1,721,768 research outputs found
Adaptive Isogeometric Methods for Boussinesq Problems
Full text linkComputational Fluid Dynamics (CFD) is the numerical study of fluid flow, heat transfer, turbulence modelling and several conservation laws. The fluids can be liquids, gases and even plasmas. There is a vast number of differential equations describing the physical problems in specific situations, and many of them have a nonlinear structure. The main goals of CFD are constructing an efficient and stable numerical technique for discretizing the equations with respect to space and time, and then solving the (nonlinear) algebraic systems of equations arising from the discretization as quick and accurate as possible. This might not be straightforward because the procedure always depends on the specific situation. The simulations are often carried out over long time intervals, and that will make high accuracy in space and time desirable. Furthermore, nonlinearity and local instabilities can also slow down the computational speed. When we couple several equations together, the solution procedure becomes even more complex.
The most common numerical procedures utilized in CFD are the Finite Difference Method (FDM), the Finite Volume Method (FVM) and the Finite Element Method (FEM). The latter one is most the general and widespread because we can apply it on arbitrary complex domains that are sufficiently smooth, and it can perform local refinement in those parts of the domain where the unknown solution lacks sufficient regularity. There are a lot of similar FEM-approaches, and they differ most with respect to the choice of basis functions. One such method is called Isogeometric Analysis (IGA). It has superior approximation properties compared with classical FEM, and its signature ability is creating an exact mesh of the domain’s geometry. The discretized equations can be solved quickly, and all these advantages make IGA well-suited for CFD applications.
The main focus of the thesis is solving the hydrodynamic Boussinesq equations for buoyancy-driven flow numerically. The PDE system consists of the Navier-Stokes equation and Advection-Diffusion equation coupled together. In particular, our research emphasizes adaptive error estimation and local refinement using isogeometric discretization. Adaptive refinement originated in the late 1970s. It was designed for reducing approximation error by generating a new mesh repeatedly until it resembled the unknown solution’s physical structure. In classical FEM, the theory of a posteriori error estimation is complete and has been applied widely to large classes of differential equations. This method is far better than a priori error estimation because it allows us to analyse local parts of the solution effectively and determine the corresponding local error. In CFD, there are many well-known situations where adaptive refinement and error estimation are desirable. We need a suitable method for reducing the error quickly without too much computational effort at the same time.
We consider qualitative analysis of efficient a posteriori error estimators for IGA. This topic is still in a development stage although the classical refinement theory is compatible with the isogeometric paradigm. Splines are in general not interpolatory like the shape functions from FEM. Since they have higher continuity and better approximation properties, there is a good reason to believe that isogeometric refinement yields very good results for smooth problems. We will investigate whether some of these classical error estimators can be adapted directly to IGA, and then test them on some major PDEs in CFD: the Stokes equation, the Navier-Stokes equations, the Advection-Diffusion equation, and the Boussinesq equations
Integrated production of polyhydroxyalkonate (bioplastic) with municipal wastewater and sludge treatment for sustainable development
No full textMunicipal wastewater is one of the wastes which can be used as a substrate for microbial growth. Municipal waste contains sludge, which is considered an end product of wastewater treatment plants, contributing to higher costs for its management. However, the sludge has the highest amount of organic matter, which can produce high-value products, especially polyhydroxyalkanoates (PHAs). Through volarization and fixation of methane by microbial consortium can lower the methane content in the sludge and can be integrated with the production of PHA. PHA has gain far more interest in past few decades due to its biodegradable and biofriendly nature towards the environment. PHA is thermoplastic polyesters produced by various classes of microorganisms such as bacteria, fungi, and algae. These are produced under stress condition like nutrient limitation. The process includes four major steps: i) Treatment of wastewater through enrichment and later, end product directed for PHA sustaining biomass; ii) production of volatile fatty acids (VFA) or VFA rich stream through acidogenic fermentation; iii) production and accumulation of PHA using VFA rich stream; and iv) downstream process for PHA recovery. The following chapter will be detailed summary the effective utilization of sewage sludge to produce PHAs via integrating municipal water treatment and PHA production
Palladium catalyzed [3+2] cycloaddition of vinyl aziridine and indane-1,3-diones: diastereo- and enantioselective access to spiro-pyrrolidines
No full textA mild and efficient palladium catalyzed [3+2] cycloaddition of vinyl aziridines and indane-1,3-diones has been realized. The resulting spiropyrrolidines were provided in excellent yields and, with the introduction of the leucine-derived phosphine ligand, moderate to good enantio- and diastereoselectivities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Minimization of Third-Party Injury in Multi-Party Water Right Transfers in Colorado
No full textIn the western United States, prior appropriation is the dominant form of water rights. In times of scarcity, the most senior water rights are given priority. Water right transfers can increase economic efficiency by moving water toward higher value uses, but the parties involved must prove that transfers do not reduce water availability for third-party users. In this study, prior appropriation and water right transfers were studied using the Upper Gunnison River Basin in Colorado as a test case. Streams and diversion structures were combined into a simplified network object in the R language. A flow allocation model was then developed to solve for the set of withdrawals and streamflows consistent with mass balance constraints and prior appropriation. The first objective of this work was to explore the drivers on water availability under prior appropriation. Specifically considered were the effects of spatial and temporal hydrologic variability, as well as the set of upstream and downstream priorities, on water availability for a given water right holder. Additionally, the effects of these drivers on water right transfers and third-party injuries were explored. Next, a number of case studies were developed which showcase strategies for using carefully constructed water right transfers for various ends. Multi-party overlapping water right transfers were considered as a solution to the problem of third-party injury. Multi-party water right transfers were also suggested as a means to reduce transaction costs in water right transfers. Symmetric, bilateral water right transfers were considered as a way of transferring hydrologic risk. Lastly, downstream water right transfers were suggested as a strategy for increasing instream flows in vulnerable reaches. In addition to these heuristic case studies, a web-based tool was developed which allows users to explore water rights within the Upper Gunnison River Basin and test the effects of multi-party transfers on third-parties and instream flows. I hope that this tool will be useful for water managers, regulators, and educators who would like to develop a better understanding of prior appropriation rules and the effects of water right transfers
- …
