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431.
Ned P. Smith 《Estuaries and Coasts》1983,6(3):180-189
Four, 32-day current meter records from the Indian River lagoon, Florida, are used to characterize flow patterns along the Intracoastal Waterway in a coastal lagoon. The M2 tidal constituent amplitude decreases from 58 cm per s near the Fort Pierce Inlet to only 7 cm per s in the interior of the lagoon. The relative importance of the nontidal variance in the current meter records increases from 0.6% to 26.6% of the total over the same distance. Plots of net displacement over time intervals of one to 16 days suggest relatively rapid flushing near the inlet, but in the interior of the lagoon periods of little or no net movement are increasingly common. Low-frequency motions at all four sites are coherent with windstress over time scales in excess of approximately two days. 相似文献
432.
Golionko B. G. Basilyan A. E. Nikolsky P. A. Kostyleva V. V. Malyshev N. A. Verzhbitsky V. E. Obmetko V. V. Borodulin A. A. 《Geotectonics》2019,53(6):675-699
Geotectonics - Detailed lithological, stratigraphic, and structural studies of the fold-thrust structures were conducted on New Siberia Island. We have established that the jointly deformed... 相似文献
433.
R. Tatavarti A. C. Narayana P. Manoj Kumar Shyam Chand 《Journal of Earth System Science》1999,108(1):57-68
Field experiments conducted in the nearshore ocean to understand the dynamics of mudbank off Kerala, south-west coast of India,
are highlighted. Real time monitoring of the nearshore ocean off Purakkad, Kerala was accomplished using pressure transducers
for nearshore surface wave measurements, and current sensors for nearshore velocity measurements. Comprehensive information
on the spatial structure of mudbank was obtained from aerial surveys. Extensive data collected on surface waves and currents
in the nearshore ocean, indicate that the infra-gravity (IG) waves (leaky modes and trapped edge wave modes), and far infra-gravity
(FIG) waves coupled with strong shoreline reflections and undertow play an important role in the dynamics associated with
the mudbanks off Kerala during the monsoon season. During the non-monsoon season evidence for progressive edge waves in the
infragravity frequency band, an energetic gravity wave band and a strong undertow with weak reflections was observed. 相似文献
434.
Dependence on pressure of conduction by hopping of small polarons in minerals of the Earth's lower mantle 总被引:1,自引:0,他引:1
Electrical conductivity of the lower mantle-like assemblage (Mg,Fe)SiO3 perovskite-(Mg,Fe)O magnesiowüstite is usually analyzed using the quasi-chemical Arrhenian approach of diffusion. The conductivity
of this assemblage has often been attributed to hopping of small polarons, because of the low value of the activation energy
and the small negative activation volume. However, the solid-state physics approach can provide more arguments, for or against
conduction by polarons. We have tried to bridge the gap between the two approaches and identify the physical quantities entering
the phenomenological activation parameters. In particular, we have investigated the pressure dependence of the activation
energy, and the physical meaning of the activation volume. Hopping is controlled by the binding energy of the polaron and
by the value of the exchange integral, which increases with pressure causing the observed decrease of the activation energy.
From the physical theory and the results of experiments at pressures up to 40 GPa and temperatures up to 400 ∘C, we have estimated the values of parameters characteristic of polarons: radius, mobility, time between jumps and adiabaticity.
These values are compatible with conduction by small adiabatic polarons. The consequences for extrapolations to lower mantle
conditions of the presence of a temperature dependent preexponential term in the expression for conductivity have been examined.
It was found that the extrapolations are not significantly different from those using the Arrhenius equation.
Received: 5 November 1998 / Revised, accepted: 4 May 1999 相似文献
435.
P. Tucker 《International Journal of Mineral Processing》1984,12(4):273-284
The size distributions of the products from laboratory-scale batch grinds, of a leadzinc ore and a tin ore, were measured as a function of pulp density. A reduction in the overall grinding rate at high pulp densities correlated well with the increase in pulp viscosity. Enhanced fines production, apparent at the higher pulp densities, was however controlled largely by the particle packing and less by viscosity effects. The individual mineral distributions themselves responded differently to changes in pulp density. In particular, the extra fines generated at the high pulp densities consisted primarily of gangue material, with the softer ore minerals actually showing a drop in production. The addition of grinding aids, essentially viscosity modifiers, increased the grinding rate under certain conditions without producing any pronounced change in the selective grinding characteristics. 相似文献
436.
Distribution of forms of sulfur in peats from saline environments in the Florida Everglades 总被引:1,自引:0,他引:1
Although there is published information on the mechanism of sedimentary pyrite formation resulting from bacterial reduction of sulfate, little is known about the distribution of forms of sulfur, including organic, in peats. In order to increase understanding of the geochemistry of sulfur in coals, we have determined distributions of forms of sulfur in five cores of saline peat and one of brackish peat, all from areas near the Shark River and Whitewater Bay in the coastal swamps of south Florida. All concentrations vary widely with depth. Total sulfur concentrations range up to 6% of dry solids. Minor amounts of sulfur are present as H2S, S0, SO42−, and acid-soluble sulfide, but the principal forms are usually pyritic and organic. The ratio, organic/pyritic, is highly variable, but at a majority of levels in a profile is considerably greater than unity. It is inferred that topochemical factors are important in determining the distribution of sulfur forms in any element of volume. 相似文献
437.
Johanna A. A. Bos Sjoerd J. P. Bohncke C. Roel Janssen 《Journal of Paleolimnology》2006,35(2):211-238
Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS 14C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands. 相似文献
438.
James P. McGuirk 《Climatic change》1982,4(1):41-56
Precipitation data at seven stations along the west coast of North America, dating back to 1851 at some stations, are synthesized
by means of empirical orthogonal function analysis. Characteristics of runs of generally wet and generally dry conditions
are quantified. A significant change in precipitation regime, lasting 41 yrs, occurred in the middle of this century and could
return in the future. Drought occurrences, similar to midwestern United States episodes, appear in the data, but are not statistically
verifiable.
A single example of the interaction of precipitation variability and society is given. Man's actions amplify the impact of
variability on hydroelectric power generation in two ways: Society adapts itself rapidly to transient beneficial conditions,
creating a false sense of well-being; technology expands to consume maximum available resources, decreasing system resilience. 相似文献
439.
The study examines three satellite-based data sets to estimate long-term precipitation for the Thailand region: the Tropical Rainfall Mapping Mission (TRMM) 3B43, the Climate Prediction Centre morphing technique (CMORPH), and a locally developed regression model using the geostationary meteorological satellite (GMS) covering the Thailand region. Data for the first two sets were available at a spatial resolution of 0.25° × 0.25°, while the local regression model used data from the GMS at a resolution of 5 km × 5 km. The statistical regression model was developed by relating long-term monthly average precipitation from 27 rain gauge stations with concurrent satellite data in the visible and thermal infrared bands. The model was then tested against independent data from 27 rain gauge stations. Satellite/rain gauge ratios were estimated, and a smooth spline surface was used to correct the error from the model. Data from the three approaches were compared with a rain gauge network. The TRMM relation performed better than CMORPH, and the performance for GMS was comparable to TRMM with root mean square different and mean bias difference of 33.6 and 4.2%, respectively. The locally developed regression model was used to produce monthly and yearly total rainfall maps from the GMS data for the entire country. 相似文献
440.
Acta Geotechnica - Obtaining in situ thermal properties of soils is often difficult and time-consuming. Here, cone penetration test (CPT) correlations are proposed and validated for thermal... 相似文献