Ion Bernstein wave heating research
International Nuclear Information System (INIS)
Ion Bernstein wave heating (IBWH) utilizes the ion Bernstein wave (IBW), a hot plasma wave, to carry the radio frequency (rf) power to heat tokamak reactor core. Earlier wave accessibility studies have shown that this finite-Larmor-radius (FLR) mode should penetrate into a hot dense reactor plasma core without significant attenuation. Moreover, the IBW's low phase velocity (ω/kperpendicular ∼ VTi much-lt Vα) greatly reduces the otherwise serious wave absorption by the 3.5 MeV fusion α-particles. In addition, the property of IBW's that kperpendicular ρi ∼ 1 makes localized bulk ion heating possible at the ion cyclotron harmonic layers. Such bulk ion heating can prove useful in optimizing fusion reactivity. In another vein, with proper selection of parameters, IBW's can be made subject to strong localized electron Landau damping near the major ion cyclotron harmonic resonance layers. This property can be useful, for example, for rf current drive in the reactor plasma core. This paper discusses this research
Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles
Franklin, F R
1999-01-01
In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode- Converted Ion Bernstein Waves (MCIBWs) and Alfvé n Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control...
Alfven Eigenmode And Ion Bernstein Wave Studies For Controlling Fusion Alpha Particles
Heeter, R F
1999-01-01
In magnetic confinement fusion reactor plasmas, the charged fusion products (such as alpha particles in deuterium-tritium plasmas) will be the dominant power source, and by controlling these charged fusion products using wave-particle interactions the reactor performance could be optimized. This thesis studies two candidate waves: Mode-Converted Ion Bernstein Waves (MCIBWs) and Alfvén Eigenmodes (AEs). Rates of MCIBW-driven losses of alpha-like fast deuterons, previously observed in the Tokamak Fusion Test Reactor (TFTR), are reproduced by a new model so that the wave-particle diffusion coefficient can be deduced. The MCIBW power in TFTR is found to be ∼ 1/3 that needed for collisionless alpha particle control. A reasonable reactor power scaling is derived. To study AEs, existing magnetic fluctuation probes at the Joint European Torus (JET) have been absolutely calibrated from 30–500 kHz for the first time, allowing fluctuation measurements with &vbm0;dBpol&vbm0;/B0&am...
Observations of Obliquely Propagating Electron Bernstein Waves
DEFF Research Database (Denmark)
Armstrong, R. J.; Juul Rasmussen, Jens; Stenzel, R. L.;
1981-01-01
Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation.......Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation....
Relativistic Bernstein waves in a degenerate plasma
International Nuclear Information System (INIS)
Bernstein mode for a relativistic degenerate electron plasma is investigated. Using relativistic Vlasov-Maxwell equations, a general expression for the conductivity tensor is derived and then employing Fermi-Dirac distribution function a generalized dispersion relation for the Bernstein mode is obtained. Two limiting cases, i.e., non-relativistic and ultra-relativistic are discussed. The dispersion relations obtained are also graphically presented for some specific values of the parameters depicting how the propagation characteristics of Bernstein waves as well as the Upper Hybrid oscillations are modified with the increase in plasma number density.
Czech Academy of Sciences Publication Activity Database
Harvey, R.W.; Cary, J.R.; Taylor, G.; Barnes, D.C.; Bigelow, T.S.; Coda, S.; Carlsson, J.; Caughman, J.B.; Carter, M.D.; Diem, S.; Efthimion, P.C.; Ellis, R.A.; Ershov, N.M.; Fonck, R.J.; Fredd, E.; Gartska, G.D.; Hosea, J.; Jaeger, F.; LeBlanck, B.; Lewicki, B.T.; Phillips, C.K.; Preinhaelter, Josef; Ram, A.K.; Rasmussen, D.A.; Smirnov, A.P.; Urban, Jakub; Wilgen, J.B.; Wilson, J.R.; Xiang, N.
Čína: IAEA, 2006, TH/P6-11. [IAEA Fusion Energy Conference/21st./. Chengdu, China (CN), 16.10.2006-21.10.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * NSTX * Particle in cell Subject RIV: BL - Plasma and Gas Discharge Physics http://www-pub.iaea.org/MTCD/Meetings/FEC2006/th_p6-11.pdf
Ion-Bernstein wave mode conversion in hot tokamak plasmas
International Nuclear Information System (INIS)
Mode conversion at the second harmonic cyclotron resonance is studied in a toroidal plasma, showing how the ion-Bernstein wave can dramatically affect the power profile and partition among the species. The results obtained with the gyrokinetic toroidal PENN code in particular suggest that off-axis electron and second harmonic core ion heating should become important when the temperatures in JET reach 10 keV. (author) 1 fig., 11 refs
Harmonic launching of ion Bernstein waves via mode transformation
International Nuclear Information System (INIS)
Ion Bernstein wave excitation and propagation via finite ion-Larmor-radium mode-transformation are investigated theoretically and experimentally. It is shown that in the ion cyclotron range of frequencies omega less than or equal to 4Ω/sub i/, with modest ion temperatures (T/sub i/ less than or equal to 10 eV), the finite-Larmor-radius effect removes the wave singularity at lower-hybrid resonance layer, enabling an externally initiated electron plasma wave to transform continuously into an ion Bernstein wave. In an ACT-1 hydrogen plasma (T/sub e/ approx. = 2.5 eV, T/sub i/ less than or equal to 2.0 eV), externally excited ion Bernstein waves have been observed for omega less than or equal to 2Ω/sub i/ as well as for omega less than or equal to 3Ω/sub i/. The finite ion-Larmor-radius mode transformation process resulting in strong ion Bernstein wave excitation has been experimentally verified. Detailed measurements of the wave dispersion relation and of the wave-packet trajectory show excellent agreement with theory. The dependence of the excited ion Bernstein wave on the antenna phasing, the plasma density, and on the neutral pressure (T/sub i/) is also investigated
Electron-Bernstein Waves in Inhomogeneous Magnetic Fields
DEFF Research Database (Denmark)
Armstrong, R. J.; Frederiksen, Å.; Pécseli, Hans;
1984-01-01
The propagation of small amplitude electron-Bernstein waves in different inhomogeneous magnetic field geometries is investigated experimentally. Wave propagation towards both cut-offs and resonances are considered. The experimental results are supported by a numerical ray-tracing analysis. Spatial...... enhancements of the wave amplitude are interpreted as a result of caustic formation....
Electron Bernstein Wave Heating and Emission in the TCV Tokamak
Anja, Mueck; Yann, Camenen; Stefano, Coda; Loïc, Curchod; Timothy P., Goodman; Heinrich P., Laqua; Antoine, Pochelon; Laurie, Porte; Victor S., Udintsev; Francesco, Volpe; Team, TCV
2007-01-01
Electron cyclotron resonance heating (ECRH) of high-density tokamak plasmas is limited because of reflections of the waves at so-called wave cutoffs. Electron Bernstein wave (EBW) heating (EBWH) via a double mode conversion process from ordinary (O)-mode, launched from the low field side, to extraordinary (X)-mode and finally to Bernstein (B)-mode offers the possibility of overcoming these density limits. In this paper, the O-X mode conversion dependence on the microwave injection angle is de...
Ion Bernstein wave experiments on the Alcator C tokamak
International Nuclear Information System (INIS)
Ion Bernstein wave experiments are carried out on the Alcator C tokamak to study wave excitation, propagation, absorption, and plasma heating due to wave power absorption. It is shown that ion Bernstein wave power is coupled into the plasma and follows the expected dispersion relation. The antenna loading is maximized when the hydrogen second harmonic layer is positioned just behind the antenna. Plasma heating results at three values of the toroidal magnetic field are presented. Central ion temperature increases of ΔT/sub i//Ti /approx lt/ 0.1 and density increases Δn/n 6s/sup /minus/1/ for plasmas within the density range 0.6 /times/ 1020m/sup /minus/3/ ≤ /bar n//sub e/ ≤ 4 /times/ 1020m/sup /minus/3/ and magnetic fields 2.4 ≥ ω/Ω/sub H/ ≥ 1.1. The density increases is usually accompanied by an improvement in the global particle confinement time relative to the Ohmic value. The ion heating rate is measured to be ΔT/sub i//P/sub rf/ ≅ 2-4.5 eV/kW at low densities. At higher densities /bar n//sub e/ ≤ 1.5 /times/ 1020m/sup /minus/3/ the ion heating rate dramatically decreases. It is shown that the decrease in the ion heating rate can be explained by the combined effects of wave scattering through the edge turbulence and the decreasing on energy confinement of these discharges with density. The effect of observed edge turbulence is shown to cause a broadening of the rf power deposition profile with increasing density. It is shown that the inferred value of the Ohmic ion thermal conduction, when compared to the Chang-Hinton neoclassical prediction, exhibits an increasing anomaly with increasing plasma density
Generation of magnetospheric radiation by decay of Bernstein waves
International Nuclear Information System (INIS)
Recent observations show that extremely narrow emission lines are present in the spectrum of the terrestrial myriametric radiation, which on the basis of earlier observations has been characterized as nonthermal contiunuum radiation. The occurance of these monochromatic emissions is not predicted by previoiusly published theories for the generation of the radiaiton. A linear instability, exciting low frequency electrostatic turbulence, is required by theories invoking a nonlinear coalescence to produce the radiation, but there are no conclusive observations associating low frequency electrostatic waves with the sources of myriametric radiation. In this study, the possibility that the radiation is produced by a nonlinear decay of electrostatic Bernstein waves with frequency near the upper hybrid frequency is considered. This mechanism can explain the narrow spectral lines, and does not require a linear instability at low frequencies. (Author)
Simulation study of Bernstein modes
International Nuclear Information System (INIS)
The properties of Bernstein modes were investigated through computer simulations using two-dimensional and two-and-one-half-dimensional (i.e., two spatial and three velocity coordinates) electrostatic models with fixed magnetic field. The measured discrete spectrum was found to agree with the linear dispersion relation for these modes. The quasi-periodic phenomenon of early phase-mixing damping and later recurrence, predicted by Baldwin and Rowlands, was observed. For large wavenumber k/sub perpendicular/, the initial damping rate is the same as that for Landau damping in an unmagnetized plasma; for small k/sub perpendicular/, however, it is much stronger. The recurrence peaks slowly damp in time at a rate proportional to k2/sub perpendicular/D, where D is the measured cross-field particle diffusion coefficient which is dominated by convective transport. Finally, splitting of the main spectral peaks and the appearance of subpeaks at half-integral multiples of the cyclotron frequency are observed and may be explained by nonlinear mode coupling
Ion Bernstein waves in the magnetic reconnection region
Narita, Y.; Nakamura, R.; Baumjohann, W.; Glassmeier, K.-H.; Motschmann, U.; Comişel, H.
2016-01-01
Four-dimensional energy spectra and a diagram for dispersion relations are determined for the first time in a magnetic reconnection region in the magnetotail using data from four-spacecraft measurements by the Cluster mission on a spatial scale of 200 km, about 0.1 ion inertial lengths. The energy spectra are anisotropic with an extension in the perpendicular direction and axially asymmetric with respect to the mean magnetic field. The dispersion diagram in the plasma rest frame is in reasonably good agreement with the ion Bernstein waves at the second and higher harmonics of the proton gyrofrequency. Perpendicular-propagating ion Bernstein waves likely exist in an outflow region of magnetic reconnection, which may contribute to bifurcation of the current sheet in the outflow region.
Thermal Electron Bernstein Wave Emission Measurements on NST
Czech Academy of Sciences Publication Activity Database
Diem, S.J.; Taylor, G.; Efthimion, P.; LeBlanc, B.P.; Philips, C.K.; Caughman, J.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, Josef; Urban, Jakub
2006-01-01
Roč. 51, č. 7 (2006), s. 134. ISSN 0003-0503. [Annual Meeting of the Division of Plasma Physics/48th./. Philadelphia, Pennsylvania, 30.10.2006-3.11.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * MAST * NSTX Subject RIV: BL - Plasma and Gas Discharge Physics http://www.aps.org/meet/DPP06/baps/all_DPP06.pdf
Electron Bernstein Wave Research on NSTX and PEGASUS
Czech Academy of Sciences Publication Activity Database
Diem, S.J.; Taylor, G.; Caughman, J.; Bigelow, T.S.; Garstka, G.D.; Harvey, R.W.; LeBlanc, B.P.; Preinhaelter, Josef; Sabbagh, S.A.; Urban, Jakub; Wilgen, J.
Vol. 933. Melville: -, 2007 - (Ryan, P.; Rasmussen, D.), s. 331-334 ISBN 978-0-7354-0444-1. ISSN 0094-243X. [Topical Conference on Radio Frequency Power in Plasmas/17th./. Clearwater (US), 07.05.2007-09.05.2007] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Cyclotron Heating * Tokamaks * Electron Bernstein waves Subject RIV: BL - Plasma and Gas Discharge Physics
Electron Bernstein Wave (EBW) Physics In NSTX and PEGASUS
Czech Academy of Sciences Publication Activity Database
Taylor, G.; Caughman, J.B.; Carter, M.D.; Diem, S.; Efthimion, P.C.; Harvey, R.W.; Preinhaelter, Josef; Wilgen, J.B.; Bigelow, T.S.; Ellis, R.A.; Ershov, N.M.; Fonck, R.J.; Fredd, E.; Gartska, G.D.; Hosea, J.; Jaeger, F.; LeBlanck, B.; Lewicki, B.T.; Philips, C.K.; Ram, A.K.; Rasmussen, D.A.; Smirnov, A.P.; Urban, Jakub; Wilson, J.R.
USA: The University of Texas at Austin, 2006, s. 1-24. [Innovative Confinement Concepts Workshop. Austin,Texas (US), 13.02.2006-16.02.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * MAST * NSTX Subject RIV: BL - Plasma and Gas Discharge Physics http://icc2006.ph.utexas.edu/proceedings.php http://icc2006.ph.utexas.edu/uploads/29/icc06_taylor_ebw_022706.pdf
Caliri, C.; Romano, F. P.; Mascali, D.; Gammino, S.; Musumarra, A.; Castro, G.; Celona, L.; Neri, L.; Altana, C.
2013-10-01
Electron Cyclotron Resonance Ion Sources (ECRIS) are based on ECR heated plasmas emitting high fluxes of X-rays. Here we illustrate a pilot study of the X-ray emission from a compact plasma-trap in which an off-resonance microwave-plasma interaction has been attempted, highlighting a possible Bernstein-Waves based heating mechanism. EBWs-heating is obtained via the inner plasma EM-to-ES wave conversion and enables to reach densities much larger than the cut-off ones. At LNS-INFN, an innovative diagnostic technique based on the design of a Pinhole Camera (PHC) coupled to a CCD device for X-ray Imaging of the plasma (XRI) has been developed, in order to integrate X-ray traditional diagnostics (XRS). The complementary use of electrostatic probes measurements and X-ray diagnostics enabled us to gain knowledge about the high energy electrons density and temperature and about the spatial structure of the source. The combination of the experimental data with appropriate modeling of the plasma-source allowed to estimate the X-ray emission intensity in different energy domains (ranging from EUV up to Hard X-rays). The use of ECRIS as X-ray source for multidisciplinary applications, is now a concrete perspective due to the intense fluxes produced by the new plasma heating mechanism.
Propagation and absorption of Ion Bernstein waves in U-2M torsatron by ray tracing technique
International Nuclear Information System (INIS)
Ion Bernstein modes with frequencies higher than the ion cyclotron frequency are planned to be applied to produce and heat the Uragan-2M plasma. This brief report gives the propagation and absorption ray-tracing studies of these waves in the Uragan-2M device, taking into account the three-dimensional non-uniformities of the plasma parameters and the magnetic field. 4 refs, 5 figs
Electron Bernstein Wave Research on NSTX and PEGASUS
Diem, S. J.; Taylor, G.; Caughman, J. B.; Bigelow, T.; Garstka, G. D.; Harvey, R. W.; LeBlanc, B. P.; Preinhaelter, J.; Sabbagh, S. A.; Urban, J.; Wilgen, J. B.
2007-09-01
Spherical tokamaks (STs) routinely operate in the overdense regime (ωpe≫ωce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees
Electron Bernstein Wave Research on NSTX and PEGASUS
International Nuclear Information System (INIS)
Spherical tokamaks (STs) routinely operate in the overdense regime (ωpe>>ωce), prohibiting the use of standard ECCD and ECRH. However, the electrostatic electron Bernstein wave (EBW) can propagate in the overdense regime and is strongly absorbed and emitted at the electron cyclotron resonances. As such, EBWs offer the potential for local electron temperature measurements and local electron heating and current drive. A critical challenge for these applications is to establish efficient coupling between the EBWs and electromagnetic waves outside the cutoff layer. Two STs in the U.S., the National Spherical Tokamak Experiment (NSTX, at Princeton Plasma Physics Laboratory) and PEGASUS Toroidal Experiment (University of Wisconsin-Madison) are focused on studying EBWs for heating and current drive. On NSTX, two remotely steered, quad-ridged antennas have been installed to measure 8-40 GHz (fundamental, second and third harmonics) thermal EBW emission (EBE) via the oblique B-X-O mode conversion process. This diagnostic has been successfully used to map the EBW mode conversion efficiency as a function of poloidal and toroidal angles on NSTX. Experimentally measured mode conversion efficiencies of 70±20% have been measured for 15.5 GHz (fundamental) emission in L-mode discharges, in agreement with a numerical EBE simulation. However, much lower mode conversion efficiencies of 25±10% have been measured for 25 GHz (second harmonic) emission in L-mode plasmas. Numerical modeling of EBW propagation and damping on the very-low aspect ratio PEGASUS Toroidal Experiment has been performed using the GENRAY ray-tracing code and CQL3D Fokker-Planck code in support of planned EBW heating and current drive (EBWCD) experiments. Calculations were performed for 2.45 GHz waves launched with a 10 cm poloidal extent for a variety of plasma equilibrium configurations. Poloidal launch scans show that driven current is maximum when the poloidal launch angle is between 10 and 25 degrees
Parameter dependence of ray trajectory and damping for the ion Bernstein wave in the TNT-A tokamak
International Nuclear Information System (INIS)
The dependence of ray trajectories and damping on various plasma parameters was studied using three-dimensional ray tracing for an ion Bernstein wave in the TNT-A tokamak. The condition for wave power absorption dominated by electron Landau damping was also estimated. (author)
Characteristics of ion Bernstein wave heating in JIPPT-II-U tokamak
International Nuclear Information System (INIS)
Using a transport code combined with an ion Bernstein wave tokamak ray tracing code, a modelling code for the ion Bernstein wave heating has been developed. Using this code, the ion Bernstein wave heating experiment on the JIPPT-II-U tokamak has been analyzed. It is assumed that the resonance layer is formed by the third harmonic of deuterium-like ions, such as fully ionized carbon, and oxygen ions near the plasma center. For wave absorption mechanisms, electron Landau damping, ion cyclotron harmonic damping, and collisional damping are considered. The characteristics of the ion Bernstein wave heating experiment, such as the ion temperature increase, the strong dependence of the quality factor on the magnetic field strength, and the dependence of the ion temperature increment on the input power, are well reproduced
Characteristics of ion Bernstein wave heating in JIPPT-II-U tokamak
Energy Technology Data Exchange (ETDEWEB)
Okamoto, M.; Ono, M.
1985-11-01
Using a transport code combined with an ion Bernstein wave tokamak ray tracing code, a modelling code for the ion Bernstein wave heating has been developed. Using this code, the ion Bernstein wave heating experiment on the JIPPT-II-U tokamak has been analyzed. It is assumed that the resonance layer is formed by the third harmonic of deuterium-like ions, such as fully ionized carbon, and oxygen ions near the plasma center. For wave absorption mechanisms, electron Landau damping, ion cyclotron harmonic damping, and collisional damping are considered. The characteristics of the ion Bernstein wave heating experiment, such as the ion temperature increase, the strong dependence of the quality factor on the magnetic field strength, and the dependence of the ion temperature increment on the input power, are well reproduced.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Jianyuan; Liu, Jian, E-mail: jliuphy@ustc.edu.cn [Department of Modern Physics and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Key Laboratory of Geospace Environment, CAS, Hefei, Anhui 230026 (China); Qin, Hong [Department of Modern Physics and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Yu, Zhi; Xiang, Nong [Theory and Simulation Division, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)
2015-09-15
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments.
International Nuclear Information System (INIS)
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments
International Nuclear Information System (INIS)
A theory of coupling between electromagnetic and electron Bernstein waves in a plasma slab is presented. The theory uses an approach that associates the linear mode conversion with the singularity of the cold plasma wave equation at the upper hybrid resonance (UHR). The singularity results in linear interaction of cold plasma (electromagnetic) and hot plasma (Bernstein) modes. Applicability of the WKB theory to interacting modes is not required. In this method the full solution of the mode conversion problem including calculation of the excited Bernstein wave complex amplitude is reduced to finding a solution to the cold plasma wave equation, which describes dissipative wave power absorption at the UHR. This method is applicable to a variety of plasma configurations practically without limitations on the inhomogeneity scale-length. It permits one to consider in the framework of a single procedure particular cases like direct tunnelling of the incident wave, O-X-B conversion and transformation of the X-mode launched from the high-field side of a tokamak and having free access to the UHR
Power Deposition of Ion Bernstein Wave Heating on the HT-7 Tokamak
Institute of Scientific and Technical Information of China (English)
BAO Yi; LI Jian-Gang; ZHAO Yan-Ping; CUI Ning-Zhuo
2001-01-01
Effcient direct heating of electrons by ion Bernstein waves has been obtained on the HT-7 tokamak. Off-axis heating, which is considered to be the result of electron Landau damping, was observed and studied by means of soft x-ray imaging. The measured power deposition was found to be independent of magnetic field through scanning the toroidal field from 1.5 to 1.7 T, in contrast to the ion heating results. It is suggested that the electron Landau damping is dominant in this heating regime.
Localized electron heating experiments by ion Bernstein wave in the TNT-A tokamak
International Nuclear Information System (INIS)
Plasma heating by ion Bernstein wave in the range of 2 ωD D is investigated in deuterium dominant plasma of the TNT-A tokamak. The localized electron heating is observed at the harmonic (3 ωD) and subharmonic (2.5 ωD) resonance layers, while the electron heating on the whole plasma region is observed at ω = 2 ωD. It is also shown that the heating is efficient and heating layer is localized by ion Bernstein wave in comparison with fast magnetosonic wave. (author)
Electron-Bernstein-wave current drive in an overdense plasma at the Wendelstein 7-AS stellarator
International Nuclear Information System (INIS)
Electron-Bernstein-wave (EBW) current drive in an overdense plasma was demonstrated at the Wendelstein 7-AS stellarator for the first time. The EBWs were generated by O-X-B mode conversion. The relatively high current drive efficiency was consistent with theoretical predictions. The experiments provided first investigations of EBW phase space interaction for wave refractive indices much larger than unity
Energy Technology Data Exchange (ETDEWEB)
A. Cardinali; A. Post-Zwicker; F. Paoletti; S. Bernabei; S. Von Goeler; W. Tighe
1998-02-01
The synergistic behavior of lower hybrid and ion Bernstein waves on the Princeton Beta Experiment-Modified tokamak [Phys. Fluids B 2, 1271 (1990)] is experimentally studied using a 2-D hard X-ray camera. The hard X-ray bremsstrahlung emission from suprathermal electrons, generated with lower hybrid current drive, is enhanced during ion Bernstein wave power injection. This enhancement is observed in limited regions of space suggesting the formation of localized current channels. The effects on plasma electrons during combined application of these two types of waves are theoretically investigated using a quasilinear model. The numerical code simultaneously solves the 3-D (R, Z, {Phi}) toroidal wave equation for the electric field (in the WKBJ approximation) and the Fokker-Planck equation for the distribution function in two dimensions (v{sub parallel}, v{sub perpendicular}) with an added quasilinear diffusion coefficient. The radial profile of the non-inductively generated current density, the transmitted power traces and the total power damping curve are calculated. The beneficial effects of a combined utilization of ion Bernstein and lower hybrid waves on the current drive are emphasized. The numerical results are compared with the experimental observations.
Boardsen, S. A.; Kim, E.-H.; Raines, J. M.; Slavin, J. A.; Gershman, D. J.; Anderson, B. J.; Korth, H.; Sundberg, T.; Schriver, D.; Travnicek, P.
2015-06-01
We show that ~1 Hz magnetic compressional waves observed in Mercury's inner magnetosphere could be interpreted as ion-Bernstein waves in a moderate proton beta ~0.1 plasma. An observation of a proton distribution with a large planetary loss cone is presented, and we show that this type of distribution is highly unstable to the generation of ion-Bernstein waves with low magnetic compression. Ray tracing shows that as these waves propagate back and forth about the magnetic equator; they cycle between a state of low and high magnetic compression. The group velocity decreases during the high-compression state leading to a pileup of compressional wave energy, which could explain the observed dominance of the highly compressional waves. This bimodal nature is due to the complexity of the index of refraction surface in a warm plasma whose upper branch has high growth rate with low compression, and its lower branch has low growth/damping rate with strong compression. Two different cycles are found: one where the compression maximum occurs at the magnetic equator and one where the compression maximum straddles the magnetic equator. The later cycle could explain observations where the maximum in compression straddles the equator. Ray tracing shows that this mode is confined within ±12° magnetic latitude which can account for the bulk of the observations. We show that the Doppler shift can account for the difference between the observed and model wave frequency, if the wave vector direction is in opposition to the plasma flow direction. We note that the Wentzel-Kramers-Brillouin approximation breaks down during the pileup of compressional energy and that a study involving full wave solutions is required.
Ion Bernstein-wave excitation via finite-Larmor-radius mode-transformation process
International Nuclear Information System (INIS)
It is shown that in the ion cyclotron range of frequency ω less than or equal to 2 Ω/sub i/, the finite-Larmor-radius effect removes the wave singularity at the lower-hybrid resonance layer, enabling an externally initiated electron plasma wave to propagate freely through the resonance layer, transforming continuously into an ion Bernstein wave. In an ACT-1 hydrogen plasma (T/sub e/ approx. = 2.5 eV, T/sub i/ approx. = 1.5 eV), linear excitation of ion Bernstein waves has been investigated experimentally for ω approx. = 2Ω/sub i/. The mode-transformation process resulting in a strong ω approx. = 2 Ω/sub i/ ion Berstein wave excitation without observable reflections has been experimentally verified. Detailed measurements of wave dispersion relation and of the wave-packet trajectory show excellent agreement with theory
Preliminary Observation on Coordination of Pellet Injection and Ion Bernstein Wave on a HT-7 Tokamak
Institute of Scientific and Technical Information of China (English)
杨愚; 赵燕平; 李建刚; 万宝年; 罗家融; 辜学茂
2002-01-01
A pellet injection (PI) experiment was performed during the application of the ion Bernstein wave on a HT-7tokamak. A preliminary coordination effect was observed. With a lower wave power, shortly after PI, the couplingof the wave was enhanced, and the particle confinement was improved. With higher power, off-axis heating for 15% at about a/3 in the low field side was observed.
Measurements of Intrinsic Ion Bernstein Waves in a Tokamak by Collective Thomson Scattering
DEFF Research Database (Denmark)
Korsholm, Søren Bang; Stejner Pedersen, Morten; Bindslev, Henrik; Furtula, Vedran; Leipold, Frank; Meo, Fernando; Michelsen, Poul; Moseev, Dmitry; Nielsen, Stefan Kragh; Salewski, Mirko; de Baar, M.; Delabie, E.; Kantor, M.; Bürger, A.
2011-01-01
In this Letter we report measurements of collective Thomson scattering (CTS) spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas. The measured spectra are in accordance with theoretical predictions and show clear sensitivity to variation in the density...
Mode-converted electron Bernstein waves for heating and current drive in NSTX
International Nuclear Information System (INIS)
The power coupled to electron Bernstein waves in a triplet mode conversion resonator from a fast X-mode at the plasma edge in NSTX is shown to be > 80% for fce ce. The EBW damping in the plasma is strong and localized and, thus, should be useful for heating, current drive, or profile control. (author)
Lower hybrid and Electron Bernstein Wave current drive experiments in MST
International Nuclear Information System (INIS)
Inductive current profile modification in MST has been successful in reducing fluctuations and transport but is transient and radially non-localized. Current profile control with rf waves offers steady and more precise control. Studies of lower hybrid (LH) wave and electron Bernstein wave (EBW) injection are underway. This first application of LH waves to the high dielectric RFP presents challenges in rf physics, e.g., limited wave accessibility. The novel interdigital line antenna, chosen because of stringent vacuum vessel constraints, operates at 800 MHz and nparallel ∼ 7.5 parameters chosen to drive current in the edge (r/a ∼ 0.8) with strong single-pass absorption. Extensive antenna loading studies have been performed to validate the design up to the present source power limit of 225 kW with up to 125 kW being coupled to the plasma. Hard-x-ray emission with energies as high as 50 keV has been observed. The emission is spatially localized to the antenna location with a toroidal spread of about 60 degrees. This interesting toroidal localization of the emission that occurs in the dominantly poloidal magnetic field of the RFP could result from the formation of a localized current structure. Presently, a 250 kW system designed to heat electrons and drive current via the electron Bernstein wave is in operation on the MST reversed field pinch. The antenna is a grill of four half-height S-band waveguides with each arm powered by a separate, phase controlled traveling wave tube amplifier at 3.6 GHz. The X-mode polarization is being used to launch electromagnetic waves that mode convert to EBWs in the edge plasma. Coupling to the plasma (as measured by the reflected power ratio) is dependent on the relative phasing between adjacent waveguides. The total reflected power can be maintained near the 10% level. The antenna face is outfitted with a pair of triple Langmuir probes to measure local electron density; the density gradient at the upper hybrid resonance
Plasma heating via electron Bernstein wave heating using ordinary and extraodinary mode
Directory of Open Access Journals (Sweden)
A. Parvazian
2008-03-01
Full Text Available Magnetically confined plasma can be heated with high power microwave sources. In spherical torus the electron plasma frequency exeeds the electron cyclotron frequency (EC and, as a consequence, electromagnetic waves at fundamental and low harmonic EC cannot propagate within the plasma. In contrast, electron Bernstein waves (EBWs readily propagate in spherical torus plasma and are absorbed strongly at the electron cyclotron resonances. In order to proagate EBWs beyond the upper hybrid resonance (UHR, that surrounds the plasma, the EBWs must convert via one of two processes to either ordinary (O-mode or extraordinary (X-mode electromagnetic waves. O-mode and X-mode electromagnetic waves lunched at the plasma edge can convert to the electron Bernstein waves (EBWs which can propagate without and cut-off into the core of the plasma and damp on electrons. Since the electron Bernstein wave (EBW has no cut-off limits, it is well suited to heat an over-dense plasma by resonant absorption. An important problem is to calculate mode conversion coefficient that is very sensitive to density. Mode conversion coefficient depends on Budden parameter ( ñ and density scale length (Ln in upper hybrid resonance (UHR. In Mega Ampere Spherical Tokamak (MAST, the optimized conversion efficiency approached 72.5% when Ln was 4.94 cm and the magnetic field was 0.475 Tesla in the core of the plasma.
A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks
Urban, Jakub; Peysson, Yves; Preinhaelter, Josef; Shevchenko, Vladimir; Taylor, Gary; Vahala, Linda; Vahala, George
2011-01-01
The electron Bernstein wave (EBW) is typically the only wave in the electron cyclotron (EC) range that can be applied in spherical tokamaks for heating and current drive (H&CD). Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-beta regimes, in which the usual EC O- and X- modes are cut-off. In this case, EBWs seem to be the only option that can provide features similar to the EC waves---controllable localized H&CD that can be utilized for core plasma heating as well as for accurate plasma stabilization. The EBW is a quasi-electrostatic wave that can be excited by mode conversion from a suitably launched O- or X-mode; its propagation further inside the plasma is strongly influenced by the plasma parameters. These rather awkward properties make its application somewhat more difficult. In this paper we perform an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX). Coupled...
Flow shear suppression of turbulence using externally driven ion Bernstein and Alfven waves
International Nuclear Information System (INIS)
The utilization of externally-launched radio-frequency waves as a means of active confinement control through the generation of sheared poloidal flows is explored. For low-frequency waves, kinetic Alfven waves are proposed, and are shown to drive sheared E x B flows as a result of the radial variation in the electromagnetic Reynolds stress. In the high frequency regime, ion Bernstein waves are considered, and shown to generate sheared poloidal rotation through the ponderomotive force. In either case, it is shown that modest amounts of absorbed power (∼ few 100 kW) are required to suppress turbulence in a region of several cm radial width. 9 refs
Bernstein-Greene-Kruskal waves in relativistic cold plasma
Singh Verma, Prabal; Sengupta, Sudip; Kaw, Predhiman
2012-03-01
We construct the longitudinal traveling wave solution [Akhiezer and Polovin, Sov. Phys. JETP 3, 696 (1956)] from the exact space and time dependent solution of relativistic cold electron fluid equations [Infeld and Rowlands, Phys. Rev. Lett. 62, 1122 (1989)]. Ions are assumed to be static. We also suggest an alternative derivation of the Akhiezer Polovin solution after making the standard traveling wave Ansatz.
A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks
Czech Academy of Sciences Publication Activity Database
Urban, Jakub; Decker, J.; Peysson, Y.; Preinhaelter, Josef; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.
2011-01-01
Roč. 51, č. 8 (2011), 083050-083050. ISSN 0029-5515 R&D Projects: GA ČR GA202/08/0419; GA MŠk 7G10072 Institutional research plan: CEZ:AV0Z20430508 Keywords : spherical tokamak * electron Bernstein wave (EBW) * heating * current drive * electron cyclotron wave Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.090, year: 2011 http://iopscience.iop.org/0029-5515/51/8/083050/pdf/0029-5515_51_8_083050.pdf
International Nuclear Information System (INIS)
The paper describes a successful proof-of-principle experimental determination of tokamak ion temperature using cw far-infrared (FIR) collective laser scattering from externally excited ion Bernstein waves. It is shown that a viable wave excitation technique for tokamak plasmas is mode conversion of an externally launched fast Alfven wave. A fit of the experimentally determined ion Bernstein wave dispersion to the temperature-dependent theoretical dispersion yields the local ion temperature. Partial ion temperature profiles (chord-averaged) have been obtained with temperature values consistent with charge-exchange measurements. (author)
Bernstein polynomials on Simplex
Bayad, A.; Kim, T.; Rim, S. -H.
2011-01-01
We prove two identities for multivariate Bernstein polynomials on simplex, which are considered on a pointwise. In this paper, we study good approximations of Bernstein polynomials for every continuous functions on simplex and the higher dimensional q-analogues of Bernstein polynomials on simplex
Ion Bernstein waves in a plasma with a kappa velocity distribution
International Nuclear Information System (INIS)
Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, κi, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if κi is reduced. For waves whose frequency lies above the lower hybrid frequency, ωLH, an increasing excess of superthermal particles (decreasing κi) reduces the frequency, ωpeak, of the characteristic peak at which the group velocity vanishes, while the associated kpeak is increased. As the ratio of ion plasma to cyclotron frequency (ωpi/ωci) is increased, the fall-off of ω at large k is smaller for lower κi and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-κi plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low κi. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed
Ion Bernstein wave heating experiments on PBX-M
International Nuclear Information System (INIS)
A multi-megawatt level IBWH experiment on PBX-M1 is in preparation. The goal of the expriment is to contribute to the attainment of the high beta, second regime of stability. The high power IBWH will be used as an additional heating power source to supplement the existing 6 MW of NBI power to achieve higher β values in PBX-M. Bulk ion heating via IBW excitation with localized, off-axis deposition can be used to modify the pressure profile for improved plasma stability at high β. The high power off-axis heating in principle can generate a significant boostrap current 2(∼30%) in the outer region of the PBX-M plasma complementing LHCD for broadening the current profiles. It is also interesting to note that the available rf power (∼4 MW) is comparable to the predicted power levels required for the rf ponderomotive stabilization of pressure driven modes (such as the high-n ballooning3 and external kink modes4) for the closely fitted stabilizing shell configuration of PBX-M. There are, however, several experimental factors that require careful consideration in planning a high power experiment. Four important factors are discussed here in some detail: 1. Antenna location. 2. Effects of parallel electric fields. 3. Modification of launched wave spectrum due to antenna misalignement 4. Possible interference of wave launching by protective limiters
The new features of ion Bernstein Wave Heating in JIPP T-IIU tokamak
International Nuclear Information System (INIS)
Ion Bernstein Wave Heating experiment was conducted in JIPP T-IIU tokamak. A relatively high frequency, 130 MHz, was used to reduce impurity influx and IBW power up to 400kW was injected without plasma disruption. It was found that the radial profiles of electron density, electron temperature, and ion temperature are all peaked during the IBWH. It was also found that ion distribution function does not have high energy tail above certain critical energy. These are favorable and useful features in optimizing fusion reactivity in reactor applications. (author)
Czech Academy of Sciences Publication Activity Database
Laqua, H.P.; Andruczyk, D.; Marsen, S.; Otte, M.; Podoba, Y.; Preinhaelter, Josef; Urban, Jakub
Geneva: IAEA, 2008, EXP6-18-EXP6-18. ISBN N. [IAEA Fusion Energy Conference/22nd./. Geneva (CH), 13.10.2008-18.10.2008] R&D Projects: GA ČR GA202/08/0419 Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Stellarators * Electron Bernstein waves * Simulation * WEGA Subject RIV: BL - Plasma and Gas Discharge Physics http://www-pub.iaea.org/MTCD/Meetings/FEC2008/ex_p6-18.pdf
Verma, Prabal Singh; Sengupta, Sudip; Kaw, Predhiman
2012-07-01
A one-dimensional particle in cell simulation of large amplitude plasma oscillations is carried out to explore the physics beyond wave breaking in a cold homogeneous unmagnetized plasma. It is shown that after wave breaking, all energy of the plasma oscillation does not end up as random kinetic energy of particles, but some fraction, which is decided by Coffey's wave breaking limit in warm plasma, always remains with two oppositely propagating coherent Bernstein-Greene-Kruskal like modes with supporting trapped particle distributions. The randomized energy distribution of untrapped particles is found to be characteristically non-Maxwellian with a preponderance of energetic particles.
Formation of core transport barrier and CH-Mode by ion Bernstein wave heating in PBX-M
International Nuclear Information System (INIS)
Observation of core transport barrier formation (for particles, ion and electron energies, and toroidal momentum) by ion Bernstein wave heating (IBWH) in PBX-M plasma is reported. The formation of a transport barrier leads to a strong peaking and significant increase of the core pressure (70%) and toroidal momentum (20%), and has been termed the core-high confinement mode (CH-Mode). This formation of a transport barrier is consistent, in terms of the expected barrier location as well as the required threshold power, with a theoretical model based on the poloidal sheared flow generation by the ion Bernstein wave power. The use of ion Bernstein wave (IBW) induced sheared flow as a tool to control plasma pressure and bootstrap current profiles shows a favorable scaling for the use in future reactor grade tokamak plasmas
Energy Technology Data Exchange (ETDEWEB)
B. Jones; G. Taylor; P.C. Efthimion; T. Munsat
2004-01-28
Measurement of the magnetic field in a spherical torus by observation of harmonic overlap frequencies in the electron Bernstein wave (EBW) spectrum has been previously suggested [V.F. Shevchenko, Plasma Phys. Reports 26 (2000) 1000]. EBW mode conversion to X-mode radiation has been studied in the Current Drive Experiment-Upgrade spherical torus, [T. Jones, Ph.D. thesis, Princeton University, 1995] with emission measured at blackbody levels [B. Jones et al., Phys. Rev. Lett. 90 (2003) article no. 165001]. Sharp transitions in the thermally emitted EBW spectrum have been observed for the first two harmonic overlaps. These transition frequencies are determined by the magnetic field and electron density at the mode conversion layer in accordance with hot-plasma wave theory. Prospects of extending this measurement to higher harmonics, necessary in order to determine the magnetic field profile, and high beta equilibria are discussed for this proposed magnetic field diagnostic.
Mode-converted electron Bernstein wave emission research on CDX-U and NSTX
International Nuclear Information System (INIS)
Electron Bernstein waves (EBWs) may enable electron temperature profile measurements and local electron heating and current drive in high β overdense (ωpe/ωce>>1) plasmas. Significant results are presented from the measurement of X-mode radiation, converted from EBWs observed normal to the magnetic field on the mid-plane of overdense plasmas in CDX-U and NSTX. A radially scannable, in-vessel, quad-ridged antenna and Langmuir probe array on CDX-U studied EBW to X-mode conversion. A local limiter optimized the conversion efficiency by modifying the density scale length at the mode conversion layer. The fundamental EBW conversion efficiency increased, by an order of magnitude, to ∼100% when the local limiter and antenna were inserted near the conversion layer. This technique can be extended to large, high temperature devices. Another significant observation was that the EBW emission source was localized near the electron cyclotron resonance. As a result, mode-converted EBW radiometry has measured radial transport in CDX-U. In addition, a threefold increase in conversion efficiency was observed at the L to H transition in NSTX. Measured conversion efficiency agreed well with theoretical predictions. EBW ray tracing and bounce-averaged Fokker-Planck codes are being used to model EBW heating and current drive scenarios for NSTX equilibria with β up to 40%. So far, results show that it is possible to drive localized currents on the high field side of the magnetic axis in NSTX at β ∼ 12% with current drive efficiency which compares favorably with ECCD. (authors)
Design and testing of an electron Bernstein wave emission radiometer for the TJ-II Stellarator
International Nuclear Information System (INIS)
Efficient Electron Bernstein wave (EBW) mode conversion is important for heating dense plasmas in TJ-II. The O-X-B mode conversion scenario is being considered for heating plasmas with densities over 1,3 x 1019 m-3, which will be very interesting to study high-density physics and for heating NBI plasmas. Measurement of the thermal EBW emission from the plasma allows the EBW mode conversion efficiency to be determined, and also has the potential to offer a diagnostic for measuring electron temperature profile evolution in overdense plasmas. A dual-polarized quad-ridged broadband horn with a focusing lens will be used to measure the EBW emission at 28 GHz on TJ-II. A focused beam is needed to achieve efficient coupling at the mode conversion layer. Emission from the plasma is reflected from a steerable internal mirror, propagates through a glass lens, and is focused on the horn. The field pattern from the horn-lens combination has been measured as a function of horn-lens spacing and lens focal length with a 3-D scanning system in an effort to minimize the beam waist at the plasma edge. Beam waist sizes have been measured at distances of up to 80 cm from the lens. Details of the experimental results and future plans will be presented. [Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725. A part of this work is performed under support of Spanish 'Subdireccion General de Proyectos de Investigacion, Ministerio de Educacion y Ciencia' with reference ENE2004-06957]. (author)
International Nuclear Information System (INIS)
A new coupling scheme of ion Bernstein waves (IBW) to plasma ions, by mode conversion of fast waves, has been tested in D-3He plasma of the JET tokamak. Injecting 4.8 MW ion cyclotron radio frequency power, 1.8 MW IBW power absorption on deuterons occurs at the fundamental cyclotron resonant layer, which is located in the high field side near the plasma edge (R = 2.1 m). Plasma sheared flows, ponderomotively induced by IBW, are observed near the edge, producing an ExB shearing rate of 5 MHz, higher than the threshold expected for turbulence suppression. Transport analysis shows a 70% reduction of the thermal diffusivity of both electrons and ions in the edge plasma region where the sheared flows are observed. (author)
International Nuclear Information System (INIS)
A high power radio wave, launched into the polar ionosphere at angle θ with the earth's magnetic field from a ground-based transmitter in the vicinity of twice the electron cyclotron frequency (2.75 MHz), is reported to create an airglow at an effective radiated power (ERP) = 10 MW. We interpret this result as a consequence of parametric decay of the radio wave into an electron Bernstein wave (EBW) and an ion acoustic wave (IAW). The oscillatory velocity of electrons due to the pump couples with the density perturbation due to the IAW to produce a current, driving the Bernstein mode. The latter, in connection with the pump, exerts a ponderomotive force on electrons, driving the IAW. The growth rate of the parametric instability is maximum for θ = 0. At the same time, for any given value of θ, the growth rate increases with b(=k12vth2/2ωc2) and attains a maximum around b ∼ 2, then falls gradually. The EBW produces energetic electrons via cyclotron damping. These electrons collide with the neutral atoms of the plasma to excite them to higher energy states. As the excited atoms return to lower energy states, they radiate in the visible
Ion Bernstein wave heating experiment on JIPPT-II-U device
International Nuclear Information System (INIS)
Ion Bernstein wave heating is investigated in the JIPPT-II-U tokamak plasma, n-bar sub(o) asymptoticaly equals 1.5 x 1013 cm-3, Tsub(eo) asymptoticaly equals 700 eV, and Tsub(io) = 300 eV for Psub(rf) 1-- 100 kW. In a two-ion-species helium-hydrogen plasma, the third harmonics of helium minority cyclotron resonance (deuterium-like) is heated. The background hydrogen ion temperature monitored by charge-exchange shows a significant rise, ΔTsub(i) 1-- 600 eV, when the helium harmonic resonance layer is placed near the center of the plasma. Typical observed hydrogen ion heating quality factor, ΔTsub(i)/Psub(rf)/n-barsub(o), is 1-- 10 eV/kW/1013cm-3. The dependence of ion heating efficiency on rf power, magnetic field and ion concentration is presented. (author)
Electron cyclotron-electron Bernstein wave emission diagnostics for the COMPASS tokamak
International Nuclear Information System (INIS)
The COMPASS tokamak recently started operation at the Institute of Plasma Physics AS CR, v.v.i., Prague. A new 16-channel radiometer, operating alternatively in three frequency bands, has been designed and constructed. The system is prepared for detection of normal electron cyclotron emission (O1 or X2) or oblique electron Bernstein wave emission. The end-to-end calibration method includes all components that influence the antenna radiation pattern. A steady recalibration is possible using a noise generator connected to the radiometer input through a fast waveguide PIN-switch. Measurements of the antenna radiation characteristics (2D electric field) were performed in free space as well as in the tokamak chamber, showing the degradation effect of structures on the Gaussian beam shape. First plasma radiation temperature measurements from low-field circular plasmas are available.
Electron heating by mode-converted ion-Bernstein waves in ICRF heating of tokamak plasmas
International Nuclear Information System (INIS)
In a tokamak plasma, ion-Bernstein waves (IBW) can be excited by mode-conversion of the externally launched fast wave for ICRF heating. This conversion process is known to be efficient for low k/sub parallel/'s which carry substantial power from a single loop antenna. A detailed numerical analysis of the propagation of the IBW shows that the initial small k/sub parallel/ are significantly enhanced along the rays due to toroidal effects. The upshift can occur for short radial distances of propagation and is large enough so that the IBW can Landau damp onto the electrons. This could help explain the observed strong electron heating by ICRF waves in tokamak plasmas. The numerical ray trajectory analysis is done in toroidal geometry for a hot Maxwellian plasma with gradients in temperature, density, toroidal and poloidal magnetic fields included in a WKB sense. A simple analytical model is derived which explains the upshift in k/sub parallel/ and gives results very close to the numerically obtained values. Approximate analytical conditions for appreciable electron Landau damping of the IBW are also given
Ion Bernstein wave antenna loading measurements on the DIII-D tokamak
Mayberry, M. J.; Pinsker, R. I.; Petty, C. C.; Porkolab, M.; Chiu, S. C.; Cary, W. P.; Prater, R.
1993-04-01
Antenna loading measurements carried out during high power ion Bernstein wave (IBW) heating experiments on the DIII-D tokamak indicate that efficient, direct coupling to the IBW at ω lesssim 2ωci as predicted by linear coupling theory did not occur. Whereas strong peaking in the loading resistance near cyclotron harmonics is predicted for high edge densities (ω front of the antenna, thus allowing coupling to the cold plasma lower hybrid wave (LHW). A linear LHW coupling code including the modified density profile due to the ponderomotive force reproduces the measured dependence of antenna loading on toroidal magnetic field, edge density, antenna frequency and antenna phasing. Further evidence for the ponderomotive force is obtained from reactive loading measurements which indicate that the plasma is pushed away from the antenna as the radiofrequency power level is increased. The results indicate that the lack of central ion heating observed during DIII-D IBW experiments may be due to a lack of efficient mode transformation from the coupled LHW to a centrally propagating IBW, possibly as a result of nonlinear mechanism(s)
Fokker-Planck/Ray Tracing for Electron Bernstein and Fast Wave Modeling in Support of NSTX
Energy Technology Data Exchange (ETDEWEB)
Harvey, R. W. [CompX, Del Mar, CA (United States)
2009-11-12
This DOE grant supported fusion energy research, a potential long-term solution to the world's energy needs. Magnetic fusion, exemplified by confinement of very hot ionized gases, i.e., plasmas, in donut-shaped tokamak vessels is a leading approach for this energy source. Thus far, a mixture of hydrogen isotopes has produced 10's of megawatts of fusion power for seconds in a tokamak reactor at Princeton Plasma Physics Laboratory in New Jersey. The research grant under consideration, ER54684, uses computer models to aid in understanding and projecting efficacy of heating and current drive sources in the National Spherical Torus Experiment, a tokamak variant, at PPPL. The NSTX experiment explores the physics of very tight aspect ratio, almost spherical tokamaks, aiming at producing steady-state fusion plasmas. The current drive is an integral part of the steady-state concept, maintaining the magnetic geometry in the steady-state tokamak. CompX further developed and applied models for radiofrequency (rf) heating and current drive for applications to NSTX. These models build on a 30 year development of rf ray tracing (the all-frequencies GENRAY code) and higher dimensional Fokker-Planck rf-collisional modeling (the 3D collisional-quasilinear CQL3D code) at CompX. Two mainline current-drive rf modes are proposed for injection into NSTX: (1) electron Bernstein wave (EBW), and (2) high harmonic fast wave (HHFW) modes. Both these current drive systems provide a means for the rf to access the especially high density plasma--termed high beta plasma--compared to the strength of the required magnetic fields. The CompX studies entailed detailed modeling of the EBW to calculate the efficiency of the current drive system, and to determine its range of flexibility for driving current at spatial locations in the plasma cross-section. The ray tracing showed penetration into NSTX bulk plasma, relatively efficient current drive, but a limited ability to produce current over
Modification of boundary plasma behavior by Ion Bernstein Wave heating on the HT-7 tokamak
International Nuclear Information System (INIS)
The boundary plasma behavior during Ion Bernstein Wave heating was investigated using Langmuir probe arrays on the HT-7 tokamak. A distinct weak turbulence regime was reproducibly observed in the 30 MHz IBW heated plasmas with RF power larger than 120 kW, which resulted in a particle confinement improvement of a factor of 2. The strong suppression and decorrelation effect of fluctuations resulted in the turbulent particle flux dropping by more than an order of magnitude in the plasma boundary region. An additional inward radial electric field and associated poloidal ExB flows were produced, which could account for the additional poloidal velocity in the electron diamagnetic direction at some radial locations of the boundary plasma. The electrostatic fluctuations were nearly completely decorrelated in the high frequency region and only low frequency fluctuations remained. The poloidal correlation was considerably reduced in the high poloidal wave number region and only the fluctuations with long poloidal wavelength remained. Three-wave nonlinear phase coupling between the whole frequency domain and the very low frequency region increased significantly in both the plasma edge and the SOL. Quite low frequency fluctuations (about 5 kHz) were generated, which dominated the boundary turbulence during IBW heating. Detailed analyses suggested that, when an IBW with a frequency of 30 MHz was launched into a plasma with the toroidal magnetic field between 1.75 T and 2.0 T, the ion cyclotron resonant layer of 5/2.D was located in the plasma edge region. The poloidal ExB sheared flows generated by IBW near this layer due to a ponderomotive interaction were found to be the mechanism underlying these phenomena. (author)
Ghizzo, A.
2013-08-01
The stationary state with magnetically trapped particles is investigated at the saturation of the relativistic Weibel instability, within the "multiring" model in a Hamiltonian framework. The multistream model and its multiring extension have been developed in Paper I, under the assumption that the generalized canonical momentum is conserved in the perpendicular direction. One dimensional relativistic Bernstein-Greene-Kruskal waves with deeply trapped particles are addressed using similar mathematical formalism developed by Lontano et al. [Phys. Plasmas 9, 2562 (2002); Phys. Plasmas 10, 639 (2003)] using several streams and in the presence of both electrostatic and magnetic trapping mechanisms.
Directory of Open Access Journals (Sweden)
Uchida Masaki
2015-01-01
Full Text Available An extremely overdense special Tokamak plasma has been non-inductively formed and maintained by electron Bernstein (EB wave heating and current drive in the Low Aspect ratio Torus Experiment (LATE device. The plasma current reaches 12 kA and the line-averaged electron density exceeds 7 times the plasma cut off density by injecting a 2.45 GHz microwave power of 60 kW. Such a highly overdense plasma is obtained when the upper hybrid resonance layer lies to the higher field side of the 2nd harmonic ECR layer, which may realize a good coupling to EB waves at their first propagation band. The effect of the injection polarization on the mode conversion rate to EB waves at the extremely overdense regime has been investigated and an improvement in the plasma current is observed.
International Nuclear Information System (INIS)
This proposal was peer reviewed and funded as a Collaboration on ''Low Phase Speed Radio Frequency Current Drive Experiments at the Tokamak Fusion Test Reactor''. The original plans we had were to carry out the collaboration proposal by including a post doctoral scientist stationed at PPPL. In response to a 60+% funding cut, all expenses were radically pruned. The post doctoral position was eliminated, and the Principal Investigator (T. Intrator) carried out the brunt of the collaboration. Visits to TFTR enabled T. Intrator to set up access to the TFTR computing network, database, and get familiar with the new antennas that were being installed in TFTR during an up to air. One unfortunate result of the budget squeeze that TFTR felt for its last year of operation was that the experiments that we specifically got funded to perform were not granted run time on TFTR., On the other hand we carried out some modeling of the electric field structure around the four strap direct launch Ion Bernstein Wave (IBW) antenna that was operated on TFTR. This turned out to be a useful exercise and shed some light on the operational characteristics of the IBW antenna and its coupling to the plasma. Because of this turn of events, the project was renamed ''Modeling of Ion Bernstein Wave Antenna Array and Coupling to Plasma on Tokamak Fusion Test Reactor''
Stefan, V. Alexander
2014-10-01
A novel method for alpha particle diagnostics is proposed. The theory of stimulated Raman scattering, SRS, of the fast wave and ion Bernstein mode, IBM, turbulence in multi-ion species plasmas, (Stefan University Press, La Jolla, CA, 2008). is utilized for the diagnostics of fast ions, (4)He (+2), in ITER plasmas. Nonlinear Landau damping of the IBM on fast ions near the plasma edge leads to the space-time changes in the turbulence level, (inverse alpha particle channeling). The space-time monitoring of the IBM turbulence via the SRS techniques may prove efficient for the real time study of the fast ion velocity distribution function, spatial distribution, and transport. Supported by Nikola Tesla Labs., La Jolla, CA 92037.
Xiao, Jianyuan; Liu, Jian; Qin, Hong; Yu, Zhi; Xiang, Nong
2015-01-01
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonli...
Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi
2009-02-01
To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic. PMID:19256646
International Nuclear Information System (INIS)
To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.
Active core profile and transport modification by application of Ion Bernstein Wave power in PBX-M
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Application of Ion Bernstein Wave Heating (IBWH) into the Princeton Beta Experiment-Modification (PBX-M) tokamak stabilizes sawtooth oscillations and generates peaked density profiles. A transport barrier, spatially correlated with the IBWH power deposition profile, is observed in the core of IBWH assisted neutral beam injection (NBI) discharges. A precursor to the fully developed barrier is seen in the soft x-ray data during edge localized mode (ELM) activity. Sustained IBWH operation is conducive to a regime where the barrier supports large triangledown ne, triangledown Te, triangledown vphi, and triangledown Ti, delimiting the confinement zone. This regime is reminiscent of the H(high)-mode but with a confinement zone moved inwards. The core region has better than H-mode confinement while the peripheral region is L(low)-mode-like. The peaked profile enhanced NBI core deposition and increases nuclear reactivity. An increase in central Ti results from χi reduction (compared to H-mode) and better beam penetration. Bootstrap current fractions of up to 0.32--0.35 locally and 0.28 overall were obtained when an additional NBI burst is applied to this plasma
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A sudden, threefold increase in emission from fundamental electrostatic electron Bernstein waves (EBW) which mode convert and tunnel to the electromagnetic X-mode has been observed during high energy and particle confinement (H-mode) transitions in the National Spherical Torus Experiment (NSTX) plasma [M. Ono, S. Kaye, M. Peng et al., in Proceedings of the 17th IAEA Fusion Energy Conference (IAEA, Vienna, Austria, 1999), Vol. 3, p. 1135]. The mode-converted EBW emission viewed normal to the magnetic field on the plasma midplane increases when the density profile steepens in the vicinity of the mode conversion layer, which is located in the plasma scrape off. The measured conversion efficiency during the H-mode is consistent with the calculated EBW to X-mode conversion efficiency derived using edge density data. Calculations indicate that there may also be a small residual contribution to the measured X-mode electromagnetic radiation from polarization-scrambled, O-mode emission, converted from EBWs
Possibility of using ion-Bernstein waves for alpha power extraction in tokamaks
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If the fusion α-particle power is directly channeled to do useful things rather than simply undergo collisional absorption, there is an opportunity for significantly improved tokamak reactor performance. In the absence of the channeling, the α-particle power results predominantly in electron heating, which is a poor use of this power. One possibility is to direct this power into waves that damp on electrons traveling in one direction to sustain the plasma current. Since the power required to drive the toroidal current is about 10% of the fusion power output, whereas the α-particle power is 20% of the fusion power output, using even a fraction of the α-particle power to amplify the waves used for current drive can result in very significant savings in the required power for the current drive. A second possibility is to direct this power into waves that damp on fuel ions to increase the plasma reactivity. Such a channeling of the α-particle power could make possible the operation of fusion reactors in regimes in which the fuel ion temperature can be much greater than the electron temperature. It may also be possible to sustain a hot, nonmaxwellian component of the fuel ions, further enhancing the reactivity. By these means, if 75% of the α-particle power is diverted, the plasma reactivity, at constant pressure, can be increased by about a factor of two. It may even be possible to achieve at once the increased reactivity and the current drive, if, for example the α-particle power is channeled into waves that damp on fast ions traveling in one toroidal direction. (author) 10 refs., 4 figs
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Full text: In LHD, electron Bernstein wave (EBW) heating was successfully demonstrated by two ways of mode conversion to EBWs from injected EC-waves, by so-called slow-XB and OXB techniques. To realize the excitation of EBWs by the slow-XB technique, EC-waves in X-mode polarization should be injected to plasmas from high magnetic field side (HFS). In LHD, newly installed inner-vessel mirror close to a helical coil is used for the HFS injection. Evident increases in Te at the plasma core region and Wp were caused by the HFS injection with 0.18 s pulse width to a plasma with ne(0) of 24 x 1019 m-3, that is, 3.3 times higher than the plasma cut-off density for O-mode waves, and 1.6 x higher than the left-hand cut-off density of 14.7 x 1019 m-3 for slow-X-mode waves. Thus, the heating effects especially the increase in Te at the plasma core region should be attributed to the mode-converted EBWs, not to the X- or O-mode waves. For excitation of EBWs by the OXB technique, O-mode waves should be injected from the low magnetic filed side toward the so-called 'mode conversion window' . Two pulses of 77 GHz, 1.05 MW EC-wave (0.1 s pulse width each with a 0.1 s interval) in O-mode polarization were injected to an NB-sustained plasma, aiming at the mode conversion window calculated in advance. With both of the two ECH pulses, increases in Wp and mitigations of decreasing trend in Te measured with ECE are recognized. The line average electron density continuously increased during the ECH pulse injection. At the start timing of the 1st pulse, ne(0) was equal to the O-mode cut-off density, 7.35 x 1019 m-3, and ne(0) gradually increased to 7.7 x 1019 m-3 at the end of the 2nd pulse. The heating efficiency Pabs/Pech is evaluated as ∼ 15%. Using the high-power, long-pulse 77 GHz ECH system, 2nd harmonic on-axis ECCD experiments with 775 kW injection power and the line average electron density of 0.3 x 1019 m-3 were conducted. At optimum beam directions, maximum EC-driven currents
Sun, Jicheng; Gao, Xinliang; Chen, Lunjin; Lu, Quanming; Tao, Xin; Wang, Shui
2016-02-01
Ion Bernstein modes, also known as magnetosonic waves in the magnetospheric community, are considered to play an important role in radiation belt electron acceleration. The detailed properties of perpendicular magnetosonic waves excited in the inner magnetosphere by a tenuous proton ring distribution are investigated in a two series paper with a combination of the linear theory and one-dimensional particle-in-cell simulations. Here, in this paper, we study the properties of the excited magnetosonic waves under different plasma conditions with the linear theory. When the proton to electron mass ratio or the ratio of the light speed to the Alfven speed is small, the excited magnetosonic waves are prone to having a discrete spectrum with only several wave modes. With the increase of the proton to electron mass ratio or the ratio of the light speed to the Alfven speed, the lower hybrid frequency also increases, which leads to the increase of both the number and frequency of the excited wave modes. Meanwhile, the growth rate of these wave modes also increases. When the proton to electron mass ratio or the ratio of the light speed to the Alfven speed is sufficiently large, the spectrum of the excited magnetic waves becomes continuous due to the overlapping of the adjacent wave modes. The increase of the density of the protons with the ring distribution can also result in the increase of the growth rate, which may also change the discrete spectrum of the excited waves to a continuous one, while the increase of the ring velocity of the tenuous proton ring distribution leads to a broader spectrum, but with a smaller growth rate.
Influence of Bernstein modes on the efficiency of electron cyclotron resonance x-ray source
International Nuclear Information System (INIS)
The article considers the factors influencing the temperature of hot electron component in an electron cyclotron resonance (ECR) x-ray source. In such sources the electron heating occurs often due to extraordinary electromagnetic wave propagating perpendicularly to the magnetic field. In this case the possibility of the absorption of Bernstein modes is regarded as an additional mechanism of electron heating. The Bernstein modes in an ECR x-ray source can arise due to either linear transformation or parametric instability of external transversal wave. The article briefly reviews also the further experiments which will be carried out to study the influence of Bernstein modes on the increase of hot electron temperature and consequently of x-ray emission
Min, Kyungguk; Liu, Kaijun
2016-04-01
Fast magnetosonic waves in Earth's inner magnetosphere, which have as their source ion Bernstein instabilities, are driven by hot proton velocity distributions (fp) with ∂fp(v⊥)/∂v⊥>0. Two typical types of distributions with such features are ring and shell velocity distributions. Both have been used in studies of ion Bernstein instabilities and fast magnetosonic waves, but the differences between instabilities driven by the two types of distributions have not been thoroughly addressed. The present study uses linear kinetic theory to examine and understand these differences. It is found that the growth rate pattern is primarily determined by the cyclotron resonance condition and the structure of the velocity distribution in gyroaveraged velocity space. For ring-driven Bernstein instabilities, as the parallel wave number (k∥) increases, the discrete unstable modes approximately follow the corresponding proton cyclotron harmonic frequencies while they become broader in frequency space. At sufficiently large k∥, the neighboring discrete modes merge into a continuum. In contrast, for shell-driven Bernstein instabilities, the curved geometry of the shell velocity distribution in gyroaveraged velocity space results in a complex alternating pattern of growth and damping rates in frequency and wave number space and confines the unstable Bernstein modes to relatively small k∥. In addition, when k∥ increases, the unstable modes are no longer limited to the proton cyclotron harmonic frequencies. The local growth rate peak near an exact harmonic at small k∥ bifurcates into two local peaks on both sides of the harmonic when k∥ becomes large.
Kalaee, Mohammad Javad; Katoh, Yuto
2016-07-01
One of the mechanisms for generating electromagnetic plasma waves (Z-mode and LO-mode) is mode conversion from electrostatic waves into electromagnetic waves in inhomogeneous plasma. Herein, we study a condition required for mode conversion of electrostatic waves propagating purely perpendicular to the ambient magnetic field, by numerically solving the full dispersion relation. An approximate model is derived describing the coupling between electrostatic waves (hot plasma Bernstein mode) and Z-mode waves at the upper hybrid frequency. The model is used to study conditions required for mode conversion from electrostatic waves (electrostatic electron cyclotron harmonic waves, including Bernstein mode) into electromagnetic plasma waves (LO-mode). It is shown that for mode conversion to occur in inhomogeneous plasma, the angle between the boundary surface and the magnetic field vector should be within a specific range. The range of the angle depends on the norm of the k vector of waves at the site of mode conversion in the inhomogeneous region. The present study reveals that inhomogeneity alone is not a sufficient condition for mode conversion from electrostatic waves to electromagnetic plasma waves and that the angle between the magnetic field and the density gradient plays an important role in the conversion process.
Bernstein functions theory and applications
Schilling, René L; Vondracek, Zoran
2010-01-01
This text is a self-contained and unified approach to Bernstein functions and their subclasses, bringing together old and establishing new connections. Applications of Bernstein functions in different fields of mathematics are given, with special attention to interpretations in probability theory. An extensive list of complete Bernstein functions with their representations is provided.
McLean, Monica; Abbas, Andrea; Ashwin, Paul
2013-01-01
This paper illustrates how critical use of Basil Bernstein's theory illuminates the mechanisms by which university knowledge, curriculum and pedagogy both reproduce and interrupt social inequalities. To this end, empirical examples are selected from the findings of the ESRC-funded project "Pedagogic Quality and Inequality in University First…
Ion wave excitation for the study of wave-induced transport
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A general program to study wave-particle interactions and wave-induced transport in a low temperature, low density, collisionless plasma has led to the application of an assortment of ion wave launching schemes. This wave launching techniques include the use of: capacitively coupled rings at the plasma periphery, inductive coils, grids immersed in the plasma, and ion wave excitation by modulation of microwaves (double resonance). The generated ion waves are either ion acoustic, the forward and backward (neutralized ion Bernstein) branches of electrostatic ion cyclotron, and/or ballistic modes. Our earlier studies have addressed the ion interaction with a single monochromatic wave, such as ion acceleration by intrinsic stochasticity induced by interaction with an ion Bernstein mode, and ion coordinate space diffusion constrained by conservation of integrals of the motion in this deterministic system. In the case of linear ion acoustic wave-particle interaction, an experimental test ion approach has yielded direct evidence of phase space orbit perturbations for ions resonant with the wave phase velocity, demonstrating on the kinetic level the essence of ion Landau damping. We are now turning our attention to the problem of stochastic interaction with two ion cyclotron modes. A detailed knowledge of the waves excited by the antenna will allow a selection of mode phase velocities such that the separation of wave-particle resonances can be controlled. In this way, the wave field amplitudes necessary for reaching the stochasticity threshold can be reduced, in comparison to the situation with one wave. This paper reviews the wave dispersion characteristics compiled during the aforementioned wave-particle interaction studies. It will be seen that the plasma dispersion relation universally determines the wave response, quite independent of the antenna configuration. (author) 9 refs., 4 figs
Sesnic, S.; Kaita, R.; Batha, S. H.; Bell, R. E.; Bernabei, S.; Chance, M. S.; DeLa Luna, E.; Dunlap, J. L.; England, A. C.; Isler, R. C.; Jones, S.; Kaye, S. M.; Kesner, J.; Kugel, H. W.; LeBlanc, B.; Levinton, F. M.; Luckhardt, S. C.; Manickam, J.; Okabayashi, M.; Ono, M.; Paoletti, F.; Paul, S. F.; Post-Zwicker, A. P.; Sanchez Sanz, J.; Sauthoff, N. R.; Seki, T.; Takahashi, H.; Tighe, W.; Von Goeler, S.; Woskov, P.; Zolfaghari, A.
1998-06-01
If the ion Bernstein wave (IBW) heating power in an H mode discharge of the PBX-M experiment exceeds a threshold power of about 200 kW, a core transport barrier is created in the central region of the plasma. At lower neutral beam injection (NBI) powers, the core barrier is accompanied by an edge L mode. The high edge localized mode (ELM) repetition frequency (1 kHz) prevents the creation of a strong barrier, so the edge first has to make an H-to-L transition before a strong core transport barrier can be created. At higher NBI powers, the ELM repetition frequency is lowered to less than 200 Hz, which allows the immediate creation of a strong core barrier. Edge localized mode loss, which propagates radially first on a fast (non-diffusive) and then on a slow (diffusive) time-scale all the way to the plasma core, is strongly reduced in the core barrier region. Correlated with the reduced ELM loss, the fluctuations in the core barrier region are also strongly reduced, both during the ELM and during the quiet periods between the ELMs. There is strong evidence that the IBW induced poloidal flow shear is responsible for the stabilization of core turbulence and the creation of the core transport barrier. The large perpendicular E × B flow shear component of the measured toroidal velocity in co-injection neutral beam heated discharges seems to be largely cancelled by the ion diamagnetic drift shear produced by large ion pressure gradients in the core barrier region. The value of IBW induced poloidal flow has not been experimentally determined, but its numerical value is found to be a factor of 4 larger than either the toroidal velocity or the ion diamagnetic drift shear components, leaving only IBW induced flow shear as the most probable cause for the turbulence stabilization. The core turbulence suppression and the creation of the core transport barrier is also consistent with expectations from a comparison between the E × B flow shear rate and a rough estimate of the
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If the ion Bernstein wave (IBW) heating power in an H mode discharge of the PBX-M experiment exceeds a threshold power of about 200 kW, a core transport barrier is created in the central region of the plasma. At lower neutral beam injection (NBI) powers, the core barrier is accompanied by an edge L mode. The high edge localized mode (ELM) repetition frequency (1 kHz) prevents the creation of a strong barrier, so the edge first has to make an H-to-L transition before a strong core transport barrier can be created. At higher NBI powers, the ELM repetition frequency is lowered to less than 200 Hz, which allows the immediate creation of a strong core barrier. Edge localized mode loss, which propagates radially first on a fast (non-diffusive) and then on a slow (diffusive) time-scale all the way to the plasma core, is strongly reduced in the core barrier region. Correlated with the reduced ELM loss, the fluctuations in the core barrier region are also strongly reduced, both during the ELM and during the quite periods between the ELMs. There is strong evidence that the IBW induced poloidal flow shear is responsible for the stabilization of core turbulence and the creation of the core transport barrier. The large perpendicular E x B flow shear component of the measured toroidal velocity in co-injection neutral beam heated discharges seems to be largely cancelled by the ion diamagnetic drift shear produced by large ion pressure gradients in the core barrier region. The value of IBW induced poloidal flow has not been experimentally determined, but its numerical value is found to be a factor of 4 larger than either the toroidal velocity or the ion diamagnetic drift shear components, leaving only IBW induced flow shear as the most probable cause for the turbulence stabilization. The core turbulence suppression and the creation of the core transport barrier is also consistent with expectations from a comparison between the E x B flow shear rate and a rough estimate of the
Generalized -Bernstein-Schurer Operators and Some Approximation Theorems
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M. Mursaleen
2013-01-01
Full Text Available We study statistical approximation properties of -Bernstein-Shurer operators and establish some direct theorems. Furthermore, we compute error estimation and show graphically the convergence for a function by operators and give its algorithm.
International Nuclear Information System (INIS)
Purpose: To acknowledge the tacit rules underpinning academic practice of undergraduate radiographers in determining normality vs. abnormality when appraising skeletal images. Methodology: Twelve students were interviewed (individually) using in-depth semi-structured questions. Interviews were mediated through a PowerPoint presentation containing two digital X-ray images. Each image was based on a level of expertise; the elementary (Case 1) and the complicated (Case 2). The questions were based on regular ‘frames’ created from observing tutor–student contact in class, and then validated through a group interview. Bernstein's theory of pedagogic discourse was then utilised as a data analysis instrument to determine how third year diagnostic radiography students interpreted X-ray images, in relation to the ‘recognition’ and ‘realisation’ rules of the Educational Theoretical Framework. Conclusion: Bernstein's framework has made it possible to specify, in detail, how issues and difficulties are formed at the level of the acquirer during interpretation. The recognition rules enabled students to meaningfully recognise what trauma characteristics can be associated with the image and the demands of a detailed scrutiny so as to enact a competent interpretation. Realisation rules, made it possible for students to establish their own systematic approach and realise legitimate meanings of normality and abnormality. Whereas obvious or visible trauma generated realisation rules (represented via homogenous terminology), latent trauma authorised students to deviate from legitimate meanings. The latter rule, in this context, has directed attention to the student issue of visioning abnormality when images are normal
Kim, E.-H.; Boardsen, S. A.; Johnson, J. R.; Slavin, J. A.
2016-02-01
This chapter provides a brief overview of the observed characteristics of ultra-low-frequency (ULF) waves at Mercury. It shows how field-aligned propagating ULF waves at Mercury can be generated by externally driven fast compressional waves (FWs) via mode conversion at the ion-ion hybrid resonance. Then, the chapter reviews the interpretation that the strong magnetic compressional waves near and its harmonics observed with 20 of Mercury's magnetic equator could be the ion Bernstein wave (IBW) mode. A recent statistical study of ULF waves at Mercury based on MESSENGER data reported the occurrence and polarization of the detected waves. The chapter further introduces the field line resonance and the electromagnetic ion Bernstein waves to explain such waves, and shows that both theories can partially explain the observations.
Institute of Scientific and Technical Information of China (English)
张海明; 陈晓非
2003-01-01
The development of seismic wave study in China in the past four years is reviewed. The discussion is divided into several aspects, including seismic wave propagation in laterally homogeneous media, laterally heterogeneous media, anisotropic and porous media, surface wave and seismic wave inversion, and seismic wave study in prospecting and logging problems. Important projects in the current studies on seismic wave is suggested as the development of high efficient numerical methods, and applying them to the studies of excitation and propagation of seismic waves in complex media and strong ground motion, which will form a foundation for refined earthquake hazard analysis and prediction.
Experimental Studies of BGK Ion Waves
Skiff, F.; Noonan, W. A.; Case, A.; Bachet, G.; Doveil, F.
2000-10-01
Since the classic work of Bernstein, Green, and Kruskal, it has been known that plasmas support a large class of propagating disturbances that are kinetic equilibria in the propagating frame. We present experimental studies of BGK ion equilibria in singly ionized Argon plasma in two contexts. The first context is the formation of an ion phase-space hole behind a weak electrostatic shock in unmagnetized plasma. The approach toward BGK equilibrium where the contours of the ion distribution function tend to align with curves of constant particle energy in the propagating frame - is observed and the structure is shown to be a solution of the kinetic equation. The second context is a low amplitude time-periodic structure that interacts primarily with ions near wave-particle resonance in magnetized plasma. There exist theoretical predictions of nonlinear waves at very low amplitude. The existence of low amplitude nonlinear waves complicates the formulation of a complete linear description. In each context, laser induced florescence is used to measure the perturbation of the ion distribution and to determine the associated electrostatic electric field.
On the approximation properties of bivariate $(p, q)-$Bernstein operators
Karaisa, Ali
2016-01-01
In the present study, we have given a corrigendum to our paper on the approximation properties of bivariate $(p, q)-$Bernstein operators. Recently, we \\cite{kar} have defined the bivariate $(p, q)-$Bernstein operators. Later, we have aware of Acar et. al \\cite{acar} already have given some moments. In this case, we have revised \\cite[Lemma 2.3]{kar}.
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We study the geometry of magnetogravity wave surfaces in an incompressible, isothermal, inviscid, nonrotating, flat, horizontally stratified perfectly conducting atmosphere. Our ultimate goal is the verification of the contention by Lighthill that such waves may contribute heavily to the heating of the upper solar atmosphere. The equations of the wave surface are determined from those of the wave normal surface using the envelope construction. For a vertical magnetic field, we find that for frequencies greater than the Vaisala-Brunt frequency N, the wave surfaces are arrow shaped, having both a point cusp and a circular cuspidal edge. The locations of these cusps are determined using the polar reciprocal relationship between the slowness (reciprocal velocity) and wave surfaces. We find that for high frequencies, these surfaces subtend small angles with respect to the origin, strongly suggesting the ability of these waves to carry energy upward. For a wave frequency equal to the Vaisala-Brunt, the surface is spherical, while for frequencies lower than the Vaisala-Brunt, the surfaces become infinite in extent. For the case of a horizontal magnetic field, we again determine the location of cuspidal edges. For oblique fields, we again find a line of self-intersection, provided the frequency ω is related to the angle zeta of the magnetic field with the vertical by ω2 > N2cos2zeta. The equation of these lines is derived: Z = cot zeta X, showing that the line is always directed along the magnetic field. The existence of the line of self-intersection suggests that magnetogravity waves, at least those of high enough frequency, can carry energy upward along the solar magnetic field, thus lending support to Lighthill's conjecture
The nonlinear Bernstein-Schr\\"odinger equation in Economics
Galichon, Alfred; Kominers, Scott; WEBER, Simon
2015-01-01
In this paper we relate the Equilibrium Assignment Problem (EAP), which is underlying in several economics models, to a system of nonlinear equations that we call the "nonlinear Bernstein-Schr\\"odinger system", which is well-known in the linear case, but whose nonlinear extension does not seem to have been studied. We apply this connection to derive an existence result for the EAP, and an efficient computational method.
The nonlinear Bernstein-Schr\\"odinger equation in Economics
Alfred Galichon; Scott Kominers; Simon Weber
2015-01-01
In this paper we relate the Equilibrium Assignment Problem (EAP), which is underlying in several economics models, to a system of nonlinear equations that we call the "nonlinear Bernstein-Schr\\"odinger system", which is well-known in the linear case, but whose nonlinear extension does not seem to have been studied. We apply this connection to derive an existence result for the EAP, and an efficient computational method.
Semiparametric Bernstein-von Mises for the error standard deviation
Jonge, de, B.; Zanten, van, M.
2013-01-01
We study Bayes procedures for nonparametric regression problems with Gaussian errors, giving conditions under which a Bernstein-von Mises result holds for the marginal posterior distribution of the error standard deviation. We apply our general results to show that a single Bayes procedure using a hierarchical spline-based prior on the regression function and an independent prior on the error variance, can simultaneously achieve adaptive, rate-optimal estimation of a smooth, multivariate regr...
Prets, A
1998-01-01
In the present Ph. D. thesis we are considering a special form of scaling limits, namely the hydrodynamic limit. Such limits are considered to explain macroscopic behavior of matter by means of microscopic dynamic laws. In this procedure a rescaling of space and time plays a central role. The limit will be formulated in a quantum mechanical way. Within this framework we study derivations of the Landau Lifshitz equation for ferromagnets. This equation is a macroscopic equation of motion for the magnetization vector and results into the theory of spin waves. Since we have no exact knowledge of the Heisenberg operator's time evolution no definitive statement an how to regain the Landau Lifshitz equation from the microscopic dynamics can be given. In contrast to the Heisenberg operator, for an Ising type interaction inside a ferromagnet one is able to recover macroscopically a solution of a linearized Landau Lifschitz equation.
CONVERGENCE ARTE FOR INTERATES OF q-BERNSTEIN POLYNOMIALS
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Recently, q-Bernstein polynomials have been intensively investigated by a number of authors. Their results show that for q ≠ 1, q-Bernstein polynomials possess of many interesting properties. In this paper, the convergence rate for iterates of both q-Bernstein when n →∞ and convergence rate of Bn(f,q;x) when f ∈ Cn-1[0, 1], q →∞ are also presented.
Iterates of Bernstein Type Operators on a Triangle with All Curved Sides
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Teodora Cătinaş
2014-01-01
Full Text Available We consider some Bernstein-type operators as well as their product and Boolean sum for a function defined on a triangle with all curved sides. Using the weakly Picard operators technique and the contraction principle, we study the convergence of the iterates of these operators.
Iterates of Bernstein Type Operators on a Triangle with All Curved Sides
Teodora Cătinaş
2014-01-01
We consider some Bernstein-type operators as well as their product and Boolean sum for a function defined on a triangle with all curved sides. Using the weakly Picard operators technique and the contraction principle, we study the convergence of the iterates of these operators.
Bernstein's Lethargy Theorem in Frechet Spaces
Aksoy, Asuman Guven; Lewicki, Grzegorz
2015-01-01
In this paper we consider Bernstein's Lethargy Theorem (BLT) in the context of Fr\\'{e}chet spaces. Let $X$ be an infinite-dimensional Fr\\'echet space and let $\\mathcal{V}=\\{V_n\\}$ be a nested sequence of subspaces of $ X$ such that $ \\bar{V_n} \\subseteq V_{n+1}$ for any $ n \\in \\mathbb{N}$ and $ X=\\bar{\\bigcup_{n=1}^{\\infty}V_n}.$ Let $ e_n$ be a decreasing sequence of positive numbers tending to 0. Under an additional natural condition on $\\sup\\{\\{dist}(x, V_n)\\}$, we prove that there exists...
Huang, S. Y.; Yuan, Z. G.; Ni, B.; Zhou, M.; Fu, H. S.; Fu, S.; Deng, X. H.; Pang, Y.; Li, H. M.; Wang, D. D.; Li, H. M.; Yu, X. D.
2015-07-01
Broadband frequency waves around the dipolarization front (DF) are believed to play a crucial role in the particle dynamics. Using the Cluster observations, we report in this study large-amplitude electromagnetic waves with frequencies just above the ion cyclotron frequency at the DF in the near-Earth magnetotail region. The waves have very large amplitudes of magnetic and electric field fluctuations, up to ~2 nT and ~10 mV/m, respectively. The magnetic fluctuations are predominately along the ambient magnetic field (B0), while the electric fluctuations are primarily perpendicular to B0. The observed waves are highly oblique with a propagation angle of ~100° with respect to the ambient magnetic field, and are also linearly polarized. These features are consistent with the properties of the ion Bernstein wave mode in the high plasma β region, and also with the properties of current-driven ion cyclotron waves driven by the electromagnetic current-driven Alfven instability. We also discuss the possibility of wave-particle interactions at the DF.
Nonlinear particle simulation of ion cyclotron waves in toroidal geometry
Energy Technology Data Exchange (ETDEWEB)
Kuley, A., E-mail: akuley@uci.edu; Lin, Z. [Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Bao, J. [Fusion Simulation Center, Peking University, Beijing (China); Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Wei, X. S.; Xiao, Y. [Institute of Fusion Theory and Simulation, Zhejiang University, Hangzhou (China)
2015-12-10
Global particle simulation model has been developed in this work to provide a first-principles tool for studying the nonlinear interactions of radio frequency (RF) waves with plasmas in tokamak. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation with realistic electron-to-ion mass ratio. Boris push scheme for the ion motion has been developed in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron and ion Bernstein waves in global gyrokinetic toroidal code (GTC). The nonlinear simulation capability is applied to study the parametric decay instability of a pump wave into an ion Bernstein wave side band and a low frequency ion cyclotron quasi mode.
Wave Dragon Buoyancy Regulation Study
DEFF Research Database (Denmark)
Jakobsen, Jens; Kofoed, Jens Peter
Wave Dragon is a wave energy converter, which was deployed offshore at Nissum Bredning in Denmark in 2003. The experience gained from operating Wave Dragon during 2003 and 2004 has shown that the buoyancy regulation system can be improved in a number of ways. This study describes the current...... situation, and proposes a number of activities in order to improve the buoyancy regulation system. This work was performed under EU ENERGIE contract no. ENK5-CT-2002-00603, and is a contribution to WP 2.3/2.4 and D40/D41....
Experimental Study on the WavePiston Wave Energy Converter
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter; Angelelli, E.
This report presents the results of an experimental study of the power performance of the WavePiston wave energy converter. It focuses mainly on evaluating the power generating capabilities of the device and the effect of the following issues: Scaling ratios PTO loading Wave height and wave period...... dependency Oblique incoming waves Distance between plates During the study, the model supplied by the client, WavePiston, has been rigorously tested as all the anticipated tests have been done thoroughly and during all tests, good quality data has been obtained from all the sensors....
MULTIVARIATE WEIGHTED BERNSTEIN-TYPE INEQUALITY AND ITS APPLICATIONS
Institute of Scientific and Technical Information of China (English)
Cao Feilong; Lin Shaobo
2012-01-01
Bernstein inequality played an important role in approximation theory and Fourier analysis.This article first introduces a general system of functions and the socalled multivariate weighted Bernstein,Nikol'skiǐ,and Ul'yanov-type inequalities.Then,the relations among these three inequalities are discussed.Namely,it is proved that a family of functions equipped with Bernstein-type inequality satisfies Nikol'skiǐ-type and Ul'yanov-type inequality.Finally,as applications,some classical inequalities are deduced from the obtained results.
Theory and observations of electrostatic ion waves in the cold Io torus
Barbosa, D. D.; Kurth, W. S.
1990-01-01
A study of the ELF plasma wave environment of the cold Io torus in Jupiter's magnetosphere is made. Voyager 1 data are presented which show three distinct types of electrostatic ion waves occurring there: the Buchsbaum ion-ion mode just below the proton cyclotron frequency f(cp), hydrogen Bernstein modes at (n + 1/2) f(cp), and lower hybrid waves near f(LHR). The presence of these waves at their characteristic frequencies is consistent with a predominantly heavy ion plasma composed of singly ionized sulfur and oxygen ions along with a small admixture of protons. The hydrogen Bernstein modes are tightly confined to the magnetic equator, occurring within + or - 4 deg of it, while the Buchsbaum mode is localized to the dense heavy ion plasma of the cold torus near the centrifugal equator. A general theory for excitation of the waves based on the ion pickup process is developed.
Generating functions for q-Bernstein, q-Meyer-Konig-Zeller and q-Beta basis
Gupta, Vijay; Kim, Taekyun; Choi, Jongsung; Kim, Young-Hee
2010-01-01
The present paper deals with the q-analogue of Bernstein, Meyer-Konig-Zeller and Beta operators. Here we estimate the generating functions for q-Bernstein, q-Meyer-Konig-Zeller and q-Beta basis functions.
Proofs of the Cantor-Bernstein theorem a mathematical excursion
Hinkis, Arie
2013-01-01
This book offers an excursion through the developmental area of research mathematics. It presents some 40 papers, published between the 1870s and the 1970s, on proofs of the Cantor-Bernstein theorem and the related Bernstein division theorem. While the emphasis is placed on providing accurate proofs, similar to the originals, the discussion is broadened to include aspects that pertain to the methodology of the development of mathematics and to the philosophy of mathematics. Works of prominent mathematicians and logicians are reviewed, including Cantor, Dedekind, Schröder, Bernstein, Borel, Zermelo, Poincaré, Russell, Peano, the Königs, Hausdorff, Sierpinski, Tarski, Banach, Brouwer and several others mainly of the Polish and the Dutch schools. In its attempt to present a diachronic narrative of one mathematical topic, the book resembles Lakatos’ celebrated book Proofs and Refutations. Indeed, some of the observations made by Lakatos are corroborated herein. The analogy between the two books is clearly an...
77 FR 75200 - AllianceBernstein Active ETFs, Inc., et al.; Notice of Application
2012-12-19
... COMMISSION AllianceBernstein Active ETFs, Inc., et al.; Notice of Application December 13, 2012. AGENCY...Bernstein Active ETFs, Inc. (``Corporation''), AllianceBernstein L.P. (``Adviser''), and ALPS Distributors... Business Day's NAV and the market closing price or mid-point of the bid/ask spread at the time...
Fu, H.; Scales, W. A.; Bernhardt, P. A.; Samimi, A.; Mahmoudian, A.; Briczinski, S. J.; McCarrick, M. J.
2013-09-01
Results of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power radio waves are reported. These results obtained at the High Frequency Active Auroral Research Program (HAARP) facility specifically considered the generation of Magnetized Stimulated Brillouin Scatter (MSBS) and Stimulated Ion Bernstein Scatter (SIBS) lines in the SEE spectrum when the transmitter frequency is near harmonics of the electron gyrofrequency. The heater antenna beam angle effect was investigated on MSBS in detail and shows a new spectral line postulated to be generated near the upper hybrid resonance region due to ion acoustic wave interaction. Frequency sweeping experiments near the electron gyroharmonics show for the first time the transition from MSBS to SIBS lines as the heater pump frequency approaches the gyroharmonic. Significantly far from the gyroharmonic, MSBS lines dominate, while close to the gyroharmonic, SIBS lines strengthen while MSBS lines weaken. New possibilities for diagnostic information are discussed in light of these new observations.
Pointwise Approximation for the Iterated Boolean Sums of Bernstein Operators
Institute of Scientific and Technical Information of China (English)
HUO Xiao-yan; LI Cui-xiang; YAO Qiu-mei
2013-01-01
In this paper,with the help of modulus of smoothness ω2r(4)(f,t),we discuss the pointwise approximation properties for the iterated Boolean sums of Bernstein operator Bnn and obtain direct and inverse theorems when 1-1/r ≤ λ ≤ 1,r ∈ N.
On -Euler Numbers Related to the Modified -Bernstein Polynomials
Min-Soo Kim; Daeyeoul Kim; Taekyun Kim
2010-01-01
We consider q-Euler numbers, polynomials, and q-Stirling numbers of first and second kinds. Finally, we investigate some interesting properties of the modified q-Bernstein polynomials related to q-Euler numbers and q-Stirling numbers by using fermionic p-adic integrals on ℤp.
Topology of relativistic refractive index surfaces for electron cyclotron waves
International Nuclear Information System (INIS)
The dispersion of electron cyclotron waves in a weakly relativistic Maxwellian plasma is investigated. It is shown that the apparently very complicated picture of the coupling of the extraordinary (X) mode to Bernstein waves can be accounted for in a simple way by considering the refractive indices as Riemann-like surfaces in the Clemmow-Mullaly-Allis (CMA) parameter space, (ωp2/ω2, ωc/ω), and by introducing a few topological concepts from the analysis of complex functions. A detailed study is made of the surface representing the X mode for perpendicular propagation, with special attention given to the connection between this mode and Gross-Bernstein modes. For perpendicular propagation non-transcendental approximations to the relativistic refractive indices for X and O modes can be given. We show that these approximations are good up to ∼ 25 keV and, at frequencies up to the second harmonic of the electron cyclotron frequency, the X mode approximation also accounts correctly for the connection of the X mode to Bernstein modes. The accuracy and the numerical efficiency of the approximations make them well suited for routine calculations for millimetre wave applications in fusion plasmas, including the analysis of X mode and O mode reflectometry. (author)
A laboratory study of breaking waves
Directory of Open Access Journals (Sweden)
Jaros³aw Têgowski
2004-09-01
Full Text Available This paper deals with some aspects of the wave-breaking phenomenon. The objectives were to study wave-breaking criteria, and the probability of whitecap coverage under fully controlled wave conditions. An additional task was to in vestigate the characteristic spectral features of the noise produced by breaking waves and the acoustic energy generated during wave breaking events. A controlled experiment was carried out in the Ocean Basin Laboratory at MARINTEK, Trondheim (Norway. Waves were generated by a computer-controlled multi-flap wave maker, which reproduced a realistic pattern of the sea surface for the prescribed spectra. Using wave staff recordings and photographic techniques, correlations between the breaking parameters and the radiated acoustic emissions were established.
Gravitational-wave Mission Study
Mcnamara, Paul; Jennrich, Oliver; Stebbins, Robin T.
2014-01-01
In November 2013, ESA selected the science theme, the "Gravitational Universe," for its third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has indicated an interest in participating. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA. The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described. Note that all results are based on models, methods and assumptions used in NASA studies
Study on guided waves in semiconductor lasers
International Nuclear Information System (INIS)
In This work we studied the guided waves in semiconductor lasers. In the first part we carried on the experimental measurements on lasers with stripe nonorthogonal to the mirrors. In the second part we developed a matrix method for the study of propagation and reflection of guided waves in lasers. (author)
Solutions of differential equations in a Bernstein polynomial basis
Idrees Bhatti, M.; Bracken, P.
2007-08-01
An algorithm for approximating solutions to differential equations in a modified new Bernstein polynomial basis is introduced. The algorithm expands the desired solution in terms of a set of continuous polynomials over a closed interval and then makes use of the Galerkin method to determine the expansion coefficients to construct a solution. Matrix formulation is used throughout the entire procedure. However, accuracy and efficiency are dependent on the size of the set of Bernstein polynomials and the procedure is much simpler compared to the piecewise B spline method for solving differential equations. A recursive definition of the Bernstein polynomials and their derivatives are also presented. The current procedure is implemented to solve three linear equations and one nonlinear equation, and excellent agreement is found between the exact and approximate solutions. In addition, the algorithm improves the accuracy and efficiency of the traditional methods for solving differential equations that rely on much more complicated numerical techniques. This procedure has great potential to be implemented in more complex systems where there are no exact solutions available except approximations.
Study of detonation wave contours in EFP warhead
Xu-dong Zu; Zheng-xiang Huang; Chuan-sheng Zhu; Qiang-qiang Xiao
2016-01-01
An analytical model for calculating the propagation time of shock wave in a wave shaper is presented in this study. The calculated results show that the contours of three typical detonation waves, such as conical detonation wave, spherical detonation wave, and planar detonation wave, can be formed in the main charge by changing the thickness of wave shaper. The results show that the planar detonation wave do better than the conical detonation and the spherical detonation wave in increasing...
Wave-Turbulence Interactions: a DPIV Study
Lang, Amy; Lalinde, David
1999-11-01
Previous studies on wave-turbulence interactions, such as the one by Olmez & Milgram (JFM, 1992), supported the hypothesis that the dominant mechanism for the dissipation of non-breaking waves by turbulence is vertical mixing, rather than wave-to-turbulence energy transfer in the wave layer. In this study, Digital Particle Image Velocimetry (DPIV) was used to study the increase in turbulence levels due to the presence of surface waves. Two types of turbulent fields were studied. A grid of cylindrical rods was placed in a water tunnel with smaller scale turbulence resulting in the wake of the grid. The second case used a flat plate grid, with the plates aligned parallel to the free-stream flow. This allowed for a range of scales to be generated within the turbulent flow-field in the test section. Next, a wave-generator was placed in the tunnel allowing waves to propagate into the area studied and interact with the grid-generated turbulence. Variation in wavelength and frequency of the surface waves was performed. Results will be presented.
Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1
International Nuclear Information System (INIS)
Electrostatic waves in the ion cyclotron range of frequencies (ICRF) were studied in the Princeton L-4 and ACT-1 devices for approximately ten years, from 1975 to 1985. The investigation began in the L-4 linear device, looking for the parametric excitation of electrostatic ion cyclotron waves in multi-ion-species plasmas. In addition, this investigation verified multi-ion-species effects on the electrostatic ion cyclotron wave dispersion religion including the ion-ion hybrid resonance. Finite-Larmor-radius modification of the wave dispersion relation was also observed, even for ion temperatures of Ti ∼ 1/40 eV. Taking advantage of the relatively high field and long device length of L-4, the existence of the cold electrostatic ion cyclotron wave (CES ICW) was verified. With the arrival of the ACT-1 toroidal device, finite-Larmor-radius (FLR) waves were studied in a relatively collisionless warm-ion hydrogen plasma. Detailed investigations of ion Bernstein waves (IBW) included the verification of mode-transformation in their launching, their wave propagation characteristics, their absorption, and the resulting ion heating. This basic physics activity played a crucial role in developing a new reactor heating concept termed ion Bernstein wave heating. Experimental research in the lower hybrid frequency range confirmed the existence of FLR effects near the lower hybrid resonance, predicted by Stix in 1965. In a neon plasma with a carefully placed phased wave exciter, the neutralized ion Bernstein wave was observed for the first time. Using a fastwave ICRF antenna, two parasitic excitation processes for IBW -- parametric instability and density-gradient-driven excitation -- were also discovered. In the concluding section of this paper, a possible application of externally launched electrostatic waves is suggested for helium ash removal from fusion reactor plasmas
A Numerical Study of Nonlinear Wave Interactions
de Bakker, A.; Tissier, M.; Ruessink, G.
2014-12-01
Nonlinear triad interactions redistribute energy among a wave field, which transforms the shape of the incident short waves (f = 0.05 - 2 Hz) and generates energy at infragravity frequencies (f = 0.005-0.05 Hz). Recently, it has been suggested that infragravity energy may dissipate by energy transfers from infragravity frequencies to either the (former) short-wave spectral peak, or through infragravity-infragravity self-interactions that cause the infragravity waves to steepen and to eventually break. To investigate these infragravity dissipation mechanisms, we use the non-hydrostatic SWASH model. In this study, we first validate the model with the high-resolution GLOBEX laboratory data set and then explore the dependence of the energy transfers, with a focus on infragravity frequencies, on beach slope. Consistent with previous studies we find that SWASH is able to reproduce the transformation and corresponding nonlinear energy transfers of shoreward propagating waves to great detail. Bispectral analysis is used to study the coupling between wave frequencies; nonlinear energy transfers are then quantified using the Boussinesq coupling coefficient. To obtain more detailed insight we divide the nonlinear interactions in four categories based on triads including 1) infragravity frequencies only, 2) two infragravity frequencies and one short-wave frequency, 3) one infragravity frequency and two short-wave frequencies and 4) short-wave frequencies only. Preliminary results suggest that interactions are rather weak on gently beach slopes (1:80) and, in the innermost part of the surf zone, are dominated by infragravity-infragravity interactions. On steeper slopes (1:20), interactions are stronger, but entirely dominated by those involving short-wave frequencies only. The dependence of the transfers on offshore wave conditions and beach shape will be explored too. Funded by NWO.
Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks
DEFF Research Database (Denmark)
Wright, J.C.; Bonoli, P.T.; Brambilla, M.;
2004-01-01
Fast wave (FW) studies of mode conversion (MC) processes at the ion-ion hybrid layer in toroidal plasmas must capture the disparate scales of the FW and mode converted ion Bernstein and ion cyclotron waves. Correct modeling of the MC layer requires resolving wavelengths on the order of k......). Two full wave codes, a massively-parallel-processor (MPP) version of the TORIC-2D finite Larmor radius code [M. Brambilla, Plasma Phys. Controlled Fusion 41, 1 (1999)] and also an all orders spectral code AORSA2D [E. F. Jaeger , Phys. Plasmas 9, 1873 (2002)], have been developed which for the first...... time are capable of achieving the resolution and speed necessary to address mode conversion phenomena in full two-dimensional (2-D) toroidal geometry. These codes have been used in conjunction with theory and experimental data from the Alcator C-Mod [I. H. Hutchinson , Phys. Plasmas 1, 1511 (1994)] to...
Study on Solitary Waves of a General Boussinesq Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, we employ the bifurcation method of dynamical systems to study the solitary waves and periodic waves of a generalized Boussinesq equations. All possible phase portraits in the parameter plane for the travelling wave systems are obtained. The possible solitary wave solutions, periodic wave solutions and cusp waves for the general Boussinesq type fluid model are also investigated.
Bernstein - Von Mises theorem and its application in survival analysis
Czech Academy of Sciences Publication Activity Database
Timková, Jana
2010-01-01
Roč. 22, č. 3 (2010), s. 115-122. ISSN 1210-8022. [16. letní škola JČMF Robust 2010. Králíky, 30.01.2010-05.02.2010] R&D Projects: GA AV ČR(CZ) IAA101120604 Institutional research plan: CEZ:AV0Z10750506 Keywords : Cox model * bayesian asymptotics * survival function Subject RIV: BB - Applied Statistics, Operational Research http://library.utia.cas.cz/separaty/2010/SI/timkova-bernstein - von mises theorem and its application in survival analysis.pdf
Study of wave-particle interaction from the linear regime to dynamical chaos in a magnetized plasma
International Nuclear Information System (INIS)
Deterministic chaos generated by the interaction between charged particles and electrostatic plasma waves has been observed in a linear magnetized plasma. The target plasma is created by a barium Q-source, guaranteeing low fluctuation levels and a high degree of uniformity over an extended plasma volume. Characteristics of the background plasma are investigated by a variety of diagnostic techniques, including laser induced fluorescence (LIF) and optical tagging (OT). Particular tagging schemes and specific theoretical approaches to data interpretation (both for LIF and OT) have been developed during this work. As part of these background plasma studies, special attention has been devoted to an investigation of test-ion cross-field transport under different conditions. Test-ions are created and followed in their motion across the magnetic field lines via spin state tagging. In the unperturbed plasma this motion is found to be a diffusive process, supported by classical mechanisms, even in the presence of relatively high pressures of non-reactive neutral gases injected into the plasma volume. Electrostatic waves are excited using a ring antenna structure encircling the plasma column and electrically isolated from it. This system has been chosen on the basis of a comparative analysis of different ion wave launching methods, including the use of grids, inductive coils coupled electromagnetically to the plasma and modulated high frequency electron waves. Two modes propagating parallel to the magnetic field, one of which has two perpendicular components (ion Bernstein and ion acoustic-like waves), characterize the spectrum excited by the electrostatic ring antenna for a single frequency, f, chosen in the range fcici. (author) figs., tabs., 134 refs
Brian Davies
2003-01-01
Neste texto o autor procura elucidar o modo pelo qual Basil Bernstein utilizou e enriqueceu a contribuição de Durkheim para a análise de questões abordadas pela sociologia da educação.The author attempts to elucidate how Basil Bernstein used and enhanced Durkheim's contribution to the analysis of issues addressed by the sociology of education.
Wave particle interactions in the high-altitude polar cusp: a Cluster case study
Directory of Open Access Journals (Sweden)
B. Grison
2005-12-01
Full Text Available On 23 March 2002, the four Cluster spacecraft crossed in close configuration (~100 km separation the high-altitude (10 R_{E} cusp region. During a large part of the crossing, the STAFF and EFW instruments have detected strong electromagnetic wave activity at low frequencies, especially when intense field-aligned proton fluxes were detected by the CIS/HIA instrument. In all likelihood, such fluxes correspond to newly-reconnected field lines. A focus on one of these ion injection periods highlights the interaction between waves and protons. The wave activity has been investigated using the k-filtering technique. Experimental dispersion relations have been built in the plasma frame for the two most energetic wave modes. Results show that kinetic Alfvén waves dominate the electromagnetic wave spectrum up to 1 Hz (in the spacecraft frame. Above 0.8 Hz, intense Bernstein waves are also observed. The close simultaneity observed between the wave and particle events is discussed as an evidence for local wave generation. A mechanism based on current instabilities is consistent with the observations of the kinetic Alfvén waves. A weak ion heating along the recently-opened field lines is also suggested from the examination of the ion distribution functions. During an injection event, a large plasma convection motion, indicative of a reconnection site location, is shown to be consistent with the velocity perturbation induced by the large-scale Alfvén wave simultaneously detected.
Numerical Study on the Influence of Different Waving Bottom Form on the Fluid Surface Wave
Directory of Open Access Journals (Sweden)
Yongxin Zhu
2013-05-01
Full Text Available In the present study, the effect of waving bottom on the surface wave is studied. Basing on the fundamental equations of potential flow theory and boundary conditions, using the multiple scales perturbation method to derive the first-order and the second-order approximate equation which the fluid surface waves satisfied in the presence of waving bottom. Under the second-order approximation, the fluid surface waveform in first-order approximate equation is numerically simulated with MATLAB in the presence of different waving bottom form. The results show that: the fluid surface waveform is composed of a harmonic wave which has the same frequency with waving bottom and a pair of KdV solitary waves that spread to both the right and the left side when the waving bottom wave is a harmonic wave; and when the waving bottom is a solitary wave packet, it consists of a solitary wave which is closely related to the specific form of waving bottom and a couple of KdV solitary waves. With the development of time, three waves in fluid surface do not affect each other and they propagate independently. Thus it can be seen the waving bottom is effective for maintaining surface wave energy balance income and expenditure in the spreading process.
Effective action approach to wave propagation in scalar QED plasmas
Shi, Yuan; Qin, Hong
2016-01-01
A relativistic quantum field theory with nontrivial background fields is developed and applied to study waves in plasmas. The effective action of the electromagnetic 4-potential is calculated ab initio from the standard action of scalar QED using path integrals. The resultant effective action is gauge invariant and contains nonlocal interactions, from which gauge bosons acquire masses without breaking the local gauge symmetry. To demonstrate how the general theory can be applied, we study a cold unmagnetized plasma and a cold uniformly magnetized plasma. Using these two examples, we show that all linear waves well-known in classical plasma physics can be recovered from relativistic quantum results when taking the classical limit. In the opposite limit, classical wave dispersion relations are modified substantially. In unmagnetized plasmas, longitudinal waves propagate with nonzero group velocities even when plasmas are cold. In magnetized plasmas, anharmonically spaced Bernstein waves persist even when plasma...
Experimental Study of Wave Breaking on Gentle Slope
Institute of Scientific and Technical Information of China (English)
2000-01-01
－An experimental study of regular wave and irregular wave breaking is performed on a gentle slope of 1:200. In the experiment, asymmetry of wave profile is analyzed to determine its effect on wave breaker indices and to explain the difference between Goda and Nelson about the breaker indices of regular waves on very mild slopes. The study shows that the breaker index of irregular waves is under less influence of bottom slope i, relative water depth d/ L0 and the asymmetry of wave profile than that of regular waves. The breaker index of regular waves from Goda may be used in the case of irregular waves, while the coefficient A should be 0.15. The ratio of irregular wavelength to the length calculated by linear wave theory is 0.74. Analysis is also made on the waveheight damping coefficient of regular waves after breaking and on the breaking probability of large irregular waves.
Alfven wave studies on a tokamak
International Nuclear Information System (INIS)
The continuum modes of the shear Alfven resonance are studied on the Tokapole II device, a small tokamak operated in a four node poloidal divertor configuration. A variety of antenna designs and the efficiency with which they deliver energy to the resonant layer are discussed. The spatial structure of the driven waves is studied by means of magnetic probes inserted into the current channel. In an attempt to optimize the coupling of energy in to the resonant layer, the angle of antenna currents with respect to the equilibrium field, antenna size, and plasma-to-antenna distance are varied. The usefulness of Faraday shields, particle shields, and local limiters are investigated. Antennas should be well shielded, either a dense Faraday shield or particle shield being satisfactory. The antenna should be large and very near to the plasma. The wave magnetic fields measured show a spatial resonance, the position of which varies with the value of the equilibrium field and mass density. They are polarized perpendicular to the equilibrium field. A wave propagates radially in to the resonant surface where it is converted to the shear Alfven wave. The signal has a short risetime and does not propagate far toroidally. These points are all consistent with a strongly damped shear Alfven wave. Comparisons of this work to theoretical predictions and results from other tokamaks are made
Mešic, Vanes; Hajder, Erna; Neumann, Knut; Erceg, Nataša
2016-01-01
Research has shown that students have tremendous difficulties developing a qualitative understanding of wave optics, at all educational levels. In this study, we investigate how three different approaches to visualizing light waves affect students' understanding of wave optics. In the first, the conventional, approach light waves are represented…
Significance of blast wave studies to propulsion.
Oppenheim, A. K.
1971-01-01
Brief survey of experimental methods currently used for the study of blast wave phenomena with emphasis on high rate exothermic processes. The experimental techniques have used such devices as divergent test sections in shock or detonation tubes, employment of proper test gases, as in marginal detonations, and a variety of explosion systems from finite source explosion apparatus to devices where virtually point explosions are obtained by local breakdown initiated by means of focused laser irradiation. Other methods used are detonation tubes where pressure waves are generated by accelerating flames or by exothermic reactions developed behind reflected shocks, as well as a variety of converging shock and implosion vessels.
$L^p$ Bernstein Inequalities and Inverse Theorems for RBF Approximation on $\\mathbb{R}^d$
Ward, John Paul
2010-01-01
Bernstein inequalities and inverse theorems are a recent development in the theory of radial basis function(RBF) approximation. The purpose of this paper is to extend what is known by deriving $L^p$ Bernstein inequalities for RBF networks on $\\mathbb{R}^d$. These inequalities involve bounding a Bessel-potential norm of an RBF network by its corresponding $L^p$ norm in terms of the separation radius associated with the network. The Bernstein inequalities will then be used to prove the corresponding inverse theorems.
External wave-launcher study. Final report
International Nuclear Information System (INIS)
The rationale for liquid dielectrically-loaded external wave-guide launchers is discussed. The arguments are strongly indicative that a liquid dielectric-filled waveguide system could be a practical technique for launching ICRH power into a fusion reactor. A detailed summary of the work performed in the study is presented
A teoria de Basil Bernstein: alguns aspectos fundamentais
Directory of Open Access Journals (Sweden)
Ana Maria Morais
2007-12-01
Full Text Available The article begins with a reference to the pieces of work that Basil Bernstein considered to have been the landmarks of the evolution of his thought. This is followed by a detailed description of the two models that contain the main concepts of his theory – Model of Cultural Reproduction and Transformation and Model of Pedagogic Discourse – where the theoretical meaning of these models and concepts is explained and where are given some examples of how to put them into practice at the level of pedagogic texts and contexts. The article also includes the most recent developments of Bernstein’s thought by explaining his ideas about the forms discourses can take – Vertical and Horizontal Discourses. Finally, Bernstein’s theory is approached within the framework of the empirical research, highlighting his epistemological positioning and explicating the methodological model that he suggested should be the driving force of any theory.
Experimental Study on the Langlee Wave Energy Converter
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter; Weisz, A.
This report presents the results of an experimental study of the wave energy converting abilities of the Langlee wave energy converter (WEC). It focused mainly on evaluating the power generating capabilities of the device, including investigations of the following issues: Scaling ratiosPTO loading......Wave height and wave period dependencyOblique incoming waves and directional spreading of waves (3D waves)Damping platesMooring forces and fixed structure setupPitch, surge and heave motion During the study the model supplied by the client (Langlee Wave Power AS) has been heavily instrumented - up to 23...
CFD study of the overtopping discharge of the Wave Dragon wave energy converter
DEFF Research Database (Denmark)
Eskilsson, K.; Palm, J.; Kofoed, Jens Peter;
2015-01-01
The Wave Dragon is a floating Wave Energy Converter (WEC) working by the overtopping principle. The overtopping discharge has been determined by model scale experiments in wave basins. In the present study we numerically simulate the overtopping behavior of the Wave Dragon device using a VOFbased...... incompressible Euler/Navier-Stokes solver in the OpenFOAM® framework. We present simulations of: (i) a complete sea state for different crest heights, and (ii) regular waves for different wave conditions and crest heights. The simulations compare reasonably well with the experimental data, albeit the irregular...... wave simulations predict a larger overtopping discharge than observed in the experiments....
Numerical method of studying nonlinear interactions between long waves and multiple short waves
International Nuclear Information System (INIS)
Although the nonlinear interactions between a single short gravity wave and a long wave can be solved analytically, the solution is less tractable in more general cases involving multiple short waves. In this work we present a numerical method of studying nonlinear interactions between a long wave and multiple short harmonic waves in infinitely deep water. Specifically, this method is applied to the calculation of the temporal and spatial evolutions of the surface elevations in which a given long wave interacts with several short harmonic waves. Another important application of our method is to quantitatively analyse the nonlinear interactions between an arbitrary short wave train and another short wave train. From simulation results, we obtain that the mechanism for the nonlinear interactions between one short wave train and another short wave train (expressed as wave train 2) leads to the energy focusing of the other short wave train (expressed as wave train 3). This mechanism occurs on wave components with a narrow frequency bandwidth, whose frequencies are near that of wave train 3. (geophysics, astronomy and astrophysics)
q-Bernstein polynomials, q-Stirling numbers and q-Bernoulli polynomials
Kim, T.
2010-01-01
In this paper, we give new identities involving Phillips q-Bernstein polynomials and we derive some interesting properties of q-Berstein polynomials associated with q-Stirling numbers and q-Bernoulli polynomials.
Directory of Open Access Journals (Sweden)
Ryoo CS
2010-01-01
Full Text Available The purpose of this paper is to give some properties of several Bernstein type polynomials to represent the fermionic -adic integral on . From these properties, we derive some interesting identities on the Euler numbers and polynomials.
Bernstein dual-Petrov-Galerkin method: application to 2D time fractional diffusion equation
Jani, Mostafa; Babolian, Esmail
2016-01-01
In this paper, we develop a dual-Petrov-Galerkin method using Bernstein polynomials. The method is then implemented for the numerical simulation of the two-dimensional subdiffusion equation. The method is based on a finite difference discretization in time and a spectral method in space utilizing a suitable compact combinations of dual Bernstein basis as the test functions and the Bernstein polynomials as the trial ones. We derive the exact sparse operational matrix of differentiation for the dual Bernstein basis which provides a matrix-based approach for spatial discretization of the problem. It is also shown that the proposed method leads to banded linear systems. Finally some numerical examples are provided to show the efficiency and accuracy of the method.
Solution of the Lane-Emden Equation Using the Bernstein Operational Matrix of Integration
Narayan Kumar; Pandey, Rajesh K.; Carlo Cattani
2011-01-01
Lane-Emden's equation has fundamental importance in the recent analysis of many problems in relativity and astrophysics including some models of density profiles for dark matter halos. An efficient numerical method is presented for linear and nonlinear Lane-Emden-type equations using the Bernstein polynomial operational matrix of integration. The proposed approach is different from other numerical techniques as it is based on the Bernstein polynomial integration matrix. Some illustrative exam...
Analytical study of dissipative solitary waves
Energy Technology Data Exchange (ETDEWEB)
Dini, Fatemeh [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Emamzadeh, Mehdi Molaie [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Khorasani, Sina [School of Electrical Engineering, Sharif University of Technology, PO Box 11365-363, Tehran (Iran, Islamic Republic of); Bobin, Jean Louis [Universite Pierre et Marie Curie, Paris (France); Amrollahi, Reza [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Sodagar, Majid [School of Electrical Engineering, Sharif University of Technology, PO Box 11365-363, Tehran (Iran, Islamic Republic of); Khoshnegar, Milad [School of Electrical Engineering, Sharif University of Technology, PO Box 11365-363, Tehran (Iran, Islamic Republic of)
2008-02-15
In this paper, the analytical solution to a new class of nonlinear solitons is presented with cubic nonlinearity, subject to a dissipation term arising as a result of a first-order derivative with respect to time, in the weakly nonlinear regime. Exact solutions are found using the combination of the perturbation and Green's function methods up to the third order. We present an example and discuss the asymptotic behavior of the Green's function. The dissipative solitary equation is also studied in the phase space in the non-dissipative and dissipative forms. Bounded and unbounded solutions of this equation are characterized, yielding an energy conversation law for non-dissipative waves. Applications of the model include weakly nonlinear solutions of terahertz Josephson plasma waves in layered superconductors and ablative Rayleigh-Taylor instability.
Analytical study of dissipative solitary waves
International Nuclear Information System (INIS)
In this paper, the analytical solution to a new class of nonlinear solitons is presented with cubic nonlinearity, subject to a dissipation term arising as a result of a first-order derivative with respect to time, in the weakly nonlinear regime. Exact solutions are found using the combination of the perturbation and Green's function methods up to the third order. We present an example and discuss the asymptotic behavior of the Green's function. The dissipative solitary equation is also studied in the phase space in the non-dissipative and dissipative forms. Bounded and unbounded solutions of this equation are characterized, yielding an energy conversation law for non-dissipative waves. Applications of the model include weakly nonlinear solutions of terahertz Josephson plasma waves in layered superconductors and ablative Rayleigh-Taylor instability
Numerical and experimental study of blast wave shape in tunnels
Pennetier, Olivier; Langlet, André; William-Louis, Mame J.-P.
2012-01-01
When an explosion occurs in a tunnel, the study of the blast wave quickly becomes complicated, due to the multiple propagation patterns of the blast wave (Incident wave, regular and Mach reflections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, one can see the well known free-field pressure wave. This overpressure, during its propagation, after multiple reflections on the tunnel's walls, can behave like a one-dimensional wave. ...
Experimental study of three-wave interactions among capillary-gravity surface waves
Haudin, Florence; Deike, Luc; Jamin, Timothée; Falcon, Eric; Berhanu, Michael
2016-01-01
In propagating wave systems, three or four-wave resonant interactions constitute a classical non-linear mechanism exchanging energy between the different scales. Here we investigate three-wave interactions for gravity-capillary surface waves in a closed laboratory tank. We generate two crossing wave-trains and we study their interaction. Using two optical methods, a local one (Laser Doppler Vibrometry) and a spatio-temporal one (Diffusive Light Photography), a third wave of smaller amplitude is detected, verifying the three-wave resonance conditions in frequency and in wavenumber. Furthermore, by focusing on the stationary regime and by taking into account viscous dissipation, we directly estimate the growth rate of the resonant mode. The latter is then compared to the predictions of the weakly non-linear triadic resonance interaction theory. The obtained results confirm qualitatively and extend previous experimental results obtained only for collinear wave-trains. Finally, we discuss the relevance of three-w...
MALDI-TOF Baseline Drift Removal Using Stochastic Bernstein Approximation
Directory of Open Access Journals (Sweden)
Howard Daniel
2006-01-01
Full Text Available Stochastic Bernstein (SB approximation can tackle the problem of baseline drift correction of instrumentation data. This is demonstrated for spectral data: matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF data. Two SB schemes for removing the baseline drift are presented: iterative and direct. Following an explanation of the origin of the MALDI-TOF baseline drift that sheds light on the inherent difficulty of its removal by chemical means, SB baseline drift removal is illustrated for both proteomics and genomics MALDI-TOF data sets. SB is an elegant signal processing method to obtain a numerically straightforward baseline shift removal method as it includes a free parameter that can be optimized for different baseline drift removal applications. Therefore, research that determines putative biomarkers from the spectral data might benefit from a sensitivity analysis to the underlying spectral measurement that is made possible by varying the SB free parameter. This can be manually tuned (for constant or tuned with evolutionary computation (for .
Institute of Scientific and Technical Information of China (English)
李翠香; 任孟霞
2007-01-01
本文利用光滑模及最佳逼近多项式的性质,研究了Bernstein-Kantorovich算子的迭代布尔和对Lp[0,1]中的函数的逼近性质,得到了逼近正定理,弱逆不等式及等价定理.
A statistical study of EMIC waves observed by Cluster: 1. Wave properties
Allen, R. C.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.; Lin, R.-L.; Klecker, B.; Dunlop, M. W.; André, M.; Jordanova, V. K.
2015-07-01
Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the occurrence rate, wave power, ellipticity, normal angle, energy propagation angle distributions, and local plasma parameters are required. Previous statistical studies have used in situ observations to investigate the distribution of these parameters in the magnetic local time versus L-shell (MLT-L) frame within a limited magnetic latitude (MLAT) range. In this study, we present a statistical analysis of EMIC wave properties using 10 years (2001-2010) of data from Cluster, totaling 25,431 min of wave activity. Due to the polar orbit of Cluster, we are able to investigate EMIC waves at all MLATs and MLTs. This allows us to further investigate the MLAT dependence of various wave properties inside different MLT sectors and further explore the effects of Shabansky orbits on EMIC wave generation and propagation. The statistical analysis is presented in two papers. This paper focuses on the wave occurrence distribution as well as the distribution of wave properties. The companion paper focuses on local plasma parameters during wave observations as well as wave generation proxies.
Supplementary report: millimeter wave study program
International Nuclear Information System (INIS)
This report describes work done during the months of December 1975 and January 1976, following the writing of the final report on the millimeter wave study program for generation of 100 kW or more power at 120 GHz. The work has been directed to three areas for application to gyrotron devices, small signal analysis, electron beam simulation, and microwave measurements on cavity coupling. A small signal analysis is presented, which allows determination of beam loading in cavities. The results are similar to previous published work, but contain a higher order relativistic correction. The electron beam simulations include two magnetron type guns and one based on electrostatic lenses
The study on the guided wave attention predicted from waves structure
International Nuclear Information System (INIS)
The key in the success of guided wave NDE is how to optimize the mode selection scheme by minimizing energy loss when a structure is in contact with liquid. In this study, the normalized out-of-plane displacements at the surface if a free plate are used to predict the variation of modal attenuation and verify the correlation between attenuation and wave structure. It turns out that the guided wave attenuation can be efficiently obtain from the out-of-plane displacement variation of a free wave guide alleviating such mathematical difficulties in extracting complex roots for the eigenvalue problem of a liquid loaded wave guide.
Experimental Study on the Langlee Wave Energy Converter
DEFF Research Database (Denmark)
Lavelle, John; Kofoed, Jens Peter
This report concerns the experimental study of the 1:20 scale model of the Langlee Wave Energy Converter (WEC) carried out at Aalborg University’s wave basin during the summer of 2010.......This report concerns the experimental study of the 1:20 scale model of the Langlee Wave Energy Converter (WEC) carried out at Aalborg University’s wave basin during the summer of 2010....
PIC Simulations of the Ion Flow Induced by Radio Frequency Waves in Ion Cyclotron Frequency Range
International Nuclear Information System (INIS)
Full text: PIC simulations have been conducted to study the nonlinear interactions of plasmas and radio frequency wave in the ion cyclotron frequency range. It is found that in the presence of the mode conversion from an electromagnetic wave into an electrostatic wave (ion Bernstein wave), the ions near the lower hybrid resonance can be heated by nonlinear Landau damping via the parametric decay. As a result, the ion velocity distribution in the poloidal direction becomes asymmetric near the lower hybrid resonance and an ion poloidal flow is thus produced. The flow directions are opposite on both sides of the lower hybrid resonance. The poloidal flow is mainly produced by the nonlinear Reynolds stress and the electromagnetic force of the incident wave in the radial direction rather than poloidal direction predicted by the existing theories. (author)
A case study of gravity waves in noctilucent clouds
Directory of Open Access Journals (Sweden)
P. Dalin
2004-06-01
Full Text Available We present a case study of a noctilucent cloud (NLC display appearing on 10-11 August 2000 over Northern Sweden. Clear wave structures were visible in the clouds and time-lapse photography was used to derive the parameters characterising the gravity waves which could account for the observed NLC modulation. Using two nearby atmospheric radars, the Esrange MST Radar data and Andoya MF radar, we have identified gravity waves propagating upward from the upper stratosphere to NLC altitudes. The wave parameters derived from the radar measurements support the suggestion that gravity waves are responsible for the observed complex wave dynamics in the NLC.
Experimental study of three-wave interactions among capillary-gravity surface waves
Haudin, Florence; Cazaubiel, Annette; Deike, Luc; Jamin, Timothée; Falcon, Eric; Berhanu, Michael
2016-04-01
In propagating wave systems, three- or four-wave resonant interactions constitute a classical nonlinear mechanism exchanging energy between the different scales. Here we investigate three-wave interactions for gravity-capillary surface waves in a closed laboratory tank. We generate two crossing wave trains and we study their interaction. Using two optical methods, a local one (laser doppler vibrometry) and a spatiotemporal one (diffusive light photography), a third wave of smaller amplitude is detected, verifying the three-wave resonance conditions in frequency and in wave number. Furthermore, by focusing on the stationary regime and by taking into account viscous dissipation, we directly estimate the growth rate of the resonant mode. The latter is then compared to the predictions of the weakly nonlinear triadic resonance interaction theory. The obtained results confirm qualitatively and extend previous experimental results obtained only for collinear wave trains. Finally, we discuss the relevance of three-wave interaction mechanisms in recent experiments studying gravity-capillary turbulence.
Computational and theoretical study of the wave-particle interaction of protons and waves
Energy Technology Data Exchange (ETDEWEB)
Moya, P.S.; Munoz, V. [Chile Univ., Santiago (Chile). Dept. de Fisica; Vinas, A.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Heliophysics Science Div.; Valdivia, J.A. [Chile Univ., Santiago (Chile). Dept. de Fisica; Centro para el Desarrollo de la Nanociencia y Nanotecnologia, CEDENNA (Chile); CEIBA complejidad, Bogota (Colombia)
2012-11-01
We study the wave-particle interaction and the evolution of electromagnetic waves propagating through a plasma composed of electrons and protons, using two approaches. First, a quasilinear kinetic theory has been developed to study the energy transfer between waves and particles, with the subsequent acceleration and heating of protons. Second, a one-dimensional hybrid numerical simulation has been performed, with and without including an expanding-box model that emulates the spherical expansion of the solar wind, to investigate the fully nonlinear evolution of this wave-particle interaction. Numerical results of both approaches show that there is an anisotropic evolution of proton temperature. (orig.)
Plane shock wave studies of geologic media
International Nuclear Information System (INIS)
Plane shock wave experiments have been conducted on eight geologic materials in an effort to determine the importance of time-dependent mechanical behavior. Of the eight rocks studied, only Westerly granite and nugget sandstone appear to show time independence. In the slightly porous materials (1-5 percent), Blair dolomite and sodium chloride, and in the highly porous (15 to 40 percent) rock, Mt. Helen tuff and Indiana limestone, time-dependent behavior is associated with the time required to close the available porosity. In water-saturated rocks the time dependence arises because the water that is present shows no indication of transformation to the higher pressure ice phases, thus suggesting the possibility that a metastable form of water exists under dynamic conditions
Study of high Mach number laser driven blast waves
International Nuclear Information System (INIS)
The study of blast waves produced by intense lasers in gases is motivated by the desire to explore astrophysically relevant hydrodynamic phenomena in the laboratory. A systematic scan of laser produced blast waves was performed and the structure of blast waves was examined over a wide range of drive laser energy. Lasers with energies ranging from 10-1000 J illuminated a pin target in either xenon or nitrogen gas, creating a spherical blast wave. A strongly radiating blast wave in xenon gas is observed while blast waves in nitrogen more closely approximate a pure Taylor-Sedov wave. It is also found that at all laser energies, blast waves traveling through xenon gas had their hydrodynamic evolution significantly affected by the passage of illumination laser
Wave Energy Study in China: Advancements and Perspectives
Institute of Scientific and Technical Information of China (English)
游亚戈; 郑永红; 沈永明; 吴必军; 刘荣
2003-01-01
The history and current status of research and development of wave energy in the world is briefly introduced. The main problems existing in these studies are pointed out. The description is focused on the current status and the advancements achieved in China. After analysis of the wave energy resources and practical situations in China, it is pointed out that the studies on wave energy should be not only concentrated on the conversion efficiency and costs of wave energy devices, but also focused on the technology of independent operation and stable output of electricity. Finally, the perspectives of application of wave energy in China are discussed.
Ng, C. S.; Soundararajan, S. J.; Yasin, E.
2012-05-01
Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region, and in association with shocks, turbulence, and magnetic reconnection. Due to potentially large amplitude of electric fields within these structures, their effects on particle heating, scattering, or acceleration can be important. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. BGK modes have been studied extensively for many decades, predominately in one dimension (1D), although there have been observations showing that some of these structures have clear 3D features. While there have been approximate solutions of higher dimensional BGK modes, an exact 3D BGK mode solution in a finite magnetic field has not been found yet. Recently we have constructed exact solutions of 2D BGK modes in a magnetized plasma with finite magnetic field strength in order to gain insights of the ultimate 3D theory [Ng, Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)]. Based on the analytic form of these solutions, as well as Particle-in-Cell (PIC) simulations, we will present numerical studies of their stability for different levels of background magnetic field strength.
A critique of Bernstein's beyond objectivism and relativism: science, hermeneutics, and praxis.
Matusitz, Jonathan; Kramer, Eric
2011-06-01
This analysis comments on Bernstein's lack of clear understanding of subjectivity, based on his book, Beyond Objectivism and Relativism: Science, Hermeneutics, and Praxis. Bernstein limits his interpretation of subjectivity to thinkers such as Gadamer and Habermas. The authors analyze the ideas of classic scholars such as Edmund Husserl and Friedrich Nietzsche. Husserl put forward his notion of transcendental subjectivity and phenomenological ramifications of the relationship between subjectivity and objectivity. Nietzsche referred to subjectivity as "perspectivism," the inescapable fact that any and all consciousnesses exist in space and time. Consciousness is fundamentally constituted of cultural, linguistic, and historical dimensions. PMID:21874130
Approximation and Shape Preserving Properties of the Bernstein Operator of Max-Product Kind
Directory of Open Access Journals (Sweden)
Barnabás Bede
2009-01-01
question of improving the order of approximation 1√(;1/ is raised. The first aim of this note is to obtain this order of approximation but by a simpler method, which in addition presents, at least, two advantages: it produces an explicit constant in front of 1√(;1/ and it can easily be extended to other max-prod operators of Bernstein type. However, for subclasses of functions including, for example, that of concave functions, we find the order of approximation 1(;1/, which for many functions is essentially better than the order of approximation obtained by the linear Bernstein operators. Finally, some shape-preserving properties are obtained.
Hilbert series of graded Milnor algebras and roots of Bernstein-Sato polynomials
Saito, Morihiko
2015-01-01
We show that there is a pair of homogeneous polynomials such that the sets of roots of their Bernstein-Sato polynomials which are strictly supported at the origin are different although the sets of roots which are not strictly supported at the origin are the same and moreover their graded Milnor algebras have the same Hilbert series. This shows that the roots of the Bernstein-Sato polynomials strictly supported at the origin cannot be determined uniquely by the Hilbert series of the Milnor al...
Wave refraction studies off Agonda beach (Goa)
Digital Repository Service at National Institute of Oceanography (India)
Krishnakumar, V.; Pathak, M.C.; Kotnala, K.L.
Analysis of wave refraction and longshore current has been carried out for a narrow strip off the shores of Agonda (Goa, India). Zones with high wave energy and rip currents have been demarcated. It is found from the analysis that the southern part...
NASA's Gravitational - Wave Mission Concept Study
Stebbins, Robin; Jennrich, Oliver; McNamara, Paul
2012-01-01
With the conclusion of the NASA/ESA partnership on the Laser Interferometer Space Antenna (LISA) Project, NASA initiated a study to explore mission concepts that will accomplish some or all of the LISA science objectives at lower cost. The Gravitational-Wave Mission Concept Study consisted of a public Request for Information (RFI), a Core Team of NASA engineers and scientists, a Community Science Team, a Science Task Force, and an open workshop. The RFI yielded were 12 mission concepts, 3 instrument concepts and 2 technologies. The responses ranged from concepts that eliminated the drag-free test mass of LISA to concepts that replace the test mass with an atom interferometer. The Core Team reviewed the noise budgets and sensitivity curves, the payload and spacecraft designs and requirements, orbits and trajectories and technical readiness and risk. The Science Task Force assessed the science performance by calculating the horizons. the detection rates and the accuracy of astrophysical parameter estimation for massive black hole mergers, stellar-mass compact objects inspiraling into central engines. and close compact binary systems. Three mission concepts have been studied by Team-X, JPL's concurrent design facility. to define a conceptual design evaluate kt,y performance parameters. assess risk and estimate cost and schedule. The Study results are summarized.
NASA's Gravitational-Wave Mission Concept Study
Stebbins, Robin; Jennrich, Oliver; McNamara, Paul
2012-07-01
With the conclusion of the NASA/ESA partnership on the Laser interferometer Space Antenna (LISA) Project, NASA initiated a study to explore mission concepts that will accomplish some or all of the LISA science objectives at lower cost. The Gravitational-Wave Mission Concept Study consisted of a public Request for Information (RFI), a Core Team of NASA engineers and scientists, a Community Science Team, a Science Task Force, and an open workshop. The RFI yielded were 12 mission concepts, 3 instrument concepts and 2 technologies. The responses ranged from concepts that eliminated the drag-free test mass of LISA to concepts that replace the test mass with an atom interferometer. The Core Team reviewed the noise budgets and sensitivity curves, the payload and spacecraft designs and requirements, orbits and trajectories and technical readiness and risk. The Science Task Force assessed the science performance by calculating the horizons, the detection rates and the accuracy of astrophysical parameter estimation for massive black hole mergers, stellar-mass compact objects inspiraling into central engines, and close compact binary systems. Three mission concepts have been studied by Team-X, JPL's concurrent design facility, to define a conceptual design, evaluate key performance parameters, assess risk and estimate cost and schedule. The Study results are summarized.
Moon, Keun Bai; Lim, Go San; Hwang, Jae Seung; Lim, Chae Hong; Lee, Jae Won; Son, Jeong Hwan; Jang, Seok Heun
2012-01-01
Purpose We aimed to compare the effects of a fast shock wave rate (120 shocks per minute) and a slow shock wave rate (60 shocks per minute) on the shock wave lithotripsy (SWL) success rate, patient's pain tolerance, and complications. Materials and Methods A total of 165 patients with radiopaque renal pelvis or upper ureter stones were included in the study. Patients were classified by use of a random numbers table. Group I (81 patients) received 60 shock waves per minute and group II (84 pat...
Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock
Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.
2010-01-01
We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.
Asymmetry of wind waves studied in a laboratory tank
Ileykin, L. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.
1995-03-01
Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.
Asymmetry of wind waves studied in a laboratory tank
Directory of Open Access Journals (Sweden)
I. A. Leykin
1995-01-01
Full Text Available Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves. At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976. The phase shift between o. harmonics is found and shown to increase with the asymmetry of the waves.
Wave propagation and absorption near the electron-cyclotron layer in the 'THOR' device
International Nuclear Information System (INIS)
The wave propagation and absorption near the electron-cyclotron frequency in a plasma with parameters as expected in the THOR device are considered. Both the ordinary and extraordinary modes are found to be only weakly damped by cyclotron damping. The extraordinary mode launched from the inside of the torus is expected to be completely absorbed at the electron-cyclotron layer via the Bernstein mode generated by mode conversion at the upper-hybrid layer. This study is preliminary to the application of high frequency microwave radiation to plasma heating near the electron-cyclotron frequency in THOR
Asymmetry of wind waves studied in a laboratory tank
Leykin, I. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.
1995-01-01
Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determi...
Mešić, Vanes; Hajder, Erna; Neumann, Knut; Erceg, Nataša
2016-06-01
Research has shown that students have tremendous difficulties developing a qualitative understanding of wave optics, at all educational levels. In this study, we investigate how three different approaches to visualizing light waves affect students' understanding of wave optics. In the first, the conventional, approach light waves are represented by sinusoidal curves. The second teaching approach includes representing light waves by a series of static images, showing the oscillating electric field vectors at characteristic, subsequent instants of time. Within the third approach phasors are used for visualizing light waves. A total of N =85 secondary school students were randomly assigned to one of the three teaching approaches, each of which lasted a period of four class hours. Students who learned with phasors and students who learned from the series of static images outperformed the students learning according to the conventional approach, i.e., they showed a much better understanding of basic wave optics, as measured by a conceptual survey administered to the students one week after the treatment. Our results suggest that visualizing light waves with phasors or oscillating electric field vectors is a promising approach to developing a deeper understanding of wave optics for students enrolled in conceptual level physics courses.
Directory of Open Access Journals (Sweden)
Jong-In Lee
2014-01-01
Full Text Available Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r2>0.8 the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A0/h0<0.07 in this study. However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification.
Experimental studies of lower hybrid wave propagation
International Nuclear Information System (INIS)
Experimental measurements of the dispersion and damping of externally excited lower hybrid waves are presented. A multiple-ring slow-wave antenna, having 2π/k/sub z/ = 23 cm, is used to excite these waves in the Princeton L3 or L4 linear devices (B = 0.5 -- 2.8 kG uniform to +- 1 percent for 1.6 m, n approximately 1010, T/sub e/ approximately 3-5 eV, T/sub i/ less than or equal to 0.1 eV, He gas, plasma diameter approximately 10 cm). The waves are localized in a spatial wave packet that propagates into the plasma along a conical trajectory which makes a small angle with respect to the confining magnetic field. Measurements of the dependence of wavelength on frequency are in good agreement with the cold plasma dispersion relation. Measured values of the wave damping are in good agreement with Landau damping by the combination of the main body of the electron distribution and a approximately 30 percent high energy (T/sub e/ approximately 15-30 eV) electron tail
Studies on the parametric decay of waves in fusion plasmas
International Nuclear Information System (INIS)
Parametric instabilities of large-amplitude electromagnetic waves are investigated in fusion applications. In laser fusion, the electromegnetic wave reflected from the overdense plasma can act as a secondary pump wave and exite parametric instabilities. In double simulated Brilloun scattering (DSBS), both the incoming and the reflected pump wave scatter from a common ion sound wave. The stationary states and the dynamics of DSBS are investigated by using a simple envelope model. The ion sound wave that is exited in DSBS is shown to have soliton-like properties. The simulated Raman scattering (SRS) of free-electron-laser radiation can be applied to current drive in tokamaks. SRS generates fast longitudinal electron plasma waves which accelerate electrons to relativistic energies. Since the energetic current-carrying electrons are almost collisionless, the current decays very slowly. The feasibility of the Raman current drive in tokamaks is investigated theoretically. The current drive efficiency and the optimum free-electron-laser parameters are determined. The energy transfer to the fast electrons from the electrostatic wave is studied with relativistic Vlasov-Maxwell simulations. The parametric decay of a wave to half-harmonics is investigated. It is shown that the growth rate of the decay vanishes in the limit of a long wavelenght of the pump wave even for general electromagnetic or electrostatic decay models. The results are applied to the decay of a fast magnetosonic waves in tokamak plasmas. (orig.)
Theoretical Study on Standing Wave Thermoacoustic Engine
Kalra, S.; Desai, K. P.; Naik, H. B.; Atrey, M. D.
Applications of thermoacoustic engines are not limited to driving pulse tube cryocoolers. The performance of a thermoacoustic engine is governed by various design parameters like type of resonator, stack geometry, frequency, type of working gas etc. and various operating parameters like heat input, charging pressure etc. It is very important to arrive at an optimum configuration of the engine for which a theoretical model is required. In the present work, a theoretical analysis, based on linear acoustic theory of a standing wave type half wavelength thermoacoustic engine is carried out using DeltaEC software. The system dimensions like length of resonator, stack, hot and cold heat exchangers are fixed with a helium-argon mixture as the working gas and a parallel plate type stack. Later on, two plate spacings, corresponding to helium-argon mixture and nitrogen gas, are used for carrying out analysis with helium, argon, nitrogen, carbon dioxide and helium-argon mixture as working gases of the system. The effect of charging pressure on the performance of the system is studied in terms of resonating frequency, onset temperature, pressure amplitude, acoustic power and efficiency. The conclusions derived from the analysis are reported in the paper.
Small amplitude variable charge dust Bernstein-Greene-Kruskal double layers
Energy Technology Data Exchange (ETDEWEB)
Amour, Rabia [Plasma Physics Group, Theoretical Physics Laboratory, Faculty of Sciences - Physics, U.S.T.H.B, Bab-Ezzouar, B.P. 32, El Alia, Algiers 16111 (Algeria); Tribeche, Mouloud [Plasma Physics Group, Theoretical Physics Laboratory, Faculty of Sciences - Physics, U.S.T.H.B, Bab-Ezzouar, B.P. 32, El Alia, Algiers 16111 (Algeria)], E-mail: mouloud-tribeche@lycos.com
2009-05-11
A first theoretical attempt is made to investigate small amplitude, variable charge dust Bernstein-Greene-Kruskal (BGK) double layers (DLs). The nature of the dust BGK-DLs (compressive or rarefactive), their strength and thickness depend sensitively on the net negative charge residing on the grain surface, the dust grain dynamics and, more interestingly, on the ion-to-electron temperatures ratio.
Code Switching and Sexual Orientation: A Test of Bernstein's Sociolinguistic Theory
Lumby, Malcolm E.
1976-01-01
Bernstein's theory was tested in the homosexual's "closed" community to determine code-switching ability and its relationship to jargon. Subjects told a story based on homoerotic photographs where knowledge of sexual orientation was varied. Results suggest that homosexual homophyly encouraged elaboration. (Author)
Translation of Bernstein Coefficients Under an Affine Mapping of the Unit Interval
Alford, John A., II
2012-01-01
We derive an expression connecting the coefficients of a polynomial expanded in the Bernstein basis to the coefficients of an equivalent expansion of the polynomial under an affine mapping of the domain. The expression may be useful in the calculation of bounds for multi-variate polynomials.
Solving Bernstein's Problem: A Proposal for the Development of Coordinated Movement by Selection.
Sporns, Olaf; Edelman, Gerald M.
1993-01-01
In the 1930s, Bernstein pointed out that more than one motor signal can trigger the same physical movement and that identical motor signals can lead to different movements, a dilemma that continues to puzzle scientists. Based on results from computer simulations, posits that these motor signals can be grouped into categories that correspond to…
Shock Wave Observation in Narrow Tubes for a Parametric Study on Micro Wave Rotor Design
Institute of Scientific and Technical Information of China (English)
Koji Okamoto; Mikiya Araki
2008-01-01
Wave rotor is expected to improve the performance of micro gas turbines drastically. In the wave rotor design, the rotor speed is determined principally by the tube length. Therefore, a longer tube is preferable for miniaturized wave rotors to avoid the difficulty in bearings and lubrication system, while it may yield thicker wall boundary layer, shock wave dissipation and so on. In the present study, an experimental apparatus was built to visualize the wave rotor internal flow dynamics in a narrow tube by schlieren method and Laser Doppler Anemometry. In addition, different lengths of the tube were adopted and compared to investigate the effect of wall friction. Finally, 2D numerical simulation was performed and the results were compared with those of experiments.
Tracer Studies In A Laboratory Beach Subjected To Waves
This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present...
A case study of gravity waves in noctilucent clouds
Dalin, P.; Kirkwood, S.; A. Moström; K. Stebel; Hoffmann, P.; Singer, W.
2004-01-01
We present a case study of a noctilucent cloud (NLC) display appearing on 10-11 August 2000 over Northern Sweden. Clear wave structures were visible in the clouds and time-lapse photography was used to derive the parameters characterising the gravity waves which could account for the observed NLC modulation. Using two nearby atmospheric radars, the Esrange MST Radar data and Andoya MF radar, we have identified gravity waves propagating upward from the upper stratosphere to NLC altitudes. The ...
Experimental study of breaking and energy dissipation in surface waves
Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael
2014-11-01
We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).
Wave energy converter effects on wave propagation: A sensitivity study in Monterey Bay, CA
Chang, G.; Jones, C. A.; Roberts, J.; Magalen, J.; Ruehl, K.; Chartrand, C.
2014-12-01
The development of renewable offshore energy in the United States is growing rapidly and wave energy is one of the largest resources currently being evaluated. The deployment of wave energy converter (WEC) arrays required to harness this resource could feasibly number in the hundreds of individual devices. The WEC arrays have the potential to alter nearshore wave propagation and circulation patterns and ecosystem processes. As the industry progresses from pilot- to commercial-scale it is important to understand and quantify the effects of WECs on the natural nearshore processes that support a local, healthy ecosystem. To help accelerate the realization of commercial-scale wave power, predictive modeling tools have been developed and utilized to evaluate the likelihood of environmental impact. At present, direct measurements of the effects of different types of WEC arrays on nearshore wave propagation are not available; therefore wave model simulations provide the groundwork for investigations of the sensitivity of model results to prescribed WEC characteristics over a range of anticipated wave conditions. The present study incorporates a modified version of an industry standard wave modeling tool, SWAN (Simulating WAves Nearshore), to simulate wave propagation through a hypothetical WEC array deployment site on the California coast. The modified SWAN, referred to as SNL-SWAN, incorporates device-specific WEC power take-off characteristics to more accurately evaluate a WEC device's effects on wave propagation. The primary objectives were to investigate the effects of a range of WEC devices and device and array characteristics (e.g., device spacing, number of WECs in an array) on nearshore wave propagation using SNL-SWAN model simulations. Results showed that significant wave height was most sensitive to variations in WEC device type and size and the number of WEC devices in an array. Locations in the lee centerline of the arrays in each modeled scenario showed the
Experimental Study of the Weptos Wave Energy Converter
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter; Larsen, Tommy;
2012-01-01
absorbed wave energy and which is connected to a common power take off system (one for each leg). The study investigates the performance of the device in a large range of wave states and estimates the performance in terms of mechanical power available to the power take off system of the WEPTOS WEC for two...... loads in extreme wave conditions. This A-shaped floating structure absorbs the energy in the waves through a multitude of rotors, the shape of which is based on the renowned Salter’s Duck. These rotors pivot around a common axle, one for each leg of the structure, to which the rotors transfer the...
Ray Tracing Study of Magnetospheric ULF Wave Propagation.
Zhang, Xinbo
1993-01-01
A semi-empirical plasma density model and Mead -Fairfield magnetic field model are incorporated into a 3-D ray tracing code to study magnetospheric ULF wave propagation from the subsolar magnetopause. The ray-tracing of Pc3 compressional waves from the magnetosheath reveals that the magnetosphere can present a major propagation barrier to the penetration of these waves to the plasmasphere. This barrier is the ion-ion cutoff between the He^+ and O ^+ gyroresonances. As a result of the frequency -dependent location of this cutoff, the magnetosphere behaves like a filter for Pc3 compressional waves, and only the low frequency components can penetrate to the inner magnetosphere. These results are in agreement with previous satellite observations. This 'filter action' strongly depends on the relative concentration of He^+ and O^+ and is, therefore, sensitive to solar and magnetic activity. The study of the propagation characteristics of Pc3 transverse Alfven waves shows that these waves cannot penetrate to low Earth altitudes for wave frequencies above about approximately 0.03 hz. The configuration of the refractive index reveals an O^+-He^+ associated cutoff located between the assumed wave source in the equatorial magnetopause and the Earth. When the O^+ concentration is removed from the plasma composition, the barrier no longer exists, and waves with much higher frequencies than 0.03 Hz can penetrate to low altitudes. The result that the 0.03 Hz or lower frequency Alfven waves can be guided to the low altitudes agrees with ground-based power spectrum observations at high latitudes. The ray tracing study of Pc 1-2 waves reproduces earlier results (Rauch and Roux, 1982) for an H ^+-He^+ two-ion-species plasma, i.e. Pc 1-2 left hand polarized Alfven mode waves originating at equatorial geostationary orbit, below He ^+ gyrofrequency, are guided to the ground. However, our ray tracing study shows that previous Pc 1-2 ray tracing results are only valid in the absence of O
NEUTRON WAVE OPTICS STUDIED WITH ULTRACOLD NEUTRONS
Steyerl, A.
1984-01-01
The paper reports experiments demonstrating or utilizing the wave properties of neutrons with wavelengths of about 100 nm. The significant effects of gravity are discussed, and special features of the flight parabola have been used in designing high-resolution instruments and image-forming systems.
Indian Academy of Sciences (India)
Naoya Suzuki; Naoto Ebuchi; Chaofang Zhao; Isao Watabe; Yasuhiro Sugimori
2002-09-01
Relationship between the non-dimensional roughness length and inverse of wave age has been discussed without consideration of wave directions, though wind wave field consists of various directional component waves. In this study we observe wave heights by an array of four wave gauges at the Hiratsuka Tower of (Independent Administrative Institution) National Research Institute for Earth Science and Disaster Prevention (NIED), Japan, and discuss the effect of wave directionality. As a result, the data sets were classified into two different groups according to the directional wave spectrum distribution. In case 1 only swell and wind waves exist and in case 2 there exist wave components from several directions. It is shown that the case of multiple- directional component waves (case 2) may affect the non-dimensional roughness length and friction velocity.
Directory of Open Access Journals (Sweden)
Mateus Casanova dos Santos
2010-12-01
Full Text Available O presente artigo é um estudo de caso investigativo de caráter participante e descritivo, a partir da vivência pedagógica no disparador de aprendizagem Simulação em Enfermagem, do segundo semestre do primeiro ciclo da graduação da Faculdade de Enfermagem (FEn da Universidade Federal de Pelotas (UFPel, onde se desenvolve a simulação clínica de semiologia e semiotécnica em Enfermagem. O objetivo é estudar a recontextualização da prática pedagógica da Simulação com base em teorizações do sociólogo da educação Basil Bernstein, contribuindo para o processo de aperfeiçoamento do planejamento de ensino e, especialmente, da avaliação deste disparador de aprendizagem. A partir das reflexões deste estudo, observa-se a teorização de Bernstein como uma potente ferramenta semiológica das práticas pedagógicas, a qual contribui para o planejamento e análise do dispositivo pedagógico curricular.Este artículo es un caso de estudio de carácter descriptivo y de investigación participante, desde la experiencia educativa de aprendizaje en el gatillo Simulación en Enfermería, de la segunda mitad del primer ciclo de la Escuela Enfermería (FEN de la Universidade Federal de Pelotas (UFPel donde se desarrolla la simulación de la semiología clínica y la semiótica en Enfermería. El objetivo es estudiar la recontextualización de la práctica pedagógica de teorías basadas en la simulación del sociólogo de la educación Basil Bernstein, contribuyendo al proceso de mejora de la educación, planificación y aprendizaje, especialmente la evaluación de gatillo. De las reflexiones de este estudio, existe la teoría de Bernstein como una poderosa herramienta de semiótica prácticas pedagógicas, lo que contribuye a la planificación y el análisis de dispositivos educativos curriculares.This article is a case study of investigative and descriptive participant character, from the educational experience of learning in the trigger
Electron Bernstein Driven and Bootstrap Current Estimations in the TJ-II Stellarator
International Nuclear Information System (INIS)
Full text: The control of the total parallel current may lead to the possibility of continuous operation in tokamak plasmas and it can provide access to improved confinement regimes in stellarators, by means of control of the rotational transform profile. In fact one of the main lines of research at the stellarator TJ-II is the relation between confinement and the magnetic configuration, putting emphasis on the rotational transform profile. The two main non-inductive parallel currents in plasma confinement devices are the bootstrap and the ones driven by external means, like radio frequency or NBI. The current drive (CD) systems must be appropriated to work on overdense plasmas, since this could be mandatory in a reactor. Therefore, electron Bernstein waves (EBW), which do not present density cut-off have been considered as CD system for TJ-II. In this work we present calculations of the bootstrap and the EBW currents in the dense plasmas confined in a complex 3D confinement device like the TJ-II stellarator. The precise calculation of the bootstrap current is a numerical challenge, since the error estimates for computations of this current, specially in the long-mean-free-path (lmfp) regime of stellarators, are very large. This issue is particularly relevant for the lmfp regime of stellarators, particularly for TJ-II, which is characterized by its very complex magnetic configuration. A new code, NEO-MC, has been developed in order to overcome this problem. It combines the standard δf method with an algorithm employing constant particle weights and re-discretizations of the test particle distribution. In this way, it is able to provide, for the first time, calculations of the contribution of the lmfp regime to the bootstrap current of TJ-II with very low error estimates. For a fast estimation of EBCD, different linear models based on the adjoint approach or Langevin equations techniques have been developed in order to simplify the task of solving the kinetic
Raghunathan, M.; Ganesh, R.
2013-03-01
In the past, long-time evolution of an initial perturbation in collisionless Maxwellian plasma (q = 1) has been simulated numerically. The controversy over the nonlinear fate of such electrostatic perturbations was resolved by Manfredi [Phys. Rev. Lett. 79, 2815-2818 (1997)] using long-time simulations up to t = 1600 ωp - 1 . The oscillations were found to continue indefinitely leading to Bernstein-Greene-Kruskal (BGK)-like phase-space vortices (from here on referred as "BGK structures"). Using a newly developed, high resolution 1D Vlasov-Poisson solver based on piecewise-parabolic method (PPM) advection scheme, we investigate the nonlinear Landau damping in 1D plasma described by toy q-distributions for long times, up to t = 3000 ωp - 1 . We show that BGK structures are found only for a certain range of q-values around q = 1. Beyond this window, for the generic parameters, no BGK structures were observed. We observe that for values of q 1 where distribution has a sharp fall in velocity, the formation of BGK structures is rendered difficult due to high wave number damping imposed by the steep velocity profile, which had not been previously reported. Wherever relevant, we compare our results with past work.
Research of closure laws from the study of wave propagation
International Nuclear Information System (INIS)
We try to obtain information concerning closure laws of averaged models from the study of the local instantaneous equations of the problem. The method employed is based on the comparison of wave propagation phenomena each kind of model can describe (id. local instantaneous model, and averaged model). Two simple examples are analytically treated: - the friction law of an unsteady laminar single phase pipe flow is obtained from the study of pressure waves; - the topological law of a stratified two phase flow is obtained from the study of surface waves
Identification of broad-band waves above the auroral acceleration region: Cluster observations
Directory of Open Access Journals (Sweden)
M. Backrud
2004-12-01
Full Text Available We investigate broad-band emissions at frequencies above the ion gyrofrequency on auroral field lines at geocentric distances of about 4.5 Earth radii. Observations by the Cluster satellites are used to study the wave characteristics and to determine the wave modes involved. All events include some bursts of broad-band emissions with a substantial component of the electric field parallel to the geomagnetic field. Studying the polarization of the emissions we find that linear waves in a homogeneous plasma can be used to theoretically describe the observations.
The broad-band emissions include short bursts of ion acoustic waves, and longer periods of ion Bernstein and Electrostatic Ion Cyclotron (EIC waves. All waves occur during the same event within a few seconds, with EIC waves as the most common. Theoretically, there is no sharp limit between these wave modes and they can be described by the same dispersion surface. These emissions are closely associated with low-frequency Alfvén waves, indicating a possible generation mechanism.
Key words. Magnetospheric physics (auroral phenomena; electric fields; plasma waves and instabilities
Shock wave studies in Blair dolomite
International Nuclear Information System (INIS)
Two types of shock wave experiments have been conducted on samples of Blair dolomite. The first employed a light-gas gun to produce uniaxial strain, while the second used a spherical high-explosive charge to cause radial deivergent flow. Comparisons of data taken from these two types of experiments (at strain rates of 106/s and 104/s, respectively) with quasi-static data (at 10-4/s) show that Blair dolomite is strongly time dependent in its behavior. This time dependence appears over the entire stress interval from 0.24 to 5.33 GPa
Verification of particle simulation of radio frequency waves in fusion plasmas
International Nuclear Information System (INIS)
Radio frequency (RF) waves can provide heating, current and flow drive, as well as instability control for steady state operations of fusion experiments. A particle simulation model has been developed in this work to provide a first-principles tool for studying the RF nonlinear interactions with plasmas. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation. This model has been implemented in a global gyrokinetic toroidal code using real electron-to-ion mass ratio. To verify the model, linear simulations of ion plasma oscillation, ion Bernstein wave, and lower hybrid wave are carried out in cylindrical geometry and found to agree well with analytic predictions
EXPERIMENTAL STUDY OF SHOCK WAVE DYNAMICS IN MAGNETIZED PLASMAS
Energy Technology Data Exchange (ETDEWEB)
Nirmol K. Podder
2009-03-17
In this four-year project (including one-year extension), the project director and his research team built a shock-wave-plasma apparatus to study shock wave dynamics in glow discharge plasmas in nitrogen and argon at medium pressure (1–20 Torr), carried out various plasma and shock diagnostics and measurements that lead to increased understanding of the shock wave acceleration phenomena in plasmas. The measurements clearly show that in the steady-state dc glow discharge plasma, at fixed gas pressure the shock wave velocity increases, its amplitude decreases, and the shock wave disperses non-linearly as a function of the plasma current. In the pulsed discharge plasma, at fixed gas pressure the shock wave dispersion width and velocity increase as a function of the delay between the switch-on of the plasma and shock-launch. In the afterglow plasma, at fixed gas pressure the shock wave dispersion width and velocity decrease as a function of the delay between the plasma switch-off and shock-launch. These changes are found to be opposite and reversing towards the room temperature value which is the initial condition for plasma ignition case. The observed shock wave properties in both igniting and afterglow plasmas correlate well with the inferred temperature changes in the two plasmas.
EXPERIMENTAL STUDY OF SHOCK WAVE DYNAMICS IN MAGNETIZED PLASMAS
International Nuclear Information System (INIS)
In this four-year project (including one-year extension), the project director and his research team built a shock-wave-plasma apparatus to study shock wave dynamics in glow discharge plasmas in nitrogen and argon at medium pressure (1-20 Torr), carried out various plasma and shock diagnostics and measurements that lead to increased understanding of the shock wave acceleration phenomena in plasmas. The measurements clearly show that in the steady-state dc glow discharge plasma, at fixed gas pressure the shock wave velocity increases, its amplitude decreases, and the shock wave disperses non-linearly as a function of the plasma current. In the pulsed discharge plasma, at fixed gas pressure the shock wave dispersion width and velocity increase as a function of the delay between the switch-on of the plasma and shock-launch. In the afterglow plasma, at fixed gas pressure the shock wave dispersion width and velocity decrease as a function of the delay between the plasma switch-off and shock-launch. These changes are found to be opposite and reversing towards the room temperature value which is the initial condition for plasma ignition case. The observed shock wave properties in both igniting and afterglow plasmas correlate well with the inferred temperature changes in the two plasmas
Study of Magnetohydrodynamic Surface Waves on Liquid Gallium
Energy Technology Data Exchange (ETDEWEB)
Hantao Ji; William Fox; David Pace; H.L. Rappaport
2004-05-13
Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.
Multicavity wave resonator design using chaos studies
Méndez-Bermúdez, J. A.; Luna-Acosta, G. A.
2007-03-01
We propose the construction of electromagnetic and electronic multicavity resonators based on the mechanism of dynamical tunneling proper of mixed chaotic systems. We use chaotic two-dimensional (2D) waveguides formed by a linear array of coupled cavities whose geometrical parameters are chosen to produce mixed phase space: chaotic regions surrounding islands of stability where ray (particle) motion is regular. Rays (particles) coming into the waveguide cannot penetrate into these islands but incoming plane waves tunnel into them at a certain discrete set of frequencies (energies) forming quasi-bound states. In this paper we demonstrate the tunneling mechanism in 2D waveguides and how it can be used to design multicavity resonators. We also discuss possible applications in the construction of microlasers and electro-optical beam splitters and switches.
Numerical study of pollutant movement in waves and wave-induced long-shore currents in surf zone
Institute of Scientific and Technical Information of China (English)
TANG Jun; SHEN Yongming; QIU Dahong
2008-01-01
Water waves,wave-induced long-shore currents and movement of pollutants in waves and currents have been numerically studied based on the hyperbolic mild-slope equation,the shallow water equation,as well as the pollutant movement equation,and the nu- merical results have also been validated by experimental data.It is shown that the long-shore current velocity and wave set-up in- crease with the increasing incident wave amplitude and slope steepness of the shore plane;the wave set-up increases with the in- creasing incident wave period;and the pollutant morement proceeds more quiekly with the increasing incident wave amplitude and slope steepness of the shore palane.In surf zones,the long-shore currents induced by the inclined incident waves have effectively affected the pollutant movement.
Comparative Study of Turbines for Wave Energy Conversion
Institute of Scientific and Technical Information of China (English)
Hideaki Maeda; Toshiaki Setoguchi; Manabu Takao; Keita Sakurada; Tae-Ho Kin; Kenji Kaneko
2001-01-01
The objective of this paper is to compare the performances of the turbines, which could be used for wave energy conversion in the near future, under various irregular wave conditions. The turbines included in the paper are as follows: (a) Wells turbine with guide vanes; (b) impulse turbine with self-pitch-controlled guide vanes; (c) impulse turbine with fixed guide vanes. In this study, experimental investigations were carried out to clarify the performances of the turbines under steady flow conditions, and then a numerical simulation was used for predicting the performances under irregular wave conditions with various significant wave heights. As a result, it was found that the running and starting characteristics of the impulse turbines could be superior to those of the Wells turbine.
An Experimental and Computational Study of Breaking Wave Impact Forces
Fu, Thomas C; Brewton, Susan; Brucker, Kyle A; Dommermuth, Douglas G
2014-01-01
The impact forces generated by the impact of a breaking wave are poorly understood. These impulsive hydrodynamic loads to a ship's hull are of short duration relative to ship motions and buoyant wave loads and often result in extremely high pressures. The physics of breaking waves is a poorly understood, complex, multiphase phenomenon involving violent jet sprays, strong free-surface turbulence, air entrainment and bubble generation, all of which interact with the flow field and the adjacent structure. This paper will describe a set of experiments that were performed, at the Naval Surface Warfare Center, Carderock Division (NSWCCD), in 2006, to measure the hydrodynamic loads of regular nonbreaking and focused breaking waves on a 0.305 m x 0.305 m (1.0 ft x 1.0 ft) square plate and discuss the results of this study. The paper will also discuss Computational Fluid Dynamics (CFD) code predictions of breaking waves and wave impact loads. The CFD code utilized in this study is Numerical Flow Analysis (NFA).
Pilot studies on two dimensional wave propagation in rock masses
Institute of Scientific and Technical Information of China (English)
LEI Wei-dong; M.H.Ashraf; ZHAO Jian
2005-01-01
Pilot studies on two dimensional(2-D) wave propagation through single joint or multiple parallel joints were comprehensively conducted, using a suitable data processing method. The possible factors influencing the transmission ratio in 2-D wave propagation under certain circumstances in rock masses were studied. It is found that in the process of 2-D wave propagation, for any radial line, the amount, the stiffness and the spacing of the joints influence the transmission ratio; by contrast, the transmission ratio at any point is independent of the radial distance from the center of wave source. It is also found that the transmission ratio for every grid-point along a single circle can present the transmission ratio for every grid-point after a certain quantity of joints. For the special radian direction(normal to the joints), it is concluded that the transmission ratio is dominated by the normal stiffness; while the influence of shear stiffness is negligible. The radius of the tunnel or borehole for the source wave does not affect the transmission ratio in 2-D wave propagation.
NUMERICAL STUDY ON EFFECT OF WAVING BED ON THE SURFACE WAVE
Institute of Scientific and Technical Information of China (English)
WU Zheng-ren; CHENG You-liang; WANG Song-ling
2006-01-01
The effect of the waving bed on the surface wave was investigated. The wave equation was reduced from the potential flow theory with the perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with the Matlab. It is shown that for the waving bed, an additional harmonic wave appears on the surface together with the solitary wave existing for the non-waving bed, and two kinds of waves do not interfere with each other. With the development of time, the waveform for the waving bed is kept invariable, and just the amplitude is reduced gradually. Wave-breaking phenomenon for the non-waving bed does not appear, so the waving bed seems useful to prevent the breaking of the wave.
Study on Rayleigh Wave Inversion for Estimating Shear-wave Velocity Profile
T.A. Sanny; Yoes Avianto
2003-01-01
Rayleigh wave or ground roll is a noise in seismic body waves. However, how to use this noise for soil characterization is very interesting since Rayleigh wave phase velocity is a function of compression-wave velocity, shear-wave velocity, density and layer thickness. In layered-medium Rayleigh wave velocity also depends on wavelength or frequency, and this phenomenon is called dispersion. Inversion procedure to get shear-wave velocity profile needs a priori information about the solution of ...
A Numerical Study on Wave-Mud Interaction
Institute of Scientific and Technical Information of China (English)
ZHANG Dao-hua; NG Chiu-on
2006-01-01
Presented in this paper is a numerical study on the interaction of progressive waves propagating in a body of water overlying a layer of viscous fluid mud on the bottom, with emphasis placed on the induced oscillatory motion of the water-mud interface. The fully nonlinear Navier-Stokes equations with the complete set of viscous boundary conditions are solved numerically by a finite difference method that is based on a time-dependent boundary-fitted curvilinear coordinate system, for the simulation of wave motion in the two-layer viscous fluid system. Waves of moderate wavelength are generated in the upper water layer by a numerical flap-type wavemaker. The dynamic pressure due to the surface wave is transmitted downward onto the lower layer, generating wave motion on the interface. On mimicking some reported experimental conditions, the ratio of interfacial to surface wave amplitudes is evaluated and the results are found to compare more favorably with the experimental data than the prediction by a linear theory.
Te(R, t) measurements using electron Bernstein wave thermal emission on NSTX
Czech Academy of Sciences Publication Activity Database
Diem, S.J.; Taylor, G.; Efthimion, P.C.; LeBlanc, P.C.; Carter, M.; Caughman, J.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, Josef; Urban, Jakub
2006-01-01
Roč. 77, č. 10 (2006), 10E919, 1-10E919,4. ISSN 0034-6748. [Topical Conference on High-Temperature Plasma Diagnostics/16th./. Williamsburg, Virginia, 7.5.2006-11.5.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Overdense plasma * Conversion * Emission * Excitation * Tokamaks * Diagnostics Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.541, year: 2006 http://link.aip.org/link/?RSI/77/10E919
Electron cyclotron-electron Bernstein wave emission diagnostics for the COMPASS tokamak
Czech Academy of Sciences Publication Activity Database
Zajac, Jaromír; Preinhaelter, Josef; Urban, Jakub; Žáček, František; Šesták, David; Nanobashvili, S.
2010-01-01
Roč. 81, č. 10 (2010), 10D911-10D911. ISSN 0034-6748. [TOPICAL CONFERENCE ON HIGH-TEMPERATURE PLASMA DIAGNOSTICS/18th./. Wildwood, New Jersey, 16.05.2010-20.05.2010] R&D Projects: GA ČR GA202/08/0419 Institutional research plan: CEZ:AV0Z20430508 Keywords : antenna radiation patterns * antennas in plasma * plasma diagnostics * Tokamak Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.598, year: 2010 http://link.aip.org/link/?RSI/81/10D911
Ibsen, Lars Bo
2008-01-01
Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for t...
DEFF Research Database (Denmark)
Ibsen, Lars Bo
2008-01-01
Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many...... times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for the UK is estimated at 25% of current demand; a lot less, but a very substantial amount nonetheless....
Studying inflation with future space-based gravitational wave detectors
International Nuclear Information System (INIS)
Motivated by recent progress in our understanding of the B-mode polarization of cosmic microwave background (CMB), which provides important information about the inflationary gravitational waves (IGWs), we study the possibility to acquire information about the early universe using future space-based gravitational wave (GW) detectors. We perform a detailed statistical analysis to estimate how well we can determine the reheating temperature after inflation as well as the amplitude, the tensor spectral index, and the running of the inflationary gravitational waves. We discuss how the accuracies depend on noise parameters of the detector and the minimum frequency available in the analysis. Implication of such a study on the test of inflation models is also discussed
Wave excitation in inhomogeneous dielectric media.
Cary, John R; Xiang, Nong
2007-11-01
The equation describing the propagation of a mode driven by external currents in an inhomogeneous dielectric is derived from the principle of the conservation of wave energy density and wave momentum density. The wave amplitude in steady state is obtained in terms of a simple spatial integration of the driving current. The contribution from the spatial derivative of the dielectric response is found to be important. The analytical predictions are verified through comparison with deltaf particle-in-cell computations of electron Bernstein wave propagation, thus showing applicability to kinetic systems. PMID:18233709
ICRF launcher studies: Progress report
International Nuclear Information System (INIS)
The research we have accomplished during the past year includes the topics of ICRF fast wave coupling to L- and H-mode edge profiles, measurements of simulated plasma loads on an 85 MHz launcher, coupling of ion Bernstein waves and a simulation of the folded waveguide launcher. We have also begun to examine coupling between launched fast waves and ion Bernstein waves driven by density gradients near the plasma edge and the effects of known edge turbulence and ponderomotive forces on the direct launching of ion Bernstein waves. We find that a TE10 ICRF fast mode waveguide launcher has only a moderate increase in its reflection coefficient when coupling into a model H-mode plasma density profile. We find that linear coupling from fast modes to ion Bernstein modes can only occur with large density gradient scale lengths near the plasma edge. The current power level of ion Bernstein wave heating experiments is found to yield ponderomotive force effects which can substantially modify plasma edge density profiles. 7 refs
Diffusing wave spectroscopy studies of gelling systems
Horne, David S.
1991-06-01
The recognition that the transmission of light through a concentrated, opaque system can be treated as a diffusion process has extended the application of photon correlation techniques to the study of particle size, mobility and interactions in such systems. Solutions of the photon diffusion equation are sensitive to the boundary conditions imposed by the geometry of the scattering apparatus. The apparatus, incorporating a bifurcated fiber optic bundle for light transmission between source, sample and detector, takes advantage of the particularly simple solution for a back-scattering configuration. Its ability to measure particle size using monodisperse polystyrene latices and to respond to concentration dependent particle interactions in a study of casein micelle mobility in skim and concentrated milks is demonstrated. Finally, the changes in dynamic light scattering behavior occurring during colloidal gel formation are described and discussed.
Millimeter wave study program. Final report
International Nuclear Information System (INIS)
The purpose of this program was to study the various approaches to building an amplifier to produce 100 kW or more cw power at 120 GHz to decide on an optimum approach, and to perform design calculations. The study has led to the conclusion that a cyclotron resonance amplifier (gyrotron) is the optimum approach for 100 kW and that this type of interaction offers the best possibilities for going to still higher power levels. This report includes discussion in depth of all the topics and approaches considered in the study. Sections 2 and 3 deal with output waveguide and window designs. The fourth section discusses linear-beam amplifiers. The fifth section considers periodic-beam (other than cyclotron resonance) devices. Cyclotron resonance devices are considered in detail. Arguments are given leading to the choice of the gyrotron as the optimum approach in section 7. Design calculations for a 100 kW gyrotron amplifier are given based on the background and theory presented in section 6
On S.N. Bernstein's derivation of Mendel's Law and 'rediscovery' of the Hardy-Weinberg distribution
Directory of Open Access Journals (Sweden)
Alan Stark
2012-01-01
Full Text Available Around 1923 the soon-to-be famous Soviet mathematician and probabilist Sergei N. Bernstein started to construct an axiomatic foundation of a theory of heredity. He began from the premise of stationarity (constancy of type proportions from the first generation of offspring. This led him to derive the Mendelian coefficients of heredity. It appears that he had no direct influence on the subsequent development of population genetics. A basic assumption of Bernstein was that parents coupled randomly to produce offspring. This paper shows that a simple model of non-random mating, which nevertheless embodies a feature of the Hardy-Weinberg Law, can produce Mendelian coefficients of heredity while maintaining the population distribution. How W. Johannsen's monograph influenced Bernstein is discussed.
On S.N. Bernstein's derivation of Mendel's Law and 'rediscovery' of the Hardy-Weinberg distribution.
Stark, Alan; Seneta, Eugene
2012-04-01
Around 1923 the soon-to-be famous Soviet mathematician and probabilist Sergei N. Bernstein started to construct an axiomatic foundation of a theory of heredity. He began from the premise of stationarity (constancy of type proportions) from the first generation of offspring. This led him to derive the Mendelian coefficients of heredity. It appears that he had no direct influence on the subsequent development of population genetics. A basic assumption of Bernstein was that parents coupled randomly to produce offspring. This paper shows that a simple model of non-random mating, which nevertheless embodies a feature of the Hardy-Weinberg Law, can produce Mendelian coefficients of heredity while maintaining the population distribution. How W. Johannsen's monograph influenced Bernstein is discussed. PMID:22888285
Bernstein diffusions for a class of linear parabolic partial differential equations
Vuillermot, Pierre-A.; Zambrini, Jean-Claude
2013-01-01
In this article we prove the existence of Bernstein processes which we associate in a natural way with a class of non-autonomous linear parabolic initial- and nal-boundary value problems de ned in bounded convex subsets of Euclidean space of arbitrary dimension. Under certain conditions regarding their joint endpoint distributions, we also prove that such processes become reversible Markov di¤usions. Furthermore we show that those di¤usions satisfy two Itô equations for some suitably constru...
Transport Implementation of the Bernstein-Vazirani Algorithm with Ion Qubits
Fallek, Spencer; McMahon, Brian; Maller, Kara; Brown, Kenneth; Amini, Jason
2016-01-01
Using trapped ion quantum bits in a scalable microfabricated surface trap, we perform the Bernstein-Vazirani algorithm. Our architecture relies upon ion transport and can readily be expanded to larger systems. The algorithm is demonstrated using two- and three-ion chains. For three ions, an improvement is achieved compared to a classical system using the same number of oracle queries. For two ions and one query, we correctly determine an unknown bit string with probability 97.6(8)%. For three ions, we succeed with probability 80.9(3)%.
PAC-Bayes-Bernstein Inequality for Martingales and its Application to Multiarmed Bandits
Seldin, Yevgeny; Auer, Peter; Laviolette, François; Shawe-Taylor, John
2011-01-01
We combine PAC-Bayesian analysis with a Bernstein-type inequality for martingales to obtain a result that makes it possible to control the concentration of multiple (possibly uncountably many) simultaneously evolving and interdependent martingales. We apply this result to derive a regret bound for the multiarmed bandit problem. Our result forms a basis for integrative simultaneous analysis of exploration-exploitation and model order selection trade-offs. It also opens a way for applying PAC-Bayesian analysis in other fields, where sequentially dependent samples and limited feedback are encountered.
Transfinite diameter of Bernstein sets in
Bialas-Cież Leokadia; Jedrzejowski Mieczysław
2002-01-01
Let be a compact set in satisfying the following generalized Bernstein inequality: for each such that , for each polynomial of degree where is a constant independent of and , is an infinite set of natural numbers that is also independent of and . We give an estimate for the transfinite diameter of the set : For satisfying the usual Bernstein inequality (i.e., ), we prove that
Study of nonlinear waves described by the cubic Schroedinger equation
International Nuclear Information System (INIS)
The cubic Schroedinger equation (CSE) is ubiquitous as a model equation for the long-time evolution of finite-amplitude near-monochromatic dispersive waves. It incorporates the effects of the radiation field pressure on the constitutive properties of the supporting medium in a self-consistent manner. The properties of the uniformly transiating periodic wave solutions of the one-dimensional CSE are studied here. These (so-called cnoidal) waves are characterized by the values of four parameters. Whitham's averaged variational principle is used to derive a system of quasilinear evolution equations (the modulational equations) for the values of these parameters when they are slowly varying in space and time. Explicit expressions for the characteristic velocities of the modulational equations are obtained for the full set of cnoidal waves. Riemann invariants are obtained for several limits for the stable case, and growth rates are obtained for several limits, including the solitary wave chain, for the unstable case. The results for several nontrivial limiting cases agree with those obtained by independent methods by others. The dynamics of the CSE generalized to two spatial dimensions are studied for the unstable case. A large class of similarity solutions with cylindrical symmetry are obtained systematically using infinitesimal transformation group techniques. The methods are adapted to obtain the symmetries of the action functional of the CSE and to deduce nine integral invariants. A numerical study of the self-similar solutions reveals that they are modulationally unstable and that singularities dominate the dynamics of the CSE in two dimensions. The CSE is derived using perturbation theory for a specific problem in plasma physics: the evolution of the envelope of a near-monochromatic electromagnetic wave in a cold magnetized plasma. 13 figures, 2 tables
Study of nonlinear waves described by the cubic Schroedinger equation
Energy Technology Data Exchange (ETDEWEB)
Walstead, A.E.
1980-03-12
The cubic Schroedinger equation (CSE) is ubiquitous as a model equation for the long-time evolution of finite-amplitude near-monochromatic dispersive waves. It incorporates the effects of the radiation field pressure on the constitutive properties of the supporting medium in a self-consistent manner. The properties of the uniformly transiating periodic wave solutions of the one-dimensional CSE are studied here. These (so-called cnoidal) waves are characterized by the values of four parameters. Whitham's averaged variational principle is used to derive a system of quasilinear evolution equations (the modulational equations) for the values of these parameters when they are slowly varying in space and time. Explicit expressions for the characteristic velocities of the modulational equations are obtained for the full set of cnoidal waves. Riemann invariants are obtained for several limits for the stable case, and growth rates are obtained for several limits, including the solitary wave chain, for the unstable case. The results for several nontrivial limiting cases agree with those obtained by independent methods by others. The dynamics of the CSE generalized to two spatial dimensions are studied for the unstable case. A large class of similarity solutions with cylindrical symmetry are obtained systematically using infinitesimal transformation group techniques. The methods are adapted to obtain the symmetries of the action functional of the CSE and to deduce nine integral invariants. A numerical study of the self-similar solutions reveals that they are modulationally unstable and that singularities dominate the dynamics of the CSE in two dimensions. The CSE is derived using perturbation theory for a specific problem in plasma physics: the evolution of the envelope of a near-monochromatic electromagnetic wave in a cold magnetized plasma. 13 figures, 2 tables.
Some phase transition studies under shock waves
International Nuclear Information System (INIS)
Experimental studies on pressure-induced phase transitions are generally conducted using both static- and shock-loading techniques. Comparison of these results is interesting as the presence of shear and high strain rate under shock compression may alter the mechanism of a transition and also its onset pressure. Recently we have carried out an gas-gun experiments to study phase transitions in GeO2, Ti and Zr. In Ti and Zr, our objective has been to understand the causes of the reported scatter in the pressure of shock induced α -> ω transition (6.0 - 11.9 GPa). Our experiments on Zr show that the initial oxygen content of the sample has a large influence on the transition pressure. For example no α to ω transition is seen up to 11 GPa in Zr samples containing oxygen concentration above 1600 ppm. Unlike that in static experiments, the effect of shear is found to be small up to 9 GPa in inclined impact experiments in Ti. The microscopic nature of the α -> ω transition in Zr has also been examined using selected area electron diffraction measurements
Space-Based Gravitational-wave Mission Concept Studies
Livas, Jeffrey C.
2012-01-01
The LISA Mission Concept has been under study for over two decades as a spacebased gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return, and in particular a family of mission concepts referred to as SGO (Space-based Gravitational-wave Observatory).
International Nuclear Information System (INIS)
Scattering experiments with a 2-mm microwave oscillator (E.I.O.) and a 337-μm HCN laser were performed to measure density fluctuations on the JIPP T-II/T-IIU tokamak in a wide range of the plasma density. It is found from the measurements of the frequency and wavenumber spectra of the instability that the density fluctuation shows characteristics of a turbulence which is originated in the instability of drift type. The dependence of the fluctuation level on the plasma parameters was investigated and compared with the scaling law of the energy confinement time of the plasma. The relation between the density fluctuation level and the confinement time was obtained. The fluctuation level decreases as the electron density is increased. The plasma temperature dependence of the density fluctuation was also investigated. During the rf heating in the ion-cyclotron range of frequency (ICRF) the increase in the density fluctuation level was observed in low-frequency and long-wavelength region. The temporal behavior of the density fluctuation was correlated with the MHD oscillation observed by magnetic probes. The excited wave during the ICRF heating experiment was studied by the HCN laser scattering. The frequency and wavenumber spectra of the excited wave observed during the heating are found to be consistent with the theoretically estimated wave dispersion of the ion Bernstein wave which is mode-converted from the fast wave in the vicinity of the ion-ion hybrid resonance layer. When the MHD activity grows and the plasma becomes unstable, the scattered signal from the ion Bernstein wave decreases, being accompanied with large pulsation. (author)
Continuing studies of the plasma beat wave accelerator
International Nuclear Information System (INIS)
This is a proposal for the release of third year funds for the ''Plasma Beat Wave Accelerator'' program (PBWA) at UCLA under the direction of Professor C. Joshi. This report is also a summary of progress on this project since March 1990; i.e., the date of the last report to the DOE. Once again we note that although the program is for historical reasons called the Plasma Beat Wave Accelerator Program, our group is active in all areas of applications of lasers and plasmas in future high energy accelerators. These are as follows: heat gradient plasma structures; excited by plasma beat wave technique; laser wake field technique; and plasma wake field technique. Development of a photoinjector-driven, 20 MeV linac; and theoretical studies of the plasma lens and use of plasmas at the final focus
Beat-wave accelerator studies at the Rutherford Appleton Laboratory
International Nuclear Information System (INIS)
The study carried out in 1982-83 at the Rutherford Appleton Laboratory to examine how one might use the beat-wave principle to construct a useful high energy accelerator is reviewed, and comments are made on later developments. A number of problems are evident to which solutions cannot at present be foreseen. (author)
A COMPARATIVE STUDY OF SPECTRAL METHODS WITH SEA WAVE DATA
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Two spectral methods are used to study sea wave data.Firstly, the estimated results calculated by the sequency spectrum method and frequency spectrum method are compared, and then the differences between the two methods are discussed.Furthermore, compared with frequency spectral analysis, sequency spectral analysis has many advantages: faster calculating speed, convenient use and high distinguishability.
Experimental Study on a Rotor for WEPTOS Wave Energy Converter
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter; Marchalot, Tanguy
This report presents the results of an experimental study of the power conversion capabilities of one single rotor of the WEPTOS wave energy converter. The investigation focuses mainly on defining the optimal weight distribution in the rotor in order to improve the hydraulic performance through...
Energy Technology Data Exchange (ETDEWEB)
Roberts, Jesse D.; Chang, Grace; Magalen, Jason; Jones, Craig
2014-09-01
A modified version of an indust ry standard wave modeling tool was evaluated, optimized, and utilized to investigate model sensitivity to input parameters a nd wave energy converter ( WEC ) array deployment scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that wave direction and WEC device type we r e most sensitive to the variation in the model parameters examined in this study . Generally, the changes in wave height we re the primary alteration caused by the presence of a WEC array. Specifically, W EC device type and subsequently their size directly re sult ed in wave height variations; however, it is important to utilize ongoing laboratory studies and future field tests to determine the most appropriate power matrix values for a particular WEC device and configuration in order to improve modeling results .
Extracting the QCD Cutoff Parameter Using the Bernstein Polynomials and the Truncated Moments
Directory of Open Access Journals (Sweden)
A. Mirjalili
2014-01-01
Full Text Available Since there are not experimental data over the whole range of x-Bjorken variable, that is, 0
Energy Technology Data Exchange (ETDEWEB)
Roberts, Jesse D.; Grace Chang; Jason Magalen; Craig Jones
2014-08-01
A n indust ry standard wave modeling tool was utilized to investigate model sensitivity to input parameters and wave energy converter ( WEC ) array deploym ent scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that b oth wave height and near - bottom orbital velocity we re subject to the largest pote ntial variations, each decreas ed in sensitivity as transmission coefficient increase d , as number and spacing of WEC devices decrease d , and as the deployment location move d offshore. Wave direction wa s affected consistently for all parameters and wave perio d was not affected (or negligibly affected) by varying model parameters or WEC configuration .
Study of wave propagation through a fast growing plasma slab
International Nuclear Information System (INIS)
Interaction between an electromagnetic wave and a fast growing plasma in a bounded region can lead to the spectral change of the original wave. Such an initial value mixed with boundary value problem is studied in the present work both experimentally and theoretically. The experiment was conducted in a similar fashion as the previous one in which two crossed microwave pulses (1μs, 3.27GHz, 35 Hz repetition rate) were used to generate a fast growing plasma in their intersection region inside a chamber made of a 2 ft cube of plexiglass and filled with dry air. The difference between the present one and the previous one is that a separate CW source wave is used in the present case to interact with the plasma. The frequency spectrum of the transmitted signal presented in the figure shows that a frequency up shifted pulse is generated. The peak line at f = 4.833 GHz is attributed to the CW source wave. The remaining part of the spectrum has a distribution of the form of | sin[2π(f-f0)τ]/(f-f0) |2 which represents a frequency up shifted (by about 2.5 MHz) microwave pulse of about 0.2μs duration. A theoretical model is developed to simulate the experiment. It considers a CW wave propagating through a fast growing plasma slab. It is used to study the dependence of the conversion efficiency and frequency shift on the density and growth rate of the plasma and the effect of finite growth rate and finite region of the plasma on the spectral quality of the converted signals
Peng, X; Fang, X; Feng, M; Liu, M; Gao, K; Peng, Xinhua; Zhu, Xiwen; Fang, Ximing; Feng, Mang; Liu, Maili; Gao, Kelin
2002-01-01
Based on ''spectral implementation'' proposed by Madi et al. (J. Chem. Phys. 109, 10603, 1998), we have experimentally realized a pseudo-pure state by the line-selective excitation and a three-qubit Bernstein-Vazirani's algorithm using a carbon-13 analine sample in NMR. The superiority of quantum computation to classical counterpart is well displayed.
Study Pelamis system to capture energy of ocean wave
Gobato, Ricardo; Fedrigo, Desire Francine Gobato
2015-01-01
Over the years, energy has become vital for humans, enabling us to comfort, leisure, mobility and other factors. The quest for cheap energy sources, renewable and clean has grown in recent years, mainly for the reduction of effects that comes degrading nature, allowing scientists and engineers to search for new technologies. Many energy sources have been researched for proper funding where some stand out for their ease of obtaining, by other low cost and others by being renewable. The main objective of this work is to study one of these energy sources - wave energy, whose capture is still in development. This energy comes from the waves of the sea and is 100% renewable and with minimal environmental impact when compared to hydro, nuclear, coal, thermal, etc. The system studied here is the Pelamis system.
Mathematical preliminaries for a study of waves in a plasma
International Nuclear Information System (INIS)
This report contains the detailed proofs of mathematical results which are used in a study of the linear and 'quasi-linear' approximation for 'electrostatic' waves in a uniform plasma. Certain classes of functions of a complex variable, which are analytic in a strip parallel to the real axis, are defined and studied. In particular, properties of convergence of a sequence and of continuity with respect to a parameter are established for functions remaining inside one such class. The results are used to prove an existence theorem for the simplest equation in the quasi-linear theory of plasma waves. A number of elementary lemmas are used in the text and proved in an appendix. (author)
Biological studies with continuous-wave radiofrequency (28 MHz) radiation
International Nuclear Information System (INIS)
Effects of high-frequency (28 MHz) continous-wave radiation have been studied in the rat and monkey. No histopathological or hematological changes could be attributed to the radiation. In the monkey there was an increase in urinary calcium concentration which was most likely due to restricted movement. In the rat there was reduced uptake of iodine by the thyroid, lower levels of plasma thyroid-stimulating hormone, and reduced ratio of protein bound to nonprotein bound iodine. Food consumption was also decreased. The changes are likely to have arisen as a compensatory response to an induced heat load. A nonthermal effect of continuous-wave high-frequency radiation has not been shown in this study. The effects were likely to be associated with either physiological compensation for induced heating or restriction of movement
Studying wave optics in exoplanet microlensing light curves
Mehrabi, Ahmad
2012-01-01
We study the wave optics feature of the gravitational microlensing by a binary system composed of parent star and a planet. In the binary system, near the caustic lines multiple images play the role of secondary sources for the observer, in analogy to the double slit Young's experiment. In the case of having coherent wave fronts from the source on the lens plane, images can produce diffraction pattern on the observer plane. For the binary lensing system we have two modes of close and wide images around the planet and lens star and these images can produce two different types of fringes with the high and low frequencies on the observer plane. By taking into account the finite size of the source star, enhancements in the diffraction fringes get dimmer. For the observational prospects, we study this effect for the SKA project in the case of resonance and the high magnification exoplanet channels. This method can partially break degeneracies between the lens parameters.
Making Waves: A Simulation and Modeling Computer-Tool for Studying Wave Phenomena.
Snir, Joseph
1989-01-01
Examines the use of a computer simulation program as a tool to help in the understanding of wave phenomena. After analyzing some of the main difficulties and common misconceptions about waves, features of the "Making Waves" software package are described. Figures showing a typical monitor display are presented. (YP)
Comparative Study of Three Sedative Techniques During Shock Wave Lithotripsy
Wafaa G. Ahmed
2009-01-01
Background: Many authors found that dexmedetomidine is an effective, safe drug for sedation during extracorporeal shock wave lithotripsy (ESWL). Dexmedetomidine is a lipophilic 2-agonist ,which sedates patients by reducing sympathetic activity and the level of arousal ,thus patients lie calmly in beds but are easily roused to full consciousness. In the present study, the sedative, haemodynamics, and respiratory effects, and recovery time of dexmedetomidine and dexmedetomidine/fentanyl combina...
Theoretical study on the first kind of density wave instabilities
International Nuclear Information System (INIS)
The present paper summarizes the theoretical studies carried out by INET (Institute of Nuclear Energy Technology) of Tsinghua University on the first kind of density wave instabilities (DWIs) of natural circulation systems. The analysis methods of DWI and mathematical models of drift flux are presented. Based on the general excess entropy production criterion of non-equilibrium thermodynamics, an energy principle of DWI is established. (author). 10 refs, 16 figs
A Study on Kinematics Characteristics of Freak Wave
Institute of Scientific and Technical Information of China (English)
CUI Cheng; ZHANG Ning-chuan; ZUO Shu-hua; FANG Zhuo
2013-01-01
Based on the 3rd-order Stokes wave theory,the speed of freak waves is formulated in terms of the period and the wave height.Finite modified wave steepness gives rise to a significant enhancement of the nonlinear contributions to the freak wave speed in comparison with the 3rd-order Stokes wave theory.For a fix modified wave steepness,the estimated amplification of the nonlinear contributions due to the deviation from the 3rd-order Stokes wave theory is 0.22～0.99.In addition,the velocity and acceleration fields are also documented in detail.In the present simulation,the horizontal velocities are smaller than the wave speed,and the freak wave exhibits a maximal horizontal velocity up to 37％ of the wave speed and a maximal vertical acceleration up to about 20％ of the gravitational acceleration.
Wave-Structure Interactions on Point Absorbers - an experimental study
DEFF Research Database (Denmark)
Jakobsen, Morten Møller
used in the case studies is a pitching point absorber (Wavestar). The central part of the thesis deals with the challenges, choices, and experi- ences gained during the Ph.D. The more in-depth technical details and results are presented in peer-reviewed publications and technical reports. The chal...... models. Using a modification by Faltinsen to take into account the relative motion of the device, the contributions from drag, excitation and body motion are determined. 2: Determining the peak pressure on the surface on the device during extreme events and in freak conditions. A great deal of work has...... been done to determine peak pressures on mono-piles worldwide, but only very little on spherical structures. In order to shed more light on the wave induced loads on a hemisphere the peak pressures are measured with the traditional drop test and during impact of so-called freak waves. 3: Implementation...
A review of micro-wave techniques in plasma studies
International Nuclear Information System (INIS)
The problem of the application of micro-wave techniques to the study of plasma properties is considered in this report. In section I, the author summarizes a few fundamental laws concerning the theory of waves in an ionised medium as well as measurable effects of transverse and longitudinal propagation. Section II is a rapid review of the experimental methods and of the various measurements which may be effected in very high frequency plasmas. Only recent experimental work carried out since the last U. R.S.I. Assembly is considered. Section III is devoted to micro-wave techniques developed during this period in the laboratories of the Applied Physics Service. These techniques deal with longitudinal propagation and in particular with the propagation along a right mode. Section IV is a general view of similar studies undertaken in European Research Centres working on plasma physics or controlled fusion. Section V is a contribution concerning three particular topics from the Juelich and Max Planck Institute laboratories. (author)
A Study of Water Wave Wakes of Washington State Ferries
Perfect, Bradley; Riley, James; Thomson, Jim; Fay, Endicott
2015-11-01
Washington State Ferries (WSF) operates a ferry route that travels through a 600m-wide channel called Rich Passage. Concerns of shoreline erosion in Rich Passage have prompted this study of the generation and propagation of surface wave wakes caused by WSF vessels. The problem was addressed in three ways: analytically, using an extension of the Kelvin wake model by Darmon et al. (J. Fluid Mech., 738, 2014); computationally, employing a RANS Navier-Stokes model in the CFD code OpenFOAM which uses the Volume of Fluid method to treat the free surface; and with field data taken in Sept-Nov, 2014, using a suite of surface wave measuring buoys. This study represents one of the first times that model predictions of ferry boat-generated wakes can be tested against measurements in open waters. The results of the models and the field data are evaluated using direct comparison of predicted and measured surface wave height as well as other metrics. Furthermore, the model predictions and field measurements suggest differences in wake amplitudes for different class vessels. Finally, the relative strengths and weaknesses of each prediction method as well as of the field measurements will be discussed. Washington State Department of Transportation.
A study on the optimal equation of the continuous wave spectrum
Directory of Open Access Journals (Sweden)
Cho Hong-Yeon
2015-11-01
Full Text Available Waves can be expressed in terms of a spectrum; that is, the energy density distribution of a representative wave can be determined using statistical analysis. The JONSWAP, PM and BM spectra have been widely used for the specific target wave data set during storms. In this case, the extracted wave data are usually discontinuous and independent and cover a very short period of the total data-recording period. Previous studies on the continuous wave spectrum have focused on wave deformation in shallow water conditions and cannot be generalized for deep water conditions. In this study, the Generalized Extreme Value (GEV function is proposed as a more-optimal function for the fitting of the continuous wave spectral shape based on long-term monitored point wave data in deep waters. The GEV function was found to be able to accurately reproduce the wave spectral shape, except for discontinuous waves of greater than 4 m in height.
An Experimental Study on A Trapezoidal Pendulum Wave Energy Converter in Regular Waves
Institute of Scientific and Technical Information of China (English)
王冬姣; 邱守强; 叶家玮
2015-01-01
Experimental studies were conducted on a trapezoidal pendulum wave energy converter in regular waves. To obtain the incident wave height, the analytical method (AM) was used to separate the incident and reflected waves propagating in a wave flume by analysing wave records measured at two locations. The response amplitude operator (RAO), primary conversion efficiency and the total conversion efficiency of the wave energy converter were studied; furthermore, the power take-off damping coefficients corresponding to the load resistances in the experiment were also obtained. The findings demonstrate that the natural period for a pendulum wave energy converter is relatively large. A lower load resistance gives rise to a larger damping coefficient. The model shows relatively higher wave energy conversion efficiency in the range of 1.0-1.2 s for the incident wave period. The maximum primary conversion efficiency achieved was 55.5%, and the maximum overall conversion efficiency was 39.4%.
How to Use a Candle to Study Sound Waves
Carvalho, P. Simeão; Briosa, E.; Rodrigues, M.; Pereira, C.; Ataíde, M.
2013-01-01
It is well known that sound waves in air are longitudinal waves. Although teachers use analogies such as compressing horizontal springs to demonstrate what longitudinal waves look like, students still present some difficulty in understanding that (1) sound waves correspond to oscillations of air particles, and (2) there is no "air flow"…
Energy Technology Data Exchange (ETDEWEB)
Watanabe, T.; Sassa, K. [Kyoto University, Kyoto (Japan); Uesaka, S. [Kyoto University, Kyoto (Japan). Faculty of Engineering
1996-10-01
The effect of initial models on full-wave inversion (FWI) analysis based on acoustic wave-equation was studied for elastic wave tomography of underground structures. At present, travel time inversion using initial motion travel time is generally used, and inverse analysis is conducted using the concept `ray,` assuming very high wave frequency. Although this method can derive stable solutions relatively unaffected by initial model, it uses only the data of initial motion travel time. FWI calculates theoretical waveform at each receiver using all of observed waveforms as data by wave equation modeling where 2-D underground structure is calculated by difference calculus under the assumption that wave propagation is described by wave equation of P wave. Although it is a weak point that FWI is easily affected by noises in an initial model and data, it is featured by high resolution of solutions. This method offers very excellent convergence as a proper initial model is used, resulting in sufficient performance, however, it is strongly affected by initial model. 2 refs., 7 figs., 1 tab.
Modeling study of mesospheric planetary waves: genesis and characteristics
Directory of Open Access Journals (Sweden)
H. G. Mayr
2004-06-01
Full Text Available The Numerical Spectral Model (NSM extends from the ground into the thermosphere and incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GWs. In the present version of the model we account for a tropospheric heat source in the zonal mean (m=0, which reproduces qualitatively the observed zonal jets near the tropopause and the accompanying reversal in the latitudinal temperature variations. In the study presented here, we discuss the planetary waves (PWs that are solely generated internally, i.e. without the explicit excitation sources related to tropospheric convection or topography. Our analysis shows that PWs are not produced when the zonally averaged heat source into the atmosphere is artificially suppressed, and that the PWs are generally weaker when the tropospheric source is not applied. Instabilities associated with the zonal mean temperature, pressure and wind fields, which still need to be explored, are exciting PWs that have amplitudes in the mesosphere comparable to those observed. Three classes of PWs are generated in the NSM. (1 Rossby type PWs, which slowly propagate westward relative to the mean zonal flow, are carried by the winds so that they appear (from the ground to propagate, respectively, eastward and westward in the winter and summer hemispheres below 80km. Depending on the zonal wave number and magnitudes of the zonal winds, and under the influence of the equatorial oscillations, these PWs typically have periods between 2 and 20 days. Their horizontal wind amplitudes can exceed 40 m/s in the lower mesosphere. (2 Rossby-gravity waves, which propagate westward at low latitudes and have periods around 2 days for zonal wave numbers m=2 to 4. (3 Eastward propagating equatorial Kelvin waves, which are generated in the upper mesosphere with periods between 1 and 3 days depending on m. A survey of the PWs reveals that the largest wind amplitudes tend to occur below 80km in the winter hemisphere
Non Axisymmetric Three-Dimensional Magnetic Bernstein-Greene-Kruskal (BGK) Modes
Ng, Chung-Sang
2013-10-01
The theory of three-dimensional (3D) magnetic Magnetic Bernstein-Greene-Kruskal (BGK) modes has been generalized to the non axisymmetric case. While the shape of the electrostatic structure is usually elongated along the direction of the strong large-scale magnetic field, a limiting case with the elongated direction along one of the perpendicular direction is also possible. Essentially this makes the solution 2D with the magnetic field on the 2D plane. Note that such 2D BGK modes are very different from those described by another theory, of which the magnetic field is perpendicular to the 2D plane. This theory might explain 2D BGK modes observed in some numerical simulations. This work is supported by a National Science Foundation grant PHY-1004357 and by the National Science Foundation of China NSFC under Grant No. 41128004.
A Lithospheric Study of Eastern Asia Using Surface Wave Dispersion
Pasyanos, M. E.; Walter, W. R.; Flanagan, M. P.
2003-12-01
We have continued our study of surface-wave group-velocity dispersion across Eastern Asia in the vicinity of the Korean Peninsula, Yellow Sea, and Sea of Japan. We primarily use seismic data from permanent stations in South Korea, China, Japan, Taiwan and Russia. We also use data from several IRIS PASSCAL deployments in China and North Korea. We measure group-velocity using multiple narrow-band filters on deconvolved displacement data. We use a conjugate gradient method to perform a high-resolution group-velocity tomography over the region. Our current results include Rayleigh wave inversions for periods from 10 to 100 seconds. There is an excellent correspondence between the group velocities and tectonic structure, including large sedimentary features and crustal thickness variations. At long periods (> 50 sec), we find that the inversion has features associated with the subduction of the Pacific and Philippine Plates under the Eurasian continent, including the effects of the subducting slab and magmatic arc. We use the group-velocity results to model the shear-velocity structure of the crust and upper mantle across the region. We employ a grid-search technique to fit the Rayleigh wave group-velocities over the whole period range. This does a very good job at retrieving features in the crust and uppermost mantle. Deeper features in the mantle, however, are harder to model directly using this method. To resolve these features, we will be forwarding modeling the structure by constructing several models of the subduction zone. We will then be testing the various models by comparing the group velocities predicted by the models to the observed group velocities along cross-sections. Preliminary results indicate that the magmatic arc has the largest affect on the long period surface waves, with the subducting slab being a much subtler feature.
Experimental Study of Wave Forces on Vertical Circular Cylinders in Long and Short Crested Sea
DEFF Research Database (Denmark)
Høgedal, Michael
in the transverse wave forces on the structure, whereas the vertical forces generally are unaffected. In this study the effect from wave directionality on the horizontal wave forces on a slender vertical cylinder in a laboratory environment is investigated. In addition wave forces from regular waves......The three-dimensional structure of ocean waves is generally ignored in favour of two-dimensional waves, which are easier to handle from a theoretical and computational point of view. For design fixed structures where horizontal in-line and resultant wave forces are important, this is normally on...... the safe side, as the directional spreading of the wave field Ieads to reduced horizontal velocities and acceleration; in the fluid and hence a reduction of the resultant and in-line wave forces on the structure. The directional spreading of the horizontal velocity field generally causes an increase...
Lay, E. H.; Shao, X. M.; Kendrick, A.
2014-12-01
Gravity waves with periods greater than 5 minutes and acoustic waves with periods between 3 and 5 minutes have been detected at ionospheric heights (250-350 km) and associated with severe thunderstorms. Modeling results support these findings, indicating that acoustic waves should be able to reach 250-350 km within ~250 km horizontally of the source, and gravity waves should be able to propagate significantly further. However, the mechanism by which the acoustic waves are generated and the ubiquity of occurrence of both types of wave is unknown. We use GPS total electron content measurements to detect gravity and acoustic waves in the ionosphere. We perform a statistical study from 2005 May - July to compare the occurrence rate and horizontal extent of the waves to storm size and convective height from NEXRAD radar measurements. It is found that both gravity waves and acoustic wave horizontal extent is primarily associated with storm size and not convective height.
BIOLOGICAL EFFECTS OF PULSED SHORT WAVE TREATMENT. AN EXPERIMENTAL STUDY
Directory of Open Access Journals (Sweden)
Dogaru Gabriela
2015-02-01
Full Text Available Pulsed short waves are short electromagnetic waves emitted as intermittent trains with a fixed duration, separated by free intervals of variable duration. The biological effects of pulsed short waves could be explained according to most of the authors by an activation of cellular enzymatic reactions, a stimulation of energy metabolism, a stimulation of liver function, of adrenal gland function and of the reticulocyte system, changes in cell permeability, by an increase of peripheral blood flow through the enhancement of local vascularization. This research aimed to investigate the biological effects of exposure to pulsed short waves at different doses on the adrenal glands of experimental animals, by structural and ultrastructural studies. The study included 35 animals assigned to 4 groups. Group I included 10 experimental animals exposed to radiation at a dose of 1/80 impulses/sec, group II, 10 animals exposed to a dose of 4/400 impulses/sec, group III, 10 animals exposed to a dose of 6/600 impulses/sec, for 10 min/day, and the control group consisted of 5 unexposed animals. Structural and ultrastructural changes of adrenal glands induced by the dose of 4/400 impulses/sec, compared to the unexposed control group and the dose of 1/80 impulses/sec, include an intensification of protein synthesis processes, an enhancement of energy metabolism in providing the energy required for an increased production of hormones, an intensification of collagen fiber synthesis processes in the capsule, necessary for healing. It was demonstrated that this dose induced an intensification of hormone synthesis and secretion, a stimulation of adrenal function. At the dose of 6/600 cycles/sec, a slight diminution of hormone synthesis and secretion activity was found, which was not below the limits existing in the unexposed control group, but was comparable to group II. This dose is probably too strong for experimental animals, inducing them a state of stress. The
Directory of Open Access Journals (Sweden)
S. Lecacheux
2012-07-01
Full Text Available This paper outlines a new approach devoted to the analysis of extreme waves in presence of several wave regimes. It entails discriminating the different wave regimes from offshore wave data using classification algorithms, before conducting the extreme wave analysis for each regime separately. The concept is applied to the pilot site of Reunion Island which is affected by three main wave regimes: southern waves, trade-wind waves and cyclonic waves. Several extreme wave scenarios are determined for each regime, based on real historical cases (for cyclonic waves and extreme value analysis (for non-cyclonic waves. For each scenario, the nearshore wave characteristics are modelled all around Reunion Island and the linear theory equations are used to back calculate the equivalent deep-water wave characteristics for each portion of the coast. The relative exposure of the coastline to the extreme waves of each regime is determined by comparing the equivalent deep-water wave characteristics.
This method provides a practical framework to perform an analysis of extremes within a complex environment presenting several sources of extreme waves. First, at a particular coastal location, it allows for inter-comparison between various kinds of extreme waves that are generated by different processes and that may occur at different periods of the year. Then, it enables us to analyse the alongshore variability in wave exposition, which is a good indicator of potential runup extreme values. For the case of Reunion Island, cyclonic waves are dominant offshore around the island, with equivalent deep-water wave heights up to 18 m for the northern part. Nevertheless, due to nearshore wave refraction, southern waves may become as energetic as cyclonic waves on the western part of the island and induce similar impacts in terms of runup and submersion. This method can be easily transposed to other case studies and can be adapted, depending on the data
Wave Energy, Lever Operated Pivoting Float LOPF Study
DEFF Research Database (Denmark)
Margheritini, Lucia
The fully instrumented Resen Waves Lever Operated Pivoting Float LOPF wave energy buoy model has gone through the first stage of testing in regular waves in scale 1:25 of the North Sea wave conditions, in the 3D deep wave basin at the Hydraulic and Coastal Engineering Laboratory of Aalborg...... for maximum energy output in regular as well as irregular waves. During storms the buoy pivots and streamlines itself to minimize loads on the mooring line. A conservative estimate shows that a full scale system for North Sea conditions has a float size width of 15 m that will, with 60% generator...
Institute of Scientific and Technical Information of China (English)
MIN Qi; YIN Yao; LI Xiaodong; LIU Ke
2011-01-01
A standing-wave tube with tapered section （STTS） was evolved from a standingwave tube with abrupt section （STAS） whose abrupt section was replaced with tapered section. The research was intended to compare the acoustic properties and the extremely nonlinear pure standing waves of STTS with those of STAS. The acoustic properties of the STTS were studied with transfer matrix. It was proved, like the STAS, that the STTS was dissonant standingwave tube. With its dissonant property, the 181 dB extremely nonlinear pure standing wave was obtained in the STTS excited at its first resonance frequency. Then the comparative experimental studies on the saturation properties of the extremely nonlinear standing waves were carried out in the STTS and the STAS with the same length. It was found that the STTS could suppress the harmonics and meanwhile reduce energy loss of the standing wave more effectively. Compared with the STAS, under the same voltage of loudspeaker, the STTS obtained a higher extremely nonlinear pure standing wave. Moreover, it was found for the STTS that the third harmonic of the third resonance frequency was close to the seventh resonance frequency of sound source impedance, to which the valley value of the sound pressure level transfer function corresponded. Because of this, the third harmonic increased rapidly with the increase of fundamental wave and tended to saturate.
Parallel Traveling-wave MRI: A Feasibility Study
Pang, Yong; Daniel B Vigneron; Zhang, Xiaoliang
2011-01-01
Traveling-wave MRI utilizes far fields of a single-piece patch antenna in the magnet bore to generate RF fields for imaging large-size samples, such as the human body. In this work, the feasibility of applying the “traveling-wave” technique to parallel imaging is studied using microstrip patch antenna arrays with both the numerical analysis and experimental tests. A specific patch array model is built and each array element is a microstrip patch antenna. Bench tests show that decoupling betwe...
Study on Rayleigh Wave Inversion for Estimating Shear-wave Velocity Profile
Directory of Open Access Journals (Sweden)
T.A. Sanny
2003-05-01
Full Text Available Rayleigh wave or ground roll is a noise in seismic body waves. However, how to use this noise for soil characterization is very interesting since Rayleigh wave phase velocity is a function of compression-wave velocity, shear-wave velocity, density and layer thickness. In layered-medium Rayleigh wave velocity also depends on wavelength or frequency, and this phenomenon is called dispersion. Inversion procedure to get shear-wave velocity profile needs a priori information about the solution of the problem to limit the unknown parameters. The Lagrange multiplier method was used to solve the constrained optimization problems or well known as a smoothing parameter in inversion problems. The advantage of our inversion procedure is that it can guarantee the convergence of solution even though the field data is incomplete, insufficient, and inconsistent. The addition of smoothing parameter can reduce the time to converge. Beside numerical stability, the statistical stability is also involved in inversion procedure. In field experiment we extracted ground roll data from seismic refraction record. The dispersion curves had been constructed by applying f-k analysis and f-k dip filtering. The dispersion curves show the dependence of Rayleigh wave phase velocities in layered media to frequency. The synthetic models also demonstrate the stability and the speed of inversion procedure.
Global ion cyclotron waves in a perpendicularly stratified, one-dimensional warm plasma
International Nuclear Information System (INIS)
The sixth-order wave equation which results from a finite temperature expansion of the Vlasov equation is solved globally in a perpendicularly stratified, one-dimensional slab plasma. The diamagnetic drift and associated anisotropy are included in the unperturbed distribution function to ensure a self-adjoint system. All x-dependence in the plasma pressure and magnetic field is retained along with the electric field parallel to vector B. Thus, Landau damping of the ion Bernstein wave is included as well. Because the wave equation is solved implicitly as a two-point boundary value problem, the evanescent short-wavelength Bernstein waves do not grow exponentially as in shooting methods. Solutions to the complete sixth-order partial differential equation are compared to those from an approximate second-order equation based on local dispersion theory. Strong variations occur in the absorption and in the structure of the wave fields as resonance topology is varied
Comparative study on spreading function for directional wave spectra
Digital Repository Service at National Institute of Oceanography (India)
Bhat, S.S.; Anand, N.M.; Nayak, B.U.
The planning and design of all coastal and offshore installations call for an information on wave directionality. This can be accurately obtained through the knowledge of the directional wave spectrum which is commonly given as a product of one...
Institute of Scientific and Technical Information of China (English)
兰朝凤; 李凤臣; 陈欢; 卢迪; 杨德森; 张梦
2015-01-01
Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves’ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.
Experimental study on the scour around a monopile in breaking waves
DEFF Research Database (Denmark)
Nielsen, Anders Wedel; Sumer, B. Mutlu; Ebbe, Sebastian Schjelde;
2012-01-01
The scour process around monopiles caused by breaking waves is studied experimentally using regular waves. The use of regular waves is conservative, which made it possible to avoid scour phenomena caused by nonbreaking waves such as scour generation and backfilling. The waves were breaking on a...... maximum scour depth found was approximately 0:60D. This was smaller than the scour observed around piles exposed to current; however, in some cases it was an order of magnitude larger than the scour caused by nonbreaking waves. This is apparently especially true for larger piles....
Numerical Study of Two-Dimensional Focusing Waves
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Two-dimensional focusing waves are generated and investigated by numerical method. The numerical model is developed by introducing the wave maker boundary on the high-order spectral (HOS) method proposed by Dommermuth and Yue in 1987 and verified by theoretical and experimental data. Some cases of focusing waves considering different parameters such as assumed focusing amplitudes, frequency bandwidth, central frequency and frequency spectrum are generated. Characteristics of the focusing wave including surface elevations, the maximum crest, shift of focusing points and frequency spectra are discussed. The results show that the focusing wave characteristics are strongly affected by focusing amplitudes, frequency bandwidth, central frequency and frequency spectrum.
Rayleigh-wave Tomography Study of Northwestern Canada
McLellan, M. E.; Audet, P.; Schaeffer, A. J.
2015-12-01
Due to the ongoing collision of the Yakutat block with the North American plate in southeastern Alaska, a significant amount of deformation is occurring in the northern Canadian Cordillera. The stress transfer associated with the accretion of this terrane is believed to be responsible for the seismicity across this widespread region. Estimates of crustal thickness within the Mackenzie and Richardson Mountains provide constraints on models describing the evolution of crustal roots responsible for supporting such belts that transmit tectonic stresses over long distances (>1000 km); unfortunately, current seismic velocity models used to map crustal thickness have limited resolution due to sparse coverage by seismograph networks. Here we use data from a new regional seismograph network (Yukon-Northwest Seismograph Network - YNSN) as well as permanent stations to map out crustal structure. Crustal thickness variations can be obtained from 3-D seismic velocity models determined from the inversion of surface-wave dispersion data. In this work we present preliminary results of a regional tomography study of northwestern Canada, encompassing the northern Canadian Cordillera, using dispersion curves derived from ambient noise cross-correlations in addition to teleseismic two-station interferometry. We collected all available vertical component seismic data from stations located in the Yukon and surrounding regions from the period between June 2012 and June 2015. Using this data set, we first cross-correlated hour-long segments of the ambient seismic noise between all available stations pairs that share common data availability and obtained virtual Rayleigh waves with energy over periods 10-50 s that are predominantly sensitive to crust and uppermost mantle structure. This data set is complemented by Rayleigh-wave dispersion measurements, spanning the period range 25—175 s, derived by cross-correlating vertical component data from teleseismic earthquakes (M>5) lying along
Buoy and Generator Interaction with Ocean Waves: Studies of a Wave Energy Conversion System
Energy Technology Data Exchange (ETDEWEB)
Lindroth, Simon
2011-07-01
On March 13th, 2006, the Div. of Electricity at Uppsala Univ. deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed. This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values. The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly. The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong. As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that
Dumitru Baleanu; Mohsen Alipour; Hossein Jafari
2013-01-01
We obtain the approximate analytical solution for the fractional quadratic Riccati differential equation with the Riemann-Liouville derivative by using the Bernstein polynomials (BPs) operational matrices. In this method, we use the operational matrix for fractional integration in the Riemann-Liouville sense. Then by using this matrix and operational matrix of product, we reduce the problem to a system of algebraic equations that can be solved easily. The efficiency and accuracy of the propos...
Recent Results of Alfven Wave Studies in TCABR
International Nuclear Information System (INIS)
The results on comparative studies of Alfven wave plasma heating by two different antenna types in TCABR are presented. Emphasis is placed on the excited wave spectra and parasitic coupling with the edge plasma. The antenna modules have two groups of RF current-carrying straps separated by a toroidal angle of approximately 22 deg. In type I antenna, each group consists of two circular loops that are cut in two half-turn windings. The feeders of each loop pair are rotated 90 deg. in the poloidal direction with respect to each other, to decrease the mutual coupling between them and make it possible to excite single helicity plasma modes (M=+1 or M=-1). In type II antenna, each group consists of two poloidal straps located at the low-magnetic-field side of the vacuum chamber. The poloidal extension of each strap is around 90 deg. and the angle between straps is also of the same value. In both antenna types, the straps have side protectors of boron nitride. Initial experiments indicate that the parasitic interaction with the edge plasma is quite different for the two antennae. Also the first type has larger self-inductance, making it more difficult to deliver high currents to the antenna without increasing the dynamic polarization voltage up to breakdown limits. Results on the excited spectrum and floating potential at the plasma edge are presented
Study of an ultrasonic generation by the electromagnetic waves
International Nuclear Information System (INIS)
The main subject of this work is the development of a bulk-wave EMAT (Electro-Magnetic Acoustic Transducer) semi-analytical model. At first, we consider the general theory behind this type of transduction, especially in the case of P-Waves; this is followed by an experimental study which points out the need of modelling for the design of EMAT probes. Under certain hypotheses, this modelling can be reduced to three separate models: one model giving the eddy currents, another one the permanent magnetic field and one for the acoustic field generated by a surface density of forces. For each of these phenomena, 3-D semi-analytical models are built: they are based on a decomposition of the source terms into elementary sources. The final solutions are obtained through a convolution of the elementary solutions and of the sources. The implementation of these models is then given, as well as some applications to the field of EC and of EMAT. (author)
Experimental study of the acoustoelastic Lamb wave in thin plates
Pei, Ning; Bond, Leonard J.
2016-02-01
Many factors can cause residual stresses in industry, like rolling, welding and coating. Residual stresses can have both benefits and shortcomings on components, so it is important to find the residual stresses out and enhance its benefits part and get rid of its harmful part. There are many methods for residual stresses detection and ultrasonic method turns out to be a good one for it is nondestructive, relative cheap and portable. The critically refracted longitudinal (LCR) wave is widely used for it is regarded most sensitive to stress and less sensitive to texture which can influence detection results. Ultrasonic methods for residual stresses detection are based on time of flight (TOF) measurement, but because the measurement should reach nanosecond to show stress change, there are many other factors that can influence TOF, like temperature, texture of the components and even the thickness of the couplant. So increasing the TOF's sensitivity to stress is very important. In this paper the relationships between velocity and frequency are studied experimentally[6] for different Lamb modes, under various stress loadings. The result shows that the sensitivity of different modes various a lot, the A1 mode is the most sensitivity, compared to S0, S1 and A0 modes; if the force is added to 100 MPa, the change stress of A1 mode can be as large to 80 m/s, which is about 10 times more sensitive than the traditional bulk wave. This makes it as a good choice for residual stress detection.
Experimental and numerical studies on standing surface acoustic wave microfluidics.
Mao, Zhangming; Xie, Yuliang; Guo, Feng; Ren, Liqiang; Huang, Po-Hsun; Chen, Yuchao; Rufo, Joseph; Costanzo, Francesco; Huang, Tony Jun
2016-02-01
Standing surface acoustic waves (SSAW) are commonly used in microfluidics to manipulate cells and other micro/nano particles. However, except for a simple one-dimensional (1D) harmonic standing waves (HSW) model, a practical model that can predict particle behaviour in SSAW microfluidics is still lacking. Herein, we established a two-dimensional (2D) SSAW microfluidic model based on the basic theory in acoustophoresis and our previous modelling strategy to predict the acoustophoresis of microparticles in SSAW microfluidics. This 2D SSAW microfluidic model considers the effects of boundary vibrations, channel materials, and channel dimensions on the acoustic propagation; as an experimental validation, the acoustophoresis of microparticles under continuous flow through narrow channels made of PDMS and silicon was studied. The experimentally observed motion of the microparticles matched well with the numerical predictions, while the 1D HSW model failed to predict many of the experimental observations. Particularly, the 1D HSW model cannot account for particle aggregation on the sidewall in PDMS channels, which is well explained by our 2D SSAW microfluidic model. Our model can be used for device design and optimization in SSAW microfluidics. PMID:26698361
Assessing the first wave of epidemiological studies of nanomaterial workers
International Nuclear Information System (INIS)
The results of early animal studies of engineered nanomaterials (ENMs) and air pollution epidemiology suggest that it is important to assess the health of ENM workers. Initial epidemiological studies of workers’ exposure to ENMs (<100 nm) are reviewed and characterized for their study designs, findings, and limitations. Of the 15 studies, 11 were cross-sectional, 4 were longitudinal (1 was both cross-sectional and longitudinal in design), and 1 was a descriptive pilot study. Generally, the studies used biologic markers as the dependent variables. All 11 cross-sectional studies showed a positive relationship between various biomarkers and ENM exposures. Three of the four longitudinal studies showed a negative relationship; the fourth showed positive findings after a 1-year follow-up. Each study considered exposure to ENMs as the independent variable. Exposure was assessed by mass concentration in 10 studies and by particle count in six studies. Six of them assessed both mass and particle concentrations. Some of the studies had limited exposure data because of inadequate exposure assessment. Generally, exposure levels were not very high in comparison to those in human inhalation chamber studies, but there were some exceptions. Most studies involved a small sample size, from 2 to 258 exposed workers. These studies represent the first wave of epidemiological studies of ENM workers. They are limited by small numbers of participants, inconsistent (and in some cases inadequate) exposure assessments, generally low exposures, and short intervals between exposure and effect. Still, these studies are a foundation for future work; they provide insight into where ENM workers are experiencing potentially adverse effects that might be related to ENM exposures
Assessing the first wave of epidemiological studies of nanomaterial workers
Energy Technology Data Exchange (ETDEWEB)
Liou, Saou-Hsing, E-mail: shliou@nhri.org.tw [National Health Research Institutes, National Institute of Environmental Health Sciences (China); Tsai, Candace S. J. [Colorado State University, Department of Environmental and Radiological Health Science (United States); Pelclova, Daniela [Charles University in Prague, Department of Occupational Medicine, First Faculty of Medicine (Czech Republic); Schubauer-Berigan, Mary K.; Schulte, Paul A. [National Institute for Occupational Safety and Health (United States)
2015-10-15
The results of early animal studies of engineered nanomaterials (ENMs) and air pollution epidemiology suggest that it is important to assess the health of ENM workers. Initial epidemiological studies of workers’ exposure to ENMs (<100 nm) are reviewed and characterized for their study designs, findings, and limitations. Of the 15 studies, 11 were cross-sectional, 4 were longitudinal (1 was both cross-sectional and longitudinal in design), and 1 was a descriptive pilot study. Generally, the studies used biologic markers as the dependent variables. All 11 cross-sectional studies showed a positive relationship between various biomarkers and ENM exposures. Three of the four longitudinal studies showed a negative relationship; the fourth showed positive findings after a 1-year follow-up. Each study considered exposure to ENMs as the independent variable. Exposure was assessed by mass concentration in 10 studies and by particle count in six studies. Six of them assessed both mass and particle concentrations. Some of the studies had limited exposure data because of inadequate exposure assessment. Generally, exposure levels were not very high in comparison to those in human inhalation chamber studies, but there were some exceptions. Most studies involved a small sample size, from 2 to 258 exposed workers. These studies represent the first wave of epidemiological studies of ENM workers. They are limited by small numbers of participants, inconsistent (and in some cases inadequate) exposure assessments, generally low exposures, and short intervals between exposure and effect. Still, these studies are a foundation for future work; they provide insight into where ENM workers are experiencing potentially adverse effects that might be related to ENM exposures.
Study on the electromagnetic waves propagation characteristics in partially ionized plasma slabs
Directory of Open Access Journals (Sweden)
Zhi-Bin Wang
2016-05-01
Full Text Available Propagation characteristics of electromagnetic (EM waves in partially ionized plasma slabs are studied in this paper. Such features are significant to applications in plasma antennas, blackout of re-entry flying vehicles, wave energy injection to plasmas, and etc. We in this paper developed a theoretical model of EM wave propagation perpendicular to a plasma slab with a one-dimensional density inhomogeneity along propagation direction to investigate essential characteristics of EM wave propagation in nonuniform plasmas. Particularly, the EM wave propagation in sub-wavelength plasma slabs, where the geometric optics approximation fails, is studied and in comparison with thicker slabs where the geometric optics approximation applies. The influences of both plasma and collisional frequencies, as well as the width of the plasma slab, on the EM wave propagation characteristics are discussed. The results can help the further understanding of propagation behaviours of EM waves in nonuniform plasma, and applications of the interactions between EM waves and plasmas.
Tidal and gravity waves study from the airglow measurements at Kolhapur (India)
Indian Academy of Sciences (India)
R N Ghodpage; Devendraa Siingh; R P Singh; G K Mukherjee; P Vohat; A K Singh
2012-12-01
Simultaneous photometric measurements of the OI 557.7 nm and OH (7, 2) band from a low latitude station, Kolhapur (16.8°N, 74.2°E) during the period 2004–2007 are analyzed to study the dominant waves present in the 80–100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours have been recorded. Some of these waves having subharmonic tidal oscillation periods 4, 6, 8 and 12 hours propagate upward with velocity lying in the range 1.6–11.3 m/s and the vertical wave length lying between 28.6 and 163 kms. The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application of these waves in studying the thermal structure of the region is discussed.
Experimental Study of Large-Amplitude Faraday Waves in Rectangular Cylinders
Iek, Chanthy; Alexander, Iwan J.; Tin, Padetha; Adamovsky, Gregory
2005-01-01
Experiment on single-mode Faraday waves having two, thee, and four wavelengths across a rectangular cylinder of high aspect ratio is the subject of discussion. Previous experiments recently done by Henderson & Miles (1989) and by Lei Jiang et. a1 (1996) focused on Faraday waves with one and two wavelengths across rectangular cylinders. In this experimental study the waves steepness ranges from small at threshold levels to a large amplitude which according to Penny & Price theory (1952) approaches the maximum sustainable amplitude for a standing wave. The waves characteristics for small amplitudes are evaluated against an existing well known linear theory by Benjamin & Ursell (l954) and against a weakly nonlinear theory by J. Miles (1984) which includes the effect of viscous damping. The evaluation includes the wave neutral stability and damping rate. In addition, a wave amplitude differential equation of a linear theory including viscous effect by Cerda & Tirapegui (1998) is solved numerically to yield prediction of temporal profiles of both wave damping and wave formation at the threshold. An interesting finding from this exercise is that the fluid kinematic viscosity needs to increase ten times in order to obtain good agreement between the theoretical prediction and the experimental data for both wave damping and wave starting. For large amplitude waves, the experimental data are evaluated against the theory of Penny & Price which predicts wave characteristics of any amplitude up to the point at which the wave reaches its maximum amplitude attainable for a standing wave. The theory yields two criteria to show the maximum wave steepness, the vertical acceleration at the wave crest of half the earth gravity field acceleration and the including angle at the crest of 90 degrees. Comparison with experimental data shows close agreement for the wave crest acceleration but a large discrepancy for the including angle. Additional information is included in the original
Results of an Experimental Study of the Langlee Wave Energy Converter
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter; Espedal, J.;
2010-01-01
This paper presents the results of the first experimental study of the Langlee wave energy converter (WEC), a semi-submerged oscillating wave surge converter. Its design extracts the energy from the surge motion of the waves through two pairs of working flaps, called water wings, which are placed...
Model Study of Wave Overtopping of Marine Structure for a Wide Range of Geometric Parameters
DEFF Research Database (Denmark)
Kofoed, Jens Peter
2000-01-01
The objective of the study described in this paper is to enable estimation of wave overtopping rates for slopes/ramps given by a wide range of geometric parameters when subjected to varying wave conditions. To achieve this a great number of model tests are carried out in a wave tank using irregul...
Brunet, P.; Baudoin, M; Matar, O. Bou; Zoueshtiagh, F.
2010-01-01
We present an experimental study of a droplet interacting with an ultrasonic surface acoustic wave (SAW). Depending on the amplitude of the wave, the drop can either experience an internal flow with its contact-line pinned, or (at higher amplitude) move along the direction of the wave also with internal flow. Both situations appear together with oscillations of the drop free-surface. The physical origins of the internal mixing flow as well as the drop displacement and surface waves are still ...
A study on the Antarctic circumpolar wave mode-A coexistence system of standing and traveling wave
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The Antarctic circumpolar wave (ACW) has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of the Antarctic Circumpolar Current (ACC). In order to analyze the mechanism of discontinuity along the latitudinal propagation, a new idea that ACW is a system with a traveling wave in the Southern Pacific and Atlantic Ocean and with a concurrent standing wave in the southern Indian Ocean is proposed in this paper. Based on the ideal wave principle, the average wave parameters of ACW is achieved using a non-linear approximation method, by which we find that the standing part and the traveling part possess similar radius frequency, proving their belonging to an integral system. We also give the latitudinal distribution of wave speed with which we could tell the reason for steady propagation during the same period. The spatial distribution of the propagation reveals complex process with variant spatial and temporal scales-The ENSO scale oscillation greatly impacts on the traveling process, while the result at the south of Australia indicates little connection between the Indian Ocean and the Pacific, which may be blocked by the vibration at the west of the Pacific. The advective effect of ACC on the propagation process should be examined clearly through dynamical method.
Energy Technology Data Exchange (ETDEWEB)
Kuwahata, A., E-mail: kuwahata@ts.t.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656 (Japan); Igami, H. [National Institute for Fusion Science, Toki 509-5292 (Japan); Kawamori, E. [Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan (China); Kogi, Y. [Fukuoka Institute of Technology, Fukuoka 811-0295 (Japan); Inomoto, M.; Ono, Y. [Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561 (Japan)
2014-10-15
We report the observation of electromagnetic radiation at high harmonics of the electron cyclotron frequency that was considered to be converted from electrostatic waves called electron Bernstein waves (EBWs) during magnetic reconnection in laboratory overdense plasmas. The excitation of EBWs was attributed to the thermalization of electrons accelerated by the reconnection electric field around the X-point. The radiative process discussed here is an acceptable explanation for observed radio waves pulsation associated with major flares.
Experimental study of internal wave generation by convection in water
Bars, Michael Le; Perrard, Stéphane; Ribeiro, Adolfo; Rodet, Laetitia; Aurnou, Jonathan M; Gal, Patrice Le
2015-01-01
We experimentally investigate the dynamics of water cooled from below at 0^oC and heated from above. Taking advantage of the unusual property that water's density maximum is at about 4^oC, this set-up allows us to simulate in the laboratory a turbulent convective layer adjacent to a stably stratified layer, which is representative of atmospheric and stellar conditions. High precision temperature and velocity measurements are described, with a special focus on the convectively excited internal waves propagating in the stratified zone. Most of the convective energy is at low frequency, and corresponding waves are localized to the vicinity of the interface. However, we show that some energy radiates far from the interface, carried by shorter horizontal wavelength, higher frequency waves. Our data suggest that the internal wave field is passively excited by the convective fluctuations, and the wave propagation is correctly described by the dissipative linear wave theory.
NUMERICAL STUDY OF SOLITARY WAVE FISSION OVER AN UNDERWATER STEP
Institute of Scientific and Technical Information of China (English)
LU Ji; YU Xi-ping
2008-01-01
Solitary wave fission over an underwater step is numerically investigated. The numerical model is based on the enhanced Boussinesq equations, which appropriately represent both the nonlinearity and dispersivity of surface water waves. The finite difference method defined on the staggered grid in space with an implicit scheme for time stepping is employed for the numerical solution of the governing equations. It is demonstrated that Boussinesq type equations, though they are vertically integrated, can describe the details of the solitary wave fission process with very good accuracy. Numerical results of the reflected and transmitting wave heights, the number of solitons emitted from the transmitting wave and their amplitudes all agree very well with the analytical solution derived from KdV equation by virtue of a linear long wave approximation in the vicinity of the underwater step.
Experimental study on modulational instability and evolution of crescent waves
Directory of Open Access Journals (Sweden)
Ya-long ZHOU
2012-12-01
Full Text Available A series of experiments on the instability of steep water wave trains in water with finite water depths and infinite water depths in a wide wave basin were performed. It was found that under the coupled development of modulational instability and class-II instability, the initial two-dimensional steep wave trains evolved into three-dimensional crescent waves, followed by the occurrence of disordered water surfaces, and that the wave energy transferred to sidebands in the amplitude spectrum of the water surface elevation. The results also show that water depth has a significant effect on the growth of modulational instability and the evolution of crescent waves. The larger the water depth, the more quickly the modulational instability suppresses class-II instability.
BIOLOGICAL EFFECTS OF PULSED SHORT WAVE TREATMENT. AN EXPERIMENTAL STUDY
Dogaru Gabriela; Crăciun Constantin
2015-01-01
Pulsed short waves are short electromagnetic waves emitted as intermittent trains with a fixed duration, separated by free intervals of variable duration. The biological effects of pulsed short waves could be explained according to most of the authors by an activation of cellular enzymatic reactions, a stimulation of energy metabolism, a stimulation of liver function, of adrenal gland function and of the reticulocyte system, changes in cell permeability, by an increase of peripheral blood flo...
Experimental Study on Silt Incipient Motion Under Wave Action
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Experiments on silt incipient motion under wave action were carried out. Under wave action, for different wave periods, water depths and bulk densities of silt, the shear stress or height of waves for incipient motion was determined, and a relation between the shear stress and bulk density of silt was established. Results indicate that the critical shear stress depends on the structure of the silt itself, related to the tightness between the grains (or bulk density). Exterior condition is only an external cause of silt incipient motion, and the critical shear stress for the incipient motion is the token of exterior condition.
Pulse wave analysis with two tonometric devices: a comparison study
International Nuclear Information System (INIS)
Pulse wave analysis is a pivotal tool to estimate central haemodynamic parameters. Available commercial devices use applanation tonometry and have been validated against invasive catheterism. We previously observed differences on a radial second systolic peak (rSPB2) between two commonly used devices: SphygmoCor (AtCor, Australia) and PulsePen (DiaTecne, Italy). The aim of our study was to further quantify differences in radial and carotid signals from the two devices.We measured radial and carotid waveforms in 38 patients with minimal changes between systolic, diastolic blood pressure and heart rate. rSBP2, mean pressure, form factor and augmentation index were different with SphygmoCor providing lower values (mean differences: 2.2 ± 3.8 mmHg; 1.5 ± 1.7 mmHg; 3.2 ± 3.5%; 4.2 ± 8.4%, respectively). Carotid augmentation index and form factor were similar. However carotid systolic pressure (cSBP) from PulsePen was higher than cSBP from SphygmoCor (2.7 ± 4.4 mmHg, p < 0.001). For both carotid and radial signals, harmonics moduli were similar across the spectrum with the exception of the 1st harmonic. PulsePen and SphygmoCor sensors are not equivalent and provide different wave shapes despite similar harmonics content with more discrepancy on radial derived parameters than on carotid derived parameters. Further studies are required to compare invasive pressure parameters to indices derived from these two devices. (paper)
A study on elastic guided wave propagation in multi-layered structures
International Nuclear Information System (INIS)
In this study, we have developed a program which can calculate phase and group velocities, attenuation and wave structures of each mode in multi-layered plates. The wave structures of each mode are obtained, varying material properties and number of layers. The correlation between attenuation and out of plane displacement is also explored. It Is shown that to improve understanding on guided wave modal characteristics is possible by evaluating corresponding wave structures. Though this study, the concept to optimize guided wave mode selection is accomplished to enhance sensitivity and efficiency in nondestructive evaluation for multi-layered structures.
Internal Wave Study in the South China Sea Using SAR
Liu, Antony K.; Hsu, Ming-Kuang; Zukor, Dorothy (Technical Monitor)
2000-01-01
Recently, the internal wave distribution maps in the China Seas have been compiled from hundreds of ERS-1/2, RADARSAT, and Space Shuttle SAR (Synthetic Aperture Radar) images from 1993 to 1999. Based on internal wave distribution map, most of internal waves in the northeast part of South China Sea were propagating westward. The wave crest can be as long as 200 km with amplitude of 100 m due to strong current from the Kuroshio branching out into the South China Sea. Based on the observations from drilling rigs near DongSha Island by Amoco Production Co., the solitons may be generated in a 4 km wide channel between Batan and Sabtang islands in Luzon Strait. The proposed generation mechanism is similar to the lee wave formation from a shallow topography. Both depression and elevation internal waves have been observed in the same RADARSAT ScanSAR image on May 4, 1998 near DongSha Island. Furthermore, depression and elevation internal waves have also been observed by SAR at the same location on the shelf in April and June, 1993 (in different seasons) respectively. Numerical models have been used to interpret their generation mechanism and evolution processes. Based on the SAR images, near DongSha Island, the westward propagating huge internal solitons are often encountered and diffracted/broken by the coral reefs on the shelf. After passing the island, the diffracted waves will re-merge or interact with each other. It has been observed that after the nonlinear wave-wave interaction, the phase of wave packet is shifted and wavelength is also changed. Examples of mesoscale features observed in SAR images, such as fronts, raincells, bathymetry, ship wakes, and oil spills will be presented. Recent mooring measurements in April 1999 near Dongsha Island, future field test ASIAEX (Asian Seas International Acoustics Experiment) planned for April 2001, and some pretest survey data will be discussed in this paper.
Wave number determination of Pc 1–2 mantle waves considering He++ ions: A Cluster study
Czech Academy of Sciences Publication Activity Database
Grison, Benjamin; Escoubet, C. P.; Santolík, Ondřej; Cornilleau-Wehrlin, N.; Khotyaintsev, Y.
2014-01-01
Roč. 119, č. 9 (2014), s. 7601-7614. ISSN 2169-9380 R&D Projects: GA MŠk 7E12026; GA ČR(CZ) GPP209/11/P848; GA MŠk LH12231 Institutional support: RVO:68378289 Keywords : EMIC * refractive index * wave number * k-filtering * Pc 1–2 mantle wave * distant cusp Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013JA019719/abstract
Theoretical and experimental study of cyclotronic waves in a fusion plasma
International Nuclear Information System (INIS)
This thesis presents a study concerning cyclotronic waves in a plasma. It starts with an illustration of the elementary interaction between electromagnetic waves and matter.It shows that electrons from tokamak absorbs waves at cyclotronic frequency. Cyclotronic waves are studied by solving the dispersion relation in plasma; it concerns polarisation, absorption, dispersion, extinction. Then, classical theories are reminded in order to speak about decoupled electrons and their interactions. Absorption and emission properties of cyclotronic waves by electrons from a queue are described. After that, cyclotronic waves propagation is studied taking into account resonance. The last part of this thesis is dedicated to the electronic distribution function that is made by a wave spectra at a inferior hybrid frequency. (TEC). 129 refs., 75 figs
Pc5 waves generated by substorm injection: a case study
Directory of Open Access Journals (Sweden)
N. A. Zolotukhina
2008-07-01
Full Text Available We analyzed the spectral-polarized characteristics of Pc5 ULF waves observed on 17 September 2000 after the 03:20:25 UT substorm onset with the satellites GOES 8 and 10 located east and west of the onset location. In the course of the event, the wave polarization changed from mixed (between toroidal and poloidal to poloidal, and then to mixed again. The hodogram of magnetic field oscillations rotated counterclockwise at GOES 8, and clockwise at GOES 10. It is suggested that the satellites detected the waves generated by the substorm injected clouds of the charged particles drifting in the magnetosphere in the opposite azimuthal directions: GOES 8 (located east of the substorm onset detected the wave generated by an electron cloud, and GOES 10 (west of the onset detected the wave generated by a positive ion cloud. This interpretation is confirmed by the energetic particles data recorded by LANL satellites.
Excitation of Large-ktheta Ion-Berstein Waves in Tokamaks
Valeo, E. J.; Fisch, N. J.
1995-01-01
The mode-converted ion-Bernstein wave excited in tokamaks is shown to exhibit certain very interesting behavior, including the attainment of very small poloidal phase velocities, the reversal of poloidal direction, and up-down asymmetries in propagation and damping. Because of these effects, this wave holds promise for channeling {$\\alpha$-particle}\\ power to ions, something that would make a tokamak fusion reactor far more attractive than presently envisioned.
EXPERIMENTAL STUDY ON WAVE ENERGY DISSIPATION AND COHESIVE SEDIMENT TRANSPORT IN SILT COAST
Institute of Scientific and Technical Information of China (English)
Shixiong HU; Onyx WAI
2001-01-01
The interaction between the wave and fluid mud layer plays an important role in the development of silt coast. Sediment is essentially transported in the form of rheological flow of mud layer under the wave action, and on the other hand, the fluid mud layer damps the wave considerably. This paper studies the laws of wave energy dissipation and mud bed deformation, and the movement of mud layer through laboratory experiments. The results show that the wave energy dissipation follows an exponential law along the propagation distance. The bulk density of the mud layer affects the rate of the wave energy dissipation greatly. The wave damping coefficient (Ki) is a fuction of the mud density affected greatly by the relative wave height (H/h).Analysis also indicates that the mud density affect the rate of mud transport and the moving velocity (Vmax) of the surface mud is inversely proportional to the mud density. Both the relative wave height (H/h) and wave-damping coefficient (Ki) are proportional to the Vmax. Analysis also shows that the mud transport rate (Tr) is proportional to the wave damping rate (1-H0/H15), the relative wave height (H/h),and inversely proportional to the volume concentration (Cv) and dimensionless coefficient of H/gT2.
Experimental Study on the Effects of A Breakwater on Wave Field Characteristics
Institute of Scientific and Technical Information of China (English)
尹彰; 周宗仁; 黄伟柏
2000-01-01
Studies on the possible effects of a detached breakwater on the characteristics of the wave field are carried out experimentally. A serpentine wave generator is used to generate both uni- and multi-directional waves. Characteristics of the wave fields analyzed here include the wave field directionality, and the probability distributions of surface elevations and of the wave heights. Owing to the presence of the breakwater, waves outside the harbour are found to be reflected with, however, concentrated energy within the harbour entrance. In general wave heights can be approximated with a Rayleigh distribution, with occasional deviations from the theory. This occurs more frequently for waves with higher peak frequency values than for those with lower values both for uni- and multi-directional waves. Surface elevations can be approximated with the Gaussian model although the Edgeworth′s form of the type A Gram-Charlier series expansions would yield better fits. Wave directionality is found to have no discernible effects on the statistical characteristics of the wave field.
Study and verification on dispersion coefficient in wave field
Institute of Scientific and Technical Information of China (English)
SHEN LiangDuo; ZOU ZhiLi
2012-01-01
Transport and diffusion caused by coastal waves have different characteristics from those induced by flows.Through solving the vertical diffusion equation by an analytic method,this paper infers a theoretical formula of dispersion coefficient under the combined action of current and waves.It divides the general dispersion coefficient into six parts,including coefficients due to tidal current,Stokes drift,wave oscillation and interaction among them.It draws a conclusion that the contribution of dispersive effect induced by coastal waves is mainly produced by Stokes drift,while the contributions to time-averaged dispersion coefficient due to wave orbital motion and interaction between current and waves are very small.The results without tidal current are in agreement with the numerical and experimental results,which proves the correctness of the theoretical derivation.This paper introduces the variation characteristics of both the time-averaged and oscillating dispersion coefficients versus relative water depth,and demonstrates the physical implications of the oscillating mixing coefficient due to waves.We also apply the results to the costal vertical circulation and give its characteristics compared to Stokes drift.
Experimental study of the formation of steep waves and breakers
Directory of Open Access Journals (Sweden)
Stanis³aw R. Massel
2001-09-01
Full Text Available Breaking waves (whitecaps are one of the most important and least understood processes associated with the evolution of the surface gravity wave field in the open sea. This process is the principal means by which energy and momentum are transferred away from a developing sea. However, an estimation of the frequency of breaking waves or the fraction of sea surface covered by whitecaps and the amount of dissipated energy induced by breaking is very difficult to carry out under real sea conditions. A controlled experiment, funded by the European Commission under the Improving Human Potential Access Infrastructures programme, was carried out in the Ocean Basin Laboratory at MARINTEK, Trondheim (Norway. Simulation of random waves of the prescribed spectra by wave makers provided a very realistic pattern of the sea surface. The number of breaking waves was estimated by photographing the sea surface and recording the noise caused by the breaking waves. The experimental data will serve for calibration of the theoretical models of the sea surface fraction related to the whitecaps.
DEFF Research Database (Denmark)
Pecher, Arthur; Kofoed, Jens Peter
This report presents the results of an experimental study that was performed on small scale model that was a replication of the full-scale Weptos WEC intended for DanWEC. The tests were performed in the circular basin at FloWave at Edinburgh University in October 2014. The laboratory facilities had...
Simulation Study on SAR Images of the Oceanic Internal Waves
Institute of Scientific and Technical Information of China (English)
Jin-song CHONG; Fei LI; Yue OUYANG
2010-01-01
Based on the research of Lynett and Liu,the horizontal fully two-dimensional,depth-integrated model for the internal wave propagation is re-deduced.By combining this model with the M4S model,the propagation process of the internal waves is simulated in Synthetic Aperture Radar (SAR) images.The simulation results clearly show the bottom effects during the propagation such as fission and isobaths-parallelized propagation direction.This simulation procedure can lay the foundation for the quantitative interaretation of internal waves from fully two-dimensional SAR images.
Starch viscoelastic properties studied with an acoustic wave sensor.
Santos, M D; Gomes, M T S R
2014-01-01
Gelatinization and retrogradation of starch was followed in real time with an acoustic wave sensor. This study relies on the monitorization of the frequency of oscillation of a piezoelectric quartz crystal in contact with a 2.5% emulsion of a commercial maize starch, during heating and cooling. The technique showed to be very powerful and sensitive to most of the changes described in the literature, which have been elucidated by some other techniques. The value for the temperature of gelatinization found using the sensor was confirmed by the analysis of the same starch emulsion by polarized light microscopy. Temperatures of gelatinization were found to vary with the sample heating rate, as follows: 73.5 °C at 2.0 °C/min, 66.0 °C at 1.0 °C/min, and 65.0 °C at 0.5 °C/min. Hysteresis of the studied system was evidenced by the frequency shift before heating and after cooling till the initial temperature. Analysis performed on a 1.5% emulsion of a rice starch heated at 2.0 °C/min and cooled as before, evidenced no hysteresis and showed complete reversibility, in which concerns to the series frequency of the piezoelectric quartz crystal. PMID:24274480
Sensitivity Studies for Third-Generation Gravitational Wave Observatories
Hild, S; Acernese, F; Amaro-Seoane, P; Andersson, N; Arun, K; Barone, F; Barr, B; Barsuglia, M; Beker, M; Beveridge, N; Birindelli, S; Bose, S; Bosi, L; Braccini, S; Bradaschia, C; Bulik, T; Calloni, E; Cella, G; Mottin, E Chassande; Chelkowski, S; Chincarini, A; Clark, J; Coccia, E; Colacino, C; Colas, J; Cumming, A; Cunningham, L; Cuoco, E; Danilishin, S; Danzmann, K; De Salvo, R; Dent, T; De Rosa, R; Di Fiore, L; Di Virgilio, A; Doets, M; Fafone, V; Falferi, P; Flaminio, R; Franc, J; Frasconi, F; Freise, A; Friedrich, D; Fulda, P; Gair, J; Gemme, G; Genin, E; Gennai, A; Giazotto, A; Glampedakis, K; Gräf, C; Granata, M; Grote, H; Guidi, G; Gurkovsky, A; Hammond, G; Hannam, M; Harms, J; Heinert, D; Hendry, M; Heng, I; Hennes, E; Hough, J; Husa, S; Huttner, S; Jones, G; Khalili, F; Kokeyama, K; Kokkotas, K; Krishnan, B; Li, T G F; Lorenzini, M; Lück, H; Majorana, E; Mandel, I; Mandic, V; Mantovani, M; Martin, I; Michel, C; Minenkov, Y; Morgado, N; Mosca, S; Mours, B; Müller-Ebhardt, H; Murray, P; Nawrodt, R; Nelson, J; Oshaughnessy, R; Ott, C D; Palomba, C; Paoli, A; Parguez, G; Pasqualetti, A; Passaquieti, R; Passuello, D; Pinard, L; Plastino, W; Poggiani1, R; Popolizio, P; Prato, M; Punturo, M; Puppo, P; Rabeling, D; Rapagnani, P; Read, J; Regimbau, T; Rehbein, H; Reid, S; Ricci, F; Richard, F; Rocchi, A; Rowan, S; Rüdiger, A; Santamaría, L; Sassolas, B; Sathyaprakash, B; Schnabel, R; Schwarz, C; Seidel, P; Sintes, A; Somiya, K; Speirits, F; Strain, K; Strigin, S; Sutton, P; Tarabrin, S; Thüring, A; Brand, J van den; van Veggel, M; Broeck, C van den; Vecchio, A; Veitch, J; Vetrano, F; Vicere, A; Vyatchanin, S; Willke, B; Woan, G; Yamamoto, K
2010-01-01
Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope, a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this article we describe sensitivity models for the Einstein Telescope and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.
Sensitivity studies for third-generation gravitational wave observatories
Energy Technology Data Exchange (ETDEWEB)
Hild, S; Abernathy, M; Barr, B; Beveridge, N [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom); Acernese, F; Barone, F; Calloni, E [INFN, Sezione di Napoli (Italy); Amaro-Seoane, P [Max Planck Institute for Gravitational Physics (Albert Einstein Institute) Am Muehlenberg 1, D-14476 Potsdam (Germany); Andersson, N [University of Southampton, Southampton SO17 1BJ (United Kingdom); Arun, K [LAL, Universite Paris-Sud, IN2P3/CNRS, F-91898 Orsay (France); Barsuglia, M; Mottin, E Chassande [AstroParticule et Cosmologie (APC), CNRS, Observatoire de Paris, Universite Denis Diderot, Paris VII (France); Beker, M [Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Birindelli, S [Universite Nice ' Sophia-Antipolis' , CNRS, Observatoire de la Cote d' Azur, F-06304 Nice (France); Bose, S [Washington State University, Pullman, WA 99164 (United States); Bosi, L [INFN, Sezione di Perugia, I-6123 Perugia (Italy); Braccini, S; Bradaschia, C; Cella, G [INFN, Sezione di Pisa (Italy); Bulik, T, E-mail: stefan.hild@glasgow.ac.uk [Astronomical Observatory, University of warsaw, Al Ujazdowskie 4, 00-478 Warsaw (Poland)
2011-05-07
Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope (ET), a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this paper we describe sensitivity models for ET and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10 Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.
Sensitivity studies for third-generation gravitational wave observatories
International Nuclear Information System (INIS)
Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope (ET), a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this paper we describe sensitivity models for ET and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10 Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.
Numerical Study of Unsteady Supercavitation Perturbed by a Pressure Wave
Zheng, J. G.; Khoo, B. C.
2016-06-01
The unsteady features of supercavitation disturbed by an introduced pressure wave are investigated numerically using a one-fluid cavitation model. The supercavitating flow is assumed to be the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. The compressibility effects of liquid water are taken into account to model the propagation of pressure wave through flow and its interaction with supercavitation bubble. The interaction between supercavity enveloping an underwater flat-nose cylinder and pressure wave is simulated and the resulting unsteady behavior of supercavitation is illustrated. It is observed that the supercavity will become unstable under the impact of the pressure wave and may collapse locally, which depends on the strength of perturbation. The huge pressure surge accompanying the collapse of supercavitation may cause the material erosion, noise, vibration and efficiency loss of operating underwater devices.
Concept Study of Foundation Systems for Wave Energy Converters
DEFF Research Database (Denmark)
Molina, Salvador Devant; Vaitkunaite, Evelina; Ibsen, Lars Bo
Analysis of possible foundation solution for Wave Energy Converters (WEC) is presented by investigating and optimizing novel foundation systems recently developed for offshore wind turbines. Gravity based, pile and bucket foundations are innovative foundation systems that are analyzed. Concept...
Verification of nonlinear particle simulation of radio frequency waves in tokamak
Energy Technology Data Exchange (ETDEWEB)
Kuley, A., E-mail: akuley@uci.edu; Lin, Z. [Department of Physics and Astronomy, University of California Irvine, California 92697 (United States); Bao, J. [Department of Physics and Astronomy, University of California Irvine, California 92697 (United States); Fusion Simulation Center, Peking University, Beijing 100871 (China); Wei, X. S.; Xiao, Y. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Zhang, W. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, G. Y. [Department of Physics, Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); Fisch, N. J. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2015-10-15
Nonlinear simulation model for radio frequency waves in fusion plasmas has been developed and verified using fully kinetic ion and drift kinetic electron. Ion cyclotron motion in the toroidal geometry is implemented using Boris push in the Boozer coordinates. Linear dispersion relation and nonlinear particle trapping are verified for the lower hybrid wave and ion Bernstein wave (IBW). Parametric decay instability is observed where a large amplitude pump wave decays into an IBW sideband and an ion cyclotron quasimode (ICQM). The ICQM induces an ion perpendicular heating, with a heating rate proportional to the pump wave intensity.
Verification of nonlinear particle simulation of radio frequency waves in tokamak
International Nuclear Information System (INIS)
Nonlinear simulation model for radio frequency waves in fusion plasmas has been developed and verified using fully kinetic ion and drift kinetic electron. Ion cyclotron motion in the toroidal geometry is implemented using Boris push in the Boozer coordinates. Linear dispersion relation and nonlinear particle trapping are verified for the lower hybrid wave and ion Bernstein wave (IBW). Parametric decay instability is observed where a large amplitude pump wave decays into an IBW sideband and an ion cyclotron quasimode (ICQM). The ICQM induces an ion perpendicular heating, with a heating rate proportional to the pump wave intensity
Wang Jiang; Qian Yong; Ye Hai-Feng; Meng Zheng-Zheng; Chen Rong; Cao Meng; Sheng Ge-Hao; Jiang Xiu-Chen
2014-01-01
When partial discharge occurs in Gas Insulated Switchgear (GIS) with insulation defects, Ultrahigh-Frequency (UHF) electromagnetic wave up to several MHz and GHz will be exited and propagate inside GIS cavity. This study, based on the propagation theory of electromagnetic waves in coaxial waveguide, performs simulation analysis of the relationship between PD pulse form and the exited UHF electromagnetic wave using Finite-Deferential Time-Domain (FDTD) algorithm. First, we study the relationsh...
A photoelastic study of the effects of an impulsive seismic wave on a nuclear containment vessel
International Nuclear Information System (INIS)
A dynamic photoelastic study of the progressive movement of a dilatational P-wave into a model of a nuclear containment vessel,is studied. The reflections at the dome abutments are observed and the strong flexural wave that deforms the dome itself is studied with photoelasticity and with dynamic strain gage procedures. (E.G.)
Directory of Open Access Journals (Sweden)
AKM Zamanul Islam Bhuiyan
2013-01-01
Full Text Available Background: Renal calculi are frequent causes of ureteric colic. Extracorporeal shock wave lithotripsy is the most common treatment of these stones. It uses focused sound waves to break up stones externally. Objective: To compare the efficiency of slow and fast delivery rate of shock waves on stone fragmentation and treatment outcome in patients with renal calculi. Materials and Methods: This prospective study was done in the department of Urology, National Institute of Kidney diseases and Urology, Sher-e-Bangla Nagar, Dhaka from July 2006 to June 2007. Total 90 patients were treated using the Storz Medical Modulith ® SLX lithotripter. Patients were divided into Group A, Group B and Group C – each group having 30 subjects. Group A was selected for extracorporeal shockwave lithotripsy (ESWL by 60 shock waves per minute, Group B by 90 shock waves per minute and Group C by 120 shock waves per minute. Results: Complete clearance of stone was observed in 24 patients in Group A and 13 patients in both Group B and Group C in first session. In Group A only 3 patients needed second session but in Group B and Group C, 12 and 8 patients needed second session. In Group A only one patient needed third session but third session was required for 3 patients in Group B and 5 patients in Group C for complete clearance of stone. In Group A, subsequent sessions were performed under spinal anesthesia and in Group B under sedation and analgesia (p>0.001. Mean number of sessions for full clearance of stones in group A was 1.37 ± 0.85, in Group B was 1.8 ± 0.887 and in Group C was 2.0 ± 1.083. Significant difference was observed in term of sessions among groups (p>0.05. In first follow-up, complete clearance of stones was seen in 24 patients in Group A and 13 in both Group B and Group C. In second follow-up, 3 patients in Group A, 12 in Group B and 8 in Group C showed complete clearance of stones. It was observed that rate of stone clearance was higher in Group A
Wave energy, lever operated pivoting float LOPF study
Energy Technology Data Exchange (ETDEWEB)
Margheritini, L.
2012-11-01
The fully instrumented Resen Waves Lever Operated Pivoting Float LOPF wave energy buoy model has gone through the first stage of testing in regular waves in scale 1:25 of the North Sea wave conditions, in the 3D deep wave basin at the Hydraulic and Coastal Engineering Laboratory of Aalborg University in Denmark. The model size was 60cm W x 90cm L x 21cm H. The 60 cm width pointed towards the wave front. The LOPF buoy is characterized by a simple mechanical design with few moving parts and direct electrical output and it is taut moored to the sea bed, so all forces are referenced to the seabed for maximum energy output in regular as well as irregular waves. During storms the buoy pivots and streamlines itself to minimize loads on the mooring line. A conservative estimate shows that a full scale system for North Sea conditions has a float size width of 15 m that will, with 60% generator efficiency, produce 610 MWh/y (609.497 kWh/y) with an average power output of 69.6 kW, which requires a generator capacity of 700 kW. It is expected the generator efficiency can be increased to 90% in the future. More specific calculations (from EnergiNet) show that with one generator of 695 kW the expected power production is 585 MWh/y; with a generator of 250 kW and 100 kW, the expected power production is 481 MWh/y and 182 MWh/y respectively. In addition there are several areas for future improvements for increased power production. (Author)
Integrability: mathematical methods for studying solitary waves theory
Wazwaz, Abdul-Majid
2014-03-01
In recent decades, substantial experimental research efforts have been devoted to linear and nonlinear physical phenomena. In particular, studies of integrable nonlinear equations in solitary waves theory have attracted intensive interest from mathematicians, with the principal goal of fostering the development of new methods, and physicists, who are seeking solutions that represent physical phenomena and to form a bridge between mathematical results and scientific structures. The aim for both groups is to build up our current understanding and facilitate future developments, develop more creative results and create new trends in the rapidly developing field of solitary waves. The notion of the integrability of certain partial differential equations occupies an important role in current and future trends, but a unified rigorous definition of the integrability of differential equations still does not exist. For example, an integrable model in the Painlevé sense may not be integrable in the Lax sense. The Painlevé sense indicates that the solution can be represented as a Laurent series in powers of some function that vanishes on an arbitrary surface with the possibility of truncating the Laurent series at finite powers of this function. The concept of Lax pairs introduces another meaning of the notion of integrability. The Lax pair formulates the integrability of nonlinear equation as the compatibility condition of two linear equations. However, it was shown by many researchers that the necessary integrability conditions are the existence of an infinite series of generalized symmetries or conservation laws for the given equation. The existence of multiple soliton solutions often indicates the integrability of the equation but other tests, such as the Painlevé test or the Lax pair, are necessary to confirm the integrability for any equation. In the context of completely integrable equations, studies are flourishing because these equations are able to describe the
Institute of Scientific and Technical Information of China (English)
WAN Yong; ZHANG Jie; MENG Junmin; WANG Jing; DAI Yongshou
2016-01-01
Wave energy resource is a very important ocean renewable energy. A reliable assessment of wave energy resources must be performed before they can be exploited. Compared with wave model, altimeter can provide more accuratein situ observations for ocean wave which can be as a novel method for wave energy assessment. The advantage of altimeter data is to provide accurate significant wave height observations for wave. In order to develop characteristic and advantage of altimeter data and apply altimeter data to wave energy assessment, in this study, we established an assessing method for wave energy in local sea area which is dedicated to altimeter data. This method includes three parts including data selection and processing, establishment of evaluation indexes system and criterion of regional division. Then a case study of Northwest Pacific was performed to discuss specific application for this method. The results show that assessing method in this paper can assess reserves and temporal and spatial distribution effectively and provide scientific references for the siting of wave power plants and the design of wave energy convertors.
A Comparative Study of Strain- and Shear-Wave-Elastography in an Elasticity Phantom
DEFF Research Database (Denmark)
Carlsen, Jonathan F; Pedersen, Malene R; Ewertsen, Caroline; Săftoiu, Adrian; Lönn, Lars; Rafaelsen, Søren R; Nielsen, Michael B
2015-01-01
OBJECTIVE. The purpose of this study was to assess the diagnostic accuracy of strain and shear-wave elastography for determining targets of varying stiffness in a phantom. The effect of target diameter on elastographic assessments and the effect of depth on shear-wave velocity were also investiga......OBJECTIVE. The purpose of this study was to assess the diagnostic accuracy of strain and shear-wave elastography for determining targets of varying stiffness in a phantom. The effect of target diameter on elastographic assessments and the effect of depth on shear-wave velocity were also...
Numerical and experimental study of Lamb wave propagation in a two-dimensional acoustic black hole
Yan, Shiling; Lomonosov, Alexey M.; Shen, Zhonghua
2016-06-01
The propagation of laser-generated Lamb waves in a two-dimensional acoustic black-hole structure was studied numerically and experimentally. The geometrical acoustic theory has been applied to calculate the beam trajectories in the region of the acoustic black hole. The finite element method was also used to study the time evolution of propagating waves. An optical system based on the laser-Doppler vibration method was assembled. The effect of the focusing wave and the reduction in wave speed of the acoustic black hole has been validated.
A study of slipstreams in triple shock wave configurations
Gvozdeva, L.; Gavrenkov, S.; Nesterov, A.
2015-05-01
A shock wave appearing in supersonic gas flow reflects in different ways depending on flow conditions. It can take the form of regular or irregular reflection. For the irregular reflection configuration of three shock waves and a slipstream arises. Mathematical investigations of the development of parameters across slipstream in triple shock configuration have been made with variation of the angle of incidence of the shock wave, the shock wave Mach number and the adiabatic index of the gas. It has been shown that the characteristic mixing parameters of the slipstream increase with the increase of Mach number of the flow and the decrease of the heat capacity ratio. This leads to an increase of vortex formation and an increase of the angular spread of the slipstream. It also has been shown that the angle between the reflected wave and the slipstream diminishes with the decrease in heat capacity ratio so that the value may become of the same order as the spread angle. This may lead to quantitative changes in the whole reflection pattern near the triple point. The evident dependence of slipstream instability magnitude on the physical and chemical transformation intensity in the fluid was previously experimentally observed. The results of an analytical investigation appeared to be in good agreement with the experimental data.
A study of the liquefaction shock wave structure
International Nuclear Information System (INIS)
The system of shock wave-induced vapor condensation in fluids of large heat capacity has been investigated theoretically. The wave structure is governed by differences in the time scales associated with various relaxation mechanisms and their coupling to the macroscopic flow. In the low to moderate Mach number range, the viscous and heat-conducting forces are localized within a discontinuous forerunner wave, while the slower nucleation and droplet growth processes are resolved inside a trailing condensation wave. A time-dependent analysis of the fluid motion is required because the phase transition can occur too slowly for the system to reach a steady state on the laboratory time scale. In the high Mach number regime, a steady-state motion is rapidly attained, but the analysis requires a simultaneous treatment of nucleation, viscosity, and heat conduction. It appears that instability mechanisms similar to the ones found in ZND detonation waves are responsible for the shock-front irregularities observed in high Mach-number flows. Based on the rapidity of the supersaturating shock compression and the time delay of nucleation, it is anticipated that metastable states near the vapor spinodal are attainable, especially at high temperatures. copyright 1996 American Institute of Physics
A study of the liquefaction shock wave structure
Energy Technology Data Exchange (ETDEWEB)
Saltz, D. [Department of Applied Mathematics and Statistics, State University of New York at Stony Brook, Stony Brook, New York 11794-3600 (United States); Guelen, S.C. [Energy Storage and Power Consultants, Mountainside, New Jersey 07092 (United States)
1996-05-01
The system of shock wave-induced vapor condensation in fluids of large heat capacity has been investigated theoretically. The wave structure is governed by differences in the time scales associated with various relaxation mechanisms and their coupling to the macroscopic flow. In the low to moderate Mach number range, the viscous and heat-conducting forces are localized within a discontinuous forerunner wave, while the slower nucleation and droplet growth processes are resolved inside a trailing condensation wave. A time-dependent analysis of the fluid motion is required because the phase transition can occur too slowly for the system to reach a steady state on the laboratory time scale. In the high Mach number regime, a steady-state motion is rapidly attained, but the analysis requires a simultaneous treatment of nucleation, viscosity, and heat conduction. It appears that instability mechanisms similar to the ones found in ZND detonation waves are responsible for the shock-front irregularities observed in high Mach-number flows. Based on the rapidity of the supersaturating shock compression and the time delay of nucleation, it is anticipated that metastable states near the vapor spinodal are attainable, especially at high temperatures. {copyright} {ital 1996 American Institute of Physics.}
LAICE CubeSat mission for gravity wave studies
Westerhoff, John; Earle, Gregory; Bishop, Rebecca; Swenson, Gary R.; Vadas, Sharon; Clemmons, James; Davidson, Ryan; Fanelli, Lucy; Fish, Chad; Garg, Vidur; Ghosh, Alex; Jagannatha, Bindu B.; Kroeker, Erik; Marquis, Peter; Martin, Daniel; Noel, Stephen; Orr, Cameron; Robertson, Robert
2015-10-01
The Lower Atmosphere/Ionosphere Coupling Experiment (LAICE) CubeSat mission will focus on understanding the interaction of atmospheric gravity waves generated by weather systems in the lower atmosphere with the mesosphere, lower thermosphere, and ionosphere (MLTI). Specifically, LAICE will focus on the energy and momentum delivered by these waves and attempt to connect the wave sources and the wave effects in three widely different altitude ranges, substantially adding to our knowledge of critical coupling processes between disparate atmospheric regions. The LAICE mission consists of a 6U CubeSat with a four-instrument payload. The retarding potential analyzer (RPA) will provide in-situ ion density and temperature measurements. A four-channel photometer will measure density and temperature variations in the mesosphere through observations of O2 (0, 0) Atmospheric band and O2 Herzberg I band airglows. There are two pressure sensors that comprise the Space Pressure Suite (SPS): the Space Neutral Pressure Instrument (SNeuPI) and the LAICE Ionization gauge Neutral Atmosphere Sensor (LINAS). Both will provide neutral density measurements, but SNeuPI is a prototype sensor that will be validated by LINAS. This CubeSat mission, scheduled for launch in early 2016 from the International Space Station, provides a cost-effective approach to measuring low altitude in-situ parameters along with simultaneous imaging that is capable of addressing the fundamental questions of atmospheric gravity wave coupling in the MLTI region.
A parametric study of self-similar blast waves.
Oppenheim, A. K.; Kuhl, A. L.; Lundstrom, E. A.; Kamel, M. M.
1972-01-01
Comprehensive examination of self-similar blast waves with respect to two parameters, one describing the front velocity and the other the variation of the ambient density immediately ahead of the front. All possible front trajectories are taken into account, including limiting cases of the exponential and logarithmic form. The structure of the waves is analyzed by means of a phase plane defined in terms of two reduced coordinates. Loci of extrema of the integral curves in the phase plane are traced, and loci of singularities are determined on the basis of their intersections. Boundary conditons are introduced for the case where the medium into which the waves propagate is at rest. Representative solutions, pertaining to all the possible cases of blast waves bounded by shock fronts propagating into an atmosphere of uniform density, are obtained by evaluating the integral curves and determining the corresponding profiles of the gasdynamic parameters. Particular examples of integral curves for waves bounded by detonations are given, and all the degenerate solutions corresponding to cases where the integral curve is reduced to a point are delineated.
A full wave code for ion cyclotron waves in toroidal plasmas
International Nuclear Information System (INIS)
The code TORIC solves the finite Larmor radius wave equations in the ion cyclotron frequency range in arbitrary axisymmetric toroidal geometry. The model used describes the compressional and torsional Alfven waves (or, depending on the parallel phase velocity, the kinetic counterpart of the latter), and ion Bernstein waves excited by mode conversion near the first ion cyclotron harmonic. In the ion response the broadening of the absorption regions due to the finite width of the cyclotron resonance of individual ions in toroidal geometry is taken into account. The parallel component of the wave electric field is evaluated on the same footing as the transverse ones; the response of the electrons includes Landau damping, Transit Time damping and the mixed term. The numerical approach uses a spectral representation of the solution in the poloidal angle θ, and cubic finite elements in the radial variable ψ. Great flexibility is provided in the way ion Bernstein waves excited by mode conversion are damped when their wavelength becomes comparable with the ion Larmor radius, in the regularization of Alfven resonances, and in the treatment of the outer plasma layers. As an option, we have also implemented the Order Reduction Algorithm, which provides a particularly fast, yet accurate evaluation of the power deposition profiles in toroidal geometry. Thee present report describes the model and its numerical implementation, and provides the information needed to use the code. A few examples illustrating applications of TORIC are also included. (orig.)
The study of laser array generation of elastic shear wave and surface wave
International Nuclear Information System (INIS)
The principle of laser light generation of ultrasound is the result of the absorption of light energy by the sample medium that is converted into thermal stress. From literature survey, single laser-generated ultrasound has some limitations. First, the high energy from laser light may cause the ablation on the material surface. Second, the single laser beam generation method is hard to control the beam-width and focusing direction of ultrasound. Third, the single laser-generated ultrasound is unable to enhance the ultrasound signal. The optical fiber phased array generation of ultrasound offer the improvement of the control of the beam-width and focusing direction, and to increase the amplitude of the generated ultrasound in the thermoelastic range. This research investigated the directivity pattern from the in-phased laser array generation of shear wave and surface wave in comparison with old and improved theoretical model. The theoretical data which was filtered by the electronic instruments were compared with the literature data, also.
User Guide "Panel Study Labour Market and Social Security" (PASS) : Wave 6
Bethmann, Arne; Fuchs, Benjamin; Wurdack, Anja; Beste, Jonas; Trappmann, Mark; Müller, Gerrit; Eggs, Johannes; Gundert, Stefanie; Wenzig, Claudia; Gebhardt, Daniel
2013-01-01
"This User Guide is meant to give information on general issues of the panel study 'Labour Market and Social Security' (PASS) and to offer assistance for the work with the datasets of the scientific use file (SUF). While the data reports, which are released for every wave, inform in detail about key statistics, data editing, generated variables and the weighting of a certain wave, the User Guide offers comprehensive information that is not specific for a single wave. Arne Bethmann, Benjamin F...
User Guide "Panel Study Labour Market and Social Security" (PASS) : Wave 3
Bethmann, Arne; Gebhardt, Daniel; Trappmann, Mark; Müller, Gerrit; Beste, Jonas; Eggs, Johannes; Gundert, Stefanie
2011-01-01
"This User Guide is meant to give information on general issues of the panel study 'Labour Market and Social Security' (PASS) and to offer assistance for the work with the datasets of the scientific use file (SUF). While the data reports, which are released for every wave, inform in detail about key statistics, data editing, generated variables and the weighting of a certain wave, the User Guide offers comprehensive information that is not specific for a single wave." (author's abstract, IAB-...
Institute of Scientific and Technical Information of China (English)
Liu Xiqiang; Zhou Huilan; Li Hong; Gai Dianguang
2000-01-01
Based on the propagation characteristics of shear wave in the anisotropic layers, thecorrelation among several splitting shear-wave identification methods hasbeen studied. Thispaper puts forward the method estimating splitting shear-wave phases and its reliability byusing of the assumption that variance of noise and useful signal data obey normaldistribution. To check the validity of new method, the identification results and errorestimation corresponding to 95% confidence level by analyzing simulation signals have beengiven.
Experimental Study of a Multi Level Overtopping Wave Power Device
DEFF Research Database (Denmark)
Kofoed, Jens Peter; Hald, Tue; Frigaard, Peter Bak
2002-01-01
, compared to only one level, has been evaluated experimentally. From the experimental results, and the performed optimizations based on these, it has been found that the efficiency of a wave power device of the overtopping type can be increased by as much as 76 % by using 5 levels instead of 1. However......, using 5 levels introduces practical problems, and is most probably not economically feasible. It is concluded that it is reasonable to use 2 levels (maybe 3), which can increase the efficiency by 25-40 % compared to using a single level.......Results of experimental investigations of a floating wave energy device called Power Pyramid is presented. The Power Pyramid utilizes reservoirs in multiple levels when capturing wave overtopping and converting it into electrical energy. The effect of capturing the overtopping in multiple levels...
Theoretical study of laser-ultrasonic wave generation
International Nuclear Information System (INIS)
We discuss the theories in the generation and detection of laser-ultrasonics and present the results obtained from the numerical calculations based on the theories. We carry out the computation of the spatial and temporal distributions of the temperature inside the material. Calculating the displacement of the surface at the epicenter, we make discussions on the characteristics of the ultrasonic wave propagation in the thermoelastic and ablation regions. The speed and the surface motion of the material element are investigated from the solution of the Rayleigh equation. We present the results obtained from the numerical computations based on the theories. The Rayleigh waves generated by the irradiation of the pulsed laser beam in the thermoelastic region and the ablation region are discussed. Also the discussions on the heat wave propagation caused by irradiations of the ultra-short laser pulses are included in the appendix
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A nonlinear, compressible, non-isothermal gravity wave model that involves photochemistry is used to study the effects of gravity wave on atmospheric chemical species distributions in this paper. The changes in the distributions of oxygen compound and hydrogen compound density induced by gravity wave propagation are simulated. The results indicate that when a gravity wave propagates through a mesopause region, even if it does not break, it can influence the background distributions of chemical species. The effect of gravity wave on chemical species at night is larger than in daytime.
Study on energy attenuation of ultrasonic Guided waves going through girth welds
Energy Technology Data Exchange (ETDEWEB)
Li Yibo; Jin Shijiu; Sun Liying [Tianjin University (China); Sha Jile [Bohai Oil Industry and Trade Company (China)
2005-07-01
Ultrasonic guided wave can be used to inspect some parts of the pipe which is inaccessible to other conventional NDT methods, and rapid, long distance inspection can be achieved. Thus, it enjoys promising broad application in the field of pipe inspection. When ultrasonic guided wave is excited at one location, its propagating distance along the pipe is depended on energy attenuation of ultrasonic guided wave. During the process of long-range pipe engineering inspection, ultrasonic guided waves may go through many girth welds and elbows. Girth weld reflects much energy of guided waves, thus they attenuate a great deal after passing several girth welds. Furthermore, defect detection either in the elbow region or beyond it is usually difficult due to its geometry complexity and flexural mode conversion in pipe elbow region. In this paper, factors that may cause attenuation of ultrasonic guided waves (longitudinal wave and torsional wave) were studied and research was carried out on energy attenuation of guided waves when going through girth welds and elbow. In the end, comparison of the two guided waves on sensitivity and location precision of defects such as notch, burr and branch was given. (author)
Quijano, J C; Raynaud, F; Nguyen, D; Piacentini, N; Meister, J J
2016-01-01
Vascular smooth muscle cells exhibit intercellular Ca(2+) waves in response to local mechanical or KCl stimulation. Recently, a new type of intercellular Ca(2+) wave was observed in vitro in a linear arrangement of smooth muscle cells. The intercellular wave was denominated ultrafast Ca(2+) wave and it was suggested to be the result of the interplay between membrane potential and Ca(2+) dynamics which depended on influx of extracellular Ca(2+), cell membrane depolarization and its intercel- lular propagation. In the present study we measured experimentally the conduction velocity of the membrane depolarization and performed simulations of the ultrafast Ca(2+) wave along coupled smooth muscle cells. Numerical results reproduced a wide spectrum of experimental observations, including Ca(2+) wave velocity, electrotonic membrane depolarization along the network, effects of inhibitors and independence of the Ca(2+) wave speed on the intracellular stores. The numerical data also provided new physiological insights suggesting ranges of crucial model parameters that may be altered experimentally and that could significantly affect wave kinetics allowing the modulation of the wave characteristics experimentally. Numerical and experimental results supported the hypothesis that the propagation of membrane depolarization acts as an intercellular messenger mediating intercellular ultrafast Ca(2+) waves in smooth muscle cells. PMID:27507785
Intercellular ultrafast Ca2+ wave in vascular smooth muscle cells: numerical and experimental study
Quijano, J. C.; Raynaud, F.; Nguyen, D.; Piacentini, N.; Meister, J. J.
2016-01-01
Vascular smooth muscle cells exhibit intercellular Ca2+ waves in response to local mechanical or KCl stimulation. Recently, a new type of intercellular Ca2+ wave was observed in vitro in a linear arrangement of smooth muscle cells. The intercellular wave was denominated ultrafast Ca2+ wave and it was suggested to be the result of the interplay between membrane potential and Ca2+ dynamics which depended on influx of extracellular Ca2+, cell membrane depolarization and its intercel- lular propagation. In the present study we measured experimentally the conduction velocity of the membrane depolarization and performed simulations of the ultrafast Ca2+ wave along coupled smooth muscle cells. Numerical results reproduced a wide spectrum of experimental observations, including Ca2+ wave velocity, electrotonic membrane depolarization along the network, effects of inhibitors and independence of the Ca2+ wave speed on the intracellular stores. The numerical data also provided new physiological insights suggesting ranges of crucial model parameters that may be altered experimentally and that could significantly affect wave kinetics allowing the modulation of the wave characteristics experimentally. Numerical and experimental results supported the hypothesis that the propagation of membrane depolarization acts as an intercellular messenger mediating intercellular ultrafast Ca2+ waves in smooth muscle cells. PMID:27507785
A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes
Institute of Scientific and Technical Information of China (English)
Yong-Hun Kweon; Heuy-Dong Kim; Toshiaki Setoguchi; Toshiyuki Aoki
2003-01-01
The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee's total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The Mach number Ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d,is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tubes, the peak pressure produced by the twin impulse waves and its location strongly depend upon the distance between two-parallel tubes, L/d and the incident shock Mach number,Ms. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.
Novel Acoustic Wave Microsystems for Biophysical Studies of Cells
Senveli, Sukru Ufuk
Single cell analysis is an important topic for understanding of diseases. In this understanding, biomechanics approach serves as an important tool as it relates and connects the mechanical properties of biological cells with diseases such as cancer. In this context, analysis methods based on ultrasonics are promising owing to their non-invasive nature and ease of use. However, there is a lack of miniature systems that provide accurate ultrasonic measurements on single cancer cells for diagnostic purposes. The platform presented in this study exploits high frequency acoustic interaction and uses direct coupling of Rayleigh type SAWs with various samples placed inside microcavities to analyze their structural properties. The samples used are aqueous glycerin solutions and polystyrene microbeads for demonstrating proper system operation, and lead up to biological cells. The microcavity is instrumental in trapping a predetermined volume of sample inside and facilitating the interaction of the surface waves with the sample in question via a resonance condition. Ultimately, the resultant SAW reaching the output transducer incurs a phase delay due to its interaction with the sample in the microcavity. The system operates in a different manner compared to similar systems as a result of multiple wave reflections in the small volume and coupling back to the piezoelectric substrate. The proposed microsystem was first analyzed using finite element methods. Liquid and solid media were modeled by considering frequency dependent characteristics. Similarly, mechanical behavior of cells with respect to different conditions is considered, and biological cells are modeled accordingly. Prototype devices were fabricated on quartz and lithium niobate in a cleanroom environment. Process steps were optimized separately for devices with microcavities. Precise fabrication, alignment, and bonding of PDMS microchannels were carried out. Soft microprobes were fabricated out of SU-8, a
International Nuclear Information System (INIS)
The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission
Theoretical and experimental study of a non-linear disintegration process for a langmuir wave
International Nuclear Information System (INIS)
Using the Vlasov equation we calculate and discuss non-linear coupling equations between three electronic plasma waves (Langmuir waves) which propagate in a cylindrical plasma column confined by a strong magnetic field. We study, in the experimental device EOS, along the magnetic field, the disintegration of a Langmuir wave excited in the plasma column by means of an antenna. Space structure measurements for various waves show that the resonance conditions (selection rules) are satisfied. The measured disintegration threshold is in agreement with the theoretical value within 30 per cent and shows that this non linear mechanism appears when the oscillating density to the mean density ratio is about 10-3 to 10-2. The variation of the spatial growth rate as a function of the amplitude of the disintegrated wave shows that the resulting waves are correlated in groups of three along the magnetic field even though the disintegrating spectrum appears in a wide frequency band. (author)
Experimental Study on Shock Wave Structures in Constant-area Passage of Cold Spray Nozzle
Institute of Scientific and Technical Information of China (English)
Hiroshi KATANODA; Takeshi MATSUOKA; Kazuyasu MATSUO
2007-01-01
Cold spray is a technique to make a coating on a wide variety of mechanical or electric parts by spraying solid particles accelerated through a high-speed gas flow in a converging-diverging nozzle. In this study, pseudo-shock waves in a modeled cold spray nozzle as well as high-speed gas jets are visualized by schlieren technique. The schlieren photographs reveals the supersonic flow with shock train in the nozzle. Static pressure along the barrel wall is also measured. The location of the head of pseudo-shock wave and its pressure distribution along the nozzle wall are analytically explained by using a formula of pseudo-shock wave. The analytical results show that the supersonic flow accompanying shock wave in the nozzle should be treated as pseudo-shock wave instead of normal shock wave.
Energy Technology Data Exchange (ETDEWEB)
Gubbiotti, G.; Tacchi, S. [Istituto Officina dei Materiali del Consiglio Nazionale delle Ricerche (IOM-CNR), Sede di Perugia, c/o Dipartimento di Fisica e Geologia, Via A. Pascoli, I-06123 Perugia (Italy); Montoncello, F.; Giovannini, L. [Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via G. Saragat 1, I-44122 Ferrara (Italy); Madami, M.; Carlotti, G. [Dipartimento di Fisica e Geologia, Università di Perugia, Via A. Pascoli, I-06123 Perugia (Italy); Ding, J.; Adeyeye, A. O. [Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)
2015-06-29
The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.
International Nuclear Information System (INIS)
After reviewing the general characteristics of electrostator waves a brief resume is given of the observations made up to the present moment. The GEOS satellite and the ''wave'' experiment are described, as well as the method and results of the statistical study of the strong electrostatic wave observed. Creating mechanisms of diffuse auroras are discussed. In a later chapter a new method of using the relaxation probe is presented as well as the results it gives on the mode of propagation of waves in the neighbourhood of the FUH frequency
Study on thermal wave based on the thermal mass theory
Institute of Scientific and Technical Information of China (English)
HU RuiFeng; CAO BingYang
2009-01-01
The conservation equations for heat conduction are established based on the concept of thermal mass. We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass. The general law introduces a damped thermal wave equation. It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected, which indicates that the CV model only considers the temporal inertia of heat flux. Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory. For larger thermal perturbation, however, the physically impossible phenomenon pre-dicted by CV model, i.e. the negative temperature induced by the thermal wave superposition, is eliminated by the general heat conduction law, which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.
Study on thermal wave based on the thermal mass theory
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The general law introduces a damped thermal wave equation.It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected,which indicates that the CV model only considers the temporal inertia of heat flux.Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory.For larger thermal perturbation,however,the physically impossible phenomenon pre-dicted by CV model,i.e.the negative temperature induced by the thermal wave superposition,is eliminated by the general heat conduction law,which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.
Nonlinear wave propagation studies, dispersion modeling, and signal parameters correction
Czech Academy of Sciences Publication Activity Database
Převorovský, Zdeněk
..: ..., 2004, 00. [European Workshop on FP6-AERONEWS /1./. Naples (IT), 13.09.2004-16.09.2004] EU Projects: European Commission(XE) 502927 - AERO-NEWS Institutional research plan: CEZ:AV0Z2076919 Keywords : nodestructive testing * nonlinear elastic wave spectroscopy Subject RIV: BI - Acoustics
Survey of Temperature Measurement Techniques For Studying Underwater Shock Waves
Danehy, Paul M.; Alderfer, David W.
2004-01-01
Several optical methods for measuring temperature near underwater shock waves are reviewed and compared. The relative merits of the different techniques are compared, considering accuracy, precision, ease of use, applicable temperature range, maturity, spatial resolution, and whether or not special additives are required.
Planar Millimeter-Wave Antennas: A Comparative Study
Pitra, K.; Z. Raida
2011-01-01
The paper describes the design and the experimental verification of three types of wideband antennas. Attention is turned to the bow-tie antenna, the Vivaldi antenna and the spiral antenna designed for the operation at millimeter waves. Bandwidth, input impedance, gain, and directivity pattern are the investigated parameters. Antennas are compared considering computer simulations in CST Microwave Studio and measured data.
Excitation of parametric instabilities by radio waves in the ionosphere.
Fejer, J. A.; Leer, E.
1972-01-01
The excitation of parametric instabilities by radio waves in a magnetoplasma is discussed. A uniform medium is assumed and linear approximations are used. Excitation by a pump wave of ordinary polarization is hardly affected by the magnetic field. Low or zero frequency ion waves and high frequency Langmuir waves are excited simultaneously. For an extraordinary pump wave, the excited high frequency electrostatic waves are in the Bernstein mode. The threshold is slightly higher and excitation can occur only within certain 'allowed' frequency bands. A new type of parametric instability in which the excited waves are electromagnetic in nature and which is more strongly affected by the inhomogeneous nature of the medium is discussed qualitatively.
Numerical study of surface water waves generated by mass movement
International Nuclear Information System (INIS)
In this paper waves generated by two-dimensional mass movement are simulated using a numerical model based on the full hydrodynamic coupling between rigid-body motion and ambient fluid flow. This approach has the capability to represent the dynamics of the moving rigid body, which avoids the need to prescribe the body velocity based on the data measurements. This model is implemented in the CFX code and uses the Reynolds average Navier–Stokes equations solver coupled to the recently developed immersed solid technique. The latter technique allows us to follow implicitly the motion of the solid block based on the rigid body solver. The volume-of-fluid method is used to track the free surface locations. The accuracy of the present model is firstly examined against the simple physical case of a freely falling rigid body into water reproducing Scott Russell's solitary waves. More complex and realistic simulations of aerial and submarine mass-movement, simulated by a rigid wedge sliding into water along a 45° slope, are then performed. Simulated results of the aerial mass movement show the complex flow patterns in terms of the velocity fields and free surface profiles. Results are in good agreement with the available experimental data. In addition, the physical processes associated with the generation of water wave by two-dimensional submarine mass-movement are explored. The effects of the initial submergence and specific gravity on the slide mass kinematics and maximum wave amplitude are investigated. The terminal velocity and initial acceleration of the slide mass are well predicted when compared to experimental results. It is found that the initial submergence did not have a significant effect on the initial acceleration of the slide block centre of mass. However, it depends nonlinearly on the specific gravity. The maximum wave amplitude and the time at which it occurred are also presented as a function of the initial submergence and specific gravity. (paper)
Studies on waves and turbulence in natural plasmas and in laboratory plasmas
International Nuclear Information System (INIS)
The project for studying plasma waves and plasma turbulence submitted to CAPES to be included in the CAPES/COFECUB international cooperation agreement is presented. The project will be carry out in cooperation with Paris University aiming to simulate in laboratory wave-particle interaction phenomena occuring in space plasma. (M.C.K.)
A Study on Parametric Wave Estimation Based on Measured Ship Motions
DEFF Research Database (Denmark)
Nielsen, Ulrik Dam; Iseki, Toshio
2011-01-01
The paper studies parametric wave estimation based on the ‘wave buoy analogy’, and data and results obtained from the training ship Shioji-maru are compared with estimates of the sea states obtained from other measurements and observations. Furthermore, the estimating characteristics of the param...
Trupti, S.; Srinivas, K. N. S. S. S.; Pavan Kishore, P.; Seshunarayana, T.
2012-04-01
Multichannel analysis of surface waves (MASW) technique was employed for site characterization studies at the identified lineament locations along coastal regions of Andhra Pradesh covering ~ 600 km to measure the shear wave velocity. The shear (S)-wave velocity of near surface materials (such as soil, rocks and pavement) and its effect on seismic wave propagation are of fundamental interest in many groundwater, engineering and environmental studies. Geologically, the study area comprises of Precambrian basement over which younger rocks commencing with Jurassic, Cretaceous, Tertiary and Quaternary have given rise to varying sequences in different parts. The study has been conducted along the lineaments and these were selected based on the analysis of IRS-1D LISS-IV satellite images and the field geological investigation. The average shear wave velocity, stiffness and the liquefaction potential were evaluated by using the obtained shear wave velocities. Soils are classified into four categories as soft soils, stiff soils, dense soils/soft rock and hard rock based on the obtained shear wave velocities. The factor of safety (FS) against liquefaction is determined and it is found that the sites with low shear wave velocity have FS construction of engineering projects such as pipelines, dams, bridges, canal alignments, and cross-drainage structures.
A Physical Study of Converted Wave AVO in a Fractured Reservoir
Chang, C. H.; Chang, Y. F.; Tsao, H. C.; Chang, J. W.
2015-12-01
Benefiting by the multicomponent seismic acquisition and processing techniques, the applications of converted waves in petroleum exploration is thus highlighted. A converted (C-) wave is initiated by a downward traveling P-wave that is converted on reflection to upcoming S-waves. Ascribing to its origins, C-wave takes the behaviors of P- and S-wave and becomes as one of the popular seismic attributes in the studies of a fractured reservoir. Making use of the scaled physical model, we aim on inspecting the azimuthal Amplitude Variation with Offset (AVO) of C-wave in a reservoir of vertically aligned fractures. In order to facilitate the objective of this study, reflection experiments were carried out on the orthogonal plane of a Horizontal Transversely Isotropic (HTI) model which is created to simulate a fractured reservoir. In laboratory manipulation, acoustic energy is triggered by a P-type transducer and the reflected energy is received an S-type transducer to detect the reflected energy, i.e. C-waves, originating by mode conversion. From fracture strike to facture normal, end-on shooting reflections were acquired from seven different directions. The angular interval in between the successive observation is 15 degrees. While viewing into the reflection profiles, events of P-, C1- and C2-waves can be readily identified. In the acquired profiles, the P-wave AVO is clearly observed and the phenomenon of C-wave splitting is revealed by the separation of traveltime-distance curves of C1- and C2-waves. However, it is aware of that the C-wave amplitudes are not simply varied or attenuated with offset in each observation. The complicated behaviors of C-wave AVO could be caused by the amount of energy, which is incident angle dependent, in reflected S-waves. Hence, our results indicate that the azimuthal C-wave AVO might not be a reliable seismic signature which can be used to delineate the fracture orientation of a fractured reservoir.
Numerical Study of Submerged Vertical Plane Jets Under Progressive Water Surface Waves
Institute of Scientific and Technical Information of China (English)
DAI Hui-chao; WANG Ling-ling
2005-01-01
When wastewater is discharged into a coastal area through an outfall system, it will always be subjected to the action of waves. It is important to study and quantify the mixing of the discharge with the ambient water so that accurate environmental impact assessment can be made for such discharge conditions. The present work aims to study the phenomenon of a plane jet discharged into water environment with regular waves. A 3D numerical model based on the full Navier-Stokes equations (NSE) in the σ-coordinate is developed to study the present problem. Turbulence effects are modeled by a subgrid-scale (SGS) model using the concept of large eddy simulation (LES). The operator splitting method is used to solve the modified NSE. The model has been applied to the simulation of three different cases of submerged plane jets with surface waves: jet with strong waves, jet with weak waves and jet without waves. Numerical results show that the waves enhance the mixing of the jet with the ambient fluid, and cause a periodic deflection of the jet. The size of the re-circulation is about 1.5～2.4 depth of water. The velocity profile of the jet is self-similar in the zone of established flow for both the pure jet and jet in wave circumstances. The spreading characteristic constant α is 0.100 and 0.105 for pure momentum jets with Re numbers 1025 and 2050. The value of α increases from 0.130 to 0.147 for a jet in weak and strong wave circumstances, showing that waves have an obvious effect on the mixing and dilution properties of jets. Numerical results are in good agreement with the experimental data for the cases of pure jets and jets with waves.
A Study of Regional Wave Source Time Functions of Central Asian Earthquakes
Xie, J.; Perry, M. R.; Schult, F. R.; Wood, J.
2014-12-01
Despite the extensive use of seismic regional waves in seismic event identification and attenuation tomography, very little is known on how seismic sources radiate energy into these waves. For example, whether regional Lg wave has the same source spectrum as that of the local S has been questioned by Harr et al. and Frenkel et al. three decades ago; many current investigators assume source spectra in Lg, Sn, Pg, Pn and Lg coda waves have either the same or very similar corner frequencies, in contrast to local P and S spectra whose corner frequencies differ. The most complete information on how the finite source ruptures radiate energy into regional waves is contained in the time domain source time functions (STFs). To estimate the STFs of regional waves using the empirical Green's function (EGF) method, we have been substantially modifying a semi-automotive computer procedure to cope with the increasingly diverse and inconsistent naming patterns of new data files from the IRIS DMC. We are applying the modified procedure to many earthquakes in central Asia to study the STFs of various regional waves to see whether they have the same durations and pulse shapes, and how frequently source directivity occur. When applicable, we also examine the differences between STFs of local P and S waves and those of regional waves. The result of these analyses will be presented at the meeting.
Energy Technology Data Exchange (ETDEWEB)
Uesaka, S. [Kyoto University, Kyoto (Japan). Faculty of Engineering; Watanabe, T.; Sassa, K. [Kyoto University, Kyoto (Japan)
1997-05-27
Algorithm is constructed and a program developed for a full-wave inversion (FWI) method utilizing the elastic wave equation in seismic exploration. The FWI method is a method for obtaining a physical property distribution using the whole observed waveforms as the data. It is capable of high resolution which is several times smaller than the wavelength since it can handle such phenomena as wave reflection and dispersion. The method for determining the P-wave velocity structure by use of the acoustic wave equation does not provide information about the S-wave velocity since it does not consider S-waves or converted waves. In an analysis using the elastic wave equation, on the other hand, not only P-wave data but also S-wave data can be utilized. In this report, under such circumstances, an inverse analysis algorithm is constructed on the basis of the elastic wave equation, and a basic program is developed. On the basis of the methods of Mora and of Luo and Schuster, the correction factors for P-wave and S-wave velocities are formulated directly from the elastic wave equation. Computations are performed and the effects of the hypocenter frequency and vibration transmission direction are examined. 6 refs., 8 figs.
Geophysical studies with laser-beam detectors of gravitational waves
Grishchuk, L P; Rudenko, V N; Serdobolski, A V
2005-01-01
The existing high technology laser-beam detectors of gravitational waves may find very useful applications in an unexpected area - geophysics. To make possible the detection of weak gravitational waves in the region of high frequencies of astrophysical interest, ~ 30 - 10^3 Hz, control systems of laser interferometers must permanently monitor, record and compensate much larger external interventions that take place in the region of low frequencies of geophysical interest, ~ 10^{-5} - 3 X 10^{-3} Hz. Such phenomena as tidal perturbations of land and gravity, normal mode oscillations of Earth, oscillations of the inner core of Earth, etc. will inevitably affect the performance of the interferometers and, therefore, the information about them will be stored in the data of control systems. We specifically identify the low-frequency information contained in distances between the interferometer mirrors (deformation of Earth) and angles between the mirrors' suspensions (deviations of local gravity vectors and plumb ...
Pilot Study on the Nano-Composites Coats of Radar Wave's Absorption
Institute of Scientific and Technical Information of China (English)
HU Chuan-xin; ZhANG Lei; GAN Ai-feng; LI Wan-zhi; LIANG Wen-ting; ZHANG Chen-jia
2004-01-01
This thesis mainly introduced the guiding principle and physical model of the research on the nano-composites coats of radar wave's absorption, and then studied the qualitative analysis of the performance ameliorating of radar wave's absorption composite coats. And on the basis of the optimum design of multilayer wave's absorption materials, two new kinds of radar wave's absorption composite coats have been made, which are composed of nano-composites hydroxyl iron powder and hollow micro-sphere. The research indicated that the surface-density of these two new composite coats is less than 3.5 Kg/m2.The coats' thickness is about 1 mm. And the waves absorption capability is above the level of 5 db, in the range of 3 ～ 18GHz. Therefore the wave's absorption performance of these two new coats is better than nano-crystalloid in low frequency area. The pilot study has proved that the nano-composites coat's performance of radar wave's absorption excels the ordinary radar wave's absorption coats, so it needs to be further studied.
Transient Stress Waves in Study of Coconut Physical Properties
Czech Academy of Sciences Publication Activity Database
Trnka, Jan; Dvořáková, Pavla
2010-01-01
Roč. 34, č. 1 (2010), s. 19-25. ISSN 0732-8818 R&D Projects: GA AV ČR IAA201990701 Institutional research plan: CEZ:AV0Z20760514 Keywords : stress waves * double-pulse holography * coconut * exploding wires Subject RIV: BI - Acoustics Impact factor: 0.505, year: 2010 http://www3.interscience.wiley.com/cgi-bin/fulltext/121567342/PDFSTART
Numerical study of surface water waves generated by mass movement
Ghozlani, Belgacem; Hafsia, Zouhaier; Maalel, Khlifa
2013-10-01
In this paper waves generated by two-dimensional mass movement are simulated using a numerical model based on the full hydrodynamic coupling between rigid-body motion and ambient fluid flow. This approach has the capability to represent the dynamics of the moving rigid body, which avoids the need to prescribe the body velocity based on the data measurements. This model is implemented in the CFX code and uses the Reynolds average Navier-Stokes equations solver coupled to the recently developed immersed solid technique. The latter technique allows us to follow implicitly the motion of the solid block based on the rigid body solver. The volume-of-fluid method is used to track the free surface locations. The accuracy of the present model is firstly examined against the simple physical case of a freely falling rigid body into water reproducing Scott Russell's solitary waves. More complex and realistic simulations of aerial and submarine mass-movement, simulated by a rigid wedge sliding into water along a 45° slope, are then performed. Simulated results of the aerial mass movement show the complex flow patterns in terms of the velocity fields and free surface profiles. Results are in good agreement with the available experimental data. In addition, the physical processes associated with the generation of water wave by two-dimensional submarine mass-movement are explored. The effects of the initial submergence and specific gravity on the slide mass kinematics and maximum wave amplitude are investigated. The terminal velocity and initial acceleration of the slide mass are well predicted when compared to experimental results. It is found that the initial submergence did not have a significant effect on the initial acceleration of the slide block centre of mass. However, it depends nonlinearly\\vadjust{\
Planar Millimeter-Wave Antennas: A Comparative Study
Directory of Open Access Journals (Sweden)
K. Pitra
2011-04-01
Full Text Available The paper describes the design and the experimental verification of three types of wideband antennas. Attention is turned to the bow-tie antenna, the Vivaldi antenna and the spiral antenna designed for the operation at millimeter waves. Bandwidth, input impedance, gain, and directivity pattern are the investigated parameters. Antennas are compared considering computer simulations in CST Microwave Studio and measured data.
Numerical study of nonlinear full wave acoustic propagation
Velasco-Segura, Roberto; Rendon, Pablo L.
2013-11-01
With the aim of describing nonlinear acoustic phenomena, a form of the conservation equations for fluid dynamics is presented, deduced using slightly less restrictive hypothesis than those necessary to obtain the well known Westervelt equation. This formulation accounts for full wave diffraction, nonlinearity, and thermoviscous dissipative effects. A CLAWPACK based, 2D finite-volume method using Roe's linearization has been implemented to obtain numerically the solution of the proposed equations. In order to validate the code, two different tests have been performed: one against a special Taylor shock-like analytic solution, the other against published results on a HIFU system, both with satisfactory results. The code is written for parallel execution on a GPU and improves performance by a factor of over 50 when compared to the standard CLAWPACK Fortran code. This code can be used to describe moderate nonlinear phenomena, at low Mach numbers, in domains as large as 100 wave lengths. Applications range from modest models of diagnostic and therapeutic HIFU, parametric acoustic arrays, to acoustic wave guides. A couple of examples will be presented showing shock formation and oblique interaction. DGAPA PAPIIT IN110411, PAEP UNAM 2013.
Study of nonlinear waves in astrophysical quantum plasmas
Energy Technology Data Exchange (ETDEWEB)
Hossen, M.R.; Mamun, A.A., E-mail: rasel.plasma@gmail.com [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh)
2015-10-01
The nonlinear propagation of the electron acoustic solitary waves (EASWs) in an unmagnetized, collisionless degenerate quantum plasma system has been investigated theoretically. Our considered model consisting of two distinct groups of electrons (one of inertial non-relativistic cold electrons and other of inertialess ultrarelativistic hot electrons) and positively charged static ions. The Korteweg-de Vries (K-dV) equation has been derived by employing the reductive perturbation method and numerically examined to identify the basic features (speed, amplitude, width, etc.) of EASWs. It is shown that only rarefactive solitary waves can propagate in such a quantum plasma system. It is found that the effect of degenerate pressure and number density of hot and cold electron fluids, and positively charged static ions, significantly modify the basic features of EASWs. It is also noted that the inertial cold electron fluid is the source of dispersion for EA waves and is responsible for the formation of solitary structures. The applications of this investigation in astrophysical compact objects (viz. non-rotating white dwarfs, neutron stars, etc.) are briefly discussed. (author)
International Nuclear Information System (INIS)
To maintain the ignition state in a tokamak fusion reactor, a control must be performed on the population of alpha-products, and this implies the ability to diagnose those α-particles. It is studied here whether the detection of emission radiated in the ion cyclotron range of frequency be a reactor plasma can provide useful information concerning fusion products, especially concerning their density profile. It is shown that the detection of the radiation emitted by the fast alpha particles along their cyclotron motion can give access to moments of their distribution function. This requires to compute the phase of the emitted field, using a full-wave approach. Such a technique allows to set in a convenient way the inverse problem of the determination of the emitting α-particles distribution through the radiation detection. A brief analysis of the expected situation in a reactor-relevant plasma is given. In parallel, the 1-D full-wave code developed in this frame is also useful for studying the physics of Fast Wave plasma heating. It enables to take into account the mode conversion of the Fast Wave into the Ion Bernstein Wave that appears near each ion cyclotron resonance. Results show that higher order terms may significantly alter the energy partitioning, in hot plasma cases involving mode conversion heating and/or ion cyclotron high harmonics heating. (author)
Energy Technology Data Exchange (ETDEWEB)
Fraboulet, D.; Becoulet, A.; Nguyen, F
1998-11-01
To maintain the ignition state in a tokamak fusion reactor, a control must be performed on the population of alpha-products, and this implies the ability to diagnose those {alpha}-particles. It is studied here whether the detection of emission radiated in the ion cyclotron range of frequency be a reactor plasma can provide useful information concerning fusion products, especially concerning their density profile. It is shown that the detection of the radiation emitted by the fast alpha particles along their cyclotron motion can give access to moments of their distribution function. This requires to compute the phase of the emitted field, using a full-wave approach. Such a technique allows to set in a convenient way the inverse problem of the determination of the emitting {alpha}-particles distribution through the radiation detection. A brief analysis of the expected situation in a reactor-relevant plasma is given. In parallel, the 1-D full-wave code developed in this frame is also useful for studying the physics of Fast Wave plasma heating. It enables to take into account the mode conversion of the Fast Wave into the Ion Bernstein Wave that appears near each ion cyclotron resonance. Results show that higher order terms may significantly alter the energy partitioning, in hot plasma cases involving mode conversion heating and/or ion cyclotron high harmonics heating. (author) 47 refs.
Lower hybrid current drive in the presence of ICRF waves
International Nuclear Information System (INIS)
Motivated by recent JET results showing an enhancement in the lower hybrid current drive (LHCD) efficiency in ICRF heated plasmas, the authors have been studying the interaction of lower hybrid generated electron tails with fast Alfven waves (FAW) and ion-Bernstein waves (IBW). The IBW's are generated by mode conversion, at the hybrid resonance layers inside the plasma, of the externally launched FAW's. The numerical solutions of the Fokker-Planck equation using CQL3D show that, for the powers used in JET, the FAW cannot significantly modify the LH electron tail and, consequently, does not play a role in the enhancement of the LHCD efficiency. Similar analysis for IBW's shows that these waves play an important role in the enhancement of the current drive efficiency. Calculations show that for small kparallel's about 20% of the FAW power is mode converted to the IBW's. Previous analysis of the propagation of IBW's has shown that the electric field amplitudes are considerably enhanced as IBW propagate in toroidal plasmas. This compensates for the possibly small fraction of the total input power that mode converts to IBW's. Furthermore, IBW's interact with electrons off-axis through Landau damping on flux surfaces where LHW's generate currents. FAW's only interact with electrons near the ion cyclotron or ion-ion hybrid resonance layers which, in the case of JET, may be near the axis of the plasma while the LH waves damp well off-axis. So IBW's are more likely to enhance the LHCD efficiency. In fact, the conditions for which JET shows an enhancement in LHCD efficiency are those for which mode conversion to IBW's occurs. The authors present detailed analytical and numerical results in support of the statements made above
Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom
Energy Technology Data Exchange (ETDEWEB)
Solis-Najera, S. E., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Neria-Pérez, J. A., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx; Medina, L., E-mail: solisnajera@ciencias.unam.mx, E-mail: angel.perez@ciencias.unam.mx, E-mail: lucia.medina@ciencias.unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, México, DF 04510 (Mexico); Garipov, R., E-mail: ruslan.garipov@mrsolutions.co.uk [MR Solutions Ltd, Surrey (United Kingdom); Rodríguez, A. O., E-mail: arog@xanum.uam.mx [Departamento Ingeniería Eléctrica, Universidad Autónoma Metropolitana Iztapalapa, México, DF 09340 (Mexico)
2014-11-07
Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot’s model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot’s waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.
High frequency fast wave results from the CDX-U spherical torus
International Nuclear Information System (INIS)
The Current Drive Experiment-Upgrade (CDX-U) is the first spherical torus (ST) to investigate radio frequency (RF) heating and current drive. To address the concern that large magnetic field line pitch at the outboard midplane of ST's could inhibit successful coupling to the high harmonic fast wave (HHFW), a rotatable, two strap antenna was installed on CDX-U. Parasitic loading and impurity generation were discovered to be weak and nearly independent of antenna phasing and angle over a wide range, and fast wave electron heating has been observed. Plasma densities up to about 1012cm-3 were obtained with noninductive startup solely with HHFW. New ST diagnostics under development on CDX-U include a multilayer mirror (MLM) detector to measure ultrasoft X-rays, a twelve spatial point Thomson scattering (TS) system, and an Electron Bernstein Wave (EBW) system for both electron heating and electron temperature measurements. Preliminary experiments with a boron low velocity edge micropellet injector have also been performed, and further studies of its effectiveness for impurity control will be conducted with a variety of spectroscopic and imaging diagnostics on CDX-U. (author)
An experimental study of plasma waves generated by co-linear optical mixing
International Nuclear Information System (INIS)
Longitudinal plasma waves produced by the resonant heating of two transverse electromagnetic waves are of interest for several reasons. First, it has been predicted theoretically and demonstrated in simulations that the exceedingly large electric field of such a wave may be used to accelerate particles to high energies. Secondly, because the plasma wave necessarily obeys the plasma dispersion relation, it may serve as a versatile and accurate plasma density probe. Furthermore, several schemes have been proposed to locally heat plasmas using the damping of these waves. The latter application is particularly relevant to the study of ionospheric plasma physics and cross-field transport. We present here results appropriate to all of these research avenues. These investigations also raise some interesting new questions concerning plasma wave-wave interactions. In co-linear optical mixing, two electromagnetic waves with slightly differing frequencies are injected parallel into a plasma. If the plasma density is such that the plasma frequency approximately matches the difference frequency of the EM waves, then a longitudinal electrostatic wave will be resonantly excited. The two EM waves in this experiment are the 9.6 μm line (4J) and the 10.6 μ line (12J) of a CO2 laser. An arc discharge preionizes hydrogen gas to provide the initial plasma. The resonant plasma density corresponding to these wavelengths, 1.1 x 1017 cm-3, is diagnosed by means of ruby Thomson scattering and tuned by varying the arc parameters. The authors observe at this resonant density ruby light, both red- and blue-shifted by ωp, at an angle of 70
Urška Valenčič Arh
2014-01-01
Bernstein, Nils (2011): „kennen sie mich herren/meine damen und herren”. Phraseologismen in Moderner Lyrik am Beispiel von Ernst Jandl und Nicanor Parra. Würzburg: Königshausen&Neumann. ISBN: 978-3-8260-4699-5, mehka vezava, 262 strani, 38,00 EUR
Directory of Open Access Journals (Sweden)
Urška Valenčič Arh
2014-01-01
Full Text Available Bernstein, Nils (2011: „kennen sie mich herren/meine damen und herren”. Phraseologismen in Moderner Lyrik am Beispiel von Ernst Jandl und Nicanor Parra. Würzburg: Königshausen&Neumann. ISBN: 978-3-8260-4699-5, mehka vezava, 262 strani, 38,00 EUR
Stratospheric gravity waves generated by typhoon--A numerical simulation study SIMULATION STUDY
Chen, Zeyu; Preusse, P.; Jarisch, M.; Ern, M.; Offermann, D.
In this presentation the results of a numerical simulation study focusing on investigating the typhoon effect of generating stratospheric GWs will be presented. With applying the PSU/NCAR mm5 model for a northwestern Pacific typhoon (Winnie, 05-23 August 1997), the critical features of the typhoon (comparing with the brightness temperature observations from GMS-5 satellite) and the mean state of the background circulations (comparing with the temperatures observations of the stratosphere from the CRISTA II mission) were captured by the simulation. Detailed investigations revealed that significant stratospheric GWs were triggered by the typhoon. A Typhoon related Gravity Waves Active Area (hereafter referred to as TGWAA) was defined. Momentum flux spectrum with respect to the zonal wave number and frequency in the TGWAA was calculated. Results indicated that the GWs dominant modes were those propagating in the upstream of the background flow (Easterly wind) with a spatial scale ranging from 500 km to 1000 km in the horizontal, and from 7 km to 10 km in the vertical. The temporal scale was rather monotonic with the periods concentrated at 15 hr. The averaged momentum flux in the TGWAA was ˜ 0.001 Pascal at 19 km altitude, 0.0008 Pascal at 25 km altitude, indicating that the waves effect on the mean flow should be paid much attention.
Elastic properties of amorphous thin films studied by Rayleigh waves
International Nuclear Information System (INIS)
Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni1-xZrx (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements limited in size by geometrical frustration
The study on the guided wave mode conversion using self-calibrating technique
International Nuclear Information System (INIS)
The guided wave mode conversion phenomena were investigated for the NDE of a plate-like structure with thickness variation. The ratios of reflection and transmission (R/T) were measured via the self-calibrating procedure which allows us to obtain experimental guided wave data in a more reliable way regardless of the coupling uncertainty between transducer and specimen. The results on R/T could be used to determine the thickness reduction of the structure. It was shown that not only the incident modes but also the converted ones need to be considered in the self-calibrating guided wave inspection to extract a reasonable correlation between experimental data and the thickness variation. Through this study, the potential of guided wave inspection as a quantitative NDE technique was explored based on the combined concept of self-calibration and multi-mode conversion in guided wave scattering problems.
Experimental Study on Local Scour Around A Large Circular Cylinder Under Irregular Waves
Institute of Scientific and Technical Information of China (English)
周益人; 陈国平
2004-01-01
A series of physical model tests are conducted for local scour around a circular cylinder of a relatively large diameter (0.15 ＜ D/L ＜ 0.5) under the action of irregular waves. The laws of change of the topography around the cylinder are systematically studied. The effects of wave height, wave period, water depth, sediment grain size and cylinder diameter are taken into account. The mechanism of formation of the topography around the cylinder is analyzed. A detailed analysis is given to bed sediment grain size, and it is considered that the depth of scour around the cylinder under wave action is not inversely proportional to the sediment grain diameter. On such a basis, an equation is proposed for calculation of the maximum depth of scour around a cylinder as well as its position under the action of irregular waves.
Dynamic cross correlation studies of wave particle interactions in ULF phenomena
Mcpherron, R. L.
1979-01-01
Magnetic field observations made by satellites in the earth's magnetic field reveal a wide variety of ULF waves. These waves interact with the ambient particle populations in complex ways, causing modulation of the observed particle fluxes. This modulation is found to be a function of species, pitch angle, energy and time. The characteristics of this modulation provide information concerning the wave mode and interaction process. One important characteristic of wave-particle interactions is the phase of the particle flux modulation relative to the magnetic field variations. To display this phase as a function of time a dynamic cross spectrum program has been developed. The program produces contour maps in the frequency time plane of the cross correlation coefficient between any particle flux time series and the magnetic field vector. This program has been utilized in several studies of ULF wave-particle interactions at synchronous orbit.
Goldberg, R. A.; Fritts, D. C.; Chou, H.-G.; Schmidlin, F. J.; Barcus, J. R.
1988-01-01
The origin of wintertime mesospheric echoes observed with the mesosphere-stratosphere-troposphere radar at Poker Flat, Alaska, was studied by probing the mesosphere with in situ rocket measurements during echo occurrences in the early spring, 1985. Within the height range 65-75 km, the structure of the large scale wave field was identified. In this region, a gravity wave with a vertical wavelength of about 2 km was found superimposed on a wave with a larger amplitude and a vertical wavelength of about 6.6 km. Because of the close correlation between the smaller amplitude wave and the modulation observed in the S/N profiles, it is concluded that the smaller wave was dominant in generating turbulence within the middle atmosphere.
Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma
International Nuclear Information System (INIS)
Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies
Theoretical studies of coherent nonlinear drift wave-zonal flow interactions
International Nuclear Information System (INIS)
Full text: We have, employing a slab model, carried out in-depth theoretical studies on the coherent nonlinear interactions between drift waves (DW) and zonal flows (ZF). In this talk, we will first review the four-wave modulational mechanism for the spontaneous excitation of zonal flow by coherent drift waves. As the amplitude of the primary (pump) drift wave attains spatial localization due to plasma non-uniformities and/or initial localized perturbations, the excited zonal flows become localized structures; leading to cascading of drift waves toward shorter (radial) wave numbers.This nonlinearly generated normal cascading and accompanied enhanced (radial) dispersiveness leads to the new novel result that, time asymptotically, coherent drift waves can be trapped by the self-induced zonal flows; similar to the Langmuir wave-density cavity soliton physics. Indeed, both analytical theories and direct numerical calculations demonstrate the formation and, consequently, radial propagation of DW-ZF solitary structures. Additional effects such as linear growth, dissipations, equilibrium non-uniformities and soliton dynamics could further lead to interesting physics; e.g., generation, destruction, collision, and reflection of solitons, as well as turbulence bursting. The propagation of DW-ZF solitons causes significant radial spreading of DW turbulence and ,hence, could qualitatively modify the transport processes. Generalization to the toroidal geometries will also be presented. Research supported by U.S. DoE. (author)
Theoretical and Numerical Studies of Wave-packet Propagation in Tokamak Plasmas
International Nuclear Information System (INIS)
Full text: Theoretical and numerical studies of wave-packet propagation are presented to analyze the time varying 2D mode structures of electrostatic fluctuations in tokamak plasmas, using general flux coordinates. Instead of solving the 2D wave equations directly, the solution of the initial value problem is obtained, following the propagation of wave-packets generated by a source and reconstructing the time varying field. As application, the 2D WKB method is applied to investigate the shaping effects (elongation and triangularity) of tokamak geometry on the lower hybrid wave propagation and absorption. Meanwhile, the mode structure decomposition (MSD) method is used to handle the boundary conditions and simplify the 2D problem, casted into two nested 1D problems. The MSD method is related to that discussed in earlier works and reduces to the well-known 'ballooning formalism', when spatial scale separation applies. This method is used to investigate the time varying 2D electrostatic ITG mode structure with a mixed WKB-full wave technique. The time varying field pattern is reconstructed and the time asymptotic structure of the wave-packet propagation gives the 2D eigenmode and the corresponding eigenvalue. As a general approach to investigate 2D mode structures in tokamak plasmas, our method also applies for electromagnetic waves with general source/sink terms, either by an internal/external antenna or nonlinear wave interaction with zonal structures. (author)
Study on a particle separator using ultrasonic wave
International Nuclear Information System (INIS)
This paper presents the theory, design and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described at the first. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lense was used to monitor the position of interested particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured. The device shows a strong levitation and separation force against 50m diameter particles mixed with water at the separation channel in the device. Experimental results also showed that the device can work at both heavy and light sand particles mixed with water due to the generated standing wave field in the separation channel.
Multi-Tone Millimeter-Wave Frequency Synthesizer for Atmospheric Propagation Studies
Simons, Rainee N.; Wintucky, Edwin G.
2014-01-01
The design and test results of a multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator is presented. The intended applications of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at Q-band (37 to 43 GHz). These studies would enable the design of robust high data rate space-to-ground satellite communication links.
International Nuclear Information System (INIS)
Backward wave oscillation based on a cylindrical surface wave of Smith-Purcell free electron laser (SP-FEL) is demonstrated. The SP-FEL is composed of a metal cylinder having a periodically corrugated wall and a surrounding hollow straight waveguide. Corrugation parameters are those used in K-band backward wave oscillators (BWOs). The metal cylinder has a surface wave due to the corrugation. The cylindrical surface wave is excited by an axially injected coaxial annular beam. Radiations due to the backward wave oscillation based on the cylindrical surface wave are examined in a weakly relativistic region less than 100 kV. An oscillation starting voltage exists for the backward wave oscillation as in the case of hollow oversized BWO. The frequencies are in K-band and are determined by the cylindrical corrugation. Radiations up to tens of kW are obtained. (author)
Study of magnetostatic mode waves using scanning Kerr imaging
Tamaru, Shingo
2005-07-01
This dissertation discusses a technique developed to measure microscopic ferromagnetic resonance, and the results of the excitation and relaxation of magnetostatic mode waves (MSW) obtained by this technique. In this technique, named spatially resolved ferromagnetic resonance-scanning Kerr effect microscopy (SRFMR-SKEM), a sample under measurement is excited by a sinusoidal field in the microwave frequency range and the entire waveform of the magnetization response over one cycle is captured by an optical system identical to that used for time resolved scanning Kerr effect microscopy. This allows one to determine not only the amplitude but also the phase of the local precessional motion with optical diffraction limited spatial and picosecond timing resolution. Using this technique, magnetic excitation and relaxation in Permalloy thin films under various conditions were measured. In the first experiment, the uniform mode (Kittel mode) was excited. The phenomenological damping parameter showed an anomalous increase in the low bias field region. 2D mapped images of magnetization response suggest that the formation of multidomain structure and ripple domains are most likely to be responsible for this behavior. In the second experiment, decaying plane MSWs were observed from which the wave number and the decay length were determined. It was found that the extended Damon-Eshbach model which includes the effect of finite damping can be used explain the results. The third experiment showed a clear signature of mode quantization of MSWs excited in a confined geometry. Finally, the fourth experiment captured spatial propagation patterns of MSWs under various conditions. Experiments suggest that these patterns are diffraction patterns of MSWs. A theory for calculating the diffraction patterns of MSWs was presented in order to understand the observation results in the fourth experiment. In this theory, the Green's function for MSWs was first derived, then a convolution
Dum, C. T.
1990-01-01
Particle simulation experiments were used to study the basic physical ingredients needed for building a global model of foreshock wave phenomena. In particular, the generation of Langmuir waves by a gentle bump-on-tail electron distribution is analyzed. It is shown that, with appropriately designed simulations experiments, quasi-linear theory can be quantitatively verified for parameters corresponding to the electron foreshock.
A parametric study of the linear growth of magnetospheric EMIC waves in a hot plasma
Wang, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Zhou, Chen; Shi, Run; Zhao, Zhengyu
2016-06-01
Since electromagnetic ion cyclotron (EMIC) waves in the terrestrial magnetosphere play a crucial role in the dynamic losses of relativistic electrons and energetic protons and in the ion heating, it is important to pursue a comprehensive understanding of the EMIC wave dispersion relation under realistic circumstances, which can shed significant light on the generation, amplification, and propagation of magnetospheric EMIC waves. The full kinetic linear dispersion relation is implemented in the present study to evaluate the linear growth of EMIC waves in a multi-ion (H+, He+, and O+) magnetospheric plasma that also consists of hot ring current protons. Introduction of anisotropic hot protons strongly modifies the EMIC wave dispersion surface and can result in the simultaneous growth of H+-, He+-, and O+-band EMIC emissions. Our parametric analysis demonstrates that an increase in the hot proton concentration can produce the generation of H+- and He+-band EMIC waves with higher possibility. While the excitation of H+-band emissions requires relatively larger temperature anisotropy of hot protons, He+-band emissions are more likely to be triggered in the plasmasphere or plasmaspheric plume where the background plasma is denser. In addition, the generation of He+-band waves is more sensitive to the variation of proton temperature than H+-band waves. Increase of cold heavy ion (He+ and O+) density increases the H+ cutoff frequency and therefore widens the frequency coverage of the stop band above the He+ gyrofrequency, leading to a significant damping of H+-band EMIC waves. In contrast, O+-band EMIC waves characteristically exhibit the temporal growth much weaker than the other two bands, regardless of all considered variables, suggesting that O+-band emissions occur at a rate much lower than H+- and He+-band emissions, which is consistent with the observations.
Study on estimate method of wave velocity and quality factor to fault seals
Institute of Scientific and Technical Information of China (English)
LI Zhensheng; LIU Deliang; LIU Bo; YANG Qiang; LI Jingming
2005-01-01
Based on ultrasonic test of fault rocks, the responses for wave velocity and quality factor (Q value) to lithology, porosity and permeability of fault rocks and mechanical property of faults are studied. In this paper, a new quantitative estimate method of fault seals is originally offered. The conclusions are as follows: (1) Wave velocity and Q value increase and porosity decreases with the increase in stress perpendicular to joint; (2) In compressive and compresso-shear fault rocks that are obviously anisotropic compared with their original rocks, the wave velocity and Q value are greater in the direction parallel with foliation, and usually less perpendicular to it. In tensile and tenso-shear fault rocks that are not obviously anisotropic, the wave velocity and Q value are under that of original rocks; (3) In foliated fault rocks, the direction with minimal wave velocity and Q value is the best direction for sealing; on the contrary it is the best for flowing; (4) Structural factures develop mainly along foliation, the minimal wave velocity and Q value reflect the flowing capacity in parallel direction to foliation, and the maximal wave velocity as well as Q value reflect the sealing capacity in normal direction to foliation. The new estimate method is based upon contrast of wave velocity and Q value between fault rocks and their original rocks, and is divided into three parts that are respectively to identify rock's lithology, to judge mechanic property of faults and to Judge sealing capacity of faults. Although there is vast scale effect between ultrasonic wave and seismic wave, they have similar regularity of response to fabric and porosity of faults. This research offers new application for seismic data and petrophysical basis for seismological estimation of fault seals. The estimate precision will be improved with the enhancement of three-dimensional seismic prospecting work.
A computational study of pressure wave reflections in the pulmonary arteries.
Qureshi, M Umar; Hill, N A
2015-12-01
Experiments using wave intensity analysis suggest that the pulmonary circulation in sheep and dogs is characterized by negative or open-end type wave reflections, that reduce the systolic pressure. Since the pulmonary physiology is similar in most mammals, including humans, we test and verify this hypothesis by using a subject specific one-dimensional model of the human pulmonary circulation and a conventional wave intensity analysis. Using the simulated pressure and velocity, we also analyse the performance of the P-U loop and sum of squares techniques for estimating the local pulse wave velocity in the pulmonary arteries, and then analyse the effects of these methods on linear wave separation in the main pulmonary artery. P-U loops are found to provide much better estimates than the sum of squares technique at proximal locations, but both techniques accumulate progressive error at distal locations away from heart, particularly near junctions. The pulse wave velocity estimated using the sum of squares method also gives rise to an artificial early systolic backward compression wave. Finally, we study the influence of three types of pulmonary hypertension viz. pulmonary arterial hypertension, chronic thromboembolic pulmonary hypertension and pulmonary hypertension associated with hypoxic lung disease. Simulating these conditions by changing the relevant parameters in the model and then applying the wave intensity analysis, we observe that for each group the early systolic backward decompression wave reflected from proximal junctions is maintained, whilst the initial forward compression and the late systolic backward compression waves amplify with increasing pathology and contribute significantly to increases in systolic pressure. PMID:25754476
An Experimental and Numerical Study of Long Wave Run-Up on a Plane Beach
Directory of Open Access Journals (Sweden)
Ulrike Drähne
2015-12-01
Full Text Available This research is to facilitate the current understanding of long wave dynamics at coasts and during on-land propagation; experimental and numerical approaches are compared against existing analytical expressions for the long wave run-up. Leading depression sinusoidal waves are chosen to model these dynamics. The experimental study was conducted using a new pump-driven wave generator and the numerical experiments were carried out with a one-dimensional discontinuous Galerkin non-linear shallow water model. The numerical model is able to accurately reproduce the run-up elevation and velocities predicted by the theoretical expressions. Depending on the surf similarity of the generated waves and due to imperfections of the experimental wave generation, riding waves are observed in the experimental results. These artifacts can also be confirmed in the numerical study when the data from the physical experiments is assimilated. Qualitatively, scale effects associated with the experimental setting are discussed. Finally, shoreline velocities, run-up and run-down are determined and shown to largely agree with analytical predictions.
Quantum Wave Packet Studies on F+HBr Reaction
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Time-dependent quantum wave packet calculations were carried out for the F + HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabilities dramatically increase near the zero collision energy and then slightly decrease with increasing collision energy, which corresponds well to the behavior of a barrierless reaction. The effects of reagent HBr excitation were examined, it is shown that both the vibrational and the rotational excitations of reagent HBr have a negative effect on the reactivity of F + HBr. The integral cross-section for the ground state of the reagent HBr decreases at a low collision energy and then becomes plat with increasing collision energy, which is reasonable for the feasibility of such an exothermal reaction. The rate constant that was obtained is slightly higher than that obtained in the quasi-classical trajectory calculation.
A study of DSN traveling wave maser system reliability
Stevens, R.; Wiggins, C. P.
1984-08-01
Reliability and availability characteristics of the DSN traveling wave maser (TWM) Assemblies are reported for the years 1981 through 1983, the charcteristics determined are: mean time between failures (MTBF) - 1200 hours; mean time to restore service (MTTRS) - 2.5 hours; and availability - 99.83%. The TWM MTBF is very good as compared to other DSN subsystems and assemblies. The TWM MTTRS is currently about three times as long as the average of other DSN subsystems. The dominant cause of TWM failures is contamination of the helium gas in the closed cycle refrigerators. Station configurations that do not provide TWM redundancy are subject to reception outages for long periods of time. Recommendations are made to improve the TWM Assembly availability characteristics for future mission support operations.
Study on S wave velocity structure beneath part stations in Shanxi Province
Institute of Scientific and Technical Information of China (English)
张学民; 束沛镒; 刁桂苓
2003-01-01
Based on S wave records of deep teleseisms on Digital Seismic Network of Shanxi Province, shear wave velocity structures beneath 6 stations were obtained by means of S wave waveform fitting. The result shows that the crust is thick in the studied region, reaching 40 km in thickness under 4 stations. The crust all alternatives high velocity layer with low velocity one. There appear varied velocity structures for different stations, and the stations around the same tectonic region exhibit similar structure characteristics. Combined with dominant depth distribution of many small-moderate earthquakes, the correlation between seismogenic layers and crustal structures of high and low velocity layers has been discussed.
A study on scattered fields analysis of ultrasonic SH-wave by boundary element method
International Nuclear Information System (INIS)
In this paper, the SH-wave scattering by multi-defects and inclusion using Boundary Element Method is studied. The effects of shape and distance of defects on transmitted and reflected fields are considered. The interaction of multi-defects in SH-wave scattering is also investigated. Numerical calculations by the BEM have been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results can be used to improve the detection sensitivity and pursue quantitative nondestructive evaluation for inverse problem.
A Study of Energy Conversion Efficiency of a Savonius Type Wave Energy Converter System
Tutar, Mustafa; Erdem, Ceyhan
In the present study, two-dimensional, two-phase and turbulent flow around a horizontal axis 3-bladed Savonius rotor is considered. Numerical wave tank (NWT) simulations based on FVM/FDM technique in association with volume of fluid (VOF) element method are performed for specified values of wave heights for no-rotor flow case. Once validated against the theoretical data, the numerical simulations are extended to investigate the overall performance of the turbine over a very large range of wave height conditions for the rotor-flow case.
Directory of Open Access Journals (Sweden)
SJ Cornelius
2012-12-01
Full Text Available Parties generally enter into contractual relations with the sincere intention to fulfil all the obligations created in terms of their contract. However, for various reasons, parties sometimes do not comply with the terms of their contract. Where a party fails to perform at the agreed date and time or after receiving a demand from the creditor, the debtor commits breach of contract in the form of mora debitoris. The question then arises whether or not a debtor would also commit breach in the form of mora debitoris if the delay in performance cannot be attributed to wilful disregard of the contract or a negligent failure to perform on time. This was the question which the court had to determine in Scoin Trading (Pty Ltd v Bernstein.
Ng, C. S.
2014-10-01
Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear steady-state solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. We generalize exact solutions of two-dimensional BGK modes in a magnetized plasma with finite magnetic field strength to cases with azimuthal magnetic fields so that these structures carry electric current as well as steady electric and magnetic fields. Such nonlinear solutions now satisfy exactly the Vlasov-Poisson-Ampere system of equations. This work is supported by a National Science Foundation Grant PHY-1004357.
Ion cyclotron wave excitation by double resonance coupling
International Nuclear Information System (INIS)
A modulated high frequency wave is used to remotely excite low frequency oscillations in a linear, strongly magnetized plasma column. An electromagnetic wave is launched as an extraordinary mode across the plasma by an external waveguide in the Upper Hybrid frequency regime f=fUH=fce=8 GHz, with P≤2 W. By frequency modulating (at fFM=1-60 kHz, with fci≅30 kHz) the pump wave, the resonant layer is swept radially across the profile and perpendicularly to the field lines at f=fFM. The resulting radial oscillation of the electron linear and non linear pressure can be considered to act as a source term for the ion wave. A localized virtual antenna is thereby created inside the plasma. Measurements of the ion dielectric response (interferograms and perturbed distribution functions) via laser induced fluorescence identify the two branches (forward, or ion-acoustic-like, and backward, or Bernstein, modes) of the electrostatic dispersion relation in the ion cyclotron frequency range. By changing the modulation bandwidth, and thus the spatial excursion of the oscillating resonant layer, a control on the perpendicular wavelength of the excited mode can be exerted. In particular, the possibility of selective excitation of the ion Bernstein wave is demonstrated experimentally. (author) 38 refs., 13 figs
Feasibility study of microwave electron heating on the C-2 field-reversed configuration device
Yang, Xiaokang; Koehn, Alf; Petrov, Yuri; Ceccherini, Francesco; Dettrick, Sean; Binderbauer, Michl
2015-12-01
Different microwave heating scenarios for the C-2 plasmas have been investigated recently with use of both the Genray ray-racing code and the IPF-FDMC full-wave code, and the study was focused on the excitation of the electron Bernstein wave (EBW) with O-mode launch. For a given antenna position on C-2 and the fixed 2D plasma density and equilibrium field profiles, simulations have been done for six selected frequencies (2.45 GHz, 5 GHz, 8 GHz, 18 GHz, 28 GHz, and 50 GHz). Launch angles have been optimized for each case in order to achieve high coupling efficiencies to the EBW by the O-X-B mode conversion process and high power deposition. Results show that among those six frequencies, the case of 8 GHz is the most promising scenario, which has both high mode conversion efficiency (90%) and the relatively deeper power deposition.
Directory of Open Access Journals (Sweden)
I. V. Subba Reddy
2005-11-01
Full Text Available MST radars are powerful tools to study the mesosphere, stratosphere and troposphere and have made considerable contributions to the studies of the dynamics of the upper, middle and lower atmosphere. Atmospheric gravity waves play a significant role in controlling middle and upper atmospheric dynamics. To date, frontal systems, convection, wind shear and topography have been thought to be the sources of gravity waves in the troposphere. All these studies pointed out that it is very essential to understand the generation, propagation and climatology of gravity waves. In this regard, several campaigns using Indian MST Radar observations have been carried out to explore the gravity wave activity over Gadanki in the troposphere and the lower stratosphere. The signatures of the gravity waves in the wind fields have been studied in four seasons viz., summer, monsoon, post-monsoon and winter. The large wind fluctuations were more prominent above 10 km during the summer and monsoon seasons. The wave periods are ranging from 10 min-175 min. The power spectral densities of gravity waves are found to be maximum in the stratospheric region. The vertical wavelength and the propagation direction of gravity waves were determined using hodograph analysis. The results show both down ward and upward propagating waves with a maximum vertical wave length of 3.3 km. The gravity wave associated momentum fluxes show that long period gravity waves carry more momentum flux than the short period waves and this is presented.
Parametric study of two-body floating-point wave absorber
Amiri, Atena; Panahi, Roozbeh; Radfar, Soheil
2016-03-01
In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter's efficiency when considering specific conditions.
Ray Tracing Study of Electromagnetic Ion Cyclotron Waves Associated with Bi-Ion Frequencies
International Nuclear Information System (INIS)
Ray tracing study of electromagnetic ion cyclotron (EMIC) waves is conducted based on a realistic plasma density model. The simulation result shows that EMIC waves propagate away from the equatorial source region to higher latitudes basically along geomagnetic field lines, and are reflected at the region where their frequency matches the local bi-ion frequency. H+ band suffers H+-He+ bi-ion frequency reflection at lower latitudes, whereas He+ band suffers He+-O+ bi-ion frequency reflection at higher latitudes. Moreover, the concentration of heavy ions slightly affects the bi-ion frequencies and then slightly determines the reflection location of ray paths of EMIC waves. The current results present the first detailed study on the propagation characteristics of EMIC waves associated with bi-ion frequencies
Theoretical analysis and experimental study of oxygen transfer under regular and non-breaking waves
Institute of Scientific and Technical Information of China (English)
尹则高; 梁丙臣; 王乐
2013-01-01
The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analysis method are employed to study the oxygen transfer under regular and non-breaking waves, and a unified oxygen transfer coefficient equation is obtained with consi-deration of the effect of kinetic energy and wave period. An oxygen transfer experiment for the intermediate depth water wave is per-formed to measure the wave parameters and the dissolved oxygen concentration. The experimental data and the least squares method are used to determine the constant in the oxygen transfer coefficient equation. The experimental data and the previous reported data are also used to further validate the oxygen transfer coefficient, and the agreement is satisfactory. The unified equation shows that the oxygen transfer coefficient increases with the increase of a parameter coupled with the wave height and the wave length, but it de-creases with the increase of the wave period, which has a much greater influence on the oxygen transfer coefficient than the coupled parameter.
Animal study on lung injury caused by simulant segmented shock waves
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Objective: To study the lung injury caused by se gmented shock waves. Methods: A total of 60 rabbits and 20 rats were used in this st udy. The process of transmission of shock waves was divided into three phases, i .e., the recompression phase (RP), the decompression phase (DP) and the underpre ssure phase (UP). And the recompression wave (RW), the decompression wave (DW) a nd the underpressure wave (UW) simulated the three phases, respectively, generat ed by the equipment designed by us. The RW test, DW test and UW test were respec tively applied to the animals. And lung injuries caused by segmented shock waves were discussed. Results: Under the experimental conditions, the RW did not caus e obvious lung injury, but the DW could cause different severities of lung injur ies. The greater the decompression ranged and the shorter the decompression dura tion was adopted, the more severe the lung injury was observed. The UW, to some extent, could cause obvious lung injury. Conclusions: It suggests that lung injury under shock waves pro bably occurs during the DP primarily. It probably does not cause direct obvious lung injury during the RP, but significantly influences the capability of causin g lung injury during the DP.
Analytical Study for Stress Wave Interaction with Rock Joints Having Unequally Close-Open Behavior
Li, J. C.; Zhao, X. B.; Li, H. B.; Chai, S. B.; Zhao, Q. H.
2016-08-01
Stress wave interaction with rock joints during wave propagation is usually dependent on the dynamic response of the joints. During wave propagation, joints may be closed and open under the effects of the stress wave and the in situ stress. A joint in nature can only resist load during close process. In this paper, the close and open behaviors of rock joints are considered to be different. The joints are assumed to be linearly elastic in close status but turn into free surfaces in open status. Wave propagation equation across joints with unequally close-open behavior is first derived and expressed as a time-differential form based on the displacement discontinuity method. SHPB test recording is then adopted to verify the present approach, which is also compared with the results from existing methods for joints with equally close-open behavior. Next, analysis is conduced for wave propagation across a single joint and a set of parallel joints with unequally close-open behavior, respectively. From the analysis, effects of unequally close-open behavior of a joint on wave propagation and the dynamic response of the joint are studied finally.
NUMERICAL STUDIES OF INTERNAL SOLITARY WAVE GENERATION AND EVOLUTION BY GRAVITY COLLAPSE
Institute of Scientific and Technical Information of China (English)
LIN Zhen-hua; SONG Jin-bao
2012-01-01
In this study,an analysis on the internal wave generation via the gravity collapse mechanism is carried out based on the theoretical formulation and the numerical simulation.With the linear theoretical model,a rectangle shape wave is generated and propagates back and forth in the domain,while a two-dimensional non-hydrostatic numerical model could reproduce all the observed phenomena in the laboratory experiments conducted by Chen et al.(2007),and the related process realistically.The model results further provide more quantitative information in the whole domain,thus allowing an in depth understanding of the corresponding internal solitary wave generation and propagation.It is shown that the initial type of the internal wave is determined by the relative height between the perturbation and the environmental density interface,while the final wave type is related to the relative height of the upper and lower layers of the environmental fluid.The shape of the internal wave generated is consistent with that predicted by the KdV and EKdV theories if its amplitude is small,as the amplitude becomes larger,the performance of the EKdV becomes better after the wave adjusts itself to the ambient stratification and reaches an equilibrium state between the nonlinear and dispersion effects.The evolution of the mechanical energy is also analyzed.
Numerical studies on wave forces and moored ship motions in intermediate and shallow water
You, Jikun
2012-01-01
Wave forces and motions of a moored ship in intermediate and shallow water depth are investigated numerically in the present thesis. The studies are carried out in the framework of potential flow theory. Three numerical models, which include a 2D and 3D fully nonlinear numerical wave tank (FNWT), a second-order perturbation method and a coupled Boussinesqpanel model, are developed and verified by available theoretical and experimental results.In the FNWT, numerical issues like accurate tracki...
Experimental Study of a Radial Turbine Using Pitch-Controlled Guide Vanes for Wave Power Conversion
Takao, Manabu; Fujioka, Yoshihiro; Homma, Hiroki; Kim, Tae-Whan; Setoguchi, Toshiaki
2006-01-01
In order to develop a high-performance radial turbine for wave power conversion, a radial turbine with pitch-controlled guide vanes has been proposed and manufactured in the study. The proposed radial turbine has been investigated experimentally by model testing under steady and sinusoidal flow conditions. Then, the experimental results have been compared with those of the conventional radial turbine for wave power conversion, that is, a radial turbine with fixed guide vanes. As a result, the...
A numerical study of the evolution of the blast wave shape in rectangular tunnels
Uystepruyst, David; Monnoyer, François
2015-01-01
When the explosion of condensed materials occurs in square or circular cross-section tunnel, the subsequent blast wave reveals two patterns: three-dimensional close to the explosive charge and one-dimensional far from the explosion. Pressure decays for these two patterns have been thoroughly studied. However, when the explosion occurs in rectangular cross-section tunnel, which is the most regular geometry for underground networks, the blast wave exhibits a third, two-dimensional, patterns. In...
Return Stroke Current and Optical Wave Speed Study with Time Domain Fractal Lightning Modelling
Liang, C.; Lehtinen, N. G.; Carlson, B. E.; Cohen, M.; Inan, U.
2013-12-01
Time domain fractal lightning modeling is capable of handling both the complex geometry of the lighting channel and the dynamic evolution of the charge and current distribution along the channel. Recent enhancement improves the model by including more accurate treatment of the thermodynamics of the lighting channel during the return stroke. Specifically, the model uses realistic high temperature air plasma properties and self-consistently solves Maxwell's equations coupled with equations of air plasma thermodynamics. Moreover, the model takes a two fluid view of the plasma in the core of the lightning channel and allows temperature separation between the electron gas and the gas formed by the other heavier particles. This is achieved by taking into account of the finite rate of kinetic energy transfer between the two gases. With these features at hand, we present numerical simulations of the current and the optical wave propagations along the lightning channel during the return stroke. This study is of particular interest because a broad range of applications including lightning geolocation, aviation safety, and lightning-ionospheric coupling are based on the predicted electromagnetic pulse of the return stroke, which are derived with assumptions on the return stroke current wave speed. A wide range of optical recordings of the return stroke is available, based on which the optical wave speed along the return stroke channel is consistently measured to be in the range of 1/3 - 2/3 of the speed of light. Direct measurement of the current wave speed is not available and it is commonly assumed to be the same as the optical wave speed. However, our model predicts a significantly higher current wave speed than the optical wave speed, as well as a finite time delay between the two waves. We also present comparisons between the observed and model predicted optical wave rise time, peak optical power decay rate with altitude, peak temperature and pressure, as well as the
Institute of Scientific and Technical Information of China (English)
XU Fu-min; XUE Hong-chao
2004-01-01
the study of wave statistical properties.
Study on data analysis techniques in gravitational wave detectors
International Nuclear Information System (INIS)
This work initially investigates the possibility of the use of an innovative time-frequency transform, known as S transform, for the data analysis of the gravitational wave detector ALLEGRO. It is verified that its utility for this kind of detector is limited due to the detectors narrow bandwidth. However, it is argued that the S transform may be useful for interferometric detectors. Then a robust data analysis method is presented based on a hypothesis test known as Neyman-Pearson criteria, which allows the determination of candidate burst events. The method consists in the construction of probability distribution functions for the weighted average energy of the data blocks registered by the detector, both in the case of absence of noise and the case of signal mixed with noise. Based on these distributions it is possible to determine the probability that the data block in which a candidate event is present does not coincide with a noise block. This way of searching candidate signals immersed in noise agrees with another method present in the literature. One concludes that this is a promising method since it does not demand the use of a more refined search for candidate events, thus reducing computational processing time. (author)
DEFF Research Database (Denmark)
Kofoed, Jens Peter; Frigaard, Peter; Sørensen, H. C.;
1998-01-01
This paper concerns with the development of the wave energy converter (WEC) Wave Dragon. This WEC is based on the overtopping principle. An overview of the performed research done concerning the Wave Dragon over the past years is given, and the results of one of the more comprehensive studies......, concerning a hydraulic evaluation and optimisation of the geometry of the Wave Dragon, is presented. Furthermore, the plans for the future development projects are sketched....
International Nuclear Information System (INIS)
We studied a G-band oversized backward wave oscillator (BWO) driven by a weakly relativistic electron beam of less than 100 kV. Rectangular corrugations are used as slow-wave structures having surface waves with upper cutoff frequencies above 150 GHz (G-band). We examine how dispersion characteristics of surface waves are affected by accuracy in machining the corrugation amplitude, width, and period length. Of these, accuracy in the amplitude has the largest effect. Uniformly distributed annular electron beams are generated by a disk-type cold cathode and injected into the G-band BWO. G-band BWO operations in 137 - 173 GHz and above 173 GHz are achieved by changing the corrugation amplitude. The radiation patterns are fairly broad, and the estimated radiation power is at kW level. (author)
Study on p-Wave Attenuation in Hydrate-Bearing Sediments Based on BISQ Model
Directory of Open Access Journals (Sweden)
Chuanhui Li
2013-01-01
Full Text Available In hydrate-bearing sediments, the elastic wave attenuation characteristics depend on the elastic properties of the sediments themselves on the one hand, and on the other hand, they also depend on the hydrate occurrence state and hydrate saturation. Since the hydrate-bearing sediments always have high porosity, so they show significant porous medium characteristics. Based on the BISQ porous medium model which is the most widely used model to study the attenuation characteristics in the porous media, we focused on p-wave attenuation in hydrate-bearing sediments in Shenhu Area, South China Sea, especially in specific seismic frequency range, which lays a foundation for the identification of gas hydrates by using seismic wave attenuation in Shenhu Area, South China Sea. Our results depict that seismic wave attenuation is an effective attribute to identify gas hydrates.
Baglivo, Fabricio Hugo; Arini, Pedro David
2011-12-01
Electrocardiographic repolarization abnormalities can be detected by Principal Components Analysis of the T-wave. In this work we studied the efect of signal averaging on the mean value and reproducibility of the ratio of the 2nd to the 1st eigenvalue of T-wave (T21W) and the absolute and relative T-wave residuum (TrelWR and TabsWR) in the ECG during ischemia induced by Percutaneous Coronary Intervention. Also, the intra-subject and inter-subject variability of T-wave parameters have been analyzed. Results showed that TrelWR and TabsWR evaluated from the average of 10 complexes had lower values and higher reproducibility than those obtained from 1 complex. On the other hand T21W calculated from 10 complexes did not show statistical diferences versus the T21W calculated on single beats. The results of this study corroborate that, with a signal averaging technique, the 2nd and the 1st eigenvalue are not afected by noise while the 4th to 8th eigenvalues are so much afected by this, suggesting the use of the signal averaged technique before calculation of absolute and relative T-wave residuum. Finally, we have shown that T-wave morphology parameters present high intra-subject stability.
Experimental study on phosphorus release from sediments of shallow lake in wave flume
Institute of Scientific and Technical Information of China (English)
SUN; Xiaojing; ZHU; Guangwei; LUO; Liancong
2006-01-01
Influence of wave on sediment resuspension and nutrients release from sediments, collected from Lake Taihu and Lake Chaohu, was studied in flume experiments. Under strong-wave conditions, concentrations of suspended solids (SS), total phosphorus (TP) and dissolved total phosphorus (DTP) in overlying water were increased significantly following the sediments re-suspension. During the experiments on sediments of Lake Taihu and Lake Chaohu, TP concentrations increased 6 times and 3 times, and DTP concentration increased 100% and 70% more than it in presuspension, respectively. Concentration of soluble reactive phosphorus (SRP) of experiment on sediment of Lake Taihu increased 25%. During the massive sediment suspension, the dissolved phosphorus in pore water and much of the phosphorus adsorbed by the sediment particles were released into overlying water. The phenomena in this wave flume experiment are quite similar to the situation observed in situ of Lake Taihu. The critical wave stresses of sediment re-suspension are nearly equal. The change of concentrations of SS, TP, and SRP was the same as that in situ situation.This study showed that concentrations of TP and SRP in lake water could be increased significantly by wave disturbance. Phosphorus release was significantly enhanced by wave disturbance at the beginning of massive sediment re-suspension, but decreased later.
Interactions between the surface gravity waves and the Von Karman streets: a numerical study
Gunnoo, Hans; Bennis, Anne-Claire; Rivier, Aurélie; Abcha, NIzar; Ezersky, Alexander
2015-04-01
The growth of renewable energy over the past decade is impressive. Offshore wind farms are planned to construct along the site of Courseulles s/mer (Normandy, France) in 2018. The ofelia project leads to study the environmental impacts of the offshore wind farms in the Channel. In parallel with the regional modeling of the changes in hydrodynamic and in sediment transport due to monopiles (Rivier et al., 2014), studies at local scales are also carried out. Laboratory experiments show that the resonance between the surface gravity waves and the Von Karman streets leads to modify the synchronisation of the vortex (Gunnoo et al., 2014). Numerical simulations are performed to reproduce this mechanism. The CFD code, IHFOAM, based on an OpenFoam Kernel, allows to simulate the wave-current interactions at local scales. First, bi-dimensional and three-dimensional simulations without waves are set-up to validate our modeling plateform. The well-known Von Karman streets are obtained. Results are in agreement with the experimental data. Second, waves are included in the simulations. The free-surface is explicitely solved by the Volume Of Fluid method. Regular and irregular wave spectrums are tested. Changes in Von Karman Streets due to waves are observed. In the future, some comparisons with the experimental results will be done.
1998-01-01
Conference "Internet, Web, What's next?" on 26 June 1998 at CERN: Mark Bernstein, Vice President of CNN Interactive, describes the impact of the Web on world media and predicts what we can expect as the next developments
International Nuclear Information System (INIS)
Spatiotemporal study of defects in positively biased electrode induced dust density wave (DDW) in cogenerated dusty plasma is reported. DDW is excited for threshold positive bias through another electrode which is placed in between two main discharge electrodes. Spatiotemporal evolution of DDW reveals wave defect and non-propagating wave mode in the DDW field. Space-time plot and time resolved Hilbert-Huang transform (HHT) was employed to analyze the spatiotemporal wave data. (author)
A study of quasilinear diffusion coefficient of the fokker-planck equation based on full wave method
International Nuclear Information System (INIS)
Based on the wave fields evaluated by full wave method, the various components of quasilinear diffusion coefficient in spherical velocity coordinates are obtained by numerically resolving. The quasilinear diffusion coefficient of Fokker-planck equation is presented for investigating fast wave current drive in the ion cyclotron range of frequencies, and the results will be used to solve bounce-averaged quasilinear Fokker-Planck equation for further study of fast wave current drive. (authors)
Wave-particle resonance condition test for ion-kinetic waves in the solar wind
Narita, Y.; Marsch, E.; Perschke, C.; Glassmeier, K.-H.; Motschmann, U.; Comişel, H.
2016-04-01
Conditions for the Landau and cyclotron resonances are tested for 543 waves (identified as local peaks in the energy spectra) in the magnetic field fluctuations of the solar wind measured by the Cluster spacecraft on a tetrahedral scale of 100 km. The resonance parameters are evaluated using the frequencies in the plasma rest frame, the parallel components of the wavevectors, the ion cyclotron frequency, and the ion thermal speed. The observed waves show a character of the sideband waves associated with the ion Bernstein mode, and are in a weak agreement with the fundamental electron cyclotron resonance in spite of the ion-kinetic scales. The electron cyclotron resonance is likely taking place in solar wind turbulence near 1 AU (astronomical unit).
International Nuclear Information System (INIS)
The long waves that cause slugs almost always form more slowly than short waves, and linear stability always predicts that the growth rate for long waves is much less than that for short waves. However, at many conditions above neutral stability, long waves dominate the wave field. Three different studies were undertaken as part of the funded work: (1) linear interaction for unsteady flows; (2) wave evolution in oil-water channel flows; (3) retrograde stability and subcritical bifurcations. The oil-water system was used as a surrogate for gas-liquid systems because the gas phase is usually turbulent, and this complication is thus avoided although the phenomena involved are similar. The following overall conclusions about flow regime development were reached: (a) Oscillations in pressure and flow rate, due to interfacial waves or a malfunctioning pump, can cause significant growth rate changes in short waves within narrow FR-equency ranges, but probably do not have a large effect on long waves and thus regime transition. (b) Linear and nonlinear processes act together to cause regime transitions; however, it is almost certain that long waves cannot form solely by nonlinear energy transfer FR-om shorter waves. (c) The nonlinear coefficient spectrum contains the information necessary to tell if certain wave interactions will occur to a significant extent
EXPERIMENTAL STUDY ON DAM-BREAK FLOOD WAVES OVER MOVABLE BED CHANNEL
Institute of Scientific and Technical Information of China (English)
J.B.LEAL; R.L.FERREIRA; A.B.FRANCO; A.H.CARDOSO
2002-01-01
This paper presents the results of an experimental study focused on the propagation of dam-break flow waves over movable beds.Tests consisted in the sudden opening of a vertical lift-gate which separated initial water and sediment levels upstream and downstream of the gate.They allowed the simulation of the following initial conditions: with or without initial bed-step at the gate cross-section; with or without water downstream of the gate; with or without sediments downstream of the gate.Test results were used to discuss the influence of the movable bed on the celerity of the wave-fronts,as well as on the downstream wave-front height.The total volume of dislodged sediments was also assessed.Some important conclusions were achieved: i) the movable bed does not affect the upstream wave-front celerity but it affects the celerity of the downstream wave-front; ii) the experimental celerities show some disagreement with the analytical solutions; iii) the existence of an initial bed-step at the lift-gate cross-section influences the downstream wave-front propagation,including the water depth.
Study of Atomization of a Water Jet by High-Intensity Aerial Ultrasonic Waves
Ito, Youichi
2001-05-01
An experimental study has been carried out on the atomization of a water jet by aerially radiating it with high-intensity ultrasonic waves. A sound source that enables the linear generation of high-intensity aerial ultrasonic waves (frequency: approximately 20 kHz) is combined with a cylindrical reflection plate in order to create a standing-wave sound field. An attempt has been made to atomize a water jet of 1 mm diameter by passing it through the above sound field at a velocity of approximately 30 m/s. It has been clarified that nodes of sound pressure in the standing-wave sound field are effective for the atomization of a water jet. In addition, the atomizing phenomenon of a water jet has been observed precisely. The relation between the intensity of sound waves required for atomization and the radiation duration has also been clarified. Even the radiation of sound waves for only 2 ms atomizes water. This suggests that a very fast water jet at 300-500 m/s might be atomized.
Comparative Study of Electromagnetic Waves at the Bow Shocks of Venus and Earth
Wei, Hanying; Russell, Christopher T.; Strangeway, Robert J.; Schwartz, Steven J.; Zhang, Tielong
2016-04-01
Although the solar interactions with Venus and Earth are quite different in many ways, they both have bow shocks formed upstream of the planet where the solar wind decelerates from a super- to sub- magnetosonic flow. In the upstream foreshock region, there is abundant wave activity generated by the shock or by the back-streaming ions and electrons from the shock. In the downstream magnetosheath region, there is also abundant wave activity either locally generated by the heated electrons or ions from the shock or transported from the shock or foreshock regions by the solar wind. The magnetometers of Venus Express and Magnetospheric Multiscale missions both occasionally record 128 Hz data during their shock crossing, which allow us the search for and analyze waves at such high frequencies. We have found short-duration wave bursts around both Venus and Earth bow shocks, with certain similarities. These waves are mostly quasi-perpendicular propagating and have amplitude and occurrence rate decreasing with distance from the bow shock. In this paper we perform statistical and comparative studies on wave properties to understand their generation mechanisms and their effects to the shock or magnetosheath plasmas.
A TWT upgrade to study wave-particle interactions in plasma
Doveil, Fabrice; Caetano de Sousa, Meirielen; Guyomarc'h, Didier; Kahli, Aissa; Elskens, Yves
2015-11-01
Beside industrial applications, Traveling Wave Tubes (TWT) are useful to mimic and study wave-particle interaction in plasma. We upgraded a TWT, whose slow wave structure is a 4 m long helix (diameter 3.4 cm, pitch 1 mm) of Be-Cu wire (diameter 0.6 mm) wrapped in insulating tape. The helix is inserted in a vacuum glass tube. At one end, an electron gun produces a beam propagating along the helix, radially confined by a constant axial magnetic field. Movable probes, capacitively coupled to the helix through the glass tube, launch and monitor waves generated by an arbitrary waveform generator at a few tens of MHz. At the other end of the helix, a trochoidal analyzer allows to reconstruct the electron distribution functions of the beam after its self-consistent interaction with the waves. Linear properties of the new device will be reported. The measured coupling coefficients of each probe with the helix are used to reconstruct the growth and saturation of a launched wave as it interacts with the electron beam. J-B. Faure and V. Long are thanked for their efficient help in designing and using a new way to build the helix.
Numerical Study of A Round Buoyant Jet Under the Effect of JONSWAP Random Waves
Institute of Scientific and Technical Information of China (English)
CHEN Yong-ping; LI Chi-wai; ZHANG Chang-kuan; XU Zhen-shan
2012-01-01
This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves.A three-dimensional large eddy simulation (LES) model is developed to simulate the buoyant jet in a stagnant ambient and JONSWAP random waves.By comparison of velocity and concentration fields,it is found that the buoyant jet exhibits faster decay of centedine velocity,wider lateral spreading and larger initial dilution under the wave effect,indicating that wave dynamics improves the jet entrainment and mixing in the near field,and subsequently mitigate the jet impacts in the far field.The effect of buoyancy force on the jet behaviours in the random waves is also numerically investigated.The results show that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force,resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy.
Wu, Dong L.; Zhang, Fuqing
2004-01-01
Satellite microwave data are used to study gravity wave properties and variabilities over the northeastern United States and the North Atlantic in the December-January periods. The gravity waves in this region, found in many winters, can reach the stratopause with growing amplitude. The Advanced Microwave Sounding Unit-A (AMSU-A) observations show that the wave occurrences are correlated well with the intensity and location of the tropospheric baroclinic jet front systems. To further investigate the cause(s) and properties of the North Atlantic gravity waves, we focus on a series of wave events during 19-21 January 2003 and compare AMSU-A observations to simulations from a mesoscale model (MM5). The simulated gravity waves compare qualitatively well with the satellite observations in terms of wave structures, timing, and overall morphology. Excitation mechanisms of these large-amplitude waves in the troposphere are complex and subject to further investigations.
Dong, Hefeng; Hovem, Jens M.; Frivik, Svein Arne
2006-10-01
Estimates of shear wave velocity profiles in seafloor sediments can be obtained from inversion of measured dispersion relations of seismo-acoustic interface waves propagating along the seabed. The interface wave velocity is directly related to shear wave velocity with value of between 87-96% of the shear wave velocity, dependent on the Poission ratio of the sediments. In this paper we present two different techniques to determine the dispersion relation: a single-sensor method used to determine group velocity and a multi-sensor method used to determine the phase velocity of the interface wave. An inversion technique is used to determine shear wave velocity versus depth and it is based on singular value decomposition and regularization theory. The technique is applied to data acquired at Steinbåen outside Horten in the Oslofjorden (Norway) and compared with the result from independent core measurements taken at the same location. The results show good agreement between the two ways of determining shear wave velocity.
Technical and economic feasibility study of a Frond type wave power generator
Energy Technology Data Exchange (ETDEWEB)
NONE
2003-07-01
This report describes the first stage of the development of a Frond type wave generator by the Engineering Business (EB) in collaboration with the University of Lancaster Engineering Department. The EB Frond concept is a sea-bed reacting, surging machine consisting of a near-surface collector mounted on an arm pivoted near the seabed. The study had six main elements (investigation, physical and mathematical modelling, site characterisation, design review and cost study). The investigation phase involved a study of wave properties and behaviour, while physical models were tested in a wave tank. A mathematical model was developed and used to assess the design's power output. The characteristics of a suitable site for EB Frond generators were determined and the process of identifying possible sites for a demonstrator machine was begun. The mechanical and system arrangement of the design were evaluated and modified. The effects of varying the installation's input parameters (e.g. wave environment factors) were examined using an energy cost model whose output is energy production and cost. It was concluded that the Frond principle was technically viable though there were some remaining engineering and other application problems. Cost modelling suggested that the EB Frond system had potential for long-term commercial prospects. The report recommends the construction and testing of an intermediate scale model with more realistic wave conditions.
International Nuclear Information System (INIS)
The authors studied brain blood flow with single photon emission computed tomography (SPECT) in two patients with plateau waves. The intracranial pressure and blood pressure were also monitored continuously in these patients. They included one patient with brain-tumor (rt. sphenoid ridge meningioma) and another with hydrocephalus after subarachnoid hemorrhage due to rupture of lt. internal carotid aneurysm. The intracranial pressure was monitored through an indwelling ventricular catheter attached to a pressure transducer. The blood pressure was recorded through an intraarterial catheter placed in the dorsalis pedis artery. Brain blood flow was studied with Headtome SET-011 (manufactured by Shimazu Co., Ltd.). For this flow measurement study, an intravenous injection of Xenon-133 of about 30 mCi was given via an antecubital vein. The position of the slice for the SPECT was selected so as to obtain information not only from the cerebral hemisphere but also from the brain stem : a cross section 25 deg over the orbito-meatal line, passing through the inferior aspect of the frontal horn, the basal ganglia, the lower recessus of the third ventricle and the brain stem. The results indicated that, in the cerebral hemisphere, plateau waves were accompanied by a decrease in blood flow, whereas, in the brain stem, the blood flow showed little change during plateau waves as compared with the interval phase between two plateau waves. These observations may explain why there is no rise in the blood pressure and why patients are often alert during plateau waves. (author)
Hedlin, Michael; de Groot-Hedlin, Catherine; Hoffmann, Lars; Alexander, M. Joan; Stephan, Claudia
2016-04-01
The upgrade of the USArray Transportable Array (TA) with microbarometers and infrasound microphones has created an opportunity for a broad range of new studies of atmospheric sources and the large- and small-scale atmospheric structure through which signals from these events propagate. These studies are akin to early studies of seismic events and the Earth's interior structure that were made possible by the first seismic networks. In one early study with the new dataset we use the method of de Groot-Hedlin and Hedlin (2015) to recast the TA as a massive collection of 3-element arrays to detect and locate large infrasonic events. Over 2,000 events have been detected in 2013. The events cluster in highly active regions on land and offshore. Stratospherically ducted signals from some of these events have been recorded more than 2,000 km from the source and clearly show dispersion due to propagation through atmospheric gravity waves. Modeling of these signals has been used to test statistical models of atmospheric gravity waves. The network is also useful for making direct observations of gravity waves. We are currently studying TA and satellite observations of gravity waves from singular events to better understand how the waves near ground level relate to those observed aloft. We are also studying the long-term statistics of these waves from the beginning of 2010 through 2014. Early work using data bandpass filtered from 1-6 hr shows that both the TA and satellite data reveal highly active source regions, such as near the Great Lakes. de Groot-Hedlin and Hedlin, 2015, A method for detecting and locating geophysical events using clusters of arrays, Geophysical Journal International, v203, p960-971, doi: 10.1093/gji/ggv345.
Studies on Shock Attenuation in Plastic Materials and Applications in Detonation Wave Shaping
International Nuclear Information System (INIS)
Pressure in plastic materials attenuates due to change of impedance, phase change in the medium and plastic deformation. A lot of theoretical and experimental efforts have been devoted to the attenuation of shock wave produced by the impact of explosive driven flyer plate. However comparatively less work has been done on the attenuation of shock waves due to contact explosive detonation. Present studies deal with the attenuation of explosive driven shock waves in various plastic materials and its applications in design of Hybrid Detonation Wave Generator In present work shock attenuating properties of different polymers such as Perspex, Teflon, nylon, polypropylene and viton has been studied experimentally using rotating mirror streak camera and electrical position pins. High explosive RDX/TNT and OCTOL of diameter 75-100mm and thickness 20 to 50mm were detonated to induce shock wave in the test specimens. From experimental determined shock velocity at different locations the attenuation in shock pressure was calculated. The attenuation of shock velocity with thickness in the material indicates exponential decay according to relation US = UOexp(-ax). In few of the experiments manganin gauge of resistance 50 ohms was used to record stress time profile across shock wave. The shock attenuation data of Viton has successfully been used in the design of hybrid detonation wave generator using Octol as high explosive. While selecting a material it was ensured that the attenuated shock remains strong enough to initiate an acceptor explosive. Theoretical calculation were supported by Autodyne 2D hydro-code simulation which were validated with the experiments conducted using high speed streak photography and electrical shock arrival pins. Shock attenuation data of Perspex was used to establishing card gap test and wedge test in which test items is subjected to known pressure pulse by selecting the thickness of the plastic material.
The mare: a 1000-pound guinea pig for study of the ovulatory follicular wave in women.
Ginther, O J
2012-03-15
The mare is a good comparative model for study of ovarian follicles in women, owing to striking similarities in follicular waves and the mechanism for selection of a dominant follicle. Commonality in follicle dynamics between mares and women include: (1) a ratio of 2.2:1 (mare:woman) in diameter of the largest follicle at wave emergence when the wave-stimulating FSH surge reaches maximum, in diameter increase of the two largest follicles between emergence and the beginning of deviation between the future dominant and subordinate follicles, in diameter of each of the two largest follicles at the beginning of deviation, and in maximum diameter of the preovulatory follicle; (2) emergence of the future ovulatory follicle before the largest subordinate follicle; (3) a mean interval of 1 day between emergence of individual follicles of the wave; (4) percentage increase in diameter of follicles for the 3 days before deviation; (5) deviation 3 or 4 days after emergence; (6) 25% incidence of a major anovulatory follicular wave emerging before the ovulatory wave; (7) 40% incidence of a predeviation follicle preceding the ovulatory wave; (8) small but significant increase in estradiol and LH before deviation; (9) cooperative roles of FSH and insulin-like growth factor 1 and its proteases in the deviation process; (10) age-related effects on the follicles and oocytes; (11) approximate 37-hour interval between administration of hCG and ovulation; and (12) similar gray-scale and color-Doppler ultrasound changes in the preovulatory follicle. In conclusion, the mare may be the premier nonprimate model for study of follicle dynamics in women. PMID:22115815
Directory of Open Access Journals (Sweden)
Moreno-Manzanaro Miriam
2011-04-01
Full Text Available Abstract Background Studies in bipolar disorder (BD to date are limited in their ability to provide a whole-disease perspective - their scope has generally been confined to a single disease phase and/or a specific treatment. Moreover, most clinical trials have focused on the manic phase of disease, and not on depression, which is associated with the greatest disease burden. There are few longitudinal studies covering both types of patients with BD (I and II and the whole course of the disease, regardless of patients' symptomatology. Therefore, the Wide AmbispectiVE study of the clinical management and burden of Bipolar Disorder (WAVE-bd (NCT01062607 aims to provide reliable information on the management of patients with BD in daily clinical practice. It also seeks to determine factors influencing clinical outcomes and resource use in relation to the management of BD. Methods WAVE-bd is a multinational, multicentre, non-interventional, longitudinal study. Approximately 3000 patients diagnosed with BD type I or II with at least one mood event in the preceding 12 months were recruited at centres in Austria, Belgium, Brazil, France, Germany, Portugal, Romania, Turkey, Ukraine and Venezuela. Site selection methodology aimed to provide a balanced cross-section of patients cared for by different types of providers of medical aid (e.g. academic hospitals, private practices in each country. Target recruitment percentages were derived either from scientific publications or from expert panels in each participating country. The minimum follow-up period will be 12 months, with a maximum of 27 months, taking into account the retrospective and the prospective parts of the study. Data on demographics, diagnosis, medical history, clinical management, clinical and functional outcomes (CGI-BP and FAST scales, adherence to treatment (DAI-10 scale and Medication Possession Ratio, quality of life (EQ-5D scale, healthcare resources, and caregiver burden (BAS scale
Peng, Xinhua; Zhu, Xiwen; Fang, Ximing; Feng, Mang; Liu, Maili; Gao, Kelin
2002-01-01
A quantum circuit is introducted to describe the preparation of a labeled pseudo-pure state by mutiplet-component excitation scheme which has been experimentally implemented on a 4-qubit nuclear magnetic resonance quantum processor. Meanwhile, we theoretically analyze and numerically inverstigate the low-power selective single-pulse implementation of a controlled-rotation gate, which manifests its validity in our experiment. Based on the labeled pseudo-pure state prepared, a 3-qubit Bernstein...
EXPERIMENTAL STUDY ON HEAVE AND PITCH MOTION CHARACTERISTICS OF A WAVE-PIERCING TRIMARAN
Vakilabadi, Karim Akbari; Khedmati, Mohammad Reza; Seif, Mohammad Saeed
2014-01-01
Dynamic behaviour of a trimaran vessel is investigated in this study. The body of the trimaran is composed of a centre hull with a quite slender wave piercing bow profile (a length-to-width ratio of 12.96) and two outriggers with Wigley mathematical body forms. Several seakeeping tests are conducted on the model of the trimaran vessel in a towing tank in order to study its heave and pitch motions at different Froude numbers of 0.2, 0.37, and 0.51. Generated waves in the towing tank are of reg...
Energy Technology Data Exchange (ETDEWEB)
Pasyanos, M E
2005-03-21
This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, and have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant
International Nuclear Information System (INIS)
Surface ionization wave discharges generated by high-voltage nanosecond pulses, propagating over a planar quartz surface and over liquid surfaces (distilled water and 1-butanol) have been studied in a rectangular cross section test cell. The discharge was initiated using a custom-made, alternating polarity, high-voltage nanosecond pulse plasma generator, operated at a pulse repetition rate of 100–500 Hz, with a pulse peak voltage and current of 10–15 kV and 7–20 A, respectively, a pulse FWHM of ∼100 ns, and a coupled pulse energy of 2–9 mJ/pulse. Wave speed was measured using a capacitive probe. ICCD camera images demonstrated that the ionization wave propagated predominantly over the quartz wall or over the liquid surface adjacent to the grounded waveguide placed along the bottom wall of the test cell. Under all experimental conditions tested, the surface plasma ‘sheet’ was diffuse and fairly uniform, both for positive and negative polarities. The parameters of ionization wave discharge propagating over distilled water and 1-butanol surfaces were close to those of the discharge over a quartz wall. No perturbation of the liquid surface by the discharge was detected. In most cases, the positive polarity surface ionization wave propagated at a higher speed and over a longer distance compared to the negative polarity wave. For all three sets of experiments (surface ionization wave discharge over quartz, water and 1-butanol), wave speed and travel distance decreased with pressure. Diffuse, highly reproducible surface ionization wave discharge was also observed over the liquid butanol–saturated butanol vapor interface, as well as over the distilled water–saturated water vapor interface, without buffer gas flow. No significant difference was detected between surface ionization discharges sustained using single-polarity (positive or negative), or alternating polarity high-voltage pulses. Plasma emission images yielded preliminary evidence of charge
Energy Technology Data Exchange (ETDEWEB)
Fang, N.; Liu, Z.; Yen, T.-J.; Zhang, X. [University of California, Center for Scalable and Integrated Nanomanufacturing (SINAM), Berkeley, CA (United States)
2005-03-01
In this paper, we investigated an essential precursor of superlensing: enhancing the transmission of evanescent waves assisted by excitation of surface plasmon. Using natural roughness as a well characterized grating, the transmission of evanescent waves is studied through silver thin films of increasing thickness. Measurements and calculations are performed in the wavelength range of 514.5 nm to 351.1 nm where the real part of the permittivity of silver is negative. Pronounced peaks due to surface-plasmon excitations are observed in the transmission spectra. We found the transmission of evanescent waves rapidly grows with the film thickness up to about 50 nm, after which it decays as loss becomes significant. As the permittivity of a silver slab approaches -1, we experimentally observed a broadening of surface plasmon bandwidth. Our study indicates a pathway to access the deep subwavelength features by metamaterial superlens. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Sun, H. [China Coal Research Institute, Beijing (China). Beijing Research Institute of Coal Mining
2001-12-01
From Maxwell's equations, the attenuation behaviours of high frequency impulse electromagnetic wave during its propagation in underground heterogeneous medium are studied and analysed. Fairly good results are obtained when it is applied to the engineering surveying of weak foundation. By introducing Cole-Cole formula to describe the attenuation behaviours of the complex dielectric constant and character factor in heterogeneous medium, the attenuation behaviours of the high frequency impulse electromagnetic wave in underground heterogeneous medium can be theoretically described. The engineering applications demonstrate the use of attenuation behaviours of GPR high frequency impulse electromagnetic wave to study fault belts, underground fissures, weak foundations above underground space etc. This makes further explanation and assessment of weak foundation feasible, and the evaluation is characterised by low investment, quick result, high precision and non-destructive detection. 6 refs., 3 figs., 1 tab.
Molecular dynamics study of accelerated ion-induced shock waves in biological media
de Vera, Pablo; Currell, Fred J; Solov'yov, Andrey V
2016-01-01
We present a molecular dynamics study of the effects of carbon- and iron-ion induced shock waves in DNA duplexes in liquid water. We use the CHARMM force field implemented within the MBN Explorer simulation package to optimize and equilibrate DNA duplexes in liquid water boxes of different sizes and shapes. The translational and vibrational degrees of freedom of water molecules are excited according to the energy deposited by the ions and the subsequent shock waves in liquid water are simulated. The pressure waves generated are studied and compared with an analytical hydrodynamics model which serves as a benchmark for evaluating the suitability of the simulation boxes. The energy deposition in the DNA backbone bonds is also monitored as an estimation of biological damage, something which lies beyond the possibilities of the analytical model.
Experimental Study on Wave Propagation Across a Rock Joint with Rough Surface
Chen, X.; Li, J. C.; Cai, M. F.; Zou, Y.; Zhao, J.
2015-11-01
Joints are an important mechanical feature of rock masses. Their effect on wave propagation is significant in characterizing dynamic behaviors of discontinuous rock masses. An experimental study on wave propagation across artificial rock joint was carried out to reveal the relation between the transmission coefficient and the contact situation of the joint surface. The modified split Hopkinson pressure bar apparatus was used in this study while all the bars and specimens were norite cored from the same site. One surface of the specimens with a number of notches was adopted to simulate the artificial rough joint. Two strain gauges were mounted on each pressure bar at a specific spacing. The incident, reflected and transmitted waves across the joints were obtained using a wave separation method. Comparisons of the transmission coefficients were made under two different conditions: with the same joint thickness but different contact area ratios, and with the same contact area ratio but different joint thicknesses. The results show the effects of contact area ratio and thickness of joints on wave transmission.
Algebraic method for constructing singular steady solitary waves: A case study
Clamond, Didier; Galligo, André
2016-01-01
This article describes the use of algebraic methods in a phase plane analysis of ordinary differential equations. The method is illustrated by the study of capillary-gravity steady surface waves propagating in shallow water. We consider the (fully nonlinear, weakly dispersive) Serre-Green-Naghdi equations with surface tension, because it provides a tractable model that, in the same time, is not too simple so the interest of the method can be emphasised. In particular, we analyse a special class of solutions, the solitary waves, which play an important role in many fields of Physics. In capillary-gravity regime, there are two kinds of localised infinitely smooth travelling wave solutions -- solitary waves of elevation and of depression. However, if we allow the solitary waves to have an angular point, the "zoology" of solutions becomes much richer and the main goal of this study is to provide a complete classification of such singular localised solutions using the methods of the effective Algebraic Geometry.
A regional study of atmospheric gravity waves using the USArray Transportable Array
Hedlin, M. A. H.; Stephan, C. C.; de Groot-Hedlin, C. D.; Alexander, M. J.; Hoffmann, L.
2015-12-01
The USArray Transportable Array (TA) is a network of approximately 400 seismo-acoustic stations deployed on a 70 km Cartesian grid covering an area of 2,000,000 km2 in the continental United States. The network moves eastward through station redeployments and is now located on the Atlantic coast. This dense network has provided unprecedented opportunities for research in seismology, infrasound and atmospheric science. We have developed a novel technique to investigate gravity wave occurrence and propagation across the network and have applied it to atmospheric pressure data recorded from Jan 1, 2010 through 2014. We divided the stations in this time range into 3,600 non-overlapping triangular arrays (triads). Each triad is most sensitive to propagating gravity waves in the 1-6 hour period range. We report two lines of research with this new dataset. First, we study individual large events in which atmospheric gravity waves are observed to cross the TA. We also study the long-term occurrence statistics of gravity waves and compare them to satellite observations of convective clouds and gravity waves in the stratosphere. We discuss plans for future work when the network is redeployed in Alaska.
Pandey, R. S.; Kaur, Rajbir
2015-10-01
Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit non-Maxwellian high-energy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electron-cyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.
Analytical study of terahertz wave intensity measurements by ZnTe electro-optic crystal
Siddique, Muhammad; Yang, Suhui; Li, Zhuo; Li, Ping
2008-03-01
An analytical study of THz-waves' intensity measurement generated by Terahertz Parametric Oscillator (TPO) and detection of the THz pulses occurs via free-space electro optic detection by ZnTe crystal has been studied. The pump-probe technique has been used to observe the dynamics of an optically excited ZnTe electro-optic crystal. THz wave will be used as modulation source for electro-optical phenomena in ZnTe crystal. The THz pulses generated by TPO are 10-25 ns pulses at a repetition rate of 1Hz. ZnTe crystal is being used for intensity measurement of THz-waves. In this theoretical proposed experiment, a short pump pulse (THz-wave) and probe pulse (near IR laser) with duration of typically 10 to 25 ns interacts in the ZnTe. In electro-optic sampling the two effects namely Pockels effect and Kerr effect have been discussed and interaction of two beams from or transmission through the ZnTe, the probe pulse Intensity contains information about the THz-waves' intensity and so on.
Wave propagation and earth satellite radio emission studies
Yeh, K. C.; Liu, C. H.; Flaherty, B. J.
1974-01-01
Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.
Impact of complex blast waves on the human head: a computational study.
Tan, Long Bin; Chew, Fatt Siong; Tse, Kwong Ming; Chye Tan, Vincent Beng; Lee, Heow Pueh
2014-12-01
Head injuries due to complex blasts are not well examined because of limited published articles on the subject. Previous studies have analyzed head injuries due to impact from a single planar blast wave. Complex or concomitant blasts refer to impacts usually caused by more than a single blast source, whereby the blast waves may impact the head simultaneously or consecutively, depending on the locations and distances of the blast sources from the subject, their blast intensities, the sequence of detonations, as well as the effect of blast wave reflections from rigid walls. It is expected that such scenarios will result in more serious head injuries as compared to impact from a single blast wave due to the larger effective duration of the blast. In this paper, the utilization of a head-helmet model for blast impact analyses in Abaqus(TM) (Dassault Systemes, Singapore) is demonstrated. The model is validated against studies published in the literature. Results show that the skull is capable of transmitting the blast impact to cause high intracranial pressures (ICPs). In addition, the pressure wave from a frontal blast may enter through the sides of the helmet and wrap around the head to result in a second impact at the rear. This study recommended better protection at the sides and rear of the helmet through the use of foam pads so as to reduce wave entry into the helmet. The consecutive frontal blasts scenario resulted in higher ICPs compared with impact from a single frontal blast. This implied that blast impingement from an immediate subsequent pressure wave would increase severity of brain injury. For the unhelmeted head case, a peak ICP of 330 kPa is registered at the parietal lobe which exceeds the 235 kPa threshold for serious head injuries. The concurrent front and side blasts scenario yielded lower ICPs and skull stresses than the consecutive frontal blasts case. It is also revealed that the additional side blast would only significantly affect ICPs at
Attenuation of surface waves due to monsoon rains: A model study for the north Indian Ocean
Digital Repository Service at National Institute of Oceanography (India)
Vethamony, P.; Kumar, B.P.; Sarma, Y.V.B.
The dynamic interaction of intense rain with waves based on momentum exchange is applied to a second generation wave model to predict wave attenuation during monsoon. The scheme takes into account the characteristics of rain and wave parameters...
Krause, G.; Cécere, M.; Francile, C.; Costa, A.; Elaskar, S.; Schneiter, M.
2015-11-01
We examine the capability of a blast-wave scenario - associated with a coronal flare or to the expansion of CME flanks - to reproduce a chromospheric Moreton phenomenon. We also simulate the Moreton event of 2006 December 06, considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock - able to generate a detectable chromospheric Moreton wave - a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that a flare ignited blast-wave or the expansion of the CME flanks emulated as an instantaneous or a temporal piston model, respectively, are capable to reproduce the observations.
Electron Cyclotron Wave Experiments at the WEGA Stellarator
Czech Academy of Sciences Publication Activity Database
Laqua, H.P.; Andruczyk, D.; Holzhauer, E.; Marsen, S.; Otte, M.; Podoba, Y.Y.; Preinhaelter, Josef; Urban, Jakub; Warr, G.B.
Warsaw : European Physical Society, 2007 - (Gąsior, P.; Wołowski, J.), s. 4-7 ISBN 978-83-926290-0-9. - (Europhysics Conference Abstracts). [European Physical Society Conference on Plasma Physics/34th./. Warsaw (PL), 02.07.2007-06.07.2007] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Stellarators * Electron Bernstein waves * Simulation Subject RIV: BL - Plasma and Gas Discharge Physics http://www.eps2007.ifpilm.waw.pl/pdf/P1_154.pdf
Numerical Study of Interaction of a Vortical Density Inhomogeneity with Shock and Expansion Waves
Povitsky, A.; Ofengeim, D.
1998-01-01
We studied the interaction of a vortical density inhomogeneity (VDI) with shock and expansion waves. We call the VDI the region of concentrated vorticity (vortex) with a density different from that of ambiance. Non-parallel directions of the density gradient normal to the VDI surface and the pressure gradient across a shock wave results in an additional vorticity. The roll-up of the initial round VDI towards a non-symmetrical shape is studied numerically. Numerical modeling of this interaction is performed by a 2-D Euler code. The use of an adaptive unstructured numerical grid makes it possible to obtain high accuracy and capture regions of induced vorticity with a moderate overall number of mesh points. For the validation of the code, the computational results are compared with available experimental results and good agreement is obtained. The interaction of the VDI with a propagating shock wave is studied for a range of initial and induced circulations and obtained flow patterns are presented. The splitting of the VDI develops into the formation of a non-symmetrical vortex pair and not in a set of vortices. A method for the analytical computation of an overall induced circulation Gamma(sub 1) as a result of the interaction of a moving VDI with a number of waves is proposed. Simplified, approximated, expressions for Gamma(sub 1) are derived and their accuracy is discussed. The splitting of the VDI passing through the Prandtl-Meyer expansion wave is studied numerically. The obtained VDI patterns are compared to those for the interaction of the VDI with a propagating shock wave for the same values of initial and induced circulations. These patterns have similar shapes for corresponding time moments.
Study of shock waves and related phenomena motivated by astrophysics
Drake, R. P.; Keiter, P. A.; Kuranz, C. C.; Malamud, G.; Manuel, M.; Di Stefano, C. A.; Gamboa, E. J.; Krauland, C. M.; MacDonald, M. J.; Wan, W. C.; Young, R. P.; Montgomery, D. S.; Stoeckl, C.; Froula, D. H.
2016-03-01
This paper discusses the recent research in High-Energy-Density Physics at our Center. Our work in complex hydrodynamics is now focused on mode coupling in the Richtmyer- Meshkov process and on the supersonic Kelvin-Helmholtz instability. These processes are believed to occur in a wide range of astrophysical circumstances. In radiation hydrodynamics, we are studying radiative reverse shocks relevant to cataclysmic variable stars. Our work on magnetized flows seeks to produce magnetized jets and study their interactions. We build the targets for all these experiments, and simulate them using our CRASH code. We also conduct diagnostic research, focused primarily on imaging x-ray spectroscopy and its applications to scattering and fluorescence.
Inelastic effects in electron transport studied with wave packet propagation
Monturet, S.; Lorente, N.
2008-01-01
A time-dependent approach is used to explore inelastic effects during electron transport through few-level systems. We study a tight-binding chain with one and two sites connected to vibrations. This simple but transparent model gives insight about inelastic effects, their meaning and the approximations currently used to treat them. Our time-dependent approach allows us to trace back the time sequence of vibrational excitation and electronic interference, the ibrationally introduced time dela...
Study of p-wave gamma-ray strength functions
International Nuclear Information System (INIS)
Gamma-ray strength functions are important for description of the gamma emission channel in nuclear reactions. The impact of different models- Weisskopf's single particle model, Brink's standard Lorentzian and Kopecky's generalized Lorentzian for gamma ray strength functions on the calculation of neutron capture related experimental quantities such as total radiation widths Γγ cross sections and gamma-ray spectra has been studied
Non linear response of plasma ions in linear electrostatic waves
International Nuclear Information System (INIS)
We present experiments which test the applicability of the Hamiltonian single particle theory to wave-particle interactions. This theory describes the chaotic acceleration of plasmas ions by electrostatic waves. The Hamiltonian description gives predictions about the threshold, fast time scale, details of the distribution function and conservation of three integrals of the motion while some of the integrals have been broken by the overlap of resonances. Both electrostatic ion cyclotron and Bernstein waves are launched from antennae at the plasma boundary. Ion motions are observed by Laser Induced Fluorescence (LIF) and optical tagging. The linear response of the ion to the wave is distinguished from the chaotic response. Several predictions of the single particle theory are observed in the experiments. In addition, evidence of self-consistent effects have been observed. (author) 14 figs., 22 refs
Internal waves and Equatorial dynamics: an observational study in the West Atlantic Ocean
Rabitti, Anna; Maas, Leo R. M.; van Haren, Hans; Gerkema, Theo
2013-04-01
Internal waves present several fascinating aspects of great relevance for geo- and astro-physical fluid dynamics. These waves are supported by all kinds of stratified and rotating fluids, such as, for example, our ocean, atmosphere, a planet fluid core or a star. In a non linear regime, because of their oblique propagation, they are thought to play a key role in diapycnal mixing, as well as in angular momentum mixing. Unfortunately, a complete analytical description of internal waves in arbitrarily shaped enclosed domains is still an ongoing challenge. On the other hand, internal wave energy is observed travelling along rays, whose behaviour can be traced and whose reflections off the container's boundaries appears crucial in producing phenomena such as focussing of wave energy onto specific trajectories (attractors), and in triggering localized instabilities. Ray tracing studies have shown that equatorial regions of stratified and/or rotating spherical shells are likely affected by these features, being the place where the simplest shaped and most energetic attractors occur. In this study we aim to investigate the possible presence and role of internal wave attractors in determining the equatorial ocean dynamics. Internal wave attractors, observed in laboratory and numerical experiments, have not been observed in Nature, yet. A unique set of observations, collected in the deep Equatorial West Atlantic Ocean, will be used here in order to explore this possibility, the dataset consisting of 1.5 year long time series of current measured acoustically and with current meters moored between 0°and 2°N, at 37°W, off the Brazilian coast. In particular, angular momentum mixing due to internal wave focussing, is explored as a possible mechanism for maintaining the Equatorial Deep Jets. These jets are stacked alternating zonal currents that are ubiquitously observed in all the oceans and whose nature is still largely unknown. Remarkably, jet like structures are also
Numerical study of electromagnetic waves interacting with negative index materials.
Kolinko, Pavel; Smith, David
2003-04-01
We study numerically the electromagnetic scattering properties of structures with negative indices of refraction. To perform this analysis, we utilize a commercial finite-element based electromagnetic solver (HFSS, Ansoft), in which a negative index material can be formed from mesh elements whose permittivity and permeability are both negative. In particular, we investigate the expected transmission characteristics of a finite beam incident on negative index prisms and lenses. We also confirm numerically the predicted superlens effect of an image formed by a planar slab with index n=-1, using two subwavelength (ë/20) slits as objects. PMID:19461776
A study of turbulence induced by sound waves
International Nuclear Information System (INIS)
The efficiency of sonic coagulation and precipitation of particles in an acoustic field is strongly reinforced above the acoustic intensity threshold corresponding to the appearance of acoustic turbulence. The aim of this work is to evaluate the turbulence properties of the experimental system in order to calculate acoustic agglomeration and precipation kernels. A study of the aerodynamic behaviour of the fluid has shown the presence of turbulence in the system. Then, turbulence spectra have been measured in order to foresee the turbulence evolution (the largest structures degenerate in small eddies; inside them sonic coagulation occurs). Finally, the energy dissipated into heat in the system - a parameter representative of turbulence - has been evaluated
Comparative study of gyrokinetic, hybrid-kinetic and fully kinetic wave physics for space plasmas
Told, Daniel; Muller, Florian; Astfalk, Patrick; Jenko, Frank
2016-01-01
A set of numerical solvers for the linear dispersion relations of the gyrokinetic, the hybrid-kinetic, and the fully kinetic model is employed to study the physics of the kinetic Alfv\\'en wave and the fast magnetosonic mode in these models. In particular, we focus on parameters that are relevant for solar wind oriented applications (using a homogeneous, isotropic background), which are characterized by wave propagation angles averaging close to 90{\\deg}. It is found that the gyrokinetic model, while lacking high-frequency solutions and cyclotron effects, faithfully reproduces the fully kinetic Alfv\\'en wave physics close to, and sometimes significantly beyond, the boundaries of its range of validity. The hybrid-kinetic model, on the other hand, is much more complete in terms of high-frequency waves, but owing to its simple electron model it is found to severely underpredict wave damping rates even on ion spatial scales across a large range of parameters, despite containing full kinetic ion physics.
Study on surface wave characteristics of free surface flow of liquid metal lithium for IFMIF
International Nuclear Information System (INIS)
The international fusion materials irradiation facility (IFMIF) presents an intense neutron source to develop fusion reactor materials. The free surface flow of a liquid metal Lithium (Li) is planned as a target irradiated by two deuteron beams to generate intense neutrons and it is thus important to obtain knowledge of the surface wave characteristic for the safety and the efficiency of system in the IFMIF. We have been studying on surface wave characteristics experimentally using the liquid metal Li circulation facility at Osaka University and numerically using computational fluid dynamics (CFD) code, FLUENT. This paper reports the results of the surface fluctuation, the wave height and the surface velocity in the free surface flow of the liquid metal Li examined experimentally and numerically. In the experiment, an electro-contact probe apparatus was used to obtain the surface fluctuation and the wave height, and a high speed video was used to measure the surface velocity. We resulted in knowledge of the surface wave growth mechanism. On the other hand, a CFD simulation was also conducted to obtain information on the relation of the free surface with the inner flow. In the simulation, the model included from a two-staged contraction nozzle to a flow channel with a free surface flow region and simulation results were compared with the experimental data. (author)
Numerical study of the KP equation for non-periodic waves
Kao, Chiu-Yen
2010-01-01
The Kadomtsev-Petviashvili (KP) equation describes weakly dispersive and small amplitude waves propagating in a quasi-two dimensional situation. Recently a large variety of exact soliton solutions of the KP equation has been found and classified. Those soliton solutions are localized along certain lines in a two-dimensional plane and decay exponentially everywhere else, and they are called line-soliton solutions in this paper. The classification is based on the far-field patterns of the solutions which consist of a finite number of line-solitons. In this paper, we study the initial value problem of the KP equation with V- and X-shape initial waves consisting of two distinct line-solitons by means of the direct numerical simulation. We then show that the solution converges asymptotically to some of those exact soliton solutions. The convergence is in a locally defined $L^2$-sense. The initial wave patterns considered in this paper are related to the rogue waves generated by nonlinear wave interactions in shall...
Simons, Rainee N.; Wintucky, Edwin G.
2014-01-01
This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.
Charland, Jenna; Touboul, Julien; Rey, Vincent
2013-04-01
Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves J. Charland * **, J. Touboul **, V. Rey ** jenna.charland@univ-tln.fr * Direction Générale de l'Armement, CNRS Délégation Normandie ** Université de Toulon, 83957 La Garde, France Mediterranean Institute of Oceanography (MIO) Aix Marseille Université, 13288 Marseille, France CNRS/INSU, IRD, MIO, UM 110 In the nearshore area, both wave propagation and currents are influenced by the bathymetry. For a better understanding of wave - current interactions in the presence of a 3D bathymetry, a large scale experiment was carried out in the Ocean Basin FIRST, Toulon, France. The 3D bathymetry consisted of two symmetric underwater mounds on both sides in the mean wave direction. The water depth at the top the mounds was hm=1,5m, the slopes of the mounds were of about 1:3, the water depth was h=3 m elsewhere. For opposite current conditions (U of order 0.30m/s), a huge focusing of the wave up to twice its incident amplitude was observed in the central part of the basin for T=1.4s. Since deep water conditions are verified, the wave amplification is ascribed to the current field. The mean velocity fields at a water depth hC=0.25m was measured by the use of an electromagnetic current meter. The results have been published in Rey et al [4]. The elliptic form of the "mild slope" equation including a uniform current on the water column (Chen et al [1]) was then used for the calculations. The calculated wave amplification of factor 1.2 is significantly smaller than observed experimentally (factor 2). So, the purpose of this study is to understand the physical processes which explain this gap. As demonstrated by Kharif & Pelinovsky [2], geometrical focusing of waves is able to modify significantly the local wave amplitude. We consider this process here. Since vertical velocity profiles measured at some locations have shown significant
International Nuclear Information System (INIS)
For structural integrity evaluation of composite rocket motor cases, acoustic emission (AE) during hydroproof test is currently used. For the suitable performance of this test, it is very important to determine the optimal component of elastic waves to be monitored. In this study, the optimal component of circumferential wave that propagate in the circumferential direction of the composite motor case has been determined experimentally. Then its potential to be served as a robust tool for nondestructive evaluation of composite motor cases was demonstrated by investigating the initial performances for flaw detection and AE source location.
Density Functional Study of the Transport and Electronic Properties of Waved Graphene Nanoribbons
Hammouri, Mahmoud; Vasiliev, Igor
2015-03-01
First principles ab initio calculations are employed to study the electronic and transport properties of waved graphene nanoribbons. Our calculations are performed using the SIESTA and TRANSIESTA density functional electronic structure codes. We find that the band gaps of graphene nanoribbons with symmetrical edges change very slightly with the increasing compression, whereas the band gaps of nanoribbons with asymmetrical edges change significantly. The computed IV-characteristics of the waved graphene nanoribbons with different compression ratios reveal the effect of compression on the transport properties of graphene nanoribbons. Supported by NMSU GREG Award and by NSF CHE-1112388.
Study on the propagation mechanism of evanescent waves in one-dimensional periodic photonic crystal
International Nuclear Information System (INIS)
Based on the evanescent waves theory, the formation condition and propagation mechanism of evanescent waves in one-dimensional periodic photonic crystal are studied. When the incident light travels through the periodic photonic crystal at a certain angle, the optical resonance will occur in the optically denser medium, and a unique photonic local feature will occur in photonic bandgap. Furthermore, the influences on transmission performance by the photonic crystal parameters are discussed respectively. The simulation results show that the structure mentioned above can achieve the performance of high transmission and high Q value, which can provide theoretical references for photonic crystal multi-channel filters
A theoretical study of hot plasma spheroids in the presence of low-frequency electromagnetic waves
Ahmadizadeh, Y.; Jazi, B.; Barjesteh, S.
2016-07-01
While taking into account thermal motion of electrons, scattering of electromagnetic waves with low frequency from hot plasma spheroids is investigated. In this theoretical research, ions are heavy to respond to electromagnetic fluctuations. The solution of scalar wave equation in spheroidal coordinates for electric potential inside the plasma spheroids are obtained. The variations of resonance frequencies vs. Debye length are studied and consistency between the obtained results in this paper and the results for the well-known plasma objects such as plasma column and spherical plasma have been proved.
STUDY ON THE SHOCK WAVE CRYSTALLIZATION OF AMORPHOUS ALLOYS BY DSC
Institute of Scientific and Technical Information of China (English)
H.Y. Zhao; H. Wang; Q.J. Liu; J.D. Kan; Z.Q. Liu
2002-01-01
Shock wave and annealing crystallization of amorphous alloys FeSiB, FeMoSiB andFeCuNbSiB were studied by isothermal and non-isothermal DSC technique. It wasfound that the shock wave crystallization is very perfect, the fraction crystallized isvery close to 100%, though the period of crystallization is very short, only about10-4-10-6 s. Their produced phases differ from the parent phase in structure andcomposition. The high velocity of the transformation is very difficult to explain by thediffusion theory of solid state phase transition.
International Nuclear Information System (INIS)
The purpose of this study is to investigate the effect of the presence of the mode conversion (nzzcritical), on the evolution of the electric field of the lower hybrid (LH) propagating wave. The propagation of the LH wave in a magnetized plasma, for both mode polarization (slow and fast), is described by a fourth order ordinary differential equation, which here has been analyzed analytically and numerically. A complete WKB solution of the 4th order equation has also been obtained showing the failure of the method near the cut-offs and the mode conversion point.
Study on the propagation mechanism of evanescent waves in one-dimensional periodic photonic crystal
Energy Technology Data Exchange (ETDEWEB)
Chen, Ying, E-mail: chenying@ysu.edu.cn [Hebei Province Key Laboratory of Test/Measurement Technology and Instrument, School of Electrical Engineering, Yanshan University, Qinhuangdao 066004 (China); Shi, Jia; Liu, Teng; Dong, Jing [Hebei Province Key Laboratory of Test/Measurement Technology and Instrument, School of Electrical Engineering, Yanshan University, Qinhuangdao 066004 (China); Zhu, Qiguang; Chen, Weidong [Key Laboratory of Special Fiber and Fiber Sensor of Hebei Province, School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)
2015-10-02
Based on the evanescent waves theory, the formation condition and propagation mechanism of evanescent waves in one-dimensional periodic photonic crystal are studied. When the incident light travels through the periodic photonic crystal at a certain angle, the optical resonance will occur in the optically denser medium, and a unique photonic local feature will occur in photonic bandgap. Furthermore, the influences on transmission performance by the photonic crystal parameters are discussed respectively. The simulation results show that the structure mentioned above can achieve the performance of high transmission and high Q value, which can provide theoretical references for photonic crystal multi-channel filters.
An analytic study of TTF of standing wave RF gap based on Bessel–Fourier expansion
International Nuclear Information System (INIS)
Transit time factor (TTF) is important in design and simulation of standing wave RF gaps. The TTF is usually constructed on the basis of a square wave model, and it is always expanded as a function of reduced velocity and structure factors. In order to express the particle's motion more authentically, the TTF is studied based on the Bessel–Fourier (B–F) expansion which is realized in BEAMPATH code. By expanding square wave electric field into harmonic electric fields, the voltage component and the TTF component of each order are obtained from corresponding harmonic electric field. The ratios of each order of voltage components and integral voltage form the weights working as coefficients of TTF components. Consequently, the effective resultant TTF depends on not only the particle's velocity and the structure factors, but also the RF phase the particle experiences. Simple expressions are derived after simplifying the complicated TTF equation in this paper
Neutron-Scattering Study of Spin Waves in the Ferrimagnet RbNiF3
DEFF Research Database (Denmark)
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1972-01-01
contains six Ni++ spins so that there are in general six distinct branches in the spin-wave spectrum. All six branches are observed in the ΓA direction (c axis), while only the lowest three are observed in the ΓM direction. The measured dispersion curves at 4.2°K may be accurately fitted using simple spin-wave...... 180° antiferromagnetic exchange between nearest-neighbor A, B spins and a 90° ferromagnetic exchange between nearest-neighbor B spins. In this paper we report a detailed inelastic-neutron-scattering study of the spin waves in RbNiF3 both at low temperatures and through Tc. The magnetic unit cell...
Current drive by EC and LH waves in Tore Supra for steady-state reactor studies
International Nuclear Information System (INIS)
A long term ECRH program in TORE SUPRA for current drive researches is proposed. The aim of the program is twofold, namely, optimization of the rf driven current in TS by an appropriate combination of LH and EC waves and the search of current drive scenarii of relevance for the steady-state reactor. It is shown that under favourable conditions, steady-state operation can be envisioned by rf current drive with a marginally acceptable efficiency. Experimental results on selective wave absorption at down shifted frequency obtained in PLT and on current drive by EC and LH wave in WT-2 and JFT-2M are given besides the studies presented on Tore Supra
A numerical study of nonlinear wave run-up on a vertical plate
DEFF Research Database (Denmark)
Jamois, Eric; Fuhrman, David R.; Bingham, Harry; Molin, Bernard
2006-01-01
decreases the total number of unknowns in two horizontal dimensions from seven to five, simplifying the implementation, and leading to increased computational efficiency. Analysis of the embedded properties demonstrates that the resulting model has applications with errors of 2 to 3% for (wavenumber times...... is then used to study physically demanding problems involving highly nonlinear wave run-up on a bottom-mounted (surface-piercing) plate. New cases involving oblique incidence are considered. In all cases, comparisons with recent physical experiments demonstrate good quantitative accuracy, even in the...... most demanding cases, where the local wave steepness can exceed (waveheight divided by wavelength) H / L = 0.20. The velocity potential model is additionally shown to have numerical advantages when dealing with wave-structure interactions, requiring less smoothing around exterior structural corners....
The New Wave of Childhood Studies: Breaking the Grip of Bio-Social Dualism?
Ryan, Kevin William
2012-01-01
The article takes as its starting point a new wave of researchers who use concepts such as "hybridity" and "multiplicity" in a bid to move the study of childhood beyond the strictures of what Lee and Motzkau call "bio-social dualism", whereby the division between the "natural child" of developmental psychology and the "social child" of…
Co-located wind-wave farm synergies (Operation and Maintenance): A case study
International Nuclear Information System (INIS)
Highlights: • The shielding effect of WECs located around the wind farm is analysed. • The height wave reductions achieved by 15 different layouts are compared. • The increase in the accessibility to the wind turbines is quantified. • Alpha Ventus offshore wind farm is considered as baseline scenario. • High-resolution numerical modelling (SWAN) and real sea conditions are used. - Abstract: Operation and maintenance can jeopardise the financial viability of an offshore wind energy project due to the cost of downtime, repairs and, above all, the inevitable uncertainties. The variability of wave climate can impede or hinder emergency repairs when a failure occurs, and the resulting delays imply additional costs which ultimately reduce the competitiveness of offshore wind energy as an alternative to fossil fuels. Co-located wind turbines and Wave Energy Converters (WECs) are proposed in this paper as a novel solution: the reduction of the significant wave height brought about by the WECs along the periphery of the wind farm results in a milder wave climate within the farm. This reduction, also called shadow effect, enlarges weather windows for Operation and Maintenance (O and M). The objective of this paper is to investigate the increase in the accessibility time to the turbines and to optimise the layout for the co-located wind-wave farm in order to maximise this time. The investigation is carried out through a case study: Alpha Ventus, an operating offshore wind farm. To maximise the reduction of wave height in the turbine area no fewer than 15 layouts are tested using high-resolution numerical modelling, and a sensitivity analysis is conducted. The results show that, thanks to the wave energy extraction by the WECs, weather windows (access time) can increase very significantly – over 80%. This substantial effect, together with other benefits from the combination of wave and offshore wind power in a co-located farm (common electrical infrastructures
Studies of thermal wave phenomena on the Jovian planets
Deming, Drake
1991-01-01
Ground based and Voyager observations of Jupiter have provided evidence that the tropospheric temperature shows global scale longitudinal variations which are often wavelike in character. Voyager data are reported to exhibit the presence of slowly moving thermal features, wherein the jovian tropospheric temperature patterns are not advected by the equatorial zonal winds, but are not found to rotate at the System III (interior) rate. Ground based data in a broad infrared band (8 to 13 micron) show a wavelike structure whose amplitude and spatial scale are similar to the reported properties of the slowly moving thermal features. This study is directed toward obtaining additional ground based data in infrared spectral bands whose contribution functions are optimized for specific atmospheric regions (tropospheric at 20 micron, and stratospheric at 7.8 micron), in order to confirm the previous results, and to identify the nature and physical significance of wavelike longitudinal temperature fluctuations on the Jovian planets. A 2-D infrared array detector and low resolution cryogenic grating spectrometer is being adapted to obtain maps in approx. 2/cm bandpasses.
Directory of Open Access Journals (Sweden)
Filleul Laurent
2009-02-01
Full Text Available Abstract Background The health impacts of heat waves are serious and have prompted the development of heat wave response plans. Even when they are efficient, these plans are developed to limit the health effects of heat waves. This study was designed to determine relevant indicators related to health effects of heat waves and to evaluate the ability of a syndromic surveillance system to monitor variations in the activity of emergency departments over time. The study uses data collected during the summer 2006 when a new heat wave occurred in France. Methods Data recorded from 49 emergency departments since July 2004, were transmitted daily via the Internet to the French Institute for Public Health Surveillance. Items collected on patients included diagnosis (ICD10 codes, outcome, and age. Statistical t-tests were used to compare, for several health conditions, the daily averages of patients within different age groups and periods (whether 'on alert' or 'off alert'. Results A limited number of adverse health conditions occurred more frequently during hot period: dehydration, hyperthermia, malaise, hyponatremia, renal colic, and renal failure. Over all health conditions, the total number of patients per day remained equal between the 'on alert' and 'off alert' periods (4,557.7/day vs. 4,511.2/day, but the number of elderly patients increased significantly during the 'on alert' period relative to the 'off alert' period (476.7/day vs. 446.2/day p Conclusion Our results show the interest to monitor specific indicators during hot periods and to focus surveillance efforts on the elderly. Syndromic surveillance allowed the collection of data in real time and the subsequent optimization of the response by public health agencies. This method of surveillance should therefore be considered as an essential part of efforts to prevent the health effects of heat waves.
Stefan, V.
2006-10-01
A novel mechanism for the suppression of Weibel instabilities in the core of advanced fast ignition pellets is addressed. The propagation of generated suprathermal electron beam toward the core may lead to the appearance of colossal (˜10MG), small scale (L˜c/φpe, c---velocity of light, φpe---local electron plasma frequency) magnetic fields. The suppression synergy of high harmonic electron Bernstein, (EB), modes and Weibel modes, (WB), in the cone-attached laser fusion pellets is based on nonlinear mode-mode coupling. EB modes are excited by ignition, a cone guided, or implosion laser beams. High harmonic EB modes easily propagate to the core of the pellet whereby they nonlinearly interact with, and suppress, the WB. The suppression synergy is maximized at the simultaneous action of ignition and implosion lasers. E. S. Weibel, Phys. Rev. Lett., 2,83 (1959) in the core of advanced fast ignition pellets M. Tabak, J. Hammer, M.E. Glinsky, W.L. Kruer, S. C. Wilks, J. Woodworth, E. M. Campbell, and M.D. Perry, Phys. Plasmas 1 (5), 1626 (1994). V. Stefan, (a) Quasi-Stationary B-Fields due to Weibel Instability in FI Laser Fusion Pellets; (b) Pellet Core Heating Via High Harmonic EB Modes in FI Laser Fusion. 35th Annual A.A.C, 2005,
Directory of Open Access Journals (Sweden)
Qian Wan
2015-04-01
Full Text Available Research on shock wave mitigation in channels has been a topic of much attention in the shock wave community. One approach to attenuate an incident shock wave is to use obstacles of various geometries arranged in different patterns. This work is inspired by the study from Chaudhuri et al. (2013, in which cylinders, squares and triangles placed in staggered and non-staggered subsequent columns were used to attenuate a planar incident shock wave. Here, we present numerical simulations using a different obstacle pattern. Instead of using a matrix of obstacles, an arrangement of square or cylindrical obstacles placed along a logarithmic spiral curve is investigated, which is motivated by our previous work on shock focusing using logarithmic spirals. Results show that obstacles placed along a logarithmic spiral can delay both the transmitted and the reflected shock wave. For different incident shock Mach numbers, away from the logarithmic spiral design Mach number, this shape is effective to either delay the transmitted or the reflected shock wave. Results also confirm that the degree of attenuation depends on the obstacle shape, effective flow area and obstacle arrangement, much like other obstacle configurations.
Sun, Yan; Song, Geng-Qing; Yin, Jieyun; Lei, Yong; Chen, Jiande D.Z.
2009-01-01
The aims of this study were to determine optimal pacing parameters of electrical stimulation on different gut segments and to investigate effects and possible mechanisms of gastrointestinal electrical stimulation on gut slow waves. Twelve female hound-mix dogs were used in this study. A total of six pairs of electrodes were implanted on the stomach, duodenum, and ascending colon. Bilateral truncal vagotomy was performed in six of the dogs. One experiment was designed to study the effects of t...
Free Surface Waves And Interacting Bouncing Droplets: A Parametric Resonance Case Study
Borja, Francisco J.
2013-07-01
Parametric resonance is a particular type of resonance in which a parameter in a system changes with time. A particularly interesting case is when the parameter changes in a periodic way, which can lead to very intricate behavior. This di↵ers from periodic forcing in that solutions are not necessarily periodic. A system in which parametric resonance is realized is when a fluid bath is shaken periodically, which leads to an e↵ective time dependent gravitational force. This system will be used to study the onset of surface waves in a bath with non-uniform topography. A linear model for the surface waves is derived from the Euler equations in the limit of shallow waves, which includes the geometry of the bottom and surface tension. Experiments are performed to compare with the proposed model and good qualitative agreement is found. Another experiment which relies on a shaking fluid bath is that of bouncing fluid droplets. In the case of two droplets the shaking allows for a larger bouncing droplet to attract a smaller moving droplet in a way that creates a bound system. This bound system is studied and shows some analogous properties to quantum systems, so a quantum mechanical model for a two dimensional atom is studied, as well as a proposed model for the droplet-wave system in terms of equations of fluid mechanics.
A Further Study on Wave Propagation Across a Single Joint with Different Roughness
Chen, X.; Li, Jian Chun; Cai, M. F.; Zou, Y.; Zhao, J.
2016-07-01
As a key dynamic feature of the rock mass, joint results in wave attenuation when a stress wave propagates across it. An experimental study has obtained the relation between the transmission coefficient and the contact area ratio of joints with different thicknesses (Chen et al. (doi: 10.1007/s00603-015-0716-z)). However, the spatial geometry of the contact surface also determines the dynamic behavior of the discontinuous masses. Thus, the present study is focused on the effects of distribution and dimension of the sawn notches on the contact surface of the joint, which lead to the different spatial geometry. The joint matching coefficient (JMC) was used in this study to define the contact condition. Using a modified SHPB apparatus, all the bars and specimens were aluminum, and the artificial joint formed a rough surface of the specimen contacted to the output bar. Based on the wave separation method, the incident, reflected and transmitted waves across the joint were acquired from the records of the strain gauges on pressure bars. Then the transmission coefficient and specific stiffness of the joint were obtained. Comparisons of them were made on different JMCs, spatial geometries and thicknesses of the joint.
A PIC simulation study on the evolution of the real and imaginary frequencies of 1D plasma waves
Grismayer, Thomas; Fahlen, Jay; Winjum, Benjamin; Tsung, Frank; Morales, George; Mori, Warren
2009-11-01
We use electrostatic PIC simulations to study the evolution of both the real and complex frequency of 1D plasma waves. We are considering especially the linear regime where the asymptotic damping rate is much bigger than the bounce frequency. In this regime the waves are typically very small and below the thermal noise. These waves can be studied using a subtraction technique where two simulations where identical random number generation seeds are carried out. In the first, a small amplitude wave is excited. In the second simulation no wave is excited. The results from each simulation are subtracted providing a clean linear wave that can be studied. As previously predicted, the damping is divided in two stages, an initial transient and an asymptotic decay (Landau's formula). The time-dependent resonant width measured in the simulations is compared with the theoretical prediction. In typical ICF plasmas nld^3 damping.
Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study
Li, Ronny X.; Luo, Jianwen; Balaram, Sandhya K.; Chaudhry, Farooq A.; Shahmirzadi, Danial; Konofagou, Elisa E.
2013-07-01
Arterial stiffness is a well-established biomarker for cardiovascular risk, especially in the case of hypertension. The progressive stages of an abdominal aortic aneurysm (AAA) have also been associated with varying arterial stiffness. Pulse wave imaging (PWI) is a noninvasive, ultrasound imaging-based technique that uses the pulse wave-induced arterial wall motion to map the propagation of the pulse wave and measure the regional pulse wave velocity (PWV) as an index of arterial stiffness. In this study, the clinical feasibility of PWI was evaluated in normal, hypertensive, and aneurysmal human aortas. Radiofrequency-based speckle tracking was used to estimate the pulse wave-induced displacements in the abdominal aortic walls of normal (N = 15, mean age 32.5 ± 10.2 years), hypertensive (N = 13, mean age 60.8 ± 15.8 years), and aneurysmal (N = 5, mean age 71.6 ± 11.8 years) human subjects. Linear regression of the spatio-temporal variation of the displacement waveform in the anterior aortic wall over a single cardiac cycle yielded the slope as the PWV and the coefficient of determination r2 as an approximate measure of the pulse wave propagation uniformity. The aortic PWV measurements in all normal, hypertensive, and AAA subjects were 6.03 ± 1.68, 6.69 ± 2.80, and 10.54 ± 6.52 m s-1, respectively. There was no significant difference (p = 0.15) between the PWVs of the normal and hypertensive subjects while the PWVs of the AAA subjects were significantly higher (p pathologies that regionally alter the arterial wall mechanics.
Fast Magnetosonic Waves Driven by Gravitational Waves
Papadopoulos, D.; Stergioulas, N.; Vlahos, L.; Kuijpers, J.
2001-01-01
The propagation of a gravitational wave (GW) through a magnetized plasma is considered. In particular, we study the excitation of fast magnetosonic waves (MSW) by a gravitational wave, using the linearized general-relativistic hydromagnetic equations. We derive the dispersion relation for the plasma, treating the gravitational wave as a perturbation in a Minkowski background space-time. We show that the presence of gravitational waves will drive magnetosonic waves in the plasma and discuss th...
Staneva, J.; Wahle, K.; Günther, H.; Stanev, E.
2015-12-01
This study addresses the impact of coupling between wind wave and circulation models on the quality of coastal ocean predicting systems. This is exemplified for the German Bight and its coastal area known as the Wadden Sea. The latter is the area between the barrier islands and the coast. This topic reflects the increased interest in operational oceanography to reduce prediction errors of state estimates at coastal scales, which in many cases are due to unresolved nonlinear feedback between strong tidal currents and wind-waves. In this study we present analysis of wave and hydrographic observations, as well as results of numerical simulations. A nested-grid modelling system is used to producing reliable nowcasts and short-term forecasts of ocean state variables, including wind waves and hydrodynamics. The data base includes ADCP observations and continuous measurements from data stations. The individual and collective role of wind, waves and tidal forcing are quantified. The performance of the forecast system is illustrated for the cases of several extreme events. Effects of ocean waves on coastal circulation and sea level are investigated by considering the wave-dependent stress and wave breaking parameterization. Also the effects which the circulation exerts on the wind waves are tested for the coastal areas using different parameterizations. The improved skill of the coupled forecasts compared to the non-coupled ones, in particular during extreme events, justifies the further enhancements of coastal operational systems by including wind wave models.
A comparative study of chop-wave and super pulse CO-2 laser surface modification of polyurethane
International Nuclear Information System (INIS)
The present study was undertaken to evaluate and compare the effects of chop wave and super pulse wave of CO2 laser on polyurethane. The results showed that at the threshold fluences of 200 and 400 mJcm-2, for chop wave and super pulse wave, the final temperatures would be about 322 and 343 K justified by their effective absorption coefficients of ∼ 1 . 2 x 1 03cm-1and 1.3 x 103cm-1, respectively. These values are well below the minimum melting temperature (≅393 K) of polymer. The ATR-FTIR spectral analysis showed four new peaks at 1436, 1370, 1259 and 958 cm-Iafter laser irradiation indicative of increased hydrogen bonding. The best surface free energy of 50 mNm-1was obtained after 8 pulses of chop wave which corresponds to a contact angle of 75 .Topological studies using SEM evaluation illustrated that a smooth wall crater can be produced by super pulse wave and chop wave at higher laser pulse numbers and relatively low input power.Finally, in our experiments the highest value of surface free energy was achieved by chop wave mode at 0.1 W after 8 pulses. Although, super pulse wave produced a narrower zone of thermal degradation, surface free energy of polymer, however was found to be weaker than chop wave mode
Computational study of shock waves propagating through air-plastic-water interfaces
Del Razo, Mauricio J
2015-01-01
The following study is motivated by experimental studies in traumatic brain injury (TBI). Recent research has demonstrated that low intensity non-impact blast wave exposure frequently leads to mild traumatic brain injury (mTBI); however, the mechanisms connecting the blast waves and the mTBI remain unclear. Collaborators at the Seattle VA Hospital are doing experiments to understand how blast waves can produce mTBI. In order to gain insight that is hard to obtain by experimental means, we have developed conservative finite volume methods for interface-shock wave interaction to simulate these experiments. A 1D model of their experimental setup has been implemented using Euler equations for compressible fluids. These equations are coupled with a Tammann equation of state (EOS) that allows us to model compressible gas along with almost incompressible fluids or elastic solids. A hybrid HLLC-exact Eulerian-Lagrangian Riemann solver for Tammann EOS with a jump in the parameters has been developed. The model has sho...
Directory of Open Access Journals (Sweden)
S. Schäfer
2007-05-01
Full Text Available Oscillating magnetic field lines are frequently observed by spacecraft in the terrestrial and other planetary magnetospheres. The CLUSTER mission is a very suitable tool to further study these Alfvén waves as the four CLUSTER spacecraft provide for an opportunity to separate spatial and temporal structures in the terrestrial magnetosphere. Using a large scaled configuration formed by the four spacecraft we are able to detect a poloidal Ultra-Low-Frequency (ULF pulsation of the magnetic and electric field in order to analyze its temporal and spatial structures. For this purpose the measurements are transformed into a specific field line related coordinate system to investigate their specific amplitude pattern depending on the path of the CLUSTER spacecraft across oscillating field lines. These measurements are then compared with modeled spacecraft observations across a localized poloidal wave resonator in the dayside plasmasphere. A detailed investigation of theoretically expected poloidal eigenfrequencies allows us to specify the observed 16 mHz pulsation as a third harmonic oscillation. Based on this we perform a case study providing a clear identification of wave properties such as an spatial scale structure of about 0.67 R_{E}, the azimuthal wave number m≈30, temporal evolution, and energy transport in the detected ULF pulsations.
The study on nondestructive evaluation for a tubular structure by the lamb-type guided wave wedge
International Nuclear Information System (INIS)
The study on the cylindrical guided wave was carried out to investigate its feasibility for nondestructive evaluation of tubular structures such as heat exchanger tubings of power industries and various pipings of chemical plants. The concept of wedge design and incident angle selection to optimize guided wave generation is presented based on the dispersion theory and the snell's law for the cylindrical guided wave. The brass tubes with artificial defects in the circumferential or axial direction were used for detect defection experiments. It was found that guided wave sensitivity for detecting an axial defect can be remarkably improved by using non-axisymmetrically launched guided waves. Through this study, it is expected that the guided wave can be successfully applied to tubular structure inspections as an more advanced and efficient NDE technique than a conventional point-by-point technique.
Study of parametric instabilities during the Alcator C lower hybrid wave heating experiments
International Nuclear Information System (INIS)
Parametric excitation of ion-cyclotron quasi-modes (ω/sub R/ approx. = nω/sub ci/) and ion-sound quasi-modes (ω/sub R/ approx. = k/sub parallel to/v/sub ti/) during lower hybrid wave heating of tokamak plasmas have been studied in detail. Such instabilities may significantly modify the incident wavenumber spectrum near the plasma edge. Convective losses for these instabilities are high if well-defined resonance cones exist, but they are significantly reduced if the resonance cones spread and fill the plasma volume (or some region of it). These instabilities preferentially excite lower hybrid waves with larger values of n/sub parallel to/ than themselves possess, and the new waves tend to be absorbed near the outer layers of the plasma. Parametric instabilities during lower hybrid heating of Alcator C plasmas have been investigated using rf probes (to study tilde phi and tilde n/sub i/) and CO2 scattering technique (to study tilde n/sub e/). At lower densities (anti n/sub e/ less than or equal to 0.5 x 1014cm-3) where waves observed in the plasma interior using CO2 scattering appear to be localized, parametric decay is very weak. Both ion-sound and ion-cyclotron parametric decay processes have been observed at higher densities (anti n greater than or equal to 1.5 x 1014cm-3) where waves appear to be unlocalized. Finally, at still higher densities (anti n /sub e/ greater than or equal to 2 x 104cm-3) pump depletion has been observed. Above these densities heating and current drive efficiencies are expected to degrade significantly
Waving Web in Tourism Higher Education—Case Study at Tourism School of GUBS
Xuan Xiao; Jianhua Wu
2012-01-01
Purpose: The purpose of this paper is to introduce some approaches to wave web in tourism higher education, with analyses on key successful factors. Design/methodology/approach—The methods of investigation used in this study include observation, in-depth interviews, survey and secondary data. Findings: A comparison study indicates that virtual learning environment is a good solution to massive course load in tourism higher education. The paper figures out three effective approaches based on B...
Crawford, F. W.
1975-01-01
A ten year summary was given of university research on the nature and characteristics of space related plasma resonance phenomena, whistler propagation in laboratory plasmas, and theoretical and experimental studies of plasma wave propagation. Data are also given on long delayed echoes, low frequency instabilities, ionospheric heating, and backscatter, and pulse propagation. A list is included of all conference papers, publications, and reports resulting from the study.
Simons, Rainee N.; Wintucky, Edwin G.
2014-01-01
This paper presents the design and test results of a multi-band multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These studies would enable the design of robust multi-Gbps data rate space-to-ground satellite communication links. Lastly, the architecture for a compact multi-tone beacon transmitter, which includes a high frequency synthesizer, a polarizer, and a conical horn antenna, has been investigated for a notional CubeSat based space-to-ground radio wave propagation experiment.
International Nuclear Information System (INIS)
This paper proposes a new electromagnetic wave absorbing control technique involving the coating-type magnetic wood in order to take advantage of the easy processing of wood materials. The experimental results show that, by changing the shape and size of the surface, the electromagnetic wave absorption characteristics can be controlled. The magnetic wood board with embedded grid lines demonstrated the best electromagnetic wave absorption characteristics among the various types that were studied
Michailidou, V. N.; Swan, J. W.; Brady, J. F.; Petekidis, G.
2013-01-01
Evanescent wave dynamic light scattering and Stokesian dynamics simulations were employed to study the dynamics of hard-sphere colloidal particles near a hard wall in concentrated suspensions. The evanescent wave averaged short-time diffusion coefficients were determined from experimental correlation functions over a range of scattering wave vectors and penetration depths. Stokesian dynamics simulations performed for similar conditions allow a direct comparison of both the short-time self- an...
Papanastasiou, D. K.; Bartzanas, T.; Panagakis, P.; Zhang, G.; Kittas, C.
2016-03-01
It is well documented that heat-stress burdens sheep welfare and productivity. Peak heat-stress levels are observed when high temperatures prevail, i.e. during heat waves; however, continuous measurements inside livestock buildings are not usually available for long periods so as to study the variation of summer heat-stress levels for several years, especially during extreme hot weather. Α methodology to develop a long time series of summer temperature and relative humidity inside naturally ventilated sheep barns is proposed. The accuracy and the transferability of the developed linear regression models were verified. Temperature Humidity Index (THI) was used to assess sheep's potential heat-stress. Τhe variation of THI inside a barn during heat wave and non-heat wave days was examined, and the results were comparatively assessed. The analysis showed that sheep were exposed to moderate, severe, and extreme severe heat-stress in 10, 21 and 66 % of hours, respectively, during heat wave days, while the corresponding values during non-heat wave days were 14, 33 and 43 %, respectively. The heat load on sheep was much higher during heat wave events than during non-heat wave periods. Additionally, based on the averaged diurnal variation of THI, it was concluded that extreme severe heat-stress conditions were prevailing between 1000 and 2400 hours local time during heat wave days. Cool off night periods were never and extremely rarely detected during heat wave and non-heat wave days, respectively.
Aryan, Homayon; Yearby, Keith; Balikhin, Michael; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Boynton, Richard
2014-08-01
Energetic electrons within the Earth's radiation belts represent a serious hazard to geostationary satellites. The interactions of electrons with chorus waves play an important role in both the acceleration and loss of radiation belt electrons. The common approach is to present model wave distributions in the inner magnetosphere under different values of geomagnetic activity as expressed by the geomagnetic indices. However, it has been shown that only around 50% of geomagnetic storms increase flux of relativistic electrons at geostationary orbit while 20% causes a decrease and the remaining 30% has relatively no effect. This emphasizes the importance of including solar wind parameters such as bulk velocity (V), density (n), flow pressure (P), and the vertical interplanetary magnetic field component (Bz) that are known to be predominately effective in the control of high energy fluxes at the geostationary orbit. Therefore, in the present study the set of parameters of the wave distributions is expanded to include the solar wind parameters in addition to the geomagnetic activity. The present study examines almost 4 years (1 January 2004 to 29 September 2007) of Spatio-Temporal Analysis of Field Fluctuation data from Double Star TC1 combined with geomagnetic indices and solar wind parameters from OMNI database in order to present a comprehensive model of wave magnetic field intensities for the chorus waves as a function of magnetic local time, L shell (L), magnetic latitude (λm), geomagnetic activity, and solar wind parameters. Generally, the results indicate that the intensity of chorus emission is not only dependent upon geomagnetic activity but also dependent on solar wind parameters with velocity and southward interplanetary magnetic field Bs (Bz < 0), evidently the most influential solar wind parameters. The largest peak chorus intensities in the order of 50 pT are observed during active conditions, high solar wind velocities, low solar wind densities, high
Simulation studies on the standing and traveling wave thermoacoustic prime movers
International Nuclear Information System (INIS)
Thermoacoustic systems have been a focus of recent research due to its structural simplicity, high reliability due to absence of moving parts, and can be driven by low grade energy such as fuel, gas, solar energy, waste heat etc. There has been extensive research on both standing wave and traveling wave systems. Towards the development of such systems, simulations can be carried out by several methods such as (a) solving the energy equation, (b) enthalpy flow model, (c) DeltaEC, a free software available from LANL, USA (d) Computational Fluid Dynamics (CFD) etc. We present here the simulation studies of standing wave and traveling wave thermoacoustic prime movers using CFD and DeltaEC. The CFD analysis is carried out using Fluent 6.3.26, incorporating the necessary boundary conditions with different working fluids at different operating pressures. The results obtained by CFD are compared with those obtained using DeltaEC. Also, the CFD simulation of the thermoacoustically driven refrigerator is presented
Effects of body mass index on gastric slow wave: a magnetogastrographic study
International Nuclear Information System (INIS)
We measured gastric slow wave activity simultaneously with magnetogastrogram (MGG), mucosal electromyogram (EMG) and electrogastrogram (EGG) in human subjects with varying body mass index (BMI) before and after a meal. In order to investigate the effect of BMI on gastric slow wave parameters, each subject's BMI was calculated and divided into two groups: subjects with BMI ≤ 27 and BMI > 27. Signals were processed with Fourier spectral analysis and second-order blind identification (SOBI) techniques. Our results showed that increased BMI does not affect signal characteristics such as frequency and amplitude of EMG and MGG. Comparison of the postprandial EGG power, on the other hand, showed a statistically significant reduction in subjects with BMI > 27 compared with BMI ≤ 27. In addition to the frequency and amplitude, the use of SOBI-computed propagation maps from MGG data allowed us to visualize the propagating slow wave and compute the propagation velocity in both BMI groups. No significant change in velocity with increasing BMI or meal was observed in our study. In conclusion, multichannel MGG provides an assessment of frequency, amplitude and propagation velocity of the slow wave in subjects with differing BMI categories and was observed to be independent of BMI. (paper)