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81.
Fully probabilistic seismic risk assessment considering local site effects for the portfolio of buildings in Medellín,Colombia 总被引:1,自引:0,他引:1
Mario A. Salgado-Gálvez Daniela Zuloaga-Romero Gabriel A. Bernal Miguel G. Mora Omar-Darío Cardona 《Bulletin of Earthquake Engineering》2014,12(2):671-695
A fully probabilistic seismic risk analysis using a comprehensive approach is conducted for Medellin, the second largest city of Colombia, using a building by building database constructed and complemented from aerial images, considering characteristics such as building use categories, socio-economic levels and replacement values. The seismic hazard used for the analysis corresponds to the most updated study available in the country with the same model that was included in the national building code maps definition. Spectral transfer functions are determined for each of the seismic microzonation zones in order to take into account the dynamic soil response and amplification effects in the risk analysis. Several building types are defined for the city and individual vulnerability functions are assigned to each of them. Risk results are presented in the state of the art metrics such as the loss exceedance curve, probable maximum losses for different return periods, average annual losses and risk maps. The obtained results can be classified by use and socio-economic sectors as well as by structural systems that may help the stakeholders to identify where the risk concentrates. 相似文献
82.
83.
In this work we study the mid-term periodicities (MTPs), between 1 and 2 years, of the sunspot groups and the flare index (FI), by separating the data into hemispheres and spectral bands (SBs) according to the most significant periodicities presented by these phenomena. We found that the MTP of sunspot groups has a diminished power during the Modern Minimum and an increased power during the Modern Maximum, with the exception of cycle 20. For flares, the MTP has a diminished power during the low activity cycle 20, and an increased power during cycles 21 and 22. Therefore, for both sunspot groups and FI, cycle 20 shows a very diminished power followed by the active and higher-power cycles 21 and 22; cycle 23 shows a weaker power than cycles 21 and 22. It is uncertain whether MTP can be a precursor of a long-term minimum of solar activity or not, as has been previously suggested. Also, there is no one-to-one correlation between the cycle intensity and the importance of MTP. Concerning the quasi-biennial periodicities and the theory of two kinds of dynamos, we notice the tendency that higher-power cycles mean weaker coupling in the model. Concerning the hemispheric north-south asymmetry, for sunspot groups the southern hemisphere dominates in most of the SBs, while for FI the northern hemisphere dominates for all the SBs. Additionally, the time lag found between the two hemispheres indicates that the degrees of coupling in the photosphere for sunspot groups and in the corona for flares are between moderate and strong. Finally, the modulation shown by the MTP time series suggests that these periodicities are the product of chaotic quasi-periodic processes and not of stochastic processes. 相似文献
84.
H. Lammer V. Eybl K. G. Kislyakova J. Weingrill M. Holmstr?m M. L. Khodachenko Yu. N. Kulikov A. Reiners M. Leitzinger P. Odert M. Xiang?Gr��? B. Dorner M. G��del A. Hanslmeier 《Astrophysics and Space Science》2011,335(1):39-50
The detection and investigation of EUV heated, extended and non-hydrostatic upper atmospheres around terrestrial exoplanets would provide important insights into the interaction of the host stars plasma environment as well as the evolution of Earth-type planets their atmospheres and possible magnetic environments. We discuss different scenarios where one can expect that Earth-like planets should experience non-hydrostatic upper atmosphere conditions so that dynamically outward flowing neutral atoms can interact with the stellar plasma flow so that huge hydrogen coronae and energetic neutral atoms (ENA) can be produced via charge exchange. By observing the size of the extended upper atmospheres and related ENA-clouds and by determining the velocities of the surrounding hydrogen atoms, conclusions can be drawn in respect to the origin of these features. Due to the large number of M-type stars in our neighbourhood and their long periods of strong and moderate stellar activity in comparison to G-stars, we expect that M-type stars represent the most promising candidates for the detection of hydrogen ENA-clouds and the subsequent study of the interaction between the host star and the planets?? upper atmosphere. We show that the low mass of M-type stars also makes them preferable targets to observe extended hydrogen clouds around terrestrial exoplanets with a mass as low as one Earth mass. Transit follow-up observations in the UV-range of terrestrial exoplanets around M-type stars with space observatories such as the World Space Observatory-UV (WSO-UV) would provide a unique opportunity to shed more light on the early evolution of Earth-like planets, including those of our own Solar System. 相似文献
85.
86.
Jennifer A. Nelson Kathy Licht Catherine Yansa Gabriel Filippelli 《Journal of Paleolimnology》2010,43(1):1-13
Records from lake sediment cores are critical for assessing the relative stability of climate and ecosystems over the Holocene.
Duck Lake in south-central Lower Michigan, USA, was the focus of a study that identified how changes in the geochemical variables
in lake sediments relate to variations in regional climate and local land use during the Holocene. More than 8.5 m of lacustrine
sediment were recovered using Livingston and freeze corers and analyzed for organic carbon, inorganic (carbonate) carbon,
total nitrogen, and trace metals. Repeating packages of sediment (1–10 cm thick) that grade from light (inorganic carbon-rich)
to dark (organic carbon-rich) were found from the surface to a depth of about 8 m. Variations in the high-resolution gray
scale data from core X-radiographs are highly correlated to the relative amount of inorganic carbon. Geochemical analyses
of the upper 8.5 m of sediment revealed a wide range of values: 0.05–10.6% for inorganic carbon (i.e. 0.5–89% calcium carbonate)
and 1.1–28% for organic carbon (i.e. 2.7–70% organic matter). Organic carbon to nitrogen ratios indicate that most of the
sediment organic matter is produced within the lake. A core chronology based on eight AMS radiocarbon dates shows low sediment
accumulation rates (0.05 cm/year) from 10,000 to 3,800 cal year BP and higher sediment accumulation rates (0.1–0.3 cm/year)
from 3,800 cal year BP to present. We suggest that carbonate accumulates during relatively dry times, whereas organic matter
accumulation dominates when nutrient input to the lake is enhanced by wetter climate. The Duck Lake core records a distinct
low point in inorganic carbon deposition that may be related to the 8.2 ka cooling event now documented from several sites
in North America. Spectral analysis of gray scale values shows significant ~200-year periodicities over the past 8,000 years,
hypothesized to result from climate changes induced by solar forcing. Concentrations of trace metals (e.g. lead, iron, copper,
zinc) indicate the onset of regional anthropogenic influence about 150 cal year BP. 相似文献
87.
88.
Velocity and Temperature Dissimilarity in the Surface Layer Uncovered by the Telegraph Approximation
We consider the Janjic (NCEP Office Note 437:61, 2001) boundary-layer model, which is one of the most widely used in numerical weather prediction models. This boundary-layer model is based on a number of length scales that are, in turn, obtained from a master length multiplied by constants. We analyze the simulation results obtained using different sets of constants with respect to measurements using sonic anemometers, and interpret these results in terms of the turbulence processes in the atmosphere and of the role played by the different length scales. The simulations are run on a virtual machine on the Chameleon cloud for low-wind-speed, unstable, and stable conditions.
相似文献89.
Iqbal Zafar Shahid Shamsuddin Ahmed Kamal Wang Xiaojun Ismail Tarmizi Gabriel Hamza Farooq 《Theoretical and Applied Climatology》2022,148(3-4):1429-1446
Theoretical and Applied Climatology - Satellite-based precipitation (SBP) is emerging as a reliable source for high-resolution rainfall estimates over the globe. However, uncertainty in SBP is... 相似文献
90.
A 7000-year record of local fire history was reconstructed from three ombrotrophic peatlands in the James Bay lowlands (northwestern Québec, Canada) using a high-resolution analysis of macroscopic charcoal (long axis ≥ 0.5 mm). The impact of fire on vegetation changes was evaluated using detailed analysis of plant macrofossils. Compared to upland boreal forest, fire incidence in these Sphagnum-dominated bogs is rather low. Past fire occurrence seems to have been controlled primarily by internal processes associated with local hydroseral succession. Size of the peatland basin and distance from the well-drained forest soils also appear to be factors controlling fire occurrence. The impact of peatland fires on long-term vegetation succession appears negligible except in a forested bog, where it initiated the replacement of Sphagnum by mosses. In some circumstances, fire caused marked changes in the bryophyte assemblages over many decades. However, ombrotrophic peatland vegetation is generally resilient to surface fire. 相似文献