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81.
为了研究垂直上升管中油气水三相流流动特性,本文利用纵向多极阵列电导式传感器(VMEA)和阵列电导探针组合测量方法在内径为125 mm多相流流动环中采集了油气水三相流电导波动信号,在定义6种油气水三相流流型基础上,绘制了4种油水混合液量下油气水三相流流型转换图,分析了含油率对流型转化及气相流速对油水相态逆转的影响.对水为连续相的5种流型VMEA传感器波动信号进行了多尺度熵分析,研究结果表明:含油率增加可使水包油段塞流在较低气相表观速度下产生;较低流速下的油水相态逆转可发生在油液比为0.9左右,气相流速增加使得逆转点向含油率低的方向偏移;多尺度熵细节可以刻画油气水三相流非线性动力学特性,而低尺度的多尺度熵变化率敏感地反映流型转变,是划分油气水三相流流型的有效准则.多尺度熵有助于理解油气水三相流流型非线性动力学特征. 相似文献
82.
Changes in channel character along a small river in the Scottish Highlands are described using measurements in seven reaches over a 3 km length with no significant tributaries but a decline in slope from 0.02 to 0.00015 because of local baselevel control. This decline in slope is associated with rapid downstream fining of the gravel bed followed by an abrupt transition to a sand bed. The channel pattern alters progressively rather than abruptly, in the sequence (1) near-braided, (2) meandering with active point-bar chutes, (3) meandering with active outer-bank talweg, (4) stable equiwidth sinuous. The changes in channel pattern and hydraulic geometry are predicted better by rational approaches based on critical shear stress or other physical concepts than by purely empirical discriminant or trend equations. Measurements in five reaches confirm a downstream decrease in shear stress and the amount and calibre of bedload. It is argued that the downstream changes in channel character in this stream are induced by profile concavity inherited from deglacial conditions, are typical of many streams in mountainous areas and can be understood in terms of slope-induced changes in hydraulic properties. 相似文献
83.
Application of Markovian models for non-ergodic and non-stationary earthquake times series for the identification of seismic patterns and future projections* 下载免费PDF全文
Hakan Karaca 《地震科学(英文版)》2020,33(2):98-106
The current earthquake forecast algorithms are not free of shortcomings due to inherent limitations. Especially, the requirement of stationarity in the evaluation of earthquake time series as a prerequisite, significantly limits the use of forecast algorithms to areas where stationary data is not available. Another shortcoming of forecast algorithms is the ergodicity assumption, which states that certain characteristics of seismicity are spatially invariant. In this study, a new earthquake forecast approach is introduced for the locations where stationary data are not available. For this purpose, the spatial activity rate density for each spatial unit is evaluated as a parameter of a Markov chain. The temporal pattern is identified by setting the states at certain spatial activity rate densities. By using the transition patterns between the states, 1- and 5-year forecasts were computed. The method is suggested as an alternative and complementary to the existing methods by proposing a solution to the issues of ergodicity and stationarity assumptions at the same time. 相似文献
84.
RIVER PATTERNS AND SPATIAL AND TEMPORAL TRANSFORMATION MODES 总被引:3,自引:0,他引:3
1 INTRODUCTIONThe river pattCths and transfo~ion of the pattenes are of great significance for flood control andmanagement of navigation system. Vallous spatial and temporal modes have been reported in theprevious stUdies. These modes depend on certain controlling factors and occur with different frequencies.These factors are related to modem fluvial processes and ancient sedimentary consequences. T'hedifferent river patterns, depending on the factors, can be either observed in nature or… 相似文献
85.
赵和云 《地震学报(英文版)》1994,7(3):465-474
ThepatterncharacteristicsofthetendencyvariationsofearthresistivityanditsrelationtoearthquakesHe-YunZHAO(赵和云)(EarthquakeResear... 相似文献
86.
The vertical position of the streambed–water boundary fluctuates during the course of sediment transport episodes, due to particle entrainment/deposition and bedform migration, amongst other hydraulic and bedload mechanisms. These vertical oscillations define a topmost stratum of the streambed (i.e. the ‘active layer or active depth’), which usually represents the main source of particles entrained during long and high-magnitude bedload transport episodes. The vertical extent of this layer is hence a capital parameter for the quantification of bedload volumes and a major driver of stream ecology in gravel-bed rivers. However, knowledge on how the active depth scales to flow strength and the nature of the different controls on the relation between the flow strength and the active depth is still scarce. In this paper we present a meta-analysis over active depth data coming from ~130 transport episodes extracted from a series of published field studies. We also incorporate our own field data for the rivers Ebro and Muga (unpublished), both in the Iberian Peninsula. We explore the database searching for the influence of flow strength, grain size, streambed mobility and channel morphology on the vertical extent of the active layer. A multivariate statistical analysis (stepwise multiple regression) confirms that the set of selected variables explains a significant amount of variance in the compiled variables. The analysis shows a positive scaling between active depth and flow strength. We have also identified some links between the active depth and particle travel distances. However, these relations are also largely modulated by other fluvial drivers, such as the grain size of the bed surface and the dominant channel macro-bedforms, with remarkable differences between plane-bed, step-pool and riffle-pool channels. © 2020 John Wiley & Sons, Ltd. 相似文献
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本在原有单项预报指标的基础上,研究西地区(N23°48′-26°20′;E97°00′-99°30′)M≥5.0级的地震。 相似文献
90.
Peijian Shi Jie Liu Zhen Yang Agricultural College Jiangxi Agricultural University Nanchang China China Earthquake Networks Center Beijing China 《地震学报(英文版)》2009,(3):231-237
For exploring the aftershock occurrence process of the 2008 Wenchuan strong earthquake, the spatio-temporal point pattern analysis method is employed to study the sequences of aftershocks with magnitude M≥4.0, M≥4.5, and M≥5.0. It is found that these data exhibit the spatio-temporal clustering on a certain distance scale and on a certain time scale. In particular, the space-time interaction obviously strengthens when the distance is less than 60 km and the time is less than 260 h for the first two aftershoc... 相似文献