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Sample records for 2d-ir vibrational echo

  1. Observation of kinetic networks of hydrogen-bond exchange using 2D IR echo spectroscopy

    Kim, Yung Sam; Hochstrasser, Robin M.

    The ultrafast H-bond motion in acetonitrile/methanol and of methanol and water around a dicarbonyl (piperidone) dominates the mechanism of vibrational coherence transfer in linear and 2D IR echo spectra. Multiple state coherence transfer and energy transfer are seen at and between the two carbonyl groups of the piperidone in both water and methanol.

  2. 2D-IR spectroscopy of hydrogen-bond-mediated vibrational excitation transfer.

    Chuntonov, Lev

    2016-05-18

    Vibrational excitation transfer along the hydrogen-bond-mediated pathways in the complex of methyl acetate (MA) and 4-cyanophenol (4CP) was studied by dual-frequency femtosecond two-dimensional infrared spectroscopy. We excited the energy-donating ester carbonyl stretching vibrational mode and followed the transfer to the energy-accepting benzene ring and cyano stretching vibrations. The complexes with no, one, and two hydrogen-bonded 4CP molecules were studied. Vibrational relaxation of the carbonyl mode is more efficient in both hydrogen-bonded complexes as compared with free MA molecules. The inter-molecular transport in a hydrogen-bonded complex involving a single 4CP molecule is slower than that in a complex with two 4CP molecules. In the former, vibrational relaxation leads to local heating, as shown by the spectroscopy of the carbonyl mode, whereas the local heating is suppressed in the latter because the excitation redistribution is more efficient. At early times, the transfer to the benzene ring is governed by its direct coupling with the energy-donating carbonyl mode, whereas at later times intermediate states are involved. The transfer to a more distant site of the cyano group in 4CP involves intermediate states at all times, since no direct coupling between the energy-donating and accepting modes was observed. We anticipate that our findings will be of importance for spectroscopic studies of bio-molecular structures and dynamics, and inter- and intra-molecular signaling pathways, and for developing molecular networking applications. PMID:27145861

  3. 2D IR Spectroscopy of Histidine: Probing Side-Chain Structure and Dynamics via Backbone Amide Vibrations

    Ghosh, Ayanjeet; Tucker, Matthew J.; Gai, Feng

    2014-01-01

    It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain. However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult. Herein we show, using a histidine dipeptide as a model, that it is possible to probe the tautomer and protonation status of a histidine residue by measuring the two-dimensional infrared (2D IR) spectrum of its amide I vibrationa...

  4. Ultrafast vibrational spectroscopy (2D-IR) of CO{sub 2} in ionic liquids: Carbon capture from carbon dioxide’s point of view

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean, E-mail: sgr@pitt.edu [Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260 (United States)

    2015-06-07

    The CO{sub 2}ν{sub 3} asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO{sub 2} is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C{sub 4}C{sub 1}im][X], where [X]{sup −} is the anion from the series hexafluorophosphate (PF{sub 6}{sup −}), tetrafluoroborate (BF{sub 4}{sup −}), bis-(trifluoromethyl)sulfonylimide (Tf{sub 2}N{sup −}), triflate (TfO{sup −}), trifluoroacetate (TFA{sup −}), dicyanamide (DCA{sup −}), and thiocyanate (SCN{sup −})). In the ionic liquids studied, the ν{sub 3} center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO{sub 2} and from CO{sub 2} to the cation. The charge transfer drives geometrical distortion of CO{sub 2}, which in turn changes the ν{sub 3} frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν{sub 2} and ν{sub 3} normal modes of CO{sub 2}. Thermal fluctuations in the ν{sub 2} population stochastically modulate the ν{sub 3} frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO{sub 2}. The results suggest that the picosecond dynamics of CO{sub 2} are gated by local diffusion of anions and cations.

  5. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide's point of view

    Brinzer, Thomas; Berquist, Eric J.; Ren, Zhe; Dutta, Samrat; Johnson, Clinton A.; Krisher, Cullen S.; Lambrecht, Daniel S.; Garrett-Roe, Sean

    2015-06-01

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]- is the anion from the series hexafluorophosphate (PF 6- ), tetrafluoroborate (BF 4- ), bis-(trifluoromethyl)sulfonylimide (Tf2N-), triflate (TfO-), trifluoroacetate (TFA-), dicyanamide (DCA-), and thiocyanate (SCN-)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations.

  6. Ultrafast vibrational spectroscopy (2D-IR) of CO2 in ionic liquids: Carbon capture from carbon dioxide’s point of view

    The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are of interest for carbon capture applications. CO2 is dissolved in a series of 1-butyl-3-methylimidazolium-based ionic liquids ([C4C1im][X], where [X]− is the anion from the series hexafluorophosphate (PF6−), tetrafluoroborate (BF4−), bis-(trifluoromethyl)sulfonylimide (Tf2N−), triflate (TfO−), trifluoroacetate (TFA−), dicyanamide (DCA−), and thiocyanate (SCN−)). In the ionic liquids studied, the ν3 center frequency is sensitive to the local solvation environment and reports on the timescales for local structural relaxation. Density functional theory calculations predict charge transfer from the anion to the CO2 and from CO2 to the cation. The charge transfer drives geometrical distortion of CO2, which in turn changes the ν3 frequency. The observed structural relaxation timescales vary by up to an order of magnitude between ionic liquids. Shoulders in the 2D-IR spectra arise from anharmonic coupling of the ν2 and ν3 normal modes of CO2. Thermal fluctuations in the ν2 population stochastically modulate the ν3 frequency and generate dynamic cross-peaks. These timescales are attributed to the breakup of ion cages that create a well-defined local environment for CO2. The results suggest that the picosecond dynamics of CO2 are gated by local diffusion of anions and cations

  7. A salt-bridge structure in solution revealed by 2D-IR spectroscopy

    Huerta-Viga, Adriana; Domingos, Sérgio R.; Amirjalayer, Saeed; Woutersen, Sander

    2014-07-01

    Salt bridges are known to be important for the stability of protein conformation, but up to now it has been difficult to study their geometry in solution. Here we characterize the spatial structure of a model salt bridge between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridging the infrared response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes involved in the salt bridge, as well as the coupling between them. In this manner we reconstruct the geometry of the solvated salt bridge.

  8. Structure of a model salt bridge in solution investigated with 2D-IR spectroscopy

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Woutersen, Sander

    2013-01-01

    Salt bridges are known to be important for the stability of protein conformation, but up to now it has been difficult to study their geometry in solution. Here we characterize the spatial structure of a model salt bridge between guanidinium (Gdm+) and acetate (Ac-) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridging the infrared response of Gdm+ and Ac- change significantly, and in the 2D-IR spectrum, salt bridging of the molecules appears as cross peaks. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes involved in the salt bridge, as well as the coupling between them. In this manner we reconstruct the geometry of the solvated salt bridge.

  9. A salt-bridge structure in solution revealed by 2D-IR spectroscopy.

    Huerta-Viga, Adriana; Domingos, Sérgio R; Amirjalayer, Saeed; Woutersen, Sander

    2014-08-14

    Salt bridges are important interactions for the stability of protein conformations, but up to now it has been difficult to determine salt-bridge geometries in solution. Here we characterize the spatial structure of a salt bridge between guanidinium (Gdm(+)) and acetate (Ac(-)) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridge formation there is a significant change in the infrared response of Gdm(+) and Ac(-), and cross peaks between them appear in the 2D-IR spectrum. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes of Gdm(+) and Ac(-), as well as the coupling between them. PMID:24676430

  10. Protein Denaturation with Guanidinium: A 2D-IR Study

    Huerta-Viga, Adriana; Woutersen, Sander

    2013-01-01

    Guanidinium (Gdm+) is a widely used denaturant, but it is still largely unknown how it operates at the molecular level. In particular, the effect of guanidinium on the different types of secondary structure motifs of proteins is at present not clear. Here, we use two-dimensional infrared spectroscopy (2D-IR) to investigate changes in the secondary structure of two proteins with mainly α-helical or β-sheet content upon addition of Gdm-13C15N3·Cl. We find that upon denaturation, the β-sheet pro...

  11. Protein Denaturation with Guanidinium: A 2D-IR Study.

    Huerta-Viga, Adriana; Woutersen, Sander

    2013-10-17

    Guanidinium (Gdm(+)) is a widely used denaturant, but it is still largely unknown how it operates at the molecular level. In particular, the effect of guanidinium on the different types of secondary structure motifs of proteins is at present not clear. Here, we use two-dimensional infrared spectroscopy (2D-IR) to investigate changes in the secondary structure of two proteins with mainly α-helical or β-sheet content upon addition of Gdm-(13)C(15)N3·Cl. We find that upon denaturation, the β-sheet protein shows a complete loss of β-sheet structure, whereas the α-helical protein maintains most of its secondary structure. These results suggest that Gdm(+) disrupts β-sheets much more efficiently than α-helices, possibly because in the former, hydrophobic interactions are more important and the number of dangling hydrogen bonds is larger. PMID:24163724

  12. Determining Transition State Geometries in Liquids Using 2D-IR

    Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.

    2007-12-11

    Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.

  13. Probing Intermolecular Interactions in Polycyclic Aromatic Hydrocarbons with 2D IR Spectroscopy

    Krummel, Amber

    2014-03-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and impact geochemical processes that are critical to sustainable energy resources. For example, asphaltenes exist naturally in geologic formations and their aggregates heavily impact the petroleum economy. Unfortunately, the chemical dynamics that drive asphaltene nanoaggregation processes are still poorly understood. Solvent dynamics and intermolecular interactions such as π-stacking interactions play integral roles in asphaltene nanoaggregation. Linear and nonlinear vibrational spectroscopy including two-dimensional infrared spectroscopy (2DIR), are well suited to explore these fundamental interactions. Teasing apart the vibrational characteristics in PAHs that model asphaltenic compounds represents an important step towards utilizing 2D IR spectroscopy to understand the intermolecular interactions that are prevalent in asphaltene nanoaggregation. A solar dye, N,N'-Dioctyl-3,4,9,10-perylenedicarboximide, is used in this work to model aphaltenes. Carbonyl and ring vibrations are used to probe the nanoaggregates of the model compounds. However, the characteristics of these normal modes change as a function of the size of the conjugated ring system. Thus, in order to fully understand the nature of these normal modes, we include a systematic study of a series of quinones. Our investigation employs a combination of 2DIR spectroscopy and electronic structure calculations to explore vibrational coupling in quinones and PAHs. We compare the calculated vibrational characteristics to those extracted from 2DIR spectra. ATK acknowledges the Donors of the American Chemical Society Petroleum Research Fund for support of this research.

  14. Communication: nanosecond folding dynamics of an alpha helix: time-dependent 2D-IR cross peaks observed using polarization-sensitive dispersed pump-probe spectroscopy.

    Panman, Matthijs R; van Dijk, Chris N; Meuzelaar, Heleen; Woutersen, S

    2015-01-28

    We present a simple method to measure the dynamics of cross peaks in time-resolved two-dimensional vibrational spectroscopy. By combining suitably weighted dispersed pump-probe spectra, we eliminate the diagonal contribution to the 2D-IR response, so that the dispersed pump-probe signal contains the projection of only the cross peaks onto one of the axes of the 2D-IR spectrum. We apply the method to investigate the folding dynamics of an alpha-helical peptide in a temperature-jump experiment and find characteristic folding and unfolding time constants of 260 ± 30 and 580 ± 70 ns at 298 K. PMID:25637962

  15. Communication: Nanosecond folding dynamics of an alpha helix: Time-dependent 2D-IR cross peaks observed using polarization-sensitive dispersed pump-probe spectroscopy

    Panman, Matthijs R.; van Dijk, Chris N.; Meuzelaar, Heleen; Woutersen, S.

    2015-01-01

    We present a simple method to measure the dynamics of cross peaks in time-resolved two-dimensional vibrational spectroscopy. By combining suitably weighted dispersed pump-probe spectra, we eliminate the diagonal contribution to the 2D-IR response, so that the dispersed pump-probe signal contains the projection of only the cross peaks onto one of the axes of the 2D-IR spectrum. We apply the method to investigate the folding dynamics of an alpha-helical peptide in a temperature-jump experiment and find characteristic folding and unfolding time constants of 260 ± 30 and 580 ± 70 ns at 298 K.

  16. The structure of salt bridges between Arg(+) and Glu(-) in peptides investigated with 2D-IR spectroscopy: Evidence for two distinct hydrogen-bond geometries.

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Domingos, Sérgio R; Meuzelaar, Heleen; Rupenyan, Alisa; Woutersen, Sander

    2015-06-01

    Salt bridges play an important role in protein folding and in supramolecular chemistry, but they are difficult to detect and characterize in solution. Here, we investigate salt bridges between glutamate (Glu(-)) and arginine (Arg(+)) using two-dimensional infrared (2D-IR) spectroscopy. The 2D-IR spectrum of a salt-bridged dimer shows cross peaks between the vibrational modes of Glu(-) and Arg(+), which provide a sensitive structural probe of Glu(-)⋯Arg(+) salt bridges. We use this probe to investigate a β-turn locked by a salt bridge, an α-helical peptide whose structure is stabilized by salt bridges, and a coiled coil that is stabilized by intra- and intermolecular salt bridges. We detect a bidentate salt bridge in the β-turn, a monodentate one in the α-helical peptide, and both salt-bridge geometries in the coiled coil. To our knowledge, this is the first time 2D-IR has been used to probe tertiary side chain interactions in peptides, and our results show that 2D-IR spectroscopy is a powerful method for investigating salt bridges in solution. PMID:26049464

  17. The structure of salt bridges between Arg+ and Glu- in peptides investigated with 2D-IR spectroscopy: Evidence for two distinct hydrogen-bond geometries

    Huerta-Viga, Adriana; Amirjalayer, Saeed; Domingos, Sérgio R.; Meuzelaar, Heleen; Rupenyan, Alisa; Woutersen, Sander

    2015-06-01

    Salt bridges play an important role in protein folding and in supramolecular chemistry, but they are difficult to detect and characterize in solution. Here, we investigate salt bridges between glutamate (Glu-) and arginine (Arg+) using two-dimensional infrared (2D-IR) spectroscopy. The 2D-IR spectrum of a salt-bridged dimer shows cross peaks between the vibrational modes of Glu- and Arg+, which provide a sensitive structural probe of Glu-⋯Arg+ salt bridges. We use this probe to investigate a β-turn locked by a salt bridge, an α-helical peptide whose structure is stabilized by salt bridges, and a coiled coil that is stabilized by intra- and intermolecular salt bridges. We detect a bidentate salt bridge in the β-turn, a monodentate one in the α-helical peptide, and both salt-bridge geometries in the coiled coil. To our knowledge, this is the first time 2D-IR has been used to probe tertiary side chain interactions in peptides, and our results show that 2D-IR spectroscopy is a powerful method for investigating salt bridges in solution.

  18. Earle K. Plyler Prize for Molecular Spectroscopy and Dynamics Lecture: 2D IR Spectroscopy of Peptide Conformation

    Tokmakoff, Andrei

    2012-02-01

    Descriptions of protein and peptide conformation are colored by the methods we use to study them. Protein x-ray and NMR structures often lead to impressions of rigid or well-defined conformations, even though these are dynamic molecules. The conformational fluctuations and disorder of proteins and peptides is more difficult to quantify. This presentation will describe an approach toward characterizing and quantifying structural heterogeneity and disorder in peptides using 2D IR spectroscopy. Using amide I vibrational spectroscopy, isotope labeling strategies, and computational modeling based on molecular dynamics simulations and Markov state models allows us to characterize distinct peptide conformers and conformational variation. The examples illustrated include the beta-hairpin tripzip2 and elastin-like peptides.

  19. Hydrogen-bond lifetime measured by time-resolved 2D-IR spectroscopy: N-methylacetamide in methanol

    Woutersen, S.; Mu, Y.; Stock, G.; Hamm, P.

    2001-05-01

    2D vibrational spectroscopy is applied to investigate the equilibrium dynamics of hydrogen bonding of N-methylacetamide (NMA) dissolved in methanol- d4. For this particular solute-solvent system, roughly equal populations are found for two conformers of the solute-solvent complex, one of which forms a hydrogen bond from the CO group of NMA to the surrounding solvent, and one of which does not. Using time-resolved 2D-IR spectroscopy on the amide I band of NMA, the exchange between both conformers is resolved. Equilibration of each conformer is completed after 4.5 ps, while the formation and breaking of the hydrogen bond occurs on a slower, 10-15 ps time scale. This interpretation is supported by classical molecular-dynamics simulations of NMA in methanol. The calculations predict a 64% population of the hydrogen-bonded conformer and an average hydrogen-bond lifetime of ≈12 ps.

  20. Temperature-dependent vibrational dephasing: Comparison of liquid and glassy solvents using frequency-selected vibrational echoes

    Xu, Qing-Hua; Fayer, M. D.

    2002-08-01

    Frequency-selected vibrational echo experiments were used to investigate the temperature dependences of vibrational dephasing associated with the 0-1 transition of the CO stretching mode of RuTPPCOPy (TPP=5,10,15,20-tetraphenylporphyrin, Py=pyridine) in two solvents: polymethylmethacrylate (PMMA) and 2-methyltetrahydrofuran (2-MTHF). In PMMA, a glass, the echo decay is exponential at all the temperatures studied, and the dephasing rate increases linearly with increasing temperature. In 2-MTHF, there is a change in the functional form of the temperature dependence when the solvent goes through the glass transition temperature (Tg). Below Tg, the dephasing rate increases linearly with temperature, while above Tg, it rises very steeply in a nonlinear manner. In the liquid at higher temperatures, the vibrational echo decays are nonexponential. A model frequency-frequency correlation function (FFCF) is proposed in which the FFCF differs for a glass and a liquid because of the intrinsic differences in the nature of the dynamics. At least two motions, inertial and diffusive, contribute to the vibrational dephasing in the liquids. The different temperature dependences of inertial and diffusive motions are discussed. Comparison of the model calculations of the vibrational echo temperature dependence and the data show reasonable, but not quantitative agreement.

  1. Interrogating Fiber Formation Kinetics with Automated 2D-IR Spectroscopy

    Strasfeld, David B.; Ling, Yun L.; Shim, Sang-Hee; Zanni, Martin T.

    A new method for collecting 2D-IR spectra that utilizes both a pump-probe beam geometry and a mid-IR pulse shaper is used to gain a fuller understanding of fiber formation in the human islet amyloid polypeptide (hIAPP). We extract structural kinetics in order to better understand aggregation in hIAPP, the protein component of the amyloid fibers found to inhibit insulin production in type II diabetes patients.

  2. Water of Hydration Dynamics in Minerals Gypsum and Bassanite: Ultrafast 2D IR Spectroscopy of Rocks.

    Yan, Chang; Nishida, Jun; Yuan, Rongfeng; Fayer, Michael D

    2016-08-01

    Water of hydration plays an important role in minerals, determining their crystal structures and physical properties. Here ultrafast nonlinear infrared (IR) techniques, two-dimensional infrared (2D IR) and polarization selective pump-probe (PSPP) spectroscopies, were used to measure the dynamics and disorder of water of hydration in two minerals, gypsum (CaSO4·2H2O) and bassanite (CaSO4·0.5H2O). 2D IR spectra revealed that water arrangement in freshly precipitated gypsum contained a small amount of inhomogeneity. Following annealing at 348 K, water molecules became highly ordered; the 2D IR spectrum became homogeneously broadened (motional narrowed). PSPP measurements observed only inertial orientational relaxation. In contrast, water in bassanite's tubular channels is dynamically disordered. 2D IR spectra showed a significant amount of inhomogeneous broadening caused by a range of water configurations. At 298 K, water dynamics cause spectral diffusion that sampled a portion of the inhomogeneous line width on the time scale of ∼30 ps, while the rest of inhomogeneity is static on the time scale of the measurements. At higher temperature, the dynamics become faster. Spectral diffusion accelerates, and a portion of the lower temperature spectral diffusion became motionally narrowed. At sufficiently high temperature, all of the dynamics that produced spectral diffusion at lower temperatures became motionally narrowed, and only homogeneous broadening and static inhomogeneity were observed. Water angular motions in bassanite exhibit temperature-dependent diffusive orientational relaxation in a restricted cone of angles. The experiments were made possible by eliminating the vast amount of scattered light produced by the granulated powder samples using phase cycling methods. PMID:27385320

  3. 2D IR spectra of cyanide in water investigated by molecular dynamics simulations

    Lee, Myung Won; Carr, Joshua K.; Göllner, Michael; Hamm, Peter; Meuwly, Markus

    2013-01-01

    Using classical molecular dynamics simulations, the 2D infrared (IR) spectroscopy of CN− solvated in D2O is investigated. Depending on the force field parametrizations, most of which are based on multipolar interactions for the CN− molecule, the frequency-frequency correlation function and observables computed from it differ. Most notably, models based on multipoles for CN− and TIP3P for water yield quantitatively correct results when compared with experiments. Furthermore, the recent finding that T 1 times are sensitive to the van der Waals ranges on the CN− is confirmed in the present study. For the linear IR spectrum, the best model reproduces the full widths at half maximum almost quantitatively (13.0 cm−1 vs. 14.9 cm−1) if the rotational contribution to the linewidth is included. Without the rotational contribution, the lines are too narrow by about a factor of two, which agrees with Raman and IR experiments. The computed and experimental tilt angles (or nodal slopes) α as a function of the 2D IR waiting time compare favorably with the measured ones and the frequency fluctuation correlation function is invariably found to contain three time scales: a sub-ps, 1 ps, and one on the 10-ps time scale. These time scales are discussed in terms of the structural dynamics of the surrounding solvent and it is found that the longest time scale (≈10 ps) most likely corresponds to solvent exchange between the first and second solvation shell, in agreement with interpretations from nuclear magnetic resonance measurements.

  4. Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory.

    Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D

    2016-07-21

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid. PMID:27363680

  5. 2D IR spectroscopy at 100 kHz utilizing a Mid-IR OPCPA laser source.

    Luther, Bradley M; Tracy, Kathryn M; Gerrity, Michael; Brown, Susannah; Krummel, Amber T

    2016-02-22

    We present a 100 kHz 2D IR spectrometer. The system utilizes a ytterbium all normal dispersion fiber oscillator as a common source for the pump and seed beams of a MgO:PPLN OPCPA. The 1030 nm OPCPA pump is generated by amplification of the oscillator in cryocooled Yb:YAG amplifiers, while the 1.68 μm seed is generated in a OPO pumped by the oscillator. The OPCPA outputs are used in a ZGP DFG stage to generate 4.65 μm pulses. A mid-IR pulse shaper delivers pulse pairs to a 2D IR spectrometer allowing for data collection at 100 kHz. PMID:26907062

  6. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes.

    Nilsen, Ian A; Osborne, Derek G; White, Aaron M; Anna, Jessica M; Kubarych, Kevin J

    2014-10-01

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C6H6Cr(CO)3, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of kBT. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 kBT above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy. PMID:25296812

  7. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C6H6Cr(CO)3, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of kBT. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 kBT above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy

  8. Azide-water intermolecular coupling measured by 2-color 2D IR spectroscopy

    Perakis F.

    2013-03-01

    Full Text Available We present 2-color two-dimensional infrared spectroscopy of intermolecular coupling between azide ions and their solvation shell water molecules. The cross-peak between azide asymmetric stretch vibration and the OD-stretch vibration is a result of low- probability uphill population transfer. Narrow bleach/excited state absorption peak shows selectivity to solvation shell water molecules only and the characteristics of the cross-peak suggest that the solvation shell hydrogen bond potential has similar anharmonic properties as the hydrogen bond in ice Ih. Population and depopulation of the excited state of the OD-stretch vibration happen on 150 fs and 1.7 ps timescales, respectively, with early manifesting heating effects that limit the selectivity to population times up to 1 ps.

  9. Ultrafast slaving dynamics at the protein-water interface studied with 2D-IR spectroscopy

    Kubarych K. J.

    2013-03-01

    Full Text Available The dynamics of hen egg white lysozyme in D2O/glycerol mixtures is studied using two-dimensional infrared spectroscopy. The hydration dynamics and the protein dynamics are studied simultaneously through vibrational probes attached to the protein surface.

  10. Computational Amide I 2D IR Spectroscopy as a Probe of Protein Structure and Dynamics

    Reppert, Mike; Tokmakoff, Andrei

    2016-05-01

    Two-dimensional infrared spectroscopy of amide I vibrations is increasingly being used to study the structure and dynamics of proteins and peptides. Amide I, a primarily carbonyl stretching vibration of the protein backbone, provides information on secondary structures as a result of vibrational couplings and on hydrogen-bonding contacts when isotope labeling is used to isolate specific sites. In parallel with experiments, computational models of amide I spectra that use atomistic structures from molecular dynamics simulations have evolved to calculate experimental spectra. Mixed quantum-classical models use spectroscopic maps to translate the structural information into a quantum-mechanical Hamiltonian for the spectroscopically observed vibrations. This allows one to model the spectroscopy of large proteins, disordered states, and protein conformational dynamics. With improvements in amide I models, quantitative modeling of time-dependent structural ensembles and of direct feedback between experiments and simulations is possible. We review the advances in developing these models, their theoretical basis, and current and future applications.

  11. Monitoring equilibrium reaction dynamics of a nearly barrierless molecular rotor using ultrafast vibrational echoes

    Nilsen, Ian A.; Osborne, Derek G.; White, Aaron M.; Anna, Jessica M.; Kubarych, Kevin J., E-mail: kubarych@umich.edu [Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109 (United States)

    2014-10-07

    Using rapidly acquired spectral diffusion, a recently developed variation of heterodyne detected infrared photon echo spectroscopy, we observe ∼3 ps solvent independent spectral diffusion of benzene chromium tricarbonyl (C{sub 6}H{sub 6}Cr(CO){sub 3}, BCT) in a series of nonpolar linear alkane solvents. The spectral dynamics is attributed to low-barrier internal torsional motion. This tripod complex has two stable minima corresponding to staggered and eclipsed conformations, which differ in energy by roughly half of k{sub B}T. The solvent independence is due to the relative size of the rotor compared with the solvent molecules, which create a solvent cage in which torsional motion occurs largely free from solvent damping. Since the one-dimensional transition state is computed to be only 0.03 k{sub B}T above the higher energy eclipsed conformation, this model system offers an unusual, nearly barrierless reaction, which nevertheless is characterized by torsional coordinate dependent vibrational frequencies. Hence, by studying the spectral diffusion of the tripod carbonyls, it is possible to gain insight into the fundamental dynamics of internal rotational motion, and we find some evidence for the importance of non-diffusive ballistic motion even in the room-temperature liquid environment. Using several different approaches to describe equilibrium kinetics, as well as the influence of reactive dynamics on spectroscopic observables, we provide evidence that the low-barrier torsional motion of BCT provides an excellent test case for detailed studies of the links between chemical exchange and linear and nonlinear vibrational spectroscopy.

  12. Interplay of Ion-Water and Water-Water Interactions within the Hydration Shells of Nitrate and Carbonate Directly Probed with 2D IR Spectroscopy.

    Fournier, Joseph A; Carpenter, William; De Marco, Luigi; Tokmakoff, Andrei

    2016-08-01

    The long-range influence of ions in solution on the water hydrogen-bond (H-bond) network remains a topic of vigorous debate. Recent spectroscopic and theoretical studies have, for the most part, reached the consensus that weakly coordinating ions only affect water molecules in the first hydration shell. Here, we apply ultrafast broadband two-dimensional infrared (2D IR) spectroscopy to aqueous nitrate and carbonate in neat H2O to study the solvation structure and dynamics of ions on opposite ends of the Hofmeister series. By exciting both the water OH stretches and ion stretches and probing the associated cross-peaks between them, we are afforded a comprehensive view into the complex nature of ion hydration. We show in aqueous nitrate that weak ion-water H-bonding leads to water-water interactions in the ion solvation shells dominating the dynamics. In contrast, the carbonate CO stretches show significant mixing with the water OH stretches due to strong ion-water H-bonding such that the water and ion modes are intimately correlated. Further, the excitonic nature of vibrations in neat H2O, which spans multiple water molecules, is an important factor in describing ion hydration. We attribute these complex dynamics to the likely presence of intermediate-range effects influenced by waters beyond the first solvation shell. PMID:27404015

  13. Rapid discrimination of extracts of Chinese propolis and poplar buds by FT-IR and 2D IR correlation spectroscopy

    Wu, Yan-Wen; Sun, Su-Qin; Zhao, Jing; Li, Yi; Zhou, Qun

    2008-07-01

    The extract of Chinese propolis (ECP) has recently been adulterated with that of poplar buds (EPB), because most of ECP is derived from the poplar plant, and ECP and EPB have almost identical chemical compositions. It is very difficult to differentiate them by using the chromatographic methods such as high performance liquid chromatography (HPLC) and gas chromatography (GC). Therefore, how to effectively discriminate these two mixtures is a problem to be solved urgently. In this paper, a rapid method for discriminating ECP and EPB was established by the Fourier transform infrared (FT-IR) spectra combined with the two-dimensional infrared correlation (2D IR) analysis. Forty-three ECP and five EPB samples collected from different areas of China were analyzed by the FT-IR spectroscopy. All the ECP and EPB samples tested show similar IR spectral profiles. The significant differences between ECP and EPB appear in the region of 3000-2800 cm -1 of the spectra. Based on such differences, the two species were successfully classified with the soft independent modeling of class analogy (SIMCA) pattern recognition technique. Furthermore, these differences were well validated by a series of temperature-dependent dynamic FT-IR spectra and the corresponding 2D IR plots. The results indicate that the differences in these two natural products are caused by the amounts of long-chain alkyl compounds (including long-chain alkanes, long-chain alkyl esters and long chain alkyl alcohols) in them, rather than the flavonoid compounds, generally recognized as the bioactive substances of propolis. There are much more long-chain alkyl compounds in ECP than those in EPB, and the carbon atoms of the compounds in ECP remain in an order Z-shaped array, but those in EPB are disorder. It suggests that FT-IR and 2D IR spectroscopy can provide a valuable method for the rapid differentiation of similar natural products, ECP and EPB. The IR spectra could directly reflect the integrated chemical

  14. Physical understanding of an echo-Doppler test with voice-induced vibration

    Alessio D'AlessandroDipartimento di fisica & INFN Genova; Massimo Calabrese(Policlinico Pammatone - Genova); Giuseppe Minetti(Policlinico Pammatone - Genova); Franco Rosso; Alessandro Villa

    2015-01-01

    The physical understanding of a method of detecting mammalian cancer via vocalization during a normal echo-Doppler test is provided. The backscattered ultrasound frequency in the case of a vocal humming resonating in the chest wall is computed: the overall effect is that the signal/noise ratio could be easily improved at no cost. Clinical results are to appear separately elsewhere.

  15. Use Impact-Echo Method to Evaluate Bond of Reinforced Concrete Subjected to Early-Age Vibration

    Hsu, Keng-Tsang; Cheng, Chia-Chi; Lin, Yiching

    The purpose of this paper is to develop a non-destructive test method for evaluating the bond of reinforcing bars in concrete structure which was damaged by earthquake while still cast in the form. In the experimental design, the specimens containing a steel reinforcing bar with one end extruded outside were constructed. Different degrees of damage on the rebar-concrete interfaces were successfully created by the resonant vibration of exposed steel bar induced by the cyclic motion of the specimen. The local bond-loss of the steel bars was evaluated by both non-destructive impact-echo tests and the destructive pullout tests. To create different kinds of failure mode in the pullout test, some of the specimens contain stirrups surrounding reinforcing bar. Poor-bond was quantitatively evaluated before the pullout test by the amplitude of the peak corresponding to the multiple reflections from the steel bar in the normalized spectra derived from the impact-echo tests. As a result, two empirical formulas displaying the proportional relations between the percentage of loss of local bond-stress and loss of steel-amplitude for specimens failed by split failure and pull-out failure modes were established.

  16. Vibrational frequency fluctuation of ions in aqueous solutions studied by three-pulse infrared photon echo method.

    Ohta, Kaoru; Tayama, Jumpei; Saito, Shinji; Tominaga, Keisuke

    2012-11-20

    In liquid water, hydrogen bonds form three-dimensional network structures, which have been modeled in various molecular dynamics simulations. Locally, the hydrogen bonds continuously form and break, and the network structure continuously fluctuates. In aqueous solutions, the water molecules perturb the solute molecules, resulting in fluctuations of the electronic and vibrational states. These thermal fluctuations are fundamental to understanding the activation processes in chemical reactions and the function of biopolymers. In this Account, we review studies of the vibrational frequency fluctuations of solute molecules in aqueous solutions using three-pulse infrared photon echo experiments. For comparison, we also briefly describe dynamic fluorescence Stokes shift experiments for investigating solvation dynamics in water. The Stokes shift technique gives a response function, which describes the energy relaxation in the nonequilibrium state and corresponds to the transition energy fluctuation of the electronic state at thermal equilibrium in linear response theorem. The dielectric response of water in the megahertz to terahertz frequency region is a key physical quantity for understanding both of these frequency fluctuations because of the influence of electrostatic interactions between the solute and solvent. We focus on the temperature dependence of the three experiments to discuss the molecular mechanisms of both the frequency fluctuations in aqueous solutions. We used a biexponential function with sub-picosecond and picosecond time constants to characterize the time-correlation functions of both the vibrational and electronic frequency fluctuations. We focus on the slower component, with time constants of 1-2 ps for both the frequency fluctuations at room temperature. However, the temperature dependence and isotope effect for the time constants differ for these two types of fluctuations. The dielectric interactions generally describe the solvation dynamics of

  17. Volatility-dependent 2D IR correlation analysis of traditional Chinese medicine ‘Red Flower Oil’ preparation from different manufacturers

    Wu, Yan-Wen; Sun, Su-Qin; Zhou, Qun; Tao, Jia-Xun; Noda, Isao

    2008-06-01

    As a traditional Chinese medicine (TCM), 'Red Flower Oil' preparation is widely used as a household remedy in China and Southeast Asia. Usually, the preparation is a mixture of several plant essential oils with different volatile features, such as wintergreen oil, turpentine oil and clove oil. The proportions of these plant essential oils in 'Red Flower Oil' vary from different manufacturers. Thus, it is important to develop a simple and rapid evaluation method for quality assurance of the preparations. Fourier transform infrared (FT-IR) was applied and two-dimensional correlation infrared spectroscopy (2D IR) based on the volatile characteristic of samples was used to enhance the resolution of FT-IR spectra. 2D IR technique could, not only easily provide the composition and their volatile sequences in 'Red flower Oil' preparations, but also rapidly discriminate the subtle differences in products from different manufacturers. Therefore, FT-IR combined with volatility-dependent 2D IR correlation analysis provides a very fast and effective method for the quality control of essential oil mixtures in TCM.

  18. Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes.

    Bodis, Pavol; Yeremenko, Sergiy; Berná, José; Buma, Wybren J; Leigh, David A; Woutersen, Sander

    2011-04-01

    We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N-H⋅⋅⋅O=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ≥200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogen-bonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N-H⋅⋅⋅O=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle-axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales. PMID:21476761

  19. Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes

    Bodis, Pavol; Yeremenko, Sergiy; Berná, José; Buma, Wybren J.; Leigh, David A.; Woutersen, Sander

    2011-04-01

    We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N-HṡṡṡO=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ⩾200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogen-bonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N-HṡṡṡO=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle-axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales.

  20. 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel

    Ghosh, Ayanjeet, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Gai, Feng, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Hochstrasser, Robin M. [Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Wang, Jun; DeGrado, William F. [Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143 (United States); Moroz, Yurii S.; Korendovych, Ivan V. [Department of Chemistry, Syracuse University, Syracuse, New York 13244 (United States); Zanni, Martin [Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2014-06-21

    Water is an integral part of the homotetrameric M2 proton channel of the influenza A virus, which not only assists proton conduction but could also play an important role in stabilizing channel-blocking drugs. Herein, we employ two dimensional infrared (2D IR) spectroscopy and site-specific IR probes, i.e., the amide I bands arising from isotopically labeled Ala30 and Gly34 residues, to probe how binding of either rimantadine or 7,7-spiran amine affects the water dynamics inside the M2 channel. Our results show, at neutral pH where the channel is non-conducting, that drug binding leads to a significant increase in the mobility of the channel water. A similar trend is also observed at pH 5.0 although the difference becomes smaller. Taken together, these results indicate that the channel water facilitates drug binding by increasing its entropy. Furthermore, the 2D IR spectral signatures obtained for both probes under different conditions collectively support a binding mechanism whereby amantadine-like drugs dock in the channel with their ammonium moiety pointing toward the histidine residues and interacting with a nearby water cluster, as predicted by molecular dynamics simulations. We believe these findings have important implications for designing new anti-influenza drugs.

  1. Characterization by Fourier transform infrared spectroscopy (FT-IR) and 2D IR correlation spectroscopy of a carbosilane dendrimer with peripheral ammonium groups

    Popescu, Maria-Cristina, E-mail: cpopescu@icmpp.ro [' Petru Poni' Institute of Macromolecular Chemistry (Romania); Gomez, Rafael; Mata, Fco Javier de la; Rasines, Beatriz [Universidad de Alcala, Departamento de Quimica Inorganica (Spain); Simionescu, Bogdan C. [' Petru Poni' Institute of Macromolecular Chemistry (Romania)

    2013-06-15

    Fourier transform infrared spectroscopy and 2D correlation spectroscopy were used to study the microstructural changes occurring on heating of a new carbosilane dendrimer with peripheral ammonium groups. Temperature-dependent spectral variations in the 3,010-2,710, 1,530-1,170, and 1,170-625 cm{sup -1} regions were monitored during the heating process. The dependence, on temperature, of integral absorptions and position of spectral bands was established and the spectral modifications associated with molecular conformation rearrangements, allowing molecular shape changes, were found. Before 180 Degree-Sign C, the studied carbosilane dendrimer proved to be stable, while at higher temperatures it oxidizes and Si-O groups appear. 2D IR correlation spectroscopy gives new information about the effect of temperature on the structure and dynamics of the system. Synchronous and asynchronous spectra indicate that, at low temperature, conformational changes of CH{sub 3} and CH{sub 3}-N{sup +} groups take place first. With increasing temperature, the intensity variation of the CH{sub 2}, C-N, Si-C and C-C groups from the dendritic core is faster than that of the terminal units. This indicates that, with increasing temperature, the segments of the dendritic core obtain enough energy to change their conformation more easily as compared to the terminal units, due to their internal flexibility.

  2. Two Keggin-type heteropolytungstates with transition metal as a central atom: Crystal structure and magnetic study with 2D-IR correlation spectroscopy

    Two Keggin-type heteropolytungstates, [Co(phen)3]3[CoW12O40]·9H2O 1 (phen=1,10-phenanthroline) and [Fe(phen)3]2[FeW12O40]·H3O·H2O 2, have been synthesized via the hydrothermal technique and characterized by single crystal X-ray diffraction analyses, IR, XPS, TG analysis, UV–DRS, XRD, thermal-dependent and magnetic-dependent 2D-COS IR (two-dimensional infrared correlation spectroscopy). Crystal structure analysis reveals that the polyanions in compound 1 are linked into 3D supramolecule through hydrogen bonding interactions between lattice water molecules and terminal oxygen atoms of polyanion units, and [Co(phen)3]2+ cations distributed in the polyanion framework with many hydrogen bonding interactions. The XPS spectra indicate that all the Co atoms in 1 are +2 oxidation state, the Fe atoms in 2 existing with +2 and +3 mixed oxidation states. - Graphical abstract: The magnetic-dependent synchronous 2D correlation IR spectra of 1 (a), 2 (b) over 0–50 mT in the range of 600–1000 cm−1, the obvious response indicate two Keggin polyanions skeleton susceptible to applied magnetic field. - Highlights: • Two Keggin-type heteropolytungstates with transition metal as a central atom has been obtained. • Compound 1 forms into 3D supramolecular architecture through hydrogen bonding between water molecules and polyanions. • Magnetic-dependent 2D-IR correlation spectroscopy was introduced to discuss the magnetism of polyoxometalate

  3. ECHO virus

    ... page: //medlineplus.gov/ency/article/001340.htm ECHO virus To use the sharing features on this page, please enable JavaScript. Enteric cytopathic human orphan (ECHO) viruses are a group of viruses that lead to ...

  4. Fractional Echoes

    Karras, G; Billard, F; Lavorel, B; Siour, G; Hartmann, J -M; Faucher, O; Gershnabel, Erez; Prior, Yehiam; Averbukh, Ilya Sh

    2016-01-01

    We report the observation of fractional echoes in a double-pulse excited nonlinear system. Unlike standard echoes which appear periodically at delays which are integer multiple of the delay between the two exciting pulses, the fractional echoes appear at rational fractions of this delay. We discuss the mechanism leading to this phenomenon, and provide the first experimental demonstration of fractional echoes by measuring third harmonic generation in a thermal gas of CO2 molecules excited by a pair of femtosecond laser pulses.

  5. Study on the Processing of Leech by FTIR and 2D-IR Correlation Spectroscopy%应用红外光谱技术研究中药水蛭的炮制过程

    李冰宁; 武彦文; 欧阳杰; 孙素琴; 陈舜琮

    2011-01-01

    考察水蚝炮制前后化学成分产生的变化,文章采用红外光谱(FTlR)二维相关红外谱图(2D-IR)对中药水蛭鲜品和制品进行了研究.结果表明:水蛭具有明显的酰胺Ⅰ和Ⅱ带蛋白质特征峰,其中鲜品的酰胺Ⅱ带吸收峰在1543 cm-1,而生品和炮制品的向低频位移至1 535cm-1;采用热微扰模拟水蛭炮制过程并分析水蛭的2D-IR,结果显示水蛭鲜品中的酰胺Ⅰ带与酰胺Ⅱ带的自动峰的强度比炮制品的更为显著.说明水蛭在炮制过程中蛋白质的空间构象破损、氢键断裂,导致变性失活,部分脂肪酸和甾醇类组分在炮制中发生氧化分解.%The chemical differences of traditional Chinese medicine leech before and after processing were analyzed by FTIR and two-dimensional correlation infrared (2D-IR) spectroscopy. The result showed that the leech was high in protein, with characteristic peaks of amide Ⅰ, Ⅱ bands. Comparing the IR spectra of samples, the primary difference was that the characteristic peak of fresh leech was at 1 543 cm-1, while that of crude and processed leech was at 1 535 cm-1. A 2D-IR spectrum with heating perturbation was used to track the processing dynamics of leech. In the 2D-IR correlation spectra, fresh leech exhibited stronger automatic peaks of the amide Ⅰ and Ⅱ hands than that of processed leech, which indicates that the protein components of the fresh leech were more sensitive to heat perturhation than the processed one. Moreover, the result of FTIR and 2D-IR correlation spectra validated that the 3-dimensional structure of protein was damaged and hydrogen bonds were broken after processing, which resulted in the inactivation of protein. The fatty acids and cholesterol components of leech were also oxidized in this process.

  6. ECHO virus

    Enteric cytopathic human orphan (ECHO) viruses are a group of viruses that lead to gastrointestinal infection and skin rashes. ... Echovirus is one of several families of viruses that affect the ... are common. In the United States, they are most common in ...

  7. Echoes of the supernova

    Malin, D.; Allen, D. (Anglo-Australian Observatory, Epping (Australia))

    1990-01-01

    The light echoes of SN 1987A are studied using photographs of the Tarantula nebula, including Sanduleak -69 deg 202, taken from 1984 to 1988. The formation of light echoes, and the process of extracting echo images for photographs are examined. The technique of photographic subtraction is described. Consideration is given to the formation of well-defined rings by light echoes. The possibility of using the photographs of SN 1987A light echoes in the construction of a three-dimensional model of the dust sheet in the LMC is noted.

  8. Structural Dynamics of Rotaxanes Studied by Infrared Photon Echo Spectroscopy

    Yeremenko, Sergey; Larsen, Olaf F. A.; Bodis, Pavol; Buma, Wybren Jan; Hannam, Jeffrey S.; Leigh, David A.; Woutersen, Sander

    The structural dynamics of a rotaxane is investigated using infrared photon echo peak shift spectroscopy on the N-H stretch vibrational mode. The results demonstrate non-Markovian character of the dynamics of this vibrational mode and an oscillatory component related to the presence of low-frequency modes that are anharmonically coupled to the N-H stretch mode.

  9. Photon Echoes Made Simple

    BEACH, R; Brody, B.; Hartmann, S. R.

    1983-01-01

    Photon Echoes in gases are analyzed via the Billiard Ball Echo Model both in the short and long pulse limit where the “atoms” are represented as spherical and elliptical billiard balls, respectively. Recent experiments demonstrating the elliptical billiard ball shape are presented using intensity data which ranges over close to eleven orders of magnitude.

  10. Moessbauer gamma echo

    By applying stepwise phase modulation of recoilless gamma radiation in a coincidence experiment, constructive interference is produced in transmission geometry between the source and the absorber fields. The resulting regenerated decay signal is called a gamma echo. Here it is demonstrated that during the decay of the 14.4 keV state of 57Fe multiple echo signals can be generated. (orig.)

  11. Happy birthday Echo!

    Staff Association

    2010-01-01

    You are reading the number hundred and one (no. 101) edition of our bulletin Echo. Just over four years ago, on 27th March 2006, the first untitled edition was published (Fig. 1 on the left). The title Echo appeared on the second edition on 10th April 2006 (Fig. 1 in the centre). Today (see Fig. 1 on the right), the layout is slightly different, but the structure of each edition has remained more or less the same: an editorial informing you of the important issues, followed by articles on club life, cultural activities (exhibitions and conferences), information from GAC-EPA, and special offers for our members.     Fig. 1 : Nos. 1, 2 and 100 of our twice-monthly publication Echo Echo was created in March 2006 when, much to our regret, CERN official communication and that of your representatives were separated. November 2009 saw a return to normal practice, and since then the CERN st...

  12. Supernovae light echoes

    The sudden brilliance of a supernova (SN) eruption will be reflected on surrounding dust grains to create a phantom nebula. If the SN is far away, the phantom nebula will be unresolved from the SN itself, and will appear as light added to the light curve and spectrum. For nearby SN like SN 1987A, the echo can be resolved as being separate from the SN itself. The dust responsible for the echo can be either in the interstellar medium (ISM) up to many parsecs away from the explosion or it can be in a circumstellar shell previously ejected by the progenitor star. The effects from echoes will be significant only if the optical depth of the dust is significant. SN 1987A, type Ia SN, and some type II SN do not have thick circumstellar shells, and hence can show echo effects only from reflections off the intervening ISM. The author reports on Monte Carlo calculations for echoes from circumstellar shells. The author has found that echo effects will often dominate the light curve and spectrum of SN at late times

  13. Generation of incoherent mid-infrared photon echoes with parametrically downconverted light

    Woutersen, Sander; Bonn, Mischa; Brugmans, Marco J. P.; Emmerichs, Uli; Bakker, Huib J.

    1996-10-01

    We present a demonstration of mid-infrared photon echoes generated with parametrically downconverted incoherent light. The photon echoes generated in this way enable one to study the dynamics of vibrations in the 1.5-4.0- mu m wavelength region with subpicosecond time resolution.

  14. Network of echoes

    The decision making model (DMM) previously developed [3,35] has been shown to generate phase transitions, to be topologically complex as manifest by inverse power-law (IPL) degree distributions, and to produce temporal complexity through IPL distributions in the switching times between the two critical states of consensus. These properties are entailed by the fundamental assumption that the network elements in the DMM imperfectly imitate one another, which is postulated herein as the echo response hypothesis; an echo being an imperfect copy of an original signal. Some implications of this hypothesis for the human sciences are explored

  15. Robust Echo Control Using a Simple Echo Path Model

    Faller, Christof; Tournery, Christophe

    2006-01-01

    In handsfree tele or video conferencing acoustic echoes arise due to the coupling between the loudspeaker and microphone. Usually an acoustic echo canceler (AEC) is used for eliminating the undesired echoes. The weaknesses of AEC are that it is relatively complex and that it is not robust against non-linearities occurring when using low-end components such as small loudspeakers. We are describing an algorithm which models the acoustic echo path by means of an overall delay and a coloration ef...

  16. Improved Echo cancellation in VOIP

    Patrashiya Magdolina Halder

    2011-11-01

    Full Text Available VoIP (voice over internet protocol is very popular communication technology of this century and has played tremendous role in communication system. It is preferred by all because it deploys many benefits it uses Internet protocol (IP networks to deliver multimedia information such as speech over a data network. VoIP system can be configured in these connection modes respectively; PC to PC, Telephony to Telephony and PC to Telephony. Echo is very annoying problem which occurs in VoIP and echo reduces the voice quality of VoIP. It is not possible to remove echo 100% from echoed signal because if echo is tried to be eliminated completely then the attempt may distort the main signal. That is why echo cannot be eliminated echo perfectly but the echo to a tolerable range. Clipping is not a good solution to suppress echo because part of speech may erroneously removed. Besides an NLP does not respond rapidly enough and also confuses the fading of the voice level at the end of a sentence with a residual echo. This paper has proposed echo cancellation in VoIP that has been tested and verified by MATLAB. The goal was to suppress echo without clipping and distorting the main signal. By the help of MATLAB program the echo is minimized to enduring level so that the received signal seems echo free. The percentage of suppressing echo varies with the amplitude of the main signal. With regarding the amplitude variation in received (echo free signal the proposed method performs better in finding the echo free signal than the other conventional system.

  17. Echo Boom Impact

    Dordai, Phillipe; Rizzo, Joseph

    2006-01-01

    Like their baby-boomer parents, the echo-boom generation is reshaping the college and university landscape. At 80 million strong, this group of children and young adults born between 1980 and 1995 now is flooding the college and university system, spurring a college building boom. According to Campus Space Crunch, a Hillier Architecture survey of…

  18. Long-Range Vibrational Dynamics Are Directed by Watson-Crick Base Pairing in Duplex DNA.

    Hithell, Gordon; Shaw, Daniel J; Donaldson, Paul M; Greetham, Gregory M; Towrie, Michael; Burley, Glenn A; Parker, Anthony W; Hunt, Neil T

    2016-05-01

    Ultrafast two-dimensional infrared (2D-IR) spectroscopy of a 15-mer A-T DNA duplex in solution has revealed structure-dependent vibrational coupling and energy transfer processes linking bases with the sugar-phosphate backbone. Duplex melting induces significant changes in the positions of off-diagonal peaks linking carbonyl and ring-stretching vibrational modes of the adenine and thymine bases with vibrations of the phosphate group and phosphodiester linkage. These indicate that Watson-Crick hydrogen bonding and helix formation lead to a unique vibrational coupling arrangement of base vibrational modes with those of the phosphate unit. On the basis of observations from time-resolved 2D-IR data, we conclude that rapid energy transfer processes occur between base and backbone, mediated by additional modes located on the deoxyribose moiety within the same nucleotide. These relaxation dynamics are insensitive to duplex melting, showing that efficient intramolecular energy relaxation to the solvent via the phosphate groups is the key to excess energy dissipation in both single- and double-stranded DNA. PMID:27079484

  19. Hydrophobic Solvation : A 2D IR Spectroscopic Inquest

    Bakulin, Artem A.; Liang, Chungwen; Jansen, Thomas La Cour; Wiersma, Douwe A.; Bakker, Huib J.; Pshenichnikov, Maxim S.

    2009-01-01

    For decades, the enigma of the hydrophobic force has captured the imagination of scientists. in particular, Frank and Evans' idea that the hydrophobic effect was mainly due to some kind of "iceberg" formation around a hydrophobic solute stimulated many experiments and molecular dynamics simulation s

  20. Echoes from the Moon

    Girlanda, Luca

    2009-01-01

    We report on a determination of the Earth-Moon distance performed by students of an Italian high school, based on measurements of the time delay of the "echo" in the radio communications between Nasa mission control in Houston and the Apollo astronauts on the lunar surface. By using an open-source audio-editing software, the distance can be determined with three digits accuracy, allowing to detect the effect due to the eccentricity of the orbit of the Moon.

  1. Spin Echo in Synchrotrons

    Chao, Alexander W.; /SLAC; Courant, Ernest D.; /Brookhaven

    2006-12-01

    As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency {Delta}{nu}{sub spin} of the beam (particularly due to its energy spread) is sufficiently large that the spin precession phases of individual particles smear out completely during the time {tau} between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference effect and a spin echo effect. This paper is to address these two effects. The interference effect occurs when {Delta}{nu}{sub spin} is too small, or when {tau} is too short, to complete the smearing process. In this case, the two resonance crossings interfere with each other, and the final polarization exhibits constructive or destructive patterns depending on the exact value of {tau}. Typically, the beam's energy spread is large and this interference effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time {tau} after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when {tau} is very large, and could be a sensitive (albeit challenging) way to experimentally test the intricate spin dynamics in a synchrotron. After giving

  2. Piston cylinder cell for high pressure ultrasonic pulse echo measurements.

    Kepa, M W; Ridley, C J; Kamenev, K V; Huxley, A D

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2. PMID:27587156

  3. Echo Cancellation I: Algorithms Simulation

    P. Sovka

    2000-04-01

    Full Text Available Echo cancellation system used in mobile communications is analyzed.Convergence behavior and misadjustment of several LMS algorithms arecompared. The misadjustment means errors in filter weight estimation.The resulting echo suppression for discussed algorithms with simulatedas well as rela speech signals is evaluated. The optional echocancellation configuration is suggested.

  4. Echo-planar imaging

    This paper demonstrates state-of-the-art echo-planar imaging (EPI) and its potential as a diagnostic modality. EPI provides 128 x 128- and 256 x 128-pixel MR images in 64 or 128 msec. The module structure of EPI, with separate spin-parameter encoding and image acquisition, allows flexible pulse sequence tailoring and interactive scanning with real-time feedback. We report the experience we have gained in over 200 EPI studies of head and body in adult and pediatric patients as well as fetuses in utero. EPI provides resolution in the millimeter range, T1 and T2 contrast, and dynamic morphologic as well as functional information. Parameters, including flow, perfusion, and relaxation, can be quantified in seconds. EPI can provide functional and morphologic information in a single examination, which is particularly useful in studies of cardiac dynamics, blood and cerebrospinal fluid flow, brain perfusion, and the GI tract

  5. Neutron phase spin echo

    Piegsa, Florian M.; Hautle, Patrick; Schanzer, Christian

    2016-04-01

    A novel neutron spin resonance technique is presented based on the well-known neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of 4 ×10-7 can be resolved, corresponding to an energy resolution of better than 3 neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing energy resolutions in the 10 peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  6. Neutron phase spin echo

    Piegsa, Florian M; Schanzer, Christian

    2016-01-01

    A novel neutron spin resonance technique is presented based on the well-know neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of $4 \\times 10^{-7}$ can be resolved, corresponding to an energy resolution of better than 3~neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing for energy resolutions in the 10~peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  7. The ECHo experiment

    The determination of the absolute scale of the neutrino masses is one of the most challenging questions in particle physics. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay and electron capture processes of suitable nuclides can provide necessary information on the electron neutrino mass value. In this talk we present the Electron Capture 163Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of 163Ho. A high precision and high statistics spectrum is measured by means of low temperature magnetic calorimeter arrays. We present preliminary results obtained with a first prototype of single channel detectors as well as the participating groups and their on-going developments.

  8. High-spatial-resolution isotropic three-dimensional fast-recovery fast spin-echo magnetic resonance dacryocystography combined with topical administration of sterile saline solution

    Objective: This study aims to investigate the clinical performance of three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) magnetic resonance dacryocystography (MRD) with topical administration of sterile saline solution for the assessment of the lacrimal drainage system (LDS). Methods: A total of 13 healthy volunteers underwent both 3D-FRFSE MRD and two-dimensional (2D)-impulse recovery (IR)-single-shot fast spin-echo (SSFSE) MRD after topical administration of sterile saline solution, and 31 patients affected by primary LDS outflow impairment or postsurgical recurrent epiphora underwent 3D-FRFSE MRD and conventional T1- and T2-weighted sequences. All patients underwent lacrimal endoscopy or surgery, which served as a standard of reference for confirming the MRD findings. Results: 3D-FRFSE MRD detected more visualized superior and inferior canaliculi and nasolacrimal duct than 2D-IR-SSFSE MRD. Compared with 2D-IR-SSFSE MRD, 3D-FRFSE MRD showed more visualized segments per LDS, although the difference was not statistically significant. Significant improvements in the inferior canaliculus and nasolacrimal duct visibility grades were achieved using 3D-FRFSE MRD. 3D-FRFSE MRD had 100% sensitivity and 63.6% specificity for detecting LDS obstruction. In 51 out of the 62 LDSs that were assessed, a 90% agreement was noted between the findings of 3D-FRFSE MRD and lacrimal endoscopy in detecting the obstruction level. Conclusion: 3D-FRFSE MRD combined with topical administration of sterile saline solution is a simple and noninvasive method of obtaining detailed morphological and functional information on the LDS. Overall, 3D-FRFSE MRD could be used as a reliable diagnostic method in many patients with epiphora prior to surgery

  9. High-spatial-resolution isotropic three-dimensional fast-recovery fast spin-echo magnetic resonance dacryocystography combined with topical administration of sterile saline solution

    Jing, Zhang, E-mail: hbtjzj@yahoo.com.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Lang, Chen, E-mail: langc731@yahoo.com.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Qiu-Xia, Wang, E-mail: guaiqiuqiu1981@163.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Rong, Liu, E-mail: rongr007@yahoo.com.cn [Department of Ophthalmology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Xin, Luo, E-mail: hoyoho2000@sina.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Wen-Zhen, Zhu, E-mail: zhuwenzhen@hotmail.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Li-Ming, Xia, E-mail: limingxia@tjh.tjmu.edu.cn [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); Jian-Pin, Qi, E-mail: qijp2k01@yahoo.com [Department of Radiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030 (China); He, Wang, E-mail: he.wang@ge.com [GE Healthcare, 1 Build, 2F C109, 1 Hua TuoRoad, Zhang Jiang Hi-Tech Park, Shanghai 201203 (China)

    2013-09-15

    Objective: This study aims to investigate the clinical performance of three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) magnetic resonance dacryocystography (MRD) with topical administration of sterile saline solution for the assessment of the lacrimal drainage system (LDS). Methods: A total of 13 healthy volunteers underwent both 3D-FRFSE MRD and two-dimensional (2D)-impulse recovery (IR)-single-shot fast spin-echo (SSFSE) MRD after topical administration of sterile saline solution, and 31 patients affected by primary LDS outflow impairment or postsurgical recurrent epiphora underwent 3D-FRFSE MRD and conventional T1- and T2-weighted sequences. All patients underwent lacrimal endoscopy or surgery, which served as a standard of reference for confirming the MRD findings. Results: 3D-FRFSE MRD detected more visualized superior and inferior canaliculi and nasolacrimal duct than 2D-IR-SSFSE MRD. Compared with 2D-IR-SSFSE MRD, 3D-FRFSE MRD showed more visualized segments per LDS, although the difference was not statistically significant. Significant improvements in the inferior canaliculus and nasolacrimal duct visibility grades were achieved using 3D-FRFSE MRD. 3D-FRFSE MRD had 100% sensitivity and 63.6% specificity for detecting LDS obstruction. In 51 out of the 62 LDSs that were assessed, a 90% agreement was noted between the findings of 3D-FRFSE MRD and lacrimal endoscopy in detecting the obstruction level. Conclusion: 3D-FRFSE MRD combined with topical administration of sterile saline solution is a simple and noninvasive method of obtaining detailed morphological and functional information on the LDS. Overall, 3D-FRFSE MRD could be used as a reliable diagnostic method in many patients with epiphora prior to surgery.

  10. Balanced echo state networks.

    Koryakin, Danil; Lohmann, Johannes; Butz, Martin V

    2012-12-01

    This paper investigates the interaction between the driving output feedback and the internal reservoir dynamics in echo state networks (ESNs). The interplay is studied experimentally on the multiple superimposed oscillators (MSOs) benchmark. The experimental data reveals a dual effect of the output feedback strength on the network dynamics: it drives the dynamic reservoir but it can also block suitable reservoir dynamics. Moreover, the data shows that the reservoir size crucially co-determines the likelihood of generating an effective ESN. We show that dependent on the complexity of the MSO dynamics somewhat smaller networks can yield better performance. Optimizing the output feedback weight range and the network size is thus crucial for generating an effective ESN. With proper parameter choices, we show that it is possible to generate ESNs that approximate MSOs with several orders of magnitude smaller errors than those previously reported. We conclude that there appears to be still much more potential in ESNs than previously thought and sketch-out some promising future research directions. PMID:23037774

  11. Simple echoes and subtle reverberations

    Keeports, David

    2010-03-01

    Reverberation within an enclosed space can be viewed as a superposition of a large number of simple echoes. The echoes that make up the sound of reverberation fall neatly into two categories, relatively loud and sparse early reflections, and relatively soft and dense late reflections. Ways in which readily available music production software can be used for the study of reverberation are suggested. Additionally, methods of adding reverberation to recorded sound are discussed.

  12. X-ray Echo Spectroscopy

    Shvyd'ko, Yuri

    2016-02-01

    X-ray echo spectroscopy, a counterpart of neutron spin echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a pointlike x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-0.02 meV ultrahigh-resolution IXS applications (resolving power >108 ) with broadband ≃5 - 13 meV dispersing systems are introduced featuring more than 103 signal enhancement. The technique is general, applicable in different photon frequency domains.

  13. X-ray echo spectroscopy

    Shvyd'ko, Yuri

    2015-01-01

    X-ray echo spectroscopy, a counterpart of neutron spin-echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a point-like x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x-rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1--0.02-meV ultra-high-resolution IXS applications (resolving power $> 10^8$) with broadband $\\simeq$~5--13~meV dispersing systems are introduced featuring more than $10^3$ signal e...

  14. Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

    Cahoon, James Francis

    2008-12-16

    One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO){sub 3} and CpFe(CO){sub 2} have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO){sub 5}[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO){sub 5} have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

  15. Commissioning the Echo-Seeding Experiment Echo-7 at SLAC

    Weathersby, S.a E.Colby; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Woodley, M.; Xiang, D.; /SLAC; Pernet, P-L.; /Ecole Polytechnique, Lausanne

    2011-06-02

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation (EEHG) FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment is intended to test the EEHG principle at low electron beam energy, 120 MeV, and determine the sensitivities and limitations to understand the expected performance at the higher energy scales and harmonic numbers required for x-ray FELs. In this paper we present the experimental results from the commissioning run of the completed experimental setup which started in April 2010.

  16. Entanglement Echoes in Quantum Computation

    Rossini, Davide; Benenti, Giuliano; Casati, Giulio

    2003-01-01

    We study the stability of entanglement in a quantum computer implementing an efficient quantum algorithm, which simulates a quantum chaotic dynamics. For this purpose, we perform a forward-backward evolution of an initial state in which two qubits are in a maximally entangled Bell state. If the dynamics is reversed after an evolution time $t_r$, there is an echo of the entanglement between these two qubits at time $t_e=2t_r$. Perturbations attenuate the pairwise entanglement echo and generate...

  17. Multifractal Modelling of Aircraft Echoes from Low-resolution Radars Based on Structural Functions

    Qiu Sheng Li

    2013-09-01

    Full Text Available As a kind of complex targets, the nonrigid vibration and attitude change of an aircraft as well as the rotation of its rotating parts will induce complex nonlinear modulation on its echo from low-resolution radars. If one performs the multifractal analysis of measures on an aircraft echo, it may offer a fine description of the dynamic characteristics which induce the echo structure. On basis of introducing multifractal theory based on structural functions, the paper models real recorded aircraft echo data from a low-resolution radar by using the random walk process and the incremental process respectively, and investigates the application of echo multifractal characteristics in aircraft target classification with low-resolution radars. The analysis shows that aircraft echoes from low-resolution radars have clear multifractal characteristics, and one should take an aircraft echo series as a random walk process to perform the multifractal analysis. The experimental results validate the classification method based on multifractal signatures.Defence Science Journal, 2013, 63(5, pp.515-520, DOI:http://dx.doi.org/10.14429/dsj.63.3773

  18. Acoustic echoes reveal room shape.

    Dokmanic, Ivan; Parhizkar, Reza; Walther, Andreas; Lu, Yue M; Vetterli, Martin

    2013-07-23

    Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room's response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to "blindfoldedly" estimate the room geometry. This is achieved by exploiting the properties of Euclidean distance matrices. Furthermore, we show that under mild conditions, first-order echoes provide a unique description of convex polyhedral rooms. Our algorithm starts from the recorded impulse responses and proceeds by learning the correct assignment of echoes to walls. In contrast to earlier methods, the proposed algorithm reconstructs the full 3D geometry of the room from a single sound emission, and with an arbitrary geometry of the microphone array. As long as the microphones can hear the echoes, we can position them as we want. Besides answering a basic question about the inverse problem of room acoustics, our results find applications in areas such as architectural acoustics, indoor localization, virtual reality, and audio forensics. PMID:23776236

  19. Phenomenological theory of echo poles

    In scattering theory the effect associated with the downward crossing of the phase-shift δℓ(k) (ℓ being the orbital angular momentum and k the momentum) through δℓ=π/2 (mod π) is called echo. In the standard nuclear theory (Breit–Wigner theory) the echo is described and evaluated in terms of scattering by an impenetrable sphere. However, this model holds only at sufficiently high energy, while it is inadequate at low energy. In this paper we show that the echo effect can be associated with two different regimes acting at low and high energy, respectively. At high energy the hard-sphere scattering model seems to describe appropriately the phenomenon. At low energy we propose a mechanism due to the exchange forces induced by the Pauli exclusion principle in the fermionic interaction, which leads to nonlocal potentials. These potentials admit for the scattering amplitude pole singularities in the fourth quadrant of the complex angular momentum plane. This paper analyzes the role played by this class of poles in the description of the low energy regime of echoes. A specific phenomenological analysis is performed, taking as typical example the α–α elastic scattering

  20. Dance of the Light Echoes

    2008-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This composite image from NASA's Spitzer Space Telescope shows the remnant of a star that exploded, called Cassiopeia A (center) and its surrounding 'light echoes' -- dances of light through dusty clouds, created when stars blast apart. The light echoes are colored and the surrounding clouds of dust are gray. In figure 1, dramatic changes are highlighted in phenomena referred to as light echoes (colored areas) around the Cassiopeia A supernova remnant (center). Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. In figure 1, this apparent motion can be seen here by the shift in colored dust clumps Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 11,000 light-years away in the northern constellation Cassiopeia. This composite consists of six processed images taken over a time span of three years. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Bluer colors represent an earlier time and redder ones, a later time. The progression of the light echo through the dust can be seen here by the shift in colored dust clumps. This light echo is the largest ever seen

  1. PHONON ECHOES IN BULK AND POWDERED MATERIALS

    Kajimura, K.

    1981-01-01

    Experimental and theoretical studies of phonon echoes in bulk and powdered materials are reviewed. Phonon echoes have been observed in many materials such as bulk piezoelectric crystals, paramagnets, glasses, doped semiconductors, and piezoelectric, magnetic, and metallic powders, etc. The echoes arise from a time reversal of the phase, like spin echoes, of a primary pulsed acoustic excitation due to a second acoustic or rf pulse. The phase reversal occurs through the nonlinear interactions o...

  2. Comparison of third-order plasma wave echoes with ballistic second-order plasma wave echoes

    The apparent dispersion of third-order plasma wave echoes observed in a high frequency plasma is compared with that of simultaneously observed ballistic second-order echoes. Amplitude and wavelength of third-order echoes are found to be always smaller than those of second-order echoes, however, the dispersion curves of both types of echoes are very similar. These observations are in qualitative agreement with calculations of special ballistic third-order echoes. The ballistic nature of the observed third-order echoes may, therefore, be concluded from these measurements. (author)

  3. Distinguishing gramicidin D conformers through two-dimensional infrared spectroscopy of vibrational excitons

    Stevenson, Paul; Tokmakoff, Andrei

    2015-06-01

    Gramicidin D is a short peptide which dimerizes to form helical pores, adopting one of two conformations in the process. These conformations differ primarily in number of residues per turn and the hydrogen-bond registry between rungs of the helix. Using amide I 2D infrared (IR) and FTIR, we have demonstrated that it is possible to distinguish between the different conformers of gramicidin D in solution. We show that the spectra observed for this helical peptide bear no resemblance to the spectra of α- or 310-helices and that while the FTIR spectra appear similar to spectra of β-sheets, 2D IR reveals that the observed resonances arise from vibrational modes unlike those observed in β-sheets. We also present an idealized model which reproduces the experimental data with high fidelity. This model is able to explain the polarization-dependence of the experimental 2D IR data. Using this model, we show the coupling between the rungs of the helix dominates the spectra, and as a consequence of this, the number of residues per turn can greatly influence the amide I spectra of gramicidin D.

  4. Harmonic Motion Detection in a Vibrating Scattering Medium

    Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

    2008-01-01

    Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating ...

  5. Molecular echoes in space and time

    Lin, Kang; Ma, Junyang; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Zhang, Wenbin; Zeng, Heping; Wu, Jian; Karras, Gabriel; Siour, Guillaume; Hartmann, Jean-Michel; Faucher, Olivier; Gershnabel, Erez; Prior, Yehiam; Averbukh, Ilya Sh

    2016-01-01

    Mountain echoes are a well-known phenomenon, where an impulse excitation is mirrored by the rocks to generate a replica of the original stimulus, often with reverberating recurrences. For spin echoes in magnetic resonance and photon echoes in atomic and molecular systems the role of the mirror is played by a second, time delayed pulse which is able to reverse the ow of time and recreate the original event. Recently, laser-induced rotational alignment and orientation echoes were introduced for molecular gases, and discussed in terms of rotational-phase-space filamentation. Here we present, for the first time, a direct spatiotemporal analysis of various molecular alignment echoes by means of coincidence Coulomb explosion imaging. We observe hitherto unreported spatially rotated echoes, that depend on the polarization direction of the pump pulses, and find surprising imaginary echoes at negative times.

  6. Independence of echo-threshold and echo-delay in the barn owl.

    Brian S Nelson

    Full Text Available Despite their prevalence in nature, echoes are not perceived as events separate from the sounds arriving directly from an active source, until the echo's delay is long. We measured the head-saccades of barn owls and the responses of neurons in their auditory space-maps while presenting a long duration noise-burst and a simulated echo. Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo. One was at the onset of the echo; the other, after the offset of the direct (leading sound, when only the echo was present. By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source. An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

  7. Principles of angular echo-spectroscopy

    Khasanov, O.K. [Joint Institute of Solid State and Semiconductor Physics, NAS Belarus, 17 P. Brovki Str., Minsk 220072 (Belarus)]. E-mail: khasanov@ifttp.bas-net.by; Fedotova, O.M. [Joint Institute of Solid State and Semiconductor Physics, NAS Belarus, 17 P. Brovki Str., Minsk 220072 (Belarus); Samartsev, V.V. [Zavoisky Physical-Technical Institute KSC RAS, Sibirskii Trakt Str., 10/7, Kazan' 420029, Tatarstan (Russian Federation)

    2007-11-15

    We study the two-pulse photon echo generation process in thin polymer films doped with organic dye, when the angle between wave vectors of the excitation pulses is varied. The temporal structure as well as the spectral features of the echo-response are analyzed. The evolution from the gradual blue shift of the echo-signal frequency to the red switch of it is predicted.

  8. Acoustic Echoes Reveal Room Shape

    Dokmanic, Ivan; Parhizkar, Reza; Walther, Andreas; Lu, Yue M.; Vetterli, Martin

    2013-01-01

    Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room’s response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to “blindfoldedly” estimate the room geometry. This is achiev...

  9. Optical echo in photonic crystals

    Antipov, A E

    2006-01-01

    The dynamics of photonic wavepacket in the effective oscillator potential is studied. The oscillator potential is constructed on a base of one dimensional photonic crystal with a period of unit cell adiabatically varied in space. The structure has a locally equidistant discrete spectrum. This leads to an echo effect, i.e. the periodical reconstruction of the packet shape. The effect can be observed in a nonlinear response of the system. Numerical estimations for porous-silicon based structures are presented for femtosecond Ti:Sapphire laser pump.

  10. Collision induced photon echo in ytterbium vapour

    Rubtsova, N. N.; Khvorostov, E. B.; Kochubei, S. A.; Ishchenko, V. N.; Yevseyev, I. V.

    2006-01-01

    Collision induced photon echo observed in ytterbium vapour at the inter-combination transition (6s6p) P-8(1) (6s(2)) S-1(0) in the presence of Kr gas as buffer. Collision echo is generated by two unidirectional resonant dye laser pulses of linear mutually orthogonal polarizations. There is practical

  11. Nonlinear Echoes from Encapsulated Antibubbles

    Johansen, Kristoffer; Kotopoulis, Spiros; Poortinga, Albert T.; Postema, Michiel

    An antibubble consists of a liquid droplet, surrounded by a gas, often with an encapsulating shell. Antibubbles of microscopic sizes suspended in fluids are acoustically active in the ultrasonic range. Antibubbles have applications in food processing and guided drug delivery. We study the sound generated from antibubbles, with droplet core sizes in the range of 0-90% of the equilibrium antibubble inner radius. The antibubble resonance frequency, the phase difference of the echo with respect to the incident acoustic pulse, and the presence of higher harmonics are strongly dependent of the core droplet size. Antibubbles oscillate highly nonlinearly around resonance size. This may allow for using antibubbles in clinical diagnostic imaging and targeted drug delivery.

  12. Ultrafast dynamics in iron tetracarbonyl olefin complexes investigated with two-dimensional vibrational spectroscopy.

    Panman, Matthijs R; Newton, Arthur C; Vos, Jannie; van den Bosch, Bart; Bocokić, Vladica; Reek, Joost N H; Woutersen, Sander

    2013-01-28

    The dynamics of iron tetracarbonyl olefin complexes has been investigated using two-dimensional infrared (2D-IR) spectroscopy. Cross peaks between all CO-stretching bands show that the CO-stretch modes are coupled, and from the cross-peak anisotropies we can confirm previous assignments of the absorption bands. From the pump-probe delay dependence of the diagonal peaks in the 2D-IR spectrum we obtain a correlation time of ∼3 ps for the spectral fluctuations of the CO-stretch modes. We observe a multi-exponential pump-probe delay dependence of the cross-peak intensities, with rate constants ranging from 0.1 ps(-1) to 0.6 ps(-1). To determine whether this delay dependence originates from fluxionality of the complex or from intramolecular vibrational relaxation (IVR), we modulate the free-energy barrier of fluxional rearrangement by varying the pi-backbonding capacities of the olefin ligand in two iron tetracarbonyl olefin complexes: Fe(CO)(4)(cinnamic acid) and Fe(CO)(4)(dimethyl fumarate). Since the pi-backbonding strongly influences the rate of fluxionality, comparing the dynamics in the two complexes allows us to determine to what extent the observed dynamics is caused by fluxionality. We conclude that on the time scale of our experiments (up to 100 ps) the cross-peak dynamics in the iron complexes is determined by intramolecular vibrational energy relaxation. Hence, in contrast to previously investigated irontricarbonyl and ironpentacarbonyl complexes, iron tetracarbonyl olefin complexes exhibit no fluxionality on the picosecond time scale. PMID:23223560

  13. Two-dimensional vibrational spectroscopy of rotaxane-based molecular machines.

    Bodis, Pavol; Panman, Matthijs R; Bakker, Bert H; Mateo-Alonso, Aurelio; Prato, Maurizio; Buma, Wybren Jan; Brouwer, Albert M; Kay, Euan R; Leigh, David A; Woutersen, Sander

    2009-09-15

    model rotaxane and a rotaxane-based molecular shuttle. Our results demonstrate the feasibility of using time-resolved 2D-IR experiments to measure externally triggered structural changes of molecular devices with subpicosecond time resolution. We can observe each of the elementary events that underlie the mechanical motion separately. With this ability to investigate the nature of the mechanical motions at the molecular level and with unprecedented time resolution, we expect that 2D-IR spectroscopy on molecular machines will lead to new insights into their function. PMID:19650645

  14. Ship Vibrations

    Sørensen, Herman

    1997-01-01

    Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...

  15. Sparse adaptive filters for echo cancellation

    Paleologu, Constantin

    2011-01-01

    Adaptive filters with a large number of coefficients are usually involved in both network and acoustic echo cancellation. Consequently, it is important to improve the convergence rate and tracking of the conventional algorithms used for these applications. This can be achieved by exploiting the sparseness character of the echo paths. Identification of sparse impulse responses was addressed mainly in the last decade with the development of the so-called ``proportionate''-type algorithms. The goal of this book is to present the most important sparse adaptive filters developed for echo cancellati

  16. Echoes in correlated neural systems

    Helias, M.; Tetzlaff, T.; Diesmann, M.

    2013-02-01

    Correlations are employed in modern physics to explain microscopic and macroscopic phenomena, like the fractional quantum Hall effect and the Mott insulator state in high temperature superconductors and ultracold atoms. Simultaneously probed neurons in the intact brain reveal correlations between their activity, an important measure to study information processing in the brain that also influences the macroscopic signals of neural activity, like the electroencephalogram (EEG). Networks of spiking neurons differ from most physical systems: the interaction between elements is directed, time delayed, mediated by short pulses and each neuron receives events from thousands of neurons. Even the stationary state of the network cannot be described by equilibrium statistical mechanics. Here we develop a quantitative theory of pairwise correlations in finite-sized random networks of spiking neurons. We derive explicit analytic expressions for the population-averaged cross correlation functions. Our theory explains why the intuitive mean field description fails, how the echo of single action potentials causes an apparent lag of inhibition with respect to excitation and how the size of the network can be scaled while maintaining its dynamical state. Finally, we derive a new criterion for the emergence of collective oscillations from the spectrum of the time-evolution propagator.

  17. MEASUREMENT OF TRANSVERSE ECHOES IN RHIC.

    FISCHER, W.; SATOGATA, T.; TOMAS. R.

    2005-05-16

    Beam echoes are a very sensitive method to measure diffusion, and longitudinal echo measurements were performed in a number of machines. In RHIC, for the first time, a transverse beam echo was observed after applying a dipole kick followed by a quadrupole .kick. After application of the dipole kick, the dipole moment decohered completely due to lattice nonlinearities. When a quadrupole kick is applied at time {tau} after the dipole kick, the beam re-cohered at time 2{tau} thus showing an echo response. We describe the experimental setup and measurement results. In the measurements the dipole and quadrupole kick amplitudes, amplitude dependent tune shift, and the time between dipole and quadrupole kick were varied. In addition, measurements were taken with gold bunches of different intensities. These should exhibit different transverse diffusion rates due to intra-beam scattering.

  18. Enforcement and Compliance History Online (ECHO) Facilities

    U.S. Environmental Protection Agency — ECHO provides integrated compliance and enforcement information for about 800,000 regulated facilities nationwide. Its features range from simple to advanced,...

  19. Time Delay Estimation Algoritms for Echo Cancellation

    Boris Simak

    2011-01-01

    Full Text Available The following case study describes how to eliminate echo in a VoIP network using delay estimation algorithms. It is known that echo with long transmission delays becomes more noticeable to users. Thus, time delay estimation, as a part of echo cancellation, is an important topic during transmission of voice signals over packetswitching telecommunication systems. An echo delay problem associated with IP-based transport networks is discussed in the following text. The paper introduces the comparative study of time delay estimation algorithm, used for estimation of the true time delay between two speech signals. Experimental results of MATLab simulations that describe the performance of several methods based on cross-correlation, normalized crosscorrelation and generalized cross-correlation are also presented in the paper.

  20. EChO - Exoplanet Characterisation Observatory

    Tinetti, G; Henning, T; Meyer, M; Micela, G; Ribas, I; Stam, D; Swain, M; Krause, O; Ollivier, M; Pace, E; Swinyard, B; Aylward, A; van Boekel, R; Coradini, A; Encrenaz, T; Snellen, I; Zapatero-Osorio, M R; Bouwman, J; Cho, J Y-K; Foresto, V Coudé du; Guillot, T; Lopez-Morales, M; Mueller-Wodarg, I; Palle, E; Selsis, F; Sozzetti, A; Ade, P A R; Achilleos, N; Adriani, A; Agnor, C B; Afonso, C; Prieto, C Allende; Bakos, G; Barber, R J; Barlow, M; Bernath, P; Bezard, B; Bordé, P; Brown, L R; Cassan, A; Cavarroc, C; Ciaravella, A; Cockell, C O U; Coustenis, A; Danielski, C; Decin, L; De Kok, R; Demangeon, O; Deroo, P; Doel, P; Drossart, P; Fletcher, L N; Focardi, M; Forget, F; Fossey, S; Fouqué, P; Frith, J; Galand, M; Gaulme, P; Hernández, J I González; Grasset, O; Grassi, D; Grenfell, J L; Griffin, M J; Griffith, C A; Grözinger, U; Guedel, M; Guio, P; Hainaut, O; Hargreaves, R; Hauschildt, P H; Heng, K; Heyrovsky, D; Hueso, R; Irwin, P; Kaltenegger, L; Kervella, P; Kipping, D; Koskinen, T T; Kovács, G; La Barbera, A; Lammer, H; Lellouch, E; Leto, G; Morales, M Lopez; Valverde, M A Lopez; Lopez-Puertas, M; Lovis, C; Maggio, A; Maillard, J P; Prado, J Maldonado; Marquette, J B; Martin-Torres, F J; Maxted, P; Miller, S; Molinari, S; Montes, D; Moro-Martin, A; Moses, J I; Mousis, O; Tuong, N Nguyen; Nelson, R; Orton, G S; Pantin, E; Pascale, E; Pezzuto, S; Pinfield, D; Poretti, E; Prinja, R; Prisinzano, L; Rees, J M; Reiners, A; Samuel, B; Sanchez-Lavega, A; Forcada, J Sanz; Sasselov, D; Savini, G; Sicardy, B; Smith, A; Stixrude, L; Strazzulla, G; Tennyson, J; Tessenyi, M; Vasisht, G; Vinatier, S; Viti, S; Waldmann, I; White, G J; Widemann, T; Wordsworth, R; Yelle, R; Yung, Y; Yurchenko, S N

    2011-01-01

    A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO -the Exoplanet Characterisation Observatory- is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. EChO will build on observations by Hubble, Spitzer and groundbased telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. EChO will simultaneously observe a broad enough spectral region -from the visible to the mid-IR- to constrain from one single spectrum the temperature structure of the atmosphere and the abundances of the major molecular species. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules to retrieve the composition and temperature str...

  1. Enforcement and Compliance History Online (ECHO) Widget

    U.S. Environmental Protection Agency — The Enforcement and Compliance History Online (ECHO) widget displays the compliance records of larger facilities within a user-specified area of interest as...

  2. Geometric spin echo under zero field.

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo

    2016-01-01

    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors. PMID:27193936

  3. Echo Theatre: From Experience to Performance

    Ulvund, Marit

    2013-01-01

    This research project investigates the characteristics of Echo Theatre, its potential to foster performative and narrative competencies in students, and the role of the teacher in this performative and educational practice. Echo Theatre is a method devised during my storytelling practice and this research confirms that there is no identical research or teaching practice which involves students staging personal narratives in the classroom in this way.The study has been informed by cross discip...

  4. Vibration sensor

    This invention relates to a sensor for detecting the vibrations of a liquid, specifically designed for detecting low frequency vibrations transmitted by a high temperature liquid, particularly the liquid metal coolant of a fast reactor. It comprises a piezoelectric transducer inside a cavity closed by a membrane in contact with the liquid and in which a vacuum is made. The membrane is connected to one of the sides of the transducer, called the first side, through a mechanical vibration transmitting part made of a thermal insulation material. The other side of the transducer, termed second side, is blocked and the cavity has at least one leak-tight passage for an electric conductor

  5. Echo cancellation techniques for ADSL transceivers

    Multicarrier transmission methods have long known to optimize the performance of data transceivers on bandlimited communication channels. One form of multicarrier transmission, known as discrete multitone modulation (DMT), is particularly attractive for its ability to be implemented using efficient digital signal processing techniques. The ANSI Tl committee has standardized discrete multitone modulation (DMT) as the line code to be used in the ADSL transmission system, due to its unique ability to overcome the severe distortion of the copper line at this frequency band. Given a basic DMT system, it is possible to increase the aggregate data rate with full duplex transmission using echo cancellation. This paper presents high speed echo cancellation techniques for full duplex data transmission using G. Lite ADSL standards. Time domain echo cancellation and mixed time and frequency domain echo cancellation techniques have been implemented for G. Lite ADSL applications. It has been observed that Time and frequency domain echo canceller (TAFDEC) achieve lower complexity for G. Lite ADSL systems that required by time domain echo canceller (TDEC) using traditional single carrier technique, such as least mean square (LMS) Hi algorithm. (author)

  6. On the Search for Quasar Light Echoes

    Visbal, Eli

    2007-01-01

    The UV radiation from a quasar leaves a characteristic pattern in the distribution of ionized hydrogen throughout the surrounding space. This pattern or light echo propagates through the intergalactic medium at the speed of light, and can be observed by its imprint on the Ly-alpha forest spectra of background sources. As the echo persists after the quasar has switched off, it offers the possibility of searching for dead quasars, and constraining their luminosities and lifetimes. We outline a technique to search for and characterize these light echoes. To test the method, we create artificial Ly-alpha forest spectra from cosmological simulations at z=3, apply light echoes and search for them. We show how the simulations can also be used to quantify the significance level of any detection. We find that light echoes from the brightest quasars could be found in observational data. With absorption line spectra of 100 redshift z~3-3.5 quasars or galaxies in a 1 square degree area, we expect that ~10 echoes from qua...

  7. Probing intermolecular couplings in liquid water with two-dimensional infrared photon echo spectroscopy

    Paarmann, A.; Hayashi, T.; Mukamel, S.; Miller, R. J. D.

    2008-05-01

    Two-dimensional infrared photon echo and pump probe studies of the OH stretch vibration provide a sensitive probe of the correlations and couplings in the hydrogen bond network of liquid water. The nonlinear response is simulated using numerical integration of the Schrödinger equation with a Hamiltonian constructed to explicitly treat intermolecular coupling and nonadiabatic effects in the highly disordered singly and doubly excited vibrational exciton manifolds. The simulated two-dimensional spectra are in close agreement with our recent experimental results. The high sensitivity of the OH stretch vibration to the bath dynamics is found to arise from intramolecular mixing between states in the two-dimensional anharmonic OH stretch potential. Surprisingly small intermolecular couplings reproduce the experimentally observed intermolecular energy transfer times.

  8. Random Vibrations

    Messaro. Semma; Harrison, Phillip

    2010-01-01

    Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

  9. Re-visiting the echo state property.

    Yildiz, Izzet B; Jaeger, Herbert; Kiebel, Stefan J

    2012-11-01

    An echo state network (ESN) consists of a large, randomly connected neural network, the reservoir, which is driven by an input signal and projects to output units. During training, only the connections from the reservoir to these output units are learned. A key requisite for output-only training is the echo state property (ESP), which means that the effect of initial conditions should vanish as time passes. In this paper, we use analytical examples to show that a widely used criterion for the ESP, the spectral radius of the weight matrix being smaller than unity, is not sufficient to satisfy the echo state property. We obtain these examples by investigating local bifurcation properties of the standard ESNs. Moreover, we provide new sufficient conditions for the echo state property of standard sigmoid and leaky integrator ESNs. We furthermore suggest an improved technical definition of the echo state property, and discuss what practicians should (and should not) observe when they optimize their reservoirs for specific tasks. PMID:22885243

  10. Modelling of Oscillations in Two-Dimensional Echo-Spectra of the Fenna-Matthews-Olson Complex

    Hein, Birgit; Kramer, Tobias; Rodríguez, Mirta

    2011-01-01

    Recent experimental observations of time-dependent beatings in the two-dimensional echo-spectra of light-harvesting complexes at ambient temperatures have opened up the question whether coherence and wave-like behaviour plays a significant role in photosynthesis. We perform a numerical study of the absorption and echo-spectra of the Fenna-Matthews-Olson (FMO) complex in chlorobium tepidum and analyse the requirements in the theoretical model needed to reproduce beatings in the calculated spectra. The energy transfer in the FMO pigment-protein complex is theoretically described by an exciton Hamiltonian coupled to a phonon bath which account for the pigments electronic and vibrational excitations respectively. We use the hierarchical equations of motions method to treat the strong couplings in a non-perturbative way. We show that the oscillations in the two-dimensional echo-spectra persist in the presence of thermal noise and static disorder.

  11. Meteor head echoes - observations and models

    A. Pellinen-Wannberg

    2005-01-01

    Full Text Available Meteor head echoes - instantaneous echoes moving with the velocities of the meteors - have been recorded since 1947. Despite many attempts, this phenomenon did not receive a comprehensive theory for over 4 decades. The High Power and Large Aperture (HPLA features, combined with present signal processing and data storage capabilities of incoherent scatter radars, may give an explanation for the old riddle. The meteoroid passage through the radar beam can be followed with simultaneous spatial-time resolution of about 100m-ms class. The current views of the meteor head echo process will be presented and discussed. These will be related to various EISCAT observations, such as dual-frequency target sizes, altitude distributions and vector velocities.

  12. Urban vibrations

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

    In   this   paper   we   describe   a   field   study   conducted   with   a   wearable   vibration   belt   where   we   test   to   determine   the   vibration   intensity   sensitivity   ranges   on   a   large   diverse   group   of   participants   with   evenly   distributed  ages  and......   lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  13. The experimental study on Doppler echo signals with different scattering surfaces for velocity measurement

    Wang, Leng-ping; Feng, Di; Ou, Pan; Yang, De-zhao

    2011-06-01

    Laser Doppler velocimetry has the ability to measure speed and surface vibrations non-intrusively with high precision. In this study the Doppler spectrum shift and spectrum broadening of echo signals by moving targets are investigated. The interaction between moving object and the laser beam of laser Doppler velocimetry have been described by varying rotating velocity, the angular velocity, distance and incident facula. By using different scattering surfaces, such as Polytetrafluoroethylene (PTFE) and sandpaper with different grain sizes, the characteristics of echo signals' Doppler spectra have been studied experimentally in detail. The results show that Doppler spectrum distribution is changed with different scattering surfaces. Meanwhile, in order to get a high measuring accuracy, the moving object's scattering characteristics must be considered carefully.

  14. Multi-Echo-Based Echo-Planar Spectroscopic Imaging Using a 3T MRI Scanner

    Jon K. Furuyama

    2011-10-01

    Full Text Available The use of spin-echoes has been employed in an Echo-Planar Spectroscopic Imaging (EPSI sequence to collect multiple phase encoded lines within a single TR in a Multi-Echo-based Echo-Planar Spectroscopic Imaging technique (MEEPSI. Despite the T2 dependence on the amplitude of the spin-echoes, the Full Width at Half Maximum (FWHM of the derived multi-echo Point Spread Function (PSF is shown to decrease, indicating an improved overall spatial resolution without requiring any additional scan time. The improved spatial resolution is demonstrated in the one-dimensional (1D spatial profiles of the N-Acetyl Aspartate (NAA singlet along the phase encode dimension in a gray matter phantom. Although the improved spatial resolution comes at the expense of spectral resolution, it is shown in vivo that peak broadening due to T2* decay is more significant than the loss of resolution from using spin-echoes and therefore does not affect the ability to quantify metabolites using the LCModel fitting algorithm.

  15. How can dolphins recognize fish according to their echoes? A statistical analysis of fish echoes.

    Yossi Yovel

    Full Text Available Echo-based object classification is a fundamental task of animals that use a biosonar system. Dolphins and porpoises should be able to rely on echoes to discriminate a predator from a prey or to select a desired prey from an undesired object. Many studies have shown that dolphins and porpoises can discriminate between objects according to their echoes. All of these studies however, used unnatural objects that can be easily characterized in human terminologies (e.g., metallic spheres, disks, cylinders. In this work, we collected real fish echoes from many angles of acquisition using a sonar system that mimics the emission properties of dolphins and porpoises. We then tested two alternative statistical approaches in classifying these echoes. Our results suggest that fish species can be classified according to echoes returning from porpoise- and dolphin-like signals. These results suggest how dolphins and porpoises can classify fish based on their echoes and provide some insight as to which features might enable the classification.

  16. Research of laser echo signal simulator

    Xu, Rui; Shi, Rui; Wang, Xin; Li, Zhou

    2015-11-01

    Laser echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR. System model and time series model of laser echo signal simulator are established. Some influential factors which could induce fixed error and random error on the simulated return signals are analyzed, and then these system insertion errors are analyzed quantitatively. Using this theoretical model, the simulation system is investigated experimentally. The results corrected by subtracting fixed error indicate that the range error of the simulated laser return signal is less than 0.25m, and the distance range that the system can simulate is from 50m to 20km.

  17. Nanosecond image processing using stimulated photon echoes.

    Xu, E Y; Kröll, S; Huestis, D L; Kachru, R; Kim, M K

    1990-05-15

    Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. % Pr(3+):LaF(3)). Two spatially encoded laser pulses (pictures) resonant with the (3)P(0)-(3)H(4) transition of Pr(3+) were stored by focusing the image pulses sequentially into the Pr(3+):LaF(3) crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the input images. Application of this scheme to high-speed pattern recognition is discussed. PMID:19768008

  18. Nanosecond image processing using stimulated photon echoes

    Xu, E Y; Kröll, Stefan; Huestis, D. L.; Kachru, R.; Kim, M. K.

    1990-01-01

    Processing of two-dimensional images on a nanosecond time scale is demonstrated using the stimulated photon echoes in a rare-earth-doped crystal (0.1 at. \\% Pr3$+$:LaF3). Two spatially encoded laser pulses (pictures) resonant with the 3P0-3H4 transition of Pr3$+$ were stored by focusing the image pulses sequentially into the Pr3$+$:LaF3 crystal. The stored information is retrieved and processed by a third read pulse, generating the echo that is the spatial convolution or correlation of the in...

  19. GESTATIONAL ECHO BIOMETRY IN BRACHYCEPHALIC PREGNANT BITCHES

    Marcus Antônio Rossi Feliciano; Giovanna Serpa Maciel; Leandro Nassar Coutinho; Vívian Tavares Almeida; Ricardo Ramirez Uscategui; Wilter Ricardo Russiano Vicente

    2015-01-01

    Ultrasonography is an accurate pregnancy diagnostic method, besides being completely innocuous for female and fetuses evaluation. The objective of this paper was to determine the reference values for gestational echo biometry of different breeds of bitches. A total of 25 multiparous females were included in the experiment, five English Bulldog bitches, five Pugs and 15 Shih Tzu, weighing 4-25 kg and aged 4-6 years. The echo biometric assessments were performed during the 2nd, 5th, 6th, 7th an...

  20. TOPICAL REVIEW: Nonlinear two-dimensional vibrational spectroscopy of peptides

    Woutersen, Sander; Hamm, Peter

    2002-10-01

    In this overview, we discuss theoretical and experimental aspects of nonlinear two-dimensional infrared (2D-IR) spectroscopy. With this technique both peptide conformation and conformational flexibility can be probed. The quantitative relation between the experimental 2D-IR spectrum and the peptide conformation is discussed, and examples of how the conformation of a peptide and the timescale of its fluctuations are derived from its (time-resolved) 2D spectrum are presented.

  1. Vibrating minds

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  2. Vibrating Manipulation

    SHEN Guo-quan; CUI Yi-jun

    2003-01-01

    @@ As a manipulation with unique therapeutic effect in TCM Tuina manipulations, Vibrating manipulation has significantly stronger effection on viscera, blood vessel, smooth muscle and gland secretion than other Tuina manipulations and it is mainly used in internal medicine, gynecology and miscellaneous diseases.

  3. Vibration sensor

    Matěj, J.

    2015-01-01

    This paper lays out a design of a system for reading the radar antenna gearbox vibrations. Firstly it names different types of sensors and defines their suitability for this usage. It describes their important electric and frequency properties. Secondly it shows a design of the data transmission system from the transducer to a computer and describes measured data changes according to the gearbox faults.

  4. Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

    Van-Han Nguyen

    2015-03-01

    Full Text Available In indoor environments, the Global Positioning System (GPS and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

  5. Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

    Van-Han Nguyen; Jae-Young Pyun

    2015-01-01

    In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving obj...

  6. Location detection and tracking of moving targets by a 2D IR-UWB radar system.

    Nguyen, Van-Han; Pyun, Jae-Young

    2015-01-01

    In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB) radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF) is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking. PMID:25808773

  7. Relationship between tornadoes and hook echoes on April 3, 1974

    Forbes, G. S.

    1975-01-01

    Radar observations of tornado families occurring on April 3, 1974 are discussed. Of the 93 tornadoes included in the sample, 81% were associated with hook-like echoes with appendages at least 40 deg to the south of the echo movement. At least one tornado was associated with 62% of the hook-like echoes observed. All of the tornadoes with intensities of F 4 and F 5 were produced by hook-like echoes; the mean intensity of all tornadoes associated with this type of echo was F 3, while the mean intensity of the remaining tornadoes was F1. The tornadic hook-like echoes moved to the right of the non-tornadic echoes forming a tornado line in advance of the squall line. Some tornadoes were associated with 'spiral' echoes.

  8. An Echo of Supernova 2008bk

    Van Dyk, Schuyler D

    2013-01-01

    I have discovered a prominent light echo around the low-luminosity Type II-Plateau Supernova (SN) 2008bk in NGC 7793, seen in archival images obtained with the Wide Field Channel of the Advanced Camera for Surveys on-board the Hubble Space Telescope (HST). The echo is a partial ring, brighter to the north and east than to the south and west. The analysis of the echo I present suggests that it is due to the SN light pulse scattered by a sheet, or sheets, of dust located ~15 pc from the SN. The composition of the dust is assumed to be of standard Galactic diffuse interstellar grains. The visual extinction of the dust responsible for the echo is A_V ~ 0.05 mag, in addition to the extinction due to the Galactic foreground toward the host galaxy. That the SN experienced much less overall extinction implies that it is seen through a less dense portion of the interstellar medium in its environment. The late-time HST photometry of SN 2008bk also clearly demonstrates that the progenitor star has vanished.

  9. Implementation Issues for acoustic echo cancellers

    Berkeman, Anders; Öwall, Viktor; Torkelson, Mats

    1999-01-01

    The high computational complexity of acoustic echo cancellation algorithms requires application specific implementations to sustain real time signal processing with affordable power consumption. This is especially true for systems where a delayless approach is considered important, e.g. wireless communication systems. The proposed paper presents architectural considerations to reach a feasible hardware solution.

  10. Acoustic Echo Cancellation: Dual Architecture Implementation

    B. Stark

    2010-01-01

    Full Text Available Problem statement: With the rise in mobile communication, it is becoming more frequent to use a communication device in an enclosed noisy environment, such as a subway or in a lobby. In this setting however, the received microphone is severely degraded by the echo from the speaker and background noise. The audio processing necessary to clarify the desired speech can be broken down into two parts, removal of the acoustic echo and removal of the background noise. Approach: This study proposed an ‘external-switched’ algorithm of a dual architecture implementation for acoustic echo cancellation. Using the orthogonality property of adaptive algorithms to detect convergence, two complete adaptive filters can be run in parallel to take advantage of each filter’s particular configuration. By configuring one filter for fast adaptation and the second for minimizing the steady state error, a system can be designed with the advantages of both without suffering from increased computational cost. Results: A slight performance improvement can be demonstrated with this system; however the greatest advantage is in the reduced filter size and calculation cost. Conclusion: This parallel approach is suitable for systems in which a single approach to acoustic echo cancellation is insufficient. Disadvantages of one algorithm can be mitigated by being able to switch to a more effective algorithm seamlessly.

  11. Echo voltage reflected by turtle on various angles

    Sunardi Sunardi; Anton Yudhana; Azrul Mahfurdz; Sharipah Salwa Mohamed

    2015-01-01

    This research proposes the acoustic measurement by using echo sounder for green turtle detection of 1 year, 12 and 18 years. Various positions or angles of turtles are head, tail, shell, lung, left and right side. MATLAB software and echo sounder are used to analyse the frequency and the response of the turtle as echo voltage and target strength parameter. Based on the experiment and analysis have been conducted, the bigger size of the turtle, the higher echo voltage and target strength. The ...

  12. Preliminary Results of the Echo-Seeding Experiment ECHO-7 at SLAC

    Xiang, D.; Colby, E.; Ding, Y.; Dunning, M.; Frederico, J.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; /SLAC; Corlett, J.; Qiang, J.; Penn, G.; Prestemon, S.; /LBL, Berkeley /LPHE, Lausanne

    2010-06-15

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.

  13. Echo Cancellation II: Double Talk Detection and Environmental Noise Influence

    P. Sovka

    2000-04-01

    Full Text Available Two problems arising in the real-life application of echo cancellationsystems are analysed.The first, simultaneous activity of both telephoneusers (double talk deteriorates the echo suppression. The second,environmental noise is the crucial point in echo cancellation systemapplications. Experimental evaluation of the influence of bothphenomena is given together with possible solution.

  14. Vibration sensors

    These sensors, which aim is the surveillance of the fast breeder reactor internal structure, were designed considering the following requirements: - long term utilization under low frequencies conditions (1 to 50 Hz) and detection of accelerations lower than 0,01 g, - operation with a temperature up to 6000C and receiving important neutron and gamma flux. Monoaxial sensors with a liquid vibrating mass (sodium) were thus developed, based on the electromagnetic flow meter principles (Faraday effect)

  15. Microscopic imaging of slow flow and diffusion: a pulsed field gradient stimulated echo sequence combined with turbo spin echo imaging

    Scheenen, T.W.J.; Vergeldt, F.J.; Windt, C.W.; Jager, de P.A.; As, van H.

    2001-01-01

    In this paper we present a pulse sequence that combines a displacement-encoded stimulated echo with rapid sampling of k-space by means of turbo spin echo imaging. The stimulated echo enables the use of long observation times between the two pulsed field gradients that sample q-space completely. Prop

  16. Anharmonicities and coherent vibrational dynamics of phosphate ions in bulk H2O.

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P

    2015-11-28

    Phosphates feature prominently in the energetics of metabolism and are important solvation sites of DNA and phospholipids. Here we investigate the ion H2PO4(-) in aqueous solution combining 2D IR spectroscopy of phosphate stretching vibrations in the range from 900-1300 cm(-1) with ab initio calculations and hybrid quantum-classical molecular dynamics based simulations of the non-linear signal. While the line shapes of diagonal peaks reveal ultrafast frequency fluctuations on a sub-100 fs timescale caused by the fluctuating hydration shell, an analysis of the diagonal and cross-peak frequency positions allows for extracting inter-mode couplings and anharmonicities of 5-10 cm(-1). The excitation with spectrally broad pulses generates a coherent superposition of symmetric and asymmetric PO2(-) stretching modes resulting in the observation of a quantum beat in aqueous solution. We follow its time evolution through the time-dependent amplitude and the shape of the cross peaks. The results provide a complete characterization of the H2PO4(-) vibrational Hamiltonian including fluctuations induced by the native water environment. PMID:26488541

  17. Features of underwater echo extraction based on signal sparse decomposition

    YANG Bo; BU Yinyong; ZHAO Haiming

    2012-01-01

    In order to better realize sound echo recognition of underwater materials with heavily uneven surface, a features abstraction method based on the theory of signal sparse decomposition has been proposed. Instead of the common time frequency dictionary, sets of training echo samples are used directly as dictionary to realize echo sparse decomposition under L1 optimization and abstract a kind of energy features of the echo. Experiments on three kinds of bottom materials including the Cobalt Crust show that the Fisher distribution with this method is superior to that of edge features and of Singular Value Decomposition (SVD) features in wavelet domain. It means no doubt that much better classification result of underwater bottom materials can be obtained with the proposed energy features than the other two. It is concluded that echo samples used as a dictionary is feasible and the class information of echo introduced by this dictionary can help to obtain better echo features.

  18. Workshop on neutron spin-echo

    This document gathers the abstracts of most papers presented at the workshop. Neutron spin-echo (NSE) spectroscopy is a well established technique with a growing expert user community, the aim of the meeting was to discuss the latest achievements in neutron spin-echo science and instrumentation. One of the applications presented is the investigation on the microscopic scale of the dynamics of water in montmorillonite clays with Na+ and Cs+ ions in monolayer and bilayer states. The NSE technique has been used in the normal and resonance modes. NSE results show consistently slower dynamics (higher relaxation times) than both time-of-flight technique (TOF) and classical molecular dynamics simulations (MD). In the present TOF and NSE experiments, anisotropy of the water motion in the interlayer is almost impossible to detect, due to the use of powder samples and insufficient resolution. (A.C.)

  19. Workshop on neutron spin-echo

    Aynajian, P.; Habicht, K.; Keller, Th.; Keimer, B.; Mezei, F.; Monkenbusch, M.; Allgaier, J.; Richter, D.; Fetters, L.J.; Muller, K.; Kreiling, S.; Dehnicke, K.; Greiner, A.; Ehlers, G.; Arbe, A.; Colmenero, J.; Richter, D.; Farago, B.; Monkenbusch, M.; Ohl, M.; Butzek, M.; Kozielewski, T.; Monkenbusch, M.; Richter, D.; Pappas, C.; Hillier, A.; Manuel, P.; Cywinski, R.; Bentley, P.; Alba, M.; Mezei, F.; Campbell, I.A.; Zimmermann, U.; Ellis, J.; Jobic, H.; Pickup, R.M.; Pappas, C.; Farago, B.; Cywinski, R.; Haussler, W.; Holderer, O.; Frielinghaus, H.; Byelov, D.; Monkenbusch, M.; Allgaier, J.; Richter, D.; Egger, H.; Hellweg, Th.; Malikova, N.; Cadene, A.; Marry, V.; Dubois, E.; Turq, P.; Gardner, J.S.; Ehlers, G.; Bramwell, St.S.; Grigoriev, S.; Kraan, W.; Rekveldt, T.; Bouwman, W.; Van Dijk, N.; Falus, P.; Vorobiev, A.; Major, J.; Felcher, G.P.; Te-velthuis, S.; Dosch, H.; Vorobiev, A.; Dridi, M.H.; Major, J.; Dosch, H.; Falus, P.; Felcher, G.P.; Te Velthuis, S.G.E.; Bleuel, M.; Broell, M.; Lang, E.; Littrell, K.; Gahler, R.; Lal, J.; Lauter, H.; Toperverg, B.; Lauter, V.; Jernenkov, M.; Stueber, S.; Enderle, M.; Janoschek, M.; Keller, Th.; Klimko, S.; Boeni, P.; Nagao, M.; Yamada, N.; Kawabata, Y.; Seto, H.; Takeda, T.; Yoshizawa, H.; Yoshida, K.; Yamaguchi, T.; Bellissent-Funel, M.C.; Longeville, St

    2005-07-01

    This document gathers the abstracts of most papers presented at the workshop. Neutron spin-echo (NSE) spectroscopy is a well established technique with a growing expert user community, the aim of the meeting was to discuss the latest achievements in neutron spin-echo science and instrumentation. One of the applications presented is the investigation on the microscopic scale of the dynamics of water in montmorillonite clays with Na{sup +} and Cs{sup +} ions in monolayer and bilayer states. The NSE technique has been used in the normal and resonance modes. NSE results show consistently slower dynamics (higher relaxation times) than both time-of-flight technique (TOF) and classical molecular dynamics simulations (MD). In the present TOF and NSE experiments, anisotropy of the water motion in the interlayer is almost impossible to detect, due to the use of powder samples and insufficient resolution. (A.C.)

  20. Wind Shear Target Echo Modeling and Simulation

    Xiaoyang Liu

    2015-01-01

    Full Text Available Wind shear is a dangerous atmospheric phenomenon in aviation. Wind shear is defined as a sudden change of speed or direction of the wind. In order to analyze the influence of wind shear on the efficiency of the airplane, this paper proposes a mathematical model of point target rain echo and weather target signal echo based on Doppler effect. The wind field model is developed in this paper, and the antenna model is also studied by using Bessel function. The spectrum distribution of symmetric and asymmetric wind fields is researched by using the mathematical model proposed in this paper. The simulation results are in accordance with radial velocity component, and the simulation results also confirm the correctness of the established model of antenna.

  1. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul;

    2015-01-01

    as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest spectral resolving power is needed, with...... systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric...... composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for...

  2. Echoes of Sophocles's Antigone in Auster's Invisible

    Waller, Kathleen

    2011-01-01

    In her article "Echoes of Sophocles's Antigone in Auster's Invisible" Kathleen Waller discusses Paul Auster's Invisible, a novel that explores Deleuze's and Guattari's ontological idea of becoming in a virtual world versus merely living in the actual, physical world. Sexual and immortal desires in the protagonist's virtual world show a near achieved nothingness, or "a space which is unlimited" and filled with the being's energy, and a being who is becoming, a "univocal being" as a "free spiri...

  3. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Gear, W.; Gesa, L; Giani, E.; Gianotti, F

    2015-01-01

    The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has b...

  4. GESTATIONAL ECHO BIOMETRY IN BRACHYCEPHALIC PREGNANT BITCHES

    Marcus Antônio Rossi Feliciano

    2015-07-01

    Full Text Available Ultrasonography is an accurate pregnancy diagnostic method, besides being completely innocuous for female and fetuses evaluation. The objective of this paper was to determine the reference values for gestational echo biometry of different breeds of bitches. A total of 25 multiparous females were included in the experiment, five English Bulldog bitches, five Pugs and 15 Shih Tzu, weighing 4-25 kg and aged 4-6 years. The echo biometric assessments were performed during the 2nd, 5th, 6th, 7th and 8th weeks of pregnancy, including gestational vesicle diameter, femur length, placenta thickness, parietal diameter, liver, heart and abdominal diameter and area. Early echo biometric study started at the second week of gestation. Measurements like fetal heart and liver diameter and area are still poorly studied, but can provide useful information for early detection of congenital anomalies that may reduce the viability of pregnancy. The significant results (P < 0.001 obtained for biometrics (P < 0.001 of the parietal (r2 = 81% and abdominal diameter (r2 = 86%, abdominal area (r2 = 80%, femur length (r2 = 84%, cardiac length (r2 = 79%, width (r2 = 79%, area (r2 = 82% and volume (r2 = 72% and liver area (r2 = 71% in brachycephalic conceptus may help to assess the development of fetuses, complementing the conventional gestational ultrasound of bitches and become a model for the study in other breeds of dogs and alternative animal species.

  5. Single-shot echo-planar imaging of multiple sclerosis: effects of varying echo time

    Our aim was to determine the relative merits of short and long echo times (TE) with single-shot echo-planar imaging for imaging cerebral lesions such as multiple sclerosis. We examined seven patients with clinically definite multiple sclerosis were imaged at 1.5 T. Patients were scanned with spin-echo, single-shot echo-planar imaging, using TEs of 45, 75, 105, and 135 ms. Region of interest (ROI) measurements were performed on 36 lesions at or above the level of the corona radiata. The mean image contrast (IC) was highest (231.1) for a TE of 45 ms, followed by 75 ms (218.9), 105 ms (217.9), and 135 ms (191.6). When mean contrast-to-noise ratios (C/N) were compared, the value was again highest (29.7) for TE 45 ms, followed by 75 ms (28.9), 105 ms (28.5), and 135 ms (26.3). In a lesion-by-lesion comparison, TE 45 ms had the highest IC and C/N in the largest number of cases (50 % and 47.2 %, respectively). IC and C/N for TE 45 ms were superior to those of 75 ms in 64 % and 58 %, respectively. These results support the use of relatively short TEs for single-shot echo-planar imaging in the setting of cerebral lesions such as multiple sclerosis. (orig.) (orig.)

  6. Temperature sheets and aspect sensitive radar echoes

    H. Luce

    Full Text Available here have been years of discussion and controversy about the existence of very thin and stable temperature sheets and their relationship to the VHF radar aspect sensitivity. It is only recently that very high-resolution in situ temperature observations have brought credence to the reality and ubiquity of these structures in the free atmosphere and to their contribution to radar echo enhancements along the vertical. Indeed, measurements with very high-resolution sensors are still extremely rare and rather difficult to obtain outside of the planetary boundary layer. They have only been carried out up to the lower stratosphere by Service d’A´ eronomie (CNRS, France for about 10 years. The controversy also persisted due to the volume resolution of the (Mesosphere-Stratosphere-Troposphere VHF radars which is coarse with respect to sheet thickness, although widely sufficient for meteorological or mesoscale investigations. The contribution within the range gate of many of these structures, which are advected by the wind, and decay and grow at different instants and could be distorted either by internal gravity waves or turbulence fields, could lead to radar echoes with statistical properties similar to those produced by anisotropic turbulence. Some questions thus remain regarding the manner in which temperature sheets contribute to VHF radar echoes. In particular, the zenithal and azimuthal angular dependence of the echo power may not only be produced by diffuse reflection on stable distorted or corrugated sheets, but also by extra contributions from anisotropic turbulence occurring in the stratified atmosphere. Thus, for several years, efforts have been put forth to improve the radar height resolution in order to better describe thin structures. Frequency interferometric techniques are widely used and have been recently further developed with the implementation of high-resolution data processings. We begin by reviewing briefly some characteristics

  7. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa; Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo; Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.; Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala, J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.; Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado, D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés, J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.; Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave, L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria, M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli, R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen, N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.; Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.; Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio, A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.; Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet, V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira, P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López, R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J.-C.; Gesa, L.; Giani, E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.; Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk, R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh, J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant, F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.; Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont, K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.; Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch, E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu, S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas, M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.; Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J.-P.; Magnes, W.; Maldonado, J.; Mall, U.; Marquette, J.-B.; Mauskopf, P.; Massi, F.; Maurin, A.-S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto, M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.; Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín, A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton, G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen, H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.; Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja, R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos, A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López, R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.; Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos, N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F.-X.; Scholz, A.; Scuderi, S.; Sethenadh, J.; Shore, S.; Showman, A.; Sicardy, B.; Sitek, P.; Smith, A.; Soret, L.; Sousa, S.; Stiepen, A.; Stolarski, M.; Strazzulla, G.; Tabernero, H. M.; Tanga, P.; Tecsa, M.; Temple, J.; Terenzi, L.; Tessenyi, M.; Testi, L.; Thompson, S.; Thrastarson, H.; Tingley, B. W.; Trifoglio, M.; Martín Torres, J.; Tozzi, A.; Turrini, D.; Varley, R.; Vakili, F.; de Val-Borro, M.; Valdivieso, M. L.; Venot, O.; Villaver, E.; Vinatier, S.; Viti, S.; Waldmann, I.; Waltham, D.; Ward-Thompson, D.; Waters, R.; Watkins, C.; Watson, D.; Wawer, P.; Wawrzaszk, A.; White, G.; Widemann, T.; Winek, W.; Wiśniowski, T.; Yelle, R.; Yung, Y.; Yurchenko, S. N.

    2015-12-01

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength

  8. EChO. Exoplanet characterisation observatory

    Tinetti, G.; Beaulieu, J. P.; Henning, T.; Meyer, M.; Micela, G.; Ribas, I.; Stam, D.; Swain, M.; Krause, O.; Ollivier, M.; Pace, E.; Swinyard, B.; Aylward, A.; van Boekel, R.; Coradini, A.; Encrenaz, T.; Snellen, I.; Zapatero-Osorio, M. R.; Bouwman, J.; Cho, J. Y.-K.; Coudé de Foresto, V.; Guillot, T.; Lopez-Morales, M.; Mueller-Wodarg, I.; Palle, E.; Selsis, F.; Sozzetti, A.; Ade, P. A. R.; Achilleos, N.; Adriani, A.; Agnor, C. B.; Afonso, C.; Allende Prieto, C.; Bakos, G.; Barber, R. J.; Barlow, M.; Batista, V.; Bernath, P.; Bézard, B.; Bordé, P.; Brown, L. R.; Cassan, A.; Cavarroc, C.; Ciaravella, A.; Cockell, C.; Coustenis, A.; Danielski, C.; Decin, L.; De Kok, R.; Demangeon, O.; Deroo, P.; Doel, P.; Drossart, P.; Fletcher, L. N.; Focardi, M.; Forget, F.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gaulme, P.; Hernández, J. I. González; Grasset, O.; Grassi, D.; Grenfell, J. L.; Griffin, M. J.; Griffith, C. A.; Grözinger, U.; Guedel, M.; Guio, P.; Hainaut, O.; Hargreaves, R.; Hauschildt, P. H.; Heng, K.; Heyrovsky, D.; Hueso, R.; Irwin, P.; Kaltenegger, L.; Kervella, P.; Kipping, D.; Koskinen, T. T.; Kovács, G.; La Barbera, A.; Lammer, H.; Lellouch, E.; Leto, G.; Lopez Morales, M.; Lopez Valverde, M. A.; Lopez-Puertas, M.; Lovis, C.; Maggio, A.; Maillard, J. P.; Maldonado Prado, J.; Marquette, J. B.; Martin-Torres, F. J.; Maxted, P.; Miller, S.; Molinari, S.; Montes, D.; Moro-Martin, A.; Moses, J. I.; Mousis, O.; Nguyen Tuong, N.; Nelson, R.; Orton, G. S.; Pantin, E.; Pascale, E.; Pezzuto, S.; Pinfield, D.; Poretti, E.; Prinja, R.; Prisinzano, L.; Rees, J. M.; Reiners, A.; Samuel, B.; Sánchez-Lavega, A.; Forcada, J. Sanz; Sasselov, D.; Savini, G.; Sicardy, B.; Smith, A.; Stixrude, L.; Strazzulla, G.; Tennyson, J.; Tessenyi, M.; Vasisht, G.; Vinatier, S.; Viti, S.; Waldmann, I.; White, G. J.; Widemann, T.; Wordsworth, R.; Yelle, R.; Yung, Y.; Yurchenko, S. N.

    2012-10-01

    A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO—the Exoplanet Characterisation Observatory—is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. The use of passive cooling, few moving parts and well established technology gives a low-risk and potentially long-lived mission. EChO will build on observations by Hubble, Spitzer and ground-based telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. However, EChO's configuration and specifications are designed to study a number of systems in a consistent manner that will eliminate the ambiguities affecting prior observations. EChO will simultaneously observe a broad enough spectral region—from the visible to the mid-infrared—to constrain from one single spectrum the temperature structure of the atmosphere, the abundances of the major carbon and oxygen bearing species, the expected photochemically-produced species and magnetospheric signatures. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules and retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures T eq up to 2,000 K, to those of a few Earth masses, with T eq u223c 300 K. The list will include planets with no Solar System analog, such as the recently discovered planets GJ1214b, whose density lies between that of terrestrial and gaseous planets, or the rocky-iron planet 55 Cnc e, with day-side temperature close to 3,000 K. As the number of detected exoplanets is growing rapidly each year, and the mass and radius of those

  9. Vibration syndrome and vibration in pedestal grinding.

    Starck, J; Färkkilä, M; Aatola, S; Pyykkö, I; Korhonen, O.

    1983-01-01

    At one Finnish foundry all the workers had typical symptoms of vibration induced white finger (VWF) after they began using a new type of pedestal grinding machine. The objectives of this study were to establish the severity of the symptoms and the difference in vibration exposure between the new and the old machines. Vibration detection thresholds and grip forces were measured, as well as the vibration in the casting and in the wrist simultaneously. The mean latency for VWF among the grinders...

  10. Echo Cancellation Research of Channel Estimation based on PN Sequence

    Yongqin Zhou

    2010-11-01

    Full Text Available For the problem of estimation sequence effect on channel estimation accuracy and echo cancellation effect, this paper, based on the basic principle of echo cancellation, analyses the effect of PN sequence mechanism and the correlation on the channel estimation parameters. Comparing with using the input signal itself as the estimation sequence. With the input signal OFDM, the results of simulation and actual operation show that the method can increase both the accuracy of channel estimation and echo cancellation effect effectively.

  11. Theory of vibration protection

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  12. Decoherence and Spin Echo in Biological Systems

    Nesterov, Alexander I

    2015-01-01

    The spin echo approach is extended to include bio-complexes for which the interaction with dynamical noise is strong. Significant restoration of the free induction decay signal due to homogeneous (decoherence) and inhomogeneous (dephasing) broadening is demonstrated analytically and numerically, for both an individual dimer of interacting chlorophylls and for an ensemble of dimers. This approach is based on an exact and closed system of ordinary differential equations that can be easily solved for a wide range of parameters that are relevant for bio-applications.

  13. Preprocessing of ionospheric echo Doppler spectra

    FANG Liang; ZHAO Zhengyu; WANG Feng; SU Fanfan

    2007-01-01

    The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system(WIOBSS),which adopts a discontinuous wave mechanism.After the characteristics of the ionospheric echo Doppler spectra were analyzed,the signal preprocessing was developed in this paper,which aimed at improving the Doppler spectra.The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6-7 dB.

  14. Nuclear spin echo model based on Floquet-Lyapunov theory

    The method of nuclear spin-echo amplitude calculation based on the density matrix technique is improved. The Floquet-Lyapunov theorem for a system of the ordinary differential equations with coefficients periodically dependent on time is used to find the solution of the Schroedinger equation for the time-evolution operator which describes behavior of a nuclear spin in the presence of a radiofrequency pulsed magnetic field. NQR spin echo for the case of nuclear spin I = 1 and NMR spin echo for I = 1/2 are considered as the simplest illustrations of the approach. The appearance of multiple spin echoes is predicted in the case of strong radiofrequency field.

  15. The EChO science case

    Tinetti, Giovanna; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Allard, Bruce Swinyard France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Beaulieu, Mariarosa Zapatero-Osorio Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Banaszkiewicz, Mark Swain Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; Foresto, Vincent Coudé du; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Adriani, Gonzalo Ramos Zapata Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Abe, Berend Winter L; Abreu, M; Achilleos, N; Ade, P; Adybekian, V; Affer, L; Agnor, C; Agundez, M; Alard, C; Alcala, J; Prieto, C Allende; Floriano, F J Alonso; Altieri, F; Iglesias, C A Alvarez; Amado, P; Andersen, A; Aylward, A; Baffa, C; Bakos, G; Ballerini, P; Banaszkiewicz, M; Barber, R J; Barrado, D; Barton, E J; Batista, V; Bellucci, G; Avilés, J A Belmonte; Berry, D; Bézard, B; Biondi, D; Błęcka, M; Boisse, I; Bonfond, B; Bordé, P; Börner, P; Bouy, H; Brown, L; Buchhave, L; Budaj, J; Bulgarelli, A; Burleigh, M; Cabral, A; Capria, M T; Cassan, A; Cavarroc, C; Cecchi-Pestellini, C; Cerulli, R; Chadney, J; Chamberlain, S; Charnoz, S; Jessen, N Christian; Ciaravella, A; Claret, A; Claudi, R; Coates, A; Cole, R; Collura, A; Cordier, D; Covino, E; Danielski, C; Damasso, M; Deeg, H J; Delgado-Mena, E; Del Vecchio, C; Demangeon, O; De Sio, A; De Wit, J; Dobrijévic, M; Doel, P; Dominic, C; Dorfi, E; Eales, S; Eiroa, C; Contreras, M Espinoza; Esposito, M; Eymet, V; Fabrizio, N; Fernández, M; Castella, B Femenía; Figueira, P; Filacchione, G; Fletcher, L; Focardi, M; Fossey, S; Fouqué, P; Frith, J; Galand, M; Gambicorti, L; Gaulme, P; López, R J García; Garcia-Piquer, A; Gear, W; Gerard, J -C; Gesa, L; Giani, E; Gianotti, F; Gillon, M; Giro, E; Giuranna, M; Gomez, H; Gomez-Leal, I; Hernandez, J Gonzalez; Merino, B González; Graczyk, R; Grassi, D; Guardia, J; Guio, P; Gustin, J; Hargrave, P; Haigh, J; Hébrard, E; Heiter, U; Heredero, R L; Herrero, E; Hersant, F; Heyrovsky, D; Hollis, M; Hubert, B; Hueso, R; Israelian, G; Iro, N; Irwin, P; Jacquemoud, S; Jones, G; Jones, H; Justtanont, K; Kehoe, T; Kerschbaum, F; Kerins, E; Kervella, P; Kipping, D; Koskinen, T; Krupp, N; Lahav, O; Laken, B; Lanza, N; Lellouch, E; Leto, G; Goldaracena, J Licandro; Lithgow-Bertelloni, C; Liu, S J; Cicero, U Lo; Lodieu, N; Lognonné, P; Lopez-Puertas, M; Lopez-Valverde, M A; Rasmussen, I Lundgaard; Luntzer, A; Machado, P; MacTavish, C; Maggio, A; Maillard, J -P; Magnes, W; Maldonado, J; Mall, U; Marquette, J -B; Mauskopf, P; Massi, F; Maurin, A -S; Medvedev, A; Michaut, C; Miles-Paez, P; Montalto, M; Rodríguez, P Montañés; Monteiro, M; Montes, D; Morais, H; Morales, J C; Morales-Calderón, M; Morello, G; Martín, A Moro; Moses, J; Bedon, A Moya; Alcaino, F Murgas; Oliva, E; Orton, G; Palla, F; Pancrazzi, M; Pantin, E; Parmentier, V; Parviainen, H; Ramírez, K Y Peña; Peralta, J; Perez-Hoyos, S; Petrov, R; Pezzuto, S; Pietrzak, R; Pilat-Lohinger, E; Piskunov, N; Prinja, R; Prisinzano, L; Polichtchouk, I; Poretti, E; Radioti, A; Ramos, A A; Rank-Lüftinger, T; Read, P; Readorn, K; López, R Rebolo; Rebordão, J; Rengel, M; Rezac, L; Rocchetto, M; Rodler, F; Béjar, V J Sánchez; Lavega, A Sanchez; Sanromá, E; Santos, N; Forcada, J Sanz; Scandariato, G; Schmider, F -X; Scholz, A; Scuderi, S; Sethenadh, J; Shore, S; Showman, A; Sicardy, B; Sitek, P; Smith, A; Soret, L; Sousa, S; Stiepen, A; Stolarski, M; Strazzulla, G; Tabernero, H M; Tanga, P; Tecsa, M; Temple, J; Terenzi, L; Tessenyi, M; Testi, L; Thompson, S; Thrastarson, H; Tingley, B W; Trifoglio, M; Torres, J Martín

    2015-01-01

    The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on find...

  16. Performance Analysis of Acoustic Echo Cancellation Techniques

    Rajeshwar Dass

    2014-07-01

    Full Text Available Mainly, the adaptive filters are implemented in time domain which works efficiently in most of the applications. But in many applications the impulse response becomes too large, which increases the complexity of the adaptive filter beyond a level where it can no longer be implemented efficiently in time domain. An example of where this can happen would be acoustic echo cancellation (AEC applications. So, there exists an alternative solution i.e. to implement the filters in frequency domain. AEC has so many applications in wide variety of problems in industrial operations, manufacturing and consumer products. Here in this paper, a comparative analysis of different acoustic echo cancellation techniques i.e. Frequency domain adaptive filter (FDAF, Least mean square (LMS, Normalized least mean square (NLMS &Sign error (SE is presented. The results are compared with different values of step sizes and the performance of these techniques is measured in terms of Error rate loss enhancement (ERLE, Mean square error (MSE& Peak signal to noise ratio (PSNR.

  17. Vibration of machine

    This book deals with vibration of machine which gives descriptions of free vibration using SDOF system, forced vibration using SDOF system, vibration of multi-degree of freedom system like introduction and normal form, distribution system such as introduction, free vibration of bar and practice problem, approximate solution like lumped approximations and Raleigh's quotient, engineering by intuition and experience, real problem and experimental method such as technology of signal, fourier transform analysis, frequency analysis and sensor and actuator.

  18. The EChO science case

    Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa; Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo; Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.; Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala, J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.; Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado, D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés, J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.; Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave, L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria, M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli, R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen, N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.; Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.; Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio, A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.; Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet, V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira, P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López, R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J.-C.; Gesa, L.; Giani, E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.; Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk, R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh, J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant, F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.; Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont, K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.; Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch, E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu, S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas, M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.; Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J.-P.; Magnes, W.; Maldonado, J.; Mall, U.; Marquette, J.-B.; Mauskopf, P.; Massi, F.; Maurin, A.-S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto, M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.; Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín, A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton, G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen, H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.; Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja, R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos, A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López, R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.; Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos, N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F.-X.; Scholz, A.; Scuderi, S.

    2015-12-01

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength

  19. Coherent Optical Information Processing Using a Stimulated Echo Hologram

    Garnaeva, G. I.; Nefediev, L. A.; Sahbieva, A. R.

    2016-01-01

    We consider information recording and reconstruction using a reversed stimulated echo hologram, when the recording medium is exposed to pulses of nonresonant electromagnetic standing waves. We show that the spatial intensity distribution in the stimulated echo hologram response depends on the strength of the electric fields in the nonresonant standing waves, which makes it possible to control the reconstructed image.

  20. Long-lasting inverted photon echo and optical memory

    Akhmediev, N.N.; Borisov, B.S.; Zuikov, V.A.; Samartsev, V.V.; Stel' makh, M.F.

    1988-06-01

    Experimental results are presented on the formation of the long-lasting inverted stimulated photon echo in the LaF3:Pr(3+) crystal. The physics of this phenomenon is explained on the basis of a three-level model. The feasibility of using this echo effect in the development of optical-memory systems is considered. 18 references.

  1. ECHOS: Early Childhood Hands-On Science Efficacy Study

    Brown, Judy A.; Greenfield, Daryl B.; Bell, Elizabeth; Juárez, Cheryl Lani; Myers, Ted; Nayfeld, Irena

    2013-01-01

    "ECHOS: Early Childhood Hands-On Science" was developed at the Miami Science Museum as a comprehensive set of science lessons sequenced to lead children toward a deeper understanding of science content and the use of science process skills. The purpose of the research is to determine whether use of the "ECHOS" model will…

  2. Echo Shaping Using Sums of Damped Complex Sinusoids

    Putnam, Lance Jonathan

    2015-01-01

    Feedback delay lines are the basis of myriad audio effects and reverberation schemes. The feedback delay line, by itself, is limited to producing an infinite sequence of exponentially decaying echoes. We introduce a new type of linear time-invariant echo effect whose impulse response is a...

  3. Myocardial contractility in the stress echo lab: from pathophysiological toy to clinical tool.

    Bombardini, Tonino; Zoppè, Monica; Ciampi, Quirino; Cortigiani, Lauro; Agricola, Eustachio; Salvadori, Stefano; Loni, Tiziana; Pratali, Lorenza; Picano, Eugenio

    2013-01-01

    vibration amplitude. We demonstrated that the sensor-derived force changes at increasing heart rates are highly related with both max dP/dt in animal models, and with the stress echo FFR in 220 humans, opening a new window for pervasive cardiac heart failure monitoring in telemedicine systems. PMID:24246005

  4. Revival of Silenced Echo and Quantum Memory for Light

    Damon, V; Louchet-Chauvet, A; Chanelière, T; Gouët, J -L Le

    2011-01-01

    We propose an original quantum memory protocol. It belongs to the class of rephasing processes and is closely related to two-pulse photon echo. It is known that the strong population inversion produced by the rephasing pulse prevents the plain two-pulse photon echo from serving as a quantum memory scheme. Indeed gain and spontaneous emission generate prohibitive noise. A second $\\pi$-pulse can be used to simultaneously reverse the atomic phase and bring the atoms back into the ground state. Then a secondary echo is radiated from a non-inverted medium, avoiding contamination by gain and spontaneous emission noise. However, one must kill the primary echo, in order to preserve all the information for the secondary signal. In the present work, spatial phase mismatching is used to silence the standard two-pulse echo. An experimental demonstration is presented.

  5. Light echoes from ancient supernovae in the Large Magellanic Cloud.

    Rest, Armin; Suntzeff, Nicholas B; Olsen, Knut; Prieto, Jose Luis; Smith, R Chris; Welch, Douglas L; Becker, Andrew; Bergmann, Marcel; Clocchiatti, Alejandro; Cook, Kem; Garg, Arti; Huber, Mark; Miknaitis, Gajus; Minniti, Dante; Nikolaev, Sergei; Stubbs, Christopher

    2005-12-22

    The light from historical supernovae could in principle still be visible as scattered-light echoes centuries after the explosion. The detection of light echoes could allow us to pinpoint the supernova event both in position and age and, most importantly, permit the acquisition of spectra to determine the 'type' of the supernova centuries after the direct light from the explosion first reached Earth. Although echoes have been discovered around some nearby extragalactic supernovae, targeted searches have not found any echoes in the regions of historical Galactic supernovae. Here we report three faint variable-surface-brightness complexes with high apparent proper motions pointing back to three of the six smallest (and probably youngest) previously catalogued supernova remnants in the Large Magellanic Cloud, which are believed to have been thermonuclear (type Ia) supernovae. Using the distance and apparent proper motions of these echo arcs, we estimate ages of 610 and 410 years for two of them. PMID:16372003

  6. The Electron Capture $^{163}$Ho Experiment ECHo

    Blaum, K; Duellmann, C E; Eberhardt, K; Eliseev, S; Enss, C; Faessler, A; Fleischmann, A; Gastaldo, L; Kempf, S; Krivoruchenko, M; Lahiri, S; Maiti, M; Novikov, Yu N; Ranitzsch, P C -O; Simkovic, F; Szusc, Z; Wegner, M

    2013-01-01

    The determination of the absolute scale of the neutrino masses is one of the most challenging questions in particle physics. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay and electron capture processes of suitable nuclides can provide necessary information on the electron neutrino mass value. In this talk we present the Electron Capture 163-Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of 163-Ho. A high precision and high statistics spectrum will be measured by means of low temperature magnetic calorimeter arrays. We present preliminary results obtained with a first prototype of single channel detectors as well as the participating groups and their on-going developments.

  7. Spin Echo Studies on Cellular Water

    Chang, D C; Nichols, B L; Rorschach, H E

    2014-01-01

    Previous studies indicated that the physical state of cellular water could be significantly different from pure liquid water. To experimentally investigate this possibility, we conducted a series of spin-echo NMR measurements on water protons in rat skeletal muscle. Our result indicated that the spin-lattice relaxation time and the spin-spin relaxation time of cellular water protons are both significantly shorter than that of pure water (by 4.3-fold and 34-fold, respectively). Furthermore, the spin diffusion coefficient of water proton is almost 1/2 of that of pure water. These data suggest that cellular water is in a more ordered state in comparison to pure water.

  8. Dual-rail optical gradient echo memory

    Higginbottom, Daniel B; Campbell, Geoff T; Hosseini, Mahdi; Cao, Ming Tao; Sparkes, Ben M; Bernu, Julian; Robins, Nick P; Lam, Ping Koy; Buchler, Ben C

    2016-01-01

    We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6 degrees phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration.

  9. Echo chambers in the age of misinformation

    Del Vicario, Michela; Zollo, Fabiana; Petroni, Fabio; Scala, Antonio; Caldarelli, Guido; Stanley, H Eugene; Quattrociocchi, Walter

    2015-01-01

    The wide availability of user-provided content in online social media facilitates the aggregation of people around common interests, worldviews, and narratives. Despite the enthusiastic rhetoric on the part of some that this process generates "collective intelligence", the WWW also allows the rapid dissemination of unsubstantiated conspiracy theories that often elicite rapid, large, but naive social responses such as the recent case of Jade Helm 15 -- where a simple military exercise turned out to be perceived as the beginning of the civil war in the US. We study how Facebook users consume information related to two different kinds of narrative: scientific and conspiracy news. We find that although consumers of scientific and conspiracy stories present similar consumption patterns with respect to content, the sizes of the spreading cascades differ. Homogeneity appears to be the primary driver for the diffusion of contents, but each echo chamber has its own cascade dynamics. To mimic these dynamics, we introdu...

  10. MR cisternography using 'long echo train length fast spin echo sequence' for demonstrating the inner ear

    Excellent quality of MR cisternography was acquired using 'long echo train length fast spin echo sequence' (TR/TE=2666/200, ETL=24.6 or 8 NEX, 3 mm thickness, 0 mm interslice gap, 19 cm FOV, 512*384, 2 DFT method). The inner ear anatomy such as canaliculus cochleae or lamina spiralis ossea were well visualized. The VII, VIIIth nerve bundles within the internal auditory canal were detectable as 1 to 4 bundles. The vessels in the cerebello-pontine angle or the internal auditory canal were also demarcated from the VII, VIIIth nerve bundles because of their flow void. Signal to noise ratio seemed to be better than 3 DFT method; however, limited spatial resolution in the cranio-caudal direction might require additional sagittal or coronal scan. (author)

  11. Recent Results for the ECHo Experiment

    Hassel, C.; Blaum, K.; Goodacre, T. Day; Dorrer, H.; Düllmann, Ch. E.; Eberhardt, K.; Eliseev, S.; Enss, C.; Filianin, P.; Fäßler, A.; Fleischmann, A.; Gastaldo, L.; Goncharov, M.; Hengstler, D.; Jochum, J.; Johnston, K.; Keller, M.; Kempf, S.; Kieck, T.; Köster, U.; Krantz, M.; Marsh, B.; Mokry, C.; Novikov, Yu. N.; Ranitzsch, P. C. O.; Rothe, S.; Rischka, A.; Runke, J.; Saenz, A.; Schneider, F.; Scholl, S.; Schüssler, R. X.; Simkovic, F.; Stora, T.; Thörle-Pospiech, P.; Türler, A.; Veinhard, M.; Wegner, M.; Wendt, K.; Zuber, K.

    2016-08-01

    The Electron Capture in ^{163}Ho experiment, ECHo, is designed to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured spectrum following the electron capture (EC) in ^{163}Ho. Arrays of low-temperature metallic magnetic calorimeters (MMCs), read-out by microwave SQUID multiplexing, will be used in this experiment. With a first MMC prototype having the ^{163}Ho source ion-implanted into the absorber, we performed the first high energy resolution measurement of the EC spectrum, which demonstrated the feasibility of such an experiment. In addition to the technological challenges for the development of MMC arrays, which preserve the single pixel performance in terms of energy resolution and bandwidth, the success of the experiment relies on the availability of large ultra-pure ^{163}Ho samples, on the precise description of the expected spectrum, and on the identification and reduction of background. We present preliminary results obtained with standard MMCs developed for soft X-ray spectroscopy, maXs-20, where the ^{163}Ho ion-implantation was performed using a high-purity ^{163}Ho source produced by advanced chemical and mass separation. With these measurements, we aim at determining an upper limit for the background level due to source contamination and provide a refined description of the calorimetrically measured spectrum. We discuss the plan for a medium scale experiment, ECHo-1k, in which about 1000 mathrm {Bq} of high-purity ^{163}Ho will be ion-implanted into detector arrays. With one year of measuring time, we will be able to achieve a sensitivity on the electron neutrino mass below 20 eV/c^2 (90 % C.L.), improving the present limit by more than one order of magnitude. This experiment will guide the necessary developments to reach the sub-eV sensitivity.

  12. Recent Results for the ECHo Experiment

    Hassel, C.; Blaum, K.; Goodacre, T. Day; Dorrer, H.; Düllmann, Ch. E.; Eberhardt, K.; Eliseev, S.; Enss, C.; Filianin, P.; Fäßler, A.; Fleischmann, A.; Gastaldo, L.; Goncharov, M.; Hengstler, D.; Jochum, J.; Johnston, K.; Keller, M.; Kempf, S.; Kieck, T.; Köster, U.; Krantz, M.; Marsh, B.; Mokry, C.; Novikov, Yu. N.; Ranitzsch, P. C. O.; Rothe, S.; Rischka, A.; Runke, J.; Saenz, A.; Schneider, F.; Scholl, S.; Schüssler, R. X.; Simkovic, F.; Stora, T.; Thörle-Pospiech, P.; Türler, A.; Veinhard, M.; Wegner, M.; Wendt, K.; Zuber, K.

    2016-02-01

    The Electron Capture in ^{163} Ho experiment, ECHo, is designed to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured spectrum following the electron capture (EC) in ^{163} Ho. Arrays of low-temperature metallic magnetic calorimeters (MMCs), read-out by microwave SQUID multiplexing, will be used in this experiment. With a first MMC prototype having the ^{163} Ho source ion-implanted into the absorber, we performed the first high energy resolution measurement of the EC spectrum, which demonstrated the feasibility of such an experiment. In addition to the technological challenges for the development of MMC arrays, which preserve the single pixel performance in terms of energy resolution and bandwidth, the success of the experiment relies on the availability of large ultra-pure ^{163} Ho samples, on the precise description of the expected spectrum, and on the identification and reduction of background. We present preliminary results obtained with standard MMCs developed for soft X-ray spectroscopy, maXs-20, where the ^{163} Ho ion-implantation was performed using a high-purity ^{163} Ho source produced by advanced chemical and mass separation. With these measurements, we aim at determining an upper limit for the background level due to source contamination and provide a refined description of the calorimetrically measured spectrum. We discuss the plan for a medium scale experiment, ECHo-1k, in which about 1000 Bq of high-purity ^{163} Ho will be ion-implanted into detector arrays. With one year of measuring time, we will be able to achieve a sensitivity on the electron neutrino mass below 20 eV/c^2 (90 % C.L.), improving the present limit by more than one order of magnitude. This experiment will guide the necessary developments to reach the sub-eV sensitivity.

  13. Resting state BOLD functional connectivity at 3T: spin echo versus gradient echo EPI.

    Piero Chiacchiaretta

    Full Text Available Previous evidence showed that, due to refocusing of static dephasing effects around large vessels, spin-echo (SE BOLD signals offer an increased linearity and promptness with respect to gradient-echo (GE acquisition, even at low field. These characteristics suggest that, despite the reduced sensitivity, SE fMRI might also provide a potential benefit when investigating spontaneous fluctuations of brain activity. However, there are no reports on the application of spin-echo fMRI for connectivity studies at low field. In this study we compared resting state functional connectivity as measured with GE and SE EPI sequences at 3T. Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies. Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences. Furthermore, the SE method performed better in the ventral portion of the default mode network, a region affected by signal dropout in standard GE acquisition. Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue.

  14. Do triatomic molecules echo atomic periodicity?

    Hefferlin, R., E-mail: hefferln@southern.edu; Barrow, J. [Southern Adventist University, PO Box 370, Collegedale, Tennessee 37315 (United States)

    2015-03-30

    Demonstrations of periodicity among triatomic-molecular spectroscopic constants underscore the role of the periodic law as a foundation of chemistry. The objective of this work is to prepare for another test using vibration frequencies ν{sub 1} of free, ground-state, main-group triatomic molecules. Using data from four data bases and from computation, we have collected ν{sub 1} data for molecules formed from second period atoms.

  15. Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase

    Lu, Jian; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A

    2016-01-01

    Ultrafast two-dimensional spectroscopy utilizes correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum. Its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. Here we report ultrafast two-dimensional terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by three terahertz field-dipole interactions. The nonlinear time-domain orientation signals are mapped into the frequency domain in two-dimensional rotational spectra which reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

  16. Prognostic for hydraulic pump based upon DCT-composite spectrum and the modified echo state network.

    Sun, Jian; Li, Hongru; Xu, Baohua

    2016-01-01

    Prognostic is a key step of the condition-based maintenance (CBM). In order to improve the predicting performance, a novel method for prognostic for the hydraulic pump is proposed in this paper. Based on the improvement of the traditional composite spectrum, the DCT-composite spectrum (DCS) fusion algorithm is initially presented to make fusion of multi-channel vibration signals. The DCS composite spectrum entropy is extracted as the feature. Furthermore, the modified echo state networks (ESN) model is established for prognostic using the extracted feature. The reservoir is updated and the elements of the neighboring matrix are redefined for improving predicting accuracy. Analysis of the application in the hydraulic pump degradation experiment demonstrates that the proposed algorithm is feasible and is meaningful for CBM. PMID:27547667

  17. Vibrations and Stability

    Thomsen, Jon Juel

    About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... and physics. This edition includes a new chapter on the useful effects of fast vibrations and many new exercise problems. Written for: Students in mechanical or structural engineering. Keywords: Nonlinear Vibrations, Bifurcations, Chaotic Vibrations, Vibrations and Stability....

  18. A comparison of multi-echo spin-echo and triple-echo steady-state T2 mapping for in vivo evaluation of articular cartilage

    Juras, Vladimir; Szomolanyi, Pavol [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Institute of Measurement Science, Department of Imaging Methods, Bratislava (Slovakia); Bohndorf, Klaus; Kronnerwetter, Claudia; Hager, Benedikt; Zbyn, Stefan [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Heule, Rahel; Bieri, Oliver [University of Basel Hospital, Division of Radiological Physics, Department of Radiology, Basel (Switzerland); Trattnig, Siegfried [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Vienna (Austria); Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna (Austria); Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Austrian Cluster for Tissue Regeneration, Vienna (Austria)

    2016-06-15

    To assess the clinical relevance of T{sub 2} relaxation times, measured by 3D triple-echo steady-state (3D-TESS), in knee articular cartilage compared to conventional multi-echo spin-echo T{sub 2}-mapping. Thirteen volunteers and ten patients with focal cartilage lesions were included in this prospective study. All subjects underwent 3-Tesla MRI consisting of a multi-echo multi-slice spin-echo sequence (CPMG) as a reference method for T{sub 2} mapping, and 3D TESS with the same geometry settings, but variable acquisition times: standard (TESSs 4:35min) and quick (TESSq 2:05min). T{sub 2} values were compared in six different regions in the femoral and tibial cartilage using a Wilcoxon signed ranks test and the Pearson correlation coefficient (r). The local ethics committee approved this study, and all participants gave written informed consent. The mean quantitative T{sub 2} values measured by CPMG (mean: 46±9ms) in volunteers were significantly higher compared to those measured with TESS (mean: 31±5ms) in all regions. Both methods performed similarly in patients, but CPMG provided a slightly higher difference between lesions and native cartilage (CPMG: 90ms→61ms [31%],p=0.0125;TESS 32ms→24ms [24%],p=0.0839). 3D-TESS provides results similar to those of a conventional multi-echo spin-echo sequence with many benefits, such as shortening of total acquisition time and insensitivity to B{sub 1} and B{sub 0} changes. (orig.)

  19. Vibrational Spectroscopy and Dynamics of Water.

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches. PMID:27096701

  20. First HF radar measurements of summer mesopause echoes at SURA

    A. N. Karashtin

    Full Text Available HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8–9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHF measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHF observations, HF mesopause echoes are almost always present.

  1. Survey of Sparse Adaptive Filters for Acoustic Echo Cancellation

    Krishna Samalla

    2013-01-01

    Full Text Available This paper reviews the existing developments of adaptive methods of sparse adaptive filters for the identification of sparse impulse response in both network and acoustic echo cancellation from the last decade. A variety of different architectures and novel training algorithms have been proposed in literature. At present most of the work in echo cancellation on using more than one method. Sparse adaptive filters take the advantage of each method and showing good improvement in the sparseness measure performance. This survey gives an overview of existing sparse adaptive filters mechanisms and discusses their advantages over the traditional adaptive filters developed for echo cancellation.

  2. Vibration of plates

    Chakraverty, Snehashish

    2008-01-01

    Plates are integral parts of most engineering structures and their vibration analysis is required for safe design. This work provides a comprehensive introduction to vibration theory and analysis of two-dimensional plates. It offers information on vibration problems along with a discussion of various plate geometries and boundary conditions.

  3. Measuring Light Echos in NGC 4051

    Turner, Tracey Jane; Reeves, James N; Braito, Valentina

    2016-01-01

    We have analyzed five archived X-ray observations of NGC~4051 taken using the NuSTAR observatory. The data show lags between flux variations in bands of different X-ray photon energy. In all pairs of bands compared, the harder band consistently lags the softer band by at least 1000s, at temporal frequencies ~5 x 10^-5 Hz. In addition, soft-band lags up to 400s are measured at temporal frequencies ~2 x 10^-4 Hz. Light echos from the inner accretion disk cannot explain the lags in these data, as a sharp soft-band lag is seen in cross-correlations where the softer band is expected to have no contribution from reflection. We find a simple top hat model to be consistent with the response function producing the reprocessed signal. The scattered fraction of X-rays is high, indicating the reprocessor to have a global covering fraction ~50% around the continuum source. The scattered fraction increases with increasing photon energy, while the maximum time delay decreases. Such a scenario may be explained by a higher fr...

  4. Quaternion-valued echo state networks.

    Xia, Yili; Jahanchahi, Cyrus; Mandic, Danilo P

    2015-04-01

    Quaternion-valued echo state networks (QESNs) are introduced to cater for 3-D and 4-D processes, such as those observed in the context of renewable energy (3-D wind modeling) and human centered computing (3-D inertial body sensors). The introduction of QESNs is made possible by the recent emergence of quaternion nonlinear activation functions with local analytic properties, required by nonlinear gradient descent training algorithms. To make QENSs second-order optimal for the generality of quaternion signals (both circular and noncircular), we employ augmented quaternion statistics to introduce widely linear QESNs. To that end, the standard widely linear model is modified so as to suit the properties of dynamical reservoir, typically realized by recurrent neural networks. This allows for a full exploitation of second-order information in the data, contained both in the covariance and pseudocovariances, and a rigorous account of second-order noncircularity (improperness), and the corresponding power mismatch and coupling between the data components. Simulations in the prediction setting on both benchmark circular and noncircular signals and on noncircular real-world 3-D body motion data support the analysis. PMID:25794374

  5. Rotary echos for the preservation of quantum memories

    Uys, Hermann; de Clerq, Ludwig; Green, Todd; Biercuk, Michael; Bollinger, John

    2011-05-01

    Dynamical decoupling is a promising technique for fighting the unwanted effects of decoherence in the context of quantum information. Decoupling techniques span two extremes from pulsed spin-echo sequences to optimized, continuous amplitude and phase modulation allowing arbitrary rotations on the Bloch sphere. On the one hand spin-echo techniques have the advantage of simplicity, while on the other optimized continuous modulation is expected to achieve better performance results at the cost complexity. That complexity exists both in the implementation and the modulation design, which either requires intimate knowledge of the relevant noise environment for numerical optimization or experimental optimization through feedback. Rotary echos represent an intermediate approach which have the advantage of continuous averaging of dephasing noise and pulsed compensation of fluctuations in the control field amplitude. Here we consider a classical dephasing noise environment and compare the performance of rotary echos to both pulsed and optimized continuous control decoupling techniques.

  6. Loschmidt echo and time reversal in complex systems.

    Goussev, Arseni; Jalabert, Rodolfo A; Pastawski, Horacio M; Wisniacki, Diego A

    2016-06-13

    Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years. PMID:27140977

  7. Classification of Underwater Target Echoes Based on Auditory Perception Characteristics

    Xiukun Li; Xiangxia Meng; Hang Liu; Mingye Liu

    2014-01-01

    In underwater target detection, the bottom reverberation has some of the same properties as the target echo, which has a great impact on the performance. It is essential to study the difference between target echo and reverberation. In this paper, based on the unique advantage of human listening ability on objects distinction, the Gammatone filter is taken as the auditory model. In addition, time-frequency perception features and auditory spectral features are extracted for active sonar target echo and bottom reverberation separation. The features of the experimental data have good concentration characteristics in the same class and have a large amount of differences between different classes, which shows that this method can effectively distinguish between the target echo and reverberation.

  8. Loschmidt echo and time reversal in complex systems

    Goussev, Arseni; Jalabert, Rodolfo A.; Pastawski, Horacio M.; Wisniacki, Diego A.

    2016-01-01

    Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years. PMID:27140977

  9. Preliminary results of the echo-seeding experiment at SLAC

    Xiang, D.; Colby, E.; Ding, Y.; Dunning, M.; Frederico, J.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Corlett, J.; Qiang, J.; Penn, G.; Prestemon, S.; Schlueter, R.; Venturini, M.; Wan, W.; Pernet, P-L.

    2010-05-23

    ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.

  10. The architecture of dynamic reservoir in the echo state network

    Cui, Hongyan; Liu, Xiang; Li, Lixiang

    2012-09-01

    Echo state network (ESN) has recently attracted increasing interests because of its superior capability in modeling nonlinear dynamic systems. In the conventional echo state network model, its dynamic reservoir (DR) has a random and sparse topology, which is far from the real biological neural networks from both structural and functional perspectives. We hereby propose three novel types of echo state networks with new dynamic reservoir topologies based on complex network theory, i.e., with a small-world topology, a scale-free topology, and a mixture of small-world and scale-free topologies, respectively. We then analyze the relationship between the dynamic reservoir structure and its prediction capability. We utilize two commonly used time series to evaluate the prediction performance of the three proposed echo state networks and compare them to the conventional model. We also use independent and identically distributed time series to analyze the short-term memory and prediction precision of these echo state networks. Furthermore, we study the ratio of scale-free topology and the small-world topology in the mixed-topology network, and examine its influence on the performance of the echo state networks. Our simulation results show that the proposed echo state network models have better prediction capabilities, a wider spectral radius, but retain almost the same short-term memory capacity as compared to the conventional echo state network model. We also find that the smaller the ratio of the scale-free topology over the small-world topology, the better the memory capacities.

  11. Performance Evaluation of Adaptive Filters Structures for Acoustic Echo Cancellation

    Sanjeev Dhull

    2011-05-01

    Full Text Available We have designed and simulated an acoustic echo cancellation system for conferencing. This system is based upon a least-mean-square (LMS adaptive algorithm and uses multi filter technique. A comparative study of both structure has been carried out and it is found that this new multi-filter converge faster than similar single long adaptive filter. Index Terms: LMS,Multiple sub filter ,Echo cancellation

  12. Vibration of hydraulic machinery

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong

    2013-01-01

    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  13. Wavelets for ultrasonic echo identification in aircraft fuel tanks

    Sadok, Mokhtar

    2002-03-01

    Recently, Goodrich Corp.- Fuels and Utility systems Division, has launched a research effort to investigate various sensing and computing techniques to gauge fuel in commercial and military aircrafts. Ultrasonics are among other techniques that were tested for such purpose. Generally, in ultrasonic fuel measurement systems, a transducer is excited to create sonic bursts into fuel and measure reflected echo off the fuel surface. A fixed target or pin is usually disposed at a fixed and predetermined distance from the ultrasonic transducer within the tank so as to compute the speed of sound through across fuel in the tank. Knowing the speed of sound in fuel and being able to measure the round trip time from when an ultrasonic burst is generated until its reflected off the fuel surface, the fuel height may be calculated. With a priori knowledge of the tank geometry, the fuel quantity can be estimated. This measurement process seems straightforward. A problem however is being able to discriminate between echoes reflected off various objects within the tank. In particular, it is crucial to discriminate among echoes reflected off various objects within the tank. In particular, it is crucial to discriminate among echoes reflected off the fuel surface and echoes reflected off other object withhin the tank, like the fixed target or tank sides. This paper presents a discrimination method based on wavelets to assign various ultrasonic echoes to their appropriate reflective surfaces.

  14. Multiple photon-echo rephasing of coherent matter waves

    Pan, Ruizhi; Yue, Xuguang; Xu, Xia; Lu, Haichang; Zhou, Xiaoji, E-mail: xjzhou@pku.edu.cn

    2015-03-20

    We investigate the multiple photon echo processes in a Bose–Einstein condensate (BEC) with inhomogeneous momentum broadening. By applying Bragg pulses with adjusted frequency mismatch to induce multiple rephasing, the BEC satisfies the coherence condition for successive superradiance. The atomic system can be efficiently transferred to a high momentum state step by step and emits multiple photon echo signals. These echo signals as a sequence show increasing widths and descending peaks, reflecting a residual dephasing effect due to kinetic-energy phase discrepancy during the population inversions. Our work may contribute to the coherence maintenance for ultracold atomic gas in the quantum information area and the high-precision measurement of atomic momentum width. - Highlights: • A multipulse protocol to induce multiple photon echo rephasing of a BEC is proposed. • Our method is a new and efficient way to transfer the BEC to high momentum modes. • Our method can extend a BEC's coherence time. • The echo sequence is analyzed to study the residual dephasing effect. • The echo decaying is useful in high-precision measurement of BEC's momentum width.

  15. Multiple photon-echo rephasing of coherent matter waves

    We investigate the multiple photon echo processes in a Bose–Einstein condensate (BEC) with inhomogeneous momentum broadening. By applying Bragg pulses with adjusted frequency mismatch to induce multiple rephasing, the BEC satisfies the coherence condition for successive superradiance. The atomic system can be efficiently transferred to a high momentum state step by step and emits multiple photon echo signals. These echo signals as a sequence show increasing widths and descending peaks, reflecting a residual dephasing effect due to kinetic-energy phase discrepancy during the population inversions. Our work may contribute to the coherence maintenance for ultracold atomic gas in the quantum information area and the high-precision measurement of atomic momentum width. - Highlights: • A multipulse protocol to induce multiple photon echo rephasing of a BEC is proposed. • Our method is a new and efficient way to transfer the BEC to high momentum modes. • Our method can extend a BEC's coherence time. • The echo sequence is analyzed to study the residual dephasing effect. • The echo decaying is useful in high-precision measurement of BEC's momentum width

  16. Velocities of auroral coherent echoes at 12 and 144 MHz

    A. V. Koustov

    Full Text Available Two Doppler coherent radar systems are currently working at Hankasalmi, Finland, the STARE and CUTLASS radars operating at ~144 MHz and ~12 MHz, respectively. The STARE beam 3 is nearly co-located with the CUTLASS beam 5, providing an opportunity for echo velocity comparison along the same direction but at significantly different radar frequencies. In this study we consider an event when STARE radar echoes are detected at the same ranges as CUT-LASS radar echoes. The observations are complemented by EISCAT measurements of the ionospheric electric field and electron density behaviour at one range of 900 km. Two separate situations are studied; for the first one, CUTLASS observed F-region echoes (including the range of the EIS-CAT measurements, while for the second one CUTLASS observed E-region echoes. In both cases STARE E-region measurements were available. We show that F-region CUT-LASS velocities agree well with the convection component along the CUTLASS radar beam, while STARE velocities are typically smaller by a factor of 2–3. For the second case, STARE velocities are found to be either smaller or larger than CUTLASS velocities, depending on the range. Plasma physics of E-and F-region irregularities is discussed in attempt to explain the inferred relationship between various velocities. Special attention is paid to ionospheric refraction that is important for the detection of 12-MHz echoes.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere

  17. Evaluation of spatial resolution on fast spin-echo images. Effect of echo train length and interecho spacing

    Fast spin echo (FSE) imaging technique has been indispensable in clinical MRI. This technique reduces acquisition time compared with conventional spin echo sequences. However, this technique introduces new factors, such as echo train length (ETL) and interecho spacing and is susceptible to a new set of artifacts, such as image blurring secondary to nonuniform sampling of K-space. Therefore, the effects of spatial resolution of FSE images on echo train length and interecho spacing were measured using the final MTF. FSE images of the chart phantom with some ETLs and bandwidth were exposed on laser films and measured by micro-densitometer in the phase-encoding direction. Using the final MTF method, the FSE images were evaluated for spatial resolution. Increasing ETL reduced spatial resolution on FSE images. The proton-density-weighted images were more conspicuous. Decreasing the bandwidth reduced spatial resolution on FSE images because of increasing interecho spacing. (author)

  18. LRS data processing methods for detection of lunar subsurface echoes

    Oshigami, Shoko; Mochizuki, Kengo; Watanabe, Shiho; Watanabe, Toshiki; Yamaguchi, Yasushi; Yamaji, Atsushi; Ono, Takayuki; Kumamoto, Atsushi; Nakagawa, Hiromu; Kobayashi, Takao; Kasahara, Yoshiya

    Lunar Radar Sounder (LRS) is an instrument for one of fifteen science missions of SE- LENE (KAGUYA). LRS is a ground-penetrating FM-CW radar system of HF-band. LRS detects echoes reflected from subsurface discontinuities where dielectric constants of the rocks change. The range resolution of LRS is 75 m in free space, whereas the sampling interval in the flight direction is about 75 m when the spacecraft altitude is 100 km. The primary objective of LRS is to investigate lunar subsurface structures. We plan to perform global soundings by LRS to contribute to studying the evolution of the Moon. In this presentation, we introduce the techniques to process LRS data to produce data products and to detect subsurface echoes. We have two standard data products of LRS under consideration. The time series data of ‘A-scope' which is a plot of signal power spectrum as a function of range derived from of the waveform data are called ‘B-scan'. Because LRS instruments change timing of data recording (measurement delay time) according to the predicted distance between KAGUYA spacecraft and lunar surface, observation range with respect to the spacecraft varies from pulse to pulse. In addition, flight altitude of KAGUYA changes in the range of several tens of kilometers. Therefore a trace of surface nadir echoes in unprocessed B-scan images does not correspond to actual lunar topography. We corrected variations of the measurement delay time and flight altitude of KAGUYA to produce a B-scan data product with the original spatial resolution (BScan high) and a reduced spatial resolution product (BScan low) both in the PDS format. The echo signals in A-scope data might be classified in the following categories; (1) a surface nadir echo, (2) surface off-nadir backscattering echoes, and (3) subsurface echoes. The most intense signal usually comes from the nadir point, when KAGUYA is flying over a level surface. The A-scope data also include various noises resulted from, for example

  19. Fast spin echo vs conventional spin echo in cervical spine imaging

    The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15-66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20%) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE. (orig.). With 3 figs

  20. About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs

    Schirmer, Mischa; Levenson, Nancy A; Fu, Hai; Davies, Rebecca L; Keel, William C; Torrey, Paul; Bennert, Vardha N; Pancoast, Anna; Turner, James E H

    2016-01-01

    We report the discovery of 14 Lyman-alpha blobs (LABs) at z~0.3, existing at least 4-7 billion years later in the Universe than all other LABs known. Their optical diameters are 20-70 kpc, and GALEX data imply Ly-alpha luminosities of (0.4-6.3)x10^43 erg/s. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z=2 and z=0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs: Their Ly-alpha and X-ray fluxes decorrelate below 10^6 years because of the delayed escape of resonantly scattering Ly-alpha photons. High Ly-alpha luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by 3-4 orders of magnit...

  1. A Pilot Validation of Multi-Echo Based Echo-Planar Correlated Spectroscopic Imaging in Human Calf Muscles

    Furuyama, JK; R. Nagarajan; Roberts, CK; Lee, CC; Hahn, TJ; Thomas, MA

    2014-01-01

    A current limitation of MR spectroscopic imaging of multiple skeletal muscles is prolonged scan duration. A significant reduction in the total scan duration using the echo-planar correlated spectroscopic imaging (EP-COSI) sequence was accomplished using two bipolar readout trains with different phase-encoded echoes for one of two spatial dimensions within a single repetition time (TR). The second bipolar readout was used for spatially encoding the outer k-space, whereas the first readout was ...

  2. Landau damping and the echo effect in a confined Bose-Einstein condensate

    Kuklov, A. B.

    1998-01-01

    Low energy collective mode of a confined Bose-Einstein condensate should demonstrate the echo effect in the regime of Landau damping. This echo is a signature of reversible nature of Landau damping. General expression for the echo profile is derived in the limit of small amplitudes of the external pulses. Several universal features of the echo are found. The existence of echo in other cases of reversible damping -- Fano effect and Caldeira-Leggett model -- is emphasized. It is suggested to te...

  3. Coherent radar imaging of mesosphere summer echoes: Influence of radar beam pattern and tilted structures on atmospheric echo center

    Chen, Jenn-Shyong; Hoffmann, Peter; Zecha, Marius; Hsieh, Cheng-Hsiung

    2008-02-01

    Multiple echo centers of a mesosphere-summer-echo layer (MSE) observed by the six-receiver OSWIN VHF radar (54.1°N, 11.8°E) were examined with the coherent radar imaging (CRI) technique. The data were collected by different observational modes: vertical and oblique radar beams with the receiving configurations of 3 × 2, 6 × 1 (meridional alignment) and 1 × 6 (zonal alignment) antenna groups. The unique receiving configurations of meridional and zonal aligned antenna groups reveal that the echo centers clustered in three distinct groups above the range height of ˜86 km. The central group of echo centers was around the direction of radar beam; however, the off-zenith angles of the two side groups, ranging between several and 20 degrees, increased with ascendant range height. Two potential causes of the echoes in the two side groups were examined on the basis of simulation calculation, namely, tilted structures in the layer and additionally, the influence of radar beam pattern. It is indicated that some echoes, originating from the lower part (˜86 km) at larger off-zenith angles. The tilted structures, which are considered to be related to wave activities, can also produce the features similar to the observations. This is demonstrated by simulation calculation with wavy reflecting layers, in which the waves are supposed to modulate the multiple reflecting layers, with increasing amplitudes, tilted shapes, asynchronous phases, and horizontal travel.

  4. Research on key technologies of LADAR echo signal simulator

    Xu, Rui; Shi, Rui; Ye, Jiansen; Wang, Xin; Li, Zhuo

    2015-10-01

    LADAR echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR, which is designed to simulate the LADAR return signal in laboratory conditions. The device can provide the laser echo signal of target and background for imaging LADAR systems to test whether it is of good performance. Some key technologies are investigated in this paper. Firstly, the 3D model of typical target is built, and transformed to the data of the target echo signal based on ranging equation and targets reflection characteristics. Then, system model and time series model of LADAR echo signal simulator are established. Some influential factors which could induce fixed delay error and random delay error on the simulated return signals are analyzed. In the simulation system, the signal propagating delay of circuits and the response time of pulsed lasers are belong to fixed delay error. The counting error of digital delay generator, the jitter of system clock and the desynchronized between trigger signal and clock signal are a part of random delay error. Furthermore, these system insertion delays are analyzed quantitatively, and the noisy data are obtained. The target echo signals are got by superimposing of the noisy data and the pure target echo signal. In order to overcome these disadvantageous factors, a method of adjusting the timing diagram of the simulation system is proposed. Finally, the simulated echo signals are processed by using a detection algorithm to complete the 3D model reconstruction of object. The simulation results reveal that the range resolution can be better than 8 cm.

  5. Bandshapes in vibrational spectroscopy

    A detailed account is given of the development of modern bandshape theories since 1965. An investigation into the relative contributions of statistical irreversible relaxation processes is described, for a series of molecules in which gradually the length of one molecular axis is increased. An investigation into the theoretical and experimental investigation of the broadening brought about by the effect of fluctuating intermolecular potentials on the vibrational frequency is also described. The effect of an intermolecular perturbative potential on anharmonic and Morse oscillators is discussed and the results are presented of a computation on the broadening of the vibrational band of some diatomic molecules in a rigid lattice type solvent. The broadening of the OH-stretching vibration in a number of aliphatic alcohols, the vibrational bandshapes of the acetylenic C-H stretching vibration and of the symmetric methyl stretching vibration are investigated. (Auth./ C.F.)

  6. A high success rate full-waveform lidar echo decomposition method

    Xu, Lijun; Li, Duan; Li, Xiaolu

    2016-01-01

    A full-waveform Light detection and ranging (LiDAR) echo decomposition method is proposed in this paper. In this method, the peak points are used to detect the separated echo components, while the inflection points are combined with corresponding peak points to detect the overlapping echo components. The detected echo components are then sorted according to their energies in a descending order. The sorted echo components are one by one added into the decomposition model according to their orders. For each addition, the parameters of all echo components already added into the decomposition model are iteratively renewed. After renewing, the amplitudes and full width at half maximums of the echo components are compared with pre-set thresholds to determine and remove the false echo components. Both simulation and experiment were carried out to evaluate the proposed method. In simulation, 4000 full-waveform echoes with different numbers and parameters of echo components were generated and decomposed using the proposed and three other commonly used methods. Results show that the proposed method is of the highest success rate, 91.43%. In experiment, 9549 Geoscience Laser Altimeter System (GLAS) echoes for Shennongjia forest district in south China were employed as test echoes. The test echoes were first decomposed using the four methods and the decomposition results were also compared with those provided by the National Snow and Ice Data Center. Comparison results show that the determination coefficient ({{R}2} ) of the proposed method is of the largest mean, 0.6838, and the smallest standard deviation, 0.3588, and the distribution of the number of the echo components decomposed from the GLAS echoes is the most satisfied with the situation of full-waveform echoes from the forest area, implying that the superposition of the echo components decomposed from a full-waveform echo by using the proposed method can best approximate the full-waveform echo.

  7. Vibrational properties of uracil

    WANG Zhiping; ZHANG Fengshou; ZENG Xianghua; ZHOU Hongyu; GU Bin; CHENG Wei

    2006-01-01

    A semiempirical molecular dynamics model is developed to study the vibrational frequencies of uracil at very low kinetic temperature by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is used to assign the vibrational frequency of each mode. The calculated frequencies are found to be in good agreement with experimental measurements. Moreover, we make up for the lost vibrational modes in experiments self-consistently. A total of 30 vibrational modes and their corresponding frequencies are reported.

  8. The effect of strong pitch angle scattering on the use of artificial auroral streaks for echo detection - Echo 5

    Swanson, R. L.; Steffen, J. E.; Winckler, J. R.

    1986-05-01

    During the Echo 5 experiment, launched November 13, 1979 from the Poker Flat Research Range (Fairbanks, AK), a 0.75 A, 37 keV electron beam was injected both up and down the field line. The objective of the experiment was to test the use of optical and X-ray methods to detect the beam as it interacted with the atmosphere below the rocket for both the downward injections (markers) and the upward injected electrons which mirrored at the Southern Hemisphere and returned echoes. A ground-based TV system, rocket-borne photometers, and X-ray detectors viewed the interaction region. The artificial auroral streaks created by the markers were easily visible on the ground TV system but the large intensity of photons produced around the rocket masked any response to the markers by the on-board photometers and X-ray detectors. No echoes were detected with any of the detection systems although the power in some of the upward injections was 7.6 times the power in a detected downward injection, thus setting an upper limit on the loss-cone echo flux. The magnitude of the bounce averaged pitch-angle-diffusion coefficient necessary to explain the lack of observable echoes was found to be 0.0004/s. Comparison with calculations done by Lyons (1974) for the pitch angle diffusion of electrons by electrostatic waves revealed that an equatorial wave electric field of 11 mV/m would account for the lack of echoes. Such fields should cause strong pitch angle scattering of up to 10 keV natural electrons and thus be consistent with the presence of diffuse aurora on the Echo 5 trajectory. Direct measurements have also revealed such fields in equatorial regions.

  9. Cluster-enhanced sparse approximation of overlapping ultrasonic echoes.

    Mor, Etai; Aladjem, Mayer; Azoulay, Amnon

    2015-02-01

    Ultrasonic pulse-echo methods have been used extensively in non-destructive testing of layered structures. In acoustic measurements on thin layers, the resulting echoes from two successive interfaces overlap in time, making it difficult to assess the individual echo parameters. Over the last decade sparse approximation methods have been extensively used to address this issue. These methods employ a large dictionary of elementary functions (atoms) and attempt to select the smallest subset of atoms (sparsest approximation) that represent the ultrasonic signal accurately. In this paper we propose the cluster-enhanced sparse approximation (CESA) method for estimating overlapping ultrasonic echoes. CESA is specifically adapted to deal with a large number of signals acquired during an ultrasonic scan. It incorporates two principal algorithms. The first is a clustering algorithm, which divides a set of signals comprising an ultrasonic scan into groups of signals that can be approximated by the same set of atoms. The second is a two-stage iterative algorithm, which alternates between update of the atoms associated with each cluster, and re-clustering of the signals according to the updated atoms. Because CESA operates on clusters of signals, it achieves improved results in terms of approximation error and computation time compared with conventional sparse methods, which operate on each signal separately. The superior ability of CESA to approximate highly overlapping ultrasonic echoes is demonstrated through simulation and experiments on adhesively bonded structures. PMID:25643086

  10. E-region echo characteristics governed by auroral arc electrodynamics

    S. E. Milan

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.

    Key words. Ionosphere (ionospheric irregularities; electric fields and currents

  11. On the theory of proton solid echo in polymer melts

    Fatkullin, N; Mattea, C; Stapf, S

    2015-01-01

    Based on a modified Anderson-Weiss approximation (N. Fatkullin, A. Gubaidullin, C. Mattea, S.Stapf, J. Chem. Phys. 137 (2012), 224907) an improved theory of proton spin solid echo in polymer melts is formulated, taking into account contribution from intermolecular magnetic dipole-dipole interactions. The solid echo build-up function defined by the relation , where , and are the respective signals arising from ( ),( ) and ( ) spin echo experiments, where is an operator rotating the spin system on the angle relatively axis , is investigated. It is shown that the intermolecular part of this function at short times , where is a characteristic time for flip-flop transitions between proton spins, contains information about the relative mean squared displacements of polymer segments at different macromolecules, opening up a new opportunity for obtaining information about polymer dynamics in the millisecond regime.

  12. Spin echo diffraction in disordered media with single length scales

    The spin echo diffraction observed in a pulsed field gradient NMR experiment is studied by simulation in computer generated two-dimensional disordered porous media characterized by a single length scale such as their mean pore diameter. In the propagator formulation of the pulsed field gradient experiments carried out in fluids confined inside porous media one expects to see a diffraction pattern characterizing the above length scale. We have explored the possibility of using this echo diffraction technique as a practical noninvasive tool to extract information about the pore geometries. It turns out that even for a disordered medium, the echo-diffraction pattern picks up the dominant length scale. copyright 1997 The American Physical Society

  13. On the lack of southern hemisphere polar mesosphere summer echoes

    Balsley, B. B.; Woodman, R. F.; Sarango, M.; RodríGuez, R.; Urbina, J.; Ragaini, E.; Carey, J.; Huaman, M.; Giraldez, A.

    1995-06-01

    We report VHF radar observations of the southern high-latitude mesopause region using wind profilers that were installed recently on King George Island, Antarctica, and Ushuaia, Argentina. Briefly, our observations, which were made during January and February 1993, show almost no evidence of so-called polar mesosphere summer echoes, or PMSE. Since these echoes are a predominant feature of the northern high-latitude mesosphere in summer, their absence in the southern hemisphere is both surprising and intriguing. In this paper we present evidence demonstrating the virtual absence of the echoes and demonstrate that our systems were capable of detecting them had they been present. We also outline some of the consequences of this intriguing result, which are supported by observed hemispheric differences in polar mesospheric clouds, mesospheric temperatures, upper atmospheric gravity wave activity, and mean circulation patterns.

  14. Properties of echo spectra observed by MST radars

    Wakasugi, K.

    1983-01-01

    Turbulent scatter and Fresnel reflection are the fundamental echoing mechanisms to interpret the signals observed by Mesosphere-stratosphere-troposphere (MST) radars. Turbulent scattered echoes provide information about the turbulence structure and mean flow of the atmosphere. Observational results with VHF MST radars, however, show the importance of Fresnel reflection due to the infinite gradient of reflectivity at the edges of a scattering layer. This condition is excluded for the weak fluctuation models but it is still possible to include the observed aspect sensitivity by assuming an anisotropic structure of fluctuations. Another explanation of the aspect sensitivity observed by MST radars is advanced. Spectral estimates by the widely used periodogram were related to a four-dimensional spectrum of atmospheric fluctuations with anisotropic structure. Effects of the radar system such as antenna beam width, beam direction and Fast Fourier Transformations (FFT) data length were discussed for the anisotropic turbulent atmosphere. Echo parameters were also estimated.

  15. Field integral correction in neutron resonance spin echo

    Neutron resonance spin echo (NRSE) as a variant of neutron spin echo (NSE) has the advantage that it needs only relatively small magnetic coils. Field inhomogeneities are therefore less important than in NSE. We have built a new type of NRSE spectrometer that overcomes the main limitation of NRSE towards high-energy resolution. Our setup profits from a new longitudinal NRSE field geometry which allows to use Fresnel coils correcting for the beam divergence effect, while former NRSE setups with transversal static magnetic fields could not use Fresnel coils. We demonstrate the function of the longitudinal resonance flip coils, and show first results of spin echo test measurements performed by means of the new setup

  16. Mechanical vibration and shock analysis, sinusoidal vibration

    Lalanne, Christian

    2014-01-01

    Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m

  17. Picking up good vibrations

    Eijk, A.

    2010-01-01

    The methods that need to be employed to develop the better vibration guidelines to assess the integrity of a reciprocating compressor system are discussed. An R&D project of the European Forum of Reciprocating Compressors (EFRC) has been initiated to develop guidelines for vibrations in reciprocatin

  18. Model Indepedent Vibration Control

    Yuan, Jing

    2010-01-01

    A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is

  19. Vibration Theory, Vol. 3

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...

  20. Vibration Theory, Vol. 3

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration...

  1. Hydroelastic Vibrations of Ships

    Jensen, Jørgen Juncher; Folsø, Rasmus

    2002-01-01

    A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...

  2. Design And Simulation Of An Acoustic Echo Cancellation System For Hand-Free Telecommunication

    Ein Gyin Pwint

    2015-06-01

    Full Text Available Abstract Acoustic echo cancellation is a common occurrence in todays telecommunication systems. The signal interference caused by acoustic echo is distracting to users and causes a reduction in the quality of the communication. This paper is implementing the overall system of acoustic echo cancellation system using LMS and NLMS algorithms for adaptive filter normalized cross correlation NCC algorithm double talk detector. The result of echo return loss enhancement ERLE and mean squared error MSE which show that how much the amount of echo signal cancelled and the amount of residual error signal for cancelling acoustic echo cancellation on a PC with the help of the MATLAB software.

  3. Handbook Of Noise And Vibration

    This book is about noise and vibration. The first chapter has explanations of noise such as basic of sound, influence of noise, assessment of noise, measurement of prevention of noise and technology, case of noise measurement and soundproof. The second chapter describes vibration with outline, theory of vibration, interpretation of vibration, measurement for reduction of vibration, case of design of protection against vibration. It deals with related regulation and method of measurement.

  4. Vibration Testing for Small Satellites

    Wilson, Delbert

    1989-01-01

    Most people involved in the design and construction of small satellites are unfamiliar with vibration testing. Yet most satellites undergo vibration testing to qualify them for flight. Some familiarity with the basic aspects of vibration testing is needed to insure that a vibration test on a satellite is valid. This paper sets forth the basic equipment, practices and concepts of vibration testing. It provides guidelines for specifying a vibration test, designing fixtures, attaching instrument...

  5. Vibration control in accelerators

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  6. Review on vibration transducers

    The vibrational behavior of a rotating machine at a certain rotational speed is carried out by a suitable non-contact transducer placed in precise selected position relative to the rotating machine. For the proper application of vibration measuring devices to the vibration parameters, these devices are classified with respect to the citation frequency and machine frequency. Sensors and transducers are categorized according to their applications. One variable can be converted into other by using electrical integrating or differentiating circuit. The differentiation accentuates the high frequency end of the spectrum while integration reduces the high frequency components. This paper presents different types of transducers, which can be used for vibration analysis purposes in rotating machinery. Factually sensors play an important role in the measurement of vibrations. Their characteristics are discussed and the sensitivity of mounting, installation and working principle is presented. The transduction mechanism has been discussed in a straightforward manner and comparison between different sensors and transduction is presented here. (author)

  7. Evaluation of combination echo sequence in knee joint MRI

    Combination echo sequence (CE) can obtain the T2-weighted SE images and gradient echo sequence (GRE) images at the same time. The CE technique was performed in 42 cases with knee joint disease and its usefulness was examined. The knee joint consists of complex elements, therefore, all sequences of T1-weighted, T2-weighted and GRE are necessary in order to clearly visualize. Thus, The CE technique, which yields the T2-weighted and GRE images is useful for routine examination of knee joint. (author)

  8. Echoes of Hylas and the Poetics of Allusion in Propertius

    Mariapia Pietropaolo

    2012-12-01

    Full Text Available For Propertius the myth of Hylas exemplifies a poetics of selective appropriation and transformation by means of echoes and allusions. He brings it into his poetry as an exemplum, both erotic and metapoetic, and offers evidence that his penchant for echoes and allusions is essentially the result of a Hylan poetics of elegy. By using the echoic mode of composition inherent in the myth of Hylas, Propertius illustrates the principle that elegiac poetry is grounded in a complex dialogue of intertextual and intratextual allusion and citations.

  9. Causality and Intervention in the Spin-Echo Experiments

    Fernanda Samaniego Bañuelos

    2013-09-01

    Full Text Available In the so-called “Spin-Echo Experiments” the behaviour of a spin’s system seems to violate the second law of thermodynamics. For this reason the “Spin-Echo Experiments” are considered of particular interest for the Foundations of Physics. Interventionists have provided a classical explanation (Blatt, 1959; Ridderbos & Redhead, 1998 and a quantum-based explanation (Hemmo & Shenker, 2005 of these experiments. Here both interventionist explanations are assessed by means of the Manipulability Theory of Causal Explanation (Woodward, 2003. It is argued that interventionism would gain explanatory depth by providing functional relations and predicting relaxation times.

  10. Quantification of severe liver iron overload using MRI offset echoes

    Magnetic resonance imaging (MRI) has become the clinical standard to estimate liver iron overload. The most commonly used method is to measure the transversal relaxation time, T2*, from a multi gradient recalled echo sequence (MGRE). While this technique is reliable in low to moderate liver iron concentrations (LIC), it will be inaccurate when it is severe. We report a case with severe liver hemochromatosis and show the benefit of using an easily implemented MRI offset echo sequence to more accurately estimate LIC. After adjusting treatment, both Ferritin and LIC decreased. Using standard MGRE this reduction could not have been detected

  11. Code division in optical memory devices based on photon echo

    Kalachev, Alexey A.; Vlasova, Daria D.

    2006-03-01

    The theory of multi-channel optical memory based on photon echo is developed. It is shown that under long-lived photon echo regime the writing and reading of information with code division is possible using phase modulation of reference and reading pulses. A simple method for construction of a system of noise-like signals, which is based on the segmentation of Frank sequence is proposed. It is shown that in comparison to the system of random biphase signals this system leads to the efficient decreasing of mutual influence of channels and increasing of random/noise ratio under reading of information.

  12. Electrorheological vibration system

    Korobko, Evguenia V.; Shulman, Zinovy P.; Korobko, Yulia O.

    2001-07-01

    The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.

  13. Seafloor characterisation using echo peak amplitudes of multibeam hydrosweep system - A preliminary study at Arabian Sea

    Chakraborty, B.; Sudhakar, T.

    In this paper an interface to acquire 59-beams echo peak amplitudes of the Hydrosweep Multibeam system is established. The echo peak amplitude values collected at varying seabed provinces of Arabian sea are presented. The study reveals...

  14. Edward Albee’s The Zoo Story: Echo/es of Contemporary Subversive Culture

    Naqibun Nabi

    2016-02-01

    Full Text Available The post-world war II American social and cultural setting was ambiguously featured with enforced conformity in the name of prosperity and Americanization of the nation. Despite of this fact, American writers, especially, dramatists conveyed their message against this fixation through variety and intellectuality. Edward Albee’s The Zoo Story is one of those literary assets which dedicatedly cut through the illusions of contemporary American social and cultural ethos. Here, his characters are seen struggling constantly with their insecurities and existential angst in the society. He presents America, the so-called ‘Land of Free and Home of Braves’ (note 1, in such a portrayal that unveils the traps of cages and confinement underneath. The target of this paper is to trace Edward Albee’s heightened awareness about the post-war American socio-cultural reality evident in The Zoo Story. It also looks for the voice in which the text echoes out the anti-communist, materialistic, gender-coded boundaries, coupled with paradoxical media representations, religious bordering and how Albee challenges these issues with an anti-establishment tone.Keywords: subversive culture, anti-communism, media, religion and homosexuality

  15. Coherent vibrational dynamics

    Lanzani, Guglielmo; De Silvestri, Sandro

    2007-01-01

    Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.

  16. Vibrational optical activity

    Recent vibrational activity (VOA) research is discussed. The vibrational circular dichroism (VCD) experiments were carried out with a Fourier transform infrared spectrometer. One of the major anticipations from VOA spectroscopy is to be able to derive new pathways for determining the molecular structure. Shown is Fourier transform infrared absorption and VCD spectra of lyxopyranose in pyradine-d5 solvent. Raman optical activity measurements are discussed, and depolarized Raman and Raman optical activity spectra for (+)-alpha-pinene are presented. It was concluded that at present Raman optical activity can be measured in the entire vibrational spectral region, where as VCD has not been measured below 600 cm-1

  17. Echo width of foam supports used in scattering measurements

    Appel-Hansen, Jørgen; Solodukhov, V. V.

    1979-01-01

    Theoretically and experimentally determined echo widths of dielectric cylinders having circular, triangular, and quadratic cross sections have been compared. The cylinders were made of foam material having a relative dielectric constant of about 1.035. The purpose of the investigation was to find a...

  18. Echo phenomenon associated with lower-hybrid-wave launching

    Lower hybrid waves at two different frequencies f1 and f2 are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequency f = f2 - f1. This phenomenon can be explained by an echo effect near the plasma surface

  19. Echo phenomenon associated with lower-hybrid wave launching

    Lower-hybrid waves at two different frequencies f1 and f2 are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequency f = f2-f1. This phenomenon can be explained by an echo effect near the plasma surface

  20. Subband Affine Projection Algorithm for Acoustic Echo Cancellation System

    Choi Hun

    2007-01-01

    Full Text Available We present a new subband affine projection (SAP algorithm for the adaptive acoustic echo cancellation with long echo path delay. Generally, the acoustic echo canceller suffers from the long echo path and large computational complexity. To solve this problem, the proposed algorithm combines merits of the affine projection (AP algorithm and the subband filtering. Convergence speed of the proposed algorithm is improved by the signal-decorrelating property of the orthogonal subband filtering and the weight updating with the prewhitened input signal of the AP algorithm. Moreover, in the proposed algorithms, as applying the polyphase decomposition, the noble identity, and the critical decimation to subband the adaptive filter, the sufficiently decomposed SAP updates the weights of adaptive subfilters without a matrix inversion. Therefore, computational complexity of the proposed method is considerably reduced. In the SAP, the derived weight updating formula for the subband adaptive filter has a simple form as ever compared with the normalized least-mean-square (NLMS algorithm. The efficiency of the proposed algorithm for the colored signal and speech signal was evaluated experimentally.

  1. Neutron spin echo spectroscopy on the spallation neutron source

    An investigation has been made into the practicability of combining the neutron spin echo and time-of-flight techniques on the Rutherford Laboratory Spallation Neutron Source. Preliminary specifications are presented for a quasielastic instrument with an energy resolution down to approximately 10 neV and an inelastic spectrometer for measuring excitation widths approximately 1 μ eV. (author)

  2. Control of spatial correlations between Rydberg excitations using rotary echo

    Thaicharoen, N; Raithel, G

    2016-01-01

    We manipulate correlations between Rydberg excitations in cold atom samples using a rotary-echo technique. The correlations are due to interactions between the Rydberg atoms. In the rotary-echo excitation sequence, the phase of the excitation pulse is flipped at a selected time during the pulse. We measure the resultant change in the spatial pair correlation function of the excitations via direct position-sensitive atom imaging. For zero detuning of the lasers from the interaction-free Rydberg-excitation resonance, the pair-correlation value at the most likely nearest-neighbor Rydberg-atom distance is substantially enhanced when the phase is flipped at the middle of the excitation pulse. In this case, the rotary echo eliminates most uncorrelated (un-paired) atoms, leaving an abundance of correlated atom pairs at the end of the sequence. In off-resonant cases, a complementary behavior is observed. We further characterize the effect of the rotary-echo excitation sequence on the excitation-number statistics of t...

  3. Characterization of trehalose aqueous solutions by neutron spin echo

    Branca, C; Magazù, S; Maisano, G; Mangione, A; Pappas, C; Triolo, A

    2002-01-01

    The present work reports neutron spin-echo (NSE) results on aqueous mixtures of trehalose, a naturally occurring disaccharide of glucose, which shows an extraordinary bioprotective effectiveness against dehydration and freezing. The aim of the work is to furnish new results on the dynamics of the trehalose/water system on the nano- and picosecond scales. (orig.)

  4. Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

    S. Kirkwood

    2006-03-01

    Full Text Available The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes - PMWE during a solar proton event in November 2004. Using the interferometric capabilities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms-1 or more, and high aspect sensitivity, with echo arrival angles spread over as little as 0.3°. ESRAD also detected, on some occasions, discrete scattering regions moving across the field of view with periodicities of a few seconds. The very narrow, vertically directed beam of the more powerful EISCAT radar allowed measurements of the spectral widths of the radar echoes both inside the PMWE and from the background plasma above and below the PMWE. Spectral widths inside the PMWE were found to be indistinguishable from those from the background plasma. We propose that scatter from highly-damped ion-acoustic waves generated by partial reflection of infrasonic waves provides a reasonable explanation of the characteristics of the very strong PMWE reported here.

  5. Analysis of multibeam-hydrosweep echo peaks for seabed characterisation

    Chakraborty, B.; Schenke, H.W.; Kodagali, V.N.; Hagen, R.

    , in general, Gaussian in nature except in the case of the Kainan Maru seamount summit (area D). The outer beams of the Enderby abyssal plain (area C) echo-peak PDF statistics reveal the highest possible large-scale feature dominance. Interestingly, Extremal...

  6. System for measuring magnetic fields using spin echo

    Description of an on-line system for magnetic field measurements on the storage rings using spin echo method is presented. In the system described the magnetic field measurement is performed in the following way. In a specimen with the required atoms (e.g. protons or lithium nuclei) spin echo is induced by effect of a pair of pulses. A NMR frequency echo-signal received from the transducer is transferred to a lower intermediate frequency where it is transformed into a digital form using analog-to-digital converter and then spectral analysis using Fourier fast transformation method is performed. Echo-signal frequency and magnetic induction values, corresponding to it are determined according to the spectrum calculated and to a certain heterodyne frequency. The system allows one to measure fields within 0.05-1 T range using two proton detectors (with 2.1-42 MHz frequency range). Relative measurement error does not exceed 3x10-6. The detecor tubes are 5 mm in diameter with 10 mm winding length and are encased into a copper shield

  7. LEGUS Discovery of a Light Echo Around Supernova 2012aw

    Van Dyk, Schuyler D; Anderson, Jay; Andrews, Jennifer E; Calzetti, Daniela; Bright, Stacey N; Ubeda, Leonardo; Smith, Linda J; Sabbi, Elena; Grebel, Eva K; Herrero, Artemio; de Mink, Selma E

    2015-01-01

    We have discovered a luminous light echo around the normal Type II-Plateau Supernova (SN) 2012aw in Messier 95 (M95; NGC 3351), detected in images obtained approximately two years after explosion with the Wide Field Channel 3 on-board the Hubble Space Telescope (HST) by the Legacy ExtraGalactic Ultraviolet Survey (LEGUS). The multi-band observations span from the near-ultraviolet through the optical (F275W, F336W, F438W, F555W, and F814W). The apparent brightness of the echo at the time was ~21--22 mag in all of these bands. The echo appears circular, although less obviously as a ring, with an inhomogeneous surface brightness, in particular, a prominent enhanced brightness to the southeast. The SN itself was still detectable, particularly in the redder bands. We are able to model the light echo as the time-integrated SN light scattered off of diffuse interstellar dust in the SN environment. We have assumed that this dust is analogous to that in the Milky Way with R_V=3.1. The SN light curves that we consider ...

  8. Echo voltage reflected by turtle on various angles

    Sunardi Sunardi

    2015-03-01

    Full Text Available This research proposes the acoustic measurement by using echo sounder for green turtle detection of 1 year, 12 and 18 years. Various positions or angles of turtles are head, tail, shell, lung, left and right side. MATLAB software and echo sounder are used to analyse the frequency and the response of the turtle as echo voltage and target strength parameter. Based on the experiment and analysis have been conducted, the bigger size of the turtle, the higher echo voltage and target strength. The target strength of turtle for lung and shell for all ages are -26.52 dB and –26.17 dB respectively. The target strength of turtles in this research is different with target strength of fish in our previous research. Therefore, for future research, the repellant system based on differences of target strength the turtle and fish for avoided the turtle trapping in the net can be implemented to protect the population of turtle from extinction

  9. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

    Kumar, Ajitesh; Karthick Kumar, S. K.; Gupta, Aditya; Goswami, Debabrata

    2011-08-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  10. Spectrally Resolved Femtosecond Photon Echo Spectroscopy of Astaxanthin

    Kumar, Ajitesh; Kumar, S. K. Karthick; Gupta, Aditya; Goswami, Debabrata

    2011-01-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  11. RESPECT: Neutron Resonance Spin-Echo Spectrometer for Extreme Studies

    Georgii, Robert; Pfleiderer, Christian; Böni, Peter

    2016-01-01

    We propose the design of a Resonance SPin-echo spECtrometer for exTreme studies, RESPECT, that is ideally suited for the exploration of non-dispersive processes such as diffusion, crystallization, slow dynamics, tunneling processes, crystal electric field excitations, and spin fluctuations. It is a variant of the conventional neutron spin-echo technique (NSE) by i) replacing the long precession coils by pairs of longitudinal neutron spin-echo coils combined with RF-spin flippers and ii) by stabilizing the neutron polarization with small longitudinal guide fields that can in addition be used as field subtraction coils thus allowing to adjust the field integrals over a range of 8 orders of magnitude. Therefore, the dynamic range of RESPECT can in principle be varied over 8 orders of magnitude in time, if neutrons with the required energy are made available. Similarly as for existing NSE-spectrometers, spin echo times of up to approximately 1 microsecond can be reached if the divergence and the correction elemen...

  12. Echo thresholds for reflections from acoustically diffusive architectural surfaces.

    Robinson, Philip W; Walther, Andreas; Faller, Christof; Braasch, Jonas

    2013-10-01

    When sound reflects from an irregular architectural surface, it spreads spatially and temporally. Extensive research has been devoted to prediction and measurement of diffusion, but less has focused on its perceptual effects. This paper examines the effect of temporal diffusion on echo threshold. There are several notable differences between the waveform of a reflection identical to the direct sound and one from an architectural surface. The onset and offset are damped and the energy is spread in time; hence, the reflection response has a lower peak amplitude, and is decorrelated from the direct sound. The perceptual consequences of these differences are previously undocumented. Echo threshold tests are conducted with speech and music signals, using direct sound and a simulated reflection that is either identical to the direct sound or has various degrees of diffusion. Results indicate that for a speech signal, diffuse reflections are less easily detectable as a separate auditory event than specular reflections of the same total energy. For a music signal, no differences are observed between the echo thresholds for reflections with and without temporal diffusion. Additionally, echo thresholds are found to be shorter for speech than for music, and shorter for spatialized than for diotic presentation of signals. PMID:24116414

  13. Performance Evaluation of Adaptive Filters Structures for Acoustic Echo Cancellation

    Sanjeev Dhull

    2011-05-01

    Full Text Available We have designed and simulated an acoustic echo cancellation system for conferencing. Thissystem is based upon a least-mean-square (LMS adaptive algorithm and uses multi filtertechnique. A comparative study of both structure has been carried out and it is found that thisnew multi-filter converge faster than similar single long adaptive filter.

  14. Stereo Echo Cancellation(SEC) employing Signal Decorrelation with emphasis on Affine Projection Algorithm(APA)

    Ande, Santosh

    2013-01-01

    Monophonic tele-conferencing systems employ acoustic echo cancellation (AEC) to reduce echoes that result from coupling between loudspeaker and microphone. Acoustic echo cancellation is simple to develope as there is a single channel. But future tele conferencing systems are expected to have multi channel communication which is necessary in hands-free multi user tele communication systems. Stereophonic echo cancellation (SEC), has been studied since the early 1990s, in hands-free tele communi...

  15. Damping Vibration at an Impeller

    Hager, J. A.; Rowan, B. F.

    1982-01-01

    Vibration of pump shaft is damped at impeller--where vibration-induced deflections are greatest--by shroud and seal. Damping reduces vibrational motion of shaft at bearings and load shaft places on them. Flow through clearance channel absorbs vibration energy.

  16. Vibration Analysis and the Accelerometer

    Hammer, Paul

    2011-01-01

    Have you ever put your hand on an electric motor or motor-driven electric appliance and felt it vibrate? Ever wonder why it vibrates? What is there about the operation of the motor, or the object to which it is attached, that causes the vibrations? Is there anything "regular" about the vibrations, or are they the result of random causes? In this…

  17. Spectral diffusion in glasses : a photon-echo study of zincporphin in ethanol

    Meijers, Hans C.; Wiersma, Douwe A.

    1991-01-01

    Results of picosecond photon-echo experiments on zincporphin in an ethanol glass at 1.5 K are reported and discussed. At 1.5 K, the two-pulse photon echo yields a pure dephasing time constant, a factor of 5.7 larger than the long-lived stimulated photon echo for a waiting time of 25 ms. This result

  18. Ultrasound pulse-echo measurements on rough surfaces with linear array transducers

    Sjøj, Sidsel M. N.; Blanco, Esther N.; Wilhjelm, Jens E.;

    2012-01-01

    The echo from planar surfaces with rms roughness, Rq, in the range from 0-155 μm was measured with a clinical linear array transducer at different angles of incidence at 6 MHz and 12 MHz. The echo-pulse from the surfaces was isolated with an equal sized window and the power of the echo-pulse was ...

  19. Echothermometry: The potential role of echo sounders in ocean acoustic thermometry

    Ainslie, M.A.; Dybedal, J.; Kinneging; Lam, F.P.A.; Simons, D.G.; Snellen, M.

    2005-01-01

    The sensitivity of sound speed to temperature makes it possible to use an echo sounder as a thermometer, provided that the salinity and water depth are known with sufficient precision. Could ‘echothermometry’ – i.e., the use of an echo sounder, or a network of echo sounders, to measure temperature i

  20. NIF Ambient Vibration Measurements

    LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B

  1. Accelerated fast spin-echo magnetic resonance imaging of the heart using a self-calibrated split-echo approach.

    Sabrina Klix

    Full Text Available PURPOSE: Design, validation and application of an accelerated fast spin-echo (FSE variant that uses a split-echo approach for self-calibrated parallel imaging. METHODS: For self-calibrated, split-echo FSE (SCSE-FSE, extra displacement gradients were incorporated into FSE to decompose odd and even echo groups which were independently phase encoded to derive coil sensitivity maps, and to generate undersampled data (reduction factor up to R = 3. Reference and undersampled data were acquired simultaneously. SENSE reconstruction was employed. RESULTS: The feasibility of SCSE-FSE was demonstrated in phantom studies. Point spread function performance of SCSE-FSE was found to be competitive with traditional FSE variants. The immunity of SCSE-FSE for motion induced mis-registration between reference and undersampled data was shown using a dynamic left ventricular model and cardiac imaging. The applicability of black blood prepared SCSE-FSE for cardiac imaging was demonstrated in healthy volunteers including accelerated multi-slice per breath-hold imaging and accelerated high spatial resolution imaging. CONCLUSION: SCSE-FSE obviates the need of external reference scans for SENSE reconstructed parallel imaging with FSE. SCSE-FSE reduces the risk for mis-registration between reference scans and accelerated acquisitions. SCSE-FSE is feasible for imaging of the heart and of large cardiac vessels but also meets the needs of brain, abdominal and liver imaging.

  2. 2008 Vibrational Spectroscopy

    Philip J. Reid

    2009-09-21

    The conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and interfaces. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of systems.

  3. Vibration intensity difference thresholds

    Forta, Nazim Gizem

    2009-01-01

    The intensity difference threshold is defined as ‘the difference in the intensity of two stimuli which is just sufficient for their difference to be detected’. The aim of this thesis is to advance understanding of the perception of vibration intensity differences in humans. In addition to increasing understanding of the tactile senses, knowledge of difference perception could inform various applications such as the optimisation of the vibration characteristics of vehicles and ...

  4. Liver fat quantification: Comparison of dual-echo and triple-echo chemical shift MRI to MR spectroscopy

    Satkunasingham, Janakan; Besa, Cecilia [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Bane, Octavia [Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Shah, Ami [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Oliveira, André de; Gilson, Wesley D.; Kannengiesser, Stephan [Siemens AG, Healthcare Sector, Erlangen (Germany); Taouli, Bachir, E-mail: bachir.taouli@mountsinai.org [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States)

    2015-08-15

    Highlights: • We present a large cohort of patients who underwent dual and triple echo chemical shift imaging against multi-echo T{sub 2} corrected MR spectroscopy (MRS) for liver fat quantification. • Our data suggests that a triple-echo sequence is highly accurate for detection of liver fat, even in the presence of T{sub 2}{sup *} shortening, with minor discrepancies when compared with the advanced fat quantification method. - Abstract: Purpose: To assess the diagnostic value of MRI using dual-echo (2PD) and triple-echo (3PD) chemical shift imaging for liver fat quantification against multi-echo T{sub 2} corrected MR spectroscopy (MRS) used as the reference standard, and examine the effect of T{sub 2}{sup *} imaging on accuracy of MRI for fat quantification. Materials and methods: Patients who underwent 1.5 T liver MRI that incorporated 2PD, 3PD, multi-echo T{sub 2}{sup *} and MRS were included in this IRB approved prospective study. Regions of interest were placed in the liver to measure fat fraction (FF) with 2PD and 3PD and compared with MRS-FF. A random subset of 25 patients with a wide range of MRS-FF was analyzed with an advanced FF calculation method, to prove concordance with the 3PD. The statistical analysis included correlation stratified according to T{sub 2}{sup *}, Bland-Altman analysis, and calculation of diagnostic accuracy for detection of MRS-FF > 6.25%. Results: 220 MRI studies were identified in 217 patients (mean BMI 28.0 ± 5.6). 57/217 (26.2%) patients demonstrated liver steatosis (MRS-FF > 6.25%). Bland-Altman analysis revealed strong agreement between 3PD and MRS (mean ± 1.96 SD: −0.5% ± 4.6%) and weaker agreement between 2PD and MRS (4.7% ± 16.0%). Sensitivity of 3PD for diagnosing FF> 6.25% was higher than that of 2PD. 3PD-FF showed minor discrepancies (coefficient of variation <10%) from FF measured with the advanced method. Conclusion: Our large series study validates the use of 3PD chemical shift sequence for detection of

  5. Liver fat quantification: Comparison of dual-echo and triple-echo chemical shift MRI to MR spectroscopy

    Highlights: • We present a large cohort of patients who underwent dual and triple echo chemical shift imaging against multi-echo T2 corrected MR spectroscopy (MRS) for liver fat quantification. • Our data suggests that a triple-echo sequence is highly accurate for detection of liver fat, even in the presence of T2* shortening, with minor discrepancies when compared with the advanced fat quantification method. - Abstract: Purpose: To assess the diagnostic value of MRI using dual-echo (2PD) and triple-echo (3PD) chemical shift imaging for liver fat quantification against multi-echo T2 corrected MR spectroscopy (MRS) used as the reference standard, and examine the effect of T2* imaging on accuracy of MRI for fat quantification. Materials and methods: Patients who underwent 1.5 T liver MRI that incorporated 2PD, 3PD, multi-echo T2* and MRS were included in this IRB approved prospective study. Regions of interest were placed in the liver to measure fat fraction (FF) with 2PD and 3PD and compared with MRS-FF. A random subset of 25 patients with a wide range of MRS-FF was analyzed with an advanced FF calculation method, to prove concordance with the 3PD. The statistical analysis included correlation stratified according to T2*, Bland-Altman analysis, and calculation of diagnostic accuracy for detection of MRS-FF > 6.25%. Results: 220 MRI studies were identified in 217 patients (mean BMI 28.0 ± 5.6). 57/217 (26.2%) patients demonstrated liver steatosis (MRS-FF > 6.25%). Bland-Altman analysis revealed strong agreement between 3PD and MRS (mean ± 1.96 SD: −0.5% ± 4.6%) and weaker agreement between 2PD and MRS (4.7% ± 16.0%). Sensitivity of 3PD for diagnosing FF> 6.25% was higher than that of 2PD. 3PD-FF showed minor discrepancies (coefficient of variation <10%) from FF measured with the advanced method. Conclusion: Our large series study validates the use of 3PD chemical shift sequence for detection of liver fat in the clinical environment, even in the presence of

  6. Prospects for Precise Measurements with Echo Atom Interferometry

    Barrett, Brynle; Beica, Hermina C; Vorozcovs, Andrejs; Pouliot, Alexander; Kumarakrishnan, A

    2016-01-01

    Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration $g$ and the determination of the atomic fine structure through measurements of the atomic recoil frequency $\\omega_q$. Here we review the development of different configurations of echo interferometers that are best suited to achieve these goals. We describe experiments that utilize near-resonant excitation of laser-cooled rubidium atoms by a sequence of standing wave pulses to measure $\\omega_q$ with a statistical uncertainty of 37 parts per billion (ppb) on a time scale of $\\sim 50$ ms and $g$ with a statistical precision of 75 ppb. Related coherent transient techniques that have achieved the most statistically precise measurements of atomic g-factor ratios are also outlined. We discuss the reduction of prominent systematic effects in these experiments using off-resonant excitation by low-cost, high-power lasers.

  7. Echo Chambers: Emotional Contagion and Group Polarization on Facebook

    Del Vicario, Michela; Bessi, Alessandro; Zollo, Fabiana; Scala, Antonio; Caldarelli, Guido; Quattrociocchi, Walter

    2016-01-01

    Recent findings showed that users on Facebook tend to select information that adhere to their system of beliefs and to form polarized groups -- i.e., echo chambers. Such a tendency dominates information cascades and might affect public debates on social relevant issues. In this work we explore the structural evolution of communities of interest by accounting for users emotions and engagement. Focusing on the Facebook pages reporting on scientific and conspiracy content, we characterize the evolution of the size of the two communities by fitting daily resolution data with three growth models -- i.e. the Gompertz model, the Logistic model, and the Log-logistic model. Then, we explore the interplay between emotional state and engagement of users in the group dynamics. Our findings show that communities' emotional behavior is affected by the users' involvement inside the echo chamber. Indeed, to an higher involvement corresponds a more negative approach. Moreover, we observe that, on average, more active users sh...

  8. Mean-field theory of echo state networks

    Massar, Marc; Massar, Serge

    2013-04-01

    Dynamical systems driven by strong external signals are ubiquitous in nature and engineering. Here we study “echo state networks,” networks of a large number of randomly connected nodes, which represent a simple model of a neural network, and have important applications in machine learning. We develop a mean-field theory of echo state networks. The dynamics of the network is captured by the evolution law, similar to a logistic map, for a single collective variable. When the network is driven by many independent external signals, this collective variable reaches a steady state. But when the network is driven by a single external signal, the collective variable is non stationary but can be characterized by its time averaged distribution. The predictions of the mean-field theory, including the value of the largest Lyapunov exponent, are compared with the numerical integration of the equations of motion.

  9. CORRELATIONS BETWEEN HAIL EVENTS AND RADAR ECHOES IN TRANSYLVANIA

    RECKERTH U. D.

    2015-03-01

    Full Text Available Over 500 hail events reported across Transylvania by meteorological and hydrological stations, with several large hail events (i.e. hail diameter ≥ 2 cm, were studied during 2004-2014. The purpose of this study was to determine the correlations between the hail events, especially the hail size, and different radar echoes, such as reflectivity, vertically integrated liquid, echo tops of the clouds, and instability indices, such as the vertical totals index, in order to provide useful information regarding forecast of hail, especially large hail. The radar data were measured by the WSR-98D Doppler radar from Bobohalma-Tarnaveni, Mures county, placed in central Transylvania. I have also studied the use of vertically integrated liquid density as an indicator for the size of hail in thunderstorms, applied in Transylvania for operational use. The methodology used in deriving this comparison is provided to assist other operational weather forecasters in developing VIL Density vs. hail size correlation.

  10. Echoes from the companion star in Sco X-1

    Muñoz-Darias, T; Casares, J; Dhillon, V S; Marsh, T R; Cornelisse, R; Steeghs, D; Charles, P A

    2007-01-01

    We present simultaneous X-ray (RXTE) and optical (ULTRACAM) narrow band (Bowen blend/HeII and nearby continuum) observations of Sco X-1 at 2-10 Hz time resolution. We find that the Bowen/HeII emission lags the X-ray light-curves with a light travel time of ~11-16s which is consistent with reprocessing in the companion star. The echo from the donor is detected at orbital phase ~0.5 when Sco X-1 is at the top of the Flaring Branch. Evidence of echoes is also seen at the bottom of the Flaring Branch but with time-lags of 5-10s which are consistent with reprocessing in an accretion disc with a radial temperature profile. We discuss the implication of our results for the orbital parameters of Sco X-1.

  11. Spin-Echo Modulation Experiments with Soft Gaussian Pulses

    Miao, Xijia; Freeman, Ray

    An analysis is presented for a homonuclear spin-echo experiment in which refocusing and spin inversion are implemented by simultaneous soft 180° pulses applied to two weakly coupled spins. It is shown that for this experiment, simple pulses of short duration (for example, Gaussian pulses) are preferable to more complex shapes such as BURP pulses or Gaussian cascades, since this limits the generation of undesirable multiple-quantum coherence. An expression is derived for the optimum delay between excitation and detection for the generation of anti-phase magnetization at the two sites. The theoretical results are in good agreement with experiment. The doubly selective spin-echo technique is shown to be useful for the determination of small unresolved spin-spin splittings, and this is illustrated with results from the 400 MHz proton spectrum of strychnine.

  12. Prospects for Precise Measurements with Echo Atom Interferometry

    Brynle Barrett

    2016-06-01

    Full Text Available Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration g and the determination of the atomic fine structure through measurements of the atomic recoil frequency ω q . Here we review the development of different configurations of echo interferometers that are best suited to achieve these goals. We describe experiments that utilize near-resonant excitation of laser-cooled rubidium atoms by a sequence of standing wave pulses to measure ω q with a statistical uncertainty of 37 parts per billion (ppb on a time scale of ∼50 ms and g with a statistical precision of 75 ppb. Related coherent transient techniques that have achieved the most statistically precise measurements of atomic g-factor ratios are also outlined. We discuss the reduction of prominent systematic effects in these experiments using off-resonant excitation by low-cost, high-power lasers.

  13. Diffusion imaging with stimulated echoes: signal models and experiment design

    Alexander, Daniel C

    2013-01-01

    Purpose: Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared to $\\ttwo$. It is important therefore for biomedical diffusion imaging applications at 7T and above where $\\ttwo$ is short. However, imaging gradients in the STEAM sequence contribute much greater diffusion weighting than in PGSE, but are often ignored during post-processing. We demonstrate here that this can severely bias parameter estimates. Method: We present models for the STEAM signal for free and restricted diffusion that account for crusher and slice-select (butterfly) gradients to avoid such bias. The butterfly gradients also disrupt experiment design, typically by skewing gradient-vectors towards the slice direction. We propose a simple compensation to the diffusion gradient vector specified to the scanner that counterbalances the butterfly gradients to preserve the intended experiment design. Results: High-field data fixed monkey brain e...

  14. Emergence of metapopulations and echo chambers in mobile agents

    Starnini, Michele; Baronchelli, Andrea

    2016-01-01

    Multi-agent models often describe populations segregated either in the physical space, i.e. subdivided in metapopulations, or in the ecology of opinions, i.e. partitioned in echo chambers. Here we show how the interplay between homophily and social influence controls the emergence of both kinds of segregation in a simple model of mobile agents, endowed with a continuous opinion variable. In the model, physical proximity determines a progressive convergence of opinions but differing opinions result in agents moving away from each others. This feedback between mobility and social dynamics determines to the onset of a stable dynamical metapopulation scenario where physically separated groups of like-minded individuals interact with each other through the exchange of agents. The further introduction of confirmation bias in social interactions, defined as the tendency of an individual to favor opinions that match his own, leads to the emergence of echo chambers where different opinions can coexist also within the ...

  15. Inaudible functional MRI using a truly mute gradient echo sequence

    Marcar, V.L. [University of Zurich, Department of Psychology, Neuropsychology, Treichlerstrasse 10, 8032 Zurich (Switzerland); Girard, F. [GE Medical Systems SA, 283, rue de la Miniere B.P. 34, 78533 Buc Cedex (France); Rinkel, Y.; Schneider, J.F.; Martin, E. [University Children' s Hospital, Neuroradiology and Magnetic Resonance, Department of Diagnostic Imaging, Steinwiesstrasse 75, 8032 Zurich (Switzerland)

    2002-11-01

    We performed functional MRI experiments using a mute version of a gradient echo sequence on adult volunteers using either a simple visual stimulus (flicker goggles: 4 subjects) or an auditory stimulus (music: 4 subjects). Because the mute sequence delivers fewer images per unit time than a fast echo planar imaging (EPI) sequence, we explored our data using a parametric ANOVA test and a non-parametric Wilcoxon-Mann-Whitney test in addition to performing a cross-correlation analysis. All three methods were in close agreement regarding the location of the BOLD contrast signal change. We demonstrated that, using appropriate statistical analysis, functional MRI using an MR sequence that is acoustically inaudible to the subject is feasible. Furthermore compared with the ''silent'' event-related procedures involving an EPI protocol, our mGE protocol compares favourably with respect to experiment time and the BOLD signal. (orig.)

  16. Inaudible functional MRI using a truly mute gradient echo sequence

    We performed functional MRI experiments using a mute version of a gradient echo sequence on adult volunteers using either a simple visual stimulus (flicker goggles: 4 subjects) or an auditory stimulus (music: 4 subjects). Because the mute sequence delivers fewer images per unit time than a fast echo planar imaging (EPI) sequence, we explored our data using a parametric ANOVA test and a non-parametric Wilcoxon-Mann-Whitney test in addition to performing a cross-correlation analysis. All three methods were in close agreement regarding the location of the BOLD contrast signal change. We demonstrated that, using appropriate statistical analysis, functional MRI using an MR sequence that is acoustically inaudible to the subject is feasible. Furthermore compared with the ''silent'' event-related procedures involving an EPI protocol, our mGE protocol compares favourably with respect to experiment time and the BOLD signal. (orig.)

  17. Stochastic Maximum Likelihood (SML parametric estimation of overlapped Doppler echoes

    E. Boyer

    2004-11-01

    Full Text Available This paper investigates the area of overlapped echo data processing. In such cases, classical methods, such as Fourier-like techniques or pulse pair methods, fail to estimate the first three spectral moments of the echoes because of their lack of resolution. A promising method, based on a modelization of the covariance matrix of the time series and on a Stochastic Maximum Likelihood (SML estimation of the parameters of interest, has been recently introduced in literature. This method has been tested on simulations and on few spectra from actual data but no exhaustive investigation of the SML algorithm has been conducted on actual data: this paper fills this gap. The radar data came from the thunderstorm campaign that took place at the National Astronomy and Ionospheric Center (NAIC in Arecibo, Puerto Rico, in 1998.

  18. Stochastic Maximum Likelihood (SML) parametric estimation of overlapped Doppler echoes

    Boyer, E.; Petitdidier, M.; Larzabal, P.

    2004-11-01

    This paper investigates the area of overlapped echo data processing. In such cases, classical methods, such as Fourier-like techniques or pulse pair methods, fail to estimate the first three spectral moments of the echoes because of their lack of resolution. A promising method, based on a modelization of the covariance matrix of the time series and on a Stochastic Maximum Likelihood (SML) estimation of the parameters of interest, has been recently introduced in literature. This method has been tested on simulations and on few spectra from actual data but no exhaustive investigation of the SML algorithm has been conducted on actual data: this paper fills this gap. The radar data came from the thunderstorm campaign that took place at the National Astronomy and Ionospheric Center (NAIC) in Arecibo, Puerto Rico, in 1998.

  19. Adaptive filtering algorithms for channel equalization and echo cancellation

    Swati Dhamija

    2011-09-01

    Full Text Available In this paper, we will be addressing the major concerns in telecommunication nowadays which are channel equalization and echo cancellation using different adaptive algorithms in order to identify the most efficient methodology. There are a number of conventional algorithms available in literature and every algorithm has its own properties, however the aim of every adaptive algorithm is to achieve minimum mean square error at a high rate of convergence and with less complexity. The experimental results prove that Least Mean Square algorithm (LMS is the best for channel equalization and Recursive Least Square (RLS is most efficient for echo cancellation. Moreover, LMS algorithms work efficiently in case of stochastic processes and on the contrary RLS is good for deterministic signals

  20. Efficient Multichannel NLMS Implementation for Acoustic Echo Cancellation

    Fredric Lindstrom

    2007-02-01

    Full Text Available An acoustic echo cancellation structure with a single loudspeaker and multiple microphones is, from a system identification perspective, generally modelled as a single-input multiple-output system. Such a system thus implies specific echo-path models (adaptive filter for every loudspeaker to microphone path. Due to the often large dimensionality of the filters, which is required to model rooms with standard reverberation time, the adaptation process can be computationally demanding. This paper presents a selective updating normalized least mean square (NLMS-based method which reduces complexity to nearly half in practical situations, while showing superior convergence speed performance as compared to conventional complexity reduction schemes. Moreover, the method concentrates the filter adaptation to the filter which is most misadjusted, which is a typically desired feature.

  1. Efficient Multichannel NLMS Implementation for Acoustic Echo Cancellation

    Schüldt Christian

    2007-01-01

    Full Text Available An acoustic echo cancellation structure with a single loudspeaker and multiple microphones is, from a system identification perspective, generally modelled as a single-input multiple-output system. Such a system thus implies specific echo-path models (adaptive filter for every loudspeaker to microphone path. Due to the often large dimensionality of the filters, which is required to model rooms with standard reverberation time, the adaptation process can be computationally demanding. This paper presents a selective updating normalized least mean square (NLMS-based method which reduces complexity to nearly half in practical situations, while showing superior convergence speed performance as compared to conventional complexity reduction schemes. Moreover, the method concentrates the filter adaptation to the filter which is most misadjusted, which is a typically desired feature.

  2. Birefringent neutron prisms for spin echo scattering angle measurement

    Pynn, Roger, E-mail: rpynn@indiana.ed [Indiana University, Bloomington, IN (United States); Oak Ridge National Laboratory, Oak Ridge, TN (United States); Fitzsimmons, M.R. [Los Alamos National Laboratory, Los Alamos, NM (United States); Lee, W.T. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Stonaha, P.; Shah, V.R.; Washington, A.L. [Indiana University, Bloomington, IN (United States); Kirby, B.J.; Majkrzak, C.F.; Maranville, B.B. [National Institute of Standards and Technology (United States)

    2009-09-01

    In the first decade of the 19th century, an English chemist, William Wollaston, invented an arrangement of birefringent prisms that splits a beam of light into two spatially separated beams with orthogonal polarizations. We have constructed similar devices for neutrons using triangular cross-section solenoids and employed them for Spin Echo Scattering Angle Measurement (SESAME). A key difference between birefringent neutron prisms and their optical analogues is that it is hard to embed the former in a medium which has absolutely no birefringence because this implies the removal of all magnetic fields. We have overcome this problem by using the symmetry properties of the Wollaston neutron prisms and of the overall spin echo arrangement. These symmetries cause a cancellation of Larmor phase aberrations and provide robust coding of neutron scattering angles with simple equipment.

  3. The Physics of Vibration

    Pippard, A. B.

    1989-11-01

    The study of vibration in physical systems is an important part of almost all fields in physics and engineering. This work, originally published in two volumes, examines the classical aspects in Part I and the quantum oscillator in Part II. The classical linear vibrator is treated first and the underlying unity of all linear oscillations in electrical, mechanical and acoustic systems is emphasized. Following this the book turns to the treatment of nonlinear vibrations, a field with which engineers and physicists are generally less familiar. In Part II the emphasis turns to quantum systems, that is those systems which can only be adequately described by quantum mechanics. The treatment concentrates on vibrations in atoms and molecules and their interaction with electromagnetic radiation. The similarities of classical and quantum methods are stressed and the limits of the classical treatment are examined. Throughout the book, each phenomenon discussed is illustrated with many examples and theory and experiment are compared. Although the reader may find that the physics discussed is demanding and the concepts are subtle in places, all mathematics used is familiar to both engineers and experimental scientists. Although not a textbook this is a useful introduction to the more advanced mathematical treatment of vibrations as it bridges the gap between the basic principles and more specialized concepts. It will be of great interest to advanced undergraduates and postgraduates as well as applied mathematicians, physicists and engineers in university and industry.

  4. Musical instrument mapping design with Echo State Networks

    Kiefer, Chris

    2014-01-01

    Echo State Networks (ESNs), a form of recurrent neural network developed in the field of Reservoir Computing, show significant potential for use as a tool in the design of mappings for digital musical instruments. They have, however, seldom been used in this area, so this paper explores their possible applications. This project contributes a new open source library, which was developed to allow ESNs to run in the Pure Data dataflow environment. Several use cases were explored, focusing on ad...

  5. Biophysical mechanisms of phase contrast in gradient echo MRI

    He, Xiang; Dmitriy A. Yablonskiy

    2009-01-01

    Recently reported contrast in phase images of human and animal brains obtained with gradient-recalled echo MRI holds great promise for the in vivo study of biological tissue structure with substantially improved resolution. Herein we investigate the origins of this contrast and demonstrate that it depends on the tissue “magnetic architecture” at the subcellular and cellular levels. This architecture is mostly determined by the structural arrangements of proteins, lipids, non-heme tissue iron,...

  6. Fetal echo doppler for early detection of congenital heart block

    Bergman, Gunnar

    2010-01-01

    Background: Fetal echo Doppler methods detecting prolonged atrioventricular (AV) time intervals, a mechanical PR interval corresponding to the electrical PR interval in ECG, have been proposed for surveillance of pregnancies at risk of complete congenital heart block (CCHB). The aim of this thesis was; to validate these Doppler methods by comparing AV time intervals from left ventricular inflow (MV), inflow and aortic outflow (MV-Ao) and superior vena cava and aortic flow ...

  7. Structural-communicative types of the perplexed echo question

    VOROBYOVA ELENA N.

    2015-01-01

    Modern linguistics has shown us that the language is not limited to questions with the standard semantics of interrogation. Among the interrogative sentences used in the secondary functions one can find inquiries with additional emotional colourings. Perplexity is the closest emotional evaluative meaning, accompanying the interrogative semantics of a question. In the paper, one of the structural-communicative types of the perplexed question (an echo question) is considered. Two structural typ...

  8. John Barth's "Echo": the story in love with its author

    Ziegler, Heide

    1980-01-01

    The emblematic quality of "Echo" derives its force from the double meaning of the word "self reflection" from both its concrete and its abstract connotations. In Barth's story, this double meaning serves to relate content and form and to establish an ironic tension between them: the encounter of mythic Narcissus, the story's protagonist. with his concrete self reflection - his image in the pool determines the content of the story; and his abstract self reflection - his search for self knowled...

  9. First experimental evidence for quantum echoes in scattering systems

    Dembowski, C.; Dietz, B.; Friedrich, T.; Graef, H. -D.; Heine, A.; Mejia-Monasterio, C.; Miski-Oglu, M.; A. Richter; T.H. Seligman

    2004-01-01

    A self-pulsing effect termed quantum echoes has been observed in experiments with an open superconducting and a normal conducting microwave billiard whose geometry provides soft chaos, i.e. a mixed phase space portrait with a large stable island. For such systems a periodic response to an incoming pulse has been predicted. Its period has been associated to the degree of development of a horseshoe describing the topology of the classical dynamics. The experiments confirm this picture and revea...

  10. "Derrida Artaud -Echos et Forçages"

    Ramond, Charles

    2014-01-01

    This article tries to characterize as accurately as possible, by taking into consideration the many texts that he wrote about Artaud, the type of relation that Derrida wishes to establish between literature and philosophy. Derrida distinguishes between two principal types of commentary: the "commentary-echo", in which the generic syllables of the commented text are repeated and amplified; and the "commentary-forcing", in which a certain displacement is imposed on the commented text. In the fi...

  11. GRMHD in axisymmetric dynamical spacetimes: the X-ECHO code

    Bucciantini, N.; Del Zanna, L.

    2010-01-01

    We present a new numerical code, X-ECHO, for general relativistic magnetohydrodynamics (GRMHD) in dynamical spacetimes. This is aimed at studying astrophysical situations where strong gravity and magnetic fields are both supposed to play an important role, such as for the evolution of magnetized neutron stars or for the gravitational collapse of the magnetized rotating cores of massive stars, which is the astrophysical scenario believed to eventually lead to (long) GRB events. The code is bas...

  12. NovoPen Echo® insulin delivery device

    Hyllested-Winge J

    2016-01-01

    Full Text Available Jacob Hyllested-Winge,1 Thomas Sparre,2 Line Kynemund Pedersen2 1Novo Nordisk Pharma Ltd, Tokyo, Japan; 2Novo Nordisk A/S, Søborg, Denmark Abstract: The introduction of insulin pen devices has provided easier, well-tolerated, and more convenient treatment regimens for patients with diabetes mellitus. When compared with vial and syringe regimens, insulin pens offer a greater clinical efficacy, improved quality of life, and increased dosing accuracy, particularly at low doses. The portable and discreet nature of pen devices reduces the burden on the patient, facilitates adherence, and subsequently contributes to the improvement in glycemic control. NovoPen Echo® is one of the latest members of the NovoPen® family that has been specifically designed for the pediatric population and is the first to combine half-unit increment (=0.5 U of insulin dosing with a simple memory function. The half-unit increment dosing amendments and accurate injection of 0.5 U of insulin are particularly beneficial for children (and insulin-sensitive adults/elders, who often require small insulin doses. The memory function can be used to record the time and amount of the last dose, reducing the fear of double dosing or missing a dose. The memory function also provides parents with extra confidence and security that their child is taking insulin at the correct doses and times. NovoPen Echo is a lightweight, durable insulin delivery pen; it is available in two different colors, which may help to distinguish between different types of insulin, providing more confidence for both users and caregivers. Studies have demonstrated a high level of patient satisfaction, with 80% of users preferring NovoPen Echo to other pediatric insulin pens. Keywords: NovoPen Echo®, memory function, half-unit increment dosing, adherence, children, adolescents 

  13. Spin-echo entanglement protection from random telegraph noise

    Franco, Rosario Lo; d'Arrigo, Antonio; Falci, Giuseppe; Compagno, Giuseppe; Paladino, Elisabetta

    2014-01-01

    We analyze local spin-echo procedures to protect entanglement between two non-interacting qubits, each subject to pure-dephasing random telegraph noise. For superconducting qubits this simple model captures characteristic features of the effect of bistable impurities coupled to the device. An analytic expression for the entanglement dynamics is reported. Peculiar features related to the non-Gaussian nature of the noise already observed in the single qubit dynamics also occur in the entangleme...

  14. The Visible and Near Infrared module of EChO

    Adriani, A; Gambicorti, L; Focardi, M; Oliva, E; Farina, M; Di Giorgio, A M; Santoli, F; Pace, E; Piccioni, G; Filacchione, G; Pancrazzi, M; Tozzi, A; Micela, G

    2014-01-01

    The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv= 9-12 and to see contrasts of the order of 10-4 - 10-5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4-2.5 micron spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4-1 and 1.0-2.5 micron spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectromete...

  15. Climatology and variability in the ECHO coupled GCM

    ECHO is a new global coupled ocean-atmosphere general circulation model (GCM), consisting of the Hamburg version of the European Centre atmospheric GCM (ECHAM) and the Hamburg Primitive Equation ocean GCM (HOPE). We performed a twenty year integration with ECHO. Climate drift is significant, but typical in the open oceans. Near the boundaries, however, SST errors are considerably larger. The coupled model simulates an irregular ENSO cycle in the tropical Pacific, with spatial patterns similar to those observed. The mechanism behind the model ENSO is related to the subsurface memory of the system, but stochastic forcing by the atmosphere seems to be also important. The variability, however, is somewhat weaker relative to observations. ECHO also simulates significant interannual variability in midlatitudes. Consistent with observations, variability over the North Pacific can be partly attributed to remote forcing from the tropics. In contract, the interannual variability over the North Atlantic appears to be generated locally. Indications for decadal-scale variability are also found over the North Atlantic. (orig.)

  16. Fiber optic vibration sensor

    Dooley, Joseph B.; Muhs, Jeffrey D.; Tobin, Kenneth W.

    1995-01-01

    A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity.

  17. Communication: Vibrational and vibronic coherences in the two dimensional spectroscopy of coupled electron-nuclear motion

    We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion

  18. Communication: Vibrational and vibronic coherences in the two dimensional spectroscopy of coupled electron-nuclear motion

    Albert, Julian; Falge, Mirjam; Hildenbrand, Heiko; Engel, Volker [Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, Campus Nord, Am Hubland, 97074 Würzburg (Germany); Gomez, Sandra; Sola, Ignacio R. [Departamento de Quimica Fisica, Universidad Complutense, 28040 Madrid (Spain)

    2015-07-28

    We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion.

  19. Spin-echo (SE) and stimulated-echo (STE) modes in combination with Gd-DTPA: MR image contrasts

    In a comparative study, the authors examined MR imaging contrast appearances in normal and pathologic tissues. The patient examinations were performed using different spin-echo (SE) and stimulated-echo (STE) sequences before and after the intravenous application of Gd-DTPA (Phillips Gyroscan S 15; 1.5 T). Most patients had tumors of the musculoskeletal system. In comparing the results of examinations performed with and without Gd-DTPA, they found that both SE and STE sequences produced more detailed information about the tumorous lesion itself, and in particular about the surrounding structures and its alterations, if Gd-DTPA was injected. In addition, the combination of STE and Gd-DTPA could have greater diagnostic potential than the combination of SE/Gd-DTPA because of increased contrast

  20. Vibrations and waves

    Kaliski, S

    2013-01-01

    This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth

  1. Usefulness of dual echo volumetric isotropic turbo spin echo acquisition (VISTA) in MR imaging of the temporomandibular joint

    We investigated the ability to detect the articular disk and joint effusion of the temporomandibular joint (TMJ) of a method of dual echo volumetric isotropic turbo spin echo acquisition (DE-VISTA) additional fusion images (AFI). DE-VISTA was performed in the 26 TMJ of 13 volunteers and 26 TMJ of 13 patients. Two-dimensional (2D) dual echo turbo spin echo was performed in the 26 TMJ of 13 volunteers. On a workstation, we added proton density-weighted images (PDWI) and T2 weighted images (T2WI) of the DE-VISTA per voxel to reconstruct DE-VISTA-AFI. Two radiologists reviewed these images visually and quantitatively. Visual evaluation of the articular disk was equivalent between DE-VISTA-AFI and 2D-PDWI. The sliding thin-slab multiplanar reformation (MPR) method of DE-VISTA-AFI could detect all articular disks. The ratio of contrast (CR) of adipose tissue by the articular disk to that of the articular disk itself was significantly higher in DE-VISTA-AFI than DE-VISTA-PDWI (P2WI but in only 3 of those joints in 2D-T2WI. The CR of joint effusion to adipose tissue on DE-VISTA-AFI did not differ significantly from that on DE-VISTA-PDWI. However, using DE-VISTA-T2WI in addition to DE-VISTA-PDWI, we could visually identify joint effusion on DE-VISTA-AFI that could not be identified on DE-VISTA-PDWI alone. DE-VISTA-AFI can depict the articular disk and a small amount of joint effusion by the required plane of MPR using the sliding thin-slab MPR method. (author)

  2. Study of gradient echo (GRE) dixon image using low-field MRI scanner for examination of metastatic bone marrow tumors. Comparison of double and single echo sequences

    We evaluated the gradient echo (GRE) Dixon method in metastatic bone tumors using a low-field MRI scanner (0.2 Tesla). This method is characterized by the double echo sequence of in-phase and opposed-phase. Studies were carried out on a phantom, 14 healthy volunteers, and clinical examples (33 vertebral bodies) using the T1-weighted spin echo, T2-weighted turbo spin echo, and GRE Dixon methods. Further, we obtained addition and subtraction images from the double echo sequence. In the clinical examples, the contrast-to-noise ratio (CNR) of the subtraction images (51.3±24.1) was significantly better than that of the T1-SE images (6.7±3.1, p<0.0001). For the examination of metastatic bone marrow tumors using a low-field MRI scanner (0.2 Tesla), subtraction images are thought to be the most effective. (author)

  3. Study of gradient echo (GRE) dixon image using low-field MRI scanner for examination of metastatic bone marrow tumors. Comparison of double and single echo sequences

    Ohno, Seiichiro; Kitayama, Takuichi; Ohkawa, Yoshihiro; Kobayashi, Hisakazu; Akagi, Noriaki; Yamashita, Eijiro; Nobuhara, Eitaro; Morioka, Yasuki [Okayama Univ. (Japan). Hospital; Togami, Izumi [Okayama Saiseikai General Hospital (Japan)

    2002-10-01

    We evaluated the gradient echo (GRE) Dixon method in metastatic bone tumors using a low-field MRI scanner (0.2 Tesla). This method is characterized by the double echo sequence of in-phase and opposed-phase. Studies were carried out on a phantom, 14 healthy volunteers, and clinical examples (33 vertebral bodies) using the T{sub 1}-weighted spin echo, T{sub 2}-weighted turbo spin echo, and GRE Dixon methods. Further, we obtained addition and subtraction images from the double echo sequence. In the clinical examples, the contrast-to-noise ratio (CNR) of the subtraction images (51.3{+-}24.1) was significantly better than that of the T{sub 1}-SE images (6.7{+-}3.1, p<0.0001). For the examination of metastatic bone marrow tumors using a low-field MRI scanner (0.2 Tesla), subtraction images are thought to be the most effective. (author)

  4. Variance of Fluctuating Radar Echoes from Thermal Noise and Randomly Distributed Scatterers

    Marco Gabella

    2014-02-01

    Full Text Available In several cases (e.g., thermal noise, weather echoes, …, the incoming signal to a radar receiver can be assumed to be Rayleigh distributed. When estimating the mean power from the inherently fluctuating Rayleigh signals, it is necessary to average either the echo power intensities or the echo logarithmic levels. Until now, it has been accepted that averaging the echo intensities provides smaller variance values, for the same number of independent samples. This has been known for decades as the implicit consequence of two works that were presented in the open literature. The present note deals with the deriving of analytical expressions of the variance of the two typical estimators of mean values of echo power, based on echo intensities and echo logarithmic levels. The derived expressions explicitly show that the variance associated to an average of the echo intensities is lower than that associated to an average of logarithmic levels. Consequently, it is better to average echo intensities rather than logarithms. With the availability of digital IF receivers, which facilitate the averaging of echo power, the result has a practical value. As a practical example, the variance obtained from two sets of noise samples, is compared with that predicted with the analytical expression derived in this note (Section 3: the measurements and theory show good agreement.

  5. Heat exchanger vibration

    The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration

  6. Blade Vibration Measurement System

    Platt, Michael J.

    2014-01-01

    The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.

  7. Compact Vibration Damper

    Ivanco, Thomas G. (Inventor)

    2014-01-01

    A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

  8. Light Echoes and Late-Time Emissions of Type Ia Supernovae

    Drozdov, Dina

    2016-05-01

    Type Ia supernovae have many applications in astronomy, yet with fundamental properties still not fully understood, new methods for investigating the environment of a supernova need to be developed. A light echo is produced from the scattering of light from a bright source and can be used to analyze the dust in the vicinity of the supernova and learn invaluable information about the source. These techniques can put constraints on explosion and progenitor models. Although light echo detections from Type Ia supernovae are rare, with only seven total extragalactic detections, this could be due to the lack of thorough late-epoch monitoring. Since key information is determined from even a single light echo detection, light echo searches should be undertaken in the future to supplement our understanding of supernovae. As part of our collaborative campaign for studying the emission of supernovae at late epochs, we have added two light echoes to a small sample size of Type Ia supernova light echo detections: SN 2009ig in NGC 1015 and a dual echo from SN 2007af in NGC 5584. Both echoes were observed with the Hubble Space Telescope and allow for the most detailed images of Type Ia supernova light echoes to date. Three filters (F555W, F814W, and F350LP) captured the echoes obtained with the Wide Field Camera 3, and since both host galaxies were imaged as part of the same observing program, these cases will be the best comparable light echo pairs. We also further investigate the light echoes from SN 2006X in NGC 4321 and SN 1998bu in NGC 3368 from Hubble Space Telescope archival images. Analyses performed on the images gives crucial insight into the dusty environment of the host galaxy and the surroundings of the supernova. The outer echo from SN 2007af was created from an interstellar dust sheet located ~800 pc in front of the supernova, while the inner echo could be from interstellar or circumstellar origin. A circumstellar light echo could imply a single degenerate

  9. Vibrational Conical Intersections: Implications for Ultrafast Vibrational Dynamics

    Dawadi, Mahesh; Prasad Thapaliya, Bishnu; Bhatta, Ram; Perry, David

    2015-03-01

    The presence of conical intersections (CIs) between electronic potential energy surfaces is known to play a key role in ultrafast electronic relaxation in diverse circumstances. Recent reports have documented the existence of vibrational CIs connecting vibrationally adiabatic surfaces. Just as electronic CIs are now appreciated to be ubiquitous, controlling the rates of many photochemical processes, the present work on methanol and methyl mercaptan suggests that vibrational CIs may also be widespread, possibly controlling the outcome of some high-energy processes where vibrationally excited species are present. Other examples of vibrational CIs include the vibrational Jahn-Teller effect in C3V organic molecules and transition metal complexes. While the present work addresses only the couplings within bound molecules, the concept of vibrational CIs providing pathways for ultrafast relaxation also applies to molecular collisions. This work is supported by DOE (DEFG02-90ER14151).

  10. Pattern recognition for rapid T2 mapping with stimulated echo compensation.

    Huang, Chuan; Altbach, Maria I; El Fakhri, Georges

    2014-09-01

    Indirect echoes (such as stimulated echoes) are a source of signal contamination in multi-echo spin-echo T2 quantification and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolved extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14-fold. PMID:24853466

  11. Pattern recognition for rapid T2 mapping with Stimulate Echo Compensation

    Huang, Chuan; Altbach, Maria I; Fakhri, Georges El

    2014-01-01

    Indirect echoes (such as stimulated echoes) are a source of signal contamination in a multi-echo spin-echo T2 quantification, and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolve extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14 fold. PMID:24853466

  12. Cerebral microhemorrhage : assessment with gradient-echo Mr

    Kim, Eung Yeop; Na, Dong Gyu; Byun, Hong Sik; Shin, Myung Hee [Samsung Medical Center, Seoul (Korea, Republic of)

    1998-05-01

    The purpose of this study is to assess the relationship between low signal intensity lesions, as seen on gradient-echo MR, and clinical factors. In 269 patients with cerebral ischemic symptoms, we analysed the results of gradient-echo MR. One hundred and thirty-nine of the patients were male and 130 were female; their ages ranged from 40 to 88 (mean, 64) years. Low signal intensity lesions were analyzed according to the dominant location ; superficial (cortex and subcortical white matter) or deep (basal ganglia, thalamus, periventricular white matter, and cerebellum). We analyzed the relationship between low signal intensity lesions and clinical factors including hypertension, diabetes mellitus (DM), and spontaneous intracerebral hemorrhage (ICH). Low signal intensity lesions were found in 66 of 269 patients (25%); hypertension was present in 57 of the 66 (86%, p< 0.05), DM in nine (14%, p>0.05), and spontaneous ICH in 26 (39 %, p<0.05). The dominant location of these lesions was superficial (n=19), deep (n=45), or both (n=2). Hypertension was deep. Hypertension was not present in nine of 66 patients (14%) with low signal intensity lesions; in six of these (66%), low signal intensity lesions were present mainly in the subcortical white matter or cortex. Cerebral low signal intensity lesions, as seen on gradient-echo MR imaging were associated with clinical factors such as hypertension and spontaneous ICH, and hypertension was more frequently found in patients in whom the location of low signal intensity lesions was deep. (author). 19 refs., 1 tab., 3 figs.

  13. NovoPen Echo(®) insulin delivery device.

    Hyllested-Winge, Jacob; Sparre, Thomas; Pedersen, Line Kynemund

    2016-01-01

    The introduction of insulin pen devices has provided easier, well-tolerated, and more convenient treatment regimens for patients with diabetes mellitus. When compared with vial and syringe regimens, insulin pens offer a greater clinical efficacy, improved quality of life, and increased dosing accuracy, particularly at low doses. The portable and discreet nature of pen devices reduces the burden on the patient, facilitates adherence, and subsequently contributes to the improvement in glycemic control. NovoPen Echo(®) is one of the latest members of the NovoPen(®) family that has been specifically designed for the pediatric population and is the first to combine half-unit increment (=0.5 U of insulin) dosing with a simple memory function. The half-unit increment dosing amendments and accurate injection of 0.5 U of insulin are particularly beneficial for children (and insulin-sensitive adults/elders), who often require small insulin doses. The memory function can be used to record the time and amount of the last dose, reducing the fear of double dosing or missing a dose. The memory function also provides parents with extra confidence and security that their child is taking insulin at the correct doses and times. NovoPen Echo is a lightweight, durable insulin delivery pen; it is available in two different colors, which may help to distinguish between different types of insulin, providing more confidence for both users and caregivers. Studies have demonstrated a high level of patient satisfaction, with 80% of users preferring NovoPen Echo to other pediatric insulin pens. PMID:26793007

  14. Effects of Refocusing Flip Angle Modulation and View Ordering in 3D Fast Spin Echo

    Busse, Reed F.; Brau, Anja C.S.; Vu, Anthony; Michelich, Charles R.; Bayram, Ersin; Kijowski, Richard; Reeder, Scott B; Howard A Rowley

    2008-01-01

    Recent advances have reduced scan time in three-dimensional fast spin echo (3D-FSE) imaging, including very long echo trains through refocusing flip angle (FA) modulation and 2D-accelerated parallel imaging. This work describes a method to modulate refocusing FAs that produces sharp point spread functions (PSFs) from very long echo trains while exercising direct control over minimum, center-k-space, and maximum FAs in order to accommodate the presence of flow and motion, SNR requirements, and...

  15. Neutron optics using transverse neutron spin echo method

    A new principle of neutron spin echo (NSE) method is proposed for neutron optics and neutron forward scattering experiments. The essential of this method is to set a sample in one of the Larmor precession fields. This sample geometry gives new physical information which has not been observed by the usual NSE method. Particularly, a refractive index of neutrons for Si single crystal which was determined to be 1-(1.85±1.16)x10-5 for 5.7 A. (author)

  16. A novel framework of multi-channel acoustic echo cancellation

    HE Zhaoshui; XIE Shengli; FU Yuli

    2006-01-01

    Conventionally, multi-channel acoustic echo cancellation (AEC) achieves the goal by estimating the impulse responses of the local room. However, generally, conventional AEC methods have no unique solutions. Due to the strong correlation of the input signals, conventional methods are with many disadvantages. To overcome this problem, a new framework is proposed in this paper based on SIMO(single input multiple output) blind deconvolution. Under the new framework, we achieve the goal by identifying the impulse responses of distant room and avoiding the disadvantages of the conventional methods.

  17. The echo-enabled harmonic generation options for FLASH II

    Deng, Haixiao; Faatz, Bart

    2011-01-01

    FLASH II is an upgrade to the existing free electron laser (FEL) FLASH. The echo-enabled harmonic generation (EEHG) scheme is proposed to be a potential seeding option of FLASH II. In this paper, the possibility of EEHG operation of FLASH II is investigated for the first time. With a combination of existing numerical codes, i.e. a laser-beam interaction code in an undulator (LBICU), a beam tracking code in a chicane (ELEGANT) and an universal FEL simulating code (GENESIS), the effects of beam energy chirp and coherent synchrotron radiation (CSR) on EEHG operation are studied as well. In addition, several interesting issues concerning EEHG simulation are discussed.

  18. CFAR Detection from Noncoherent Radar Echoes Using Bayesian Theory

    Wataru Suganuma

    2010-01-01

    Full Text Available We propose a new constant false alarm rate (CFAR detection method from noncoherent radar echoes, considering heterogeneous sea clutter. It applies the Bayesian theory for adaptive estimation of the local clutter statistical distribution in the cell under test. The detection technique can be readily implemented in existing noncoherent marine radar systems, which makes it particularly attractive for economical CFAR detection systems. Monte Carlo simulations were used to investigate the detection performance and demonstrated that the proposed technique provides a higher probability of detection than conventional techniques, such as cell averaging CFAR (CA-CFAR, especially with a small number of reference cells.

  19. Animal Communications Through Seismic Vibrations

    Hill, Peggy (University of Tulsa)

    2001-05-02

    Substrate vibration has been important to animals as a channel of communication for millions of years, but our literature on vibration in this context of biologically relevant information is only decades old. The jaw mechanism of the earliest land vertebrates allowed them to perceive substrate vibrations as their heads lay on the ground long before airborne sounds could be heard. Although the exact mechanism of vibration production and the precise nature of the wave produced are not always understood, recent development of affordable instrumentation to detect and measure vibrations has allowed researchers to answer increasingly sophisticated questions about how animals send and receive vibration signals. We now know that vibration provides information used in predator defense, prey detection, recruitment to food, mate choice, intrasexual competition, and maternal/brood social interactions in a variety of insect orders, spiders, crabs, scorpions, chameleons, frogs, golden moles, mole rats, kangaroos rats, wallabies, elephants and bison.

  20. Improved Active Vibration Isolation Systems

    2007-01-01

    The control force, feedback gain, and actuator stroke of several active vibration isolation systems were analyzed based on a single-layer active vibration isolation system. The analysis shows that the feedback gain and actuator stroke cannot be selected independently and the active isolation system design must make a compromise between the feedback gain and actuator stroke. The performance of active isolation systems can be improved by the joint vibration reduction using an active vibration isolation system with an adaptive dynamic vibration absorber. The results show that the joint vibration reduction method can successfully avoid the compromise between the feedback gain and actuator stroke. The control force and the object vibration amplitude are also greatly reduced.

  1. Efficient Fast Stereo Acoustic Echo Cancellation Based on Pairwise Optimal Weight Realization Technique

    Yukawa Masahiro

    2006-01-01

    Full Text Available In stereophonic acoustic echo cancellation (SAEC problem, fast and accurate tracking of echo path is strongly required for stable echo cancellation. In this paper, we propose a class of efficient fast SAEC schemes with linear computational complexity (with respect to filter length. The proposed schemes are based on pairwise optimal weight realization (POWER technique, thus realizing a "best" strategy (in the sense of pairwise and worst-case optimization to use multiple-state information obtained by preprocessing. Numerical examples demonstrate that the proposed schemes significantly improve the convergence behavior compared with conventional methods in terms of system mismatch as well as echo return loss enhancement (ERLE.

  2. Echo scintillation Index affected by cat-eye target's caliber with Cassegrain lens

    Shan, Cong-miao; Sun, Hua-yan; Zhao, Yan-zhong; Zheng, Yong-hui

    2015-10-01

    The optical aperture of cat-eye target has the aperture averaging effect to the active detecting laser of active laser detection system, which can be used to identify optical targets. The echo scintillation characteristics of the transmission-type lens target have been studied in previous work. Discussing the differences of the echo scintillation characteristics between the transmission-type lens target and Cassegrain lens target can be helpful to targets classified. In this paper, the echo scintillation characteristics of Cat-eye target's caliber with Cassegrain lens has been discussed . By using the flashing theory of spherical wave in the weak atmospheric turbulence, the annular aperture filter function and the Kolmogorov power spectrum, the analytic expression of the scintillation index of the cat-eye target echo of the horizontal path two-way transmission was given when the light is normal incidence. Then the impact of turbulence inner and outer scale to the echo scintillation index and the analytic expression of the echo scintillation index at the receiving aperture were presented using the modified Hill spectrum and the modified Von Karman spectrum. Echo scintillation index shows the tendency of decreasing with the target aperture increases and different ratios of the inner and outer aperture diameter show the different echo scintillation index curves. This conclusion has a certain significance for target recognition in the active laser detection system that can largely determine the target type by largely determining the scope of the cat-eye target which depending on echo scintillation index.

  3. A Comparative Study of Acoustic Echo Cancellation Algorithms in Sparse Impulse Response.

    Meenal Mahajan

    2015-01-01

    Full Text Available This paper aims at studying and comparing the performance of typical sparse algorithms for acoustic echo cancellation. When the echo path is sparse, the conventional Normalized Least Mean Square (NLMS algorithm suffers from slow convergence. Thus, sparse adaptive filtering algorithms were introduced to overcome the convergence problem of adaptive filters in sparse impulse response. To determine the algorithm with best performance in echo cancellers, the comparison between these algorithms based on Echo Return Loss Enhancement (ERLE and Mean Square Error (MSE is carried out using MATLAB.

  4. Noninvasive temperature estimation by detecting echo-strain change including thermal expansion

    Ma Yong; Zhang Dong; Gong Xiu-Fen; Liu Xiao-Zhou; Ma Qing-Yu; Qiu Yuan-Yuan

    2007-01-01

    This article studies the feasibility of noninvasive temperature estimation by detecting echo-strain including thermal expansion in therapeutic ultrasound treatment. This technique evaluates distributions of echo-strain and temperature inside the tissue by detecting echo signals pre- and post-heating, in combination with the temperature dependence of sound speed and thermal expansion. In the computer simulation and experimental study, echo signals pre- and postheating are acquired and then the temperature elevation is evaluated by correlation analysis. Results demonstrate that this technique can effectively extend the measured temperature range up to 75℃ with an accuracy of ±2 ℃.

  5. Vibration-induced field fluctuations in a superconducting magnet

    Britton, J W; Bohnet, J G; Uys, H; Biercuk, M J; Bollinger, J J

    2015-01-01

    Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed matter systems, and fundamental atomic particles. In high-precision applications, a common view is that that slow (<1 Hz) drift of the homogeneous magnetic field limits control and measurement precision. We report on previously undocumented higher-frequency field noise (10 Hz to 200 Hz) that limits the coherence time of 9Be+ electron-spin qubits in the 4.46 T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ~6 ms for the 9Be+ electron-spin resonance at 124 GHz, limited by part-per-billion fractional fluctuations in the magnet's homogeneous field. Vibration isolation of the magnet improved T2 to ~50 ms.

  6. Vibration control for piping system using dynamic vibration absorbers

    In order to bring about the degree of freedom in thermal expansion and contraction, piping systems are made so as to be flexible and easy to deflect, consequently, those are apt to be affected by vibration sources and cause troubles. The vibration is generally complex, and is to cause such problems as the fatigue damage due to resonance and vibration noise. In order to prevent them, the method of supporting piping systems has been taken, but it constrains largely the arrangement of piping systems. Recently, the move to control the vibration of piping systems as they are flexible by supporting them with high damping visco-elastic matters or positively giving damping to them by introducing dynamic vibration absorbers has begun. In this report, the basic knowledge on dynamic vibration absorbers is described, and the method of controlling vibration in a multiple degrees of freedom system is explained. Next, a simple three-dimensional piping system is taken up as an example, and its vibration modes from first order to third order are investigated. Thereafter, the optimum places for installing dynamic vibration absorbers in respective modes and the procedure of designing dynamic vibration absorbers are shown. (K.I.)

  7. Lattice Vibrations in Chlorobenzenes:

    Reynolds, P. A.; Kjems, Jørgen; White, J. W.

    1974-01-01

    Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K was...

  8. Vibrating Rays Theory

    Bilbao, Luis; Minotti, Fernando

    2014-01-01

    The present work is aimed to explain why we started to consider Vibrating Rays Theory (VRT) as a viable representation of nature, and to elaborate some of its consequences. In 1846 Faraday introduced the concept of vibrating rays, in which an atom is conceived as having rays that extend to infinity and move with it. According to this point of view, electromagnetic radiative phenomena correspond to vibration of these rays, which propagate at speed c relative to the rays (and the atom). Although a discussion on this subject might seem to be out-of-date, there are many reasons that justified this debate. The first reason is based on the fact that the constancy of the speed of light, irrespective of the source movement, has not been demonstrated experimentally in a conclusive way. In fact, only ballistic emission theories can be discarded by the experimental results. The second reason is based on the fact that study of radiometric data from spacecrafts indicates the existence of different kinds of anomalous Doppl...

  9. Pickin’ up good vibrations

    Katarina Anthony

    2015-01-01

    In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins.   A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...

  10. Vibrational stability of graphene

    Yangfan Hu

    2013-05-01

    Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

  11. An adjusted location model for SuperDARN backscatter echoes

    E. X. Liu

    2012-12-01

    Full Text Available The radars that form the Super Dual Auroral Radar Network (SuperDARN receive scatter from ionospheric irregularities in both the E- and F-regions, as well as the Earth's surface, either ground or sea. For ionospheric scatter, the current SuperDARN standard software considers a straight-line propagation from the radar to the scattering zone with an altitude assigned by a standard height model. The knowledge of the group delay to a scatter volume is not sufficient for an exact determination of the location of the irregularities. In this study, the difference between the locations of the backscatter echoes determined by SuperDARN standard software and by ray tracing has been evaluated, using the ionosonde data collected at Sodankylä, which is in the field-of-view of Hankasalmi SuperDARN radar. By studying elevation angle information of backscattered echoes from the data sets of Hankasalmi radar in 2008, we have proposed an adjusted fitting location model determined by slant range and elevation angle. To test the reliability of the adjusted model, an independent data set is selected in 2009. The result shows that the difference between the adjusted model and the ray tracing is significantly reduced and the adjusted model could provide a more accurate location for backscatter targets.

  12. The Balloon-Borne Exoplanet Experiment (EchoBeach)

    Pascale, E.

    2013-09-01

    The Balloon-Borne Exoplanet Experiment (EchoBeach) is a proposed sub-orbital spectroscopic instrument. Its primary scientific goal is to detect and characterize the atmospheres of transiting exoplanets in the Mid-IR part of the electromagnetic spectrum from 4 to 20 μm using a 1.6m diameter telescope. It is in this wavelength range where the contrast between the star and planet emission grows exponentially, and this spectral region is key to answering important questions about the existence and composition of exp-atmospheres. Due to the Earth atmospheric absorption and emission, bservations at these wavelength are impossible from the ground or even at aircraft altitudes, but become available to balloon-born instrumentation flying in the upper stratosphere. At present we have high fidelity Mid-IR spectra of just two exoplanets of any type. EchoBeach can greatly improve on this by observing a multitude of transiting exoplanets, well in advance of any planned space-mission.

  13. Modeling of cortical signals using echo state networks

    Zhou, Hanying; Wang, Yongji; Huang, Jiangshuai

    2009-10-01

    Diverse modeling frameworks have been utilized with the ultimate goal of translating brain cortical signals into prediction of visible behavior. The inputs to these models are usually multidimensional neural recordings collected from relevant regions of a monkey's brain while the outputs are the associated behavior which is typically the 2-D or 3-D hand position of a primate. Here our task is to set up a proper model in order to figure out the move trajectories by input the neural signals which are simultaneously collected in the experiment. In this paper, we propose to use Echo State Networks (ESN) to map the neural firing activities into hand positions. ESN is a newly developed recurrent neural network(RNN) model. Besides its dynamic property and short term memory just as other recurrent neural networks have, it has a special echo state property which endows it with the ability to model nonlinear dynamic systems powerfully. What distinguished it from transitional recurrent neural networks most significantly is its special learning method. In this paper we train this net with a refined version of its typical training method and get a better model.

  14. GRMHD in axisymmetric dynamical spacetimes: the X-ECHO code

    Bucciantini, N

    2010-01-01

    We present a new numerical code, X-ECHO, for general relativistic magnetohydrodynamics (GRMHD) in dynamical spacetimes. This is aimed at studying astrophysical situations where strong gravity and magnetic fields are both supposed to play an important role, such as for the evolution of magnetized neutron stars or for the gravitational collapse of the magnetized rotating cores of massive stars, which is the astrophysical scenario believed to eventually lead to (long) GRB events. The code is based on the extension of the Eulerian conservative high-order (ECHO) scheme [Del Zanna et al., A&A 473, 11 (2007)] for GRMHD, here coupled to a novel solver for the Einstein equations in the extended conformally flat condition (XCFC). We fully exploit the 3+1 Eulerian formalism, so that all the equations are written in terms of familiar 3D vectors and tensors alone, we adopt spherical coordinates for the conformal background metric, and we consider axisymmetric spacetimes and fluid configurations. The GRMHD conservation...

  15. Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV)

    Falahatpisheh, Ahmad; Kheradvar, Arash

    2015-11-01

    Measurement of 3D flow field inside the cardiac chambers has proven to be a challenging task. Current laser-based 3D PIV methods estimate the third component of the velocity rather than directly measuring it and also cannot be used to image the opaque heart chambers. Modern echocardiography systems are equipped with 3D probes that enable imaging the entire 3D opaque field. However, this feature has not yet been employed for 3D vector characterization of blood flow. For the first time, we introduce a method that generates velocity vector field in 4D based on volumetric echocardiographic images. By assuming the conservation of brightness in 3D, blood speckles are tracked. A hierarchical 3D PIV method is used to account for large particle displacement. The discretized brightness transport equation is solved in a least square sense in interrogation windows of size 163 voxels. We successfully validate the method in analytical and experimental cases. Volumetric echo data of a left ventricle is then processed in the systolic phase. The expected velocity fields were successfully predicted by V-Echo-PIV. In this work, we showed a method to image blood flow in 3D based on volumetric images of human heart using no contrast agent.

  16. Intramembrane Polarity by Electron Spin Echo Spectroscopy of Labeled Lipids

    Bartucci, Rosa; Guzzi, Rita; Marsh, Derek; Sportelli, Luigi

    2003-01-01

    The association of water (D2O) with phospholipid membranes was studied by using pulsed-electron spin resonance techniques. We measured the deuterium electron spin echo modulation of spin-labeled phospholipids by D2O in membranes of dipalmitoyl phosphatidylcholine with and without 50 mol% of cholesterol. The Fourier transform of the relaxation-corrected two-pulse echo decay curve reveals peaks, at one and two times the deuterium NMR frequency, that arise from the dipolar hyperfine interaction of the deuterium nucleus with the unpaired electron spin of the nitroxide-labeled lipid. For phosphatidylcholine spin-labeled at different positions down the sn-2 chain, the amplitude of the deuterium signal decreases toward the center of the membrane, and is reduced to zero from the C-12 atom position onward. At chain positions C-5 and C-7 closer to the phospholipid headgroups, the amplitude of the deuterium signal is greater in the presence of cholesterol than in its absence. These results are in good agreement with more indirect measurements of the transmembrane polarity profile that are based on the 14N-hyperfine splittings in the conventional continuous-wave electron spin resonance spectrum. PMID:12547783

  17. A conception of a new neutron spin echo reflectometer

    Complete text of publication follows. The tilted field technique in the neutron spin echo (NSE) spectroscopy came into the centre of attention in the recent few years. The method was first proposed by F. Mezei and R. Pynn in 1980. A real measurement for high resolution small angle scattering (SANS) on their resonance spin-echo spectrometer was published by Keller et al. [1]. A conception of a new instrument was proposed by M.T. Rekveldt [2] for SANS and reflectometry, using dc field perpendicular to the neutron beam. By further developing these ideas, the setup of a multitask instrument using the traditional way (dc field parallel to the beam) is discussed. This spectrometer may be best applicable in liquid surface reflectometry combining NSE by separating specular and nonspecular reflection. This instrument setup uses wide wavelength band and/or non-collimated neutron beam. (author) [1] T. Keller et al, Neutron News 6, no 3 (1995) 16.; [2] M.T. Rekveldt, Nuc. Inst. and Meth. in Physics Res. B 114 (1996) 366

  18. Photon echo spectroscopy reveals structure-dynamics relationships in carotenoids

    Christensson, N.; Polivka, T.; Yartsev, A.; Pullerits, T.

    2009-06-01

    Based on simultaneous analysis of the frequency-resolved transient grating, peak shift, and echo width signals, we present a model for the third-order optical response of carotenoids including population dynamics and system-bath interactions. Our frequency-resolved photon echo experiments show that the model needs to incorporate the excited-state absorption from both the S2 and the S1 states. We apply our model to analyze the experimental results on astaxanthin and lycopene, aiming to elucidate the relation between structure and system-bath interactions. Our analysis allows us to relate structural motifs to changes in the energy-gap correlation functions. We find that the terminal rings of astaxanthin lead to increased coupling between slow molecular motions and the electronic transition. We also find evidence for stronger coupling to higher frequency overdamped modes in astaxanthin, pointing to the importance of the functional groups in providing coupling to fluctuations influencing the dynamics in the passage through the conical intersection governing the S2-S1 relaxation.

  19. Magnetization transfer prepared gradient echo MRI for CEST imaging.

    Zhuozhi Dai

    Full Text Available Chemical exchange saturation transfer (CEST is an emerging MRI contrast mechanism that is capable of noninvasively imaging dilute CEST agents and local properties such as pH and temperature, augmenting the routine MRI methods. However, the routine CEST MRI includes a long RF saturation pulse followed by fast image readout, which is associated with high specific absorption rate and limited spatial resolution. In addition, echo planar imaging (EPI-based fast image readout is prone to image distortion, particularly severe at high field. To address these limitations, we evaluated magnetization transfer (MT prepared gradient echo (GRE MRI for CEST imaging. We proved the feasibility using numerical simulations and experiments in vitro and in vivo. Then we optimized the sequence by serially evaluating the effects of the number of saturation steps, MT saturation power (B1, GRE readout flip angle (FA, and repetition time (TR upon the CEST MRI, and further demonstrated the endogenous amide proton CEST imaging in rats brains (n = 5 that underwent permanent middle cerebral artery occlusion. The CEST images can identify ischemic lesions in the first 3 hours after occlusion. In summary, our study demonstrated that the readily available MT-prepared GRE MRI, if optimized, is CEST-sensitive and remains promising for translational CEST imaging.

  20. Demystifying the Digital Adaptive Filters Conducts in Acoustic Echo Cancellation

    Mohammad Anamul Haque

    2010-12-01

    Full Text Available A digital sound system resembles the wireless network link transmission system. A wireless network link is affected by several disturbing factors: fading, attenuation, non-linear distortion and noise. These factors are also unavoidable in acoustic echo cancellation. A few number of digital adaptive filter algorithms are approached to detect and cancel the noise in a system. Among these algorithms Least Mean Square, Block Frequency Domain Adaptive Filter and Kalman Filter are widely used to predict and remove the noise or unwanted signals. It is found that performances of these filters varied and depends upon the system of application. Therefore, a detailed performance analysis is exigent. The goal of this paper is to use an approach to analyze and figure out the best performed filter by performance evaluation in the context of acoustic echo cancellation.

  1. [Minimally invasive hemodynamic monitoring with esophageal echoDoppler].

    Monge, M I; Estella, A; Díaz, J C; Gil, A

    2008-01-01

    Hemodynamic monitoring is a key element in the care of the critical patients, providing an unquestionable aid in the attendance to diagnosis and the choice of the adequate treatment. Minimally invasive devices have been emerging over the past few years as an effective alternative to classic monitoring tools. The esophageal echoDoppler is among these. It makes it possible to obtain continuous and minimally invasive monitoring of the cardiac output in addition to other useful parameters by measuring the blood flow rate and the diameter of the thoracic descending aorta, which provides a sufficiently extensive view of the hemodynamic state of the patient and facilitates early detection of the changes produced by a sudden clinical derangement. Although several studies have demonstrated the usefulness of the esophageal Doppler in the surgical scene, there is scarce and dispersed evidence in the literature on its benefits in critical patients. Nevertheless, its advantages make it an attractive element to take into account within the diagnostic arsenal in the intensive care. The purpose of the following article is to describe how it works, its degree of validation with other monitoring methods and the role of esophageal echoDoppler as a minimally invasive monitoring tool for measuring cardiac output in the daily clinical practice, contributing with our own experience in the critical patient. PMID:18221711

  2. Motion and distortion correction of skeletal muscle echo planar images.

    Davis, Andrew D; Noseworthy, Michael D

    2016-07-01

    This paper examines two artifacts facing researchers who use gradient echo (GRE) echo planar imaging (EPI) for time series studies of skeletal muscles in limbs. The first is through-plane blood flow during the acquisition, causing a vessel motion artifact that inhibits proper motion correction of the data. The second is distortion of EPI images caused by B0 field inhomogeneities. Though software tools are available for correcting these artifacts in brain EPI images, the tools do not perform well on muscle images. The severity of the two artifacts was described using image similarity measures, and the data was processed with both a conventional motion correction program and custom written tools. The conventional program did not perform well on the limb images, in fact significantly degrading image quality in some trials. Data is presented which proves that arterial pulsatile signal caused the impairment in motion correction. The new tools were shown to perform much better, achieving substantial motion correction and distortion correction of the muscle EPI images. PMID:26972774

  3. MR evaluation of coronary stents with navigator echo and breath-hold cine gradient-echo techniques

    The aim of this study was to evaluate coronary artery stents with MR. Thirty-eight patients underwent MR imaging 48.1±6.6 days (range 38-60 days) after placement of 47 coronary stents of 11 different types, using navigator echo (NE) and cine gradient-echo (GE) techniques. For both sequences the low signal artifact was used to localize the stent, whereas the flow-related high signal before and distal to the stent was considered as a patency sign. Exercise electrocardiographic test (EET) had been performed 1-7 days before MR. No adverse event with possible relation to the MR examination was observed. All the stents were recognized as signal void with GE, and all but one with NE. Of the 2 patients with positive EET, the first one, with a stent on the left anterior descending coronary artery, presented low signal distal to the stent at both MR sequences, suggesting dysfunction [60% stenosis at conventional coronary angiography (CCA)]; the second one, with two sequential stents on the right coronary artery, presented lack of signal distal to the stents at both MR sequences, suggesting occlusion (97% stenosis at CCA). For the 44 remaining stents in 36 patients with negative EET, MR high signal before and distal to the stent suggested patency at both sequences. MR seems to be a safe and promising technique for non-invasive evaluation of coronary stents. (orig.)

  4. A Comparison Study of Single-Echo Susceptibility Weighted Imaging and Combined Multi-Echo Susceptibility Weighted Imaging in Visualizing Asymmetric Medullary Veins in Stroke Patients

    Wang, Chao; Qiu, Tiantian; Song, Ruirui; Jiaerken, Yerfan; Yang, Linglin; Wang, Shaoze

    2016-01-01

    Background Asymmetric medullary veins (AMV) are frequently observed in stroke patients and single-echo susceptibility weighted imaging (SWIs) is the main technique in detecting AMV. Our study aimed to investigate which echo time (TE) on single-echo susceptibility is the optimal echo for visualizing AMV and to compare the ability in detecting AMV in stroke patients between SWIs and multi-echo susceptibility weighted imaging (SWIc). Materials and Methods Twenty patients with middle cerebral artery stroke were included. SWI was acquired by using a multi-echo gradient-echo sequence with six echoes ranging from 5 ms to 35.240 ms. Three different echoes of SWIs including SWIs1 (TE = 23.144 ms), SWIs2 (TE = 29.192 ms) and SWIs3 (TE = 35.240 ms) were reconstructed. SWIc was averaged using the three echoes of SWIs. Image quality and venous contrast of medullary veins were compared between SWIs and SWIc using peak signal-to-noise ratio (PSNR), mean opinion score (MOS), contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). The presence of AMV was evaluated in each SWIs (1–3) and SWIc. Results SWIs2 had the highest PSNR, MOS and CNR and SWIs1 had the highest SNR among three different echoes of SWIs. No significant difference was found in SNR between SWIs1 and SWIs2. PSNR, MOS and CNR in SWIc were significantly increased by 27.9%, 28.2% and 17.2% compared with SWIs2 and SNR in SWIc was significantly increased by 32.4% compared with SWIs1. 55% of patients with AMV were detected in SWIs2, SWIs3 and SWIc, while 50% AMV were found in SWIs1. Conclusions SWIs using TE around 29ms was optimal in visualizing AMV. SWIc could improve image quality and venous contrast, but was equal to SWIs using a relative long TE in evaluating AMV. These results provide the technique basis for further research of AMV in stroke. PMID:27494171

  5. VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS

    Smirnov Vladimir Alexandrovich

    2012-10-01

    Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.

  6. Investigations on resolution enhancement in EPR by means of electron spin echoes

    The electron spin echo technique has been applied in four types of experiments: the measurement of electric field induced shifts of the EPR line; the detection of electron spin echo ENDOR; a relaxation measurement and the measurement of hyperfine interactions via the nuclear modulation effect. (Auth.)

  7. Zonal asymmetry of daytime 150-km echoes observed by Equatorial Atmosphere Radar in Indonesia

    T. Yokoyama

    2009-03-01

    Full Text Available Multi-beam observations of the daytime ionospheric E-region irregularities and the so-called 150-km echoes with the 47-MHz Equatorial Atmosphere Radar (EAR in West Sumatra, Indonesia (0.20° S, 100.32° E, 10.36° S dip latitude are presented. 150-km echoes have been frequently observed by the EAR, and their characteristics are basically the same as the equatorial ones, except for an intriguing zonal asymmetry; stronger echoes in lower altitudes in the east directions, and weaker echoes in higher altitudes in the west. The highest occurrence is seen at 5.7° east with respect to the magnetic meridian, and the altitude gradually increases as viewing from the east to west. Arc structures which return backscatter echoes are proposed to explain the asymmetry. While the strength of radar echoes below 105 km is uniform within the wide coverage of azimuthal directions, the upper E-region (105–120 km echoes also show a different type of zonal asymmetry, which should be generated by an essentially different mechanism from the lower E-region and 150-km echoes.

  8. The Echo Approach in Developing Items for Student Evaluation of Teaching Performance

    Cunningham, J. Barton; MacGregor, James N.

    2006-01-01

    This article illustrates the application of the Echo approach, originally designed to identify values of different cultures and subcultures, to the generation of questionnaire items for students to evaluate faculty teaching performance. Students preferred items generated using the Echo method over faculty-designed items and items developed by…

  9. Strong correlation between quasiperiodic echoes and plasma drift in the E region

    Chen, Gang; Jin, Han; Huang, Xueqin; Zhong, Dingkun; Yan, Chunxiao; Yang, Guotao

    2015-10-01

    Simultaneous observations of quasiperiodic (QP) echoes and plasma drift in the ionospheric E region were conducted in Fuke (19.5°N, 109.1°E), Hainan province, China, to investigate the QP striation tilts under varying plasma drift conditions. The E region field-aligned irregularities (FAIs), observed using the Hainan VHF radar, and the drift velocities of the plasma blobs in the Es layer, recorded by the Hainan Digisonde operating in drift mode, are reported. The QP echoes and drift data recorded during the entire year of 2013 were analyzed and compared. A surprising consistency between the striation tilt of the QP echoes and the drift direction of the plasma blobs was discovered. A negative echo striation of the QP FAIs was recorded when the measured drift direction of the plasma blobs was southward, whereas a positive echo striation was observed during the northward drift. Furthermore, the echo trace was continuous, whereas the QP striation changed from negative to positive, and vice versa. Thus, it can be concluded that the morphology of the QP echoes may be controlled by the background wind fields in the E region. The northward/southward-drifting striated FAIs in the observation region of a coherent scatter radar might induce the positive/negative QP echo striation in the range-time-intensity plots.

  10. Variations in the occurrence of SuperDARN F region echoes

    Ghezelbash, M.; Fiori, R. A. D.; Koustov, A. V.

    2014-02-01

    The occurrence of F region ionospheric echoes observed by a number of SuperDARN HF radars is analyzed statistically in order to infer solar cycle, seasonal, and diurnal trends. The major focus is on Saskatoon radar data for 1994-2012. The distribution of the echo occurrence rate is presented in terms of month of observation and magnetic local time. Clear repetitive patterns are identified during periods of solar maximum and solar minimum. For years near solar maximum, echoes are most frequent near midnight during winter. For years near solar minimum, echoes occur more frequently near noon during winter, near dusk and dawn during equinoxes and near midnight during summer. Similar features are identified for the Hankasalmi and Prince George radars in the northern hemisphere and the Bruny Island TIGER radar in the southern hemisphere. Echo occurrence for the entire SuperDARN network demonstrates patterns similar to patterns in the echo occurrence for the Saskatoon radar and for other radars considered individually. In terms of the solar cycle, the occurrence rate of nightside echoes is shown to increase by a factor of at least 3 toward solar maximum while occurrence of the near-noon echoes does not significantly change with the exception of a clear depression during the declining phase of the solar cycle.

  11. Signal changes in gradient echo images of human brain induced by hypo- and hyperoxia

    Rostrup, Egill; Larsson, H B; Toft, P B; Garde, K; Henriksen, O

    1995-01-01

    The effect of hypoxia (inspired oxygen fraction, FiO2 of 10% and 16%) and hyperoxia (FiO2) of 100%) on gradient echo images of the brain using long echo times was investigated in six healthy volunteers (age 24-28 years). Different flip angles were used with an FiO2 of 10% to assess the importance...

  12. Stationary echo canceling in velocity estimation by time-domain cross-correlation

    Jensen, Jørgen Arendt

    1993-01-01

    The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated that...

  13. Vibration issues in passenger car

    Rafał BURDZIK; Konieczny, Łukasz

    2014-01-01

    Vibration phenomena occurring in vehicles are very relevant for safety and comfort. Passenger car must be considered as a multi-technical system in which there are non-linear phenomena. Therefore, vibrations occurring in vehicles should be analyzed in many points of car structure and relate them to other criteria analysis. The paper presents examples of the results of vibration and their distribution at selected points during laboratory research and road tests.

  14. Vibration issues in passenger car

    Rafał BURDZIK

    2014-09-01

    Full Text Available Vibration phenomena occurring in vehicles are very relevant for safety and comfort. Passenger car must be considered as a multi-technical system in which there are non-linear phenomena. Therefore, vibrations occurring in vehicles should be analyzed in many points of car structure and relate them to other criteria analysis. The paper presents examples of the results of vibration and their distribution at selected points during laboratory research and road tests.

  15. Comparison between two.magnetic resonance sequences (spin-echo and gradient-echo) in the analysis of lesions of the knee joint meniscus

    To compare the diagnostic reliability, the proportion of common diagnoses and the degree of agreement between the results of two magnetic resonance (MR) sequences in the diagnosis of lesions of the meniscus of the knee. One hundred consecutive patients were studied prospectively by MR (1,5 Teslas). All of them underwent T1-weighted spin-echo and T1 and T2-weighted gradient-echo sequences. The final diagnosis was based on the combined results of four imaging sequences. The sensitivity, specificity, positive predictive value (PPV) and negative predictive (NPV) in terms of the final diagnosis were calculated for each meniscus and MR technique. The chi.squared test and kappa test were employed for the statistical analysis. There were discrepancies between the final diagnosis and the spin-echo sequence in 4 cases and between the final diagnosis and the gradient-echo sequences in 5 Both spin-echo and gradient-echo sequences showed the same diagnostic reliabilities: sensitivity of 0.98, specificity of 0.99, PPV of 0.98 and NPV of 0.99. The correlation between the two sequences was highly significant (chi-squared, p < 0.001) with a very high rate of agreement (kappa=0.84). The two sequences can be considered equally reliable in the study of meniscal lesions. (Author) 7 refs

  16. CUTLASS HF radar observations of high-velocity E-region echoes

    M. V. Uspensky

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms1 , while the other group had significantly larger velocities, of the order of 700 ms1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  17. Lever mechanism for vibration isolation

    Mitchell Gohnert

    2010-04-01

    Full Text Available By introducing lever mechanism into the conventional vibration isolation system, new vibration isolation systems such as lever-damper isolator (LDI, lever-spring isolator (LSI and lever-spring-mass isolator (LSMI can be developed. The transmissibility of LDI, transmissibility of LSI and that of LSMI are obtained analytically. With numerical simulation, the vibration isolation performance of these systems and the effect of parameters on the performance are investigated. The results show that the performance of traditional vibration isolator can be improved by the introducing of lever mechanism. The results also show that the new systems have less constraint in design.

  18. Chaotic vortex induced vibrations

    Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)

    2014-12-15

    This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.

  19. Digital analysis of vibrations

    Vibrational measurements, e.g. on turbomachinery, can be evaluated rapidly and economically with the aid of a combination of the following instruments: a desk-top computer, a two-channel vector filter and a FFT spectral analyzer. This equipment combination is available within the Allianz Centre for Technology and has also been used for mobile, on-site investigations during the last year. It enables calculation and display of time functions, kinetic shaft orbits, displacement diagrams. Bode plots, polar-coordinate plots, cascade diagrams and histograms. (orig.)

  20. Structural Acoustics and Vibrations

    Chaigne, Antoine

    This structural chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  1. Nonlinear interferometric vibrational imaging

    Marks, D L

    2003-01-01

    Coherent Anti-Stokes Raman Scattering (CARS) processes are ``coherent,'' but the phase of the anti-Stokes radiation is usually lost by most incoherent spectroscopic CARS measurements. We propose a novel Raman microscopy imaging method called Nonlinear Interferometric Vibrational Imaging, which measures Raman spectra by obtaining the temporal anti-Stokes signal through nonlinear interferometry. With a more complete knowledge of the anti-Stokes signal, we show through simulations that a high-resolution Raman spectrum can be obtained of a molecule in a single pulse using broadband radiation. This could be useful for identifying the three-dimensional spatial distribution of molecular species in tissue.

  2. Vibration control, machine diagnostics

    Changing vibrations announce damage in the form of wear or cracks on components of, e.g., engine rotors, pumps, power plant turbo sets, rounding-up tools, or marine diesel engines. Therefore, machine diagnostics use frequency analyses, system tests, trend analyses as well as expert systems to localize or estimate the causes of these damages and malfunctions. Data acquisistion, including not only sensors, but also reliable and redundant data processing systems and analyzing systems, play an important role. The lectures pertaining to the data base are covered in detail. (DG)

  3. Adaptive Echo Noise Elimination for Speech Enhancement of Tamil letter ‘Zha’

    A. Srinivasan

    2009-12-01

    Full Text Available Acoustic echo depends on time delay between initial and reflected sound wave, strength of reflected sound. In the speech processing of letter ‘zha’ [11], echo of the recorded voice gives the spurious results. Such complexity can be avoided by suitable pyramidalmethod like adaptive filtering technique. Adaptive filtering tries to adjust these parameters with the aim of meeting some well-defined target, which depends upon the state of the system and surroundings. In speech recognition, the acoustic echo gives the faulty results.Objective of this paper is to analyze the performance of various adaptive filtering algorithms for acoustic echo cancellation in recorded speech enhancement of the letter ‘Zha’ in Tamil language. These algorithms are simulated in MATLAB and compared with theperformance of those algorithms based on parameters such us computational complexity, convergence rate and amount of echo attenuation.

  4. Recurrent kernel machines: computing with infinite echo state networks.

    Hermans, Michiel; Schrauwen, Benjamin

    2012-01-01

    Echo state networks (ESNs) are large, random recurrent neural networks with a single trained linear readout layer. Despite the untrained nature of the recurrent weights, they are capable of performing universal computations on temporal input data, which makes them interesting for both theoretical research and practical applications. The key to their success lies in the fact that the network computes a broad set of nonlinear, spatiotemporal mappings of the input data, on which linear regression or classification can easily be performed. One could consider the reservoir as a spatiotemporal kernel, in which the mapping to a high-dimensional space is computed explicitly. In this letter, we build on this idea and extend the concept of ESNs to infinite-sized recurrent neural networks, which can be considered recursive kernels that subsequently can be used to create recursive support vector machines. We present the theoretical framework, provide several practical examples of recursive kernels, and apply them to typical temporal tasks. PMID:21851278

  5. Extending stability through hierarchical clusters in Echo State Networks

    Sarah Jarvis

    2010-07-01

    Full Text Available Echo State Networks (ESN are reservoir networks that satisfy well-established criteria for stability when constructed as feedforward networks. Recent evidence suggests that stability criteria are altered in the presence of reservoir substructures, such as clusters. Understanding how the reservoir architecture affects stability is thus important for the appropriate design of any ESN. To quantitatively determine the influence of the most relevant network parameters, we analysed the impact of reservoir substructures on stability in hierarchically clustered ESNs (HESN, as they allow a smooth transition from highly structured to increasingly homogeneous reservoirs. Previous studies used the largest eigenvalue of the reservoir connectivity matrix (spectral radius as a predictor for stable network dynamics. Here, we evaluate the impact of clusters, hierarchy and intercluster connectivity on the predictive power of the spectral radius for stability. Both hierarchy and low relative cluster sizes extend the range of spectral radius values, leading to stable networks, while increasing intercluster connectivity decreased maximal spectral radius.

  6. Photon echo quantum RAM integration in quantum computer

    Moiseev, Sergey A

    2012-01-01

    We have analyzed an efficient integration of the multi-qubit echo quantum memory into the quantum computer scheme on the atomic resonant ensembles in quantum electrodynamics cavity. Here, one atomic ensemble with controllable inhomogeneous broadening is used for the quantum memory node and other atomic ensembles characterized by the homogeneous broadening of the resonant line are used as processing nodes. We have found optimal conditions for efficient integration of multi-qubit quantum memory modified for this analyzed physical scheme and we have determined a specified shape of the self temporal modes providing a perfect reversible transfer of the photon qubits between the quantum memory node and arbitrary processing nodes. The obtained results open the way for realization of full-scale solid state quantum computing based on using the efficient multi-qubit quantum memory.

  7. Experiments with Coherent γ Fields: Gamma Echo and Related Phenomena

    The role of coherence played in several phenomena in the gamma energy region has not been well recognised until recently. The Moessbauer source nuclei are noncorrelated, but the absorber response has a well-defined phase relation to the instantaneous source radiation within the relaxation time of the nuclear system. By rapidly changing this phase relation with mechanical displacement, new types of coherent transients in gamma regime have been observed. The gamma echo, replicating and amplifying the enchained decay through a thick sample, is perhaps the best known example of these phenomena. In addition, a simple gamma-ray interferometer based on rapid transit through the resonance has been demonstrated. Fast and intense gamma pulses have been obtained with stepwise phase modulation. These and the gamma-NMR double resonance experiments are reviewed in this paper

  8. Echo Tomography of Reprocessing Sites in X-Ray Binaries

    Patterson, Joseph; Haswell, Carole

    1998-01-01

    We discovered correlated rapid variability between the optical/UV and X-ray emission for the first time in a soft X-ray transient, GRO J1655-40. Hubble Space Telescope light curves show features similar to those seen by the Rossi X-ray Timing Explorer, but with a mean delay of up to 10 - 20 s. We interpret the correlation as the result of reprocessing of X-rays into optical and UV emission, with a delay owing to finite light travel time; this assumption enables us to perform echo mapping of the system. The time-delay distribution has a mean of 14.6 +/-1.4 s and a dispersion of 10.5+/-1.9 s at binary phase 0.4. This establishes that the reprocessing region is the accretion disk around the compact star, rather than the mass-donating secondary. These results have been published.

  9. Unitary equilibrations: probability distribution of the Loschmidt echo

    Venuti, Lorenzo Campos

    2009-01-01

    Closed quantum systems evolve unitarily and therefore cannot converge in a strong sense to an equilibrium state starting out from a generic pure state. Nevertheless for large system size one observes temporal typicality. Namely, for the overwhelming majority of the time instants, the statistics of observables is practically indistinguishable from an effective equilibrium one. In this paper we consider the Loschmidt echo (LE) to study this sort of unitary equilibration after a quench. We draw several conclusions on general grounds and on the basis of an exactly-solvable example of a quasi-free system. In particular we focus on the whole probability distribution of observing a given value of the LE after waiting a long time. Depending on the interplay between the initial state and the quench Hamiltonian, we find different regimes reflecting different equilibration dynamics. When the perturbation is small and the system is away from criticality the probability distribution is Gaussian. However close to criticali...

  10. Neutron spin interferometry using transverse neutron spin echo method

    Authors have constructed a transverse neutron spin echo (NSE) instrument which has been installed at CN3 guide tube of the cold neutron source at Kyoto University Reactor (KUR). It can be used as a neutron spin interferometer by setting magnetic mirrors in the Larmor precession field. Larmor precession is represented as interference of wave functions between two Stern-Gerlach states ↑ and ↓. In a homogeneous magnetic field, a coupled neutron wave packet of the two spin states splits into two partial wave packets having wave vectors k+ and k-. By observed Larmor precession of neutrons transmitted through a magnetic FeGe multilayer mirror with the condition of magnetic Bragg diffraction, the state of recombination of ↓ spin wave function and multiple reflection of ↑ spin wave function transmitted the magnetic FeGe multilayer mirror was detected as the change of NSE signal. (author)

  11. Neutron spin echo study of well organized soft matter systems

    Neutron spin echo (NSE) is a technique which has considerably extended the energy range covered by neutron scattering by improving resolution about three orders of magnitude. While significant new territories have been covered in the field of magnetism, glass transition and other solid state physics subjects, probably the most return came from soft matter physics. In this paper we present three experimentally challenging measurements on well organized systems. The first two is on cubic phase surfactant systems where in spite of the long range 2D ordering large amplitude fluctuations still persist. The third on free standing thin film, and this is a first example where NSE and X-ray photon show excellent complementarity

  12. EChO payload electronics architecture and SW design

    Focardi, M.; Di Giorgio, A. M.; Farina, M.; Pancrazzi, M.; Ottensamer, R.; Lim, T. L.; Pezzuto, S.; Micela, G.; Pace, E.

    2015-12-01

    EChO is a three-modules (VNIR, SWIR, MWIR), highly integrated spectrometer, covering the wavelength range from 0.55 μ m to 11.0 μ m. The baseline design includes the goal wavelength extension to 0.4 μ m while an optional LWIR module extends the range to the goal wavelength of 16.0 μ m. An Instrument Control Unit (ICU) is foreseen as the main electronic subsystem interfacing the spacecraft and collecting data from all the payload spectrometers modules. ICU is in charge of two main tasks: the overall payload control ( Instrument Control Function) and the housekeepings and scientific data digital processing ( Data Processing Function), including the lossless compression prior to store the science data to the Solid State Mass Memory of the Spacecraft. These two main tasks are accomplished thanks to the Payload On Board Software (P-OBSW) running on the ICU CPUs.

  13. Heavy ion collision evolution modeling with ECHO-QGP

    Rolando, V.; Inghirami, G.; Beraudo, A.; Del Zanna, L.; Becattini, F.; Chandra, V.; De Pace, A.; Nardi, M.

    2014-11-01

    We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in (3 + 1)D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.

  14. Heavy Ions Collision evolution modeling with ECHO-QGP

    Rolando, Valentina; Beraudo, Andrea; Del Zanna, Luca; Becattini, Francesco; Chandra, Vinod; De Pace, Arturo; Nardi, Marzia

    2014-01-01

    We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in $(3+1)-$D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.

  15. Single chain dynamics of polyisobutylene. A neutron spin echo study

    Complete text of publication follows. A neutron spin echo investigation is presented of the single chain motions of monodisperse polyisobutylene chains in the melt. Thereby a wide range in momentum space over a large dynamic range was covered. Motional processes from the center of mass diffusion, the Rouse dynamics to the more local relaxation processes which limit the validity of the standard Rouse model were elucidated. Dynamic structure factors were analyzed in terms of relevant theoretical approaches addressing the limiting factors of the Rouse model. It was found that other than claimed in the literature effects of local chain stiffness cannot account for the experimental observations. It appears that additional damping effects related to an internal viscosity of the chain have to be involved, in order to explain the experimental results. (author)

  16. Heavy ion collision evolution modeling with ECHO-QGP

    Rolando, V. [Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy); INFN – Sezione di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy); Inghirami, G. [Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INFN – Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); Beraudo, A. [INFN – Sezione di Torino, Via P. Giuria 1, I-10125 Torino (Italy); Del Zanna, L. [Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INFN – Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INAF – Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Becattini, F. [Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INFN – Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); Chandra, V. [INFN – Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); De Pace, A.; Nardi, M. [INFN – Sezione di Torino, Via P. Giuria 1, I-10125 Torino (Italy)

    2014-11-15

    We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in (3+1)D, with dissipative terms included within the framework of Israel–Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper–Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel–Stewart case, up to very large times and without any ad hoc tuning of the algorithm.

  17. APA with Evolving Order and Variable Regularization for Echo Cancellation

    Chang-Peng Ji

    2014-01-01

    Full Text Available Recently APA has become one of most popular algorithms in application of Acoustic Echo Cancellation. Because of the contradictory factors of convergence rate and steady-state misalignment, a new algorithm by the behavior of associating variable regularization and evolving order has been proposed in this paper. Despite of the conventional assumption that the a posteriori error is zero, we take the statistical characteristic of the noise into consideration during the adaptation process. Exact and approximate formulations for the optimal regularization factor are derived. Numerical simulation results show that the proposed algorithm improves the performance of the APA in terms of its faster convergence rate and lower steady-state misalignment compared to existing variable regularization APA and evolving order APA, respectively. Meanwhile it can be seen that near-end speech signal has been restored more effectively

  18. EChO Payload electronics architecture and SW design

    Focardi, M; Farina, M; Pancrazzi, M; Ottensamer, R; Lim, T L; Pezzuto, S; Micela, G; Pace, E

    2014-01-01

    EChO is a three-modules (VNIR, SWIR, MWIR), highly integrated spectrometer, covering the wavelength range from 0.55 $\\mu$m, to 11.0 $\\mu$m. The baseline design includes the goal wavelength extension to 0.4 $\\mu$m while an optional LWIR module extends the range to the goal wavelength of 16.0 $\\mu$m. An Instrument Control Unit (ICU) is foreseen as the main electronic subsystem interfacing the spacecraft and collecting data from all the payload spectrometers modules. ICU is in charge of two main tasks: the overall payload control (Instrument Control Function) and the housekeepings and scientific data digital processing (Data Processing Function), including the lossless compression prior to store the science data to the Solid State Mass Memory of the Spacecraft. These two main tasks are accomplished thanks to the Payload On Board Software (P-OBSW) running on the ICU CPUs.

  19. Spin echo and nuclear orientation study of metallic glasses

    Hyperfine fields on Co nuclei in amorphous as-quenched and heat-treated Co75Fe5B20 samples were studied by conventional NMR and by very low temperature nuclear orientation techniques. The 59Co spin echo measurement at 1.4 K yielded broad spectra between 130 - 260 MHz, with narrow maxima at 145.5 MHz and 155.1 MHz for as-quenched sample and with a broad maximum at 227 MHz for heat-treated sample well below the recrystallization point. The 60Co nuclear orientation measurements gave the mean value of the hyperfine field 15 T nearly independent of the sample heat-treatment. The spin-lattice relaxation was studied by pulse NMR and also by nuclear orientation thermal cycling technique. (Auth.)

  20. Nonlinear echoes and Landau damping with insufficient regularity

    Bedrossian, Jacob

    2016-01-01

    We prove that the theorem of Mouhot and Villani on Landau damping near equilibrium for the Vlasov-Poisson equations on $\\mathbb T \\times \\mathbb R$ cannot, in general, be extended to Sobolev spaces. This is demonstrated by constructing a sequence of homogeneous background distributions and arbitrarily small perturbations in $H^s$ which deviate arbitrarily far from free transport for long times (in a sense to be made precise). The density experiences a sequence of nonlinear oscillations that damp at a rate which is arbitrarily slow compared to the predictions of the linearized Vlasov equations. The nonlinear instability is due to the repeated re-excitation of a resonance known as a plasma echo. The results hold for a specific, small background distribution, but include both electrostatic and gravitational interactions.

  1. Artificial intelligence for the EChO mission planning tool

    Garcia-Piquer, Alvaro; Ribas, Ignasi; Colomé, Josep

    2015-12-01

    The Exoplanet Characterisation Observatory (EChO) has as its main goal the measurement of atmospheres of transiting planets. This requires the observation of two types of events: primary and secondary eclipses. In order to yield measurements of sufficient Signal-to-Noise Ratio to fulfil the mission objectives, the events of each exoplanet have to be observed several times. In addition, several criteria have to be considered to carry out each observation, such as the exoplanet visibility, its event duration, and no overlapping with other tasks. It is expected that a suitable mission plan increases the efficiency of telescope operation, which will represent an important benefit in terms of scientific return and operational costs. Nevertheless, to obtain a long term mission plan becomes unaffordable for human planners due to the complexity of computing the huge number of possible combinations for finding an optimum solution. In this contribution we present a long term mission planning tool based on Genetic Algorithms, which are focused on solving optimization problems such as the planning of several tasks. Specifically, the proposed tool finds a solution that highly optimizes the defined objectives, which are based on the maximization of the time spent on scientific observations and the scientific return (e.g., the coverage of the mission survey). The results obtained on the large experimental set up support that the proposed scheduler technology is robust and can function in a variety of scenarios, offering a competitive performance which does not depend on the collection of exoplanets to be observed. Specifically, the results show that, with the proposed tool, EChO uses 94% of the available time of the mission, so the amount of downtime is small, and it completes 98% of the targets.

  2. High signal intensity of fat on fast spin echo imaging

    The fast spin echo (FSE) technique of producing T2-weighted images in greatly reduced imaging times has recently been used for routine clinical study. FSE images show contrast that is very similar in most tissues to that of conventional SE images. However, fat shows a high signal intensity that is influenced by j-coupling and the magnetization transfer effect. The purpose of this study was to assess whether the higher signal intensity of fat is different among MRI systems and to examine the effects of j-coupling and magnetization transfer on the high signal intensity of fat on FSE. The contrast in signal intensity between fat and water was measured for various echo train lengths (ETL) with and without multislicing on FSE using a contrast phantom. Measurements were obtained with four different MRI systems. In addition, the effective T2 values of fat were calculated for the above conditions. Results indicated that contrast for fat and water was reduced with increased ETL and by using multislicing and was different among the four MRI systems. The effective T2 values of fat were extended for increased ETL and were not dependent on multislicing. They also differed among the four MRI systems. The extent of effective T2 values was affected by j-coupling. In this study, it was indicated that the degree of the high signal intensity of fat on FSE differed for different MRI systems. In addition, the reasons for the high signal intensity of fat on FSE were related to the effects of j-coupling and magnetization transfer. (author)

  3. Trawling bats exploit an echo-acoustic ground effect

    Sandor eZsebok

    2013-04-01

    Full Text Available A water surface acts not only as an optic mirror but also as an acoustic mirror. Echolocation calls emitted by bats at low heights above water are reflected away from the bat, and hence the background clutter is reduced. Moreover, targets on the surface create an enhanced echo. Here, we formally quantified the effect of the substrate and target height on both target detection and –discrimination in a combined laboratory and field approach with Myotis daubentonii. In a two-alternative, forced-choice paradigm, the bats had to detect a mealworm and discriminate it from an inedible dummy (20 mm PVC disc. Psychophysical performance was measured as a function of height above either smooth substrates (water or PVC or above a clutter substrate (artificial grass. At low heights above the clutter substrate (10, 20 or 35 cm, the bats’ detection performance was worse than above a smooth substrate. At a height of 50 cm, the substrate structure had no influence on target detection. Above the clutter surface, also target discrimination was significantly impaired with decreasing target height. A detailed analysis of the bats’ echolocation calls during target approach shows that above the clutter substrate, the bats produce calls with significantly higher peak frequency. Flight-path reconstruction revealed that the bats attacked an object from below over water but from above over a clutter substrate.These results are consistent with the hypothesis that trawling bats exploit an echo-acoustic ground effect, in terms of a spatio-temporal integration of direct reflections with indirect reflections from the water surface, to optimize prey detection and –discrimination not only for prey on the water but also for some range above.

  4. Vibrations and Stability: Solved Problems

    Thomsen, Jon Juel

    Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....

  5. The study of eccentric vibrator

    The developed mathematical model of the motion of the eccentric vibrator allowed to define two own frequencies of oscillations of the mechanical system. To confirm the nominated theoretical positions, the motion of the eccentric vibrator is simulated with the aid of the ADAMS (Automated Dynamic Analysis of Mechanical Systems) software complex

  6. Coupling of Carbon Dioxide Stretch and Bend Vibrations Reveals Thermal Population Dynamics in an Ionic Liquid.

    Giammanco, Chiara H; Kramer, Patrick L; Yamada, Steven A; Nishida, Jun; Tamimi, Amr; Fayer, Michael D

    2016-01-28

    The population relaxation of carbon dioxide dissolved in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) was investigated using polarization-selective ultrafast infrared pump-probe spectroscopy and two-dimensional infrared (2D IR) spectroscopy. Due to the coupling of the bend with the asymmetric stretch, excitation of the asymmetric stretch of a molecule with a thermally populated bend leads to an additional peak, a hot band, which is red-shifted from the main asymmetric absorption band by the combination band shift. This hot band peak exchanges population with the main peak through the gain and loss of bend excitation quanta. The isotropic pump-probe signal originating from the unexcited bend state displays a fast, relatively small amplitude, initial growth followed by a longer time scale exponential decay. The signal is analyzed over its full time range using a kinetic model to determine both the vibrational lifetime (the final decay) and rate constant for the loss of the bend energy. This bend relaxation manifests as the fast initial growth of the stretch/no bend signal because the hot band (stretch with bend) is "over pumped" relative to the ground state equilibrium. The nonequilibrium pumping occurs because the hot band has a larger transition dipole moment than the stretch/no bend peak. The system is then prepared, utilizing an acousto-optic mid-infrared pulse shaper to cut a hole in the excitation pulse spectrum, such that the hot band is not pumped. The isotropic pump-probe signal from the stretch/no bend state is altered because the initial excited state population ratio has changed. Instead of a growth due to relaxation of bend quanta, a fast initial decay is observed because of thermal excitation of the bend. Fitting this curve gives the rate constant for thermal excitation of the bend and the lifetime, which agree with those determined in the pump-probe experiments without frequency

  7. The origins of vibration theory

    Dimarogonas, A. D.

    1990-07-01

    The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.

  8. Vibration analysis using digital correlation

    Gilbert, John A.; Lehner, David L.; Dudderar, T. Dixon; Matthys, Donald R.

    1988-01-01

    This paper demonstrates the use of a computer-based optical method for locating the positions of nodes and antinodes in vibrating members. Structured light patterns are projected at an angle onto the vibrating surface using a 35 mm slide projector. The vibrating surface and the projected images are captured in a time averaged photograph which is subsequently digitized. The inherent fringe patterns are filtered to determine amplitudes of vibration, and computer programs are used to compare the time averaged images to images recorded prior to excitation to locate nodes and antinodes. Some of the influences of pattern regularity on digital correlation are demonstrated, and a speckle-based method for determining the mode shapes and the amplitudes of vibration with variable sensitivity is suggested.

  9. Time-dependent ultrasound echo changes occur in tendon during viscoelastic testing.

    Duenwald-Kuehl, Sarah; Kobayashi, Hirohito; Lakes, Roderic; Vanderby, Ray

    2012-11-01

    The viscoelastic behavior of tendons has been extensively studied in vitro. A noninvasive method by which to acquire mechanical data would be highly beneficial, as it could lead to the collection of viscoelastic data in vivo. Our lab has previously presented acoustoelasticity as an alternative ultrasound-based method of measuring tendon stress and strain by reporting a relationship between ultrasonic echo intensity (B mode ultrasound image brightness) and mechanical behavior of tendon under pseudoelastic in vitro conditions [Duenwald, S., Kobayashi, H., Frisch, K., Lakes, R., and Vanderby Jr, R., 2011, "Ultrasound Echo is Related to Stress and Strain in Tendon," J. Biomech., 44(3), pp. 424-429]. Viscoelastic properties of the tendons were not examined in that study, so the presence of time-dependent echo intensity changes has not been verified. In this study, porcine flexor tendons were subjected to relaxation and cyclic testing while ultrasonic echo response was recorded. We report that time- and strain history-dependent mechanical properties during viscoelastic testing are manifested in ultrasonic echo intensity changes. We also report that the patterns of the echo intensity changes do not directly mimic the patterns of viscoelastic load changes, but the intensity changed in a repeatable (and therefore predictable) fashion. Although mechanisms need further elucidation, viscoelastic behavior can be anticipated from echo intensity changes. This phenomenon could potentially lead to a more extensive characterization of in vivo tissue behavior. PMID:23387788

  10. Strong Correlation between Quasi-periodic Echoes and Plasma Drift in E-region

    Jin, H.; Chen, G.

    2015-12-01

    It is for the first time that the simultaneous observations of the quasi-periodic (QP) echoes and the plasma drift in the ionospheric E-region. This experiment was carried out in Fuke (19.5ºN, 109.1ºE), Hainan province, China. The Hainan VHF radar was used to observe the E-region field-aligned irregularities (FAIs) and the Hainan Digisonde was operated in the drift mode to record the drift velocities of the plasma blobs in the Es-layer. The QP echoes and the drift data of the whole year of 2013 were analyzed and compared. A surprising consistency between the striation tilt of the QP echoes and the drift direction of the plasma blobs was discovered. When the measured drift direction of the plasma blobs was southward, the negative echo striation of the QP FAIs was recorded, and vice versa. Furthermore, the phase of the echo trace was continuous, while the QP striation changed from negative to positive, or in contrary. Thus, a conclusion can be reached that the morphology of the QP echoes may be controlled by the background wind fields in the E-region. The northward/ southward drifting striated FAIs in the observing region of a coherent scatter radar possibly induce the positive/ negative QP echo striation in the range-time-intensity plots.

  11. Azimuthal distribution of HF slant E echoes and its relationship to the polar cap electric field

    A study was conducted to investigate the azimuthal distribution of high-frequency slant E echoes and its relationship to the polar cap electric field. Analysis of data obtained with a oblique step sounder and a rotatable log periodic antenna located at Resolute Bay, Canada, showed that the highest frequency of the slant E echo trace during any given azimuth scan was found to maximize in the direction of the E region current vector. This relationship is inferred from the striking 15-deg/h diurnal variation in the direction of the highest-frequency slant E echo, the change of this direction with the sign of the azimuthal component of the interplanetary magnetic field, and the general agreement of the direction of slant E echo maxima with the directions shown by equivalent current systems derived from polar cap magnetometer data. This directional relationships is interpreted in terms of conditions established by the Buneman-Farley two-stream instability, the magnetic aspect sensitivity, and the ionospheric refraction. Slant E echoes, which were also observed at angles near perpendicular to the current flow, are thought to be due to secondary plasma waves generated by a mechanism similar to that proposed by Sudan et al. (1973). The possibility that some of the slant E echoes used in the analysis are really slant F echoes remains to be investigated

  12. Man-Induced Vibrations

    Jönsson, Jeppe; Hansen, Lars Pilegaard

    1994-01-01

    Human motion can cause various types of periodic or transient dynamic loads. The periodic loads are mainly due to jumping, running, dancing, walking and body rocking. Transient loads primarily result from single impulse loads, such as jumping and falling from elevated positions. The response...... to these loads are of primary interest for the structural engineer, whereas the exact load as a function of time generally is of minor importance. This is true when the loading time (contact duration) tp is smal1 compared to the largest natura1 periods Tn = 2π/ωn of the structure. The present study is mainly...... work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...

  13. Study of susceptibility-induced artefacts in GRASE with different echo train length

    The aim of this study was to evaluate the sensitivity of gradient-and-spin-echo (GRASE) sequences to susceptibility effects. GRASE sequences with 21 and 33 echoes per echo train were compared with a T2-weighted FSE sequence with an echo train length of 5 by means of MRI in phantoms, volunteers (n = 10), and patients (n = 19) with old hemorrhagic brain lesions. All experiments were performed on a 1.0-T clinical MR system (Impact Expert, Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations, of brain areas with physiological iron deposition (red nucleus, substantia nigra), and of areas of old brain hemorrhage were calculated for FSE and GRASE pulse sequences. Areas of old brain hemorrhage were also qualitatively analyzed for the degree of visible susceptibility effects by blinded reading. The CNR of iron oxide tubes and iron-containing brain areas decreased with increasing echo trains of GRASE sequences. The CNR of GRASE sequences decreased when compared with CNR of their FSE counterparts (GRASE 21 echo trains 23.8 ± 0.8, FSE 5 echo trains 26.7 ± 0.9; p ≤ 0.01). Qualitative analysis confirmed these measurements. FSE with an ETL of 5 demonstrated significantly stronger susceptibility effects than their GRASE counterpart with an ETL of 21. The results demonstrate that GRASE sequences do not necessarily compensate for the reduced sensitivity of FSE to susceptibility effects. The complex signal behavior of GRASE makes conventional SE, gradient echo, or FSE sequences containing shorter echo trains preferable when patients with intracranial hemorrhage are clinically evaluated. (orig.)

  14. Echo-Enhanced Ultrasonography: Is It the Future Gold Standard of Imaging in Acute Pancreatitis?

    Emilio Brocchi

    2005-04-01

    Full Text Available We report the imaging of a patient in whom the diagnosis of acute pancreatitis and the assessment of disease severity was carried out using echo-enhanced ultrasonography. Contrast-enhanced computed tomography confirmed the echo-enhanced ultrasonography picture. Echo-enhanced ultrasonography may become the imaging technique of choice in assessing the severity of acute pancreatitis since it is easy to perform, safe and lends itself to emergency situations. Most importantly, this technique should be also useful for following-up patients and it may be also an alternative to MRI in those patients in whom contrast-enhanced computed tomography cannot be carried out.

  15. Middle ear muscle contractions and their relation to pulse and echo evoked potentials in the bat

    Henson, O. W., Jr.; Henson, M. M.

    1972-01-01

    An analysis is made of pulse and echo orientation cries of the Mustache Bat. That bat's cries are characterized by a long, 60 to 30 msec, pure tone component and brief beginning and terminal FM sweeps. In addition to obvious echo overlap and middle ear muscle contractions, the following are examined: (1) characteristics of pulse- and echo-evoked potential under various conditions, (2) evidence of changes in hearing sensitivity during and after pulse emission, and (3) the role of the middle ear muscles in bringing about these changes.

  16. Wideband Radar Echo Frequency-domain Simulation and Analysis for High Speed Moving Targets

    Ning Chao

    2014-04-01

    Full Text Available A frequency-domain method is proposed for wideband radar echo simulation of high-speed moving targets. Based on the physical process of electromagnetic waves observing a moving target, a frequency-domain echo model of wideband radar is constructed, and the block diagram of the radar echo simulation in frequency-domain is presented. Then, the impacts of radial velocity and slant range on the matching filtering of LFM radar are analyzed, and some quantitative conclusions on the shift and expansion of the radar profiles are obtained. Simulation results illustrate the correctness and efficiency of the proposed method.

  17. ECHOES - KAIKUJA : Raportti kahden taiteellisen opinnäytetyön muodostamasta teosillasta

    Stenberg, Anna; Hakkarainen, Inka-Leea

    2014-01-01

    Echoes- Kaikuja teosilta koostuu Anna Stenbergin ja Inka-Leea Hakkaraisen taiteellisista opinnäytetöistä.Teokset esitettiin 22.2. ja 23.2. 2014 Sotkulla, Lähtölaukaus-tanssifestivaalin yhteydessä. Molemmat nykytanssiteokset ovat kestoltaan noin 20 minuuttia ja niissä kummassakin esiintyy neljä tanssijaa. Tämä raportti käsittelee näiden taiteellisten opinnäytetöiden luomisprosesseja sekä toteutettua Echoes - Kaikuja teosiltaa kokonaisuutena. Ydinajatuksena Echoes - Kaikuja teosillalle oli...

  18. Estimating evaporation duct heights from radar sea echo

    Rogers, L. Ted; Hattan, Claude P.; Stapleton, Janet K.

    2000-07-01

    The evaporation duct is a downward refracting layer that results from the rapid decrease in humidity with respect to altitude occurring in the atmospheric surface layer above bodies of water. The evaporation duct affects radar detection ranges at frequencies of approximately 1 GHz and above. Models based on Monin-Obukhov similarity theory are usually used to calculate evaporation duct refractivity profiles from bulk measurements of air temperature, humidity, wind speed, and the sea surface temperature. Modeling results by Pappert et al. [1992] indicated that the falloff of radar sea echo as a function of range was an increasing function of the evaporation duct height. On the basis of those results, the authors proposed inferring the evaporation duct height by a slope fit to modeled clutter power, a nonlinear least squares inversion procedure. Data for testing the inversion procedure were obtained using the S band Space Range Radar at Wallops Island, Virginia. Evaporation duct heights were inferred from the radar data on the basis of the assumption of a range-independent evaporation duct height and sea clutter radar cross section (σ°). Validation data consist of buoy and boat in situ bulk measurements. The result of comparing the radar-inferred evaporation duct heights and those calculated from bulk measurements indicates that the radar-inferred duct heights are strongly correlated with those from the in situ measurements, but there is some uncertainty as to whether they are biased or unbiased. That uncertainty arises from the assumed dependence of σ° on the grazing angle ψ. That dependence is currently a matter of debate in the open literature, with the lower and upper ends of modeling results being σ° ∝ ψ0; and σ° ∝ ψ4, respectively. We show results for both dependencies and note that the σ° ∝ ψ0; provides the best agreement with our measurements. It should be noted that inferring the evaporation duct height from radar sea echo is a problem

  19. Echoes of ECOs: gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale

    Cardoso, Vitor; Macedo, Caio F B; Palenzuela, Carlos; Pani, Paolo

    2016-01-01

    Gravitational waves from binary coalescences provide one of the cleanest signatures of the nature of compact objects. It has been recently argued that the post-merger ringdown waveform of exotic ultracompact objects is initially identical to that of a black-hole, and that putative corrections at the horizon scale will appear as secondary pulses after the main burst of radiation. Here we extend this analysis in three important directions: (i)~we show that this result applies to a large class of exotic compact objects with a photon sphere for generic orbits in the test-particle limit; (ii)~we investigate the late-time ringdown in more detail, showing that it is universally characterized by a modulated and distorted train of "echoes" of the modes of vibration associated with the photon sphere; (iii)~we study for the first time equal-mass, head-on collisions of two ultracompact boson stars and compare their gravitational-wave signal to that produced by a pair of black-holes. If the initial objects are compact eno...

  20. Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers

    A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm−1 to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ∼70 as. The anharmonicity of smaller than 10−4 cm−1 was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 μrad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy

  1. Study of Magnetic Vibration Absorber with Permanent Magnets along Vibrating Beam Structure

    F. B. Sayyad; Gadhave, N. D.

    2013-01-01

    The vibration absorbers are frequently used to control and minimize excess vibration in structural system. Dynamic vibration absorbers are used to reduce the undesirable vibration in many applications such as pumps, gas turbines, engine, bridge, and electrical generator. To reduce the vibration of the system, the frequency of absorber should be equal to the excitation frequency. The aim of this study is to investigate the effect of magnetic vibration absorber along vibrating cantilever beam. ...

  2. Comparison of SE and short TE three-dimensional gradient-echo imaging of the temporomandibular region

    Conventional spin-echo (SE) images and three-dimensional (3D) gradient-echo images with short TE obtained at 1.5 T were obtained of temporomandibular (TMJ) regions in four volunteers and 10 patients. Short TE (echo time = 5.5 msec), 3D, gradient-echo images with nearly symmetric data acquisition caused negligible susceptibility artifacts. The TMJ disk was better visualized with 3D, gradient, fast-low-angle-shot (FLASH) images with small (Ernst) angles than it was with 3D, gradient-echo, fast- imaging-with-steady-precession (FISP) images. T1-weighted SE imaging revealed higher contrast resolution of the disk than did 3D gradient-echo images and is the preferred method to evaluate TMJ disorders. However, short TE 3D gradient-echo images revealed marked improvement in the delineation of the facial nerve canal in the temporomastoid region

  3. Vehicle wheels vibration suppression by dynamic vibration absorber

    Zinovij STOTSKO

    2007-01-01

    Full Text Available The article deals with the methods of calculation and optimization ofdynamic processes in vibroexcitated constructions with dynamic absorbers. The improved constructions of such absorbers for vehicle wheels vibration suppression are discussed.

  4. Molecular vibrations the theory of infrared and Raman vibrational spectra

    Wilson, E Bright; Cross, Paul C

    2012-01-01

    Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.

  5. Vibrational Spectroscopy of Methyl benzoate

    Maiti, Kiran Sankar

    2014-01-01

    Methyl benzoate (MB) is studied as a model compound for the development of new IR pulse schemes with possible applicability to biomolecules. Anharmonic vibrational modes of MB are calculated on different level (MP2, SCS, CCSD(T) with varying basis sets) ab-initio PESs using the vibrational self-consistent field (VSCF) method and its correlation corrected extensions. Dual level schemes, combining different quantum chemical methods for diagonal and coupling potentials, are systematically studied and applied successfully to reduce the computational cost. Isotopic substitution of {\\beta}-hydrogen by deuterium is studied to obtain a better understanding of the molecular vibrational coupling topology.

  6. Vibration feeder of powered materials

    The design and function test of two models of a new vibration feeder of powdered materials are described. Powder particles in a storage bin discharging hole are stirred with a vibrating cone and allowed to fall down around the cone perimeter. The dosing rate can be controlled by the cone lift, by the amplitude of the vibrations and by the flow rate of an inert gas around the cone. The results of dosing U3O8 and zinc powders are presented and discussed. (author). 10 figs., 1 tab., 8 refs

  7. Echoing echoes / Reet Sool

    Sool, Reet, 1951-

    2003-01-01

    Kajastatakse ja analüüsitakse tudengite arvamusi, kes lugesid Lawrence Ferlinghetti luuletust "A report on a happening in Washington Square San Francisco" ilma autorit teadmata ; ka "autorist" üldisemalt kirjandusteooria seisukohalt

  8. Vibration Mitigation of Nonlinear Vibrating Structures using Nonlinear Energy Sinks

    Viguié, Régis; Peeters, Maxime; Kerschen, Gaëtan; Golinval, Jean-Claude

    2008-01-01

    The tuned mass damper (TMD) is a simple and efficient device, but it is only effective when it is precisely tuned to the frequency of a vibration mode. Because nonlinear vibrating structures have resonant frequencies that vary with the amount of total energy in the system, the efficiency of a TMD is questionable in this case. In the present study, the performance of an essentially nonlinear attachment, termed a nonlinear energy sink (NES), is assessed. It is shown that, unlike the TMD, an ...

  9. ACTIVE VIBRATION ISOLATION OF MECHANICAL VIBRATION IN RAILWAY PASSENGER CAR

    Aleksander SŁADKOWSKI

    2015-06-01

    Full Text Available This paper presents an attempt of numerical description of the active vibration isolation system of railway passenger car. Computer simulations were performed for different speeds of the passenger car riding along the same track. Formal basis to solve the formulated research problem was achieved by using the law and the principles of mechanics and control theory. Model results clearly indicate that the use of active vibration reduction systems in rail transport can significantly increase comfort

  10. ac Stark gradient echo memory in cold atoms

    The burgeoning fields of quantum computing and quantum key distribution have created a demand for a quantum memory. The gradient echo memory scheme is a quantum memory candidate for light storage that can boast efficiencies approaching unity, as well as the flexibility to work with either two- or three-level atoms. The key to this scheme is the frequency gradient that is placed across the memory. Currently, the three-level implementation uses a Zeeman gradient and warm atoms. In this article we model an alternate gradient-creation mechanism--the ac Stark effect--to provide an improvement in the flexibility of gradient-creation and field-switching times. We propose this scheme in concert with a move to cold atoms (≅1 mK). These temperatures would increase the storage times possible, and the small ensemble volumes would enable large ac Stark shifts with reasonable laser power. We find that memory bandwidths on the order of MHz can be produced with experimentally achievable laser powers and trapping volumes, with high precision in gradient creation and switching times on the order of nanoseconds possible. By looking at the different decoherence mechanisms present in this system, we determine that coherence times on the order of tens of milliseconds are possible, as are delay-bandwidth products of approximately 50 and efficiencies over 90%.

  11. Learning to decode human emotions with Echo State Networks.

    Bozhkov, Lachezar; Koprinkova-Hristova, Petia; Georgieva, Petia

    2016-06-01

    The aim of this paper is to identify the common neural signatures based on which the positive and negative valence of human emotions across multiple subjects can be reliably discriminated. The brain activity is observed via Event Related Potentials (ERPs). ERPs are transient components in the Electroencephalography (EEG) generated in response to a stimulus. ERPs were collected while subjects were viewing images with positive or negative emotional content. Building inter-subject discrimination models is a challenging problem due to the high ERPs variability between individuals. We propose to solve this problem with the aid of the Echo State Networks (ESN) as a general framework for extracting the most relevant discriminative features between multiple subjects. The original feature vector is mapped into the reservoir feature space defined by the number of the reservoir equilibrium states. The dominant features are extracted iteratively from low dimensional combinations of reservoir states. The relevance of the new feature space was validated by experiments with standard supervised and unsupervised machine learning techniques. From one side this proof of concept application enhances the usability context of the reservoir computing for high dimensional static data representations by low-dimensional feature transformation as functions of the reservoir states. From other side, the proposed solution for emotion valence detection across subjects is suitable for brain studies as a complement to statistical methods. This problem is important because such decision making systems constitute "virtual sensors" of hidden emotional states, which are useful in psychology science research and clinical applications. PMID:26422421

  12. Reflections on Reflexions: I. Light Echoes in Type Ia Supernovae

    Patat, F

    2004-01-01

    In the last ten years, observational evidences about a possible connection between Type Ia Supernovae (SNe) properties and the environment where they explode have been steadily growing. In this paper I discuss, from a theoretical point of view but with an observer's perspective, the usage of light echoes (LEs) to probe the CSM around SNe of Type Ia since, in principle, they give us a unique opportunity of getting a three-dimensional description of the SN environment. In turn, this can be used to check the often suggested association of some Ia's with dusty/star forming regions, which would point to a young population for the progenitors. After giving a brief introduction to the LE phenomenon in single scattering approximation, I derive analytical and numerical solutions for the optical light and colour curves for a few simple dust geometries. A fully 3D multiple scattering treatment has also been implemented in a Monte Carlo code, which I have used to investigate the effects of multiple scattering. In particu...

  13. Investigating echo state networks dynamics by means of recurrence analysis

    Bianchi, Filippo Maria; Alippi, Cesare

    2016-01-01

    In this paper, we elaborate over the well-known interpretability issue in echo state networks. The idea is to investigate the dynamics of reservoir neurons with time-series analysis techniques taken from research on complex systems. Notably, we analyze time-series of neuron activations with Recurrence Plots (RPs) and Recurrence Quantification Analysis (RQA), which permit to visualize and characterize high-dimensional dynamical systems. We show that this approach is useful in a number of ways. First, the two-dimensional representation offered by RPs provides a way for visualizing the high-dimensional dynamics of a reservoir. Our results suggest that, if the network is stable, reservoir and input denote similar line patterns in the respective RPs. Conversely, the more unstable the ESN, the more the RP of the reservoir presents instability patterns. As a second result, we show that the $\\mathrm{L_{max}}$ measure is highly correlated with the well-established maximal local Lyapunov exponent. This suggests that co...

  14. Fast spin-echo MR imaging of the eye

    Magnetic resonance imaging of the eye usually includes T2-weighted images both for screening purposes and for characterization of melanoma. Conventional T2-weighted spin-echo (SE) imaging suffers both from long acquisition times and incomplete recovery of the virteous' signal. A fast SE sequence was therefore compared prospectively with conventional sequences in 29 consecutive patients with lesions of the eye. Fast SE images delineated melanoma and other lesions of the eye from vitreous better than conventional T2-weighted images. Image quality and lesion conspicuity were improved on the fast sequence. Whereas melanoma appeared hypointense to vitreous on both types of images, subretinal effusion was hypointense on fast images and hyperintense on conventional T2-weighted images. Ghosting of the globe, which, however, did not decrease diagnostic value, was more pronounced on fast images. Conventional T2-weighted images may be replaced by fast SE images in MR studies of the eye with a gain in lesion conspicuity and significant time saving. (orig.)

  15. Phase transition of social learning collectives and "Echo chamber"

    Mori, Shintaro; Hisakado, Masato

    2016-01-01

    An "Echo chamber" is the state of social learning agents whose performances are deteriorated by excessive observation of others. We understand this to be the collective behavior of agents in a restless multi-armed bandit. The bandit has $M$ good levers and bad levers. A good lever changes to a bad one randomly with probability $q_{C}$ and a new good lever appears. $N$ agents exploit ones' lever if they know that it is a good one. Otherwise, they search for a good one by (i) random search (success probability $q_{I}$) and (ii) observe a good lever that is known by other agents (success probability $q_{O}$) with probability $1-p$ and $p$, respectively. The distribution of agents in good levers obeys the Yule distribution with power law exponent $1+\\gamma$ in the limit $N,M\\to \\infty$ and $\\gamma=1+\\frac{(1-p)q_{I}}{pq_{O}}$. The expected value of the number of the agents with a good lever $N_{1}$ increases with $p$. The system shows a phase transition at $p_{c}=\\frac{q_{I}}{q_{I}+q_{o}}$. For $pp_{c})$, the var...

  16. Networks of echoes imitation, innovation and invisible leaders

    West, Bruce J; Grigolini, Paolo

    2014-01-01

    Networks of Echoes: Imitation, Innovation and Invisible Leaders is a mathematically rigorous and data rich book on a fascinating area of the science and engineering of social webs.  There are hundreds of complex network phenomena whose statistical properties are described by inverse power laws.  The phenomena of interest are not arcane events that we encounter only fleetingly, but are events that dominate our lives. We examine how this intermittent statistical behavior intertwines itself with what appears to be the organized activity of social groups.  The book is structured as answers to a sequence of questions such as: How are decisions reached in elections and boardrooms?  How is the stability of a society undermined by zealots and committed minorities, and how is that stability re-established?  Can we learn to answer such questions about human behavior by studying the way flocks of birds retain their formation when eluding a predator?  These questions and others are answered using a generic model of...

  17. High temporal resolution functional MRI using parallel echo volumar imaging

    Purpose: To combine parallel imaging with 3D single-shot acquisition (echo volumar imaging, EVI) in order to acquire high temporal resolution volumar functional MRI (fMRI) data. Materials and Methods: An improved EVI sequence was associated with parallel acquisition and field of view reduction in order to acquire a large brain volume in 200 msec. Temporal stability and functional sensitivity were increased through optimization of all imaging parameters and Tikhonov regularization of parallel reconstruction. Two human volunteers were scanned with parallel EVI in a 1.5 T whole-body MR system, while submitted to a slow event-related auditory paradigm. Results: Thanks to parallel acquisition, the EVI volumes display a low level of geometric distortions and signal losses. After removal of low-frequency drifts and physiological artifacts,activations were detected in the temporal lobes of both volunteers and voxel-wise hemodynamic response functions (HRF) could be computed. On these HRF different habituation behaviors in response to sentence repetition could be identified. Conclusion: This work demonstrates the feasibility of high temporal resolution 3D fMRI with parallel EVI. Combined with advanced estimation tools,this acquisition method should prove useful to measure neural activity timing differences or study the nonlinearities and non-stationarities of the BOLD response. (authors)

  18. High temporal resolution functional MRI using parallel echo volumar imaging

    Rabrait, C.; Ciuciu, P.; Ribes, A.; Poupon, C.; Dehaine-Lambertz, G.; LeBihan, D.; Lethimonnier, F. [CEA Saclay, DSV, I2BM, Neurospin, F-91191 Gif Sur Yvette (France); Le Roux, P. [GEHC, Buc (France); Dehaine-Lambertz, G. [Unite INSERM 562, Gif Sur Yvette (France)

    2008-07-01

    Purpose: To combine parallel imaging with 3D single-shot acquisition (echo volumar imaging, EVI) in order to acquire high temporal resolution volumar functional MRI (fMRI) data. Materials and Methods: An improved EVI sequence was associated with parallel acquisition and field of view reduction in order to acquire a large brain volume in 200 msec. Temporal stability and functional sensitivity were increased through optimization of all imaging parameters and Tikhonov regularization of parallel reconstruction. Two human volunteers were scanned with parallel EVI in a 1.5 T whole-body MR system, while submitted to a slow event-related auditory paradigm. Results: Thanks to parallel acquisition, the EVI volumes display a low level of geometric distortions and signal losses. After removal of low-frequency drifts and physiological artifacts,activations were detected in the temporal lobes of both volunteers and voxel-wise hemodynamic response functions (HRF) could be computed. On these HRF different habituation behaviors in response to sentence repetition could be identified. Conclusion: This work demonstrates the feasibility of high temporal resolution 3D fMRI with parallel EVI. Combined with advanced estimation tools,this acquisition method should prove useful to measure neural activity timing differences or study the nonlinearities and non-stationarities of the BOLD response. (authors)

  19. [Echo-color-Doppler in male pelvic congestion syndrome].

    Sarteschi, Lelio Mario; Simi, Stefano; Turchi, Paolo; DeMaria, Maurizio; Morelli, Girolamo

    2002-12-01

    The pelvic congestion syndrome has been widely studied in the female sex, while there are not many publications on the male equivalent. Prostatitis represent the most frequent affections of the genito-urinary male tract that require the urologic consult, but in the majority of the cases the etiology of such affections remains unknown. Some forms of microscopic hematuria or macroscopic hematuria are also cryptogenetic. Varicocelectomy is widely given in the infertile patients, but not always the intervention achieves a recovery of the semen quality. In this work we revisit the anatomy of the pelvic male venous drain and we depict its objective findings with the echo-color-Doppler sonography (ECD). The purpose of the study is to encourage a polycentric uro-andrologic search on large numbers, with the goal of resolve if the ECD pictures of congestion pelvic syndrome could have relation with some "prostatitis syndromes", with some cryptogenetic hematuria and/or with the prognosis of the infertile patients undergone to varicocelectomy. PMID:12508723

  20. Comparaison between conventional and fast spin-echo STIR sequences

    Purpose: To evaluate the common characteristics and differences in contrast behavior of short-TI-inversion-recovery (STIR) and short-TI-inversion-recovery fast spinecho (TurboSTIR) sequences. Material and Methods: Phantoms doped with increasing doses of Gd-DTPA and a pork-fat phantom were used to evaluate the dependence of the STIR and TurboSTIR signals on the T1 relaxation time. Clinical TurboSTIR images were obtained from 30 patients with musculoskeletal abnormalities and compared to conventional STIR images in 15 cases and to postcontrast TurboSTIR images in another 15 cases. Results: In the phantom measurements, a significantly shorter inversion time (TI) was needed to achive fat suppression on TurboSTIR images, and, with an identical number of signal averages, contrast-to-noise ratios were lower on TurboSTIR images. These differences between STIR and TurboSTIR can be attributed to the contribution of stimulated echoes to overall TurboSTIR signal and can be compensated by a shorter TI and a higher number of signal averages for TurboSTIR, respectively. With these adaptations, clinical TurboSTIR and STIR images showed an identical contrast behavior with fat suppression and a high sensitivity to pathological lesions but TurboSTIR saved a significant amount of scan time and reduced some types of artifacts. Contrast uptake impaired lesion conspicuity on TurboSTIR images. Conclusion: TurboSTIR sequences should replace conventional STIR sequences and should be performed before contrast administration. (orig.)

  1. MRI detection of hypointense brain lesions in patients with multiple sclerosis: T1 spin-echo vs. gradient-echo

    Dupuy, Sheena L.; Tauhid, Shahamat; Kim, Gloria; Chu, Renxin; Tummala, Subhash [Departments of Neurology, Brigham and Women' s Hospital, Laboratory for Neuroimaging Research, Partners MS Center, Harvard Medical School, Boston, MA (United States); Hurwitz, Shelley [Departments of Medicine, Brigham and Women' s Hospital, Harvard Medical School, Boston, MA (United States); Bakshi, Rohit, E-mail: rbakshi@bwh.harvard.edu [Departments of Neurology, Brigham and Women' s Hospital, Laboratory for Neuroimaging Research, Partners MS Center, Harvard Medical School, Boston, MA (United States); Departments of Radiology, Brigham and Women' s Hospital, Harvard Medical School, Boston, MA (United States)

    2015-08-15

    Highlights: • Compared T1SE and T1GE in detecting hypointense brain lesions in MS patients. • T1GE detected a higher cerebral lesion volume and number than T1SE. • T1SE correlated significantly with disability, while T1GE did not. • Hypointense lesions on T1SE and T1GE are not interchangeable in patients with MS. - Abstract: Objective: Compare T1 spin-echo (T1SE) and T1 gradient-echo (T1GE) sequences in detecting hypointense brain lesions in multiple sclerosis (MS). Background: Chronic hypointense lesions on T1SE MRI scans are a surrogate of severe demyelination and axonal loss in MS. The role of T1GE images in the detection of such lesions has not been clarified. Design/methods: In 45 patients with MS [Expanded Disability Status Scale (EDSS) score (mean ± SD) 3.5 ± 2.0; 37 relapsing-remitting (RR); 8 secondary progressive (SP)], cerebral T1SE, T1GE, and T2-weighted fluid-attenuated inversion-recovery (FLAIR) images were acquired on a 1.5 T MRI scanner. Images were re-sampled to axial 5 mm slices before directly comparing lesion detectability using Jim (v.7, Xinapse Systems). Statistical methods included Wilcoxon signed rank tests to compare sequences and Spearman correlations to test associations. Results: Considering the entire cohort, T1GE detected a higher lesion volume (5.90 ± 6.21 vs. 4.17 ± 4.84 ml, p < 0.0001) and higher lesion number (27.82 ± 20.66 vs. 25.20 ± 20.43, p < 0.05) than T1SE. Lesion volume differences persisted when considering RR and SP patients separately (both p < 0.01). A higher lesion number by T1GE was seen only in the RR group (p < 0.05). When comparing correlations between lesion volume and overall neurologic disability (EDSS score), T1SE correlated with EDSS (Spearman r = 0.29, p < 0.05) while T1GE (r = 0.23, p = 0.13) and FLAIR (r = 0.24, p = 0.12) did not. Conclusion: Our data suggest that hypointense lesions on T1SE and T1GE are not interchangeable in patients with MS. Based on these results, we hypothesize that T1GE

  2. Comparison of 1H MR spectroscopy, 3-point DIXON, and multi-echo gradient echo for measuring hepatic fat fraction

    We evaluated and compared the reproducibility, diagnostic accuracy, and sequence dependency of the fat fraction (FF) determined by 3-point Dixon (DIXON) and multi-echo gradient-echo (MEGE) methods to those of the FF determined by magnetic resonance spectroscopy (MRS). Our study included 98 volunteers, ten of whom underwent scanning twice to evaluate sequence reproducibility. We compared the FFs determined by the DIXON and MEGE methods to that by MRS as the gold standard, calculated sensitivity and specificity for each image analysis method at a threshold value of 6.25% of spectroscopic value, and used Pearson's correlation coefficient and Bland-Altman analysis to compare agreement among the repeated measurements and FF values with the 3 methods, in 98 volunteers. There was no significant difference in repeated scans in any sequence with Wilcoxon's t-test. Each correlation coefficient (r) exceeded 0.930 for the repeated measurements of all 3 sequences. Sensitivity of DIXON was 82% and specificity, 96%; sensitivity of MEGE was 70% and specificity, 99%. The FFs determined by DIXON and MEGE correlated well with that by MRS (r=0.920) but showed significant difference (paired t-test, P<0.001). The mean difference between the FF determined by DIXON and that by MEGE were 0.93 and -1.16, respectively. The slope of the regression lines as determined by DIXON was -0.655 (P<0.001) and that by MEGE was -0.527 (P<0.001). When the FF by MRS was less than 6.25%, the FF values by DIXON and MEGE were significantly higher; when the spectroscopic value was greater than 6.25%, their values were significantly lower. We demonstrated the high reproducibility of each FF measurement using MRS, DIXON, and MEGE. Compared to MRS, both DIXON and MEGE showed high sensitivity and specificity for determining FF. The FFs by DIXON and MEGE showed sequence dependency because DIXON had proportional and additional errors, and MEGE had a proportional error. (author)

  3. MRI detection of hypointense brain lesions in patients with multiple sclerosis: T1 spin-echo vs. gradient-echo

    Highlights: • Compared T1SE and T1GE in detecting hypointense brain lesions in MS patients. • T1GE detected a higher cerebral lesion volume and number than T1SE. • T1SE correlated significantly with disability, while T1GE did not. • Hypointense lesions on T1SE and T1GE are not interchangeable in patients with MS. - Abstract: Objective: Compare T1 spin-echo (T1SE) and T1 gradient-echo (T1GE) sequences in detecting hypointense brain lesions in multiple sclerosis (MS). Background: Chronic hypointense lesions on T1SE MRI scans are a surrogate of severe demyelination and axonal loss in MS. The role of T1GE images in the detection of such lesions has not been clarified. Design/methods: In 45 patients with MS [Expanded Disability Status Scale (EDSS) score (mean ± SD) 3.5 ± 2.0; 37 relapsing-remitting (RR); 8 secondary progressive (SP)], cerebral T1SE, T1GE, and T2-weighted fluid-attenuated inversion-recovery (FLAIR) images were acquired on a 1.5 T MRI scanner. Images were re-sampled to axial 5 mm slices before directly comparing lesion detectability using Jim (v.7, Xinapse Systems). Statistical methods included Wilcoxon signed rank tests to compare sequences and Spearman correlations to test associations. Results: Considering the entire cohort, T1GE detected a higher lesion volume (5.90 ± 6.21 vs. 4.17 ± 4.84 ml, p < 0.0001) and higher lesion number (27.82 ± 20.66 vs. 25.20 ± 20.43, p < 0.05) than T1SE. Lesion volume differences persisted when considering RR and SP patients separately (both p < 0.01). A higher lesion number by T1GE was seen only in the RR group (p < 0.05). When comparing correlations between lesion volume and overall neurologic disability (EDSS score), T1SE correlated with EDSS (Spearman r = 0.29, p < 0.05) while T1GE (r = 0.23, p = 0.13) and FLAIR (r = 0.24, p = 0.12) did not. Conclusion: Our data suggest that hypointense lesions on T1SE and T1GE are not interchangeable in patients with MS. Based on these results, we hypothesize that T1GE

  4. T2* and proton density measurement of normal human lung parenchyma using submillisecond echo time gradient echo magnetic resonance imaging

    Hatabu, Hiroto; Alsop, David C.; Listerud, John; Bonnet, Mathieu; Gefter, Warren B

    1999-03-01

    Objective: To obtain T2* and proton density measurements of normal human lung parenchyma in vivo using submillisecond echo time (TE) gradient echo (GRE) magnetic resonance (MR) imaging. Materials and methods: Six normal volunteers were scanned using a 1.5-T system equipped with a prototype enhanced gradient (GE Signa, Waukausha, WI). Images were obtained during breath-holding with acquisition times of 7-16 s. Multiple TEs ranging from 0.7 to 2.5 ms were tested. Linear regression was performed on the logarithmic plots of signal intensity versus TE, yielding measurements of T2* and proton density relative to chest wall muscle. Measurements in supine and prone positions were compared, and effects of the level of lung inflation on lung signal were also evaluated. Results: The signal from the lung parenchyma diminished exponentially with prolongation of TE. The measured T2* in six normal volunteers ranged from 0.89 to 2.18 ms (1.43{+-}0.41 ms, mean{+-}S.D.). The measured relative proton density values ranged between 0.21 and 0.45 (0.29{+-}0.08, mean{+-}S.D.). Calculated T2* values of 1.46{+-}0.50, 1.01{+-}0.29 and 1.52{+-}0.18 ms, and calculated relative proton densities of 0.20{+-}0.03, 0.32{+-}0.13 and 0.35{+-}0.10 were obtained from the anterior, middle and posterior portions of the supine right lung, respectively. The anterior-posterior proton density gradient was reversed in the prone position. There was a pronounced increase in signal from lung parenchyma at maximum expiration compared with maximum inspiration. The ultrashort TE GRE technique yielded images demonstrating signal from lung parenchyma with minimal motion-induced noise. Conclusion: Quantitative in vivo measurements of lung T2* and relative proton density in conjunction with high-signal parenchymal images can be obtained using a set of very rapid breath-hold images with a recently developed ultrashort TE GRE sequence.

  5. Vibration transmissibility characteristics of smart spring vibration isolation system

    倪德; 朱如鹏; 陆凤霞; 鲍和云; 付秋菊

    2014-01-01

    The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

  6. Clinical evaluation of a motion compensated double echo sequence in MRI of the brain

    This study is a clinical evaluation on 5 volunteers and 20 patients of an improved sequence using rephasing gradients for motion compensation, applied to MR imaging of the brain at 1.5 T. The sequence is a double spin echo sequence with a normal first echo at TE = 15 ms and a second echo at TE = 90 ms with first and second order motion compensation in the readout gradient direction; the band width of the second echo is halved for improved S/N. Results demonstrate a dramatic improvement in image quality. Vascular and CSF flow are rephased, ghosting is reduced and signal voids no longer exist. Most remarkable is the substantial suppression of artifacts from voluntary movements such as from swallowing or rotation of the eyes. ECG triggering does not further improve image quality and is thus no longer needed. (orig.)

  7. Multisensor data fusion for impact-echo testing of concrete structures

    Based on the investigation of spatial variations of impact-echo signals for different source and receiver locations, a simple multisensor data fusion strategy is proposed to increase the accuracy of nondestructive evaluation of concrete structures using the impact-echo test. The data fusion strategy fuses the ratios between spectral amplitudes of the delamination and concrete bottom echo signals (D/B ratios) from multiple source–receiver arrays. The fused D/B ratios demonstrate different characteristics for test locations above the delamination, above the sound concrete, and across the delamination boundary. These characteristics can be used to accurately locate the delamination and its boundaries without increasing testing time. The applicability of the multisensor data fusion for impact-echo testing is validated using both numerical simulation and experimental testings. (paper)

  8. Preference of echo features for classification of seafloor sediments using neural networks

    De, C.; Chakraborty, B.

    Selection of a set of dominant echo features to classify seafloor sediments using a multilayer perceptron neural network is investigated at two acoustic frequencies (33 and 210 kHz). Several sets of inputs with different combinations of two, three...

  9. Ultrasonic echo waveshape features extraction based on QPSO-matching pursuit for online wear debris discrimination

    Xu, Chao; Zhang, Peilin; Wang, Huaiguang; Li, Yining; Lv, Chun

    2015-08-01

    The ultrasonic echoes reflected from debris in lubricant contain a lot of useful information, which can represent the size, material and geometric characteristics of the debris. Our preliminary simulation investigations and physical model analysis results show that the waveshape features are feasible and essential to discriminate debris in lubricant. An accurate waveshape features extraction method of debris echoes is presented based on the matching pursuit (MP). The dictionary of Gabor functions, which is suitable for ultrasonic signal processing, is adopted for MP. To seek faster and more accurate calculation of MP, quantum-behaved particle swarm optimization (QPSO) is introduced to optimize the MP algorithm. The simulation and experimental results reveal that the proposed method can effectively extract the waveshape features of debris echoes and air bubble echoes. Utilizing the extracted waveshape features, the debris with different shapes and air bubble can be distinguished.

  10. Worldwide Echo-Sounding Correction Tables to Convert to Standard Velocity Depths

    National Oceanic and Atmospheric Administration, Department of Commerce — Echo-sounding tables (3rd Edition) were prepared by D.J.T. Carter of the Marine Information and Advisory Service (United Kingdom) for the conversion of raw...

  11. Conditions for Using Stimulated Photon Echo to Record and Reproduce Information in Three-Level Systems

    Nefediev, L. A.; Nizamova, E. I.

    2016-01-01

    The conditions for observing photon echo signals in crystals with excitation and detection in different resonant transitions with a single common energy level are studied. Uncorrelated inhomogeneous broadening in different resonance transitions is shown to influence the formation of stimulated photon echo in three-level systems. Lowering the sample temperature makes it possible to increase the relaxation time, which is used in experiments for observing photon echo. Uncorrelated inhomogeneous broadening in different resonance transitions is temperature independent and affects the intensity of the response at low temperatures, as well. Observation of stimulated photon echo in solid three-level samples requires a correct choice of the time interval between the first and second exciting pulses, but is not related to the magnitude of the irreversible transverse relaxation of the system.

  12. Numerical calculation of spin echo amplitude in pulsed NMR: effects of quadrupole interaction

    The spin echo obtained by nuclear magnetic resonance, in systems which atomic nuclei interact with magnetic fields and electric field gradients, present oscillations in function of the time interval between two excitations pulses. Using the density matrix formalism, the amplitudes of these echo is calculated, analytically. In this work, echo amplitudes obtained under different excitation conditions for nuclei of different nuclear spin values are calculated. The numerical results are compared with disposable analytical solutions. Applications of this method to the case of electric field gradient without axial symmetry were studied. Within the used approximation limits, an expression for attnuation of oscillatory behaviour of echo amplitude in function of the time interval between experimentally observed pulses was obtained. (M.C.K.)

  13. Detection Algorithm for LFM Echo of Underwater Moving Targets Based on Discrete Fractional Fourier Transform

    2007-01-01

    The mismatch between echo and replica caused by underwater moving target(UMT)'s radial velocity degrades the detection performance of the matched filter(MF) for the linear frequency modulation(LFM) signal. By using the focusing property of fractional Fourier transform(FRFT) to that signal, a detection algorithm for UMT's LFM echo based on the discrete fractional Fourier transform(DFRFT) is proposed. This algorithm is less affected by the target's radial velocity compared with the other MF detection algorithm utilizing zero radial velocity replica(ZRVR), and the mathematical relation between the output peak positions of these two algorithms exists in the case of existence of target echo. The algorithm can also estimate the target distance by using this relation. The simulation and experiment show that this algorithm's detection performance is better than or equivalent to that of the other MF algorithm utilizing ZRVR for the LFM echo of UMT with unknown radial velocity under reverberation noise background.

  14. Evaluation of thermal sprayed coating using ultrasonic inspection by means of bottom echo back reflection

    Toshifumi KUBOHORI; Toru ITO; Wahidullah WAHI; Yasuyuki INUI; Toshiro IKUTA

    2009-01-01

    Thermal spraying technique is widely used in various mechanical parts as a surface reforming technique. However, as demand to maintain superior mechanical performance in harsh operating environment increases, the need for non-destructive evaluation method for thermal spray coating becomes more important. For this purpose, we thinned the thickness of the thermal sprayed coating by abrasion with blasting and used ultrasonic inspection by means of bottom echo reflection for effective measurement of abrasion quantity in thermal sprayed coating. The results obtained are summarized as follows. When the thickness of thermal sprayed coating becomes thin, the echo height increases. This is because thermal sprayed coatings absorb ultrasonic energy. Ultrasonic energy absorbed by Al2O3 is smaller compared with Fe-13Cr coating. Thermal sprayed coatings submerged in water have a lower echo height compared with air. As mentioned above, the thermal sprayed coating thickness can be estimated using ultrasonic inspection by means of bottom echo back reflection.

  15. AFSC/ABL: Frederick Sound Echo-integrated Trawl Survey, 2001 to 2004

    National Oceanic and Atmospheric Administration, Department of Commerce — The acoustic trawl database for Frederick Sounds echo-trawl survey was conducted from 2001 to 2004. The surveys were conducted throughout most of the southern part...

  16. AFSC/ABL: Lynn Canal Echo-Integrated Trawl Surveys, 2001-2004

    National Oceanic and Atmospheric Administration, Department of Commerce — The acoustic trawl database for Lynn Canals echo-trawl survey was conducted from 2001 to 2004 throughout southern Lynn Canal in southeast Alaska. Acoustic surveys...

  17. Sub-band Implementation of Adaptive Nonlinear Filter for Adaptive Nonlinear Echo Cancellation

    Dayong Zhou

    2007-04-01

    Full Text Available The adaptive Volterra filter has been successfully applied in nonlinear acoustic echo cancellation (AEC systems and nonlinear line echo cancellation systems, but its applications are limited by its required computational complexity and slow convergence rate, especially for systems with long memory length. In this paper, we first apply a more general nonlinear filter, the function expansion nonlinear filter, in the acoustic echo cancellation - the Volterra filter can be regarded as special case of the function expansion nonlinear filter. Then by leveraging to a multi-channel configuration of the function expansion nonlinear filter and the sampling theory for nonlinear systems, we extend linear sub-band delay-less adaptive filter techniques to develop an efficient sub-band implementation of the adaptive function expansion nonlinear filter. The developed sub-band configuration of the adaptive nonlinear filter can greatly improve the convergence rate and reduce the computational complexity of nonlinear echo cancellers, which is shown by analyses and simulations.

  18. Structure and apparent dispersion of ballistic plasma wave echoes of second order

    The spatial structure of electron plasma wave echoes is investigated with special regard to the apparent dispersion, i.e. the relation between echo wavelength and frequency. The apparent dispersion is obtained by separately recording echo phase and amplitude, using an r.f.-interferometer combined with a network analyzer. Comparison with theory reveals the ballistic nature of the second order echoes investigated; due to the dispersion as a quantitative measure of the velocity diffusion, it yields furthermore a velocity-independent diffusion coefficient D2 = (1.5 +- 0.5) x 1017 m2 s-3, two orders of magnitude larger than expected from equilibrium theory. The enhanced velocity diffusion can be related to non-equilibrium fluctuations due to ion-acoustic turbulence present in the target plasma. (author)

  19. 14 CFR 33.33 - Vibration.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.33 Section 33.33 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.33 Vibration. The... vibration and without imparting excessive vibration forces to the aircraft structure....

  20. 14 CFR 33.63 - Vibration.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.63 Section 33.63 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.63 Vibration. Each engine... because of vibration and without imparting excessive vibration forces to the aircraft structure....

  1. Rectangular Parallelepiped Vibration in Plane Strain State

    Hanckowiak, Jerzy

    2004-01-01

    In this paper we present a vibration spectrum of a homogenous parallelepiped (HP) under the action of volume and surface forces resulting from the exponent displacements entering the Fourier transforms. Vibration under the action of axial surface tractions and the free vibration are described separately. A relationship between the high frequency vibration and boundary conditions (BC) is also considered.

  2. Decoherence as attenuation of mesoscopic echoes in a spin-chain channel

    Alvarez, Gonzalo A.; Danieli, Ernesto P.; Levstein, Patricia R.; Pastawski, Horacio M.

    2010-01-01

    An initial local excitation in a confined quantum system evolves exploring the whole system, returning to the initial position as a mesoscopic echo at the Heisenberg time. We consider a two weakly coupled spin chains, a spin ladder, where one is a quantum channel while the other represents an environment. We quantify decoherence in the quantum channel through the attenuation of the mesoscopic echoes. We evaluate decoherence rates for different ratios between sources of amplitude fluctuation a...

  3. Delay accuracy in bat sonar is related to the reciprocal of normalized echo bandwidth, or Q

    Simmons, James A.; Neretti, Nicola; Intrator, Nathan; Altes, Richard A.; Ferragamo, Michael J.; Sanderson, Mark I.

    2004-01-01

    Big brown bats (Eptesicus fuscus) emit wideband, frequency-modulated biosonar sounds and perceive the distance to objects from the delay of echoes. Bats remember delays and patterns of delay from one broadcast to the next, and they may rely on delays to perceive target scenes. While emitting a series of broadcasts, they can detect very small changes in delay based on their estimates of delay for successive echoes, which are derived from an auditory time/frequency representation of frequency-m...

  4. Detection-Discrimination Method for Multiple Repeater False Targets Based on Radar Polarization Echoes

    ZONG, Z. W.; L. F. SHI; Y. Z. LI; X.S. Wang

    2014-01-01

    Multiple repeat false targets (RFTs), created by the digital radio frequency memory (DRFM) system of jammer, are widely used in practical to effectively exhaust the limited tracking and discrimination resource of defence radar. In this paper, common characteristic of radar polarization echoes of multiple RFTs is used for target recognition. Based on the echoes from two receiving polarization channels, the instantaneous polarization radio (IPR) is defined and its variance is derived by employi...

  5. The Application of Impact Echo Scanning on Nondestructive Test of Pavement

    2006-01-01

    A new nondestructive test method-Impact Echo Scanning was introduced. Application of this method on pavement structure test was discussed. A method to increase the measurement accuracy of the test on multi-layers was proposed, and was verified by field test. The test results show that the basic structural information can obtained rapidly and accurately by 3-D scanning of the impact echo system.

  6. Target echo strength modelling at FOI, including results from the BeTSSi II workshop

    Östberg, Martin

    2016-01-01

    An overview of the target echo strength (TS) modelling capacity at the Swedish Defense Research Agency (FOI) is presented. The modelling methods described range from approximate ones, such as raytracing and Kirchhoff approximation codes, to high accuracy full field codes including boundary integral equation methods and finite elements methods. Illustrations of the applicability of the codes are given for a few simple cases tackled during the BeTTSi II (Benchmark Target Echo Strength Simulation) workshop held in Kiel 2014.

  7. Light Echoes of Ancient Transients with the Blanco CTIO 4m Telescope

    Rest, A; Welch, D L; Prieto, J L; Bianco, F B; Matheson, T; Smith, R C; Suntzeff, N B

    2015-01-01

    For over a century, light echoes have been observed around variable stars and transients. The discovery of centuries-old light echoes from supernovae in the Large Magellanic Cloud has allowed the spectroscopic characterization of these events using modern instrumentation, even in the complete absence of any visual record of those events. Here we review the pivotal role the Blanco 4m telescope played in these discoveries.

  8. On the origin of 150-km echoes: Recent observational results and current understanding

    Patra, Amit

    2012-07-01

    Discovered nearly 45 years ago, the so-called 150-km echoing phenomenon continues to be a puzzle. These are the coherent radar echoes coming from the height region of 140-180 km during daytime and are of special interest to the ionospheric scientists since they are very useful means for estimating the daytime electric fields, a crucial parameter for studying daytime electrodynamics and plasma physics, and can be observed by radar with moderate sensitivity. Although the 150-km echoes are being regularly used for studying low latitude electrodynamics, it is a bit awkward using them in the scientific work without knowing their origin. This paper is meant to present and discuss new results obtained from Gadanki (13.5o N, 79.2o E, mag. lat. 6.5o N), India to elucidate the underlying physical processes, not considered before. Two new findings, one obtained during the passage of a solar eclipse and another linked with the intermediate layer type descending properties of 150-km echoes, clearly indicate the role of electron density gradient in generating the irregularities responsible for the 150-km radar echoes, not envisioned before. Given the fact that Gadanki is located at magnetically low latitude, it is proposed that the descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal/gravity waves quite similar to that observed during nighttime. Comparative anatomy of daytime 150-km echoes and nighttime intermediate layer echoes will also be presented and discussed in an effort to have a deeper understanding on the underlying instability processes.

  9. Spontaneous cerebral microbleeds on gradient echo MR imaging in the stroke patients

    To investigate the spontaneous cerebral microbleeding occurring at gradient-echo MRI, and its relationship with associated stroke lesions and risk factors. Between September 2001 and December, 2002, 32 patients (21 men and 11 women; mean age 63 years) in whom cerebral microbleeding occurred at gradient-echo MRI were retrospectively investigated. Using a 1.5T MR imager, spin-echo T1-weighted, fast spin-echo T2-weighted, diffusion-weighted, and gradient-echo images were obtained. The number and location of microbleeds seen on gradient echo images, patients data, and associated stroke lesions such as intracerebral hemorrhage and lacunar and territorial infarction were assessed. Among the 32 patients, 563 microbleeds and between 1 and 66 (mean, 17.6) were noted at gradient-echo imaging. Microbleeding occurred in the cortical/subcortical area (n=216), the basal ganglia (n=173), thalamus (n=92), cerebellum (n=41), brainstem (n=36) and corpus callosum (n=1), and in 20 patients was bilateral. Patients had a history of hypertension (n=26), hypertriglycemia (n=12), heart disease (n=4), and diabetes mellitus (n=3). Stroke lesions were seen in 27 patients, intracerebral hemorrhage in ten, lacunar infarction in 24, and territorial infarction in four. The incidence and number of microbleeds was greater in older patients and in those with hypertension, hypertriglycemia, and stroke lesions such as intracerebral hemorrhage or lacunar infarction. The detection of microbleeding at gradient-echo imaging is helpful, since it predicts the possibility of cerebral hemorrhage in these patients

  10. Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo.

    David Milford

    Full Text Available T2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfections contribute significantly to the offset. We further introduce a simple method to reduce the systematic error in T2 by discarding the first echo and using the offset fitting approach.Signal curves of T2 relaxometry were simulated based on extended phase graph theory and evaluated for 4 different methods (inclusion and exclusion of the first echo, while fitting with and without the offset. We further performed T2 relaxometry in a phantom at 9.4T magnetic resonance imaging scanner and used the same methods for post-processing as in the extended phase graph simulated data. Single spin echo sequences were used to determine the correct T2 time.The simulation data showed that the systematic error in T2 and the offset depends on the refocusing pulse, the echo spacing and the echo train length. The systematic error could be reduced by discarding the first echo. Further reduction of the systematic T2 error was reached by using the offset as fitting parameter. The phantom experiments confirmed these findings.The fitted offset parameter in T2 relaxometry is influenced by imperfect refocusing pulses. Using the offset as a fitting parameter and discarding the first echo is a fast and easy method to minimize the error in T2, particularly for low to intermediate echo train length.

  11. Anomalous Propagation Echo Classification of Imbalanced Radar Data with Support Vector Machine

    Hansoo Lee; Eun Kyeong Kim; Sungshin Kim

    2016-01-01

    A number of technologically advanced devices, such as radars and satellites, are used in an actual weather forecasting process. Among these devices, the radar is essential equipment in this process because it has a wide observation area and fine resolution in both the time and the space domains. However, the radar can also observe unwanted nonweather phenomena. Anomalous propagation echo is one of the representative nonprecipitation echoes generated by an abnormal refraction phenomenon of a r...

  12. Vibration damping of mechanical seals

    Hammond, R. R.

    1970-01-01

    Bellows seal filled with spherical powder reacts to vibration inputs by absorbing displacement energy through inertia and friction of the particle masses acting on the inside surface of the cylinders.

  13. Energetics, structures, vibrational frequencies, vibrational absorption, vibrational circular dichroism and Raman intensities of Leu-enkephalin

    Jalkanen, Karl J.

    2003-01-01

    Here we present several low energy conformers of Leu-enkephalin (LeuE) calculated with the density functional theory using the Becke 3LYP hybrid functional and the 6-31G* basis set. The structures, conformational energies, vibrational frequencies, vibrational absorption (VA) intensities......, vibrational circular dichroism (VCD) intensities and Raman scattering intensities are reported for the conformers of LeuE which are expected to be populated at room temperature. The species of LeuE-present in non-polar solvents is the neutral non-ionic species with the NH2 and CO2H groups, in contrast to the...

  14. Vibrational Damping of Composite Materials

    Biggerstaff, Janet M.

    2006-01-01

    The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss facto...

  15. Harmonic vibrations of multispan beams

    Dyrbye, Claes

    1996-01-01

    Free and forced harmonic vibrations of multispan beams are determined by a method which implies 1 equation regardless of the configuration. The necessary formulas are given in the paper. For beams with simple supports and the same length of all (n) spans, there is a rather big difference between...... the n´th and the (n+1)´th eigenfrequency. The reason for this phenomenon is explained.Keywords: Vibrations, Eigenfrequencies, Beams....

  16. Vibrational Spectral Studies of Gemfibrozil

    Benitta, T. Asenath; Balendiran, G. K.; James, C.

    2008-11-01

    The Fourier Transform Raman and infrared spectra of the crystallized drug molecule 5-(2,5-Dimethylphenoxy)-2,2-dimethylpentanoic acid (Gemfibrozil) have been recorded and analyzed. Quantum chemical computational methods have been employed using Gaussian 03 software package based on Hartree Fock method for theoretically modeling the grown molecule. The optimized geometry and vibrational frequencies have been predicted. Observed vibrational modes have been assigned with the aid of normal coordinate analysis.

  17. Harmonic vibrations of multispan beams

    Dyrbye, Claes

    Free and forced harmonic vibrations of multispan beams are determined by a method which implies 1 equation regardless of the configuration. The necessary formulas are given in the paper. For beams with simple supports and the same length of all (n) spans, there is a rather big difference between...... the n´th and the (n+1)´th eigenfrequency. The reason for this phenomenon is explained.Keywords: Vibrations, Eigenfrequencies, Beams....

  18. Vibration Theory, Vol. 1B

    Asmussen, J. C.; Nielsen, Søren R. K.

    The present collection of MATLAB exercises has been published as a supplement to the textbook, Svingningsteori, Bind 1 and the collection of exercises in Vibration theory, Vol. 1A, Solved Problems. Throughout the exercise references are made to these books. The purpose of the MATLAB exercises is to...... give a better understanding of the physical problems in linear vibration theory and to surpress the mathematical analysis used to solve the problems. For this purpose the MATLAB environment is excellent....

  19. Vibrational spectroscopy at electrified interfaces

    Wieckowski, Andrzej; Braunschweig, Björn

    2013-01-01

    Reviews the latest theory, techniques, and applications Surface vibrational spectroscopy techniques probe the structure and composition of interfaces at the molecular level. Their versatility, coupled with their non-destructive nature, enables in-situ measurements of operating devices and the monitoring of interface-controlled processes under reactive conditions. Vibrational Spectroscopy at Electrified Interfaces explores new and emerging applications of Raman, infrared, and non-linear optical spectroscopy for the study of charged interfaces. The book draws from hu

  20. Vibration analysis of a VAWT

    Redín Larrea, Leyre

    2013-01-01

    This research analyses the vibrations in a special type of vertical axis wind turbine with parabolic blades called Darrieus. The study will be focused on the vibrations of the tower. It is really important to know the tower ́s behaviour against them in order to choose the best material for it and to avoid problems such as frequent maintenance and even wind turbine breakage. For developing this thesis a vast array of in formation has been gathered from technical ...

  1. Utility of echo-planar gradient-echo T2*-weighted MR images in patients with primary intracerebral hemorrhage

    Magnetic resonance imaging (MRI) has the potential to reveal residues of intracerabral hemorrhage (ICH) throughout life because of the high sensitivity for iron-containing compounds. Gradient-echo T2*-weighted MR imaging (T2*MRI) requiring short times for complete acquisition is known to detect small areas of signal loss without surrounding edema representing microbleeds (MBs). MBs in the basal ganglia including the thalami are suggested to be closely related to intracerebral atherosclerotic microangiopathy. We looked for more than 3 MBs in basal ganglia or thalamus of patients with and without episodes of previous ICH. Twelve patients with previous hemorrhagic stroke and 82 without were studied. Multiple MBs in those regions were significantly more frequent in patients with recurrent ICH. In addition, a 76-year-old woman with a history of hypertension was transferred to our hospital for treatment of head injury. She had multiple incidental old basal ganglionic and thalamic MBs. The patient had an asymptomatic primary ICH on computed tomography (CT) 3 months later. In conclusion, MR evidence of multiple MBs in the basal ganglia and thalamus might identify patients at a risk for new and recurrent ICH. Therefore, patients with multiple MBs in those regions should be treated for cerebrovascular risk factors, especially hypertension. Our results appear to confirm the utility of T2*MRI in hemorrhagic stroke. (author)

  2. Observations of fast magnetospheric echoes of artificially injected electrons above an auroral arc

    Electron beam experiments using rocket-borne instrumentation have confirmed earlier observations of fast magnetospheric echoes of artificially injected energetic electrons. These experiments were jointly carried out by the University of Minnesota, the National Research Council of Canada and the Max-Planck-Institut fuer Aeronomie. A total of 234 echoes have been observed in a pitch angle range from 00 to 1100 at energies of 1.87 and 3.90 keV. Out of this number, 95 echoes could unambiguously be identified with known accelerator operations at 2, 4 or 8 keV energy and highest current levels resulting in the determination of transit times of typically 400 ms. In most cases, when echoes were present in both energy channels, the higher energy electrons led the lower energy ones by approximately 50 ms. No echoes have been found in the 7.9 keV-detector channels. Adiabatic theory applied to these observations yields a reflection height of 3000 to 4000 km. The injection process is briefly discussed as the strong beam-plasma interaction that occurred near the electron accelerator appears to be instrumental in generating the source of heated electrons required for successful echo detection. Two consequences of this interaction, namely, strong energy and pitch angle diffusion and electron acceleration are illustrated with several examples. (orig.)

  3. Expanding Health Care Access Through Education: Dissemination and Implementation of the ECHO Model.

    Katzman, Joanna G; Galloway, Kevin; Olivas, Cynthia; McCoy-Stafford, Kimberly; Duhigg, Daniel; Comerci, George; Kalishman, Summers; Buckenmaier, Chester C; McGhee, Laura; Joltes, Kristin; Bradford, Andrea; Shelley, Brian; Hernandez, Jessica; Arora, Sanjeev

    2016-03-01

    Project ECHO (Extension for Community Healthcare Outcomes) is an evidence-based model that provides high-quality medical education for common and complex diseases through telementoring and comanagement of patients with primary care clinicians. In a one to many knowledge network, the ECHO model helps to bridge the gap between primary care clinicians and specialists by enhancing the knowledge, skills, confidence, and practice of primary care clinicians in their local communities. As a result, patients in rural and urban underserved areas are able to receive best practice care without long waits or having to travel long distances. The ECHO model has been replicated in 43 university hubs in the United States and five other countries. A new replication tool was developed by the Project ECHO Pain team and U.S. Army Medical Command to ensure a high-fidelity replication of the model. The adoption of the tool led to successful replication of ECHO in the Army Pain initiative. This replication tool has the potential to improve the fidelity of ECHO replication efforts around the world. PMID:26926747

  4. Pre-ejection period by radial artery tonometry supplements echo doppler findings during biventricular pacemaker optimization

    Qamruddin Salima

    2011-07-01

    Full Text Available Abstract Background Biventricular (Biv pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP assessment by radial artery tonometry in guiding Biv pacemaker optimization. Methods Blinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV ejection fraction (EF 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI, ejection time (ET, myocardial performance index (MPI, radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated. Results Significant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p Conclusion An acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization.

  5. Software Applications to Access Earth Science Data: Building an ECHO Client

    Cohen, A.; Cechini, M.; Pilone, D.

    2010-12-01

    Historically, developing an ECHO (NASA’s Earth Observing System (EOS) ClearingHOuse) client required interaction with its SOAP API. SOAP, as a framework for web service communication has numerous advantages for Enterprise applications and Java/C# type programming languages. However, as interest has grown for quick development cycles and more intriguing “mashups,” ECHO has seen the SOAP API lose its appeal. In order to address these changing needs, ECHO has introduced two new interfaces facilitating simple access to its metadata holdings. The first interface is built upon the OpenSearch format and ESIP Federated Search framework. The second interface is built upon the Representational State Transfer (REST) architecture. Using the REST and OpenSearch APIs to access ECHO makes development with modern languages much more feasible and simpler. Client developers can leverage the simple interaction with ECHO to focus more of their time on the advanced functionality they are presenting to users. To demonstrate the simplicity of developing with the REST API, participants will be led through a hands-on experience where they will develop an ECHO client that performs the following actions: + Login + Provider discovery + Provider based dataset discovery + Dataset, Temporal, and Spatial constraint based Granule discovery + Online Data Access

  6. Generation of an optimal target list for the Exoplanet Characterisation Observatory (EChO)

    Varley, Ryan; Pascale, Enzo; Tessenyi, Marcell; Hollis, Morgan; Morales, Juan Carlos; Tinetti, Giovanna; Swinyard, Bruce; Deroo, Pieter; Ollivier, Marc; Micela, Giusi

    2014-01-01

    The Exoplanet Characterisation Observatory EChO is a space mission concept studied by the European Space Agency in the context of the M3 selection process. Through direct measurement of the atmospheric chemical composition of hundreds of exoplanets, EChO would address fundamental questions such as: What are exoplanets made of? How do planets form and evolve? What is the origin of exoplanet diversity? More specifically, EChO is a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planetary sample within its four to six year mission lifetime. In this paper we use the end-to-end instrument simulator EChOSim to model the currently discovered targets, to gauge which targets are observable and assess the EChO performances obtainable for each observing tier and time. We show that EChO would be capable of observing a large and diverse sample of planets even if it were launched today, and the wealth of optimal targets for EChO expected to be discovered ...

  7. Defect discrimination by cross correlation between ultrasonic echoes and incident waves

    Discrimination of defects from geometric reflectors which is essential in ultrasonic inspection of piping systems in nuclear power plants is described. A new method is proposed which is based on whether or not a detected echo is of the same phase as the incident waves in the pulse echo technique. Experimental results indicate that the method can discriminate between slits and drilled holes or circular bottom surfaces at a refracted angle of 45 degrees. Discriminating between reflectors in an object to be inspected is essential to ultrasonic inspection of piping systems as well as defect sizing. Because of the ultrasonic beam spread, conventional ultrasonic methods cannot easily discriminate cracks from inner surface beams or voids based only on the reflector's location and/or the shape of the maximum echo envelope. In the hope of increasing agreement between the actual and predicted situations, the ultrasonic waveforms themselves have been utilized to classify the reflectors. One of these papers used pulse orientations of the echo, but showed that certain difficulties were still involved in evaluating them. As a simple and reliable technique, the authors present an ultrasonic echo phase technique for discriminating cracks from other reflectors. Purposes of this paper are to derive an algorithm for the echo phase evaluation and to clarify its discrimination ability through experiments

  8. Dynamic Echo Information Guides Flight in the Big Brown Bat.

    Warnecke, Michaela; Lee, Wu-Jung; Krishnan, Anand; Moss, Cynthia F

    2016-01-01

    Animals rely on sensory feedback from their environment to guide locomotion. For instance, visually guided animals use patterns of optic flow to control their velocity and to estimate their distance to objects (e.g., Srinivasan et al., 1991, 1996). In this study, we investigated how acoustic information guides locomotion of animals that use hearing as a primary sensory modality to orient and navigate in the dark, where visual information is unavailable. We studied flight and echolocation behaviors of big brown bats as they flew under infrared illumination through a corridor with walls constructed from a series of individual vertical wooden poles. The spacing between poles on opposite walls of the corridor was experimentally manipulated to create dense/sparse and balanced/imbalanced spatial structure. The bats' flight trajectories and echolocation signals were recorded with high-speed infrared motion-capture cameras and ultrasound microphones, respectively. As bats flew through the corridor, successive biosonar emissions returned cascades of echoes from the walls of the corridor. The bats flew through the center of the corridor when the pole spacing on opposite walls was balanced and closer to the side with wider pole spacing when opposite walls had an imbalanced density. Moreover, bats produced shorter duration echolocation calls when they flew through corridors with smaller spacing between poles, suggesting that clutter density influences features of the bat's sonar signals. Flight speed and echolocation call rate did not, however, vary with dense and sparse spacing between the poles forming the corridor walls. Overall, these data demonstrate that bats adapt their flight and echolocation behavior dynamically when flying through acoustically complex environments. PMID:27199690

  9. Dynamic echo information guides flight in the big brown bat

    Michaela Warnecke

    2016-04-01

    Full Text Available Animals rely on sensory feedback from their environment to guide locomotion. For instance, visually guided animals use patterns of optic flow to control their velocity and to estimate their distance to objects (e.g. Srinivasan et al. 1991, 1996. In this study, we investigated how acoustic information guides locomotion of animals that use hearing as a primary sensory modality to orient and navigate in the dark, where visual information is unavailable. We studied flight and echolocation behaviors of big brown bats as they flew under infrared illumination through a corridor with walls constructed from a series of individual vertical wooden poles. The spacing between poles on opposite walls of the corridor was experimentally manipulated to create dense/sparse and balanced/imbalanced spatial structure. The bats’ flight trajectories and echolocation signals were recorded with high-speed infrared motion-capture cameras and ultrasound microphones, respectively. As bats flew through the corridor, successive biosonar emissions returned cascades of echoes from the walls of the corridor. The bats flew through the center of the corridor when the pole spacing on opposite walls was balanced and closer to the side with wider pole spacing when opposite walls had an imbalanced density. Moreover, bats produced shorter duration echolocation calls when they flew through corridors with smaller spacing between poles, suggesting that clutter density influences features of the bat’s sonar signals. Flight speed and echolocation call rate did not, however, vary with dense and sparse spacing between the poles forming the corridor walls. Overall, these data demonstrate that bats adapt their flight and echolocation behavior dynamically when flying through acoustically complex environments.

  10. Polar mesosphere summer echoes (PMSE) a southern hemisphere perspective

    Morris, R. J.; Murphy, D. J.; Klekociuk, A. R.; Holdsworth, D. A.

    The existence of Polar Mesosphere Summer Echoes PMSE in the Southern Hemisphere SH has recently been confirmed using HF radar Ogawa et al 2002 MST radar Morris et al 2004 and a Dynasonde Jarvis et al 2005 following earlier observations using MST radar Woodman et al 1999 These studies spanned the geographic latitudes 62 1 r S Machu Picchu 68 6 r S Davis 69 0 r S Syowa and 75 5 r S Halley Bay The emerging array of SH SuperDARN radars provide an opportunity to extend the spatial coverage of PMSE observations An understanding of the occurrence and intensity of PMSE against latitude in the SH is needed to facilitate a comparison with the better spatial coverage of Northern Hemisphere NH PMSE observations Such a comparison will contribute to the ongoing debate as to whether PMSE can provide a proxy for mesosphere temperature and thus shed light on the existence of any interhemispheric asymmetry or otherwise in the polar mesosphere regions The argument for different polar mesosphere environments spawned in part by the reported lack of SH PMSE observations Recent PMSE reflectivity and intensity results from Davis 68 6 r S and Andenes 69 0 r N are given The characteristics and morphology of PMSE events above these Antarctic stations are considered in the context of the thermal and dynamical state of the mesosphere as deduced from satellite i e SABER and AURA and radar i e MF and MST observations respectively A brief account of recent coincident PMSE MST radar and Polar Mesospheric Cloud PMC

  11. Radio-echo sounding of 'active' Antarctic subglacial lakes

    Siegert, M. J.; Ross, N.; Blankenship, D. D.; Young, D. A.; Greenbaum, J. S.; Richter, T.; Rippin, D. M.; Le Brocq, A. M.; Wright, A.; Bingham, R.; Corr, H.; Ferraccioli, F.; Jordan, T. A.; Smith, B. E.; Payne, A. J.; Dowdeswell, J. A.; Bamber, J. L.

    2013-12-01

    Repeat-pass satellite altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts, however. Over the last 5 years, major geophysical campaigns have acquired RES data from several 'active' lake sites, including the US-UK-Australian ICECAP programme in East Antactica and the UK survey of the Institute Ice Stream in West Antarctica. In the latter case, a targeted RES survey of one 'active' lake was undertaken. RES evidence of the subglacial bed beneath 'active' lakes in both East and West Antarctica will be presented, and the evidence for pooled subglacial water from these data will be assessed. Based on this assessment, the nature of 'active' subglacial lakes, and their associated hydrology and relationship with surrounding topography will be discussed, as will the likelihood of further 'active' lakes in Antarctica. Hydraulic potential map of the Byrd Glacier catchment with contours at 5 MPa intervals. Predicted subglacial flowpaths are shown in blue. Subglacial lakes known from previous geophysical surveys are shown as black triangles while the newly discovered 'Three-tier lakes' are shown in dashed black outline. Surface height change features within the Byrd subglacial catchment are shown in outline and are shaded to indicate whether they were rising or falling during the ICESat campaign. Those features are labelled in-line with the numbering system of Smith et al. (J. Glac. 2009).

  12. A whale better adjusts the biosonar to ordered rather than to random changes in the echo parameters.

    Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

    2012-09-01

    A false killer whale's (Pseudorca crassidens) sonar clicks and auditory evoked potentials (AEPs) were recorded during echolocation with simulated echoes in two series of experiments. In the first, both the echo delay and transfer factor (which is the dB-ratio of the echo sound-pressure level to emitted pulse source level) were varied randomly from trial to trial until enough data were collected (random presentation). In the second, a combination of the echo delay and transfer factor was kept constant until enough data were collected (ordered presentation). The mean click level decreased with shortening the delay and increasing the transfer factor, more at the ordered presentation rather than at the random presentation. AEPs to the self-heard emitted clicks decreased with shortening the delay and increasing the echo level equally in both series. AEPs to echoes increased with increasing the echo level, little dependent on the echo delay at random presentations but much more dependent on delay with ordered presentations. So some adjustment of the whale's biosonar was possible without prior information about the echo parameters; however, the availability of prior information about echoes provided additional whale capabilities to adjust both the transmitting and receiving parts of the biosonar. PMID:22978908

  13. Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study

    Ma Yingliang; Penney, Graeme P; Razavi, Reza; Rhode, Kawal S [Division of Imaging Sciences, King' s College, London SE1 7EH (United Kingdom); Bos, Dennis; Frissen, Peter [Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven (Netherlands); Rinaldi, C Aldo, E-mail: y.ma@kcl.ac.u [Department of Cardiology, Guy' s and St Thomas' NHS Foundation Trust, London SE1 7EH (United Kingdom)

    2010-07-07

    We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers. (note)

  14. A novel time series analysis approach for prediction of dialysis in critically ill patients using echo-state networks

    De Turck F

    2010-01-01

    Full Text Available Abstract Background Echo-state networks (ESN are part of a group of reservoir computing methods and are basically a form of recurrent artificial neural networks (ANN. These methods can perform classification tasks on time series data. The recurrent ANN of an echo-state network has an 'echo-state' characteristic. This 'echo-state' functions as a fading memory: samples that have been introduced into the network in a further past, are faded away. The echo-state approach for the training of recurrent neural networks was first described by Jaeger H. et al. In clinical medicine, until this moment, no original research articles have been published to examine the use of echo-state networks. Methods This study examines the possibility of using an echo-state network for prediction of dialysis in the ICU. Therefore, diuresis values and creatinine levels of the first three days after ICU admission were collected from 830 patients admitted to the intensive care unit (ICU between May 31th 2003 and November 17th 2007. The outcome parameter was the performance by the echo-state network in predicting the need for dialysis between day 5 and day 10 of ICU admission. Patients with an ICU length of stay Results The AUC's in the three developed echo-state networks were 0.822, 0.818, and 0.817. These results were comparable to the results obtained by the SVM and the NB algorithm. Conclusions This proof of concept study is the first to evaluate the performance of echo-state networks in an ICU environment. This echo-state network predicted the need for dialysis in ICU patients. The AUC's of the echo-state networks were good and comparable to the performance of other classification algorithms. Moreover, the echo-state network was more easily configured than other time series modeling technologies.

  15. Vibrational spectroscopy of proteins

    Two important steps for the development of a biosensor are the immobilization of the biological component (e.g. protein) on a surface and the enhancement of the signal to improve the sensitivity of detection. To address these subjects, the present work describes Fourier transform infrared (FTIR) investigations of several proteins bound to the surface of an attenuated total reflection (ATR) crystal. Furthermore, new nanostructured surfaces for signal enhancement were developed for use in FTIR microscopy. The mitochondrial redox-protein cytochrome c oxidase (CcO) was incorporated into a protein-tethered bilayer lipid membrane (ptBLM) on an ATR crystal featuring a roughened two-layer gold surface for signal enhancement. Electrochemical excitation by periodic potential pulses at different modulation frequencies was followed by time-resolved FTIR spectroscopy. Phase sensitive detection was used for deconvolution of the IR spectra into vibrational components. A model based on protonation-dependent chemical reaction kinetics could be fitted to the time evolution of IR bands attributed to several different redox centers of the CcO. Further investigations involved the odorant binding protein 14 (OBP14) of the honey bee (Apis mellifera), which was studied using ATR-FTIR spectroscopy and circular dichroism. OBP14 was found to be thermally stable up to 45 °C, thus permitting the potential application of this protein for the fabrication of biosensors. Thermal denaturation measurements showed that odorant binding increases the thermal stability of the OBP-odorant complex. In another project, plasmonic nanostructures were fabricated that enhance the absorbance in FTIR microscopy measurements. The nanostructures are composed of an array of round-shaped insulator and gold discs on top of a continuous gold layer. Enhancement factors of up to ⁓125 could be observed with self-assembled monolayers of dodecanethiol molecules immobilized on the gold surface (author)

  16. Evolution of Web Services in EOSDIS: Search and Order Metadata Registry (ECHO)

    Mitchell, Andrew; Ramapriyan, Hampapuram; Lowe, Dawn

    2009-01-01

    During 2005 through 2008, NASA defined and implemented a major evolutionary change in it Earth Observing system Data and Information System (EOSDIS) to modernize its capabilities. This implementation was based on a vision for 2015 developed during 2005. The EOSDIS 2015 Vision emphasizes increased end-to-end data system efficiency and operability; increased data usability; improved support for end users; and decreased operations costs. One key feature of the Evolution plan was achieving higher operational maturity (ingest, reconciliation, search and order, performance, error handling) for the NASA s Earth Observing System Clearinghouse (ECHO). The ECHO system is an operational metadata registry through which the scientific community can easily discover and exchange NASA's Earth science data and services. ECHO contains metadata for 2,726 data collections comprising over 87 million individual data granules and 34 million browse images, consisting of NASA s EOSDIS Data Centers and the United States Geological Survey's Landsat Project holdings. ECHO is a middleware component based on a Service Oriented Architecture (SOA). The system is comprised of a set of infrastructure services that enable the fundamental SOA functions: publish, discover, and access Earth science resources. It also provides additional services such as user management, data access control, and order management. The ECHO system has a data registry and a services registry. The data registry enables organizations to publish EOS and other Earth-science related data holdings to a common metadata model. These holdings are described through metadata in terms of datasets (types of data) and granules (specific data items of those types). ECHO also supports browse images, which provide a visual representation of the data. The published metadata can be mapped to and from existing standards (e.g., FGDC, ISO 19115). With ECHO, users can find the metadata stored in the data registry and then access the data either

  17. Echo III: The study of electric and magnetic fields with conjugate echoes from artificial electron beams injected into the auroral zone ionosphere

    The third in a series of rocket flights carrying large electron guns for electron beam-plasma analysis and magnetosphere probing has been carried out from the Poker Flat rocket range near Fairbanks, Alaska at L=6. Echoes from the injected electrons mirroring at the southern hemisphere conjugate point were observed on the rocket by particle detectors and in the nearby ionosphere by photometers on board the rocket. The bounce time and drift velocities of the echoes were measured using the known trajectory and aspect of the rocket. Ionospheric electric fields near the rocket were inferred from drift motion of the ambient ion population measured by two techniques, electrostatic analyzers on board the rocket and incoherent backscatter radar from the ground. Using model magnetic fields, gradient and curvature drift and bound times have been computed under the conditions appropriate for this experiment. Assuming that field lines are equipotentials, the addition of the observed ionospheric electric field drift to the model-independent gradient and curvature drifts predicts a net echo drift velocity that is in agreement with the observations, provided the Mead-Fairfield 1972--73 model is used. The observed bounce time constitutes an independent model check and is in better agreement with the Olson-Pfitzer model. Echo spatial and temporal fluctuations reflected the turbulence associated with the diffuse aurora into which the rocket was launched

  18. Experimental characterization of a nonlinear vibration absorber using free vibration

    Tang, Bin; Brennan, M. J.; Gatti, G.; Ferguson, N. S.

    2016-04-01

    Knowledge of the nonlinear characteristics of a vibration absorber is important if its performance is to be predicted accurately when connected to a host structure. This can be achieved theoretically, but experimental validation is necessary to verify the modelling procedure and assumptions. This paper describes the characterization of such an absorber using a novel experimental procedure. The estimation method is based on a free vibration test, which is appropriate for a lightly damped device. The nonlinear absorber is attached to a shaker which is operated such that the shaker works in its mass-controlled regime, which means that the shaker dynamics, which are also included in the measurement, are considerably simplified, which facilitates a simple estimation of the absorber properties. From the free vibration time history, the instantaneous amplitude and instantaneous damped natural frequency are estimated using the Hilbert transform. The stiffness and damping of the nonlinear vibration absorber are then estimated from these quantities. The results are compared with an analytical solution for the free vibration of the nonlinear system with cubic stiffness and viscous damping, which is also derived in the paper using an alternative approach to the conventional perturbation methods. To further verify the approach, the results are compared with a method in which the internal forces are balanced at each measured instant in time.

  19. MR imaging of short T2 components with three dimension ultrashort echo time double echo pulse sequence: investigation of factors affecting imaging quality

    Objective: To investigate the effect of imaging parameters and postprocessing methods on the quality of MR imaging of short T2 components with 3D ultrashort TE (UTE) double echo pulse sequence. Methods: 3D UTE double echo pulse sequence was performed on dry human femoral specimen and the tibial diaphyses, knee joints, and tendons of ankles of a group of healthy volunteers. To investigate the effect of different trajectory delays of the imaging system ( -6, -3, -2, -1, 0, 1, 2, 3 s), different flip angles (4°, 8°, 12°, 16°, 20°, 24°), different TEs (0.08, 0.16, 0.24, 0.35 ms) and different postprocessing methods (difference imaging of subtracted volume and non-volume UTE) on the 3D UTE MR imaging quality, the SNR and CNR were calculated and compared, and the artifacts of the images were analysed. Results: The cortical bone, periosteum, tendon and meniscus showed high signal intensity on the images of UTE pulse sequence. The best SNR was acquired with 2 s trajectory delay. The best flip angle was 8° to 12° for the human UTE imaging in vivo. The highest CNR was obtained from the TE of 0.08 ms. The longer the TE was, the more artifacts appeared. The SNR of difference image was improved when image subtraction was performed after multiplanar reconstruction (MPR) of the primary double echo images. Conclusions: The short T2 components show high signal intensity on the MRI of 3D UTE double echo pulse sequence. The imaging quality can be improved by shortening TE, using appropriate flip angle and performing subtraction for difference image after MPR of the primary double echo images. (authors)

  20. Vibration Compensation for Scanning Tunneling Microscope

    LI Meng-chao; FU Xing; WEI Xiao-lei; HU Xiao-tang

    2003-01-01

    The influence of vibration is already one of main obstacles for improving the nano measuring accuracy.The techniques of anti-vibration,vibration isolation and vibration compensation become an important branch in nano measuring field.Starting with the research of sensitivity to vibration of scanning tunneling microscope(STM),the theory,techniques and realization methods of nano vibration sensor based on tunnel effect are initially investigated,followed by developing the experimental devices.The experiments of the vibration detection and vibration compensation are carried out.The experimental results show that vibration sensor based on tunnel effect is characterized by high sensitivity,good frequency characteristic and the same vibratory response characteristic consistent with STM.

  1. Investigation for parametric vibration of rolling mill

    唐华平; 丁睿; 吴运新; 钟掘

    2002-01-01

    The vibration unsteady condition of rolling mill caused by flexural vibration of strip has been investigated. The parametric flexural vibration equation of rolled strip has been established. The parametric flexural vibration stability of rolled strip has been studied and the regions of stability and unstability have been determined based on Floquet theory and perturbation method. The flexural-vibration of strip is unstable when the frequency of variable tension is two times as the natural frequency of flexural-vibration strip. The characteristic of current in a temp driving motor's main loop has been studied and tested, it has been proved that there are 6 harmonic component and 12 harmonic component in main loop of driving motor electricity. The vertical vibration of working roller has been tested, the test result approves that the running unsteady is caused by parametric vibration. It attaches importance to the parametric vibration of rolling mill.

  2. Adaptive learning algorithms for vibration energy harvesting

    By scavenging energy from their local environment, portable electronic devices such as MEMS devices, mobile phones, radios and wireless sensors can achieve greater run times with potentially lower weight. Vibration energy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as human movement, wind, seismic forces and traffic. Existing approaches to vibration energy harvesting typically utilize a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibration energy harvesting, including adaptation to non-periodic vibrations so as to extract the maximum amount of vibration energy available. Experimental results of an experimental apparatus using an off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27–34%

  3. The phase 0/A study of the ESA M3 mission candidate EChO

    Puig, Ludovic; Isaak, Kate; Linder, Martin; Escudero, Isabel; Crouzet, Pierre-Elie; Walker, Roger; Ehle, Matthias; Hübner, Jutta; Timm, Rainer; de Vogeleer, Bram; Drossart, Pierre; Hartogh, Paul; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Tinetti, Giovanna; Eccleston, Paul

    2015-12-01

    EChO, the Exoplanet Characterisation Observatory, has been one of the five M-class mission candidates competing for the M3 launch slot within the science programme Cosmic Vision 2015-2025 of the European Space Agency (ESA). As such, EChO has been the subject of a Phase 0/A study that involved European Industry, research institutes and universities from ESA member states and that concluded in September 2013. EChO is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. With simultaneous and uninterrupted spectral coverage from the visible to infrared wavelengths, EChO targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to temperate zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own solar system in the context of other planetary systems in the Milky Way. A review of the performance requirements of the EChO mission was held at ESA at the end of 2013, with the objective of assessing the readiness of the mission to progress to the Phase B1 study phase. No critical issues were identified from a technical perspective, however a number of recommendations were made for future work. Since the mission was not selected for the M3 launch slot, EChO is no longer under study at ESA. In this paper we give an overview of the final mission concept for EChO as of the end of the study, from scientific, technical and operational perspectives.

  4. A quadrature demodulation method based on tracking the ultrasound echo frequency.

    Feng, Naizhang; Zhang, Jianqiu; Wang, Weiqi

    2006-12-22

    The ultrasound echo attenuation depends on frequency, propagating depth and tissue characteristics. Thus, the attenuation dependent on frequency results in a larger attenuation of high frequencies than lower when the wave propagates through the tissue. As a result, the central frequency of the echo generates the increasing downshift with the increasing of depth. In the traditional I/Q demodulation method, it is assumed that the central frequency of the echo is the same as the transmitting frequency and unchanged all time. The assumption directly causes that the acquired I/Q signals are not perfect baseband ones but biased due to the echo attenuation. In addition, the unreasonable assumption will keep the echo from getting better signal-to-noise ratio. A quadrature demodulation method based on tracking the ultrasound echo frequency is proposed in this paper. The method consists of the traditional I/Q demodulator, the frequency tracking module, the phase compensation module and the dynamic filtering module. The outputs of I/Q demodulator are biased. Autocorrelation technique is utilized in the frequency tracking unit to estimate the frequency bias according to the outputs of I/Q demodulator. The estimated bias feeds to the phase compensation unit which can eliminate the frequency bias by simple trigonometric function transform. The compensated signals feed to the dynamic filter and are further processed. The bandwidth of the dynamic filter decreases with the increasing of the depth, which makes the echo acquire better SNR in different depth. The efficiency of the proposed method is testified by both simulations and experiments. PMID:16860363

  5. [Optimization of Three-dimensional Ultrashort Echo Time Magnetic Resonance Imaging at a Low Field].

    Huang, Yuli; Du, Yiping

    2015-12-01

    Conventional magnetic resonance (MR) pulse sequences typically have an echo time (TE) of 1 ms or longer, providing an excellent contrast between different soft tissues. However, some short T2 tissues appear dark in conventional MR images because the signal from these tissues has decayed to nearly zero before the center of k-space is acquired. Because of the ability of directly imaging short T2 tissues, ultrashort echo time technique has been widely studied in recent years. An overwhelming majority of the studies were carried out at high fields, while many low- field scanner systems are still used in developing countries. To investigate the effects of the delay between analog-to-digital converter sampling and the readout gradient, the TE of the second echo used to calculate the R2 * map, and the undersampling ratio on the results of three-dimensional (3D) ultrashort echo time imaging at a low field, we implemented a 3D ultrashort echo time sequence on a 0. 35T scanner. Different parameters were used and the reconstructed images and R2 * maps were compared. Images reconstructed with slightly varying delays appeared quite different. Different contrast between short and long T2 tissues were found in R2 * maps calculated with different echoes. The result of undersampling study indicated that excessive undersampling could cause unwanted blurring, making it difficult to better visualize the short T2 tissues in the R2 * map. The results suggested that cautions should be taken in the choice of these parameters in 3D ultrashort echo time imaging. Short T2 tissues can be visualized with appropriate imaging parameters at this low field. PMID:27079094

  6. Hand-arm vibration syndrome.

    Pelmear, P L; Taylor, W

    1994-02-01

    The hand-arm vibration syndrome affects workers who perform tasks that generate vibration. Raynaud's phenomenon and sensory impairment of the fingers are the predominant effects. A history of hand-arm vibration (HAV) exposure in a patient with these symptoms should alert the physician to the diagnosis. Referral to a special clinic or hospital department for multiple clinical tests is required to confirm the diagnosis and, using the Stockholm classification, to grade the severity in each hand. The assessment permits the patient to be monitored either for progression of or recovery from the syndrome. Avoidance of further vibration exposure is recommended, together with the prescription of a slow-release calcium channel blocker to improve peripheral circulation. Hand-arm vibration syndrome should be distinguished from carpal tunnel syndrome (CTS), which may have similar symptomatology but requires different treatments. Surgery is contraindicated in the former and should be the last resort for carpal tunnel syndrome in a worker requiring good grip-strength in future employment. PMID:8185734

  7. Vibrational Microspectroscopy for Cancer Screening

    Fiona M. Lyng

    2015-02-01

    Full Text Available Vibrational spectroscopy analyses vibrations within a molecule and can be used to characterise a molecular structure. Raman spectroscopy is one of the vibrational spectroscopic techniques, in which incident radiation is used to induce vibrations in the molecules of a sample, and the scattered radiation may be used to characterise the sample in a rapid and non-destructive manner. Infrared (IR spectroscopy is a complementary vibrational spectroscopic technique based on the absorption of IR radiation by the sample. Molecules absorb specific frequencies of the incident light which are characteristic of their structure. IR and Raman spectroscopy are sensitive to subtle biochemical changes occurring at the molecular level allowing spectral variations corresponding to disease onset to be detected. Over the past 15 years, there have been numerous reports demonstrating the potential of IR and Raman spectroscopy together with multivariate statistical analysis techniques for the detection of a variety of cancers including, breast, lung, brain, colon, oral, oesophageal, prostate and cervical cancer. This paper discusses the recent advances and the future perspectives in relation to cancer screening applications, focussing on cervical and oral cancer.

  8. PC based vibration monitoring system

    Health of large rotating machinery gets reflected in the vibration signature of the rotor and supporting structures and proper recording of these signals and their analysis can give a clear picture of the health of the machine. Using these data and their trending, it is possible to predict an impending trouble in the machine so that preventive action can be taken in time and catastrophic failure can be avoided. Continuous monitoring and analysis can give quick warning and enable operator to take preventive measures. Reactor Control Division, BARC is developing a PC based Vibration monitoring system for turbo generator machinery. The System can acquire 20 vibration signals at a rate of 5000 samples per second and also 15 process signals at a rate of 100 samples/ sec. The software for vibration monitoring system includes acquisition modules, analysis modules and Graphical User Interface module. The acquisition module involves initialization, setting of required parameters and acquiring the data from PC-based data acquisition cards. The acquired raw vibration data is then stored for analysis using various software packages. The display and analysis of acquired data is done in LabVIEW 7.0 where the data is displayed in time as well as frequency domain along with the RMS value of the signal. (author)

  9. Good vibrations at PARR-1

    Following an upgrading of the cooling system in the Pakistan Research Reactor-1 (PARR-1), vibration analyses were carried out to determine the operating condition of the two primary pumps PW-P1 and PW-P2. A piezolelectric accelerometer was used to measure vibrations at various monitoring points on the pumps. The accelerometer signal frequency spectra for PW-P1 showed on analysis an indication of imbalance and misalignment leading to a constant centrifugal thrust on the impellar vanes. The spectra for PW-P2 also indicated unbalance, but possibly not due to misalignment. Physical inspection revealed misalignment of both the pump and the motor coupling of PW-P1 and loose baseplate bolts giving rise to the unbalance in PW-P2. Further vibration measurements after repairs were carried out showed a decrease in the vibration level on each pump to the ''just tolerable'' region. The replacement of the motor front bearing on PW-P1 and changes to two check valves reduced the vibration level to ''allowable'' for both pumps. (UK)

  10. Good vibrations at PARR-1

    Ayazuddin, S.K.; Baig, A.R.; Pervez, S.; Salahuddin, A. [Nuclear Engineering Division, Islamabad (Pakistan)

    1996-01-01

    Following an upgrading of the cooling system in the Pakistan Research Reactor-1 (PARR-1), vibration analyses were carried out to determine the operating condition of the two primary pumps PW-P1 and PW-P2. A piezolelectric accelerometer was used to measure vibrations at various monitoring points on the pumps. The accelerometer signal frequency spectra for PW-P1 showed on analysis an indication of imbalance and misalignment leading to a constant centrifugal thrust on the impellar vanes. The spectra for PW-P2 also indicated unbalance, but possibly not due to misalignment. Physical inspection revealed misalignment of both the pump and the motor coupling of PW-P1 and loose baseplate bolts giving rise to the unbalance in PW-P2. Further vibration measurements after repairs were carried out showed a decrease in the vibration level on each pump to the ``just tolerable`` region. The replacement of the motor front bearing on PW-P1 and changes to two check valves reduced the vibration level to ``allowable`` for both pumps. (UK).

  11. Design for Vibrator Field Experiment Based- on Vibrator- earth System

    Chen Zubin; Lin Jun; Liang Tiecheng; Zhang Linhang

    2000-01-01

    Source- generated energy in seismic vibrator records high frequency harmonic behavior. Conventional vibratorearth coupling model was set up on the linear system. Some assumptions in the application of linear theory to the vibrator problem play an insignificant role in the overall coupling structure. Obviously, non- linear behaviors can be modeled using a "hard - spring" form of the Duffing equation. Model dedicates that a qualitatively similar harmonic component is present for a broad range of possible mathematical descriptions. After some qualitative analysis about the non- linear system, some conclusion can be drawn. Firstly, The design of the vibrator weight should be abided by two points as followed: In order to avoid decoupling for the vibrator to the earth, the weight should be greater than the peak of the driving force amplitude as to keep the resultant force pointing to the earth's core. On the other hand, for the limited energy output, the vibrator overweight may damage the system high - frequency ability. Secondly, as the driving force frequency approaching to the ground hard- spring inherent frequency, the energy transmission was found to climb its peak from the system energy absorbed curve. At last, due to the non- linear coupling model system, its load curve would come into unstable frequency range,which might limit the application of the Vibroseis conventional sweeping pattern - linear sweep. A new sweeping pattern was listed: the driving signal was the pseudo- random sequence modulated by a fixed frequency cosine signal satisfying with the exploration precision and absorbing efficiency. The synthesized signal was ready to be realized by the electromagnetic driven system. Even the side- lobes noise of its auto- correlation function was restrained well. The theory coming from the Vibrator- earth coupling model was applied to the design of the Portable High- frequency Vibrator System (PHVS), and the good result was obtained. By the analysis of the

  12. SIMULATION OF VIBRATION STRESS RELIEF AFTER WELDING BASED ON FEM

    X.C.Zhao; Y.D.Zhang; H.W.Zhang; Q.Wu

    2008-01-01

    A finite element model is developed for the simulation of vibration stress relief (VSR) after welding.For the nonresonant vibration,the reduction in stress strongly depends on the amplitude of vibration.For the resonant vibration,the vibration frequency is the key for stress relief.The vibration frequency should be close to the structure natural frequency for the desired vibration mode.Only small vibration amplitude is required,which will be amplified during vibration.Vibration time does not have a major impact on vibration stress relief.When the amplitude of vibration stress relief is large,the treatment will be more effective.

  13. Echo Planar Correlated Spectroscopic Imaging (EP-COSI): Implementation and Pilot Evaluation in Human Calf in Vivo#

    Lipnick, Scott; Verma, Gaurav; Ramadan, Saadallah; Furuyama, Jon; Thomas, M. Albert

    2010-01-01

    Exploiting the speed benefits of echo-planar imaging (EPI), the echo-planar spectroscopic imaging (EPSI) sequence facilitates recording of one spectral and two to three spatial dimensions faster than the conventional MR Spectroscopic Imaging (MRSI). A novel four dimensional (4D) echo-planar correlated spectroscopic imaging (EP-COSI) was implemented on a whole body 3T MRI scanner combining two spectral with two spatial encodings. Similar to EPSI, the EP-COSI sequence used a bipolar spatial rea...

  14. Research on cylindrical shell vibration reduction systems

    XING Xiao-liang; WANG Min-qing

    2008-01-01

    Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.

  15. Diagrammatic Vibrational Coupled-Cluster

    Faucheaux, Jacob A.; Hirata, So

    2015-06-01

    A diagrammatic vibrational coupled-cluster method for calculation of zero-point energies and an equation-of-motion coupled-cluster method for calculation of anharmonic vibrational frequencies are developed. The methods, which we refer to as XVCC and EOM-XVCC respectively, rely on the size-extensive vibrational self-consistient field (XVSCF) method for reference wave functions. The methods retain the efficiency advantages of XVSCF making them suitable for applications to large molecules and solids, while they are numerically shown to accurately predict zero-point energies and frequencies of small molecules as well. In particular, EOM-XVCC is shown to perform well for modes which undergo Fermi resonance where traditional perturbative methods fail. Rules for the systematic generation and interpretation of the XVCC and EOM-XVCC diagrams to any order are presented.

  16. General vibration monitoring: Experimental hall

    The reported vibration data were generated from measurements made on the experimental hall floor on December 2, 1992. At the time of the measurements, the ESRF hydrolevel was set-up in the Early Assembly Area (EAA) of the experimental hall and was being used to measure static displacement (settlement) of the floor. The vibration measurement area was on and adjacent to the EAA, in the vicinity of the ESRF hydrolevel test which was in progress. This report summarizes the objectives, instrumentation, measurement locations, observations, and conclusions, and provides selected results in the form of RMS vs. time plots, and power spectral densities from which frequency information can be derived. Measured response amplitudes were within the vibration criteria established for the APS

  17. Re-sounding Radicalism: Echo in William Blake and the Chartist Poets Ernest Jones and Gerald Massey

    Mccawley, Nichola Lee

    2012-01-01

    This thesis argues that William Blake’s poetry creates meaning through internal poetic echoes, and that these Blakean echoes re-sound in Ernest Jones and Gerald Massey’s Poetry. There is no demonstrable link between Blake and Chartism; this raises the question of how to account for poetic echoes that occur in the absence of a direct link. The thesis uses two complementary methodological strategies. The significance of the Blakean echoes in Jones and Massey’s work will be demonstrated through ...

  18. Meniscal tears of the knee : diagnosis with fast spin-echo MR imaging and role of gadolinium-enhancement

    Moon, Kyung Mi; Jee, Won Hee; Choe, Bo Young; Rhim, Soo A.; Lee, Jung Whee; Ku, Young Mi; Yoon, Young Hyun; Choi, Si Young; Choi, Kyu Ho; Shinn, Kyung Sub [Catholic Univ., Seoul (Korea, Republic of). Medical Coll.

    1998-01-01

    The usefulness of fast spin-echo MR imaging for the diagnosis of meniscal tear to the knee is a matter of debate. The purpose of this study was to evaluate the accuracy of diagnosis of meniscal tears by fast spin-echo MR imaging and the role of gadolinium enhancement. In 68 cases of arthroscopically-proven meniscal tears, MR sensitivity to tear was 93% (63/68) for spin-echo alone and 96% (40/41) for combined fast spin-echo and fat-suppressed gadolinium-enhanced T1-weighted MR images. MR sensitivity to medial meniscus tear was 98% (40/41) for fast spin-echo alone and 98% (40/41) for combined fast spin-echo and fat-suppressed gadolinium-enhanced T1-weighted MR images. MR sensitivity to lateral meniscus tear was 85 % (23/27) for fast spin-echo alone and 93% (25/27) for combined fast spin-echo and fat-suppressed gadolinium-enhanced T1-weighted MR images. Fast spin-echo MR imaging with adequate imaging parameters is suitable for the diagnosis of meniscal tears, and additional fat-suppressed gadolinium-enhanced T1-weighted MR imaging may increase diagnostic sensitivity to such tears. (author). 13 refs., 1 tab., 3 figs.

  19. Seasonal and diel patterns in sedimentary flux of krill fecal pellets recorded by an echo sounder

    Røstad, Anders

    2013-11-01

    We used a moored upward-facing 200 kHz echo sounder to address sedimentation of fecal pellets (FPs) from dielly migrating Meganyctiphanes norvegica. The echo sounder was located on the bottom at 150 m depth in the Oslofjord, Norway, and was cabled to shore for continuous measurements during winter and spring. Records of sinking pellets were for the first time observed with an echo sounder. Seasonal patterns of sedimentation of krill FPs were strongly correlated with data from continuous measurement of fluorescence, which illustrate the development of the spring bloom. Sedimenting particles were first observed as fluorescence values started to increase at the end of February and continued to increase until the bloom suddenly culminated at the end of March. This collapse of the bloom was detected on the echo sounder as a pulse of slowly sinking acoustic targets over a 2 d period. Prior to this event, there was a strong diel pattern in sedimentation, which correlated, with some time lag, with the diel migration of krill foraging at night near the surface. Pellet average sinking speeds ranged between 423 m d−1 and 804 m d−1, with a strong relation to pellet target strength, which is an acoustic proxy for size. This novel approach shows that echo sounders may be a valuable tool in studies of vertical pellet flux and, thereby, carbon flux, providing temporal resolution and direct observation of the sedimentation process, which are not obtained from standard methods.

  20. Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers

    Q. H. Zhou

    2004-02-01

    Full Text Available The aspect sensitivity of VHF echoes from field aligned irregularities (FAI within meteor trails and thin ionization layers is studied using numerical models. Although the maximum power is obtained when a radar is pointed perpendicular to the field line (perpendicular to B, substantial power can be obtained off the perpendicular to B direction if the ionization trail/layer is thin. When the FAI length is 20 m, the power observed 6° off perpendicular to B is about 10 db below that perpendicular to the B direction. Meteoric FAI echoes can potentially be used to determine the diffusion rate in the mesopause region. Based on the aspect sensitivity analysis, we conclude that the range spread trail echoes far off perpendicular to B observed by powerful VHF radars are likely due to overdense meteors. Our simulation also shows that ionospheric FAI echoes can have an altitude smearing effect of about 4 km if the vertical extension of a FAI layer is around 100 m, which has often been observed at Arecibo. The altitude smearing effect can account for the fact that the Es layers observed by the Arecibo incoherent scatter radar are typically much narrower than FAI layers and the occurrence of double spectral peaks around the Es layer altitude in FAI echoes.