32,222 research outputs found
Profitability, success probabilities, and incentives for cooperative R&D
As is widely conjectured, duopolists form a cost-sharing cooperative R&D alliance to develop a product - regardless of the probability of research success is either very high or very low. This study establishes that most low probabilities of research success cannot induce a financially successful cooperative R&D alliance. Incorporating the constraints in non-negative expected profits eliminates more than 95% probability of the parameter space where the probability of success is lower than 0.5. Our results further demonstrate that non-negative expected profits are attainable when the monopoly profit is not large in relation to duopoly profits, the fixed cost of R&D investment is low and the demand is large.Cooperative R&D; uncertainty; profitability
Ultra accurate collaborative information filtering via directed user similarity
A key challenge of the collaborative filtering (CF) information filtering is
how to obtain the reliable and accurate results with the help of peers'
recommendation. Since the similarities from small-degree users to large-degree
users would be larger than the ones opposite direction, the large-degree users'
selections are recommended extensively by the traditional second-order CF
algorithms. By considering the users' similarity direction and the second-order
correlations to depress the influence of mainstream preferences, we present the
directed second-order CF (HDCF) algorithm specifically to address the challenge
of accuracy and diversity of the CF algorithm. The numerical results for two
benchmark data sets, MovieLens and Netflix, show that the accuracy of the new
algorithm outperforms the state-of-the-art CF algorithms. Comparing with the CF
algorithm based on random-walks proposed in the Ref.7, the average ranking
score could reach 0.0767 and 0.0402, which is enhanced by 27.3\% and 19.1\% for
MovieLens and Netflix respectively. In addition, the diversity, precision and
recall are also enhanced greatly. Without relying on any context-specific
information, tuning the similarity direction of CF algorithms could obtain
accurate and diverse recommendations. This work suggests that the user
similarity direction is an important factor to improve the personalized
recommendation performance.Comment: 6 pages, 4 figure
Two-photon and two-gluon decays of p-wave heavy quarkonium using a covariant light-front approach
In this paper, a study of two-photon and two-gluon decays in the context of
p-wave heavy quarkonia is presented. Within the covariant light-front
framework, the annihilation rates of scalar and tensor quarkonium states are
derived. In the absence of free parameters in this case, the results for the
charmonium decay widths are consistent with the experimental data. However, in
comparison to other theoretical calculations, there are large discrepancies in
our results regarding bottomonia.Comment: 19 pages, 3 figures, 3 tables, some typos are corrected, version to
be published in Phys. Rev.
Geographical, socioeconomic, and ecological determinants of exotic plant naturalization in the United States : insights and updates from improved data
Previous studies on alien species establishment in the United States and around the world have drastically improved our understanding of the patterns of species naturalization, biological invasions, and underlying mechanisms. Meanwhile, relevant new data have been added and the data quality has significantly increased along with the consistency of related concepts and terminology that are being developed. Here using new and/or improved data on the native and exotic plant richness and many socioeconomic and physical variables at the state level in the United States, we attempt to test whether previously discovered patterns still hold, particularly how native and exotic species are related and what are the dominant factors controlling the plant naturalization. We found that, while the number of native species is largely controlled by natural factors such as area and temperature, exotic species and exotic fraction are predominantly influenced by social factors such as human population. When domestically introduced species were included, several aspects in earlier findings were somewhat altered and additional insights regarding the mechanisms of naturalization could be achieved. With increased data availability, however, a greater challenge ahead appears to be how many and which variables to include in analyses
The nature of states from a combined analysis of and
With a combined analysis of data on and in an effective field theory approach, we determine resonance
parameters of states in two scenarios. In one scenario we assume that
states are pure molecular states, while in the other one we assume that
states contain compact components. We find that the present data favor
that there should be some compact components inside associated
with the molecular components. By fitting the invariant mass spectra of
and , we determine that the probability of finding the
compact components in states may be as large as about .Comment: Discussions added, version published in EPJ
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