661 research outputs found
Scaling relations for diversity of languages
The distribution of living languages is investigated and scaling relations
are found for the diversity of languages as a function of the country area and
population. These results are compared with data from Ecology and from computer
simulations of fragmentation dynamics where similar scalings appear. The
language size distribution is also studied and shown to display two scaling
regions: (i) one for the largest (in population) languages and (ii) another one
for intermediate-size languages. It is then argued that these two classes of
languages may have distinct growth dynamics, being distributed on the sets of
different fractal dimensions.Comment: 10 pages, 4 figure
Análise dinâmica de colisão de comboios para projeto de segurança passiva
Trabalho final de mestrado para obtenção do grau Mestre em Engenharia MecânicaEste trabalho visa a modelação multicorpo da colisão de comboios com o objetivo de
permitir efetuar simulações da colisão, de modo a observar os fenómenos de absorção de
energia, de modo a permitir uma redução dos custos computacionais, mas também dos custos
com testes reais. O modelo desenvolvido replica de forma bastante correta uma colisão,
podendo servir para análise da colisão.
O modelo desenvolvido tem por base um modelo real, sendo este modelo constituído por
carruagens, onde uma das carruagens apresenta uma dada velocidade inicial enquanto as outras
se encontram em repouso, e buffers, sendo estes últimos estruturas de absorção de energia, estas
estruturas encontram-se acopladas às carruagens por molas não lineares. Uma vez que os
resultados dependem da curva de rigidez das molas é relativamente simples alterar as
características do modelo de modo a simular diferentes tipo de colisão a diferentes velocidades
e com diferentes massas.
Uma vez que se verifica que quando existe o impacto entre carruagens, não existe recuo
do corpo que se encontra inicialmente em movimento, é necessário garantir que o mesmo se
verifica nas simulações, esta situação apresentou um grande desafio de simulação, sendo que
foram necessárias várias tentativas e modelos, de modo a conseguir replicar o melhor possível
este fenómeno.
Este projeto oferece uma ferramenta de análise da colisão de carruagens, sendo que a
utilização do modelo desenvolvido pode ser útil no projeto e fabrico de carruagens, bem como
em projetos de segurança passiva de passageiros.This paper aims the multibody modeling of railway collisions, with the purpose of allow
collision simulations, in order to observe the energy absorption phenomena, in order to allow
reducing the computing cost, and real test cost as well. The model was developed to replicate
quite accurately a collision and can be used for collision analysis.
The developed model was based on a real model, being this model was made by carriages,
where one of them has an initial velocity while the others are at rest, the model also have buffers,
wich are structures for energy absorption, these structures are coupled to the carriages by
nonlinear springs. Since the results depend on the springs stiffness curve it is relatively simple
to change the characteristics of the model in order to simulate different types of collision, at
different velocities with different masses.
Since it is found that when there is an impact between carriages there is no recoil of the
body that was initially moving, it is necessary to ensure this is what happens in the simulations,
this situation presented a big challenge, and several models and trials was made in order to
replicate this phenomenon as best as possible.
This project offers a different railway crash analysis tool, and the use of the developed
model can be useful in the project and manufacture of rail carriages, as well as passive passenger
safety projects.N/
Solving the Sports League Scheduling Problem with Tabu Search
In this paper we present a tabu approach for a version of the Sports League Scheduling Problem. The approach adopted is based on a formulation of the problem as a Constraint Satisfaction Problem (CSP). Tests were carried out on problem instances of up to 40 teams representing 780 integer variables with 780 values per variable. Experimental results show that this approach outperforms some existing methods and is one of the most promising methods for solving problems of this type
Can the Pioneer anomaly be of gravitational origin? A phenomenological answer
In order to satisfy the equivalence principle, any non-conventional mechanism
proposed to gravitationally explain the Pioneer anomaly, in the form in which
it is presently known from the so-far analyzed Pioneer 10/11 data, cannot leave
out of consideration its impact on the motion of the planets of the Solar
System as well, especially those orbiting in the regions in which the anomalous
behavior of the Pioneer probes manifested itself. In this paper we, first,
discuss the residuals of the right ascension \alpha and declination \delta of
Uranus, Neptune and Pluto obtained by processing various data sets with
different, well established dynamical theories (JPL DE, IAA EPM, VSOP). Second,
we use the latest determinations of the perihelion secular advances of some
planets in order to put on the test two gravitational mechanisms recently
proposed to accommodate the Pioneer anomaly based on two models of modified
gravity. Finally, we adopt the ranging data to Voyager 2 when it encountered
Uranus and Neptune to perform a further, independent test of the hypothesis
that a Pioneer-like acceleration can also affect the motion of the outer
planets of the Solar System. The obtained answers are negative.Comment: Latex2e, 26 pages, 6 tables, 2 figure, 47 references. It is the
merging of gr-qc/0608127, gr-qc/0608068, gr-qc/0608101 and gr-qc/0611081.
Final version to appear in Foundations of Physic
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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