1,181 research outputs found
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Tangential slip noise of V-ribbed belts
This paper reports the results of a study into V-ribbed belt noise generated as a result of
tangential belt slip. The results of experimental studies to identify the belt operating conditions
associated with belt noise are presented, together with the results of analytical studies to identify the
mechanism of noise generation. It is concluded that tangential slip V-ribbed belt noise generation is
controlled only by the amount of slip, and that the mechanism of noise generation is harmonic
excitation of the fundamental vibration mode of the belt, with stick¿slip frictional behaviour providing
the impetus for the vibratio
Recommended from our members
Automotive timing belt life laws and a user design guide
The paper presents a computer-based guide of the effect of layout and loading (tension and
torque) on the timing belt life and uses it to show the sensitivity of life to changed conditions in an
automotive camshaft drive. The predictions are in line with experience. The guide requires belt property
information, such as the tooth and tension member stiffness, the friction coefficient between the belt lands
and pulleys and the pitch difference from the pulley, in order to calculate the tooth deflections caused by
the belt loadings on the various pulleys in the layout. It also requires information on how the belt life
depends on the tooth deflections. Experimental data are presented on the life±deflection relations of a
commercial automotive timing belt tested between 100 and 140 8C, although the bulk of the data has been
obtained at 120 8C. Four different life laws have been found, depending on whether the failure-initiating
deflection occurred on a driver or a driven pulley, and whether at entry to or exit from the pulley.
Theoretical analysis of the tooth loading in the partial meshing state shows that, in three cases out of the
four, the different life±deflection laws transform to a single relation between the life and the tooth root
strain. The exception is failure caused by driven entry conditions; work is continuing to understand better
the causes of failure in this circumstanc
Making Adaptive an Interval Constraint Propagation Algorithm Exploiting Monotonicity
International audienceA new interval constraint propagation algorithm, called MOnotonic Hull Consistency (Mohc), has recently been proposed. Mohc exploits monotonicity of functions to better filter variable domains. Embedded in an interval-based solver, Mohc shows very high performance for solving systems of numerical constraints (equations or inequalities) over the reals. However, the main drawback is that its revise procedure depends on two user-defined parameters. This paper reports a rigourous empirical study resulting in a variant of Mohc that avoids a manual tuning of the parameters. In particular, we propose a policy to adjust in an auto-adaptive way, during the search, the parameter sensitive to the monotonicity of the revised function
Towards eco-efficient lean production systems
Lean Production has proved itself a worthwhile production strategy in many
distinct industries across all regions of the planet by achieving higher levels of
production efficiency. Several authors identified that Lean inadvertently has
had significant environmental gains. Such achievements are considered of
special relevance in a global and highly competitive economy which is
progressively both tied-up and driven by an environmental agenda. The main
goal of the present study is to enlighten the contribution of Lean for achieving
a better environmental performance of production systems and identify this as
an emergent business model for supporting eco-efficiency
Substructures in lens galaxies: PG1115+080 and B1555+375, two fold configurations
We study the anomalous flux ratio which is observed in some four-image lens
systems, where the source lies close to a fold caustic. In this case two of the
images are close to the critical curve and their flux ratio should be equal to
unity, instead in several cases the observed value differs significantly. The
most plausible solution is to invoke the presence of substructures, as for
instance predicted by the Cold Dark Matter scenario, located near the two
images. In particular, we analyze the two fold lens systems PG1115+080 and
B1555+375, for which there are not yet satisfactory models which explain the
observed anomalous flux ratios. We add to a smooth lens model, which reproduces
well the positions of the images but not the anomalous fluxes, one or two
substructures described as singular isothermal spheres. For PG1115+080 we
consider a smooth model with the influence of the group of galaxies described
by a SIS and a substructure with mass as well as a
smooth model with an external shear and one substructure with mass . For B1555+375 either a strong external shear or two substructures
with mass reproduce the data quite well.Comment: 26 pages, updated bibliography, Accepted for publication in
Astrophysics & Space Scienc
A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams
An ion beam cooler and buncher has been developed for the manipulation of
radioactive ion beams. The gas-filled linear radiofrequency ion trap system is
installed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Its
purpose is to accumulate the 60-keV continuous ISOLDE ion beam with high
efficiency and to convert it into low-energy low-emittance ion pulses. The
efficiency was found to exceed 10% in agreement with simulations. A more than
10-fold reduction of the ISOLDE beam emittance can be achieved. The system has
been used successfully for first on-line experiments. Its principle, setup and
performance will be discussed
Invariant structure of the hierarchy theory of fractional quantum Hall states with spin
We describe the invariant structure common to abelian fractional quantum Hall
systems with spin. It appears in a generalization of the lattice description of
the polarized hierarchy that encompasses both partially polarized and
unpolarized ground state systems. We formulate, using the spin-charge
decomposition, conditions that should be satisfied so that the description is
SU(2) invariant. In the case of the spin- singlet hierarchy construction, we
find that there are as many SU(2) symmetries as there are levels in the
construction. We show the existence of a spin and charge lattice for the
systems with spin. The ``gluing'' of the charge and spin degrees of freedom in
their bulk is described by the gluing theory of lattices.Comment: 21 pages, LaTex, Submitted to Phys. Rev.
Draft genome sequence of extended-spectrum-β-lactamase-producing Escherichia coli strain CCUG 62462, isolated from a urine sample
The draft genome sequence has been determined for an extended-spectrum-β-lactamase (ESBL)-producing (blaCTX-M-15) Escherichia coli strain (CCUG 62462), composed of 119 contigs and a total size of 5.27 Mb. This E. coli is serotype O25b and sequence type 131, a pandemic clonal group, causing worldwide antimicrobial-resistant infections
Critical points in edge tunneling between generic FQH states
A general description of weak and strong tunneling fixed points is developed
in the chiral-Luttinger-liquid model of quantum Hall edge states. Tunneling
fixed points are a subset of `termination' fixed points, which describe
boundary conditions on a multicomponent edge. The requirement of unitary time
evolution at the boundary gives a nontrivial consistency condition for possible
low-energy boundary conditions. The effect of interactions and random hopping
on fixed points is studied through a perturbative RG approach which generalizes
the Giamarchi-Schulz RG for disordered Luttinger liquids to broken left-right
symmetry and multiple modes. The allowed termination points of a multicomponent
edge are classified by a B-matrix with rational matrix elements. We apply our
approach to a number of examples, such as tunneling between a quantum Hall edge
and a superconductor and tunneling between two quantum Hall edges in the
presence of interactions. Interactions are shown to induce a continuous
renormalization of effective tunneling charge for the integrable case of
tunneling between two Laughlin states. The correlation functions of
electronlike operators across a junction are found from the B matrix using a
simple image-charge description, along with the induced lattice of boundary
operators. Many of the results obtained are also relevant to ordinary Luttinger
liquids.Comment: 23 pages, 6 figures. Xiao-Gang Wen: http://dao.mit.edu/~we
Theoretical Evaluations of the Fission Cross Section of the 77 eV Isomer of 235-U
We have developed models of the fission barrier (barrier heights and
transition state spectra) that reproduce reasonably well the measured fission
cross section of U from neutron energy of 1 keV to 2 MeV. From these
models we have calculated the fission cross section of the 77 eV isomer of
U over the same energy range. We find that the ratio of the isomer
cross section to that of the ground state lies between about 0.45 and 0.55 at
low neutron energies. The cross sections become approximately equal above 1
MeV. The ratio of the neutron capture cross section to the fission cross
section for the isomer is predicted to be about a factor of 3 larger for the
isomer than for the ground state of U at keV neutron energies. We have
also calculated the cross section for the population of the isomer by inelastic
neutron scattering form the U ground state. We find that the isomer is
strongly populated, and for the cross section
leading to the population of the isomer is of the order of 0.5 barn. Thus,
neutron reaction network calculations involving the uranium isotopes in a high
neutron fluence are likely to be affected by the 77 eV isomer of U.
With these same models the fission cross sections of U and U
can be reproduced approximately using only minor adjustments to the barrier
heights. With the significant lowering of the outer barrier that is expected
for the outer barrier the general behavior of the fission cross section of
Pu can also be reproduced.Comment: 17 pages including 8 figure
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