8,388 research outputs found
Computing Matveev's complexity via crystallization theory: the boundary case
The notion of Gem-Matveev complexity has been introduced within
crystallization theory, as a combinatorial method to estimate Matveev's
complexity of closed 3-manifolds; it yielded upper bounds for interesting
classes of such manifolds. In this paper we extend the definition to the case
of non-empty boundary and prove that for each compact irreducible and
boundary-irreducible 3-manifold it coincides with the modified Heegaard
complexity introduced by Cattabriga, Mulazzani and Vesnin. Moreover, via
Gem-Matveev complexity, we obtain an estimation of Matveev's complexity for all
Seifert 3-manifolds with base and two exceptional fibers and,
therefore, for all torus knot complements.Comment: 27 pages, 14 figure
Report on the EU-US Workshop on Large Scientific Databases
This joint workshop was set up under the auspices of the Joint European Commission/National Science Foundation Strategy Group that met in Budapest in September 1998. The meeting derived from a joint collaboration agreement between the EC and NSF, signed by Dr. George Metakides (Director of Information Technologies for the EC) and Prof. Juris Hartmanis (Director of Computer and Information Science and Engineering at the NSF). Some themes that were identified include:
digital libraries
human-centered computing and virtual environments
large scientific databases, and
intelligent implants
This report expresses the conclusions and recommendations of the Workshop on Large Scientific Databases, held in Annapolis, Maryland, USA in September 1999. The purpose of the workshop was to develop a report to the funding agencies outlining a possible solicitation to the research community, with emphasis on joint European-US work on Large Scientific Databases. Before the workshop, each participant submitted a position paper (these are available at the web site http://www.cacr.caltech.edu/euus). The results of the position papers, presentations, and group discussion are summarized in this report. There were 12 participants from Europe and 12 from the United States, and they are listed at the end of this report. The last section of this report describes possible funding mechanisms
Global analysis of muon decay measurements
We have performed a global analysis of muon decay measurements to establish
model-independent limits on the space-time structure of the muon decay matrix
element. We find limits on the scalar, vector and tensor coupling of right- and
left-handed muons to right- and left-handed electrons. The limits on those
terms that involve the decay of right-handed muons to left-handed electrons are
more restrictive than in previous global analyses, while the limits on the
other non-standard model interactions are comparable. The value of the Michel
parameter eta found in the global analysis is -0.0036 \pm 0.0069, slightly more
precise than the value found in a more restrictive analysis of a recent
measurement. This has implications for the Fermi coupling constant G_F.Comment: 5 pages, 3 table
Refractive effects in the scattering of loosely bound nuclei
A study of the interaction of loosely bound nuclei 6,7Li at 9 and 19 AMeV
with light targets has been undertaken. With the determination of unambiguous
optical potentials in mind, elastic data for four projectile-target
combinations and one neutron transfer reaction 13C(7Li,8Li)12C have been
measured on a large angular range. The kinematical regime encompasses a region
where the mean field (optical potential) has a marked variation with mass and
energy, but turns out to be sufficiently surface transparent to allow strong
refractive effects to be manifested in elastic scattering data at intermediate
angles. The identified exotic feature, a "plateau" in the angular distributions
at intermediate angles, is fully confirmed in four reaction channels and
interpreted as a pre-rainbow oscillation resulting from the interference of the
barrier and internal barrier farside scattering subamplitudes.Comment: 19 pages, 14 figures, 3 tables to submit to Phys. Rev.
Tratamento térmico para o controle in vitro do agente causal da podridão-de-fusário em frutos de melão.
A combinatorial smoothness criterion for spherical varieties
We suggest a combinatorial criterion for the smoothness of an arbitrary
spherical variety using the classification of multiplicity-free spaces,
generalizing an earlier result of Camus for spherical varieties of type .Comment: 14 pages, 2 table
Deployment challenges and developments in wireless sensor networks clustering
Clustering techniques for wireless sensor networks (WSNs) have been extensively studied and proven to improve the network lifetime, a primary metric, used for performance evaluation of sensor networks. Although introduction of clustering techniques has the potential to reduce energy consumption and extend the lifetime of the network by decreasing the contention through either power control or node scheduling, scalability remains an issue. Therefore, the optimality of the cluster size still needs to be thoroughly investigated. In this paper, a single cluster head (CH) queuing model is presented. Using an event based simulation tool (Castalia), key issues that affect the practical deployment of clustering techniques in wireless sensor networks are analysed. These include identifying the bottlenecks in terms of cluster scalability and predicting the nature of data packets arrival distribution at the CH. Results presented show that this analysis can be used to specify the size of a cluster, when a specific flow of data is expected from the sensing nodes based on a particular application and also the distribution of the inter-arrival times of data packets at the CH follows exponential distribution
Efeito da radiação ultravioleta pulsada no controle de Fusarium palidoroseum em melões 'Gália' e 'Amarelo'.
Compact 3-manifolds via 4-colored graphs
We introduce a representation of compact 3-manifolds without spherical
boundary components via (regular) 4-colored graphs, which turns out to be very
convenient for computer aided study and tabulation. Our construction is a
direct generalization of the one given in the eighties by S. Lins for closed
3-manifolds, which is in turn dual to the earlier construction introduced by
Pezzana's school in Modena. In this context we establish some results
concerning fundamental groups, connected sums, moves between graphs
representing the same manifold, Heegaard genus and complexity, as well as an
enumeration and classification of compact 3-manifolds representable by graphs
with few vertices ( in the non-orientable case and in the
orientable one).Comment: 25 pages, 11 figures; changes suggested by referee: references added,
figure 2 modified, results about classification of the manifolds in
Proposition 17 announced at the end of section 9. Accepted for publication in
RACSAM. The final publication is available at Springer (see DOI
- …