2,914 research outputs found
Four-state rock-paper-scissors games on constrained Newman-Watts networks
We study the cyclic dominance of three species in two-dimensional constrained
Newman-Watts networks with a four-state variant of the rock-paper-scissors
game. By limiting the maximal connection distance in Newman-Watts
networks with the long-rang connection probability , we depict more
realistically the stochastic interactions among species within ecosystems. When
we fix mobility and vary the value of or , the Monte Carlo
simulations show that the spiral waves grow in size, and the system becomes
unstable and biodiversity is lost with increasing or . These
results are similar to recent results of Reichenbach \textit{et al.} [Nature
(London) \textbf{448}, 1046 (2007)], in which they increase the mobility only
without including long-range interactions. We compared extinctions with or
without long-range connections and computed spatial correlation functions and
correlation length. We conclude that long-range connections could improve the
mobility of species, drastically changing their crossover to extinction and
making the system more unstable.Comment: 6 pages, 7 figure
A Sodium laser guide star coupling efficiency measurement method
Large telescope's adaptive optics (AO) system requires one or several bright
artificial laser guide stars to improve its sky coverage. The recent advent of
high power sodium laser is perfect for such application. However, besides the
output power, other parameters of the laser also have significant impact on the
brightness of the generated sodium laser guide star mostly in non-linear
relationships. When tuning and optimizing these parameters it is necessary to
tune based on a laser guide star generation performance metric. Although return
photon flux is widely used, variability of atmosphere and sodium layer make it
difficult to compare from site to site even within short time period for the
same site. A new metric, coupling efficiency is adopted in our field tests. In
this paper, we will introduce our method for measuring the coupling efficiency
of a 20W class pulse sodium laser for AO application during field tests that
were conducted during 2013-2015
Container vehicle-truss bridge coupled vibration analysis and structural safety assessment under stochastic excitation
The container vehicle-truss bridge coupled vibration greatly affects the automated container terminalsā (ACT) structural safety and handling efficiency. Using free-interface component mode synthesis (CMS) method, the coupled vibration time-domain responses, under self-excitation including track irregularity and hunting movement as well as environmental excitations such as wind and seismic load, were obtained. Stochastic simulation of track irregularity and fluctuating wind time-history was generated based on the numerical simulation method of multidimensional homogeneous process. A scale model test was introduced to validate the CMS methodās effectiveness and vehicle speedās influence on coupled vibration response. In this case, the vehicle-bridge vertical vibration is caused mainly by the vehicle moving load, and self-excitation is a major factor. Wind, seismic load will greatly enhance the lateral vibration. And the sensitivity of the response to the seismic load is greater than operational wind load. As vehicle velocity, fluctuating wind mean velocity or ground motion intensity increase, the responses increase. Then, the structural safety, running safety and stability were assessed by the indicators such as deflection-span ratio, acceleration response etc., under wind load only and under operational wind and ground motion excited simultaneously. It is proved by both prototype simulation and model test results that, lead rubber bearing (LRB) can effectively reduce the acceleration response of both the vehicle and the bridge; therefore, can raise vehicle speed limits for structural and running safety
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