Wavelike Surface Research Articles

Unoccupied density of states in solid Xe from electron-phonon scattering spectroscopy.

A new geometry for electron-phonon scattering spectroscopy (EPSS) is proposed and applied to study the unoccupied density of states in solid Xe. It makes use of a substrate with a wavelike surface topology to support thick films of the material under study. In this way, EPSS can be applied to the study of wide-gap materials, without the previous limitation concerning the magnitude of the band gap. Experimental results obtained with this method are presented for a thick film of solid Xe and compared with other experimental and theoretical results from the literature.

CHARACTERISTIC AND SPECIFIC HISTOLOGICAL FINDINGS IN RHEUMATOID PLEURISY

The histological findings in rheumatoid pleuritis (RP), as seen in thoracoscopical biopsies, are found to be: A slightly inflamed stroma with a wave-like surface due to vessel-containing flattened papillae. The surface is covered by layers of pseudostratified epithelioid cells and scattered multinucleated giant cells, layers that easily detach as membranes, leaving the stroma surface "naked". These findings, in combination with the absence of mesothelial cell covering, are viewed as characteristic and specific, as based on a blind review of 17 pleural biopsies from RP patients and 14 biopsies from a control group.

Resilient mounting structure

A noise-preventing shock absorber adapted to suppress noise and absorb shock created by moving objects such as moving machine parts engaging mating surfaces and decelerating to zero velocity within a short stroke or travel distance. The shock absorber includes a unitary resilient member which is annularly shaped in plan view and provided with an axial opening, with the peripheral surface of the axial opening comprising an inner force-transmitting surface that is formed with a wavelike configuration in vertical cross section. An upper force-receiving shaft is disposed in the resilient member axial opening and has an exterior peripheral surface which is provided with a wavelike configuration in vertical cross section that mates with and is bonded to the wavelike inner force-transmitting surface of the resilient member. The resilient member is provided with a peripheral outer force-transmitting surface that is concentric with and axially offset downwardly from said inner force-transmitting surface, and which is provided with a wavelike configuration in vertical cross section. A lower force-receiving tube having an interior surface provided with a wavelike configuration in vertical cross section mates with and is bonded to the wavelike outer force-transmitting surface of the resilient member. The shock absorber member can be used in a stacked arrangement to provide shock-absorbing and noise-suppressing units of various capacities.

A wave theory for sandwaves in shelf-seas

Sea-waves are understood more easily if they are considered to move with constant velocity and without changing shape. A convenient mathematical technique is to imagine that these waves can be arrested in space and analysed as for flowing streams with a steady wave-like surface deformation. Hitherto, this technique has been used almost exclusively to study progressive surface waves. For depths as great as 45 m, such wave-like deformations occur on the sea surface as a weakly coupled mirror-image of sandwaves on the seabed. By assuming that these surface deformations are real arrested progressive waves and not merely analogous, we now show that sand-dunes are related empirically by a small-amplitude surface wave dispersion equation. Furthermore, finite-amplitude wave theory (that is, steepest wave theory) is related to the steepest dunes on a stream bed where previously, for want of a better theory, steepest dune wavelengths have been explained in terms of fluid turbulence. In particular, if the dune wavelengths associated here with Gerstner's finite amplitude theory are combined in a manner similar to a beat effect, the predicted wavelengths are in good agreement with the lengths of marine sandwaves.

Fine‐scale characteristics of interplanetary sector boundaries

This investigation has studied the structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions during the time interval from December 1974 to April 1975. A sector transition region is the region of variable magnetic field magnitude and direction observed in or near the ecliptic plane between magnetic sectors in the interplanetary magnetic field (IMF). Such regions are found generally to be complex in character, consisting of intermediate (nonspiral) average field orientations in some cases, as well as a number of large‐angle (120° ≤ω ≤180°) directional discontinuities (DD's) on the fine scale (time scales <1 h). Such DD's are found to be more similar to tangential than rotational discontinuities, to be oriented on average more nearly perpendicular than parallel to the ecliptic plane (the mean tilt is ∼58°), to be accompanied usually by a large dip (≳80%) in B (≡|B|), and, with a most probable thickness of 3 × 104 km, significantly thicker structures on average (by a factor of 10 or more) than ordinary DD's previously studied in the IMF. It is hypothesized that the observed structures represent multiple traversals of the global heliospheric current sheet caused by local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05–0.1 AU, superimposed on the large‐scale structure. The observed steep inclinations could be produced by a combination of current sheet warping at the sun, a global wave structure, and the observed small‐scale fluctuations. No radial distance dependence is found for the current sheet properties studied.

Geomagnetopause surface fluctuations observed by Voyager 1

As Voyager 1 moved out of the dawnside of the earth's magnetosphere on September 5, 1977 (at position (−2.6, −16.5, 1.1) earth radii in GSE), it crossed the magnetopause apparently seven times, despite the high spacecraft speed of 11 km/s. Normals to the magnetopause and their associated error cones were well determined for each of the crossings through the use of a minimum variance analysis of the internal magnetic field. The oscillating nature of the ecliptic plane component of these normals indicates that most of the multiple crossings were due to a wavelike surface disturbance moving tailward along the magnetopause. We modeled the wave, which was aperiodic, as a sequence of sine waves with amplitude Ai, wavelength λi, and speed Vi. These quantities were determined for two pairs of intervals from the measured slopes, occurrence times, and relative positions of six magnetopause crossings. The average amplitude was A =2100−500+3800 km, and the wavelengths were of the order of 47,000−12,000+30,000km. The wave speed was approximately 340−95+210 km/s, and typical periods were in the neighborhood of 170±60 s. The magnetopause thickness was estimated to lie in the range 300–700 km with higher values possible. The estimated amplitude of these waves was obviously small compared to their wavelengths; this conclusion is independent of any bulk normal motion of the magnetopause that might have been present.

Contour dynamics for the Euler equations in two dimensions

We present a contour dynamics algorithm for the Euler equations of fluid dynamics in two dimensions. This is applied to regions of piecewise-constant vorticity within finite-area-vortex regions (FAVR's). Essentially, this reduces the dimensionality by one and we are treating the interaction of closed polygonal contours whose nodes are advected by the total fluid motion computed self-consistently. A leapfrog centered scheme is used for temporal advancement. Computer simulation results are given for two and four like-signed interacting FAVR's. In all cases wavelike surface deformations are observed. If the distance between FAVR's is comparable to their extent (“diameter”), these surface deformations are large. They play an essential role in the observed coalescence of FAVR's.

Flow of specular points on a random wave-like surface

Specular-point flow on a stationary wave-like random surface with respect to a reference frame moving with a source–observer is described. The time rate of change of specular point densities and the differential changes caused by creations and annihilations are used to calculate the divergence of the mean flow field. The divergence has been integrated, and both mean flow and mean velocity fields have been calculated. The flow pattern is particularly complex when the source–observer motion includes a vertical component. In such a case, there is a small but nonzero vertical component of flow, and specular points at extremal surface heights may flow in opposite directions to the major flow which occurs near the mean surface plane.

Relaxation of a liquid layer under the action of capillary forces

The theory of creeping motion is used to study the relaxation of an infinite viscous fluid layer (membrane) of nonuniform thickness. The propagation of boundary perturbations in a semi-infinite layer under the action of surface-tension forces is also considered. The layer has at least one common boundary with a gas. It is found that relaxation processes of an infinite layer or the propagation of boundary perturbations inside a bounded layer are non-monotonic, and that wave-like surface perturbations always arise. Relaxation times are determined. Maximum distances are found over which separate regions of the layer can affect each other.