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1.
The aim of this interdisciplinary study is to examine a component of the hydrological cycle in Galapagos by characterizing
soil properties. Nine soil profiles were sampled on two islands. Their physical and hydrodynamic properties were analyzed,
along with their mineralogical composition. Two groups of soils were identified, with major differences between them. The
first group consists of soils located in the highlands (>350 m a.s.l.), characterized by low hydraulic conductivity (<10−5 m s−1) and low porosity (<25%). These soils are thick (several meters) and homogeneous without coarse components. Their clay fraction
is considerable and dominated by gibbsite. The second group includes soils located in the low parts of the islands (<300 m
a.s.l.). These soils are characterized by high hydraulic conductivity (>10−3 m s−1) and high porosity (>35%). The structure of these soils is heterogeneous and includes coarse materials. The physical properties
of the soils are in good agreement with the variations of the rainfall according to the elevation, which appears as the main
factor controlling the soil development. The clayey alteration products constrain soils physical and hydrodynamic properties
by reducing the porosity and consequently the permeability and also by increasing water retention. 相似文献
2.
Until recently the traditional spatial configuration of the European geography was based upon the core-periphery model. The
‘pentagon’, broadly defined as lying between London, Paris, Milan, Munich and Hamburg, was seen as the core area characterised
by having the highest concentration of economic development in the European Union (EU), with the remainder of the European
territory viewed as peripheral, albeit to varying degrees. In a number of cases such peripheral areas equated with clear regional
disparities. The elaboration of the European Spatial Development Perspective (ESDP) (CEC, European spatial development perspective, towards balanced and sustainable development in the territory of the
European Union, 1999) challenged this core-periphery model. European spatial planning policies, aimed at encouraging social
and economic, and with ever increasing importance, territorial cohesion, seek amongst other aspects to encourage the development
of a balanced and polycentric urban system. This paper adopts a network analysis approach to the analysis of air passenger
flows between some 28 principal European metropolitan urban regions. The evaluation of these flows contributes to an enhanced
comprehension of the spatial dynamics of the European metropolitan territory which goes beyond that deriving from the more
standard analyses of the individual components of the urban system. Several indicators are used, deriving from gravitational
modelling techniques, to analyse the complexity of the air passenger flows. A multidimensional scaling (MDS) technique is
introduced in order to interpret and visualise the resulting spatial configuration and positioning of the different metropolitan
centres within the conceptual European ‘space of air passenger flows’, thereby contrasting with the more traditional map-based
geographical image of Europe, based upon Cartesian coordinates.
相似文献
Malcolm C. BurnsEmail: |
3.
位于辽东湾西部低凸起北端的JZ20-2超压凝析气田,离供烃中心较远,压力系数却达到1.56~1.7,这在我国东部裂谷盆地比较少见。经过综合分析,作者认为JZ20-2凝析气田异常高压的形成与其所处的特殊地质背景紧密相关,辽中凹陷沙河街组三段超压凝析油气沿不整合面、砂体输导通道向辽东湾西部低凸起的运移、充注和能量的侧向传递是JZ20-2凝析气田异常高压形成的根本原因,而上覆东营组二段下亚段-东营组三段巨厚的强超压泥岩封盖和辽西3号边界断层侧向遮挡共同构成的优越封闭环境是超压保存的必要条件。本文分析了该气田超压特征及其远距离超压侧向传递的成因机制,不仅有助于揭示辽东湾西部低凸起超压流体运移聚集的规律和成藏作用,而且可能提供了一个超压远距离侧向传递的典型实例。 相似文献
4.
Eduardo E. Alonso Sarah M. Springman Charles W. W. Ng 《Geotechnical and Geological Engineering》2008,26(6):817-826
Two large-scale “in situ” demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment)
involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer
water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced
by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive
cells, psychrometers, TDR’s) and a comparison of fill behaviour with modelling results. The long term performance of some
instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data
during long transient periods characterised by very large variations of suction within the bentonite. 相似文献
5.
Alessandro Tarantino Andrew M. Ridley David G. Toll 《Geotechnical and Geological Engineering》2008,26(6):751-782
This paper presents a review of techniques for field measurement of suction, water content, and water hydraulic conductivity
(permeability). Main problems in the use of field tensiometers are addressed and hints on how to improve tensiometer performance
are given. Advantages and limitations of instruments for indirect measurement of suction including electrical conductivity
sensors, thermal conductivity sensors, dielectric permittivity sensors, filter paper, and psychrometer are discussed. Techniques
for water content measurement based on dielectric methods are then presented. These include time and amplitude domain reflectometry
and capacitance. Finally, a brief overview of methods for measurement of water permeability in the field is presented. 相似文献
6.
7.
8.
本文主要介绍了1988年寿光县对虾养殖期间(5~9月)水环境和底泥环境中微生物种群的变化。据不同的地理位置,选择不同的养殖虾池;分别将水样和底泥环境中的弧菌、异养菌,及硫酸盐还原菌进行培养、分离计数。据对虾养殖期5个月的数据分析,不同的养殖虾池有不同的菌数波动范围。底泥与水环境中的菌数分布各有不同。异养菌在水样中的分布最高值为736×10~2个/ml,最低值为268.1×10~2个/ml;湿泥样中的最高值为372.7×10~4个/g最低值为125.9×10~4个/g。弧菌在水样中的最高值为12.33×10~2个/ml,最低值为0.5×10~4个/ml。据综合资料分析,对虾养殖池中的各种细菌分布,底泥高于水样,高温季节高于低温季节。底泥和水环境中有机物的含量与细菌数的分布成正比。底泥中硫酸盐还原菌的数量,是底泥环境中有机物污染程度的标志之一。根据硫酸盐还原菌的数量分布,可以有效地控制有机质(如对虾饵料)的投放量等。 相似文献
9.
M.F. Lavín P.C. Fiedler J.A. Amador L.T. Ballance J. Frber-Lorda A.M. Mestas-Nuez 《Progress in Oceanography》2006,69(2-4):391
The collection of articles in this volume reviewing eastern tropical Pacific oceanography is briefly summarized, and updated references are given. The region is an unusual biological environment as a consequence of physical characteristics and patterns of forcing – including a strong and shallow thermocline, the ITCZ and coastal wind jets, equatorial upwelling, the Costa Rica Dome, eastern boundary and equatorial current systems, low iron input, inadequate ventilation of subthermocline waters, and dominance of ENSO-scale temporal variability. Remaining unanswered questions are presented. 相似文献
10.
An overview of the Oyashio ecosystem 总被引:3,自引:0,他引:3
The Oyashio shelf region and the seasonally ice-covered areas north of Hokkaido are highly productive, supporting a wide range of species including marine mammals, seabirds and commercially important species in the western subarctic Pacific. The fishes include gadids, such as walleye pollock and Pacific cod, and subarctic migratory pelagic fishes such as chum salmon and pink salmon. It is also an important summer feeding ground for subtropical migrants such as the Japanese sardine, Japanese anchovy, Pacific saury, mackerels, Japanese common squid, whales and seabirds. In recent decades, some components of the Oyashio ecosystem (i.e., phytoplankton, mesozooplankton, gadid fish, and subtropical migrants) have shown changes in species abundance or distribution that are correlated with environmental changes such as the 1976/1977 and 1988/1989 regime shifts. The First Oyashio Intrusion moved northward from the mid-1960s until the late 1970s, when it moved southward until the 1980s, after which it returned to the north again after the mid-1990s. The sea-surface temperature in spring decreased after the late 1970s, increased after the late 1980s, and remained high during the 1990s. The extent of ice cover in the Sea of Okhostk also decreased during the latest warming in the 1980–1990s but has increased again since the late 1990s. This and other variabilities affect the Oyashio ecosystem and the surrounding region. 相似文献