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991.
J. V. Smith 《Australian Journal of Earth Sciences》2013,60(5):807-815
Strongly boudinaged sandstone beds in a Palaeozoic accretionary complex are exposed on Great Keppel Island, off the central Queensland coast. Viewed in profile, the boudins are folded around mesoscopic F2 hinge zones and overprinted by S2 foliation indicating formation either during Late Carboniferous subduction accretion (D1) or during a previously unrecognised discrete early phase of the Permian deformation (D2). Boudin profiles record an average stretch of 1.51, although the contribution of D2 and later deformation is not determined. Viewed in the plane of bedding, vein traces are variable and oblique to boudin necks by an average of 12° anticlockwise. The overall en echelon arrangement of veins in boudin necks is a primary feature of the structure and cannot be attributed to later deformation. This pattern of veining indicates oblique extension of the boudin necks by low‐vorticity non‐coaxial flow within the plane of bedding. One possible setting with such kinematics is the limb of a non‐cylindrical fold. 相似文献
992.
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
993.
Bender Elements在测试土样剪切波速中的应用 总被引:4,自引:0,他引:4
本文以作者在香港理工大学土木与结构工程系设计制作的一套BenderElements为例,介绍了BenderElements的原理、发展历史、应用范围、使用方法和注意事项等。BenderElements是由压电陶瓷材料制成的,在拉伸、压缩作用下,会产生正、负电荷,反过来,给它施加正、负电荷后,它又可产生弯曲振动,正是利用它的这一特性,将其作成接收和发射装置,来测试土样的剪切波速Vs。BenderElements在安装使用时,防水和静电屏蔽十分关键。Vs可在场地地震反应、液化判别、动力基础设计、检测地基改良效果等方面获得应用。震相识别的原则是接收信号的第一个峰值为到时。 相似文献
994.
J. Krause G. E. Brügmann E. V. Pushkarev 《Contributions to Mineralogy and Petrology》2011,161(2):255-273
Uralian-Alaskan-type mafic–ultramafic complexes are recognized as a distinct class of intrusions regarding lithologic assemblage,
mineral chemistry and petrogenetic setting. In the present study, we discuss new data on the distribution of major elements
in minerals of the spinel group in rocks from Uralian-Alaskan-type complexes in the Ural Mountains, Russia. Cr-rich spinel
(Cr2O3 = 20–53 wt%) in dunite with interstitial clinopyroxene and in wehrlite cumulates indicate that it reacted with interstitial
liquid resulting in the progressive substitution of Al2O2 and Cr2O3 by Fe2O3 and TiO2. A distinct change in the spinel chemistry in dunite (Cr2O3 = 47–53 wt%), towards Al2O3- and Cr2O3-poor but Fe2O3-rich compositions monitors the onset of clinopyroxene fractionation in wehrlite (Cr2O3 = 15–35 wt%, Al2O3 = 1–8 wt%, Fe2O3 = 25–55 wt%). In more fractionated mafic rocks, the calculated initial composition of exsolved spinel traces the sustained
crystallization of clinopyroxene by decreasing Cr2O3 and increasing FeO, Fe2O3 and fO2. Finally, the initiation of feldspar crystallization buffers the Al2O3 content in most of the spinels in mafic rocks at very low Cr2O3 contents (<5 wt%). The fractionation path all along and the reaction with interstitial liquid are accompanied by increasing
Fe2O3 contents in the spinel. This likely is caused by a significant increase in the oxygen fugacity, which suggests closed system
fractionation processes. Spinel with Cr2O3 < 27 wt% is exsolved into a Fe2O3-rich and an Al2O3-rich phase forming a variety of textures. Remarkably, exsolved spinel in different lithologies from complexes 200 km apart
follows one distinct solvus line defining a temperature of ca. 600°C. This indicates that the parental magmas were emplaced
and eventually cooled at similar levels in the lithosphere, likely near the crust–mantle boundary. Eventually, these 600°C
hot bodies were rapidly transported into colder regions of the upper crust during a regional tectonic event, probably during
the major active phase of the Main Uralian Fault. 相似文献
995.
W. M. Rizzo S. K. Dailey G. J. Lackey R. R. Christian B. E. Berry R. L. Wetzel 《Estuaries and Coasts》1996,19(2):247-256
We determined fluxes of oxygen and nutrients between water and sediments at 21 sites primarily in Virginia and North Carolina estuaries, over the past 15 yr. These sites represented broad ranges in salinity, tidal amplitude, hydrology, nutrient availability, turbidity, light availability, depth, sediment grain size, and anthropogenic disturbance. In general, we found that heterotrophically dominated sediments had the potential to degrade water quality, whereas photoautotrophy in the sediments ameliorated this impact. We propose a benthic trophic state index as a management tool to make general assessments of the degree to which sediments support ecological processes related to photoautotrophy. The index can be based on simple measurements of metabolic parameters. We also evaluated the relative significance of variability in the index across a number of spatial and temporal scales. Reduced photoautotrophy and/or enhanced heterotrophy tended to be associated with finer-grained, organic-rich sediments. This sediment type was common in oligohaline areas at water depths exceeding 2 m. Temporally, autotrophy declined from winter to spring particularly at sandy sites, while interannual variability was more pronounced for mud sites. *** DIRECT SUPPORT *** A01BY074 00011 相似文献
996.
The influence of the organic aerosol component on CCN supersaturation spectra for different aerosol types 总被引:5,自引:0,他引:5
MIHAELA MIRCEA MARIA CRISTINA FACCHINI STEFANO DECESARI SANDRO FUZZI ROBERT J. CHARLSON 《Tellus. Series B, Chemical and physical meteorology》2002,54(1):74-81
Abstract This paper describes the effect of the presence of water-soluble organic compounds (WSOC) in aerosol particles on the aerosol critical supersaturation as defined by the Köhler theory and on cloud condensation nuclei (CCN) number concentration. Taking into account both the soluble mass increase and the surface tension depression due to WSOC, we calculated a substantial decrease of the aerosol critical supersaturation, which results in a large increase in CCN number concentration. CCN supersaturation spectra were computed for three different aerosol types: marine, rural and urban. The increase of CCN number concentration in the presence of WSOC (with respect to the case when only the inorganic aerosol compounds are considered) varies with aerosol type, with an increase up to 13% in the marine case, up to 97% in the rural case, and up to 110% in the urban case, for the supersaturation range typical of atmospheric conditions. 相似文献
997.
Wind sedimentation in the Jafurah sand sea, Saudi Arabia 总被引:2,自引:0,他引:2
STEVEN G. FRYBERGER ABDULKADER M. AL-SARI THOMAS J. CLISHAM† SYED A. R. RIZVI KHATTAB G. AL-HINAI 《Sedimentology》1984,31(3):413-431
The Jafurah sand sea of the Eastern Province of Saudi Arabia extends along the Arabian Gulf coastline from Kuwait in the north to the Rub Al Khali in the south, a distance of about 800 km. Sand drifts southward to south-eastward from regions of high wind energy in the north to low wind energy in the south. The aeolian landscape is zoned, with areas of deflation, transport and deposition from north to south. Drift rates in the zone of transport, near Abqaiq, range from 2 m3 m-w-1 yr-1 on sabkhas, to 29 m3 m-w-1 yr-1 on the crests of dunes. Average drift rates of approximately 18 m3 m-w-1 yr-1 observed during the study can cause about 1 m of accumulation per 5500 yr in a 100 km zone of deposition downwind, not including the bulk transport represented by the forward advance of dunes. Dune advance ranged from 23 m (2.9 m high dune) to 3 m (23 m high dune) during April-October 1980. The study area consists of dune, interdune, sand sheet and siliciclastic sabkha terrains, each of which is characterized by differing drift rates, and differing rates of erosion or deposition. Sedimentation occurs by lateral movement of dunes and interdunes, and vertical accretion by sand sheets and sabkhas. 相似文献
998.
Jeffrey J. Cook 《社会与自然资源》2014,27(12):1257-1270
The preproposal stage of the rulemaking process is notoriously understudied, but enormously important in determining regulatory outputs. Recently, Rinfret (2011c) analyzed the U.S. Fish and Wildlife Service (USFWS) rulemaking process and developed a frame analysis model to interpret stakeholder influence during the preproposal stage. Rinfret argues that stakeholders use three frames to influence agency rulemaking, including an expertise, a fiscal feasibility, and an information frame. This article tests this model to determine whether it is applicable to other federal agencies such as the National Park Service (NPS). Through an analysis of stakeholder framing within the 2012 NPS Yellowstone Winter Use Rule, this research confirms that Rinfret's model is indeed applicable to the NPS process. Therefore, this research suggests that this theoretical model examining stakeholder influence is applicable to other public land agencies, and arguably can be applied across the bureaucracy. 相似文献
999.
Hans von Storch Eduardo Zorita Fidel González-Rouco 《International Journal of Earth Sciences》2009,98(1):67-82
The performance of statistical climate reconstruction methods in the pre-instrumental period is uncertain, as they are calibrated
in a short instrumental period but applied to much longer reconstructions time spans. Here, the virtual reality created by
a climate simulation of the past millennium with the model ECHO-G is used as a test bed of three methods to reconstruct the
annual Northern Hemisphere temperature. The methods are Composite plus Scaling, the inverse regression method of Mann et al.
(Nature 392:779–787, 1998) and a direct principal-components regression method. The testing methodology is based on the construction of pseudo-proxies
derived from the climate model output, the application of each of these methods to pseudo-proxy timeseries, and the comparison
of their result with the simulated mean temperature. Different structures of the noise have been used to construct pseudo-proxies,
ranging from the simulated grid-point precipitation. Also, one sparse and one denser pseudo-proxy network, co-located with
two real networks, have been considered. All three methods underestimate the simulated variations of the Northern Hemisphere
temperature, but the Composite plus Scaling method clearly displays a better performance and is robust against the different
noise models and network size. The most relevant factor determining the skill of the reconstruction appears to be the network
size, whereas the different noise models tend to yield similar results. 相似文献
1000.
The Duna-Tisza Interfluve, Hungary has an agricultural economy but is plagued by severe problems of soil and wetland salinization despite 200 years of intensive research. The study’s objective was to determine the origin of salts and the mechanisms of salinity distribution. To this end, flow-patterns and chemistry of groundwater were evaluated in a 100 km?×?65 km area, with emphasis on the Kolon- and Kelemenszék Lakes region. The lakes are located 13 km apart and have chemically contrasting water and soil types. Two groundwater flow-domains were identified: a gravity-drive meteoric fresh water and an over-pressured deeper domain of saline water. The waters are channeled by a highly permeable gravel aquifer to the surface and may merge near Kelemenszék Lake, causing it to be saline. Kolon Lake receives meteoric groundwater only, hence its fresh chemical character. The cross-formational ascent of the deep waters, combined with the gravitational systems’ geometry and the flow-channeling effect of the near-surface rocks, explains the contrasting chemistry between lakes, and the origin and pattern of soil salinization. The scheme is proposed as a generally valid hydrogeological profile for the interfluve, and has been named the Duna-Tisza Interfluve Hydrogeological Type Section. 相似文献