2,809 research outputs found
Vibration analysis of a beam on a moving vehicle under the road excitation with different contact models
Dynamic analysis of a beam on a moving vehicle is presented in this paper. The vehicle is simulated by a four degrees-of-freedom mass-spring system and the beam on top is supported by spring-damping systems. Two contact models named the ‘point contact’ and the ‘patch contact’ respectively, are adopted to simulate the interaction between road surface and vehicular tyres. The equation of motion of the beam-vehicle system is formulated and the dynamic response on the beam under the excitation of the irregular road surface is derived. Numerical simulations are conducted to demonstrate the influence of different factors, such as the length of the contact, the velocity of vehicle, the road condition and the bracing stiffness, etc. on the vibration level of the beam structure, which aims to provide references on the vibration problem in transporting a beam-shaped package
Real Scalar Field Scattering with Polynomial Approximation around Schwarzschild-de Sitter Black-hole
As one of the fitting methods, the polynomial approximation is effective to
process sophisticated problem. In this paper, we employ this approach to handle
the scattering of scalar field around the Schwarzschild-de Sitter black-hole.
The complex relationship between tortoise coordinate and radial coordinate is
replaced by the approximate polynomial. The Schrdinger-like equation,
the real boundary conditions and the polynomial approximation construct a full
Sturm-Liouville type problem. Then this boundary value problem can be solved
numerically according to two limiting cases: the first one is the Nariai
black-hole whose horizons are close to each other, the second one is when the
horizons are widely separated. Compared with previous results (Brevik and
Tian), the field near the event horizon and cosmological horizon can have a
better description.Comment: revtex4 source file, 11 pages, 8 figure
How to realize Lie algebras by vector fields
An algorithm for embedding finite dimensional Lie algebras into Lie algebras
of vector fields (and Lie superalgebras into Lie superalgebras of vector
fields) is offered in a way applicable over ground fields of any
characteristic. The algorithm is illustrated by reproducing Cartan's
interpretations of the Lie algebra of G(2) as the Lie algebra that preserves
certain non-integrable distributions. Similar algorithm and interpretation are
applicable to other exceptional simple Lie algebras, as well as to all
non-exceptional simple ones and many non-simple ones, and to many Lie
superalgebras.Comment: 17 pages, LaTe
Learning to Assist Bimanual Teleoperation using Interval Type-2 Polynomial Fuzzy Inference
Assisting humans in collaborative tasks is a promising application for robots, however effective assistance remains challenging. In this paper, we propose a method for providing intuitive robotic assistance based on learning from human natural limb coordination. To encode coupling between multiple-limb motions, we use a novel interval type-2 (IT2) polynomial fuzzy inference for modeling trajectory adaptation. The associated polynomial coefficients are estimated using a modified recursive least-square with a dynamic forgetting factor. We propose to employ a Gaussian process to produce robust human motion predictions, and thus address the uncertainty and measurement noise of the system caused by interactive environments. Experimental results on two types of interaction tasks demonstrate the effectiveness of this approach, which achieves high accuracy in predicting assistive limb motion and enables humans to perform bimanual tasks using only one limb
Consistency of shared reference frames should be reexamined
In a recent Letter [G. Chiribella et al., Phys. Rev. Lett. 98, 120501
(2007)], four protocols were proposed to secretly transmit a reference frame.
Here We point out that in these protocols an eavesdropper can change the
transmitted reference frame without being detected, which means the consistency
of the shared reference frames should be reexamined. The way to check the above
consistency is discussed. It is shown that this problem is quite different from
that in previous protocols of quantum cryptography.Comment: 3 pages, 1 figure, comments are welcom
Visual processing recruits the auditory cortices in prelingually deaf children and influences cochlear implant outcomes.
Objective: Although visual processing recruitment of the auditory cortices has been reported previously in prelingually deaf children who have a rapidly developing brain and no auditory processing, the visual processing recruitment of auditory cortices might be different in processing different visual stimuli and may affect cochlear implant (CI) outcomes.
Methods: Ten prelingually deaf children, 4–6 years old, were recruited for the study. Twenty prelingually deaf subjects, 4–6 years old with CIs for 1 year, were also recruited; 10 with well-performing CIs, 10 with poorly performing CIs. Ten age and sex-matched normal-hearing children were recruited as controls. Visual (‘sound’ photo (photograph with imaginative sound) and ‘non-sound’ photo (photograph without imaginative sound)) evoked potentials were measured in all subjects. P1 at Oz and N1 at the bilateral temporal-frontal areas (FC3 and FC4) were compared.
Results: N1 amplitudes were strongest in the deaf children, followed by those with poorly performing CIs, controls and those with well-performing CIs. There was no significant difference between controls and those with well-performing CIs. ‘Sound’ photo stimuli evoked a stronger N1 than ‘non-sound’ photo stimuli. Further analysis showed that only at FC4 in deaf subjects and those with poorly performing CIs were the N1 responses to ‘sound’ photo stimuli stronger than those to ‘non-sound’ photo stimuli. No significant difference was found for the FC3 and FC4 areas. No significant difference was found in N1 latencies and P1 amplitudes or latencies.
Conclusions: The results indicate enhanced visual recruitment of the auditory cortices in prelingually deaf children. Additionally, the decrement in visual recruitment of auditory cortices was related to good CI outcomes
Time scales of epidemic spread and risk perception on adaptive networks
Incorporating dynamic contact networks and delayed awareness into a contagion
model with memory, we study the spreading patterns of infectious diseases in
connected populations. It is found that the spread of an infectious disease is
not only related to the past exposures of an individual to the infected but
also to the time scales of risk perception reflected in the social network
adaptation. The epidemic threshold is found to decrease with the rise
of the time scale parameter s and the memory length T, they satisfy the
equation .
Both the lifetime of the epidemic and the topological property of the evolved
network are considered. The standard deviation of the degree
distribution increases with the rise of the absorbing time , a power-law
relation is found
Tunable hybrid surface waves supported by a graphene layer
We study surface waves localized near a surface of a semi-infinite dielectric
medium covered by a layer of graphene in the presence of a strong external
magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can
propagate along the graphene surface. We analyze the effect of the Hall
conductivity on the disper- sion of hybrid surface waves and suggest a
possibility to tune the plasmon dispersion by the magnetic field.Comment: 3 pages, 3 figure
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