10,520 research outputs found
Gear mesh compliance modeling
A computer model has been constructed to simulate the compliance and load sharing in a spur gear mesh. The model adds the effect of rim deflections to previously developed state-of-the-art gear tooth deflection models. The effects of deflections on mesh compliance and load sharing are examined. The model can treat gear meshes composed to two external gears or an external gear driving an internal gear. The model includes deflection contributions from the bending and shear in the teeth, the Hertzian contact deformations, and primary and secondary rotations of the gear rims. The model shows that rimmed gears increase mesh compliance and, in some cases, improve load sharing
Phantom Accretion by Five Dimensional Charged Black Hole
This paper deals with the dynamical behavior of phantom field near five
dimensional charged black hole. We formulate equations of motion for
steady-state spherically symmetric flow of phantom fluids. It is found that
phantom energy accretes onto black holes for . Further, the location of
critical point of accretion are evaluated that leads to mass to charge ratio
for 5D charged black hole. This ratio implies that accretion cannot transform a
black hole into a naked singularity. We would like to mention here that this
work is an irreducible extension of 4D charged black hole.Comment: 8 pages, accepted for publication in Mod. Phys. Lett.
On big rip singularities
In this comment we discuss big rip singularities occurring in typical phantom
models by violation of the weak energy condition. After that, we compare them
with future late-time singularities arising in models where the scale factor
ends in a constant value and there is no violation of the strong energy
condition. In phantom models the equation of state is well defined along the
whole evolution, even at the big rip. However, both the pressure and the energy
density of the phantom field diverge. In contrast, in the second kind of model
the equation of state is not defined at the big rip because the pressure bursts
at a finite value of the energy density.Comment: 8 page
Determining cosmological parameters from X-ray measurements of strong lensing clusters
We discuss a new method which is potentially capable of constraining
cosmological parameters using observations of giant luminous arcs in rich X-ray
clusters of galaxies. The mass profile and the mass normalization of the lenses
are determined from X-ray measurements. The method also allows to probe the
amount and equation of state of the dark energy in the universe. The analysis
of a preliminary sample of 6 luminous, relatively relaxed clusters of galaxies
strongly favours an accelerating expansion of the universe. Under the
assumption that the dark energy is in the form of a cosmological constant, the
data provide an estimate of with a statistical error of
. Including the constraint of a flat universe and an equation of state
for the dark energy , we obtain and
. Relaxing the prior on , we find that the null
energy condition is satisfied at the 3- confidence level.Comment: 9 pages; 5 figures; accepted for publication in MNRA
Study of an advanced transport airplane design concept known as Flatbed
The design concept and configuration of the Flatbed transport aircraft are presented. The Flatbed configuration combines into one frame, the ability to haul cargo, virtually unrestrained by cross sectional dimensions of the fuselage. The feasibility and capability of the Flatbed is discussed in depth
Dexterous Grasping by Manipulability Selection for Mobile Manipulator with Visual Guidance
Industry 4.0 demands the heavy usage of robotic mobile manipulators with high autonomy and intelligence. The goal is to accomplish dexterous manipulation tasks without prior knowledge of the object status in unstructured environments. It is important for the mobile manipulator to recognize and detect the objects, determine manipulation pose, and adjust its pose in the workspace fast and accurately. In this research, we developed a stereo vision algorithm for the object pose estimation using point cloud data from multiple stereo vision systems. An improved iterative closest point algorithm method is developed for the pose estimation. With the pose input, algorithms and several criteria are studied for the robot to select and adjust its pose by maximizing its manipulability on a given manipulation task. The performance of each technical module and the complete robotic system is finally shown by the virtual robot in the simulator and real robot in experiments. This study demonstrates a setup of autonomous mobile manipulator for various flexible manufacturing and logistical scenarios
Protein-mediated dethreading of a biotin-functionalised pseudorotaxane
In this article, we describe the synthesis of new biotin-functionalised naphthalene derivatives 3 and 4 and their complexation behaviour with avidin and neutravidin using a range of analytical techniques. We have shown using 2-(4prime or minute-hydroxyazobenzene)benzoic acid displacement and ITC experiments{,} that compounds 3 and 4 have the propensity to form reasonably high-affinity bioconjugates with avidin and neutravidin. We have also demonstrated using 1H NMR{,} UV-vis and fluorescence spectroscopy that the naphthalene moiety of 3 and 4 facilitates the formation of pseudorotaxane-like structures with 1 in water. We have then investigated the ability of avidin and neutravidin to modulate the complexation between 1 and 3 or 4. UV-vis and fluorescence spectroscopy has shown that in both cases the addition of the protein disrupts complexation between the naphthalene moieties of 3 and 4 with 1
Large-Scale Bulk Motions Complicate the Hubble Diagram
We investigate the extent to which correlated distortions of the luminosity
distance-redshift relation due to large-scale bulk flows limit the precision
with which cosmological parameters can be measured. In particular, peculiar
velocities of type 1a supernovae at low redshifts may prevent a sufficient
calibration of the Hubble diagram necessary to measure the dark energy equation
of state to better than 10%, and diminish the resolution of the equation of
state time-derivative projected for planned surveys. We consider similar
distortions of the angular-diameter distance, as well as the Hubble constant.
We show that the measurement of correlations in the large-scale bulk flow at
low redshifts using these distance indicators may be possible with a cumulative
signal-to-noise ratio of order 7 in a survey of 300 type 1a supernovae spread
over 20,000 square degrees.Comment: 6 pages; 4 figure
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