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61.
Soil was modelled with linearly elastic three-dimensional finite elements. Lateral spring stiffness was calculated from FE results. Spring stiffness is shown varying linearly with shaft diameter. It is also found that spring stiffness is inversely proportional to powers (less than unity) of pile flexural rigidity. Scaling factors for shaft diameter and pile flexural rigidity are introduced. Basic stiffness of lateral spring is studied considering both full vertical slippage and zero slippage between the soil and the pile. Relevant relationships for stiffness are proposed. Some applications are suggested. 相似文献
62.
Christoph Adam David Kampenhuber Luis F. Ibarra Styliani Tsantaki 《Journal of Earthquake Engineering》2013,17(7):1189-1195
This study proposes an “optimal” spectral acceleration-based intensity measure (IM) to assess the collapse capacity of highly inelastic frame structures vulnerable to the P-delta effect. The IM is derived from the geometric mean of the spectral pseudo-acceleration over a certain period interval. The lower bound period of the averaging interval is related to the mode in which 95% of the effective modal mass is exceeded. The upper bound period is 1.6 times the fundamental period. This IM provides minimum, or close to the minimum, dispersion for frames with different fundamental periods of vibration, or number of stories. 相似文献
63.
The time series of two continuously operating gas monitoring stations at Oldřišská and Nový Kostel located along seismoactive faults in the epicentral area of the NW Bohemian swarm earthquakes (Czech Republic) are compared with water level fluctuations in two boreholes positioned along these faults and with gas flux variations of a mofette at the Soos mofette field at 9 km distance. The seasonal trend of the monitored CO2 concentration with a maximum in November and a minimum in March/April is governed by groundwater temperatures, superimposed in spring by soil temperatures. CO2 concentration variations identified at Oldřišská are also reflected in gas flux variations in the Soos mofette and/or water level fluctuations of two boreholes. Variations in the gas monitoring recordings of station at Nový Kostel are also linked with variations at Oldřišská. In all data sets, diurnal variations generated by earth tides occur, reflecting a daily stress – fault permeability cycle. Additional stress interferes with this cycle. Significant, abrupt changes are attributed to geodynamic processes linked with seismic events, as revealed by local seismicity or by the transient of waves of a strong remote earthquake. Simultaneous variations of the gas concentrations in the Nový Kostel area and in the gas flux in the Soos point to an interconnected hydraulic conductive fault systems present in the northern part of the Cheb Basin. Sharp falls in gas concentration, during or subsequent to, earthquake swarms may reflect fault compression associated with impeded gas migration. However, gas variations also occur in periods without seismic activity, indicating changes in fault permeability were caused by local aseismic fault movements, as revealed by events with opposite trends in the gas recordings at Oldřišská, Nový Kostel and the Soos. Therefore, a mathematical approach to establish a correlation between seismicity and gas geochemical variations is not possible. 相似文献
64.
Chenyang Cai Dave J. Clarke Diying Huang André Nel 《Alcheringa: An Australasian Journal of Paleontology》2013,37(4):557-562
Cai, C., Clarke, D.J., Huang, D. & Nel, A., 2014. A new genus and species of Steninae from the late Eocene of France (Coleoptera, Staphylinidae). Alcheringa 38, 557–562. ISSN 0311-5518.A remarkable new genus and species of rove beetle, Eocenostenus fossilis gen. et sp. nov., is described and figured based on one well-preserved specimen from the late Eocene of Monteils (near Alès, Gard, France). Eocenostenus is definitively placed in the extant subfamily Steninae, based on the combination of dense and coarse body punctation, globular and protruding eyes, exposed and closely spaced antennal insertions on the vertex, and six visible abdominal terga. Eocenostenus differs from the two extant stenine genera Stenus and Dianous most notably in the structure of the prothorax, which is strongly transverse and with unusual anterolateral projections, and in the anteriorly placed antennal insertions. This new discovery highlights the palaeodiversity of a genus-poor subfamily and suggests that the early diversification of Steninae is probably complicated.Chenyang Cai [caichenyang1988@163. com] and Diying Huang [dyhuang@nigpas. ac. cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Rd., Nanjing 210008, PR China; Dave J Clarke [dclarke@fieldmuseum. org], Integrative Research Center, Field Museum of Natural History, 1400 S Lake Shore Drive, Chicago, IL 60605, USA; and André Nel [anel@mnhn. fr], Muséum National d’Histoire Naturelle, Institut de Systématique, Evolution, Biodiversité, ISYEB, UMR 7205 CNRS UPMC EPHE, CP50, 45 rue Buffon, F-75005 Paris, France. Received 23.1.2014; revised 2.5.2014; accepted 12.5.2014. 相似文献
65.
Martin Valent Ladislav Marek 《Alcheringa: An Australasian Journal of Paleontology》2013,37(1):115-124
VALENT, M., FATKA, O. & MAREK, L., iFirst article. Gracilitheca and Nephrotheca (Hyolitha, Orthothecida) in the Cambrian of the Barrandian area, Czech Republic. Alcheringa, 1–10. ISSN 0311-5518. Five orthothecid hyoliths, Gracilitheca mirabilis sp. nov., Gracilitheca triangularis sp. nov., Gracilitheca sp., Nephrotheca betula sp. nov. and Nephrotheca sp. are described from the ‘middle’ Cambrian Buchava Formation of the Skryje–Tý?ovice Basin in the Czech Republic. The new forms are based on about forty well-preserved external and internal moulds of conchs; opercula of all species remain unknown. Stratigraphic ranges and geographic distributions within the Skryje Tý?ovice Basin are established for all taxa. 相似文献
66.
乌江流域地处西南边陲,境内少数民族众多,宋廷因地制宜,组建了多支少数民族军队。这些地方武力主要由御前屯驻大军和乡军组成,在南宋抗蒙(元)战争中贡献卓著,并与宋朝国祚相始终。此外,它在保卫边防、稳定当地秩序、开发边疆等方面也发挥了积极作用。 相似文献
67.
68.
Abundant illite precipitation in Proterozoic rocks from Northern Lawn Hill Platform, Mt Isa Basin, Australia, occurred in organic matter‐rich black shales rather than in sandstones, siltstones and organic matter‐poor shales. Sandstones and siltstones acted as impermeable rocks, as early diagenetic quartz and carbonate minerals reduced the porosity–permeability. Scanning and transmission electron microscopy (SEM and TEM) studies indicate a relation between creation of microporosity–permeability and organic matter alteration, suitable for subsequent mineral precipitation. K–Ar data indicate that organic matter alteration and the subsequent illite precipitation within the organic matter occurred during the regional hydrothermal event at 1172 ± 50 (2σ) Ma. Hot circulating fluids are considered to be responsible for organic matter alteration, migration and removal of volatile hydrocarbon, and consequently porosity–permeability creation. Those rocks lacking sufficient porosity–permeability, such as sandstones, siltstones and organic matter poor shales, may not have been affected by fluid movement. In hydrothermal systems, shales and mudstones may not be impermeable as usually assumed because of hydrocarbons being rapidly removed by fluid, even with relatively low total organic carbon. 相似文献
69.
Todd A. Surovell Judson Byrd Finley Geoffrey M. Smith P. Jeffrey Brantingham Robert Kelly 《Journal of archaeological science》2009
In this paper, we expand upon a prior study [Surovell, T.A., Brantingham, P.J., 2007. A note on the use of temporal frequency distributions in studies of prehistoric demography. Journal of Archaeological Science 34, 1868–1877.] that explored the problem of taphonomic bias. Taphonomic bias refers to the tendency for younger things to be over-represented relative to older things in the archaeological record due to the operation of destructive processes like erosion and weathering. Using a database of radiocarbon dated volcanic deposits from Bryson, R.U., Bryson, R.A., Ruter, A. [2006. A calibrated radiocarbon database of late Quaternary volcanic eruptions. Earth Discussions 1, 123–124.], we develop an empirical model of taphonomic bias. In contrast to our prior study in which we modeled taphonomic bias as an exponential function wherein the likelihood of site loss remains constant through time, we argue that the probability of site destruction actually decreases with site age. We further demonstrate how this model can be used to correct temporal frequency distributions and extract demographic histories. We illustrate this approach using databases of radiocarbon dates from rockshelter and open-air sites in the Bighorn Basin, Wyoming, USA, and mammoths and humans in Siberia, Russia. 相似文献
70.
乌江流域土司时期的文化环境是该地社会进步、经济发展和民族团结的现实空间,地域特征极其鲜明。一是有深厚的人文积淀,二是强化的汉文化教育,三是开放的文化心态,四是丰富的物质资源,五是鲜明的民族风情,六是剧烈的社会动荡。笔者认为,理清乌江流域土司时期的文化环境,对挖掘该地深厚的土司文化资源,促进现今民族地区的经济发展、社会进步和民族团结具有十分重要的意义。 相似文献