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排序方式： 共有223条查询结果，搜索用时 593 毫秒
101.
102.
针对地震行业网络运行的特殊需求,以目前运行的山西地震信息网络系统为研究平台,对其可能面临的安全风险进行分析,总结归纳网络安全隐患,结合实际运行经验与网络安全技术,给出进一步做好网络安全风险防范的建议,并针对一些常见网络突发事件,介绍山西地震信息网络的应对预案与流程. 相似文献
103.
《Quaternary Research》2011,76(3):393-396
A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500 km2 and held a volume of ~ 3000 km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~ 13 cal ka BP inferred from Arctic Ocean sediments. 相似文献
104.
Kang Ping Chen 《International Journal of Coal Geology》2011,87(2):72-79
An instantaneous coal outburst is a sudden and violent simultaneous ejection of large amounts of coal and gas (methane, carbon dioxide) from the working coalface during underground mining. The occurrence of such an outburst usually leads to a gas explosion and pollution of the mine. Despite extensive research efforts in the past 150 years, the physical mechanisms causing coal outbursts are still poorly understood. Here we present a new model combining fracture mechanics, gas dynamics and rock mechanics to elucidate the physical mechanisms leading to instantaneous outbursts. This model suggests a domino effect that leads to a catastrophic failure of the coal and an instantaneous outburst. The model identifies a critical condition for the onset of instantaneous outbursts, and it successfully predicts all of the observed phenomena preceding outbursts, most of which are explained for the first time. The model also predicts a fracture aperture size effect which is confirmed by the existing observation-based fracture classification scheme used to assess outburst proneness. 相似文献
105.
长白山天池火山是目前最具潜在喷发危险的活火山。依据长白山天池火山的最新监测研究成果,结合地形地貌、水文流域特点及天池火山历史喷发类型,重点分析了长白山天池火山未来喷发时发生溃湖洪水的危险性。利用相关的水动力学公式,建立了溃口规模和洪水湿周、流量和流速的内在关系。详细分析溃湖洪峰在下游二道白河镇、白山水电站、红石水电站等关键位置的最大流量及流速。结果表明,若天池火山湖水溃泄一半即10亿m3时,距火山口50km处的二道白河镇瞬时洪水流速达84 904m3/s,该镇将全部被淹没。下游的白山水库、丰满水库将分别受到流量23 560m3/s和1 505m3/s洪水的冲击,水库安全受到严重威胁。 相似文献
106.
Valentina Krysanova Michel Wortmann Tobias Bolch Bruno Merz Doris Duethmann Judith Walter 《水文科学杂志》2013,58(4):566-590
AbstractClimate variability and change play a crucial role in the vulnerable system of the Aksu River basin located in Kyrgyzstan and northwest China, providing precious water resources for the intense oasis agriculture of the Xinjiang Province (China). Ubiquitous warming and increase in precipitation (in the lower part of the basin) have been detected. Glaciers in the region are retreating. Seasonal trends in river discharge show an increase. A clear link could be demonstrated between daily temperature and lagged river discharge at two headwater stations in summer. However, the correlation breaks over short periods in the end of summer or beginning of autumn at the Xiehela station, when the high (over 95th percentile) flow peaks caused by the glacier lake outburst floods of the Merzbacher Lake occur. This feature is a challenge for the climate impact assessment in the region, as these regular outbursts have to be represented in the projections for the future as well.
Editor D. Koutsoyiannis 相似文献
107.
An assessment of conditions before and after the 1998 Tam Pokhari outburst in the Nepal Himalaya and an evaluation of the future outburst hazard 
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下载免费PDF全文 Damodar Lamsal Takanobu Sawagaki Teiji Watanabe Alton C. Byers Daene C. McKinney 《水文研究》2016,30(5):676-691
On 3 September 1998, a glacial lake outburst flood (GLOF) that originated from Tam Pokhari occurred in the Hinku valley of the eastern Nepal Himalaya. This study analyses the lake's geomorphic and hydrologic conditions prior to the outburst, and evaluates the conditions that could contribute to a future flood through photogrammetric techniques. We processed high‐resolution Corona KH‐4A (2.7 m) and ALOS PRISM (2.5 m) stereo‐images taken before and after the GLOF event, and produced detailed topographic maps (2‐m contour interval) and DEMs (5 m × 5 m). We (re‐) constructed lake water surfaces before (4410 ± 5 m) and after (4356 ± 5 m) the outburst, and reliably estimated the lake water surface lowering (54 ± 5 m) and the water volume released (19.5 ± 2.2 × 106 m3) from the lake, showing good agreement with the results obtained from ground‐based measurements. The most relevant conditions that may have influenced the catastrophic drainage of Tam Pokhari in 1998 include the presence of: (i) a narrow (75 ± 6 m), steep (up to 50°) and high (120 ± 5 m) moraine dam; (ii) high lake level (8 ± 5 m of freeboard) and (iii) a steep overhanging glacier (>40°). The lake outburst substantially altered the immediate area, creating a low and wide (>500 m) outwash plain below the lake, a wide lake outlet channel (~50 m) and a gentle channel slope (~3–5°). Our new data suggest that the likelihood of a future lake outburst is low. Our results demonstrate that the datasets produced by photogrammetric techniques provide an excellent representation of micro‐landform features on moraine dams, lake water surfaces and the changes in both over time, thereby allowing highly accurate pre‐ and post‐GLOF (volumetric) change analysis of glacial lakes. Furthermore, it enables precise measurement of several predictive variables of GLOFs that can be useful for identifying potentially dangerous glacial lakes or prioritizing them for detailed field investigations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
108.
矿井巷道在穿越含瓦斯断层或揭煤掘进过程中常常遇到前方岩柱保护厚度与延期突出问题。为了探索岩柱防突厚 度与时间的非线性耦合关系,应用RLW-2000型岩石三轴流变仪,对含煤岩系中的砂质泥岩、砂岩和泥岩进行了分级加载条件下的单轴压缩蠕变试验。通过对经典流变组合模型的分析及Matlab最小二乘迭代法的拟合,建立了改进的的七元件非线性黏弹塑性本构模型,并建立了基于岩体流变性的岩柱临界安全厚度的计算模型。豫西大平煤矿实例计算表明,埋深612 m的泥岩巷道,防突岩柱使用年限在10、20、30 a时相应的保护厚度分别为8.73、23.56、39.41 m;理论安全岩柱厚度与该矿“10 ? 20”瓦斯突出案例较为吻合,计算模型对同类工程具有一定的借鉴意义。 相似文献
109.
西藏喜马拉雅山地区冰湖溃决的预测模型及其应用研究 总被引：2，自引：1，他引：1
以西藏喜马拉雅山地区的冰湖为研究对象,基于现有的冰湖溃决预测方法,提出了建立冰湖溃决预测方法的关键点,即选取的指标必须能够体现冰湖的动态变化特征.在定量分析的建模过程中应该采用不确定性的数学理论,对于冰湖溃决可能性的等级划分需要进行合理性及实用性验证.选取坝顶宽度、湖水面距坝顶高度与坝高之比、冰湖面积和补给冰川面积为预测指标,通过对西藏喜马拉雅山地区29个冰湖样本进行逻辑回归分析,建立了冰湖溃决的预测模型,并用所有样本进行了交叉验证.结果表明：该模型能够在分类应用中取得较好效果,根据溃决冰湖累积百分数随冰湖溃决可能性大小的变化曲线,将冰湖溃决的可能性划分为四个等级.以黄湖为例,把湖水面距坝顶高度与坝高之比作为冰湖溃决的诱变指标,分析了冰湖溃决可能性大小的变化规律.结合现有的冰湖溃决预测的定性方法,讨论了所建立的冰湖溃决预测模型的优点和缺点. 相似文献
110.
煤与瓦斯突出过程中的瓦斯压力效应 总被引：1，自引：0，他引：1
为探讨煤与瓦斯突出过程中的瓦斯压力效应,利用自行研制的煤岩瓦斯动力灾害模拟试验系统和配比而成的中硬度的大型煤样,在煤样的含水率、配比方案、煤样成型压力等参数均恒定的条件下,恒定3种轴向载荷时,开展了5种不同瓦斯压力梯度的煤与瓦斯突出的相似模拟实验。实验表明,煤与瓦斯相对突出强度存在一个瓦斯压力阈值,超过此阈值时,随着瓦斯压力的增大则相对突出强度大大增强,且相对强度与瓦斯压力呈现正指数的关系;瓦斯压力作为突出发生的动力并对突出煤粉有一定的粉碎和搬运作用,可形成腹大口小的倒梨形突出孔洞;轴向应力对中硬度的含瓦斯煤岩体的突出具有正作用。 相似文献