The coalescence of water drops II. The coalescence problem and coalescence efficiency

By the use of the model of approaching drops (Arbel and Levin, 1977) the coalescence efficiencies of drops are computed. It is found that for interactions of drops at their terminal velocities the coalescence depends both on the size of the large drop and on the size ratio of the interacting drops in agreement with the experimental results of Whelpdale and List (1971) and Levin and Machnes (1977).The results were found to be sensitive to the assumption of the drops deformation and to the critical separation distance. This distance is defined as the distance at which the drops begin to merge. The variations of the coalescence efficiency with these parameters is discussed.Appendix: List of symbols D distance between the deformed surfaces of the drops - D _o initial value ofD - D _s stop distance, the distance at which the impact velocity vanishes - D _c critical coalescence distance - E collection efficiency - E ₁ collision efficiency - E ₂ coalescence efficiency - E _2R coalescence efficiency for collisions with stationary targets - F _c centrifugal force - p ratio of the radii of the interacting drops - r _o initial distance between drops' centers - R _L radius of larger drop - R _s radius of smaller drop - R _D radius of deformation - v approach velocity of two deformed surfaces - v _o initial value ofv - V _i impact velocity (given negative sign when drops approach each other) - V _c critical impact velocity - W _i velocity of the smaller drop at infinity for it to reachD _o with velocityv _o - x _i impact distance, the distance between the trajectories of the two drops - x _c critical impact distance for coalescence -  average critical impact distance for coalescence - X _c critical impact distance for collisions - coefficient of deformation given in equation 1 - _i impact angle defined byWhelpdale andList (1971) given also inArbel andLevin (1977) - coefficient of deformation given in equation 2 - viscosity of air - _i impact angle used inArbel andLevin (1977) and here - _c critical angle for coalescence - average critical angle for coalescence On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Shallow landslides in deeply weathered slates of the Sierra de Collcerola (Catalonian Coastal Range, Spain)

Stability conditions in an area located NW of Barcelona (Spain) are discussed. Here, several mass movements were observed, mainly affecting weathered Paleozoic slates. Many of these failures involved slopes cut along recent infrastructures: debris flows, wedge and plane failures, generally surficial, occurred more frequently. After a detailed geological and geomorphologic survey, geomechanic characterization was carried out, according to RMR and SMR classifications. This rating gave a prediction of slope behaviour, in fairly good agreement with the real observed one.

Stability numerical analysis was carried out for the main cut slopes, based upon the Limit Equilibrium Method. First of all, the deterministic factor of safety was computed using the mean values of parameters. After that, a simulation technique based upon the Monte Carlo Method was applied in order to obtain factor of safety distributions. The probability of failure was estimated as P(F<1).

Finally, results from deterministic and probabilistic approaches were compared. The effectiveness of different possible remedial measures was highlighted by means of a sensitivity analysis, which showed that the more important parameters in the study area are the geometrical ones (height, slope and failure plane angles). The final technical solutions adopted are briefly outlined.     

Molecular orbitals of Si2O 7 6− , Si3O 10 8− , etc., and mixed (B,Al,P,Si) m applied to clusters and X-ray spectroscopy data of silicates

The Si, Al L_{II, III} and OK_α emission and quantum yield spectra were obtained for 24 silicates. It was found that in minerals of a homogeneous anion composition the Si L_{II, III} line has double-humped structure, and when in addition to SiO ₄ ^4? ions of other composition (BeO ₄ ^6? , AlO ₄ ^5? etc.) are present it has triple-humped structure. The process of crystal-glass transition was studied by X-ray spectroscopy. The result is that in spite of the original form of the Si L_{II, III} line of the mineral this line changes its structure in glass and exhibits a typical double-humped structure. The CNDO/2 approach was used to calculate the electronic structure of basic structural groups of silicates from SiO ₄ ^4? to Si₅O ₁₆ ^12? by replacing one or two of the Si atoms by Be, B, Al and P. A qualitative interpretation of the X-ray spectra is presented.     

Peculiarities of the within-year distribution of earthquakes in the Kuril region

Recent investigations have shown that the probability of the occurrence of earthquakes in a specified region depends on several factors, such as the latitude of the study region, as well as the lunar and solar tidal forces, which are governed by the mutual arrangement of bodies in the Sun-Earth-Moon system. The objective of our work is to prove that the irregularity of the within-year distribution of seismic events in the Pacific regions (the Kuril Islands and Hokkaido Island) is a statistically significant process, which is manifested in different ways for earthquakes with various source depths and energy levels. The hypothesis about the uniform within-year distribution of earthquakes is refuted for shallow events. However, it is shown that deep earthquakes are distributed uniformly. This work attempts for the first time to determine the stability degree of the within-year irregularity of seismic events with respect to the observation time interval (from 28 to 5 years). Two peaks are noted in the annual distribution of the earthquakes. The relation of the peaks of the within-year seismic activity to the Earth’s position on the ecliptic plane, as well as the relationships between the peaks, the magnitude range of the events, and the position of the specified subregion, is considered. The principal maximum of the seismic activity falls in the November-March period, which matches the minimum Earth-Sun distance.     

Structure of the thermal lithosphere and asthenosphere beneath oceans and continents

The lithosphere and asthenosphere make up a common geodynamic system but are characterized by different physical parameters. The former has a temperature of 1200–1300°C, a density of 3.3 g/cm³, and a viscosity of 10²² poise, while the latter has a density of 3.23 g/cm³, a viscosity in the range 10²¹-10^18–19 poise, and a temperature from 1200–1300°C to 1600–1700°C. The asthenosphere is distinguished by a great variability of its physical state in the lateral and vertical directions. This circumstance necessitates the recognition of the different types of the asthenosphere: seismic (LVZ zone), electrical, thermal, and seismological. The structure and the physical state of the thermal asthenosphere is considered in this paper on the basis of P-T parameters. Its state normally fits viscous Newtonian liquid beneath the continents and provides partial (5–20%) melting in spreading zones and along continental margins. No partial melting is detected beneath the main portion of the continents. The interaction between the asthenosphere and lithosphere is characterized by spatiotemporal migration of partial melting zones and asthenosphere upwelling, and such interaction determines the entire range of geodynamic processes from spreading and rifting to collision and vertical motions of different senses.     

A comparison of early juvenile red drum densities among various habitat types in Galveston Bay, Texas

Seagrass meadows are often cited as important nursery areas for newly settled red drum even though many estuaries, such as Galveston Bay, Texas, support large numbers of red drum and have limited seagrass cover, suggesting the use of alternate nursery areas. We examined patterns of habitat use for newly settled red drum at six sampling areas in Galveston Bay; two areas had seagrass beds and four areas had no seagrass. We measured densities in different habitat types using epibenthic sleds and enclosure samplers. Peak recruitment of young red drum to the estuary occurred during September through December. Highest densities of new settlers were found in seagrass meadows (primarilyHalodule wrightii), but when seagrass was absent, the highest densities of red drum occurred along theSpartina alterniflora marsh edge interface. Densities were relatively low on nonvegetated bottom away from the marsh edge. We also examined density patterns in other habitat types at selected sampling areas and found no red drum within marsh vegetation away from the marsh edge interface (5 and 10 m into the marsh interior). Oyster reefCrassostrea virginica was sampled using lift nets, and we found no red drum using this habitat, although adjacent seagrass and marsh interface habitats were used. Even though red drum densities in marsh edge were low relative to seagrass, the large areal extent of marshes in the bay complex probably makes marsh edge the most important nursery habitat for red drum in Galveston Bay.     

High-precision geoid determination in small areas: A case study in Doñana National Park (Spain)

Doñana National Park is an area of approximately 500 km² located on the SW coast of Spain that shows one of the greatest geoid gradients on the entire Iberian Peninsula, due to its peculiar tectonic characteristics. So, it is necessary to elaborate an accurate geoid model that can be used with GPS for precise surveying, since the existing ones are insufficient, due to their poor resolution and their limited adaptation to a small area with such a strong gradient. The least squares prediction method was tested in order to obtain the undulation from GPS/orthometric points. The results obtained were unsatisfactory because of the strong geoid gradient. In order to improve accuracy the remove-restore technique was used. Global geopotential model EIGEN-CG01C and a Digital Elevation Model (DEM) with a 25 × 25 m resolution and an accuracy better than 3 m were used. Thus, the final geometrical geoid obtained reaches the precision required by other disciplines (3 cm in any point within the Park). Particularly, the geoid model has allowed for the acquisition of a precision DEM that is essential to formulate a hydrodynamic model for the Doñana marsh functions.     

GPS monitoring of recent crustal movements in Kamchatka and the Commander Islands during 1997–2007

This is a review of the geodetic monitoring of the horizontal component of recent crustal movements (RCMs) in Kamchatka and the Commander Islands for the period 1979–2007. Examples are provided of the RCMs recorded in Kamchatka and the Commander Islands for the period 1997–2007 by the Kamchatka regional GPS network (KAMNET) set up by workers at the Kamchatka Branch of the RAS Geophysical Service (KB GS RAS) in collaboration with the Institute of Volcanology and Seismology of the Far East Division of the Russian Academy of Sciences to study the geodynamic processes that are occurring in the Kamchatka subduction zone. An interpretation of examples of recorded RCMs is given.