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201.
正1.Introduction The impacts arising from climate change and climate variability pose major challenges to global and regional security and economic prosperity(UNFCCC,2015).Some regions are more at risk than others,through heightened exposure to climatic hazards,and high vulnerability and exposure to such hazards.China,with its rapid economic development,large 相似文献
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The Tycho Epoch Photometry Annex A, a data base of photometry of more than 34 000 bright stars, has been searched for periodic variable stars with approximately sinusoidal light curves. Advantage was taken of special properties of the observing programme (photometry in two wavebands, availability of repeated measurements) to use simple but efficient variable selection criteria. Details of 70 strong candidate variables are presented. 相似文献
205.
Summary On 29 October 1998, the RGS-IBG invited delegates to a conference entitled 'Social exclusion and the city', with Geoff Mulgan (founder of the think-tank Demos and a policy advisor to Prime Minister Blair) as the keynote speaker. The event was well attended, providing much useful insight into the government policies of the 'Social Exclusion Unit' and ongoing academic research into the processes and problems of 'social exclusion'. Here we provide some general observations on the conference and some suggestions regarding the possible directions of the debate on social exclusion and inclusion. 相似文献
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Numerical Modeling of Perched Water Under Yucca Mountain, Nevada 总被引:1,自引:0,他引:1
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Marthinus Cloete Rodger J. Hart Herbert K. Schmid Martyn Drury Chris M. Demanet K. Vijaya Sankar 《Contributions to Mineralogy and Petrology》1999,137(3):232-245
Submicroscopic opaque particles from highly shocked granite-gneisses close to the core of the Vredefort impact structure
have been investigated by means of micro-analytical techniques with high spatial resolution such as electron diffraction,
orientation contrast imagery and magnetic force microscopy. The opaque particles have been identified as nano- to micro-sized
magnetite that occur in several distinct modes. In one sample magnetite occurs along relict planar deformation features (PDFs)
in quartz, generally accepted as typical shock lamellae. The magnetite particles along shock lamellae in quartz grains virtually
all show uniform crystallographic orientations. In most instances, the groups of magnetite within different quartz grains
are systematically misorientated such that they share a subparallel <101> direction. The magnetite groups of all measured
quartz grains thus appear to have a crystallographic preferred orientation in space. In a second sample, orientations of magnetite
particles have been measured in microfractures (non-diagnostic of shock) of quartz, albite and in the alteration halos, (e.g.
biotite grains breaking down to chlorite). The crystallographic orientations of magnetite particles are diverse, with only
a minor portion having a preferred orientation. Scanning electron microscopy shows that magnetite along the relict PDFs is
invariably associated with other microcrystalline phases such as quartz, K-feldspar and biotite. Petrographic observations
suggest that these microcrystalline phases crystallized from locally formed micro-melts that intruded zones of weakness such
as microfractures and PDFs shortly after the shock event. The extremely narrow widths of the PDFs suggest that heat may have
dissipated rapidly resulting in melts crystallizing relatively close to where they were generated. Magnetic force microscopy
confirms the presence of magnetic particles along PDFs. The smallest particles, <5 μm with high aspect ratios 15:1 usually
exhibit intense, uniform magnetic signals characteristic of single-domain magnetite. Consistent offsets between attractive
and repulsive magnetic signals of individual single-domain particles suggest consistent directions of magnetization for a
large proportion of particles.
Received: 16 November 1998 / Accepted: 17 May 1999 相似文献
210.
Daryl?LamEmail authorView authors OrcID profile Chris?Thompson Jacky?Croke 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(8):2011-2031
Extreme flood events have detrimental effects on society, the economy and the environment. Widespread flooding across South East Queensland in 2011 and 2013 resulted in the loss of lives and significant cost to the economy. In this region, flood risk planning and the use of traditional flood frequency analysis (FFA) to estimate both the magnitude and frequency of the 1-in-100 year flood is severely limited by short gauging station records. On average, these records are 42 years in Eastern Australia and many have a poor representation of extreme flood events. The major aim of this study is to test the application of an alternative method to estimate flood frequency in the form of the Probabilistic Regional Envelope Curve (PREC) approach which integrates additional spatial information of extreme flood events. In order to better define and constrain a working definition of an extreme flood, an Australian Envelope Curve is also produced from available gauging station data. Results indicate that the PREC method shows significant changes to the larger recurrence intervals (≥100 years) in gauges with either too few, or too many, extreme flood events. A decision making process is provided to ascertain when this method is preferable for FFA. 相似文献