Surface state atoms and their contribution to the surface tension of quantum liquids

We investigate the new type of excitations on the surface of liquid helium. These excitations, called surfons, appear because helium atoms have discrete energy level at the liquid surface, being attracted to the surface by the van der Waals force and repulsed at a hard-core interatomic distance. The concentration of the surfons increases with temperature. The surfons propagate along the surface and form a two-dimensional gas. Basing on the simple model of the surfon microscopic structure, we estimate the surfon activation energy and effective mass for both helium isotopes. We also calculate the contribution of the surfons to the temperature dependence of the surface tension. This contribution explains the great and long-standing discrepancy between theory and experiment on this temperature dependence in both helium isotopes. The achieved agreement between our theory and experiment is extremely high. The comparison with experiment allows to extract the surfon activation energy and effective mass. The values of these surfon microscopic parameters are in a reasonable agreement with the calculated from the proposed simple model of surfon structure.Comment: 10 pages, 6 figure

Track A Basic Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd

Moderator's report on session 5: geophysical testing

Chapter summary:*Introduction*The Potential Benefits of Geophysics*Available Geophysical Techniques — Categories*Improving the Chances of Success*Contributions to this Conference*Topics for Discussion<br/

In situ determination of Ghh at Bothkennar using a novel seismic method

The paper describes a novel seismic method for determining the variation of velocity with depth of horizontally propagating, horizontally polarized shear waves (Sh,h). The technique exploits the curved paths of seismic waves in deposits with increasing velocity properties with depth. The new method has been applied at the soft clay test site at Bothkennar, and the results of this survey are compared with Sh,h and Sv,h wave velocity profiles obtained using conventional crosshole survey techniques at the site. The seismic data are further compared with the results of recently reported bender element tests on unconfined samples from the bedded and mottled Bothkennar clay. It is shown that, at the site investigated, the new method presents results comparable to those from the established field survey techniques. Neither the seismic nor the bender element data indicate significant stiffness anisotropy at the site. <br/

Helsingin pitäjän kirkon lasimaalaus (1894) : vertaileva analyysi lasimaalauksen alkuperästä

Solar radiation reflected by the Earth's surface to satellite sensors is modified by its interaction with the atmosphere. The objective of atmospheric correction is to determine true surface reflectance values by removing atmospheric effects from satellite images. Atmospheric correction is arguably the most important part of the pre-processing of satellite remotely sensed data and any omission produces erroneous results. The effects of the atmosphere are more severe for dark targets such as water reservoirs. The paper presents two methods of assessing the need for atmospheric correction, and addresses the importance of removing atmospheric effects in the satellite remote sensing of large reservoirs. <br/

The geotechnical value of ground stiffness determined using seismic methods

Geotechnical design routinely requires that the in situ strength, stiffness and permeability of the ground be determined. Most satisfactory designs for constructions such as buildings, excavations and tunnels ensure that an adequate margin of safety is maintained, and, under these conditions, measurements of the stiffness of the ground are required so that movements in the ground, both during and after construction, can be calculated. Over the past two decades the careful back-analysis of the behaviour of the ground around constructions such as tunnels and excavations has repeatedly shown that the in situ stiffness of soils and rocks is much higher than was previously thought, and that stress—strain behaviour of these materials is non-linear in most cases. Numerical analyses, using finite element and finite difference computations and field observations, have demonstrated that when margins of safety are adequate the strain levels in the ground around retaining walls, foundations and tunnels are small, and typically of the order of 0.0-l%–0.1%. Improved measurements in the laboratory have confirmed the non-linear stress-strain behaviour of soil, and shown that stiffness is much higher when measured locally and at small strain levels than when determined using conventional laboratory techniques. The realization that strain levels around construction are small, and that field stiffnesses are much higher than previously measured in the laboratory, has led us to re-appraise the value of stiffnesses derived from field seismic geophysical methods. Such methods allow stiffnesses to be determined on representative volumes of the ground, and at the in situ stress state, and for this reason may provide valuable data. This paper reviews the importance of stiffness in geotechnical design and how seismic methods are used in ground stiffness investigations. <br/