Showing papers on "Wavelength published in 1983"
TL;DR: In this paper, a theory for laser-induced periodic surface structure was developed by associating each Fourier component of induced structure with the corresponding Fourier components of inhomogeneous energy deposition just beneath the surface.
Abstract: We develop a theory for laser-induced periodic surface structure by associating each Fourier component of induced structure with the corresponding Fourier component of inhomogeneous energy deposition just beneath the surface. We assume that surface roughness, confined to a region of height much less than the wavelength of light, is responsible for the symmetry breaking leading to this inhomogeneous deposition; we find strong peaks in this deposition in Fourier space, which leads to predictions of induced fringe patterns with spacing and orientation dependent on the angle of incidence and polarization of the damaging beam. The nature of the generated electromagnetic field structures and their relation to the simple "surface-scattered wave" model for periodic surface damage are discussed. Our calculation, which is for arbitrary angle of incidence and polarization, applies a new approach to the electrodynamics of randomly rough surfaces, introducing a variational principle to deal with the longitudinal fields responsible for local field, or "depolarization," corrections. For a $p$-polarized damaging beam our results depend on shape and filling factors of the surface roughness, but for $s$-polarized light they are essentially independent of these generally unknown parameters; thus an unambiguous comparison of our theory with experiment is possible.
1,144 citations
TL;DR: In this article, the vertical flux of horizontal momentum can be measured by ground-based radars using two or more radar beams each offset from the vertical to measure the atmospheric motions by the Doppler technique.
Abstract: Recent theoretical studies have emphasized the probable importance of internal gravity waves in balancing the momentum budget of the mesosphere. In this paper, we propose a method by which the vertical flux of horizontal momentum can be measured by ground based radars. The method uses two or more radar beams each offset from the vertical to measure the atmospheric motions by the Doppler technique. Provided there is horizontal homogeneity, the momentum flux is proportional to the difference of the variances of the Doppler velocities measured in each beam. The flux convergence and, hence, the associated body force acting on the atmosphere can be inferred by measuring the flux as a function of height. It is shown that mean wind components can also be measured by this method and, under certain circumstances, so can the horizontal wavelengths and phase velocities of the internal waves. Observations of the vertical flux of zonal momentum made with this technique using an HF radar located near Adelaide,...
367 citations
TL;DR: In this article, the authors used matched asymptotic expansions to study the generation of Tollmien-Schlichting waves by free-stream disturbances incident on a flat-plate boundary layer.
Abstract: The method of matched asymptotic expansions is used to study the generation of Tollmien-Schlichting waves by free-stream disturbances incident on a flat-plate boundary layer. Near the leading edge, the motion is governed by the unsteady boundary-layer equation, while farther downstream it is governed (to lowest order) by the Orr-Sommerfeld equation with slowly varying coefficients. It is shown that there is an overlap domain where the Tollmien-Schlichting wave solutions to the Orr-Sommerfeld equation and appropriate asymptotic solutions of the unsteady boundary-layer equation match, in the matched-asymptotic-expansion sense. The analysis explains how long-wavelength free-stream disturbances can generate Tollmien-Schlichting waves of much shorter wavelength. It also leads to a set of scaling laws for the asymptotic structure of the unsteady boundary layer.
317 citations
TL;DR: In this paper, the authors compared the performance of cyclotron autoresonance masers (CARM's) and ubitrons at mm and sbmm waves.
Abstract: FEL's based on the stimulated undulator radiation (ubitrons) are compared with those based on the stimulated cyclotron radiation [cyclotron autoresonance masers (CARM's)]. If the high-current accelerators are used as electron injectors, then from the viewpoint of simplicity of oscillatory electron energy pumping, criticality with respect to electron velocity dispersion, and efficiency, CARM's seem to be more effective than ubitrons at mm and sbmm waves. For such HF generators, resonators based on selective Bragg reflection of electromagnetic waves in corrugated metallic tubes are most atractive. CARM's of this type yield 6 MW at a 4 mm wavelength and 10 MW at a 2 mm wavelength in the single-mode regime.
279 citations
TL;DR: In this article, the authors report the results of some numerical experiments that bring out the lowpass characteristics of a purely elastic medium with a heterogeneous velocity structure and show that attenuation by intrinsic friction and scattering are approximately additive.
Abstract: We report the results of some numerical experiments that bring out the lowpass characteristics of a purely elastic medium with a heterogeneous velocity structure. Although the typical fluctuation is spatially confined within less than a wavelength, waves propagating over a sufficiently long path suffer major cumulative effects. We summarize the removal of high frequencies during transmission by a frequency-independent apparent Q, and show that attenuation by intrinsic friction and scattering are approximately additive. We propose some diagnostics that might help to distinguish the presence of velocity fluctuations and resultant scattering from the presence of anelasticity and true dissipation. When scattering dominates over intrinsic friction: (1) the coda of a transmitted wave contains relatively higher frequencies than the initial pulse; (2) the attenuation deduced from the power spectrum of the transmitted wave is greater than that deduced from the phase spectrum; (3) compressional and shear wave apparent Q's are approximately equal; and (4) estimates of apparent Q made from reflected coda vary with frequency, while estimates made from the transmitted waves do not. We also outline several topics in the theory of wave propagation that will be relevant in a satisfactory interpretation of short-period observations, if the amplitude of such signals is affected by scattering.
264 citations
TL;DR: In this paper, a high resolution x-ray diffractometer is described in which a compact four-crystal monochromator produces a highly parallel and non-convex incident beam of tuneable wavelength (divergence Δθ=5″, wavelength band Δλ/λ=2.3×10−5, intensity 3×104 photons/s
Abstract: A high resolution x‐ray diffractometer is described in which a compact four‐crystal monochromator produces a highly parallel and monochromatic incident beam of tuneable wavelength (divergence Δθ=5″, wavelength band Δλ/λ=2.3×10−5, intensity 3×104 photons/s mm2). The instrument is very suitable for the nondestructive measurement of concentration depth profiles produced in semiconductor single crystals by epitaxy, diffusion, or implantation. The equipment is useful for measuring x‐ray rocking curves of any lattice plane of any material and also lattice constants can be determined on absolute scale using the Bond procedure. A special solution has been derived from the dynamical theory of x‐ray diffraction, which gives the reflectivity of an absorbing layer as a function of layer thickness. This new expression takes the effects of absorption and extinction into account and has been used to determine the layer thickness of epitaxial layers grown on [001] oriented InP.
263 citations
TL;DR: In this article, the authors analyzed the ocean's response to a steadily moving storm using a numerical model for an inviscid, multi-layered fluid, which is made up of a geostrophic component and a three-dimensional wake of inertial-internal waves.
Abstract: The ocean's baroclinic response to a steadily moving storm is analyzed using a numerical model for an inviscid, multi-layered fluid. This first part of a two-part study gives a detailed account of the response to a rapidly moving hurricane, while parameter dependence is examined in the second part. A central theme of both parts is the coupling between wind-forcing, the surface mixed layer, and the thermocline. The baroclinic response is made up of a geostrophic component and a three-dimensional wake of inertial-internal waves which is emphasized. These waves initially have large horizontal spatial scales set directly by the storm. Their along-storm track wavelength is the storm translation speed times the wave period, which is typically five percent less than the local inertial period. Their cross-track scale is the storm scale. If the storm is intense as it is here, finite amplitude effects soon produce a double inertial frequency wave and smaller spatial scales. An important qualitative result ...
252 citations
TL;DR: In this article, the plasma rest frame frequencies and polarizations of the large amplitude low frequency (0.03 Hz) upstream waves are investigated using magnetic field data from the dual ISEE 1 and 2 spacecraft.
Abstract: The plasma rest frame frequencies and polarizations of the large amplitude low frequency (0.03 Hz) upstream waves are investigated using magnetic field data from the dual ISEE 1 and 2 spacecraft. The monochromatic sinusoidal waves associated with intermediate ion fluxes are propagating in both the Alfven and magnetosonic modes, in both cases with typical frequencies approximately 0.1 times the local proton gyrofrequency and wavelengths of approximately 1 R(E). It is shown that the generation of the magnetosonic mode can be explained by the cyclotron resonance mechanism driven by narrow reflected ion beams, but the concurrent observation of Alfven mode waves appears to require wave generation by the more isotropic diffuse ion distributions as well.
244 citations
Patent•
19 Oct 1983
TL;DR: In this paper, a bifocal contact lens has diffractive power added to the basic refractive power provided by the material of the lens and the basic curvature of its front and rear surfaces to direct design wavelength light predominantly into a required order and sign of diffraction, while other wavelength light is predominantly transmitted at zero order.
Abstract: A bifocal contact lens has diffractive power added to the basic refractive power provided by the material of the lens and the basic curvature of its front and rear surfaces. The diffractive power arises from concentric zones, each providing an asymmetric retardation of light across the zone width to direct design wavelength light predominantly into a required order and sign of diffraction, while other wavelength light is predominantly transmitted at zero order. Design wavelength light from an object at one distance can then be focused by way of diffraction of that order and sign, and other wavelength light from an object at another distance can be focused by way of zero order transmission. Preferably the zones are defined, and the asymmetric retardation provided, by a rear surface contour having steps but which approximates to the required basic curvature.
206 citations
TL;DR: In this paper, the authors derived a method for finding small amplitude high frequency solutions to hyperbolic systems of quasilinear partial differential equations, where each high frequency wave displays nonlinear distortion of the wave profile and shocks may form.
Abstract: : In this paper we derive a method for finding small amplitude high frequency solutions to hyperbolic systems of quasilinear partial differential equations. Our solution is the sum of two parts: (i) a superposition of small amplitude high frequency waves; (ii) a slowly varying 'mean solution'. Each high frequency wave displays nonlinear distortion of the wave profile and shocks may form. Shock conditions are derived for conservative systems. Different high frequency waves do not interact provided the frequencies and wave numbers of two waves are not linearly related to those of a third. The mean solution is found by solving a linear partial differential equation. This method generalizes Whitham's nonlinearization technique 9 for single waves, to problems where many waves are present. We obtain these results by generalizing a scheme first proposed by Choquet-Bruhat 1 which employs the method of multiple scales. (Author)
169 citations
TL;DR: In this paper, the authors examined whether magnetohydrodynamical oscillations in a density enhancement, treated for simplicity as a straight magnetic slab, can explain the observed short periods.
Abstract: Pulsations in radio emission from the solar coronal plasma have been detected for over a decade1–9. The oscillations are quasiperiodic, with periods of typically a second or so. Recently, sub-second time structures have been found in hard X rays10, and simultaneously in hard X rays and microwaves11. Here we examine whether magnetohydrodynamical oscillations in a density enhancement, treated for simplicity as a straight magnetic slab, can explain the observed short periods. A dense region in the corona (for example, a loop) can act as a wave trap, and symmetrical oscillations within that trap must be of short wavelength with correspondingly short period. An impulsive source (such as a flare) naturally gives rise to a quasiperiodic disturbance. Such oscillations are closely akin to the Pekeris modes of oceanography, the Love waves of seismology and the dielectric waves of fibre optics.
TL;DR: In this article, the effect of irradiation nonuniformity on target dynamics is illustrated by an implosion simulation using laser-target conditions anticipated for near-term high-density experiments.
Abstract: Laser driven fusion requires a high degree of uniformity in laser energy deposition in order to achieve the high density compressions required for sustaining a thermonuclear burn. The characteristic nonuniformities produced by laser irradiation, with multiple overlapping beams, are examined for a variety of laser-target configurations, Conditions are found for which the rms variation in uniformity is less than 1%. The analysis is facilitated by separating the contributions from (1) the geometrical effects related to the number and orientation of the laser beams and (2) the details of ray trajectories for the overlapping beams. Emphasis is placed on the wavelength of the nonuniformities in addition to their magnitudes, as the shorter wavelength nonuniformities are more easily smoothed by thermal conduction within the target. It is demonstrated how the geometrical symmetry of the laser system effectively eliminates the longer wavelengths, and how shorter wavelength nonuniformities can be “tuned out” by varying parameters such as the focal position and the radial intensity profile of the beam. The distance required for adequate thermal smoothing of the irradiation nonuniformities is found to be 2 to 3 times smaller than previously estimated due mainly to the relatively small spatial wavelength of the nonuniformities. This is a consequence of the geometrical symmetry of the laser system and is relatively insensitive to the details of overlapping beam profiles. The results are particularly important for irradiation with short wavelength laser light (e.g. 0.35 µm), as the small smoothing distances anticipated for moderate laser intensities are found to still produce adequate attenuation of the calculated nonuniformities. The effect of irradiation nonuniformity on target dynamics is illustrated by an implosion simulation using laser-target conditions anticipated for near-term high-density experiments.
TL;DR: In this article, two-dimensional solitary and periodic waves in water of finite depth were considered and it was shown that elevation solitary waves cannot be obtained as the continuous limit of periodic waves as the wavelength tends to infinity.
Abstract: Two-dimensional solitary and periodic waves in water of finite depth are considered. The waves propagate under the combined influence of gravity and surface tension. The flow, the surface profile and the phase velocity are functions of the amplitude of the wave and the parameters l = λ/H and τ = T/ρgH2. Here λ is the wavelength, H the depth, T the surface tension, ρ the density and g the acceleration due to gravity. For . In addition, it is shown that elevation solitary waves cannot be obtained as the continuous limit of periodic waves as the wavelength tends to infinity. Graphs of the results are included.
TL;DR: In this paper, a laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas, where the laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time.
Abstract: A laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas. The laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time. Expressions are obtained relating the overall energy transfer to total laser power and wavelength, and to gas index and interaction length. With laser powers now available, energy increments of tens of GeV are possible. For comparative purposes, a related alternative scheme involving electrons in vacuum and evanescent laser fields is also analyzed. It is found that the method applies particularly well to adding energy to the electron bunches produced by large microwave accelerators, as collision effects are less troublesome at high injection energies.
TL;DR: In this article, an automatic search with finite Fourier transforms located 13 density waves excited by resonances with Saturn's satellites and estimated the total ring mass as 5 x 10 to the -8th of the mass of Saturn.
TL;DR: In this paper, the Schumann-Runge bands (12, 0) through (1, 0), with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines mm −1 grating and having an instrumental width (FWHM) of 0.0013 nm, have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3-201.5 nm.
TL;DR: In this paper, the Korteweg-de Vries equation was extended to second order in wave amplitude and the second order correction to the wave profile and the phase speed and the first order correction of the wavelength were determined.
Abstract: Solitary waves in density stratified fluids of shallow depth are described, to first order in wave amplitude, by the Korteweg–de Vries equation; the solution for a single solitary wave has the familiar ‘‘sech2’’ profile and a phase speed which varies linearly with the wave amplitude. This theory is here extended to second order in wave amplitude. The second‐order correction to the wave profile and the phase speed and the first‐order correction to the wavelength are all determined. Four special cases are discussed in detail. In certain special circumstances the first‐order theory may fail due to the vanishing of the nonlinear coefficient in the Korteweg–de Vries equation. When this occurs a different theory is required which leads to an equation with both quadratic and cubic nonlinearities.
TL;DR: In this article, the damping of long wavelength, hydromagnetic waves in molecular cloud environments is studied with the aim of determining whether the supersonic motions observed in such clouds are likely to be due to the waves.
Abstract: The damping of long wavelength, hydromagnetic waves in molecular cloud environments is studied with the aim of determining whether the supersonic motions observed in such clouds are likely to be due to the waves. It is found that Alfven waves propagating parallel to the average magnetic field are the longest lived wave modes. Such waves can typically survive for as long as one-million years if the wavelength is as long as a few tenths of a pc and the magnetic field is 0.1-1 milligauss. Nonlinear steepening of the waves followed by ion-neutral friction in the steepened wave profiles appears to be the most effective damping mechanism.
TL;DR: In this article, the authors show that the shape of the dispersion curve resembles that of solid argon except for a wave-length region where the oscillation frequency vanished as predicted by kinetic theory.
Abstract: Neutron scattering experiments on liquid argon show evidence for the existence of well defined though strongly damped sound waves with wavelengths comparable to the size of the atoms. The dynamic structure factor can be described in terms of Rayleigh and Brillouin lines. The sound oscillation frequency shows an anomaly consistent with the mode-coupling theory. The shape of the dispersion curve resembles that of solid argon except for a wave-length region where the oscillation frequency vanished as predicted by kinetic theory.
TL;DR: The synthetic aperture radar (SAR) on SEASAT has yielded well-defined images of quasi-periodic internal waves in the waters on the west side of Baja California as discussed by the authors.
Abstract: The synthetic aperture radar (SAR) on SEASAT has yielded well-defined images of quasi-periodic internal waves in the waters on the west side of Baja California. These waves occur in groupings separated by 15–23 km, each group having 2–20 striations with wavelengths of the order of 300 m or longer. They appear in water approximately 200 m deep, shoreward of several banks at the continental shelf edge whose depths are as shallow as 15 m. The wave surface signatures exhibit clear nonlinear features: higher-than-linear group velocities, and decreases in wavelength, crest length, and amplitude toward the rear of the packet. Environmental data for the area have been examined, and these show a well-developed mixed layer, low winds, and vigorous tidal action. Thus, stratification, wind speed, tidal current, and bottom topography apparently combine to establish proper conditions for tidal generation of internal waves. The images have been analyzed from the standpoint of nonlinear wave theory, and it is shown that the vertical displacement of an isopycnal surface can be estimated from a combination of SAR imagery, vertical density profiles, and simple theoretical expressions. Numerical examples are given.
TL;DR: In this paper, the effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of incident SV waves and the results show that the surface displacement is very much influenced by surface irregularities when the incident wavelengths are comparable to the size of the topographic features.
Abstract: The effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of incident SV waves Several types of topography, such as a cliff, a cliff with a soft layer and filled land, are considered Computations are made using a new method combining a particle model with a finite element method The accuracy of this method is discussed through comparisons with Wong's solutions, which are in good agreement It is found that the surface displacement is very much influenced by surface irregularities when the incident wavelengths are comparable to the size of the topographic features Rayleigh waves are strongly produced in the neighbourhoods of the slopes of a cliff and a cliff with a soft layer, the latter being a cliff adjacent to and covered at its foot by a soft layer Thus, a zone of large amplification takes place near a slope, combining incident SV waves and Rayleigh waves A large displacement also occurs at the upper corner of the slope In filled land, vertical and horizontal displacements are produced, which are 3 times larger than those at a distance The present results are considered to be significant from the viewpoint of engineering seismology
TL;DR: In this paper, the properties of the short-crested wave were examined and it was shown that the wave can be up to 60% steeper than the two-dimensional progressive wave.
Abstract: The properties of a fully three-dimensional surface gravity wave, the short-crested wave, are examined. Linearly, a short-crested wave is formed by two wavetrains of equal amplitudes and wavelengths propagating at an angle to each other. Resonant interactions between the fundamental and its harmonics are a major feature of short-crested waves and a major complication to the use at finite wave steepness of the derived perturbation expansion. Nonetheless, estimates are made of the maximum steepnesses, and wave properties are calculated over the range of steepnesses. Although results for values of the parameter θ near 20° remain uncertain, we find that short-crested waves can be up to 60% steeper than the two-dimensional progressive wave. At limits of the parameter range the results compare well with those for known two-dimensional progressive and standing water waves.
TL;DR: In this paper, a solution for electromagnetic-wave scattering from a dielectric disk of arbitrary shape and orientation was developed by approximating the fields inside the disk with the fields induced inside an identically oriented dielectoric slab having the same thickness and dielectrics constant.
Abstract: A solution has been developed for electromagnetic-wave scattering from a dielectric disk of arbitrary shape and orientation The solution is obtained by approximating the fields inside the disk with the fields induced inside an identically oriented dielectric slab having the same thickness and dielectric constant The fields inside the disk excite conduction and polarization currents, which are in turn used to calculate the fields scattered from the disk This computation has been executed for observers in the far field of the disk for arbitrarily polarized incident waves, and the solution has been expressed in the form of a dyadic scattering amplitude The results apply when the minimum dimension of the disk’s cross section is large compared with both wavelength and disk thickness, although the thickness need not be small compared with wavelength Examples of the dependence of the scattering amplitude on frequency, relative dielectric constant, and disk orientation are presented for disks of circular cross section
TL;DR: In this article, an analysis of the magnetic field and plasma observations using spectral methods is presented, which is consistent with the hypothesis that these fluctuations are driven by streaming ions, possibly protons.
Abstract: As Voyager 2 approached Jupiter's bow shock, large-amplitude fluctuations were seen in both the magnetic field and plasma fluid velocity. These fluctuations generally coincided with the occurrence of long-lived energetic particle events similar to the upstream waves often observed near the earth's bow shock. In this paper an analysis of the magnetic field and plasma observations using spectral methods is presented. The characteristic spectral features related to the upstream waves are generally seen near 1 mHz. The measured correlation lengths of these fluctuations suggest that they are coherent over only a few wavelengths. The analysis is consistent with the hypothesis that these fluctuations are driven by streaming ions, possibly protons. No evidence for the existence of whistler waves is found. It is argued that some of the observed spectral features suggest that dynamical turbulent processes are occurring in the uptream wave region, including a possible observation of an inverse cascade of magnetic helicity to large spatial scales.
TL;DR: The nonlinear parameter of water was measured and agreed well with values obtained by other techniques and may well provide a new and powerful tool for characterizing both biological and nonbiological media.
TL;DR: In this article, a linear relation between the time-averaged amplitude of the envelope of the backscattered acoustic pulse at 192 kHz and the square root of suspended sediment concentration in the 10 to 103 mg 1−1 range was found.
Abstract: Experimental results are presented which indicate a linear relation between the time-averaged amplitude of the envelope of the backscattered acoustic pulse at 192 kHz and the square root of suspended sediment concentration in the 10 to 103 mg 1−1 range. Particle sizes ranged from 2 to 140 μm. The measurements were made in a negatively buoyant, mine-tailing discharge plume in a submarine channel at depths of 60 to 90 m in Rupert Inlet, British Columbia. From the theory of acoustic backscatter from a solid elastic sphere in the Rayleigh region it is shown that if the pressure amplitude of the backscattered wave is Rayleigh distributed, then such a linear relation is to be expected. Expressions for the optimum acoustic frequency for the detection of dilute suspensions at a given range and for the minimum detectable concentration are obtained assuming a thermal noise background. The possibility that bubbles contribute to the backscatter is considered and found to be unlikely on the basis of probable bubble lifetimes.
TL;DR: In this article, the authors investigated the scattering of lower-hybrid waves by density fluctuations arising from drift waves in tokamaks and derived the optical depth τ for scattering through a significant angle, which is given by τ≊(2/N2∥) (ωpi0/ω)2 (mec2/2Ti) 1/2 [c/α(ΩiΩe)1/2 ].
Abstract: The investigation of the scattering of lower‐hybrid waves by density fluctuations arising from drift waves in tokamaks is distinguished by the presence in the wave equation of a large, random, derivative‐coupling term The propagation of the lower‐hybrid waves is well represented by a radiative transfer equation when the scale size of the density fluctuations is small compared to the overall plasma size The radiative transfer equation is solved in two limits: first, the forward scattering limit, where the scale size of density fluctuations is large compared to the lower‐hybrid perpendicular wavelength, and second, the large‐angle scattering limit, where this inequality is reversed The most important features of these solutions are well represented by analytical formulas derived by simple arguments Based on conventional estimates for density fluctuations arising from drift waves and a parabolic density profile, the optical depth τ for scattering through a significant angle, is given by τ≊(2/N2∥) (ωpi0/ω)2 (mec2/2Ti)1/2 [c/α(ΩiΩe)1/2 ], where ωpi0 is the central ion plasma frequency and Ti denotes the ion temperature near the edge of the plasma Most of the scattering occurs near the surface The transmission through the scattering region scales as τ−1 and the emerging intensity has an angular spectrum proportional to cos θ, where sin θ=k⊥⋅Bp/(k⊥Bp), and Bp is the poloidal field
TL;DR: In this paper, a series of severe storms which occurred in the north central United States on 9 May 1979 and whose spatial distribution and movement correlate well with observed gravity waves were identified through power spectra analysis and cross-correlation techniques applied to National Weather Service barograph traces.
Abstract: An analysis is presented of a series of severe storms which occurred in the north central United States on 9 May 1979 and whose spatial distribution and movement correlate well with observed gravity waves. Two gravity wave trains of 2.1-3 mb amplitude, 2.5-3.3 h period and 240-265 km horizontal wavelength were isolated through power spectra analysis and cross-correlation techniques applied to National Weather Service barograph traces. The wave trains propagated in the 200 deg direction, which coincided with the jet axis, with a phase velocity of 20-30 m/s and within a 300 km wide band. The storms were identified on enhanced infrared GOES satellite pictures with the help of radar summaries. These convective systems initially developed in Nebraska and propagated north-northeast at 25 m/s, revealing wave-like characteristics with a separation of 300-400 km. The convective systems were closely linked to the observed wave trains with cell intensity, height and associated rainfall maximized at the wave ridge. One of the two wave trains developed in regions of weak or no convection and appeared to initiate more intense convective clusters downstream from the point of origin. It is shown that the characteristics of the wave trains are consistent with those of gravity waves generated in a region of strong vertical shear associated with the jet. It is suggested that the wave trains continue to extract energy from the basic state all along their track through critical level interaction.
TL;DR: In this paper, diffusion theory is applied to the transmission of an optical beam through randomly distributed particles, and theoretical calculations are compared with experimental data for a beam at 0.6 μm propagating through latex scatterers of sizes 0.109 and 2.02 μm.
Abstract: Diffusion theory is applied to the transmission of an optical beam through randomly distributed particles, and the theoretical calculations are compared with experimental data for an optical beam at 0.6 μm propagating through latex scatterers of sizes 0.109 and 2.02 μm. It is shown that, for particles small compared with the wavelength, the diffusion theory gives good agreement with experimental data; whereas for particles large compared with the wavelength, the diffusion theory is applicable when the optical depth is greater than about 20. For shorter optical depth, experimental results are also compared with the first-order scattering theory.
TL;DR: In this paper, attenuation of capillary and gravity water waves by two oleyl alcohol and one methyl oleate surface films (‘slicks’) was investigated.
Abstract: During the MARSEN 79 experiment, attenuation of capillary and gravity water waves by two oleyl alcohol and one methyl oleate surface films (‘slicks’) was investigated. A slight influence of an oleyl alcohol slick occurs at frequencies between 0.5 Hz and 0.7 Hz and above 0.7 Hz (wavelength L = 3.2 m) wave attenuation becomes significant. A methyl oleate slick causes only a slight wave damping in the frequency range ƒ 6.7 cm). In the capillary wave range ƒ≥14 Hz the wave-damping characteristics for the two surface film substances are comparable. In the high-frequency capillary wave range ƒ>20 Hz, however, methyl oleate surface films act more strongly on the wave field, as was demonstrated by additional wind-wave tunnel experiments. The different wave attenuation characteristics of these two surface active compounds are attributed to different interaction between their hydrophilic part and the adjacent water layer.