Search results for "intersection"
showing 10 items of 213 documents
Robustifying principal component analysis with spatial sign vectors
2012
Abstract In this paper, we apply orthogonally equivariant spatial sign covariance matrices as well as their affine equivariant counterparts in principal component analysis. The influence functions and asymptotic covariance matrices of eigenvectors based on robust covariance estimators are derived in order to compare the robustness and efficiency properties. We show in particular that the estimators that use pairwise differences of the observed data have very good efficiency properties, providing practical robust alternatives to classical sample covariance matrix based methods.
Estimation of orientation characteristic of fibrous material
2001
A new statistical method for estimating the orientation distribution of fibres in a fibre process is suggested where the process is observed in the form of a degraded digital greyscale image. The method is based on line transect sampling of the image in a few fixed directions. A well-known method based on stereology is available if the intersections between the transects and fibres can be counted. We extend this to the case where, instead of the intersection points, only scaled variograms of grey levels along the transects are observed. The nonlinear estimation equations for a parametric orientation distribution as well as a numerical algorithm are given. The method is illustrated by a real…
Weak intermolecular interactions promote blue luminescence of protonated 2,2′-dipyridylamine salts
2014
In this work we demonstrate that protonation and π-stacking can be exploited to convert non-luminescent 2,2′-dipyridylamine into blue-emitting derivatives. We have synthesized a series of luminescent 2,2′-dipyridylamine (dpa) salts, i.e., (dpaH)X·nSolv (dpa = 2,2′-dipyridylamine, X = HF2, n = 0.5, Solv = H2O 1; X = Cl, n = 2, Solv = H2O 2; X = Br, n = 2, Solv = H2O 3; X = I n = 1, Solv = H2O 4a; X = I n = 1, Solv = CHCl34b), (dpaH)2[SiF6]·H2O 5 and (dpaH)X (X = I36; SbF67; BF48) and characterized their emission properties, both in the solid-state and in solution. To rationalize our observations and relate the luminescence properties to the structure in the solid state and in solution, we ha…
Conclusion: University Ambiguities and Analytic Eclecticism
2018
This volume has examined six cases of university engagement in peripheral regions. While these regions have often been overlooked in the mainstream literature on university-region dynamics because they do not readily offer up success stories, they do facilitate an exploration into the challenges and difficulties that arise at the intersection of the university and region. Beginning with a theory rooted in institutionalist literature that depicts the university as a set of five ambiguities rather than as a coherent whole, the chapters have sought to apply the ambiguities of intention, causality, history, structure, and meaning to their regional context. In this conclusion, we pull together a…
Intersectionalities, dis/abilities and subjectification in deaf LGBT people: An exploratory study in Sicily
2016
The article discusses the multiple discrimination, normalization and stigmatization experienced by deaf LGBT youth in Sicily, Italy, on the basis of a study of their everyday life (specifically school years and peer interactions). So far in Italy, very little attention has been paid to multiple discrimination and, specifically, to homophobic violence towards disabled individuals. It is, therefore, impossible to consider any valid sampling of the desired population and very few reports have been produced. The authors, a sociologist and a psychologist, carry out an analysis of the results obtained from interviews with 15 LGBT individuals recruited through social networks, thematic chats, and …
The Feast of Life or the Feast of Reason – Kierkegaard Versus Plato
2011
The article consists of three sections. The first section “Dialogue at the intersection of literature and philosophy” analyzes the fundamental differences between the two modes of human intellectual activity – philosophy and literature on the basis of Anna-Teresa Tymieniecka’s philosophy. Nevertheless, the intersection is possible in the form of dialogue. The second chapter “Negative existential maeutics” is dedicated to Kierkegaard’s conception of existential maeutics in comparison with the Socratic maeutics. The stress is put upon its negative characteristics – the distance, the interruption, the situation of existential shock. These restrictions are necessary to allow the participants’ s…
GEPOL: An improved description of molecular surfaces II. Computing the molecular area and volume
1991
The algorithm used by the program GEPOL for a finer description of molecular surface (for a fast calculation of molecular area and volume and for an efficient selection of sampling points) is presented in detail. Different types of surfaces such as van der Waals and Richard's molecular surfaces can be computed. As we described in the first article (J.L. Pascual-Ahuir and E. Silla, J. Comp. Chem., 11, 1047(1990)), GEPOL begins by building a set of spherical surfaces which fill the space which is not solvent accessible. In this second article, a triangular tessellation approach to select the parts of these spherical surfaces which form the molecular surface is described. By using a data coded…
Topological classification of 4-dimensional complete intersections
1996
Let X,,(d) C C P "+r denote a complete intersection, the transversal intersection of r hypersurfaces in C P ~+r defined by r homogeneous polynomials of degrees (d l , . . . ,dr) =: d, with dld2...d,. =: d the total degree. It is well-known that the diffeomorphism type of X,,(d) is determined by n and d. In [7] and [8], Libgober and Wood showed that in dimension n -~ 2, there exist k distinct multidegrees ibr any integer k 6 N such that the corresponding complete intersections are all diffeomorphic. For n = 1,3, the diffeomorphism classification of Xn(d) is well-known by surface theory and the classification of 1-connected six-manifolds [12] respectively. For 7z = 2, at least the topological…
Mainstreaming gender and sustainability jointly: a case study from a local government in Spain
2020
ABSTRACTAfter the approval of the Sustainable Development Goals in 2015, mainstreaming has regained attention as a key strategy to advance towards sustainable development (SD). Taking into account ...
The Role of Covariance Matrix Forecasting Method in the Performance of Minimum-Variance Portfolios
2014
Providing a more accurate covariance matrix forecast can substantially improve the performance of optimized portfolios. Using out-of-sample tests, in this paper, we evaluate alternative covariance matrix forecasting methods by looking at (1) their forecast accuracy, (2) their ability to track the volatility of the minimum-variance portfolio, and (3) their ability to keep the volatility of the minimum-variance portfolio at a target level. We find large differences between the methods. Our results suggest that shrinkage of the sample covariance matrix improves neither the forecast accuracy nor the performance of minimum-variance portfolios. In contrast, switching from the sample covariance ma…