131,594 research outputs found
The PolFusion Experiment: Measurement of the d-d-Fusion Spin-Dependence
No full textA double-polarized dd-fusion experiment is under preparation at PNPI,
Gatchina. The experimental program includes themeasurements of the asymmetry in
the differential cross section of the reactions d_pol + d_pol → 3He + n and d_pol + d_pol → t + p. The spin-correlation coefficients Cz,z and Czz,zz will be measured to determine
the quintet-state suppression factors for both reactions, for which quite different
theoretical predictions were made and which are very important for the design of
future neutron-lean fusion reactors. The total cross sectionmodification for polarized
d–d fusion will also be investigated. An increase by a factor of 1.5 was already
deduced for the d + 3He and the d + t reactions. The experimental setup and the
future upgrade plans are described
TRANSVERSITY 2008 Proceedings of the Second Workshop on Transverse Polarization Phenomena in Hard Processes
No full textTransversity 2008, the second workshop on Transverse polarization phenomena in hard processes, follows the first one held in Como after three years. As in that case, the event comes at the end of a two-years project financed by the Italian Ministry of Education. In the time between the two Workshops, decisive steps towards the revealing of the transverse spin structure of the proton were taken on both the theoretical and experimental sides. The milestone of the first extraction of Transversity and the Sivers function for the u- and d-quarks deserves a special mention. In the same period, historic experiments that in the last decade contributed to the first pioneering measurements in the SIDIS sector, have concluded their data taking, and their place is being taken by upgrades of existing or new facilities. These are the result of the new interesting phenomena which are appearing and call for additional experimental information and novel experimental techniques. Over 80 physicists took part in the Workshop. Equally involved were experimentalists and theoreticians engaged in investigating the nature of transverse spin. The heterogeneous public favoured vivid discussions and fruitful exchange of up-to-date theoretical and experimental ideas on this constantly evolving subject
Polarized Fusion: still open question to be solved. A project to D↑-D↑ interaction at PNPI.
No full textIn order to answer to still open questions:
can the total cross section of the fusion reactions be increased by polarized fuel?
Is a better control on the ejectiles possible?,
a project is under study and design in order to measure spin-dependent parameters useful to addressing polarized fusion.
The project comes from the experience in polarized atomic beams and targets for nuclear physics in experiments related to collaborations at COSY (PAX - ANKE project) among INFN-Ferrara, IKP-J\"ulich and PNPI- St. Petersburg.
The perspectives of it will be presented
How much can large-scale Video-On-Demand benefit from users' cooperation?
No full textWe propose an analytical framework to tightly characterize the scaling laws for the additional bandwidth that servers must supply to guarantee perfect service in peer-assisted Video-on-Demand systems, taking into account essential aspects such as peer churn, bandwidth heterogeneity, and Zipf-like video popularity. Our results reveal that the catalog size and the content popularity distribution have a huge effect on the system performance. We show that users' cooperation can effectively reduce the servers' burden for a wide range of system parameters, confirming to be an attractive solution to limit the costs incurred by content providers as the system scales to large populations of user
The H and D Polarized Target for Spin-Filtering Measurements at COSY
No full textIn the main frame of the PAX (Polarized Antiproton eXperiments) collaboration, which engaged the challenging purpose of polarizing antiproton beams, the possibility to have H or D polarized targets requires a daily switchable source and its diagnostics: mainly change is a dual cavity tunable for H and D. The commissioning of PAX has been full-filled, for the transverse case, on the COSY (COoler SYnchrotron) proton ring, achieving milestones on spin-dependent cross-section measurements. Now the longitudinal case could provide sensitive polarization results. An H or D source allows the exploration of the spin-filtering process with a deuterium polarized target, and opens new chances for testing Time Reversal Invariance at COSY (TRIC)
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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