Search results for "Graph Theory"
showing 10 items of 784 documents
Resonant formation of pionic atoms with neutron collisions
1992
We study the {ital n}+{ital A}{r arrow}({ital A}{prime}{pi}{sub {ital b}}{sup {minus}}){r arrow}{ital n}+{ital A} reaction, or resonant formation of pionic atoms, with neutron scattering. We evaluate the contribution of the interference of this reaction channel in {sup 40}Ca and {sup 208}Pb to the elastic scattering amplitude at backward angles. The ratio of signal to the background at 80{degree} is about 10{sup {minus}3}, and we estimate that the ratio does not improve at higher angles, hence making this reaction impractical. Our findings have repercussions on a similar reaction now running at the Indiana University Cyclotron Facility.
Nearly tight bounds on the learnability of evolution
2002
Evolution is often modeled as a stochastic process which modifies DNA. One of the most popular and successful such processes are the Cavender-Farris (CF) trees, which are represented as edge weighted trees. The Phylogeny Construction Problem is that of, given /spl kappa/ samples drawn from a CF tree, output a CF tree which is close to the original. Each CF tree naturally defines a random variable, and the gold standard for reconstructing such trees is the maximum likelihood estimator of this variable. This approach is notoriously computationally expensive. We show that a very simple algorithm, which is a variant on one of the most popular algorithms used by practitioners, converges on the t…
Intelligent Multi-Start Methods
2018
Heuristic search procedures aimed at finding globally optimal solutions to hard combinatorial optimization problems usually require some type of diversification to overcome local optimality. One way to achieve diversification is to re-start the procedure from a new solution once a region has been explored, which constitutes a multi-start procedure. In this chapter we describe the best known multi-start methods for solving optimization problems. We also describe their connections with other metaheuristic methodologies. We propose classifying these methods in terms of their use of randomization, memory and degree of rebuild. We also present a computational comparison of these methods on solvi…
Scatter Search and Path-Relinking: Fundamentals, Advances, and Applications
2010
Scatter search is an evolutionary metaheuristic that explores solution spaces by evolving a set of reference points, operating on a small set of solutions while making only limited use of randomization. We give a comprehensive description of the elements and methods that make up its template, including the most recent elements incorporated in successful applications in both global and combinatorial optimization. Path-relinking is an intensification strategy to explore trajectories connecting elite solutions obtained by heuristic methods such as scatter search, tabu search, and GRASP. We describe its mechanics, implementation issues, randomization, the use of pools of high-quality solutions …
Representing 2D Digital Objects
2000
The paper describes the combination a multi-views approach to represent connected components of 2D binary images. The approach is based on the Object Connectivity Graph (OCG), which is a sub-graph of the connectivity graph generated by the Discrete Cylindrical Algebraic Decomposition(DCAD) performed in the 2D discrete space. This construction allows us to find the number of connected components, to determine their connectivity degree, and to solve visibility problem. We show that the CAD construction, when performed on two orthogonal views, supply information to avoid ambiguities in the interpretation of each image component. The implementation of the algorithm is outlined and the computati…
Is sustainable transportation limited by urban form? An international GIS-based approach
2019
International audience
Stereocontrolled approach to quinuclidine derivatives
1998
Abstract Asymmetric Michael-type cyclization of chiral enamino ester (S)-7 furnished the quinuclidinone derivative (3R, 4S)-5, with a high degree of stereoselectivity.
Reply to Comment on ‘An educational path for the magnetic vector potential and its physical implications’
2014
In this reply we respond to the comment made by Heras on our paper (Barbieri et al 2013 Eur. J. Phys. 34 1209), in which we presented an educational path on the magnetic vector potential A, aimed at undergraduate students and pre-service physics teachers.
Applied Linear Algebra: Electrical Networks
2016
This chapter shows how mathematical theory is not an abstract subject which has no connection with the real world. On the contrary, this entire book is written by stating that mathematics in general, and algebra in this case, is an integrating part of every day real life and that the professional life of computational scientists and engineers requires a solid mathematical background. In order to show how the contents of the previous chapters have an immediate technical application, the last chapter of this book describes a core engineering subject, i.e. electrical networks, as an algebraic exercise. Furthermore, this chapter shows how the combination of the algebraic topics give a natural r…
Analysing Intercultural Dialogue Through Conceptual Densities
2020
In this chapter, we exemplify our methodological approach to analysing ‘densities’ of interrelated concepts in European education policy documents. We scrutinize instances where many of the core concepts of intercultural dialogue appear in the documents at the same time. Four core educational themes and four longer excerpts from the selected policy documents are examined in more detail. The chosen documents deal especially with multilingualism, migration, history teaching, and lifelong learning. The analysis of the conceptual densities in the chosen excerpts indicates how the meanings of intercultural dialogue are constructed through the conceptual frameworks and co-occurrences of their cor…