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  • Resultat 1-10 av 4072
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  • Andersson, Fredrik K., et al. (författare)
  • The mathematics of internet search engines
  • 2008
  • Ingår i: Acta Applicandae Mathematicae - An International Survey Journal on Applying Mathematics and Mathematical Applications. - Springer. - 0167-8019. ; 104:2, s. 211-242
  • Tidskriftsartikel (refereegranskat)abstract
    • This article presents a survey of techniques for ranking results in search engines, with emphasis on link-based ranking methods and the PageRank algorithm. The problem of selecting, in relation to a user search query, the most relevant documents from an unstructured source such as the WWW is discussed in detail. The need for extending classical information retrieval techniques such as boolean searching and vector space models with link-based ranking methods is demonstrated. The PageRank algorithm is introduced, and its numerical and spectral properties are discussed. The article concludes with an alternative means of computing PageRank, along with some example applications of this new method.
  • Lundengård, Karl, 1987- (författare)
  • Generalized Vandermonde matrices and determinants in electromagnetic compatibility
  • 2017
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Matrices whose rows (or columns) consists of monomials of sequential powers are called Vandermonde matrices and can be used to describe several useful concepts and have properties that can be helpful for solving many kinds of problems. In this thesis we will discuss this matrix and some of its properties as well as a generalization of it and how it can be applied to curve fitting discharge current for the purpose of ensuring electromagnetic compatibility.In the first chapter the basic theory for later chapters is introduced. This includes the Vandermonde matrix and some of its properties, history, applications and generalizations, interpolation and regression problems, optimal experiment design and modelling of electrostatic discharge currents with the purpose to ensure electromagnetic compatibility.The second chapter focuses on finding the extreme points for the determinant for the Vandermonde matrix on various surfaces including spheres, ellipsoids, cylinders and tori. The extreme points are analysed in three dimensions or more.The third chapter discusses fitting a particular model called the p-peaked Analytically Extended Function (AEF) to data taken either from a standard for electromagnetic compatibility or experimental measurements. More specifically the AEF will be fitted to discharge currents from the IEC 62305-1 and IEC 61000-4-2 standards for lightning protection and electrostatic discharge immunity as well as some experimentally measured data of similar phenomena.
  • Gerlee, Philip, 1980-, et al. (författare)
  • Scientific Models
  • 2016
  • Bok (övrigt vetenskapligt)
  • Eriksson, Henrik, et al. (författare)
  • Conjugacy of Coxeter elements
  • 2009
  • Ingår i: The Electronic Journal of Combinatorics. - 1077-8926. ; 16:2, s. R4
  • Tidskriftsartikel (refereegranskat)abstract
    • For a Coxeter group (W, S), a permutation of the set S is called a Coxeter word and the group element represented by the product is called a Coxeter element. Moving the first letter to the end of the word is called a rotation and two Coxeter elements are rotation equivalent if their words can be transformed into each other through a sequence of rotations and legal commutations. We prove that Coxeter elements are conjugate if and only if they are rotation equivalent. This was known for some special cases but not for Coxeter groups in general.
  • Hamon, Thierry, et al. (författare)
  • Term Ranking Adaptation to the Domain : Genetic Algorithm-Based Optimisation of the C-Value
  • 2014
  • Ingår i: Advances in Natural Language Processing : 9th International Conference on NLP, PolTAL 2014, Warsaw, Poland, September 17-19, 2014. Proceedings. - Springer International Publishing. - 978-3-319-10888-9 ; s. 71-83
  • Konferensbidrag (refereegranskat)abstract
    • Term extraction methods based on linguistic rules have been proposed to help the terminology building from corpora. As they face the difficulty of identifying the relevant terms among the noun phrases extracted, statistical measures have been proposed. However, the term selection results may depend on corpus and strong assumptions reflecting specific terminological practice. We tackle this problem by proposing a parametrised C-Value which optimally considers the length and the syntactic roles of the nested terms thanks to a genetic algorithm. We compare its impact on the ranking of terms extracted from three corpora. Results show average precision increased by 9% above the frequency-based ranking and by 12% above the C-Value-based ranking.
  • Jagers, Peter, 1941- (författare)
  • Matematikens ord
  • 2009
  • Ingår i: LexicoNordica. ; 16, s. 315-318
  • Tidskriftsartikel (refereegranskat)
  • Thörnblad, Karin, 1971-, et al. (författare)
  • Scheduling optimization of a real flexible job shop including side constraints regarding maintenance, fixtures, and night shifts
  • 2013
  • Annan publikation (övrigt vetenskapligt)abstract
    • We present a generic iterative scheduling procedure for the scheduling of a real flexible job shop, the so-called multitask cell at GKN Aerospace Engine Systems in Sweden. A time-indexed formulation of the problem is presented including side constraints regarding preventive maintenance, fixture availability, and unmanned night shifts. This paper continues the work in [35], with an improvement of the iterative solution procedure and the inclusion of constraints regarding night shifts during which only unmanned processing is allowed. The resulting schedules are compared with schedules constructed using two priority dispatching rules. Computational results show that the gain of including the night shifts constraints is significant and that the methodology developed is able to produce near-optimal schedules for industrial data instances for the coming shift within an acceptable practical time frame.
  • Hashorva, Enkelejd, et al. (författare)
  • Approximation of a Random Process with Variable Smoothness
  • 2015
  • Ingår i: Mathematical Statistics and Limit Theorems : Festschrift in Honour of Paul Deheuvels. - Springer. - 978-3-319-12441-4 (Print) - 978-3-319-12442-1 (online) ; s. 189-208
  • Bokkapitel (övrigt vetenskapligt)abstract
    • We consider the rate of piecewise constant approximation to a locally stationary process X(t),t ε [0,1]  , having a variable smoothness index α(t). Assuming that α(⋅)  attains its unique minimum at zero and satisfies<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csmall%5Calpha%20(t)=%5Calpha%20_0+b%20t%5E%5Cgamma%20+%20%5Cmathrm%7Bo%7D(t%5E%5Cgamma%20)%20%5Cquad%20%7Bas%7D%20%5C%20t%20%5Crightarrow%200," />we propose a method for construction of observation points (composite dilated design) such that the integrated mean square error<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csmall%5Cint%20_0%5E1%20%7B%5Cmathbb%20E%7D%5C%7B(X(t)-X_n(t))%5E2%5C%7D%20dt%20%5Csim%20%5Cfrac%7BK%7D%7Bn%5E%7B%5Calpha%20_0%7D(%5Clog%20n)%5E%7B(%5Calpha%20_0+1)/%5Cgamma%20%7D%7D%20%5Cqquad%20%7Bas%7D%20%5C%20n%5Crightarrow%20%5Cinfty," />where a piecewise constant approximation X n   is based on N(n) ∼ n  observations of X  . Further, we prove that the suggested approximation rate is optimal, and then show how to find an optimal constant K.
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