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141.
142.
A structure incorporating the mechanism of sliding, as used in seismic isolation, along with the mechanism of uplift, but at a different elevation, is proposed to study the possible beneficial effects on the response of the structure, as compared to allowing partial base uplift only. A two-mass model of system uplift and sliding is established. The equations of motion for both the phase of full contact and the phase of base uplift are derived. The criteria governing the transformation of these two phases are given. Both the time history and the response spectrum results show that the structure with both uplift and sliding mechanisms is superior to that with only the uplift mechanism. Not only is the response of the structure lessened, but also the amount of uplift is greatly reduced because of the added sliding mechanism. 相似文献
143.
Phillip R. Kemmerly 《地球表面变化过程与地形》1979,4(2):201-202
144.
Bartholomew Nagy Lois Anne Nagy John E. Zumberge Deborah S. Sklarew Phillip Anderson 《Precambrian Research》1977,5(2):109-120
Micropaleontological observations and organic geochemical analyses imply, but certainly do not prove, that life may not have been present ~3,800 Ma ago in Southwestern Greenland; however, physiologically complex prokaryotes flourished by the Early Proterozoic in other locations. It is, of course, also possible that life may have appeared earlier in locations other than Greenland. Investigations of Precambrian biological and biochemical evolutionary trends require interdisciplinary efforts, up-to-date instrumentation and methodology (such as ultramicrochemical analyses of individual microfossils/microstructures), and caution in the interpretation of experimental results. 相似文献
145.
Phillip Dustan 《Environmental Geology》1977,2(1):51-58
Recently, questions about the health of the coral reefs of the Florida Keys have been raised. Estimates of net recruitment
and mortality of reef corals on Carysfort Reef, Key Largo, Florida, suggest that these populations declined over the 14 month
interval studied. The greatest rate of change on Carysfort Reef, the most well developed reef in the northern Keys, occurred
in the zone of richest coverage by corals. Water pollution associated with the tremendous increase in the human population
of South Florida in the last twenty years may be contributing to the reef's decline. 相似文献
146.
Size affects digestive responses to increasing temperature in fishes: physiological implications of being small under climate change 下载免费PDF全文
Digestive metabolism is considered key to resilience of fish populations as it determines energy and nutrient availability for growth and survival. In cleaner fishes, digestion performance also influences the amount and the rate at which parasites can be removed from co‐operating fishes, called hosts. Therefore, understanding the effect of temperature on digestive metabolic scope (i.e. the energy allocated to digestive processes) is crucial to predicting responses of fish communities to ocean warming. Body size can affect many physiologic processes and is thought to decrease with increasing temperature; therefore, we examined the effect of body mass and warming on digestive metabolic scopes in two sister species of cleaner gobies of the genus Elacatinus that reach different adult sizes. The dwarf‐size Elacatinus lobeli increased digestive metabolic rates and scope while the larger Elacatinus oceanops decreased digestive metabolic scope with warming. Intra‐specifically, larger E. lobeli also showed a decreased scope when compared to smaller individuals. Results from this study suggest that perhaps smaller fishes may have a digestive and metabolic advantage at higher temperatures and may be more resilient under warming temperatures. 相似文献
147.
Eighty-two palaeomagnetic samples of calcareous and jaspilitic grainstones (iron-formation or ‘taconite’) and chert carbonate were collected from the 1.88-Ga Gunflint Formation at 22 sites in the Thunder Bay area, Ontario. Twenty clasts of Gunflint taconite also were sampled from the basal conglomerate of the overlying Mesoproterozoic Sibley Group. Anisotropy of magnetic susceptibility measurements indicate the Gunflint Formation in the sampling area has not experienced regional dynamic metamorphism. Analyses by variable-field translation balance and X-ray diffraction show that the predominant magnetic mineral is hematite but a small amount of magnetite also is present in some samples. Altogether, 213 Gunflint specimens and 59 Sibley conglomerate specimens were subjected to stepwise thermal demagnetisation and 74 Gunflint specimens to stepwise alternating-frequency demagnetisation. The following components were isolated for the taconites:
- • Gunflint magnetite: normal declination D=293.4°, inclination I=30.8°, α95=7.2°, n=21; reverse D=86.7°, I=–54.6°, α95=5.8°, n=29.
- • Gunflint hematite: normal D=243.6°, I=23.6°, α95=6.0°, n=11; reverse D=70.3°, I=–51.4°, α95=3.2°, n=79.
- • Sibley clasts magnetite: normal D=282.7°, I=33.4°, α95=7.6°, n=20.
- • Sibley clasts hematite: normal D=254.5°, I=56.2°, α95=8.4°, n=13; reverse D=110.6°, I=–55.7°, α95=8.3°, n=11.
148.
Phillip B. Fenberg Jennifer E. Caselle Joachim Claudet Michaela Clemence Steven D. Gaines Jose Antonio García-Charton Emanuel J. Gonçalves Kirsten Grorud-Colvert Paolo Guidetti Stuart R. Jenkins Peter J.S. Jones Sarah E. Lester Rob McAllen Even Moland Serge Planes Thomas K. Sørensen 《Marine Policy》2012
The ecologically and socio-economically important marine ecosystems of Europe are facing severe threats from a variety of human impacts. To mitigate and potentially reverse some of these impacts, the European Union (EU) has mandated the implementation of the Marine Strategy Framework Directive (MSFD) in order to achieve Good Environmental Status (GES) in EU waters by 2020. The primary initiative for achieving GES is the implementation of coherent networks of marine protected areas (MPAs). Marine reserves are an important type of MPA in which no extraction is allowed, but their usefulness depends upon a number of ecological, management, and political factors. This paper provides a synthesis of the ecological effects of existing European marine reserves and the factors (social and ecological) underlying their effectiveness. Results show that existing European marine reserves foster significant positive increases in key biological variables (density, biomass, body size, and species richness) compared with areas receiving less protection, a pattern mirrored by marine reserves around the globe. For marine reserves to achieve their ecological and social goals, however, they must be designed, managed, and enforced properly. In addition, identifying whether protected areas are ecologically connected as a network, as well as where new MPAs should be established according to the MSFD, requires information on the connectivity of populations across large areas. The adoption of the MSFD demonstrates willingness to achieve the long-term protection of Europe's marine ecosystems, but whether the political will (local, regional, and continent wide) is strong enough to see its mandates through remains to be seen. Although the MSFD does not explicitly require marine reserves, an important step towards the protection of Europe's marine ecosystems is the establishment of marine reserves within wider-use MPAs as connected networks across large spatial scales. 相似文献
149.
关于在基础设施抗震规范中规定最低设防要求的一点建议 总被引:1,自引:1,他引:0
作者针对目前我国基础设施抗震设计时遇到的问题,给出了以下建议:①根据地震作用水平,对结构不同部位、不同构件制定不同的设计目标,明确设计构件所用的强度、延性参数指标;②我国地震动区划图提供的地震动参数仅仅是中震水平(地震重现期475年),实际发生的地震可能远远超过中震水平,在基础设施设计时应对大震(罕遇地震)有所考虑,甚至应考虑超预期地震发生后的应对、应急措施;③提高最低设防水准,并非是提高一度设防,应通过确定最小地震动参数满足最低设防要求,并在地震动区划图中以地震重现期代表地震危险程度;④对于Ⅵ度以下设防地区的基础设施结构物,都应按照Ⅵ度设防标准设计并考虑采取相应的抗震措施. 相似文献
150.
Greater Cook Strait (GCS) lies between the North and the South Islands of New Zealand. Its location at the convergence of
the Pacific and Indo-Australian tectonic plates leads to interesting bathymetry with an adjacent shallow shelf and deep ocean
trench as well as numerous crossing faults and complex shoreline geometry. Our purpose in this study is to examine tides and
currents in GCS and, in particular, identify the major forcing mechanisms for the residual currents. Toward this end, we use
an unstructured-grid numerical model to reproduce the tides and currents, verify these results with observations and then
use the model to separate the various forcing mechanisms. The physical forcing includes nonlinear generation from tides and
tidal currents, differences in sea level between the Pacific Ocean and Tasman Sea boundaries, density variations, wind stress
and river discharge into GCS. Each of these mechanisms is important in different areas. 相似文献