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351.
The characteristic functions relating relative permeabilities and capillary pressures to fluid saturations (kr–S–Pc models) are of great importance for the modelling of sub-surface multi-phase flow and transport. In order to test their performance and to identify their important parameters, four well-known three-phase kr–S–Pc models have been tested against published experimental data on non-aqueous phase liquid (NAPL) migration in the unsaturated zone. Both homogenous systems and systems with embedded heterogeneities have been analysed. 相似文献
352.
Weathering can be used as a highly effective relative age indicator. One such application involves etching of hornblende grains in soils. Etching increases with time (duration) and decreases with depth in soils and surficial sediments. Other variables, related to intensity of weathering and soil formation, are generally held as constant as possible so as to only minimally influence the time-etching relationship. Our study focuses on one of the variables usually held constant—climate—by examining hornblende etching and quartz/feldspar ratios in soils of similar age but varying degrees of development due to climatic factors. We examined the assumption that the degree of etching varies as a function of soil development, even in soils of similar age. The Spodosols we studied form a climate-mediated development sequence on a 13,000-yr-old outwash plain in Michigan. Their pedogenic development was compared to weathering-related data from the same soils. In general, soils data paralleled weathering data. Hornblende etching was most pronounced in the A and E horizons, and decreased rapidly with depth. Quartz/feldspar ratios showed similar but more variable trends. In the two most weakly developed soils, the Q/F ratio was nearly constant with depth, implying that this ratio may not be as effective a measure as are etching data for minimally weathered soils. Our data indicate that hornblende etching should not be used as a stand-alone relative age indicator, especially in young soils and in contexts where the degree of pedogenic variability on the geomorphic surface is large. 相似文献
353.
354.
应用电导法测定了KCl在水和异丙醇混合溶剂中的活度系数,讨论了电解质溶液活度系数与浓度和温度的关系,并计算了电解质溶液在混合溶剂中的相对偏摩尔自由能、相对偏摩尔焓、相对偏摩尔熵,对其相对偏摩尔性质的某些变化规律作了初步的讨论。 相似文献
355.
356.
地球磁场相对强度研究现状与展望 总被引:2,自引:6,他引:2
对利用沉积物确定地球磁场相对强度的实验方法进行了综述评述,在些基础上本文总结了目前常用的恢复沉复沉积物记录古强度的方法,重点介绍了全新世、晚更新世和布容时地球磁场相对强度变化特征,评价了环境因素对沉积物记录地球磁场相对强度的影响。对未来有关地球磁场相对强度研究发展趋势提出了借鉴。 相似文献
357.
Giovanni Scicchitano Fabrizio Antonioli Elena Flavia Castagnino Berlinghieri Andrea Dutton Carmelo Monaco 《Quaternary Research》2008,70(1):26-39
Precise measurements of submerged archaeological markers in the Siracusa coast (Southeastern Sicily, Italy) provide new data on relative sea-level change during the late Holocene. Four submerged archaeological sites have been studied and investigated through direct observations. Two of them are Greek archaic in age (2.5–2.7 ka) and are now 0.98–1.48 m below sea level; the other two developed during the Bronze age (3.2–3.8 ka) and are now 1.03–1.97 m below sea level. These archaeological data have been integrated with information derived from a submerged speleothem collected in a cave located along the Siracusa coast at − 20 m depth. The positions of the archaeological markers have been measured with respect to present sea level, corrected for tide and pressure at the time of surveys. These data were compared with predicted sea-level rise curves for the Holocene using a glacio-hydro-isostatic model. The comparison with the curve for the southeastern Sicily coast yields a tectonic component of relative sea-level change related to regional uplift. Uplift rates between 0.3 and 0.8 mm/yr have been estimated. 相似文献
358.
We use the radiocarbon ages of marine shells and terrestrial vegetation to reconstruct relative sea level (RSL) history in northern Southeast Alaska. RSL fell below its present level around 13,900 cal yr BP, suggesting regional deglaciation was complete by then. RSL stayed at least several meters below modern levels until the mid-Holocene, when it began a fluctuating rise that probably tracked isostatic depression and rebound caused by varying ice loads in nearby Glacier Bay. This fluctuating RSL rise likely reflects the episodic but progressive advance of ice in Glacier Bay that started around 6000 cal yr BP. After that time, RSL low stands probably signaled minor episodes of glacier retreat/thinning that triggered isostatic rebound and land uplift. Progressive, down-fjord advance of the Glacier Bay glacier during the late Holocene is consistent with the main driver of this glacial system being the dynamics of its terminus rather than climate change directly. Only after the glacier reached an exposed position protruding into Icy Strait ca. AD 1750, did its terminus succumb - a century before the climate changes that marked the end of the Little Ice Age - to the catastrophic retreat that triggered the rapid isostatic rebound and RSL fall occurring today in Icy Strait. 相似文献
359.
Joseph Kuchar Glenn Milne Alun Hubbard Henry Patton Sarah Bradley Ian Shennan Robin Edwards 《第四纪科学杂志》2012,27(6):597-605
The glacial isostatic adjustment (GIA) of the British Isles is complex due to the interplay between local and non‐local signals. A number of recent studies have modelled the GIA response of the British Isles using relative sea‐level data. This study extends these previous analyses by using output from a numerical glaciological model as input to a GIA model. This is a necessary step towards more realistic GIA models, and although there have been similar studies for the major late Pleistocene ice sheets, this is the first study to do so for the British Isles. We test three reconstructions, classed as ‘minimal’, ‘median’ and ‘maximal’ in terms of their volume at maximum extent, and find it is possible to obtain good data–model fits. The minimal reconstruction is clearly preferred by the sea‐level data. The ice reconstructions tested were not constrained by geomorphological information of past ice extent (lateral and vertical). As a consequence, the reconstructions extend further than much of this information suggests, particularly in terms of ice thickness. It is notable, however, that the reconstructions produce good fits to many sea‐level data from central, mountainous regions (e.g. Scottish highlands), which lends support to the suggestion that trimlines, often used as an constraint on the palaeo ice surface location, are in fact features formed at the transition from warm‐ to cold‐based ice and so mark a minimum constraint on the ice surface altitude. Based on data–model misfits, suggestions are made for improving the ice model reconstructions. However, in many locations, the cause of the misfit could be due to non‐local, predominantly Fennoscandian ice and so interpretation is not straightforward. As a result, we suggest that future analyses of this type consider models and observations for both Fennoscandia and the British Isles. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
360.
Existing resistance formulas produce a wide range of friction-factor estimates for gravel bed streams. The purpose of this paper is to develop a reliable resistance formula in terms of the Darcy-Weisbach friction factor f Published data were screened and used to establish the formula. The existing formulas have considered thatfis a function of relative roughness D84/R only, where R is the hydraulic radius and 1984 is the particle size referred to the intermediate diameter that equals or exceeds that of 84 percent of bed sediments. In this paper, f is considered as a ftmction of Froude number in addition to the relative roughness, ffor D84/R〉l displays a different trend than that for Dsn/R〈l perhaps due to the invalid assumption of a logarithmic velocity distribution for D84/R〉l. Anfformula for Dsa/R〈l has been established. 相似文献