2,744 research outputs found
Coupling Stokes-Darcy flow with transport on irregular geometries
No full textThis thesis studies a mathematical model, in which Stokes-Darcy flow system is coupled with a transport equation. The objective is to develop stable and convergent numerical schemes that could be used in environmental applications. Special attention is given to discretization methods which can handle irregular geometry.
First, we will use a multiscale mortar finite element method to discretize coupled Stokes-Darcy flows on irregular domains. Especially, we will utilize a special discretization method called multi-point flux mixed finite element method to handle Darcy flow. This method is accurate for rough grids and rough full tensor coefficients, and reduces to a cell-centered pressure scheme. On quadrilaterals and hexahedra the method can be formulated either on the physical space or on the reference space, leading to a non-symmetric or symmetric scheme, respectively. While Stokes region is discretized by standard inf-sup stable elements. The mortar space can be coarser and it is used to approximate the normal stress on the interface and to impose weakly continuity of normal flux. The interfaces can be curved and matching conditions are imposed via appropriate mappings from physical grids to reference grids with flat interfaces.
Another approach that we use to deal with the flow equations is based on non-overlapping domain decomposition. Domain decomposition enables us to solve the coupled Stokes-Darcy flow problem in parallel by partitioning the computational domain into subdomains, upon which families of coupled local problems of lower complexity are formulated. The coupling of the subdomain problems is removed through an iterative procedure. We investigate the properties of this method and derive estimates for the condition number of the associated algebraic system.
To discretize the transport equation we develop a local discontinuous Galerkin mortar method. In the method, the subdomain grids need not match and the mortar grid may be much coarser, giving a two-scale method. We weakly impose the boundary condition on the inflow part of the interface and the Dirichlet boundary condition on the elliptic part of the interface via Lagrange multipliers. We develop stability for the concentration and the diffusive flux in the transport equation
Domain Decomposition for Stokes-Darcy Flows with Curved Interfaces
No full textAbstractA non-overlapping domain decomposition method is developed for coupled Stokes-Darcy flows in irregular domains. The Stokes region is discretized by standard Stokes finite elements while the Darcy region is discretized by the multipoint flux mixed finite element method. The subdomain grids may not match on the interfaces and mortar finite elements are employed to impose weakly interface continuity conditions. The interfaces can be curved and matching conditions are imposed via appropriate mappings from physical grids to reference grids with flat interfaces. The global problem is reduced to a mortar interface problem, which is solved by the conjugate gradient method. Each iteration involves solving subdomain problems of either Stokes or Darcy type, which is done in parallel. Computational experiments are presented to illustrate the convergence of the discretization and the condition number of the interface operator
Physics-Informed Neural Networks for Solving Coupled Stokes–Darcy Equation
No full textIn this paper, a grid-free deep learning method based on a physics-informed neural network is proposed for solving coupled Stokes–Darcy equations with Bever–Joseph–Saffman interface conditions. This method has the advantage of avoiding grid generation and can greatly reduce the amount of computation when solving complex problems. Although original physical neural network algorithms have been used to solve many differential equations, we find that the direct use of physical neural networks to solve coupled Stokes–Darcy equations does not provide accurate solutions in some cases, such as rigid terms due to small parameters and interface discontinuity problems. In order to improve the approximation ability of a physics-informed neural network, we propose a loss-function-weighted function strategy, a parallel network structure strategy, and a local adaptive activation function strategy. In addition, the physical information neural network with an added strategy provides inspiration for solving other more complicated problems of multi-physical field coupling. Finally, the effectiveness of the proposed strategy is verified by numerical experiments
A novel molecular class that recruits HDAC/MECP2 complexes to PU.1 motifs reduces neuroinflammation
No full textPervasive neuroinflammation occurs in many neurodegenerative diseases, including Alzheimer’s disease (AD). SPI1/PU.1 is a transcription factor located at a genome-wide significant AD-risk locus and its reduced expression is associated with delayed onset of AD. We analyzed single-cell transcriptomic datasets from microglia of human AD patients and found an enrichment of PU.1-binding motifs in the differentially expressed genes. In hippocampal tissues from transgenic mice with neurodegeneration, we found vastly increased genomic PU.1 binding. We then screened for PU.1 inhibitors using a PU.1 reporter cell line and discovered A11, a molecule with anti-inflammatory efficacy and nanomolar potency. A11 regulated genes putatively by recruiting a repressive complex containing MECP2, HDAC1, SIN3A, and DNMT3A to PU.1 motifs, thus representing a novel mechanism and class of molecules. In mouse models of AD, A11 ameliorated neuroinflammation, loss of neuronal integrity, AD pathology, and improved cognitive performance. This study uncovers a novel class of anti-inflammatory molecules with therapeutic potential for neurodegenerative disorders
Automating the determination of wave speed using the pu-loop method
No full textThe PU-loop (pressure-velocity loop) is a method for determining wave speed and relies on the linear relationship between the pressure and velocity in the absence of reflected waves. This linearity of the PU-loop during early systole, which is directly related to wave speed, has always been established by eye. This paper presents a new technique that establishes this linearity and thus determining wave speed online. Pressure and flow were measured in the ascending aorta of 11 anesthetised dogs. The slope of the PU-loop, indicating wave speed was determined by eye and by using the new technique. The difference between the slopes of the two methods is in the order of 3%. The new technique is convenient and allows for the online assessment of wave speed, which could be used as a bedside tool for the assessment of arterial compliance
A pu -k lativusrag fejleményei a déli szamojédban
No full textIn the light of newly published material, the author investigates various Selkup and Kamassian suffixes containing the developments of PU -K and gives her reasons why she does interpret them as continuations of the PU lative suffix
KELVIN-HELMHOLTZ INSTABILITY IN COLLISIONLESS SPACE PLASMAS
No full textPhysics, Fluids & PlasmasSCI(E)9ARTICLE2440-447
Literacy and the vernacular : a case study based on the post-colonial history of Mauritius, with particular reference to Mauritian Creole
No full textThis thesis examines the process of the literization of the vernacular, and seeks to establish the island of Mauritius as a case study of this process. The concept of literization equates standardization of the vernacular with its use as a written language. Four issues are established as central to this process: ideological, educational, sociocultural and technical.
The thesis investigates the particular sociolinguistic situation of Mauritius, and examines each of these issues in relation to Mauritian Creole. It demonstrates the role that Mauritian Creole plays in Mauritian society, and how, since independence, issues relating to ideology, education, and the cultural and technical aspects of standardization, have been involved in the promotion of the language. The interaction between these issues is apparent throughout the thesis, and manifested in the work of Ledikasyon pu Travayer (LPT), the only organization in Mauritius to provide literacy tuition in Mauritian Creole. The thesis seeks to show that their unified approach to literacy, standardization, and the promotion of Mauritian Creole exemplifies the issues involved, and provides the best basis for the establishment of Mauritian Creole as a standard language.
The analysis of the situation in Mauritius within the framework of wider issues of the literization of the vernacular permits a comparison to other former colonies facing problems of language choice, and places these issues within the wider sociolinguistic context of standardization
Molecular size distribution of Pu in the presence of humic substances in river and groundwaters
No full textThe association properties of Pu with aquatic humic substances in a 0.01M NaClO4 solution at pH 6–8 were studied on the basis of molecular size distribution. Seven humic substances were isolated from river water and groundwaters using XAD extraction technique. They were used for comparing their effects on the association of Pu. In the presence of humic acid, the dominant molecular size of Pu was 100–30 kDa. In the presence of fulvic acid, Pu exhibited three dominant molecular sizes: 30–10 kDa, 30–5 kDa, and less than 5 kDa. The association of Pu-humus complexes might be controlled by the molecular size distribution of humic substances and characteristics of their respective size fractions
Electron Elastic Collisions with Pu, Am and Lr Actinide Atoms
No full textSynopsis The robust Regge-pole methodology which embeds the crucial electron correlations and the vital core-polarization interaction is used to explore negative-ion formation in the actinide atoms Pu, Am and Lr through the electron elastic total cross sections (TCSs) calculation. The TCSs are found to be characterized by ground, metastable and excited anionic formation, whence we extract the anionic binding energies and compare them with existing electron affinities. The TCSs exhibit both atomic and molecular behavior in addition to polar- ization-induced metastable TCSs
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