1,720,958 research outputs found
Hydraulic fracture propagation model for porous media
No full textIn recent years, humanity became strongly dependent on the deep subsurface. It can be used as the energy source as well as the storage facility. At some stage, both listed applications require injection of fluid or gas into the subsurface porous media. Under certain conditions, it may provoke growth of hydraulic fractures. The appearance of fractures significantly changes properties of the permeable media which, in its turn, affects the operational performance of thesubsurface reservoir. Apart from that, hydraulic fracturing may also cause a nuisance to the human environment in the form of earthquakes. Ability to predict growth of hydraulic fractures and their geometry becomes crucial. For this purposes, numerical models are extensively used.In this work, a fully coupled hydro-mechanical model for hydraulic fracturing of porous media was proposed. Based on this model, an explicit computational framework was developed in C++ programming language allowing efficient modeling of a single fracture propagating. Proposed algorithm consists of the Discrete Fracture Model for multi-phase flow and contact-enriched Finite Element Model for geomechanics. Irwin’s failure criterion from Linear Elastic Fracture Mechanics concepts was adapted. Stress Intensity Factors are evaluated employing displacement extrapolation technique.The proposed model was extensively tested in various set-ups including single- and multi-phase flow in isothermal and thermal conditions. Both straight and turning fractures were modeled. Effects of the mesh geometry, material properties, and stress field anisotropy were analyzed in a series of tests. Obtained results were validated with the semi-analytical solutions. Proposednumerical scheme demonstrated its applicability to a wide range of tasks and showed a great potential for its extension to a larger group of applications.Geo-Engineerin
Guiding Deep Probabilistic Models
No full textDeep probabilistic models utilize deep neural networks to learn probability distributions in high-dimensional data spaces. Learning and inference in these models are complicated due to the difficulty of direct evaluation of the differences between the model distribution and the target. This thesis addresses this challenge and develops novel algorithms for learning and inference based on the guidance of complex parameterized distributions towards desired configurations via signals from auxiliary discriminative models.
In the first part of the thesis, we develop novel stable training objectives for Generative Adversarial Networks (GANs). We show that under standard unary-discriminator objectives, most of the valid solutions, where the learned distribution is aligned with the target, are unstable. We propose training objectives based on pairwise discriminators that provably preserve distribution alignment and demonstrate improved training stability in image generation tasks.
In the second part of the thesis, we introduce distribution support alignment as an alternative to the distribution alignment objective and develop a learning algorithm that guides distributions towards support alignment. We demonstrate the effectiveness of our approach in unsupervised domain adaptation under label distribution shift. Recent works have shown that under cross-domain label distribution shift, optimizing for distribution alignment is excessively restrictive and causes performance degradation. Our algorithm, which is based on support alignment, alleviates this issue.
In the third part of the thesis, we develop a novel approach to compositional generation in iterative generative processes: diffusion models and Generative Flow Networks (GFlowNets). Motivated by the growing prominence of generative models pre-trained at scale and the high training costs, we propose composition operations and guidance-based sampling algorithms that enable the combination of multiple pre-trained iterative generative processes. We offer empirical results on image and molecular generation tasks.Ph.D
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
Обоснование арендной платы за землю на основе материалов государственной кадастровой оценки земель
No full textВ данной научно-исследовательской работе проводится обоснование составных элементов расчета размера арендной платы за земли, находящиеся в государственной и муниципальной собственности, на основе материалов государственной кадастровой оценки земель на примере Ленинградской области РФ. В работе изучены теоретические положения кадастровой оценки земель и ее правового обеспечения, выявлены особенности арендной платы за земли, а также ее роль в формировании экономики страны, обоснованы корректирующие коэффициенты, необходимые для расчета арендной платы за землю и проведен сравнительный анализ удельных показателей кадастровой стоимости и базовых ставок арендной платы. Научно-исследовательская работа состоит из введения, трех глав, заключения, списка использованной литературы и приложений. В работе использовано 5 таблиц, 6 картосхем, 4 диаграммы, 3 блок-схемы, 2 приложения, 30 источников литературы. Количество страниц научно-исследовательской работы без приложений - 77.The research work focus on rationale of component elements of calculation land rent based on the state cadastral valuation of lands on example of Leningrad region. In the research work author analyzed theoretical positions of the state cadastral valuation of lands and its regulations, identified features of land rent and role of land rent in the formation of the state economy, correcting factors necessary for calculating the land rent are justified and analyzed a comparative analysis of specific indicators of cadastral value and basic rates of land rent. Research work consists of an introduction, three chapters, conclusion, a list of used literature and applications. In the research work 5 tables, 6 maps, 4 diagrams, 3 block diagrams, 2 applications, 30 sources of literature were used. Number of pages of research work without applications is 77
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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