35,527 research outputs found
Old chinese and friends: new approaches to historical linguistics of the Sino-Tibetan area
List J-M, Starostin G, Yunfan L. “Old Chinese and Friends”: new approaches to historical linguistics of the Sino-Tibetan area. Journal of Language Relationship. 2019;17(1-2):1-6
Effects of demographic noise on the synchronization of a metapopulation in a fluctuating environment
We use the theory of noise-induced phase synchronization to analyze the effects of demographic noise on the synchronization of a metapopulation of predator-prey systems within a fluctuating environment (Moran effect). Treating each local predator–prey population as a stochastic urn model, we derive a Langevin equation for the stochastic dynamics of the metapopulation. Assuming each local population acts as a limit cycle oscillator in the deterministic limit, we use phase reduction and averaging methods to derive the steady state probability density for pairwise phase differences between oscillators, which is then used to determine the degree of synchronization of\ud
the metapopulation
Nonlinear robust controller design for multi-robot systems with unknown payloads
This work is concerned with the control problem of a multi-robot system handling a payload with unknown mass properties. Force constraints at the grasp points are considered. Robust control schemes are proposed that cope with the model uncertainty and achieve asymptotic path tracking. To deal with the force constraints, a strategy for optimally sharing the task is suggested. This strategy basically consists of two steps. The first detects the robots that need help and the second arranges that help. It is shown that the overall system is not only robust to uncertain payload parameters, but also satisfies the force constraints
Asteroseismology of the Scuti star HD 50844
Aims. We aim to probe the internal structure and investigate more detailed
information of the Scuti star HD 50844 with asteroseismology. Methods.
We analyse the observed frequencies of the Scuti star HD 50844
obtained by Balona (2014), and search for possible multiplets based on the
rotational splitting law of g-mode. We tried to disentangle the frequency
spectra of HD 50844 by means of the rotational splitting only. We then compare
them with theoretical pulsation modes, which correspond to stellar evolutionary
models with various sets of initial metallicity and stellar mass, to find the
best-fitting model. Results. There are three multiplets including two complete
triplets and one incomplete quintuplet, in which mode identifications for
spherical harmonic degree and azimuthal number are unique. The
corresponding rotational period of HD 50844 is found to be
2.44 days. The physical parameters of HD 50844 are well
limited in a small region by three modes identified as nonradial ones
(, , and ) and by the fundamental radial mode
(). Our results show that the three nonradial modes (, ,
and ) are all mixed modes, which mainly represent the property of the
helium core. The fundamental radial mode () mainly represents the
property of the stellar envelope. In order to fit these four pulsation modes,
both the helium core and the stellar envelope must be matched to the actual
structure of HD 50844. Finally, the mass of the helium core of HD 50844 is
estimated to be 0.173 0.004 for the first time. The physical
parameters of HD 50844 are determined to be 1.81 0.01 ,
0.008 0.001. 7508 125 K, log 3.658
0.004, 3.300 0.023 , 30.98 2.39 .Comment: 11 pages, 7 figures, 6 tables, accepted for publication in A&
Impact of edge-removal on the centrality betweenness of the best spreaders
The control of epidemic spreading is essential to avoid potential fatal
consequences and also, to lessen unforeseen socio-economic impact. The need for
effective control is exemplified during the severe acute respiratory syndrome
(SARS) in 2003, which has inflicted near to a thousand deaths as well as
bankruptcies of airlines and related businesses. In this article, we examine
the efficacy of control strategies on the propagation of infectious diseases
based on removing connections within real world airline network with the
associated economic and social costs taken into account through defining
appropriate quantitative measures. We uncover the surprising results that
removing less busy connections can be far more effective in hindering the
spread of the disease than removing the more popular connections. Since
disconnecting the less popular routes tend to incur less socio-economic cost,
our finding suggests the possibility of trading minimal reduction in
connectivity of an important hub with efficiencies in epidemic control. In
particular, we demonstrate the performance of various local epidemic control
strategies, and show how our approach can predict their cost effectiveness
through the spreading control characteristics.Comment: 11 pages, 4 figure
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