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911.
利用岩石声发射凯塞效应测定岩体地应力 总被引:4,自引:0,他引:4
将砂岩在整个变形阶段的声发射信号特征可划分为加载初期、压密阶段、裂纹稳定扩展阶段、裂纹非稳定扩展阶段、砂岩破坏阶段5部分。利用岩样声发射信号的特征,确定出岩石的凯塞效应点与其裂纹稳定扩展阶段的起始点相对应,并进一步得出岩石凯塞效应点的上限为裂纹稳定扩展阶段的终点,裂纹非稳定扩展阶段的起始点。凯塞效应点受岩样两端面的平行度、压机加载速率等有关,岩样端面不平整,在加载初期会有强烈的声发射信号;压机加载速率过大,声发射信号可能显示不出来或被后续更强的声发射信号所掩盖。计算出深度为670m处巷道周围天然应力3个主应力的大小和方向,与在现场用应力解除法和水压致裂法测得的天然应力相比,其数值基本一致,但方向存在一定的偏差。 相似文献
912.
当代摄影测量与遥感技术的迅速发展,已经步入大数据时代,如何对获得的海量数字影像的辐射质量进行评价是一个值得重视的问题。本文从信息量、清晰度、灰度分布3个方面选择了10个评价指标作为影像特征,利用支持向量机监督学习的方法对以资源三号为例的遥感影像的辐射质量进行评价及结果分析。试验结果表明,本文方法得到的评价结果与人工评价结果较为一致,准确度较高,并且自动化程度高,可应用于遥感影像的辐射质量评价。 相似文献
913.
Kangjoo Kim Hyun-Jung Kim Byoung-Young Choi Seok-Hwi Kim Ki-hoon Park Eungyu Park Dong-Chan Koh Seong-Taek Yun 《Applied Geochemistry》2008
Iron and Mn concentrations in fresh groundwaters of alluvial aquifers are generally high in reducing conditions reflecting low SO4 concentrations. The mass balance and isotopic approaches of this study demonstrate that reduction of SO4, supplied from agricultural activities such as fertilization and irrigation, is important in lowering Fe and Mn levels in alluvial groundwaters underneath a paddy field. This study was performed to investigate the processes regulating Fe and Mn levels in groundwaters of a point bar area, which has been intensively used for flood cultivation. Four multilevel-groundwater samplers were installed to examine the relationship between geology and the vertical changes in water chemistry. The results show that Fe and Mn levels are regulated by the presence of NO3 at shallow depths and by SO4 reduction at the greater depths. Isotopic and mass balance analyses revealed that NO3 and SO4 in groundwater are mostly supplied from the paddy field, suggesting that the Fe-and Mn-rich zone of the study area is confined by the agricultural activities. For this reason, the geologic conditions controlling the infiltration of agrochemicals are also important for the occurrence of Fe/Mn-rich groundwaters in the paddy field area. 相似文献
914.
A physically based distributed slope stability model derived from the integration of hydrologic analysis and slope stability analysis is presented for GIS based modeling on a catchment scale. The catchment is represented by a mesh of squares with vertical columns. The hydrologic model calculates subsurface flow and resulting pore-water pressure during rainfall in each cell for every time step. The slope stability module then calculates the stability of each cell for the changing water pressure scenario. There are very few input data requirements, which makes the model applicable to ungauged catchments, also where the record of the past landslides and associated rainfall are not available. The model was tested in Garjuwa catchment, Nepal where all landslide scars were documented. The model reproduces the observed distribution of landslide locations in a consistent way. Several model runs were conducted, increasing the intensity of rainfall to see corresponding increase in instability. The results show that there is a critical rainfall intensity for the catchment, beyond which increase in rainfall intensity does not increase instability significantly. 相似文献
915.
基于乌鲁木齐区域数值预报业务系统,运用MET检验工具,对2017年各季节DOGRAFSv1.0预报性能进行客观检验。结果表明:(1)2m温度日间预报温度整体偏低,夜间多数站点预报温度偏高;冬季预报温度偏高,其他三个季节温度预报整体偏低。10m风速冬季模拟性能最差,春季次之;所有季节风速预报均偏大。(2)夏季、秋季高空温度预报误差小,在3.0℃以内,冬季误差最大,温度预报整体呈冷偏差;不同季节高空位势高度随高度增加误差增大,误差约在6.5~12.0gpm,预报高度比实际高度偏低;不同季节高空U、V风随高度增加误差先增大后减小,均方根误差分别为2.4~6.2m/s和1.8~5.2m/s,U风预报整体比实况偏小,V风预报整体比实况偏大。(3)冬季大阈值降水漏报率较高,12.1mm阈值降水Bias评分仅为0.2,秋季大阈值降水空报率较高,12.1mm阈值降水Bias评分在2.0以上,夏季空、漏报率较低;在新疆地区,四个时段中14~20 BJT 、20~次日02 BJT空报站点数多于漏报,14~20 BJT空报率最高,02~08 BJT漏报率最高,08~14BJT晴雨预报以漏报为主;日间Ts评分高于夜间。 相似文献
916.
Yoo-Jun Kim Byung-Gon Kim Jae-Kwan Shim Byoung-Choel Choi 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):499-510
The Yeongdong region of the Korean Peninsula is vulnerable to high-impact weather events, because of its complicated geographical characteristics and East Sea effect, such that heavy snowfall episodes have frequently occurred in winter. Snow crystal play an important role in cloud and precipitation physics because it is an essential element for improvement of numerical model, and remote sensing retrieval such as radar and satellite. In this study, the high-temporal resolution (3-hourly) dataset of radiosonde soundings and snow particle photographs during the intensive observation period for 2013–2016 has been used to understand characteristics of snow particles for the different meteorological conditions in the Yeongdong region. We also attempt to simulate two episodes that occurred on 23–24 February and 13–14 December 2016; one has a single-layered cloud and the other has two-layered cloud structure. This study demonstrates that the rimed particles in the first period tend to shift to aggregates of dendrites with the decrease of 850-hPa temperature. In general, the low-level clouds in the Yeongdong region are observed along with the distinctive wind shear and strong inversion in equivalent potential temperature around 2 ~ 3 km above the sea level. The simulation successfully represents the variations of the characteristics of snow particles as well as different cloud structure for both episodes. The observation and model simulations clearly suggest that snow particles primarily depend on the 850-hPa temperature. 相似文献
917.
Wonbae Jeon Yunsoo Choi Anirban Roy Shuai Pan Daniel Price Mi-Kyoung Hwang Kyu Rang Kim Inbo Oh 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):33-41
Oak pollen concentrations over the Houston-Galveston-Brazoria (HGB) area in southeastern Texas were modeled and evaluated against in-situ data. We modified the Community Multi-scale Air Quality (CMAQ) model to include oak pollen emission, dispersion, and deposition. The Oak Pollen Emission Model (OPEM) calculated gridded oak pollen emissions, which are based on a parameterized equation considering a plant-specific factor (C e ), surface characteristics, and meteorology. The simulation period was chosen to be February 21 to April 30 in the spring of 2010, when the observed monthly mean oak pollen concentrations were the highest in six years (2009-2014). The results indicated C e and meteorology played an important role in the calculation of oak pollen emissions. While C e was critical in determining the magnitude of oak pollen emissions, meteorology determined their variability. In particular, the contribution of the meteorology to the variation in oak pollen emissions increased with the oak pollen emission rate. The evaluation results using in-situ surface data revealed that the model underestimated pollen concentrations and was unable to accurately reproduce the peak pollen episodes. The model error was likely due to uncertainty in climatology-based C e used for the estimation of oak pollen emissions and inaccuracy in the wind fields from the Weather Research and Forecast (WRF) model. 相似文献
918.
为提高探空气球的施放高度,利用克拉玛依国家基本气象站2011年以来的观测数据作为研究对象,选取净举力、天气现象、风向、风速、温度、气压、湿度、降水量8个影响因子,突破以往定性的研究模式,首次从定量的角度通过大量实验数据借助SPSS软件构建了多元线性回归模型,比较深入地研究了探空高度与净举力及常规可控气象要素之间的关系,对该模型进行了检验优化,确定了最优的回归模型,并对模型进行了预测验证。研究结果表明,该模型预测效果良好,能有效地应用到克拉玛依探空气象的实际观测工作中。根据上述研究结果,总结出了不同天气下净举力的选取范围,从而为克拉玛依探空提供具有实际可操作性的作业指导。 相似文献
919.
降雨量的测量,目前业务上应用较为广泛的是翻斗式雨量计,它只能测降雨,对于冰雹、降雪等固态降水的测量采用人工观测为主,称重式雨量计与翻斗式雨量计相比,其优势在于能实现所有类型降水的全天候自动化观测。本研究随机选择了一天无降水数据确定了滤波参数Q和R(过程噪声方差和观测噪声方差),根据确定的滤波参数,随机选择了无降水(2016年4月3日)和有降水(2015年7月21日、2015年8月7日)日采用卡尔曼滤波,并结合翻斗雨量传感器数据进行验证,结果表明,本研究确定的滤波参数采用卡尔曼滤波后能够有效去除称重雨量中的噪声,使滤波后的曲线变得平稳光滑,减小了数据的抖动频率和误差。 相似文献
920.