coastal areas influenced by breaking waves. Dominant sound sources include locally generated ship noise (66% of total hours contain local ship noise), breaking surf, wind induced wave breaking and baleen whale vocalizations. Additionally, an increase in spectral levels for frequencies ranging from 35 to 100 Hz is attributed to noise radiated from distant commercial ship commerce. One-second root mean square (rms) sound pressure level (SPLrms) estimates calculated across the 10-840 Hz frequency band for the entire year long deployment show minimum, mean, and maximum values of 84 dB, 101 dB, and 152 dB re 1 μPa.

Active control of transmission loss with smart foams.

PubMed

Kundu, Abhishek; Berry, Alain

2011-02-01

Smart foams combine the complimentary advantages of passive foam material and spatially distributed piezoelectric actuator embedded in it for active noise control applications. In this paper, the problem of improving the transmission loss of smart foams using active control strategies has been investigated both numerically and experimentally inside a waveguide under the condition of plane wave propagation. The finite element simulation of a coupled noise control system has been undertaken with three different smart foam designs and their effectiveness in cancelling the transmitted wave downstream of the smart foam have been studied. The simulation results provide insight into the physical phenomenon of active noise cancellation and explain the impact of the smart foam designs on the optimal active control results. Experimental studies aimed at implementing the real-time control for transmission loss optimization have been performed using the classical single input/single output filtered-reference least mean squares algorithm. The active control results with broadband and single frequency primary source inputs demonstrate a good improvement in the transmission loss of the smart foams. The study gives a comparative description of the transmission and absorption control problems in light of the modification of the vibration response of the piezoelectric actuator under active control.

The Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey

NASA Technical Reports Server (NTRS)

Marriage, T. A.; Juin, J. B.; Lin, Y. T.; Marsden, D.; Nolta, M. R.; Partridge, B.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.;

Highly Compact Circulators in Square-Lattice Photonic Crystal Waveguides

PubMed Central

Jin, Xin; Ouyang, Zhengbiao; Wang, Qiong; Lin, Mi; Wen, Guohua; Wang, Jingjing

2014-01-01

We propose, demonstrate and investigate highly compact circulators with ultra-low insertion loss in square-lattice- square-rod-photonic-crystal waveguides. Only a single magneto- optical square rod is required to be inserted into the cross center of waveguides, making the structure very compact and ultra efficient. The square rods around the center defect rod are replaced by several right-angled-triangle rods, reducing the insertion loss further and promoting the isolations as well. By choosing a linear-dispersion region and considering the mode patterns in the square magneto-optical rod, the operating mechanism of the circulator is analyzed. By applying the finite-element method together with the Nelder-Mead optimization method, an extremely low insertion loss of 0.02 dB for the transmitted wave and ultra high isolation of 46 dB∼48 dB for the isolated port are obtained. The idea presented can be applied to build circulators in different wavebands, e.g., microwave or Tera-Hertz. PMID:25415417

Highly compact circulators in square-lattice photonic crystal waveguides.

PubMed

Jin, Xin; Ouyang, Zhengbiao; Wang, Qiong; Lin, Mi; Wen, Guohua; Wang, Jingjing

2014-01-01

We propose, demonstrate and investigate highly compact circulators with ultra-low insertion loss in square-lattice- square-rod-photonic-crystal waveguides. Only a single magneto- optical square rod is required to be inserted into the cross center of waveguides, making the structure very compact and ultra efficient. The square rods around the center defect rod are replaced by several right-angled-triangle rods, reducing the insertion loss further and promoting the isolations as well. By choosing a linear-dispersion region and considering the mode patterns in the square magneto-optical rod, the operating mechanism of the circulator is analyzed. By applying the finite-element method together with the Nelder-Mead optimization method, an extremely low insertion loss of 0.02 dB for the transmitted wave and ultra high isolation of 46 dB∼48 dB for the isolated port are obtained. The idea presented can be applied to build circulators in different wavebands, e.g., microwave or Tera-Hertz.

Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation.

PubMed

Suizu, Koji; Koketsu, Kaoru; Shibuya, Takayuki; Tsutsui, Toshihiro; Akiba, Takuya; Kawase, Kodo

2009-04-13

Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such a development of efficient and wide tunable THz-wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-wave generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. 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. We fabricated MgO-doped lithium niobate slab waveguide with 3.8 microm of thickness and demonstrated difference frequency generation of THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-wave generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10(-5) %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-wave sources.

Source signature estimation from multimode surface waves via mode-separated virtual real source method

NASA Astrophysics Data System (ADS)

Gao, Lingli; Pan, Yudi

2018-05-01

The correct estimation of the seismic source signature is crucial to exploration geophysics. Based on seismic interferometry, the virtual real source (VRS) method provides a model-independent way for source signature estimation. However, when encountering multimode surface waves, which are commonly seen in the shallow seismic survey, strong spurious events appear in seismic interferometric results. These spurious events introduce errors in the virtual-source recordings and reduce the accuracy of the source signature estimated by the VRS method. In order to estimate a correct source signature from multimode surface waves, we propose a mode-separated VRS method. In this method, multimode surface waves are mode separated before seismic interferometry. Virtual-source recordings are then obtained by applying seismic interferometry to each mode individually. Therefore, artefacts caused by cross-mode correlation are excluded in the virtual-source recordings and the estimated source signatures. A synthetic example showed that a correct source signature can be estimated with the proposed method, while strong spurious oscillation occurs in the estimated source signature if we do not apply mode separation first. We also applied the proposed method to a field example, which verified its validity and effectiveness in estimating seismic source signature from shallow seismic shot gathers containing multimode surface waves.

Capillary wave Hamiltonian for the Landau-Ginzburg-Wilson density functional

NASA Astrophysics Data System (ADS)

Chacón, Enrique; Tarazona, Pedro

2016-06-01

We study the link between the density functional (DF) formalism and the capillary wave theory (CWT) for liquid surfaces, focused on the Landau-Ginzburg-Wilson (LGW) model, or square gradient DF expansion, with a symmetric double parabola free energy, which has been extensively used in theoretical studies of this problem. We show the equivalence between the non-local DF results of Parry and coworkers and the direct evaluation of the mean square fluctuations of the intrinsic surface, as is done in the intrinsic sampling method for computer simulations. The definition of effective wave-vector dependent surface tensions is reviewed and we obtain new proposals for the LGW model. The surface weight proposed by Blokhuis and the surface mode analysis proposed by Stecki provide consistent and optimal effective definitions for the extended CWT Hamiltonian associated to the DF model. A non-local, or coarse-grained, definition of the intrinsic surface provides the missing element to get the mesoscopic surface Hamiltonian from the molecular DF description, as had been proposed a long time ago by Dietrich and coworkers.

Capillary wave Hamiltonian for the Landau-Ginzburg-Wilson density functional.

PubMed

Chacón, Enrique; Tarazona, Pedro

2016-06-22

We study the link between the density functional (DF) formalism and the capillary wave theory (CWT) for liquid surfaces, focused on the Landau-Ginzburg-Wilson (LGW) model, or square gradient DF expansion, with a symmetric double parabola free energy, which has been extensively used in theoretical studies of this problem. We show the equivalence between the non-local DF results of Parry and coworkers and the direct evaluation of the mean square fluctuations of the intrinsic surface, as is done in the intrinsic sampling method for computer simulations. The definition of effective wave-vector dependent surface tensions is reviewed and we obtain new proposals for the LGW model. The surface weight proposed by Blokhuis and the surface mode analysis proposed by Stecki provide consistent and optimal effective definitions for the extended CWT Hamiltonian associated to the DF model. A non-local, or coarse-grained, definition of the intrinsic surface provides the missing element to get the mesoscopic surface Hamiltonian from the molecular DF description, as had been proposed a long time ago by Dietrich and coworkers.

Modelling the vestibular head tilt response.

PubMed

Heibert, D; Lithgow, B

2005-03-01

This paper attempts to verify the existence of potentially diagnostically significant periodic signals thought to exist in recordings of neural activity originating from the vestibular nerve, following a single tilt of the head. It then attempts to find the physiological basis of this signal, in particular focusing on the mechanical response of the vestibular system. Simple mechanical models of the semi circular canals having angular velocities applied to them were looked at. A simple single canal model was simulated using CFX software. Finally, a simple model of all three canals with elastic duct walls and a moving cupula was constructed. Pressure waves within the canals were simulated using water hammer or pressure transient theory. In particular, it was investigated whether pressure waves within the utricle following a square pulse angular velocity applied to the canal(s) may be responsible for quasi-periodic oscillatory signals. The simulations showed that there are no pressure waves resonating within the canals following a square pulse angular velocity applied to the canal(s). The results show that the oscillatory signals are most likely not mechanical in origin. It was concluded that further investigation is required.

Bandgaps and directional properties of two-dimensional square beam-like zigzag lattices

NASA Astrophysics Data System (ADS)

Wang, Yan-Feng; Wang, Yue-Sheng; Zhang, Chuanzeng

2014-12-01

In this paper we propose four kinds of two-dimensional square beam-like zigzag lattice structures and study their bandgaps and directional propagation of elastic waves. The band structures are calculated by using the finite element method. Both the in-plane and out-of-plane waves are investigated simultaneously via the three-dimensional Euler beam elements. The mechanism of the bandgap generation is analyzed by studying the vibration modes at the bandgap edges. The effects of the geometry parameters of the xy- and z-zigzag lattices on the bandgaps are investigated and discussed. Multiple complete bandgaps are found owing to the separation of the degeneracy by introducing bending arms. The bandgaps are sensitive to the geometry parameters of the periodic systems. The deformed displacement fields of the harmonic responses of a finite lattice structure subjected to harmonic loads at different positions are illustrated to show the directional wave propagation. An extension of the proposed concept to the hexagonal lattices is also presented. The research work in this paper is relevant to the practical design of cellular structures with enhanced vibro-acoustics performance.

Noncoherent detection of periodic signals

NASA Technical Reports Server (NTRS)

Gagliardi, R. M.

1974-01-01

The optimal Bayes detector for a general periodic waveform having uniform delay and additive white Gaussian noise is examined. It is shown that the detector is much more complex than that for the well known cases of pure sine waves (i.e. classical noncoherent detection) and narrowband signals. An interpretation of the optimal processing is presented, and several implementations are discussed. The results have application to the noncoherent detection of optical square waves.

Note: Low phase noise programmable phase-locked loop with high temperature stability.

PubMed

Michálek, Vojtěch; Procházka, Ivan

2017-03-01

The design and construction of low jitter programmable phase-locked loop with low temperature coefficient of phase are presented. It has been designed for demanding high precision timing applications, especially as a clock source for event timer with subpicosecond precision. The phase-locked loop itself has a jitter of few hundreds of femtoseconds. It produces square wave with programmable output frequency from 100 MHz to 500 MHz and programmable amplitude of 0.25 V to 1.2 V peak-to-peak, which is locked to 5 MHz or 10 MHz reference frequency common for disciplined oscillators and highly stable clocks such as hydrogen maser. Moreover, it comprises an on-board temperature compensated crystal oscillator for stand-alone usage. The device provides temperature coefficient of the phase lock of 0.9 ps/K near room temperature.

Experimental study of the reversible behavior of modulational instability in optical fibers

NASA Astrophysics Data System (ADS)

van Simaeys, Gaetan; Emplit, Philippe; Haelterman, Marc

2002-03-01

We report what is to our knowledge the first clear-cut experimental evidence of the reversibility of modulational instability in dispersive Kerr media. It was possible to perform this experiment with standard telecommunication fiber because we used a specially designed 550-ps square-pulse laser source based on the two-wavelength configuration of a nonlinear optical loop mirror. Our observations demonstrate that reversibility is due to well-balanced and synchronous energy transfer among a significant number of spectral wave components. These results provide what we believe is the first evidence, in the field of nonlinear optics, of the universal Fermi-Pasta-Ulam recurrence phenomenon that has been predicted for a large number of conservative nonlinear systems, including those described by a nonlinear Schrödinger equation that is relevant to the context of the present study.

A dynamic system with digital lock-in-photon-counting for pharmacokinetic diffuse fluorescence tomography

NASA Astrophysics Data System (ADS)

Yin, Guoyan; Zhang, Limin; Zhang, Yanqi; Liu, Han; Du, Wenwen; Ma, Wenjuan; Zhao, Huijuan; Gao, Feng

2018-02-01

Pharmacokinetic diffuse fluorescence tomography (DFT) can describe the metabolic processes of fluorescent agents in biomedical tissue and provide helpful information for tumor differentiation. In this paper, a dynamic DFT system was developed by employing digital lock-in-photon-counting with square wave modulation, which predominates in ultra-high sensitivity and measurement parallelism. In this system, 16 frequency-encoded laser diodes (LDs) driven by self-designed light source system were distributed evenly in the imaging plane and irradiated simultaneously. Meanwhile, 16 detection fibers collected emission light in parallel by the digital lock-in-photon-counting module. The fundamental performances of the proposed system were assessed with phantom experiments in terms of stability, linearity, anti-crosstalk as well as images reconstruction. The results validated the availability of the proposed dynamic DFT system.

Affect of Brush Seals on Wave Rotor Performance Assessed

NASA Technical Reports Server (NTRS)

1995-01-01

The NASA Lewis Research Center's experimental and theoretical research shows that wave rotor topping can significantly enhance gas turbine engine performance levels. Engine-specific fuel consumption and specific power are potentially enhanced by 15 and 20 percent, respectively, in small (e.g., 400 to 700 hp) and intermediate (e.g., 3000 to 5000 hp) turboshaft engines. Furthermore, there is potential for a 3- to 6-percent specific fuel consumption enhancement in large (e.g., 80,000 to 100,000 lbf) turbofan engines. This wave-rotor-enhanced engine performance is accomplished within current material-limited temperature constraints. The completed first phase of experimental testing involved a three-port wave rotor cycle in which medium total pressure inlet air was divided into two outlet streams, one of higher total pressure and one of lower total pressure. The experiment successfully provided the data needed to characterize viscous, partial admission, and leakage loss mechanisms. Statistical analysis indicated that wave rotor product efficiency decreases linearly with the rotor to end-wall gap, the square of the friction factor, and the square of the passage of nondimensional opening time. Brush seals were installed to further minimize rotor passage-to-cavity leakage. The graph shows the effect of brush seals on wave rotor product efficiency. For the second-phase experiment, which involves a four-port wave rotor cycle in which heat is added to the Brayton cycle in an external burner, a one-dimensional design/analysis code is used in conjunction with a wave rotor performance optimization scheme and a two-dimensional Navier-Stokes code. The purpose of the four-port experiment is to demonstrate and validate the numerically predicted four-port pressure ratio versus temperature ratio at pressures and temperatures lower than those that would be encountered in a future wave rotor/demonstrator engine test. Lewis and the Allison Engine Company are collaborating to investigate wave rotor integration in an existing turboshaft engine. Recent theoretical efforts include simulating wave rotor dynamics (e.g., startup and load-change transient analysis), modifying the one-dimensional wave rotor code to simulate combustion internal to the wave rotor, and developing an analytical wave rotor design/analysis tool based on macroscopic balances for parametric wave rotor/engine analysis.

Sea surface mean square slope from Ku-band backscatter data

NASA Technical Reports Server (NTRS)

Jackson, F. C.; Walton, W. T.; Hines, D. E.; Walter, B. A.; Peng, C. Y.

1992-01-01

A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.

Initial observations from seismometers frozen into a borehole through the McMurdo Ice Shelf.

NASA Astrophysics Data System (ADS)

Prior, David; Eccles, Jennifer; Cooper, Joanna; Craw, Lisa; van Haastrecht, Laurine; Hamish Bowman, M.; Stevens, Craig; Gamble Rosevear, Madi; Hulbe, Christina; Gorman, Andrew; Horgan, Huw; Pyne, Alex

2017-04-01

A seismometer cable with two, three-component seismometers was frozen into a hot water borehole through the McMurdo Ice Shelf at Windless Bight in late December 2016. The seismometers are at 39m and 189m depth. The upper seismometer lies just below the firn-ice transition ( 37m) and very close to sea level ( 38m). The lower seismometer is positioned 30m above the base of the ice shelf ( 222m). The seismometers froze in within 40 (upper) to 60 (lower) hours of the last reaming operation. The temperature evolution during freezing is complicated, particularly for the lower seismometer. The complications are interpreted as the result of brine expulsion and brine pocket migration. We conducted an active source experiment using the frozen-in seismometers together with a surface seismometer and four lines of geophones radiating from the borehole, at 45-degree angles, to a distance of 240m. Sources included a traditional hammer and surface plate, two types of hammer activated surface shear wave sources (for hard and soft surfaces) and a hammer activated borehole source. The frozen-in seismometers show excellent separation of P - wave and S - wave arrivals for all sources, particularly on the lower seismometer. The surface shear sources give clearer separation of arrivals on the vertical and horizontal components. For some source to receiver geometries the surface shear sources give no P - wave arrival on the horizontal seismometer components and a very strong S - wave arrival that is partitioned between the horizontal components in correspondence with the source orientation. The borehole source (at 3 to 10m in the firn) also gives clearer separation of P - wave and S - wave arrivals compared to a surface hammer and plate. The frozen-in seismometers were also used to listen for natural events in the ice. Comparing the same events recorded at the surface and at depth, the latter are much less noisy than the former, leading to more clear interpretation. As in the active source experiments, P-wave and S-wave arrivals are clear and the partitioning onto different components (vertical and horizontal) is very clear. Using seismology to interpret the physical properties of ice masses is dependent on quality data. The patterns of anisotropy related to ice crystallographic preferred orientations (CPOs) are particularly rich for S - waves and the ability to measure S - wave velocities and shear wave splitting is of particular importance in using seismology to constrain CPOs. Our initial observations suggest that seismometers frozen-in at depth, together with artificial sources with controlled shear wave kinematics have great potential to help us constrain ice CPOs and resultant plastic anisotropy through seismic data.

Path-Specific Effects on Shear Motion Generation Using LargeN Array Waveform Data at the Source Physics Experiment (SPE) Site

NASA Astrophysics Data System (ADS)

Pitarka, A.; Mellors, R. J.; Walter, W. R.

2016-12-01

Depending on emplacement conditions and underground structure, and contrary to what is theoretically predicted for isotropic sources, recorded local, regional, and teleseismic waveforms from chemical explosions often contain shear waves with substantial energy. Consequently, the transportability of empirical techniques for yield estimation and source discrimination to regions with complex underground structure becomes problematic. Understanding the mechanisms of generation and conversion of shear waves caused by wave path effects during explosions can help improve techniques used in nuclear explosion monitoring. We used seismic data from LargeN, a dense array of three and one component geophones, to analyze far-field waveforms from the underground chemical explosion recorded during shot 5 of the Source Physics Experiment (SPE-5) at the Nevada National Security Site. Combined 3D elastic wave propagation modeling and frequency-wavenumber beam-forming on small arrays containing selected stations were used to detect and identify several wave phases, including primary and secondary S waves, and Rgwaves, and determine their direction of propagation. We were able to attribute key features of the waveforms, and wave phases to either source processes or propagation path effects, such as focusing and wave conversions. We also found that coda waves were more likely generated by path effects outside the source region, rather than by interaction of source generated waves with the emplacement structure. Waveform correlation and statistical analysis were performed to estimate average correlation length of small-scale heterogeneity in the upper sedimentary layers of the Yucca Flat basin in the area covered by the array. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS- 699180

Multimessenger astronomy with pulsar timing and X-ray observations of massive black hole binaries

NASA Astrophysics Data System (ADS)

Sesana, A.; Roedig, C.; Reynolds, M. T.; Dotti, M.

2012-02-01

In the decade of the dawn of gravitational wave astronomy, the concept of multimessenger astronomy, combining gravitational wave signals to conventional electromagnetic observation, has attracted the attention of the astrophysical community. So far, most of the effort has been focused on ground- and space-based laser interferometer sources, with little attention devoted to the ongoing and upcoming pulsar timing arrays (PTAs). We argue in this paper that PTA sources, being very massive (>108 M⊙) cosmologically nearby (z < 1) black hole binaries (MBHBs), are particularly appealing multimessenger carriers. According to current models for massive black hole formation and evolution, the planned Square Kilometre Array will observe thousands of such massive systems, being able to individually resolve and locate in the sky several of them (maybe up to a hundred). MBHBs form in galaxy mergers, which are usually accompanied by strong inflows of gas in the centre of the merger remnant. By employing a standard model for the evolution of MBHBs in circumbinary discs, with the aid of dedicated numerical simulations, we characterize the gas-binary interplay, identifying possible electromagnetic signatures of the PTA sources. We concentrate our investigation on two particularly promising scenarios in the high-energy domain, namely the detection of X-ray periodic variability and double broad Kα iron lines. Up to several hundreds of periodic X-ray sources with a flux >10-13 erg s-1 cm-2 will be in the reach of upcoming X-ray observatories; in the most optimistic case, a few of them may be already being observed by the MAXI detector placed on the International Space Station. Double relativistic Kα lines may be observable in a handful of low-redshift (z < 0.3) sources by proposed deep X-ray probes, such as Athena. The exact figures depend on the details of the adopted MBHB population and on the properties of the circumbinary discs, but the existence of a sizeable population of sources suitable to multimessenger astronomy is a robust prediction of our investigation.

Flip-Flop Digital Modulator

NASA Technical Reports Server (NTRS)

Eno, R. F.

1984-01-01

Clock switched on and off in response to data signal. Flip-flop modulator generates square-wave carrier frequency that is half clock frequency and turns carrier on and off. Final demodulator output logical inverse of data input.

Contrasts Between Young Males Dying by Suicide, Those Dying From Other Causes and Those Still Living: Observations From the National Longitudinal Survey of Adolescent to Adult Health.

PubMed

Feigelman, William; Joiner, Thomas; Rosen, Zohn; Silva, Caroline; Mueller, Anna S

2016-07-02

Utilizing Add Health longitudinal data, we compared 21 male suicide casualties to 10,101 living respondents identifying suicide correlates. 21 suicide decedents completed surveys in 1994/1995 (Wave 1) and 11 completed at Wave 3; responses were compared with Chi-square and oneway ANOVA tests. Suicide decedents were prone to higher delinquency and fighting at Wave 1, but not at Wave 3. At Wave 1 suicide decedents remained undistinguished from living respondents in depression, self-esteem, and drug uses. Yet, after Wave 3, the 11 respondents dying by suicide showed significantly higher depression, drug use and lower self-esteem. Delinquency trends can readily understood, but more complex causes are needed to account for unexpected changes in self-esteem, depression and drug uses.

Wave theory of turbulence in compressible media (acoustic theory of turbulence)

NASA Technical Reports Server (NTRS)

Kentzer, C. P.

1975-01-01

The generation and the transmission of sound in turbulent flows are treated as one of the several aspects of wave propagation in turbulence. Fluid fluctuations are decomposed into orthogonal Fourier components, with five interacting modes of wave propagation: two vorticity modes, one entropy mode, and two acoustic modes. Wave interactions, governed by the inhomogeneous and nonlinear terms of the perturbed Navier-Stokes equations, are modeled by random functions which give the rates of change of wave amplitudes equal to the averaged interaction terms. The statistical framework adopted is a quantum-like formulation in terms of complex distribution functions. The spatial probability distributions are given by the squares of the absolute values of the complex characteristic functions. This formulation results in nonlinear diffusion-type transport equations for the probability densities of the five modes of wave propagation.

Symbol signal-to-noise ratio loss in square-wave subcarrier downconversion

NASA Technical Reports Server (NTRS)

Feria, Y.; Statman, J.

1993-01-01

This article presents the simulated results of the signal-to-noise ratio (SNR) loss in the process of a square-wave subcarrier down conversion. In a previous article, the SNR degradation was evaluated at the output of the down converter based on the signal and noise power change. Unlike in the previous article, the SNR loss is defined here as the difference between the actual and theoretical symbol SNR's for the same symbol-error rate at the output of the symbol matched filter. The results show that an average SNR loss of 0.3 dB can be achieved with tenth-order infinite impulse response (IIR) filters. This loss is a 0.2-dB increase over the SNR degradation in the previous analysis where neither the signal distortion nor the symbol detector was considered.

Bifurcation and Firing Patterns of the Pancreatic β-Cell

NASA Astrophysics Data System (ADS)

Wang, Jing; Liu, Shenquan; Liu, Xuanliang; Zeng, Yanjun

Using a model of individual isolated pancreatic β-cells, we investigated bifurcation diagrams of interspike intervals (ISIs) and largest Lyapunov exponents (LLE), which clearly demonstrated a wide range of transitions between different firing patterns. The numerical simulation results revealed the effect of different time constants and ion channels on the neuronal discharge rhythm. Furthermore, an individual cell exhibited tonic spiking, square-wave bursting, and tapered bursting. Additionally, several bifurcation phenomena can be observed in this paper, such as period-doubling, period-adding, inverse period-doubling and inverse period-adding scenarios. In addition, we researched the mechanisms underlying two kinds of bursting (tapered and square-wave bursting) by use of fast-slow dynamics analysis. Finally, we analyzed the codimension-two bifurcation of the fast subsystem and studied cusp bifurcation, generalized Hopf (or Bautin) bifurcation and Bogdanov-Takens bifurcation.

Waveguide-mode polarization gaps in square spiral photonic crystals

NASA Astrophysics Data System (ADS)

Liu, Rong-Juan; John, Sajeev; Li, Zhi-Yuan

2015-09-01

We designed waveguide channels in two types of square spiral photonic crystals. Wide polarization gaps, in which only one circular polarization wave is allowed while the other counter-direction circular polarization wave is forbidden, can be opened up on the waveguide modes within the fundamental photonic band gap according to the calculation of band structures and transmission spectra. This phenomenon is ascribed to the chirality of the waveguide and is independent of the chirality of the background photonic crystal. Moreover, the transmission spectra show a good one-way property of the waveguide channels. The chiral quality factor demonstrates the handedness of the allowed and impeded chiral waveguide modes, and further proved the property of the waveguide-mode polarization gap. Such waveguides with waveguide-mode polarization gap are a good candidate for one-way waveguides with robust backscattering-immune transport.

Sensorimotor recovery following spaceflight may be due to frequent square-wave saccadic intrusions

NASA Technical Reports Server (NTRS)

Reschke, Millard; Somers, Jeffrey T.; Leigh, R. John; Krnavek, Jody M.; Kornilova, Ludmila; Kozlovskaya, Inessa; Bloomberg, Jacob J.; Paloski, William H.

2004-01-01

Square-wave jerks (SWJs) are small, involuntary saccades that disrupt steady fixation. We report the case of an astronaut (approximately 140 d on orbit) who showed frequent SWJs, especially postflight, but who showed no impairment of vision or decrement of postflight performance. These data support the view that SWJs do not impair vision because they are paired movements, consisting of a small saccade away from the fixation position followed, within 200 ms, by a corrective saccade that brings the eye back on target. Since many returning astronauts show a decrement of dynamic visual function during postflight locomotion, it seems possible that frequent SWJs improved this astronaut's visual function by providing postsaccadic enhancement of visual fixation, which aided postflight performance. Certainly, frequent SWJs did not impair performance in this astronaut, who had no other neurological disorder.

Flight Test of Orthogonal Square Wave Inputs for Hybrid-Wing-Body Parameter Estimation

NASA Technical Reports Server (NTRS)

Taylor, Brian R.; Ratnayake, Nalin A.

2011-01-01

As part of an effort to improve emissions, noise, and performance of next generation aircraft, it is expected that future aircraft will use distributed, multi-objective control effectors in a closed-loop flight control system. Correlation challenges associated with parameter estimation will arise with this expected aircraft configuration. The research presented in this paper focuses on addressing the correlation problem with an appropriate input design technique in order to determine individual control surface effectiveness. This technique was validated through flight-testing an 8.5-percent-scale hybrid-wing-body aircraft demonstrator at the NASA Dryden Flight Research Center (Edwards, California). An input design technique that uses mutually orthogonal square wave inputs for de-correlation of control surfaces is proposed. Flight-test results are compared with prior flight-test results for a different maneuver style.

Complete band gaps of phononic crystal plates with square rods.

PubMed

El-Naggar, Sahar A; Mostafa, Samia I; Rafat, Nadia H

2012-04-01

Much of previous work has been devoted in studying complete band gaps for bulk phononic crystal (PC). In this paper, we theoretically investigate the existence and widths of these gaps for PC plates. We focus our attention on steel rods of square cross sectional area embedded in epoxy matrix. The equations for calculating the dispersion relation for square rods in a square or a triangular lattice have been derived. Our analysis is based on super cell plane wave expansion (SC-PWE) method. The influence of inclusions filling factor and plate thickness on the existence and width of the phononic band gaps has been discussed. Our calculations show that there is a certain filling factor (f=0.55) below which arrangement of square rods in a triangular lattice is superior to the arrangement in a square lattice. A comparison between square and circular cross sectional rods reveals that the former has superior normalized gap width than the latter in case of a square lattice. This situation is switched in case of a triangular lattice. Moreover, a maximum normalized gap width of 0.7 can be achieved for PC plate of square rods embedded in a square lattice and having height 90% of the lattice constant. Copyright © 2011 Elsevier B.V. All rights reserved.

Multi-Gaussian fitting for pulse waveform using Weighted Least Squares and multi-criteria decision making method.

PubMed

Wang, Lu; Xu, Lisheng; Feng, Shuting; Meng, Max Q-H; Wang, Kuanquan

2013-11-01

Analysis of pulse waveform is a low cost, non-invasive method for obtaining vital information related to the conditions of the cardiovascular system. In recent years, different Pulse Decomposition Analysis (PDA) methods have been applied to disclose the pathological mechanisms of the pulse waveform. All these methods decompose single-period pulse waveform into a constant number (such as 3, 4 or 5) of individual waves. Furthermore, those methods do not pay much attention to the estimation error of the key points in the pulse waveform. The estimation of human vascular conditions depends on the key points' positions of pulse wave. In this paper, we propose a Multi-Gaussian (MG) model to fit real pulse waveforms using an adaptive number (4 or 5 in our study) of Gaussian waves. The unknown parameters in the MG model are estimated by the Weighted Least Squares (WLS) method and the optimized weight values corresponding to different sampling points are selected by using the Multi-Criteria Decision Making (MCDM) method. Performance of the MG model and the WLS method has been evaluated by fitting 150 real pulse waveforms of five different types. The resulting Normalized Root Mean Square Error (NRMSE) was less than 2.0% and the estimation accuracy for the key points was satisfactory, demonstrating that our proposed method is effective in compressing, synthesizing and analyzing pulse waveforms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Voltammetry of naltrexone in commercial formulation and human body fluids: Quantification and pharmacokinetic studies.

PubMed

Ghoneim, Mohamed M; El-Desoky, Hanaa S; Abdel-Galeil, Mohamed M

2011-06-01

Naltrexone HCl (NAL.HCl) has been reduced at the mercury electrode in Britton-Robinson universal buffer of pH values 2-11 with a mechanism involving the quasi-reversible uptake of the first transferring electron followed by a rate-determining protonation step of its C=O double bond at position C-6. Simple, sensitive, selective and reliable linear-sweep and square-wave adsorptive cathodic stripping voltammetry methods have been described for trace quantitation of NAL.HCl in bulk form, commercial formulation and human body fluids without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis. Limits of quantitation of 6.0×10(-9)M and 8.0×10(-10)M NAL.HCl in bulk form or commercial formulation and of 9.0×10(-9) and 1.0×10(-9)M NAL.HCl in spiked human serum samples were achieved by the described linear and square-wave stripping voltammetry methods, respectively. Furthermore, pharmacokinetic parameters of the drug in human plasma samples of healthy volunteers following the administration of an oral single dose of 50mg NAL.HCl (one Revia(®) tablet) were estimated by means of the described square-wave stripping voltammetry method without interferences from the drug's metabolites and/or endogenous human plasma constituents. The estimated pharmacokinetic parameters were favorably compared with those reported in literature. Copyright © 2011 Elsevier B.V. All rights reserved.

Lead detection using micro/nanocrystalline boron-doped diamond by square-wave anodic stripping voltammetry.

PubMed

Arantes, Tatiane M; Sardinha, André; Baldan, Mauricio R; Cristovan, Fernando H; Ferreira, Neidenei G

2014-10-01

Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 μg L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio. Copyright © 2014 Elsevier B.V. All rights reserved.

Decompression management by 43 models of dive computer: single square-wave exposures to between 15 and 50 metres' depth.

PubMed

Sayer, Martin D J; Azzopardi, Elaine; Sieber, Arne

2014-12-01

Dive computers are used in some occupational diving sectors to manage decompression but there is little independent assessment of their performance. A significant proportion of occupational diving operations employ single square-wave pressure exposures in support of their work. Single examples of 43 models of dive computer were compressed to five simulated depths between 15 and 50 metres' sea water (msw) and maintained at those depths until they had registered over 30 minutes of decompression. At each depth, and for each model, downloaded data were used to collate the times at which the unit was still registering "no decompression" and the times at which various levels of decompression were indicated or exceeded. Each depth profile was replicated three times for most models. Decompression isopleths for no-stop dives indicated that computers tended to be more conservative than standard decompression tables at depths shallower than 30 msw but less conservative between 30-50 msw. For dives requiring decompression, computers were predominantly more conservative than tables across the whole depth range tested. There was considerable variation between models in the times permitted at all of the depth/decompression combinations. The present study would support the use of some dive computers for controlling single, square-wave diving by some occupational sectors. The choice of which makes and models to use would have to consider their specific dive management characteristics which may additionally be affected by the intended operational depth and whether staged decompression was permitted.

Elastic Bottom Propagation Mechanisms Investigated by Parabolic Equation Methods

DTIC Science & Technology

2014-09-30

channel propagation of oceanic T waves from seismic sources in the presence of intervening seamounts or coral reef barriers is established using elastic PE...environments in the form of scattering at an elastic interface, oceanic T - waves , and Scholte waves . OBJECTIVES To implement explosive and earthquake...oceanic T - waves , which are acoustic waves that result from earthquake or buried explosive sources, and Rayleigh-type waves along the ocean floor, whose

A previously unreported type of seismic source in the firn layer of the East Antarctic Ice Sheet

NASA Astrophysics Data System (ADS)

Lough, Amanda C.; Barcheck, C. Grace; Wiens, Douglas A.; Nyblade, Andrew; Anandakrishnan, Sridhar

2015-11-01

We identify a unique type of seismic source in the uppermost part of the East Antarctic Ice Sheet recorded by temporary broadband seismic arrays in East Antarctica. These sources, termed "firnquakes," are characterized by dispersed surface wave trains with frequencies of 1-10 Hz detectable at distances up to 1000 km. Events show strong dispersed Rayleigh wave trains and an absence of observable body wave arrivals; most events also show weaker Love waves. Initial events were discovered by standard detection schemes; additional events were then detected with a correlation scanner using the initial arrivals as templates. We locate sources by determining the L2 misfit for a grid of potential source locations using Rayleigh wave arrival times and polarization directions. We then perform a multiple-filter analysis to calculate the Rayleigh wave group velocity dispersion and invert the group velocity for shear velocity structure. The resulting velocity structure is used as an input model to calculate synthetic seismograms. Inverting the dispersion curves yields ice velocity structures consistent with a low-velocity firn layer ~100 m thick and show that velocity structure is laterally variable. The absence of observable body wave phases and the relative amplitudes of Rayleigh waves and noise constrain the source depth to be less than 20 m. The presence of Love waves for most events suggests the source is not isotropic. We propose the events are linked to the formation of small crevasses in the firn, and several events correlate with shallow crevasse fields mapped in satellite imagery.

Wave field synthesis of moving virtual sound sources with complex radiation properties.

PubMed

Ahrens, Jens; Spors, Sascha

2011-11-01

An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source.

Numerical simulation of seismic wave propagation from land-excited large volume air-gun source

NASA Astrophysics Data System (ADS)

Cao, W.; Zhang, W.

2017-12-01

The land-excited large volume air-gun source can be used to study regional underground structures and to detect temporal velocity changes. The air-gun source is characterized by rich low frequency energy (from bubble oscillation, 2-8Hz) and high repeatability. It can be excited in rivers, reservoirs or man-made pool. Numerical simulation of the seismic wave propagation from the air-gun source helps to understand the energy partitioning and characteristics of the waveform records at stations. However, the effective energy recorded at a distance station is from the process of bubble oscillation, which can not be approximated by a single point source. We propose a method to simulate the seismic wave propagation from the land-excited large volume air-gun source by finite difference method. The process can be divided into three parts: bubble oscillation and source coupling, solid-fluid coupling and the propagation in the solid medium. For the first part, the wavelet of the bubble oscillation can be simulated by bubble model. We use wave injection method combining the bubble wavelet with elastic wave equation to achieve the source coupling. Then, the solid-fluid boundary condition is implemented along the water bottom. And the last part is the seismic wave propagation in the solid medium, which can be readily implemented by the finite difference method. Our method can get accuracy waveform of land-excited large volume air-gun source. Based on the above forward modeling technology, we analysis the effect of the excited P wave and the energy of converted S wave due to different water shapes. We study two land-excited large volume air-gun fields, one is Binchuan in Yunnan, and the other is Hutubi in Xinjiang. The station in Binchuan, Yunnan is located in a large irregular reservoir, the waveform records have a clear S wave. Nevertheless, the station in Hutubi, Xinjiang is located in a small man-made pool, the waveform records have very weak S wave. Better understanding of the characteristics of land-excited large volume air-gun can help to better use of the air-gun source.

Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37 to 42 GHz) and V/W-band (71 to 76 GHz) satellite-to-ground signals.

Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.

Power conditioning equipment for a thermoelectric outer planet spacecraft, volume 1, book 1

NASA Technical Reports Server (NTRS)

Andrews, R. E. (Editor)

1972-01-01

Equipment was designed to receive power from a radioisotope thermoelectric generator source, condition, distribute, and control this power for the spacecraft loads. The TOPS mission, aimed at a representative tour of the outer planets, would operate for an estimated 12 year period. Unique design characteristics required for the power conditioning equipment results from the long mission time and the need for autonomous on-board operations due to large communications distances and the associated time delays of ground initiated actions. The salient features of the selected power subsystem configuration are: (1) The PCE regulates the power from the radioisotope thermoelectric generator power source at 30 vdc by means of a quad-redundant shunt regulator; (2) 30 vdc power is used by certain loads, but is more generally inverted and distributed as square-wave ac power; (3) a protected bus is used to assure that power is always available to the control computer subsystem to permit corrective action to be initiated in response to fault conditions; and (4) various levels of redundancy are employed to provide high subsystem reliability.

Localization of short-range acoustic and seismic wideband sources: Algorithms and experiments

NASA Astrophysics Data System (ADS)

Stafsudd, J. Z.; Asgari, S.; Hudson, R.; Yao, K.; Taciroglu, E.

2008-04-01

We consider the determination of the location (source localization) of a disturbance source which emits acoustic and/or seismic signals. We devise an enhanced approximate maximum-likelihood (AML) algorithm to process data collected at acoustic sensors (microphones) belonging to an array of, non-collocated but otherwise identical, sensors. The approximate maximum-likelihood algorithm exploits the time-delay-of-arrival of acoustic signals at different sensors, and yields the source location. For processing the seismic signals, we investigate two distinct algorithms, both of which process data collected at a single measurement station comprising a triaxial accelerometer, to determine direction-of-arrival. The direction-of-arrivals determined at each sensor station are then combined using a weighted least-squares approach for source localization. The first of the direction-of-arrival estimation algorithms is based on the spectral decomposition of the covariance matrix, while the second is based on surface wave analysis. Both of the seismic source localization algorithms have their roots in seismology; and covariance matrix analysis had been successfully employed in applications where the source and the sensors (array) are typically separated by planetary distances (i.e., hundreds to thousands of kilometers). Here, we focus on very-short distances (e.g., less than one hundred meters) instead, with an outlook to applications in multi-modal surveillance, including target detection, tracking, and zone intrusion. We demonstrate the utility of the aforementioned algorithms through a series of open-field tests wherein we successfully localize wideband acoustic and/or seismic sources. We also investigate a basic strategy for fusion of results yielded by acoustic and seismic arrays.

Method of Characteristics Calculations and Computer Code for Materials with Arbitrary Equations of State and Using Orthogonal Polynomial Least Square Surface Fits

NASA Technical Reports Server (NTRS)

Chang, T. S.

1974-01-01

A numerical scheme using the method of characteristics to calculate the flow properties and pressures behind decaying shock waves for materials under hypervelocity impact is developed. Time-consuming double interpolation subroutines are replaced by a technique based on orthogonal polynomial least square surface fits. Typical calculated results are given and compared with the double interpolation results. The complete computer program is included.

Results and prospects in multi-messenger particle astrophysics

NASA Astrophysics Data System (ADS)

Mostafa, Miguel

2017-01-01

In high-energy particle astrophysics the old days were certainly not better than these. Our field has thrived in the past decade with experiments covering thousands of square kilometers to measure the suppression in the flux of the highest energy cosmic rays ever observed, instrumenting a cubic kilometer of Antarctic ice to discover astrophysical neutrinos, and measuring a change in arm length as small as 10-19 m for the ground-breaking direct observation of gravitational waves. Additionally, the current generation of space-borne and ground-based gamma-ray experiments have revealed a plethora of gamma-ray sources, including pulsars, compact binaries, the galactic center, and extragalactic sources such as starburst galaxies and radio galaxies. Before the next generation of instruments bring us yet another order of magnitude in sensitivity, we can combine current observations to probe physics beyond the standard model, and to extend the high-energy frontier well above the energies accessible to laboratory accelerators. One example of this potential is the search for dark-matter annihilation and decay products. To use the multi-messenger approach effectively for probing dark-matter signatures and physics beyond the LHC energy requires understanding the origin (or acceleration mechanism) and the propagation processes. High energy protons and nuclei, neutrinos, gamma-rays, X-rays, and gravitational waves bring new and complementary views of the astrophysical sources. By comparing observations through different windows, we can use the sites of violent phenomena as a laboratory to probe the physical processes under extreme conditions throughout the Universe, and to test the fundamental laws of particle physics and gravitation. As a community we need to engage in a bold synergistic approach to understanding the violent processes that give rise to the high-energy cosmic phenomena in the Universe. In this invited talk, I will present on-going multi-messenger studies to obtain new information about cosmic sources, and I will discuss the prospects of combining data from the electromagnetic, particle, and gravitational windows to advance high energy astrophysics into a new era.

Kramers-Kronig based quality factor for shear wave propagation in soft tissue

PubMed Central

Urban, M W; Greenleaf, J F

2009-01-01

Shear wave propagation techniques have been introduced for measuring the viscoelastic material properties of tissue, but assessing the accuracy of these measurements is difficult for in vivo measurements in tissue. We propose using the Kramers-Kronig relationships to assess the consistency and quality of the measurements of shear wave attenuation and phase velocity. In ex vivo skeletal muscle we measured the wave attenuation at different frequencies, and then applied finite bandwidth Kramers-Kronig equations to predict the phase velocities. We compared these predictions with the measured phase velocities and assessed the mean square error (MSE) as a quality factor. An algorithm was derived for computing a quality factor using the Kramers-Kronig relationships. PMID:19759409

Short-period atmospheric gravity waves - A study of their statistical properties and source mechanisms

NASA Technical Reports Server (NTRS)

Gedzelman, S. D.

1983-01-01

Gravity waves for the one year period beginning 19 October 1976 around Palisades, New York, are investigated to determine their statistical properties and sources. The waves have typical periods of 10 min, pressure amplitudes of 3 Pa and velocities of 30 m/s. In general, the largest, amplitude waves occur during late fall and early winter when the upper tropospheric winds directly overhead are fastest and the static stability of the lower troposphere is greatest. Mean wave amplitudes correlate highly with the product of the mean maximum wind speed and the mean low level stratification directly aloft. A distinct diurnal variation of wave amplitudes with the largest waves occurring in the pre-dawn hours is also observed as a result of the increased static stability then. The majority of waves are generated by shear instability; however, a number of waves are generated by distant sources such as nuclear detonations or large thunderstorms. The waves with distant sources can be distinguished on the basis of their generally much higher coherency across the grid and velocities that depart markedly from the wind velocity at any point in the sounding.

Optimization of a Focusable and Rotatable Shear-Wave Periodic Permanent Magnet Electromagnetic Acoustic Transducers for Plates Inspection

PubMed Central

Qiu, Gongzhe

2017-01-01

Due to the symmetry of conventional periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs), two shear (SH) waves can be generated and propagated simultaneously in opposite directions, which makes the signal recognition and interpretation complicatedly. Thus, this work presents a new SH wave PPM EMAT design, rotating the parallel line sources to realize the wave beam focusing in a single-direction. The theoretical model of distributed line sources was deduced firstly, and the effects of some parameters, such as the inner coil width, adjacent line sources spacing and the angle between parallel line sources, on SH wave focusing and directivity were studied mainly with the help of 3D FEM. Employing the proposed PPM EMATs, some experiments are carried out to verify the reliability of FEM simulation. The results indicate that rotating the parallel line sources can strength the wave on the closing side of line sources, decreasing the inner coil width and the adjacent line sources spacing can improve the amplitude and directivity of signals excited by transducers. Compared with traditional PPM EMATs, both the capacity of unidirectional excitation and directivity of the proposed PPM EMATs are improved significantly. PMID:29186790

Optimization of a Focusable and Rotatable Shear-Wave Periodic Permanent Magnet Electromagnetic Acoustic Transducers for Plates Inspection.

PubMed

Song, Xiaochun; Qiu, Gongzhe

2017-11-24

Due to the symmetry of conventional periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs), two shear (SH) waves can be generated and propagated simultaneously in opposite directions, which makes the signal recognition and interpretation complicatedly. Thus, this work presents a new SH wave PPM EMAT design, rotating the parallel line sources to realize the wave beam focusing in a single-direction. The theoretical model of distributed line sources was deduced firstly, and the effects of some parameters, such as the inner coil width, adjacent line sources spacing and the angle between parallel line sources, on SH wave focusing and directivity were studied mainly with the help of 3D FEM. Employing the proposed PPM EMATs, some experiments are carried out to verify the reliability of FEM simulation. The results indicate that rotating the parallel line sources can strength the wave on the closing side of line sources, decreasing the inner coil width and the adjacent line sources spacing can improve the amplitude and directivity of signals excited by transducers. Compared with traditional PPM EMATs, both the capacity of unidirectional excitation and directivity of the proposed PPM EMATs are improved significantly.

The interaction of sound with a poroelastic ground

NASA Astrophysics Data System (ADS)

Hickey, C. J.

2012-12-01

An airborne acoustic wave impinging on the surface of the ground provides a good mechanical source for investigating the near surface. Since the ground is porous, the impinging sound wave induces motion of the fluid within the pores as well as vibrating the solid framework. The most complete understanding of the interaction of airborne sound with the ground is to treat the ground as a poroelastic or poroviscoelastic medium. This treatment predicts that three types of waves can propagate in a ground with a deformable framework: two compressional waves, the fast or Type I and slow or Type II wave and one shear wave. Model calculations of the energy partition and an air-soil interface predict that most of the energy is partitioned into the Type II compressional wave, less into the Type I compressional wave, and little energy is partitioned into the shear wave. However, when measuring the solid motion of the soil one must consider how much of that wave energy is in terms of solid velocity. The deformation associated with Type II compressional wave has only a small contribution from the solid component whereas the bulk deformation of the Type I compressional wave has a solid to fluid deformation ratio of approximately one. This modeling suggests that the soil solid velocity induced by an acoustic source is associated with the Type I compressional wave. In other words, the airborne source is simply an inefficient seismic source.

Trajectories and traversal times in quantum tunneling

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

Huang, Zhi Hong.

1989-01-01

The classical concepts of trajectories and traversal times applied to quantum tunneling are discussed. By using the Wentzel-Kramers-Brillouin approximation, it is found that in a forbidden region of a multidimensional space the wave function can be described by two sets of trajectories, or equivalently by two sets of wave fronts. The trajectories belonging to different sets are mutually orthogonal. An extended Huygens construction is proposed to determine these wave fronts and trajectories. In contrast to the classical results in the allowed region, these trajectories couple to each other. However, if the incident wave is normal to the turning surface, themore » trajectories are found to be independent and can be determined by Newton's equations of motion with inverted potential and energy. The multidimensional tunneling theory is then applied to the scanning tunneling microscope to calculate the current density distribution and to derive the expressions for the lateral resolution and the surface corrugation amplitude. The traversal time in quantum tunneling, i.e. tunneling time, is found to depend on model calculations and simulations. Computer simulation of a wave packet tunneling through a square barrier is performed. Several approaches, including the phase method, Larmor clock, and time-dependent barrier model, are investigated. For a square barrier, two characteristic times are found: One is equal to the barrier width divided by the magnitude of the imaginary velocity; the other is equal to the decay length divided by the incident velocity. It is believed that the tunneling time can only be defined operationally.« less

Optical evaluation of the wave filtering properties of graded undulated lattices

NASA Astrophysics Data System (ADS)

Trainiti, G.; Rimoli, J. J.; Ruzzene, M.

2018-03-01

We investigate and experimentally demonstrate the elastic wave filtering properties of graded undulated lattices. Square reticulates composed of curved beams are characterized by graded mechanical properties which result from the spatial modulation of the curvature parameter. Among such properties, the progressive formation of frequency bandgaps leads to strong wave attenuation over a broad frequency range. The experimental investigation of wave transmission and the detection of full wavefields effectively illustrate this behavior. Transmission measurements are conducted using a scanning laser Doppler vibrometer, while a dedicated digital image correlation procedure is implemented to capture in-plane wave motion at selected frequencies. The presented results illustrate the broadband attenuation characteristics resulting from spatial grading of the lattice curvature, whose in-depth investigation is enabled by the presented experimental procedures.

The Microtremor H/V Spectral Ratio: The Physical Basis of the Diffuse Field Assumption

NASA Astrophysics Data System (ADS)

Sanchez-Sesma, F. J.

2016-12-01

The microtremor H/V spectral ratio (MHVSR) is popular to obtain the dominant frequency at a site. Despite the success of MHVSR some controversy arose regarding its physical basis. One approach is the Diffuse Field Assumption, DFA. It is then assumed that noise diffuse features come from multiple scattering within the medium. According to theory, the average of the autocorrelation is proportional to directional energy density (DED) and to the imaginary part of the Green's function for same source and receiver. Then, the square of MHVSR is a ratio of DEDs which, in a horizontally layered system, is 2xImG11/ImG33, where ImG11 and ImG33 are the imaginary parts of Green's functions for horizontal and vertical components. This has physical implications that emerge from the duality DED-force, implicit in the DFA. Consider a surface force at a half-space. The radiated energy is carried away by various wave types and the proportions of each one are precisely the fractions of the energy densities of a diffuse elastic wave field at the free surface. Thus, some properties of applied forces are also characteristics of DEDs. For example, consider a Poisson solid. For a normal point load, 67 per cent of energy is carried away by Rayleigh waves. For the tangential case, it is less well known that, 77 per cent of energy goes as shear waves. In a full space, 92 per cent of the energy is emitted as shear waves. The horizontal DED at the half-space surface implies significant emission of down-going shear waves that explains the curious stair-like resonance spectrum of ImG11. Both ImG11 and ImG33 grow linearly versus frequency and this represents wave emission. For a layered medium, besides wave emission, the ensuing variations correspond to reflected waves. For high frequencies, ImG33 depends on the properties of the top layer. Reflected body waves are very small and Rayleigh waves behave in the top layer as in a kind of mini half-space. From HVSR one can invert the velocity model using the DFA. It is possible to compute efficiently the imaginary part of the Green's functions from the integrals along the radial wavenumber k. This can be made using either the Bouchon DWN method or the Cauchy residue theorem to get the pole contributions of Rayleigh and Love surface waves in the k complex plane. This allows separating the contributions of each wave type.

Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

The design and test results of a novel waveguide multimode directional coupler for a CW millimeter-wave satellite beacon source are presented. The coupler separates the second harmonic power from the fundamental output power of a traveling-wave tube amplifier. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37 to 42 GHz) and VW-band (71 to 76 GHz) satellite-to-ground signals.

An overview of wave-mean flow interactions during the winter of 1978-79 derived from LIMS observations. [Limb Infrared Monitor of Stratosphere

NASA Technical Reports Server (NTRS)

Gille, J. C.; Lyjak, L. V.

1984-01-01

Gradient winds, Eliassen-Palm (EP) fluxes and flux divergences, and the squared refractive index for planetary waves have been calculated from mapped data from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on Nimbus 7. The changes in the zonal mean atmospheric state, from early winter through 3 disturbances, is described. Convergence or divergence of the EP fluxes clearly produces changes in the zonal mean wind. The steering of the waves by the refractive index structure is not as clear on a daily basis.

Ultrasonic measurements of the reflection coefficient at a water/polyurethane foam interface.

PubMed

Sagers, Jason D; Haberman, Michael R; Wilson, Preston S

2013-09-01

Measured ultrasonic reflection coefficients as a function of normal incidence angle are reported for several samples of polyurethane foam submerged in a water bath. Three reflection coefficient models are employed as needed in this analysis to approximate the measured data: (1) an infinite plane wave impinging on an elastic halfspace, (2) an infinite plane wave impinging on a single fluid layer overlying a fluid halfspace, and (3) a finite acoustic beam impinging on an elastic halfspace. The compressional wave speed in each sample is calculated by minimizing the sum of squared error (SSE) between the measured and modeled data.

Photoacoustic Effect Generated from an Expanding Spherical Source

NASA Astrophysics Data System (ADS)

Bai, Wenyu; Diebold, Gerald J.

2018-02-01

Although the photoacoustic effect is typically generated by amplitude-modulated continuous or pulsed radiation, the form of the wave equation for pressure that governs the generation of sound indicates that optical sources moving in an absorbing fluid can produce sound as well. Here, the characteristics of the acoustic wave produced by a radially symmetric Gaussian source expanding outwardly from the origin are found. The unique feature of the photoacoustic effect from the spherical source is a trailing compressive wave that arises from reflection of an inwardly propagating component of the wave. Similar to the one-dimensional geometry, an unbounded amplification effect is found for the Gaussian source expanding at the sound speed.

Modelling the performance of interferometric gravitational-wave detectors with realistically imperfect optics

NASA Astrophysics Data System (ADS)

Bochner, Brett

The LIGO project is part of a world-wide effort to detect the influx of Gravitational Waves upon the earth from astrophysical sources, via their interaction with laser beams in interferometric detectors that are designed for extraordinarily high sensitivity. Central to the successful performance of LIGO detectors is the quality of their optical components, and the efficient optimization of interferometer configuration parameters. To predict LIGO performance with optics possessing realistic imperfections, we have developed a numerical simulation program to compute the steady-state electric fields of a complete, coupled-cavity LIGO interferometer. The program can model a wide variety of deformations, including laser beam mismatch and/or misalignment, finite mirror size, mirror tilts, curvature distortions, mirror surface roughness, and substrate inhomogeneities. Important interferometer parameters are automatically optimized during program execution to achieve the best possible sensitivity for each new set of perturbed mirrors. This thesis includes investigations of two interferometer designs: the initial LIGO system, and an advanced LIGO configuration called Dual Recycling. For Initial-LIGO simulations, the program models carrier and sideband frequency beams to compute the explicit shot-noise-limited gravitational wave sensitivity of the interferometer. It is demonstrated that optics of exceptional quality (root-mean-square deformations of less than ~1 nm in the central mirror regions) are necessary to meet Initial-LIGO performance requirements, but that they can be feasibly met. It is also shown that improvements in mirror quality can substantially increase LIGO's sensitivity to selected astrophysical sources. For Dual Recycling, the program models gravitational- wave-induced sidebands over a range of frequencies to demonstrate that the tuned and narrow-banded signal responses predicted for this configuration can be achieved with imperfect optics. Dual Recycling has lower losses at the interferometer signal port than the Initial-LIGO system, though not significantly improved tolerance to mirror roughness deformations in terms of maintaining high signals. Finally, it is shown that 'Wavefront Healing', the claim that losses can be re- injected into the system to feed the gravitational wave signals, is successful in theory, but limited in practice for optics which cause large scattering losses. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

Modelling the performance of interferometric gravitational-wave detectors with realistically imperfect optics

NASA Astrophysics Data System (ADS)

Bochner, Brett

1998-12-01

The LIGO project is part of a world-wide effort to detect the influx of Gravitational Waves upon the earth from astrophysical sources, via their interaction with laser beams in interferometric detectors that are designed for extraordinarily high sensitivity. Central to the successful performance of LIGO detectors is the quality of their optical components, and the efficient optimization of interferometer configuration parameters. To predict LIGO performance with optics possessing realistic imperfections, we have developed a numerical simulation program to compute the steady-state electric fields of a complete, coupled-cavity LIGO interferometer. The program can model a wide variety of deformations, including laser beam mismatch and/or misalignment, finite mirror size, mirror tilts, curvature distortions, mirror surface roughness, and substrate inhomogeneities. Important interferometer parameters are automatically optimized during program execution to achieve the best possible sensitivity for each new set of perturbed mirrors. This thesis includes investigations of two interferometer designs: the initial LIGO system, and an advanced LIGO configuration called Dual Recycling. For Initial-LIGO simulations, the program models carrier and sideband frequency beams to compute the explicit shot-noise-limited gravitational wave sensitivity of the interferometer. It is demonstrated that optics of exceptional quality (root-mean-square deformations of less than ~1 nm in the central mirror regions) are necessary to meet Initial-LIGO performance requirements, but that they can be feasibly met. It is also shown that improvements in mirror quality can substantially increase LIGO's sensitivity to selected astrophysical sources. For Dual Recycling, the program models gravitational- wave-induced sidebands over a range of frequencies to demonstrate that the tuned and narrow-banded signal responses predicted for this configuration can be achieved with imperfect optics. Dual Recycling has lower losses at the interferometer signal port than the Initial-LIGO system, though not significantly improved tolerance to mirror roughness deformations in terms of maintaining high signals. Finally, it is shown that 'Wavefront Healing', the claim that losses can be re- injected into the system to feed the gravitational wave signals, is successful in theory, but limited in practice for optics which cause large scattering losses. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

The Confirmation of the Inverse Square Law Using Diffraction Gratings

ERIC Educational Resources Information Center

Papacosta, Pangratios; Linscheid, Nathan

2014-01-01

Understanding the inverse square law, how for example the intensity of light or sound varies with distance, presents conceptual and mathematical challenges. Students know intuitively that intensity decreases with distance. A light source appears dimmer and sound gets fainter as the distance from the source increases. The difficulty is in…

A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters

NASA Astrophysics Data System (ADS)

Ren, Luchuan

2015-04-01

A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters Luchuan Ren, Jianwei Tian, Mingli Hong Institute of Disaster Prevention, Sanhe, Heibei Province, 065201, P.R. China It is obvious that the uncertainties of the maximum tsunami wave heights in offshore area are partly from uncertainties of the potential seismic tsunami source parameters. A global sensitivity analysis method on the maximum tsunami wave heights to the potential seismic source parameters is put forward in this paper. The tsunami wave heights are calculated by COMCOT ( the Cornell Multi-grid Coupled Tsunami Model), on the assumption that an earthquake with magnitude MW8.0 occurred at the northern fault segment along the Manila Trench and triggered a tsunami in the South China Sea. We select the simulated results of maximum tsunami wave heights at specific sites in offshore area to verify the validity of the method proposed in this paper. For ranking importance order of the uncertainties of potential seismic source parameters (the earthquake's magnitude, the focal depth, the strike angle, dip angle and slip angle etc..) in generating uncertainties of the maximum tsunami wave heights, we chose Morris method to analyze the sensitivity of the maximum tsunami wave heights to the aforementioned parameters, and give several qualitative descriptions of nonlinear or linear effects of them on the maximum tsunami wave heights. We quantitatively analyze the sensitivity of the maximum tsunami wave heights to these parameters and the interaction effects among these parameters on the maximum tsunami wave heights by means of the extended FAST method afterward. The results shows that the maximum tsunami wave heights are very sensitive to the earthquake magnitude, followed successively by the epicenter location, the strike angle and dip angle, the interactions effect between the sensitive parameters are very obvious at specific site in offshore area, and there exist differences in importance order in generating uncertainties of the maximum tsunami wave heights for same group parameters at different specific sites in offshore area. These results are helpful to deeply understand the relationship between the tsunami wave heights and the seismic tsunami source parameters. Keywords: Global sensitivity analysis; Tsunami wave height; Potential seismic tsunami source parameter; Morris method; Extended FAST method

Modeling Study for Tangier Island Jetties, Tangier Island, Virginia

DTIC Science & Technology

2015-03-01

meteorological and oceanographic (metocean) inputs used as forcing conditions. CENAO provided survey data available for Tangier Is- land from a...and 5 ft or 1.5 m). Wave direction is meteorological (e.g., direction waves coming from). Figure 55. Ten selected locations (black squares) in Alt...given in the previous sections. The Hud- son equation is well known and has been used for years to determine ar- mor stability ( Hudson 1959; Shore

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source.

NASA Astrophysics Data System (ADS)

Averbuch, Gil; Price, Colin

2015-04-01

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source. G. Averbuch, C. Price Department of Geosciences, Tel Aviv University, Israel Infrasound is one of the four Comprehensive Nuclear-Test Ban Treaty technologies for monitoring nuclear explosions. This technology measures the acoustic waves generated by the explosions followed by their propagation through the atmosphere. There are also natural phenomena that can act as an infrasound sources like sprites, volcanic eruptions and earthquakes. The infrasound waves generated from theses phenomena can also be detected by the infrasound arrays. In order to study the behavior of these waves, i.e. the physics of wave propagation in the atmosphere, their evolution and their trajectories, numerical methods are required. This presentation will deal with the evolution of acoustic waves generated by underground sources (earthquakes and underground explosions). A 2D Spectral elements formulation for lithosphere-atmosphere coupling will be presented. The formulation includes the elastic wave equation for the seismic waves and the momentum, mass and state equations for the acoustic waves in a moving stratified atmosphere. The coupling of the two media is made by boundary conditions that ensures the continuity of traction and velocity (displacement) in the normal component to the interface. This work has several objectives. The first is to study the evolution of acoustic waves in the atmosphere from an underground source. The second is to derive transmission coefficients for the energy flux with respect to the seismic magnitude and earth density. The third will be the generation of seismic waves from acoustic waves in the atmosphere. Is it possible?

Connecting Numerical Relativity and Data Analysis of Gravitational Wave Detectors

NASA Astrophysics Data System (ADS)

Shoemaker, Deirdre; Jani, Karan; London, Lionel; Pekowsky, Larne

Gravitational waves deliver information in exquisite detail about astrophysical phenomena, among them the collision of two black holes, a system completely invisible to the eyes of electromagnetic telescopes. Models that predict gravitational wave signals from likely sources are crucial for the success of this endeavor. Modeling binary black hole sources of gravitational radiation requires solving the Einstein equations of General Relativity using powerful computer hardware and sophisticated numerical algorithms. This proceeding presents where we are in understanding ground-based gravitational waves resulting from the merger of black holes and the implications of these sources for the advent of gravitational-wave astronomy.

Oblique wave trapping by vertical permeable membrane barriers located near a wall

NASA Astrophysics Data System (ADS)

Koley, Santanu; Sahoo, Trilochan

2017-12-01

The effectiveness of a vertical partial flexible porous membrane wave barrier located near a rigid vertical impermeable seawall for trapping obliquely incident surface gravity waves are analyzed in water of uniform depth under the assumption of linear water wave theory and small amplitude membrane barrier response. From the general formulation of the submerged membrane barrier, results for bottom-standing and surface-piercing barriers are computed and analyzed in special cases. Using the eigenfunction expansion method, the boundary-value problems are converted into series relations and then the required unknowns are obtained using the least squares approximation method. Various physical quantities of interests like reflection coefficient, wave energy dissipation, wave forces acting on the membrane barrier and the seawall are computed and analyzed for different values of the wave and structural parameters. The study will be useful in the design of the membrane wave barrier for the creation of tranquility zone in the lee side of the barrier to protect the seawall.

Quantum phase transition in strongly correlated systems

NASA Astrophysics Data System (ADS)

Jiang, Longhua

In this thesis, we investigated the strongly correlated phenomena in bilayer quantum Hall effect, inhomogeneous superconductivity and Boson Hubbard model. Bilayer quantum Hall system is studied in chapter 2. By using the Composite Boson (CB) theory developed by J. Ye, we derive the ground state, quasihole and a quasihole-pair wave functions from the CB theory and its dual action. We find that the ground state wave function is the product of two parts, one in the charge sector which is the well known Halperin's (111) wave function and the other in the spin sector which is non-trivial at any finite d due to the gapless mode. So the total groundstate wave function differs from the well known (111) wave function at any finite d. In addition to commonly known multiplicative factors, the quasihole and quasihole-pair wave functions also contain non-trivial normalization factors multiplying the correct ground state wave function. Then we continue to study the quantum phase transition from the excitonic superfluid (ESF) to a possible pseudo-spin density wave (PSDW) at some intermediate distances driven by the magneto-roton minimum collapsing at a finite wavevector. We analyze the properties of the PSDW and explicitly show that a square lattice is the favored lattice. We suggest that correlated hopping of vacancies in the active and passive layers in the PSDW state leads to very large and temperature-dependent drag, consistent with the experimental data. Comparisons with previous microscopic numerical calculations are made. Further experimental implications are given. In chapter 3, we investigate inhomogeneous superconductivity. Starting from the Ginzburg-Landau free energy describing the normal state to Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state transition, we evaluate the free energy of seven most common lattice structures: stripe, square, triangular, Simple Cubic (SC), Face centered Cubic (FCC), Body centered Cubic (BCC) and Quasicrystal (QC). We find that the stripe phase, which is the original LO state, is the most stable phase. This result may be relevant to the detection of the FFLO state in some heavy fermion compounds and the pairing lattice structure of fermions with unequal populations on the BCS side of the Feshbach resonance in ultra-cold atoms. In chapter 4, the Boson Hubbard model is studied by duality transformation. Interacting bosons at filling factor f = p/q hopping on a lattice can be mapped to interacting vortices hopping on the dual lattice subject to a fluctuating dual " magnetic field" whose average strength through a dual plaquette is equal to the boson density f = p/q. So the kinetic term of the vortices is the same as the Hofstadter problem of electrons moving in a lattice in the presence of f = p/q flux per plaquette. Motivated by this mapping, we study the Hofstadter bands of vortices hopping in the presence of magnetic flux f = p/q per plaquette on the 5 most common bipartite and frustrated lattices namely square, honeycomb, triangular, dice and kagome lattices. We count the total number of bands and determine the number of minima in the lowest band and their locations. We also numerically calculate the bandwidths of the lowest Hofstadter bands in these lattices, which directly measure the mobility of the dual vortices. The less mobile the dual vortices are, the more likely the bosons are in a superfluid state. We find that, except for the kagome lattice at odd q, they all satisfy the exponential decay law W = Ae-cq even at the smallest q. At given q, the bandwidth W decreases in the order: triangle, square and honeycomb lattice. This indicates that the domain of the superfluid state of the original bosons increases in the order of the corresponding direct lattices: honeycome, square and triangular. When q = 2, we find that the lowest Hofstadter band is completely flat for both kagome and dice lattices. There is a gap on the kagome lattice, but no gap on dice lattice. This indicates that the boson ground state at half filling with nearest neighbor hopping on kagome lattice is always a superfluid state. The superfluid state remains stable slightly away from half filling. Our results show that the behaviors of bosons at or near half filling on kagome lattice are quite distinct from those on square, honeycomb and triangular lattices studied previously.

Investigation of Ionospheric Turbulence and Whistler Wave Interactions with Space Plasmas

DTIC Science & Technology

2012-11-21

an oscillating LOS velocity with the same periodicity as the heating modulation pattern. A set of Fourier periodogram from the MUIR LOS velocity...scale ionospheric turbulence are discussed separately, viz., (a) anomalous heat source-induced acoustic gravity waves (AGW), and (b) HF radio wave...ionospheric ducts, acoustic gravity waves (AGWs), anomalous heat sources, inner and outer radiation belts, L parameter, whistler wave interactions

Source Regions of the Type II Radio Burst Observed During a CME-CME Interaction on 2013 May 22

NASA Technical Reports Server (NTRS)

Makela, P.; Gopalswamy, N.; Reiner, M. J.; Akiyama, S.; Krupar, V.

2016-01-01

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction finding analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio observations at decameter-hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source, indicating that the spatial location of the dominant source of the type II emission varies during the CME-CME interaction. The WAVES source directions close to 1MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME-CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.

Elastic parabolic equation solutions for underwater acoustic problems using seismic sources.

PubMed

Frank, Scott D; Odom, Robert I; Collis, Jon M

2013-03-01

Several problems of current interest involve elastic bottom range-dependent ocean environments with buried or earthquake-type sources, specifically oceanic T-wave propagation studies and interface wave related analyses. Additionally, observed deep shadow-zone arrivals are not predicted by ray theoretic methods, and attempts to model them with fluid-bottom parabolic equation solutions suggest that it may be necessary to account for elastic bottom interactions. In order to study energy conversion between elastic and acoustic waves, current elastic parabolic equation solutions must be modified to allow for seismic starting fields for underwater acoustic propagation environments. Two types of elastic self-starter are presented. An explosive-type source is implemented using a compressional self-starter and the resulting acoustic field is consistent with benchmark solutions. A shear wave self-starter is implemented and shown to generate transmission loss levels consistent with the explosive source. Source fields can be combined to generate starting fields for source types such as explosions, earthquakes, or pile driving. Examples demonstrate the use of source fields for shallow sources or deep ocean-bottom earthquake sources, where down slope conversion, a known T-wave generation mechanism, is modeled. Self-starters are interpreted in the context of the seismic moment tensor.

Source and listener directivity for interactive wave-based sound propagation.

PubMed

Mehra, Ravish; Antani, Lakulish; Kim, Sujeong; Manocha, Dinesh

2014-04-01

We present an approach to model dynamic, data-driven source and listener directivity for interactive wave-based sound propagation in virtual environments and computer games. Our directional source representation is expressed as a linear combination of elementary spherical harmonic (SH) sources. In the preprocessing stage, we precompute and encode the propagated sound fields due to each SH source. At runtime, we perform the SH decomposition of the varying source directivity interactively and compute the total sound field at the listener position as a weighted sum of precomputed SH sound fields. We propose a novel plane-wave decomposition approach based on higher-order derivatives of the sound field that enables dynamic HRTF-based listener directivity at runtime. We provide a generic framework to incorporate our source and listener directivity in any offline or online frequency-domain wave-based sound propagation algorithm. We have integrated our sound propagation system in Valve's Source game engine and use it to demonstrate realistic acoustic effects such as sound amplification, diffraction low-passing, scattering, localization, externalization, and spatial sound, generated by wave-based propagation of directional sources and listener in complex scenarios. We also present results from our preliminary user study.

Stress Wave Source Characterization: Impact, Fracture, and Sliding Friction

NASA Astrophysics Data System (ADS)

McLaskey, Gregory Christofer

Rapidly varying forces, such as those associated with impact, rapid crack propagation, and fault rupture, are sources of stress waves which propagate through a solid body. This dissertation investigates how properties of a stress wave source can be identified or constrained using measurements recorded at an array of sensor sites located far from the source. This methodology is often called the method of acoustic emission and is useful for structural health monitoring and the noninvasive study of material behavior such as friction and fracture. In this dissertation, laboratory measurements of 1--300 mm wavelength stress waves are obtained by means of piezoelectric sensors which detect high frequency (10 kHz--3MHz) motions of a specimen's surface, picometers to nanometers in amplitude. Then, stress wave source characterization techniques are used to study ball impact, drying shrinkage cracking in concrete, and the micromechanics of stick-slip friction of Poly(methyl methacrylate) (PMMA) and rock/rock interfaces. In order to quantitatively relate recorded signals obtained with an array of sensors to a particular stress wave source, wave propagation effects and sensor distortions must be accounted for. This is achieved by modeling the physics of wave propagation and transduction as linear transfer functions. Wave propagation effects are precisely modeled by an elastodynamic Green's function, sensor distortion is characterized by an instrument response function, and the stress wave source is represented with a force moment tensor. These transfer function models are verified though calibration experiments which employ two different mechanical calibration sources: ball impact and glass capillary fracture. The suitability of the ball impact source model, based on Hertzian contact theory, is experimentally validated for small (˜1 mm) balls impacting massive plates composed of four different materials: aluminum, steel, glass, and PMMA. Using this transfer function approach and the two mechanical calibration sources, four types of piezoelectric sensors were calibrated: three commercially available sensors and the Glaser-type conical piezoelectric sensor, which was developed in the Glaser laboratory. The distorting effects of each sensor are modeled using autoregressive-moving average (ARMA) models, and because vital phase information is robustly incorporated into these models, they are useful for simulating or removing sensor-induced distortions, so that a displacement time history can be retrieved from recorded signals. The Glaser-type sensor was found to be very well modeled as a unidirectional displacement sensor which detects stress wave disturbances down to about 1 picometer in amplitude. Finally, the merits of a fully calibrated experimental system are demonstrated in a study of stress wave sources arising from sliding friction, and the relationship between those sources and earthquakes. A laboratory friction apparatus was built for this work which allows the micro-mechanisms of friction to be studied with stress wave analysis. Using an array of 14 Glaser-type sensors, and precise models of wave propagation effects and the sensor distortions, the physical origins of the stress wave sources are explored. Force-time functions and focal mechanisms are determined for discrete events found amid the "noise" of friction. These localized events are interpreted to be the rupture of micrometer-sized contacts, known as asperities. By comparing stress wave sources from stick-slip experiments on plastic/plastic and rock/rock interfaces, systematic differences were found. The rock interface produces very rapid (<1 microsecond) implosive forces indicative of brittle asperity failure and fault gouge formation, while rupture on the plastic interface releases only shear force and produces a source more similar to earthquakes commonly recorded in the field. The difference between the mechanisms is attributed to the vast differences in the hardness and melting temperatures of the two materials, which affect the distribution of asperities as well as their failure behavior. With proper scaling, the strong link between material properties and laboratory earthquakes will aid in our understanding of fault mechanics and the generation of earthquakes and seismic tremor.

Body and Surface Wave Modeling of Observed Seismic Events. Part 2.

DTIC Science & Technology

1987-05-12

is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical S coordinates in an asymptotic form which...using line source (2-D) theory. It is based on expand - ing the complete three dimensional solution of the wave equation expressed in cylindrical...generating synthetic point-source seismograms for shear dislocation sources using line source (2-D) theory. It is based on expanding the complete three

A Hammer-Impact, Aluminum, Shear-Wave Seismic Source

USGS Publications Warehouse

Haines, Seth

2007-01-01

Near-surface seismic surveys often employ hammer impacts to create seismic energy. Shear-wave surveys using horizontally polarized waves require horizontal hammer impacts against a rigid object (the source) that is coupled to the ground surface. I have designed, built, and tested a source made out of aluminum and equipped with spikes to improve coupling. The source is effective in a variety of settings, and it is relatively simple and inexpensive to build.

Green’s functions for a volume source in an elastic half-space

PubMed Central

Zabolotskaya, Evgenia A.; Ilinskii, Yurii A.; Hay, Todd A.; Hamilton, Mark F.

2012-01-01

Green’s functions are derived for elastic waves generated by a volume source in a homogeneous isotropic half-space. The context is sources at shallow burial depths, for which surface (Rayleigh) and bulk waves, both longitudinal and transverse, can be generated with comparable magnitudes. Two approaches are followed. First, the Green’s function is expanded with respect to eigenmodes that correspond to Rayleigh waves. While bulk waves are thus ignored, this approximation is valid on the surface far from the source, where the Rayleigh wave modes dominate. The second approach employs an angular spectrum that accounts for the bulk waves and yields a solution that may be separated into two terms. One is associated with bulk waves, the other with Rayleigh waves. The latter is proved to be identical to the Green’s function obtained following the first approach. The Green’s function obtained via angular spectrum decomposition is analyzed numerically in the time domain for different burial depths and distances to the receiver, and for parameters relevant to seismo-acoustic detection of land mines and other buried objects. PMID:22423682

Source spectral variation and yield estimation for small, near-source explosions

NASA Astrophysics Data System (ADS)

Yoo, S.; Mayeda, K. M.

2012-12-01

Significant S-wave generation is always observed from explosion sources which can lead to difficulty in discriminating explosions from natural earthquakes. While there are numerous S-wave generation mechanisms that are currently the topic of significant research, the mechanisms all remain controversial and appear to be dependent upon the near-source emplacement conditions of that particular explosion. To better understand the generation and partitioning of the P and S waves from explosion sources and to enhance the identification and discrimination capability of explosions, we investigate near-source explosion data sets from the 2008 New England Damage Experiment (NEDE), the Humble-Redwood (HR) series of explosions, and a Massachusetts quarry explosion experiment. We estimate source spectra and characteristic source parameters using moment tensor inversions, direct P and S waves multi-taper analysis, and improved coda spectral analysis using high quality waveform records from explosions from a variety of emplacement conditions (e.g., slow/fast burning explosive, fully tamped, partially tamped, single/ripple-fired, and below/above ground explosions). The results from direct and coda waves are compared to theoretical explosion source model predictions. These well-instrumented experiments provide us with excellent data from which to document the characteristic spectral shape, relative partitioning between P and S-waves, and amplitude/yield dependence as a function of HOB/DOB. The final goal of this study is to populate a comprehensive seismic source reference database for small yield explosions based on the results and to improve nuclear explosion monitoring capability.

Power from Ocean Waves.

ERIC Educational Resources Information Center

Newman, J. N.

1979-01-01

Discussed is the utilization of surface ocean waves as a potential source of power. Simple and large-scale wave power devices and conversion systems are described. Alternative utilizations, environmental impacts, and future prospects of this alternative energy source are detailed. (BT)

Self-attraction into spinning eigenstates of a mobile wave source by its emission back-reaction

NASA Astrophysics Data System (ADS)

Labousse, Matthieu; Perrard, Stéphane; Couder, Yves; Fort, Emmanuel

2016-10-01

The back-reaction of a radiated wave on the emitting source is a general problem. In the most general case, back-reaction on moving wave sources depends on their whole history. Here we study a model system in which a pointlike source is piloted by its own memory-endowed wave field. Such a situation is implemented experimentally using a self-propelled droplet bouncing on a vertically vibrated liquid bath and driven by the waves it generates along its trajectory. The droplet and its associated wave field form an entity having an intrinsic dual particle-wave character. The wave field encodes in its interference structure the past trajectory of the droplet. In the present article we show that this object can self-organize into a spinning state in which the droplet possesses an orbiting motion without any external interaction. The rotation is driven by the wave-mediated attractive interaction of the droplet with its own past. The resulting "memory force" is investigated and characterized experimentally, numerically, and theoretically. Orbiting with a radius of curvature close to half a wavelength is shown to be a memory-induced dynamical attractor for the droplet's motion.

Nonlinear interaction of an intense radio wave with ionospheric D/E layer plasma

NASA Astrophysics Data System (ADS)

Sodha, Mahendra Singh; Agarwal, Sujeet Kumar

2018-05-01

This paper considers the nonlinear interaction of an intense electromagnetic wave with the D/E layer plasma in the ionosphere. A simultaneous solution of the electromagnetic wave equation and the equations describing the kinetics of D/E layer plasma is obtained; the phenomenon of ohmic heating of electrons by the electric field of the wave causes enhanced collision frequency and ionization of neutral species. Electron temperature dependent recombination of electrons with ions, electron attachment to O 2 molecules, and detachment of electrons from O2 - ions has also been taken into account. The dependence of the plasma parameters on the square of the electric vector of the wave E0 2 has been evaluated for three ionospheric heights (viz., 90, 100, and 110 km) corresponding to the mid-latitude mid-day ionosphere and discussed; these results are used to investigate the horizontal propagation of an intense radio wave at these heights.

Mapping Hurricane Inland-Storm Tides

NASA Astrophysics Data System (ADS)

Turco, M.; East, J. W.; Dorsey, M. E.; McGee, B. D.; McCallum, B. E.; Pearman, J. L.; Sallenger, A. H.; Holmes, R. R.; Berembrock, C. E.; Turnipseed, D. P.; Mason, R. R.

2008-12-01

Historically, hurricane-induced storm-tides were documented through analysis of structural or vegetative damage and high-water marks. However, these sources rarely provided quantitative information about the timing of the flooding, the sequencing of multiple paths by which the storm-surge waters arrived, or the magnitude of waves and wave run-up comprising floodwaters. In response to these deficiencies, the U.S. Geological Survey (USGS) developed and deployed an experimental mobile storm-surge network to provide detailed time-series data for selected hurricane landfalls. The USGS first deployed the network in September 2005 as Hurricane Rita approached the Texas and Louisiana coasts. The network for Rita consisted of 32 water-level and 14 barometric-pressure monitoring sites. Sensors were located at distances ranging from a few hundred feet to approximately 30 miles inland and sampled 4,000 square miles. Deployments have also occurred for Hurricanes Wilma, Gustav, and Ike. For Hurricane Gustav, more than 100 water level sensors were deployed. Analysis of the water-level data enable construction of maps depicting surge topography through time and space, essentially rendering elements of a 3-dimensional view of the storm-surge dome as it moves on- shore, as well as a map of maximum water-level elevations. The USGS also acquired LIDAR topographic data from coasts impacted by hurricanes. These data reveal extreme changes to the beaches and barrier islands that arise from hurricane storm surge and waves. By better understanding where extreme changes occur along our coasts, we will be able to position coastal structures away from hazards.

Excitation of a buried magmatic pipe: A seismic source model for volcanic tremor

NASA Astrophysics Data System (ADS)

Chouet, Bernard

1985-02-01

Recent observations of seismic events at various volcanoes suggest that harmonic tremor results from the sustained occurrence of so-called long-period or low-frequency events. Accordingly, we can view the long-period volcanic event as the elementary process of tremor and interpret it as the impulse response of the tremor-generating system. We present a seismic model in which the source of tremor is the acoustic resonance of a fluid-filled volcanic pipe triggered by excess gas pressure. The model consists of three elements, namely, a triggering mechanism, a resonator, and a radiator. For simplicity, we assume a hemispherical trigger, cylindrial resonator, and circular radiator set in a vertical configuration with the trigger capping the top of the pipe and the disk-shaped radiator shutting off its bottom. Considering the simple case of a source buried in a homogeneous half space, we then apply the discrete wave number method to obtain a complete representation of the ground motion response at near and intermediate distances. The results demonstrate that the displacement attributed to the pipe dominates the near-field motion, while that due to the disk is representative of the intermediate and far fields. The trigger itself has a smaller contribution, mainly limited to the field in the proximity of the source. The characteristics displayed by the free surface response evolve from a strong impulsive signature in the immediate vicinity of the epicenter to a well-developed harmonic wave train dominated by Rayleigh waves at larger distances. No clear shear arrival can be detected in the synthetic seismograms. The displacement spectrum reflects the organ-pipe modes of the conduit, and the bandwidth associated with the dominant spectral peak of motion is controlled by the combined losses due to viscous attenuation in the fluid and elastic radiation into the solid. In the case of the cylindrical magma column considered, the radiation loss is proportional to the square of the pipe radius, while the loss related to viscous damping is inversely proportional to the same factor, indicating that the relative importance of the two loss mechanisms is critically dependent on the geometry of the magma reservoir. The relative importance of the pipe and disk elements, likewise, is a function of the conduit cross section. This suggests the possibility of determining the geometry of the source as well as the radiation loss and in situ magma viscosity from a comparison of near- and far-field observations.

On the Assessment of Acoustic Scattering and Shielding by Time Domain Boundary Integral Equation Solutions

NASA Technical Reports Server (NTRS)

Hu, Fang Q.; Pizzo, Michelle E.; Nark, Douglas M.

2016-01-01

Based on the time domain boundary integral equation formulation of the linear convective wave equation, a computational tool dubbed Time Domain Fast Acoustic Scattering Toolkit (TD-FAST) has recently been under development. The time domain approach has a distinct advantage that the solutions at all frequencies are obtained in a single computation. In this paper, the formulation of the integral equation, as well as its stabilization by the Burton-Miller type reformulation, is extended to cases of a constant mean flow in an arbitrary direction. In addition, a "Source Surface" is also introduced in the formulation that can be employed to encapsulate regions of noise sources and to facilitate coupling with CFD simulations. This is particularly useful for applications where the noise sources are not easily described by analytical source terms. Numerical examples are presented to assess the accuracy of the formulation, including a computation of noise shielding by a thin barrier motivated by recent Historical Baseline F31A31 open rotor noise shielding experiments. Furthermore, spatial resolution requirements of the time domain boundary element method are also assessed using point per wavelength metrics. It is found that, using only constant basis functions and high-order quadrature for surface integration, relative errors of less than 2% may be obtained when the surface spatial resolution is 5 points-per-wavelength (PPW) or 25 points-per-wavelength squared (PPW2).

Multi-channel unidirectional transmission of phononic crystal heterojunctions

NASA Astrophysics Data System (ADS)

Xu, Zhenlong; Tong, Jie; Wu, Fugen

2018-02-01

Two square steel columns are arranged in air to form two-dimensional square lattice phononic crystals (PNCs). Two PNCs can be combined into a non-orthogonal 45∘ heterojunction when the difference in the directional band gaps of the two PNC types is utilized. The finite element method is used to calculate the acoustic band structure, the heterogeneous junction transmission characteristics, acoustic field distribution, and many others. Results show that a non-orthogonal PNC heterojunction can produce a multi-channel unidirectional transmission of acoustic waves. With the square scatterer rotated, the heterojunction can select a frequency band for unidirectional transmission performance. This capability is particularly useful for constructing acoustic diodes with wide-bands and high-efficiency unidirectional transmission characteristics.

3D crustal structure of the Alpine belt and foreland basins as imaged by ambient-noise surface wave

NASA Astrophysics Data System (ADS)

Molinari, Irene; Morelli, Andrea; Cardi, Riccardo; Boschi, Lapo; Poli, Piero; Kissling, Edi

2016-04-01

We derive a 3-D crustal structure (S wave velocity) underneath northern Italy and the wider Alpine region, from an extensive data set of measurements of Rayleigh-wave phase- and group-velocities from ambient noise correlation among all seismographic stations available to date in the region, via a constrained tomographic inversion made to honor detailed active source reflection/refraction profiles and other geological information. We first derive a regional-scale surface wave tomography from ambient-noise-based phase- and group- surface wave velocity observations (Verbeke et al., 2012). Our regional 3D model (Molinari et al., 2015) shows the low velocity area beneath the Po Plain and the Molasse basin; the contrast between the low-velocity crust of the Adriatic domain and the high-velocity crust of the Tyrrhenian domain is clearly seen, as well as an almost uniform crystalline crust beneath the Alpine belt. However, higher frequency data can be exploited to achieve higher resolution images of the Po Plain and Alpine foreland 3D crustal structure. We collected and analyze one year of noise records (2011) of ~100 North Italy seismic broadband stations, we derive the Green functions between each couple of stations and we measure the phase- and group-Rayleigh wave velocity. We conduct a suite of linear least squares inversion of both phase- and group-velocity data, resulting in 2-D maps of Rayleigh-wave phase and group velocity at periods between 3 and 40s with a resolution of 0.1x0.1 degrees. The maps are then inverted to get the 3D structure with unprecedented details. We present here our results, we compare them with other studies, and we discuss geological/geodynamical implications. We believe that such a model stands for the most up-to-date seismological information on the crustal structure of the Alpine belt and foreland basins, and it can represent a reliable reference for further, more detailed, studies to come, based on the high seismograph station density being accomplished by the AlpArray project.

Variable-pulse switching circuit accurately controls solenoid-valve actuations

NASA Technical Reports Server (NTRS)

Gillett, J. D.

1967-01-01

Solid state circuit generating adjustable square wave pulses of sufficient power operates a 28 volt dc solenoid valve at precise time intervals. This circuit is used for precise time control of fluid flow in combustion experiments.

Multivariate regression methods for estimating velocity of ictal discharges from human microelectrode recordings

NASA Astrophysics Data System (ADS)

Liou, Jyun-you; Smith, Elliot H.; Bateman, Lisa M.; McKhann, Guy M., II; Goodman, Robert R.; Greger, Bradley; Davis, Tyler S.; Kellis, Spencer S.; House, Paul A.; Schevon, Catherine A.

2017-08-01

Objective. Epileptiform discharges, an electrophysiological hallmark of seizures, can propagate across cortical tissue in a manner similar to traveling waves. Recent work has focused attention on the origination and propagation patterns of these discharges, yielding important clues to their source location and mechanism of travel. However, systematic studies of methods for measuring propagation are lacking. Approach. We analyzed epileptiform discharges in microelectrode array recordings of human seizures. The array records multiunit activity and local field potentials at 400 micron spatial resolution, from a small cortical site free of obstructions. We evaluated several computationally efficient statistical methods for calculating traveling wave velocity, benchmarking them to analyses of associated neuronal burst firing. Main results. Over 90% of discharges met statistical criteria for propagation across the sampled cortical territory. Detection rate, direction and speed estimates derived from a multiunit estimator were compared to four field potential-based estimators: negative peak, maximum descent, high gamma power, and cross-correlation. Interestingly, the methods that were computationally simplest and most efficient (negative peak and maximal descent) offer non-inferior results in predicting neuronal traveling wave velocities compared to the other two, more complex methods. Moreover, the negative peak and maximal descent methods proved to be more robust against reduced spatial sampling challenges. Using least absolute deviation in place of least squares error minimized the impact of outliers, and reduced the discrepancies between local field potential-based and multiunit estimators. Significance. Our findings suggest that ictal epileptiform discharges typically take the form of exceptionally strong, rapidly traveling waves, with propagation detectable across millimeter distances. The sequential activation of neurons in space can be inferred from clinically-observable EEG data, with a variety of straightforward computation methods available. This opens possibilities for systematic assessments of ictal discharge propagation in clinical and research settings.

Design and performance of dual-polarization lumped-element kinetic inductance detectors for millimeter-wave polarimetry

NASA Astrophysics Data System (ADS)

McCarrick, H.; Jones, G.; Johnson, B. R.; Abitbol, M. H.; Ade, P. A. R.; Bryan, S.; Day, P.; Essinger-Hileman, T.; Flanigan, D.; Leduc, H. G.; Limon, M.; Mauskopf, P.; Miller, A.; Tucker, C.

2018-02-01

Aims: Lumped-element kinetic inductance detectors (LEKIDs) are an attractive technology for millimeter-wave observations that require large arrays of extremely low-noise detectors. We designed, fabricated and characterized 64-element (128 LEKID) arrays of horn-coupled, dual-polarization LEKIDs optimized for ground-based CMB polarimetry. Our devices are sensitive to two orthogonal polarizations in a single spectral band centered on 150 GHz with Δν/ν = 0.2. The 65 × 65 mm square arrays are designed to be tiled into the focal plane of an optical system. We demonstrate the viability of these dual-polarization LEKIDs with laboratory measurements. Methods: The LEKID modules are tested with an FPGA-based readout system in a sub-kelvin cryostat that uses a two-stage adiabatic demagnetization refrigerator. The devices are characterized using a blackbody and a millimeter-wave source. The polarization properties are measured with a cryogenic stepped half-wave plate. We measure the resonator parameters and the detector sensitivity, noise spectrum, dynamic range, and polarization response. Results: The resonators have internal quality factors approaching 1 × 106. The detectors have uniform response between orthogonal polarizations and a large dynamic range. The detectors are photon-noise limited above 1 pW of absorbed power. The noise-equivalent temperatures under a 3.4 K blackbody load are <100 μK √s. The polarization fractions of detectors sensitive to orthogonal polarizations are >80%. The entire array is multiplexed on a single readout line, demonstrating a multiplexing factor of 128. The array and readout meet the requirements for 4 arrays to be read out simultaneously for a multiplexing factor of 512. Conclusions: This laboratory study demonstrates the first dual-polarization LEKID array optimized specifically for CMB polarimetry and shows the readiness of the detectors for on-sky observations.

Interferometry

NASA Technical Reports Server (NTRS)

Ridgway, Stephen; Wilson, Robert W.; Begelman, Mitchell C.; Bender, Peter; Burke, Bernard F.; Cornwell, Tim; Drever, Ronald; Dyck, H. Melvin; Johnston, Kenneth J.; Kibblewhite, Edward

1991-01-01

The following recommended programs are reviewed: (1) infrared and optical interferometry (a ground-based and space programs); (2) compensation for the atmosphere with adaptive optics (a program for development and implementation of adaptive optics); and (3) gravitational waves (high frequency gravitational wave sources (LIGO), low frequency gravitational wave sources (LAGOS), a gravitational wave observatory program, laser gravitational wave observatory in space, and technology development during the 1990's). Prospects for international collaboration and related issues are also discussed.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard A.; Davis, Andrew E.; Wang, Qing X.; Yamamoto, Takashi; Cerkoney, Daniel P.; Reid, Candy; Koopman, Maximiliaan L.; Minami, Hidetoshi; Kashiwagi, Takanari; Rain, Joseph R.; Doty, Constance M.; Sedlack, Michael A.; Morales, Manuel A.; Watanabe, Chiharu; Tsujimoto, Manabu; Delfanazari, Kaveh; Kadowaki, Kazuo

2017-12-01

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C ∞v , C 4v , and C 3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Electroanalytical method for determination of lead(II) in orange and apple using kaolin modified platinum electrode.

PubMed

El Mhammedi, M A; Achak, M; Bakasse, M; Chtaini, A

2009-08-01

This paper reports on the use of platinum electrode modified with kaolin (K/Pt) and square wave voltammetry for analytical detection of trace lead(II) in pure water, orange and apple samples. The electroanalytical procedure for determination of the Pb(II) comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using square wave voltammetry. The analytical performances of the extraction method has been explored by studying the incubating time, and effect of interferences due to other ions. During the preconcentration step, Pb(II) was accumulated on the surface of the kaolin. The observed detection and quantification limits in pure water were 3.6x10(-9)molL(-1) and 1.2x10(-8)molL(-1), respectively. The precision of the method was also determined; the results was 2.35% (n=5).

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

PubMed

Moradian, A; Miri, M F

2011-02-01

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

Tunable broadband unidirectional acoustic transmission based on a waveguide with phononic crystal

NASA Astrophysics Data System (ADS)

Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Wan, Lele

2016-08-01

In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

Dissipative and Autonomous Square-Wave Self-Oscillation of a Macroscopic Hybrid Self-Assembly under Continuous Light Irradiation.

PubMed

Ikegami, Tomonori; Kageyama, Yoshiyuki; Obara, Kazuma; Takeda, Sadamu

2016-07-11

Building a bottom-up supramolecular system to perform continuously autonomous motions will pave the way for the next generation of biomimetic mechanical systems. In biological systems, hierarchical molecular synchronization underlies the generation of spatio-temporal patterns with dissipative structures. However, it remains difficult to build such self-organized working objects via artificial techniques. Herein, we show the first example of a square-wave limit-cycle self-oscillatory motion of a noncovalent assembly of oleic acid and an azobenzene derivative. The assembly steadily flips under continuous blue-light irradiation. Mechanical self-oscillation is established by successively alternating photoisomerization processes and multi-stable phase transitions. These results offer a fundamental strategy for creating a supramolecular motor that works progressively under the operation of molecule-based machines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Memristive behavior of the SnO2/TiO2 interface deposited by sol-gel

NASA Astrophysics Data System (ADS)

Boratto, Miguel H.; Ramos, Roberto A.; Congiu, Mirko; Graeff, Carlos F. O.; Scalvi, Luis V. A.

2017-07-01

A novel and cheap Resistive Random Access Memory (RRAM) device is proposed within this work, based on the interface between antimony doped Tin Oxide (4%at Sb:SnO2) and Titanium Oxide (TiO2) thin films, entirely prepared through a low-temperature sol-gel process. The device was fabricated on glass slides using evaporated aluminum electrodes. Typical bipolar memristive behavior under cyclic voltage sweeping and square wave voltages, with well-defined high and low resistance states (HRS and LRS), and set and reset voltages are shown in our samples. The switching mechanism, explained by charges trapping/de-trapping by defects in the SnO2/TiO2 interface, is mainly driven by the external electric field. The calculated on/off ratio was about 8 × 102 in best conditions with good reproducibility over repeated measurement cycles under cyclic voltammetry and about 102 under applied square wave voltage.

Magnetic Correlations and Pairing in the 1/5-Depleted Square Lattice Hubbard Model

DOE PAGES

Khatemi, Ehsan; Singh, Rajiv R. P.; Pickett, Warren E.; ...

2014-09-04

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV 4O 9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to themore » Néel phase. These findings have intriguing connections to iron-based superconductors, and suggest that some physics of multiorbital systems can be captured by a single-orbital model at different dopings.« less

The synoptic setting and possible energy sources for mesoscale wave disturbances

NASA Technical Reports Server (NTRS)

Uccellini, Louis W.; Koch, Steven E.

1987-01-01

Published data on 13 cases of mesoscale wave disturbances and their environment were examined to isolate common features for these cases and to determine possible energy sources for the waves. These events are characterized by either a singular wave of depression or wave packets with periods of 1-4 h, horizontal wavelengths of 50-500 km, and surface-pressure perturbation amplitudes of 0.2-7.0 mb. These wave events are shown to be associated with a distinct synoptic pattern (including the existence of a strong inversion in the lower troposphere and the propagation of a jet streak toward a ridge axis in the upper troposphere) while displaying little correlation with the presence of convective storm cells. The observed development of the waves is consistent with the hypothesis that the energy source needed to initiate and sustain the wave disturbances may be related to a geostrophic adjustment process associated with upper-tropospheric jet streaks.

Corrections to the Thomson cross section caused by relativistic effects and by the presence of the drift velocity of a classical charged particle in the field of a monochromatic plane wave

NASA Astrophysics Data System (ADS)

Perestoronin, A. V.

2017-03-01

An approach to the solution of the relativistic problem of the motion of a classical charged particle in the field of a monochromatic plane wave with an arbitrary polarization (linear, circular, or elliptic) is proposed. It is based on the analysis of the 4-vector equation of motion of the charged particle together with the 4-vector and tensor equations for the components of the electromagnetic field tensor of a monochromatic plane wave. This approach provides analytical expressions for the time-averaged square of the 4-acceleration of the charge, as well as for the averaged values of any quantities periodic in the time of the reference frame. Expressions for the integral power of scattered radiation, which is proportional to the time-averaged square of the 4-acceleration of the charge, and for the integral scattering cross section, which is the ratio of the power of scattered radiation to the intensity of incident radiation, are obtained for an arbitrary inertial reference frame. An expression for the scattering cross section, which coincides with the known results at the circular and linear polarizations of the incident waves and describes the case of elliptic polarization of the incident wave, is obtained for the reference frame where the charged particle is on average at rest. An expression for the scattering cross section including relativistic effects and the nonzero drift velocity of a particle in this system is obtained for the laboratory reference frame, where the initial velocity of the charged particle is zero. In the case of the circular polarization of the incident wave, the scattering cross section in the laboratory frame is equal to the Thompson cross section.

Eruptive Source Parameters from Near-Source Gravity Waves Induced by Large Vulcanian eruptions

NASA Astrophysics Data System (ADS)

Barfucci, Giulia; Ripepe, Maurizio; De Angelis, Silvio; Lacanna, Giorgio; Marchetti, Emanuele

2016-04-01

The sudden ejection of hot material from volcanic vent perturbs the atmosphere generating a broad spectrum of pressure oscillations from acoustic infrasound (<10 Hz) to gravity waves (<0.03 Hz). However observations of gravity waves excited by volcanic eruptions are still rare, mostly limited to large sub-plinian eruptions and frequently at large distance from the source (>100 km). Atmospheric Gravity waves are induced by perturbations of the hydrostatic equilibrium of the atmosphere and propagate within a medium with internal density stratification. They are initiated by mechanisms that cause the atmosphere to be displaced as for the injection of volcanic ash plume during an eruption. We use gravity waves to infer eruptive source parameters, such as mass eruption rate (MER) and duration of the eruption, which may be used as inputs in the volcanic ash transport and dispersion models. We present the analysis of near-field observations (<7 km) of atmospheric gravity waves, with frequencies of 0.97 and 1.15 mHz, recorded by a pressure sensors network during two explosions in July and December 2008 at Soufrière Hills Volcano, Montserrat. We show that gravity waves at Soufrière Hills Volcano originate above the volcanic dome and propagate with an apparent horizontal velocities of 8-10 m/s. Assuming a single mass injection point source model, we constrain the source location at ~3.5 km a.s.l., above the vent, duration of the gas thrust < 140 s and MERs of 2.6 and 5.4 x10E7 kg/s, for the two eruptive events. Source duration and MER derived by modeling Gravity Waves are fully compatible with others independent estimates from field observations. Our work strongly supports the use of gravity waves to model eruption source parameters and can have a strong impact on our ability to monitor volcanic eruption at a large distance and may have future application in assessing the relative magnitude of volcanic explosions.

Bending and splitting of spoof surface acoustic waves through structured rigid surface

NASA Astrophysics Data System (ADS)

Xie, Sujun; Ouyang, Shiliang; He, Zhaojian; Wang, Xiaoyun; Deng, Ke; Zhao, Heping

2018-03-01

In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC), which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect), the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

Analysis of Measured and Simulated Supraglottal Acoustic Waves.

PubMed

Fraile, Rubén; Evdokimova, Vera V; Evgrafova, Karina V; Godino-Llorente, Juan I; Skrelin, Pavel A

2016-09-01

To date, although much attention has been paid to the estimation and modeling of the voice source (ie, the glottal airflow volume velocity), the measurement and characterization of the supraglottal pressure wave have been much less studied. Some previous results have unveiled that the supraglottal pressure wave has some spectral resonances similar to those of the voice pressure wave. This makes the supraglottal wave partially intelligible. Although the explanation for such effect seems to be clearly related to the reflected pressure wave traveling upstream along the vocal tract, the influence that nonlinear source-filter interaction has on it is not as clear. This article provides an insight into this issue by comparing the acoustic analyses of measured and simulated supraglottal and voice waves. Simulations have been performed using a high-dimensional discrete vocal fold model. Results of such comparative analysis indicate that spectral resonances in the supraglottal wave are mainly caused by the regressive pressure wave that travels upstream along the vocal tract and not by source-tract interaction. On the contrary and according to simulation results, source-tract interaction has a role in the loss of intelligibility that happens in the supraglottal wave with respect to the voice wave. This loss of intelligibility mainly corresponds to spectral differences for frequencies above 1500 Hz. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Addendum to foundations of multidimensional wave field signal theory: Gaussian source function

NASA Astrophysics Data System (ADS)

Baddour, Natalie

2018-02-01

Many important physical phenomena are described by wave or diffusion-wave type equations. Recent work has shown that a transform domain signal description from linear system theory can give meaningful insight to multi-dimensional wave fields. In N. Baddour [AIP Adv. 1, 022120 (2011)], certain results were derived that are mathematically useful for the inversion of multi-dimensional Fourier transforms, but more importantly provide useful insight into how source functions are related to the resulting wave field. In this short addendum to that work, it is shown that these results can be applied with a Gaussian source function, which is often useful for modelling various physical phenomena.

A constrained robust least squares approach for contaminant release history identification

NASA Astrophysics Data System (ADS)

Sun, Alexander Y.; Painter, Scott L.; Wittmeyer, Gordon W.

2006-04-01

Contaminant source identification is an important type of inverse problem in groundwater modeling and is subject to both data and model uncertainty. Model uncertainty was rarely considered in the previous studies. In this work, a robust framework for solving contaminant source recovery problems is introduced. The contaminant source identification problem is first cast into one of solving uncertain linear equations, where the response matrix is constructed using a superposition technique. The formulation presented here is general and is applicable to any porous media flow and transport solvers. The robust least squares (RLS) estimator, which originated in the field of robust identification, directly accounts for errors arising from model uncertainty and has been shown to significantly reduce the sensitivity of the optimal solution to perturbations in model and data. In this work, a new variant of RLS, the constrained robust least squares (CRLS), is formulated for solving uncertain linear equations. CRLS allows for additional constraints, such as nonnegativity, to be imposed. The performance of CRLS is demonstrated through one- and two-dimensional test problems. When the system is ill-conditioned and uncertain, it is found that CRLS gave much better performance than its classical counterpart, the nonnegative least squares. The source identification framework developed in this work thus constitutes a reliable tool for recovering source release histories in real applications.

Halos--a problem for all myopes? A comparison between spectacles, contact lenses, and photorefractive keratectomy.

PubMed

Lohmann, C P; Fitzke, F W; O'Brart, D; Muir, M K; Marshall, J

1993-01-01

After photorefractive keratectomy (PRK) using excimer lasers (193 nm) many patients report the presence of halos around light sources at night. However, halos are not unique to PRK patients, as they are a common observation in myopic contact lens wearers. We present an objective measurement of the halos using a computerized technique. The patient fixated on a red cross within a white circle in the center of a video monitor which served as the halo source. The screen surrounding the circle was not illuminated. The operator controlled the movement of the white spot and moved the spot toward the halo source until the subject indicated when the cursor was at the outer parameter of the halo. Measurements were made at 30 degree intervals around the halo source and expressed as square degrees. The study found that spectacles, soft contact lenses, and excimer laser surgery were superior to hard contact lenses in terms of the size of the halo. A mean value of 2.51 square degrees was obtained for spectacles wearers compared with 3.18 square degrees for soft contact lenses, 3.14 square degrees for excimer laser patients with 4-millimeter ablation zone, 2.76 square degrees for excimer laser patients with a 5-millimeter ablation zone, and 89.5 square degrees for hard contact lenses. It appears that this device is very useful for measuring the halo size after excimer laser PRK. We concluded that halos were not a problem for our patients after excimer laser photorefractive keratectomy.

Wave and pseudo-diffusion equations from squeezed states

NASA Technical Reports Server (NTRS)

Daboul, Jamil

1993-01-01

We show that the probability distributions P(sub n)(q,p;y) := the absolute value squared of (n(p,q;y), which are obtained from squeezed states, obey an interesting partial differential equation, to which we give two intuitive interpretations: as a wave equation in one space dimension; and as a pseudo-diffusion equation. We also study the corresponding Wehrl entropies S(sub n)(y), and we show that they have minima at zero squeezing, y = 0.

Breakup of Solid Ice Covers Due to Rapid Water Level Variations,

DTIC Science & Technology

1982-02-01

Larsen, and Dr. Devinder S. Sodhi for their valuable comments and reviews of the report. He also thanks Dr. Ashton and Guenther E. Frankenstein for the...for wave periods larger than about 10 seconds. What are the minimum wave lengths that might be generated by discharge variations at a hydro- electric ...Canadian Electrical Association, Research and Development, Suite 580, One Westmount Square, Montreal, Canada. 2. Ashton, G.D. (1974a) Entrainment of ice

Antiferromagnetism and DX2-Y2-WAVE Pairing in the Colored Hubbard Model

NASA Astrophysics Data System (ADS)

Baier, Tobias; Bick, Eike

2001-08-01

We introduce a new formulation of the 2d Hubbard model on a square lattice (the "colored" Hubbard model). In this formulation interesting physical nonlocal properties as antiferromagnetic or dx2-y2-wave superconducting behavior are included in an explicit way. Analyzing the phase diagram in a mean field approximation numerically, we show that our approach yields results which are in qualitative agreement with experiment.

Observations of Sea Surface Mean Square Slope During the Southern Ocean Waves Experiment

NASA Technical Reports Server (NTRS)

Walsh, E. J.; Vandemark, D. C.; Hines, D. E.; Banner, M. L.; Chen, W.; Swift, R. N.; Scott, J. F.; Jensen, J.; Lee, S.; Fandry, C.

1999-01-01

For the Southern Ocean Waves Experiment (SOWEX), conducted in June 1992 out of Hobart, Tasmania, the 36 GHz (8.3 mm) NASA Scanning Radar Altimeter (SRA) was shipped to Australia and installed on a CSIRO Fokker F-27 research aircraft instrumented to make comprehensive surface layer measurements of air-sea interaction fluxes. The sea surface mean square slope (mss), which is predominantly caused by the short waves, was determined from the backscattered power falloff with incidence angle measured by the SRA in the plane normal to the aircraft heading. On each flight, data were acquired at 240 m altitude while the aircraft was in a 7 deg roll attitude, interrogating off-nadir incidence angles from -15 deg through nadir to +29 deg. The aircraft turned azimuthally through 810 deg in this attitude, mapping the azimuthal dependence of the backscattered power falloff with incidence angle. Two sets of turning data were acquired on each day, before and after the aircraft measured wind stress at low altitude (12 m to 65 m). Wave topography and backscattered power for mss were also acquired during those level flight segments whenever the aircraft altitude was above the SRA minimum range of 35 m. A unique feature of this experiment was the use of a nadir-directed low-gain horn antenna (35 deg beamwidth) to acquire azimuthally integrated backscattered power data versus incidence angle before and after the turn data.

Reducing boll weevil populations by clipping terminal buds and removing abscised fruiting bodies

USDA-ARS?s Scientific Manuscript database

The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae) punctures cotton squares and young bolls during feeding and oviposition, causing abscission of flower buds (squares) in the instance of oviposition. Fallen squares are a source of next generation adult boll weevils that...

Direct Measurement of Wave Kernels in Time-Distance Helioseismology

NASA Technical Reports Server (NTRS)

Duvall, T. L., Jr.

2006-01-01

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

Kinetic Monte Carlo simulations of travelling pulses and spiral waves in the lattice Lotka-Volterra model.

PubMed

Makeev, Alexei G; Kurkina, Elena S; Kevrekidis, Ioannis G

2012-06-01

Kinetic Monte Carlo simulations are used to study the stochastic two-species Lotka-Volterra model on a square lattice. For certain values of the model parameters, the system constitutes an excitable medium: travelling pulses and rotating spiral waves can be excited. Stable solitary pulses travel with constant (modulo stochastic fluctuations) shape and speed along a periodic lattice. The spiral waves observed persist sometimes for hundreds of rotations, but they are ultimately unstable and break-up (because of fluctuations and interactions between neighboring fronts) giving rise to complex dynamic behavior in which numerous small spiral waves rotate and interact with each other. It is interesting that travelling pulses and spiral waves can be exhibited by the model even for completely immobile species, due to the non-local reaction kinetics.

Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

USGS Publications Warehouse

Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

2017-10-19

Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

Joint inversion of fundamental and higher mode Rayleigh waves

USGS Publications Warehouse

Luo, Y.-H.; Xia, J.-H.; Liu, J.-P.; Liu, Q.-S.

2008-01-01

In this paper, we analyze the characteristics of the phase velocity of fundamental and higher mode Rayleigh waves in a six-layer earth model. The results show that fundamental mode is more sensitive to the shear velocities of shallow layers (< 7 m) and concentrated in a very narrow band (around 18 Hz) while higher modes are more sensitive to the parameters of relatively deeper layers and distributed over a wider frequency band. These properties provide a foundation of using a multi-mode joint inversion to define S-wave velocity. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least squares method and the SVD (Singular Value Decomposition) technique to invert Rayleigh waves of fundamental and higher modes can effectively reduce the ambiguity and improve the accuracy of inverted S-wave velocities.

Thermal modeling for pulsed radiofrequency ablation: analytical study based on hyperbolic heat conduction.

PubMed

López Molina, Juan A; Rivera, María J; Trujillo, Macarena; Berjano, Enrique J

2009-04-01

The objectives of this study were to model the temperature progress of a pulsed radiofrequency (RF) power during RF heating of biological tissue, and to employ the hyperbolic heat transfer equation (HHTE), which takes the thermal wave behavior into account, and compare the results to those obtained using the heat transfer equation based on Fourier theory (FHTE). A theoretical model was built based on an active spherical electrode completely embedded in the biological tissue, after which HHTE and FHTE were analytically solved. We found three typical waveforms for the temperature progress depending on the relations between the dimensionless duration of the RF pulse delta(a) and the expression square root of lambda(rho-1), with lambda as the dimensionless thermal relaxation time of the tissue and rho as the dimensionless position. In the case of a unique RF pulse, the temperature at any location was the result of the overlapping of two different heat sources delayed for a duration delta(a) (each heat source being produced by a RF pulse of limitless duration). The most remarkable feature in the HHTE analytical solution was the presence of temperature peaks traveling through the medium at a finite speed. These peaks not only occurred during the RF power switch-on period but also during switch off. Finally, a physical explanation for these temperature peaks is proposed based on the interaction of forward and reverse thermal waves. All-purpose analytical solutions for FHTE and HHTE were obtained during pulsed RF heating of biological tissues, which could be used for any value of pulsing frequency and duty cycle.

Stiffness at shear-wave elastography and patient presentation predicts upgrade at surgery following an ultrasound-guided core biopsy diagnosis of ductal carcinoma in situ.

PubMed

Evans, A; Purdie, C A; Jordan, L; Macaskill, E J; Flynn, J; Vinnicombe, S

2016-11-01

The aim of this study is to establish predictors of invasion in lesions yielding an ultrasound-guided biopsy diagnosis of ductal carcinoma in situ (DCIS). Patients subjected to ultrasound-guided core biopsy yielding DCIS were studied. At shear-wave elastography (SWE) a threshold of 50 kPa was used for mean elasticity (Emean) to dichotomise the elasticity data between invasive and non-invasive masses. Data recorded included the mammographic and ultrasound features, the referral source, and grade of DCIS in the biopsy. The chi-square test was used to detect statistical significance. Of 57 lesions, 24 (42%) had invasion at excision. Symptomatic patients and patients with stiff lesions were more likely to have invasion than patients presenting through screening and with soft lesions (58% [14 of 24] versus 30% [10 of 33], p=0.03) and (51% [20 of 39] versus 22% [4 of 18], p=0.04). No other factors showed a relationship with invasion. Combining the two predictors of invasion improved risk stratification with symptomatic and stiff lesions having a risk of invasion of 67% (12 of 18) and soft lesions presenting at screening having only a 17% (2 of 12) risk of invasion (p=0.02). Stiffness on SWE and the referral source of the patient are predictors of occult invasion in women with an ultrasound-guided core biopsy diagnosis of DCIS. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Fast prediction of pulsed nonlinear acoustic fields from clinically relevant sources using Time-Averaged Wave Envelope approach: comparison of numerical simulations and experimental results

PubMed Central

Wójcik, J.; Kujawska, T.; Nowicki, A.; Lewin, P.A.

2008-01-01

The primary goal of this work was to verify experimentally the applicability of the recently introduced Time-Averaged Wave Envelope (TAWE) method [1] as a tool for fast prediction of four dimensional (4D) pulsed nonlinear pressure fields from arbitrarily shaped acoustic sources in attenuating media. The experiments were performed in water at the fundamental frequency of 2.8 MHz for spherically focused (focal length F = 80 mm) square (20 × 20 mm) and rectangular (10 × 25 mm) sources similar to those used in the design of 1D linear arrays operating with ultrasonic imaging systems. The experimental results obtained with 10-cycle tone bursts at three different excitation levels corresponding to linear, moderately nonlinear and highly nonlinear propagation conditions (0.045, 0.225 and 0.45 MPa on-source pressure amplitude, respectively) were compared with those yielded using the TAWE approach [1]. The comparison of the experimental results and numerical simulations has shown that the TAWE approach is well suited to predict (to within ± 1 dB) both the spatial-temporal and spatial-spectral pressure variations in the pulsed nonlinear acoustic beams. The obtained results indicated that implementation of the TAWE approach enabled shortening of computation time in comparison with the time needed for prediction of the full 4D pulsed nonlinear acoustic fields using a conventional (Fourier-series) approach [2]. The reduction in computation time depends on several parameters, including the source geometry, dimensions, fundamental resonance frequency, excitation level as well as the strength of the medium nonlinearity. For the non-axisymmetric focused transducers mentioned above and excited by a tone burst corresponding to moderately nonlinear and highly nonlinear conditions the execution time of computations was 3 and 12 hours, respectively, when using a 1.5 GHz clock frequency, 32-bit processor PC laptop with 2 GB RAM memory, only. Such prediction of the full 4D pulsed field is not possible when using conventional, Fourier-series scheme as it would require increasing the RAM memory by at least 2 orders of magnitude. PMID:18474387

Push-pull switching power amplifier

NASA Technical Reports Server (NTRS)

Cuk, Slobodan M. (Inventor)

1980-01-01

A true push-pull switching power amplifier is disclosed utilizing two dc-to-dc converters. Each converter is comprised of two inductances, one inductance in series with a DC source and the other inductor in series with the output load, and an electrical energy transferring device with storage capability, namely storage capacitance, with suitable switching means between the inductances to obtain DC level conversion, where the switching means allows bidirectional current (and power) flow, and the switching means of one dc-to-dc converter is driven by the complement of a square-wave switching signal for the other dc-to-dc converter for true push-pull operation. For reduction of current ripple, the inductances in each of the two converters may be coupled, and with proper design of the coupling, the ripple can be reduced to zero at either the input or the output, but preferably the output.

Aperture averaging and BER for Gaussian beam in underwater oceanic turbulence

NASA Astrophysics Data System (ADS)

Gökçe, Muhsin Caner; Baykal, Yahya

2018-03-01

In an underwater wireless optical communication (UWOC) link, power fluctuations over finite-sized collecting lens are investigated for a horizontally propagating Gaussian beam wave. The power scintillation index, also known as the irradiance flux variance, for the received irradiance is evaluated in weak oceanic turbulence by using the Rytov method. This lets us further quantify the associated performance indicators, namely, the aperture averaging factor and the average bit-error rate (). The effects on the UWOC link performance of the oceanic turbulence parameters, i.e., the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature, Kolmogorov microscale, the ratio of temperature to salinity contributions to the refractive index spectrum as well as system parameters, i.e., the receiver aperture diameter, Gaussian source size, laser wavelength and the link distance are investigated.

High resolution extensometer based on optical encoder for measurement of small landslide displacements

NASA Astrophysics Data System (ADS)

Afandi, M. I.; Adinanta, H.; Setiono, A.; Qomaruddin; Widiyatmoko, B.

2018-03-01

There are many ways to measure landslide displacement using sensors such as multi-turn potentiometer, fiber optic strain sensor, GPS, geodetic measurement, ground penetrating radar, etc. The proposed way is to use an optical encoder that produces pulse signal with high stability of measurement resolution despite voltage source instability. The landslide measurement using extensometer based on optical encoder has the ability of high resolution for wide range measurement and for a long period of time. The type of incremental optical encoder provides information about the pulse and direction of a rotating shaft by producing quadrature square wave cycle per increment of shaft movement. The result of measurement using 2,000 pulses per resolution of optical encoder has been obtained. Resolution of extensometer is 36 μm with speed limit of about 3.6 cm/s. System test in hazard landslide area has been carried out with good reliability for small landslide displacement monitoring.

The Confrontation between General Relativity and Experiment.

PubMed

Will, Clifford M

2006-01-01

The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and other binary pulsar systems have yielded other tests, especially of strong-field effects. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.

The Confrontation between General Relativity and Experiment.

PubMed

Will, Clifford M

2001-01-01

The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law will search for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light defl ection the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to half a percent using the Hulse-Taylor binary pulsar, and new binary pulsar systems may yield further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.

Ultrasonic Leak Detection System

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor); Moerk, J. Steven (Inventor)

1998-01-01

A system for detecting ultrasonic vibrations. such as those generated by a small leak in a pressurized container. vessel. pipe. or the like. comprises an ultrasonic transducer assembly and a processing circuit for converting transducer signals into an audio frequency range signal. The audio frequency range signal can be used to drive a pair of headphones worn by an operator. A diode rectifier based mixing circuit provides a simple, inexpensive way to mix the transducer signal with a square wave signal generated by an oscillator, and thereby generate the audio frequency signal. The sensitivity of the system is greatly increased through proper selection and matching of the system components. and the use of noise rejection filters and elements. In addition, a parabolic collecting horn is preferably employed which is mounted on the transducer assembly housing. The collecting horn increases sensitivity of the system by amplifying the received signals. and provides directionality which facilitates easier location of an ultrasonic vibration source.

Transistorized PWM inverter-induction motor drive system

NASA Technical Reports Server (NTRS)

Peak, S. C.; Plunkett, A. B.

1982-01-01

This paper describes the development of a transistorized PWM inverter-induction motor traction drive system. A vehicle performance analysis was performed to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of inverter and motor specifications. The inverter was a transistorized three-phase bridge using General Electric power Darlington transistors. The description of the design and development of this inverter is the principal object of this paper. The high-speed induction motor is a design which is optimized for use with an inverter power source. The primary feedback control is a torque angle control with voltage and torque outer loop controls. A current-controlled PWM technique is used to control the motor voltage. The drive has a constant torque output with PWM operation to base motor speed and a constant horsepower output with square wave operation to maximum speed. The drive system was dynamometer tested and the results are presented.

Shock Waves in a Bose-Einstein Condensate

NASA Technical Reports Server (NTRS)

Kulikov, Igor; Zak, Michail

2005-01-01

A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC). The mathematical model of the BEC in this study is a nonlinear Schroedinger equation (NLSE) in which (1) the role of the wave function of a single particle in the traditional Schroedinger equation is played by a space- and time-dependent complex order parameter (x,t) proportional to the square root of the density of atoms and (2) the atoms engage in a repulsive interaction characterized by a potential proportional to | (x,t)|2. Equations that describe macroscopic perturbations of the BEC at zero temperature are derived from the NLSE and simplifying assumptions are made, leading to equations for the propagation of sound waves and the transformation of sound waves into shock waves. Equations for the speeds of shock waves and the relationships between jumps of velocity and density across shock fronts are derived. Similarities and differences between this theory and the classical theory of sound waves and shocks in ordinary gases are noted. The present theory is illustrated by solving the equations for the example of a shock wave propagating in a cigar-shaped BEC.

Joint inversion of high-frequency surface waves with fundamental and higher modes

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Liu, Q.; Xu, S.

2007-01-01

Joint inversion of multimode surface waves for estimating the shear (S)-wave velocity has received much attention in recent years. In this paper, we first analyze sensitivity of phase velocities of multimodes of surface waves for a six-layer earth model, and then we invert surface-wave dispersion curves of the theoretical model and a real-world example. Sensitivity analysis shows that fundamental mode data are more sensitive to the S-wave velocities of shallow layers and are concentrated on a very narrow frequency band, while higher mode data are more sensitive to the parameters of relatively deeper layers and are distributed over a wider frequency band. These properties provide a foundation of using a multimode joint inversion to define S-wave velocities. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least-square method and the singular-value decomposition technique to invert high-frequency surface waves with fundamental and higher mode data simultaneously can effectively reduce the ambiguity and improve the accuracy of S-wave velocities. ?? 2007.

Instantaneous phase estimation to measure weak velocity variations: application to noise correlation on seismic data at the exploration scale

NASA Astrophysics Data System (ADS)

Corciulo, M.; Roux, P.; Campillo, M.; Dubucq, D.

2010-12-01

Passive imaging from noise cross-correlation is a consolidated analysis applied at continental and regional scale whereas its use at local scale for seismic exploration purposes is still uncertain. The development of passive imaging by cross-correlation analysis is based on the extraction of the Green’s function from seismic noise data. In a completely random field in time and space, the cross-correlation permits to retrieve the complete Green’s function whatever the complexity of the medium. At the exploration scale and at frequency above 2 Hz, the noise sources are not ideally distributed around the stations which strongly affect the extraction of the direct arrivals from the noise cross-correlation process. In order to overcome this problem, the coda waves extracted from noise correlation could be useful. Coda waves describe long and scattered paths sampling the medium in different ways such that they become sensitive to weak velocity variations without being dependent on the noise source distribution. Indeed, scatters in the medium behave as a set of secondary noise sources which randomize the spatial distribution of noise sources contributing to the coda waves in the correlation process. We developed a new technique to measure weak velocity changes based on the computation of the local phase variations (instantaneous phase variation or IPV) of the cross-correlated signals. This newly-developed technique takes advantage from the doublet and stretching techniques classically used to monitor weak velocity variation from coda waves. We apply IPV to data acquired in Northern America (Canada) on a 1-km side square seismic network laid out by 397 stations. Data used to study temporal variations are cross-correlated signals computed on 10-minutes ambient noise in the frequency band 2-5 Hz. As the data set was acquired over five days, about 660 files are processed to perform a complete temporal analysis for each stations pair. The IPV permits to estimate the phase shift all over the signal length without any assumption on the medium velocity. The instantaneous phase is computed using the Hilbert transform of the signal. For each stations pair, we measure the phase difference between successive correlation functions calculated for 10 minutes of ambient noise. We then fit the instantaneous phase shift using a first-order polynomial function. The measure of the velocity variation corresponds to the slope of this fit. Compared to other techniques, the advantage of IPV is a very fast procedure which efficiently provides the measure of velocity variation on large data sets. Both experimental results and numerical tests on synthetic signals will be presented to assess the reliability of the IPV technique, with comparison to the doublet and stretching methods.

SOURCE REGIONS OF THE TYPE II RADIO BURST OBSERVED DURING A CME–CME INTERACTION ON 2013 MAY 22

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

Mäkelä, P.; Reiner, M. J.; Akiyama, S.

2016-08-20

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind /WAVES and STEREO /WAVES (SWAVES) radio observations at decameter–hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radiomore » source, indicating that the spatial location of the dominant source of the type II emission varies during the CME–CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME–CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.« less

Relationships of the group velocity of the time-reversed Lamb wave with bone properties in cortical bone in vitro.

PubMed

Lee, Kang Il; Yoon, Suk Wang

2017-04-11

The present study aims to investigate the feasibility of using the time-reversed Lamb wave as a new method for noninvasive characterization of long cortical bones. The group velocity of the time-reversed Lamb wave launched by using the modified time reversal method was measured in 15 bovine tibiae, and their correlations with the bone properties of the tibia were examined. The group velocity of the time-reversed Lamb wave showed significant positive correlations with the bone properties (r=0.55-0.81). The best univariate predictor of the group velocity of the time-reversed Lamb wave was the cortical thickness, yielding an adjusted squared correlation coefficient (r 2 ) of 0.64. These results imply that the group velocity of the time-reversed Lamb wave, in addition to the velocities of the first arriving signal and the slow guided wave, could potentially be used as a discriminator for osteoporosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Variable selection based near infrared spectroscopy quantitative and qualitative analysis on wheat wet gluten

NASA Astrophysics Data System (ADS)

Lü, Chengxu; Jiang, Xunpeng; Zhou, Xingfan; Zhang, Yinqiao; Zhang, Naiqian; Wei, Chongfeng; Mao, Wenhua

2017-10-01

Wet gluten is a useful quality indicator for wheat, and short wave near infrared spectroscopy (NIRS) is a high performance technique with the advantage of economic rapid and nondestructive test. To study the feasibility of short wave NIRS analyzing wet gluten directly from wheat seed, 54 representative wheat seed samples were collected and scanned by spectrometer. 8 spectral pretreatment method and genetic algorithm (GA) variable selection method were used to optimize analysis. Both quantitative and qualitative model of wet gluten were built by partial least squares regression and discriminate analysis. For quantitative analysis, normalization is the optimized pretreatment method, 17 wet gluten sensitive variables are selected by GA, and GA model performs a better result than that of all variable model, with R2V=0.88, and RMSEV=1.47. For qualitative analysis, automatic weighted least squares baseline is the optimized pretreatment method, all variable models perform better results than those of GA models. The correct classification rates of 3 class of <24%, 24-30%, >30% wet gluten content are 95.45, 84.52, and 90.00%, respectively. The short wave NIRS technique shows potential for both quantitative and qualitative analysis of wet gluten for wheat seed.

Particle detection and non-detection in a quantum time of arrival measurement

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

Sombillo, Denny Lane B., E-mail: dsombillo@nip.upd.edu.ph; Galapon, Eric A.

2016-01-15

The standard time-of-arrival distribution cannot reproduce both the temporal and the spatial profile of the modulus squared of the time-evolved wave function for an arbitrary initial state. In particular, the time-of-arrival distribution gives a non-vanishing probability even if the wave function is zero at a given point for all values of time. This poses a problem in the standard formulation of quantum mechanics where one quantizes a classical observable and uses its spectral resolution to calculate the corresponding distribution. In this work, we show that the modulus squared of the time-evolved wave function is in fact contained in one ofmore » the degenerate eigenfunctions of the quantized time-of-arrival operator. This generalizes our understanding of quantum arrival phenomenon where particle detection is not a necessary requirement, thereby providing a direct link between time-of-arrival quantization and the outcomes of the two-slit experiment. -- Highlights: •The time-evolved position density is contained in the standard TOA distribution. •Particle may quantum mechanically arrive at a given point without being detected. •The eigenstates of the standard TOA operator are linked to the two-slit experiment.« less

Matter-wave propagation in optical lattices: geometrical and flat-band effects

DOE PAGES

Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; ...

2016-03-17

Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square latticemore » has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.« less

Detection of Fiber Layer-Up Lamination Order of CFRP Composite Using Thermal-Wave Radar Imaging

NASA Astrophysics Data System (ADS)

Wang, Fei; Liu, Junyan; Liu, Yang; Wang, Yang; Gong, Jinlong

2016-09-01

In this paper, thermal-wave radar imaging (TWRI) is used as a nondestructive inspection method to evaluate carbon-fiber-reinforced-polymer (CFRP) composite. An inverse methodology that combines TWRI with numerical optimization technique is proposed to determine the fiber layer-up lamination sequences of anisotropic CFRP composite. A 7-layer CFRP laminate [0°/45°/90°/0°]_{{s}} is heated by a chirp-modulated Gaussian laser beam, and then finite element method (FEM) is employed to calculate the temperature field of CFRP laminates. The phase based on lock-in correlation between reference chirp signal and the thermal-wave signal is performed to obtain the phase image of TWRI, and the least square method is applied to reconstruct the cost function that minimizes the square of the difference between the phase of TWRI inspection and numerical calculation. A hybrid algorithm that combines the simulation annealing with Nelder-Mead simplex research method is employed to solve the reconstructed cost function and find the global optimal solution of the layer-up sequences of CFRP composite. The result shows the feasibility of estimating the fiber layer-up lamination sequences of CFRP composite with optimal discrete and constraint conditions.

Ca transport in membrane vesicles from pinto bean leaves and its alteration after ozone exposure.

PubMed

Castillo, F J; Heath, R L

1990-10-01

The influence of ozone on Ca(2+) transport in plant membranes from pinto bean (Phaseolus vulgaris L. var Pinto) leaves was investigated in vitro by means of a filtration method using purified vesicles. Two transport mechanisms located at the plasma membrane are involved in a response to ozone: (a) passive Ca(2+) influx into the cell and (b) active Ca(2+) efflux driven by an ATP-dependent system, which has two components: a primary Ca(2+) transport directly linked to ATP which is partially activated by calmodulin and a H(+)/Ca(2+) antiport coupled to activity of a H(+)-ATPase. The passive Ca(2+) permeability is increased by ozone. A triangular pulse of ozone stimulates a higher influx of Ca(2+) than does a square wave, even though the total dose was the same (0.6 microliter per liter x hour). Leaves exposed to a square wave did not exhibit visible injury and were still able to recover from oxidant stress by activation of calmodulin-dependent Ca(2+) extrusion mechanisms. On the other hand, leaves exposed to a triangular wave of ozone, exhibit visible injury and lost the ability of extruding Ca(2+) out of the cell.

Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies

PubMed Central

Hettich, Mike; Jacob, Karl; Ristow, Oliver; Schubert, Martin; Bruchhausen, Axel; Gusev, Vitalyi; Dekorsy, Thomas

2016-01-01

We investigate the viscoelastic properties of confined molecular nano-layers by time resolved optical pump-probe measurements. Access to the elastic properties is provided by the damping time of acoustic eigenmodes of thin metal films deposited on the molecular nano-layers which show a strong dependence on the molecular layer thickness and on the acoustic eigen-mode frequencies. An analytical model including the viscoelastic properties of the molecular layer allows us to obtain the longitudinal sound velocity as well as the acoustic absorption coefficient of the layer. Our experiments and theoretical analysis indicate for the first time that the molecular nano-layers are much more viscous than elastic in the investigated frequency range from 50 to 120 GHz and thus show pronounced acoustic absorption. The longitudinal acoustic wavenumber has nearly equal real and imaginary parts, both increasing proportional to the square root of the frequency. Thus, both acoustic velocity and acoustic absorption are proportional to the square root of frequency and the propagation of compressional/dilatational acoustic waves in the investigated nano-layers is of the diffusional type, similar to the propagation of shear waves in viscous liquids and thermal waves in solids. PMID:27633351

Faraday instability in a near-critical fluid under weightlessness.

PubMed

Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

2014-01-01

Experiments on near-critical hydrogen have been conducted under magnetic compensation of gravity to investigate the Faraday instability that arises at the liquid-vapor interface under zero-gravity conditions. We investigated such instability in the absence of stabilizing gravity. Under such conditions, vibration orients the interface and can destabilize it. The experiments confirm the existence of Faraday waves and demonstrate a transition from a square to a line pattern close to the critical point. They also show a transition very close to the critical point from Faraday to periodic layering of the vapor-liquid interface perpendicular to vibration. It was seen that the Faraday wave instability is favored when the liquid-vapor density difference is large enough (fluid far from the critical point), whereas periodic layering predominates for small difference in the liquid and vapor densities (close to the critical point). It was observed for the Faraday wave instability that the wavelength of the instability decreases as one approaches the critical point. The experimental results demonstrate good agreement to the dispersion relation for zero gravity except for temperatures very close to the critical point where a transition from a square pattern to a line pattern is detected, similarly to what is observed under 1g conditions.

Recent Advances in Catalyst Accelerated Stress Tests for Polymer Electrolyte Membrane Fuel Cells

DOE PAGES

Stariha, Sarah; Macauley, Natalia; Sneed, Brian T.; ...

2018-03-15

The U.S. Department of Energy (DOE) set the 2020 durability target for polymer electrolyte membrane fuel cell transportation applications at 5000 hours. Since it is impractical to test every fuel cell for this length of time, there is ever increasing interest in developing accelerated stress tests (ASTs) that can accurately simulate the material component degradation in the membrane electrode assembly (MEA) observed under automotive operating conditions, but over a much shorter time frame. In this study, a square-wave catalyst AST was examined that shows a 5X time acceleration factor over the triangle-wave catalyst AST and a 25X time acceleration factormore » over the modified wet drive-cycle catalyst durability protocol, significantly decreasing the testing time. These acceleration factors were correlated to the platinum (Pt) particle size increase and associated decrease in electrochemical surface area (ECSA). This square-wave AST has been adopted by the DOE as a standard protocol to evaluate catalyst durability. We also compare three catalyst-durability protocols using state-of-the-art platinum-cobalt catalysts supported on high surface area carbon (SOA Pt-Co/HSAC) in the cathode catalyst layer. The results for each of the three tests showed both catalyst particle size increase and transition metal leaching. Moreover the acceleration factors for the alloy catalysts were smaller due to Co leaching being the predominant mechanism of voltage decay in ~5 nm PtCo/C catalysts. Finally, an extremely harsh carbon corrosion AST was run using the same SOA Pt-Co/HSAC catalyst. This showed minimal change in particle size and a low percentage Co loss from the cathode catalyst particles, despite a significant loss in catalyst layer thickness and cell performance. The carbon corrosion rates during these various ASTs were directly measured by monitoring the CO 2 emission from the cathode, further confirming the ability of the square-wave AST to evaluate the electro-catalyst independently of the support.« less

Recent Advances in Catalyst Accelerated Stress Tests for Polymer Electrolyte Membrane Fuel Cells

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

Stariha, Sarah; Macauley, Natalia; Sneed, Brian T.

The U.S. Department of Energy (DOE) set the 2020 durability target for polymer electrolyte membrane fuel cell transportation applications at 5000 hours. Since it is impractical to test every fuel cell for this length of time, there is ever increasing interest in developing accelerated stress tests (ASTs) that can accurately simulate the material component degradation in the membrane electrode assembly (MEA) observed under automotive operating conditions, but over a much shorter time frame. In this study, a square-wave catalyst AST was examined that shows a 5X time acceleration factor over the triangle-wave catalyst AST and a 25X time acceleration factormore » over the modified wet drive-cycle catalyst durability protocol, significantly decreasing the testing time. These acceleration factors were correlated to the platinum (Pt) particle size increase and associated decrease in electrochemical surface area (ECSA). This square-wave AST has been adopted by the DOE as a standard protocol to evaluate catalyst durability. We also compare three catalyst-durability protocols using state-of-the-art platinum-cobalt catalysts supported on high surface area carbon (SOA Pt-Co/HSAC) in the cathode catalyst layer. The results for each of the three tests showed both catalyst particle size increase and transition metal leaching. Moreover the acceleration factors for the alloy catalysts were smaller due to Co leaching being the predominant mechanism of voltage decay in ~5 nm PtCo/C catalysts. Finally, an extremely harsh carbon corrosion AST was run using the same SOA Pt-Co/HSAC catalyst. This showed minimal change in particle size and a low percentage Co loss from the cathode catalyst particles, despite a significant loss in catalyst layer thickness and cell performance. The carbon corrosion rates during these various ASTs were directly measured by monitoring the CO 2 emission from the cathode, further confirming the ability of the square-wave AST to evaluate the electro-catalyst independently of the support.« less

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

Stariha, Sarah; Macauley, Natalia; Sneed, Brian T.

The U.S. Department of Energy (DOE) set the 2020 durability target for polymer electrolyte membrane fuel cell transportation applications at 5000 hours. Since it is impractical to test every fuel cell for this length of time, there is ever increasing interest in developing accelerated stress tests (ASTs) that can accurately simulate the material component degradation in the membrane electrode assembly (MEA) observed under automotive operating conditions, but over a much shorter time frame. In this study, a square-wave catalyst AST was examined that shows a 5X time acceleration factor over the triangle-wave catalyst AST and a 25X time acceleration factormore » over the modified wet drive-cycle catalyst durability protocol, significantly decreasing the testing time. These acceleration factors were correlated to the platinum (Pt) particle size increase and associated decrease in electrochemical surface area (ECSA). This square-wave AST has been adopted by the DOE as a standard protocol to evaluate catalyst durability. We also compare three catalyst-durability protocols using state-of-the-art platinum-cobalt catalysts supported on high surface area carbon (SOA Pt-Co/HSAC) in the cathode catalyst layer. The results for each of the three tests showed both catalyst particle size increase and transition metal leaching. Moreover the acceleration factors for the alloy catalysts were smaller due to Co leaching being the predominant mechanism of voltage decay in ~5 nm PtCo/C catalysts. Finally, an extremely harsh carbon corrosion AST was run using the same SOA Pt-Co/HSAC catalyst. This showed minimal change in particle size and a low percentage Co loss from the cathode catalyst particles, despite a significant loss in catalyst layer thickness and cell performance. The carbon corrosion rates during these various ASTs were directly measured by monitoring the CO 2 emission from the cathode, further confirming the ability of the square-wave AST to evaluate the electro-catalyst independently of the support.« less