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91.
InSAR detection of residual settlement of an ocean reclamation engineering project: a case study of Hong Kong International Airport 总被引:2,自引:1,他引:1
Qing Zhao Hui Lin Wei Gao Howard A. Zebker Albert Chen Kin Yeung 《Journal of Oceanography》2011,67(4):415-426
Man-made land or islands that are reclaimed from the sea are suitable for building airports, harbors, and industry parks for
material transportation because of their broad air and land spaces. However, the reclaimed foundation settlement process is
of public concern, including the continuous impact of ocean processes on its stability. The majority of the buildings and
facilities of Hong Kong International Airport (HKIA) are built on a reclaimed foundation. The reclaimed foundation has been
in residual settlement since completion of the filling project in 1994. In this study, we use persistent scatterer interferometry
(PSI) and ENVISAT (European Satellite) advanced synthetic aperture radar (ASAR) data to detect the residual settlement rates
from 19 April 2006 to 9 January 2008. We use ground truth data to develop empirical correction models for correcting systematic
biases in the ASAR PSI-detected settlement rates. The corrected data follow the Lorentz distribution well, implying that the
residual settlement process is dominated by two modes or categories of settlement rates. The first category represents a relatively
stable state and the second category represents a continuous settlement state. A ground settlement rate map of HKIA shows
that an area of the Passenger Terminal Building and an area of the Southern Runway are two relatively stable areas. There
are two major continuous settlement areas. One covers the airport Midfield. Another is along the coastline, implying that
attention should be paid to impacts of ocean processes on the stability of airport foundations. 相似文献
92.
93.
94.
Current chemical dispersant effectiveness tests for product selection are commonly performed with bench-scale testing apparatus. However, for the assessment of oil dispersant effectiveness under real sea state conditions, test protocols are required to have hydrodynamic conditions closer to the natural environment, including transport and dilution effects. To achieve this goal, Fisheries and Oceans Canada and the US Environmental Protection Agency (EPA) designed and constructed a wave tank system to study chemical dispersant effectiveness under controlled mixing energy conditions (regular non-breaking, spilling breaking, and plunging breaking waves). Quantification of oil dispersant effectiveness was based on observed changes in dispersed oil concentrations and oil-droplet size distribution. The study results quantitatively demonstrated that total dispersed oil concentration and breakup kinetics of oil droplets in the water column were strongly dependent on the presence of chemical dispersants and the influence of breaking waves. These data on the effectiveness of dispersants as a function of sea state will have significant implications in the drafting of future operational guidelines for dispersant use at sea. 相似文献
95.
96.
The cartography of land covers was used to study fertility and soil evolution in a mountainous Mediterranean area during the anthropocene period ( Crutzen P J 2002 Geology of mankind Nature 415 23). The aim was to determine changes in fertility as agricultural lands were abandoned in the 14 000 hectare area that constitutes Sant Llorenç del Munt Natural Park in a pre-coastal Catalan mountain range (north-eastern Iberian Peninsula). The analysis of land covers using vegetation maps, orthorectified images and aerial photography has allowed us to differentiate six vegetation groups: holm-oak wood, pine grove, oak wood, scrub, active agricultural fields and abandoned agricultural fields. The anthropic covers over the past 100 years were subdivided into five categories: active fields and those abandoned over four time periods. Study variables include field shape (concave, convex, flat), orientation (north, south) and slope (ranging from 12º to 24º). The parameters used for the physical-chemical soil analysis included organic material, phosphorous and potassium; fertility was classified based on groups, types and classes. The results indicate that even when the visual appearance of certain landscapes is similar, the edaphic characteristics may be very different. Changes induced by human disturbance share this phenomenon. Therefore, land management should be considered globally, taking into account vegetation, soils and water as interdependent factors, since it is their interaction that produces landscape and most affects its evolution over time. 相似文献
97.
98.
Calcium and magnesium isotope systematics in rivers draining the Himalaya-Tibetan-Plateau region: Lithological or fractionation control? 总被引:1,自引:0,他引:1
In rivers draining the Himalaya-Tibetan-Plateau region, the 26Mg/24Mg ratio has a range of 2‰ and the 44Ca/42Ca ratio has a range of 0.6‰. The average δ26Mg values of tributaries from each of the main lithotectonic units (Tethyan Sedimentary Series (TSS), High Himalayan Crystalline Series (HHCS) and Lesser Himalayan Series (LHS)) are within 2 standard deviation analytical uncertainty (0.14‰). The consistency of average riverine δ26Mg values is in contrast to the main rock types (limestone, dolostone and silicate) which range in their average δ26Mg values by more than 2‰. Tributaries draining the dolostones of the LHS differ in their values compared to tributaries from the TSS and HHCS. The chemistry of these river waters is strongly influenced by dolostone (solute Mg/Ca close to unity) and both δ26Mg (−1.31‰) and (0.64‰) values are within analytical uncertainty of the LHS dolostone. These are the most elevated values in rivers and rock reported so far demonstrating that both riverine and bedrock values may show greater variability than previously thought.Although rivers draining TSS limestone have the lowest values at −1.41 and 0.42‰, respectively, both are offset to higher values compared to bedrock TSS limestone. The average δ26Mg value of rivers draining mainly silicate rock of the HHCS is −1.25‰, lower by 0.63‰ than the average silicate rock. These differences are consistent with a fractionation of δ26Mg values during silicate weathering. Given that the proportion of Mg exported from the Himalaya as solute Mg is small, the difference in 26Mg/24Mg ratios between silicate rock and solute Mg reflects the 26Mg/24Mg isotopic fractionation factor () between silicate and dissolved Mg during incongruent silicate weathering. The value of of 0.99937 implies that in the TSS, solute Mg is primarily derived from silicate weathering, whereas the source of Ca is overwhelmingly derived from carbonate weathering. The average value in HHCS rivers is within uncertainty of silicate rock at 0.39‰. The widespread hot springs of the High Himalaya have an average δ26Mg value of −0.46‰ and an average value of 0.5‰, distinct from riverine values for δ26Mg but similar to riverine values. Although rivers draining each major rock type have and δ26Mg values in part inherited from bedrock, there is no correlation with proxies for carbonate or silicate lithology such as Na/Ca ratios, suggesting that Ca and Mg are in part recycled. However, in spite of the vast contrast in vegetation density between the arid Tibetan Plateau and the tropical Lesser Himalaya, the isotopic fractionation factor for Ca and Mg between solute and rocks are not systematically different suggesting that vegetation may only recycle a small amount of Ca and Mg in these catchments.The discrepancy between solute and solid Ca and Mg isotope ratios in these rivers from diverse weathering environments highlight our lack of understanding concerning the origin and subsequent path of Ca and Mg, bound as minerals in rock, and released as cations in rivers. The fractionation of Ca and Mg isotope ratios may prove useful for tracing mechanisms of chemical alteration. Ca isotope ratios of solute riverine Ca show a greater variability than previously acknowledged. The variability of Ca isotope ratios in modern rivers will need to be better quantified and accounted for in future models of global Ca cycling, if past variations in oceanic Ca isotope ratios are to be of use in constraining the past carbon cycle. 相似文献
99.
Markov chain Monte Carlo methods for conditioning a permeability field to pressure data 总被引:3,自引:0,他引:3
Generating one realization of a random permeability field that is consistent with observed pressure data and a known variogram
model is not a difficult problem. If, however, one wants to investigate the uncertainty of reservior behavior, one must generate
a large number of realizations and ensure that the distribution of realizations properly reflects the uncertainty in reservoir
properties. The most widely used method for conditioning permeability fields to production data has been the method of simulated
annealing, in which practitioners attempt to minimize the difference between the ’ ’true and simulated production data, and
“true” and simulated variograms. Unfortunately, the meaning of the resulting realization is not clear and the method can be
extremely slow. In this paper, we present an alternative approach to generating realizations that are conditional to pressure
data, focusing on the distribution of realizations and on the efficiency of the method. Under certain conditions that can
be verified easily, the Markov chain Monte Carlo method is known to produce states whose frequencies of appearance correspond
to a given probability distribution, so we use this method to generate the realizations. To make the method more efficient,
we perturb the states in such a way that the variogram is satisfied automatically and the pressure data are approximately
matched at every step. These perturbations make use of sensitivity coefficients calculated from the reservoir simulator. 相似文献
100.
Albert J. Parker 《The Professional geographer》1992,44(2):147-160
Variation in seedling/sapling densities and stand diameter forms for six coniferous tree species is related to stand structural development and to elevation and topography in Lassen Volcanic National Park, California. Understory density patterns reflect differences in species tolerance; densities decrease with stand development for shade intolerant pines, but increase for shade tolerant firs and mountain hemlock. Pine species exhibit reverse-J diamter structures on recently disturbed sites, and decreaser and random forms elsewhere. More tolerant fir species show topographically mediated patterns of diameter structure, with reverse-J form common on northerly exposures and upland sites, but with decreaser and random forms on more xeric slopes. Interaction among species tolerance, environmental setting, and disturbance history yields a complex mosaic of stand diameter structures in the Lassen landscape. 相似文献