Experimental investigation of hydrate formation in water-dominated pipeline and its influential factors     

Li Huang  Jia-le Kang  Xiao-dong Shen  Jian-ye Sun  Qing-guo Meng  Qiang Chen  Gao-wei Hu  Chang-ling Liu  Neng-you Wu 《China Geology》2022,5(2):310-321

Blockage in water-dominated flow pipelines due to hydrate reformation has been suggested as a potential safety issue during the hydrate production. In this work, flow velocity-dependent hydrate formation features are investigated in a fluid circulation system with a total length of 39 m. A 9-m section pipe is transparent consisted of two complete rectangular loops. By means of pressurization with gas-saturated water, the system can gradually reach the equilibrium conditions. The result shows that the hydrates are delayed to appear as floccules or thin films covering the methane bubbles. When the circulation velocity is below 750 rpm, hydrate is finally deposited as a “hydrate bed” at upmost of inner wall, narrowing the flow channel of the pipeline. Nevertheless, no plugging is observed during all the experimental runs. The five stages of hydrate deposition are proposed based on the experimental results. It is also revealed that a higher driving pressure is needed at a lower flow rate. The driving force of hydrate formation from gas and water obtained by melting hydrate is higher than that from fresh water with no previous hydrate history. The authors hope that this work will be beneficial for the flow assurance of the following oceanic field hydrate recovery trials.©2022 China Geology Editorial Office.  相似文献   

基于三维激光扫描技术的岩质边坡泥化夹层空间分布和几何形态     

刘文连  张家明  王志强  徐则民 《吉林大学学报(地球科学版)》2021,51(4):1139-1151

为了定量研究泥化夹层的空间分布和几何形态,以云南省玉溪市生活垃圾焚烧发电厂高边坡局部开挖剖面为对象,利用徕卡ScanStation C10三维激光扫描仪和瑞典ROMER RA-7520-2六轴关节臂三维测量仪进行扫描,得到了开挖剖面和泥化夹层的原始点云数据;然后采用Cyclone和Geomagic Wrap软件对点云数据进行一系列处理,分析了泥化夹层的三维空间分布、层面产状、间距、层面粗糙度和几何形态。结果表明：大部分泥化夹层横向分布于整个扫描剖面,少数呈局部分布;泥化夹层的平均倾向为196.41°±5.51°,平均倾角为22.27°±2.23°,间距在3.7~49.1 cm之间,平均值为（20.4±12.0）cm;不同层位及同一层位不同横向位置的泥化夹层厚度都不等,最厚约20 mm,最薄小于1 mm;泥化夹层顶面局部典型区域的平面拟合偏差在-22.4~32.5 mm之间,沿夹层倾向的粗糙度系数在5.67~16.77之间,平均值为10.11±3.25;泥化夹层的表面积与体积之比在5.14~5.86 cm^-1之间。运用三维激光扫描技术研究泥化夹层的空间分布和几何形态是可行的。玉溪市生活垃圾焚烧发电厂高边坡的泥化夹层具有宏观整体上相对平直、相互近似平行、非等距分布、间距小、层数多、厚度薄,细观上顶面粗糙底面相对光滑、三维形态复杂的特点。  相似文献   

基于区域多次回波点密度分析的城区LiDAR建筑物提取     

李乐林  江万寿  郭程方 《国土资源遥感》2015,(2):29-35

以正确提取城区Li DAR点云中建筑物为目标,综合利用不同类别目标点云的回波特征以及地形信息,提出了一种基于区域多次回波密度分析的Li DAR点云建筑物提取方法。首先,将点云构建不规则三角网(triangulated irregular network,TIN),获取封闭的等高线;然后,利用等高线间的拓扑关系得到等高线族区域;最后,统计每一区域的多次回波点云密度信息,通过建筑物和树木区域多次回波点云在区域密度上的巨大差异来识别建筑物点云和树木点云。研究结果表明:该方法既充分利用了建筑物表面与植被间多次回波特性的差异,又不否定建筑物边缘同样存在多次回波的现象;通过封闭的等高线自适应地检测出地物目标的轮廓,弥补了传统Li DAR建筑物提取方法的不足;该方法能够较其他方法更准确地提取建筑物。  相似文献   

融合光谱-空间信息的高光谱遥感影像增量分类算法   总被引：1，自引：1，他引：0  

王俊淑  江南  张国明  李杨  吕恒 《测绘学报》2015,44(9):1003-1013

提出了一种融合光谱和空间结构信息的高光谱遥感影像增量分类算法INC_SPEC_MPext。通过主成分分析(PCA)提取高光谱影像的若干主成分,利用数学形态学提取各主分量影像对应的形态学剖面(MP),再将所有主分量影像的形态学剖面归并联结,组成扩展的形态学剖面(MPext)。将MPext与光谱信息相结合以增加知识,最大限度地挖掘未标记样本的有用信息,优化分类器的学习能力。不断从分类器对未标记样本的预测结果中甄选置信度高的样本加入训练集,并迭代地利用扩大的训练集进行分类器构建和样本预测。以不同地表覆盖类型的AVIRIS Indian Pines和Hyperion EO-1Botswana作为测试数据,分别与基于光谱、MPext、光谱和MPext融合的分类方法进行比对。试验结果表明,在训练样本数量有限情况下,INC_SPEC_MPext算法在降低分类成本的同时,分类精度和Kappa系数都有不同程度的提高。  相似文献   

我国瓯江口和珠江口凤鲚洄游模式和生境利用研究     

姜涛  刘洪波  黄洪辉  杨健 《海洋学报(英文版)》2019,38(8):35-40

Habitat use of the tapertail anchovy(Coilia mystus Linnaeus, 1758) from the Oujiang River Estuary and the Zhujiang(Pearl) River Estuary was studied by examining the environmental signatures of Sr and Ca in otoliths using electron probe microanalysis. Individuals from the Oujiang River had higher and varied Sr:Ca ratios(expressed as(Sr:Ca)×1 000, 3.83–13.0 average) in the otolith core regions, suggesting that they were born in brackish or sea waters, and that a freshwater habitat might not be necessary for egg hatching and larval growth.While, individuals from the Zhujiang River had lower Sr:Ca ratios(0.39–2.51 average) in the core regions,suggesting a freshwater origin. After hatching, anchovies from the Zhujiang River migrate downstream to the river estuary close to brackish water. Our results demonstrated varied habitat use for spawning during stages of early life history between the two populations, and suggested that such variations are promoting diversity of life history strategies of this species.  相似文献   

Basin‐scale methods for predicting salmonid spawning habitat via grain size and riffle spacing,tested in a California coastal drainage          下载免费PDF全文

Allison M. Pfeiffer  Noah J. Finnegan 《地球表面变化过程与地形》2017,42(6):941-955

Basin‐scale predictive geomorphic models for river characteristics, particularly grain size, can aid in salmonid habitat identification. However, these basin‐scale methods are largely untested with actual habitat usage data. Here, we develop and test an approach for predicting grain size distributions from high resolution LiDAR (Light Detection and Ranging)‐derived topographic data for a 77 km² watershed along the central California Coast. This approach improves on previous efforts in that it predicts the full grain size distribution and incorporates an empirically calibrated shear stress partitioning factor. The predicted grain size distributions are used to calculate the fraction of the bed area movable by spawning fish. We then compare the ‘movable fraction’ with 7 years of observed spawning data. We find that predicted movable fraction explains the paucity of spawning in the upper reaches of the study drainage, but does not explain variation along the mainstem. In search of another morphologic characteristic that may help explain the variation within the mainstem, we measure riffle density, a proxy for physical habitat complexity. We find that field surveys of riffle density explain 64% of the variation in spawning in these mainstem reaches, suggesting that within reaches of appropriate sized gravel, spawning density is related to riffle density. Because riffle density varies systematically with channel width, predicting riffle spacing is straightforward with LiDAR data. Taken together, these findings demonstrate the efficacy of basin‐scale spawning habitat predictions made using high‐resolution digital elevation models. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Predicting gravel bed river response to environmental change: the strengths and limitations of a regime‐based approach          下载免费PDF全文

Brett Eaton  Robert Millar 《地球表面变化过程与地形》2017,42(6):994-1008

Rivers respond to environmental changes such as climate shifts, land use changes and the construction of hydro‐power dams in a variety of ways. Often there are multiple potential responses to any given change. Traditionally, potential stream channel response has been assessed using simple, qualitative frameworks based largely on professional judgement and field experience, or using some form of regime theory. Regime theory represents an attempt to use a physically based approach to predict the configuration of stable channels that can transport the imposed sediment supply with the available discharge. We review the development of regime theory, and then present a specific regime model that we have created as a stand‐alone computer program, called the UBC Regime Model (UBCRM). UBCRM differs from other regime models in that it constrains its predictions using a bank stability criterion, as well as a pattern stability criterion; it predicts both the stable channel cross‐sectional dimensions as well as the number of anabranches that the stream must have in order to establish a stable channel pattern. UBCRM also differs from other models in that it can be used in a stochastic modelling mode that translates uncertainty in the input variables into uncertainty in the predicted channel characteristics. However, since regime models are fundamentally based on the concept of grade, there are circumstances in which the model does not perform well. We explore the strengths and weaknesses of the UBCRM in this paper, and we attempt to illustrate how the UBCRM can be used to augment the existing qualitative frameworks, and to help guide professionals in their assessments. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Morphological and sedimentary features of sandy-muddy transitional beaches in estuaries and bays along mesotidal to macrotidal coasts     

Shaohua Zhao  Hongshuai Qi  Feng Cai  Jun Zhu  Xiang Zhou  Gang Lei 《地球表面变化过程与地形》2020,45(7):1660-1676

Sandy-muddy transitional beaches (SMT-Beaches), representing the transition from sandy beaches to tidal mudflats, should theoretically develop very different morphological and sedimentological characteristics in river estuaries and in semi-enclosed bays due to their contrasting dynamic sedimentary environments. Evidence, however, is rare in the scientific literature. To reveal these morphological and sedimentary differences, the sand–mud transition (SMT) boundary distribution, beach profiles, and surface and downcore sediment grain-size compositions of 27 SMT-Beaches located along mesotidal to macrotidal coasts of the western Taiwan Strait, southeastern China, were investigated. The results show that typical estuarine SMT-Beaches are mainly characterized by an ambiguous SMT, a long distance between the SMT and the coastline (31–302 m), lower SMT and inflection point altitudes (average –0.76 m and –0.04 m), and lower upper beach gradients (~0.068) with fine sand. Estuarine SMT-Beach sediments display clear interbedded mud and sand layers, implying potential SMT migrations over various timescales. By contrast, typical bay SMT-Beaches are characterized by distinct SMT, a short distance between the SMT and the coastline (11–52 m), higher SMT and inflection point altitudes (~0.24 m and ~0.35 m), and narrower upper beaches with higher gradients (~0.095) and coarse sand. Bay SMT-Beaches present relatively stable sedimentary sequences and a narrow gravel belt surrounding the inflection point and/or SMT. These morphological and sedimentary differences between the two SMT-Beach types are initially constrained by sediment supply and transport and are further affected by tide conditions and wave climate. Sediment supply and transport predominately control the sediment structures, while the tidal range strongly influences spatial variations in SMT distances. Wave climate normally drives SMT altitude variations. This study highlights the morphological and sedimentary differences in SMT-Beaches in estuaries and bays, providing important knowledge for further revealing their morphodynamic processes and potential future nourishment. © 2020 John Wiley & Sons, Ltd.  相似文献   

The influence of channel morphology on bedload path lengths: Insights from a survival process model     

Conor McDowell  Marwan A. Hassan 《地球表面变化过程与地形》2020,45(12):2982-2997

Tracer studies are a commonly used tool to develop and test Einstein-type stochastic bedload transport models. The movements of these tracers are controlled by many factors including grain characteristics, hydrologic forcing, and channel morphology. Although the influence of these sediment storage zones related to morphological features (e.g., bars, pools, riffles) have long been observed to “trap” bedload particles in transport, this influence has not been adequately quantified. In this paper we explore the influence of channel morphology on particle travel distances through the development of a Bayesian survival process model. This model simulates particle path length distributions using a location-specific “trapping probability” parameter (p_i ), which is estimated using the starting and ending locations of bedload tracers. We test this model using a field tracer study from Halfmoon Creek, Colorado. We find that (1) the model is able to adequately recreate the observed multi-modal path length distributions, (2) particles tend to accumulate in trapping zones, especially during large floods, and (3) particles entrained near a trapping zone will travel a shorter distance than one that is further away. Particle starting positions can affect path lengths by as much as a factor of two, which we confirm by modelling “starting-location-specific” path length probability distributions. This study highlights the importance of considering both tracer locations and channel topography in examinations of field tracer studies. © 2020 John Wiley & Sons, Ltd.  相似文献   

遥感影像线状地物智能化提取算法研究     

张金梅 《测绘与空间地理信息》2020,(2):169-171

对遥感影像线状地物的提取进行了深入研究分析,分别采用Snakes模型、二值形态学和面向对象处理等3种算法智能化提取线状地物。通过实验验证,3种智能算法都是行之有效的,且Snakes模型在各种线状地物提取上表现稳定,而二值形态学和面向对象算法在部分线状地物提取上表现较为突出,整体稳定性却不如Snakes模型。  相似文献