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The connection between avalanche dynamics and space physics has been studied for several years. In that context we recently suggested an avalanche model which explains the phenomena of reconnection. In this work the model is generalized to include the influence of an extremely strong perturbation, reflecting the effect of plasma storms originating from the sun. In addition, we allow for diffusion processes and show that the behavior changes with the onset of diffusion processes, rendering it quasi-periodic, along with the supression of small-size avalanches. 相似文献
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Some problems associated with past mining at a mine in the Witbank coalfield, South Africa 总被引：2，自引：0，他引：2
Mining in the Witbank Coalfield commenced at the turn of the century. Initially there was little environmental degradation
associated with mining activities; however, in the late 1930s and early 1940s a pillar-robbing programme commenced. At one
particular mine this has had marked effects on the environment. Primary effects include subsidence, the appearance of tension
cracks at the surface and crownhole development. Secondary effects include spontaneous combustion of the coal worked, as air
has been provided with ready access to the mine, accelerated subsidence due to the strength of many pillars being reduced
by burning, and a marked deterioration in groundwater quality in the area. Spoil heaps also form blemishes on the landscape.
These contain significant amounts of coal and have undergone spontaneous combustion. The deterioration in the water quality
has led to the decimation of vegetation in some areas and the eradication of aquatic flora and fauna in a nearby stream.
Received: 5 March 1997 · Accepted: 1 July 1997 相似文献
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Abrahamson and Dinniss [2000. Ball lightning caused by oxidation of nanoparticle networks from normal lightning strikes on soil. Nature 403, 519–521] proposed a theory of ball lighting in which silicon nanoparticles undergo slow oxidation and emit light. Paiva et al. [2007. Production of ball-lightning-like luminous balls by electrical discharges in silicon. Physical Review Letters 98, 048501] reported that an electric arc to silicon produced long-lasting luminous white spheres showing many characteristics of ball lightning. We show experimentally that these consist of burning molten silicon spheres with diameters in the 0.1–1 mm range. The evidence of our experiments leads us to propose that a subset of ball lightning events may consist of macro-scale molten spheres of burning metallic materials likely to be ejected from a conventional lightning strike to earth. 相似文献
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Southsea Looproad at Brymbo suffers large and varied settlements where the highway crosses a smouldering coal refuse bank. A sudden surge in combustion activity during 1991 resulted in considerable subsidence within the carriageway and posed recurring and persistent difficulties for road safety and highway maintenance. Initial investigations involved subsurface temperature measurements to delimit the hot spots and provide a basis for the design of remedial works. The aim of remediation was to extinguish the migrating fire in the outer loop area and to control the burning throughout the remaining areas. The principal strand of the remediation strategy involved excavating the burning coal refuse, cooling, mixing with pulverized fuel ash and compacting. Supplementary containment measures included limestone-filled cut-off trenches, cementitious grout curtains and impervious clay blankets. The works achieved the design objectives, however, small pockets of smouldering material remained within the inner loop. Subsequent monitoring of the site disclosed two markedly different patterns of temperature response on each side of the road. On the outer rim of the looproad temperature trends were steadily downwards in accordance with expectations and indeed reached ambient temperature within about one year. However, on the inside of the looproad seasonal surges in temperature have been recorded during winter months every year since the completion of the remedial works in 1993. The explanation for this unusual pattern of combustion activity is thought to be related to climatic effects and particularly the combined influence of rainfall, atmospheric pressure, air temperature and wind strength and direction. The relative contribution of these factors remains uncertain. Temperature monitoring continues in order to identify the eventual end of combustion activity and determine the appropriate time to complete reinstatement of the carriageway. 相似文献
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为了获取大气湍流和空间三维风场结构,利用3台同型号的测风激光雷达开展协同观测试验。（1）利用虚拟铁塔协同观测技术开展大气湍流探测,与香河102 m铁塔安装的三维超声风速仪观测结果做对比,32 m处高频（10 Hz）风速的相关系数高达0.92,平均误差为0.77 m/s,均方根误差为0.41 m/s;大气湍流强度（TKE）的相关系数高达0.99,平均误差为?0.02 m2/s2,均方根误差为0.08 m2/s2,并且协同观测的高频风速与三维超声风速仪的观测结果具有相同的频谱结构。（2）利用扫描协同观测技术开展三维风场探测,与铁塔上的常规测风设备相比,其90 m高度处的水平风速和风向的相关系数分别为0.92和0.93,平均误差为?0.41 m/s和0°,均方根误差为0.73 m/s和34°。相比于单台测风激光雷达,基于3台测风激光雷达协同观测技术具有一定的优势:不需要风场水平均匀的假设、探测精度更高等。但其对观测环境的要求较高:观测路径上不能有遮挡、观测必须协同等。在科研业务应用中,需要根据实际的观测需求合理制定观测方案。 相似文献
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Since 1986, Burning Man has evolved from an obscure bohemian San Francisco solstice celebration into the world's largest intentional community, anchored by annual burns on a playa in Nevada's Black Rock country. Participants embrace an ethos that radically challenges mainstream culture through Black Rock City's yearly (re)formation, negotiation, immolation, and deconstruction. Voicing curiosity, as humanists, in who we are, what we do, and why we do it, we examine rituals associated with this transitory yet international‐scale event. Such happenings imply a human need to seek clarity, dwell in close confines, and engage with a utopian desire for concerted communal participation. Yet, there exist historical‐cultural paradoxes associated with Burning Man, including steep entry barriers that reinforce an elite homogeneous population no longer representative of Burning Man's distinctive California roots. 相似文献
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This paper draws on research conducted with Aboriginal land managers across Northern Australia to show how and why payments for ecosystem service (PES) schemes should be framed around Indigenous rights to and relationships with their traditional estates. PES schemes offer opportunities to recognize and support Aboriginal communities' land and sea management knowledge and practices, and there is strong evidence that Indigenous communities are seeking to engage with such schemes. We focus on Aboriginal savanna landscape management, particularly traditional burning practices, to extend the ecosystem services framework to recognize Indigenous values and interactions with their lands as a critical service for Indigenous well-being. Drawing on case-study analysis of PES projects negotiated to support Aboriginal fire management programs across Northern Australia, we show how cultural ecosystem services can be applied to represent the active, dynamic and often interdependent relationships inherent in Indigenous human-environment relationships. 相似文献
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Prescribed fire in a Great Basin sagebrush ecosystem: Dynamics of soil extractable nitrogen and phosphorus 总被引：1，自引：0，他引：1
Pinyon and juniper have been expanding into sagebrush (Artemisia tridentata) ecosystems since settlement of the Great Basin around 1860. Herbaceous understory vegetation is eliminated as stand densities increase and the potential for catastrophic fires increases. Prescribed fire is increasingly used to remove trees and promote recovery of sagebrush ecosystems. We quantified the effects of prescribed fire, vegetation type, and time following fire on soil KCl extractable nitrogen and NaHCO3 extractable phosphorus in a pinyon–juniper woodland and its associated sagebrush ecosystem immediately before and for 4 years after a spring prescribed burn. Potassium chloride extractable NH4+ and total inorganic-N increased immediately following prescribed fire, and extractable NO3− decreased immediately after the burn. In the surface layer (top 8 cm), extractable NH4+ remained elevated compared to the control through year 2 after the burn. By the first fall post-burn extractable NO3− and total extractable inorganic-N increased and remained elevated over the control through year 3 after the burn in the surface layer. For the entire soil profile (52 cm), the burn had no effect on NH4+, and the effects on total extractable inorganic-N were no longer significant after year 1. However, NO3− remained elevated over the control through year 2 post-fire for the soil profile. Near surface NaHCO3 extractable ortho-P increased immediately following fire, and remained elevated through year 2 post-fire. No fire effects were observed for extractable ortho-P in deeper horizons. Our data show that plant available nitrogen can remain elevated for extended periods following prescribed fire. This can influence regrowth and seedling establishment of native plant species, invasion of exotic plant species and, ultimately, site recovery potential. 相似文献
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吉林省冬季燃煤民居室内CO污染监测分析 总被引：1，自引：0，他引：1
利用多功能无线电采集器在吉林省开展了冬季燃煤民居室内CO、CO2、气温自动观测和室内外对比观测试验,分析了CO和CO2浓度的变化特征及与用火规律、室内温度的关系。结果表明：吉林省冬季燃煤民居中普遍存在CO污染,60 %的民居出现浓度持续超过125mg·m-3的高污染;CO浓度的逐月变化与燃煤量有关,日变化与用火过程、燃烧阶段和燃烧状态有关;在不同季节、不同城市、不同民居、不同室温以及不同燃烧过程中,CO在烟气中所占的比例不同;在点火、持续燃烧、压炉子和熄火等不同燃烧阶段及旺火燃烧、急倒烟和慢倒烟等不同燃烧状态下,CO浓度的变化特征有显著差异。 相似文献
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