Survey of Coherent Approximately 1 Hz Waves in Mercury's Inner Magnetosphere from MESSENGER Observations

NASA Technical Reports Server (NTRS)

Boardsen, Scott A.; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Schriver, David; Solomon, Sean C.

2012-01-01

We summarize observations by the MESSENGER spacecraft of highly coherent waves at frequencies between 0.4 and 5 Hz in Mercury's inner magnetosphere. This survey covers the time period from 24 March to 25 September 2011, or 2.1 Mercury years. These waves typically exhibit banded harmonic structure that drifts in frequency as the spacecraft traverses the magnetic equator. The waves are seen at all magnetic local times, but their observed rate of occurrence is much less on the dayside, at least in part the result of MESSENGER's orbit. On the nightside, on average, wave power is maximum near the equator and decreases with increasing magnetic latitude, consistent with an equatorial source. When the spacecraft traverses the plasma sheet during its equatorial crossings, wave power is a factor of 2 larger than for equatorial crossings that do not cross the plasma sheet. The waves are highly transverse at large magnetic latitudes but are more compressional near the equator. However, at the equator the transverse component of these waves increases relative to the compressional component as the degree of polarization decreases. Also, there is a substantial minority of events that are transverse at all magnetic latitudes, including the equator. A few of these latter events could be interpreted as ion cyclotron waves. In general, the waves tend to be strongly linear and characterized by values of the ellipticity less than 0.3 and wave-normal angles peaked near 90 deg. Their maxima in wave power at the equator coupled with their narrow-band character suggests that these waves might be generated locally in loss cone plasma characterized by high values of the ratio beta of plasma pressure to magnetic pressure. Presumably both electromagnetic ion cyclotron waves and electromagnetic ion Bernstein waves can be generated by ion loss cone distributions. If proton beta decreases with increasing magnetic latitude along a field line, then electromagnetic ion Bernstein waves are predicted to transition from compressional to transverse, a pattern consistent with our observations. We hypothesize that these local instabilities can lead to enhanced ion precipitation and directly feed field-line resonances.

Two Contemporary Problems in Magnetized Plasmas: the ion-ion hybrid resonator and MHD stability in a snowflake divertor

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

Farmer, William Anthony

2014-01-01

The rst part of the dissertation investigates the e ects of multiple-ions on the propagation of shear Alfv en waves. It is shown that the presence of a second ion-species allows for the formation of an ion-ion hybrid resonator in the presence of a magnetic well. A fullwave description is shown to explain the measured eigenfrequencies and spatial form of the resonator modes identi ed in experiments in the Large Plasma Device (LAPD) at UCLA. However, it is determined that neither electron collisions or radial convection of the mode due to coupling to either the compressional or ion-Bernstein wave canmore » explain the observed dissipation.« less

Observation of Bernstein Waves Excited by Newborn Interstellar Pickup Ions in the Solar Wind

NASA Technical Reports Server (NTRS)

Joyce, Colin J.; Smith, Charles W.; Isenberg, Philip A.; Gary, S. Peter; Murphy, Neil; Gray, Perry C.; Burlaga, Leonard F.

2012-01-01

A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.

Wind Observations of Wave Heating and/or Particle Energization at Supercritical Interplanetary Shocks

NASA Technical Reports Server (NTRS)

Wilson, Lynn Bruce, III; Szabo, Adam; Koval, Andriy; Cattell, Cynthia A.; Kellogg, Paul J.; Goetz, Keith; Breneman, Aaron; Kersten, Kris; Kasper, Justin C.; Pulupa, Marc

2011-01-01

We present the first observations at supercritical interplanetary shocks of large amplitude (> 100 mV/m pk-pk) solitary waves, approx.30 mV/m pk-pk waves exhibiting characteristics consistent with electron Bernstein waves, and > 20 nT pk-pk electromagnetic lower hybrid-like waves, with simultaneous evidence for wave heating and particle energization. The solitary waves and the Bernstein-like waves were likely due to instabilities driven by the free energy provided by reflected ions [Wilson III et al., 2010]. They were associated with strong particle heating in both the electrons and ions. We also show a case example of parallel electron energization and perpendicular ion heating due to a electromagnetic lower hybrid-like wave. Both studies provide the first experimental evidence of wave heating and/or particle energization at interplanetary shocks. Our experimental results, together with the results of recent Vlasov [Petkaki and Freeman, 2008] and PIC [Matsukyo and Scholer, 2006] simulations using realistic mass ratios provide new evidence to suggest that the importance of wave-particle dissipation at shocks may be greater than previously thought.

Electrostatic wave heating and possible formation of self-generated high electric fields in a magnetized plasma

NASA Astrophysics Data System (ADS)

Mascali, D.; Celona, L.; Gammino, S.; Miracoli, R.; Castro, G.; Gambino, N.; Ciavola, G.

2011-10-01

A plasma reactor operates at the Laboratori Nazionali del Sud of INFN, Catania, and it has been used as a test-bench for the investigation of innovative mechanisms of plasma ignition based on electrostatic waves (ES-W), obtained via the inner plasma EM-to-ES wave conversion. Evidences of Bernstein wave (BW) generation will be shown. The Langmuir probe measurements have revealed a strong increase of the ion saturation current, where the BW are generated or absorbed, this being a signature of possible high energy ion flows. The results are interpreted through the Bernstein wave heating theory, which predicts the formation of high speed rotating layers of the plasma (a dense plasma ring is in fact observed). High intensity inner plasma self-generated electric fields (on the order of several tens of kV/cm) come out by our calculations.

On S.N. Bernstein's derivation of Mendel's Law and 'rediscovery' of the Hardy-Weinberg distribution.

PubMed

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.

Ion Bernstein instability as a possible source for oxygen ion cyclotron harmonic waves

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Denton, Richard E.; Liu, Kaijun; Gary, S. Peter; Spence, Harlan E.

2017-05-01

This paper demonstrates that an ion Bernstein instability can be a possible source for recently reported electromagnetic waves with frequencies at or near the singly ionized oxygen ion cyclotron frequency, ΩO+, and its harmonics. The particle measurements during strong wave activity revealed a relatively high concentration of oxygen ions (˜15%) whose phase space density exhibits a local peak at energy ˜20 keV. Given that the electron plasma-to-cyclotron frequency ratio is ωpe/Ωe≳1, this energy corresponds to the particle speed v/vA≳0.3, where vA is the oxygen Alfvén speed. Using the observational key plasma parameters, a simplified ion velocity distribution is constructed, where the local peak in the oxygen ion velocity distribution is represented by an isotropic shell distribution. Kinetic linear dispersion theory then predicts unstable Bernstein modes at or near the harmonics of ΩO+ and at propagation quasi-perpendicular to the background magnetic field, B0. If the cold ions are mostly protons, these unstable modes are characterized by a low compressibility (|δB∥|2/|δB|2≲0.01), a small phase speed (vph˜0.2vA), a relatively small ratio of the electric field energy to the magnetic field energy (between 10-4 and 10-3), and the Poynting vector directed almost parallel to B0. These linear properties are overall in good agreement with the properties of the observed waves. We demonstrate that superposition of the predicted unstable Bernstein modes at quasi-perpendicular propagation can produce the observed polarization properties, including the minimum variance direction on average almost parallel to B0.

Novel Reactor Relevant RF Actuator Schemes for the Lower Hybrid and the Ion Cyclotron Range of Frequencies

NASA Astrophysics Data System (ADS)

Bonoli, Paul

2014-10-01

This paper presents a fresh physics perspective on the onerous problem of coupling and successfully utilizing ion cyclotron range of frequencies (ICRF) and lower hybrid range of frequencies (LHRF) actuators in the harsh environment of a nuclear fusion reactor. The ICRF and LH launchers are essentially first wall components in a fusion reactor and as such will be subjected to high heat fluxes. The high field side (HFS) of the plasma offers a region of reduced heat flux together with a quiescent scrape off layer (SOL). Placement of the ICRF and LHRF launchers on the tokamak HFS also offers distinct physics advantages: The higher toroidal magnetic field makes it possible to couple faster phase velocity LH waves that can penetrate farther into the plasma core and be absorbed by higher energy electrons, thereby increasing the current drive efficiency. In addition, re-location of the LH launcher off the mid-plane (i.e., poloidal ``steering'') allows further control of the deposition location. Also ICRF waves coupled from the HFS couple strongly to mode converted ion Bernstein waves and ion cyclotron waves waves as the minority density is increased, thus opening the possibility of using this scheme for flow drive and pressure control. Finally the quiescent nature of the HFS scrape off layer should minimize the effects of RF wave scattering from density fluctuations. Ray tracing / Fokker Planck simulations will be presented for LHRF applications in devices such as the proposed Advanced Divertor Experiment (ADX) and extending to ITER and beyond. Full-wave simulations will also be presented which demonstrate the possible combinations of electron and ion heating via ICRF mode conversion. Work supported by the US DoE under Contract Numbers DE-FC02-01ER54648 and DE-FC02-99ER54512.

On the multistream approach of relativistic Weibel instability. II. Bernstein-Greene-Kruskal-type waves in magnetic trapping

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

Ghizzo, A.

2013-08-15

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.

Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1

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

Ono, Masayuki

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 T{sub i} {approx} 1/40 eV. Taking advantage of the relatively high field and long device length ofmore » 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.« less

Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1

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

Ono, Masayuki.

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 T[sub i] [approx] 1/40 eV. Taking advantage of the relatively high field and long device length ofmore » 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.« less

Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

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

Arefiev, A. V.; Dodin, I. Y.; Kohn, A.

Spherical tokamak plasmas are typically overdense and thus inaccessible to externally-injected microwaves in the electron cyclotron range. The electrostatic electron Bernstein wave (EBW), however, provides a method to access the plasma core for heating and diagnostic purposes. Understanding the details of the coupling process to electromagnetic waves is thus important both for the interpretation of microwave diagnostic data and for assessing the feasibility of EBW heating and current drive. While the coupling is reasonably well–understood in the linear regime, nonlinear physics arising from high input power has not been previously quantified. To tackle this problem, we have performed one- andmore » two-dimensional fully kinetic particle-in-cell simulations of the two possible coupling mechanisms, namely X-B and O-X-B mode conversion. We find that the ion dynamics has a profound effect on the field structure in the nonlinear regime, as high amplitude short-scale oscillations of the longitudinal electric field are excited in the region below the high-density cut-off prior to the arrival of the EBW. We identify this effect as the instability of the X wave with respect to resonant scattering into an EBW and a lower-hybrid wave. Finally, we calculate the instability rate analytically and find this basic theory to be in reasonable agreement with our simulation results.« less

Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

DOE PAGES

Arefiev, A. V.; Dodin, I. Y.; Kohn, A.; ...

2017-08-09

Spherical tokamak plasmas are typically overdense and thus inaccessible to externally-injected microwaves in the electron cyclotron range. The electrostatic electron Bernstein wave (EBW), however, provides a method to access the plasma core for heating and diagnostic purposes. Understanding the details of the coupling process to electromagnetic waves is thus important both for the interpretation of microwave diagnostic data and for assessing the feasibility of EBW heating and current drive. While the coupling is reasonably well–understood in the linear regime, nonlinear physics arising from high input power has not been previously quantified. To tackle this problem, we have performed one- andmore » two-dimensional fully kinetic particle-in-cell simulations of the two possible coupling mechanisms, namely X-B and O-X-B mode conversion. We find that the ion dynamics has a profound effect on the field structure in the nonlinear regime, as high amplitude short-scale oscillations of the longitudinal electric field are excited in the region below the high-density cut-off prior to the arrival of the EBW. We identify this effect as the instability of the X wave with respect to resonant scattering into an EBW and a lower-hybrid wave. Finally, we calculate the instability rate analytically and find this basic theory to be in reasonable agreement with our simulation results.« less

Two Contemporary Problems in Magnetized Plasmas: The ion-ion hybrid resonator and MHD stability in a snowflake divertor

NASA Astrophysics Data System (ADS)

Farmer, William Anthony

The first part of the dissertation investigates the effects of multiple-ions on the propagation of shear Alfven waves. It is shown that the presence of a second ion-species allows for the formation of an ion-ion hybrid resonator in the presence of a magnetic well. A full-wave description is shown to explain the measured eigenfrequencies and spatial form of the resonator modes identified in experiments in the Large Plasma Device (LAPD) at UCLA. However, it is determined that neither electron collisions or radial convection of the mode due to coupling to either the compressional or ion-Bernstein wave can explain the observed dissipation. Ray tracing studies for shear Alfven waves are performed in various magnetic geometries of contemporary interest. In a tokamak, it is found that the hybrid resonator can exist in the cold-plasma regime, but that ion-temperature effects combined with curvature effects cause the wave reflection point to shift towards the cyclotron frequency of the heavier ion. A one-dimensional WKB model is applied to a tokamak geometry for conditions corresponding to a burning fusion plasma to characterize the resonator. Instability due to fusion-born alpha particles is assessed. An approximate form of the global eigenmode is considered. It is identified that magnetic field shear combined with large ion temperature can cause coupling to an ion-Bernstein wave, which can limit the instability. Finally, the radiation pattern of shear Alfven waves generated by a burst of charged particles in the presence of two-ion species is considered. The spectral content and spatial patterns of the radiated waves are determined. The second part of the dissertation considers the MHD stability of the plasma near a divertor in a tokamak. Two types of modes are considered: a ballooning mode and an axisymmetric, quasi-flute mode. Instability thresholds are derived for both modes and numerically evaluated for parameters relevant to recent experiments. This is done to determine whether these modes could be responsible for convection of the plasma in the vicinity of the poloidal null point. It is determined that MHD instability about a standard equilibrium is unlikely to explain the experimental results observed on the tokamak, TCV [Reimerdes et al., Plasma Phys. Contr. Fusion 55, 124027 (2013)]. From these results, it is concluded that the most likely explanation for the discrepancy is that the underlying equilibrium assumed in the calculation does not contain all the complexities present in the experiments.

Electrostatic odd symmetric eigenmode in inhomogeneous Bernstein-Greene-Kruskal equilibrium

NASA Astrophysics Data System (ADS)

Woo, M.-H.; Dokgo, K.; Yoon, Peter H.; Lee, D.-Y.; Choi, Cheong R.

2018-04-01

A self-consistent electrostatic odd-symmetric eigenmode (OEM) is analytically found in a solitary type Bernstein-Greene-Kruskal (BGK) equilibrium. The frequency of the OEM is order of the electron bounce frequency and it is spatially odd-symmetric with the scale comparable to that of the solitary BGK equilibrium structure. Such an OEM is consistent with the recent observation from particle-in-cell simulation of the solitary wave [Dokgo et al., Phys. Plasmas 23, 092107 (2016)]. The mode can be driven unstable by trapped electrons within the hole structure of the solitary wave. Such a low frequency, pure electron mode, which may possibly interact resonantly with the ion acoustic mode, provides a possible damping mechanism of the BGK equilibrium.

Comparison between off-resonance and electron Bernstein waves heating regime in a microwave discharge ion source

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

Castro, G.; Di Giugno, R.; Miracoli, R.

2012-02-15

A microwave discharge ion source (MDIS) operating at the Laboratori Nazionali del Sud of INFN, Catania has been used to compare the traditional electron cyclotron resonance (ECR) heating with an innovative mechanisms of plasma ignition based on the electrostatic Bernstein waves (EBW). EBW are obtained via the inner plasma electromagnetic-to-electrostatic wave conversion and they are absorbed by the plasma at cyclotron resonance harmonics. The heating of plasma by means of EBW at particular frequencies enabled us to reach densities much larger than the cutoff ones. Evidences of EBW generation and absorption together with X-ray emissions due to high energy electronsmore » will be shown. A characterization of the discharge heating process in MDISs as a generalization of the ECR heating mechanism by means of ray tracing will be shown in order to highlight the fundamental physical differences between ECR and EBW heating.« less

On S.N. Bernstein’s derivation of Mendel’s Law and ‘rediscovery’ of the Hardy-Weinberg distribution

PubMed Central

Stark, Alan; Seneta, Eugene

2012-01-01

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

ITER Plasma at Ion Cyclotron Frequency Domain: The Fusion Alpha Particles Diagnostics Based on the Stimulated Raman Scattering of Fast Magnetosonic Wave off High Harmonic Ion Bernstein Modes

NASA Astrophysics Data System (ADS)

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.

Theory of ion Bernstein wave induced shear suppression of turbulence

NASA Astrophysics Data System (ADS)

Craddock, G. G.; Diamond, P. H.; Ono, M.; Biglari, H.

1994-06-01

The theory of radio frequency induced ion Bernstein wave- (IBW) driven shear flow in the edge is examined, with the goal of application of shear suppression of fluctuations. This work is motivated by the observed confinement improvement on IBW heated tokamaks [Phys. Fluids B 5, 241 (1993)], and by previous low-frequency work on RF-driven shear flows [Phys. Rev. Lett. 67, 1535 (1991)]. It is found that the poloidal shear flow is driven electrostatically by both Reynolds stress and a direct ion momentum source, analogous to the concepts of helicity injection and electron momentum input in current drive, respectively. Flow drive by the former does not necessarily require momentum input to the plasma to induce a shear flow. For IBW, the direct ion momentum can be represented by direct electron momentum input, and a charge separation induced stress that imparts little momentum to the plasma. The derived Er profile due to IBW predominantly points inward, with little possibility of direction change, unlike low-frequency Alfvénic RF drive. The profile scale is set by the edge density gradient and electron dissipation. Due to the electrostatic nature of ion Bernstein waves, the poloidal flow contribution dominates in Er. Finally, the necessary edge power absorbed for shear suppression on Princeton Beta Experiment-Modified (PBX-M) [9th Topical Conference on Radio Frequency Power in Plasmas, Charleston, SC, 1991 (American Institute of Physics, New York, 1991), p. 129] is estimated to be 100 kW distributed over 5 cm.

Design of an RF System for Electron Bernstein Wave Studies in MST

NASA Astrophysics Data System (ADS)

Kauffold, J. X.; Seltzman, A. H.; Anderson, J. K.; Nonn, P. D.; Forest, C. B.

2010-11-01

Motivated by the possibility of current profile control a 5.5GHz RF system for EBW is being developed. The central component is a standard radar Klystron with 1.2MW peak power and 4μs typical pulse length. Meaningful experiments require RF pulse lengths similar to the characteristic electron confinement times in MST necessitating the creation of a power supply providing 80kV at 40A for 10ms. A low inductance IGBT network switches power at 20kHz from an electrolytic capacitor bank into the primary of a three-phase resonant transformer system that is then rectified and filtered. The system uses three magnetically separate transformers with microcrystalline iron cores to provide suitable volt-seconds and low hysteresis losses. Each phase has a secondary with a large leakage inductance and a parallel capacitor providing a boost ratio greater than 60:1 with a physical turns ratio of 13.5:1. A microprocessor feedback control system varies the drive frequency around resonance to regulate the boost ratio and provide a stable output as the storage bank discharges. The completed system will deliver RF to the plasma boundary where coupling to the Bernstein mode and subsequent heating and current drive can occur.

Bernstein modes in a non-neutral plasma column

NASA Astrophysics Data System (ADS)

Walsh, Daniel; Dubin, Daniel H. E.

2018-05-01

This paper presents theory and numerical calculations of electrostatic Bernstein modes in an inhomogeneous cylindrical plasma column. These modes rely on finite Larmor radius effects to propagate radially across the column until they are reflected when their frequency matches the upper hybrid frequency. This reflection sets up an internal normal mode on the column and also mode-couples to the electrostatic surface cyclotron wave (which allows the normal mode to be excited and observed using external electrodes). Numerical results predicting the mode spectra, using a novel linear Vlasov code on a cylindrical grid, are presented and compared to an analytical Wentzel Kramers Brillouin (WKB) theory. A previous version of the theory [D. H. E. Dubin, Phys. Plasmas 20(4), 042120 (2013)] expanded the plasma response in powers of 1/B, approximating the local upper hybrid frequency, and consequently, its frequency predictions are spuriously shifted with respect to the numerical results presented here. A new version of the WKB theory avoids this approximation using the exact cold fluid plasma response and does a better job of reproducing the numerical frequency spectrum. The effect of multiple ion species on the mode spectrum is also considered, to make contact with experiments that observe cyclotron modes in a multi-species pure ion plasma [M. Affolter et al., Phys. Plasmas 22(5), 055701 (2015)].

Electron Bernstein Wave Research on NSTX and CDX-U

NASA Astrophysics Data System (ADS)

Taylor, G.; Efthimion, P. C.; Jones, B.; Bell, G. L.; Bers, A.; Bigelow, T. S.; Carter, M. D.; Harvey, R. W.; Ram, A. K.; Rasmussen, D. A.; Smirnov, A. P.; Wilgen, J. B.; Wilson, J. R.

2003-12-01

Studies of thermally emitted electron Bernstein waves (EBWs) on CDX-U and NSTX, via mode conversion (MC) to electromagnetic radiation, support the use of EBWs to measure the Te profile and provide local electron heating and current drive (CD) in overdense spherical torus plasmas. An X-mode antenna with radially adjustable limiters successfully controlled EBW MC on CDX-U and enhanced MC efficiency to ˜ 100%. So far the X-mode MC efficiency on NSTX has been increased by a similar technique to 40-50% and future experiments are focused on achieving ⩾ 80% MC. MC efficiencies on both machines agree well with theoretical predictions. Ray tracing and Fokker-Planck modeling for NSTX equilibria are being conducted to support the design of a 3 MW, 15 GHz EBW heating and CD system for NSTX to assist non-inductive plasma startup, current ramp up, and to provide local electron heating and CD in high β NSTX plasmas.

X-ray analysis of electron Bernstein wave heating in MST

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

Seltzman, A. H., E-mail: seltzman@wisc.edu; Anderson, J. K.; DuBois, A. M.

2016-11-15

A pulse height analyzing x-ray tomography system has been developed to detect x-rays from electron Bernstein wave heated electrons in the Madison symmetric torus reversed field pinch (RFP). Cadmium zinc telluride detectors are arranged in a parallel beam array with two orthogonal multi-chord detectors that may be used for tomography. In addition a repositionable 16 channel fan beam camera with a 55° field of view is used to augment data collected with the Hard X-ray array. The chord integrated signals identify target emission from RF heated electrons striking a limiter located 12° toroidally away from the RF injection port. Thismore » provides information on heated electron spectrum, transport, and diffusion. RF induced x-ray emission from absorption on harmonic electron cyclotron resonances in low current (<250 kA) RFP discharges has been observed.« less

Ion Bernstein instability dependence on the proton-to-electron mass ratio: Linear dispersion theory

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun

2016-07-01

Fast magnetosonic waves, which have as their source ion Bernstein instabilities driven by tenuous ring-like proton velocity distributions, are frequently observed in the inner magnetosphere. One major difficulty in the simulation of these waves is that they are excited in a wide frequency range with discrete harmonic nature and require time-consuming computations. To overcome this difficulty, recent simulation studies assumed a reduced proton-to-electron mass ratio, mp/me, and a reduced light-to-Alfvén speed ratio, c/vA, to reduce the number of unstable modes and, therefore, computational costs. Although these studies argued that the physics of wave-particle interactions would essentially remain the same, detailed investigation of the effect of this reduced system on the excited waves has not been done. In this study, we investigate how the complex frequency, ω = ωr+iγ, of the ion Bernstein modes varies with mp/me for a sufficiently large c/vA (such that ωpe2/Ωe2≡(me/mp)(c/vA)2≫1) using linear dispersion theory assuming two different types of energetic proton velocity distributions, namely, ring and shell. The results show that low- and high-frequency harmonic modes respond differently to the change of mp/me. For the low harmonic modes (i.e., ωr˜Ωp), both ωr/Ωp and γ/Ωp are roughly independent of mp/me, where Ωp is the proton cyclotron frequency. For the high harmonic modes (i.e., Ωp≪ωr≲ωlh, where ωlh is the lower hybrid frequency), γ/ωlh (at fixed ωr/ωlh) stays independent of mp/me when the parallel wave number, k∥, is sufficiently large and becomes inversely proportional to (mp/me)1/4 when k∥ goes to zero. On the other hand, the frequency range of the unstable modes normalized to ωlh remains independent of mp/me, regardless of k∥.

Kinetic scale structure of low-frequency waves and fluctuations

NASA Astrophysics Data System (ADS)

Lopez Herrera, R. A.; Figueroa-Vinas, A.; Araneda, J. A.; Yoon, P. H.

2017-12-01

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

Simulation of mode converted ion Bernstein wave - beam deuteron interactions on TFTR

NASA Astrophysics Data System (ADS)

Herrmann, Mark; Fisch, Nathaniel

1998-11-01

Experiments on TFTR have documented strong interactions between mode converted ion Bernstein waves (MCIBW) and beam deuterons(D. S. Darrow et al.), Nucl. Fusion 36, 509 (1996).^,(N. J. Fisch et al.), IAEA, Vol. 1, p. 271 (1996). This is of particular interest in the study of α channelling, since the most promising scenarios(M. C. Herrmann and N. J. Fisch, Phys. Rev. Lett. 79), 1495 (1997). rely on a suitable combination of MCIBW and Alfvén eigenmodes to achieve the cooling of the α particles. Collisional effects, realistic wave fields, and a detailed model of the wave-particle interaction have been added to the Monte Carlo simulations which are used to simulate α channelling in order to model TFTR experiments(M. C. Herrmann, Ph.D. thesis, Princeton University, 1998.). The results are found to be in qualitative agreement with the data. In addition, the simulation is used, in conjunction with the data, to demonstrate the existence of the k_\\|-flip of the MCIBW, and to infer a diffusion coefficient for the beam deuterons interacting with the wave. This diffusion coefficient significantly exceeds what would be expected on the basis of quasilinear theory with the fields specified by 1 D ray tracing of the MCIBW.

Parametric decay of plasma waves near the upper-hybrid resonance

DOE PAGES

Dodin, I. Y.; Arefiev, A. V.

2017-03-28

An intense X wave propagating perpendicularly to dc magnetic field is unstable with respect to a parametric decay into an electron Bernstein wave and a lower-hybrid wave. A modified theory of this effect is proposed that extends to the high-intensity regime, where the instability rate γ ceases to be a linear function of the incident-wave amplitude. An explicit formula for γ is derived and expressed in terms of cold-plasma parameters. Here, theory predictions are in reasonable agreement with the results of the particle-in-cell simulations presented in a separate publication.

Averaged variational principle for autoresonant Bernstein-Greene-Kruskal modes

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

Khain, P.; Friedland, L.

2010-10-15

Whitham's averaged variational principle is applied in studying dynamics of formation of autoresonant (continuously phase-locked) Bernstein-Greene-Kruskal (BGK) modes in a plasma driven by a chirped frequency ponderomotive wave. A flat-top electron velocity distribution is used as a model allowing a variational formulation within the water bag theory. The corresponding Lagrangian, averaged over the fast phase variable yields evolution equations for the slow field variables, allows uniform description of all stages of excitation of driven-chirped BGK modes, and predicts modulational stability of these nonlinear phase-space structures. Numerical solutions of the system of slow variational equations are in good agreement with Vlasov-Poissonmore » simulations.« less

Stimulated Brillouin scatter and stimulated ion Bernstein scatter during electron gyroharmonic heating experiments

NASA Astrophysics Data System (ADS)

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.

Impurity behavior during ion-Bernstein wave heating in PBX-M

NASA Astrophysics Data System (ADS)

Isler, R. C.; Post-Zwicker, A. P.; Paul, S. F.; Tighe, W.; Ono, M.; Leblanc, B. P.; Bell, R.; Kugel, H. W.; Kaita, R.

1994-07-01

Ion-Bernstein-wave heating (IBWH) has been tested in several tokamaks. In some cases the results have been quite positive, producing temperature increases and also improving both energy and particle confinement times, whereas in others, no distinctive changes were observed. Most recently, IBWH has been utilized in the Princeton Beta Experiment-Modified (PBX-M) where the long-range goal is the achievement of operation in the second stable region by current and pressure profile control. Investigations have been performed in this machine using IBWH as the sole source of auxiliary power or using IBWH in conjunction with neutral-beam injection (NBI) or with lower-hybrid current drive (LHCD). Impurity studies seem particularly important for IBWH since not only have influxes often been observed to increase, but the global impurity confinement time has also been shown to lengthen as the confinement of the working gas improved. The authors present here a set of characteristic experimental results regarding the impurity behavior in PBX-M; in general, these are consonant with previous observations in other tokamaks.

Proton velocity ring-driven instabilities and their dependence on the ring speed: Linear theory

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun; Gary, S. Peter

2017-08-01

Linear dispersion theory is used to study the Alfvén-cyclotron, mirror and ion Bernstein instabilities driven by a tenuous (1%) warm proton ring velocity distribution with a ring speed, vr, varying between 2vA and 10vA, where vA is the Alfvén speed. Relatively cool background protons and electrons are assumed. The modeled ring velocity distributions are unstable to both the Alfvén-cyclotron and ion Bernstein instabilities whose maximum growth rates are roughly a linear function of the ring speed. The mirror mode, which has real frequency ωr=0, becomes the fastest growing mode for sufficiently large vr/vA. The mirror and Bernstein instabilities have maximum growth at propagation oblique to the background magnetic field and become more field-aligned with an increasing ring speed. Considering its largest growth rate, the mirror mode, in addition to the Alfvén-cyclotron mode, can cause pitch angle diffusion of the ring protons when the ring speed becomes sufficiently large. Moreover, because the parallel phase speed, v∥ph, becomes sufficiently small relative to vr, the low-frequency Bernstein waves can also aid the pitch angle scattering of the ring protons for large vr. Potential implications of including these two instabilities at oblique propagation on heliospheric pickup ion dynamics are discussed.

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

Simulation of linear and nonlinear Landau damping of lower hybrid waves

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

Qi, Lei; Wang, X. Y.; Lin, Y.

2013-06-15

The linear physics of lower hybrid waves (LHWs) and their nonlinear interaction with particles through Landau damping are studied with the gyrokinetic electron and fully kinetic ion (GeFi) particle simulation model in the electrostatic limit. Unlike most other wave modes, the LHWs can resonantly interact with both electrons and ions, with the former being highly magnetized and latter nearly unmagnetized around the lower hybrid frequency. Direct interactions of LHWs with electrons and/or ions are investigated for cases with various k{sub ∥}/k,T{sub i}/T{sub e}, and wave amplitudes. In the linear electron Landau damping (ELD), the dispersion relation and the linear dampingmore » rate obtained from our simulation agree well with the analytical linear theory. As the wave amplitude increases, the nonlinear Landau effects are present, and a transition from strong decay at smaller amplitudes to weak decay at larger amplitudes is observed. In the nonlinear stage, the LHWs in the long time evolution finally exhibit a steady Bernstein-Greene-Kruskal mode, in which the wave amplitude is saturated above the noise level. While the resonant electrons are trapped in the wave field in the nonlinear ELD, the resonant ions are untrapped in the LHW time scales. The ion Landau damping is thus predominantly in a linear fashion, leading to a wave saturation level significantly lower than that in the ELD. On the long time scales, however, the ions are still weakly trapped. The results show a coupling between the LHW frequency and the ion cyclotron frequency during the long-time LHW evolution.« less

Kinetic Scale Structure of Low-frequency Waves and Fluctuations

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

López, Rodrigo A.; Yoon, Peter H.; Viñas, Adolfo F.

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

Mode conversion and heating in a UCLA-high schools collaborative experiment

NASA Astrophysics Data System (ADS)

Smith, Miana; Buckley-Bonnano, Samuel; Pribyl, Patrick; Gekelman, Walter; Wise, Joe; Baker, Bob; Marmie, Ken

2016-10-01

A small plasma device is in operation for use by undergraduates and high school students at UCLA. Magnetic field up to 100 G, with density 108 <=ne <=1011cm-3 and temperature Te < 3eV are available in a 50 cm diameter plasma 2 meters long. The plasma is generated by an ICP source at one end operating at about 500 kHz. For this experiment, a small plate located near the edge of the plasma column is used as an electrostatic launcher. High frequency waves ωce < ω < 3ωce are launched radially from the plate in the low-density region, with electric field perpendicular to B and to the density gradient. A Langmuir probe located some distance away axially measures plasma heating along a field line that passes several cm in front of the launcher, localized in radius with δr 1cm Absorption and strong electron heating are observed at the plasma resonant layer. We explore the ``double resonance condition at which ωpe = 2ωce . Here strong interaction with electron Bernstein waves is expected. The Bernstein waves are also launched at low power and their dispersion relation verified. Work done at the BaPSF at UCLA which is supported by the DOE/NSF.

Observation of Electron Bernstein Wave Heating in the RFP

NASA Astrophysics Data System (ADS)

Seltzman, Andrew; Anderson, Jay; Goetz, John; Forest, Cary

2017-10-01

The first observation of RF heating in a reversed field pinch (RFP) using the electron Bernstein wave (EBW) has been demonstrated on MST. Efficient mode conversion of an outboard-launched X mode wave at 5.5 GHz leads to Doppler-shifted resonant absorption (ωrf = nωce-k||v||) for a broad range (n =1-7) of harmonics. The dynamics of EBW-heated electrons are measured using a spatial distribution of solid targets with diametrically opposed x-ray detectors. EBW heating produces a clear supra-thermal electron tail in MST. Radial deposition of the EBW is controlled with |B|and is measured using the HXR flux emitted from an insertable probe. In the thick-shelled MST RFP, the radial accessibility of EBW is limited to r/a >0.8 ( 10cm) by magnetic field error induced by the porthole necessary for the antenna. Experimental measurements show EBW propagation inward through a stochastic magnetic field. EBW-heated test electrons are used as a direct probe of edge (r/a >0.9) radial transport, showing a modest transition from `standard' to reduced-tearing RFP operation. Electron loss is too fast for collisional effects and implies a large non-collisional radial diffusivity. EBW heating has been demonstrated in reduced magnetic stochasticity plasmas with β = 15-20%. Work supported by USDOE.

On a new scenario for the saturation of the low-threshold two-plasmon parametric decay instability of an extraordinary wave in the inhomogeneous plasma of magnetic traps

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

Gusakov, E. Z., E-mail: Evgeniy.Gusakov@mail.ioffe.ru; Popov, A. Yu., E-mail: a.popov@mail.ioffe.ru; Irzak, M. A., E-mail: irzak@mail.ioffe.ru

The most probable scenario for the saturation of the low-threshold two-plasmon parametric decay instability of an electron cyclotron extraordinary wave has been analyzed. Within this scenario two upperhybrid plasmons at frequencies close to half the pump wave frequency radially trapped in the vicinity of the local maximum of the plasma density profile are excited due to the excitation of primary instability. The primary instability saturation results from the decays of the daughter upper-hybrid waves into secondary upperhybrid waves that are also radially trapped in the vicinity of the local maximum of the plasma density profile and ion Bernstein waves.

Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas

NASA Astrophysics Data System (ADS)

Hansen, S. K.; Nielsen, S. K.; Salewski, M.; Stejner, M.; Stober, J.; the ASDEX Upgrade Team

2017-10-01

In this paper we investigate parametric decay of an electromagnetic pump wave into two electrostatic daughter waves, particularly an X-mode pump wave decaying into a warm upper hybrid wave (a limit of an electron Bernstein wave) and a warm lower hybrid wave. We describe the general theory of the above parametric decay instability (PDI), unifying earlier treatments, and show that it may occur in underdense and weakly overdense plasmas. The PDI theory is used to explain anomalous sidebands observed in collective Thomson scattering (CTS) spectra at the ASDEX Upgrade tokamak. The theory may also account for similar observations during CTS experiments in stellarators, as well as in some 1st harmonic electron cyclotron resonance and O-X-B heating experiments.

Basil Bernstein: Agency, Structure and Linguistic Conception of Class

ERIC Educational Resources Information Center

Best, Shaun

2007-01-01

The paper outlines an interpretation of Bernstein's contribution to the sociology of education that stands in contrast to the common interpretations of Bernstein's work. It is commonly assumed that Bernstein constructed a simplistic "deficit model" of educational failure, or alternatively, that Bernstein was a structuralist who did not give any…

Generation of Langmuir wave supercontinuum by phase-preserving equilibration of plasmons with irreversible wave-particle interaction

NASA Astrophysics Data System (ADS)

Eiichirou, Kawamori

2018-04-01

We report the observation of supercontinuum of Langmuir plasma waves, that exhibits broad power spectrum having significant spatio-temporal coherence grown from a monochromatic seed-wave, in one-dimensional particle-in-cell simulations. The Langmuir wave supercontinuum (LWSC) is formed when the seed wave excites side-band fields efficiently by the modulational instabilities. Its identification is achieved by the use of the tricoherence analysis, which detects four wave mixings (FWMs) of plasmons (plasma wave quanta), and evaluation of the first order coherence, which is a measure of temporal coherence, of the wave electric fields. The irreversible evolution to the coherent LWSC from the seed wave is realized by the wave-particle interactions causing stochastic electron motions in the phase space and the coherence of LWSC is maintained by the phase-preserving FWMs of plasmons. The LWSC corresponds to a quasi Bernstein-Greene-Kruskal mode.

Electromagnetic radiation by parametric decay of upper hybrid waves in ionospheric modification experiments

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

Leyser, T.B.

1994-06-01

A nonlinear dispersion relation for the parametric decay of an electrostatic upper hybrid wave into an ordinary mode electromagnetic wave, propagating parallel to the ambient magnetic field, and an electrostatic low frequency wave, being either a lower hybrid wave or a high harmonic ion Bernstein wave, is derived. The coherent and resonant wave interaction is considered to take place in a weakly magnetized and collisionless Vlasov plasma. The instability growth rate is computed for parameter values typical of ionospheric modification experiments, in which a powerful high frequency electromagnetic pump wave is injected into the ionospheric F-region from ground-based transmitters. Themore » electromagnetic radiation which is excited by the decaying upper hybrid wave is found to be consistent with the prominent and commonly observed downshifted maximum (DM) emission in the spectrum of stimulated electromagnetic emission.« less

Generation of cyclotron harmonic waves in the ionospheric modification experiments

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

Janabi, A.H.A.; Kumar, A.; Sharma, R.P.

1994-02-01

In the present paper, the parametric decay instability of the pump X-mode into electron Bernstein wave (EBW) near second harmonics of electron cyclotron frequency and IBW at different harmonics ([omega] < n[omega][sub ci];n = 2, 3, 4) is examined. Expressions are derived for homogeneous threshold, growth rate and convective threshold for this instability. Applications and relevances of the present investigation to ionospheric modification experiment in the F-layer of the ionosphere as well as during intense electron cyclotron resonance heating in the upcoming MTX tokamak have been given.

Active core profile and transport modification by application of ion Bernstein wave power in the Princeton Beta Experiment-Modification

NASA Astrophysics Data System (ADS)

LeBlanc, B.; Batha, S.; Bell, R.; Bernabei, S.; Blush, L.; de la Luna, E.; Doerner, R.; Dunlap, J.; England, A.; Garcia, I.; Ignat, D.; Isler, R.; Jones, S.; Kaita, R.; Kaye, S.; Kugel, H.; Levinton, F.; Luckhardt, S.; Mutoh, T.; Okabayashi, M.; Ono, M.; Paoletti, F.; Paul, S.; Petravich, G.; Post-Zwicker, A.; Sauthoff, N.; Schmitz, L.; Sesnic, S.; Takahashi, H.; Talvard, M.; Tighe, W.; Tynan, G.; von Goeler, S.; Woskov, P.; Zolfaghari, A.

1995-03-01

Application of Ion Bernstein Wave Heating (IBWH) into the Princeton Beta Experiment-Modification (PBX-M) [Phys. Fluids B 2, 1271 (1990)] 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 ∇ne, ∇Te, ∇νφ, and ∇Ti, delimiting the confinement zone. This regime is reminiscent of the H(high) mode, but with a confinement zone moved inward. The core region has better than H-mode confinement while the peripheral region is L(low)-mode-like. The peaked profile enhances NBI core deposition and increases nuclear reactivity. An increase in central Ti results from χi reduction (compared to the 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.

Particle-in-cell Simulations of Waves in a Plasma Described by Kappa Velocity Distribution as Observed in the Saturńs Magnetosphere

NASA Astrophysics Data System (ADS)

Alves, M. V.; Barbosa, M. V. G.; Simoes, F. J. L., Jr.

2016-12-01

Observations have shown that several regions in space plasmas exhibit non-Maxwellian distributions with high energy superthermal tails. Kappa velocity distribution functions can describe many of these regions and have been used since the 60's. They suit well to represent superthermal tails in solar wind as well as to obtain plasma parameters of plasma within planetary magnetospheres. A set of initial velocities following kappa distribution functions is used in KEMPO1 particle simulation code to analyze the normal modes of wave propagation. Initial conditions are determined using observed characteristics for Saturńs magnetosphere. Two electron species with different temperatures and densities and ions as a third species are used. Each electron population is described by a different kappa index. Particular attention is given to perpendicular propagation, Bernstein modes, and parallel propagation, Langmuir and electron-acoustic modes. The dispersion relation for the Bernstein modes is strongly influenced by the shape of the velocity distribution and consequently by the value of kappa index. Simulation results are compared with numerical solutions of the dispersion relation obtained in the literature and they are in good agreement.

Observation of Electron Bernstein Wave Heating in the MST Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Seltzman, Andrew; Anderson, Jay; Dubois, Ami; Almagri, Abdulgader; Nonn, Paul; McCollam, Karsten; Chapman, Brett; Goetz, John; Forest, Cary

2016-10-01

We report the first observation of electron Bernstein wave heating in the MST RFP. Similar to a high density stellarator, the RFP is inaccessible to electromagnetic ECRH. The plasma current and |B|operating range of MST allows a 5.5 GHz RF source (100kW, 4ms pulse) to heat on the fundamental and up to 4th harmonic EC resonances. With an x-ray diagnostic most sensitive to edge electrons located +12 degrees toroidally from the antenna, the measured emission is a strong function of predicted heating inside versus outside the Bt =0 reversal layer of the RFP. Measured during a scan of plasma current, distinct edges in a plot of emissivity versus predicted deposition layer align with the deposition layers crossing of this reversal layer and confirm EBW heating on the fundamental through 4th EC harmonic. Additional confirmation of the absorption location has been demonstrated by using auxiliary poloidal current drive to reduce electron diffusion rates and sweep the location of the Bt =0 surface across a static RF absorption location in RFP discharges. In these discharges EBW enhancement of the 15-40keV x-ray energies has been observed. Work supported by USDOE.

On the Relevance of Bernstein for German-Speaking Switzerland

ERIC Educational Resources Information Center

Bolander, Brook

2009-01-01

This article assesses the relevance of Basil Bernstein for German-speaking Switzerland. It argues that Bernstein is potentially relevant for German-speaking Switzerland in light of contemporary studies which highlight a connection between social background and differential school achievement. After contextualising Bernstein's theoretical outlook…

SEE Observations of Ionospheric Heating from HAARP Using Orbital Angular Momentum

NASA Astrophysics Data System (ADS)

Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.

2013-12-01

High power HF radio waves exciting the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, providing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emission (SEE) is of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. These production modes have been extensively studied at HAARP using traditional beam heating patterns and SEE detection. New results are present from HAARP experiments using an excitation mode that attempts to impart orbital angular momentum (OAM) into the heating region. This OAM mode is also referred to as a 'twisted beam.' Previous analysis of twisted beam heating shows that the SEE results obtained are nearly identical to the modes without OAM. Recent twisted beam heating experiments have produced SEE modes not previously characterized. These new modes are presented and discussed. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional 'solid spot' region. The ring heating pattern may be more conducive to the creation of artificial ionization clouds. The results of these runs include artificial ionization creation and evolution as pertaining to the twisted beam pattern.

77 FR 75200 - AllianceBernstein Active ETFs, Inc., et al.; Notice of Application

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-19

... SECURITIES AND EXCHANGE COMMISSION [Investment Company Act Release No. 30305; 812-13797] AllianceBernstein Active ETFs, Inc., et al.; Notice of Application December 13, 2012. AGENCY: Securities and...Bernstein Active ETFs, Inc. (``Corporation''), AllianceBernstein L.P. (``Adviser''), and ALPS Distributors...

Prompt Disappearance and Emergence of Radiation Belt Magnetosonic Waves Induced by Solar Wind Dynamic Pressure Variations

NASA Astrophysics Data System (ADS)

Liu, Nigang; Su, Zhenpeng; Zheng, Huinan; Wang, Yuming; Wang, Shui

2018-01-01

Magnetosonic waves are highly oblique whistler mode emissions transferring energy from the ring current protons to the radiation belt electrons in the inner magnetosphere. Here we present the first report of prompt disappearance and emergence of magnetosonic waves induced by the solar wind dynamic pressure variations. The solar wind dynamic pressure reduction caused the magnetosphere expansion, adiabatically decelerated the ring current protons for the Bernstein mode instability, and produced the prompt disappearance of magnetosonic waves. On the contrary, because of the adiabatic acceleration of the ring current protons by the solar wind dynamic pressure enhancement, magnetosonic waves emerged suddenly. In the absence of impulsive injections of hot protons, magnetosonic waves were observable even only during the time period with the enhanced solar wind dynamic pressure. Our results demonstrate that the solar wind dynamic pressure is an essential parameter for modeling of magnetosonic waves and their effect on the radiation belt electrons.

Music on the Move: Methodological Applications of Bernstein's Concepts in a Secondary School Music Context

ERIC Educational Resources Information Center

McPhail, Graham J.

2016-01-01

In 2002 Parlo Singh outlined Bernstein's theory of the pedagogic device, elaborating the potential in Bernstein's complex theoretical framework for empirical research. In particular, Singh suggests that Bernstein's concepts provide the means of making explicit the macro and micro structuring of knowledge into pedagogic communication. More…

Survey of EBW Mode-Conversion Characteristics for Various Boundary Conditions

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

Tanaka, H.; Maekawa, T.; Igami, H.

2005-09-26

A survey of linear mode-conversion characteristics between external transverse electromagnetic (TEM) waves and electron Bernstein waves (EBW) for various plasma and wave parameters has been presented. It is shown that if the wave propagation angle and polarization are adjusted appropriately for each individual case of the plasma parameters, efficient mode conversion occur for wide range of plasma parameters where the conventional 'XB' and 'OXB' scheme cannot cover. It is confirmed that the plasma parameters just at the upper hybrid resonance (UHR) layer strongly affect the mode conversion process and the influence of the plasma profiles distant from the UHR layermore » is not so much. The results of this survey is useful enough to examine wave injection/detection condition for efficient ECH/ECCD or measurement of emissive TEM waves for each individual experimental condition of overdense plasmas.« less

Electron Bernstein Wave Studies in MST

NASA Astrophysics Data System (ADS)

Seltzman, Andrew; Anderson, Jay; Forest, Cary; Nonn, Paul; Thomas, Mark; Almagri, Abdulgader; Chapman, Brett; Dubois, Ami; Goetz, John; McCollam, Karsten

2015-11-01

The RFP plasma is inaccessible to ECRH, requiring the electron Bernstein wave (EBW) for edge localized heating and current drive. MST is capable of generating RFPs or overdense tokamaks with Bt(0) ~ 0.08-0.14T in which a 5.55 GHz RF source (450kW, 2ms pulse) can heat at fundamental and harmonic EC resonances. The design of a suitable antenna is challenging in the RFP due to a magnetic field geometry that requires a low-field-side launch. The small vacuum gap between the close-fitting conducting shell and plasma leads to substantial antenna-plasma interaction. A minimized port hole size is required to limit error fields. Even so the port hole induced magnetic field perturbation in the antenna near-field that affects the mode conversion process and introduces EC resonances. A 5cm diameter cylindrical antenna centered in 5cm and 11cm diameter portholes is used. A multi-chord time-resolved x-ray detector and GENRAY ray tracing verifies EBW heating at higher harmonics in an MST tokamak with 10-40keV detected x-ray energies. Evidence of RF-induced emission from absorption at higher harmonics (4th / 5th) in low current RFP discharges has been observed. Simultaneous reflected power changes correspond to termination of x-ray emission indicating power limits. Work supported by USDOE.

Vlasov simulations of electron acceleration by radio frequency heating near the upper hybrid layer

NASA Astrophysics Data System (ADS)

Najmi, A.; Eliasson, B.; Shao, X.; Milikh, G.; Sharma, A. S.; Papadopoulos, K.

2017-10-01

It is shown by using a combination of Vlasov and test particles simulations that the electron distribution function resulting from energization due to Upper Hybrid (UH) plasma turbulence depends critically on the closeness of the pump wave to the double resonance, defined as ω ≈ ωUH ≈ nωce, where n is an integer. For pump frequencies, away from the double resonance, the electron distribution function is very close to Maxwellian, while as the pump frequency approaches the double resonance, it develops a high energy tail. The simulations show turbulence involving coupling between Lower Hybrid (LH) and UH waves, followed by excitation of Electron Bernstein (EB) modes. For the particular case of a pump with frequency between n = 3 and n = 4, the EB modes cover the range from the first to the 5th mode. The simulations show that when the injected wave frequency is between the 3rd and 4th harmonics of the electron cyclotron frequency, bulk electron heating occurs due to the interaction between the electrons and large amplitude EB waves, primarily on the first EB branch leading to an essentially thermal distribution. On the other hand, when the frequency is slightly above the 4th electron cyclotron harmonic, the resonant interaction is predominantly due to the UH branch and leads to a further acceleration of high-velocity electrons and a distribution function with a suprathermal tail of energetic electrons. The results are consistent with ionospheric experiments and relevant to the production of Artificial Ionospheric Plasma Layers.

The very real dangers of executive coaching.

PubMed

Berglas, Steven

2002-06-01

A personal coach to help your most promising executives reach their potential--sounds good, doesn't it? But, according to Steven Berglas, executive coaches can make a bad situation worse. Because of their backgrounds and biases, they ignore psychological problems they don't understand. Companies need to consider psychotherapeutic intervention when the symptoms plaguing an executive are stubborn or severe. Executives with issues that require more than coaching come in many shapes and sizes. Consider Rob Bernstein, an executive vice president of sales at an automotive parts distributor. According to the CEO, Bernstein had just the right touch with clients but caused personnel problems inside the company. The last straw came when Bernstein publicly humiliated a mail clerk who had interrupted a meeting to ask someone to sign for a package. At that point, the CEO assigned Tom Davis to coach Bernstein. Davis, a former corporate lawyer, worked with Bernstein for four years. But Davis only exacerbated the problem by teaching Bernstein techniques for "handling" employees--methods that were condescending at best. While Bernstein appeared to be improving, he was in fact getting worse. Bernstein's real problems went undetected, and when his boss left the company, he was picked as the successor. Soon enough, Bernstein was again in trouble, suspected of embezzlement. This time, the CEO didn't call Davis; instead, he turned to the author, a trained psychotherapist, for help. Berglas soon realized that Bernstein had a serious narcissistic personality disorder and executive coaching could not help him. As that tale and others in the article teach us, executives to be coached should at the very least first receive a psychological evaluation. And company leaders should beware that executive coaches given free rein can end up wreaking personnel havoc.

On the nature of kinetic electrostatic electron nonlinear (KEEN) waves

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

Dodin, I. Y.; Fisch, N. J.

2014-03-15

An analytical theory is proposed for the kinetic electrostatic electron nonlinear (KEEN) waves originally found in simulations by Afeyan et al. [arXiv:1210.8105]. We suggest that KEEN waves represent saturated states of the negative mass instability (NMI) reported recently by Dodin et al. [Phys. Rev. Lett. 110, 215006 (2013)]. Due to the NMI, trapped electrons form macroparticles that produce field oscillations at harmonics of the bounce frequency. At large enough amplitudes, these harmonics can phase-lock to the main wave and form stable nonlinear dissipationless structures that are nonstationary but otherwise similar to Bernstein-Greene-Kruskal modes. The theory explains why the formation ofmore » KEEN modes is sensitive to the excitation scenario and yields estimates that agree with the numerical results of Afeyan et al. A new type of KEEN wave may be possible at even larger amplitudes of the driving field than those used in simulations so far.« less

Verification of nonlinear particle simulation of radio frequency waves in fusion plasmas

NASA Astrophysics Data System (ADS)

Kuley, Animesh; Bao, Jian; Lin, Zhihong

2015-11-01

Nonlinear global particle simulation model has been developed in GTC to study 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. Boris push scheme for the ion motion has been implemented in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron, ion Bernstein and lower hybrid waves. The nonlinear GTC simulation of the lower hybrid wave shows that the amplitude of the electrostatic potential is oscillatory due to the trapping of resonant electrons by the electric field of the lower hybrid wave. The nonresonant parametric decay is observed an IBW sideband and an ion cyclotron quasimode (ICQM). The ICQM induces an ion perpendicular heating with a heating rate proportional to the pump wave intensity. This work is supported by PPPL subcontract number S013849-F and US Department of Energy (DOE) SciDAC GSEP Program.

Basil Bernstein and Emile Durkheim: Two Theories of Change in Educational Systems

ERIC Educational Resources Information Center

Cherkaoui, Mohamed

1977-01-01

Attempts to draw out parallels and differences between Emile Durkheim's and Basil Bernstein's theories of educational systems and highlights Bernstein's reformulation of certain features of Durkheim's thought. Focuses on the role of the school, curriculum change, and social conflict. (Author/RK)

EBW H&CD Potential for Spherical Tokamaks

NASA Astrophysics Data System (ADS)

Urban, J.; Decker, J.; Peysson, Y.; Preinhaelter, J.; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.

2011-12-01

Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-ß regimes, in which the usual EC O- and X- modes are cut-off. In this case, electron Bernstein waves (EBWs) seem to be the only option that can provide features similar to the EC waves—controllable localized heating and current drive (H&) that can be utilized for core plasma heating as well as for accurate plasma stabilization. We first derive an analytical expression for Gaussian beam OXB conversion efficiency. Then, an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX) is performed. Coupled ray-tracing (AMR) and Fokker-Planck (LUKE) codes are employed to simulate EBWs of varying frequencies and launch conditions. Our results indicate that an efficient and universal EBW H&CD system is indeed viable. In particular, power can be deposited and current reasonably efficiently driven across the whole plasma radius. Such a system could be controlled by a suitably chosen launching antenna vertical position and would also be sufficiently robust.

Bernstein's "Codes" and the Linguistics of "Deficit"

ERIC Educational Resources Information Center

Jones, Peter E.

2013-01-01

This paper examines the key linguistic arguments underpinning Basil Bernstein's theory of "elaborated" and "restricted" "codes". Building on a review of selected highlights from the collective critical response to Bernstein, the paper attempts to clarify the relationship of the theory to "deficit" views…

Kinetic description of cyclotron-range oscillations of a non-neutral plasma column

NASA Astrophysics Data System (ADS)

Neu, S. C.; Morales, G. J.

1998-04-01

The kinetic analysis introduced by Prasad, Morales, and Fried [Prasad et al., Phys. Fluids 30, 3093 (1987)] is used to derive damping conditions and a differential equation for azimuthally propagating waves in a non-neutral plasma column in the limits rl/L≪1 and krl≪1 (where rl is the Larmor radius, k is the wave number, and L is the density scale length). The predictions of the kinetic analysis are verified using a two-dimensional particle-in-cell simulation of Bernstein modes in a thermal rigid-rotor equilibrium. Differences between modes in a strongly magnetized limit and near the Brillouin limit are studied in the simulation.

76 FR 75922 - AllianceBernstein Cap Fund, Inc., et al.; Notice of Application

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-05

... SECURITIES AND EXCHANGE COMMISSION [Investment Company Act Release No. 29876; File No. 812-13939] AllianceBernstein Cap Fund, Inc., et al.; Notice of Application November 29, 2011. AGENCY: Securities and... 12d1-2 under the Act to invest in certain financial instruments. APPLICANTS: AllianceBernstein Cap Fund...

Re-Reading and Rehabilitating Basil Bernstein

ERIC Educational Resources Information Center

Bolander, Brook; Watts, Richard J.

2009-01-01

This article constitutes a re-reading of and an attempt to rehabilitate Basil Bernstein, both of which are important in light of the interpretation of Bernstein as a proponent of the verbal deficit view, and the general discrediting of his work on social class differences in the British educational system, as related to what he later called…

High power plasma heating experiments on the Proto-MPEX facility

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Beers, C. J.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Diem, S. J.; Goulding, R. H.; Green, D. L.; Kafle, N.; Rapp, J.; Showers, M. A.

2017-10-01

Work is underway to maximize the power delivered to the plasma that is available from heating sources installed on the Prototype Materials Plasma Exposure eXperiment (Proto-MPEX) at ORNL. Proto-MPEX is a linear device that has a >100 kW, 13.56 MHz helicon plasma generator available and is intended for material sample exposure to plasmas. Additional plasma heating systems include a 10 kW 18 GHz electron cyclotron heating (ECH) system, a 25 kW 8 MHz ion cyclotron heating ICH system, and a 200 kW 28 GHz electron Bernstein wave (EBW) and ECH system. Most of the heating systems have relatively good power transmission efficiency, however, the 28 GHz EBW system has a lower efficiency owing to stringent requirements on the microwave launch characteristics for EBW coupling combined with the lower output mode purity of the early-model gyrotron in use and its compact mode converter system. A goal for the Proto-MPEX is to have a combined heating power of 200 kW injected into the plasma. Infrared emission diagnostics of the target plate combined with Thomson Scattering, Langmuir probe, and energy analyzer measurements near the target are utilized to characterize the plasmas and coupling efficiency of the heating systems. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC-05-00OR22725.

Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at HAARP and EISCAT

NASA Astrophysics Data System (ADS)

Scales, W.; Mahmoudian, A.; Fu, H.; Bordikar, M. R.; Samimi, A.; Bernhardt, P. A.; Briczinski, S. J., Jr.; Kosch, M. J.; Senior, A.; Isham, B.

2014-12-01

There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities and computational modeling will be provided. Possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, electron temperature measurements in the heated volume and detection of heavy ion species. Finally potential for observing such SEE at the European Incoherent Scatter EISCAT facility will be discussed.

Collisional effects on the numerical recurrence in Vlasov-Poisson simulations

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

Pezzi, Oreste; Valentini, Francesco; Camporeale, Enrico

The initial state recurrence in numerical simulations of the Vlasov-Poisson system is a well-known phenomenon. Here, we study the effect on recurrence of artificial collisions modeled through the Lenard-Bernstein operator [A. Lenard and I. B. Bernstein, Phys. Rev. 112, 1456–1459 (1958)]. By decomposing the linear Vlasov-Poisson system in the Fourier-Hermite space, the recurrence problem is investigated in the linear regime of the damping of a Langmuir wave and of the onset of the bump-on-tail instability. The analysis is then confirmed and extended to the nonlinear regime through an Eulerian collisional Vlasov-Poisson code. It is found that, despite being routinely used,more » an artificial collisionality is not a viable way of preventing recurrence in numerical simulations without compromising the kinetic nature of the solution. Moreover, it is shown how numerical effects associated to the generation of fine velocity scales can modify the physical features of the system evolution even in nonlinear regime. This means that filamentation-like phenomena, usually associated with low amplitude fluctuations contexts, can play a role even in nonlinear regime.« less

Basil Bernstein's Theory of the Pedagogic Device and Formal Music Schooling: Putting the Theory into Practice

ERIC Educational Resources Information Center

Wright, Ruth; Froehlich, Hildegard

2012-01-01

This article describes Basil Bernstein's theory of the pedagogic device as applied to school music instruction. Showing that educational practices are not personal choices alone, but the result of socio-political mandates, the article traces how education functions as a vehicle for social reproduction. Bernstein called this process the…

Damping of Bernstein-Greene-Kruskal modes in collisional plasmas

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

Valentini, Francesco

2008-02-15

In this paper, the effect of Coulomb collisions on the stability of Bernstein-Greene-Kruskal (BGK) modes [I. B. Bernstein, J. M. Greene, and M. D. Krukal, Phys. Rev. 108, 546 (1957)] is analyzed by comparing the numerical results of collisional particle-in-cell (PIC) simulations with the theoretical predictions by Zakharov and Karpman [V. E. Zakharov and V. I. Karpman, Sov. Phys. JETP 16, 351 (1963)], for the collisional damping of nonlinear plasma waves. In the absence of collisions, BGK modes are undamped nonlinear electrostatic oscillations, solutions of the Vlasov-Poisson equations; in these structures nonlinearity manifests as the formation of a plateau inmore » the resonant region of the particle distribution function, due to trapping of resonant particles, thus preventing linear Landau damping. When particle-particle Coulomb collisions are effective, this plateau is smoothed out since collisions drive the velocity distribution towards the Maxwellian shape, thus destroying the BGK structure. As shown by Zakharov and Karpman in 1963, under certain assumptions, an exponential time decay with constant damping rate is predicted for the electric field amplitude and a linear dependence of the damping rate on the collision frequency is found. In this paper, the theory by Zakharov and Karpman is revisited and the effects of collisions on the stability of BGK modes and on the long time evolution of nonlinear Landau damping are numerically investigated. The numerical results are obtained through a collisional PIC code that reproduces a physical phenomenology also observed in recent experiments with trapped pure electron plasmas.« less

Electron Bernstein Wave Emission Studies on the TJ-II Stellarator

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

Caughman, John B; Fernandez, A.; Cappa, A.

2009-01-01

Electron Bernstein Wave (EBW) heating is important for high-beta plasma experiments and will be used for heating over-dense plasmas on TJ-II. TJ-II is a medium sized Heliac operating at CIEMAT in Madrid, whose plasmas are created and heated by ECH via two 300 kW gyrotrons at second harmonic X-mode (53.2 GHz), with additional heating provided by two neutral beam injectors. Theoretical work has shown that the most suitable scheme for launching EBWs in TJ-II is O-X-B mode conversion, which has acceptable heating efficiency for central densities above 1.2 x 1019 m-3.[1] A system based on a 28 GHz-100ms diode gyrotronmore » will be used to deliver 300 kW through a corrugated waveguide. The microwave heating beam will be directed and focused by a steering mirror located inside the vacuum vessel. Prior to the heating experiments, measurement of the thermal EBW emission (EBE) from the plasma is being made to help determine the optimum launch angle for EBW mode conversion, and also to provide an indication of the electron temperature evolution in over-dense plasmas. A dual-polarized quad-ridged broadband horn is used to measure the EBW emission and polarization at 28 GHz. Initial measurements indicate that the emission in under-dense plasmas corresponds to oblique electron cyclotron emission (ECE) and then converts to EBE when the plasma becomes over-dense during neutral beam injection.« less

Bernstein and the Explanation of Social Disparities in Education: A Realist Critique of the Socio-Linguistic Thesis

ERIC Educational Resources Information Center

Nash, Roy

2006-01-01

Can an explanation of the origins of social disparities in educational achievement be assisted by a critical examination of Bernstein's sociology? This central question is approached by a consideration of the status of Bernstein's socio-linguistic thesis. The focus is on the nature of the explanations provided. The paper asks: What is the…

Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at the HAARP Facility

NASA Astrophysics Data System (ADS)

Scales, Wayne; Bernhardt, Paul; McCarrick, Michael; Briczinski, Stanley; Mahmoudian, Alireza; Fu, Haiyang; Ranade Bordikar, Maitrayee; Samimi, Alireza

There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. There is also important parametric behavior on both classes of NSEE depending on the pump wave parameters including the field strength, antenna beam angle, and electron gyro-harmonic number. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities will be provided. Computer simulation model results will be presented to provide insight into associated higher order nonlinear effects including particle acceleration and wave-wave processes. Both theory and model results will be put into the context of the experimental observations. Finally, possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, and electron temperature measurements in the heated volume.

Harmonic effects on ion-bulk waves and simulation of stimulated ion-bulk-wave scattering in CH plasmas

NASA Astrophysics Data System (ADS)

Feng, Q. S.; Zheng, C. Y.; Liu, Z. J.; Cao, L. H.; Xiao, C. Z.; Wang, Q.; Zhang, H. C.; He, X. T.

2017-08-01

Ion-bulk (IBk) wave, a novel branch with a phase velocity close to the ion’s thermal velocity, discovered by Valentini et al (2011 Plasma Phys. Control. Fusion 53 105017), is recently considered as an important electrostatic activity in solar wind, and thus of great interest to space physics and also inertial confinement fusion. The harmonic effects on IBk waves has been researched by Vlasov simulation for the first time. The condition of excitation of the large-amplitude IBk waves is given. The nature of nonlinear IBk waves in the condition of k< {k}{{lor}}/2 (k lor is the wave number at loss-of-resonance point) is undamped Bernstein-Greene-Kruskal-like waves with harmonic superposition. Only when the wave number k of IBk waves satisfies {k}{{lor}}/2≲ k≤slant {k}{{lor}}, can a large-amplitude and mono-frequency IBk wave be excited. A novel stimulated scattering from IBk modes called stimulated ion-bulk-wave scattering (SIBS) or stimulated Feng scattering (SFS) has been proposed and also verified by Vlasov-Maxwell code. In CH plasmas, in addition to the stimulated Brillouin scattering from multi ion-acoustic waves, there exists SIBS simultaneously. This research gives an insight into the SIBS in the field of laser plasma interaction.

Re-Examining Bernstein: From Peer-Group Ways of Speaking to "Schriftsprache"--A Study of Turkish-German "Hauptschule" Students in Mannheim

ERIC Educational Resources Information Center

Keim, Inken

2009-01-01

This paper begins by looking at responses to Bernstein in Germany in the 1970s that criticized his notions of class difference in sociolinguistic codes. As part of a re-examination of Bernstein's ideas, the paper goes on to look at the current communicative situation in German education where urban schools have many second-generation immigrant…

Towards a better comprehension of plasma formation and heating in high performances electron cyclotron resonance ion sources (invited)

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

Mascali, D.; Gammino, S.; Celona, L.

2012-02-15

Further improvements of electron cyclotron resonance ion sources (ECRIS) output currents and average charge state require a deep understanding of electron and ion dynamics in the plasma. This paper will discuss the most recent advances about modeling of non-classical evidences like the sensitivity of electron energy distribution function to the magnetic field detuning, the influence of plasma turbulences on electron heating and ion confinement, the coupling between electron and ion dynamics. All these issues have in common the non-homogeneous distribution of the plasma inside the source: the abrupt density drop at the resonance layer regulates the heating regimes (from collectivemore » to turbulent), the beam formation mechanism and emittance. Possible means to boost the performances of future ECRIS will be proposed. In particular, the use of Bernstein waves, in preliminary experiments performed at Laboratori Nazionali del Sud (LNS) on MDIS (microwave discharge ion sources)-type sources, has permitted to sustain largely overdense plasmas enhancing the warm electron temperature, which will make possible in principle the construction of sources for high intensity multicharged ions beams with simplified magnetic structures.« less

A folded waveguide ICRF antenna for PBX-M and TFTR

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Carter, M. D.; Fogelman, C. H.; Yugo, J. J.; Baity, F. W.; Bell, G. L.; Gardner, W. L.; Goulding, R. H.; Hoffman, D. J.; Ryan, P. M.; Swain, D. W.; Taylor, D. J.; Wilson, R.; Bernabei, S.; Kugel, H.; Ono, M.

1996-02-01

The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current-strap type antennas. These features are particularly beneficial for reactor-relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX-M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross-section that can be installed as either a fast wave (FW) or ion-Bernstein wave (IBW) launcher by 90° rotation. Two new features of the design are: a shorter quarter-wavelength resonator configuration and a rear-feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.

Direct observation of generation and propagation of magnetosonic waves following substorm injection

NASA Astrophysics Data System (ADS)

Su, Z.; Wang, G.; Liu, N.; Zheng, H.; Wang, Y.; Wang, S.

2017-12-01

Magnetosonic whistler mode waves play an important role in the radiation belt electron dynamics. Previous theory has suggested that these waves are excited by the ring distributions of hot protons and can propagate radially and azimuthally over a broad spatial range. However, because of the challenging requirements on satellite locations and data-processing techniques, this theory was difficult to validate directly. Here we present some experimental tests of the theory on the basis of Van Allen Probes observations of magnetosonic waves following substorm injections. At higher L-shells with significant substorm injections, the discrete magnetosonic emission lines started approximately at the proton gyrofrequency harmonics, qualitatively consistent with the prediction of linear proton Bernstein mode instability. In the frequency-time spectrograms, these emission lines exhibited a clear rising tone characteristic with a long duration of 15-25 mins, implying the additional contribution of other undiscovered mechanisms. Nearly at the same time, the magnetosonic waves arose at lower L-shells without substorm injections. The wave signals at two different locations, separated by ΔL up to 2.0 and by ΔMLT up to 4.2, displayed the consistent frequency-time structures, strongly supporting the hypothesis about the radial and azimuthal propagation of magnetosonic waves.

Numerical Solutions of the Nonlinear Fractional-Order Brusselator System by Bernstein Polynomials

PubMed Central

Khan, Rahmat Ali; Tajadodi, Haleh; Johnston, Sarah Jane

2014-01-01

In this paper we propose the Bernstein polynomials to achieve the numerical solutions of nonlinear fractional-order chaotic system known by fractional-order Brusselator system. We use operational matrices of fractional integration and multiplication of Bernstein polynomials, which turns the nonlinear fractional-order Brusselator system to a system of algebraic equations. Two illustrative examples are given in order to demonstrate the accuracy and simplicity of the proposed techniques. PMID:25485293

Waves generated in the plasma plume of helicon magnetic nozzle

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

Singh, Nagendra; Rao, Sathyanarayan; Ranganath, Praveen

2013-03-15

Experimental measurements have shown that the plasma plume created in a helicon plasma device contains a conical structure in the plasma density and a U-shaped double layer (US-DL) tightly confined near the throat where plasma begins to expand from the source. Recently reported two-dimensional particle-in-cell simulations verified these density and US-DL features of the plasma plume. Simulations also showed that the plasma in the plume develops non-thermal feature consisting of radial ion beams with large densities near the conical surface of the density structure. The plasma waves that are generated by the radial ion beams affecting the structure of themore » plasma plume are studied here. We find that most intense waves persist in the high-density regions of the conical density structure, where the transversely accelerated ions in the radial electric fields in the plume are reflected setting up counter-streaming. The waves generated are primarily ion Bernstein modes. The nonlinear evolution of the waves leads to magnetic field-aligned striations in the fields and the plasma near the conical surface of the density structure.« less

Low frequency electromagnetic fluctuations in Kappa magnetized plasmas

NASA Astrophysics Data System (ADS)

Kim, Sunjung; Lazar, M.; Schlickeiser, R.; López, R. A.; Yoon, P. H.

2018-07-01

The present paper provides a theoretical approach for the evaluation of the low frequency spontaneously emitted electromagnetic (EM) fluctuations in Kappa magnetized plasmas, which include the kinetic Alfvén, fast magnetosonic/whistler, kinetic slow mode, ion Bernstein cyclotron modes, and higher-order modes. The model predictions are consistent with particle-in-cell simulations. Effects of suprathermal particles on low frequency fluctuations are studied by varying the power index, either for ions (κ i) or for electrons (κ e). Computations for an arbitrary wave vector orientation and wave polarization provide the intensity of spontaneous emissions to be enhanced in the presence of suprathermal populations. These results strongly suggest that spontaneous fluctuations may significantly contribute to the EM fluctuations observed in space plasmas, where suprathermal Kappa distributed particles are ubiquitous.

Voronovskaja's theorem revisited

NASA Astrophysics Data System (ADS)

Tachev, Gancho T.

2008-07-01

We represent a new quantitative variant of Voronovskaja's theorem for Bernstein operator. This estimate improves the recent quantitative versions of Voronovskaja's theorem for certain Bernstein-type operators, obtained by H. Gonska, P. Pitul and I. Rasa in 2006.

Approximation by the iterates of Bernstein operator

NASA Astrophysics Data System (ADS)

Zapryanova, Teodora; Tachev, Gancho

2012-11-01

We study the degree of pointwise approximation of the iterated Bernstein operators to its limiting operator. We obtain a quantitative estimates related to the conjecture of Gonska and Raşa from 2006.

Generalized neurofuzzy network modeling algorithms using Bézier-Bernstein polynomial functions and additive decomposition.

PubMed

Hong, X; Harris, C J

2000-01-01

This paper introduces a new neurofuzzy model construction algorithm for nonlinear dynamic systems based upon basis functions that are Bézier-Bernstein polynomial functions. This paper is generalized in that it copes with n-dimensional inputs by utilising an additive decomposition construction to overcome the curse of dimensionality associated with high n. This new construction algorithm also introduces univariate Bézier-Bernstein polynomial functions for the completeness of the generalized procedure. Like the B-spline expansion based neurofuzzy systems, Bézier-Bernstein polynomial function based neurofuzzy networks hold desirable properties such as nonnegativity of the basis functions, unity of support, and interpretability of basis function as fuzzy membership functions, moreover with the additional advantages of structural parsimony and Delaunay input space partition, essentially overcoming the curse of dimensionality associated with conventional fuzzy and RBF networks. This new modeling network is based on additive decomposition approach together with two separate basis function formation approaches for both univariate and bivariate Bézier-Bernstein polynomial functions used in model construction. The overall network weights are then learnt using conventional least squares methods. Numerical examples are included to demonstrate the effectiveness of this new data based modeling approach.

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

Qin, Hong; Liu, Jian; Xiao, Jianyuan

Particle-in-cell (PIC) simulation is the most important numerical tool in plasma physics. However, its long-term accuracy has not been established. To overcome this difficulty, we developed a canonical symplectic PIC method for the Vlasov-Maxwell system by discretising its canonical Poisson bracket. A fast local algorithm to solve the symplectic implicit time advance is discovered without root searching or global matrix inversion, enabling applications of the proposed method to very large-scale plasma simulations with many, e.g. 10(9), degrees of freedom. The long-term accuracy and fidelity of the algorithm enables us to numerically confirm Mouhot and Villani's theory and conjecture on nonlinearmore » Landau damping over several orders of magnitude using the PIC method, and to calculate the nonlinear evolution of the reflectivity during the mode conversion process from extraordinary waves to Bernstein waves.« less

Dark Energy Survey Group

Science.gov Websites

Student Conference 2011-09 Kuehn TIPP 2011-06 Kuehn CESR 2011-02 Kuehn AAS 2011-01 Santa Fe Cosmology Workshop 2010-07 Bernstein JHU DES 2010-07 Kuehn Great Lakes Cosmology Workshop 2010-06 Bernstein DES SN

Mode conversion in three ion species ICRF heating scenario

NASA Astrophysics Data System (ADS)

Lin, Y.; Edlund, E.; Ennever, P.; Porkolab, M.; Wright, J.; Wukitch, S.

2016-10-01

Three-ion species ICRF heating has been studied on Alcator C-Mod and on JET. It has been shown to heat the plasma and generate energetic particles. In a typical three-ion scenario, the plasma consists of 60-70% D, 30-40% H and a trace level (1% or less) of 3He. This species mixture creates two hybrid resonances (D-3He and 3He-H) in the plasma, in the vicinity of the 3He IC resonance (on both sides). The fast wave can undergo mode conversion (MC) to ion Bernstein waves and ion cyclotron waves at the two hybrid resonances. A phase contrast imaging (PCI) system has been used to measure the RF waves in the three-ion heating experiment. The experimentally measured MC locations and the separating distance between the two MC regions help to determine the concentration of the three species. The PCI signal amplitudes for the RF waves are found to be sensitive to RF and plasma parameters, including PRF, Te, ne and also the species mix concentration. The parameter dependences found in the experiment will be compared with ICRF code simulations. Supported by USDoE Awards DE-FC02-99ER54512 and DE-FG02-94-ER54235.

Transport modeling of convection dominated helicon discharges in Proto-MPEX with the B2.5-Eirene code

NASA Astrophysics Data System (ADS)

Owen, L. W.; Rapp, J.; Canik, J.; Lore, J. D.

2017-11-01

Data-constrained interpretative analyses of plasma transport in convection dominated helicon discharges in the Proto-MPEX linear device, and predictive calculations with additional Electron Cyclotron Heating/Electron Bernstein Wave (ECH/EBW) heating, are reported. The B2.5-Eirene code, in which the multi-fluid plasma code B2.5 is coupled to the kinetic Monte Carlo neutrals code Eirene, is used to fit double Langmuir probe measurements and fast camera data in front of a stainless-steel target. The absorbed helicon and ECH power (11 kW) and spatially constant anomalous transport coefficients that are deduced from fitting of the probe and optical data are additionally used for predictive simulations of complete axial distributions of the densities, temperatures, plasma flow velocities, particle and energy fluxes, and possible effects of alternate fueling and pumping scenarios. The somewhat hollow electron density and temperature radial profiles from the probe data suggest that Trivelpiece-Gould wave absorption is the dominant helicon electron heating source in the discharges analyzed here. There is no external ion heating, but the corresponding calculated ion temperature radial profile is not hollow. Rather it reflects ion heating by the electron-ion equilibration terms in the energy balance equations and ion radial transport resulting from the hollow density profile. With the absorbed power and the transport model deduced from fitting the sheath limited discharge data, calculated conduction limited higher recycling conditions were produced by reducing the pumping and increasing the gas fueling rate, resulting in an approximate doubling of the target ion flux and reduction of the target heat flux.

A critique of Bernstein's beyond objectivism and relativism: science, hermeneutics, and praxis.

PubMed

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.

On Bernstein type inequalities and a weighted Chebyshev approximation problem on ellipses

NASA Technical Reports Server (NTRS)

Freund, Roland

1989-01-01

A classical inequality due to Bernstein which estimates the norm of polynomials on any given ellipse in terms of their norm on any smaller ellipse with the same foci is examined. For the uniform and a certain weighted uniform norm, and for the case that the two ellipses are not too close, sharp estimates of this type were derived and the corresponding extremal polynomials were determined. These Bernstein type inequalities are closely connected with certain constrained Chebyshev approximation problems on ellipses. Some new results were also presented for a weighted approximation problem of this type.

Exciting Alfven Waves using Modulated Electron Heating by High Power Microwaves

NASA Astrophysics Data System (ADS)

Wang, Yuhou; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Papadopoulos, Konstantinos

2014-10-01

Experiments exploring the physics of ionospheric modification with intense perpendicular propagating waves (k-> ⊥B->0) on the Large Plasma Device (LaPD) at UCLA have been upgraded with the addition of a high power rapidly pulsed microwave source. The plasma is irradiated with ten pulses (250 kW X-band) near the upper-hybrid frequency. The pulses are modulated at a frequency of a fraction (0.1-1.0) of fci (ion cyclotron frequency). Based on a previous single-pulse experiment, the modulated electron heating may drive a large amplitude shear Alfvén wave (f

Robust Fixed-Structure Control

DTIC Science & Technology

1994-10-30

Deterministic Foundation for Statistical Energy Analysis ," J. Sound Vibr., to appear. 1.96 D. S. Bernstein and S. P. Bhat, "Lyapunov Stability, Semistability...S. Bernstein, "Power Flow, Energy Balance, and Statistical Energy Analysis for Large Scale, Interconnected Systems," Proc. Amer. Contr. Conf., pp

Pedagogic Governance: Theorising with/after Bernstein

ERIC Educational Resources Information Center

Singh, Parlo

2017-01-01

Researchers interested in new modes of social control and regulation through pedagogic means have increasingly drawn on Bernstein's theories of social control through pedagogic means and the emergence of a totally pedagogised society. This article explores this aspect of the Bernsteinian theoretical project by extrapolating and contrasting…

Code Switching and Sexual Orientation: A Test of Bernstein's Sociolinguistic Theory

ERIC Educational Resources Information Center

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)

Saturation mechanisms of backward stimulated Raman scattering in a one-dimensional geometry

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

Friou, A.; Bénisti, D.; Gremillet, L.

2013-10-15

In this paper, we investigate the saturation mechanisms of backward stimulated Raman scattering (BSRS) induced by nonlinear kinetic effects. In particular, we stress the importance of accounting for both the nonlinear frequency shift of the electron plasma wave and the growth of sidebands, in order to understand what stops the coherent growth of Raman scattering. Using a Bernstein-Greene-Kruskal approach, we provide an estimate for the maximum amplitude reached by a BSRS-driven plasma wave after the phase of monotonic growth. This estimate is in very good agreement with the results from kinetic simulations of stimulated Raman scattering using both a Vlasovmore » and a Particle in Cell code. Our analysis, which may be generalized to a multidimensional geometry, should provide a means to estimate the limits of backward Raman amplification or the effectiveness of strategies that aim at strongly reducing Raman reflectivity in a fusion plasma.« less

Unveiling the South African Official Primary Mathematics Teacher Pedagogic Identity

ERIC Educational Resources Information Center

Pausigere, Peter; Graven, Mellony

2013-01-01

This article is theoretically informed by Bernstein's (2000) notion of pedagogic identity, supplemented by Tyler's (1999) elaboration of Bernstein's theory into an analytical framework that describes four possible identity positions relating to classification and framing properties. The article analyses key primary mathematics curriculum policy…

Why Photonic Systems for Space?

DTIC Science & Technology

2006-08-01

AUG 2006 Conference Paper Postprint Oct 98 - Aug 00 WHY PHOTONIC SYSTEMS FOR SPACE? In-House 62204F LINK SN 01 Norman Bernstein, George Brost ...Invited Paper Why photonic systems for space? Norman P. Bernstein*, George A. Rrost. Michael J. Hayduk. James R. Hunter, James E. Nichter, Paul M

Bernstein's levels of movement construction: A contemporary perspective.

PubMed

Profeta, Vitor L S; Turvey, Michael T

2018-02-01

Explanation of how goal-directed movements are made manifest is the ultimate aim of the field classically referred to as "motor control". Essential to the sought-after explanation is comprehension of the supporting functional architecture. Seven decades ago, the Russian physiologist and movement scientist Nikolai A. Bernstein proposed a hierarchical model to explain the construction of movements. In his model, the levels of the hierarchy share a common language (i.e., they are commensurate) and perform complementing functions to bring about dexterous movements. The science of the control and coordination of movement in the phylum Craniata has made considerable progress in the intervening seven decades. The contemporary body of knowledge about each of Bernstein's hypothesized functional levels is both more detailed and more sophisticated. A natural consequence of this progress, however, is the relatively independent theoretical development of a given level from the other levels. In this essay, we revisit each level of Bernstein's hierarchy from the joint perspectives of (a) the ecological approach to perception-action and (b) dynamical systems theory. We review a substantial and relevant body of literature produced in different areas of study that are accommodated by this ecological-dynamical version of Bernstein's levels. Implications for the control and coordination of movement and the challenges to producing a unified theory are discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Translation of Bernstein Coefficients Under an Affine Mapping of the Unit Interval

NASA Technical Reports Server (NTRS)

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.

Bernstein Revisited: The Recontextualisation of Equity in Contemporary Australian School Education

ERIC Educational Resources Information Center

Loughland, Tony; Sriprakash, Arathi

2016-01-01

This article draws on the sociology of Basil Bernstein to show how his detailed theories of "recontextualisation" and the "pedagogic device" provide useful analytic levers to examine the politics of educational change. We focus on recent policy developments that have significantly impacted Australian school education: the…

Eulerian simulations of collisional effects on electrostatic plasma waves

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

Pezzi, Oreste; Valentini, Francesco; Perrone, Denise

2013-09-15

The problem of collisions in a plasma is a wide subject with a huge historical literature. In fact, the description of realistic plasmas is a tough problem to attack, both from the theoretical and the numerical point of view. In this paper, a Eulerian time-splitting algorithm for the study of the propagation of electrostatic waves in collisional plasmas is presented. Collisions are modeled through one-dimensional operators of the Fokker-Planck type, both in linear and nonlinear forms. The accuracy of the numerical code is discussed by comparing the numerical results to the analytical predictions obtained in some limit cases when tryingmore » to evaluate the effects of collisions in the phenomenon of wave plasma echo and collisional dissipation of Bernstein-Greene-Kruskal waves. Particular attention is devoted to the study of the nonlinear Dougherty collisional operator, recently used to describe the collisional dissipation of electron plasma waves in a pure electron plasma column [M. W. Anderson and T. M. O'Neil, Phys. Plasmas 14, 112110 (2007)]. Finally, for the study of collisional plasmas, a recipe to set the simulation parameters in order to prevent the filamentation problem can be provided, by exploiting the property of velocity diffusion operators to smooth out small velocity scales.« less

[Recontextualization of nursing clinical simulation based on Basil Bernstein: semiology of pedagogical practice].

PubMed

dos Santos, Mateus Casanova; Leite, Maria Cecília Lorea; Heck, Rita Maria

2010-12-01

This is an investigative case study with descriptive and participative character, based on an educational experience with the Simulation in Nursing learning trigger. It was carried out during the second semester of the first cycle of Faculdade de Enfermagem (FEN), Universidade Federal de Pelotas (UFPel). The aim is to study the recontextualization of pedagogic practice of simulation-based theories developed by Basil Bernstein, an education sociologist, and to contribute with the improvement process of education planning, and especially the evaluation of learning trigger. The research shows that Bernstein's theory is a powerful tool semiotic pedagogical of practices which contributes to the planning and analysis of curricular educational device.

Theorising Catholic Education: The Relevance of Bourdieu and Bernstein for Empirical Research

ERIC Educational Resources Information Center

Byrne, Richard; Devine, Dympna

2017-01-01

The broader theoretical frameworks of both Bourdieu (and his concepts of habitus, field, doxa, collusio and capital) and Bernstein (and his concepts of classification, framing and ritual) provide a deeper understanding of the distinctiveness of Catholic schooling. This article presents a model for theorising Catholic schooling in which levels of…

75 FR 58426 - Notice of Inventory Completion: The Colorado College, Colorado Springs, CO; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-24

... Counsel, The Colorado College c/o Jan Bernstein, President, Bernstein & Associates - NAGPRA Consultants... responsible for notifying the Hopi Tribe of Arizona; Navajo Nation, Arizona, New Mexico & Utah; Ohkay Owingeh, New Mexico; Pueblo of Acoma, New Mexico; Pueblo of Cochiti, New Mexico; Pueblo of Isleta, New Mexico...

New Bernstein type inequalities for polynomials on ellipses

NASA Technical Reports Server (NTRS)

Freund, Roland; Fischer, Bernd

1990-01-01

New and sharp estimates are derived for the growth in the complex plane of polynomials known to have a curved majorant on a given ellipse. These so-called Bernstein type inequalities are closely connected with certain constrained Chebyshev approximation problems on ellipses. Also presented are some new results for approximation problems of this type.

Codes, Code-Switching, and Context: Style and Footing in Peer Group Bilingual Play

ERIC Educational Resources Information Center

Kyratzis, Amy; Tang, Ya-Ting; Koymen, S. Bahar

2009-01-01

According to Bernstein (A sociolinguistic approach to socialization; with some reference to educability, Basil Blackwell Ltd., 1972), middle-class parents transmit an elaborated code to their children that relies on verbal means, rather than paralinguistic devices or shared assumptions, to express meanings. Bernstein's ideas were used to argue…

Contesting Reform: Bernstein's Pedagogic Device and Madrasah Education in Singapore

ERIC Educational Resources Information Center

Tan, Charlene

2010-01-01

This paper highlights the active role played by various pedagogic agents in contesting the state educational reforms for madrasahs in Singapore. Drawing upon Basil Bernstein's pedagogic device, the paper identifies tensions and challenges that arise from the attempts by the state to implement curriculum reforms. The paper contends that the stakes…

Regulating the Unthinkable: Bernstein's Pedagogic Device and the Paradox of Control

ERIC Educational Resources Information Center

Lim, Leonel

2016-01-01

Drawing upon Bernstein's writings on the pedagogic device, this article examines how critical thinking is regulated in Singapore through the process of pedagogic recontextualization. The potential of critical thinking to speak to alternative possibilities and notions of individual autonomy as well as its assumptions of a liberal arrangement of…

Seeing Epistemic Order: Construction and Transmission of Evaluative Criteria

ERIC Educational Resources Information Center

Shalem, Yael; Slonimsky, Lynne

2010-01-01

This paper focuses on formative assessment in the field of higher education. It examines Bernstein's work on vertical discourses and knowledge structures with the view to deepening understanding of the concept of assessment "for" learning. The first part of the paper draws on Vygotsky's work on concept development and Bernstein's work on…

A mechanism for beam-driven excitation of ion cyclotron harmonic waves in the Tokamak Fusion Test Reactor

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

Dendy, R.O.; McClements, K.G.; Lashmore-Davies, C.N.

1994-10-01

A mechanism is proposed for the excitation of waves at harmonics of the injected ion cyclotron frequencies in neutral beam-heated discharges in the Tokamak Fusion Test Reactor (TFTR) [[ital Proceedings] [ital of] [ital the] 17[ital th] [ital European] [ital Conference] [ital on] [ital Controlled] [ital Fusion] [ital and] [ital Plasma] [ital Heating] (European Physical Society, Petit-Lancy, Switzerland, 1990), p. 1540]. Such waves are observed to originate from the outer midplane edge of the plasma. It is shown that ion cyclotron harmonic waves can be destabilized by a low concentration of sub-Alfvenic deuterium or tritium beam ions, provided these ions havemore » a narrow distribution of speeds parallel to the magnetic field. Such a distribution is likely to occur in the edge plasma, close to the point of beam injection. The predicted instability gives rise to wave emission at propagation angles lying almost perpendicular to the field. In contrast to the magnetoacoustic cyclotron instability proposed as an excitation mechanism for fusion-product-driven ion cyclotron emission in the Joint European Torus (JET) [Phys. Plasmas [bold 1], 1918 (1994)], the instability proposed here does not involve resonant fast Alfven and ion Bernstein waves, and can be driven by sub-Alfvenic energetic ions. It is concluded that the observed emission from TFTR can be driven by beam ions.« less

Science, School Science, and School: Looking at Science Learning in Classrooms from the Perspective of Basil Bernstein's Theory of the Structure of Pedagogic Discourse

NASA Astrophysics Data System (ADS)

Campbell, Ralph Ian

This analytic paper asks one question: How does Basil Bernstein's concept of the structure of pedagogic discourse (SPD) contribute to our understanding of the role of teacher-student interactions in science learning in the classroom? Applying Bernstein's theory of the SPD to an analysis of current research in science education explores the structure of Bernstein's theory as a tool for understanding the challenges and questions related to current concerns about classroom science learning. This analysis applies Bernstein's theory of the SPD as a heuristic through a secondary reading of selected research from the past fifteen years and prompts further consideration of Bernstein's ideas. This leads to a reevaluation of the categories of regulative discourse (RD) and instructional discourse (ID) as structures that frame learning environments and the dynamics of student-teacher interactions, which determine learning outcomes. The SPD becomes a simple but flexible heuristic, offering a useful deconstruction of teaching and learning dynamics in three different classroom environments. Understanding the framing interactions of RD and ID provides perspectives on the balance of agency and expectation, suggesting some causal explanations for the student learning outcomes described by the authors. On one hand, forms of open inquiry and student-driven instruction may lack the structure to ensure the appropriation of desired forms of scientific thinking. On the other hand, well-designed pathways towards the understanding of fundamental concepts in science may lack the forms of more open-ended inquiry that develop transferable understanding. Important ideas emerge about the complex dynamics of learning communities, the materials of learning, and the dynamic role of the teacher as facilitator and expert. Simultaneously, the SPD as a flexible heuristic proves ambiguous, prompting a reevaluation of Bernstein's organization of RD and ID. The hierarchical structure of pedagogic discourse becomes a problematic distinction. Regulative discourse is often more instructional and instructional discourse more instrumental in shaping roles and relationships within the learning community. This analysis suggests an agenda for future classroom research and the education of teachers, capitalizing on the SPD as heuristic and reevaluating the ways that social dynamics and structures for domain-specific learning interact in the realization of classroom learning.

Argonne/HEP Dark Energy Survey Group

Science.gov Websites

Kuehn U of C Summer School at Yerkes Observatory 2012-07 Kuehn Lemont High 2012-02 Kuehn Canada-America -Mexico Physics Grad Student Conference 2012-02 Bernstein ANL QuarkNet 2011-03 Kuhlmann Rockford High Kids2Work 2010-04 Kuhlmann Rockford High School 2010-02 Bernstein ANL QuarkNet 2010-02 Kuhlmann Rockford

The Use and Value of Bernstein's Work in Studying (In)Equalities in Undergraduate Social Science Education

ERIC Educational Resources Information Center

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…

Explorations in Policy Enactment: Feminist Thought Experiments with Basil Bernstein's Code Theory

ERIC Educational Resources Information Center

Singh, Parlo; Pini, Barbara; Glasswell, Kathryn

2018-01-01

This paper builds on feminist elaborations of Bernstein's code theory to engage in a series of thought experiments with interview data produced during a co-inquiry design-based research intervention project. It presents three accounts of thinking/writing with data. Our purpose in presenting three different accounts of interview data is to…

David, Mr Bear and Bernstein: Searching for an Equitable Pedagogy through Guided Group Work

ERIC Educational Resources Information Center

Boyle, Bill; Charles, Marie

2012-01-01

The authors' experiences of observing teaching and learning in schools have led them to become concerned at the dominant paradigm of a "pedagogy of poverty" at the expense of a "pedagogy of plenty". Bernstein's theory of power and control of education knowledge is overtly practised in classrooms globally. This is evidenced in…

From Chebyshev to Bernstein: A Tour of Polynomials Small and Large

ERIC Educational Resources Information Center

Boelkins, Matthew; Miller, Jennifer; Vugteveen, Benjamin

2006-01-01

Consider the family of monic polynomials of degree n having zeros at -1 and +1 and all their other real zeros in between these two values. This article explores the size of these polynomials using the supremum of the absolute value on [-1, 1], showing that scaled Chebyshev and Bernstein polynomials give the extremes.

Measurements of ion energies during plasma heating of the Proto-MPEX High Intensity Plasma Source

NASA Astrophysics Data System (ADS)

Caughman, J. B. O.; Goulding, R. H.; Biewer, T. M.; Bigelow, T. S.; Caneses, J.; Diem, S. J.; Green, D. L.; Isler, R. C.; Rapp, J.; Piotrowicz, P.; Beers, C. J.; Kafle, N.; Showers, M. A.

2017-10-01

The Prototype Materials Plasma Exposure eXperiment (Proto-MPEX) is a linear high-intensity RF plasma source that combines a high-density helicon plasma generator with ion and electron heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration with the goal of delivering a plasma heat flux of 10 MW/m2 at a target. The helicon plasma is produced by coupling 13.56 MHz RF power at levels >100 kW. Additional heating is provided by ion cyclotron heating (ICH) ( 25 kW) and electron Bernstein wave (EBW) heating ( 25 kW) at 28 GHz. Measurements of the ion energy distribution with a retarding field energy analyzer (RFEA) show an increase in ion energies in the edge of the plasma when ICH is applied, which is consistent with COMSOL modeling of the power deposition from the antenna. Views of the target plate with an infrared camera show an increase in the surface temperature at large radii during ICH, and these areas map back to magnetic field lines near the antenna. The change in the power deposition at the target during ICH is compared with Thomson Scattering and RFEA measurements near the target. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC-05-00OR22725.

The Social Construction of Time in Contemporary Education: Implications for Technology, Equality and Bernstein's "Conditions for Democracy"

ERIC Educational Resources Information Center

Leaton Gray, Sandra

2017-01-01

This article discusses how the introduction of technology has led to a fundamental shift in the relationship between education and time. As a means of analysing the extent of such changes on pupils from different backgrounds, I use Bernstein's "conditions for democracy" as a framework for evaluating the impact new understandings of time…

Weakly collisional Landau damping and three-dimensional Bernstein-Greene-Kruskal modes: New results on old problems

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

Ng, C.; Bhattacharjee, A.; Skiff, F.

2006-05-15

Landau damping and Bernstein-Greene-Kruskal (BGK) modes are among the most fundamental concepts in plasma physics. While the former describes the surprising damping of linear plasma waves in a collisionless plasma, the latter describes exact undamped nonlinear solutions of the Vlasov equation. There does exist a relationship between the two: Landau damping can be described as the phase mixing of undamped eigenmodes, the so-called Case-Van Kampen modes, which can be viewed as BGK modes in the linear limit. While these concepts have been around for a long time, unexpected new results are still being discovered. For Landau damping, we show thatmore » the textbook picture of phase mixing is altered profoundly in the presence of collision. In particular, the continuous spectrum of Case-Van Kampen modes is eliminated and replaced by a discrete spectrum, even in the limit of zero collision. Furthermore, we show that these discrete eigenmodes form a complete set of solutions. Landau-damped solutions are then recovered as true eigenmodes (which they are not in the collisionless theory). For BGK modes, our interest is motivated by recent discoveries of electrostatic solitary waves in magnetospheric plasmas. While one-dimensional BGK theory is quite mature, there appear to be no exact three-dimensional solutions in the literature (except for the limiting case when the magnetic field is sufficiently strong so that one can apply the guiding-center approximation). We show, in fact, that two- and three-dimensional solutions that depend only on energy do not exist. However, if solutions depend on both energy and angular momentum, we can construct exact three-dimensional solutions for the unmagnetized case, and two-dimensional solutions for the case with a finite magnetic field. The latter are shown to be exact, fully electromagnetic solutions of the steady-state Vlasov-Poisson-Ampere system.« less

Proposal and verification numerical simulation for a microwave forward scattering technique at upper hybrid resonance for the measurement of electron gyroscale density fluctuations in the electron cyclotron frequency range in magnetized plasmas

NASA Astrophysics Data System (ADS)

Kawamori, E.; Igami, H.

2017-11-01

A diagnostic technique for detecting the wave numbers of electron density fluctuations at electron gyro-scales in an electron cyclotron frequency range is proposed, and the validity of the idea is checked by means of a particle-in-cell (PIC) numerical simulation. The technique is a modified version of the scattering technique invented by Novik et al. [Plasma Phys. Controlled Fusion 36, 357-381 (1994)] and Gusakov et al., [Plasma Phys. Controlled Fusion 41, 899-912 (1999)]. The novel method adopts forward scattering of injected extraordinary probe waves at the upper hybrid resonance layer instead of the backward-scattering adopted by the original method, enabling the measurement of the wave-numbers of the fine scale density fluctuations in the electron-cyclotron frequency band by means of phase measurement of the scattered waves. The verification numerical simulation with the PIC method shows that the technique has a potential to be applicable to the detection of electron gyro-scale fluctuations in laboratory plasmas if the upper-hybrid resonance layer is accessible to the probe wave. The technique is a suitable means to detect electron Bernstein waves excited via linear mode conversion from electromagnetic waves in torus plasma experiments. Through the numerical simulations, some problems that remain to be resolved are revealed, which include the influence of nonlinear processes such as the parametric decay instability of the probe wave in the scattering process, and so on.

Ball catching in children with developmental coordination disorder: control of degrees of freedom.

PubMed

Utley, Andrea; Steenbergen, Bert; Astill, Sarah Louise

2007-01-01

This study investigated two-handed catching in eight children (four males, four females) aged 7 to 8 years (mean 7y 4mo [SD 3mo]) with developmental coordination disorder (DCD) and their age-matched controls (AMCs). Kinematic data were collected to examine Bernstein's (1967) notion of freezing and releasing degrees of freedom (DF). Participants were asked to catch a ball 30 times, delivered in three blocks of 10 trials. Video analysis showed that children with DCD caught significantly fewer balls than their AMCs (p< or =0.001) counterparts. Kinematic analyses showed that children with DCD exhibited smaller ranges of motion and less variable angular excursions of the elbow joints than their AMCs, and that their elbows are more rigidly coupled (p< or =0.001). These data suggest that children with DCD rigidly fix and couple their limbs to reduce the number of DF actively involved in the task.

On method of solving third-order ordinary differential equations directly using Bernstein polynomials

NASA Astrophysics Data System (ADS)

Khataybeh, S. N.; Hashim, I.

2018-04-01

In this paper, we propose for the first time a method based on Bernstein polynomials for solving directly a class of third-order ordinary differential equations (ODEs). This method gives a numerical solution by converting the equation into a system of algebraic equations which is solved directly. Some numerical examples are given to show the applicability of the method.

On the Effects of Social Class on Language Use: A Fresh Look at Bernstein's Theory

ERIC Educational Resources Information Center

Aliakbari, Mohammad; Allahmoradi, Nazal

2014-01-01

Basil Bernstein (1971) introduced the notion of the Restricted and the Elaborated code, claiming that working-class speakers have access only to the former but middle-class members to both. In an attempt to test this theory in the Iranian context and to investigate the effect of social class on the quality of students language use, we examined the…

Two-Dimensional Vlasov Simulations of Fast Stochastic Electron Heating in Ionospheric Modification Experiments

NASA Astrophysics Data System (ADS)

Speirs, David Carruthers; Eliasson, Bengt; Daldorff, Lars K. S.

2017-10-01

Ionospheric heating experiments using high-frequency ordinary (O)-mode electromagnetic waves have shown the induced formation of magnetic field-aligned density striations in the ionospheric F region, in association with lower hybrid (LH) and upper hybrid (UH) turbulence. In recent experiments using high-power transmitters, the creation of new plasma regions and the formation of descending artificial ionospheric layers (DAILs) have been observed. These are attributed to suprathermal electrons ionizing the neutral gas, so that the O-mode reflection point and associated turbulence is moving to a progressively lower altitude. We present the results of two-dimensional (2-D) Vlasov simulations used to study the mode conversion of an O-mode pump wave to trapped UH waves in a small-scale density striation of circular cross section. Subsequent multiwave parametric decays lead to UH and LH turbulence and to the excitation of electron Bernstein (EB) waves. Large-amplitude EB waves result in rapid stochastic electron heating when the wave amplitude exceeds a threshold value. For typical experimental parameters, the electron temperature is observed to rise from 1,500 K to about 8,000 K in a fraction of a millisecond, much faster than Ohmic heating due to collisions which occurs on a timescale of an order of a second. This initial heating could then lead to further acceleration due to Langmuir turbulence near the critical layer. Stochastic electron heating therefore represents an important potential mechanism for the formation of DAILs.

Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

DOE PAGES

Meneghini, Orso; Volpe, Francesco A.

2016-08-19

An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contain information on the magnetic field vector B at the cutoff layer. By probing the plasma with different wave frequencies it provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry.more » Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. We proposed an reflectometric approach in order to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit Electron Bernstein Waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Furthermore, frequencies above the edge electron-cyclotron frequency (f >28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.« less

Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

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

Meneghini, Orso; Volpe, Francesco A., E-mail: fvolpe@columbia.edu

An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contains information on the magnetic field vector B at the cutoff layer. Probing the plasma with different wave frequencies provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirmsmore » the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. The proposed reflectometric approach is expected to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit electron Bernstein waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Frequencies above the edge electron-cyclotron frequency (f > 28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.« less

Searching for O-X-B mode-conversion window with monitoring of stray microwave radiation in LHD

NASA Astrophysics Data System (ADS)

Igami, H.; Kubo, S.; Laqua, H. P.; Nagasaki, K.; Inagaki, S.; Notake, T.; Shimozuma, T.; Yoshimura, Y.; Mutoh, T.; LHD Experimental Group

2006-10-01

In the Large Helical Device, the stray microwave radiation is monitored by using so-called sniffer probes during electron cyclotron heating. In monitoring the stray radiation, we changed the microwave beam injection angle and search the O-X-B mode-conversion window to excite electron Bernstein waves (EBWs). When the microwave beam is injected toward the vicinity of the predicted O-X-B mode-conversion window, the electron temperature rises in the central part of overdense plasmas. In that case, the stray radiation level near the injection antenna becomes low. These results indicate that monitoring the stray radiation near the injection antenna is helpful in confirming the effectiveness of excitation of EBWs simply without precise analysis.

Nonlinear Landau damping and formation of Bernstein-Greene-Kruskal structures for plasmas with q-nonextensive velocity distributions

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

Raghunathan, M.; Ganesh, R.

2013-03-15

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{omega}{sub p}{sup -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,more » up to t=3000{omega}{sub p}{sup -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 velocity distributions have long tails, strong Landau damping inhibits the formation of BGK structures. On the other hand, for 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.« less

Knowledge Distribution and Power Relations in HIV-Related Education and Prevention for Gay Men: An Application of Bernstein to Australian Community-Based Pedagogical Devices

ERIC Educational Resources Information Center

McInnes, David; Murphy, Dean

2011-01-01

This paper seeks to make a theoretical and analytic intervention into the field of HIV-related education and prevention by applying the pedagogy framework of Basil Bernstein to a series of pedagogical devices developed and used in community-based programmes targeting gay men in Australia. The paper begins by outlining why it is such an…

Changes in the Classification and Framing of Education in Britain, 1950s to 2000s: An Interpretive Essay after Bernstein

ERIC Educational Resources Information Center

Grace, Gerald

2008-01-01

Using the concepts of classification and framing and other relevant writings by Basil Bernstein, an attempt will be made to construct a theorised account of changes in the socio-political context of education in Britain; of the mode of governance in education and of the constructs and practice of educational leadership from the 1950s to the…

Human Performance: Women in Nontraditional Occupations and the Influence of the Menstrual Cycle (A Selected Bibliography)

DTIC Science & Technology

1980-05-01

rhythms and human performance . New York: Academic Press, 1971. Richter, C. P.,Periodic phenomena in man and animals: Their relation neuroendoctine...Research Board, 1928, Lo. 45, 43-63. Bernstein, B. E. The relationship between menstruation and academic performance in high- and low-motivated...9780) Bernstein, B. E. Effect of menstruation on academic performance among college women. Archives of Sexual Behavior, 1977, 5, 289-296. l Bilhuber

Binding energies of the ground triplet state a{sup 3}Σ{sub u}{sup +} of Rb{sub 2} and Cs{sub 2} in terms of the generalized Le Roy–Bernstein near-dissociation expansion

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

Sovkov, V. B.; Ivanov, V. S.

Formulae of Le Roy–Bernstein near-dissociation theory are derived in a general isotope–invariant form, applicable to any term in the rotational expansion of a diatomic ro-vibrational term value. It is proposed to use the generalized Le Roy–Bernstein expansion to describe the binding energies (ro-vibrational term values) of the ground triplet state a{sup 3}Σ{sub u}{sup +} of alkali metal dimers. The parameters of this description are determined for Rb{sub 2} and Cs{sub 2} molecules. This approach gives a recipe to calculate the whole variety of the binding energies with characteristic accuracies from ∼1 × 10{sup −3} to 1 × 10{sup −2} cm{supmore » −1} using a relatively simple algebraic equation.« less

Ion Bernstein wave heating research

NASA Astrophysics Data System (ADS)

Ono, Masayuki

1993-02-01

Ion Bernstein wave heating (IBWH) utilizes the ion Bernstein wave (IBW), a hot plasma wave, to carry the radio frequency (rf) power to heat the 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 perpendicular phase velocity (ω/k⊥≊VTi≪Vα) greatly reduces the otherwise serious wave absorption by the 3.5 MeV fusion α particles. In addition, the property of IBW's that k⊥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. IBW's can be excited with loop antennas or with a lower-hybrid-like waveguide launcher at the plasma edge, the latter structure being one that is especially compatible with reactor application. In either case, the mode at the plasma edge is an electron plasma wave (EPW). Deeper in the plasma, the EPW is mode transformed into an IBW. Such launching and mode transformation of IBW's were first demonstrated in experiments in the Advanced Concepts Torus-1 (ACT-1) [Phys. Rev. Lett. 45, 1105 (1980)] plasma torus and in particle simulation calculations. These and other aspects of IBW heating physics have been investigated through a number of experiments performed on ACT-1, the Japanese Institute of Plasma Physics Tokamak II-Upgrade (JIPPTII-U) [Phys. Rev. Lett. 54, 2339 (1985)], the Tokyo University Non-Circular Tokamak (TNT) [Nucl. Fusion 26, 1097 (1986)], the Princeton Large Tokamak (PLT) [Phys. Rev. Lett. 60, 294 (1988)], and Alcator-C [Phys. Rev. Lett. 60, 298 (1988)]. In these experiments both linear and nonlinear heating processes have been observed. Interestingly, improvement of plasma confinement was also observed in the PLT and Alcator-C experiments, opening up the possible use of IBW's for the active control of plasma transport. Two theoretical explanations have been proposed: one based on four-wave mixing of IBW with low-frequency turbulence, the other on the nonlinear generation of a velocity-shear layer. Both models are consistent with the observed threshold power level of a few hundred kW in the experiments. Experiments on lower field plasmas on JFTII-M [Eighth Topical Conference on Radio-Frequency Power in Plasmas, Irvine, CA, 1989 (American Institute of Physics, New York, 1989), p. 350] and DIII-D [Eighth Topical Conference on Radio-Frequency Power in Plasmas, Irvine, CA, 1989 (American Institute of Physics, New York, 1989), p. 314] have raised some concern with the IBW wave-launching process. The experiments showed serious impurity release from the walls but little or no core heating, a combination of circumstances strongly suggestive of edge heating. Possible parasitic channels could include the excitation of short wavelength modes by the Faraday shield's fringing fields, antenna-sheath-wave excitation, an axial-convective loss channel, and nonlinear processes such as parametric instability and ponderomotive effects. Suggested remedies include changes in the antenna phasing, the use of low-Z insulators, operating at higher frequencies, positioning the plasma differently with respect to the antenna, eliminating the Faraday shields, and using a waveguide launcher. The recent JIPPTII-U experiment, employing a 0-π phased antenna array with a higher frequency 130 MHz source, demonstrated that those remedies can indeed work. Looking to the future, one seeks additional ways in which IBWH can improve tokamak performance. The strong ponderomotive potential of the IBWH antenna may be used to stabilize external kinks and, acting as an rf limiter, to control the plasma edge. Control of the plasma pressure profile with local IBWH heating is already an important part of the Princeton Beta Experiment-Modified (PBX-M) [Ninth Topical Conference on Radio-Frequency Power in Plasmas, Charleston, SC, 1991 (American Institute of Physics, New York, 1991), p. 129] program in its exploration of the second-stability regime. Application of IBWH may also improve the performance of neutral beam heating and the efficiency and localization of lower-hybrid current drive for current profile control. Used with pellet injection, IBWH may also prolong the period of good confinement. The three planned high-power IBWH experiments covering vastly different parameters: f=40-80 MHz for PBX-M; f=130 MHz for JIPPT-II-U; and f=430 MHz for the Frascati Tokamak-Upgrade (FT-U) [16th European Physical Society Conference on Controlled Fusion and Plasma Physics, Venice, Italy, 1989 (European Physical Society, Amsterdam, 1989), Vol. III, p. 1069] appear to be well positioned to explore these possibilities and to clarify other issues including the physics of wave launching and associated nonlinear processes.

Potential Role of the Mirror and Ion Bernstein Instabilities on the Pickup Ion Dynamics in the Outer Heliosheath: Linear Theory and Hybrid Simulations

NASA Astrophysics Data System (ADS)

Min, K.; Liu, K.; Gary, S. P.

2017-12-01

The main challenge of the secondary ENA mechanism, a theory put forth to explain the IBEX ENA ribbon, is maintaining the stability of the pickup ion velocity distribution before the pickup ions in the outer heliosheath go through two consecutive charge exchanges. The Alfvén/ion-cyclotron instability, which has its maximum growth at propagation parallel to Bo, the background magnetic field, is believed to be the main agent leading to rapid isotropization of the pickup ions. However, recent studies found that this instability can be suppressed when parallel temperatures of the background plasma and the pickup ion ring distribution are comparable, allowing the pickup ion distribution to remain stable for a long period. This paper demonstrates that a pickup ion ring distribution can also drive the mirror and ion Bernstein instabilities which lead to growing modes at propagation oblique to Bo. For idealized proton-electron plasmas where relatively cool background electron and proton populations are represented by isotropic Maxwellian distributions and tenuous (1%) pickup protons are represented by a Maxwellian-ring distribution (assuming a 90˚ pickup angle), linear Vlasov theory predicts unstable mirror and ion Bernstein modes with growth rates comparable to or exceeding that of the Alfvén-cyclotron instability. According to quasilinear theory, interactions with these obliquely-propagating modes can lead to substantial pitch angle scattering of the ring protons. Two-dimensional hybrid (kinetic ions and massless fluid electrons) simulations are carried out to examine the nonlinear consequences of the mirror and Bernstein instabilities. The preliminary simulation results are presented. The study suggests a scenario that the oblique mirror and ion Bernstein modes can be an active agent of the pickup ion isotropization when the condition is such that the Alfvén-cyclotron instability is suppressed.

Electron plasma wave filamentation in the kinetic regime

NASA Astrophysics Data System (ADS)

Lushnikov, Pavel; Rose, Harvey; Silantyev, Denis

2016-10-01

We consider nonlinear electron plasma wave (EPW) dynamics in the kinetic wavenumber regime, 0.25 < kλD < 0.45 , which is typical for current high temperature laser-plasma interaction experiments, where k is the EPW wavenumber and λD is the electron Debye length. In this kinetic regime, EPW frequency reduction due to electron trapping may dominate the ponderomotive frequency shift. Previous 3D PIC simulations showed that the trapped electron EPW filamentation instability can saturate stimulated Raman backscatter by reducing the EPWs coherence but multidimensional Vlasov simulations [1] are needed to address that saturation in details. We performed nonlinear, non-equilibrium 2D Vlasov simulations to study the EPW filamentation. The initial conditions are created either by external forcing or by constructing the appropriate 1D travelling Bernstein-Greene-Kruskal (BGK) mode. Transverse perturbations of any of these initial conditions grow with time eventually producing strongly nonlinear filamentation followed by plasma turbulence. We compared these simulations with the theoretical results on growth rates of the transverse instability BGK mode showing the satisfactory agreement. Supported by the New Mexico Consortium and NSF DMS-1412140.

Bivariate tensor product [Formula: see text]-analogue of Kantorovich-type Bernstein-Stancu-Schurer operators.

PubMed

Cai, Qing-Bo; Xu, Xiao-Wei; Zhou, Guorong

2017-01-01

In this paper, we construct a bivariate tensor product generalization of Kantorovich-type Bernstein-Stancu-Schurer operators based on the concept of [Formula: see text]-integers. We obtain moments and central moments of these operators, give the rate of convergence by using the complete modulus of continuity for the bivariate case and estimate a convergence theorem for the Lipschitz continuous functions. We also give some graphs and numerical examples to illustrate the convergence properties of these operators to certain functions.

Exploring EBW conversion physics with applications to NSTX-U

NASA Astrophysics Data System (ADS)

Lopez, N. A.; Ram, A. K.; Poli, F. M.; Du Toit, E. J.

2017-10-01

Radiofrequency waves are commonly used on traditional tokamaks to assist plasma formation and to provide non-inductive heating and current drive (NI H&CD). Their applicability to spherical tokamaks (STs), however, is complicated by the latter's comparatively high densities and low field strengths. Electron Bernstein waves (EBW) are attractive for NI H&CD on STs because they do not experience a density cutoff and they damp strongly in the vicinity of cyclotron harmonics, even at low temperatures typical of startup. The excitation of EBWs using vacuum-launched electromagnetic waves requires a mode conversion that is highly sensitive to the choice of launch polarization and to local plasma parameters. Common theoretical models employ a 1D slab geometry to study such conversion processes; however, these models may be insufficient to describe the EBW conversion physics in STs, in which equilibria are typically strongly-shaped with large magnetic shear. We report our progress on a theoretical study of EBW conversion physics that emphasizes the inherent idiosyncrasies of the ST equilibrium. Additionally, using a recently developed OD2V kinetic model along with GENRAY simulations, we assess the EBW NI H&CD on NSTX-U using the OXB startup technique that has been developed on MAST. We then make recommendations regarding its implementation in future experimental campaigns.

Reflection and transmission of elastic waves through a couple-stress elastic slab sandwiched between two half-spaces

NASA Astrophysics Data System (ADS)

Wang, Changda; Chen, Xuejun; Wei, Peijun; Li, Yueqiu

2017-12-01

The reflection and transmission of elastic waves through a couple-stress elastic slab that is sandwiched between two couple-stress elastic half-spaces are studied in this paper. Because of the couple-stress effects, there are three types of elastic waves in the couple-stress elastic solid, two of which are dispersive. The interface conditions between two couple-stress solids involve the surface couple and rotation apart from the surface traction and displacement. The nontraditional interface conditions between the slab and two solid half-spaces are used to obtain the linear algebraic equation sets from which the amplitude ratios of reflection and transmission waves to the incident wave can be determined. Then, the energy fluxes carried by the various reflection and transmission waves are calculated numerically and the normal energy flux conservation is used to validate the numerical results. The special case, couple-stress elastic slab sandwiched by the classical elastic half-spaces, is also studied and compared with the situation that the classical elastic slab sandwiched by the classical elastic half-spaces. Incident longitudinal wave (P wave) and incident transverse wave (SV wave) are both considered. The influences of the couple-stress are mainly discussed based on the numerical results. It is found that the couple-stress mainly influences the transverse modes of elastic waves.

a Vacuum Ultraviolet Study of the Alcator C Tokamak Plasma Using a High Resolution, One-Dimensional Photon Counting Detector.

NASA Astrophysics Data System (ADS)

Benjamin, Russell D.

A photon counting detector based on an image intensified photodiode array was developed to meet the needs of one particular area of spectroscopic study, the determination of the kinetic temperature of impurity species. The image intensifier incorporates 3 high strip current ( ~300 muA) microchannel plates in a 'Z' configuration to achieve the gain required for the detection of single photon events. The design, construction, and laboratory testing of this system to determine its suitability for fusion plasma diagnostics is described, in particular, the ability to measure emission line profiles in order to determine the kinetic temperature of the emitting species. The photon counting detector, mounted on the exit plane of a 1m Ebert-Fastie spectrometer, was used to make spectroscopic measurements of the local ion temperature in Alcator C plasmas using impurity emission lines. Alcator experiments on one particular method of RF heating in a tokamak plasma, the launching of Ion Bernstein waves (IBW), are discussed. The O V kinetic temperature increases during IBW injection as the pre-RF plasma density is raised (on a shot-to-shot basis) above the region in which significant increases in the central ion temperature are observed. In addition, ion temperature profiles were measured during Ion Bernstein wave experiments by combining this point derived from the fit to the emission line of O VII with neutral particle analyzer data. The incorporation of the O VII temperature point in the determination of the pre-RF ion temperature profile results in a significant reduction (~0.4 cm) in the characteristic width of this profile. The high resolution and geometric stability of the photon counting detector made possible the measurement of small wavelength shifts (Deltalambda ~ 0.01 A) and, therefore, the determination of small bulk plasma motions (in this case, poloidal rotation of the plasma) through the Doppler shift of impurity emission lines. The Zeeman effect makes a significant contribution to the measured line profile in high field tokamaks, even in the ultraviolet. Modelling of the Zeeman effect is discussed and applied to the impurity species observed in Alcator C plasmas. (Abstract shortened with permission of author.).

The role of Upper Hybrid Turbulence on HF Artificial Ionization

NASA Astrophysics Data System (ADS)

Papadopoulos, Konstantinos Dennis; Najmi, Amir; Eliasson, Bengt; Milikh, Gennady

2016-07-01

One of the most fascinating and scientifically interesting phenomena of active space experiments is the discovery of artificial ionization by Todd Pedersen when the HAARP ERP reached the GW level. The phenomenon has been well documented experimentally. A theoretical model based on ionization by energetic electrons accelerated by 50-100 V/m localized electric fields due to Strong Langmuir Turbulence (SLT) near the reflection surface of the HF pump wave, reproduced the observed dynamics of the descending plasma layer quite accurately. A major defect of the model was that the electron temperature in the SLT region was a free parameter. When taken as the 2000 K representing the ambient electron temperature the SLT driven electron flux was insufficient to produce ionization. An equivalent electron temperature of 5000 K or higher was necessary to reproduce the observations. The needed electron heating was attributed to the interaction of the HF at the Upper Hybrid (UH) resonant layer, approximately 5 Km below the reflection region where the HF electric field is perpendicular to the ambient magnetic field. The heated electrons expanded upwards along the magnetic field line and interacted with SLT fields near the resonance region. A consequence of this defect was that the theory could not explain the puzzling double resonance effect. Namely the observation that the ionization level was much stronger when the HF frequency and the UH resonance were a multiple of the electron cyclotron frequency. To remedy this we used a series of Vlasov simulations to explore the HF-plasma interaction in the vicinity of the UH resonance. The simulations followed the evolution of the spectral density of the electric field over a 7.5 MHz frequency band and cm scale lengths and of the electron distribution function over one millisecond for both double resonant and non-resonant cases. Many new features were revealed by the analysis of the simulations such as: 1. Broadening of the wave-number spectral region at the at the UH frequency 2. Excitation of all Bernstein modes associated with cyclotron frequency harmonics both below and above the UH frequency for both the resonant and non0resonant cases. 3. Moderate electron heating, in the form of bulk heating caused by first Bernstein mode, although its wave intensity is more than 20 dB lower than the intensity of the UH branch for all non-resonant cases. 4. Strong generation of non-thermal tails for the resonant cases, by the UH waves downshifted by the lower hybrid frequency when the downshifted frequency was equal to an harmonic of the electron gyro-frequency. The new UH turbulence resolves several f the mysteries associated with artificial ionization and suggests several new observations. Acknowledgment:Work supported by AFOSR MURI grant FA95501410019.

Transport implementation of the Bernstein-Vazirani algorithm with ion qubits

NASA Astrophysics Data System (ADS)

Fallek, S. D.; Herold, C. D.; McMahon, B. J.; Maller, K. M.; Brown, K. R.; Amini, J. M.

2016-08-01

Using trapped ion quantum bits in a scalable microfabricated surface trap, we perform the Bernstein-Vazirani algorithm. Our architecture takes advantage of the ion transport capabilities of such a trap. 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)%.

The Two Electron Oxidation of Cobalt Phthalocyanines by Thionyl Chloride: Implications for Lithium/Thionyl Chloride Batteries

DTIC Science & Technology

1989-10-20

Phthalocyanines by Thionyl Chloride. Implications for Lithium /Thionyl Chloride Batteries By P.A. Bernstein and A.B.P. Lever* D T IC in NOV.0 3.1W9. M...Thionyl Chloride. Implications forI Lithium /Thionvl Chloride Batteries 12 PERSONAL AUTHOR(S) P.A. Bernstein and A.B.P. Lever* 13a. TYPE OF REPORT 13b...SUBJECT TERMS (Continue on reverse if necessary and identify by olock numoer) FIELD GROUP SUB-GROUP .’ Phthalocyanine," Lithium Battery, Thionyl

Fast and Exact Continuous Collision Detection with Bernstein Sign Classification

PubMed Central

Tang, Min; Tong, Ruofeng; Wang, Zhendong; Manocha, Dinesh

2014-01-01

We present fast algorithms to perform accurate CCD queries between triangulated models. Our formulation uses properties of the Bernstein basis and Bézier curves and reduces the problem to evaluating signs of polynomials. We present a geometrically exact CCD algorithm based on the exact geometric computation paradigm to perform reliable Boolean collision queries. Our algorithm is more than an order of magnitude faster than prior exact algorithms. We evaluate its performance for cloth and FEM simulations on CPUs and GPUs, and highlight the benefits. PMID:25568589

Bernstein-Greene-Kruskal Modes in a Three-Dimensional Plasma

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

Ng, C.S.; Bhattacharjee, A.

2005-12-09

Bernstein-Greene-Kruskal modes in a three-dimensional (3D) unmagnetized plasma are constructed. It is shown that 3D solutions that depend only on energy do not exist. However, 3D solutions that depend on energy and additional constants of motion (such as angular momentum) do exist. Exact analytical as well as numerical solutions are constructed assuming spherical symmetry, and their properties are contrasted with those of 1D solutions. Possible extensions to solutions with cylindrical symmetry with or without a finite magnetic guide field are discussed.

Evanescent wave coupling in terahertz waveguide arrays.

PubMed

Reichel, K S; Sakoda, N; Mendis, R; Mittleman, D M

2013-07-15

We study energy transfer among an array of identical finite-width parallel-plate waveguides in close proximity, via evanescent wave coupling of broadband terahertz waves. We observe stronger coupling with larger plate separations and longer propagation paths. This work establishes a platform to investigate new opportunities for THz components and devices based on evanescent wave coupling.

The role of satellite directional wave spectra for the improvement of the ocean-waves coupling

NASA Astrophysics Data System (ADS)

Aouf, Lotfi; Hauser, Danièle; Chapron, Bertrand

2017-04-01

Swell waves are well captured by the Synthetic Aperture Radar (SAR) which provides the directional wave spectra for waves roughly larger than 200 m. Since the launch of sentinel-1A and 1B SAR directional wave spectra are available to improve the swell wave forecasting and the coupling processes at the air-sea interface. Moreover next year CFOSAT mission will provide directional wave spectra for waves with wavelengths comprised between 70 to 500 m. This study aims to evaluate the assimilation of SAR and synthetic CFOSAT wave spectra on the coupling between the wave model MFWAM and the ocean model NEMO. Three coupling processes as described in Breivik et al. (2014) of Stokes-Coriolis forcing, the ocean side stress and the turbulence injected by the wave breaking in the ocean mixed layer have been used. a coupling run is performed with and without assimilation of directional wave spectra. the impact of SAR wave data on key parameters such as surface sea temperature, currents and salinity is investigated. Particular attention is carried out for ocean areas with swell dominant wave climate.

Optical rogue waves associated with the negative coherent coupling in an isotropic medium.

PubMed

Sun, Wen-Rong; Tian, Bo; Jiang, Yan; Zhen, Hui-Ling

2015-02-01

Optical rogue waves of the coupled nonlinear Schrödinger equations with negative coherent coupling, which describe the propagation of orthogonally polarized optical waves in an isotropic medium, are reported. We construct and discuss a family of the vector rogue-wave solutions, including the bright rogue waves, four-petaled rogue waves, and dark rogue waves. A bright rogue wave without a valley can split up, giving birth to two bright rogue waves, and an eye-shaped rogue wave can split up, giving birth to two dark rogue waves.

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

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

Gao, Zhen; Gao, Fei; Zhang, Baile, E-mail: blzhang@ntu.edu.sg

2016-01-25

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find usemore » in the design of integrated surface-wave devices with suppressed crosstalk.« less

Development of Operational Wave-Tide-Storm surges Coupling Prediction System

NASA Astrophysics Data System (ADS)

You, S. H.; Park, S. W.; Kim, J. S.; Kim, K. L.

2009-04-01

The Korean Peninsula is surrounded by the Yellow Sea, East China Sea, and East Sea. This complex oceanographic system includes large tides in the Yellow Sea and seasonally varying monsoon and typhoon events. For Korea's coastal regions, floods caused by wave and storm surges are among the most serious threats. To predict more accurate wave and storm surges, the development of coupling wave-tide-storm surges prediction system is essential. For the time being, wave and storm surges predictions are still made separately in KMA (Korea Meteorological Administration) and most operational institute. However, many researchers have emphasized the effects of tides and storm surges on wind waves and recommended further investigations into the effects of wave-tide-storm surges interactions and coupling module. In Korea, especially, tidal height and current give a great effect on the wave prediction in the Yellow sea where is very high tide and related research is not enough. At present, KMA has operated the wave (RWAM : Regional Wave Model) and storm surges/tide prediction system (STORM : Storm Surges/Tide Operational Model) for ocean forecasting. The RWAM is WAVEWATCH III which is a third generation wave model developed by Tolman (1989). The STORM is based on POM (Princeton Ocean Model, Blumberg and Mellor, 1987). The RWAM and STORM cover the northwestern Pacific Ocean from 115°E to 150°E and from 20°N to 52°N. The horizontal grid intervals are 1/12° in both latitudinal and longitudinal directions. These two operational models are coupled to simulate wave heights for typhoon case. The sea level and current simulated by storm surge model are used for the input of wave model with 3 hour interval. The coupling simulation between wave and storm surge model carried out for Typhoon Nabi (0514), Shanshan(0613) and Nari (0711) which were effected on Korea directly. We simulated significant wave height simulated by wave model and coupling model and compared difference between uncoupling and coupling cases for each typhoon. When the typhoon Nabi hit at southern coast of Kyushu, predicted significant wave height reached over 10 m. The difference of significant wave height between wave and wave-tide-storm surges model represents large variation at the southwestern coast of Korea with about 0.5 m. Other typhoon cases also show similar results with typhoon Nabi case. For typhoon Shanshan case the difference of significant wave height reached up to 0.3 m. When the typhoon Nari was affected in the southern coast of Korea, predicted significant wave height was about 5m. The typhoon Nari case also shows the difference of significant wave height similar with other typhoon cases. Using the observation from ocean buoy operated by KMA, we compared wave information simulated by wave and wave-storm surges coupling model. The significant wave height simulated by wave-tide-storm surges model shows the tidal modulation features in the western and southern coast of Korea. And the difference of significant wave height between two models reached up to 0.5 m. The coupling effect also can be identified in the wave direction, wave period and wave length. In addition, wave spectrum is also changeable due to coupling effect of wave-tide-storm surges model. The development, testing and application of a coupling module in which wave-tide-storm surges are incorporated within the frame of KMA Ocean prediction system, has been considered as a step forward in respect of ocean forecasting. In addition, advanced wave prediction model will be applicable to the effect of ocean in the weather forecasting system. The main purpose of this study is to show how the coupling module developed and to report on a series of experiments dealing with the sensitivities and real case prediction of coupling wave-tide-storm surges prediction system.

A numerical study of wave-current interaction through surface and bottom stresses: Coastal ocean response to Hurricane Fran of 1996

NASA Astrophysics Data System (ADS)

Xie, L.; Pietrafesa, L. J.; Wu, K.

2003-02-01

A three-dimensional wave-current coupled modeling system is used to examine the influence of waves on coastal currents and sea level. This coupled modeling system consists of the wave model-WAM (Cycle 4) and the Princeton Ocean Model (POM). The results from this study show that it is important to incorporate surface wave effects into coastal storm surge and circulation models. Specifically, we find that (1) storm surge models without coupled surface waves generally under estimate not only the peak surge but also the coastal water level drop which can also cause substantial impact on the coastal environment, (2) introducing wave-induced surface stress effect into storm surge models can significantly improve storm surge prediction, (3) incorporating wave-induced bottom stress into the coupled wave-current model further improves storm surge prediction, and (4) calibration of the wave module according to minimum error in significant wave height does not necessarily result in an optimum wave module in a wave-current coupled system for current and storm surge prediction.

Scattering of plane evanescent waves by cylindrical shells and wave vector coupling conditions for exciting flexural waves

NASA Astrophysics Data System (ADS)

Marston, Philip L.

2002-05-01

The coupling of sound to buried targets can be associated with acoustic evanescent waves when the sea bottom is smooth. To understand the excitation of flexural waves on buried shells by acoustic evanescent waves, the partial wave series for the scattering is found for cylindrical shells at normal incidence in an unbounded medium. The formulation uses the simplifications of thin-shell dynamics. In the case of ordinary waves incident on a shell, a ray formulation is available to describe the coupling to subsonic flexural waves [P. L. Marston and N. H. Sun, J. Acoust. Soc. Am. 97, 777-783 (1995)]. When the incident wave is evanescent, the distance between propagating plane wavefronts is smaller than the ordinary acoustical wavelength at the same frequency and the coupling condition for the excitation of flexural waves on shells or plates is modified. Instead of matching the flexural wave number with the propagating part of the acoustic wave number only at the coincidence frequency, a second low-frequency wave number matching condition is found for highly evanescent waves. Numerical evaluation of the modified partial-wave-series appropriate for an evanescent wave is used to investigate the low-frequency coupling of evanescent waves with flexural wave resonances of shells.

The transparency trap.

PubMed

Bernstein, Ethan

2014-10-01

To promote accountability, productivity, and shared learning, many organizations create open work environments and gather reams of data on how individuals spend their time. A few years ago, HBS professor Ethan Bernstein set out to find empirical evidence that such approaches improve organizational performance. What he discovered is that this kind of transparency often has an unintended consequence: It can leave employees feeling vulnerable and exposed. When that happens, they conceal any conduct that deviates from the norm so that they won't have to explain it. Unrehearsed, experimental behaviors sometimes stop altogether. But Bernstein also discovered organizations that had established zones of privacy within open environments by setting four types of boundaries: around teams, between feedback and evaluation, between decision rights and improvement rights, and around periods of experimentation. Moreover, across several studies, the companies that had done all this were the ones that consistently got the most creative, efficient, and thoughtful work from their employees. Bernstein's conclusion? By balancing transparency and privacy, organizations can capture the benefits of both, and encourage just the right amount of "positive deviance" needed to increase innovation and productivity.

Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma

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

Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp; Ichimura, M.; Okada, T.

2015-09-15

A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in themore » magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.« less

ECRH launching scenario in FFHR-d1

NASA Astrophysics Data System (ADS)

Yanagihara, Kota; Kubo, Shin; Shimozuma, Takashi; Yoshimura, Yasuo; Igami, Hiroe; Takahashi, Hiromi; Tsujimura, Tohru; Makino, Ryohhei

2016-10-01

ECRH is promising as a principal heating system in a prototype helical reactor FFHR-d1 where the heating power of 80 MW is required to bring the plasma parameter to break even condition. To generate the plasma and bring it to ignition condition in FFHR-d1, it is effective to heat the under/over-dense plasma with normal ECRH or Electron Bernstein Wave (EBW). Normal ECRH is well established but heating via EBW need sophisticated injection control. EBW can be excited via the O(ordinary)-X(extraordinary)-B(EBW) mode conversion process by launching the ordinary wave from the low field side to plasma cut-off layer with optimum injection angle, and the range of injection angle to get high OXB mode conversion rate is called OXB mode conversion window. Since the window position can change as the plasma parameter, it is necessary to optimize the injection angle so as to aim the window in response to the plasma parameters. Candidates of antenna positions are determined by optimum injection points on the plasma facing wall calculated by the injection angle. Given such picked up area, detailed analysis using ray-tracing calculations and engineering antenna design will be performed.

Statistics and classification of the microwave zebra patterns associated with solar flares

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

Tan, Baolin; Tan, Chengming; Zhang, Yin

2014-01-10

The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis of a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ondŕejov Radiospectrograph in the Czech Republic at frequencies of 1.00-7.60 GHz from 2000 to 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree,more » duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into three types: equidistant ZPs, variable-distant ZPs, and growing-distant ZPs, possibly corresponding to mechanisms of the Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models and understand the physical processes in the source regions.« less

Mode-coupling and wave-particle interactions for unstable ion-acoustic waves.

NASA Technical Reports Server (NTRS)

Martin, P.; Fried, B. D.

1972-01-01

A theory for the spatial development of linearly unstable, coupled waves is presented in which both quasilinear and mode-coupling effects are treated in a self-consistent manner. Steady-state excitation of two waves is assumed at the boundary x = 0, the plasma being homogeneous in the y and z directions. Coupled equations are derived for the x dependence of the amplitudes of the primary waves and the secondary waves, correct through terms of second order in the wave amplitude, but without the usual approximation of small growth rates. This general formalism is then applied to the case of coupled ion-acoustic waves driven unstable by an ion beam streaming in the direction of the x axis. If the modifications of the ion beam by the waves (quasilinear effects) are ignored, explosive instabilities (singularities in all of the amplitudes at finite x) are found even when all of the waves have positive energy. If these wave-particle interactions are included, the solutions are no longer singular, and all of the amplitudes have finite maxima.

Mode coupling and wave particle interactions for unstable ion acoustic waves

NASA Technical Reports Server (NTRS)

Martin, P.; Fried, B. D.

1972-01-01

A theory for the spatial development of linearly unstable, coupled waves is presented in which both quasi-linear and mode coupling effects are treated in a self-consistent manner. Steady state excitation of two waves is assumed at the boundary x = 0, the plasma being homogeneous in the y and z directions. Coupled equations are derived for the x dependence of the amplitudes of the primary waves and the secondary waves, correct through second order terms in the wave amplitude, but without usual approximation of small growth rates. This general formalism is then applied to the case of coupled ion acoustic waves driven unstable by an ion beam streaming in the direction of the x axis. If the modifications of the ion beam by the waves (quasi-linear effects) are ignored, explosive instabilities (singularities in all of the amplitudes at finite x) are found, even when all of the waves have positive energy. If these wave-particle interactions are included, the solutions are no longer singular, and all of the amplitudes have finite maxima.

The Use of a 28 GHz Gyrotron for EBW Startup Experiments on MAST

NASA Astrophysics Data System (ADS)

Caughman, J. B.; Bigelow, T. S.; Diem, S. J.; Peng, Y. K. M.; Rasmussen, D. A.; Shevchenko, V.; Hawes, J.; Lloyd, B.

2009-11-01

The use of electron Bernstein waves for non-inductive plasma current startup in MAST has recently been demonstrated [1]. The injection of 100 kW at 28 GHz generated plasma currents of up to 33 kA without the use of solenoid flux, and limited solenoid assist resulted in up to 55 kA of plasma current. A higher power 28 GHz gyrotron, with power levels of up to 300 kW for 0.5 seconds, is currently being commissioned. It is being used to investigate the scaling of startup current with microwave power and power profile as a function of time. Power modulation experiments are also being explored. Gyrotron performance and experimental results will be presented. [4pt] [1] V. Shevchenko, et al., Proceedings of the 15^th Joint Workshop on ECE and ECRH, Yosimite, USA, p. 68 (2009)

The Physics of Tokamak Start-up

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

D. Mueller

Tokamak start-up on present-day devices usually relies on inductively induced voltage from a central solenoid. In some cases inductive startup is assisted with auxiliary power from electron cyclotron radio frequency heating. ITER, the National Spherical Torus eXperiment Upgrade and JT60, now under construction, will make use of the understanding gained from present-day devices to ensure successful start-up. Design of a spherical tokamak (ST) with DT capability for nuclear component testing would require an alternative to a central solenoid because the small central column in an ST has insufficient space to provide shielding for the insulators in the solenoid. Alternative start-upmore » techniques such as induction using outer poloidal field coils, electron Bernstein wave start-up, coaxial helicity injection and point source helicity injection have been used with success, but require demonstration of scaling to higher plasma current.« less

The physics of tokamak start-up

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

Mueller, D.

Tokamak start-up on present-day devices usually relies on inductively induced voltage from a central solenoid. In some cases, inductive startup is assisted with auxiliary power from electron cyclotron radio frequency heating. International Thermonuclear Experimental Reactor, the National Spherical Torus Experiment Upgrade and JT60, now under construction, will make use of the understanding gained from present-day devices to ensure successful start-up. Design of a spherical tokamak (ST) with DT capability for nuclear component testing would require an alternative to a central solenoid because the small central column in an ST has insufficient space to provide shielding for the insulators in themore » solenoid. Alternative start-up techniques such as induction using outer poloidal field coils, electron Bernstein wave start-up, coaxial helicity injection, and point source helicity injection have been used with success, but require demonstration of scaling to higher plasma current.« less

Atmosphere-Wave-Ocean Coupling from Regional to Global Earth System Models for High-Impact Extreme Weather Prediction

NASA Astrophysics Data System (ADS)

Chen, S. S.; Curcic, M.

2017-12-01

The need for acurrate and integrated impact forecasts of extreme wind, rain, waves, and storm surge is growing as coastal population and built environment expand worldwide. A key limiting factor in forecasting impacts of extreme weather events associated with tropical cycle and winter storms is fully coupled atmosphere-wave-ocean model interface with explicit momentum and energy exchange. It is not only critical for accurate prediction of storm intensity, but also provides coherent wind, rian, ocean waves and currents forecasts for forcing for storm surge. The Unified Wave INterface (UWIN) has been developed for coupling of the atmosphere-wave-ocean models. UWIN couples the atmosphere, wave, and ocean models using the Earth System Modeling Framework (ESMF). It is a physically based and computationally efficient coupling sytem that is flexible to use in a multi-model system and portable for transition to the next generation global Earth system prediction mdoels. This standardized coupling framework allows researchers to develop and test air-sea coupling parameterizations and coupled data assimilation, and to better facilitate research-to-operation activities. It has been used and extensively tested and verified in regional coupled model forecasts of tropical cycles and winter storms (Chen and Curcic 2016, Curcic et al. 2016, and Judt et al. 2016). We will present 1) an overview of UWIN and its applications in fully coupled atmosphere-wave-ocean model predictions of hurricanes and coastal winter storms, and 2) implenmentation of UWIN in the NASA GMAO GEOS-5.

Correlation between hypersensitivity induced by esophageal acid infusion and the baseline impedance level in patients with suspected gastroesophageal reflux.

PubMed

Seo, A Young; Shin, Cheol Min; Kim, Nayoung; Yoon, Hyuk; Park, Young Soo; Lee, Dong Ho

2015-07-01

To evaluate the relevance between the pH parameters and baseline impedance level or esophageal hypomotility in patients with suspected gastroesophageal reflux. The recordings of 51 patients with heartburn, acid regurgitation, globus or noncardiac chest pain were analyzed. Evaluation included a 24-h multichannel intraluminal impedance-pH test while on off-proton pump inhibitor therapy over 1 week, high-resolution manometry and Bernstein test. Mean baseline impedance level at the most distal portion of the impedance channel was assessed manually. Esophageal hypomotility was evaluated using transitional zone defect (TZD) and distal break (DB) length measurement. In the study subjects (n = 51), 6 had a DeMeester score of more than 14.7 and 14 had a positive symptom index. The Bernstein test was positive in ten patients. The baseline impedance level was inversely correlated with the acid exposure time % (r = -0.660, P < 0.001). Also, all reflux and weakly acid reflux time % measured by impedance monitoring showed a weak correlation with TZD + DB length (r = 0.327 and 0.324, P = 0.019 and 0.020, respectively). Although a positive Bernstein test has no relevance for the acid exposure time or acid-related symptoms as represented by the DeMeester score or symptom index, the baseline impedance level was significantly lower in patients with a positive Bernstein test than in those with a negative one (2,628.4 ± 862.7 vs. 1,752.2 ± 611.1 Ω, P = 0.004). A lower baseline impedance level is closely related to increased esophageal acid exposure. Hypersensitivity induced by esophageal acid infusion might be attributed to acid-induced mucosal changes of the esophagus.

Attraction and repulsion of spiral waves by inhomogeneity of conduction anisotropy--a model of spiral wave interaction with electrical remodeling of heart tissue.

PubMed

Kuklik, Pawel; Sanders, Prashanthan; Szumowski, Lukasz; Żebrowski, Jan J

2013-01-01

Various forms of heart disease are associated with remodeling of the heart muscle, which results in a perturbation of cell-to-cell electrical coupling. These perturbations may alter the trajectory of spiral wave drift in the heart muscle. We investigate the effect of spatially extended inhomogeneity of transverse cell coupling on the spiral wave trajectory using a simple active media model. The spiral wave was either attracted or repelled from the center of inhomogeneity as a function of cell excitability and gradient of the cell coupling. High levels of excitability resulted in an attraction of the wave to the center of inhomogeneity, whereas low levels resulted in an escape and termination of the spiral wave. The spiral wave drift velocity was related to the gradient of the coupling and the initial position of the wave. In a diseased heart, a region of altered transverse coupling corresponds with local gap junction remodeling that may be responsible for stabilization-destabilization of spiral waves and hence reflect potentially important targets in the treatment of heart arrhythmias.

Investigation of hurricane Ivan using the coupled ocean-atmosphere-wave-sediment transport (COAWST) model

USGS Publications Warehouse

Zambon, Joseph B.; He, Ruoying; Warner, John C.

2014-01-01

The coupled ocean–atmosphere–wave–sediment transport (COAWST) model is used to hindcast Hurricane Ivan (2004), an extremely intense tropical cyclone (TC) translating through the Gulf of Mexico. Sensitivity experiments with increasing complexity in ocean–atmosphere–wave coupled exchange processes are performed to assess the impacts of coupling on the predictions of the atmosphere, ocean, and wave environments during the occurrence of a TC. Modest improvement in track but significant improvement in intensity are found when using the fully atmosphere–ocean-wave coupled configuration versus uncoupled (e.g., standalone atmosphere, ocean, or wave) model simulations. Surface wave fields generated in the fully coupled configuration also demonstrates good agreement with in situ buoy measurements. Coupled and uncoupled model-simulated sea surface temperature (SST) fields are compared with both in situ and remote observations. Detailed heat budget analysis reveals that the mixed layer temperature cooling in the deep ocean (on the shelf) is caused primarily by advection (equally by advection and diffusion).

Millimeter-Wave Generation Via Plasma Three-Wave Mixing

DTIC Science & Technology

1988-06-01

are coupled to a third space -charge wave with dispersion 2w W k -k k . (16) A plasma-loaded-waveguide mode is excited at the intersection of this...DISPERSION "FAST" W PLASMA WAVE Wc PLASMA WAVE A-lA oppositely directed EPWs with different phase velocities (wp/k., and wO/k. 2) are coupled to a third ... space -charge wave with dispersion 2w I- k k .(16) e 2 A plaama-loaded-waveguide mode is excited at the intersection of this coupled space-charge wave

Two-dimensional solitary waves and periodic waves on coupled nonlinear electrical transmission lines

NASA Astrophysics Data System (ADS)

Wang, Heng; Zheng, Shuhua

2017-06-01

By using the dynamical system approach, the exact travelling wave solutions for a system of coupled nonlinear electrical transmission lines are studied. Based on this method, the bifurcations of phase portraits of a dynamical system are given. The two-dimensional solitary wave solutions and periodic wave solutions on coupled nonlinear transmission lines are obtained. With the aid of Maple, the numerical simulations are conducted for solitary wave solutions and periodic wave solutions to the model equation. The results presented in this paper improve upon previous studies.

Beta value coupled wave theory for nonslanted reflection gratings.

PubMed

Neipp, Cristian; Francés, Jorge; Gallego, Sergi; Bleda, Sergio; Martínez, Francisco Javier; Pascual, Inmaculada; Beléndez, Augusto

2014-01-01

We present a modified coupled wave theory to describe the properties of nonslanted reflection volume diffraction gratings. The method is based on the beta value coupled wave theory, which will be corrected by using appropriate boundary conditions. The use of this correction allows predicting the efficiency of the reflected order for nonslanted reflection gratings embedded in two media with different refractive indices. The results obtained by using this method will be compared to those obtained using a matrix method, which gives exact solutions in terms of Mathieu functions, and also to Kogelnik's coupled wave theory. As will be demonstrated, the technique presented in this paper means a significant improvement over Kogelnik's coupled wave theory.

Beta Value Coupled Wave Theory for Nonslanted Reflection Gratings

PubMed Central

Neipp, Cristian; Francés, Jorge; Gallego, Sergi; Bleda, Sergio; Martínez, Francisco Javier; Pascual, Inmaculada; Beléndez, Augusto

2014-01-01

We present a modified coupled wave theory to describe the properties of nonslanted reflection volume diffraction gratings. The method is based on the beta value coupled wave theory, which will be corrected by using appropriate boundary conditions. The use of this correction allows predicting the efficiency of the reflected order for nonslanted reflection gratings embedded in two media with different refractive indices. The results obtained by using this method will be compared to those obtained using a matrix method, which gives exact solutions in terms of Mathieu functions, and also to Kogelnik's coupled wave theory. As will be demonstrated, the technique presented in this paper means a significant improvement over Kogelnik's coupled wave theory. PMID:24723811

Strongly coupled stress waves in heterogeneous plates.

NASA Technical Reports Server (NTRS)

Wang, A. S. D.; Chou, P. C.; Rose, J. L.

1972-01-01

Consideration of coupled stress waves generated by an impulsive load applied at one end of a semiinfinite plate. For the field equations governing the one-dimensional coupled waves a hyperbolic system of equations is obtained in which a strong coupling in the second derivatives exists. The method of characteristics described by Chou and Mortimer (1967) is extended to cover the case of strong coupling, and a study is made of the transient stress waves in a semiinfinite plate subjected to an initial step input. Coupled discontinuity fronts are found to propagate at different velocities. The normal plate stress and the bending moment at different time regimes are illustrated by graphs.

Flux-corrected transport algorithms for continuous Galerkin methods based on high order Bernstein finite elements

NASA Astrophysics Data System (ADS)

Lohmann, Christoph; Kuzmin, Dmitri; Shadid, John N.; Mabuza, Sibusiso

2017-09-01

This work extends the flux-corrected transport (FCT) methodology to arbitrary order continuous finite element discretizations of scalar conservation laws on simplex meshes. Using Bernstein polynomials as local basis functions, we constrain the total variation of the numerical solution by imposing local discrete maximum principles on the Bézier net. The design of accuracy-preserving FCT schemes for high order Bernstein-Bézier finite elements requires the development of new algorithms and/or generalization of limiting techniques tailored for linear and multilinear Lagrange elements. In this paper, we propose (i) a new discrete upwinding strategy leading to local extremum bounded low order approximations with compact stencils, (ii) high order variational stabilization based on the difference between two gradient approximations, and (iii) new localized limiting techniques for antidiffusive element contributions. The optional use of a smoothness indicator, based on a second derivative test, makes it possible to potentially avoid unnecessary limiting at smooth extrema and achieve optimal convergence rates for problems with smooth solutions. The accuracy of the proposed schemes is assessed in numerical studies for the linear transport equation in 1D and 2D.

Waveform Modeling of the Crust and Upper Mantle Using S, Sp, SsPmP, and Shear-Coupled PL Waves

DTIC Science & Technology

2008-05-10

and excitation of shear-coupled Pl waves with distance and corresponding phase velocity ( Vph )-period (T) curve: αN and βN are the P and S wave...Pulliam and Sen, 2005) (b) Propagation characteristics and excitation of shear-coupled Pl waves with distance and corresponding phase velocity ( Vph

Generation mechanisms of fundamental rogue wave spatial-temporal structure.

PubMed

Ling, Liming; Zhao, Li-Chen; Yang, Zhan-Ying; Guo, Boling

2017-08-01

We discuss the generation mechanism of fundamental rogue wave structures in N-component coupled systems, based on analytical solutions of the nonlinear Schrödinger equation and modulational instability analysis. Our analysis discloses that the pattern of a fundamental rogue wave is determined by the evolution energy and growth rate of the resonant perturbation that is responsible for forming the rogue wave. This finding allows one to predict the rogue wave pattern without the need to solve the N-component coupled nonlinear Schrödinger equation. Furthermore, our results show that N-component coupled nonlinear Schrödinger systems may possess N different fundamental rogue wave patterns at most. These results can be extended to evaluate the type and number of fundamental rogue wave structure in other coupled nonlinear systems.

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

DOEpatents

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

1999-03-23

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

Modulational instability, beak-shaped rogue waves, multi-dark-dark solitons and dynamics in pair-transition-coupled nonlinear Schrödinger equations.

PubMed

Zhang, Guoqiang; Yan, Zhenya; Wen, Xiao-Yong

2017-07-01

The integrable coupled nonlinear Schrödinger equations with four-wave mixing are investigated. We first explore the conditions for modulational instability of continuous waves of this system. Secondly, based on the generalized N -fold Darboux transformation (DT), beak-shaped higher-order rogue waves (RWs) and beak-shaped higher-order rogue wave pairs are derived for the coupled model with attractive interaction in terms of simple determinants. Moreover, we derive the simple multi-dark-dark and kink-shaped multi-dark-dark solitons for the coupled model with repulsive interaction through the generalizing DT. We explore their dynamics and classifications by different kinds of spatial-temporal distribution structures including triangular, pentagonal, 'claw-like' and heptagonal patterns. Finally, we perform the numerical simulations to predict that some dark solitons and RWs are stable enough to develop within a short time. The results would enrich our understanding on nonlinear excitations in many coupled nonlinear wave systems with transition coupling effects.

Coupling of an acoustic wave to shear motion due to viscous heating

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

Liu, Bin; Goree, J.

2016-07-15

Viscous heating due to shear motion in a plasma can result in the excitation of a longitudinal acoustic wave, if the shear motion is modulated in time. The coupling mechanism is a thermal effect: time-dependent shear motion causes viscous heating, which leads to a rarefaction that can couple into a longitudinal wave, such as an acoustic wave. This coupling mechanism is demonstrated in an electrostatic three-dimensional (3D) simulation of a dusty plasma, in which a localized shear flow is initiated as a pulse, resulting in a delayed outward propagation of a longitudinal acoustic wave. This coupling effect can be profoundmore » in plasmas that exhibit localized viscous heating, such as the dusty plasma we simulated using parameters typical of the PK-4 experiment. We expect that a similar phenomenon can occur with other kinds of plasma waves.« less

Plasma source development for fusion-relevant material testing

DOE PAGES

Caughman, John B. O.; Goulding, Richard H.; Biewer, Theodore M.; ...

2017-05-01

Plasma facing materials in the divertor of a magnetic fusion reactor will have to tolerate steady-state plasma heat fluxes in the range of 10 MW/m2 for ~107 sec, in addition to fusion neutron fluences, which can damage the plasma facing materials to high displacements per atom (dpa) of ~50 dpa . Material solutions needed for the plasma facing components are yet to be developed and tested. The Materials Plasma Exposure eXperiment (MPEX) is a newly proposed steady state linear plasma device that is designed to deliver the necessary plasma heat flux to a target for this material testing, including themore » capability to expose a-priori neutron damaged material samples to those plasmas. The requirements of the plasma source needed to deliver this plasma heat flux are being developed on the Proto-MPEX device, which is a linear high-intensity radio frequency (RF) plasma source that combines a high-density helicon plasma generator with electron and ion heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration. The helicon plasma is operated at 13.56 MHz with RF power levels up to 120 kW. Microwaves at 28 GHz (~30 kW) are coupled to the electrons in the over-dense helicon plasma via Electron Bernstein Waves (EBW), and ion cyclotron heating at 7-9 MHz (~30 kW) is via a magnetic beach approach. High plasma densities >6x1019/m3 have been produced in deuterium, with electron temperatures that can range from 2 to >10 eV. Operation with on-axis magnetic field strengths between 0.6 and 1.4 T is typical. The plasma heat flux delivered to a target can be > 10 MW/m2, depending on the operating conditions.« less

Plasma source development for fusion-relevant material testing

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

Caughman, John B. O.; Goulding, Richard H.; Biewer, Theodore M.

Plasma facing materials in the divertor of a magnetic fusion reactor will have to tolerate steady-state plasma heat fluxes in the range of 10 MW/m2 for ~107 sec, in addition to fusion neutron fluences, which can damage the plasma facing materials to high displacements per atom (dpa) of ~50 dpa . Material solutions needed for the plasma facing components are yet to be developed and tested. The Materials Plasma Exposure eXperiment (MPEX) is a newly proposed steady state linear plasma device that is designed to deliver the necessary plasma heat flux to a target for this material testing, including themore » capability to expose a-priori neutron damaged material samples to those plasmas. The requirements of the plasma source needed to deliver this plasma heat flux are being developed on the Proto-MPEX device, which is a linear high-intensity radio frequency (RF) plasma source that combines a high-density helicon plasma generator with electron and ion heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration. The helicon plasma is operated at 13.56 MHz with RF power levels up to 120 kW. Microwaves at 28 GHz (~30 kW) are coupled to the electrons in the over-dense helicon plasma via Electron Bernstein Waves (EBW), and ion cyclotron heating at 7-9 MHz (~30 kW) is via a magnetic beach approach. High plasma densities >6x1019/m3 have been produced in deuterium, with electron temperatures that can range from 2 to >10 eV. Operation with on-axis magnetic field strengths between 0.6 and 1.4 T is typical. The plasma heat flux delivered to a target can be > 10 MW/m2, depending on the operating conditions.« less

Wave propagation problem for a micropolar elastic waveguide

NASA Astrophysics Data System (ADS)

Kovalev, V. A.; Murashkin, E. V.; Radayev, Y. N.

2018-04-01

A propagation problem for coupled harmonic waves of translational displacements and microrotations along the axis of a long cylindrical waveguide is discussed at present study. Microrotations modeling is carried out within the linear micropolar elasticity frameworks. The mathematical model of the linear (or even nonlinear) micropolar elasticity is also expanded to a field theory model by variational least action integral and the least action principle. The governing coupled vector differential equations of the linear micropolar elasticity are given. The translational displacements and microrotations in the harmonic coupled wave are decomposed into potential and vortex parts. Calibrating equations providing simplification of the equations for the wave potentials are proposed. The coupled differential equations are then reduced to uncoupled ones and finally to the Helmholtz wave equations. The wave equations solutions for the translational and microrotational waves potentials are obtained for a high-frequency range.

Breathers and solitons on two different backgrounds in a generalized coupled Hirota system with four wave mixing

NASA Astrophysics Data System (ADS)

Xu, Han-Xiang; Yang, Zhan-Ying; Zhao, Li-Chen; Duan, Liang; Yang, Wen-Li

2018-07-01

We study breathers and solitons on different backgrounds in optical fiber system, which is governed by generalized coupled Hirota equations with four wave mixing effect. On plane wave background, a transformation between different types of solitons is discovered. Then, on periodic wave background, we find breather-like nonlinear localized waves of which formation mechanism are related to the energy conversion between two components. The energy conversion results from four wave mixing. Furthermore, we prove that this energy conversion is controlled by amplitude and period of backgrounds. Finally, solitons on periodic wave background are also exhibited. These results would enrich our knowledge of nonlinear localized waves' excitation in coupled system with four wave mixing effect.

Traveling wave in a three-dimensional array of conformist and contrarian oscillators

NASA Astrophysics Data System (ADS)

Hoang, Danh-Tai; Jo, Junghyo; Hong, Hyunsuk

2015-03-01

We consider a system of conformist and contrarian oscillators coupled locally in a three-dimensional cubic lattice and explore collective behavior of the system. The conformist oscillators attractively interact with the neighbor oscillators and therefore tend to be aligned with the neighbors' phase. The contrarian oscillators interact repulsively with the neighbors and therefore tend to be out of phase with them. In this paper, we investigate whether many peculiar dynamics that have been observed in the mean-field system with global coupling can emerge even with local coupling. In particular, we pay attention to the possibility that a traveling wave may arise. We find that the traveling wave occurs due to coupling asymmetry and not by global coupling; this observation confirms that the global coupling is not essential to the occurrence of a traveling wave in the system. The traveling wave can be a mechanism for the coherent rhythm generation of the circadian clock or of hormone secretion in biological systems under local coupling.

A Revised Method of Presenting Wavenumber-Frequency Power Spectrum Diagrams That Reveals the Asymmetric Nature of Tropical Large-scale Waves

NASA Technical Reports Server (NTRS)

Chao, Winston C.; Yang, Bo; Fu, Xiouhua

2007-01-01

The popular method of presenting wavenumber-frequency power spectrum diagrams for studying tropical large-scale waves in the literature is shown to give an incomplete presentation of these waves. The so-called "convectively-coupled Kelvin (mixed Rossby-gravity) waves" are presented as existing only in the symmetric (antisymmetric) component of the diagrams. This is obviously not consistent with the published composite/regression studies of "convectively-coupled Kelvin waves," which illustrate the asymmetric nature of these waves. The cause of this inconsistency is revealed in this note and a revised method of presenting the power spectrum diagrams is proposed. When this revised method is used, "convectively-coupled Kelvin waves" do show anti-symmetric components, and "convectively-coupled mixed Rossby-gravity waves (also known as Yanai waves)" do show a hint of symmetric components. These results bolster a published proposal that these waves be called "chimeric Kelvin waves," "chimeric mixed Rossby-gravity waves," etc. This revised method of presenting power spectrum diagrams offers a more rigorous means of comparing the General Circulation Models (GCM) output with observations by calling attention to the capability of GCMs in correctly simulating the asymmetric characteristics of the equatorial waves.

Toward nonlinear magnonics: Intensity-dependent spin-wave switching in insulating side-coupled magnetic stripes

NASA Astrophysics Data System (ADS)

Sadovnikov, A. V.; Odintsov, S. A.; Beginin, E. N.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Nikitov, S. A.

2017-10-01

We demonstrate that the nonlinear spin-wave transport in two laterally parallel magnetic stripes exhibit the intensity-dependent power exchange between the adjacent spin-wave channels. By the means of Brillouin light scattering technique, we investigate collective nonlinear spin-wave dynamics in the presence of magnetodipolar coupling. The nonlinear intensity-dependent effect reveals itself in the spin-wave mode transformation and differential nonlinear spin-wave phase shift in each adjacent magnetic stripe. The proposed analytical theory, based on the coupled Ginzburg-Landau equations, predicts the geometry design involving the reduction of power requirement to the all-magnonic switching. A very good agreement between calculation and experiment was found. In addition, a micromagnetic and finite-element approach has been independently used to study the nonlinear behavior of spin waves in adjacent stripes and the nonlinear transformation of spatial profiles of spin-wave modes. Our results show that the proposed spin-wave coupling mechanism provides the basis for nonlinear magnonic circuits and opens the perspectives for all-magnonic computing architecture.

Regional seismic wavefield computation on a 3-D heterogeneous Earth model by means of coupled traveling wave synthesis

USGS Publications Warehouse

Pollitz, F.F.

2002-01-01

I present a new algorithm for calculating seismic wave propagation through a three-dimensional heterogeneous medium using the framework of mode coupling theory originally developed to perform very low frequency (f < ???0.01-0.05 Hz) seismic wavefield computation. It is a Greens function approach for multiple scattering within a defined volume and employs a truncated traveling wave basis set using the locked mode approximation. Interactions between incident and scattered wavefields are prescribed by mode coupling theory and account for the coupling among surface waves, body waves, and evanescent waves. The described algorithm is, in principle, applicable to global and regional wave propagation problems, but I focus on higher frequency (typically f ??????0.25 Hz) applications at regional and local distances where the locked mode approximation is best utilized and which involve wavefields strongly shaped by propagation through a highly heterogeneous crust. Synthetic examples are shown for P-SV-wave propagation through a semi-ellipsoidal basin and SH-wave propagation through a fault zone.

Discrete Kinetic Eigenmode Spectra of Electron Plasma Oscillations in Weakly Collisional Plasma: A Numerical Study

NASA Technical Reports Server (NTRS)

Black, Carrie; Germaschewski, Kai; Bhattacharjee, Amitava; Ng, C. S.

2013-01-01

It has been demonstrated that in the presence of weak collisions, described by the Lenard-Bernstein collision operator, the Landau-damped solutions become true eigenmodes of the system and constitute a complete set. We present numerical results from an Eulerian Vlasov code that incorporates the Lenard-Bernstein collision operator. The effect of the collisions on the numerical recursion phenomenon seen in Vlasov codes is discussed. The code is benchmarked against exact linear eigenmode solutions in the presence of weak collisions, and a spectrum of Landau-damped solutions is determined within the limits of numerical resolution. Tests of the orthogonality and the completeness relation are presented.

Helicon wave coupling in KSTAR plasmas for off-axis current drive in high electron pressure plasmas

NASA Astrophysics Data System (ADS)

Wang, S. J.; Wi, H. H.; Kim, H. J.; Kim, J.; Jeong, J. H.; Kwak, J. G.

2017-04-01

A helicon wave current drive is proposed as an efficient off-axis current drive in the high electron β plasmas that are expected in fusion reactors. A high frequency helicon wave coupling was analyzed using the surface impedance at a plasma boundary. A slow wave coupling, which may compete with the helicon wave coupling at a frequency of 500 MHz, is estimated to be lower than the fast wave coupling by an order of magnitude in the KSTAR edge plasma density and in practical Faraday shield misalignment with the magnetic pitch. A traveling wave antenna, which is a two port combline antenna, was analyzed using a simplified lumped element model. The results show that the traveling wave antenna provides load resiliency because of its insensitivity to loading resistance, provided that the loading resistance at a radiating element is limited within a practical range. The combline antenna is attractive because it does not require a matching system and exhibits a high selectivity of parallel refractive index. Based on the analysis, a seven element combline antenna was fabricated and installed at an off-mid-plane offset of 30 cm from the mid-plane in KSTAR. The low power RF characteristics measured during several plasma discharges showed no evidence of slow wave coupling. This is consistent with the expectation made through the surface impedance analysis which predicted low slow wave coupling. The wave coupling to the plasma is easily controlled by a radial outer-gap control and gas puffing. No plasma confinement degradation was observed during the radial outer-gap control of up to 3 cm in H-mode discharges. In a ELMy plasmas, only a small reflection peak was observed during a very short portion of the ELM bursting period. If the number of radiating elements is increased for high power operation, then complete load resiliency can be expected. A very large coupling can be problematic for maintaining a parallel refractive index, although this issue can be mitigated by increasing the number of elements.

Air-Sea Momentum and Enthalpy Exchange in Coupled Atmosphere-Wave-Ocean Modeling of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Curcic, M.; Chen, S. S.

2016-02-01

The atmosphere and ocean are coupled through momentum, enthalpy, and mass fluxes. Accurate representation of these fluxes in a wide range of weather and climate conditions is one of major challenges in prediction models. Their current parameterizations are based on sparse observations in low-to-moderate winds and are not suited for high wind conditions such as tropical cyclones (TCs) and winter storms. In this study, we use the Unified Wave INterface - Coupled Model (UWIN-CM), a high resolution, fully-coupled atmosphere-wave-ocean model, to better understand the role of ocean surface waves in mediating air-sea momentum and enthalpy exchange in TCs. In particular, we focus on the explicit treatment of wave growth and dissipation for calculating atmospheric and oceanic stress, and its role in upper ocean mixing and surface cooling in the wake of the storm. Wind-wave misalignment and local wave disequilibrium result in difference between atmospheric and oceanic stress being largest on the left side of the storm. We find that explicit wave calculation in the coupled model reduces momentum transfer into the ocean by more than 10% on average, resulting in reduced cooling in TC's wake and subsequent weakening of the storm. We also investigate the impacts of sea surface temperature and upper ocean parameterization on air-sea enthalpy fluxes in the fully coupled model. High-resolution UWIN-CM simulations of TCs with various intensities and structure are conducted in this study to better understand the complex TC-ocean interaction and improve the representation of air-sea coupling processes in coupled prediction models.

Nonlinear transient waves in coupled phase oscillators with inertia.

PubMed

Jörg, David J

2015-05-01

Like the inertia of a physical body describes its tendency to resist changes of its state of motion, inertia of an oscillator describes its tendency to resist changes of its frequency. Here, we show that finite inertia of individual oscillators enables nonlinear phase waves in spatially extended coupled systems. Using a discrete model of coupled phase oscillators with inertia, we investigate these wave phenomena numerically, complemented by a continuum approximation that permits the analytical description of the key features of wave propagation in the long-wavelength limit. The ability to exhibit traveling waves is a generic feature of systems with finite inertia and is independent of the details of the coupling function.

Heterogeneity and nearest-neighbor coupling can explain small-worldness and wave properties in pancreatic islets

NASA Astrophysics Data System (ADS)

Cappon, Giacomo; Pedersen, Morten Gram

2016-05-01

Many multicellular systems consist of coupled cells that work as a syncytium. The pancreatic islet of Langerhans is a well-studied example of such a microorgan. The islets are responsible for secretion of glucose-regulating hormones, mainly glucagon and insulin, which are released in distinct pulses. In order to observe pulsatile insulin secretion from the β-cells within the islets, the cellular responses must be synchronized. It is now well established that gap junctions provide the electrical nearest-neighbor coupling that allows excitation waves to spread across islets to synchronize the β-cell population. Surprisingly, functional coupling analysis of calcium responses in β-cells shows small-world properties, i.e., a high degree of local coupling with a few long-range "short-cut" connections that reduce the average path-length greatly. Here, we investigate how such long-range functional coupling can appear as a result of heterogeneity, nearest-neighbor coupling, and wave propagation. Heterogeneity is also able to explain a set of experimentally observed synchronization and wave properties without introducing all-or-none cell coupling and percolation theory. Our theoretical results highlight how local biological coupling can give rise to functional small-world properties via heterogeneity and wave propagation.

Building unbiased estimators from non-gaussian likelihoods with application to shear estimation

DOE PAGES

Madhavacheril, Mathew S.; McDonald, Patrick; Sehgal, Neelima; ...

2015-01-15

We develop a general framework for generating estimators of a given quantity which are unbiased to a given order in the difference between the true value of the underlying quantity and the fiducial position in theory space around which we expand the likelihood. We apply this formalism to rederive the optimal quadratic estimator and show how the replacement of the second derivative matrix with the Fisher matrix is a generic way of creating an unbiased estimator (assuming choice of the fiducial model is independent of data). Next we apply the approach to estimation of shear lensing, closely following the workmore » of Bernstein and Armstrong (2014). Our first order estimator reduces to their estimator in the limit of zero shear, but it also naturally allows for the case of non-constant shear and the easy calculation of correlation functions or power spectra using standard methods. Both our first-order estimator and Bernstein and Armstrong’s estimator exhibit a bias which is quadratic in true shear. Our third-order estimator is, at least in the realm of the toy problem of Bernstein and Armstrong, unbiased to 0.1% in relative shear errors Δg/g for shears up to |g| = 0.2.« less

Building unbiased estimators from non-Gaussian likelihoods with application to shear estimation

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

Madhavacheril, Mathew S.; Sehgal, Neelima; McDonald, Patrick

2015-01-01

We develop a general framework for generating estimators of a given quantity which are unbiased to a given order in the difference between the true value of the underlying quantity and the fiducial position in theory space around which we expand the likelihood. We apply this formalism to rederive the optimal quadratic estimator and show how the replacement of the second derivative matrix with the Fisher matrix is a generic way of creating an unbiased estimator (assuming choice of the fiducial model is independent of data). Next we apply the approach to estimation of shear lensing, closely following the workmore » of Bernstein and Armstrong (2014). Our first order estimator reduces to their estimator in the limit of zero shear, but it also naturally allows for the case of non-constant shear and the easy calculation of correlation functions or power spectra using standard methods. Both our first-order estimator and Bernstein and Armstrong's estimator exhibit a bias which is quadratic in true shear. Our third-order estimator is, at least in the realm of the toy problem of Bernstein and Armstrong, unbiased to 0.1% in relative shear errors Δg/g for shears up to |g|=0.2.« less

Integrated Scenario Modeling of NSTX Advanced Plasma Configurations

NASA Astrophysics Data System (ADS)

Kessel, Charles; Synakowski, Edward

2003-10-01

The Spherical Torus will provide an attractive fusion energy source if it can demonstrate the following major features: high elongation and triangularity, 100% non-inductive current with a credible path to high bootstrap fractions, non-solenoidal startup and current rampup, high beta with stabilization of RWM instabilities, and sufficiently high energy confinement. NSTX has specific experimental milestones to examine these features, and integrated scenario modeling is helping to understand how these configurations might be produced and what tools are needed to access this operating space. Simulations with the Tokamak Simulation Code (TSC), CURRAY, and JSOLVER/BALMSC/PEST2 have identified fully non-inductively sustained, high beta plasmas that rely on strong plasma shaping accomplished with a PF coil modification, off-axis current drive from Electron Bernstein Waves (EBW), flexible on-axis heating and CD from High Harmonic Fast Wave (HHFW) and Neutral Beam Injection (NBI), and density control. Ideal MHD stability shows that with wall stabilization through plasma rotation and/or RWM feedback coils, a beta of 40% is achievable, with 100% non-inductive current sustained for 4 current diffusion times. Experimental data and theory are combined to produce a best extrapolation to these regimes, which is continuously improved as the discharges approach these parameters, and theoretical/computational methods expand. Further investigations and development for integrated scenario modeling on NSTX is discussed.

One-dimensional kinetic description of nonlinear traveling-pulse and traveling-wave disturbances in long coasting charged particle beams

DOE PAGES

Davidson, Ronald C.; Qin, Hong

2015-09-21

This study makes use of a one-dimensional kinetic model to investigate the nonlinear longitudinal dynamics of a long coasting beam propagating through a perfectly conducting circular pipe with radius r w. The average axial electric field is expressed as < E z >=-(∂/∂z)=-e bg 0∂λ b/∂z-e bg 2r 2 w∂ 3λ b/∂z 3, where g 0 and g 2 are constant geometric factors, λ b(z,t)=∫dp zF b(z,p z,t) is the line density of beam particles, and F b(z,p z,t) satisfies the 1D Vlasov equation. Detailed nonlinear properties of traveling-wave and traveling-pulse (soliton) solutions with time-stationary waveform are examined for amore » wide range of system parameters extending from moderate-amplitudes to large-amplitude modulations of the beam charge density. Two classes of solutions for the beam distribution function are considered, corresponding to: (i) the nonlinear waterbag distribution, where F b=const in a bounded region of p z-space; and (ii) nonlinear Bernstein-Green-Kruskal (BGK)-like solutions, allowing for both trapped and untrapped particle distributions to interact with the self-generated electric field < E z >.« less

Equiparatition of energy for turbulent astrophysical fluids: Accounting for the unseen energy in molecular clouds

NASA Technical Reports Server (NTRS)

Zweibel, Ellen G.; Mckee, Christopher F.

1995-01-01

Molecular clouds are observed to be partially supported by turbulent pressure. The kinetic energy of the turbulence is directly measurable, but the potential energy, which consists of magnetic, thermal, and gravitational potential energy, is largly unseen. We have extended previous results on equipartition between kinetic and potential energy to show that it is likely to be a very good approximation in molecular clouds. We have used two separate approaches to demonstrate this result: For small-amplitude perturbations of a static equilibrium, we have used the energy principle analysis of Bernstein et al. (1958); this derivation applies to perturbations of arbitary wavelength. To treat perturbations of a nonstatic equilibrium, we have used the Lagrangian analysis of Dewar (1970); this analysis applies only to short-wavelength perturbations. Both analysis assume conservation of energy. Wave damping has only a small effect on equipartition if the wave frequency is small compared to the neutral-ion collision frequency; for the particular case we considered, radiative losses have no effect on equipartition. These results are then incorporated in a simple way into analyses of cloud equilibrium and global stability. We discuss the effect of Alfvenic turbulence on the Jeans mass and show that it has little effect on the magnetic critical mass.

One-dimensional kinetic description of nonlinear traveling-pulse and traveling-wave disturbances in long coasting charged particle beams

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

Davidson, Ronald C.; Qin, Hong

This study makes use of a one-dimensional kinetic model to investigate the nonlinear longitudinal dynamics of a long coasting beam propagating through a perfectly conducting circular pipe with radius r w. The average axial electric field is expressed as < E z >=-(∂/∂z)=-e bg 0∂λ b/∂z-e bg 2r 2 w∂ 3λ b/∂z 3, where g 0 and g 2 are constant geometric factors, λ b(z,t)=∫dp zF b(z,p z,t) is the line density of beam particles, and F b(z,p z,t) satisfies the 1D Vlasov equation. Detailed nonlinear properties of traveling-wave and traveling-pulse (soliton) solutions with time-stationary waveform are examined for amore » wide range of system parameters extending from moderate-amplitudes to large-amplitude modulations of the beam charge density. Two classes of solutions for the beam distribution function are considered, corresponding to: (i) the nonlinear waterbag distribution, where F b=const in a bounded region of p z-space; and (ii) nonlinear Bernstein-Green-Kruskal (BGK)-like solutions, allowing for both trapped and untrapped particle distributions to interact with the self-generated electric field < E z >.« less

High Order Accurate Finite Difference Modeling of Seismo-Acoustic Wave Propagation in a Moving Atmosphere and a Heterogeneous Earth Model Coupled Across a Realistic Topography

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

Petersson, N. Anders; Sjogreen, Bjorn

Here, we develop a numerical method for simultaneously simulating acoustic waves in a realistic moving atmosphere and seismic waves in a heterogeneous earth model, where the motions are coupled across a realistic topography. We model acoustic wave propagation by solving the linearized Euler equations of compressible fluid mechanics. The seismic waves are modeled by the elastic wave equation in a heterogeneous anisotropic material. The motion is coupled by imposing continuity of normal velocity and normal stresses across the topographic interface. Realistic topography is resolved on a curvilinear grid that follows the interface. The governing equations are discretized using high ordermore » accurate finite difference methods that satisfy the principle of summation by parts. We apply the energy method to derive the discrete interface conditions and to show that the coupled discretization is stable. The implementation is verified by numerical experiments, and we demonstrate a simulation of coupled wave propagation in a windy atmosphere and a realistic earth model with non-planar topography.« less

High Order Accurate Finite Difference Modeling of Seismo-Acoustic Wave Propagation in a Moving Atmosphere and a Heterogeneous Earth Model Coupled Across a Realistic Topography

DOE PAGES

Petersson, N. Anders; Sjogreen, Bjorn

2017-04-18

Here, we develop a numerical method for simultaneously simulating acoustic waves in a realistic moving atmosphere and seismic waves in a heterogeneous earth model, where the motions are coupled across a realistic topography. We model acoustic wave propagation by solving the linearized Euler equations of compressible fluid mechanics. The seismic waves are modeled by the elastic wave equation in a heterogeneous anisotropic material. The motion is coupled by imposing continuity of normal velocity and normal stresses across the topographic interface. Realistic topography is resolved on a curvilinear grid that follows the interface. The governing equations are discretized using high ordermore » accurate finite difference methods that satisfy the principle of summation by parts. We apply the energy method to derive the discrete interface conditions and to show that the coupled discretization is stable. The implementation is verified by numerical experiments, and we demonstrate a simulation of coupled wave propagation in a windy atmosphere and a realistic earth model with non-planar topography.« less

Seismic excitation by space shuttles

USGS Publications Warehouse

Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

1992-01-01

Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were simultaneously hit by the space shuttle shock waves. The proximity of the natural periods of the high rise buildings and the modal periods of the Los Angeles basin enabled efficient energy transfer from shock wave to seismic wave. ?? 1992 Springer-Verlag.

A coupled "AB" system: Rogue waves and modulation instabilities.

PubMed

Wu, C F; Grimshaw, R H J; Chow, K W; Chan, H N

2015-10-01

Rogue waves are unexpectedly large and localized displacements from an equilibrium position or an otherwise calm background. For the nonlinear Schrödinger (NLS) model widely used in fluid mechanics and optics, these waves can occur only when dispersion and nonlinearity are of the same sign, a regime of modulation instability. For coupled NLS equations, rogue waves will arise even if dispersion and nonlinearity are of opposite signs in each component as new regimes of modulation instability will appear in the coupled system. The same phenomenon will be demonstrated here for a coupled "AB" system, a wave-current interaction model describing baroclinic instability processes in geophysical flows. Indeed, the onset of modulation instability correlates precisely with the existence criterion for rogue waves for this system. Transitions from "elevation" rogue waves to "depression" rogue waves are elucidated analytically. The dispersion relation as a polynomial of the fourth order may possess double pairs of complex roots, leading to multiple configurations of rogue waves for a given set of input parameters. For special parameter regimes, the dispersion relation reduces to a cubic polynomial, allowing the existence criterion for rogue waves to be computed explicitly. Numerical tests correlating modulation instability and evolution of rogue waves were conducted.

Validation of the Fully-Coupled Air-Sea-Wave COAMPS System

NASA Astrophysics Data System (ADS)

Smith, T.; Campbell, T. J.; Chen, S.; Gabersek, S.; Tsu, J.; Allard, R. A.

2017-12-01

A fully-coupled, air-sea-wave numerical model, COAMPS®, has been developed by the Naval Research Laboratory to further enhance understanding of oceanic, atmospheric, and wave interactions. The fully-coupled air-sea-wave system consists of an atmospheric component with full physics parameterizations, an ocean model, NCOM (Navy Coastal Ocean Model), and two wave components, SWAN (Simulating Waves Nearshore) and WaveWatch III. Air-sea interactions between the atmosphere and ocean components are accomplished through bulk flux formulations of wind stress and sensible and latent heat fluxes. Wave interactions with the ocean include the Stokes' drift, surface radiation stresses, and enhancement of the bottom drag coefficient in shallow water due to the wave orbital velocities at the bottom. In addition, NCOM surface currents are provided to SWAN and WaveWatch III to simulate wave-current interaction. The fully-coupled COAMPS system was executed for several regions at both regional and coastal scales for the entire year of 2015, including the U.S. East Coast, Western Pacific, and Hawaii. Validation of COAMPS® includes observational data comparisons and evaluating operational performance on the High Performance Computing (HPC) system for each of these regions.

Statistical analysis of plasmaspheric magnetosonic mode waves from Van Allen Probes observations

NASA Astrophysics Data System (ADS)

Nomura, K.; Miyoshi, Y.; Keika, K.; Shoji, M.; Kurita, S.; Kitamura, N.; Machida, S.; Santolik, O.; Kletzing, C.; Boardsen, S. A.

2015-12-01

Magnetosonic waves (MSWs) are electromagnetic emissions whose properites can be described by the cold plasma extraordinary mode, which are typically generated at frequencies (f) between the proton cyclotron frequency (fcp) and the lower hybrid resonant frequency. It has been suggested that MSWs can contribute to the acceleration of relativistic electrons in the radiation belts. In this study, we investigate the Poynting vector of plasmaspheric MSWs using the spectral matrix data from the EMFISIS instrument onboard the Van Allen Probes spacecraft. We derived the polarization and planarity from the spectrum matrix using the SVD method (Santolik et al., 2003) and also estimated the Poynting vector. The planarity is used as a proxy to distinguish presence of a single wave vector from mixture of waves propagating in different directions. The Poynting vector of MSWs with high planarity shows that the MSWs are observed to propagate radially as well as longitudinally. The occurrence probability of the propagation directions depends on the geomagnetic activities. During the geomagnetically quiet periods　(Kp < 3), the percentage of inward, outward, and longitudinal propagations of MSWs at 60 Hz are 22%, 36% and 42% respectively. On the other hand, during the geomagnetically active periods (Kp > 5), the percentages are 53%, 21%, and 26%, respectively. The result indicates that the MSWs tend to propagate inward during the geomagnetically active periods. Since the fundamental frequency of the ion Bernstein mode would be local cyclotron frequency, we also investigate the source of MSWs from the minimum frequency of MSWs. It is found that a large number of MSWs tend to be generated at L=3.0-3.5 inside the plasmapause. We will also discuss the validity of the Poynting flux computation as a function of f/fcp.

Weakly and strongly coupled Belousov-Zhabotinsky patterns.

PubMed

Weiss, Stephan; Deegan, Robert D

2017-02-01

We investigate experimentally and numerically the synchronization of two-dimensional spiral wave patterns in the Belousov-Zhabotinsky reaction due to point-to-point coupling of two separate domains. Different synchronization modalities appear depending on the coupling strength and the initial patterns in each domain. The behavior as a function of the coupling strength falls into two qualitatively different regimes. The weakly coupled regime is characterized by inter-domain interactions that distorted but do not break wave fronts. Under weak coupling, spiral cores are pushed around by wave fronts in the other domain, resulting in an effective interaction between cores in opposite domains. In the case where each domain initially contains a single spiral, the cores form a bound pair and orbit each other at quantized distances. When the starting patterns consist of multiple randomly positioned spiral cores, the number of cores decreases with time until all that remains are a few cores that are synchronized with a partner in the other domain. The strongly coupled regime is characterized by interdomain interactions that break wave fronts. As a result, the wave patterns in both domains become identical.

Weakly and strongly coupled Belousov-Zhabotinsky patterns

NASA Astrophysics Data System (ADS)

Weiss, Stephan; Deegan, Robert D.

2017-02-01

We investigate experimentally and numerically the synchronization of two-dimensional spiral wave patterns in the Belousov-Zhabotinsky reaction due to point-to-point coupling of two separate domains. Different synchronization modalities appear depending on the coupling strength and the initial patterns in each domain. The behavior as a function of the coupling strength falls into two qualitatively different regimes. The weakly coupled regime is characterized by inter-domain interactions that distorted but do not break wave fronts. Under weak coupling, spiral cores are pushed around by wave fronts in the other domain, resulting in an effective interaction between cores in opposite domains. In the case where each domain initially contains a single spiral, the cores form a bound pair and orbit each other at quantized distances. When the starting patterns consist of multiple randomly positioned spiral cores, the number of cores decreases with time until all that remains are a few cores that are synchronized with a partner in the other domain. The strongly coupled regime is characterized by interdomain interactions that break wave fronts. As a result, the wave patterns in both domains become identical.

Assessment of the importance of the current-wave coupling in the shelf ocean forecasts

NASA Astrophysics Data System (ADS)

Jordà, G.; Bolaños, R.; Espino, M.; Sánchez-Arcilla, A.

2006-10-01

The effects of wave-current interactions on shelf ocean forecasts is investigated in the framework of the MFSTEP (Mediterranean Forecasting System Project Towards Enviromental Predictions) project. A one way sequential coupling approach is adopted to link the wave model (WAM) to the circulation model (SYMPHONIE). The coupling of waves and currents has been done considering four main processes: wave refraction due to currents, surface wind drag and bo€ttom drag modifications due to waves, and the wave induced mass flux. The coupled modelling system is implemented in the southern Catalan shelf (NW Mediterranean), a region with characteristics similar to most of the Mediterranean shelves. The sensitivity experiments are run in a typical operational configuration. The wave refraction by currents seems to be not very relevant in a microtidal context such as the western Mediterranean. The main effect of waves on current forecasts is through the modification of the wind drag. The Stokes drift also plays a significant role due to its spatial and temporal characteristics. Finally, the enhanced bottom friction is just noticeable in the inner shelf.

Evaluation of Simulated Marine Aerosol Production Using the WaveWatchIII Prognostic Wave Model Coupled to the Community Atmosphere Model within the Community Earth System Model

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

Long, M. S.; Keene, William C.; Zhang, J.

2016-11-08

Primary marine aerosol (PMA) is emitted into the atmosphere via breaking wind waves on the ocean surface. Most parameterizations of PMA emissions use 10-meter wind speed as a proxy for wave action. This investigation coupled the 3 rd generation prognostic WAVEWATCH-III wind-wave model within a coupled Earth system model (ESM) to drive PMA production using wave energy dissipation rate – analogous to whitecapping – in place of 10-meter wind speed. The wind speed parameterization did not capture basin-scale variability in relations between wind and wave fields. Overall, the wave parameterization did not improve comparison between simulated versus measured AOD ormore » Na +, thus highlighting large remaining uncertainties in model physics. Results confirm the efficacy of prognostic wind-wave models for air-sea exchange studies coupled with laboratory- and field-based characterizations of the primary physical drivers of PMA production. No discernible correlations were evident between simulated PMA fields and observed chlorophyll or sea surface temperature.« less

Fluid-structure interaction simulation of floating structures interacting with complex, large-scale ocean waves and atmospheric turbulence with application to floating offshore wind turbines

NASA Astrophysics Data System (ADS)

Calderer, Antoni; Guo, Xin; Shen, Lian; Sotiropoulos, Fotis

2018-02-01

We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid-structure interaction (FSI). The large-scale wind-wave interaction model is based on a two-fluid dynamically-coupled approach that employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. The two-phase flow FSI solver is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wave field solver is coupled with the near-field FSI solver with a one-way coupling approach by feeding into the latter waves via a pressure-forcing method combined with the level set method. We validate the model for both simple wave trains and three-dimensional directional waves and compare the results with experimental and theoretical solutions. Finally, we demonstrate the capabilities of the new computational framework by carrying out large-eddy simulation of a floating offshore wind turbine interacting with realistic ocean wind and waves.

Generalized three-dimensional simulation of ferruled coupled-cavity traveling-wave-tube dispersion and impedance characteristics

NASA Technical Reports Server (NTRS)

Maruschek, Joseph W.; Kory, Carol L.; Wilson, Jeffrey D.

1993-01-01

The frequency-phase dispersion and Pierce on-axis interaction impedance of a ferruled, coupled-cavity, traveling-wave tube (TWT), slow-wave circuit were calculated using the three-dimensional simulation code Micro-SOS. The utilization of the code to reduce costly and time-consuming experimental cold tests is demonstrated by the accuracy achieved in calculating these parameters. A generalized input file was developed so that ferruled coupled-cavity TWT slow-wave circuits of arbitrary dimensions could be easily modeled. The practicality of the generalized input file was tested by applying it to the ferruled coupled-cavity slow-wave circuit of the Hughes Aircraft Company model 961HA TWT and by comparing the results with experimental results.

Very small IF resonator filters using reflection of shear horizontal wave at free edges of substrate.

PubMed

Kadota, Michio; Ago, Junya; Horiuchi, Hideya; Ikeura, Mamoru

2002-09-01

A shear horizontal (SH) wave has the characteristic of complete reflection at the free edges of a substrate with a large dielectric constant. A conventional surface acoustic wave (SAW) resonator filter requires reflectors consisting of numerous grating fingers on both sides of interdigital transducers (IDTs). On the contrary, it is considered that small-sized and low loss resonator filters without reflectors consisting of grating fingers can be realized by exploiting this characteristic of the SH wave or the Bleustein-Gulyaev-Shimizu (BGS) wave. There are two types of resonator filters: transversely coupled and longitudinally coupled. No transversely coupled filters (neither conventional nor edge-reflection) using the SH wave on a single-crystal substrate have been realized until now, because two transverse modes (symmetrical and asymmetrical modes) are not easily coupled. However, the authors have realized small low loss transversely coupled resonator filters in the range of 25 to 52 MHz using edge reflections of the BGS wave on piezoelectric ceramic (PZT: Pb(Zr,Ti)O3) substrates for the first time by developing methods by which the two transverse modes could be coupled. On the other hand, longitudinally coupled resonator filters using edge reflection of the SH or BGS wave always have large spurious responses because of the even modes in the out-of-band range, because the frequencies of even modes do not coincide with the nulls of the frequency spectra of the IDTs. Consequently, longitudinally coupled resonator filters using the edge reflection of the SH wave have not been realized. By developing a method of reducing the spurious responses without increasing of the insertion loss, the authors have realized small low loss longitudinally coupled resonator filters in the range of 40 to 190 MHz using edge reflection of BGS or SH waves on PZT or 36 degrees-rotated-Y X-propagation LiTaO3 substrates for the first time. Despite being intermediate frequency (IF) filters, their package (3 x 3 x 1.03 mm3) sizes are as small as those of radio frequency (RF) SAW filters.

Slow wave contraction frequency plateaus in the small intestine are composed of discrete waves of interval increase associated with dislocations.

PubMed

Parsons, Sean P; Huizinga, Jan D

2018-06-03

What is the central question of this study? What is the nature of slow wave driven contraction frequency gradients in the small intestine? What is the main finding and its importance? Frequency plateaus are composed of discrete waves of increased interval, each wave associated with a contraction dislocation. Smooth frequency gradients are generated by localised neural modulation of wave frequency, leading to functionally important wave turbulence. Both patterns are emergent properties of a network of coupled oscillators, the interstitial cells of Cajal. A gut-wide network of interstitial cells of Cajal (ICC) generate electrical oscillations (slow waves) that orchestrate waves of muscle contraction. In the small intestine there is a gradient in slow wave frequency from high at the duodenum to low at the terminal ileum. Time-averaged measurements of frequency have suggested either a smooth or stepped (plateaued) gradient. We measured individual contraction intervals from diameter maps of the mouse small intestine to create interval maps (IMaps). IMaps showed that each frequency plateau was composed of discrete waves of increased interval. Each interval wave originated at a terminating contraction wave, a "dislocation", at the plateau's proximal boundary. In a model chain of coupled phase oscillators, interval wave frequency increased as coupling decreased or as the natural frequency gradient or noise increased. Injuring the intestine at a proximal point to destroy coupling, suppressed distal steps which then reappeared with gap junction block by carbenoxolone. This lent further support to our previous hypothesis that lines of dislocations were fixed by points of low coupling strength. Dislocations induced by electrical field pulses in the intestine and by equivalent phase shift in the model, were associated with interval waves. When the enteric nervous system was active, IMaps showed a chaotic, turbulent pattern of interval change with no frequency steps or plateaus. This probably resulted from local, stochastic release of neurotransmitters. Plateaus, dislocations, interval waves and wave turbulence arise from a dynamic interplay between natural frequency and coupling in the ICC network. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Dynamics of scroll waves with time-delay propagation in excitable media

NASA Astrophysics Data System (ADS)

Chen, Jiang-Xing; Xiao, Jie; Qiao, Li-Yan; Xu, Jiang-Rong

2018-06-01

Information transmission delay can be widely observed in various systems. Here, we study the dynamics of scroll waves with time-delay propagation among slices in excitable media. Weak time delay induces scroll waves to meander. Through increasing the time delay, we find a series of dynamical transitions. Firstly, the straight filament of a scroll wave becomes twisted. Then, the scroll wave breaks and forms interesting patterns. With long time delay, loosed scroll waves are maintained while their period are greatly decreased. Also, cylinder waves appears. The influences of diffusively coupling strength on the time-delay-induced scroll waves are studied. It is found that the critical time delay characterizing those transitions decreases as the coupling strength is increased. A phase diagram in the diffusive coupling-time delay plane is presented.

Non-linear Frequency Shifts, Mode Couplings, and Decay Instability of Plasma Waves

NASA Astrophysics Data System (ADS)

Affolter, Mathew; Anderegg, F.; Driscoll, C. F.; Valentini, F.

2015-11-01

We present experiments and theory for non-linear plasma wave decay to longer wavelengths, in both the oscillatory coupling and exponential decay regimes. The experiments are conducted on non-neutral plasmas in cylindrical Penning-Malmberg traps, θ-symmetric standing plasma waves have near acoustic dispersion ω (kz) ~kz - αkz2 , discretized by kz =mz (π /Lp) . Large amplitude waves exhibit non-linear frequency shifts δf / f ~A2 and Fourier harmonic content, both of which are increased as the plasma dispersion is reduced. Non-linear coupling rates are measured between large amplitude mz = 2 waves and small amplitude mz = 1 waves, which have a small detuning Δω = 2ω1 -ω2 . At small excitation amplitudes, this detuning causes the mz = 1 mode amplitude to ``bounce'' at rate Δω , with amplitude excursions ΔA1 ~ δn2 /n0 consistent with cold fluid theory and Vlasov simulations. At larger excitation amplitudes, where the non-linear coupling exceeds the dispersion, phase-locked exponential growth of the mz = 1 mode is observed, in qualitative agreement with simple 3-wave instability theory. However, significant variations are observed experimentally, and N-wave theory gives stunningly divergent predictions that depend sensitively on the dispersion-moderated harmonic content. Measurements on higher temperature Langmuir waves and the unusual ``EAW'' (KEEN) waves are being conducted to investigate the effects of wave-particle kinetics on the non-linear coupling rates. Department of Energy Grants DE-SC0002451and DE-SC0008693.

Shallow-trap-induced positive absorptive two-beam coupling 'gain' and light-induced transparency in nominally undoped barium titanate

NASA Technical Reports Server (NTRS)

Garrett, M. H.; Tayebati, P.; Chang, J. Y.; Jenssen, H. P.; Warde, C.

1992-01-01

The asymmetry of beam coupling with respect to the orientation of the polar axis in a nominally undoped barium titanate crystal is used to determine the electro-optic and absorptive 'gain' in the usual beam-coupling geometry. For small grating wave vectors, the electrooptic coupling vanishes but the absorptive coupling remains finite and positive. Positive absorptive coupling at small grating wave vectors is correlated with the light-induced transparency of the crystal described herein. The intensity and grating wave vector dependence of the electrooptic and absorptive coupling, and the light-induced transparency are consistent with a model incorporating deep and shallow levels.

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling

DTIC Science & Technology

2015-09-30

Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind- Wave Coupling Peter S. Guest (NPS Technical Contact) Naval...surface fluxes and ocean waves in coupled models in the Beaufort and Chukchi Seas. 2. Understand the physics of heat and mass transfer from the ocean...to the atmosphere. 3. Improve forecasting of waves on the open ocean and in the marginal ice zone. 2 OBJECTIVES 1. Quantifying the open-ocean

Chaotic neoclassical separatrix dissipation in parametric drift-wave decay.

PubMed

Kabantsev, A A; Tsidulko, Yu A; Driscoll, C F

2014-02-07

Experiments and theory characterize a parametric decay instability between plasma drift waves when the nonlinear coupling is modified by an electrostatic barrier. Novel mode coupling terms representing enhanced dissipation and mode phase shifts are caused by chaotic separatrix crossings on the wave-ruffled separatrix. Experimental determination of these coupling terms is in broad agreement with new chaotic neoclassical transport analyses.

Instability of Longitudinal Wave in Magnetized Strongly Coupled Dusty Plasma

NASA Astrophysics Data System (ADS)

Xie, Bai-Song

2003-12-01

Instability of longitudinal wave in magnetized strongly coupled dusty plasmas is investigated. The dust charging relaxation is taken into account. It is found that there exists threshold of interdust distance for the instability of wave, which is determined significantly by the dust charging relaxation, the coupling parameter of high correlation of dust as well the strength of magnetic field.

Inductive-dynamic magnetosphere-ionosphere coupling via MHD waves

NASA Astrophysics Data System (ADS)

Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.

2014-01-01

In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.

Non-autonomous multi-rogue waves for spin-1 coupled nonlinear Gross-Pitaevskii equation and management by external potentials.

PubMed

Li, Li; Yu, Fajun

2017-09-06

We investigate non-autonomous multi-rogue wave solutions in a three-component(spin-1) coupled nonlinear Gross-Pitaevskii(GP) equation with varying dispersions, higher nonlinearities, gain/loss and external potentials. The similarity transformation allows us to relate certain class of multi-rogue wave solutions of the spin-1 coupled nonlinear GP equation to the solutions of integrable coupled nonlinear Schrödinger(CNLS) equation. We study the effect of time-dependent quadratic potential on the profile and dynamic of non-autonomous rogue waves. With certain requirement on the backgrounds, some non-autonomous multi-rogue wave solutions exhibit the different shapes with two peaks and dip in bright-dark rogue waves. Then, the managements with external potential and dynamic behaviors of these solutions are investigated analytically. The results could be of interest in such diverse fields as Bose-Einstein condensates, nonlinear fibers and super-fluids.

Electron Acceleration and Ionization Production in High-Power Heating Experiments at HAARP

NASA Astrophysics Data System (ADS)

Mishin, E. V.; Pedersen, T.

2012-12-01

Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60-80 km. Artificial ionization production is indicated by significant 427.8 nm emissions from the 1st negative band of N2+ and the appearance of transmitter-induced bottomside traces in ionosonde data during the periods of most intense optical emissions. However, the exact mechanisms producing the artificial plasmas remain to be determined. Yet the only existing theoretical models explain the development of artificial plasma as an ionizing wavefront moving downward due to ionization by electrons accelerated by HF-excited strong Langmuir turbulence (SLT) generated near the plasma resonance, where the pump frequency matches the plasma frequency. However, the observations suggest also the significance of interactions with upper hybrid and electron Bernstein waves near multiples of the electron gyrofrequency. We describe recent observations and discuss suitable acceleration mechanisms.

Status of Electron Bernstein Wave (EBW) Research on NSTX and CDX-U

NASA Astrophysics Data System (ADS)

Taylor, G.; Efthimion, P. C.; Jones, B. M.; Wilson, J. R.; Wilgen, J. B.; Bell, G. L.; Bigelow, T. S.; Rasmussen, D. A.; Ram, A. K.; Bers, A.; Harvey, R. W.

2002-11-01

Recent studies of EBWs, via mode conversion (MC) to X-mode electromagnetic radiation on the CDX-U and NSTX spherical torus (ST) plasmas, support the use of EBWs to measure the Te profile and allow local heating and current drive in ST plasmas. An in-vessel antenna with a local adjustable limiter has successfully controlled the density scale length at the MC layer in CDX-U increasing the MC by an order of magnitude to ˜ 100%. A similar technique on NSTX has so far increased MC efficiency fivefold to ˜ 50%. Both results are in good agreement with theoretical predictions. Experiments focused on achieving >= 80% MC on NSTX are planned for the coming year. Ray tracing and Fokker-Planck modeling support the design of a ˜ 1 MW EBW heating and current drive system for NSTX that will assist plasma startup, locally heat electrons, drive non-inductive current and may suppress tearing modes or other MHD that limit high β operation.

A revised method of presenting wavenumber-frequency power spectrum diagrams that reveals the asymmetric nature of tropical large-scale waves

NASA Astrophysics Data System (ADS)

Chao, Winston C.; Yang, Bo; Fu, Xiouhua

2009-11-01

The popular method of presenting wavenumber-frequency power spectrum diagrams for studying tropical large-scale waves in the literature is shown to give an incomplete presentation of these waves. The so-called “convectively coupled Kelvin (mixed Rossby-gravity) waves” are presented as existing only in the symmetric (anti-symmetric) component of the diagrams. This is obviously not consistent with the published composite/regression studies of “convectively coupled Kelvin waves,” which illustrate the asymmetric nature of these waves. The cause of this inconsistency is revealed in this note and a revised method of presenting the power spectrum diagrams is proposed. When this revised method is used, “convectively coupled Kelvin waves” do show anti-symmetric components, and “convectively coupled mixed Rossby-gravity waves (also known as Yanai waves)” do show a hint of symmetric components. These results bolster a published proposal that these waves should be called “chimeric Kelvin waves,” “chimeric mixed Rossby-gravity waves,” etc. This revised method of presenting power spectrum diagrams offers an additional means of comparing the GCM output with observations by calling attention to the capability of GCMs to correctly simulate the asymmetric characteristics of equatorial waves.

Preliminary Study on Coupling Wave-Tide-Storm Surges Prediction System

NASA Astrophysics Data System (ADS)

You, S.; Park, S.; Seo, J.; Kim, K.

2008-12-01

The Korean Peninsula is surrounded by the Yellow Sea, East China Sea, and East Sea. This complex oceanographic system includes large tides in the Yellow Sea and seasonally varying monsoon and typhoon events. For Korea's coastal regions, floods caused by wave and storm surges are among the most serious threats. To predict more accurate wave and storm surge, the development of coupling wave-tide-storm surges prediction system is essential. For the time being, wave and storm surges predictions are still made separately in KMA (Korea Meteorological Administration) and most operational institute. However, many researchers have emphasized the effects of tides and storm surges on wind waves and recommended further investigations into the effects of wave-tide-storm surges interactions and coupling module on wave heights. However, tidal height and current give a great effect on the wave prediction in the Yellow sea where is very high tide and related research is not enough. At present, KMA has operated the wave (RWAM : Regional Wave Model) and storm surges/tide prediction system (RTSM : Regional Tide/Storm Surges Model) for ocean forecasting. The RWAM is WAVEWATCH III which is a third generation wave model developed by Tolman (1989). The RTSM is based on POM (Princeton Ocean Model, Blumberg and Mellor, 1987). The RWAM and RTSM cover the northwestern Pacific Ocean from 115°E to 150°E and from 20°N to 52°N. The horizontal grid intervals are 1/12° in both latitudinal and longitudinal directions. The development, testing and application of a coupling module in which wave-tide-storm surges are incorporated within the frame of KMA Ocean prediction system, has been considered as a step forward in respect of ocean forecasting. In addition, advanced wave prediction model will be applicable to the effect of ocean in the weather forecasting system. The main purpose of this study is to show how the coupling module developed and to report on a series of experiments dealing with the sensitivities and real case prediction of coupling wave-tide-storm surges prediction system.

Factors associated with relationship dissolution and post-dissolution adjustment among lesbian adoptive couples.

PubMed

Farr, Rachel H

2017-01-02

Same-sex adoptive couples are increasingly visible, yet few studies have addressed relationship stability and dissolution among these couples. In this study, using a theoretical framework based on Investment Models and Vulnerability-Stress-Adaptation Theory, factors associated with dissolution and post-dissolution adjustment among 27 lesbian adoptive couples were examined across two points. At Wave 1, all 27 couples were together; children were on average 3 years old. Results revealed that nearly one third broke up over 5 years (between Waves 1 and 2). Factors related to shorter relationship length and undermining coparenting at Wave 1 distinguished women who later broke up versus stayed together. Worse mental health at Wave 2 characterized women in dissolved rather than sustained relationships, even with comparable individual adjustment at Wave 1. Weaker parenting alliance and greater dissatisfaction with childcare divisions were reported by women no longer with their partners at Wave 2 as compared with those in enduring partnerships. This research has implications for understanding lesbian relationship dynamics and associations with individual adjustment.

Dark- and bright-rogue-wave solutions for media with long-wave-short-wave resonance.

PubMed

Chen, Shihua; Grelu, Philippe; Soto-Crespo, J M

2014-01-01

Exact explicit rogue-wave solutions of intricate structures are presented for the long-wave-short-wave resonance equation. These vector parametric solutions feature coupled dark- and bright-field counterparts of the Peregrine soliton. Numerical simulations show the robustness of dark and bright rogue waves in spite of the onset of modulational instability. Dark fields originate from the complex interplay between anomalous dispersion and the nonlinearity driven by the coupled long wave. This unusual mechanism, not available in scalar nonlinear wave equation models, can provide a route to the experimental realization of dark rogue waves in, for instance, negative index media or with capillary-gravity waves.

Dynamics of coupled plasmon polariton wave packets excited at a subwavelength slit in optically thin metal films

NASA Astrophysics Data System (ADS)

Wang, Lei-Ming; Zhang, Lingxiao; Seideman, Tamar; Petek, Hrvoje

2012-10-01

We study by numerical simulations the excitation and propagation dynamics of coupled surface plasmon polariton (SPP) wave packets (WPs) in optically thin Ag films and a bulk Ag/vacuum interface under the illumination of a subwavelength slit by 400 nm continuous wave (cw) and femtosecond pulsed light. The generated surface fields include contributions from both SPPs and quasicylindrical waves, which dominate in different regimes. We explore aspects of the coupled SPP modes in Ag thin films, including symmetry, propagation, attenuation, and the variation of coupling with incident angle and film thickness. Simulations of the electromagnetic transients initiated with femtosecond pulses reveal new features of coupled SPP WP generation and propagation in thin Ag films. Our results show that, under pulsed excitation, the SPP modes in an Ag thin film break up into two distinct bound surface wave packets characterized by marked differences in symmetries, group velocities, attenuation lengths, and dispersion properties. The nanometer spatial and femtosecond temporal scale excitation and propagation dynamics of the coupled SPP WPs are revealed in detail by movies recording the evolution of their transient field distributions.

Pulse

MedlinePlus

... to take your wrist pulse References Bernstein D. History and physical examination. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics . 20th ed. Philadelphia, PA: Elsevier; 2016: ...

Interactions of localized wave structures and dynamics in the defocusing coupled nonlinear Schrödinger equations.

PubMed

Zhang, Guoqiang; Yan, Zhenya; Wen, Xiao-Yong; Chen, Yong

2017-04-01

We investigate the defocusing coupled nonlinear Schrödinger equations from a 3×3 Lax pair. The Darboux transformations with the nonzero plane-wave solutions are presented to derive the newly localized wave solutions including dark-dark and bright-dark solitons, breather-breather solutions, and different types of new vector rogue wave solutions, as well as interactions between distinct types of localized wave solutions. Moreover, we analyze these solutions by means of parameters modulation. Finally, the perturbed wave propagations of some obtained solutions are explored by means of systematic simulations, which demonstrates that nearly stable and strongly unstable solutions. Our research results could constitute a significant contribution to explore the distinct nonlinear waves (e.g., dark solitons, breather solutions, and rogue wave solutions) dynamics of the coupled system in related fields such as nonlinear optics, plasma physics, oceanography, and Bose-Einstein condensates.

Plasma current start-up experiments without the central solenoid in the TST-2 spherical tokamak

NASA Astrophysics Data System (ADS)

Takase, Y.; Ejiri, A.; Shiraiwa, S.; Adachi, Y.; Ishii, N.; Kasahara, H.; Nuga, H.; Ono, Y.; Oosako, T.; Sasaki, M.; Shimada, Y.; Sumitomo, N.; Taguchi, I.; Tojo, H.; Tsujimura, J.; Ushigome, M.; Yamada, T.; Hanada, K.; Hasegawa, M.; Idei, H.; Nakamura, K.; Sakamoto, M.; Sasaki, K.; Sato, K. N.; Zushi, H.; Nishino, N.; Mitarai, O.

2006-08-01

Several techniques for initiating the plasma current without the use of the central solenoid are being developed in TST-2. While TST-2 was temporarily located at Kyushu University, two types of start-up scenarios were demonstrated. (1) A plasma current of 4 kA was generated and sustained for 0.28 s by either electron cyclotron wave or electron Bernstein wave, without induction. (2) A plasma current of 10 kA was obtained transiently by induction using only outboard poloidal field coils. In the second scenario, it is important to supply sufficient power for ionization (100 kW of EC power was sufficient in this case), since the vertical field during start-up is not adequate to maintain plasma equilibrium. In addition, electron heating experiments using the X-B mode conversion scenario were performed, and a heating efficiency of 60% was observed at a 100 kW RF power level. TST-2 is now located at the Kashiwa Campus of the University of Tokyo. Significant upgrades were made in both magnetic coil power supplies and RF systems, and plasma experiments have restarted. RF power of up to 400 kW is available in the high-harmonic fast wave frequency range around 20 MHz. Four 200 MHz transmitters are now being prepared for plasma current start-up experiments using RF power in the lower-hybrid frequency range. Preparations are in progress for a new plasma merging experiment (UTST) aimed at the formation and sustainment of ultra-high β ST plasmas.

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

Non-contact ultrasonic gas flow metering using air-coupled leaky Lamb waves.

PubMed

Fan, Zichuan; Jiang, Wentao; Wright, William M D

2018-04-23

This paper describes a completely non-contact ultrasonic method of gas flow metering using air-coupled leaky Lamb waves. To show proof of principle, a simplified representation of gas flow in a duct, comprising two separated thin isotropic plates with a gas flowing between them, has been modelled and investigated experimentally. An airborne compression wave emitted from an air-coupled capacitive ultrasonic transducer excited a leaky Lamb wave in the first plate in a non-contact manner. The leakage of this Lamb wave crossed the gas flow at an angle between the two plates as a compression wave, and excited a leaky Lamb wave in the second plate. An air-coupled capacitive ultrasonic transducer on the opposite side of this second plate then detected the airborne compression wave leakage from the second Lamb wave. As the gas flow shifted the wave field between the two plates, the point of Lamb wave excitation in the second plate was displaced in proportion to the gas flow rate. Two such measurements, in opposite directions, formed a completely non-contact contra-propagating Lamb wave flow meter, allowing measurement of the flow velocity between the plates. A COMSOL Multiphysics® model was used to visualize the wave fields, and accurately predicted the time differences that were then measured experimentally. Experiments using different Lamb wave frequencies and plate materials were also similarly verified. This entirely non-contact airborne approach to Lamb wave flow metering could be applied in place of clamp-on techniques in thin-walled ducts or pipes. Copyright © 2018 Elsevier B.V. All rights reserved.

Models for Convectively Coupled Tropical Waves

NASA Astrophysics Data System (ADS)

Majda, A. J.

2001-05-01

\\small{The tropical Western Pacific is a key area with large input on short-term climate. There are many recent observations of convective complexes feeding into equatorially trapped planetary waves [5], [6] which need a theoretical explanation and also are poorly treated in contemporary General Circulation Models (GCM's). This area presents wonderful new research opportunities for applied mathematicians interested in nonlinear waves interacting over many spatio-temporal scales. This talk describes some ongoing recent activities of the speaker related to these important issues. A simplified intermediate model for analyzing and parametrizing convectively coupled tropical waves is introduced in [2]. This model has two baroclinic modes of vertical structure, a direct heating mode and a stratiform mode. The key essential parameter in these models is the area fraction occupied by deep convection, σ c. The unstable convectively coupled waves that emerge from perturbation of a radiative convective equilibrium are discussed in detail through linearized stability analysis. Without any mean flow, for an overall cooling rate of 1 K/day as the area fraction parameter increases from σ c=0.001 to σ c=0.0014 the waves pass from a regime with stable moist convective damping (MCD) to a regime of ``stratiform'' instability with convectively coupled waves propagating at speeds of roughly 15~m~s-1,instabilities for a band wavelengths in the super-cluster regime, O(1000) to O(2000) km, and a vertical structure in the upper troposphere lags behind that in the lower troposphere - thus, these convectively coupled waves in the model reproduce several key features of convectively coupled waves in the troposphere processed from recent observational data by Wheeler and Kiladis ([5], [6]). As the parameter σ c is increased further to values such as σ c=0.01, the band of unstable waves increase and spreads toward mesoscale wavelengths of O(100) km while the same wave structure and quantitative features mentioned above are retained wave structure and quantitative features mentioned above are retained for O(1000) km. A detailed analysis of the temporal development of instability of these convectively coupled waves is presented here. In the first stage of instability, a high CAPE region generates deep convection and front-to-rear ascending flow with enhanced vertical shear in a stratiform wake region. Thus, these intermediate models may be useful prototypes for studying the parametrization of upscale convective momentum transport due to organized convection [4], [3]. In the second stage of instability, detailed analysis of the CAPE budget establishes that the effects of the second baroclinic mode in the stratiform wake produce new CAPE, which regenerates the first half of the wake cycle. Finally, since these convectively coupled stratiform waves do not require a barotropic mean flow, a barotropic mean flow which alters the surface fluxes, is added to study the effect of their stability. These effects of a barotropic mean flow are secondary; an easterly mean flow enhances instability of the eastward propagating convectively coupled waves and diminishes the instability of the westward propagating waves through a WISHE mechanism. Finally, new models for treating the equatorial wave guide [1], [8] which are intermediate between full meriodonal resolution and the equatorial long wave approximation will be discussed. If time permits, the use of these models in efficient numerical schemes which allow for cloud resolving modeling [7], but also include large scale interaction in the equatorial wave guide will be outlined [8].}

Modulation of wave fields by current and wind intensifications off the Catalan coast

NASA Astrophysics Data System (ADS)

Pallares Lopez, Elena; Sánchez-Arcilla, Agustin; Espino, Manuel

2017-04-01

The coupling between waves, ocean and atmospheric models has been one of the main topics in the physical oceanography community for the last decade. The resulting challenge is more difficult and relevant in coastal areas, where the interaction between wind, waves and currents fields is far from negligible, and therefore some sort of model coupling is required. However, it is important to remark that it is only during energetic "enough" events that the coupling becomes quantitatively significant. The Western Mediterranean sea is an area characterised by calm periods most of the year. However, coastal areas often present highly variable and heterogeneous wind, wave and current conditions, which make the numerical prediction of meteo-oceanographic processes difficult and with large associated local errors. Specifically, the Catalan coast is frequently affected by offshore wind intensifications channel by river valleys and by local current intensifications associated to coastal "bulges" (e.g. deltaic forms) that can reach up to 1 m/s in the surface. In this study we present different coupling strategies applied to both calm periods and energetic events, represented by the wind jets or current intensifications mentioned before, with the objective to quantify the effect of model coupling on the resulting wave fields off the Catalan coast. The SWAN wave model is used to model the wave fields, together with the ROMS oceanic model and the WRF atmospheric model. Two different types of coupling are considered: the first is a one-way coupling consisting in introducing the current field as an input for the SWAN wave model; the second one, consists in running in parallel the ROMS circulation model, the WRF atmospheric model and the SWAN wave model. The second methodology is more complex and should better reproduce the physics involved in the interactions, but requires an important computational capacity, not always available, so a critical comparison between the two methodologies, balancing costs and benefits will be presented and analysed. From the results obtained from a set of typical synoptic situations, it can be concluded that during most of the time, with the calm conditions typical of the Mediterranean coast, it is not necessary to consider the coupling in any of its forms to provide accurate wave simulations. However, when a wind or current intensification occurs, the results improve considerably with the coupled model and the robustness of predictions greatly improves. Because of that an "intelligent" modelling sequence that activates the coupling in terms of the expected meteo-oceanography is proposed for operational applications.

Linear and Nonlinear Coupling of Electrostatic Drift and Acoustic Perturbations in a Nonuniform Bi-Ion Plasma with Non-Maxwellian Electrons

NASA Astrophysics Data System (ADS)

Ali, Gul-e.; Ahmad, Ali; Masood, W.; Mirza, Arshad M.

2017-12-01

Linear and nonlinear coupling of drift and ion acoustic waves are studied in a nonuniform magnetized plasma comprising of Oxygen and Hydrogen ions with nonthermal distribution of electrons. It has been observed that different ratios of ion number densities and kappa and Cairns distributed electrons significantly modify the linear dispersion characteristics of coupled drift-ion acoustic waves. In the nonlinear regime, KdV (for pure drift waves) and KP (for coupled drift-ion acoustic waves) like equations have been derived to study the nonlinear evolution of drift solitary waves in one and two dimensions. The dependence of drift solitary structures on different ratios of ion number densities and nonthermal distribution of electrons has also been explored in detail. It has been found that the ratio of the diamagnetic drift velocity to the velocity of the nonlinear structure determines the existence regimes for the drift solitary waves. The present investigation may be beneficial to understand the formation of solitons in the ionospheric F-region.

Semirational rogue waves for the three-coupled fourth-order nonlinear Schrödinger equations in an alpha helical protein

NASA Astrophysics Data System (ADS)

Du, Zhong; Tian, Bo; Qu, Qi-Xing; Chai, Han-Peng; Wu, Xiao-Yu

2017-12-01

Investigated in this paper are the three-coupled fourth-order nonlinear Schrödinger equations, which describe the dynamics of alpha helical protein with the interspine coupling at the higher order. We show that the representation of the Lax pair with Expressions (42) -(45) in Ref. [25] is not correct, because the three-coupled fourth-order nonlinear Schrödinger equations can not be reproduced by the Lax pair with Expressions (42) -(45) in Ref. [25] through the compatibility condition. Therefore, we recalculate the Lax pair. Based on the recalculated Lax pair, we construct the generalized Darboux transformation, and derive the first- and second-order semirational solutions. Through such solutions, dark-bright-bright soliton, breather-breather-bright soliton, breather soliton and rogue waves are analyzed. It is found that the rogue waves in the three components are mutually proportional. Moreover, three types of the semirational rogue waves consisting of the rogue waves and solitons are presented: (1) consisting of the first-order rogue wave and one soliton; (2) consisting of the first-order rogue wave and two solitons; (3) consisting of the second-order rogue wave and two solitons.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Multi-mode Spiral Wave in a Coupled Oscillatory Medium

NASA Astrophysics Data System (ADS)

Wang, Qun; Gao, Qing-Yu; Lü, Hua-Ping; Zheng, Zhi-Gang

2010-05-01

Multi-mode spiral wave and its breakup in 1-d and 2-d coupled oscillatory media is studied here by theoretic analysis and numerical simulations. The analysis in 1-d system shows that the dispersion relation curve could be non-monotonic depending on the coupling strength. It may also lead to the coexistence of different wave numbers within one system. Direct numerical observations in 1-d and 2-d systems conform to the prediction of dispersion relation analysis. Our findings indicate that the wave grouping can also be observed in oscillatory media without tip meandering and waves with negative group velocity can occur without inhomogeneity.

Experimental Test of Coupled Wave Model of Large Coils

DTIC Science & Technology

1985-06-01

46556 Abstract: Recent data from Time Domain Pulse Reflectometry experiments on a three turn coil in the form of a race track corroborate the...Domain Pulse Reflectometry experiments on a three turn coil in the form of a race track corroborate the theory of coupled wave model for large coils...Gabriel, "Coupled Wave Model for Large Magnet Coils", NASA Contractor Report 3332, National Aeronautics and Space Administration, Washington, DC

Wave-Coupled Millimeter-Wave Electro-Optic Techniques

DTIC Science & Technology

2001-03-01

This report details results on two antenna-coupled millimeter-wave electro - optic modulators, the slot-vee antenna-coupled modulator and a 94 GHz...study of the effects of velocity mismatch on linearized electro - optic modulators was made and the results published. A key result was that directional...drift in electro - optic modulators was made and protons were determined to be the cause. Several inventions were made to reduce or eliminate proton-caused bias drift.

Influence of the frequency detuning on the four-wave mixing efficiency in three-level system coupled by standing-wave

NASA Astrophysics Data System (ADS)

Zhou, Hai-Tao; Che, Shao-Na; Han, Yu-Hong; Wang, Dan

2018-05-01

In a Λ-type three-level atomic system coupled by an off-resonant standing-wave, the reflected four-wave mixing (FWM) spectrum is studied. It shows that the maximum reflection efficiency occurs when both of the coupling and probe fields are tuned off resonances from the atomic transitions. The essence of enhanced reflection is that the nonlinear efficiency of the FWM based on coherent atoms is improved due to the significant reduction of phase mismatch. The theoretical analysis shows good agreement with the experimental results. Furthermore, the influence of the atomic number density on the coupling frequency detuning of the optimum reflection efficiency and the linewidth are also investigated.

On the convergence of the coupled-wave approach for lamellar diffraction gratings

NASA Technical Reports Server (NTRS)

Li, Lifeng; Haggans, Charles W.

1992-01-01

Among the many existing rigorous methods for analyzing diffraction of electromagnetic waves by diffraction gratings, the coupled-wave approach stands out because of its versatility and simplicity. It can be applied to volume gratings and surface relief gratings, and its numerical implementation is much simpler than others. In addition, its predictions were experimentally validated in several cases. These facts explain the popularity of the coupled-wave approach among many optical engineers in the field of diffractive optics. However, a comprehensive analysis of the convergence of the model predictions has never been presented, although several authors have recently reported convergence difficulties with the model when it is used for metallic gratings in TM polarization. Herein, three points are made: (1) in the TM case, the coupled-wave approach converges much slower than the modal approach of Botten et al; (2) the slow convergence is caused by the use of Fourier expansions for the permittivity and the fields in the grating region; and (3) is manifested by the slow convergence of the eigenvalues and the associated modal fields. The reader is assumed to be familiar with the mathematical formulations of the coupled-wave approach and the modal approach.

Tube-wave seismic imaging

DOEpatents

Korneev, Valeri A [Lafayette, CA; Bakulin, Andrey [Houston, TX

2009-10-13

The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

Tube-wave seismic imaging

DOEpatents

Korneev, Valeri A [LaFayette, CA

2009-05-05

The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

Modeling and Theory of RF Antenna Systems on Proto-MPEX

NASA Astrophysics Data System (ADS)

Piotrowicz, P. A.; Caneses, J. F.; Goulding, R. H.; Green, D.; Caughman, J. B. O.; Ruzic, D. N.; Proto-MPEX Team

2017-10-01

The RF wave coupling of the helicon and ICH antennas installed on the Prototype Material Plasma Exposure eXperiment (MPEX) has been explored theoretically and via a full wave model implemented in COMSOL Multiphysics. The high-density mode in Proto-MPEX has been shown to occur when exciting radial eigenmodes of the plasma column which coincides with entering a Trivelpiece Gould (TG) anti-resonant regime, therefore suppressing edge heating in favor of core power deposition. The fast wave launched by the helicon antenna has a large wavelength and travels at a steep group velocity angle with the background magnetic field; for this reason the fast wave launched by the helicon antenna efficiently couples power to the core plasma. However, the ICH heating scheme relies on a small wavelength slow wave to couple power to the core of the plasma column. Coupling slow wave power to the core of the plasma column is sensitive to the location of the Alfven resonance. The wave-vector and group velocity vector of the slow wave in this parameter regime undergoes a drastic change in behavior when approaching the Alfven resonance. Full wave simulation results and dispersion analysis will be presented with suggestions to guide experimental progress. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

Acousto-optic modulation and opto-acoustic gating in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Ilic, B. Robert; Kyhm, Ji-Hoon; Song, Jin Dong; Srinivasan, Kartik

2017-01-01

Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic gating, in which the application of modulated optical pulses interferometrically gates the transmission of propagating acoustic pulses. The time-domain characteristics of this system under both pulsed RF and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modelled through the coupled mode equations of cavity optomechanics. PMID:28580373

Ocean surface waves in Hurricane Ike (2008) and Superstorm Sandy (2012): Coupled model predictions and observations

NASA Astrophysics Data System (ADS)

Chen, Shuyi S.; Curcic, Milan

2016-07-01

Forecasting hurricane impacts of extreme winds and flooding requires accurate prediction of hurricane structure and storm-induced ocean surface waves days in advance. The waves are complex, especially near landfall when the hurricane winds and water depth varies significantly and the surface waves refract, shoal and dissipate. In this study, we examine the spatial structure, magnitude, and directional spectrum of hurricane-induced ocean waves using a high resolution, fully coupled atmosphere-wave-ocean model and observations. The coupled model predictions of ocean surface waves in Hurricane Ike (2008) over the Gulf of Mexico and Superstorm Sandy (2012) in the northeastern Atlantic and coastal region are evaluated with the NDBC buoy and satellite altimeter observations. Although there are characteristics that are general to ocean waves in both hurricanes as documented in previous studies, wave fields in Ike and Sandy possess unique properties due mostly to the distinct wind fields and coastal bathymetry in the two storms. Several processes are found to significantly modulate hurricane surface waves near landfall. First, the phase speed and group velocities decrease as the waves become shorter and steeper in shallow water, effectively increasing surface roughness and wind stress. Second, the bottom-induced refraction acts to turn the waves toward the coast, increasing the misalignment between the wind and waves. Third, as the hurricane translates over land, the left side of the storm center is characterized by offshore winds over very short fetch, which opposes incoming swell. Landfalling hurricanes produce broader wave spectra overall than that of the open ocean. The front-left quadrant is most complex, where the combination of windsea, swell propagating against the wind, increasing wind-wave stress, and interaction with the coastal topography requires a fully coupled model to meet these challenges in hurricane wave and surge prediction.

Influence of lattice vibrations on the field driven electronic transport in chains with correlated disorder

NASA Astrophysics Data System (ADS)

da Silva, L. D.; Sales, M. O.; Ranciaro Neto, A.; Lyra, M. L.; de Moura, F. A. B. F.

2016-12-01

We investigate electronic transport in a one-dimensional model with four different types of atoms and long-ranged correlated disorder. The latter was attained by choosing an adequate distribution of on-site energies. The wave-packet dynamics is followed by taking into account effects due to a static electric field and electron-phonon coupling. In the absence of electron-phonon coupling, the competition between correlated disorder and the static electric field promotes the occurrence of wave-packet oscillations in the regime of strong correlations. When the electron-lattice coupling is switched on, phonon scattering degrades the Bloch oscillations. For weak electron-phonon couplings, a coherent oscillatory-like dynamics of the wave-packet centroid persists for short periods of time. For strong couplings the wave-packet acquires a diffusive-like displacement and spreading. A slower sub-diffusive spreading takes place in the regime of weak correlations.

Observation of beat oscillation generation by coupled waves associated with parametric decay during radio frequency wave heating of a spherical tokamak plasma.

PubMed

Nagashima, Yoshihiko; Oosako, Takuya; Takase, Yuichi; Ejiri, Akira; Watanabe, Osamu; Kobayashi, Hiroaki; Adachi, Yuuki; Tojo, Hiroshi; Yamaguchi, Takashi; Kurashina, Hiroki; Yamada, Kotaro; An, Byung Il; Kasahara, Hiroshi; Shimpo, Fujio; Kumazawa, Ryuhei; Hayashi, Hiroyuki; Matsuzawa, Haduki; Hiratsuka, Junichi; Hanashima, Kentaro; Kakuda, Hidetoshi; Sakamoto, Takuya; Wakatsuki, Takuma

2010-06-18

We present an observation of beat oscillation generation by coupled modes associated with parametric decay instability (PDI) during radio frequency (rf) wave heating experiments on the Tokyo Spherical Tokamak-2. Nearly identical PDI spectra, which are characterized by the coexistence of the rf pump wave, the lower-sideband wave, and the low-frequency oscillation in the ion-cyclotron range of frequency, are observed at various locations in the edge plasma. A bispectral power analysis was used to experimentally discriminate beat oscillation from the resonant mode for the first time. The pump and lower-sideband waves have resonant mode components, while the low-frequency oscillation is exclusively excited by nonlinear coupling of the pump and lower-sideband waves. Newly discovered nonlocal transport channels in spectral space and in real space via PDI are described.

Composite rogue waves and modulation instability for the three-coupled Hirota system in an optical fiber

NASA Astrophysics Data System (ADS)

Chai, Han-Peng; Tian, Bo; Chai, Jun; Du, Zhong

2017-10-01

We investigate the three-coupled Hirota system, which is applied to model the long distance communication and ultrafast signal routing systems governing the propagation of light pulses. With the aid of the Darboux dressing transformation, composite rogue wave solutions are derived. Spatial-temporal structures, including the four-petaled structure for the three-coupled Hirota system, are exhibited. We find that the four-petaled rogue waves occur in two of the three components, whereas the eye-shaped rogue wave occurs in the other one. The composite rogue waves can split up into two or three single rogue waves. The corresponding conditions for the occurrence of such phenomena are discussed and presented. We find that the relative position of every single rogue wave is influenced by the ratios of certain parameters. Besides, the linear instability analysis is performed, and our results agree with those from the baseband modulation instability theory.

Microwave-plasma in a simple magnetized torus

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

Rypdal, K.; Fredriksen, M.; Olsen, O.M.

1997-05-01

In a magnetized torus with no poloidal field component, a weakly ionized plasma is produced by microwaves at 2.45 GHz in the O-mode as well as the X-mode. The neutral gas pressure p{sub g} ranges from 5{times}10{sup {minus}5} to 1{times}10{sup {minus}3} mbar, n{sub e}{approximately}1{minus}5{times}10{sup 16}m{sup {minus}3}, and T{sub e}{approximately}2{minus}6 eV. The O-mode is only weakly absorbed at the electron cyclotron resonance (ECR), but is partly converted to the X-mode by wall reflections. The X-mode is absorbed via the upper hybrid resonance (UHR), presumably through conversion to and absorption of electron Bernstein waves (EBW). For p{sub g}{gt}1{times}10{sup {minus}3} mbar the EBWmore » absorption is collisional, but for lower p{sub g} a collisionless transit particle mechanism could be responsible. Typically the spatial plasma distribution depends mainly on the major radius R, and the measured n{sub e}(R) increases monotonically with R from the ECR to an UHR near the outer wall. T{sub e} is determined by the particle balance, and is proportional to the ionization energy. The average n{sub e} is determined by power balance, and increases with wave power. {copyright} {ital 1997 American Institute of Physics.}« less

The Effect of the Leeuwin Current on Offshore Surface Gravity Waves in Southwest Western Australia

NASA Astrophysics Data System (ADS)

Wandres, Moritz; Wijeratne, E. M. S.; Cosoli, Simone; Pattiaratchi, Charitha

2017-11-01

The knowledge of regional wave regimes is critical for coastal zone planning, protection, and management. In this study, the influence of the offshore current regime on surface gravity waves on the southwest Western Australian (SWWA) continental shelf was examined. This was achieved by coupling the three dimensional, free surface, terrain-following hydrodynamic Regional Ocean Modelling System (ROMS) and the third generation wave model Simulating WAves Nearshore (SWAN) using the Coupled Ocean-Atmosphere-WaveSediment Transport (COAWST) model. Different representative states of the Leeuwin Current (LC), a strong pole-ward flowing boundary current with a persistent eddy field along the SWWA shelf edge were simulated and used to investigate their influence on different large wave events. The coupled wave-current simulations were compared to wave only simulations, which represented scenarios in the absence of a background current field. Results showed that the LC and the eddy field significantly impact SWWA waves. Significant wave heights increased (decreased) when currents were opposing (aligning with) the incoming wave directions. During a fully developed LC system significant wave heights were altered by up to ±25% and wave directions by up to ±20°. The change in wave direction indicates that the LC may modify nearshore wave dynamics and consequently alter sediment patterns. Operational regional wave forecasts and hindcasts may give flawed predictions if wave-current interaction is not properly accounted for.

Pseudopotential SCF-MO studies of hypervalent compounds. II. XeF+5 and XeF6

NASA Astrophysics Data System (ADS)

Rothman, Michael J.; Bartell, Lawrence S.; Ewig, Carl S.; Van Wazer, John R.

1980-07-01

New evidence bearing upon the anomalous properties of xenon hexafluoride has been obtained via the ab initio molecular orbital approach applied successfully to the di- and tetrafluorides in paper I. Structures of both XeF+5 and XeF6 are governed by a stereochemically active lone pair. In the case of the square-pyramidal cation the Fax-Xe-Feq angle calculated for the bare ion is within 2° of the value observed in the crystalline complex. For the hexafluoride, however, the calculated deformation from Oh symmetry is appreciably greater than that deduced from electron diffraction intensities. Nevertheless, the results of calculations are in sufficient conformity with the Bartell-Gavin, Pitzer-Bernstein interpretation and at variance with the ''electronic-isomers'' interpretation to leave little doubt about the answer. With increasing fluorination in the XeFn series the HOMO-LUMO energy difference decreases and the second-order Jahn-Teller effect is enhanced. Increasing fluorination (and increased positive charge on Xe) also shortens bond lengths; calculated shortenings parallel observed shortenings. The deformation of XeF6 from Oh is along t1u bend and stretch coordinates to a C3v structure with long bonds adjacent to the lone pair, as expected according to the valence-shell-electron-pair-repulsion model. Pure t2g deformations are destabilizing but anharmonic t1u-t2g coupling significantly stabilizes the deformation. Steric aspects of the structure and force field are diagnosed and found to be minor. Values for the force constants f44, f55, f¯4444, f¯444'4', and f¯445 are derived and found to be of the magnitude forecast in the Bartell-Gavin and Pitzer-Bernstein treatments except that the calculations do not reproduce the delicate balances believed to lead to almost free pseudorotation in XeF6.

Ambient seismic wave field

PubMed Central

NISHIDA, Kiwamu

2017-01-01

The ambient seismic wave field, also known as ambient noise, is excited by oceanic gravity waves primarily. This can be categorized as seismic hum (1–20 mHz), primary microseisms (0.02–0.1 Hz), and secondary microseisms (0.1–1 Hz). Below 20 mHz, pressure fluctuations of ocean infragravity waves reach the abyssal floor. Topographic coupling between seismic waves and ocean infragravity waves at the abyssal floor can explain the observed shear traction sources. Below 5 mHz, atmospheric disturbances may also contribute to this excitation. Excitation of primary microseisms can be attributed to topographic coupling between ocean swell and seismic waves on subtle undulation of continental shelves. Excitation of secondary microseisms can be attributed to non-linear forcing by standing ocean swell at the sea surface in both pelagic and coastal regions. Recent developments in source location based on body-wave microseisms enable us to estimate forcing quantitatively. For a comprehensive understanding, we must consider the solid Earth, the ocean, and the atmosphere as a coupled system. PMID:28769015

Rogue wave in coupled electric transmission line

NASA Astrophysics Data System (ADS)

Duan, J. K.; Bai, Y. L.

2018-03-01

Distributed electrical transmission lines that consist of a large number of identical sections have been theoretically studied in the present paper. The rogue wave is analyzed and predicted using the nonlinear Schrodinger equation (NLSE). The results indicate that, in the continuum limit, the voltage for the transmission line is described in some cases by the NLSE that is obtained using the traditional perturbation technique. The dependences of the characteristics of the rouge wave parameters on the coupled electric transmission line are shown in the paper. As is well known, rogue waves can be found for a large number of oceanic disasters, and such waves may be disastrous. However, the results of the present paper for coupled electric transmission lines may be useful.

Study on the electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices.

PubMed

Chen, Shi; Zhang, Yinhong; Lin, Shuyu; Fu, Zhiqiang

2014-02-01

The electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices is investigated by the transfer matrix method. Research results show the high electromechanical coupling coefficient can be obtained in these systems. The optimization design of it is also discussed fully. It is significantly influenced by electrical boundary conditions on interfaces, thickness ratios of piezoelectric and non-piezoelectric layers, and material parameters (such as velocities of pure longitudinal and transversal bulk waves in non-piezoelectric layers). In order to obtain higher electromechanical coupling coefficient, shorted interfaces, non-piezoelectric materials with large velocities of longitudinal and transversal bulk waves, and proper thickness ratios should be chosen. Copyright © 2013 Elsevier B.V. All rights reserved.

Observation of two coupled Faraday waves in a vertically vibrating Hele-Shaw cell with one of them oscillating horizontally

NASA Astrophysics Data System (ADS)

Li, Xiaochen; Li, Xiaoming; Liao, Shijun

2018-01-01

A system of two coupled Faraday waves is experimentally observed at the two interfaces of the three layers of fluids (air, pure ethanol, and silicon oil) in a covered Hele-Shaw cell with periodic vertical vibration. Both the upper and lower Faraday waves are subharmonic, but they coexist in different forms: the upper one vibrates vertically, while the crests of the lower one oscillate horizontally with unchanged wave height, and the troughs of the lower one usually remain in the same place (relative to the basin). Besides, they are strongly coupled: the wave height of the lower Faraday waves is either a linear function (when forcing frequency is fixed) or a parabolic function (when acceleration amplitude is fixed) of that of the upper one with a same wavelength.

The New Students: A Dialectic between Language and Learning

ERIC Educational Resources Information Center

Perl, Sondra

1975-01-01

Examines Basil Bernstein's principles on language as set forth in "Class, Codes and Control: Theoretical Studies towards a Sociology of Language" and applies them to the teaching of English composition. (RB)

Rigorous coupled wave analysis of acousto-optics with relativistic considerations.

PubMed

Xia, Guoqiang; Zheng, Weijian; Lei, Zhenggang; Zhang, Ruolan

2015-09-01

A relativistic analysis of acousto-optics is presented, and a rigorous coupled wave analysis is generalized for the diffraction of the acousto-optical effect. An acoustic wave generates a grating with temporally and spatially modulated permittivity, hindering direct applications of the rigorous coupled wave analysis for the acousto-optical effect. In a reference frame which moves with the acoustic wave, the grating is static, the medium moves, and the coupled wave equations for the static grating may be derived. Floquet's theorem is then applied to cast these equations into an eigenproblem. Using a Lorentz transformation, the electromagnetic fields in the grating region are transformed to the lab frame where the medium is at rest, and relativistic Doppler frequency shifts are introduced into various diffraction orders. In the lab frame, the boundary conditions are considered and the diffraction efficiencies of various orders are determined. This method is rigorous and general, and the plane waves in the resulting expansion satisfy the dispersion relation of the medium and are propagation modes. Properties of various Bragg diffractions are results, rather than preconditions, of this method. Simulations of an acousto-optical tunable filter made by paratellurite, TeO(2), are given as examples.

Modeling of atmospheric-coupled Rayleigh waves on planets with atmosphere: From Earth observation to Mars and Venus perspectives.

PubMed

Lognonné, Philippe; Karakostas, Foivos; Rolland, Lucie; Nishikawa, Yasuhiro

2016-08-01

Acoustic coupling between solid Earth and atmosphere has been observed since the 1960s, first from ground-based seismic, pressure, and ionospheric sensors and since 20 years with various satellite measurements, including with global positioning system (GPS) satellites. This coupling leads to the excitation of the Rayleigh surface waves by local atmospheric sources such as large natural explosions from volcanoes, meteor atmospheric air-bursts, or artificial explosions. It contributes also in the continuous excitation of Rayleigh waves and associated normal modes by atmospheric winds and pressure fluctuations. The same coupling allows the observation of Rayleigh waves in the thermosphere most of the time through ionospheric monitoring with Doppler sounders or GPS. The authors review briefly in this paper observations made on Earth and describe the general frame of the theory enabling the computation of Rayleigh waves for models of telluric planets with atmosphere. The authors then focus on Mars and Venus and give in both cases the atmospheric properties of the Rayleigh normal modes and associated surface waves compared to Earth. The authors then conclude on the observation perspectives especially for Rayleigh waves excited by atmospheric sources on Mars and for remote ionospheric observations of Rayleigh waves excited by quakes on Venus.

Nonlinear propagation of electromagnetic waves in negative-refraction-index composite materials.

PubMed

Kourakis, I; Shukla, P K

2005-07-01

We investigate the nonlinear propagation of electromagnetic waves in left-handed materials. For this purpose, we consider a set of coupled nonlinear Schrödinger (CNLS) equations, which govern the dynamics of coupled electric and magnetic field envelopes. The CNLS equations are used to obtain a nonlinear dispersion, which depicts the modulational stability profile of the coupled plane-wave solutions in left-handed materials. An exact (in)stability criterion for modulational interactions is derived, and analytical expressions for the instability growth rate are obtained.

Spiral waves in driven strongly coupled Yukawa systems

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Das, Amita

2018-06-01

Spiral wave formations are ubiquitous in nature. In the present paper, the excitation of spiral waves in the context of driven two-dimensional dusty plasma (Yukawa system) has been demonstrated at particle level using molecular-dynamics simulations. The interaction amidst dust particles is modeled by the Yukawa potential to take account of the shielding of dust charges by the lighter electron and ion species. The spatiotemporal evolution of these spiral waves has been characterized as a function of the frequency and amplitude of the driving force and dust neutral collisions. The effect of strong coupling has been studied, which shows that the excited spiral wave structures get clearer as the medium gets more strongly coupled. The radial propagation speed of the spiral wave is observed to remain unaltered with the coupling parameter. However, it is found to depend on the screening parameter of the dust medium and decreases when it is increased. In the crystalline phase (with screening parameter κ >0.58 ), the spiral wavefronts are shown to be hexagonal in shape. This shows that the radial propagation speed depends on the interparticle spacing.

Development and applications of a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System

NASA Astrophysics Data System (ADS)

Warner, J. C.; Armstrong, B. N.; He, R.; Zambon, J. B.; Olabarrieta, M.; Voulgaris, G.; Kumar, N.; Haas, K. A.

2012-12-01

Understanding processes responsible for coastal change is important for managing both our natural and economic coastal resources. Coastal processes respond from both local scale and larger regional scale forcings. Understanding these processes can lead to significant insight into how the coastal zone evolves. Storms are one of the primary driving forces causing coastal change from a coupling of wave and wind driven flows. Here we utilize a numerical modeling approach to investigate these dynamics of coastal storm impacts. We use the Coupled Ocean - Atmosphere - Wave - Sediment Transport (COAWST) Modeling System that utilizes the Model Coupling Toolkit to exchange prognostic variables between the ocean model ROMS, atmosphere model WRF, wave model SWAN, and the Community Sediment Transport Modeling System (CSTMS) sediment routines. The models exchange fields of sea-surface temperature, ocean currents, water levels, bathymetry, wave heights, lengths, periods, bottom orbital velocities, and atmospheric surface heat and momentum fluxes, atmospheric pressure, precipitation, and evaporation. Data fields are exchanged using regridded flux conservative sparse matrix interpolation weights computed from the SCRIP spherical coordinate remapping interpolation package. We describe the modeling components and the model field exchange methods. As part of the system, the wave and ocean models run with cascading, refined, spatial grids to provide increased resolution, scaling down to resolve nearshore wave driven flows simulated by the vortex force formulation, all within selected regions of a larger, coarser-scale coastal modeling system. The ocean and wave models are driven by the atmospheric component, which is affected by wave dependent ocean-surface roughness and sea surface temperature which modify the heat and momentum fluxes at the ocean-atmosphere interface. We describe the application of the modeling system to several regions of multi-scale complexity to identify the significance of larger scale forcing cascading down to smaller scales and to investigate the interactions of the coupled system with increasing degree of model-model interactions. Three examples include the impact of Hurricane Ivan in 2004 in the Gulf of Mexico, Hurricane Ida in 2009 that evolved into a tropical storm on the US East coast, and passage of strong cold fronts across the US southeast. Results identify that hurricane intensity is extremely sensitive to sea-surface temperature, with a reduction in intensity when the atmosphere is coupled to the ocean model due to rapid cooling of the ocean from the surface through the mixed layer. Coupling of the ocean to the atmosphere also results in decreased boundary layer stress and coupling of the waves to the atmosphere results in increased sea-surface stress. Wave results are sensitive to both ocean and atmospheric coupling due to wave-current interactions with the ocean and wave-growth from the atmospheric wind stress. Sediment resuspension at regional scale during the hurricane is controlled by shelf width and wave propagation during hurricane approach. Results from simulation of passage of cold fronts suggest that synoptic meteorological systems can strongly impact surf zone and inner shelf response, therefore act as a strong driver for long term littoral sediment transport. We will also present some of the challenges faced to develop the modeling system.

Nonlinear vibrations analysis of rotating drum-disk coupling structure

NASA Astrophysics Data System (ADS)

Chaofeng, Li; Boqing, Miao; Qiansheng, Tang; Chenyang, Xi; Bangchun, Wen

2018-04-01

A dynamic model of a coupled rotating drum-disk system with elastic support is developed in this paper. By considering the effects of centrifugal and Coriolis forces as well as rotation-induced hoop stress, the governing differential equation of the drum-disk is derived by Donnell's shell theory. The nonlinear amplitude-frequency characteristics of coupled structure are studied. The results indicate that the natural characteristics of the coupling structure are sensitive to the supporting stiffness of the disk, and the sensitive range is affected by rotating speeds. The circumferential wave numbers can affect the characteristics of the drum-disk structure. If the circumferential wave number n = 1 , the vibration response of the drum keeps a stable value under an unbalanced load of the disk, there is no coupling effect if n ≠ 1 . Under the excitation, the nonlinear hardening characteristics of the forward traveling wave are more evident than that of the backward traveling wave. Moreover, because of the coupling effect of the drum and the disk, the supporting stiffness of the disk has certain effect on the nonlinear characteristics of the forward and backward traveling waves. In addition, small length-radius and thickness-radius ratios have a significant effect on the nonlinear characteristics of the coupled structure, which means nonlinear shell theory should be adopted to design rotating drum's parameter for its specific structural parameters.

Rogue-wave pattern transition induced by relative frequency.

PubMed

Zhao, Li-Chen; Xin, Guo-Guo; Yang, Zhan-Ying

2014-08-01

We revisit a rogue wave in a two-mode nonlinear fiber whose dynamics is described by two-component coupled nonlinear Schrödinger equations. The relative frequency between two modes can induce different rogue wave patterns transition. In particular, we find a four-petaled flower structure rogue wave can exist in the two-mode coupled system, which possesses an asymmetric spectrum distribution. Furthermore, spectrum analysis is performed on these different type rogue waves, and the spectrum relations between them are discussed. We demonstrate qualitatively that different modulation instability gain distribution can induce different rogue wave excitation patterns. These results would deepen our understanding of rogue wave dynamics in complex systems.

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source.

NASA Astrophysics Data System (ADS)

Averbuch, Gil; Price, Colin

2015-04-01

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source. G. Averbuch, C. Price Department of Geosciences, Tel Aviv University, Israel Infrasound is one of the four Comprehensive Nuclear-Test Ban Treaty technologies for monitoring nuclear explosions. This technology measures the acoustic waves generated by the explosions followed by their propagation through the atmosphere. There are also natural phenomena that can act as an infrasound sources like sprites, volcanic eruptions and earthquakes. The infrasound waves generated from theses phenomena can also be detected by the infrasound arrays. In order to study the behavior of these waves, i.e. the physics of wave propagation in the atmosphere, their evolution and their trajectories, numerical methods are required. This presentation will deal with the evolution of acoustic waves generated by underground sources (earthquakes and underground explosions). A 2D Spectral elements formulation for lithosphere-atmosphere coupling will be presented. The formulation includes the elastic wave equation for the seismic waves and the momentum, mass and state equations for the acoustic waves in a moving stratified atmosphere. The coupling of the two media is made by boundary conditions that ensures the continuity of traction and velocity (displacement) in the normal component to the interface. This work has several objectives. The first is to study the evolution of acoustic waves in the atmosphere from an underground source. The second is to derive transmission coefficients for the energy flux with respect to the seismic magnitude and earth density. The third will be the generation of seismic waves from acoustic waves in the atmosphere. Is it possible?

Observation of the seismic anisotropy effects on free oscillations below 4 mHz

NASA Astrophysics Data System (ADS)

Hu, X.; Liu, L.

2009-12-01

We present observations of significant fundamental spheroidal-toroidal mode coupling at frequencies below 4 mHz in the early part of vertical component records from seismic stations on near-equatorial source-receiver propagation paths and in Antarctica after the 26 December 2004 and 28 March 2005 great Sumatra earthquakes. When seismic surface waves propagate along the equator, the particle motion of Love waves runs parallels to the Earth’s rotation axis, and the particle motion of Rayleigh waves runs perpendicular to it, thus the Coriolis force has no vertical deflection effect on Love waves and no transverse deflection effect on the Rayleigh waves. Coriolis coupling can be naturally minimized at a station on a nearequatorial source-receiver propagation path. In Antarctica, especially near the South Pole, the vertical deflection of toroidial motion is very weak but there are lateral gradients in the anisotropic properties of upper mantle. Therefore, we can find a chance to directly observe seismic anisotropy coupling below 4 mHz without the disturbance of Coriolis coupling at Antarctic station, and at the seismic station locate close to the Earth’s equator when the epicenter also locates close to the equator. Our observations of strong anomalous toroidal-spheroidal coupling at these stations provide direct evidence to confirm the theory that the azimuthal anisotropy has pronounced effects on the quasi-toroidal mode excitations at the frequencies below 4 mHz, which can convince the skeptics that anisotropy really is visible in the low-frequency normal mode data. Strong anisotropic coupling is usually observed at stations having the geometric nodes for the spheroidal fundamentals, giving the association of quasi-toroidal excitation with the geometric effect. The presence of significant anisotropy coupling below 4 mHz depends not only on anisotropic depth, anisotropic identities and orientations but also on radiation nodes for Rayleigh waves and geometry nodes for spheroidal fundamentals. The quasi-toroidal modes below 4 mHz have significant sensitivity throughout most of the mantle, extending into the lower mantle, and therefore, it is likely that the resolution of locating the depth of origin of azimuthal anisotropy in the mantle will be improved by joint inversions that take advantage of the partly complementary depth resolution of anisotropy coupling measurements, quasi-Love surface-wave measurements, body wave splitting measurements and surface-wave dispersion measurements.

Field coupling-induced pattern formation in two-layer neuronal network

NASA Astrophysics Data System (ADS)

Qin, Huixin; Wang, Chunni; Cai, Ning; An, Xinlei; Alzahrani, Faris

2018-07-01

The exchange of charged ions across membrane can generate fluctuation of membrane potential and also complex effect of electromagnetic induction. Diversity in excitability of neurons induces different modes selection and dynamical responses to external stimuli. Based on a neuron model with electromagnetic induction, which is described by magnetic flux and memristor, a two-layer network is proposed to discuss the pattern control and wave propagation in the network. In each layer, gap junction coupling is applied to connect the neurons, while field coupling is considered between two layers of the network. The field coupling is approached by using coupling of magnetic flux, which is associated with distribution of electromagnetic field. It is found that appropriate intensity of field coupling can enhance wave propagation from one layer to another one, and beautiful spatial patterns are formed. The developed target wave in the second layer shows some difference from target wave triggered in the first layer of the network when two layers are considered by different excitabilities. The potential mechanism could be pacemaker-like driving from the first layer will be encoded by the second layer.

78 FR 20646 - National Committee on Vital and Health Statistics, Population Health Subcommittee: Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-05

... of data by communities to improve population health; (2) refine its Stewardship Framework for the Use... Maya Bernstein, lead staff for the Privacy, Confidentiality & Security Subcommittee, NCVHS, Hubert H...

Cancer Prevention: Opportunities for Action

Cancer.gov

Leslie Bernstein, PhD, AFLAC, Inc., Chair in Cancer Research; Professor, Preventive Medicine; and Senior Associate Dean, Faculty Affairs at Keck School of Medicine, University of Southern California, Los Angeles, CA, presented "Cancer Prevention: Opportunities for Action".

Two-way coupling of magnetohydrodynamic simulations with embedded particle-in-cell simulations

NASA Astrophysics Data System (ADS)

Makwana, K. D.; Keppens, R.; Lapenta, G.

2017-12-01

We describe a method for coupling an embedded domain in a magnetohydrodynamic (MHD) simulation with a particle-in-cell (PIC) method. In this two-way coupling we follow the work of Daldorff et al. (2014) [19] in which the PIC domain receives its initial and boundary conditions from MHD variables (MHD to PIC coupling) while the MHD simulation is updated based on the PIC variables (PIC to MHD coupling). This method can be useful for simulating large plasma systems, where kinetic effects captured by particle-in-cell simulations are localized but affect global dynamics. We describe the numerical implementation of this coupling, its time-stepping algorithm, and its parallelization strategy, emphasizing the novel aspects of it. We test the stability and energy/momentum conservation of this method by simulating a steady-state plasma. We test the dynamics of this coupling by propagating plasma waves through the embedded PIC domain. Coupling with MHD shows satisfactory results for the fast magnetosonic wave, but significant distortion for the circularly polarized Alfvén wave. Coupling with Hall-MHD shows excellent coupling for the whistler wave. We also apply this methodology to simulate a Geospace Environmental Modeling (GEM) challenge type of reconnection with the diffusion region simulated by PIC coupled to larger scales with MHD and Hall-MHD. In both these cases we see the expected signatures of kinetic reconnection in the PIC domain, implying that this method can be used for reconnection studies.

Observation of helicon wave with m = 0 antenna in a weakly magnetized inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Ellingboe, Bert; Sirse, Nishant; Moloney, Rachel; McCarthy, John

2015-09-01

Bounded whistler wave, called ``helicon wave,'' is known to produce high-density plasmas and has been exploited as a high density plasma source for many applications, including electric propulsion for spacecraft. In a helicon plasma source, an antenna wrapped around the magnetized plasma column launches a low frequency wave, ωce/2 >ωhelicon >ωce/100, in the plasma which is responsible for maintaining high density plasma. Several antenna designs have been proposed in order to match efficiently the wave modes. In our experiment, helicon wave mode is observed using an m = 0 antenna. A floating B dot probe, compensated to the capacitively coupled E field, is employed to measure axial-wave-field-profiles (z, r, and θ components) in the plasma at multiple radial positions as a function of rf power and pressure. The Bθ component of the rf-field is observed to be unaffected as the wave propagates in the axial direction. Power coupling between the antenna and the plasma column is identified and agrees with the E, H, and wave coupling regimes previously seen in M =1 antenna systems. That is, the Bz component of the rf-field is observed at low plasma density as the Bz component from the antenna penetrates the plasma. The Bz component becomes very small at medium density due to shielding at the centre of the plasma column; however, with increasing density, a sudden ``jump'' occurs in the Bz component above which a standing wave under the antenna with a propagating wave away from the antenna are observed.

Regarding the optimization of O1-mode ECRH and the feasibility of EBW startup on NSTX-U

NASA Astrophysics Data System (ADS)

Lopez, N. A.; Poli, F. M.

2018-06-01

Recently published scenarios for fully non-inductive startup and operation on the National Spherical Torus eXperiment Upgrade (NSTX-U) (Menard et al 2012 Nucl. Fusion 52 083015) show Electron Cyclotron Resonance Heating (ECRH) as an important component in preparing a target plasma for efficient High Harmonic Fast Wave and Neutral Beam heating. The modeling of the propagation and absorption of EC waves in the evolving plasma is required to define the most effective window of operation, and to optimize the launcher geometry for maximal heating and current drive during this window. Here, we extend a previous optimization of O1-mode ECRH on NSTX-U to account for the full time-dependent performance of the ECRH using simulations performed with TRANSP. We find that the evolution of the density profile has a prominent role in the optimization by defining the time window of operation, which in certain cases may be a more important metric to compare launcher performance than the average power absorption. This feature cannot be captured by analysis on static profiles, and should be accounted for when optimizing ECRH on any device that operates near the cutoff density. Additionally, the utility of the electron Bernstein wave (EBW) in driving current and generating closed flux surfaces in the early startup phase has been demonstrated on a number of devices. Using standalone GENRAY simulations, we find that efficient EBW current drive is possible on NSTX-U if the injection angle is shifted below the midplane and aimed towards the top half of the vacuum vessel. However, collisional damping of the EBW is projected to be significant, in some cases accounting for up to 97% of the absorbed EBW power.

Regarding the optimization of O1-mode ECRH and the feasibility of EBW startup on NSTX-U

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

Lopez, Nicolas; Poli, Francesca M.

Recently published scenarios for fully non-inductive startup and operation on the National Spherical Torus eXperiment Upgrade (NSTX-U) [Menard J et al 2012 Nucl. Fusion 52 083015] show Electron Cyclotron Resonance Heating (ECRH) as an important component in preparing a target plasma for efficient High Harmonic Fast Wave and Neutral Beam heating. The modelling of the propagation and absorption of EC waves in the evolving plasma is required to define the most effective window of operation, and to optimize the launcher geometry for maximal heating and current drive during this window. Here in this paper, we extend a previous optimization ofmore » O1-mode ECRH on NSTX-U to account for the full time-dependent performance of the ECRH using simulations performed with TRANSP. We find that the evolution of the density profile has a prominent role in the optimization by defining the time window of operation, which in certain cases may be a more important metric to compare launcher performance than the average power absorption. This feature cannot be captured by analysis on static profiles, and should be accounted for when optimizing ECRH on any device that operates near the cutoff density. Additionally, the utility of the electron Bernstein wave (EBW) in driving current and generating closed flux surfaces in the early startup phase has been demonstrated on a number of devices. Using standalone GENRAY simulations, we find that efficient EBW current drive is possible on NSTX-U if the injection angle is shifted below the midplane and aimed towards the top half of the vacuum vessel. However, collisional damping of the EBW is projected to be significant, in some cases accounting for up to 97\\% of the absorbed EBW power.« less

Regarding the optimization of O1-mode ECRH and the feasibility of EBW startup on NSTX-U

DOE PAGES

Lopez, Nicolas; Poli, Francesca M.

2018-03-29

Recently published scenarios for fully non-inductive startup and operation on the National Spherical Torus eXperiment Upgrade (NSTX-U) [Menard J et al 2012 Nucl. Fusion 52 083015] show Electron Cyclotron Resonance Heating (ECRH) as an important component in preparing a target plasma for efficient High Harmonic Fast Wave and Neutral Beam heating. The modelling of the propagation and absorption of EC waves in the evolving plasma is required to define the most effective window of operation, and to optimize the launcher geometry for maximal heating and current drive during this window. Here in this paper, we extend a previous optimization ofmore » O1-mode ECRH on NSTX-U to account for the full time-dependent performance of the ECRH using simulations performed with TRANSP. We find that the evolution of the density profile has a prominent role in the optimization by defining the time window of operation, which in certain cases may be a more important metric to compare launcher performance than the average power absorption. This feature cannot be captured by analysis on static profiles, and should be accounted for when optimizing ECRH on any device that operates near the cutoff density. Additionally, the utility of the electron Bernstein wave (EBW) in driving current and generating closed flux surfaces in the early startup phase has been demonstrated on a number of devices. Using standalone GENRAY simulations, we find that efficient EBW current drive is possible on NSTX-U if the injection angle is shifted below the midplane and aimed towards the top half of the vacuum vessel. However, collisional damping of the EBW is projected to be significant, in some cases accounting for up to 97\\% of the absorbed EBW power.« less

Theory of a Traveling Wave Feed for a Planar Slot Array Antenna

NASA Technical Reports Server (NTRS)

Rengarajan, Sembiam

2012-01-01

Planar arrays of waveguide-fed slots have been employed in many radar and remote sensing applications. Such arrays are designed in the standing wave configuration because of high efficiency. Traveling wave arrays can produce greater bandwidth at the expense of efficiency due to power loss in the load or loads. Traveling wave planar slot arrays may be designed with a long feed waveguide consisting of centered-inclined coupling slots. The feed waveguide is terminated in a matched load, and the element spacing in the feed waveguide is chosen to produce a beam squinted from the broadside. The traveling wave planar slot array consists of a long feed waveguide containing resonant-centered inclined coupling slots in the broad wall, coupling power into an array of stacked radiating waveguides orthogonal to it. The radiating waveguides consist of longitudinal offset radiating slots in a standing wave configuration. For the traveling wave feed of a planar slot array, one has to design the tilt angle and length of each coupling slot such that the amplitude and phase of excitation of each radiating waveguide are close to the desired values. The coupling slot spacing is chosen for an appropriate beam squint. Scattering matrix parameters of resonant coupling slots are used in the design process to produce appropriate excitations of radiating waveguides with constraints placed only on amplitudes. Since the radiating slots in each radiating waveguide are designed to produce a certain total admittance, the scattering (S) matrix of each coupling slot is reduced to a 2x2 matrix. Elements of each 2x2 S-matrix and the amount of coupling into the corresponding radiating waveguide are expressed in terms of the element S11. S matrices are converted into transmission (T) matrices, and the T matrices are multiplied to cascade the coupling slots and waveguide sections, starting from the load end and proceeding towards the source. While the use of non-resonant coupling slots may provide an additional degree of freedom in the design, resonant coupling slots simplify the design process. The amplitude of the wave going to the load is set at unity. The S11 parameter, r of the coupling slot closest to the load, is assigned an arbitrary value. A larger value of r will reduce the power dissipated in the load while increasing the reflection coefficient at the input port. It is now possible to obtain the excitation of the radiating waveguide closest to the load and the coefficients of the wave incident and reflected at the input port of this coupling slot. The next coupling slot parameter, r , is chosen to realize the excitation of that radiating waveguide. One continues this process moving towards the source, until all the coupling slot parameters r and hence the S11 parameter of the 4-port coupler, r, are known for each coupling slot. The goal is to produce the desired array aperture distribution in the feed direction. From an interpolation of the computed moment method data for the slot parameters, all the coupling slot tilt angles and lengths are obtained. From the excitations of the radiating waveguides computed from the coupling values, radiating slot parameters may be obtained so as to attain the desired total normalized slot admittances. This process yields the radiating slot parameters, offsets, and lengths. The design is repeated by choosing different values of r for the last coupling slot until the percentage of power dissipated in the load and the input reflection coefficient values are satisfactory. Numerical results computed for the radiation pattern, the tilt angles and lengths of coupling slots, and excitation phases of the radiating waveguides, are presented for an array with uniform amplitude excitation. The design process has been validated using computer simulations. This design procedure is valid for non-uniform amplitude excitations as well.

Ring Current Ion Coupling with Electromagnetic Ion Cyclotron Waves

NASA Technical Reports Server (NTRS)

Khazanov. G. V.; Gamayunov, K. V.; Jordanova, V. K.; Six, N. Frank (Technical Monitor)

2002-01-01

A new ring current global model has been developed that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes wave evolution of electromagnetic ion cyclotron waves (EMIC). The coupled model is able to simulate, for the first time self-consistently calculated RC ion kinetic and evolution of EMIC waves that propagate along geomagnetic field lines and reflect from the ionosphere. Ionospheric properties affect the reflection index through the integral Pedersen and Hall conductivities. The structure and dynamics of the ring current proton precipitating flux regions, intensities of EMIC global RC energy balance, and some other parameters will be studied in detail for the selected geomagnetic storms.

Strong wave/mean-flow coupling in baroclinic acoustic streaming

NASA Astrophysics Data System (ADS)

Chini, Greg; Michel, Guillaume

2017-11-01

Recently, Chini et al. demonstrated the potential for large-amplitude acoustic streaming in compressible channel flows subjected to strong background cross-channel density variations. In contrast with classic Rayleigh streaming, standing acoustic waves of O (ɛ) amplitude acquire vorticity owing to baroclinic torques acting throughout the domain rather than via viscous torques acting in Stokes boundary layers. More significantly, these baroclinically-driven streaming flows have a magnitude that also is O (ɛ) , i.e. comparable to that of the sound waves. In the present study, the consequent potential for fully two-way coupling between the waves and streaming flows is investigated using a novel WKBJ analysis. The analysis confirms that the wave-driven streaming flows are sufficiently strong to modify the background density gradient, thereby modifying the leading-order acoustic wave structure. Simulations of the wave/mean-flow system enabled by the WKBJ analysis are performed to illustrate the nature of the two-way coupling, which contrasts sharply with classic Rayleigh streaming, for which the waves can first be determined and the streaming flows subsequently computed.

Wave-Ice interaction in the Marginal Ice Zone: Toward a Wave-Ocean-Ice Coupled Modeling System

DTIC Science & Technology

2015-09-30

MIZ using WW3 (3 frequency bins, ice retreat in August and ice advance in October); Blue (solid): Based on observations near Antarctica by Meylan...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Wave- Ice interaction in the Marginal Ice Zone: Toward a...Wave-Ocean- Ice Coupled Modeling System W. E. Rogers Naval Research Laboratory, Code 7322 Stennis Space Center, MS 39529 phone: (228) 688-4727

Directional multimode coupler for planar magnonics: Side-coupled magnetic stripes

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

Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A.; Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009

We experimentally demonstrate spin waves coupling in two laterally adjacent magnetic stripes. By the means of Brillouin light scattering spectroscopy, we show that the coupling efficiency depends both on the magnonic waveguides' geometry and the characteristics of spin-wave modes. In particular, the lateral confinement of coupled yttrium-iron-garnet stripes enables the possibility of control over the spin-wave propagation characteristics. Numerical simulations (in time domain and frequency domain) reveal the nature of intermodal coupling between two magnonic stripes. The proposed topology of multimode magnonic coupler can be utilized as a building block for fabrication of integrated parallel functional and logic devices suchmore » as the frequency selective directional coupler or tunable splitter, enabling a number of potential applications for planar magnonics.« less

Spiral waves in driven dusty plasma medium: Generalized hydrodynamic fluid description

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Patel, Bhavesh; Das, Amita

2018-04-01

Spiral waves are observed in many natural phenomena. They have been extensively represented by the mathematical FitzHugh-Nagumo model [Barkley et al., Phys. Rev. A 42, 2489 (1990)] of excitable media. Also, in incompressible fluid simulations, the excitation of thermal spiral waves has been reported by Li et al. [Phys. of Fluids 22, 011701 (2010)]. In the present paper, the spatiotemporal development of spiral waves in the context of weak and strong coupling limits has been shown. While the weakly coupled medium has been represented by a simple fluid description, for strong coupling, a generalized visco-elastic fluid description has been employed. The medium has been driven by an external force in the form of a rotating electric field. It is shown that when the amplitude of force is small, the density perturbations in the medium are also small. In this case, the excitations do not develop as a spiral wave. Only when the amplitude of force is high so as to drive the density perturbations to nonlinear amplitudes does the spiral density wave formation occurs. The role of the forcing frequency and the effect of strong coupling and the sound velocity of medium in the formation and evolution of spiral waves have been investigated in detail.

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

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

Dynamics of severe storms through the study of thermospheric-tropospheric coupling

NASA Technical Reports Server (NTRS)

Hung, R. J.; Smith, R. E.

1979-01-01

Atmospheric acoustic-gravity waves associated with severe local thunderstorms, tornadoes, and hurricanes can be studied through the coupling between the thermosphere and the troposphere. Reverse group ray tracing computations of acoustic-gravity waves, observed by an ionospheric Doppler sounder array, show that the wave sources are in the neighborhood of storm systems and the waves are excited prior to the storms. It is suggested that the overshooting and ensuing collapse of convective turrets may be responsible for generating the acoustic-gravity waves observed. The results of this study also show that the study of wave-wave resonant interactions may be a potential tool for investigating the dynamical behavior of severe storm systems using ionospheric observations of atmospheric acoustic-gravity waves associated with severe storms.

On the coupled evolution of oceanic internal waves and quasi-geostrophic flow

NASA Astrophysics Data System (ADS)

Wagner, Gregory LeClaire

Oceanic motion outside thin boundary layers is primarily a mixture of quasi-geostrophic flow and internal waves with either near-inertial frequencies or the frequency of the semidiurnal lunar tide. This dissertation seeks a deeper understanding of waves and flow through reduced models that isolate their nonlinear and coupled evolution from the Boussinesq equations. Three physical-space models are developed: an equation that describes quasi-geostrophic evolution in an arbitrary and prescribed field of hydrostatic internal waves; a three-component model that couples quasi-geostrophic flow to both near-inertial waves and the near-inertial second harmonic; and a model for the slow evolution of hydrostatic internal tides in quasi-geostrophic flow of near-arbitrary scale. This slow internal tide equation opens the path to a coupled model for the energetic interaction of quasi-geostrophic flow and oceanic internal tides. Four results emerge. First, the wave-averaged quasi-geostrophic equation reveals that finite-amplitude waves give rise to a mean flow that advects quasi-geostrophic potential vorticity. Second is the definition of a new material invariant: Available Potential Vorticity, or APV. APV isolates the part of Ertel potential vorticity available for balanced-flow evolution in Eulerian frames and proves necessary in the separating waves and quasi-geostrophic flow. The third result, hashed out for near-inertial waves and quasi-geostrophic flow, is that wave-flow interaction leads to energy exchange even under conditions of weak nonlinearity. For storm-forced oceanic near-inertial waves the interaction often energizes waves at the expense of flow. We call this extraction of balanced quasi-geostrophic energy 'stimulated generation' since it requires externally-forced rather than spontaneously-generated waves. The fourth result is that quasi-geostrophic flow can encourage or 'catalyze' a nonlinear interaction between a near-inertial wave field and its second harmonic that transfers energy to the small near-inertial vertical scales of wave breaking and mixing.

Wave effects on ocean-ice interaction in the marginal ice zone

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Hakkinen, Sirpa; Peng, Chih Y.

1993-01-01

The effects of wave train on ice-ocean interaction in the marginal ice zone are studied through numerical modeling. A coupled two-dimensional ice-ocean model has been developed to include wave effects and wind stress for the predictions of ice edge dynamics. The sea ice model is coupled to the reduced-gravity ocean model through interfacial stresses. The main dynamic balance in the ice momentum is between water-ice stress, wind stress, and wave radiation stresses. By considering the exchange of momentum between waves and ice pack through radiation stress for decaying waves, a parametric study of the effects of wave stress and wind stress on ice edge dynamics has been performed. The numerical results show significant effects from wave action. The ice edge is sharper, and ice edge meanders form in the marginal ice zone owing to forcing by wave action and refraction of swell system after a couple of days. Upwelling at the ice edge and eddy formation can be enhanced by the nonlinear effects of wave action; wave action sharpens the ice edge and can produce ice meandering, which enhances local Ekman pumping and pycnocline anomalies. The resulting ice concentration, pycnocline changes, and flow velocity field are shown to be consistent with previous observations.

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

DOE PAGES

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2017-08-14

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this study, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. Themore » general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Finally, our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.« less

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian.

PubMed

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J

2017-08-01

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this paper, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. The general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

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

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this study, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. Themore » general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Finally, our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.« less

Experimental Verification of the Bernstein Effect "Repetition without Repetition".

PubMed

Zilov, V G; Eskov, V M; Khadartsev, A A; Eskov, V V

2017-05-01

The necessity of studying the Bernstein effect "repetition without repetition" is dictated by the absence of quantitative description of this effect and models that could describe such unique phenomena as repeated limb movements in a person in various mental states. In 30 nominally healthy volunteers (15 men, 15 women aged 24-25 years), tappingrams and tremorograms were recorded using an eddy current sensor with an oscillatory circuit (1 MHz) and an amplifier with recording frequency 0-1000 Hz and minimum amplitude of 0.01 mm. The results were recorded as files, processed as matrices of paired comparisons of samples, the number of matching sample pairs was determined (significance level p>0.05), and phase trajectories of finger movement were plotted. The effect was observed for both tapping and tremor and it is advisable to calculate the parameters of quasi-attractors that changed upon shifts in homeostasis.

A water bag theory of autoresonant Bernstein-Greene-Kruskal modes

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

Khain, P.; Friedland, L.

2007-08-15

The adiabatic water bag theory describing formation and passage through phase-space of driven, continuously phase-locked (autoresonant) coherent structures in plasmas [L. Friedland et al., Phys. Rev. Lett. 96, 225001 (2006)] and of the associated Bernstein-Greene-Kruskal (BGK) modes is developed. The phase-locking is achieved by using a chirped frequency ponderomotive drive, passing through kinetic Cerenkov-type resonances. The theory uses the adiabatic invariants (conserved actions of limiting trajectories) in the problem and, for a flat-top initial distribution of the electrons, reduces the calculation of the self-field of the driven BGK mode to solution of a few algebraic equations. The adiabatic multiwater bagmore » extension of the theory for applications to autoresonant BGK structures with more general initial distributions is suggested. The results of the theories are in very good agreement with numerical simulations.« less

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

Xiao, Jianyuan; Liu, Jian; He, Yang

Explicit high-order non-canonical symplectic particle-in-cell algorithms for classical particle-field systems governed by the Vlasov-Maxwell equations are developed. The algorithms conserve a discrete non-canonical symplectic structure derived from the Lagrangian of the particle-field system, which is naturally discrete in particles. The electromagnetic field is spatially discretized using the method of discrete exterior calculus with high-order interpolating differential forms for a cubic grid. The resulting time-domain Lagrangian assumes a non-canonical symplectic structure. It is also gauge invariant and conserves charge. The system is then solved using a structure-preserving splitting method discovered by He et al. [preprint http://arxiv.org/abs/arXiv:1505.06076 (2015)], which produces five exactlymore » soluble sub-systems, and high-order structure-preserving algorithms follow by combinations. The explicit, high-order, and conservative nature of the algorithms is especially suitable for long-term simulations of particle-field systems with extremely large number of degrees of freedom on massively parallel supercomputers. The algorithms have been tested and verified by the two physics problems, i.e., the nonlinear Landau damping and the electron Bernstein wave.« less

Coupling of free space sub-terahertz waves into dielectric slabs using PC waveguides.

PubMed

Ghattan, Z; Hasek, T; Shahabadi, M; Koch, M

2008-04-28

The paper presents theoretical and experimental results on photonic crystal structures which work under the self-collimation condition to couple free space waves into dielectric slabs in the sub-terahertz range. Using a standard machining process, two-dimensional photonic crystal structures consisting of a square array of air holes in the dielectric medium are fabricated. One of the structures has two adjacent parallel line-defects that improve the coupling efficiency. This leads to a combination of self-collimation and directional emission of electromagnetic waves. The experimental results are in good agreement with those of the Finite- Element-Method calculations. Experimentally we achieve a coupling efficiency of 63%.

Plate Wave Resonance with Air-Coupled Ultrasonics

NASA Astrophysics Data System (ADS)

Bar, H. N.; Dayal, V.; Barnard, D.; Hsu, D. K.

2010-02-01

Air-coupled ultrasonic transducers can excite plate waves in metals and composites. The coincidence effect, i.e., the wave vector of plate wave coincides with projection of exciting airborne sound vector, leads to a resonance which strongly amplifies the sound transmission through the plate. The resonance depends on the angle of incidence and the frequency. In the present study, the incidence angle for maximum transmission (θmax) is measured in plates of steel, aluminum, carbon fiber reinforced composites and honeycomb sandwich panels. The variations of (θmax) with plate thickness are compared with theoretical values in steel, aluminum and quasi-isotropic carbon fiber composites. The enhanced transmission of air-coupled ultrasound at oblique incidence can substantially improve the probability of flaw detection in plates and especially in honeycomb structures. Experimental air-coupled ultrasonic scan of subtle flaws in CFRP laminates showed definite improvement of signal-to-noise ratio with oblique incidence at θmax.

Numerical simulation of the solitary wave interacting with an elastic structure using MPS-FEM coupled method

NASA Astrophysics Data System (ADS)

Rao, Chengping; Zhang, Youlin; Wan, Decheng

2017-12-01

Fluid-Structure Interaction (FSI) caused by fluid impacting onto a flexible structure commonly occurs in naval architecture and ocean engineering. Research on the problem of wave-structure interaction is important to ensure the safety of offshore structures. This paper presents the Moving Particle Semi-implicit and Finite Element Coupled Method (MPS-FEM) to simulate FSI problems. The Moving Particle Semi-implicit (MPS) method is used to calculate the fluid domain, while the Finite Element Method (FEM) is used to address the structure domain. The scheme for the coupling of MPS and FEM is introduced first. Then, numerical validation and convergent study are performed to verify the accuracy of the solver for solitary wave generation and FSI problems. The interaction between the solitary wave and an elastic structure is investigated by using the MPS-FEM coupled method.

Modeling High-Resolution Coastal Ocean Dynamics with COAMPS: System Overview, Applications and Future Directions

NASA Astrophysics Data System (ADS)

Allard, R. A.; Campbell, T. J.; Edwards, K. L.; Smith, T.; Martin, P.; Hebert, D. A.; Rogers, W.; Dykes, J. D.; Jacobs, G. A.; Spence, P. L.; Bartels, B.

2014-12-01

The Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS®) is an atmosphere-ocean-wave modeling system developed by the Naval Research Laboratory which can be configured to cycle regional forecasts/analysis models in single-model (atmosphere, ocean, and wave) or coupled-model (atmosphere-ocean, ocean-wave, and atmosphere-ocean-wave) modes. The model coupling is performed using the Earth System Modeling Framework (ESMF). The ocean component is the Navy Coastal Ocean Model (NCOM), and the wave components include Simulating WAves Nearshore (SWAN) and WaveWatch-III. NCOM has been modified to include wetting and drying, the effects of Stokes drift current, wave radiation stresses due to horizontal gradients of the momentum flux of surface waves, enhancement of bottom drag in shallow water, and enhanced vertical mixing due to Langmuir turbulence. An overview of the modeling system including ocean data assimilation and specification of boundary conditions will be presented. Results from a high-resolution (10-250m) modeling study from the Surfzone Coastal Oil Pathways Experiment (SCOPE) near Ft. Walton Beach, Florida in December 2013 will be presented. ®COAMPS is a registered trademark of the Naval Research Laboratory

Parametric Decay Instability of Near-Acoustic Waves in Fluid and Kinetic Regimes

NASA Astrophysics Data System (ADS)

Affolter, M.; Anderegg, F.; Driscoll, C. F.; Valentini, F.

2016-10-01

We present quantitative measurements of parametric wave-wave coupling rates and decay instabilities in the range 10 meV Δω /2. In contrast, at higher temperatures, the mz = 2 wave is more unstable. The instability threshold is reduced from the cold fluid prediction as the plasma temperature is increased, which is in qualitative agreement with Vlasov simulations, but is not yet understood theoretically. Supported by DOE/HEDLP Grant DE-SC0008693 and DOE Fusion Energy Science Postdoctoral Research Program administered by the Oak Ridge Institute for Science and Education.

Mediterranea Forecasting System: a focus on wave-current coupling

NASA Astrophysics Data System (ADS)

Clementi, Emanuela; Delrosso, Damiano; Pistoia, Jenny; Drudi, Massimiliano; Fratianni, Claudia; Grandi, Alessandro; Pinardi, Nadia; Oddo, Paolo; Tonani, Marina

2016-04-01

The Mediterranean Forecasting System (MFS) is a numerical ocean prediction system that produces analyses, reanalyses and short term forecasts for the entire Mediterranean Sea and its Atlantic Ocean adjacent areas. MFS became operational in the late 90's and has been developed and continuously improved in the framework of a series of EU and National funded programs and is now part of the Copernicus Marine Service. The MFS is composed by the hydrodynamic model NEMO (Nucleus for European Modelling of the Ocean) 2-way coupled with the third generation wave model WW3 (WaveWatchIII) implemented in the Mediterranean Sea with 1/16 horizontal resolution and forced by ECMWF atmospheric fields. The model solutions are corrected by the data assimilation system (3D variational scheme adapted to the oceanic assimilation problem) with a daily assimilation cycle, using a background error correlation matrix varying seasonally and in different sub-regions of the Mediterranean Sea. The focus of this work is to present the latest modelling system upgrades and the related achieved improvements. In order to evaluate the performance of the coupled system a set of experiments has been built by coupling the wave and circulation models that hourly exchange the following fields: the sea surface currents and air-sea temperature difference are transferred from NEMO model to WW3 model modifying respectively the mean momentum transfer of waves and the wind speed stability parameter; while the neutral drag coefficient computed by WW3 model is passed to NEMO that computes the turbulent component. In order to validate the modelling system, numerical results have been compared with in-situ and remote sensing data. This work suggests that a coupled model might be capable of a better description of wave-current interactions, in particular feedback from the ocean to the waves might assess an improvement on the prediction capability of wave characteristics, while suggests to proceed toward a fully coupled modelling system in order to achieve stronger enhancements of the hydrodynamic fields.

Modeling of Inner Magnetosphere Coupling Processes

NASA Technical Reports Server (NTRS)

Khazanov, George V.

2011-01-01

The Ring Current (RC) is the biggest energy player in the inner magnetosphere. It is the source of free energy for Electromagnetic Ion Cyclotron (EMIC) wave excitation provided by a temperature anisotropy of RC ions, which develops naturally during inward E B convection from the plasmasheet. The cold plasmasphere, which is under the strong influence of the magnetospheric electric field, strongly mediates the RC-EMIC wave-particle-coupling process and ultimately becomes part of the particle and energy interplay. On the other hand, there is a strong influence of the RC on the inner magnetospheric electric and magnetic field configurations and these configurations, in turn, are important to RC dynamics. Therefore, one of the biggest needs for inner magnetospheric research is the continued progression toward a coupled, interconnected system with the inclusion of nonlinear feedback mechanisms between the plasma populations, the electric and magnetic fields, and plasma waves. As we clearly demonstrated in our studies, EMIC waves strongly interact with electrons and ions of energies ranging from approx.1 eV to approx.10 MeV, and that these waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer RB relativistic electrons. As we found, the rate of ion and electron scattering/heating in the Earth's magnetosphere is not only controlled by the wave intensity-spatial-temporal distribution but also strongly depends on the spectral distribution of the wave power. The latter is also a function of the plasmaspheric heavy ion content, and the plasma density and temperature distributions along the magnetic field lines. The above discussion places RC-EMIC wave coupling dynamics in context with inner magnetospheric coupling processes and, ultimately, relates RC studies with plasmaspheric and Superthermal Electrons formation processes as well as with outer RB physics.

Effects of nonuniform Mach-number entrance on scramjet nozzle flowfield and performance

NASA Astrophysics Data System (ADS)

Zhang, Pu; Xu, Jinglei; Quan, Zhibin; Mo, Jianwei

2016-12-01

Considering the non-uniformities of nozzle entrance influenced by the upstream, the effects of nonuniform Mach-number coupled with shock and expansion-wave on the flowfield and performances of single expansion ramp nozzle (SERN) are numerically studied using Reynolds-Averaged Navier-Stokes equations. The adopted Reynolds-averaged Navier-Stokes methodology is validated by comparing the numerical results with the cold experimental data, and the average method used in this paper is discussed. Uniform and nonuniform facility nozzles are designed to generate different Mach-number profile for the inlet of SERN, which is direct-connected with different facility nozzle, and the whole flowfield is simulated. Because of the coupling of shock and expansion-wave, flow direction of nonuniform SERN entrance is distorted. Compared with Mach contour of uniform case, the line is more curved for coupling shock-wave entrance (SWE) case, and flatter for the coupling expansion-wave entrance (EWE) case. Wall pressure distribution of SWE case appears rising region, whereas decreases like stairs of EWE case. The numerical results reveal that the coupled shock and expansion-wave play significant roles on nozzle performances. Compared with the SERN performances of uniform entrance case at the same work conditions, the thrust of nonuniform entrance cases reduces by 3-6%, pitch moment decreases by 2.5-7%. The negative lift presents an incremental trend with EWE while the situation is the opposite with SWE. These results confirm that considering the entrance flow parameter nonuniformities of a scramjet nozzle coupled with shock or expansion-wave from the upstream is necessary.

Wave Coupling between the Lower and Middle Thermosphere as Viewed from Quasi-Sun-Synchronous Satellites

NASA Astrophysics Data System (ADS)

Gasperini, Federico

In a society increasingly dependent on space technology, space weather has become a prominent scientific paradigm. In the last decade evidence has shown that terrestrial weather significantly influences space weather. Periodic absorption of solar radiation in local time and longitude by tropospheric water vapor and stratospheric ozone as well as latent heat release in clouds generate a spatially- and temporally-evolving spectrum of global-scale atmospheric waves (i.e., tides, planetary waves and Kelvin waves). A subset of these waves propagates vertically, evolving with height due to wave-mean flow, wave-wave, and wave-plasma interactions, and driving electric fields of tidal origin in the dynamo region. While considerable improvements have been made on the understanding of MLT dynamics, driven in part by the development and deployment of new instruments and techniques, relatively little is known about the coupling of waves in the 120-300 km `thermospheric gap' between satellite remote-sensing and in-situ wave diagnostics. The dissertation herein reveals vertical wave coupling in this height region and quantifies its role in determining thermospheric variability. This objective is accomplished employing quasi-Sun-synchronous satellite measurements (i.e., TIMED, CHAMP, and GOCE) and state-of-the-art numerical modeling simulations (i.e., TIME-GCM/MERRA). Evidence is found for the vertical propagation from the lower to the middle thermosphere of the eastward propagating diurnal tide with zonal wave number 3 (DE3) and the 3-day ultra-fast Kelvin wave (UFKW), two major global-scale atmospheric oscillations of tropospheric origin. These waves are shown to nonlinearly interact and produce secondary waves responsible for significant longitudinal and day-to-day variability. For solar and geomagnetic quiet conditions, atmospheric waves are found to be responsible for up to 60% of the total variability, demonstrating lower atmosphere coupling as a key contributor to thermosphere weather, at least in the absence of major solar-driven variability. Additionally, background atmospheric conditions (i.e., dissipation and zonal mean winds) and found to significantly impact the latitudinal-temporal evolution of upward propagating waves.

Three-wave and four-wave interactions in gravity wave turbulence

NASA Astrophysics Data System (ADS)

Aubourg, Quentin; Campagne, Antoine; Peureux, Charles; Ardhuin, Fabrice; Sommeria, Joel; Viboud, Samuel; Mordant, Nicolas

2017-11-01

Weak-turbulence theory is a statistical framework to describe a large ensemble of nonlinearly interacting waves. The archetypal example of such system is the ocean surface that is made of interacting surface gravity waves. Here we describe a laboratory experiment dedicated to probe the statistical properties of turbulent gravity waves. We set up an isotropic state of interacting gravity waves in the Coriolis facility (13-m-diam circular wave tank) by exciting waves at 1 Hz by wedge wave makers. We implement a stereoscopic technique to obtain a measurement of the surface elevation that is resolved in both space and time. Fourier analysis shows that the laboratory spectra are systematically steeper than the theoretical predictions and the field observations in the Black Sea by Leckler et al. [F. Leckler et al., J. Phys. Oceanogr. 45, 2484 (2015), 10.1175/JPO-D-14-0237.1]. We identify a strong impact of surface dissipation on the scaling of the Fourier spectrum at the scales that are accessible in the experiments. We use bicoherence and tricoherence statistical tools in frequency and/or wave-vector space to identify the active nonlinear coupling. These analyses are also performed on the field data by Leckler et al. for comparison with the laboratory data. Three-wave coupling is characterized by and shown to involve mostly quasiresonances of waves with second- or higher-order harmonics. Four-wave coupling is not observed in the laboratory but is evidenced in the field data. We discuss temporal scale separation to explain our observations.

Study of Rayleigh-Love coupling from Spatial Gradient Observation

NASA Astrophysics Data System (ADS)

Lin, C. J.; Hosseini, K.; Donner, S.; Vernon, F.; Wassermann, J. M.; Igel, H.

2017-12-01

We present a new method to study Rayleigh-Love coupling. Instead of using seismograms solely, where ground motion is recorded as function of time, we incorporate with rotation and strain, also called spatial gradient where ground is represented as function of distance. Seismic rotation and strain are intrinsic different observable wavefield so are helpful to indentify wave type and wave propagation. A Mw 7.5 earthquake on 29 March 2015 occurred in Kokopo, Papua New Guinea recorded by a dense seismic array at PFO, California are used to obtaint seismic spatial gradient. We firstly estimate time series of azimuthal direction and phase velocity of SH wave and Rayleigh wave by analyzing collocated seismograms and rotations. This result also compares with frequency wavenumber methods using a nearby ANZA seismic array. We find the direction of Rayleigh wave fits well with great-circle back azimuth during wave propagation, while the direction of Love wave deviates from that, especially when main energy of Rayleigh wave arrives. From the analysis of cross-correlation between areal strain and vertical rotation, it reveals that high coherence, either positive or negative, happens at the same time when Love wave deparate from great-circle path. We also find the observed azimuth of Love wave and polarized particle motion of Rayleigh wave fits well with the fast direction of Rayleigh wave, for the period of 50 secs. We conclude the cause of deviated azimuth of Love wave is due to Rayleigh-Love coupling, as surface wave propagates through the area with anisotropic structure.

High-order rogue waves in vector nonlinear Schrödinger equations.

PubMed

Ling, Liming; Guo, Boling; Zhao, Li-Chen

2014-04-01

We study the dynamics of high-order rogue waves (RWs) in two-component coupled nonlinear Schrödinger equations. We find that four fundamental rogue waves can emerge from second-order vector RWs in the coupled system, in contrast to the high-order ones in single-component systems. The distribution shape can be quadrilateral, triangle, and line structures by varying the proper initial excitations given by the exact analytical solutions. The distribution pattern for vector RWs is more abundant than that for scalar rogue waves. Possibilities to observe these new patterns for rogue waves are discussed for a nonlinear fiber.

Piezoelectric shear wave resonator and method of making same

DOEpatents

Wang, Jin S.; Lakin, Kenneth M.; Landin, Allen R.

1988-01-01

An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/.degree.C.

Method of making a piezoelectric shear wave resonator

DOEpatents

Wang, Jin S.; Lakin, Kenneth M.; Landin, Allen R.

1987-02-03

An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/.degree.C.

Universal relations for spin-orbit-coupled Fermi gas near an s -wave resonance

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Sun, Ning

2018-04-01

Synthetic spin-orbit-coupled quantum gases have been widely studied both experimentally and theoretically in the past decade. As shown in previous studies, this modification of single-body dispersion will in general couple different partial waves of the two-body scattering and thus distort the wave function of few-body bound states which determines the short-distance behavior of many-body wave function. In this work, we focus on the two-component Fermi gas with one-dimensional or three-dimensional spin-orbit coupling (SOC) near an s -wave resonance. Using the method of effective field theory and the operator product expansion, we derive universal relations for both systems, including the adiabatic theorem, viral theorem, and pressure relation, and obtain the momentum distribution matrix 〈ψa†(q ) ψb(q ) 〉 at large q (a ,b are spin indices). The momentum distribution matrix shows both spin-dependent and spatial anisotropic features. And the large momentum tail is modified at the subleading order thanks to the SOC. We also discuss the experimental implication of these results depending on the realization of the SOC.

Review of rigorous coupled-wave analysis and of homogeneous effective medium approximations for high spatial-frequency surface-relief gratings

NASA Technical Reports Server (NTRS)

Glytsis, Elias N.; Brundrett, David L.; Gaylord, Thomas K.

1993-01-01

A review of the rigorous coupled-wave analysis as applied to the diffraction of electro-magnetic waves by gratings is presented. The analysis is valid for any polarization, angle of incidence, and conical diffraction. Cascaded and/or multiplexed gratings as well as material anisotropy can be incorporated under the same formalism. Small period rectangular groove gratings can also be modeled using approximately equivalent uniaxial homogeneous layers (effective media). The ordinary and extraordinary refractive indices of these layers depend on the gratings filling factor, the refractive indices of the substrate and superstrate, and the ratio of the freespace wavelength to grating period. Comparisons of the homogeneous effective medium approximations with the rigorous coupled-wave analysis are presented. Antireflection designs (single-layer or multilayer) using the effective medium models are presented and compared. These ultra-short period antireflection gratings can also be used to produce soft x-rays. Comparisons of the rigorous coupled-wave analysis with experimental results on soft x-ray generation by gratings are also included.

Traveling wave linear accelerator with RF power flow outside of accelerating cavities

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

Dolgashev, Valery A.

A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities hasmore » a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.« less

Hydroelectromechanical modelling of a piezoelectric wave energy converter

NASA Astrophysics Data System (ADS)

Renzi, E.

2016-11-01

We investigate the hydroelectromechanical-coupled dynamics of a piezoelectric wave energy converter. The converter is made of a flexible bimorph plate, clamped at its ends and forced to motion by incident ocean surface waves. The piezoceramic layers are connected in series and transform the elastic motion of the plate into useful electricity by means of the piezoelectric effect. By using a distributed-parameter analytical approach, we couple the linear piezoelectric constitutive equations for the plate with the potential-flow equations for the surface water waves. The resulting system of governing partial differential equations yields a new hydroelectromechanical dispersion relation, whose complex roots are determined with a numerical approach. The effect of the piezoelectric coupling in the hydroelastic domain generates a system of short- and long-crested weakly damped progressive waves travelling along the plate. We show that the short-crested flexural wave component gives a dominant contribution to the generated power. We determine the hydroelectromechanical resonant periods of the device, at which the power output is significant.

Bifurcation analysis for ion acoustic waves in a strongly coupled plasma including trapped electrons

NASA Astrophysics Data System (ADS)

El-Labany, S. K.; El-Taibany, W. F.; Atteya, A.

2018-02-01

The nonlinear ion acoustic wave propagation in a strongly coupled plasma composed of ions and trapped electrons has been investigated. The reductive perturbation method is employed to derive a modified Korteweg-de Vries-Burgers (mKdV-Burgers) equation. To solve this equation in case of dissipative system, the tangent hyperbolic method is used, and a shock wave solution is obtained. Numerical investigations show that, the ion acoustic waves are significantly modified by the effect of polarization force, the trapped electrons and the viscosity coefficients. Applying the bifurcation theory to the dynamical system of the derived mKdV-Burgers equation, the phase portraits of the traveling wave solutions of both of dissipative and non-dissipative systems are analyzed. The present results could be helpful for a better understanding of the waves nonlinear propagation in a strongly coupled plasma, which can be produced by photoionizing laser-cooled and trapped electrons [1], and also in neutron stars or white dwarfs interior.

Ion acoustic wave assisted laser beat wave terahertz generation in a plasma channel

NASA Astrophysics Data System (ADS)

Tyagi, Yachna; Tripathi, Deepak; Walia, Keshav; Garg, Deepak

2018-04-01

Resonant excitation of terahertz (THz) radiation by non-linear mixing of two lasers in the presence of an electrostatic wave is investigated. The electrostatic wave assists in k matching and contributes to non-linear coupling. In this plasma channel, the electron plasma frequency becomes minimum on the axis. The beat frequency ponderomotive force imparts an oscillating velocity to the electrons. In the presence of an ion-acoustic wave, density perturbation due to the ion-acoustic wave couples with the oscillating velocity of the electrons and give rise to non-linear current that gives rise to an ion-acoustic wave frequency assisted THz radiation field. The normalized field amplitude of ion acoustic wave assisted THz varies inversely for ω/ωp . The field amplitude of ion acoustic wave assisted THz decreases as ω/ωp increases.

A coupling modulation model of capillary waves from gravity waves: Theoretical analysis and experimental validation

NASA Astrophysics Data System (ADS)

Chen, Pengzhen; Wang, Xiaoqing; Liu, Li; Chong, Jinsong

2016-06-01

According to Bragg theory, capillary waves are the predominant scatterers of high-frequency band (such as Ka-band) microwave radiation from the surface of the ocean. Therefore, understanding the modulation mechanism of capillary waves is an important foundation for interpreting high-frequency microwave remote sensing images of the surface of the sea. In our experiments, we discovered that modulations of capillary waves are significantly larger than the values predicted by the classical theory. Further, analysis shows that the difference in restoring force results in an inflection point while the phase velocity changes from gravity waves region to capillary waves region, and this results in the capillary waves being able to resonate with gravity waves when the phase velocity of the gravity waves is equal to the group velocity of the capillary waves. Consequently, we propose a coupling modulation model in which the current modulates the capillary wave indirectly by modulating the resonant gravity waves, and the modulation of the former is approximated by that of the latter. This model very effectively explains the results discovered in our experiments. Further, based on Bragg scattering theory and this coupling modulation model, we simulate the modulation of normalized radar cross section (NRCS) of typical internal waves and show that the high-frequency bands are superior to the low-frequency bands because of their greater modulation of NRCS and better radiometric resolution. This result provides new support for choice of radar band for observation of wave-current modulation oceanic phenomena such as internal waves, fronts, and shears.

Coupled atmosphere-ocean-wave simulations of a storm event over the Gulf of Lion and Balearic Sea

USGS Publications Warehouse

Renault, Lionel; Chiggiato, Jacopo; Warner, John C.; Gomez, Marta; Vizoso, Guillermo; Tintore, Joaquin

2012-01-01

The coastal areas of the North-Western Mediterranean Sea are one of the most challenging places for ocean forecasting. This region is exposed to severe storms events that are of short duration. During these events, significant air-sea interactions, strong winds and large sea-state can have catastrophic consequences in the coastal areas. To investigate these air-sea interactions and the oceanic response to such events, we implemented the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System simulating a severe storm in the Mediterranean Sea that occurred in May 2010. During this event, wind speed reached up to 25 m.s-1 inducing significant sea surface cooling (up to 2°C) over the Gulf of Lion (GoL) and along the storm track, and generating surface waves with a significant height of 6 m. It is shown that the event, associated with a cyclogenesis between the Balearic Islands and the GoL, is relatively well reproduced by the coupled system. A surface heat budget analysis showed that ocean vertical mixing was a major contributor to the cooling tendency along the storm track and in the GoL where turbulent heat fluxes also played an important role. Sensitivity experiments on the ocean-atmosphere coupling suggested that the coupled system is sensitive to the momentum flux parameterization as well as air-sea and air-wave coupling. Comparisons with available atmospheric and oceanic observations showed that the use of the fully coupled system provides the most skillful simulation, illustrating the benefit of using a fully coupled ocean-atmosphere-wave model for the assessment of these storm events.

Verification and Validation of COAMPS: Results from a Fully-Coupled Air/Sea/Wave Modeling System

NASA Astrophysics Data System (ADS)

Smith, T.; Allard, R. A.; Campbell, T. J.; Chu, Y. P.; Dykes, J.; Zamudio, L.; Chen, S.; Gabersek, S.

2016-02-01

The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) is a state-of-the art, fully-coupled air/sea/wave modeling system that is currently being validated for operational transition to both the Naval Oceanographic Office (NAVO) and to the Fleet Numerical Meteorology and Oceanography Center (FNMOC). COAMPS is run at the Department of Defense Supercomputing Resource Center (DSRC) operated by the DoD High Performance Computing Modernization Program (HPCMP). A total of four models including the Naval Coastal Ocean Model (NCOM), Simulating Waves Nearshore (SWAN), WaveWatch III, and the COAMPS atmospheric model are coupled through both the Earth System Modeling Framework (ESMF). Results from regions of naval operational interests, including the Western Atlantic (U.S. East Coast), RIMPAC (Hawaii), and DYNAMO (Indian Ocean), will show the advantages of utilizing a coupled modeling system versus an uncoupled or stand alone model. Statistical analyses, which include model/observation comparisons, will be presented in the form of operationally approved scorecards for both the atmospheric and oceanic output. Also, computational logistics involving the HPC resources for the COAMPS simulations will be shown.

Performance of wave function and density functional methods for water hydrogen bond spin-spin coupling constants.

PubMed

García de la Vega, J M; Omar, S; San Fabián, J

2017-04-01

Spin-spin coupling constants in water monomer and dimer have been calculated using several wave function and density functional-based methods. CCSD, MCSCF, and SOPPA wave functions methods yield similar results, specially when an additive approach is used with the MCSCF. Several functionals have been used to analyze their performance with the Jacob's ladder and a set of functionals with different HF exchange were tested. Functionals with large HF exchange appropriately predict 1 J O H , 2 J H H and 2h J O O couplings, while 1h J O H is better calculated with functionals that include a reduced fraction of HF exchange. Accurate functionals for 1 J O H and 2 J H H have been tested in a tetramer water model. The hydrogen bond effects on these intramolecular couplings are additive when they are calculated by SOPPA(CCSD) wave function and DFT methods. Graphical Abstract Evaluation of the additive effect of the hydrogen bond on spin-spin coupling constants of water using WF and DFT methods.

FIBER AND INTEGRATED OPTICS: Influence of diffraction-induced emission of light on resonant conversion of surface waves in diffraction-coupled optical waveguides

NASA Astrophysics Data System (ADS)

Kiselev, V. A.; Shaposhnikov, S. N.

1989-09-01

An investigation is reported of diffraction-induced emission of surface waves under conditions of resonant transfer of light between different regular and corrugated waveguides. It is shown that the part of the emitted light flux carried by surface waves along diffraction-coupled waveguides depends strongly on the ratio of the effective refractive indices of the guides. The dependences of the optical coupling length and of the corresponding emitted light flux on the distance between the waveguides and on the difference between their refractive indices are given.

Acoustic mode coupling induced by shallow water nonlinear internal waves: sensitivity to environmental conditions and space-time scales of internal waves.

PubMed

Colosi, John A

2008-09-01

While many results have been intuited from numerical simulation studies, the precise connections between shallow-water acoustic variability and the space-time scales of nonlinear internal waves (NLIWs) as well as the background environmental conditions have not been clearly established analytically. Two-dimensional coupled mode propagation through NLIWs is examined using a perturbation series solution in which each order n is associated with nth-order multiple scattering. Importantly, the perturbation solution gives resonance conditions that pick out specific NLIW scales that cause coupling, and seabed attenuation is demonstrated to broaden these resonances, fundamentally changing the coupling behavior at low frequency. Sound-speed inhomogeneities caused by internal solitary waves (ISWs) are primarily considered and the dependence of mode coupling on ISW amplitude, range width, depth structure, location relative to the source, and packet characteristics are delineated as a function of acoustic frequency. In addition, it is seen that significant energy transfer to modes with initially low or zero energy involves at least a second order scattering process. Under moderate scattering conditions, comparisons of first order, single scattering theoretical predictions to direct numerical simulation demonstrate the accuracy of the approach for acoustic frequencies upto 400 Hz and for single as well as multiple ISW wave packets.

Long-range intercellular Ca2+ wave patterns

NASA Astrophysics Data System (ADS)

Tabi, C. B.; Maïna, I.; Mohamadou, A.; Ekobena, H. P. F.; Kofané, T. C.

2015-10-01

Modulational instability is utilized to investigate intercellular Ca2+ wave propagation in an array of diffusively coupled cells. Cells are supposed to be connected via paracrine signaling, where long-range effects, due to the presence of extracellular messengers, are included. The multiple-scale expansion is used to show that the whole dynamics of Ca2+ waves, from the endoplasmic reticulum to the cytosol, can be reduced to a single differential-difference nonlinear equation whose solutions are assumed to be plane waves. Their linear stability analysis is studied, with emphasis on the impact of long-range coupling, via the range parameter s. It is shown that s, as well as the number of interacting cells, importantly modifies the features of modulational instability, as small values of s imply a strong coupling, and increasing its value rather reduces the problem to a first-neighbor one. Our theoretical findings are numerically tested, as the generic equations are fully integrated, leading to the emergence of nonlinear patterns of Ca2+ waves. Strong long-range coupling is pictured by extended trains of breather-like structures whose frequency decreases with increasing s. We also show numerically that the number of interacting cells plays on the spatio-temporal formation of Ca2+ patterns, whilst the quasi-perfect intercellular communication depends on the paracrine coupling parameter.

Evidence for infragravity wave-tide resonance in deep oceans.

PubMed

Sugioka, Hiroko; Fukao, Yoshio; Kanazawa, Toshihiko

2010-10-05

Ocean tides are the oscillatory motions of seawater forced by the gravitational attraction of the Moon and Sun with periods of a half to a day and wavelengths of the semi-Pacific to Pacific scale. Ocean infragravity (IG) waves are sea-surface gravity waves with periods of several minutes and wavelengths of several dozen kilometres. Here we report the first evidence of the resonance between these two ubiquitous phenomena, mutually very different in period and wavelength, in deep oceans. The evidence comes from long-term, large-scale observations with arrays of broadband ocean-bottom seismometers located at depths of more than 4,000 m in the Pacific Ocean. This observational evidence is substantiated by a theoretical argument that IG waves and the tide can resonantly couple and that such coupling occurs over unexpectedly wide areas of the Pacific Ocean. Through this resonant coupling, some of ocean tidal energy is transferred in deep oceans to IG wave energy.

Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

DOE PAGES

García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; ...

2011-12-23

Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore » channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

Coupled Transmission Line Based Slow Wave Structures for Traveling Wave Tubes Applications

NASA Astrophysics Data System (ADS)

Zuboraj, Md. Rashedul Alam

High power microwave devices especially Traveling Wave Tubes (TWTs) and Backward Wave Oscillators (BWOs) are largely dependent on Slow Wave Structures for efficient beam to RF coupling. In this work, a novel approach of analyzing SWSs is proposed and investigated. Specifically, a rigorous study of helical geometries is carried out and a novel SWS "Half-Ring-Helix" is designed. This Half-Ring-Helix circuit achieves 27% miniaturization and delivers 10dB more gain than conventional helices. A generalization of the helix structures is also proposed in the form of Coupled Transmission Line (CTL). It is demonstrated that control of coupling among the CTLs leads to new propagation properties. With this in mind, a novel geometry referred to as "Curved Ring-Bar" is introduced. This geometry is shown to deliver 1MW power across a 33% bandwidth. Notably, this is the first demonstration of MW power TWT across large bandwidth. The CTL is further expanded to enable engineered propagation characteristics. This is done by introducing CTLs having non-identical transmission lines and CTLs with as many as four transmission lines in the same slow wave structure circuit. These non-identical CTLs are demonstrated to generate fourth order dispersion curves. Building on the property of CTLs, a `butterfly' slow wave structure is developed and demonstrated to provide degenerate band edge (DBE) mode. This mode are known to provide large feld enhancement that can be exploited to design high power backward wave oscillators.

Synchrony, waves and ripple in spatially coupled Kuramoto oscillators with Mexican hat connectivity.

PubMed

Heitmann, Stewart; Ermentrout, G Bard

2015-06-01

Spatiotemporal waves of synchronized activity are known to arise in oscillatory neural networks with lateral inhibitory coupling. How such patterns respond to dynamic changes in coupling strength is largely unexplored. The present study uses analysis and simulation to investigate the evolution of wave patterns when the strength of lateral inhibition is varied dynamically. Neural synchronization was modeled by a spatial ring of Kuramoto oscillators with Mexican hat lateral coupling. Broad bands of coexisting stable wave solutions were observed at all levels of inhibition. The stability of these waves was formally analyzed in both the infinite ring and the finite ring. The broad range of multi-stability predicted hysteresis in transitions between neighboring wave solutions when inhibition is slowly varied. Numerical simulation confirmed the predicted transitions when inhibition was ramped down from a high initial value. However, non-wave solutions emerged from the uniform solution when inhibition was ramped upward from zero. These solutions correspond to spatially periodic deviations of phase that we call ripple states. Numerical continuation showed that stable ripple states emerge from synchrony via a supercritical pitchfork bifurcation. The normal form of this bifurcation was derived analytically, and its predictions compared against the numerical results. Ripple states were also found to bifurcate from wave solutions, but these were locally unstable. Simulation also confirmed the existence of hysteresis and ripple states in two spatial dimensions. Our findings show that spatial synchronization patterns can remain structurally stable despite substantial changes in network connectivity.

Full thermomechanical coupling in modelling of micropolar thermoelasticity

NASA Astrophysics Data System (ADS)

Murashkin, E. V.; Radayev, Y. N.

2018-04-01

The present paper is devoted to plane harmonic waves of displacements and microrotations propagating in fully coupled thermoelastic continua. The analysis is carried out in the framework of linear conventional thermoelastic micropolar continuum model. The reduced energy balance equation and the special form of the Helmholtz free energy are discussed. The constitutive constants providing fully coupling of equations of motion and heat conduction are considered. The dispersion equation is derived and analysed in the form bi-cubic and bi-quadratic polynoms product. The equation are analyzed by the computer algebra system Mathematica. Algebraic forms expressed by complex multivalued square and cubic radicals are obtained for wavenumbers of transverse and longitudinal waves. The exact forms of wavenumbers of a plane harmonic coupled thermoelastic waves are computed.

Effects of gap junction inhibition on contraction waves in the murine small intestine in relation to coupled oscillator theory.

PubMed

Parsons, Sean P; Huizinga, Jan D

2015-02-15

Waves of contraction in the small intestine correlate with slow waves generated by the myenteric network of interstitial cells of Cajal. Coupled oscillator theory has been used to explain steplike gradients in the frequency (frequency plateaux) of contraction waves along the length of the small intestine. Inhibition of gap junction coupling between oscillators should lead to predictable effects on these plateaux and the wave dislocation (wave drop) phenomena associated with their boundaries. It is these predictions that we wished to test. We used a novel multicamera diameter-mapping system to measure contraction along 25- to 30-cm lengths of murine small intestine. There were typically two to three plateaux per length of intestine. Dislocations could be limited to the wavefronts immediately about the terminated wave, giving the appearance of a three-pronged fork, i.e., a fork dislocation; additionally, localized decreases in velocity developed across a number of wavefronts, ending with the terminated wave, which could appear as a fork, i.e., slip dislocations. The gap junction inhibitor carbenoxolone increased the number of plateaux and dislocations and decreased contraction wave velocity. In some cases, the usual frequency gradient was reversed, with a plateau at a higher frequency than its proximal neighbor; thus fork dislocations were inverted, and the direction of propagation was reversed. Heptanol had no effect on the frequency or velocity of contractions but did reduce their amplitude. To understand intestinal motor patterns, the pacemaker network of the interstitial cells of Cajal is best evaluated as a system of coupled oscillators. Copyright © 2015 the American Physiological Society.

A new hybrid code (CHIEF) implementing the inertial electron fluid equation without approximation

NASA Astrophysics Data System (ADS)

Muñoz, P. A.; Jain, N.; Kilian, P.; Büchner, J.

2018-03-01

We present a new hybrid algorithm implemented in the code CHIEF (Code Hybrid with Inertial Electron Fluid) for simulations of electron-ion plasmas. The algorithm treats the ions kinetically, modeled by the Particle-in-Cell (PiC) method, and electrons as an inertial fluid, modeled by electron fluid equations without any of the approximations used in most of the other hybrid codes with an inertial electron fluid. This kind of code is appropriate to model a large variety of quasineutral plasma phenomena where the electron inertia and/or ion kinetic effects are relevant. We present here the governing equations of the model, how these are discretized and implemented numerically, as well as six test problems to validate our numerical approach. Our chosen test problems, where the electron inertia and ion kinetic effects play the essential role, are: 0) Excitation of parallel eigenmodes to check numerical convergence and stability, 1) parallel (to a background magnetic field) propagating electromagnetic waves, 2) perpendicular propagating electrostatic waves (ion Bernstein modes), 3) ion beam right-hand instability (resonant and non-resonant), 4) ion Landau damping, 5) ion firehose instability, and 6) 2D oblique ion firehose instability. Our results reproduce successfully the predictions of linear and non-linear theory for all these problems, validating our code. All properties of this hybrid code make it ideal to study multi-scale phenomena between electron and ion scales such as collisionless shocks, magnetic reconnection and kinetic plasma turbulence in the dissipation range above the electron scales.

Overview of MST Results and Plans

NASA Astrophysics Data System (ADS)

Sarff, J. S.

2008-11-01

Improved confinement with high beta has been established in MST over its full range of plasma current capability using transient inductive current profile control. Both thermal electron and ion confinement are increased, and energetic electrons are observed to 100 keV. The global energy confinement time is 12 ms at high current and high temperature (Te=2 keV, Ti =1 keV), with βtot=10% (only Ohmic heating). Maximum βtot=26% is attained at lower current and temperature with D2 pellet injection, without evidence of hard-beta-limit phenomena. Momentum transport associated with MHD tearing shows the fascinating behavior that the Maxwell and Reynolds turbulent stresses are both large but oppositely directed in sawtooth magnetic relaxation events. Momentum is transported rapidly in these events, presumably through the imbalance in the stresses. Electron temperature fluctuations associated with MHD tearing are measured using a multi-point, multi-pulse Thomson scattering diagnostic. A 5-250 kHz pulse-burst laser is under construction to extend the Thomson capability to high frequency. Lower hybrid and electron Bernstein wave injection are under development to provide more sustained current profile control and heating. X-ray emission from the plasma is observed for both waves at 175 kW injected power. Substantial new experimental capability will be provided by a recently installed programmable power supply for the toroidal field, a new 1 MW, 20 ms neutral beam injection system, and upgraded OFCD system. Supported by U.S. DoE and NSF.

Ring/Shell Ion Distributions at Geosynchronous Orbit

NASA Astrophysics Data System (ADS)

Thomsen, M. F.; Denton, M. H.; Gary, S. P.; Liu, Kaijun; Min, Kyungguk

2017-12-01

One year's worth of plasma observations from geosynchronous orbit is examined for ion distributions that may simultaneously be subject to the ion Bernstein (IB) instability (generating fast magnetosonic waves) and the Alfvén cyclotron (AC) instability (generating electromagnetic ion cyclotron waves). Confirming past analyses, distributions with robust ∂fp(v⊥)/∂v⊥ > 0 near v|| = 0, which we denote as "ring/shell" distributions, are commonly found primarily on the dayside of the magnetosphere. A new approach to high-fidelity representation of the observed ring/shell distribution functions in a form readily suited to both analytical moment calculation and linear dispersion analysis is presented, which allows statistical analysis of the ring/shell properties. The ring/shell temperature anisotropy is found to have a clear upper limit that depends on the parallel beta of the ring/shell (β||r) in a manner that is diagnostic of the operation of the AC instability. This upper limit is only reached in the postnoon events, which are primarily produced by the energy- and pitch angle-dependent magnetic drifts of substorm-injected ions. Further, it is primarily the leading edge of such injections, where the distribution is strongly ring-like, that the AC instability appears to be operating. By contrast, the ratio of the ring energy to the Alfvén energy remains well within the range of 0.25-4.0 suitable for IB instability throughout essentially all of the events, except those that occur in denser cold plasma of the outer plasmasphere.

Size and location of defects at the coupling interface affect lithotripter performance.

PubMed

Li, Guangyan; Williams, James C; Pishchalnikov, Yuri A; Liu, Ziyue; McAteer, James A

2012-12-01

Study Type--Therapy (case series) Level of Evidence 4. What's known on the subject? and What does the study add? In shock wave lithotripsy air pockets tend to get caught between the therapy head of the lithotripter and the skin of the patient. Defects at the coupling interface hinder the transmission of shock wave energy into the body, reducing the effectiveness of treatment. This in vitro study shows that ineffective coupling not only blocks the transmission of acoustic pulses but also alters the properties of shock waves involved in the mechanisms of stone breakage, with the effect dependent on the size and location of defects at the coupling interface. • To determine how the size and location of coupling defects caught between the therapy head of a lithotripter and the skin of a surrogate patient (i.e. the acoustic window of a test chamber) affect the features of shock waves responsible for stone breakage. • Model defects were placed in the coupling gel between the therapy head of a Dornier Compact-S electromagnetic lithotripter (Dornier MedTech, Kennesaw, GA, USA) and the Mylar (biaxially oriented polyethylene terephthalate) (DuPont Teijin Films, Chester, VA, USA) window of a water-filled coupling test system. • A fibre-optic probe hydrophone was used to measure acoustic pressures and map the lateral dimensions of the focal zone of the lithotripter. • The effect of coupling conditions on stone breakage was assessed using gypsum model stones. • Stone breakage decreased in proportion to the area of the coupling defect; a centrally located defect blocking only 18% of the transmission area reduced stone breakage by an average of almost 30%. • The effect on stone breakage was greater for defects located on-axis and decreased as the defect was moved laterally; an 18% defect located near the periphery of the coupling window (2.0 cm off-axis) reduced stone breakage by only ~15% compared to when coupling was completely unobstructed. • Defects centred within the coupling window acted to narrow the focal width of the lithotripter; an 8.2% defect reduced the focal width ~30% compared to no obstruction (4.4 mm vs 6.5 mm). • Coupling defects located slightly off centre disrupted the symmetry of the acoustic field; an 18% defect positioned 1.0 cm off-axis shifted the focus of maximum positive pressure ~1.0 mm laterally. • Defects on and off-axis imposed a significant reduction in the energy density of shock waves across the focal zone. • In addition to blocking the transmission of shock-wave energy, coupling defects also disrupt the properties of shock waves that play a role in stone breakage, including the focal width of the lithotripter and the symmetry of the acoustic field • The effect is dependent on the size and location of defects, with defects near the centre of the coupling window having the greatest effect. • These data emphasize the importance of eliminating air pockets from the coupling interface, particularly defects located near the centre of the coupling window. © 2012 BJU INTERNATIONAL.

Conceptual study of an ICRH traveling-wave antenna system for low-coupling conditions as expected in DEMO

NASA Astrophysics Data System (ADS)

Ragona, R.; Messiaen, A.

2016-07-01

For the central heating of a fusion reactor ion cyclotron radio frequency heating (ICRH) is the first choice method as it is able to couple RF power to the ions without density limit. The drawback of this heating method is the problem of excitation of the magneto-sonic wave through the plasma boundary layer from the antenna located along the wall, without exceeding its voltage standoff. The amount of coupling depends on the antenna excitation and the surface admittance at the antenna output due to the plasma profile. The paper deals with the optimization of the antenna excitation by the use of sections of traveling-wave antennas (TWAs) distributed all along the reactor wall between the blanket modules. They are mounted and fed in resonant ring system(s). First, the physics of the coupling of a strap array is studied by simple models and the coupling code ANTITER II. Then, after the study of the basic properties of a TWA section, its feeding problem is solved by hybrids driving them in resonant ring circuit(s). The complete modeling is obtained from the matrices of the TWA sections connected to one of the feeding hybrid(s). The solution is iterated with the coupling code to determine the loading for a reference low-coupling ITER plasma profile. The resulting wave pattern up to the plasma bulk is derived. The proposed system is totally load resilient and allows us to obtain a very selective exciting wave spectrum. A discussion of some practical implementation problems is added.

Localized waves in three-component coupled nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Xu, Tao; Chen, Yong

2016-09-01

We study the generalized Darboux transformation to the three-component coupled nonlinear Schrödinger equation. First- and second-order localized waves are obtained by this technique. In first-order localized wave, we get the interactional solutions between first-order rogue wave and one-dark, one-bright soliton respectively. Meanwhile, the interactional solutions between one-breather and first-order rogue wave are also given. In second-order localized wave, one-dark-one-bright soliton together with second-order rogue wave is presented in the first component, and two-bright soliton together with second-order rogue wave are gained respectively in the other two components. Besides, we observe second-order rogue wave together with one-breather in three components. Moreover, by increasing the absolute values of two free parameters, the nonlinear waves merge with each other distinctly. These results further reveal the interesting dynamic structures of localized waves in the three-component coupled system. Project supported by the Global Change Research Program of China (Grant No. 2015CB953904), the National Natural Science Foundation of China (Grant Nos. 11275072 and 11435005), the Doctoral Program of Higher Education of China (Grant No. 20120076110024), the Network Information Physics Calculation of Basic Research Innovation Research Group of China (Grant No. 61321064), and Shanghai Collaborative Innovation Center of Trustworthy Software for Internet of Things, China (Grant No. ZF1213).

Modulational instability and higher-order rogue waves with parameters modulation in a coupled integrable AB system via the generalized Darboux transformation.

PubMed

Wen, Xiao-Yong; Yan, Zhenya

2015-12-01

We study higher-order rogue wave (RW) solutions of the coupled integrable dispersive AB system (also called Pedlosky system), which describes the evolution of wave-packets in a marginally stable or unstable baroclinic shear flow in geophysical fluids. We propose its continuous-wave (CW) solutions and existent conditions for their modulation instability to form the rogue waves. A new generalized N-fold Darboux transformation (DT) is proposed in terms of the Taylor series expansion for the spectral parameter in the Darboux matrix and its limit procedure and applied to the CW solutions to generate multi-rogue wave solutions of the coupled AB system, which satisfy the general compatibility condition. The dynamical behaviors of these higher-order rogue wave solutions demonstrate both strong and weak interactions by modulating parameters, in which some weak interactions can generate the abundant triangle, pentagon structures, etc. Particularly, the trajectories of motion of peaks and depressions of profiles of the first-order RWs are explicitly analyzed. The generalized DT method used in this paper can be extended to other nonlinear integrable systems. These results may be useful for understanding the corresponding rogue-wave phenomena in fluid mechanics and related fields.

Performance of an ion-cyclotron-wave plasma apparatus operated in the radiofrequency sustained mode

NASA Technical Reports Server (NTRS)

Swett, C. C.; Woollett, R. R.

1973-01-01

An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode, that is, a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave propagation and wave damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of five times 10 to the 12th power cu cm and RF power of 90 kW. Coupling efficiency is 70 percent.

Operating features of an ion-cyclotron-wave plasma apparatus running in the RF-sustained mode

NASA Technical Reports Server (NTRS)

Swett, C. C.

1972-01-01

An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode. This is a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave-propagation and wave-damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of 5 times 10 to the 12th power per cubic centimeter and RF power of 90 kW. Coupling efficiency is 70 percent.

Symmetric rotating-wave approximation for the generalized single-mode spin-boson system

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

Albert, Victor V.; Scholes, Gregory D.; Brumer, Paul

2011-10-15

The single-mode spin-boson model exhibits behavior not included in the rotating-wave approximation (RWA) in the ultra and deep-strong coupling regimes, where counter-rotating contributions become important. We introduce a symmetric rotating-wave approximation that treats rotating and counter-rotating terms equally, preserves the invariances of the Hamiltonian with respect to its parameters, and reproduces several qualitative features of the spin-boson spectrum not present in the original rotating-wave approximation both off-resonance and at deep-strong coupling. The symmetric rotating-wave approximation allows for the treatment of certain ultra- and deep-strong coupling regimes with similar accuracy and mathematical simplicity as does the RWA in the weak-coupling regime.more » Additionally, we symmetrize the generalized form of the rotating-wave approximation to obtain the same qualitative correspondence with the addition of improved quantitative agreement with the exact numerical results. The method is readily extended to higher accuracy if needed. Finally, we introduce the two-photon parity operator for the two-photon Rabi Hamiltonian and obtain its generalized symmetric rotating-wave approximation. The existence of this operator reveals a parity symmetry similar to that in the Rabi Hamiltonian as well as another symmetry that is unique to the two-photon case, providing insight into the mathematical structure of the two-photon spectrum, significantly simplifying the numerics, and revealing some interesting dynamical properties.« less

Simulation of Wave-Current Interaction Using a Three-Dimensional Hydrodynamic Model Coupled With a Phase Averaged Wave Model

NASA Astrophysics Data System (ADS)

Marsooli, R.; Orton, P. M.; Georgas, N.; Blumberg, A. F.

2016-02-01

The Stevens Institute of Technology Estuarine and Coastal Ocean Model (sECOM) has been coupled with a more advanced surface wave model to simulate wave‒current interaction, and results have been validated in estuarine and nearshore waters. sECOM is a three‒dimensional, hydrostatic, free surface, primitive equation model. It solves the Navier‒Stokes equations and the conservation equations for temperature and salinity using a finite‒difference method on an Arakawa C‒grid with a terrain‒following (sigma) vertical coordinate and orthogonal curvilinear horizontal coordinate system. The model is coupled with the surface wave model developed by Mellor et al. (2008), which solves the spectral equation and takes into account depth and current refraction, and deep and shallow water. The wave model parameterizes the energy distribution in frequency space and the wave‒wave interaction process by using a specified spectrum shape. The coupled wave‒hydrodynamic model considers the wave‒current interaction through wave‒induced bottom stress, depth‒dependent radiation stress, and wave effects on wind‒induced surface stress. The model is validated using the data collected at a natural sandy beach at Duck, North Carolina, during the DUCK94 experiment. This test case reveals the capability of the model to simulate the wave‒current interaction in nearshore coastal systems. The model is further validated using the data collected in Jamaica Bay, a semi‒enclosed body of water located in New York City region. This test reveals the applicability of the model to estuarine systems. These validations of the model and comparisons to its prior wave model, the Great Lakes Environmental Research Laboratory (GLERL) wave model (Donelan 1977), are presented and discussed. ReferencesG.L. Mellor, M.A. Donelan, and L‒Y. Oey, 2008, A Surface Wave Model for Coupling with Numerical Ocean Circulation Models. J. Atmos. Oceanic Technol., 25, 1785‒1807.Donelan, M. A 1977. A simple numerical model for wave and wind stress application. Report, National Water Research Institute, Burlington, Ontario, Canada, 28 pp.

Wideband helicity dependent spoof surface plasmon polaritons coupling metasurface based on dispersion design.

PubMed

Dong, Guoxiang; Shi, Hongyu; He, Yuchen; Zhang, Anxue; Wei, Xiaoyong; Zhuang, Yongyong; Du, Bai; Xia, Song; Xu, Zhuo

2016-12-06

The surface plasmon polaritons (SPPs) have many potential application due to their local field enhancement and sub-wavelength characteristics. Recently, the gradient metasurface is introduced to couple the spoof SPPs in microwave frequency band. One of the most important issue which should be solved is the narrowband of spoof SPPs coupling on the gradient metasurface. Here, the metasurface is proposed to achieve the wideband helicity dependent directional spoof SPPs coupling for circular polarized light. Our research show that the coupling frequency of spoof SPPs on the gradient metasurface is determined by the dispersion of the metasurface, so the coupling frequency can be controlled by dispersion design. The careful design of each cell geometric parameters has provided many appropriate dispersion relations possessed by just one metasurface. The wave vector matching between the propagating wave and the spoof SPPs has been achieved at several frequencies for certain wave vector provided by the metasurface, which leads to wideband spoof SPPs coupling. This work has shown that wideband helicity dependent directional spoof SPPs coupling has been achieved with a high efficiency. Hence, the proposed wideband spoof SPPs coupling presents the improvement in practice applications.

Wideband helicity dependent spoof surface plasmon polaritons coupling metasurface based on dispersion design

PubMed Central

Dong, Guoxiang; Shi, Hongyu; He, Yuchen; Zhang, Anxue; Wei, Xiaoyong; Zhuang, Yongyong; Du, Bai; Xia, Song; Xu, Zhuo

2016-01-01

The surface plasmon polaritons (SPPs) have many potential application due to their local field enhancement and sub-wavelength characteristics. Recently, the gradient metasurface is introduced to couple the spoof SPPs in microwave frequency band. One of the most important issue which should be solved is the narrowband of spoof SPPs coupling on the gradient metasurface. Here, the metasurface is proposed to achieve the wideband helicity dependent directional spoof SPPs coupling for circular polarized light. Our research show that the coupling frequency of spoof SPPs on the gradient metasurface is determined by the dispersion of the metasurface, so the coupling frequency can be controlled by dispersion design. The careful design of each cell geometric parameters has provided many appropriate dispersion relations possessed by just one metasurface. The wave vector matching between the propagating wave and the spoof SPPs has been achieved at several frequencies for certain wave vector provided by the metasurface, which leads to wideband spoof SPPs coupling. This work has shown that wideband helicity dependent directional spoof SPPs coupling has been achieved with a high efficiency. Hence, the proposed wideband spoof SPPs coupling presents the improvement in practice applications. PMID:27922132

75 FR 9415 - Notice of Hearing Schedule; Passenger Vessel Financial Responsibility

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-02

... Inc...... Charles A. Robertson, 15 Chairman & Chief Executive Officer. Carnival Corporation & PLC..... David Bernstein, Senior 15 Vice President & Chief Financial Officer. Crystal Cruises, Inc Ann G. Miller... FEDERAL MARITIME COMMISSION Notice of Hearing Schedule; Passenger Vessel Financial Responsibility...

Voices.

ERIC Educational Resources Information Center

Insights on Law & Society, 2000

2000-01-01

Provides viewpoints on whether the constitutional amendment process needs to be changed or not: (1) "When in Doubt, Do Nothing" (R. B. Bernstein); (2) "Citizens for the Constitution" (Erwin Chemerinsky); (3) "Constitutional Proposals from the States" (John Kincaid); and (4) "I Have a Better Way" (Gregory D.…

Development of a coupled wave-flow-vegetation interaction model

USGS Publications Warehouse

Beudin, Alexis; Kalra, Tarandeep S.; Ganju, Neil K.; Warner, John C.

2017-01-01

Emergent and submerged vegetation can significantly affect coastal hydrodynamics. However, most deterministic numerical models do not take into account their influence on currents, waves, and turbulence. In this paper, we describe the implementation of a wave-flow-vegetation module into a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that includes a flow model (ROMS) and a wave model (SWAN), and illustrate various interacting processes using an idealized shallow basin application. The flow model has been modified to include plant posture-dependent three-dimensional drag, in-canopy wave-induced streaming, and production of turbulent kinetic energy and enstrophy to parameterize vertical mixing. The coupling framework has been updated to exchange vegetation-related variables between the flow model and the wave model to account for wave energy dissipation due to vegetation. This study i) demonstrates the validity of the plant posture-dependent drag parameterization against field measurements, ii) shows that the model is capable of reproducing the mean and turbulent flow field in the presence of vegetation as compared to various laboratory experiments, iii) provides insight into the flow-vegetation interaction through an analysis of the terms in the momentum balance, iv) describes the influence of a submerged vegetation patch on tidal currents and waves separately and combined, and v) proposes future directions for research and development.

Polarization characteristics of Whispering-Gallery-Mode fiber lasers based on evanescent-wave-coupled gain.

PubMed

Zhang, Yuan-Xian; Pu, Xiao-Yun; Feng, Li; Han, De-Yu; Ren, Yi-Tao

2013-05-20

The polarization characteristics of Whispering-Gallery-Mode (WGM) fiber lasers based on evanescent-wave-coupled gain are investigated. For the laser gain is excited by side-pumping scheme, it is found that the polarization property of lasing emission is simply dependent on the polarized states of the pump beams. The polarization property of lasing emission depends on the propagating situation of the pump beams in an optical fiber if the laser gain is excited by evanescent-wave pumping scheme, that is, if the pump beams within the fiber are meridional beams, the lasing emission is a transverse electric (TE) wave that forms a special radial polarization emission. However, if the pump beams within the fiber are skew beams, both transverse magnetic (TM) and TE waves exist simultaneously in lasing emission that forms a special axially and radially mixed polarization emission. Pumped by skew beams, the wave-number differences between TE and TM waves are also investigated quantitatively, the results demonstrate that the wave-number difference decreases with the increase of the fiber diameter and the refractive index (RI) of the cladding solution. The observed polarization characteristics have been well explained based on lasing radiation mechanism of WGM fiber laser of gain coupled by evanescent wave.

The Shock and Vibration Digest, Volume 14, Number 2, February 1982

DTIC Science & Technology

1982-02-01

figurations. 75 4J DUCTS 82-424 (Also see No. 346) Coupling Lou Factors for Statistical Energy Analysis of Sound Transnission at Rectangular...waves, Sound waves, Wave props- tures by means of statistical energy analysis (SEA) coupling gation loss factors for the structure-borne sound...multilayered panels are discussed. Statistical energy analysis (SEA) has proved to be a promising Experimental results of stiffened panels, damping tape

Spatio-temporal dynamics induced by competing instabilities in two asymmetrically coupled nonlinear evolution equations.

PubMed

Schüler, D; Alonso, S; Torcini, A; Bär, M

2014-12-01

Pattern formation often occurs in spatially extended physical, biological, and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue, we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexisting static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular, revealing for the Swift-Hohenberg equations, a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of a weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.

Electron attachment in F2 - Conclusive demonstration of nonresonant, s-wave coupling in the limit of zero electron energy

NASA Technical Reports Server (NTRS)

Chutjian, A.; Alajajian, S. H.

1987-01-01

Dissociative electron attachment to F2 has been observed in the energy range 0-140 meV, at a resolution of 6 meV (full width at half maximum). Results show conclusively a sharp, resolution-limited threshold behavior consistent with an s-wave cross section varying as sq rt of epsilon. Two accurate theoretical calculations predict only p-wave behavior varying as the sq rt of epsilon. Several nonadiabatic coupling effects leading to s-wave behavior are outlined.

Non-linear resonant coupling of tsunami edge waves using stochastic earthquake source models

USGS Publications Warehouse

Geist, Eric L.

2016-01-01

Non-linear resonant coupling of edge waves can occur with tsunamis generated by large-magnitude subduction zone earthquakes. Earthquake rupture zones that straddle beneath the coastline of continental margins are particularly efficient at generating tsunami edge waves. Using a stochastic model for earthquake slip, it is shown that a wide range of edge-wave modes and wavenumbers can be excited, depending on the variability of slip. If two modes are present that satisfy resonance conditions, then a third mode can gradually increase in amplitude over time, even if the earthquake did not originally excite that edge-wave mode. These three edge waves form a resonant triad that can cause unexpected variations in tsunami amplitude long after the first arrival. An M ∼ 9, 1100 km-long continental subduction zone earthquake is considered as a test case. For the least-variable slip examined involving a Gaussian random variable, the dominant resonant triad includes a high-amplitude fundamental mode wave with wavenumber associated with the along-strike dimension of rupture. The two other waves that make up this triad include subharmonic waves, one of fundamental mode and the other of mode 2 or 3. For the most variable slip examined involving a Cauchy-distributed random variable, the dominant triads involve higher wavenumbers and modes because subevents, rather than the overall rupture dimension, control the excitation of edge waves. Calculation of the resonant period for energy transfer determines which cases resonant coupling may be instrumentally observed. For low-mode triads, the maximum transfer of energy occurs approximately 20–30 wave periods after the first arrival and thus may be observed prior to the tsunami coda being completely attenuated. Therefore, under certain circumstances the necessary ingredients for resonant coupling of tsunami edge waves exist, indicating that resonant triads may be observable and implicated in late, large-amplitude tsunami arrivals.

On the interaction between the shock wave attached to a wedge and freestream disturbances

NASA Technical Reports Server (NTRS)

Duck, Peter W.; Lasseigne, D. Glenn; Hussaini, M. Y.

1993-01-01

A study of the interaction of small amplitude, unsteady, freestream disturbances with a shock wave induced by a wedge in supersonic flow is presented. These disturbances may be acoustic waves, vorticity waves, or entropy waves (or indeed a combination of all three). Their interactions then generate behind the shock disturbances of all three classes, an aspect that is investigated in some detail, our motivation being to investigate possible mechanisms for boundary-layer receptivity, caused through the amplification and modification of freestream turbulence through the shock-body coupling. Also, the possibility of enhanced mixing owing to additional vorticity produced by the shock-body coupling is investigated.

Piezoelectric shear wave resonator and method of making same

DOEpatents

Wang, J.S.; Lakin, K.M.; Landin, A.R.

1985-05-20

An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppM//sup 0/C.

Piezoelectric shear wave resonator and method of making same

DOEpatents

Wang, J.S.; Lakin, K.M.; Landin, A.R.

1983-10-25

An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppM//sup 0/C.

Wave-current interaction: Effect on the wave field in a semi-enclosed basin

NASA Astrophysics Data System (ADS)

Benetazzo, A.; Carniel, S.; Sclavo, M.; Bergamasco, A.

2013-10-01

The effect on waves of the Wave-Current Interaction (WCI) process in the semi-enclosed Gulf of Venice (northern region of the Adriatic Sea) was investigated using the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system. COAWST relies on the ocean model ROMS (Regional Ocean Modeling System), the wave model SWAN (Simulating WAves Nearshore), and the CSTMS (Community Sediment Transport Modeling System) routines. The two-way data transfer between circulation and wave models was synchronous via MCT (Model Coupling Toolkit), with ROMS providing: current field, free surface elevation, and bathymetry to SWAN. For coupling, the 3-D current profiles were averaged using a formulation which integrated the near-surface velocity over a depth controlled by the spectral mean wavenumber. COAWST system was implemented on a parent grid (with horizontal resolution of 2.0 km) covering the whole Adriatic Sea with one-way nesting to a child grid resolving the northern area (Gulf of Venice) at a resolution of 0.5 km. The meteorological forcings provided by the operational meteorological model COSMO-I7 (a mesoscale model developed in the framework of the COSMO Consortium) were used to drive the modeling system in the period bracketing September 2010-August 2011. The adopted winds and the simulated waves were compared with observations at the CNR-ISMAR Acqua Alta oceanographic tower, located off the Venice littoral. Wave heights and sea surface winds were also compared with satellite-derived data. The analysis of WCI was performed on the child grid over the winter season (January-March 2011) with particular focus on the waves generated by prevailing and dominant winds blowing on the Adriatic Sea: Bora and Sirocco. Due to the variable wind direction with respect to the ocean current direction different effects on WCI were depicted, showing that within the northern Adriatic Sea the ocean-wave interactions are strongly dependent on the wind forcing direction. Further investigations reveal that, when applied to intense storms, the effect of coupling on waves results in variations of significant wave height up to 0.6 m, with some areas experiencing significant increase/decrease of wave spectral energy for opposite/following currents respectively.

Coupling of Waves, Turbulence and Thermodynamics Across the Marginal Ice Zone

DTIC Science & Technology

2015-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Coupling of Waves, Turbulence and Thermodynamics across...developing Thermodynamically Forced Marginal Ice Zone. Submitted to JGR. Heiles,A. S., NPS thesis, Sep. 2014 Schmidt, B. K., NPS thesis March 2012 Shaw

Old Brains Come Uncoupled in Sleep: Slow Wave-Spindle Synchrony, Brain Atrophy, and Forgetting.

PubMed

Helfrich, Randolph F; Mander, Bryce A; Jagust, William J; Knight, Robert T; Walker, Matthew P

2018-01-03

The coupled interaction between slow-wave oscillations and sleep spindles during non-rapid-eye-movement (NREM) sleep has been proposed to support memory consolidation. However, little evidence in humans supports this theory. Moreover, whether such dynamic coupling is impaired as a consequence of brain aging in later life, contributing to cognitive and memory decline, is unknown. Combining electroencephalography (EEG), structural MRI, and sleep-dependent memory assessment, we addressed these questions in cognitively normal young and older adults. Directional cross-frequency coupling analyses demonstrated that the slow wave governs a precise temporal coordination of sleep spindles, the quality of which predicts overnight memory retention. Moreover, selective atrophy within the medial frontal cortex in older adults predicted a temporal dispersion of this slow wave-spindle coupling, impairing overnight memory consolidation and leading to forgetting. Prefrontal-dependent deficits in the spatiotemporal coordination of NREM sleep oscillations therefore represent one pathway explaining age-related memory decline. Copyright © 2017 Elsevier Inc. All rights reserved.

Supermode-density-wave-polariton condensation with a Bose–Einstein condensate in a multimode cavity

PubMed Central

Kollár, Alicia J.; Papageorge, Alexander T.; Vaidya, Varun D.; Guo, Yudan; Keeling, Jonathan; Lev, Benjamin L.

2017-01-01

Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. By placing cold atoms in optical cavities and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a non-equilibrium phase transition, the condensation of supermode-density-wave polaritons. These polaritons are formed from a superposition of cavity photon eigenmodes (a supermode), coupled to atomic density waves of a quantum gas. As the cavity supports multiple photon spatial modes and because the light–matter coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the light–matter coupling on condensation. By demonstrating the ability to observe and understand density-wave-polariton condensation in the few-mode-degenerate cavity regime, our results show the potential to study similar questions in fully multimode cavities. PMID:28211455

PLATE WAVE RESONANCE WITH AIR-COUPLED ULTRASONICS

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

Bar, H. N.; Dayal, V.; Barnard, D.

2010-02-22

Air-coupled ultrasonic transducers can excite plate waves in metals and composites. The coincidence effect, i.e., the wave vector of plate wave coincides with projection of exciting airborne sound vector, leads to a resonance which strongly amplifies the sound transmission through the plate. The resonance depends on the angle of incidence and the frequency. In the present study, the incidence angle for maximum transmission (theta{sub max}) is measured in plates of steel, aluminum, carbon fiber reinforced composites and honeycomb sandwich panels. The variations of (theta{sub max}) with plate thickness are compared with theoretical values in steel, aluminum and quasi-isotropic carbon fibermore » composites. The enhanced transmission of air-coupled ultrasound at oblique incidence can substantially improve the probability of flaw detection in plates and especially in honeycomb structures. Experimental air-coupled ultrasonic scan of subtle flaws in CFRP laminates showed definite improvement of signal-to-noise ratio with oblique incidence at theta{sub max}.« less

Nonlinear to Linear Elastic Code Coupling in 2-D Axisymmetric Media.

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

Preston, Leiph

Explosions within the earth nonlinearly deform the local media, but at typical seismological observation distances, the seismic waves can be considered linear. Although nonlinear algorithms can simulate explosions in the very near field well, these codes are computationally expensive and inaccurate at propagating these signals to great distances. A linearized wave propagation code, coupled to a nonlinear code, provides an efficient mechanism to both accurately simulate the explosion itself and to propagate these signals to distant receivers. To this end we have coupled Sandia's nonlinear simulation algorithm CTH to a linearized elastic wave propagation code for 2-D axisymmetric media (axiElasti)more » by passing information from the nonlinear to the linear code via time-varying boundary conditions. In this report, we first develop the 2-D axisymmetric elastic wave equations in cylindrical coordinates. Next we show how we design the time-varying boundary conditions passing information from CTH to axiElasti, and finally we demonstrate the coupling code via a simple study of the elastic radius.« less

Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere-ocean-wave model

NASA Astrophysics Data System (ADS)

Prakash, Kumar Ravi; Nigam, Tanuja; Pant, Vimlesh

2018-04-01

A coupled atmosphere-ocean-wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB) during 10-14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15 m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere-ocean-wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere-ocean-wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave-current interaction and nonlinear wave-wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations.

Experimental characterization and modelling of non-linear coupling of the lower hybrid current drive power on Tore Supra

NASA Astrophysics Data System (ADS)

Preynas, M.; Goniche, M.; Hillairet, J.; Litaudon, X.; Ekedahl, A.; Colas, L.

2013-01-01

To achieve steady-state operation on future fusion devices, in particular on ITER, the coupling of the lower hybrid wave must be optimized on a wide range of edge conditions. However, under some specific conditions, deleterious effects on the lower hybrid current drive (LHCD) coupling are sometimes observed on Tore Supra. In this way, dedicated LHCD experiments have been performed using the LHCD system of Tore Supra, composed of two different conceptual designs of launcher: the fully active multi-junction (FAM) and the new passive active multi-junction (PAM) antennas. A non-linear interaction between the electron density and the electric field has been characterized in a thin plasma layer in front of the two LHCD antennas. The resulting dependence of the power reflection coefficient (RC) with the LHCD power is not predicted by the standard linear theory of the LH wave coupling. A theoretical model is suggested to describe the non-linear wave-plasma interaction induced by the ponderomotive effect and implemented in a new full wave LHCD code, PICCOLO-2D (ponderomotive effect in a coupling code of lower hybrid wave-2D). The code self-consistently treats the wave propagation in the antenna vicinity and its interaction with the local edge plasma density. The simulation reproduces very well the occurrence of a non-linear behaviour in the coupling observed in the LHCD experiments. The important differences and trends between the FAM and the PAM antennas, especially a larger increase in RC for the FAM, are also reproduced by the PICCOLO-2D simulation. The working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling is therefore validated through this comprehensive modelling for the first time on the FAM and PAM antennas on Tore Supra.

Directional nonlinear guided wave mixing: Case study of counter-propagating shear horizontal waves

NASA Astrophysics Data System (ADS)

Hasanian, Mostafa; Lissenden, Cliff J.

2018-04-01

While much nonlinear ultrasonics research has been conducted on higher harmonic generation, wave mixing provides the potential for sensitive measurements of incipient damage unencumbered by instrumentation nonlinearity. Studies of nonlinear ultrasonic wave mixing, both collinear and noncollinear, for bulk waves have shown the robust capability of wave mixing for early damage detection. One merit of bulk wave mixing lies in their non-dispersive nature, but guided waves enable inspection of otherwise inaccessible material and a variety of mixing options. Co-directional guided wave mixing was studied previously, but arbitrary direction guided wave mixing has not been addressed until recently. Wave vector analysis is applied to study variable mixing angles to find wave mode triplets (two primary waves and a secondary wave) resulting in the phase matching condition. As a case study, counter-propagating Shear Horizontal (SH) guided wave mixing is analyzed. SH wave interactions generate a secondary Lamb wave mode that is readily receivable. Reception of the secondary Lamb wave mode is compared for an angle beam transducer, an air coupled transducer, and a laser Doppler vibrometer (LDV). Results from the angle beam and air coupled transducers are quite consistent, while the LDV measurement is plagued by variability issues.

Body frame close coupling wave packet approach to gas phase atom-rigid rotor inelastic collisions

NASA Technical Reports Server (NTRS)

Sun, Y.; Judson, R. S.; Kouri, D. J.

1989-01-01

The close coupling wave packet (CCWP) method is formulated in a body-fixed representation for atom-rigid rotor inelastic scattering. For J greater than j-max (where J is the total angular momentum and j is the rotational quantum number), the computational cost of propagating the coupled channel wave packets in the body frame is shown to scale approximately as N exp 3/2, where N is the total number of channels. For large numbers of channels, this will be much more efficient than the space frame CCWP method previously developed which scales approximately as N-squared under the same conditions.

Finite temperature m=0 Bernstein modes in a non-neutral plasma, theory and simulation

NASA Astrophysics Data System (ADS)

Hart, Grant W.; Spencer, Ross L.; Takeshi Nakata, M.

2008-11-01

Axisymmetric upper-hybrid oscillations have been known to exist in non-neutral plasmas and FTICR/MS devices for a number of years. However, because they are electrostatic in nature and axisymmetric, they are self-shielding and therefore difficult to detect in long systems. Previous theoretical studies have assumed a zero temperature plasma. In the zero temperature limit these oscillations are not properly represented as a mode, because the frequency at a given radius depends only on the local density and is not coupled to neighboring radii, much like the zero temperature plasma oscillation. Finite temperature provides the coupling which links the oscillation into a coherent mode. We have analyzed the finite-temperature theory of these modes and find that they form an infinite set of modes with frequencies above 2̂c- 2̂p. We have simulated these modes in our r-θ particle-in-cell code that includes a full Lorentz-force mover and find that in a mostly flat-top plasma there are two eigenmodes that have essentially the same shape in the bulk of the plasma, but different frequencies. It appears likely that they have different boundary conditions in the boundary region. J.J. Bollinger, et al., Phys. Rev. A 48, 525 (1993). S.E. Barlow, et al., Int. J. Mass Spectrom. Ion Processes 74, 97 (1986). M. Takeshi Nakata, et al., Bull. Am. Phys. Soc. 51, 245 (2006).

A Hammer-Impact, Aluminum, Shear-Wave Seismic Source

USGS Publications Warehouse

Haines, Seth

2007-01-01

Near-surface seismic surveys often employ hammer impacts to create seismic energy. Shear-wave surveys using horizontally polarized waves require horizontal hammer impacts against a rigid object (the source) that is coupled to the ground surface. I have designed, built, and tested a source made out of aluminum and equipped with spikes to improve coupling. The source is effective in a variety of settings, and it is relatively simple and inexpensive to build.

Rg-Lg coupling as a Lg-wave excitation mechanism

NASA Astrophysics Data System (ADS)

Ge, Z.; Xie, X.

2003-12-01

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

Sound radiation from a water-filled pipe, radiation into light fluid.

PubMed

Liu, Bilong; Pan, Jie; Li, Xiaodong; Tian, Jing

2002-12-01

This paper is concerned with the sound radiation from a water-filled exhaust pipe. The pipe opening and a plate attached to it form a vibrating surface for this radiation. Fluid-structural coupling between the pipe and enclosed fluid is included in the system modeling, but light fluid assumption is used for sound radiation into the space above the vibrating surface. In this paper, a numerical study on the n = 0 mode in the pipe shows that the wave types associated with this mode have different characteristics in two regions of the nondimensional frequency omega. In the first region of 0

Surface wave effects in the NEMO ocean model: Forced and coupled experiments

NASA Astrophysics Data System (ADS)

Breivik, Øyvind; Mogensen, Kristian; Bidlot, Jean-Raymond; Balmaseda, Magdalena Alonso; Janssen, Peter A. E. M.

2015-04-01

The NEMO general circulation ocean model is extended to incorporate three physical processes related to ocean surface waves, namely the surface stress (modified by growth and dissipation of the oceanic wavefield), the turbulent kinetic energy flux from breaking waves, and the Stokes-Coriolis force. Experiments are done with NEMO in ocean-only (forced) mode and coupled to the ECMWF atmospheric and wave models. Ocean-only integrations are forced with fields from the ERA-Interim reanalysis. All three effects are noticeable in the extratropics, but the sea-state-dependent turbulent kinetic energy flux yields by far the largest difference. This is partly because the control run has too vigorous deep mixing due to an empirical mixing term in NEMO. We investigate the relation between this ad hoc mixing and Langmuir turbulence and find that it is much more effective than the Langmuir parameterization used in NEMO. The biases in sea surface temperature as well as subsurface temperature are reduced, and the total ocean heat content exhibits a trend closer to that observed in a recent ocean reanalysis (ORAS4) when wave effects are included. Seasonal integrations of the coupled atmosphere-wave-ocean model consisting of NEMO, the wave model ECWAM, and the atmospheric model of ECMWF similarly show that the sea surface temperature biases are greatly reduced when the mixing is controlled by the sea state and properly weighted by the thickness of the uppermost level of the ocean model. These wave-related physical processes were recently implemented in the operational coupled ensemble forecast system of ECMWF.

On the incorporation of the geometric phase in general single potential energy surface dynamics: A removable approximation to ab initio data.

PubMed

Malbon, Christopher L; Zhu, Xiaolei; Guo, Hua; Yarkony, David R

2016-12-21

For two electronic states coupled by conical intersections, the line integral of the derivative coupling can be used to construct a complex-valued multiplicative phase factor that makes the real-valued adiabatic electronic wave function single-valued, provided that the curl of the derivative coupling is zero. Unfortunately for ab initio determined wave functions, the curl is never rigorously zero. However, when the wave functions are determined from a coupled two diabatic state Hamiltonian H d (fit to ab initio data), the resulting derivative couplings are by construction curl free, except at points of conical intersection. In this work we focus on a recently introduced diabatization scheme that produces the H d by fitting ab initio determined energies, energy gradients, and derivative couplings to the corresponding H d determined quantities in a least squares sense, producing a removable approximation to the ab initio determined derivative coupling. This approach and related numerical issues associated with the nonremovable ab initio derivative couplings are illustrated using a full 33-dimensional representation of phenol photodissociation. The use of this approach to provide a general framework for treating the molecular Aharonov Bohm effect is demonstrated.

Drinking Patterns Among Older Couples: Longitudinal Associations With Negative Marital Quality.

PubMed

Birditt, Kira S; Cranford, James A; Manalel, Jasmine A; Antonucci, Toni C

2018-04-16

Research with younger couples indicates that alcohol use has powerful effects on marital quality, but less work has examined the effects of drinking among older couples. This study examined whether dyadic patterns of drinking status among older couples are associated with negative marital quality over time. Married participants (N = 4864) from the Health and Retirement Study reported on alcohol consumption (whether they drink alcohol and average amount consumed per week) and negative marital quality (e.g., criticism and demands) across two waves (Wave 1 2006/2008 and Wave 2 2010/2012). Concordant drinking couples reported decreased negative marital quality over time, and these links were significantly greater among wives. Wives who reported drinking alcohol reported decreased negative marital quality over time when husbands also reported drinking and increased negative marital quality over time when husbands reported not drinking. The present findings stress the importance of considering the drinking status rather than the amount of alcohol consumed of both members of the couple when attempting to understand drinking and marital quality among older couples. These findings are particularly salient given the increased drinking among baby boomers and the importance of marital quality for health among older couples.

Generation of Rayleigh waves into mortar and concrete samples.

PubMed

Piwakowski, B; Fnine, Abdelilah; Goueygou, M; Buyle-Bodin, F

2004-04-01

The paper deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound. In a preliminary study, the authors emphasized on the interest of using higher frequency Rayleigh waves (within the 0.2-1 MHz frequency band) for on-site inspection of concrete structures with subsurface damage. The present study represents a continuation of the previous work and aims at optimizing the generation and reception of Rayleigh waves into mortar and concrete be means of wedge transducers. This is performed experimentally by checking the influence of the wedge material and coupling agent on the surface wave parameters. The selection of the best combination wedge/coupling is performed by searching separately for the best wedge material and the best coupling material. Three wedge materials and five coupling agents were tested. For each setup the five parameters obtained from the surface wave measurement i.e. the frequency band, the maximal available central frequency, the group velocity error and its standard deviation and finally the error in velocity dispersion characteristic were investigated and classed as a function of the wedge material and the coupling agent. The selection criteria were chosen so as to minimize the absorption of both materials, the randomness of measurements and the systematic error of the group velocity and of dispersion characteristic. Among the three tested wedge materials, Teflon was found to be the best. The investigation on the coupling agent shows that the gel type materials are the best solutions. The "thick" materials displaying higher viscosity were found as the worst. The results show also that the use of a thin plastic film combined with the coupling agent even increases the bandwidth and decreases the uncertainty of measurements.

A New Coupled Ocean-Waves-Atmosphere Model Designed for Tropical Storm Studies: Example of Tropical Cyclone Bejisa (2013-2014) in the South-West Indian Ocean

NASA Astrophysics Data System (ADS)

Pianezze, J.; Barthe, C.; Bielli, S.; Tulet, P.; Jullien, S.; Cambon, G.; Bousquet, O.; Claeys, M.; Cordier, E.

2018-03-01

Ocean-Waves-Atmosphere (OWA) exchanges are not well represented in current Numerical Weather Prediction (NWP) systems, which can lead to large uncertainties in tropical cyclone track and intensity forecasts. In order to explore and better understand the impact of OWA interactions on tropical cyclone modeling, a fully coupled OWA system based on the atmospheric model Meso-NH, the oceanic model CROCO, and the wave model WW3 and called MSWC was designed and applied to the case of tropical cyclone Bejisa (2013-2014). The fully coupled OWA simulation shows good agreement with the literature and available observations. In particular, simulated significant wave height is within 30 cm of measurements made with buoys and altimeters. Short-term (< 2 days) sensitivity experiments used to highlight the effect of oceanic waves coupling show limited impact on the track, the intensity evolution, and the turbulent surface fluxes of the tropical cyclone. However, it is also shown that using a fully coupled OWA system is essential to obtain consistent sea salt emissions. Spatial and temporal coherence of the sea state with the 10 m wind speed are necessary to produce sea salt aerosol emissions in the right place (in the eyewall of the tropical cyclone) and with the right size distribution, which is critical for cloud microphysics.

The Coordinated Ocean Wave Climate Project

NASA Astrophysics Data System (ADS)

Hemer, Mark; Dobrynin, Mikhail; Erikson, Li; Lionello, Piero; Mori, Nobuhito; Semedo, Alvaro; Wang, Xiaolan

2016-04-01

Future 21st Century changes in wind-wave climate have broad implications for marine and coastal infrastructure and ecosystems. Atmosphere-ocean general circulation models (GCM) are now routinely used for assessing and providing future projections of climatological parameters such as temperature and precipitation, but generally these provide no information on ocean wind-waves. To fill this information gap a growing number of studies are using GCM outputs and independently producing global and regional scale wind-wave climate projections. Furthermore, additional studies are actively coupling wind-wave dependent atmosphere-ocean exchanges into GCMs, to improve physical representation and quantify the impact of waves in the coupled climate system, and can also deliver wave characteristics as another variable in the climate system. To consolidate these efforts, understand the sources of variance between projections generated by different methodologies and International groups, and ultimately provide a robust picture of the role of wind-waves in the climate system and their projected changes, we present outcomes of the JCOMM supported Coordinated Ocean Wave Climate Project (COWCLIP). The objective of COWCLIP is twofold: to make community based ensembles of wave climate projections openly accessible, to provide the necessary information to support diligent marine and coastal impacts of climate change studies; and to understand the effects and feedback influences of wind-waves in the coupled ocean-atmosphere climate system. We will present the current status of COWCLIP, providing an overview of the objectives, analysis and results of the initial phase - now complete - and the progress of ongoing phases of the project.

A Novel Approach to Resonant Absorption of the Fast Magnetohydrodynamic Eigenmodes of a Coronal Arcade

NASA Astrophysics Data System (ADS)

Hindman, Bradley W.; Jain, Rekha

2018-05-01

The arched field lines forming coronal arcades are often observed to undulate as magnetohydrodynamic waves propagate both across and along the magnetic field. These waves are most likely a combination of resonantly coupled fast magnetoacoustic waves and Alfvén waves. The coupling results in resonant absorption of the fast waves, converting fast wave energy into Alfvén waves. The fast eigenmodes of the arcade have proven difficult to compute or derive analytically, largely because of the mathematical complexity that the coupling introduces. When a traditional spectral decomposition is employed, the discrete spectrum associated with the fast eigenmodes is often subsumed into the continuous Alfvén spectrum. Thus fast eigenmodes become collective modes or quasi-modes. Here we present a spectral decomposition that treats the eigenmodes as having real frequencies but complex wavenumbers. Using this procedure we derive dispersion relations, spatial damping rates, and eigenfunctions for the resonant, fast eigenmodes of the arcade. We demonstrate that resonant absorption introduces a fast mode that would not exist otherwise. This new mode is heavily damped by resonant absorption, travelling only a few wavelengths before losing most of its energy.

Ciliary metachronal wave propagation on the compliant surface of Paramecium cells.

PubMed

Narematsu, Naoki; Quek, Raymond; Chiam, Keng-Hwee; Iwadate, Yoshiaki

2015-12-01

Ciliary movements in protozoa exhibit metachronal wave-like coordination, in which a constant phase difference is maintained between adjacent cilia. It is at present generally thought that metachronal waves require hydrodynamic coupling between adjacent cilia and the extracellular fluid. To test this hypothesis, we aspirated a Paramecium cell using a micropipette which completely sealed the surface of the cell such that no fluid could pass through the micropipette. Thus, the anterior and the posterior regions of the cell were hydrodynamically decoupled. Nevertheless, we still observed that metachronal waves continued to propagate from the anterior to the posterior ends of the cell, suggesting that in addition to hydrodynamic coupling, there are other mechanisms that can also transmit the metachronal waves. Such transmission was also observed in computational modeling where the fluid was fully decoupled between two partitions of a beating ciliary array. We also imposed cyclic stretching on the surface of live Paramecium cells and found that metachronal waves persisted in the presence of cyclic stretching. This demonstrated that, in addition to hydrodynamic coupling, a compliant substrate can also play a critical role in mediating the propagation of metachronal waves. © 2015 Wiley Periodicals, Inc.

Stimulated scattering of electromagnetic waves carrying orbital angular momentum in quantum plasmas.

PubMed

Shukla, P K; Eliasson, B; Stenflo, L

2012-07-01

We investigate stimulated scattering instabilities of coherent circularly polarized electromagnetic (CPEM) waves carrying orbital angular momentum (OAM) in dense quantum plasmas with degenerate electrons and nondegenerate ions. For this purpose, we employ the coupled equations for the CPEM wave vector potential and the driven (by the ponderomotive force of the CPEM waves) equations for the electron and ion plasma oscillations. The electrons are significantly affected by the quantum forces (viz., the quantum statistical pressure, the quantum Bohm potential, as well as the electron exchange and electron correlations due to electron spin), which are included in the framework of the quantum hydrodynamical description of the electrons. Furthermore, our investigation of the stimulated Brillouin instability of coherent CPEM waves uses the generalized ion momentum equation that includes strong ion coupling effects. The nonlinear equations for the coupled CPEM and quantum plasma waves are then analyzed to obtain nonlinear dispersion relations which exhibit stimulated Raman, stimulated Brillouin, and modulational instabilities of CPEM waves carrying OAM. The present results are useful for understanding the origin of scattered light off low-frequency density fluctuations in high-energy density plasmas where quantum effects are eminent.

Bottom boundary layer forced by finite amplitude long and short surface waves motions

NASA Astrophysics Data System (ADS)

Elsafty, H.; Lynett, P.

2018-04-01

A multiple-scale perturbation approach is implemented to solve the Navier-Stokes equations while including bottom boundary layer effects under a single wave and under two interacting waves. In this approach, fluid velocities and the pressure field are decomposed into two components: a potential component and a rotational component. In this study, the two components are exist throughout the entire water column and each is scaled with appropriate length and time scales. A one-way coupling between the two components is implemented. The potential component is assumed to be known analytically or numerically a prior, and the rotational component is forced by the potential component. Through order of magnitude analysis, it is found that the leading-order coupling between the two components occurs through the vertical convective acceleration. It is shown that this coupling plays an important role in the bottom boundary layer behavior. Its effect on the results is discussed for different wave-forcing conditions: purely harmonic forcing and impurely harmonic forcing. The approach is then applied to derive the governing equations for the bottom boundary layer developed under two interacting wave motions. Both motions-the shorter and the longer wave-are decomposed into two components, potential and rotational, as it is done in the single wave. Test cases are presented wherein two different wave forcings are simulated: (1) two periodic oscillatory motions and (2) short waves interacting with a solitary wave. The analysis of the two periodic motions indicates that nonlinear effects in the rotational solution may be significant even though nonlinear effects are negligible in the potential forcing. The local differences in the rotational velocity due to the nonlinear vertical convection coupling term are found to be on the order of 30% of the maximum boundary layer velocity for the cases simulated in this paper. This difference is expected to increase with the increase in wave nonlinearity.

Visualization of stress wave propagation via air-coupled acoustic emission sensors

NASA Astrophysics Data System (ADS)

Rivey, Joshua C.; Lee, Gil-Yong; Yang, Jinkyu; Kim, Youngkey; Kim, Sungchan

2017-02-01

We experimentally demonstrate the feasibility of visualizing stress waves propagating in plates using air-coupled acoustic emission sensors. Specifically, we employ a device that embeds arrays of microphones around an optical lens in a helical pattern. By implementing a beamforming technique, this remote sensing system allows us to record wave propagation events in situ via a single-shot and full-field measurement. This is a significant improvement over the conventional wave propagation tracking approaches based on laser doppler vibrometry or digital image correlation techniques. In this paper, we focus on demonstrating the feasibility and efficacy of this air-coupled acoustic emission technique by using large metallic plates exposed to external impacts. The visualization results of stress wave propagation will be shown under various impact scenarios. The proposed technique can be used to characterize and localize damage by detecting the attenuation, reflection, and scattering of stress waves that occurs at damage locations. This can ultimately lead to the development of new structural health monitoring and nondestructive evaluation methods for identifying hidden cracks or delaminations in metallic or composite plate structures, simultaneously negating the need for mounted contact sensors.

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

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

The dynamics of a forced coupled network of active elements

NASA Astrophysics Data System (ADS)

Parks, Helen F.; Ermentrout, Bard; Rubin, Jonathan E.

2011-03-01

This paper presents the derivation and analysis of mathematical models motivated by the experimental induction of contour phosphenes in the retina. First, a spatially discrete chain of periodically forced coupled oscillators is considered via reduction to a chain of scalar phase equations. Each isolated oscillator locks in a 1:2 manner with the forcing so that there is intrinsic bistability, with activity peaking on either the odd or even cycles of the forcing. If half the chain is started on the odd cycle and half on the even cycle (“split state”), then with sufficiently strong coupling, a wave can be produced that can travel in either direction due to symmetry. Numerical and analytic methods are employed to determine the size of coupling necessary for the split state solution to destabilize such that waves appear. Taking a continuum limit, we reduce the chain to a partial differential equation. We use a Melnikov function to compute, to leading order, the speed of the traveling wave solution to the partial differential equation as a function of the form of coupling and the forcing parameters and compare our result to the numerically computed discrete and continuum wave speeds.

Coupling of WRF meteorological model to WAM spectral wave model through sea surface roughness at the Balearic Sea: impact on wind and wave forecasts

NASA Astrophysics Data System (ADS)

Tolosana-Delgado, R.; Soret, A.; Jorba, O.; Baldasano, J. M.; Sánchez-Arcilla, A.

2012-04-01

Meteorological models, like WRF, usually describe the earth surface characteristics by tables that are function of land-use. The roughness length (z0) is an example of such approach. However, over sea z0 is modeled by the Charnock (1955) relation, linking the surface friction velocity u*2 with the roughness length z0 of turbulent air flow, z0 = α-u2* g The Charnock coefficient α may be considered a measure of roughness. For the sea surface, WRF considers a constant roughness α = 0.0185. However, there is evidence that sea surface roughness should depend on wave energy (Donelan, 1982). Spectral wave models like WAM, model the evolution and propagation of wave energy as a function of wind, and include a richer sea surface roughness description. Coupling WRF and WAM is thus a common way to improve the sea surface roughness description of WRF. WAM is a third generation wave model, solving the equation of advection of wave energy subject to input/output terms of: wind growth, energy dissipation and resonant non-linear wave-wave interactions. Third generation models work on the spectral domain. WAM considers the Charnock coefficient α a complex yet known function of the total wind input term, which depends on the wind velocity and on the Charnock coefficient again. This is solved iteratively (Janssen et al., 1990). Coupling of meteorological and wave models through a common Charnock coefficient is operationally done in medium-range met forecasting systems (e.g., at ECMWF) though the impact of coupling for smaller domains is not yet clearly assessed (Warner et al, 2010). It is unclear to which extent the additional effort of coupling improves the local wind and wave fields, in comparison to the effects of other factors, like e.g. a better bathymetry and relief resolution, or a better circulation information which might have its influence on local-scale meteorological processes (local wind jets, local convection, daily marine wind regimes, etc.). This work, within the scope of the 7th EU FP Project FIELD_AC, assesses the impact of coupling WAM and WRF on wind and wave forecasts on the Balearic Sea, and compares it with other possible improvements, like using available high-resolution circulation information from MyOcean GMES core services, or assimilating altimeter data on the Western Mediterranean. This is done in an ordered fashion following statistical design rules, which allows to extract main effects of each of the factors considered (coupling, better circulation information, data assimilation following Lionello et al., 1992) as well as two-factor interactions. Moreover, the statistical significance of these improvements can be tested in the future, though this requires maximum likelihood ratio tests with correlated data. Charnock, H. (1955) Wind stress on a water surface. Quart.J. Row. Met. Soc. 81: 639-640 Donelan, M. (1982) The dependence of aerodynamic drag coefficient on wave parameters. Proc. 1st Int. Conf. on Meteorology and Air-Sea Interactions of teh Coastal Zone. The Hague (Netherlands). AMS. 381-387 Janssen, P.A.E.M., Doyle, J., Bidlot, J., Hansen, B., Isaksen, L. and Viterbo, P. (1990) The impact of oean waves on the atmosphere. Seminars of the ECMWF. Lionello, P., Günther, H., and Janssen P.A.E.M. (1992) Assimilation of altimeter data in a global third-generation wave model. Journal of Geophysical Research 97 (C9): 453-474. Warner, J., Armstrong, B., He, R. and Zambon, J.B. (2010) Development of a Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System. Ocean Modelling 35: 230-244.

Self-pumped Gaussian beam-coupling and stimulated backscatter due to reflection gratings in a photorefractive material

NASA Astrophysics Data System (ADS)

Saleh, Mohammad Abu

2007-05-01

When overlapping monochromatic light beams interfere in a photorefractive material, the resulting intensity fringes create a spatially modulated charge distribution. The resulting refractive index grating may cause power transfer from one beam (the pump) to the other beam (the signal). In a special case of the reflection grating geometry, the Fresnel reflection of the pump beam from the rear surface of the crystal is used as the signal beam. It has been noted that for this self-pumped, contra-directional two-beam coupling (SPCD-TBC) geometry, the coupling efficiency seems to be strongly dependent on the focal position and spot size, which is attributed to diffraction and the resulting change in the spatial overlaps between the pump and signal. In this work a full diffraction based simulation of SPCD-TBC for a Gaussian beam is developed with a novel algorithm. In a related context involving reflection gratings, a particular phenomenon named six-wave mixing has received some interest in the photorefractive research. The generation of multiple waves during near-oblique incidence of a 532 nm weakly focused laser light on photorefractive iron doped lithium niobate in a typical reflection geometry configuration is studied. It is shown that these waves are produced through two-wave coupling (self-diffraction) and four-wave mixing (parametric diffraction). One of these waves, the stimulated photorefractive backscatter produced from parametric diffraction, contains the self-phase conjugate. The dynamics of six-wave mixing, and their dependence on crystal parameters, angle of incidence, and pump power are analyzed. A novel order analysis of the interaction equations provides further insight into experimental observations in the steady state. The quality of the backscatter is evaluated through image restoration, interference experiments, and visibility measurement. Reduction of two-wave coupling may significantly improve the quality of the self-phase conjugate.

Magnonic waveguide based on exchange-spring magnetic structure

NASA Astrophysics Data System (ADS)

Wang, Lixiang; Gao, Leisen; Jin, Lichuan; Liao, Yulong; Wen, Tianlong; Tang, Xiaoli; Zhang, Huaiwu; Zhong, Zhiyong

2018-05-01

A soft/hard exchange-spring coupled bilayer magnetic structure is proposed to obtain a narrow channel for spin-wave propagation. Micromagnetic simulations show that broad-band Damon-Eshbach geometry spin waves are strongly constrained within the channel and propagate effectively with a high group velocity. The beam width of the bound spin waves is almost independent from the frequency and is smaller than 24nm. Two side spin beams appearing at the low-frequency excitation are demonstrated to be coupled with the channel spins by dipole-dipole interaction. In contrast to a domain wall, the channel formed by exchange-spring coupling is easier to be realized in experimental scenarios and holds stronger immunity to surroundings. This work is expected to open new possibilities for energy-efficient spin-wave guiding as well as to help shape the field of beam magnonics.

Localization and oscillations of Majorana fermions in a two-dimensional electron gas coupled with d -wave superconductors

NASA Astrophysics Data System (ADS)

Ortiz, L.; Varona, S.; Viyuela, O.; Martin-Delgado, M. A.

2018-02-01

We study the localization and oscillation properties of the Majorana fermions that arise in a two-dimensional electron gas (2DEG) with spin-orbit coupling (SOC) and a Zeeman field coupled with a d -wave superconductor. Despite the angular dependence of the d -wave pairing, localization and oscillation properties are found to be similar to the ones seen in conventional s -wave superconductors. In addition, we study a microscopic lattice version of the previous system that can be characterized by a topological invariant. We derive its real space representation that involves nearest and next-to-nearest-neighbors pairing. Finally, we show that the emerging chiral Majorana fermions are indeed robust against static disorder. This analysis has potential applications to quantum simulations and experiments in high-Tc superconductors.

Ring Current Ion Coupling with Electromagnetic Ion Cyclotron Waves

NASA Technical Reports Server (NTRS)

Khazanov, George V.

2002-01-01

A new ring current global model has been developed for the first time that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes wave evolution of electromagnetic ion cyclotron waves (EMIC). The coupled model is able to simulate, for the first time self-consistently calculated RC ion kinetic and evolution of EMIC waves that propagate along geomagnetic field lines and reflect from the ionosphere. Ionospheric properties affect the reflection index through the integral Pedersen and Hall coductivities. The structure and dynamics of the ring current proton precipitating flux regions, intensities of EMIC, global RC energy balance, and some other parameters will be studied in detail for the selected geomagnetic storms. The space whether aspects of RC modelling and comparison with the data will also be discussed.

Traveling-wave solutions in continuous chains of unidirectionally coupled oscillators

NASA Astrophysics Data System (ADS)

Glyzin, S. D.; Kolesov, A. Yu; Rozov, N. Kh

2017-12-01

Proposed is a mathematical model of a continuous annular chain of unidirectionally coupled generators given by certain nonlinear advection-type hyperbolic boundary value problem. Such problems are constructed by a limit transition from annular chains of unidirectionally coupled ordinary differential equations with an unbounded increase in the number of links. It is shown that any preassigned finite number of stable periodic motions of the traveling-wave type can coexist in the model.

Rogue waves for a discrete (2+1)-dimensional Ablowitz-Ladik equation in the nonlinear optics and Bose-Einstein condensation

NASA Astrophysics Data System (ADS)

Wu, Xiao-Yu; Tian, Bo; Chai, Han-Peng; Du, Zhong

2018-03-01

Under investigation in this paper is a discrete (2+1)-dimensional Ablowitz-Ladik equation, which is used to model the nonlinear waves in the nonlinear optics and Bose-Einstein condensation. Employing the Kadomtsev-Petviashvili hierarchy reduction, we obtain the rogue wave solutions in terms of the Gramian. We graphically study the first-, second- and third-order rogue waves with the influence of the focusing coefficient and coupling strength. When the value of the focusing coefficient increases, both the peak of the rogue wave and background decrease. When the value of the coupling strength increases, the rogue wave raises and decays in a shorter time. High-order rogue waves are exhibited as one single highest peak and some lower humps, and such lower humps are shown as the triangular and circular patterns.

Spiral wave chimera states in large populations of coupled chemical oscillators

NASA Astrophysics Data System (ADS)

Totz, Jan Frederik; Rode, Julian; Tinsley, Mark R.; Showalter, Kenneth; Engel, Harald

2018-03-01

The coexistence of coherent and incoherent dynamics in a population of identically coupled oscillators is known as a chimera state1,2. Discovered in 20023, this counterintuitive dynamical behaviour has inspired extensive theoretical and experimental activity4-15. The spiral wave chimera is a particularly remarkable chimera state, in which an ordered spiral wave rotates around a core consisting of asynchronous oscillators. Spiral wave chimeras were theoretically predicted in 200416 and numerically studied in a variety of systems17-23. Here, we report their experimental verification using large populations of nonlocally coupled Belousov-Zhabotinsky chemical oscillators10,18 in a two-dimensional array. We characterize previously unreported spatiotemporal dynamics, including erratic motion of the asynchronous spiral core, growth and splitting of the cores, as well as the transition from the chimera state to disordered behaviour. Spiral wave chimeras are likely to occur in other systems with long-range interactions, such as cortical tissues24, cilia carpets25, SQUID metamaterials26 and arrays of optomechanical oscillators9.

Nonlinear layered lattice model and generalized solitary waves in imperfectly bonded structures.

PubMed

Khusnutdinova, Karima R; Samsonov, Alexander M; Zakharov, Alexey S

2009-05-01

We study nonlinear waves in a two-layered imperfectly bonded structure using a nonlinear lattice model. The key element of the model is an anharmonic chain of oscillating dipoles, which can be viewed as a basic lattice analog of a one-dimensional macroscopic waveguide. Long nonlinear longitudinal waves in a layered lattice with a soft middle (or bonding) layer are governed by a system of coupled Boussinesq-type equations. For this system we find conservation laws and show that pure solitary waves, which exist in a single equation and can exist in the coupled system in the symmetric case, are structurally unstable and are replaced with generalized solitary waves.

Spatio-temporal dynamics induced by competing instabilities in two asymmetrically coupled nonlinear evolution equations

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

Schüler, D.; Alonso, S.; Bär, M.

2014-12-15

Pattern formation often occurs in spatially extended physical, biological, and chemical systems due to an instability of the homogeneous steady state. The type of the instability usually prescribes the resulting spatio-temporal patterns and their characteristic length scales. However, patterns resulting from the simultaneous occurrence of instabilities cannot be expected to be simple superposition of the patterns associated with the considered instabilities. To address this issue, we design two simple models composed by two asymmetrically coupled equations of non-conserved (Swift-Hohenberg equations) or conserved (Cahn-Hilliard equations) order parameters with different characteristic wave lengths. The patterns arising in these systems range from coexistingmore » static patterns of different wavelengths to traveling waves. A linear stability analysis allows to derive a two parameter phase diagram for the studied models, in particular, revealing for the Swift-Hohenberg equations, a co-dimension two bifurcation point of Turing and wave instability and a region of coexistence of stationary and traveling patterns. The nonlinear dynamics of the coupled evolution equations is investigated by performing accurate numerical simulations. These reveal more complex patterns, ranging from traveling waves with embedded Turing patterns domains to spatio-temporal chaos, and a wide hysteretic region, where waves or Turing patterns coexist. For the coupled Cahn-Hilliard equations the presence of a weak coupling is sufficient to arrest the coarsening process and to lead to the emergence of purely periodic patterns. The final states are characterized by domains with a characteristic length, which diverges logarithmically with the coupling amplitude.« less

Reflections on the Field of Educational Management Studies.

ERIC Educational Resources Information Center

Fitz, John

1999-01-01

Explores educational management studies as an intellectual field. Draws on Bernstein and Bourieu's theorization of "field" to identify its specialized discourse, field positions and their objective relations, and the location of field occupants (the academic, the practitioner, and the entrepreneur). This configuration shapes educational…

Salt Effects in Photoinduced Electron Transfer Reactions.

DTIC Science & Technology

1986-09-14

Department of Chemistry University of California Howard University Los Angeles, California 90024 Washington, D.C. 20059 Dr. E. R. Bernstein Dr. Joe Brandellk...ana, Illinois 61801 Durham, New Hampshire 03824 Dr. J.B. Halpern Dr. Kent R. Wilson Department of Chemistry Chemistry Department Howard University University

Echinococcus vogeli Rausch and Bernstein, 1972, from the paca, Cuniculus paca L. (Rodentia: Dasyproctidae), in the Departamento de Santa Cruz, Bolivia.

PubMed

Gardner, S L; Rausch, R L; Camacho, O C

1988-06-01

Among approximately 2,000 mammals examined for helminths in various regions of Bolivia during 1983-1987, cysts of Echinococcus vogeli Rausch and Bernstein, 1972, were found in a single paca, Cuniculus paca L., collected at La Laguna, Departamento de Santa Cruz (lat. 16 degrees 36'W; long. 62 degrees 42'S). This record, the first from Bolivia, represents a considerable extension of the known geographic range of this species in South America. Upon analysis of the morphologic characteristics of the protoscoleces derived from the cysts, the sizes of rostellar hooks from the material from the paca were found to be well within the ranges reported in previous studies. Statistical analysis of frequency distributions of hook characteristics revealed some deviations from normality. These results indicate that parametric statistics should be applied with caution in analyses of inter-and intraspecific variation of morphologic characteristics of hooks of metacestodes of the genus Echinococcus.

Kostant polynomials and the cohomology ring for G/B

PubMed Central

Billey, Sara C.

1997-01-01

The Schubert calculus for G/B can be completely determined by a certain matrix related to the Kostant polynomials introduced in section 5 of Bernstein, Gelfand, and Gelfand [Bernstein, I., Gelfand, I. & Gelfand, S. (1973) Russ. Math. Surv. 28, 1–26]. The polynomials are defined by vanishing properties on the orbit of a regular point under the action of the Weyl group. For each element w in the Weyl group the polynomials also have nonzero values on the orbit points corresponding to elements which are larger in the Bruhat order than w. The main theorem given here is an explicit formula for these values. The matrix of orbit values can be used to determine the cup product for the cohomology ring for G/B, using only linear algebra or as described by Lascoux and Schützenberger [Lascoux, A. & Schützenberger, M.-P. (1982) C. R. Seances Acad. Sci. Ser. A 294, 447–450]. Complete proofs of all the theorems will appear in a forthcoming paper. PMID:11038536

Investigation of magneto-hemodynamic flow in a semi-porous channel using orthonormal Bernstein polynomials

NASA Astrophysics Data System (ADS)

Hosseini, E.; Loghmani, G. B.; Heydari, M.; Rashidi, M. M.

2017-07-01

In this paper, the problem of the magneto-hemodynamic laminar viscous flow of a conducting physiological fluid in a semi-porous channel under a transverse magnetic field is investigated numerically. Using a Berman's similarity transformation, the two-dimensional momentum conservation partial differential equations can be written as a system of nonlinear ordinary differential equations incorporating Lorentizian magneto-hydrodynamic body force terms. A new computational method based on the operational matrix of derivative of orthonormal Bernstein polynomials for solving the resulting differential systems is introduced. Moreover, by using the residual correction process, two types of error estimates are provided and reported to show the strength of the proposed method. Graphical and tabular results are presented to investigate the influence of the Hartmann number ( Ha) and the transpiration Reynolds number ( Re on velocity profiles in the channel. The results are compared with those obtained by previous works to confirm the accuracy and efficiency of the proposed scheme.

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

Develop and Test Coupled Physical Parameterizations and Tripolar Wave Model Grid: NAVGEM / WaveWatch III / HYCOM

DTIC Science & Technology

2013-09-30

Tripolar Wave Model Grid: NAVGEM / WaveWatch III / HYCOM W. Erick Rogers Naval Research Laboratory, Code 7322 Stennis Space Center, MS 39529...Parameterizations and Tripolar Wave Model Grid: NAVGEM / WaveWatch III / HYCOM 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

Propagation and dispersion of shock waves in magnetoelastic materials

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

Crum, R. S.; Domann, J. P.; Carman, G. P.

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into anmore » acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Lastly, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.« less

Propagation and dispersion of shock waves in magnetoelastic materials

NASA Astrophysics Data System (ADS)

Crum, R. S.; Domann, J. P.; Carman, G. P.; Gupta, V.

2017-12-01

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into an acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Finally, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.

Spin Josephson effect in topological superconductor-ferromagnet junction

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

Ren, C. D.; Wang, J., E-mail: jwang@seu.edu.cn

2014-03-21

The composite topological superconductor (TS), made of one-dimensional spin-orbit coupled nanowire with proximity-induced s-wave superconductivity, is not a pure p-wave superconductor but still has a suppressed s-wave pairing. We propose to probe the spin texture of the p-wave pairing in this composite TS by examining possible spin supercurrents in an unbiased TS/ferromagnet junction. It is found that both the exchange-coupling induced and spin-flip reflection induced spin currents exist in the setup and survive even in the topological phase. We showed that besides the nontrivial p-wave pairing state accounting for Majorana Fermions, there shall be a trivial p-wave pairing state thatmore » contributes to spin supercurrent. The trivial p-wave pairing state is diagnosed from the mixing effect between the suppressed s-wave pairing and the topologically nontrivial p-wave pairing. The d vector of the TS is proved not to be rigorously perpendicular to the spin projection of p-wave pairings. Our findings are also confirmed by the Kitaev's p-wave model with a nonzero s-wave pairing.« less

Propagation and dispersion of shock waves in magnetoelastic materials

DOE PAGES

Crum, R. S.; Domann, J. P.; Carman, G. P.; ...

2017-11-15

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into anmore » acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Lastly, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.« less

Spatiotemporal Stochastic Resonance:Theory and Experiment

NASA Astrophysics Data System (ADS)

Peter, Jung

1996-03-01

The amplification of weak periodic signals in bistable or excitable systems via stochastic resonance has been studied intensively over the last years. We are going one step further and ask: Can noise enhance spatiotemporal patterns in excitable media and can this effect be observed in nature? To this end, we are looking at large, two dimensional arrays of coupled excitable elements. Due to the coupling, excitation can propagate through the array in form of nonlinear waves. We observe target waves, rotating spiral waves and other wave forms. If the coupling between the elements is below a critical threshold, any excitational pattern will die out in the absence of noise. Below this threshold, large scale rotating spiral waves - as they are observed above threshold - can be maintained by a proper level of the noise[1]. Furthermore, their geometric features, such as the curvature can be controlled by the homogeneous noise level[2]. If the noise level is too large, break up of spiral waves and collisions with spontaneously nucleated waves yields spiral turbulence. Driving our array with a spatiotemporal pattern, e.g. a rotating spiral wave, we show that for weak coupling the excitational response of the array shows stochastic resonance - an effect we have termed spatiotemporal stochastic resonance. In the last part of the talk I'll make contact with calcium waves, observed in astrocyte cultures and hippocampus slices[3]. A. Cornell-Bell and collaborators[3] have pointed out the role of calcium waves for long-range glial signaling. We demonstrate the similarity of calcium waves with nonlinear waves in noisy excitable media. The noise level in the tissue is characterized by spontaneous activity and can be controlled by applying neuro-transmitter substances[3]. Noise effects in our model are compared with the effect of neuro-transmitters on calcium waves. [1]P. Jung and G. Mayer-Kress, CHAOS 5, 458 (1995). [2]P. Jung and G. Mayer-Kress, Phys. Rev. Lett.62, 2682 (1995). [3] A. Cornell-Bell, Steven M. Finkbeiner, Mark.S. Cooper and Stephen J. Smith, SCIENCE, 247, 373 (1990).

Development of performance specifications for hybrid modeling of floating wind turbines in wave basin tests

DOE PAGES

Hall, Matthew; Goupee, Andrew; Jonkman, Jason

2017-08-24

Hybrid modeling—combining physical testing and numerical simulation in real time$-$opens new opportunities in floating wind turbine research. Wave basin testing is an important validation step for floating support structure design, but the conventional approaches that use physical wind above the basin are limited by scaling problems in the aerodynamics. Applying wind turbine loads with an actuation system that is controlled by a simulation responding to the basin test in real time offers a way to avoid scaling problems and reduce cost barriers for floating wind turbine design validation in realistic coupled wind and wave conditions. This paper demonstrates the developmentmore » of performance specifications for a system that couples a wave basin experiment with a wind turbine simulation. Two different points for the hybrid coupling are considered: the tower-base interface and the aero-rotor interface (the boundary between aerodynamics and the rotor structure). Analyzing simulations of three floating wind turbine designs across seven load cases reveals the motion and force requirements of the coupling system. By simulating errors in the hybrid coupling system, the sensitivity of the floating wind turbine response to coupling quality can be quantified. The sensitivity results can then be used to determine tolerances for motion tracking errors, force actuation errors, bandwidth limitations, and latency in the hybrid coupling system. These tolerances can guide the design of hybrid coupling systems to achieve desired levels of accuracy. An example demonstrates how the developed methods can be used to generate performance specifications for a system at 1:50 scale. Results show that sensitivities vary significantly between support structure designs and that coupling at the aero-rotor interface has less stringent requirements than those for coupling at the tower base. As a result, the methods and results presented here can inform design of future hybrid coupling systems and enhance understanding of how test results are affected by hybrid coupling quality.« less

Development of performance specifications for hybrid modeling of floating wind turbines in wave basin tests

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

Hall, Matthew; Goupee, Andrew; Jonkman, Jason

Hybrid modeling—combining physical testing and numerical simulation in real time$-$opens new opportunities in floating wind turbine research. Wave basin testing is an important validation step for floating support structure design, but the conventional approaches that use physical wind above the basin are limited by scaling problems in the aerodynamics. Applying wind turbine loads with an actuation system that is controlled by a simulation responding to the basin test in real time offers a way to avoid scaling problems and reduce cost barriers for floating wind turbine design validation in realistic coupled wind and wave conditions. This paper demonstrates the developmentmore » of performance specifications for a system that couples a wave basin experiment with a wind turbine simulation. Two different points for the hybrid coupling are considered: the tower-base interface and the aero-rotor interface (the boundary between aerodynamics and the rotor structure). Analyzing simulations of three floating wind turbine designs across seven load cases reveals the motion and force requirements of the coupling system. By simulating errors in the hybrid coupling system, the sensitivity of the floating wind turbine response to coupling quality can be quantified. The sensitivity results can then be used to determine tolerances for motion tracking errors, force actuation errors, bandwidth limitations, and latency in the hybrid coupling system. These tolerances can guide the design of hybrid coupling systems to achieve desired levels of accuracy. An example demonstrates how the developed methods can be used to generate performance specifications for a system at 1:50 scale. Results show that sensitivities vary significantly between support structure designs and that coupling at the aero-rotor interface has less stringent requirements than those for coupling at the tower base. As a result, the methods and results presented here can inform design of future hybrid coupling systems and enhance understanding of how test results are affected by hybrid coupling quality.« less

Observation of dust acoustic shock wave in a strongly coupled dusty plasma

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

Sharma, Sumita K., E-mail: sumita-sharma82@yahoo.com; Boruah, A.; Nakamura, Y.

2016-05-15

Dust acoustic shock wave is observed in a strongly coupled laboratory dusty plasma. A supersonic flow of charged microparticles is allowed to perturb a stationary dust fluid to excite dust acoustic shock wave. The evolution process beginning with steepening of initial wave front and then formation of a stable shock structure is similar to the numerical results of the Korteweg-de Vries-Burgers equation. The measured Mach number of the observed shock wave agrees with the theoretical results. Reduction of shock amplitude at large distances is also observed due to the dust neutral collision and viscosity effects. The dispersion relation and themore » spatial damping of a linear dust acoustic wave are also measured and compared with the relevant theory.« less

Ultrasonic input-output for transmitting and receiving longitudinal transducers coupled to same face of isotropic elastic plate

NASA Technical Reports Server (NTRS)

Williams, J. H., Jr.; Karagulle, H.; Lee, S. S.

1982-01-01

The quantitative understanding of ultrasonic nondestructive evaluation parameters such as the stress wave factor were studied. Ultrasonic input/output characteristics for an isotropic elastic plate with transmitting and receiving longitudinal transducers coupled to the same face were analyzed. The asymptotic normal stress is calculated for an isotropic elastic half space subjected to a uniform harmonic normal stress applied to a circular region at the surface. The radiated stress waves are traced within the plate by considering wave reflections at the top and bottom faces. The output voltage amplitude of the receiving transducer is estimated by considering only longitudinal waves. Agreement is found between the output voltage wave packet amplitudes and times of arrival due to multiple reflections of the longitudinal waves.

Wave mixing in coupled phononic crystals via a variable stiffness mechanism

NASA Astrophysics Data System (ADS)

Lee, Gil-Yong; Chong, Christopher; Kevrekidis, Panayotis G.; Yang, Jinkyu

2016-10-01

We investigate wave mixing effects in a phononic crystal that couples the wave dynamics of two channels - primary and control ones - via a variable stiffness mechanism. We demonstrate analytically and numerically that the wave transmission in the primary channel can be manipulated by the control channel's signal. We show that the application of control waves allows the selection of a specific mode through the primary channel. We also demonstrate that the mixing of two wave modes is possible whereby a modulation effect is observed. A detailed study of the design parameters is also carried out to optimize the switching capabilities of the proposed system. Finally, we verify that the system can fulfill both switching and amplification functionalities, potentially enabling the realization of an acoustic transistor.

The choice of speed and clearance for RAS on 3D method

NASA Astrophysics Data System (ADS)

Wang, Jian-Fang; Li, Ji-De; Cai, Xin-Gong

2003-12-01

In this paper, a 3D source distribution technique is used to calculate the coupled motions between two ships which advance in the wave with the same speed. The numerical results of coupled motions for a frigate and a supply ship have a good agreement with the experimental results. Based on the 3D coupled motions of two ships, a spectral analysis is employed to clearly observe the effect of speed, clearance and wave heading on the significant relative motion amplitude (SRMA) of two ships. The method presented in this paper will be helpful to select suitable clearance, speed and wave heading for underway replenishment at sea(RAS).

Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

NASA Astrophysics Data System (ADS)

Bandyopadhyay, P.; Prasad, G.; Sen, A.; Kaw, P. K.

2007-09-01

The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO2 dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of ∂ω/∂k<0 are identified as signatures of dust dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.

Generation of zonal magnetic fields by low-frequency dispersive electromagnetic waves in a nonuniform dusty magnetoplasma.

PubMed

Shukla, P K

2004-04-01

It is shown that zonal magnetic fields can be parametrically excited by low-frequency dispersive driftlike compressional electromagnetic (DDCEM) modes in a nonuniform dusty magnetoplasma. For this purpose, we derive a pair of coupled equations which exhibits the nonlinear coupling between DDCEM modes and zonal magnetic fields. The coupled mode equations are Fourier analyzed to derive a nonlinear dispersion relation. The latter depicts that zonal magnetic fields are nonlinearly generated at the expense of the low-frequency DDCEM wave energy. The relevance of our investigation to the transfer of energy from short scale DDCEM waves to long scale zonal magnetic field structures in dark molecular clouds is discussed.

Vector semirational rogue waves and modulation instability for the coupled higher-order nonlinear Schrödinger equations in the birefringent optical fibers.

PubMed

Sun, Wen-Rong; Liu, De-Yin; Xie, Xi-Yang

2017-04-01

We report the existence and properties of vector breather and semirational rogue-wave solutions for the coupled higher-order nonlinear Schrödinger equations, which describe the propagation of ultrashort optical pulses in birefringent optical fibers. Analytic vector breather and semirational rogue-wave solutions are obtained with Darboux dressing transformation. We observe that the superposition of the dark and bright contributions in each of the two wave components can give rise to complicated breather and semirational rogue-wave dynamics. We show that the bright-dark type vector solitons (or breather-like vector solitons) with nonconstant speed interplay with Akhmediev breathers, Kuznetsov-Ma solitons, and rogue waves. By adjusting parameters, we note that the rogue wave and bright-dark soliton merge, generating the boomeron-type bright-dark solitons. We prove that the rogue wave can be excited in the baseband modulation instability regime. These results may provide evidence of the collision between the mixed ultrashort soliton and rogue wave.

Study of Linear and Nonlinear Wave Excitation

NASA Astrophysics Data System (ADS)

Chu, Feng; Berumen, Jorge; Hood, Ryan; Mattingly, Sean; Skiff, Frederick

2013-10-01

We report an experimental study of externally excited low-frequency waves in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional. Wave excitation in the drift wave frequency range is accomplished by low-percentage amplitude modulation of the RF plasma source. Laser-induced fluorescence is adopted to study ion-density fluctuations in phase space. The laser is chopped to separate LIF from collisional fluorescence. A single negatively-biased Langmuir probe is used to detect ion-density fluctuations in the plasma. A ring array of Langmuir probes is also used to analyze the spatial and spectral structure of the excited waves. We apply coherent detection with respect to the wave frequency to obtain the ion distribution function associated with externally generated waves. Higher-order spectra are computed to evaluate the nonlinear coupling between fluctuations at various frequencies produced by the externally generated waves. Parametric decay of the waves is observed. This work is supported by U.S. DOE Grant No. DE-FG02-99ER54543.

The effect of wave current interactions on the storm surge and inundation in Charleston Harbor during Hurricane Hugo 1989

NASA Astrophysics Data System (ADS)

Xie, Lian; Liu, Huiqing; Peng, Machuan

The effects of wave-current interactions on the storm surge and inundation induced by Hurricane Hugo in and around the Charleston Harbor and its adjacent coastal regions are examined by using a three-dimensional (3-D) wave-current coupled modeling system. The 3-D storm surge and inundation modeling component of the coupled system is based on the Princeton ocean model (POM), whereas the wave modeling component is based on the third-generation wave model, simulating waves nearshore (SWAN). The results indicate that the effects of wave-induced surface, bottom, and radiation stresses can separately or in combination produce significant changes in storm surge and inundation. The effects of waves vary spatially. In some areas, the contribution of waves to peak storm surge during Hurricane Hugo reached as high as 0.76 m which led to substantial changes in the inundation and drying areas simulated by the storm surge model.

High-frequency homogenization for travelling waves in periodic media.

PubMed

Harutyunyan, Davit; Milton, Graeme W; Craster, Richard V

2016-07-01

We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 1 plus a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 2 . We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω 1 = ω 2 and [Formula: see text] where Λ =(λ 1 λ 2 …λ d ) is the periodicity cell of the medium and for any two vectors [Formula: see text] the product a ⊙ b is defined to be the vector ( a 1 b 1 , a 2 b 2 ,…, a d b d ). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

The role of the global phase in the spatio-temporal evolution of strong-coupling Brillouin scattering

NASA Astrophysics Data System (ADS)

Amiranoff, F.; Riconda, C.; Chiaramello, M.; Lancia, L.; Marquès, J. R.; Weber, S.

2018-01-01

The role of the global phase in the spatio-temporal evolution of the 3-wave coupled equations for backscattering is analyzed in the strong-coupling regime of Brillouin scattering. This is of particular interest for controlled backscattering in the case of plasma-based amplification to produce short and intense laser pulses. It is shown that the analysis of the envelope equations of the three waves involved, pump, seed, and ion wave, in terms of phase and amplitude fully describes the coupling dynamics. In particular, it helps understanding the role of the chirp of the laser beams and of the plasma density profile. The results can be used to optimize or quench the coupling mechanism. It is found that the directionality of the energy transfer is imposed by the phase relation at the leading edge of the pulse. This actually ensures continued energy transfer even if the intensity of the seed pulse is already higher than the pump pulse intensity.

Bernstein in the Urban Classroom: A Case Study

ERIC Educational Resources Information Center

Barrett, Brian D.

2017-01-01

Despite a long-standing concern within the sociology of education for ameliorating educational inequality, the challenge of improving educational opportunities for disadvantaged students remains deeply entrenched. While 'macro' issues such as segregation and systemic inequalities in school funding and access to qualified teachers must be addressed…

Grammaticality and Educational Research

ERIC Educational Resources Information Center

Hordern, Jim

2017-01-01

This paper uses Bernstein's concept of grammar to illuminate aspects of educational research. The relationship between internal and external languages of description in the production of disciplinary knowledge is examined. This leads to a reflection on the various factors both internal and external to the discipline of educational studies that…

Taiwan: America’s Next War?

DTIC Science & Technology

1998-04-08

7. 29 Megatrends China, Beijing: Hauling Publishing House, May 1996, as cited in Richard Bernstein and Ross H. Munro, The Coming Conflict with...other economic interests in Asia  To prevent, deter and reduce the threat of nuclear, biological , and chemical (NBC) attacks on the U.S. and its

Ordering within Moral Orders to Manage Classroom Trouble

ERIC Educational Resources Information Center

Doherty, Catherine; McGregor, Rowena; Shield, Paul

2016-01-01

This paper demonstrates how classroom trouble warranting teacher intervention can stem from transgressions in different layers of the complex moral order regulating classroom interactions. The paper builds from Durkheim's treatment of schooling as the institution responsible for the inculcation of a shared moral order, Bernstein's distinction…

The International Baccalaureate Diploma Programme and the Construction of Pedagogic Identity: A Preliminary Study

ERIC Educational Resources Information Center

Cambridge, James

2010-01-01

Bernstein (1999, 2000) proposes that contrasting educational discourses construct contrasting retrospective, prospective, decentred (market) and decentred (therapeutic) pedagogic identities. In different times and geographical locations the International Baccalaureate (IB) Diploma Programme (DP) has been projected onto a variety of pedagogic…

Embedding the dynamics of a single delay system into a feed-forward ring.

PubMed

Klinshov, Vladimir; Shchapin, Dmitry; Yanchuk, Serhiy; Wolfrum, Matthias; D'Huys, Otti; Nekorkin, Vladimir

2017-10-01

We investigate the relation between the dynamics of a single oscillator with delayed self-feedback and a feed-forward ring of such oscillators, where each unit is coupled to its next neighbor in the same way as in the self-feedback case. We show that periodic solutions of the delayed oscillator give rise to families of rotating waves with different wave numbers in the corresponding ring. In particular, if for the single oscillator the periodic solution is resonant to the delay, it can be embedded into a ring with instantaneous couplings. We discover several cases where the stability of a periodic solution for the single unit can be related to the stability of the corresponding rotating wave in the ring. As a specific example, we demonstrate how the complex bifurcation scenario of simultaneously emerging multijittering solutions can be transferred from a single oscillator with delayed pulse feedback to multijittering rotating waves in a sufficiently large ring of oscillators with instantaneous pulse coupling. Finally, we present an experimental realization of this dynamical phenomenon in a system of coupled electronic circuits of FitzHugh-Nagumo type.

Standing waves, clustering, and phase waves in 1D simulations of kinetic relaxation oscillations in NO+NH 3 on Pt(1 0 0) coupled by diffusion

NASA Astrophysics Data System (ADS)

Uecker, Hannes

2004-04-01

The Lombardo-Imbihl-Fink (LFI) ODE model of the NO+NH 3 reaction on a Pt(1 0 0) surface shows stable relaxation oscillations with very sharp transitions for temperatures T between 404 and 433 K. Here we study numerically the effect of linear diffusive coupling of these oscillators in one spatial dimension. Depending on the parameters and initial conditions we find a rich variety of spatio-temporal patterns which we group into four main regimes: bulk oscillations (BOs), standing waves (SW), phase clusters (PC), and phase waves (PW). Two key ingredients for SW and PC are identified, namely the relaxation type of the ODE oscillations and a nonlocal (and nonglobal) coupling due to relatively fast diffusion of the kinetically slaved variables NH 3 and H. In particular, the latter replaces the global coupling through the gas phase used to obtain SW and PC in models of related surface reactions. The PW exist only under the assumption of (relatively) slow diffusion of NH 3 and H.

Circuit quantum acoustodynamics with surface acoustic waves.

PubMed

Manenti, Riccardo; Kockum, Anton F; Patterson, Andrew; Behrle, Tanja; Rahamim, Joseph; Tancredi, Giovanna; Nori, Franco; Leek, Peter J

2017-10-17

The experimental investigation of quantum devices incorporating mechanical resonators has opened up new frontiers in the study of quantum mechanics at a macroscopic level. It has recently been shown that surface acoustic waves (SAWs) can be piezoelectrically coupled to superconducting qubits, and confined in high-quality Fabry-Perot cavities in the quantum regime. Here we present measurements of a device in which a superconducting qubit is coupled to a SAW cavity, realising a surface acoustic version of cavity quantum electrodynamics. We use measurements of the AC Stark shift between the two systems to determine the coupling strength, which is in agreement with a theoretical model. This quantum acoustodynamics architecture may be used to develop new quantum acoustic devices in which quantum information is stored in trapped on-chip acoustic wavepackets, and manipulated in ways that are impossible with purely electromagnetic signals, due to the 10 5 times slower mechanical waves.In this work, Manenti et al. present measurements of a device in which a tuneable transmon qubit is piezoelectrically coupled to a surface acoustic wave cavity, realising circuit quantum acoustodynamic architecture. This may be used to develop new quantum acoustic devices.

Shock transmission in coupled beams and rib stiffened structures

NASA Technical Reports Server (NTRS)

Pope, L. D.; Manning, J. E.; Scharton, T. D.

1971-01-01

Shock transmission in a simple coupled beam structure and in a ring-stringer stiffened cylinder is investigated experimentally and analytically using wave transmission and statistical energy analysis concepts. The use of the response spectrum to characterize the excitation provided to a simple beam by a force pulse is studied. Analysis of the transmission of a dilatation wave in a periodically stiffened plate indicates that the stiffeners are fairly transparent to the wave, but some of the dilatational energy is scattered into bending at each support.

Self-consistent Model of Magnetospheric Electric Field, RC and EMIC Waves

NASA Technical Reports Server (NTRS)

Gamayunov, K. V.; Khazanov, G. V.; Liemohn, M. W.; Fok, M.-C.

2007-01-01

Electromagnetic ion cyclotron (EMIC) waves are an important magnetospheric emission, which is excited near the magnetic equator with frequencies below the proton gyro-frequency. The source of bee energy for wave growth is provided by temperature anisotropy of ring current (RC) ions, which develops naturally during inward convection from the plasma sheet These waves strongly affect the dynamic s of resonant RC ions, thermal electrons and ions, and the outer radiation belt relativistic electrons, leading to non-adiabatic particle heating and/or pitch-angle scattering and loss to the atmosphere. The rate of ion and electron scattering/heating is strongly controlled by the Wave power spectral and spatial distributions, but unfortunately, the currently available observational information regarding EMIC wave power spectral density is poor. So combinations of reliable data and theoretical models should be utilized in order to obtain the power spectral density of EMIC waves over the entire magnetosphere throughout the different storm phases. In this study, we present the simulation results, which are based on two coupled RC models that our group has developed. The first model deals with the large-scale magnetosphere-ionosphere electrodynamic coupling, and provides a self-consistent description of RC ions/electrons and the magnetospheric electric field. The second model is based on a coupled system of two kinetic equations, one equation describes the RC ion dynamics and another equation describes the power spectral density evolution of EMIC waves, and self-consistently treats a micro-scale electrodynamic coupling of RC and EMIC waves. So far, these two models have been applied independently. However, the large-scale magnetosphere-ionosphere electrodynamics controls the convective patterns of both the RC ions and plasmasphere altering conditions for EMIC wave-particle interaction. In turn, the wave induced RC precipitation Changes the local field-aligned current distributions and the ionospheric conductances, which are crucial for a large-scale electrodynamics. The initial results from this new self-consistent model of the magnetospheric electric field, RC and EMIC waves will be shown in this presentation.

Quantitative modeling of coupled piezo-elastodynamic behavior of piezoelectric actuators bonded to an elastic medium for structural health monitoring: a review.

PubMed

Huang, Guoliang; Song, Fei; Wang, Xiaodong

2010-01-01

Elastic waves, especially guided waves, generated by a piezoelectric actuator/sensor network, have shown great potential for on-line health monitoring of advanced aerospace, nuclear, and automotive structures in recent decades. Piezoelectric materials can function as both actuators and sensors in these applications due to wide bandwidth, quick response and low costs. One of the most fundamental issues surrounding the effective use of piezoelectric actuators is the quantitative evaluation of the resulting elastic wave propagation by considering the coupled piezo-elastodynamic behavior between the actuator and the host medium. Accurate characterization of the local interfacial stress distribution between the actuator and the host medium is the key issue for the problem. This paper presents a review of the development of analytical, numerical and hybrid approaches for modeling of the coupled piezo-elastodynamic behavior. The resulting elastic wave propagation for structural health monitoring is also summarized.

Nonminimal couplings, gravitational waves, and torsion in Horndeski's theory

NASA Astrophysics Data System (ADS)

Barrientos, José; Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Medina, Perla; Narbona, Daniela; Rodríguez, Eduardo; Valdivia, Omar

2017-10-01

The Horndeski Lagrangian brings together all possible interactions between gravity and a scalar field that yield second-order field equations in four-dimensional spacetime. As originally proposed, it only addresses phenomenology without torsion, which is a non-Riemannian feature of geometry. Since torsion can potentially affect interesting phenomena such as gravitational waves and early universe inflation, in this paper we allow torsion to exist and propagate within the Horndeski framework. To achieve this goal, we cast the Horndeski Lagrangian in Cartan's first-order formalism and introduce wave operators designed to act covariantly on p -form fields that carry Lorentz indices. We find that nonminimal couplings and second-order derivatives of the scalar field in the Lagrangian are indeed generic sources of torsion. Metric perturbations couple to the background torsion, and new torsional modes appear. These may be detected via gravitational waves but not through Yang-Mills gauge bosons.

Orthogonality catastrophe and fractional exclusion statistics

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Orthogonality catastrophe and fractional exclusion statistics.

PubMed

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

2018-02-01

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

Two-dimensional wave patterns of spreading depolarization: Retracting, re-entrant, and stationary waves

NASA Astrophysics Data System (ADS)

Dahlem, Markus A.; Graf, Rudolf; Strong, Anthony J.; Dreier, Jens P.; Dahlem, Yuliya A.; Sieber, Michaela; Hanke, Wolfgang; Podoll, Klaus; Schöll, Eckehard

2010-06-01

We present spatio-temporal characteristics of spreading depolarizations (SD) in two experimental systems: retracting SD wave segments observed with intrinsic optical signals in chicken retina, and spontaneously occurring re-entrant SD waves that repeatedly spread across gyrencephalic feline cortex observed by laser speckle flowmetry. A mathematical framework of reaction-diffusion systems with augmented transmission capabilities is developed to explain the emergence and transitions between these patterns. Our prediction is that the observed patterns are reaction-diffusion patterns controlled and modulated by weak nonlocal coupling such as long-range, time-delayed, and global coupling. The described spatio-temporal characteristics of SD are of important clinical relevance under conditions of migraine and stroke. In stroke, the emergence of re-entrant SD waves is believed to worsen outcome. In migraine, retracting SD wave segments cause neurological symptoms and transitions to stationary SD wave patterns may cause persistent symptoms without evidence from noninvasive imaging of infarction.

Simulations of moving effect of coastal vegetation on tsunami damping

NASA Astrophysics Data System (ADS)

Tsai, Ching-Piao; Chen, Ying-Chi; Octaviani Sihombing, Tri; Lin, Chang

2017-05-01

A coupled wave-vegetation simulation is presented for the moving effect of the coastal vegetation on tsunami wave height damping. The problem is idealized by solitary wave propagation on a group of emergent cylinders. The numerical model is based on general Reynolds-averaged Navier-Stokes equations with renormalization group turbulent closure model by using volume of fluid technique. The general moving object (GMO) model developed in computational fluid dynamics (CFD) code Flow-3D is applied to simulate the coupled motion of vegetation with wave dynamically. The damping of wave height and the turbulent kinetic energy along moving and stationary cylinders are discussed. The simulated results show that the damping of wave height and the turbulent kinetic energy by the moving cylinders are clearly less than by the stationary cylinders. The result implies that the wave decay by the coastal vegetation may be overestimated if the vegetation was represented as stationary state.

Nonlinear coupling of left and right handed circularly polarized dispersive Alfvén wave

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

Sharma, R. P., E-mail: rpsharma@ces.iitd.ac.in; Sharma, Swati, E-mail: swati.sharma704@gmail.com; Gaur, Nidhi, E-mail: nidhiphysics@gmail.com

2014-07-15

The nonlinear phenomena are of prominent interests in understanding the particle acceleration and transportation in the interplanetary space. The ponderomotive nonlinearity causing the filamentation of the parallel propagating circularly polarized dispersive Alfvén wave having a finite frequency may be one of the mechanisms that contribute to the heating of the plasmas. The contribution will be different of the left (L) handed mode, the right (R) handed mode, and the mix mode. The contribution also depends upon the finite frequency of the circularly polarized waves. In the present paper, we have investigated the effect of the nonlinear coupling of the Lmore » and R circularly polarized dispersive Alfvén wave on the localized structures formation and the respective power spectra. The dynamical equations are derived in the presence of the ponderomotive nonlinearity of the L and R pumps and then studied semi-analytically as well as numerically. The ponderomotive nonlinearity accounts for the nonlinear coupling between both the modes. In the presence of the adiabatic response of the density fluctuations, the nonlinear dynamical equations satisfy the modified nonlinear Schrödinger equation. The equations thus obtained are solved in solar wind regime to study the coupling effect on localization and the power spectra. The effect of coupling is also studied on Faraday rotation and ellipticity of the wave caused due to the difference in the localization of the left and the right modes with the distance of propagation.« less

Asymptotics of QCD traveling waves with fluctuations and running coupling effects

NASA Astrophysics Data System (ADS)

Beuf, Guillaume

2008-09-01

Extending the Balitsky-Kovchegov (BK) equation independently to running coupling or to fluctuation effects due to pomeron loops is known to lead in both cases to qualitative changes of the traveling-wave asymptotic solutions. In this paper we study the extension of the forward BK equation, including both running coupling and fluctuations effects, extending the method developed for the fixed coupling case [E. Brunet, B. Derrida, A.H. Mueller, S. Munier, Phys. Rev. E 73 (2006) 056126, cond-mat/0512021]. We derive the exact asymptotic behavior in rapidity of the probabilistic distribution of the saturation scale.

Highly efficient all-fiber tunable polarization filter using torsional acoustic wave.

PubMed

Lee, Kwang Jo; Park, Hyun Chul; Kim, Byoung Yoon

2007-09-17

We demonstrate an all-fiber tunable polarization filter with high coupling efficiency based on acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent single mode optical fiber. An over-coupling between the two polarization modes is realized over the wavelength range from 1530 nm to 1610 nm using traveling torsional acoustic wave. The measured 3-dB optical bandwidth of the filter was 4.8 nm at the wavelength around 1550 nm. The details of the filter transmission and the coupling characteristics are discussed.

Research of the impact of coupling between unit cells on performance of linear-to-circular polarization conversion metamaterial with half transmission and half reflection

NASA Astrophysics Data System (ADS)

Guo, Mengchao; Zhou, Kan; Wang, Xiaokun; Zhuang, Haiyan; Tang, Dongming; Zhang, Baoshan; Yang, Yi

2018-04-01

In this paper, the impact of coupling between unit cells on the performance of linear-to-circular polarization conversion metamaterial with half transmission and half reflection is analyzed by changing the distance between the unit cells. An equivalent electrical circuit model is then built to explain it based on the analysis. The simulated results show that, when the distance between the unit cells is 23 mm, this metamaterial converts half of the incident linearly-polarized wave into reflected left-hand circularly-polarized wave and converts the other half of it into transmitted left-hand circularly-polarized wave at 4.4 GHz; when the distance is 28 mm, this metamaterial reflects all of the incident linearly-polarized wave at 4.4 GHz; and when the distance is 32 mm, this metamaterial converts half of the incident linearly-polarized wave into reflected right-hand circularly-polarized wave and converts the other half of it into transmitted right-hand circularly-polarized wave at 4.4 GHz. The tunability is realized successfully. The analysis shows that the changes of coupling between unit cells lead to the changes of performance of this metamaterial. The coupling between the unit cells is then considered when building the equivalent electrical circuit model. The built equivalent electrical circuit model can be used to perfectly explain the simulated results, which confirms the validity of it. It can also give help to the design of tunable polarization conversion metamaterials.

Robust magnon-photon coupling in a planar-geometry hybrid of inverted split-ring resonator and YIG film.

PubMed

Bhoi, Biswanath; Kim, Bosung; Kim, Junhoe; Cho, Young-Jun; Kim, Sang-Koog

2017-09-20

We experimentally demonstrate strongly enhanced coupling between excited magnons in an Yttrium Iron Garnet (YIG) film and microwave photons in an inverted pattern of split-ring resonator (noted as ISRR). The anti-crossing effects of the ISRR's photon mode and the YIG's magnon modes were found from |S 21 |-versus-frequency measurements for different strengths and directions of externally applied magnetic fields. The spin-number-normalized coupling strength (i.e. single spin-photon coupling) [Formula: see text] was determined to 0.194 Hz ([Formula: see text] = 90 MHz) at 3.7 GHz frequency. Furthermore, we found that additional fine features in the anti-crossing region originate from the excitation of different spin-wave modes (such as the magnetostatic surface and the backward-volume magnetostatic spin-waves) rather than the Kittel-type mode. These spin-wave modes, as coupled with the ISRR mode, modify the anti-crossing effect as well as their coupling strength. An equivalent circuit model very accurately reproduced the observed anti-crossing effect and its coupling strength variation with the magnetic field direction in the planar-geometry ISRR/YIG hybrid system. This work paves the way for the design of new types of high-gain magnon-photon coupling systems in planar geometry.

Lamb wave extraction of dispersion curves in micro/nano-plates using couple stress theories

NASA Astrophysics Data System (ADS)

Ghodrati, Behnam; Yaghootian, Amin; Ghanbar Zadeh, Afshin; Mohammad-Sedighi, Hamid

2018-01-01

In this paper, Lamb wave propagation in a homogeneous and isotropic non-classical micro/nano-plates is investigated. To consider the effect of material microstructure on the wave propagation, three size-dependent models namely indeterminate-, modified- and consistent couple stress theories are used to extract the dispersion equations. In the mentioned theories, a parameter called 'characteristic length' is used to consider the size of material microstructure in the governing equations. To generalize the parametric studies and examine the effect of thickness, propagation wavelength, and characteristic length on the behavior of miniature plate structures, the governing equations are nondimensionalized by defining appropriate dimensionless parameters. Then the dispersion curves for phase and group velocities are plotted in terms of a wide frequency-thickness range to study the lamb waves propagation considering microstructure effects in very high frequencies. According to the illustrated results, it was observed that the couple stress theories in the Cosserat type material predict more rigidity than the classical theory; so that in a plate with constant thickness, by increasing the thickness to characteristic length ratio, the results approach to the classical theory, and by reducing this ratio, wave propagation speed in the plate is significantly increased. In addition, it is demonstrated that for high-frequency Lamb waves, it converges to dispersive Rayleigh wave velocity.

Chiral dynamics of the p wave in K-p and coupled states

NASA Astrophysics Data System (ADS)

Jido, D.; Oset, E.; Ramos, A.

2002-11-01

We perform an evaluation of the p-wave amplitudes of meson-baryon scattering in the strangeness S=-1 sector starting from the lowest order chiral Lagrangians and introducing explicitly the Σ* field with couplings to the meson-baryon states obtained using SU(6) symmetry. The N/D method of unitarization is used, equivalent, in practice, to the use of the Bethe-Salpeter equation with a cutoff. The procedure leaves no freedom for the p-waves once the s-waves are fixed and thus one obtains genuine predictions for the p-wave scattering amplitudes, which are in good agreement with experimental results for differential cross sections, as well as for the width and partial decay widths of the Σ*(1385).

Coriolis effect in optics: unified geometric phase and spin-Hall effect.

PubMed

Bliokh, Konstantin Y; Gorodetski, Yuri; Kleiner, Vladimir; Hasman, Erez

2008-07-18

We examine the spin-orbit coupling effects that appear when a wave carrying intrinsic angular momentum interacts with a medium. The Berry phase is shown to be a manifestation of the Coriolis effect in a noninertial reference frame attached to the wave. In the most general case, when both the direction of propagation and the state of the wave are varied, the phase is given by a simple expression that unifies the spin redirection Berry phase and the Pancharatnam-Berry phase. The theory is supported by the experiment demonstrating the spin-orbit coupling of electromagnetic waves via a surface plasmon nanostructure. The measurements verify the unified geometric phase, demonstrated by the observed polarization-dependent shift (spin-Hall effect) of the waves.

Impact of wave mixing on the sea ice cover

NASA Astrophysics Data System (ADS)

Rynders, Stefanie; Aksenov, Yevgeny; Madec, Gurvan; Nurser, George; Feltham, Daniel

2017-04-01

As information on surface waves in ice-covered regions becomes available in ice-ocean models, there is an opportunity to model wave-related processes more accurate. Breaking waves cause mixing of the upper water column and present mixing schemes in ocean models take this into account through surface roughness. A commonly used approach is to calculate surface roughness from significant wave height, parameterised from wind speed. We present results from simulations using modelled significant wave height instead, which accounts for the presence of sea ice and the effect of swell. The simulations use the NEMO ocean model coupled to the CICE sea ice model, with wave information from the ECWAM model of the European Centre for Medium-Range Weather Forecasts (ECMWF). The new waves-in-ice module allows waves to propagate in sea ice and attenuates waves according to multiple scattering and non-elastic losses. It is found that in the simulations with wave mixing the mixed layer depth (MLD) under ice cover is reduced, since the parameterisation from wind speed overestimates wave height in the ice-covered regions. The MLD change, in turn, affects sea ice concentration and ice thickness. In the Arctic, reduced MLD in winter translates into increased ice thicknesses overall, with higher increases in the Western Arctic and decreases along the Siberian coast. In summer, shallowing of the mixed layer results in more heat accumulating in the surface ocean, increasing ice melting. In the Southern Ocean the meridional gradient in ice thickness and concentration is increased. We argue that coupling waves with sea ice - ocean models can reduce negative biases in sea ice cover, affecting the distribution of nutrients and, thus, biological productivity and ecosystems. This coupling will become more important in the future, when wave heights in a large part of the Arctic are expected to increase due to sea ice retreat and a larger wave fetch. Therefore, wave mixing constitutes a possible positive feedback mechanism.

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

NASA Astrophysics Data System (ADS)

Fu, H. Y.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Ruohoniemi, J. M.

2015-08-01

Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

The Material Plasma Exposure eXperiment (MPEX)

NASA Astrophysics Data System (ADS)

Rapp, J.; Biewer, T. M.; Bigelow, T. S.; Canik, J.; Caughman, J. B. O.; Duckworth, R. C.; Goulding, R. H.; Hillis, D. L.; Lore, J. D.; Lumsdaine, A.; McGinnis, W. D.; Meitner, S. J.; Owen, L. W.; Shaw, G. C.; Luo, G.-N.

2014-10-01

Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The Material Plasma Exposure eXperiment (MPEX) will address this regime with electron temperatures of 1--10 eV and electron densities of 1021--1020 m-3. The resulting heat fluxes are about 10 MW/m2. MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with Electron Bernstein Wave (EBW) heating and Ion Cyclotron Resonance Heating (ICRH). Preliminary modeling has been used for pre-design studies of MPEX. MPEX will be capable to expose neutron irradiated samples. In this concept targets will be irradiated in ORNL's High Flux Isotope Reactor (HFIR) or possibly at the Spallation Neutron Source (SNS) and then subsequently (after a sufficient long cool-down period) exposed to fusion reactor relevant plasmas in MPEX. The current state of the pre-design of MPEX including the concept of handling irradiated samples will be presented. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under Contract DE-AC-05-00OR22725.

Large-scale variation of electron parameters from Quasi-Thermal Noise during WIND perigees in the Earth's magnetosphere

NASA Astrophysics Data System (ADS)

Issautier, Karine; Ongala-Edoumou, Samuel; Moncuquet, Michel

2016-04-01

The quasi-thermal noise (QTN) method consists in measuring the electrostatic fluctuations produced by the thermal motion of the ambient particles. This noise is detected with a sensitive wave receiver and measured at the terminal of a passive electric antenna, which is immersed in a stable plasma. The analysis of the so-called QTN provides in situ measurements, mainly the total electron density, with a good accuracy, and thermal temperature in a large number of space media. We create a preliminary electron database to analyse the anti-correlation between electron density and temperature deduced from WIND perigees in the Earth's plasmasphere. We analyse the radio power spectra measured by the Thermal Noise Receiver (TNR), using the 100-m long dipole antenna, onboard WIND spacecraft. We develop a systematic routine to determine the electron density, core and halo temperature and the magnitude of the magnetic field based on QTN in Bernstein modes. Indeed, the spectra are weakly banded between gyroharmonics below the upper hybrid frequency, from which we derive the local electron density. From the gyrofrequency determination, we obtain an independent measure of the magnetic field magnitude, which is in close agreement with the onboard magnetometer.

Explicit high-order non-canonical symplectic particle-in-cell algorithms for Vlasov-Maxwell systems

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

Xiao, Jianyuan; Qin, Hong; Liu, Jian

2015-11-01

Explicit high-order non-canonical symplectic particle-in-cell algorithms for classical particle-field systems governed by the Vlasov-Maxwell equations are developed. The algorithms conserve a discrete non-canonical symplectic structure derived from the Lagrangian of the particle-field system, which is naturally discrete in particles. The electromagnetic field is spatially discretized using the method of discrete exterior calculus with high-order interpolating differential forms for a cubic grid. The resulting time-domain Lagrangian assumes a non-canonical symplectic structure. It is also gauge invariant and conserves charge. The system is then solved using a structure-preserving splitting method discovered by He et al. [preprint arXiv: 1505.06076 (2015)], which produces fivemore » exactly soluble sub-systems, and high-order structure-preserving algorithms follow by combinations. The explicit, high-order, and conservative nature of the algorithms is especially suitable for long-term simulations of particle-field systems with extremely large number of degrees of freedom on massively parallel supercomputers. The algorithms have been tested and verified by the two physics problems, i.e., the nonlinear Landau damping and the electron Bernstein wave. (C) 2015 AIP Publishing LLC.« less

Overview of MST Research

NASA Astrophysics Data System (ADS)

Sarff, J. S.; MST Team

2011-10-01

MST progress in advancing the RFP for (1) fusion plasma confinement with minimal external magnetization, (2) toroidal confinement physics, and (3) basic plasma physics is summarized. New tools and diagnostics are accessing physics barely studied in the RFP. Several diagnostic advances are important for ITER/burning plasma. A 1 MW neutral beam injector operates routinely for fast ion, heating, and transport investigations. Energetic ions are also created spontaneously by tearing mode reconnection, reminiscent of astrophysical plasmas. Classical confinement of impurity ions is measured in reduced-tearing plasmas. Fast ion slowing-down is also classical. Alfven-eigenmode-like activity occurs with NBI, but apparently not TAE. Stellarator-like helical structure appears in the core of high current plasmas, with improved confinement characteristics. FIR interferometry, Thomson scattering, and HIBP diagnostics are beginning to explore microturbulence scales, an opportunity to exploit the RFP's high beta and strong magnetic shear parameter space. A programmable power supply for the toroidal field flexibly explores scenarios from advanced inductive profile control to low current tokamak operation. A 1 MW 5.5 GHz source for electron Bernstein wave injection is nearly complete to investigate heating and current drive in over-dense plasmas. Supported by DOE and NSF.

Effects of wave-current interaction on storm surge in the Taiwan Strait: Insights from Typhoon Morakot

NASA Astrophysics Data System (ADS)

Yu, Xiaolong; Pan, Weiran; Zheng, Xiangjing; Zhou, Shenjie; Tao, Xiaoqin

2017-08-01

The effects of wave-current interaction on storm surge are investigated by a two-dimensional wave-current coupling model through simulations of Typhoon Morakot in the Taiwan Strait. The results show that wind wave and slope of sea floor govern wave setup modulations within the nearshore surf zone. Wave setup during Morakot can contribute up to 24% of the total storm surge with a maximum value of 0.28 m. The large wave setup commonly coincides with enhanced radiation stress gradient, which is itself associated with transfer of wave momentum flux. Water levels are to leading order in modulating significant wave height inside the estuary. High water levels due to tidal change and storm surge stabilize the wind wave and decay wave breaking. Outside of the estuary, waves are mainly affected by the current-induced modification of wind energy input to the wave generation. By comparing the observed significant wave height and water level with the results from uncoupled and coupled simulations, the latter shows a better agreement with the observations. It suggests that wave-current interaction plays an important role in determining the extreme storm surge and wave height in the study area and should not be neglected in a typhoon forecast.

Shock Wave Technology and Application: An Update☆

PubMed Central

Rassweiler, Jens J.; Knoll, Thomas; Köhrmann, Kai-Uwe; McAteer, James A.; Lingeman, James E.; Cleveland, Robin O.; Bailey, Michael R.; Chaussy, Christian

2012-01-01

Context The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems. Objective To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies. Evidence acquisition We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy. Evidence synthesis Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60–80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures. Conclusions New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL. PMID:21354696

Evaluating wave-current interaction in an urban estuary and flooding implications for coastal communities

NASA Astrophysics Data System (ADS)

Cifuentes-Lorenzen, A.; O'Donnell, J.; Howard-Strobel, M. M.; Fake, T.; McCardell, G.

2016-12-01

Accurate hydrodynamic-wave coupled coastal circulation models aid the prediction of storm impacts, particularly in areas where data is absent, and can inform mitigation options. They are essential everywhere to account for the effects of climate change. Here, the Finite Volume Community Ocean Model (FVCOM) was used to estimate the residual circulation inside a small urban estuary, Long Island Sound, during three severe weather events of different magnitude (i.e. 1/5, 1/25 and 1/50 year events). The effect of including wave coupling using a log-layer bottom boundary and the bottom wave-current coupling, following the approach of Madsen (1994) on the simulated residual circulation was assessed. Significant differences in the solutions were constrained to the near surface (s>-0.3) region. No significant difference in the depth-averaged residual circulation was detected. When the Madsen (1994) bottom boundary layer model for wave-current interaction was employed, differences in residual circulation resulted. The bottom wave-current interaction also plays an important role in the wave dynamics. Significant wave heights along the northern Connecticut shoreline were enhanced by up to 15% when the bottom wave-current interaction was included in the simulations. The wave-induced bottom drag enhancement has a substantial effect on tides in the Sound, possibly because it is nearly resonant at semidiurnal frequencies. This wave-current interaction current leads to severe tidal dampening ( 40% amplitude reduction) at the Western end of the estuary in the modeled sea surface displacement. The potential magnitude of these effects means that wave current interaction should be included and carefully evaluated in models of estuaries that are useful.

Phase locking of convectively coupled equatorial atmospheric Kelvin waves over Indian Ocean basin

NASA Astrophysics Data System (ADS)

Baranowski, Dariusz; Flatau, Maria; Flatau, Piotr; Matthews, Adrian

2015-04-01

The properties of convectively coupled Kelvin waves in the Indian Ocean and their propagation over the Maritime Continent are studied. It is shown that Kelvin waves are longitude - diurnal cycle phase locked over the Maritime Continent, Africa and the Indian Ocean. Thus, it is shown that they tend to propagate over definite areas during specific times of the day. Over the Maritime Continent, longitude-diurnal cycle phase locking is such that it agrees with mean, local diurnal cycle of convection. The strength of the longitude-diurnal cycle phase locking differs between 'non-blocked' Kelvin waves, which make successful transition over the Maritime Continent, and 'blocked' waves that terminated within it. It is shown that a specific combination of Kelvin wave phase speed and time of the day at which a wave approaches the Maritime Continent influence the chance of successful transition into the Western Pacific. Kelvin waves that maintain phase speed of 10 to 11 degrees per day over the central-eastern Indian Ocean and arrive at 90E between 9UTC and 18UTC have the highest chance of being 'non-blocked' by the Maritime Continent. The distance between the islands of Sumatra and Borneo agrees with the distance travelled by an average convectively coupled Kelvin wave in one day. This suggests that the Maritime Continent may act as a 'filter' for Kelvin waves favoring successful propagation of those waves for which propagation is in phase with the local diurnal cycle of precipitation. The AmPm index, a simple measure of local diurnal cycle for propagating disturbances, is introduced and shown to be useful metric depicting key characteristics of the convection associated with propagating Kelvin waves.

Gravitational Wave Oscillations in Bigravity.

PubMed

Max, Kevin; Platscher, Moritz; Smirnov, Juri

2017-09-15

We derive consistent equations for gravitational wave oscillations in bigravity. In this framework a second dynamical tensor field is introduced in addition to general relativity and coupled such that one massless and one massive linear combination arise. Only one of the two tensors is the physical metric coupling to matter, and thus the basis in which gravitational waves propagate is different from the basis where the wave is produced and detected. Therefore, one should expect-in analogy to neutrino oscillations-to observe an oscillatory behavior. We show for the first time how this behavior arises explicitly, discuss phenomenological implications, and present new limits on the graviton parameter space in bigravity.

On the Periodic Solutions of the Five-Dimensional Lorenz Equation Modeling Coupled Rosby Waves and Gravity Waves

NASA Astrophysics Data System (ADS)

Carvalho, Tiago; Llibre, Jaume

2017-06-01

Lorenz studied the coupled Rosby waves and gravity waves using the differential system U˙ = -VW + bVZ,V˙ = UW - bUZ,Ẇ = -UV,Ẋ = -Z,Ż = bUV + X. This system has the two first integrals H1 = U2 + V2,H 2 = V2 + W2 + X2 + Z2. Our main result shows that in each invariant set {H1 = h1 > 0}∩{H2 = h2 > 0} there are at least four (resp., 2) periodic solutions of the differential system with b≠0 and h2 > h1 (resp., h2 < h1).

Spiral-Wave Dynamics in a Mathematical Model of Human Ventricular Tissue with Myocytes and Fibroblasts

PubMed Central

Nayak, Alok Ranjan; Shajahan, T. K.; Panfilov, A. V.; Pandit, Rahul

2013-01-01

Cardiac fibroblasts, when coupled functionally with myocytes, can modulate the electrophysiological properties of cardiac tissue. We present systematic numerical studies of such modulation of electrophysiological properties in mathematical models for (a) single myocyte-fibroblast (MF) units and (b) two-dimensional (2D) arrays of such units; our models build on earlier ones and allow for zero-, one-, and two-sided MF couplings. Our studies of MF units elucidate the dependence of the action-potential (AP) morphology on parameters such as , the fibroblast resting-membrane potential, the fibroblast conductance , and the MF gap-junctional coupling . Furthermore, we find that our MF composite can show autorhythmic and oscillatory behaviors in addition to an excitable response. Our 2D studies use (a) both homogeneous and inhomogeneous distributions of fibroblasts, (b) various ranges for parameters such as , and , and (c) intercellular couplings that can be zero-sided, one-sided, and two-sided connections of fibroblasts with myocytes. We show, in particular, that the plane-wave conduction velocity decreases as a function of , for zero-sided and one-sided couplings; however, for two-sided coupling, decreases initially and then increases as a function of , and, eventually, we observe that conduction failure occurs for low values of . In our homogeneous studies, we find that the rotation speed and stability of a spiral wave can be controlled either by controlling or . Our studies with fibroblast inhomogeneities show that a spiral wave can get anchored to a local fibroblast inhomogeneity. We also study the efficacy of a low-amplitude control scheme, which has been suggested for the control of spiral-wave turbulence in mathematical models for cardiac tissue, in our MF model both with and without heterogeneities. PMID:24023798

Wave energy transmission apparatus for high-temperature environments

NASA Technical Reports Server (NTRS)

Buckley, John D. (Inventor); Edwards, William C. (Inventor); Kelliher, Warren C. (Inventor); Carlberg, Ingrid A. (Inventor)

2010-01-01

A wave energy transmission apparatus has a conduit made from a refractory oxide. A transparent, refractory ceramic window is coupled to the conduit. Wave energy passing through the window enters the conduit.

Fiber optic laser rod

DOEpatents

Erickson, G.F.

1988-04-13

A laser rod is formed from a plurality of optical fibers, each forming an individual laser. Synchronization of the individual fiber lasers is obtained by evanescent wave coupling between adjacent optical fiber cores. The fiber cores are dye-doped and spaced at a distance appropriate for evanescent wave coupling at the wavelength of the selected dye. An interstitial material having an index of refraction lower than that of the fiber core provides the optical isolation for effective lasing action while maintaining the cores at the appropriate coupling distance. 2 figs.

T sub 1-echo sequence: Protecting the State of a Qubit in the Presence of Coherent Interaction

DTIC Science & Technology

2012-09-25

memory is at energy m, and they are coupled with a coupling strength v⊥. We write the coupling in the rotating - wave approximation , assuming q,m...important for the time evolution. In the validity range of the rotating - wave approximation , the above Hamiltonian preserves the total number of...excited state) in total is involved in the dynamics, the underlying Jaynes - Cummings Hamiltonian will lead to the same results as the ones presented here

Modeling Wave-Ice Interactions in the Marginal Ice Zone

NASA Astrophysics Data System (ADS)

Orzech, Mark; Shi, Fengyan; Bateman, Sam; Veeramony, Jay; Calantoni, Joe

2015-04-01

The small-scale (O(m)) interactions between waves and ice floes in the marginal ice zone (MIZ) are investigated with a coupled model system. Waves are simulated with the non-hydrostatic finite-volume model NHWAVE (Ma et al., 2012) and ice floes are represented as bonded collections of smaller particles with the discrete element system LIGGGHTS (Kloss et al., 2012). The physics of fluid and ice are recreated as authentically as possible, to allow the coupled system to supplement and/or substitute for more costly and demanding field experiments. The presentation will first describe the development and validation of the coupled system, then discuss the results of a series of virtual experiments in which ice floe and wave characteristics are varied to examine their effects on energy dissipation, MIZ floe size distribution, and ice pack retreat rates. Although Wadhams et al. (1986) suggest that only a small portion (roughly 10%) of wave energy entering the MIZ is reflected, dissipation mechanisms for the remaining energy have yet to be delineated or measured. The virtual experiments are designed to focus on specific properties and processes - such as floe size and shape, collision and fracturing events, and variations in wave climate - and measure their relative roles the transfer of energy and momentum from waves to ice. Questions to be examined include: How is energy dissipated by ice floe collisions, fracturing, and drag, and how significant is the wave attenuation associated with each process? Do specific wave/floe length scale ratios cause greater wave attenuation? How does ice material strength affect the rate of wave energy loss? The coupled system will ultimately be used to test and improve upon wave-ice parameterizations for large-scale climate models. References: >Kloss, C., C. Goniva, A. Hager, S. Amberger, and S. Pirker (2012). Models, algorithms and validation for opensource DEM and CFD-DEM. Progress in Computational Fluid Dynamics 12(2/3), 140-152. >Ma, G., F. Shi, and J.T. Kirby (2012). Shock-capturing non-hydrostatic model for fully dispersive surface wave processes. Ocean Modelling 43-44, 22-35. >Wadhams P., V. Squire, J.A. Ewing, and R.W. Pascal (1986). The effect of the marginal ice zone on the directional wave spectrum of the ocean. J. Phys. Oceanog., 16(2), 358-376.

Quasi-optical theory of relativistic surface-wave oscillators with one-dimensional and two-dimensional periodic planar structures

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

Ginzburg, N. S.; Zaslavsky, V. Yu.; Institute of Applied Physics of Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950

2013-11-15

Within the framework of a quasi-optical approach, we develop 2D and 3D self-consistent theory of relativistic surface-wave oscillators. Presenting the radiation field as a sum of two counter-propagating wavebeams coupled on a shallow corrugated surface, we describe formation of an evanescent slow wave. Dispersion characteristics of the evanescent wave following from this method are in good compliance with those found from the direct cst simulations. Considering excitation of the slow wave by a sheet electron beam, we simulate linear and nonlinear stages of interaction, which allows us to determine oscillation threshold conditions, electron efficiency, and output coupling. The transition frommore » the model of surface-wave oscillator operating in the π-mode regime to the canonical model of relativistic backward wave oscillator is considered. We also described a modified scheme of planar relativistic surface-wave oscillators exploiting two-dimensional periodic gratings. Additional transverse propagating waves emerging on these gratings synchronize the emission from a wide sheet rectilinear electron beam allowing realization of a Cherenkov millimeter-wave oscillators with subgigawatt output power level.« less

Planetary Wave-Tide Interactions in Atmosphere-Ionosphere Coupling, Xiaoli Zhang, Jeffrey M. Forbes, Astrid Maute, and Maura E. Hagan

NASA Astrophysics Data System (ADS)

Zhang, X.; Forbes, J. M.; Maute, A. I.

2017-12-01

Planetary Wave-Tide Interactions in Atmosphere-Ionosphere Coupling Xiaoli Zhang, Jeffrey M. Forbes, Astrid Maute, and Maura E. Hagan The existence of secondary waves in the mesosphere and thermosphere due to nonlinear interactions between atmospheric tides and longer-period waves have been revealed in both satellite data and in the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM). The longer-period waves include the quasi-2-day and 6-day westward-propagating "normal modes" of the atmosphere, and eastward-propagating ultra-fast Kelvin waves with periods between 2 and 4 days. The secondary waves add to both the temporal and longitude variability of the atmosphere beyond that associated with the linear superposition of the interacting waves, thus adding "complexity" to the system. Based on our knowledge of the processes governing atmosphere-ionosphere interactions, similar revelations are expected to occur in electric fields, vertical plasma drifts and F-region electron densities. Towards this end, examples of such ionospheric manifestations of wave-wave interactions in TIE-GCM simulations will be presented.

Teaching, School Management and the Ideology of Pragmatism

ERIC Educational Resources Information Center

Moore, Alex

2005-01-01

With reference to Bernstein's theories concerning the pulls and tensions of competing pedagogic identities, this article draws on original research to suggest that a culture of pragmatism may be currently rooting itself in English schools. This culture is understood partly as an instrumental response to rapid and extensive educational reform, and…

Analysis of Low Frequency Ground Motions Induced by Near-Surface and Atmospheric Explosions.

DTIC Science & Technology

1982-08-01

Library S-CUBED ATTN: J. Murphy Institute for Defense Analyses ATTN: Classified Library Science Applications, Inc ATTN: Technical Library Kaman...AviDyne ATTN: Library Science Applications, Inc ATTN: N. Hobbs ATTN: D. Maxwell ATTN: D. Bernstein Kaman Sciences Corp ATTN: Library Science Applications

Towards a Realist Sociology of Education: A Polyphonic Review Essay

ERIC Educational Resources Information Center

Grenfell, Michael; Hood, Susan; Barrett, Brian D.; Schubert, Dan

2017-01-01

This review essay evaluates Karl Maton's "Knowledge and Knowers: Towards a Realist Sociology of Education" as a recent examination of the sociological causes and effects of education in the tradition of the French social theorist Pierre Bourdieu and the British educational sociologist Basil Bernstein. Maton's book synthesizes the…

Framing of Transitional Pedagogic Practices in the Sciences: Enabling Access

ERIC Educational Resources Information Center

Ellery, Karen

2017-01-01

Educational literature shows that students from working-class backgrounds are significantly less likely to persist to completion in higher education than middle-class students. This paper draws theoretically and analytically on Bernstein's ([1990. "Class, Codes and Control, Volume IV: The Structuring of Pedagogic Discourse." London:…

Cumulative and Segmented Learning: Exploring the Role of Curriculum Structures in Knowledge-Building

ERIC Educational Resources Information Center

Maton, Karl

2009-01-01

The present article extends Basil Bernstein's theorisation of "discourses" and "knowledge structures" to explore the potential of educational knowledge structures to enable or constrain cumulative learning, where students can transfer knowledge across contexts and build knowledge over time. It offers a means of overcoming…

Opening Opportunities for Disadvantaged Learners.

ERIC Educational Resources Information Center

Passow, A. Harry, Ed.

Contents of this book include: "Urban environment in the 1970's," A. Harry Passow; "Educational strategies and the disadvantaged," S.M. Miller and Pamela Roby; "A critique of the concept of 'compensatory education,'" Basil Bernstein; "Early childhood education for the disadvantaged," Helen Robison; "Up from poverty: the price of 'making it' in a…

Emotional Closeness with Perpetrators and Amnesia for Child Sexual Abuse

ERIC Educational Resources Information Center

Schultz, Tammy; Passmore, J. Lawrence; Yoder, C. Y.

2003-01-01

Over the past decade, a contentious debate regarding delayed memories of childhood sexual abuse (CSA) has existed. In order to address this debate, 240 female participants completed questions about CSA, the Dissociative Experience Scale (Bernstein & Putnam, 1986), Perceived Emotional Closeness with Perpetrator Scale (Schultz, Passmore, &…

"Control Must Be Maintained": Exploring Teachers' Pedagogical Practice outside the Classroom

ERIC Educational Resources Information Center

Glackin, Melissa

2018-01-01

Drawing on qualitative data, this article presents an analysis of six secondary science teachers' expectations and practices related to teaching outdoors during a professional development programme. Using Foucault's and Bernstein's theories of "space", routines and set practices, I argue that participant teachers' fear of losing control…

Evidence-Based Practice in Communication Disorders: Progress Not Perfection

ERIC Educational Resources Information Center

Kent, Ray D.

2006-01-01

Purpose: This commentary is written in response to a companion paper by Nan Bernstein Ratner ("Evidence-Based Practice: An Examination of its Ramifications for the Practice of Speech-Language Pathology"). Method: The comments reflect my experience as Vice President for Research and Technology of the American Speech-Language-Hearing Association…

Primates and their habitats in northern Colombia with recommendations for future management and research

USGS Publications Warehouse

Scott, Norman J.; Struhsaker, Thomas T.; Glander, Kenneth; Chiriví, Hernano

1976-01-01

This report covers a survey of forests and wild primates carried out by its authors in northern Colombia during May, July, and August 1974. The results of a 1973 field report on this report by Bernstein et al. (1) are also included.

Higher Apprenticeships and the Shaping of Vocational Knowledge

ERIC Educational Resources Information Center

Hordern, Jim

2015-01-01

Higher apprenticeships are celebrated in current policy discourses as an alternative to traditional higher education, with the claim that they will prepare higher apprentices for their future careers and enhance industrial productivity through higher skill levels. This paper aims to scrutinise these claims using notions developed by Bernstein and…

"We Are Textbook 'Badnekais'!": A Bernsteinian Analysis of Textbook Culture in Science Classrooms

ERIC Educational Resources Information Center

Vijaysimha, Indira

2013-01-01

This article is an empirical study of science teaching practices using a Bernsteinian framework. It provides a comparative analysis through ethnographic examination of pedagogic recontextualisation in different school types--government, private unaided and international. Bernstein drew attention to the process of pedagogic recontextualisation and…

Teaching, Teacher Formation, and Specialised Professional Practice

ERIC Educational Resources Information Center

Hordern, Jim

2015-01-01

This paper starts by exploring the relevance of Bernstein's work on vertical and horizontal discourses and the constitution of professional knowledge for conceptualisation of the knowledge needed for teaching practice. Building on arguments for the differentiated nature of knowledge, and drawing on the work of Winch, Young and Muller on expertise,…

A Pedagogy of Conceptual Progression and the Case for Academic Knowledge

ERIC Educational Resources Information Center

Rata, Elizabeth

2016-01-01

The potential for academic knowledge to "interrupt" inter-generational reproduction in education is located in the structural contradictions that shape knowledge and democracy. Since the late 1990s research in the sociology of education, which theorises curriculum knowledge using the ideas of Durkheim, Vygotsky and Bernstein, suggests…

Making Gazes Explicit: Facilitating Epistemic Access in the Humanities

ERIC Educational Resources Information Center

Luckett, Kathy; Hunma, Aditi

2014-01-01

This paper addresses the problem of curriculum design in the Humanities and Social Sciences, and more specifically the challenge of designing foundation courses for first-generation or "disadvantaged" learners. Located in the social realist school of the sociology of education studies that builds on the legacy of Basil Bernstein, we…

The Road to Oxbridge: Schools and Elite University Choices

ERIC Educational Resources Information Center

Donnelly, Michael

2014-01-01

This paper explores hidden messages sent out by schools about Oxbridge, using Basil Bernstein's concepts of classification and framing. Research in three case-study schools captured these messages from their everyday practices and processes, including their events and activities, sorting mechanisms, interactions and resources. Whilst all of the…

What Is Not Said on Hearing Poetry in the Classroom

ERIC Educational Resources Information Center

Gordon, John

2010-01-01

This article considers an exchange between pupils in response to heard poetry, approaching it through a "conversation analytic mentality" informed by the theories of Basil Bernstein. Using his terms, it describes an existing "pedagogic device" of poetry study for schools, to which responses under discussion do not easily…

A Bernsteinian Analysis of Content Area Literacy

ERIC Educational Resources Information Center

Collin, Ross

2014-01-01

This article examines two approaches to teaching content area literacy: a strategies approach focused on general practices of reading and writing and a disciplinary approach attuned to the particular discourses of particular domains. Basil Bernstein's theory of the pedagogic device is used to critique both approaches' assumptions about…

Classification and Framing in the Case Method: Discussion Leaders' Questions

ERIC Educational Resources Information Center

Badger, James

2010-01-01

Basil Bernstein's classification and framing was adopted as a theoretical model to analyse the instruction of two university professors who incorporated case studies into their graduate business and education courses. Classification and framing allows for a meaningful analysis of the discussion leader's questions that facilitate students'…

The Contributions of Bernstein's Sociology to Education Development Research

ERIC Educational Resources Information Center

Sriprakash, Arathi

2011-01-01

Global and national agendas to improve the "quality" of Education For All have brought focus to pedagogic processes in developing country contexts. How can development research pay attention to the social and political significance of pedagogical projects and understand the micro-processes of classroom reform? This paper considers how…

Towards a Bernsteinian Language of Description for Mathematics Classroom Discourse

ERIC Educational Resources Information Center

Straehler-Pohl, Hauke; Gellert, Uwe

2013-01-01

This article aims at developing an external language of description to investigate the problem of why particular groups of students are systematically not provided access to school mathematical knowledge. Based on Basil Bernstein's conceptualisation of power in classification, we develop a three-dimensional model that operationalises the…

Integrable pair-transition-coupled nonlinear Schrödinger equations.

PubMed

Ling, Liming; Zhao, Li-Chen

2015-08-01

We study integrable coupled nonlinear Schrödinger equations with pair particle transition between components. Based on exact solutions of the coupled model with attractive or repulsive interaction, we predict that some new dynamics of nonlinear excitations can exist, such as the striking transition dynamics of breathers, new excitation patterns for rogue waves, topological kink excitations, and other new stable excitation structures. In particular, we find that nonlinear wave solutions of this coupled system can be written as a linear superposition of solutions for the simplest scalar nonlinear Schrödinger equation. Possibilities to observe them are discussed in a cigar-shaped Bose-Einstein condensate with two hyperfine states. The results would enrich our knowledge on nonlinear excitations in many coupled nonlinear systems with transition coupling effects, such as multimode nonlinear fibers, coupled waveguides, and a multicomponent Bose-Einstein condensate system.

Resilience of branching and massive corals to wave loading under sea level rise--a coupled computational fluid dynamics-structural analysis.

PubMed

Baldock, Tom E; Karampour, Hassan; Sleep, Rachael; Vyltla, Anisha; Albermani, Faris; Golshani, Aliasghar; Callaghan, David P; Roff, George; Mumby, Peter J

2014-09-15

Measurements of coral structural strength are coupled with a fluid dynamics-structural analysis to investigate the resilience of coral to wave loading under sea level rise and a typical Great Barrier Reef lagoon wave climate. The measured structural properties were used to determine the wave conditions and flow velocities that lead to structural failure. Hydrodynamic modelling was subsequently used to investigate the type of the bathymetry where coral is most vulnerable to breakage under cyclonic wave conditions, and how sea level rise (SLR) changes this vulnerability. Massive corals are determined not to be vulnerable to wave induced structural damage, whereas branching corals are susceptible at wave induced orbital velocities exceeding 0.5m/s. Model results from a large suite of idealised bathymetry suggest that SLR of 1m or a loss of skeleton strength of order 25% significantly increases the area of reef flat where branching corals are exposed to damaging wave induced flows. Copyright © 2014 Elsevier Ltd. All rights reserved.

Coupled wave model for large magnet coils

NASA Technical Reports Server (NTRS)

Gabriel, G. J.

1980-01-01

A wave coupled model based on field theory is evolved for analysis of fast electromagnetic transients on superconducting coils. It is expected to play a useful role in the design of protection methods against damage due to high voltages or any adverse effects that might arise from unintentional transients. The significant parameters of the coil are identified to be the turn to turn wave coupling coefficients and the travel time of an electromagnetic disturbance around a single turn. Unlike circuit theoretic inductor, the coil response evolves in discrete steps having durations equal to this travel time. It is during such intervals that high voltages are likely to occur. The model also bridges the gap between the low and high ends of the frequency spectrum.

Surface acoustic wave regulated single photon emission from a coupled quantum dot–nanocavity system

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

Weiß, M.; Kapfinger, S.; Wixforth, A.

2016-07-18

A coupled quantum dot–nanocavity system in the weak coupling regime of cavity-quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a f{sub SAW} ≃ 800 MHz surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function, g{sup (2)}. All relevant frequencies of our experiment are faithfully identified in the Fourier transform of g{sup (2)}, demonstrating high fidelity regulation of the stream of single photonsmore » emitted by the system.« less

Effective modeling and reverse-time migration for novel pure acoustic wave in arbitrary orthorhombic anisotropic media

NASA Astrophysics Data System (ADS)

Xu, Shigang; Liu, Yang

2018-03-01

The conventional pseudo-acoustic wave equations (PWEs) in arbitrary orthorhombic anisotropic (OA) media usually have coupled P- and SV-wave modes. These coupled equations may introduce strong SV-wave artifacts and numerical instabilities in P-wave simulation results and reverse-time migration (RTM) profiles. However, pure acoustic wave equations (PAWEs) completely decouple the P-wave component from the full elastic wavefield and naturally solve all the aforementioned problems. In this article, we present a novel PAWE in arbitrary OA media and compare it with the conventional coupled PWEs. Through decomposing the solution of the corresponding eigenvalue equation for the original PWE into an ellipsoidal differential operator (EDO) and an ellipsoidal scalar operator (ESO), the new PAWE in time-space domain is constructed by applying the combination of these two solvable operators and can effectively describe P-wave features in arbitrary OA media. Furthermore, we adopt the optimal finite-difference method (FDM) to solve the newly derived PAWE. In addition, the three-dimensional (3D) hybrid absorbing boundary condition (HABC) with some reasonable modifications is developed for reducing artificial edge reflections in anisotropic media. To improve computational efficiency in 3D case, we adopt graphic processing unit (GPU) with Compute Unified Device Architecture (CUDA) instead of traditional central processing unit (CPU) architecture. Several numerical experiments for arbitrary OA models confirm that the proposed schemes can produce pure, stable and accurate P-wave modeling results and RTM images with higher computational efficiency. Moreover, the 3D numerical simulations can provide us with a comprehensive and real description of wave propagation.

Analysis of the Tangjiaxi landslide-generated waves in the Zhexi Reservoir, China, by a granular flow coupling model

NASA Astrophysics Data System (ADS)

Huang, Bolin; Yin, Yueping; Wang, Shichang; Tan, Jianmin; Liu, Guangning

2017-05-01

A rocky granular flow is commonly formed after the failure of rocky bank slopes. An impulse wave disaster may also be initiated if the rocky granular flow rushes into a river with a high velocity. Currently, the granular mass-water body coupling study is an important trend in the field of landslide-induced impulse waves. In this paper, a full coupling numerical model for landslide-induced impulse waves is developed based on a non-coherent granular flow equation, i.e., the Mih equation. In this model, the Mih equation for continuous non-coherent granular flow controls movements of sliding mass, the two-phase flow equation regulates the interaction between sliding mass and water, and the renormalization group (RNG) turbulence model governs the movement of the water body. The proposed model is validated and applied for the 2014 Tangjiaxi landslide of the Zhexi Reservoir located in Hunan Province, China, to analyze the characteristics of both landslide motion and its following impulse waves. On 16 July 2014, a rocky debris flow was formed after the failure of the Tangjiaxi landslide, damming the Tangjiaxi stream and causing an impulse wave disaster with three dead and nine missing bodies. Based on the full coupling numerical analysis, the granular flow impacts the water with a maximum velocity of about 22.5 m s-1. Moreover, the propagation velocity of the generated waves reaches up to 12 m s-1. The maximum calculated run-up of 21.8 m is close enough to the real value of 22.7 m. The predicted landslide final deposit and wave run-up heights are in a good agreement with the field survey data. These facts verify the ability of the proposed model for simulating the real impulse wave generated by rocky granular flow events.

Incredible negative values of effective electromechanical coupling coefficient for surface acoustic waves in piezoelectrics.

PubMed

Mozhaev, V G; Weihnacht, M

2000-07-01

The extraordinary case of increase in velocity of surface acoustic waves (SAW) caused by electrical shorting of the surface of the superstrong piezoelectric crystal potassium niobate, KNbO3, is numerically found. The explanation of this effect is based on considering SAWs as coupled Rayleigh and Bleustein-Gulyaev modes. A general procedure of approximate decoupling of the modes is suggested for piezoelectric crystals of arbitrary anisotropy. The effect under study takes place when the phase velocity of uncoupled sagittally polarized Rayleigh waves is intermediate between the phase velocities of uncoupled shear-horizontal Bleustein Gulyaev waves at the free and metallized surfaces. In this case, the metallization of the surface by an infinitely thin layer may cause a crossover of the velocity curves of the uncoupled waves. The presence of the mode coupling results in splitting of the curves with transition from one uncoupled branch to the other. This transition is responsible for the increase in SAW velocity, which appears to be greater than its common decrease produced by electrical shorting of the substrate surface.

Wave Coupling in the Atmosphere-Ionosphere System

NASA Astrophysics Data System (ADS)

Forbes, J. M.

2016-12-01

Vertically-propagating solar and lunar tides, Kelvin waves, gravity waves (GW) and planetary waves (PW) constitute the primary mechanism for transmitting lower atmosphere variability to the upper atmosphere and ionosphere. Vertically propagating waves grow exponentially with height into the more rarified atmosphere where they dissipate, deposit net momentum and heat, and induce net constituent transport. Some waves penetrate to the base of the exosphere (ca. 500-600 km). Over the past decade, a mature knowledge of the tidal part of the spectrum has emerged, in an average or climatological sense, up to about 110 km. This knowledge has largely accrued as a result of remote sensing observations made from the TIMED satellite. These observations have also enabled limited studies on day-to-day variability of atmospheric tides, the PW and Kelvin wave spectra up to 110 km, and PW-tide coupling. Complementary ionospheric observations made by GPS receivers, COSMIC, CHAMP, and ROCSAT contain signatures of plasma redistributions induced by these waves, and ionosphere-thermosphere (IT) general circulation models have been developed that provide a corroborating theoretical foundation. Pioneering theoretical and modeling work also demonstrate the importance of the GW part of the spectrum on thermosphere circulation and thermal structure. While significant strides have been made, critical shortcomings in our understanding of atmosphere-IT coupling remain. In particular, we are practically absent any observations of the vertical evolution and dissipation of the wave spectrum between 100 and 200 km, which is also the region where electric fields and currents are generated by dynamo action. Moreover, the day-to-day variability of the wave spectrum and secondary wave generation remain to be quantified in this critical region. In this talk, the above progress and knowledge gaps will be examined in light of imminent and potential future missions.

New classes of solutions in the coupled PT symmetric nonlocal nonlinear Schrödinger equations with four wave mixing

NASA Astrophysics Data System (ADS)

Vinayagam, P. S.; Radha, R.; Al Khawaja, U.; Ling, Liming

2018-06-01

We investigate generalized nonlocal coupled nonlinear Schorödinger equation containing Self-Phase Modulation, Cross-Phase Modulation and four wave mixing involving nonlocal interaction. By means of Darboux transformation we obtained a family of exact breathers and solitons including the Peregrine soliton, Kuznetsov-Ma breather, Akhmediev breather along with all kinds of soliton-soliton and breather-soltion interactions. We analyze and emphasize the impact of the four-wave mixing on the nature and interaction of the solutions. We found that the presence of four wave mixing converts a two-soliton solution into an Akhmediev breather. In particular, the inclusion of four wave mixing results in the generation of a new solutions which is spatially and temporally periodic called "Soliton (Breather) lattice".

Correct definition of color singlet P-wave non-perturbative matrix element of heavy quarkonium production

NASA Astrophysics Data System (ADS)

Nayak, Gouranga C.

2017-09-01

Recently we have proved factorization of infrared divergences in NRQCD S-wave heavy quarkonium production at high energy colliders at all orders in coupling constant. One of the problem which still exists in the higher order pQCD calculation of color singlet P-wave heavy quarkonium production/anihillation is the appearance of noncanceling infrared divergences due to real soft gluons exchange, although no such infrared divergences are present in the color singlet S-wave heavy quarkonium. In this paper we find that since the non-perturbative matrix element of the color singlet P-wave heavy quarkonium production contains derivative operators, the gauge links are necessary to make it gauge invariant and be consistent with the factorization of such non-canceling infrared divergences at all orders in coupling constant.

Models for short-wave instability in inviscid shear flows

NASA Astrophysics Data System (ADS)

Grimshaw, Roger

1999-11-01

The generation of instability in an invsicid fluid occurs by a resonance between two wave modes, where here the resonance occurs by a coincidence of phase speeds for a finite, non-zero wavenumber. We show that in the weakly nonlinear limit, the appropriate model consists of two coupled equations for the envelopes of the wave modes, in which the nonlinear terms are balanced with low-order cross-coupling linear dispersive terms rather than the more familiar high-order terms which arise in the nonlinear Schrodinger equation, for instance. We will show that this system may either contain gap solitons as solutions in the linearly stable case, or wave breakdown in the linearly unstable case. In this latter circumstance, the system either exhibits wave collapse in finite time, or disintegration into fine-scale structures.

Solvable model of spiral wave chimeras.

PubMed

Martens, Erik A; Laing, Carlo R; Strogatz, Steven H

2010-01-29

Spiral waves are ubiquitous in two-dimensional systems of chemical or biological oscillators coupled locally by diffusion. At the center of such spirals is a phase singularity, a topological defect where the oscillator amplitude drops to zero. But if the coupling is nonlocal, a new kind of spiral can occur, with a circular core consisting of desynchronized oscillators running at full amplitude. Here, we provide the first analytical description of such a spiral wave chimera and use perturbation theory to calculate its rotation speed and the size of its incoherent core.

Activity of convective coupled equatorial wave in tropical Tropopause layer in reanalysis and high-top CMIP5 models

NASA Astrophysics Data System (ADS)

Harza, Alia; Lubis, Sandro W.; Setiawan, Sonni

2018-05-01

The activity of convectively coupled equatorial waves (CCEWs), including Kelvin waves, Mixed Rossby-Gravity (MRG), and Equatorial Rossby (ER), in the tropical tropopause layer (TTL) is investigated in the Reanalysis and nine high-top CMIP5 models using the zonal wave number-frequency spectral analysis with equatorially symmetric-antisymmetric decomposition. We found that the TTL activities in the high-top CMIP5 models show significant difference among the high-top CMIP5 models with respect to the observation. The MIROC and HadGEM2-CC models work best in simulating Kelvin wave in the TTL, while the HadGEM2-CC and MPI-ESM-LR models work best in simulating MRG waves. The ER waves in TTL are best simulated in the MRI-CGCM model. None of the models are good in simulating all waves at once. It is concluded that the broad range of wave activity found in the different CMIP5 models depend on the convective parameterization used by each model and the representation of the tropical stratosphere variability, including the QBO.

Stability of post-fertilization traveling waves

NASA Astrophysics Data System (ADS)

Flores, Gilberto; Plaza, Ramón G.

This paper studies the stability of a family of traveling wave solutions to the system proposed by Lane et al. [D.C. Lane, J.D. Murray, V.S. Manoranjan, Analysis of wave phenomena in a morphogenetic mechanochemical model and an application to post-fertilization waves on eggs, IMA J. Math. Appl. Med. Biol. 4 (4) (1987) 309-331], to model a pair of mechanochemical phenomena known as post-fertilization waves on eggs. The waves consist of an elastic deformation pulse on the egg's surface, and a free calcium concentration front. The family is indexed by a coupling parameter measuring contraction stress effects on the calcium concentration. This work establishes the spectral, linear and nonlinear orbital stability of these post-fertilization waves for small values of the coupling parameter. The usual methods for the spectral and evolution equations cannot be applied because of the presence of mixed partial derivatives in the elastic equation. Nonetheless, exponential decay of the directly constructed semigroup on the complement of the zero eigenspace is established. We show that small perturbations of the waves yield solutions to the nonlinear equations decaying exponentially to a phase-modulated traveling wave.