1,721,112 research outputs found
Efficient implementation of the Yule-Simon stochastic process for modeling internet and software development activities
No full textWe develop three different algorithms for implementing the Preferential Attachment mechanism, with regards to the Yule process, able to describe how statistical power-law distributions, for various properties of OO software systems and of the internet, are generated. Since modern software systems have reached a huge dimension, counting tens, or hundreds of thousand, of units or modules, the efficiency of algorithms for their simulation is a critical issue. We discuss their efficiency for different parameters value, their scaling with system size, and analyze in which cases one is preferable with respect to the others
Y2O3:Eu and the Mössbauer isomer shift coefficient of Eu compounds from ab-initio simulations
Full text linkWe report on a full potential density functional theory characterization of Y2O3 upon Eu doping on the two inequivalent crystallographic sites 24d and 8b. We analyze local structural relaxation, electronic properties and the relative stability of the two sites. The simulations are used to extract the contact charge density at the Eu nucleus. Then we construct the experimental isomer shift (IS) versus contact charge density calibration curve, by considering an ample set of Eu compounds: EuF3, EuO, EuF2, EuS, EuSe, EuTe, EuPd3 and the Eu metal. The, expected, linear dependence has a slope of α = 0.054 mm s-1 Å-3, which corresponds to nuclear expansion parameter ΔR/R = 6.0 × 10-5. α allows to obtain an unbiased and accurate estimation of the IS for any Eu compound. We test this approach on two mixed-valence compounds Eu3S4 and Eu2SiN3, and use it to predict the Y2O3:Eu IS with the result +1.04 mm s-1 at the 24d site and +1.00 mm s-1 at the 8b site
NVAF:UN FRAMEWORK PER UNA VALUTAZIONE DI TIPO COMPARATIVO DELLE SOLUZIONI SOFTWARE NELLE PUBBLICHE AMMINISTRAZIONI
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Simulation of the On Demand Software Market, Including Vendors Oering Source Code Availability
No full textIn recent years, the power balance between software firms and enterprise customers has been heavily changing. The contractual power of customers is increasing and the firms must take this fact into account. Stated the common need to save money, the opportunities to adopt new software solutions with tight budgets, or with substantial savings, are limited. The better way to obtain operational savings seems to be shifting to the use of open source software, obtaining in this way all the benefits of this software typology: lower costs, greater adherence to open standards, a broader vendor choice and service suppliers, no vendor lock-in and flexible, incremental architectures. In this work, a business model is proposed to analyse the competition among on-demand customer relationship management (CRM) firms, in particular among firms offering CRM products with or without source code availability. The model can also be customized to study other kinds of markets, and other assumptions can be made for studying their implications to the software business
Three efficient algorithms for implementing the preferential attachment mechanism in Yule-Simon Stochastic Process
No full textWe describe how different optimized algorithms may be effective in implementing the preferential attachment mechanism in different cases. We analyze performances with respect to different values of some parameters related to the Yule process associated to the preferential attachment. We examine how performance scales with system size and provide extensive simulations to support our theoretical findings
An Approach to Multimedia Content Management
No full textStandardized formalizations of the knowledge are used by domain experts to share information in the form
of reusable knowledge. The primary objective of our work is the definition of an approach for multimedia
content management. We reached that goal through a validation activity which lasted for the last three
years, and was carried on through the application on different case studies, some of them described in detail
in previously published papers. This approach aims to represent the knowledge through a mixed-iterative
approach, where top-down and bottom-up analyses are applied on the knowledge domain we want to
represent. We focused our research on some issues concerning Knowledge Management, strictly related to
the process of making multimedia content-related knowledge easily available to users. We need to represent
and manage this knowledge, in order to formalize and codify all the knowledge in the domain. This
formalization can eventually lead us to easily manage that knowledge through the use of repositories
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