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1.
明确裂隙间的相交关系,去除那些对流体流动与溶质运移无贡献的、与其他裂隙不联通的裂隙,能够大大提高裂隙中流体流动和溶质运移数值模拟的效率.提出一种基于空间索引的随机分布三维裂隙网络中裂隙对逐步相交判断的方法.通过数值模拟试验比较了该方法与传统的穷举法,结果表明,该方法速度快、成本低,大大减少了裂隙岩体渗流计算量,缩短了裂隙岩体流体渗流和溶质运移数值模拟计算时间. 相似文献
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本文介绍了裂隙岩体立方定理的应用及演化,裂隙岩体渗流应力耦合模型研究,裂隙岩体溶质运移研究。综述了国内外关于裂隙岩体的渗流、水力耦合、溶质运移的试验及理论研究。通过分析表明,立方定理等理论研究当前仍具有不可靠性,在未来的研究中,需要通过物理模型试验对这些理论进一步修正,在建立物模试验研究系统时,可采用粒子追踪技术进行传质研究,建立裂隙网络模型与渗流传质特性的定量评估方法,并应用于实际工程中去。 相似文献
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基于离散裂隙网络模型和裂隙介质管道流模型,在室内建立一套裂隙介质管道网络试验装置,并开展裂隙渗流和溶质运移试验.结果表明,在相同定水头的饱和渗流条件下,不同几何参数组成的裂隙网络的渗流流量及溶质通量存在较大差异,表现出流量和溶质运移通量与裂隙管网物理模型的有效空隙率、裂隙密度、裂隙产状、进出口数量等均存在非常显著的相关性.经进一步回归分析获知,流量与有效空隙率及裂隙密度、溶质通量与流量及裂隙密度之间皆存在较好的统计关系. 相似文献
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1,序言地下水对岩体稳定性有着重要影响,已引起学术界和工程界的普遍重视。地下水因素是边坡变形破坏和滑坡灾害的主要内在或触发原因之一。一般地,岩土边坡坍塌和滑坡等地质灾害地发生同地下水渗流场动态特征和变化规律具有密切关系。对于边坡稳定性评价,必须先对边坡渗流场的变化进行充分的了解,在此基础上,才能正确分析边坡的稳定状态,为其稳定性评价和治理工程措施的实施提供坚实基础。因此,对岩体中地下水的渗流状态进行监测,对于岩体工程稳定性评价以及灾害预测预防具有十分重要的意义。 相似文献
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基于双重介质模型对裂隙岩体进行数值模拟,可以更为贴近实际情况.本文在研究孔隙介质和裂隙的渗流控制方程的基础上,利用数值模拟软件进行建模,并根据研究的需要,分别针对不同裂隙宽度和不同渗透系数的孔隙介质模块组合对出水量分配的影响;增加不同渗透系数孔隙介质模块对出水量分配的影响、不同孔隙介质对出水量分配的影响等方面进行研究.研究结果表明:在层流状态下,双重介质渗流的水量交换主要特点如下随裂隙宽度增加,裂隙出水量占出水总量百分比显著上升;随孔隙介质模块组合渗透系数的增加,裂隙出水量占出水总量百分比下降但幅度不大. 相似文献
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随着长江流域与环鄱阳湖经济带的兴起,赣北长江流域与鄱阳湖周边工业企业得到快速发展,但由于发展与环境未能做到和谐统一,引发了一系列生态环境变化。部分地区存在地下污染物长期富集,污染物随河湖地表水扩散,甚至污染物直接泄漏,导致土壤和地下水水质恶化的现象。本文以长江鄱阳湖湖口附近一处硫酸泄漏区为研究对象,在对研究区地下硫酸污染物在土壤和地下水中运移情况调查的基础上,利用地下水水流和溶质运移模拟技术,提出类似河湖相沉积区地下污染物调查评价技术。研究成果对该地区污染物调查指导和环境保护具有重要意义。 相似文献
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岩体形成需要经过一个非常复杂的过程,因此在岩体中就很容易出现大量的空隙、裂隙、地下水和节理等,这就使得岩体在成体结构呈上现出一种多介质的不连续情况,对其相关参数进行的现场量测工作存在极大的困难。 相似文献
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中国科学院栾城农业生态系统试验站(以下简称"栾城站")位于华北太行山前冲洪积平原的中段,是地下水灌区高产农业生态类型的典型代表。由于近几十年来大规模、高强度的农业生产,区域地下水超采严重,地下水污染风险加剧。然而,人类活动影响下的地表生态系统与地下含水层被厚包气带隔开,地表农业生产活动对地下水水量和水质的影响机理尚不明确。目前,开展贯穿整个包气带的原位监测试验,是揭示这一过程机理的唯一途径。因此,建立大型农田关键带观测平台,是开展农业与地下水关系研究的重要需求。在中国科学院野外站网络重点科技基础设施建设项目的支持下,栾城站建设的"栾城关键带观测平台",通过对作物根系层—深层包气带—饱和带的土壤水、热、溶质等关键要素和变量的监测,可开展水分、溶质和污染物在厚包气带内的运移、转化规律研究,揭示饱和—非饱和过渡带水文过程及其与地下水补给关系,阐明农田生产活动的水肥迁移、转化及其对地下水量质变化的影响机制,为回答地表过程对地下水量质演化影响机理提供实验平台支持。 相似文献
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Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed. 相似文献
12.
Roland R. Mielke 《Journal of The Franklin Institute》1978,305(3):143-159
Topological analysis of the signal flow graph associated with the hybrid system of equations for a linear active or passive electrical network for which the element admittance matrix exists and is diagonal is considered. First, the term cancellation which occurs in Mason's topological formulas is investigated. Necessary and sufficient conditions on the signal flow graph topology such that a term in the expansion of the graph determinant and cofactors either cancels out with another term in the expansion or does not cancel are established. Properties of the associated network which result in non-cancelling terms are given and the number of non-cancelling terms is determined. Second, new signal flow graph topological formulas for the graph determinant and cofactors are proven. These formulas are such that no term cancellation occurs and are readily adaptable to computer implementation. In addition, the number of terms in these formulas is independent of the network tree used to formulate the signal flow graph. Examples are given to illustrate the new formulas. 相似文献
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《Information processing & management》2020,57(3):102062
Refugee experience of resettlement into a third country is problematised by posing the question, what happens when an established information landscape fractures? Themes of disjuncture, intensification and liminality that have emerged from the author's research are described, using social theories as the analytical lens to shape the contours of fracture. Two other questions are posed How is digital space implicated in rebuilding information landscapes that have become fractured? and; What is the role of technology in enabling or constraining the conditions for remaking place? 相似文献
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Ibrahim Kocabas 《Journal of The Franklin Institute》2011,348(7):1339-1362
The Laplace transformation technique has been widely applied to modeling of tracer transport in oil and geothermal reservoirs, and in groundwater aquifers. However, mathematical models of many flow and transport problems could only be obtained as Laplace space solutions, and hence, their computations had to involve a numerical inversion technique.In this work, we employ the iterated Laplace transformation technique to develop novel closed form solutions to the tracer transport models in heterogeneous media. Two types of configurations have been considered: tracer transport in single fracture located in low-permeability matrix and tracer transport in a double porosity medium consisting of flowing and dead-end pore systems. In addition, both linear and radial flow geometries have been considered for both configurations. Applications of iterated Laplace transform technique to these four types of models are presented as fundamental examples and their numerical results were used as benchmarking for the numerical inversion results from Stehfest and Dubner and Abate algorithms.As the technique is quite versatile, we expect that the method should gain widespread acceptance to develop solutions to a wide range of problems in flow and transport in porous media and improve the application of nonlinear regression technique to these solutions.This work has achieved four important objectives: first, two novel Laplace transform relations that are useful in tracer studies are presented. Second, the present work serves to verify/invalidate the results of numerical inversion algorithms. In addition, it provides better insight into tracer transport mechanisms. Finally, it serves as a powerful tool of design and interpretation of tracer tests. All four objectives are illustrated in this work. 相似文献
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Generalized difference simulation for coupled transport models of unsaturated soil water flow and solute 总被引：1，自引：0，他引：1
Huanrong Li 《Journal of The Franklin Institute》2011,348(9):2378-2389
The generalized difference methods (GDM) have been successfully used in numerical simulations of unsaturated soil water flow problems. The object of this paper is to extend applications of the GDM, that is, apply GDM to numerically solve one-dimensional coupled transport models of unsaturated soil water flow and solute. The semi-discrete and fully discrete generalized difference schemes are established, and the detailed algorithm of numerical approximation schemes is provided. Moreover, some numerical examples illustrate that the generalized difference methods are feasible and efficient to find the numerical solutions of one-dimensional coupled transport models in this paper. Finally, satisfactory results and some other significant and valuable conclusions are obtained from studies. 相似文献
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《Journal of The Franklin Institute》2006,343(4-5):495-500
In this paper, results of the simulated interaction of ultrasound waves with a fractured Tibia are presented. The Tibia bone fracture is one of the most difficult fractures to treat because of the slow healing process which may take up to 5 months. The human body is modeled as a four layer medium: skin, fasciae with fat, muscle and bone. Each of these layers is characterized by its acoustic impedance. These impedances influence the incident, transmitted and reflected ultrasound pressure waves. A mathematical model which describes these interactions was developed and used to compute the reflection coefficient at the transducer side. This coefficient will then be used to quantify the bone healing process. 相似文献
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The architecture of microfluidic networks can significantly impact the flow distribution within its different branches and thereby influence tracer transport within the network. In this paper, we study the flow rate distribution within a network of parallel microfluidic channels with a single input and single output, using a combination of theoretical modeling and microfluidic experiments. Within the ladder network, the flow rate distribution follows a U-shaped profile, with the highest flow rate occurring in the initial and final branches. The contrast with the central branches is controlled by a single dimensionless parameter, namely, the ratio of hydrodynamic resistance between the distribution channel and the side branches. This contrast in flow rates decreases when the resistance of the side branches increases relative to the resistance of the distribution channel. When the inlet flow is composed of two parallel streams, one of which transporting a diffusing species, a concentration variation is produced within the side branches of the network. The shape of this concentration gradient is fully determined by two dimensionless parameters: the ratio of resistances, which determines the flow rate distribution, and the Péclet number, which characterizes the relative speed of diffusion and advection. Depending on the values of these two control parameters, different distribution profiles can be obtained ranging from a flat profile to a step distribution of solute, with well-distributed gradients between these two limits. Our experimental results are in agreement with our numerical model predictions, based on a simplified 2D advection-diffusion problem. Finally, two possible applications of this work are presented: the first one combines the present design with self-digitization principle to encapsulate the controlled concentration in nanoliter chambers, while the second one extends the present design to create a continuous concentration gradient within an open flow chamber. 相似文献
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《Information processing & management》2022,59(3):102916
Graph convolutional network (GCN) is a powerful tool to process the graph data and has achieved satisfactory performance in the task of node classification. In general, GCN uses a fixed graph to guide the graph convolutional operation. However, the fixed graph from the original feature space may contain noises or outliers, which may degrade the effectiveness of GCN. To address this issue, in this paper, we propose a robust graph learning convolutional network (RGLCN). Specifically, we design a robust graph learning model based on the sparse constraint and strong connectivity constraint to achieve the smoothness of the graph learning. In addition, we introduce graph learning model into GCN to explore the representative information, aiming to learning a high-quality graph for the downstream task. Experiments on citation network datasets show that the proposed RGLCN outperforms the existing comparison methods with respect to the task of node classification. 相似文献
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《Information processing & management》2023,60(4):103387
Precise prediction of Multivariate Time Series (MTS) has been playing a pivotal role in numerous kinds of applications. Existing works have made significant efforts to capture temporal tendency and periodical patterns, but they always ignore abrupt variations and heterogeneous/spatial associations of sensory data. In this paper, we develop a dual normalization (dual-norm) based dynamic graph diffusion network (DNGDN) to capture hidden intricate correlations of MTS data for temporal prediction. Specifically, we design time series decomposition and dual-norm mechanism to learn the latent dependencies and alleviate the adverse effect of abnormal MTS data. Furthermore, a dynamic graph diffusion network is adopted for adaptively exploring the spatial correlations among variables. Extensive experiments are performed on 3 real world experimental datasets with 8 representative baselines for temporal prediction. The performances of DNGDN outperforms all baselines with at least 4% lower MAPE over all datasets. 相似文献
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为了得到带有异常处理结构的切片,文章从传统控制流图到系统依赖图进行了层层改进,给出了构造系统依赖图的算法,并以此为基础得到精确的程序切片。该方法可以处理因为异常结构而引起的数据流和控制流的变化,有助于实现基于异常传播的程序依赖性分析的自动处理。 相似文献