8 research outputs found
A fixed point index approach to Krasnosel’skiĭ-Precup fixed point theorem in cones and applications
No full textWe present an alternative approach to the vector version of Krasnosel’skiĭ compression–expansion fixed point theorem due to Precup, which is based on the fixed point index. It allows us to obtain new general versions of this fixed point theorem and also multiplicity results. We emphasize that all of them are coexistence fixed point theorems for operator systems, that means that every component of the fixed points obtained is non-trivial. Finally, these coexistence fixed point theorems are applied to obtain results concerning the existence of positive solutions for systems of Hammerstein integral equations and radially symmetric solutions of (P1,P2) Laplacian systemsJorge Rodríguez–López was partially supported by Xunta de Galicia (Spain), project ED431C 2019/02 and AEI, Spain and FEDER , grant PID2020-113275GB-I00. The author thanks the referee for useful comments which led to the improvement of his paper and for the suggested additional referencesS
An experimental protocol for in situ colorectal liver metastases ablation by radiofrequency toward a standard procedure
No full textThe Economic Growth and the Opportunity for the Private Equity Funds to Divest: An Empirical Analysis for Eastern Europe
No full textThe author studies the private equity divestments in Eastern Europe and tests a long-term relation between these divestments and the real GDP variation. This research paper focuses on a sample covering the period 2000-2013 which considers the dynamics of the private equity divestments during the last financial crisis. The empirical analysis follows the methodology developed by Granger (1969), Toda and Yamamoto (1995), Dufour and Renault (1998), Konya (2004), Foresti (2006) and Onuoha, Okonkwo, Okoro, Kingsley (2018). The analysis shows that Eastern European private equity divestment market is still emerging characterized by high volatilities. The results prove that GDP recession explains in at certain degree the evolution of private equity divestments during the crisis. However, the Granger causality test shows that the information provided by the past variation of the real GDP cannot allow us to predict the short-term movements of private equity divestments in Eastern Europe
The Economic Growth and the Opportunity for the Private Equity Funds to Divest: An Empirical Analysis for Eastern Europe
No full textThe author studies the private equity divestments in Eastern Europe and tests a long-term relation between these divestments and the real GDP variation. This research paper focuses on a sample covering the period 2000-2013 which considers the dynamics of the private equity divestments during the last financial crisis. The empirical analysis follows the methodology developed by Granger (1969), Toda and Yamamoto (1995), Dufour and Renault (1998), Konya (2004), Foresti (2006) and Onuoha, Okonkwo, Okoro, Kingsley (2018). The analysis shows that Eastern European private equity divestment market is still emerging characterized by high volatilities. The results prove that GDP recession explains in at certain degree the evolution of private equity divestments during the crisis. However, the Granger causality test shows that the information provided by the past variation of the real GDP cannot allow us to predict the short-term movements of private equity divestments in Eastern Europe
Efficient model-based exploration in continuous state-space environments
No full textThe impetus for exploration in reinforcement learning (RL) is decreasing uncertainty about the environment for the purpose of better decision making. As such, exploration plays a crucial role in the efficiency of RL algorithms. In this dissertation, I consider continuous state control problems and introduce a new methodology for representing uncertainty that engenders more efficient algorithms. I argue that the new notion of uncertainty allows for more efficient use of function approximation, which is essential for learning in continuous spaces. In particular, I focus on a class of algorithms referred to as model-based methods and develop several such algorithms that are much more efficient than the current state-of-the-art methods. These algorithms attack the long-standing "curse of dimensionality''--- learning complexity often scales exponentially with problem dimensionality. I introduce algorithms that can exploit the dependency structure between state variables to exponentially decrease the sample complexity of learning, both in cases where the dependency structure is provided by the user a priori and cases where the algorithm has to find it on its own. I also use the new uncertainty notion to derive a multi-resolution exploration scheme, and demonstrate how this new technique achieves anytime behavior, which is very important in real-life applications. Finally, using a set of rich experiments, I show how the new exploration mechanisms affect the efficiency of learning, especially in real-life domains where acquiring samples is expensive.Ph.D.Includes bibliographical referencesIncludes vitaby Ali Nour
Traumatic Peregrinations: Intergenerational Memory and Migration in Nina Bunjevac’s Fatherland
No full textThis essay analyzes images of both movement and immobility in Nina Bunjevac’s Fatherland, a Canadian graphic memoir in which the author/illustrator traces her father’s involvement in a Serbian nationalist terrorist cell. Although, as scholars such as Mihaela Precup have convincingly argued, Bunjevac depicts her father as trapped by historical circumstances he cannot control—and her larger family as “frozen in disbelief, anger, and sadness” (220)—I maintain that such immobility is paradoxically the consequence of constant movement. In the course of her narrative, Bunjevac, while she does not excuse her father’s actions or even depict him sympathetically, nevertheless shows how three generations of wartime displacement and transnational migration traumatized her father and in turn her immediate family. Thus, I maintain that her graphic narrative demonstrates how Astrid Erll’s concept of “travelling memory” might be enlarged to address how traumatic memories follow, and become uncannily reenacted by, migrants and displaced people. Bunjevac’s text is a particularly effective demonstration of this dimension of travelling memory because its very form as a graphic memoir necessarily depends on such elements of fracture, repetition, and difference
Gröbner Geometry for Hessenberg Varieties
No full textWe study Hessenberg varieties in type A via their local defining equations, called patch ideals. We focus on two main classes of Hessenberg varieties: those associated to a regular nilpotent operator and to those associated to a semisimple operator.
In the setting of regular semisimple Hessenberg varieties, which are known to be smooth and irreducible, we determine that their patch ideals are triangular complete intersections, as defined by Da Silva and Harada. For semisimple Hessenberg varieties, we give a partial positive answer to a conjecture of Insko and Precup that a given family of set-theoretic local defining ideals are radical.
A regular nilpotent Hessenberg Schubert cell is the intersection of a Schubert cell with a regular nilpotent Hessenberg variety. Following the work of the author with Da Silva, Harada, and Rajchgot, we construct an embedding of the regular nilpotent Hessenberg Schubert cells into the coordinate chart of the regular nilpotent Hessenberg variety corresponding to the longest-word permutation in Bruhat order. This allows us to use work of Da Silva and Harada to conclude that regular nilpotent Hessenberg Schubert cells are also local triangular complete intersections.ThesisMaster of Science (MSc)Algebraic varieties provide a generalization of curves in the plane, such as parabolas and ellipses. One such family of these varieties are called Hessenberg varieties, and they are known to have connections to other areas of pure and applied mathematics, including to numerical linear algebra, combinatorics, and geometric representation theory.
In this thesis, we view Hessenberg varieties as a collection of subvarieties, called coordinate charts, and study the computational geometry of each coordinate chart. Although this is a local approach, we recover global geometric data on Hessenberg varieties. We also provide a partial positive answer to an open question in the area
Search based software engineering: Trends, techniques and applications
No full text© ACM, 2012. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version is available from the link below.In the past five years there has been a dramatic increase in work on Search-Based Software Engineering (SBSE), an approach to Software Engineering (SE) in which Search-Based Optimization (SBO) algorithms are used to address problems in SE. SBSE has been applied to problems throughout the SE lifecycle, from requirements and project planning to maintenance and reengineering. The approach is attractive because it offers a suite of adaptive automated and semiautomated solutions in situations typified by large complex problem spaces with multiple competing and conflicting objectives.
This article provides a review and classification of literature on SBSE. The work identifies research trends and relationships between the techniques applied and the applications to which they have been applied and highlights gaps in the literature and avenues for further research.EPSRC and E
