Ion Bernstein wave heating research
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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)
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
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
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
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
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)
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)
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
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
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
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
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
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.
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.
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
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
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
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
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
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
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
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
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
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.
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.
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}.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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
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 .
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
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
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
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
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
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
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
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
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
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
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)
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
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
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.
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
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
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
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
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
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.
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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...
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
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
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
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
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
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
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
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).
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
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
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
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
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...
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
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
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
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
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
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
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
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
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
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
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
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"…
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
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