17,788 research outputs found
Multiobjective analysis for the design and control of an electromagnetic valve actuator
The electromagnetic valve actuator can deliver much improved fuel efficiency and reduced emissions in spark ignition (SI) engines owing to the potential for variable valve timing when compared with cam-operated, or conventional, variable valve strategies. The possibility exists to reduce pumping losses by throttle-free operation, along with closed-valve engine braking. However, further development is required to make the technology suitable for accept- ance into the mass production market. This paper investigates the application of multiobjective optimization techniques to the conflicting objective functions inherent in the operation of such a device. The techniques are utilized to derive the optimal force–displacement characteristic for the solenoid actuator, along with its controllability and dynamic/steady state performance
Low-momentum interactions in three- and four-nucleon scattering
Low momentum two-nucleon interactions obtained with the renormalization group
method and the similarity renormalization group method are used to study the
cutoff dependence of low energy 3N and 4N scattering observables. The residual
cutoff dependence arises from omitted short-ranged 3N (and higher) forces that
are induced by the renormalization group transformations, and may help to
estimate the sensitivity of various 3N and 4N scattering observables to
short-ranged many-body forces.Comment: 5 pages, 8 figures, to be published in Phys. Rev.
Three-body Faddeev-Alt-Grassberger-Sandhas approach to direct nuclear reactions
Momentum space three-body Faddeev-like equations are used to calculate
elastic, transfer and charge exchange reactions resulting from the scattering
of deuterons on 12C and 16O or protons on 13C and 17O; 12C and 16O are treated
as inert cores. All possible reactions are calculated in the framework of the
same model space. Comparison with previous calculations based on approximate
methods used in nuclear reaction theory is discussed.Comment: 10 pages, 13 figures, to be published in Phys. Rev.
New calculation schemes for proton-deuteron scattering including the Coulomb interaction
The Coulomb interaction between the protons is included in the description of
proton-deuteron scattering using the screening and renormalization approach in
the framework of momentum-space integral equations. Two new calculational
schemes are presented that confirm the reliability of the perturbative approach
for treating the screened Coulomb interaction in high partial waves, used by us
in earlier works.Comment: To be published in Phys. Rev.
Photodisintegration of the triton with realistic potentials
The process is treated by means of three-body integral
equations employing in their kernel the W-Matrix representation of the
subsystem amplitudes. As compared to the plane wave (Born) approximation the
full solution of the integral equations, which takes into account the final
state interaction, shows at low energies a 24% enhancement. The calculations
are based on the semirealistic Malfliet-Tjon and the realistic Paris and Bonn B
potentials. For comparison with earlier calculations we also present results
for the Yamaguchi potential. In the low-energy region a remarkable potential
dependence is observed, which vanishes at higher energies.Comment: 16 pages REVTeX, 8 postscript figures included, uses epsfig.st
Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes
Helical or coiled nanostructures have been object of intense experimental and
theoretical studies due to their special electronic and mechanical properties.
Recently, it was experimentally reported that the dynamical response of
foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a
nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The
physical origin of this unusual behavior is not yet fully understood. In this
work, based on analytical models, we show that the entanglement among
neighboring coils in the superior part of the forest surface must be taken into
account for a full description of the strongly nonlinear behavior of the impact
response of a drop-ball onto a forest of coiled carbon nanotubes.Comment: 4 pages, 3 figure
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