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941.
942.
943.
944.
黑龙江省春季浅层(0~20cm)地温变化特征及预报 总被引:5,自引:4,他引:5
利用1981-2012年黑龙江省74个气象观测站的气温、0 cm、10 cm、20 cm地温春季(3-5月)逐日资料,分析了黑龙江省春季浅层地温、气温变化特征.结果表明:0 cm地温年际间波动大,全省平均1987年最低,2008年最高;全省变化存在明显的空间一致性;尽管气候变暖使1990年代以后春季0 cm地温偏低年出现相对减少,但是出现春季浅层地温偏低的年份比例仍超过三分之一,并具有南部、北部反向变化的特征,2005年以后南北差异有减小的趋势.各地3月份开始解冻,主要农区10 cm地温稳定通过6℃的日期主要集中在4月中下旬.以10 cm地温为预报量,利用黑龙江省逐日气温、20 cm地温资料建立春季浅层地温预报模型,回代和2013年预报检验平均绝对误差平均为1.05℃,绝对误差最大值为1.9℃,4月份的预报结果要好于3、5月,可以应用于业务指导. 相似文献
945.
Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock,
but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact,
and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced
ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration.
The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a
screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration,
namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in
two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were
analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness
of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes,
distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used
as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with
and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier
transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method
of blast-induced waves was considerably effective under certain design conditions. The design details for field application
have also been proposed. 相似文献
946.
应力波与可滑移岩石界面间的相互作用研究 总被引:10,自引:1,他引:10
研究了应力波与用节理刚度系数描述的线性滑移岩石界面间的相互作用,给出了其透、反射波幅的一般表达式。通过应力波垂直人射界面时的具体分析,反映出岩石界面的节理刚度对应力波传播的重要影响,并揭示了岩石界面对应力波的高频滤波作用。 相似文献
947.
水文气候因子模拟预测对气候变化研究、农业墒情预报、生态环境改善、水资源合理开发利用等具有一定参考意义。均生函数、BP神经网络及其结合改进方式在模拟预测中各有优点,被广泛应用,但仍有进一步改进空间。针对MGF、MGF-OSR、MGF-OSR-BP等方法粗选因子集、粗选集组合筛选、收敛适应性、精度控制等可改进空间,进一步发挥均生函数和BP神经网络优势,建立了MGF-BP-I模拟预测模型。利用MGF-OSR、MGF-OSR-BP、MGF-BP-I对科尔沁沙地区域平均年降水进行了模拟预测。结果表明,建模期MGF-OSR-BP、MGF-BP-I拟合效果均较好,MGF-BP-I建模阶段最优模式精度优于MGF-OSR-BP,MGF-BP-I整体同时最优模式结果也非常好。检验期,MGF-BP-I检验阶段最优及整体同时最优两种模式拟合效果最好,相比其他模式精度有所提高。MGF-BP-I考虑更加全面,充分发挥了均生函数和BP神经网络优势,精度远高于MGF-OSR和MGF-OSR-BP,MGF-BP-I整体同时最优模式更符合实际应用,效果理想,可用于水文气候因子模拟预测。 相似文献
948.
Rock fracturing by explosive energy: review of state-of-the-art 总被引:1,自引:0,他引:1
M. R. Saharan H. S. Mitri J. L. Jethwa 《Fragblast: International Journal for Blasting and Fragmentation》2006,10(1):61-81
A study of the dynamic rock fracture initiation and propagation due to explosive energy is presented through a detailed state-of-the-art review. Explosive energy dissipation in crushing and fracturing is examined and the various means to enhance the explosive energy utilization for dynamic rock fracturing are reviewed. The study highlights the need for a better understanding of the dynamic fracturing process particularly in the presence of in situ stresses in the rock mass. 相似文献
949.
The major obstacles for modelling flood processes in karst areas are a lack of understanding and model representations of
the distinctive features and processes associated with runoff generation and often a paucity of field data. In this study,
a distributed flood-modelling approach, WetSpa, is modified and applied to simulate the hydrological features and processes
in the karst Suoimuoi catchment in northwest Vietnam. With input of topography, land use and soil types in a GIS format, the
model is calibrated based on 15 months of hourly meteorological and hydrological data, and is used to simulate both fast surface
and conduit flows, and groundwater discharges from karst and non-karst aquifers. Considerable variability in the simulation
accuracy is found among storm events and within the catchment. The simulation results show that the model is able to represent
reasonably well the stormflows generated by rainfall events in the study catchment. 相似文献
950.