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871.
We examine the behavior of non-thermal electrons injected into a tapered magnetic loop, under the action of both Coulomb collisional and magnetic field gradient forces. An approximate analytic formula for the heating rate as a function of distance along the loop is developed, and found to be in good agreement with exact numerical solutions of the relevant equations. Such a formula is useful as a source term in many situations, such as hydrodynamic simulations of atmospheric response to flare energy input.Presidential Young Investigator. 相似文献
872.
Amira is a powerful three-dimensional visualization package that has been employed recently by the science and engineering communities to gain insight into their data. We discuss a new paradigm for the use of Amira in the Earth sciences that relies on the client-server paradigm. We have developed a module called WEB-IS2, which provides web-based access to Amira. This tool allows Earth scientists to manipulate Amira controls remotely and to analyze, render and view large datasets through the Internet without regard for time or location. This could have important ramifications for GRID computing.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s10069-003-0013-y 相似文献
873.
Temperature variability over the past millennium inferred from Northwestern Alaska tree rings 总被引:3,自引:0,他引:3
Rosanne D’Arrigo Erika Mashig David Frank Rob Wilson Gordon Jacoby 《Climate Dynamics》2005,24(2-3):227-236
We describe a new tree-ring width data set of 14 white spruce chronologies for the Seward Peninsula (SP), Alaska, based on living and subfossil wood dating from 1358 to 2001 AD. A composite chronology derived from these data correlates positively and significantly with summer temperatures at Nome from 1910 to 1970, after which there is some loss of positive temperature response. There is inferred cooling during periods within the Little Ice Age (LIA) from the early to middle 1600s and late 1700s to middle 1800s; and warming from the middle 1600s to early 1700s. We also present a larger composite data set covering 978–2001 AD, utilizing the SP ring-width data in combination with archaeological wood measurements and other recent collections from northwestern Alaska. The Regional Curve Standardization (RCS) method was employed to maximize potential low-frequency information in this data set. The RCS chronology shows intervals of persistent above-average growth around the time of the Medieval Warm Period (MWP) early in the millennium, which are comparable to growth levels in recent centuries. There is a more sustained cold interval during the LIA inferred from the RCS record as compared to the SP ring-width series. The chronologies correlate significantly with Bering and Chukchi Sea sea surface temperatures and with the Pacific Decadal Oscillation index. These atmosphere–ocean linkages probably account for the differences between these records and large-scale reconstructions of Arctic and Northern Hemisphere temperatures based largely on continental interior proxy data. 相似文献
874.
Airborne digital imaging technology: a new overview 总被引:2,自引:1,他引:2
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Gordon M. Winder 《New Zealand geographer》2006,62(1):50-64
Abstract: In 1908 Auckland City was the commercial hub for a small and remote provincial economy and cannot have supported more than modest, locally orientated enterprises. This paper argues that such a view is conditioned by a 'landlubber's gaze'. By envisaging a seafarer alighting on the City's wharves from a 1908 steamship to encounter the city's commercial heart, it demonstrates that Queen Street opened to a maritime world where Auckland enterprises enjoyed extensive networks and markets. Indeed, Auckland's 'floating world' rivalled its 'residential world'. Such an approach may force us to recast Auckland Province in archipelago and network terms. 相似文献
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Seasonal changes in pasture biomass, production and offtake under the transhumance system in northern Pakistan 总被引:1,自引:0,他引:1
R.M. Omer A.J. Hester I.J. Gordon M.D. Swaine S.M. Raffique 《Journal of Arid Environments》2006,67(4):641-660
An understanding of seasonal changes in pasture biomass, production and offtake of different range types is fundamentally important for the efficient management of livestock grazing. However, few studies have quantified these changes for transhumance systems, despite the fact that transhumance is still the main form of livestock management in several regions of the world and is often critical for the livelihoods of the people. One such area is the Northern Areas of Pakistan, where six villages and their pastures were selected for study. Pastures were categorized within foothill, dry temperate and alpine range types, and seasonal biomass, production and offtake of the vegetation was estimated by clipping paired caged and uncaged quadrats. The alpine range type had by far the highest biomass and offtake; the foothill and dry temperate range types were much more sparsely vegetated. Although alpine pastures were heavily used, particularly in spring, there was no evidence for consistent over-utilization of pasture resources. Within the dry temperate range type, production was highest during spring but significantly under-used. This indicates a potential for increased use of dry temperate pastures during spring, an important period both for early recovery of livestock body condition after winter and to reduce the heavy pressure on the alpine pastures at this time. 相似文献
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