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991.
Urban forest management is being increasingly recognized as a viable policy vehicle for improving community health, sustainable development, and well-being for city dwellers. To improve our understanding of public concern for the local urban forest, a theoretical framework employing concepts traditionally explored in social–psychological and environmental concern studies was tested using data from a public opinion survey of 800 homeowners living in a major urban area in Southern Appalachia, USA. Publicly available geographic information system (GIS) data were analyzed to measure tree canopy density around survey respondents’ properties. Structural equation modeling was used to test the validity of the hypothesized relationships among the survey-derived constructs and the spatial data as predictors of public support for urban forest protection policy. The results suggest that homeowners living around urban trees place greater importance on various attributes of trees, and that tree knowledge and experience are indirectly and positively related to support for urban forest protection. 相似文献
992.
Thomas W. Gillespie John A. Agnew Erika Mariano Scott Mossler Nolan Jones MattBraughton Jorge Gonzalez 《遥感学报》2011,15(4):869-874
本·拉登到底在哪里?这是我们这个时代最重要的政治问题之一。在这篇文章中,我们依据反映生物分布和灭绝规律的生物地理学理论(距离衰减理论、岛屿生物地理理论、本·拉登个人数据),结合遥感数据(陆地卫星 ETM+、航天雷达地形测图、QuickBird),从全球、区域、局部三个空间尺度分析并最终指出本·拉登当前最可能的所在地。这是第一次运用科学手段来确定本·拉登居所。该方法具有可重复性:一旦美国情报部门提供新的信息,便可通过该方法重新定位本·拉登当前最有可能的藏身场所。 相似文献
993.
In order to estimating satellite interfrequency bias Tgd for the anomalously behaving SVN49, a modified JPL GIM software suite is presented. This research assumed that the single-frequency
user will not need to perform any modification in the receiver software and will not need any detailed knowledge of the satellite
anomaly using the code observable. We performed a point positioning analysis and investigated the range residuals for SVN49.
It was discovered that the new satellite bias estimate resulted in near zero mean residuals with the shape of P2-P1 and L1-L2
observables being consistent with shapes from other satellites. Also, computed is a 10-day average of the estimated satellite
interfrequency bias Tgd, which turned out to be −19.13 ns. 相似文献
994.
995.
996.
Morgan T. Jones Deborah J. Hembury Martin R. Palmer Bill Tonge W. George Darling Susan C. Loughlin 《Bulletin of Volcanology》2011,73(3):207-222
The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the
island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering
fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We
examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the
initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles
arc. The silicate weathering may have consumed 1.3% of the early CO2 emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat
are a net sink for atmospheric CO2 due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as
a source or sink for atmospheric CO2 is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as
the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière
Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism.
This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s
inhabitants. 相似文献
997.
Matthew R. Patrick Tim Orr David Wilson David Dow Richard Freeman 《Bulletin of Volcanology》2011,73(6):639-653
In late 2007, a perched lava channel, built up to 45 m above the preexisting surface, developed during the ongoing eruption
near Pu‘u ‘Ō‘ō cone on Kīlauea Volcano’s east rift zone. The lava channel was segmented into four pools extending over a total
of 1.4 km. From late October to mid-December, a cyclic behavior, consisting of steady lava level rise terminated by vigorous
spattering and an abrupt drop in lava level, was commonly observed in pool 1. We use geologic observations, video, time-lapse
camera images, and seismicity to characterize and understand this cyclic behavior. Spattering episodes occurred at intervals
of 40–100 min during peak activity and involved small (5–10-m-high) fountains limited to the margins of the pool. Most spattering
episodes had fountains which migrated downchannel. Each spattering episode was associated with a rapid lava level drop of
about 1 m, which was concurrent with a conspicuous cigar-shaped tremor burst with peak frequencies of 4–5 Hz. We interpret
this cyclic behavior to be gas pistoning, and this is the first documented instance of gas pistoning in lava well away from
the deeper conduit. Our observations and data indicate that the gas pistoning was driven by gas accumulation beneath the visco-elastic
component of the surface crust, contrary to other studies which attribute similar behavior to the periodic rise of gas slugs.
The gas piston events typically had a gas mass of about 2,500 kg (similar to the explosions at Stromboli), with gas accumulation
and release rates of about 1.1 and 5.7 kg s−1, respectively. The time-averaged gas output rate of the gas pistoning events accounted for about 1–2% of the total gas output
rate of the east rift zone eruption. 相似文献
998.
999.
An unstructured mesh tidal model of the west coast of Britain, covering the Celtic Sea and Irish Sea is used to compare tidal distributions computed with finite element (FE) and finite volume (FV) models. Both models cover an identical region, use the same mesh, and have topography and tidal boundary forcing from a finite difference model that can reproduce the tides in the region. By this means, solutions from both models can be compared without any bias towards one model or another. Two-dimensional calculations show that for a given friction coefficient, there is more damping in the FV model than the FE model. As bottom friction coefficient is reduced, the two models show comparable changes in tidal distributions. In terms of mesh resolution, calculations show that for the M2 tide, the mesh is sufficiently fine to yield an accurate solution over the whole domain. However, in terms of higher harmonics of the tide, in particular the M6 component, its small-scale variability in near-shore regions which is comparable to the mesh of the model, suggests that the mesh resolution is insufficient in the near-coastal regions. Even with a finer mesh in these areas, without detailed bottom topography and a spatial varying friction depending on bed types and bed forms, which is not available, model skill would probably not be improved. In addition in the near-shore region, as shown in the literature, the solution is sensitive to the form of the wetting/drying algorithm used in the model. Calculations with a 3D version of the FV model show that for a given value of k, damping is reduced compared to the 2D version due to the differences in bed stress formulation, with the 3D model yielding an accurate tidal distribution over the region. 相似文献
1000.
Zhiguang Song Keith W. Jones Nebojsa Marinkovic Xian Ming Xiao Huan Feng Elli Tchouparova 《洁净——土壤、空气、水》2011,39(12):1041-1049
Dredging and remediation of contaminated Harbor sediments requires characterization of organic pollutants. In this paper, we apply a combination of Fourier transform IR attenuated total reflectance (FTIR‐ATR) and synchrotron FTIR techniques to the investigation of sediments and related materials from New York/New Jersey Harbor and other locations. The FTIR techniques give information on the functional groups of the compounds found in the sediments and make possible measurements with a spatial resolution of about 0.015 mm. Comparisons of natural organic materials namely, river and groundwater humic substances, recent marine and lacustrine sediments, and ancient sedimentary kerogen show that contaminated NY/NJ Harbor sediments display a strong and distinct absorption in their IR spectra at 2850–2950 cm?1 identified as a C? H stretching band, indicative of the presence of anthropogenic hydrocarbons. We suggest that the presence of this band could be used for rapid screening for the presence of contaminant organic compounds in sediments encountered in dredging operations and/or as an indicator for the efficacy of sediment decontamination technologies used for treatment of dredged material. 相似文献