6,873 research outputs found
Status of Lattice QCD
Significant progress has recently been achieved in the lattice gauge theory
calculations required for extracting the fundamental parameters of the standard
model from experiment. Recent lattice determinations of such quantities as the
kaon parameter, the mass of the quark, and the strong coupling constant
have produced results and uncertainties as good or better than the best
conventional determinations. Many other calculations crucial to extracting the
fundamental parameters of the standard model from experimental data are
undergoing very active development. I review the status of such applications of
lattice QCD to standard model phenomenology, and discuss the prospects for the
near future.Comment: 20 pages, 8 embedded figures, uuencoded, 2 missing figures. (Talk
presented at the Lepton-Photon Symposium, Cornell University, Aug. 10-15,
1993.
Variable Powder Flow Rate Control in Laser Metal Deposition Processes
This paper proposes a novel technique, called Variable Powder Flow Rate Control (VPFRC), for
the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to
adjust the powder flow rate to maintain a uniform powder deposition per unit length even when
disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the
powder delivery system motor and the powder transport system (i.e., five–meter pipe, powder
dispenser, and cladding head) are first constructed. A general tracking controller is then designed
to track variable powder flow rate references. Since the powder flow rate at the nozzle exit
cannot be directly measured, it is estimated using the powder transport system model. The input
to this model is the DC motor rotation speed, which is estimated on–line using a Kalman filter.
Experiments are conducted to examine the performance of the proposed control methodology.
The experimental results demonstrate that VPFRC is successful in maintaining a uniform track
morphology, even when the motion control system accelerates and decelerates.Mechanical Engineerin
Elliptic CR-manifolds and shear invariant ODE with additional symmetries
We classify the ODEs that correspond to elliptic CR-manifolds with maximal
isotropy. It follows that the dimension of the isotropy group of an elliptic
CR-manifold can be only 10 (for the quadric), 4 (for the listed examples) or
less. This is in contrast with the situation of hyperbolic CR-manifolds, where
the dimension can be 10 (for the quadric), 6 or 5 (for semi-quadrics) or less
than 4. We also prove that, for all elliptic CR-manifolds with non-linearizable
istropy group, except for two special manifolds, the points with
non-linearizable isotropy form exactly some complex curve on the manifold
Fluctuating Hydrodynamics in a Dilute Gas
Hydrodynamic fluctuations in a dilute gas subjected to a constant heat flux are studied by both a computer simulation and the Landau-Lifshitz formalism. The latter explicitly incorporates the boundary conditions of the finite system, thus permitting quantitative comparison with the former. Good agreement is demonstrated
Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model
The neutron-proton effective -mass splitting in asymmetric nucleonic
matter of isospin asymmetry and normal density is found to be
from analyzing
globally 1088 sets of reaction and angular differential cross sections of
proton elastic scattering on 130 targets with beam energies from 0.783 MeV to
200 MeV, and 1161 sets of data of neutron elastic scattering on 104 targets
with beam energies from 0.05 MeV to 200 MeV within an isospin dependent
non-relativistic optical potential model. It sets a useful reference for
testing model predictions on the momentum dependence of the nucleon isovector
potential necessary for understanding novel structures and reactions of rare
isotopes.Comment: Published version, Physics Letters B743 (2015) 40
Symmetry, singularities and integrability in complex dynamics III: approximate symmetries and invariants
The different natures of approximate symmetries and their corresponding first
integrals/invariants are delineated in the contexts of both Lie symmetries of
ordinary differential equations and Noether symmetries of the Action Integral.
Particular note is taken of the effect of taking higher orders of the
perturbation parameter. Approximate symmetries of approximate first
integrals/invariants and the problems of calculating them using the Lie method
are considered
Batteries for wearables
This perspective article highlights the recent advances and future challenges of battery technologies for wearables
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