570,990 research outputs found
Two span bridge under moving load
The dynamic effect of the moving load on the bridge construction is the subject of the solution in this article. The bridge is modeled as two span continuous beam with two degrees of freedom. The assumption describing the dynamic deflection curve and the assumption describing the load distribution on individual lumped masses are adopted at the creation of bridge computational model. The plane computational model of heavy vehicle with five degrees of freedom is adopted. The problem is described by ordinary differential equations which are solved numerically by using MATLAB. The results are presented by graphical and numerical form
Envelope analysis equations for two-span continuous girder bridges
In this paper, envelope analysis equations for two-span continuous girder bridges were presented by deriving the analysis equation for uniformly distributed loading, concentrated loading and moving loads (single and multiple wheel loads). Most bridge engineers are using special software’s to find the moment, shear and deflection envelopes for bridge girder, the complexity for this analysis increasing with the number of spans, most of cases are one-span and two-span continuous bridge, the two-span continuous bridge is more complicated which was presented in this paper, the same methodology can be applied in one-span bridge. The objective of this paper was to give all the bridge engineers direct equations for complete analysis (moment, shear and deflection) for two-span continuous bridge with more accuracy than most bridge software’s by adapting continuous moving of wheel loads rather than using interval check distance to move the concentrated loads as in most of bridge software’s. Pinned end boundary condition was presented here. The results were showed that shear envelope, moment envelope and maximum envelope deflection values were obtained by direct equations for two-span continuous girder bridges under single and multiple moving loads
Development and flight evaluation of active controls in the L-1011
Active controls in the Lockheed L-1011 for increased energy efficiency are discussed. Active wing load alleviation for extended span, increased aspect ratio, and active stability augmentation with a smaller tail for reduced drag and weight are among the topics considered. Flight tests of active wing load alleviation on the baseline aircraft and moving-base piloted simulation developing criteria for stability augmentation are described
Response of beams resting on viscoelastically damped foundation to moving oscillators
The response of beams resting on viscoelastically damped foundation under moving SDoF oscillators is scrutinized through a novel state-space formulation, in which a number of internal variables is introduced with the aim of representing the frequency-dependent behaviour of the viscoelastic foundation. A suitable single-step scheme is provided for the numerical integration of the equations of motion, and the Dimensional Analysis is applied in order to define the dimensionless combinations of the design parameters that rule the responses of beam and moving oscillator. The effects of boundary conditions, span length and number of modes of the beam, along with those of the mechanical properties of oscillator and foundation, are investigated in a new dimensionless form, and some interesting trends are highlighted. The inaccuracy associated with the use of effective values of stiffness and damping for the viscoelastic foundation, as usual in the present state-of-practice, is also quantified
Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene
Mirroring their role in electrical and optical physics, two-dimensional
crystals are emerging as novel platforms for fluid separations and water
desalination, which are hydrodynamic processes that occur in nanoscale
environments. For numerical simulation to play a predictive and descriptive
role, one must have theoretically sound methods that span orders of magnitude
in physical scales, from the atomistic motions of particles inside the channels
to the large-scale hydrodynamic gradients that drive transport. Here, we use
constraint dynamics to derive a nonequilibrium molecular dynamics method for
simulating steady-state mass flow of a fluid moving through the nanoscopic
spaces of a porous solid. After validating our method on a model system, we use
it to study the hydrophobic effect of water moving through pores of
electrically doped single-layer graphene. The trend in permeability that we
calculate does not follow the hydrophobicity of the membrane, but is instead
governed by a crossover between two competing molecular transport mechanisms.Comment: 6 pages, 3 figure
Proper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
We search for stars with proper motions in a set of twenty deep Subaru
images, covering about 0.28 square degrees to a depth of i ~ 25, taken over a
span of six years. In this paper, we describe in detail our reduction and
techniques to identify moving objects. We present a first sample of 99 stars
with motions of high significance, and discuss briefly the populations from
which they are likely drawn. Based on photometry and motions alone, we expect
that 9 of the candidates may be white dwarfs. We also find a group of stars
which may be extremely metal-poor subdwarfs in the halo.Comment: 12 pages, 8 figures, submitted to PAS
Spin light of neutrino in gravitational fields
We predict a new mechanism for the spin light of neutrino () that can
be emitted by a neutrino moving in gravitational fields. This effect is studied
on the basis of the quasiclassical equation for the neutrino spin evolution in
a gravitational field. It is shown that the gravitational field of a rotating
object, in the weak-field limit, can be considered as an axial vector external
field which induces the neutrino spin procession. The corresponding probability
of the neutrino spin oscillations in the gravitational field has been derived
for the first time. The considered in this paper can be produced in the
neutrino spin-flip transitions in gravitational fields. It is shown that the
total power of this radiation is proportional to the neutrino gamma factor to
the fourth power, and the emitted photon energy, for the case of an ultra
relativistic neutrino, could span up to gamma-rays. We investigate the
caused by both gravitational and electromagnetic fields, also accounting for
effects of arbitrary moving and polarized matter, in various astrophysical
environments. In particular, we discuss the emitted by a neutrino
moving in the vicinity of a rotating neutron star, black hole surrounded by
dense matter, as well as by a neutrino propagating in the relativistic jet from
a quasar.Comment: 14 pages in LaTex with 1 eps figure; derivation of the neutrino spin
oscillations probability in gravitational fields and several clarifying notes
are added, typos correcte
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