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51.
Widespread use of social media during crises has become commonplace, as shown by the volume of messages during the Haiti earthquake of 2010 and Japan tsunami of 2011. Location mentions are particularly important in disaster messages as they can show emergency responders where problems have occurred. This article explores the sorts of locations that occur in disaster‐related social messages, how well off‐the‐shelf software identifies those locations, and what is needed to improve automated location identification, called geo‐parsing. To do this, we have sampled Twitter messages from the February 2011 earthquake in Christchurch, Canterbury, New Zealand. We annotated locations in messages manually to make a gold standard by which to measure locations identified by a Named Entity Recognition software. The Stanford NER software found some locations that were proper nouns, but did not identify locations that were not capitalized, local streets and buildings, or non‐standard place abbreviations and mis‐spellings that are plentiful in microtext. We review how these problems might be solved in software research, and model a readable crisis map that shows crisis location clusters via enlarged place labels. 相似文献
52.
Physics of seasonally ice-covered lakes: a review 总被引:2,自引:0,他引:2
53.
The aurora and other phenomena in near Earth space are becoming a considerable part of the science curriculum in upper secondary school (high school) in Norway. Introducing scientific methods to the young students is an important objective of the education, but experimental experience is mainly restricted to simple laboratory exercises under controlled conditions; observations of uncontrollable natural phenomena are generally left to academic scientists and researchers. The Space Physics Group and The Science Education and Outreach Group at The Department of Physics and Technology, University of Bergen, are constructing a Space Science Suitcase with a set of simple versions of instruments for monitoring solar and geophysical activity in near Earth space. The instruments will be lent to physics classes in upper secondary schools. 相似文献
54.
It is expected that a warmer climate would be beneficial for agriculture in high latitudes. However, this general tendency
is not necessarily true for all northern countries, as a short growing period is not the only factor limiting agriculture.
For Russia, our model shows that the remarkable increase in potential yield in central and northern-forested regions would
not compensate for a sharp drop in yields due to increasing frequency of droughts in the currently most productive southern
European regions. If this scenario is indeed realized, the majority of Russian regions will continue to rely on import of
agricultural products from a few regions with the best soils, and a system of interregional grain trade will remain critical
for food security. However, the basic rules of interregional food market have varied widely over the past century. We have
attempted an analysis of the potential impact of these basic rules on regional food security by describing four basic historical
market scenarios and applying these scenarios to our results for climate change impact on agriculture in the 2020s and 2070s.
We show that the current system, if it continues, would bring the worst results. We also show that the traditionally effective
planned adaptation measures would help little in future climate conditions if the current market system were still in place. 相似文献
55.
56.
Petrogenesis of group A eclogites and websterites: evidence from the Obnazhennaya kimberlite,Yakutia
Lawrence?A.?TaylorEmail author Gregory?A.?Snyder Randall?Keller David?A.?Remley Mahesh?Anand Rene?Wiesli John?Valley Nikolai?V.?Sobolev 《Contributions to Mineralogy and Petrology》2003,145(4):424-443
Mantle xenoliths from the Obnazhennaya kimberlite pipe, Yakutia, possess a large range of mineralogical and chemical compositions, from both group A and B eclogites. Major-element contents of the group A eclogites exhibit transitional features between the group B eclogites and peridotite. The Mg# of clinopyroxenes is 0.86–0.94, with 0.60–0.84 for garnets. Differences in concentration of LREEs exist between the Obnazhennaya group A and the well-studied group B eclogites from the Udachnaya kimberlite pipe. In general, garnets in the group A eclogites contain lower LREEs than those from the group B eclogites; however, the trend for clinopyroxene is reversed. High d 18O (5.46–7.81) values, and the positive Eu anomalies in the garnets and clinopyroxenes (Eu/Eu* 1.2–1.4) demonstrate the involvement of an oceanic crustal component in the formation of the group A eclogites. The group A eclogites formed between 21.0 and 37.6 kbar, and 711 and 923 °C, in a time interval of 1,071–1,237 Ma. An innovative model is proposed to explain the formation of the group A eclogites and websterites. It involves the reaction of a depleted mantle peridotite with TTG and carbonatite melts closely related to the subduction of oceanic crust. 相似文献
57.
Results of a combined analysis of data from a C-band polarimetric Doppler radar and a 3D VHF interferometric lightning mapping system, as obtained during the European Lightning Nitrogen Oxides project (EULINOX) field campaign, are presented. For 21 July 1998, the lightning data from a supercell thunderstorm weakly indicate a tendency for a bi-level vertical distribution of lightning VHF emissions around the −15°C and −30°C temperature levels. Also, in some parts of the clouds, evidence is found for the presence of a lower positive charge center near the freezing level. However, where strong vertical motions prevail, VHF emissions are not organized in horizontal layers but in oblique or vertical regions. Correlation of VHF signals with radar quantities shows that in the growing storm, peak VHF activity is low and related to reflectivity factors around 30 dBZ, while after the mature stage, the peak VHF activity is about three times larger. The highest density of VHF signals is now found near reflectivity factors of 45 dBZ. A polarimetric hydrometeor classification indicates that during storm development, most lightning activity occurs where graupel and, secondarily, snow and small dry hail are present. In the decaying phase of the supercell hailstorm, however, most lightning VHF emissions stem from the region with hail and heavy rain. Furthermore, while the VHF signal frequency per cubic kilometer in the graupel and rain regions remains nearly constant throughout the supercell life cycle, the signal frequency in the hail region rises during storm decay. 相似文献
58.
Peter Nozharov Nikolai Petkov Slavcho Yanev Vladimír Kropáček Miroslav Krs Petr Pruner Reviewer J. Pícha 《Studia Geophysica et Geodaetica》1980,24(3):252-284
Summary In order to obtain basic palaeomagnetic data on Upper Carboniferous, Permian and Triassic sediments collected from the NW Bulgaria, laboratory stability tests were extended from A.C. and thermal treatments to studies of mineral phase changes and to investigations of changes of magnetic anisotropy during laboratory procedures. Laboratory criteria were found which permitted to distinguish samples suitable for palaeomagnetic analyses from those representing rocks totally or almost totally chemically reworked during their history. Palaeomagnetic directions and pole positions derived from Stephanian, Lower Permian and Triassic rocks from the southern margin of the Moesian Platform are compatible with the values obtained for the tectonically stable North-European Platform. 相似文献
59.
The reversed natural remanent magnetisation (NRM) of the volcanic features at Laschamp and Olby (Chaîne des Puys, Auvergne, France) is commonly believed to document the youngest excursion of the geomagnetic field during the present Brunhes epoch. Recent radiometric dating determines the age of these lavas to be 35000–45000 y. Continuous thermal demagnetisation indicates that under laboratory conditions the NRM of many Olby samples undergoes complete or partial self-reversal; to a lesser extent this is also true for the Laschamp material. Thus self-reversal may be another possible explanation of the reversed NRM directions. Magnetic, optical and microprobe analyses suggest that the self-reversal mechanism is based upon magnetostatic interaction between differently oxidised titanomagnetite phases. 相似文献
60.
Water mass distributions, upwelling and filament formation are of complex significance for biological and chemical processes.
Temperature and salinity are routinely used to characterize these hydrographic conditions. In situ profiles and sample analyses
from the cruise So119 of RV Sonne in May 1997 into the Arabian Sea indicate that optical parameters such as the fluorescence of phytoplankton pigments, gelbstoff
and proteins reflect hydrographic processes as well, and are useful to describe and explain biochemical processes. The dependence
of bio-optical parameters to DOC and chlorophyll a concentrations is examined. While the relation between extracted chlorophyll and chlorophyll fluorescence is quite reasonable,
DOC and gelbstoff fluorescence do not show a functional dependency. This is mainly due to sunlight-induced degradation of
fluorophores in the surface layer. Enhanced gelbstoff signals in intermediate and deep waters are related to Persian Gulf
Water. The optical data reveal a relation between the depth of the chlorophyll maximum, the depth of 1% surface light and
the geographical latitude. In the context of remote sensing of phytoplankton biomass from ocean colour images, the depth of
the chlorophyll maximum is a crucial parameter. Thus, the revealed dependency on latitude is useful for the evaluation of
primary production with satellite remote sensing.
Received: 22 May 2002 / Accepted: 18 February 2003
Responsible Editor: Andreas Oschlies
Acknowledgements. This work was supported by a grant from the Federal Minister of Education and Technology, Bonn, within the framework of the
JGOFS Arabian Sea program. We are grateful to the captain and the crew of RV Sonne for their support. Special thanks are given to the chief scientist of the cruise, Pr. V. Ittekkot, for helpful discussions.
We are indebted to Mr. Rüdiger Heuermann and Mr. Nils Bürckel for their participation in the cruise and their support in the
data analysis. 相似文献