DEFF Research Database (Denmark)
Christensen, Poul Rind; Kirketerp, Anne
2006-01-01
The paper shortly reveals the history of a small school - the KaosPilots - dedicated to educate young people to carriers as entrepreneurs. In this contribution we want to explore how the KaosPilots managed to break the waves of institutionalised concepts and practices of teaching entrepreneurship...
Physicochemical and Optical Characterization of Aerosol Fields from Coastal Breaking Waves
2016-06-07
difference in offshore topography mentioned above we might expect that the effects of breaking waves will be more pronounced when winds originate...in the shore break. Also note the strong relative increase in scattering just before [55.75] and just after [56.5] the wind switches to offshore flow...that can be described in terms of coastline properties and basic meteorological/oceanic parameters such as wind speed, wind direction, fetch, tides
DEFF Research Database (Denmark)
Christensen, Poul Rind; Kirketerp, Anne
2006-01-01
The paper shortly reveals the history of a small school - the KaosPilots - dedicated to educate young people to carriers as entrepreneurs. In this contribution we want to explore how the KaosPilots managed to break the waves of institutionalised concepts and practices of teaching entrepreneurship....... Following the so-called 'Dogma' concept developed by Danish filmmakers, this contribution aim to explore the key elements making up the recipes guiding the entrepreneurship training program exercised by the school. Key factors forming a community of learning practice are outlined as well as the critical...... pedagogical elements on which the education in entrepreneurship rests....
Sediment transport under breaking waves
DEFF Research Database (Denmark)
Christensen, Erik Damgaard; Hjelmager Jensen, Jacob; Mayer, Stefan
2000-01-01
generated at the surface where the wave breaks as well as the turbulence generated near the bed due to the wave-motion and the undertow. In general, the levels of turbulent kinetic energy are found to be higher than experiments show. This results in an over prediction of the sediment transport. Nevertheless...
A Boussinesq Equation-Based Model for Nearshore Wave Breaking
Institute of Scientific and Technical Information of China (English)
余建星; 张伟; 王广东; 杨树清
2004-01-01
Based on the wave breaking model by Li and Wang (1999), this work is to apply Dally' s analytical solution to the wave-height decay irstead of the empirical and semi-empirical hypotheses of wave-height distribution within the wave breaking zone. This enhances the applicability of the model. Computational results of shoaling, location of wave breaking, wave-height decay after wave breaking, set-down and set-up for incident regular waves are shown to have good agreement with experimental and field data.
DEFF Research Database (Denmark)
Bredmose, Henrik; Peregrine, D.H.; Bullock, G.N.
2009-01-01
for a homogeneous mixture of incompressible liquid and ideal gas. This enables a numerical description of both trapped air pockets and the propagation of pressure shock waves through the aerated water. An exact Riemann solver is developed to permit a finite-volume solution to the flow model with smallest possible...... local error. The high pressures measured during wave impacts on a breakwater are reproduced and it is shown that trapped air can be compressed to a pressure of several atmospheres. Pressure shock waves, reflected off nearby surfaces such as the seabed, can lead to pressures comparable with those...
Breaking Wave Characteristics and Breaking Wave Forces on Slender Cylinders
Chella, Mayilvahanan Alagan
2016-01-01
Offshore wind farms have become an increasingly important source of clean and renewable energy. Most recent offshore wind farms are deployed close to the coast in shallow waters. One of the major factors influencing the initial investment of this technology is the design of the substructure and foundation. The physical processes associated with the non-linear shallow water hydrodynamics are rather complex since the wave motion is strongly influenced by the seabed. Breaking wave...
Kinematic criterion for breaking of shoaling waves
Liberzon, Dan; Itay, Uri
2016-11-01
Validity of a kinematic criterion for breaking of shoaling waves was examined experimentally. Results obtained by simultaneous measurements of water surface velocity by PTV and of the propagation velocity of a steep crest up to the point of breaking inception during shoaling will be reported. The experiments performed in a large wave tank examining breaking behavior of gentle spillers during shoaling on three different slopes suggest a validity of the recently proposed kinematic criterion. The breaking inception was found to occur when the horizontal velocity of the water surface on the steep (local steepness of 0.41-0.6) crest reaches a threshold value of 0.85-0.95 of that of the crest propagation. The exact moment and position of breaking inception detected using a Phase Time Method (PTM), characterizing a unique shape of the local frequency fluctuations at the inception. Future implementation of the PTM method for detection of breaking events in irregular wave fields will be discussed. Supported by German-Israeli Foundation for Scientific Research and Development (GIF) Grant #2019392.
Numerical study of airflow over breaking waves
Yang, Zixuan; Shen, Lian
2016-11-01
We present direct numerical simulation (DNS) results on airflow over breaking waves. Air and water are simulated as a coherent system. The initial condition for the simulation is a fully-developed turbulent airflow over strongly-forced steep waves. The airflow is driven by a shear stress at the top. The effects of the initial wave steepness and wave age are studied systematically. Because wave breaking is an unsteady process, we use ensemble averaging of a large number of runs to obtain turbulent statistics. Simulation results show that the airflow above does not see the wave trough during wave breaking. Vortex structures at different stages of wave breaking are analyzed based on a linear stochastic estimation method. It is found that the wave breaking alters the pattern of vortex structures.
A laboratory study of breaking waves
Directory of Open Access Journals (Sweden)
Jaros³aw Têgowski
2004-09-01
Full Text Available This paper deals with some aspects of the wave-breaking phenomenon. The objectives were to study wave-breaking criteria, and the probability of whitecap coverage under fully controlled wave conditions. An additional task was to in vestigate the characteristic spectral features of the noise produced by breaking waves and the acoustic energy generated during wave breaking events. A controlled experiment was carried out in the Ocean Basin Laboratory at MARINTEK, Trondheim (Norway. Waves were generated by a computer-controlled multi-flap wave maker, which reproduced a realistic pattern of the sea surface for the prescribed spectra. Using wave staff recordings and photographic techniques, correlations between the breaking parameters and the radiated acoustic emissions were established.
Nonlinear wave breaking in self-gravitating viscoelastic quantum fluid
Energy Technology Data Exchange (ETDEWEB)
Mitra, Aniruddha, E-mail: anibabun@gmail.com [Center for Plasma Studies, Department of Instrumentation Science, Jadavpur University, Kolkata, 700 032 (India); Roychoudhury, Rajkumar, E-mail: rajdaju@rediffmail.com [Advanced Centre for Nonlinear and Complex Phenomena, 1175 Survey Park, Kolkata 700075 (India); Department of Mathematics, Bethune College, Kolkata 700006 (India); Bhar, Radhaballav [Center for Plasma Studies, Department of Instrumentation Science, Jadavpur University, Kolkata, 700 032 (India); Khan, Manoranjan, E-mail: mkhan.ju@gmail.com [Center for Plasma Studies, Department of Instrumentation Science, Jadavpur University, Kolkata, 700 032 (India)
2017-02-12
The stability of a viscoelastic self-gravitating quantum fluid has been studied. Symmetry breaking instability of solitary wave has been observed through ‘viscosity modified Ostrovsky equation’ in weak gravity limit. In presence of strong gravitational field, the solitary wave breaks into shock waves. Response to a Gaussian perturbation, the system produces quasi-periodic short waves, which in terns predicts the existence of gravito-acoustic quasi-periodic short waves in lower solar corona region. Stability analysis of this dynamical system predicts gravity has the most prominent effect on the phase portraits, therefore, on the stability of the system. The non-existence of chaotic solution has also been observed at long wavelength perturbation through index value theorem. - Highlights: • In weak gravitational field, viscoelastic quantum fluid exhibits symmetry breaking instability. • Gaussian perturbation produces quasi-periodic gravito-acoustic waves into the system. • There exists no chaotic state of the system against long wavelength perturbations.
Improving Short Wave Breaking Behavior In Surfbeat Models
Roelvink, J.; Daly, C.; Vandongeren, A. R.; van Thiel de Vries, J.; McCall, R.
2009-12-01
C. Obviously this has important consequences for the forcing of both long waves and mean currents. In our presentation we will show results of comparisons of both formulations. References. Arcilla, A.S., Roelvink, J.A., O'Connor, B.A. Reniers, A., and Jimenez. J.A. The Delta Flume '93 Experiment. Coastal Dynamics '94. Arcilla, Stive and Kraus (eds), ASCE, New York, pp. 488-502. Battjes, J.A. and J.P.F.M. Janssen, (1978), Energy loss and set-up due to breaking in random waves, Proc. 16th Int. Coastal Eng. Conf., Hamburg, vol. 1: 569-587. Dally, W.R. (1992) Random breaking waves: Field verification of a wave-by-wave algorithm for engineering application. Coastal Engineering, Volume 16, Issue 4, March 1992, Pages 369-397. Roelvink, Dano, Ad Reniers, Ap van Dongeren, Jaap van Thiel de Vries, Robert McCall, Jamie Lescinski. Modelling storm impacts on beaches, dunes and barrier islands, Coast. Eng. (2009), doi:10.1016/j.coastaleng.2009.08.006 Roelvink, J.A. Dissipation in random wave groups incident on a beach. Coastal Eng., 19 (1993) pp. 127-150.
Large eddy simulation of breaking waves
DEFF Research Database (Denmark)
Christensen, Erik Damgaard; Deigaard, Rolf
2001-01-01
is described by large eddy simulation where the larger turbulent features are simulated by solving the flow equations, and the small scale turbulence that is not resolved by the flow model is represented by a sub-grid model. A simple Smagorinsky sub-grid model has been used for the present simulations......A numerical model is used to simulate wave breaking, the large scale water motions and turbulence induced by the breaking process. The model consists of a free surface model using the surface markers method combined with a three-dimensional model that solves the flow equations. The turbulence....... The incoming waves are specified by a flux boundary condition. The waves are approaching in the shore-normal direction and are breaking on a plane, constant slope beach. The first few wave periods are simulated by a two-dimensional model in the vertical plane normal to the beach line. The model describes...
Multiscale Simulation of Breaking Wave Impacts
DEFF Research Database (Denmark)
Lindberg, Ole
-distance based adaptivity method and redistributed via a point position filtering method. The incompressible and inviscid ALE-WLS model is applied to the following standard validation test cases: deforming elliptical drop, small amplitude standing waves and the dam break problem. The deforming elliptical drop...... and mass conservation is satisfied through a pressure-corrector type calculation of the pressure. The weighted least squares method (WLS) is combined with approximate Riemann solvers to introduce numerical smoothing of the solution around steep gradients in the velocity and pressure fields. The Poisson...... equation is solved and the pressure boundary conditions are satisfied by a generalized finite pointset method (GFPM); This provides a geometrically flexible and stable solution for the fluid pressure. The numerical approximations of these equations are performed on unstructured point distributions...
Breaking a Dark Degeneracy with Gravitational Waves
Lombriser, Lucas
2015-01-01
We identify a scalar-tensor model embedded in the Horndeski action whose cosmological background and linear scalar fluctuations are degenerate with the concordance cosmology. The model admits a self-accelerated background expansion at late times that is stable against perturbations with a sound speed attributed to the new field that is equal to the speed of light. While degenerate in scalar fluctuations, self acceleration of the model implies a present cosmological tensor mode propagation at 5% less efficient than in general relativity. These discrepancies will be testable with future measurements of gravitational waves emitted by events at cosmological distances. Hence, they can be used to break the dark degeneracy in our current observations between two fundamentally different explanations of cosmic acceleration - a cosmological constant and a scalar-tensor modification of gravity.
Numerical Study on Breaking Criteria for Solitary Waves
Institute of Scientific and Technical Information of China (English)
Chung-ren CHOU; Ruey-syan SHIH; John Z. YIM
2003-01-01
Studies of the breaking criteria for solitary waves on a slope are presented in this paper. The boundary element method is used to model the processes of shoaling and breaking of solitary waves on various slopes. Empirical formulae that can be used to characterize the breaking of solitary waves are presented. These include the breaking index, the wave height, the water depth, and the maximum particle velocity at the point of breaking. Comparisons with the results of other researches are given.
Nonlinear wave breaking in self-gravitating viscoelastic quantum fluid
Mitra, Aniruddha; Roychoudhury, Rajkumar; Bhar, Radhaballav; Khan, Manoranjan
2017-02-01
The stability of a viscoelastic self-gravitating quantum fluid has been studied. Symmetry breaking instability of solitary wave has been observed through 'viscosity modified Ostrovsky equation' in weak gravity limit. In presence of strong gravitational field, the solitary wave breaks into shock waves. Response to a Gaussian perturbation, the system produces quasi-periodic short waves, which in terns predicts the existence of gravito-acoustic quasi-periodic short waves in lower solar corona region. Stability analysis of this dynamical system predicts gravity has the most prominent effect on the phase portraits, therefore, on the stability of the system. The non-existence of chaotic solution has also been observed at long wavelength perturbation through index value theorem.
Short wave breaking effects on low frequency waves
Daly, C.; Roelvink, J.A.; Van Dongeren, A.; Van Thiel de Vries, J.S.M.; McCall, R.T.
2010-01-01
The effect of short wave breaking on low frequency waves is investigated using two breaker formulations implemented in a time-dependent numerical model (XBeach): (1) an advective-deterministic approach (ADA) and (2) the probabilistic breaker formulation of Roelvink (1993). Previous research has show
An Experimental and Computational Study of Breaking Wave Impact Forces
Fu, Thomas C; Brewton, Susan; Brucker, Kyle A; Dommermuth, Douglas G
2014-01-01
The impact forces generated by the impact of a breaking wave are poorly understood. These impulsive hydrodynamic loads to a ship's hull are of short duration relative to ship motions and buoyant wave loads and often result in extremely high pressures. The physics of breaking waves is a poorly understood, complex, multiphase phenomenon involving violent jet sprays, strong free-surface turbulence, air entrainment and bubble generation, all of which interact with the flow field and the adjacent structure. This paper will describe a set of experiments that were performed, at the Naval Surface Warfare Center, Carderock Division (NSWCCD), in 2006, to measure the hydrodynamic loads of regular nonbreaking and focused breaking waves on a 0.305 m x 0.305 m (1.0 ft x 1.0 ft) square plate and discuss the results of this study. The paper will also discuss Computational Fluid Dynamics (CFD) code predictions of breaking waves and wave impact loads. The CFD code utilized in this study is Numerical Flow Analysis (NFA).
Initial Wave Breaking Dynamics of Peregrine-Type Rogue Waves: A Numerical and Experimental Study
Peric, R; Chabchoub, A
2014-01-01
The Peregrine breather, today widely regarded as a prototype for spatio-temporally localized rogue waves on the ocean caused by nonlinear focusing, is analyzed by direct numerical simulations based on two-phase Navier-Stokes equations. A finite-volume approach with a volume of fluid method is applied to study the Peregrine breather dynamics up to the initial stages of wave breaking. The comparison of the numerical results with laboratory experiments to validate the numerical approach shows very good agreement and suggests that the chosen method is an effective tool to study modulation instability and breather dynamics in water waves with high accuracy even up to the onset of wave breaking. The numerical results also indicate some previously unnoticed characteristics of the flow fields below the water surface of breathers, which might be of significance for short-term prediction of rogue waves. Recurrent wave breaking is also observed.
Surface tension effects in breaking wave noise.
Deane, Grant B
2012-08-01
The role of surface active materials in the sea surface microlayer on the production of underwater noise by breaking waves is considered. Wave noise is assumed to be generated by bubbles formed within actively breaking whitecaps, driven into breathing mode oscillation at the moment of their formation by non-equilibrium, surface tension forces. Two significant effects associated with surface tension are identified-a reduction in low frequency noise (bubbles by fluid turbulence within the whitecap and a reduction in overall noise level due to a decrease in the excitation amplitude of bubbles associated with reduced surface tension. The impact of the latter effect on the accuracy of Weather Observations Through Ambient Noise estimates of wind speed is assessed and generally found to be less than ±1 m s(-1) for wind speeds less than 10 m s(-1) and typical values of surfactant film pressure within sea slicks.
Wave breaking in tapered holey fibers
Institute of Scientific and Technical Information of China (English)
Shuguang Li; Lei Zhang; Bo Fu; Yi Zheng; Ying Han; Xingtao Zhao
2011-01-01
We numerically study the propagation of 1-ps laser pulse in three tapered holey fibers (THFs). The curvature indices of the concave, linear, and convex tapers are 2.0, 1.0, and 0.5, respectively. The central wavelength, located in the normal dispersion regime, is 800 nm. The nonlinear coefficient of the THFs increases from the initial 0.095 m-1· W-1 to the final 0.349 m-l·W-1. Wave breaking accompanied by oscillatory structures occurs near pulse edges, and sidelobes appear in the pulse spectrum. With the increase in propagation distance z, the pulse shape becomes broader and the pulse spectrum flattens. A concave THF is advantageous to the generation of wave breaking and enables easier achievement of super fiat spectra at short lengths.%@@ We numerically study the propagation of 1-ps laser pulse in three tapered holey fibers (THFs).The curvature indices of the concave, linear, and convex tapers are 2.0, 1.0, and 0.5, respectively.The central wavelength, located in the normal dispersion regime, is 800 nm.The nonlinear coefficient of the THFs increases from the initial 0.095 m-1.W-1 to the final 0.349 m-1.W-1.Wave breaking accompanied by oscillatory structures occurs near pulse edges, and sidelobes appear in the pulse spectrum.With the increase in propagation distance z, the pulse shape becomes broader and the pulse spectrum flattens.A concave THF is advantageous to the generation of wave breaking and enables easier achievement of super flat spectra at short lengths.
Gravity with background fields and diffeomorphism breaking
Bluhm, Robert
2016-01-01
Effective gravitational field theories with background fields break local Lorentz symmetry and diffeomorphism invariance. Examples include Chern-Simons gravity, massive gravity, and the Standard-Model Extension (SME). The physical properties and behavior of these theories depend greatly on whether the spacetime symmetry breaking is explicit or spontaneous. With explicit breaking, the background fields are fixed and nondynamical, and the resulting theories are fundamentally different from Einstein's General Relativity (GR). However, when the symmetry breaking is spontaneous, the background fields are dynamical in origin, and many of the usual features of Einstein's GR still apply.
Three-Dimensional Simulations of Deep-Water Breaking Waves
Brucker, Kyle A; Dommermuth, Douglas G; Adams, Paul
2014-01-01
The formulation of a canonical deep-water breaking wave problem is introduced, and the results of a set of three-dimensional numerical simulations for deep-water breaking waves are presented. In this paper fully nonlinear progressive waves are generated by applying a normal stress to the free surface. Precise control of the forcing allows for a systematic study of four types of deep-water breaking waves, characterized herein as weak plunging, plunging, strong plunging, and very strong plunging.
Experimental Study of Wave Breaking on Gentle Slope
Institute of Scientific and Technical Information of China (English)
2000-01-01
－An experimental study of regular wave and irregular wave breaking is performed on a gentle slope of 1:200. In the experiment, asymmetry of wave profile is analyzed to determine its effect on wave breaker indices and to explain the difference between Goda and Nelson about the breaker indices of regular waves on very mild slopes. The study shows that the breaker index of irregular waves is under less influence of bottom slope i, relative water depth d/ L0 and the asymmetry of wave profile than that of regular waves. The breaker index of regular waves from Goda may be used in the case of irregular waves, while the coefficient A should be 0.15. The ratio of irregular wavelength to the length calculated by linear wave theory is 0.74. Analysis is also made on the waveheight damping coefficient of regular waves after breaking and on the breaking probability of large irregular waves.
Shear stresses and mean flow in shoaling and breaking waves
Stive, M.J.F.; De Vriend, H.J.
1994-01-01
We investigate the vertical, wave averaged distributions of shear stresses and Eulerian flow in normally incident, shoaling and breaking waves. It is found that shear stresses are solely due to wave amplitude variations, which can be caused by shoaling, boundary layer dissipation and/or breaking wav
Statistical model on the surface elevation of waves with breaking
Institute of Scientific and Technical Information of China (English)
2008-01-01
In the surface wind drift layer with constant momentum flux, two sets of the consistent surface eleva- tion expressions with breaking and occurrence conditions for breaking are deduced from the first in- tegrals of the energy and vortex variations and the kinetic and mathematic breaking criterions, then the expression of the surface elevation with wave breaking is established by using the Heaviside function. On the basis of the form of the sea surface elevation with wave breaking and the understanding of small slope sea waves, a triple composite function of real sea waves is presented including the func- tions for the breaking, weak-nonlinear and basic waves. The expression of the triple composite func- tion and the normal distribution of basic waves are the expected theoretical model for surface elevation statistics.
Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing
Prusa, Joseph M.; Smolarkiewicz, Piotr K.; Garcia, Rolando R.
1996-01-01
An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.
Breaking of Waves over a Steep Bottom Slope
DEFF Research Database (Denmark)
Jensen, Morten S.
in the hydraulic laboratory are performed. Based on the experimental tests several formulae developed. Formulae are capable of predicting the transmitted wave height and wave energy flux, respectively. Futhermore, a numerical wave model based on the extended Mild-Slope equation has been developed. The model......The thesis deals with the wave breaking process of waves propagating over a steep submerged bottom slope. The amount of energy dissipated in the wave breaking process is focused upon. An extensive number of experimental tests (>400) using regular and irregular waves breaking over a simulated reef...... is capable of generating progressive irregular waves. Wave breaking has been included using a modification of the Battjes and Janssen [1978] periodic bore approach. The results from this study be applicable in the design of coastal structures as submerged breakwaters or artificial reefs....
Numerical modelling of wind effects on breaking waves in the surf zone
Xie, Zhihua
2017-10-01
Wind effects on periodic breaking waves in the surf zone have been investigated in this study using a two-phase flow model. The model solves the Reynolds-averaged Navier-Stokes equations with the k - 𝜖 turbulence model simultaneously for the flows both in the air and water. Both spilling and plunging breakers over a 1:35 sloping beach have been studied under the influence of wind, with a focus during wave breaking. Detailed information of the distribution of wave amplitudes and mean water level, wave-height-to-water-depth ratio, the water surface profiles, velocity, vorticity, and turbulence fields have been presented and discussed. The inclusion of wind alters the air flow structure above water waves, increases the generation of vorticity, and affects the wave shoaling, breaking, overturning, and splash-up processes. Wind increases the water particle velocities and causes water waves to break earlier and seaward, which agrees with the previous experiment.
Extracting Supersymmetry-Breaking Effects from Wave-Function Renormalization
Giudice, Gian Francesco
1998-01-01
We show that in theories in which supersymmetry breaking is communicated by renormalizable perturbative interactions, it is possible to extract the soft terms for the observable fields from wave-function renormalization. Therefore all the information about soft terms can be obtained from anomalous dimensions and beta functions, with no need to further compute any Feynman diagram. This method greatly simplifies calculations which are rather involved if performed in terms of component fields. For illustrative purposes we reproduce known results of theories with gauge-mediated supersymmetry breaking. We then use our method to obtain new results of phenomenological importance. We calculate the next-to-leading correction to the Higgs mass parameters, the two-loop soft terms induced by messenger-matter superpotential couplings, and the soft terms generated by messengers belonging to vector supermultiplets.
Video measurements of fluid velocities and water levels in breaking waves
CSIR Research Space (South Africa)
Govender, K
2002-01-01
Full Text Available The cost-effective measurement of the velocity flow fields in breaking water waves, using particle and correlation image velocimetry, is described. The fluid velocities are estimated by tracking the motion of neutrally buoyant particles and aeration...
Physical Investigation of Directional Wave Focusing and Breaking Waves in Wave Basin
Institute of Scientific and Technical Information of China (English)
LIU Shu-xue; Keyyong HONG
2005-01-01
An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are studied. The distribution of maximum amplitude and the evolution of time series and spectra during wave packet propagation and the variation of water surface parameters are extensively investigated. The results reveal that the characteristics of focusing waves are significantly influenced by wave directionality and that the breaking criteria for directional waves are distinctly different from those for unidirectional waves.
A Comparison of Measured and Predicted Wave-Impact Pressures from Breaking and Non-breaking Waves
Fullerton, Anne M; Brewton, Susan; Brucker, Kyle A; O'Shea, Thomas T; Dommermuth, Douglas G
2014-01-01
Impact loads from waves on vessels and coastal structures are complex and may involve wave breaking, which has made these loads difficult to estimate numerically or empirically. Results from previous experiments have shown a wide range of forces and pressures measured from breaking and nonbreaking waves, with no clear trend between wave characteristics and the localized forces and pressures that they generate. In 2008, a canonical breaking wave impact data set was obtained at the Naval Surface Warfare Center, Carderock Division, by measuring the distribution of impact pressures of incident nonbreaking and breaking waves on one face of a cube. This experimental effort was sponsored by the Office of Naval Research (ONR), under the Dynamics of Interacting Platforms Program, Program Manager Dr. Ron Joslin. The effects of wave height, wavelength, face orientation, face angle, and submergence depth were investigated. Additionally, a limited number of runs were made at low forward speeds, ranging from about 0.5 to 2...
Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking
Leifer, I.; Caulliez, G.; Leeuw, G. de
2007-01-01
Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened w
Breaking wave impacts on offshore wind turbine foundations
DEFF Research Database (Denmark)
Bredmose, Henrik; Jacobsen, Niels Gjøl
2010-01-01
that for the impacts of spilling breakers the peak force gets smaller the more developed the breaking is. This is in qualitative agreement with a finding from shallow water impacts on vertical walls: the strongest wave loads are associated with breakers that hit the structure with slightly overturning front......Extreme wave loads from breaking waves on a monopile foundation are computed within a 3D CFD model. The wave impacts are obtained by application of focused wave groups. For a fixed position of the monopile, the focus location of the wave group is varied to produce impacts with front shapes...... that varies from early stages of breaking to broken waves. The CFD results for in-line force are compared to load estimates obtained from the Morison equation. The peak loads determined with this simple method are smaller than those of the CFD solution. The computational results appear to suggest...
Callaghan, A. H.; Deane, G. B.; Stokes, M. D.
2016-11-01
Oceanic air-entraining breaking waves fundamentally influence weather and climate through bubble-mediated ocean-atmosphere exchanges, and influence marine engineering design by impacting statistics of wave heights, crest heights, and wave loading. However, estimating individual breaking wave energy dissipation in the field remains a fundamental problem. Using laboratory experiments, we introduce a new method to estimate energy dissipation by individual breaking waves using above-water images of evolving foam. The data show the volume of the breaking wave two-phase flow integrated in time during active breaking scales linearly with wave energy dissipated. To determine the volume time-integral, above-water images of surface foam provide the breaking wave timescale and horizontal extent of the submerged bubble plume, and the foam decay time provides an estimate of the bubble plume penetration depth. We anticipate that this novel remote sensing method will improve predictions of air-sea exchanges, validate models of wave energy dissipation, and inform ocean engineering design.
Modeling of the eddy viscosity by breaking waves
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The energy loss from wave breaking and the bubble plume penetration depth are estimated. As a consequence, the vertical distribution of the turbulent kinetic energy (TKE), the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided. It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface. High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than υwl(=κu *wz), the value predicted for the wall layer scaling close to the surface, where u *w is the friction velocity in water, κ with 0.4 is the von Kármán constant, and z is the water depth, and the strength of the eddy viscosity depends both on wind speed and sea state, and decays rapidly through the depth. This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer, well above the classical values expected from the similarity theory. Deeper down, however, the effects of wave breaking on the vertical mixing become less important.
Dynamic Excitation of Monopiles by Steep and Breaking Waves: Experimental and Numerical Study
DEFF Research Database (Denmark)
Bredmose, Henrik; Slabiak, Peter; Sahlberg-Nielsen, Lasse;
2013-01-01
. The measured data for structural acceleration is analysed with respect to individual wave parameters. It is found that the largest accelerations occur for breaking waves. The measured wave field and structural response are reproduced numerically with a fully nonlinear potential flow solver for the undisturbed...... wave kinematics, combined with a finite element model with Morison-based forcing. A good overall reproduction of the wave field and structural response is achieved for two selected episodes. For some of the waves, however, the numerical response magnitude does not match the observed excitations...
Approximate equations at breaking for nearshore wave transformation coefficients
Digital Repository Service at National Institute of Oceanography (India)
Chandramohan, P.; Nayak, B.U.; SanilKumar, V.
Based on small amplitude wave theory approximate equations are evaluated for determining the coefficients of shoaling, refraction, bottom friction, bottom percolation and viscous dissipation at breaking. The results obtainEd. by these equations...
Energy dissipation through wind-generated breaking waves
Institute of Scientific and Technical Information of China (English)
ZHANG Shuwen; CAO Ruixue; XIE Lingling
2012-01-01
Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.
Experimental study of breaking and energy dissipation in surface waves
Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael
2014-11-01
We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).
Wavelength selection and symmetry breaking in orbital wave ripples
Nienhuis, Jaap H.; Perron, J. Taylor; Kao, Justin C. T.; Myrow, Paul M.
2014-10-01
Sand ripples formed by waves have a uniform wavelength while at equilibrium and develop defects while adjusting to changes in the flow. These patterns arise from the interaction of the flow with the bed topography, but the specific mechanisms have not been fully explained. We use numerical flow models and laboratory wave tank experiments to explore the origins of these patterns. The wavelength of "orbital" wave ripples (λ) is directly proportional to the oscillating flow's orbital diameter (d), with many experimental and field studies finding λ/d ≈ 0.65. We demonstrate a coupling that selects this ratio: the maximum length of the flow separation zone downstream of a ripple crest equals λ when λ/d ≈ 0.65. We show that this condition maximizes the growth rate of ripples. Ripples adjusting to changed flow conditions develop defects that break the bed's symmetry. When d is shortened sufficiently, two new incipient crests appear in every trough, but only one grows into a full-sized crest. Experiments have shown that the same side (right or left) wins in every trough. We find that this occurs because incipient secondary crests slow the flow and encourage the growth of crests on the next flank. Experiments have also shown that when d is lengthened, ripple crests become increasingly sinuous and eventually break up. We find that this occurs because crests migrate preferentially toward the nearest adjacent crest, amplifying any initial sinuosity. Our results reveal the mechanisms that form common wave ripple patterns and highlight interactions among unsteady flows, sediment transport, and bed topography.
Large Eddy Simulation for Wave Breaking in the Surf Zone
Institute of Scientific and Technical Information of China (English)
白玉川; 蒋昌波; 沈焕庭
2001-01-01
In this paper, the large eddy simulation method is used combined with the marker and cell method to study the wave propagation or shoaling and breaking process. As wave propagates into shallow water, the shoaling leads to the increase of wave height, and then at a certain position, the wave will be breaking. The breaking wave is a powerful agent for generating turbulence, which plays an important role in most of the fluid dynamic processes throughout the sarf zone, such as transformation of wave energy, generation of near-shore current and diffusion of materials. So a proper numerical model for describing the turbulence effect is needed. In this paper, a revised Smagorinsky subgrid-scale model is used to describe the turbulence effect. The present study reveals that the coefficient of the Smagorinsky model for wave propagation or breaking simulation may be taken as a varying function of the water depth and distance away from the wave breaking point. The large eddy simulation model presented in this paper has been used to study the propagation of the solitary wave in constant water depth and the shoaling of the non-breaking solitary wave on a beach. The model is based on large eddy simulation, and to track free-surface movements, the Tokyo University Modified Marker and Cell (TUMMAC) method is employed. In order to ensure the accuracy of each component of this wave mathematical model,several steps have been taken to verify calculated solutions with either analytical solutions or experimental data. For non-breaking waves, very accurate results are obtained for a solitary wave propagating over a constant depth and on a beach. Application of the model to cnoidal wave breaking in the surf zone shows that the model results are in good agreement with analytical solution and experimental data. From the present model results, it can be seen that the turbulent eddy viscosity increases from the bottom to the water surface in surf zone. In the eddy viscosity curve, there is a
One-Dimensional Horizontal Boussinesq Model Enhanced for Non-Breaking and Breaking Waves
Institute of Scientific and Technical Information of China (English)
DONG Guo-hai; MA Xiao-zhou; TENG Bin
2008-01-01
Based on a set of fully nonlinear Boussinesq equations up to the order of O(μ2, ε3μ2) (where ε is the ratio of wave amplitude to water depth and μ is the ratio of water depth to wave length) a numerical wave model is formulated. The model's linear dispersion is acceptably accurate to μ≌1.0, which is confirmed by comparisons between the simulated and measured time series of the regular waves propagating on a submerged bar. The moving shoreline is treated numerically by replacing the solid beach with a permeable beach. Run-up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves. The inclusion of wave breaking is fulfilled by introducing an eddy term in the momentum equation to serve as the breaking wave force term to dissipate wave energy in the surf zone. The model is applied to cross-shore motions of regular waves including various types of breaking on plane sloping beaches. Comparisons of the model test results comprising spatial distribution of wave height and mean water level with experimental data are presented.
A new statistical model of wave heights based on the concept of wave breaking critical zone
Institute of Scientific and Technical Information of China (English)
YANG Jiaxuan; LI Xunqiang; ZHU Shouxian; ZHANG Wenjing; WANG Lei
2015-01-01
When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calculation model of surf was derived mainly from the wave energy conservation equation and the linear wave dispersion relation, but it cannot reflect accurately the process which is a rapid increasing in wave height near the broken point. So, the concept of a surf breaking critical zone is presented. And the nearshore is divided as deep water zone, shallow water zone, surf breaking critical zone and after breaking zone. Besides, the calculation formula for the height of the surf breaking critical zone has founded based on flume experiments, thereby a new statistical calculation model on the surf has been established. Using the new model, the calculation error of wave height maximum is reduced from 17.62% to 6.43%.
A numerical study of the breaking of modulated waves generated at a wave maker
Andonowati,; Kusumawinahyu, W.M; Groesen, van E.
2006-01-01
This paper is concerned with breaking criteria for generated waves. An input in the form of a time signal is prescribed to a wave maker located at one end of a wave tank as used in hydrodynamic laboratories. The motion of this wave maker produces waves propagating into initially still water in the t
Modeling radar backscatter from breaking waves on the surface
Melief, H.W.; Greidanus, H.S.F.; Hoogeboom, P.; Genderen, P. van
2003-01-01
A model for describing radar sea clutter is proposed. It consists of two parts, an oceanographic and an electromagnetic one. The former contains swell, small capillary and gravity waves as well as breaking wave events. The latter combines ray tracing, Bragg scattering and the Method of Moments. It i
Efficient rendering of breaking waves using MPS method
Institute of Scientific and Technical Information of China (English)
WANG Qiang; ZHENG Yao; CHEN Chun; FUJIMOTO Tadahiro; CHIBA Norishige
2006-01-01
This paper proposes an approach for rendering breaking waves out of large-scale ofparticle-based simulation. Moving particle semi-implicit (MPS) is used to solve the governing equation, and 2D simulation is expanded to 3D representation by giving motion variation using fractional Brownian motion (fBm). The waterbody surface is reconstructed from the outlines of 2D simulation. The splashing effect is computed according to the properties of the particles. Realistic features of the wave are rendered on GPU, including the reflective and refractive effect and the effect of splash. Experiments showed that the proposed method can simulate large scale breaking waves efficiently.
Dynamical symmetry breaking in quantum field theories
Miransky, Vladimir A
1993-01-01
The phenomenon of dynamical symmetry breaking (DSB) in quantum field theory is discussed in a detailed and comprehensive way. The deep connection between this phenomenon in condensed matter physics and particle physics is emphasized. The realizations of DSB in such realistic theories as quantum chromodynamics and electroweak theory are considered. Issues intimately connected with DSB such as critical phenomenona and effective lagrangian approach are also discussed.
Breaking of Large Amplitude Electron Plasma Wave in a Maxwellian Plasma
Mukherjee, Arghya
2016-01-01
The determination of maximum possible amplitude of a coherent longitudinal plasma oscillation/wave is a topic of fundamental importance in non-linear plasma physics. The amplitudes of these large amplitude plasma waves is limited by a phenomena called wave breaking which may be induced by several non-linear processes. It was shown by Coffey [T. P. Coffey, Phys. Fluids 14, 1402 (1971)] using a "water-bag" distribution for electrons that, in a warm plasma the maximum electric field amplitude and density amplitude implicitly depend on the electron temperature, known as Coffey's limit. In this paper, the breaking of large amplitude freely running electron plasma wave in a homogeneous warm plasma where electron's velocity distribution is Maxwellian has been studied numerically using 1D Particle in Cell (PIC) simulation method. It is found that Coffey's propagating wave solutions, which was derived using a "water-bag" distribution for electrons, also represent propagating waves in a Maxwellian plasma. Coffey's wave...
Breaking Wave on a Slender Cylinder
DEFF Research Database (Denmark)
Ramirez, Jorge Robert Rodriguez; Frigaard, Peter; Andersen, Thomas Lykke
2012-01-01
CFD models are promising in predicting non-linear wave loads on fixed and floating offshore structures. The NS3 model is described in this paper and it has been validated by means of model test such as wave run-up on monopiles in regular waves. The goal for the use of the NS3 model is to make...... a detailed investigation of the effect of 2D waves on the run-up height. The focused wave is designed by choosing the phases of the linear harmonic components such that they are in phase at a certain target location. The aim of this paper is the approach on the ability of NS3 model to reproduce these focused...
Wave breaking on turbulent energy budget in the ocean surface mixed layer
Institute of Scientific and Technical Information of China (English)
SUN Qun; GUAN Changlong; SONG Jinbao
2008-01-01
As an important physical process at the air-sea interface.wave movement and breaking have a significant effect on the ocean surface mixed layer (OSML).When breaking waves occur at the ocean surface,turbulent kinetic energy (TKE) is input downwards,and a sublayer is formed near the surface and turbulence vertical mixing is intensively enhanced.A one-dimensional ocean model including the Mellor-Yamada level 2.5 turbulence closure equations was employed in our research on variations in turbulent energy budget wimin OSML.The influence of wave breaking could be introduced into the model by modifying an existing surface boundary condition of the TKE equation and specifying its input.The vertical diffusion and dissipation of TKE were effectively enhanced in the sublayer when wave breaking was considered.Turbulent energy dissipated in the sublayer was about 92.0% of the total depth-integrated dissipated TKE,which is twice higher than that of non-wave breaking.The shear production of TKE decreased bv 3.5% because the mean flow fields tended to be uniform due to wave-enhanced turbulent mixing.As a result.a new local equilibrium between diffusion and dissipation of TKE was reached in the wave-enhanced layer.Below the sublayer,the local equilibrium between shear production and dissipation of TKE agreed with the conclusion drawn from the classical law-of-the-wall (Craig and Banner,1994).
Convective Wave Breaking in the KdV Equation
Brun, Mats K
2016-01-01
The KdV equation is a model equation for waves at the surface of an inviscid incompressible fluid, and it is well known that the equation describes the evolution of unidirectional waves of small amplitude and long wavelength fairly accurately if the waves fall into the Boussinesq regime. The KdV equation allows a balance of nonlinear steepening effects and dispersive spreading which leads to the formation of steady wave profiles in the form of solitary waves and cnoidal waves. While these wave profiles are solutions of the KdV equation for any amplitude, it is shown here that there for both the solitary and the cnoidal waves, there are critical amplitudes for which the horizontal component of the particle velocity matches the phase velocity of the wave. Solitary or cnoidal solutions of the KdV equation which surpass these amplitudes feature incipient wave breaking as the particle velocity exceeds the phase velocity near the crest of the wave, and the model breaks down due to violation of the kinematic surface...
Large-field inflation and supersymmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, Wilfried; Wieck, Clemens [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Dudas, Emilian; Heurtier, Lucien [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ecole Polytechnique, Palaiseau (France). CPht
2014-07-15
Large-field inflation is an interesting and predictive scenario. Its non-trivial embedding in supergravity was intensively studied in the recent literature, whereas its interplay with supersymmetry breaking has been less thoroughly investigated. We consider the minimal viable model of chaotic inflation in supergravity containing a stabilizer field, and add a Polonyi field. Furthermore, we study two possible extensions of the minimal setup. We show that there are various constraints: first of all, it is very hard to couple an O'Raifeartaigh sector with the inflaton sector, the simplest viable option being to couple them only through gravity. Second, even in the simplest model the gravitino mass is bounded from above parametrically by the inflaton mass. Therefore, high-scale supersymmetry breaking is hard to implement in a chaotic inflation setup. As a separate comment we analyze the simplest chaotic inflation construction without a stabilizer field, together with a supersymmetrically stabilized Kaehler modulus. Without a modulus, the potential of such a model is unbounded from below. We show that a heavy modulus cannot solve this problem.
Spontaneous symmetry breaking in correlated wave functions
Kaneko, Ryui; Tocchio, Luca F.; Valentí, Roser; Becca, Federico; Gros, Claudius
2016-03-01
We show that Jastrow-Slater wave functions, in which a density-density Jastrow factor is applied onto an uncorrelated fermionic state, may possess long-range order even when all symmetries are preserved in the wave function. This fact is mainly related to the presence of a sufficiently strong Jastrow term (also including the case of full Gutzwiller projection, suitable for describing spin models). Selected examples are reported, including the spawning of Néel order and dimerization in spin systems, and the stabilization of charge and orbital order in itinerant electronic systems.
Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng
2016-11-01
We examine wave-breaking predictions ranging from shallow- to deep-water conditions using a non-hydrostatic σ-coordinate RANS model NHWAVE as described in Derakhti et al. (2016a), comparing results both with corresponding experiments and with the results of a volume-of-fluid (VOF)/Navier-Stokes solver (Ma et al., 2011; Derakhti and Kirby, 2014a,b). Our study includes regular and irregular depth-limited breaking waves on planar and barred beaches as well as steepness-limited unsteady breaking focused wave packets in intermediate and deep water. In Part 1 of this paper, it is shown that the model resolves organized wave motions in terms of free-surface evolution, spectral evolution, organized wave velocity evolution and wave statistics, using a few vertical σ-levels. In addition, the relative contribution of modeled physical dissipation and numerical dissipation to the integral breaking-induced wave energy loss is discussed. In steepness-limited unsteady breaking focused wave packets, the turbulence model has not been triggered, and all the dissipation is imposed indirectly by the numerical scheme. Although the total wave-breaking-induced energy dissipation is underestimated in the unsteady wave packets, the model is capable of predicting the dispersive and nonlinear properties of different wave packet components before and after the break point, as well as the overall wave height decay and the evolution of organized wave velocity field and power spectrum density over the breaking region. In Part 2 (Derakhti et al., 2016b), model reproduction of wave-breaking-induced turbulence and mean circulation is examined in detail. The same equations and numerical methods are used for the various depth regimes, and no ad-hoc treatment, such as imposing hydrostatic conditions, is involved in triggering breaking. Vertical grid resolution in all simulated cases is at least an order of magnitude coarser than that of typical VOF-based simulations.
Singularity and Breaking of the Third Order Stokes Waves
Institute of Scientific and Technical Information of China (English)
孙孚; 高山; 王伟; 钱成春
2003-01-01
In this paper, the fact is revealed that the surface elevation of the third order Stokes waves in implicit form could have no solution or have simultaneously a trivial one and a singular one on certain conditions. Based on this fact, the relative breaking width, a more reasonable quantity in agreement with the definition of whitecapping coverage rate, is obtained directly from the assumption that no solution means breaking. The implications of the singular solution existing in the third order stokes waves are also discussed briefly.
Slamming of a breaking wave on a wall
Shu, Jian-Jun
2014-01-01
This paper is intended to study impact forces of breaking waves on a rigid wall based on a nonlinear potential-flow theory. This is a model problem for some technologically important design issues such as the impact of breaking waves on ships, coastal and offshore structures. We are interested in the short-time successive triggering of nonlinear effects using a small-time expansion. The analytical solutions for the impact force on a rigid wall and the free-surface profile are derived.
Numerical Simulation of Sediment Transport due to Plunging Breaking Waves
DEFF Research Database (Denmark)
Pedersen, Claus
A numerical model simulating the sediment transport due to plunging breaking waves has been developed. The model is two-dimensional, assuming conditions in the long-shore direction invariable. A plunging breaker is simulated by superimposing a non-breaking wave with a jet. Based on the description...... of the sediment transport rates, a simple model describing the morphological changes has been applied to simulate the evolution of a plunge point generated vorticity included, the bottom topography from the experiments by Dette & Uliczka was not in equilibrium according to the model....
Institute of Scientific and Technical Information of China (English)
ZHANG; Shuwen; YUAN; Yeli
2004-01-01
Wave breaking statistics, such as the whitecap coverage and average volume of broken seawater, are evaluated in terms of wave parameters by use of wave breaking model (Yuan et al., 1988) taking the fifth order Stokes's wave as the analog of the original wave field. Based on the observed fact that breaking waves play an important role in the exchange of mass, momentum and energy between the atmosphere and the ocean, the influence of wave breaking on air-sea fluxes of heat and moisture is investigated. Theoretical expressions of bubble-volume flux and sea spray spectrum at the sea surface and models for bubble-induced and spray droplet-induced heat and moisture fluxes are established. This work can be taken as the basis for further understanding the mechanism of air-sea coupling and parameterization models.
Breaking strain of neutron star crust and gravitational waves.
Horowitz, C J; Kadau, Kai
2009-05-15
Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares.
Energy dissipation in breaking solitary and periodic waves
Battjes, J.A.
1986-01-01
It is well known (see Divoky et al., 1970, for a review) that on gentle slopes (slope S < 1:30, say) the wave height after breaking does not decay in proportion to the mean depth. The curve H/Hb vs h/hb is concave upwards (for plane bottom). The concavity increases with decreasing S and with inc
Around the cusp singularity and the breaking of waves
Tejerina-Risso, J
2012-01-01
We record the breaking of water waves focusing at the Huygens Cusp of a parabolic wave maker using a fast video camera at a rate of 2000 images per second. The movie shows the very early time of the water tongue plunging ahead of the wave crest. Soon after, some capillarity wavelets are clearly visible. The image analysis of these space time data permits the measurement of the expected 3/2 power of time law as dictated by the cusp singular geometry given by the Catastrophe Theory. To our knowledge this is the first time that this scaling law is measured from fluid dynamics videos.
A Numerical Simulation of a Plunging Breaking Wave
Adams, Paul; Stephens, Mike; Brucker, Kyle A; O'Shea, Thomas; Dommermuth, Douglas
2009-01-01
This article describes the fluid dynamics video, "A Numerical Simulation of a Plunging Breaking Wave", which was submitted to the gallery of fluid motion at the 2009 APS/DFD conference. The simulation was of a deep-water plunging breaking wave. It was a two-phase calculation which used a Volume of Fluid (VOF) method to simulate the interface between the two immiscible fluids. Surface tension and viscous effects were not considered. The initial wave was generated by applying a spatio-temporal pressure forcing on the free surface. The video shows the 50% isocontour of the volume fraction from several different perspectives. Significant air entrainment is observed as well as the presence of stream-wise vortex structures.
Direct bed stress measurements under solitary tsunami-type waves and breaking tsunami wave fronts
Digital Repository Service at National Institute of Oceanography (India)
JayaKumar, S.; Baldock, T.E.
in the stability of submarine sediments. Laboratory experiments were performed to obtain total shear stresses under tsunami-type breaking and non-breaking solitary waves. The total stress comprises arises from a pressure gradient force and a skin friction shear...
Electromagnetic fields and waves
Iskander, Magdy F
2013-01-01
The latest edition of Electromagnetic Fields and Waves retains an authoritative, balanced approach, in-depth coverage, extensive analysis, and use of computational techniques to provide a complete understanding of electromagnetic—important to all electrical engineering students. An essential feature of this innovative text is the early introduction of Maxwell's equations, together with the quantifying experimental observations made by the pioneers who discovered electromagnetics. This approach directly links the mathematical relations in Maxwell's equations to real experiments and facilitates a fundamental understanding of wave propagation and use in modern practical applications, especially in today's wireless world. New and expanded topics include the conceptual relationship between Coulomb's law and Gauss's law for calculating electric fields, the relationship between Biot-Savart's and Ampere's laws and their use in calculating magnetic fields from current sources, the development of Faraday's law from e...
Solitary wave shoaling and breaking in a regularized Boussinesq system
Senthilkumar, Amutha
2016-01-01
A coupled BBM system of equations is studied in the situation of water waves propagating over decreasing fluid depth. A conservation equation for mass and a wave breaking criterion valid in the Boussinesq approximation is found. A Fourier collocation method coupled with a 4-stage Runge-Kutta time integration scheme is employed to approximate solutions of the BBM system. The mass conservation equation is used to quantify the role of reflection in the shoaling of solitary waves on a sloping bottom. Shoaling results based on an adiabatic approximation are analyzed. Wave shoaling and the criterion of breaking solitary waves on a sloping bottom is studied. To validate the numerical model the simulation results are compared with those obtained by Grilli et al.[16] and a good agreement between them is observed. Shoaling of solitary waves of two different types of mild slope model systems in [8] and [13] are compared, and it is found that each of these models works well in their respective regimes of applicability.
A Microscopic View of Oil Slick Break-Up and Emulsion Formation in Breaking Waves
Law, J.; Shahrokhi, H.; Shaw, J. M.
1996-11-01
The hydrodynamic behaviour of oil spills in breaking waves determines the appropriateness and effectiveness of remedial measures during clean-up operations. Oil slicks either disperse as fine drops or form water in oil emulsions when exposed to breaking waves. However, there is little agreement with respect to the controlling variables or mechanisms for emulsification or dispersion and predictions are unreliable. For example, predicted energy dissipation rates in breaking waves are too low to account for the drop sizes encountered experimentally[1]. In this paper, we assess the impact of hydrodynamics and physical properties on the formation of dispersions or emulsions. The maximum stable drop size for dispersions arising from oil slicks and water in oil emulsions are shown to be controlled by Raleigh-Taylor instability or the prevalent local shear stress. Data from four experimental studies[2-5], with a broad range of physical properties were fitted quantitatively. As high shear events are intermittent, stable water in oil emulsions can be formed by dispersion inversion near the water air interface or by water entrained by gas bubbles passing through oil slicks. 1) Li & Garrett, 19th AMOP, Calgary AB, 1, 185-198 (1996). 2) Lin et al., Report CG-D-54-78, U.S. Coast Guard, Washington D.C. (1978). 3) Buist, MASc Thesis, University of Toronto (1979). 4) Wallace et al., 9th AMOP, Edmonton AB, 2, 421-429, June 10-12 (1986). 5) Ross Environmental Research Ltd., Ottawa ON, Report EE-96, (1987).
Dependence of Wave-Breaking Statistics on Wind Stress and Wave Development
Katsaros, Kristina B.; Atakturk, Serhad S.
1992-01-01
Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m/s. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events. Wave forcing as measured by wind stress (or friction velocity, u(sub *), squared) and by inverse wave age, u(sub *)/Cp where Cp is the phase velocity of the waves at the peak of the frequency spectrum, were found to be good prerictors of percentage of breaking crests. When combined in a two parameter regression, those two variables gave small standard deviation and had a high correlation coefficient (66 percent). The combination of u(sub *)(exp 2) and u(sub *)/Cp can be understood in physical terms. Furthermore, for the larger values of u(sub *)(exp 2) the dependence of wave braking and wave age was stronger than at the low end of the values u(sub *)(exp 2) and u(sub *)/Cp. Thus, both the level of wave development as determined by inverse wave age, which we may term relative wind effectiveness for wave forcing and the wind forcing on the water surface determine the incidence of wave breaking. Substituting U(sub 10)(sup 3.75) (which is the dependence of whitecap cover found by Monahan and coworkers) an equivalent correlation was found to the prediction by u(sub *)(exp 2). Slightly better standard deviation value and higher correlation coefficient were found by using a Reynolds number as predictor. A two-parameter regression involving u(sub *)(exp 2) and a Reynold's number proposed by Toba and his colleagues which relates u(sub *)(exp 2) and peak wave frequency, improves the correlation even more but is less easy to interpret in physical terms. The equivalent percentage of
Evanescent Wave-Assisted Symmetry Breaking of Gold Dipolar Nanoantennas
Yang, Jhen-Hong; Chen, Kuo-Ping
2016-09-01
Symmetry-breaking and scattering cancellation were observed in the dark-mode resonance of dipolar gold nanoantennas (NAs) on glass substrates coupled with oblique incidence and total internal reflection. With the assistance of evanescent waves, the coupling efficiency was twice as strong when the incidence angle was larger than the critical angle. The Hamiltonian equation and absorption spectra were used to analyze the hybridization model of symmetric dipolar gold NAs. The antibonding mode could be coupled successfully by both transverse-magnetic (TM) and transverse-electric (TE) polarizations to NAs when the dimers orientation is parallel to the propagation direction of evanescent waves.
Three-dimensional vortex structures under breaking waves
WATANABE Yasunori; Saeki, Hiroshi; Hosking, Roger J.
2005-01-01
The large-scale vortex structures under spilling and plunging breakers are investigated, using a fully three-dimensional large-eddy simulation (LES). When an overturning jet projecting from the crest in a breaking wave rebounds from the water surface ahead, the vorticity becomes unstable in a saddle region of strain between the rebounding jet and a primary spanwise vortex, resulting in spanwise undulations of the vorticity. The undulations are amplified on a braid in this saddle region, leadi...
Experimental investigation of two oil dispersion pathways by breaking waves
Li, Cheng; Katz, Joseph
2014-11-01
This experimental study focuses on generation and size distribution of airborne and subsurface oil droplets as breaking surface waves interact with a crude oil slick (MC252 surrogate). Experiments in a specialized wave tank investigate the effects of wave height and wave properties (e.g. spilling vs. plunging), as well as drastically reducing the oil-water interfacial tension by orders of magnitude by introducing dispersant (Coexist 9500-A). This dispersant is applied at varying dispersant-to-oil ratios either by premixing or surface spraying, the latter consistent with typical application. The data include high-speed visualizations of processes affecting the entrainment of subsurface oil and bubbles as well as airborne aerosols. High-speed digital holographic cinematography is employed to track the droplet trajectories, and quantify the droplet size distributions above and below the surface. Introduction of dispersants drastically reduces the size of subsurface droplets to micron and even submicron levels. Ahead of the wave, the 25 μm (our present resolution limit) to 2 mm airborne droplet trajectories are aligned with the wave direction. Behind the wave, these droplets reverse their direction, presumably due to the airflow above the wave. Supported by Gulf of Mexico Research Initiative (GoMRI).
Theoretical Study of Wave Breaking for Nonlinear Water Waves Propagating on a Sloping Bottom
Chen, Y. Y.; Hsu, H. C.; Li, M. S.
2012-04-01
In this paper, a third-order asymptotic solution in a Lagrangian framework describing nonlinear water wave propagation on the surface of a uniform sloping bottom is presented. A two-parameter perturbation method is used to develop a new mathematical derivation. The particle trajectories, wave pressure and Lagrangian velocity potential are obtained as a function of the nonlinear wave steepness and the bottom slope perturbed to third order. This theoretical solution in Lagrangian form satisfies state of the normal pressure at the free surface. The condition of the conservation of mass flux is examined in detail for the first time. The two important properties in Lagrangian coordinates, Lagrangian wave frequency and Lagrangian mean level, are included in the third-order solution. The solution can also be used to estimate the mean return current for waves progressing over the sloping bottom. The Lagrangian solution untangle the description of the features of wave shoaling in the direction of wave propagation from deep to shallow water, as well as the process of successive deformation of a wave profile and water particle trajectories leading to wave breaking. A series of experiment was conducted to validate the obtained theoretical solution. The proposed solution will be used to determine the wave shoaling and breaking process and the comparisons between the experimental and theoretical results are excellent. For example, the variations of phase velocity on sloping bottom are obtained by 7 set of two close wave gauges and the theoretical result could accurately predict the measured phase velocity. The theoretical wave breaking index can be derived by use of the kinematic stability parameter (K.P.S). The comparisons between the theory, experiment (present study, Iwagali et al.(1974), Deo et al.(2003) and Tsai et al.(2005)) and empirical formula of Goda (2004) for the breaking index(u/C) versus the relative water depth(d/L) under two different bottom slopes shows that the
Leifer, I.; Caulliez, G.; Leeuw, G.de
2006-01-01
Measurements of breaking-wave-generated bubble plumes were made in fresh (but not clean) water in a large wind-wave tunnel. To preserve diversity, a classification scheme was developed on the basis of plume dimensions and "optical density," or the plume's ability to obscure the background. Optically
Numerical Simulation of Breaking Wave Based on Higher-Order Mild Slope Equation
Institute of Scientific and Technical Information of China (English)
陶建华; 韩光
2001-01-01
The "surface roller" to simulate wave energy dissipation of wave breaking is introduced into the random wave model based on approximate parabolic mild slope equation in this paper to simulate the random wave transportation including diffraction, refraction and breaking in nearshore areas. The roller breaking random wave higher-order approximate parabolic equation model has been verified by the existing experimental data for a plane slope beach and a circularshoal, and the numerical results of random wave breaking model agree with the experimental data very well. This modelcan be applied to calculate random wave propagation from deep to shallow water in large areas near the shore over natural topography.
The gravitational wave spectrum from cosmological B-L breaking
Energy Technology Data Exchange (ETDEWEB)
Buchmüller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg (Germany); Schmitz, K., E-mail: buchmuwi@mail.desy.de, E-mail: valerie.domcke@desy.de, E-mail: kohei.kamada@desy.de, E-mail: kai.schmitz@ipmu.jp [Kavli IPMU (WPI), University of Tokyo, Kashiwa 277-8583 (Japan)
2013-10-01
Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying Ω{sub GW}h{sup 2} ∼ 10{sup −13}–10{sup −8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.
The gravitational wave spectrum from cosmological B-L breaking
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Schmitz, K. [Tokyo Univ., Kashiwa (Japan). Kavli IPMU (WPI)
2013-05-15
Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying {Omega}{sub GW}h{sup 2}{proportional_to}10{sup -13}-10{sup -8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO and BBO/DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.
Wave Energy Dissipation of Waves Breaking on a Reef with a Steep Front Slope
DEFF Research Database (Denmark)
Jensen, M.S.; Burcharth, Hans F.; Brorsen, Michael
2005-01-01
The Transformation of waves propagating over a steep bottom slope is of great importance regarding the coastal processes in the near-shore area.This study will contribute with tools to predict the dissipated wave energy for irregular waves passing a steep submerged slope. An extensive number...... of test with regular and irregular waves breaking over a steep bottom slope have been performed in the Hydraulics & Coastal Engineering Laboratory, Aalborg University. Based on these experimental data formulae have been developed capable of predicting he transmitted wave energy over steep slopes....
A Study of Two-Dimensional Unsteady Breaking Waves in Finite-Depth Water
2010-01-01
1880). [8] J. H. Duncan, “An experimental investigation of breaking waves produced by a towed hydrofoil ,” Proc. R. Soc. London, Ser. A 377, 331(1981...measured the drag per unit length due to quasi-steady breaking waves generated with a submerged hydrofoil . His measurements illustrated that the... hydrofoil . Proc. R. Soc. London Ser. A 377, 331-348. DUNCAN, J. H. 1983 The breaking and non-breaking wave resistance of a two- dimensional hydrofoil . J
Gas transfer under high wind and its dependence on wave breaking and sea state
Brumer, Sophia; Zappa, Christopher; Fairall, Christopher; Blomquist, Byron; Brooks, Ian; Yang, Mingxi
2016-04-01
Quantifying greenhouse gas fluxes on regional and global scales relies on parameterizations of the gas transfer velocity K. To first order, K is dictated by wind speed (U) and is typically parameterized as a non-linear functions of U. There is however a large spread in K predicted by the traditional parameterizations at high wind speed. This is because a large variety of environmental forcing and processes (Wind, Currents, Rain, Waves, Breaking, Surfactants, Fetch) actually influence K and wind speed alone cannot capture the variability of air-water gas exchange. At high wind speed especially, breaking waves become a key factor to take into account when estimating gas fluxes. The High Wind Gas exchange Study (HiWinGS) presents the unique opportunity to gain new insights on this poorly understood aspects of air-sea interaction under high winds. The HiWinGS cruise took place in the North Atlantic during October and November 2013. Wind speeds exceeded 15 m s-1 25% of the time, including 48 hrs with U10 > 20 m s-1. Continuous measurements of turbulent fluxes of heat, momentum, and gas (CO2, DMS, acetone and methanol) were taken from the bow of the R/V Knorr. The wave field was sampled by a wave rider buoy and breaking events were tracked in visible imagery was acquired from the port and starboard side of the flying bridge during daylight hours at 20Hz. Taking advantage of the range of physical forcing and wave conditions sampled during HiWinGS, we test existing parameterizations and explore ways of better constraining K based on whitecap coverage, sea state and breaking statistics contrasting pure windseas to swell dominated periods. We distinguish between windseas and swell based on a separation algorithm applied to directional wave spectra for mixed seas, system alignment is considered when interpreting results. The four gases sampled during HiWinGS ranged from being mostly waterside controlled to almost entirely airside controlled. While bubble-mediated transfer
Gravitational Wave - Gauge Field Oscillations
Caldwell, R R; Maksimova, N A
2016-01-01
Gravitational waves propagating through a stationary gauge field transform into gauge field waves and back again. When multiple families of flavor-space locked gauge fields are present, the gravitational and gauge field waves exhibit novel dynamics. At high frequencies, the system behaves like coupled oscillators in which the gravitational wave is the central pacemaker. Due to energy conservation and exchange among the oscillators, the wave amplitudes lie on a multi-dimensional sphere, reminiscent of neutrino flavor oscillations. This phenomenon has implications for cosmological scenarios based on flavor-space locked gauge fields.
Investigation of water wave breaking phenomena: experiment and theory
Chybicki, W.; Staroszczyk, R.
2009-09-01
The phenomenon of water wave breaking and the link between the wave breaking and the velocities of water particles on the free surface are investigated. Results of experiments carried out in a laboratory flume are presented, and then compared with predictions of a theoretical model that has also been outlined in the paper. The experiments have been conducted in a 64 m long water channel at the Institute of Hydro-Engineering of the Polish Academy of Sciences in Gdansk, Poland. The experiments have been focused on measurements of Lagrangian velocities of fluid particles on the free surface of water. The motion of the fluid was induced by a piston-type wave maker that generated short trains of mono- and bi-chromatic waves propagating in water of a mean-level depth of 40 cm, in which an underwater inclined ramp, of a slope of 10 per cent and a height of 30 cm, was mounted. The height of a generated wave was adjusted in such a way that the wave breaking occurred in a chosen location over the ramp. The wave breaking was of a spilling type. The fluid particle velocities were measured by putting floating markers (small plastic beads of densities very close to that of water) on the free surface of water, and then by recording their movements by means of a camera during the process of wave breaking. The displacements of the markers in time were determined from the analysis of their positions in successive frames of the film. In the paper also a theoretical model describing the propagation of waves over an uneven bottom is presented. The model is formulated in the Lagrangian variables. A key simplification on which the proposed theory is based is that the vertical displacements of fluid particles are related to an assumed variation of the horizontal displacements, the continuity equation, and the boundary condition at the bottom. The momentum equation, derived by applying a variational principle and making use of the latter assumptions, is equivalent to the Boussinesq
Relativistic electron beam driven longitudinal wake-wave breaking in a cold plasma
Bera, Ratan Kumar; Sengupta, Sudip; Das, Amita
2016-01-01
Space-time evolution of relativistic electron beam driven wake-field in a cold, homogeneous plasma, is studied using 1D-fluid simulation techniques. It is observed that the wake wave gradu- ally evolves and eventually breaks, exhibiting sharp spikes in the density profile and sawtooth like features in the electric field profile [1]. It is shown here that the excited wakefield is a longitudi- nal Akhiezer-Polovin mode [2] and its steepening (breaking) can be understood in terms of phase mixing of this mode, which arises because of relativistic mass variation effects. Further the phase mixing time (breaking time) is studied as a function of beam density and beam velocity and is found to follow the well known scaling presented in ref.[3].
Experiments and computation of onshore breaking solitary waves
DEFF Research Database (Denmark)
Jensen, A.; Mayer, Stefan; Pedersen, G.K.
2005-01-01
This is a combined experimental and computational study of solitary waves that break on-shore. Velocities and accelerations are measured by a two-camera PIV technique and compared to theoretical values from an Euler model with a VOF method for the free surface. In particular, the dynamics of a so......-called collapsing breaker is scrutinized and the closure between the breaker and the beach is found to be akin to slamming. To the knowledge of the authors, no velocity measurements for this kind of breaker have been previously reported....
Transverse bending waves and the breaking broomstick demonstration
Vandegrift, Guy
1997-06-01
When a broomstick is supported at both ends by two wine glasses, a strong downward blow to the center will break the stick, leaving the wine glasses undisturbed, provided care is taken to cushion the wine glasses against an initial and brief downward motion of the ends of the broomstick. This downward motion is analyzed and estimated to be about 1 mm in magnitude. Qualitative experimental evidence of this motion is easily obtained using a force probe to monitor a light and nondestructive tap to a 2-m measuring stick. The method of analysis developed here leads to a simple derivation of the dispersion relation for transverse bending waves on a long rod.
A Coupled VOF-Eulerian Multiphase CFD Model to Simulate Breaking Wave Impacts on Offshore Structures
DEFF Research Database (Denmark)
Tomaselli, Pietro; Christensen, Erik Damgaard
2016-01-01
Breaking wave-induced loads on offshore structures can be extremely severe. The air entrainment mechanism during the breaking process plays a not well-known role in the exerted forces. This paper present a CFD solver, developed in the Open-FOAM environment, capable of simulating the wave breaking...
Bubble size distribution in surface wave breaking entraining process
Institute of Scientific and Technical Information of China (English)
HAN; Lei; YUAN; YeLi
2007-01-01
From the similarity theorem,an expression of bubble population is derived as a function of the air entrainment rate,the turbulent kinetic energy (TKE) spectrum density and the surface tension.The bubble size spectrum that we obtain has a dependence of a-2.5+nd on the bubble radius,in which nd is positive and dependent on the form of TKE spectrum within the viscous dissipation range.To relate the bubble population with wave parameters,an expression about the air entrainment rate is deduced by introducing two statistical relations to wave breaking.The bubble population vertical distribution is also derived,based on two assumptions from two typical observation results.
Impact of an oblique breaking wave on a wall
Shu, Jian-Jun
2014-01-01
The intention of this paper is to study impact force of an oblique-angled slamming wave acting on a rigid wall. In the present study the analytical approach is pursued based on a technique proposed by the author. A nonlinear theory in the context of potential flow is presented for determining accurately the free-surface profiles immediately after an oblique breaking wave impingement on the rigid vertical wall that suddenly starts from rest. The small-time expansion is taken as far as necessary to include the accelerating effect. The analytical solutions for the free-surface elevation are derived up to the third order. The results derived in this paper are of particular interest to the marine and offshore engineering industries, which will find the information useful for the design of ships, coastal and offshore.
Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng
2016-11-01
Field-scale modeling of wave-breaking-induced turbulence and mean circulation is still challenging. Although Boussinesq-type models have been successfully used to study field-scale wave transformation and wave-breaking-driven circulation, they cannot provide turbulence or the vertical structure of the velocity field. In addition, the applicability of such models is limited to shallow water. In Part 1 (Derakhti et al., 2016b) of this study, we showed that the non-hydrostatic σ-coordinate RANS model NHWAVE, as described by Derakhti et al. (2016a), accurately predicts organized wave motions and total wave-breaking-induced energy dissipation from deep-water up to the swash zone using a few vertical σ-layers. In this paper, our goal is to examine what level of detail of wave-breaking-induced turbulence and mean circulation, both in depth- and steepness-limited breaking waves, can be reproduced by NHWAVE. Further, effects of modeled turbulent eddy viscosity on the predicted time-averaged velocity distribution is discussed. We establish that NHWAVE is capable of predicting the structure of the mean velocity and vorticity fields including large-scale breaking-induced coherent vortices in deep-water breaking events; where the absence of turbulence-induced eddy viscosity results in the overprediction of the velocity and vorticity field in the breaking region. We show that NHWAVE reduces the required CPU time up to two orders of magnitude in comparison with a comparable VOF-based simulation.
Mediation of Supersymmetry Breaking via Anti-Generation Fields
Ito, M
2000-01-01
In the context of the weakly coupled heterotic string, we propose a new model of mediating supersymmetry breaking. The breakdown of supersymmetry in the hidden sector is transmitted to anti-generation fields via gravitational interactions. Subsequent transmission of the breaking to the MSSM sector occurs via gauge interactions. It is shown that the mass spectra of superparticles are phenomenologically viable.
Symmetry breaking and cosmic acceleration in scalar field models
Sadjadi, M Mohseni; Sepangi, H R
2015-01-01
We study the possible role of symmetry breaking in the onset of the acceleration of the Universe in a scalar field dark energy model. We propose a new scenario in which acceleration of the Universe is driven by a positive potential produced by means of symmetry breaking.
The Gravitational Wave Spectrum from Cosmological B-L Breaking
Buchmuller, Wilfried; Kamada, Kohei; Schmitz, Kai
2013-01-01
Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying \\Omega_GW h^2 ~ 10^{-13} - 10^{-8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eL...
Wave breaking and shock waves for a periodic shallow water equation.
Escher, Joachim
2007-09-15
This paper is devoted to the study of a recently derived periodic shallow water equation. We discuss in detail the blow-up scenario of strong solutions and present several conditions on the initial profile, which ensure the occurrence of wave breaking. We also present a family of global weak solutions, which may be viewed as global periodic shock waves to the equation under discussion.
Diffusion, intermittency and scaling in wave breaking turbulence
Redondo, J. M.; Mosso, C.; Marino, R.
2009-04-01
Measurements of 3D turbulent velocity have been made near the coast for a variety of weather conditions in the wave breaking zone, and these values have been compared with flume measurements at a 100m long wave tank. There is a strong dependence of the integral lenthscales with the Wave Reynolds number as well as with the position and the wind, quantified through the friction velocity from wind profiles measured at the coastline. Earlier results have been published in Bezerra et al. (1998) and Rodriguez et al(1999). Several effects are important and give several decades of variation of eddy diffusivities measured near the coastline (between 0.0001 and 2 m2s-1)Inman et al.(1971), Zeitler(1976). Measurements of electromagnetic and ADV velocity measurements of the Coastal wave generated turbulence are compared in order to invest the scaling and intermittency of the turbulence produced by wave breaking. The velocity measurements were performed with an array of electromagnetic sensors that could be placed along the coastline in a stainless steel sledge. Rodriguez et al.(1994,1999) showed a parabolic shape of cross-shore diffusivity values but present analysis also shows the crosshore dependence of the intermittency as well as changes in the spectral slopes. Bezerra M.O., Diez M., Medeiros C., Rodriguez A., Bahia E. Sanchez-Arcilla A. y Redondo J.M. (1998) Study on the influence of waves on coastal diffusion using image analysis Applied Scientific Research. 59, 191-204. Rodriguez A., Sanchez-Arcilla A., Redondo J.M and C. Mosso (1999) Macroturbulence measurements with electromagnetic and ultrasonic sensors: a comparison under high-turbulent flows. Experiments in Fluids, 27, 31-42. Inman, D. L.; Tait, R.J.; Nordstrom, C.E. (1971). Mixing in the surf zone. Journal of Geophysical Research, vol 76, n° 15, 3493 - 3514. Zeidler, R. B. (1976) Coastal dispersion of pollutants, Journal of the Waterways Harbors and Coastal Engineering Division, 235 - 254 p. Rodriguez, A.; Bahia
Analytical Derivation of Three Dimensional Vorticity Function for wave breaking in Surf Zone
Dutta, R
2015-01-01
In this report, Mathematical model for generalized nonlinear three dimensional wave breaking equations was de- veloped analytically using fully nonlinear extended Boussinesq equations to encompass rotational dynamics in wave breaking zone. The three dimensional equations for vorticity distributions are developed from Reynold based stress equations. Vorticity transport equations are also developed for wave breaking zone. This equations are basic model tools for numerical simulation of surf zone to explain wave breaking phenomena. The model reproduces most of the dynamics in the surf zone. Non linearity for wave height predictions is also shown close to the breaking both in shoaling as well as surf zone. Keyword Wave breaking, Boussinesq equation, shallow water, surf zone. PACS : 47.32-y
Numerical studies of large-amplitude internal waves shoaling and breaking at shelf slopes
Thiem, Øyvind; Berntsen, Jarle
2009-12-01
Hydro carbon fields beyond the shelf break are presently being explored and developed, which has increased the scientific focus in this area. Measurements from the slopes reveal large variability in temperature and velocity, and some of the observed events are due to interactions between large-amplitude oscillations of the thermocline and the topography. The present study focuses on the strong currents that are generated near the seabed during shoaling and breaking of internal waves along shelf slopes. The parameter regime used is similar to the one for the Nordic Seas. The results show that, during shoaling of large internal waves along (gentle) slopes, the energy is transferred towards smaller scales and strong velocities (over 1 m s - 1) can be generated. To resolve all scales involved is still not feasible, and therefore, the model results are sensitive to the grid size and the subgrid scale closure.
Directory of Open Access Journals (Sweden)
Jong-In Lee
2014-01-01
Full Text Available Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r2>0.8 the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A0/h0<0.07 in this study. However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification.
van der Zanden, J.; van der A, D. A.; Hurther, D.; Cáceres, I.; O'Donoghue, T.; Ribberink, J. S.
2016-08-01
Detailed measurements are presented of velocities and turbulence under a large-scale regular plunging breaking wave in a wave flume. Measurements were obtained at 12 cross-shore locations around a mobile medium-sand breaker bar. They focused particularly on the dynamics of the wave bottom boundary layer (WBL) and near-bed turbulent kinetic energy (TKE), measured with an Acoustic Concentration and Velocity Profiler (ACVP). The breaking process and outer flow hydrodynamics are in agreement with previous laboratory and field observations of plunging waves, including a strong undertow in the bar trough region. The WBL thickness matches with previous studies at locations offshore from the bar crest, but it increases near the breaking-wave plunge point. This relates possibly to breaking-induced TKE or to the diverging flow at the shoreward slope of the bar. Outer flow TKE is dominated by wave breaking and exhibits strong spatial variation with largest TKE above the breaker bar crest. Below the plunge point, breaking-induced turbulence invades the WBL during both crest and trough half cycle. This results in an increase in the time-averaged TKE in the WBL (with a factor 3) and an increase in peak onshore and offshore near-bed Reynolds stresses (with a factor 2) from shoaling to breaking region. A fraction of locally produced TKE is advected offshore over a distance of a few meters to shoaling locations during the wave trough phase, and travels back onshore during the crest half cycle. The results imply that breaking-induced turbulence, for large-scale conditions, may significantly affect near-bed sediment transport processes.
A microwave emissivity model of sea surface under wave breaking
Institute of Scientific and Technical Information of China (English)
Wei En-Bo; Ge Yong
2005-01-01
With the effective medium approximation theory of composites, a remedial model is proposed for estimating the microwave emissivity of sea surface under wave breaking driven by strong wind on the basis of an empirical model given by Pandey and Kakar. In our model, the effects of the shapes of seawater droplets and the thickness of whitecap layer (i.e. a composite layer of air and sea water droplets) over the sea surface on the microwave emissivity are investigated by calculating the effective dielectric constant of whitecaps layer. The wind speed is included in our model, and the responses of water droplets shapes, such as sphere and ellipsoid, to the emissivity are also discussed at different microwave frequencies. The model is in good agreement with the experimental data of microwave emissivity of sea surface at microwave frequencies of 6.6, 10.7 and 37GHz.
Breaking phase focused wave group loads on offshore wind turbine monopiles
Ghadirian, A.; Bredmose, H.; Dixen, M.
2016-09-01
The current method for calculating extreme wave loads on offshore wind turbine structures is based on engineering models for non-breaking regular waves. The present article has the aim of validating previously developed models at DTU, namely the OceanWave3D potential flow wave model and a coupled OceanWave3D-OpenFOAM solver, against measurements of focused wave group impacts on a monopile. The focused 2D and 3D wave groups are reproduced and the free surface elevation and the in-line forces are compared to the experimental results. In addition, the pressure distribution on the monopile is examined at the time of maximum force and discussed in terms of shape and magnitude. Relative pressure time series are also compared between the simulations and experiments and detailed pressure fields for a 2D and 3D impact are discussed in terms of impact type. In general a good match for free surface elevation, in-line force and wave-induced pressures is found.
The wave breaking phenomena as a tool for environmental friendly shore protection.
Kabdaşli, M S; Türker, U
2002-01-01
An experimental study was carried out to evaluate the rate of energy dissipation during wave breaking and the dependence of dissipation on the breaker type. The splash mechanism that occurs just after the breaking is also examined based on knowledge of external and macroscopic properties of breakers only. During the experiments, it is observed that most of the energy is dissipated while the water jet formed during wave breaking hits the water surface. It has been found that the percentage of wave energy dissipated in plunging type waves is larger than in spilling type waves.
Refined Source Terms in WAVEWATCH III with Wave Breaking and Sea Spray Forecasts
2015-09-30
shallow water outside the surf zone. After careful testing within a comprehensive suite of test bed cases, these refined source terms will be...including significant wave height, wave periods, wave train evolution, breaking wave probabilities, spectral crest length per unit area distributions...formulating the breaking strength b(k) in terms of the square root of the normalised saturation above a threshold, the Λ(k) values are obtained from
DEFF Research Database (Denmark)
Martinelli, Luca; Lamberti, Alberto; Frigaard, Peter
2007-01-01
This paper addresses wave forces applied to vertical caisson breakwaters. Design diagrams are proposed to evaluate the reduction of the breaker wave force with increasing horizontal length of the units. A model in 1:100 scale of a typical Italian vertical breakwater was tested under...... multidirectional waves, causing mainly spilling and occasionally plunging breakers, in the CRF-LSF (Wallingford, UK) wave basin. Seven adjacent modules were instrumented with synchronized force transducers. Pulsating and breaking loads were distinguished on the basis of the frequency content and the spatial...... correlation of the force per unit length was fitted to a single or a double bell shaped distribution. The experimental autocorrelation function for pulsating loads agrees with theoretical solutions; for breaking waves it has a Taylor microscale which is approximately 7% of wavelength, only slightly dependent...
Suction removal of sediment from between armor blocks. III: Breaking waves
DEFF Research Database (Denmark)
Nielsen, Anders Wedel; Sumer, B. Mutlu; Fredsøe, Jørgen
2012-01-01
When a sediment beach covered by stones or an armor layer is exposed to breaking waves, the turbulence generated by the breaking waves can cause mobilization and removal of the sediment underneath the stones. In two earlier studies by the Technical University of Denmark (DTU)-group, the suction...
Generation of fast electrons by breaking of a laser-induced plasma wave
Trines, Rmgm; Goloviznin, V. V.; Kamp, L. P. J.; Schep, T. J.
2001-01-01
A one-dimensional model for fast electron generation by an intense, nonevolving laser pulse propagating through an underdense plasma has been developed. Plasma wave breaking is considered to be the dominant mechanism behind this process, and wave breaking both in front of and behind the laser pulse
Lorentz symmetry breaking as a quantum field theory regulator
Visser, Matt
2009-01-01
Perturbative expansions of relativistic quantum field theories typically contain ultraviolet divergences requiring regularization and renormalization. Many different regularization techniques have been developed over the years, but most regularizations require severe mutilation of the logical foundations of the theory. In contrast, breaking Lorentz invariance, while it is certainly a radical step, at least does not damage the logical foundations of the theory. We shall explore the features of a Lorentz symmetry breaking regulator in a simple polynomial scalar field theory, and discuss its implications. We shall quantify just "how much" Lorentz symmetry breaking is required to fully regulate the theory and render it finite. This scalar field theory provides a simple way of understanding many of the key features of Horava's recent article [arXiv:0901.3775 [hep-th
Direct Simulations of Wind-Driven Breaking Ocean Waves with Data Assimilation
Dommermuth, Douglas G; Tran, Vu H; Valenciano, Miguel A
2014-01-01
A formulation is developed to assimilate ocean-wave data into the Numerical Flow Analysis (NFA) code. NFA is a Cartesian-based implicit Large-Eddy Simulation (LES) code with Volume of Fluid (VOF) interface capturing. The sequential assimilation of data into NFA permits detailed analysis of ocean-wave physics with higher bandwidths than is possible using either other formulations, such as High-Order Spectral (HOS) methods, or field measurements. A framework is provided for assimilating the wavy and vortical portions of the flow. Nudging is used to assimilate wave data at low wavenumbers, and the wave data at high wavenumbers form naturally through nonlinear interactions, wave breaking, and wind forcing. Similarly, the vertical profiles of the mean vortical flow in the wind and the wind drift are nudged, and the turbulent fluctuations are allowed to form naturally. As a demonstration, the results of a HOS of a JONSWAP wave spectrum are assimilated to study short-crested seas in equilibrium with the wind. Log pr...
Kaihatu, J. M.; Goertz, J.; Sheremet, A.; Weiss, R.
2014-12-01
It has been observed that the front face of landfalling tsunamis often feature dispersive "fission" waves. These are short, almost monochromatic coherent waves which result from the piling up of water as the tsunami rapidly decelerates upon encountering land. Photographs taken during the 2004 Indian Ocean tsunami show these waves to resemble cnoidal waves in shape and have a spatial and temporal scale of the same order as swell waves. As part of our goal to study the tsunami in concert with other aspects of the physical environment, we investigate possible physical linkages between the background random swell, monochromatic fission waves, and the long-scale tsunami waves. This particular investigation involves the modification of the dissipation characteristics of random surface waves when interacting with a coherent wavefield (e.g., laboratory proxies for the fission wave or the tsunami). Data from laboratory experiments conducted at the Large Wave Flume at Oregon State University (part of the Network for Earthquake Engineering Simulation supported by the National Science Foundation) were analyzed and the dissipation characteristics inferred using a steepness-regulated instantaneous dissipation mechanism. It is shown that, for random waves, the instances of significant dissipation events temporally correspond to the appearance of high frequency energy in the time-frequency spectrogram. Furthermore, these observations are strongly affected by the presence of an underlying coherent wave signal, particularly in the case of interaction with a tsunami. We further discuss the possible effect of these interactions on the forces in the hydrodynamic field responsible for sediment transport.
Verma, Prabal Singh; Sengupta, Sudip; Kaw, Predhiman
2012-07-01
A one-dimensional particle in cell simulation of large amplitude plasma oscillations is carried out to explore the physics beyond wave breaking in a cold homogeneous unmagnetized plasma. It is shown that after wave breaking, all energy of the plasma oscillation does not end up as random kinetic energy of particles, but some fraction, which is decided by Coffey's wave breaking limit in warm plasma, always remains with two oppositely propagating coherent Bernstein-Greene-Kruskal like modes with supporting trapped particle distributions. The randomized energy distribution of untrapped particles is found to be characteristically non-Maxwellian with a preponderance of energetic particles.
Electromagnetic fields and waves
Rojansky, Vladimir
2012-01-01
This comprehensive introduction to classical electromagnetic theory covers the major aspects, including scalar fields, vectors, laws of Ohm, Joule, Coulomb, Faraday, Maxwell's equation, and more. With numerous diagrams and illustrations.
Paffenholz, Joseph; Fox, Jon W.; Gu, Xiaobai; Jewett, Greg S.; Datta, Subhendu K.
1990-01-01
Scattering of Rayleigh-Lamb waves by a normal surface-breaking crack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scattering of waves generated by this impact source by the crack is subsequently solved by employing a Green's function integral expression for the scattered field coupled with a finite element representation of the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implication for practical applications are discussed.
Large Scale Experiments on the Interaction of a Caisson Breakwater with Breaking Waves
DEFF Research Database (Denmark)
Stagonas, Dimitris; Marzeddu, Andrea; Buccino, Mariano;
2014-01-01
Tests looking at the interaction of a caisson breakwater with steep, breaking waves are outlined here. 4 different wave generation methodologies were employed allowing for experiments with regular, irregular, focused and tailored made waves. The emphasis, however, is given in tests with focused...... waves, which resulted in impulsive conditions at the face of the caisson. Amongst our objectives was to look at the mechanisms occurring when a wave breaks at the structure and to investigate the validity of tactile pressure sensors. As such, for all experiments, pressure, force and surface elevation...
Laboratory Studies of Steep and Breaking Deep Water Waves in a Convergent Channel
2015-05-28
the " young " wave regime. For wave steepnesses between 0.3 < ak < 0.38 the wave profiles became increasingly asymmetric with a steep forward face...Wave Characteristics " Young " waves-symmetric about the crest; Stokes’ fifth-order theory applies. 0.3<akɘ.38 "Pre-breaking" waves-asymmetric waves...careful dynamic calibrations of the offending device. The experiments were conducted at seven wave periods and at a variety of wavemaker strokes as
To break a coralline: mechanical constraints on the size and survival of a wave-swept seaweed.
Martone, Patrick T; Denny, Mark W
2008-11-01
Previous studies have hypothesized that wave-induced drag forces may constrain the size of intertidal organisms by dislodging or breaking organisms that exceed some critical dimension. In this study, we explored constraints on the size of the articulated coralline alga Calliarthron, which thrives in wave-exposed intertidal habitats. Its ability to survive depends critically upon its segmented morphology (calcified segments separated by flexible joints or ;genicula'), which allows otherwise rigid fronds to bend and thereby reduce drag. However, bending also amplifies stress within genicula near the base of fronds. We quantified breakage of genicula in bending by applying known forces to fronds until they broke. Using a mathematical model, we demonstrate the mitigating effect of neighboring fronds on breakage and show that fronds growing within dense populations are no more likely to break in bending than in tension, suggesting that genicular morphology approaches an engineering optimum, possibly reflecting adaptation to hydrodynamic stress. We measured drag in a re-circulating water flume (0.23-3.6 m s(-1)) and a gravity-accelerated water flume, which generates jets of water that mimic the impact of breaking waves (6-10 m s(-1)). We used frond Reynolds number to extrapolate drag coefficients in the field and to predict water velocities necessary to break fronds of given sizes. Laboratory data successfully predicted frond sizes found in the field, suggesting that, although Calliarthron is well adapted to resist breakage, wave forces may ultimately limit the size of intertidal fronds.
Large Scale Experiments on the Interaction of a Caisson Breakwater with Breaking Waves
DEFF Research Database (Denmark)
Stagonas, Dimitris; Marzeddu, Andrea; Buccino, Mariano
2014-01-01
Tests looking at the interaction of a caisson breakwater with steep, breaking waves are outlined here. 4 different wave generation methodologies were employed allowing for experiments with regular, irregular, focused and tailored made waves. The emphasis, however, is given in tests with focused w...
Wave-Breaking Phenomena and Existence of Peakons for a Generalized Compressible Elastic-Rod Equation
Directory of Open Access Journals (Sweden)
Xiaolian Ai
2014-01-01
Full Text Available Consideration in this paper is the Cauchy problem of a generalized hyperelastic-rod wave equation. We first derive a wave-breaking mechanism for strong solutions, which occurs in finite time for certain initial profiles. In addition, we determine the existence of some new peaked solitary wave solutions.
Hwang, P. A.; Savelyev, I. B.; Anguelova, M. D.
2016-05-01
Simultaneous measurements of sea spray aerosol (SSA), wind, wave, and microwave brightness temperature are obtained in the open ocean on-board Floating Instrument Platform (FLIP). These data are analysed to clarify the ocean surface processes important to SSA production. Parameters are formulated to represent surface processes with characteristic length scales spanning a broad range. The investigation reveals distinct differences of the SSA properties in rising winds and falling winds, with higher SSA volume in falling winds. Also, in closely related measurements of whitecap coverage, higher whitecap fraction as a function of wind speed is found in falling winds than in rising winds or in older seas than in younger seas. Similar trend is found in the short scale roughness reflected in the microwave brightness temperature data. In the research of length and velocity scales of breaking waves, it has been observed that the length scale of wave breaking is shorter in mixed seas than in wind seas. For example, source function analysis of short surface waves shows that the characteristic length scale of the dissipation function shifts toward higher wavenumber (shorter wavelength) in mixed seas than in wind seas. Similarly, results from feature tracking or Doppler analysis of microwave radar sea spikes, which are closely associated with breaking waves, show that the magnitude of the average breaking wave velocity is smaller in mixed seas than in wind seas. Furthermore, breaking waves are observed to possess geometric similarity. Applying the results of breaking wave analyses to the SSA and whitecap observations described above, it is suggestive that larger air cavities resulting from the longer breakers are entrained in rising high winds. The larger air cavities escape rapidly due to buoyancy before they can be fully broken down into small bubbles for the subsequent SSA production or whitecap manifestation. In contrast, in falling winds (with mixed seas more likely), the
Modification of AMD wave functions and application to the breaking of the N=20 magic number
Energy Technology Data Exchange (ETDEWEB)
Kimura, Masaaki; Horiuchi, Hisashi [Kyoto Univ. (Japan). Dept. of Physics
2001-09-01
By using the deformed Gaussian instead of the spherical one, we have modified the AMD (Antisymmetrized Molecular Dynamics) wave functions. The calculation results with this modified AMD shows the drastic improvement of the deformation properties of Mg isotopes. This improvement means that this new version of AMD can treat the deformation of mean field properly than before and the deformation of mean field is important in Mg isotopes. With this new version of AMD, we have also calculated 32Mg in which the breaking of magic number N=20 is experimentally known. In this nucleus, {beta}-energy surface is also drastically changed by the modification AMD wave function. Our results show that this nucleus is indeed deformed and neutron's 2p2h state is dominant in its ground state. This ground state reproduces the experimental data and shows the breaking of the magic number N=20 clearly. Additionally, near the ground state, there is also very interesting state which has neutron's 4p4h structure and shows parity violating density distribution and cluster-like nature. (author)
Symmetry-Breaking Zeeman-Coherence Parametric Wave Mixing Magnetometry
Zhou, Feng; Hagley, E W; Deng, L
2016-01-01
The nonlinear magneto-optical effect has significantly impacted modern society with prolific applications ranging from precision mapping of the Earth's magnetic field to bio-magnetic sensing. Pioneering works on collisional spin-exchange effects have led to ultra-high magnetic field detection sensitivities at the level of $fT/\\sqrt{Hz}$ using a single linearly-polarized probe light field. Here we demonstrate a nonlinear Zeeman-coherence parametric wave-mixing optical-atomic magnetometer using room temperature rubidium vapor that results in more than a three-order-of-magnitude optical signal-to-noise ratio (SNR) enhancement for extremely weak magnetic field sensing. This unprecedented enhancement was achieved with nearly a two-order-of-magnitude reduction in laser power while preserving the sensitivity of the widely-used single-probe beam optical-atomic magnetometry method. This new method opens a myriad of applications ranging from bio-magnetic imaging to precision measurement of the magnetic properties of su...
Lorentz breaking Effective Field Theory and observational tests
Liberati, Stefano
2012-01-01
Analogue models of gravity have provided an experimentally realizable test field for our ideas on quantum field theory in curved spacetimes but they have also inspired the investigation of possible departures from exact Lorentz invariance at microscopic scales. In this role they have joined, and sometime anticipated, several quantum gravity models characterized by Lorentz breaking phenomenology. A crucial difference between these speculations and other ones associated to quantum gravity scenarios, is the possibility to carry out observational and experimental tests which have nowadays led to a broad range of constraints on departures from Lorentz invariance. We shall review here the effective field theory approach to Lorentz breaking in the matter sector, present the constraints provided by the available observations and finally discuss the implications of the persisting uncertainty on the composition of the ultra high energy cosmic rays for the constraints on the higher order, analogue gravity inspired, Lore...
Model for predicting mountain wave field uncertainties
Damiens, Florentin; Lott, François; Millet, Christophe; Plougonven, Riwal
2017-04-01
Studying the propagation of acoustic waves throughout troposphere requires knowledge of wind speed and temperature gradients from the ground up to about 10-20 km. Typical planetary boundary layers flows are known to present vertical low level shears that can interact with mountain waves, thereby triggering small-scale disturbances. Resolving these fluctuations for long-range propagation problems is, however, not feasible because of computer memory/time restrictions and thus, they need to be parameterized. When the disturbances are small enough, these fluctuations can be described by linear equations. Previous works by co-authors have shown that the critical layer dynamics that occur near the ground produces large horizontal flows and buoyancy disturbances that result in intense downslope winds and gravity wave breaking. While these phenomena manifest almost systematically for high Richardson numbers and when the boundary layer depth is relatively small compare to the mountain height, the process by which static stability affects downslope winds remains unclear. In the present work, new linear mountain gravity wave solutions are tested against numerical predictions obtained with the Weather Research and Forecasting (WRF) model. For Richardson numbers typically larger than unity, the mesoscale model is used to quantify the effect of neglected nonlinear terms on downslope winds and mountain wave patterns. At these regimes, the large downslope winds transport warm air, a so called "Foehn" effect than can impact sound propagation properties. The sensitivity of small-scale disturbances to Richardson number is quantified using two-dimensional spectral analysis. It is shown through a pilot study of subgrid scale fluctuations of boundary layer flows over realistic mountains that the cross-spectrum of mountain wave field is made up of the same components found in WRF simulations. The impact of each individual component on acoustic wave propagation is discussed in terms of
Kazolea, M.; Delis, A. I.; Synolakis, C. E.
2014-08-01
A new methodology is presented to handle wave breaking over complex bathymetries in extended two-dimensional Boussinesq-type (BT) models which are solved by an unstructured well-balanced finite volume (FV) scheme. The numerical model solves the 2D extended BT equations proposed by Nwogu (1993), recast in conservation law form with a hyperbolic flux identical to that of the Non-linear Shallow Water (NSW) equations. Certain criteria, along with their proper implementation, are established to characterize breaking waves. Once breaking waves are recognized, we switch locally in the computational domain from the BT to NSW equations by suppressing the dispersive terms in the vicinity of the wave fronts. Thus, the shock-capturing features of the FV scheme enable an intrinsic representation of the breaking waves, which are handled as shocks by the NSW equations. An additional methodology is presented on how to perform a stable switching between the BT and NSW equations within the unstructured FV framework. Extensive validations are presented, demonstrating the performance of the proposed wave breaking treatment, along with some comparisons with other well-established wave breaking mechanisms that have been proposed for BT models.
Catalysis of dynamical symmetry breaking by a magnetic field
Miransky, V A
1995-01-01
A constant magnetic field in 3+1 and 2+1 dimensions is a strong catalyst of dynamical chiral symmetry breaking, leading to the generation of a fermion mass even at the weakest attractive interaction between fermions. The essence of this effect is the dimensional reduction D/rightarrow D-2 in the dynamics of fermion pairing in a magnetic field. The effect is illustrated in the Nambu-Jona-Lasinio model and QED. Possible applications of this effect and its extension to inhomogeneous field configurations are discussed.
Prediction of Impact Pressure Induced by Breaking Waves on Marine Systems in Random Seas.
1983-07-01
probability density function of the excursion and time interval for Type I and Type II excursions U Figure 6 Spectral density function of significant wave...the wave spectral density function a = 0.196 for r-sec-units Wave breaking takes place in the region where the wave excursion exceeds the criterion...double amplitude), /m. with = A "A = magnitude of the positive maxima mo = area under the spectral density function The joint probability density
Simulation of breaking gravity waves during the south foehn of 7 - 13 January 1996
Energy Technology Data Exchange (ETDEWEB)
Schmid, H.; Doernbrack, A.
1998-07-01
A high-resolution mesoscale model with horizontal mesh size of 6 km is applied to simulate upper-level wave breaking above the Alps during a south foehn event in January 1996. The model reproduces the key synoptic and mesoscale features of cross-alpine airflow during foehn. High-resolution radiosonde ascents at Munich and Innsbruck are used to evaluate the quality of the model simulations. The simulations predict breaking gravity waves above the jet stream in a layer between 10 and 15 km altitude where the shear is maximum. In part of the foehn period a critical level is present at about 200 hPa that results in wave steepening below and no wave activity aloft. Regions where aircraft report clear-air turbulence encounters agree reasonably with the simulated locations of gravity wave breaking. (orig.)
Run-up distributions of waves breaking on sloping walls
Battjes, J.A.
1969-01-01
Distributions of run-up are calculated by assigning to each individual wave in an irregular wave train a run-up value according to Hunt's formula. The use of this formula permits a normalization of the run-up in such a way that the run-up distributions are independent of slope angle, mean wave
Investigation on the Use of a Multiphase Eulerian CFD solver to simulate breaking waves
DEFF Research Database (Denmark)
Tomaselli, Pietro D.; Christensen, Erik Damgaard
2015-01-01
for mass and momentum transfer among phases, was satisfactorily tested against an experimental bubble column flow. The model was then used to simulate the propagation of a laboratory solitary breaking wave. The motion of the free surface was successfully reproduced up to the breaking point. Further......The main challenge in CFD multiphase simulations of breaking waves is the wide range of interfacial length scales occurring in the flow: from the free surface measurable in meters down to the entrapped air bubbles with size of a fraction of a millimeter. This paper presents a preliminary...
Breaking Kelvin-Helmholtz waves and cloud-top entrainment as revealed by K-band Doppler radar
Martner, Brooks E.; Ralph, F. Martin
1993-01-01
Radars have occasionally detected breaking Kelvin-Helmholtz (KH) waves under clear-air conditions in the atmospheric boundary layer and in the free troposphere. However, very few direct measurements of such waves within clouds have previously been reported and those have not clearly documented wave breaking. In this article, we present some of the most detailed and striking radar observations to date of breaking KH waves within clouds and at cloud top and discuss their relevance to the issue of cloud-top entrainment, which is believed to be important in convective and stratiform clouds. Aircraft observations reported by Stith suggest that vortex-like circulations near cloud top are an entrainment mechanism in cumuliform clouds. Laboratory and modeling studies have examined possibility that KH instability may be responsible for mixing at cloud top, but direct observations have not yet been presented. Preliminary analyses shown here may help fill this gap. The data presented in this paper were obtained during two field projects in 1991 that included observations from the NOAA Wave Propagation Laboratory's K-band Doppler radar (wavelength = 8.7 mm) and special rawinsonde ascents. The sensitivity (-30 dBZ at 10 km range), fine spatial resolution (375-m pulse length and 0.5 degrees beamwidth), velocity measurement precision (5-10 cm s-1), scanning capability, and relative immunity to ground clutter make it sensitive to non-precipitating and weakly precipitating clouds, and make it an excellent instrument to study gravity waves in clouds. In particular, the narrow beam width and short pulse length create scattering volumes that are cylinders 37.5 m long and 45 m (90 m) in diameter at 5 km (10 km) range. These characteristics allow the radar to resolve the detailed structure in breaking KH waves such as have been seen in photographic cloud images.
Institute of Scientific and Technical Information of China (English)
ZHENG Jin-hai; TANG Yu
2009-01-01
A quasi three-dimensional numerical model of wave-driven coastal currents with the effects of surface rollers is developed for the study of the spatial lag between the location of the maximum wave-induced current and the wave breaking point.The governing equations are derived from Navier-Stokes equations and solved by the hybrid method combining the fractional step finite different method in the horizontal plane with a Galerkin finite element method in the vertical direction.The surface rollers effects are considered through incorporating the creation and evolution of the roller area into the free surface shear stress.An energy equation facilitates the computation process which transfers the wave breaking energy dissipation to the surface roller energy.The wave driver model is a phase-averaged wave model based on the wave action balance equation.Two sets of laboratory experiments producing breaking waves that generated longshore currents on a planar beach are used to evaluate the model's performance.The present wave-driven coastal current model with the roller effect in the surface shear stress term can produce satisfactory results by increasing the wave-induced nearshore current velocity inside the surf zone and shifting the location of the maximum longshore current velocity landward.
Moulin, F.; Flor, J.
We present the results of an experimental investigation on the material transport across the shear zone of a cyclonic vortex induced by the breaking of inertia-gravity waves. As has been suggested by McIntyre (1995) this could be a possible mechamism of ozone transport across the dynamical barrier of the polar vortex. The experiments were conducted in a 1 meter size tank containing a rotating stratified fluid. Barotropic vortices were generated by siphoning off fluid with a long perforated tube and per- turbed by planar internal waves generated by the vertical oscillation of a horizontal circular cylinder. As predicted by theorical results based on the WKB approximation, the waves opposing the vortex velocity field were trapped in the outer edge of the vor- tex. In some cases, the increase of wave energy in this region was strong enough to lead to 3-dimensional breaking of the wave pattern. Experimental visualization tech- niques were used to determine the class of instability responsible for this breaking and to measure the induced mixing. A simple model to predict the efficiency of the mixing process will be presented.
Dynamical properties of breaking waves: dissipation, air entrainment and spray generation
Deike, Luc; Melville, W. Kendall; Popinet, Stephane
2016-11-01
Wave breaking in the ocean is of fundamental importance in order to quantify wave dissipation and air-sea interaction, including gas and momentum exchange, and to improve parametrization for ocean-atmosphere exchange in weather and climate models. Here, we present 2D and 3D direct numerical simulations of breaking waves, compared with laboratory measurements. The dissipation due to breaking in the 2D and 3D simulations is found to be in good agreement with experimental observations and inertial-scaling arguments. We discuss the transition from a 2D to a 3D flow during breaking. We present a model for air entrainment and bubble statistics that describes well the experimental and numerical data, and is based on turbulent fragmentation of the bubbles and a balance between buoyancy forces and viscous dissipation. Finally we discuss the generation of large drops during the impact and splashing process.
Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles
Leifer, I.; Leeuw, G. de
2006-01-01
Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical
Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles
Leifer, I.; Leeuw, G. de
2006-01-01
Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical extent
Breaking discrete symmetries in the effective field theory of inflation
Energy Technology Data Exchange (ETDEWEB)
Cannone, Dario [Dipartimento di Fisica e Astronomia “G. Galilei”, Università degli Studi di Padova,Padova, I-35131 (Italy); INFN, Sezione di Padova,Padova, I-35131 (Italy); Gong, Jinn-Ouk [Asia Pacific Center for Theoretical Physics,Pohang, 790-784 (Korea, Republic of); Department of Physics,Postech, Pohang, 790-784 (Korea, Republic of); Tasinato, Gianmassimo [Department of Physics, Swansea University,Swansea, SA2 8PP (United Kingdom)
2015-08-03
We study the phenomenon of discrete symmetry breaking during the inflationary epoch, using a model-independent approach based on the effective field theory of inflation. We work in a context where both time reparameterization symmetry and spatial diffeomorphism invariance can be broken during inflation. We determine the leading derivative operators in the quadratic action for fluctuations that break parity and time-reversal. Within suitable approximations, we study their consequences for the dynamics of linearized fluctuations. Both in the scalar and tensor sectors, we show that such operators can lead to new direction-dependent phases for the modes involved. They do not affect the power spectra, but can have consequences for higher correlation functions. Moreover, a small quadrupole contribution to the sound speed can be generated.
Simulation of the ocean surface mixed layer under the wave breaking
Institute of Scientific and Technical Information of China (English)
SUN Qun; SONG Jinbao; GUAN Changlong
2005-01-01
A one-dimensional mixed-layer model, including a Mellor-Yamada level 2.5 turbulence closure scheme, was implemented to investigate the dynamical and thermal structures of the ocean surface mixed layer in the northern South China Sea. The turbulent kinetic energy released through wave breaking was incorporated into the model as a source of energy at the ocean surface, and the influence of the breaking waves on the mixed layer was studied. The numerical simulations show that the simulated SST is overestimated in summer without the breaking waves. However, the cooler SST is simulated when the effect of the breaking waves is considered, the corresponding discrepancy with the observed data decreases up to 20% and the MLD calculated averagely deepens 3.8 m. Owing to the wave-enhanced turbulence mixing in the summertime, the stratification at the bottom of the mixed layer was modified and the temperature gradient spread throughout the whole thermocline compared with the concentrated distribution without wave breaking.
Bulk gauge fields in warped space and localized supersymmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Chacko, Z.; Ponton, Eduardo
2003-11-01
We consider five dimensional supersymmetric warped scenarios in which the Standard Model quark and lepton fields are localized on the ultraviolet brane, while the Standard Model gauge fields propagate in the bulk. Supersymmetry is assumed to be broken on the infrared brane. The relative sizes of supersymmetry breaking effects are found to depend on the hierarchy between the infrared scale and the weak scale. If the infrared scale is much larger than the weak scale the leading supersymmetry breaking effect on the visible brane is given by gaugino mediation. The gaugino masses at the weak scale are proportional to the square of the corresponding gauge coupling, while the dominant contribution to the scalar masses arises from logarithmically enhanced radiative effects involving the gaugino mass that are cutoff at the infrared scale. While the LSP is the gravitino, the NLSP which is the stau is stable on collider time scales. If however the infrared scale is close to the weak scale then the effects of hard supersymmetry breaking operators on the scalar masses can become comparable to those from gaugino mediation. These operators alter the relative strengths of the couplings of gauge bosons and gauginos to matter, and give loop contributions to the scalar masses that are also cutoff at the infrared scale. The gaugino masses, while exhibiting a more complicated dependence on the corresponding gauge coupling, remain hierarchical and become proportional to the corresponding gauge coupling in the limit of strong supersymmetry breaking. The scalar masses are finite and a loop factor smaller than the gaugino masses. The LSP remains the gravitino.
A VOF-based numerical model for breaking waves in surf zone
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
This paper introduces a numerical model for studying the evolution of a periodic wave train,shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes (RANS) equations for a mean flow, and the k-ε equations for turbulence kinetic energy k and turbulence dissipation rate ε. To track a free surface, the volume of fluid (VOF) function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data.
Nayeh, S; Arbabi, S; Ghominejad, M
2015-01-01
The equations for gravitational plane waves produced by a typical binary system as a solution of linear approximation of Einstein equations is derived. The dynamics of the corresponding gravitational field is analyzed in a 4-dimensional space-time manifold, endowed with a metric and taking into account the torsion. In this context, the geometrical reason of the existence of torsion due to the presence of gravitational waves, as an asymmetry of connection coefficients with respect of the swapping of indices's is highlighted. In a laser interferometer gravitational detector The delay time between the arrivals of the two laser beams traveling back and forth along the two arms of in presence of gravitational waves, is interpreted from this point of view. The geometrical interpretation of torsion, links this delay time to the breaking of the parallelogram formed by the trajectories of the laser beams in space-time. This delay is calculated for a typical NS-NS binary pulsar in two specific orientations with respect...
Doubly Periodic Propagating Wave for (2+1)-Dimensional Breaking Soliton Equation
Institute of Scientific and Technical Information of China (English)
WANG Yi-Hong; HUANG Wen-Hua; WANG Sheng-Kui; LIU Yu-Lu; ZHANG Jie-Fang
2008-01-01
Using the variable separation approach, we obtain a general exact solution with arbitrary variable separation functions for the (2+1)-dimensional breaking soliton system. By introducing Jacobi elliptic functions in the seed solution, two famines of doubly periodic propagating wave patterns are derived. We investigate these periodic wave solutions with different modulus m selections, many important and interesting properties are revealed. The interaction of Jabcobi e11iptic function waves are graphically considered and found to be nonelastic.
Symmetry breakings and topological solitons in mercury based d-wave superconductors
Energy Technology Data Exchange (ETDEWEB)
Onbasli, Ulker [Department of Physics, University of Marmara, Ridvan Pasa Cad. 3. Sok. 85/12, Goztepe, Istanbul (Turkey)], E-mail: phonon@doruk.net.tr; Ozdemir, Zeynep Gueven [Department of Physics, Yildiz Technical University, Davutpasa Mah. Davutpasa Caddesi 34220 Esenler, Istanbul (Turkey)], E-mail: zguvenozdemir@yahoo.com; Aslan, Ozden [Anatuerkler Educational Consultancy and Trading Company, Orhan Veli Kanik Cad., Guener Is Mer., 6/1, Kavacik, 34810 Beykoz, Istanbul (Turkey)
2009-11-30
This study is devoted to examine high temperature superconductors by the concept of symmetry breakings. The global gauge symmetry is broken at Meissner transition temperature, T{sub c}, in high temperature d-wave superconductors. In addition to this symmetry breaking, the time reversal symmetry breaking phenomenon becomes observable on paramagnetic Meissner effect at paramagnetic Meissner effect temperature, T{sub PME}. Furthermore, the concept of symmetry breakings has been discussed by the phenomenon of critical quantum chaos in the mercury cuprates which is one of the best examples to understand the chaotic transitions. From this point of view, T{sub c} and T{sub PME} have been suggested as chaotic transition points. Moreover, T{sub PME} is predicted as the breaking point of electroweak symmetry as well. Furthermore, we have also proposed that the double helix quantum wave occurs in the quantum primitive cell of cuprates due to the breaking of the room temperature symmetry of the system at T{sub c}. When time period of the wave is taken infinite, the double helix quantum wave can be considered as a topological soliton of the coherent system.
An Improved Nearshore Wave Breaking Model Based on the Fully Nonlinear Boussinesq Equations
Institute of Scientific and Technical Information of China (English)
LI Shao-wu; LI Chun-ying; SHI Zhong; GU Han-bin
2005-01-01
This paper aims to propose an improved numerical model for wave breaking in the nearshore region based on the fully nonlinear form of Boussinesq equations. The model uses the κ equation turbulence scheme to determine the eddy viscosity in the Boussinesq equations. To calculate the turbulence production term in the equation, a new formula is derived based on the concept of surface roller. By use of this formula, the turbulence production in the one-equation turbulence scheme is directly related to the difference between the water particle velocity and the wave celerity. The model is verified by Hansen and Svendsen's experimental data (1979) in terms of wave height and setup and setdown. The comparison between the model and experimental results of wave height and setup and setdown shows satisfactory agreement. The modeled turbulence energy decreases as waves attenuate in the surf zone. The modeled production term peaks at the breaking point and decreases as waves propagate shoreward. It is also suggested that both convection and diffusion play their important roles in the transport of turbulence energy immediately after wave breaking. When waves approach to the shoreline, the production and dissipation of turbulence energy are almost balanced. By use of the slot technique for the simulation of the movable shoreline boundary, wave runup in the swash zone is well simulated by the present model.
A CFD Model for Wave Transformation and Breaking in the Surf Zone
Chopakatla, S. C.; Lippmann, T. C.; Richardson, J. E.; Thornton, E. B.; Holman, R. A.
2002-12-01
Wind-generated surface gravity waves are the major driving force for nearshore circulation and sediment transport. As waves shoal in shallow coastal waters, spectra evolve strongly owing to refraction, nonlinear energy transfers, and dissipation caused by wave breaking and bottom friction. Although considerable progress has been made in modeling wave propagation over complex bottom topography, the dissipation mechanisms are still poorly understood. As a consequence, wave transformation models for the surf zone use crude descriptions of the wave breaking process based on simple saturation criteria or empirical probability distributions that do not always work well for the range of bathymetric and wave conditions commonly observed in nature. In this report, we will discuss the results of studies made with the commercially available Computational Fluid Dynamics (CFD) software system known as FLOW-3D (Flow Science, Inc., Sante Fe, NM). FLOW-3D is designed to solve transient, free surface flow problems based on the solution of the Navier-Stokes equations in three-dimensions. As part of FLOW-3D's formulation, the dissipation of energy is determined by use of coupled turbulence closure schemes (e.g., closure schemes based on the solution of turbulent kinetic energy transport equations). In this study, fine scale pressures and velocities are computed over a two-dimensional beach profile measured during the 1990 Delilah experiment. The model is driven by observed wave spectra obtained in 8 meter water depths, and results compared with a cross-shore array of pressure sensors and current meters spanning the width of the surf zone. In the calculations, wave breaking is a natural consequence of the fluid dynamics and does not require the use of empirical formulations, or breaking criteria. The spatial and temporal variability in the wave breaking locations will be compared with video observations obtained during the experiment. Good comparison between modeled and observed wave
Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement.
Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing
2016-03-05
An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength.
On the Upper Ocean Turbulent Dissipation Rate due to Very Short Breaking Wind-Waves
Banner, Michael L
2016-01-01
Sutherland and Melville (2015a) investigated the relative contributions to the total dissipation rate in the ocean surface wave boundary layer of different breaking wave scales, from large-scale whitecaps to micro-breakers. Based on their measurements of geometric/kinematic properties of breaking waves for a wide range of wave ages, they inferred the dissipation rates from breaking as a function of scale. These results were compared with their complementary measurements of the total dissipation rate in the underlying wave boundary layer. They reported that the total depth-integrated dissipation rate in the water column agreed well with dissipation rate from breaking waves for young to very old wind seas. They also reported high observed levels of dissipation rate very near the sea surface. They concluded that this showed a large fraction of the total dissipation rate was due to non-air entraining micro-breakers and very small whitecaps. Because of its fundamental importance, both physically and for accurate a...
Sloping beach with wave breaking and moving shoreline on Romanian Black Sea coast
Panaitescu, F. V.; Panaitescu, M.; Anton, I. A.
2016-08-01
Purpose of the work: wave breaking and wave run-up on a gently sloping plane beach from Romanian Black Sea Coast. That coast has a length of 244 km and an almost linear configuration with the exception of build-up areas. The paper concentrates on shoaling of regular waves and spilling type of wave breaking running with a simulation on software MIKE 21. Research and methodology: the paper contents the measurements for spilling and plunging type of breakers on a plane sloping beach with a slope of 1/45 starting in depth of 0.23 m to 0.46 m. A moving shoreline is included in the simulations. With respect to the parameters of the breaker model the standard values are applied. An explicit filter is introduced near the still water shoreline to remove short-wave instabilities and to dissipate the wave energy in the model. Results: the obtained values indicate the wave breaking and wave run-up processes, the spatial variation of a number of phase-averaged quantities and the shoreline motion converted intro a vertical and a horizontal displacement.
Oil slicks on water surface: Breakup, coalescence, and droplet formation under breaking waves.
Nissanka, Indrajith D; Yapa, Poojitha D
2017-01-15
The ability to calculate the oil droplet size distribution (DSD) and its dynamic behavior in the water column is important in oil spill modeling. Breaking waves disperse oil from a surface slick into the water column as droplets of varying sizes. Oil droplets undergo further breakup and coalescence in the water column due to the turbulence. Available models simulate oil DSD based on empirical/equilibrium equations. However, the oil DSD evolution due to subsequent droplet breakup and coalescence in the water column can be best represented by a dynamic population model. This paper develops a phenomenological model to calculate the oil DSD in wave breaking conditions and ocean turbulence and is based on droplet breakup and coalescence. Its results are compared with data from laboratory experiments that include different oil types, different weathering times, and different breaking wave heights. The model comparisons showed a good agreement with experimental data.
Effect of Breaking Waves on Scour Processes around Circular Offshore Wind Turbine Foundations
DEFF Research Database (Denmark)
Frigaard, Peter; Hansen, Erik Asp; Christensen, Erik Damgaard
2005-01-01
Scour and scour protection is a major issue for the construction of offshore wind farms. The engineer can either include the scour in his design or he can place a scour protection on the seabed. The optimal solution is highly dependent on the maximal scour depth an unprotected foundation...... will experience during its lifetime. Today's design practice has not yet been defined for foundations placed in areas with breaking waves. Some engineers include possible wave breaking in the design by increasing scour depth for current alone. So that the design scour depth is considered to be more than 1.5 times...
THE MOVEMENT OF OIL UNDER NON-BREAKING WAVES
The combined effects of wave kinematics, turbulent diffusion, and buoyancy on the transport of oil droplets at sea were investigated in this work using random walk techniques in a Monte Carlo framework. Six hundred oil particles were placed at the water surface and tracked for 5...
THE MOVEMENT OF OIL UNDER NON-BREAKING WAVES
The combined effects of wave kinematics, turbulent diffusion, and buoyancy on the transport of oil droplets at sea were investigated in this work using random walk techniques in a Monte Carlo framework. Six hundred oil particles were placed at the water surface and tracked for 5...
Energy Technology Data Exchange (ETDEWEB)
Zhang, Sun, E-mail: szhang@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Key Laboratory of Dark Matter and Space Astronomy, Chinese Academy of Sciences, Nanjing 210008 (China); Joint Center for Particle, Nuclear Physics and Cosmology (J-CPNPC), PMO-NJU, Nanjing 210008 (China)
2014-02-05
In this Letter, we have studied the shock wave and discontinuity propagation for relativistic superfluid with spontaneous U(1) symmetry breaking in the framework of hydrodynamics. General features of shock waves are provided, the propagation of discontinuity and the sound modes of shock waves are also presented. The first sound and the second sound are identified as the propagation of discontinuity, and the results are in agreement with earlier theoretical studies. Moreover, a differential equation, called the growth equation, is obtained to describe the decay and growth of the discontinuity propagating along its normal trajectory. The solution is in an integral form and special cases of diverging waves are also discussed.
This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...
Ma, X.; Yan, J.; Hou, Y.; Lin, F.; Zheng, X.
2016-12-01
The northern South China Sea provides prominent examples of internal waves, however, rare studies have been done on the associated bedforms and sediment transport near the shelf break. Here, we report the unique data of bedform details which probably caused by the internal solitary waves and internal tides near the shelf break in the areas west of Dongsha Atoll. In the study area, most internal solitary waves (ISWs) are found to propagate onto the shelf obliquely in an approximately 290° through the MODIS image. Several typical events of ISWs were also captured during our observation by an mooring system on the continental slope. Bottom current data near the shelf break showed that extremely strong speed (exceeding 80 cm/s) occurred when the obliquely incident ISWs propagated. The strong currents have the capability to move coarse grains or suspend and transport fine grains but, cannot change the long-term trend of sediment transport on the slope (γ/c>1). Two types of sand waves were also found on the seabed. The upslope-dipping sand waves (type 1) are only found at depths of 120-150 m with flat crests and intersecting the depth contours, being ascribed to the obliquely incident ISWs. In contrast, the downslope-dipping sand waves (type 2) are parallel to the depth contours and obviously migrated over eight months, which were probably caused by internal tides. The ISWs could also produce along-slope currents to form and maintain channels on seabed with a larger gradient (γ>0.8°). The bedforms are likely widespread near the shelf break in the northern South China Sea and other seas but are limited on mild slopes where ISWs do not break. Additional detailed research needs to be deployed on wave behaviors, sediment transport, and the bedforms associated with obliquely incident ISWs.
Spontaneous axisymmetry breaking of Saturn's external magnetic field
Goldreich, P; Goldreich, Peter; Farmer, Alison J.
2006-01-01
Saturn's magnetic field is remarkably axisymmetric. Its dipole axis is inclined by less than 0.2 deg with respect to its rotation axis. Rotationally driven convection of magnetospheric plasma breaks the axisymmetry of its external magnetic field. Field aligned currents transfer angular momentum from the planet to a tongue of outflowing plasma. This transfer slows the rate of rotation of the ionosphere relative to that of the underlying atmosphere. The currents are the source for the non-axisymmetric components of the field. The common rotation rates of these components and Saturn's kilometric radio (SKR) bursts is that of the plasma near the orbit of Enceladus, and by extension the rotation rate in the ionosphere to which this plasma is coupled. That rate tells us nothing about the rotation rate of Saturn's deep interior. Of that we remain ignorant. Magnetic perturbations with magnitudes similar to those observed by Cassini are produced for Mdot ~ 10^4 g/s, a value similar to estimates for the rate of product...
Translational symmetry breaking in field theories and the cosmological constant
Evans, Nick; Morris, Tim R.; Scott, Marc
2016-01-01
We argue, at a very basic effective field theory level, that higher dimension operators in scalar theories that break symmetries at scales close to their ultraviolet completion cutoff include terms that favor the breaking of translation (Lorentz) invariance, potentially resulting in striped, checkerboard or general crystal-like phases. Such descriptions can be thought of as the effective low energy description of QCD-like gauge theories near their strong coupling scale where terms involving higher dimension operators are generated. Our low energy theory consists of scalar fields describing operators such as q ¯q and q ¯F(2 n )q . Such scalars can have kinetic mixing terms that generate effective momentum dependent contributions to the mass matrix. We show that these can destabilize the translationally invariant vacuum. It is possible that in some real gauge theory such operators could become sufficiently dominant to realize such phases, and it would be interesting to look for them in lattice simulations. We present a holographic model of the same phenomena which includes renormalization group running. A key phenomenological motive to look at such states is recent work that shows that the nonlinear response in R2 gravity to such short-range fluctuations can mimic a cosmological constant. Intriguingly in a cosmology with such a Starobinsky inflation term, to generate the observed value of the present day acceleration would require stripes at the electroweak scale. Unfortunately, low energy phenomenological constraints on Lorentz violation in the electron-photon system appear to strongly rule out any such possibility outside of a disconnected dark sector.
Influence of ambient air pressure on impact pressure caused by breaking waves
Moutzouris, C.
1979-01-01
Engineers are interested in the dynamics of the interface waterstructure. In case of breaking of water waves on a structure high positive and sometimes negative pressures of very short duration occur. Not only the maxima and minima of the pressures on the structure are important to a designing
Strong coupling of gold dipolar nanoantennas by symmetry-breaking in evanescent wave
Yang, Jhen-Hong; Chen, Kuo-Ping
2016-09-01
Observing the resonance wavelengths of nanoantennas (NAs) with changing incident angles in TM and TE polarization. Extinction cross section shows the dark and bright coupling modes at resonance wavelength of NAs with symmetry breaking oblique incidence. The plasmonic enhancement is stronger under evanescent wave in total internal reflection.
The wave function of the universe and spontaneous breaking of supersymmetry
Obregón, O; Socorro, J; Tkach, V I
1998-01-01
In this work we define a scalar product ``weighted'' with the scalar factor $R$ and show how to find a normalized wave function for the supersymmetric quantum FRW cosmological model using the idea of supersymmetry breaking selection rules under local n=2 conformal supersymmetry. We also calculate the expectation value of the scalar factor R in this model and its corresponding behaviour.
Influence of ambient air pressure on impact pressure caused by breaking waves
Moutzouris, C.
1979-01-01
Engineers are interested in the dynamics of the interface waterstructure. In case of breaking of water waves on a structure high positive and sometimes negative pressures of very short duration occur. Not only the maxima and minima of the pressures on the structure are important to a designing engin
Sea spray aerosol production from waves breaking in the surf zone
Leeuw, G. de
1999-01-01
Sea spray aerosol is a product of wave breaking. A very strong source of this aerosol is the surf zone. In this sense, measurements in the surf zone can be suitable for the assessment of the contributions of the various spray production mechanisms to the total concentrations. At present, a comprehen
Fluid Dynamical Control of Spacing and Symmetry Breaking in Orbital Wave Ripples
Nienhuis, J.; Perron, J.; Kao, J. C.; Myrow, P.
2013-12-01
select ripple crests become increasingly sinuous before breaking up. The origins of these transient phenomena are not yet understood. We extracted side-looking 1D-profiles from field-scale laboratory experiments in a wave tank to study the incipient response of ripples to a step change in wave conditions, and used the numerical flow model to calculate stresses over the evolving bed. Combining these calculations with real-time video and time-lapse imagery, we tracked the hydrodynamic and morphodynamic evolution of individual ripples. When the wave orbital diameter is shortened, incipient secondary crests act as 'speed bumps,' shortening the separation zone and encouraging the growth of crests on the next flank. This feedback appears to be the mechanism that systematically favors incipient crests on the same side of each trough. When the orbital diameter is lengthened, the nearly straight crests of equilibrium ripples become unstable: crests migrate preferentially towards the nearest adjacent crest that is closer, which amplifies crest sinuosity and may lead to the observed bulging instability. Understanding the mechanisms of ripple adjustment provides insight into bedform dynamics and paleoenvironmental reconstructions, and should aid in the development of reduced-complexity morphodynamic models by providing a basis for parameterizing complicated flow effects.
Breaking wave impact forces on truss support structures for offshore wind turbines
Cieślikiewicz, Witold; Gudmestad, Ove T.; Podrażka, Olga
2014-05-01
Due to depletion of the conventional energy sources, wind energy is becoming more popular these days. Wind energy is being produced mostly from onshore farms, but there is a clear tendency to transfer wind farms to the sea. The foundations of offshore wind turbines may be truss structures and might be located in shallow water, where are subjected to highly varying hydrodynamic loads, particularly from plunging breaking waves. There are models for impact forces prediction on monopiles. Typically the total wave force on slender pile from breaking waves is a superposition of slowly varying quasi-static force, calculated from the Morison equation and additional dynamical, short duration force due to the impact of the breaker front or breaker tongue. There is not much research done on the truss structures of wind turbines and there are still uncertainties on slamming wave forces, due to plunging breaking waves on those structures. Within the WaveSlam (Wave slamming forces on truss structures in shallow water) project the large scale tests were carried out in 2013 at the Large Wave Flume in Forschungszentrum Küste (FZK) in Hannover, Germany. The following institutions participated in this initiative: the University of Stavanger and the Norwegian University of Science and Technology (project management), University of Gdańsk, Poland, Hamburg University of Technology and the University of Rostock, Germany and Reinertsen AS, Norway. This work was supported by the EU 7th Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB IV. The main aim of the experiment was to investigate the wave slamming forces on truss structures, development of new and improvement of existing methods to calculate forces from the plunging breakers. The majority of the measurements were carried out for regular waves with specified frequencies and wave heights as well as for the irregular waves based on JONSWAP spectrum. The truss structure was equipped with both
Wave breaking onset of two-dimensional deep-water wave groups in the presence and absence of wind
Saket, Arvin; Banner, Michael L; Barthelemy, Xavier; Allis, Michael J
2015-01-01
The criterion for the initiation of breaking demonstrated numerically by Barthelemy et al. (2015) has been investigated in the laboratory for unidirectional wave groups in deep-water and extended to include conditions of moderate wind forcing. Thermal Image Velocimetry was used to compare measurements of the crest surface water particle velocity (Us) with the wave crest velocity (C), as determined by an array of closely-spaced wave gauges. The energy flux ratio Bx = Us/C that distinguishes maximum recurrence from marginal breaking was found to be 0.840 $\\pm$ 0.016 in good agreement with the numerically determined value of 0.855. Further, the threshold was found to be robust for different classes of wave groups of distinct characteristic steepness at the breaking threshold. Increasing wind forcing from zero to U{\\lambda}/4/C0=1.42 increased this threshold by 2%. Increasing the spectral bandwidth (decreasing the Benjamin-Feir index from 0.39 to 0.31) systematically reduced the threshold by 1.5%.
Wave-Breaking Turbulence in the Ocean Surface Layer
2016-06-01
al. (2010) requires specifi- cation of a parameter bmax, which is used to compensate for the mean bias of the input wind fields or lack thereof; bmax...zw, to a fixed reference frame z. e. Turbulent dissipation rate estimates « The SWIFTs collected pulse-coherent Doppler sonar (Nortek Aquadopp HR...variance from noise in the Doppler mea- surements; it is a free parameter in the fit to r 2/3 and is checked against the expected noise of the profiler
Atmospheric Transport and Mixing linked to Rossby Wave Breaking in GFDL Dynamical Core
Liu, C.; Barnes, E. A.
2015-12-01
Atmospheric transport and mixing plays an important role in the global energy balance and the distribution of health-related chemical constituents. Previous studies suggest a close linkage between large-scale transport and Rossby wave breaking (RWB). In this work, we use the GFDL spectral dynamical core to investigate this relationship and study the response of RWB-related transport in different climate scenarios. In a standard control run, we quantify the contribution of RWB to the total transport and mixing of an idealized tracer. In addition, we divide the contribution further into the two types of RWB - anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB) -- and contrast their efficiency at transport and mixing. Our results are compared to a previous study in which the transport ability of the two types of RWB is studied for individual baroclinic wave life-cycles. In a series of sensitivity runs, we study the response of RWB-related transport and mixing to various states of the jet streams. The responses of the mean strength, frequency, and the efficiency of RWB-related transport are documented and the implications for the transport and mixing in a warmer climate are discussed.
Closed superstrings in magnetic field instabilities and supersymmetry breaking
Tseytlin, Arkady A
1995-01-01
We consider a 2-parameter class of solvable closed superstring models which `interpolate' between Kaluza-Klein and dilatonic Melvin magnetic flux tube backgrounds. The spectrum of string states has similarities with Landau spectrum for a charged particle in a uniform magnetic field. The presence of spin-dependent `gyromagnetic' interaction implies breaking of supersymmetry and possible existence (for certain values of magnetic parameters) of tachyonic instabilities. We study in detail the simplest example of the Kaluza-Klein Melvin model describing a superstring moving in flat but non-trivial 10-d space containing a 3-d factor which is a `twisted' product of a 2-plane and an internal circle. We also discuss the compact version of this model constructed by `twisting' the product of the two groups in SU(2) x U(1) WZNW theory without changing the local geometry (and thus the central charge). We explain how the supersymmetry is broken by continuous `magnetic' twist parameters and comment on possible implications ...
Breaking of storm waves on sand and reef zone in the Lesser Antilles Arc
Dorville, Jean-François; Berthelot, Hugues; Zahibo, Narcisse
2010-05-01
The most part of the exposed coastal zone of the Lesser Antilles Arc are composed by sand and coral reef. The high frequencies of passage of cyclones near these islands and anticyclone's swell subject them to waves of large amplitude. These waves are 4 to 5 times lager to the normal conditions. The weak slopes observed on these zones are particularly sensitive to this type of waves and cause the process of surfing. The mode of dissipation of these waves influenced the run-up and the floods on the coast. The surf zones are situated in 5 in 20 meters of the line of coast. A displacement of sea water towards the coast line is provoked by the breaking of the waves. These quantities of water are held by the particularly bathymetry of these islands and provoke a raised of the sea level. The propagation of the waves are allowed by the sea elevation in the surf zone In the evaluation of the marine risk in the Lesser Antilles Arc, a model of sea state forecast are developed in the Laboratory of Geosciences and Energy (LaRGE) in the French West Indies and French Guiana University (Guadeloupe , FWI). This forecast model is based on the coupling of several numerical models. WaveWatch III and SWAN are used for the wave propagation on large and small sectors. An ocean circulation model based on POM is used to evaluate the sea current and the sea level. To improve the forecasts on the exposed coast, in the zone included between the surf and swash, the sea elevation induced by the large amplitude wave are particularly studies. The numerical model of wave propagation near the coast SWAN is used to determine the sea state before the surf zone. The dissipation and the breaking of the large amplitude waves are studied with the spectral values give by SWAN and the local conditions (bathymetry, sea level, slope, bottom friction). During the months of November and December 2009, several large amplitude waves, coming from the North Atlantic Ocean, impact the west coast of Guadeloupe. The
Flach, S
1995-01-01
We study tangent bifurcation of band edge plane waves in nonlinear Hamiltonian lattices. The lattice is translationally invariant. We argue for the breaking of permutational symmetry by the new bifurcated periodic orbits. The case of two coupled oscillators is considered as an example for the perturbation analysis, where the symmetry breaking can be traced using Poincare maps. Next we consider a lattice and derive the dependence of the bifurcation energy on the parameters of the Hamiltonian function in the limit of large system sizes. A necessary condition for the occurence of the bifurcation is the repelling of the band edge plane wave's frequency from the linear spectrum with increasing energy. We conclude that the bifurcated orbits will consequently exponentially localize in the configurational space.
Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking
Resch, F.; Avellan, F.
1982-01-01
The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.
Threshold electric field in unconventional density waves
Dóra, Balázs; Virosztek, Attila; Maki, Kazumi
2001-07-01
As it is well known most charge-density waves (CDW's) and spin-density waves exhibit nonlinear transport with well-defined threshold electric field ET. Here we study theoretically the threshold electric field of unconventional density waves. We find that the threshold field increases monotonically with temperature without divergent behavior at Tc, unlike the one in conventional CDW. The present result in the three-dimensional weak pinning limit appears to describe rather well the threshold electric field observed recently in the low-temperature phase of α-(BEDT-TTF)2KHg(SCN)4.
Noncommutative Field Theory on Homogeneous Gravitational Waves
Halliday, S; Halliday, Sam; Szabo, Richard J.
2006-01-01
We describe an algebraic approach to the time-dependent noncommutative geometry of a six-dimensional Cahen-Wallach pp-wave string background supported by a constant Neveu-Schwarz flux, and develop a general formalism to construct and analyse quantum field theories defined thereon. Various star-products are derived in closed explicit form and the Hopf algebra of twisted isometries of the plane wave is constructed. Scalar field theories are defined using explicit forms of derivative operators, traces and noncommutative frame fields for the geometry, and various physical features are described. Noncommutative worldvolume field theories of D-branes in the pp-wave background are also constructed.
Marivela, Roberto; Synolakis, Costas
2016-01-01
A plethora of studies in the past decade describe tsunami hazards and study their evolution from the source to the target coastline, but mainly focus on coastal inundation and maximum runup. Nonetheless, anecdotal reports from eyewitnesses, photographs and videos suggest counterintuitive flow dynamics, for example rapid initial acceleration when the wave first strikes the initial shoreline. Further, the details of the flow field at or within tens of meters of the shoreline are exquisitely important in determining damage to structures and evacuation times. Based on a set of three-dimensional numerical simulations using solitary waves as a model, we show the spatial-temporal distribution of the flow momentum, kinetic energy and force during the breaking process. We infer that the flow reaches its highest destructive capacity not when flow momentum or kinetic energy reach their maxima, but when flow force reaches its. This occurs in the initial shoreline environment, which needs to be considered in nearshore str...
Effects of blast wave to main steam piping under high energy line break condition by TNT model
Energy Technology Data Exchange (ETDEWEB)
Kim, Seung Hyun; Lee, Eung Seok; Chang, Yoon Suk [Kyung Hee University, Yongin (Korea, Republic of)
2016-05-15
The aim of this study is to examine effect of the blast wave according to pipe break position through FE (Finite Element) analyses. If HELB (High Energy Line Break) accident occurs in nuclear power plants, not only environmental effect such as release of radioactive material but also secondary structural defects should be considered. Sudden pipe rupture causes ejection of high temperature and pressure fluid, which acts as a blast wave around the break location. The blast wave caused by the HELB has a possibility to induce structural defects around the components such as safe-related injection pipes and other structures.
EIT waves and coronal magnetic field diagnostics
Institute of Scientific and Technical Information of China (English)
CHEN PengFei
2009-01-01
Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. By contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measured with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal seismology based on MHD waves in the corona. Compared to the waves trapped in the localized coronal loops, EIT waves are the only global-scale wave phenomenon, and thus are the ideal tool for the coronal global seismology. In this paper, we review the observations and modelings of EIT waves, and illustrate how they can be applied to probe the global magnetic field in the corona.
Vibrating-Sliding Motion of Caisson Breakwaters Under Various Breaking Wave Impact Forces
Institute of Scientific and Technical Information of China (English)
王元战; 于红霞
2003-01-01
Sliding is one of the principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. Herein, the mass-spring-dashpot model of caisson-base system is used to simulate the vibrating-sliding motion of the caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave impacts and the sliding motion on the dynamic response behaviors of caisson breakwaters are investigated and the calculation of relevant system parameters is discussed. It is shown that the dynamic responses of the caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. The amplitude of dynamic response of the caisson is lower under single peak impact excitation than that under double peak impact or shock-damping oscillation impact excitation. Though the displacement of the caisson is large due to sliding, the rotation, the sliding force and the overturning moment of the caisson are significantly reduced.
VIBRATING-UPLIFT ROCKING MOTION OF CAISSON BREAKWATERS UNDER VARIOUS BREAKING WAVE IMPACT FORCES
Institute of Scientific and Technical Information of China (English)
WANG Yuan-zhan; ZHOU Zhi-rong; YANG Hai-dong
2005-01-01
Overturning is one of principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. The mass-springdashpot model of caisson-foundation system is used to simulate the vibrating-uplift rocking motion of caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave types and the uplift rocking motion on dynamic response behaviors of caisson breakwaters are investigated. It is shown that the dynamic responses of a caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. Though the rotation of a caisson is larger due to the uplift rocking motion, the displacement, the sliding force and the overturning moment of the caisson are significantly reduced. It provides the theoretical base for the design idea that the uplift rocking motion of caisson is allowed in design.
Isospin-symmetry-breaking effects in A∼70 nuclei within beyond-mean-field approach
Energy Technology Data Exchange (ETDEWEB)
Petrovici, A.; Andrei, O. [National Institute for Physics and Nuclear Engineering, R-077125 Bucharest (Romania)
2015-02-24
Particular isospin-symmetry-breaking probes including Coulomb energy differences (CED), mirror energy differences (MED), and triplet energy differences (TED) manifest anomalies in the A∼70 isovector triplets of nuclei. The structure of proton-rich nuclei in the A∼70 mass region suggests shape coexistence and competition between pairing correlations in different channels. Recent results concerning the interplay between isospin-mixing and shape-coexistence effects on exotic phenomena in A∼70 nuclei obtained within the beyond-mean-field complex Excited Vampir variational model with symmetry projection before variation using a realistic effective interaction in a relatively large model space are presented. Excited Vampir predictions concerning the Gamow-Teller β decay to the odd-odd N=Z {sup 66}As and {sup 70}Br nuclei correlated with the pair structure analysis in the T=1 and T=0 channel of the involved wave functions are discussed.
Directory of Open Access Journals (Sweden)
Ferrari Simone
2016-01-01
Full Text Available To design longshore breakwaters, the evaluation of the wave motion transformations over the structures and of the energy they are able to absorb, dissipate and reflect is necessary. To characterize features and transformations of monochromatic wave trains above a breakwater, both submerged and emerged, we have designed and developed a non-intrusive and continuous-in-space technique, based on Image Analysis, and carried out an experimental campaign, in a laboratory flume equipped with a wave-maker, in order to test it. The investigation area was lighted with a light sheet and images were recorded by a video-camera. The working fluid was seeded with non buoyant particles to make it bright and clearly distinct from dark background and breakwater. The technique, that is based on a robust algorithm to identify the free surface, has showed to properly work also in prohibitive situations for traditional resistive probes (e.g., very shallow waters and/or breaking waves and to be able to measure the free surface all over the investigation field in a non-intrusive way. Two kind of analysis were mainly performed, a statistical and a spectral one. The peculiarities of the measurement technique allowed to describe the whole wave transformation and to supply useful information for design purposes.
Theoretical analysis and experimental study of oxygen transfer under regular and non-breaking waves
Institute of Scientific and Technical Information of China (English)
尹则高; 梁丙臣; 王乐
2013-01-01
The dissolved oxygen concentration is an important index of water quality, and the atmosphere is one of the important sources of the dissolved oxygen. In this paper, the mass conservation law and the dimensional analysis method are employed to study the oxygen transfer under regular and non-breaking waves, and a unified oxygen transfer coefficient equation is obtained with consi-deration of the effect of kinetic energy and wave period. An oxygen transfer experiment for the intermediate depth water wave is per-formed to measure the wave parameters and the dissolved oxygen concentration. The experimental data and the least squares method are used to determine the constant in the oxygen transfer coefficient equation. The experimental data and the previous reported data are also used to further validate the oxygen transfer coefficient, and the agreement is satisfactory. The unified equation shows that the oxygen transfer coefficient increases with the increase of a parameter coupled with the wave height and the wave length, but it de-creases with the increase of the wave period, which has a much greater influence on the oxygen transfer coefficient than the coupled parameter.
High order Hamiltonian water wave models with wave-breaking mechanism
Kurnia, R.; Groesen, van E.
2014-01-01
Based on the Hamiltonian formulation of water waves, using Hamiltonian consistent modelling methods, we derive higher order Hamiltonian equations by Taylor expansions of the potential and the vertical velocity around the still water level. The polynomial expansion in wave height is mixed with pseudo
Magnetic Fields inside Extremely Fast Shock Waves
Wiersma, J.
2007-01-01
The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier
Magnetic Fields inside Extremely Fast Shock Waves
Wiersma, J.
2007-01-01
The aim of my research on magnetic fields in extremely fast shock waves has been to predict the properties of shock waves that move almost with the speed of light. These shocks are created in the tenuous interstellar medium by catastrophic events such as the explosion of stars many times heavier
Whistler modes with wave magnetic fields exceeding the ambient field.
Stenzel, R L; Urrutia, J M; Strohmaier, K D
2006-03-10
Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.
Binocular rivalry waves in a directionally selective neural field model
Carroll, Samuel R.; Bressloff, Paul C.
2014-10-01
We extend a neural field model of binocular rivalry waves in the visual cortex to incorporate direction selectivity of moving stimuli. For each eye, we consider a one-dimensional network of neurons that respond maximally to a fixed orientation and speed of a grating stimulus. Recurrent connections within each one-dimensional network are taken to be excitatory and asymmetric, where the asymmetry captures the direction and speed of the moving stimuli. Connections between the two networks are taken to be inhibitory (cross-inhibition). As per previous studies, we incorporate slow adaption as a symmetry breaking mechanism that allows waves to propagate. We derive an analytical expression for traveling wave solutions of the neural field equations, as well as an implicit equation for the wave speed as a function of neurophysiological parameters, and analyze their stability. Most importantly, we show that propagation of traveling waves is faster in the direction of stimulus motion than against it, which is in agreement with previous experimental and computational studies.
Axisymmetry Breaking to Travelling Waves in the Cylinder with Partially Heated Sidewall
Institute of Scientific and Technical Information of China (English)
MA Dong-Jun; SUN De-Jun; YIN Xie-Yuan
2006-01-01
The transition from an axisymmetric stationary now to three-dimensional time-dependent Hows is carefully studied in a vertical cylinder partially heated from the side, with the aspect ratio A = 2 and Prandtl number Pr = 0.021. The now develops from the steady toroidal pattern beyond the first instability threshold, breaks the axisymmetric state at a Rayleigh number near 2000, and transits to standing or travelling azirnuthal waves. A new result is observed that a slightly unstable now pattern of standing waves exists and will transit to stable travelling waves after a long time evolution. The onset of oscillations is associated with a supercritical Hopf bifurcation in a system with O(2) symmetry.
A flexible genuinely nonlinear approach for nonlinear wave propagation, breaking and run-up
Filippini, A. G.; Kazolea, M.; Ricchiuto, M.
2016-04-01
In this paper we evaluate hybrid strategies for the solution of the Green-Naghdi system of equations for the simulation of fully nonlinear and weakly dispersive free surface waves. We consider a two step solution procedure composed of: a first step where the non-hydrostatic source term is recovered by inverting the elliptic coercive operator associated to the dispersive effects; a second step which involves the solution of the hyperbolic shallow water system with the source term, computed in the previous phase, which accounts for the non-hydrostatic effects. Appropriate numerical methods, that can be also generalized on arbitrary unstructured meshes, are used to discretize the two stages: the standard C0 Galerkin finite element method for the elliptic phase; either third order Finite Volume or third order stabilized Finite Element method for the hyperbolic phase. The discrete dispersion properties of the fully coupled schemes obtained are studied, showing accuracy close to or better than that of a fourth order finite difference method. The hybrid approach of locally reverting to the nonlinear shallow water equations is used to recover energy dissipation in breaking regions. To this scope we evaluate two strategies: simply neglecting the non-hydrostatic contribution in the hyperbolic phase; imposing a tighter coupling of the two phases, with a wave breaking indicator embedded in the elliptic phase to smoothly turn off the dispersive effects. The discrete models obtained are thoroughly tested on benchmarks involving wave dispersion, breaking and run-up, showing a very promising potential for the simulation of complex near shore wave physics in terms of accuracy and robustness.
Directory of Open Access Journals (Sweden)
Proshyn Denys
2015-12-01
Full Text Available David Rapoport’s Wave theory of terrorism is one of the most oftencited theories in the literature on terrorist violence. Rapoport is praised for having provided researchers with a universal instrument which allows them to explain the origin and transformation of various historical types of terrorism by applying to them the concept of global waves of terrorist violence driven by universal political impulses. This article, testing the Wave theory against the recent phenomenon of homegrown jihadism in Europe, uncovers this theory’s fundamental weaknesses and questions its real academic and practical value.
EXPERIMENTAL STUDY ON DAM-BREAK FLOOD WAVES OVER MOVABLE BED CHANNEL
Institute of Scientific and Technical Information of China (English)
J.B.LEAL; R.L.FERREIRA; A.B.FRANCO; A.H.CARDOSO
2002-01-01
This paper presents the results of an experimental study focused on the propagation of dam-break flow waves over movable beds.Tests consisted in the sudden opening of a vertical lift-gate which separated initial water and sediment levels upstream and downstream of the gate.They allowed the simulation of the following initial conditions: with or without initial bed-step at the gate cross-section; with or without water downstream of the gate; with or without sediments downstream of the gate.Test results were used to discuss the influence of the movable bed on the celerity of the wave-fronts,as well as on the downstream wave-front height.The total volume of dislodged sediments was also assessed.Some important conclusions were achieved: i) the movable bed does not affect the upstream wave-front celerity but it affects the celerity of the downstream wave-front; ii) the experimental celerities show some disagreement with the analytical solutions; iii) the existence of an initial bed-step at the lift-gate cross-section influences the downstream wave-front propagation,including the water depth.
Cassani, W E R
2001-01-01
As a substitute for the current hypothesis of space-time continuity, we show the nature and the characteristics of a Schild's discrete space-time. With the wave perturbations of its metrical structure we formulate the working hypothesis that all subatomic particles are elementary sources of spherical waves constituting on the whole the mass fields, the electromagnetic and the nuclear field we attribute to the particles. The explicative effectiveness of the new wave unification between quantum mechanics and general relativity is shown by a wave interpretation of three experimental phenomena that lie different physics: astrophysics, optics and quantum physics. A further use of wave Compton effect leads us to discover a mechanism of wave resonance which is able to verify the possible existence of a source of elementary waves that shows a wave model of electron and all the particles. The wave nature of masses and the generalized effect of a Relative Symmetry Principle leads us to consider the inertia as a local c...
Liu, Yu; Yu, Xiping
2016-09-01
A coupled phase-field and volume-of-fluid method is developed to study the sensitive behavior of water waves during breaking. The THINC model is employed to solve the volume-of-fluid function over the entire domain covered by a relatively coarse grid while the phase-field model based on Allen-Cahn equation is applied over the fine grid. A special algorithm that takes into account the sharpness of the diffuse-interface is introduced to correlate the order parameter obtained on the fine grid and the volume-of-fluid function obtained on the coarse grid. The coupled model is then applied to the study of water waves generated by moving pressures on the free surface. The deformation process of the wave crest during the initial stage of breaking is discussed in details. It is shown that there is a significant variation of the free nappe developed at the front side of the wave crest as the wave steepness differs. It is of a plunging type at large wave steepness while of a spilling type at small wave steepness. The numerical results also indicate that breaking occurs later and the duration of breaking is shorter for waves of smaller steepness and vice versa. Neglecting the capillary effect leads to wave breaking with a sharper nappe and a more dynamic plunging process. The surface tension also has an effect to prevent the formation of a free nappe at the front side of the wave crest in some cases.
Vibrating-Rocking Motion of Caisson Breakwater Under Breaking Wave Impact
Institute of Scientific and Technical Information of China (English)
王元战; 郑斌
2001-01-01
The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding andvibrating-rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an earlypaper. In this paper, a model of vibrating-rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated. In casethe overturning moment exceeds the stability moment ofa caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle. It is shown that the sliding force and overturning moment of break-waters can be reduced effectively due to the rocking motion. It is proposed that some rocking motion should be allowedin breakwater design.
Field sources in a Lorentz-symmetry breaking scenario with a single background vector
Energy Technology Data Exchange (ETDEWEB)
Borges, L.H.C. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil); Barone, F.A. [IFQ, Universidade Federal de Itajuba, Av. BPS 1303, Pinheirinho, Caixa Postal 50, Itajuba, MG (Brazil); Helayel-Neto, J.A. [Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil)
2014-06-15
This paper is devoted to an investigation of the interactions between stationary sources of the electromagnetic field, in a model which exhibits explicit Lorentz-symmetry breaking due to the presence of a single background vector. We focus on physical phenomena that emerge from this kind of breaking and which have no counterpart in Maxwell electrodynamics. (orig.)
Bartolo, Nicola; Orlando, Giorgio
2017-07-01
Considering high-energy modifications of Einstein gravity during inflation is an interesting issue. We can constrain the strength of the new gravitational terms through observations of inflationary imprints in the actual universe. In this paper we analyze the effects on slow-roll models due to a Chern-Simons term coupled to the inflaton field through a generic coupling function f(phi). A well known result is the polarization of primordial gravitational waves (PGW) into left and right eigenstates, as a consequence of parity breaking. In such a scenario the modifications to the power spectrum of PGW are suppressed under the conditions that allow to avoid the production of ghost gravitons at a certain energy scale, the so-called Chern-Simons mass MCS. In general it has been recently pointed out that there is very little hope to efficiently constrain chirality of PGW on the basis solely of two-point statistics from future CMB data, even in the most optimistic cases. Thus we search if significant parity breaking signatures can arise at least in the bispectrum statistics. We find that the tensor-tensor-scalar bispectra langle γ γ ζ rangle for each polarization state are the only ones that are not suppressed. Their amplitude, setting the level of parity breaking during inflation, is proportional to the second derivative of the coupling function f(phi) and they turn out to be maximum in the squeezed limit. We comment on the squeezed-limit consistency relation arising in the case of chiral gravitational waves, and on possible observables to constrain these signatures.
DEFF Research Database (Denmark)
Burcharth, H. F.; Liu, Z.
In nature coastal structures are exposed to oblique short-crested waves. The effect of wave incident angle on total wave force on a long caisson are twofold. The one is the force reduction due to the reduction of instantaneous point pressure on the caisson, named point-pressure force reduction...... on the peak-delay force reduction of caissons exposed to non-breaking short-crested waves. Battjes (1982) has investigated theoretically the peak-delay force reduction of shortcrested waves with only one frequency component. Such a force reduction factor cannot be applied because in nature waves are composed...... of many linear components with various frequencies. In this paper the peak-delay force reduction factor is defined on basis of zero-moment of the force spectrum. Based on linear wave theory, formulae for calculation of peakdelay force reduction factor for linear, long-crested and short-crested non-breaking...
Evolution and breaking of a propagating internal wave in stratified ocean
Institute of Scientific and Technical Information of China (English)
LI Bingrui; FAN Haimei; TIAN Jiwei; SUN Bo; ZHANG Zhanhai
2008-01-01
The evolution and breaking of a propagating internal wave are directly numerically simulated using a pseudo-spectral method.The mechanism of PSI (parametric subharmonic instability) involved in the evolution is testified clearly.It dominates gradually in nonlinear resonant interactions.As a consequence,the energy cascades to a second plant wave packet which has lower frequencies and higher wavenumbers than that of the primary wave.With the growth of this wave packet,wave breaking occurs and causes strongly nonlinear regime,I.e.stratified turbulence.The strong mixing and intermittent of the turbulence can be learned from the evolution of the total energy and kurtosis of vortieity vs.time.Some statistic properties of the stratified turbulence are also ana- lyzed,including the spectra of KE (kinetic energy) and PE (potential energy).The results show that the PE spectra display a wavenumber range scaling as 0.2 N4k-3r(N is the Brunt-Vaisala frequency,ky is the vertical wavenumber),which is called buoyancy sub-range.However,the KE spectra cannot satisfy the negative cubic law of vertical wavenumber,which have a much larger downtrend than that of the PE spectra,for the potential energy is transferred more efficiently toward small scales than the ki-netic energy.The Cox number of diapycnal diffusivity is also calculated,and it shows a good consistency with the observations and deductions in the ocean interior,during the stage of the stratified turbulence maintaining a fairly active level.
Pilot-wave theory and quantum fields
Struyve, Ward
2010-10-01
Pilot-wave theories provide possible solutions to the measurement problem. In such theories, quantum systems are not only described by the state vector but also by some additional variables. These additional variables, also called beables, can be particle positions, field configurations, strings, etc. In this paper we focus our attention on pilot-wave theories in which the additional variables are field configurations. The first such theory was proposed by Bohm for the free electromagnetic field. Since Bohm, similar pilot-wave theories have been proposed for other quantum fields. The purpose of this paper is to present an overview and further development of these proposals. We discuss various bosonic quantum field theories such as the Schrödinger field, the free electromagnetic field, scalar quantum electrodynamics and the Abelian Higgs model. In particular, we compare the pilot-wave theories proposed by Bohm and by Valentini for the electromagnetic field, finding that they are equivalent. We further discuss the proposals for fermionic fields by Holland and Valentini. In the case of Holland's model we indicate that further work is required in order to show that the model is capable of reproducing the standard quantum predictions. We also consider a similar model, which does not seem to reproduce the standard quantum predictions. In the case of Valentini's model we point out a problem that seems hard to overcome.
Optical evidence for Alfven wave breaking in the near-Earth magnetosphere
Semeter, J.; Blixt, M.
2006-12-01
Alfvén waves propagating obliquely to the Earth's magnetic lines of force become dispersive when the perpendicular wavelength approaches the collisionless electron skin depth. The dispersion results in two simultaneous effects: (1) wave energy becomes coupled to particle kinetic energy such that parallel acceleration of electrons is possible, and (2) wave energy spreads azimuthally across the background magnetic field, with phase- and group-velocities oppositely directed. Validation of this mechanism requires two-dimensional, time-dependent measurements of the dispersing wave packet. Such evidence should be available in video measurements of the aurora-borealis. An analysis of high-speed, narrow-field, intensified video of dynamic aurora event is presented, confirming the salient predictions for inertial Alfvén wave dispersion.
Institute of Scientific and Technical Information of China (English)
XIA Yun-feng; XU Hua; CHEN Zhong; WU Dao-wen; ZHANG Shi-zhao
2011-01-01
In this paper,flume experiments are focused on sediment transport inside and outside the surf zone.According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump,formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves.Assuming that the sediment diffusion coefficient,which is related with energy dissipation,is proportional to water depth,formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves,and the prediction shows a good agreement with the measurement.
Energy Technology Data Exchange (ETDEWEB)
Bartels, J.; Peters, D. [Rostock Univ. (Germany). Inst. fuer Atmosphaerenphysik
1997-12-31
The poleward advection of upper-tropospheric air is investigated for poleward Rossby wave breaking events. During boreal winter months the isentropic deformations of the tropopause are examined using maps of Ertel`s potential vorticity (EPV) and contour advection (CA) calculations. The role of ambient baro-tropic flow is further examined by idealized numerical models. In the vicinity of the tropopause the characteristic Lagrangian transport of air masses for ECMWF-analysis data are compared with high resolution (T106) ECHAM4 experiments. (author) 3 refs.
Priestley, Matthew D. K.; Joaquim G. Pinto; Dacre, Helen F.; Shaffrey, Len C.
2017-01-01
Winter 2013/14 was the stormiest on record for the UK and was characterized by recurrent clustering of extratropical cyclones. This clustering was associated with a strong, straight and persistent North Atlantic jet and was also associated with Rossby wave breaking (RWB) on both flanks, pinning the jet in place. The occurrence of RWB and cyclone clustering is further studied in 36 years of the ERA-Interim Reanalysis. Clustering at 55°N is associated with an extended and anomalously strong edd...
Imaging dynamical chiral-symmetry breaking: pion wave function on the light front.
Chang, Lei; Cloët, I C; Cobos-Martinez, J J; Roberts, C D; Schmidt, S M; Tandy, P C
2013-03-29
We project onto the light front the pion's Poincaré-covariant Bethe-Salpeter wave function obtained using two different approximations to the kernels of quantum chromodynamics' Dyson-Schwinger equations. At an hadronic scale, both computed results are concave and significantly broader than the asymptotic distribution amplitude, φ(π)(asy)(x)=6x(1-x); e.g., the integral of φ(π)(x)/φ(π)(asy)(x) is 1.8 using the simplest kernel and 1.5 with the more sophisticated kernel. Independent of the kernels, the emergent phenomenon of dynamical chiral-symmetry breaking is responsible for hardening the amplitude.
Measurement of Wave Chaotic Eigenfunctions in the Time-Reversal Symmetry-Breaking Crossover Regime
Chung, S H; Wu, D H; Bridgewater, A; Anlage, S M; Chung, Seok-Hwan; Gokirmak, Ali; Wu, Dong-Ho; Anlage, Steven M.
1999-01-01
We present experimental results on eigenfunctions of a wave chaotic system in the continuous crossover regime between time-reversal symmetric and time-reversal symmetry-broken states. The statistical properties of the eigenfunctions of a two-dimensional microwave resonator are analyzed as a function of an experimentally determined time-reversal symmetry breaking parameter. We test four theories of eigenfunction statistics in the crossover regime. We also find a universal correlation between the one-point and two-point statistical parameters for the crossover eigenfunctions.
Gravitational waves induced by spinor fields
Feng, Kaixi
2015-01-01
In realistic model-building, spinor fields with various masses are present. During inflation, spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of single massive spinor field to the power spectrum of primordial gravitational wave by using retarded Green propagator. We find that the correction is scale-invariant and of order $H^4/M_P^4$ for arbitrary spinor mass $m_{\\psi}$. Additionally, we also observe that when $m_\\psi \\gtrsim H$, the dependence of correction on $m_\\psi/H$ is nontrivial.
National Park Service, Department of the Interior — This point file contains 282 point locations of field plot and observation data used by, and collected for, the vegetation mapping project for Cedar Breaks National...
Exact plane gravitational waves and electromagnetic fields
Montanari, E; Montanari, Enrico; Calura, Mirco
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exactgravitational plane wave is investigated in the framework of Einstein's generalrelativity. We have expressed the general solution to the de Rham equations asa Fourier-like integral. In the general case we have reduced the problem to aset of ordinary differential equations and have explicitly written the solutionin the case of linear polarization of the gravitational wave. We have expressedour results by means of Fermi Normal Coordinates (FNC), which define the properreference frame of the laboratory. Moreover we have provided some "gedankenexperiments", showing that an external gravitational wave induces measurableeffects of non tidal nature via electromagnetic interaction. Consequently it isnot possible to eliminate gravitational effects on electromagnetic field, evenin an arbitrarily small spatial region around an observer freely falling in thefield of a gravitational wave. This is opposite to the case of mechanicalinteraction invo...
Dynamics of Peccei-Quinn breaking field after inflation and axion isocurvature perturbations
Energy Technology Data Exchange (ETDEWEB)
Harigaya, Keisuke; Ibe, Masahiro; Kawasaki, Masahiro [ICRR, University of Tokyo,Kashiwa, Chiba 277-8582 (Japan); Kavli IPMU (WPI), UTIAS, University of Tokyo,Kashiwa, Chiba 277-8583 (Japan); Yanagida, Tsutomu T. [Kavli IPMU (WPI), UTIAS, University of Tokyo,Kashiwa, Chiba 277-8583 (Japan)
2015-11-04
The Peccei-Quinn mechanism suffers from the problem of the isocurvature perturbations. The isocurvature perturbations are suppressed if the Peccei-Quinn breaking scale is large during inflation. The oscillation of the Peccei-Quinn breaking field after inflation, however, leads to the formation of domain walls due to the parametric resonance effect. In this paper, we discuss the evolution of the Peccei-Quinn breaking field after inflation in detail, and propose a model where the parametric resonance is ineffective and hence domain walls are not formed. We also discuss consistency of our model with supersymmetric theory.
Wave Superposition Based Sound Field Reconstruction
Institute of Scientific and Technical Information of China (English)
LI Jia-qing; CHEN Jin; YANG Chao
2008-01-01
In order to overcome the obstacle of singular integral in boundary element method (BEM), wepresented an efficient sound field reconstruction technique based on the wave superposition method (WSM). Itsprinciple includes three steps: first, the sound pressure field of an arbitrary shaped radiator is measured witha microphone array; then, the exterior sound field of the radiator is computed backward and forward using theWSM; at last, the final results are visualized in terms of sound pressure contours or animations. With thesevisualized contours or animations, noise sources can be easily located and quantified; also noise transmissionpath can be found out. By numerical simulation and experimental results, we proved that the technique aresuitable and accurate for sound field reconstruction. In addition, we presented a sound field reconstruction sys-tem prototype on the basis of this technique. It makes a foundation for the application of wave superpositionin the sound field reconstruction in industry situations.
Exact plane gravitational waves and electromagnetic fields
Enrico MontanariUniversity of Ferrara and INFN sezione di Ferrara, Italy; Mirco Calura(University of Ferrara and INFN sezione di Ferrara, Italy)
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exact gravitational plane wave is investigated in the framework of Einstein's general relativity. We have expressed the general solution to the de Rham equations as a Fourier-like integral. In the general case we have reduced the problem to a set of ordinary differential equations and have explicitly written the solution in the case of linear polarization of the gravitational wave. We have expressed our ...
Gravitational Waves from Abelian Gauge Fields and Cosmic Strings at Preheating
Dufaux, Jean-Francois; Garcia-Bellido, Juan
2010-01-01
Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space, and show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearence of new peaks at characteristic frequencies that are related to...
A second order volume of fluid (VOF) scheme for numerical simulation of 2-D breaking waves
Institute of Scientific and Technical Information of China (English)
ZONG Zhi; DONG Guo-hai
2007-01-01
Among all environmental forces acting on ocean structures and marine vessels, those resulting from wave impacts are likely to yield the highest loads. Being highly nonlinear, transient and complex, a theoretical analysis of their impact would be impossible without numerical simulations. In this paper,a pressure-split two-stage numerical algorithm is proposed based on Volume Of Fluid (VOF) methodology.The algorithm is characterized by introduction of two pressures at each half and full cycle time step, and thus it is a second-order accurate algorithm in time. A simplified second-order Godunov-type solver is used for the continuity equations. The method is applied to simulation of breaking waves in a 2-D water tank, and a qualitative comparison with experimental photo observations is made. Quite consistent results are observed between simulations and experiments. Commercially available software and Boundary Integral Method (BIM) have also been used to simulate the same problem. The results from present code and BIM are in good agreement with respect to breaking location and timing, while the results obtained from the commercial software which is only first-order accurate in time has clearly showed a temporal and spatial lag, verifying the need to use a higher order numerical scheme.
Scalar Field (Wave) Dark Matter
Matos, T
2016-01-01
Recent high-quality observations of dwarf and low surface brightness (LSB) galaxies have shown that their dark matter (DM) halos prefer flat central density profiles. On the other hand the standard cold dark matter model simulations predict a more cuspy behavior. Feedback from star formation has been widely used to reconcile simulations with observations, this might be successful in field dwarf galaxies but its success in low mass galaxies remains uncertain. One model that have received much attention is the scalar field dark matter model. Here the dark matter is a self-interacting ultra light scalar field that forms a cosmological Bose-Einstein condensate, a mass of $10^{-22}$eV/c$^2$ is consistent with flat density profiles in the centers of dwarf spheroidal galaxies, reduces the abundance of small halos, might account for the rotation curves even to large radii in spiral galaxies and has an early galaxy formation. The next generation of telescopes will provide better constraints to the model that will help...
Subsurface Droplet Size Distribution generated as breaking waves entrain an oil slick
Li, Cheng; Miller, Jesse; Katz, Joseph
2016-11-01
Breaking waves are a primary mechanism for entraining and dispersing oil spills. Knowledge of the resulting droplet size distribution is crucial for predicting the transport and fate of this oil. In this on-going experimental study, a controlled oil slick of varying viscosity (μd) , density (ρd), interfacial tension (σ) , and thickness δ = 0.5mm are entrained by waves of varying energy (Ew) . The changes to droplet size over time, from seconds to hours, are measured at several locations using multi-resolution holography, which covers sizes ranging from μm to mm. Using dispersants to reduce σ, the Webber number, We =Ew δ / σ , and Ohnesorge number, Oh =μd /(ρd δσ) 0 . 5 , are varied from 6 to 813 and from 0.09 to 0.95, respectively. Droplets smaller than the turbulence scale (2-30 μm - diameter), are generated by "micro-threading". Their size distribution becomes steeper and their total number increase substantially with decreasing interfacial tension. For slopes smaller than -3, measured for σ around 10-1 mN/m, the volumetric size distribution decreases with diameter, i.e. most of the oil breaks into micron-scale droplets. For high interfacial tension oil, the concentration of small droplets increases with wave energy, but this effect diminishes as σ decreases. Droplets larger than 100 μm are generated by turbulent shear. Hence, their number is impacted by μd and Ew. Increasing We from 6 to 15 (Oh from 0.09 to 2.95) increases the initial number of droplets by up to 5 times, but the distribution slopes remain largely similar. Supported by Gulf of Mexico Research Initiative (GoMRI).
The interaction between warm conveyor belts and breaking Rossby waves: a climatological perspective.
Madonna, Erica; Joos, Hanna; Martius, Olivia; Aebi, Christine; Limbach, Sebastian
2014-05-01
Warm conveyor belts (WCBs) are moist ascending airstreams in extratropical cyclones. Climatologically, they are key for the meridional and vertical transport of water vapour and heat. The rapid ascent of WCBs from the boundary layer to the upper troposphere in about 1-2 days leads to cloud formation, (intense) precipitation and the release of latent heat, which modifies their potential vorticity (PV) value in a significant way. Typically WCBs reach the tropopause level with low PV values (~0.5 pvu) and therefore the cross-isentropic transport of low-PV air in WCBs can amplify upper-level Rossby waves and contribute to the formation of PV streamers downstream. Here, filamentary PV streamers are regarded as clear signs of breaking Rossby waves. They in turn can act as precursors of extreme weather events and/or trigger the genesis of another cyclone, potentially generating a new WCB. The aim of this study is to quantify the interaction of WCBs and PV-streamers from a climatological point of view for the ERA-Interim data set for the period 1989-2010. WCBs are identified from comprehensive trajectory calculations that select air parcels in the vicinity of cyclones with a minimum ascent of 600 hPa in 48 hours. From these WCB trajectories, coherent features of WCB outflows are derived and checked for overlapping with PV streamers, which are identified using a contour searching algorithm. Both, WCBs and PV-streamers are then tracked using a novel feature tracking technique, which is based upon a modified region growing approach. With this technique, the interaction of WCBs and PV-streamers is analysed for a 22-years period leading to novel insight about the role of WCBs for triggering the breaking of Rossby waves, as well as, vice versa, about the importance of PV-streamers for the formation of new WCBs.
Study of symmetry breaking of charged scalar field: Hydrodynamic version
Matos, T
2015-01-01
We rewrite the Klein-Gordon (KG) equation for a complex scalar field as a new Gross-Pitaevskii (GP)-like equation. The potential of the scalar field is a mexican-hat potential and the field is in a thermal bath with one loop contribution. We interpret the new GP equation as a finite temperature generalization of the GP equation for a charged field. We find its hydrodynamic version as well and using it, we derive the corresponding thermodynamics. We also obtain a generalized first law for a charged Bose-Einstein Condensate (BEC).
Study of symmetry breaking of charged scalar field: Hydrodynamic version
Matos, T.; Rodríguez-Meza, M. A.
2014-11-01
We rewrite the Klein-Gordon (KG) equation for a complex scalar field as a new Gross-Pitaevskii (GP)-like equation. The potential of the scalar field is a mexican-hat potential and the field is in a thermal bath with one loop contribution. We interpret the new GP equation as a finite temperature generalization of the GP equation for a charged field. We find its hydrodynamic version as well and using it, we derive the corresponding thermodynamics. We also obtain a generalized first law for a charged Bose-Einstein Condensate (BEC).
Directory of Open Access Journals (Sweden)
J. Ungermann
2013-10-01
Full Text Available This paper presents a set of observations and analyses of trace gas cross sections in the extratropical upper troposphere/lower stratosphere (UTLS. The spatially highly resolved (≈0.5 km vertically and 12.5 km horizontally cross sections of ozone (O3, nitric acid (HNO3, and peroxyacetyl nitrate (PAN, retrieved from the measurements of the CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica, revealed intricate layer structures in the region of the subtropical tropopause break. The chemical structure in this region shows an intertwined stratosphere and troposphere. The observed filaments in all discussed trace gases are of a spatial scale of less than 0.8 km vertically and about 200 km horizontally across the jet stream. Backward trajectory calculations confirm that the observed filaments are the result of a breaking Rossby wave in the preceding days. An analysis of the trace gas relationships between PAN and O3 identifies four distinct groups of air mass: polluted subtropical tropospheric air, clean tropical upper-tropospheric air, the lowermost stratospheric air, and air from the deep stratosphere. The tracer relationships further allow the identification of tropospheric, stratospheric, and the transitional air mass made of a mixture of UT and LS air. Mapping of these air mass types onto the geo-spatial location in the cross sections reveals a highly structured extratropical transition layer (ExTL. Finally, the ratio between the measured reactive nitrogen species (HNO3 + PAN + ClONO2 and O3 is analysed to estimate the influence of tropospheric pollution on the extratropical UTLS. In combination, these diagnostics provide the first example of a multi-species two-dimensional picture of the inhomogeneous distribution of chemical species within the UTLS region. Since Rossby wave breaking occurs frequently in the region of the tropopause break, these observed fine-scale filaments are likely ubiquitous in the region. The
Directory of Open Access Journals (Sweden)
J. Ungermann
2013-02-01
Full Text Available This paper presents a set of observations and analyses of trace gas cross-sections in the extratropical upper troposphere/lower stratosphere (UTLS. The spatially highly-resolved (≈0.5 km vertically and 12.5 km horizontally cross-sections of ozone (O_{3}, nitric acid (HNO_{3}, and peroxyacetyl nitrate (PAN, retrieved from the measurements of the CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica, revealed intricate layer structures in the region of the subtropical tropopause break. The chemical structure in this region shows an intertwined stratosphere and troposphere. The observed filaments in all discussed trace gases are of a spatial scale of less than 0.8 km vertically and about 200 km horizontally across the jet-stream. Backward trajectory calculations confirm that the observed filaments are the result of a breaking Rossby wave in the preceding days. An analysis of the trace gas relationships between PAN and O_{3} identifies four distinct groups of air mass: polluted subtropical tropospheric air, clean tropical upper-tropospheric air, the lowermost stratospheric air, and air from the deep stratosphere. The tracer relationships further allow the identification of tropospheric, stratospheric, and the transitional air mass made of a mixture of UT and LS air. Mapping of these air mass types onto the geo-spatial location in the cross-sections reveals a highly structured extratropical transition layer (ExTL. Finally, the ratio between the measured reactive nitrogen species (HNO_{3} + PAN + ClONO_{2} and O_{3} is analysed to estimate the influence of tropospheric pollution on the extratropical UTLS.
In combination, these diagnostics provide the first example of a multi-species two-dimensional picture of a chemically inhomogeneous UTLS region. Since Rossby wave breaking occurs frequently in the region of the tropopause break, these observed fine scale filaments are
Chiral Symmetry Breaking in Planar QED in External Magnetic Fields
Cea, Paolo; Giudice, Pietro; Papa, Alessandro
2012-01-01
We investigate planar quantum electrodynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. We argue that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak-coupling region. We extrapolate our lattice results to the quantum Hall effect in graphene.
Primordial Gravitational Waves from Axion-Gauge Fields Dynamics
Dimastrogiovanni, Emanuela; Fujita, Tomohiro
2016-01-01
Inspired by the chromo-natural inflation model of Adshead&Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a Chern-Simons-type term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theory parameters values, also its tilt. This production process breaks the well-known relation between the tensor-to-scalar ratio and the energy scale of inflation. As a result, even if the Hubble rate is itself too small for the vacuum to generate a tensor amplitude detectable by upcoming experiments, this model still supports observable gravitational waves.
Primordial gravitational waves from axion-gauge fields dynamics
Dimastrogiovanni, Emanuela; Fasiello, Matteo; Fujita, Tomohiro
2017-01-01
Inspired by the chromo-natural inflation model of Adshead&Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a Chern-Simons-type term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theory parameters values, also its tilt. This production process breaks the well-known relation between the tensor-to-scalar ratio and the energy scale of inflation. As a result, even if the Hubble rate is itself too small for the vacuum to generate a tensor amplitude detectable by upcoming experiments, this model still supports observable gravitational waves.
Directory of Open Access Journals (Sweden)
Chanjo Woo
2017-07-01
Full Text Available The present study numerically analyzed the dynamic behavior of 3D framed structures subject to impulsive slamming forces by violent breaking waves. The structures were modeled using multiple lumped masses for the vertical projections of each member, and the slamming forces from the breaking waves were concentrated on these lumped masses. A numerical algorithm was developed to properly incorporate the slamming forces into a dynamic analysis to numerically determine the structural responses. Then, the validity of the numerical analysis was verified using the results of an existing hydraulic experiment. The numerical and experimental results for various model structures were generally in good agreement. The uncertainties concerning the properties of the breaking waves used in the verification are also discussed here.
Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects
Vigeesh, G.; Jackiewicz, J.; Steiner, O.
2017-02-01
Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high-β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.
Energy Technology Data Exchange (ETDEWEB)
Lim, S C [Faculty of Engineering, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia); Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia)], E-mail: sclim@mmu.edu.my, E-mail: lpteo@mmu.edu.my
2008-04-11
Quartic self-interacting fractional Klein-Gordon scalar massive and massless field theories on toroidal spacetime are studied. The effective potential and topologically generated mass are determined using zeta-function regularization technique. Renormalization of these quantities are derived. Conditions for symmetry breaking are obtained analytically. Simulations are carried out to illustrate regions or values of compactified dimensions where symmetry-breaking mechanisms appear.
Hard and soft supersymmetry breaking for ‘graphinos’ in uniform magnetic fields
Hernández-Ortíz, S.; Murguía, G.; Raya, A.
2012-01-01
Using irreducible and reducible representations of the Dirac matrices, we study the two- and four-component quantum mechanical supersymmetric (SUSY) theories for ultrarelativistic fermions in (2 + 1) dimensions (‘graphinos’) in a background uniform magnetic field perpendicular to their plane of motion. We then consider ordinary and parity-violating mass terms and identify the former as a soft SUSY breaking term and the latter as the hard SUSY breaking one.
Breaking phase focused wave group loads on offshore wind turbine monopiles
DEFF Research Database (Denmark)
Ghadirian, Amin; Bredmose, Henrik; Dixen, M.
2016-01-01
OceanWave3D-OpenFOAM solver, against measurements of focused wave group impacts on a monopile. The focused 2D and 3D wave groups are reproduced and the free surface elevation and the in-line forces are compared to the experimental results. In addition, the pressure distribution on the monopile...... is examined at the time of maximum force and discussed in terms of shape and magnitude. Relative pressure time series are also compared between the simulations and experiments and detailed pressure fields for a 2D and 3D impact are discussed in terms of impact type. In general a good match for free surface...... elevation, in-line force and wave-induced pressures is found....
DEFF Research Database (Denmark)
Martinelli, Luca; Lamberti, Alberto; Frigaard, Peter
2007-01-01
This paper addresses wave forces applied to vertical caisson breakwaters. Design diagrams are proposed to evaluate the reduction of the breaker wave force with increasing horizontal length of the units. A model in 1:100 scale of a typical Italian vertical breakwater was tested under multidirectio...
Two-phase SPH modelling of waves caused by dam break over a movable bed
Institute of Scientific and Technical Information of China (English)
Seyedeh Leila RAZAVITOOSI; Seyed Ali AYYOUBZADEH; Alireza VALIZADEH
2014-01-01
This paper describes the application of the Smoothed Particle Hydrodynamics (SPH) method for modeling two dimensional waves caused by dam break over a movable bed in two dimensions. The two phase SPH method is developed to solve the Navier-Stokes equations. Both fluid and sediment phases are described by particles as weakly compressible fluids and the incompressibility is achieved by the equation of state. The sediment phase is modeled as a non-Newtonian fluid using three alternative approaches of artificial viscosity and Bingham Model. In this paper, the new formulations for two-phase flows are proposed. The numerical results obtained from the developed SPH model show acceptable accuracy with comparison to experimental data.
Application of effective medium approximation theory to ocean remote sensing under wave breaking
Institute of Scientific and Technical Information of China (English)
WEI EnBo; LIU Ye
2007-01-01
Based on the effective medium approximation theory of composites,the empirical model proposed by Pandey and Kakar is remedied to investigate the microwave emissivity of sea surface under wave breaking driven by strong wind.In the improved model,the effects of seawater bubbles,droplets and difference in temperature of air and sea interface (DTAS) on the emissivity of sea surface covered by whitecaps are discussed.The model results indicate that the effective emissivity of sea surface increases with DTAS increasing,and the impacts of bubble structures and thickness of whitecaps layer on the emissivity are included in the model by introducing the effective dielectric constant of whitecaps layer.Moreover,a good agreement is obtained by comparing the model results with the Rose's experimental data.
Application of effective medium approximation theory to ocean remote sensing under wave breaking
Institute of Scientific and Technical Information of China (English)
2007-01-01
Based on the effective medium approximation theory of composites, the empirical model proposed by Pandey and Kakar is remedied to investigate the microwave emissivity of sea surface under wave breaking driven by strong wind. In the improved model, the effects of seawater bubbles, droplets and difference in temperature of air and sea interface (DTAS) on the emissivity of sea surface covered by whitecaps are discussed. The model results indicate that the effective emissivity of sea surface in-creases with DTAS increasing, and the impacts of bubble structures and thickness of whitecaps layer on the emissivity are included in the model by introducing the effective dielectric constant of whitecaps layer. Moreover, a good agreement is obtained by comparing the model results with the Rose’s ex-perimental data.
Automatic detection of tulip breaking virus (TBV) in tulip fields using machine vision
Polder, G.; Heijden, van der G.W.A.M.; Doorn, van J.; Baltissen, A.H.M.C.
2012-01-01
Tulip breaking virus (TBV) causes severe economic losses for the Netherlands. Infected plants must be removed from the field as soon as possible to prevent further spread by aphids. Until now screening is done by visual inspection in the field. As the availability of human experts is limited there
Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5
Energy Technology Data Exchange (ETDEWEB)
Helm, T. [MPI-CPFS (Germany); Bachmann, M. [MPI-CPFS (Germany); Moll, P.J.W. [MPI-CPFS (Germany); Balicas, L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Chan, Mun Keat [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramshaw, Brad [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Balakirev, Fedor Fedorovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bauer, Eric Dietzgen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ronning, Filip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-03-23
Electronic nematicity appears in proximity to unconventional high-temperature superconductivity in the cuprates and iron-arsenides, yet whether they cooperate or compete is widely discussed. While many parallels are drawn between high-T_{c} and heavy fermion superconductors, electronic nematicity was not believed to be an important aspect in their superconductivity. We have found evidence for a field-induced strong electronic in-plane symmetry breaking in the tetragonal heavy fermion superconductor CeRhIn_{5}. At ambient pressure and zero field, it hosts an anti-ferromagnetic order (AFM) of nominally localized 4f electrons at TN=3.8K(1). Moderate pressure of 17kBar suppresses the AFM order and a dome of superconductivity appears around the quantum critical point. Similarly, a density-wave-like correlated phase appears centered around the field-induced AFM quantum critical point. In this phase, we have now observed electronic nematic behavior.
Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking
Yin Poo; Cheng He; Chao Xiao; Ming-Hui Lu; Rui-Xin Wu; Yan-Feng Chen
2016-01-01
One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-rever...
THOR Fields and Wave Processor - FWP
Soucek, Jan; Rothkaehl, Hanna; Ahlen, Lennart; Balikhin, Michael; Carr, Christopher; Dekkali, Moustapha; Khotyaintsev, Yuri; Lan, Radek; Magnes, Werner; Morawski, Marek; Nakamura, Rumi; Uhlir, Ludek; Yearby, Keith; Winkler, Marek; Zaslavsky, Arnaud
2017-04-01
If selected, Turbulence Heating ObserveR (THOR) will become the first spacecraft mission dedicated to the study of plasma turbulence. The Fields and Waves Processor (FWP) is an integrated electronics unit for all electromagnetic field measurements performed by THOR. FWP will interface with all THOR fields sensors: electric field antennas of the EFI instrument, the MAG fluxgate magnetometer, and search-coil magnetometer (SCM), and perform signal digitization and on-board data processing. FWP box will house multiple data acquisition sub-units and signal analyzers all sharing a common power supply and data processing unit and thus a single data and power interface to the spacecraft. Integrating all the electromagnetic field measurements in a single unit will improve the consistency of field measurement and accuracy of time synchronization. The scientific value of highly sensitive electric and magnetic field measurements in space has been demonstrated by Cluster (among other spacecraft) and THOR instrumentation will further improve on this heritage. Large dynamic range of the instruments will be complemented by a thorough electromagnetic cleanliness program, which will prevent perturbation of field measurements by interference from payload and platform subsystems. Taking advantage of the capabilities of modern electronics and the large telemetry bandwidth of THOR, FWP will provide multi-component electromagnetic field waveforms and spectral data products at a high time resolution. Fully synchronized sampling of many signals will allow to resolve wave phase information and estimate wavelength via interferometric correlations between EFI probes. FWP will also implement a plasma resonance sounder and a digital plasma quasi-thermal noise analyzer designed to provide high cadence measurements of plasma density and temperature complementary to data from particle instruments. FWP will rapidly transmit information about magnetic field vector and spacecraft potential to the
THOR Field and Wave Processor - FWP
Soucek, Jan; Rothkaehl, Hanna; Balikhin, Michael; Zaslavsky, Arnaud; Nakamura, Rumi; Khotyaintsev, Yuri; Uhlir, Ludek; Lan, Radek; Yearby, Keith; Morawski, Marek; Winkler, Marek
2016-04-01
If selected, Turbulence Heating ObserveR (THOR) will become the first mission ever flown in space dedicated to plasma turbulence. The Fields and Waves Processor (FWP) is an integrated electronics unit for all electromagnetic field measurements performed by THOR. FWP will interface with all fields sensors: electric field antennas of the EFI instrument, the MAG fluxgate magnetometer and search-coil magnetometer (SCM) and perform data digitization and on-board processing. FWP box will house multiple data acquisition sub-units and signal analyzers all sharing a common power supply and data processing unit and thus a single data and power interface to the spacecraft. Integrating all the electromagnetic field measurements in a single unit will improve the consistency of field measurement and accuracy of time synchronization. The feasibility of making highly sensitive electric and magnetic field measurements in space has been demonstrated by Cluster (among other spacecraft) and THOR instrumentation complemented by a thorough electromagnetic cleanliness program will further improve on this heritage. Taking advantage of the capabilities of modern electronics, FWP will provide simultaneous synchronized waveform and spectral data products at high time resolution from the numerous THOR sensors, taking advantage of the large telemetry bandwidth of THOR. FWP will also implement a plasma a resonance sounder and a digital plasma quasi-thermal noise analyzer designed to provide high cadence measurements of plasma density and temperature complementary to data from particle instruments. FWP will be interfaced with the particle instrument data processing unit (PPU) via a dedicated digital link which will enable performing on board correlation between waves and particles, quantifying the transfer of energy between waves and particles. The FWP instrument shall be designed and built by an international consortium of scientific institutes from Czech Republic, Poland, France, UK, Sweden
Inversion symmetry breaking of atomic bound states in strong and short laser fields
Stooß, Veit; Ott, Christian; Blättermann, Alexander; Ding, Thomas; Pfeifer, Thomas
2015-01-01
In any atomic species, the spherically symmetric potential originating from the charged nucleus results in fundamental symmetry properties governing the structure of atomic states and transition rules between them. If atoms are exposed to external electric fields, these properties are modified giving rise to energy shifts such as the AC Stark-effect in varying fields and, contrary to this in a constant (DC) electric field for high enough field strengths, the breaking of the atomic symmetry which causes fundamental changes in the atom's properties. This has already been observed for atomic Rydberg states with high principal quantum numbers. Here, we report on the observation of symmetry breaking effects in Helium atoms for states with principal quantum number n=2 utilizing strong visible laser fields. These findings were enabled by temporally resolving the dynamics better than the sub-optical cycle of the applied laser field, utilizing the method of attosecond transient absorption spectroscopy (ATAS). We ident...
Determination of wave fields from perturbed particle orbits
Skiff, Fred
1992-12-01
The linear problem of determining wave electric fields from measured perturbed particle distributions is considered. Previous work is extended to consider the case of arbitrary wave structure transverse to the magnetic field. The calculations are limited to electrostatic waves, although the ideas extend naturally to electromagnetic waves, and are illustrated in the one-dimensional case using data taken by laser-induced fluorescence.
Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.
1983-01-01
Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.
The dynamical impact of Rossby wave breaking upon UK PM10 concentration
Webber, Christopher P.; Dacre, Helen F.; Collins, William J.; Masato, Giacomo
2017-01-01
Coarse particulate matter (PM10) has long been understood to be hazardous to human health, with mortality rates increasing as a result of raised ground level concentrations. We explore the influence of synoptic-scale meteorology on daily mean observed PM10 concentration ([PM10]) using Rossby wave breaking (RWB). Meteorological reanalysis data for the winter months (DJF) between January 1999 and December 2008 and observed PM10 data for three urban background UK (Midland) sites were analysed. Three RWB diagnostics were used to identify RWB that had significant influence on UK Midland PM10. RWB events were classified according to whether the RWB was cyclonic or anticyclonic in its direction of breaking and whether the RWB event was influenced more by poleward or equatorial air masses. We find that there is a strong link between RWB events and UK [PM10]. Significant increases (p UK [PM10] were seen 1 day following RWB occurring in spatially constrained northeast Atlantic-European regions. Analysis into episodic PM10 exceedance events shows increased probability of [PM10] exceedance associated with all RWB subsets. The greatest probability of exceeding the UK [PM10] threshold was associated with cyclonic RWB preceded by anticyclonic RWB forming an Ω block synoptic pattern. This mechanism suggests an easterly advection of European PM10 followed by prolonged stagnant conditions within the UK and led to an almost threefold increase in the probability of the UK Midlands exceeding a hazardous [PM10] threshold (0.383), when compared to days where no RWB was detected (0.129).
2012-09-30
codes are parallelized using message passing interface (MPI) based on domain decomposition. For SPH , graphics processing unit (GPU) computing, which is...aims at developing a numerical capability using a Lagrangian Smoothed Particle Hydrodynamics ( SPH ) method and an Eulerian Level-Set Method (LSM) for...the SPH and LSM with environmental input provided by coupled wind and wave simulations at far field; (2) Use the numerical method developed in (1
Kartashova, Elena
2013-01-01
In this Letter we study the form of the energy spectrum of Riemann waves in weakly nonlinear non-dispersive media. For quadratic and cubic nonlinearity we demonstrate that the deformation of an Riemann wave over time yields an exponential energy spectrum which turns into power law asymptotic with the slope being approximately -8/3 at the last stage of evolution before breaking. We argue, that this is the universal asymptotic behaviour of Riemann waves in any nonlinear non-dispersive medium at the point of breaking. The results reported in this Letter can be used in various non-dispersive media, e.g. magneto-hydro dynamics, physical oceanography, nonlinear acoustics.
Further Investigation on Chiral Symmetry Breaking in a Uniform External Magnetic Field
Jasinski, P
2004-01-01
We study chiral symmetry breaking in QED when a uniform external magnetic field is present. We calculate higher order corrections to the dynamically generated fermion mass and find them to be small. In so doing we correct an error in the literature regarding the matrix structure of the fermion self-energy.
Field trials results of guided wave tomography
Volker, Arno; van Zon, Tim; van der Leden, Edwin
2015-03-01
Corrosion is one of the industries major issues regarding the integrity of assets. Guided wave travel time tomography is a method capable of providing an absolute wall thickness map. This method is currently making the transition from the laboratory to the field. For this purpose a dedicated data acquisition system and special purpose EMAT sensor rings have been developed. The system can be deployed for permanent monitoring and inspections. Field trials have been conducted on various pipes with different diameters, containing either liquid or gas. The main focus has been on pipe supports. The results demonstrate the successful operation of the technology in the field. Expected corrosion damage was clearly visible on the produced results enabling asset owner to make calculated decisions on the pipelines safety, maintenance and operations.
Superconformal partial waves in Grassmannian field theories
Doobary, Reza
2015-01-01
We derive superconformal partial waves for all scalar four-point functions on a super Grassmannian space Gr(m|n,2m|2n) for all m,n. This family of four-point functions includes those of all (arbitrary weight) half BPS operators in both N=4 SYM (m=n=2) and in N=2 superconformal field theories in four dimensions (m=2,n=1) on analytic superspace. It also includes four-point functions of all (arbitrary dimension) scalar fields in non-supersymmetric conformal field theories (m=2,n=0) on Minkowski space, as well as those of a certain class of representations of the compact SU(2n) coset spaces. As an application we then specialise to N=4 SYM and use these results to perform a detailed superconformal partial wave analysis of the four- point functions of arbitrary weight half BPS operators. We discuss the non-trivial separation of protected and unprotected sectors for the , and cases in an SU(N) gauge theory at finite N. The correlator predicts a non-trivial protected twist four sector for which we can completely ...
Chiral Symmetry Breaking and External Fields in the Kuperstein-Sonnenschein Model
Alam, M Sohaib; Kundu, Arnab
2012-01-01
A novel holographic model of chiral symmetry breaking has been proposed by Kuperstein and Sonnenschein by embedding non-supersymmetric probe D7 and anti-D7 branes in the Klebanov-Witten background. We study the dynamics of the probe flavours in this model in the presence of finite temperature and a constant electromagnetic field. In keeping with the weakly coupled field theory intuition, we find the magnetic field promotes spontaneous breaking of chiral symmetry whereas the electric field restores it. The former effect is universally known as the "magnetic catalysis" in chiral symmetry breaking. In the presence of an electric field such a condensation is inhibited and a current flows. Thus we are faced with a steady-state situation rather than a system in equilibrium. We conjecture a definition of thermodynamic free energy for this steady-state phase and using this proposal we study the detailed phase structure when both electric and magnetic fields are present in two representative configurations: mutually p...
DAM-BREAK SHOCK WAVES WITH FLOATING DEBRIS: EXPERIMENTALANALYSIS AND TWO-PHASE MODELLING
Directory of Open Access Journals (Sweden)
Stefano Mambretti
2008-06-01
Full Text Available To predict floods and debris flow dynamics a numerical model, based on 1D De Saint Venant (SV equations, was developed. The McCormack – Jameson shock capturing scheme was employed for the solution of the equations, written in a conservative law form. This technique was applied to determine both the propagation and the profile of a two – phase debris flow resulting from the instantaneous and complete collapse of a storage dam. To validate the model, comparisons have been made between its predictions and laboratory measurements concerning flows of water and homogeneous granular mixtures in a uniform geometry flume reproducing dam – break waves. Agreements between computational and experimental results are considered very satisfactory for mature (non – stratified debris flows, which embrace most real cases. To better predict immature (stratified flows, the model should be improved in order to feature, in a more realistic way, the distribution of the particles of different size within the mixture. On the whole, the model proposed can easily be extended to channels with arbitrary cross sections for debris flow routing, as well as for solving different problems of unsteady flow in open channels by incorporating the appropriate initial and boundary conditions.
Dam break flood wave under different reservoir’s capacities and lengths
Indian Academy of Sciences (India)
FARHAD HOOSHYARIPOR; AHMAD TAHERSHAMSI; SAHAND RAZI
2017-09-01
Dam failure has been the subject of many hydraulic engineering studies due to its complicated physics with many uncertainties involved and the potential to cause many losses of lives and economical losses. A primary source of uncertainties in many dam failure analyses refers to prediction of the reservoir’s outflow hydrograph, which is studied in the present investigation. This paper presents an experimental study on instantaneous dam failure flood under different reservoir’s capacities and lengths in which the side slopes change within a range of 30°–90°. Thus, several outflow hydrographs are calculated and compared. The results reveal the role of the side slopes on dam break flood wave, such that lower side slope creates more catastrophic outflow.The reservoir capacity and length are also recognized to be important factors, such that they do affect peak discharge and time to peak of the outflow hydrograph. Finally, the paper presents two simple relations for peak discharge and maximum water level estimation at any downstream location.
Multidimensional wave field signal theory: Mathematical foundations
Directory of Open Access Journals (Sweden)
Natalie Baddour
2011-06-01
Full Text Available Many important physical phenomena are described by wave or diffusion-wave type equations. Since these equations are linear, it would be useful to be able to use tools from the theory of linear signals and systems in solving related forward or inverse problems. In particular, the transform domain signal description from linear system theory has shown concrete promise for the solution of problems that are governed by a multidimensional wave field. The aim is to develop a unified framework for the description of wavefields via multidimensional signals. However, certain preliminary mathematical results are crucial for the development of this framework. This first paper on this topic thus introduces the mathematical foundations and proves some important mathematical results. The foundation of the framework starts with the inhomogeneous Helmholtz or pseudo-Helmholtz equation, which is the mathematical basis of a large class of wavefields. Application of the appropriate multi-dimensional Fourier transform leads to a transfer function description. To return to the physical spatial domain, certain mathematical results are necessary and these are presented and proved here as six fundamental theorems. These theorems are crucial for the evaluation of a certain class of improper integrals which arise in the evaluation of inverse multi-dimensional Fourier and Hankel transforms, upon which the framework is based. Subsequently, applications of these theorems are demonstrated, in particular for the derivation of Green's functions in different coordinate systems.
Cai, Xuguang; Yuan, Tao; Zhao, Yucheng; Pautet, Pierre-Dominique; Taylor, Mike J.; Pendleton, W. R.
2014-08-01
The impacts of gravity wave (GW) on the thermal and dynamic characteristics within the mesosphere/lower thermosphere, especially on the atmospheric instabilities, are still not fully understood. In this paper, we conduct a comprehensive and detailed investigation on one GW breaking event during a collaborative campaign between the Utah State University Na lidar and the Advanced Mesospheric Temperature Mapper (AMTM) on 9 September 2012. The AMTM provides direct evidence of the GW breaking as well as the horizontal parameters of the GWs involved, while the Na lidar's full diurnal cycle observations are utilized to uncover the roles of tide and GWs in generating a dynamical instability layer. By studying the changes of the OH layer peak altitude, we located the wave breaking altitude as well as the significance of a 2 h wave that are essential to this instability formation. By reconstructing the mean fields, tidal and GW variations during the wave breaking event, we find that the large-amplitude GWs significantly changed the Brunt-Vaisala frequency square and the horizontal wind shear when superimposed on the tidal wind, producing a transient dynamic unstable region between 84 km and 87 km around 11:00 UT that caused a subsequent small-scale GW breaking.
CURVATURE RELATION OF WAVE FRONT AND WAVE CHANGING IN EXTERNAL FIELD
Institute of Scientific and Technical Information of China (English)
LIU Shen-quan; SONG Le
2005-01-01
The changing of wave structure in excitable media in external field is studied and the curvature relation of wave front is analyzed. Under external stimulus the normal velocity of wave front has linear relation with mean curvature of wave front, plane velocity and external field. The simulation methods have been used to analyze BarEiswirth model with external field and obtain the wave pattern of excitable media contained external stimulus. These theoretical analysis and simulation results are identical with experiments of BZ reaction. So the results here theoretically explain the BZ phenomenon under external field and the simulation results here have rich wave patterns.
Subtraction of power counting breaking terms in chiral perturbation theory: spinless matter fields
Du, Meng-Lin; Meißner, Ulf-G
2016-01-01
When matter fields are included in chiral perturbation theory, the nonvanishing mass in the chiral limit introduces a new energy scale so that the loop diagrams including such matter field propagators spoil the usual power counting. However, the power counting breaking terms can be absorbed into counterterms in the chiral Lagrangian. In this paper, we systematically derive these terms to leading one-loop order (next-to-next-to leading order in the chiral expansion) at once by calculating the generating functional using the path integral. They are then absorbed by counterterms in the next-to-leading order Lagrangian. The method can be extended to calculating power counting breaking terms for other matter fields.
Whitecapping and wave field evolution in a coastal bay
Mulligan, R.P.; Bowen, A.J.; Hay, A.E.; Van der Westhuysen, A.J.; Battjes, J.A.
2008-01-01
Evolution of the wave field in a coastal bay is investigated, by comparison between field observations and numerical simulations using a spectral wave model (Simulating WAves Nearshore (SWAN)). The simulations were conducted for the passage of an extratropical storm, during which surface elevation s
External Fields and Chiral Symmetry Breaking in the Sakai-Sugimoto Model
Johnson, Clifford V
2008-01-01
Using the Sakai-Sugimoto model we study the effect of an external magnetic field on the dynamics of fundamental flavours in both the confined and deconfined phases of a large N_c gauge theory. We find that an external magnetic field promotes chiral symmetry breaking, consistent with the ``magnetic catalysis'' observed in the field theory literature, and seen in other studies using holographic duals. The external field increases the separation between the deconfinement temperature and the chiral symmetry restoring temperature. In the deconfined phase we investigate the temperature-magnetic field phase diagram and observe, for example, there exists a maximum critical temperature (at which symmetry is restored) for very large magnetic field. We find that this and certain other phenomena persist for the Sakai-Sugimoto type models with probe branes of diverse dimensions. We comment briefly on the dynamics in the presence of an external electric field.
DEFF Research Database (Denmark)
Burcharth, H. F.; Sørensen, Jørgen S.; Christiani, E.
1994-01-01
Impulsive wave breaking forces on a vertical caisson breakwater has been included by Takahashi et al, (1994) in Goda's wave pressure formula (Goda et al. 1972 and Goda 1974). Based on these formulae a deterministic design method following the Japanese recommendations has been used for the design ...... stability analysis is presented by the example of a rotation slip failure involving kinematically correct slip surfaces and failure zones in undrained clay. A conventional static quasi-static analysis based on equating external and internal work is used....
A CFD Investigation on the Effect of the Air Entrainment in Breaking Wave Impacts on a Mono-Pile
DEFF Research Database (Denmark)
Tomaselli, Pietro; Christensen, Erik Damgaard
2017-01-01
In impacts of breaking waves on offshore structures, it is still not well-known how the air entrainment phenomenon affects the exerted loads. In this paper, a developed CFD solver capable of simulating the air entrainment process was employed to repro-duce an experimental investigation...... on the impact of a spilling wave against a circular cylinder. The exerted in-line force was computed with and without the inclusion of dispersed bubbles. Results showed that the magnitude of the computed force was affected when the entrainment of bubbles was simulated....
Garcia, R. R.
1986-01-01
The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.
Electric-Field Switchable Second-Harmonic Generation in Bilayer MoS2 by Inversion Symmetry Breaking.
Klein, J; Wierzbowski, J; Steinhoff, A; Florian, M; Rösner, M; Heimbach, F; Müller, K; Jahnke, F; Wehling, T O; Finley, J J; Kaniber, M
2017-01-11
We demonstrate pronounced electric-field-induced second-harmonic generation in naturally inversion symmetric 2H stacked bilayer MoS2 embedded into microcapacitor devices. By applying strong external electric field perturbations (|F| = ±2.6 MV cm(-1)) perpendicular to the basal plane of the crystal, we control the inversion symmetry breaking and, hereby, tune the nonlinear conversion efficiency. Strong tunability of the nonlinear response is observed throughout the energy range (Eω ∼ 1.25-1.47 eV) probed by measuring the second-harmonic response at E2ω, spectrally detuned from both the A- and B-exciton resonances. A 60-fold enhancement of the second-order nonlinear signal is obtained for emission at E2ω = 2.49 eV, energetically detuned by ΔE = E2ω - EC = -0.26 eV from the C-resonance (EC = 2.75 eV). The pronounced spectral dependence of the electric-field-induced second-harmonic generation signal reflects the bandstructure and wave function admixture and exhibits particularly strong tunability below the C-resonance, in good agreement with density functional theory calculations. Moreover, we show that the field-induced second-harmonic generation relies on the interlayer coupling in the bilayer. Our findings strongly suggest that the strong tunability of the electric-field-induced second-harmonic generation signal in bilayer transition metal dichalcogenides may find applications in miniaturized electrically switchable nonlinear devices.
Fritz, Sean; Hernandez-Castillo, Alicia O.; Abeysekera, Chamara; Zwier, Timothy S.
2017-06-01
The 8-18 GHz conformer specific rotational spectrum of gauche- and anti-3-phenylpropionitrile (C6H5-CH2-CH2-CN) conformers has been recorded using the strong field coherence breaking (SFCB) technique [1] with a modified line picking scheme for multiple selective excitations (MSE). As the recombination product of benzyl and cyanomethyl resonance-stabilized radicals, 3-phenylpropionitrile is a likely component of the complex organics in Titan's atmosphere, motivating its structural characterization. Details of the modified line picking scheme, hyperfine constants and relative population ratios of the two conformers will be presented. [1] A.O Hernandez-Castillo, Chamara Abeysekera, Brian M. Hays, Timothy S. Zwier, "Broadband Multi-Resonant Strong Field Coherence Breaking as a Tool for Single Isomer Microwave Spectroscopy." J. Chem. Phys. 145, 114203 (2016).
Synthesizing Waves from Animated Height Fields
DEFF Research Database (Denmark)
Nielsen, Michael Bang; Söderström, Andreas; Bridson, Robert
2013-01-01
for synthesizing Fourier-based ocean waves that match a previs input, allowing artists to quickly enhance the input wave animation with additional higher-frequency detail that moves consistently with the coarse waves, tweak the wave shapes to flatten troughs and sharpen peaks if desired (as is characteristic...
Mean flow-storm track relationship and Rossby wave breaking in two types of El-Niño
Liu, Chengji; Ren, Xuejuan; Yang, Xiuqun
2014-01-01
The features of large-scale circulation, storm tracks and the dynamical relationship between them were examined by investigating Rossby wave breaking (RWB) processes associated with Eastern Pacific (EP) and Central Pacific (CP) El-Niño. During EP El-Niño, the geopotential height anomaly at 500 hPa (Z500) exhibits a Pacific-North America (PNA) pattern. During CP El-Niño, the Z500 anomaly shows a north positive-south negative pattern over the North Pacific. The anomalous distributions of baroclinicity and storm track are consistent with those of upper-level zonal wind for both EP and CP El-Niño, suggesting impacts of mean flow on storm track variability. Anticyclonic wave breaking (AWB) occurs less frequently in EP El-Niño years, while cyclonic wave breaking (CWB) occurs more frequently in CP El-Niño years over the North Pacific sector. Outside the North Pacific, more CWB events occur over North America during EP El-Niño. When AWB events occur less frequently over the North Pacific during EP El-Niño, Z500 decreases locally and the zonal wind is strengthened (weakened) to the south (north). This is because AWB events reflect a monopole high anomaly at the centroid of breaking events. When CWB events occur more frequently over the North Pacific under CP El-Niño conditions, and over North America under EP El-Niño condition, Z500 increases (decreases) to the northeast (southwest), since CWB events are related to a northeast-southwest dipole Z500 anomaly. The anomalous RWB events act to invigorate and reinforce the circulation anomalies over the North Pacific-North America region linked with the two types of El-Niño.
Stable Propagating Waves and Wake Fields in Relativistic Electromagnetic Plasma
Institute of Scientific and Technical Information of China (English)
DUAN Yi-Shi; XIE Bai-Song; TIAN Miao; YIN Xin-Tao; ZHANG Xin-Hui
2008-01-01
Stable propagating waves and wake fields in relativistic electromagnetic plasma are investigated. The incident electromagnetic field has a finite initial constant amplitude meanwhile the longitudinal momentum of electrons is taken into account in the problem. It is found that in the moving frame with transverse wave group velocity the stable propagating transverse electromagnetic waves and longitudinal plasma wake fields can exist in the appropriate regime of plasma.
Wave Grouping of a Drifting Spiral Wave in the Presence of an External Field
Institute of Scientific and Technical Information of China (English)
YANG Hu-Jiang; YANG Jun-Zhong; HU Gang
2007-01-01
The phenomenon of wave grouping, in which the dense waves and the sparse waves can form groups in front of the spiral tip when the spiral wave is meandering, has been reported in a chemical reaction system recently. We present a method to realize the phenomenon of wave grouping by applying an external field to the system. The numerical simulations are carried out on the basis of the FitzHugh-Nagumo equations.
Adler, Stephen L
2016-01-01
We study $SU(8)$ symmetry breaking induced by minimizing the Coleman-Weinberg effective potential for a third rank antisymmetric tensor scalar field in the 56 representation. Instead of breaking $SU(8) \\supset SU(3) \\times SU(5)$, we find that the stable minimum of the potential breaks the original symmetry according to $SU(8) \\supset SU(3) \\times Sp(4)$. Using both numerical and analytical methods, we present results for the potential minimum, the corresponding Goldstone boson structure and BEH mechanism, and the group-theoretic classification of the residual states after symmetry breaking.
Adler, Stephen L.
2016-08-01
We study SU(8) symmetry breaking induced by minimizing the Coleman-Weinberg effective potential for a third rank antisymmetric tensor scalar field in the 56 representation. Instead of breaking {SU}(8)\\supset {SU}(3)× {SU}(5), we find that the stable minimum of the potential breaks the original symmetry according to {SU}(8)\\supset {SU}(3)× {Sp}(4). Using both numerical and analytical methods, we present results for the potential minimum, the corresponding Goldstone boson structure and BEH mechanism, and the group-theoretic classification of the residual states after symmetry breaking.
Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking.
Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng
2016-07-08
One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking.
Effective Field Theory of Emergent Symmetry Breaking in Deformed Atomic Nuclei
Papenbrock, T
2015-01-01
Spontaneous symmetry breaking in non-relativistic quantum systems has previously been addressed in the framework of effective field theory. Low-lying excitations are constructed from Nambu-Goldstone modes using symmetry arguments only. We extend that approach to finite systems. The approach is very general. To be specific, however, we consider atomic nuclei with intrinsically deformed ground states. The emergent symmetry breaking in such systems requires the introduction of additional degrees of freedom on top of the Nambu-Goldstone modes. Symmetry arguments suffice to construct the low-lying states of the system. In deformed nuclei these are vibrational modes each of which serves as band head of a rotational band.
Direct analysis of dispersive wave fields from near-field pressure measurements
Horchens, L.
2011-01-01
Flexural waves play a significant role for the radiation of sound from plates. The analysis of flexural wave fields enables the detection of sources and transmission paths in plate-like structures. The measurement of these wave fields can be carried out indirectly by means of near-field acoustic hol
May, Nathaniel W.; Axson, Jessica L.; Watson, Alexa; Pratt, Kerri A.; Ault, Andrew P.
2016-09-01
Wave-breaking action in bodies of freshwater produces atmospheric aerosols via a similar mechanism to sea spray aerosol (SSA) from seawater. The term lake spray aerosol (LSA) is proposed to describe particles formed by this mechanism, which have been observed over the Laurentian Great Lakes. Though LSA has been identified from size distribution measurements during a single measurement campaign, no measurements of LSA composition or relationship to bubble-bursting dynamics have been conducted. An LSA generator utilizing a plunging jet, similar to many SSA generators, was constructed for the generation of aerosol from freshwater samples and model salt solutions. To evaluate this new generator, bubble and aerosol number size distributions were measured for salt solutions representative of freshwater (CaCO3) and seawater (NaCl) at concentrations ranging from that of freshwater to seawater (0.05-35 g kg-1), synthetic seawater (inorganic), synthetic freshwater (inorganic), and a freshwater sample from Lake Michigan. Following validation of the bubble and aerosol size distributions using synthetic seawater, a range of salt concentrations were investigated. The systematic studies of the model salts, synthetic freshwater, and Lake Michigan sample indicate that LSA is characterized by a larger number size distribution mode diameter of 300 nm (lognormal), compared to seawater at 110 nm. Decreasing salt concentrations from seawater to freshwater led to greater bubble coalescence and formation of larger bubbles, which generated larger particles and lower aerosol number concentrations. This resulted in a bimodal number size distribution with a primary mode (180 ± 20 nm) larger than that of SSA, as well as a secondary mode (46 ± 6 nm) smaller than that of SSA. This new method for studying LSA under isolated conditions is needed as models, at present, utilize SSA parameterizations for freshwater systems, which do not accurately predict the different size distributions observed
Electron-Bernstein Waves in Inhomogeneous Magnetic Fields
DEFF Research Database (Denmark)
Armstrong, R. J.; Frederiksen, Å.; Pécseli, Hans
1984-01-01
The propagation of small amplitude electron-Bernstein waves in different inhomogeneous magnetic field geometries is investigated experimentally. Wave propagation towards both cut-offs and resonances are considered. The experimental results are supported by a numerical ray-tracing analysis. Spatial...... enhancements of the wave amplitude are interpreted as a result of caustic formation....
Wave directional spreading from point field measurements
McAllister, M. L.; Venugopal, V.; Borthwick, A. G. L.
2017-04-01
Ocean waves have multidirectional components. Most wave measurements are taken at a single point, and so fail to capture information about the relative directions of the wave components directly. Conventional means of directional estimation require a minimum of three concurrent time series of measurements at different spatial locations in order to derive information on local directional wave spreading. Here, the relationship between wave nonlinearity and directionality is utilized to estimate local spreading without the need for multiple concurrent measurements, following Adcock & Taylor (Adcock & Taylor 2009 Proc. R. Soc. A 465, 3361-3381. (doi:10.1098/rspa.2009.0031)), with the assumption that directional spreading is frequency independent. The method is applied to measurements recorded at the North Alwyn platform in the northern North Sea, and the results compared against estimates of wave spreading by conventional measurement methods and hindcast data. Records containing freak waves were excluded. It is found that the method provides accurate estimates of wave spreading over a range of conditions experienced at North Alwyn, despite the noisy chaotic signals that characterize such ocean wave data. The results provide further confirmation that Adcock and Taylor's method is applicable to metocean data and has considerable future promise as a technique to recover estimates of wave spreading from single point wave measurement devices.
Could a change in magnetic field geometry cause the break in the wind-activity relation?
Vidotto, A A; Jardine, M; See, V; Petit, P; Boisse, I; Saikia, S Boro; Hebrard, E; Jeffers, S V; Marsden, S C; Morin, J
2015-01-01
Wood et al suggested that mass-loss rate is a function of X-ray flux ($\\dot{M} \\propto F_x^{1.34}$) for dwarf stars with $F_x \\lesssim F_{x,6} \\equiv 10^6$ erg cm$^{-2}$ s$^{-1}$. However, more active stars do not obey this relation. These authors suggested that the break at $F_{x,6}$ could be caused by significant changes in magnetic field topology that would inhibit stellar wind generation. Here, we investigate this hypothesis by analysing the stars in Wood et al's sample that had their surface magnetic fields reconstructed through Zeeman-Doppler Imaging (ZDI). Although the solar-like outliers in the $\\dot{M}$ -- $F_x$ relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at $F_{x,6}$. To confirm this, further wind measurements and ZDI observations at both sides of the break are required. As active stars can jump between states with highly toroidal to highly poloidal fields, we expect significant scatter in magnetic field topology to exi...
A current filamentation mechanism for breaking magnetic field lines during reconnection.
Che, H; Drake, J F; Swisdak, M
2011-06-01
During magnetic reconnection, the field lines must break and reconnect to release the energy that drives solar and stellar flares and other explosive events in space and in the laboratory. Exactly how this happens has been unclear, because dissipation is needed to break magnetic field lines and classical collisions are typically weak. Ion-electron drag arising from turbulence, dubbed 'anomalous resistivity', and thermal momentum transport are two mechanisms that have been widely invoked. Measurements of enhanced turbulence near reconnection sites in space and in the laboratory support the anomalous resistivity idea but there has been no demonstration from measurements that this turbulence produces the necessary enhanced drag. Here we report computer simulations that show that neither of the two previously favoured mechanisms controls how magnetic field lines reconnect in the plasmas of greatest interest, those in which the magnetic field dominates the energy budget. Rather, we find that when the current layers that form during magnetic reconnection become too intense, they disintegrate and spread into a complex web of filaments that causes the rate of reconnection to increase abruptly. This filamentary web can be explored in the laboratory or in space with satellites that can measure the resulting electromagnetic turbulence.
Analysis of Waves in the Near-Field of Wave Energy Converter Arrays through Stereo Video
Black, C.; Haller, M. C.
2013-12-01
Oregon State University conducted a series of laboratory experiments to measure and quantify the near-field wave effects caused within arrays of 3 and 5 Wave Energy Converters (WEC). As the waves and WECs interact, significant scattering and radiation occurs increasing/decreasing the wave heights as well as changing the direction the wave is traveling. These effects may vary based on the number of WECs within an array and their respective locations. The findings of this analysis will assist in selecting the WEC farm location and in improving WEC design. Analyzing the near-field waves will help determine the relative importance of absorption, scattering, and radiation as a function of the incident wave conditions and device performance. The WEC mooring system design specifications may also be impacted if the wave heights in the near-field are greater than expected. It is imperative to fully understand the near-field waves before full-scale WEC farms can be installed. Columbia Power Technologies' Manta served as the test WEC prototype on a 1 to 33 scale. Twenty-three wave gages measured the wave heights in both regular and real sea conditions at locations surrounding and within the WEC arrays. While these gages give a good overall picture of the water elevation behavior, it is difficult to resolve the complicated wave field within the WEC array using point gages. Here stereo video techniques are applied to extract the 3D water surface elevations at high resolution in order to reconstruct the multi-directional wave field in the near-field of the WEC array. The video derived wave information will also be compared against the wave gage data.
Shear waves in inhomogeneous, compressible fluids in a gravity field.
Godin, Oleg A
2014-03-01
While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.
The plane wave spectrum representation of electromagnetic fields
Clemmow, P C
1966-01-01
The Plane Wave Spectrum Representation of Electromagnetic Fields presents the theory of the electromagnetic field with emphasis to the plane wave. This book explains how fundamental electromagnetic fields can be represented by the superstition of plane waves traveling in different directions. Organized into two parts encompassing eight chapters, this book starts with an overview of the methods whereby plane wave spectrum representation can be used in attacking different characteristic problems belonging to the theories of radiation, diffraction, and propagation. This book then discusses the co
Li, Jia; Zhang, Hongchao; Ni, Chenyin; Shen, Zhonghua
2013-06-20
This research focuses on analyzing the frequency characteristics of ultrasonic waves induced by a partially closed surface-breaking crack. When acoustic waves interact with the crack, transmission, reflection, and mode conversions occur and the frequency characteristics of signals perform obvious changes. A pulsed laser line source is used to generate ultrasonic waves in the sample with a partially closed surface-breaking crack, and one can see how the frequency characteristics of detected signals change as the pulsed laser beam scans across the sample surface. The optical deflection beam method is developed to detect the ultrasonic signals experimentally. The fast Fourier transform (FFT) is used to analyze the time-domain data, and the FFT data are visualized by a B-scan plot. A clear disruption in the B-scan can be observed when the laser beam illuminates directly onto the crack, which is due to the changes of frequency characteristics induced by the partially closed crack. A frequency-domain B-scan of numerical simulation results is presented, and the clear disruption can also be observed clearly.
Long-term trends in synoptic-scale Rossby wave-breaking and the jet strength at tropopause levels
Isotta, F.; Martius, O.; Sprenger, M.; Schwierz, C.
2009-04-01
Breaking synoptic-scale Rossby waves are frequent features of the upper troposphere and lower stratosphere (UTLS) which affect both global- and regional-scale dynamics. Furthermore, they directly influence ozone distribution through meridional transport of ozone-rich air towards the south and ozone-poor air towards the north. Here, trends in the frequency of these breaking waves are assessed by analysing a 44-year climatology (1958-2002) of potential vorticity (PV) streamers on isentropic surfaces from 310 to 350 K. These streamers are viewed as breaking Rossby waves. Two complementary techniques are used to analyse the trends. First, linear trends are computed using the least-squares regression technique. Statistically significant linear trends are found to vary in location and magnitude between isentropic levels and the four seasons. In winter significant trends are detected in the eastern Pacific between 340 and 350 K. A positive trend of stratospheric streamers in the Tropics is related to an increase of total column ozone, whereas the positive trend of tropospheric streamers in the mid-latitudes is associated with a decrease of total ozone. Secondly, a nonlinear trend analysis is performed using the seasonal-trend decomposition procedure based on Loess (STL). With this technique, the low-frequency variability of the time series is analysed during the 44-year period. For instance, over the eastern Atlantic on 350 K, a phase of decreasing PV streamer frequencies in the 1950s and 1960s is followed by a positive streamer tendency after the 1970s. Additionally, trends of the zonal wind are investigated. One prominent outcome of this analysis is the observation that equatorial easterlies over the Atlantic are weakening. A dynamically meaningful link exists between the trends observed in both wind velocity and PV streamers.
Imagawa, Daisuke; Kawamura, Hikaru
2004-02-20
The spin and the chirality orderings of the three-dimensional Heisenberg spin glass with the weak random anisotropy are studied under applied magnetic fields by equilibrium Monte Carlo simulations. A replica symmetry breaking transition occurs in the chiral sector accompanied by the simultaneous spin-glass order. The ordering behavior differs significantly from that of the Ising spin glass, despite the similarity in the global symmetry. Our observation is consistent with the spin-chirality decoupling-recoupling scenario of a spin-glass transition.
Spontaneous Symmetry Breaking and Higgs Field in Higher Derivative Gravity Theory
Naboulsi, R
2003-01-01
Spontaneous symetry breaking in the context of higher derivative gravity theory is studied. For 2Lambda = 3m^2, where Lambda is the cosmological constant and m is the mass of the Klein-Gordon field and at initial temperature of the massless spinless quanta, the physical gravitional constant is less than the Plank-Wheeler inverse square mass, but the physical cosmological constant turns to be equal to the classical Einstein-Hilbert one. The critical temperature is shown to be different from zero and depends on the scalar curvature via the higher order correction parameter.
Spontaneous symmetry breaking, and strings defects in hypercomplex gauge field theories
Cartas-Fuentevilla, R
2015-01-01
Inspired by the appearance of split-complex structures in the dimensional reduction of string theory, and in the theories emerging as byproducts, we study the hyper-complex formulation of Abelian gauge field theories, by incorporating a new complex unit to the usual complex one. The hypercomplex version of the traditional Mexican hat potential associated with the $U(1)$ gauge field theory, corresponds to a {\\it hybrid} potential with two real components, and with $U(1)\\times SO(1,1)$ as symmetry group. Each component corresponds to a deformation of the hat potential, with the appearance of a new degenerate vacuum. Hypercomplex electrodynamics will show novel properties, such as the spontaneous symmetry breaking scenarios with running masses for the vectorial and scalar Higgs fields, and the Aharonov-Bohm type strings defects as exact solutions; these topological defects may be detected only by quantum interference of charged particles through gauge invariant loop integrals. In a particular limit, the {\\it hyp...
Symmetry breaking induced by charge density and the entropy of interacting fields
Bekenstein, Jacob D.; Guendelman, E. I.
1987-01-01
We study interacting complex scalar field theories with global U(1) symmetry and concave potentials. It is usually assumed that spontaneous symmetry breaking is excluded for such interaction. However, we show that degenerate ground states appear when the system is considered as a charged medium, which we take to be so large that it makes sense to speak of a uniform, finite, charge density. This of course implies that we are considering as ground states solutions that select a particular Lorentz frame. The consequent symmetry breaking is accompanied by the usual Goldstone modes. It makes topological solitons possible in 1+1 dimensions. Further, a new kind of nontopological solitons appears, again in 1+1 dimensions. These are embedded in a uniformly charged background. Unlike the Friedberg-Lee-Sirlin solitons, those studied here do not require a complicatedly shaped potential to exist. Although Derrick's theorem, which forbids higher-dimensional solitons, cannot be proved in the present context, it appears that such solitons are still forbidden in the presence of finite charge density. When the field is confined to a box, the frequency spectrum is, classically, a continuum. This is in sharp contrast to the situation for linear fields. However, semiclassical quantization, or the requirement that charge be quantized, both make the spectrum discrete. We show by general arguments that the energy spectrum (distinct from the frequency spectrum for nonlinear fields) for the interacting field in a box must have widely spaced levels. For the case of a quartic potential we compute the energy levels exactly in 1+1 dimensions, and verify this conclusion directly. The interacting scalar field thus complies in detail with the bound on specific entropy proposed by one of us earlier as applicable to all finite physical systems.
Zhang, Yu; Xu, Yixian; Xia, Jianghai
2012-12-01
A better understanding of the influences of different surface fluid drainage conditions on the propagation and attenuation of surface waves as the stipulated frequency is varied is a key issue to apply surface wave method to detect subsurface hydrological properties. Our study develops three-dimensional dynamical Green's functions in poroelastic media for Rayleigh waves of possible free surface conditions: permeable - "open pore," impermeable - "closed pore," and partially permeable boundaries. The full transient response of wave fields and spectra due to a stress impulse wavelet on the surface are investigated in the exploration seismic frequency band for typical surface drainage conditions, viscous coupling-damping, solid frame properties and porous fluid flowing configuration. Our numerical results show that, due to the slow dilatational wave - P2 wave, two types of Rayleigh waves, designated as R1 and R2 waves, exist along the surface. R1 wave possesses high energy as classic Rayleigh waves in pure elastic media for each porous materials. A surface fluid drainage condition is a significant factor to influence dispersion and attenuation, especially attenuation of R1 waves. R2 wave for closed pore and partially permeable surfaces is only observed for a low coupling-damping coefficient. The non-physical wave for partially surface conditions causes the R1 wave radiates into the R2 wave in the negative attenuation frequency range. It makes weaker R1 wave and stronger R2 wave to closed pore surface. Moreover, it is observed that wave fields and spectra of R1 wave are sensitive to frame elastic moduli change for an open pore surface, and to pore fluid flow condition change for closed pore and partially permeable surface.
Synthesizing Waves from Animated Height Fields
DEFF Research Database (Denmark)
Nielsen, Michael Bang; Söderström, Andreas; Bridson, Robert
2013-01-01
Computer animated ocean waves for feature films are typically carefully choreographed to match the vision of the director and to support the telling of the story. The rough shape of these waves is established in the previsualization (previs) stage, where artists use a variety of modeling tools...
Springing Response Due to Directional Wave Field Excitation
DEFF Research Database (Denmark)
Vidic-Perunovic, Jelena; Jensen, Jørgen Juncher
2004-01-01
This paper analyses the wave-induced high-frequency bending moment response of ships, denoted springing. The aim is to predict measured severe springing responses in a large bulk carrier. It is shown that the most important springing contribution is due to the resultant second order excitation...... in multidirectional sea. The incident pressure field from the second order bidirectional wave field is derived, including the non-linear cross-coupling terms between the two wave systems (e.g. wind driven waves and swell). The resulting effect of the super-harmonic cross-coupling interaction terms on the springing...... response is discussed. An example with opposing waves is given, representing probably the 'worst' case for energy exchange between the wave systems. Theoretical predictions of standard deviation of wave- and springing-induced stress amidships are compared with full-scale measurements for a bulk carrier....
Reverberant shear wave fields and estimation of tissue properties
Parker, Kevin J.; Ormachea, Juvenal; Zvietcovich, Fernando; Castaneda, Benjamin
2017-02-01
The determination of shear wave speed is an important subject in the field of elastography, since elevated shear wave speeds can be directly linked to increased stiffness of tissues. MRI and ultrasound scanners are frequently used to detect shear waves and a variety of estimators are applied to calculate the underlying shear wave speed. The estimators can be relatively simple if plane wave behavior is assumed with a known direction of propagation. However, multiple reflections from organ boundaries and internal inhomogeneities and mode conversions can create a complicated field in time and space. Thus, we explore the mathematics of multiple component shear wave fields and derive the basic properties, from which efficient estimators can be obtained. We approach this problem from the historic perspective of reverberant fields, a conceptual framework used in architectural acoustics and related fields. The framework can be recast for the alternative case of shear waves in a bounded elastic media, and the expected value of displacement patterns in shear reverberant fields are derived, along with some practical estimators of shear wave speed. These are applied to finite element models and phantoms to illustrate the characteristics of reverberant fields and provide preliminary confirmation of the overall framework.
Directory of Open Access Journals (Sweden)
Yao-zhong YANG
2010-03-01
Full Text Available According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method, a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathymetry factor into account has been developed. The deformed mild-slope equation is used to eliminate the restriction of wave length on calculation steps. Using the hard disk to record data during the calculation process, the enhanced numerical method can save computer memory space to a certain extent, so that a large-scale sea area can be calculated with high-resolution grids. This model was applied to wave field integral calculation over a radial sand ridge field in the South Yellow Sea. The results demonstrate some features of the wave field: (1 the wave-height contour lines are arc-shaped near the shore; (2 waves break many times when they propagate toward the shore; (3 wave field characteristics on the northern and southern sides of Huangshayang are different; and (4 the characteristics of wave distribution match the terrain features. The application of this model in the region of the radial sand ridge field suggests that it is a feasible way to analyze wave refraction-diffraction effects under natural sea conditions.
Measurement of velocity field in parametrically excited solitary waves
Gordillo, Leonardo
2014-01-01
Paramerically excited solitary waves emerge as localized structures in high-aspect-ratio free surfaces subject to vertical vibrations. Herein, we provide the first experimental characterization of the hydrodynamics of thess waves using Particle Image Velocimetry. We show that the underlying velocity field of parametrically excited solitary waves is mainly composed by an oscillatory velocity field. Our results confirm the accuracy of Hamiltonian models with added dissipation in describing this field. Remarkably, our measurements also uncover the onset of a streaming velocity field which is shown to be as important as other crucial nonlinear terms in the current theory. The observed streaming pattern is particularly interesting due to the presence of oscillatory meniscii.
Existence and breaking property of real loop-solutions of two nonlinear wave equations
Institute of Scientific and Technical Information of China (English)
Ji-bin LI
2009-01-01
Dynamical analysis has revealed that,for some nonlinear wave equations,loop- and inverted loop-soliton solutions are actually visual artifacts. The so-called loop-soliton solution consists of three solutions,and is not a real solution. This paper answers the question as to whether or not nonlinear wave equations exist for which a "real" loop-solution exists,and if so,what are the precise parametric representations of these loop traveling wave solutions.
Strongly nonlinear models for internal waves: an application for the dam-break problem
Chen, Shengqian
2016-01-01
Strongly nonlinear models of internal wave propagation for incompressible stratified Euler fluids are investigated numerically and analytically to determine the evolution of a class of initial conditions of interest in laboratory experiments. This class of step-like initial data severely tests the robustness of the models beyond their strict long-wave asymptotic validity, and model fidelity is assessed by direct numerical simulations (DNS) of the parent Euler system. It is found that the primary dynamics of near-solitary wave formation is remarkably well predicted by the models for both wave and fluid properties, at a fraction of the computational costs of the DNS code.
Dam break problem for the focusing nonlinear Schrödinger equation and the generation of rogue waves
El, G. A.; Khamis, E. G.; Tovbis, A.
2016-09-01
We propose a novel, analytically tractable, scenario of the rogue wave formation in the framework of the small-dispersion focusing nonlinear Schrödinger (NLS) equation with the initial condition in the form of a rectangular barrier (a ‘box’). We use the Whitham modulation theory combined with the nonlinear steepest descent for the semi-classical inverse scattering transform, to describe the evolution and interaction of two counter-propagating nonlinear wave trains—the dispersive dam break flows—generated in the NLS box problem. We show that the interaction dynamics results in the emergence of modulated large-amplitude quasi-periodic breather lattices whose amplitude profiles are closely approximated by the Akhmediev and Peregrine breathers within certain space-time domain. Our semi-classical analytical results are shown to be in excellent agreement with the results of direct numerical simulations of the small-dispersion focusing NLS equation.
Wave packet dynamics of the matter wave field of a Bose-Einstein condensate
Sudheesh, C; Lakshmibala, S
2004-01-01
We show in the framework of a tractable model that revivals and fractional revivals of wave packets afford clear signatures of the extent of departure from coherence and from Poisson statistics of the matter wave field in a Bose-Einstein condensate, or of a suitably chosen initial state of the radiation field propagating in a Kerr-like medium.
Bouscasse, Benjamin; Souto-Iglesias, Antonio; Pita, José Luis Cercós
2013-01-01
A single degree of freedom angular motion dynamical system involving the coupling of a moving mass that creates an external torque, a rigid tank, driven by this torque, and fluid which partially fills the tank, is analyzed in the present paper series. The analysis of such a system is relevant for understanding the energy dissipation mechanisms resulting from fluid sloshing and wave breaking. Understanding such mechanisms poses open problems in the fluid mechanics field, and they are relevant for the design of a wide range of Tuned Liquid Damper devices of substantial industrial applicability. In Part I the dynamical system is described in detail to show its nonlinear features both in terms of mechanical and fluid dynamical aspects. A semi-analytical model of the energy dissipated by the fluid, based on a hydraulic jump solution and valid for small oscillation angles, is developed. In order to extend the analysis to large oscillation angles, a Smoothed Particle Hydrodynamics solver is also developed, adapting ...
3-D Effects Force Reduction of Short-Crested Non-Breaking Waves on Caissons
DEFF Research Database (Denmark)
Burcharth, H. F.; Liu, Z.
1998-01-01
The effect of wave short-crestedness on the horizontal wave force on a caisson is twofold. The one is the force reduction due to the reduction of point pressure on the caisson, named point-pressure reduction. The other is the force reduction due to the fact that the peak pressures do not occur si...
Electronic Wave Packet in a Quantized Electromagnetic Field
Institute of Scientific and Technical Information of China (English)
程太旺; 薛艳丽; 李晓峰; 吴令安; 傅盘铭
2002-01-01
We study a non-stationary electronic wave packet in a quantized electromagnetic field. Generally, the electron and field become entangled as the electronic wave packet evolves. Here we find that, when the initial photon state is a coherent one, the wavefunction of the system can be factorized if we neglect the transferred photon number. In this case, the quantized-field calculation is equivalent to the semi-classical calculation.
Phase transition from the symmetry breaking of charged Klein–Gordon fields
Energy Technology Data Exchange (ETDEWEB)
Matos, T.; Castellanos, E. [Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, A.P. 14-740, 07000 México D.F. (Mexico)
2014-01-14
We analyze the phase transition associated with the U(1) symmetry breaking of the complex Klein–Gordon (KG) equation with a Mexican–hat scalar field potential up to one loop in perturbations immersed in a thermal bath. We show that the KG equation reduces to a Gross–Pitaevskii like–equation (GP), which also contains the entire information of the phase transition. Indeed, the thermal bath contributions, together with the corresponding U(1) local symmetry, allow us to interpret the resulting GP equation as a charged and finite temperature version of the system. Finally, we obtain the hydrodynamics and consequently, the corresponding thermodynamics, and show that breakdown of the U(1) local symmetry of the KG field into the new version of the GP equation corresponds, under certain circumstances, to a phase transition of the gas into a condensate, superfluid, and/or superconductor.
Cosmology of an asymptotically free scalar field with spontaneous symmetry breaking
Huang, Kerson; Tung, Roh-Suan
2010-01-01
We solve Einstein's equation with Robertson-Walker metric as an initial-value problem, using as the source of gravity a Halpern-Huang real scalar field, which was derived from renormalization-group analysis, with a potential that exhibits asymptotic freedom and spontaneous symmetry breaking. Both properties are crucial to the formulation of the problem. Numerical solutions show that the universe expands at an accelerated rate, with the radius increasing like the exponential of a power of the time. This is relevant to "dark energy" and "cosmic inflation". Extension to the complex scalar field will make the universe a superfluid. The vortex dynamics that emerges offers explanations for other cosmological problems, namely, matter creation, galactic voids, and the "dark mass".
A Coupled Finite Difference and Moving Least Squares Simulation of Violent Breaking Wave Impact
DEFF Research Database (Denmark)
Lindberg, Ole; Bingham, Harry B.; Engsig-Karup, Allan Peter
2012-01-01
Two model for simulation of free surface flow is presented. The first model is a finite difference based potential flow model with non-linear kinematic and dynamic free surface boundary conditions. The second model is a weighted least squares based incompressible and inviscid flow model. A special...... feature of this model is a generalized finite point set method which is applied to the solution of the Poisson equation on an unstructured point distribution. The presented finite point set method is generalized to arbitrary order of approximation. The two models are applied to simulation of steep...... and overturning wave impacts on a vertical breakwater. Wave groups with five different wave heights are propagated from offshore to the vicinity of the breakwater, where the waves are steep, but still smooth and non-overturning. These waves are used as initial condition for the weighted least squares based...
Ma, Xiaochuan; Yan, Jun; Hou, Yijun; Lin, Feilong; Zheng, Xufeng
2016-12-01
A mooring system and two sites of bottom currents were deployed over the slope and near the shelf break on the propagating paths of internal solitary waves (ISWs), west off Dongsha Atoll in the northern South China Sea. Data indicated that energetic ISWs obliquely shoaled onto the shelf west off Dongsha Atoll in an approximately 290° direction, causing strong reversing currents (some exceeding 80 cm/s) near the bottom. Two types of sandwaves and short scour channels are discernible on the seafloor near the shelf break, which have reasonable correlations with the obliquely incident ISWs and internal tides. Type 1 sandwaves, featured by ISWs at the depths of 130-150 m, have flat crests interacting with the isobaths at an angle of nearly 45° which slightly incline and migrate upslope. Type 2 sandwaves are associated with internal tides, which have crests parallel to the isobaths and distinctly incline and migrate downslope. Short channels are parallel to the depth contours and truncate the strata, which could be formed and maintained by along-slope currents that are probably produced by the obliquely ISWs on a large gradient (γ > 0.8°). The ISWs can move coarse grains or suspend fine grains but do not change the long-term trend of sediment transport on the seabed with larger gradients (γ/c > 1), which is dominated by internal tides. These features are likely widespread near the shelf break in the northern South China Sea and other seas but are limited on mild slopes where ISWs do not break.
Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea
2011-01-01
Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s−1 PMID:21540838
Wave rectification in plasma sheaths surrounding electric field antennas
Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Ergun, R. E.; Mozer, F. S.
1994-01-01
Combined measurements of Langmuir or broadband whistler wave intensity and lower-frequency electric field waveforms, all at 10-microsecond time resolution, were made on several recent sounding rockets in the auroral ionosphere. It is found that Langmuir and whistler waves are partically rectified in the plasma sheaths surrounding the payload and the spheres used as antennas. This sheath rectification occurs whenever the high frequency (HF) potential across the sheath becomes of the same order as the electron temperature or higher, for wave frequencies near or above the ion plasma frequency. This rectification can introduce false low-frequency waves into measurements of electric field spectra when strong high-frequency waves are present. Second harmonic signals are also generated, although at much lower levels. The effect occurs in many different plasma conditions, primarily producing false waves at frequencies that are low enough for the antenna coupling to the plasma to be resistive.
Gravitational wave stress tensor from the linearised field equations
Balbus, Steven A
2016-01-01
A conserved stress energy tensor for weak field gravitational waves in standard general relativity is derived directly from the linearised wave equation alone, for an arbitrary gauge. The form of the tensor leads directly to the classical expression for the outgoing wave energy in any harmonic gauge. The method described here, however, is a much simpler, shorter, and more physically motivated approach than is the customary procedure, which involves a lengthy and cumbersome second-order (in wave-amplitude) calculation starting with the Einstein tensor. Our method has the added advantage of exhibiting the direct coupling between the outgoing energy flux in gravitational waves and the work done by the gravitational field on the sources. For nonharmonic gauges, the derived wave stress tensor has an index asymmetry. This coordinate artefact may be removed by techniques similar to those used in classical electrodynamics (where this issue also arises), but only by appeal to a more lengthy calculation. For any harmon...
Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields
Di Piazza, A
2014-01-01
The problem of an ultrarelativistic charge in the presence of an atomic and a plane-wave field is investigated in the quasiclassical regime by including exactly the effects of both background fields. Starting from the quasiclassical Green's function obtained in [Phys. Lett. B \\textbf{717}, 224 (2012)], the corresponding in- and out-wave functions are derived in the experimentally relevant case of the particle initially counterpropagating with respect to the plane wave. The knowledge of these electron wave functions opens the possibility of investigating a variety of problems in strong-field QED, where both the atomic field and the laser field are strong enough to be taken into account exactly from the beginning in the calculations.
Trapping and breaking of in vivo nicked DNA during pulsed field gel electrophoresis.
Khan, Sharik R; Kuzminov, Andrei
2013-12-15
Pulsed field gel electrophoresis (PFGE) offers a high-resolution approach to quantify chromosomal fragmentation in bacteria, measured as percentage of chromosomal DNA entering the gel. The degree of separation in pulsed field gel (PFG) depends on the size of DNA as well as various conditions of electrophoresis such as electric field strength, time of electrophoresis, switch time, and buffer composition. Here we describe a new parameter, the structural integrity of the sample DNA itself, that influences its migration through PFGs. We show that subchromosomal fragments containing both spontaneous and DNA damage-induced nicks are prone to breakage during PFGE. Such breakage at single-strand interruptions results in artifactual decrease in molecular weight of linear DNA making accurate determination of the number of double-strand breaks difficult. Although breakage of nicked subchromosomal fragments is field strength independent, some high-molecular-weight subchromosomal fragments are also trapped within wells under the standard PFGE conditions. This trapping can be minimized by lowering the field strength and increasing the time of electrophoresis. We discuss how breakage of nicked DNA may be mechanistically linked to trapping. Our results suggest how to optimize conditions for PFGE when quantifying chromosomal fragmentation induced by DNA damage. Copyright © 2013 Elsevier Inc. All rights reserved.
Globally linked vortex clusters in trapped wave fields.
Crasovan, Lucian-Cornel; Molina-Terriza, Gabriel; Torres, Juan P; Torner, Lluis; Pérez-García, Víctor M; Mihalache, Dumitru
2002-09-01
We put forward the existence of a rich variety of fully stationary vortex structures, termed H clusters, made of an increasing number of vortices nested in paraxial wave fields confined by trapping potentials. However, we show that the constituent vortices are globally linked, rather than products of independent vortices. Also, they always feature a monopolar global wave front and exist in nonlinear systems, such as the Bose-Einstein condensates. Clusters with multipolar global wave fronts are nonstationary or, at best, flipping.
Radiation of Electron in the Field of Plane Light Wave
Energy Technology Data Exchange (ETDEWEB)
Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; /Kharkov, KIPT; Tatchyn, R.; /SLAC
2006-02-24
Results of integration of a Lorentz equation for a relativistic electron moving in the field of running, plane, linear polarized electromagnetic wave are presented in the paper. It is shown that electron velocities in the field of the wave are almost periodic functions of time. For calculations of angular spectrum of electron radiation intensity expansion of the electromagnetic field in a wave zone into generalized Fourier series was used. Expressions for the radiation intensity spectrum are presented in the paper. Derived results are illustrated for electron and laser beam parameters of NSC KIPT X-ray generator NESTOR. It is shown that for low intensity of the interacting electromagnetic wave the results of energy and angular spectrum calculations in the frame of classical electrodynamics completely coincide with calculation results produced using quantum electrodynamics. Simultaneously, derived expressions give possibilities to investigate dependence of energy and angular Compton radiation spectrum on phase of interaction and the interacting wave intensity.
Lamb wave scattering by a surface-breaking crack in a plate
Datta, S. K.; Al-Nassar, Y.; Shah, A. H.
1991-01-01
An NDE method based on finite-element representation and modal expansion has been developed for solving the scattering of Lamb waves in an elastic plate waveguide. This method is very powerful for handling discontinuities of arbitrary shape, weldments of different orientations, canted cracks, etc. The advantage of the method is that it can be used to study the scattering of Lamb waves in anisotropic elastic plates and in multilayered plates as well.
Evolution of Spiral Waves under Modulated Electric Fields
Institute of Scientific and Technical Information of China (English)
MA Jun; YING He-Ping; PAN Guo-Wei; PU Zhong-Sheng
2005-01-01
@@ Spirals generated from the excitable media within the Barkley model is investigated under the gradient electric fields by a numerical simulation. The spiral drift and spiral break up are observed when the amplitude of the electric fields is modulated by a constant signal or a chaotic signal. It is also verified that, even in the presence of the white noise, the whole system can reach homogeneous states after the spiral breakup, by using an adaptive strategy.
Benchmark Modeling of the Near-Field and Far-Field Wave Effects of Wave Energy Arrays
Energy Technology Data Exchange (ETDEWEB)
Rhinefrank, Kenneth E; Haller, Merrick C; Ozkan-Haller, H Tuba
2013-01-26
This project is an industry-led partnership between Columbia Power Technologies and Oregon State University that will perform benchmark laboratory experiments and numerical modeling of the near-field and far-field impacts of wave scattering from an array of wave energy devices. These benchmark experimental observations will help to fill a gaping hole in our present knowledge of the near-field effects of multiple, floating wave energy converters and are a critical requirement for estimating the potential far-field environmental effects of wave energy arrays. The experiments will be performed at the Hinsdale Wave Research Laboratory (Oregon State University) and will utilize an array of newly developed Buoys' that are realistic, lab-scale floating power converters. The array of Buoys will be subjected to realistic, directional wave forcing (1:33 scale) that will approximate the expected conditions (waves and water depths) to be found off the Central Oregon Coast. Experimental observations will include comprehensive in-situ wave and current measurements as well as a suite of novel optical measurements. These new optical capabilities will include imaging of the 3D wave scattering using a binocular stereo camera system, as well as 3D device motion tracking using a newly acquired LED system. These observing systems will capture the 3D motion history of individual Buoys as well as resolve the 3D scattered wave field; thus resolving the constructive and destructive wave interference patterns produced by the array at high resolution. These data combined with the device motion tracking will provide necessary information for array design in order to balance array performance with the mitigation of far-field impacts. As a benchmark data set, these data will be an important resource for testing of models for wave/buoy interactions, buoy performance, and far-field effects on wave and current patterns due to the presence of arrays. Under the proposed project we will initiate
The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the ...
The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the ...
Gravitational waves as exact solutions of Einstein field equations
Energy Technology Data Exchange (ETDEWEB)
Vilasi, G [Dipartimento di Fisica, Universita di Salerno Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Gruppo Collegato di Salerno Via S. Allende, I-84081 Baronissi (Salerno) (Italy)
2007-11-15
Exact solutions of Einstein field equations invariant for a non-Abelian 2-dimensional Lie algebra of Killing fields are described. A sub-class of these gravitational fields have a wave-like character; it is shown that they have spin-1.
Exciton-phonon interaction breaking all antiunitary symmetries in external magnetic fields
Schweiner, Frank; Rommel, Patric; Main, Jörg; Wunner, Günter
2017-07-01
Recent experimental investigations by M. Aßmann et al. [Nat. Mater. 15, 741 (2016), 10.1038/nmat4622] on the spectrum of magnetoexcitons in cuprous oxide revealed the statistics of a Gaussian unitary ensemble (GUE). The model of F. Schweiner et al. [Phys. Rev. Lett. 118, 046401 (2017), 10.1103/PhysRevLett.118.046401], which includes the complete cubic valence band structure of the solid, can explain the appearance of GUE statistics if the magnetic field is not oriented in one of the symmetry planes of the cubic lattice. However, it cannot explain the experimental observation of GUE statistics for all orientations of the field. In this paper we investigate the effect of quasiparticle interactions or especially the exciton-phonon interaction on the level statistics of magnetoexcitons and show that the motional Stark field induced by the exciton-phonon interaction leads to the occurrence of GUE statistics for arbitrary orientations of the magnetic field in agreement with experimental observations. Importantly, the breaking of all antiunitary symmetries can be explained only by considering both the exciton-phonon interaction and the cubic crystal lattice.
Rogue waves of the Kundu-Eckhaus equation in a chaotic wave field
Bayindir, Cihan
2016-01-01
In this paper we study the properties of the chaotic wave fields generated in the frame of the Kundu-Eckhaus equation (KEE). Modulation instability results in a chaotic wave field which exhibits small-scale filaments with a free propagation constant, k. The average velocity of the filaments is approximately given by the average group velocity calculated from the dispersion relation for the plane-wave solution however direction of propagation is controlled by the $\\beta$ parameter, the constant in front of the Raman-effect term. We have also calculated the probabilities of the rogue wave occurrence for various values of propagation constant k and showed that the probability of rogue wave occurrence depends on k. Additionally, we have showed that the probability of rogue wave occurrence significantly depends on the quintic and the Raman-effect nonlinear terms of the KEE. Statistical comparisons between the KEE and the cubic nonlinear Schrodinger equation have also been presented.
Rogue waves of the Kundu-Eckhaus equation in a chaotic wave field.
Bayindir, Cihan
2016-03-01
In this paper we study the properties of the chaotic wave fields generated in the frame of the Kundu-Eckhaus equation (KEE). Modulation instability results in a chaotic wave field which exhibits small-scale filaments with a free propagation constant, k. The average velocity of the filaments is approximately given by the average group velocity calculated from the dispersion relation for the plane-wave solution; however, direction of propagation is controlled by the β parameter, the constant in front of the Raman-effect term. We have also calculated the probabilities of the rogue wave occurrence for various values of propagation constant k and showed that the probability of rogue wave occurrence depends on k. Additionally, we have showed that the probability of rogue wave occurrence significantly depends on the quintic and the Raman-effect nonlinear terms of the KEE. Statistical comparisons between the KEE and the cubic nonlinear Schrödinger equation have also been presented.
Carcione, José M
2014-01-01
Authored by the internationally renowned José M. Carcione, Wave Fields in Real Media: Wave Propagation in Anisotropic, Anelastic, Porous and Electromagnetic Media examines the differences between an ideal and a real description of wave propagation, starting with the introduction of relevant stress-strain relations. The combination of this relation and the equations of momentum conservation lead to the equation of motion. The differential formulation is written in terms of memory variables, and Biot's theory is used to describe wave propagation in porous media. For each rheology, a plane-wave analysis is performed in order to understand the physics of wave propagation. This book contains a review of the main direct numerical methods for solving the equation of motion in the time and space domains. The emphasis is on geophysical applications for seismic exploration, but researchers in the fields of earthquake seismology, rock acoustics, and material science - including many branches of acoustics of fluids and ...
Electromagnetic Fields and Waves in Fractional Dimensional Space
Zubair, Muhammad; Naqvi, Qaisar Abbas
2012-01-01
This book presents the concept of fractional dimensional space applied to the use of electromagnetic fields and waves. It provides demonstrates the advantages in studying the behavior of electromagnetic fields and waves in fractal media. The book presents novel fractional space generalization of the differential electromagnetic equations is provided as well as a new form of vector differential operators is formulated in fractional space. Using these modified vector differential operators, the classical Maxwell's electromagnetic equations are worked out. The Laplace's, Poisson's and Helmholtz's
Ionizing gas breakdown waves in strong electric fields.
Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.
1972-01-01
A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.
AN ASYMPTOTIC SOLUTION OF VELOCITY FIELD IN SHIP WAVES
Institute of Scientific and Technical Information of China (English)
WU Yun-gang; TAO Ming-de
2006-01-01
The stationary phase method in conventional Lighthill's two-stage scheme to get the expressions of the velocity field was given up in this paper. The method that Ursell had used in deducing the elevation expression of ship wave was adopted, and an asymptotic solution of velocity field of ship waves on an inviscid fluid that is perfectly fit for the region inside and outside the critical lines was obtained. It is very convenient to be used in SAR technique.
Field verification of reconstructed dam-break flood, Laurel Run, Pennsylvania
Chen, Cheng-lung; Armbruster, Jeffrey T.
1979-01-01
A one-dimensional dam-break flood routing model is verified by using observed data on the flash flood resulting from the failure of Laurel Run Reservoir Dam near Johnstown, Pennsylvania. The model has been developed on the basis of an explicit scheme of the characteristics method with specified time intervals. The model combines one of the characteristic equations with the Rankine-Hugoniot shock equations to trace the corresponding characteristic backward to the known state for solving the depth and velocity of flow at the wave front. The previous version of the model has called for a modification of the method of solution to overcome the computational difficulty at the narrow breach and at any geomorphological constraints where channel geometry changes rapidly. The large reduction in the computational inaccuracies and oscillations was achieved by introducing the actual "storage width" in the equation of continuity and the imaginary "conveyance width" in the equation of motion. Close agreement between observed and computed peak stages at several stations downstream of the dam strongly suggests the validity and applicability of the model. However, small numerical noise appearing in the computed stage and discharge hydrographs at the dam site as well as discrepancy of attenuated peaks in the discharge hydrographs indicate the need for further model improvement.
Santucci, F.; Santini, P. M.
2016-10-01
We study the generalization of the dispersionless Kadomtsev-Petviashvili (dKP) equation in n+1 dimensions and with nonlinearity of degree m+1, a model equation describing the propagation of weakly nonlinear, quasi one-dimensional waves in the absence of dispersion and dissipation, and arising in several physical contexts, like acoustics, plasma physics, hydrodynamics and nonlinear optics. In 2 + 1 dimensions and with quadratic nonlinearity, this equation is integrable through a novel inverse scattering transform, and it has been recently shown to be a prototype model equation in the description of the two-dimensional wave breaking of localized initial data. In higher dimensions and with higher nonlinearity, the generalized dKP equations are not integrable, but their invariance under motions on the paraboloid allows one to construct in this paper a family of exact solutions describing waves constant on their paraboloidal wave front and breaking simultaneously in all points of it, developing after breaking either multivaluedness or single-valued discontinuous profiles (shocks). Then such exact solutions are used to build the longtime behavior of the solutions of the Cauchy problem, for small and localized initial data, showing that wave breaking of small initial data takes place in the longtime regime if and only if m(n-1)≤slant 2. Lastly, the analytic aspects of such wave breaking are investigated in detail in terms of the small initial data, in both cases in which the solution becomes multivalued after breaking or it develops a shock. These results, contained in the 2012 master’s thesis of one of the authors (FS) [1], generalize those obtained in [2] for the dKP equation in n+1 dimensions with quadratic nonlinearity, and are obtained following the same strategy.
Magnetic and Electric Field Polarizations of Oblique Magnetospheric Chorus Waves
Verkhoglyadova, Olga; Tsurutani, Bruce T.; Lakhina, Gurbax S.
2012-01-01
A theory was developed to explain the properties of the chorus magnetic and electric field components in the case of an arbitrary propagation angle. The new theory shows that a whistler wave has circularly polarized magnetic fields for oblique propagation. This theoretical result is verified by GEOTAIL observations. The wave electric field polarization plane is not orthogonal to the wave vector, and in general is highly elliptically polarized. A special case of the whistler wave called the Gendrin mode is also discussed. This will help to construct a detailed and realistic picture of wave interaction with magnetosphere electrons. It is the purpose of this innovation to study the magnetic and electric polarization properties of chorus at all frequencies, and at all angles of propagation. Even though general expressions for electromagnetic wave polarization in anisotropic plasma are derived in many textbooks, to the knowledge of the innovators, a detailed analysis for oblique whistler wave mode is lacking. Knowledge of the polarization properties is critical for theoretical calculations of resonant wave-particle interactions.
Comparative study on breaking wave forces on vertical walls with cantilever surfaces
Kisacik, D.; Bogaert, P; Troch, P.
2010-01-01
Physical experiments (at a scale of 1/20) are carried out using two different models: a vertical wall with cantilevering slab and a simple vertical wall. Tests are conducted for a range of values of water depth, wave period and wave height. The largest peak pressures were recorded at the SWL (82 pghs) on the vertical part and at the fixed corner of the cantilever slab (90 pghs). Pressure measurements and derived force calculations on the simple vertical wall were used to evaluate the existing...
Revisiting large break LOCA with the CATHARE-3 three-field model
Energy Technology Data Exchange (ETDEWEB)
Valette, Michel, E-mail: michel.valette@cea.fr [CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Pouvreau, Jerome, E-mail: jerome.pouvreau@cea.fr [CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Bestion, Dominique, E-mail: dominique.bestion@cea.fr [CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Emonot, Philippe, E-mail: philippe.emonot@cea.fr [CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France)
2011-11-15
Highlights: Black-Right-Pointing-Pointer CATHARE 3 enables a three-field analysis of a LB LOCA. Black-Right-Pointing-Pointer Reflooding experiments in isolated rod bundles are satisfactory predicted. Black-Right-Pointing-Pointer A BETHSY integral test simulation supports the CATHARE 3 3-field assessment. - Abstract: Some aspects of large break LOCA analysis (steam binding, oscillatory reflooding, top-down reflooding) are expected to be improved in advanced system codes from more detailed description of flows by adding a third field for droplets. The future system code CATHARE-3 is under development by CEA and supported by EDF, AREVA-NP and IRSN in the frame of the NEPTUNE project and this paper shows some preliminary results obtained in reflooding conditions. A three-field model has been implemented, including vapor, continuous liquid and liquid droplet fields. This model features a set of nine equations of mass, momentum and energy balance. Such a model allows a more detailed description of the droplet transportation from core to steam generator, while countercurrent flow of continuous liquid is allowed. Code assessment against reflooding experiments in a rod bundle is presented, using 1D meshing of the bundle. Comparisons of CATHARE-3 simulations against data series from PERICLES and RBHT full scale experiments show satisfactory results. Quench front motions are well predicted, as well as clad temperatures in most of the tested runs. The BETHSY 6.7C Integral Effect Test simulating the gravity driven reflooding process in a scaled PWR circuit is then compared to CATHARE-3 simulation. The three-field model is applied in several parts of the circuit: core, upper plenum, hot leg and steam generator, represented by either 1D or 3D modules, while the classic six-equation model is used in the other parts of the loop. An analysis of these first results is presented and future work is defined for improving the droplet behavior simulation in both the upper plenum and the
Nonlinear electron acoustic waves in presence of shear magnetic field
Energy Technology Data Exchange (ETDEWEB)
Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata 700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)
2013-12-15
Nonlinear electron acoustic waves are studied in a quasineutral plasma in the presence of a variable magnetic field. The fluid model is used to describe the dynamics of two temperature electron species in a stationary positively charged ion background. Linear analysis of the governing equations manifests dispersion relation of electron magneto sonic wave. Whereas, nonlinear wave dynamics is being investigated by introducing Lagrangian variable method in long wavelength limit. It is shown from finite amplitude analysis that the nonlinear wave characteristics are well depicted by KdV equation. The wave dispersion arising in quasineutral plasma is induced by transverse magnetic field component. The results are discussed in the context of plasma of Earth's magnetosphere.
Primordial Gravitational Waves Induced by Magnetic Fields in Ekpyrotic Scenario
Ito, Asuka
2016-01-01
Both inflationary and ekpyrotic scenarios can account for the origin of the large scale structure of the universe. It is often said that detecting primordial gravitational waves is the key to distinguish both scenarios. We show that this is not true if the gauge kinetic function is present in the ekpyrotic scenario. In fact, primordial gravitational waves sourced by the gauge field can be produced in an ekpyrotic universe. We also study scalar fluctuations sourced by the gauge field and show that it is negligible compared to primordial gravitational waves. This comes from the fact that the fast roll condition holds in ekpyrotic models.
Field analysis and CAD millimeter wave VCO
Jiang, Xiao-Hong; Hong, Wei
1992-12-01
In this paper, the CAD of millimeter wave VCO is investigated based on a frequency-domain harmonic balance technique, where the external-circuit mutual impedances looking outside from two active devices are calculated in terms of a rigorous definition and a mixed technique of modes expansion, Galerkin method and collocation method. The CAD results are in agreement with the experimental results, which shows the raliability of the presented model and optimisation.
Spontaneous symmetry breaking, and strings defects in hypercomplex gauge field theories
Energy Technology Data Exchange (ETDEWEB)
Cartas-Fuentevilla, R. [Universidad Autonoma de Puebla, Instituto de Fisica, Puebla, Pue. (Mexico); Meza-Aldama, O. [Universidad Autonoma de Puebla, Facultad de Ciencias Fisico-Matematicas, Puebla, Pue. (Mexico)
2016-02-15
Inspired by the appearance of split-complex structures in the dimensional reduction of string theory, and in the theories emerging as byproducts, we study the hypercomplex formulation of Abelian gauge field theories by incorporating a new complex unit to the usual complex one. The hypercomplex version of the traditional Mexican hat potential associated with the U(1) gauge field theory, corresponds to a hybrid potential with two real components, and with U(1) x SO(1,1) as symmetry group. Each component corresponds to a deformation of the hat potential, with the appearance of a new degenerate vacuum. Hypercomplex electrodynamics will show novel properties, such as spontaneous symmetry breaking scenarios with running masses for the vectorial and scalar Higgs fields, and such as Aharonov-Bohm type strings defects as exact solutions; these topological defects may be detected only by quantum interference of charged particles through gauge invariant loop integrals. In a particular limit, the hyperbolic electrodynamics does not admit topological defects associated with continuous symmetries. (orig.)
Trapping and breaking of in vivo nicked DNA during pulsed-field gel electrophoresis
Khan, Sharik R.; Kuzminov, Andrei
2013-01-01
Pulsed field gel electrophoresis (PFGE) offers a high-resolution approach to quantify chromosomal fragmentation in bacteria, measured as percent of chromosomal DNA entering the gel. The degree of separation in PFG depends upon the size of DNA, as well as various conditions of electrophoresis, such as electric field strength (FS), time of electrophoresis, switch time and buffer composition. Here we describe a new parameter, the structural integrity of the sample DNA itself, that influences its migration through PFGs. We show that sub-chromosomal fragments containing both spontaneous and DNA damage-induced nicks are prone to breakage during PFGE. Such breakage at single strand interruptions results in artefactual decrease in molecular weight of linear DNA making accurate determination of the number of double strand breaks difficult. While breakage of nicked sub-chromosomal fragments is FS-independent, some high molecular weight sub-chromosomal fragments are also trapped within wells under the standard PFGE conditions. This trapping can be minimized by lowering the field strength and increasing the time of electrophoresis. We discuss how breakage of nicked DNA may be mechanistically linked to trapping. Our results suggest how to optimize conditions for PFGE when quantifying chromosomal fragmentation induced by DNA damage. PMID:23770235
Spontaneous symmetry breaking, and strings defects in hypercomplex gauge field theories
Cartas-Fuentevilla, R.; Meza-Aldama, O.
2016-02-01
Inspired by the appearance of split-complex structures in the dimensional reduction of string theory, and in the theories emerging as byproducts, we study the hypercomplex formulation of Abelian gauge field theories by incorporating a new complex unit to the usual complex one. The hypercomplex version of the traditional Mexican hat potential associated with the U(1) gauge field theory, corresponds to a hybrid potential with two real components, and with U(1)× SO(1,1) as symmetry group. Each component corresponds to a deformation of the hat potential, with the appearance of a new degenerate vacuum. Hypercomplex electrodynamics will show novel properties, such as spontaneous symmetry breaking scenarios with running masses for the vectorial and scalar Higgs fields, and such as Aharonov-Bohm type strings defects as exact solutions; these topological defects may be detected only by quantum interference of charged particles through gauge invariant loop integrals. In a particular limit, the hyperbolic electrodynamics does not admit topological defects associated with continuous symmetries.
THE WAVE INTERACTION OF HEAVY BREAKS IN THE WATER WITH ELASTIC BARRIER
Directory of Open Access Journals (Sweden)
Ivanchenko G.M.
2014-06-01
Full Text Available Transformation of underwater shock wave spherical front geometry and chauge of impulse carried by it at interaction witu elastic shield is numerically investigated witu the use of zero approximation of ray technique. It is established, that in the vicinity of spots of total internal reflection in the plane interface between water and elastic body the additional internal stresses tend to infinity.
Breaking Waves. IUTAM Symposium Held in Sydney, Australia on July 15-19, 1991
1991-01-01
lines markt the approximate range contained in the wave number spectra shown in Fig. 10 The curves are labelled witlh wind speed U,0 irn ",/s From Jilhne...the interface of fluids I and 2; the ý-coordinate points in the direction along the interface; E, and ., are the segments of the contour c, which are
The New Wave of Childhood Studies: Breaking the Grip of Bio-Social Dualism?
Ryan, Kevin William
2012-01-01
The article takes as its starting point a new wave of researchers who use concepts such as "hybridity" and "multiplicity" in a bid to move the study of childhood beyond the strictures of what Lee and Motzkau call "bio-social dualism", whereby the division between the "natural child" of developmental psychology and the "social child" of…
The New Wave of Childhood Studies: Breaking the Grip of Bio-Social Dualism?
Ryan, Kevin William
2012-01-01
The article takes as its starting point a new wave of researchers who use concepts such as "hybridity" and "multiplicity" in a bid to move the study of childhood beyond the strictures of what Lee and Motzkau call "bio-social dualism", whereby the division between the "natural child" of developmental psychology and the "social child" of…
Wang, L. R.; Liu, X. M.; Gong, Y. K.; Mao, D.; Duan, L. N.
2011-10-01
Supercontinuum (SC) generation is experimentally achieved in a compact all-fiber laser system by using high-energy wave-breaking-free dissipative soliton (DS) pulses. The pulses exhibit Gaussian (rectangular) shape profiles in spectral (temporal) domain, which is even reversed of the typical rectangular-spectrum DSs. With the increase of pump power the pulse duration enlarges dramatically whereas the bandwidth and peak power of the pulse keep almost constant, which enables the pulse to accumulate much higher energy during the pulse-shaping process. When inputting the amplified pulse into the single-mode fiber, SC with excellent flatness is generated with the spectral range from about 1550 to 1700 nm. Broader SC with the bandwidth of even larger than 1000 nm can also be generated by this kind of pulse in the near-zero-dispersion-flattened photonic-crystal fiber through strong nonlinear effects.
Ungermann, Joern; Friedl-Vallon, Felix; Höpfner, Michael; Preusse, Peter; Riese, Martin
2016-04-01
The Gimbaled Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a 2-D infrared detector with a Fourier transform spectrometer. It was operated aboard the German Gulfstream G550 research aircraft HALO during a series of simultaneous campaigns (POLSTRACC, SALSA, GWLCYCLE, GWEX) during the winter of 2015/2016 over Europe and the Arctic. This poster shows a set of GLORIA observations and analyses of 2-D trace gas cross-sections in the extratropical upper troposphere / lower stratosphere (UTLS). The spatially highly-resolved temperature, H2O, O3 and HNO3 data reveal an intricate layered structure in the extratropical Transition Layer (exTL). This heterogeneous structure was caused by Rossby wave breaking and is similar to the state found during previous measurements in summer 2012 over Europe. This study presents first analyses of the stirring and stratosphere-troposphere-exchange by means of backward-trajectory calculation.
Zhou, Faran; Golubev, Timofey; Hwang, Bin; Ruan, Chong-Yu; Duxbury, Phil; Malliakas, Christos; Kanatzidis, Mercouri
2015-03-01
Electron-phonon interactions can give rise to various charge-ordered states, especially at low dimensions, where Fermi surface is more prone to form nesting. Rare earth tritellurides compound ErTe3 develops charge density waves (CDW) along two perpendicular directions at different temperatures. By directly probing the order parameters of the two CDWs using femtosecond electron crystallography under different temperatures and driving photonic energy, we investigated the emergences of competing CDW orders in a dynamical phase diagram. The anisotropic symmetry breaking and the role of electron-phonon coupling, and photo-doping effect are discussed in reference to other CDW systems. Our work is supported by Department of Energy under Grant No. DE-FG02-06ER46309.
Cosmological Electromagnetic Fields due to Gravitational Wave Perturbations
Marklund, M; Brodin, G; Marklund, Mattias; Dunsby, Peter K. S.; Brodin, Gert
2000-01-01
We consider the dynamics of electromagnetic fields in an almost-Friedmann-Robertson-Walker universe using the covariant and gauge-invariant approach of Ellis and Bruni. Focusing on the situation where deviations from the background model are generated by tensor perturbations only, we demonstrate that the coupling between gravitational waves and a weak magnetic test field can generate electromagnetic waves. We show that this coupling leads to an initial pulse of electromagnetic waves whose width and amplitude is determined by the wavelengths of the magnetic field and gravitational waves. A number of implications for cosmology are discussed, in particular we calculate an upper bound of the magnitude of this effect using limits on the quadrapole anisotropy of the Cosmic Microwave Background.
Nonlinear spin-wave excitations at low magnetic bias fields
Woltersdorf, Georg
We investigate experimentally and theoretically the nonlinear magnetization dynamics in magnetic films at low magnetic bias fields. Nonlinear magnetization dynamics is essential for the operation of numerous spintronic devices ranging from magnetic memory to spin torque microwave generators. Examples are microwave-assisted switching of magnetic structures and the generation of spin currents at low bias fields by high-amplitude ferromagnetic resonance. In the experiments we use X-ray magnetic circular dichroism to determine the number density of excited magnons in magnetically soft Ni80Fe20 thin films. Our data show that the common Suhl instability model of nonlinear ferromagnetic resonance is not adequate for the description of the nonlinear behavior in the low magnetic field limit. Here we derive a model of parametric spin-wave excitation, which correctly predicts nonlinear threshold amplitudes and decay rates at high and at low magnetic bias fields. In fact, a series of critical spin-wave modes with fast oscillations of the amplitude and phase is found, generalizing the theory of parametric spin-wave excitation to large modulation amplitudes. For these modes, we also find pronounced frequency locking effects that may be used for synchronization purposes in magnonic devices. By using this effect, effective spin-wave sources based on parametric spin-wave excitation may be realized. Our results also show that it is not required to invoke a wave vector-dependent damping parameter in the interpretation of nonlinear magnetic resonance experiments performed at low bias fields.
Sparrow, Amy R; Mollicone, Daniel J; Kan, Kevin; Bartels, Rachel; Satterfield, Brieann C; Riedy, Samantha M; Unice, Aaron; Van Dongen, Hans P A
2016-08-01
Commercial motor vehicle (CMV) drivers in the US may start a new duty cycle after taking a 34-h restart break. A restart break provides an opportunity for sleep recuperation to help prevent the build-up of fatigue across duty cycles. However, the effectiveness of a restart break may depend on its timing, and on how many nighttime opportunities for sleep it contains. For daytime drivers, a 34-h restart break automatically includes two nighttime periods. For nighttime drivers, who are arguably at increased risk of fatigue, a 34-h restart break contains only one nighttime period. To what extent this is relevant for fatigue depends in part on whether nighttime drivers revert back to a nighttime-oriented sleep schedule during the restart break. We conducted a naturalistic field study with 106 CMV drivers working their normal schedules and performing their normal duties. These drivers were studied during two duty cycles and during the intervening restart break. They provided a total of 1260days of data and drove a total of 414,937 miles during the study. Their duty logs were used to identify the periods when they were on duty and when they were driving and to determine their duty cycles and restart breaks. Sleep/wake patterns were measured continuously by means of wrist actigraphy. Fatigue was assessed three times per day by means of a brief psychomotor vigilance test (PVT-B) and a subjective sleepiness scale. Data from a truck-based lane tracking and data acquisition system were used to compute lane deviation (variability in lateral lane position). Statistical analyses focused on 24-h patterns of duty, driving, sleep, PVT-B performance, subjective sleepiness, and lane deviation. Duty cycles preceded by a restart break containing only one nighttime period (defined as 01:00-05:00) were compared with duty cycles preceded by a restart break containing more than one nighttime period. During duty cycles preceded by a restart break with only one nighttime period, drivers
Yang-Mills theory in 2+1 dimensions: Coupling of matter fields and string-breaking effects
Energy Technology Data Exchange (ETDEWEB)
Agarwal, Abhishek [Physics Department, City College of the CUNY, New York, NY 10031 (United States)], E-mail: abhishek@sci.ccny.cuny.edu; Karabali, Dimitra [Department of Physics and Astronomy, Lehman College of the CUNY, Bronx, NY 10468 (United States)], E-mail: dimitra.karabali@lehman.cuny.edu; Nair, V.P. [Physics Department, City College of the CUNY, New York, NY 10031 (United States)], E-mail: vpn@sci.ccny.cuny.edu
2008-02-11
We explore further the Hamiltonian formulation of Yang-Mills theory in 2+1 dimensions in terms of gauge-invariant matrix variables. Coupling to scalar matter fields is discussed in terms of gauge-invariant fields. We analyze how the screening of adjoint (and other screenable) representations can arise in this formalism. A Schroedinger equation is then derived for the gluelump states which are the daughter states when an adjoint string breaks. A variational solution of this Schroedinger equation leads to an analytic estimate of the string-breaking energy which is within 8.8% of the latest lattice estimates.
Symmetry breaking of localized discrete matter waves induced by spin–orbit coupling
Energy Technology Data Exchange (ETDEWEB)
Salerno, M. [Dipartimento di Fisica “E.R. Caianiello”, CNISM and INFN–Gruppo Collegato di Salerno, Universitá di Salerno, Via Giovanni Paolo II, 84084 Fisciano (Italy); Abdullaev, F.Kh., E-mail: fatkhulla@yahoo.com [Department of Physics, Kulliyyah of Science, International Islamic University of Malaysia, 25200 Kuantan, Pahang (Malaysia)
2015-10-02
We study localized nonlinear excitations of a dilute Bose–Einstein condensate (BEC) with spin–orbit coupling in a deep optical lattice (OL). For this we introduce a tight-binding model that includes the spin–orbit coupling (SOC) at the discrete level in the form of a generalized discrete nonlinear Schrödinger equation. Existence and stability of discrete solitons of different symmetry types is demonstrated. Quite interestingly, we find three distinctive regions in which discrete solitons undergo spontaneously symmetry breaking, passing from on-site to inter-site and to asymmetric, simply by varying the interatomic interactions. Existence ranges of discrete solitons with inter-site symmetry depend on SOC and shrink to zero as the SOC parameter is increased. Asymmetric discrete solitons appear as novel excitations specific of the SOC. Possible experimental implementation of these results is briefly discussed.
Non Breaking Wave Forces at the Front Face of Seawave Slotcone Generators
Directory of Open Access Journals (Sweden)
Mario Calabrese
2012-11-01
Full Text Available The Seawave Slotcone Generator (WAVEnergy SAS, 2003 is a wave energy converter based on the overtopping principle. Although it has been effectively researched during the last decade, no design tool has been supplied to estimate the hydrodynamic loads the waves exert on its front face. In this article a set of well reliable 3D experiments has been re-analyzed, in order to get indications on possible calculation methods. It is shown that the Japanese design tools for monolithic sea dikes may be reasonably adapted to the present case. Finally a new approach is presented, which is based on the so called momentum flux principle; the resulting predictive equation fits the experimental data remarkably well.
Breaking the waves: a poisson regression approach to Schumpeterian clustering of basic innovations
Silverberg, G.P.; Verspagen, B.
2000-01-01
The Schumpeterian theory of long waves has given rise to an intense debate on the existenceof clusters of basic innovations. Silverberg and Lehnert have criticized the empirical part ofthis literature on several methodological accounts. In this paper, we propose the methodologyof Poisson regression as a logical way to incorporate this criticism. We construct a new timeseries for basic innovations (based on previously used time series), and use this to test thehypothesis that basic innovations...
Polarization operator for plane-wave background fields
Meuren, S; Di Piazza, A
2013-01-01
We derive an alternative representation of the leading-order contribution to the polarization operator in strong-field QED with a plane-wave electromagnetic background field, which is manifestly symmetric with respect to the external photon momenta. Our derivation is based on a direct evaluation of the corresponding Feynman diagram, using the Volkov-representation of the dressed fermion propagator. Furthermore, the validity of the Ward-Takahashi identity is shown for general loop diagrams in an external plane-wave background field.
Massive to gauge field reduction and gravitational wave zone information
Deser, S
2016-01-01
We show explicitly that massive, Abelian, vector, just like (properly defined) massive tensor, fields limit smoothly to their massless, gauge, versions: they emit only maximal helicity radiation and mediate Coulomb and (special relativistic) Newtonian, forces between their (conserved) sources. Our main motivation, though, is to show that the recent gravitational wave detection probably cannot directly rule out very long-range gravity: Even though the waves were emitted in a strong field regime, their being detected in the weak field wave zone means the above equivalences apply. There remains the, not unlikely, possibility that no strong field generation of radiation in massive models can reproduce the observed ring-down patterns. Separately, the smooth linear limiting behaviors show that the discontinuity lies not in the mass alone, but rather in Abelian versus non-Abelian, Yang-Mills and General Relativity, regimes, whose respective massive versions are known to be non-physical.
Korotkov, V. S.; Krasnoperov, E. P.; Kartamyshev, A. A.
2017-09-01
During the pulsed field magnetization of a high-T c annulus in liquid nitrogen the shielding current drops abruptly, providing rapid penetration of the magnetic flux into the hole of the superconductor. After the break of current the trapped field in the hole is small and negative although the body of the annulus remains highly magnetized. In the present work the current breaking effect is investigated both experimentally and numerically. The influence of the pulse parameter on the shielding current evolution during the break is researched. A simple model for the qualitative description of this process is proposed. The model shows the development of heating localized on the inhomogeneity of the high-temperature superconductor annulus providing the formation of a high resistive channel with temperature near to T c. The appearance of this hot channel leads to the rapid reduction of the shielding current and presents a new scenario of flux jump at high temperature.
Line Nodes and Time Reversal Symmetry Breaking in p-wave Sr2RuO4
Annett, Jf; Gyorffy, Bl; Litak, G.; Wysokinski, Ki
2001-03-01
The superconductor Sr_2RuO4 exhibits broken time reversal symmetry and has a contant Knight shift below Tc. These experiments suggest a pairing state of the ^3He-A type, d(k) = (k_x+ik_y)hatz. On the other hand specific heat measurements of Nishizaki Maeno and Mao (J. Phys. Soc. Japan 69, 572 (2000)) imply that the gap has line nodes. To resolve this contradiction we calculate the energy gap and heat capacity in several alternative scenarios for the pairing interaction. We find that on-site Hunds rule exchange cannot produce the observed T_c. Nearest neighbour spin independent attraction leads to d-wave pairing, while nearest neighbour parallel spin interaction leads to a p-wave state with no line nodes. However we can also obtain a state with line nodes on the alpha-beta Fermi surface sheets, and time reversal symmetry breaking on the gamma sheet. We discuss the possible physical origin of this state and the comparison with available experimental data.
Gravitational waves and large field inflation
Linde, Andrei
2016-01-01
According to the famous Lyth bound, one can confirm large field inflation by finding tensor modes with sufficiently large tensor-to-scalar ratio $r$. Here we will try to answer two related questions: Is it possible to rule out all large field inflationary models by not finding tensor modes with $r$ above some critical value, and what can we say about the scale of inflation by measuring $r$? However, in order to answer these questions one should distinguish between two different definitions of the large field inflation and three different definitions of the scale of inflation. We will examine these issues using the theory of cosmological $\\alpha$-attractors as a convenient testing ground.
Gravitational waves and large field inflation
Linde, Andrei
2017-02-01
According to the famous Lyth bound, one can confirm large field inflation by finding tensor modes with sufficiently large tensor-to-scalar ratio r. Here we will try to answer two related questions: is it possible to rule out all large field inflationary models by not finding tensor modes with r above some critical value, and what can we say about the scale of inflation by measuring r? However, in order to answer these questions one should distinguish between two different definitions of the large field inflation and three different definitions of the scale of inflation. We will examine these issues using the theory of cosmological α-attractors as a convenient testing ground.
VELOCITY FIELD IN SHIP WAVES ON THE VISCOUS FLUID
Institute of Scientific and Technical Information of China (English)
刘敏嘉; 陶明德
2002-01-01
From the Navier-Stokes equations, the integral expressions of the free-surface elevation and the velocity field in ship waves of a moving waterborne body are obtained.Next, Lighthill's two-stage scheme is employed to change the above-mentioned integral expressions to algebraic expressions.Compared with the results obtained when the seawater is idealized to an inviscid fluid, the singularities are dispelled or weakened, and the accuracy of the digit information of ship waves is improved.
Twisted Backgrounds, PP-Waves and Nonlocal Field Theories
Alishahiha, M; Alishahiha, Mohsen; Ganor, Ori J.
2003-01-01
We study partially supersymmetric plane-wave like deformations of string theories and M-theory on brane backgrounds. These deformations are dual to nonlocal field theories. We calculate various expectation values of configurations of closed as well as open Wilson loops and Wilson surfaces in those theories. We also discuss the manifestation of the nonlocality structure in the supergravity backgrounds. A plane-wave like deformation of little string theory has also been studied.
Analysis of circular wave packets generated by pulsed electric fields
Energy Technology Data Exchange (ETDEWEB)
Yoshida, S., E-mail: shuhei@concord.itp.tuwien.ac.at [Institute for Theoretical Physics, Vienna University of Technology, Vienna (Austria); Reinhold, C.O. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States); Department of Physics, University of Tennessee, Knoxville, TN 37996 (United States); Burgdoerfer, J. [Institute for Theoretical Physics, Vienna University of Technology, Vienna (Austria); Department of Physics, University of Tennessee, Knoxville, TN 37996 (United States); Wyker, B.; Ye, S.; Dunning, F.B. [Department of Physics and Astronomy and the Rice Quantum Institute, Rice University, Houston, TX 77005-1892 (United States)
2012-05-15
We demonstrate that circular wave packets in high Rydberg states generated by a pulsed electric field applied to extreme Stark states are characterized by a position-dependent energy gradient that leads to a correlation between the principal quantum number n and the spatial coordinate. This correlation is rather insensitive to the initial state and can be seen even in an incoherent mix of states such as is generated experimentally allowing information to be placed into, and extracted from, such wave packets. We show that detailed information on the spatial distribution of a circular wave packet can be extracted by analyzing the complex phase of its expansion coefficients.
Schneider, Andreas; Söder, Jens; Gerding, Michael; Wagner, Johannes; Lübken, Franz-Josef
2016-04-01
Gravity waves in their final stage produce turbulence and dissipation. In the stratosphere only few studies of this phenomenon exist because the observation is technically challenging. In order to precisely infer energy dissipation rates, the viscous subrange has to be covered, which in the stratosphere lies at scales of centimetres and below. With our balloon-borne instrument LITOS (Leibniz-Institute Turbulence Observations in the Stratosphere), which has a vertical resolution below 1 mm, measurements were performed from Kiruna (68°N, 21°E) as well as from Kühlungsborn (54°N, 12°E). To characterise the atmospheric background conditions, WRF simulations driven by ECMWF reanalysis data were performed for the times of the flights. Averaged dissipation rates observed by LITOS are connected to wave signatures seen in the model. Particularly, larger dissipation rates correlate to larger amplitudes seen in the horizontal divergence or vertical winds in the model and vice versa. For one flight, a very pronounced maximum in dissipation is observed below the tropopause. It is connected to a wind reversal and dynamic instability. In the corresponding WRF simulation, turbulent kinetic energies (TKE) and amplitudes in horizontal divergence are enhanced in this region. For the other flights, no such pronounced maximum in dissipation but also no enhanced values of TKE outside of the boundary layer are observed. That means that low and moderate turbulence is not resolved in WRF, but is observed by LITOS throughout all altitudes.
Institute of Scientific and Technical Information of China (English)
GONG Sheng-wu; ZHAO Fu-jun
2008-01-01
The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45° and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.
Particle production from symmetry breaking after inflation
García-Bellido, J; Garcia-Bellido, Juan; Morales, Ester Ruiz
2002-01-01
Recent studies suggest that the process of symmetry breaking after inflation typically occurs very fast, within a single oscillation of the symmetry-breaking field, due to the spinodal growth of its long-wave modes, otherwise known as `tachyonic preheating'. In this letter we show how this sudden transition from the false to the true vacuum can induce a significant production of particles, bosons and fermions, coupled to the symmetry-breaking field. We find that this new mechanism of particle production in the early Universe may have interesting consequences for the origin of dark matter and the generation of the observed baryon asymmetry through leptogenesis.
Multi-Center Vector Field Methods for Wave Equations
Soffer, Avy; Xiao, Jianguo
2016-12-01
We develop the method of vector-fields to further study Dispersive Wave Equations. Radial vector fields are used to get a-priori estimates such as the Morawetz estimate on solutions of Dispersive Wave Equations. A key to such estimates is the repulsiveness or nontrapping conditions on the flow corresponding to the wave equation. Thus this method is limited to potential perturbations which are repulsive, that is the radial derivative pointing away from the origin. In this work, we generalize this method to include potentials which are repulsive relative to a line in space (in three or higher dimensions), among other cases. This method is based on constructing multi-centered vector fields as multipliers, cancellation lemmas and energy localization.
Near-Field Cross Section Imaging of Wideband Millimeter Wave
Directory of Open Access Journals (Sweden)
Kan Yingzhi
2016-01-01
Full Text Available Near-field millimeter wave imaging has been a hot topic recent years for its importance applications in the area of anti-terrorism. The penetrating characteristic of millimeter wave is of significant importance to security, such as the concealed weapons detection, ground-penetrating radar imaging, through-barrier imaging and so on. Cross section imaging is a basic aspect for near-field millimeter wave imaging, which includes antenna array distribution and wideband signal processing. This paper utilizes back projection method in space area to realize ultra-band nearfield cross section imaging. We induce two dimensional direction integral formulas to obtain the reconstruction image of the near-field imaging area, and the simulation results validate the effectiveness of this imaging algorithm.
Pilot-wave approaches to quantum field theory
Struyve, Ward
2011-01-01
The purpose of this paper is to present an overview of recent work on pilot-wave approaches to quantum field theory. In such approaches, systems are not only described by their wave function, as in standard quantum theory, but also by some additional variables. In the non-relativistic pilot-wave theory of de Broglie and Bohm those variables are particle positions. In the context of quantum field theory, there are two natural choices, namely particle positions and fields. The incorporation of those variables makes it possible to provide an objective description of nature in which rather ambiguous notions such as `measurement' and `observer' play no fundamental role. As such, the theory is free of the conceptual difficulties, such as the measurement problem, that plague standard quantum theory.
Magnetic field dependence of the threshold electric field in unconventional charge density waves
Dóra, Balázs; Virosztek, Attila; Maki, Kazumi
2002-04-01
Many experiments suggest that the unidentified low-temperature phase of α-(BEDT-TTF)2KHg(SCN)4 is most likely unconventional charge density wave (UCDW). To further extend this identification we present our theoretical study of the threshold electric field of UCDW in a magnetic field. The magnetic field-temperature phase diagram is very similar to those in a d-wave superconductor. The optical conductivity shows clear features characteristic to both UDW and magnetic field. We find a rather strong field dependence of the threshold electric field, which shows qualitatively good agreement with the experimental data.
A Coupled Finite Difference and Moving Least Squares Simulation of Violent Breaking Wave Impact
DEFF Research Database (Denmark)
Lindberg, Ole; Bingham, Harry B.; Engsig-Karup, Allan Peter
2012-01-01
incompressible and inviscid model and the wave impacts on the vertical breakwater are simulated in this model. The resulting maximum pressures and forces on the breakwater are relatively high when compared with other studies and this is due to the incompressible nature of the present model.......Two model for simulation of free surface flow is presented. The first model is a finite difference based potential flow model with non-linear kinematic and dynamic free surface boundary conditions. The second model is a weighted least squares based incompressible and inviscid flow model. A special...... feature of this model is a generalized finite point set method which is applied to the solution of the Poisson equation on an unstructured point distribution. The presented finite point set method is generalized to arbitrary order of approximation. The two models are applied to simulation of steep...
Skewon field and cosmic wave propagation
Ni, Wei-Tou
2013-01-01
For the study of the gravitational coupling of electromagnetism and the equivalence principle, we have used the spacetime constitutive tensor density {chi}ijkl, and discovered the nonmetric (axion) part (A){chi}ijkl (equal to {phi}eijkl) of {chi}ijkl worthy investigation. Since we have used Lagrangian formalism, {chi}ijkl is effectively symmetric under the interchange of index pairs, ij and kl, and has 21 independent degrees of freedom. Hehl, Obukhov and Rubilar have started from charge-flux formalism to study electromagnetism, discovered the antisymmetric part (Sk){chi}ijkl (15 degrees of freedom) of {chi}ijkl under the interchange of index pairs ij and kl worthy investigation, and called it skewon field. In this paper, we study the propagation of the Hehl-Obukhov-Rubilar skewon field in weak gravity field/dilute matter or with weak violation of the Einstein Equivalence Principle (EEP), and further classify it into Type I and Type II skewons. From the dispersion relation we show that no dissipation/no amplif...
Spiral Wave Generation in a Vortex Electric Field
Institute of Scientific and Technical Information of China (English)
YUAN Xiao-Ping; CHEN Jiang-Xing; ZHAO Ye-Hua; LOU Qin; WANG Lu-Lu; SIIEN Qian
2011-01-01
The effect of a vortical electric field on nonlinear patterns in excitable media is studied. When an appropriate vortex electric field is applied, the system exhibits pattern transition from chemical turbulence to spiral waves, which possess the same chtality as the vortex electric field. The underlying mechanism of this is discussed. We also show the meandering behavior of a spiral under the taming of a vortex electric field. The results obtained here may contribute to control strategies of patterns on surface reaction.%The effect of a vortical electric field on nonlinear patterns in excitable media is studied.When an appropriate vortex electric field is applied,the system exhibits pattern transition from chemical turbulence to spiral waves,which possess the same chirality as the vortex electric field.The underlying mechanism of this is discussed.We also show the meandering behavior of a spiral under the taming of a vortex electric field.The results obtained here may contribute to control strategies of patterns on surface reaction.Spiral waves are one of the most common and widely studied patterns in nature.They appear in hydrodynamic systems,chemical reactions and a large variety of biological,chemical and physical systems.[1-5] Much attention has been paid to their rich nonlinear dynamics,as well as potential applications in various biological or physiological systems,since the emergence and instability of spirals usually lead to abnormal states,for example in cardiac arrythmia[6,7] and epilepsy[8].Much research has been carried out in studying pattern formations in catalytic CO oxidation on Pt(110),[9-11] because they provide practical utilization in industry.A rich variety of spatiotemporal patterns,including travelling pulses,standing waves,target patterns,spiral waves and chemical turbulence have been observed in this system.[12-16
Challenges in assessing the contribution of climate change to observed record-breaking heat waves
Perlwitz, J.; Xu, T.; Quan, X.; Hoerling, M. P.; Dole, R. M.
2013-12-01
Record-setting heat waves have large impacts on public health and society due to increased mortality rate, wild fires, property damages and agricultural loss. There is increasing interest in understanding the causes of such extreme events including the role of climate change. We use the example of the link between atmospheric blocking frequency and summertime seasonal temperature extreme to address some challenges in determining the relative contributions of natural variability and climate change on the occurrence and magnitude of extreme climate-related events. We utilize the 62-year record of observational data from 1960 to 2011 and long integrations with the NCARs Community Climate System Model Version 4 (CCSM4). This climate model represents well atmospheric blocking frequency and related weather features over the European/Ural region. Both observations and long climate integrations suggest that seasonal temperature extremes over the Northern European/Ural region are strongly conditioned by blocking. We illustrate that one challenge in climate event attribution is related to the fact that very long records are necessary to sufficiently sample the frequency of occurrence of the principal driver of a record-setting climate event. We further illustrate that there is a strong regional dependence on how the link between blocking frequency and extreme temperature anomalies is modified due to climate change suggesting that event attribution results are often not transferable from one region to another.
A Simple Mixing Scheme for Models that Resolve Breaking Internal Waves
2010-03-23
these have been treated with large-scale general circulation models (i.e. POM Merri - field and Holloway (2002) or ROMS), or with specialized non...We integrate the dissipation (figure 4) for the whole water column between−25 km < x < 25 km, to get D = ∫ A [ Az ( ∂u ∂z )2 +Ah ( ∂u ∂x )2] dA (4) 7
Energy Technology Data Exchange (ETDEWEB)
Shan, Jaffry Syed [Hamdard University, Karachi (Pakistan); Abbas, Syed Haider; Lee, Jung Ryul [Dept. of Aerospace Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kang, Dong Hoon [Advanced Materials Research Team, Korea Railroad Research Institute, Uiwang (Korea, Republic of)
2015-12-15
Recently, wave propagation imaging based on laser scanning-generated elastic waves has been intensively used for nondestructive inspection. However, the proficiency of the conventional software based system reduces when the scan area is large since the processing time increases significantly due to unavoidable processor multitasking, where computing resources are shared with multiple processes. Hence, the field programmable gate array (FPGA) was introduced for a wave propagation imaging method in order to obtain extreme processing time reduction. An FPGA board was used for the design, implementing post-processing ultrasonic wave propagation imaging (UWPI). The results were compared with the conventional system and considerable improvement was observed, with at least 78% (scanning of 100x100mm{sup 2} with 0.5 mm interval) to 87.5% (scanning of 200x200mm{sup 2} with 0.5 mm interval) less processing time, strengthening the claim for the research. This new concept to implement FPGA technology into the UPI system will act as a break-through technology for full-scale automatic inspection.
Analytic Beyond-Mean-Field BEC Wave Functions
Dunn, Martin; Laing, W. Blake; Watson, Deborah K.; Loeser, John G.
2006-05-01
We present analytic N-body beyond-mean-field wave functions for Bose-Einstein condensates. This extends our previous beyond-mean-field energy calculations to the substantially more difficult problem of determining correlated N-body wave functions for a confined system. The tools used to achieve this have been carefully chosen to maximize the use of symmetry and minimize the dependence on numerical computation. We handle the huge number of interactions when N is large (˜N^2/2 two-body interactions) by bringing together three theoretical methods. These are dimensional perturbation theory, the FG method of Wilson et al, and the group theory of the symmetric group. The wave function is then used to derive the density profile of a condensate in a cylindrical trap.This method makes no assumptions regarding the form or strength of the interactions and is applicable to both small-N and large-N systems.
Propagation of Vortex Electron Wave Functions in a Magnetic Field
Gallatin, Gregg M
2012-01-01
The physics of coherent beams of photons carrying axial orbital angular momentum (OAM) is well understood and such beams, sometimes known as vortex beams, have found applications in optics and microscopy. Recently electron beams carrying very large values of axial OAM have been generated. In the absence of coupling to an external electromagnetic field the propagation of such vortex electron beams is virtually identical mathematically to that of vortex photon beams propagating in a medium with a homogeneous index of refraction. But when coupled to an external electromagnetic field the propagation of vortex electron beams is distinctly different from photons. Here we use the exact path integral solution to Schrodingers equation to examine the time evolution of an electron wave function carrying axial OAM. Interestingly we find that the nonzero OAM wave function can be obtained from the zero OAM wave function, in the case considered here, simply by multipling it by an appropriate time and position dependent pref...
Spherical wave rotation in spherical near-field antenna measurements
DEFF Research Database (Denmark)
Wu, Jian; Larsen, Flemming Holm; Lemanczyk, J.
1991-01-01
The rotation of spherical waves in spherical near-field antenna measurement is discussed. Considering the many difficult but interesting features of the rotation coefficients, an efficient rotation scheme is derived. The main feature of the proposed scheme is to ignore the calculation of the very...
Carcione, José M
2007-01-01
This book examines the differences between an ideal and a real description of wave propagation, where ideal means an elastic (lossless), isotropic and single-phase medium, and real means an anelastic, anisotropic and multi-phase medium. The analysis starts by introducing the relevant stress-strain relation. This relation and the equations of momentum conservation are combined to give the equation of motion. The differential formulation is written in terms of memory variables, and Biot's theory is used to describe wave propagation in porous media. For each rheology, a plane-wave analysis is performed in order to understand the physics of wave propagation. The book contains a review of the main direct numerical methods for solving the equation of motion in the time and space domains. The emphasis is on geophysical applications for seismic exploration, but researchers in the fields of earthquake seismology, rock acoustics, and material science - including many branches of acoustics of fluids and solids - may als...
Characteristic analysis of wind field and sea wave field over the NW Pacific Ocean
Institute of Scientific and Technical Information of China (English)
刘金芳; 唐晓卫; 何丹华
2001-01-01
According to ship observation data over the NW Pacific Ocean during 1950 - 1995, taking 5°x5° grid, the characteristics and variation rule of wind, wave and swell are analyzed. This area is typical monsoon area. In the period of monsoon, the directions of wind, sea wave and swell are roughly consistent. Sea wave of northeasterly is always prevailing in equatorial zone. The monsoon in winter is stronger than in summer, correspondingly, average wave height is higher, and the frequencies of high sea and heavy swell are also bigger. Both of North Indian Ocean and adjacent sea area is also monsoon area, but characteristic is opposite. This paper provides specific data of wind field and wave field and variaton for ship navigation, operation and scientific experiment in the NW Pacific Ocean.
Volumetric characterization of delamination fields via angle longitudinal wave ultrasound
Wertz, John; Wallentine, Sarah; Welter, John; Dierken, Josiah; Aldrin, John
2017-02-01
The volumetric characterization of delaminations necessarily precedes rigorous composite damage progression modeling. Yet, inspection of composite structures for subsurface damage remains largely focused on detection, resulting in a capability gap. In response to this need, angle longitudinal wave ultrasound was employed to characterize a composite surrogate containing a simulated three-dimensional delamination field with distinct regions of occluded features (shadow regions). Simple analytical models of the specimen were developed to guide subsequent experimentation through identification of optimal scanning parameters. The ensuing experiments provided visual evidence of the complete delamination field, including indications of features within the shadow regions. The results of this study demonstrate proof-of-principle for the use of angle longitudinal wave ultrasonic inspection for volumetric characterization of three-dimensional delamination fields. Furthermore, the techniques developed herein form the foundation of succeeding efforts to characterize impact delaminations within inhomogeneous laminar materials such as polymer matrix composites.
Analysis of Circular Wave Packets Generated by Pulsed Electric Fields
Energy Technology Data Exchange (ETDEWEB)
Yoshida, S. [Vienna University of Technology, Austria; Reinhold, Carlos O [ORNL; Burgdorfer, J. [Vienna University of Technology, Austria; Wyker, B. [Rice University; Ye, S. [Rice University; Dunning, F. B. [Rice University
2011-01-01
We demonstrate that circular wave packets in high Rydberg states generated using a pulsed electric field applied to extreme Stark states are characterized by a position-dependent energy gradient that leads to a correlation between the principal quantum number n and the spatial coordinate. This correlation is rather insensitive to the initial state and can be seen even in an incoherent mix of states such as is generated experimentally allowing information to be placed into, and extracted from, such wavepackets. We show that detailed information on the spatial distribution of a circular wave packet can be extracted by analyzing the complex phase of its expansion coefficient.
Wave packet dynamics under effect of a pulsed electric field
da Silva, A. R. C. B.; de Moura, F. A. B. F.; Dias, W. S.
2016-06-01
We studied the dynamics of an electron in a crystalline one-dimensional model under effect of a time-dependent Gaussian field. The time evolution of an initially Gaussian wave packet it was obtained through the numerical solution of the time-dependent Schrödinger equation. Our analysis consists of computing the electronic centroid as well as the mean square displacement. We observe that the electrical pulse is able to promote a special kind of displacement along the chain. We demonstrated a direct relation between the group velocity of the wave packet and the applied electrical pulses. We compare those numerical calculations with a semi-classical approach.
Enhancement of electric and magnetic wave fields at density gradients
Directory of Open Access Journals (Sweden)
A. Reiniusson
2006-03-01
Full Text Available We use Freja satellite data to investigate irregular small-scale density variations. The observations are made in the auroral region at about 1000-1700 km. The density variations are a few percent, and the structures are found to be spatial down to a scale length of a few ion gyroradii. Irregular density variations are often found in an environment of whistler mode/lower hybrid waves and we show that at the density gradients both the electric and magnetic wave fields are enhanced.
Ahmed, Shaikh; Usman, Muhammad; Heitzinger, Clemens; Rahman, Rajib; Schliwa, Andrei; Klimeck, Gerhard
2007-04-01
Electrons and holes captured in self-assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo-electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.
Institute of Scientific and Technical Information of China (English)
翁羽翔
2004-01-01
Considering the role of mechanical forces playing in the morphogenetic pattern formation, we propose a secondorder differential equation for the growth and form of plants based on the turgor pressure field at the organ and cellular level. The solutions can well describe various kinds of morphological features of flowers under certain hypotheses. The plant morphology is considered as the spontaneous symmetry breaking of a circular growing boundary, while the employed hypotheses are subjected to further experimental confirmation.
Drift-wave stability in the field-reversed configuration
Lau, C. K.; Fulton, D. P.; Holod, I.; Lin, Z.; Binderbauer, M.; Tajima, T.; Schmitz, L.
2017-08-01
Gyrokinetic simulations of C-2-like field-reversed configuration (FRC) find that electrostatic drift-waves are locally stable in the core. The stabilization mechanisms include finite Larmor radius effects, magnetic well (negative grad-B), and fast electron short circuit effects. In the scrape-off layer (SOL), collisionless electrostatic drift-waves in the ion-to-electron-scale are destabilized by electron temperature gradients due to the resonance with locally barely trapped electrons. Collisions can suppress this instability, but a collisional drift-wave instability still exists at realistic pressure gradients. Simulation results are in qualitative agreement with C-2 FRC experiments. In particular, the lack of ion-scale instability in the core is not inconsistent with experimental measurements of a fluctuation spectrum showing a depression at ion-scales. The pressure gradient thresholds for the SOL instability from simulations are also consistent with the critical gradient behavior observed in experiments.
Increasing the structural variety of discrete nondiffracting wave fields
Energy Technology Data Exchange (ETDEWEB)
Boguslawski, Martin; Rose, Patrick; Denz, Cornelia [Institut fuer Angewandte Physik and Center for Nonlinear Science (CeNoS), Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 2/4, D-48149 Muenster (Germany)
2011-07-15
We investigate discrete nondiffracting beams (DNBs) being the foundation of periodic and quasiperiodic intensity distributions. Besides the number of interfering plane waves, the phase relation among these waves is decisive to form a particular intensity lattice. In this manner, we systematize different classes of DNBs and present similarities as well as differences. As one prominent instance, we introduce the class of sixfold nondiffracting beams, offering four entirely different transverse intensity distributions: in detail, the hexagonal, kagome, and honeycomb pattern, as well as a hexagonal vortex beam. We further extend our considerations to quasiperiodic structures and show the changeover to Bessel beams. In addition, we introduce a highly flexible implementation of the experimental analog of DNBs, namely discrete pseudo-nondiffracting beams, and present locally resolved intensity and phase measurements, which underline the nondiffracting character of the generated wave fields.
Empirical Mode Decomposition of the atmospheric wave field
Directory of Open Access Journals (Sweden)
A. J. McDonald
2007-03-01
Full Text Available This study examines the utility of the Empirical Mode Decomposition (EMD time-series analysis technique to separate the horizontal wind field observed by the Scott Base MF radar (78° S, 167° E into its constituent parts made up of the mean wind, gravity waves, tides, planetary waves and instrumental noise. Analysis suggests that EMD effectively separates the wind field into a set of Intrinsic Mode Functions (IMFs which can be related to atmospheric waves with different temporal scales. The Intrinsic Mode Functions resultant from application of the EMD technique to Monte-Carlo simulations of white- and red-noise processes are compared to those obtained from the measurements and are shown to be significantly different statistically. Thus, application of the EMD technique to the MF radar horizontal wind data can be used to prove that this data contains information on internal gravity waves, tides and planetary wave motions.
Examination also suggests that the EMD technique has the ability to highlight amplitude and frequency modulations in these signals. Closer examination of one of these regions of amplitude modulation associated with dominant periods close to 12 h is suggested to be related to a wave-wave interaction between the semi-diurnal tide and a planetary wave. Application of the Hilbert transform to the IMFs forms a Hilbert-Huang spectrum which provides a way of viewing the data in a similar manner to the analysis from a continuous wavelet transform. However, the fact that the basis function of EMD is data-driven and does not need to be selected a priori is a major advantage. In addition, the skeleton diagrams, produced from the results of the Hilbert-Huang spectrum, provide a method of presentation which allows quantitative information on the instantaneous period and amplitude squared to be displayed as a function of time. Thus, it provides a novel way to view frequency and amplitude-modulated wave phenomena and potentially non
Effective Orthorhombic Anisotropic Models for Wave field Extrapolation
Ibanez Jacome, Wilson
2013-05-01
Wavefield extrapolation in orthorhombic anisotropic media incorporates complicated but realistic models, to reproduce wave propagation phenomena in the Earth\\'s subsurface. Compared with the representations used for simpler symmetries, such as transversely isotropic or isotropic, orthorhombic models require an extended and more elaborated formulation that also involves more expensive computational processes. The acoustic assumption yields more efficient description of the orthorhombic wave equation that also provides a simplified representation for the orthorhombic dispersion relation. However, such representation is hampered by the sixth-order nature of the acoustic wave equation, as it also encompasses the contribution of shear waves. To reduce the computational cost of wavefield extrapolation in such media, I generate effective isotropic inhomogeneous models that are capable of reproducing the first-arrival kinematic aspects of the orthorhombic wavefield. First, in order to compute traveltimes in vertical orthorhombic media, I develop a stable, efficient and accurate algorithm based on the fast marching method. The derived orthorhombic acoustic dispersion relation, unlike the isotropic or transversely isotropic one, is represented by a sixth order polynomial equation that includes the fastest solution corresponding to outgoing P-waves in acoustic media. The effective velocity models are then computed by evaluating the traveltime gradients of the orthorhombic traveltime solution, which is done by explicitly solving the isotropic eikonal equation for the corresponding inhomogeneous isotropic velocity field. The inverted effective velocity fields are source dependent and produce equivalent first-arrival kinematic descriptions of wave propagation in orthorhombic media. I extrapolate wavefields in these isotropic effective velocity models using the more efficient isotropic operator, and the results compare well, especially kinematically, with those obtained from the
Analysis of Wave Fields induced by Offshore Pile Driving
Ruhnau, M.; Heitmann, K.; Lippert, T.; Lippert, S.; von Estorff, O.
2015-12-01
Impact pile driving is the common technique to install foundations for offshore wind turbines. With each hammer strike the steel pile - often exceeding 6 m in diameter and 80 m in length - radiates energy into the surrounding water and soil, until reaching its targeted penetration depth. Several European authorities introduced limitations regarding hydroacoustic emissions during the construction process to protect marine wildlife. Satisfying these regulations made the development and application of sound mitigation systems (e.g. bubble curtains or insulation screens) inevitable, which are commonly installed within the water column surrounding the pile or even the complete construction site. Last years' advances have led to a point, where the seismic energy tunneling the sound mitigation systems through the soil and radiating back towards the water column gains importance, as it confines the maximum achievable sound mitigation. From an engineering point of view, the challenge of deciding on an effective noise mitigation layout arises, which especially requires a good understanding of the soil-dependent wave field. From a geophysical point of view, the pile acts like a very unique line source, generating a characteristic wave field dominated by inclined wave fronts, diving as well as head waves. Monitoring the seismic arrivals while the pile penetration steadily increases enables to perform quasi-vertical seismic profiling. This work is based on datasets that have been collected within the frame of three comprehensive offshore measurement campaigns during pile driving and demonstrates the potential of seismic arrivals induced by pile driving for further soil characterization.
Scanning Michelson interferometer for imaging surface acoustic wave fields.
Knuuttila, J V; Tikka, P T; Salomaa, M M
2000-05-01
A scanning homodyne Michelson interferometer is constructed for two-dimensional imaging of high-frequency surface acoustic wave (SAW) fields in SAW devices. The interferometer possesses a sensitivity of ~10(-5)nm/ radicalHz , and it is capable of directly measuring SAW's with frequencies ranging from 0.5 MHz up to 1 GHz. The fast scheme used for locating the optimum operation point of the interferometer facilitates high measuring speeds, up to 50,000 points/h. The measured field image has a lateral resolution of better than 1 mu;m . The fully optical noninvasive scanning system can be applied to SAW device development and research, providing information on acoustic wave distribution that cannot be obtained by merely electrical measurements.
Thermodynamics of relativistic quantum fields: extracting energy from gravitational waves
Bruschi, David Edward
2016-01-01
We investigate the quantum thermodynamical properties of localised relativistic quantum fields that can be used as quantum thermal machines. We study the efficiency and power of energy transfer between the classical degrees of freedom, such as the energy input due to motion or to an impinging gravitational wave, and the excitations of the confined quantum field. We find that the efficiency of energy transfer depends dramatically on the input initial state of the system. Furthermore, we investigate the ability to extract the energy and to store it in a battery. This process is inefficient in optical cavities but is significantly enhanced when employing trapped Bose Einstein Condensates. Finally, we apply our techniques to a setup where an impinging gravitational wave excites the phononic modes of a Bose Einstein Condensate. We find that, in this case, the amount of energy transfer to the phonons increases with time and quickly approaches unity. These results suggest that, in the future, it might be possible to...
Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate
Acedo, L
2015-01-01
The gravitational redshift forms the central part of the majority of the classical tests for the general theory of relativity. It could be successfully checked even in laboratory experiments on the earth's surface. The standard derivation of this effect is based on the distortion of the local structure of spacetime induced by large masses. The resulting gravitational time-dilation near these masses gives rise to a frequency change of any periodic process, including electromagnetic oscillations as the wave propagates across the gravitational field. This phenomenon can be tackled with classical electrodynamics assuming a curved spacetime background and Maxwell's equations in a generally covariant form. In the present paper, we show that in a classical field-theoretical context the gravitational redshift can be interpreted as the propagation of electromagnetic waves in a medium with corresponding conductivity $\\sigma=g/(\\mu_0 c^3)$, where $g$ is the gravitational acceleration and $\\mu_0$ is the vacuum magnetic p...
DEFF Research Database (Denmark)
Neergaard, Helle; Christensen, Dorthe Refslund
2015-01-01
Learning is related to the environment created for the learning experience. This learning environment is often highly routinized and involves a certain social structure but in entrepreneurship education such routinization and structure may actually counteract the learning goals. The purpose...... of this paper is therefore to investigate how classroom routines and rituals impact on entrepreneurship education in order to problematize how existing classroom environments may hinder critical learning experiences from taking place. Previously, rituals have predominantly been examined with an emphasis...... on religious aspects, structures and values of society. Rituals are actions that we undertake with a particular observance, which makes them special and creates structures of order, providing a feeling of security through familiarity. Rituals further help create social relationships and they may even have...
DEFF Research Database (Denmark)
Neergaard, Helle; Christensen, Dorthe Refslund
2017-01-01
an ‘identity shaping dimension in that they establish order by creating social feelings ensuring unity through emotional and symbolic dimensions’. Many rituals used in the classroom originate from behaviourism but in entrepreneurship education we often replace these with new ones. The paper builds on extensive...... insight from six cohorts of students at two Scandinavian universities over a four-year period (2012-2015). The data was procured using an experiential-explorative research approach in which the researchers were personally involved in reflective processes as co-learners. The findings illustrate how...
Four-wave dark-field electron holography for imaging strain fields
Denneulin, T.; Hÿtch, M.
2016-06-01
Strain characterization by transmission electron microscopy is an active area of research especially for microelectronics applications. Two-wave dark-field electron holography (DFEH) was previously introduced as a reliable strain mapping technique. Here, DFEH with four electron waves was investigated in order to image equi-displacement lines as amplitude modulations of the holographic fringes. Two perpendicular electrostatic biprisms are used to interfere three reference waves diffracted by a substrate and one object wave diffracted by an epitaxially strained region. This technique provides a different way to represent the displacement field. It might be helpful to obtain information about the strain state during in situ experiments. A dummy p-MOSFET device with embedded SiGe source and drain is used for experimental demonstration.
Spectrum of classes of point emitters of electromagnetic wave fields.
Castañeda, Román
2016-09-01
The spectrum of classes of point emitters has been introduced as a numerical tool suitable for the design, analysis, and synthesis of non-paraxial optical fields in arbitrary states of spatial coherence. In this paper, the polarization state of planar electromagnetic wave fields is included in the spectrum of classes, thus increasing its modeling capabilities. In this context, optical processing is realized as a filtering on the spectrum of classes of point emitters, performed by the complex degree of spatial coherence and the two-point correlation of polarization, which could be implemented dynamically by using programmable optical devices.
NEAR-FIELD ACOUSTIC HOLOGRAPHY FOR SEMI-FREE ACOUSTIC FIELD BASED ON WAVE SUPERPOSITION APPROACH
Institute of Scientific and Technical Information of China (English)
LI Weibing; CHEN Jian; YU Fei; CHEN Xinzhao
2006-01-01
In the semi-free acoustic field, the actual acoustic pressure at any point is composed of two parts: The direct acoustic pressure and the reflected acoustic pressure. The general acoustic holographic theories and algorithms request that there is only the direct acoustic pressure contained in the pressure at any point on the hologram surface, consequently, they cannot be used to reconstruct acoustic source and predict acoustic field directly. To take the reflected pressure into consideration, near-field acoustic holography for semi-free acoustic field based on wave superposition approach is proposed to realize the holographic reconstruction and prediction of the semi-free acoustic field, and the wave superposition approach is adopted as a holographic transform algorithm. The proposed theory and algorithm are realized and verified with a numerical example,and the drawbacks of the general theories and algorithms in the holographic reconstruction and prediction of the semi-free acoustic field are also demonstrated by this numerical example.
Hydromagnetic Waves in a Compressed Dipole Field via Field-Aligned Klein-Gordon Equations
Zheng, Jinlei; McKenzie, J F; Webb, G M
2014-01-01
Hydromagnetic waves, especially those of frequencies in the range of a few milli-Hz to a few Hz observed in the Earth's magnetosphere, are categorized as Ultra Low Frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach in examining the toroidal standing Aflv\\'{e}n waves in a background magnetic field by recasting the wave equation into a Klein-Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigen-frequency is greater than a cut-off frequency and an evanescent type otherwise. We apply the approach to a compressed dipole magnetic field model of the inner magnetosphere, and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidal mode standing Alfv\\'{e}n waves...
Interaction of aerosol particles with a standing wave optical field
Curry, John J.
2016-09-01
Trajectories of spherical dielectric particles carried across an optical standing wave by a flowing medium are investigated. Trajectories are determined by a three-dimensional Monte Carlo calculation that includes drag forces, Brownian motion, and optical gradient forces. We analyze the case of polystyrene particles with radii of order 100 nm carried across a Gaussian-mode standing wave by slowly flowing air. Particles are injected into the flowing air from a small source area such as the end of a capillary tube. Different sizes are dispersed continuously in space on the opposite side of the standing wave, demonstrating a practical way to sort particles. Certain discrete values of particle size show no interaction with the optical field, independent of intensity. These particles can be sorted with exceptionally high resolution. For example, particles with radii of 275 nm can be sorted with 1 nm resolution. This sorting scheme has the advantages of accommodating a high throughput, producing a continuous stream of continuously dispersed particles, and exhibiting excellent size resolution. The Monte Carlo results are in agreement with those obtained by a much simpler, and faster, fluid calculation based on effective velocities and effective diffusion coefficients, both obtained by averaging trajectories over multiple fringes of the optical field.
Fast wave power flow along SOL field lines in NSTX
Perkins, R. J.; Bell, R. E.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; Leblanc, B. P.; Kramer, G. J.; Phillips, C. K.; Roquemore, L.; Taylor, G.; Wilson, J. R.; Ahn, J.-W.; Gray, T. K.; Green, D. L.; McLean, A.; Maingi, R.; Ryan, P. M.; Jaeger, E. F.; Sabbagh, S.
2012-10-01
On NSTX, a major loss of high-harmonic fast wave (HHFW) power can occur along open field lines passing in front of the antenna over the width of the scrape-off layer (SOL). Up to 60% of the RF power can be lost and at least partially deposited in bright spirals on the divertor floor and ceiling [1,2]. The flow of HHFW power from the antenna region to the divertor is mostly aligned along the SOL magnetic field [3], which explains the pattern of heat deposition as measured with infrared (IR) cameras. By tracing field lines from the divertor back to the midplane, the IR data can be used to estimate the profile of HHFW power coupled to SOL field lines. We hypothesize that surface waves are being excited in the SOL, and these results should benchmark advanced simulations of the RF power deposition in the SOL (e.g., [4]). Minimizing this loss is critical optimal high-power long-pulse ICRF heating on ITER while guarding against excessive divertor erosion.[4pt] [1] J.C. Hosea et al., AIP Conf Proceedings 1187 (2009) 105. [0pt] [2] G. Taylor et al., Phys. Plasmas 17 (2010) 056114. [0pt] [3] R.J. Perkins et al., to appear in Phys. Rev. Lett. [0pt] [4] D.L. Green et al., Phys. Rev. Lett. 107 (2011) 145001.
Wave field synthesis of a sound field described by spherical harmonics expansion coefficients.
Ahrens, Jens; Spors, Sascha
2012-03-01
Near-field compensated higher order Ambisonics (NFC-HOA) and wave field synthesis (WFS) constitute the two best-known analytic sound field synthesis methods. While WFS is typically used for the synthesis of virtual sound scenes, NFC-HOA is typically employed in order to synthesize sound fields that have been captured with appropriate microphone arrays. Such recorded sound fields are essentially represented by the coefficients of the underlying surface spherical harmonics expansion. A sound field described by such coefficients cannot be straightforwardly synthesized in WFS. This is a consequence of the fact that, unlike in NFC-HOA, it is critical in WFS to carefully select those loudspeakers that contribute to the synthesis of a given sound source in a sound field under consideration. In order to enable such a secondary source selection, it is proposed to employ the well-known concept of decomposing the sound field under consideration into a continuum of plane waves, for which the secondary source selection is straightforward. The plane wave representation is projected onto the horizontal plane and a closed form expression of the secondary source driving signals for horizontal WFS systems of arbitrary convex shape is derived.
Yoo, J.; Shin, S.; Jun, K.; Shim, J.
2011-12-01
Surf-zone wave dynamics are one of important driving forces in coastal morphology by inducing beach erosions and sediment transports in inter-tidal shallow water areas, due to active wave breaking, energetic turbulence and violent near-bed velocities. Morphological beach changes are also considerably associated with other surf-zone hydro-dynamics such as nearshore wave transformation, water levels, wave run-up, set-up and coastal currents. In earlier studies, the COBRAS model (a RANS model, developed by Lin and Liu of Cornell University) has been used to investigate such beach processes with reasonable success, mostly, in wave dominant micro-tidal environments. The model solves the RANS equations using VOF method and k-epsilon closure scheme. Recently, intensive field experiments were carried out at a macro-tide environment (i.e. the Mallipo sand beach located in the west coast of Korea, having a large inter-tidal range of 7 m to investigate the complicated surf zone hydro-dynamics under interactions of coastal waves, strong tidal currents, and nearshore bathymetries. The field observation data are used to evaluate the capability of the RANS model to predict the cross-shore variations of free surface, wave set-up, wave run-up, and velocities on the Mallipo Beach. Since the dataset of water surface elevations includes both waves and tides, the COBRAS model was tried to simulate waves accompanied with tidal currents. The measured water surface elevation data were divided into wave and tidal components, in order to be used as inputs of the model. Comparisons of the measurements and the predictions show (1) performance of the model for the wave transformation, wave set-up, and wave run-up on the macro-tidal beach, (2) predictive capability for the turbulence closure scheme in the surf and swash zones, and (3) overall skills to predict under-tows and tidal currents. Acknowledgement This work was supported by the KORDI (Grant PE98572, PE98573 and PM56300). This work was
Mean field theory of charge-density wave state in magnetic field
Grigoriev, Pavel; Lyubshin, Dmitrij
2005-03-01
We develop a mean field theory of charge-density wave (CDW) state in magnetic field and study properties of this state below the transition temperature. We show that the CDW state with shifted wave vector in high magnetic field (CDWx phase) has a double harmonic modulation on the most part of the phase diagram. At perfect nesting the single harmonic CDW state with shifted wave vector exists only in a very narrow region near the triple point. We show that the transition from CDW0 to CDWx state below the critical temperature is accompanied by a jump of the CDW order parameter and of the CDW wave vector rather than by their continuous increase. This implies a first order transition between these CDW states and explains a strong hysteresis accompanying this transition. The similarities between CDW in high magnetic field and nonuniform LOFF superconducting phase are pointed out. Our investigation provides a theoretical description for recent experiments on organic metal α-(BEDT-TTF)2KHg(SCN)4 and other compounds. In particular, we explain the higher value of the kink transition field and provide the calculation of the phase diagram in the case of perfect nesting.
Yang, Si-Tong; Wei, Jiu-Chuan; Cheng, Jiu-Long; Shi, Long-Qing; Wen, Zhi-Jie
2016-12-01
Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling twodimensional wave fields and therefore cannot accurately simulate three-dimensional (3-D) full-wave fields or seismic records in a full-space observation system. In this study, we use the first-order velocity-stress staggered-grid finite difference algorithm to simulate 3-D full-wave fields with P-wave sources in front of coal mine roadways. We determine the three components of velocity V x, V y, and V z for the same node in 3-D staggered-grid finite difference models by calculating the average value of V y, and V z of the nodes around the same node. We ascertain the wave patterns and their propagation characteristics in both symmetrical and asymmetric coal mine roadway models. Our simulation results indicate that the Rayleigh channel wave is stronger than the Love channel wave in front of the roadway face. The reflected Rayleigh waves from the roadway face are concentrated in the coal seam, release less energy to the roof and floor, and propagate for a longer distance. There are surface waves and refraction head waves around the roadway. In the seismic records, the Rayleigh wave energy is stronger than that of the Love channel wave along coal walls of the roadway, and the interference of the head waves and surface waves with the Rayleigh channel wave is weaker than with the Love channel wave. It is thus difficult to identify the Love channel wave in the seismic records. Increasing the depth of the receivers in the coal walls can effectively weaken the interference of surface waves with the Rayleigh channel wave, but cannot weaken the interference of surface waves with the Love channel wave. Our research results also suggest that the Love channel wave, which is often used to detect geological structures in coal mine stopes, is not suitable for detecting geological structures in front of coal mine roadways
A statistical model of the wave field in a bounded domain
Hellsten, T.
2017-02-01
Numerical simulations of plasma heating with radiofrequency waves often require repetitive calculations of wave fields as the plasma evolves. To enable effective simulations, bench marked formulas of the power deposition have been developed. Here, a statistical model applicable to waves with short wavelengths is presented, which gives the expected amplitude of the wave field as a superposition of four wave fields with weight coefficients depending on the single pass damping, as. The weight coefficient for the wave field coherent with that calculated in the absence of reflection agrees with the coefficient for strong single pass damping of an earlier developed heuristic model, for which the weight coefficients were obtained empirically using a full wave code to calculate the wave field and power deposition. Antennas launching electromagnetic waves into bounded domains are often designed to produce localised wave fields and power depositions in the limit of strong single pass damping. The reflection of the waves changes the coupling that partly destroys the localisation of the wave field, which explains the apparent paradox arising from the earlier developed heuristic formula that only a fraction as2(2-as) and not as of the power is absorbed with a profile corresponding to the power deposition for the first pass of the rays. A method to account for the change in the coupling spectrum caused by reflection for modelling the wave field with ray tracing in bounded media is proposed, which should be applicable to wave propagation in non-uniform media in more general geometries.
Light fields in complex media: Mesoscopic scattering meets wave control
Rotter, Stefan; Gigan, Sylvain
2017-01-01
The newly emerging field of wave front shaping in complex media has recently seen enormous progress. The driving force behind these advances has been the experimental accessibility of the information stored in the scattering matrix of a disordered medium, which can nowadays routinely be exploited to focus light as well as to image or to transmit information even across highly turbid scattering samples. An overview of these new techniques, their experimental implementations, and the underlying theoretical concepts following from mesoscopic scattering theory is provided. In particular, the intimate connections between quantum transport phenomena and the scattering of light fields in disordered media, which can both be described by the same theoretical concepts, are highlighted. Particular emphasis is put on how these topics relate to application-oriented research fields such as optical imaging, sensing, and communication.
Mean-field studies of time reversal breaking states in super-heavy nuclei with the Gogny force
Energy Technology Data Exchange (ETDEWEB)
Robledo, L. M., E-mail: luis.robledo@uam.es [Departamento Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain)
2015-10-15
Recent progress on the description of time reversal breaking (odd mass and multi-quasiparticle excitation) states in super-heavy nuclei within a mean field framework and using several flavors of the Gogny interaction is reported. The study includes ground and excited states in selected odd mass isotopes of nobelium and mendelevium as well as high K isomeric states in {sup 254}No. These are two and four-quasiparticle excitations that are treated in the same self-consistent HFB plus blocking framework as the odd mass states.
Ayala, Alejandro; Gutierrez, Enif; Raya, Alfredo; Sanchez, Angel
2010-01-01
We study chiral symmetry breaking for relativistic fermions, described by a parity violating Lagrangian in 2+1-dimensions, in the presence of a heat bath and a uniform external magnetic field. Working within their four-component formalism allows for the inclusion of both parity-even and -odd mass terms. Therefore, we can define two types of fermion anti-fermion condensates. For a given value of the magnetic field, there exist two different critical temperatures which would render one of these condensates identically zero, while the other would survive. Our analysis is completely general: it requires no particular simplifying hierarchy among the energy scales involved, namely, bare masses, field strength and temperature. However, we do reproduce some earlier results, obtained or anticipated in literature, corresponding to special kinematical regimes for the parity conserving case. Relating the chiral condensate to the one-loop effective Lagrangian, we also obtain the magnetization and the pair production rate ...
Institute of Scientific and Technical Information of China (English)
CHEN Wan-Chun; CHEN Xiao-Long
2007-01-01
@@ We investigate the influence of dc electric field on chiral symmetry breaking during the growing process of NaClO3 crystal. Nucleation and growth of NaClO3 are completed from an aqueous solution by a fast cooling temperature technology. A pair of polarization microscopes are used to identify a distribution of chiral crystals. Experimental results indicate that the dc electric field has an effect on distribution of chirality, but the direction of the dc electric field is not sensitive to the chiral autocatalysis and selectivity, i.e. the nature convection driving by the gravity does not play an important role on a thin layer of NaClO3 solution. The experimental phenomena may be elucidated by the ECSN mechanism.
Coaxial waveguide for travelling wave MRI at ultrahigh fields.
Andreychenko, Anna; Kroeze, Hugo; Klomp, Dennis W J; Lagendijk, Jan J W; Luijten, Peter R; van den Berg, Cornelis A T
2013-09-01
At high magnetic fields the performance of a volume-type body coil inside a human sized MR-scanner is influenced by the waveguide action of the scanner's bore. This can result in undesirable strong radio frequency fields B1+) outside the coil's target volume. A radio frequency (RF) transmit system, exploiting this waveguide action of the bore, is proposed in this work. A coaxial waveguide section is introduced between the antenna and the imaging region. It is shown that the coaxial waveguide has several advantages over the initially proposed travelling wave setup based on the cylindrical waveguide. First, a novel radio frequency matching principle (based on the transmission line impedance matching) is feasible with the coaxial waveguide achieving better radio frequency transmission characteristics, such as homogeneity and power efficiency of B1+ field. In case of body torso imaging, the coaxial waveguide prevents unwanted specific absorptive rate (SAR) deposition outside the target region and thus, effectively decreases local peak SAR values by factor of 5. A 3-fold B1+ gain in the prostate can be achieved with the coaxial waveguide in comparison with the initially proposed travelling wave setup.
From supersonic shear wave imaging to full-field optical coherence shear wave elastography
Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A.
2013-12-01
Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.
Near Field Imaging at Microwave and Millemeter Wave Frequencies
Energy Technology Data Exchange (ETDEWEB)
Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.
2007-06-03
Near field imaging at microwave and millimeter wave frequencies is useful for a wide variety of applications including concealed weapon detection, through-wall and inner-wall imaging, ground penetrating radar imaging, radar cross section analysis, and non-destructive evaluation of materials. A variety of novel imaging techniques have been developed for many of these applications at the Pacific Northwest National Laboratory (PNNL) . These techniques make use of wideband holographic wavefront reconstruction methods, and have been developed to optimize the image quality and resolution. This paper will summarize several of these techniques and show imaging results for several interesting application areas.
Proposal for generating Fock states in traveling wave fields
Energy Technology Data Exchange (ETDEWEB)
Benmoussa, Adil [Department of Physics and Astronomy, Lehman College, The City University of New York, Bronx, NY 10468-1589 (United States)]. E-mail: adil.benmoussa@lehman.cuny.edu; Gerry, Christopher C. [Department of Physics and Astronomy, Lehman College, The City University of New York, Bronx, NY 10468-1589 (United States)
2007-05-28
We describe a proposal for the generation of a single-mode photonic number state, |N>, in a traveling wave optical field. The state is obtained by state reduction from an input coherent state using Kerr media. Our method is based on a previous scheme used for hole burning in the Fock space by minimizing the Mandel Q parameter. The same method was used by Maia et al., but ours is different, it requires only one single photon injected in the entire setup and one photon detection at the end.
Energy Technology Data Exchange (ETDEWEB)
Chanson, H. [Queensland Univ., Dept. of Civil Engineering (Australia)
2006-07-01
Dam break waves have been responsible for numerous losses and tragedies. The present work is focused on simple solutions of the dam break wave problem using the Saint-Venant equations. Theoretical solutions are developed for instantaneous dam break of semi-infinite reservoir in initially-dry channels. Both laminar and turbulent flow conditions are considered. Solutions for horizontal inverts are compared successfully with previous experimental results, and they are then extended to sloping channels. The results yield a series of simple analytical solutions that are well-suited for educational purposes as well as for emergency services. (author)
Velocity flow field and water level measurements in shoaling and breaking water waves
CSIR Research Space (South Africa)
Mukaro, R
2010-01-01
Full Text Available and creates micro-environments for the small creatures that form the basis for life in the oceans. For the above Seventh South African Conference on Computational and Applied Mechanics SACAM10 Pretoria, 10?13 January 2010 ? SACAM 2 reasons...
Simulations of nonlinear continuous wave pressure fields in FOCUS
Zhao, Xiaofeng; Hamilton, Mark F.; McGough, Robert J.
2017-03-01
The Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation is a parabolic approximation to the Westervelt equation that models the effects of diffraction, attenuation, and nonlinearity. Although the KZK equation is only valid in the far field of the paraxial region for mildly focused or unfocused transducers, the KZK equation is widely applied in medical ultrasound simulations. For a continuous wave input, the KZK equation is effectively modeled by the Bergen Code [J. Berntsen, Numerical Calculations of Finite Amplitude Sound Beams, in M. F. Hamilton and D. T. Blackstock, editors, Frontiers of Nonlinear Acoustics: Proceedings of 12th ISNA, Elsevier, 1990], which is a finite difference model that utilizes operator splitting. Similar C++ routines have been developed for FOCUS, the `Fast Object-Oriented C++ Ultrasound Simulator' (http://www.egr.msu.edu/˜fultras-web) to calculate nonlinear pressure fields generated by axisymmetric flat circular and spherically focused ultrasound transducers. This new routine complements an existing FOCUS program that models nonlinear ultrasound propagation with the angular spectrum approach [P. T. Christopher and K. J. Parker, J. Acoust. Soc. Am. 90, 488-499 (1991)]. Results obtained from these two nonlinear ultrasound simulation approaches are evaluated and compared for continuous wave linear simulations. The simulation results match closely in the farfield of the paraxial region, but the results differ in the nearfield. The nonlinear pressure field generated by a spherically focused transducer with a peak surface pressure of 0.2MPa radiating in a lossy medium with β = 3.5 is simulated, and the computation times are also evaluated. The nonlinear simulation results demonstrate acceptable agreement in the focal zone. These two related nonlinear simulation approaches are now included with FOCUS to enable convenient simulations of nonlinear pressure fields on desktop and laptop computers.
Progress of the studies on ocean internal wave breaking%海洋内波破碎问题的研究
Institute of Scientific and Technical Information of China (English)
梁建军; 杜涛
2012-01-01
从理论、观测、数值实验和实验室实验四个方面对国内外近20年来关于海洋内波破碎问题的研究成果进行了分析总结.数值实验和实验室实验表明:中高频内波破碎时,初始的不稳定是二维的,当最终有横向对流卷团形成时,能量开始大量耗散,这时不稳定发展成为三维的；从初始的二维不稳定到对流卷团的产生这一过程,到底是一个剪切不稳定过程,还是一个对流不稳定过程,或者是对流不稳定和剪切不稳定共同存在的一个过程,取决于海水的层化、地形、背景剪切流和内波的自身性质.现场曾观测到内孤立波破碎时存在的剪切不稳定过程,数值研究模拟出了内孤立波破碎时存在的对流不稳定过程.现有的海洋内波破碎判据主要是关于中高频海洋内波的.理论分析侧重于确定线性或弱非线性内波的破碎机制和破碎条件.%The development of internal waves breaking in recently twenty years is reviewed from theories, observation results, numerical experiments and laboratory experiments aspects. Numerical and laboratory experiments indicate that initial instability leading to internal wave breaking is almost two dimensional. When the cross section convective rolls are formed, the energy begins to dissipate massively and ultimately three-dimensional-instability is dominated. During the process of the initial instability to the formation of the convective rolls, the intermediate process may be a shear instability, a convective instability or a combination of both, which depends on the stratification, background shear flows, topography features and characterics of internal wave. It' s validated by in situ data that the internal solitary wave breaking was caused by shear instability. The numerical simulation also illustrates the importance of convective instability. Existing internal wave breaking criterion mostly involves internal solitary waves. Theoretical analyses
On the gravitational fields created by the electromagnetic waves
Loinger, A.; Marsico, T.
2011-01-01
We show that the Maxwell equations describing an electromagnetic wave are a mathematical consequence of the Einstein equations for the same wave. This fact is significant for the problem of the Einsteinian metrics corresponding to the electromagnetic waves.
Wind fields of storms from surface isobars for wave hindcasting
Digital Repository Service at National Institute of Oceanography (India)
Varkey, M.J.; Vaithiyanathan, R.; Santanam, K.
Marine operations of various types are critically linked to mean and extreme wave statistics. In the Indian seas extreme wave conditions are caused by cyclones and steady strong monsoon winds. Wave data from cyclone areas are not directly available...
Adaptive wave field synthesis for active sound field reproduction: experimental results.
Gauthier, Philippe-Aubert; Berry, Alain
2008-04-01
Sound field reproduction has applications in music reproduction, spatial audio, sound environment reproduction, and experimental acoustics. Sound field reproduction can be used to artificially reproduce the spatial character of natural hearing. The objective is then to reproduce a sound field in a real reproduction environment. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. The room response thus reduces the quality of the physical sound field reproduction by WFS. In recent research papers, adaptive wave field synthesis (AWFS) was defined as a potential solution to compensate for these quality reductions from which WFS objective performance suffers. In this paper, AWFS is experimentally investigated as an active sound field reproduction system with a limited number of reproduction error sensors to compensate for the response of the listening environment. Two digital signal processing algorithms for AWFS are used for comparison purposes, one of which is based on independent radiation mode control. AWFS performed propagating sound field reproduction better than WFS in three tested reproduction spaces (hemianechoic chamber, standard laboratory space, and reverberation chamber).
A wave field synthesis approach to reproduction of spatially correlated sound fields.
Berry, Alain; Dia, Rokhiya; Robin, Olivier
2012-02-01
This article discusses an open-loop wave field synthesis (WFS) approach for the reproduction of spatially correlated sound fields. The main application concerns laboratory reproduction of turbulent boundary layer wall pressure on aircraft fuselages and measurement of their sound transmission loss. The problem configuration involves reconstruction of random sound pressure distributions on a planar reproduction surface using a planar array of reproduction monopoles parallel to the reproduction plane. In this paper, the WFS formulation is extended to sound fields with imposed time and spatial correlation properties (or equivalently imposed cross-spectral density in the frequency and wave number domains). Numerical examples are presented for the reproduction of a propagating plane wave, diffuse acoustic field and wall pressure in subsonic or supersonic turbulent boundary layers. The reproduction accuracy is examined in terms of the size of the source plane and reproduction plane, their separation, and the number of reproduction sources required per acoustic wavelength. While the reproduction approach cannot reconstruct sub-wavelength correlation scales of subsonic turbulent boundary layers, it effectively reconstructs correlation scales larger than the acoustic wavelength, making it appropriate for diffuse acoustic field and supersonic turbulent layers.
Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A
2016-01-01
Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.
Nearshore bars and the break-point hypothesis
Sallenger, A.H.; Howd, P.A.
1989-01-01
The set of hypotheses calling for bar formation at the break point was tested with field data. During two different experiments, waves were measured across the surf zone coincident with the development of a nearshore bar. We use a criterion, based on the wave height to depth ratio, to determine the offshore limit of the inner surf zone. During the first experiment, the bar became better developed and migrated offshore while remaining well within the inner surf zone. During the second experiment, the surf zone was narrower and we cannot rule out the possibility of break point processes contributing to bar development. We conclude that bars are not necessarily coupled with the break point and can become better developed and migrate offshore while being in the inner surf zone landward from initial wave breaking in the outer surf zone. ?? 1989.
Measurement of Wave Electric Fields in Plasmas by Electro-Optic Probe
Nishiura, M; Mushiake, T; Kawazura, Y; Osawa, R; Fujinami, K; Yano, Y; Saitoh, H; Yamasaki, M; Kashyap, A; Takahashi, N; Nakatsuka, M; Fukuyama, A
2016-01-01
Electric field measurement in plasmas permits quantitative comparison between the experiment and the simulation in this study. An electro-optic (EO) sensor based on Pockels effect is demonstrated to measure wave electric fields in the laboratory magnetosphere of the RT-1 device with high frequency heating sources. This system gives the merits that electric field measurements can detect electrostatic waves separated clearly from wave magnetic fields, and that the sensor head is separated electrically from strong stray fields in circumference. The electromagnetic waves are excited at the double loop antenna for ion heating in electron cyclotron heated plasmas. In the air, the measured wave electric fields are in good absolute agreement with those predicted by the TASK/WF2 code. In inhomogeneous plasmas, the wave electric fields in the peripheral region are enhanced compared with the simulated electric fields. The potential oscillation of the antenna is one of the possible reason to explain the experimental resu...
Zhang, Xiao-Tian; Shindou, Ryuichi
2017-05-01
Three-dimensional (3D) metals/semimetals under magnetic field have an instability toward a density wave (DW) ordering which breaks a translational symmetry along the field direction. Effective boson models for the DW phases take forms of X Y models with/without Potts terms. Longitudinal conductivity along the field direction is calculated in the DW phases with inclusion of effects of low-energy charge fluctuation (phason) and disorder. A single-particle imaginary-time Green function is identified with a partition function of 3D X Y models in the presence of pairs of magnetic monopoles. In terms of the celebrated electromagnetic duality, electronic spectral function is calculated near the DW phase transition. The calculated result shows that the single-particle spectral function acquires an additional low-energy feature due to the strong phason fluctuation. Relevance to an in-plane conductance due to surface chiral Fermi arc states is also discussed.
Gravitational Waves in Bouncing Cosmologies from Gauge Field Production
Ben-Dayan, Ido
2016-01-01
We calculate the gravitational waves (GW) spectrum produced in various Early Universe scenarios from gauge field sources, thus generalizing earlier inflationary calculations to bouncing cosmologies. We consider generic couplings between the gauge fields and the scalar field dominating the energy density of the Universe. We analyze the requirements needed to avoid a backreaction that will spoil the background evolution. When the scalar is coupled only to $F \\tilde F$ term, the sourced GW spectrum is exponentially enhanced and parametrically the square of the vacuum fluctuations spectrum, ${\\cal P}^s_T\\sim ({\\cal P}^v_T)^2$, giving an even bluer spectrum than the standard vacuum one. When the scalar field is also coupled to $F^2$ term, the amplitude is still exponentially enhanced, but the spectrum can be arbitrarily close to scale invariant (still slightly blue), $n_T\\gtrsim 0$, that is distinguishable form the slightly red inflationary one. Hence, we have a proof of concept of observable GW on CMB scales in a...
Gravitational waves in bouncing cosmologies from gauge field production
Ben-Dayan, Ido
2016-09-01
We calculate the gravitational waves (GW) spectrum produced in various Early Universe scenarios from gauge field sources, thus generalizing earlier inflationary calculations to bouncing cosmologies. We consider generic couplings between the gauge fields and the scalar field dominating the energy density of the Universe. We analyze the requirements needed to avoid a backreaction that will spoil the background evolution. When the scalar is coupled only to Ftilde F term, the sourced GW spectrum is exponentially enhanced and parametrically the square of the vacuum fluctuations spectrum, Script PsT ~ (Script PvT)2, giving an even bluer spectrum than the standard vacuum one. When the scalar field is also coupled to F2 term, the amplitude is still exponentially enhanced, but the spectrum can be arbitrarily close to scale invariant (still slightly blue), nT gtrsim 0, that is distinguishable form the slightly red inflationary one. Hence, we have a proof of concept of observable GW on CMB scales in a bouncing cosmology.
Electromagnetic waves destabilized by runaway electrons in near-critical electric fields
Kómár, A; Fülöp, T
2013-01-01
Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.
Parameterization of the Near-Field Internal Wave Field Generated by a Submarine
Rottman, James W; Dommermuth, Douglas; Broutman, Dave
2014-01-01
We attempt to gain some insight into the modeling of the generation of internal waves produced by submarines traveling in the littoral regions of the ocean with the use of high fidelity numerical simulations. These numerical simulations are shown to be capable of simulating high Reynolds number flow around bodies, including the effects of stable stratification. In addition, we use the results of these detailed numerical studies to test and revise the source distribution parameterizations of the near-field waves that have been used in analytical studies based on linear theory. Such parameterizations have been shown to be useful in initializing ray-tracing schemes that can be used for computing wave propagation through realistic oceans with variable background properties. For simplicity, we focus on the idealized case of a spherical body traveling horizontally at constant speed through a uniformly stratified fluid.
Energy Technology Data Exchange (ETDEWEB)
Roberts, Jesse D.; Chang, Grace; Magalen, Jason; Jones, Craig
2014-09-01
A modified version of an indust ry standard wave modeling tool was evaluated, optimized, and utilized to investigate model sensitivity to input parameters a nd wave energy converter ( WEC ) array deployment scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that wave direction and WEC device type we r e most sensitive to the variation in the model parameters examined in this study . Generally, the changes in wave height we re the primary alteration caused by the presence of a WEC array. Specifically, W EC device type and subsequently their size directly re sult ed in wave height variations; however, it is important to utilize ongoing laboratory studies and future field tests to determine the most appropriate power matrix values for a particular WEC device and configuration in order to improve modeling results .
Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5
Ronning, F.; Helm, T.; Shirer, K. R.; Bachmann, M. D.; Balicas, L.; Chan, M. K.; Ramshaw, B. J.; McDonald, R. D.; Balakirev, F. F.; Jaime, M.; Bauer, E. D.; Moll, P. J. W.
2017-08-01
Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at Hc ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.
Spontaneous symmetry breaking of binary fields in a nonlinear double-well structure
Acus, Arturas; Shnir, Yakov
2012-01-01
We introduce a one-dimensional two-component system with the self-focusing cubic nonlinearity concentrated at a symmetric set of two spots. Effects of the spontaneous symmetry breaking (SSB) of localized modes were previously studied in the single-component version of this system. In this work, we study the evolution (in the configuration space of the system) and SSB scenarios for two-component modes of three generic types, as concerns the spatial symmetry of each component: symmetric-symmetric (Sm-Sm), antisymmetric-antisymmetric (AS-AS), and symmetric-antisymmetric (S-AS) ones. In the limit case of the nonlinear potential represented by two $% \\delta $-functions, solutions are obtained in a semi-analytical form. They feature novel properties, in comparison with the previously studied single-component model. In particular, the SSB of antisymmetric modes is possible solely in the two-component system, and, obviously, S-AS states exist only in the two-component system too. In the general case of the symmetric ...
The Wave Field around DEXA Devices and Implications for Coastal Protection
DEFF Research Database (Denmark)
Zanuttigh, Barbara; Angelelli, Elisa; Castagnetti, Mirko
2011-01-01
The purpose of this paper is to examine the hydrodynamics around floating wave energy converters (f-WECs). In particular, the paper considers the case of the f-WEC of the Wave Activated Body type, named DEXA. Based on 3D wave experiments in the Laboratory of the Aalborg University (DK), the modif......The purpose of this paper is to examine the hydrodynamics around floating wave energy converters (f-WECs). In particular, the paper considers the case of the f-WEC of the Wave Activated Body type, named DEXA. Based on 3D wave experiments in the Laboratory of the Aalborg University (DK......), the modified wave field around a wave energy farm (composed by three 1:60 scale models) and around a single device (1:30 scale model) is investigated. Specific results include wave reflection, wave transmission and wave disturbance around the device. The results are examined considering scale effects...
Closed-Field Coronal Heating Driven by Wave Turbulence
Downs, Cooper; Mikić, Zoran; Linker, Jon A; Velli, Marco
2016-01-01
To simulate the energy balance of coronal plasmas on macroscopic scales, we often require the specification of the coronal heating mechanism in some functional form. To go beyond empirical formulations and to build a more physically motivated heating function, we investigate the wave-turbulence-driven (WTD) phenomenology for the heating of closed coronal loops. Our implementation is designed to capture the large-scale propagation, reflection, and dissipation of wave turbulence along a loop. The parameter space of this model is explored by solving the coupled WTD and hydrodynamic evolution in 1D for an idealized loop. The relevance to a range of solar conditions is also established by computing solutions for over one hundred loops extracted from a realistic 3D coronal field. Due to the implicit dependence of the WTD heating model on loop geometry and plasma properties along the loop and at the footpoints, we find that this model can significantly reduce the number of free parameters when compared to traditiona...
Numerical Simulation of Wave Field near Submerged Bars by PLIC-VOF Model
Institute of Scientific and Technical Information of China (English)
LIU Cheng; LIU Xiao-qing; JIANG Chang-bo
2005-01-01
Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over submerged bars, using PLIC-VOF (Piecewise Linear Interface Construction) to trace the free surface of wave and finite difference method to solve vertical 2D Navier-Stokes (N-S) equations. A comparison of the numerical results for two kinds of submerged bars with the experimental ones shows that the PLIC-VOF model used in this study is effective and can compute the wave field precisely.
Acoustic and Cavitation Fields of Shock Wave Therapy Devices
Chitnis, Parag V.; Cleveland, Robin O.
2006-05-01
Extracorporeal shock wave therapy (ESWT) is considered a viable treatment modality for orthopedic ailments. Despite increasing clinical use, the mechanisms by which ESWT devices generate a therapeutic effect are not yet understood. The mechanistic differences in various devices and their efficacies might be dependent on their acoustic and cavitation outputs. We report acoustic and cavitation measurements of a number of different shock wave therapy devices. Two devices were electrohydraulic: one had a large reflector (HMT Ossatron) and the other was a hand-held source (HMT Evotron); the other device was a pneumatically driven device (EMS Swiss DolorClast Vet). Acoustic measurements were made using a fiber-optic probe hydrophone and a PVDF hydrophone. A dual passive cavitation detection system was used to monitor cavitation activity. Qualitative differences between these devices were also highlighted using a high-speed camera. We found that the Ossatron generated focused shock waves with a peak positive pressure around 40 MPa. The Evotron produced peak positive pressure around 20 MPa, however, its acoustic output appeared to be independent of the power setting of the device. The peak positive pressure from the DolorClast was about 5 MPa without a clear shock front. The DolorClast did not generate a focused acoustic field. Shadowgraph images show that the wave propagating from the DolorClast is planar and not focused in the vicinity of the hand-piece. All three devices produced measurable cavitation with a characteristic time (cavitation inception to bubble collapse) that varied between 95 and 209 μs for the Ossatron, between 59 and 283 μs for the Evotron, and between 195 and 431 μs for the DolorClast. The high-speed camera images show that the cavitation activity for the DolorClast is primarily restricted to the contact surface of the hand-piece. These data indicate that the devices studied here vary in acoustic and cavitation output, which may imply that the
Energy Technology Data Exchange (ETDEWEB)
Szirmai, G.; Szirmai, E. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Research Institute for Solid State Physics and Optics, P.O. Box 49, H-1525 Budapest (Hungary); Zamora, A. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Lewenstein, M. [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, Lluis Companys 23, E-08010 Barcelona (Spain)
2011-07-15
We propose an experimentally feasible setup with ultracold alkaline-earth-metal atoms to simulate the dynamics of U(1) lattice gauge theories in 2 + 1 dimensions with a Chern-Simons term. To this end we consider the ground-state properties of spin-5/2 alkaline-earth-metal fermions in a honeycomb lattice. We use the Gutzwiller projected variational approach in the strongly repulsive regime in the case of filling 1/6. The ground state of the system is a chiral spin-liquid state with 2{pi}/3 flux per plaquette, which violates time-reversal invariance. We demonstrate that due to the breaking of time-reversal symmetry the system exhibits quantum Hall effect and chiral edge states. We relate the experimentally accessible spin fluctuations to the emerging gauge-field dynamics. We discuss also properties of the lowest energy competing orders.
Linking Dynamical Gluon Mass to Chiral Symmetry Breaking via a QCD Low Energy Effective Field Theory
Oliveira, O; Frederico, T
2011-01-01
A low energy effective field theory model for QCD with a scalar color octet field is discussed. The model relates the gluon mass, the constituent quark masses and the quark condensate. The gluon mass comes about $\\sqrt{N_c}\\, \\Lambda_{QCD}$ with the quark condensate being proportional to the gluon mass squared. The model suggests that the restoration of chiral symmetry and the deconfinement transition occur at the same temperature and that, near the transition, the critical exponent for the condensate is twice the gluon mass one. The model also favors the decoupling like solution for the gluon propagator.
DEFF Research Database (Denmark)
Burcharth, Hans F.; Liu, Zhou
1999-01-01
The effect of wave short-crestedness on the horizontal wave force on a caisson is twofold. The one is the force reduction due to the reduction of point pressure on the caisson, named point-pressure reduction. The other is the force reduction due to the fact that the peak pressures do not occur si...
Wave trains induced by circularly polarized electric fields in cardiac tissues.
Feng, Xia; Gao, Xiang; Tang, Juan-Mei; Pan, Jun-Ting; Zhang, Hong
2015-08-25
Clinically, cardiac fibrillation caused by spiral and turbulent waves can be terminated by globally resetting electric activity in cardiac tissues with a single high-voltage electric shock, but it is usually associated with severe side effects. Presently, a promising alternative uses wave emission from heterogeneities induced by a sequence of low-voltage uniform electric field pulses. Nevertheless, this method can only emit waves locally near obstacles in turbulent waves and thereby requires multiple obstacles to globally synchronize myocardium and thus to terminate fibrillation. Here we propose a new approach using wave emission from heterogeneities induced by a low-voltage circularly polarized electric field (i.e., a rotating uniform electric field). We find that, this approach can generate circular wave trains near obstacles and they propagate outwardly. We study the characteristics of such circular wave trains and further find that, the higher-frequency circular wave trains can effectively suppress spiral turbulence.
TMS pulses on the frontal eye fields break coupling between visuospatial attention and eye movements
Neggers, S.F.W.; Huijbers, W.; Vrijlandt, C.M.; Vlaskamp, B.N.S.; Schutter, D.J.L.G.; Kenemans, J.L.
2007-01-01
While preparing a saccadic eye movement, visual processing of the saccade goal is prioritized. Here, we provide evidence that the frontal eye fields (FEFs) are responsible for this coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging ( fMRI)-guid
Adaptive wave field synthesis for broadband active sound field reproduction: signal processing.
Gauthier, Philippe-Aubert; Berry, Alain
2008-04-01
Sound field reproduction is a physical approach to the reproduction of the natural spatial character of hearing. It is also useful in experimental acoustics and psychoacoustics. Wave field synthesis (WFS) is a known open-loop technology which assumes that the reproduction environment is anechoic. A real reflective reproduction space thus reduces the objective accuracy of WFS. Recently, adaptive wave field synthesis (AWFS) was defined as a combination of WFS and active compensation. AWFS is based on the minimization of reproduction errors and on the penalization of departure from the WFS solution. This paper focuses on signal processing for AWFS. A classical adaptive algorithm is modified for AWFS: filtered-reference least-mean-square. This modified algorithm and the classical equivalent leaky algorithm have similar convergence properties except that the WFS solution influences the adaptation rule of the modified algorithm. The paper also introduces signal processing for independent radiation mode control of AWFS on the basis of plant decoupling. Simulation results for AWFS are introduced for free-field and reflective spaces. The two algorithms effectively reproduce the sound field and compensate for the reproduction errors at the error sensors. The independent radiation mode control allows a more flexible tuning of the algorithm.
Analysis of Magnetic Fields in Inertial Alfven Wave Collisions
Drake, Dereth J; Shanken, Brian C; Howes, Gregory G; Skiff, Frederick; Kletzing, Craig A; Carter, Troy A; Dorfman, Seth
2014-01-01
Turbulence in astrophysical and space plasmas is dominated by the nonlinear interaction of counterpropagating Alfven waves. Most Alfven wave turbulence theories have been based on ideal plasma models, such as incompressible MHD, for Alfven waves at large scales. However, in the inertial Alfven wave regime (vA > vthe), relevant to magnetospheric plasmas, how the turbulent nonlinear interactions are modified by the dispersive nature of the waves remains to be explored. Here we present the first laboratory evidence of the nonlinear interaction in the inertial regime. A comparison is made with the theory for MHD Alfven waves.
Directory of Open Access Journals (Sweden)
C. H. Schmidt
2009-05-01
Full Text Available The radiation of large antennas and those operating at low frequencies can be determined efficiently by near-field measurement techniques and a subsequent near-field far-field transformation. Various approaches and algorithms have been researched but for electrically large antennas and irregular measurement contours advanced algorithms with low computation complexity are required. In this paper an algorithm employing plane waves as equivalent sources and utilising efficient diagonal translation operators is presented. The efficiency is further enhanced using simple far-field translations in combination with the expensive near-field translations. In this way a low complexity near-field transformation is achieved, which works for arbitrary sample point distributions and incorporates a full probe correction without increasing the complexity.
Rectified Circulation of the Arabian Sea and its Seasonal Internal Wave Field
2015-09-30
residual circulation and internal wave field of the Arabian Sea as well as its connectivity with adjacent basins. OBJECTIVES (1) To characterize and...dissipation, and mixing in the Arabian Sea and investigate the relationship between seasonal changes in the internal wave field and variability in the...the internal wave field. These are important drivers of stratification and sea surface temperature (SST) changes across the Arabian Sea . Hence, our
Sharp-front wave of strong magnetic field diffusion in solid metal
Xiao, Bo; Gu, Zhuo-wei; Kan, Ming-xian; Wang, Gang-hua; Zhao, Jian-heng
2016-08-01
When a strong magnetic field diffuses into a solid metal, if the metal's resistance possesses an abrupt rise at some critical temperature and the magnetic field strength is above some critical value, the magnetic field will diffuse into the metal in the form of a sharp-front wave. Formulas for the critical conditions under which a sharp-front magnetic diffusion wave emerges and a formula for the wave-front velocity are derived in this work.
Experimental Investigation of Wave Heights in A Directional Wave Field Through Image Sequences
Institute of Scientific and Technical Information of China (English)
Chung-Ren CHOU; Teng-Wei LIN; Ruey-Syan SHIH; John Z. YIM
2005-01-01
Measurements of wave heights with image sequences from a Charged Coupled Device(CCD) camera were made. Sinusoidal, as well as unidirectional and directional, waves were used for the experiments. A transfer function was obtained by calibration of the magnitudes of the gray values of the images against the results of wave gauge measurements for directional waves. With this transfer function, wave heights for regular waves were deduced. It is shown that the average relative errors are smaller than 16% for both unidirectional and directional waves.
Kasaba, Y.; Bougeret, J.-L.; Blomberg, L. G.; Kojima, H.; Yagitani, S.; Moncuquet, M.; Trotignon, J.-G.; Chanteur, G.; Kumamoto, A.; Kasahara, Y.; Lichtenberger, J.; Omura, Y.; Ishisaka, K.; Matsumoto, H.
2010-01-01
The BepiColombo Mercury Magnetospheric Orbiter (MMO) spacecraft includes the plasma and radio wave observation system called Plasma Wave Investigation (PWI). Since the receivers for electric field, plasma waves, and radio waves are not installed in any of the preceding spacecraft to Mercury, the PWI will provide the first opportunity for conducting in-situ and remote-sensing observations of electric fields, plasma waves, and radio waves in the Hermean magnetosphere and exosphere. These observations are valuable in studying structure, dynamics, and energy exchange processes in the unique magnetosphere of Mercury. They are characterized by the key words of the non-MHD environment and the peculiar interaction between the relatively large planet without ionosphere and the solar wind with high dynamic pressure. The PWI consists of three sets of receivers (EWO, SORBET, and AM 2P), connected to two sets of electric field sensors (MEFISTO and WPT) and two kinds of magnetic field sensors (LF-SC and DB-SC). The PWI will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.3 Hz to 640 kHz for the magnetic field. From 2008, we will start the development of the engineering model, which is conceptually consistent with the flight model design. The present paper discusses the significance and objectives of plasma/radio wave observations in the Hermean magnetosphere, and describes the PWI sensors, receivers and their performance as well as the onboard data processing.
Energy Technology Data Exchange (ETDEWEB)
Roberts, Jesse D.; Grace Chang; Jason Magalen; Craig Jones
2014-08-01
A n indust ry standard wave modeling tool was utilized to investigate model sensitivity to input parameters and wave energy converter ( WEC ) array deploym ent scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that b oth wave height and near - bottom orbital velocity we re subject to the largest pote ntial variations, each decreas ed in sensitivity as transmission coefficient increase d , as number and spacing of WEC devices decrease d , and as the deployment location move d offshore. Wave direction wa s affected consistently for all parameters and wave perio d was not affected (or negligibly affected) by varying model parameters or WEC configuration .
The influence of an electromagnetic field on the wave-current interaction
Rousseaux, Germain
2010-01-01
We study the propagation of surface waves on a current in the presence of an electromagnetic field. A horizontal (vertical) field strengthens (weakens) the counter-current which blocks the waves. We compute the phase space diagrams (blocking velocities versus period of the waves) with and without surface tension. Three new dimensionless numbers are introduced to compare the relative strengths of gravity, surface tension and field effects. This work shows the importance of an electromagnetic field in order to design wave-breakers or in microfluidics applications.
A wave guide model of lightning currents and their electromagnetic field
Volland, H.
1980-01-01
Lightning channels are considered as resonant wave guides in which only standing resonant wave modes can be excited. Two types of discharging currents develop. Type 1 is an aperiodic wave; type 2 is a damped oscillation. The electromagnetic radiation field of both types of currents is calculated and compared with the observation.
Experimental Study on the Effects of A Breakwater on Wave Field Characteristics
Institute of Scientific and Technical Information of China (English)
尹彰; 周宗仁; 黄伟柏
2000-01-01
Studies on the possible effects of a detached breakwater on the characteristics of the wave field are carried out experimentally. A serpentine wave generator is used to generate both uni- and multi-directional waves. Characteristics of the wave fields analyzed here include the wave field directionality, and the probability distributions of surface elevations and of the wave heights. Owing to the presence of the breakwater, waves outside the harbour are found to be reflected with, however, concentrated energy within the harbour entrance. In general wave heights can be approximated with a Rayleigh distribution, with occasional deviations from the theory. This occurs more frequently for waves with higher peak frequency values than for those with lower values both for uni- and multi-directional waves. Surface elevations can be approximated with the Gaussian model although the Edgeworth′s form of the type A Gram-Charlier series expansions would yield better fits. Wave directionality is found to have no discernible effects on the statistical characteristics of the wave field.
Vacuum Radiation and Symmetry Breaking in Conformally Invariant Quantum Field Theory
Aldaya, V; Cerveró, J M
1999-01-01
The underlying reasons for the difficulty of unitarily implementing the whole conformal group $SO(4,2)$ in a massless Quantum Field Theory (QFT) are investigated in this paper. Firstly, we demonstrate that the singular action of the subgroup of special conformal transformations (SCT), on the standard Minkowski space $M$, cannot be primarily associated with the vacuum radiation problems, the reason being more profound and related to the dynamical breakdown of part of the conformal symmetry (the SCT subgroup, to be more precise) when representations of null mass are selected inside the representations of the whole conformal group. Then we show how the vacuum of the massless QFT radiates under the action of SCT (usually interpreted as transitions to a uniformly accelerated frame) and we calculate exactly the spectrum of the outgoing particles, which proves to be a generalization of the Planckian one, this recovered as a given limit.
Farhad Kiyaei, Forough; Dorranian, Davoud
2017-01-01
Effects of the obliqueness and the strength of external magnetic field on the ion acoustic (IA) cnoidal wave in a nonextensive plasma are investigated. The reductive perturbation method is employed to derive the corresponding KdV equation for the IA wave. Sagdeev potential is extracted, and the condition of generation of IA waves in the form of cnoidal waves or solitons is discussed in detail. In this work, the domain of allowable values of nonextensivity parameter q for generation of the IA cnoidal wave in the plasma medium is considered. The results show that only the compressive IA wave may generate and propagate in the plasma medium. Increasing the strength of external magnetic field will increase the frequency of the wave and decrease its amplitude, while increasing the angle of propagation will decrease the frequency of the wave and increase its amplitude.
Refinement of a discontinuity-free edge-diffraction model describing focused wave fields.
Sedukhin, Andrey G
2010-03-01
Two equivalent forms of a refined discontinuity-free edge-diffraction model describing the structure of a stationary focused wave field are presented that are valid in the framework of the scalar Debye integral representation for a diffracted rotationally symmetric converging spherical wave of a limited yet not-too-low angular opening. The first form describes the field as the sum of a direct quasi-spherical wave and a plurality of edge quasi-conical waves of different orders, the optimum discontinuity-free angular spectrum functions of all the waves being dependent on the polar angle only. According to the second form, the focused field is fully characterized by only three components--the same quasi-spherical wave and two edge quasi-conical waves of the zero and first order, of which the optimum discontinuity-free angular spectrum functions are dependent on both the polar angle and the polar radius counted from the geometrical focus.
Effect of nonlinear wave-current interaction on flow fields and hydrodynamic forces
Institute of Scientific and Technical Information of China (English)
王涛; 李家春
1997-01-01
A fifth-order theory for solving the problem of interaction between Stokes waves and exponential profile currents is proposed. The calculated flow fields are compared with measurements. Then the errors caused by the linear superposition method and approximate theory are discussed. It is found that the total wave-current field consists of pure wave, pure current and interaction components. The shear current not only directly changes the flow field, but also indirectly does so by changing the wave parameters due to wave-current interaction. The present theory can predict the wave kinematics on shear currents satisfactorily. The linear superposition method may give rise to more than 40% loading error in extreme conditions. When the apparent wave period is used and the Wheeler stretching method is adopted to extrapolate the current, application of the approximate theory is the best.
Directory of Open Access Journals (Sweden)
Ion C. Baianu
2009-04-01
Full Text Available A novel algebraic topology approach to supersymmetry (SUSY and symmetry breaking in quantum field and quantum gravity theories is presented with a view to developing a wide range of physical applications. These include: controlled nuclear fusion and other nuclear reaction studies in quantum chromodynamics, nonlinear physics at high energy densities, dynamic Jahn-Teller effects, superfluidity, high temperature superconductors, multiple scattering by molecular systems, molecular or atomic paracrystal structures, nanomaterials, ferromagnetism in glassy materials, spin glasses, quantum phase transitions and supergravity. This approach requires a unified conceptual framework that utilizes extended symmetries and quantum groupoid, algebroid and functorial representations of non-Abelian higher dimensional structures pertinent to quantized spacetime topology and state space geometry of quantum operator algebras. Fourier transforms, generalized Fourier-Stieltjes transforms, and duality relations link, respectively, the quantum groups and quantum groupoids with their dual algebraic structures; quantum double constructions are also discussed in this context in relation to quasi-triangular, quasi-Hopf algebras, bialgebroids, Grassmann-Hopf algebras and higher dimensional algebra. On the one hand, this quantum algebraic approach is known to provide solutions to the quantum Yang-Baxter equation. On the other hand, our novel approach to extended quantum symmetries and their associated representations is shown to be relevant to locally covariant general relativity theories that are consistent with either nonlocal quantum field theories or local bosonic (spin models with the extended quantum symmetry of entangled, 'string-net condensed' (ground states.
A UV Ultra-luminous Lyman Break Galaxy at Z=2.78 in NDWFS Bootes Field
Bian, Fuyan; Jiang, Linhua; Dey, Arjun; Green, Richard F; Maiolino, Roberto; Walter, Fabian; McGreer, Ian; Wang, Ran; Lin, Yen-Ting
2012-01-01
We present one of the most ultraviolet (UV) luminous Lyman Break Galaxies (LBGs) (J1432+3358) at z=2.78, discovered in the NOAO Deep Wide-Field Survey (NDWFS) Bootes field. The R-band magnitude of J1432+3358 is 22.29 AB, more than two magnitudes brighter than typical L* LBGs at this redshift. The deep z-band image reveals two components of J1432+3358 separated by 1.0" with flux ratio of 3:1. The high signal-to-noise ratio (S/N) rest-frame UV spectrum shows Lya emission line and interstellar medium absorption lines. The absence of NV and CIV emission lines, the non-detection in X-ray and radio wavelengths and mid-infrared (MIR) colors indicate no or weak active galactic nuclei (AGN) (<10%) in this galaxy. The galaxy shows broader line profile with the full width half maximum (FWHM) of about 1000 km/s and larger outflow velocity (~500 km/s) than those of typical z~3 LBGs. The physical properties are derived by fitting the spectral energy distribution (SED) with stellar synthesis models. The dust extinction, ...
Anisotropic effects of background fields on Born-Infeld electromagnetic waves
Aiello, Matias; Bengochea, Gabriel; Ferraro, Rafael
2006-01-01
We show exact solutions of Born-Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of Born-Infeld equations generates an interaction between background and wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction --a behavior resembling the one of a wave in an anisotropic medium--. This...
Imaging the Morrow A Sandstone Using Shear Wave VSP Data, Postle Field, Oklahoma
Directory of Open Access Journals (Sweden)
Naser Tamimi
2012-01-01
potential to enhance shear wave imaging of the thin heterogeneous Morrow A sandstone at Postle Field. The zero-offset VSP results confirm the advantages of shear wave over compressional wave in imaging the Morrow A sandstone. Also, the final shear wave VSP image shows that, applying the proposed processing flow, we are able to image the Morrow A sandstone where the thickness is as thin as 8.5 m.
Santos Júnior, S. I.; Cardoso, J. G.
2016-10-01
The world formulation of the full theory of classical Proca fields in generally relativistic spacetimes is reviewed. Subsequently, the entire set of field equations is transcribed in a straightforward way into the framework of one of the Infeld-van der Waerden formalisms. Some well-known calculational techniques are then utilized for deriving the wave equations that control the propagation of the fields allowed for. It appears that no interaction couplings between such fields and electromagnetic curvatures are ultimately carried by the wave equations at issue. What results is, in effect, that the only interactions which occur in the theoretical context under consideration involve strictly Proca fields and wave functions for gravitons.
Contributions of Higgs bosons in anomalous momentum of electron in plane-wave field
Klimenko, E Y
2002-01-01
The Higgs bosons contribution to the anomalous magnetic momentum of the electron, moving in the field representing the superposition of the constant crossed field and plane electromagnetic wave of the elliptical polarization are considered in this work
Field structure of collapsing wave packets in 3D strong Langmuir turbulence
Newman, D. L.; Robinson, P. A.; Goldman, M. V.
1989-01-01
A simple model is constructed for the electric fields in the collapsing wave packets found in 3D simulations of driven and damped isotropic strong Langmuir turbulence. This model, based on a spherical-harmonic decomposition of the electrostatic potential, accounts for the distribution of wave-packet shapes observed in the simulations, particularly the predominance of oblate wave packets. In contrast with predictions for undamped and undriven subsonic collapse of scalar fields, oblate vector-field wave packets do not flatten during collapse but, instead, remain approximately self-similar and rigid.
Body-wave retrieval and imaging from ambient seismic fields with very dense arrays
Nakata, N.; Boué, P.; Beroza, G. C.
2015-12-01
Correlation-based analyses of ambient seismic wavefields is a powerful tool for retrieving subsurface information such as stiffness, anisotropy, and heterogeneity at a variety of scales. These analyses can be considered to be data-driven wavefield modeling. Studies of ambient-field tomography have been mostly focused on the surface waves, especially fundamental-mode Rayleigh waves. Although the surface-wave tomography is useful to model 3D velocities, the spatial resolution is limited due to the extended depth sensitivity of the surface wave measurements. Moreover, to represent elastic media, we need at least two stiffness parameters (e.g., shear and bulk moduli). We develop a technique to retrieve P diving waves from the ambient field observed by the dense geophone network (~2500 receivers with 100-m spacing) at Long Beach, California. With two-step filtering, we improve the signal-to-noise ratio of body waves to extract P wave observations that we use for tomography to estimate 3D P-wave velocity structure. The small scale-length heterogeneity of the velocity model follows a power law with ellipsoidal anisotropy. We also discuss possibilities to retrieve reflected waves from the ambient field and show other applications of the body-wave extraction at different locations and scales. Note that reflected waves penetrate deeper than diving waves and have the potential to provide much higher spatial resolution.
Near-field millimeter-wave imaging for weapon detection
Energy Technology Data Exchange (ETDEWEB)
Sheen, D.M.; McMakin, D.L.; Collins, H.D.; Hall, T.E.
1992-11-01
Various millimeter-wave imaging systems capable of imaging through clothing for the detection of contraband metal, plastic, or ceramic weapons, have been developed at PNL. Two dimensional scanned holographic systems, developed at 35, 90, and 350 GHz, are used to obtain high resolution images of metal and plastic targets concealed by clothing. Coherent single-frequency amplitude and phase data, which is gathered over a two-dimensional scanned aperture, is reconstructed to the target plane using a holographic wavefront reconstruction technique. Practical weapon detection systems require high-speed scanning. To achieve this goal, a 35 GHz linear sequentially switched array has been built and integrated into a high speed linear scanner. This system poses special challenges on calibration / signal processing of the holographic system. Further, significant improvements in speed are required to achieve real time operation. Toward this goal, a wideband scanned system which allows for a two-dimensional image formation from a one-dimensional scanned (or array) system has been developed . Signal / image processing techniques developed and implemented for this technique are a variation on conventional synthetic aperture radar (SAR) techniques which eliminate far-field and narrow bandwidth requirements. Performance of this technique is demonstrated with imaging results obtained from a K[sub a]-band system.
Near-field millimeter-wave imaging for weapon detection
Energy Technology Data Exchange (ETDEWEB)
Sheen, D.M.; McMakin, D.L.; Collins, H.D.; Hall, T.E.
1992-11-01
Various millimeter-wave imaging systems capable of imaging through clothing for the detection of contraband metal, plastic, or ceramic weapons, have been developed at PNL. Two dimensional scanned holographic systems, developed at 35, 90, and 350 GHz, are used to obtain high resolution images of metal and plastic targets concealed by clothing. Coherent single-frequency amplitude and phase data, which is gathered over a two-dimensional scanned aperture, is reconstructed to the target plane using a holographic wavefront reconstruction technique. Practical weapon detection systems require high-speed scanning. To achieve this goal, a 35 GHz linear sequentially switched array has been built and integrated into a high speed linear scanner. This system poses special challenges on calibration / signal processing of the holographic system. Further, significant improvements in speed are required to achieve real time operation. Toward this goal, a wideband scanned system which allows for a two-dimensional image formation from a one-dimensional scanned (or array) system has been developed . Signal / image processing techniques developed and implemented for this technique are a variation on conventional synthetic aperture radar (SAR) techniques which eliminate far-field and narrow bandwidth requirements. Performance of this technique is demonstrated with imaging results obtained from a K{sub a}-band system.
Multidimensional Wave Field Signal Theory: Transfer Function Relationships
Directory of Open Access Journals (Sweden)
Natalie Baddour
2012-01-01
Full Text Available The transmission of information by propagating or diffusive waves is common to many fields of engineering and physics. Such physical phenomena are governed by a Helmholtz (real wavenumber or pseudo-Helmholtz (complex wavenumber equation. Since these equations are linear, it would be useful to be able to use tools from signal theory in solving related problems. The aim of this paper is to derive multidimensional input/output transfer function relationships in the spatial domain for these equations in order to permit such a signal theoretic approach to problem solving. This paper presents such transfer function relationships for the spatial (not Fourier domain within appropriate coordinate systems. It is shown that the relationships assume particularly simple and computationally useful forms once the appropriate curvilinear version of a multidimensional spatial Fourier transform is used. These results are shown for both real and complex wavenumbers. Fourier inversion of these formulas would have applications for tomographic problems in various modalities. In the case of real wavenumbers, these inversion formulas are presented in closed form, whereby an input can be calculated from a given or measured wavefield.
Generalized plane gravitational waves of non-symmetric unified field theories in plane symmetry
Directory of Open Access Journals (Sweden)
Sanjiv R. Bhoyar
2012-12-01
Full Text Available In this paper we investigated the plane wave solutions of both the weak and strong non-symmetric unified field equations of Einstein and Bonner in a generalized plane symmetric space-time in the sense of Taub [Ann. Math. 53, 472 (1951] for plane gravitational waves. We show that the plane wave solutions of Einstein and Bonner field equations exist in plane symmetry.
Setälä, Tero
2003-01-01
In this thesis, partial polarization and spatial correlation properties of electromagnetic optical fields are investigated. The emphasis is on near fields which exist only within the distance of the light wavelength from the emitting or scattering object. In the near-field region, the contribution of the evanescent (non-radiating) waves is overwhelming compared to the propagating waves that can be observed far from the source. Certain fundamental issues related to the optical near-fields ...
Massless and Massive Gauge-Invariant Fields in the Theory of Relativistic Wave Equations
Pletyukhov, V A
2010-01-01
In this work consideration is given to massless and massive gauge-invariant spin 0 and spin 1 fields (particles) within the scope of a theory of the generalized relativistic wave equations with an extended set of the Lorentz group representations. The results obtained may be useful as regards the application of a relativistic wave-equation theory in modern field models.
Ji, Yongxin; He, Qina; Sun, Yulong; Tong, Jian; Cao, Yi
2016-01-01
The aim of this study was to examine whether radiofrequency field (RF) preexposure induced adaptive responses (AR) in mouse bone-marrow stromal cells (BMSC) and the mechanisms underlying the observed findings. Cells were preexposed to 900-MHz radiofrequency fields (RF) at 120 μW/cm(2) power intensity for 4 h/d for 5 d. Some cells were subjected to 1.5 Gy γ-radiation (GR) 4 h following the last RF exposure. The intensity of strand breaks in the DNA was assessed immediately at 4 h. Subsequently, some BMSC were examined at 30, 60, 90, or 120 min utilizing the alkaline comet assay and γ-H2AX foci technique. Data showed no significant differences in number and intensity of strand breaks in DNA between RF-exposed and control cells. A significant increase in number and intensity of DNA strand breaks was noted in cells exposed to GR exposure alone. RF followed by GR exposure significantly decreased number of strand breaks and resulted in faster kinetics of repair of DNA strand breaks compared to GR alone. Thus, data suggest that RF preexposure protected cells from damage induced by GR. Evidence indicates that in RF-mediated AR more rapid repair kinetics occurs under conditions of GR-induced damage, which may be attributed to diminished DNA strand breakage.
Generating a hexagonal lattice wave-field with a gradient basis structure
Kumar, Manish
2016-01-01
We present a new, single step approach for generating a hexagonal lattice wave-field with a gradient local basis structure. We incorporate this by coherently superposing two (or more) hexagonal lattice wave-fields which differ in their basis structures. The basis of the resultant lattice wave-field is highly dependent on the relative strengths of constituent wave-fields and a desired spatial modulation of basis structure is thus obtained by controlling the spatial modulation of relative strengths of constituent wave-fields. The experimental realization of gradient lattice is achieved by using a phase only spatial light modulator (SLM) in an optical 4f Fourier filter setup where the SLM is displayed with numerically calculated gradient phase mask. The presented method is wavelength independent and is completely scalable making it very promising for micro-fabrication of corresponding structures.
Deformations of charge-density wave crystals under electric field
Energy Technology Data Exchange (ETDEWEB)
Pokrovskii, V.Ya. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation)], E-mail: pok@cplire.ru; Zybtsev, S.G.; Loginov, V.B. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation); Timofeev, V.N. [Baikov Institute of Metallurgy of RAS, Leninsky prosp. 49, 119991 Moscow (Russian Federation); Kolesov, D.V.; Yaminsky, I.V. [Advanced Technologies Center, Department of Physics, Moscow State University, Leninskie Gori, 119991 Moscow (Russian Federation); Gorlova, I.G. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation)
2009-03-01
We report the effects of electric field induced deformations of quasi one-dimensional conductors with charge-density wave (CDW). The most pronounced sort of deformation is torsional strain (TS). The TS is found to comprise two contributions. The features of the 1st-the larger one-are threshold hysteretic dependence on electric field and high relaxation time {tau}: For o-TaS{sub 3}{tau}{approx}10{sup -2} s at T=80 K and falls as exp(900 K/T) with increasing T. The 2nd contribution is linear in electric field and does not drop with frequency increase. The amplitude of this contribution falls abruptly with T approaching the Peierls transition temperature T{sub P} from below. Similar features of TS are demonstrated for other CDW compounds: (TaSe{sub 4}){sub 2}I, K{sub 0.3}MoO{sub 3} and NbS{sub 3} type II, for which T{sub P}{approx}360 K. We attribute the 1st and the 2nd contributions to large (hysteretic) and small (near-equilibrium) CDW deformations, respectively, likely-shear at the surface. The TS is observed also above T{sub P}: For TaS{sub 3} and (TaSe{sub 4}){sub 2}I typical torsional amplitude is 10{sup -1} deg./V in the resonance regimes, corresponding to the piezomodulus {approx}10{sup -9} m/V. A separate study of TS was performed at room temperature with AFM technique. Apart from this ('intrinsic') effect, we observe electrostatic contribution to the TS. In contrast to the intrinsic response, the electrostatic one is proportional to the potential either over the sample, or over an additional electrode ('gate') placed nearby, but not to the difference of potentials between the sample ends. It is typically 2 orders of magnitude less. The intrinsic TS reveals a new electromechanical effect at room temperature, presumably associated with the excitations of the pinned mode of the CDW fluctuations. Its observation opens prospects for application of quasi one-dimensional conductors as micro- and nano-actuators. Basing on the electrostatic
About wave field modeling in hierarchic medium with fractal inclusions
Hachay, Olga; Khachay, Andrey
2014-05-01
The processes of oil gaseous deposits outworking are linked with moving of polyphase multicomponent media, which are characterized by no equilibrium and nonlinear rheological features. The real behavior of layered systems is defined as complicated rheology moving liquids and structural morphology of porous media. It is eargently needed to account those factors for substantial description of the filtration processes. Additionally we must account also the synergetic effects. That allows suggesting new methods of control and managing of complicated natural systems, which can research these effects. Thus our research is directed to the layered system, from which we have to outwork oil and which is a complicated hierarchic dynamical system with fractal inclusions. In that paper we suggest the algorithm of modeling of 2-d seismic field distribution in the heterogeneous medium with hierarchic inclusions. Also we can compare the integral 2-D for seismic field in a frame of local hierarchic heterogeneity with a porous inclusion and pure elastic inclusion for the case when the parameter Lame is equal to zero for the inclusions and the layered structure. For that case we can regard the problem for the latitude and longitudinal waves independently. Here we shall analyze the first case. The received results can be used for choosing criterions of joined seismic methods for high complicated media research.If the boundaries of the inclusion of the k rank are fractals, the surface and contour integrals in the integral equations must be changed to repeated fractional integrals of Riman-Liuvill type .Using the developed earlier 3-d method of induction electromagnetic frequency geometric monitoring we showed the opportunity of defining of physical and structural features of hierarchic oil layer structure and estimating of water saturating by crack inclusions. For visualization we had elaborated some algorithms and programs for constructing cross sections for two hierarchic structural
vanWaarde, MAWH; vanAssen, AJ; Konings, AWT; Kampinga, HH
1996-01-01
Purpose: To examine the technical feasibility of pulsed field gel electrophoresis (PFGE) as a predictive assay for the radioresponsiveness of tumors. Induction and repair of DNA double strand breaks (DSBs) in a freshly prepared cell suspension from a RIF-1 tumor (irradiated ex vivo) was compared
Influence of electromagnetism field on the flame transmission and shock wave in gas explosion
Energy Technology Data Exchange (ETDEWEB)
Li Jing [Anhui University of Technology, Maanshan (China). College of Metallurgy and Resources
2008-01-15
The influence of electromagnetic field on flame transmission and explosion wave overpressure in gas explosions was investigated. The research results show that the velocity of flame propagation and the explosion wave overpressure in an electromagnetic field is much higher than that in plain tube, and the stronger the electromagnetic field, the greater the influence. Based on experimental results, the influence of electromagnetic field on gas explosion propagation was analyzed and a reasonable explanation was put forward. The influence of electromagnetic field is not equal to the sum of the electric field and the magnetic field. 7 refs., 4 figs., 2 tabs.
Wave attenuation in mangroves; a quantitative approach to field observations
Horstman, Erik; Dohmen-Janssen, Catarine M.; Narra, P.M.F.; van den Berg, N.J.F.; Siemerink, M.; Hulscher, Suzanne J.M.H.
2014-01-01
Coastal mangroves, dwelling at the interface between land and sea, provide an important contribution to reducing risk from coastal hazards by attenuating incident waves and by trapping and stabilizing sediments. This paper focusses on relations between vegetation densities, wave attenuation rates,
Field Evaluation of Ocean Wave Measurement With GPS Buoys
2010-09-01
surface waves. In the experiment, conducted off the coast of California near Bodega Bay, clusters off Datawell and prototype GPS buoys were...receivers to measure ocean surface waves. In the experiment, conducted off the coast of California near Bodega Bay, clusters off Datawell and...the coast near Bodega Bay, CA. .............................................................................................17 Figure 4. R/P FLIP
Wave attenuation in mangroves; a quantitative approach to field observations
Horstman, E.M.; Dohmen-Janssen, C.M.; Narra, P.M.F.; Berg, van den N.J.F.; Siemerink, M.; Hulscher, S.J.M.H.
2014-01-01
Coastal mangroves, dwelling at the interface between land and sea, provide an important contribution to reducing risk from coastal hazards by attenuating incident waves and by trapping and stabilizing sediments. This paper focusses on relations between vegetation densities, wave attenuation rates, s
Luminosity Functions of Lyman-Break Galaxies at z~4 and 5 in the Subaru Deep Field
Yoshida, M; Kashikawa, N; Ouchi, M; Okamura, S; Yoshida, Makiko; Shimasaku, Kazuhiro; Kashikawa, Nobunari; Ouchi, Masami; Okamura, Sadanori
2006-01-01
We investigate the luminosity functions of Lyman-break galaxies (LBG) at z~4 and 5 based on the optical imaging data obtained in the Subaru Deep Field Project. Three samples of LBGs in a contiguous 875 arcmin^2 area are constructed. One consists of 3,808 LBGs at z~4 down to i'=26.85 selected with the B-R vs R-i' diagram. The other two consist of 539 and 240 LBGs at z~5 down to z'=26.05 selected with two kinds of two-color diagrams: V-i' vs i'-z' and R-i' vs i'-z'. The adopted selection criteria are proved to be fairly reliable by spectroscopic observation. We derive the luminosity functions of the LBGs at rest-frame ultraviolet wavelengths down to M_{UV}=-19.2 at z~4 and M_{UV}=-20.3 at z~5. We find clear evolution of the luminosity function over the redshift range of 04.
Orbital quantization in the high-magnetic-field state of a charge-density-wave system
Andres, D.; Kartsovnik, M. V.; Grigoriev, P. D.; Biberacher, W.; Müller, H.
2003-11-01
A superposition of the Pauli and orbital couplings of a high magnetic field to charge carriers in a charge-density-wave (CDW) system is proposed to give rise to transitions between subphases with quantized values of the CDW wave vector. By contrast to the purely orbital field-induced density-wave effects which require a strongly imperfect nesting of the Fermi surface, the new transitions can occur even if the Fermi surface is well nested at zero field. We suggest that such transitions are observed in the organic metal α-(BEDT-TTF)2KHg(SCN)4 under a strongly tilted magnetic field.
Gisin, Boris V
2012-01-01
Dirac's equation in the field of a circularly polarized electromagnetic wave and constant magnetic field has exact localized non-stationary solutions. The solutions corresponds relativistic fermions only. Among them singular solutions with energy eigenvalues close to each other are found. The solutions are most practicable and can be separated by means of the phase matching between the momentum of the electromagnetic wave and spinor. Characteristic parameters of the singular states are defined.
CSIR Research Space (South Africa)
Smith, GG
2002-07-30
Full Text Available of instrumentation, ?ume geometry, water-levels, wave conditions tested, etc. reference is made to Sanchez-Arcilla et al. (1994). For the purpose of the present study, use was primarily made of instrumentation attached to a roving car- riage deployed at various... the carriage to measure beach pro?les (San- chez-Arcilla et al., 1994). The present study makes use of measurements taken during the second series of tests at LIP11D (Tests 2A and 2B). Test 2A was commenced with a Dean-type beach pro?le, with a dune included...
Study and verification on dispersion coefficient in wave field
Institute of Scientific and Technical Information of China (English)
SHEN LiangDuo; ZOU ZhiLi
2012-01-01
Transport and diffusion caused by coastal waves have different characteristics from those induced by flows.Through solving the vertical diffusion equation by an analytic method,this paper infers a theoretical formula of dispersion coefficient under the combined action of current and waves.It divides the general dispersion coefficient into six parts,including coefficients due to tidal current,Stokes drift,wave oscillation and interaction among them.It draws a conclusion that the contribution of dispersive effect induced by coastal waves is mainly produced by Stokes drift,while the contributions to time-averaged dispersion coefficient due to wave orbital motion and interaction between current and waves are very small.The results without tidal current are in agreement with the numerical and experimental results,which proves the correctness of the theoretical derivation.This paper introduces the variation characteristics of both the time-averaged and oscillating dispersion coefficients versus relative water depth,and demonstrates the physical implications of the oscillating mixing coefficient due to waves.We also apply the results to the costal vertical circulation and give its characteristics compared to Stokes drift.
Behavior of Torsional Alfven Waves and Field Line Resonance on Rotating Magnetars
Kojima, T O Y
2005-01-01
Torsional Alfven waves are likely excited with bursts in rotating magnetars. These waves are probably propagated through corotating atmospheres toward a vacuum exterior. We have studied the physical effects of the azimuthal wave number and the characteristic height of the plasma medium on wave transmission. In this work, explicit calculations were carried out based on the three-layered cylindrical model. We found that the coupling strength between the internal shear and the external Alfven modes is drastically enhanced, when resonance occurs in the corotating plasma cavity. The spatial structure of the electromagnetic fields in the resonance cavity is also investigated when Alfven waves exhibit resonance.
Compressive sensing of full wave field data for structural health monitoring applications
DEFF Research Database (Denmark)
di Ianni, Tommaso; De Marchi, Luca; Perelli, Alessandro
2015-01-01
Numerous nondestructive evaluations and structural health monitoring approaches based on guide waves rely on analysis of wave fields recorded through scanning laser Doppler vibrometers (SLDVs) or ultrasonic scanners. The informative content which can be extracted from these inspections is relevant...... performance is mostly influenced by the choice of a proper decomposition basis to exploit the sparsity of the acquired signal. Here, different bases have been tested to recover the guided waves wave field acquired on both an aluminum and a composite plate. Experimental results show that the proposed approach...
Magnetic field effects on nonlocal wave dispersion characteristics of size-dependent nanobeams
Ebrahimi, Farzad; Barati, Mohammad Reza
2017-01-01
In this paper, wave propagation analysis of functionally graded size-dependent nanobeams embedded in elastic foundation exposed to a longitudinal magnetic field is conducted based on nonlocal elasticity theory. Material properties of nanobeam change gradually according to the sigmoid function. Applying an analytical solution, the acoustical and optical dispersion relations are explored for various wave number, nonlocality parameter, material composition, elastic foundation constants and magnetic field intensity. It is found that frequency and phase velocity of waves propagating in S-FGM nanobeam are significantly affected by these parameters. Also the presence of cutoff and escape frequencies in wave propagation analysis of embedded S-FGM nanobeams is investigated.
Hybrid single-beam reconstruction technique for slow and fast varying wave fields.
Falaggis, Konstantinos; Kozacki, Tomasz; Kujawinska, Malgorzata
2015-06-01
An iterative single-beam wave field reconstruction technique that employs both non-paraxial, wave propagation based and paraxial deterministic phase retrieval techniques is presented. This approach overcomes two major obstacles that exist in the current state of the art techniques: iterative methods do not reconstruct slowly varying wave fields due to slow convergence and stagnation, and deterministic methods have paraxial limits, making the reconstructions of quickly varying object features impossible. In this work, a hybrid approach is reported that uses paraxial wave field corrections within iterative phase retrieval solvers. This technique is suitable for cases ranging from slow to fast varying wave fields, and unlike the currently available methods, can also reconstruct measurement objects with different regions of both slowly and quickly varying object features. It is further shown that this technique gives a higher accuracy than current single-beam phase retrieval techniques, and in comparison to the iterative methods, has a higher convergence speed.
Magnetic Spin Waves in CsNiF3 with an Applied Field
DEFF Research Database (Denmark)
Steiner, M.; Kjems, Jørgen
1977-01-01
The spin wave dispersion in the planar 1D ferromagnet CsNiF3 has been measured by inelastic neutron scattering in an external field. The spin wave linewidths are found to decrease with increasing field and become resolution-limited for H>10 kG at 4.2K. At high fields, H>10 kG, both energies...... and intensities are found to follow linear spin wave theory. The analysis resolves a discrepancy between the anisotropy constants, A, derived earlier from spin-wave and susceptibility measurements, respectively. It turns out that a quantum correction is necessary in order to get consistent parameters. Two...... parameters namely the nearest-neighbour exchange, J/k=11.5+or-0.05K and A/k=8.9+or-0.2K, are needed to fully describe the system. The temperature dependence of the spin waves in an external field was also studied....
The Fock-Kemmer approach to precursor shock waves in relativistic field theory
Abdullah, Rawand H
2016-01-01
We use distribution theory (generalized functions) to extend and justify the Fock-Kemmer approach to the propagation of precursor shock wave discontinuities in classical and quantum field theory. We apply lightcone causality arguments to propose that shock wave singularities in non-linear classical field theories and in Maxwell's equations for responsive media require a form of classical renormalization analogous to Wilson operator product expansions in quantum field theories.
Srivastava, A K; Ofman, Leon; Dwivedi, B N
2016-01-01
Using MHD seismology by observed kink waves, the magnetic field profile of a coronal streamer has been investigated. STEREO-B/EUVI temporal image data on 7 March 2012 shows an evolution of two consecutive EUV waves that interact with the footpoint of a coronal streamer evident in the co-spatial and co-temporal STEREO-B/COR-I observations. The evolution of EUV waves is clearly evident in STEREO-B/EUVI, and its energy exchange with coronal streamer generates kink oscillations. We estimate the phase velocities of the kink wave perturbations by tracking it at different heights of the coronal streamer. We also estimate the electron densities inside and outside the streamer using SSI of polarized brightness images in STEREO-B/COR-1 observations. Taking into account the MHD theory of kink waves in a cylindrical waveguide, their observed properties at various heights, and density contrast of the streamer, we estimate the radial profile of magnetic field within this magnetic structure. Both the kink waves diagnose the...
Li, Xiao; Roy, Bitan; Das Sarma, S.
2016-11-01
We theoretically address the effects of strong magnetic fields in three-dimensional Weyl semimetals (WSMs) built out of Weyl nodes with a monopole charge n . For n =1 , 2, and 3 we realize single, double, and triple WSM, respectively, and the monopole charge n determines the integer topological invariant of the WSM. Within the linearized continuum description, the quasiparticle spectrum is then composed of Landau levels (LLs), containing exactly n number of chiral zeroth Landau levels (ZLLs), irrespective of the orientation of the magnetic field. In the presence of strong backscattering, for example (due to quenched disorder associated with random impurities), these systems generically give rise to longitudinal magnetotransport. Restricting ourselves to the quantum limit (and assuming only the subspace of the ZLLs to be partially filled) and mainly accounting for Gaussian impurities, we show that the longitudinal magnetoconductivity (LMC) in all members of the Weyl family displays a positive linear-B scaling when the field is applied along the axis that separates the Weyl nodes. But, in double and triple WSM, LMC displays a smooth crossover to a nonlinear B dependence as the field is tilted away from such a high-symmetry direction. In addition, due to the enhanced density of states, the LL quantization can trigger instabilities toward the formation of translational symmetry-breaking density-wave orderings for sufficiently weak interaction (BCS instability), which gaps out the ZLLs. Concomitantly as the temperature (magnetic field) is gradually decreased (increased) the LMC becomes negative. Thus WSMs with arbitrary monopole charge (n ) can host an intriguing interplay of LL quantization, longitudinal magnetotransport (a possible manifestation of one-dimensional chiral or axial anomaly), and density-wave ordering, when placed in a strong magnetic field.
Mathematical Modeling of the Pressure Field Generated by Ocean Wave at the Bottom of the Ocean
Institute of Scientific and Technical Information of China (English)
龚沈光; 唐劲飞; 颜冰
2002-01-01
This paper develops a new method for calculating the pressure-tirme processof the pressure field generated by ocean wave at sea bottom based on the surface wavespectrum of the ocean wave. The basic assumptions of modeling are that the surfaceocean wave pressure equals to the atmospheric pressure and that the viscidity of seawater is neglected. The steps of modeling are described below. First the power spectraldensity of ocean wave is discretized and the amplitude spectra of harmonic ocean waveare obtained. Then the amplitude spectra of harmonic pressure are obtained accordingto the amplitude spectrum of surface wave and the depth of the sea. Finally, based onthe oceanographic theory of representing a fixed wave surface by summing up random-phase sinusoids, the pressure-time process of pressure field at sea bottom is obtained bysumming up the amplitude spectrum of pressure. The paper also develops a method ofdetermining the relationship between mean wave period and wave heights undershallow water condition, thus the pressure-time process of pressure field produced bynon-well-developed ocean wave can be directly calculated once the mean wave heightand period are known.
The generation of gravitational waves. 1. Weak-field sources: A plug-in-and-grind formalism
Thorne, K. S.; Kovacs, S. J.
1974-01-01
A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standard linearized theory. Whether or not gravity affects the motions, if the motions are slow and internal stresses are weak, then the new formalism reduces to the standard quadrupole-moment formalism. In the general case the new formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime, and then breaks the Green's-function integral into five easily understood pieces: direct radiation, produced directly by the motions of the sources; whump radiation, produced by the the gravitational stresses of the source; transition radiation, produced by a time-changing time delay (Shapiro effect) in the propagation of the nonradiative, 1/r field of the source; focussing radiation produced when one portion of the source focusses, in a time-dependent way, the nonradiative field of another portion of the source, and tail radiation, produced by backscatter of the nonradiative field in regions of focussing.
Institute of Scientific and Technical Information of China (English)
周良明; 郭佩芳; 王强; 杜伊
2004-01-01
Based on the maximum entropy principle, a probability density function (PDF) is derived for the distribution of wave heights in a random wave field, without any more hypothesis. The present PDF, being a non-Rayleigh form, involves two parameters: the average wave height H and the state parameter γ. The role of γ in the distribution of wave heights is examined. It is found that γ may be a certain measure of sea state. A least square method for determining γ from measured data is proposed. In virtue of the method, the values of γ are determined for three sea states from the data measured in the East China Sea. The present PDF is compared with the well known Rayleigh PDF of wave height and it is shown that it much better fits the data than the Rayleigh PDF. It is expected that the present PDF would fit some other wave variables, since its derivation is not restricted only to the wave height.
Bayindir, Cihan
2016-01-01
In this paper we propose an extended Kundu-Eckhaus equation (KEE) for modeling the dynamics of skewed rogue waves emerging in the vicinity of a wave blocking point due to opposing current. The equation we propose is a KEE with an additional potential term therefore the results presented in this paper can easily be generalized to study the quantum tunneling properties of the rogue waves and ultrashort (femtosecond) pulses of the KEE. In the frame of the extended KEE, we numerically show that the chaotic perturbations of the ocean current trigger the occurrence of the rogue waves on the ocean surface. We propose and implement a split-step scheme and show that the extended KEE that we propose is unstable against random chaotic perturbations in the current profile. These perturbations transform the monochromatic wave field into a chaotic sea state with many peaks. We numerically show that the shapes of rogue waves due to perturbations in the current profile closely follow the form of rational rogue wave solutions...
Plasma production by helicon waves with single mode number in low magnetic fields
Sato, G; Hatakeyama, R; Sato, Genta; Oohara, Wataru; Hatakeyama, Rikizo
2004-01-01
Radio-frequency discharges are performed in low magnetic fields (0-10 mT) using three types of helicon-wave exciting antennas with the azimuthal mode number of $|m|$ = 1. The most pronounced peak of plasma density is generated in the case of phased helical antenna at only a few mT, where the helicon wave with $|m| = 1$ is purely excited and propagates. An analysis based on the dispersion relation well explains the density-peak phenomenon in terms of the correspondence between the antenna one-wavelength and the helicon wavelength. The $m=+1$ helicon wave propagates even in high magnetic fields where the density peaks are not observed, but the $m=-1$ helicon wave disappers. It is expected theoretically that the $m=-1$ helicon wave shows cutoff behavior in a low density region, [M. Kramer, Phys. Plasmas 6, 1052 (1999)], and the cutoff of $m=-1$ helicon wave experimentally observed coincides with the calculated one.
Enhancement of wave and acceleration of electron in plasma in the external field
Institute of Scientific and Technical Information of China (English)
2008-01-01
This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma.in the presence of an external transverse field.Based on hydrodynamic equations,an equation formulizing the parametric instability was derived.Furthermore,the formula for ponderomotive force and the expression that describes the electron acceleration were obtained.The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave.In addition,it can be concluded that ponderomotive force,due to the coupling of the external field(pump)to the Langmuir wave(ion-acoustic wave),is the driving force to excite the parametric instability and comprises the high- and low-frequency components.
Dynamics of surfactants in the field of edge and internal waves in coastal areas
Averbukh, L.; Kurkina, O.; Kurkin, A.
2012-04-01
Edge waves are topographically trapped waves, which can be considered as an important factor impacting upon coastline and nearshore bottom relief, beaches and coastal constructions. Large amplitude nonlinear edge waves are possible due to the action of different mechanisms. Their dynamics can be described by nonlinear Shrodinger equation, and the signs of its coefficients correspond to modulation instability of wave packets. The mechanisms of possible anomalous edge wave appearance are dispersion enhancement and self-modulation; they can lead to forming of abnormal edge wave. In the present paper we consider processes of edge wave propagation and amplification along a cylindrical shelf taking into account horizontal alongshore flow and Earth rotation. Internal waves exist in stratified coastal areas, and for them extreme regimes are also well-known, including propagation of such energetic events as solitary waves and breathers. The existence of waves of both type lead to formation of wave-induced currents, which can be quite strong and can significantly affect the surrounding environment. In particular, these currents can influence upon pollutants, admixtures and films on the surface of the sea causing their redistribution according to zones of convergence and divergence of the velocity fields. These specific pictures on the surface can be used in the interpretation of remote sensing data and diagnostics and identification of underlying wave processes. In the present study we demonstrate dynamics of surfactants in the field of edge and internal waves in coastal areas. Numerical modeling is based on the balance equation of the surface concentration. Film dynamics was considered in the advection - diffusion - relaxation model. We show a number of unsteady effects in the edge and internal waves and their manifestation in the surfactants. For edge waves we considered the passage of linear traveling and standing waves, the wave amplitude changes due to slow longshore
Similon, Philippe L.; Sudan, R. N.
1989-01-01
The importance of field line geometry for shear Alfven wave dissipation in coronal arches is demonstrated. An eikonal formulation makes it possible to account for the complicated magnetic geometry typical in coronal loops. An interpretation of Alfven wave resonance is given in terms of gradient steepening, and dissipation efficiencies are studied for two configurations: the well-known slab model with a straight magnetic field, and a new model with stochastic field lines. It is shown that a large fraction of the Alfven wave energy flux can be effectively dissipated in the corona.
Ghobakhloo E.; Pourlak M.; Razmkhah A.
2015-01-01
The study of the effect of seismic wave scattering has attracted extensive attention in the past couple of decades especially in infrastructures like tunnels. A seismic wave, meeting the tunnel, can generate scattering which, in most cases, may incur damages in adjacent structures. In this study, using Finite Element Method (FEM), the effect of seismic wave scattering in far field has been investigated. The twin tunnels of Shiraz subway system are selected as the case study in this research a...
Gornyi, I. V.; Dmitriev, A. P.; Mirlin, A. D.; Protopopov, I. V.
2016-08-01
We have studied the motion of an electron in a membrane under the influence of flexural vibrations with a correlator that decreases upon an increase in the distance in accordance with the law r-2η. We have conducted a detailed consideration of the case with η < 1/2, in which the perturbation theory is inapplicable, even for an arbitrarily weak interaction. It is shown that, in this case, reciprocal quantum time 1/τ q is proportional to g 1/(1-η) T (2-η)/(2-2η), where g is the electron-phonon interaction constant and T is the temperature. The method developed here is applied for calculating the electron density of states in a magnetic field perpendicular to the membrane. In particular, it is shown that the Landau levels in the regime with ω c τ q » 1 have a Gaussian shape with a width that depends on the magnetic field as B η. In addition, we calculate the time τφ of dephasing of the electron wave function that emerges due to the interaction with flexural phonons for η < 1/2. It has been shown that, in several temperature intervals, quantity 1/τφ can be expressed by various power functions of the electron-phonon interaction constant, temperature, and electron energy.
Alpha Channeling with High-field Launch of Lower Hybrid Waves
Ochs, Ian E; Fisch, Nathaniel J
2015-01-01
Although lower hybrid waves are effective at driving currents in present-day tokamaks, they are expected to interact strongly with high-energy particles in extrapolating to reactors. In the presence of a radial alpha particle birth gradient, this interaction can take the form of wave amplification rather than damping. While it is known that this amplification more easily occurs when launching from the tokamak high-field side, the extent of this amplification has not been made quantitative. Here, by tracing rays launched from the high- field-side of a tokamak, the required radial gradients to achieve amplification are calculated for a temperature and density regime consistent with a hot-ion-mode fusion reactor. These simulations, while valid only in the linear regime of wave amplification, nonetheless illustrate the possibilities for wave amplification using high-field launch of the lower hybrid wave.
Frequency-domain electromagnetic sounding with combination wave in near-field zone
Institute of Scientific and Technical Information of China (English)
苏发; 何继善
1996-01-01
By analysing the propagation law of electromagnetic wave,the distribution pattern of the field and the theory of frequency electromagnetic sounding,the physical mechanisms that make the frequency electromagnetic sounding in near-field zone difficult are discussed.Based on the theory of near source field,a new method of dual-frequency electromagnetic sounding of combination wave in near-field zone is advanced.Meanwhile,the method of measurement of fields,the definition of apparent resistivity and the numerical algorithm are approached.
Vortex induced vibrations of pipe in high waves. Field measurements
Energy Technology Data Exchange (ETDEWEB)
Hansen Ottesen, N.-E.; Pedersen, B.
1999-07-01
Vortex induced vibrations have been measured full scale on an instrumented pipe placed vertically in the crest zone of high and steep waves. The Reynolds numbers were in the range 105 to 106. It was found that the vortex induced vibrations in the wave motion were generated within a reduced velocity range of 4 and 8. The vibrations grew intermittently with the passing waves. The vibrations took place in 2-3 modes simultaneously. One mode, however, dominated over the other. The growths of the VIV using a modal analysis were consistent with a basic correlation length of 3 diameters for a stationary pipe with a linear growth of the correlation length of 10 diameter for each 0.1 diameter amplitude. (au)
Wave-Sediment Interaction in Muddy Environments: Subbottom Field Experiment
2012-09-30
Berkeley, Doctoral thesis, 149p. Chou, H.-T., M.A. Foda , and J.R. Hunt (1993). Rheological response of cohesive sediments to oscillatory forcing”, In...dissipation by muddy seafloors, Geophys. Res. Lett. 35/7, L07611. Foda , A.M., J.R. Hunt, and H.-T. Chou (1993). A nonlinear model for the...fluidization of marine mud by waves, J. Geophys. Res. 98, 7039-7047. Foda M.A. and S.Y., Tzang (1994). Resonant fluidization of silty soil by water waves
Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows
Energy Technology Data Exchange (ETDEWEB)
Saleem, H. [Department of Space Science, Institute of Space Technology, 1-Islamabad Highway, Islamabad (Pakistan); Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); Ali, S. [Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); National Centre for Physics (NCP) at Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Haque, Q. [Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); National Centre for Physics (NCP) at Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)
2015-08-15
The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Korteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.
The Application of Mutual Energy Theorem in Expansion of Radiation Field in Spherical Waves
Zhao, Shuang-Ren
2016-01-01
In recent years the shperical wave expansion method has been widely applied to the theory and calculation of electromagnetic fields. But the inner product exist in reference[1] is defined on the Banach space[2]. Through redefining the inner product this article limits the wave expansion method to Hibert space[3]. For this reason the mutual energy theorem is introduced.
Xi, Xiaoxiang; Hwang, J; Martin, C; Tanner, D B; Carr, G L
2010-12-17
We report the complex optical conductivity of a superconducting thin film of Nb 0.5 Ti 0.5 N in an external magnetic field. The field was applied parallel to the film surface and the conductivity extracted from far-infrared transmission and reflection measurements. The real part shows the superconducting gap, which we observe to be suppressed by the applied magnetic field. We compare our results with the pair-breaking theory of Abrikosov and Gor'kov and confirm directly the theory's validity for the optical conductivity.